1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * kernel/sched/core.c 4 * 5 * Core kernel scheduler code and related syscalls 6 * 7 * Copyright (C) 1991-2002 Linus Torvalds 8 */ 9 #define CREATE_TRACE_POINTS 10 #include <trace/events/sched.h> 11 #undef CREATE_TRACE_POINTS 12 13 #include "sched.h" 14 15 #include <linux/nospec.h> 16 #include <linux/blkdev.h> 17 #include <linux/kcov.h> 18 #include <linux/scs.h> 19 20 #include <asm/switch_to.h> 21 #include <asm/tlb.h> 22 23 #include "../workqueue_internal.h" 24 #include "../../fs/io-wq.h" 25 #include "../smpboot.h" 26 27 #include "pelt.h" 28 #include "smp.h" 29 30 /* 31 * Export tracepoints that act as a bare tracehook (ie: have no trace event 32 * associated with them) to allow external modules to probe them. 33 */ 34 EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_cfs_tp); 35 EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_rt_tp); 36 EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_dl_tp); 37 EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_irq_tp); 38 EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_se_tp); 39 EXPORT_TRACEPOINT_SYMBOL_GPL(sched_cpu_capacity_tp); 40 EXPORT_TRACEPOINT_SYMBOL_GPL(sched_overutilized_tp); 41 EXPORT_TRACEPOINT_SYMBOL_GPL(sched_util_est_cfs_tp); 42 EXPORT_TRACEPOINT_SYMBOL_GPL(sched_util_est_se_tp); 43 EXPORT_TRACEPOINT_SYMBOL_GPL(sched_update_nr_running_tp); 44 45 DEFINE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues); 46 47 #ifdef CONFIG_SCHED_DEBUG 48 /* 49 * Debugging: various feature bits 50 * 51 * If SCHED_DEBUG is disabled, each compilation unit has its own copy of 52 * sysctl_sched_features, defined in sched.h, to allow constants propagation 53 * at compile time and compiler optimization based on features default. 54 */ 55 #define SCHED_FEAT(name, enabled) \ 56 (1UL << __SCHED_FEAT_##name) * enabled | 57 const_debug unsigned int sysctl_sched_features = 58 #include "features.h" 59 0; 60 #undef SCHED_FEAT 61 62 /* 63 * Print a warning if need_resched is set for the given duration (if 64 * LATENCY_WARN is enabled). 65 * 66 * If sysctl_resched_latency_warn_once is set, only one warning will be shown 67 * per boot. 68 */ 69 __read_mostly int sysctl_resched_latency_warn_ms = 100; 70 __read_mostly int sysctl_resched_latency_warn_once = 1; 71 #endif /* CONFIG_SCHED_DEBUG */ 72 73 /* 74 * Number of tasks to iterate in a single balance run. 75 * Limited because this is done with IRQs disabled. 76 */ 77 #ifdef CONFIG_PREEMPT_RT 78 const_debug unsigned int sysctl_sched_nr_migrate = 8; 79 #else 80 const_debug unsigned int sysctl_sched_nr_migrate = 32; 81 #endif 82 83 /* 84 * period over which we measure -rt task CPU usage in us. 85 * default: 1s 86 */ 87 unsigned int sysctl_sched_rt_period = 1000000; 88 89 __read_mostly int scheduler_running; 90 91 #ifdef CONFIG_SCHED_CORE 92 93 DEFINE_STATIC_KEY_FALSE(__sched_core_enabled); 94 95 /* kernel prio, less is more */ 96 static inline int __task_prio(struct task_struct *p) 97 { 98 if (p->sched_class == &stop_sched_class) /* trumps deadline */ 99 return -2; 100 101 if (rt_prio(p->prio)) /* includes deadline */ 102 return p->prio; /* [-1, 99] */ 103 104 if (p->sched_class == &idle_sched_class) 105 return MAX_RT_PRIO + NICE_WIDTH; /* 140 */ 106 107 return MAX_RT_PRIO + MAX_NICE; /* 120, squash fair */ 108 } 109 110 /* 111 * l(a,b) 112 * le(a,b) := !l(b,a) 113 * g(a,b) := l(b,a) 114 * ge(a,b) := !l(a,b) 115 */ 116 117 /* real prio, less is less */ 118 static inline bool prio_less(struct task_struct *a, struct task_struct *b, bool in_fi) 119 { 120 121 int pa = __task_prio(a), pb = __task_prio(b); 122 123 if (-pa < -pb) 124 return true; 125 126 if (-pb < -pa) 127 return false; 128 129 if (pa == -1) /* dl_prio() doesn't work because of stop_class above */ 130 return !dl_time_before(a->dl.deadline, b->dl.deadline); 131 132 if (pa == MAX_RT_PRIO + MAX_NICE) /* fair */ 133 return cfs_prio_less(a, b, in_fi); 134 135 return false; 136 } 137 138 static inline bool __sched_core_less(struct task_struct *a, struct task_struct *b) 139 { 140 if (a->core_cookie < b->core_cookie) 141 return true; 142 143 if (a->core_cookie > b->core_cookie) 144 return false; 145 146 /* flip prio, so high prio is leftmost */ 147 if (prio_less(b, a, !!task_rq(a)->core->core_forceidle_count)) 148 return true; 149 150 return false; 151 } 152 153 #define __node_2_sc(node) rb_entry((node), struct task_struct, core_node) 154 155 static inline bool rb_sched_core_less(struct rb_node *a, const struct rb_node *b) 156 { 157 return __sched_core_less(__node_2_sc(a), __node_2_sc(b)); 158 } 159 160 static inline int rb_sched_core_cmp(const void *key, const struct rb_node *node) 161 { 162 const struct task_struct *p = __node_2_sc(node); 163 unsigned long cookie = (unsigned long)key; 164 165 if (cookie < p->core_cookie) 166 return -1; 167 168 if (cookie > p->core_cookie) 169 return 1; 170 171 return 0; 172 } 173 174 void sched_core_enqueue(struct rq *rq, struct task_struct *p) 175 { 176 rq->core->core_task_seq++; 177 178 if (!p->core_cookie) 179 return; 180 181 rb_add(&p->core_node, &rq->core_tree, rb_sched_core_less); 182 } 183 184 void sched_core_dequeue(struct rq *rq, struct task_struct *p, int flags) 185 { 186 rq->core->core_task_seq++; 187 188 if (sched_core_enqueued(p)) { 189 rb_erase(&p->core_node, &rq->core_tree); 190 RB_CLEAR_NODE(&p->core_node); 191 } 192 193 /* 194 * Migrating the last task off the cpu, with the cpu in forced idle 195 * state. Reschedule to create an accounting edge for forced idle, 196 * and re-examine whether the core is still in forced idle state. 197 */ 198 if (!(flags & DEQUEUE_SAVE) && rq->nr_running == 1 && 199 rq->core->core_forceidle_count && rq->curr == rq->idle) 200 resched_curr(rq); 201 } 202 203 /* 204 * Find left-most (aka, highest priority) task matching @cookie. 205 */ 206 static struct task_struct *sched_core_find(struct rq *rq, unsigned long cookie) 207 { 208 struct rb_node *node; 209 210 node = rb_find_first((void *)cookie, &rq->core_tree, rb_sched_core_cmp); 211 /* 212 * The idle task always matches any cookie! 213 */ 214 if (!node) 215 return idle_sched_class.pick_task(rq); 216 217 return __node_2_sc(node); 218 } 219 220 static struct task_struct *sched_core_next(struct task_struct *p, unsigned long cookie) 221 { 222 struct rb_node *node = &p->core_node; 223 224 node = rb_next(node); 225 if (!node) 226 return NULL; 227 228 p = container_of(node, struct task_struct, core_node); 229 if (p->core_cookie != cookie) 230 return NULL; 231 232 return p; 233 } 234 235 /* 236 * Magic required such that: 237 * 238 * raw_spin_rq_lock(rq); 239 * ... 240 * raw_spin_rq_unlock(rq); 241 * 242 * ends up locking and unlocking the _same_ lock, and all CPUs 243 * always agree on what rq has what lock. 244 * 245 * XXX entirely possible to selectively enable cores, don't bother for now. 246 */ 247 248 static DEFINE_MUTEX(sched_core_mutex); 249 static atomic_t sched_core_count; 250 static struct cpumask sched_core_mask; 251 252 static void sched_core_lock(int cpu, unsigned long *flags) 253 { 254 const struct cpumask *smt_mask = cpu_smt_mask(cpu); 255 int t, i = 0; 256 257 local_irq_save(*flags); 258 for_each_cpu(t, smt_mask) 259 raw_spin_lock_nested(&cpu_rq(t)->__lock, i++); 260 } 261 262 static void sched_core_unlock(int cpu, unsigned long *flags) 263 { 264 const struct cpumask *smt_mask = cpu_smt_mask(cpu); 265 int t; 266 267 for_each_cpu(t, smt_mask) 268 raw_spin_unlock(&cpu_rq(t)->__lock); 269 local_irq_restore(*flags); 270 } 271 272 static void __sched_core_flip(bool enabled) 273 { 274 unsigned long flags; 275 int cpu, t; 276 277 cpus_read_lock(); 278 279 /* 280 * Toggle the online cores, one by one. 281 */ 282 cpumask_copy(&sched_core_mask, cpu_online_mask); 283 for_each_cpu(cpu, &sched_core_mask) { 284 const struct cpumask *smt_mask = cpu_smt_mask(cpu); 285 286 sched_core_lock(cpu, &flags); 287 288 for_each_cpu(t, smt_mask) 289 cpu_rq(t)->core_enabled = enabled; 290 291 cpu_rq(cpu)->core->core_forceidle_start = 0; 292 293 sched_core_unlock(cpu, &flags); 294 295 cpumask_andnot(&sched_core_mask, &sched_core_mask, smt_mask); 296 } 297 298 /* 299 * Toggle the offline CPUs. 300 */ 301 cpumask_copy(&sched_core_mask, cpu_possible_mask); 302 cpumask_andnot(&sched_core_mask, &sched_core_mask, cpu_online_mask); 303 304 for_each_cpu(cpu, &sched_core_mask) 305 cpu_rq(cpu)->core_enabled = enabled; 306 307 cpus_read_unlock(); 308 } 309 310 static void sched_core_assert_empty(void) 311 { 312 int cpu; 313 314 for_each_possible_cpu(cpu) 315 WARN_ON_ONCE(!RB_EMPTY_ROOT(&cpu_rq(cpu)->core_tree)); 316 } 317 318 static void __sched_core_enable(void) 319 { 320 static_branch_enable(&__sched_core_enabled); 321 /* 322 * Ensure all previous instances of raw_spin_rq_*lock() have finished 323 * and future ones will observe !sched_core_disabled(). 324 */ 325 synchronize_rcu(); 326 __sched_core_flip(true); 327 sched_core_assert_empty(); 328 } 329 330 static void __sched_core_disable(void) 331 { 332 sched_core_assert_empty(); 333 __sched_core_flip(false); 334 static_branch_disable(&__sched_core_enabled); 335 } 336 337 void sched_core_get(void) 338 { 339 if (atomic_inc_not_zero(&sched_core_count)) 340 return; 341 342 mutex_lock(&sched_core_mutex); 343 if (!atomic_read(&sched_core_count)) 344 __sched_core_enable(); 345 346 smp_mb__before_atomic(); 347 atomic_inc(&sched_core_count); 348 mutex_unlock(&sched_core_mutex); 349 } 350 351 static void __sched_core_put(struct work_struct *work) 352 { 353 if (atomic_dec_and_mutex_lock(&sched_core_count, &sched_core_mutex)) { 354 __sched_core_disable(); 355 mutex_unlock(&sched_core_mutex); 356 } 357 } 358 359 void sched_core_put(void) 360 { 361 static DECLARE_WORK(_work, __sched_core_put); 362 363 /* 364 * "There can be only one" 365 * 366 * Either this is the last one, or we don't actually need to do any 367 * 'work'. If it is the last *again*, we rely on 368 * WORK_STRUCT_PENDING_BIT. 369 */ 370 if (!atomic_add_unless(&sched_core_count, -1, 1)) 371 schedule_work(&_work); 372 } 373 374 #else /* !CONFIG_SCHED_CORE */ 375 376 static inline void sched_core_enqueue(struct rq *rq, struct task_struct *p) { } 377 static inline void 378 sched_core_dequeue(struct rq *rq, struct task_struct *p, int flags) { } 379 380 #endif /* CONFIG_SCHED_CORE */ 381 382 /* 383 * part of the period that we allow rt tasks to run in us. 384 * default: 0.95s 385 */ 386 int sysctl_sched_rt_runtime = 950000; 387 388 389 /* 390 * Serialization rules: 391 * 392 * Lock order: 393 * 394 * p->pi_lock 395 * rq->lock 396 * hrtimer_cpu_base->lock (hrtimer_start() for bandwidth controls) 397 * 398 * rq1->lock 399 * rq2->lock where: rq1 < rq2 400 * 401 * Regular state: 402 * 403 * Normal scheduling state is serialized by rq->lock. __schedule() takes the 404 * local CPU's rq->lock, it optionally removes the task from the runqueue and 405 * always looks at the local rq data structures to find the most eligible task 406 * to run next. 407 * 408 * Task enqueue is also under rq->lock, possibly taken from another CPU. 409 * Wakeups from another LLC domain might use an IPI to transfer the enqueue to 410 * the local CPU to avoid bouncing the runqueue state around [ see 411 * ttwu_queue_wakelist() ] 412 * 413 * Task wakeup, specifically wakeups that involve migration, are horribly 414 * complicated to avoid having to take two rq->locks. 415 * 416 * Special state: 417 * 418 * System-calls and anything external will use task_rq_lock() which acquires 419 * both p->pi_lock and rq->lock. As a consequence the state they change is 420 * stable while holding either lock: 421 * 422 * - sched_setaffinity()/ 423 * set_cpus_allowed_ptr(): p->cpus_ptr, p->nr_cpus_allowed 424 * - set_user_nice(): p->se.load, p->*prio 425 * - __sched_setscheduler(): p->sched_class, p->policy, p->*prio, 426 * p->se.load, p->rt_priority, 427 * p->dl.dl_{runtime, deadline, period, flags, bw, density} 428 * - sched_setnuma(): p->numa_preferred_nid 429 * - sched_move_task()/ 430 * cpu_cgroup_fork(): p->sched_task_group 431 * - uclamp_update_active() p->uclamp* 432 * 433 * p->state <- TASK_*: 434 * 435 * is changed locklessly using set_current_state(), __set_current_state() or 436 * set_special_state(), see their respective comments, or by 437 * try_to_wake_up(). This latter uses p->pi_lock to serialize against 438 * concurrent self. 439 * 440 * p->on_rq <- { 0, 1 = TASK_ON_RQ_QUEUED, 2 = TASK_ON_RQ_MIGRATING }: 441 * 442 * is set by activate_task() and cleared by deactivate_task(), under 443 * rq->lock. Non-zero indicates the task is runnable, the special 444 * ON_RQ_MIGRATING state is used for migration without holding both 445 * rq->locks. It indicates task_cpu() is not stable, see task_rq_lock(). 446 * 447 * p->on_cpu <- { 0, 1 }: 448 * 449 * is set by prepare_task() and cleared by finish_task() such that it will be 450 * set before p is scheduled-in and cleared after p is scheduled-out, both 451 * under rq->lock. Non-zero indicates the task is running on its CPU. 452 * 453 * [ The astute reader will observe that it is possible for two tasks on one 454 * CPU to have ->on_cpu = 1 at the same time. ] 455 * 456 * task_cpu(p): is changed by set_task_cpu(), the rules are: 457 * 458 * - Don't call set_task_cpu() on a blocked task: 459 * 460 * We don't care what CPU we're not running on, this simplifies hotplug, 461 * the CPU assignment of blocked tasks isn't required to be valid. 462 * 463 * - for try_to_wake_up(), called under p->pi_lock: 464 * 465 * This allows try_to_wake_up() to only take one rq->lock, see its comment. 466 * 467 * - for migration called under rq->lock: 468 * [ see task_on_rq_migrating() in task_rq_lock() ] 469 * 470 * o move_queued_task() 471 * o detach_task() 472 * 473 * - for migration called under double_rq_lock(): 474 * 475 * o __migrate_swap_task() 476 * o push_rt_task() / pull_rt_task() 477 * o push_dl_task() / pull_dl_task() 478 * o dl_task_offline_migration() 479 * 480 */ 481 482 void raw_spin_rq_lock_nested(struct rq *rq, int subclass) 483 { 484 raw_spinlock_t *lock; 485 486 /* Matches synchronize_rcu() in __sched_core_enable() */ 487 preempt_disable(); 488 if (sched_core_disabled()) { 489 raw_spin_lock_nested(&rq->__lock, subclass); 490 /* preempt_count *MUST* be > 1 */ 491 preempt_enable_no_resched(); 492 return; 493 } 494 495 for (;;) { 496 lock = __rq_lockp(rq); 497 raw_spin_lock_nested(lock, subclass); 498 if (likely(lock == __rq_lockp(rq))) { 499 /* preempt_count *MUST* be > 1 */ 500 preempt_enable_no_resched(); 501 return; 502 } 503 raw_spin_unlock(lock); 504 } 505 } 506 507 bool raw_spin_rq_trylock(struct rq *rq) 508 { 509 raw_spinlock_t *lock; 510 bool ret; 511 512 /* Matches synchronize_rcu() in __sched_core_enable() */ 513 preempt_disable(); 514 if (sched_core_disabled()) { 515 ret = raw_spin_trylock(&rq->__lock); 516 preempt_enable(); 517 return ret; 518 } 519 520 for (;;) { 521 lock = __rq_lockp(rq); 522 ret = raw_spin_trylock(lock); 523 if (!ret || (likely(lock == __rq_lockp(rq)))) { 524 preempt_enable(); 525 return ret; 526 } 527 raw_spin_unlock(lock); 528 } 529 } 530 531 void raw_spin_rq_unlock(struct rq *rq) 532 { 533 raw_spin_unlock(rq_lockp(rq)); 534 } 535 536 #ifdef CONFIG_SMP 537 /* 538 * double_rq_lock - safely lock two runqueues 539 */ 540 void double_rq_lock(struct rq *rq1, struct rq *rq2) 541 { 542 lockdep_assert_irqs_disabled(); 543 544 if (rq_order_less(rq2, rq1)) 545 swap(rq1, rq2); 546 547 raw_spin_rq_lock(rq1); 548 if (__rq_lockp(rq1) == __rq_lockp(rq2)) 549 return; 550 551 raw_spin_rq_lock_nested(rq2, SINGLE_DEPTH_NESTING); 552 } 553 #endif 554 555 /* 556 * __task_rq_lock - lock the rq @p resides on. 557 */ 558 struct rq *__task_rq_lock(struct task_struct *p, struct rq_flags *rf) 559 __acquires(rq->lock) 560 { 561 struct rq *rq; 562 563 lockdep_assert_held(&p->pi_lock); 564 565 for (;;) { 566 rq = task_rq(p); 567 raw_spin_rq_lock(rq); 568 if (likely(rq == task_rq(p) && !task_on_rq_migrating(p))) { 569 rq_pin_lock(rq, rf); 570 return rq; 571 } 572 raw_spin_rq_unlock(rq); 573 574 while (unlikely(task_on_rq_migrating(p))) 575 cpu_relax(); 576 } 577 } 578 579 /* 580 * task_rq_lock - lock p->pi_lock and lock the rq @p resides on. 581 */ 582 struct rq *task_rq_lock(struct task_struct *p, struct rq_flags *rf) 583 __acquires(p->pi_lock) 584 __acquires(rq->lock) 585 { 586 struct rq *rq; 587 588 for (;;) { 589 raw_spin_lock_irqsave(&p->pi_lock, rf->flags); 590 rq = task_rq(p); 591 raw_spin_rq_lock(rq); 592 /* 593 * move_queued_task() task_rq_lock() 594 * 595 * ACQUIRE (rq->lock) 596 * [S] ->on_rq = MIGRATING [L] rq = task_rq() 597 * WMB (__set_task_cpu()) ACQUIRE (rq->lock); 598 * [S] ->cpu = new_cpu [L] task_rq() 599 * [L] ->on_rq 600 * RELEASE (rq->lock) 601 * 602 * If we observe the old CPU in task_rq_lock(), the acquire of 603 * the old rq->lock will fully serialize against the stores. 604 * 605 * If we observe the new CPU in task_rq_lock(), the address 606 * dependency headed by '[L] rq = task_rq()' and the acquire 607 * will pair with the WMB to ensure we then also see migrating. 608 */ 609 if (likely(rq == task_rq(p) && !task_on_rq_migrating(p))) { 610 rq_pin_lock(rq, rf); 611 return rq; 612 } 613 raw_spin_rq_unlock(rq); 614 raw_spin_unlock_irqrestore(&p->pi_lock, rf->flags); 615 616 while (unlikely(task_on_rq_migrating(p))) 617 cpu_relax(); 618 } 619 } 620 621 /* 622 * RQ-clock updating methods: 623 */ 624 625 static void update_rq_clock_task(struct rq *rq, s64 delta) 626 { 627 /* 628 * In theory, the compile should just see 0 here, and optimize out the call 629 * to sched_rt_avg_update. But I don't trust it... 630 */ 631 s64 __maybe_unused steal = 0, irq_delta = 0; 632 633 #ifdef CONFIG_IRQ_TIME_ACCOUNTING 634 irq_delta = irq_time_read(cpu_of(rq)) - rq->prev_irq_time; 635 636 /* 637 * Since irq_time is only updated on {soft,}irq_exit, we might run into 638 * this case when a previous update_rq_clock() happened inside a 639 * {soft,}irq region. 640 * 641 * When this happens, we stop ->clock_task and only update the 642 * prev_irq_time stamp to account for the part that fit, so that a next 643 * update will consume the rest. This ensures ->clock_task is 644 * monotonic. 645 * 646 * It does however cause some slight miss-attribution of {soft,}irq 647 * time, a more accurate solution would be to update the irq_time using 648 * the current rq->clock timestamp, except that would require using 649 * atomic ops. 650 */ 651 if (irq_delta > delta) 652 irq_delta = delta; 653 654 rq->prev_irq_time += irq_delta; 655 delta -= irq_delta; 656 #endif 657 #ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING 658 if (static_key_false((¶virt_steal_rq_enabled))) { 659 steal = paravirt_steal_clock(cpu_of(rq)); 660 steal -= rq->prev_steal_time_rq; 661 662 if (unlikely(steal > delta)) 663 steal = delta; 664 665 rq->prev_steal_time_rq += steal; 666 delta -= steal; 667 } 668 #endif 669 670 rq->clock_task += delta; 671 672 #ifdef CONFIG_HAVE_SCHED_AVG_IRQ 673 if ((irq_delta + steal) && sched_feat(NONTASK_CAPACITY)) 674 update_irq_load_avg(rq, irq_delta + steal); 675 #endif 676 update_rq_clock_pelt(rq, delta); 677 } 678 679 void update_rq_clock(struct rq *rq) 680 { 681 s64 delta; 682 683 lockdep_assert_rq_held(rq); 684 685 if (rq->clock_update_flags & RQCF_ACT_SKIP) 686 return; 687 688 #ifdef CONFIG_SCHED_DEBUG 689 if (sched_feat(WARN_DOUBLE_CLOCK)) 690 SCHED_WARN_ON(rq->clock_update_flags & RQCF_UPDATED); 691 rq->clock_update_flags |= RQCF_UPDATED; 692 #endif 693 694 delta = sched_clock_cpu(cpu_of(rq)) - rq->clock; 695 if (delta < 0) 696 return; 697 rq->clock += delta; 698 update_rq_clock_task(rq, delta); 699 } 700 701 #ifdef CONFIG_SCHED_HRTICK 702 /* 703 * Use HR-timers to deliver accurate preemption points. 704 */ 705 706 static void hrtick_clear(struct rq *rq) 707 { 708 if (hrtimer_active(&rq->hrtick_timer)) 709 hrtimer_cancel(&rq->hrtick_timer); 710 } 711 712 /* 713 * High-resolution timer tick. 714 * Runs from hardirq context with interrupts disabled. 715 */ 716 static enum hrtimer_restart hrtick(struct hrtimer *timer) 717 { 718 struct rq *rq = container_of(timer, struct rq, hrtick_timer); 719 struct rq_flags rf; 720 721 WARN_ON_ONCE(cpu_of(rq) != smp_processor_id()); 722 723 rq_lock(rq, &rf); 724 update_rq_clock(rq); 725 rq->curr->sched_class->task_tick(rq, rq->curr, 1); 726 rq_unlock(rq, &rf); 727 728 return HRTIMER_NORESTART; 729 } 730 731 #ifdef CONFIG_SMP 732 733 static void __hrtick_restart(struct rq *rq) 734 { 735 struct hrtimer *timer = &rq->hrtick_timer; 736 ktime_t time = rq->hrtick_time; 737 738 hrtimer_start(timer, time, HRTIMER_MODE_ABS_PINNED_HARD); 739 } 740 741 /* 742 * called from hardirq (IPI) context 743 */ 744 static void __hrtick_start(void *arg) 745 { 746 struct rq *rq = arg; 747 struct rq_flags rf; 748 749 rq_lock(rq, &rf); 750 __hrtick_restart(rq); 751 rq_unlock(rq, &rf); 752 } 753 754 /* 755 * Called to set the hrtick timer state. 756 * 757 * called with rq->lock held and irqs disabled 758 */ 759 void hrtick_start(struct rq *rq, u64 delay) 760 { 761 struct hrtimer *timer = &rq->hrtick_timer; 762 s64 delta; 763 764 /* 765 * Don't schedule slices shorter than 10000ns, that just 766 * doesn't make sense and can cause timer DoS. 767 */ 768 delta = max_t(s64, delay, 10000LL); 769 rq->hrtick_time = ktime_add_ns(timer->base->get_time(), delta); 770 771 if (rq == this_rq()) 772 __hrtick_restart(rq); 773 else 774 smp_call_function_single_async(cpu_of(rq), &rq->hrtick_csd); 775 } 776 777 #else 778 /* 779 * Called to set the hrtick timer state. 780 * 781 * called with rq->lock held and irqs disabled 782 */ 783 void hrtick_start(struct rq *rq, u64 delay) 784 { 785 /* 786 * Don't schedule slices shorter than 10000ns, that just 787 * doesn't make sense. Rely on vruntime for fairness. 788 */ 789 delay = max_t(u64, delay, 10000LL); 790 hrtimer_start(&rq->hrtick_timer, ns_to_ktime(delay), 791 HRTIMER_MODE_REL_PINNED_HARD); 792 } 793 794 #endif /* CONFIG_SMP */ 795 796 static void hrtick_rq_init(struct rq *rq) 797 { 798 #ifdef CONFIG_SMP 799 INIT_CSD(&rq->hrtick_csd, __hrtick_start, rq); 800 #endif 801 hrtimer_init(&rq->hrtick_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD); 802 rq->hrtick_timer.function = hrtick; 803 } 804 #else /* CONFIG_SCHED_HRTICK */ 805 static inline void hrtick_clear(struct rq *rq) 806 { 807 } 808 809 static inline void hrtick_rq_init(struct rq *rq) 810 { 811 } 812 #endif /* CONFIG_SCHED_HRTICK */ 813 814 /* 815 * cmpxchg based fetch_or, macro so it works for different integer types 816 */ 817 #define fetch_or(ptr, mask) \ 818 ({ \ 819 typeof(ptr) _ptr = (ptr); \ 820 typeof(mask) _mask = (mask); \ 821 typeof(*_ptr) _old, _val = *_ptr; \ 822 \ 823 for (;;) { \ 824 _old = cmpxchg(_ptr, _val, _val | _mask); \ 825 if (_old == _val) \ 826 break; \ 827 _val = _old; \ 828 } \ 829 _old; \ 830 }) 831 832 #if defined(CONFIG_SMP) && defined(TIF_POLLING_NRFLAG) 833 /* 834 * Atomically set TIF_NEED_RESCHED and test for TIF_POLLING_NRFLAG, 835 * this avoids any races wrt polling state changes and thereby avoids 836 * spurious IPIs. 837 */ 838 static bool set_nr_and_not_polling(struct task_struct *p) 839 { 840 struct thread_info *ti = task_thread_info(p); 841 return !(fetch_or(&ti->flags, _TIF_NEED_RESCHED) & _TIF_POLLING_NRFLAG); 842 } 843 844 /* 845 * Atomically set TIF_NEED_RESCHED if TIF_POLLING_NRFLAG is set. 846 * 847 * If this returns true, then the idle task promises to call 848 * sched_ttwu_pending() and reschedule soon. 849 */ 850 static bool set_nr_if_polling(struct task_struct *p) 851 { 852 struct thread_info *ti = task_thread_info(p); 853 typeof(ti->flags) old, val = READ_ONCE(ti->flags); 854 855 for (;;) { 856 if (!(val & _TIF_POLLING_NRFLAG)) 857 return false; 858 if (val & _TIF_NEED_RESCHED) 859 return true; 860 old = cmpxchg(&ti->flags, val, val | _TIF_NEED_RESCHED); 861 if (old == val) 862 break; 863 val = old; 864 } 865 return true; 866 } 867 868 #else 869 static bool set_nr_and_not_polling(struct task_struct *p) 870 { 871 set_tsk_need_resched(p); 872 return true; 873 } 874 875 #ifdef CONFIG_SMP 876 static bool set_nr_if_polling(struct task_struct *p) 877 { 878 return false; 879 } 880 #endif 881 #endif 882 883 static bool __wake_q_add(struct wake_q_head *head, struct task_struct *task) 884 { 885 struct wake_q_node *node = &task->wake_q; 886 887 /* 888 * Atomically grab the task, if ->wake_q is !nil already it means 889 * it's already queued (either by us or someone else) and will get the 890 * wakeup due to that. 891 * 892 * In order to ensure that a pending wakeup will observe our pending 893 * state, even in the failed case, an explicit smp_mb() must be used. 894 */ 895 smp_mb__before_atomic(); 896 if (unlikely(cmpxchg_relaxed(&node->next, NULL, WAKE_Q_TAIL))) 897 return false; 898 899 /* 900 * The head is context local, there can be no concurrency. 901 */ 902 *head->lastp = node; 903 head->lastp = &node->next; 904 return true; 905 } 906 907 /** 908 * wake_q_add() - queue a wakeup for 'later' waking. 909 * @head: the wake_q_head to add @task to 910 * @task: the task to queue for 'later' wakeup 911 * 912 * Queue a task for later wakeup, most likely by the wake_up_q() call in the 913 * same context, _HOWEVER_ this is not guaranteed, the wakeup can come 914 * instantly. 915 * 916 * This function must be used as-if it were wake_up_process(); IOW the task 917 * must be ready to be woken at this location. 918 */ 919 void wake_q_add(struct wake_q_head *head, struct task_struct *task) 920 { 921 if (__wake_q_add(head, task)) 922 get_task_struct(task); 923 } 924 925 /** 926 * wake_q_add_safe() - safely queue a wakeup for 'later' waking. 927 * @head: the wake_q_head to add @task to 928 * @task: the task to queue for 'later' wakeup 929 * 930 * Queue a task for later wakeup, most likely by the wake_up_q() call in the 931 * same context, _HOWEVER_ this is not guaranteed, the wakeup can come 932 * instantly. 933 * 934 * This function must be used as-if it were wake_up_process(); IOW the task 935 * must be ready to be woken at this location. 936 * 937 * This function is essentially a task-safe equivalent to wake_q_add(). Callers 938 * that already hold reference to @task can call the 'safe' version and trust 939 * wake_q to do the right thing depending whether or not the @task is already 940 * queued for wakeup. 941 */ 942 void wake_q_add_safe(struct wake_q_head *head, struct task_struct *task) 943 { 944 if (!__wake_q_add(head, task)) 945 put_task_struct(task); 946 } 947 948 void wake_up_q(struct wake_q_head *head) 949 { 950 struct wake_q_node *node = head->first; 951 952 while (node != WAKE_Q_TAIL) { 953 struct task_struct *task; 954 955 task = container_of(node, struct task_struct, wake_q); 956 /* Task can safely be re-inserted now: */ 957 node = node->next; 958 task->wake_q.next = NULL; 959 960 /* 961 * wake_up_process() executes a full barrier, which pairs with 962 * the queueing in wake_q_add() so as not to miss wakeups. 963 */ 964 wake_up_process(task); 965 put_task_struct(task); 966 } 967 } 968 969 /* 970 * resched_curr - mark rq's current task 'to be rescheduled now'. 971 * 972 * On UP this means the setting of the need_resched flag, on SMP it 973 * might also involve a cross-CPU call to trigger the scheduler on 974 * the target CPU. 975 */ 976 void resched_curr(struct rq *rq) 977 { 978 struct task_struct *curr = rq->curr; 979 int cpu; 980 981 lockdep_assert_rq_held(rq); 982 983 if (test_tsk_need_resched(curr)) 984 return; 985 986 cpu = cpu_of(rq); 987 988 if (cpu == smp_processor_id()) { 989 set_tsk_need_resched(curr); 990 set_preempt_need_resched(); 991 return; 992 } 993 994 if (set_nr_and_not_polling(curr)) 995 smp_send_reschedule(cpu); 996 else 997 trace_sched_wake_idle_without_ipi(cpu); 998 } 999 1000 void resched_cpu(int cpu) 1001 { 1002 struct rq *rq = cpu_rq(cpu); 1003 unsigned long flags; 1004 1005 raw_spin_rq_lock_irqsave(rq, flags); 1006 if (cpu_online(cpu) || cpu == smp_processor_id()) 1007 resched_curr(rq); 1008 raw_spin_rq_unlock_irqrestore(rq, flags); 1009 } 1010 1011 #ifdef CONFIG_SMP 1012 #ifdef CONFIG_NO_HZ_COMMON 1013 /* 1014 * In the semi idle case, use the nearest busy CPU for migrating timers 1015 * from an idle CPU. This is good for power-savings. 1016 * 1017 * We don't do similar optimization for completely idle system, as 1018 * selecting an idle CPU will add more delays to the timers than intended 1019 * (as that CPU's timer base may not be uptodate wrt jiffies etc). 1020 */ 1021 int get_nohz_timer_target(void) 1022 { 1023 int i, cpu = smp_processor_id(), default_cpu = -1; 1024 struct sched_domain *sd; 1025 const struct cpumask *hk_mask; 1026 1027 if (housekeeping_cpu(cpu, HK_FLAG_TIMER)) { 1028 if (!idle_cpu(cpu)) 1029 return cpu; 1030 default_cpu = cpu; 1031 } 1032 1033 hk_mask = housekeeping_cpumask(HK_FLAG_TIMER); 1034 1035 rcu_read_lock(); 1036 for_each_domain(cpu, sd) { 1037 for_each_cpu_and(i, sched_domain_span(sd), hk_mask) { 1038 if (cpu == i) 1039 continue; 1040 1041 if (!idle_cpu(i)) { 1042 cpu = i; 1043 goto unlock; 1044 } 1045 } 1046 } 1047 1048 if (default_cpu == -1) 1049 default_cpu = housekeeping_any_cpu(HK_FLAG_TIMER); 1050 cpu = default_cpu; 1051 unlock: 1052 rcu_read_unlock(); 1053 return cpu; 1054 } 1055 1056 /* 1057 * When add_timer_on() enqueues a timer into the timer wheel of an 1058 * idle CPU then this timer might expire before the next timer event 1059 * which is scheduled to wake up that CPU. In case of a completely 1060 * idle system the next event might even be infinite time into the 1061 * future. wake_up_idle_cpu() ensures that the CPU is woken up and 1062 * leaves the inner idle loop so the newly added timer is taken into 1063 * account when the CPU goes back to idle and evaluates the timer 1064 * wheel for the next timer event. 1065 */ 1066 static void wake_up_idle_cpu(int cpu) 1067 { 1068 struct rq *rq = cpu_rq(cpu); 1069 1070 if (cpu == smp_processor_id()) 1071 return; 1072 1073 if (set_nr_and_not_polling(rq->idle)) 1074 smp_send_reschedule(cpu); 1075 else 1076 trace_sched_wake_idle_without_ipi(cpu); 1077 } 1078 1079 static bool wake_up_full_nohz_cpu(int cpu) 1080 { 1081 /* 1082 * We just need the target to call irq_exit() and re-evaluate 1083 * the next tick. The nohz full kick at least implies that. 1084 * If needed we can still optimize that later with an 1085 * empty IRQ. 1086 */ 1087 if (cpu_is_offline(cpu)) 1088 return true; /* Don't try to wake offline CPUs. */ 1089 if (tick_nohz_full_cpu(cpu)) { 1090 if (cpu != smp_processor_id() || 1091 tick_nohz_tick_stopped()) 1092 tick_nohz_full_kick_cpu(cpu); 1093 return true; 1094 } 1095 1096 return false; 1097 } 1098 1099 /* 1100 * Wake up the specified CPU. If the CPU is going offline, it is the 1101 * caller's responsibility to deal with the lost wakeup, for example, 1102 * by hooking into the CPU_DEAD notifier like timers and hrtimers do. 1103 */ 1104 void wake_up_nohz_cpu(int cpu) 1105 { 1106 if (!wake_up_full_nohz_cpu(cpu)) 1107 wake_up_idle_cpu(cpu); 1108 } 1109 1110 static void nohz_csd_func(void *info) 1111 { 1112 struct rq *rq = info; 1113 int cpu = cpu_of(rq); 1114 unsigned int flags; 1115 1116 /* 1117 * Release the rq::nohz_csd. 1118 */ 1119 flags = atomic_fetch_andnot(NOHZ_KICK_MASK | NOHZ_NEWILB_KICK, nohz_flags(cpu)); 1120 WARN_ON(!(flags & NOHZ_KICK_MASK)); 1121 1122 rq->idle_balance = idle_cpu(cpu); 1123 if (rq->idle_balance && !need_resched()) { 1124 rq->nohz_idle_balance = flags; 1125 raise_softirq_irqoff(SCHED_SOFTIRQ); 1126 } 1127 } 1128 1129 #endif /* CONFIG_NO_HZ_COMMON */ 1130 1131 #ifdef CONFIG_NO_HZ_FULL 1132 bool sched_can_stop_tick(struct rq *rq) 1133 { 1134 int fifo_nr_running; 1135 1136 /* Deadline tasks, even if single, need the tick */ 1137 if (rq->dl.dl_nr_running) 1138 return false; 1139 1140 /* 1141 * If there are more than one RR tasks, we need the tick to affect the 1142 * actual RR behaviour. 1143 */ 1144 if (rq->rt.rr_nr_running) { 1145 if (rq->rt.rr_nr_running == 1) 1146 return true; 1147 else 1148 return false; 1149 } 1150 1151 /* 1152 * If there's no RR tasks, but FIFO tasks, we can skip the tick, no 1153 * forced preemption between FIFO tasks. 1154 */ 1155 fifo_nr_running = rq->rt.rt_nr_running - rq->rt.rr_nr_running; 1156 if (fifo_nr_running) 1157 return true; 1158 1159 /* 1160 * If there are no DL,RR/FIFO tasks, there must only be CFS tasks left; 1161 * if there's more than one we need the tick for involuntary 1162 * preemption. 1163 */ 1164 if (rq->nr_running > 1) 1165 return false; 1166 1167 return true; 1168 } 1169 #endif /* CONFIG_NO_HZ_FULL */ 1170 #endif /* CONFIG_SMP */ 1171 1172 #if defined(CONFIG_RT_GROUP_SCHED) || (defined(CONFIG_FAIR_GROUP_SCHED) && \ 1173 (defined(CONFIG_SMP) || defined(CONFIG_CFS_BANDWIDTH))) 1174 /* 1175 * Iterate task_group tree rooted at *from, calling @down when first entering a 1176 * node and @up when leaving it for the final time. 1177 * 1178 * Caller must hold rcu_lock or sufficient equivalent. 1179 */ 1180 int walk_tg_tree_from(struct task_group *from, 1181 tg_visitor down, tg_visitor up, void *data) 1182 { 1183 struct task_group *parent, *child; 1184 int ret; 1185 1186 parent = from; 1187 1188 down: 1189 ret = (*down)(parent, data); 1190 if (ret) 1191 goto out; 1192 list_for_each_entry_rcu(child, &parent->children, siblings) { 1193 parent = child; 1194 goto down; 1195 1196 up: 1197 continue; 1198 } 1199 ret = (*up)(parent, data); 1200 if (ret || parent == from) 1201 goto out; 1202 1203 child = parent; 1204 parent = parent->parent; 1205 if (parent) 1206 goto up; 1207 out: 1208 return ret; 1209 } 1210 1211 int tg_nop(struct task_group *tg, void *data) 1212 { 1213 return 0; 1214 } 1215 #endif 1216 1217 static void set_load_weight(struct task_struct *p, bool update_load) 1218 { 1219 int prio = p->static_prio - MAX_RT_PRIO; 1220 struct load_weight *load = &p->se.load; 1221 1222 /* 1223 * SCHED_IDLE tasks get minimal weight: 1224 */ 1225 if (task_has_idle_policy(p)) { 1226 load->weight = scale_load(WEIGHT_IDLEPRIO); 1227 load->inv_weight = WMULT_IDLEPRIO; 1228 return; 1229 } 1230 1231 /* 1232 * SCHED_OTHER tasks have to update their load when changing their 1233 * weight 1234 */ 1235 if (update_load && p->sched_class == &fair_sched_class) { 1236 reweight_task(p, prio); 1237 } else { 1238 load->weight = scale_load(sched_prio_to_weight[prio]); 1239 load->inv_weight = sched_prio_to_wmult[prio]; 1240 } 1241 } 1242 1243 #ifdef CONFIG_UCLAMP_TASK 1244 /* 1245 * Serializes updates of utilization clamp values 1246 * 1247 * The (slow-path) user-space triggers utilization clamp value updates which 1248 * can require updates on (fast-path) scheduler's data structures used to 1249 * support enqueue/dequeue operations. 1250 * While the per-CPU rq lock protects fast-path update operations, user-space 1251 * requests are serialized using a mutex to reduce the risk of conflicting 1252 * updates or API abuses. 1253 */ 1254 static DEFINE_MUTEX(uclamp_mutex); 1255 1256 /* Max allowed minimum utilization */ 1257 unsigned int sysctl_sched_uclamp_util_min = SCHED_CAPACITY_SCALE; 1258 1259 /* Max allowed maximum utilization */ 1260 unsigned int sysctl_sched_uclamp_util_max = SCHED_CAPACITY_SCALE; 1261 1262 /* 1263 * By default RT tasks run at the maximum performance point/capacity of the 1264 * system. Uclamp enforces this by always setting UCLAMP_MIN of RT tasks to 1265 * SCHED_CAPACITY_SCALE. 1266 * 1267 * This knob allows admins to change the default behavior when uclamp is being 1268 * used. In battery powered devices, particularly, running at the maximum 1269 * capacity and frequency will increase energy consumption and shorten the 1270 * battery life. 1271 * 1272 * This knob only affects RT tasks that their uclamp_se->user_defined == false. 1273 * 1274 * This knob will not override the system default sched_util_clamp_min defined 1275 * above. 1276 */ 1277 unsigned int sysctl_sched_uclamp_util_min_rt_default = SCHED_CAPACITY_SCALE; 1278 1279 /* All clamps are required to be less or equal than these values */ 1280 static struct uclamp_se uclamp_default[UCLAMP_CNT]; 1281 1282 /* 1283 * This static key is used to reduce the uclamp overhead in the fast path. It 1284 * primarily disables the call to uclamp_rq_{inc, dec}() in 1285 * enqueue/dequeue_task(). 1286 * 1287 * This allows users to continue to enable uclamp in their kernel config with 1288 * minimum uclamp overhead in the fast path. 1289 * 1290 * As soon as userspace modifies any of the uclamp knobs, the static key is 1291 * enabled, since we have an actual users that make use of uclamp 1292 * functionality. 1293 * 1294 * The knobs that would enable this static key are: 1295 * 1296 * * A task modifying its uclamp value with sched_setattr(). 1297 * * An admin modifying the sysctl_sched_uclamp_{min, max} via procfs. 1298 * * An admin modifying the cgroup cpu.uclamp.{min, max} 1299 */ 1300 DEFINE_STATIC_KEY_FALSE(sched_uclamp_used); 1301 1302 /* Integer rounded range for each bucket */ 1303 #define UCLAMP_BUCKET_DELTA DIV_ROUND_CLOSEST(SCHED_CAPACITY_SCALE, UCLAMP_BUCKETS) 1304 1305 #define for_each_clamp_id(clamp_id) \ 1306 for ((clamp_id) = 0; (clamp_id) < UCLAMP_CNT; (clamp_id)++) 1307 1308 static inline unsigned int uclamp_bucket_id(unsigned int clamp_value) 1309 { 1310 return min_t(unsigned int, clamp_value / UCLAMP_BUCKET_DELTA, UCLAMP_BUCKETS - 1); 1311 } 1312 1313 static inline unsigned int uclamp_none(enum uclamp_id clamp_id) 1314 { 1315 if (clamp_id == UCLAMP_MIN) 1316 return 0; 1317 return SCHED_CAPACITY_SCALE; 1318 } 1319 1320 static inline void uclamp_se_set(struct uclamp_se *uc_se, 1321 unsigned int value, bool user_defined) 1322 { 1323 uc_se->value = value; 1324 uc_se->bucket_id = uclamp_bucket_id(value); 1325 uc_se->user_defined = user_defined; 1326 } 1327 1328 static inline unsigned int 1329 uclamp_idle_value(struct rq *rq, enum uclamp_id clamp_id, 1330 unsigned int clamp_value) 1331 { 1332 /* 1333 * Avoid blocked utilization pushing up the frequency when we go 1334 * idle (which drops the max-clamp) by retaining the last known 1335 * max-clamp. 1336 */ 1337 if (clamp_id == UCLAMP_MAX) { 1338 rq->uclamp_flags |= UCLAMP_FLAG_IDLE; 1339 return clamp_value; 1340 } 1341 1342 return uclamp_none(UCLAMP_MIN); 1343 } 1344 1345 static inline void uclamp_idle_reset(struct rq *rq, enum uclamp_id clamp_id, 1346 unsigned int clamp_value) 1347 { 1348 /* Reset max-clamp retention only on idle exit */ 1349 if (!(rq->uclamp_flags & UCLAMP_FLAG_IDLE)) 1350 return; 1351 1352 WRITE_ONCE(rq->uclamp[clamp_id].value, clamp_value); 1353 } 1354 1355 static inline 1356 unsigned int uclamp_rq_max_value(struct rq *rq, enum uclamp_id clamp_id, 1357 unsigned int clamp_value) 1358 { 1359 struct uclamp_bucket *bucket = rq->uclamp[clamp_id].bucket; 1360 int bucket_id = UCLAMP_BUCKETS - 1; 1361 1362 /* 1363 * Since both min and max clamps are max aggregated, find the 1364 * top most bucket with tasks in. 1365 */ 1366 for ( ; bucket_id >= 0; bucket_id--) { 1367 if (!bucket[bucket_id].tasks) 1368 continue; 1369 return bucket[bucket_id].value; 1370 } 1371 1372 /* No tasks -- default clamp values */ 1373 return uclamp_idle_value(rq, clamp_id, clamp_value); 1374 } 1375 1376 static void __uclamp_update_util_min_rt_default(struct task_struct *p) 1377 { 1378 unsigned int default_util_min; 1379 struct uclamp_se *uc_se; 1380 1381 lockdep_assert_held(&p->pi_lock); 1382 1383 uc_se = &p->uclamp_req[UCLAMP_MIN]; 1384 1385 /* Only sync if user didn't override the default */ 1386 if (uc_se->user_defined) 1387 return; 1388 1389 default_util_min = sysctl_sched_uclamp_util_min_rt_default; 1390 uclamp_se_set(uc_se, default_util_min, false); 1391 } 1392 1393 static void uclamp_update_util_min_rt_default(struct task_struct *p) 1394 { 1395 struct rq_flags rf; 1396 struct rq *rq; 1397 1398 if (!rt_task(p)) 1399 return; 1400 1401 /* Protect updates to p->uclamp_* */ 1402 rq = task_rq_lock(p, &rf); 1403 __uclamp_update_util_min_rt_default(p); 1404 task_rq_unlock(rq, p, &rf); 1405 } 1406 1407 static void uclamp_sync_util_min_rt_default(void) 1408 { 1409 struct task_struct *g, *p; 1410 1411 /* 1412 * copy_process() sysctl_uclamp 1413 * uclamp_min_rt = X; 1414 * write_lock(&tasklist_lock) read_lock(&tasklist_lock) 1415 * // link thread smp_mb__after_spinlock() 1416 * write_unlock(&tasklist_lock) read_unlock(&tasklist_lock); 1417 * sched_post_fork() for_each_process_thread() 1418 * __uclamp_sync_rt() __uclamp_sync_rt() 1419 * 1420 * Ensures that either sched_post_fork() will observe the new 1421 * uclamp_min_rt or for_each_process_thread() will observe the new 1422 * task. 1423 */ 1424 read_lock(&tasklist_lock); 1425 smp_mb__after_spinlock(); 1426 read_unlock(&tasklist_lock); 1427 1428 rcu_read_lock(); 1429 for_each_process_thread(g, p) 1430 uclamp_update_util_min_rt_default(p); 1431 rcu_read_unlock(); 1432 } 1433 1434 static inline struct uclamp_se 1435 uclamp_tg_restrict(struct task_struct *p, enum uclamp_id clamp_id) 1436 { 1437 /* Copy by value as we could modify it */ 1438 struct uclamp_se uc_req = p->uclamp_req[clamp_id]; 1439 #ifdef CONFIG_UCLAMP_TASK_GROUP 1440 unsigned int tg_min, tg_max, value; 1441 1442 /* 1443 * Tasks in autogroups or root task group will be 1444 * restricted by system defaults. 1445 */ 1446 if (task_group_is_autogroup(task_group(p))) 1447 return uc_req; 1448 if (task_group(p) == &root_task_group) 1449 return uc_req; 1450 1451 tg_min = task_group(p)->uclamp[UCLAMP_MIN].value; 1452 tg_max = task_group(p)->uclamp[UCLAMP_MAX].value; 1453 value = uc_req.value; 1454 value = clamp(value, tg_min, tg_max); 1455 uclamp_se_set(&uc_req, value, false); 1456 #endif 1457 1458 return uc_req; 1459 } 1460 1461 /* 1462 * The effective clamp bucket index of a task depends on, by increasing 1463 * priority: 1464 * - the task specific clamp value, when explicitly requested from userspace 1465 * - the task group effective clamp value, for tasks not either in the root 1466 * group or in an autogroup 1467 * - the system default clamp value, defined by the sysadmin 1468 */ 1469 static inline struct uclamp_se 1470 uclamp_eff_get(struct task_struct *p, enum uclamp_id clamp_id) 1471 { 1472 struct uclamp_se uc_req = uclamp_tg_restrict(p, clamp_id); 1473 struct uclamp_se uc_max = uclamp_default[clamp_id]; 1474 1475 /* System default restrictions always apply */ 1476 if (unlikely(uc_req.value > uc_max.value)) 1477 return uc_max; 1478 1479 return uc_req; 1480 } 1481 1482 unsigned long uclamp_eff_value(struct task_struct *p, enum uclamp_id clamp_id) 1483 { 1484 struct uclamp_se uc_eff; 1485 1486 /* Task currently refcounted: use back-annotated (effective) value */ 1487 if (p->uclamp[clamp_id].active) 1488 return (unsigned long)p->uclamp[clamp_id].value; 1489 1490 uc_eff = uclamp_eff_get(p, clamp_id); 1491 1492 return (unsigned long)uc_eff.value; 1493 } 1494 1495 /* 1496 * When a task is enqueued on a rq, the clamp bucket currently defined by the 1497 * task's uclamp::bucket_id is refcounted on that rq. This also immediately 1498 * updates the rq's clamp value if required. 1499 * 1500 * Tasks can have a task-specific value requested from user-space, track 1501 * within each bucket the maximum value for tasks refcounted in it. 1502 * This "local max aggregation" allows to track the exact "requested" value 1503 * for each bucket when all its RUNNABLE tasks require the same clamp. 1504 */ 1505 static inline void uclamp_rq_inc_id(struct rq *rq, struct task_struct *p, 1506 enum uclamp_id clamp_id) 1507 { 1508 struct uclamp_rq *uc_rq = &rq->uclamp[clamp_id]; 1509 struct uclamp_se *uc_se = &p->uclamp[clamp_id]; 1510 struct uclamp_bucket *bucket; 1511 1512 lockdep_assert_rq_held(rq); 1513 1514 /* Update task effective clamp */ 1515 p->uclamp[clamp_id] = uclamp_eff_get(p, clamp_id); 1516 1517 bucket = &uc_rq->bucket[uc_se->bucket_id]; 1518 bucket->tasks++; 1519 uc_se->active = true; 1520 1521 uclamp_idle_reset(rq, clamp_id, uc_se->value); 1522 1523 /* 1524 * Local max aggregation: rq buckets always track the max 1525 * "requested" clamp value of its RUNNABLE tasks. 1526 */ 1527 if (bucket->tasks == 1 || uc_se->value > bucket->value) 1528 bucket->value = uc_se->value; 1529 1530 if (uc_se->value > READ_ONCE(uc_rq->value)) 1531 WRITE_ONCE(uc_rq->value, uc_se->value); 1532 } 1533 1534 /* 1535 * When a task is dequeued from a rq, the clamp bucket refcounted by the task 1536 * is released. If this is the last task reference counting the rq's max 1537 * active clamp value, then the rq's clamp value is updated. 1538 * 1539 * Both refcounted tasks and rq's cached clamp values are expected to be 1540 * always valid. If it's detected they are not, as defensive programming, 1541 * enforce the expected state and warn. 1542 */ 1543 static inline void uclamp_rq_dec_id(struct rq *rq, struct task_struct *p, 1544 enum uclamp_id clamp_id) 1545 { 1546 struct uclamp_rq *uc_rq = &rq->uclamp[clamp_id]; 1547 struct uclamp_se *uc_se = &p->uclamp[clamp_id]; 1548 struct uclamp_bucket *bucket; 1549 unsigned int bkt_clamp; 1550 unsigned int rq_clamp; 1551 1552 lockdep_assert_rq_held(rq); 1553 1554 /* 1555 * If sched_uclamp_used was enabled after task @p was enqueued, 1556 * we could end up with unbalanced call to uclamp_rq_dec_id(). 1557 * 1558 * In this case the uc_se->active flag should be false since no uclamp 1559 * accounting was performed at enqueue time and we can just return 1560 * here. 1561 * 1562 * Need to be careful of the following enqueue/dequeue ordering 1563 * problem too 1564 * 1565 * enqueue(taskA) 1566 * // sched_uclamp_used gets enabled 1567 * enqueue(taskB) 1568 * dequeue(taskA) 1569 * // Must not decrement bucket->tasks here 1570 * dequeue(taskB) 1571 * 1572 * where we could end up with stale data in uc_se and 1573 * bucket[uc_se->bucket_id]. 1574 * 1575 * The following check here eliminates the possibility of such race. 1576 */ 1577 if (unlikely(!uc_se->active)) 1578 return; 1579 1580 bucket = &uc_rq->bucket[uc_se->bucket_id]; 1581 1582 SCHED_WARN_ON(!bucket->tasks); 1583 if (likely(bucket->tasks)) 1584 bucket->tasks--; 1585 1586 uc_se->active = false; 1587 1588 /* 1589 * Keep "local max aggregation" simple and accept to (possibly) 1590 * overboost some RUNNABLE tasks in the same bucket. 1591 * The rq clamp bucket value is reset to its base value whenever 1592 * there are no more RUNNABLE tasks refcounting it. 1593 */ 1594 if (likely(bucket->tasks)) 1595 return; 1596 1597 rq_clamp = READ_ONCE(uc_rq->value); 1598 /* 1599 * Defensive programming: this should never happen. If it happens, 1600 * e.g. due to future modification, warn and fixup the expected value. 1601 */ 1602 SCHED_WARN_ON(bucket->value > rq_clamp); 1603 if (bucket->value >= rq_clamp) { 1604 bkt_clamp = uclamp_rq_max_value(rq, clamp_id, uc_se->value); 1605 WRITE_ONCE(uc_rq->value, bkt_clamp); 1606 } 1607 } 1608 1609 static inline void uclamp_rq_inc(struct rq *rq, struct task_struct *p) 1610 { 1611 enum uclamp_id clamp_id; 1612 1613 /* 1614 * Avoid any overhead until uclamp is actually used by the userspace. 1615 * 1616 * The condition is constructed such that a NOP is generated when 1617 * sched_uclamp_used is disabled. 1618 */ 1619 if (!static_branch_unlikely(&sched_uclamp_used)) 1620 return; 1621 1622 if (unlikely(!p->sched_class->uclamp_enabled)) 1623 return; 1624 1625 for_each_clamp_id(clamp_id) 1626 uclamp_rq_inc_id(rq, p, clamp_id); 1627 1628 /* Reset clamp idle holding when there is one RUNNABLE task */ 1629 if (rq->uclamp_flags & UCLAMP_FLAG_IDLE) 1630 rq->uclamp_flags &= ~UCLAMP_FLAG_IDLE; 1631 } 1632 1633 static inline void uclamp_rq_dec(struct rq *rq, struct task_struct *p) 1634 { 1635 enum uclamp_id clamp_id; 1636 1637 /* 1638 * Avoid any overhead until uclamp is actually used by the userspace. 1639 * 1640 * The condition is constructed such that a NOP is generated when 1641 * sched_uclamp_used is disabled. 1642 */ 1643 if (!static_branch_unlikely(&sched_uclamp_used)) 1644 return; 1645 1646 if (unlikely(!p->sched_class->uclamp_enabled)) 1647 return; 1648 1649 for_each_clamp_id(clamp_id) 1650 uclamp_rq_dec_id(rq, p, clamp_id); 1651 } 1652 1653 static inline void uclamp_rq_reinc_id(struct rq *rq, struct task_struct *p, 1654 enum uclamp_id clamp_id) 1655 { 1656 if (!p->uclamp[clamp_id].active) 1657 return; 1658 1659 uclamp_rq_dec_id(rq, p, clamp_id); 1660 uclamp_rq_inc_id(rq, p, clamp_id); 1661 1662 /* 1663 * Make sure to clear the idle flag if we've transiently reached 0 1664 * active tasks on rq. 1665 */ 1666 if (clamp_id == UCLAMP_MAX && (rq->uclamp_flags & UCLAMP_FLAG_IDLE)) 1667 rq->uclamp_flags &= ~UCLAMP_FLAG_IDLE; 1668 } 1669 1670 static inline void 1671 uclamp_update_active(struct task_struct *p) 1672 { 1673 enum uclamp_id clamp_id; 1674 struct rq_flags rf; 1675 struct rq *rq; 1676 1677 /* 1678 * Lock the task and the rq where the task is (or was) queued. 1679 * 1680 * We might lock the (previous) rq of a !RUNNABLE task, but that's the 1681 * price to pay to safely serialize util_{min,max} updates with 1682 * enqueues, dequeues and migration operations. 1683 * This is the same locking schema used by __set_cpus_allowed_ptr(). 1684 */ 1685 rq = task_rq_lock(p, &rf); 1686 1687 /* 1688 * Setting the clamp bucket is serialized by task_rq_lock(). 1689 * If the task is not yet RUNNABLE and its task_struct is not 1690 * affecting a valid clamp bucket, the next time it's enqueued, 1691 * it will already see the updated clamp bucket value. 1692 */ 1693 for_each_clamp_id(clamp_id) 1694 uclamp_rq_reinc_id(rq, p, clamp_id); 1695 1696 task_rq_unlock(rq, p, &rf); 1697 } 1698 1699 #ifdef CONFIG_UCLAMP_TASK_GROUP 1700 static inline void 1701 uclamp_update_active_tasks(struct cgroup_subsys_state *css) 1702 { 1703 struct css_task_iter it; 1704 struct task_struct *p; 1705 1706 css_task_iter_start(css, 0, &it); 1707 while ((p = css_task_iter_next(&it))) 1708 uclamp_update_active(p); 1709 css_task_iter_end(&it); 1710 } 1711 1712 static void cpu_util_update_eff(struct cgroup_subsys_state *css); 1713 static void uclamp_update_root_tg(void) 1714 { 1715 struct task_group *tg = &root_task_group; 1716 1717 uclamp_se_set(&tg->uclamp_req[UCLAMP_MIN], 1718 sysctl_sched_uclamp_util_min, false); 1719 uclamp_se_set(&tg->uclamp_req[UCLAMP_MAX], 1720 sysctl_sched_uclamp_util_max, false); 1721 1722 rcu_read_lock(); 1723 cpu_util_update_eff(&root_task_group.css); 1724 rcu_read_unlock(); 1725 } 1726 #else 1727 static void uclamp_update_root_tg(void) { } 1728 #endif 1729 1730 int sysctl_sched_uclamp_handler(struct ctl_table *table, int write, 1731 void *buffer, size_t *lenp, loff_t *ppos) 1732 { 1733 bool update_root_tg = false; 1734 int old_min, old_max, old_min_rt; 1735 int result; 1736 1737 mutex_lock(&uclamp_mutex); 1738 old_min = sysctl_sched_uclamp_util_min; 1739 old_max = sysctl_sched_uclamp_util_max; 1740 old_min_rt = sysctl_sched_uclamp_util_min_rt_default; 1741 1742 result = proc_dointvec(table, write, buffer, lenp, ppos); 1743 if (result) 1744 goto undo; 1745 if (!write) 1746 goto done; 1747 1748 if (sysctl_sched_uclamp_util_min > sysctl_sched_uclamp_util_max || 1749 sysctl_sched_uclamp_util_max > SCHED_CAPACITY_SCALE || 1750 sysctl_sched_uclamp_util_min_rt_default > SCHED_CAPACITY_SCALE) { 1751 1752 result = -EINVAL; 1753 goto undo; 1754 } 1755 1756 if (old_min != sysctl_sched_uclamp_util_min) { 1757 uclamp_se_set(&uclamp_default[UCLAMP_MIN], 1758 sysctl_sched_uclamp_util_min, false); 1759 update_root_tg = true; 1760 } 1761 if (old_max != sysctl_sched_uclamp_util_max) { 1762 uclamp_se_set(&uclamp_default[UCLAMP_MAX], 1763 sysctl_sched_uclamp_util_max, false); 1764 update_root_tg = true; 1765 } 1766 1767 if (update_root_tg) { 1768 static_branch_enable(&sched_uclamp_used); 1769 uclamp_update_root_tg(); 1770 } 1771 1772 if (old_min_rt != sysctl_sched_uclamp_util_min_rt_default) { 1773 static_branch_enable(&sched_uclamp_used); 1774 uclamp_sync_util_min_rt_default(); 1775 } 1776 1777 /* 1778 * We update all RUNNABLE tasks only when task groups are in use. 1779 * Otherwise, keep it simple and do just a lazy update at each next 1780 * task enqueue time. 1781 */ 1782 1783 goto done; 1784 1785 undo: 1786 sysctl_sched_uclamp_util_min = old_min; 1787 sysctl_sched_uclamp_util_max = old_max; 1788 sysctl_sched_uclamp_util_min_rt_default = old_min_rt; 1789 done: 1790 mutex_unlock(&uclamp_mutex); 1791 1792 return result; 1793 } 1794 1795 static int uclamp_validate(struct task_struct *p, 1796 const struct sched_attr *attr) 1797 { 1798 int util_min = p->uclamp_req[UCLAMP_MIN].value; 1799 int util_max = p->uclamp_req[UCLAMP_MAX].value; 1800 1801 if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MIN) { 1802 util_min = attr->sched_util_min; 1803 1804 if (util_min + 1 > SCHED_CAPACITY_SCALE + 1) 1805 return -EINVAL; 1806 } 1807 1808 if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MAX) { 1809 util_max = attr->sched_util_max; 1810 1811 if (util_max + 1 > SCHED_CAPACITY_SCALE + 1) 1812 return -EINVAL; 1813 } 1814 1815 if (util_min != -1 && util_max != -1 && util_min > util_max) 1816 return -EINVAL; 1817 1818 /* 1819 * We have valid uclamp attributes; make sure uclamp is enabled. 1820 * 1821 * We need to do that here, because enabling static branches is a 1822 * blocking operation which obviously cannot be done while holding 1823 * scheduler locks. 1824 */ 1825 static_branch_enable(&sched_uclamp_used); 1826 1827 return 0; 1828 } 1829 1830 static bool uclamp_reset(const struct sched_attr *attr, 1831 enum uclamp_id clamp_id, 1832 struct uclamp_se *uc_se) 1833 { 1834 /* Reset on sched class change for a non user-defined clamp value. */ 1835 if (likely(!(attr->sched_flags & SCHED_FLAG_UTIL_CLAMP)) && 1836 !uc_se->user_defined) 1837 return true; 1838 1839 /* Reset on sched_util_{min,max} == -1. */ 1840 if (clamp_id == UCLAMP_MIN && 1841 attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MIN && 1842 attr->sched_util_min == -1) { 1843 return true; 1844 } 1845 1846 if (clamp_id == UCLAMP_MAX && 1847 attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MAX && 1848 attr->sched_util_max == -1) { 1849 return true; 1850 } 1851 1852 return false; 1853 } 1854 1855 static void __setscheduler_uclamp(struct task_struct *p, 1856 const struct sched_attr *attr) 1857 { 1858 enum uclamp_id clamp_id; 1859 1860 for_each_clamp_id(clamp_id) { 1861 struct uclamp_se *uc_se = &p->uclamp_req[clamp_id]; 1862 unsigned int value; 1863 1864 if (!uclamp_reset(attr, clamp_id, uc_se)) 1865 continue; 1866 1867 /* 1868 * RT by default have a 100% boost value that could be modified 1869 * at runtime. 1870 */ 1871 if (unlikely(rt_task(p) && clamp_id == UCLAMP_MIN)) 1872 value = sysctl_sched_uclamp_util_min_rt_default; 1873 else 1874 value = uclamp_none(clamp_id); 1875 1876 uclamp_se_set(uc_se, value, false); 1877 1878 } 1879 1880 if (likely(!(attr->sched_flags & SCHED_FLAG_UTIL_CLAMP))) 1881 return; 1882 1883 if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MIN && 1884 attr->sched_util_min != -1) { 1885 uclamp_se_set(&p->uclamp_req[UCLAMP_MIN], 1886 attr->sched_util_min, true); 1887 } 1888 1889 if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MAX && 1890 attr->sched_util_max != -1) { 1891 uclamp_se_set(&p->uclamp_req[UCLAMP_MAX], 1892 attr->sched_util_max, true); 1893 } 1894 } 1895 1896 static void uclamp_fork(struct task_struct *p) 1897 { 1898 enum uclamp_id clamp_id; 1899 1900 /* 1901 * We don't need to hold task_rq_lock() when updating p->uclamp_* here 1902 * as the task is still at its early fork stages. 1903 */ 1904 for_each_clamp_id(clamp_id) 1905 p->uclamp[clamp_id].active = false; 1906 1907 if (likely(!p->sched_reset_on_fork)) 1908 return; 1909 1910 for_each_clamp_id(clamp_id) { 1911 uclamp_se_set(&p->uclamp_req[clamp_id], 1912 uclamp_none(clamp_id), false); 1913 } 1914 } 1915 1916 static void uclamp_post_fork(struct task_struct *p) 1917 { 1918 uclamp_update_util_min_rt_default(p); 1919 } 1920 1921 static void __init init_uclamp_rq(struct rq *rq) 1922 { 1923 enum uclamp_id clamp_id; 1924 struct uclamp_rq *uc_rq = rq->uclamp; 1925 1926 for_each_clamp_id(clamp_id) { 1927 uc_rq[clamp_id] = (struct uclamp_rq) { 1928 .value = uclamp_none(clamp_id) 1929 }; 1930 } 1931 1932 rq->uclamp_flags = UCLAMP_FLAG_IDLE; 1933 } 1934 1935 static void __init init_uclamp(void) 1936 { 1937 struct uclamp_se uc_max = {}; 1938 enum uclamp_id clamp_id; 1939 int cpu; 1940 1941 for_each_possible_cpu(cpu) 1942 init_uclamp_rq(cpu_rq(cpu)); 1943 1944 for_each_clamp_id(clamp_id) { 1945 uclamp_se_set(&init_task.uclamp_req[clamp_id], 1946 uclamp_none(clamp_id), false); 1947 } 1948 1949 /* System defaults allow max clamp values for both indexes */ 1950 uclamp_se_set(&uc_max, uclamp_none(UCLAMP_MAX), false); 1951 for_each_clamp_id(clamp_id) { 1952 uclamp_default[clamp_id] = uc_max; 1953 #ifdef CONFIG_UCLAMP_TASK_GROUP 1954 root_task_group.uclamp_req[clamp_id] = uc_max; 1955 root_task_group.uclamp[clamp_id] = uc_max; 1956 #endif 1957 } 1958 } 1959 1960 #else /* CONFIG_UCLAMP_TASK */ 1961 static inline void uclamp_rq_inc(struct rq *rq, struct task_struct *p) { } 1962 static inline void uclamp_rq_dec(struct rq *rq, struct task_struct *p) { } 1963 static inline int uclamp_validate(struct task_struct *p, 1964 const struct sched_attr *attr) 1965 { 1966 return -EOPNOTSUPP; 1967 } 1968 static void __setscheduler_uclamp(struct task_struct *p, 1969 const struct sched_attr *attr) { } 1970 static inline void uclamp_fork(struct task_struct *p) { } 1971 static inline void uclamp_post_fork(struct task_struct *p) { } 1972 static inline void init_uclamp(void) { } 1973 #endif /* CONFIG_UCLAMP_TASK */ 1974 1975 bool sched_task_on_rq(struct task_struct *p) 1976 { 1977 return task_on_rq_queued(p); 1978 } 1979 1980 unsigned long get_wchan(struct task_struct *p) 1981 { 1982 unsigned long ip = 0; 1983 unsigned int state; 1984 1985 if (!p || p == current) 1986 return 0; 1987 1988 /* Only get wchan if task is blocked and we can keep it that way. */ 1989 raw_spin_lock_irq(&p->pi_lock); 1990 state = READ_ONCE(p->__state); 1991 smp_rmb(); /* see try_to_wake_up() */ 1992 if (state != TASK_RUNNING && state != TASK_WAKING && !p->on_rq) 1993 ip = __get_wchan(p); 1994 raw_spin_unlock_irq(&p->pi_lock); 1995 1996 return ip; 1997 } 1998 1999 static inline void enqueue_task(struct rq *rq, struct task_struct *p, int flags) 2000 { 2001 if (!(flags & ENQUEUE_NOCLOCK)) 2002 update_rq_clock(rq); 2003 2004 if (!(flags & ENQUEUE_RESTORE)) { 2005 sched_info_enqueue(rq, p); 2006 psi_enqueue(p, flags & ENQUEUE_WAKEUP); 2007 } 2008 2009 uclamp_rq_inc(rq, p); 2010 p->sched_class->enqueue_task(rq, p, flags); 2011 2012 if (sched_core_enabled(rq)) 2013 sched_core_enqueue(rq, p); 2014 } 2015 2016 static inline void dequeue_task(struct rq *rq, struct task_struct *p, int flags) 2017 { 2018 if (sched_core_enabled(rq)) 2019 sched_core_dequeue(rq, p, flags); 2020 2021 if (!(flags & DEQUEUE_NOCLOCK)) 2022 update_rq_clock(rq); 2023 2024 if (!(flags & DEQUEUE_SAVE)) { 2025 sched_info_dequeue(rq, p); 2026 psi_dequeue(p, flags & DEQUEUE_SLEEP); 2027 } 2028 2029 uclamp_rq_dec(rq, p); 2030 p->sched_class->dequeue_task(rq, p, flags); 2031 } 2032 2033 void activate_task(struct rq *rq, struct task_struct *p, int flags) 2034 { 2035 enqueue_task(rq, p, flags); 2036 2037 p->on_rq = TASK_ON_RQ_QUEUED; 2038 } 2039 2040 void deactivate_task(struct rq *rq, struct task_struct *p, int flags) 2041 { 2042 p->on_rq = (flags & DEQUEUE_SLEEP) ? 0 : TASK_ON_RQ_MIGRATING; 2043 2044 dequeue_task(rq, p, flags); 2045 } 2046 2047 static inline int __normal_prio(int policy, int rt_prio, int nice) 2048 { 2049 int prio; 2050 2051 if (dl_policy(policy)) 2052 prio = MAX_DL_PRIO - 1; 2053 else if (rt_policy(policy)) 2054 prio = MAX_RT_PRIO - 1 - rt_prio; 2055 else 2056 prio = NICE_TO_PRIO(nice); 2057 2058 return prio; 2059 } 2060 2061 /* 2062 * Calculate the expected normal priority: i.e. priority 2063 * without taking RT-inheritance into account. Might be 2064 * boosted by interactivity modifiers. Changes upon fork, 2065 * setprio syscalls, and whenever the interactivity 2066 * estimator recalculates. 2067 */ 2068 static inline int normal_prio(struct task_struct *p) 2069 { 2070 return __normal_prio(p->policy, p->rt_priority, PRIO_TO_NICE(p->static_prio)); 2071 } 2072 2073 /* 2074 * Calculate the current priority, i.e. the priority 2075 * taken into account by the scheduler. This value might 2076 * be boosted by RT tasks, or might be boosted by 2077 * interactivity modifiers. Will be RT if the task got 2078 * RT-boosted. If not then it returns p->normal_prio. 2079 */ 2080 static int effective_prio(struct task_struct *p) 2081 { 2082 p->normal_prio = normal_prio(p); 2083 /* 2084 * If we are RT tasks or we were boosted to RT priority, 2085 * keep the priority unchanged. Otherwise, update priority 2086 * to the normal priority: 2087 */ 2088 if (!rt_prio(p->prio)) 2089 return p->normal_prio; 2090 return p->prio; 2091 } 2092 2093 /** 2094 * task_curr - is this task currently executing on a CPU? 2095 * @p: the task in question. 2096 * 2097 * Return: 1 if the task is currently executing. 0 otherwise. 2098 */ 2099 inline int task_curr(const struct task_struct *p) 2100 { 2101 return cpu_curr(task_cpu(p)) == p; 2102 } 2103 2104 /* 2105 * switched_from, switched_to and prio_changed must _NOT_ drop rq->lock, 2106 * use the balance_callback list if you want balancing. 2107 * 2108 * this means any call to check_class_changed() must be followed by a call to 2109 * balance_callback(). 2110 */ 2111 static inline void check_class_changed(struct rq *rq, struct task_struct *p, 2112 const struct sched_class *prev_class, 2113 int oldprio) 2114 { 2115 if (prev_class != p->sched_class) { 2116 if (prev_class->switched_from) 2117 prev_class->switched_from(rq, p); 2118 2119 p->sched_class->switched_to(rq, p); 2120 } else if (oldprio != p->prio || dl_task(p)) 2121 p->sched_class->prio_changed(rq, p, oldprio); 2122 } 2123 2124 void check_preempt_curr(struct rq *rq, struct task_struct *p, int flags) 2125 { 2126 if (p->sched_class == rq->curr->sched_class) 2127 rq->curr->sched_class->check_preempt_curr(rq, p, flags); 2128 else if (p->sched_class > rq->curr->sched_class) 2129 resched_curr(rq); 2130 2131 /* 2132 * A queue event has occurred, and we're going to schedule. In 2133 * this case, we can save a useless back to back clock update. 2134 */ 2135 if (task_on_rq_queued(rq->curr) && test_tsk_need_resched(rq->curr)) 2136 rq_clock_skip_update(rq); 2137 } 2138 2139 #ifdef CONFIG_SMP 2140 2141 static void 2142 __do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask, u32 flags); 2143 2144 static int __set_cpus_allowed_ptr(struct task_struct *p, 2145 const struct cpumask *new_mask, 2146 u32 flags); 2147 2148 static void migrate_disable_switch(struct rq *rq, struct task_struct *p) 2149 { 2150 if (likely(!p->migration_disabled)) 2151 return; 2152 2153 if (p->cpus_ptr != &p->cpus_mask) 2154 return; 2155 2156 /* 2157 * Violates locking rules! see comment in __do_set_cpus_allowed(). 2158 */ 2159 __do_set_cpus_allowed(p, cpumask_of(rq->cpu), SCA_MIGRATE_DISABLE); 2160 } 2161 2162 void migrate_disable(void) 2163 { 2164 struct task_struct *p = current; 2165 2166 if (p->migration_disabled) { 2167 p->migration_disabled++; 2168 return; 2169 } 2170 2171 preempt_disable(); 2172 this_rq()->nr_pinned++; 2173 p->migration_disabled = 1; 2174 preempt_enable(); 2175 } 2176 EXPORT_SYMBOL_GPL(migrate_disable); 2177 2178 void migrate_enable(void) 2179 { 2180 struct task_struct *p = current; 2181 2182 if (p->migration_disabled > 1) { 2183 p->migration_disabled--; 2184 return; 2185 } 2186 2187 if (WARN_ON_ONCE(!p->migration_disabled)) 2188 return; 2189 2190 /* 2191 * Ensure stop_task runs either before or after this, and that 2192 * __set_cpus_allowed_ptr(SCA_MIGRATE_ENABLE) doesn't schedule(). 2193 */ 2194 preempt_disable(); 2195 if (p->cpus_ptr != &p->cpus_mask) 2196 __set_cpus_allowed_ptr(p, &p->cpus_mask, SCA_MIGRATE_ENABLE); 2197 /* 2198 * Mustn't clear migration_disabled() until cpus_ptr points back at the 2199 * regular cpus_mask, otherwise things that race (eg. 2200 * select_fallback_rq) get confused. 2201 */ 2202 barrier(); 2203 p->migration_disabled = 0; 2204 this_rq()->nr_pinned--; 2205 preempt_enable(); 2206 } 2207 EXPORT_SYMBOL_GPL(migrate_enable); 2208 2209 static inline bool rq_has_pinned_tasks(struct rq *rq) 2210 { 2211 return rq->nr_pinned; 2212 } 2213 2214 /* 2215 * Per-CPU kthreads are allowed to run on !active && online CPUs, see 2216 * __set_cpus_allowed_ptr() and select_fallback_rq(). 2217 */ 2218 static inline bool is_cpu_allowed(struct task_struct *p, int cpu) 2219 { 2220 /* When not in the task's cpumask, no point in looking further. */ 2221 if (!cpumask_test_cpu(cpu, p->cpus_ptr)) 2222 return false; 2223 2224 /* migrate_disabled() must be allowed to finish. */ 2225 if (is_migration_disabled(p)) 2226 return cpu_online(cpu); 2227 2228 /* Non kernel threads are not allowed during either online or offline. */ 2229 if (!(p->flags & PF_KTHREAD)) 2230 return cpu_active(cpu) && task_cpu_possible(cpu, p); 2231 2232 /* KTHREAD_IS_PER_CPU is always allowed. */ 2233 if (kthread_is_per_cpu(p)) 2234 return cpu_online(cpu); 2235 2236 /* Regular kernel threads don't get to stay during offline. */ 2237 if (cpu_dying(cpu)) 2238 return false; 2239 2240 /* But are allowed during online. */ 2241 return cpu_online(cpu); 2242 } 2243 2244 /* 2245 * This is how migration works: 2246 * 2247 * 1) we invoke migration_cpu_stop() on the target CPU using 2248 * stop_one_cpu(). 2249 * 2) stopper starts to run (implicitly forcing the migrated thread 2250 * off the CPU) 2251 * 3) it checks whether the migrated task is still in the wrong runqueue. 2252 * 4) if it's in the wrong runqueue then the migration thread removes 2253 * it and puts it into the right queue. 2254 * 5) stopper completes and stop_one_cpu() returns and the migration 2255 * is done. 2256 */ 2257 2258 /* 2259 * move_queued_task - move a queued task to new rq. 2260 * 2261 * Returns (locked) new rq. Old rq's lock is released. 2262 */ 2263 static struct rq *move_queued_task(struct rq *rq, struct rq_flags *rf, 2264 struct task_struct *p, int new_cpu) 2265 { 2266 lockdep_assert_rq_held(rq); 2267 2268 deactivate_task(rq, p, DEQUEUE_NOCLOCK); 2269 set_task_cpu(p, new_cpu); 2270 rq_unlock(rq, rf); 2271 2272 rq = cpu_rq(new_cpu); 2273 2274 rq_lock(rq, rf); 2275 BUG_ON(task_cpu(p) != new_cpu); 2276 activate_task(rq, p, 0); 2277 check_preempt_curr(rq, p, 0); 2278 2279 return rq; 2280 } 2281 2282 struct migration_arg { 2283 struct task_struct *task; 2284 int dest_cpu; 2285 struct set_affinity_pending *pending; 2286 }; 2287 2288 /* 2289 * @refs: number of wait_for_completion() 2290 * @stop_pending: is @stop_work in use 2291 */ 2292 struct set_affinity_pending { 2293 refcount_t refs; 2294 unsigned int stop_pending; 2295 struct completion done; 2296 struct cpu_stop_work stop_work; 2297 struct migration_arg arg; 2298 }; 2299 2300 /* 2301 * Move (not current) task off this CPU, onto the destination CPU. We're doing 2302 * this because either it can't run here any more (set_cpus_allowed() 2303 * away from this CPU, or CPU going down), or because we're 2304 * attempting to rebalance this task on exec (sched_exec). 2305 * 2306 * So we race with normal scheduler movements, but that's OK, as long 2307 * as the task is no longer on this CPU. 2308 */ 2309 static struct rq *__migrate_task(struct rq *rq, struct rq_flags *rf, 2310 struct task_struct *p, int dest_cpu) 2311 { 2312 /* Affinity changed (again). */ 2313 if (!is_cpu_allowed(p, dest_cpu)) 2314 return rq; 2315 2316 update_rq_clock(rq); 2317 rq = move_queued_task(rq, rf, p, dest_cpu); 2318 2319 return rq; 2320 } 2321 2322 /* 2323 * migration_cpu_stop - this will be executed by a highprio stopper thread 2324 * and performs thread migration by bumping thread off CPU then 2325 * 'pushing' onto another runqueue. 2326 */ 2327 static int migration_cpu_stop(void *data) 2328 { 2329 struct migration_arg *arg = data; 2330 struct set_affinity_pending *pending = arg->pending; 2331 struct task_struct *p = arg->task; 2332 struct rq *rq = this_rq(); 2333 bool complete = false; 2334 struct rq_flags rf; 2335 2336 /* 2337 * The original target CPU might have gone down and we might 2338 * be on another CPU but it doesn't matter. 2339 */ 2340 local_irq_save(rf.flags); 2341 /* 2342 * We need to explicitly wake pending tasks before running 2343 * __migrate_task() such that we will not miss enforcing cpus_ptr 2344 * during wakeups, see set_cpus_allowed_ptr()'s TASK_WAKING test. 2345 */ 2346 flush_smp_call_function_from_idle(); 2347 2348 raw_spin_lock(&p->pi_lock); 2349 rq_lock(rq, &rf); 2350 2351 /* 2352 * If we were passed a pending, then ->stop_pending was set, thus 2353 * p->migration_pending must have remained stable. 2354 */ 2355 WARN_ON_ONCE(pending && pending != p->migration_pending); 2356 2357 /* 2358 * If task_rq(p) != rq, it cannot be migrated here, because we're 2359 * holding rq->lock, if p->on_rq == 0 it cannot get enqueued because 2360 * we're holding p->pi_lock. 2361 */ 2362 if (task_rq(p) == rq) { 2363 if (is_migration_disabled(p)) 2364 goto out; 2365 2366 if (pending) { 2367 p->migration_pending = NULL; 2368 complete = true; 2369 2370 if (cpumask_test_cpu(task_cpu(p), &p->cpus_mask)) 2371 goto out; 2372 } 2373 2374 if (task_on_rq_queued(p)) 2375 rq = __migrate_task(rq, &rf, p, arg->dest_cpu); 2376 else 2377 p->wake_cpu = arg->dest_cpu; 2378 2379 /* 2380 * XXX __migrate_task() can fail, at which point we might end 2381 * up running on a dodgy CPU, AFAICT this can only happen 2382 * during CPU hotplug, at which point we'll get pushed out 2383 * anyway, so it's probably not a big deal. 2384 */ 2385 2386 } else if (pending) { 2387 /* 2388 * This happens when we get migrated between migrate_enable()'s 2389 * preempt_enable() and scheduling the stopper task. At that 2390 * point we're a regular task again and not current anymore. 2391 * 2392 * A !PREEMPT kernel has a giant hole here, which makes it far 2393 * more likely. 2394 */ 2395 2396 /* 2397 * The task moved before the stopper got to run. We're holding 2398 * ->pi_lock, so the allowed mask is stable - if it got 2399 * somewhere allowed, we're done. 2400 */ 2401 if (cpumask_test_cpu(task_cpu(p), p->cpus_ptr)) { 2402 p->migration_pending = NULL; 2403 complete = true; 2404 goto out; 2405 } 2406 2407 /* 2408 * When migrate_enable() hits a rq mis-match we can't reliably 2409 * determine is_migration_disabled() and so have to chase after 2410 * it. 2411 */ 2412 WARN_ON_ONCE(!pending->stop_pending); 2413 task_rq_unlock(rq, p, &rf); 2414 stop_one_cpu_nowait(task_cpu(p), migration_cpu_stop, 2415 &pending->arg, &pending->stop_work); 2416 return 0; 2417 } 2418 out: 2419 if (pending) 2420 pending->stop_pending = false; 2421 task_rq_unlock(rq, p, &rf); 2422 2423 if (complete) 2424 complete_all(&pending->done); 2425 2426 return 0; 2427 } 2428 2429 int push_cpu_stop(void *arg) 2430 { 2431 struct rq *lowest_rq = NULL, *rq = this_rq(); 2432 struct task_struct *p = arg; 2433 2434 raw_spin_lock_irq(&p->pi_lock); 2435 raw_spin_rq_lock(rq); 2436 2437 if (task_rq(p) != rq) 2438 goto out_unlock; 2439 2440 if (is_migration_disabled(p)) { 2441 p->migration_flags |= MDF_PUSH; 2442 goto out_unlock; 2443 } 2444 2445 p->migration_flags &= ~MDF_PUSH; 2446 2447 if (p->sched_class->find_lock_rq) 2448 lowest_rq = p->sched_class->find_lock_rq(p, rq); 2449 2450 if (!lowest_rq) 2451 goto out_unlock; 2452 2453 // XXX validate p is still the highest prio task 2454 if (task_rq(p) == rq) { 2455 deactivate_task(rq, p, 0); 2456 set_task_cpu(p, lowest_rq->cpu); 2457 activate_task(lowest_rq, p, 0); 2458 resched_curr(lowest_rq); 2459 } 2460 2461 double_unlock_balance(rq, lowest_rq); 2462 2463 out_unlock: 2464 rq->push_busy = false; 2465 raw_spin_rq_unlock(rq); 2466 raw_spin_unlock_irq(&p->pi_lock); 2467 2468 put_task_struct(p); 2469 return 0; 2470 } 2471 2472 /* 2473 * sched_class::set_cpus_allowed must do the below, but is not required to 2474 * actually call this function. 2475 */ 2476 void set_cpus_allowed_common(struct task_struct *p, const struct cpumask *new_mask, u32 flags) 2477 { 2478 if (flags & (SCA_MIGRATE_ENABLE | SCA_MIGRATE_DISABLE)) { 2479 p->cpus_ptr = new_mask; 2480 return; 2481 } 2482 2483 cpumask_copy(&p->cpus_mask, new_mask); 2484 p->nr_cpus_allowed = cpumask_weight(new_mask); 2485 } 2486 2487 static void 2488 __do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask, u32 flags) 2489 { 2490 struct rq *rq = task_rq(p); 2491 bool queued, running; 2492 2493 /* 2494 * This here violates the locking rules for affinity, since we're only 2495 * supposed to change these variables while holding both rq->lock and 2496 * p->pi_lock. 2497 * 2498 * HOWEVER, it magically works, because ttwu() is the only code that 2499 * accesses these variables under p->pi_lock and only does so after 2500 * smp_cond_load_acquire(&p->on_cpu, !VAL), and we're in __schedule() 2501 * before finish_task(). 2502 * 2503 * XXX do further audits, this smells like something putrid. 2504 */ 2505 if (flags & SCA_MIGRATE_DISABLE) 2506 SCHED_WARN_ON(!p->on_cpu); 2507 else 2508 lockdep_assert_held(&p->pi_lock); 2509 2510 queued = task_on_rq_queued(p); 2511 running = task_current(rq, p); 2512 2513 if (queued) { 2514 /* 2515 * Because __kthread_bind() calls this on blocked tasks without 2516 * holding rq->lock. 2517 */ 2518 lockdep_assert_rq_held(rq); 2519 dequeue_task(rq, p, DEQUEUE_SAVE | DEQUEUE_NOCLOCK); 2520 } 2521 if (running) 2522 put_prev_task(rq, p); 2523 2524 p->sched_class->set_cpus_allowed(p, new_mask, flags); 2525 2526 if (queued) 2527 enqueue_task(rq, p, ENQUEUE_RESTORE | ENQUEUE_NOCLOCK); 2528 if (running) 2529 set_next_task(rq, p); 2530 } 2531 2532 void do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask) 2533 { 2534 __do_set_cpus_allowed(p, new_mask, 0); 2535 } 2536 2537 int dup_user_cpus_ptr(struct task_struct *dst, struct task_struct *src, 2538 int node) 2539 { 2540 if (!src->user_cpus_ptr) 2541 return 0; 2542 2543 dst->user_cpus_ptr = kmalloc_node(cpumask_size(), GFP_KERNEL, node); 2544 if (!dst->user_cpus_ptr) 2545 return -ENOMEM; 2546 2547 cpumask_copy(dst->user_cpus_ptr, src->user_cpus_ptr); 2548 return 0; 2549 } 2550 2551 static inline struct cpumask *clear_user_cpus_ptr(struct task_struct *p) 2552 { 2553 struct cpumask *user_mask = NULL; 2554 2555 swap(p->user_cpus_ptr, user_mask); 2556 2557 return user_mask; 2558 } 2559 2560 void release_user_cpus_ptr(struct task_struct *p) 2561 { 2562 kfree(clear_user_cpus_ptr(p)); 2563 } 2564 2565 /* 2566 * This function is wildly self concurrent; here be dragons. 2567 * 2568 * 2569 * When given a valid mask, __set_cpus_allowed_ptr() must block until the 2570 * designated task is enqueued on an allowed CPU. If that task is currently 2571 * running, we have to kick it out using the CPU stopper. 2572 * 2573 * Migrate-Disable comes along and tramples all over our nice sandcastle. 2574 * Consider: 2575 * 2576 * Initial conditions: P0->cpus_mask = [0, 1] 2577 * 2578 * P0@CPU0 P1 2579 * 2580 * migrate_disable(); 2581 * <preempted> 2582 * set_cpus_allowed_ptr(P0, [1]); 2583 * 2584 * P1 *cannot* return from this set_cpus_allowed_ptr() call until P0 executes 2585 * its outermost migrate_enable() (i.e. it exits its Migrate-Disable region). 2586 * This means we need the following scheme: 2587 * 2588 * P0@CPU0 P1 2589 * 2590 * migrate_disable(); 2591 * <preempted> 2592 * set_cpus_allowed_ptr(P0, [1]); 2593 * <blocks> 2594 * <resumes> 2595 * migrate_enable(); 2596 * __set_cpus_allowed_ptr(); 2597 * <wakes local stopper> 2598 * `--> <woken on migration completion> 2599 * 2600 * Now the fun stuff: there may be several P1-like tasks, i.e. multiple 2601 * concurrent set_cpus_allowed_ptr(P0, [*]) calls. CPU affinity changes of any 2602 * task p are serialized by p->pi_lock, which we can leverage: the one that 2603 * should come into effect at the end of the Migrate-Disable region is the last 2604 * one. This means we only need to track a single cpumask (i.e. p->cpus_mask), 2605 * but we still need to properly signal those waiting tasks at the appropriate 2606 * moment. 2607 * 2608 * This is implemented using struct set_affinity_pending. The first 2609 * __set_cpus_allowed_ptr() caller within a given Migrate-Disable region will 2610 * setup an instance of that struct and install it on the targeted task_struct. 2611 * Any and all further callers will reuse that instance. Those then wait for 2612 * a completion signaled at the tail of the CPU stopper callback (1), triggered 2613 * on the end of the Migrate-Disable region (i.e. outermost migrate_enable()). 2614 * 2615 * 2616 * (1) In the cases covered above. There is one more where the completion is 2617 * signaled within affine_move_task() itself: when a subsequent affinity request 2618 * occurs after the stopper bailed out due to the targeted task still being 2619 * Migrate-Disable. Consider: 2620 * 2621 * Initial conditions: P0->cpus_mask = [0, 1] 2622 * 2623 * CPU0 P1 P2 2624 * <P0> 2625 * migrate_disable(); 2626 * <preempted> 2627 * set_cpus_allowed_ptr(P0, [1]); 2628 * <blocks> 2629 * <migration/0> 2630 * migration_cpu_stop() 2631 * is_migration_disabled() 2632 * <bails> 2633 * set_cpus_allowed_ptr(P0, [0, 1]); 2634 * <signal completion> 2635 * <awakes> 2636 * 2637 * Note that the above is safe vs a concurrent migrate_enable(), as any 2638 * pending affinity completion is preceded by an uninstallation of 2639 * p->migration_pending done with p->pi_lock held. 2640 */ 2641 static int affine_move_task(struct rq *rq, struct task_struct *p, struct rq_flags *rf, 2642 int dest_cpu, unsigned int flags) 2643 { 2644 struct set_affinity_pending my_pending = { }, *pending = NULL; 2645 bool stop_pending, complete = false; 2646 2647 /* Can the task run on the task's current CPU? If so, we're done */ 2648 if (cpumask_test_cpu(task_cpu(p), &p->cpus_mask)) { 2649 struct task_struct *push_task = NULL; 2650 2651 if ((flags & SCA_MIGRATE_ENABLE) && 2652 (p->migration_flags & MDF_PUSH) && !rq->push_busy) { 2653 rq->push_busy = true; 2654 push_task = get_task_struct(p); 2655 } 2656 2657 /* 2658 * If there are pending waiters, but no pending stop_work, 2659 * then complete now. 2660 */ 2661 pending = p->migration_pending; 2662 if (pending && !pending->stop_pending) { 2663 p->migration_pending = NULL; 2664 complete = true; 2665 } 2666 2667 task_rq_unlock(rq, p, rf); 2668 2669 if (push_task) { 2670 stop_one_cpu_nowait(rq->cpu, push_cpu_stop, 2671 p, &rq->push_work); 2672 } 2673 2674 if (complete) 2675 complete_all(&pending->done); 2676 2677 return 0; 2678 } 2679 2680 if (!(flags & SCA_MIGRATE_ENABLE)) { 2681 /* serialized by p->pi_lock */ 2682 if (!p->migration_pending) { 2683 /* Install the request */ 2684 refcount_set(&my_pending.refs, 1); 2685 init_completion(&my_pending.done); 2686 my_pending.arg = (struct migration_arg) { 2687 .task = p, 2688 .dest_cpu = dest_cpu, 2689 .pending = &my_pending, 2690 }; 2691 2692 p->migration_pending = &my_pending; 2693 } else { 2694 pending = p->migration_pending; 2695 refcount_inc(&pending->refs); 2696 /* 2697 * Affinity has changed, but we've already installed a 2698 * pending. migration_cpu_stop() *must* see this, else 2699 * we risk a completion of the pending despite having a 2700 * task on a disallowed CPU. 2701 * 2702 * Serialized by p->pi_lock, so this is safe. 2703 */ 2704 pending->arg.dest_cpu = dest_cpu; 2705 } 2706 } 2707 pending = p->migration_pending; 2708 /* 2709 * - !MIGRATE_ENABLE: 2710 * we'll have installed a pending if there wasn't one already. 2711 * 2712 * - MIGRATE_ENABLE: 2713 * we're here because the current CPU isn't matching anymore, 2714 * the only way that can happen is because of a concurrent 2715 * set_cpus_allowed_ptr() call, which should then still be 2716 * pending completion. 2717 * 2718 * Either way, we really should have a @pending here. 2719 */ 2720 if (WARN_ON_ONCE(!pending)) { 2721 task_rq_unlock(rq, p, rf); 2722 return -EINVAL; 2723 } 2724 2725 if (task_running(rq, p) || READ_ONCE(p->__state) == TASK_WAKING) { 2726 /* 2727 * MIGRATE_ENABLE gets here because 'p == current', but for 2728 * anything else we cannot do is_migration_disabled(), punt 2729 * and have the stopper function handle it all race-free. 2730 */ 2731 stop_pending = pending->stop_pending; 2732 if (!stop_pending) 2733 pending->stop_pending = true; 2734 2735 if (flags & SCA_MIGRATE_ENABLE) 2736 p->migration_flags &= ~MDF_PUSH; 2737 2738 task_rq_unlock(rq, p, rf); 2739 2740 if (!stop_pending) { 2741 stop_one_cpu_nowait(cpu_of(rq), migration_cpu_stop, 2742 &pending->arg, &pending->stop_work); 2743 } 2744 2745 if (flags & SCA_MIGRATE_ENABLE) 2746 return 0; 2747 } else { 2748 2749 if (!is_migration_disabled(p)) { 2750 if (task_on_rq_queued(p)) 2751 rq = move_queued_task(rq, rf, p, dest_cpu); 2752 2753 if (!pending->stop_pending) { 2754 p->migration_pending = NULL; 2755 complete = true; 2756 } 2757 } 2758 task_rq_unlock(rq, p, rf); 2759 2760 if (complete) 2761 complete_all(&pending->done); 2762 } 2763 2764 wait_for_completion(&pending->done); 2765 2766 if (refcount_dec_and_test(&pending->refs)) 2767 wake_up_var(&pending->refs); /* No UaF, just an address */ 2768 2769 /* 2770 * Block the original owner of &pending until all subsequent callers 2771 * have seen the completion and decremented the refcount 2772 */ 2773 wait_var_event(&my_pending.refs, !refcount_read(&my_pending.refs)); 2774 2775 /* ARGH */ 2776 WARN_ON_ONCE(my_pending.stop_pending); 2777 2778 return 0; 2779 } 2780 2781 /* 2782 * Called with both p->pi_lock and rq->lock held; drops both before returning. 2783 */ 2784 static int __set_cpus_allowed_ptr_locked(struct task_struct *p, 2785 const struct cpumask *new_mask, 2786 u32 flags, 2787 struct rq *rq, 2788 struct rq_flags *rf) 2789 __releases(rq->lock) 2790 __releases(p->pi_lock) 2791 { 2792 const struct cpumask *cpu_allowed_mask = task_cpu_possible_mask(p); 2793 const struct cpumask *cpu_valid_mask = cpu_active_mask; 2794 bool kthread = p->flags & PF_KTHREAD; 2795 struct cpumask *user_mask = NULL; 2796 unsigned int dest_cpu; 2797 int ret = 0; 2798 2799 update_rq_clock(rq); 2800 2801 if (kthread || is_migration_disabled(p)) { 2802 /* 2803 * Kernel threads are allowed on online && !active CPUs, 2804 * however, during cpu-hot-unplug, even these might get pushed 2805 * away if not KTHREAD_IS_PER_CPU. 2806 * 2807 * Specifically, migration_disabled() tasks must not fail the 2808 * cpumask_any_and_distribute() pick below, esp. so on 2809 * SCA_MIGRATE_ENABLE, otherwise we'll not call 2810 * set_cpus_allowed_common() and actually reset p->cpus_ptr. 2811 */ 2812 cpu_valid_mask = cpu_online_mask; 2813 } 2814 2815 if (!kthread && !cpumask_subset(new_mask, cpu_allowed_mask)) { 2816 ret = -EINVAL; 2817 goto out; 2818 } 2819 2820 /* 2821 * Must re-check here, to close a race against __kthread_bind(), 2822 * sched_setaffinity() is not guaranteed to observe the flag. 2823 */ 2824 if ((flags & SCA_CHECK) && (p->flags & PF_NO_SETAFFINITY)) { 2825 ret = -EINVAL; 2826 goto out; 2827 } 2828 2829 if (!(flags & SCA_MIGRATE_ENABLE)) { 2830 if (cpumask_equal(&p->cpus_mask, new_mask)) 2831 goto out; 2832 2833 if (WARN_ON_ONCE(p == current && 2834 is_migration_disabled(p) && 2835 !cpumask_test_cpu(task_cpu(p), new_mask))) { 2836 ret = -EBUSY; 2837 goto out; 2838 } 2839 } 2840 2841 /* 2842 * Picking a ~random cpu helps in cases where we are changing affinity 2843 * for groups of tasks (ie. cpuset), so that load balancing is not 2844 * immediately required to distribute the tasks within their new mask. 2845 */ 2846 dest_cpu = cpumask_any_and_distribute(cpu_valid_mask, new_mask); 2847 if (dest_cpu >= nr_cpu_ids) { 2848 ret = -EINVAL; 2849 goto out; 2850 } 2851 2852 __do_set_cpus_allowed(p, new_mask, flags); 2853 2854 if (flags & SCA_USER) 2855 user_mask = clear_user_cpus_ptr(p); 2856 2857 ret = affine_move_task(rq, p, rf, dest_cpu, flags); 2858 2859 kfree(user_mask); 2860 2861 return ret; 2862 2863 out: 2864 task_rq_unlock(rq, p, rf); 2865 2866 return ret; 2867 } 2868 2869 /* 2870 * Change a given task's CPU affinity. Migrate the thread to a 2871 * proper CPU and schedule it away if the CPU it's executing on 2872 * is removed from the allowed bitmask. 2873 * 2874 * NOTE: the caller must have a valid reference to the task, the 2875 * task must not exit() & deallocate itself prematurely. The 2876 * call is not atomic; no spinlocks may be held. 2877 */ 2878 static int __set_cpus_allowed_ptr(struct task_struct *p, 2879 const struct cpumask *new_mask, u32 flags) 2880 { 2881 struct rq_flags rf; 2882 struct rq *rq; 2883 2884 rq = task_rq_lock(p, &rf); 2885 return __set_cpus_allowed_ptr_locked(p, new_mask, flags, rq, &rf); 2886 } 2887 2888 int set_cpus_allowed_ptr(struct task_struct *p, const struct cpumask *new_mask) 2889 { 2890 return __set_cpus_allowed_ptr(p, new_mask, 0); 2891 } 2892 EXPORT_SYMBOL_GPL(set_cpus_allowed_ptr); 2893 2894 /* 2895 * Change a given task's CPU affinity to the intersection of its current 2896 * affinity mask and @subset_mask, writing the resulting mask to @new_mask 2897 * and pointing @p->user_cpus_ptr to a copy of the old mask. 2898 * If the resulting mask is empty, leave the affinity unchanged and return 2899 * -EINVAL. 2900 */ 2901 static int restrict_cpus_allowed_ptr(struct task_struct *p, 2902 struct cpumask *new_mask, 2903 const struct cpumask *subset_mask) 2904 { 2905 struct cpumask *user_mask = NULL; 2906 struct rq_flags rf; 2907 struct rq *rq; 2908 int err; 2909 2910 if (!p->user_cpus_ptr) { 2911 user_mask = kmalloc(cpumask_size(), GFP_KERNEL); 2912 if (!user_mask) 2913 return -ENOMEM; 2914 } 2915 2916 rq = task_rq_lock(p, &rf); 2917 2918 /* 2919 * Forcefully restricting the affinity of a deadline task is 2920 * likely to cause problems, so fail and noisily override the 2921 * mask entirely. 2922 */ 2923 if (task_has_dl_policy(p) && dl_bandwidth_enabled()) { 2924 err = -EPERM; 2925 goto err_unlock; 2926 } 2927 2928 if (!cpumask_and(new_mask, &p->cpus_mask, subset_mask)) { 2929 err = -EINVAL; 2930 goto err_unlock; 2931 } 2932 2933 /* 2934 * We're about to butcher the task affinity, so keep track of what 2935 * the user asked for in case we're able to restore it later on. 2936 */ 2937 if (user_mask) { 2938 cpumask_copy(user_mask, p->cpus_ptr); 2939 p->user_cpus_ptr = user_mask; 2940 } 2941 2942 return __set_cpus_allowed_ptr_locked(p, new_mask, 0, rq, &rf); 2943 2944 err_unlock: 2945 task_rq_unlock(rq, p, &rf); 2946 kfree(user_mask); 2947 return err; 2948 } 2949 2950 /* 2951 * Restrict the CPU affinity of task @p so that it is a subset of 2952 * task_cpu_possible_mask() and point @p->user_cpu_ptr to a copy of the 2953 * old affinity mask. If the resulting mask is empty, we warn and walk 2954 * up the cpuset hierarchy until we find a suitable mask. 2955 */ 2956 void force_compatible_cpus_allowed_ptr(struct task_struct *p) 2957 { 2958 cpumask_var_t new_mask; 2959 const struct cpumask *override_mask = task_cpu_possible_mask(p); 2960 2961 alloc_cpumask_var(&new_mask, GFP_KERNEL); 2962 2963 /* 2964 * __migrate_task() can fail silently in the face of concurrent 2965 * offlining of the chosen destination CPU, so take the hotplug 2966 * lock to ensure that the migration succeeds. 2967 */ 2968 cpus_read_lock(); 2969 if (!cpumask_available(new_mask)) 2970 goto out_set_mask; 2971 2972 if (!restrict_cpus_allowed_ptr(p, new_mask, override_mask)) 2973 goto out_free_mask; 2974 2975 /* 2976 * We failed to find a valid subset of the affinity mask for the 2977 * task, so override it based on its cpuset hierarchy. 2978 */ 2979 cpuset_cpus_allowed(p, new_mask); 2980 override_mask = new_mask; 2981 2982 out_set_mask: 2983 if (printk_ratelimit()) { 2984 printk_deferred("Overriding affinity for process %d (%s) to CPUs %*pbl\n", 2985 task_pid_nr(p), p->comm, 2986 cpumask_pr_args(override_mask)); 2987 } 2988 2989 WARN_ON(set_cpus_allowed_ptr(p, override_mask)); 2990 out_free_mask: 2991 cpus_read_unlock(); 2992 free_cpumask_var(new_mask); 2993 } 2994 2995 static int 2996 __sched_setaffinity(struct task_struct *p, const struct cpumask *mask); 2997 2998 /* 2999 * Restore the affinity of a task @p which was previously restricted by a 3000 * call to force_compatible_cpus_allowed_ptr(). This will clear (and free) 3001 * @p->user_cpus_ptr. 3002 * 3003 * It is the caller's responsibility to serialise this with any calls to 3004 * force_compatible_cpus_allowed_ptr(@p). 3005 */ 3006 void relax_compatible_cpus_allowed_ptr(struct task_struct *p) 3007 { 3008 struct cpumask *user_mask = p->user_cpus_ptr; 3009 unsigned long flags; 3010 3011 /* 3012 * Try to restore the old affinity mask. If this fails, then 3013 * we free the mask explicitly to avoid it being inherited across 3014 * a subsequent fork(). 3015 */ 3016 if (!user_mask || !__sched_setaffinity(p, user_mask)) 3017 return; 3018 3019 raw_spin_lock_irqsave(&p->pi_lock, flags); 3020 user_mask = clear_user_cpus_ptr(p); 3021 raw_spin_unlock_irqrestore(&p->pi_lock, flags); 3022 3023 kfree(user_mask); 3024 } 3025 3026 void set_task_cpu(struct task_struct *p, unsigned int new_cpu) 3027 { 3028 #ifdef CONFIG_SCHED_DEBUG 3029 unsigned int state = READ_ONCE(p->__state); 3030 3031 /* 3032 * We should never call set_task_cpu() on a blocked task, 3033 * ttwu() will sort out the placement. 3034 */ 3035 WARN_ON_ONCE(state != TASK_RUNNING && state != TASK_WAKING && !p->on_rq); 3036 3037 /* 3038 * Migrating fair class task must have p->on_rq = TASK_ON_RQ_MIGRATING, 3039 * because schedstat_wait_{start,end} rebase migrating task's wait_start 3040 * time relying on p->on_rq. 3041 */ 3042 WARN_ON_ONCE(state == TASK_RUNNING && 3043 p->sched_class == &fair_sched_class && 3044 (p->on_rq && !task_on_rq_migrating(p))); 3045 3046 #ifdef CONFIG_LOCKDEP 3047 /* 3048 * The caller should hold either p->pi_lock or rq->lock, when changing 3049 * a task's CPU. ->pi_lock for waking tasks, rq->lock for runnable tasks. 3050 * 3051 * sched_move_task() holds both and thus holding either pins the cgroup, 3052 * see task_group(). 3053 * 3054 * Furthermore, all task_rq users should acquire both locks, see 3055 * task_rq_lock(). 3056 */ 3057 WARN_ON_ONCE(debug_locks && !(lockdep_is_held(&p->pi_lock) || 3058 lockdep_is_held(__rq_lockp(task_rq(p))))); 3059 #endif 3060 /* 3061 * Clearly, migrating tasks to offline CPUs is a fairly daft thing. 3062 */ 3063 WARN_ON_ONCE(!cpu_online(new_cpu)); 3064 3065 WARN_ON_ONCE(is_migration_disabled(p)); 3066 #endif 3067 3068 trace_sched_migrate_task(p, new_cpu); 3069 3070 if (task_cpu(p) != new_cpu) { 3071 if (p->sched_class->migrate_task_rq) 3072 p->sched_class->migrate_task_rq(p, new_cpu); 3073 p->se.nr_migrations++; 3074 rseq_migrate(p); 3075 perf_event_task_migrate(p); 3076 } 3077 3078 __set_task_cpu(p, new_cpu); 3079 } 3080 3081 #ifdef CONFIG_NUMA_BALANCING 3082 static void __migrate_swap_task(struct task_struct *p, int cpu) 3083 { 3084 if (task_on_rq_queued(p)) { 3085 struct rq *src_rq, *dst_rq; 3086 struct rq_flags srf, drf; 3087 3088 src_rq = task_rq(p); 3089 dst_rq = cpu_rq(cpu); 3090 3091 rq_pin_lock(src_rq, &srf); 3092 rq_pin_lock(dst_rq, &drf); 3093 3094 deactivate_task(src_rq, p, 0); 3095 set_task_cpu(p, cpu); 3096 activate_task(dst_rq, p, 0); 3097 check_preempt_curr(dst_rq, p, 0); 3098 3099 rq_unpin_lock(dst_rq, &drf); 3100 rq_unpin_lock(src_rq, &srf); 3101 3102 } else { 3103 /* 3104 * Task isn't running anymore; make it appear like we migrated 3105 * it before it went to sleep. This means on wakeup we make the 3106 * previous CPU our target instead of where it really is. 3107 */ 3108 p->wake_cpu = cpu; 3109 } 3110 } 3111 3112 struct migration_swap_arg { 3113 struct task_struct *src_task, *dst_task; 3114 int src_cpu, dst_cpu; 3115 }; 3116 3117 static int migrate_swap_stop(void *data) 3118 { 3119 struct migration_swap_arg *arg = data; 3120 struct rq *src_rq, *dst_rq; 3121 int ret = -EAGAIN; 3122 3123 if (!cpu_active(arg->src_cpu) || !cpu_active(arg->dst_cpu)) 3124 return -EAGAIN; 3125 3126 src_rq = cpu_rq(arg->src_cpu); 3127 dst_rq = cpu_rq(arg->dst_cpu); 3128 3129 double_raw_lock(&arg->src_task->pi_lock, 3130 &arg->dst_task->pi_lock); 3131 double_rq_lock(src_rq, dst_rq); 3132 3133 if (task_cpu(arg->dst_task) != arg->dst_cpu) 3134 goto unlock; 3135 3136 if (task_cpu(arg->src_task) != arg->src_cpu) 3137 goto unlock; 3138 3139 if (!cpumask_test_cpu(arg->dst_cpu, arg->src_task->cpus_ptr)) 3140 goto unlock; 3141 3142 if (!cpumask_test_cpu(arg->src_cpu, arg->dst_task->cpus_ptr)) 3143 goto unlock; 3144 3145 __migrate_swap_task(arg->src_task, arg->dst_cpu); 3146 __migrate_swap_task(arg->dst_task, arg->src_cpu); 3147 3148 ret = 0; 3149 3150 unlock: 3151 double_rq_unlock(src_rq, dst_rq); 3152 raw_spin_unlock(&arg->dst_task->pi_lock); 3153 raw_spin_unlock(&arg->src_task->pi_lock); 3154 3155 return ret; 3156 } 3157 3158 /* 3159 * Cross migrate two tasks 3160 */ 3161 int migrate_swap(struct task_struct *cur, struct task_struct *p, 3162 int target_cpu, int curr_cpu) 3163 { 3164 struct migration_swap_arg arg; 3165 int ret = -EINVAL; 3166 3167 arg = (struct migration_swap_arg){ 3168 .src_task = cur, 3169 .src_cpu = curr_cpu, 3170 .dst_task = p, 3171 .dst_cpu = target_cpu, 3172 }; 3173 3174 if (arg.src_cpu == arg.dst_cpu) 3175 goto out; 3176 3177 /* 3178 * These three tests are all lockless; this is OK since all of them 3179 * will be re-checked with proper locks held further down the line. 3180 */ 3181 if (!cpu_active(arg.src_cpu) || !cpu_active(arg.dst_cpu)) 3182 goto out; 3183 3184 if (!cpumask_test_cpu(arg.dst_cpu, arg.src_task->cpus_ptr)) 3185 goto out; 3186 3187 if (!cpumask_test_cpu(arg.src_cpu, arg.dst_task->cpus_ptr)) 3188 goto out; 3189 3190 trace_sched_swap_numa(cur, arg.src_cpu, p, arg.dst_cpu); 3191 ret = stop_two_cpus(arg.dst_cpu, arg.src_cpu, migrate_swap_stop, &arg); 3192 3193 out: 3194 return ret; 3195 } 3196 #endif /* CONFIG_NUMA_BALANCING */ 3197 3198 /* 3199 * wait_task_inactive - wait for a thread to unschedule. 3200 * 3201 * If @match_state is nonzero, it's the @p->state value just checked and 3202 * not expected to change. If it changes, i.e. @p might have woken up, 3203 * then return zero. When we succeed in waiting for @p to be off its CPU, 3204 * we return a positive number (its total switch count). If a second call 3205 * a short while later returns the same number, the caller can be sure that 3206 * @p has remained unscheduled the whole time. 3207 * 3208 * The caller must ensure that the task *will* unschedule sometime soon, 3209 * else this function might spin for a *long* time. This function can't 3210 * be called with interrupts off, or it may introduce deadlock with 3211 * smp_call_function() if an IPI is sent by the same process we are 3212 * waiting to become inactive. 3213 */ 3214 unsigned long wait_task_inactive(struct task_struct *p, unsigned int match_state) 3215 { 3216 int running, queued; 3217 struct rq_flags rf; 3218 unsigned long ncsw; 3219 struct rq *rq; 3220 3221 for (;;) { 3222 /* 3223 * We do the initial early heuristics without holding 3224 * any task-queue locks at all. We'll only try to get 3225 * the runqueue lock when things look like they will 3226 * work out! 3227 */ 3228 rq = task_rq(p); 3229 3230 /* 3231 * If the task is actively running on another CPU 3232 * still, just relax and busy-wait without holding 3233 * any locks. 3234 * 3235 * NOTE! Since we don't hold any locks, it's not 3236 * even sure that "rq" stays as the right runqueue! 3237 * But we don't care, since "task_running()" will 3238 * return false if the runqueue has changed and p 3239 * is actually now running somewhere else! 3240 */ 3241 while (task_running(rq, p)) { 3242 if (match_state && unlikely(READ_ONCE(p->__state) != match_state)) 3243 return 0; 3244 cpu_relax(); 3245 } 3246 3247 /* 3248 * Ok, time to look more closely! We need the rq 3249 * lock now, to be *sure*. If we're wrong, we'll 3250 * just go back and repeat. 3251 */ 3252 rq = task_rq_lock(p, &rf); 3253 trace_sched_wait_task(p); 3254 running = task_running(rq, p); 3255 queued = task_on_rq_queued(p); 3256 ncsw = 0; 3257 if (!match_state || READ_ONCE(p->__state) == match_state) 3258 ncsw = p->nvcsw | LONG_MIN; /* sets MSB */ 3259 task_rq_unlock(rq, p, &rf); 3260 3261 /* 3262 * If it changed from the expected state, bail out now. 3263 */ 3264 if (unlikely(!ncsw)) 3265 break; 3266 3267 /* 3268 * Was it really running after all now that we 3269 * checked with the proper locks actually held? 3270 * 3271 * Oops. Go back and try again.. 3272 */ 3273 if (unlikely(running)) { 3274 cpu_relax(); 3275 continue; 3276 } 3277 3278 /* 3279 * It's not enough that it's not actively running, 3280 * it must be off the runqueue _entirely_, and not 3281 * preempted! 3282 * 3283 * So if it was still runnable (but just not actively 3284 * running right now), it's preempted, and we should 3285 * yield - it could be a while. 3286 */ 3287 if (unlikely(queued)) { 3288 ktime_t to = NSEC_PER_SEC / HZ; 3289 3290 set_current_state(TASK_UNINTERRUPTIBLE); 3291 schedule_hrtimeout(&to, HRTIMER_MODE_REL_HARD); 3292 continue; 3293 } 3294 3295 /* 3296 * Ahh, all good. It wasn't running, and it wasn't 3297 * runnable, which means that it will never become 3298 * running in the future either. We're all done! 3299 */ 3300 break; 3301 } 3302 3303 return ncsw; 3304 } 3305 3306 /*** 3307 * kick_process - kick a running thread to enter/exit the kernel 3308 * @p: the to-be-kicked thread 3309 * 3310 * Cause a process which is running on another CPU to enter 3311 * kernel-mode, without any delay. (to get signals handled.) 3312 * 3313 * NOTE: this function doesn't have to take the runqueue lock, 3314 * because all it wants to ensure is that the remote task enters 3315 * the kernel. If the IPI races and the task has been migrated 3316 * to another CPU then no harm is done and the purpose has been 3317 * achieved as well. 3318 */ 3319 void kick_process(struct task_struct *p) 3320 { 3321 int cpu; 3322 3323 preempt_disable(); 3324 cpu = task_cpu(p); 3325 if ((cpu != smp_processor_id()) && task_curr(p)) 3326 smp_send_reschedule(cpu); 3327 preempt_enable(); 3328 } 3329 EXPORT_SYMBOL_GPL(kick_process); 3330 3331 /* 3332 * ->cpus_ptr is protected by both rq->lock and p->pi_lock 3333 * 3334 * A few notes on cpu_active vs cpu_online: 3335 * 3336 * - cpu_active must be a subset of cpu_online 3337 * 3338 * - on CPU-up we allow per-CPU kthreads on the online && !active CPU, 3339 * see __set_cpus_allowed_ptr(). At this point the newly online 3340 * CPU isn't yet part of the sched domains, and balancing will not 3341 * see it. 3342 * 3343 * - on CPU-down we clear cpu_active() to mask the sched domains and 3344 * avoid the load balancer to place new tasks on the to be removed 3345 * CPU. Existing tasks will remain running there and will be taken 3346 * off. 3347 * 3348 * This means that fallback selection must not select !active CPUs. 3349 * And can assume that any active CPU must be online. Conversely 3350 * select_task_rq() below may allow selection of !active CPUs in order 3351 * to satisfy the above rules. 3352 */ 3353 static int select_fallback_rq(int cpu, struct task_struct *p) 3354 { 3355 int nid = cpu_to_node(cpu); 3356 const struct cpumask *nodemask = NULL; 3357 enum { cpuset, possible, fail } state = cpuset; 3358 int dest_cpu; 3359 3360 /* 3361 * If the node that the CPU is on has been offlined, cpu_to_node() 3362 * will return -1. There is no CPU on the node, and we should 3363 * select the CPU on the other node. 3364 */ 3365 if (nid != -1) { 3366 nodemask = cpumask_of_node(nid); 3367 3368 /* Look for allowed, online CPU in same node. */ 3369 for_each_cpu(dest_cpu, nodemask) { 3370 if (is_cpu_allowed(p, dest_cpu)) 3371 return dest_cpu; 3372 } 3373 } 3374 3375 for (;;) { 3376 /* Any allowed, online CPU? */ 3377 for_each_cpu(dest_cpu, p->cpus_ptr) { 3378 if (!is_cpu_allowed(p, dest_cpu)) 3379 continue; 3380 3381 goto out; 3382 } 3383 3384 /* No more Mr. Nice Guy. */ 3385 switch (state) { 3386 case cpuset: 3387 if (cpuset_cpus_allowed_fallback(p)) { 3388 state = possible; 3389 break; 3390 } 3391 fallthrough; 3392 case possible: 3393 /* 3394 * XXX When called from select_task_rq() we only 3395 * hold p->pi_lock and again violate locking order. 3396 * 3397 * More yuck to audit. 3398 */ 3399 do_set_cpus_allowed(p, task_cpu_possible_mask(p)); 3400 state = fail; 3401 break; 3402 case fail: 3403 BUG(); 3404 break; 3405 } 3406 } 3407 3408 out: 3409 if (state != cpuset) { 3410 /* 3411 * Don't tell them about moving exiting tasks or 3412 * kernel threads (both mm NULL), since they never 3413 * leave kernel. 3414 */ 3415 if (p->mm && printk_ratelimit()) { 3416 printk_deferred("process %d (%s) no longer affine to cpu%d\n", 3417 task_pid_nr(p), p->comm, cpu); 3418 } 3419 } 3420 3421 return dest_cpu; 3422 } 3423 3424 /* 3425 * The caller (fork, wakeup) owns p->pi_lock, ->cpus_ptr is stable. 3426 */ 3427 static inline 3428 int select_task_rq(struct task_struct *p, int cpu, int wake_flags) 3429 { 3430 lockdep_assert_held(&p->pi_lock); 3431 3432 if (p->nr_cpus_allowed > 1 && !is_migration_disabled(p)) 3433 cpu = p->sched_class->select_task_rq(p, cpu, wake_flags); 3434 else 3435 cpu = cpumask_any(p->cpus_ptr); 3436 3437 /* 3438 * In order not to call set_task_cpu() on a blocking task we need 3439 * to rely on ttwu() to place the task on a valid ->cpus_ptr 3440 * CPU. 3441 * 3442 * Since this is common to all placement strategies, this lives here. 3443 * 3444 * [ this allows ->select_task() to simply return task_cpu(p) and 3445 * not worry about this generic constraint ] 3446 */ 3447 if (unlikely(!is_cpu_allowed(p, cpu))) 3448 cpu = select_fallback_rq(task_cpu(p), p); 3449 3450 return cpu; 3451 } 3452 3453 void sched_set_stop_task(int cpu, struct task_struct *stop) 3454 { 3455 static struct lock_class_key stop_pi_lock; 3456 struct sched_param param = { .sched_priority = MAX_RT_PRIO - 1 }; 3457 struct task_struct *old_stop = cpu_rq(cpu)->stop; 3458 3459 if (stop) { 3460 /* 3461 * Make it appear like a SCHED_FIFO task, its something 3462 * userspace knows about and won't get confused about. 3463 * 3464 * Also, it will make PI more or less work without too 3465 * much confusion -- but then, stop work should not 3466 * rely on PI working anyway. 3467 */ 3468 sched_setscheduler_nocheck(stop, SCHED_FIFO, ¶m); 3469 3470 stop->sched_class = &stop_sched_class; 3471 3472 /* 3473 * The PI code calls rt_mutex_setprio() with ->pi_lock held to 3474 * adjust the effective priority of a task. As a result, 3475 * rt_mutex_setprio() can trigger (RT) balancing operations, 3476 * which can then trigger wakeups of the stop thread to push 3477 * around the current task. 3478 * 3479 * The stop task itself will never be part of the PI-chain, it 3480 * never blocks, therefore that ->pi_lock recursion is safe. 3481 * Tell lockdep about this by placing the stop->pi_lock in its 3482 * own class. 3483 */ 3484 lockdep_set_class(&stop->pi_lock, &stop_pi_lock); 3485 } 3486 3487 cpu_rq(cpu)->stop = stop; 3488 3489 if (old_stop) { 3490 /* 3491 * Reset it back to a normal scheduling class so that 3492 * it can die in pieces. 3493 */ 3494 old_stop->sched_class = &rt_sched_class; 3495 } 3496 } 3497 3498 #else /* CONFIG_SMP */ 3499 3500 static inline int __set_cpus_allowed_ptr(struct task_struct *p, 3501 const struct cpumask *new_mask, 3502 u32 flags) 3503 { 3504 return set_cpus_allowed_ptr(p, new_mask); 3505 } 3506 3507 static inline void migrate_disable_switch(struct rq *rq, struct task_struct *p) { } 3508 3509 static inline bool rq_has_pinned_tasks(struct rq *rq) 3510 { 3511 return false; 3512 } 3513 3514 #endif /* !CONFIG_SMP */ 3515 3516 static void 3517 ttwu_stat(struct task_struct *p, int cpu, int wake_flags) 3518 { 3519 struct rq *rq; 3520 3521 if (!schedstat_enabled()) 3522 return; 3523 3524 rq = this_rq(); 3525 3526 #ifdef CONFIG_SMP 3527 if (cpu == rq->cpu) { 3528 __schedstat_inc(rq->ttwu_local); 3529 __schedstat_inc(p->stats.nr_wakeups_local); 3530 } else { 3531 struct sched_domain *sd; 3532 3533 __schedstat_inc(p->stats.nr_wakeups_remote); 3534 rcu_read_lock(); 3535 for_each_domain(rq->cpu, sd) { 3536 if (cpumask_test_cpu(cpu, sched_domain_span(sd))) { 3537 __schedstat_inc(sd->ttwu_wake_remote); 3538 break; 3539 } 3540 } 3541 rcu_read_unlock(); 3542 } 3543 3544 if (wake_flags & WF_MIGRATED) 3545 __schedstat_inc(p->stats.nr_wakeups_migrate); 3546 #endif /* CONFIG_SMP */ 3547 3548 __schedstat_inc(rq->ttwu_count); 3549 __schedstat_inc(p->stats.nr_wakeups); 3550 3551 if (wake_flags & WF_SYNC) 3552 __schedstat_inc(p->stats.nr_wakeups_sync); 3553 } 3554 3555 /* 3556 * Mark the task runnable and perform wakeup-preemption. 3557 */ 3558 static void ttwu_do_wakeup(struct rq *rq, struct task_struct *p, int wake_flags, 3559 struct rq_flags *rf) 3560 { 3561 check_preempt_curr(rq, p, wake_flags); 3562 WRITE_ONCE(p->__state, TASK_RUNNING); 3563 trace_sched_wakeup(p); 3564 3565 #ifdef CONFIG_SMP 3566 if (p->sched_class->task_woken) { 3567 /* 3568 * Our task @p is fully woken up and running; so it's safe to 3569 * drop the rq->lock, hereafter rq is only used for statistics. 3570 */ 3571 rq_unpin_lock(rq, rf); 3572 p->sched_class->task_woken(rq, p); 3573 rq_repin_lock(rq, rf); 3574 } 3575 3576 if (rq->idle_stamp) { 3577 u64 delta = rq_clock(rq) - rq->idle_stamp; 3578 u64 max = 2*rq->max_idle_balance_cost; 3579 3580 update_avg(&rq->avg_idle, delta); 3581 3582 if (rq->avg_idle > max) 3583 rq->avg_idle = max; 3584 3585 rq->wake_stamp = jiffies; 3586 rq->wake_avg_idle = rq->avg_idle / 2; 3587 3588 rq->idle_stamp = 0; 3589 } 3590 #endif 3591 } 3592 3593 static void 3594 ttwu_do_activate(struct rq *rq, struct task_struct *p, int wake_flags, 3595 struct rq_flags *rf) 3596 { 3597 int en_flags = ENQUEUE_WAKEUP | ENQUEUE_NOCLOCK; 3598 3599 lockdep_assert_rq_held(rq); 3600 3601 if (p->sched_contributes_to_load) 3602 rq->nr_uninterruptible--; 3603 3604 #ifdef CONFIG_SMP 3605 if (wake_flags & WF_MIGRATED) 3606 en_flags |= ENQUEUE_MIGRATED; 3607 else 3608 #endif 3609 if (p->in_iowait) { 3610 delayacct_blkio_end(p); 3611 atomic_dec(&task_rq(p)->nr_iowait); 3612 } 3613 3614 activate_task(rq, p, en_flags); 3615 ttwu_do_wakeup(rq, p, wake_flags, rf); 3616 } 3617 3618 /* 3619 * Consider @p being inside a wait loop: 3620 * 3621 * for (;;) { 3622 * set_current_state(TASK_UNINTERRUPTIBLE); 3623 * 3624 * if (CONDITION) 3625 * break; 3626 * 3627 * schedule(); 3628 * } 3629 * __set_current_state(TASK_RUNNING); 3630 * 3631 * between set_current_state() and schedule(). In this case @p is still 3632 * runnable, so all that needs doing is change p->state back to TASK_RUNNING in 3633 * an atomic manner. 3634 * 3635 * By taking task_rq(p)->lock we serialize against schedule(), if @p->on_rq 3636 * then schedule() must still happen and p->state can be changed to 3637 * TASK_RUNNING. Otherwise we lost the race, schedule() has happened, and we 3638 * need to do a full wakeup with enqueue. 3639 * 3640 * Returns: %true when the wakeup is done, 3641 * %false otherwise. 3642 */ 3643 static int ttwu_runnable(struct task_struct *p, int wake_flags) 3644 { 3645 struct rq_flags rf; 3646 struct rq *rq; 3647 int ret = 0; 3648 3649 rq = __task_rq_lock(p, &rf); 3650 if (task_on_rq_queued(p)) { 3651 /* check_preempt_curr() may use rq clock */ 3652 update_rq_clock(rq); 3653 ttwu_do_wakeup(rq, p, wake_flags, &rf); 3654 ret = 1; 3655 } 3656 __task_rq_unlock(rq, &rf); 3657 3658 return ret; 3659 } 3660 3661 #ifdef CONFIG_SMP 3662 void sched_ttwu_pending(void *arg) 3663 { 3664 struct llist_node *llist = arg; 3665 struct rq *rq = this_rq(); 3666 struct task_struct *p, *t; 3667 struct rq_flags rf; 3668 3669 if (!llist) 3670 return; 3671 3672 /* 3673 * rq::ttwu_pending racy indication of out-standing wakeups. 3674 * Races such that false-negatives are possible, since they 3675 * are shorter lived that false-positives would be. 3676 */ 3677 WRITE_ONCE(rq->ttwu_pending, 0); 3678 3679 rq_lock_irqsave(rq, &rf); 3680 update_rq_clock(rq); 3681 3682 llist_for_each_entry_safe(p, t, llist, wake_entry.llist) { 3683 if (WARN_ON_ONCE(p->on_cpu)) 3684 smp_cond_load_acquire(&p->on_cpu, !VAL); 3685 3686 if (WARN_ON_ONCE(task_cpu(p) != cpu_of(rq))) 3687 set_task_cpu(p, cpu_of(rq)); 3688 3689 ttwu_do_activate(rq, p, p->sched_remote_wakeup ? WF_MIGRATED : 0, &rf); 3690 } 3691 3692 rq_unlock_irqrestore(rq, &rf); 3693 } 3694 3695 void send_call_function_single_ipi(int cpu) 3696 { 3697 struct rq *rq = cpu_rq(cpu); 3698 3699 if (!set_nr_if_polling(rq->idle)) 3700 arch_send_call_function_single_ipi(cpu); 3701 else 3702 trace_sched_wake_idle_without_ipi(cpu); 3703 } 3704 3705 /* 3706 * Queue a task on the target CPUs wake_list and wake the CPU via IPI if 3707 * necessary. The wakee CPU on receipt of the IPI will queue the task 3708 * via sched_ttwu_wakeup() for activation so the wakee incurs the cost 3709 * of the wakeup instead of the waker. 3710 */ 3711 static void __ttwu_queue_wakelist(struct task_struct *p, int cpu, int wake_flags) 3712 { 3713 struct rq *rq = cpu_rq(cpu); 3714 3715 p->sched_remote_wakeup = !!(wake_flags & WF_MIGRATED); 3716 3717 WRITE_ONCE(rq->ttwu_pending, 1); 3718 __smp_call_single_queue(cpu, &p->wake_entry.llist); 3719 } 3720 3721 void wake_up_if_idle(int cpu) 3722 { 3723 struct rq *rq = cpu_rq(cpu); 3724 struct rq_flags rf; 3725 3726 rcu_read_lock(); 3727 3728 if (!is_idle_task(rcu_dereference(rq->curr))) 3729 goto out; 3730 3731 rq_lock_irqsave(rq, &rf); 3732 if (is_idle_task(rq->curr)) 3733 resched_curr(rq); 3734 /* Else CPU is not idle, do nothing here: */ 3735 rq_unlock_irqrestore(rq, &rf); 3736 3737 out: 3738 rcu_read_unlock(); 3739 } 3740 3741 bool cpus_share_cache(int this_cpu, int that_cpu) 3742 { 3743 if (this_cpu == that_cpu) 3744 return true; 3745 3746 return per_cpu(sd_llc_id, this_cpu) == per_cpu(sd_llc_id, that_cpu); 3747 } 3748 3749 static inline bool ttwu_queue_cond(int cpu, int wake_flags) 3750 { 3751 /* 3752 * Do not complicate things with the async wake_list while the CPU is 3753 * in hotplug state. 3754 */ 3755 if (!cpu_active(cpu)) 3756 return false; 3757 3758 /* 3759 * If the CPU does not share cache, then queue the task on the 3760 * remote rqs wakelist to avoid accessing remote data. 3761 */ 3762 if (!cpus_share_cache(smp_processor_id(), cpu)) 3763 return true; 3764 3765 /* 3766 * If the task is descheduling and the only running task on the 3767 * CPU then use the wakelist to offload the task activation to 3768 * the soon-to-be-idle CPU as the current CPU is likely busy. 3769 * nr_running is checked to avoid unnecessary task stacking. 3770 */ 3771 if ((wake_flags & WF_ON_CPU) && cpu_rq(cpu)->nr_running <= 1) 3772 return true; 3773 3774 return false; 3775 } 3776 3777 static bool ttwu_queue_wakelist(struct task_struct *p, int cpu, int wake_flags) 3778 { 3779 if (sched_feat(TTWU_QUEUE) && ttwu_queue_cond(cpu, wake_flags)) { 3780 if (WARN_ON_ONCE(cpu == smp_processor_id())) 3781 return false; 3782 3783 sched_clock_cpu(cpu); /* Sync clocks across CPUs */ 3784 __ttwu_queue_wakelist(p, cpu, wake_flags); 3785 return true; 3786 } 3787 3788 return false; 3789 } 3790 3791 #else /* !CONFIG_SMP */ 3792 3793 static inline bool ttwu_queue_wakelist(struct task_struct *p, int cpu, int wake_flags) 3794 { 3795 return false; 3796 } 3797 3798 #endif /* CONFIG_SMP */ 3799 3800 static void ttwu_queue(struct task_struct *p, int cpu, int wake_flags) 3801 { 3802 struct rq *rq = cpu_rq(cpu); 3803 struct rq_flags rf; 3804 3805 if (ttwu_queue_wakelist(p, cpu, wake_flags)) 3806 return; 3807 3808 rq_lock(rq, &rf); 3809 update_rq_clock(rq); 3810 ttwu_do_activate(rq, p, wake_flags, &rf); 3811 rq_unlock(rq, &rf); 3812 } 3813 3814 /* 3815 * Invoked from try_to_wake_up() to check whether the task can be woken up. 3816 * 3817 * The caller holds p::pi_lock if p != current or has preemption 3818 * disabled when p == current. 3819 * 3820 * The rules of PREEMPT_RT saved_state: 3821 * 3822 * The related locking code always holds p::pi_lock when updating 3823 * p::saved_state, which means the code is fully serialized in both cases. 3824 * 3825 * The lock wait and lock wakeups happen via TASK_RTLOCK_WAIT. No other 3826 * bits set. This allows to distinguish all wakeup scenarios. 3827 */ 3828 static __always_inline 3829 bool ttwu_state_match(struct task_struct *p, unsigned int state, int *success) 3830 { 3831 if (IS_ENABLED(CONFIG_DEBUG_PREEMPT)) { 3832 WARN_ON_ONCE((state & TASK_RTLOCK_WAIT) && 3833 state != TASK_RTLOCK_WAIT); 3834 } 3835 3836 if (READ_ONCE(p->__state) & state) { 3837 *success = 1; 3838 return true; 3839 } 3840 3841 #ifdef CONFIG_PREEMPT_RT 3842 /* 3843 * Saved state preserves the task state across blocking on 3844 * an RT lock. If the state matches, set p::saved_state to 3845 * TASK_RUNNING, but do not wake the task because it waits 3846 * for a lock wakeup. Also indicate success because from 3847 * the regular waker's point of view this has succeeded. 3848 * 3849 * After acquiring the lock the task will restore p::__state 3850 * from p::saved_state which ensures that the regular 3851 * wakeup is not lost. The restore will also set 3852 * p::saved_state to TASK_RUNNING so any further tests will 3853 * not result in false positives vs. @success 3854 */ 3855 if (p->saved_state & state) { 3856 p->saved_state = TASK_RUNNING; 3857 *success = 1; 3858 } 3859 #endif 3860 return false; 3861 } 3862 3863 /* 3864 * Notes on Program-Order guarantees on SMP systems. 3865 * 3866 * MIGRATION 3867 * 3868 * The basic program-order guarantee on SMP systems is that when a task [t] 3869 * migrates, all its activity on its old CPU [c0] happens-before any subsequent 3870 * execution on its new CPU [c1]. 3871 * 3872 * For migration (of runnable tasks) this is provided by the following means: 3873 * 3874 * A) UNLOCK of the rq(c0)->lock scheduling out task t 3875 * B) migration for t is required to synchronize *both* rq(c0)->lock and 3876 * rq(c1)->lock (if not at the same time, then in that order). 3877 * C) LOCK of the rq(c1)->lock scheduling in task 3878 * 3879 * Release/acquire chaining guarantees that B happens after A and C after B. 3880 * Note: the CPU doing B need not be c0 or c1 3881 * 3882 * Example: 3883 * 3884 * CPU0 CPU1 CPU2 3885 * 3886 * LOCK rq(0)->lock 3887 * sched-out X 3888 * sched-in Y 3889 * UNLOCK rq(0)->lock 3890 * 3891 * LOCK rq(0)->lock // orders against CPU0 3892 * dequeue X 3893 * UNLOCK rq(0)->lock 3894 * 3895 * LOCK rq(1)->lock 3896 * enqueue X 3897 * UNLOCK rq(1)->lock 3898 * 3899 * LOCK rq(1)->lock // orders against CPU2 3900 * sched-out Z 3901 * sched-in X 3902 * UNLOCK rq(1)->lock 3903 * 3904 * 3905 * BLOCKING -- aka. SLEEP + WAKEUP 3906 * 3907 * For blocking we (obviously) need to provide the same guarantee as for 3908 * migration. However the means are completely different as there is no lock 3909 * chain to provide order. Instead we do: 3910 * 3911 * 1) smp_store_release(X->on_cpu, 0) -- finish_task() 3912 * 2) smp_cond_load_acquire(!X->on_cpu) -- try_to_wake_up() 3913 * 3914 * Example: 3915 * 3916 * CPU0 (schedule) CPU1 (try_to_wake_up) CPU2 (schedule) 3917 * 3918 * LOCK rq(0)->lock LOCK X->pi_lock 3919 * dequeue X 3920 * sched-out X 3921 * smp_store_release(X->on_cpu, 0); 3922 * 3923 * smp_cond_load_acquire(&X->on_cpu, !VAL); 3924 * X->state = WAKING 3925 * set_task_cpu(X,2) 3926 * 3927 * LOCK rq(2)->lock 3928 * enqueue X 3929 * X->state = RUNNING 3930 * UNLOCK rq(2)->lock 3931 * 3932 * LOCK rq(2)->lock // orders against CPU1 3933 * sched-out Z 3934 * sched-in X 3935 * UNLOCK rq(2)->lock 3936 * 3937 * UNLOCK X->pi_lock 3938 * UNLOCK rq(0)->lock 3939 * 3940 * 3941 * However, for wakeups there is a second guarantee we must provide, namely we 3942 * must ensure that CONDITION=1 done by the caller can not be reordered with 3943 * accesses to the task state; see try_to_wake_up() and set_current_state(). 3944 */ 3945 3946 /** 3947 * try_to_wake_up - wake up a thread 3948 * @p: the thread to be awakened 3949 * @state: the mask of task states that can be woken 3950 * @wake_flags: wake modifier flags (WF_*) 3951 * 3952 * Conceptually does: 3953 * 3954 * If (@state & @p->state) @p->state = TASK_RUNNING. 3955 * 3956 * If the task was not queued/runnable, also place it back on a runqueue. 3957 * 3958 * This function is atomic against schedule() which would dequeue the task. 3959 * 3960 * It issues a full memory barrier before accessing @p->state, see the comment 3961 * with set_current_state(). 3962 * 3963 * Uses p->pi_lock to serialize against concurrent wake-ups. 3964 * 3965 * Relies on p->pi_lock stabilizing: 3966 * - p->sched_class 3967 * - p->cpus_ptr 3968 * - p->sched_task_group 3969 * in order to do migration, see its use of select_task_rq()/set_task_cpu(). 3970 * 3971 * Tries really hard to only take one task_rq(p)->lock for performance. 3972 * Takes rq->lock in: 3973 * - ttwu_runnable() -- old rq, unavoidable, see comment there; 3974 * - ttwu_queue() -- new rq, for enqueue of the task; 3975 * - psi_ttwu_dequeue() -- much sadness :-( accounting will kill us. 3976 * 3977 * As a consequence we race really badly with just about everything. See the 3978 * many memory barriers and their comments for details. 3979 * 3980 * Return: %true if @p->state changes (an actual wakeup was done), 3981 * %false otherwise. 3982 */ 3983 static int 3984 try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags) 3985 { 3986 unsigned long flags; 3987 int cpu, success = 0; 3988 3989 preempt_disable(); 3990 if (p == current) { 3991 /* 3992 * We're waking current, this means 'p->on_rq' and 'task_cpu(p) 3993 * == smp_processor_id()'. Together this means we can special 3994 * case the whole 'p->on_rq && ttwu_runnable()' case below 3995 * without taking any locks. 3996 * 3997 * In particular: 3998 * - we rely on Program-Order guarantees for all the ordering, 3999 * - we're serialized against set_special_state() by virtue of 4000 * it disabling IRQs (this allows not taking ->pi_lock). 4001 */ 4002 if (!ttwu_state_match(p, state, &success)) 4003 goto out; 4004 4005 trace_sched_waking(p); 4006 WRITE_ONCE(p->__state, TASK_RUNNING); 4007 trace_sched_wakeup(p); 4008 goto out; 4009 } 4010 4011 /* 4012 * If we are going to wake up a thread waiting for CONDITION we 4013 * need to ensure that CONDITION=1 done by the caller can not be 4014 * reordered with p->state check below. This pairs with smp_store_mb() 4015 * in set_current_state() that the waiting thread does. 4016 */ 4017 raw_spin_lock_irqsave(&p->pi_lock, flags); 4018 smp_mb__after_spinlock(); 4019 if (!ttwu_state_match(p, state, &success)) 4020 goto unlock; 4021 4022 trace_sched_waking(p); 4023 4024 /* 4025 * Ensure we load p->on_rq _after_ p->state, otherwise it would 4026 * be possible to, falsely, observe p->on_rq == 0 and get stuck 4027 * in smp_cond_load_acquire() below. 4028 * 4029 * sched_ttwu_pending() try_to_wake_up() 4030 * STORE p->on_rq = 1 LOAD p->state 4031 * UNLOCK rq->lock 4032 * 4033 * __schedule() (switch to task 'p') 4034 * LOCK rq->lock smp_rmb(); 4035 * smp_mb__after_spinlock(); 4036 * UNLOCK rq->lock 4037 * 4038 * [task p] 4039 * STORE p->state = UNINTERRUPTIBLE LOAD p->on_rq 4040 * 4041 * Pairs with the LOCK+smp_mb__after_spinlock() on rq->lock in 4042 * __schedule(). See the comment for smp_mb__after_spinlock(). 4043 * 4044 * A similar smb_rmb() lives in try_invoke_on_locked_down_task(). 4045 */ 4046 smp_rmb(); 4047 if (READ_ONCE(p->on_rq) && ttwu_runnable(p, wake_flags)) 4048 goto unlock; 4049 4050 #ifdef CONFIG_SMP 4051 /* 4052 * Ensure we load p->on_cpu _after_ p->on_rq, otherwise it would be 4053 * possible to, falsely, observe p->on_cpu == 0. 4054 * 4055 * One must be running (->on_cpu == 1) in order to remove oneself 4056 * from the runqueue. 4057 * 4058 * __schedule() (switch to task 'p') try_to_wake_up() 4059 * STORE p->on_cpu = 1 LOAD p->on_rq 4060 * UNLOCK rq->lock 4061 * 4062 * __schedule() (put 'p' to sleep) 4063 * LOCK rq->lock smp_rmb(); 4064 * smp_mb__after_spinlock(); 4065 * STORE p->on_rq = 0 LOAD p->on_cpu 4066 * 4067 * Pairs with the LOCK+smp_mb__after_spinlock() on rq->lock in 4068 * __schedule(). See the comment for smp_mb__after_spinlock(). 4069 * 4070 * Form a control-dep-acquire with p->on_rq == 0 above, to ensure 4071 * schedule()'s deactivate_task() has 'happened' and p will no longer 4072 * care about it's own p->state. See the comment in __schedule(). 4073 */ 4074 smp_acquire__after_ctrl_dep(); 4075 4076 /* 4077 * We're doing the wakeup (@success == 1), they did a dequeue (p->on_rq 4078 * == 0), which means we need to do an enqueue, change p->state to 4079 * TASK_WAKING such that we can unlock p->pi_lock before doing the 4080 * enqueue, such as ttwu_queue_wakelist(). 4081 */ 4082 WRITE_ONCE(p->__state, TASK_WAKING); 4083 4084 /* 4085 * If the owning (remote) CPU is still in the middle of schedule() with 4086 * this task as prev, considering queueing p on the remote CPUs wake_list 4087 * which potentially sends an IPI instead of spinning on p->on_cpu to 4088 * let the waker make forward progress. This is safe because IRQs are 4089 * disabled and the IPI will deliver after on_cpu is cleared. 4090 * 4091 * Ensure we load task_cpu(p) after p->on_cpu: 4092 * 4093 * set_task_cpu(p, cpu); 4094 * STORE p->cpu = @cpu 4095 * __schedule() (switch to task 'p') 4096 * LOCK rq->lock 4097 * smp_mb__after_spin_lock() smp_cond_load_acquire(&p->on_cpu) 4098 * STORE p->on_cpu = 1 LOAD p->cpu 4099 * 4100 * to ensure we observe the correct CPU on which the task is currently 4101 * scheduling. 4102 */ 4103 if (smp_load_acquire(&p->on_cpu) && 4104 ttwu_queue_wakelist(p, task_cpu(p), wake_flags | WF_ON_CPU)) 4105 goto unlock; 4106 4107 /* 4108 * If the owning (remote) CPU is still in the middle of schedule() with 4109 * this task as prev, wait until it's done referencing the task. 4110 * 4111 * Pairs with the smp_store_release() in finish_task(). 4112 * 4113 * This ensures that tasks getting woken will be fully ordered against 4114 * their previous state and preserve Program Order. 4115 */ 4116 smp_cond_load_acquire(&p->on_cpu, !VAL); 4117 4118 cpu = select_task_rq(p, p->wake_cpu, wake_flags | WF_TTWU); 4119 if (task_cpu(p) != cpu) { 4120 if (p->in_iowait) { 4121 delayacct_blkio_end(p); 4122 atomic_dec(&task_rq(p)->nr_iowait); 4123 } 4124 4125 wake_flags |= WF_MIGRATED; 4126 psi_ttwu_dequeue(p); 4127 set_task_cpu(p, cpu); 4128 } 4129 #else 4130 cpu = task_cpu(p); 4131 #endif /* CONFIG_SMP */ 4132 4133 ttwu_queue(p, cpu, wake_flags); 4134 unlock: 4135 raw_spin_unlock_irqrestore(&p->pi_lock, flags); 4136 out: 4137 if (success) 4138 ttwu_stat(p, task_cpu(p), wake_flags); 4139 preempt_enable(); 4140 4141 return success; 4142 } 4143 4144 /** 4145 * task_call_func - Invoke a function on task in fixed state 4146 * @p: Process for which the function is to be invoked, can be @current. 4147 * @func: Function to invoke. 4148 * @arg: Argument to function. 4149 * 4150 * Fix the task in it's current state by avoiding wakeups and or rq operations 4151 * and call @func(@arg) on it. This function can use ->on_rq and task_curr() 4152 * to work out what the state is, if required. Given that @func can be invoked 4153 * with a runqueue lock held, it had better be quite lightweight. 4154 * 4155 * Returns: 4156 * Whatever @func returns 4157 */ 4158 int task_call_func(struct task_struct *p, task_call_f func, void *arg) 4159 { 4160 struct rq *rq = NULL; 4161 unsigned int state; 4162 struct rq_flags rf; 4163 int ret; 4164 4165 raw_spin_lock_irqsave(&p->pi_lock, rf.flags); 4166 4167 state = READ_ONCE(p->__state); 4168 4169 /* 4170 * Ensure we load p->on_rq after p->__state, otherwise it would be 4171 * possible to, falsely, observe p->on_rq == 0. 4172 * 4173 * See try_to_wake_up() for a longer comment. 4174 */ 4175 smp_rmb(); 4176 4177 /* 4178 * Since pi->lock blocks try_to_wake_up(), we don't need rq->lock when 4179 * the task is blocked. Make sure to check @state since ttwu() can drop 4180 * locks at the end, see ttwu_queue_wakelist(). 4181 */ 4182 if (state == TASK_RUNNING || state == TASK_WAKING || p->on_rq) 4183 rq = __task_rq_lock(p, &rf); 4184 4185 /* 4186 * At this point the task is pinned; either: 4187 * - blocked and we're holding off wakeups (pi->lock) 4188 * - woken, and we're holding off enqueue (rq->lock) 4189 * - queued, and we're holding off schedule (rq->lock) 4190 * - running, and we're holding off de-schedule (rq->lock) 4191 * 4192 * The called function (@func) can use: task_curr(), p->on_rq and 4193 * p->__state to differentiate between these states. 4194 */ 4195 ret = func(p, arg); 4196 4197 if (rq) 4198 rq_unlock(rq, &rf); 4199 4200 raw_spin_unlock_irqrestore(&p->pi_lock, rf.flags); 4201 return ret; 4202 } 4203 4204 /** 4205 * wake_up_process - Wake up a specific process 4206 * @p: The process to be woken up. 4207 * 4208 * Attempt to wake up the nominated process and move it to the set of runnable 4209 * processes. 4210 * 4211 * Return: 1 if the process was woken up, 0 if it was already running. 4212 * 4213 * This function executes a full memory barrier before accessing the task state. 4214 */ 4215 int wake_up_process(struct task_struct *p) 4216 { 4217 return try_to_wake_up(p, TASK_NORMAL, 0); 4218 } 4219 EXPORT_SYMBOL(wake_up_process); 4220 4221 int wake_up_state(struct task_struct *p, unsigned int state) 4222 { 4223 return try_to_wake_up(p, state, 0); 4224 } 4225 4226 /* 4227 * Perform scheduler related setup for a newly forked process p. 4228 * p is forked by current. 4229 * 4230 * __sched_fork() is basic setup used by init_idle() too: 4231 */ 4232 static void __sched_fork(unsigned long clone_flags, struct task_struct *p) 4233 { 4234 p->on_rq = 0; 4235 4236 p->se.on_rq = 0; 4237 p->se.exec_start = 0; 4238 p->se.sum_exec_runtime = 0; 4239 p->se.prev_sum_exec_runtime = 0; 4240 p->se.nr_migrations = 0; 4241 p->se.vruntime = 0; 4242 INIT_LIST_HEAD(&p->se.group_node); 4243 4244 #ifdef CONFIG_FAIR_GROUP_SCHED 4245 p->se.cfs_rq = NULL; 4246 #endif 4247 4248 #ifdef CONFIG_SCHEDSTATS 4249 /* Even if schedstat is disabled, there should not be garbage */ 4250 memset(&p->stats, 0, sizeof(p->stats)); 4251 #endif 4252 4253 RB_CLEAR_NODE(&p->dl.rb_node); 4254 init_dl_task_timer(&p->dl); 4255 init_dl_inactive_task_timer(&p->dl); 4256 __dl_clear_params(p); 4257 4258 INIT_LIST_HEAD(&p->rt.run_list); 4259 p->rt.timeout = 0; 4260 p->rt.time_slice = sched_rr_timeslice; 4261 p->rt.on_rq = 0; 4262 p->rt.on_list = 0; 4263 4264 #ifdef CONFIG_PREEMPT_NOTIFIERS 4265 INIT_HLIST_HEAD(&p->preempt_notifiers); 4266 #endif 4267 4268 #ifdef CONFIG_COMPACTION 4269 p->capture_control = NULL; 4270 #endif 4271 init_numa_balancing(clone_flags, p); 4272 #ifdef CONFIG_SMP 4273 p->wake_entry.u_flags = CSD_TYPE_TTWU; 4274 p->migration_pending = NULL; 4275 #endif 4276 } 4277 4278 DEFINE_STATIC_KEY_FALSE(sched_numa_balancing); 4279 4280 #ifdef CONFIG_NUMA_BALANCING 4281 4282 void set_numabalancing_state(bool enabled) 4283 { 4284 if (enabled) 4285 static_branch_enable(&sched_numa_balancing); 4286 else 4287 static_branch_disable(&sched_numa_balancing); 4288 } 4289 4290 #ifdef CONFIG_PROC_SYSCTL 4291 int sysctl_numa_balancing(struct ctl_table *table, int write, 4292 void *buffer, size_t *lenp, loff_t *ppos) 4293 { 4294 struct ctl_table t; 4295 int err; 4296 int state = static_branch_likely(&sched_numa_balancing); 4297 4298 if (write && !capable(CAP_SYS_ADMIN)) 4299 return -EPERM; 4300 4301 t = *table; 4302 t.data = &state; 4303 err = proc_dointvec_minmax(&t, write, buffer, lenp, ppos); 4304 if (err < 0) 4305 return err; 4306 if (write) 4307 set_numabalancing_state(state); 4308 return err; 4309 } 4310 #endif 4311 #endif 4312 4313 #ifdef CONFIG_SCHEDSTATS 4314 4315 DEFINE_STATIC_KEY_FALSE(sched_schedstats); 4316 4317 static void set_schedstats(bool enabled) 4318 { 4319 if (enabled) 4320 static_branch_enable(&sched_schedstats); 4321 else 4322 static_branch_disable(&sched_schedstats); 4323 } 4324 4325 void force_schedstat_enabled(void) 4326 { 4327 if (!schedstat_enabled()) { 4328 pr_info("kernel profiling enabled schedstats, disable via kernel.sched_schedstats.\n"); 4329 static_branch_enable(&sched_schedstats); 4330 } 4331 } 4332 4333 static int __init setup_schedstats(char *str) 4334 { 4335 int ret = 0; 4336 if (!str) 4337 goto out; 4338 4339 if (!strcmp(str, "enable")) { 4340 set_schedstats(true); 4341 ret = 1; 4342 } else if (!strcmp(str, "disable")) { 4343 set_schedstats(false); 4344 ret = 1; 4345 } 4346 out: 4347 if (!ret) 4348 pr_warn("Unable to parse schedstats=\n"); 4349 4350 return ret; 4351 } 4352 __setup("schedstats=", setup_schedstats); 4353 4354 #ifdef CONFIG_PROC_SYSCTL 4355 int sysctl_schedstats(struct ctl_table *table, int write, void *buffer, 4356 size_t *lenp, loff_t *ppos) 4357 { 4358 struct ctl_table t; 4359 int err; 4360 int state = static_branch_likely(&sched_schedstats); 4361 4362 if (write && !capable(CAP_SYS_ADMIN)) 4363 return -EPERM; 4364 4365 t = *table; 4366 t.data = &state; 4367 err = proc_dointvec_minmax(&t, write, buffer, lenp, ppos); 4368 if (err < 0) 4369 return err; 4370 if (write) 4371 set_schedstats(state); 4372 return err; 4373 } 4374 #endif /* CONFIG_PROC_SYSCTL */ 4375 #endif /* CONFIG_SCHEDSTATS */ 4376 4377 /* 4378 * fork()/clone()-time setup: 4379 */ 4380 int sched_fork(unsigned long clone_flags, struct task_struct *p) 4381 { 4382 __sched_fork(clone_flags, p); 4383 /* 4384 * We mark the process as NEW here. This guarantees that 4385 * nobody will actually run it, and a signal or other external 4386 * event cannot wake it up and insert it on the runqueue either. 4387 */ 4388 p->__state = TASK_NEW; 4389 4390 /* 4391 * Make sure we do not leak PI boosting priority to the child. 4392 */ 4393 p->prio = current->normal_prio; 4394 4395 uclamp_fork(p); 4396 4397 /* 4398 * Revert to default priority/policy on fork if requested. 4399 */ 4400 if (unlikely(p->sched_reset_on_fork)) { 4401 if (task_has_dl_policy(p) || task_has_rt_policy(p)) { 4402 p->policy = SCHED_NORMAL; 4403 p->static_prio = NICE_TO_PRIO(0); 4404 p->rt_priority = 0; 4405 } else if (PRIO_TO_NICE(p->static_prio) < 0) 4406 p->static_prio = NICE_TO_PRIO(0); 4407 4408 p->prio = p->normal_prio = p->static_prio; 4409 set_load_weight(p, false); 4410 4411 /* 4412 * We don't need the reset flag anymore after the fork. It has 4413 * fulfilled its duty: 4414 */ 4415 p->sched_reset_on_fork = 0; 4416 } 4417 4418 if (dl_prio(p->prio)) 4419 return -EAGAIN; 4420 else if (rt_prio(p->prio)) 4421 p->sched_class = &rt_sched_class; 4422 else 4423 p->sched_class = &fair_sched_class; 4424 4425 init_entity_runnable_average(&p->se); 4426 4427 #ifdef CONFIG_SCHED_INFO 4428 if (likely(sched_info_on())) 4429 memset(&p->sched_info, 0, sizeof(p->sched_info)); 4430 #endif 4431 #if defined(CONFIG_SMP) 4432 p->on_cpu = 0; 4433 #endif 4434 init_task_preempt_count(p); 4435 #ifdef CONFIG_SMP 4436 plist_node_init(&p->pushable_tasks, MAX_PRIO); 4437 RB_CLEAR_NODE(&p->pushable_dl_tasks); 4438 #endif 4439 return 0; 4440 } 4441 4442 void sched_post_fork(struct task_struct *p, struct kernel_clone_args *kargs) 4443 { 4444 unsigned long flags; 4445 #ifdef CONFIG_CGROUP_SCHED 4446 struct task_group *tg; 4447 #endif 4448 4449 raw_spin_lock_irqsave(&p->pi_lock, flags); 4450 #ifdef CONFIG_CGROUP_SCHED 4451 tg = container_of(kargs->cset->subsys[cpu_cgrp_id], 4452 struct task_group, css); 4453 p->sched_task_group = autogroup_task_group(p, tg); 4454 #endif 4455 rseq_migrate(p); 4456 /* 4457 * We're setting the CPU for the first time, we don't migrate, 4458 * so use __set_task_cpu(). 4459 */ 4460 __set_task_cpu(p, smp_processor_id()); 4461 if (p->sched_class->task_fork) 4462 p->sched_class->task_fork(p); 4463 raw_spin_unlock_irqrestore(&p->pi_lock, flags); 4464 4465 uclamp_post_fork(p); 4466 } 4467 4468 unsigned long to_ratio(u64 period, u64 runtime) 4469 { 4470 if (runtime == RUNTIME_INF) 4471 return BW_UNIT; 4472 4473 /* 4474 * Doing this here saves a lot of checks in all 4475 * the calling paths, and returning zero seems 4476 * safe for them anyway. 4477 */ 4478 if (period == 0) 4479 return 0; 4480 4481 return div64_u64(runtime << BW_SHIFT, period); 4482 } 4483 4484 /* 4485 * wake_up_new_task - wake up a newly created task for the first time. 4486 * 4487 * This function will do some initial scheduler statistics housekeeping 4488 * that must be done for every newly created context, then puts the task 4489 * on the runqueue and wakes it. 4490 */ 4491 void wake_up_new_task(struct task_struct *p) 4492 { 4493 struct rq_flags rf; 4494 struct rq *rq; 4495 4496 raw_spin_lock_irqsave(&p->pi_lock, rf.flags); 4497 WRITE_ONCE(p->__state, TASK_RUNNING); 4498 #ifdef CONFIG_SMP 4499 /* 4500 * Fork balancing, do it here and not earlier because: 4501 * - cpus_ptr can change in the fork path 4502 * - any previously selected CPU might disappear through hotplug 4503 * 4504 * Use __set_task_cpu() to avoid calling sched_class::migrate_task_rq, 4505 * as we're not fully set-up yet. 4506 */ 4507 p->recent_used_cpu = task_cpu(p); 4508 rseq_migrate(p); 4509 __set_task_cpu(p, select_task_rq(p, task_cpu(p), WF_FORK)); 4510 #endif 4511 rq = __task_rq_lock(p, &rf); 4512 update_rq_clock(rq); 4513 post_init_entity_util_avg(p); 4514 4515 activate_task(rq, p, ENQUEUE_NOCLOCK); 4516 trace_sched_wakeup_new(p); 4517 check_preempt_curr(rq, p, WF_FORK); 4518 #ifdef CONFIG_SMP 4519 if (p->sched_class->task_woken) { 4520 /* 4521 * Nothing relies on rq->lock after this, so it's fine to 4522 * drop it. 4523 */ 4524 rq_unpin_lock(rq, &rf); 4525 p->sched_class->task_woken(rq, p); 4526 rq_repin_lock(rq, &rf); 4527 } 4528 #endif 4529 task_rq_unlock(rq, p, &rf); 4530 } 4531 4532 #ifdef CONFIG_PREEMPT_NOTIFIERS 4533 4534 static DEFINE_STATIC_KEY_FALSE(preempt_notifier_key); 4535 4536 void preempt_notifier_inc(void) 4537 { 4538 static_branch_inc(&preempt_notifier_key); 4539 } 4540 EXPORT_SYMBOL_GPL(preempt_notifier_inc); 4541 4542 void preempt_notifier_dec(void) 4543 { 4544 static_branch_dec(&preempt_notifier_key); 4545 } 4546 EXPORT_SYMBOL_GPL(preempt_notifier_dec); 4547 4548 /** 4549 * preempt_notifier_register - tell me when current is being preempted & rescheduled 4550 * @notifier: notifier struct to register 4551 */ 4552 void preempt_notifier_register(struct preempt_notifier *notifier) 4553 { 4554 if (!static_branch_unlikely(&preempt_notifier_key)) 4555 WARN(1, "registering preempt_notifier while notifiers disabled\n"); 4556 4557 hlist_add_head(¬ifier->link, ¤t->preempt_notifiers); 4558 } 4559 EXPORT_SYMBOL_GPL(preempt_notifier_register); 4560 4561 /** 4562 * preempt_notifier_unregister - no longer interested in preemption notifications 4563 * @notifier: notifier struct to unregister 4564 * 4565 * This is *not* safe to call from within a preemption notifier. 4566 */ 4567 void preempt_notifier_unregister(struct preempt_notifier *notifier) 4568 { 4569 hlist_del(¬ifier->link); 4570 } 4571 EXPORT_SYMBOL_GPL(preempt_notifier_unregister); 4572 4573 static void __fire_sched_in_preempt_notifiers(struct task_struct *curr) 4574 { 4575 struct preempt_notifier *notifier; 4576 4577 hlist_for_each_entry(notifier, &curr->preempt_notifiers, link) 4578 notifier->ops->sched_in(notifier, raw_smp_processor_id()); 4579 } 4580 4581 static __always_inline void fire_sched_in_preempt_notifiers(struct task_struct *curr) 4582 { 4583 if (static_branch_unlikely(&preempt_notifier_key)) 4584 __fire_sched_in_preempt_notifiers(curr); 4585 } 4586 4587 static void 4588 __fire_sched_out_preempt_notifiers(struct task_struct *curr, 4589 struct task_struct *next) 4590 { 4591 struct preempt_notifier *notifier; 4592 4593 hlist_for_each_entry(notifier, &curr->preempt_notifiers, link) 4594 notifier->ops->sched_out(notifier, next); 4595 } 4596 4597 static __always_inline void 4598 fire_sched_out_preempt_notifiers(struct task_struct *curr, 4599 struct task_struct *next) 4600 { 4601 if (static_branch_unlikely(&preempt_notifier_key)) 4602 __fire_sched_out_preempt_notifiers(curr, next); 4603 } 4604 4605 #else /* !CONFIG_PREEMPT_NOTIFIERS */ 4606 4607 static inline void fire_sched_in_preempt_notifiers(struct task_struct *curr) 4608 { 4609 } 4610 4611 static inline void 4612 fire_sched_out_preempt_notifiers(struct task_struct *curr, 4613 struct task_struct *next) 4614 { 4615 } 4616 4617 #endif /* CONFIG_PREEMPT_NOTIFIERS */ 4618 4619 static inline void prepare_task(struct task_struct *next) 4620 { 4621 #ifdef CONFIG_SMP 4622 /* 4623 * Claim the task as running, we do this before switching to it 4624 * such that any running task will have this set. 4625 * 4626 * See the ttwu() WF_ON_CPU case and its ordering comment. 4627 */ 4628 WRITE_ONCE(next->on_cpu, 1); 4629 #endif 4630 } 4631 4632 static inline void finish_task(struct task_struct *prev) 4633 { 4634 #ifdef CONFIG_SMP 4635 /* 4636 * This must be the very last reference to @prev from this CPU. After 4637 * p->on_cpu is cleared, the task can be moved to a different CPU. We 4638 * must ensure this doesn't happen until the switch is completely 4639 * finished. 4640 * 4641 * In particular, the load of prev->state in finish_task_switch() must 4642 * happen before this. 4643 * 4644 * Pairs with the smp_cond_load_acquire() in try_to_wake_up(). 4645 */ 4646 smp_store_release(&prev->on_cpu, 0); 4647 #endif 4648 } 4649 4650 #ifdef CONFIG_SMP 4651 4652 static void do_balance_callbacks(struct rq *rq, struct callback_head *head) 4653 { 4654 void (*func)(struct rq *rq); 4655 struct callback_head *next; 4656 4657 lockdep_assert_rq_held(rq); 4658 4659 while (head) { 4660 func = (void (*)(struct rq *))head->func; 4661 next = head->next; 4662 head->next = NULL; 4663 head = next; 4664 4665 func(rq); 4666 } 4667 } 4668 4669 static void balance_push(struct rq *rq); 4670 4671 struct callback_head balance_push_callback = { 4672 .next = NULL, 4673 .func = (void (*)(struct callback_head *))balance_push, 4674 }; 4675 4676 static inline struct callback_head *splice_balance_callbacks(struct rq *rq) 4677 { 4678 struct callback_head *head = rq->balance_callback; 4679 4680 lockdep_assert_rq_held(rq); 4681 if (head) 4682 rq->balance_callback = NULL; 4683 4684 return head; 4685 } 4686 4687 static void __balance_callbacks(struct rq *rq) 4688 { 4689 do_balance_callbacks(rq, splice_balance_callbacks(rq)); 4690 } 4691 4692 static inline void balance_callbacks(struct rq *rq, struct callback_head *head) 4693 { 4694 unsigned long flags; 4695 4696 if (unlikely(head)) { 4697 raw_spin_rq_lock_irqsave(rq, flags); 4698 do_balance_callbacks(rq, head); 4699 raw_spin_rq_unlock_irqrestore(rq, flags); 4700 } 4701 } 4702 4703 #else 4704 4705 static inline void __balance_callbacks(struct rq *rq) 4706 { 4707 } 4708 4709 static inline struct callback_head *splice_balance_callbacks(struct rq *rq) 4710 { 4711 return NULL; 4712 } 4713 4714 static inline void balance_callbacks(struct rq *rq, struct callback_head *head) 4715 { 4716 } 4717 4718 #endif 4719 4720 static inline void 4721 prepare_lock_switch(struct rq *rq, struct task_struct *next, struct rq_flags *rf) 4722 { 4723 /* 4724 * Since the runqueue lock will be released by the next 4725 * task (which is an invalid locking op but in the case 4726 * of the scheduler it's an obvious special-case), so we 4727 * do an early lockdep release here: 4728 */ 4729 rq_unpin_lock(rq, rf); 4730 spin_release(&__rq_lockp(rq)->dep_map, _THIS_IP_); 4731 #ifdef CONFIG_DEBUG_SPINLOCK 4732 /* this is a valid case when another task releases the spinlock */ 4733 rq_lockp(rq)->owner = next; 4734 #endif 4735 } 4736 4737 static inline void finish_lock_switch(struct rq *rq) 4738 { 4739 /* 4740 * If we are tracking spinlock dependencies then we have to 4741 * fix up the runqueue lock - which gets 'carried over' from 4742 * prev into current: 4743 */ 4744 spin_acquire(&__rq_lockp(rq)->dep_map, 0, 0, _THIS_IP_); 4745 __balance_callbacks(rq); 4746 raw_spin_rq_unlock_irq(rq); 4747 } 4748 4749 /* 4750 * NOP if the arch has not defined these: 4751 */ 4752 4753 #ifndef prepare_arch_switch 4754 # define prepare_arch_switch(next) do { } while (0) 4755 #endif 4756 4757 #ifndef finish_arch_post_lock_switch 4758 # define finish_arch_post_lock_switch() do { } while (0) 4759 #endif 4760 4761 static inline void kmap_local_sched_out(void) 4762 { 4763 #ifdef CONFIG_KMAP_LOCAL 4764 if (unlikely(current->kmap_ctrl.idx)) 4765 __kmap_local_sched_out(); 4766 #endif 4767 } 4768 4769 static inline void kmap_local_sched_in(void) 4770 { 4771 #ifdef CONFIG_KMAP_LOCAL 4772 if (unlikely(current->kmap_ctrl.idx)) 4773 __kmap_local_sched_in(); 4774 #endif 4775 } 4776 4777 /** 4778 * prepare_task_switch - prepare to switch tasks 4779 * @rq: the runqueue preparing to switch 4780 * @prev: the current task that is being switched out 4781 * @next: the task we are going to switch to. 4782 * 4783 * This is called with the rq lock held and interrupts off. It must 4784 * be paired with a subsequent finish_task_switch after the context 4785 * switch. 4786 * 4787 * prepare_task_switch sets up locking and calls architecture specific 4788 * hooks. 4789 */ 4790 static inline void 4791 prepare_task_switch(struct rq *rq, struct task_struct *prev, 4792 struct task_struct *next) 4793 { 4794 kcov_prepare_switch(prev); 4795 sched_info_switch(rq, prev, next); 4796 perf_event_task_sched_out(prev, next); 4797 rseq_preempt(prev); 4798 fire_sched_out_preempt_notifiers(prev, next); 4799 kmap_local_sched_out(); 4800 prepare_task(next); 4801 prepare_arch_switch(next); 4802 } 4803 4804 /** 4805 * finish_task_switch - clean up after a task-switch 4806 * @prev: the thread we just switched away from. 4807 * 4808 * finish_task_switch must be called after the context switch, paired 4809 * with a prepare_task_switch call before the context switch. 4810 * finish_task_switch will reconcile locking set up by prepare_task_switch, 4811 * and do any other architecture-specific cleanup actions. 4812 * 4813 * Note that we may have delayed dropping an mm in context_switch(). If 4814 * so, we finish that here outside of the runqueue lock. (Doing it 4815 * with the lock held can cause deadlocks; see schedule() for 4816 * details.) 4817 * 4818 * The context switch have flipped the stack from under us and restored the 4819 * local variables which were saved when this task called schedule() in the 4820 * past. prev == current is still correct but we need to recalculate this_rq 4821 * because prev may have moved to another CPU. 4822 */ 4823 static struct rq *finish_task_switch(struct task_struct *prev) 4824 __releases(rq->lock) 4825 { 4826 struct rq *rq = this_rq(); 4827 struct mm_struct *mm = rq->prev_mm; 4828 long prev_state; 4829 4830 /* 4831 * The previous task will have left us with a preempt_count of 2 4832 * because it left us after: 4833 * 4834 * schedule() 4835 * preempt_disable(); // 1 4836 * __schedule() 4837 * raw_spin_lock_irq(&rq->lock) // 2 4838 * 4839 * Also, see FORK_PREEMPT_COUNT. 4840 */ 4841 if (WARN_ONCE(preempt_count() != 2*PREEMPT_DISABLE_OFFSET, 4842 "corrupted preempt_count: %s/%d/0x%x\n", 4843 current->comm, current->pid, preempt_count())) 4844 preempt_count_set(FORK_PREEMPT_COUNT); 4845 4846 rq->prev_mm = NULL; 4847 4848 /* 4849 * A task struct has one reference for the use as "current". 4850 * If a task dies, then it sets TASK_DEAD in tsk->state and calls 4851 * schedule one last time. The schedule call will never return, and 4852 * the scheduled task must drop that reference. 4853 * 4854 * We must observe prev->state before clearing prev->on_cpu (in 4855 * finish_task), otherwise a concurrent wakeup can get prev 4856 * running on another CPU and we could rave with its RUNNING -> DEAD 4857 * transition, resulting in a double drop. 4858 */ 4859 prev_state = READ_ONCE(prev->__state); 4860 vtime_task_switch(prev); 4861 perf_event_task_sched_in(prev, current); 4862 finish_task(prev); 4863 tick_nohz_task_switch(); 4864 finish_lock_switch(rq); 4865 finish_arch_post_lock_switch(); 4866 kcov_finish_switch(current); 4867 /* 4868 * kmap_local_sched_out() is invoked with rq::lock held and 4869 * interrupts disabled. There is no requirement for that, but the 4870 * sched out code does not have an interrupt enabled section. 4871 * Restoring the maps on sched in does not require interrupts being 4872 * disabled either. 4873 */ 4874 kmap_local_sched_in(); 4875 4876 fire_sched_in_preempt_notifiers(current); 4877 /* 4878 * When switching through a kernel thread, the loop in 4879 * membarrier_{private,global}_expedited() may have observed that 4880 * kernel thread and not issued an IPI. It is therefore possible to 4881 * schedule between user->kernel->user threads without passing though 4882 * switch_mm(). Membarrier requires a barrier after storing to 4883 * rq->curr, before returning to userspace, so provide them here: 4884 * 4885 * - a full memory barrier for {PRIVATE,GLOBAL}_EXPEDITED, implicitly 4886 * provided by mmdrop(), 4887 * - a sync_core for SYNC_CORE. 4888 */ 4889 if (mm) { 4890 membarrier_mm_sync_core_before_usermode(mm); 4891 mmdrop_sched(mm); 4892 } 4893 if (unlikely(prev_state == TASK_DEAD)) { 4894 if (prev->sched_class->task_dead) 4895 prev->sched_class->task_dead(prev); 4896 4897 /* Task is done with its stack. */ 4898 put_task_stack(prev); 4899 4900 put_task_struct_rcu_user(prev); 4901 } 4902 4903 return rq; 4904 } 4905 4906 /** 4907 * schedule_tail - first thing a freshly forked thread must call. 4908 * @prev: the thread we just switched away from. 4909 */ 4910 asmlinkage __visible void schedule_tail(struct task_struct *prev) 4911 __releases(rq->lock) 4912 { 4913 /* 4914 * New tasks start with FORK_PREEMPT_COUNT, see there and 4915 * finish_task_switch() for details. 4916 * 4917 * finish_task_switch() will drop rq->lock() and lower preempt_count 4918 * and the preempt_enable() will end up enabling preemption (on 4919 * PREEMPT_COUNT kernels). 4920 */ 4921 4922 finish_task_switch(prev); 4923 preempt_enable(); 4924 4925 if (current->set_child_tid) 4926 put_user(task_pid_vnr(current), current->set_child_tid); 4927 4928 calculate_sigpending(); 4929 } 4930 4931 /* 4932 * context_switch - switch to the new MM and the new thread's register state. 4933 */ 4934 static __always_inline struct rq * 4935 context_switch(struct rq *rq, struct task_struct *prev, 4936 struct task_struct *next, struct rq_flags *rf) 4937 { 4938 prepare_task_switch(rq, prev, next); 4939 4940 /* 4941 * For paravirt, this is coupled with an exit in switch_to to 4942 * combine the page table reload and the switch backend into 4943 * one hypercall. 4944 */ 4945 arch_start_context_switch(prev); 4946 4947 /* 4948 * kernel -> kernel lazy + transfer active 4949 * user -> kernel lazy + mmgrab() active 4950 * 4951 * kernel -> user switch + mmdrop() active 4952 * user -> user switch 4953 */ 4954 if (!next->mm) { // to kernel 4955 enter_lazy_tlb(prev->active_mm, next); 4956 4957 next->active_mm = prev->active_mm; 4958 if (prev->mm) // from user 4959 mmgrab(prev->active_mm); 4960 else 4961 prev->active_mm = NULL; 4962 } else { // to user 4963 membarrier_switch_mm(rq, prev->active_mm, next->mm); 4964 /* 4965 * sys_membarrier() requires an smp_mb() between setting 4966 * rq->curr / membarrier_switch_mm() and returning to userspace. 4967 * 4968 * The below provides this either through switch_mm(), or in 4969 * case 'prev->active_mm == next->mm' through 4970 * finish_task_switch()'s mmdrop(). 4971 */ 4972 switch_mm_irqs_off(prev->active_mm, next->mm, next); 4973 4974 if (!prev->mm) { // from kernel 4975 /* will mmdrop() in finish_task_switch(). */ 4976 rq->prev_mm = prev->active_mm; 4977 prev->active_mm = NULL; 4978 } 4979 } 4980 4981 rq->clock_update_flags &= ~(RQCF_ACT_SKIP|RQCF_REQ_SKIP); 4982 4983 prepare_lock_switch(rq, next, rf); 4984 4985 /* Here we just switch the register state and the stack. */ 4986 switch_to(prev, next, prev); 4987 barrier(); 4988 4989 return finish_task_switch(prev); 4990 } 4991 4992 /* 4993 * nr_running and nr_context_switches: 4994 * 4995 * externally visible scheduler statistics: current number of runnable 4996 * threads, total number of context switches performed since bootup. 4997 */ 4998 unsigned int nr_running(void) 4999 { 5000 unsigned int i, sum = 0; 5001 5002 for_each_online_cpu(i) 5003 sum += cpu_rq(i)->nr_running; 5004 5005 return sum; 5006 } 5007 5008 /* 5009 * Check if only the current task is running on the CPU. 5010 * 5011 * Caution: this function does not check that the caller has disabled 5012 * preemption, thus the result might have a time-of-check-to-time-of-use 5013 * race. The caller is responsible to use it correctly, for example: 5014 * 5015 * - from a non-preemptible section (of course) 5016 * 5017 * - from a thread that is bound to a single CPU 5018 * 5019 * - in a loop with very short iterations (e.g. a polling loop) 5020 */ 5021 bool single_task_running(void) 5022 { 5023 return raw_rq()->nr_running == 1; 5024 } 5025 EXPORT_SYMBOL(single_task_running); 5026 5027 unsigned long long nr_context_switches(void) 5028 { 5029 int i; 5030 unsigned long long sum = 0; 5031 5032 for_each_possible_cpu(i) 5033 sum += cpu_rq(i)->nr_switches; 5034 5035 return sum; 5036 } 5037 5038 /* 5039 * Consumers of these two interfaces, like for example the cpuidle menu 5040 * governor, are using nonsensical data. Preferring shallow idle state selection 5041 * for a CPU that has IO-wait which might not even end up running the task when 5042 * it does become runnable. 5043 */ 5044 5045 unsigned int nr_iowait_cpu(int cpu) 5046 { 5047 return atomic_read(&cpu_rq(cpu)->nr_iowait); 5048 } 5049 5050 /* 5051 * IO-wait accounting, and how it's mostly bollocks (on SMP). 5052 * 5053 * The idea behind IO-wait account is to account the idle time that we could 5054 * have spend running if it were not for IO. That is, if we were to improve the 5055 * storage performance, we'd have a proportional reduction in IO-wait time. 5056 * 5057 * This all works nicely on UP, where, when a task blocks on IO, we account 5058 * idle time as IO-wait, because if the storage were faster, it could've been 5059 * running and we'd not be idle. 5060 * 5061 * This has been extended to SMP, by doing the same for each CPU. This however 5062 * is broken. 5063 * 5064 * Imagine for instance the case where two tasks block on one CPU, only the one 5065 * CPU will have IO-wait accounted, while the other has regular idle. Even 5066 * though, if the storage were faster, both could've ran at the same time, 5067 * utilising both CPUs. 5068 * 5069 * This means, that when looking globally, the current IO-wait accounting on 5070 * SMP is a lower bound, by reason of under accounting. 5071 * 5072 * Worse, since the numbers are provided per CPU, they are sometimes 5073 * interpreted per CPU, and that is nonsensical. A blocked task isn't strictly 5074 * associated with any one particular CPU, it can wake to another CPU than it 5075 * blocked on. This means the per CPU IO-wait number is meaningless. 5076 * 5077 * Task CPU affinities can make all that even more 'interesting'. 5078 */ 5079 5080 unsigned int nr_iowait(void) 5081 { 5082 unsigned int i, sum = 0; 5083 5084 for_each_possible_cpu(i) 5085 sum += nr_iowait_cpu(i); 5086 5087 return sum; 5088 } 5089 5090 #ifdef CONFIG_SMP 5091 5092 /* 5093 * sched_exec - execve() is a valuable balancing opportunity, because at 5094 * this point the task has the smallest effective memory and cache footprint. 5095 */ 5096 void sched_exec(void) 5097 { 5098 struct task_struct *p = current; 5099 unsigned long flags; 5100 int dest_cpu; 5101 5102 raw_spin_lock_irqsave(&p->pi_lock, flags); 5103 dest_cpu = p->sched_class->select_task_rq(p, task_cpu(p), WF_EXEC); 5104 if (dest_cpu == smp_processor_id()) 5105 goto unlock; 5106 5107 if (likely(cpu_active(dest_cpu))) { 5108 struct migration_arg arg = { p, dest_cpu }; 5109 5110 raw_spin_unlock_irqrestore(&p->pi_lock, flags); 5111 stop_one_cpu(task_cpu(p), migration_cpu_stop, &arg); 5112 return; 5113 } 5114 unlock: 5115 raw_spin_unlock_irqrestore(&p->pi_lock, flags); 5116 } 5117 5118 #endif 5119 5120 DEFINE_PER_CPU(struct kernel_stat, kstat); 5121 DEFINE_PER_CPU(struct kernel_cpustat, kernel_cpustat); 5122 5123 EXPORT_PER_CPU_SYMBOL(kstat); 5124 EXPORT_PER_CPU_SYMBOL(kernel_cpustat); 5125 5126 /* 5127 * The function fair_sched_class.update_curr accesses the struct curr 5128 * and its field curr->exec_start; when called from task_sched_runtime(), 5129 * we observe a high rate of cache misses in practice. 5130 * Prefetching this data results in improved performance. 5131 */ 5132 static inline void prefetch_curr_exec_start(struct task_struct *p) 5133 { 5134 #ifdef CONFIG_FAIR_GROUP_SCHED 5135 struct sched_entity *curr = (&p->se)->cfs_rq->curr; 5136 #else 5137 struct sched_entity *curr = (&task_rq(p)->cfs)->curr; 5138 #endif 5139 prefetch(curr); 5140 prefetch(&curr->exec_start); 5141 } 5142 5143 /* 5144 * Return accounted runtime for the task. 5145 * In case the task is currently running, return the runtime plus current's 5146 * pending runtime that have not been accounted yet. 5147 */ 5148 unsigned long long task_sched_runtime(struct task_struct *p) 5149 { 5150 struct rq_flags rf; 5151 struct rq *rq; 5152 u64 ns; 5153 5154 #if defined(CONFIG_64BIT) && defined(CONFIG_SMP) 5155 /* 5156 * 64-bit doesn't need locks to atomically read a 64-bit value. 5157 * So we have a optimization chance when the task's delta_exec is 0. 5158 * Reading ->on_cpu is racy, but this is ok. 5159 * 5160 * If we race with it leaving CPU, we'll take a lock. So we're correct. 5161 * If we race with it entering CPU, unaccounted time is 0. This is 5162 * indistinguishable from the read occurring a few cycles earlier. 5163 * If we see ->on_cpu without ->on_rq, the task is leaving, and has 5164 * been accounted, so we're correct here as well. 5165 */ 5166 if (!p->on_cpu || !task_on_rq_queued(p)) 5167 return p->se.sum_exec_runtime; 5168 #endif 5169 5170 rq = task_rq_lock(p, &rf); 5171 /* 5172 * Must be ->curr _and_ ->on_rq. If dequeued, we would 5173 * project cycles that may never be accounted to this 5174 * thread, breaking clock_gettime(). 5175 */ 5176 if (task_current(rq, p) && task_on_rq_queued(p)) { 5177 prefetch_curr_exec_start(p); 5178 update_rq_clock(rq); 5179 p->sched_class->update_curr(rq); 5180 } 5181 ns = p->se.sum_exec_runtime; 5182 task_rq_unlock(rq, p, &rf); 5183 5184 return ns; 5185 } 5186 5187 #ifdef CONFIG_SCHED_DEBUG 5188 static u64 cpu_resched_latency(struct rq *rq) 5189 { 5190 int latency_warn_ms = READ_ONCE(sysctl_resched_latency_warn_ms); 5191 u64 resched_latency, now = rq_clock(rq); 5192 static bool warned_once; 5193 5194 if (sysctl_resched_latency_warn_once && warned_once) 5195 return 0; 5196 5197 if (!need_resched() || !latency_warn_ms) 5198 return 0; 5199 5200 if (system_state == SYSTEM_BOOTING) 5201 return 0; 5202 5203 if (!rq->last_seen_need_resched_ns) { 5204 rq->last_seen_need_resched_ns = now; 5205 rq->ticks_without_resched = 0; 5206 return 0; 5207 } 5208 5209 rq->ticks_without_resched++; 5210 resched_latency = now - rq->last_seen_need_resched_ns; 5211 if (resched_latency <= latency_warn_ms * NSEC_PER_MSEC) 5212 return 0; 5213 5214 warned_once = true; 5215 5216 return resched_latency; 5217 } 5218 5219 static int __init setup_resched_latency_warn_ms(char *str) 5220 { 5221 long val; 5222 5223 if ((kstrtol(str, 0, &val))) { 5224 pr_warn("Unable to set resched_latency_warn_ms\n"); 5225 return 1; 5226 } 5227 5228 sysctl_resched_latency_warn_ms = val; 5229 return 1; 5230 } 5231 __setup("resched_latency_warn_ms=", setup_resched_latency_warn_ms); 5232 #else 5233 static inline u64 cpu_resched_latency(struct rq *rq) { return 0; } 5234 #endif /* CONFIG_SCHED_DEBUG */ 5235 5236 /* 5237 * This function gets called by the timer code, with HZ frequency. 5238 * We call it with interrupts disabled. 5239 */ 5240 void scheduler_tick(void) 5241 { 5242 int cpu = smp_processor_id(); 5243 struct rq *rq = cpu_rq(cpu); 5244 struct task_struct *curr = rq->curr; 5245 struct rq_flags rf; 5246 unsigned long thermal_pressure; 5247 u64 resched_latency; 5248 5249 arch_scale_freq_tick(); 5250 sched_clock_tick(); 5251 5252 rq_lock(rq, &rf); 5253 5254 update_rq_clock(rq); 5255 thermal_pressure = arch_scale_thermal_pressure(cpu_of(rq)); 5256 update_thermal_load_avg(rq_clock_thermal(rq), rq, thermal_pressure); 5257 curr->sched_class->task_tick(rq, curr, 0); 5258 if (sched_feat(LATENCY_WARN)) 5259 resched_latency = cpu_resched_latency(rq); 5260 calc_global_load_tick(rq); 5261 sched_core_tick(rq); 5262 5263 rq_unlock(rq, &rf); 5264 5265 if (sched_feat(LATENCY_WARN) && resched_latency) 5266 resched_latency_warn(cpu, resched_latency); 5267 5268 perf_event_task_tick(); 5269 5270 #ifdef CONFIG_SMP 5271 rq->idle_balance = idle_cpu(cpu); 5272 trigger_load_balance(rq); 5273 #endif 5274 } 5275 5276 #ifdef CONFIG_NO_HZ_FULL 5277 5278 struct tick_work { 5279 int cpu; 5280 atomic_t state; 5281 struct delayed_work work; 5282 }; 5283 /* Values for ->state, see diagram below. */ 5284 #define TICK_SCHED_REMOTE_OFFLINE 0 5285 #define TICK_SCHED_REMOTE_OFFLINING 1 5286 #define TICK_SCHED_REMOTE_RUNNING 2 5287 5288 /* 5289 * State diagram for ->state: 5290 * 5291 * 5292 * TICK_SCHED_REMOTE_OFFLINE 5293 * | ^ 5294 * | | 5295 * | | sched_tick_remote() 5296 * | | 5297 * | | 5298 * +--TICK_SCHED_REMOTE_OFFLINING 5299 * | ^ 5300 * | | 5301 * sched_tick_start() | | sched_tick_stop() 5302 * | | 5303 * V | 5304 * TICK_SCHED_REMOTE_RUNNING 5305 * 5306 * 5307 * Other transitions get WARN_ON_ONCE(), except that sched_tick_remote() 5308 * and sched_tick_start() are happy to leave the state in RUNNING. 5309 */ 5310 5311 static struct tick_work __percpu *tick_work_cpu; 5312 5313 static void sched_tick_remote(struct work_struct *work) 5314 { 5315 struct delayed_work *dwork = to_delayed_work(work); 5316 struct tick_work *twork = container_of(dwork, struct tick_work, work); 5317 int cpu = twork->cpu; 5318 struct rq *rq = cpu_rq(cpu); 5319 struct task_struct *curr; 5320 struct rq_flags rf; 5321 u64 delta; 5322 int os; 5323 5324 /* 5325 * Handle the tick only if it appears the remote CPU is running in full 5326 * dynticks mode. The check is racy by nature, but missing a tick or 5327 * having one too much is no big deal because the scheduler tick updates 5328 * statistics and checks timeslices in a time-independent way, regardless 5329 * of when exactly it is running. 5330 */ 5331 if (!tick_nohz_tick_stopped_cpu(cpu)) 5332 goto out_requeue; 5333 5334 rq_lock_irq(rq, &rf); 5335 curr = rq->curr; 5336 if (cpu_is_offline(cpu)) 5337 goto out_unlock; 5338 5339 update_rq_clock(rq); 5340 5341 if (!is_idle_task(curr)) { 5342 /* 5343 * Make sure the next tick runs within a reasonable 5344 * amount of time. 5345 */ 5346 delta = rq_clock_task(rq) - curr->se.exec_start; 5347 WARN_ON_ONCE(delta > (u64)NSEC_PER_SEC * 3); 5348 } 5349 curr->sched_class->task_tick(rq, curr, 0); 5350 5351 calc_load_nohz_remote(rq); 5352 out_unlock: 5353 rq_unlock_irq(rq, &rf); 5354 out_requeue: 5355 5356 /* 5357 * Run the remote tick once per second (1Hz). This arbitrary 5358 * frequency is large enough to avoid overload but short enough 5359 * to keep scheduler internal stats reasonably up to date. But 5360 * first update state to reflect hotplug activity if required. 5361 */ 5362 os = atomic_fetch_add_unless(&twork->state, -1, TICK_SCHED_REMOTE_RUNNING); 5363 WARN_ON_ONCE(os == TICK_SCHED_REMOTE_OFFLINE); 5364 if (os == TICK_SCHED_REMOTE_RUNNING) 5365 queue_delayed_work(system_unbound_wq, dwork, HZ); 5366 } 5367 5368 static void sched_tick_start(int cpu) 5369 { 5370 int os; 5371 struct tick_work *twork; 5372 5373 if (housekeeping_cpu(cpu, HK_FLAG_TICK)) 5374 return; 5375 5376 WARN_ON_ONCE(!tick_work_cpu); 5377 5378 twork = per_cpu_ptr(tick_work_cpu, cpu); 5379 os = atomic_xchg(&twork->state, TICK_SCHED_REMOTE_RUNNING); 5380 WARN_ON_ONCE(os == TICK_SCHED_REMOTE_RUNNING); 5381 if (os == TICK_SCHED_REMOTE_OFFLINE) { 5382 twork->cpu = cpu; 5383 INIT_DELAYED_WORK(&twork->work, sched_tick_remote); 5384 queue_delayed_work(system_unbound_wq, &twork->work, HZ); 5385 } 5386 } 5387 5388 #ifdef CONFIG_HOTPLUG_CPU 5389 static void sched_tick_stop(int cpu) 5390 { 5391 struct tick_work *twork; 5392 int os; 5393 5394 if (housekeeping_cpu(cpu, HK_FLAG_TICK)) 5395 return; 5396 5397 WARN_ON_ONCE(!tick_work_cpu); 5398 5399 twork = per_cpu_ptr(tick_work_cpu, cpu); 5400 /* There cannot be competing actions, but don't rely on stop-machine. */ 5401 os = atomic_xchg(&twork->state, TICK_SCHED_REMOTE_OFFLINING); 5402 WARN_ON_ONCE(os != TICK_SCHED_REMOTE_RUNNING); 5403 /* Don't cancel, as this would mess up the state machine. */ 5404 } 5405 #endif /* CONFIG_HOTPLUG_CPU */ 5406 5407 int __init sched_tick_offload_init(void) 5408 { 5409 tick_work_cpu = alloc_percpu(struct tick_work); 5410 BUG_ON(!tick_work_cpu); 5411 return 0; 5412 } 5413 5414 #else /* !CONFIG_NO_HZ_FULL */ 5415 static inline void sched_tick_start(int cpu) { } 5416 static inline void sched_tick_stop(int cpu) { } 5417 #endif 5418 5419 #if defined(CONFIG_PREEMPTION) && (defined(CONFIG_DEBUG_PREEMPT) || \ 5420 defined(CONFIG_TRACE_PREEMPT_TOGGLE)) 5421 /* 5422 * If the value passed in is equal to the current preempt count 5423 * then we just disabled preemption. Start timing the latency. 5424 */ 5425 static inline void preempt_latency_start(int val) 5426 { 5427 if (preempt_count() == val) { 5428 unsigned long ip = get_lock_parent_ip(); 5429 #ifdef CONFIG_DEBUG_PREEMPT 5430 current->preempt_disable_ip = ip; 5431 #endif 5432 trace_preempt_off(CALLER_ADDR0, ip); 5433 } 5434 } 5435 5436 void preempt_count_add(int val) 5437 { 5438 #ifdef CONFIG_DEBUG_PREEMPT 5439 /* 5440 * Underflow? 5441 */ 5442 if (DEBUG_LOCKS_WARN_ON((preempt_count() < 0))) 5443 return; 5444 #endif 5445 __preempt_count_add(val); 5446 #ifdef CONFIG_DEBUG_PREEMPT 5447 /* 5448 * Spinlock count overflowing soon? 5449 */ 5450 DEBUG_LOCKS_WARN_ON((preempt_count() & PREEMPT_MASK) >= 5451 PREEMPT_MASK - 10); 5452 #endif 5453 preempt_latency_start(val); 5454 } 5455 EXPORT_SYMBOL(preempt_count_add); 5456 NOKPROBE_SYMBOL(preempt_count_add); 5457 5458 /* 5459 * If the value passed in equals to the current preempt count 5460 * then we just enabled preemption. Stop timing the latency. 5461 */ 5462 static inline void preempt_latency_stop(int val) 5463 { 5464 if (preempt_count() == val) 5465 trace_preempt_on(CALLER_ADDR0, get_lock_parent_ip()); 5466 } 5467 5468 void preempt_count_sub(int val) 5469 { 5470 #ifdef CONFIG_DEBUG_PREEMPT 5471 /* 5472 * Underflow? 5473 */ 5474 if (DEBUG_LOCKS_WARN_ON(val > preempt_count())) 5475 return; 5476 /* 5477 * Is the spinlock portion underflowing? 5478 */ 5479 if (DEBUG_LOCKS_WARN_ON((val < PREEMPT_MASK) && 5480 !(preempt_count() & PREEMPT_MASK))) 5481 return; 5482 #endif 5483 5484 preempt_latency_stop(val); 5485 __preempt_count_sub(val); 5486 } 5487 EXPORT_SYMBOL(preempt_count_sub); 5488 NOKPROBE_SYMBOL(preempt_count_sub); 5489 5490 #else 5491 static inline void preempt_latency_start(int val) { } 5492 static inline void preempt_latency_stop(int val) { } 5493 #endif 5494 5495 static inline unsigned long get_preempt_disable_ip(struct task_struct *p) 5496 { 5497 #ifdef CONFIG_DEBUG_PREEMPT 5498 return p->preempt_disable_ip; 5499 #else 5500 return 0; 5501 #endif 5502 } 5503 5504 /* 5505 * Print scheduling while atomic bug: 5506 */ 5507 static noinline void __schedule_bug(struct task_struct *prev) 5508 { 5509 /* Save this before calling printk(), since that will clobber it */ 5510 unsigned long preempt_disable_ip = get_preempt_disable_ip(current); 5511 5512 if (oops_in_progress) 5513 return; 5514 5515 printk(KERN_ERR "BUG: scheduling while atomic: %s/%d/0x%08x\n", 5516 prev->comm, prev->pid, preempt_count()); 5517 5518 debug_show_held_locks(prev); 5519 print_modules(); 5520 if (irqs_disabled()) 5521 print_irqtrace_events(prev); 5522 if (IS_ENABLED(CONFIG_DEBUG_PREEMPT) 5523 && in_atomic_preempt_off()) { 5524 pr_err("Preemption disabled at:"); 5525 print_ip_sym(KERN_ERR, preempt_disable_ip); 5526 } 5527 if (panic_on_warn) 5528 panic("scheduling while atomic\n"); 5529 5530 dump_stack(); 5531 add_taint(TAINT_WARN, LOCKDEP_STILL_OK); 5532 } 5533 5534 /* 5535 * Various schedule()-time debugging checks and statistics: 5536 */ 5537 static inline void schedule_debug(struct task_struct *prev, bool preempt) 5538 { 5539 #ifdef CONFIG_SCHED_STACK_END_CHECK 5540 if (task_stack_end_corrupted(prev)) 5541 panic("corrupted stack end detected inside scheduler\n"); 5542 5543 if (task_scs_end_corrupted(prev)) 5544 panic("corrupted shadow stack detected inside scheduler\n"); 5545 #endif 5546 5547 #ifdef CONFIG_DEBUG_ATOMIC_SLEEP 5548 if (!preempt && READ_ONCE(prev->__state) && prev->non_block_count) { 5549 printk(KERN_ERR "BUG: scheduling in a non-blocking section: %s/%d/%i\n", 5550 prev->comm, prev->pid, prev->non_block_count); 5551 dump_stack(); 5552 add_taint(TAINT_WARN, LOCKDEP_STILL_OK); 5553 } 5554 #endif 5555 5556 if (unlikely(in_atomic_preempt_off())) { 5557 __schedule_bug(prev); 5558 preempt_count_set(PREEMPT_DISABLED); 5559 } 5560 rcu_sleep_check(); 5561 SCHED_WARN_ON(ct_state() == CONTEXT_USER); 5562 5563 profile_hit(SCHED_PROFILING, __builtin_return_address(0)); 5564 5565 schedstat_inc(this_rq()->sched_count); 5566 } 5567 5568 static void put_prev_task_balance(struct rq *rq, struct task_struct *prev, 5569 struct rq_flags *rf) 5570 { 5571 #ifdef CONFIG_SMP 5572 const struct sched_class *class; 5573 /* 5574 * We must do the balancing pass before put_prev_task(), such 5575 * that when we release the rq->lock the task is in the same 5576 * state as before we took rq->lock. 5577 * 5578 * We can terminate the balance pass as soon as we know there is 5579 * a runnable task of @class priority or higher. 5580 */ 5581 for_class_range(class, prev->sched_class, &idle_sched_class) { 5582 if (class->balance(rq, prev, rf)) 5583 break; 5584 } 5585 #endif 5586 5587 put_prev_task(rq, prev); 5588 } 5589 5590 /* 5591 * Pick up the highest-prio task: 5592 */ 5593 static inline struct task_struct * 5594 __pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) 5595 { 5596 const struct sched_class *class; 5597 struct task_struct *p; 5598 5599 /* 5600 * Optimization: we know that if all tasks are in the fair class we can 5601 * call that function directly, but only if the @prev task wasn't of a 5602 * higher scheduling class, because otherwise those lose the 5603 * opportunity to pull in more work from other CPUs. 5604 */ 5605 if (likely(prev->sched_class <= &fair_sched_class && 5606 rq->nr_running == rq->cfs.h_nr_running)) { 5607 5608 p = pick_next_task_fair(rq, prev, rf); 5609 if (unlikely(p == RETRY_TASK)) 5610 goto restart; 5611 5612 /* Assume the next prioritized class is idle_sched_class */ 5613 if (!p) { 5614 put_prev_task(rq, prev); 5615 p = pick_next_task_idle(rq); 5616 } 5617 5618 return p; 5619 } 5620 5621 restart: 5622 put_prev_task_balance(rq, prev, rf); 5623 5624 for_each_class(class) { 5625 p = class->pick_next_task(rq); 5626 if (p) 5627 return p; 5628 } 5629 5630 BUG(); /* The idle class should always have a runnable task. */ 5631 } 5632 5633 #ifdef CONFIG_SCHED_CORE 5634 static inline bool is_task_rq_idle(struct task_struct *t) 5635 { 5636 return (task_rq(t)->idle == t); 5637 } 5638 5639 static inline bool cookie_equals(struct task_struct *a, unsigned long cookie) 5640 { 5641 return is_task_rq_idle(a) || (a->core_cookie == cookie); 5642 } 5643 5644 static inline bool cookie_match(struct task_struct *a, struct task_struct *b) 5645 { 5646 if (is_task_rq_idle(a) || is_task_rq_idle(b)) 5647 return true; 5648 5649 return a->core_cookie == b->core_cookie; 5650 } 5651 5652 static inline struct task_struct *pick_task(struct rq *rq) 5653 { 5654 const struct sched_class *class; 5655 struct task_struct *p; 5656 5657 for_each_class(class) { 5658 p = class->pick_task(rq); 5659 if (p) 5660 return p; 5661 } 5662 5663 BUG(); /* The idle class should always have a runnable task. */ 5664 } 5665 5666 extern void task_vruntime_update(struct rq *rq, struct task_struct *p, bool in_fi); 5667 5668 static struct task_struct * 5669 pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) 5670 { 5671 struct task_struct *next, *p, *max = NULL; 5672 const struct cpumask *smt_mask; 5673 bool fi_before = false; 5674 bool core_clock_updated = (rq == rq->core); 5675 unsigned long cookie; 5676 int i, cpu, occ = 0; 5677 struct rq *rq_i; 5678 bool need_sync; 5679 5680 if (!sched_core_enabled(rq)) 5681 return __pick_next_task(rq, prev, rf); 5682 5683 cpu = cpu_of(rq); 5684 5685 /* Stopper task is switching into idle, no need core-wide selection. */ 5686 if (cpu_is_offline(cpu)) { 5687 /* 5688 * Reset core_pick so that we don't enter the fastpath when 5689 * coming online. core_pick would already be migrated to 5690 * another cpu during offline. 5691 */ 5692 rq->core_pick = NULL; 5693 return __pick_next_task(rq, prev, rf); 5694 } 5695 5696 /* 5697 * If there were no {en,de}queues since we picked (IOW, the task 5698 * pointers are all still valid), and we haven't scheduled the last 5699 * pick yet, do so now. 5700 * 5701 * rq->core_pick can be NULL if no selection was made for a CPU because 5702 * it was either offline or went offline during a sibling's core-wide 5703 * selection. In this case, do a core-wide selection. 5704 */ 5705 if (rq->core->core_pick_seq == rq->core->core_task_seq && 5706 rq->core->core_pick_seq != rq->core_sched_seq && 5707 rq->core_pick) { 5708 WRITE_ONCE(rq->core_sched_seq, rq->core->core_pick_seq); 5709 5710 next = rq->core_pick; 5711 if (next != prev) { 5712 put_prev_task(rq, prev); 5713 set_next_task(rq, next); 5714 } 5715 5716 rq->core_pick = NULL; 5717 return next; 5718 } 5719 5720 put_prev_task_balance(rq, prev, rf); 5721 5722 smt_mask = cpu_smt_mask(cpu); 5723 need_sync = !!rq->core->core_cookie; 5724 5725 /* reset state */ 5726 rq->core->core_cookie = 0UL; 5727 if (rq->core->core_forceidle_count) { 5728 if (!core_clock_updated) { 5729 update_rq_clock(rq->core); 5730 core_clock_updated = true; 5731 } 5732 sched_core_account_forceidle(rq); 5733 /* reset after accounting force idle */ 5734 rq->core->core_forceidle_start = 0; 5735 rq->core->core_forceidle_count = 0; 5736 rq->core->core_forceidle_occupation = 0; 5737 need_sync = true; 5738 fi_before = true; 5739 } 5740 5741 /* 5742 * core->core_task_seq, core->core_pick_seq, rq->core_sched_seq 5743 * 5744 * @task_seq guards the task state ({en,de}queues) 5745 * @pick_seq is the @task_seq we did a selection on 5746 * @sched_seq is the @pick_seq we scheduled 5747 * 5748 * However, preemptions can cause multiple picks on the same task set. 5749 * 'Fix' this by also increasing @task_seq for every pick. 5750 */ 5751 rq->core->core_task_seq++; 5752 5753 /* 5754 * Optimize for common case where this CPU has no cookies 5755 * and there are no cookied tasks running on siblings. 5756 */ 5757 if (!need_sync) { 5758 next = pick_task(rq); 5759 if (!next->core_cookie) { 5760 rq->core_pick = NULL; 5761 /* 5762 * For robustness, update the min_vruntime_fi for 5763 * unconstrained picks as well. 5764 */ 5765 WARN_ON_ONCE(fi_before); 5766 task_vruntime_update(rq, next, false); 5767 goto done; 5768 } 5769 } 5770 5771 /* 5772 * For each thread: do the regular task pick and find the max prio task 5773 * amongst them. 5774 * 5775 * Tie-break prio towards the current CPU 5776 */ 5777 for_each_cpu_wrap(i, smt_mask, cpu) { 5778 rq_i = cpu_rq(i); 5779 5780 /* 5781 * Current cpu always has its clock updated on entrance to 5782 * pick_next_task(). If the current cpu is not the core, 5783 * the core may also have been updated above. 5784 */ 5785 if (i != cpu && (rq_i != rq->core || !core_clock_updated)) 5786 update_rq_clock(rq_i); 5787 5788 p = rq_i->core_pick = pick_task(rq_i); 5789 if (!max || prio_less(max, p, fi_before)) 5790 max = p; 5791 } 5792 5793 cookie = rq->core->core_cookie = max->core_cookie; 5794 5795 /* 5796 * For each thread: try and find a runnable task that matches @max or 5797 * force idle. 5798 */ 5799 for_each_cpu(i, smt_mask) { 5800 rq_i = cpu_rq(i); 5801 p = rq_i->core_pick; 5802 5803 if (!cookie_equals(p, cookie)) { 5804 p = NULL; 5805 if (cookie) 5806 p = sched_core_find(rq_i, cookie); 5807 if (!p) 5808 p = idle_sched_class.pick_task(rq_i); 5809 } 5810 5811 rq_i->core_pick = p; 5812 5813 if (p == rq_i->idle) { 5814 if (rq_i->nr_running) { 5815 rq->core->core_forceidle_count++; 5816 if (!fi_before) 5817 rq->core->core_forceidle_seq++; 5818 } 5819 } else { 5820 occ++; 5821 } 5822 } 5823 5824 if (schedstat_enabled() && rq->core->core_forceidle_count) { 5825 rq->core->core_forceidle_start = rq_clock(rq->core); 5826 rq->core->core_forceidle_occupation = occ; 5827 } 5828 5829 rq->core->core_pick_seq = rq->core->core_task_seq; 5830 next = rq->core_pick; 5831 rq->core_sched_seq = rq->core->core_pick_seq; 5832 5833 /* Something should have been selected for current CPU */ 5834 WARN_ON_ONCE(!next); 5835 5836 /* 5837 * Reschedule siblings 5838 * 5839 * NOTE: L1TF -- at this point we're no longer running the old task and 5840 * sending an IPI (below) ensures the sibling will no longer be running 5841 * their task. This ensures there is no inter-sibling overlap between 5842 * non-matching user state. 5843 */ 5844 for_each_cpu(i, smt_mask) { 5845 rq_i = cpu_rq(i); 5846 5847 /* 5848 * An online sibling might have gone offline before a task 5849 * could be picked for it, or it might be offline but later 5850 * happen to come online, but its too late and nothing was 5851 * picked for it. That's Ok - it will pick tasks for itself, 5852 * so ignore it. 5853 */ 5854 if (!rq_i->core_pick) 5855 continue; 5856 5857 /* 5858 * Update for new !FI->FI transitions, or if continuing to be in !FI: 5859 * fi_before fi update? 5860 * 0 0 1 5861 * 0 1 1 5862 * 1 0 1 5863 * 1 1 0 5864 */ 5865 if (!(fi_before && rq->core->core_forceidle_count)) 5866 task_vruntime_update(rq_i, rq_i->core_pick, !!rq->core->core_forceidle_count); 5867 5868 rq_i->core_pick->core_occupation = occ; 5869 5870 if (i == cpu) { 5871 rq_i->core_pick = NULL; 5872 continue; 5873 } 5874 5875 /* Did we break L1TF mitigation requirements? */ 5876 WARN_ON_ONCE(!cookie_match(next, rq_i->core_pick)); 5877 5878 if (rq_i->curr == rq_i->core_pick) { 5879 rq_i->core_pick = NULL; 5880 continue; 5881 } 5882 5883 resched_curr(rq_i); 5884 } 5885 5886 done: 5887 set_next_task(rq, next); 5888 return next; 5889 } 5890 5891 static bool try_steal_cookie(int this, int that) 5892 { 5893 struct rq *dst = cpu_rq(this), *src = cpu_rq(that); 5894 struct task_struct *p; 5895 unsigned long cookie; 5896 bool success = false; 5897 5898 local_irq_disable(); 5899 double_rq_lock(dst, src); 5900 5901 cookie = dst->core->core_cookie; 5902 if (!cookie) 5903 goto unlock; 5904 5905 if (dst->curr != dst->idle) 5906 goto unlock; 5907 5908 p = sched_core_find(src, cookie); 5909 if (p == src->idle) 5910 goto unlock; 5911 5912 do { 5913 if (p == src->core_pick || p == src->curr) 5914 goto next; 5915 5916 if (!cpumask_test_cpu(this, &p->cpus_mask)) 5917 goto next; 5918 5919 if (p->core_occupation > dst->idle->core_occupation) 5920 goto next; 5921 5922 deactivate_task(src, p, 0); 5923 set_task_cpu(p, this); 5924 activate_task(dst, p, 0); 5925 5926 resched_curr(dst); 5927 5928 success = true; 5929 break; 5930 5931 next: 5932 p = sched_core_next(p, cookie); 5933 } while (p); 5934 5935 unlock: 5936 double_rq_unlock(dst, src); 5937 local_irq_enable(); 5938 5939 return success; 5940 } 5941 5942 static bool steal_cookie_task(int cpu, struct sched_domain *sd) 5943 { 5944 int i; 5945 5946 for_each_cpu_wrap(i, sched_domain_span(sd), cpu) { 5947 if (i == cpu) 5948 continue; 5949 5950 if (need_resched()) 5951 break; 5952 5953 if (try_steal_cookie(cpu, i)) 5954 return true; 5955 } 5956 5957 return false; 5958 } 5959 5960 static void sched_core_balance(struct rq *rq) 5961 { 5962 struct sched_domain *sd; 5963 int cpu = cpu_of(rq); 5964 5965 preempt_disable(); 5966 rcu_read_lock(); 5967 raw_spin_rq_unlock_irq(rq); 5968 for_each_domain(cpu, sd) { 5969 if (need_resched()) 5970 break; 5971 5972 if (steal_cookie_task(cpu, sd)) 5973 break; 5974 } 5975 raw_spin_rq_lock_irq(rq); 5976 rcu_read_unlock(); 5977 preempt_enable(); 5978 } 5979 5980 static DEFINE_PER_CPU(struct callback_head, core_balance_head); 5981 5982 void queue_core_balance(struct rq *rq) 5983 { 5984 if (!sched_core_enabled(rq)) 5985 return; 5986 5987 if (!rq->core->core_cookie) 5988 return; 5989 5990 if (!rq->nr_running) /* not forced idle */ 5991 return; 5992 5993 queue_balance_callback(rq, &per_cpu(core_balance_head, rq->cpu), sched_core_balance); 5994 } 5995 5996 static void sched_core_cpu_starting(unsigned int cpu) 5997 { 5998 const struct cpumask *smt_mask = cpu_smt_mask(cpu); 5999 struct rq *rq = cpu_rq(cpu), *core_rq = NULL; 6000 unsigned long flags; 6001 int t; 6002 6003 sched_core_lock(cpu, &flags); 6004 6005 WARN_ON_ONCE(rq->core != rq); 6006 6007 /* if we're the first, we'll be our own leader */ 6008 if (cpumask_weight(smt_mask) == 1) 6009 goto unlock; 6010 6011 /* find the leader */ 6012 for_each_cpu(t, smt_mask) { 6013 if (t == cpu) 6014 continue; 6015 rq = cpu_rq(t); 6016 if (rq->core == rq) { 6017 core_rq = rq; 6018 break; 6019 } 6020 } 6021 6022 if (WARN_ON_ONCE(!core_rq)) /* whoopsie */ 6023 goto unlock; 6024 6025 /* install and validate core_rq */ 6026 for_each_cpu(t, smt_mask) { 6027 rq = cpu_rq(t); 6028 6029 if (t == cpu) 6030 rq->core = core_rq; 6031 6032 WARN_ON_ONCE(rq->core != core_rq); 6033 } 6034 6035 unlock: 6036 sched_core_unlock(cpu, &flags); 6037 } 6038 6039 static void sched_core_cpu_deactivate(unsigned int cpu) 6040 { 6041 const struct cpumask *smt_mask = cpu_smt_mask(cpu); 6042 struct rq *rq = cpu_rq(cpu), *core_rq = NULL; 6043 unsigned long flags; 6044 int t; 6045 6046 sched_core_lock(cpu, &flags); 6047 6048 /* if we're the last man standing, nothing to do */ 6049 if (cpumask_weight(smt_mask) == 1) { 6050 WARN_ON_ONCE(rq->core != rq); 6051 goto unlock; 6052 } 6053 6054 /* if we're not the leader, nothing to do */ 6055 if (rq->core != rq) 6056 goto unlock; 6057 6058 /* find a new leader */ 6059 for_each_cpu(t, smt_mask) { 6060 if (t == cpu) 6061 continue; 6062 core_rq = cpu_rq(t); 6063 break; 6064 } 6065 6066 if (WARN_ON_ONCE(!core_rq)) /* impossible */ 6067 goto unlock; 6068 6069 /* copy the shared state to the new leader */ 6070 core_rq->core_task_seq = rq->core_task_seq; 6071 core_rq->core_pick_seq = rq->core_pick_seq; 6072 core_rq->core_cookie = rq->core_cookie; 6073 core_rq->core_forceidle_count = rq->core_forceidle_count; 6074 core_rq->core_forceidle_seq = rq->core_forceidle_seq; 6075 core_rq->core_forceidle_occupation = rq->core_forceidle_occupation; 6076 6077 /* 6078 * Accounting edge for forced idle is handled in pick_next_task(). 6079 * Don't need another one here, since the hotplug thread shouldn't 6080 * have a cookie. 6081 */ 6082 core_rq->core_forceidle_start = 0; 6083 6084 /* install new leader */ 6085 for_each_cpu(t, smt_mask) { 6086 rq = cpu_rq(t); 6087 rq->core = core_rq; 6088 } 6089 6090 unlock: 6091 sched_core_unlock(cpu, &flags); 6092 } 6093 6094 static inline void sched_core_cpu_dying(unsigned int cpu) 6095 { 6096 struct rq *rq = cpu_rq(cpu); 6097 6098 if (rq->core != rq) 6099 rq->core = rq; 6100 } 6101 6102 #else /* !CONFIG_SCHED_CORE */ 6103 6104 static inline void sched_core_cpu_starting(unsigned int cpu) {} 6105 static inline void sched_core_cpu_deactivate(unsigned int cpu) {} 6106 static inline void sched_core_cpu_dying(unsigned int cpu) {} 6107 6108 static struct task_struct * 6109 pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) 6110 { 6111 return __pick_next_task(rq, prev, rf); 6112 } 6113 6114 #endif /* CONFIG_SCHED_CORE */ 6115 6116 /* 6117 * Constants for the sched_mode argument of __schedule(). 6118 * 6119 * The mode argument allows RT enabled kernels to differentiate a 6120 * preemption from blocking on an 'sleeping' spin/rwlock. Note that 6121 * SM_MASK_PREEMPT for !RT has all bits set, which allows the compiler to 6122 * optimize the AND operation out and just check for zero. 6123 */ 6124 #define SM_NONE 0x0 6125 #define SM_PREEMPT 0x1 6126 #define SM_RTLOCK_WAIT 0x2 6127 6128 #ifndef CONFIG_PREEMPT_RT 6129 # define SM_MASK_PREEMPT (~0U) 6130 #else 6131 # define SM_MASK_PREEMPT SM_PREEMPT 6132 #endif 6133 6134 /* 6135 * __schedule() is the main scheduler function. 6136 * 6137 * The main means of driving the scheduler and thus entering this function are: 6138 * 6139 * 1. Explicit blocking: mutex, semaphore, waitqueue, etc. 6140 * 6141 * 2. TIF_NEED_RESCHED flag is checked on interrupt and userspace return 6142 * paths. For example, see arch/x86/entry_64.S. 6143 * 6144 * To drive preemption between tasks, the scheduler sets the flag in timer 6145 * interrupt handler scheduler_tick(). 6146 * 6147 * 3. Wakeups don't really cause entry into schedule(). They add a 6148 * task to the run-queue and that's it. 6149 * 6150 * Now, if the new task added to the run-queue preempts the current 6151 * task, then the wakeup sets TIF_NEED_RESCHED and schedule() gets 6152 * called on the nearest possible occasion: 6153 * 6154 * - If the kernel is preemptible (CONFIG_PREEMPTION=y): 6155 * 6156 * - in syscall or exception context, at the next outmost 6157 * preempt_enable(). (this might be as soon as the wake_up()'s 6158 * spin_unlock()!) 6159 * 6160 * - in IRQ context, return from interrupt-handler to 6161 * preemptible context 6162 * 6163 * - If the kernel is not preemptible (CONFIG_PREEMPTION is not set) 6164 * then at the next: 6165 * 6166 * - cond_resched() call 6167 * - explicit schedule() call 6168 * - return from syscall or exception to user-space 6169 * - return from interrupt-handler to user-space 6170 * 6171 * WARNING: must be called with preemption disabled! 6172 */ 6173 static void __sched notrace __schedule(unsigned int sched_mode) 6174 { 6175 struct task_struct *prev, *next; 6176 unsigned long *switch_count; 6177 unsigned long prev_state; 6178 struct rq_flags rf; 6179 struct rq *rq; 6180 int cpu; 6181 6182 cpu = smp_processor_id(); 6183 rq = cpu_rq(cpu); 6184 prev = rq->curr; 6185 6186 schedule_debug(prev, !!sched_mode); 6187 6188 if (sched_feat(HRTICK) || sched_feat(HRTICK_DL)) 6189 hrtick_clear(rq); 6190 6191 local_irq_disable(); 6192 rcu_note_context_switch(!!sched_mode); 6193 6194 /* 6195 * Make sure that signal_pending_state()->signal_pending() below 6196 * can't be reordered with __set_current_state(TASK_INTERRUPTIBLE) 6197 * done by the caller to avoid the race with signal_wake_up(): 6198 * 6199 * __set_current_state(@state) signal_wake_up() 6200 * schedule() set_tsk_thread_flag(p, TIF_SIGPENDING) 6201 * wake_up_state(p, state) 6202 * LOCK rq->lock LOCK p->pi_state 6203 * smp_mb__after_spinlock() smp_mb__after_spinlock() 6204 * if (signal_pending_state()) if (p->state & @state) 6205 * 6206 * Also, the membarrier system call requires a full memory barrier 6207 * after coming from user-space, before storing to rq->curr. 6208 */ 6209 rq_lock(rq, &rf); 6210 smp_mb__after_spinlock(); 6211 6212 /* Promote REQ to ACT */ 6213 rq->clock_update_flags <<= 1; 6214 update_rq_clock(rq); 6215 6216 switch_count = &prev->nivcsw; 6217 6218 /* 6219 * We must load prev->state once (task_struct::state is volatile), such 6220 * that: 6221 * 6222 * - we form a control dependency vs deactivate_task() below. 6223 * - ptrace_{,un}freeze_traced() can change ->state underneath us. 6224 */ 6225 prev_state = READ_ONCE(prev->__state); 6226 if (!(sched_mode & SM_MASK_PREEMPT) && prev_state) { 6227 if (signal_pending_state(prev_state, prev)) { 6228 WRITE_ONCE(prev->__state, TASK_RUNNING); 6229 } else { 6230 prev->sched_contributes_to_load = 6231 (prev_state & TASK_UNINTERRUPTIBLE) && 6232 !(prev_state & TASK_NOLOAD) && 6233 !(prev->flags & PF_FROZEN); 6234 6235 if (prev->sched_contributes_to_load) 6236 rq->nr_uninterruptible++; 6237 6238 /* 6239 * __schedule() ttwu() 6240 * prev_state = prev->state; if (p->on_rq && ...) 6241 * if (prev_state) goto out; 6242 * p->on_rq = 0; smp_acquire__after_ctrl_dep(); 6243 * p->state = TASK_WAKING 6244 * 6245 * Where __schedule() and ttwu() have matching control dependencies. 6246 * 6247 * After this, schedule() must not care about p->state any more. 6248 */ 6249 deactivate_task(rq, prev, DEQUEUE_SLEEP | DEQUEUE_NOCLOCK); 6250 6251 if (prev->in_iowait) { 6252 atomic_inc(&rq->nr_iowait); 6253 delayacct_blkio_start(); 6254 } 6255 } 6256 switch_count = &prev->nvcsw; 6257 } 6258 6259 next = pick_next_task(rq, prev, &rf); 6260 clear_tsk_need_resched(prev); 6261 clear_preempt_need_resched(); 6262 #ifdef CONFIG_SCHED_DEBUG 6263 rq->last_seen_need_resched_ns = 0; 6264 #endif 6265 6266 if (likely(prev != next)) { 6267 rq->nr_switches++; 6268 /* 6269 * RCU users of rcu_dereference(rq->curr) may not see 6270 * changes to task_struct made by pick_next_task(). 6271 */ 6272 RCU_INIT_POINTER(rq->curr, next); 6273 /* 6274 * The membarrier system call requires each architecture 6275 * to have a full memory barrier after updating 6276 * rq->curr, before returning to user-space. 6277 * 6278 * Here are the schemes providing that barrier on the 6279 * various architectures: 6280 * - mm ? switch_mm() : mmdrop() for x86, s390, sparc, PowerPC. 6281 * switch_mm() rely on membarrier_arch_switch_mm() on PowerPC. 6282 * - finish_lock_switch() for weakly-ordered 6283 * architectures where spin_unlock is a full barrier, 6284 * - switch_to() for arm64 (weakly-ordered, spin_unlock 6285 * is a RELEASE barrier), 6286 */ 6287 ++*switch_count; 6288 6289 migrate_disable_switch(rq, prev); 6290 psi_sched_switch(prev, next, !task_on_rq_queued(prev)); 6291 6292 trace_sched_switch(sched_mode & SM_MASK_PREEMPT, prev, next); 6293 6294 /* Also unlocks the rq: */ 6295 rq = context_switch(rq, prev, next, &rf); 6296 } else { 6297 rq->clock_update_flags &= ~(RQCF_ACT_SKIP|RQCF_REQ_SKIP); 6298 6299 rq_unpin_lock(rq, &rf); 6300 __balance_callbacks(rq); 6301 raw_spin_rq_unlock_irq(rq); 6302 } 6303 } 6304 6305 void __noreturn do_task_dead(void) 6306 { 6307 /* Causes final put_task_struct in finish_task_switch(): */ 6308 set_special_state(TASK_DEAD); 6309 6310 /* Tell freezer to ignore us: */ 6311 current->flags |= PF_NOFREEZE; 6312 6313 __schedule(SM_NONE); 6314 BUG(); 6315 6316 /* Avoid "noreturn function does return" - but don't continue if BUG() is a NOP: */ 6317 for (;;) 6318 cpu_relax(); 6319 } 6320 6321 static inline void sched_submit_work(struct task_struct *tsk) 6322 { 6323 unsigned int task_flags; 6324 6325 if (task_is_running(tsk)) 6326 return; 6327 6328 task_flags = tsk->flags; 6329 /* 6330 * If a worker goes to sleep, notify and ask workqueue whether it 6331 * wants to wake up a task to maintain concurrency. 6332 */ 6333 if (task_flags & (PF_WQ_WORKER | PF_IO_WORKER)) { 6334 if (task_flags & PF_WQ_WORKER) 6335 wq_worker_sleeping(tsk); 6336 else 6337 io_wq_worker_sleeping(tsk); 6338 } 6339 6340 if (tsk_is_pi_blocked(tsk)) 6341 return; 6342 6343 /* 6344 * If we are going to sleep and we have plugged IO queued, 6345 * make sure to submit it to avoid deadlocks. 6346 */ 6347 if (blk_needs_flush_plug(tsk)) 6348 blk_flush_plug(tsk->plug, true); 6349 } 6350 6351 static void sched_update_worker(struct task_struct *tsk) 6352 { 6353 if (tsk->flags & (PF_WQ_WORKER | PF_IO_WORKER)) { 6354 if (tsk->flags & PF_WQ_WORKER) 6355 wq_worker_running(tsk); 6356 else 6357 io_wq_worker_running(tsk); 6358 } 6359 } 6360 6361 asmlinkage __visible void __sched schedule(void) 6362 { 6363 struct task_struct *tsk = current; 6364 6365 sched_submit_work(tsk); 6366 do { 6367 preempt_disable(); 6368 __schedule(SM_NONE); 6369 sched_preempt_enable_no_resched(); 6370 } while (need_resched()); 6371 sched_update_worker(tsk); 6372 } 6373 EXPORT_SYMBOL(schedule); 6374 6375 /* 6376 * synchronize_rcu_tasks() makes sure that no task is stuck in preempted 6377 * state (have scheduled out non-voluntarily) by making sure that all 6378 * tasks have either left the run queue or have gone into user space. 6379 * As idle tasks do not do either, they must not ever be preempted 6380 * (schedule out non-voluntarily). 6381 * 6382 * schedule_idle() is similar to schedule_preempt_disable() except that it 6383 * never enables preemption because it does not call sched_submit_work(). 6384 */ 6385 void __sched schedule_idle(void) 6386 { 6387 /* 6388 * As this skips calling sched_submit_work(), which the idle task does 6389 * regardless because that function is a nop when the task is in a 6390 * TASK_RUNNING state, make sure this isn't used someplace that the 6391 * current task can be in any other state. Note, idle is always in the 6392 * TASK_RUNNING state. 6393 */ 6394 WARN_ON_ONCE(current->__state); 6395 do { 6396 __schedule(SM_NONE); 6397 } while (need_resched()); 6398 } 6399 6400 #if defined(CONFIG_CONTEXT_TRACKING) && !defined(CONFIG_HAVE_CONTEXT_TRACKING_OFFSTACK) 6401 asmlinkage __visible void __sched schedule_user(void) 6402 { 6403 /* 6404 * If we come here after a random call to set_need_resched(), 6405 * or we have been woken up remotely but the IPI has not yet arrived, 6406 * we haven't yet exited the RCU idle mode. Do it here manually until 6407 * we find a better solution. 6408 * 6409 * NB: There are buggy callers of this function. Ideally we 6410 * should warn if prev_state != CONTEXT_USER, but that will trigger 6411 * too frequently to make sense yet. 6412 */ 6413 enum ctx_state prev_state = exception_enter(); 6414 schedule(); 6415 exception_exit(prev_state); 6416 } 6417 #endif 6418 6419 /** 6420 * schedule_preempt_disabled - called with preemption disabled 6421 * 6422 * Returns with preemption disabled. Note: preempt_count must be 1 6423 */ 6424 void __sched schedule_preempt_disabled(void) 6425 { 6426 sched_preempt_enable_no_resched(); 6427 schedule(); 6428 preempt_disable(); 6429 } 6430 6431 #ifdef CONFIG_PREEMPT_RT 6432 void __sched notrace schedule_rtlock(void) 6433 { 6434 do { 6435 preempt_disable(); 6436 __schedule(SM_RTLOCK_WAIT); 6437 sched_preempt_enable_no_resched(); 6438 } while (need_resched()); 6439 } 6440 NOKPROBE_SYMBOL(schedule_rtlock); 6441 #endif 6442 6443 static void __sched notrace preempt_schedule_common(void) 6444 { 6445 do { 6446 /* 6447 * Because the function tracer can trace preempt_count_sub() 6448 * and it also uses preempt_enable/disable_notrace(), if 6449 * NEED_RESCHED is set, the preempt_enable_notrace() called 6450 * by the function tracer will call this function again and 6451 * cause infinite recursion. 6452 * 6453 * Preemption must be disabled here before the function 6454 * tracer can trace. Break up preempt_disable() into two 6455 * calls. One to disable preemption without fear of being 6456 * traced. The other to still record the preemption latency, 6457 * which can also be traced by the function tracer. 6458 */ 6459 preempt_disable_notrace(); 6460 preempt_latency_start(1); 6461 __schedule(SM_PREEMPT); 6462 preempt_latency_stop(1); 6463 preempt_enable_no_resched_notrace(); 6464 6465 /* 6466 * Check again in case we missed a preemption opportunity 6467 * between schedule and now. 6468 */ 6469 } while (need_resched()); 6470 } 6471 6472 #ifdef CONFIG_PREEMPTION 6473 /* 6474 * This is the entry point to schedule() from in-kernel preemption 6475 * off of preempt_enable. 6476 */ 6477 asmlinkage __visible void __sched notrace preempt_schedule(void) 6478 { 6479 /* 6480 * If there is a non-zero preempt_count or interrupts are disabled, 6481 * we do not want to preempt the current task. Just return.. 6482 */ 6483 if (likely(!preemptible())) 6484 return; 6485 6486 preempt_schedule_common(); 6487 } 6488 NOKPROBE_SYMBOL(preempt_schedule); 6489 EXPORT_SYMBOL(preempt_schedule); 6490 6491 #ifdef CONFIG_PREEMPT_DYNAMIC 6492 DEFINE_STATIC_CALL(preempt_schedule, __preempt_schedule_func); 6493 EXPORT_STATIC_CALL_TRAMP(preempt_schedule); 6494 #endif 6495 6496 6497 /** 6498 * preempt_schedule_notrace - preempt_schedule called by tracing 6499 * 6500 * The tracing infrastructure uses preempt_enable_notrace to prevent 6501 * recursion and tracing preempt enabling caused by the tracing 6502 * infrastructure itself. But as tracing can happen in areas coming 6503 * from userspace or just about to enter userspace, a preempt enable 6504 * can occur before user_exit() is called. This will cause the scheduler 6505 * to be called when the system is still in usermode. 6506 * 6507 * To prevent this, the preempt_enable_notrace will use this function 6508 * instead of preempt_schedule() to exit user context if needed before 6509 * calling the scheduler. 6510 */ 6511 asmlinkage __visible void __sched notrace preempt_schedule_notrace(void) 6512 { 6513 enum ctx_state prev_ctx; 6514 6515 if (likely(!preemptible())) 6516 return; 6517 6518 do { 6519 /* 6520 * Because the function tracer can trace preempt_count_sub() 6521 * and it also uses preempt_enable/disable_notrace(), if 6522 * NEED_RESCHED is set, the preempt_enable_notrace() called 6523 * by the function tracer will call this function again and 6524 * cause infinite recursion. 6525 * 6526 * Preemption must be disabled here before the function 6527 * tracer can trace. Break up preempt_disable() into two 6528 * calls. One to disable preemption without fear of being 6529 * traced. The other to still record the preemption latency, 6530 * which can also be traced by the function tracer. 6531 */ 6532 preempt_disable_notrace(); 6533 preempt_latency_start(1); 6534 /* 6535 * Needs preempt disabled in case user_exit() is traced 6536 * and the tracer calls preempt_enable_notrace() causing 6537 * an infinite recursion. 6538 */ 6539 prev_ctx = exception_enter(); 6540 __schedule(SM_PREEMPT); 6541 exception_exit(prev_ctx); 6542 6543 preempt_latency_stop(1); 6544 preempt_enable_no_resched_notrace(); 6545 } while (need_resched()); 6546 } 6547 EXPORT_SYMBOL_GPL(preempt_schedule_notrace); 6548 6549 #ifdef CONFIG_PREEMPT_DYNAMIC 6550 DEFINE_STATIC_CALL(preempt_schedule_notrace, __preempt_schedule_notrace_func); 6551 EXPORT_STATIC_CALL_TRAMP(preempt_schedule_notrace); 6552 #endif 6553 6554 #endif /* CONFIG_PREEMPTION */ 6555 6556 #ifdef CONFIG_PREEMPT_DYNAMIC 6557 6558 #include <linux/entry-common.h> 6559 6560 /* 6561 * SC:cond_resched 6562 * SC:might_resched 6563 * SC:preempt_schedule 6564 * SC:preempt_schedule_notrace 6565 * SC:irqentry_exit_cond_resched 6566 * 6567 * 6568 * NONE: 6569 * cond_resched <- __cond_resched 6570 * might_resched <- RET0 6571 * preempt_schedule <- NOP 6572 * preempt_schedule_notrace <- NOP 6573 * irqentry_exit_cond_resched <- NOP 6574 * 6575 * VOLUNTARY: 6576 * cond_resched <- __cond_resched 6577 * might_resched <- __cond_resched 6578 * preempt_schedule <- NOP 6579 * preempt_schedule_notrace <- NOP 6580 * irqentry_exit_cond_resched <- NOP 6581 * 6582 * FULL: 6583 * cond_resched <- RET0 6584 * might_resched <- RET0 6585 * preempt_schedule <- preempt_schedule 6586 * preempt_schedule_notrace <- preempt_schedule_notrace 6587 * irqentry_exit_cond_resched <- irqentry_exit_cond_resched 6588 */ 6589 6590 enum { 6591 preempt_dynamic_undefined = -1, 6592 preempt_dynamic_none, 6593 preempt_dynamic_voluntary, 6594 preempt_dynamic_full, 6595 }; 6596 6597 int preempt_dynamic_mode = preempt_dynamic_undefined; 6598 6599 int sched_dynamic_mode(const char *str) 6600 { 6601 if (!strcmp(str, "none")) 6602 return preempt_dynamic_none; 6603 6604 if (!strcmp(str, "voluntary")) 6605 return preempt_dynamic_voluntary; 6606 6607 if (!strcmp(str, "full")) 6608 return preempt_dynamic_full; 6609 6610 return -EINVAL; 6611 } 6612 6613 void sched_dynamic_update(int mode) 6614 { 6615 /* 6616 * Avoid {NONE,VOLUNTARY} -> FULL transitions from ever ending up in 6617 * the ZERO state, which is invalid. 6618 */ 6619 static_call_update(cond_resched, __cond_resched); 6620 static_call_update(might_resched, __cond_resched); 6621 static_call_update(preempt_schedule, __preempt_schedule_func); 6622 static_call_update(preempt_schedule_notrace, __preempt_schedule_notrace_func); 6623 static_call_update(irqentry_exit_cond_resched, irqentry_exit_cond_resched); 6624 6625 switch (mode) { 6626 case preempt_dynamic_none: 6627 static_call_update(cond_resched, __cond_resched); 6628 static_call_update(might_resched, (void *)&__static_call_return0); 6629 static_call_update(preempt_schedule, NULL); 6630 static_call_update(preempt_schedule_notrace, NULL); 6631 static_call_update(irqentry_exit_cond_resched, NULL); 6632 pr_info("Dynamic Preempt: none\n"); 6633 break; 6634 6635 case preempt_dynamic_voluntary: 6636 static_call_update(cond_resched, __cond_resched); 6637 static_call_update(might_resched, __cond_resched); 6638 static_call_update(preempt_schedule, NULL); 6639 static_call_update(preempt_schedule_notrace, NULL); 6640 static_call_update(irqentry_exit_cond_resched, NULL); 6641 pr_info("Dynamic Preempt: voluntary\n"); 6642 break; 6643 6644 case preempt_dynamic_full: 6645 static_call_update(cond_resched, (void *)&__static_call_return0); 6646 static_call_update(might_resched, (void *)&__static_call_return0); 6647 static_call_update(preempt_schedule, __preempt_schedule_func); 6648 static_call_update(preempt_schedule_notrace, __preempt_schedule_notrace_func); 6649 static_call_update(irqentry_exit_cond_resched, irqentry_exit_cond_resched); 6650 pr_info("Dynamic Preempt: full\n"); 6651 break; 6652 } 6653 6654 preempt_dynamic_mode = mode; 6655 } 6656 6657 static int __init setup_preempt_mode(char *str) 6658 { 6659 int mode = sched_dynamic_mode(str); 6660 if (mode < 0) { 6661 pr_warn("Dynamic Preempt: unsupported mode: %s\n", str); 6662 return 0; 6663 } 6664 6665 sched_dynamic_update(mode); 6666 return 1; 6667 } 6668 __setup("preempt=", setup_preempt_mode); 6669 6670 static void __init preempt_dynamic_init(void) 6671 { 6672 if (preempt_dynamic_mode == preempt_dynamic_undefined) { 6673 if (IS_ENABLED(CONFIG_PREEMPT_NONE)) { 6674 sched_dynamic_update(preempt_dynamic_none); 6675 } else if (IS_ENABLED(CONFIG_PREEMPT_VOLUNTARY)) { 6676 sched_dynamic_update(preempt_dynamic_voluntary); 6677 } else { 6678 /* Default static call setting, nothing to do */ 6679 WARN_ON_ONCE(!IS_ENABLED(CONFIG_PREEMPT)); 6680 preempt_dynamic_mode = preempt_dynamic_full; 6681 pr_info("Dynamic Preempt: full\n"); 6682 } 6683 } 6684 } 6685 6686 #else /* !CONFIG_PREEMPT_DYNAMIC */ 6687 6688 static inline void preempt_dynamic_init(void) { } 6689 6690 #endif /* #ifdef CONFIG_PREEMPT_DYNAMIC */ 6691 6692 /* 6693 * This is the entry point to schedule() from kernel preemption 6694 * off of irq context. 6695 * Note, that this is called and return with irqs disabled. This will 6696 * protect us against recursive calling from irq. 6697 */ 6698 asmlinkage __visible void __sched preempt_schedule_irq(void) 6699 { 6700 enum ctx_state prev_state; 6701 6702 /* Catch callers which need to be fixed */ 6703 BUG_ON(preempt_count() || !irqs_disabled()); 6704 6705 prev_state = exception_enter(); 6706 6707 do { 6708 preempt_disable(); 6709 local_irq_enable(); 6710 __schedule(SM_PREEMPT); 6711 local_irq_disable(); 6712 sched_preempt_enable_no_resched(); 6713 } while (need_resched()); 6714 6715 exception_exit(prev_state); 6716 } 6717 6718 int default_wake_function(wait_queue_entry_t *curr, unsigned mode, int wake_flags, 6719 void *key) 6720 { 6721 WARN_ON_ONCE(IS_ENABLED(CONFIG_SCHED_DEBUG) && wake_flags & ~WF_SYNC); 6722 return try_to_wake_up(curr->private, mode, wake_flags); 6723 } 6724 EXPORT_SYMBOL(default_wake_function); 6725 6726 static void __setscheduler_prio(struct task_struct *p, int prio) 6727 { 6728 if (dl_prio(prio)) 6729 p->sched_class = &dl_sched_class; 6730 else if (rt_prio(prio)) 6731 p->sched_class = &rt_sched_class; 6732 else 6733 p->sched_class = &fair_sched_class; 6734 6735 p->prio = prio; 6736 } 6737 6738 #ifdef CONFIG_RT_MUTEXES 6739 6740 static inline int __rt_effective_prio(struct task_struct *pi_task, int prio) 6741 { 6742 if (pi_task) 6743 prio = min(prio, pi_task->prio); 6744 6745 return prio; 6746 } 6747 6748 static inline int rt_effective_prio(struct task_struct *p, int prio) 6749 { 6750 struct task_struct *pi_task = rt_mutex_get_top_task(p); 6751 6752 return __rt_effective_prio(pi_task, prio); 6753 } 6754 6755 /* 6756 * rt_mutex_setprio - set the current priority of a task 6757 * @p: task to boost 6758 * @pi_task: donor task 6759 * 6760 * This function changes the 'effective' priority of a task. It does 6761 * not touch ->normal_prio like __setscheduler(). 6762 * 6763 * Used by the rt_mutex code to implement priority inheritance 6764 * logic. Call site only calls if the priority of the task changed. 6765 */ 6766 void rt_mutex_setprio(struct task_struct *p, struct task_struct *pi_task) 6767 { 6768 int prio, oldprio, queued, running, queue_flag = 6769 DEQUEUE_SAVE | DEQUEUE_MOVE | DEQUEUE_NOCLOCK; 6770 const struct sched_class *prev_class; 6771 struct rq_flags rf; 6772 struct rq *rq; 6773 6774 /* XXX used to be waiter->prio, not waiter->task->prio */ 6775 prio = __rt_effective_prio(pi_task, p->normal_prio); 6776 6777 /* 6778 * If nothing changed; bail early. 6779 */ 6780 if (p->pi_top_task == pi_task && prio == p->prio && !dl_prio(prio)) 6781 return; 6782 6783 rq = __task_rq_lock(p, &rf); 6784 update_rq_clock(rq); 6785 /* 6786 * Set under pi_lock && rq->lock, such that the value can be used under 6787 * either lock. 6788 * 6789 * Note that there is loads of tricky to make this pointer cache work 6790 * right. rt_mutex_slowunlock()+rt_mutex_postunlock() work together to 6791 * ensure a task is de-boosted (pi_task is set to NULL) before the 6792 * task is allowed to run again (and can exit). This ensures the pointer 6793 * points to a blocked task -- which guarantees the task is present. 6794 */ 6795 p->pi_top_task = pi_task; 6796 6797 /* 6798 * For FIFO/RR we only need to set prio, if that matches we're done. 6799 */ 6800 if (prio == p->prio && !dl_prio(prio)) 6801 goto out_unlock; 6802 6803 /* 6804 * Idle task boosting is a nono in general. There is one 6805 * exception, when PREEMPT_RT and NOHZ is active: 6806 * 6807 * The idle task calls get_next_timer_interrupt() and holds 6808 * the timer wheel base->lock on the CPU and another CPU wants 6809 * to access the timer (probably to cancel it). We can safely 6810 * ignore the boosting request, as the idle CPU runs this code 6811 * with interrupts disabled and will complete the lock 6812 * protected section without being interrupted. So there is no 6813 * real need to boost. 6814 */ 6815 if (unlikely(p == rq->idle)) { 6816 WARN_ON(p != rq->curr); 6817 WARN_ON(p->pi_blocked_on); 6818 goto out_unlock; 6819 } 6820 6821 trace_sched_pi_setprio(p, pi_task); 6822 oldprio = p->prio; 6823 6824 if (oldprio == prio) 6825 queue_flag &= ~DEQUEUE_MOVE; 6826 6827 prev_class = p->sched_class; 6828 queued = task_on_rq_queued(p); 6829 running = task_current(rq, p); 6830 if (queued) 6831 dequeue_task(rq, p, queue_flag); 6832 if (running) 6833 put_prev_task(rq, p); 6834 6835 /* 6836 * Boosting condition are: 6837 * 1. -rt task is running and holds mutex A 6838 * --> -dl task blocks on mutex A 6839 * 6840 * 2. -dl task is running and holds mutex A 6841 * --> -dl task blocks on mutex A and could preempt the 6842 * running task 6843 */ 6844 if (dl_prio(prio)) { 6845 if (!dl_prio(p->normal_prio) || 6846 (pi_task && dl_prio(pi_task->prio) && 6847 dl_entity_preempt(&pi_task->dl, &p->dl))) { 6848 p->dl.pi_se = pi_task->dl.pi_se; 6849 queue_flag |= ENQUEUE_REPLENISH; 6850 } else { 6851 p->dl.pi_se = &p->dl; 6852 } 6853 } else if (rt_prio(prio)) { 6854 if (dl_prio(oldprio)) 6855 p->dl.pi_se = &p->dl; 6856 if (oldprio < prio) 6857 queue_flag |= ENQUEUE_HEAD; 6858 } else { 6859 if (dl_prio(oldprio)) 6860 p->dl.pi_se = &p->dl; 6861 if (rt_prio(oldprio)) 6862 p->rt.timeout = 0; 6863 } 6864 6865 __setscheduler_prio(p, prio); 6866 6867 if (queued) 6868 enqueue_task(rq, p, queue_flag); 6869 if (running) 6870 set_next_task(rq, p); 6871 6872 check_class_changed(rq, p, prev_class, oldprio); 6873 out_unlock: 6874 /* Avoid rq from going away on us: */ 6875 preempt_disable(); 6876 6877 rq_unpin_lock(rq, &rf); 6878 __balance_callbacks(rq); 6879 raw_spin_rq_unlock(rq); 6880 6881 preempt_enable(); 6882 } 6883 #else 6884 static inline int rt_effective_prio(struct task_struct *p, int prio) 6885 { 6886 return prio; 6887 } 6888 #endif 6889 6890 void set_user_nice(struct task_struct *p, long nice) 6891 { 6892 bool queued, running; 6893 int old_prio; 6894 struct rq_flags rf; 6895 struct rq *rq; 6896 6897 if (task_nice(p) == nice || nice < MIN_NICE || nice > MAX_NICE) 6898 return; 6899 /* 6900 * We have to be careful, if called from sys_setpriority(), 6901 * the task might be in the middle of scheduling on another CPU. 6902 */ 6903 rq = task_rq_lock(p, &rf); 6904 update_rq_clock(rq); 6905 6906 /* 6907 * The RT priorities are set via sched_setscheduler(), but we still 6908 * allow the 'normal' nice value to be set - but as expected 6909 * it won't have any effect on scheduling until the task is 6910 * SCHED_DEADLINE, SCHED_FIFO or SCHED_RR: 6911 */ 6912 if (task_has_dl_policy(p) || task_has_rt_policy(p)) { 6913 p->static_prio = NICE_TO_PRIO(nice); 6914 goto out_unlock; 6915 } 6916 queued = task_on_rq_queued(p); 6917 running = task_current(rq, p); 6918 if (queued) 6919 dequeue_task(rq, p, DEQUEUE_SAVE | DEQUEUE_NOCLOCK); 6920 if (running) 6921 put_prev_task(rq, p); 6922 6923 p->static_prio = NICE_TO_PRIO(nice); 6924 set_load_weight(p, true); 6925 old_prio = p->prio; 6926 p->prio = effective_prio(p); 6927 6928 if (queued) 6929 enqueue_task(rq, p, ENQUEUE_RESTORE | ENQUEUE_NOCLOCK); 6930 if (running) 6931 set_next_task(rq, p); 6932 6933 /* 6934 * If the task increased its priority or is running and 6935 * lowered its priority, then reschedule its CPU: 6936 */ 6937 p->sched_class->prio_changed(rq, p, old_prio); 6938 6939 out_unlock: 6940 task_rq_unlock(rq, p, &rf); 6941 } 6942 EXPORT_SYMBOL(set_user_nice); 6943 6944 /* 6945 * can_nice - check if a task can reduce its nice value 6946 * @p: task 6947 * @nice: nice value 6948 */ 6949 int can_nice(const struct task_struct *p, const int nice) 6950 { 6951 /* Convert nice value [19,-20] to rlimit style value [1,40]: */ 6952 int nice_rlim = nice_to_rlimit(nice); 6953 6954 return (nice_rlim <= task_rlimit(p, RLIMIT_NICE) || 6955 capable(CAP_SYS_NICE)); 6956 } 6957 6958 #ifdef __ARCH_WANT_SYS_NICE 6959 6960 /* 6961 * sys_nice - change the priority of the current process. 6962 * @increment: priority increment 6963 * 6964 * sys_setpriority is a more generic, but much slower function that 6965 * does similar things. 6966 */ 6967 SYSCALL_DEFINE1(nice, int, increment) 6968 { 6969 long nice, retval; 6970 6971 /* 6972 * Setpriority might change our priority at the same moment. 6973 * We don't have to worry. Conceptually one call occurs first 6974 * and we have a single winner. 6975 */ 6976 increment = clamp(increment, -NICE_WIDTH, NICE_WIDTH); 6977 nice = task_nice(current) + increment; 6978 6979 nice = clamp_val(nice, MIN_NICE, MAX_NICE); 6980 if (increment < 0 && !can_nice(current, nice)) 6981 return -EPERM; 6982 6983 retval = security_task_setnice(current, nice); 6984 if (retval) 6985 return retval; 6986 6987 set_user_nice(current, nice); 6988 return 0; 6989 } 6990 6991 #endif 6992 6993 /** 6994 * task_prio - return the priority value of a given task. 6995 * @p: the task in question. 6996 * 6997 * Return: The priority value as seen by users in /proc. 6998 * 6999 * sched policy return value kernel prio user prio/nice 7000 * 7001 * normal, batch, idle [0 ... 39] [100 ... 139] 0/[-20 ... 19] 7002 * fifo, rr [-2 ... -100] [98 ... 0] [1 ... 99] 7003 * deadline -101 -1 0 7004 */ 7005 int task_prio(const struct task_struct *p) 7006 { 7007 return p->prio - MAX_RT_PRIO; 7008 } 7009 7010 /** 7011 * idle_cpu - is a given CPU idle currently? 7012 * @cpu: the processor in question. 7013 * 7014 * Return: 1 if the CPU is currently idle. 0 otherwise. 7015 */ 7016 int idle_cpu(int cpu) 7017 { 7018 struct rq *rq = cpu_rq(cpu); 7019 7020 if (rq->curr != rq->idle) 7021 return 0; 7022 7023 if (rq->nr_running) 7024 return 0; 7025 7026 #ifdef CONFIG_SMP 7027 if (rq->ttwu_pending) 7028 return 0; 7029 #endif 7030 7031 return 1; 7032 } 7033 7034 /** 7035 * available_idle_cpu - is a given CPU idle for enqueuing work. 7036 * @cpu: the CPU in question. 7037 * 7038 * Return: 1 if the CPU is currently idle. 0 otherwise. 7039 */ 7040 int available_idle_cpu(int cpu) 7041 { 7042 if (!idle_cpu(cpu)) 7043 return 0; 7044 7045 if (vcpu_is_preempted(cpu)) 7046 return 0; 7047 7048 return 1; 7049 } 7050 7051 /** 7052 * idle_task - return the idle task for a given CPU. 7053 * @cpu: the processor in question. 7054 * 7055 * Return: The idle task for the CPU @cpu. 7056 */ 7057 struct task_struct *idle_task(int cpu) 7058 { 7059 return cpu_rq(cpu)->idle; 7060 } 7061 7062 #ifdef CONFIG_SMP 7063 /* 7064 * This function computes an effective utilization for the given CPU, to be 7065 * used for frequency selection given the linear relation: f = u * f_max. 7066 * 7067 * The scheduler tracks the following metrics: 7068 * 7069 * cpu_util_{cfs,rt,dl,irq}() 7070 * cpu_bw_dl() 7071 * 7072 * Where the cfs,rt and dl util numbers are tracked with the same metric and 7073 * synchronized windows and are thus directly comparable. 7074 * 7075 * The cfs,rt,dl utilization are the running times measured with rq->clock_task 7076 * which excludes things like IRQ and steal-time. These latter are then accrued 7077 * in the irq utilization. 7078 * 7079 * The DL bandwidth number otoh is not a measured metric but a value computed 7080 * based on the task model parameters and gives the minimal utilization 7081 * required to meet deadlines. 7082 */ 7083 unsigned long effective_cpu_util(int cpu, unsigned long util_cfs, 7084 unsigned long max, enum cpu_util_type type, 7085 struct task_struct *p) 7086 { 7087 unsigned long dl_util, util, irq; 7088 struct rq *rq = cpu_rq(cpu); 7089 7090 if (!uclamp_is_used() && 7091 type == FREQUENCY_UTIL && rt_rq_is_runnable(&rq->rt)) { 7092 return max; 7093 } 7094 7095 /* 7096 * Early check to see if IRQ/steal time saturates the CPU, can be 7097 * because of inaccuracies in how we track these -- see 7098 * update_irq_load_avg(). 7099 */ 7100 irq = cpu_util_irq(rq); 7101 if (unlikely(irq >= max)) 7102 return max; 7103 7104 /* 7105 * Because the time spend on RT/DL tasks is visible as 'lost' time to 7106 * CFS tasks and we use the same metric to track the effective 7107 * utilization (PELT windows are synchronized) we can directly add them 7108 * to obtain the CPU's actual utilization. 7109 * 7110 * CFS and RT utilization can be boosted or capped, depending on 7111 * utilization clamp constraints requested by currently RUNNABLE 7112 * tasks. 7113 * When there are no CFS RUNNABLE tasks, clamps are released and 7114 * frequency will be gracefully reduced with the utilization decay. 7115 */ 7116 util = util_cfs + cpu_util_rt(rq); 7117 if (type == FREQUENCY_UTIL) 7118 util = uclamp_rq_util_with(rq, util, p); 7119 7120 dl_util = cpu_util_dl(rq); 7121 7122 /* 7123 * For frequency selection we do not make cpu_util_dl() a permanent part 7124 * of this sum because we want to use cpu_bw_dl() later on, but we need 7125 * to check if the CFS+RT+DL sum is saturated (ie. no idle time) such 7126 * that we select f_max when there is no idle time. 7127 * 7128 * NOTE: numerical errors or stop class might cause us to not quite hit 7129 * saturation when we should -- something for later. 7130 */ 7131 if (util + dl_util >= max) 7132 return max; 7133 7134 /* 7135 * OTOH, for energy computation we need the estimated running time, so 7136 * include util_dl and ignore dl_bw. 7137 */ 7138 if (type == ENERGY_UTIL) 7139 util += dl_util; 7140 7141 /* 7142 * There is still idle time; further improve the number by using the 7143 * irq metric. Because IRQ/steal time is hidden from the task clock we 7144 * need to scale the task numbers: 7145 * 7146 * max - irq 7147 * U' = irq + --------- * U 7148 * max 7149 */ 7150 util = scale_irq_capacity(util, irq, max); 7151 util += irq; 7152 7153 /* 7154 * Bandwidth required by DEADLINE must always be granted while, for 7155 * FAIR and RT, we use blocked utilization of IDLE CPUs as a mechanism 7156 * to gracefully reduce the frequency when no tasks show up for longer 7157 * periods of time. 7158 * 7159 * Ideally we would like to set bw_dl as min/guaranteed freq and util + 7160 * bw_dl as requested freq. However, cpufreq is not yet ready for such 7161 * an interface. So, we only do the latter for now. 7162 */ 7163 if (type == FREQUENCY_UTIL) 7164 util += cpu_bw_dl(rq); 7165 7166 return min(max, util); 7167 } 7168 7169 unsigned long sched_cpu_util(int cpu, unsigned long max) 7170 { 7171 return effective_cpu_util(cpu, cpu_util_cfs(cpu), max, 7172 ENERGY_UTIL, NULL); 7173 } 7174 #endif /* CONFIG_SMP */ 7175 7176 /** 7177 * find_process_by_pid - find a process with a matching PID value. 7178 * @pid: the pid in question. 7179 * 7180 * The task of @pid, if found. %NULL otherwise. 7181 */ 7182 static struct task_struct *find_process_by_pid(pid_t pid) 7183 { 7184 return pid ? find_task_by_vpid(pid) : current; 7185 } 7186 7187 /* 7188 * sched_setparam() passes in -1 for its policy, to let the functions 7189 * it calls know not to change it. 7190 */ 7191 #define SETPARAM_POLICY -1 7192 7193 static void __setscheduler_params(struct task_struct *p, 7194 const struct sched_attr *attr) 7195 { 7196 int policy = attr->sched_policy; 7197 7198 if (policy == SETPARAM_POLICY) 7199 policy = p->policy; 7200 7201 p->policy = policy; 7202 7203 if (dl_policy(policy)) 7204 __setparam_dl(p, attr); 7205 else if (fair_policy(policy)) 7206 p->static_prio = NICE_TO_PRIO(attr->sched_nice); 7207 7208 /* 7209 * __sched_setscheduler() ensures attr->sched_priority == 0 when 7210 * !rt_policy. Always setting this ensures that things like 7211 * getparam()/getattr() don't report silly values for !rt tasks. 7212 */ 7213 p->rt_priority = attr->sched_priority; 7214 p->normal_prio = normal_prio(p); 7215 set_load_weight(p, true); 7216 } 7217 7218 /* 7219 * Check the target process has a UID that matches the current process's: 7220 */ 7221 static bool check_same_owner(struct task_struct *p) 7222 { 7223 const struct cred *cred = current_cred(), *pcred; 7224 bool match; 7225 7226 rcu_read_lock(); 7227 pcred = __task_cred(p); 7228 match = (uid_eq(cred->euid, pcred->euid) || 7229 uid_eq(cred->euid, pcred->uid)); 7230 rcu_read_unlock(); 7231 return match; 7232 } 7233 7234 static int __sched_setscheduler(struct task_struct *p, 7235 const struct sched_attr *attr, 7236 bool user, bool pi) 7237 { 7238 int oldpolicy = -1, policy = attr->sched_policy; 7239 int retval, oldprio, newprio, queued, running; 7240 const struct sched_class *prev_class; 7241 struct callback_head *head; 7242 struct rq_flags rf; 7243 int reset_on_fork; 7244 int queue_flags = DEQUEUE_SAVE | DEQUEUE_MOVE | DEQUEUE_NOCLOCK; 7245 struct rq *rq; 7246 7247 /* The pi code expects interrupts enabled */ 7248 BUG_ON(pi && in_interrupt()); 7249 recheck: 7250 /* Double check policy once rq lock held: */ 7251 if (policy < 0) { 7252 reset_on_fork = p->sched_reset_on_fork; 7253 policy = oldpolicy = p->policy; 7254 } else { 7255 reset_on_fork = !!(attr->sched_flags & SCHED_FLAG_RESET_ON_FORK); 7256 7257 if (!valid_policy(policy)) 7258 return -EINVAL; 7259 } 7260 7261 if (attr->sched_flags & ~(SCHED_FLAG_ALL | SCHED_FLAG_SUGOV)) 7262 return -EINVAL; 7263 7264 /* 7265 * Valid priorities for SCHED_FIFO and SCHED_RR are 7266 * 1..MAX_RT_PRIO-1, valid priority for SCHED_NORMAL, 7267 * SCHED_BATCH and SCHED_IDLE is 0. 7268 */ 7269 if (attr->sched_priority > MAX_RT_PRIO-1) 7270 return -EINVAL; 7271 if ((dl_policy(policy) && !__checkparam_dl(attr)) || 7272 (rt_policy(policy) != (attr->sched_priority != 0))) 7273 return -EINVAL; 7274 7275 /* 7276 * Allow unprivileged RT tasks to decrease priority: 7277 */ 7278 if (user && !capable(CAP_SYS_NICE)) { 7279 if (fair_policy(policy)) { 7280 if (attr->sched_nice < task_nice(p) && 7281 !can_nice(p, attr->sched_nice)) 7282 return -EPERM; 7283 } 7284 7285 if (rt_policy(policy)) { 7286 unsigned long rlim_rtprio = 7287 task_rlimit(p, RLIMIT_RTPRIO); 7288 7289 /* Can't set/change the rt policy: */ 7290 if (policy != p->policy && !rlim_rtprio) 7291 return -EPERM; 7292 7293 /* Can't increase priority: */ 7294 if (attr->sched_priority > p->rt_priority && 7295 attr->sched_priority > rlim_rtprio) 7296 return -EPERM; 7297 } 7298 7299 /* 7300 * Can't set/change SCHED_DEADLINE policy at all for now 7301 * (safest behavior); in the future we would like to allow 7302 * unprivileged DL tasks to increase their relative deadline 7303 * or reduce their runtime (both ways reducing utilization) 7304 */ 7305 if (dl_policy(policy)) 7306 return -EPERM; 7307 7308 /* 7309 * Treat SCHED_IDLE as nice 20. Only allow a switch to 7310 * SCHED_NORMAL if the RLIMIT_NICE would normally permit it. 7311 */ 7312 if (task_has_idle_policy(p) && !idle_policy(policy)) { 7313 if (!can_nice(p, task_nice(p))) 7314 return -EPERM; 7315 } 7316 7317 /* Can't change other user's priorities: */ 7318 if (!check_same_owner(p)) 7319 return -EPERM; 7320 7321 /* Normal users shall not reset the sched_reset_on_fork flag: */ 7322 if (p->sched_reset_on_fork && !reset_on_fork) 7323 return -EPERM; 7324 } 7325 7326 if (user) { 7327 if (attr->sched_flags & SCHED_FLAG_SUGOV) 7328 return -EINVAL; 7329 7330 retval = security_task_setscheduler(p); 7331 if (retval) 7332 return retval; 7333 } 7334 7335 /* Update task specific "requested" clamps */ 7336 if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP) { 7337 retval = uclamp_validate(p, attr); 7338 if (retval) 7339 return retval; 7340 } 7341 7342 if (pi) 7343 cpuset_read_lock(); 7344 7345 /* 7346 * Make sure no PI-waiters arrive (or leave) while we are 7347 * changing the priority of the task: 7348 * 7349 * To be able to change p->policy safely, the appropriate 7350 * runqueue lock must be held. 7351 */ 7352 rq = task_rq_lock(p, &rf); 7353 update_rq_clock(rq); 7354 7355 /* 7356 * Changing the policy of the stop threads its a very bad idea: 7357 */ 7358 if (p == rq->stop) { 7359 retval = -EINVAL; 7360 goto unlock; 7361 } 7362 7363 /* 7364 * If not changing anything there's no need to proceed further, 7365 * but store a possible modification of reset_on_fork. 7366 */ 7367 if (unlikely(policy == p->policy)) { 7368 if (fair_policy(policy) && attr->sched_nice != task_nice(p)) 7369 goto change; 7370 if (rt_policy(policy) && attr->sched_priority != p->rt_priority) 7371 goto change; 7372 if (dl_policy(policy) && dl_param_changed(p, attr)) 7373 goto change; 7374 if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP) 7375 goto change; 7376 7377 p->sched_reset_on_fork = reset_on_fork; 7378 retval = 0; 7379 goto unlock; 7380 } 7381 change: 7382 7383 if (user) { 7384 #ifdef CONFIG_RT_GROUP_SCHED 7385 /* 7386 * Do not allow realtime tasks into groups that have no runtime 7387 * assigned. 7388 */ 7389 if (rt_bandwidth_enabled() && rt_policy(policy) && 7390 task_group(p)->rt_bandwidth.rt_runtime == 0 && 7391 !task_group_is_autogroup(task_group(p))) { 7392 retval = -EPERM; 7393 goto unlock; 7394 } 7395 #endif 7396 #ifdef CONFIG_SMP 7397 if (dl_bandwidth_enabled() && dl_policy(policy) && 7398 !(attr->sched_flags & SCHED_FLAG_SUGOV)) { 7399 cpumask_t *span = rq->rd->span; 7400 7401 /* 7402 * Don't allow tasks with an affinity mask smaller than 7403 * the entire root_domain to become SCHED_DEADLINE. We 7404 * will also fail if there's no bandwidth available. 7405 */ 7406 if (!cpumask_subset(span, p->cpus_ptr) || 7407 rq->rd->dl_bw.bw == 0) { 7408 retval = -EPERM; 7409 goto unlock; 7410 } 7411 } 7412 #endif 7413 } 7414 7415 /* Re-check policy now with rq lock held: */ 7416 if (unlikely(oldpolicy != -1 && oldpolicy != p->policy)) { 7417 policy = oldpolicy = -1; 7418 task_rq_unlock(rq, p, &rf); 7419 if (pi) 7420 cpuset_read_unlock(); 7421 goto recheck; 7422 } 7423 7424 /* 7425 * If setscheduling to SCHED_DEADLINE (or changing the parameters 7426 * of a SCHED_DEADLINE task) we need to check if enough bandwidth 7427 * is available. 7428 */ 7429 if ((dl_policy(policy) || dl_task(p)) && sched_dl_overflow(p, policy, attr)) { 7430 retval = -EBUSY; 7431 goto unlock; 7432 } 7433 7434 p->sched_reset_on_fork = reset_on_fork; 7435 oldprio = p->prio; 7436 7437 newprio = __normal_prio(policy, attr->sched_priority, attr->sched_nice); 7438 if (pi) { 7439 /* 7440 * Take priority boosted tasks into account. If the new 7441 * effective priority is unchanged, we just store the new 7442 * normal parameters and do not touch the scheduler class and 7443 * the runqueue. This will be done when the task deboost 7444 * itself. 7445 */ 7446 newprio = rt_effective_prio(p, newprio); 7447 if (newprio == oldprio) 7448 queue_flags &= ~DEQUEUE_MOVE; 7449 } 7450 7451 queued = task_on_rq_queued(p); 7452 running = task_current(rq, p); 7453 if (queued) 7454 dequeue_task(rq, p, queue_flags); 7455 if (running) 7456 put_prev_task(rq, p); 7457 7458 prev_class = p->sched_class; 7459 7460 if (!(attr->sched_flags & SCHED_FLAG_KEEP_PARAMS)) { 7461 __setscheduler_params(p, attr); 7462 __setscheduler_prio(p, newprio); 7463 } 7464 __setscheduler_uclamp(p, attr); 7465 7466 if (queued) { 7467 /* 7468 * We enqueue to tail when the priority of a task is 7469 * increased (user space view). 7470 */ 7471 if (oldprio < p->prio) 7472 queue_flags |= ENQUEUE_HEAD; 7473 7474 enqueue_task(rq, p, queue_flags); 7475 } 7476 if (running) 7477 set_next_task(rq, p); 7478 7479 check_class_changed(rq, p, prev_class, oldprio); 7480 7481 /* Avoid rq from going away on us: */ 7482 preempt_disable(); 7483 head = splice_balance_callbacks(rq); 7484 task_rq_unlock(rq, p, &rf); 7485 7486 if (pi) { 7487 cpuset_read_unlock(); 7488 rt_mutex_adjust_pi(p); 7489 } 7490 7491 /* Run balance callbacks after we've adjusted the PI chain: */ 7492 balance_callbacks(rq, head); 7493 preempt_enable(); 7494 7495 return 0; 7496 7497 unlock: 7498 task_rq_unlock(rq, p, &rf); 7499 if (pi) 7500 cpuset_read_unlock(); 7501 return retval; 7502 } 7503 7504 static int _sched_setscheduler(struct task_struct *p, int policy, 7505 const struct sched_param *param, bool check) 7506 { 7507 struct sched_attr attr = { 7508 .sched_policy = policy, 7509 .sched_priority = param->sched_priority, 7510 .sched_nice = PRIO_TO_NICE(p->static_prio), 7511 }; 7512 7513 /* Fixup the legacy SCHED_RESET_ON_FORK hack. */ 7514 if ((policy != SETPARAM_POLICY) && (policy & SCHED_RESET_ON_FORK)) { 7515 attr.sched_flags |= SCHED_FLAG_RESET_ON_FORK; 7516 policy &= ~SCHED_RESET_ON_FORK; 7517 attr.sched_policy = policy; 7518 } 7519 7520 return __sched_setscheduler(p, &attr, check, true); 7521 } 7522 /** 7523 * sched_setscheduler - change the scheduling policy and/or RT priority of a thread. 7524 * @p: the task in question. 7525 * @policy: new policy. 7526 * @param: structure containing the new RT priority. 7527 * 7528 * Use sched_set_fifo(), read its comment. 7529 * 7530 * Return: 0 on success. An error code otherwise. 7531 * 7532 * NOTE that the task may be already dead. 7533 */ 7534 int sched_setscheduler(struct task_struct *p, int policy, 7535 const struct sched_param *param) 7536 { 7537 return _sched_setscheduler(p, policy, param, true); 7538 } 7539 7540 int sched_setattr(struct task_struct *p, const struct sched_attr *attr) 7541 { 7542 return __sched_setscheduler(p, attr, true, true); 7543 } 7544 7545 int sched_setattr_nocheck(struct task_struct *p, const struct sched_attr *attr) 7546 { 7547 return __sched_setscheduler(p, attr, false, true); 7548 } 7549 EXPORT_SYMBOL_GPL(sched_setattr_nocheck); 7550 7551 /** 7552 * sched_setscheduler_nocheck - change the scheduling policy and/or RT priority of a thread from kernelspace. 7553 * @p: the task in question. 7554 * @policy: new policy. 7555 * @param: structure containing the new RT priority. 7556 * 7557 * Just like sched_setscheduler, only don't bother checking if the 7558 * current context has permission. For example, this is needed in 7559 * stop_machine(): we create temporary high priority worker threads, 7560 * but our caller might not have that capability. 7561 * 7562 * Return: 0 on success. An error code otherwise. 7563 */ 7564 int sched_setscheduler_nocheck(struct task_struct *p, int policy, 7565 const struct sched_param *param) 7566 { 7567 return _sched_setscheduler(p, policy, param, false); 7568 } 7569 7570 /* 7571 * SCHED_FIFO is a broken scheduler model; that is, it is fundamentally 7572 * incapable of resource management, which is the one thing an OS really should 7573 * be doing. 7574 * 7575 * This is of course the reason it is limited to privileged users only. 7576 * 7577 * Worse still; it is fundamentally impossible to compose static priority 7578 * workloads. You cannot take two correctly working static prio workloads 7579 * and smash them together and still expect them to work. 7580 * 7581 * For this reason 'all' FIFO tasks the kernel creates are basically at: 7582 * 7583 * MAX_RT_PRIO / 2 7584 * 7585 * The administrator _MUST_ configure the system, the kernel simply doesn't 7586 * know enough information to make a sensible choice. 7587 */ 7588 void sched_set_fifo(struct task_struct *p) 7589 { 7590 struct sched_param sp = { .sched_priority = MAX_RT_PRIO / 2 }; 7591 WARN_ON_ONCE(sched_setscheduler_nocheck(p, SCHED_FIFO, &sp) != 0); 7592 } 7593 EXPORT_SYMBOL_GPL(sched_set_fifo); 7594 7595 /* 7596 * For when you don't much care about FIFO, but want to be above SCHED_NORMAL. 7597 */ 7598 void sched_set_fifo_low(struct task_struct *p) 7599 { 7600 struct sched_param sp = { .sched_priority = 1 }; 7601 WARN_ON_ONCE(sched_setscheduler_nocheck(p, SCHED_FIFO, &sp) != 0); 7602 } 7603 EXPORT_SYMBOL_GPL(sched_set_fifo_low); 7604 7605 void sched_set_normal(struct task_struct *p, int nice) 7606 { 7607 struct sched_attr attr = { 7608 .sched_policy = SCHED_NORMAL, 7609 .sched_nice = nice, 7610 }; 7611 WARN_ON_ONCE(sched_setattr_nocheck(p, &attr) != 0); 7612 } 7613 EXPORT_SYMBOL_GPL(sched_set_normal); 7614 7615 static int 7616 do_sched_setscheduler(pid_t pid, int policy, struct sched_param __user *param) 7617 { 7618 struct sched_param lparam; 7619 struct task_struct *p; 7620 int retval; 7621 7622 if (!param || pid < 0) 7623 return -EINVAL; 7624 if (copy_from_user(&lparam, param, sizeof(struct sched_param))) 7625 return -EFAULT; 7626 7627 rcu_read_lock(); 7628 retval = -ESRCH; 7629 p = find_process_by_pid(pid); 7630 if (likely(p)) 7631 get_task_struct(p); 7632 rcu_read_unlock(); 7633 7634 if (likely(p)) { 7635 retval = sched_setscheduler(p, policy, &lparam); 7636 put_task_struct(p); 7637 } 7638 7639 return retval; 7640 } 7641 7642 /* 7643 * Mimics kernel/events/core.c perf_copy_attr(). 7644 */ 7645 static int sched_copy_attr(struct sched_attr __user *uattr, struct sched_attr *attr) 7646 { 7647 u32 size; 7648 int ret; 7649 7650 /* Zero the full structure, so that a short copy will be nice: */ 7651 memset(attr, 0, sizeof(*attr)); 7652 7653 ret = get_user(size, &uattr->size); 7654 if (ret) 7655 return ret; 7656 7657 /* ABI compatibility quirk: */ 7658 if (!size) 7659 size = SCHED_ATTR_SIZE_VER0; 7660 if (size < SCHED_ATTR_SIZE_VER0 || size > PAGE_SIZE) 7661 goto err_size; 7662 7663 ret = copy_struct_from_user(attr, sizeof(*attr), uattr, size); 7664 if (ret) { 7665 if (ret == -E2BIG) 7666 goto err_size; 7667 return ret; 7668 } 7669 7670 if ((attr->sched_flags & SCHED_FLAG_UTIL_CLAMP) && 7671 size < SCHED_ATTR_SIZE_VER1) 7672 return -EINVAL; 7673 7674 /* 7675 * XXX: Do we want to be lenient like existing syscalls; or do we want 7676 * to be strict and return an error on out-of-bounds values? 7677 */ 7678 attr->sched_nice = clamp(attr->sched_nice, MIN_NICE, MAX_NICE); 7679 7680 return 0; 7681 7682 err_size: 7683 put_user(sizeof(*attr), &uattr->size); 7684 return -E2BIG; 7685 } 7686 7687 static void get_params(struct task_struct *p, struct sched_attr *attr) 7688 { 7689 if (task_has_dl_policy(p)) 7690 __getparam_dl(p, attr); 7691 else if (task_has_rt_policy(p)) 7692 attr->sched_priority = p->rt_priority; 7693 else 7694 attr->sched_nice = task_nice(p); 7695 } 7696 7697 /** 7698 * sys_sched_setscheduler - set/change the scheduler policy and RT priority 7699 * @pid: the pid in question. 7700 * @policy: new policy. 7701 * @param: structure containing the new RT priority. 7702 * 7703 * Return: 0 on success. An error code otherwise. 7704 */ 7705 SYSCALL_DEFINE3(sched_setscheduler, pid_t, pid, int, policy, struct sched_param __user *, param) 7706 { 7707 if (policy < 0) 7708 return -EINVAL; 7709 7710 return do_sched_setscheduler(pid, policy, param); 7711 } 7712 7713 /** 7714 * sys_sched_setparam - set/change the RT priority of a thread 7715 * @pid: the pid in question. 7716 * @param: structure containing the new RT priority. 7717 * 7718 * Return: 0 on success. An error code otherwise. 7719 */ 7720 SYSCALL_DEFINE2(sched_setparam, pid_t, pid, struct sched_param __user *, param) 7721 { 7722 return do_sched_setscheduler(pid, SETPARAM_POLICY, param); 7723 } 7724 7725 /** 7726 * sys_sched_setattr - same as above, but with extended sched_attr 7727 * @pid: the pid in question. 7728 * @uattr: structure containing the extended parameters. 7729 * @flags: for future extension. 7730 */ 7731 SYSCALL_DEFINE3(sched_setattr, pid_t, pid, struct sched_attr __user *, uattr, 7732 unsigned int, flags) 7733 { 7734 struct sched_attr attr; 7735 struct task_struct *p; 7736 int retval; 7737 7738 if (!uattr || pid < 0 || flags) 7739 return -EINVAL; 7740 7741 retval = sched_copy_attr(uattr, &attr); 7742 if (retval) 7743 return retval; 7744 7745 if ((int)attr.sched_policy < 0) 7746 return -EINVAL; 7747 if (attr.sched_flags & SCHED_FLAG_KEEP_POLICY) 7748 attr.sched_policy = SETPARAM_POLICY; 7749 7750 rcu_read_lock(); 7751 retval = -ESRCH; 7752 p = find_process_by_pid(pid); 7753 if (likely(p)) 7754 get_task_struct(p); 7755 rcu_read_unlock(); 7756 7757 if (likely(p)) { 7758 if (attr.sched_flags & SCHED_FLAG_KEEP_PARAMS) 7759 get_params(p, &attr); 7760 retval = sched_setattr(p, &attr); 7761 put_task_struct(p); 7762 } 7763 7764 return retval; 7765 } 7766 7767 /** 7768 * sys_sched_getscheduler - get the policy (scheduling class) of a thread 7769 * @pid: the pid in question. 7770 * 7771 * Return: On success, the policy of the thread. Otherwise, a negative error 7772 * code. 7773 */ 7774 SYSCALL_DEFINE1(sched_getscheduler, pid_t, pid) 7775 { 7776 struct task_struct *p; 7777 int retval; 7778 7779 if (pid < 0) 7780 return -EINVAL; 7781 7782 retval = -ESRCH; 7783 rcu_read_lock(); 7784 p = find_process_by_pid(pid); 7785 if (p) { 7786 retval = security_task_getscheduler(p); 7787 if (!retval) 7788 retval = p->policy 7789 | (p->sched_reset_on_fork ? SCHED_RESET_ON_FORK : 0); 7790 } 7791 rcu_read_unlock(); 7792 return retval; 7793 } 7794 7795 /** 7796 * sys_sched_getparam - get the RT priority of a thread 7797 * @pid: the pid in question. 7798 * @param: structure containing the RT priority. 7799 * 7800 * Return: On success, 0 and the RT priority is in @param. Otherwise, an error 7801 * code. 7802 */ 7803 SYSCALL_DEFINE2(sched_getparam, pid_t, pid, struct sched_param __user *, param) 7804 { 7805 struct sched_param lp = { .sched_priority = 0 }; 7806 struct task_struct *p; 7807 int retval; 7808 7809 if (!param || pid < 0) 7810 return -EINVAL; 7811 7812 rcu_read_lock(); 7813 p = find_process_by_pid(pid); 7814 retval = -ESRCH; 7815 if (!p) 7816 goto out_unlock; 7817 7818 retval = security_task_getscheduler(p); 7819 if (retval) 7820 goto out_unlock; 7821 7822 if (task_has_rt_policy(p)) 7823 lp.sched_priority = p->rt_priority; 7824 rcu_read_unlock(); 7825 7826 /* 7827 * This one might sleep, we cannot do it with a spinlock held ... 7828 */ 7829 retval = copy_to_user(param, &lp, sizeof(*param)) ? -EFAULT : 0; 7830 7831 return retval; 7832 7833 out_unlock: 7834 rcu_read_unlock(); 7835 return retval; 7836 } 7837 7838 /* 7839 * Copy the kernel size attribute structure (which might be larger 7840 * than what user-space knows about) to user-space. 7841 * 7842 * Note that all cases are valid: user-space buffer can be larger or 7843 * smaller than the kernel-space buffer. The usual case is that both 7844 * have the same size. 7845 */ 7846 static int 7847 sched_attr_copy_to_user(struct sched_attr __user *uattr, 7848 struct sched_attr *kattr, 7849 unsigned int usize) 7850 { 7851 unsigned int ksize = sizeof(*kattr); 7852 7853 if (!access_ok(uattr, usize)) 7854 return -EFAULT; 7855 7856 /* 7857 * sched_getattr() ABI forwards and backwards compatibility: 7858 * 7859 * If usize == ksize then we just copy everything to user-space and all is good. 7860 * 7861 * If usize < ksize then we only copy as much as user-space has space for, 7862 * this keeps ABI compatibility as well. We skip the rest. 7863 * 7864 * If usize > ksize then user-space is using a newer version of the ABI, 7865 * which part the kernel doesn't know about. Just ignore it - tooling can 7866 * detect the kernel's knowledge of attributes from the attr->size value 7867 * which is set to ksize in this case. 7868 */ 7869 kattr->size = min(usize, ksize); 7870 7871 if (copy_to_user(uattr, kattr, kattr->size)) 7872 return -EFAULT; 7873 7874 return 0; 7875 } 7876 7877 /** 7878 * sys_sched_getattr - similar to sched_getparam, but with sched_attr 7879 * @pid: the pid in question. 7880 * @uattr: structure containing the extended parameters. 7881 * @usize: sizeof(attr) for fwd/bwd comp. 7882 * @flags: for future extension. 7883 */ 7884 SYSCALL_DEFINE4(sched_getattr, pid_t, pid, struct sched_attr __user *, uattr, 7885 unsigned int, usize, unsigned int, flags) 7886 { 7887 struct sched_attr kattr = { }; 7888 struct task_struct *p; 7889 int retval; 7890 7891 if (!uattr || pid < 0 || usize > PAGE_SIZE || 7892 usize < SCHED_ATTR_SIZE_VER0 || flags) 7893 return -EINVAL; 7894 7895 rcu_read_lock(); 7896 p = find_process_by_pid(pid); 7897 retval = -ESRCH; 7898 if (!p) 7899 goto out_unlock; 7900 7901 retval = security_task_getscheduler(p); 7902 if (retval) 7903 goto out_unlock; 7904 7905 kattr.sched_policy = p->policy; 7906 if (p->sched_reset_on_fork) 7907 kattr.sched_flags |= SCHED_FLAG_RESET_ON_FORK; 7908 get_params(p, &kattr); 7909 kattr.sched_flags &= SCHED_FLAG_ALL; 7910 7911 #ifdef CONFIG_UCLAMP_TASK 7912 /* 7913 * This could race with another potential updater, but this is fine 7914 * because it'll correctly read the old or the new value. We don't need 7915 * to guarantee who wins the race as long as it doesn't return garbage. 7916 */ 7917 kattr.sched_util_min = p->uclamp_req[UCLAMP_MIN].value; 7918 kattr.sched_util_max = p->uclamp_req[UCLAMP_MAX].value; 7919 #endif 7920 7921 rcu_read_unlock(); 7922 7923 return sched_attr_copy_to_user(uattr, &kattr, usize); 7924 7925 out_unlock: 7926 rcu_read_unlock(); 7927 return retval; 7928 } 7929 7930 #ifdef CONFIG_SMP 7931 int dl_task_check_affinity(struct task_struct *p, const struct cpumask *mask) 7932 { 7933 int ret = 0; 7934 7935 /* 7936 * If the task isn't a deadline task or admission control is 7937 * disabled then we don't care about affinity changes. 7938 */ 7939 if (!task_has_dl_policy(p) || !dl_bandwidth_enabled()) 7940 return 0; 7941 7942 /* 7943 * Since bandwidth control happens on root_domain basis, 7944 * if admission test is enabled, we only admit -deadline 7945 * tasks allowed to run on all the CPUs in the task's 7946 * root_domain. 7947 */ 7948 rcu_read_lock(); 7949 if (!cpumask_subset(task_rq(p)->rd->span, mask)) 7950 ret = -EBUSY; 7951 rcu_read_unlock(); 7952 return ret; 7953 } 7954 #endif 7955 7956 static int 7957 __sched_setaffinity(struct task_struct *p, const struct cpumask *mask) 7958 { 7959 int retval; 7960 cpumask_var_t cpus_allowed, new_mask; 7961 7962 if (!alloc_cpumask_var(&cpus_allowed, GFP_KERNEL)) 7963 return -ENOMEM; 7964 7965 if (!alloc_cpumask_var(&new_mask, GFP_KERNEL)) { 7966 retval = -ENOMEM; 7967 goto out_free_cpus_allowed; 7968 } 7969 7970 cpuset_cpus_allowed(p, cpus_allowed); 7971 cpumask_and(new_mask, mask, cpus_allowed); 7972 7973 retval = dl_task_check_affinity(p, new_mask); 7974 if (retval) 7975 goto out_free_new_mask; 7976 again: 7977 retval = __set_cpus_allowed_ptr(p, new_mask, SCA_CHECK | SCA_USER); 7978 if (retval) 7979 goto out_free_new_mask; 7980 7981 cpuset_cpus_allowed(p, cpus_allowed); 7982 if (!cpumask_subset(new_mask, cpus_allowed)) { 7983 /* 7984 * We must have raced with a concurrent cpuset update. 7985 * Just reset the cpumask to the cpuset's cpus_allowed. 7986 */ 7987 cpumask_copy(new_mask, cpus_allowed); 7988 goto again; 7989 } 7990 7991 out_free_new_mask: 7992 free_cpumask_var(new_mask); 7993 out_free_cpus_allowed: 7994 free_cpumask_var(cpus_allowed); 7995 return retval; 7996 } 7997 7998 long sched_setaffinity(pid_t pid, const struct cpumask *in_mask) 7999 { 8000 struct task_struct *p; 8001 int retval; 8002 8003 rcu_read_lock(); 8004 8005 p = find_process_by_pid(pid); 8006 if (!p) { 8007 rcu_read_unlock(); 8008 return -ESRCH; 8009 } 8010 8011 /* Prevent p going away */ 8012 get_task_struct(p); 8013 rcu_read_unlock(); 8014 8015 if (p->flags & PF_NO_SETAFFINITY) { 8016 retval = -EINVAL; 8017 goto out_put_task; 8018 } 8019 8020 if (!check_same_owner(p)) { 8021 rcu_read_lock(); 8022 if (!ns_capable(__task_cred(p)->user_ns, CAP_SYS_NICE)) { 8023 rcu_read_unlock(); 8024 retval = -EPERM; 8025 goto out_put_task; 8026 } 8027 rcu_read_unlock(); 8028 } 8029 8030 retval = security_task_setscheduler(p); 8031 if (retval) 8032 goto out_put_task; 8033 8034 retval = __sched_setaffinity(p, in_mask); 8035 out_put_task: 8036 put_task_struct(p); 8037 return retval; 8038 } 8039 8040 static int get_user_cpu_mask(unsigned long __user *user_mask_ptr, unsigned len, 8041 struct cpumask *new_mask) 8042 { 8043 if (len < cpumask_size()) 8044 cpumask_clear(new_mask); 8045 else if (len > cpumask_size()) 8046 len = cpumask_size(); 8047 8048 return copy_from_user(new_mask, user_mask_ptr, len) ? -EFAULT : 0; 8049 } 8050 8051 /** 8052 * sys_sched_setaffinity - set the CPU affinity of a process 8053 * @pid: pid of the process 8054 * @len: length in bytes of the bitmask pointed to by user_mask_ptr 8055 * @user_mask_ptr: user-space pointer to the new CPU mask 8056 * 8057 * Return: 0 on success. An error code otherwise. 8058 */ 8059 SYSCALL_DEFINE3(sched_setaffinity, pid_t, pid, unsigned int, len, 8060 unsigned long __user *, user_mask_ptr) 8061 { 8062 cpumask_var_t new_mask; 8063 int retval; 8064 8065 if (!alloc_cpumask_var(&new_mask, GFP_KERNEL)) 8066 return -ENOMEM; 8067 8068 retval = get_user_cpu_mask(user_mask_ptr, len, new_mask); 8069 if (retval == 0) 8070 retval = sched_setaffinity(pid, new_mask); 8071 free_cpumask_var(new_mask); 8072 return retval; 8073 } 8074 8075 long sched_getaffinity(pid_t pid, struct cpumask *mask) 8076 { 8077 struct task_struct *p; 8078 unsigned long flags; 8079 int retval; 8080 8081 rcu_read_lock(); 8082 8083 retval = -ESRCH; 8084 p = find_process_by_pid(pid); 8085 if (!p) 8086 goto out_unlock; 8087 8088 retval = security_task_getscheduler(p); 8089 if (retval) 8090 goto out_unlock; 8091 8092 raw_spin_lock_irqsave(&p->pi_lock, flags); 8093 cpumask_and(mask, &p->cpus_mask, cpu_active_mask); 8094 raw_spin_unlock_irqrestore(&p->pi_lock, flags); 8095 8096 out_unlock: 8097 rcu_read_unlock(); 8098 8099 return retval; 8100 } 8101 8102 /** 8103 * sys_sched_getaffinity - get the CPU affinity of a process 8104 * @pid: pid of the process 8105 * @len: length in bytes of the bitmask pointed to by user_mask_ptr 8106 * @user_mask_ptr: user-space pointer to hold the current CPU mask 8107 * 8108 * Return: size of CPU mask copied to user_mask_ptr on success. An 8109 * error code otherwise. 8110 */ 8111 SYSCALL_DEFINE3(sched_getaffinity, pid_t, pid, unsigned int, len, 8112 unsigned long __user *, user_mask_ptr) 8113 { 8114 int ret; 8115 cpumask_var_t mask; 8116 8117 if ((len * BITS_PER_BYTE) < nr_cpu_ids) 8118 return -EINVAL; 8119 if (len & (sizeof(unsigned long)-1)) 8120 return -EINVAL; 8121 8122 if (!alloc_cpumask_var(&mask, GFP_KERNEL)) 8123 return -ENOMEM; 8124 8125 ret = sched_getaffinity(pid, mask); 8126 if (ret == 0) { 8127 unsigned int retlen = min(len, cpumask_size()); 8128 8129 if (copy_to_user(user_mask_ptr, mask, retlen)) 8130 ret = -EFAULT; 8131 else 8132 ret = retlen; 8133 } 8134 free_cpumask_var(mask); 8135 8136 return ret; 8137 } 8138 8139 static void do_sched_yield(void) 8140 { 8141 struct rq_flags rf; 8142 struct rq *rq; 8143 8144 rq = this_rq_lock_irq(&rf); 8145 8146 schedstat_inc(rq->yld_count); 8147 current->sched_class->yield_task(rq); 8148 8149 preempt_disable(); 8150 rq_unlock_irq(rq, &rf); 8151 sched_preempt_enable_no_resched(); 8152 8153 schedule(); 8154 } 8155 8156 /** 8157 * sys_sched_yield - yield the current processor to other threads. 8158 * 8159 * This function yields the current CPU to other tasks. If there are no 8160 * other threads running on this CPU then this function will return. 8161 * 8162 * Return: 0. 8163 */ 8164 SYSCALL_DEFINE0(sched_yield) 8165 { 8166 do_sched_yield(); 8167 return 0; 8168 } 8169 8170 #if !defined(CONFIG_PREEMPTION) || defined(CONFIG_PREEMPT_DYNAMIC) 8171 int __sched __cond_resched(void) 8172 { 8173 if (should_resched(0)) { 8174 preempt_schedule_common(); 8175 return 1; 8176 } 8177 /* 8178 * In preemptible kernels, ->rcu_read_lock_nesting tells the tick 8179 * whether the current CPU is in an RCU read-side critical section, 8180 * so the tick can report quiescent states even for CPUs looping 8181 * in kernel context. In contrast, in non-preemptible kernels, 8182 * RCU readers leave no in-memory hints, which means that CPU-bound 8183 * processes executing in kernel context might never report an 8184 * RCU quiescent state. Therefore, the following code causes 8185 * cond_resched() to report a quiescent state, but only when RCU 8186 * is in urgent need of one. 8187 */ 8188 #ifndef CONFIG_PREEMPT_RCU 8189 rcu_all_qs(); 8190 #endif 8191 return 0; 8192 } 8193 EXPORT_SYMBOL(__cond_resched); 8194 #endif 8195 8196 #ifdef CONFIG_PREEMPT_DYNAMIC 8197 DEFINE_STATIC_CALL_RET0(cond_resched, __cond_resched); 8198 EXPORT_STATIC_CALL_TRAMP(cond_resched); 8199 8200 DEFINE_STATIC_CALL_RET0(might_resched, __cond_resched); 8201 EXPORT_STATIC_CALL_TRAMP(might_resched); 8202 #endif 8203 8204 /* 8205 * __cond_resched_lock() - if a reschedule is pending, drop the given lock, 8206 * call schedule, and on return reacquire the lock. 8207 * 8208 * This works OK both with and without CONFIG_PREEMPTION. We do strange low-level 8209 * operations here to prevent schedule() from being called twice (once via 8210 * spin_unlock(), once by hand). 8211 */ 8212 int __cond_resched_lock(spinlock_t *lock) 8213 { 8214 int resched = should_resched(PREEMPT_LOCK_OFFSET); 8215 int ret = 0; 8216 8217 lockdep_assert_held(lock); 8218 8219 if (spin_needbreak(lock) || resched) { 8220 spin_unlock(lock); 8221 if (!_cond_resched()) 8222 cpu_relax(); 8223 ret = 1; 8224 spin_lock(lock); 8225 } 8226 return ret; 8227 } 8228 EXPORT_SYMBOL(__cond_resched_lock); 8229 8230 int __cond_resched_rwlock_read(rwlock_t *lock) 8231 { 8232 int resched = should_resched(PREEMPT_LOCK_OFFSET); 8233 int ret = 0; 8234 8235 lockdep_assert_held_read(lock); 8236 8237 if (rwlock_needbreak(lock) || resched) { 8238 read_unlock(lock); 8239 if (!_cond_resched()) 8240 cpu_relax(); 8241 ret = 1; 8242 read_lock(lock); 8243 } 8244 return ret; 8245 } 8246 EXPORT_SYMBOL(__cond_resched_rwlock_read); 8247 8248 int __cond_resched_rwlock_write(rwlock_t *lock) 8249 { 8250 int resched = should_resched(PREEMPT_LOCK_OFFSET); 8251 int ret = 0; 8252 8253 lockdep_assert_held_write(lock); 8254 8255 if (rwlock_needbreak(lock) || resched) { 8256 write_unlock(lock); 8257 if (!_cond_resched()) 8258 cpu_relax(); 8259 ret = 1; 8260 write_lock(lock); 8261 } 8262 return ret; 8263 } 8264 EXPORT_SYMBOL(__cond_resched_rwlock_write); 8265 8266 /** 8267 * yield - yield the current processor to other threads. 8268 * 8269 * Do not ever use this function, there's a 99% chance you're doing it wrong. 8270 * 8271 * The scheduler is at all times free to pick the calling task as the most 8272 * eligible task to run, if removing the yield() call from your code breaks 8273 * it, it's already broken. 8274 * 8275 * Typical broken usage is: 8276 * 8277 * while (!event) 8278 * yield(); 8279 * 8280 * where one assumes that yield() will let 'the other' process run that will 8281 * make event true. If the current task is a SCHED_FIFO task that will never 8282 * happen. Never use yield() as a progress guarantee!! 8283 * 8284 * If you want to use yield() to wait for something, use wait_event(). 8285 * If you want to use yield() to be 'nice' for others, use cond_resched(). 8286 * If you still want to use yield(), do not! 8287 */ 8288 void __sched yield(void) 8289 { 8290 set_current_state(TASK_RUNNING); 8291 do_sched_yield(); 8292 } 8293 EXPORT_SYMBOL(yield); 8294 8295 /** 8296 * yield_to - yield the current processor to another thread in 8297 * your thread group, or accelerate that thread toward the 8298 * processor it's on. 8299 * @p: target task 8300 * @preempt: whether task preemption is allowed or not 8301 * 8302 * It's the caller's job to ensure that the target task struct 8303 * can't go away on us before we can do any checks. 8304 * 8305 * Return: 8306 * true (>0) if we indeed boosted the target task. 8307 * false (0) if we failed to boost the target. 8308 * -ESRCH if there's no task to yield to. 8309 */ 8310 int __sched yield_to(struct task_struct *p, bool preempt) 8311 { 8312 struct task_struct *curr = current; 8313 struct rq *rq, *p_rq; 8314 unsigned long flags; 8315 int yielded = 0; 8316 8317 local_irq_save(flags); 8318 rq = this_rq(); 8319 8320 again: 8321 p_rq = task_rq(p); 8322 /* 8323 * If we're the only runnable task on the rq and target rq also 8324 * has only one task, there's absolutely no point in yielding. 8325 */ 8326 if (rq->nr_running == 1 && p_rq->nr_running == 1) { 8327 yielded = -ESRCH; 8328 goto out_irq; 8329 } 8330 8331 double_rq_lock(rq, p_rq); 8332 if (task_rq(p) != p_rq) { 8333 double_rq_unlock(rq, p_rq); 8334 goto again; 8335 } 8336 8337 if (!curr->sched_class->yield_to_task) 8338 goto out_unlock; 8339 8340 if (curr->sched_class != p->sched_class) 8341 goto out_unlock; 8342 8343 if (task_running(p_rq, p) || !task_is_running(p)) 8344 goto out_unlock; 8345 8346 yielded = curr->sched_class->yield_to_task(rq, p); 8347 if (yielded) { 8348 schedstat_inc(rq->yld_count); 8349 /* 8350 * Make p's CPU reschedule; pick_next_entity takes care of 8351 * fairness. 8352 */ 8353 if (preempt && rq != p_rq) 8354 resched_curr(p_rq); 8355 } 8356 8357 out_unlock: 8358 double_rq_unlock(rq, p_rq); 8359 out_irq: 8360 local_irq_restore(flags); 8361 8362 if (yielded > 0) 8363 schedule(); 8364 8365 return yielded; 8366 } 8367 EXPORT_SYMBOL_GPL(yield_to); 8368 8369 int io_schedule_prepare(void) 8370 { 8371 int old_iowait = current->in_iowait; 8372 8373 current->in_iowait = 1; 8374 if (current->plug) 8375 blk_flush_plug(current->plug, true); 8376 8377 return old_iowait; 8378 } 8379 8380 void io_schedule_finish(int token) 8381 { 8382 current->in_iowait = token; 8383 } 8384 8385 /* 8386 * This task is about to go to sleep on IO. Increment rq->nr_iowait so 8387 * that process accounting knows that this is a task in IO wait state. 8388 */ 8389 long __sched io_schedule_timeout(long timeout) 8390 { 8391 int token; 8392 long ret; 8393 8394 token = io_schedule_prepare(); 8395 ret = schedule_timeout(timeout); 8396 io_schedule_finish(token); 8397 8398 return ret; 8399 } 8400 EXPORT_SYMBOL(io_schedule_timeout); 8401 8402 void __sched io_schedule(void) 8403 { 8404 int token; 8405 8406 token = io_schedule_prepare(); 8407 schedule(); 8408 io_schedule_finish(token); 8409 } 8410 EXPORT_SYMBOL(io_schedule); 8411 8412 /** 8413 * sys_sched_get_priority_max - return maximum RT priority. 8414 * @policy: scheduling class. 8415 * 8416 * Return: On success, this syscall returns the maximum 8417 * rt_priority that can be used by a given scheduling class. 8418 * On failure, a negative error code is returned. 8419 */ 8420 SYSCALL_DEFINE1(sched_get_priority_max, int, policy) 8421 { 8422 int ret = -EINVAL; 8423 8424 switch (policy) { 8425 case SCHED_FIFO: 8426 case SCHED_RR: 8427 ret = MAX_RT_PRIO-1; 8428 break; 8429 case SCHED_DEADLINE: 8430 case SCHED_NORMAL: 8431 case SCHED_BATCH: 8432 case SCHED_IDLE: 8433 ret = 0; 8434 break; 8435 } 8436 return ret; 8437 } 8438 8439 /** 8440 * sys_sched_get_priority_min - return minimum RT priority. 8441 * @policy: scheduling class. 8442 * 8443 * Return: On success, this syscall returns the minimum 8444 * rt_priority that can be used by a given scheduling class. 8445 * On failure, a negative error code is returned. 8446 */ 8447 SYSCALL_DEFINE1(sched_get_priority_min, int, policy) 8448 { 8449 int ret = -EINVAL; 8450 8451 switch (policy) { 8452 case SCHED_FIFO: 8453 case SCHED_RR: 8454 ret = 1; 8455 break; 8456 case SCHED_DEADLINE: 8457 case SCHED_NORMAL: 8458 case SCHED_BATCH: 8459 case SCHED_IDLE: 8460 ret = 0; 8461 } 8462 return ret; 8463 } 8464 8465 static int sched_rr_get_interval(pid_t pid, struct timespec64 *t) 8466 { 8467 struct task_struct *p; 8468 unsigned int time_slice; 8469 struct rq_flags rf; 8470 struct rq *rq; 8471 int retval; 8472 8473 if (pid < 0) 8474 return -EINVAL; 8475 8476 retval = -ESRCH; 8477 rcu_read_lock(); 8478 p = find_process_by_pid(pid); 8479 if (!p) 8480 goto out_unlock; 8481 8482 retval = security_task_getscheduler(p); 8483 if (retval) 8484 goto out_unlock; 8485 8486 rq = task_rq_lock(p, &rf); 8487 time_slice = 0; 8488 if (p->sched_class->get_rr_interval) 8489 time_slice = p->sched_class->get_rr_interval(rq, p); 8490 task_rq_unlock(rq, p, &rf); 8491 8492 rcu_read_unlock(); 8493 jiffies_to_timespec64(time_slice, t); 8494 return 0; 8495 8496 out_unlock: 8497 rcu_read_unlock(); 8498 return retval; 8499 } 8500 8501 /** 8502 * sys_sched_rr_get_interval - return the default timeslice of a process. 8503 * @pid: pid of the process. 8504 * @interval: userspace pointer to the timeslice value. 8505 * 8506 * this syscall writes the default timeslice value of a given process 8507 * into the user-space timespec buffer. A value of '0' means infinity. 8508 * 8509 * Return: On success, 0 and the timeslice is in @interval. Otherwise, 8510 * an error code. 8511 */ 8512 SYSCALL_DEFINE2(sched_rr_get_interval, pid_t, pid, 8513 struct __kernel_timespec __user *, interval) 8514 { 8515 struct timespec64 t; 8516 int retval = sched_rr_get_interval(pid, &t); 8517 8518 if (retval == 0) 8519 retval = put_timespec64(&t, interval); 8520 8521 return retval; 8522 } 8523 8524 #ifdef CONFIG_COMPAT_32BIT_TIME 8525 SYSCALL_DEFINE2(sched_rr_get_interval_time32, pid_t, pid, 8526 struct old_timespec32 __user *, interval) 8527 { 8528 struct timespec64 t; 8529 int retval = sched_rr_get_interval(pid, &t); 8530 8531 if (retval == 0) 8532 retval = put_old_timespec32(&t, interval); 8533 return retval; 8534 } 8535 #endif 8536 8537 void sched_show_task(struct task_struct *p) 8538 { 8539 unsigned long free = 0; 8540 int ppid; 8541 8542 if (!try_get_task_stack(p)) 8543 return; 8544 8545 pr_info("task:%-15.15s state:%c", p->comm, task_state_to_char(p)); 8546 8547 if (task_is_running(p)) 8548 pr_cont(" running task "); 8549 #ifdef CONFIG_DEBUG_STACK_USAGE 8550 free = stack_not_used(p); 8551 #endif 8552 ppid = 0; 8553 rcu_read_lock(); 8554 if (pid_alive(p)) 8555 ppid = task_pid_nr(rcu_dereference(p->real_parent)); 8556 rcu_read_unlock(); 8557 pr_cont(" stack:%5lu pid:%5d ppid:%6d flags:0x%08lx\n", 8558 free, task_pid_nr(p), ppid, 8559 read_task_thread_flags(p)); 8560 8561 print_worker_info(KERN_INFO, p); 8562 print_stop_info(KERN_INFO, p); 8563 show_stack(p, NULL, KERN_INFO); 8564 put_task_stack(p); 8565 } 8566 EXPORT_SYMBOL_GPL(sched_show_task); 8567 8568 static inline bool 8569 state_filter_match(unsigned long state_filter, struct task_struct *p) 8570 { 8571 unsigned int state = READ_ONCE(p->__state); 8572 8573 /* no filter, everything matches */ 8574 if (!state_filter) 8575 return true; 8576 8577 /* filter, but doesn't match */ 8578 if (!(state & state_filter)) 8579 return false; 8580 8581 /* 8582 * When looking for TASK_UNINTERRUPTIBLE skip TASK_IDLE (allows 8583 * TASK_KILLABLE). 8584 */ 8585 if (state_filter == TASK_UNINTERRUPTIBLE && state == TASK_IDLE) 8586 return false; 8587 8588 return true; 8589 } 8590 8591 8592 void show_state_filter(unsigned int state_filter) 8593 { 8594 struct task_struct *g, *p; 8595 8596 rcu_read_lock(); 8597 for_each_process_thread(g, p) { 8598 /* 8599 * reset the NMI-timeout, listing all files on a slow 8600 * console might take a lot of time: 8601 * Also, reset softlockup watchdogs on all CPUs, because 8602 * another CPU might be blocked waiting for us to process 8603 * an IPI. 8604 */ 8605 touch_nmi_watchdog(); 8606 touch_all_softlockup_watchdogs(); 8607 if (state_filter_match(state_filter, p)) 8608 sched_show_task(p); 8609 } 8610 8611 #ifdef CONFIG_SCHED_DEBUG 8612 if (!state_filter) 8613 sysrq_sched_debug_show(); 8614 #endif 8615 rcu_read_unlock(); 8616 /* 8617 * Only show locks if all tasks are dumped: 8618 */ 8619 if (!state_filter) 8620 debug_show_all_locks(); 8621 } 8622 8623 /** 8624 * init_idle - set up an idle thread for a given CPU 8625 * @idle: task in question 8626 * @cpu: CPU the idle task belongs to 8627 * 8628 * NOTE: this function does not set the idle thread's NEED_RESCHED 8629 * flag, to make booting more robust. 8630 */ 8631 void __init init_idle(struct task_struct *idle, int cpu) 8632 { 8633 struct rq *rq = cpu_rq(cpu); 8634 unsigned long flags; 8635 8636 __sched_fork(0, idle); 8637 8638 raw_spin_lock_irqsave(&idle->pi_lock, flags); 8639 raw_spin_rq_lock(rq); 8640 8641 idle->__state = TASK_RUNNING; 8642 idle->se.exec_start = sched_clock(); 8643 /* 8644 * PF_KTHREAD should already be set at this point; regardless, make it 8645 * look like a proper per-CPU kthread. 8646 */ 8647 idle->flags |= PF_IDLE | PF_KTHREAD | PF_NO_SETAFFINITY; 8648 kthread_set_per_cpu(idle, cpu); 8649 8650 #ifdef CONFIG_SMP 8651 /* 8652 * It's possible that init_idle() gets called multiple times on a task, 8653 * in that case do_set_cpus_allowed() will not do the right thing. 8654 * 8655 * And since this is boot we can forgo the serialization. 8656 */ 8657 set_cpus_allowed_common(idle, cpumask_of(cpu), 0); 8658 #endif 8659 /* 8660 * We're having a chicken and egg problem, even though we are 8661 * holding rq->lock, the CPU isn't yet set to this CPU so the 8662 * lockdep check in task_group() will fail. 8663 * 8664 * Similar case to sched_fork(). / Alternatively we could 8665 * use task_rq_lock() here and obtain the other rq->lock. 8666 * 8667 * Silence PROVE_RCU 8668 */ 8669 rcu_read_lock(); 8670 __set_task_cpu(idle, cpu); 8671 rcu_read_unlock(); 8672 8673 rq->idle = idle; 8674 rcu_assign_pointer(rq->curr, idle); 8675 idle->on_rq = TASK_ON_RQ_QUEUED; 8676 #ifdef CONFIG_SMP 8677 idle->on_cpu = 1; 8678 #endif 8679 raw_spin_rq_unlock(rq); 8680 raw_spin_unlock_irqrestore(&idle->pi_lock, flags); 8681 8682 /* Set the preempt count _outside_ the spinlocks! */ 8683 init_idle_preempt_count(idle, cpu); 8684 8685 /* 8686 * The idle tasks have their own, simple scheduling class: 8687 */ 8688 idle->sched_class = &idle_sched_class; 8689 ftrace_graph_init_idle_task(idle, cpu); 8690 vtime_init_idle(idle, cpu); 8691 #ifdef CONFIG_SMP 8692 sprintf(idle->comm, "%s/%d", INIT_TASK_COMM, cpu); 8693 #endif 8694 } 8695 8696 #ifdef CONFIG_SMP 8697 8698 int cpuset_cpumask_can_shrink(const struct cpumask *cur, 8699 const struct cpumask *trial) 8700 { 8701 int ret = 1; 8702 8703 if (!cpumask_weight(cur)) 8704 return ret; 8705 8706 ret = dl_cpuset_cpumask_can_shrink(cur, trial); 8707 8708 return ret; 8709 } 8710 8711 int task_can_attach(struct task_struct *p, 8712 const struct cpumask *cs_cpus_allowed) 8713 { 8714 int ret = 0; 8715 8716 /* 8717 * Kthreads which disallow setaffinity shouldn't be moved 8718 * to a new cpuset; we don't want to change their CPU 8719 * affinity and isolating such threads by their set of 8720 * allowed nodes is unnecessary. Thus, cpusets are not 8721 * applicable for such threads. This prevents checking for 8722 * success of set_cpus_allowed_ptr() on all attached tasks 8723 * before cpus_mask may be changed. 8724 */ 8725 if (p->flags & PF_NO_SETAFFINITY) { 8726 ret = -EINVAL; 8727 goto out; 8728 } 8729 8730 if (dl_task(p) && !cpumask_intersects(task_rq(p)->rd->span, 8731 cs_cpus_allowed)) 8732 ret = dl_task_can_attach(p, cs_cpus_allowed); 8733 8734 out: 8735 return ret; 8736 } 8737 8738 bool sched_smp_initialized __read_mostly; 8739 8740 #ifdef CONFIG_NUMA_BALANCING 8741 /* Migrate current task p to target_cpu */ 8742 int migrate_task_to(struct task_struct *p, int target_cpu) 8743 { 8744 struct migration_arg arg = { p, target_cpu }; 8745 int curr_cpu = task_cpu(p); 8746 8747 if (curr_cpu == target_cpu) 8748 return 0; 8749 8750 if (!cpumask_test_cpu(target_cpu, p->cpus_ptr)) 8751 return -EINVAL; 8752 8753 /* TODO: This is not properly updating schedstats */ 8754 8755 trace_sched_move_numa(p, curr_cpu, target_cpu); 8756 return stop_one_cpu(curr_cpu, migration_cpu_stop, &arg); 8757 } 8758 8759 /* 8760 * Requeue a task on a given node and accurately track the number of NUMA 8761 * tasks on the runqueues 8762 */ 8763 void sched_setnuma(struct task_struct *p, int nid) 8764 { 8765 bool queued, running; 8766 struct rq_flags rf; 8767 struct rq *rq; 8768 8769 rq = task_rq_lock(p, &rf); 8770 queued = task_on_rq_queued(p); 8771 running = task_current(rq, p); 8772 8773 if (queued) 8774 dequeue_task(rq, p, DEQUEUE_SAVE); 8775 if (running) 8776 put_prev_task(rq, p); 8777 8778 p->numa_preferred_nid = nid; 8779 8780 if (queued) 8781 enqueue_task(rq, p, ENQUEUE_RESTORE | ENQUEUE_NOCLOCK); 8782 if (running) 8783 set_next_task(rq, p); 8784 task_rq_unlock(rq, p, &rf); 8785 } 8786 #endif /* CONFIG_NUMA_BALANCING */ 8787 8788 #ifdef CONFIG_HOTPLUG_CPU 8789 /* 8790 * Ensure that the idle task is using init_mm right before its CPU goes 8791 * offline. 8792 */ 8793 void idle_task_exit(void) 8794 { 8795 struct mm_struct *mm = current->active_mm; 8796 8797 BUG_ON(cpu_online(smp_processor_id())); 8798 BUG_ON(current != this_rq()->idle); 8799 8800 if (mm != &init_mm) { 8801 switch_mm(mm, &init_mm, current); 8802 finish_arch_post_lock_switch(); 8803 } 8804 8805 /* finish_cpu(), as ran on the BP, will clean up the active_mm state */ 8806 } 8807 8808 static int __balance_push_cpu_stop(void *arg) 8809 { 8810 struct task_struct *p = arg; 8811 struct rq *rq = this_rq(); 8812 struct rq_flags rf; 8813 int cpu; 8814 8815 raw_spin_lock_irq(&p->pi_lock); 8816 rq_lock(rq, &rf); 8817 8818 update_rq_clock(rq); 8819 8820 if (task_rq(p) == rq && task_on_rq_queued(p)) { 8821 cpu = select_fallback_rq(rq->cpu, p); 8822 rq = __migrate_task(rq, &rf, p, cpu); 8823 } 8824 8825 rq_unlock(rq, &rf); 8826 raw_spin_unlock_irq(&p->pi_lock); 8827 8828 put_task_struct(p); 8829 8830 return 0; 8831 } 8832 8833 static DEFINE_PER_CPU(struct cpu_stop_work, push_work); 8834 8835 /* 8836 * Ensure we only run per-cpu kthreads once the CPU goes !active. 8837 * 8838 * This is enabled below SCHED_AP_ACTIVE; when !cpu_active(), but only 8839 * effective when the hotplug motion is down. 8840 */ 8841 static void balance_push(struct rq *rq) 8842 { 8843 struct task_struct *push_task = rq->curr; 8844 8845 lockdep_assert_rq_held(rq); 8846 8847 /* 8848 * Ensure the thing is persistent until balance_push_set(.on = false); 8849 */ 8850 rq->balance_callback = &balance_push_callback; 8851 8852 /* 8853 * Only active while going offline and when invoked on the outgoing 8854 * CPU. 8855 */ 8856 if (!cpu_dying(rq->cpu) || rq != this_rq()) 8857 return; 8858 8859 /* 8860 * Both the cpu-hotplug and stop task are in this case and are 8861 * required to complete the hotplug process. 8862 */ 8863 if (kthread_is_per_cpu(push_task) || 8864 is_migration_disabled(push_task)) { 8865 8866 /* 8867 * If this is the idle task on the outgoing CPU try to wake 8868 * up the hotplug control thread which might wait for the 8869 * last task to vanish. The rcuwait_active() check is 8870 * accurate here because the waiter is pinned on this CPU 8871 * and can't obviously be running in parallel. 8872 * 8873 * On RT kernels this also has to check whether there are 8874 * pinned and scheduled out tasks on the runqueue. They 8875 * need to leave the migrate disabled section first. 8876 */ 8877 if (!rq->nr_running && !rq_has_pinned_tasks(rq) && 8878 rcuwait_active(&rq->hotplug_wait)) { 8879 raw_spin_rq_unlock(rq); 8880 rcuwait_wake_up(&rq->hotplug_wait); 8881 raw_spin_rq_lock(rq); 8882 } 8883 return; 8884 } 8885 8886 get_task_struct(push_task); 8887 /* 8888 * Temporarily drop rq->lock such that we can wake-up the stop task. 8889 * Both preemption and IRQs are still disabled. 8890 */ 8891 raw_spin_rq_unlock(rq); 8892 stop_one_cpu_nowait(rq->cpu, __balance_push_cpu_stop, push_task, 8893 this_cpu_ptr(&push_work)); 8894 /* 8895 * At this point need_resched() is true and we'll take the loop in 8896 * schedule(). The next pick is obviously going to be the stop task 8897 * which kthread_is_per_cpu() and will push this task away. 8898 */ 8899 raw_spin_rq_lock(rq); 8900 } 8901 8902 static void balance_push_set(int cpu, bool on) 8903 { 8904 struct rq *rq = cpu_rq(cpu); 8905 struct rq_flags rf; 8906 8907 rq_lock_irqsave(rq, &rf); 8908 if (on) { 8909 WARN_ON_ONCE(rq->balance_callback); 8910 rq->balance_callback = &balance_push_callback; 8911 } else if (rq->balance_callback == &balance_push_callback) { 8912 rq->balance_callback = NULL; 8913 } 8914 rq_unlock_irqrestore(rq, &rf); 8915 } 8916 8917 /* 8918 * Invoked from a CPUs hotplug control thread after the CPU has been marked 8919 * inactive. All tasks which are not per CPU kernel threads are either 8920 * pushed off this CPU now via balance_push() or placed on a different CPU 8921 * during wakeup. Wait until the CPU is quiescent. 8922 */ 8923 static void balance_hotplug_wait(void) 8924 { 8925 struct rq *rq = this_rq(); 8926 8927 rcuwait_wait_event(&rq->hotplug_wait, 8928 rq->nr_running == 1 && !rq_has_pinned_tasks(rq), 8929 TASK_UNINTERRUPTIBLE); 8930 } 8931 8932 #else 8933 8934 static inline void balance_push(struct rq *rq) 8935 { 8936 } 8937 8938 static inline void balance_push_set(int cpu, bool on) 8939 { 8940 } 8941 8942 static inline void balance_hotplug_wait(void) 8943 { 8944 } 8945 8946 #endif /* CONFIG_HOTPLUG_CPU */ 8947 8948 void set_rq_online(struct rq *rq) 8949 { 8950 if (!rq->online) { 8951 const struct sched_class *class; 8952 8953 cpumask_set_cpu(rq->cpu, rq->rd->online); 8954 rq->online = 1; 8955 8956 for_each_class(class) { 8957 if (class->rq_online) 8958 class->rq_online(rq); 8959 } 8960 } 8961 } 8962 8963 void set_rq_offline(struct rq *rq) 8964 { 8965 if (rq->online) { 8966 const struct sched_class *class; 8967 8968 for_each_class(class) { 8969 if (class->rq_offline) 8970 class->rq_offline(rq); 8971 } 8972 8973 cpumask_clear_cpu(rq->cpu, rq->rd->online); 8974 rq->online = 0; 8975 } 8976 } 8977 8978 /* 8979 * used to mark begin/end of suspend/resume: 8980 */ 8981 static int num_cpus_frozen; 8982 8983 /* 8984 * Update cpusets according to cpu_active mask. If cpusets are 8985 * disabled, cpuset_update_active_cpus() becomes a simple wrapper 8986 * around partition_sched_domains(). 8987 * 8988 * If we come here as part of a suspend/resume, don't touch cpusets because we 8989 * want to restore it back to its original state upon resume anyway. 8990 */ 8991 static void cpuset_cpu_active(void) 8992 { 8993 if (cpuhp_tasks_frozen) { 8994 /* 8995 * num_cpus_frozen tracks how many CPUs are involved in suspend 8996 * resume sequence. As long as this is not the last online 8997 * operation in the resume sequence, just build a single sched 8998 * domain, ignoring cpusets. 8999 */ 9000 partition_sched_domains(1, NULL, NULL); 9001 if (--num_cpus_frozen) 9002 return; 9003 /* 9004 * This is the last CPU online operation. So fall through and 9005 * restore the original sched domains by considering the 9006 * cpuset configurations. 9007 */ 9008 cpuset_force_rebuild(); 9009 } 9010 cpuset_update_active_cpus(); 9011 } 9012 9013 static int cpuset_cpu_inactive(unsigned int cpu) 9014 { 9015 if (!cpuhp_tasks_frozen) { 9016 if (dl_cpu_busy(cpu)) 9017 return -EBUSY; 9018 cpuset_update_active_cpus(); 9019 } else { 9020 num_cpus_frozen++; 9021 partition_sched_domains(1, NULL, NULL); 9022 } 9023 return 0; 9024 } 9025 9026 int sched_cpu_activate(unsigned int cpu) 9027 { 9028 struct rq *rq = cpu_rq(cpu); 9029 struct rq_flags rf; 9030 9031 /* 9032 * Clear the balance_push callback and prepare to schedule 9033 * regular tasks. 9034 */ 9035 balance_push_set(cpu, false); 9036 9037 #ifdef CONFIG_SCHED_SMT 9038 /* 9039 * When going up, increment the number of cores with SMT present. 9040 */ 9041 if (cpumask_weight(cpu_smt_mask(cpu)) == 2) 9042 static_branch_inc_cpuslocked(&sched_smt_present); 9043 #endif 9044 set_cpu_active(cpu, true); 9045 9046 if (sched_smp_initialized) { 9047 sched_domains_numa_masks_set(cpu); 9048 cpuset_cpu_active(); 9049 } 9050 9051 /* 9052 * Put the rq online, if not already. This happens: 9053 * 9054 * 1) In the early boot process, because we build the real domains 9055 * after all CPUs have been brought up. 9056 * 9057 * 2) At runtime, if cpuset_cpu_active() fails to rebuild the 9058 * domains. 9059 */ 9060 rq_lock_irqsave(rq, &rf); 9061 if (rq->rd) { 9062 BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span)); 9063 set_rq_online(rq); 9064 } 9065 rq_unlock_irqrestore(rq, &rf); 9066 9067 return 0; 9068 } 9069 9070 int sched_cpu_deactivate(unsigned int cpu) 9071 { 9072 struct rq *rq = cpu_rq(cpu); 9073 struct rq_flags rf; 9074 int ret; 9075 9076 /* 9077 * Remove CPU from nohz.idle_cpus_mask to prevent participating in 9078 * load balancing when not active 9079 */ 9080 nohz_balance_exit_idle(rq); 9081 9082 set_cpu_active(cpu, false); 9083 9084 /* 9085 * From this point forward, this CPU will refuse to run any task that 9086 * is not: migrate_disable() or KTHREAD_IS_PER_CPU, and will actively 9087 * push those tasks away until this gets cleared, see 9088 * sched_cpu_dying(). 9089 */ 9090 balance_push_set(cpu, true); 9091 9092 /* 9093 * We've cleared cpu_active_mask / set balance_push, wait for all 9094 * preempt-disabled and RCU users of this state to go away such that 9095 * all new such users will observe it. 9096 * 9097 * Specifically, we rely on ttwu to no longer target this CPU, see 9098 * ttwu_queue_cond() and is_cpu_allowed(). 9099 * 9100 * Do sync before park smpboot threads to take care the rcu boost case. 9101 */ 9102 synchronize_rcu(); 9103 9104 rq_lock_irqsave(rq, &rf); 9105 if (rq->rd) { 9106 update_rq_clock(rq); 9107 BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span)); 9108 set_rq_offline(rq); 9109 } 9110 rq_unlock_irqrestore(rq, &rf); 9111 9112 #ifdef CONFIG_SCHED_SMT 9113 /* 9114 * When going down, decrement the number of cores with SMT present. 9115 */ 9116 if (cpumask_weight(cpu_smt_mask(cpu)) == 2) 9117 static_branch_dec_cpuslocked(&sched_smt_present); 9118 9119 sched_core_cpu_deactivate(cpu); 9120 #endif 9121 9122 if (!sched_smp_initialized) 9123 return 0; 9124 9125 ret = cpuset_cpu_inactive(cpu); 9126 if (ret) { 9127 balance_push_set(cpu, false); 9128 set_cpu_active(cpu, true); 9129 return ret; 9130 } 9131 sched_domains_numa_masks_clear(cpu); 9132 return 0; 9133 } 9134 9135 static void sched_rq_cpu_starting(unsigned int cpu) 9136 { 9137 struct rq *rq = cpu_rq(cpu); 9138 9139 rq->calc_load_update = calc_load_update; 9140 update_max_interval(); 9141 } 9142 9143 int sched_cpu_starting(unsigned int cpu) 9144 { 9145 sched_core_cpu_starting(cpu); 9146 sched_rq_cpu_starting(cpu); 9147 sched_tick_start(cpu); 9148 return 0; 9149 } 9150 9151 #ifdef CONFIG_HOTPLUG_CPU 9152 9153 /* 9154 * Invoked immediately before the stopper thread is invoked to bring the 9155 * CPU down completely. At this point all per CPU kthreads except the 9156 * hotplug thread (current) and the stopper thread (inactive) have been 9157 * either parked or have been unbound from the outgoing CPU. Ensure that 9158 * any of those which might be on the way out are gone. 9159 * 9160 * If after this point a bound task is being woken on this CPU then the 9161 * responsible hotplug callback has failed to do it's job. 9162 * sched_cpu_dying() will catch it with the appropriate fireworks. 9163 */ 9164 int sched_cpu_wait_empty(unsigned int cpu) 9165 { 9166 balance_hotplug_wait(); 9167 return 0; 9168 } 9169 9170 /* 9171 * Since this CPU is going 'away' for a while, fold any nr_active delta we 9172 * might have. Called from the CPU stopper task after ensuring that the 9173 * stopper is the last running task on the CPU, so nr_active count is 9174 * stable. We need to take the teardown thread which is calling this into 9175 * account, so we hand in adjust = 1 to the load calculation. 9176 * 9177 * Also see the comment "Global load-average calculations". 9178 */ 9179 static void calc_load_migrate(struct rq *rq) 9180 { 9181 long delta = calc_load_fold_active(rq, 1); 9182 9183 if (delta) 9184 atomic_long_add(delta, &calc_load_tasks); 9185 } 9186 9187 static void dump_rq_tasks(struct rq *rq, const char *loglvl) 9188 { 9189 struct task_struct *g, *p; 9190 int cpu = cpu_of(rq); 9191 9192 lockdep_assert_rq_held(rq); 9193 9194 printk("%sCPU%d enqueued tasks (%u total):\n", loglvl, cpu, rq->nr_running); 9195 for_each_process_thread(g, p) { 9196 if (task_cpu(p) != cpu) 9197 continue; 9198 9199 if (!task_on_rq_queued(p)) 9200 continue; 9201 9202 printk("%s\tpid: %d, name: %s\n", loglvl, p->pid, p->comm); 9203 } 9204 } 9205 9206 int sched_cpu_dying(unsigned int cpu) 9207 { 9208 struct rq *rq = cpu_rq(cpu); 9209 struct rq_flags rf; 9210 9211 /* Handle pending wakeups and then migrate everything off */ 9212 sched_tick_stop(cpu); 9213 9214 rq_lock_irqsave(rq, &rf); 9215 if (rq->nr_running != 1 || rq_has_pinned_tasks(rq)) { 9216 WARN(true, "Dying CPU not properly vacated!"); 9217 dump_rq_tasks(rq, KERN_WARNING); 9218 } 9219 rq_unlock_irqrestore(rq, &rf); 9220 9221 calc_load_migrate(rq); 9222 update_max_interval(); 9223 hrtick_clear(rq); 9224 sched_core_cpu_dying(cpu); 9225 return 0; 9226 } 9227 #endif 9228 9229 void __init sched_init_smp(void) 9230 { 9231 sched_init_numa(); 9232 9233 /* 9234 * There's no userspace yet to cause hotplug operations; hence all the 9235 * CPU masks are stable and all blatant races in the below code cannot 9236 * happen. 9237 */ 9238 mutex_lock(&sched_domains_mutex); 9239 sched_init_domains(cpu_active_mask); 9240 mutex_unlock(&sched_domains_mutex); 9241 9242 /* Move init over to a non-isolated CPU */ 9243 if (set_cpus_allowed_ptr(current, housekeeping_cpumask(HK_FLAG_DOMAIN)) < 0) 9244 BUG(); 9245 current->flags &= ~PF_NO_SETAFFINITY; 9246 sched_init_granularity(); 9247 9248 init_sched_rt_class(); 9249 init_sched_dl_class(); 9250 9251 sched_smp_initialized = true; 9252 } 9253 9254 static int __init migration_init(void) 9255 { 9256 sched_cpu_starting(smp_processor_id()); 9257 return 0; 9258 } 9259 early_initcall(migration_init); 9260 9261 #else 9262 void __init sched_init_smp(void) 9263 { 9264 sched_init_granularity(); 9265 } 9266 #endif /* CONFIG_SMP */ 9267 9268 int in_sched_functions(unsigned long addr) 9269 { 9270 return in_lock_functions(addr) || 9271 (addr >= (unsigned long)__sched_text_start 9272 && addr < (unsigned long)__sched_text_end); 9273 } 9274 9275 #ifdef CONFIG_CGROUP_SCHED 9276 /* 9277 * Default task group. 9278 * Every task in system belongs to this group at bootup. 9279 */ 9280 struct task_group root_task_group; 9281 LIST_HEAD(task_groups); 9282 9283 /* Cacheline aligned slab cache for task_group */ 9284 static struct kmem_cache *task_group_cache __read_mostly; 9285 #endif 9286 9287 DECLARE_PER_CPU(cpumask_var_t, load_balance_mask); 9288 DECLARE_PER_CPU(cpumask_var_t, select_idle_mask); 9289 9290 void __init sched_init(void) 9291 { 9292 unsigned long ptr = 0; 9293 int i; 9294 9295 /* Make sure the linker didn't screw up */ 9296 BUG_ON(&idle_sched_class + 1 != &fair_sched_class || 9297 &fair_sched_class + 1 != &rt_sched_class || 9298 &rt_sched_class + 1 != &dl_sched_class); 9299 #ifdef CONFIG_SMP 9300 BUG_ON(&dl_sched_class + 1 != &stop_sched_class); 9301 #endif 9302 9303 wait_bit_init(); 9304 9305 #ifdef CONFIG_FAIR_GROUP_SCHED 9306 ptr += 2 * nr_cpu_ids * sizeof(void **); 9307 #endif 9308 #ifdef CONFIG_RT_GROUP_SCHED 9309 ptr += 2 * nr_cpu_ids * sizeof(void **); 9310 #endif 9311 if (ptr) { 9312 ptr = (unsigned long)kzalloc(ptr, GFP_NOWAIT); 9313 9314 #ifdef CONFIG_FAIR_GROUP_SCHED 9315 root_task_group.se = (struct sched_entity **)ptr; 9316 ptr += nr_cpu_ids * sizeof(void **); 9317 9318 root_task_group.cfs_rq = (struct cfs_rq **)ptr; 9319 ptr += nr_cpu_ids * sizeof(void **); 9320 9321 root_task_group.shares = ROOT_TASK_GROUP_LOAD; 9322 init_cfs_bandwidth(&root_task_group.cfs_bandwidth); 9323 #endif /* CONFIG_FAIR_GROUP_SCHED */ 9324 #ifdef CONFIG_RT_GROUP_SCHED 9325 root_task_group.rt_se = (struct sched_rt_entity **)ptr; 9326 ptr += nr_cpu_ids * sizeof(void **); 9327 9328 root_task_group.rt_rq = (struct rt_rq **)ptr; 9329 ptr += nr_cpu_ids * sizeof(void **); 9330 9331 #endif /* CONFIG_RT_GROUP_SCHED */ 9332 } 9333 #ifdef CONFIG_CPUMASK_OFFSTACK 9334 for_each_possible_cpu(i) { 9335 per_cpu(load_balance_mask, i) = (cpumask_var_t)kzalloc_node( 9336 cpumask_size(), GFP_KERNEL, cpu_to_node(i)); 9337 per_cpu(select_idle_mask, i) = (cpumask_var_t)kzalloc_node( 9338 cpumask_size(), GFP_KERNEL, cpu_to_node(i)); 9339 } 9340 #endif /* CONFIG_CPUMASK_OFFSTACK */ 9341 9342 init_rt_bandwidth(&def_rt_bandwidth, global_rt_period(), global_rt_runtime()); 9343 init_dl_bandwidth(&def_dl_bandwidth, global_rt_period(), global_rt_runtime()); 9344 9345 #ifdef CONFIG_SMP 9346 init_defrootdomain(); 9347 #endif 9348 9349 #ifdef CONFIG_RT_GROUP_SCHED 9350 init_rt_bandwidth(&root_task_group.rt_bandwidth, 9351 global_rt_period(), global_rt_runtime()); 9352 #endif /* CONFIG_RT_GROUP_SCHED */ 9353 9354 #ifdef CONFIG_CGROUP_SCHED 9355 task_group_cache = KMEM_CACHE(task_group, 0); 9356 9357 list_add(&root_task_group.list, &task_groups); 9358 INIT_LIST_HEAD(&root_task_group.children); 9359 INIT_LIST_HEAD(&root_task_group.siblings); 9360 autogroup_init(&init_task); 9361 #endif /* CONFIG_CGROUP_SCHED */ 9362 9363 for_each_possible_cpu(i) { 9364 struct rq *rq; 9365 9366 rq = cpu_rq(i); 9367 raw_spin_lock_init(&rq->__lock); 9368 rq->nr_running = 0; 9369 rq->calc_load_active = 0; 9370 rq->calc_load_update = jiffies + LOAD_FREQ; 9371 init_cfs_rq(&rq->cfs); 9372 init_rt_rq(&rq->rt); 9373 init_dl_rq(&rq->dl); 9374 #ifdef CONFIG_FAIR_GROUP_SCHED 9375 INIT_LIST_HEAD(&rq->leaf_cfs_rq_list); 9376 rq->tmp_alone_branch = &rq->leaf_cfs_rq_list; 9377 /* 9378 * How much CPU bandwidth does root_task_group get? 9379 * 9380 * In case of task-groups formed thr' the cgroup filesystem, it 9381 * gets 100% of the CPU resources in the system. This overall 9382 * system CPU resource is divided among the tasks of 9383 * root_task_group and its child task-groups in a fair manner, 9384 * based on each entity's (task or task-group's) weight 9385 * (se->load.weight). 9386 * 9387 * In other words, if root_task_group has 10 tasks of weight 9388 * 1024) and two child groups A0 and A1 (of weight 1024 each), 9389 * then A0's share of the CPU resource is: 9390 * 9391 * A0's bandwidth = 1024 / (10*1024 + 1024 + 1024) = 8.33% 9392 * 9393 * We achieve this by letting root_task_group's tasks sit 9394 * directly in rq->cfs (i.e root_task_group->se[] = NULL). 9395 */ 9396 init_tg_cfs_entry(&root_task_group, &rq->cfs, NULL, i, NULL); 9397 #endif /* CONFIG_FAIR_GROUP_SCHED */ 9398 9399 rq->rt.rt_runtime = def_rt_bandwidth.rt_runtime; 9400 #ifdef CONFIG_RT_GROUP_SCHED 9401 init_tg_rt_entry(&root_task_group, &rq->rt, NULL, i, NULL); 9402 #endif 9403 #ifdef CONFIG_SMP 9404 rq->sd = NULL; 9405 rq->rd = NULL; 9406 rq->cpu_capacity = rq->cpu_capacity_orig = SCHED_CAPACITY_SCALE; 9407 rq->balance_callback = &balance_push_callback; 9408 rq->active_balance = 0; 9409 rq->next_balance = jiffies; 9410 rq->push_cpu = 0; 9411 rq->cpu = i; 9412 rq->online = 0; 9413 rq->idle_stamp = 0; 9414 rq->avg_idle = 2*sysctl_sched_migration_cost; 9415 rq->wake_stamp = jiffies; 9416 rq->wake_avg_idle = rq->avg_idle; 9417 rq->max_idle_balance_cost = sysctl_sched_migration_cost; 9418 9419 INIT_LIST_HEAD(&rq->cfs_tasks); 9420 9421 rq_attach_root(rq, &def_root_domain); 9422 #ifdef CONFIG_NO_HZ_COMMON 9423 rq->last_blocked_load_update_tick = jiffies; 9424 atomic_set(&rq->nohz_flags, 0); 9425 9426 INIT_CSD(&rq->nohz_csd, nohz_csd_func, rq); 9427 #endif 9428 #ifdef CONFIG_HOTPLUG_CPU 9429 rcuwait_init(&rq->hotplug_wait); 9430 #endif 9431 #endif /* CONFIG_SMP */ 9432 hrtick_rq_init(rq); 9433 atomic_set(&rq->nr_iowait, 0); 9434 9435 #ifdef CONFIG_SCHED_CORE 9436 rq->core = rq; 9437 rq->core_pick = NULL; 9438 rq->core_enabled = 0; 9439 rq->core_tree = RB_ROOT; 9440 rq->core_forceidle_count = 0; 9441 rq->core_forceidle_occupation = 0; 9442 rq->core_forceidle_start = 0; 9443 9444 rq->core_cookie = 0UL; 9445 #endif 9446 } 9447 9448 set_load_weight(&init_task, false); 9449 9450 /* 9451 * The boot idle thread does lazy MMU switching as well: 9452 */ 9453 mmgrab(&init_mm); 9454 enter_lazy_tlb(&init_mm, current); 9455 9456 /* 9457 * The idle task doesn't need the kthread struct to function, but it 9458 * is dressed up as a per-CPU kthread and thus needs to play the part 9459 * if we want to avoid special-casing it in code that deals with per-CPU 9460 * kthreads. 9461 */ 9462 WARN_ON(!set_kthread_struct(current)); 9463 9464 /* 9465 * Make us the idle thread. Technically, schedule() should not be 9466 * called from this thread, however somewhere below it might be, 9467 * but because we are the idle thread, we just pick up running again 9468 * when this runqueue becomes "idle". 9469 */ 9470 init_idle(current, smp_processor_id()); 9471 9472 calc_load_update = jiffies + LOAD_FREQ; 9473 9474 #ifdef CONFIG_SMP 9475 idle_thread_set_boot_cpu(); 9476 balance_push_set(smp_processor_id(), false); 9477 #endif 9478 init_sched_fair_class(); 9479 9480 psi_init(); 9481 9482 init_uclamp(); 9483 9484 preempt_dynamic_init(); 9485 9486 scheduler_running = 1; 9487 } 9488 9489 #ifdef CONFIG_DEBUG_ATOMIC_SLEEP 9490 9491 void __might_sleep(const char *file, int line) 9492 { 9493 unsigned int state = get_current_state(); 9494 /* 9495 * Blocking primitives will set (and therefore destroy) current->state, 9496 * since we will exit with TASK_RUNNING make sure we enter with it, 9497 * otherwise we will destroy state. 9498 */ 9499 WARN_ONCE(state != TASK_RUNNING && current->task_state_change, 9500 "do not call blocking ops when !TASK_RUNNING; " 9501 "state=%x set at [<%p>] %pS\n", state, 9502 (void *)current->task_state_change, 9503 (void *)current->task_state_change); 9504 9505 __might_resched(file, line, 0); 9506 } 9507 EXPORT_SYMBOL(__might_sleep); 9508 9509 static void print_preempt_disable_ip(int preempt_offset, unsigned long ip) 9510 { 9511 if (!IS_ENABLED(CONFIG_DEBUG_PREEMPT)) 9512 return; 9513 9514 if (preempt_count() == preempt_offset) 9515 return; 9516 9517 pr_err("Preemption disabled at:"); 9518 print_ip_sym(KERN_ERR, ip); 9519 } 9520 9521 static inline bool resched_offsets_ok(unsigned int offsets) 9522 { 9523 unsigned int nested = preempt_count(); 9524 9525 nested += rcu_preempt_depth() << MIGHT_RESCHED_RCU_SHIFT; 9526 9527 return nested == offsets; 9528 } 9529 9530 void __might_resched(const char *file, int line, unsigned int offsets) 9531 { 9532 /* Ratelimiting timestamp: */ 9533 static unsigned long prev_jiffy; 9534 9535 unsigned long preempt_disable_ip; 9536 9537 /* WARN_ON_ONCE() by default, no rate limit required: */ 9538 rcu_sleep_check(); 9539 9540 if ((resched_offsets_ok(offsets) && !irqs_disabled() && 9541 !is_idle_task(current) && !current->non_block_count) || 9542 system_state == SYSTEM_BOOTING || system_state > SYSTEM_RUNNING || 9543 oops_in_progress) 9544 return; 9545 9546 if (time_before(jiffies, prev_jiffy + HZ) && prev_jiffy) 9547 return; 9548 prev_jiffy = jiffies; 9549 9550 /* Save this before calling printk(), since that will clobber it: */ 9551 preempt_disable_ip = get_preempt_disable_ip(current); 9552 9553 pr_err("BUG: sleeping function called from invalid context at %s:%d\n", 9554 file, line); 9555 pr_err("in_atomic(): %d, irqs_disabled(): %d, non_block: %d, pid: %d, name: %s\n", 9556 in_atomic(), irqs_disabled(), current->non_block_count, 9557 current->pid, current->comm); 9558 pr_err("preempt_count: %x, expected: %x\n", preempt_count(), 9559 offsets & MIGHT_RESCHED_PREEMPT_MASK); 9560 9561 if (IS_ENABLED(CONFIG_PREEMPT_RCU)) { 9562 pr_err("RCU nest depth: %d, expected: %u\n", 9563 rcu_preempt_depth(), offsets >> MIGHT_RESCHED_RCU_SHIFT); 9564 } 9565 9566 if (task_stack_end_corrupted(current)) 9567 pr_emerg("Thread overran stack, or stack corrupted\n"); 9568 9569 debug_show_held_locks(current); 9570 if (irqs_disabled()) 9571 print_irqtrace_events(current); 9572 9573 print_preempt_disable_ip(offsets & MIGHT_RESCHED_PREEMPT_MASK, 9574 preempt_disable_ip); 9575 9576 dump_stack(); 9577 add_taint(TAINT_WARN, LOCKDEP_STILL_OK); 9578 } 9579 EXPORT_SYMBOL(__might_resched); 9580 9581 void __cant_sleep(const char *file, int line, int preempt_offset) 9582 { 9583 static unsigned long prev_jiffy; 9584 9585 if (irqs_disabled()) 9586 return; 9587 9588 if (!IS_ENABLED(CONFIG_PREEMPT_COUNT)) 9589 return; 9590 9591 if (preempt_count() > preempt_offset) 9592 return; 9593 9594 if (time_before(jiffies, prev_jiffy + HZ) && prev_jiffy) 9595 return; 9596 prev_jiffy = jiffies; 9597 9598 printk(KERN_ERR "BUG: assuming atomic context at %s:%d\n", file, line); 9599 printk(KERN_ERR "in_atomic(): %d, irqs_disabled(): %d, pid: %d, name: %s\n", 9600 in_atomic(), irqs_disabled(), 9601 current->pid, current->comm); 9602 9603 debug_show_held_locks(current); 9604 dump_stack(); 9605 add_taint(TAINT_WARN, LOCKDEP_STILL_OK); 9606 } 9607 EXPORT_SYMBOL_GPL(__cant_sleep); 9608 9609 #ifdef CONFIG_SMP 9610 void __cant_migrate(const char *file, int line) 9611 { 9612 static unsigned long prev_jiffy; 9613 9614 if (irqs_disabled()) 9615 return; 9616 9617 if (is_migration_disabled(current)) 9618 return; 9619 9620 if (!IS_ENABLED(CONFIG_PREEMPT_COUNT)) 9621 return; 9622 9623 if (preempt_count() > 0) 9624 return; 9625 9626 if (time_before(jiffies, prev_jiffy + HZ) && prev_jiffy) 9627 return; 9628 prev_jiffy = jiffies; 9629 9630 pr_err("BUG: assuming non migratable context at %s:%d\n", file, line); 9631 pr_err("in_atomic(): %d, irqs_disabled(): %d, migration_disabled() %u pid: %d, name: %s\n", 9632 in_atomic(), irqs_disabled(), is_migration_disabled(current), 9633 current->pid, current->comm); 9634 9635 debug_show_held_locks(current); 9636 dump_stack(); 9637 add_taint(TAINT_WARN, LOCKDEP_STILL_OK); 9638 } 9639 EXPORT_SYMBOL_GPL(__cant_migrate); 9640 #endif 9641 #endif 9642 9643 #ifdef CONFIG_MAGIC_SYSRQ 9644 void normalize_rt_tasks(void) 9645 { 9646 struct task_struct *g, *p; 9647 struct sched_attr attr = { 9648 .sched_policy = SCHED_NORMAL, 9649 }; 9650 9651 read_lock(&tasklist_lock); 9652 for_each_process_thread(g, p) { 9653 /* 9654 * Only normalize user tasks: 9655 */ 9656 if (p->flags & PF_KTHREAD) 9657 continue; 9658 9659 p->se.exec_start = 0; 9660 schedstat_set(p->stats.wait_start, 0); 9661 schedstat_set(p->stats.sleep_start, 0); 9662 schedstat_set(p->stats.block_start, 0); 9663 9664 if (!dl_task(p) && !rt_task(p)) { 9665 /* 9666 * Renice negative nice level userspace 9667 * tasks back to 0: 9668 */ 9669 if (task_nice(p) < 0) 9670 set_user_nice(p, 0); 9671 continue; 9672 } 9673 9674 __sched_setscheduler(p, &attr, false, false); 9675 } 9676 read_unlock(&tasklist_lock); 9677 } 9678 9679 #endif /* CONFIG_MAGIC_SYSRQ */ 9680 9681 #if defined(CONFIG_IA64) || defined(CONFIG_KGDB_KDB) 9682 /* 9683 * These functions are only useful for the IA64 MCA handling, or kdb. 9684 * 9685 * They can only be called when the whole system has been 9686 * stopped - every CPU needs to be quiescent, and no scheduling 9687 * activity can take place. Using them for anything else would 9688 * be a serious bug, and as a result, they aren't even visible 9689 * under any other configuration. 9690 */ 9691 9692 /** 9693 * curr_task - return the current task for a given CPU. 9694 * @cpu: the processor in question. 9695 * 9696 * ONLY VALID WHEN THE WHOLE SYSTEM IS STOPPED! 9697 * 9698 * Return: The current task for @cpu. 9699 */ 9700 struct task_struct *curr_task(int cpu) 9701 { 9702 return cpu_curr(cpu); 9703 } 9704 9705 #endif /* defined(CONFIG_IA64) || defined(CONFIG_KGDB_KDB) */ 9706 9707 #ifdef CONFIG_IA64 9708 /** 9709 * ia64_set_curr_task - set the current task for a given CPU. 9710 * @cpu: the processor in question. 9711 * @p: the task pointer to set. 9712 * 9713 * Description: This function must only be used when non-maskable interrupts 9714 * are serviced on a separate stack. It allows the architecture to switch the 9715 * notion of the current task on a CPU in a non-blocking manner. This function 9716 * must be called with all CPU's synchronized, and interrupts disabled, the 9717 * and caller must save the original value of the current task (see 9718 * curr_task() above) and restore that value before reenabling interrupts and 9719 * re-starting the system. 9720 * 9721 * ONLY VALID WHEN THE WHOLE SYSTEM IS STOPPED! 9722 */ 9723 void ia64_set_curr_task(int cpu, struct task_struct *p) 9724 { 9725 cpu_curr(cpu) = p; 9726 } 9727 9728 #endif 9729 9730 #ifdef CONFIG_CGROUP_SCHED 9731 /* task_group_lock serializes the addition/removal of task groups */ 9732 static DEFINE_SPINLOCK(task_group_lock); 9733 9734 static inline void alloc_uclamp_sched_group(struct task_group *tg, 9735 struct task_group *parent) 9736 { 9737 #ifdef CONFIG_UCLAMP_TASK_GROUP 9738 enum uclamp_id clamp_id; 9739 9740 for_each_clamp_id(clamp_id) { 9741 uclamp_se_set(&tg->uclamp_req[clamp_id], 9742 uclamp_none(clamp_id), false); 9743 tg->uclamp[clamp_id] = parent->uclamp[clamp_id]; 9744 } 9745 #endif 9746 } 9747 9748 static void sched_free_group(struct task_group *tg) 9749 { 9750 free_fair_sched_group(tg); 9751 free_rt_sched_group(tg); 9752 autogroup_free(tg); 9753 kmem_cache_free(task_group_cache, tg); 9754 } 9755 9756 static void sched_free_group_rcu(struct rcu_head *rcu) 9757 { 9758 sched_free_group(container_of(rcu, struct task_group, rcu)); 9759 } 9760 9761 static void sched_unregister_group(struct task_group *tg) 9762 { 9763 unregister_fair_sched_group(tg); 9764 unregister_rt_sched_group(tg); 9765 /* 9766 * We have to wait for yet another RCU grace period to expire, as 9767 * print_cfs_stats() might run concurrently. 9768 */ 9769 call_rcu(&tg->rcu, sched_free_group_rcu); 9770 } 9771 9772 /* allocate runqueue etc for a new task group */ 9773 struct task_group *sched_create_group(struct task_group *parent) 9774 { 9775 struct task_group *tg; 9776 9777 tg = kmem_cache_alloc(task_group_cache, GFP_KERNEL | __GFP_ZERO); 9778 if (!tg) 9779 return ERR_PTR(-ENOMEM); 9780 9781 if (!alloc_fair_sched_group(tg, parent)) 9782 goto err; 9783 9784 if (!alloc_rt_sched_group(tg, parent)) 9785 goto err; 9786 9787 alloc_uclamp_sched_group(tg, parent); 9788 9789 return tg; 9790 9791 err: 9792 sched_free_group(tg); 9793 return ERR_PTR(-ENOMEM); 9794 } 9795 9796 void sched_online_group(struct task_group *tg, struct task_group *parent) 9797 { 9798 unsigned long flags; 9799 9800 spin_lock_irqsave(&task_group_lock, flags); 9801 list_add_rcu(&tg->list, &task_groups); 9802 9803 /* Root should already exist: */ 9804 WARN_ON(!parent); 9805 9806 tg->parent = parent; 9807 INIT_LIST_HEAD(&tg->children); 9808 list_add_rcu(&tg->siblings, &parent->children); 9809 spin_unlock_irqrestore(&task_group_lock, flags); 9810 9811 online_fair_sched_group(tg); 9812 } 9813 9814 /* rcu callback to free various structures associated with a task group */ 9815 static void sched_unregister_group_rcu(struct rcu_head *rhp) 9816 { 9817 /* Now it should be safe to free those cfs_rqs: */ 9818 sched_unregister_group(container_of(rhp, struct task_group, rcu)); 9819 } 9820 9821 void sched_destroy_group(struct task_group *tg) 9822 { 9823 /* Wait for possible concurrent references to cfs_rqs complete: */ 9824 call_rcu(&tg->rcu, sched_unregister_group_rcu); 9825 } 9826 9827 void sched_release_group(struct task_group *tg) 9828 { 9829 unsigned long flags; 9830 9831 /* 9832 * Unlink first, to avoid walk_tg_tree_from() from finding us (via 9833 * sched_cfs_period_timer()). 9834 * 9835 * For this to be effective, we have to wait for all pending users of 9836 * this task group to leave their RCU critical section to ensure no new 9837 * user will see our dying task group any more. Specifically ensure 9838 * that tg_unthrottle_up() won't add decayed cfs_rq's to it. 9839 * 9840 * We therefore defer calling unregister_fair_sched_group() to 9841 * sched_unregister_group() which is guarantied to get called only after the 9842 * current RCU grace period has expired. 9843 */ 9844 spin_lock_irqsave(&task_group_lock, flags); 9845 list_del_rcu(&tg->list); 9846 list_del_rcu(&tg->siblings); 9847 spin_unlock_irqrestore(&task_group_lock, flags); 9848 } 9849 9850 static void sched_change_group(struct task_struct *tsk, int type) 9851 { 9852 struct task_group *tg; 9853 9854 /* 9855 * All callers are synchronized by task_rq_lock(); we do not use RCU 9856 * which is pointless here. Thus, we pass "true" to task_css_check() 9857 * to prevent lockdep warnings. 9858 */ 9859 tg = container_of(task_css_check(tsk, cpu_cgrp_id, true), 9860 struct task_group, css); 9861 tg = autogroup_task_group(tsk, tg); 9862 tsk->sched_task_group = tg; 9863 9864 #ifdef CONFIG_FAIR_GROUP_SCHED 9865 if (tsk->sched_class->task_change_group) 9866 tsk->sched_class->task_change_group(tsk, type); 9867 else 9868 #endif 9869 set_task_rq(tsk, task_cpu(tsk)); 9870 } 9871 9872 /* 9873 * Change task's runqueue when it moves between groups. 9874 * 9875 * The caller of this function should have put the task in its new group by 9876 * now. This function just updates tsk->se.cfs_rq and tsk->se.parent to reflect 9877 * its new group. 9878 */ 9879 void sched_move_task(struct task_struct *tsk) 9880 { 9881 int queued, running, queue_flags = 9882 DEQUEUE_SAVE | DEQUEUE_MOVE | DEQUEUE_NOCLOCK; 9883 struct rq_flags rf; 9884 struct rq *rq; 9885 9886 rq = task_rq_lock(tsk, &rf); 9887 update_rq_clock(rq); 9888 9889 running = task_current(rq, tsk); 9890 queued = task_on_rq_queued(tsk); 9891 9892 if (queued) 9893 dequeue_task(rq, tsk, queue_flags); 9894 if (running) 9895 put_prev_task(rq, tsk); 9896 9897 sched_change_group(tsk, TASK_MOVE_GROUP); 9898 9899 if (queued) 9900 enqueue_task(rq, tsk, queue_flags); 9901 if (running) { 9902 set_next_task(rq, tsk); 9903 /* 9904 * After changing group, the running task may have joined a 9905 * throttled one but it's still the running task. Trigger a 9906 * resched to make sure that task can still run. 9907 */ 9908 resched_curr(rq); 9909 } 9910 9911 task_rq_unlock(rq, tsk, &rf); 9912 } 9913 9914 static inline struct task_group *css_tg(struct cgroup_subsys_state *css) 9915 { 9916 return css ? container_of(css, struct task_group, css) : NULL; 9917 } 9918 9919 static struct cgroup_subsys_state * 9920 cpu_cgroup_css_alloc(struct cgroup_subsys_state *parent_css) 9921 { 9922 struct task_group *parent = css_tg(parent_css); 9923 struct task_group *tg; 9924 9925 if (!parent) { 9926 /* This is early initialization for the top cgroup */ 9927 return &root_task_group.css; 9928 } 9929 9930 tg = sched_create_group(parent); 9931 if (IS_ERR(tg)) 9932 return ERR_PTR(-ENOMEM); 9933 9934 return &tg->css; 9935 } 9936 9937 /* Expose task group only after completing cgroup initialization */ 9938 static int cpu_cgroup_css_online(struct cgroup_subsys_state *css) 9939 { 9940 struct task_group *tg = css_tg(css); 9941 struct task_group *parent = css_tg(css->parent); 9942 9943 if (parent) 9944 sched_online_group(tg, parent); 9945 9946 #ifdef CONFIG_UCLAMP_TASK_GROUP 9947 /* Propagate the effective uclamp value for the new group */ 9948 mutex_lock(&uclamp_mutex); 9949 rcu_read_lock(); 9950 cpu_util_update_eff(css); 9951 rcu_read_unlock(); 9952 mutex_unlock(&uclamp_mutex); 9953 #endif 9954 9955 return 0; 9956 } 9957 9958 static void cpu_cgroup_css_released(struct cgroup_subsys_state *css) 9959 { 9960 struct task_group *tg = css_tg(css); 9961 9962 sched_release_group(tg); 9963 } 9964 9965 static void cpu_cgroup_css_free(struct cgroup_subsys_state *css) 9966 { 9967 struct task_group *tg = css_tg(css); 9968 9969 /* 9970 * Relies on the RCU grace period between css_released() and this. 9971 */ 9972 sched_unregister_group(tg); 9973 } 9974 9975 /* 9976 * This is called before wake_up_new_task(), therefore we really only 9977 * have to set its group bits, all the other stuff does not apply. 9978 */ 9979 static void cpu_cgroup_fork(struct task_struct *task) 9980 { 9981 struct rq_flags rf; 9982 struct rq *rq; 9983 9984 rq = task_rq_lock(task, &rf); 9985 9986 update_rq_clock(rq); 9987 sched_change_group(task, TASK_SET_GROUP); 9988 9989 task_rq_unlock(rq, task, &rf); 9990 } 9991 9992 static int cpu_cgroup_can_attach(struct cgroup_taskset *tset) 9993 { 9994 struct task_struct *task; 9995 struct cgroup_subsys_state *css; 9996 int ret = 0; 9997 9998 cgroup_taskset_for_each(task, css, tset) { 9999 #ifdef CONFIG_RT_GROUP_SCHED 10000 if (!sched_rt_can_attach(css_tg(css), task)) 10001 return -EINVAL; 10002 #endif 10003 /* 10004 * Serialize against wake_up_new_task() such that if it's 10005 * running, we're sure to observe its full state. 10006 */ 10007 raw_spin_lock_irq(&task->pi_lock); 10008 /* 10009 * Avoid calling sched_move_task() before wake_up_new_task() 10010 * has happened. This would lead to problems with PELT, due to 10011 * move wanting to detach+attach while we're not attached yet. 10012 */ 10013 if (READ_ONCE(task->__state) == TASK_NEW) 10014 ret = -EINVAL; 10015 raw_spin_unlock_irq(&task->pi_lock); 10016 10017 if (ret) 10018 break; 10019 } 10020 return ret; 10021 } 10022 10023 static void cpu_cgroup_attach(struct cgroup_taskset *tset) 10024 { 10025 struct task_struct *task; 10026 struct cgroup_subsys_state *css; 10027 10028 cgroup_taskset_for_each(task, css, tset) 10029 sched_move_task(task); 10030 } 10031 10032 #ifdef CONFIG_UCLAMP_TASK_GROUP 10033 static void cpu_util_update_eff(struct cgroup_subsys_state *css) 10034 { 10035 struct cgroup_subsys_state *top_css = css; 10036 struct uclamp_se *uc_parent = NULL; 10037 struct uclamp_se *uc_se = NULL; 10038 unsigned int eff[UCLAMP_CNT]; 10039 enum uclamp_id clamp_id; 10040 unsigned int clamps; 10041 10042 lockdep_assert_held(&uclamp_mutex); 10043 SCHED_WARN_ON(!rcu_read_lock_held()); 10044 10045 css_for_each_descendant_pre(css, top_css) { 10046 uc_parent = css_tg(css)->parent 10047 ? css_tg(css)->parent->uclamp : NULL; 10048 10049 for_each_clamp_id(clamp_id) { 10050 /* Assume effective clamps matches requested clamps */ 10051 eff[clamp_id] = css_tg(css)->uclamp_req[clamp_id].value; 10052 /* Cap effective clamps with parent's effective clamps */ 10053 if (uc_parent && 10054 eff[clamp_id] > uc_parent[clamp_id].value) { 10055 eff[clamp_id] = uc_parent[clamp_id].value; 10056 } 10057 } 10058 /* Ensure protection is always capped by limit */ 10059 eff[UCLAMP_MIN] = min(eff[UCLAMP_MIN], eff[UCLAMP_MAX]); 10060 10061 /* Propagate most restrictive effective clamps */ 10062 clamps = 0x0; 10063 uc_se = css_tg(css)->uclamp; 10064 for_each_clamp_id(clamp_id) { 10065 if (eff[clamp_id] == uc_se[clamp_id].value) 10066 continue; 10067 uc_se[clamp_id].value = eff[clamp_id]; 10068 uc_se[clamp_id].bucket_id = uclamp_bucket_id(eff[clamp_id]); 10069 clamps |= (0x1 << clamp_id); 10070 } 10071 if (!clamps) { 10072 css = css_rightmost_descendant(css); 10073 continue; 10074 } 10075 10076 /* Immediately update descendants RUNNABLE tasks */ 10077 uclamp_update_active_tasks(css); 10078 } 10079 } 10080 10081 /* 10082 * Integer 10^N with a given N exponent by casting to integer the literal "1eN" 10083 * C expression. Since there is no way to convert a macro argument (N) into a 10084 * character constant, use two levels of macros. 10085 */ 10086 #define _POW10(exp) ((unsigned int)1e##exp) 10087 #define POW10(exp) _POW10(exp) 10088 10089 struct uclamp_request { 10090 #define UCLAMP_PERCENT_SHIFT 2 10091 #define UCLAMP_PERCENT_SCALE (100 * POW10(UCLAMP_PERCENT_SHIFT)) 10092 s64 percent; 10093 u64 util; 10094 int ret; 10095 }; 10096 10097 static inline struct uclamp_request 10098 capacity_from_percent(char *buf) 10099 { 10100 struct uclamp_request req = { 10101 .percent = UCLAMP_PERCENT_SCALE, 10102 .util = SCHED_CAPACITY_SCALE, 10103 .ret = 0, 10104 }; 10105 10106 buf = strim(buf); 10107 if (strcmp(buf, "max")) { 10108 req.ret = cgroup_parse_float(buf, UCLAMP_PERCENT_SHIFT, 10109 &req.percent); 10110 if (req.ret) 10111 return req; 10112 if ((u64)req.percent > UCLAMP_PERCENT_SCALE) { 10113 req.ret = -ERANGE; 10114 return req; 10115 } 10116 10117 req.util = req.percent << SCHED_CAPACITY_SHIFT; 10118 req.util = DIV_ROUND_CLOSEST_ULL(req.util, UCLAMP_PERCENT_SCALE); 10119 } 10120 10121 return req; 10122 } 10123 10124 static ssize_t cpu_uclamp_write(struct kernfs_open_file *of, char *buf, 10125 size_t nbytes, loff_t off, 10126 enum uclamp_id clamp_id) 10127 { 10128 struct uclamp_request req; 10129 struct task_group *tg; 10130 10131 req = capacity_from_percent(buf); 10132 if (req.ret) 10133 return req.ret; 10134 10135 static_branch_enable(&sched_uclamp_used); 10136 10137 mutex_lock(&uclamp_mutex); 10138 rcu_read_lock(); 10139 10140 tg = css_tg(of_css(of)); 10141 if (tg->uclamp_req[clamp_id].value != req.util) 10142 uclamp_se_set(&tg->uclamp_req[clamp_id], req.util, false); 10143 10144 /* 10145 * Because of not recoverable conversion rounding we keep track of the 10146 * exact requested value 10147 */ 10148 tg->uclamp_pct[clamp_id] = req.percent; 10149 10150 /* Update effective clamps to track the most restrictive value */ 10151 cpu_util_update_eff(of_css(of)); 10152 10153 rcu_read_unlock(); 10154 mutex_unlock(&uclamp_mutex); 10155 10156 return nbytes; 10157 } 10158 10159 static ssize_t cpu_uclamp_min_write(struct kernfs_open_file *of, 10160 char *buf, size_t nbytes, 10161 loff_t off) 10162 { 10163 return cpu_uclamp_write(of, buf, nbytes, off, UCLAMP_MIN); 10164 } 10165 10166 static ssize_t cpu_uclamp_max_write(struct kernfs_open_file *of, 10167 char *buf, size_t nbytes, 10168 loff_t off) 10169 { 10170 return cpu_uclamp_write(of, buf, nbytes, off, UCLAMP_MAX); 10171 } 10172 10173 static inline void cpu_uclamp_print(struct seq_file *sf, 10174 enum uclamp_id clamp_id) 10175 { 10176 struct task_group *tg; 10177 u64 util_clamp; 10178 u64 percent; 10179 u32 rem; 10180 10181 rcu_read_lock(); 10182 tg = css_tg(seq_css(sf)); 10183 util_clamp = tg->uclamp_req[clamp_id].value; 10184 rcu_read_unlock(); 10185 10186 if (util_clamp == SCHED_CAPACITY_SCALE) { 10187 seq_puts(sf, "max\n"); 10188 return; 10189 } 10190 10191 percent = tg->uclamp_pct[clamp_id]; 10192 percent = div_u64_rem(percent, POW10(UCLAMP_PERCENT_SHIFT), &rem); 10193 seq_printf(sf, "%llu.%0*u\n", percent, UCLAMP_PERCENT_SHIFT, rem); 10194 } 10195 10196 static int cpu_uclamp_min_show(struct seq_file *sf, void *v) 10197 { 10198 cpu_uclamp_print(sf, UCLAMP_MIN); 10199 return 0; 10200 } 10201 10202 static int cpu_uclamp_max_show(struct seq_file *sf, void *v) 10203 { 10204 cpu_uclamp_print(sf, UCLAMP_MAX); 10205 return 0; 10206 } 10207 #endif /* CONFIG_UCLAMP_TASK_GROUP */ 10208 10209 #ifdef CONFIG_FAIR_GROUP_SCHED 10210 static int cpu_shares_write_u64(struct cgroup_subsys_state *css, 10211 struct cftype *cftype, u64 shareval) 10212 { 10213 if (shareval > scale_load_down(ULONG_MAX)) 10214 shareval = MAX_SHARES; 10215 return sched_group_set_shares(css_tg(css), scale_load(shareval)); 10216 } 10217 10218 static u64 cpu_shares_read_u64(struct cgroup_subsys_state *css, 10219 struct cftype *cft) 10220 { 10221 struct task_group *tg = css_tg(css); 10222 10223 return (u64) scale_load_down(tg->shares); 10224 } 10225 10226 #ifdef CONFIG_CFS_BANDWIDTH 10227 static DEFINE_MUTEX(cfs_constraints_mutex); 10228 10229 const u64 max_cfs_quota_period = 1 * NSEC_PER_SEC; /* 1s */ 10230 static const u64 min_cfs_quota_period = 1 * NSEC_PER_MSEC; /* 1ms */ 10231 /* More than 203 days if BW_SHIFT equals 20. */ 10232 static const u64 max_cfs_runtime = MAX_BW * NSEC_PER_USEC; 10233 10234 static int __cfs_schedulable(struct task_group *tg, u64 period, u64 runtime); 10235 10236 static int tg_set_cfs_bandwidth(struct task_group *tg, u64 period, u64 quota, 10237 u64 burst) 10238 { 10239 int i, ret = 0, runtime_enabled, runtime_was_enabled; 10240 struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth; 10241 10242 if (tg == &root_task_group) 10243 return -EINVAL; 10244 10245 /* 10246 * Ensure we have at some amount of bandwidth every period. This is 10247 * to prevent reaching a state of large arrears when throttled via 10248 * entity_tick() resulting in prolonged exit starvation. 10249 */ 10250 if (quota < min_cfs_quota_period || period < min_cfs_quota_period) 10251 return -EINVAL; 10252 10253 /* 10254 * Likewise, bound things on the other side by preventing insane quota 10255 * periods. This also allows us to normalize in computing quota 10256 * feasibility. 10257 */ 10258 if (period > max_cfs_quota_period) 10259 return -EINVAL; 10260 10261 /* 10262 * Bound quota to defend quota against overflow during bandwidth shift. 10263 */ 10264 if (quota != RUNTIME_INF && quota > max_cfs_runtime) 10265 return -EINVAL; 10266 10267 if (quota != RUNTIME_INF && (burst > quota || 10268 burst + quota > max_cfs_runtime)) 10269 return -EINVAL; 10270 10271 /* 10272 * Prevent race between setting of cfs_rq->runtime_enabled and 10273 * unthrottle_offline_cfs_rqs(). 10274 */ 10275 cpus_read_lock(); 10276 mutex_lock(&cfs_constraints_mutex); 10277 ret = __cfs_schedulable(tg, period, quota); 10278 if (ret) 10279 goto out_unlock; 10280 10281 runtime_enabled = quota != RUNTIME_INF; 10282 runtime_was_enabled = cfs_b->quota != RUNTIME_INF; 10283 /* 10284 * If we need to toggle cfs_bandwidth_used, off->on must occur 10285 * before making related changes, and on->off must occur afterwards 10286 */ 10287 if (runtime_enabled && !runtime_was_enabled) 10288 cfs_bandwidth_usage_inc(); 10289 raw_spin_lock_irq(&cfs_b->lock); 10290 cfs_b->period = ns_to_ktime(period); 10291 cfs_b->quota = quota; 10292 cfs_b->burst = burst; 10293 10294 __refill_cfs_bandwidth_runtime(cfs_b); 10295 10296 /* Restart the period timer (if active) to handle new period expiry: */ 10297 if (runtime_enabled) 10298 start_cfs_bandwidth(cfs_b); 10299 10300 raw_spin_unlock_irq(&cfs_b->lock); 10301 10302 for_each_online_cpu(i) { 10303 struct cfs_rq *cfs_rq = tg->cfs_rq[i]; 10304 struct rq *rq = cfs_rq->rq; 10305 struct rq_flags rf; 10306 10307 rq_lock_irq(rq, &rf); 10308 cfs_rq->runtime_enabled = runtime_enabled; 10309 cfs_rq->runtime_remaining = 0; 10310 10311 if (cfs_rq->throttled) 10312 unthrottle_cfs_rq(cfs_rq); 10313 rq_unlock_irq(rq, &rf); 10314 } 10315 if (runtime_was_enabled && !runtime_enabled) 10316 cfs_bandwidth_usage_dec(); 10317 out_unlock: 10318 mutex_unlock(&cfs_constraints_mutex); 10319 cpus_read_unlock(); 10320 10321 return ret; 10322 } 10323 10324 static int tg_set_cfs_quota(struct task_group *tg, long cfs_quota_us) 10325 { 10326 u64 quota, period, burst; 10327 10328 period = ktime_to_ns(tg->cfs_bandwidth.period); 10329 burst = tg->cfs_bandwidth.burst; 10330 if (cfs_quota_us < 0) 10331 quota = RUNTIME_INF; 10332 else if ((u64)cfs_quota_us <= U64_MAX / NSEC_PER_USEC) 10333 quota = (u64)cfs_quota_us * NSEC_PER_USEC; 10334 else 10335 return -EINVAL; 10336 10337 return tg_set_cfs_bandwidth(tg, period, quota, burst); 10338 } 10339 10340 static long tg_get_cfs_quota(struct task_group *tg) 10341 { 10342 u64 quota_us; 10343 10344 if (tg->cfs_bandwidth.quota == RUNTIME_INF) 10345 return -1; 10346 10347 quota_us = tg->cfs_bandwidth.quota; 10348 do_div(quota_us, NSEC_PER_USEC); 10349 10350 return quota_us; 10351 } 10352 10353 static int tg_set_cfs_period(struct task_group *tg, long cfs_period_us) 10354 { 10355 u64 quota, period, burst; 10356 10357 if ((u64)cfs_period_us > U64_MAX / NSEC_PER_USEC) 10358 return -EINVAL; 10359 10360 period = (u64)cfs_period_us * NSEC_PER_USEC; 10361 quota = tg->cfs_bandwidth.quota; 10362 burst = tg->cfs_bandwidth.burst; 10363 10364 return tg_set_cfs_bandwidth(tg, period, quota, burst); 10365 } 10366 10367 static long tg_get_cfs_period(struct task_group *tg) 10368 { 10369 u64 cfs_period_us; 10370 10371 cfs_period_us = ktime_to_ns(tg->cfs_bandwidth.period); 10372 do_div(cfs_period_us, NSEC_PER_USEC); 10373 10374 return cfs_period_us; 10375 } 10376 10377 static int tg_set_cfs_burst(struct task_group *tg, long cfs_burst_us) 10378 { 10379 u64 quota, period, burst; 10380 10381 if ((u64)cfs_burst_us > U64_MAX / NSEC_PER_USEC) 10382 return -EINVAL; 10383 10384 burst = (u64)cfs_burst_us * NSEC_PER_USEC; 10385 period = ktime_to_ns(tg->cfs_bandwidth.period); 10386 quota = tg->cfs_bandwidth.quota; 10387 10388 return tg_set_cfs_bandwidth(tg, period, quota, burst); 10389 } 10390 10391 static long tg_get_cfs_burst(struct task_group *tg) 10392 { 10393 u64 burst_us; 10394 10395 burst_us = tg->cfs_bandwidth.burst; 10396 do_div(burst_us, NSEC_PER_USEC); 10397 10398 return burst_us; 10399 } 10400 10401 static s64 cpu_cfs_quota_read_s64(struct cgroup_subsys_state *css, 10402 struct cftype *cft) 10403 { 10404 return tg_get_cfs_quota(css_tg(css)); 10405 } 10406 10407 static int cpu_cfs_quota_write_s64(struct cgroup_subsys_state *css, 10408 struct cftype *cftype, s64 cfs_quota_us) 10409 { 10410 return tg_set_cfs_quota(css_tg(css), cfs_quota_us); 10411 } 10412 10413 static u64 cpu_cfs_period_read_u64(struct cgroup_subsys_state *css, 10414 struct cftype *cft) 10415 { 10416 return tg_get_cfs_period(css_tg(css)); 10417 } 10418 10419 static int cpu_cfs_period_write_u64(struct cgroup_subsys_state *css, 10420 struct cftype *cftype, u64 cfs_period_us) 10421 { 10422 return tg_set_cfs_period(css_tg(css), cfs_period_us); 10423 } 10424 10425 static u64 cpu_cfs_burst_read_u64(struct cgroup_subsys_state *css, 10426 struct cftype *cft) 10427 { 10428 return tg_get_cfs_burst(css_tg(css)); 10429 } 10430 10431 static int cpu_cfs_burst_write_u64(struct cgroup_subsys_state *css, 10432 struct cftype *cftype, u64 cfs_burst_us) 10433 { 10434 return tg_set_cfs_burst(css_tg(css), cfs_burst_us); 10435 } 10436 10437 struct cfs_schedulable_data { 10438 struct task_group *tg; 10439 u64 period, quota; 10440 }; 10441 10442 /* 10443 * normalize group quota/period to be quota/max_period 10444 * note: units are usecs 10445 */ 10446 static u64 normalize_cfs_quota(struct task_group *tg, 10447 struct cfs_schedulable_data *d) 10448 { 10449 u64 quota, period; 10450 10451 if (tg == d->tg) { 10452 period = d->period; 10453 quota = d->quota; 10454 } else { 10455 period = tg_get_cfs_period(tg); 10456 quota = tg_get_cfs_quota(tg); 10457 } 10458 10459 /* note: these should typically be equivalent */ 10460 if (quota == RUNTIME_INF || quota == -1) 10461 return RUNTIME_INF; 10462 10463 return to_ratio(period, quota); 10464 } 10465 10466 static int tg_cfs_schedulable_down(struct task_group *tg, void *data) 10467 { 10468 struct cfs_schedulable_data *d = data; 10469 struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth; 10470 s64 quota = 0, parent_quota = -1; 10471 10472 if (!tg->parent) { 10473 quota = RUNTIME_INF; 10474 } else { 10475 struct cfs_bandwidth *parent_b = &tg->parent->cfs_bandwidth; 10476 10477 quota = normalize_cfs_quota(tg, d); 10478 parent_quota = parent_b->hierarchical_quota; 10479 10480 /* 10481 * Ensure max(child_quota) <= parent_quota. On cgroup2, 10482 * always take the min. On cgroup1, only inherit when no 10483 * limit is set: 10484 */ 10485 if (cgroup_subsys_on_dfl(cpu_cgrp_subsys)) { 10486 quota = min(quota, parent_quota); 10487 } else { 10488 if (quota == RUNTIME_INF) 10489 quota = parent_quota; 10490 else if (parent_quota != RUNTIME_INF && quota > parent_quota) 10491 return -EINVAL; 10492 } 10493 } 10494 cfs_b->hierarchical_quota = quota; 10495 10496 return 0; 10497 } 10498 10499 static int __cfs_schedulable(struct task_group *tg, u64 period, u64 quota) 10500 { 10501 int ret; 10502 struct cfs_schedulable_data data = { 10503 .tg = tg, 10504 .period = period, 10505 .quota = quota, 10506 }; 10507 10508 if (quota != RUNTIME_INF) { 10509 do_div(data.period, NSEC_PER_USEC); 10510 do_div(data.quota, NSEC_PER_USEC); 10511 } 10512 10513 rcu_read_lock(); 10514 ret = walk_tg_tree(tg_cfs_schedulable_down, tg_nop, &data); 10515 rcu_read_unlock(); 10516 10517 return ret; 10518 } 10519 10520 static int cpu_cfs_stat_show(struct seq_file *sf, void *v) 10521 { 10522 struct task_group *tg = css_tg(seq_css(sf)); 10523 struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth; 10524 10525 seq_printf(sf, "nr_periods %d\n", cfs_b->nr_periods); 10526 seq_printf(sf, "nr_throttled %d\n", cfs_b->nr_throttled); 10527 seq_printf(sf, "throttled_time %llu\n", cfs_b->throttled_time); 10528 10529 if (schedstat_enabled() && tg != &root_task_group) { 10530 struct sched_statistics *stats; 10531 u64 ws = 0; 10532 int i; 10533 10534 for_each_possible_cpu(i) { 10535 stats = __schedstats_from_se(tg->se[i]); 10536 ws += schedstat_val(stats->wait_sum); 10537 } 10538 10539 seq_printf(sf, "wait_sum %llu\n", ws); 10540 } 10541 10542 seq_printf(sf, "nr_bursts %d\n", cfs_b->nr_burst); 10543 seq_printf(sf, "burst_time %llu\n", cfs_b->burst_time); 10544 10545 return 0; 10546 } 10547 #endif /* CONFIG_CFS_BANDWIDTH */ 10548 #endif /* CONFIG_FAIR_GROUP_SCHED */ 10549 10550 #ifdef CONFIG_RT_GROUP_SCHED 10551 static int cpu_rt_runtime_write(struct cgroup_subsys_state *css, 10552 struct cftype *cft, s64 val) 10553 { 10554 return sched_group_set_rt_runtime(css_tg(css), val); 10555 } 10556 10557 static s64 cpu_rt_runtime_read(struct cgroup_subsys_state *css, 10558 struct cftype *cft) 10559 { 10560 return sched_group_rt_runtime(css_tg(css)); 10561 } 10562 10563 static int cpu_rt_period_write_uint(struct cgroup_subsys_state *css, 10564 struct cftype *cftype, u64 rt_period_us) 10565 { 10566 return sched_group_set_rt_period(css_tg(css), rt_period_us); 10567 } 10568 10569 static u64 cpu_rt_period_read_uint(struct cgroup_subsys_state *css, 10570 struct cftype *cft) 10571 { 10572 return sched_group_rt_period(css_tg(css)); 10573 } 10574 #endif /* CONFIG_RT_GROUP_SCHED */ 10575 10576 #ifdef CONFIG_FAIR_GROUP_SCHED 10577 static s64 cpu_idle_read_s64(struct cgroup_subsys_state *css, 10578 struct cftype *cft) 10579 { 10580 return css_tg(css)->idle; 10581 } 10582 10583 static int cpu_idle_write_s64(struct cgroup_subsys_state *css, 10584 struct cftype *cft, s64 idle) 10585 { 10586 return sched_group_set_idle(css_tg(css), idle); 10587 } 10588 #endif 10589 10590 static struct cftype cpu_legacy_files[] = { 10591 #ifdef CONFIG_FAIR_GROUP_SCHED 10592 { 10593 .name = "shares", 10594 .read_u64 = cpu_shares_read_u64, 10595 .write_u64 = cpu_shares_write_u64, 10596 }, 10597 { 10598 .name = "idle", 10599 .read_s64 = cpu_idle_read_s64, 10600 .write_s64 = cpu_idle_write_s64, 10601 }, 10602 #endif 10603 #ifdef CONFIG_CFS_BANDWIDTH 10604 { 10605 .name = "cfs_quota_us", 10606 .read_s64 = cpu_cfs_quota_read_s64, 10607 .write_s64 = cpu_cfs_quota_write_s64, 10608 }, 10609 { 10610 .name = "cfs_period_us", 10611 .read_u64 = cpu_cfs_period_read_u64, 10612 .write_u64 = cpu_cfs_period_write_u64, 10613 }, 10614 { 10615 .name = "cfs_burst_us", 10616 .read_u64 = cpu_cfs_burst_read_u64, 10617 .write_u64 = cpu_cfs_burst_write_u64, 10618 }, 10619 { 10620 .name = "stat", 10621 .seq_show = cpu_cfs_stat_show, 10622 }, 10623 #endif 10624 #ifdef CONFIG_RT_GROUP_SCHED 10625 { 10626 .name = "rt_runtime_us", 10627 .read_s64 = cpu_rt_runtime_read, 10628 .write_s64 = cpu_rt_runtime_write, 10629 }, 10630 { 10631 .name = "rt_period_us", 10632 .read_u64 = cpu_rt_period_read_uint, 10633 .write_u64 = cpu_rt_period_write_uint, 10634 }, 10635 #endif 10636 #ifdef CONFIG_UCLAMP_TASK_GROUP 10637 { 10638 .name = "uclamp.min", 10639 .flags = CFTYPE_NOT_ON_ROOT, 10640 .seq_show = cpu_uclamp_min_show, 10641 .write = cpu_uclamp_min_write, 10642 }, 10643 { 10644 .name = "uclamp.max", 10645 .flags = CFTYPE_NOT_ON_ROOT, 10646 .seq_show = cpu_uclamp_max_show, 10647 .write = cpu_uclamp_max_write, 10648 }, 10649 #endif 10650 { } /* Terminate */ 10651 }; 10652 10653 static int cpu_extra_stat_show(struct seq_file *sf, 10654 struct cgroup_subsys_state *css) 10655 { 10656 #ifdef CONFIG_CFS_BANDWIDTH 10657 { 10658 struct task_group *tg = css_tg(css); 10659 struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth; 10660 u64 throttled_usec, burst_usec; 10661 10662 throttled_usec = cfs_b->throttled_time; 10663 do_div(throttled_usec, NSEC_PER_USEC); 10664 burst_usec = cfs_b->burst_time; 10665 do_div(burst_usec, NSEC_PER_USEC); 10666 10667 seq_printf(sf, "nr_periods %d\n" 10668 "nr_throttled %d\n" 10669 "throttled_usec %llu\n" 10670 "nr_bursts %d\n" 10671 "burst_usec %llu\n", 10672 cfs_b->nr_periods, cfs_b->nr_throttled, 10673 throttled_usec, cfs_b->nr_burst, burst_usec); 10674 } 10675 #endif 10676 return 0; 10677 } 10678 10679 #ifdef CONFIG_FAIR_GROUP_SCHED 10680 static u64 cpu_weight_read_u64(struct cgroup_subsys_state *css, 10681 struct cftype *cft) 10682 { 10683 struct task_group *tg = css_tg(css); 10684 u64 weight = scale_load_down(tg->shares); 10685 10686 return DIV_ROUND_CLOSEST_ULL(weight * CGROUP_WEIGHT_DFL, 1024); 10687 } 10688 10689 static int cpu_weight_write_u64(struct cgroup_subsys_state *css, 10690 struct cftype *cft, u64 weight) 10691 { 10692 /* 10693 * cgroup weight knobs should use the common MIN, DFL and MAX 10694 * values which are 1, 100 and 10000 respectively. While it loses 10695 * a bit of range on both ends, it maps pretty well onto the shares 10696 * value used by scheduler and the round-trip conversions preserve 10697 * the original value over the entire range. 10698 */ 10699 if (weight < CGROUP_WEIGHT_MIN || weight > CGROUP_WEIGHT_MAX) 10700 return -ERANGE; 10701 10702 weight = DIV_ROUND_CLOSEST_ULL(weight * 1024, CGROUP_WEIGHT_DFL); 10703 10704 return sched_group_set_shares(css_tg(css), scale_load(weight)); 10705 } 10706 10707 static s64 cpu_weight_nice_read_s64(struct cgroup_subsys_state *css, 10708 struct cftype *cft) 10709 { 10710 unsigned long weight = scale_load_down(css_tg(css)->shares); 10711 int last_delta = INT_MAX; 10712 int prio, delta; 10713 10714 /* find the closest nice value to the current weight */ 10715 for (prio = 0; prio < ARRAY_SIZE(sched_prio_to_weight); prio++) { 10716 delta = abs(sched_prio_to_weight[prio] - weight); 10717 if (delta >= last_delta) 10718 break; 10719 last_delta = delta; 10720 } 10721 10722 return PRIO_TO_NICE(prio - 1 + MAX_RT_PRIO); 10723 } 10724 10725 static int cpu_weight_nice_write_s64(struct cgroup_subsys_state *css, 10726 struct cftype *cft, s64 nice) 10727 { 10728 unsigned long weight; 10729 int idx; 10730 10731 if (nice < MIN_NICE || nice > MAX_NICE) 10732 return -ERANGE; 10733 10734 idx = NICE_TO_PRIO(nice) - MAX_RT_PRIO; 10735 idx = array_index_nospec(idx, 40); 10736 weight = sched_prio_to_weight[idx]; 10737 10738 return sched_group_set_shares(css_tg(css), scale_load(weight)); 10739 } 10740 #endif 10741 10742 static void __maybe_unused cpu_period_quota_print(struct seq_file *sf, 10743 long period, long quota) 10744 { 10745 if (quota < 0) 10746 seq_puts(sf, "max"); 10747 else 10748 seq_printf(sf, "%ld", quota); 10749 10750 seq_printf(sf, " %ld\n", period); 10751 } 10752 10753 /* caller should put the current value in *@periodp before calling */ 10754 static int __maybe_unused cpu_period_quota_parse(char *buf, 10755 u64 *periodp, u64 *quotap) 10756 { 10757 char tok[21]; /* U64_MAX */ 10758 10759 if (sscanf(buf, "%20s %llu", tok, periodp) < 1) 10760 return -EINVAL; 10761 10762 *periodp *= NSEC_PER_USEC; 10763 10764 if (sscanf(tok, "%llu", quotap)) 10765 *quotap *= NSEC_PER_USEC; 10766 else if (!strcmp(tok, "max")) 10767 *quotap = RUNTIME_INF; 10768 else 10769 return -EINVAL; 10770 10771 return 0; 10772 } 10773 10774 #ifdef CONFIG_CFS_BANDWIDTH 10775 static int cpu_max_show(struct seq_file *sf, void *v) 10776 { 10777 struct task_group *tg = css_tg(seq_css(sf)); 10778 10779 cpu_period_quota_print(sf, tg_get_cfs_period(tg), tg_get_cfs_quota(tg)); 10780 return 0; 10781 } 10782 10783 static ssize_t cpu_max_write(struct kernfs_open_file *of, 10784 char *buf, size_t nbytes, loff_t off) 10785 { 10786 struct task_group *tg = css_tg(of_css(of)); 10787 u64 period = tg_get_cfs_period(tg); 10788 u64 burst = tg_get_cfs_burst(tg); 10789 u64 quota; 10790 int ret; 10791 10792 ret = cpu_period_quota_parse(buf, &period, "a); 10793 if (!ret) 10794 ret = tg_set_cfs_bandwidth(tg, period, quota, burst); 10795 return ret ?: nbytes; 10796 } 10797 #endif 10798 10799 static struct cftype cpu_files[] = { 10800 #ifdef CONFIG_FAIR_GROUP_SCHED 10801 { 10802 .name = "weight", 10803 .flags = CFTYPE_NOT_ON_ROOT, 10804 .read_u64 = cpu_weight_read_u64, 10805 .write_u64 = cpu_weight_write_u64, 10806 }, 10807 { 10808 .name = "weight.nice", 10809 .flags = CFTYPE_NOT_ON_ROOT, 10810 .read_s64 = cpu_weight_nice_read_s64, 10811 .write_s64 = cpu_weight_nice_write_s64, 10812 }, 10813 { 10814 .name = "idle", 10815 .flags = CFTYPE_NOT_ON_ROOT, 10816 .read_s64 = cpu_idle_read_s64, 10817 .write_s64 = cpu_idle_write_s64, 10818 }, 10819 #endif 10820 #ifdef CONFIG_CFS_BANDWIDTH 10821 { 10822 .name = "max", 10823 .flags = CFTYPE_NOT_ON_ROOT, 10824 .seq_show = cpu_max_show, 10825 .write = cpu_max_write, 10826 }, 10827 { 10828 .name = "max.burst", 10829 .flags = CFTYPE_NOT_ON_ROOT, 10830 .read_u64 = cpu_cfs_burst_read_u64, 10831 .write_u64 = cpu_cfs_burst_write_u64, 10832 }, 10833 #endif 10834 #ifdef CONFIG_UCLAMP_TASK_GROUP 10835 { 10836 .name = "uclamp.min", 10837 .flags = CFTYPE_NOT_ON_ROOT, 10838 .seq_show = cpu_uclamp_min_show, 10839 .write = cpu_uclamp_min_write, 10840 }, 10841 { 10842 .name = "uclamp.max", 10843 .flags = CFTYPE_NOT_ON_ROOT, 10844 .seq_show = cpu_uclamp_max_show, 10845 .write = cpu_uclamp_max_write, 10846 }, 10847 #endif 10848 { } /* terminate */ 10849 }; 10850 10851 struct cgroup_subsys cpu_cgrp_subsys = { 10852 .css_alloc = cpu_cgroup_css_alloc, 10853 .css_online = cpu_cgroup_css_online, 10854 .css_released = cpu_cgroup_css_released, 10855 .css_free = cpu_cgroup_css_free, 10856 .css_extra_stat_show = cpu_extra_stat_show, 10857 .fork = cpu_cgroup_fork, 10858 .can_attach = cpu_cgroup_can_attach, 10859 .attach = cpu_cgroup_attach, 10860 .legacy_cftypes = cpu_legacy_files, 10861 .dfl_cftypes = cpu_files, 10862 .early_init = true, 10863 .threaded = true, 10864 }; 10865 10866 #endif /* CONFIG_CGROUP_SCHED */ 10867 10868 void dump_cpu_task(int cpu) 10869 { 10870 pr_info("Task dump for CPU %d:\n", cpu); 10871 sched_show_task(cpu_curr(cpu)); 10872 } 10873 10874 /* 10875 * Nice levels are multiplicative, with a gentle 10% change for every 10876 * nice level changed. I.e. when a CPU-bound task goes from nice 0 to 10877 * nice 1, it will get ~10% less CPU time than another CPU-bound task 10878 * that remained on nice 0. 10879 * 10880 * The "10% effect" is relative and cumulative: from _any_ nice level, 10881 * if you go up 1 level, it's -10% CPU usage, if you go down 1 level 10882 * it's +10% CPU usage. (to achieve that we use a multiplier of 1.25. 10883 * If a task goes up by ~10% and another task goes down by ~10% then 10884 * the relative distance between them is ~25%.) 10885 */ 10886 const int sched_prio_to_weight[40] = { 10887 /* -20 */ 88761, 71755, 56483, 46273, 36291, 10888 /* -15 */ 29154, 23254, 18705, 14949, 11916, 10889 /* -10 */ 9548, 7620, 6100, 4904, 3906, 10890 /* -5 */ 3121, 2501, 1991, 1586, 1277, 10891 /* 0 */ 1024, 820, 655, 526, 423, 10892 /* 5 */ 335, 272, 215, 172, 137, 10893 /* 10 */ 110, 87, 70, 56, 45, 10894 /* 15 */ 36, 29, 23, 18, 15, 10895 }; 10896 10897 /* 10898 * Inverse (2^32/x) values of the sched_prio_to_weight[] array, precalculated. 10899 * 10900 * In cases where the weight does not change often, we can use the 10901 * precalculated inverse to speed up arithmetics by turning divisions 10902 * into multiplications: 10903 */ 10904 const u32 sched_prio_to_wmult[40] = { 10905 /* -20 */ 48388, 59856, 76040, 92818, 118348, 10906 /* -15 */ 147320, 184698, 229616, 287308, 360437, 10907 /* -10 */ 449829, 563644, 704093, 875809, 1099582, 10908 /* -5 */ 1376151, 1717300, 2157191, 2708050, 3363326, 10909 /* 0 */ 4194304, 5237765, 6557202, 8165337, 10153587, 10910 /* 5 */ 12820798, 15790321, 19976592, 24970740, 31350126, 10911 /* 10 */ 39045157, 49367440, 61356676, 76695844, 95443717, 10912 /* 15 */ 119304647, 148102320, 186737708, 238609294, 286331153, 10913 }; 10914 10915 void call_trace_sched_update_nr_running(struct rq *rq, int count) 10916 { 10917 trace_sched_update_nr_running_tp(rq, count); 10918 } 10919