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