x86/mm/srat: Print non-volatile flag in SRAT
[linux/fpc-iii.git] / kernel / workqueue.c
blob4c4f06176f748616b180254e94eda6bbed7dde25
1 /*
2 * kernel/workqueue.c - generic async execution with shared worker pool
4 * Copyright (C) 2002 Ingo Molnar
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>
12 * Made to use alloc_percpu by Christoph Lameter.
14 * Copyright (C) 2010 SUSE Linux Products GmbH
15 * Copyright (C) 2010 Tejun Heo <tj@kernel.org>
17 * This is the generic async execution mechanism. Work items as are
18 * executed in process context. The worker pool is shared and
19 * automatically managed. There are two worker pools for each CPU (one for
20 * normal work items and the other for high priority ones) and some extra
21 * pools for workqueues which are not bound to any specific CPU - the
22 * number of these backing pools is dynamic.
24 * Please read Documentation/workqueue.txt for details.
27 #include <linux/export.h>
28 #include <linux/kernel.h>
29 #include <linux/sched.h>
30 #include <linux/init.h>
31 #include <linux/signal.h>
32 #include <linux/completion.h>
33 #include <linux/workqueue.h>
34 #include <linux/slab.h>
35 #include <linux/cpu.h>
36 #include <linux/notifier.h>
37 #include <linux/kthread.h>
38 #include <linux/hardirq.h>
39 #include <linux/mempolicy.h>
40 #include <linux/freezer.h>
41 #include <linux/kallsyms.h>
42 #include <linux/debug_locks.h>
43 #include <linux/lockdep.h>
44 #include <linux/idr.h>
45 #include <linux/jhash.h>
46 #include <linux/hashtable.h>
47 #include <linux/rculist.h>
48 #include <linux/nodemask.h>
49 #include <linux/moduleparam.h>
50 #include <linux/uaccess.h>
52 #include "workqueue_internal.h"
54 enum {
56 * worker_pool flags
58 * A bound pool is either associated or disassociated with its CPU.
59 * While associated (!DISASSOCIATED), all workers are bound to the
60 * CPU and none has %WORKER_UNBOUND set and concurrency management
61 * is in effect.
63 * While DISASSOCIATED, the cpu may be offline and all workers have
64 * %WORKER_UNBOUND set and concurrency management disabled, and may
65 * be executing on any CPU. The pool behaves as an unbound one.
67 * Note that DISASSOCIATED should be flipped only while holding
68 * attach_mutex to avoid changing binding state while
69 * worker_attach_to_pool() is in progress.
71 POOL_DISASSOCIATED = 1 << 2, /* cpu can't serve workers */
73 /* worker flags */
74 WORKER_DIE = 1 << 1, /* die die die */
75 WORKER_IDLE = 1 << 2, /* is idle */
76 WORKER_PREP = 1 << 3, /* preparing to run works */
77 WORKER_CPU_INTENSIVE = 1 << 6, /* cpu intensive */
78 WORKER_UNBOUND = 1 << 7, /* worker is unbound */
79 WORKER_REBOUND = 1 << 8, /* worker was rebound */
81 WORKER_NOT_RUNNING = WORKER_PREP | WORKER_CPU_INTENSIVE |
82 WORKER_UNBOUND | WORKER_REBOUND,
84 NR_STD_WORKER_POOLS = 2, /* # standard pools per cpu */
86 UNBOUND_POOL_HASH_ORDER = 6, /* hashed by pool->attrs */
87 BUSY_WORKER_HASH_ORDER = 6, /* 64 pointers */
89 MAX_IDLE_WORKERS_RATIO = 4, /* 1/4 of busy can be idle */
90 IDLE_WORKER_TIMEOUT = 300 * HZ, /* keep idle ones for 5 mins */
92 MAYDAY_INITIAL_TIMEOUT = HZ / 100 >= 2 ? HZ / 100 : 2,
93 /* call for help after 10ms
94 (min two ticks) */
95 MAYDAY_INTERVAL = HZ / 10, /* and then every 100ms */
96 CREATE_COOLDOWN = HZ, /* time to breath after fail */
99 * Rescue workers are used only on emergencies and shared by
100 * all cpus. Give MIN_NICE.
102 RESCUER_NICE_LEVEL = MIN_NICE,
103 HIGHPRI_NICE_LEVEL = MIN_NICE,
105 WQ_NAME_LEN = 24,
109 * Structure fields follow one of the following exclusion rules.
111 * I: Modifiable by initialization/destruction paths and read-only for
112 * everyone else.
114 * P: Preemption protected. Disabling preemption is enough and should
115 * only be modified and accessed from the local cpu.
117 * L: pool->lock protected. Access with pool->lock held.
119 * X: During normal operation, modification requires pool->lock and should
120 * be done only from local cpu. Either disabling preemption on local
121 * cpu or grabbing pool->lock is enough for read access. If
122 * POOL_DISASSOCIATED is set, it's identical to L.
124 * A: pool->attach_mutex protected.
126 * PL: wq_pool_mutex protected.
128 * PR: wq_pool_mutex protected for writes. Sched-RCU protected for reads.
130 * PW: wq_pool_mutex and wq->mutex protected for writes. Either for reads.
132 * PWR: wq_pool_mutex and wq->mutex protected for writes. Either or
133 * sched-RCU for reads.
135 * WQ: wq->mutex protected.
137 * WR: wq->mutex protected for writes. Sched-RCU protected for reads.
139 * MD: wq_mayday_lock protected.
142 /* struct worker is defined in workqueue_internal.h */
144 struct worker_pool {
145 spinlock_t lock; /* the pool lock */
146 int cpu; /* I: the associated cpu */
147 int node; /* I: the associated node ID */
148 int id; /* I: pool ID */
149 unsigned int flags; /* X: flags */
151 struct list_head worklist; /* L: list of pending works */
152 int nr_workers; /* L: total number of workers */
154 /* nr_idle includes the ones off idle_list for rebinding */
155 int nr_idle; /* L: currently idle ones */
157 struct list_head idle_list; /* X: list of idle workers */
158 struct timer_list idle_timer; /* L: worker idle timeout */
159 struct timer_list mayday_timer; /* L: SOS timer for workers */
161 /* a workers is either on busy_hash or idle_list, or the manager */
162 DECLARE_HASHTABLE(busy_hash, BUSY_WORKER_HASH_ORDER);
163 /* L: hash of busy workers */
165 /* see manage_workers() for details on the two manager mutexes */
166 struct mutex manager_arb; /* manager arbitration */
167 struct worker *manager; /* L: purely informational */
168 struct mutex attach_mutex; /* attach/detach exclusion */
169 struct list_head workers; /* A: attached workers */
170 struct completion *detach_completion; /* all workers detached */
172 struct ida worker_ida; /* worker IDs for task name */
174 struct workqueue_attrs *attrs; /* I: worker attributes */
175 struct hlist_node hash_node; /* PL: unbound_pool_hash node */
176 int refcnt; /* PL: refcnt for unbound pools */
179 * The current concurrency level. As it's likely to be accessed
180 * from other CPUs during try_to_wake_up(), put it in a separate
181 * cacheline.
183 atomic_t nr_running ____cacheline_aligned_in_smp;
186 * Destruction of pool is sched-RCU protected to allow dereferences
187 * from get_work_pool().
189 struct rcu_head rcu;
190 } ____cacheline_aligned_in_smp;
193 * The per-pool workqueue. While queued, the lower WORK_STRUCT_FLAG_BITS
194 * of work_struct->data are used for flags and the remaining high bits
195 * point to the pwq; thus, pwqs need to be aligned at two's power of the
196 * number of flag bits.
198 struct pool_workqueue {
199 struct worker_pool *pool; /* I: the associated pool */
200 struct workqueue_struct *wq; /* I: the owning workqueue */
201 int work_color; /* L: current color */
202 int flush_color; /* L: flushing color */
203 int refcnt; /* L: reference count */
204 int nr_in_flight[WORK_NR_COLORS];
205 /* L: nr of in_flight works */
206 int nr_active; /* L: nr of active works */
207 int max_active; /* L: max active works */
208 struct list_head delayed_works; /* L: delayed works */
209 struct list_head pwqs_node; /* WR: node on wq->pwqs */
210 struct list_head mayday_node; /* MD: node on wq->maydays */
213 * Release of unbound pwq is punted to system_wq. See put_pwq()
214 * and pwq_unbound_release_workfn() for details. pool_workqueue
215 * itself is also sched-RCU protected so that the first pwq can be
216 * determined without grabbing wq->mutex.
218 struct work_struct unbound_release_work;
219 struct rcu_head rcu;
220 } __aligned(1 << WORK_STRUCT_FLAG_BITS);
223 * Structure used to wait for workqueue flush.
225 struct wq_flusher {
226 struct list_head list; /* WQ: list of flushers */
227 int flush_color; /* WQ: flush color waiting for */
228 struct completion done; /* flush completion */
231 struct wq_device;
234 * The externally visible workqueue. It relays the issued work items to
235 * the appropriate worker_pool through its pool_workqueues.
237 struct workqueue_struct {
238 struct list_head pwqs; /* WR: all pwqs of this wq */
239 struct list_head list; /* PR: list of all workqueues */
241 struct mutex mutex; /* protects this wq */
242 int work_color; /* WQ: current work color */
243 int flush_color; /* WQ: current flush color */
244 atomic_t nr_pwqs_to_flush; /* flush in progress */
245 struct wq_flusher *first_flusher; /* WQ: first flusher */
246 struct list_head flusher_queue; /* WQ: flush waiters */
247 struct list_head flusher_overflow; /* WQ: flush overflow list */
249 struct list_head maydays; /* MD: pwqs requesting rescue */
250 struct worker *rescuer; /* I: rescue worker */
252 int nr_drainers; /* WQ: drain in progress */
253 int saved_max_active; /* WQ: saved pwq max_active */
255 struct workqueue_attrs *unbound_attrs; /* PW: only for unbound wqs */
256 struct pool_workqueue *dfl_pwq; /* PW: only for unbound wqs */
258 #ifdef CONFIG_SYSFS
259 struct wq_device *wq_dev; /* I: for sysfs interface */
260 #endif
261 #ifdef CONFIG_LOCKDEP
262 struct lockdep_map lockdep_map;
263 #endif
264 char name[WQ_NAME_LEN]; /* I: workqueue name */
267 * Destruction of workqueue_struct is sched-RCU protected to allow
268 * walking the workqueues list without grabbing wq_pool_mutex.
269 * This is used to dump all workqueues from sysrq.
271 struct rcu_head rcu;
273 /* hot fields used during command issue, aligned to cacheline */
274 unsigned int flags ____cacheline_aligned; /* WQ: WQ_* flags */
275 struct pool_workqueue __percpu *cpu_pwqs; /* I: per-cpu pwqs */
276 struct pool_workqueue __rcu *numa_pwq_tbl[]; /* PWR: unbound pwqs indexed by node */
279 static struct kmem_cache *pwq_cache;
281 static cpumask_var_t *wq_numa_possible_cpumask;
282 /* possible CPUs of each node */
284 static bool wq_disable_numa;
285 module_param_named(disable_numa, wq_disable_numa, bool, 0444);
287 /* see the comment above the definition of WQ_POWER_EFFICIENT */
288 static bool wq_power_efficient = IS_ENABLED(CONFIG_WQ_POWER_EFFICIENT_DEFAULT);
289 module_param_named(power_efficient, wq_power_efficient, bool, 0444);
291 static bool wq_numa_enabled; /* unbound NUMA affinity enabled */
293 /* buf for wq_update_unbound_numa_attrs(), protected by CPU hotplug exclusion */
294 static struct workqueue_attrs *wq_update_unbound_numa_attrs_buf;
296 static DEFINE_MUTEX(wq_pool_mutex); /* protects pools and workqueues list */
297 static DEFINE_SPINLOCK(wq_mayday_lock); /* protects wq->maydays list */
299 static LIST_HEAD(workqueues); /* PR: list of all workqueues */
300 static bool workqueue_freezing; /* PL: have wqs started freezing? */
302 static cpumask_var_t wq_unbound_cpumask; /* PL: low level cpumask for all unbound wqs */
304 /* the per-cpu worker pools */
305 static DEFINE_PER_CPU_SHARED_ALIGNED(struct worker_pool [NR_STD_WORKER_POOLS],
306 cpu_worker_pools);
308 static DEFINE_IDR(worker_pool_idr); /* PR: idr of all pools */
310 /* PL: hash of all unbound pools keyed by pool->attrs */
311 static DEFINE_HASHTABLE(unbound_pool_hash, UNBOUND_POOL_HASH_ORDER);
313 /* I: attributes used when instantiating standard unbound pools on demand */
314 static struct workqueue_attrs *unbound_std_wq_attrs[NR_STD_WORKER_POOLS];
316 /* I: attributes used when instantiating ordered pools on demand */
317 static struct workqueue_attrs *ordered_wq_attrs[NR_STD_WORKER_POOLS];
319 struct workqueue_struct *system_wq __read_mostly;
320 EXPORT_SYMBOL(system_wq);
321 struct workqueue_struct *system_highpri_wq __read_mostly;
322 EXPORT_SYMBOL_GPL(system_highpri_wq);
323 struct workqueue_struct *system_long_wq __read_mostly;
324 EXPORT_SYMBOL_GPL(system_long_wq);
325 struct workqueue_struct *system_unbound_wq __read_mostly;
326 EXPORT_SYMBOL_GPL(system_unbound_wq);
327 struct workqueue_struct *system_freezable_wq __read_mostly;
328 EXPORT_SYMBOL_GPL(system_freezable_wq);
329 struct workqueue_struct *system_power_efficient_wq __read_mostly;
330 EXPORT_SYMBOL_GPL(system_power_efficient_wq);
331 struct workqueue_struct *system_freezable_power_efficient_wq __read_mostly;
332 EXPORT_SYMBOL_GPL(system_freezable_power_efficient_wq);
334 static int worker_thread(void *__worker);
335 static void workqueue_sysfs_unregister(struct workqueue_struct *wq);
337 #define CREATE_TRACE_POINTS
338 #include <trace/events/workqueue.h>
340 #define assert_rcu_or_pool_mutex() \
341 rcu_lockdep_assert(rcu_read_lock_sched_held() || \
342 lockdep_is_held(&wq_pool_mutex), \
343 "sched RCU or wq_pool_mutex should be held")
345 #define assert_rcu_or_wq_mutex(wq) \
346 rcu_lockdep_assert(rcu_read_lock_sched_held() || \
347 lockdep_is_held(&wq->mutex), \
348 "sched RCU or wq->mutex should be held")
350 #define assert_rcu_or_wq_mutex_or_pool_mutex(wq) \
351 rcu_lockdep_assert(rcu_read_lock_sched_held() || \
352 lockdep_is_held(&wq->mutex) || \
353 lockdep_is_held(&wq_pool_mutex), \
354 "sched RCU, wq->mutex or wq_pool_mutex should be held")
356 #define for_each_cpu_worker_pool(pool, cpu) \
357 for ((pool) = &per_cpu(cpu_worker_pools, cpu)[0]; \
358 (pool) < &per_cpu(cpu_worker_pools, cpu)[NR_STD_WORKER_POOLS]; \
359 (pool)++)
362 * for_each_pool - iterate through all worker_pools in the system
363 * @pool: iteration cursor
364 * @pi: integer used for iteration
366 * This must be called either with wq_pool_mutex held or sched RCU read
367 * locked. If the pool needs to be used beyond the locking in effect, the
368 * caller is responsible for guaranteeing that the pool stays online.
370 * The if/else clause exists only for the lockdep assertion and can be
371 * ignored.
373 #define for_each_pool(pool, pi) \
374 idr_for_each_entry(&worker_pool_idr, pool, pi) \
375 if (({ assert_rcu_or_pool_mutex(); false; })) { } \
376 else
379 * for_each_pool_worker - iterate through all workers of a worker_pool
380 * @worker: iteration cursor
381 * @pool: worker_pool to iterate workers of
383 * This must be called with @pool->attach_mutex.
385 * The if/else clause exists only for the lockdep assertion and can be
386 * ignored.
388 #define for_each_pool_worker(worker, pool) \
389 list_for_each_entry((worker), &(pool)->workers, node) \
390 if (({ lockdep_assert_held(&pool->attach_mutex); false; })) { } \
391 else
394 * for_each_pwq - iterate through all pool_workqueues of the specified workqueue
395 * @pwq: iteration cursor
396 * @wq: the target workqueue
398 * This must be called either with wq->mutex held or sched RCU read locked.
399 * If the pwq needs to be used beyond the locking in effect, the caller is
400 * responsible for guaranteeing that the pwq stays online.
402 * The if/else clause exists only for the lockdep assertion and can be
403 * ignored.
405 #define for_each_pwq(pwq, wq) \
406 list_for_each_entry_rcu((pwq), &(wq)->pwqs, pwqs_node) \
407 if (({ assert_rcu_or_wq_mutex(wq); false; })) { } \
408 else
410 #ifdef CONFIG_DEBUG_OBJECTS_WORK
412 static struct debug_obj_descr work_debug_descr;
414 static void *work_debug_hint(void *addr)
416 return ((struct work_struct *) addr)->func;
420 * fixup_init is called when:
421 * - an active object is initialized
423 static int work_fixup_init(void *addr, enum debug_obj_state state)
425 struct work_struct *work = addr;
427 switch (state) {
428 case ODEBUG_STATE_ACTIVE:
429 cancel_work_sync(work);
430 debug_object_init(work, &work_debug_descr);
431 return 1;
432 default:
433 return 0;
438 * fixup_activate is called when:
439 * - an active object is activated
440 * - an unknown object is activated (might be a statically initialized object)
442 static int work_fixup_activate(void *addr, enum debug_obj_state state)
444 struct work_struct *work = addr;
446 switch (state) {
448 case ODEBUG_STATE_NOTAVAILABLE:
450 * This is not really a fixup. The work struct was
451 * statically initialized. We just make sure that it
452 * is tracked in the object tracker.
454 if (test_bit(WORK_STRUCT_STATIC_BIT, work_data_bits(work))) {
455 debug_object_init(work, &work_debug_descr);
456 debug_object_activate(work, &work_debug_descr);
457 return 0;
459 WARN_ON_ONCE(1);
460 return 0;
462 case ODEBUG_STATE_ACTIVE:
463 WARN_ON(1);
465 default:
466 return 0;
471 * fixup_free is called when:
472 * - an active object is freed
474 static int work_fixup_free(void *addr, enum debug_obj_state state)
476 struct work_struct *work = addr;
478 switch (state) {
479 case ODEBUG_STATE_ACTIVE:
480 cancel_work_sync(work);
481 debug_object_free(work, &work_debug_descr);
482 return 1;
483 default:
484 return 0;
488 static struct debug_obj_descr work_debug_descr = {
489 .name = "work_struct",
490 .debug_hint = work_debug_hint,
491 .fixup_init = work_fixup_init,
492 .fixup_activate = work_fixup_activate,
493 .fixup_free = work_fixup_free,
496 static inline void debug_work_activate(struct work_struct *work)
498 debug_object_activate(work, &work_debug_descr);
501 static inline void debug_work_deactivate(struct work_struct *work)
503 debug_object_deactivate(work, &work_debug_descr);
506 void __init_work(struct work_struct *work, int onstack)
508 if (onstack)
509 debug_object_init_on_stack(work, &work_debug_descr);
510 else
511 debug_object_init(work, &work_debug_descr);
513 EXPORT_SYMBOL_GPL(__init_work);
515 void destroy_work_on_stack(struct work_struct *work)
517 debug_object_free(work, &work_debug_descr);
519 EXPORT_SYMBOL_GPL(destroy_work_on_stack);
521 void destroy_delayed_work_on_stack(struct delayed_work *work)
523 destroy_timer_on_stack(&work->timer);
524 debug_object_free(&work->work, &work_debug_descr);
526 EXPORT_SYMBOL_GPL(destroy_delayed_work_on_stack);
528 #else
529 static inline void debug_work_activate(struct work_struct *work) { }
530 static inline void debug_work_deactivate(struct work_struct *work) { }
531 #endif
534 * worker_pool_assign_id - allocate ID and assing it to @pool
535 * @pool: the pool pointer of interest
537 * Returns 0 if ID in [0, WORK_OFFQ_POOL_NONE) is allocated and assigned
538 * successfully, -errno on failure.
540 static int worker_pool_assign_id(struct worker_pool *pool)
542 int ret;
544 lockdep_assert_held(&wq_pool_mutex);
546 ret = idr_alloc(&worker_pool_idr, pool, 0, WORK_OFFQ_POOL_NONE,
547 GFP_KERNEL);
548 if (ret >= 0) {
549 pool->id = ret;
550 return 0;
552 return ret;
556 * unbound_pwq_by_node - return the unbound pool_workqueue for the given node
557 * @wq: the target workqueue
558 * @node: the node ID
560 * This must be called with any of wq_pool_mutex, wq->mutex or sched RCU
561 * read locked.
562 * If the pwq needs to be used beyond the locking in effect, the caller is
563 * responsible for guaranteeing that the pwq stays online.
565 * Return: The unbound pool_workqueue for @node.
567 static struct pool_workqueue *unbound_pwq_by_node(struct workqueue_struct *wq,
568 int node)
570 assert_rcu_or_wq_mutex_or_pool_mutex(wq);
571 return rcu_dereference_raw(wq->numa_pwq_tbl[node]);
574 static unsigned int work_color_to_flags(int color)
576 return color << WORK_STRUCT_COLOR_SHIFT;
579 static int get_work_color(struct work_struct *work)
581 return (*work_data_bits(work) >> WORK_STRUCT_COLOR_SHIFT) &
582 ((1 << WORK_STRUCT_COLOR_BITS) - 1);
585 static int work_next_color(int color)
587 return (color + 1) % WORK_NR_COLORS;
591 * While queued, %WORK_STRUCT_PWQ is set and non flag bits of a work's data
592 * contain the pointer to the queued pwq. Once execution starts, the flag
593 * is cleared and the high bits contain OFFQ flags and pool ID.
595 * set_work_pwq(), set_work_pool_and_clear_pending(), mark_work_canceling()
596 * and clear_work_data() can be used to set the pwq, pool or clear
597 * work->data. These functions should only be called while the work is
598 * owned - ie. while the PENDING bit is set.
600 * get_work_pool() and get_work_pwq() can be used to obtain the pool or pwq
601 * corresponding to a work. Pool is available once the work has been
602 * queued anywhere after initialization until it is sync canceled. pwq is
603 * available only while the work item is queued.
605 * %WORK_OFFQ_CANCELING is used to mark a work item which is being
606 * canceled. While being canceled, a work item may have its PENDING set
607 * but stay off timer and worklist for arbitrarily long and nobody should
608 * try to steal the PENDING bit.
610 static inline void set_work_data(struct work_struct *work, unsigned long data,
611 unsigned long flags)
613 WARN_ON_ONCE(!work_pending(work));
614 atomic_long_set(&work->data, data | flags | work_static(work));
617 static void set_work_pwq(struct work_struct *work, struct pool_workqueue *pwq,
618 unsigned long extra_flags)
620 set_work_data(work, (unsigned long)pwq,
621 WORK_STRUCT_PENDING | WORK_STRUCT_PWQ | extra_flags);
624 static void set_work_pool_and_keep_pending(struct work_struct *work,
625 int pool_id)
627 set_work_data(work, (unsigned long)pool_id << WORK_OFFQ_POOL_SHIFT,
628 WORK_STRUCT_PENDING);
631 static void set_work_pool_and_clear_pending(struct work_struct *work,
632 int pool_id)
635 * The following wmb is paired with the implied mb in
636 * test_and_set_bit(PENDING) and ensures all updates to @work made
637 * here are visible to and precede any updates by the next PENDING
638 * owner.
640 smp_wmb();
641 set_work_data(work, (unsigned long)pool_id << WORK_OFFQ_POOL_SHIFT, 0);
644 static void clear_work_data(struct work_struct *work)
646 smp_wmb(); /* see set_work_pool_and_clear_pending() */
647 set_work_data(work, WORK_STRUCT_NO_POOL, 0);
650 static struct pool_workqueue *get_work_pwq(struct work_struct *work)
652 unsigned long data = atomic_long_read(&work->data);
654 if (data & WORK_STRUCT_PWQ)
655 return (void *)(data & WORK_STRUCT_WQ_DATA_MASK);
656 else
657 return NULL;
661 * get_work_pool - return the worker_pool a given work was associated with
662 * @work: the work item of interest
664 * Pools are created and destroyed under wq_pool_mutex, and allows read
665 * access under sched-RCU read lock. As such, this function should be
666 * called under wq_pool_mutex or with preemption disabled.
668 * All fields of the returned pool are accessible as long as the above
669 * mentioned locking is in effect. If the returned pool needs to be used
670 * beyond the critical section, the caller is responsible for ensuring the
671 * returned pool is and stays online.
673 * Return: The worker_pool @work was last associated with. %NULL if none.
675 static struct worker_pool *get_work_pool(struct work_struct *work)
677 unsigned long data = atomic_long_read(&work->data);
678 int pool_id;
680 assert_rcu_or_pool_mutex();
682 if (data & WORK_STRUCT_PWQ)
683 return ((struct pool_workqueue *)
684 (data & WORK_STRUCT_WQ_DATA_MASK))->pool;
686 pool_id = data >> WORK_OFFQ_POOL_SHIFT;
687 if (pool_id == WORK_OFFQ_POOL_NONE)
688 return NULL;
690 return idr_find(&worker_pool_idr, pool_id);
694 * get_work_pool_id - return the worker pool ID a given work is associated with
695 * @work: the work item of interest
697 * Return: The worker_pool ID @work was last associated with.
698 * %WORK_OFFQ_POOL_NONE if none.
700 static int get_work_pool_id(struct work_struct *work)
702 unsigned long data = atomic_long_read(&work->data);
704 if (data & WORK_STRUCT_PWQ)
705 return ((struct pool_workqueue *)
706 (data & WORK_STRUCT_WQ_DATA_MASK))->pool->id;
708 return data >> WORK_OFFQ_POOL_SHIFT;
711 static void mark_work_canceling(struct work_struct *work)
713 unsigned long pool_id = get_work_pool_id(work);
715 pool_id <<= WORK_OFFQ_POOL_SHIFT;
716 set_work_data(work, pool_id | WORK_OFFQ_CANCELING, WORK_STRUCT_PENDING);
719 static bool work_is_canceling(struct work_struct *work)
721 unsigned long data = atomic_long_read(&work->data);
723 return !(data & WORK_STRUCT_PWQ) && (data & WORK_OFFQ_CANCELING);
727 * Policy functions. These define the policies on how the global worker
728 * pools are managed. Unless noted otherwise, these functions assume that
729 * they're being called with pool->lock held.
732 static bool __need_more_worker(struct worker_pool *pool)
734 return !atomic_read(&pool->nr_running);
738 * Need to wake up a worker? Called from anything but currently
739 * running workers.
741 * Note that, because unbound workers never contribute to nr_running, this
742 * function will always return %true for unbound pools as long as the
743 * worklist isn't empty.
745 static bool need_more_worker(struct worker_pool *pool)
747 return !list_empty(&pool->worklist) && __need_more_worker(pool);
750 /* Can I start working? Called from busy but !running workers. */
751 static bool may_start_working(struct worker_pool *pool)
753 return pool->nr_idle;
756 /* Do I need to keep working? Called from currently running workers. */
757 static bool keep_working(struct worker_pool *pool)
759 return !list_empty(&pool->worklist) &&
760 atomic_read(&pool->nr_running) <= 1;
763 /* Do we need a new worker? Called from manager. */
764 static bool need_to_create_worker(struct worker_pool *pool)
766 return need_more_worker(pool) && !may_start_working(pool);
769 /* Do we have too many workers and should some go away? */
770 static bool too_many_workers(struct worker_pool *pool)
772 bool managing = mutex_is_locked(&pool->manager_arb);
773 int nr_idle = pool->nr_idle + managing; /* manager is considered idle */
774 int nr_busy = pool->nr_workers - nr_idle;
776 return nr_idle > 2 && (nr_idle - 2) * MAX_IDLE_WORKERS_RATIO >= nr_busy;
780 * Wake up functions.
783 /* Return the first idle worker. Safe with preemption disabled */
784 static struct worker *first_idle_worker(struct worker_pool *pool)
786 if (unlikely(list_empty(&pool->idle_list)))
787 return NULL;
789 return list_first_entry(&pool->idle_list, struct worker, entry);
793 * wake_up_worker - wake up an idle worker
794 * @pool: worker pool to wake worker from
796 * Wake up the first idle worker of @pool.
798 * CONTEXT:
799 * spin_lock_irq(pool->lock).
801 static void wake_up_worker(struct worker_pool *pool)
803 struct worker *worker = first_idle_worker(pool);
805 if (likely(worker))
806 wake_up_process(worker->task);
810 * wq_worker_waking_up - a worker is waking up
811 * @task: task waking up
812 * @cpu: CPU @task is waking up to
814 * This function is called during try_to_wake_up() when a worker is
815 * being awoken.
817 * CONTEXT:
818 * spin_lock_irq(rq->lock)
820 void wq_worker_waking_up(struct task_struct *task, int cpu)
822 struct worker *worker = kthread_data(task);
824 if (!(worker->flags & WORKER_NOT_RUNNING)) {
825 WARN_ON_ONCE(worker->pool->cpu != cpu);
826 atomic_inc(&worker->pool->nr_running);
831 * wq_worker_sleeping - a worker is going to sleep
832 * @task: task going to sleep
833 * @cpu: CPU in question, must be the current CPU number
835 * This function is called during schedule() when a busy worker is
836 * going to sleep. Worker on the same cpu can be woken up by
837 * returning pointer to its task.
839 * CONTEXT:
840 * spin_lock_irq(rq->lock)
842 * Return:
843 * Worker task on @cpu to wake up, %NULL if none.
845 struct task_struct *wq_worker_sleeping(struct task_struct *task, int cpu)
847 struct worker *worker = kthread_data(task), *to_wakeup = NULL;
848 struct worker_pool *pool;
851 * Rescuers, which may not have all the fields set up like normal
852 * workers, also reach here, let's not access anything before
853 * checking NOT_RUNNING.
855 if (worker->flags & WORKER_NOT_RUNNING)
856 return NULL;
858 pool = worker->pool;
860 /* this can only happen on the local cpu */
861 if (WARN_ON_ONCE(cpu != raw_smp_processor_id() || pool->cpu != cpu))
862 return NULL;
865 * The counterpart of the following dec_and_test, implied mb,
866 * worklist not empty test sequence is in insert_work().
867 * Please read comment there.
869 * NOT_RUNNING is clear. This means that we're bound to and
870 * running on the local cpu w/ rq lock held and preemption
871 * disabled, which in turn means that none else could be
872 * manipulating idle_list, so dereferencing idle_list without pool
873 * lock is safe.
875 if (atomic_dec_and_test(&pool->nr_running) &&
876 !list_empty(&pool->worklist))
877 to_wakeup = first_idle_worker(pool);
878 return to_wakeup ? to_wakeup->task : NULL;
882 * worker_set_flags - set worker flags and adjust nr_running accordingly
883 * @worker: self
884 * @flags: flags to set
886 * Set @flags in @worker->flags and adjust nr_running accordingly.
888 * CONTEXT:
889 * spin_lock_irq(pool->lock)
891 static inline void worker_set_flags(struct worker *worker, unsigned int flags)
893 struct worker_pool *pool = worker->pool;
895 WARN_ON_ONCE(worker->task != current);
897 /* If transitioning into NOT_RUNNING, adjust nr_running. */
898 if ((flags & WORKER_NOT_RUNNING) &&
899 !(worker->flags & WORKER_NOT_RUNNING)) {
900 atomic_dec(&pool->nr_running);
903 worker->flags |= flags;
907 * worker_clr_flags - clear worker flags and adjust nr_running accordingly
908 * @worker: self
909 * @flags: flags to clear
911 * Clear @flags in @worker->flags and adjust nr_running accordingly.
913 * CONTEXT:
914 * spin_lock_irq(pool->lock)
916 static inline void worker_clr_flags(struct worker *worker, unsigned int flags)
918 struct worker_pool *pool = worker->pool;
919 unsigned int oflags = worker->flags;
921 WARN_ON_ONCE(worker->task != current);
923 worker->flags &= ~flags;
926 * If transitioning out of NOT_RUNNING, increment nr_running. Note
927 * that the nested NOT_RUNNING is not a noop. NOT_RUNNING is mask
928 * of multiple flags, not a single flag.
930 if ((flags & WORKER_NOT_RUNNING) && (oflags & WORKER_NOT_RUNNING))
931 if (!(worker->flags & WORKER_NOT_RUNNING))
932 atomic_inc(&pool->nr_running);
936 * find_worker_executing_work - find worker which is executing a work
937 * @pool: pool of interest
938 * @work: work to find worker for
940 * Find a worker which is executing @work on @pool by searching
941 * @pool->busy_hash which is keyed by the address of @work. For a worker
942 * to match, its current execution should match the address of @work and
943 * its work function. This is to avoid unwanted dependency between
944 * unrelated work executions through a work item being recycled while still
945 * being executed.
947 * This is a bit tricky. A work item may be freed once its execution
948 * starts and nothing prevents the freed area from being recycled for
949 * another work item. If the same work item address ends up being reused
950 * before the original execution finishes, workqueue will identify the
951 * recycled work item as currently executing and make it wait until the
952 * current execution finishes, introducing an unwanted dependency.
954 * This function checks the work item address and work function to avoid
955 * false positives. Note that this isn't complete as one may construct a
956 * work function which can introduce dependency onto itself through a
957 * recycled work item. Well, if somebody wants to shoot oneself in the
958 * foot that badly, there's only so much we can do, and if such deadlock
959 * actually occurs, it should be easy to locate the culprit work function.
961 * CONTEXT:
962 * spin_lock_irq(pool->lock).
964 * Return:
965 * Pointer to worker which is executing @work if found, %NULL
966 * otherwise.
968 static struct worker *find_worker_executing_work(struct worker_pool *pool,
969 struct work_struct *work)
971 struct worker *worker;
973 hash_for_each_possible(pool->busy_hash, worker, hentry,
974 (unsigned long)work)
975 if (worker->current_work == work &&
976 worker->current_func == work->func)
977 return worker;
979 return NULL;
983 * move_linked_works - move linked works to a list
984 * @work: start of series of works to be scheduled
985 * @head: target list to append @work to
986 * @nextp: out parameter for nested worklist walking
988 * Schedule linked works starting from @work to @head. Work series to
989 * be scheduled starts at @work and includes any consecutive work with
990 * WORK_STRUCT_LINKED set in its predecessor.
992 * If @nextp is not NULL, it's updated to point to the next work of
993 * the last scheduled work. This allows move_linked_works() to be
994 * nested inside outer list_for_each_entry_safe().
996 * CONTEXT:
997 * spin_lock_irq(pool->lock).
999 static void move_linked_works(struct work_struct *work, struct list_head *head,
1000 struct work_struct **nextp)
1002 struct work_struct *n;
1005 * Linked worklist will always end before the end of the list,
1006 * use NULL for list head.
1008 list_for_each_entry_safe_from(work, n, NULL, entry) {
1009 list_move_tail(&work->entry, head);
1010 if (!(*work_data_bits(work) & WORK_STRUCT_LINKED))
1011 break;
1015 * If we're already inside safe list traversal and have moved
1016 * multiple works to the scheduled queue, the next position
1017 * needs to be updated.
1019 if (nextp)
1020 *nextp = n;
1024 * get_pwq - get an extra reference on the specified pool_workqueue
1025 * @pwq: pool_workqueue to get
1027 * Obtain an extra reference on @pwq. The caller should guarantee that
1028 * @pwq has positive refcnt and be holding the matching pool->lock.
1030 static void get_pwq(struct pool_workqueue *pwq)
1032 lockdep_assert_held(&pwq->pool->lock);
1033 WARN_ON_ONCE(pwq->refcnt <= 0);
1034 pwq->refcnt++;
1038 * put_pwq - put a pool_workqueue reference
1039 * @pwq: pool_workqueue to put
1041 * Drop a reference of @pwq. If its refcnt reaches zero, schedule its
1042 * destruction. The caller should be holding the matching pool->lock.
1044 static void put_pwq(struct pool_workqueue *pwq)
1046 lockdep_assert_held(&pwq->pool->lock);
1047 if (likely(--pwq->refcnt))
1048 return;
1049 if (WARN_ON_ONCE(!(pwq->wq->flags & WQ_UNBOUND)))
1050 return;
1052 * @pwq can't be released under pool->lock, bounce to
1053 * pwq_unbound_release_workfn(). This never recurses on the same
1054 * pool->lock as this path is taken only for unbound workqueues and
1055 * the release work item is scheduled on a per-cpu workqueue. To
1056 * avoid lockdep warning, unbound pool->locks are given lockdep
1057 * subclass of 1 in get_unbound_pool().
1059 schedule_work(&pwq->unbound_release_work);
1063 * put_pwq_unlocked - put_pwq() with surrounding pool lock/unlock
1064 * @pwq: pool_workqueue to put (can be %NULL)
1066 * put_pwq() with locking. This function also allows %NULL @pwq.
1068 static void put_pwq_unlocked(struct pool_workqueue *pwq)
1070 if (pwq) {
1072 * As both pwqs and pools are sched-RCU protected, the
1073 * following lock operations are safe.
1075 spin_lock_irq(&pwq->pool->lock);
1076 put_pwq(pwq);
1077 spin_unlock_irq(&pwq->pool->lock);
1081 static void pwq_activate_delayed_work(struct work_struct *work)
1083 struct pool_workqueue *pwq = get_work_pwq(work);
1085 trace_workqueue_activate_work(work);
1086 move_linked_works(work, &pwq->pool->worklist, NULL);
1087 __clear_bit(WORK_STRUCT_DELAYED_BIT, work_data_bits(work));
1088 pwq->nr_active++;
1091 static void pwq_activate_first_delayed(struct pool_workqueue *pwq)
1093 struct work_struct *work = list_first_entry(&pwq->delayed_works,
1094 struct work_struct, entry);
1096 pwq_activate_delayed_work(work);
1100 * pwq_dec_nr_in_flight - decrement pwq's nr_in_flight
1101 * @pwq: pwq of interest
1102 * @color: color of work which left the queue
1104 * A work either has completed or is removed from pending queue,
1105 * decrement nr_in_flight of its pwq and handle workqueue flushing.
1107 * CONTEXT:
1108 * spin_lock_irq(pool->lock).
1110 static void pwq_dec_nr_in_flight(struct pool_workqueue *pwq, int color)
1112 /* uncolored work items don't participate in flushing or nr_active */
1113 if (color == WORK_NO_COLOR)
1114 goto out_put;
1116 pwq->nr_in_flight[color]--;
1118 pwq->nr_active--;
1119 if (!list_empty(&pwq->delayed_works)) {
1120 /* one down, submit a delayed one */
1121 if (pwq->nr_active < pwq->max_active)
1122 pwq_activate_first_delayed(pwq);
1125 /* is flush in progress and are we at the flushing tip? */
1126 if (likely(pwq->flush_color != color))
1127 goto out_put;
1129 /* are there still in-flight works? */
1130 if (pwq->nr_in_flight[color])
1131 goto out_put;
1133 /* this pwq is done, clear flush_color */
1134 pwq->flush_color = -1;
1137 * If this was the last pwq, wake up the first flusher. It
1138 * will handle the rest.
1140 if (atomic_dec_and_test(&pwq->wq->nr_pwqs_to_flush))
1141 complete(&pwq->wq->first_flusher->done);
1142 out_put:
1143 put_pwq(pwq);
1147 * try_to_grab_pending - steal work item from worklist and disable irq
1148 * @work: work item to steal
1149 * @is_dwork: @work is a delayed_work
1150 * @flags: place to store irq state
1152 * Try to grab PENDING bit of @work. This function can handle @work in any
1153 * stable state - idle, on timer or on worklist.
1155 * Return:
1156 * 1 if @work was pending and we successfully stole PENDING
1157 * 0 if @work was idle and we claimed PENDING
1158 * -EAGAIN if PENDING couldn't be grabbed at the moment, safe to busy-retry
1159 * -ENOENT if someone else is canceling @work, this state may persist
1160 * for arbitrarily long
1162 * Note:
1163 * On >= 0 return, the caller owns @work's PENDING bit. To avoid getting
1164 * interrupted while holding PENDING and @work off queue, irq must be
1165 * disabled on entry. This, combined with delayed_work->timer being
1166 * irqsafe, ensures that we return -EAGAIN for finite short period of time.
1168 * On successful return, >= 0, irq is disabled and the caller is
1169 * responsible for releasing it using local_irq_restore(*@flags).
1171 * This function is safe to call from any context including IRQ handler.
1173 static int try_to_grab_pending(struct work_struct *work, bool is_dwork,
1174 unsigned long *flags)
1176 struct worker_pool *pool;
1177 struct pool_workqueue *pwq;
1179 local_irq_save(*flags);
1181 /* try to steal the timer if it exists */
1182 if (is_dwork) {
1183 struct delayed_work *dwork = to_delayed_work(work);
1186 * dwork->timer is irqsafe. If del_timer() fails, it's
1187 * guaranteed that the timer is not queued anywhere and not
1188 * running on the local CPU.
1190 if (likely(del_timer(&dwork->timer)))
1191 return 1;
1194 /* try to claim PENDING the normal way */
1195 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work)))
1196 return 0;
1199 * The queueing is in progress, or it is already queued. Try to
1200 * steal it from ->worklist without clearing WORK_STRUCT_PENDING.
1202 pool = get_work_pool(work);
1203 if (!pool)
1204 goto fail;
1206 spin_lock(&pool->lock);
1208 * work->data is guaranteed to point to pwq only while the work
1209 * item is queued on pwq->wq, and both updating work->data to point
1210 * to pwq on queueing and to pool on dequeueing are done under
1211 * pwq->pool->lock. This in turn guarantees that, if work->data
1212 * points to pwq which is associated with a locked pool, the work
1213 * item is currently queued on that pool.
1215 pwq = get_work_pwq(work);
1216 if (pwq && pwq->pool == pool) {
1217 debug_work_deactivate(work);
1220 * A delayed work item cannot be grabbed directly because
1221 * it might have linked NO_COLOR work items which, if left
1222 * on the delayed_list, will confuse pwq->nr_active
1223 * management later on and cause stall. Make sure the work
1224 * item is activated before grabbing.
1226 if (*work_data_bits(work) & WORK_STRUCT_DELAYED)
1227 pwq_activate_delayed_work(work);
1229 list_del_init(&work->entry);
1230 pwq_dec_nr_in_flight(pwq, get_work_color(work));
1232 /* work->data points to pwq iff queued, point to pool */
1233 set_work_pool_and_keep_pending(work, pool->id);
1235 spin_unlock(&pool->lock);
1236 return 1;
1238 spin_unlock(&pool->lock);
1239 fail:
1240 local_irq_restore(*flags);
1241 if (work_is_canceling(work))
1242 return -ENOENT;
1243 cpu_relax();
1244 return -EAGAIN;
1248 * insert_work - insert a work into a pool
1249 * @pwq: pwq @work belongs to
1250 * @work: work to insert
1251 * @head: insertion point
1252 * @extra_flags: extra WORK_STRUCT_* flags to set
1254 * Insert @work which belongs to @pwq after @head. @extra_flags is or'd to
1255 * work_struct flags.
1257 * CONTEXT:
1258 * spin_lock_irq(pool->lock).
1260 static void insert_work(struct pool_workqueue *pwq, struct work_struct *work,
1261 struct list_head *head, unsigned int extra_flags)
1263 struct worker_pool *pool = pwq->pool;
1265 /* we own @work, set data and link */
1266 set_work_pwq(work, pwq, extra_flags);
1267 list_add_tail(&work->entry, head);
1268 get_pwq(pwq);
1271 * Ensure either wq_worker_sleeping() sees the above
1272 * list_add_tail() or we see zero nr_running to avoid workers lying
1273 * around lazily while there are works to be processed.
1275 smp_mb();
1277 if (__need_more_worker(pool))
1278 wake_up_worker(pool);
1282 * Test whether @work is being queued from another work executing on the
1283 * same workqueue.
1285 static bool is_chained_work(struct workqueue_struct *wq)
1287 struct worker *worker;
1289 worker = current_wq_worker();
1291 * Return %true iff I'm a worker execuing a work item on @wq. If
1292 * I'm @worker, it's safe to dereference it without locking.
1294 return worker && worker->current_pwq->wq == wq;
1297 static void __queue_work(int cpu, struct workqueue_struct *wq,
1298 struct work_struct *work)
1300 struct pool_workqueue *pwq;
1301 struct worker_pool *last_pool;
1302 struct list_head *worklist;
1303 unsigned int work_flags;
1304 unsigned int req_cpu = cpu;
1307 * While a work item is PENDING && off queue, a task trying to
1308 * steal the PENDING will busy-loop waiting for it to either get
1309 * queued or lose PENDING. Grabbing PENDING and queueing should
1310 * happen with IRQ disabled.
1312 WARN_ON_ONCE(!irqs_disabled());
1314 debug_work_activate(work);
1316 /* if draining, only works from the same workqueue are allowed */
1317 if (unlikely(wq->flags & __WQ_DRAINING) &&
1318 WARN_ON_ONCE(!is_chained_work(wq)))
1319 return;
1320 retry:
1321 if (req_cpu == WORK_CPU_UNBOUND)
1322 cpu = raw_smp_processor_id();
1324 /* pwq which will be used unless @work is executing elsewhere */
1325 if (!(wq->flags & WQ_UNBOUND))
1326 pwq = per_cpu_ptr(wq->cpu_pwqs, cpu);
1327 else
1328 pwq = unbound_pwq_by_node(wq, cpu_to_node(cpu));
1331 * If @work was previously on a different pool, it might still be
1332 * running there, in which case the work needs to be queued on that
1333 * pool to guarantee non-reentrancy.
1335 last_pool = get_work_pool(work);
1336 if (last_pool && last_pool != pwq->pool) {
1337 struct worker *worker;
1339 spin_lock(&last_pool->lock);
1341 worker = find_worker_executing_work(last_pool, work);
1343 if (worker && worker->current_pwq->wq == wq) {
1344 pwq = worker->current_pwq;
1345 } else {
1346 /* meh... not running there, queue here */
1347 spin_unlock(&last_pool->lock);
1348 spin_lock(&pwq->pool->lock);
1350 } else {
1351 spin_lock(&pwq->pool->lock);
1355 * pwq is determined and locked. For unbound pools, we could have
1356 * raced with pwq release and it could already be dead. If its
1357 * refcnt is zero, repeat pwq selection. Note that pwqs never die
1358 * without another pwq replacing it in the numa_pwq_tbl or while
1359 * work items are executing on it, so the retrying is guaranteed to
1360 * make forward-progress.
1362 if (unlikely(!pwq->refcnt)) {
1363 if (wq->flags & WQ_UNBOUND) {
1364 spin_unlock(&pwq->pool->lock);
1365 cpu_relax();
1366 goto retry;
1368 /* oops */
1369 WARN_ONCE(true, "workqueue: per-cpu pwq for %s on cpu%d has 0 refcnt",
1370 wq->name, cpu);
1373 /* pwq determined, queue */
1374 trace_workqueue_queue_work(req_cpu, pwq, work);
1376 if (WARN_ON(!list_empty(&work->entry))) {
1377 spin_unlock(&pwq->pool->lock);
1378 return;
1381 pwq->nr_in_flight[pwq->work_color]++;
1382 work_flags = work_color_to_flags(pwq->work_color);
1384 if (likely(pwq->nr_active < pwq->max_active)) {
1385 trace_workqueue_activate_work(work);
1386 pwq->nr_active++;
1387 worklist = &pwq->pool->worklist;
1388 } else {
1389 work_flags |= WORK_STRUCT_DELAYED;
1390 worklist = &pwq->delayed_works;
1393 insert_work(pwq, work, worklist, work_flags);
1395 spin_unlock(&pwq->pool->lock);
1399 * queue_work_on - queue work on specific cpu
1400 * @cpu: CPU number to execute work on
1401 * @wq: workqueue to use
1402 * @work: work to queue
1404 * We queue the work to a specific CPU, the caller must ensure it
1405 * can't go away.
1407 * Return: %false if @work was already on a queue, %true otherwise.
1409 bool queue_work_on(int cpu, struct workqueue_struct *wq,
1410 struct work_struct *work)
1412 bool ret = false;
1413 unsigned long flags;
1415 local_irq_save(flags);
1417 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1418 __queue_work(cpu, wq, work);
1419 ret = true;
1422 local_irq_restore(flags);
1423 return ret;
1425 EXPORT_SYMBOL(queue_work_on);
1427 void delayed_work_timer_fn(unsigned long __data)
1429 struct delayed_work *dwork = (struct delayed_work *)__data;
1431 /* should have been called from irqsafe timer with irq already off */
1432 __queue_work(dwork->cpu, dwork->wq, &dwork->work);
1434 EXPORT_SYMBOL(delayed_work_timer_fn);
1436 static void __queue_delayed_work(int cpu, struct workqueue_struct *wq,
1437 struct delayed_work *dwork, unsigned long delay)
1439 struct timer_list *timer = &dwork->timer;
1440 struct work_struct *work = &dwork->work;
1442 WARN_ON_ONCE(timer->function != delayed_work_timer_fn ||
1443 timer->data != (unsigned long)dwork);
1444 WARN_ON_ONCE(timer_pending(timer));
1445 WARN_ON_ONCE(!list_empty(&work->entry));
1448 * If @delay is 0, queue @dwork->work immediately. This is for
1449 * both optimization and correctness. The earliest @timer can
1450 * expire is on the closest next tick and delayed_work users depend
1451 * on that there's no such delay when @delay is 0.
1453 if (!delay) {
1454 __queue_work(cpu, wq, &dwork->work);
1455 return;
1458 timer_stats_timer_set_start_info(&dwork->timer);
1460 dwork->wq = wq;
1461 dwork->cpu = cpu;
1462 timer->expires = jiffies + delay;
1464 if (unlikely(cpu != WORK_CPU_UNBOUND))
1465 add_timer_on(timer, cpu);
1466 else
1467 add_timer(timer);
1471 * queue_delayed_work_on - queue work on specific CPU after delay
1472 * @cpu: CPU number to execute work on
1473 * @wq: workqueue to use
1474 * @dwork: work to queue
1475 * @delay: number of jiffies to wait before queueing
1477 * Return: %false if @work was already on a queue, %true otherwise. If
1478 * @delay is zero and @dwork is idle, it will be scheduled for immediate
1479 * execution.
1481 bool queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
1482 struct delayed_work *dwork, unsigned long delay)
1484 struct work_struct *work = &dwork->work;
1485 bool ret = false;
1486 unsigned long flags;
1488 /* read the comment in __queue_work() */
1489 local_irq_save(flags);
1491 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1492 __queue_delayed_work(cpu, wq, dwork, delay);
1493 ret = true;
1496 local_irq_restore(flags);
1497 return ret;
1499 EXPORT_SYMBOL(queue_delayed_work_on);
1502 * mod_delayed_work_on - modify delay of or queue a delayed work on specific CPU
1503 * @cpu: CPU number to execute work on
1504 * @wq: workqueue to use
1505 * @dwork: work to queue
1506 * @delay: number of jiffies to wait before queueing
1508 * If @dwork is idle, equivalent to queue_delayed_work_on(); otherwise,
1509 * modify @dwork's timer so that it expires after @delay. If @delay is
1510 * zero, @work is guaranteed to be scheduled immediately regardless of its
1511 * current state.
1513 * Return: %false if @dwork was idle and queued, %true if @dwork was
1514 * pending and its timer was modified.
1516 * This function is safe to call from any context including IRQ handler.
1517 * See try_to_grab_pending() for details.
1519 bool mod_delayed_work_on(int cpu, struct workqueue_struct *wq,
1520 struct delayed_work *dwork, unsigned long delay)
1522 unsigned long flags;
1523 int ret;
1525 do {
1526 ret = try_to_grab_pending(&dwork->work, true, &flags);
1527 } while (unlikely(ret == -EAGAIN));
1529 if (likely(ret >= 0)) {
1530 __queue_delayed_work(cpu, wq, dwork, delay);
1531 local_irq_restore(flags);
1534 /* -ENOENT from try_to_grab_pending() becomes %true */
1535 return ret;
1537 EXPORT_SYMBOL_GPL(mod_delayed_work_on);
1540 * worker_enter_idle - enter idle state
1541 * @worker: worker which is entering idle state
1543 * @worker is entering idle state. Update stats and idle timer if
1544 * necessary.
1546 * LOCKING:
1547 * spin_lock_irq(pool->lock).
1549 static void worker_enter_idle(struct worker *worker)
1551 struct worker_pool *pool = worker->pool;
1553 if (WARN_ON_ONCE(worker->flags & WORKER_IDLE) ||
1554 WARN_ON_ONCE(!list_empty(&worker->entry) &&
1555 (worker->hentry.next || worker->hentry.pprev)))
1556 return;
1558 /* can't use worker_set_flags(), also called from create_worker() */
1559 worker->flags |= WORKER_IDLE;
1560 pool->nr_idle++;
1561 worker->last_active = jiffies;
1563 /* idle_list is LIFO */
1564 list_add(&worker->entry, &pool->idle_list);
1566 if (too_many_workers(pool) && !timer_pending(&pool->idle_timer))
1567 mod_timer(&pool->idle_timer, jiffies + IDLE_WORKER_TIMEOUT);
1570 * Sanity check nr_running. Because wq_unbind_fn() releases
1571 * pool->lock between setting %WORKER_UNBOUND and zapping
1572 * nr_running, the warning may trigger spuriously. Check iff
1573 * unbind is not in progress.
1575 WARN_ON_ONCE(!(pool->flags & POOL_DISASSOCIATED) &&
1576 pool->nr_workers == pool->nr_idle &&
1577 atomic_read(&pool->nr_running));
1581 * worker_leave_idle - leave idle state
1582 * @worker: worker which is leaving idle state
1584 * @worker is leaving idle state. Update stats.
1586 * LOCKING:
1587 * spin_lock_irq(pool->lock).
1589 static void worker_leave_idle(struct worker *worker)
1591 struct worker_pool *pool = worker->pool;
1593 if (WARN_ON_ONCE(!(worker->flags & WORKER_IDLE)))
1594 return;
1595 worker_clr_flags(worker, WORKER_IDLE);
1596 pool->nr_idle--;
1597 list_del_init(&worker->entry);
1600 static struct worker *alloc_worker(int node)
1602 struct worker *worker;
1604 worker = kzalloc_node(sizeof(*worker), GFP_KERNEL, node);
1605 if (worker) {
1606 INIT_LIST_HEAD(&worker->entry);
1607 INIT_LIST_HEAD(&worker->scheduled);
1608 INIT_LIST_HEAD(&worker->node);
1609 /* on creation a worker is in !idle && prep state */
1610 worker->flags = WORKER_PREP;
1612 return worker;
1616 * worker_attach_to_pool() - attach a worker to a pool
1617 * @worker: worker to be attached
1618 * @pool: the target pool
1620 * Attach @worker to @pool. Once attached, the %WORKER_UNBOUND flag and
1621 * cpu-binding of @worker are kept coordinated with the pool across
1622 * cpu-[un]hotplugs.
1624 static void worker_attach_to_pool(struct worker *worker,
1625 struct worker_pool *pool)
1627 mutex_lock(&pool->attach_mutex);
1630 * set_cpus_allowed_ptr() will fail if the cpumask doesn't have any
1631 * online CPUs. It'll be re-applied when any of the CPUs come up.
1633 set_cpus_allowed_ptr(worker->task, pool->attrs->cpumask);
1636 * The pool->attach_mutex ensures %POOL_DISASSOCIATED remains
1637 * stable across this function. See the comments above the
1638 * flag definition for details.
1640 if (pool->flags & POOL_DISASSOCIATED)
1641 worker->flags |= WORKER_UNBOUND;
1643 list_add_tail(&worker->node, &pool->workers);
1645 mutex_unlock(&pool->attach_mutex);
1649 * worker_detach_from_pool() - detach a worker from its pool
1650 * @worker: worker which is attached to its pool
1651 * @pool: the pool @worker is attached to
1653 * Undo the attaching which had been done in worker_attach_to_pool(). The
1654 * caller worker shouldn't access to the pool after detached except it has
1655 * other reference to the pool.
1657 static void worker_detach_from_pool(struct worker *worker,
1658 struct worker_pool *pool)
1660 struct completion *detach_completion = NULL;
1662 mutex_lock(&pool->attach_mutex);
1663 list_del(&worker->node);
1664 if (list_empty(&pool->workers))
1665 detach_completion = pool->detach_completion;
1666 mutex_unlock(&pool->attach_mutex);
1668 /* clear leftover flags without pool->lock after it is detached */
1669 worker->flags &= ~(WORKER_UNBOUND | WORKER_REBOUND);
1671 if (detach_completion)
1672 complete(detach_completion);
1676 * create_worker - create a new workqueue worker
1677 * @pool: pool the new worker will belong to
1679 * Create and start a new worker which is attached to @pool.
1681 * CONTEXT:
1682 * Might sleep. Does GFP_KERNEL allocations.
1684 * Return:
1685 * Pointer to the newly created worker.
1687 static struct worker *create_worker(struct worker_pool *pool)
1689 struct worker *worker = NULL;
1690 int id = -1;
1691 char id_buf[16];
1693 /* ID is needed to determine kthread name */
1694 id = ida_simple_get(&pool->worker_ida, 0, 0, GFP_KERNEL);
1695 if (id < 0)
1696 goto fail;
1698 worker = alloc_worker(pool->node);
1699 if (!worker)
1700 goto fail;
1702 worker->pool = pool;
1703 worker->id = id;
1705 if (pool->cpu >= 0)
1706 snprintf(id_buf, sizeof(id_buf), "%d:%d%s", pool->cpu, id,
1707 pool->attrs->nice < 0 ? "H" : "");
1708 else
1709 snprintf(id_buf, sizeof(id_buf), "u%d:%d", pool->id, id);
1711 worker->task = kthread_create_on_node(worker_thread, worker, pool->node,
1712 "kworker/%s", id_buf);
1713 if (IS_ERR(worker->task))
1714 goto fail;
1716 set_user_nice(worker->task, pool->attrs->nice);
1718 /* prevent userland from meddling with cpumask of workqueue workers */
1719 worker->task->flags |= PF_NO_SETAFFINITY;
1721 /* successful, attach the worker to the pool */
1722 worker_attach_to_pool(worker, pool);
1724 /* start the newly created worker */
1725 spin_lock_irq(&pool->lock);
1726 worker->pool->nr_workers++;
1727 worker_enter_idle(worker);
1728 wake_up_process(worker->task);
1729 spin_unlock_irq(&pool->lock);
1731 return worker;
1733 fail:
1734 if (id >= 0)
1735 ida_simple_remove(&pool->worker_ida, id);
1736 kfree(worker);
1737 return NULL;
1741 * destroy_worker - destroy a workqueue worker
1742 * @worker: worker to be destroyed
1744 * Destroy @worker and adjust @pool stats accordingly. The worker should
1745 * be idle.
1747 * CONTEXT:
1748 * spin_lock_irq(pool->lock).
1750 static void destroy_worker(struct worker *worker)
1752 struct worker_pool *pool = worker->pool;
1754 lockdep_assert_held(&pool->lock);
1756 /* sanity check frenzy */
1757 if (WARN_ON(worker->current_work) ||
1758 WARN_ON(!list_empty(&worker->scheduled)) ||
1759 WARN_ON(!(worker->flags & WORKER_IDLE)))
1760 return;
1762 pool->nr_workers--;
1763 pool->nr_idle--;
1765 list_del_init(&worker->entry);
1766 worker->flags |= WORKER_DIE;
1767 wake_up_process(worker->task);
1770 static void idle_worker_timeout(unsigned long __pool)
1772 struct worker_pool *pool = (void *)__pool;
1774 spin_lock_irq(&pool->lock);
1776 while (too_many_workers(pool)) {
1777 struct worker *worker;
1778 unsigned long expires;
1780 /* idle_list is kept in LIFO order, check the last one */
1781 worker = list_entry(pool->idle_list.prev, struct worker, entry);
1782 expires = worker->last_active + IDLE_WORKER_TIMEOUT;
1784 if (time_before(jiffies, expires)) {
1785 mod_timer(&pool->idle_timer, expires);
1786 break;
1789 destroy_worker(worker);
1792 spin_unlock_irq(&pool->lock);
1795 static void send_mayday(struct work_struct *work)
1797 struct pool_workqueue *pwq = get_work_pwq(work);
1798 struct workqueue_struct *wq = pwq->wq;
1800 lockdep_assert_held(&wq_mayday_lock);
1802 if (!wq->rescuer)
1803 return;
1805 /* mayday mayday mayday */
1806 if (list_empty(&pwq->mayday_node)) {
1808 * If @pwq is for an unbound wq, its base ref may be put at
1809 * any time due to an attribute change. Pin @pwq until the
1810 * rescuer is done with it.
1812 get_pwq(pwq);
1813 list_add_tail(&pwq->mayday_node, &wq->maydays);
1814 wake_up_process(wq->rescuer->task);
1818 static void pool_mayday_timeout(unsigned long __pool)
1820 struct worker_pool *pool = (void *)__pool;
1821 struct work_struct *work;
1823 spin_lock_irq(&pool->lock);
1824 spin_lock(&wq_mayday_lock); /* for wq->maydays */
1826 if (need_to_create_worker(pool)) {
1828 * We've been trying to create a new worker but
1829 * haven't been successful. We might be hitting an
1830 * allocation deadlock. Send distress signals to
1831 * rescuers.
1833 list_for_each_entry(work, &pool->worklist, entry)
1834 send_mayday(work);
1837 spin_unlock(&wq_mayday_lock);
1838 spin_unlock_irq(&pool->lock);
1840 mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INTERVAL);
1844 * maybe_create_worker - create a new worker if necessary
1845 * @pool: pool to create a new worker for
1847 * Create a new worker for @pool if necessary. @pool is guaranteed to
1848 * have at least one idle worker on return from this function. If
1849 * creating a new worker takes longer than MAYDAY_INTERVAL, mayday is
1850 * sent to all rescuers with works scheduled on @pool to resolve
1851 * possible allocation deadlock.
1853 * On return, need_to_create_worker() is guaranteed to be %false and
1854 * may_start_working() %true.
1856 * LOCKING:
1857 * spin_lock_irq(pool->lock) which may be released and regrabbed
1858 * multiple times. Does GFP_KERNEL allocations. Called only from
1859 * manager.
1861 static void maybe_create_worker(struct worker_pool *pool)
1862 __releases(&pool->lock)
1863 __acquires(&pool->lock)
1865 restart:
1866 spin_unlock_irq(&pool->lock);
1868 /* if we don't make progress in MAYDAY_INITIAL_TIMEOUT, call for help */
1869 mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INITIAL_TIMEOUT);
1871 while (true) {
1872 if (create_worker(pool) || !need_to_create_worker(pool))
1873 break;
1875 schedule_timeout_interruptible(CREATE_COOLDOWN);
1877 if (!need_to_create_worker(pool))
1878 break;
1881 del_timer_sync(&pool->mayday_timer);
1882 spin_lock_irq(&pool->lock);
1884 * This is necessary even after a new worker was just successfully
1885 * created as @pool->lock was dropped and the new worker might have
1886 * already become busy.
1888 if (need_to_create_worker(pool))
1889 goto restart;
1893 * manage_workers - manage worker pool
1894 * @worker: self
1896 * Assume the manager role and manage the worker pool @worker belongs
1897 * to. At any given time, there can be only zero or one manager per
1898 * pool. The exclusion is handled automatically by this function.
1900 * The caller can safely start processing works on false return. On
1901 * true return, it's guaranteed that need_to_create_worker() is false
1902 * and may_start_working() is true.
1904 * CONTEXT:
1905 * spin_lock_irq(pool->lock) which may be released and regrabbed
1906 * multiple times. Does GFP_KERNEL allocations.
1908 * Return:
1909 * %false if the pool doesn't need management and the caller can safely
1910 * start processing works, %true if management function was performed and
1911 * the conditions that the caller verified before calling the function may
1912 * no longer be true.
1914 static bool manage_workers(struct worker *worker)
1916 struct worker_pool *pool = worker->pool;
1919 * Anyone who successfully grabs manager_arb wins the arbitration
1920 * and becomes the manager. mutex_trylock() on pool->manager_arb
1921 * failure while holding pool->lock reliably indicates that someone
1922 * else is managing the pool and the worker which failed trylock
1923 * can proceed to executing work items. This means that anyone
1924 * grabbing manager_arb is responsible for actually performing
1925 * manager duties. If manager_arb is grabbed and released without
1926 * actual management, the pool may stall indefinitely.
1928 if (!mutex_trylock(&pool->manager_arb))
1929 return false;
1930 pool->manager = worker;
1932 maybe_create_worker(pool);
1934 pool->manager = NULL;
1935 mutex_unlock(&pool->manager_arb);
1936 return true;
1940 * process_one_work - process single work
1941 * @worker: self
1942 * @work: work to process
1944 * Process @work. This function contains all the logics necessary to
1945 * process a single work including synchronization against and
1946 * interaction with other workers on the same cpu, queueing and
1947 * flushing. As long as context requirement is met, any worker can
1948 * call this function to process a work.
1950 * CONTEXT:
1951 * spin_lock_irq(pool->lock) which is released and regrabbed.
1953 static void process_one_work(struct worker *worker, struct work_struct *work)
1954 __releases(&pool->lock)
1955 __acquires(&pool->lock)
1957 struct pool_workqueue *pwq = get_work_pwq(work);
1958 struct worker_pool *pool = worker->pool;
1959 bool cpu_intensive = pwq->wq->flags & WQ_CPU_INTENSIVE;
1960 int work_color;
1961 struct worker *collision;
1962 #ifdef CONFIG_LOCKDEP
1964 * It is permissible to free the struct work_struct from
1965 * inside the function that is called from it, this we need to
1966 * take into account for lockdep too. To avoid bogus "held
1967 * lock freed" warnings as well as problems when looking into
1968 * work->lockdep_map, make a copy and use that here.
1970 struct lockdep_map lockdep_map;
1972 lockdep_copy_map(&lockdep_map, &work->lockdep_map);
1973 #endif
1974 /* ensure we're on the correct CPU */
1975 WARN_ON_ONCE(!(pool->flags & POOL_DISASSOCIATED) &&
1976 raw_smp_processor_id() != pool->cpu);
1979 * A single work shouldn't be executed concurrently by
1980 * multiple workers on a single cpu. Check whether anyone is
1981 * already processing the work. If so, defer the work to the
1982 * currently executing one.
1984 collision = find_worker_executing_work(pool, work);
1985 if (unlikely(collision)) {
1986 move_linked_works(work, &collision->scheduled, NULL);
1987 return;
1990 /* claim and dequeue */
1991 debug_work_deactivate(work);
1992 hash_add(pool->busy_hash, &worker->hentry, (unsigned long)work);
1993 worker->current_work = work;
1994 worker->current_func = work->func;
1995 worker->current_pwq = pwq;
1996 work_color = get_work_color(work);
1998 list_del_init(&work->entry);
2001 * CPU intensive works don't participate in concurrency management.
2002 * They're the scheduler's responsibility. This takes @worker out
2003 * of concurrency management and the next code block will chain
2004 * execution of the pending work items.
2006 if (unlikely(cpu_intensive))
2007 worker_set_flags(worker, WORKER_CPU_INTENSIVE);
2010 * Wake up another worker if necessary. The condition is always
2011 * false for normal per-cpu workers since nr_running would always
2012 * be >= 1 at this point. This is used to chain execution of the
2013 * pending work items for WORKER_NOT_RUNNING workers such as the
2014 * UNBOUND and CPU_INTENSIVE ones.
2016 if (need_more_worker(pool))
2017 wake_up_worker(pool);
2020 * Record the last pool and clear PENDING which should be the last
2021 * update to @work. Also, do this inside @pool->lock so that
2022 * PENDING and queued state changes happen together while IRQ is
2023 * disabled.
2025 set_work_pool_and_clear_pending(work, pool->id);
2027 spin_unlock_irq(&pool->lock);
2029 lock_map_acquire_read(&pwq->wq->lockdep_map);
2030 lock_map_acquire(&lockdep_map);
2031 trace_workqueue_execute_start(work);
2032 worker->current_func(work);
2034 * While we must be careful to not use "work" after this, the trace
2035 * point will only record its address.
2037 trace_workqueue_execute_end(work);
2038 lock_map_release(&lockdep_map);
2039 lock_map_release(&pwq->wq->lockdep_map);
2041 if (unlikely(in_atomic() || lockdep_depth(current) > 0)) {
2042 pr_err("BUG: workqueue leaked lock or atomic: %s/0x%08x/%d\n"
2043 " last function: %pf\n",
2044 current->comm, preempt_count(), task_pid_nr(current),
2045 worker->current_func);
2046 debug_show_held_locks(current);
2047 dump_stack();
2051 * The following prevents a kworker from hogging CPU on !PREEMPT
2052 * kernels, where a requeueing work item waiting for something to
2053 * happen could deadlock with stop_machine as such work item could
2054 * indefinitely requeue itself while all other CPUs are trapped in
2055 * stop_machine. At the same time, report a quiescent RCU state so
2056 * the same condition doesn't freeze RCU.
2058 cond_resched_rcu_qs();
2060 spin_lock_irq(&pool->lock);
2062 /* clear cpu intensive status */
2063 if (unlikely(cpu_intensive))
2064 worker_clr_flags(worker, WORKER_CPU_INTENSIVE);
2066 /* we're done with it, release */
2067 hash_del(&worker->hentry);
2068 worker->current_work = NULL;
2069 worker->current_func = NULL;
2070 worker->current_pwq = NULL;
2071 worker->desc_valid = false;
2072 pwq_dec_nr_in_flight(pwq, work_color);
2076 * process_scheduled_works - process scheduled works
2077 * @worker: self
2079 * Process all scheduled works. Please note that the scheduled list
2080 * may change while processing a work, so this function repeatedly
2081 * fetches a work from the top and executes it.
2083 * CONTEXT:
2084 * spin_lock_irq(pool->lock) which may be released and regrabbed
2085 * multiple times.
2087 static void process_scheduled_works(struct worker *worker)
2089 while (!list_empty(&worker->scheduled)) {
2090 struct work_struct *work = list_first_entry(&worker->scheduled,
2091 struct work_struct, entry);
2092 process_one_work(worker, work);
2097 * worker_thread - the worker thread function
2098 * @__worker: self
2100 * The worker thread function. All workers belong to a worker_pool -
2101 * either a per-cpu one or dynamic unbound one. These workers process all
2102 * work items regardless of their specific target workqueue. The only
2103 * exception is work items which belong to workqueues with a rescuer which
2104 * will be explained in rescuer_thread().
2106 * Return: 0
2108 static int worker_thread(void *__worker)
2110 struct worker *worker = __worker;
2111 struct worker_pool *pool = worker->pool;
2113 /* tell the scheduler that this is a workqueue worker */
2114 worker->task->flags |= PF_WQ_WORKER;
2115 woke_up:
2116 spin_lock_irq(&pool->lock);
2118 /* am I supposed to die? */
2119 if (unlikely(worker->flags & WORKER_DIE)) {
2120 spin_unlock_irq(&pool->lock);
2121 WARN_ON_ONCE(!list_empty(&worker->entry));
2122 worker->task->flags &= ~PF_WQ_WORKER;
2124 set_task_comm(worker->task, "kworker/dying");
2125 ida_simple_remove(&pool->worker_ida, worker->id);
2126 worker_detach_from_pool(worker, pool);
2127 kfree(worker);
2128 return 0;
2131 worker_leave_idle(worker);
2132 recheck:
2133 /* no more worker necessary? */
2134 if (!need_more_worker(pool))
2135 goto sleep;
2137 /* do we need to manage? */
2138 if (unlikely(!may_start_working(pool)) && manage_workers(worker))
2139 goto recheck;
2142 * ->scheduled list can only be filled while a worker is
2143 * preparing to process a work or actually processing it.
2144 * Make sure nobody diddled with it while I was sleeping.
2146 WARN_ON_ONCE(!list_empty(&worker->scheduled));
2149 * Finish PREP stage. We're guaranteed to have at least one idle
2150 * worker or that someone else has already assumed the manager
2151 * role. This is where @worker starts participating in concurrency
2152 * management if applicable and concurrency management is restored
2153 * after being rebound. See rebind_workers() for details.
2155 worker_clr_flags(worker, WORKER_PREP | WORKER_REBOUND);
2157 do {
2158 struct work_struct *work =
2159 list_first_entry(&pool->worklist,
2160 struct work_struct, entry);
2162 if (likely(!(*work_data_bits(work) & WORK_STRUCT_LINKED))) {
2163 /* optimization path, not strictly necessary */
2164 process_one_work(worker, work);
2165 if (unlikely(!list_empty(&worker->scheduled)))
2166 process_scheduled_works(worker);
2167 } else {
2168 move_linked_works(work, &worker->scheduled, NULL);
2169 process_scheduled_works(worker);
2171 } while (keep_working(pool));
2173 worker_set_flags(worker, WORKER_PREP);
2174 sleep:
2176 * pool->lock is held and there's no work to process and no need to
2177 * manage, sleep. Workers are woken up only while holding
2178 * pool->lock or from local cpu, so setting the current state
2179 * before releasing pool->lock is enough to prevent losing any
2180 * event.
2182 worker_enter_idle(worker);
2183 __set_current_state(TASK_INTERRUPTIBLE);
2184 spin_unlock_irq(&pool->lock);
2185 schedule();
2186 goto woke_up;
2190 * rescuer_thread - the rescuer thread function
2191 * @__rescuer: self
2193 * Workqueue rescuer thread function. There's one rescuer for each
2194 * workqueue which has WQ_MEM_RECLAIM set.
2196 * Regular work processing on a pool may block trying to create a new
2197 * worker which uses GFP_KERNEL allocation which has slight chance of
2198 * developing into deadlock if some works currently on the same queue
2199 * need to be processed to satisfy the GFP_KERNEL allocation. This is
2200 * the problem rescuer solves.
2202 * When such condition is possible, the pool summons rescuers of all
2203 * workqueues which have works queued on the pool and let them process
2204 * those works so that forward progress can be guaranteed.
2206 * This should happen rarely.
2208 * Return: 0
2210 static int rescuer_thread(void *__rescuer)
2212 struct worker *rescuer = __rescuer;
2213 struct workqueue_struct *wq = rescuer->rescue_wq;
2214 struct list_head *scheduled = &rescuer->scheduled;
2215 bool should_stop;
2217 set_user_nice(current, RESCUER_NICE_LEVEL);
2220 * Mark rescuer as worker too. As WORKER_PREP is never cleared, it
2221 * doesn't participate in concurrency management.
2223 rescuer->task->flags |= PF_WQ_WORKER;
2224 repeat:
2225 set_current_state(TASK_INTERRUPTIBLE);
2228 * By the time the rescuer is requested to stop, the workqueue
2229 * shouldn't have any work pending, but @wq->maydays may still have
2230 * pwq(s) queued. This can happen by non-rescuer workers consuming
2231 * all the work items before the rescuer got to them. Go through
2232 * @wq->maydays processing before acting on should_stop so that the
2233 * list is always empty on exit.
2235 should_stop = kthread_should_stop();
2237 /* see whether any pwq is asking for help */
2238 spin_lock_irq(&wq_mayday_lock);
2240 while (!list_empty(&wq->maydays)) {
2241 struct pool_workqueue *pwq = list_first_entry(&wq->maydays,
2242 struct pool_workqueue, mayday_node);
2243 struct worker_pool *pool = pwq->pool;
2244 struct work_struct *work, *n;
2246 __set_current_state(TASK_RUNNING);
2247 list_del_init(&pwq->mayday_node);
2249 spin_unlock_irq(&wq_mayday_lock);
2251 worker_attach_to_pool(rescuer, pool);
2253 spin_lock_irq(&pool->lock);
2254 rescuer->pool = pool;
2257 * Slurp in all works issued via this workqueue and
2258 * process'em.
2260 WARN_ON_ONCE(!list_empty(scheduled));
2261 list_for_each_entry_safe(work, n, &pool->worklist, entry)
2262 if (get_work_pwq(work) == pwq)
2263 move_linked_works(work, scheduled, &n);
2265 if (!list_empty(scheduled)) {
2266 process_scheduled_works(rescuer);
2269 * The above execution of rescued work items could
2270 * have created more to rescue through
2271 * pwq_activate_first_delayed() or chained
2272 * queueing. Let's put @pwq back on mayday list so
2273 * that such back-to-back work items, which may be
2274 * being used to relieve memory pressure, don't
2275 * incur MAYDAY_INTERVAL delay inbetween.
2277 if (need_to_create_worker(pool)) {
2278 spin_lock(&wq_mayday_lock);
2279 get_pwq(pwq);
2280 list_move_tail(&pwq->mayday_node, &wq->maydays);
2281 spin_unlock(&wq_mayday_lock);
2286 * Put the reference grabbed by send_mayday(). @pool won't
2287 * go away while we're still attached to it.
2289 put_pwq(pwq);
2292 * Leave this pool. If need_more_worker() is %true, notify a
2293 * regular worker; otherwise, we end up with 0 concurrency
2294 * and stalling the execution.
2296 if (need_more_worker(pool))
2297 wake_up_worker(pool);
2299 rescuer->pool = NULL;
2300 spin_unlock_irq(&pool->lock);
2302 worker_detach_from_pool(rescuer, pool);
2304 spin_lock_irq(&wq_mayday_lock);
2307 spin_unlock_irq(&wq_mayday_lock);
2309 if (should_stop) {
2310 __set_current_state(TASK_RUNNING);
2311 rescuer->task->flags &= ~PF_WQ_WORKER;
2312 return 0;
2315 /* rescuers should never participate in concurrency management */
2316 WARN_ON_ONCE(!(rescuer->flags & WORKER_NOT_RUNNING));
2317 schedule();
2318 goto repeat;
2321 struct wq_barrier {
2322 struct work_struct work;
2323 struct completion done;
2324 struct task_struct *task; /* purely informational */
2327 static void wq_barrier_func(struct work_struct *work)
2329 struct wq_barrier *barr = container_of(work, struct wq_barrier, work);
2330 complete(&barr->done);
2334 * insert_wq_barrier - insert a barrier work
2335 * @pwq: pwq to insert barrier into
2336 * @barr: wq_barrier to insert
2337 * @target: target work to attach @barr to
2338 * @worker: worker currently executing @target, NULL if @target is not executing
2340 * @barr is linked to @target such that @barr is completed only after
2341 * @target finishes execution. Please note that the ordering
2342 * guarantee is observed only with respect to @target and on the local
2343 * cpu.
2345 * Currently, a queued barrier can't be canceled. This is because
2346 * try_to_grab_pending() can't determine whether the work to be
2347 * grabbed is at the head of the queue and thus can't clear LINKED
2348 * flag of the previous work while there must be a valid next work
2349 * after a work with LINKED flag set.
2351 * Note that when @worker is non-NULL, @target may be modified
2352 * underneath us, so we can't reliably determine pwq from @target.
2354 * CONTEXT:
2355 * spin_lock_irq(pool->lock).
2357 static void insert_wq_barrier(struct pool_workqueue *pwq,
2358 struct wq_barrier *barr,
2359 struct work_struct *target, struct worker *worker)
2361 struct list_head *head;
2362 unsigned int linked = 0;
2365 * debugobject calls are safe here even with pool->lock locked
2366 * as we know for sure that this will not trigger any of the
2367 * checks and call back into the fixup functions where we
2368 * might deadlock.
2370 INIT_WORK_ONSTACK(&barr->work, wq_barrier_func);
2371 __set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(&barr->work));
2372 init_completion(&barr->done);
2373 barr->task = current;
2376 * If @target is currently being executed, schedule the
2377 * barrier to the worker; otherwise, put it after @target.
2379 if (worker)
2380 head = worker->scheduled.next;
2381 else {
2382 unsigned long *bits = work_data_bits(target);
2384 head = target->entry.next;
2385 /* there can already be other linked works, inherit and set */
2386 linked = *bits & WORK_STRUCT_LINKED;
2387 __set_bit(WORK_STRUCT_LINKED_BIT, bits);
2390 debug_work_activate(&barr->work);
2391 insert_work(pwq, &barr->work, head,
2392 work_color_to_flags(WORK_NO_COLOR) | linked);
2396 * flush_workqueue_prep_pwqs - prepare pwqs for workqueue flushing
2397 * @wq: workqueue being flushed
2398 * @flush_color: new flush color, < 0 for no-op
2399 * @work_color: new work color, < 0 for no-op
2401 * Prepare pwqs for workqueue flushing.
2403 * If @flush_color is non-negative, flush_color on all pwqs should be
2404 * -1. If no pwq has in-flight commands at the specified color, all
2405 * pwq->flush_color's stay at -1 and %false is returned. If any pwq
2406 * has in flight commands, its pwq->flush_color is set to
2407 * @flush_color, @wq->nr_pwqs_to_flush is updated accordingly, pwq
2408 * wakeup logic is armed and %true is returned.
2410 * The caller should have initialized @wq->first_flusher prior to
2411 * calling this function with non-negative @flush_color. If
2412 * @flush_color is negative, no flush color update is done and %false
2413 * is returned.
2415 * If @work_color is non-negative, all pwqs should have the same
2416 * work_color which is previous to @work_color and all will be
2417 * advanced to @work_color.
2419 * CONTEXT:
2420 * mutex_lock(wq->mutex).
2422 * Return:
2423 * %true if @flush_color >= 0 and there's something to flush. %false
2424 * otherwise.
2426 static bool flush_workqueue_prep_pwqs(struct workqueue_struct *wq,
2427 int flush_color, int work_color)
2429 bool wait = false;
2430 struct pool_workqueue *pwq;
2432 if (flush_color >= 0) {
2433 WARN_ON_ONCE(atomic_read(&wq->nr_pwqs_to_flush));
2434 atomic_set(&wq->nr_pwqs_to_flush, 1);
2437 for_each_pwq(pwq, wq) {
2438 struct worker_pool *pool = pwq->pool;
2440 spin_lock_irq(&pool->lock);
2442 if (flush_color >= 0) {
2443 WARN_ON_ONCE(pwq->flush_color != -1);
2445 if (pwq->nr_in_flight[flush_color]) {
2446 pwq->flush_color = flush_color;
2447 atomic_inc(&wq->nr_pwqs_to_flush);
2448 wait = true;
2452 if (work_color >= 0) {
2453 WARN_ON_ONCE(work_color != work_next_color(pwq->work_color));
2454 pwq->work_color = work_color;
2457 spin_unlock_irq(&pool->lock);
2460 if (flush_color >= 0 && atomic_dec_and_test(&wq->nr_pwqs_to_flush))
2461 complete(&wq->first_flusher->done);
2463 return wait;
2467 * flush_workqueue - ensure that any scheduled work has run to completion.
2468 * @wq: workqueue to flush
2470 * This function sleeps until all work items which were queued on entry
2471 * have finished execution, but it is not livelocked by new incoming ones.
2473 void flush_workqueue(struct workqueue_struct *wq)
2475 struct wq_flusher this_flusher = {
2476 .list = LIST_HEAD_INIT(this_flusher.list),
2477 .flush_color = -1,
2478 .done = COMPLETION_INITIALIZER_ONSTACK(this_flusher.done),
2480 int next_color;
2482 lock_map_acquire(&wq->lockdep_map);
2483 lock_map_release(&wq->lockdep_map);
2485 mutex_lock(&wq->mutex);
2488 * Start-to-wait phase
2490 next_color = work_next_color(wq->work_color);
2492 if (next_color != wq->flush_color) {
2494 * Color space is not full. The current work_color
2495 * becomes our flush_color and work_color is advanced
2496 * by one.
2498 WARN_ON_ONCE(!list_empty(&wq->flusher_overflow));
2499 this_flusher.flush_color = wq->work_color;
2500 wq->work_color = next_color;
2502 if (!wq->first_flusher) {
2503 /* no flush in progress, become the first flusher */
2504 WARN_ON_ONCE(wq->flush_color != this_flusher.flush_color);
2506 wq->first_flusher = &this_flusher;
2508 if (!flush_workqueue_prep_pwqs(wq, wq->flush_color,
2509 wq->work_color)) {
2510 /* nothing to flush, done */
2511 wq->flush_color = next_color;
2512 wq->first_flusher = NULL;
2513 goto out_unlock;
2515 } else {
2516 /* wait in queue */
2517 WARN_ON_ONCE(wq->flush_color == this_flusher.flush_color);
2518 list_add_tail(&this_flusher.list, &wq->flusher_queue);
2519 flush_workqueue_prep_pwqs(wq, -1, wq->work_color);
2521 } else {
2523 * Oops, color space is full, wait on overflow queue.
2524 * The next flush completion will assign us
2525 * flush_color and transfer to flusher_queue.
2527 list_add_tail(&this_flusher.list, &wq->flusher_overflow);
2530 mutex_unlock(&wq->mutex);
2532 wait_for_completion(&this_flusher.done);
2535 * Wake-up-and-cascade phase
2537 * First flushers are responsible for cascading flushes and
2538 * handling overflow. Non-first flushers can simply return.
2540 if (wq->first_flusher != &this_flusher)
2541 return;
2543 mutex_lock(&wq->mutex);
2545 /* we might have raced, check again with mutex held */
2546 if (wq->first_flusher != &this_flusher)
2547 goto out_unlock;
2549 wq->first_flusher = NULL;
2551 WARN_ON_ONCE(!list_empty(&this_flusher.list));
2552 WARN_ON_ONCE(wq->flush_color != this_flusher.flush_color);
2554 while (true) {
2555 struct wq_flusher *next, *tmp;
2557 /* complete all the flushers sharing the current flush color */
2558 list_for_each_entry_safe(next, tmp, &wq->flusher_queue, list) {
2559 if (next->flush_color != wq->flush_color)
2560 break;
2561 list_del_init(&next->list);
2562 complete(&next->done);
2565 WARN_ON_ONCE(!list_empty(&wq->flusher_overflow) &&
2566 wq->flush_color != work_next_color(wq->work_color));
2568 /* this flush_color is finished, advance by one */
2569 wq->flush_color = work_next_color(wq->flush_color);
2571 /* one color has been freed, handle overflow queue */
2572 if (!list_empty(&wq->flusher_overflow)) {
2574 * Assign the same color to all overflowed
2575 * flushers, advance work_color and append to
2576 * flusher_queue. This is the start-to-wait
2577 * phase for these overflowed flushers.
2579 list_for_each_entry(tmp, &wq->flusher_overflow, list)
2580 tmp->flush_color = wq->work_color;
2582 wq->work_color = work_next_color(wq->work_color);
2584 list_splice_tail_init(&wq->flusher_overflow,
2585 &wq->flusher_queue);
2586 flush_workqueue_prep_pwqs(wq, -1, wq->work_color);
2589 if (list_empty(&wq->flusher_queue)) {
2590 WARN_ON_ONCE(wq->flush_color != wq->work_color);
2591 break;
2595 * Need to flush more colors. Make the next flusher
2596 * the new first flusher and arm pwqs.
2598 WARN_ON_ONCE(wq->flush_color == wq->work_color);
2599 WARN_ON_ONCE(wq->flush_color != next->flush_color);
2601 list_del_init(&next->list);
2602 wq->first_flusher = next;
2604 if (flush_workqueue_prep_pwqs(wq, wq->flush_color, -1))
2605 break;
2608 * Meh... this color is already done, clear first
2609 * flusher and repeat cascading.
2611 wq->first_flusher = NULL;
2614 out_unlock:
2615 mutex_unlock(&wq->mutex);
2617 EXPORT_SYMBOL_GPL(flush_workqueue);
2620 * drain_workqueue - drain a workqueue
2621 * @wq: workqueue to drain
2623 * Wait until the workqueue becomes empty. While draining is in progress,
2624 * only chain queueing is allowed. IOW, only currently pending or running
2625 * work items on @wq can queue further work items on it. @wq is flushed
2626 * repeatedly until it becomes empty. The number of flushing is determined
2627 * by the depth of chaining and should be relatively short. Whine if it
2628 * takes too long.
2630 void drain_workqueue(struct workqueue_struct *wq)
2632 unsigned int flush_cnt = 0;
2633 struct pool_workqueue *pwq;
2636 * __queue_work() needs to test whether there are drainers, is much
2637 * hotter than drain_workqueue() and already looks at @wq->flags.
2638 * Use __WQ_DRAINING so that queue doesn't have to check nr_drainers.
2640 mutex_lock(&wq->mutex);
2641 if (!wq->nr_drainers++)
2642 wq->flags |= __WQ_DRAINING;
2643 mutex_unlock(&wq->mutex);
2644 reflush:
2645 flush_workqueue(wq);
2647 mutex_lock(&wq->mutex);
2649 for_each_pwq(pwq, wq) {
2650 bool drained;
2652 spin_lock_irq(&pwq->pool->lock);
2653 drained = !pwq->nr_active && list_empty(&pwq->delayed_works);
2654 spin_unlock_irq(&pwq->pool->lock);
2656 if (drained)
2657 continue;
2659 if (++flush_cnt == 10 ||
2660 (flush_cnt % 100 == 0 && flush_cnt <= 1000))
2661 pr_warn("workqueue %s: drain_workqueue() isn't complete after %u tries\n",
2662 wq->name, flush_cnt);
2664 mutex_unlock(&wq->mutex);
2665 goto reflush;
2668 if (!--wq->nr_drainers)
2669 wq->flags &= ~__WQ_DRAINING;
2670 mutex_unlock(&wq->mutex);
2672 EXPORT_SYMBOL_GPL(drain_workqueue);
2674 static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr)
2676 struct worker *worker = NULL;
2677 struct worker_pool *pool;
2678 struct pool_workqueue *pwq;
2680 might_sleep();
2682 local_irq_disable();
2683 pool = get_work_pool(work);
2684 if (!pool) {
2685 local_irq_enable();
2686 return false;
2689 spin_lock(&pool->lock);
2690 /* see the comment in try_to_grab_pending() with the same code */
2691 pwq = get_work_pwq(work);
2692 if (pwq) {
2693 if (unlikely(pwq->pool != pool))
2694 goto already_gone;
2695 } else {
2696 worker = find_worker_executing_work(pool, work);
2697 if (!worker)
2698 goto already_gone;
2699 pwq = worker->current_pwq;
2702 insert_wq_barrier(pwq, barr, work, worker);
2703 spin_unlock_irq(&pool->lock);
2706 * If @max_active is 1 or rescuer is in use, flushing another work
2707 * item on the same workqueue may lead to deadlock. Make sure the
2708 * flusher is not running on the same workqueue by verifying write
2709 * access.
2711 if (pwq->wq->saved_max_active == 1 || pwq->wq->rescuer)
2712 lock_map_acquire(&pwq->wq->lockdep_map);
2713 else
2714 lock_map_acquire_read(&pwq->wq->lockdep_map);
2715 lock_map_release(&pwq->wq->lockdep_map);
2717 return true;
2718 already_gone:
2719 spin_unlock_irq(&pool->lock);
2720 return false;
2724 * flush_work - wait for a work to finish executing the last queueing instance
2725 * @work: the work to flush
2727 * Wait until @work has finished execution. @work is guaranteed to be idle
2728 * on return if it hasn't been requeued since flush started.
2730 * Return:
2731 * %true if flush_work() waited for the work to finish execution,
2732 * %false if it was already idle.
2734 bool flush_work(struct work_struct *work)
2736 struct wq_barrier barr;
2738 lock_map_acquire(&work->lockdep_map);
2739 lock_map_release(&work->lockdep_map);
2741 if (start_flush_work(work, &barr)) {
2742 wait_for_completion(&barr.done);
2743 destroy_work_on_stack(&barr.work);
2744 return true;
2745 } else {
2746 return false;
2749 EXPORT_SYMBOL_GPL(flush_work);
2751 struct cwt_wait {
2752 wait_queue_t wait;
2753 struct work_struct *work;
2756 static int cwt_wakefn(wait_queue_t *wait, unsigned mode, int sync, void *key)
2758 struct cwt_wait *cwait = container_of(wait, struct cwt_wait, wait);
2760 if (cwait->work != key)
2761 return 0;
2762 return autoremove_wake_function(wait, mode, sync, key);
2765 static bool __cancel_work_timer(struct work_struct *work, bool is_dwork)
2767 static DECLARE_WAIT_QUEUE_HEAD(cancel_waitq);
2768 unsigned long flags;
2769 int ret;
2771 do {
2772 ret = try_to_grab_pending(work, is_dwork, &flags);
2774 * If someone else is already canceling, wait for it to
2775 * finish. flush_work() doesn't work for PREEMPT_NONE
2776 * because we may get scheduled between @work's completion
2777 * and the other canceling task resuming and clearing
2778 * CANCELING - flush_work() will return false immediately
2779 * as @work is no longer busy, try_to_grab_pending() will
2780 * return -ENOENT as @work is still being canceled and the
2781 * other canceling task won't be able to clear CANCELING as
2782 * we're hogging the CPU.
2784 * Let's wait for completion using a waitqueue. As this
2785 * may lead to the thundering herd problem, use a custom
2786 * wake function which matches @work along with exclusive
2787 * wait and wakeup.
2789 if (unlikely(ret == -ENOENT)) {
2790 struct cwt_wait cwait;
2792 init_wait(&cwait.wait);
2793 cwait.wait.func = cwt_wakefn;
2794 cwait.work = work;
2796 prepare_to_wait_exclusive(&cancel_waitq, &cwait.wait,
2797 TASK_UNINTERRUPTIBLE);
2798 if (work_is_canceling(work))
2799 schedule();
2800 finish_wait(&cancel_waitq, &cwait.wait);
2802 } while (unlikely(ret < 0));
2804 /* tell other tasks trying to grab @work to back off */
2805 mark_work_canceling(work);
2806 local_irq_restore(flags);
2808 flush_work(work);
2809 clear_work_data(work);
2812 * Paired with prepare_to_wait() above so that either
2813 * waitqueue_active() is visible here or !work_is_canceling() is
2814 * visible there.
2816 smp_mb();
2817 if (waitqueue_active(&cancel_waitq))
2818 __wake_up(&cancel_waitq, TASK_NORMAL, 1, work);
2820 return ret;
2824 * cancel_work_sync - cancel a work and wait for it to finish
2825 * @work: the work to cancel
2827 * Cancel @work and wait for its execution to finish. This function
2828 * can be used even if the work re-queues itself or migrates to
2829 * another workqueue. On return from this function, @work is
2830 * guaranteed to be not pending or executing on any CPU.
2832 * cancel_work_sync(&delayed_work->work) must not be used for
2833 * delayed_work's. Use cancel_delayed_work_sync() instead.
2835 * The caller must ensure that the workqueue on which @work was last
2836 * queued can't be destroyed before this function returns.
2838 * Return:
2839 * %true if @work was pending, %false otherwise.
2841 bool cancel_work_sync(struct work_struct *work)
2843 return __cancel_work_timer(work, false);
2845 EXPORT_SYMBOL_GPL(cancel_work_sync);
2848 * flush_delayed_work - wait for a dwork to finish executing the last queueing
2849 * @dwork: the delayed work to flush
2851 * Delayed timer is cancelled and the pending work is queued for
2852 * immediate execution. Like flush_work(), this function only
2853 * considers the last queueing instance of @dwork.
2855 * Return:
2856 * %true if flush_work() waited for the work to finish execution,
2857 * %false if it was already idle.
2859 bool flush_delayed_work(struct delayed_work *dwork)
2861 local_irq_disable();
2862 if (del_timer_sync(&dwork->timer))
2863 __queue_work(dwork->cpu, dwork->wq, &dwork->work);
2864 local_irq_enable();
2865 return flush_work(&dwork->work);
2867 EXPORT_SYMBOL(flush_delayed_work);
2870 * cancel_delayed_work - cancel a delayed work
2871 * @dwork: delayed_work to cancel
2873 * Kill off a pending delayed_work.
2875 * Return: %true if @dwork was pending and canceled; %false if it wasn't
2876 * pending.
2878 * Note:
2879 * The work callback function may still be running on return, unless
2880 * it returns %true and the work doesn't re-arm itself. Explicitly flush or
2881 * use cancel_delayed_work_sync() to wait on it.
2883 * This function is safe to call from any context including IRQ handler.
2885 bool cancel_delayed_work(struct delayed_work *dwork)
2887 unsigned long flags;
2888 int ret;
2890 do {
2891 ret = try_to_grab_pending(&dwork->work, true, &flags);
2892 } while (unlikely(ret == -EAGAIN));
2894 if (unlikely(ret < 0))
2895 return false;
2897 set_work_pool_and_clear_pending(&dwork->work,
2898 get_work_pool_id(&dwork->work));
2899 local_irq_restore(flags);
2900 return ret;
2902 EXPORT_SYMBOL(cancel_delayed_work);
2905 * cancel_delayed_work_sync - cancel a delayed work and wait for it to finish
2906 * @dwork: the delayed work cancel
2908 * This is cancel_work_sync() for delayed works.
2910 * Return:
2911 * %true if @dwork was pending, %false otherwise.
2913 bool cancel_delayed_work_sync(struct delayed_work *dwork)
2915 return __cancel_work_timer(&dwork->work, true);
2917 EXPORT_SYMBOL(cancel_delayed_work_sync);
2920 * schedule_on_each_cpu - execute a function synchronously on each online CPU
2921 * @func: the function to call
2923 * schedule_on_each_cpu() executes @func on each online CPU using the
2924 * system workqueue and blocks until all CPUs have completed.
2925 * schedule_on_each_cpu() is very slow.
2927 * Return:
2928 * 0 on success, -errno on failure.
2930 int schedule_on_each_cpu(work_func_t func)
2932 int cpu;
2933 struct work_struct __percpu *works;
2935 works = alloc_percpu(struct work_struct);
2936 if (!works)
2937 return -ENOMEM;
2939 get_online_cpus();
2941 for_each_online_cpu(cpu) {
2942 struct work_struct *work = per_cpu_ptr(works, cpu);
2944 INIT_WORK(work, func);
2945 schedule_work_on(cpu, work);
2948 for_each_online_cpu(cpu)
2949 flush_work(per_cpu_ptr(works, cpu));
2951 put_online_cpus();
2952 free_percpu(works);
2953 return 0;
2957 * execute_in_process_context - reliably execute the routine with user context
2958 * @fn: the function to execute
2959 * @ew: guaranteed storage for the execute work structure (must
2960 * be available when the work executes)
2962 * Executes the function immediately if process context is available,
2963 * otherwise schedules the function for delayed execution.
2965 * Return: 0 - function was executed
2966 * 1 - function was scheduled for execution
2968 int execute_in_process_context(work_func_t fn, struct execute_work *ew)
2970 if (!in_interrupt()) {
2971 fn(&ew->work);
2972 return 0;
2975 INIT_WORK(&ew->work, fn);
2976 schedule_work(&ew->work);
2978 return 1;
2980 EXPORT_SYMBOL_GPL(execute_in_process_context);
2983 * free_workqueue_attrs - free a workqueue_attrs
2984 * @attrs: workqueue_attrs to free
2986 * Undo alloc_workqueue_attrs().
2988 void free_workqueue_attrs(struct workqueue_attrs *attrs)
2990 if (attrs) {
2991 free_cpumask_var(attrs->cpumask);
2992 kfree(attrs);
2997 * alloc_workqueue_attrs - allocate a workqueue_attrs
2998 * @gfp_mask: allocation mask to use
3000 * Allocate a new workqueue_attrs, initialize with default settings and
3001 * return it.
3003 * Return: The allocated new workqueue_attr on success. %NULL on failure.
3005 struct workqueue_attrs *alloc_workqueue_attrs(gfp_t gfp_mask)
3007 struct workqueue_attrs *attrs;
3009 attrs = kzalloc(sizeof(*attrs), gfp_mask);
3010 if (!attrs)
3011 goto fail;
3012 if (!alloc_cpumask_var(&attrs->cpumask, gfp_mask))
3013 goto fail;
3015 cpumask_copy(attrs->cpumask, cpu_possible_mask);
3016 return attrs;
3017 fail:
3018 free_workqueue_attrs(attrs);
3019 return NULL;
3022 static void copy_workqueue_attrs(struct workqueue_attrs *to,
3023 const struct workqueue_attrs *from)
3025 to->nice = from->nice;
3026 cpumask_copy(to->cpumask, from->cpumask);
3028 * Unlike hash and equality test, this function doesn't ignore
3029 * ->no_numa as it is used for both pool and wq attrs. Instead,
3030 * get_unbound_pool() explicitly clears ->no_numa after copying.
3032 to->no_numa = from->no_numa;
3035 /* hash value of the content of @attr */
3036 static u32 wqattrs_hash(const struct workqueue_attrs *attrs)
3038 u32 hash = 0;
3040 hash = jhash_1word(attrs->nice, hash);
3041 hash = jhash(cpumask_bits(attrs->cpumask),
3042 BITS_TO_LONGS(nr_cpumask_bits) * sizeof(long), hash);
3043 return hash;
3046 /* content equality test */
3047 static bool wqattrs_equal(const struct workqueue_attrs *a,
3048 const struct workqueue_attrs *b)
3050 if (a->nice != b->nice)
3051 return false;
3052 if (!cpumask_equal(a->cpumask, b->cpumask))
3053 return false;
3054 return true;
3058 * init_worker_pool - initialize a newly zalloc'd worker_pool
3059 * @pool: worker_pool to initialize
3061 * Initialize a newly zalloc'd @pool. It also allocates @pool->attrs.
3063 * Return: 0 on success, -errno on failure. Even on failure, all fields
3064 * inside @pool proper are initialized and put_unbound_pool() can be called
3065 * on @pool safely to release it.
3067 static int init_worker_pool(struct worker_pool *pool)
3069 spin_lock_init(&pool->lock);
3070 pool->id = -1;
3071 pool->cpu = -1;
3072 pool->node = NUMA_NO_NODE;
3073 pool->flags |= POOL_DISASSOCIATED;
3074 INIT_LIST_HEAD(&pool->worklist);
3075 INIT_LIST_HEAD(&pool->idle_list);
3076 hash_init(pool->busy_hash);
3078 init_timer_deferrable(&pool->idle_timer);
3079 pool->idle_timer.function = idle_worker_timeout;
3080 pool->idle_timer.data = (unsigned long)pool;
3082 setup_timer(&pool->mayday_timer, pool_mayday_timeout,
3083 (unsigned long)pool);
3085 mutex_init(&pool->manager_arb);
3086 mutex_init(&pool->attach_mutex);
3087 INIT_LIST_HEAD(&pool->workers);
3089 ida_init(&pool->worker_ida);
3090 INIT_HLIST_NODE(&pool->hash_node);
3091 pool->refcnt = 1;
3093 /* shouldn't fail above this point */
3094 pool->attrs = alloc_workqueue_attrs(GFP_KERNEL);
3095 if (!pool->attrs)
3096 return -ENOMEM;
3097 return 0;
3100 static void rcu_free_wq(struct rcu_head *rcu)
3102 struct workqueue_struct *wq =
3103 container_of(rcu, struct workqueue_struct, rcu);
3105 if (!(wq->flags & WQ_UNBOUND))
3106 free_percpu(wq->cpu_pwqs);
3107 else
3108 free_workqueue_attrs(wq->unbound_attrs);
3110 kfree(wq->rescuer);
3111 kfree(wq);
3114 static void rcu_free_pool(struct rcu_head *rcu)
3116 struct worker_pool *pool = container_of(rcu, struct worker_pool, rcu);
3118 ida_destroy(&pool->worker_ida);
3119 free_workqueue_attrs(pool->attrs);
3120 kfree(pool);
3124 * put_unbound_pool - put a worker_pool
3125 * @pool: worker_pool to put
3127 * Put @pool. If its refcnt reaches zero, it gets destroyed in sched-RCU
3128 * safe manner. get_unbound_pool() calls this function on its failure path
3129 * and this function should be able to release pools which went through,
3130 * successfully or not, init_worker_pool().
3132 * Should be called with wq_pool_mutex held.
3134 static void put_unbound_pool(struct worker_pool *pool)
3136 DECLARE_COMPLETION_ONSTACK(detach_completion);
3137 struct worker *worker;
3139 lockdep_assert_held(&wq_pool_mutex);
3141 if (--pool->refcnt)
3142 return;
3144 /* sanity checks */
3145 if (WARN_ON(!(pool->cpu < 0)) ||
3146 WARN_ON(!list_empty(&pool->worklist)))
3147 return;
3149 /* release id and unhash */
3150 if (pool->id >= 0)
3151 idr_remove(&worker_pool_idr, pool->id);
3152 hash_del(&pool->hash_node);
3155 * Become the manager and destroy all workers. Grabbing
3156 * manager_arb prevents @pool's workers from blocking on
3157 * attach_mutex.
3159 mutex_lock(&pool->manager_arb);
3161 spin_lock_irq(&pool->lock);
3162 while ((worker = first_idle_worker(pool)))
3163 destroy_worker(worker);
3164 WARN_ON(pool->nr_workers || pool->nr_idle);
3165 spin_unlock_irq(&pool->lock);
3167 mutex_lock(&pool->attach_mutex);
3168 if (!list_empty(&pool->workers))
3169 pool->detach_completion = &detach_completion;
3170 mutex_unlock(&pool->attach_mutex);
3172 if (pool->detach_completion)
3173 wait_for_completion(pool->detach_completion);
3175 mutex_unlock(&pool->manager_arb);
3177 /* shut down the timers */
3178 del_timer_sync(&pool->idle_timer);
3179 del_timer_sync(&pool->mayday_timer);
3181 /* sched-RCU protected to allow dereferences from get_work_pool() */
3182 call_rcu_sched(&pool->rcu, rcu_free_pool);
3186 * get_unbound_pool - get a worker_pool with the specified attributes
3187 * @attrs: the attributes of the worker_pool to get
3189 * Obtain a worker_pool which has the same attributes as @attrs, bump the
3190 * reference count and return it. If there already is a matching
3191 * worker_pool, it will be used; otherwise, this function attempts to
3192 * create a new one.
3194 * Should be called with wq_pool_mutex held.
3196 * Return: On success, a worker_pool with the same attributes as @attrs.
3197 * On failure, %NULL.
3199 static struct worker_pool *get_unbound_pool(const struct workqueue_attrs *attrs)
3201 u32 hash = wqattrs_hash(attrs);
3202 struct worker_pool *pool;
3203 int node;
3205 lockdep_assert_held(&wq_pool_mutex);
3207 /* do we already have a matching pool? */
3208 hash_for_each_possible(unbound_pool_hash, pool, hash_node, hash) {
3209 if (wqattrs_equal(pool->attrs, attrs)) {
3210 pool->refcnt++;
3211 return pool;
3215 /* nope, create a new one */
3216 pool = kzalloc(sizeof(*pool), GFP_KERNEL);
3217 if (!pool || init_worker_pool(pool) < 0)
3218 goto fail;
3220 lockdep_set_subclass(&pool->lock, 1); /* see put_pwq() */
3221 copy_workqueue_attrs(pool->attrs, attrs);
3224 * no_numa isn't a worker_pool attribute, always clear it. See
3225 * 'struct workqueue_attrs' comments for detail.
3227 pool->attrs->no_numa = false;
3229 /* if cpumask is contained inside a NUMA node, we belong to that node */
3230 if (wq_numa_enabled) {
3231 for_each_node(node) {
3232 if (cpumask_subset(pool->attrs->cpumask,
3233 wq_numa_possible_cpumask[node])) {
3234 pool->node = node;
3235 break;
3240 if (worker_pool_assign_id(pool) < 0)
3241 goto fail;
3243 /* create and start the initial worker */
3244 if (!create_worker(pool))
3245 goto fail;
3247 /* install */
3248 hash_add(unbound_pool_hash, &pool->hash_node, hash);
3250 return pool;
3251 fail:
3252 if (pool)
3253 put_unbound_pool(pool);
3254 return NULL;
3257 static void rcu_free_pwq(struct rcu_head *rcu)
3259 kmem_cache_free(pwq_cache,
3260 container_of(rcu, struct pool_workqueue, rcu));
3264 * Scheduled on system_wq by put_pwq() when an unbound pwq hits zero refcnt
3265 * and needs to be destroyed.
3267 static void pwq_unbound_release_workfn(struct work_struct *work)
3269 struct pool_workqueue *pwq = container_of(work, struct pool_workqueue,
3270 unbound_release_work);
3271 struct workqueue_struct *wq = pwq->wq;
3272 struct worker_pool *pool = pwq->pool;
3273 bool is_last;
3275 if (WARN_ON_ONCE(!(wq->flags & WQ_UNBOUND)))
3276 return;
3278 mutex_lock(&wq->mutex);
3279 list_del_rcu(&pwq->pwqs_node);
3280 is_last = list_empty(&wq->pwqs);
3281 mutex_unlock(&wq->mutex);
3283 mutex_lock(&wq_pool_mutex);
3284 put_unbound_pool(pool);
3285 mutex_unlock(&wq_pool_mutex);
3287 call_rcu_sched(&pwq->rcu, rcu_free_pwq);
3290 * If we're the last pwq going away, @wq is already dead and no one
3291 * is gonna access it anymore. Schedule RCU free.
3293 if (is_last)
3294 call_rcu_sched(&wq->rcu, rcu_free_wq);
3298 * pwq_adjust_max_active - update a pwq's max_active to the current setting
3299 * @pwq: target pool_workqueue
3301 * If @pwq isn't freezing, set @pwq->max_active to the associated
3302 * workqueue's saved_max_active and activate delayed work items
3303 * accordingly. If @pwq is freezing, clear @pwq->max_active to zero.
3305 static void pwq_adjust_max_active(struct pool_workqueue *pwq)
3307 struct workqueue_struct *wq = pwq->wq;
3308 bool freezable = wq->flags & WQ_FREEZABLE;
3310 /* for @wq->saved_max_active */
3311 lockdep_assert_held(&wq->mutex);
3313 /* fast exit for non-freezable wqs */
3314 if (!freezable && pwq->max_active == wq->saved_max_active)
3315 return;
3317 spin_lock_irq(&pwq->pool->lock);
3320 * During [un]freezing, the caller is responsible for ensuring that
3321 * this function is called at least once after @workqueue_freezing
3322 * is updated and visible.
3324 if (!freezable || !workqueue_freezing) {
3325 pwq->max_active = wq->saved_max_active;
3327 while (!list_empty(&pwq->delayed_works) &&
3328 pwq->nr_active < pwq->max_active)
3329 pwq_activate_first_delayed(pwq);
3332 * Need to kick a worker after thawed or an unbound wq's
3333 * max_active is bumped. It's a slow path. Do it always.
3335 wake_up_worker(pwq->pool);
3336 } else {
3337 pwq->max_active = 0;
3340 spin_unlock_irq(&pwq->pool->lock);
3343 /* initialize newly alloced @pwq which is associated with @wq and @pool */
3344 static void init_pwq(struct pool_workqueue *pwq, struct workqueue_struct *wq,
3345 struct worker_pool *pool)
3347 BUG_ON((unsigned long)pwq & WORK_STRUCT_FLAG_MASK);
3349 memset(pwq, 0, sizeof(*pwq));
3351 pwq->pool = pool;
3352 pwq->wq = wq;
3353 pwq->flush_color = -1;
3354 pwq->refcnt = 1;
3355 INIT_LIST_HEAD(&pwq->delayed_works);
3356 INIT_LIST_HEAD(&pwq->pwqs_node);
3357 INIT_LIST_HEAD(&pwq->mayday_node);
3358 INIT_WORK(&pwq->unbound_release_work, pwq_unbound_release_workfn);
3361 /* sync @pwq with the current state of its associated wq and link it */
3362 static void link_pwq(struct pool_workqueue *pwq)
3364 struct workqueue_struct *wq = pwq->wq;
3366 lockdep_assert_held(&wq->mutex);
3368 /* may be called multiple times, ignore if already linked */
3369 if (!list_empty(&pwq->pwqs_node))
3370 return;
3372 /* set the matching work_color */
3373 pwq->work_color = wq->work_color;
3375 /* sync max_active to the current setting */
3376 pwq_adjust_max_active(pwq);
3378 /* link in @pwq */
3379 list_add_rcu(&pwq->pwqs_node, &wq->pwqs);
3382 /* obtain a pool matching @attr and create a pwq associating the pool and @wq */
3383 static struct pool_workqueue *alloc_unbound_pwq(struct workqueue_struct *wq,
3384 const struct workqueue_attrs *attrs)
3386 struct worker_pool *pool;
3387 struct pool_workqueue *pwq;
3389 lockdep_assert_held(&wq_pool_mutex);
3391 pool = get_unbound_pool(attrs);
3392 if (!pool)
3393 return NULL;
3395 pwq = kmem_cache_alloc_node(pwq_cache, GFP_KERNEL, pool->node);
3396 if (!pwq) {
3397 put_unbound_pool(pool);
3398 return NULL;
3401 init_pwq(pwq, wq, pool);
3402 return pwq;
3406 * wq_calc_node_cpumask - calculate a wq_attrs' cpumask for the specified node
3407 * @attrs: the wq_attrs of the default pwq of the target workqueue
3408 * @node: the target NUMA node
3409 * @cpu_going_down: if >= 0, the CPU to consider as offline
3410 * @cpumask: outarg, the resulting cpumask
3412 * Calculate the cpumask a workqueue with @attrs should use on @node. If
3413 * @cpu_going_down is >= 0, that cpu is considered offline during
3414 * calculation. The result is stored in @cpumask.
3416 * If NUMA affinity is not enabled, @attrs->cpumask is always used. If
3417 * enabled and @node has online CPUs requested by @attrs, the returned
3418 * cpumask is the intersection of the possible CPUs of @node and
3419 * @attrs->cpumask.
3421 * The caller is responsible for ensuring that the cpumask of @node stays
3422 * stable.
3424 * Return: %true if the resulting @cpumask is different from @attrs->cpumask,
3425 * %false if equal.
3427 static bool wq_calc_node_cpumask(const struct workqueue_attrs *attrs, int node,
3428 int cpu_going_down, cpumask_t *cpumask)
3430 if (!wq_numa_enabled || attrs->no_numa)
3431 goto use_dfl;
3433 /* does @node have any online CPUs @attrs wants? */
3434 cpumask_and(cpumask, cpumask_of_node(node), attrs->cpumask);
3435 if (cpu_going_down >= 0)
3436 cpumask_clear_cpu(cpu_going_down, cpumask);
3438 if (cpumask_empty(cpumask))
3439 goto use_dfl;
3441 /* yeap, return possible CPUs in @node that @attrs wants */
3442 cpumask_and(cpumask, attrs->cpumask, wq_numa_possible_cpumask[node]);
3443 return !cpumask_equal(cpumask, attrs->cpumask);
3445 use_dfl:
3446 cpumask_copy(cpumask, attrs->cpumask);
3447 return false;
3450 /* install @pwq into @wq's numa_pwq_tbl[] for @node and return the old pwq */
3451 static struct pool_workqueue *numa_pwq_tbl_install(struct workqueue_struct *wq,
3452 int node,
3453 struct pool_workqueue *pwq)
3455 struct pool_workqueue *old_pwq;
3457 lockdep_assert_held(&wq_pool_mutex);
3458 lockdep_assert_held(&wq->mutex);
3460 /* link_pwq() can handle duplicate calls */
3461 link_pwq(pwq);
3463 old_pwq = rcu_access_pointer(wq->numa_pwq_tbl[node]);
3464 rcu_assign_pointer(wq->numa_pwq_tbl[node], pwq);
3465 return old_pwq;
3468 /* context to store the prepared attrs & pwqs before applying */
3469 struct apply_wqattrs_ctx {
3470 struct workqueue_struct *wq; /* target workqueue */
3471 struct workqueue_attrs *attrs; /* attrs to apply */
3472 struct list_head list; /* queued for batching commit */
3473 struct pool_workqueue *dfl_pwq;
3474 struct pool_workqueue *pwq_tbl[];
3477 /* free the resources after success or abort */
3478 static void apply_wqattrs_cleanup(struct apply_wqattrs_ctx *ctx)
3480 if (ctx) {
3481 int node;
3483 for_each_node(node)
3484 put_pwq_unlocked(ctx->pwq_tbl[node]);
3485 put_pwq_unlocked(ctx->dfl_pwq);
3487 free_workqueue_attrs(ctx->attrs);
3489 kfree(ctx);
3493 /* allocate the attrs and pwqs for later installation */
3494 static struct apply_wqattrs_ctx *
3495 apply_wqattrs_prepare(struct workqueue_struct *wq,
3496 const struct workqueue_attrs *attrs)
3498 struct apply_wqattrs_ctx *ctx;
3499 struct workqueue_attrs *new_attrs, *tmp_attrs;
3500 int node;
3502 lockdep_assert_held(&wq_pool_mutex);
3504 ctx = kzalloc(sizeof(*ctx) + nr_node_ids * sizeof(ctx->pwq_tbl[0]),
3505 GFP_KERNEL);
3507 new_attrs = alloc_workqueue_attrs(GFP_KERNEL);
3508 tmp_attrs = alloc_workqueue_attrs(GFP_KERNEL);
3509 if (!ctx || !new_attrs || !tmp_attrs)
3510 goto out_free;
3513 * Calculate the attrs of the default pwq.
3514 * If the user configured cpumask doesn't overlap with the
3515 * wq_unbound_cpumask, we fallback to the wq_unbound_cpumask.
3517 copy_workqueue_attrs(new_attrs, attrs);
3518 cpumask_and(new_attrs->cpumask, new_attrs->cpumask, wq_unbound_cpumask);
3519 if (unlikely(cpumask_empty(new_attrs->cpumask)))
3520 cpumask_copy(new_attrs->cpumask, wq_unbound_cpumask);
3523 * We may create multiple pwqs with differing cpumasks. Make a
3524 * copy of @new_attrs which will be modified and used to obtain
3525 * pools.
3527 copy_workqueue_attrs(tmp_attrs, new_attrs);
3530 * If something goes wrong during CPU up/down, we'll fall back to
3531 * the default pwq covering whole @attrs->cpumask. Always create
3532 * it even if we don't use it immediately.
3534 ctx->dfl_pwq = alloc_unbound_pwq(wq, new_attrs);
3535 if (!ctx->dfl_pwq)
3536 goto out_free;
3538 for_each_node(node) {
3539 if (wq_calc_node_cpumask(new_attrs, node, -1, tmp_attrs->cpumask)) {
3540 ctx->pwq_tbl[node] = alloc_unbound_pwq(wq, tmp_attrs);
3541 if (!ctx->pwq_tbl[node])
3542 goto out_free;
3543 } else {
3544 ctx->dfl_pwq->refcnt++;
3545 ctx->pwq_tbl[node] = ctx->dfl_pwq;
3549 /* save the user configured attrs and sanitize it. */
3550 copy_workqueue_attrs(new_attrs, attrs);
3551 cpumask_and(new_attrs->cpumask, new_attrs->cpumask, cpu_possible_mask);
3552 ctx->attrs = new_attrs;
3554 ctx->wq = wq;
3555 free_workqueue_attrs(tmp_attrs);
3556 return ctx;
3558 out_free:
3559 free_workqueue_attrs(tmp_attrs);
3560 free_workqueue_attrs(new_attrs);
3561 apply_wqattrs_cleanup(ctx);
3562 return NULL;
3565 /* set attrs and install prepared pwqs, @ctx points to old pwqs on return */
3566 static void apply_wqattrs_commit(struct apply_wqattrs_ctx *ctx)
3568 int node;
3570 /* all pwqs have been created successfully, let's install'em */
3571 mutex_lock(&ctx->wq->mutex);
3573 copy_workqueue_attrs(ctx->wq->unbound_attrs, ctx->attrs);
3575 /* save the previous pwq and install the new one */
3576 for_each_node(node)
3577 ctx->pwq_tbl[node] = numa_pwq_tbl_install(ctx->wq, node,
3578 ctx->pwq_tbl[node]);
3580 /* @dfl_pwq might not have been used, ensure it's linked */
3581 link_pwq(ctx->dfl_pwq);
3582 swap(ctx->wq->dfl_pwq, ctx->dfl_pwq);
3584 mutex_unlock(&ctx->wq->mutex);
3587 static void apply_wqattrs_lock(void)
3589 /* CPUs should stay stable across pwq creations and installations */
3590 get_online_cpus();
3591 mutex_lock(&wq_pool_mutex);
3594 static void apply_wqattrs_unlock(void)
3596 mutex_unlock(&wq_pool_mutex);
3597 put_online_cpus();
3600 static int apply_workqueue_attrs_locked(struct workqueue_struct *wq,
3601 const struct workqueue_attrs *attrs)
3603 struct apply_wqattrs_ctx *ctx;
3604 int ret = -ENOMEM;
3606 /* only unbound workqueues can change attributes */
3607 if (WARN_ON(!(wq->flags & WQ_UNBOUND)))
3608 return -EINVAL;
3610 /* creating multiple pwqs breaks ordering guarantee */
3611 if (WARN_ON((wq->flags & __WQ_ORDERED) && !list_empty(&wq->pwqs)))
3612 return -EINVAL;
3614 ctx = apply_wqattrs_prepare(wq, attrs);
3616 /* the ctx has been prepared successfully, let's commit it */
3617 if (ctx) {
3618 apply_wqattrs_commit(ctx);
3619 ret = 0;
3622 apply_wqattrs_cleanup(ctx);
3624 return ret;
3628 * apply_workqueue_attrs - apply new workqueue_attrs to an unbound workqueue
3629 * @wq: the target workqueue
3630 * @attrs: the workqueue_attrs to apply, allocated with alloc_workqueue_attrs()
3632 * Apply @attrs to an unbound workqueue @wq. Unless disabled, on NUMA
3633 * machines, this function maps a separate pwq to each NUMA node with
3634 * possibles CPUs in @attrs->cpumask so that work items are affine to the
3635 * NUMA node it was issued on. Older pwqs are released as in-flight work
3636 * items finish. Note that a work item which repeatedly requeues itself
3637 * back-to-back will stay on its current pwq.
3639 * Performs GFP_KERNEL allocations.
3641 * Return: 0 on success and -errno on failure.
3643 int apply_workqueue_attrs(struct workqueue_struct *wq,
3644 const struct workqueue_attrs *attrs)
3646 int ret;
3648 apply_wqattrs_lock();
3649 ret = apply_workqueue_attrs_locked(wq, attrs);
3650 apply_wqattrs_unlock();
3652 return ret;
3656 * wq_update_unbound_numa - update NUMA affinity of a wq for CPU hot[un]plug
3657 * @wq: the target workqueue
3658 * @cpu: the CPU coming up or going down
3659 * @online: whether @cpu is coming up or going down
3661 * This function is to be called from %CPU_DOWN_PREPARE, %CPU_ONLINE and
3662 * %CPU_DOWN_FAILED. @cpu is being hot[un]plugged, update NUMA affinity of
3663 * @wq accordingly.
3665 * If NUMA affinity can't be adjusted due to memory allocation failure, it
3666 * falls back to @wq->dfl_pwq which may not be optimal but is always
3667 * correct.
3669 * Note that when the last allowed CPU of a NUMA node goes offline for a
3670 * workqueue with a cpumask spanning multiple nodes, the workers which were
3671 * already executing the work items for the workqueue will lose their CPU
3672 * affinity and may execute on any CPU. This is similar to how per-cpu
3673 * workqueues behave on CPU_DOWN. If a workqueue user wants strict
3674 * affinity, it's the user's responsibility to flush the work item from
3675 * CPU_DOWN_PREPARE.
3677 static void wq_update_unbound_numa(struct workqueue_struct *wq, int cpu,
3678 bool online)
3680 int node = cpu_to_node(cpu);
3681 int cpu_off = online ? -1 : cpu;
3682 struct pool_workqueue *old_pwq = NULL, *pwq;
3683 struct workqueue_attrs *target_attrs;
3684 cpumask_t *cpumask;
3686 lockdep_assert_held(&wq_pool_mutex);
3688 if (!wq_numa_enabled || !(wq->flags & WQ_UNBOUND) ||
3689 wq->unbound_attrs->no_numa)
3690 return;
3693 * We don't wanna alloc/free wq_attrs for each wq for each CPU.
3694 * Let's use a preallocated one. The following buf is protected by
3695 * CPU hotplug exclusion.
3697 target_attrs = wq_update_unbound_numa_attrs_buf;
3698 cpumask = target_attrs->cpumask;
3700 copy_workqueue_attrs(target_attrs, wq->unbound_attrs);
3701 pwq = unbound_pwq_by_node(wq, node);
3704 * Let's determine what needs to be done. If the target cpumask is
3705 * different from the default pwq's, we need to compare it to @pwq's
3706 * and create a new one if they don't match. If the target cpumask
3707 * equals the default pwq's, the default pwq should be used.
3709 if (wq_calc_node_cpumask(wq->dfl_pwq->pool->attrs, node, cpu_off, cpumask)) {
3710 if (cpumask_equal(cpumask, pwq->pool->attrs->cpumask))
3711 return;
3712 } else {
3713 goto use_dfl_pwq;
3716 /* create a new pwq */
3717 pwq = alloc_unbound_pwq(wq, target_attrs);
3718 if (!pwq) {
3719 pr_warn("workqueue: allocation failed while updating NUMA affinity of \"%s\"\n",
3720 wq->name);
3721 goto use_dfl_pwq;
3724 /* Install the new pwq. */
3725 mutex_lock(&wq->mutex);
3726 old_pwq = numa_pwq_tbl_install(wq, node, pwq);
3727 goto out_unlock;
3729 use_dfl_pwq:
3730 mutex_lock(&wq->mutex);
3731 spin_lock_irq(&wq->dfl_pwq->pool->lock);
3732 get_pwq(wq->dfl_pwq);
3733 spin_unlock_irq(&wq->dfl_pwq->pool->lock);
3734 old_pwq = numa_pwq_tbl_install(wq, node, wq->dfl_pwq);
3735 out_unlock:
3736 mutex_unlock(&wq->mutex);
3737 put_pwq_unlocked(old_pwq);
3740 static int alloc_and_link_pwqs(struct workqueue_struct *wq)
3742 bool highpri = wq->flags & WQ_HIGHPRI;
3743 int cpu, ret;
3745 if (!(wq->flags & WQ_UNBOUND)) {
3746 wq->cpu_pwqs = alloc_percpu(struct pool_workqueue);
3747 if (!wq->cpu_pwqs)
3748 return -ENOMEM;
3750 for_each_possible_cpu(cpu) {
3751 struct pool_workqueue *pwq =
3752 per_cpu_ptr(wq->cpu_pwqs, cpu);
3753 struct worker_pool *cpu_pools =
3754 per_cpu(cpu_worker_pools, cpu);
3756 init_pwq(pwq, wq, &cpu_pools[highpri]);
3758 mutex_lock(&wq->mutex);
3759 link_pwq(pwq);
3760 mutex_unlock(&wq->mutex);
3762 return 0;
3763 } else if (wq->flags & __WQ_ORDERED) {
3764 ret = apply_workqueue_attrs(wq, ordered_wq_attrs[highpri]);
3765 /* there should only be single pwq for ordering guarantee */
3766 WARN(!ret && (wq->pwqs.next != &wq->dfl_pwq->pwqs_node ||
3767 wq->pwqs.prev != &wq->dfl_pwq->pwqs_node),
3768 "ordering guarantee broken for workqueue %s\n", wq->name);
3769 return ret;
3770 } else {
3771 return apply_workqueue_attrs(wq, unbound_std_wq_attrs[highpri]);
3775 static int wq_clamp_max_active(int max_active, unsigned int flags,
3776 const char *name)
3778 int lim = flags & WQ_UNBOUND ? WQ_UNBOUND_MAX_ACTIVE : WQ_MAX_ACTIVE;
3780 if (max_active < 1 || max_active > lim)
3781 pr_warn("workqueue: max_active %d requested for %s is out of range, clamping between %d and %d\n",
3782 max_active, name, 1, lim);
3784 return clamp_val(max_active, 1, lim);
3787 struct workqueue_struct *__alloc_workqueue_key(const char *fmt,
3788 unsigned int flags,
3789 int max_active,
3790 struct lock_class_key *key,
3791 const char *lock_name, ...)
3793 size_t tbl_size = 0;
3794 va_list args;
3795 struct workqueue_struct *wq;
3796 struct pool_workqueue *pwq;
3798 /* see the comment above the definition of WQ_POWER_EFFICIENT */
3799 if ((flags & WQ_POWER_EFFICIENT) && wq_power_efficient)
3800 flags |= WQ_UNBOUND;
3802 /* allocate wq and format name */
3803 if (flags & WQ_UNBOUND)
3804 tbl_size = nr_node_ids * sizeof(wq->numa_pwq_tbl[0]);
3806 wq = kzalloc(sizeof(*wq) + tbl_size, GFP_KERNEL);
3807 if (!wq)
3808 return NULL;
3810 if (flags & WQ_UNBOUND) {
3811 wq->unbound_attrs = alloc_workqueue_attrs(GFP_KERNEL);
3812 if (!wq->unbound_attrs)
3813 goto err_free_wq;
3816 va_start(args, lock_name);
3817 vsnprintf(wq->name, sizeof(wq->name), fmt, args);
3818 va_end(args);
3820 max_active = max_active ?: WQ_DFL_ACTIVE;
3821 max_active = wq_clamp_max_active(max_active, flags, wq->name);
3823 /* init wq */
3824 wq->flags = flags;
3825 wq->saved_max_active = max_active;
3826 mutex_init(&wq->mutex);
3827 atomic_set(&wq->nr_pwqs_to_flush, 0);
3828 INIT_LIST_HEAD(&wq->pwqs);
3829 INIT_LIST_HEAD(&wq->flusher_queue);
3830 INIT_LIST_HEAD(&wq->flusher_overflow);
3831 INIT_LIST_HEAD(&wq->maydays);
3833 lockdep_init_map(&wq->lockdep_map, lock_name, key, 0);
3834 INIT_LIST_HEAD(&wq->list);
3836 if (alloc_and_link_pwqs(wq) < 0)
3837 goto err_free_wq;
3840 * Workqueues which may be used during memory reclaim should
3841 * have a rescuer to guarantee forward progress.
3843 if (flags & WQ_MEM_RECLAIM) {
3844 struct worker *rescuer;
3846 rescuer = alloc_worker(NUMA_NO_NODE);
3847 if (!rescuer)
3848 goto err_destroy;
3850 rescuer->rescue_wq = wq;
3851 rescuer->task = kthread_create(rescuer_thread, rescuer, "%s",
3852 wq->name);
3853 if (IS_ERR(rescuer->task)) {
3854 kfree(rescuer);
3855 goto err_destroy;
3858 wq->rescuer = rescuer;
3859 rescuer->task->flags |= PF_NO_SETAFFINITY;
3860 wake_up_process(rescuer->task);
3863 if ((wq->flags & WQ_SYSFS) && workqueue_sysfs_register(wq))
3864 goto err_destroy;
3867 * wq_pool_mutex protects global freeze state and workqueues list.
3868 * Grab it, adjust max_active and add the new @wq to workqueues
3869 * list.
3871 mutex_lock(&wq_pool_mutex);
3873 mutex_lock(&wq->mutex);
3874 for_each_pwq(pwq, wq)
3875 pwq_adjust_max_active(pwq);
3876 mutex_unlock(&wq->mutex);
3878 list_add_tail_rcu(&wq->list, &workqueues);
3880 mutex_unlock(&wq_pool_mutex);
3882 return wq;
3884 err_free_wq:
3885 free_workqueue_attrs(wq->unbound_attrs);
3886 kfree(wq);
3887 return NULL;
3888 err_destroy:
3889 destroy_workqueue(wq);
3890 return NULL;
3892 EXPORT_SYMBOL_GPL(__alloc_workqueue_key);
3895 * destroy_workqueue - safely terminate a workqueue
3896 * @wq: target workqueue
3898 * Safely destroy a workqueue. All work currently pending will be done first.
3900 void destroy_workqueue(struct workqueue_struct *wq)
3902 struct pool_workqueue *pwq;
3903 int node;
3905 /* drain it before proceeding with destruction */
3906 drain_workqueue(wq);
3908 /* sanity checks */
3909 mutex_lock(&wq->mutex);
3910 for_each_pwq(pwq, wq) {
3911 int i;
3913 for (i = 0; i < WORK_NR_COLORS; i++) {
3914 if (WARN_ON(pwq->nr_in_flight[i])) {
3915 mutex_unlock(&wq->mutex);
3916 return;
3920 if (WARN_ON((pwq != wq->dfl_pwq) && (pwq->refcnt > 1)) ||
3921 WARN_ON(pwq->nr_active) ||
3922 WARN_ON(!list_empty(&pwq->delayed_works))) {
3923 mutex_unlock(&wq->mutex);
3924 return;
3927 mutex_unlock(&wq->mutex);
3930 * wq list is used to freeze wq, remove from list after
3931 * flushing is complete in case freeze races us.
3933 mutex_lock(&wq_pool_mutex);
3934 list_del_rcu(&wq->list);
3935 mutex_unlock(&wq_pool_mutex);
3937 workqueue_sysfs_unregister(wq);
3939 if (wq->rescuer)
3940 kthread_stop(wq->rescuer->task);
3942 if (!(wq->flags & WQ_UNBOUND)) {
3944 * The base ref is never dropped on per-cpu pwqs. Directly
3945 * schedule RCU free.
3947 call_rcu_sched(&wq->rcu, rcu_free_wq);
3948 } else {
3950 * We're the sole accessor of @wq at this point. Directly
3951 * access numa_pwq_tbl[] and dfl_pwq to put the base refs.
3952 * @wq will be freed when the last pwq is released.
3954 for_each_node(node) {
3955 pwq = rcu_access_pointer(wq->numa_pwq_tbl[node]);
3956 RCU_INIT_POINTER(wq->numa_pwq_tbl[node], NULL);
3957 put_pwq_unlocked(pwq);
3961 * Put dfl_pwq. @wq may be freed any time after dfl_pwq is
3962 * put. Don't access it afterwards.
3964 pwq = wq->dfl_pwq;
3965 wq->dfl_pwq = NULL;
3966 put_pwq_unlocked(pwq);
3969 EXPORT_SYMBOL_GPL(destroy_workqueue);
3972 * workqueue_set_max_active - adjust max_active of a workqueue
3973 * @wq: target workqueue
3974 * @max_active: new max_active value.
3976 * Set max_active of @wq to @max_active.
3978 * CONTEXT:
3979 * Don't call from IRQ context.
3981 void workqueue_set_max_active(struct workqueue_struct *wq, int max_active)
3983 struct pool_workqueue *pwq;
3985 /* disallow meddling with max_active for ordered workqueues */
3986 if (WARN_ON(wq->flags & __WQ_ORDERED))
3987 return;
3989 max_active = wq_clamp_max_active(max_active, wq->flags, wq->name);
3991 mutex_lock(&wq->mutex);
3993 wq->saved_max_active = max_active;
3995 for_each_pwq(pwq, wq)
3996 pwq_adjust_max_active(pwq);
3998 mutex_unlock(&wq->mutex);
4000 EXPORT_SYMBOL_GPL(workqueue_set_max_active);
4003 * current_is_workqueue_rescuer - is %current workqueue rescuer?
4005 * Determine whether %current is a workqueue rescuer. Can be used from
4006 * work functions to determine whether it's being run off the rescuer task.
4008 * Return: %true if %current is a workqueue rescuer. %false otherwise.
4010 bool current_is_workqueue_rescuer(void)
4012 struct worker *worker = current_wq_worker();
4014 return worker && worker->rescue_wq;
4018 * workqueue_congested - test whether a workqueue is congested
4019 * @cpu: CPU in question
4020 * @wq: target workqueue
4022 * Test whether @wq's cpu workqueue for @cpu is congested. There is
4023 * no synchronization around this function and the test result is
4024 * unreliable and only useful as advisory hints or for debugging.
4026 * If @cpu is WORK_CPU_UNBOUND, the test is performed on the local CPU.
4027 * Note that both per-cpu and unbound workqueues may be associated with
4028 * multiple pool_workqueues which have separate congested states. A
4029 * workqueue being congested on one CPU doesn't mean the workqueue is also
4030 * contested on other CPUs / NUMA nodes.
4032 * Return:
4033 * %true if congested, %false otherwise.
4035 bool workqueue_congested(int cpu, struct workqueue_struct *wq)
4037 struct pool_workqueue *pwq;
4038 bool ret;
4040 rcu_read_lock_sched();
4042 if (cpu == WORK_CPU_UNBOUND)
4043 cpu = smp_processor_id();
4045 if (!(wq->flags & WQ_UNBOUND))
4046 pwq = per_cpu_ptr(wq->cpu_pwqs, cpu);
4047 else
4048 pwq = unbound_pwq_by_node(wq, cpu_to_node(cpu));
4050 ret = !list_empty(&pwq->delayed_works);
4051 rcu_read_unlock_sched();
4053 return ret;
4055 EXPORT_SYMBOL_GPL(workqueue_congested);
4058 * work_busy - test whether a work is currently pending or running
4059 * @work: the work to be tested
4061 * Test whether @work is currently pending or running. There is no
4062 * synchronization around this function and the test result is
4063 * unreliable and only useful as advisory hints or for debugging.
4065 * Return:
4066 * OR'd bitmask of WORK_BUSY_* bits.
4068 unsigned int work_busy(struct work_struct *work)
4070 struct worker_pool *pool;
4071 unsigned long flags;
4072 unsigned int ret = 0;
4074 if (work_pending(work))
4075 ret |= WORK_BUSY_PENDING;
4077 local_irq_save(flags);
4078 pool = get_work_pool(work);
4079 if (pool) {
4080 spin_lock(&pool->lock);
4081 if (find_worker_executing_work(pool, work))
4082 ret |= WORK_BUSY_RUNNING;
4083 spin_unlock(&pool->lock);
4085 local_irq_restore(flags);
4087 return ret;
4089 EXPORT_SYMBOL_GPL(work_busy);
4092 * set_worker_desc - set description for the current work item
4093 * @fmt: printf-style format string
4094 * @...: arguments for the format string
4096 * This function can be called by a running work function to describe what
4097 * the work item is about. If the worker task gets dumped, this
4098 * information will be printed out together to help debugging. The
4099 * description can be at most WORKER_DESC_LEN including the trailing '\0'.
4101 void set_worker_desc(const char *fmt, ...)
4103 struct worker *worker = current_wq_worker();
4104 va_list args;
4106 if (worker) {
4107 va_start(args, fmt);
4108 vsnprintf(worker->desc, sizeof(worker->desc), fmt, args);
4109 va_end(args);
4110 worker->desc_valid = true;
4115 * print_worker_info - print out worker information and description
4116 * @log_lvl: the log level to use when printing
4117 * @task: target task
4119 * If @task is a worker and currently executing a work item, print out the
4120 * name of the workqueue being serviced and worker description set with
4121 * set_worker_desc() by the currently executing work item.
4123 * This function can be safely called on any task as long as the
4124 * task_struct itself is accessible. While safe, this function isn't
4125 * synchronized and may print out mixups or garbages of limited length.
4127 void print_worker_info(const char *log_lvl, struct task_struct *task)
4129 work_func_t *fn = NULL;
4130 char name[WQ_NAME_LEN] = { };
4131 char desc[WORKER_DESC_LEN] = { };
4132 struct pool_workqueue *pwq = NULL;
4133 struct workqueue_struct *wq = NULL;
4134 bool desc_valid = false;
4135 struct worker *worker;
4137 if (!(task->flags & PF_WQ_WORKER))
4138 return;
4141 * This function is called without any synchronization and @task
4142 * could be in any state. Be careful with dereferences.
4144 worker = probe_kthread_data(task);
4147 * Carefully copy the associated workqueue's workfn and name. Keep
4148 * the original last '\0' in case the original contains garbage.
4150 probe_kernel_read(&fn, &worker->current_func, sizeof(fn));
4151 probe_kernel_read(&pwq, &worker->current_pwq, sizeof(pwq));
4152 probe_kernel_read(&wq, &pwq->wq, sizeof(wq));
4153 probe_kernel_read(name, wq->name, sizeof(name) - 1);
4155 /* copy worker description */
4156 probe_kernel_read(&desc_valid, &worker->desc_valid, sizeof(desc_valid));
4157 if (desc_valid)
4158 probe_kernel_read(desc, worker->desc, sizeof(desc) - 1);
4160 if (fn || name[0] || desc[0]) {
4161 printk("%sWorkqueue: %s %pf", log_lvl, name, fn);
4162 if (desc[0])
4163 pr_cont(" (%s)", desc);
4164 pr_cont("\n");
4168 static void pr_cont_pool_info(struct worker_pool *pool)
4170 pr_cont(" cpus=%*pbl", nr_cpumask_bits, pool->attrs->cpumask);
4171 if (pool->node != NUMA_NO_NODE)
4172 pr_cont(" node=%d", pool->node);
4173 pr_cont(" flags=0x%x nice=%d", pool->flags, pool->attrs->nice);
4176 static void pr_cont_work(bool comma, struct work_struct *work)
4178 if (work->func == wq_barrier_func) {
4179 struct wq_barrier *barr;
4181 barr = container_of(work, struct wq_barrier, work);
4183 pr_cont("%s BAR(%d)", comma ? "," : "",
4184 task_pid_nr(barr->task));
4185 } else {
4186 pr_cont("%s %pf", comma ? "," : "", work->func);
4190 static void show_pwq(struct pool_workqueue *pwq)
4192 struct worker_pool *pool = pwq->pool;
4193 struct work_struct *work;
4194 struct worker *worker;
4195 bool has_in_flight = false, has_pending = false;
4196 int bkt;
4198 pr_info(" pwq %d:", pool->id);
4199 pr_cont_pool_info(pool);
4201 pr_cont(" active=%d/%d%s\n", pwq->nr_active, pwq->max_active,
4202 !list_empty(&pwq->mayday_node) ? " MAYDAY" : "");
4204 hash_for_each(pool->busy_hash, bkt, worker, hentry) {
4205 if (worker->current_pwq == pwq) {
4206 has_in_flight = true;
4207 break;
4210 if (has_in_flight) {
4211 bool comma = false;
4213 pr_info(" in-flight:");
4214 hash_for_each(pool->busy_hash, bkt, worker, hentry) {
4215 if (worker->current_pwq != pwq)
4216 continue;
4218 pr_cont("%s %d%s:%pf", comma ? "," : "",
4219 task_pid_nr(worker->task),
4220 worker == pwq->wq->rescuer ? "(RESCUER)" : "",
4221 worker->current_func);
4222 list_for_each_entry(work, &worker->scheduled, entry)
4223 pr_cont_work(false, work);
4224 comma = true;
4226 pr_cont("\n");
4229 list_for_each_entry(work, &pool->worklist, entry) {
4230 if (get_work_pwq(work) == pwq) {
4231 has_pending = true;
4232 break;
4235 if (has_pending) {
4236 bool comma = false;
4238 pr_info(" pending:");
4239 list_for_each_entry(work, &pool->worklist, entry) {
4240 if (get_work_pwq(work) != pwq)
4241 continue;
4243 pr_cont_work(comma, work);
4244 comma = !(*work_data_bits(work) & WORK_STRUCT_LINKED);
4246 pr_cont("\n");
4249 if (!list_empty(&pwq->delayed_works)) {
4250 bool comma = false;
4252 pr_info(" delayed:");
4253 list_for_each_entry(work, &pwq->delayed_works, entry) {
4254 pr_cont_work(comma, work);
4255 comma = !(*work_data_bits(work) & WORK_STRUCT_LINKED);
4257 pr_cont("\n");
4262 * show_workqueue_state - dump workqueue state
4264 * Called from a sysrq handler and prints out all busy workqueues and
4265 * pools.
4267 void show_workqueue_state(void)
4269 struct workqueue_struct *wq;
4270 struct worker_pool *pool;
4271 unsigned long flags;
4272 int pi;
4274 rcu_read_lock_sched();
4276 pr_info("Showing busy workqueues and worker pools:\n");
4278 list_for_each_entry_rcu(wq, &workqueues, list) {
4279 struct pool_workqueue *pwq;
4280 bool idle = true;
4282 for_each_pwq(pwq, wq) {
4283 if (pwq->nr_active || !list_empty(&pwq->delayed_works)) {
4284 idle = false;
4285 break;
4288 if (idle)
4289 continue;
4291 pr_info("workqueue %s: flags=0x%x\n", wq->name, wq->flags);
4293 for_each_pwq(pwq, wq) {
4294 spin_lock_irqsave(&pwq->pool->lock, flags);
4295 if (pwq->nr_active || !list_empty(&pwq->delayed_works))
4296 show_pwq(pwq);
4297 spin_unlock_irqrestore(&pwq->pool->lock, flags);
4301 for_each_pool(pool, pi) {
4302 struct worker *worker;
4303 bool first = true;
4305 spin_lock_irqsave(&pool->lock, flags);
4306 if (pool->nr_workers == pool->nr_idle)
4307 goto next_pool;
4309 pr_info("pool %d:", pool->id);
4310 pr_cont_pool_info(pool);
4311 pr_cont(" workers=%d", pool->nr_workers);
4312 if (pool->manager)
4313 pr_cont(" manager: %d",
4314 task_pid_nr(pool->manager->task));
4315 list_for_each_entry(worker, &pool->idle_list, entry) {
4316 pr_cont(" %s%d", first ? "idle: " : "",
4317 task_pid_nr(worker->task));
4318 first = false;
4320 pr_cont("\n");
4321 next_pool:
4322 spin_unlock_irqrestore(&pool->lock, flags);
4325 rcu_read_unlock_sched();
4329 * CPU hotplug.
4331 * There are two challenges in supporting CPU hotplug. Firstly, there
4332 * are a lot of assumptions on strong associations among work, pwq and
4333 * pool which make migrating pending and scheduled works very
4334 * difficult to implement without impacting hot paths. Secondly,
4335 * worker pools serve mix of short, long and very long running works making
4336 * blocked draining impractical.
4338 * This is solved by allowing the pools to be disassociated from the CPU
4339 * running as an unbound one and allowing it to be reattached later if the
4340 * cpu comes back online.
4343 static void wq_unbind_fn(struct work_struct *work)
4345 int cpu = smp_processor_id();
4346 struct worker_pool *pool;
4347 struct worker *worker;
4349 for_each_cpu_worker_pool(pool, cpu) {
4350 mutex_lock(&pool->attach_mutex);
4351 spin_lock_irq(&pool->lock);
4354 * We've blocked all attach/detach operations. Make all workers
4355 * unbound and set DISASSOCIATED. Before this, all workers
4356 * except for the ones which are still executing works from
4357 * before the last CPU down must be on the cpu. After
4358 * this, they may become diasporas.
4360 for_each_pool_worker(worker, pool)
4361 worker->flags |= WORKER_UNBOUND;
4363 pool->flags |= POOL_DISASSOCIATED;
4365 spin_unlock_irq(&pool->lock);
4366 mutex_unlock(&pool->attach_mutex);
4369 * Call schedule() so that we cross rq->lock and thus can
4370 * guarantee sched callbacks see the %WORKER_UNBOUND flag.
4371 * This is necessary as scheduler callbacks may be invoked
4372 * from other cpus.
4374 schedule();
4377 * Sched callbacks are disabled now. Zap nr_running.
4378 * After this, nr_running stays zero and need_more_worker()
4379 * and keep_working() are always true as long as the
4380 * worklist is not empty. This pool now behaves as an
4381 * unbound (in terms of concurrency management) pool which
4382 * are served by workers tied to the pool.
4384 atomic_set(&pool->nr_running, 0);
4387 * With concurrency management just turned off, a busy
4388 * worker blocking could lead to lengthy stalls. Kick off
4389 * unbound chain execution of currently pending work items.
4391 spin_lock_irq(&pool->lock);
4392 wake_up_worker(pool);
4393 spin_unlock_irq(&pool->lock);
4398 * rebind_workers - rebind all workers of a pool to the associated CPU
4399 * @pool: pool of interest
4401 * @pool->cpu is coming online. Rebind all workers to the CPU.
4403 static void rebind_workers(struct worker_pool *pool)
4405 struct worker *worker;
4407 lockdep_assert_held(&pool->attach_mutex);
4410 * Restore CPU affinity of all workers. As all idle workers should
4411 * be on the run-queue of the associated CPU before any local
4412 * wake-ups for concurrency management happen, restore CPU affinity
4413 * of all workers first and then clear UNBOUND. As we're called
4414 * from CPU_ONLINE, the following shouldn't fail.
4416 for_each_pool_worker(worker, pool)
4417 WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task,
4418 pool->attrs->cpumask) < 0);
4420 spin_lock_irq(&pool->lock);
4421 pool->flags &= ~POOL_DISASSOCIATED;
4423 for_each_pool_worker(worker, pool) {
4424 unsigned int worker_flags = worker->flags;
4427 * A bound idle worker should actually be on the runqueue
4428 * of the associated CPU for local wake-ups targeting it to
4429 * work. Kick all idle workers so that they migrate to the
4430 * associated CPU. Doing this in the same loop as
4431 * replacing UNBOUND with REBOUND is safe as no worker will
4432 * be bound before @pool->lock is released.
4434 if (worker_flags & WORKER_IDLE)
4435 wake_up_process(worker->task);
4438 * We want to clear UNBOUND but can't directly call
4439 * worker_clr_flags() or adjust nr_running. Atomically
4440 * replace UNBOUND with another NOT_RUNNING flag REBOUND.
4441 * @worker will clear REBOUND using worker_clr_flags() when
4442 * it initiates the next execution cycle thus restoring
4443 * concurrency management. Note that when or whether
4444 * @worker clears REBOUND doesn't affect correctness.
4446 * ACCESS_ONCE() is necessary because @worker->flags may be
4447 * tested without holding any lock in
4448 * wq_worker_waking_up(). Without it, NOT_RUNNING test may
4449 * fail incorrectly leading to premature concurrency
4450 * management operations.
4452 WARN_ON_ONCE(!(worker_flags & WORKER_UNBOUND));
4453 worker_flags |= WORKER_REBOUND;
4454 worker_flags &= ~WORKER_UNBOUND;
4455 ACCESS_ONCE(worker->flags) = worker_flags;
4458 spin_unlock_irq(&pool->lock);
4462 * restore_unbound_workers_cpumask - restore cpumask of unbound workers
4463 * @pool: unbound pool of interest
4464 * @cpu: the CPU which is coming up
4466 * An unbound pool may end up with a cpumask which doesn't have any online
4467 * CPUs. When a worker of such pool get scheduled, the scheduler resets
4468 * its cpus_allowed. If @cpu is in @pool's cpumask which didn't have any
4469 * online CPU before, cpus_allowed of all its workers should be restored.
4471 static void restore_unbound_workers_cpumask(struct worker_pool *pool, int cpu)
4473 static cpumask_t cpumask;
4474 struct worker *worker;
4476 lockdep_assert_held(&pool->attach_mutex);
4478 /* is @cpu allowed for @pool? */
4479 if (!cpumask_test_cpu(cpu, pool->attrs->cpumask))
4480 return;
4482 /* is @cpu the only online CPU? */
4483 cpumask_and(&cpumask, pool->attrs->cpumask, cpu_online_mask);
4484 if (cpumask_weight(&cpumask) != 1)
4485 return;
4487 /* as we're called from CPU_ONLINE, the following shouldn't fail */
4488 for_each_pool_worker(worker, pool)
4489 WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task,
4490 pool->attrs->cpumask) < 0);
4494 * Workqueues should be brought up before normal priority CPU notifiers.
4495 * This will be registered high priority CPU notifier.
4497 static int workqueue_cpu_up_callback(struct notifier_block *nfb,
4498 unsigned long action,
4499 void *hcpu)
4501 int cpu = (unsigned long)hcpu;
4502 struct worker_pool *pool;
4503 struct workqueue_struct *wq;
4504 int pi;
4506 switch (action & ~CPU_TASKS_FROZEN) {
4507 case CPU_UP_PREPARE:
4508 for_each_cpu_worker_pool(pool, cpu) {
4509 if (pool->nr_workers)
4510 continue;
4511 if (!create_worker(pool))
4512 return NOTIFY_BAD;
4514 break;
4516 case CPU_DOWN_FAILED:
4517 case CPU_ONLINE:
4518 mutex_lock(&wq_pool_mutex);
4520 for_each_pool(pool, pi) {
4521 mutex_lock(&pool->attach_mutex);
4523 if (pool->cpu == cpu)
4524 rebind_workers(pool);
4525 else if (pool->cpu < 0)
4526 restore_unbound_workers_cpumask(pool, cpu);
4528 mutex_unlock(&pool->attach_mutex);
4531 /* update NUMA affinity of unbound workqueues */
4532 list_for_each_entry(wq, &workqueues, list)
4533 wq_update_unbound_numa(wq, cpu, true);
4535 mutex_unlock(&wq_pool_mutex);
4536 break;
4538 return NOTIFY_OK;
4542 * Workqueues should be brought down after normal priority CPU notifiers.
4543 * This will be registered as low priority CPU notifier.
4545 static int workqueue_cpu_down_callback(struct notifier_block *nfb,
4546 unsigned long action,
4547 void *hcpu)
4549 int cpu = (unsigned long)hcpu;
4550 struct work_struct unbind_work;
4551 struct workqueue_struct *wq;
4553 switch (action & ~CPU_TASKS_FROZEN) {
4554 case CPU_DOWN_PREPARE:
4555 /* unbinding per-cpu workers should happen on the local CPU */
4556 INIT_WORK_ONSTACK(&unbind_work, wq_unbind_fn);
4557 queue_work_on(cpu, system_highpri_wq, &unbind_work);
4559 /* update NUMA affinity of unbound workqueues */
4560 mutex_lock(&wq_pool_mutex);
4561 list_for_each_entry(wq, &workqueues, list)
4562 wq_update_unbound_numa(wq, cpu, false);
4563 mutex_unlock(&wq_pool_mutex);
4565 /* wait for per-cpu unbinding to finish */
4566 flush_work(&unbind_work);
4567 destroy_work_on_stack(&unbind_work);
4568 break;
4570 return NOTIFY_OK;
4573 #ifdef CONFIG_SMP
4575 struct work_for_cpu {
4576 struct work_struct work;
4577 long (*fn)(void *);
4578 void *arg;
4579 long ret;
4582 static void work_for_cpu_fn(struct work_struct *work)
4584 struct work_for_cpu *wfc = container_of(work, struct work_for_cpu, work);
4586 wfc->ret = wfc->fn(wfc->arg);
4590 * work_on_cpu - run a function in user context on a particular cpu
4591 * @cpu: the cpu to run on
4592 * @fn: the function to run
4593 * @arg: the function arg
4595 * It is up to the caller to ensure that the cpu doesn't go offline.
4596 * The caller must not hold any locks which would prevent @fn from completing.
4598 * Return: The value @fn returns.
4600 long work_on_cpu(int cpu, long (*fn)(void *), void *arg)
4602 struct work_for_cpu wfc = { .fn = fn, .arg = arg };
4604 INIT_WORK_ONSTACK(&wfc.work, work_for_cpu_fn);
4605 schedule_work_on(cpu, &wfc.work);
4606 flush_work(&wfc.work);
4607 destroy_work_on_stack(&wfc.work);
4608 return wfc.ret;
4610 EXPORT_SYMBOL_GPL(work_on_cpu);
4611 #endif /* CONFIG_SMP */
4613 #ifdef CONFIG_FREEZER
4616 * freeze_workqueues_begin - begin freezing workqueues
4618 * Start freezing workqueues. After this function returns, all freezable
4619 * workqueues will queue new works to their delayed_works list instead of
4620 * pool->worklist.
4622 * CONTEXT:
4623 * Grabs and releases wq_pool_mutex, wq->mutex and pool->lock's.
4625 void freeze_workqueues_begin(void)
4627 struct workqueue_struct *wq;
4628 struct pool_workqueue *pwq;
4630 mutex_lock(&wq_pool_mutex);
4632 WARN_ON_ONCE(workqueue_freezing);
4633 workqueue_freezing = true;
4635 list_for_each_entry(wq, &workqueues, list) {
4636 mutex_lock(&wq->mutex);
4637 for_each_pwq(pwq, wq)
4638 pwq_adjust_max_active(pwq);
4639 mutex_unlock(&wq->mutex);
4642 mutex_unlock(&wq_pool_mutex);
4646 * freeze_workqueues_busy - are freezable workqueues still busy?
4648 * Check whether freezing is complete. This function must be called
4649 * between freeze_workqueues_begin() and thaw_workqueues().
4651 * CONTEXT:
4652 * Grabs and releases wq_pool_mutex.
4654 * Return:
4655 * %true if some freezable workqueues are still busy. %false if freezing
4656 * is complete.
4658 bool freeze_workqueues_busy(void)
4660 bool busy = false;
4661 struct workqueue_struct *wq;
4662 struct pool_workqueue *pwq;
4664 mutex_lock(&wq_pool_mutex);
4666 WARN_ON_ONCE(!workqueue_freezing);
4668 list_for_each_entry(wq, &workqueues, list) {
4669 if (!(wq->flags & WQ_FREEZABLE))
4670 continue;
4672 * nr_active is monotonically decreasing. It's safe
4673 * to peek without lock.
4675 rcu_read_lock_sched();
4676 for_each_pwq(pwq, wq) {
4677 WARN_ON_ONCE(pwq->nr_active < 0);
4678 if (pwq->nr_active) {
4679 busy = true;
4680 rcu_read_unlock_sched();
4681 goto out_unlock;
4684 rcu_read_unlock_sched();
4686 out_unlock:
4687 mutex_unlock(&wq_pool_mutex);
4688 return busy;
4692 * thaw_workqueues - thaw workqueues
4694 * Thaw workqueues. Normal queueing is restored and all collected
4695 * frozen works are transferred to their respective pool worklists.
4697 * CONTEXT:
4698 * Grabs and releases wq_pool_mutex, wq->mutex and pool->lock's.
4700 void thaw_workqueues(void)
4702 struct workqueue_struct *wq;
4703 struct pool_workqueue *pwq;
4705 mutex_lock(&wq_pool_mutex);
4707 if (!workqueue_freezing)
4708 goto out_unlock;
4710 workqueue_freezing = false;
4712 /* restore max_active and repopulate worklist */
4713 list_for_each_entry(wq, &workqueues, list) {
4714 mutex_lock(&wq->mutex);
4715 for_each_pwq(pwq, wq)
4716 pwq_adjust_max_active(pwq);
4717 mutex_unlock(&wq->mutex);
4720 out_unlock:
4721 mutex_unlock(&wq_pool_mutex);
4723 #endif /* CONFIG_FREEZER */
4725 static int workqueue_apply_unbound_cpumask(void)
4727 LIST_HEAD(ctxs);
4728 int ret = 0;
4729 struct workqueue_struct *wq;
4730 struct apply_wqattrs_ctx *ctx, *n;
4732 lockdep_assert_held(&wq_pool_mutex);
4734 list_for_each_entry(wq, &workqueues, list) {
4735 if (!(wq->flags & WQ_UNBOUND))
4736 continue;
4737 /* creating multiple pwqs breaks ordering guarantee */
4738 if (wq->flags & __WQ_ORDERED)
4739 continue;
4741 ctx = apply_wqattrs_prepare(wq, wq->unbound_attrs);
4742 if (!ctx) {
4743 ret = -ENOMEM;
4744 break;
4747 list_add_tail(&ctx->list, &ctxs);
4750 list_for_each_entry_safe(ctx, n, &ctxs, list) {
4751 if (!ret)
4752 apply_wqattrs_commit(ctx);
4753 apply_wqattrs_cleanup(ctx);
4756 return ret;
4760 * workqueue_set_unbound_cpumask - Set the low-level unbound cpumask
4761 * @cpumask: the cpumask to set
4763 * The low-level workqueues cpumask is a global cpumask that limits
4764 * the affinity of all unbound workqueues. This function check the @cpumask
4765 * and apply it to all unbound workqueues and updates all pwqs of them.
4767 * Retun: 0 - Success
4768 * -EINVAL - Invalid @cpumask
4769 * -ENOMEM - Failed to allocate memory for attrs or pwqs.
4771 int workqueue_set_unbound_cpumask(cpumask_var_t cpumask)
4773 int ret = -EINVAL;
4774 cpumask_var_t saved_cpumask;
4776 if (!zalloc_cpumask_var(&saved_cpumask, GFP_KERNEL))
4777 return -ENOMEM;
4779 cpumask_and(cpumask, cpumask, cpu_possible_mask);
4780 if (!cpumask_empty(cpumask)) {
4781 apply_wqattrs_lock();
4783 /* save the old wq_unbound_cpumask. */
4784 cpumask_copy(saved_cpumask, wq_unbound_cpumask);
4786 /* update wq_unbound_cpumask at first and apply it to wqs. */
4787 cpumask_copy(wq_unbound_cpumask, cpumask);
4788 ret = workqueue_apply_unbound_cpumask();
4790 /* restore the wq_unbound_cpumask when failed. */
4791 if (ret < 0)
4792 cpumask_copy(wq_unbound_cpumask, saved_cpumask);
4794 apply_wqattrs_unlock();
4797 free_cpumask_var(saved_cpumask);
4798 return ret;
4801 #ifdef CONFIG_SYSFS
4803 * Workqueues with WQ_SYSFS flag set is visible to userland via
4804 * /sys/bus/workqueue/devices/WQ_NAME. All visible workqueues have the
4805 * following attributes.
4807 * per_cpu RO bool : whether the workqueue is per-cpu or unbound
4808 * max_active RW int : maximum number of in-flight work items
4810 * Unbound workqueues have the following extra attributes.
4812 * id RO int : the associated pool ID
4813 * nice RW int : nice value of the workers
4814 * cpumask RW mask : bitmask of allowed CPUs for the workers
4816 struct wq_device {
4817 struct workqueue_struct *wq;
4818 struct device dev;
4821 static struct workqueue_struct *dev_to_wq(struct device *dev)
4823 struct wq_device *wq_dev = container_of(dev, struct wq_device, dev);
4825 return wq_dev->wq;
4828 static ssize_t per_cpu_show(struct device *dev, struct device_attribute *attr,
4829 char *buf)
4831 struct workqueue_struct *wq = dev_to_wq(dev);
4833 return scnprintf(buf, PAGE_SIZE, "%d\n", (bool)!(wq->flags & WQ_UNBOUND));
4835 static DEVICE_ATTR_RO(per_cpu);
4837 static ssize_t max_active_show(struct device *dev,
4838 struct device_attribute *attr, char *buf)
4840 struct workqueue_struct *wq = dev_to_wq(dev);
4842 return scnprintf(buf, PAGE_SIZE, "%d\n", wq->saved_max_active);
4845 static ssize_t max_active_store(struct device *dev,
4846 struct device_attribute *attr, const char *buf,
4847 size_t count)
4849 struct workqueue_struct *wq = dev_to_wq(dev);
4850 int val;
4852 if (sscanf(buf, "%d", &val) != 1 || val <= 0)
4853 return -EINVAL;
4855 workqueue_set_max_active(wq, val);
4856 return count;
4858 static DEVICE_ATTR_RW(max_active);
4860 static struct attribute *wq_sysfs_attrs[] = {
4861 &dev_attr_per_cpu.attr,
4862 &dev_attr_max_active.attr,
4863 NULL,
4865 ATTRIBUTE_GROUPS(wq_sysfs);
4867 static ssize_t wq_pool_ids_show(struct device *dev,
4868 struct device_attribute *attr, char *buf)
4870 struct workqueue_struct *wq = dev_to_wq(dev);
4871 const char *delim = "";
4872 int node, written = 0;
4874 rcu_read_lock_sched();
4875 for_each_node(node) {
4876 written += scnprintf(buf + written, PAGE_SIZE - written,
4877 "%s%d:%d", delim, node,
4878 unbound_pwq_by_node(wq, node)->pool->id);
4879 delim = " ";
4881 written += scnprintf(buf + written, PAGE_SIZE - written, "\n");
4882 rcu_read_unlock_sched();
4884 return written;
4887 static ssize_t wq_nice_show(struct device *dev, struct device_attribute *attr,
4888 char *buf)
4890 struct workqueue_struct *wq = dev_to_wq(dev);
4891 int written;
4893 mutex_lock(&wq->mutex);
4894 written = scnprintf(buf, PAGE_SIZE, "%d\n", wq->unbound_attrs->nice);
4895 mutex_unlock(&wq->mutex);
4897 return written;
4900 /* prepare workqueue_attrs for sysfs store operations */
4901 static struct workqueue_attrs *wq_sysfs_prep_attrs(struct workqueue_struct *wq)
4903 struct workqueue_attrs *attrs;
4905 lockdep_assert_held(&wq_pool_mutex);
4907 attrs = alloc_workqueue_attrs(GFP_KERNEL);
4908 if (!attrs)
4909 return NULL;
4911 copy_workqueue_attrs(attrs, wq->unbound_attrs);
4912 return attrs;
4915 static ssize_t wq_nice_store(struct device *dev, struct device_attribute *attr,
4916 const char *buf, size_t count)
4918 struct workqueue_struct *wq = dev_to_wq(dev);
4919 struct workqueue_attrs *attrs;
4920 int ret = -ENOMEM;
4922 apply_wqattrs_lock();
4924 attrs = wq_sysfs_prep_attrs(wq);
4925 if (!attrs)
4926 goto out_unlock;
4928 if (sscanf(buf, "%d", &attrs->nice) == 1 &&
4929 attrs->nice >= MIN_NICE && attrs->nice <= MAX_NICE)
4930 ret = apply_workqueue_attrs_locked(wq, attrs);
4931 else
4932 ret = -EINVAL;
4934 out_unlock:
4935 apply_wqattrs_unlock();
4936 free_workqueue_attrs(attrs);
4937 return ret ?: count;
4940 static ssize_t wq_cpumask_show(struct device *dev,
4941 struct device_attribute *attr, char *buf)
4943 struct workqueue_struct *wq = dev_to_wq(dev);
4944 int written;
4946 mutex_lock(&wq->mutex);
4947 written = scnprintf(buf, PAGE_SIZE, "%*pb\n",
4948 cpumask_pr_args(wq->unbound_attrs->cpumask));
4949 mutex_unlock(&wq->mutex);
4950 return written;
4953 static ssize_t wq_cpumask_store(struct device *dev,
4954 struct device_attribute *attr,
4955 const char *buf, size_t count)
4957 struct workqueue_struct *wq = dev_to_wq(dev);
4958 struct workqueue_attrs *attrs;
4959 int ret = -ENOMEM;
4961 apply_wqattrs_lock();
4963 attrs = wq_sysfs_prep_attrs(wq);
4964 if (!attrs)
4965 goto out_unlock;
4967 ret = cpumask_parse(buf, attrs->cpumask);
4968 if (!ret)
4969 ret = apply_workqueue_attrs_locked(wq, attrs);
4971 out_unlock:
4972 apply_wqattrs_unlock();
4973 free_workqueue_attrs(attrs);
4974 return ret ?: count;
4977 static ssize_t wq_numa_show(struct device *dev, struct device_attribute *attr,
4978 char *buf)
4980 struct workqueue_struct *wq = dev_to_wq(dev);
4981 int written;
4983 mutex_lock(&wq->mutex);
4984 written = scnprintf(buf, PAGE_SIZE, "%d\n",
4985 !wq->unbound_attrs->no_numa);
4986 mutex_unlock(&wq->mutex);
4988 return written;
4991 static ssize_t wq_numa_store(struct device *dev, struct device_attribute *attr,
4992 const char *buf, size_t count)
4994 struct workqueue_struct *wq = dev_to_wq(dev);
4995 struct workqueue_attrs *attrs;
4996 int v, ret = -ENOMEM;
4998 apply_wqattrs_lock();
5000 attrs = wq_sysfs_prep_attrs(wq);
5001 if (!attrs)
5002 goto out_unlock;
5004 ret = -EINVAL;
5005 if (sscanf(buf, "%d", &v) == 1) {
5006 attrs->no_numa = !v;
5007 ret = apply_workqueue_attrs_locked(wq, attrs);
5010 out_unlock:
5011 apply_wqattrs_unlock();
5012 free_workqueue_attrs(attrs);
5013 return ret ?: count;
5016 static struct device_attribute wq_sysfs_unbound_attrs[] = {
5017 __ATTR(pool_ids, 0444, wq_pool_ids_show, NULL),
5018 __ATTR(nice, 0644, wq_nice_show, wq_nice_store),
5019 __ATTR(cpumask, 0644, wq_cpumask_show, wq_cpumask_store),
5020 __ATTR(numa, 0644, wq_numa_show, wq_numa_store),
5021 __ATTR_NULL,
5024 static struct bus_type wq_subsys = {
5025 .name = "workqueue",
5026 .dev_groups = wq_sysfs_groups,
5029 static ssize_t wq_unbound_cpumask_show(struct device *dev,
5030 struct device_attribute *attr, char *buf)
5032 int written;
5034 mutex_lock(&wq_pool_mutex);
5035 written = scnprintf(buf, PAGE_SIZE, "%*pb\n",
5036 cpumask_pr_args(wq_unbound_cpumask));
5037 mutex_unlock(&wq_pool_mutex);
5039 return written;
5042 static ssize_t wq_unbound_cpumask_store(struct device *dev,
5043 struct device_attribute *attr, const char *buf, size_t count)
5045 cpumask_var_t cpumask;
5046 int ret;
5048 if (!zalloc_cpumask_var(&cpumask, GFP_KERNEL))
5049 return -ENOMEM;
5051 ret = cpumask_parse(buf, cpumask);
5052 if (!ret)
5053 ret = workqueue_set_unbound_cpumask(cpumask);
5055 free_cpumask_var(cpumask);
5056 return ret ? ret : count;
5059 static struct device_attribute wq_sysfs_cpumask_attr =
5060 __ATTR(cpumask, 0644, wq_unbound_cpumask_show,
5061 wq_unbound_cpumask_store);
5063 static int __init wq_sysfs_init(void)
5065 int err;
5067 err = subsys_virtual_register(&wq_subsys, NULL);
5068 if (err)
5069 return err;
5071 return device_create_file(wq_subsys.dev_root, &wq_sysfs_cpumask_attr);
5073 core_initcall(wq_sysfs_init);
5075 static void wq_device_release(struct device *dev)
5077 struct wq_device *wq_dev = container_of(dev, struct wq_device, dev);
5079 kfree(wq_dev);
5083 * workqueue_sysfs_register - make a workqueue visible in sysfs
5084 * @wq: the workqueue to register
5086 * Expose @wq in sysfs under /sys/bus/workqueue/devices.
5087 * alloc_workqueue*() automatically calls this function if WQ_SYSFS is set
5088 * which is the preferred method.
5090 * Workqueue user should use this function directly iff it wants to apply
5091 * workqueue_attrs before making the workqueue visible in sysfs; otherwise,
5092 * apply_workqueue_attrs() may race against userland updating the
5093 * attributes.
5095 * Return: 0 on success, -errno on failure.
5097 int workqueue_sysfs_register(struct workqueue_struct *wq)
5099 struct wq_device *wq_dev;
5100 int ret;
5103 * Adjusting max_active or creating new pwqs by applying
5104 * attributes breaks ordering guarantee. Disallow exposing ordered
5105 * workqueues.
5107 if (WARN_ON(wq->flags & __WQ_ORDERED))
5108 return -EINVAL;
5110 wq->wq_dev = wq_dev = kzalloc(sizeof(*wq_dev), GFP_KERNEL);
5111 if (!wq_dev)
5112 return -ENOMEM;
5114 wq_dev->wq = wq;
5115 wq_dev->dev.bus = &wq_subsys;
5116 wq_dev->dev.init_name = wq->name;
5117 wq_dev->dev.release = wq_device_release;
5120 * unbound_attrs are created separately. Suppress uevent until
5121 * everything is ready.
5123 dev_set_uevent_suppress(&wq_dev->dev, true);
5125 ret = device_register(&wq_dev->dev);
5126 if (ret) {
5127 kfree(wq_dev);
5128 wq->wq_dev = NULL;
5129 return ret;
5132 if (wq->flags & WQ_UNBOUND) {
5133 struct device_attribute *attr;
5135 for (attr = wq_sysfs_unbound_attrs; attr->attr.name; attr++) {
5136 ret = device_create_file(&wq_dev->dev, attr);
5137 if (ret) {
5138 device_unregister(&wq_dev->dev);
5139 wq->wq_dev = NULL;
5140 return ret;
5145 dev_set_uevent_suppress(&wq_dev->dev, false);
5146 kobject_uevent(&wq_dev->dev.kobj, KOBJ_ADD);
5147 return 0;
5151 * workqueue_sysfs_unregister - undo workqueue_sysfs_register()
5152 * @wq: the workqueue to unregister
5154 * If @wq is registered to sysfs by workqueue_sysfs_register(), unregister.
5156 static void workqueue_sysfs_unregister(struct workqueue_struct *wq)
5158 struct wq_device *wq_dev = wq->wq_dev;
5160 if (!wq->wq_dev)
5161 return;
5163 wq->wq_dev = NULL;
5164 device_unregister(&wq_dev->dev);
5166 #else /* CONFIG_SYSFS */
5167 static void workqueue_sysfs_unregister(struct workqueue_struct *wq) { }
5168 #endif /* CONFIG_SYSFS */
5170 static void __init wq_numa_init(void)
5172 cpumask_var_t *tbl;
5173 int node, cpu;
5175 if (num_possible_nodes() <= 1)
5176 return;
5178 if (wq_disable_numa) {
5179 pr_info("workqueue: NUMA affinity support disabled\n");
5180 return;
5183 wq_update_unbound_numa_attrs_buf = alloc_workqueue_attrs(GFP_KERNEL);
5184 BUG_ON(!wq_update_unbound_numa_attrs_buf);
5187 * We want masks of possible CPUs of each node which isn't readily
5188 * available. Build one from cpu_to_node() which should have been
5189 * fully initialized by now.
5191 tbl = kzalloc(nr_node_ids * sizeof(tbl[0]), GFP_KERNEL);
5192 BUG_ON(!tbl);
5194 for_each_node(node)
5195 BUG_ON(!zalloc_cpumask_var_node(&tbl[node], GFP_KERNEL,
5196 node_online(node) ? node : NUMA_NO_NODE));
5198 for_each_possible_cpu(cpu) {
5199 node = cpu_to_node(cpu);
5200 if (WARN_ON(node == NUMA_NO_NODE)) {
5201 pr_warn("workqueue: NUMA node mapping not available for cpu%d, disabling NUMA support\n", cpu);
5202 /* happens iff arch is bonkers, let's just proceed */
5203 return;
5205 cpumask_set_cpu(cpu, tbl[node]);
5208 wq_numa_possible_cpumask = tbl;
5209 wq_numa_enabled = true;
5212 static int __init init_workqueues(void)
5214 int std_nice[NR_STD_WORKER_POOLS] = { 0, HIGHPRI_NICE_LEVEL };
5215 int i, cpu;
5217 WARN_ON(__alignof__(struct pool_workqueue) < __alignof__(long long));
5219 BUG_ON(!alloc_cpumask_var(&wq_unbound_cpumask, GFP_KERNEL));
5220 cpumask_copy(wq_unbound_cpumask, cpu_possible_mask);
5222 pwq_cache = KMEM_CACHE(pool_workqueue, SLAB_PANIC);
5224 cpu_notifier(workqueue_cpu_up_callback, CPU_PRI_WORKQUEUE_UP);
5225 hotcpu_notifier(workqueue_cpu_down_callback, CPU_PRI_WORKQUEUE_DOWN);
5227 wq_numa_init();
5229 /* initialize CPU pools */
5230 for_each_possible_cpu(cpu) {
5231 struct worker_pool *pool;
5233 i = 0;
5234 for_each_cpu_worker_pool(pool, cpu) {
5235 BUG_ON(init_worker_pool(pool));
5236 pool->cpu = cpu;
5237 cpumask_copy(pool->attrs->cpumask, cpumask_of(cpu));
5238 pool->attrs->nice = std_nice[i++];
5239 pool->node = cpu_to_node(cpu);
5241 /* alloc pool ID */
5242 mutex_lock(&wq_pool_mutex);
5243 BUG_ON(worker_pool_assign_id(pool));
5244 mutex_unlock(&wq_pool_mutex);
5248 /* create the initial worker */
5249 for_each_online_cpu(cpu) {
5250 struct worker_pool *pool;
5252 for_each_cpu_worker_pool(pool, cpu) {
5253 pool->flags &= ~POOL_DISASSOCIATED;
5254 BUG_ON(!create_worker(pool));
5258 /* create default unbound and ordered wq attrs */
5259 for (i = 0; i < NR_STD_WORKER_POOLS; i++) {
5260 struct workqueue_attrs *attrs;
5262 BUG_ON(!(attrs = alloc_workqueue_attrs(GFP_KERNEL)));
5263 attrs->nice = std_nice[i];
5264 unbound_std_wq_attrs[i] = attrs;
5267 * An ordered wq should have only one pwq as ordering is
5268 * guaranteed by max_active which is enforced by pwqs.
5269 * Turn off NUMA so that dfl_pwq is used for all nodes.
5271 BUG_ON(!(attrs = alloc_workqueue_attrs(GFP_KERNEL)));
5272 attrs->nice = std_nice[i];
5273 attrs->no_numa = true;
5274 ordered_wq_attrs[i] = attrs;
5277 system_wq = alloc_workqueue("events", 0, 0);
5278 system_highpri_wq = alloc_workqueue("events_highpri", WQ_HIGHPRI, 0);
5279 system_long_wq = alloc_workqueue("events_long", 0, 0);
5280 system_unbound_wq = alloc_workqueue("events_unbound", WQ_UNBOUND,
5281 WQ_UNBOUND_MAX_ACTIVE);
5282 system_freezable_wq = alloc_workqueue("events_freezable",
5283 WQ_FREEZABLE, 0);
5284 system_power_efficient_wq = alloc_workqueue("events_power_efficient",
5285 WQ_POWER_EFFICIENT, 0);
5286 system_freezable_power_efficient_wq = alloc_workqueue("events_freezable_power_efficient",
5287 WQ_FREEZABLE | WQ_POWER_EFFICIENT,
5289 BUG_ON(!system_wq || !system_highpri_wq || !system_long_wq ||
5290 !system_unbound_wq || !system_freezable_wq ||
5291 !system_power_efficient_wq ||
5292 !system_freezable_power_efficient_wq);
5293 return 0;
5295 early_initcall(init_workqueues);