1 /* 2 * kernel/workqueue.c - generic async execution with shared worker pool 3 * 4 * Copyright (C) 2002 Ingo Molnar 5 * 6 * Derived from the taskqueue/keventd code by: 7 * David Woodhouse <dwmw2@infradead.org> 8 * Andrew Morton 9 * Kai Petzke <wpp@marie.physik.tu-berlin.de> 10 * Theodore Ts'o <tytso@mit.edu> 11 * 12 * Made to use alloc_percpu by Christoph Lameter. 13 * 14 * Copyright (C) 2010 SUSE Linux Products GmbH 15 * Copyright (C) 2010 Tejun Heo <tj@kernel.org> 16 * 17 * This is the generic async execution mechanism. Work items as are 18 * executed in process context. The worker pool is shared and 19 * automatically managed. There are two worker pools for each CPU (one for 20 * normal work items and the other for high priority ones) and some extra 21 * pools for workqueues which are not bound to any specific CPU - the 22 * number of these backing pools is dynamic. 23 * 24 * Please read Documentation/workqueue.txt for details. 25 */ 26 27 #include <linux/export.h> 28 #include <linux/kernel.h> 29 #include <linux/sched.h> 30 #include <linux/init.h> 31 #include <linux/signal.h> 32 #include <linux/completion.h> 33 #include <linux/workqueue.h> 34 #include <linux/slab.h> 35 #include <linux/cpu.h> 36 #include <linux/notifier.h> 37 #include <linux/kthread.h> 38 #include <linux/hardirq.h> 39 #include <linux/mempolicy.h> 40 #include <linux/freezer.h> 41 #include <linux/kallsyms.h> 42 #include <linux/debug_locks.h> 43 #include <linux/lockdep.h> 44 #include <linux/idr.h> 45 #include <linux/jhash.h> 46 #include <linux/hashtable.h> 47 #include <linux/rculist.h> 48 #include <linux/nodemask.h> 49 #include <linux/moduleparam.h> 50 #include <linux/uaccess.h> 51 52 #include "workqueue_internal.h" 53 54 enum { 55 /* 56 * worker_pool flags 57 * 58 * A bound pool is either associated or disassociated with its CPU. 59 * While associated (!DISASSOCIATED), all workers are bound to the 60 * CPU and none has %WORKER_UNBOUND set and concurrency management 61 * is in effect. 62 * 63 * While DISASSOCIATED, the cpu may be offline and all workers have 64 * %WORKER_UNBOUND set and concurrency management disabled, and may 65 * be executing on any CPU. The pool behaves as an unbound one. 66 * 67 * Note that DISASSOCIATED should be flipped only while holding 68 * attach_mutex to avoid changing binding state while 69 * worker_attach_to_pool() is in progress. 70 */ 71 POOL_DISASSOCIATED = 1 << 2, /* cpu can't serve workers */ 72 73 /* worker flags */ 74 WORKER_DIE = 1 << 1, /* die die die */ 75 WORKER_IDLE = 1 << 2, /* is idle */ 76 WORKER_PREP = 1 << 3, /* preparing to run works */ 77 WORKER_CPU_INTENSIVE = 1 << 6, /* cpu intensive */ 78 WORKER_UNBOUND = 1 << 7, /* worker is unbound */ 79 WORKER_REBOUND = 1 << 8, /* worker was rebound */ 80 81 WORKER_NOT_RUNNING = WORKER_PREP | WORKER_CPU_INTENSIVE | 82 WORKER_UNBOUND | WORKER_REBOUND, 83 84 NR_STD_WORKER_POOLS = 2, /* # standard pools per cpu */ 85 86 UNBOUND_POOL_HASH_ORDER = 6, /* hashed by pool->attrs */ 87 BUSY_WORKER_HASH_ORDER = 6, /* 64 pointers */ 88 89 MAX_IDLE_WORKERS_RATIO = 4, /* 1/4 of busy can be idle */ 90 IDLE_WORKER_TIMEOUT = 300 * HZ, /* keep idle ones for 5 mins */ 91 92 MAYDAY_INITIAL_TIMEOUT = HZ / 100 >= 2 ? HZ / 100 : 2, 93 /* call for help after 10ms 94 (min two ticks) */ 95 MAYDAY_INTERVAL = HZ / 10, /* and then every 100ms */ 96 CREATE_COOLDOWN = HZ, /* time to breath after fail */ 97 98 /* 99 * Rescue workers are used only on emergencies and shared by 100 * all cpus. Give MIN_NICE. 101 */ 102 RESCUER_NICE_LEVEL = MIN_NICE, 103 HIGHPRI_NICE_LEVEL = MIN_NICE, 104 105 WQ_NAME_LEN = 24, 106 }; 107 108 /* 109 * Structure fields follow one of the following exclusion rules. 110 * 111 * I: Modifiable by initialization/destruction paths and read-only for 112 * everyone else. 113 * 114 * P: Preemption protected. Disabling preemption is enough and should 115 * only be modified and accessed from the local cpu. 116 * 117 * L: pool->lock protected. Access with pool->lock held. 118 * 119 * X: During normal operation, modification requires pool->lock and should 120 * be done only from local cpu. Either disabling preemption on local 121 * cpu or grabbing pool->lock is enough for read access. If 122 * POOL_DISASSOCIATED is set, it's identical to L. 123 * 124 * A: pool->attach_mutex protected. 125 * 126 * PL: wq_pool_mutex protected. 127 * 128 * PR: wq_pool_mutex protected for writes. Sched-RCU protected for reads. 129 * 130 * PW: wq_pool_mutex and wq->mutex protected for writes. Either for reads. 131 * 132 * PWR: wq_pool_mutex and wq->mutex protected for writes. Either or 133 * sched-RCU for reads. 134 * 135 * WQ: wq->mutex protected. 136 * 137 * WR: wq->mutex protected for writes. Sched-RCU protected for reads. 138 * 139 * MD: wq_mayday_lock protected. 140 */ 141 142 /* struct worker is defined in workqueue_internal.h */ 143 144 struct worker_pool { 145 spinlock_t lock; /* the pool lock */ 146 int cpu; /* I: the associated cpu */ 147 int node; /* I: the associated node ID */ 148 int id; /* I: pool ID */ 149 unsigned int flags; /* X: flags */ 150 151 unsigned long watchdog_ts; /* L: watchdog timestamp */ 152 153 struct list_head worklist; /* L: list of pending works */ 154 int nr_workers; /* L: total number of workers */ 155 156 /* nr_idle includes the ones off idle_list for rebinding */ 157 int nr_idle; /* L: currently idle ones */ 158 159 struct list_head idle_list; /* X: list of idle workers */ 160 struct timer_list idle_timer; /* L: worker idle timeout */ 161 struct timer_list mayday_timer; /* L: SOS timer for workers */ 162 163 /* a workers is either on busy_hash or idle_list, or the manager */ 164 DECLARE_HASHTABLE(busy_hash, BUSY_WORKER_HASH_ORDER); 165 /* L: hash of busy workers */ 166 167 /* see manage_workers() for details on the two manager mutexes */ 168 struct mutex manager_arb; /* manager arbitration */ 169 struct worker *manager; /* L: purely informational */ 170 struct mutex attach_mutex; /* attach/detach exclusion */ 171 struct list_head workers; /* A: attached workers */ 172 struct completion *detach_completion; /* all workers detached */ 173 174 struct ida worker_ida; /* worker IDs for task name */ 175 176 struct workqueue_attrs *attrs; /* I: worker attributes */ 177 struct hlist_node hash_node; /* PL: unbound_pool_hash node */ 178 int refcnt; /* PL: refcnt for unbound pools */ 179 180 /* 181 * The current concurrency level. As it's likely to be accessed 182 * from other CPUs during try_to_wake_up(), put it in a separate 183 * cacheline. 184 */ 185 atomic_t nr_running ____cacheline_aligned_in_smp; 186 187 /* 188 * Destruction of pool is sched-RCU protected to allow dereferences 189 * from get_work_pool(). 190 */ 191 struct rcu_head rcu; 192 } ____cacheline_aligned_in_smp; 193 194 /* 195 * The per-pool workqueue. While queued, the lower WORK_STRUCT_FLAG_BITS 196 * of work_struct->data are used for flags and the remaining high bits 197 * point to the pwq; thus, pwqs need to be aligned at two's power of the 198 * number of flag bits. 199 */ 200 struct pool_workqueue { 201 struct worker_pool *pool; /* I: the associated pool */ 202 struct workqueue_struct *wq; /* I: the owning workqueue */ 203 int work_color; /* L: current color */ 204 int flush_color; /* L: flushing color */ 205 int refcnt; /* L: reference count */ 206 int nr_in_flight[WORK_NR_COLORS]; 207 /* L: nr of in_flight works */ 208 int nr_active; /* L: nr of active works */ 209 int max_active; /* L: max active works */ 210 struct list_head delayed_works; /* L: delayed works */ 211 struct list_head pwqs_node; /* WR: node on wq->pwqs */ 212 struct list_head mayday_node; /* MD: node on wq->maydays */ 213 214 /* 215 * Release of unbound pwq is punted to system_wq. See put_pwq() 216 * and pwq_unbound_release_workfn() for details. pool_workqueue 217 * itself is also sched-RCU protected so that the first pwq can be 218 * determined without grabbing wq->mutex. 219 */ 220 struct work_struct unbound_release_work; 221 struct rcu_head rcu; 222 } __aligned(1 << WORK_STRUCT_FLAG_BITS); 223 224 /* 225 * Structure used to wait for workqueue flush. 226 */ 227 struct wq_flusher { 228 struct list_head list; /* WQ: list of flushers */ 229 int flush_color; /* WQ: flush color waiting for */ 230 struct completion done; /* flush completion */ 231 }; 232 233 struct wq_device; 234 235 /* 236 * The externally visible workqueue. It relays the issued work items to 237 * the appropriate worker_pool through its pool_workqueues. 238 */ 239 struct workqueue_struct { 240 struct list_head pwqs; /* WR: all pwqs of this wq */ 241 struct list_head list; /* PR: list of all workqueues */ 242 243 struct mutex mutex; /* protects this wq */ 244 int work_color; /* WQ: current work color */ 245 int flush_color; /* WQ: current flush color */ 246 atomic_t nr_pwqs_to_flush; /* flush in progress */ 247 struct wq_flusher *first_flusher; /* WQ: first flusher */ 248 struct list_head flusher_queue; /* WQ: flush waiters */ 249 struct list_head flusher_overflow; /* WQ: flush overflow list */ 250 251 struct list_head maydays; /* MD: pwqs requesting rescue */ 252 struct worker *rescuer; /* I: rescue worker */ 253 254 int nr_drainers; /* WQ: drain in progress */ 255 int saved_max_active; /* WQ: saved pwq max_active */ 256 257 struct workqueue_attrs *unbound_attrs; /* PW: only for unbound wqs */ 258 struct pool_workqueue *dfl_pwq; /* PW: only for unbound wqs */ 259 260 #ifdef CONFIG_SYSFS 261 struct wq_device *wq_dev; /* I: for sysfs interface */ 262 #endif 263 #ifdef CONFIG_LOCKDEP 264 struct lockdep_map lockdep_map; 265 #endif 266 char name[WQ_NAME_LEN]; /* I: workqueue name */ 267 268 /* 269 * Destruction of workqueue_struct is sched-RCU protected to allow 270 * walking the workqueues list without grabbing wq_pool_mutex. 271 * This is used to dump all workqueues from sysrq. 272 */ 273 struct rcu_head rcu; 274 275 /* hot fields used during command issue, aligned to cacheline */ 276 unsigned int flags ____cacheline_aligned; /* WQ: WQ_* flags */ 277 struct pool_workqueue __percpu *cpu_pwqs; /* I: per-cpu pwqs */ 278 struct pool_workqueue __rcu *numa_pwq_tbl[]; /* PWR: unbound pwqs indexed by node */ 279 }; 280 281 static struct kmem_cache *pwq_cache; 282 283 static cpumask_var_t *wq_numa_possible_cpumask; 284 /* possible CPUs of each node */ 285 286 static bool wq_disable_numa; 287 module_param_named(disable_numa, wq_disable_numa, bool, 0444); 288 289 /* see the comment above the definition of WQ_POWER_EFFICIENT */ 290 static bool wq_power_efficient = IS_ENABLED(CONFIG_WQ_POWER_EFFICIENT_DEFAULT); 291 module_param_named(power_efficient, wq_power_efficient, bool, 0444); 292 293 static bool wq_numa_enabled; /* unbound NUMA affinity enabled */ 294 295 /* buf for wq_update_unbound_numa_attrs(), protected by CPU hotplug exclusion */ 296 static struct workqueue_attrs *wq_update_unbound_numa_attrs_buf; 297 298 static DEFINE_MUTEX(wq_pool_mutex); /* protects pools and workqueues list */ 299 static DEFINE_SPINLOCK(wq_mayday_lock); /* protects wq->maydays list */ 300 301 static LIST_HEAD(workqueues); /* PR: list of all workqueues */ 302 static bool workqueue_freezing; /* PL: have wqs started freezing? */ 303 304 /* PL: allowable cpus for unbound wqs and work items */ 305 static cpumask_var_t wq_unbound_cpumask; 306 307 /* CPU where unbound work was last round robin scheduled from this CPU */ 308 static DEFINE_PER_CPU(int, wq_rr_cpu_last); 309 310 /* 311 * Local execution of unbound work items is no longer guaranteed. The 312 * following always forces round-robin CPU selection on unbound work items 313 * to uncover usages which depend on it. 314 */ 315 #ifdef CONFIG_DEBUG_WQ_FORCE_RR_CPU 316 static bool wq_debug_force_rr_cpu = true; 317 #else 318 static bool wq_debug_force_rr_cpu = false; 319 #endif 320 module_param_named(debug_force_rr_cpu, wq_debug_force_rr_cpu, bool, 0644); 321 322 /* the per-cpu worker pools */ 323 static DEFINE_PER_CPU_SHARED_ALIGNED(struct worker_pool [NR_STD_WORKER_POOLS], cpu_worker_pools); 324 325 static DEFINE_IDR(worker_pool_idr); /* PR: idr of all pools */ 326 327 /* PL: hash of all unbound pools keyed by pool->attrs */ 328 static DEFINE_HASHTABLE(unbound_pool_hash, UNBOUND_POOL_HASH_ORDER); 329 330 /* I: attributes used when instantiating standard unbound pools on demand */ 331 static struct workqueue_attrs *unbound_std_wq_attrs[NR_STD_WORKER_POOLS]; 332 333 /* I: attributes used when instantiating ordered pools on demand */ 334 static struct workqueue_attrs *ordered_wq_attrs[NR_STD_WORKER_POOLS]; 335 336 struct workqueue_struct *system_wq __read_mostly; 337 EXPORT_SYMBOL(system_wq); 338 struct workqueue_struct *system_highpri_wq __read_mostly; 339 EXPORT_SYMBOL_GPL(system_highpri_wq); 340 struct workqueue_struct *system_long_wq __read_mostly; 341 EXPORT_SYMBOL_GPL(system_long_wq); 342 struct workqueue_struct *system_unbound_wq __read_mostly; 343 EXPORT_SYMBOL_GPL(system_unbound_wq); 344 struct workqueue_struct *system_freezable_wq __read_mostly; 345 EXPORT_SYMBOL_GPL(system_freezable_wq); 346 struct workqueue_struct *system_power_efficient_wq __read_mostly; 347 EXPORT_SYMBOL_GPL(system_power_efficient_wq); 348 struct workqueue_struct *system_freezable_power_efficient_wq __read_mostly; 349 EXPORT_SYMBOL_GPL(system_freezable_power_efficient_wq); 350 351 static int worker_thread(void *__worker); 352 static void workqueue_sysfs_unregister(struct workqueue_struct *wq); 353 354 #define CREATE_TRACE_POINTS 355 #include <trace/events/workqueue.h> 356 357 #define assert_rcu_or_pool_mutex() \ 358 RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held() && \ 359 !lockdep_is_held(&wq_pool_mutex), \ 360 "sched RCU or wq_pool_mutex should be held") 361 362 #define assert_rcu_or_wq_mutex(wq) \ 363 RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held() && \ 364 !lockdep_is_held(&wq->mutex), \ 365 "sched RCU or wq->mutex should be held") 366 367 #define assert_rcu_or_wq_mutex_or_pool_mutex(wq) \ 368 RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held() && \ 369 !lockdep_is_held(&wq->mutex) && \ 370 !lockdep_is_held(&wq_pool_mutex), \ 371 "sched RCU, wq->mutex or wq_pool_mutex should be held") 372 373 #define for_each_cpu_worker_pool(pool, cpu) \ 374 for ((pool) = &per_cpu(cpu_worker_pools, cpu)[0]; \ 375 (pool) < &per_cpu(cpu_worker_pools, cpu)[NR_STD_WORKER_POOLS]; \ 376 (pool)++) 377 378 /** 379 * for_each_pool - iterate through all worker_pools in the system 380 * @pool: iteration cursor 381 * @pi: integer used for iteration 382 * 383 * This must be called either with wq_pool_mutex held or sched RCU read 384 * locked. If the pool needs to be used beyond the locking in effect, the 385 * caller is responsible for guaranteeing that the pool stays online. 386 * 387 * The if/else clause exists only for the lockdep assertion and can be 388 * ignored. 389 */ 390 #define for_each_pool(pool, pi) \ 391 idr_for_each_entry(&worker_pool_idr, pool, pi) \ 392 if (({ assert_rcu_or_pool_mutex(); false; })) { } \ 393 else 394 395 /** 396 * for_each_pool_worker - iterate through all workers of a worker_pool 397 * @worker: iteration cursor 398 * @pool: worker_pool to iterate workers of 399 * 400 * This must be called with @pool->attach_mutex. 401 * 402 * The if/else clause exists only for the lockdep assertion and can be 403 * ignored. 404 */ 405 #define for_each_pool_worker(worker, pool) \ 406 list_for_each_entry((worker), &(pool)->workers, node) \ 407 if (({ lockdep_assert_held(&pool->attach_mutex); false; })) { } \ 408 else 409 410 /** 411 * for_each_pwq - iterate through all pool_workqueues of the specified workqueue 412 * @pwq: iteration cursor 413 * @wq: the target workqueue 414 * 415 * This must be called either with wq->mutex held or sched RCU read locked. 416 * If the pwq needs to be used beyond the locking in effect, the caller is 417 * responsible for guaranteeing that the pwq stays online. 418 * 419 * The if/else clause exists only for the lockdep assertion and can be 420 * ignored. 421 */ 422 #define for_each_pwq(pwq, wq) \ 423 list_for_each_entry_rcu((pwq), &(wq)->pwqs, pwqs_node) \ 424 if (({ assert_rcu_or_wq_mutex(wq); false; })) { } \ 425 else 426 427 #ifdef CONFIG_DEBUG_OBJECTS_WORK 428 429 static struct debug_obj_descr work_debug_descr; 430 431 static void *work_debug_hint(void *addr) 432 { 433 return ((struct work_struct *) addr)->func; 434 } 435 436 /* 437 * fixup_init is called when: 438 * - an active object is initialized 439 */ 440 static int work_fixup_init(void *addr, enum debug_obj_state state) 441 { 442 struct work_struct *work = addr; 443 444 switch (state) { 445 case ODEBUG_STATE_ACTIVE: 446 cancel_work_sync(work); 447 debug_object_init(work, &work_debug_descr); 448 return 1; 449 default: 450 return 0; 451 } 452 } 453 454 /* 455 * fixup_activate is called when: 456 * - an active object is activated 457 * - an unknown object is activated (might be a statically initialized object) 458 */ 459 static int work_fixup_activate(void *addr, enum debug_obj_state state) 460 { 461 struct work_struct *work = addr; 462 463 switch (state) { 464 465 case ODEBUG_STATE_NOTAVAILABLE: 466 /* 467 * This is not really a fixup. The work struct was 468 * statically initialized. We just make sure that it 469 * is tracked in the object tracker. 470 */ 471 if (test_bit(WORK_STRUCT_STATIC_BIT, work_data_bits(work))) { 472 debug_object_init(work, &work_debug_descr); 473 debug_object_activate(work, &work_debug_descr); 474 return 0; 475 } 476 WARN_ON_ONCE(1); 477 return 0; 478 479 case ODEBUG_STATE_ACTIVE: 480 WARN_ON(1); 481 482 default: 483 return 0; 484 } 485 } 486 487 /* 488 * fixup_free is called when: 489 * - an active object is freed 490 */ 491 static int work_fixup_free(void *addr, enum debug_obj_state state) 492 { 493 struct work_struct *work = addr; 494 495 switch (state) { 496 case ODEBUG_STATE_ACTIVE: 497 cancel_work_sync(work); 498 debug_object_free(work, &work_debug_descr); 499 return 1; 500 default: 501 return 0; 502 } 503 } 504 505 static struct debug_obj_descr work_debug_descr = { 506 .name = "work_struct", 507 .debug_hint = work_debug_hint, 508 .fixup_init = work_fixup_init, 509 .fixup_activate = work_fixup_activate, 510 .fixup_free = work_fixup_free, 511 }; 512 513 static inline void debug_work_activate(struct work_struct *work) 514 { 515 debug_object_activate(work, &work_debug_descr); 516 } 517 518 static inline void debug_work_deactivate(struct work_struct *work) 519 { 520 debug_object_deactivate(work, &work_debug_descr); 521 } 522 523 void __init_work(struct work_struct *work, int onstack) 524 { 525 if (onstack) 526 debug_object_init_on_stack(work, &work_debug_descr); 527 else 528 debug_object_init(work, &work_debug_descr); 529 } 530 EXPORT_SYMBOL_GPL(__init_work); 531 532 void destroy_work_on_stack(struct work_struct *work) 533 { 534 debug_object_free(work, &work_debug_descr); 535 } 536 EXPORT_SYMBOL_GPL(destroy_work_on_stack); 537 538 void destroy_delayed_work_on_stack(struct delayed_work *work) 539 { 540 destroy_timer_on_stack(&work->timer); 541 debug_object_free(&work->work, &work_debug_descr); 542 } 543 EXPORT_SYMBOL_GPL(destroy_delayed_work_on_stack); 544 545 #else 546 static inline void debug_work_activate(struct work_struct *work) { } 547 static inline void debug_work_deactivate(struct work_struct *work) { } 548 #endif 549 550 /** 551 * worker_pool_assign_id - allocate ID and assing it to @pool 552 * @pool: the pool pointer of interest 553 * 554 * Returns 0 if ID in [0, WORK_OFFQ_POOL_NONE) is allocated and assigned 555 * successfully, -errno on failure. 556 */ 557 static int worker_pool_assign_id(struct worker_pool *pool) 558 { 559 int ret; 560 561 lockdep_assert_held(&wq_pool_mutex); 562 563 ret = idr_alloc(&worker_pool_idr, pool, 0, WORK_OFFQ_POOL_NONE, 564 GFP_KERNEL); 565 if (ret >= 0) { 566 pool->id = ret; 567 return 0; 568 } 569 return ret; 570 } 571 572 /** 573 * unbound_pwq_by_node - return the unbound pool_workqueue for the given node 574 * @wq: the target workqueue 575 * @node: the node ID 576 * 577 * This must be called with any of wq_pool_mutex, wq->mutex or sched RCU 578 * read locked. 579 * If the pwq needs to be used beyond the locking in effect, the caller is 580 * responsible for guaranteeing that the pwq stays online. 581 * 582 * Return: The unbound pool_workqueue for @node. 583 */ 584 static struct pool_workqueue *unbound_pwq_by_node(struct workqueue_struct *wq, 585 int node) 586 { 587 assert_rcu_or_wq_mutex_or_pool_mutex(wq); 588 589 /* 590 * XXX: @node can be NUMA_NO_NODE if CPU goes offline while a 591 * delayed item is pending. The plan is to keep CPU -> NODE 592 * mapping valid and stable across CPU on/offlines. Once that 593 * happens, this workaround can be removed. 594 */ 595 if (unlikely(node == NUMA_NO_NODE)) 596 return wq->dfl_pwq; 597 598 return rcu_dereference_raw(wq->numa_pwq_tbl[node]); 599 } 600 601 static unsigned int work_color_to_flags(int color) 602 { 603 return color << WORK_STRUCT_COLOR_SHIFT; 604 } 605 606 static int get_work_color(struct work_struct *work) 607 { 608 return (*work_data_bits(work) >> WORK_STRUCT_COLOR_SHIFT) & 609 ((1 << WORK_STRUCT_COLOR_BITS) - 1); 610 } 611 612 static int work_next_color(int color) 613 { 614 return (color + 1) % WORK_NR_COLORS; 615 } 616 617 /* 618 * While queued, %WORK_STRUCT_PWQ is set and non flag bits of a work's data 619 * contain the pointer to the queued pwq. Once execution starts, the flag 620 * is cleared and the high bits contain OFFQ flags and pool ID. 621 * 622 * set_work_pwq(), set_work_pool_and_clear_pending(), mark_work_canceling() 623 * and clear_work_data() can be used to set the pwq, pool or clear 624 * work->data. These functions should only be called while the work is 625 * owned - ie. while the PENDING bit is set. 626 * 627 * get_work_pool() and get_work_pwq() can be used to obtain the pool or pwq 628 * corresponding to a work. Pool is available once the work has been 629 * queued anywhere after initialization until it is sync canceled. pwq is 630 * available only while the work item is queued. 631 * 632 * %WORK_OFFQ_CANCELING is used to mark a work item which is being 633 * canceled. While being canceled, a work item may have its PENDING set 634 * but stay off timer and worklist for arbitrarily long and nobody should 635 * try to steal the PENDING bit. 636 */ 637 static inline void set_work_data(struct work_struct *work, unsigned long data, 638 unsigned long flags) 639 { 640 WARN_ON_ONCE(!work_pending(work)); 641 atomic_long_set(&work->data, data | flags | work_static(work)); 642 } 643 644 static void set_work_pwq(struct work_struct *work, struct pool_workqueue *pwq, 645 unsigned long extra_flags) 646 { 647 set_work_data(work, (unsigned long)pwq, 648 WORK_STRUCT_PENDING | WORK_STRUCT_PWQ | extra_flags); 649 } 650 651 static void set_work_pool_and_keep_pending(struct work_struct *work, 652 int pool_id) 653 { 654 set_work_data(work, (unsigned long)pool_id << WORK_OFFQ_POOL_SHIFT, 655 WORK_STRUCT_PENDING); 656 } 657 658 static void set_work_pool_and_clear_pending(struct work_struct *work, 659 int pool_id) 660 { 661 /* 662 * The following wmb is paired with the implied mb in 663 * test_and_set_bit(PENDING) and ensures all updates to @work made 664 * here are visible to and precede any updates by the next PENDING 665 * owner. 666 */ 667 smp_wmb(); 668 set_work_data(work, (unsigned long)pool_id << WORK_OFFQ_POOL_SHIFT, 0); 669 /* 670 * The following mb guarantees that previous clear of a PENDING bit 671 * will not be reordered with any speculative LOADS or STORES from 672 * work->current_func, which is executed afterwards. This possible 673 * reordering can lead to a missed execution on attempt to qeueue 674 * the same @work. E.g. consider this case: 675 * 676 * CPU#0 CPU#1 677 * ---------------------------- -------------------------------- 678 * 679 * 1 STORE event_indicated 680 * 2 queue_work_on() { 681 * 3 test_and_set_bit(PENDING) 682 * 4 } set_..._and_clear_pending() { 683 * 5 set_work_data() # clear bit 684 * 6 smp_mb() 685 * 7 work->current_func() { 686 * 8 LOAD event_indicated 687 * } 688 * 689 * Without an explicit full barrier speculative LOAD on line 8 can 690 * be executed before CPU#0 does STORE on line 1. If that happens, 691 * CPU#0 observes the PENDING bit is still set and new execution of 692 * a @work is not queued in a hope, that CPU#1 will eventually 693 * finish the queued @work. Meanwhile CPU#1 does not see 694 * event_indicated is set, because speculative LOAD was executed 695 * before actual STORE. 696 */ 697 smp_mb(); 698 } 699 700 static void clear_work_data(struct work_struct *work) 701 { 702 smp_wmb(); /* see set_work_pool_and_clear_pending() */ 703 set_work_data(work, WORK_STRUCT_NO_POOL, 0); 704 } 705 706 static struct pool_workqueue *get_work_pwq(struct work_struct *work) 707 { 708 unsigned long data = atomic_long_read(&work->data); 709 710 if (data & WORK_STRUCT_PWQ) 711 return (void *)(data & WORK_STRUCT_WQ_DATA_MASK); 712 else 713 return NULL; 714 } 715 716 /** 717 * get_work_pool - return the worker_pool a given work was associated with 718 * @work: the work item of interest 719 * 720 * Pools are created and destroyed under wq_pool_mutex, and allows read 721 * access under sched-RCU read lock. As such, this function should be 722 * called under wq_pool_mutex or with preemption disabled. 723 * 724 * All fields of the returned pool are accessible as long as the above 725 * mentioned locking is in effect. If the returned pool needs to be used 726 * beyond the critical section, the caller is responsible for ensuring the 727 * returned pool is and stays online. 728 * 729 * Return: The worker_pool @work was last associated with. %NULL if none. 730 */ 731 static struct worker_pool *get_work_pool(struct work_struct *work) 732 { 733 unsigned long data = atomic_long_read(&work->data); 734 int pool_id; 735 736 assert_rcu_or_pool_mutex(); 737 738 if (data & WORK_STRUCT_PWQ) 739 return ((struct pool_workqueue *) 740 (data & WORK_STRUCT_WQ_DATA_MASK))->pool; 741 742 pool_id = data >> WORK_OFFQ_POOL_SHIFT; 743 if (pool_id == WORK_OFFQ_POOL_NONE) 744 return NULL; 745 746 return idr_find(&worker_pool_idr, pool_id); 747 } 748 749 /** 750 * get_work_pool_id - return the worker pool ID a given work is associated with 751 * @work: the work item of interest 752 * 753 * Return: The worker_pool ID @work was last associated with. 754 * %WORK_OFFQ_POOL_NONE if none. 755 */ 756 static int get_work_pool_id(struct work_struct *work) 757 { 758 unsigned long data = atomic_long_read(&work->data); 759 760 if (data & WORK_STRUCT_PWQ) 761 return ((struct pool_workqueue *) 762 (data & WORK_STRUCT_WQ_DATA_MASK))->pool->id; 763 764 return data >> WORK_OFFQ_POOL_SHIFT; 765 } 766 767 static void mark_work_canceling(struct work_struct *work) 768 { 769 unsigned long pool_id = get_work_pool_id(work); 770 771 pool_id <<= WORK_OFFQ_POOL_SHIFT; 772 set_work_data(work, pool_id | WORK_OFFQ_CANCELING, WORK_STRUCT_PENDING); 773 } 774 775 static bool work_is_canceling(struct work_struct *work) 776 { 777 unsigned long data = atomic_long_read(&work->data); 778 779 return !(data & WORK_STRUCT_PWQ) && (data & WORK_OFFQ_CANCELING); 780 } 781 782 /* 783 * Policy functions. These define the policies on how the global worker 784 * pools are managed. Unless noted otherwise, these functions assume that 785 * they're being called with pool->lock held. 786 */ 787 788 static bool __need_more_worker(struct worker_pool *pool) 789 { 790 return !atomic_read(&pool->nr_running); 791 } 792 793 /* 794 * Need to wake up a worker? Called from anything but currently 795 * running workers. 796 * 797 * Note that, because unbound workers never contribute to nr_running, this 798 * function will always return %true for unbound pools as long as the 799 * worklist isn't empty. 800 */ 801 static bool need_more_worker(struct worker_pool *pool) 802 { 803 return !list_empty(&pool->worklist) && __need_more_worker(pool); 804 } 805 806 /* Can I start working? Called from busy but !running workers. */ 807 static bool may_start_working(struct worker_pool *pool) 808 { 809 return pool->nr_idle; 810 } 811 812 /* Do I need to keep working? Called from currently running workers. */ 813 static bool keep_working(struct worker_pool *pool) 814 { 815 return !list_empty(&pool->worklist) && 816 atomic_read(&pool->nr_running) <= 1; 817 } 818 819 /* Do we need a new worker? Called from manager. */ 820 static bool need_to_create_worker(struct worker_pool *pool) 821 { 822 return need_more_worker(pool) && !may_start_working(pool); 823 } 824 825 /* Do we have too many workers and should some go away? */ 826 static bool too_many_workers(struct worker_pool *pool) 827 { 828 bool managing = mutex_is_locked(&pool->manager_arb); 829 int nr_idle = pool->nr_idle + managing; /* manager is considered idle */ 830 int nr_busy = pool->nr_workers - nr_idle; 831 832 return nr_idle > 2 && (nr_idle - 2) * MAX_IDLE_WORKERS_RATIO >= nr_busy; 833 } 834 835 /* 836 * Wake up functions. 837 */ 838 839 /* Return the first idle worker. Safe with preemption disabled */ 840 static struct worker *first_idle_worker(struct worker_pool *pool) 841 { 842 if (unlikely(list_empty(&pool->idle_list))) 843 return NULL; 844 845 return list_first_entry(&pool->idle_list, struct worker, entry); 846 } 847 848 /** 849 * wake_up_worker - wake up an idle worker 850 * @pool: worker pool to wake worker from 851 * 852 * Wake up the first idle worker of @pool. 853 * 854 * CONTEXT: 855 * spin_lock_irq(pool->lock). 856 */ 857 static void wake_up_worker(struct worker_pool *pool) 858 { 859 struct worker *worker = first_idle_worker(pool); 860 861 if (likely(worker)) 862 wake_up_process(worker->task); 863 } 864 865 /** 866 * wq_worker_waking_up - a worker is waking up 867 * @task: task waking up 868 * @cpu: CPU @task is waking up to 869 * 870 * This function is called during try_to_wake_up() when a worker is 871 * being awoken. 872 * 873 * CONTEXT: 874 * spin_lock_irq(rq->lock) 875 */ 876 void wq_worker_waking_up(struct task_struct *task, int cpu) 877 { 878 struct worker *worker = kthread_data(task); 879 880 if (!(worker->flags & WORKER_NOT_RUNNING)) { 881 WARN_ON_ONCE(worker->pool->cpu != cpu); 882 atomic_inc(&worker->pool->nr_running); 883 } 884 } 885 886 /** 887 * wq_worker_sleeping - a worker is going to sleep 888 * @task: task going to sleep 889 * 890 * This function is called during schedule() when a busy worker is 891 * going to sleep. Worker on the same cpu can be woken up by 892 * returning pointer to its task. 893 * 894 * CONTEXT: 895 * spin_lock_irq(rq->lock) 896 * 897 * Return: 898 * Worker task on @cpu to wake up, %NULL if none. 899 */ 900 struct task_struct *wq_worker_sleeping(struct task_struct *task) 901 { 902 struct worker *worker = kthread_data(task), *to_wakeup = NULL; 903 struct worker_pool *pool; 904 905 /* 906 * Rescuers, which may not have all the fields set up like normal 907 * workers, also reach here, let's not access anything before 908 * checking NOT_RUNNING. 909 */ 910 if (worker->flags & WORKER_NOT_RUNNING) 911 return NULL; 912 913 pool = worker->pool; 914 915 /* this can only happen on the local cpu */ 916 if (WARN_ON_ONCE(pool->cpu != raw_smp_processor_id())) 917 return NULL; 918 919 /* 920 * The counterpart of the following dec_and_test, implied mb, 921 * worklist not empty test sequence is in insert_work(). 922 * Please read comment there. 923 * 924 * NOT_RUNNING is clear. This means that we're bound to and 925 * running on the local cpu w/ rq lock held and preemption 926 * disabled, which in turn means that none else could be 927 * manipulating idle_list, so dereferencing idle_list without pool 928 * lock is safe. 929 */ 930 if (atomic_dec_and_test(&pool->nr_running) && 931 !list_empty(&pool->worklist)) 932 to_wakeup = first_idle_worker(pool); 933 return to_wakeup ? to_wakeup->task : NULL; 934 } 935 936 /** 937 * worker_set_flags - set worker flags and adjust nr_running accordingly 938 * @worker: self 939 * @flags: flags to set 940 * 941 * Set @flags in @worker->flags and adjust nr_running accordingly. 942 * 943 * CONTEXT: 944 * spin_lock_irq(pool->lock) 945 */ 946 static inline void worker_set_flags(struct worker *worker, unsigned int flags) 947 { 948 struct worker_pool *pool = worker->pool; 949 950 WARN_ON_ONCE(worker->task != current); 951 952 /* If transitioning into NOT_RUNNING, adjust nr_running. */ 953 if ((flags & WORKER_NOT_RUNNING) && 954 !(worker->flags & WORKER_NOT_RUNNING)) { 955 atomic_dec(&pool->nr_running); 956 } 957 958 worker->flags |= flags; 959 } 960 961 /** 962 * worker_clr_flags - clear worker flags and adjust nr_running accordingly 963 * @worker: self 964 * @flags: flags to clear 965 * 966 * Clear @flags in @worker->flags and adjust nr_running accordingly. 967 * 968 * CONTEXT: 969 * spin_lock_irq(pool->lock) 970 */ 971 static inline void worker_clr_flags(struct worker *worker, unsigned int flags) 972 { 973 struct worker_pool *pool = worker->pool; 974 unsigned int oflags = worker->flags; 975 976 WARN_ON_ONCE(worker->task != current); 977 978 worker->flags &= ~flags; 979 980 /* 981 * If transitioning out of NOT_RUNNING, increment nr_running. Note 982 * that the nested NOT_RUNNING is not a noop. NOT_RUNNING is mask 983 * of multiple flags, not a single flag. 984 */ 985 if ((flags & WORKER_NOT_RUNNING) && (oflags & WORKER_NOT_RUNNING)) 986 if (!(worker->flags & WORKER_NOT_RUNNING)) 987 atomic_inc(&pool->nr_running); 988 } 989 990 /** 991 * find_worker_executing_work - find worker which is executing a work 992 * @pool: pool of interest 993 * @work: work to find worker for 994 * 995 * Find a worker which is executing @work on @pool by searching 996 * @pool->busy_hash which is keyed by the address of @work. For a worker 997 * to match, its current execution should match the address of @work and 998 * its work function. This is to avoid unwanted dependency between 999 * unrelated work executions through a work item being recycled while still 1000 * being executed. 1001 * 1002 * This is a bit tricky. A work item may be freed once its execution 1003 * starts and nothing prevents the freed area from being recycled for 1004 * another work item. If the same work item address ends up being reused 1005 * before the original execution finishes, workqueue will identify the 1006 * recycled work item as currently executing and make it wait until the 1007 * current execution finishes, introducing an unwanted dependency. 1008 * 1009 * This function checks the work item address and work function to avoid 1010 * false positives. Note that this isn't complete as one may construct a 1011 * work function which can introduce dependency onto itself through a 1012 * recycled work item. Well, if somebody wants to shoot oneself in the 1013 * foot that badly, there's only so much we can do, and if such deadlock 1014 * actually occurs, it should be easy to locate the culprit work function. 1015 * 1016 * CONTEXT: 1017 * spin_lock_irq(pool->lock). 1018 * 1019 * Return: 1020 * Pointer to worker which is executing @work if found, %NULL 1021 * otherwise. 1022 */ 1023 static struct worker *find_worker_executing_work(struct worker_pool *pool, 1024 struct work_struct *work) 1025 { 1026 struct worker *worker; 1027 1028 hash_for_each_possible(pool->busy_hash, worker, hentry, 1029 (unsigned long)work) 1030 if (worker->current_work == work && 1031 worker->current_func == work->func) 1032 return worker; 1033 1034 return NULL; 1035 } 1036 1037 /** 1038 * move_linked_works - move linked works to a list 1039 * @work: start of series of works to be scheduled 1040 * @head: target list to append @work to 1041 * @nextp: out parameter for nested worklist walking 1042 * 1043 * Schedule linked works starting from @work to @head. Work series to 1044 * be scheduled starts at @work and includes any consecutive work with 1045 * WORK_STRUCT_LINKED set in its predecessor. 1046 * 1047 * If @nextp is not NULL, it's updated to point to the next work of 1048 * the last scheduled work. This allows move_linked_works() to be 1049 * nested inside outer list_for_each_entry_safe(). 1050 * 1051 * CONTEXT: 1052 * spin_lock_irq(pool->lock). 1053 */ 1054 static void move_linked_works(struct work_struct *work, struct list_head *head, 1055 struct work_struct **nextp) 1056 { 1057 struct work_struct *n; 1058 1059 /* 1060 * Linked worklist will always end before the end of the list, 1061 * use NULL for list head. 1062 */ 1063 list_for_each_entry_safe_from(work, n, NULL, entry) { 1064 list_move_tail(&work->entry, head); 1065 if (!(*work_data_bits(work) & WORK_STRUCT_LINKED)) 1066 break; 1067 } 1068 1069 /* 1070 * If we're already inside safe list traversal and have moved 1071 * multiple works to the scheduled queue, the next position 1072 * needs to be updated. 1073 */ 1074 if (nextp) 1075 *nextp = n; 1076 } 1077 1078 /** 1079 * get_pwq - get an extra reference on the specified pool_workqueue 1080 * @pwq: pool_workqueue to get 1081 * 1082 * Obtain an extra reference on @pwq. The caller should guarantee that 1083 * @pwq has positive refcnt and be holding the matching pool->lock. 1084 */ 1085 static void get_pwq(struct pool_workqueue *pwq) 1086 { 1087 lockdep_assert_held(&pwq->pool->lock); 1088 WARN_ON_ONCE(pwq->refcnt <= 0); 1089 pwq->refcnt++; 1090 } 1091 1092 /** 1093 * put_pwq - put a pool_workqueue reference 1094 * @pwq: pool_workqueue to put 1095 * 1096 * Drop a reference of @pwq. If its refcnt reaches zero, schedule its 1097 * destruction. The caller should be holding the matching pool->lock. 1098 */ 1099 static void put_pwq(struct pool_workqueue *pwq) 1100 { 1101 lockdep_assert_held(&pwq->pool->lock); 1102 if (likely(--pwq->refcnt)) 1103 return; 1104 if (WARN_ON_ONCE(!(pwq->wq->flags & WQ_UNBOUND))) 1105 return; 1106 /* 1107 * @pwq can't be released under pool->lock, bounce to 1108 * pwq_unbound_release_workfn(). This never recurses on the same 1109 * pool->lock as this path is taken only for unbound workqueues and 1110 * the release work item is scheduled on a per-cpu workqueue. To 1111 * avoid lockdep warning, unbound pool->locks are given lockdep 1112 * subclass of 1 in get_unbound_pool(). 1113 */ 1114 schedule_work(&pwq->unbound_release_work); 1115 } 1116 1117 /** 1118 * put_pwq_unlocked - put_pwq() with surrounding pool lock/unlock 1119 * @pwq: pool_workqueue to put (can be %NULL) 1120 * 1121 * put_pwq() with locking. This function also allows %NULL @pwq. 1122 */ 1123 static void put_pwq_unlocked(struct pool_workqueue *pwq) 1124 { 1125 if (pwq) { 1126 /* 1127 * As both pwqs and pools are sched-RCU protected, the 1128 * following lock operations are safe. 1129 */ 1130 spin_lock_irq(&pwq->pool->lock); 1131 put_pwq(pwq); 1132 spin_unlock_irq(&pwq->pool->lock); 1133 } 1134 } 1135 1136 static void pwq_activate_delayed_work(struct work_struct *work) 1137 { 1138 struct pool_workqueue *pwq = get_work_pwq(work); 1139 1140 trace_workqueue_activate_work(work); 1141 if (list_empty(&pwq->pool->worklist)) 1142 pwq->pool->watchdog_ts = jiffies; 1143 move_linked_works(work, &pwq->pool->worklist, NULL); 1144 __clear_bit(WORK_STRUCT_DELAYED_BIT, work_data_bits(work)); 1145 pwq->nr_active++; 1146 } 1147 1148 static void pwq_activate_first_delayed(struct pool_workqueue *pwq) 1149 { 1150 struct work_struct *work = list_first_entry(&pwq->delayed_works, 1151 struct work_struct, entry); 1152 1153 pwq_activate_delayed_work(work); 1154 } 1155 1156 /** 1157 * pwq_dec_nr_in_flight - decrement pwq's nr_in_flight 1158 * @pwq: pwq of interest 1159 * @color: color of work which left the queue 1160 * 1161 * A work either has completed or is removed from pending queue, 1162 * decrement nr_in_flight of its pwq and handle workqueue flushing. 1163 * 1164 * CONTEXT: 1165 * spin_lock_irq(pool->lock). 1166 */ 1167 static void pwq_dec_nr_in_flight(struct pool_workqueue *pwq, int color) 1168 { 1169 /* uncolored work items don't participate in flushing or nr_active */ 1170 if (color == WORK_NO_COLOR) 1171 goto out_put; 1172 1173 pwq->nr_in_flight[color]--; 1174 1175 pwq->nr_active--; 1176 if (!list_empty(&pwq->delayed_works)) { 1177 /* one down, submit a delayed one */ 1178 if (pwq->nr_active < pwq->max_active) 1179 pwq_activate_first_delayed(pwq); 1180 } 1181 1182 /* is flush in progress and are we at the flushing tip? */ 1183 if (likely(pwq->flush_color != color)) 1184 goto out_put; 1185 1186 /* are there still in-flight works? */ 1187 if (pwq->nr_in_flight[color]) 1188 goto out_put; 1189 1190 /* this pwq is done, clear flush_color */ 1191 pwq->flush_color = -1; 1192 1193 /* 1194 * If this was the last pwq, wake up the first flusher. It 1195 * will handle the rest. 1196 */ 1197 if (atomic_dec_and_test(&pwq->wq->nr_pwqs_to_flush)) 1198 complete(&pwq->wq->first_flusher->done); 1199 out_put: 1200 put_pwq(pwq); 1201 } 1202 1203 /** 1204 * try_to_grab_pending - steal work item from worklist and disable irq 1205 * @work: work item to steal 1206 * @is_dwork: @work is a delayed_work 1207 * @flags: place to store irq state 1208 * 1209 * Try to grab PENDING bit of @work. This function can handle @work in any 1210 * stable state - idle, on timer or on worklist. 1211 * 1212 * Return: 1213 * 1 if @work was pending and we successfully stole PENDING 1214 * 0 if @work was idle and we claimed PENDING 1215 * -EAGAIN if PENDING couldn't be grabbed at the moment, safe to busy-retry 1216 * -ENOENT if someone else is canceling @work, this state may persist 1217 * for arbitrarily long 1218 * 1219 * Note: 1220 * On >= 0 return, the caller owns @work's PENDING bit. To avoid getting 1221 * interrupted while holding PENDING and @work off queue, irq must be 1222 * disabled on entry. This, combined with delayed_work->timer being 1223 * irqsafe, ensures that we return -EAGAIN for finite short period of time. 1224 * 1225 * On successful return, >= 0, irq is disabled and the caller is 1226 * responsible for releasing it using local_irq_restore(*@flags). 1227 * 1228 * This function is safe to call from any context including IRQ handler. 1229 */ 1230 static int try_to_grab_pending(struct work_struct *work, bool is_dwork, 1231 unsigned long *flags) 1232 { 1233 struct worker_pool *pool; 1234 struct pool_workqueue *pwq; 1235 1236 local_irq_save(*flags); 1237 1238 /* try to steal the timer if it exists */ 1239 if (is_dwork) { 1240 struct delayed_work *dwork = to_delayed_work(work); 1241 1242 /* 1243 * dwork->timer is irqsafe. If del_timer() fails, it's 1244 * guaranteed that the timer is not queued anywhere and not 1245 * running on the local CPU. 1246 */ 1247 if (likely(del_timer(&dwork->timer))) 1248 return 1; 1249 } 1250 1251 /* try to claim PENDING the normal way */ 1252 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) 1253 return 0; 1254 1255 /* 1256 * The queueing is in progress, or it is already queued. Try to 1257 * steal it from ->worklist without clearing WORK_STRUCT_PENDING. 1258 */ 1259 pool = get_work_pool(work); 1260 if (!pool) 1261 goto fail; 1262 1263 spin_lock(&pool->lock); 1264 /* 1265 * work->data is guaranteed to point to pwq only while the work 1266 * item is queued on pwq->wq, and both updating work->data to point 1267 * to pwq on queueing and to pool on dequeueing are done under 1268 * pwq->pool->lock. This in turn guarantees that, if work->data 1269 * points to pwq which is associated with a locked pool, the work 1270 * item is currently queued on that pool. 1271 */ 1272 pwq = get_work_pwq(work); 1273 if (pwq && pwq->pool == pool) { 1274 debug_work_deactivate(work); 1275 1276 /* 1277 * A delayed work item cannot be grabbed directly because 1278 * it might have linked NO_COLOR work items which, if left 1279 * on the delayed_list, will confuse pwq->nr_active 1280 * management later on and cause stall. Make sure the work 1281 * item is activated before grabbing. 1282 */ 1283 if (*work_data_bits(work) & WORK_STRUCT_DELAYED) 1284 pwq_activate_delayed_work(work); 1285 1286 list_del_init(&work->entry); 1287 pwq_dec_nr_in_flight(pwq, get_work_color(work)); 1288 1289 /* work->data points to pwq iff queued, point to pool */ 1290 set_work_pool_and_keep_pending(work, pool->id); 1291 1292 spin_unlock(&pool->lock); 1293 return 1; 1294 } 1295 spin_unlock(&pool->lock); 1296 fail: 1297 local_irq_restore(*flags); 1298 if (work_is_canceling(work)) 1299 return -ENOENT; 1300 cpu_relax(); 1301 return -EAGAIN; 1302 } 1303 1304 /** 1305 * insert_work - insert a work into a pool 1306 * @pwq: pwq @work belongs to 1307 * @work: work to insert 1308 * @head: insertion point 1309 * @extra_flags: extra WORK_STRUCT_* flags to set 1310 * 1311 * Insert @work which belongs to @pwq after @head. @extra_flags is or'd to 1312 * work_struct flags. 1313 * 1314 * CONTEXT: 1315 * spin_lock_irq(pool->lock). 1316 */ 1317 static void insert_work(struct pool_workqueue *pwq, struct work_struct *work, 1318 struct list_head *head, unsigned int extra_flags) 1319 { 1320 struct worker_pool *pool = pwq->pool; 1321 1322 /* we own @work, set data and link */ 1323 set_work_pwq(work, pwq, extra_flags); 1324 list_add_tail(&work->entry, head); 1325 get_pwq(pwq); 1326 1327 /* 1328 * Ensure either wq_worker_sleeping() sees the above 1329 * list_add_tail() or we see zero nr_running to avoid workers lying 1330 * around lazily while there are works to be processed. 1331 */ 1332 smp_mb(); 1333 1334 if (__need_more_worker(pool)) 1335 wake_up_worker(pool); 1336 } 1337 1338 /* 1339 * Test whether @work is being queued from another work executing on the 1340 * same workqueue. 1341 */ 1342 static bool is_chained_work(struct workqueue_struct *wq) 1343 { 1344 struct worker *worker; 1345 1346 worker = current_wq_worker(); 1347 /* 1348 * Return %true iff I'm a worker execuing a work item on @wq. If 1349 * I'm @worker, it's safe to dereference it without locking. 1350 */ 1351 return worker && worker->current_pwq->wq == wq; 1352 } 1353 1354 /* 1355 * When queueing an unbound work item to a wq, prefer local CPU if allowed 1356 * by wq_unbound_cpumask. Otherwise, round robin among the allowed ones to 1357 * avoid perturbing sensitive tasks. 1358 */ 1359 static int wq_select_unbound_cpu(int cpu) 1360 { 1361 static bool printed_dbg_warning; 1362 int new_cpu; 1363 1364 if (likely(!wq_debug_force_rr_cpu)) { 1365 if (cpumask_test_cpu(cpu, wq_unbound_cpumask)) 1366 return cpu; 1367 } else if (!printed_dbg_warning) { 1368 pr_warn("workqueue: round-robin CPU selection forced, expect performance impact\n"); 1369 printed_dbg_warning = true; 1370 } 1371 1372 if (cpumask_empty(wq_unbound_cpumask)) 1373 return cpu; 1374 1375 new_cpu = __this_cpu_read(wq_rr_cpu_last); 1376 new_cpu = cpumask_next_and(new_cpu, wq_unbound_cpumask, cpu_online_mask); 1377 if (unlikely(new_cpu >= nr_cpu_ids)) { 1378 new_cpu = cpumask_first_and(wq_unbound_cpumask, cpu_online_mask); 1379 if (unlikely(new_cpu >= nr_cpu_ids)) 1380 return cpu; 1381 } 1382 __this_cpu_write(wq_rr_cpu_last, new_cpu); 1383 1384 return new_cpu; 1385 } 1386 1387 static void __queue_work(int cpu, struct workqueue_struct *wq, 1388 struct work_struct *work) 1389 { 1390 struct pool_workqueue *pwq; 1391 struct worker_pool *last_pool; 1392 struct list_head *worklist; 1393 unsigned int work_flags; 1394 unsigned int req_cpu = cpu; 1395 1396 /* 1397 * While a work item is PENDING && off queue, a task trying to 1398 * steal the PENDING will busy-loop waiting for it to either get 1399 * queued or lose PENDING. Grabbing PENDING and queueing should 1400 * happen with IRQ disabled. 1401 */ 1402 WARN_ON_ONCE(!irqs_disabled()); 1403 1404 debug_work_activate(work); 1405 1406 /* if draining, only works from the same workqueue are allowed */ 1407 if (unlikely(wq->flags & __WQ_DRAINING) && 1408 WARN_ON_ONCE(!is_chained_work(wq))) 1409 return; 1410 retry: 1411 if (req_cpu == WORK_CPU_UNBOUND) 1412 cpu = wq_select_unbound_cpu(raw_smp_processor_id()); 1413 1414 /* pwq which will be used unless @work is executing elsewhere */ 1415 if (!(wq->flags & WQ_UNBOUND)) 1416 pwq = per_cpu_ptr(wq->cpu_pwqs, cpu); 1417 else 1418 pwq = unbound_pwq_by_node(wq, cpu_to_node(cpu)); 1419 1420 /* 1421 * If @work was previously on a different pool, it might still be 1422 * running there, in which case the work needs to be queued on that 1423 * pool to guarantee non-reentrancy. 1424 */ 1425 last_pool = get_work_pool(work); 1426 if (last_pool && last_pool != pwq->pool) { 1427 struct worker *worker; 1428 1429 spin_lock(&last_pool->lock); 1430 1431 worker = find_worker_executing_work(last_pool, work); 1432 1433 if (worker && worker->current_pwq->wq == wq) { 1434 pwq = worker->current_pwq; 1435 } else { 1436 /* meh... not running there, queue here */ 1437 spin_unlock(&last_pool->lock); 1438 spin_lock(&pwq->pool->lock); 1439 } 1440 } else { 1441 spin_lock(&pwq->pool->lock); 1442 } 1443 1444 /* 1445 * pwq is determined and locked. For unbound pools, we could have 1446 * raced with pwq release and it could already be dead. If its 1447 * refcnt is zero, repeat pwq selection. Note that pwqs never die 1448 * without another pwq replacing it in the numa_pwq_tbl or while 1449 * work items are executing on it, so the retrying is guaranteed to 1450 * make forward-progress. 1451 */ 1452 if (unlikely(!pwq->refcnt)) { 1453 if (wq->flags & WQ_UNBOUND) { 1454 spin_unlock(&pwq->pool->lock); 1455 cpu_relax(); 1456 goto retry; 1457 } 1458 /* oops */ 1459 WARN_ONCE(true, "workqueue: per-cpu pwq for %s on cpu%d has 0 refcnt", 1460 wq->name, cpu); 1461 } 1462 1463 /* pwq determined, queue */ 1464 trace_workqueue_queue_work(req_cpu, pwq, work); 1465 1466 if (WARN_ON(!list_empty(&work->entry))) { 1467 spin_unlock(&pwq->pool->lock); 1468 return; 1469 } 1470 1471 pwq->nr_in_flight[pwq->work_color]++; 1472 work_flags = work_color_to_flags(pwq->work_color); 1473 1474 if (likely(pwq->nr_active < pwq->max_active)) { 1475 trace_workqueue_activate_work(work); 1476 pwq->nr_active++; 1477 worklist = &pwq->pool->worklist; 1478 if (list_empty(worklist)) 1479 pwq->pool->watchdog_ts = jiffies; 1480 } else { 1481 work_flags |= WORK_STRUCT_DELAYED; 1482 worklist = &pwq->delayed_works; 1483 } 1484 1485 insert_work(pwq, work, worklist, work_flags); 1486 1487 spin_unlock(&pwq->pool->lock); 1488 } 1489 1490 /** 1491 * queue_work_on - queue work on specific cpu 1492 * @cpu: CPU number to execute work on 1493 * @wq: workqueue to use 1494 * @work: work to queue 1495 * 1496 * We queue the work to a specific CPU, the caller must ensure it 1497 * can't go away. 1498 * 1499 * Return: %false if @work was already on a queue, %true otherwise. 1500 */ 1501 bool queue_work_on(int cpu, struct workqueue_struct *wq, 1502 struct work_struct *work) 1503 { 1504 bool ret = false; 1505 unsigned long flags; 1506 1507 local_irq_save(flags); 1508 1509 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) { 1510 __queue_work(cpu, wq, work); 1511 ret = true; 1512 } 1513 1514 local_irq_restore(flags); 1515 return ret; 1516 } 1517 EXPORT_SYMBOL(queue_work_on); 1518 1519 void delayed_work_timer_fn(unsigned long __data) 1520 { 1521 struct delayed_work *dwork = (struct delayed_work *)__data; 1522 1523 /* should have been called from irqsafe timer with irq already off */ 1524 __queue_work(dwork->cpu, dwork->wq, &dwork->work); 1525 } 1526 EXPORT_SYMBOL(delayed_work_timer_fn); 1527 1528 static void __queue_delayed_work(int cpu, struct workqueue_struct *wq, 1529 struct delayed_work *dwork, unsigned long delay) 1530 { 1531 struct timer_list *timer = &dwork->timer; 1532 struct work_struct *work = &dwork->work; 1533 1534 WARN_ON_ONCE(timer->function != delayed_work_timer_fn || 1535 timer->data != (unsigned long)dwork); 1536 WARN_ON_ONCE(timer_pending(timer)); 1537 WARN_ON_ONCE(!list_empty(&work->entry)); 1538 1539 /* 1540 * If @delay is 0, queue @dwork->work immediately. This is for 1541 * both optimization and correctness. The earliest @timer can 1542 * expire is on the closest next tick and delayed_work users depend 1543 * on that there's no such delay when @delay is 0. 1544 */ 1545 if (!delay) { 1546 __queue_work(cpu, wq, &dwork->work); 1547 return; 1548 } 1549 1550 timer_stats_timer_set_start_info(&dwork->timer); 1551 1552 dwork->wq = wq; 1553 dwork->cpu = cpu; 1554 timer->expires = jiffies + delay; 1555 1556 if (unlikely(cpu != WORK_CPU_UNBOUND)) 1557 add_timer_on(timer, cpu); 1558 else 1559 add_timer(timer); 1560 } 1561 1562 /** 1563 * queue_delayed_work_on - queue work on specific CPU after delay 1564 * @cpu: CPU number to execute work on 1565 * @wq: workqueue to use 1566 * @dwork: work to queue 1567 * @delay: number of jiffies to wait before queueing 1568 * 1569 * Return: %false if @work was already on a queue, %true otherwise. If 1570 * @delay is zero and @dwork is idle, it will be scheduled for immediate 1571 * execution. 1572 */ 1573 bool queue_delayed_work_on(int cpu, struct workqueue_struct *wq, 1574 struct delayed_work *dwork, unsigned long delay) 1575 { 1576 struct work_struct *work = &dwork->work; 1577 bool ret = false; 1578 unsigned long flags; 1579 1580 /* read the comment in __queue_work() */ 1581 local_irq_save(flags); 1582 1583 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) { 1584 __queue_delayed_work(cpu, wq, dwork, delay); 1585 ret = true; 1586 } 1587 1588 local_irq_restore(flags); 1589 return ret; 1590 } 1591 EXPORT_SYMBOL(queue_delayed_work_on); 1592 1593 /** 1594 * mod_delayed_work_on - modify delay of or queue a delayed work on specific CPU 1595 * @cpu: CPU number to execute work on 1596 * @wq: workqueue to use 1597 * @dwork: work to queue 1598 * @delay: number of jiffies to wait before queueing 1599 * 1600 * If @dwork is idle, equivalent to queue_delayed_work_on(); otherwise, 1601 * modify @dwork's timer so that it expires after @delay. If @delay is 1602 * zero, @work is guaranteed to be scheduled immediately regardless of its 1603 * current state. 1604 * 1605 * Return: %false if @dwork was idle and queued, %true if @dwork was 1606 * pending and its timer was modified. 1607 * 1608 * This function is safe to call from any context including IRQ handler. 1609 * See try_to_grab_pending() for details. 1610 */ 1611 bool mod_delayed_work_on(int cpu, struct workqueue_struct *wq, 1612 struct delayed_work *dwork, unsigned long delay) 1613 { 1614 unsigned long flags; 1615 int ret; 1616 1617 do { 1618 ret = try_to_grab_pending(&dwork->work, true, &flags); 1619 } while (unlikely(ret == -EAGAIN)); 1620 1621 if (likely(ret >= 0)) { 1622 __queue_delayed_work(cpu, wq, dwork, delay); 1623 local_irq_restore(flags); 1624 } 1625 1626 /* -ENOENT from try_to_grab_pending() becomes %true */ 1627 return ret; 1628 } 1629 EXPORT_SYMBOL_GPL(mod_delayed_work_on); 1630 1631 /** 1632 * worker_enter_idle - enter idle state 1633 * @worker: worker which is entering idle state 1634 * 1635 * @worker is entering idle state. Update stats and idle timer if 1636 * necessary. 1637 * 1638 * LOCKING: 1639 * spin_lock_irq(pool->lock). 1640 */ 1641 static void worker_enter_idle(struct worker *worker) 1642 { 1643 struct worker_pool *pool = worker->pool; 1644 1645 if (WARN_ON_ONCE(worker->flags & WORKER_IDLE) || 1646 WARN_ON_ONCE(!list_empty(&worker->entry) && 1647 (worker->hentry.next || worker->hentry.pprev))) 1648 return; 1649 1650 /* can't use worker_set_flags(), also called from create_worker() */ 1651 worker->flags |= WORKER_IDLE; 1652 pool->nr_idle++; 1653 worker->last_active = jiffies; 1654 1655 /* idle_list is LIFO */ 1656 list_add(&worker->entry, &pool->idle_list); 1657 1658 if (too_many_workers(pool) && !timer_pending(&pool->idle_timer)) 1659 mod_timer(&pool->idle_timer, jiffies + IDLE_WORKER_TIMEOUT); 1660 1661 /* 1662 * Sanity check nr_running. Because wq_unbind_fn() releases 1663 * pool->lock between setting %WORKER_UNBOUND and zapping 1664 * nr_running, the warning may trigger spuriously. Check iff 1665 * unbind is not in progress. 1666 */ 1667 WARN_ON_ONCE(!(pool->flags & POOL_DISASSOCIATED) && 1668 pool->nr_workers == pool->nr_idle && 1669 atomic_read(&pool->nr_running)); 1670 } 1671 1672 /** 1673 * worker_leave_idle - leave idle state 1674 * @worker: worker which is leaving idle state 1675 * 1676 * @worker is leaving idle state. Update stats. 1677 * 1678 * LOCKING: 1679 * spin_lock_irq(pool->lock). 1680 */ 1681 static void worker_leave_idle(struct worker *worker) 1682 { 1683 struct worker_pool *pool = worker->pool; 1684 1685 if (WARN_ON_ONCE(!(worker->flags & WORKER_IDLE))) 1686 return; 1687 worker_clr_flags(worker, WORKER_IDLE); 1688 pool->nr_idle--; 1689 list_del_init(&worker->entry); 1690 } 1691 1692 static struct worker *alloc_worker(int node) 1693 { 1694 struct worker *worker; 1695 1696 worker = kzalloc_node(sizeof(*worker), GFP_KERNEL, node); 1697 if (worker) { 1698 INIT_LIST_HEAD(&worker->entry); 1699 INIT_LIST_HEAD(&worker->scheduled); 1700 INIT_LIST_HEAD(&worker->node); 1701 /* on creation a worker is in !idle && prep state */ 1702 worker->flags = WORKER_PREP; 1703 } 1704 return worker; 1705 } 1706 1707 /** 1708 * worker_attach_to_pool() - attach a worker to a pool 1709 * @worker: worker to be attached 1710 * @pool: the target pool 1711 * 1712 * Attach @worker to @pool. Once attached, the %WORKER_UNBOUND flag and 1713 * cpu-binding of @worker are kept coordinated with the pool across 1714 * cpu-[un]hotplugs. 1715 */ 1716 static void worker_attach_to_pool(struct worker *worker, 1717 struct worker_pool *pool) 1718 { 1719 mutex_lock(&pool->attach_mutex); 1720 1721 /* 1722 * set_cpus_allowed_ptr() will fail if the cpumask doesn't have any 1723 * online CPUs. It'll be re-applied when any of the CPUs come up. 1724 */ 1725 set_cpus_allowed_ptr(worker->task, pool->attrs->cpumask); 1726 1727 /* 1728 * The pool->attach_mutex ensures %POOL_DISASSOCIATED remains 1729 * stable across this function. See the comments above the 1730 * flag definition for details. 1731 */ 1732 if (pool->flags & POOL_DISASSOCIATED) 1733 worker->flags |= WORKER_UNBOUND; 1734 1735 list_add_tail(&worker->node, &pool->workers); 1736 1737 mutex_unlock(&pool->attach_mutex); 1738 } 1739 1740 /** 1741 * worker_detach_from_pool() - detach a worker from its pool 1742 * @worker: worker which is attached to its pool 1743 * @pool: the pool @worker is attached to 1744 * 1745 * Undo the attaching which had been done in worker_attach_to_pool(). The 1746 * caller worker shouldn't access to the pool after detached except it has 1747 * other reference to the pool. 1748 */ 1749 static void worker_detach_from_pool(struct worker *worker, 1750 struct worker_pool *pool) 1751 { 1752 struct completion *detach_completion = NULL; 1753 1754 mutex_lock(&pool->attach_mutex); 1755 list_del(&worker->node); 1756 if (list_empty(&pool->workers)) 1757 detach_completion = pool->detach_completion; 1758 mutex_unlock(&pool->attach_mutex); 1759 1760 /* clear leftover flags without pool->lock after it is detached */ 1761 worker->flags &= ~(WORKER_UNBOUND | WORKER_REBOUND); 1762 1763 if (detach_completion) 1764 complete(detach_completion); 1765 } 1766 1767 /** 1768 * create_worker - create a new workqueue worker 1769 * @pool: pool the new worker will belong to 1770 * 1771 * Create and start a new worker which is attached to @pool. 1772 * 1773 * CONTEXT: 1774 * Might sleep. Does GFP_KERNEL allocations. 1775 * 1776 * Return: 1777 * Pointer to the newly created worker. 1778 */ 1779 static struct worker *create_worker(struct worker_pool *pool) 1780 { 1781 struct worker *worker = NULL; 1782 int id = -1; 1783 char id_buf[16]; 1784 1785 /* ID is needed to determine kthread name */ 1786 id = ida_simple_get(&pool->worker_ida, 0, 0, GFP_KERNEL); 1787 if (id < 0) 1788 goto fail; 1789 1790 worker = alloc_worker(pool->node); 1791 if (!worker) 1792 goto fail; 1793 1794 worker->pool = pool; 1795 worker->id = id; 1796 1797 if (pool->cpu >= 0) 1798 snprintf(id_buf, sizeof(id_buf), "%d:%d%s", pool->cpu, id, 1799 pool->attrs->nice < 0 ? "H" : ""); 1800 else 1801 snprintf(id_buf, sizeof(id_buf), "u%d:%d", pool->id, id); 1802 1803 worker->task = kthread_create_on_node(worker_thread, worker, pool->node, 1804 "kworker/%s", id_buf); 1805 if (IS_ERR(worker->task)) 1806 goto fail; 1807 1808 set_user_nice(worker->task, pool->attrs->nice); 1809 kthread_bind_mask(worker->task, pool->attrs->cpumask); 1810 1811 /* successful, attach the worker to the pool */ 1812 worker_attach_to_pool(worker, pool); 1813 1814 /* start the newly created worker */ 1815 spin_lock_irq(&pool->lock); 1816 worker->pool->nr_workers++; 1817 worker_enter_idle(worker); 1818 wake_up_process(worker->task); 1819 spin_unlock_irq(&pool->lock); 1820 1821 return worker; 1822 1823 fail: 1824 if (id >= 0) 1825 ida_simple_remove(&pool->worker_ida, id); 1826 kfree(worker); 1827 return NULL; 1828 } 1829 1830 /** 1831 * destroy_worker - destroy a workqueue worker 1832 * @worker: worker to be destroyed 1833 * 1834 * Destroy @worker and adjust @pool stats accordingly. The worker should 1835 * be idle. 1836 * 1837 * CONTEXT: 1838 * spin_lock_irq(pool->lock). 1839 */ 1840 static void destroy_worker(struct worker *worker) 1841 { 1842 struct worker_pool *pool = worker->pool; 1843 1844 lockdep_assert_held(&pool->lock); 1845 1846 /* sanity check frenzy */ 1847 if (WARN_ON(worker->current_work) || 1848 WARN_ON(!list_empty(&worker->scheduled)) || 1849 WARN_ON(!(worker->flags & WORKER_IDLE))) 1850 return; 1851 1852 pool->nr_workers--; 1853 pool->nr_idle--; 1854 1855 list_del_init(&worker->entry); 1856 worker->flags |= WORKER_DIE; 1857 wake_up_process(worker->task); 1858 } 1859 1860 static void idle_worker_timeout(unsigned long __pool) 1861 { 1862 struct worker_pool *pool = (void *)__pool; 1863 1864 spin_lock_irq(&pool->lock); 1865 1866 while (too_many_workers(pool)) { 1867 struct worker *worker; 1868 unsigned long expires; 1869 1870 /* idle_list is kept in LIFO order, check the last one */ 1871 worker = list_entry(pool->idle_list.prev, struct worker, entry); 1872 expires = worker->last_active + IDLE_WORKER_TIMEOUT; 1873 1874 if (time_before(jiffies, expires)) { 1875 mod_timer(&pool->idle_timer, expires); 1876 break; 1877 } 1878 1879 destroy_worker(worker); 1880 } 1881 1882 spin_unlock_irq(&pool->lock); 1883 } 1884 1885 static void send_mayday(struct work_struct *work) 1886 { 1887 struct pool_workqueue *pwq = get_work_pwq(work); 1888 struct workqueue_struct *wq = pwq->wq; 1889 1890 lockdep_assert_held(&wq_mayday_lock); 1891 1892 if (!wq->rescuer) 1893 return; 1894 1895 /* mayday mayday mayday */ 1896 if (list_empty(&pwq->mayday_node)) { 1897 /* 1898 * If @pwq is for an unbound wq, its base ref may be put at 1899 * any time due to an attribute change. Pin @pwq until the 1900 * rescuer is done with it. 1901 */ 1902 get_pwq(pwq); 1903 list_add_tail(&pwq->mayday_node, &wq->maydays); 1904 wake_up_process(wq->rescuer->task); 1905 } 1906 } 1907 1908 static void pool_mayday_timeout(unsigned long __pool) 1909 { 1910 struct worker_pool *pool = (void *)__pool; 1911 struct work_struct *work; 1912 1913 spin_lock_irq(&pool->lock); 1914 spin_lock(&wq_mayday_lock); /* for wq->maydays */ 1915 1916 if (need_to_create_worker(pool)) { 1917 /* 1918 * We've been trying to create a new worker but 1919 * haven't been successful. We might be hitting an 1920 * allocation deadlock. Send distress signals to 1921 * rescuers. 1922 */ 1923 list_for_each_entry(work, &pool->worklist, entry) 1924 send_mayday(work); 1925 } 1926 1927 spin_unlock(&wq_mayday_lock); 1928 spin_unlock_irq(&pool->lock); 1929 1930 mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INTERVAL); 1931 } 1932 1933 /** 1934 * maybe_create_worker - create a new worker if necessary 1935 * @pool: pool to create a new worker for 1936 * 1937 * Create a new worker for @pool if necessary. @pool is guaranteed to 1938 * have at least one idle worker on return from this function. If 1939 * creating a new worker takes longer than MAYDAY_INTERVAL, mayday is 1940 * sent to all rescuers with works scheduled on @pool to resolve 1941 * possible allocation deadlock. 1942 * 1943 * On return, need_to_create_worker() is guaranteed to be %false and 1944 * may_start_working() %true. 1945 * 1946 * LOCKING: 1947 * spin_lock_irq(pool->lock) which may be released and regrabbed 1948 * multiple times. Does GFP_KERNEL allocations. Called only from 1949 * manager. 1950 */ 1951 static void maybe_create_worker(struct worker_pool *pool) 1952 __releases(&pool->lock) 1953 __acquires(&pool->lock) 1954 { 1955 restart: 1956 spin_unlock_irq(&pool->lock); 1957 1958 /* if we don't make progress in MAYDAY_INITIAL_TIMEOUT, call for help */ 1959 mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INITIAL_TIMEOUT); 1960 1961 while (true) { 1962 if (create_worker(pool) || !need_to_create_worker(pool)) 1963 break; 1964 1965 schedule_timeout_interruptible(CREATE_COOLDOWN); 1966 1967 if (!need_to_create_worker(pool)) 1968 break; 1969 } 1970 1971 del_timer_sync(&pool->mayday_timer); 1972 spin_lock_irq(&pool->lock); 1973 /* 1974 * This is necessary even after a new worker was just successfully 1975 * created as @pool->lock was dropped and the new worker might have 1976 * already become busy. 1977 */ 1978 if (need_to_create_worker(pool)) 1979 goto restart; 1980 } 1981 1982 /** 1983 * manage_workers - manage worker pool 1984 * @worker: self 1985 * 1986 * Assume the manager role and manage the worker pool @worker belongs 1987 * to. At any given time, there can be only zero or one manager per 1988 * pool. The exclusion is handled automatically by this function. 1989 * 1990 * The caller can safely start processing works on false return. On 1991 * true return, it's guaranteed that need_to_create_worker() is false 1992 * and may_start_working() is true. 1993 * 1994 * CONTEXT: 1995 * spin_lock_irq(pool->lock) which may be released and regrabbed 1996 * multiple times. Does GFP_KERNEL allocations. 1997 * 1998 * Return: 1999 * %false if the pool doesn't need management and the caller can safely 2000 * start processing works, %true if management function was performed and 2001 * the conditions that the caller verified before calling the function may 2002 * no longer be true. 2003 */ 2004 static bool manage_workers(struct worker *worker) 2005 { 2006 struct worker_pool *pool = worker->pool; 2007 2008 /* 2009 * Anyone who successfully grabs manager_arb wins the arbitration 2010 * and becomes the manager. mutex_trylock() on pool->manager_arb 2011 * failure while holding pool->lock reliably indicates that someone 2012 * else is managing the pool and the worker which failed trylock 2013 * can proceed to executing work items. This means that anyone 2014 * grabbing manager_arb is responsible for actually performing 2015 * manager duties. If manager_arb is grabbed and released without 2016 * actual management, the pool may stall indefinitely. 2017 */ 2018 if (!mutex_trylock(&pool->manager_arb)) 2019 return false; 2020 pool->manager = worker; 2021 2022 maybe_create_worker(pool); 2023 2024 pool->manager = NULL; 2025 mutex_unlock(&pool->manager_arb); 2026 return true; 2027 } 2028 2029 /** 2030 * process_one_work - process single work 2031 * @worker: self 2032 * @work: work to process 2033 * 2034 * Process @work. This function contains all the logics necessary to 2035 * process a single work including synchronization against and 2036 * interaction with other workers on the same cpu, queueing and 2037 * flushing. As long as context requirement is met, any worker can 2038 * call this function to process a work. 2039 * 2040 * CONTEXT: 2041 * spin_lock_irq(pool->lock) which is released and regrabbed. 2042 */ 2043 static void process_one_work(struct worker *worker, struct work_struct *work) 2044 __releases(&pool->lock) 2045 __acquires(&pool->lock) 2046 { 2047 struct pool_workqueue *pwq = get_work_pwq(work); 2048 struct worker_pool *pool = worker->pool; 2049 bool cpu_intensive = pwq->wq->flags & WQ_CPU_INTENSIVE; 2050 int work_color; 2051 struct worker *collision; 2052 #ifdef CONFIG_LOCKDEP 2053 /* 2054 * It is permissible to free the struct work_struct from 2055 * inside the function that is called from it, this we need to 2056 * take into account for lockdep too. To avoid bogus "held 2057 * lock freed" warnings as well as problems when looking into 2058 * work->lockdep_map, make a copy and use that here. 2059 */ 2060 struct lockdep_map lockdep_map; 2061 2062 lockdep_copy_map(&lockdep_map, &work->lockdep_map); 2063 #endif 2064 /* ensure we're on the correct CPU */ 2065 WARN_ON_ONCE(!(pool->flags & POOL_DISASSOCIATED) && 2066 raw_smp_processor_id() != pool->cpu); 2067 2068 /* 2069 * A single work shouldn't be executed concurrently by 2070 * multiple workers on a single cpu. Check whether anyone is 2071 * already processing the work. If so, defer the work to the 2072 * currently executing one. 2073 */ 2074 collision = find_worker_executing_work(pool, work); 2075 if (unlikely(collision)) { 2076 move_linked_works(work, &collision->scheduled, NULL); 2077 return; 2078 } 2079 2080 /* claim and dequeue */ 2081 debug_work_deactivate(work); 2082 hash_add(pool->busy_hash, &worker->hentry, (unsigned long)work); 2083 worker->current_work = work; 2084 worker->current_func = work->func; 2085 worker->current_pwq = pwq; 2086 work_color = get_work_color(work); 2087 2088 list_del_init(&work->entry); 2089 2090 /* 2091 * CPU intensive works don't participate in concurrency management. 2092 * They're the scheduler's responsibility. This takes @worker out 2093 * of concurrency management and the next code block will chain 2094 * execution of the pending work items. 2095 */ 2096 if (unlikely(cpu_intensive)) 2097 worker_set_flags(worker, WORKER_CPU_INTENSIVE); 2098 2099 /* 2100 * Wake up another worker if necessary. The condition is always 2101 * false for normal per-cpu workers since nr_running would always 2102 * be >= 1 at this point. This is used to chain execution of the 2103 * pending work items for WORKER_NOT_RUNNING workers such as the 2104 * UNBOUND and CPU_INTENSIVE ones. 2105 */ 2106 if (need_more_worker(pool)) 2107 wake_up_worker(pool); 2108 2109 /* 2110 * Record the last pool and clear PENDING which should be the last 2111 * update to @work. Also, do this inside @pool->lock so that 2112 * PENDING and queued state changes happen together while IRQ is 2113 * disabled. 2114 */ 2115 set_work_pool_and_clear_pending(work, pool->id); 2116 2117 spin_unlock_irq(&pool->lock); 2118 2119 lock_map_acquire_read(&pwq->wq->lockdep_map); 2120 lock_map_acquire(&lockdep_map); 2121 trace_workqueue_execute_start(work); 2122 worker->current_func(work); 2123 /* 2124 * While we must be careful to not use "work" after this, the trace 2125 * point will only record its address. 2126 */ 2127 trace_workqueue_execute_end(work); 2128 lock_map_release(&lockdep_map); 2129 lock_map_release(&pwq->wq->lockdep_map); 2130 2131 if (unlikely(in_atomic() || lockdep_depth(current) > 0)) { 2132 pr_err("BUG: workqueue leaked lock or atomic: %s/0x%08x/%d\n" 2133 " last function: %pf\n", 2134 current->comm, preempt_count(), task_pid_nr(current), 2135 worker->current_func); 2136 debug_show_held_locks(current); 2137 dump_stack(); 2138 } 2139 2140 /* 2141 * The following prevents a kworker from hogging CPU on !PREEMPT 2142 * kernels, where a requeueing work item waiting for something to 2143 * happen could deadlock with stop_machine as such work item could 2144 * indefinitely requeue itself while all other CPUs are trapped in 2145 * stop_machine. At the same time, report a quiescent RCU state so 2146 * the same condition doesn't freeze RCU. 2147 */ 2148 cond_resched_rcu_qs(); 2149 2150 spin_lock_irq(&pool->lock); 2151 2152 /* clear cpu intensive status */ 2153 if (unlikely(cpu_intensive)) 2154 worker_clr_flags(worker, WORKER_CPU_INTENSIVE); 2155 2156 /* we're done with it, release */ 2157 hash_del(&worker->hentry); 2158 worker->current_work = NULL; 2159 worker->current_func = NULL; 2160 worker->current_pwq = NULL; 2161 worker->desc_valid = false; 2162 pwq_dec_nr_in_flight(pwq, work_color); 2163 } 2164 2165 /** 2166 * process_scheduled_works - process scheduled works 2167 * @worker: self 2168 * 2169 * Process all scheduled works. Please note that the scheduled list 2170 * may change while processing a work, so this function repeatedly 2171 * fetches a work from the top and executes it. 2172 * 2173 * CONTEXT: 2174 * spin_lock_irq(pool->lock) which may be released and regrabbed 2175 * multiple times. 2176 */ 2177 static void process_scheduled_works(struct worker *worker) 2178 { 2179 while (!list_empty(&worker->scheduled)) { 2180 struct work_struct *work = list_first_entry(&worker->scheduled, 2181 struct work_struct, entry); 2182 process_one_work(worker, work); 2183 } 2184 } 2185 2186 /** 2187 * worker_thread - the worker thread function 2188 * @__worker: self 2189 * 2190 * The worker thread function. All workers belong to a worker_pool - 2191 * either a per-cpu one or dynamic unbound one. These workers process all 2192 * work items regardless of their specific target workqueue. The only 2193 * exception is work items which belong to workqueues with a rescuer which 2194 * will be explained in rescuer_thread(). 2195 * 2196 * Return: 0 2197 */ 2198 static int worker_thread(void *__worker) 2199 { 2200 struct worker *worker = __worker; 2201 struct worker_pool *pool = worker->pool; 2202 2203 /* tell the scheduler that this is a workqueue worker */ 2204 worker->task->flags |= PF_WQ_WORKER; 2205 woke_up: 2206 spin_lock_irq(&pool->lock); 2207 2208 /* am I supposed to die? */ 2209 if (unlikely(worker->flags & WORKER_DIE)) { 2210 spin_unlock_irq(&pool->lock); 2211 WARN_ON_ONCE(!list_empty(&worker->entry)); 2212 worker->task->flags &= ~PF_WQ_WORKER; 2213 2214 set_task_comm(worker->task, "kworker/dying"); 2215 ida_simple_remove(&pool->worker_ida, worker->id); 2216 worker_detach_from_pool(worker, pool); 2217 kfree(worker); 2218 return 0; 2219 } 2220 2221 worker_leave_idle(worker); 2222 recheck: 2223 /* no more worker necessary? */ 2224 if (!need_more_worker(pool)) 2225 goto sleep; 2226 2227 /* do we need to manage? */ 2228 if (unlikely(!may_start_working(pool)) && manage_workers(worker)) 2229 goto recheck; 2230 2231 /* 2232 * ->scheduled list can only be filled while a worker is 2233 * preparing to process a work or actually processing it. 2234 * Make sure nobody diddled with it while I was sleeping. 2235 */ 2236 WARN_ON_ONCE(!list_empty(&worker->scheduled)); 2237 2238 /* 2239 * Finish PREP stage. We're guaranteed to have at least one idle 2240 * worker or that someone else has already assumed the manager 2241 * role. This is where @worker starts participating in concurrency 2242 * management if applicable and concurrency management is restored 2243 * after being rebound. See rebind_workers() for details. 2244 */ 2245 worker_clr_flags(worker, WORKER_PREP | WORKER_REBOUND); 2246 2247 do { 2248 struct work_struct *work = 2249 list_first_entry(&pool->worklist, 2250 struct work_struct, entry); 2251 2252 pool->watchdog_ts = jiffies; 2253 2254 if (likely(!(*work_data_bits(work) & WORK_STRUCT_LINKED))) { 2255 /* optimization path, not strictly necessary */ 2256 process_one_work(worker, work); 2257 if (unlikely(!list_empty(&worker->scheduled))) 2258 process_scheduled_works(worker); 2259 } else { 2260 move_linked_works(work, &worker->scheduled, NULL); 2261 process_scheduled_works(worker); 2262 } 2263 } while (keep_working(pool)); 2264 2265 worker_set_flags(worker, WORKER_PREP); 2266 sleep: 2267 /* 2268 * pool->lock is held and there's no work to process and no need to 2269 * manage, sleep. Workers are woken up only while holding 2270 * pool->lock or from local cpu, so setting the current state 2271 * before releasing pool->lock is enough to prevent losing any 2272 * event. 2273 */ 2274 worker_enter_idle(worker); 2275 __set_current_state(TASK_INTERRUPTIBLE); 2276 spin_unlock_irq(&pool->lock); 2277 schedule(); 2278 goto woke_up; 2279 } 2280 2281 /** 2282 * rescuer_thread - the rescuer thread function 2283 * @__rescuer: self 2284 * 2285 * Workqueue rescuer thread function. There's one rescuer for each 2286 * workqueue which has WQ_MEM_RECLAIM set. 2287 * 2288 * Regular work processing on a pool may block trying to create a new 2289 * worker which uses GFP_KERNEL allocation which has slight chance of 2290 * developing into deadlock if some works currently on the same queue 2291 * need to be processed to satisfy the GFP_KERNEL allocation. This is 2292 * the problem rescuer solves. 2293 * 2294 * When such condition is possible, the pool summons rescuers of all 2295 * workqueues which have works queued on the pool and let them process 2296 * those works so that forward progress can be guaranteed. 2297 * 2298 * This should happen rarely. 2299 * 2300 * Return: 0 2301 */ 2302 static int rescuer_thread(void *__rescuer) 2303 { 2304 struct worker *rescuer = __rescuer; 2305 struct workqueue_struct *wq = rescuer->rescue_wq; 2306 struct list_head *scheduled = &rescuer->scheduled; 2307 bool should_stop; 2308 2309 set_user_nice(current, RESCUER_NICE_LEVEL); 2310 2311 /* 2312 * Mark rescuer as worker too. As WORKER_PREP is never cleared, it 2313 * doesn't participate in concurrency management. 2314 */ 2315 rescuer->task->flags |= PF_WQ_WORKER; 2316 repeat: 2317 set_current_state(TASK_INTERRUPTIBLE); 2318 2319 /* 2320 * By the time the rescuer is requested to stop, the workqueue 2321 * shouldn't have any work pending, but @wq->maydays may still have 2322 * pwq(s) queued. This can happen by non-rescuer workers consuming 2323 * all the work items before the rescuer got to them. Go through 2324 * @wq->maydays processing before acting on should_stop so that the 2325 * list is always empty on exit. 2326 */ 2327 should_stop = kthread_should_stop(); 2328 2329 /* see whether any pwq is asking for help */ 2330 spin_lock_irq(&wq_mayday_lock); 2331 2332 while (!list_empty(&wq->maydays)) { 2333 struct pool_workqueue *pwq = list_first_entry(&wq->maydays, 2334 struct pool_workqueue, mayday_node); 2335 struct worker_pool *pool = pwq->pool; 2336 struct work_struct *work, *n; 2337 bool first = true; 2338 2339 __set_current_state(TASK_RUNNING); 2340 list_del_init(&pwq->mayday_node); 2341 2342 spin_unlock_irq(&wq_mayday_lock); 2343 2344 worker_attach_to_pool(rescuer, pool); 2345 2346 spin_lock_irq(&pool->lock); 2347 rescuer->pool = pool; 2348 2349 /* 2350 * Slurp in all works issued via this workqueue and 2351 * process'em. 2352 */ 2353 WARN_ON_ONCE(!list_empty(scheduled)); 2354 list_for_each_entry_safe(work, n, &pool->worklist, entry) { 2355 if (get_work_pwq(work) == pwq) { 2356 if (first) 2357 pool->watchdog_ts = jiffies; 2358 move_linked_works(work, scheduled, &n); 2359 } 2360 first = false; 2361 } 2362 2363 if (!list_empty(scheduled)) { 2364 process_scheduled_works(rescuer); 2365 2366 /* 2367 * The above execution of rescued work items could 2368 * have created more to rescue through 2369 * pwq_activate_first_delayed() or chained 2370 * queueing. Let's put @pwq back on mayday list so 2371 * that such back-to-back work items, which may be 2372 * being used to relieve memory pressure, don't 2373 * incur MAYDAY_INTERVAL delay inbetween. 2374 */ 2375 if (need_to_create_worker(pool)) { 2376 spin_lock(&wq_mayday_lock); 2377 get_pwq(pwq); 2378 list_move_tail(&pwq->mayday_node, &wq->maydays); 2379 spin_unlock(&wq_mayday_lock); 2380 } 2381 } 2382 2383 /* 2384 * Put the reference grabbed by send_mayday(). @pool won't 2385 * go away while we're still attached to it. 2386 */ 2387 put_pwq(pwq); 2388 2389 /* 2390 * Leave this pool. If need_more_worker() is %true, notify a 2391 * regular worker; otherwise, we end up with 0 concurrency 2392 * and stalling the execution. 2393 */ 2394 if (need_more_worker(pool)) 2395 wake_up_worker(pool); 2396 2397 rescuer->pool = NULL; 2398 spin_unlock_irq(&pool->lock); 2399 2400 worker_detach_from_pool(rescuer, pool); 2401 2402 spin_lock_irq(&wq_mayday_lock); 2403 } 2404 2405 spin_unlock_irq(&wq_mayday_lock); 2406 2407 if (should_stop) { 2408 __set_current_state(TASK_RUNNING); 2409 rescuer->task->flags &= ~PF_WQ_WORKER; 2410 return 0; 2411 } 2412 2413 /* rescuers should never participate in concurrency management */ 2414 WARN_ON_ONCE(!(rescuer->flags & WORKER_NOT_RUNNING)); 2415 schedule(); 2416 goto repeat; 2417 } 2418 2419 /** 2420 * check_flush_dependency - check for flush dependency sanity 2421 * @target_wq: workqueue being flushed 2422 * @target_work: work item being flushed (NULL for workqueue flushes) 2423 * 2424 * %current is trying to flush the whole @target_wq or @target_work on it. 2425 * If @target_wq doesn't have %WQ_MEM_RECLAIM, verify that %current is not 2426 * reclaiming memory or running on a workqueue which doesn't have 2427 * %WQ_MEM_RECLAIM as that can break forward-progress guarantee leading to 2428 * a deadlock. 2429 */ 2430 static void check_flush_dependency(struct workqueue_struct *target_wq, 2431 struct work_struct *target_work) 2432 { 2433 work_func_t target_func = target_work ? target_work->func : NULL; 2434 struct worker *worker; 2435 2436 if (target_wq->flags & WQ_MEM_RECLAIM) 2437 return; 2438 2439 worker = current_wq_worker(); 2440 2441 WARN_ONCE(current->flags & PF_MEMALLOC, 2442 "workqueue: PF_MEMALLOC task %d(%s) is flushing !WQ_MEM_RECLAIM %s:%pf", 2443 current->pid, current->comm, target_wq->name, target_func); 2444 WARN_ONCE(worker && ((worker->current_pwq->wq->flags & 2445 (WQ_MEM_RECLAIM | __WQ_LEGACY)) == WQ_MEM_RECLAIM), 2446 "workqueue: WQ_MEM_RECLAIM %s:%pf is flushing !WQ_MEM_RECLAIM %s:%pf", 2447 worker->current_pwq->wq->name, worker->current_func, 2448 target_wq->name, target_func); 2449 } 2450 2451 struct wq_barrier { 2452 struct work_struct work; 2453 struct completion done; 2454 struct task_struct *task; /* purely informational */ 2455 }; 2456 2457 static void wq_barrier_func(struct work_struct *work) 2458 { 2459 struct wq_barrier *barr = container_of(work, struct wq_barrier, work); 2460 complete(&barr->done); 2461 } 2462 2463 /** 2464 * insert_wq_barrier - insert a barrier work 2465 * @pwq: pwq to insert barrier into 2466 * @barr: wq_barrier to insert 2467 * @target: target work to attach @barr to 2468 * @worker: worker currently executing @target, NULL if @target is not executing 2469 * 2470 * @barr is linked to @target such that @barr is completed only after 2471 * @target finishes execution. Please note that the ordering 2472 * guarantee is observed only with respect to @target and on the local 2473 * cpu. 2474 * 2475 * Currently, a queued barrier can't be canceled. This is because 2476 * try_to_grab_pending() can't determine whether the work to be 2477 * grabbed is at the head of the queue and thus can't clear LINKED 2478 * flag of the previous work while there must be a valid next work 2479 * after a work with LINKED flag set. 2480 * 2481 * Note that when @worker is non-NULL, @target may be modified 2482 * underneath us, so we can't reliably determine pwq from @target. 2483 * 2484 * CONTEXT: 2485 * spin_lock_irq(pool->lock). 2486 */ 2487 static void insert_wq_barrier(struct pool_workqueue *pwq, 2488 struct wq_barrier *barr, 2489 struct work_struct *target, struct worker *worker) 2490 { 2491 struct list_head *head; 2492 unsigned int linked = 0; 2493 2494 /* 2495 * debugobject calls are safe here even with pool->lock locked 2496 * as we know for sure that this will not trigger any of the 2497 * checks and call back into the fixup functions where we 2498 * might deadlock. 2499 */ 2500 INIT_WORK_ONSTACK(&barr->work, wq_barrier_func); 2501 __set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(&barr->work)); 2502 init_completion(&barr->done); 2503 barr->task = current; 2504 2505 /* 2506 * If @target is currently being executed, schedule the 2507 * barrier to the worker; otherwise, put it after @target. 2508 */ 2509 if (worker) 2510 head = worker->scheduled.next; 2511 else { 2512 unsigned long *bits = work_data_bits(target); 2513 2514 head = target->entry.next; 2515 /* there can already be other linked works, inherit and set */ 2516 linked = *bits & WORK_STRUCT_LINKED; 2517 __set_bit(WORK_STRUCT_LINKED_BIT, bits); 2518 } 2519 2520 debug_work_activate(&barr->work); 2521 insert_work(pwq, &barr->work, head, 2522 work_color_to_flags(WORK_NO_COLOR) | linked); 2523 } 2524 2525 /** 2526 * flush_workqueue_prep_pwqs - prepare pwqs for workqueue flushing 2527 * @wq: workqueue being flushed 2528 * @flush_color: new flush color, < 0 for no-op 2529 * @work_color: new work color, < 0 for no-op 2530 * 2531 * Prepare pwqs for workqueue flushing. 2532 * 2533 * If @flush_color is non-negative, flush_color on all pwqs should be 2534 * -1. If no pwq has in-flight commands at the specified color, all 2535 * pwq->flush_color's stay at -1 and %false is returned. If any pwq 2536 * has in flight commands, its pwq->flush_color is set to 2537 * @flush_color, @wq->nr_pwqs_to_flush is updated accordingly, pwq 2538 * wakeup logic is armed and %true is returned. 2539 * 2540 * The caller should have initialized @wq->first_flusher prior to 2541 * calling this function with non-negative @flush_color. If 2542 * @flush_color is negative, no flush color update is done and %false 2543 * is returned. 2544 * 2545 * If @work_color is non-negative, all pwqs should have the same 2546 * work_color which is previous to @work_color and all will be 2547 * advanced to @work_color. 2548 * 2549 * CONTEXT: 2550 * mutex_lock(wq->mutex). 2551 * 2552 * Return: 2553 * %true if @flush_color >= 0 and there's something to flush. %false 2554 * otherwise. 2555 */ 2556 static bool flush_workqueue_prep_pwqs(struct workqueue_struct *wq, 2557 int flush_color, int work_color) 2558 { 2559 bool wait = false; 2560 struct pool_workqueue *pwq; 2561 2562 if (flush_color >= 0) { 2563 WARN_ON_ONCE(atomic_read(&wq->nr_pwqs_to_flush)); 2564 atomic_set(&wq->nr_pwqs_to_flush, 1); 2565 } 2566 2567 for_each_pwq(pwq, wq) { 2568 struct worker_pool *pool = pwq->pool; 2569 2570 spin_lock_irq(&pool->lock); 2571 2572 if (flush_color >= 0) { 2573 WARN_ON_ONCE(pwq->flush_color != -1); 2574 2575 if (pwq->nr_in_flight[flush_color]) { 2576 pwq->flush_color = flush_color; 2577 atomic_inc(&wq->nr_pwqs_to_flush); 2578 wait = true; 2579 } 2580 } 2581 2582 if (work_color >= 0) { 2583 WARN_ON_ONCE(work_color != work_next_color(pwq->work_color)); 2584 pwq->work_color = work_color; 2585 } 2586 2587 spin_unlock_irq(&pool->lock); 2588 } 2589 2590 if (flush_color >= 0 && atomic_dec_and_test(&wq->nr_pwqs_to_flush)) 2591 complete(&wq->first_flusher->done); 2592 2593 return wait; 2594 } 2595 2596 /** 2597 * flush_workqueue - ensure that any scheduled work has run to completion. 2598 * @wq: workqueue to flush 2599 * 2600 * This function sleeps until all work items which were queued on entry 2601 * have finished execution, but it is not livelocked by new incoming ones. 2602 */ 2603 void flush_workqueue(struct workqueue_struct *wq) 2604 { 2605 struct wq_flusher this_flusher = { 2606 .list = LIST_HEAD_INIT(this_flusher.list), 2607 .flush_color = -1, 2608 .done = COMPLETION_INITIALIZER_ONSTACK(this_flusher.done), 2609 }; 2610 int next_color; 2611 2612 lock_map_acquire(&wq->lockdep_map); 2613 lock_map_release(&wq->lockdep_map); 2614 2615 mutex_lock(&wq->mutex); 2616 2617 /* 2618 * Start-to-wait phase 2619 */ 2620 next_color = work_next_color(wq->work_color); 2621 2622 if (next_color != wq->flush_color) { 2623 /* 2624 * Color space is not full. The current work_color 2625 * becomes our flush_color and work_color is advanced 2626 * by one. 2627 */ 2628 WARN_ON_ONCE(!list_empty(&wq->flusher_overflow)); 2629 this_flusher.flush_color = wq->work_color; 2630 wq->work_color = next_color; 2631 2632 if (!wq->first_flusher) { 2633 /* no flush in progress, become the first flusher */ 2634 WARN_ON_ONCE(wq->flush_color != this_flusher.flush_color); 2635 2636 wq->first_flusher = &this_flusher; 2637 2638 if (!flush_workqueue_prep_pwqs(wq, wq->flush_color, 2639 wq->work_color)) { 2640 /* nothing to flush, done */ 2641 wq->flush_color = next_color; 2642 wq->first_flusher = NULL; 2643 goto out_unlock; 2644 } 2645 } else { 2646 /* wait in queue */ 2647 WARN_ON_ONCE(wq->flush_color == this_flusher.flush_color); 2648 list_add_tail(&this_flusher.list, &wq->flusher_queue); 2649 flush_workqueue_prep_pwqs(wq, -1, wq->work_color); 2650 } 2651 } else { 2652 /* 2653 * Oops, color space is full, wait on overflow queue. 2654 * The next flush completion will assign us 2655 * flush_color and transfer to flusher_queue. 2656 */ 2657 list_add_tail(&this_flusher.list, &wq->flusher_overflow); 2658 } 2659 2660 check_flush_dependency(wq, NULL); 2661 2662 mutex_unlock(&wq->mutex); 2663 2664 wait_for_completion(&this_flusher.done); 2665 2666 /* 2667 * Wake-up-and-cascade phase 2668 * 2669 * First flushers are responsible for cascading flushes and 2670 * handling overflow. Non-first flushers can simply return. 2671 */ 2672 if (wq->first_flusher != &this_flusher) 2673 return; 2674 2675 mutex_lock(&wq->mutex); 2676 2677 /* we might have raced, check again with mutex held */ 2678 if (wq->first_flusher != &this_flusher) 2679 goto out_unlock; 2680 2681 wq->first_flusher = NULL; 2682 2683 WARN_ON_ONCE(!list_empty(&this_flusher.list)); 2684 WARN_ON_ONCE(wq->flush_color != this_flusher.flush_color); 2685 2686 while (true) { 2687 struct wq_flusher *next, *tmp; 2688 2689 /* complete all the flushers sharing the current flush color */ 2690 list_for_each_entry_safe(next, tmp, &wq->flusher_queue, list) { 2691 if (next->flush_color != wq->flush_color) 2692 break; 2693 list_del_init(&next->list); 2694 complete(&next->done); 2695 } 2696 2697 WARN_ON_ONCE(!list_empty(&wq->flusher_overflow) && 2698 wq->flush_color != work_next_color(wq->work_color)); 2699 2700 /* this flush_color is finished, advance by one */ 2701 wq->flush_color = work_next_color(wq->flush_color); 2702 2703 /* one color has been freed, handle overflow queue */ 2704 if (!list_empty(&wq->flusher_overflow)) { 2705 /* 2706 * Assign the same color to all overflowed 2707 * flushers, advance work_color and append to 2708 * flusher_queue. This is the start-to-wait 2709 * phase for these overflowed flushers. 2710 */ 2711 list_for_each_entry(tmp, &wq->flusher_overflow, list) 2712 tmp->flush_color = wq->work_color; 2713 2714 wq->work_color = work_next_color(wq->work_color); 2715 2716 list_splice_tail_init(&wq->flusher_overflow, 2717 &wq->flusher_queue); 2718 flush_workqueue_prep_pwqs(wq, -1, wq->work_color); 2719 } 2720 2721 if (list_empty(&wq->flusher_queue)) { 2722 WARN_ON_ONCE(wq->flush_color != wq->work_color); 2723 break; 2724 } 2725 2726 /* 2727 * Need to flush more colors. Make the next flusher 2728 * the new first flusher and arm pwqs. 2729 */ 2730 WARN_ON_ONCE(wq->flush_color == wq->work_color); 2731 WARN_ON_ONCE(wq->flush_color != next->flush_color); 2732 2733 list_del_init(&next->list); 2734 wq->first_flusher = next; 2735 2736 if (flush_workqueue_prep_pwqs(wq, wq->flush_color, -1)) 2737 break; 2738 2739 /* 2740 * Meh... this color is already done, clear first 2741 * flusher and repeat cascading. 2742 */ 2743 wq->first_flusher = NULL; 2744 } 2745 2746 out_unlock: 2747 mutex_unlock(&wq->mutex); 2748 } 2749 EXPORT_SYMBOL(flush_workqueue); 2750 2751 /** 2752 * drain_workqueue - drain a workqueue 2753 * @wq: workqueue to drain 2754 * 2755 * Wait until the workqueue becomes empty. While draining is in progress, 2756 * only chain queueing is allowed. IOW, only currently pending or running 2757 * work items on @wq can queue further work items on it. @wq is flushed 2758 * repeatedly until it becomes empty. The number of flushing is determined 2759 * by the depth of chaining and should be relatively short. Whine if it 2760 * takes too long. 2761 */ 2762 void drain_workqueue(struct workqueue_struct *wq) 2763 { 2764 unsigned int flush_cnt = 0; 2765 struct pool_workqueue *pwq; 2766 2767 /* 2768 * __queue_work() needs to test whether there are drainers, is much 2769 * hotter than drain_workqueue() and already looks at @wq->flags. 2770 * Use __WQ_DRAINING so that queue doesn't have to check nr_drainers. 2771 */ 2772 mutex_lock(&wq->mutex); 2773 if (!wq->nr_drainers++) 2774 wq->flags |= __WQ_DRAINING; 2775 mutex_unlock(&wq->mutex); 2776 reflush: 2777 flush_workqueue(wq); 2778 2779 mutex_lock(&wq->mutex); 2780 2781 for_each_pwq(pwq, wq) { 2782 bool drained; 2783 2784 spin_lock_irq(&pwq->pool->lock); 2785 drained = !pwq->nr_active && list_empty(&pwq->delayed_works); 2786 spin_unlock_irq(&pwq->pool->lock); 2787 2788 if (drained) 2789 continue; 2790 2791 if (++flush_cnt == 10 || 2792 (flush_cnt % 100 == 0 && flush_cnt <= 1000)) 2793 pr_warn("workqueue %s: drain_workqueue() isn't complete after %u tries\n", 2794 wq->name, flush_cnt); 2795 2796 mutex_unlock(&wq->mutex); 2797 goto reflush; 2798 } 2799 2800 if (!--wq->nr_drainers) 2801 wq->flags &= ~__WQ_DRAINING; 2802 mutex_unlock(&wq->mutex); 2803 } 2804 EXPORT_SYMBOL_GPL(drain_workqueue); 2805 2806 static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr) 2807 { 2808 struct worker *worker = NULL; 2809 struct worker_pool *pool; 2810 struct pool_workqueue *pwq; 2811 2812 might_sleep(); 2813 2814 local_irq_disable(); 2815 pool = get_work_pool(work); 2816 if (!pool) { 2817 local_irq_enable(); 2818 return false; 2819 } 2820 2821 spin_lock(&pool->lock); 2822 /* see the comment in try_to_grab_pending() with the same code */ 2823 pwq = get_work_pwq(work); 2824 if (pwq) { 2825 if (unlikely(pwq->pool != pool)) 2826 goto already_gone; 2827 } else { 2828 worker = find_worker_executing_work(pool, work); 2829 if (!worker) 2830 goto already_gone; 2831 pwq = worker->current_pwq; 2832 } 2833 2834 check_flush_dependency(pwq->wq, work); 2835 2836 insert_wq_barrier(pwq, barr, work, worker); 2837 spin_unlock_irq(&pool->lock); 2838 2839 /* 2840 * If @max_active is 1 or rescuer is in use, flushing another work 2841 * item on the same workqueue may lead to deadlock. Make sure the 2842 * flusher is not running on the same workqueue by verifying write 2843 * access. 2844 */ 2845 if (pwq->wq->saved_max_active == 1 || pwq->wq->rescuer) 2846 lock_map_acquire(&pwq->wq->lockdep_map); 2847 else 2848 lock_map_acquire_read(&pwq->wq->lockdep_map); 2849 lock_map_release(&pwq->wq->lockdep_map); 2850 2851 return true; 2852 already_gone: 2853 spin_unlock_irq(&pool->lock); 2854 return false; 2855 } 2856 2857 /** 2858 * flush_work - wait for a work to finish executing the last queueing instance 2859 * @work: the work to flush 2860 * 2861 * Wait until @work has finished execution. @work is guaranteed to be idle 2862 * on return if it hasn't been requeued since flush started. 2863 * 2864 * Return: 2865 * %true if flush_work() waited for the work to finish execution, 2866 * %false if it was already idle. 2867 */ 2868 bool flush_work(struct work_struct *work) 2869 { 2870 struct wq_barrier barr; 2871 2872 lock_map_acquire(&work->lockdep_map); 2873 lock_map_release(&work->lockdep_map); 2874 2875 if (start_flush_work(work, &barr)) { 2876 wait_for_completion(&barr.done); 2877 destroy_work_on_stack(&barr.work); 2878 return true; 2879 } else { 2880 return false; 2881 } 2882 } 2883 EXPORT_SYMBOL_GPL(flush_work); 2884 2885 struct cwt_wait { 2886 wait_queue_t wait; 2887 struct work_struct *work; 2888 }; 2889 2890 static int cwt_wakefn(wait_queue_t *wait, unsigned mode, int sync, void *key) 2891 { 2892 struct cwt_wait *cwait = container_of(wait, struct cwt_wait, wait); 2893 2894 if (cwait->work != key) 2895 return 0; 2896 return autoremove_wake_function(wait, mode, sync, key); 2897 } 2898 2899 static bool __cancel_work_timer(struct work_struct *work, bool is_dwork) 2900 { 2901 static DECLARE_WAIT_QUEUE_HEAD(cancel_waitq); 2902 unsigned long flags; 2903 int ret; 2904 2905 do { 2906 ret = try_to_grab_pending(work, is_dwork, &flags); 2907 /* 2908 * If someone else is already canceling, wait for it to 2909 * finish. flush_work() doesn't work for PREEMPT_NONE 2910 * because we may get scheduled between @work's completion 2911 * and the other canceling task resuming and clearing 2912 * CANCELING - flush_work() will return false immediately 2913 * as @work is no longer busy, try_to_grab_pending() will 2914 * return -ENOENT as @work is still being canceled and the 2915 * other canceling task won't be able to clear CANCELING as 2916 * we're hogging the CPU. 2917 * 2918 * Let's wait for completion using a waitqueue. As this 2919 * may lead to the thundering herd problem, use a custom 2920 * wake function which matches @work along with exclusive 2921 * wait and wakeup. 2922 */ 2923 if (unlikely(ret == -ENOENT)) { 2924 struct cwt_wait cwait; 2925 2926 init_wait(&cwait.wait); 2927 cwait.wait.func = cwt_wakefn; 2928 cwait.work = work; 2929 2930 prepare_to_wait_exclusive(&cancel_waitq, &cwait.wait, 2931 TASK_UNINTERRUPTIBLE); 2932 if (work_is_canceling(work)) 2933 schedule(); 2934 finish_wait(&cancel_waitq, &cwait.wait); 2935 } 2936 } while (unlikely(ret < 0)); 2937 2938 /* tell other tasks trying to grab @work to back off */ 2939 mark_work_canceling(work); 2940 local_irq_restore(flags); 2941 2942 flush_work(work); 2943 clear_work_data(work); 2944 2945 /* 2946 * Paired with prepare_to_wait() above so that either 2947 * waitqueue_active() is visible here or !work_is_canceling() is 2948 * visible there. 2949 */ 2950 smp_mb(); 2951 if (waitqueue_active(&cancel_waitq)) 2952 __wake_up(&cancel_waitq, TASK_NORMAL, 1, work); 2953 2954 return ret; 2955 } 2956 2957 /** 2958 * cancel_work_sync - cancel a work and wait for it to finish 2959 * @work: the work to cancel 2960 * 2961 * Cancel @work and wait for its execution to finish. This function 2962 * can be used even if the work re-queues itself or migrates to 2963 * another workqueue. On return from this function, @work is 2964 * guaranteed to be not pending or executing on any CPU. 2965 * 2966 * cancel_work_sync(&delayed_work->work) must not be used for 2967 * delayed_work's. Use cancel_delayed_work_sync() instead. 2968 * 2969 * The caller must ensure that the workqueue on which @work was last 2970 * queued can't be destroyed before this function returns. 2971 * 2972 * Return: 2973 * %true if @work was pending, %false otherwise. 2974 */ 2975 bool cancel_work_sync(struct work_struct *work) 2976 { 2977 return __cancel_work_timer(work, false); 2978 } 2979 EXPORT_SYMBOL_GPL(cancel_work_sync); 2980 2981 /** 2982 * flush_delayed_work - wait for a dwork to finish executing the last queueing 2983 * @dwork: the delayed work to flush 2984 * 2985 * Delayed timer is cancelled and the pending work is queued for 2986 * immediate execution. Like flush_work(), this function only 2987 * considers the last queueing instance of @dwork. 2988 * 2989 * Return: 2990 * %true if flush_work() waited for the work to finish execution, 2991 * %false if it was already idle. 2992 */ 2993 bool flush_delayed_work(struct delayed_work *dwork) 2994 { 2995 local_irq_disable(); 2996 if (del_timer_sync(&dwork->timer)) 2997 __queue_work(dwork->cpu, dwork->wq, &dwork->work); 2998 local_irq_enable(); 2999 return flush_work(&dwork->work); 3000 } 3001 EXPORT_SYMBOL(flush_delayed_work); 3002 3003 /** 3004 * cancel_delayed_work - cancel a delayed work 3005 * @dwork: delayed_work to cancel 3006 * 3007 * Kill off a pending delayed_work. 3008 * 3009 * Return: %true if @dwork was pending and canceled; %false if it wasn't 3010 * pending. 3011 * 3012 * Note: 3013 * The work callback function may still be running on return, unless 3014 * it returns %true and the work doesn't re-arm itself. Explicitly flush or 3015 * use cancel_delayed_work_sync() to wait on it. 3016 * 3017 * This function is safe to call from any context including IRQ handler. 3018 */ 3019 bool cancel_delayed_work(struct delayed_work *dwork) 3020 { 3021 unsigned long flags; 3022 int ret; 3023 3024 do { 3025 ret = try_to_grab_pending(&dwork->work, true, &flags); 3026 } while (unlikely(ret == -EAGAIN)); 3027 3028 if (unlikely(ret < 0)) 3029 return false; 3030 3031 set_work_pool_and_clear_pending(&dwork->work, 3032 get_work_pool_id(&dwork->work)); 3033 local_irq_restore(flags); 3034 return ret; 3035 } 3036 EXPORT_SYMBOL(cancel_delayed_work); 3037 3038 /** 3039 * cancel_delayed_work_sync - cancel a delayed work and wait for it to finish 3040 * @dwork: the delayed work cancel 3041 * 3042 * This is cancel_work_sync() for delayed works. 3043 * 3044 * Return: 3045 * %true if @dwork was pending, %false otherwise. 3046 */ 3047 bool cancel_delayed_work_sync(struct delayed_work *dwork) 3048 { 3049 return __cancel_work_timer(&dwork->work, true); 3050 } 3051 EXPORT_SYMBOL(cancel_delayed_work_sync); 3052 3053 /** 3054 * schedule_on_each_cpu - execute a function synchronously on each online CPU 3055 * @func: the function to call 3056 * 3057 * schedule_on_each_cpu() executes @func on each online CPU using the 3058 * system workqueue and blocks until all CPUs have completed. 3059 * schedule_on_each_cpu() is very slow. 3060 * 3061 * Return: 3062 * 0 on success, -errno on failure. 3063 */ 3064 int schedule_on_each_cpu(work_func_t func) 3065 { 3066 int cpu; 3067 struct work_struct __percpu *works; 3068 3069 works = alloc_percpu(struct work_struct); 3070 if (!works) 3071 return -ENOMEM; 3072 3073 get_online_cpus(); 3074 3075 for_each_online_cpu(cpu) { 3076 struct work_struct *work = per_cpu_ptr(works, cpu); 3077 3078 INIT_WORK(work, func); 3079 schedule_work_on(cpu, work); 3080 } 3081 3082 for_each_online_cpu(cpu) 3083 flush_work(per_cpu_ptr(works, cpu)); 3084 3085 put_online_cpus(); 3086 free_percpu(works); 3087 return 0; 3088 } 3089 3090 /** 3091 * execute_in_process_context - reliably execute the routine with user context 3092 * @fn: the function to execute 3093 * @ew: guaranteed storage for the execute work structure (must 3094 * be available when the work executes) 3095 * 3096 * Executes the function immediately if process context is available, 3097 * otherwise schedules the function for delayed execution. 3098 * 3099 * Return: 0 - function was executed 3100 * 1 - function was scheduled for execution 3101 */ 3102 int execute_in_process_context(work_func_t fn, struct execute_work *ew) 3103 { 3104 if (!in_interrupt()) { 3105 fn(&ew->work); 3106 return 0; 3107 } 3108 3109 INIT_WORK(&ew->work, fn); 3110 schedule_work(&ew->work); 3111 3112 return 1; 3113 } 3114 EXPORT_SYMBOL_GPL(execute_in_process_context); 3115 3116 /** 3117 * free_workqueue_attrs - free a workqueue_attrs 3118 * @attrs: workqueue_attrs to free 3119 * 3120 * Undo alloc_workqueue_attrs(). 3121 */ 3122 void free_workqueue_attrs(struct workqueue_attrs *attrs) 3123 { 3124 if (attrs) { 3125 free_cpumask_var(attrs->cpumask); 3126 kfree(attrs); 3127 } 3128 } 3129 3130 /** 3131 * alloc_workqueue_attrs - allocate a workqueue_attrs 3132 * @gfp_mask: allocation mask to use 3133 * 3134 * Allocate a new workqueue_attrs, initialize with default settings and 3135 * return it. 3136 * 3137 * Return: The allocated new workqueue_attr on success. %NULL on failure. 3138 */ 3139 struct workqueue_attrs *alloc_workqueue_attrs(gfp_t gfp_mask) 3140 { 3141 struct workqueue_attrs *attrs; 3142 3143 attrs = kzalloc(sizeof(*attrs), gfp_mask); 3144 if (!attrs) 3145 goto fail; 3146 if (!alloc_cpumask_var(&attrs->cpumask, gfp_mask)) 3147 goto fail; 3148 3149 cpumask_copy(attrs->cpumask, cpu_possible_mask); 3150 return attrs; 3151 fail: 3152 free_workqueue_attrs(attrs); 3153 return NULL; 3154 } 3155 3156 static void copy_workqueue_attrs(struct workqueue_attrs *to, 3157 const struct workqueue_attrs *from) 3158 { 3159 to->nice = from->nice; 3160 cpumask_copy(to->cpumask, from->cpumask); 3161 /* 3162 * Unlike hash and equality test, this function doesn't ignore 3163 * ->no_numa as it is used for both pool and wq attrs. Instead, 3164 * get_unbound_pool() explicitly clears ->no_numa after copying. 3165 */ 3166 to->no_numa = from->no_numa; 3167 } 3168 3169 /* hash value of the content of @attr */ 3170 static u32 wqattrs_hash(const struct workqueue_attrs *attrs) 3171 { 3172 u32 hash = 0; 3173 3174 hash = jhash_1word(attrs->nice, hash); 3175 hash = jhash(cpumask_bits(attrs->cpumask), 3176 BITS_TO_LONGS(nr_cpumask_bits) * sizeof(long), hash); 3177 return hash; 3178 } 3179 3180 /* content equality test */ 3181 static bool wqattrs_equal(const struct workqueue_attrs *a, 3182 const struct workqueue_attrs *b) 3183 { 3184 if (a->nice != b->nice) 3185 return false; 3186 if (!cpumask_equal(a->cpumask, b->cpumask)) 3187 return false; 3188 return true; 3189 } 3190 3191 /** 3192 * init_worker_pool - initialize a newly zalloc'd worker_pool 3193 * @pool: worker_pool to initialize 3194 * 3195 * Initialize a newly zalloc'd @pool. It also allocates @pool->attrs. 3196 * 3197 * Return: 0 on success, -errno on failure. Even on failure, all fields 3198 * inside @pool proper are initialized and put_unbound_pool() can be called 3199 * on @pool safely to release it. 3200 */ 3201 static int init_worker_pool(struct worker_pool *pool) 3202 { 3203 spin_lock_init(&pool->lock); 3204 pool->id = -1; 3205 pool->cpu = -1; 3206 pool->node = NUMA_NO_NODE; 3207 pool->flags |= POOL_DISASSOCIATED; 3208 pool->watchdog_ts = jiffies; 3209 INIT_LIST_HEAD(&pool->worklist); 3210 INIT_LIST_HEAD(&pool->idle_list); 3211 hash_init(pool->busy_hash); 3212 3213 init_timer_deferrable(&pool->idle_timer); 3214 pool->idle_timer.function = idle_worker_timeout; 3215 pool->idle_timer.data = (unsigned long)pool; 3216 3217 setup_timer(&pool->mayday_timer, pool_mayday_timeout, 3218 (unsigned long)pool); 3219 3220 mutex_init(&pool->manager_arb); 3221 mutex_init(&pool->attach_mutex); 3222 INIT_LIST_HEAD(&pool->workers); 3223 3224 ida_init(&pool->worker_ida); 3225 INIT_HLIST_NODE(&pool->hash_node); 3226 pool->refcnt = 1; 3227 3228 /* shouldn't fail above this point */ 3229 pool->attrs = alloc_workqueue_attrs(GFP_KERNEL); 3230 if (!pool->attrs) 3231 return -ENOMEM; 3232 return 0; 3233 } 3234 3235 static void rcu_free_wq(struct rcu_head *rcu) 3236 { 3237 struct workqueue_struct *wq = 3238 container_of(rcu, struct workqueue_struct, rcu); 3239 3240 if (!(wq->flags & WQ_UNBOUND)) 3241 free_percpu(wq->cpu_pwqs); 3242 else 3243 free_workqueue_attrs(wq->unbound_attrs); 3244 3245 kfree(wq->rescuer); 3246 kfree(wq); 3247 } 3248 3249 static void rcu_free_pool(struct rcu_head *rcu) 3250 { 3251 struct worker_pool *pool = container_of(rcu, struct worker_pool, rcu); 3252 3253 ida_destroy(&pool->worker_ida); 3254 free_workqueue_attrs(pool->attrs); 3255 kfree(pool); 3256 } 3257 3258 /** 3259 * put_unbound_pool - put a worker_pool 3260 * @pool: worker_pool to put 3261 * 3262 * Put @pool. If its refcnt reaches zero, it gets destroyed in sched-RCU 3263 * safe manner. get_unbound_pool() calls this function on its failure path 3264 * and this function should be able to release pools which went through, 3265 * successfully or not, init_worker_pool(). 3266 * 3267 * Should be called with wq_pool_mutex held. 3268 */ 3269 static void put_unbound_pool(struct worker_pool *pool) 3270 { 3271 DECLARE_COMPLETION_ONSTACK(detach_completion); 3272 struct worker *worker; 3273 3274 lockdep_assert_held(&wq_pool_mutex); 3275 3276 if (--pool->refcnt) 3277 return; 3278 3279 /* sanity checks */ 3280 if (WARN_ON(!(pool->cpu < 0)) || 3281 WARN_ON(!list_empty(&pool->worklist))) 3282 return; 3283 3284 /* release id and unhash */ 3285 if (pool->id >= 0) 3286 idr_remove(&worker_pool_idr, pool->id); 3287 hash_del(&pool->hash_node); 3288 3289 /* 3290 * Become the manager and destroy all workers. Grabbing 3291 * manager_arb prevents @pool's workers from blocking on 3292 * attach_mutex. 3293 */ 3294 mutex_lock(&pool->manager_arb); 3295 3296 spin_lock_irq(&pool->lock); 3297 while ((worker = first_idle_worker(pool))) 3298 destroy_worker(worker); 3299 WARN_ON(pool->nr_workers || pool->nr_idle); 3300 spin_unlock_irq(&pool->lock); 3301 3302 mutex_lock(&pool->attach_mutex); 3303 if (!list_empty(&pool->workers)) 3304 pool->detach_completion = &detach_completion; 3305 mutex_unlock(&pool->attach_mutex); 3306 3307 if (pool->detach_completion) 3308 wait_for_completion(pool->detach_completion); 3309 3310 mutex_unlock(&pool->manager_arb); 3311 3312 /* shut down the timers */ 3313 del_timer_sync(&pool->idle_timer); 3314 del_timer_sync(&pool->mayday_timer); 3315 3316 /* sched-RCU protected to allow dereferences from get_work_pool() */ 3317 call_rcu_sched(&pool->rcu, rcu_free_pool); 3318 } 3319 3320 /** 3321 * get_unbound_pool - get a worker_pool with the specified attributes 3322 * @attrs: the attributes of the worker_pool to get 3323 * 3324 * Obtain a worker_pool which has the same attributes as @attrs, bump the 3325 * reference count and return it. If there already is a matching 3326 * worker_pool, it will be used; otherwise, this function attempts to 3327 * create a new one. 3328 * 3329 * Should be called with wq_pool_mutex held. 3330 * 3331 * Return: On success, a worker_pool with the same attributes as @attrs. 3332 * On failure, %NULL. 3333 */ 3334 static struct worker_pool *get_unbound_pool(const struct workqueue_attrs *attrs) 3335 { 3336 u32 hash = wqattrs_hash(attrs); 3337 struct worker_pool *pool; 3338 int node; 3339 int target_node = NUMA_NO_NODE; 3340 3341 lockdep_assert_held(&wq_pool_mutex); 3342 3343 /* do we already have a matching pool? */ 3344 hash_for_each_possible(unbound_pool_hash, pool, hash_node, hash) { 3345 if (wqattrs_equal(pool->attrs, attrs)) { 3346 pool->refcnt++; 3347 return pool; 3348 } 3349 } 3350 3351 /* if cpumask is contained inside a NUMA node, we belong to that node */ 3352 if (wq_numa_enabled) { 3353 for_each_node(node) { 3354 if (cpumask_subset(attrs->cpumask, 3355 wq_numa_possible_cpumask[node])) { 3356 target_node = node; 3357 break; 3358 } 3359 } 3360 } 3361 3362 /* nope, create a new one */ 3363 pool = kzalloc_node(sizeof(*pool), GFP_KERNEL, target_node); 3364 if (!pool || init_worker_pool(pool) < 0) 3365 goto fail; 3366 3367 lockdep_set_subclass(&pool->lock, 1); /* see put_pwq() */ 3368 copy_workqueue_attrs(pool->attrs, attrs); 3369 pool->node = target_node; 3370 3371 /* 3372 * no_numa isn't a worker_pool attribute, always clear it. See 3373 * 'struct workqueue_attrs' comments for detail. 3374 */ 3375 pool->attrs->no_numa = false; 3376 3377 if (worker_pool_assign_id(pool) < 0) 3378 goto fail; 3379 3380 /* create and start the initial worker */ 3381 if (!create_worker(pool)) 3382 goto fail; 3383 3384 /* install */ 3385 hash_add(unbound_pool_hash, &pool->hash_node, hash); 3386 3387 return pool; 3388 fail: 3389 if (pool) 3390 put_unbound_pool(pool); 3391 return NULL; 3392 } 3393 3394 static void rcu_free_pwq(struct rcu_head *rcu) 3395 { 3396 kmem_cache_free(pwq_cache, 3397 container_of(rcu, struct pool_workqueue, rcu)); 3398 } 3399 3400 /* 3401 * Scheduled on system_wq by put_pwq() when an unbound pwq hits zero refcnt 3402 * and needs to be destroyed. 3403 */ 3404 static void pwq_unbound_release_workfn(struct work_struct *work) 3405 { 3406 struct pool_workqueue *pwq = container_of(work, struct pool_workqueue, 3407 unbound_release_work); 3408 struct workqueue_struct *wq = pwq->wq; 3409 struct worker_pool *pool = pwq->pool; 3410 bool is_last; 3411 3412 if (WARN_ON_ONCE(!(wq->flags & WQ_UNBOUND))) 3413 return; 3414 3415 mutex_lock(&wq->mutex); 3416 list_del_rcu(&pwq->pwqs_node); 3417 is_last = list_empty(&wq->pwqs); 3418 mutex_unlock(&wq->mutex); 3419 3420 mutex_lock(&wq_pool_mutex); 3421 put_unbound_pool(pool); 3422 mutex_unlock(&wq_pool_mutex); 3423 3424 call_rcu_sched(&pwq->rcu, rcu_free_pwq); 3425 3426 /* 3427 * If we're the last pwq going away, @wq is already dead and no one 3428 * is gonna access it anymore. Schedule RCU free. 3429 */ 3430 if (is_last) 3431 call_rcu_sched(&wq->rcu, rcu_free_wq); 3432 } 3433 3434 /** 3435 * pwq_adjust_max_active - update a pwq's max_active to the current setting 3436 * @pwq: target pool_workqueue 3437 * 3438 * If @pwq isn't freezing, set @pwq->max_active to the associated 3439 * workqueue's saved_max_active and activate delayed work items 3440 * accordingly. If @pwq is freezing, clear @pwq->max_active to zero. 3441 */ 3442 static void pwq_adjust_max_active(struct pool_workqueue *pwq) 3443 { 3444 struct workqueue_struct *wq = pwq->wq; 3445 bool freezable = wq->flags & WQ_FREEZABLE; 3446 3447 /* for @wq->saved_max_active */ 3448 lockdep_assert_held(&wq->mutex); 3449 3450 /* fast exit for non-freezable wqs */ 3451 if (!freezable && pwq->max_active == wq->saved_max_active) 3452 return; 3453 3454 spin_lock_irq(&pwq->pool->lock); 3455 3456 /* 3457 * During [un]freezing, the caller is responsible for ensuring that 3458 * this function is called at least once after @workqueue_freezing 3459 * is updated and visible. 3460 */ 3461 if (!freezable || !workqueue_freezing) { 3462 pwq->max_active = wq->saved_max_active; 3463 3464 while (!list_empty(&pwq->delayed_works) && 3465 pwq->nr_active < pwq->max_active) 3466 pwq_activate_first_delayed(pwq); 3467 3468 /* 3469 * Need to kick a worker after thawed or an unbound wq's 3470 * max_active is bumped. It's a slow path. Do it always. 3471 */ 3472 wake_up_worker(pwq->pool); 3473 } else { 3474 pwq->max_active = 0; 3475 } 3476 3477 spin_unlock_irq(&pwq->pool->lock); 3478 } 3479 3480 /* initialize newly alloced @pwq which is associated with @wq and @pool */ 3481 static void init_pwq(struct pool_workqueue *pwq, struct workqueue_struct *wq, 3482 struct worker_pool *pool) 3483 { 3484 BUG_ON((unsigned long)pwq & WORK_STRUCT_FLAG_MASK); 3485 3486 memset(pwq, 0, sizeof(*pwq)); 3487 3488 pwq->pool = pool; 3489 pwq->wq = wq; 3490 pwq->flush_color = -1; 3491 pwq->refcnt = 1; 3492 INIT_LIST_HEAD(&pwq->delayed_works); 3493 INIT_LIST_HEAD(&pwq->pwqs_node); 3494 INIT_LIST_HEAD(&pwq->mayday_node); 3495 INIT_WORK(&pwq->unbound_release_work, pwq_unbound_release_workfn); 3496 } 3497 3498 /* sync @pwq with the current state of its associated wq and link it */ 3499 static void link_pwq(struct pool_workqueue *pwq) 3500 { 3501 struct workqueue_struct *wq = pwq->wq; 3502 3503 lockdep_assert_held(&wq->mutex); 3504 3505 /* may be called multiple times, ignore if already linked */ 3506 if (!list_empty(&pwq->pwqs_node)) 3507 return; 3508 3509 /* set the matching work_color */ 3510 pwq->work_color = wq->work_color; 3511 3512 /* sync max_active to the current setting */ 3513 pwq_adjust_max_active(pwq); 3514 3515 /* link in @pwq */ 3516 list_add_rcu(&pwq->pwqs_node, &wq->pwqs); 3517 } 3518 3519 /* obtain a pool matching @attr and create a pwq associating the pool and @wq */ 3520 static struct pool_workqueue *alloc_unbound_pwq(struct workqueue_struct *wq, 3521 const struct workqueue_attrs *attrs) 3522 { 3523 struct worker_pool *pool; 3524 struct pool_workqueue *pwq; 3525 3526 lockdep_assert_held(&wq_pool_mutex); 3527 3528 pool = get_unbound_pool(attrs); 3529 if (!pool) 3530 return NULL; 3531 3532 pwq = kmem_cache_alloc_node(pwq_cache, GFP_KERNEL, pool->node); 3533 if (!pwq) { 3534 put_unbound_pool(pool); 3535 return NULL; 3536 } 3537 3538 init_pwq(pwq, wq, pool); 3539 return pwq; 3540 } 3541 3542 /** 3543 * wq_calc_node_cpumask - calculate a wq_attrs' cpumask for the specified node 3544 * @attrs: the wq_attrs of the default pwq of the target workqueue 3545 * @node: the target NUMA node 3546 * @cpu_going_down: if >= 0, the CPU to consider as offline 3547 * @cpumask: outarg, the resulting cpumask 3548 * 3549 * Calculate the cpumask a workqueue with @attrs should use on @node. If 3550 * @cpu_going_down is >= 0, that cpu is considered offline during 3551 * calculation. The result is stored in @cpumask. 3552 * 3553 * If NUMA affinity is not enabled, @attrs->cpumask is always used. If 3554 * enabled and @node has online CPUs requested by @attrs, the returned 3555 * cpumask is the intersection of the possible CPUs of @node and 3556 * @attrs->cpumask. 3557 * 3558 * The caller is responsible for ensuring that the cpumask of @node stays 3559 * stable. 3560 * 3561 * Return: %true if the resulting @cpumask is different from @attrs->cpumask, 3562 * %false if equal. 3563 */ 3564 static bool wq_calc_node_cpumask(const struct workqueue_attrs *attrs, int node, 3565 int cpu_going_down, cpumask_t *cpumask) 3566 { 3567 if (!wq_numa_enabled || attrs->no_numa) 3568 goto use_dfl; 3569 3570 /* does @node have any online CPUs @attrs wants? */ 3571 cpumask_and(cpumask, cpumask_of_node(node), attrs->cpumask); 3572 if (cpu_going_down >= 0) 3573 cpumask_clear_cpu(cpu_going_down, cpumask); 3574 3575 if (cpumask_empty(cpumask)) 3576 goto use_dfl; 3577 3578 /* yeap, return possible CPUs in @node that @attrs wants */ 3579 cpumask_and(cpumask, attrs->cpumask, wq_numa_possible_cpumask[node]); 3580 return !cpumask_equal(cpumask, attrs->cpumask); 3581 3582 use_dfl: 3583 cpumask_copy(cpumask, attrs->cpumask); 3584 return false; 3585 } 3586 3587 /* install @pwq into @wq's numa_pwq_tbl[] for @node and return the old pwq */ 3588 static struct pool_workqueue *numa_pwq_tbl_install(struct workqueue_struct *wq, 3589 int node, 3590 struct pool_workqueue *pwq) 3591 { 3592 struct pool_workqueue *old_pwq; 3593 3594 lockdep_assert_held(&wq_pool_mutex); 3595 lockdep_assert_held(&wq->mutex); 3596 3597 /* link_pwq() can handle duplicate calls */ 3598 link_pwq(pwq); 3599 3600 old_pwq = rcu_access_pointer(wq->numa_pwq_tbl[node]); 3601 rcu_assign_pointer(wq->numa_pwq_tbl[node], pwq); 3602 return old_pwq; 3603 } 3604 3605 /* context to store the prepared attrs & pwqs before applying */ 3606 struct apply_wqattrs_ctx { 3607 struct workqueue_struct *wq; /* target workqueue */ 3608 struct workqueue_attrs *attrs; /* attrs to apply */ 3609 struct list_head list; /* queued for batching commit */ 3610 struct pool_workqueue *dfl_pwq; 3611 struct pool_workqueue *pwq_tbl[]; 3612 }; 3613 3614 /* free the resources after success or abort */ 3615 static void apply_wqattrs_cleanup(struct apply_wqattrs_ctx *ctx) 3616 { 3617 if (ctx) { 3618 int node; 3619 3620 for_each_node(node) 3621 put_pwq_unlocked(ctx->pwq_tbl[node]); 3622 put_pwq_unlocked(ctx->dfl_pwq); 3623 3624 free_workqueue_attrs(ctx->attrs); 3625 3626 kfree(ctx); 3627 } 3628 } 3629 3630 /* allocate the attrs and pwqs for later installation */ 3631 static struct apply_wqattrs_ctx * 3632 apply_wqattrs_prepare(struct workqueue_struct *wq, 3633 const struct workqueue_attrs *attrs) 3634 { 3635 struct apply_wqattrs_ctx *ctx; 3636 struct workqueue_attrs *new_attrs, *tmp_attrs; 3637 int node; 3638 3639 lockdep_assert_held(&wq_pool_mutex); 3640 3641 ctx = kzalloc(sizeof(*ctx) + nr_node_ids * sizeof(ctx->pwq_tbl[0]), 3642 GFP_KERNEL); 3643 3644 new_attrs = alloc_workqueue_attrs(GFP_KERNEL); 3645 tmp_attrs = alloc_workqueue_attrs(GFP_KERNEL); 3646 if (!ctx || !new_attrs || !tmp_attrs) 3647 goto out_free; 3648 3649 /* 3650 * Calculate the attrs of the default pwq. 3651 * If the user configured cpumask doesn't overlap with the 3652 * wq_unbound_cpumask, we fallback to the wq_unbound_cpumask. 3653 */ 3654 copy_workqueue_attrs(new_attrs, attrs); 3655 cpumask_and(new_attrs->cpumask, new_attrs->cpumask, wq_unbound_cpumask); 3656 if (unlikely(cpumask_empty(new_attrs->cpumask))) 3657 cpumask_copy(new_attrs->cpumask, wq_unbound_cpumask); 3658 3659 /* 3660 * We may create multiple pwqs with differing cpumasks. Make a 3661 * copy of @new_attrs which will be modified and used to obtain 3662 * pools. 3663 */ 3664 copy_workqueue_attrs(tmp_attrs, new_attrs); 3665 3666 /* 3667 * If something goes wrong during CPU up/down, we'll fall back to 3668 * the default pwq covering whole @attrs->cpumask. Always create 3669 * it even if we don't use it immediately. 3670 */ 3671 ctx->dfl_pwq = alloc_unbound_pwq(wq, new_attrs); 3672 if (!ctx->dfl_pwq) 3673 goto out_free; 3674 3675 for_each_node(node) { 3676 if (wq_calc_node_cpumask(new_attrs, node, -1, tmp_attrs->cpumask)) { 3677 ctx->pwq_tbl[node] = alloc_unbound_pwq(wq, tmp_attrs); 3678 if (!ctx->pwq_tbl[node]) 3679 goto out_free; 3680 } else { 3681 ctx->dfl_pwq->refcnt++; 3682 ctx->pwq_tbl[node] = ctx->dfl_pwq; 3683 } 3684 } 3685 3686 /* save the user configured attrs and sanitize it. */ 3687 copy_workqueue_attrs(new_attrs, attrs); 3688 cpumask_and(new_attrs->cpumask, new_attrs->cpumask, cpu_possible_mask); 3689 ctx->attrs = new_attrs; 3690 3691 ctx->wq = wq; 3692 free_workqueue_attrs(tmp_attrs); 3693 return ctx; 3694 3695 out_free: 3696 free_workqueue_attrs(tmp_attrs); 3697 free_workqueue_attrs(new_attrs); 3698 apply_wqattrs_cleanup(ctx); 3699 return NULL; 3700 } 3701 3702 /* set attrs and install prepared pwqs, @ctx points to old pwqs on return */ 3703 static void apply_wqattrs_commit(struct apply_wqattrs_ctx *ctx) 3704 { 3705 int node; 3706 3707 /* all pwqs have been created successfully, let's install'em */ 3708 mutex_lock(&ctx->wq->mutex); 3709 3710 copy_workqueue_attrs(ctx->wq->unbound_attrs, ctx->attrs); 3711 3712 /* save the previous pwq and install the new one */ 3713 for_each_node(node) 3714 ctx->pwq_tbl[node] = numa_pwq_tbl_install(ctx->wq, node, 3715 ctx->pwq_tbl[node]); 3716 3717 /* @dfl_pwq might not have been used, ensure it's linked */ 3718 link_pwq(ctx->dfl_pwq); 3719 swap(ctx->wq->dfl_pwq, ctx->dfl_pwq); 3720 3721 mutex_unlock(&ctx->wq->mutex); 3722 } 3723 3724 static void apply_wqattrs_lock(void) 3725 { 3726 /* CPUs should stay stable across pwq creations and installations */ 3727 get_online_cpus(); 3728 mutex_lock(&wq_pool_mutex); 3729 } 3730 3731 static void apply_wqattrs_unlock(void) 3732 { 3733 mutex_unlock(&wq_pool_mutex); 3734 put_online_cpus(); 3735 } 3736 3737 static int apply_workqueue_attrs_locked(struct workqueue_struct *wq, 3738 const struct workqueue_attrs *attrs) 3739 { 3740 struct apply_wqattrs_ctx *ctx; 3741 3742 /* only unbound workqueues can change attributes */ 3743 if (WARN_ON(!(wq->flags & WQ_UNBOUND))) 3744 return -EINVAL; 3745 3746 /* creating multiple pwqs breaks ordering guarantee */ 3747 if (WARN_ON((wq->flags & __WQ_ORDERED) && !list_empty(&wq->pwqs))) 3748 return -EINVAL; 3749 3750 ctx = apply_wqattrs_prepare(wq, attrs); 3751 if (!ctx) 3752 return -ENOMEM; 3753 3754 /* the ctx has been prepared successfully, let's commit it */ 3755 apply_wqattrs_commit(ctx); 3756 apply_wqattrs_cleanup(ctx); 3757 3758 return 0; 3759 } 3760 3761 /** 3762 * apply_workqueue_attrs - apply new workqueue_attrs to an unbound workqueue 3763 * @wq: the target workqueue 3764 * @attrs: the workqueue_attrs to apply, allocated with alloc_workqueue_attrs() 3765 * 3766 * Apply @attrs to an unbound workqueue @wq. Unless disabled, on NUMA 3767 * machines, this function maps a separate pwq to each NUMA node with 3768 * possibles CPUs in @attrs->cpumask so that work items are affine to the 3769 * NUMA node it was issued on. Older pwqs are released as in-flight work 3770 * items finish. Note that a work item which repeatedly requeues itself 3771 * back-to-back will stay on its current pwq. 3772 * 3773 * Performs GFP_KERNEL allocations. 3774 * 3775 * Return: 0 on success and -errno on failure. 3776 */ 3777 int apply_workqueue_attrs(struct workqueue_struct *wq, 3778 const struct workqueue_attrs *attrs) 3779 { 3780 int ret; 3781 3782 apply_wqattrs_lock(); 3783 ret = apply_workqueue_attrs_locked(wq, attrs); 3784 apply_wqattrs_unlock(); 3785 3786 return ret; 3787 } 3788 3789 /** 3790 * wq_update_unbound_numa - update NUMA affinity of a wq for CPU hot[un]plug 3791 * @wq: the target workqueue 3792 * @cpu: the CPU coming up or going down 3793 * @online: whether @cpu is coming up or going down 3794 * 3795 * This function is to be called from %CPU_DOWN_PREPARE, %CPU_ONLINE and 3796 * %CPU_DOWN_FAILED. @cpu is being hot[un]plugged, update NUMA affinity of 3797 * @wq accordingly. 3798 * 3799 * If NUMA affinity can't be adjusted due to memory allocation failure, it 3800 * falls back to @wq->dfl_pwq which may not be optimal but is always 3801 * correct. 3802 * 3803 * Note that when the last allowed CPU of a NUMA node goes offline for a 3804 * workqueue with a cpumask spanning multiple nodes, the workers which were 3805 * already executing the work items for the workqueue will lose their CPU 3806 * affinity and may execute on any CPU. This is similar to how per-cpu 3807 * workqueues behave on CPU_DOWN. If a workqueue user wants strict 3808 * affinity, it's the user's responsibility to flush the work item from 3809 * CPU_DOWN_PREPARE. 3810 */ 3811 static void wq_update_unbound_numa(struct workqueue_struct *wq, int cpu, 3812 bool online) 3813 { 3814 int node = cpu_to_node(cpu); 3815 int cpu_off = online ? -1 : cpu; 3816 struct pool_workqueue *old_pwq = NULL, *pwq; 3817 struct workqueue_attrs *target_attrs; 3818 cpumask_t *cpumask; 3819 3820 lockdep_assert_held(&wq_pool_mutex); 3821 3822 if (!wq_numa_enabled || !(wq->flags & WQ_UNBOUND) || 3823 wq->unbound_attrs->no_numa) 3824 return; 3825 3826 /* 3827 * We don't wanna alloc/free wq_attrs for each wq for each CPU. 3828 * Let's use a preallocated one. The following buf is protected by 3829 * CPU hotplug exclusion. 3830 */ 3831 target_attrs = wq_update_unbound_numa_attrs_buf; 3832 cpumask = target_attrs->cpumask; 3833 3834 copy_workqueue_attrs(target_attrs, wq->unbound_attrs); 3835 pwq = unbound_pwq_by_node(wq, node); 3836 3837 /* 3838 * Let's determine what needs to be done. If the target cpumask is 3839 * different from the default pwq's, we need to compare it to @pwq's 3840 * and create a new one if they don't match. If the target cpumask 3841 * equals the default pwq's, the default pwq should be used. 3842 */ 3843 if (wq_calc_node_cpumask(wq->dfl_pwq->pool->attrs, node, cpu_off, cpumask)) { 3844 if (cpumask_equal(cpumask, pwq->pool->attrs->cpumask)) 3845 return; 3846 } else { 3847 goto use_dfl_pwq; 3848 } 3849 3850 /* create a new pwq */ 3851 pwq = alloc_unbound_pwq(wq, target_attrs); 3852 if (!pwq) { 3853 pr_warn("workqueue: allocation failed while updating NUMA affinity of \"%s\"\n", 3854 wq->name); 3855 goto use_dfl_pwq; 3856 } 3857 3858 /* Install the new pwq. */ 3859 mutex_lock(&wq->mutex); 3860 old_pwq = numa_pwq_tbl_install(wq, node, pwq); 3861 goto out_unlock; 3862 3863 use_dfl_pwq: 3864 mutex_lock(&wq->mutex); 3865 spin_lock_irq(&wq->dfl_pwq->pool->lock); 3866 get_pwq(wq->dfl_pwq); 3867 spin_unlock_irq(&wq->dfl_pwq->pool->lock); 3868 old_pwq = numa_pwq_tbl_install(wq, node, wq->dfl_pwq); 3869 out_unlock: 3870 mutex_unlock(&wq->mutex); 3871 put_pwq_unlocked(old_pwq); 3872 } 3873 3874 static int alloc_and_link_pwqs(struct workqueue_struct *wq) 3875 { 3876 bool highpri = wq->flags & WQ_HIGHPRI; 3877 int cpu, ret; 3878 3879 if (!(wq->flags & WQ_UNBOUND)) { 3880 wq->cpu_pwqs = alloc_percpu(struct pool_workqueue); 3881 if (!wq->cpu_pwqs) 3882 return -ENOMEM; 3883 3884 for_each_possible_cpu(cpu) { 3885 struct pool_workqueue *pwq = 3886 per_cpu_ptr(wq->cpu_pwqs, cpu); 3887 struct worker_pool *cpu_pools = 3888 per_cpu(cpu_worker_pools, cpu); 3889 3890 init_pwq(pwq, wq, &cpu_pools[highpri]); 3891 3892 mutex_lock(&wq->mutex); 3893 link_pwq(pwq); 3894 mutex_unlock(&wq->mutex); 3895 } 3896 return 0; 3897 } else if (wq->flags & __WQ_ORDERED) { 3898 ret = apply_workqueue_attrs(wq, ordered_wq_attrs[highpri]); 3899 /* there should only be single pwq for ordering guarantee */ 3900 WARN(!ret && (wq->pwqs.next != &wq->dfl_pwq->pwqs_node || 3901 wq->pwqs.prev != &wq->dfl_pwq->pwqs_node), 3902 "ordering guarantee broken for workqueue %s\n", wq->name); 3903 return ret; 3904 } else { 3905 return apply_workqueue_attrs(wq, unbound_std_wq_attrs[highpri]); 3906 } 3907 } 3908 3909 static int wq_clamp_max_active(int max_active, unsigned int flags, 3910 const char *name) 3911 { 3912 int lim = flags & WQ_UNBOUND ? WQ_UNBOUND_MAX_ACTIVE : WQ_MAX_ACTIVE; 3913 3914 if (max_active < 1 || max_active > lim) 3915 pr_warn("workqueue: max_active %d requested for %s is out of range, clamping between %d and %d\n", 3916 max_active, name, 1, lim); 3917 3918 return clamp_val(max_active, 1, lim); 3919 } 3920 3921 struct workqueue_struct *__alloc_workqueue_key(const char *fmt, 3922 unsigned int flags, 3923 int max_active, 3924 struct lock_class_key *key, 3925 const char *lock_name, ...) 3926 { 3927 size_t tbl_size = 0; 3928 va_list args; 3929 struct workqueue_struct *wq; 3930 struct pool_workqueue *pwq; 3931 3932 /* see the comment above the definition of WQ_POWER_EFFICIENT */ 3933 if ((flags & WQ_POWER_EFFICIENT) && wq_power_efficient) 3934 flags |= WQ_UNBOUND; 3935 3936 /* allocate wq and format name */ 3937 if (flags & WQ_UNBOUND) 3938 tbl_size = nr_node_ids * sizeof(wq->numa_pwq_tbl[0]); 3939 3940 wq = kzalloc(sizeof(*wq) + tbl_size, GFP_KERNEL); 3941 if (!wq) 3942 return NULL; 3943 3944 if (flags & WQ_UNBOUND) { 3945 wq->unbound_attrs = alloc_workqueue_attrs(GFP_KERNEL); 3946 if (!wq->unbound_attrs) 3947 goto err_free_wq; 3948 } 3949 3950 va_start(args, lock_name); 3951 vsnprintf(wq->name, sizeof(wq->name), fmt, args); 3952 va_end(args); 3953 3954 max_active = max_active ?: WQ_DFL_ACTIVE; 3955 max_active = wq_clamp_max_active(max_active, flags, wq->name); 3956 3957 /* init wq */ 3958 wq->flags = flags; 3959 wq->saved_max_active = max_active; 3960 mutex_init(&wq->mutex); 3961 atomic_set(&wq->nr_pwqs_to_flush, 0); 3962 INIT_LIST_HEAD(&wq->pwqs); 3963 INIT_LIST_HEAD(&wq->flusher_queue); 3964 INIT_LIST_HEAD(&wq->flusher_overflow); 3965 INIT_LIST_HEAD(&wq->maydays); 3966 3967 lockdep_init_map(&wq->lockdep_map, lock_name, key, 0); 3968 INIT_LIST_HEAD(&wq->list); 3969 3970 if (alloc_and_link_pwqs(wq) < 0) 3971 goto err_free_wq; 3972 3973 /* 3974 * Workqueues which may be used during memory reclaim should 3975 * have a rescuer to guarantee forward progress. 3976 */ 3977 if (flags & WQ_MEM_RECLAIM) { 3978 struct worker *rescuer; 3979 3980 rescuer = alloc_worker(NUMA_NO_NODE); 3981 if (!rescuer) 3982 goto err_destroy; 3983 3984 rescuer->rescue_wq = wq; 3985 rescuer->task = kthread_create(rescuer_thread, rescuer, "%s", 3986 wq->name); 3987 if (IS_ERR(rescuer->task)) { 3988 kfree(rescuer); 3989 goto err_destroy; 3990 } 3991 3992 wq->rescuer = rescuer; 3993 kthread_bind_mask(rescuer->task, cpu_possible_mask); 3994 wake_up_process(rescuer->task); 3995 } 3996 3997 if ((wq->flags & WQ_SYSFS) && workqueue_sysfs_register(wq)) 3998 goto err_destroy; 3999 4000 /* 4001 * wq_pool_mutex protects global freeze state and workqueues list. 4002 * Grab it, adjust max_active and add the new @wq to workqueues 4003 * list. 4004 */ 4005 mutex_lock(&wq_pool_mutex); 4006 4007 mutex_lock(&wq->mutex); 4008 for_each_pwq(pwq, wq) 4009 pwq_adjust_max_active(pwq); 4010 mutex_unlock(&wq->mutex); 4011 4012 list_add_tail_rcu(&wq->list, &workqueues); 4013 4014 mutex_unlock(&wq_pool_mutex); 4015 4016 return wq; 4017 4018 err_free_wq: 4019 free_workqueue_attrs(wq->unbound_attrs); 4020 kfree(wq); 4021 return NULL; 4022 err_destroy: 4023 destroy_workqueue(wq); 4024 return NULL; 4025 } 4026 EXPORT_SYMBOL_GPL(__alloc_workqueue_key); 4027 4028 /** 4029 * destroy_workqueue - safely terminate a workqueue 4030 * @wq: target workqueue 4031 * 4032 * Safely destroy a workqueue. All work currently pending will be done first. 4033 */ 4034 void destroy_workqueue(struct workqueue_struct *wq) 4035 { 4036 struct pool_workqueue *pwq; 4037 int node; 4038 4039 /* drain it before proceeding with destruction */ 4040 drain_workqueue(wq); 4041 4042 /* sanity checks */ 4043 mutex_lock(&wq->mutex); 4044 for_each_pwq(pwq, wq) { 4045 int i; 4046 4047 for (i = 0; i < WORK_NR_COLORS; i++) { 4048 if (WARN_ON(pwq->nr_in_flight[i])) { 4049 mutex_unlock(&wq->mutex); 4050 return; 4051 } 4052 } 4053 4054 if (WARN_ON((pwq != wq->dfl_pwq) && (pwq->refcnt > 1)) || 4055 WARN_ON(pwq->nr_active) || 4056 WARN_ON(!list_empty(&pwq->delayed_works))) { 4057 mutex_unlock(&wq->mutex); 4058 return; 4059 } 4060 } 4061 mutex_unlock(&wq->mutex); 4062 4063 /* 4064 * wq list is used to freeze wq, remove from list after 4065 * flushing is complete in case freeze races us. 4066 */ 4067 mutex_lock(&wq_pool_mutex); 4068 list_del_rcu(&wq->list); 4069 mutex_unlock(&wq_pool_mutex); 4070 4071 workqueue_sysfs_unregister(wq); 4072 4073 if (wq->rescuer) 4074 kthread_stop(wq->rescuer->task); 4075 4076 if (!(wq->flags & WQ_UNBOUND)) { 4077 /* 4078 * The base ref is never dropped on per-cpu pwqs. Directly 4079 * schedule RCU free. 4080 */ 4081 call_rcu_sched(&wq->rcu, rcu_free_wq); 4082 } else { 4083 /* 4084 * We're the sole accessor of @wq at this point. Directly 4085 * access numa_pwq_tbl[] and dfl_pwq to put the base refs. 4086 * @wq will be freed when the last pwq is released. 4087 */ 4088 for_each_node(node) { 4089 pwq = rcu_access_pointer(wq->numa_pwq_tbl[node]); 4090 RCU_INIT_POINTER(wq->numa_pwq_tbl[node], NULL); 4091 put_pwq_unlocked(pwq); 4092 } 4093 4094 /* 4095 * Put dfl_pwq. @wq may be freed any time after dfl_pwq is 4096 * put. Don't access it afterwards. 4097 */ 4098 pwq = wq->dfl_pwq; 4099 wq->dfl_pwq = NULL; 4100 put_pwq_unlocked(pwq); 4101 } 4102 } 4103 EXPORT_SYMBOL_GPL(destroy_workqueue); 4104 4105 /** 4106 * workqueue_set_max_active - adjust max_active of a workqueue 4107 * @wq: target workqueue 4108 * @max_active: new max_active value. 4109 * 4110 * Set max_active of @wq to @max_active. 4111 * 4112 * CONTEXT: 4113 * Don't call from IRQ context. 4114 */ 4115 void workqueue_set_max_active(struct workqueue_struct *wq, int max_active) 4116 { 4117 struct pool_workqueue *pwq; 4118 4119 /* disallow meddling with max_active for ordered workqueues */ 4120 if (WARN_ON(wq->flags & __WQ_ORDERED)) 4121 return; 4122 4123 max_active = wq_clamp_max_active(max_active, wq->flags, wq->name); 4124 4125 mutex_lock(&wq->mutex); 4126 4127 wq->saved_max_active = max_active; 4128 4129 for_each_pwq(pwq, wq) 4130 pwq_adjust_max_active(pwq); 4131 4132 mutex_unlock(&wq->mutex); 4133 } 4134 EXPORT_SYMBOL_GPL(workqueue_set_max_active); 4135 4136 /** 4137 * current_is_workqueue_rescuer - is %current workqueue rescuer? 4138 * 4139 * Determine whether %current is a workqueue rescuer. Can be used from 4140 * work functions to determine whether it's being run off the rescuer task. 4141 * 4142 * Return: %true if %current is a workqueue rescuer. %false otherwise. 4143 */ 4144 bool current_is_workqueue_rescuer(void) 4145 { 4146 struct worker *worker = current_wq_worker(); 4147 4148 return worker && worker->rescue_wq; 4149 } 4150 4151 /** 4152 * workqueue_congested - test whether a workqueue is congested 4153 * @cpu: CPU in question 4154 * @wq: target workqueue 4155 * 4156 * Test whether @wq's cpu workqueue for @cpu is congested. There is 4157 * no synchronization around this function and the test result is 4158 * unreliable and only useful as advisory hints or for debugging. 4159 * 4160 * If @cpu is WORK_CPU_UNBOUND, the test is performed on the local CPU. 4161 * Note that both per-cpu and unbound workqueues may be associated with 4162 * multiple pool_workqueues which have separate congested states. A 4163 * workqueue being congested on one CPU doesn't mean the workqueue is also 4164 * contested on other CPUs / NUMA nodes. 4165 * 4166 * Return: 4167 * %true if congested, %false otherwise. 4168 */ 4169 bool workqueue_congested(int cpu, struct workqueue_struct *wq) 4170 { 4171 struct pool_workqueue *pwq; 4172 bool ret; 4173 4174 rcu_read_lock_sched(); 4175 4176 if (cpu == WORK_CPU_UNBOUND) 4177 cpu = smp_processor_id(); 4178 4179 if (!(wq->flags & WQ_UNBOUND)) 4180 pwq = per_cpu_ptr(wq->cpu_pwqs, cpu); 4181 else 4182 pwq = unbound_pwq_by_node(wq, cpu_to_node(cpu)); 4183 4184 ret = !list_empty(&pwq->delayed_works); 4185 rcu_read_unlock_sched(); 4186 4187 return ret; 4188 } 4189 EXPORT_SYMBOL_GPL(workqueue_congested); 4190 4191 /** 4192 * work_busy - test whether a work is currently pending or running 4193 * @work: the work to be tested 4194 * 4195 * Test whether @work is currently pending or running. There is no 4196 * synchronization around this function and the test result is 4197 * unreliable and only useful as advisory hints or for debugging. 4198 * 4199 * Return: 4200 * OR'd bitmask of WORK_BUSY_* bits. 4201 */ 4202 unsigned int work_busy(struct work_struct *work) 4203 { 4204 struct worker_pool *pool; 4205 unsigned long flags; 4206 unsigned int ret = 0; 4207 4208 if (work_pending(work)) 4209 ret |= WORK_BUSY_PENDING; 4210 4211 local_irq_save(flags); 4212 pool = get_work_pool(work); 4213 if (pool) { 4214 spin_lock(&pool->lock); 4215 if (find_worker_executing_work(pool, work)) 4216 ret |= WORK_BUSY_RUNNING; 4217 spin_unlock(&pool->lock); 4218 } 4219 local_irq_restore(flags); 4220 4221 return ret; 4222 } 4223 EXPORT_SYMBOL_GPL(work_busy); 4224 4225 /** 4226 * set_worker_desc - set description for the current work item 4227 * @fmt: printf-style format string 4228 * @...: arguments for the format string 4229 * 4230 * This function can be called by a running work function to describe what 4231 * the work item is about. If the worker task gets dumped, this 4232 * information will be printed out together to help debugging. The 4233 * description can be at most WORKER_DESC_LEN including the trailing '\0'. 4234 */ 4235 void set_worker_desc(const char *fmt, ...) 4236 { 4237 struct worker *worker = current_wq_worker(); 4238 va_list args; 4239 4240 if (worker) { 4241 va_start(args, fmt); 4242 vsnprintf(worker->desc, sizeof(worker->desc), fmt, args); 4243 va_end(args); 4244 worker->desc_valid = true; 4245 } 4246 } 4247 4248 /** 4249 * print_worker_info - print out worker information and description 4250 * @log_lvl: the log level to use when printing 4251 * @task: target task 4252 * 4253 * If @task is a worker and currently executing a work item, print out the 4254 * name of the workqueue being serviced and worker description set with 4255 * set_worker_desc() by the currently executing work item. 4256 * 4257 * This function can be safely called on any task as long as the 4258 * task_struct itself is accessible. While safe, this function isn't 4259 * synchronized and may print out mixups or garbages of limited length. 4260 */ 4261 void print_worker_info(const char *log_lvl, struct task_struct *task) 4262 { 4263 work_func_t *fn = NULL; 4264 char name[WQ_NAME_LEN] = { }; 4265 char desc[WORKER_DESC_LEN] = { }; 4266 struct pool_workqueue *pwq = NULL; 4267 struct workqueue_struct *wq = NULL; 4268 bool desc_valid = false; 4269 struct worker *worker; 4270 4271 if (!(task->flags & PF_WQ_WORKER)) 4272 return; 4273 4274 /* 4275 * This function is called without any synchronization and @task 4276 * could be in any state. Be careful with dereferences. 4277 */ 4278 worker = probe_kthread_data(task); 4279 4280 /* 4281 * Carefully copy the associated workqueue's workfn and name. Keep 4282 * the original last '\0' in case the original contains garbage. 4283 */ 4284 probe_kernel_read(&fn, &worker->current_func, sizeof(fn)); 4285 probe_kernel_read(&pwq, &worker->current_pwq, sizeof(pwq)); 4286 probe_kernel_read(&wq, &pwq->wq, sizeof(wq)); 4287 probe_kernel_read(name, wq->name, sizeof(name) - 1); 4288 4289 /* copy worker description */ 4290 probe_kernel_read(&desc_valid, &worker->desc_valid, sizeof(desc_valid)); 4291 if (desc_valid) 4292 probe_kernel_read(desc, worker->desc, sizeof(desc) - 1); 4293 4294 if (fn || name[0] || desc[0]) { 4295 printk("%sWorkqueue: %s %pf", log_lvl, name, fn); 4296 if (desc[0]) 4297 pr_cont(" (%s)", desc); 4298 pr_cont("\n"); 4299 } 4300 } 4301 4302 static void pr_cont_pool_info(struct worker_pool *pool) 4303 { 4304 pr_cont(" cpus=%*pbl", nr_cpumask_bits, pool->attrs->cpumask); 4305 if (pool->node != NUMA_NO_NODE) 4306 pr_cont(" node=%d", pool->node); 4307 pr_cont(" flags=0x%x nice=%d", pool->flags, pool->attrs->nice); 4308 } 4309 4310 static void pr_cont_work(bool comma, struct work_struct *work) 4311 { 4312 if (work->func == wq_barrier_func) { 4313 struct wq_barrier *barr; 4314 4315 barr = container_of(work, struct wq_barrier, work); 4316 4317 pr_cont("%s BAR(%d)", comma ? "," : "", 4318 task_pid_nr(barr->task)); 4319 } else { 4320 pr_cont("%s %pf", comma ? "," : "", work->func); 4321 } 4322 } 4323 4324 static void show_pwq(struct pool_workqueue *pwq) 4325 { 4326 struct worker_pool *pool = pwq->pool; 4327 struct work_struct *work; 4328 struct worker *worker; 4329 bool has_in_flight = false, has_pending = false; 4330 int bkt; 4331 4332 pr_info(" pwq %d:", pool->id); 4333 pr_cont_pool_info(pool); 4334 4335 pr_cont(" active=%d/%d%s\n", pwq->nr_active, pwq->max_active, 4336 !list_empty(&pwq->mayday_node) ? " MAYDAY" : ""); 4337 4338 hash_for_each(pool->busy_hash, bkt, worker, hentry) { 4339 if (worker->current_pwq == pwq) { 4340 has_in_flight = true; 4341 break; 4342 } 4343 } 4344 if (has_in_flight) { 4345 bool comma = false; 4346 4347 pr_info(" in-flight:"); 4348 hash_for_each(pool->busy_hash, bkt, worker, hentry) { 4349 if (worker->current_pwq != pwq) 4350 continue; 4351 4352 pr_cont("%s %d%s:%pf", comma ? "," : "", 4353 task_pid_nr(worker->task), 4354 worker == pwq->wq->rescuer ? "(RESCUER)" : "", 4355 worker->current_func); 4356 list_for_each_entry(work, &worker->scheduled, entry) 4357 pr_cont_work(false, work); 4358 comma = true; 4359 } 4360 pr_cont("\n"); 4361 } 4362 4363 list_for_each_entry(work, &pool->worklist, entry) { 4364 if (get_work_pwq(work) == pwq) { 4365 has_pending = true; 4366 break; 4367 } 4368 } 4369 if (has_pending) { 4370 bool comma = false; 4371 4372 pr_info(" pending:"); 4373 list_for_each_entry(work, &pool->worklist, entry) { 4374 if (get_work_pwq(work) != pwq) 4375 continue; 4376 4377 pr_cont_work(comma, work); 4378 comma = !(*work_data_bits(work) & WORK_STRUCT_LINKED); 4379 } 4380 pr_cont("\n"); 4381 } 4382 4383 if (!list_empty(&pwq->delayed_works)) { 4384 bool comma = false; 4385 4386 pr_info(" delayed:"); 4387 list_for_each_entry(work, &pwq->delayed_works, entry) { 4388 pr_cont_work(comma, work); 4389 comma = !(*work_data_bits(work) & WORK_STRUCT_LINKED); 4390 } 4391 pr_cont("\n"); 4392 } 4393 } 4394 4395 /** 4396 * show_workqueue_state - dump workqueue state 4397 * 4398 * Called from a sysrq handler and prints out all busy workqueues and 4399 * pools. 4400 */ 4401 void show_workqueue_state(void) 4402 { 4403 struct workqueue_struct *wq; 4404 struct worker_pool *pool; 4405 unsigned long flags; 4406 int pi; 4407 4408 rcu_read_lock_sched(); 4409 4410 pr_info("Showing busy workqueues and worker pools:\n"); 4411 4412 list_for_each_entry_rcu(wq, &workqueues, list) { 4413 struct pool_workqueue *pwq; 4414 bool idle = true; 4415 4416 for_each_pwq(pwq, wq) { 4417 if (pwq->nr_active || !list_empty(&pwq->delayed_works)) { 4418 idle = false; 4419 break; 4420 } 4421 } 4422 if (idle) 4423 continue; 4424 4425 pr_info("workqueue %s: flags=0x%x\n", wq->name, wq->flags); 4426 4427 for_each_pwq(pwq, wq) { 4428 spin_lock_irqsave(&pwq->pool->lock, flags); 4429 if (pwq->nr_active || !list_empty(&pwq->delayed_works)) 4430 show_pwq(pwq); 4431 spin_unlock_irqrestore(&pwq->pool->lock, flags); 4432 } 4433 } 4434 4435 for_each_pool(pool, pi) { 4436 struct worker *worker; 4437 bool first = true; 4438 4439 spin_lock_irqsave(&pool->lock, flags); 4440 if (pool->nr_workers == pool->nr_idle) 4441 goto next_pool; 4442 4443 pr_info("pool %d:", pool->id); 4444 pr_cont_pool_info(pool); 4445 pr_cont(" hung=%us workers=%d", 4446 jiffies_to_msecs(jiffies - pool->watchdog_ts) / 1000, 4447 pool->nr_workers); 4448 if (pool->manager) 4449 pr_cont(" manager: %d", 4450 task_pid_nr(pool->manager->task)); 4451 list_for_each_entry(worker, &pool->idle_list, entry) { 4452 pr_cont(" %s%d", first ? "idle: " : "", 4453 task_pid_nr(worker->task)); 4454 first = false; 4455 } 4456 pr_cont("\n"); 4457 next_pool: 4458 spin_unlock_irqrestore(&pool->lock, flags); 4459 } 4460 4461 rcu_read_unlock_sched(); 4462 } 4463 4464 /* 4465 * CPU hotplug. 4466 * 4467 * There are two challenges in supporting CPU hotplug. Firstly, there 4468 * are a lot of assumptions on strong associations among work, pwq and 4469 * pool which make migrating pending and scheduled works very 4470 * difficult to implement without impacting hot paths. Secondly, 4471 * worker pools serve mix of short, long and very long running works making 4472 * blocked draining impractical. 4473 * 4474 * This is solved by allowing the pools to be disassociated from the CPU 4475 * running as an unbound one and allowing it to be reattached later if the 4476 * cpu comes back online. 4477 */ 4478 4479 static void wq_unbind_fn(struct work_struct *work) 4480 { 4481 int cpu = smp_processor_id(); 4482 struct worker_pool *pool; 4483 struct worker *worker; 4484 4485 for_each_cpu_worker_pool(pool, cpu) { 4486 mutex_lock(&pool->attach_mutex); 4487 spin_lock_irq(&pool->lock); 4488 4489 /* 4490 * We've blocked all attach/detach operations. Make all workers 4491 * unbound and set DISASSOCIATED. Before this, all workers 4492 * except for the ones which are still executing works from 4493 * before the last CPU down must be on the cpu. After 4494 * this, they may become diasporas. 4495 */ 4496 for_each_pool_worker(worker, pool) 4497 worker->flags |= WORKER_UNBOUND; 4498 4499 pool->flags |= POOL_DISASSOCIATED; 4500 4501 spin_unlock_irq(&pool->lock); 4502 mutex_unlock(&pool->attach_mutex); 4503 4504 /* 4505 * Call schedule() so that we cross rq->lock and thus can 4506 * guarantee sched callbacks see the %WORKER_UNBOUND flag. 4507 * This is necessary as scheduler callbacks may be invoked 4508 * from other cpus. 4509 */ 4510 schedule(); 4511 4512 /* 4513 * Sched callbacks are disabled now. Zap nr_running. 4514 * After this, nr_running stays zero and need_more_worker() 4515 * and keep_working() are always true as long as the 4516 * worklist is not empty. This pool now behaves as an 4517 * unbound (in terms of concurrency management) pool which 4518 * are served by workers tied to the pool. 4519 */ 4520 atomic_set(&pool->nr_running, 0); 4521 4522 /* 4523 * With concurrency management just turned off, a busy 4524 * worker blocking could lead to lengthy stalls. Kick off 4525 * unbound chain execution of currently pending work items. 4526 */ 4527 spin_lock_irq(&pool->lock); 4528 wake_up_worker(pool); 4529 spin_unlock_irq(&pool->lock); 4530 } 4531 } 4532 4533 /** 4534 * rebind_workers - rebind all workers of a pool to the associated CPU 4535 * @pool: pool of interest 4536 * 4537 * @pool->cpu is coming online. Rebind all workers to the CPU. 4538 */ 4539 static void rebind_workers(struct worker_pool *pool) 4540 { 4541 struct worker *worker; 4542 4543 lockdep_assert_held(&pool->attach_mutex); 4544 4545 /* 4546 * Restore CPU affinity of all workers. As all idle workers should 4547 * be on the run-queue of the associated CPU before any local 4548 * wake-ups for concurrency management happen, restore CPU affinity 4549 * of all workers first and then clear UNBOUND. As we're called 4550 * from CPU_ONLINE, the following shouldn't fail. 4551 */ 4552 for_each_pool_worker(worker, pool) 4553 WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task, 4554 pool->attrs->cpumask) < 0); 4555 4556 spin_lock_irq(&pool->lock); 4557 pool->flags &= ~POOL_DISASSOCIATED; 4558 4559 for_each_pool_worker(worker, pool) { 4560 unsigned int worker_flags = worker->flags; 4561 4562 /* 4563 * A bound idle worker should actually be on the runqueue 4564 * of the associated CPU for local wake-ups targeting it to 4565 * work. Kick all idle workers so that they migrate to the 4566 * associated CPU. Doing this in the same loop as 4567 * replacing UNBOUND with REBOUND is safe as no worker will 4568 * be bound before @pool->lock is released. 4569 */ 4570 if (worker_flags & WORKER_IDLE) 4571 wake_up_process(worker->task); 4572 4573 /* 4574 * We want to clear UNBOUND but can't directly call 4575 * worker_clr_flags() or adjust nr_running. Atomically 4576 * replace UNBOUND with another NOT_RUNNING flag REBOUND. 4577 * @worker will clear REBOUND using worker_clr_flags() when 4578 * it initiates the next execution cycle thus restoring 4579 * concurrency management. Note that when or whether 4580 * @worker clears REBOUND doesn't affect correctness. 4581 * 4582 * ACCESS_ONCE() is necessary because @worker->flags may be 4583 * tested without holding any lock in 4584 * wq_worker_waking_up(). Without it, NOT_RUNNING test may 4585 * fail incorrectly leading to premature concurrency 4586 * management operations. 4587 */ 4588 WARN_ON_ONCE(!(worker_flags & WORKER_UNBOUND)); 4589 worker_flags |= WORKER_REBOUND; 4590 worker_flags &= ~WORKER_UNBOUND; 4591 ACCESS_ONCE(worker->flags) = worker_flags; 4592 } 4593 4594 spin_unlock_irq(&pool->lock); 4595 } 4596 4597 /** 4598 * restore_unbound_workers_cpumask - restore cpumask of unbound workers 4599 * @pool: unbound pool of interest 4600 * @cpu: the CPU which is coming up 4601 * 4602 * An unbound pool may end up with a cpumask which doesn't have any online 4603 * CPUs. When a worker of such pool get scheduled, the scheduler resets 4604 * its cpus_allowed. If @cpu is in @pool's cpumask which didn't have any 4605 * online CPU before, cpus_allowed of all its workers should be restored. 4606 */ 4607 static void restore_unbound_workers_cpumask(struct worker_pool *pool, int cpu) 4608 { 4609 static cpumask_t cpumask; 4610 struct worker *worker; 4611 4612 lockdep_assert_held(&pool->attach_mutex); 4613 4614 /* is @cpu allowed for @pool? */ 4615 if (!cpumask_test_cpu(cpu, pool->attrs->cpumask)) 4616 return; 4617 4618 /* is @cpu the only online CPU? */ 4619 cpumask_and(&cpumask, pool->attrs->cpumask, cpu_online_mask); 4620 if (cpumask_weight(&cpumask) != 1) 4621 return; 4622 4623 /* as we're called from CPU_ONLINE, the following shouldn't fail */ 4624 for_each_pool_worker(worker, pool) 4625 WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task, 4626 pool->attrs->cpumask) < 0); 4627 } 4628 4629 /* 4630 * Workqueues should be brought up before normal priority CPU notifiers. 4631 * This will be registered high priority CPU notifier. 4632 */ 4633 static int workqueue_cpu_up_callback(struct notifier_block *nfb, 4634 unsigned long action, 4635 void *hcpu) 4636 { 4637 int cpu = (unsigned long)hcpu; 4638 struct worker_pool *pool; 4639 struct workqueue_struct *wq; 4640 int pi; 4641 4642 switch (action & ~CPU_TASKS_FROZEN) { 4643 case CPU_UP_PREPARE: 4644 for_each_cpu_worker_pool(pool, cpu) { 4645 if (pool->nr_workers) 4646 continue; 4647 if (!create_worker(pool)) 4648 return NOTIFY_BAD; 4649 } 4650 break; 4651 4652 case CPU_DOWN_FAILED: 4653 case CPU_ONLINE: 4654 mutex_lock(&wq_pool_mutex); 4655 4656 for_each_pool(pool, pi) { 4657 mutex_lock(&pool->attach_mutex); 4658 4659 if (pool->cpu == cpu) 4660 rebind_workers(pool); 4661 else if (pool->cpu < 0) 4662 restore_unbound_workers_cpumask(pool, cpu); 4663 4664 mutex_unlock(&pool->attach_mutex); 4665 } 4666 4667 /* update NUMA affinity of unbound workqueues */ 4668 list_for_each_entry(wq, &workqueues, list) 4669 wq_update_unbound_numa(wq, cpu, true); 4670 4671 mutex_unlock(&wq_pool_mutex); 4672 break; 4673 } 4674 return NOTIFY_OK; 4675 } 4676 4677 /* 4678 * Workqueues should be brought down after normal priority CPU notifiers. 4679 * This will be registered as low priority CPU notifier. 4680 */ 4681 static int workqueue_cpu_down_callback(struct notifier_block *nfb, 4682 unsigned long action, 4683 void *hcpu) 4684 { 4685 int cpu = (unsigned long)hcpu; 4686 struct work_struct unbind_work; 4687 struct workqueue_struct *wq; 4688 4689 switch (action & ~CPU_TASKS_FROZEN) { 4690 case CPU_DOWN_PREPARE: 4691 /* unbinding per-cpu workers should happen on the local CPU */ 4692 INIT_WORK_ONSTACK(&unbind_work, wq_unbind_fn); 4693 queue_work_on(cpu, system_highpri_wq, &unbind_work); 4694 4695 /* update NUMA affinity of unbound workqueues */ 4696 mutex_lock(&wq_pool_mutex); 4697 list_for_each_entry(wq, &workqueues, list) 4698 wq_update_unbound_numa(wq, cpu, false); 4699 mutex_unlock(&wq_pool_mutex); 4700 4701 /* wait for per-cpu unbinding to finish */ 4702 flush_work(&unbind_work); 4703 destroy_work_on_stack(&unbind_work); 4704 break; 4705 } 4706 return NOTIFY_OK; 4707 } 4708 4709 #ifdef CONFIG_SMP 4710 4711 struct work_for_cpu { 4712 struct work_struct work; 4713 long (*fn)(void *); 4714 void *arg; 4715 long ret; 4716 }; 4717 4718 static void work_for_cpu_fn(struct work_struct *work) 4719 { 4720 struct work_for_cpu *wfc = container_of(work, struct work_for_cpu, work); 4721 4722 wfc->ret = wfc->fn(wfc->arg); 4723 } 4724 4725 /** 4726 * work_on_cpu - run a function in thread context on a particular cpu 4727 * @cpu: the cpu to run on 4728 * @fn: the function to run 4729 * @arg: the function arg 4730 * 4731 * It is up to the caller to ensure that the cpu doesn't go offline. 4732 * The caller must not hold any locks which would prevent @fn from completing. 4733 * 4734 * Return: The value @fn returns. 4735 */ 4736 long work_on_cpu(int cpu, long (*fn)(void *), void *arg) 4737 { 4738 struct work_for_cpu wfc = { .fn = fn, .arg = arg }; 4739 4740 INIT_WORK_ONSTACK(&wfc.work, work_for_cpu_fn); 4741 schedule_work_on(cpu, &wfc.work); 4742 flush_work(&wfc.work); 4743 destroy_work_on_stack(&wfc.work); 4744 return wfc.ret; 4745 } 4746 EXPORT_SYMBOL_GPL(work_on_cpu); 4747 #endif /* CONFIG_SMP */ 4748 4749 #ifdef CONFIG_FREEZER 4750 4751 /** 4752 * freeze_workqueues_begin - begin freezing workqueues 4753 * 4754 * Start freezing workqueues. After this function returns, all freezable 4755 * workqueues will queue new works to their delayed_works list instead of 4756 * pool->worklist. 4757 * 4758 * CONTEXT: 4759 * Grabs and releases wq_pool_mutex, wq->mutex and pool->lock's. 4760 */ 4761 void freeze_workqueues_begin(void) 4762 { 4763 struct workqueue_struct *wq; 4764 struct pool_workqueue *pwq; 4765 4766 mutex_lock(&wq_pool_mutex); 4767 4768 WARN_ON_ONCE(workqueue_freezing); 4769 workqueue_freezing = true; 4770 4771 list_for_each_entry(wq, &workqueues, list) { 4772 mutex_lock(&wq->mutex); 4773 for_each_pwq(pwq, wq) 4774 pwq_adjust_max_active(pwq); 4775 mutex_unlock(&wq->mutex); 4776 } 4777 4778 mutex_unlock(&wq_pool_mutex); 4779 } 4780 4781 /** 4782 * freeze_workqueues_busy - are freezable workqueues still busy? 4783 * 4784 * Check whether freezing is complete. This function must be called 4785 * between freeze_workqueues_begin() and thaw_workqueues(). 4786 * 4787 * CONTEXT: 4788 * Grabs and releases wq_pool_mutex. 4789 * 4790 * Return: 4791 * %true if some freezable workqueues are still busy. %false if freezing 4792 * is complete. 4793 */ 4794 bool freeze_workqueues_busy(void) 4795 { 4796 bool busy = false; 4797 struct workqueue_struct *wq; 4798 struct pool_workqueue *pwq; 4799 4800 mutex_lock(&wq_pool_mutex); 4801 4802 WARN_ON_ONCE(!workqueue_freezing); 4803 4804 list_for_each_entry(wq, &workqueues, list) { 4805 if (!(wq->flags & WQ_FREEZABLE)) 4806 continue; 4807 /* 4808 * nr_active is monotonically decreasing. It's safe 4809 * to peek without lock. 4810 */ 4811 rcu_read_lock_sched(); 4812 for_each_pwq(pwq, wq) { 4813 WARN_ON_ONCE(pwq->nr_active < 0); 4814 if (pwq->nr_active) { 4815 busy = true; 4816 rcu_read_unlock_sched(); 4817 goto out_unlock; 4818 } 4819 } 4820 rcu_read_unlock_sched(); 4821 } 4822 out_unlock: 4823 mutex_unlock(&wq_pool_mutex); 4824 return busy; 4825 } 4826 4827 /** 4828 * thaw_workqueues - thaw workqueues 4829 * 4830 * Thaw workqueues. Normal queueing is restored and all collected 4831 * frozen works are transferred to their respective pool worklists. 4832 * 4833 * CONTEXT: 4834 * Grabs and releases wq_pool_mutex, wq->mutex and pool->lock's. 4835 */ 4836 void thaw_workqueues(void) 4837 { 4838 struct workqueue_struct *wq; 4839 struct pool_workqueue *pwq; 4840 4841 mutex_lock(&wq_pool_mutex); 4842 4843 if (!workqueue_freezing) 4844 goto out_unlock; 4845 4846 workqueue_freezing = false; 4847 4848 /* restore max_active and repopulate worklist */ 4849 list_for_each_entry(wq, &workqueues, list) { 4850 mutex_lock(&wq->mutex); 4851 for_each_pwq(pwq, wq) 4852 pwq_adjust_max_active(pwq); 4853 mutex_unlock(&wq->mutex); 4854 } 4855 4856 out_unlock: 4857 mutex_unlock(&wq_pool_mutex); 4858 } 4859 #endif /* CONFIG_FREEZER */ 4860 4861 static int workqueue_apply_unbound_cpumask(void) 4862 { 4863 LIST_HEAD(ctxs); 4864 int ret = 0; 4865 struct workqueue_struct *wq; 4866 struct apply_wqattrs_ctx *ctx, *n; 4867 4868 lockdep_assert_held(&wq_pool_mutex); 4869 4870 list_for_each_entry(wq, &workqueues, list) { 4871 if (!(wq->flags & WQ_UNBOUND)) 4872 continue; 4873 /* creating multiple pwqs breaks ordering guarantee */ 4874 if (wq->flags & __WQ_ORDERED) 4875 continue; 4876 4877 ctx = apply_wqattrs_prepare(wq, wq->unbound_attrs); 4878 if (!ctx) { 4879 ret = -ENOMEM; 4880 break; 4881 } 4882 4883 list_add_tail(&ctx->list, &ctxs); 4884 } 4885 4886 list_for_each_entry_safe(ctx, n, &ctxs, list) { 4887 if (!ret) 4888 apply_wqattrs_commit(ctx); 4889 apply_wqattrs_cleanup(ctx); 4890 } 4891 4892 return ret; 4893 } 4894 4895 /** 4896 * workqueue_set_unbound_cpumask - Set the low-level unbound cpumask 4897 * @cpumask: the cpumask to set 4898 * 4899 * The low-level workqueues cpumask is a global cpumask that limits 4900 * the affinity of all unbound workqueues. This function check the @cpumask 4901 * and apply it to all unbound workqueues and updates all pwqs of them. 4902 * 4903 * Retun: 0 - Success 4904 * -EINVAL - Invalid @cpumask 4905 * -ENOMEM - Failed to allocate memory for attrs or pwqs. 4906 */ 4907 int workqueue_set_unbound_cpumask(cpumask_var_t cpumask) 4908 { 4909 int ret = -EINVAL; 4910 cpumask_var_t saved_cpumask; 4911 4912 if (!zalloc_cpumask_var(&saved_cpumask, GFP_KERNEL)) 4913 return -ENOMEM; 4914 4915 cpumask_and(cpumask, cpumask, cpu_possible_mask); 4916 if (!cpumask_empty(cpumask)) { 4917 apply_wqattrs_lock(); 4918 4919 /* save the old wq_unbound_cpumask. */ 4920 cpumask_copy(saved_cpumask, wq_unbound_cpumask); 4921 4922 /* update wq_unbound_cpumask at first and apply it to wqs. */ 4923 cpumask_copy(wq_unbound_cpumask, cpumask); 4924 ret = workqueue_apply_unbound_cpumask(); 4925 4926 /* restore the wq_unbound_cpumask when failed. */ 4927 if (ret < 0) 4928 cpumask_copy(wq_unbound_cpumask, saved_cpumask); 4929 4930 apply_wqattrs_unlock(); 4931 } 4932 4933 free_cpumask_var(saved_cpumask); 4934 return ret; 4935 } 4936 4937 #ifdef CONFIG_SYSFS 4938 /* 4939 * Workqueues with WQ_SYSFS flag set is visible to userland via 4940 * /sys/bus/workqueue/devices/WQ_NAME. All visible workqueues have the 4941 * following attributes. 4942 * 4943 * per_cpu RO bool : whether the workqueue is per-cpu or unbound 4944 * max_active RW int : maximum number of in-flight work items 4945 * 4946 * Unbound workqueues have the following extra attributes. 4947 * 4948 * id RO int : the associated pool ID 4949 * nice RW int : nice value of the workers 4950 * cpumask RW mask : bitmask of allowed CPUs for the workers 4951 */ 4952 struct wq_device { 4953 struct workqueue_struct *wq; 4954 struct device dev; 4955 }; 4956 4957 static struct workqueue_struct *dev_to_wq(struct device *dev) 4958 { 4959 struct wq_device *wq_dev = container_of(dev, struct wq_device, dev); 4960 4961 return wq_dev->wq; 4962 } 4963 4964 static ssize_t per_cpu_show(struct device *dev, struct device_attribute *attr, 4965 char *buf) 4966 { 4967 struct workqueue_struct *wq = dev_to_wq(dev); 4968 4969 return scnprintf(buf, PAGE_SIZE, "%d\n", (bool)!(wq->flags & WQ_UNBOUND)); 4970 } 4971 static DEVICE_ATTR_RO(per_cpu); 4972 4973 static ssize_t max_active_show(struct device *dev, 4974 struct device_attribute *attr, char *buf) 4975 { 4976 struct workqueue_struct *wq = dev_to_wq(dev); 4977 4978 return scnprintf(buf, PAGE_SIZE, "%d\n", wq->saved_max_active); 4979 } 4980 4981 static ssize_t max_active_store(struct device *dev, 4982 struct device_attribute *attr, const char *buf, 4983 size_t count) 4984 { 4985 struct workqueue_struct *wq = dev_to_wq(dev); 4986 int val; 4987 4988 if (sscanf(buf, "%d", &val) != 1 || val <= 0) 4989 return -EINVAL; 4990 4991 workqueue_set_max_active(wq, val); 4992 return count; 4993 } 4994 static DEVICE_ATTR_RW(max_active); 4995 4996 static struct attribute *wq_sysfs_attrs[] = { 4997 &dev_attr_per_cpu.attr, 4998 &dev_attr_max_active.attr, 4999 NULL, 5000 }; 5001 ATTRIBUTE_GROUPS(wq_sysfs); 5002 5003 static ssize_t wq_pool_ids_show(struct device *dev, 5004 struct device_attribute *attr, char *buf) 5005 { 5006 struct workqueue_struct *wq = dev_to_wq(dev); 5007 const char *delim = ""; 5008 int node, written = 0; 5009 5010 rcu_read_lock_sched(); 5011 for_each_node(node) { 5012 written += scnprintf(buf + written, PAGE_SIZE - written, 5013 "%s%d:%d", delim, node, 5014 unbound_pwq_by_node(wq, node)->pool->id); 5015 delim = " "; 5016 } 5017 written += scnprintf(buf + written, PAGE_SIZE - written, "\n"); 5018 rcu_read_unlock_sched(); 5019 5020 return written; 5021 } 5022 5023 static ssize_t wq_nice_show(struct device *dev, struct device_attribute *attr, 5024 char *buf) 5025 { 5026 struct workqueue_struct *wq = dev_to_wq(dev); 5027 int written; 5028 5029 mutex_lock(&wq->mutex); 5030 written = scnprintf(buf, PAGE_SIZE, "%d\n", wq->unbound_attrs->nice); 5031 mutex_unlock(&wq->mutex); 5032 5033 return written; 5034 } 5035 5036 /* prepare workqueue_attrs for sysfs store operations */ 5037 static struct workqueue_attrs *wq_sysfs_prep_attrs(struct workqueue_struct *wq) 5038 { 5039 struct workqueue_attrs *attrs; 5040 5041 lockdep_assert_held(&wq_pool_mutex); 5042 5043 attrs = alloc_workqueue_attrs(GFP_KERNEL); 5044 if (!attrs) 5045 return NULL; 5046 5047 copy_workqueue_attrs(attrs, wq->unbound_attrs); 5048 return attrs; 5049 } 5050 5051 static ssize_t wq_nice_store(struct device *dev, struct device_attribute *attr, 5052 const char *buf, size_t count) 5053 { 5054 struct workqueue_struct *wq = dev_to_wq(dev); 5055 struct workqueue_attrs *attrs; 5056 int ret = -ENOMEM; 5057 5058 apply_wqattrs_lock(); 5059 5060 attrs = wq_sysfs_prep_attrs(wq); 5061 if (!attrs) 5062 goto out_unlock; 5063 5064 if (sscanf(buf, "%d", &attrs->nice) == 1 && 5065 attrs->nice >= MIN_NICE && attrs->nice <= MAX_NICE) 5066 ret = apply_workqueue_attrs_locked(wq, attrs); 5067 else 5068 ret = -EINVAL; 5069 5070 out_unlock: 5071 apply_wqattrs_unlock(); 5072 free_workqueue_attrs(attrs); 5073 return ret ?: count; 5074 } 5075 5076 static ssize_t wq_cpumask_show(struct device *dev, 5077 struct device_attribute *attr, char *buf) 5078 { 5079 struct workqueue_struct *wq = dev_to_wq(dev); 5080 int written; 5081 5082 mutex_lock(&wq->mutex); 5083 written = scnprintf(buf, PAGE_SIZE, "%*pb\n", 5084 cpumask_pr_args(wq->unbound_attrs->cpumask)); 5085 mutex_unlock(&wq->mutex); 5086 return written; 5087 } 5088 5089 static ssize_t wq_cpumask_store(struct device *dev, 5090 struct device_attribute *attr, 5091 const char *buf, size_t count) 5092 { 5093 struct workqueue_struct *wq = dev_to_wq(dev); 5094 struct workqueue_attrs *attrs; 5095 int ret = -ENOMEM; 5096 5097 apply_wqattrs_lock(); 5098 5099 attrs = wq_sysfs_prep_attrs(wq); 5100 if (!attrs) 5101 goto out_unlock; 5102 5103 ret = cpumask_parse(buf, attrs->cpumask); 5104 if (!ret) 5105 ret = apply_workqueue_attrs_locked(wq, attrs); 5106 5107 out_unlock: 5108 apply_wqattrs_unlock(); 5109 free_workqueue_attrs(attrs); 5110 return ret ?: count; 5111 } 5112 5113 static ssize_t wq_numa_show(struct device *dev, struct device_attribute *attr, 5114 char *buf) 5115 { 5116 struct workqueue_struct *wq = dev_to_wq(dev); 5117 int written; 5118 5119 mutex_lock(&wq->mutex); 5120 written = scnprintf(buf, PAGE_SIZE, "%d\n", 5121 !wq->unbound_attrs->no_numa); 5122 mutex_unlock(&wq->mutex); 5123 5124 return written; 5125 } 5126 5127 static ssize_t wq_numa_store(struct device *dev, struct device_attribute *attr, 5128 const char *buf, size_t count) 5129 { 5130 struct workqueue_struct *wq = dev_to_wq(dev); 5131 struct workqueue_attrs *attrs; 5132 int v, ret = -ENOMEM; 5133 5134 apply_wqattrs_lock(); 5135 5136 attrs = wq_sysfs_prep_attrs(wq); 5137 if (!attrs) 5138 goto out_unlock; 5139 5140 ret = -EINVAL; 5141 if (sscanf(buf, "%d", &v) == 1) { 5142 attrs->no_numa = !v; 5143 ret = apply_workqueue_attrs_locked(wq, attrs); 5144 } 5145 5146 out_unlock: 5147 apply_wqattrs_unlock(); 5148 free_workqueue_attrs(attrs); 5149 return ret ?: count; 5150 } 5151 5152 static struct device_attribute wq_sysfs_unbound_attrs[] = { 5153 __ATTR(pool_ids, 0444, wq_pool_ids_show, NULL), 5154 __ATTR(nice, 0644, wq_nice_show, wq_nice_store), 5155 __ATTR(cpumask, 0644, wq_cpumask_show, wq_cpumask_store), 5156 __ATTR(numa, 0644, wq_numa_show, wq_numa_store), 5157 __ATTR_NULL, 5158 }; 5159 5160 static struct bus_type wq_subsys = { 5161 .name = "workqueue", 5162 .dev_groups = wq_sysfs_groups, 5163 }; 5164 5165 static ssize_t wq_unbound_cpumask_show(struct device *dev, 5166 struct device_attribute *attr, char *buf) 5167 { 5168 int written; 5169 5170 mutex_lock(&wq_pool_mutex); 5171 written = scnprintf(buf, PAGE_SIZE, "%*pb\n", 5172 cpumask_pr_args(wq_unbound_cpumask)); 5173 mutex_unlock(&wq_pool_mutex); 5174 5175 return written; 5176 } 5177 5178 static ssize_t wq_unbound_cpumask_store(struct device *dev, 5179 struct device_attribute *attr, const char *buf, size_t count) 5180 { 5181 cpumask_var_t cpumask; 5182 int ret; 5183 5184 if (!zalloc_cpumask_var(&cpumask, GFP_KERNEL)) 5185 return -ENOMEM; 5186 5187 ret = cpumask_parse(buf, cpumask); 5188 if (!ret) 5189 ret = workqueue_set_unbound_cpumask(cpumask); 5190 5191 free_cpumask_var(cpumask); 5192 return ret ? ret : count; 5193 } 5194 5195 static struct device_attribute wq_sysfs_cpumask_attr = 5196 __ATTR(cpumask, 0644, wq_unbound_cpumask_show, 5197 wq_unbound_cpumask_store); 5198 5199 static int __init wq_sysfs_init(void) 5200 { 5201 int err; 5202 5203 err = subsys_virtual_register(&wq_subsys, NULL); 5204 if (err) 5205 return err; 5206 5207 return device_create_file(wq_subsys.dev_root, &wq_sysfs_cpumask_attr); 5208 } 5209 core_initcall(wq_sysfs_init); 5210 5211 static void wq_device_release(struct device *dev) 5212 { 5213 struct wq_device *wq_dev = container_of(dev, struct wq_device, dev); 5214 5215 kfree(wq_dev); 5216 } 5217 5218 /** 5219 * workqueue_sysfs_register - make a workqueue visible in sysfs 5220 * @wq: the workqueue to register 5221 * 5222 * Expose @wq in sysfs under /sys/bus/workqueue/devices. 5223 * alloc_workqueue*() automatically calls this function if WQ_SYSFS is set 5224 * which is the preferred method. 5225 * 5226 * Workqueue user should use this function directly iff it wants to apply 5227 * workqueue_attrs before making the workqueue visible in sysfs; otherwise, 5228 * apply_workqueue_attrs() may race against userland updating the 5229 * attributes. 5230 * 5231 * Return: 0 on success, -errno on failure. 5232 */ 5233 int workqueue_sysfs_register(struct workqueue_struct *wq) 5234 { 5235 struct wq_device *wq_dev; 5236 int ret; 5237 5238 /* 5239 * Adjusting max_active or creating new pwqs by applying 5240 * attributes breaks ordering guarantee. Disallow exposing ordered 5241 * workqueues. 5242 */ 5243 if (WARN_ON(wq->flags & __WQ_ORDERED)) 5244 return -EINVAL; 5245 5246 wq->wq_dev = wq_dev = kzalloc(sizeof(*wq_dev), GFP_KERNEL); 5247 if (!wq_dev) 5248 return -ENOMEM; 5249 5250 wq_dev->wq = wq; 5251 wq_dev->dev.bus = &wq_subsys; 5252 wq_dev->dev.release = wq_device_release; 5253 dev_set_name(&wq_dev->dev, "%s", wq->name); 5254 5255 /* 5256 * unbound_attrs are created separately. Suppress uevent until 5257 * everything is ready. 5258 */ 5259 dev_set_uevent_suppress(&wq_dev->dev, true); 5260 5261 ret = device_register(&wq_dev->dev); 5262 if (ret) { 5263 kfree(wq_dev); 5264 wq->wq_dev = NULL; 5265 return ret; 5266 } 5267 5268 if (wq->flags & WQ_UNBOUND) { 5269 struct device_attribute *attr; 5270 5271 for (attr = wq_sysfs_unbound_attrs; attr->attr.name; attr++) { 5272 ret = device_create_file(&wq_dev->dev, attr); 5273 if (ret) { 5274 device_unregister(&wq_dev->dev); 5275 wq->wq_dev = NULL; 5276 return ret; 5277 } 5278 } 5279 } 5280 5281 dev_set_uevent_suppress(&wq_dev->dev, false); 5282 kobject_uevent(&wq_dev->dev.kobj, KOBJ_ADD); 5283 return 0; 5284 } 5285 5286 /** 5287 * workqueue_sysfs_unregister - undo workqueue_sysfs_register() 5288 * @wq: the workqueue to unregister 5289 * 5290 * If @wq is registered to sysfs by workqueue_sysfs_register(), unregister. 5291 */ 5292 static void workqueue_sysfs_unregister(struct workqueue_struct *wq) 5293 { 5294 struct wq_device *wq_dev = wq->wq_dev; 5295 5296 if (!wq->wq_dev) 5297 return; 5298 5299 wq->wq_dev = NULL; 5300 device_unregister(&wq_dev->dev); 5301 } 5302 #else /* CONFIG_SYSFS */ 5303 static void workqueue_sysfs_unregister(struct workqueue_struct *wq) { } 5304 #endif /* CONFIG_SYSFS */ 5305 5306 /* 5307 * Workqueue watchdog. 5308 * 5309 * Stall may be caused by various bugs - missing WQ_MEM_RECLAIM, illegal 5310 * flush dependency, a concurrency managed work item which stays RUNNING 5311 * indefinitely. Workqueue stalls can be very difficult to debug as the 5312 * usual warning mechanisms don't trigger and internal workqueue state is 5313 * largely opaque. 5314 * 5315 * Workqueue watchdog monitors all worker pools periodically and dumps 5316 * state if some pools failed to make forward progress for a while where 5317 * forward progress is defined as the first item on ->worklist changing. 5318 * 5319 * This mechanism is controlled through the kernel parameter 5320 * "workqueue.watchdog_thresh" which can be updated at runtime through the 5321 * corresponding sysfs parameter file. 5322 */ 5323 #ifdef CONFIG_WQ_WATCHDOG 5324 5325 static void wq_watchdog_timer_fn(unsigned long data); 5326 5327 static unsigned long wq_watchdog_thresh = 30; 5328 static struct timer_list wq_watchdog_timer = 5329 TIMER_DEFERRED_INITIALIZER(wq_watchdog_timer_fn, 0, 0); 5330 5331 static unsigned long wq_watchdog_touched = INITIAL_JIFFIES; 5332 static DEFINE_PER_CPU(unsigned long, wq_watchdog_touched_cpu) = INITIAL_JIFFIES; 5333 5334 static void wq_watchdog_reset_touched(void) 5335 { 5336 int cpu; 5337 5338 wq_watchdog_touched = jiffies; 5339 for_each_possible_cpu(cpu) 5340 per_cpu(wq_watchdog_touched_cpu, cpu) = jiffies; 5341 } 5342 5343 static void wq_watchdog_timer_fn(unsigned long data) 5344 { 5345 unsigned long thresh = READ_ONCE(wq_watchdog_thresh) * HZ; 5346 bool lockup_detected = false; 5347 struct worker_pool *pool; 5348 int pi; 5349 5350 if (!thresh) 5351 return; 5352 5353 rcu_read_lock(); 5354 5355 for_each_pool(pool, pi) { 5356 unsigned long pool_ts, touched, ts; 5357 5358 if (list_empty(&pool->worklist)) 5359 continue; 5360 5361 /* get the latest of pool and touched timestamps */ 5362 pool_ts = READ_ONCE(pool->watchdog_ts); 5363 touched = READ_ONCE(wq_watchdog_touched); 5364 5365 if (time_after(pool_ts, touched)) 5366 ts = pool_ts; 5367 else 5368 ts = touched; 5369 5370 if (pool->cpu >= 0) { 5371 unsigned long cpu_touched = 5372 READ_ONCE(per_cpu(wq_watchdog_touched_cpu, 5373 pool->cpu)); 5374 if (time_after(cpu_touched, ts)) 5375 ts = cpu_touched; 5376 } 5377 5378 /* did we stall? */ 5379 if (time_after(jiffies, ts + thresh)) { 5380 lockup_detected = true; 5381 pr_emerg("BUG: workqueue lockup - pool"); 5382 pr_cont_pool_info(pool); 5383 pr_cont(" stuck for %us!\n", 5384 jiffies_to_msecs(jiffies - pool_ts) / 1000); 5385 } 5386 } 5387 5388 rcu_read_unlock(); 5389 5390 if (lockup_detected) 5391 show_workqueue_state(); 5392 5393 wq_watchdog_reset_touched(); 5394 mod_timer(&wq_watchdog_timer, jiffies + thresh); 5395 } 5396 5397 void wq_watchdog_touch(int cpu) 5398 { 5399 if (cpu >= 0) 5400 per_cpu(wq_watchdog_touched_cpu, cpu) = jiffies; 5401 else 5402 wq_watchdog_touched = jiffies; 5403 } 5404 5405 static void wq_watchdog_set_thresh(unsigned long thresh) 5406 { 5407 wq_watchdog_thresh = 0; 5408 del_timer_sync(&wq_watchdog_timer); 5409 5410 if (thresh) { 5411 wq_watchdog_thresh = thresh; 5412 wq_watchdog_reset_touched(); 5413 mod_timer(&wq_watchdog_timer, jiffies + thresh * HZ); 5414 } 5415 } 5416 5417 static int wq_watchdog_param_set_thresh(const char *val, 5418 const struct kernel_param *kp) 5419 { 5420 unsigned long thresh; 5421 int ret; 5422 5423 ret = kstrtoul(val, 0, &thresh); 5424 if (ret) 5425 return ret; 5426 5427 if (system_wq) 5428 wq_watchdog_set_thresh(thresh); 5429 else 5430 wq_watchdog_thresh = thresh; 5431 5432 return 0; 5433 } 5434 5435 static const struct kernel_param_ops wq_watchdog_thresh_ops = { 5436 .set = wq_watchdog_param_set_thresh, 5437 .get = param_get_ulong, 5438 }; 5439 5440 module_param_cb(watchdog_thresh, &wq_watchdog_thresh_ops, &wq_watchdog_thresh, 5441 0644); 5442 5443 static void wq_watchdog_init(void) 5444 { 5445 wq_watchdog_set_thresh(wq_watchdog_thresh); 5446 } 5447 5448 #else /* CONFIG_WQ_WATCHDOG */ 5449 5450 static inline void wq_watchdog_init(void) { } 5451 5452 #endif /* CONFIG_WQ_WATCHDOG */ 5453 5454 static void __init wq_numa_init(void) 5455 { 5456 cpumask_var_t *tbl; 5457 int node, cpu; 5458 5459 if (num_possible_nodes() <= 1) 5460 return; 5461 5462 if (wq_disable_numa) { 5463 pr_info("workqueue: NUMA affinity support disabled\n"); 5464 return; 5465 } 5466 5467 wq_update_unbound_numa_attrs_buf = alloc_workqueue_attrs(GFP_KERNEL); 5468 BUG_ON(!wq_update_unbound_numa_attrs_buf); 5469 5470 /* 5471 * We want masks of possible CPUs of each node which isn't readily 5472 * available. Build one from cpu_to_node() which should have been 5473 * fully initialized by now. 5474 */ 5475 tbl = kzalloc(nr_node_ids * sizeof(tbl[0]), GFP_KERNEL); 5476 BUG_ON(!tbl); 5477 5478 for_each_node(node) 5479 BUG_ON(!zalloc_cpumask_var_node(&tbl[node], GFP_KERNEL, 5480 node_online(node) ? node : NUMA_NO_NODE)); 5481 5482 for_each_possible_cpu(cpu) { 5483 node = cpu_to_node(cpu); 5484 if (WARN_ON(node == NUMA_NO_NODE)) { 5485 pr_warn("workqueue: NUMA node mapping not available for cpu%d, disabling NUMA support\n", cpu); 5486 /* happens iff arch is bonkers, let's just proceed */ 5487 return; 5488 } 5489 cpumask_set_cpu(cpu, tbl[node]); 5490 } 5491 5492 wq_numa_possible_cpumask = tbl; 5493 wq_numa_enabled = true; 5494 } 5495 5496 static int __init init_workqueues(void) 5497 { 5498 int std_nice[NR_STD_WORKER_POOLS] = { 0, HIGHPRI_NICE_LEVEL }; 5499 int i, cpu; 5500 5501 WARN_ON(__alignof__(struct pool_workqueue) < __alignof__(long long)); 5502 5503 BUG_ON(!alloc_cpumask_var(&wq_unbound_cpumask, GFP_KERNEL)); 5504 cpumask_copy(wq_unbound_cpumask, cpu_possible_mask); 5505 5506 pwq_cache = KMEM_CACHE(pool_workqueue, SLAB_PANIC); 5507 5508 cpu_notifier(workqueue_cpu_up_callback, CPU_PRI_WORKQUEUE_UP); 5509 hotcpu_notifier(workqueue_cpu_down_callback, CPU_PRI_WORKQUEUE_DOWN); 5510 5511 wq_numa_init(); 5512 5513 /* initialize CPU pools */ 5514 for_each_possible_cpu(cpu) { 5515 struct worker_pool *pool; 5516 5517 i = 0; 5518 for_each_cpu_worker_pool(pool, cpu) { 5519 BUG_ON(init_worker_pool(pool)); 5520 pool->cpu = cpu; 5521 cpumask_copy(pool->attrs->cpumask, cpumask_of(cpu)); 5522 pool->attrs->nice = std_nice[i++]; 5523 pool->node = cpu_to_node(cpu); 5524 5525 /* alloc pool ID */ 5526 mutex_lock(&wq_pool_mutex); 5527 BUG_ON(worker_pool_assign_id(pool)); 5528 mutex_unlock(&wq_pool_mutex); 5529 } 5530 } 5531 5532 /* create the initial worker */ 5533 for_each_online_cpu(cpu) { 5534 struct worker_pool *pool; 5535 5536 for_each_cpu_worker_pool(pool, cpu) { 5537 pool->flags &= ~POOL_DISASSOCIATED; 5538 BUG_ON(!create_worker(pool)); 5539 } 5540 } 5541 5542 /* create default unbound and ordered wq attrs */ 5543 for (i = 0; i < NR_STD_WORKER_POOLS; i++) { 5544 struct workqueue_attrs *attrs; 5545 5546 BUG_ON(!(attrs = alloc_workqueue_attrs(GFP_KERNEL))); 5547 attrs->nice = std_nice[i]; 5548 unbound_std_wq_attrs[i] = attrs; 5549 5550 /* 5551 * An ordered wq should have only one pwq as ordering is 5552 * guaranteed by max_active which is enforced by pwqs. 5553 * Turn off NUMA so that dfl_pwq is used for all nodes. 5554 */ 5555 BUG_ON(!(attrs = alloc_workqueue_attrs(GFP_KERNEL))); 5556 attrs->nice = std_nice[i]; 5557 attrs->no_numa = true; 5558 ordered_wq_attrs[i] = attrs; 5559 } 5560 5561 system_wq = alloc_workqueue("events", 0, 0); 5562 system_highpri_wq = alloc_workqueue("events_highpri", WQ_HIGHPRI, 0); 5563 system_long_wq = alloc_workqueue("events_long", 0, 0); 5564 system_unbound_wq = alloc_workqueue("events_unbound", WQ_UNBOUND, 5565 WQ_UNBOUND_MAX_ACTIVE); 5566 system_freezable_wq = alloc_workqueue("events_freezable", 5567 WQ_FREEZABLE, 0); 5568 system_power_efficient_wq = alloc_workqueue("events_power_efficient", 5569 WQ_POWER_EFFICIENT, 0); 5570 system_freezable_power_efficient_wq = alloc_workqueue("events_freezable_power_efficient", 5571 WQ_FREEZABLE | WQ_POWER_EFFICIENT, 5572 0); 5573 BUG_ON(!system_wq || !system_highpri_wq || !system_long_wq || 5574 !system_unbound_wq || !system_freezable_wq || 5575 !system_power_efficient_wq || 5576 !system_freezable_power_efficient_wq); 5577 5578 wq_watchdog_init(); 5579 5580 return 0; 5581 } 5582 early_initcall(init_workqueues); 5583