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>
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 is one worker pool for each CPU and
20 * one extra for works which are better served by workers which are
21 * not bound to any specific CPU.
23 * Please read Documentation/workqueue.txt for details.
26 #include <linux/export.h>
27 #include <linux/kernel.h>
28 #include <linux/sched.h>
29 #include <linux/init.h>
30 #include <linux/signal.h>
31 #include <linux/completion.h>
32 #include <linux/workqueue.h>
33 #include <linux/slab.h>
34 #include <linux/cpu.h>
35 #include <linux/notifier.h>
36 #include <linux/kthread.h>
37 #include <linux/hardirq.h>
38 #include <linux/mempolicy.h>
39 #include <linux/freezer.h>
40 #include <linux/kallsyms.h>
41 #include <linux/debug_locks.h>
42 #include <linux/lockdep.h>
43 #include <linux/idr.h>
44 #include <linux/hashtable.h>
46 #include "workqueue_internal.h"
52 * A bound pool is either associated or disassociated with its CPU.
53 * While associated (!DISASSOCIATED), all workers are bound to the
54 * CPU and none has %WORKER_UNBOUND set and concurrency management
57 * While DISASSOCIATED, the cpu may be offline and all workers have
58 * %WORKER_UNBOUND set and concurrency management disabled, and may
59 * be executing on any CPU. The pool behaves as an unbound one.
61 * Note that DISASSOCIATED can be flipped only while holding
62 * assoc_mutex to avoid changing binding state while
63 * create_worker() is in progress.
65 POOL_MANAGE_WORKERS
= 1 << 0, /* need to manage workers */
66 POOL_MANAGING_WORKERS
= 1 << 1, /* managing workers */
67 POOL_DISASSOCIATED
= 1 << 2, /* cpu can't serve workers */
68 POOL_FREEZING
= 1 << 3, /* freeze in progress */
71 WORKER_STARTED
= 1 << 0, /* started */
72 WORKER_DIE
= 1 << 1, /* die die die */
73 WORKER_IDLE
= 1 << 2, /* is idle */
74 WORKER_PREP
= 1 << 3, /* preparing to run works */
75 WORKER_CPU_INTENSIVE
= 1 << 6, /* cpu intensive */
76 WORKER_UNBOUND
= 1 << 7, /* worker is unbound */
78 WORKER_NOT_RUNNING
= WORKER_PREP
| WORKER_UNBOUND
|
81 NR_STD_WORKER_POOLS
= 2, /* # standard pools per cpu */
83 BUSY_WORKER_HASH_ORDER
= 6, /* 64 pointers */
85 MAX_IDLE_WORKERS_RATIO
= 4, /* 1/4 of busy can be idle */
86 IDLE_WORKER_TIMEOUT
= 300 * HZ
, /* keep idle ones for 5 mins */
88 MAYDAY_INITIAL_TIMEOUT
= HZ
/ 100 >= 2 ? HZ
/ 100 : 2,
89 /* call for help after 10ms
91 MAYDAY_INTERVAL
= HZ
/ 10, /* and then every 100ms */
92 CREATE_COOLDOWN
= HZ
, /* time to breath after fail */
95 * Rescue workers are used only on emergencies and shared by
98 RESCUER_NICE_LEVEL
= -20,
99 HIGHPRI_NICE_LEVEL
= -20,
103 * Structure fields follow one of the following exclusion rules.
105 * I: Modifiable by initialization/destruction paths and read-only for
108 * P: Preemption protected. Disabling preemption is enough and should
109 * only be modified and accessed from the local cpu.
111 * L: pool->lock protected. Access with pool->lock held.
113 * X: During normal operation, modification requires pool->lock and should
114 * be done only from local cpu. Either disabling preemption on local
115 * cpu or grabbing pool->lock is enough for read access. If
116 * POOL_DISASSOCIATED is set, it's identical to L.
118 * F: wq->flush_mutex protected.
120 * W: workqueue_lock protected.
123 /* struct worker is defined in workqueue_internal.h */
126 spinlock_t lock
; /* the pool lock */
127 unsigned int cpu
; /* I: the associated cpu */
128 int id
; /* I: pool ID */
129 unsigned int flags
; /* X: flags */
131 struct list_head worklist
; /* L: list of pending works */
132 int nr_workers
; /* L: total number of workers */
134 /* nr_idle includes the ones off idle_list for rebinding */
135 int nr_idle
; /* L: currently idle ones */
137 struct list_head idle_list
; /* X: list of idle workers */
138 struct timer_list idle_timer
; /* L: worker idle timeout */
139 struct timer_list mayday_timer
; /* L: SOS timer for workers */
141 /* workers are chained either in busy_hash or idle_list */
142 DECLARE_HASHTABLE(busy_hash
, BUSY_WORKER_HASH_ORDER
);
143 /* L: hash of busy workers */
145 struct mutex assoc_mutex
; /* protect POOL_DISASSOCIATED */
146 struct ida worker_ida
; /* L: for worker IDs */
149 * The current concurrency level. As it's likely to be accessed
150 * from other CPUs during try_to_wake_up(), put it in a separate
153 atomic_t nr_running ____cacheline_aligned_in_smp
;
154 } ____cacheline_aligned_in_smp
;
157 * The per-pool workqueue. While queued, the lower WORK_STRUCT_FLAG_BITS
158 * of work_struct->data are used for flags and the remaining high bits
159 * point to the pwq; thus, pwqs need to be aligned at two's power of the
160 * number of flag bits.
162 struct pool_workqueue
{
163 struct worker_pool
*pool
; /* I: the associated pool */
164 struct workqueue_struct
*wq
; /* I: the owning workqueue */
165 int work_color
; /* L: current color */
166 int flush_color
; /* L: flushing color */
167 int nr_in_flight
[WORK_NR_COLORS
];
168 /* L: nr of in_flight works */
169 int nr_active
; /* L: nr of active works */
170 int max_active
; /* L: max active works */
171 struct list_head delayed_works
; /* L: delayed works */
172 struct list_head pwqs_node
; /* I: node on wq->pwqs */
173 } __aligned(1 << WORK_STRUCT_FLAG_BITS
);
176 * Structure used to wait for workqueue flush.
179 struct list_head list
; /* F: list of flushers */
180 int flush_color
; /* F: flush color waiting for */
181 struct completion done
; /* flush completion */
185 * All cpumasks are assumed to be always set on UP and thus can't be
186 * used to determine whether there's something to be done.
189 typedef cpumask_var_t mayday_mask_t
;
190 #define mayday_test_and_set_cpu(cpu, mask) \
191 cpumask_test_and_set_cpu((cpu), (mask))
192 #define mayday_clear_cpu(cpu, mask) cpumask_clear_cpu((cpu), (mask))
193 #define for_each_mayday_cpu(cpu, mask) for_each_cpu((cpu), (mask))
194 #define alloc_mayday_mask(maskp, gfp) zalloc_cpumask_var((maskp), (gfp))
195 #define free_mayday_mask(mask) free_cpumask_var((mask))
197 typedef unsigned long mayday_mask_t
;
198 #define mayday_test_and_set_cpu(cpu, mask) test_and_set_bit(0, &(mask))
199 #define mayday_clear_cpu(cpu, mask) clear_bit(0, &(mask))
200 #define for_each_mayday_cpu(cpu, mask) if ((cpu) = 0, (mask))
201 #define alloc_mayday_mask(maskp, gfp) true
202 #define free_mayday_mask(mask) do { } while (0)
206 * The externally visible workqueue abstraction is an array of
207 * per-CPU workqueues:
209 struct workqueue_struct
{
210 unsigned int flags
; /* W: WQ_* flags */
212 struct pool_workqueue __percpu
*pcpu
;
213 struct pool_workqueue
*single
;
215 } pool_wq
; /* I: pwq's */
216 struct list_head pwqs
; /* I: all pwqs of this wq */
217 struct list_head list
; /* W: list of all workqueues */
219 struct mutex flush_mutex
; /* protects wq flushing */
220 int work_color
; /* F: current work color */
221 int flush_color
; /* F: current flush color */
222 atomic_t nr_pwqs_to_flush
; /* flush in progress */
223 struct wq_flusher
*first_flusher
; /* F: first flusher */
224 struct list_head flusher_queue
; /* F: flush waiters */
225 struct list_head flusher_overflow
; /* F: flush overflow list */
227 mayday_mask_t mayday_mask
; /* cpus requesting rescue */
228 struct worker
*rescuer
; /* I: rescue worker */
230 int nr_drainers
; /* W: drain in progress */
231 int saved_max_active
; /* W: saved pwq max_active */
232 #ifdef CONFIG_LOCKDEP
233 struct lockdep_map lockdep_map
;
235 char name
[]; /* I: workqueue name */
238 static struct kmem_cache
*pwq_cache
;
240 struct workqueue_struct
*system_wq __read_mostly
;
241 EXPORT_SYMBOL_GPL(system_wq
);
242 struct workqueue_struct
*system_highpri_wq __read_mostly
;
243 EXPORT_SYMBOL_GPL(system_highpri_wq
);
244 struct workqueue_struct
*system_long_wq __read_mostly
;
245 EXPORT_SYMBOL_GPL(system_long_wq
);
246 struct workqueue_struct
*system_unbound_wq __read_mostly
;
247 EXPORT_SYMBOL_GPL(system_unbound_wq
);
248 struct workqueue_struct
*system_freezable_wq __read_mostly
;
249 EXPORT_SYMBOL_GPL(system_freezable_wq
);
251 #define CREATE_TRACE_POINTS
252 #include <trace/events/workqueue.h>
254 #define for_each_std_worker_pool(pool, cpu) \
255 for ((pool) = &std_worker_pools(cpu)[0]; \
256 (pool) < &std_worker_pools(cpu)[NR_STD_WORKER_POOLS]; (pool)++)
258 #define for_each_busy_worker(worker, i, pool) \
259 hash_for_each(pool->busy_hash, i, worker, hentry)
261 static inline int __next_wq_cpu(int cpu
, const struct cpumask
*mask
,
264 if (cpu
< nr_cpu_ids
) {
266 cpu
= cpumask_next(cpu
, mask
);
267 if (cpu
< nr_cpu_ids
)
271 return WORK_CPU_UNBOUND
;
279 * An extra cpu number is defined using an invalid cpu number
280 * (WORK_CPU_UNBOUND) to host workqueues which are not bound to any
281 * specific CPU. The following iterators are similar to for_each_*_cpu()
282 * iterators but also considers the unbound CPU.
284 * for_each_wq_cpu() : possible CPUs + WORK_CPU_UNBOUND
285 * for_each_online_wq_cpu() : online CPUs + WORK_CPU_UNBOUND
287 #define for_each_wq_cpu(cpu) \
288 for ((cpu) = __next_wq_cpu(-1, cpu_possible_mask, 3); \
289 (cpu) < WORK_CPU_END; \
290 (cpu) = __next_wq_cpu((cpu), cpu_possible_mask, 3))
292 #define for_each_online_wq_cpu(cpu) \
293 for ((cpu) = __next_wq_cpu(-1, cpu_online_mask, 3); \
294 (cpu) < WORK_CPU_END; \
295 (cpu) = __next_wq_cpu((cpu), cpu_online_mask, 3))
298 * for_each_pool - iterate through all worker_pools in the system
299 * @pool: iteration cursor
300 * @id: integer used for iteration
302 #define for_each_pool(pool, id) \
303 idr_for_each_entry(&worker_pool_idr, pool, id)
306 * for_each_pwq - iterate through all pool_workqueues of the specified workqueue
307 * @pwq: iteration cursor
308 * @wq: the target workqueue
310 #define for_each_pwq(pwq, wq) \
311 list_for_each_entry((pwq), &(wq)->pwqs, pwqs_node)
313 #ifdef CONFIG_DEBUG_OBJECTS_WORK
315 static struct debug_obj_descr work_debug_descr
;
317 static void *work_debug_hint(void *addr
)
319 return ((struct work_struct
*) addr
)->func
;
323 * fixup_init is called when:
324 * - an active object is initialized
326 static int work_fixup_init(void *addr
, enum debug_obj_state state
)
328 struct work_struct
*work
= addr
;
331 case ODEBUG_STATE_ACTIVE
:
332 cancel_work_sync(work
);
333 debug_object_init(work
, &work_debug_descr
);
341 * fixup_activate is called when:
342 * - an active object is activated
343 * - an unknown object is activated (might be a statically initialized object)
345 static int work_fixup_activate(void *addr
, enum debug_obj_state state
)
347 struct work_struct
*work
= addr
;
351 case ODEBUG_STATE_NOTAVAILABLE
:
353 * This is not really a fixup. The work struct was
354 * statically initialized. We just make sure that it
355 * is tracked in the object tracker.
357 if (test_bit(WORK_STRUCT_STATIC_BIT
, work_data_bits(work
))) {
358 debug_object_init(work
, &work_debug_descr
);
359 debug_object_activate(work
, &work_debug_descr
);
365 case ODEBUG_STATE_ACTIVE
:
374 * fixup_free is called when:
375 * - an active object is freed
377 static int work_fixup_free(void *addr
, enum debug_obj_state state
)
379 struct work_struct
*work
= addr
;
382 case ODEBUG_STATE_ACTIVE
:
383 cancel_work_sync(work
);
384 debug_object_free(work
, &work_debug_descr
);
391 static struct debug_obj_descr work_debug_descr
= {
392 .name
= "work_struct",
393 .debug_hint
= work_debug_hint
,
394 .fixup_init
= work_fixup_init
,
395 .fixup_activate
= work_fixup_activate
,
396 .fixup_free
= work_fixup_free
,
399 static inline void debug_work_activate(struct work_struct
*work
)
401 debug_object_activate(work
, &work_debug_descr
);
404 static inline void debug_work_deactivate(struct work_struct
*work
)
406 debug_object_deactivate(work
, &work_debug_descr
);
409 void __init_work(struct work_struct
*work
, int onstack
)
412 debug_object_init_on_stack(work
, &work_debug_descr
);
414 debug_object_init(work
, &work_debug_descr
);
416 EXPORT_SYMBOL_GPL(__init_work
);
418 void destroy_work_on_stack(struct work_struct
*work
)
420 debug_object_free(work
, &work_debug_descr
);
422 EXPORT_SYMBOL_GPL(destroy_work_on_stack
);
425 static inline void debug_work_activate(struct work_struct
*work
) { }
426 static inline void debug_work_deactivate(struct work_struct
*work
) { }
429 /* Serializes the accesses to the list of workqueues. */
430 static DEFINE_SPINLOCK(workqueue_lock
);
431 static LIST_HEAD(workqueues
);
432 static bool workqueue_freezing
; /* W: have wqs started freezing? */
435 * The CPU and unbound standard worker pools. The unbound ones have
436 * POOL_DISASSOCIATED set, and their workers have WORKER_UNBOUND set.
438 static DEFINE_PER_CPU_SHARED_ALIGNED(struct worker_pool
[NR_STD_WORKER_POOLS
],
439 cpu_std_worker_pools
);
440 static struct worker_pool unbound_std_worker_pools
[NR_STD_WORKER_POOLS
];
442 /* idr of all pools */
443 static DEFINE_MUTEX(worker_pool_idr_mutex
);
444 static DEFINE_IDR(worker_pool_idr
);
446 static int worker_thread(void *__worker
);
448 static struct worker_pool
*std_worker_pools(int cpu
)
450 if (cpu
!= WORK_CPU_UNBOUND
)
451 return per_cpu(cpu_std_worker_pools
, cpu
);
453 return unbound_std_worker_pools
;
456 static int std_worker_pool_pri(struct worker_pool
*pool
)
458 return pool
- std_worker_pools(pool
->cpu
);
461 /* allocate ID and assign it to @pool */
462 static int worker_pool_assign_id(struct worker_pool
*pool
)
466 mutex_lock(&worker_pool_idr_mutex
);
467 idr_pre_get(&worker_pool_idr
, GFP_KERNEL
);
468 ret
= idr_get_new(&worker_pool_idr
, pool
, &pool
->id
);
469 mutex_unlock(&worker_pool_idr_mutex
);
475 * Lookup worker_pool by id. The idr currently is built during boot and
476 * never modified. Don't worry about locking for now.
478 static struct worker_pool
*worker_pool_by_id(int pool_id
)
480 return idr_find(&worker_pool_idr
, pool_id
);
483 static struct worker_pool
*get_std_worker_pool(int cpu
, bool highpri
)
485 struct worker_pool
*pools
= std_worker_pools(cpu
);
487 return &pools
[highpri
];
490 static struct pool_workqueue
*get_pwq(unsigned int cpu
,
491 struct workqueue_struct
*wq
)
493 if (!(wq
->flags
& WQ_UNBOUND
)) {
494 if (likely(cpu
< nr_cpu_ids
))
495 return per_cpu_ptr(wq
->pool_wq
.pcpu
, cpu
);
496 } else if (likely(cpu
== WORK_CPU_UNBOUND
))
497 return wq
->pool_wq
.single
;
501 static unsigned int work_color_to_flags(int color
)
503 return color
<< WORK_STRUCT_COLOR_SHIFT
;
506 static int get_work_color(struct work_struct
*work
)
508 return (*work_data_bits(work
) >> WORK_STRUCT_COLOR_SHIFT
) &
509 ((1 << WORK_STRUCT_COLOR_BITS
) - 1);
512 static int work_next_color(int color
)
514 return (color
+ 1) % WORK_NR_COLORS
;
518 * While queued, %WORK_STRUCT_PWQ is set and non flag bits of a work's data
519 * contain the pointer to the queued pwq. Once execution starts, the flag
520 * is cleared and the high bits contain OFFQ flags and pool ID.
522 * set_work_pwq(), set_work_pool_and_clear_pending(), mark_work_canceling()
523 * and clear_work_data() can be used to set the pwq, pool or clear
524 * work->data. These functions should only be called while the work is
525 * owned - ie. while the PENDING bit is set.
527 * get_work_pool() and get_work_pwq() can be used to obtain the pool or pwq
528 * corresponding to a work. Pool is available once the work has been
529 * queued anywhere after initialization until it is sync canceled. pwq is
530 * available only while the work item is queued.
532 * %WORK_OFFQ_CANCELING is used to mark a work item which is being
533 * canceled. While being canceled, a work item may have its PENDING set
534 * but stay off timer and worklist for arbitrarily long and nobody should
535 * try to steal the PENDING bit.
537 static inline void set_work_data(struct work_struct
*work
, unsigned long data
,
540 WARN_ON_ONCE(!work_pending(work
));
541 atomic_long_set(&work
->data
, data
| flags
| work_static(work
));
544 static void set_work_pwq(struct work_struct
*work
, struct pool_workqueue
*pwq
,
545 unsigned long extra_flags
)
547 set_work_data(work
, (unsigned long)pwq
,
548 WORK_STRUCT_PENDING
| WORK_STRUCT_PWQ
| extra_flags
);
551 static void set_work_pool_and_keep_pending(struct work_struct
*work
,
554 set_work_data(work
, (unsigned long)pool_id
<< WORK_OFFQ_POOL_SHIFT
,
555 WORK_STRUCT_PENDING
);
558 static void set_work_pool_and_clear_pending(struct work_struct
*work
,
562 * The following wmb is paired with the implied mb in
563 * test_and_set_bit(PENDING) and ensures all updates to @work made
564 * here are visible to and precede any updates by the next PENDING
568 set_work_data(work
, (unsigned long)pool_id
<< WORK_OFFQ_POOL_SHIFT
, 0);
571 static void clear_work_data(struct work_struct
*work
)
573 smp_wmb(); /* see set_work_pool_and_clear_pending() */
574 set_work_data(work
, WORK_STRUCT_NO_POOL
, 0);
577 static struct pool_workqueue
*get_work_pwq(struct work_struct
*work
)
579 unsigned long data
= atomic_long_read(&work
->data
);
581 if (data
& WORK_STRUCT_PWQ
)
582 return (void *)(data
& WORK_STRUCT_WQ_DATA_MASK
);
588 * get_work_pool - return the worker_pool a given work was associated with
589 * @work: the work item of interest
591 * Return the worker_pool @work was last associated with. %NULL if none.
593 static struct worker_pool
*get_work_pool(struct work_struct
*work
)
595 unsigned long data
= atomic_long_read(&work
->data
);
596 struct worker_pool
*pool
;
599 if (data
& WORK_STRUCT_PWQ
)
600 return ((struct pool_workqueue
*)
601 (data
& WORK_STRUCT_WQ_DATA_MASK
))->pool
;
603 pool_id
= data
>> WORK_OFFQ_POOL_SHIFT
;
604 if (pool_id
== WORK_OFFQ_POOL_NONE
)
607 pool
= worker_pool_by_id(pool_id
);
613 * get_work_pool_id - return the worker pool ID a given work is associated with
614 * @work: the work item of interest
616 * Return the worker_pool ID @work was last associated with.
617 * %WORK_OFFQ_POOL_NONE if none.
619 static int get_work_pool_id(struct work_struct
*work
)
621 unsigned long data
= atomic_long_read(&work
->data
);
623 if (data
& WORK_STRUCT_PWQ
)
624 return ((struct pool_workqueue
*)
625 (data
& WORK_STRUCT_WQ_DATA_MASK
))->pool
->id
;
627 return data
>> WORK_OFFQ_POOL_SHIFT
;
630 static void mark_work_canceling(struct work_struct
*work
)
632 unsigned long pool_id
= get_work_pool_id(work
);
634 pool_id
<<= WORK_OFFQ_POOL_SHIFT
;
635 set_work_data(work
, pool_id
| WORK_OFFQ_CANCELING
, WORK_STRUCT_PENDING
);
638 static bool work_is_canceling(struct work_struct
*work
)
640 unsigned long data
= atomic_long_read(&work
->data
);
642 return !(data
& WORK_STRUCT_PWQ
) && (data
& WORK_OFFQ_CANCELING
);
646 * Policy functions. These define the policies on how the global worker
647 * pools are managed. Unless noted otherwise, these functions assume that
648 * they're being called with pool->lock held.
651 static bool __need_more_worker(struct worker_pool
*pool
)
653 return !atomic_read(&pool
->nr_running
);
657 * Need to wake up a worker? Called from anything but currently
660 * Note that, because unbound workers never contribute to nr_running, this
661 * function will always return %true for unbound pools as long as the
662 * worklist isn't empty.
664 static bool need_more_worker(struct worker_pool
*pool
)
666 return !list_empty(&pool
->worklist
) && __need_more_worker(pool
);
669 /* Can I start working? Called from busy but !running workers. */
670 static bool may_start_working(struct worker_pool
*pool
)
672 return pool
->nr_idle
;
675 /* Do I need to keep working? Called from currently running workers. */
676 static bool keep_working(struct worker_pool
*pool
)
678 return !list_empty(&pool
->worklist
) &&
679 atomic_read(&pool
->nr_running
) <= 1;
682 /* Do we need a new worker? Called from manager. */
683 static bool need_to_create_worker(struct worker_pool
*pool
)
685 return need_more_worker(pool
) && !may_start_working(pool
);
688 /* Do I need to be the manager? */
689 static bool need_to_manage_workers(struct worker_pool
*pool
)
691 return need_to_create_worker(pool
) ||
692 (pool
->flags
& POOL_MANAGE_WORKERS
);
695 /* Do we have too many workers and should some go away? */
696 static bool too_many_workers(struct worker_pool
*pool
)
698 bool managing
= pool
->flags
& POOL_MANAGING_WORKERS
;
699 int nr_idle
= pool
->nr_idle
+ managing
; /* manager is considered idle */
700 int nr_busy
= pool
->nr_workers
- nr_idle
;
703 * nr_idle and idle_list may disagree if idle rebinding is in
704 * progress. Never return %true if idle_list is empty.
706 if (list_empty(&pool
->idle_list
))
709 return nr_idle
> 2 && (nr_idle
- 2) * MAX_IDLE_WORKERS_RATIO
>= nr_busy
;
716 /* Return the first worker. Safe with preemption disabled */
717 static struct worker
*first_worker(struct worker_pool
*pool
)
719 if (unlikely(list_empty(&pool
->idle_list
)))
722 return list_first_entry(&pool
->idle_list
, struct worker
, entry
);
726 * wake_up_worker - wake up an idle worker
727 * @pool: worker pool to wake worker from
729 * Wake up the first idle worker of @pool.
732 * spin_lock_irq(pool->lock).
734 static void wake_up_worker(struct worker_pool
*pool
)
736 struct worker
*worker
= first_worker(pool
);
739 wake_up_process(worker
->task
);
743 * wq_worker_waking_up - a worker is waking up
744 * @task: task waking up
745 * @cpu: CPU @task is waking up to
747 * This function is called during try_to_wake_up() when a worker is
751 * spin_lock_irq(rq->lock)
753 void wq_worker_waking_up(struct task_struct
*task
, unsigned int cpu
)
755 struct worker
*worker
= kthread_data(task
);
757 if (!(worker
->flags
& WORKER_NOT_RUNNING
)) {
758 WARN_ON_ONCE(worker
->pool
->cpu
!= cpu
);
759 atomic_inc(&worker
->pool
->nr_running
);
764 * wq_worker_sleeping - a worker is going to sleep
765 * @task: task going to sleep
766 * @cpu: CPU in question, must be the current CPU number
768 * This function is called during schedule() when a busy worker is
769 * going to sleep. Worker on the same cpu can be woken up by
770 * returning pointer to its task.
773 * spin_lock_irq(rq->lock)
776 * Worker task on @cpu to wake up, %NULL if none.
778 struct task_struct
*wq_worker_sleeping(struct task_struct
*task
,
781 struct worker
*worker
= kthread_data(task
), *to_wakeup
= NULL
;
782 struct worker_pool
*pool
;
785 * Rescuers, which may not have all the fields set up like normal
786 * workers, also reach here, let's not access anything before
787 * checking NOT_RUNNING.
789 if (worker
->flags
& WORKER_NOT_RUNNING
)
794 /* this can only happen on the local cpu */
795 if (WARN_ON_ONCE(cpu
!= raw_smp_processor_id()))
799 * The counterpart of the following dec_and_test, implied mb,
800 * worklist not empty test sequence is in insert_work().
801 * Please read comment there.
803 * NOT_RUNNING is clear. This means that we're bound to and
804 * running on the local cpu w/ rq lock held and preemption
805 * disabled, which in turn means that none else could be
806 * manipulating idle_list, so dereferencing idle_list without pool
809 if (atomic_dec_and_test(&pool
->nr_running
) &&
810 !list_empty(&pool
->worklist
))
811 to_wakeup
= first_worker(pool
);
812 return to_wakeup
? to_wakeup
->task
: NULL
;
816 * worker_set_flags - set worker flags and adjust nr_running accordingly
818 * @flags: flags to set
819 * @wakeup: wakeup an idle worker if necessary
821 * Set @flags in @worker->flags and adjust nr_running accordingly. If
822 * nr_running becomes zero and @wakeup is %true, an idle worker is
826 * spin_lock_irq(pool->lock)
828 static inline void worker_set_flags(struct worker
*worker
, unsigned int flags
,
831 struct worker_pool
*pool
= worker
->pool
;
833 WARN_ON_ONCE(worker
->task
!= current
);
836 * If transitioning into NOT_RUNNING, adjust nr_running and
837 * wake up an idle worker as necessary if requested by
840 if ((flags
& WORKER_NOT_RUNNING
) &&
841 !(worker
->flags
& WORKER_NOT_RUNNING
)) {
843 if (atomic_dec_and_test(&pool
->nr_running
) &&
844 !list_empty(&pool
->worklist
))
845 wake_up_worker(pool
);
847 atomic_dec(&pool
->nr_running
);
850 worker
->flags
|= flags
;
854 * worker_clr_flags - clear worker flags and adjust nr_running accordingly
856 * @flags: flags to clear
858 * Clear @flags in @worker->flags and adjust nr_running accordingly.
861 * spin_lock_irq(pool->lock)
863 static inline void worker_clr_flags(struct worker
*worker
, unsigned int flags
)
865 struct worker_pool
*pool
= worker
->pool
;
866 unsigned int oflags
= worker
->flags
;
868 WARN_ON_ONCE(worker
->task
!= current
);
870 worker
->flags
&= ~flags
;
873 * If transitioning out of NOT_RUNNING, increment nr_running. Note
874 * that the nested NOT_RUNNING is not a noop. NOT_RUNNING is mask
875 * of multiple flags, not a single flag.
877 if ((flags
& WORKER_NOT_RUNNING
) && (oflags
& WORKER_NOT_RUNNING
))
878 if (!(worker
->flags
& WORKER_NOT_RUNNING
))
879 atomic_inc(&pool
->nr_running
);
883 * find_worker_executing_work - find worker which is executing a work
884 * @pool: pool of interest
885 * @work: work to find worker for
887 * Find a worker which is executing @work on @pool by searching
888 * @pool->busy_hash which is keyed by the address of @work. For a worker
889 * to match, its current execution should match the address of @work and
890 * its work function. This is to avoid unwanted dependency between
891 * unrelated work executions through a work item being recycled while still
894 * This is a bit tricky. A work item may be freed once its execution
895 * starts and nothing prevents the freed area from being recycled for
896 * another work item. If the same work item address ends up being reused
897 * before the original execution finishes, workqueue will identify the
898 * recycled work item as currently executing and make it wait until the
899 * current execution finishes, introducing an unwanted dependency.
901 * This function checks the work item address, work function and workqueue
902 * to avoid false positives. Note that this isn't complete as one may
903 * construct a work function which can introduce dependency onto itself
904 * through a recycled work item. Well, if somebody wants to shoot oneself
905 * in the foot that badly, there's only so much we can do, and if such
906 * deadlock actually occurs, it should be easy to locate the culprit work
910 * spin_lock_irq(pool->lock).
913 * Pointer to worker which is executing @work if found, NULL
916 static struct worker
*find_worker_executing_work(struct worker_pool
*pool
,
917 struct work_struct
*work
)
919 struct worker
*worker
;
921 hash_for_each_possible(pool
->busy_hash
, worker
, hentry
,
923 if (worker
->current_work
== work
&&
924 worker
->current_func
== work
->func
)
931 * move_linked_works - move linked works to a list
932 * @work: start of series of works to be scheduled
933 * @head: target list to append @work to
934 * @nextp: out paramter for nested worklist walking
936 * Schedule linked works starting from @work to @head. Work series to
937 * be scheduled starts at @work and includes any consecutive work with
938 * WORK_STRUCT_LINKED set in its predecessor.
940 * If @nextp is not NULL, it's updated to point to the next work of
941 * the last scheduled work. This allows move_linked_works() to be
942 * nested inside outer list_for_each_entry_safe().
945 * spin_lock_irq(pool->lock).
947 static void move_linked_works(struct work_struct
*work
, struct list_head
*head
,
948 struct work_struct
**nextp
)
950 struct work_struct
*n
;
953 * Linked worklist will always end before the end of the list,
954 * use NULL for list head.
956 list_for_each_entry_safe_from(work
, n
, NULL
, entry
) {
957 list_move_tail(&work
->entry
, head
);
958 if (!(*work_data_bits(work
) & WORK_STRUCT_LINKED
))
963 * If we're already inside safe list traversal and have moved
964 * multiple works to the scheduled queue, the next position
965 * needs to be updated.
971 static void pwq_activate_delayed_work(struct work_struct
*work
)
973 struct pool_workqueue
*pwq
= get_work_pwq(work
);
975 trace_workqueue_activate_work(work
);
976 move_linked_works(work
, &pwq
->pool
->worklist
, NULL
);
977 __clear_bit(WORK_STRUCT_DELAYED_BIT
, work_data_bits(work
));
981 static void pwq_activate_first_delayed(struct pool_workqueue
*pwq
)
983 struct work_struct
*work
= list_first_entry(&pwq
->delayed_works
,
984 struct work_struct
, entry
);
986 pwq_activate_delayed_work(work
);
990 * pwq_dec_nr_in_flight - decrement pwq's nr_in_flight
991 * @pwq: pwq of interest
992 * @color: color of work which left the queue
994 * A work either has completed or is removed from pending queue,
995 * decrement nr_in_flight of its pwq and handle workqueue flushing.
998 * spin_lock_irq(pool->lock).
1000 static void pwq_dec_nr_in_flight(struct pool_workqueue
*pwq
, int color
)
1002 /* ignore uncolored works */
1003 if (color
== WORK_NO_COLOR
)
1006 pwq
->nr_in_flight
[color
]--;
1009 if (!list_empty(&pwq
->delayed_works
)) {
1010 /* one down, submit a delayed one */
1011 if (pwq
->nr_active
< pwq
->max_active
)
1012 pwq_activate_first_delayed(pwq
);
1015 /* is flush in progress and are we at the flushing tip? */
1016 if (likely(pwq
->flush_color
!= color
))
1019 /* are there still in-flight works? */
1020 if (pwq
->nr_in_flight
[color
])
1023 /* this pwq is done, clear flush_color */
1024 pwq
->flush_color
= -1;
1027 * If this was the last pwq, wake up the first flusher. It
1028 * will handle the rest.
1030 if (atomic_dec_and_test(&pwq
->wq
->nr_pwqs_to_flush
))
1031 complete(&pwq
->wq
->first_flusher
->done
);
1035 * try_to_grab_pending - steal work item from worklist and disable irq
1036 * @work: work item to steal
1037 * @is_dwork: @work is a delayed_work
1038 * @flags: place to store irq state
1040 * Try to grab PENDING bit of @work. This function can handle @work in any
1041 * stable state - idle, on timer or on worklist. Return values are
1043 * 1 if @work was pending and we successfully stole PENDING
1044 * 0 if @work was idle and we claimed PENDING
1045 * -EAGAIN if PENDING couldn't be grabbed at the moment, safe to busy-retry
1046 * -ENOENT if someone else is canceling @work, this state may persist
1047 * for arbitrarily long
1049 * On >= 0 return, the caller owns @work's PENDING bit. To avoid getting
1050 * interrupted while holding PENDING and @work off queue, irq must be
1051 * disabled on entry. This, combined with delayed_work->timer being
1052 * irqsafe, ensures that we return -EAGAIN for finite short period of time.
1054 * On successful return, >= 0, irq is disabled and the caller is
1055 * responsible for releasing it using local_irq_restore(*@flags).
1057 * This function is safe to call from any context including IRQ handler.
1059 static int try_to_grab_pending(struct work_struct
*work
, bool is_dwork
,
1060 unsigned long *flags
)
1062 struct worker_pool
*pool
;
1063 struct pool_workqueue
*pwq
;
1065 local_irq_save(*flags
);
1067 /* try to steal the timer if it exists */
1069 struct delayed_work
*dwork
= to_delayed_work(work
);
1072 * dwork->timer is irqsafe. If del_timer() fails, it's
1073 * guaranteed that the timer is not queued anywhere and not
1074 * running on the local CPU.
1076 if (likely(del_timer(&dwork
->timer
)))
1080 /* try to claim PENDING the normal way */
1081 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT
, work_data_bits(work
)))
1085 * The queueing is in progress, or it is already queued. Try to
1086 * steal it from ->worklist without clearing WORK_STRUCT_PENDING.
1088 pool
= get_work_pool(work
);
1092 spin_lock(&pool
->lock
);
1094 * work->data is guaranteed to point to pwq only while the work
1095 * item is queued on pwq->wq, and both updating work->data to point
1096 * to pwq on queueing and to pool on dequeueing are done under
1097 * pwq->pool->lock. This in turn guarantees that, if work->data
1098 * points to pwq which is associated with a locked pool, the work
1099 * item is currently queued on that pool.
1101 pwq
= get_work_pwq(work
);
1102 if (pwq
&& pwq
->pool
== pool
) {
1103 debug_work_deactivate(work
);
1106 * A delayed work item cannot be grabbed directly because
1107 * it might have linked NO_COLOR work items which, if left
1108 * on the delayed_list, will confuse pwq->nr_active
1109 * management later on and cause stall. Make sure the work
1110 * item is activated before grabbing.
1112 if (*work_data_bits(work
) & WORK_STRUCT_DELAYED
)
1113 pwq_activate_delayed_work(work
);
1115 list_del_init(&work
->entry
);
1116 pwq_dec_nr_in_flight(get_work_pwq(work
), get_work_color(work
));
1118 /* work->data points to pwq iff queued, point to pool */
1119 set_work_pool_and_keep_pending(work
, pool
->id
);
1121 spin_unlock(&pool
->lock
);
1124 spin_unlock(&pool
->lock
);
1126 local_irq_restore(*flags
);
1127 if (work_is_canceling(work
))
1134 * insert_work - insert a work into a pool
1135 * @pwq: pwq @work belongs to
1136 * @work: work to insert
1137 * @head: insertion point
1138 * @extra_flags: extra WORK_STRUCT_* flags to set
1140 * Insert @work which belongs to @pwq after @head. @extra_flags is or'd to
1141 * work_struct flags.
1144 * spin_lock_irq(pool->lock).
1146 static void insert_work(struct pool_workqueue
*pwq
, struct work_struct
*work
,
1147 struct list_head
*head
, unsigned int extra_flags
)
1149 struct worker_pool
*pool
= pwq
->pool
;
1151 /* we own @work, set data and link */
1152 set_work_pwq(work
, pwq
, extra_flags
);
1153 list_add_tail(&work
->entry
, head
);
1156 * Ensure either worker_sched_deactivated() sees the above
1157 * list_add_tail() or we see zero nr_running to avoid workers
1158 * lying around lazily while there are works to be processed.
1162 if (__need_more_worker(pool
))
1163 wake_up_worker(pool
);
1167 * Test whether @work is being queued from another work executing on the
1170 static bool is_chained_work(struct workqueue_struct
*wq
)
1172 struct worker
*worker
;
1174 worker
= current_wq_worker();
1176 * Return %true iff I'm a worker execuing a work item on @wq. If
1177 * I'm @worker, it's safe to dereference it without locking.
1179 return worker
&& worker
->current_pwq
->wq
== wq
;
1182 static void __queue_work(unsigned int cpu
, struct workqueue_struct
*wq
,
1183 struct work_struct
*work
)
1185 struct pool_workqueue
*pwq
;
1186 struct list_head
*worklist
;
1187 unsigned int work_flags
;
1188 unsigned int req_cpu
= cpu
;
1191 * While a work item is PENDING && off queue, a task trying to
1192 * steal the PENDING will busy-loop waiting for it to either get
1193 * queued or lose PENDING. Grabbing PENDING and queueing should
1194 * happen with IRQ disabled.
1196 WARN_ON_ONCE(!irqs_disabled());
1198 debug_work_activate(work
);
1200 /* if dying, only works from the same workqueue are allowed */
1201 if (unlikely(wq
->flags
& WQ_DRAINING
) &&
1202 WARN_ON_ONCE(!is_chained_work(wq
)))
1205 /* determine the pwq to use */
1206 if (!(wq
->flags
& WQ_UNBOUND
)) {
1207 struct worker_pool
*last_pool
;
1209 if (cpu
== WORK_CPU_UNBOUND
)
1210 cpu
= raw_smp_processor_id();
1213 * It's multi cpu. If @work was previously on a different
1214 * cpu, it might still be running there, in which case the
1215 * work needs to be queued on that cpu to guarantee
1218 pwq
= get_pwq(cpu
, wq
);
1219 last_pool
= get_work_pool(work
);
1221 if (last_pool
&& last_pool
!= pwq
->pool
) {
1222 struct worker
*worker
;
1224 spin_lock(&last_pool
->lock
);
1226 worker
= find_worker_executing_work(last_pool
, work
);
1228 if (worker
&& worker
->current_pwq
->wq
== wq
) {
1229 pwq
= get_pwq(last_pool
->cpu
, wq
);
1231 /* meh... not running there, queue here */
1232 spin_unlock(&last_pool
->lock
);
1233 spin_lock(&pwq
->pool
->lock
);
1236 spin_lock(&pwq
->pool
->lock
);
1239 pwq
= get_pwq(WORK_CPU_UNBOUND
, wq
);
1240 spin_lock(&pwq
->pool
->lock
);
1243 /* pwq determined, queue */
1244 trace_workqueue_queue_work(req_cpu
, pwq
, work
);
1246 if (WARN_ON(!list_empty(&work
->entry
))) {
1247 spin_unlock(&pwq
->pool
->lock
);
1251 pwq
->nr_in_flight
[pwq
->work_color
]++;
1252 work_flags
= work_color_to_flags(pwq
->work_color
);
1254 if (likely(pwq
->nr_active
< pwq
->max_active
)) {
1255 trace_workqueue_activate_work(work
);
1257 worklist
= &pwq
->pool
->worklist
;
1259 work_flags
|= WORK_STRUCT_DELAYED
;
1260 worklist
= &pwq
->delayed_works
;
1263 insert_work(pwq
, work
, worklist
, work_flags
);
1265 spin_unlock(&pwq
->pool
->lock
);
1269 * queue_work_on - queue work on specific cpu
1270 * @cpu: CPU number to execute work on
1271 * @wq: workqueue to use
1272 * @work: work to queue
1274 * Returns %false if @work was already on a queue, %true otherwise.
1276 * We queue the work to a specific CPU, the caller must ensure it
1279 bool queue_work_on(int cpu
, struct workqueue_struct
*wq
,
1280 struct work_struct
*work
)
1283 unsigned long flags
;
1285 local_irq_save(flags
);
1287 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT
, work_data_bits(work
))) {
1288 __queue_work(cpu
, wq
, work
);
1292 local_irq_restore(flags
);
1295 EXPORT_SYMBOL_GPL(queue_work_on
);
1298 * queue_work - queue work on a workqueue
1299 * @wq: workqueue to use
1300 * @work: work to queue
1302 * Returns %false if @work was already on a queue, %true otherwise.
1304 * We queue the work to the CPU on which it was submitted, but if the CPU dies
1305 * it can be processed by another CPU.
1307 bool queue_work(struct workqueue_struct
*wq
, struct work_struct
*work
)
1309 return queue_work_on(WORK_CPU_UNBOUND
, wq
, work
);
1311 EXPORT_SYMBOL_GPL(queue_work
);
1313 void delayed_work_timer_fn(unsigned long __data
)
1315 struct delayed_work
*dwork
= (struct delayed_work
*)__data
;
1317 /* should have been called from irqsafe timer with irq already off */
1318 __queue_work(dwork
->cpu
, dwork
->wq
, &dwork
->work
);
1320 EXPORT_SYMBOL(delayed_work_timer_fn
);
1322 static void __queue_delayed_work(int cpu
, struct workqueue_struct
*wq
,
1323 struct delayed_work
*dwork
, unsigned long delay
)
1325 struct timer_list
*timer
= &dwork
->timer
;
1326 struct work_struct
*work
= &dwork
->work
;
1328 WARN_ON_ONCE(timer
->function
!= delayed_work_timer_fn
||
1329 timer
->data
!= (unsigned long)dwork
);
1330 WARN_ON_ONCE(timer_pending(timer
));
1331 WARN_ON_ONCE(!list_empty(&work
->entry
));
1334 * If @delay is 0, queue @dwork->work immediately. This is for
1335 * both optimization and correctness. The earliest @timer can
1336 * expire is on the closest next tick and delayed_work users depend
1337 * on that there's no such delay when @delay is 0.
1340 __queue_work(cpu
, wq
, &dwork
->work
);
1344 timer_stats_timer_set_start_info(&dwork
->timer
);
1348 timer
->expires
= jiffies
+ delay
;
1350 if (unlikely(cpu
!= WORK_CPU_UNBOUND
))
1351 add_timer_on(timer
, cpu
);
1357 * queue_delayed_work_on - queue work on specific CPU after delay
1358 * @cpu: CPU number to execute work on
1359 * @wq: workqueue to use
1360 * @dwork: work to queue
1361 * @delay: number of jiffies to wait before queueing
1363 * Returns %false if @work was already on a queue, %true otherwise. If
1364 * @delay is zero and @dwork is idle, it will be scheduled for immediate
1367 bool queue_delayed_work_on(int cpu
, struct workqueue_struct
*wq
,
1368 struct delayed_work
*dwork
, unsigned long delay
)
1370 struct work_struct
*work
= &dwork
->work
;
1372 unsigned long flags
;
1374 /* read the comment in __queue_work() */
1375 local_irq_save(flags
);
1377 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT
, work_data_bits(work
))) {
1378 __queue_delayed_work(cpu
, wq
, dwork
, delay
);
1382 local_irq_restore(flags
);
1385 EXPORT_SYMBOL_GPL(queue_delayed_work_on
);
1388 * queue_delayed_work - queue work on a workqueue after delay
1389 * @wq: workqueue to use
1390 * @dwork: delayable work to queue
1391 * @delay: number of jiffies to wait before queueing
1393 * Equivalent to queue_delayed_work_on() but tries to use the local CPU.
1395 bool queue_delayed_work(struct workqueue_struct
*wq
,
1396 struct delayed_work
*dwork
, unsigned long delay
)
1398 return queue_delayed_work_on(WORK_CPU_UNBOUND
, wq
, dwork
, delay
);
1400 EXPORT_SYMBOL_GPL(queue_delayed_work
);
1403 * mod_delayed_work_on - modify delay of or queue a delayed work on specific CPU
1404 * @cpu: CPU number to execute work on
1405 * @wq: workqueue to use
1406 * @dwork: work to queue
1407 * @delay: number of jiffies to wait before queueing
1409 * If @dwork is idle, equivalent to queue_delayed_work_on(); otherwise,
1410 * modify @dwork's timer so that it expires after @delay. If @delay is
1411 * zero, @work is guaranteed to be scheduled immediately regardless of its
1414 * Returns %false if @dwork was idle and queued, %true if @dwork was
1415 * pending and its timer was modified.
1417 * This function is safe to call from any context including IRQ handler.
1418 * See try_to_grab_pending() for details.
1420 bool mod_delayed_work_on(int cpu
, struct workqueue_struct
*wq
,
1421 struct delayed_work
*dwork
, unsigned long delay
)
1423 unsigned long flags
;
1427 ret
= try_to_grab_pending(&dwork
->work
, true, &flags
);
1428 } while (unlikely(ret
== -EAGAIN
));
1430 if (likely(ret
>= 0)) {
1431 __queue_delayed_work(cpu
, wq
, dwork
, delay
);
1432 local_irq_restore(flags
);
1435 /* -ENOENT from try_to_grab_pending() becomes %true */
1438 EXPORT_SYMBOL_GPL(mod_delayed_work_on
);
1441 * mod_delayed_work - modify delay of or queue a delayed work
1442 * @wq: workqueue to use
1443 * @dwork: work to queue
1444 * @delay: number of jiffies to wait before queueing
1446 * mod_delayed_work_on() on local CPU.
1448 bool mod_delayed_work(struct workqueue_struct
*wq
, struct delayed_work
*dwork
,
1449 unsigned long delay
)
1451 return mod_delayed_work_on(WORK_CPU_UNBOUND
, wq
, dwork
, delay
);
1453 EXPORT_SYMBOL_GPL(mod_delayed_work
);
1456 * worker_enter_idle - enter idle state
1457 * @worker: worker which is entering idle state
1459 * @worker is entering idle state. Update stats and idle timer if
1463 * spin_lock_irq(pool->lock).
1465 static void worker_enter_idle(struct worker
*worker
)
1467 struct worker_pool
*pool
= worker
->pool
;
1469 if (WARN_ON_ONCE(worker
->flags
& WORKER_IDLE
) ||
1470 WARN_ON_ONCE(!list_empty(&worker
->entry
) &&
1471 (worker
->hentry
.next
|| worker
->hentry
.pprev
)))
1474 /* can't use worker_set_flags(), also called from start_worker() */
1475 worker
->flags
|= WORKER_IDLE
;
1477 worker
->last_active
= jiffies
;
1479 /* idle_list is LIFO */
1480 list_add(&worker
->entry
, &pool
->idle_list
);
1482 if (too_many_workers(pool
) && !timer_pending(&pool
->idle_timer
))
1483 mod_timer(&pool
->idle_timer
, jiffies
+ IDLE_WORKER_TIMEOUT
);
1486 * Sanity check nr_running. Because wq_unbind_fn() releases
1487 * pool->lock between setting %WORKER_UNBOUND and zapping
1488 * nr_running, the warning may trigger spuriously. Check iff
1489 * unbind is not in progress.
1491 WARN_ON_ONCE(!(pool
->flags
& POOL_DISASSOCIATED
) &&
1492 pool
->nr_workers
== pool
->nr_idle
&&
1493 atomic_read(&pool
->nr_running
));
1497 * worker_leave_idle - leave idle state
1498 * @worker: worker which is leaving idle state
1500 * @worker is leaving idle state. Update stats.
1503 * spin_lock_irq(pool->lock).
1505 static void worker_leave_idle(struct worker
*worker
)
1507 struct worker_pool
*pool
= worker
->pool
;
1509 if (WARN_ON_ONCE(!(worker
->flags
& WORKER_IDLE
)))
1511 worker_clr_flags(worker
, WORKER_IDLE
);
1513 list_del_init(&worker
->entry
);
1517 * worker_maybe_bind_and_lock - try to bind %current to worker_pool and lock it
1518 * @pool: target worker_pool
1520 * Bind %current to the cpu of @pool if it is associated and lock @pool.
1522 * Works which are scheduled while the cpu is online must at least be
1523 * scheduled to a worker which is bound to the cpu so that if they are
1524 * flushed from cpu callbacks while cpu is going down, they are
1525 * guaranteed to execute on the cpu.
1527 * This function is to be used by unbound workers and rescuers to bind
1528 * themselves to the target cpu and may race with cpu going down or
1529 * coming online. kthread_bind() can't be used because it may put the
1530 * worker to already dead cpu and set_cpus_allowed_ptr() can't be used
1531 * verbatim as it's best effort and blocking and pool may be
1532 * [dis]associated in the meantime.
1534 * This function tries set_cpus_allowed() and locks pool and verifies the
1535 * binding against %POOL_DISASSOCIATED which is set during
1536 * %CPU_DOWN_PREPARE and cleared during %CPU_ONLINE, so if the worker
1537 * enters idle state or fetches works without dropping lock, it can
1538 * guarantee the scheduling requirement described in the first paragraph.
1541 * Might sleep. Called without any lock but returns with pool->lock
1545 * %true if the associated pool is online (@worker is successfully
1546 * bound), %false if offline.
1548 static bool worker_maybe_bind_and_lock(struct worker_pool
*pool
)
1549 __acquires(&pool
->lock
)
1553 * The following call may fail, succeed or succeed
1554 * without actually migrating the task to the cpu if
1555 * it races with cpu hotunplug operation. Verify
1556 * against POOL_DISASSOCIATED.
1558 if (!(pool
->flags
& POOL_DISASSOCIATED
))
1559 set_cpus_allowed_ptr(current
, get_cpu_mask(pool
->cpu
));
1561 spin_lock_irq(&pool
->lock
);
1562 if (pool
->flags
& POOL_DISASSOCIATED
)
1564 if (task_cpu(current
) == pool
->cpu
&&
1565 cpumask_equal(¤t
->cpus_allowed
,
1566 get_cpu_mask(pool
->cpu
)))
1568 spin_unlock_irq(&pool
->lock
);
1571 * We've raced with CPU hot[un]plug. Give it a breather
1572 * and retry migration. cond_resched() is required here;
1573 * otherwise, we might deadlock against cpu_stop trying to
1574 * bring down the CPU on non-preemptive kernel.
1582 * Rebind an idle @worker to its CPU. worker_thread() will test
1583 * list_empty(@worker->entry) before leaving idle and call this function.
1585 static void idle_worker_rebind(struct worker
*worker
)
1587 /* CPU may go down again inbetween, clear UNBOUND only on success */
1588 if (worker_maybe_bind_and_lock(worker
->pool
))
1589 worker_clr_flags(worker
, WORKER_UNBOUND
);
1591 /* rebind complete, become available again */
1592 list_add(&worker
->entry
, &worker
->pool
->idle_list
);
1593 spin_unlock_irq(&worker
->pool
->lock
);
1597 * Function for @worker->rebind.work used to rebind unbound busy workers to
1598 * the associated cpu which is coming back online. This is scheduled by
1599 * cpu up but can race with other cpu hotplug operations and may be
1600 * executed twice without intervening cpu down.
1602 static void busy_worker_rebind_fn(struct work_struct
*work
)
1604 struct worker
*worker
= container_of(work
, struct worker
, rebind_work
);
1606 if (worker_maybe_bind_and_lock(worker
->pool
))
1607 worker_clr_flags(worker
, WORKER_UNBOUND
);
1609 spin_unlock_irq(&worker
->pool
->lock
);
1613 * rebind_workers - rebind all workers of a pool to the associated CPU
1614 * @pool: pool of interest
1616 * @pool->cpu is coming online. Rebind all workers to the CPU. Rebinding
1617 * is different for idle and busy ones.
1619 * Idle ones will be removed from the idle_list and woken up. They will
1620 * add themselves back after completing rebind. This ensures that the
1621 * idle_list doesn't contain any unbound workers when re-bound busy workers
1622 * try to perform local wake-ups for concurrency management.
1624 * Busy workers can rebind after they finish their current work items.
1625 * Queueing the rebind work item at the head of the scheduled list is
1626 * enough. Note that nr_running will be properly bumped as busy workers
1629 * On return, all non-manager workers are scheduled for rebind - see
1630 * manage_workers() for the manager special case. Any idle worker
1631 * including the manager will not appear on @idle_list until rebind is
1632 * complete, making local wake-ups safe.
1634 static void rebind_workers(struct worker_pool
*pool
)
1636 struct worker
*worker
, *n
;
1639 lockdep_assert_held(&pool
->assoc_mutex
);
1640 lockdep_assert_held(&pool
->lock
);
1642 /* dequeue and kick idle ones */
1643 list_for_each_entry_safe(worker
, n
, &pool
->idle_list
, entry
) {
1645 * idle workers should be off @pool->idle_list until rebind
1646 * is complete to avoid receiving premature local wake-ups.
1648 list_del_init(&worker
->entry
);
1651 * worker_thread() will see the above dequeuing and call
1652 * idle_worker_rebind().
1654 wake_up_process(worker
->task
);
1657 /* rebind busy workers */
1658 for_each_busy_worker(worker
, i
, pool
) {
1659 struct work_struct
*rebind_work
= &worker
->rebind_work
;
1660 struct workqueue_struct
*wq
;
1662 if (test_and_set_bit(WORK_STRUCT_PENDING_BIT
,
1663 work_data_bits(rebind_work
)))
1666 debug_work_activate(rebind_work
);
1669 * wq doesn't really matter but let's keep @worker->pool
1670 * and @pwq->pool consistent for sanity.
1672 if (std_worker_pool_pri(worker
->pool
))
1673 wq
= system_highpri_wq
;
1677 insert_work(get_pwq(pool
->cpu
, wq
), rebind_work
,
1678 worker
->scheduled
.next
,
1679 work_color_to_flags(WORK_NO_COLOR
));
1683 static struct worker
*alloc_worker(void)
1685 struct worker
*worker
;
1687 worker
= kzalloc(sizeof(*worker
), GFP_KERNEL
);
1689 INIT_LIST_HEAD(&worker
->entry
);
1690 INIT_LIST_HEAD(&worker
->scheduled
);
1691 INIT_WORK(&worker
->rebind_work
, busy_worker_rebind_fn
);
1692 /* on creation a worker is in !idle && prep state */
1693 worker
->flags
= WORKER_PREP
;
1699 * create_worker - create a new workqueue worker
1700 * @pool: pool the new worker will belong to
1702 * Create a new worker which is bound to @pool. The returned worker
1703 * can be started by calling start_worker() or destroyed using
1707 * Might sleep. Does GFP_KERNEL allocations.
1710 * Pointer to the newly created worker.
1712 static struct worker
*create_worker(struct worker_pool
*pool
)
1714 const char *pri
= std_worker_pool_pri(pool
) ? "H" : "";
1715 struct worker
*worker
= NULL
;
1718 spin_lock_irq(&pool
->lock
);
1719 while (ida_get_new(&pool
->worker_ida
, &id
)) {
1720 spin_unlock_irq(&pool
->lock
);
1721 if (!ida_pre_get(&pool
->worker_ida
, GFP_KERNEL
))
1723 spin_lock_irq(&pool
->lock
);
1725 spin_unlock_irq(&pool
->lock
);
1727 worker
= alloc_worker();
1731 worker
->pool
= pool
;
1734 if (pool
->cpu
!= WORK_CPU_UNBOUND
)
1735 worker
->task
= kthread_create_on_node(worker_thread
,
1736 worker
, cpu_to_node(pool
->cpu
),
1737 "kworker/%u:%d%s", pool
->cpu
, id
, pri
);
1739 worker
->task
= kthread_create(worker_thread
, worker
,
1740 "kworker/u:%d%s", id
, pri
);
1741 if (IS_ERR(worker
->task
))
1744 if (std_worker_pool_pri(pool
))
1745 set_user_nice(worker
->task
, HIGHPRI_NICE_LEVEL
);
1748 * Determine CPU binding of the new worker depending on
1749 * %POOL_DISASSOCIATED. The caller is responsible for ensuring the
1750 * flag remains stable across this function. See the comments
1751 * above the flag definition for details.
1753 * As an unbound worker may later become a regular one if CPU comes
1754 * online, make sure every worker has %PF_THREAD_BOUND set.
1756 if (!(pool
->flags
& POOL_DISASSOCIATED
)) {
1757 kthread_bind(worker
->task
, pool
->cpu
);
1759 worker
->task
->flags
|= PF_THREAD_BOUND
;
1760 worker
->flags
|= WORKER_UNBOUND
;
1766 spin_lock_irq(&pool
->lock
);
1767 ida_remove(&pool
->worker_ida
, id
);
1768 spin_unlock_irq(&pool
->lock
);
1775 * start_worker - start a newly created worker
1776 * @worker: worker to start
1778 * Make the pool aware of @worker and start it.
1781 * spin_lock_irq(pool->lock).
1783 static void start_worker(struct worker
*worker
)
1785 worker
->flags
|= WORKER_STARTED
;
1786 worker
->pool
->nr_workers
++;
1787 worker_enter_idle(worker
);
1788 wake_up_process(worker
->task
);
1792 * destroy_worker - destroy a workqueue worker
1793 * @worker: worker to be destroyed
1795 * Destroy @worker and adjust @pool stats accordingly.
1798 * spin_lock_irq(pool->lock) which is released and regrabbed.
1800 static void destroy_worker(struct worker
*worker
)
1802 struct worker_pool
*pool
= worker
->pool
;
1803 int id
= worker
->id
;
1805 /* sanity check frenzy */
1806 if (WARN_ON(worker
->current_work
) ||
1807 WARN_ON(!list_empty(&worker
->scheduled
)))
1810 if (worker
->flags
& WORKER_STARTED
)
1812 if (worker
->flags
& WORKER_IDLE
)
1815 list_del_init(&worker
->entry
);
1816 worker
->flags
|= WORKER_DIE
;
1818 spin_unlock_irq(&pool
->lock
);
1820 kthread_stop(worker
->task
);
1823 spin_lock_irq(&pool
->lock
);
1824 ida_remove(&pool
->worker_ida
, id
);
1827 static void idle_worker_timeout(unsigned long __pool
)
1829 struct worker_pool
*pool
= (void *)__pool
;
1831 spin_lock_irq(&pool
->lock
);
1833 if (too_many_workers(pool
)) {
1834 struct worker
*worker
;
1835 unsigned long expires
;
1837 /* idle_list is kept in LIFO order, check the last one */
1838 worker
= list_entry(pool
->idle_list
.prev
, struct worker
, entry
);
1839 expires
= worker
->last_active
+ IDLE_WORKER_TIMEOUT
;
1841 if (time_before(jiffies
, expires
))
1842 mod_timer(&pool
->idle_timer
, expires
);
1844 /* it's been idle for too long, wake up manager */
1845 pool
->flags
|= POOL_MANAGE_WORKERS
;
1846 wake_up_worker(pool
);
1850 spin_unlock_irq(&pool
->lock
);
1853 static bool send_mayday(struct work_struct
*work
)
1855 struct pool_workqueue
*pwq
= get_work_pwq(work
);
1856 struct workqueue_struct
*wq
= pwq
->wq
;
1859 if (!(wq
->flags
& WQ_RESCUER
))
1862 /* mayday mayday mayday */
1863 cpu
= pwq
->pool
->cpu
;
1864 /* WORK_CPU_UNBOUND can't be set in cpumask, use cpu 0 instead */
1865 if (cpu
== WORK_CPU_UNBOUND
)
1867 if (!mayday_test_and_set_cpu(cpu
, wq
->mayday_mask
))
1868 wake_up_process(wq
->rescuer
->task
);
1872 static void pool_mayday_timeout(unsigned long __pool
)
1874 struct worker_pool
*pool
= (void *)__pool
;
1875 struct work_struct
*work
;
1877 spin_lock_irq(&pool
->lock
);
1879 if (need_to_create_worker(pool
)) {
1881 * We've been trying to create a new worker but
1882 * haven't been successful. We might be hitting an
1883 * allocation deadlock. Send distress signals to
1886 list_for_each_entry(work
, &pool
->worklist
, entry
)
1890 spin_unlock_irq(&pool
->lock
);
1892 mod_timer(&pool
->mayday_timer
, jiffies
+ MAYDAY_INTERVAL
);
1896 * maybe_create_worker - create a new worker if necessary
1897 * @pool: pool to create a new worker for
1899 * Create a new worker for @pool if necessary. @pool is guaranteed to
1900 * have at least one idle worker on return from this function. If
1901 * creating a new worker takes longer than MAYDAY_INTERVAL, mayday is
1902 * sent to all rescuers with works scheduled on @pool to resolve
1903 * possible allocation deadlock.
1905 * On return, need_to_create_worker() is guaranteed to be false and
1906 * may_start_working() true.
1909 * spin_lock_irq(pool->lock) which may be released and regrabbed
1910 * multiple times. Does GFP_KERNEL allocations. Called only from
1914 * false if no action was taken and pool->lock stayed locked, true
1917 static bool maybe_create_worker(struct worker_pool
*pool
)
1918 __releases(&pool
->lock
)
1919 __acquires(&pool
->lock
)
1921 if (!need_to_create_worker(pool
))
1924 spin_unlock_irq(&pool
->lock
);
1926 /* if we don't make progress in MAYDAY_INITIAL_TIMEOUT, call for help */
1927 mod_timer(&pool
->mayday_timer
, jiffies
+ MAYDAY_INITIAL_TIMEOUT
);
1930 struct worker
*worker
;
1932 worker
= create_worker(pool
);
1934 del_timer_sync(&pool
->mayday_timer
);
1935 spin_lock_irq(&pool
->lock
);
1936 start_worker(worker
);
1937 if (WARN_ON_ONCE(need_to_create_worker(pool
)))
1942 if (!need_to_create_worker(pool
))
1945 __set_current_state(TASK_INTERRUPTIBLE
);
1946 schedule_timeout(CREATE_COOLDOWN
);
1948 if (!need_to_create_worker(pool
))
1952 del_timer_sync(&pool
->mayday_timer
);
1953 spin_lock_irq(&pool
->lock
);
1954 if (need_to_create_worker(pool
))
1960 * maybe_destroy_worker - destroy workers which have been idle for a while
1961 * @pool: pool to destroy workers for
1963 * Destroy @pool workers which have been idle for longer than
1964 * IDLE_WORKER_TIMEOUT.
1967 * spin_lock_irq(pool->lock) which may be released and regrabbed
1968 * multiple times. Called only from manager.
1971 * false if no action was taken and pool->lock stayed locked, true
1974 static bool maybe_destroy_workers(struct worker_pool
*pool
)
1978 while (too_many_workers(pool
)) {
1979 struct worker
*worker
;
1980 unsigned long expires
;
1982 worker
= list_entry(pool
->idle_list
.prev
, struct worker
, entry
);
1983 expires
= worker
->last_active
+ IDLE_WORKER_TIMEOUT
;
1985 if (time_before(jiffies
, expires
)) {
1986 mod_timer(&pool
->idle_timer
, expires
);
1990 destroy_worker(worker
);
1998 * manage_workers - manage worker pool
2001 * Assume the manager role and manage the worker pool @worker belongs
2002 * to. At any given time, there can be only zero or one manager per
2003 * pool. The exclusion is handled automatically by this function.
2005 * The caller can safely start processing works on false return. On
2006 * true return, it's guaranteed that need_to_create_worker() is false
2007 * and may_start_working() is true.
2010 * spin_lock_irq(pool->lock) which may be released and regrabbed
2011 * multiple times. Does GFP_KERNEL allocations.
2014 * spin_lock_irq(pool->lock) which may be released and regrabbed
2015 * multiple times. Does GFP_KERNEL allocations.
2017 static bool manage_workers(struct worker
*worker
)
2019 struct worker_pool
*pool
= worker
->pool
;
2022 if (pool
->flags
& POOL_MANAGING_WORKERS
)
2025 pool
->flags
|= POOL_MANAGING_WORKERS
;
2028 * To simplify both worker management and CPU hotplug, hold off
2029 * management while hotplug is in progress. CPU hotplug path can't
2030 * grab %POOL_MANAGING_WORKERS to achieve this because that can
2031 * lead to idle worker depletion (all become busy thinking someone
2032 * else is managing) which in turn can result in deadlock under
2033 * extreme circumstances. Use @pool->assoc_mutex to synchronize
2034 * manager against CPU hotplug.
2036 * assoc_mutex would always be free unless CPU hotplug is in
2037 * progress. trylock first without dropping @pool->lock.
2039 if (unlikely(!mutex_trylock(&pool
->assoc_mutex
))) {
2040 spin_unlock_irq(&pool
->lock
);
2041 mutex_lock(&pool
->assoc_mutex
);
2043 * CPU hotplug could have happened while we were waiting
2044 * for assoc_mutex. Hotplug itself can't handle us
2045 * because manager isn't either on idle or busy list, and
2046 * @pool's state and ours could have deviated.
2048 * As hotplug is now excluded via assoc_mutex, we can
2049 * simply try to bind. It will succeed or fail depending
2050 * on @pool's current state. Try it and adjust
2051 * %WORKER_UNBOUND accordingly.
2053 if (worker_maybe_bind_and_lock(pool
))
2054 worker
->flags
&= ~WORKER_UNBOUND
;
2056 worker
->flags
|= WORKER_UNBOUND
;
2061 pool
->flags
&= ~POOL_MANAGE_WORKERS
;
2064 * Destroy and then create so that may_start_working() is true
2067 ret
|= maybe_destroy_workers(pool
);
2068 ret
|= maybe_create_worker(pool
);
2070 pool
->flags
&= ~POOL_MANAGING_WORKERS
;
2071 mutex_unlock(&pool
->assoc_mutex
);
2076 * process_one_work - process single work
2078 * @work: work to process
2080 * Process @work. This function contains all the logics necessary to
2081 * process a single work including synchronization against and
2082 * interaction with other workers on the same cpu, queueing and
2083 * flushing. As long as context requirement is met, any worker can
2084 * call this function to process a work.
2087 * spin_lock_irq(pool->lock) which is released and regrabbed.
2089 static void process_one_work(struct worker
*worker
, struct work_struct
*work
)
2090 __releases(&pool
->lock
)
2091 __acquires(&pool
->lock
)
2093 struct pool_workqueue
*pwq
= get_work_pwq(work
);
2094 struct worker_pool
*pool
= worker
->pool
;
2095 bool cpu_intensive
= pwq
->wq
->flags
& WQ_CPU_INTENSIVE
;
2097 struct worker
*collision
;
2098 #ifdef CONFIG_LOCKDEP
2100 * It is permissible to free the struct work_struct from
2101 * inside the function that is called from it, this we need to
2102 * take into account for lockdep too. To avoid bogus "held
2103 * lock freed" warnings as well as problems when looking into
2104 * work->lockdep_map, make a copy and use that here.
2106 struct lockdep_map lockdep_map
;
2108 lockdep_copy_map(&lockdep_map
, &work
->lockdep_map
);
2111 * Ensure we're on the correct CPU. DISASSOCIATED test is
2112 * necessary to avoid spurious warnings from rescuers servicing the
2113 * unbound or a disassociated pool.
2115 WARN_ON_ONCE(!(worker
->flags
& WORKER_UNBOUND
) &&
2116 !(pool
->flags
& POOL_DISASSOCIATED
) &&
2117 raw_smp_processor_id() != pool
->cpu
);
2120 * A single work shouldn't be executed concurrently by
2121 * multiple workers on a single cpu. Check whether anyone is
2122 * already processing the work. If so, defer the work to the
2123 * currently executing one.
2125 collision
= find_worker_executing_work(pool
, work
);
2126 if (unlikely(collision
)) {
2127 move_linked_works(work
, &collision
->scheduled
, NULL
);
2131 /* claim and dequeue */
2132 debug_work_deactivate(work
);
2133 hash_add(pool
->busy_hash
, &worker
->hentry
, (unsigned long)work
);
2134 worker
->current_work
= work
;
2135 worker
->current_func
= work
->func
;
2136 worker
->current_pwq
= pwq
;
2137 work_color
= get_work_color(work
);
2139 list_del_init(&work
->entry
);
2142 * CPU intensive works don't participate in concurrency
2143 * management. They're the scheduler's responsibility.
2145 if (unlikely(cpu_intensive
))
2146 worker_set_flags(worker
, WORKER_CPU_INTENSIVE
, true);
2149 * Unbound pool isn't concurrency managed and work items should be
2150 * executed ASAP. Wake up another worker if necessary.
2152 if ((worker
->flags
& WORKER_UNBOUND
) && need_more_worker(pool
))
2153 wake_up_worker(pool
);
2156 * Record the last pool and clear PENDING which should be the last
2157 * update to @work. Also, do this inside @pool->lock so that
2158 * PENDING and queued state changes happen together while IRQ is
2161 set_work_pool_and_clear_pending(work
, pool
->id
);
2163 spin_unlock_irq(&pool
->lock
);
2165 lock_map_acquire_read(&pwq
->wq
->lockdep_map
);
2166 lock_map_acquire(&lockdep_map
);
2167 trace_workqueue_execute_start(work
);
2168 worker
->current_func(work
);
2170 * While we must be careful to not use "work" after this, the trace
2171 * point will only record its address.
2173 trace_workqueue_execute_end(work
);
2174 lock_map_release(&lockdep_map
);
2175 lock_map_release(&pwq
->wq
->lockdep_map
);
2177 if (unlikely(in_atomic() || lockdep_depth(current
) > 0)) {
2178 pr_err("BUG: workqueue leaked lock or atomic: %s/0x%08x/%d\n"
2179 " last function: %pf\n",
2180 current
->comm
, preempt_count(), task_pid_nr(current
),
2181 worker
->current_func
);
2182 debug_show_held_locks(current
);
2186 spin_lock_irq(&pool
->lock
);
2188 /* clear cpu intensive status */
2189 if (unlikely(cpu_intensive
))
2190 worker_clr_flags(worker
, WORKER_CPU_INTENSIVE
);
2192 /* we're done with it, release */
2193 hash_del(&worker
->hentry
);
2194 worker
->current_work
= NULL
;
2195 worker
->current_func
= NULL
;
2196 worker
->current_pwq
= NULL
;
2197 pwq_dec_nr_in_flight(pwq
, work_color
);
2201 * process_scheduled_works - process scheduled works
2204 * Process all scheduled works. Please note that the scheduled list
2205 * may change while processing a work, so this function repeatedly
2206 * fetches a work from the top and executes it.
2209 * spin_lock_irq(pool->lock) which may be released and regrabbed
2212 static void process_scheduled_works(struct worker
*worker
)
2214 while (!list_empty(&worker
->scheduled
)) {
2215 struct work_struct
*work
= list_first_entry(&worker
->scheduled
,
2216 struct work_struct
, entry
);
2217 process_one_work(worker
, work
);
2222 * worker_thread - the worker thread function
2225 * The worker thread function. There are NR_CPU_WORKER_POOLS dynamic pools
2226 * of these per each cpu. These workers process all works regardless of
2227 * their specific target workqueue. The only exception is works which
2228 * belong to workqueues with a rescuer which will be explained in
2231 static int worker_thread(void *__worker
)
2233 struct worker
*worker
= __worker
;
2234 struct worker_pool
*pool
= worker
->pool
;
2236 /* tell the scheduler that this is a workqueue worker */
2237 worker
->task
->flags
|= PF_WQ_WORKER
;
2239 spin_lock_irq(&pool
->lock
);
2241 /* we are off idle list if destruction or rebind is requested */
2242 if (unlikely(list_empty(&worker
->entry
))) {
2243 spin_unlock_irq(&pool
->lock
);
2245 /* if DIE is set, destruction is requested */
2246 if (worker
->flags
& WORKER_DIE
) {
2247 worker
->task
->flags
&= ~PF_WQ_WORKER
;
2251 /* otherwise, rebind */
2252 idle_worker_rebind(worker
);
2256 worker_leave_idle(worker
);
2258 /* no more worker necessary? */
2259 if (!need_more_worker(pool
))
2262 /* do we need to manage? */
2263 if (unlikely(!may_start_working(pool
)) && manage_workers(worker
))
2267 * ->scheduled list can only be filled while a worker is
2268 * preparing to process a work or actually processing it.
2269 * Make sure nobody diddled with it while I was sleeping.
2271 WARN_ON_ONCE(!list_empty(&worker
->scheduled
));
2274 * When control reaches this point, we're guaranteed to have
2275 * at least one idle worker or that someone else has already
2276 * assumed the manager role.
2278 worker_clr_flags(worker
, WORKER_PREP
);
2281 struct work_struct
*work
=
2282 list_first_entry(&pool
->worklist
,
2283 struct work_struct
, entry
);
2285 if (likely(!(*work_data_bits(work
) & WORK_STRUCT_LINKED
))) {
2286 /* optimization path, not strictly necessary */
2287 process_one_work(worker
, work
);
2288 if (unlikely(!list_empty(&worker
->scheduled
)))
2289 process_scheduled_works(worker
);
2291 move_linked_works(work
, &worker
->scheduled
, NULL
);
2292 process_scheduled_works(worker
);
2294 } while (keep_working(pool
));
2296 worker_set_flags(worker
, WORKER_PREP
, false);
2298 if (unlikely(need_to_manage_workers(pool
)) && manage_workers(worker
))
2302 * pool->lock is held and there's no work to process and no need to
2303 * manage, sleep. Workers are woken up only while holding
2304 * pool->lock or from local cpu, so setting the current state
2305 * before releasing pool->lock is enough to prevent losing any
2308 worker_enter_idle(worker
);
2309 __set_current_state(TASK_INTERRUPTIBLE
);
2310 spin_unlock_irq(&pool
->lock
);
2316 * rescuer_thread - the rescuer thread function
2319 * Workqueue rescuer thread function. There's one rescuer for each
2320 * workqueue which has WQ_RESCUER set.
2322 * Regular work processing on a pool may block trying to create a new
2323 * worker which uses GFP_KERNEL allocation which has slight chance of
2324 * developing into deadlock if some works currently on the same queue
2325 * need to be processed to satisfy the GFP_KERNEL allocation. This is
2326 * the problem rescuer solves.
2328 * When such condition is possible, the pool summons rescuers of all
2329 * workqueues which have works queued on the pool and let them process
2330 * those works so that forward progress can be guaranteed.
2332 * This should happen rarely.
2334 static int rescuer_thread(void *__rescuer
)
2336 struct worker
*rescuer
= __rescuer
;
2337 struct workqueue_struct
*wq
= rescuer
->rescue_wq
;
2338 struct list_head
*scheduled
= &rescuer
->scheduled
;
2339 bool is_unbound
= wq
->flags
& WQ_UNBOUND
;
2342 set_user_nice(current
, RESCUER_NICE_LEVEL
);
2345 * Mark rescuer as worker too. As WORKER_PREP is never cleared, it
2346 * doesn't participate in concurrency management.
2348 rescuer
->task
->flags
|= PF_WQ_WORKER
;
2350 set_current_state(TASK_INTERRUPTIBLE
);
2352 if (kthread_should_stop()) {
2353 __set_current_state(TASK_RUNNING
);
2354 rescuer
->task
->flags
&= ~PF_WQ_WORKER
;
2359 * See whether any cpu is asking for help. Unbounded
2360 * workqueues use cpu 0 in mayday_mask for CPU_UNBOUND.
2362 for_each_mayday_cpu(cpu
, wq
->mayday_mask
) {
2363 unsigned int tcpu
= is_unbound
? WORK_CPU_UNBOUND
: cpu
;
2364 struct pool_workqueue
*pwq
= get_pwq(tcpu
, wq
);
2365 struct worker_pool
*pool
= pwq
->pool
;
2366 struct work_struct
*work
, *n
;
2368 __set_current_state(TASK_RUNNING
);
2369 mayday_clear_cpu(cpu
, wq
->mayday_mask
);
2371 /* migrate to the target cpu if possible */
2372 worker_maybe_bind_and_lock(pool
);
2373 rescuer
->pool
= pool
;
2376 * Slurp in all works issued via this workqueue and
2379 WARN_ON_ONCE(!list_empty(&rescuer
->scheduled
));
2380 list_for_each_entry_safe(work
, n
, &pool
->worklist
, entry
)
2381 if (get_work_pwq(work
) == pwq
)
2382 move_linked_works(work
, scheduled
, &n
);
2384 process_scheduled_works(rescuer
);
2387 * Leave this pool. If keep_working() is %true, notify a
2388 * regular worker; otherwise, we end up with 0 concurrency
2389 * and stalling the execution.
2391 if (keep_working(pool
))
2392 wake_up_worker(pool
);
2394 rescuer
->pool
= NULL
;
2395 spin_unlock_irq(&pool
->lock
);
2398 /* rescuers should never participate in concurrency management */
2399 WARN_ON_ONCE(!(rescuer
->flags
& WORKER_NOT_RUNNING
));
2405 struct work_struct work
;
2406 struct completion done
;
2409 static void wq_barrier_func(struct work_struct
*work
)
2411 struct wq_barrier
*barr
= container_of(work
, struct wq_barrier
, work
);
2412 complete(&barr
->done
);
2416 * insert_wq_barrier - insert a barrier work
2417 * @pwq: pwq to insert barrier into
2418 * @barr: wq_barrier to insert
2419 * @target: target work to attach @barr to
2420 * @worker: worker currently executing @target, NULL if @target is not executing
2422 * @barr is linked to @target such that @barr is completed only after
2423 * @target finishes execution. Please note that the ordering
2424 * guarantee is observed only with respect to @target and on the local
2427 * Currently, a queued barrier can't be canceled. This is because
2428 * try_to_grab_pending() can't determine whether the work to be
2429 * grabbed is at the head of the queue and thus can't clear LINKED
2430 * flag of the previous work while there must be a valid next work
2431 * after a work with LINKED flag set.
2433 * Note that when @worker is non-NULL, @target may be modified
2434 * underneath us, so we can't reliably determine pwq from @target.
2437 * spin_lock_irq(pool->lock).
2439 static void insert_wq_barrier(struct pool_workqueue
*pwq
,
2440 struct wq_barrier
*barr
,
2441 struct work_struct
*target
, struct worker
*worker
)
2443 struct list_head
*head
;
2444 unsigned int linked
= 0;
2447 * debugobject calls are safe here even with pool->lock locked
2448 * as we know for sure that this will not trigger any of the
2449 * checks and call back into the fixup functions where we
2452 INIT_WORK_ONSTACK(&barr
->work
, wq_barrier_func
);
2453 __set_bit(WORK_STRUCT_PENDING_BIT
, work_data_bits(&barr
->work
));
2454 init_completion(&barr
->done
);
2457 * If @target is currently being executed, schedule the
2458 * barrier to the worker; otherwise, put it after @target.
2461 head
= worker
->scheduled
.next
;
2463 unsigned long *bits
= work_data_bits(target
);
2465 head
= target
->entry
.next
;
2466 /* there can already be other linked works, inherit and set */
2467 linked
= *bits
& WORK_STRUCT_LINKED
;
2468 __set_bit(WORK_STRUCT_LINKED_BIT
, bits
);
2471 debug_work_activate(&barr
->work
);
2472 insert_work(pwq
, &barr
->work
, head
,
2473 work_color_to_flags(WORK_NO_COLOR
) | linked
);
2477 * flush_workqueue_prep_pwqs - prepare pwqs for workqueue flushing
2478 * @wq: workqueue being flushed
2479 * @flush_color: new flush color, < 0 for no-op
2480 * @work_color: new work color, < 0 for no-op
2482 * Prepare pwqs for workqueue flushing.
2484 * If @flush_color is non-negative, flush_color on all pwqs should be
2485 * -1. If no pwq has in-flight commands at the specified color, all
2486 * pwq->flush_color's stay at -1 and %false is returned. If any pwq
2487 * has in flight commands, its pwq->flush_color is set to
2488 * @flush_color, @wq->nr_pwqs_to_flush is updated accordingly, pwq
2489 * wakeup logic is armed and %true is returned.
2491 * The caller should have initialized @wq->first_flusher prior to
2492 * calling this function with non-negative @flush_color. If
2493 * @flush_color is negative, no flush color update is done and %false
2496 * If @work_color is non-negative, all pwqs should have the same
2497 * work_color which is previous to @work_color and all will be
2498 * advanced to @work_color.
2501 * mutex_lock(wq->flush_mutex).
2504 * %true if @flush_color >= 0 and there's something to flush. %false
2507 static bool flush_workqueue_prep_pwqs(struct workqueue_struct
*wq
,
2508 int flush_color
, int work_color
)
2511 struct pool_workqueue
*pwq
;
2513 if (flush_color
>= 0) {
2514 WARN_ON_ONCE(atomic_read(&wq
->nr_pwqs_to_flush
));
2515 atomic_set(&wq
->nr_pwqs_to_flush
, 1);
2518 for_each_pwq(pwq
, wq
) {
2519 struct worker_pool
*pool
= pwq
->pool
;
2521 spin_lock_irq(&pool
->lock
);
2523 if (flush_color
>= 0) {
2524 WARN_ON_ONCE(pwq
->flush_color
!= -1);
2526 if (pwq
->nr_in_flight
[flush_color
]) {
2527 pwq
->flush_color
= flush_color
;
2528 atomic_inc(&wq
->nr_pwqs_to_flush
);
2533 if (work_color
>= 0) {
2534 WARN_ON_ONCE(work_color
!= work_next_color(pwq
->work_color
));
2535 pwq
->work_color
= work_color
;
2538 spin_unlock_irq(&pool
->lock
);
2541 if (flush_color
>= 0 && atomic_dec_and_test(&wq
->nr_pwqs_to_flush
))
2542 complete(&wq
->first_flusher
->done
);
2548 * flush_workqueue - ensure that any scheduled work has run to completion.
2549 * @wq: workqueue to flush
2551 * Forces execution of the workqueue and blocks until its completion.
2552 * This is typically used in driver shutdown handlers.
2554 * We sleep until all works which were queued on entry have been handled,
2555 * but we are not livelocked by new incoming ones.
2557 void flush_workqueue(struct workqueue_struct
*wq
)
2559 struct wq_flusher this_flusher
= {
2560 .list
= LIST_HEAD_INIT(this_flusher
.list
),
2562 .done
= COMPLETION_INITIALIZER_ONSTACK(this_flusher
.done
),
2566 lock_map_acquire(&wq
->lockdep_map
);
2567 lock_map_release(&wq
->lockdep_map
);
2569 mutex_lock(&wq
->flush_mutex
);
2572 * Start-to-wait phase
2574 next_color
= work_next_color(wq
->work_color
);
2576 if (next_color
!= wq
->flush_color
) {
2578 * Color space is not full. The current work_color
2579 * becomes our flush_color and work_color is advanced
2582 WARN_ON_ONCE(!list_empty(&wq
->flusher_overflow
));
2583 this_flusher
.flush_color
= wq
->work_color
;
2584 wq
->work_color
= next_color
;
2586 if (!wq
->first_flusher
) {
2587 /* no flush in progress, become the first flusher */
2588 WARN_ON_ONCE(wq
->flush_color
!= this_flusher
.flush_color
);
2590 wq
->first_flusher
= &this_flusher
;
2592 if (!flush_workqueue_prep_pwqs(wq
, wq
->flush_color
,
2594 /* nothing to flush, done */
2595 wq
->flush_color
= next_color
;
2596 wq
->first_flusher
= NULL
;
2601 WARN_ON_ONCE(wq
->flush_color
== this_flusher
.flush_color
);
2602 list_add_tail(&this_flusher
.list
, &wq
->flusher_queue
);
2603 flush_workqueue_prep_pwqs(wq
, -1, wq
->work_color
);
2607 * Oops, color space is full, wait on overflow queue.
2608 * The next flush completion will assign us
2609 * flush_color and transfer to flusher_queue.
2611 list_add_tail(&this_flusher
.list
, &wq
->flusher_overflow
);
2614 mutex_unlock(&wq
->flush_mutex
);
2616 wait_for_completion(&this_flusher
.done
);
2619 * Wake-up-and-cascade phase
2621 * First flushers are responsible for cascading flushes and
2622 * handling overflow. Non-first flushers can simply return.
2624 if (wq
->first_flusher
!= &this_flusher
)
2627 mutex_lock(&wq
->flush_mutex
);
2629 /* we might have raced, check again with mutex held */
2630 if (wq
->first_flusher
!= &this_flusher
)
2633 wq
->first_flusher
= NULL
;
2635 WARN_ON_ONCE(!list_empty(&this_flusher
.list
));
2636 WARN_ON_ONCE(wq
->flush_color
!= this_flusher
.flush_color
);
2639 struct wq_flusher
*next
, *tmp
;
2641 /* complete all the flushers sharing the current flush color */
2642 list_for_each_entry_safe(next
, tmp
, &wq
->flusher_queue
, list
) {
2643 if (next
->flush_color
!= wq
->flush_color
)
2645 list_del_init(&next
->list
);
2646 complete(&next
->done
);
2649 WARN_ON_ONCE(!list_empty(&wq
->flusher_overflow
) &&
2650 wq
->flush_color
!= work_next_color(wq
->work_color
));
2652 /* this flush_color is finished, advance by one */
2653 wq
->flush_color
= work_next_color(wq
->flush_color
);
2655 /* one color has been freed, handle overflow queue */
2656 if (!list_empty(&wq
->flusher_overflow
)) {
2658 * Assign the same color to all overflowed
2659 * flushers, advance work_color and append to
2660 * flusher_queue. This is the start-to-wait
2661 * phase for these overflowed flushers.
2663 list_for_each_entry(tmp
, &wq
->flusher_overflow
, list
)
2664 tmp
->flush_color
= wq
->work_color
;
2666 wq
->work_color
= work_next_color(wq
->work_color
);
2668 list_splice_tail_init(&wq
->flusher_overflow
,
2669 &wq
->flusher_queue
);
2670 flush_workqueue_prep_pwqs(wq
, -1, wq
->work_color
);
2673 if (list_empty(&wq
->flusher_queue
)) {
2674 WARN_ON_ONCE(wq
->flush_color
!= wq
->work_color
);
2679 * Need to flush more colors. Make the next flusher
2680 * the new first flusher and arm pwqs.
2682 WARN_ON_ONCE(wq
->flush_color
== wq
->work_color
);
2683 WARN_ON_ONCE(wq
->flush_color
!= next
->flush_color
);
2685 list_del_init(&next
->list
);
2686 wq
->first_flusher
= next
;
2688 if (flush_workqueue_prep_pwqs(wq
, wq
->flush_color
, -1))
2692 * Meh... this color is already done, clear first
2693 * flusher and repeat cascading.
2695 wq
->first_flusher
= NULL
;
2699 mutex_unlock(&wq
->flush_mutex
);
2701 EXPORT_SYMBOL_GPL(flush_workqueue
);
2704 * drain_workqueue - drain a workqueue
2705 * @wq: workqueue to drain
2707 * Wait until the workqueue becomes empty. While draining is in progress,
2708 * only chain queueing is allowed. IOW, only currently pending or running
2709 * work items on @wq can queue further work items on it. @wq is flushed
2710 * repeatedly until it becomes empty. The number of flushing is detemined
2711 * by the depth of chaining and should be relatively short. Whine if it
2714 void drain_workqueue(struct workqueue_struct
*wq
)
2716 unsigned int flush_cnt
= 0;
2717 struct pool_workqueue
*pwq
;
2720 * __queue_work() needs to test whether there are drainers, is much
2721 * hotter than drain_workqueue() and already looks at @wq->flags.
2722 * Use WQ_DRAINING so that queue doesn't have to check nr_drainers.
2724 spin_lock_irq(&workqueue_lock
);
2725 if (!wq
->nr_drainers
++)
2726 wq
->flags
|= WQ_DRAINING
;
2727 spin_unlock_irq(&workqueue_lock
);
2729 flush_workqueue(wq
);
2731 for_each_pwq(pwq
, wq
) {
2734 spin_lock_irq(&pwq
->pool
->lock
);
2735 drained
= !pwq
->nr_active
&& list_empty(&pwq
->delayed_works
);
2736 spin_unlock_irq(&pwq
->pool
->lock
);
2741 if (++flush_cnt
== 10 ||
2742 (flush_cnt
% 100 == 0 && flush_cnt
<= 1000))
2743 pr_warn("workqueue %s: flush on destruction isn't complete after %u tries\n",
2744 wq
->name
, flush_cnt
);
2748 spin_lock_irq(&workqueue_lock
);
2749 if (!--wq
->nr_drainers
)
2750 wq
->flags
&= ~WQ_DRAINING
;
2751 spin_unlock_irq(&workqueue_lock
);
2753 EXPORT_SYMBOL_GPL(drain_workqueue
);
2755 static bool start_flush_work(struct work_struct
*work
, struct wq_barrier
*barr
)
2757 struct worker
*worker
= NULL
;
2758 struct worker_pool
*pool
;
2759 struct pool_workqueue
*pwq
;
2762 pool
= get_work_pool(work
);
2766 spin_lock_irq(&pool
->lock
);
2767 /* see the comment in try_to_grab_pending() with the same code */
2768 pwq
= get_work_pwq(work
);
2770 if (unlikely(pwq
->pool
!= pool
))
2773 worker
= find_worker_executing_work(pool
, work
);
2776 pwq
= worker
->current_pwq
;
2779 insert_wq_barrier(pwq
, barr
, work
, worker
);
2780 spin_unlock_irq(&pool
->lock
);
2783 * If @max_active is 1 or rescuer is in use, flushing another work
2784 * item on the same workqueue may lead to deadlock. Make sure the
2785 * flusher is not running on the same workqueue by verifying write
2788 if (pwq
->wq
->saved_max_active
== 1 || pwq
->wq
->flags
& WQ_RESCUER
)
2789 lock_map_acquire(&pwq
->wq
->lockdep_map
);
2791 lock_map_acquire_read(&pwq
->wq
->lockdep_map
);
2792 lock_map_release(&pwq
->wq
->lockdep_map
);
2796 spin_unlock_irq(&pool
->lock
);
2801 * flush_work - wait for a work to finish executing the last queueing instance
2802 * @work: the work to flush
2804 * Wait until @work has finished execution. @work is guaranteed to be idle
2805 * on return if it hasn't been requeued since flush started.
2808 * %true if flush_work() waited for the work to finish execution,
2809 * %false if it was already idle.
2811 bool flush_work(struct work_struct
*work
)
2813 struct wq_barrier barr
;
2815 lock_map_acquire(&work
->lockdep_map
);
2816 lock_map_release(&work
->lockdep_map
);
2818 if (start_flush_work(work
, &barr
)) {
2819 wait_for_completion(&barr
.done
);
2820 destroy_work_on_stack(&barr
.work
);
2826 EXPORT_SYMBOL_GPL(flush_work
);
2828 static bool __cancel_work_timer(struct work_struct
*work
, bool is_dwork
)
2830 unsigned long flags
;
2834 ret
= try_to_grab_pending(work
, is_dwork
, &flags
);
2836 * If someone else is canceling, wait for the same event it
2837 * would be waiting for before retrying.
2839 if (unlikely(ret
== -ENOENT
))
2841 } while (unlikely(ret
< 0));
2843 /* tell other tasks trying to grab @work to back off */
2844 mark_work_canceling(work
);
2845 local_irq_restore(flags
);
2848 clear_work_data(work
);
2853 * cancel_work_sync - cancel a work and wait for it to finish
2854 * @work: the work to cancel
2856 * Cancel @work and wait for its execution to finish. This function
2857 * can be used even if the work re-queues itself or migrates to
2858 * another workqueue. On return from this function, @work is
2859 * guaranteed to be not pending or executing on any CPU.
2861 * cancel_work_sync(&delayed_work->work) must not be used for
2862 * delayed_work's. Use cancel_delayed_work_sync() instead.
2864 * The caller must ensure that the workqueue on which @work was last
2865 * queued can't be destroyed before this function returns.
2868 * %true if @work was pending, %false otherwise.
2870 bool cancel_work_sync(struct work_struct
*work
)
2872 return __cancel_work_timer(work
, false);
2874 EXPORT_SYMBOL_GPL(cancel_work_sync
);
2877 * flush_delayed_work - wait for a dwork to finish executing the last queueing
2878 * @dwork: the delayed work to flush
2880 * Delayed timer is cancelled and the pending work is queued for
2881 * immediate execution. Like flush_work(), this function only
2882 * considers the last queueing instance of @dwork.
2885 * %true if flush_work() waited for the work to finish execution,
2886 * %false if it was already idle.
2888 bool flush_delayed_work(struct delayed_work
*dwork
)
2890 local_irq_disable();
2891 if (del_timer_sync(&dwork
->timer
))
2892 __queue_work(dwork
->cpu
, dwork
->wq
, &dwork
->work
);
2894 return flush_work(&dwork
->work
);
2896 EXPORT_SYMBOL(flush_delayed_work
);
2899 * cancel_delayed_work - cancel a delayed work
2900 * @dwork: delayed_work to cancel
2902 * Kill off a pending delayed_work. Returns %true if @dwork was pending
2903 * and canceled; %false if wasn't pending. Note that the work callback
2904 * function may still be running on return, unless it returns %true and the
2905 * work doesn't re-arm itself. Explicitly flush or use
2906 * cancel_delayed_work_sync() to wait on it.
2908 * This function is safe to call from any context including IRQ handler.
2910 bool cancel_delayed_work(struct delayed_work
*dwork
)
2912 unsigned long flags
;
2916 ret
= try_to_grab_pending(&dwork
->work
, true, &flags
);
2917 } while (unlikely(ret
== -EAGAIN
));
2919 if (unlikely(ret
< 0))
2922 set_work_pool_and_clear_pending(&dwork
->work
,
2923 get_work_pool_id(&dwork
->work
));
2924 local_irq_restore(flags
);
2927 EXPORT_SYMBOL(cancel_delayed_work
);
2930 * cancel_delayed_work_sync - cancel a delayed work and wait for it to finish
2931 * @dwork: the delayed work cancel
2933 * This is cancel_work_sync() for delayed works.
2936 * %true if @dwork was pending, %false otherwise.
2938 bool cancel_delayed_work_sync(struct delayed_work
*dwork
)
2940 return __cancel_work_timer(&dwork
->work
, true);
2942 EXPORT_SYMBOL(cancel_delayed_work_sync
);
2945 * schedule_work_on - put work task on a specific cpu
2946 * @cpu: cpu to put the work task on
2947 * @work: job to be done
2949 * This puts a job on a specific cpu
2951 bool schedule_work_on(int cpu
, struct work_struct
*work
)
2953 return queue_work_on(cpu
, system_wq
, work
);
2955 EXPORT_SYMBOL(schedule_work_on
);
2958 * schedule_work - put work task in global workqueue
2959 * @work: job to be done
2961 * Returns %false if @work was already on the kernel-global workqueue and
2964 * This puts a job in the kernel-global workqueue if it was not already
2965 * queued and leaves it in the same position on the kernel-global
2966 * workqueue otherwise.
2968 bool schedule_work(struct work_struct
*work
)
2970 return queue_work(system_wq
, work
);
2972 EXPORT_SYMBOL(schedule_work
);
2975 * schedule_delayed_work_on - queue work in global workqueue on CPU after delay
2977 * @dwork: job to be done
2978 * @delay: number of jiffies to wait
2980 * After waiting for a given time this puts a job in the kernel-global
2981 * workqueue on the specified CPU.
2983 bool schedule_delayed_work_on(int cpu
, struct delayed_work
*dwork
,
2984 unsigned long delay
)
2986 return queue_delayed_work_on(cpu
, system_wq
, dwork
, delay
);
2988 EXPORT_SYMBOL(schedule_delayed_work_on
);
2991 * schedule_delayed_work - put work task in global workqueue after delay
2992 * @dwork: job to be done
2993 * @delay: number of jiffies to wait or 0 for immediate execution
2995 * After waiting for a given time this puts a job in the kernel-global
2998 bool schedule_delayed_work(struct delayed_work
*dwork
, unsigned long delay
)
3000 return queue_delayed_work(system_wq
, dwork
, delay
);
3002 EXPORT_SYMBOL(schedule_delayed_work
);
3005 * schedule_on_each_cpu - execute a function synchronously on each online CPU
3006 * @func: the function to call
3008 * schedule_on_each_cpu() executes @func on each online CPU using the
3009 * system workqueue and blocks until all CPUs have completed.
3010 * schedule_on_each_cpu() is very slow.
3013 * 0 on success, -errno on failure.
3015 int schedule_on_each_cpu(work_func_t func
)
3018 struct work_struct __percpu
*works
;
3020 works
= alloc_percpu(struct work_struct
);
3026 for_each_online_cpu(cpu
) {
3027 struct work_struct
*work
= per_cpu_ptr(works
, cpu
);
3029 INIT_WORK(work
, func
);
3030 schedule_work_on(cpu
, work
);
3033 for_each_online_cpu(cpu
)
3034 flush_work(per_cpu_ptr(works
, cpu
));
3042 * flush_scheduled_work - ensure that any scheduled work has run to completion.
3044 * Forces execution of the kernel-global workqueue and blocks until its
3047 * Think twice before calling this function! It's very easy to get into
3048 * trouble if you don't take great care. Either of the following situations
3049 * will lead to deadlock:
3051 * One of the work items currently on the workqueue needs to acquire
3052 * a lock held by your code or its caller.
3054 * Your code is running in the context of a work routine.
3056 * They will be detected by lockdep when they occur, but the first might not
3057 * occur very often. It depends on what work items are on the workqueue and
3058 * what locks they need, which you have no control over.
3060 * In most situations flushing the entire workqueue is overkill; you merely
3061 * need to know that a particular work item isn't queued and isn't running.
3062 * In such cases you should use cancel_delayed_work_sync() or
3063 * cancel_work_sync() instead.
3065 void flush_scheduled_work(void)
3067 flush_workqueue(system_wq
);
3069 EXPORT_SYMBOL(flush_scheduled_work
);
3072 * execute_in_process_context - reliably execute the routine with user context
3073 * @fn: the function to execute
3074 * @ew: guaranteed storage for the execute work structure (must
3075 * be available when the work executes)
3077 * Executes the function immediately if process context is available,
3078 * otherwise schedules the function for delayed execution.
3080 * Returns: 0 - function was executed
3081 * 1 - function was scheduled for execution
3083 int execute_in_process_context(work_func_t fn
, struct execute_work
*ew
)
3085 if (!in_interrupt()) {
3090 INIT_WORK(&ew
->work
, fn
);
3091 schedule_work(&ew
->work
);
3095 EXPORT_SYMBOL_GPL(execute_in_process_context
);
3097 int keventd_up(void)
3099 return system_wq
!= NULL
;
3102 static int alloc_and_link_pwqs(struct workqueue_struct
*wq
)
3104 bool highpri
= wq
->flags
& WQ_HIGHPRI
;
3107 if (!(wq
->flags
& WQ_UNBOUND
)) {
3108 wq
->pool_wq
.pcpu
= alloc_percpu(struct pool_workqueue
);
3109 if (!wq
->pool_wq
.pcpu
)
3112 for_each_possible_cpu(cpu
) {
3113 struct pool_workqueue
*pwq
= get_pwq(cpu
, wq
);
3115 pwq
->pool
= get_std_worker_pool(cpu
, highpri
);
3116 list_add_tail(&pwq
->pwqs_node
, &wq
->pwqs
);
3119 struct pool_workqueue
*pwq
;
3121 pwq
= kmem_cache_zalloc(pwq_cache
, GFP_KERNEL
);
3125 wq
->pool_wq
.single
= pwq
;
3126 pwq
->pool
= get_std_worker_pool(WORK_CPU_UNBOUND
, highpri
);
3127 list_add_tail(&pwq
->pwqs_node
, &wq
->pwqs
);
3133 static void free_pwqs(struct workqueue_struct
*wq
)
3135 if (!(wq
->flags
& WQ_UNBOUND
))
3136 free_percpu(wq
->pool_wq
.pcpu
);
3138 kmem_cache_free(pwq_cache
, wq
->pool_wq
.single
);
3141 static int wq_clamp_max_active(int max_active
, unsigned int flags
,
3144 int lim
= flags
& WQ_UNBOUND
? WQ_UNBOUND_MAX_ACTIVE
: WQ_MAX_ACTIVE
;
3146 if (max_active
< 1 || max_active
> lim
)
3147 pr_warn("workqueue: max_active %d requested for %s is out of range, clamping between %d and %d\n",
3148 max_active
, name
, 1, lim
);
3150 return clamp_val(max_active
, 1, lim
);
3153 struct workqueue_struct
*__alloc_workqueue_key(const char *fmt
,
3156 struct lock_class_key
*key
,
3157 const char *lock_name
, ...)
3159 va_list args
, args1
;
3160 struct workqueue_struct
*wq
;
3161 struct pool_workqueue
*pwq
;
3164 /* determine namelen, allocate wq and format name */
3165 va_start(args
, lock_name
);
3166 va_copy(args1
, args
);
3167 namelen
= vsnprintf(NULL
, 0, fmt
, args
) + 1;
3169 wq
= kzalloc(sizeof(*wq
) + namelen
, GFP_KERNEL
);
3173 vsnprintf(wq
->name
, namelen
, fmt
, args1
);
3178 * Workqueues which may be used during memory reclaim should
3179 * have a rescuer to guarantee forward progress.
3181 if (flags
& WQ_MEM_RECLAIM
)
3182 flags
|= WQ_RESCUER
;
3184 max_active
= max_active
?: WQ_DFL_ACTIVE
;
3185 max_active
= wq_clamp_max_active(max_active
, flags
, wq
->name
);
3189 wq
->saved_max_active
= max_active
;
3190 mutex_init(&wq
->flush_mutex
);
3191 atomic_set(&wq
->nr_pwqs_to_flush
, 0);
3192 INIT_LIST_HEAD(&wq
->pwqs
);
3193 INIT_LIST_HEAD(&wq
->flusher_queue
);
3194 INIT_LIST_HEAD(&wq
->flusher_overflow
);
3196 lockdep_init_map(&wq
->lockdep_map
, lock_name
, key
, 0);
3197 INIT_LIST_HEAD(&wq
->list
);
3199 if (alloc_and_link_pwqs(wq
) < 0)
3202 for_each_pwq(pwq
, wq
) {
3203 BUG_ON((unsigned long)pwq
& WORK_STRUCT_FLAG_MASK
);
3205 pwq
->flush_color
= -1;
3206 pwq
->max_active
= max_active
;
3207 INIT_LIST_HEAD(&pwq
->delayed_works
);
3210 if (flags
& WQ_RESCUER
) {
3211 struct worker
*rescuer
;
3213 if (!alloc_mayday_mask(&wq
->mayday_mask
, GFP_KERNEL
))
3216 wq
->rescuer
= rescuer
= alloc_worker();
3220 rescuer
->rescue_wq
= wq
;
3221 rescuer
->task
= kthread_create(rescuer_thread
, rescuer
, "%s",
3223 if (IS_ERR(rescuer
->task
))
3226 rescuer
->task
->flags
|= PF_THREAD_BOUND
;
3227 wake_up_process(rescuer
->task
);
3231 * workqueue_lock protects global freeze state and workqueues
3232 * list. Grab it, set max_active accordingly and add the new
3233 * workqueue to workqueues list.
3235 spin_lock_irq(&workqueue_lock
);
3237 if (workqueue_freezing
&& wq
->flags
& WQ_FREEZABLE
)
3238 for_each_pwq(pwq
, wq
)
3239 pwq
->max_active
= 0;
3241 list_add(&wq
->list
, &workqueues
);
3243 spin_unlock_irq(&workqueue_lock
);
3249 free_mayday_mask(wq
->mayday_mask
);
3255 EXPORT_SYMBOL_GPL(__alloc_workqueue_key
);
3258 * destroy_workqueue - safely terminate a workqueue
3259 * @wq: target workqueue
3261 * Safely destroy a workqueue. All work currently pending will be done first.
3263 void destroy_workqueue(struct workqueue_struct
*wq
)
3265 struct pool_workqueue
*pwq
;
3267 /* drain it before proceeding with destruction */
3268 drain_workqueue(wq
);
3271 for_each_pwq(pwq
, wq
) {
3274 for (i
= 0; i
< WORK_NR_COLORS
; i
++)
3275 if (WARN_ON(pwq
->nr_in_flight
[i
]))
3277 if (WARN_ON(pwq
->nr_active
) ||
3278 WARN_ON(!list_empty(&pwq
->delayed_works
)))
3283 * wq list is used to freeze wq, remove from list after
3284 * flushing is complete in case freeze races us.
3286 spin_lock_irq(&workqueue_lock
);
3287 list_del(&wq
->list
);
3288 spin_unlock_irq(&workqueue_lock
);
3290 if (wq
->flags
& WQ_RESCUER
) {
3291 kthread_stop(wq
->rescuer
->task
);
3292 free_mayday_mask(wq
->mayday_mask
);
3299 EXPORT_SYMBOL_GPL(destroy_workqueue
);
3302 * pwq_set_max_active - adjust max_active of a pwq
3303 * @pwq: target pool_workqueue
3304 * @max_active: new max_active value.
3306 * Set @pwq->max_active to @max_active and activate delayed works if
3310 * spin_lock_irq(pool->lock).
3312 static void pwq_set_max_active(struct pool_workqueue
*pwq
, int max_active
)
3314 pwq
->max_active
= max_active
;
3316 while (!list_empty(&pwq
->delayed_works
) &&
3317 pwq
->nr_active
< pwq
->max_active
)
3318 pwq_activate_first_delayed(pwq
);
3322 * workqueue_set_max_active - adjust max_active of a workqueue
3323 * @wq: target workqueue
3324 * @max_active: new max_active value.
3326 * Set max_active of @wq to @max_active.
3329 * Don't call from IRQ context.
3331 void workqueue_set_max_active(struct workqueue_struct
*wq
, int max_active
)
3333 struct pool_workqueue
*pwq
;
3335 max_active
= wq_clamp_max_active(max_active
, wq
->flags
, wq
->name
);
3337 spin_lock_irq(&workqueue_lock
);
3339 wq
->saved_max_active
= max_active
;
3341 for_each_pwq(pwq
, wq
) {
3342 struct worker_pool
*pool
= pwq
->pool
;
3344 spin_lock(&pool
->lock
);
3346 if (!(wq
->flags
& WQ_FREEZABLE
) ||
3347 !(pool
->flags
& POOL_FREEZING
))
3348 pwq_set_max_active(pwq
, max_active
);
3350 spin_unlock(&pool
->lock
);
3353 spin_unlock_irq(&workqueue_lock
);
3355 EXPORT_SYMBOL_GPL(workqueue_set_max_active
);
3358 * workqueue_congested - test whether a workqueue is congested
3359 * @cpu: CPU in question
3360 * @wq: target workqueue
3362 * Test whether @wq's cpu workqueue for @cpu is congested. There is
3363 * no synchronization around this function and the test result is
3364 * unreliable and only useful as advisory hints or for debugging.
3367 * %true if congested, %false otherwise.
3369 bool workqueue_congested(unsigned int cpu
, struct workqueue_struct
*wq
)
3371 struct pool_workqueue
*pwq
= get_pwq(cpu
, wq
);
3373 return !list_empty(&pwq
->delayed_works
);
3375 EXPORT_SYMBOL_GPL(workqueue_congested
);
3378 * work_busy - test whether a work is currently pending or running
3379 * @work: the work to be tested
3381 * Test whether @work is currently pending or running. There is no
3382 * synchronization around this function and the test result is
3383 * unreliable and only useful as advisory hints or for debugging.
3386 * OR'd bitmask of WORK_BUSY_* bits.
3388 unsigned int work_busy(struct work_struct
*work
)
3390 struct worker_pool
*pool
= get_work_pool(work
);
3391 unsigned long flags
;
3392 unsigned int ret
= 0;
3394 if (work_pending(work
))
3395 ret
|= WORK_BUSY_PENDING
;
3398 spin_lock_irqsave(&pool
->lock
, flags
);
3399 if (find_worker_executing_work(pool
, work
))
3400 ret
|= WORK_BUSY_RUNNING
;
3401 spin_unlock_irqrestore(&pool
->lock
, flags
);
3406 EXPORT_SYMBOL_GPL(work_busy
);
3411 * There are two challenges in supporting CPU hotplug. Firstly, there
3412 * are a lot of assumptions on strong associations among work, pwq and
3413 * pool which make migrating pending and scheduled works very
3414 * difficult to implement without impacting hot paths. Secondly,
3415 * worker pools serve mix of short, long and very long running works making
3416 * blocked draining impractical.
3418 * This is solved by allowing the pools to be disassociated from the CPU
3419 * running as an unbound one and allowing it to be reattached later if the
3420 * cpu comes back online.
3423 static void wq_unbind_fn(struct work_struct
*work
)
3425 int cpu
= smp_processor_id();
3426 struct worker_pool
*pool
;
3427 struct worker
*worker
;
3430 for_each_std_worker_pool(pool
, cpu
) {
3431 WARN_ON_ONCE(cpu
!= smp_processor_id());
3433 mutex_lock(&pool
->assoc_mutex
);
3434 spin_lock_irq(&pool
->lock
);
3437 * We've claimed all manager positions. Make all workers
3438 * unbound and set DISASSOCIATED. Before this, all workers
3439 * except for the ones which are still executing works from
3440 * before the last CPU down must be on the cpu. After
3441 * this, they may become diasporas.
3443 list_for_each_entry(worker
, &pool
->idle_list
, entry
)
3444 worker
->flags
|= WORKER_UNBOUND
;
3446 for_each_busy_worker(worker
, i
, pool
)
3447 worker
->flags
|= WORKER_UNBOUND
;
3449 pool
->flags
|= POOL_DISASSOCIATED
;
3451 spin_unlock_irq(&pool
->lock
);
3452 mutex_unlock(&pool
->assoc_mutex
);
3456 * Call schedule() so that we cross rq->lock and thus can guarantee
3457 * sched callbacks see the %WORKER_UNBOUND flag. This is necessary
3458 * as scheduler callbacks may be invoked from other cpus.
3463 * Sched callbacks are disabled now. Zap nr_running. After this,
3464 * nr_running stays zero and need_more_worker() and keep_working()
3465 * are always true as long as the worklist is not empty. Pools on
3466 * @cpu now behave as unbound (in terms of concurrency management)
3467 * pools which are served by workers tied to the CPU.
3469 * On return from this function, the current worker would trigger
3470 * unbound chain execution of pending work items if other workers
3473 for_each_std_worker_pool(pool
, cpu
)
3474 atomic_set(&pool
->nr_running
, 0);
3478 * Workqueues should be brought up before normal priority CPU notifiers.
3479 * This will be registered high priority CPU notifier.
3481 static int __cpuinit
workqueue_cpu_up_callback(struct notifier_block
*nfb
,
3482 unsigned long action
,
3485 unsigned int cpu
= (unsigned long)hcpu
;
3486 struct worker_pool
*pool
;
3488 switch (action
& ~CPU_TASKS_FROZEN
) {
3489 case CPU_UP_PREPARE
:
3490 for_each_std_worker_pool(pool
, cpu
) {
3491 struct worker
*worker
;
3493 if (pool
->nr_workers
)
3496 worker
= create_worker(pool
);
3500 spin_lock_irq(&pool
->lock
);
3501 start_worker(worker
);
3502 spin_unlock_irq(&pool
->lock
);
3506 case CPU_DOWN_FAILED
:
3508 for_each_std_worker_pool(pool
, cpu
) {
3509 mutex_lock(&pool
->assoc_mutex
);
3510 spin_lock_irq(&pool
->lock
);
3512 pool
->flags
&= ~POOL_DISASSOCIATED
;
3513 rebind_workers(pool
);
3515 spin_unlock_irq(&pool
->lock
);
3516 mutex_unlock(&pool
->assoc_mutex
);
3524 * Workqueues should be brought down after normal priority CPU notifiers.
3525 * This will be registered as low priority CPU notifier.
3527 static int __cpuinit
workqueue_cpu_down_callback(struct notifier_block
*nfb
,
3528 unsigned long action
,
3531 unsigned int cpu
= (unsigned long)hcpu
;
3532 struct work_struct unbind_work
;
3534 switch (action
& ~CPU_TASKS_FROZEN
) {
3535 case CPU_DOWN_PREPARE
:
3536 /* unbinding should happen on the local CPU */
3537 INIT_WORK_ONSTACK(&unbind_work
, wq_unbind_fn
);
3538 queue_work_on(cpu
, system_highpri_wq
, &unbind_work
);
3539 flush_work(&unbind_work
);
3547 struct work_for_cpu
{
3548 struct work_struct work
;
3554 static void work_for_cpu_fn(struct work_struct
*work
)
3556 struct work_for_cpu
*wfc
= container_of(work
, struct work_for_cpu
, work
);
3558 wfc
->ret
= wfc
->fn(wfc
->arg
);
3562 * work_on_cpu - run a function in user context on a particular cpu
3563 * @cpu: the cpu to run on
3564 * @fn: the function to run
3565 * @arg: the function arg
3567 * This will return the value @fn returns.
3568 * It is up to the caller to ensure that the cpu doesn't go offline.
3569 * The caller must not hold any locks which would prevent @fn from completing.
3571 long work_on_cpu(unsigned int cpu
, long (*fn
)(void *), void *arg
)
3573 struct work_for_cpu wfc
= { .fn
= fn
, .arg
= arg
};
3575 INIT_WORK_ONSTACK(&wfc
.work
, work_for_cpu_fn
);
3576 schedule_work_on(cpu
, &wfc
.work
);
3577 flush_work(&wfc
.work
);
3580 EXPORT_SYMBOL_GPL(work_on_cpu
);
3581 #endif /* CONFIG_SMP */
3583 #ifdef CONFIG_FREEZER
3586 * freeze_workqueues_begin - begin freezing workqueues
3588 * Start freezing workqueues. After this function returns, all freezable
3589 * workqueues will queue new works to their frozen_works list instead of
3593 * Grabs and releases workqueue_lock and pool->lock's.
3595 void freeze_workqueues_begin(void)
3597 struct worker_pool
*pool
;
3598 struct workqueue_struct
*wq
;
3599 struct pool_workqueue
*pwq
;
3602 spin_lock_irq(&workqueue_lock
);
3604 WARN_ON_ONCE(workqueue_freezing
);
3605 workqueue_freezing
= true;
3608 for_each_pool(pool
, id
) {
3609 spin_lock(&pool
->lock
);
3610 WARN_ON_ONCE(pool
->flags
& POOL_FREEZING
);
3611 pool
->flags
|= POOL_FREEZING
;
3612 spin_unlock(&pool
->lock
);
3615 /* suppress further executions by setting max_active to zero */
3616 list_for_each_entry(wq
, &workqueues
, list
) {
3617 if (!(wq
->flags
& WQ_FREEZABLE
))
3620 for_each_pwq(pwq
, wq
) {
3621 spin_lock(&pwq
->pool
->lock
);
3622 pwq
->max_active
= 0;
3623 spin_unlock(&pwq
->pool
->lock
);
3627 spin_unlock_irq(&workqueue_lock
);
3631 * freeze_workqueues_busy - are freezable workqueues still busy?
3633 * Check whether freezing is complete. This function must be called
3634 * between freeze_workqueues_begin() and thaw_workqueues().
3637 * Grabs and releases workqueue_lock.
3640 * %true if some freezable workqueues are still busy. %false if freezing
3643 bool freeze_workqueues_busy(void)
3646 struct workqueue_struct
*wq
;
3647 struct pool_workqueue
*pwq
;
3649 spin_lock_irq(&workqueue_lock
);
3651 WARN_ON_ONCE(!workqueue_freezing
);
3653 list_for_each_entry(wq
, &workqueues
, list
) {
3654 if (!(wq
->flags
& WQ_FREEZABLE
))
3657 * nr_active is monotonically decreasing. It's safe
3658 * to peek without lock.
3660 for_each_pwq(pwq
, wq
) {
3661 WARN_ON_ONCE(pwq
->nr_active
< 0);
3662 if (pwq
->nr_active
) {
3669 spin_unlock_irq(&workqueue_lock
);
3674 * thaw_workqueues - thaw workqueues
3676 * Thaw workqueues. Normal queueing is restored and all collected
3677 * frozen works are transferred to their respective pool worklists.
3680 * Grabs and releases workqueue_lock and pool->lock's.
3682 void thaw_workqueues(void)
3684 struct workqueue_struct
*wq
;
3685 struct pool_workqueue
*pwq
;
3686 struct worker_pool
*pool
;
3689 spin_lock_irq(&workqueue_lock
);
3691 if (!workqueue_freezing
)
3694 /* clear FREEZING */
3695 for_each_pool(pool
, id
) {
3696 spin_lock(&pool
->lock
);
3697 WARN_ON_ONCE(!(pool
->flags
& POOL_FREEZING
));
3698 pool
->flags
&= ~POOL_FREEZING
;
3699 spin_unlock(&pool
->lock
);
3702 /* restore max_active and repopulate worklist */
3703 list_for_each_entry(wq
, &workqueues
, list
) {
3704 if (!(wq
->flags
& WQ_FREEZABLE
))
3707 for_each_pwq(pwq
, wq
) {
3708 spin_lock(&pwq
->pool
->lock
);
3709 pwq_set_max_active(pwq
, wq
->saved_max_active
);
3710 spin_unlock(&pwq
->pool
->lock
);
3715 for_each_pool(pool
, id
) {
3716 spin_lock(&pool
->lock
);
3717 wake_up_worker(pool
);
3718 spin_unlock(&pool
->lock
);
3721 workqueue_freezing
= false;
3723 spin_unlock_irq(&workqueue_lock
);
3725 #endif /* CONFIG_FREEZER */
3727 static int __init
init_workqueues(void)
3731 /* make sure we have enough bits for OFFQ pool ID */
3732 BUILD_BUG_ON((1LU << (BITS_PER_LONG
- WORK_OFFQ_POOL_SHIFT
)) <
3733 WORK_CPU_END
* NR_STD_WORKER_POOLS
);
3735 WARN_ON(__alignof__(struct pool_workqueue
) < __alignof__(long long));
3737 pwq_cache
= KMEM_CACHE(pool_workqueue
, SLAB_PANIC
);
3739 cpu_notifier(workqueue_cpu_up_callback
, CPU_PRI_WORKQUEUE_UP
);
3740 hotcpu_notifier(workqueue_cpu_down_callback
, CPU_PRI_WORKQUEUE_DOWN
);
3742 /* initialize CPU pools */
3743 for_each_wq_cpu(cpu
) {
3744 struct worker_pool
*pool
;
3746 for_each_std_worker_pool(pool
, cpu
) {
3747 spin_lock_init(&pool
->lock
);
3749 pool
->flags
|= POOL_DISASSOCIATED
;
3750 INIT_LIST_HEAD(&pool
->worklist
);
3751 INIT_LIST_HEAD(&pool
->idle_list
);
3752 hash_init(pool
->busy_hash
);
3754 init_timer_deferrable(&pool
->idle_timer
);
3755 pool
->idle_timer
.function
= idle_worker_timeout
;
3756 pool
->idle_timer
.data
= (unsigned long)pool
;
3758 setup_timer(&pool
->mayday_timer
, pool_mayday_timeout
,
3759 (unsigned long)pool
);
3761 mutex_init(&pool
->assoc_mutex
);
3762 ida_init(&pool
->worker_ida
);
3765 BUG_ON(worker_pool_assign_id(pool
));
3769 /* create the initial worker */
3770 for_each_online_wq_cpu(cpu
) {
3771 struct worker_pool
*pool
;
3773 for_each_std_worker_pool(pool
, cpu
) {
3774 struct worker
*worker
;
3776 if (cpu
!= WORK_CPU_UNBOUND
)
3777 pool
->flags
&= ~POOL_DISASSOCIATED
;
3779 worker
= create_worker(pool
);
3781 spin_lock_irq(&pool
->lock
);
3782 start_worker(worker
);
3783 spin_unlock_irq(&pool
->lock
);
3787 system_wq
= alloc_workqueue("events", 0, 0);
3788 system_highpri_wq
= alloc_workqueue("events_highpri", WQ_HIGHPRI
, 0);
3789 system_long_wq
= alloc_workqueue("events_long", 0, 0);
3790 system_unbound_wq
= alloc_workqueue("events_unbound", WQ_UNBOUND
,
3791 WQ_UNBOUND_MAX_ACTIVE
);
3792 system_freezable_wq
= alloc_workqueue("events_freezable",
3794 BUG_ON(!system_wq
|| !system_highpri_wq
|| !system_long_wq
||
3795 !system_unbound_wq
|| !system_freezable_wq
);
3798 early_initcall(init_workqueues
);