2 * linux/kernel/workqueue.c
4 * Generic mechanism for defining kernel helper threads for running
5 * arbitrary tasks in process context.
7 * Started by Ingo Molnar, Copyright (C) 2002
9 * Derived from the taskqueue/keventd code by:
11 * David Woodhouse <dwmw2@infradead.org>
13 * Kai Petzke <wpp@marie.physik.tu-berlin.de>
14 * Theodore Ts'o <tytso@mit.edu>
16 * Made to use alloc_percpu by Christoph Lameter.
19 #include <linux/module.h>
20 #include <linux/kernel.h>
21 #include <linux/sched.h>
22 #include <linux/init.h>
23 #include <linux/signal.h>
24 #include <linux/completion.h>
25 #include <linux/workqueue.h>
26 #include <linux/slab.h>
27 #include <linux/cpu.h>
28 #include <linux/notifier.h>
29 #include <linux/kthread.h>
30 #include <linux/hardirq.h>
31 #include <linux/mempolicy.h>
32 #include <linux/freezer.h>
33 #include <linux/kallsyms.h>
34 #include <linux/debug_locks.h>
35 #include <linux/lockdep.h>
36 #include <linux/idr.h>
38 #include "workqueue_sched.h"
41 /* global_cwq flags */
42 GCWQ_MANAGE_WORKERS
= 1 << 0, /* need to manage workers */
43 GCWQ_MANAGING_WORKERS
= 1 << 1, /* managing workers */
44 GCWQ_DISASSOCIATED
= 1 << 2, /* cpu can't serve workers */
45 GCWQ_FREEZING
= 1 << 3, /* freeze in progress */
46 GCWQ_HIGHPRI_PENDING
= 1 << 4, /* highpri works on queue */
49 WORKER_STARTED
= 1 << 0, /* started */
50 WORKER_DIE
= 1 << 1, /* die die die */
51 WORKER_IDLE
= 1 << 2, /* is idle */
52 WORKER_PREP
= 1 << 3, /* preparing to run works */
53 WORKER_ROGUE
= 1 << 4, /* not bound to any cpu */
54 WORKER_REBIND
= 1 << 5, /* mom is home, come back */
55 WORKER_CPU_INTENSIVE
= 1 << 6, /* cpu intensive */
56 WORKER_UNBOUND
= 1 << 7, /* worker is unbound */
58 WORKER_NOT_RUNNING
= WORKER_PREP
| WORKER_ROGUE
| WORKER_REBIND
|
59 WORKER_CPU_INTENSIVE
| WORKER_UNBOUND
,
61 /* gcwq->trustee_state */
62 TRUSTEE_START
= 0, /* start */
63 TRUSTEE_IN_CHARGE
= 1, /* trustee in charge of gcwq */
64 TRUSTEE_BUTCHER
= 2, /* butcher workers */
65 TRUSTEE_RELEASE
= 3, /* release workers */
66 TRUSTEE_DONE
= 4, /* trustee is done */
68 BUSY_WORKER_HASH_ORDER
= 6, /* 64 pointers */
69 BUSY_WORKER_HASH_SIZE
= 1 << BUSY_WORKER_HASH_ORDER
,
70 BUSY_WORKER_HASH_MASK
= BUSY_WORKER_HASH_SIZE
- 1,
72 MAX_IDLE_WORKERS_RATIO
= 4, /* 1/4 of busy can be idle */
73 IDLE_WORKER_TIMEOUT
= 300 * HZ
, /* keep idle ones for 5 mins */
75 MAYDAY_INITIAL_TIMEOUT
= HZ
/ 100, /* call for help after 10ms */
76 MAYDAY_INTERVAL
= HZ
/ 10, /* and then every 100ms */
77 CREATE_COOLDOWN
= HZ
, /* time to breath after fail */
78 TRUSTEE_COOLDOWN
= HZ
/ 10, /* for trustee draining */
81 * Rescue workers are used only on emergencies and shared by
84 RESCUER_NICE_LEVEL
= -20,
88 * Structure fields follow one of the following exclusion rules.
90 * I: Set during initialization and read-only afterwards.
92 * P: Preemption protected. Disabling preemption is enough and should
93 * only be modified and accessed from the local cpu.
95 * L: gcwq->lock protected. Access with gcwq->lock held.
97 * X: During normal operation, modification requires gcwq->lock and
98 * should be done only from local cpu. Either disabling preemption
99 * on local cpu or grabbing gcwq->lock is enough for read access.
100 * If GCWQ_DISASSOCIATED is set, it's identical to L.
102 * F: wq->flush_mutex protected.
104 * W: workqueue_lock protected.
110 * The poor guys doing the actual heavy lifting. All on-duty workers
111 * are either serving the manager role, on idle list or on busy hash.
114 /* on idle list while idle, on busy hash table while busy */
116 struct list_head entry
; /* L: while idle */
117 struct hlist_node hentry
; /* L: while busy */
120 struct work_struct
*current_work
; /* L: work being processed */
121 struct cpu_workqueue_struct
*current_cwq
; /* L: current_work's cwq */
122 struct list_head scheduled
; /* L: scheduled works */
123 struct task_struct
*task
; /* I: worker task */
124 struct global_cwq
*gcwq
; /* I: the associated gcwq */
125 /* 64 bytes boundary on 64bit, 32 on 32bit */
126 unsigned long last_active
; /* L: last active timestamp */
127 unsigned int flags
; /* X: flags */
128 int id
; /* I: worker id */
129 struct work_struct rebind_work
; /* L: rebind worker to cpu */
133 * Global per-cpu workqueue. There's one and only one for each cpu
134 * and all works are queued and processed here regardless of their
138 spinlock_t lock
; /* the gcwq lock */
139 struct list_head worklist
; /* L: list of pending works */
140 unsigned int cpu
; /* I: the associated cpu */
141 unsigned int flags
; /* L: GCWQ_* flags */
143 int nr_workers
; /* L: total number of workers */
144 int nr_idle
; /* L: currently idle ones */
146 /* workers are chained either in the idle_list or busy_hash */
147 struct list_head idle_list
; /* X: list of idle workers */
148 struct hlist_head busy_hash
[BUSY_WORKER_HASH_SIZE
];
149 /* L: hash of busy workers */
151 struct timer_list idle_timer
; /* L: worker idle timeout */
152 struct timer_list mayday_timer
; /* L: SOS timer for dworkers */
154 struct ida worker_ida
; /* L: for worker IDs */
156 struct task_struct
*trustee
; /* L: for gcwq shutdown */
157 unsigned int trustee_state
; /* L: trustee state */
158 wait_queue_head_t trustee_wait
; /* trustee wait */
159 struct worker
*first_idle
; /* L: first idle worker */
160 } ____cacheline_aligned_in_smp
;
163 * The per-CPU workqueue. The lower WORK_STRUCT_FLAG_BITS of
164 * work_struct->data are used for flags and thus cwqs need to be
165 * aligned at two's power of the number of flag bits.
167 struct cpu_workqueue_struct
{
168 struct global_cwq
*gcwq
; /* I: the associated gcwq */
169 struct workqueue_struct
*wq
; /* I: the owning workqueue */
170 int work_color
; /* L: current color */
171 int flush_color
; /* L: flushing color */
172 int nr_in_flight
[WORK_NR_COLORS
];
173 /* L: nr of in_flight works */
174 int nr_active
; /* L: nr of active works */
175 int max_active
; /* L: max active works */
176 struct list_head delayed_works
; /* L: delayed works */
180 * Structure used to wait for workqueue flush.
183 struct list_head list
; /* F: list of flushers */
184 int flush_color
; /* F: flush color waiting for */
185 struct completion done
; /* flush completion */
189 * All cpumasks are assumed to be always set on UP and thus can't be
190 * used to determine whether there's something to be done.
193 typedef cpumask_var_t mayday_mask_t
;
194 #define mayday_test_and_set_cpu(cpu, mask) \
195 cpumask_test_and_set_cpu((cpu), (mask))
196 #define mayday_clear_cpu(cpu, mask) cpumask_clear_cpu((cpu), (mask))
197 #define for_each_mayday_cpu(cpu, mask) for_each_cpu((cpu), (mask))
198 #define alloc_mayday_mask(maskp, gfp) alloc_cpumask_var((maskp), (gfp))
199 #define free_mayday_mask(mask) free_cpumask_var((mask))
201 typedef unsigned long mayday_mask_t
;
202 #define mayday_test_and_set_cpu(cpu, mask) test_and_set_bit(0, &(mask))
203 #define mayday_clear_cpu(cpu, mask) clear_bit(0, &(mask))
204 #define for_each_mayday_cpu(cpu, mask) if ((cpu) = 0, (mask))
205 #define alloc_mayday_mask(maskp, gfp) true
206 #define free_mayday_mask(mask) do { } while (0)
210 * The externally visible workqueue abstraction is an array of
211 * per-CPU workqueues:
213 struct workqueue_struct
{
214 unsigned int flags
; /* I: WQ_* flags */
216 struct cpu_workqueue_struct __percpu
*pcpu
;
217 struct cpu_workqueue_struct
*single
;
219 } cpu_wq
; /* I: cwq's */
220 struct list_head list
; /* W: list of all workqueues */
222 struct mutex flush_mutex
; /* protects wq flushing */
223 int work_color
; /* F: current work color */
224 int flush_color
; /* F: current flush color */
225 atomic_t nr_cwqs_to_flush
; /* flush in progress */
226 struct wq_flusher
*first_flusher
; /* F: first flusher */
227 struct list_head flusher_queue
; /* F: flush waiters */
228 struct list_head flusher_overflow
; /* F: flush overflow list */
230 mayday_mask_t mayday_mask
; /* cpus requesting rescue */
231 struct worker
*rescuer
; /* I: rescue worker */
233 int saved_max_active
; /* W: saved cwq max_active */
234 const char *name
; /* I: workqueue name */
235 #ifdef CONFIG_LOCKDEP
236 struct lockdep_map lockdep_map
;
240 struct workqueue_struct
*system_wq __read_mostly
;
241 struct workqueue_struct
*system_long_wq __read_mostly
;
242 struct workqueue_struct
*system_nrt_wq __read_mostly
;
243 struct workqueue_struct
*system_unbound_wq __read_mostly
;
244 EXPORT_SYMBOL_GPL(system_wq
);
245 EXPORT_SYMBOL_GPL(system_long_wq
);
246 EXPORT_SYMBOL_GPL(system_nrt_wq
);
247 EXPORT_SYMBOL_GPL(system_unbound_wq
);
249 #define for_each_busy_worker(worker, i, pos, gcwq) \
250 for (i = 0; i < BUSY_WORKER_HASH_SIZE; i++) \
251 hlist_for_each_entry(worker, pos, &gcwq->busy_hash[i], hentry)
253 static inline int __next_gcwq_cpu(int cpu
, const struct cpumask
*mask
,
256 if (cpu
< nr_cpu_ids
) {
258 cpu
= cpumask_next(cpu
, mask
);
259 if (cpu
< nr_cpu_ids
)
263 return WORK_CPU_UNBOUND
;
265 return WORK_CPU_NONE
;
268 static inline int __next_wq_cpu(int cpu
, const struct cpumask
*mask
,
269 struct workqueue_struct
*wq
)
271 return __next_gcwq_cpu(cpu
, mask
, !(wq
->flags
& WQ_UNBOUND
) ? 1 : 2);
277 * An extra gcwq is defined for an invalid cpu number
278 * (WORK_CPU_UNBOUND) to host workqueues which are not bound to any
279 * specific CPU. The following iterators are similar to
280 * for_each_*_cpu() iterators but also considers the unbound gcwq.
282 * for_each_gcwq_cpu() : possible CPUs + WORK_CPU_UNBOUND
283 * for_each_online_gcwq_cpu() : online CPUs + WORK_CPU_UNBOUND
284 * for_each_cwq_cpu() : possible CPUs for bound workqueues,
285 * WORK_CPU_UNBOUND for unbound workqueues
287 #define for_each_gcwq_cpu(cpu) \
288 for ((cpu) = __next_gcwq_cpu(-1, cpu_possible_mask, 3); \
289 (cpu) < WORK_CPU_NONE; \
290 (cpu) = __next_gcwq_cpu((cpu), cpu_possible_mask, 3))
292 #define for_each_online_gcwq_cpu(cpu) \
293 for ((cpu) = __next_gcwq_cpu(-1, cpu_online_mask, 3); \
294 (cpu) < WORK_CPU_NONE; \
295 (cpu) = __next_gcwq_cpu((cpu), cpu_online_mask, 3))
297 #define for_each_cwq_cpu(cpu, wq) \
298 for ((cpu) = __next_wq_cpu(-1, cpu_possible_mask, (wq)); \
299 (cpu) < WORK_CPU_NONE; \
300 (cpu) = __next_wq_cpu((cpu), cpu_possible_mask, (wq)))
302 #ifdef CONFIG_LOCKDEP
304 * in_workqueue_context() - in context of specified workqueue?
305 * @wq: the workqueue of interest
307 * Checks lockdep state to see if the current task is executing from
308 * within a workqueue item. This function exists only if lockdep is
311 int in_workqueue_context(struct workqueue_struct
*wq
)
313 return lock_is_held(&wq
->lockdep_map
);
317 #ifdef CONFIG_DEBUG_OBJECTS_WORK
319 static struct debug_obj_descr work_debug_descr
;
322 * fixup_init is called when:
323 * - an active object is initialized
325 static int work_fixup_init(void *addr
, enum debug_obj_state state
)
327 struct work_struct
*work
= addr
;
330 case ODEBUG_STATE_ACTIVE
:
331 cancel_work_sync(work
);
332 debug_object_init(work
, &work_debug_descr
);
340 * fixup_activate is called when:
341 * - an active object is activated
342 * - an unknown object is activated (might be a statically initialized object)
344 static int work_fixup_activate(void *addr
, enum debug_obj_state state
)
346 struct work_struct
*work
= addr
;
350 case ODEBUG_STATE_NOTAVAILABLE
:
352 * This is not really a fixup. The work struct was
353 * statically initialized. We just make sure that it
354 * is tracked in the object tracker.
356 if (test_bit(WORK_STRUCT_STATIC_BIT
, work_data_bits(work
))) {
357 debug_object_init(work
, &work_debug_descr
);
358 debug_object_activate(work
, &work_debug_descr
);
364 case ODEBUG_STATE_ACTIVE
:
373 * fixup_free is called when:
374 * - an active object is freed
376 static int work_fixup_free(void *addr
, enum debug_obj_state state
)
378 struct work_struct
*work
= addr
;
381 case ODEBUG_STATE_ACTIVE
:
382 cancel_work_sync(work
);
383 debug_object_free(work
, &work_debug_descr
);
390 static struct debug_obj_descr work_debug_descr
= {
391 .name
= "work_struct",
392 .fixup_init
= work_fixup_init
,
393 .fixup_activate
= work_fixup_activate
,
394 .fixup_free
= work_fixup_free
,
397 static inline void debug_work_activate(struct work_struct
*work
)
399 debug_object_activate(work
, &work_debug_descr
);
402 static inline void debug_work_deactivate(struct work_struct
*work
)
404 debug_object_deactivate(work
, &work_debug_descr
);
407 void __init_work(struct work_struct
*work
, int onstack
)
410 debug_object_init_on_stack(work
, &work_debug_descr
);
412 debug_object_init(work
, &work_debug_descr
);
414 EXPORT_SYMBOL_GPL(__init_work
);
416 void destroy_work_on_stack(struct work_struct
*work
)
418 debug_object_free(work
, &work_debug_descr
);
420 EXPORT_SYMBOL_GPL(destroy_work_on_stack
);
423 static inline void debug_work_activate(struct work_struct
*work
) { }
424 static inline void debug_work_deactivate(struct work_struct
*work
) { }
427 /* Serializes the accesses to the list of workqueues. */
428 static DEFINE_SPINLOCK(workqueue_lock
);
429 static LIST_HEAD(workqueues
);
430 static bool workqueue_freezing
; /* W: have wqs started freezing? */
433 * The almighty global cpu workqueues. nr_running is the only field
434 * which is expected to be used frequently by other cpus via
435 * try_to_wake_up(). Put it in a separate cacheline.
437 static DEFINE_PER_CPU(struct global_cwq
, global_cwq
);
438 static DEFINE_PER_CPU_SHARED_ALIGNED(atomic_t
, gcwq_nr_running
);
441 * Global cpu workqueue and nr_running counter for unbound gcwq. The
442 * gcwq is always online, has GCWQ_DISASSOCIATED set, and all its
443 * workers have WORKER_UNBOUND set.
445 static struct global_cwq unbound_global_cwq
;
446 static atomic_t unbound_gcwq_nr_running
= ATOMIC_INIT(0); /* always 0 */
448 static int worker_thread(void *__worker
);
450 static struct global_cwq
*get_gcwq(unsigned int cpu
)
452 if (cpu
!= WORK_CPU_UNBOUND
)
453 return &per_cpu(global_cwq
, cpu
);
455 return &unbound_global_cwq
;
458 static atomic_t
*get_gcwq_nr_running(unsigned int cpu
)
460 if (cpu
!= WORK_CPU_UNBOUND
)
461 return &per_cpu(gcwq_nr_running
, cpu
);
463 return &unbound_gcwq_nr_running
;
466 static struct cpu_workqueue_struct
*get_cwq(unsigned int cpu
,
467 struct workqueue_struct
*wq
)
469 if (!(wq
->flags
& WQ_UNBOUND
)) {
470 if (likely(cpu
< nr_cpu_ids
)) {
472 return per_cpu_ptr(wq
->cpu_wq
.pcpu
, cpu
);
474 return wq
->cpu_wq
.single
;
477 } else if (likely(cpu
== WORK_CPU_UNBOUND
))
478 return wq
->cpu_wq
.single
;
482 static unsigned int work_color_to_flags(int color
)
484 return color
<< WORK_STRUCT_COLOR_SHIFT
;
487 static int get_work_color(struct work_struct
*work
)
489 return (*work_data_bits(work
) >> WORK_STRUCT_COLOR_SHIFT
) &
490 ((1 << WORK_STRUCT_COLOR_BITS
) - 1);
493 static int work_next_color(int color
)
495 return (color
+ 1) % WORK_NR_COLORS
;
499 * A work's data points to the cwq with WORK_STRUCT_CWQ set while the
500 * work is on queue. Once execution starts, WORK_STRUCT_CWQ is
501 * cleared and the work data contains the cpu number it was last on.
503 * set_work_{cwq|cpu}() and clear_work_data() can be used to set the
504 * cwq, cpu or clear work->data. These functions should only be
505 * called while the work is owned - ie. while the PENDING bit is set.
507 * get_work_[g]cwq() can be used to obtain the gcwq or cwq
508 * corresponding to a work. gcwq is available once the work has been
509 * queued anywhere after initialization. cwq is available only from
510 * queueing until execution starts.
512 static inline void set_work_data(struct work_struct
*work
, unsigned long data
,
515 BUG_ON(!work_pending(work
));
516 atomic_long_set(&work
->data
, data
| flags
| work_static(work
));
519 static void set_work_cwq(struct work_struct
*work
,
520 struct cpu_workqueue_struct
*cwq
,
521 unsigned long extra_flags
)
523 set_work_data(work
, (unsigned long)cwq
,
524 WORK_STRUCT_PENDING
| WORK_STRUCT_CWQ
| extra_flags
);
527 static void set_work_cpu(struct work_struct
*work
, unsigned int cpu
)
529 set_work_data(work
, cpu
<< WORK_STRUCT_FLAG_BITS
, WORK_STRUCT_PENDING
);
532 static void clear_work_data(struct work_struct
*work
)
534 set_work_data(work
, WORK_STRUCT_NO_CPU
, 0);
537 static struct cpu_workqueue_struct
*get_work_cwq(struct work_struct
*work
)
539 unsigned long data
= atomic_long_read(&work
->data
);
541 if (data
& WORK_STRUCT_CWQ
)
542 return (void *)(data
& WORK_STRUCT_WQ_DATA_MASK
);
547 static struct global_cwq
*get_work_gcwq(struct work_struct
*work
)
549 unsigned long data
= atomic_long_read(&work
->data
);
552 if (data
& WORK_STRUCT_CWQ
)
553 return ((struct cpu_workqueue_struct
*)
554 (data
& WORK_STRUCT_WQ_DATA_MASK
))->gcwq
;
556 cpu
= data
>> WORK_STRUCT_FLAG_BITS
;
557 if (cpu
== WORK_CPU_NONE
)
560 BUG_ON(cpu
>= nr_cpu_ids
&& cpu
!= WORK_CPU_UNBOUND
);
561 return get_gcwq(cpu
);
565 * Policy functions. These define the policies on how the global
566 * worker pool is managed. Unless noted otherwise, these functions
567 * assume that they're being called with gcwq->lock held.
570 static bool __need_more_worker(struct global_cwq
*gcwq
)
572 return !atomic_read(get_gcwq_nr_running(gcwq
->cpu
)) ||
573 gcwq
->flags
& GCWQ_HIGHPRI_PENDING
;
577 * Need to wake up a worker? Called from anything but currently
580 static bool need_more_worker(struct global_cwq
*gcwq
)
582 return !list_empty(&gcwq
->worklist
) && __need_more_worker(gcwq
);
585 /* Can I start working? Called from busy but !running workers. */
586 static bool may_start_working(struct global_cwq
*gcwq
)
588 return gcwq
->nr_idle
;
591 /* Do I need to keep working? Called from currently running workers. */
592 static bool keep_working(struct global_cwq
*gcwq
)
594 atomic_t
*nr_running
= get_gcwq_nr_running(gcwq
->cpu
);
596 return !list_empty(&gcwq
->worklist
) && atomic_read(nr_running
) <= 1;
599 /* Do we need a new worker? Called from manager. */
600 static bool need_to_create_worker(struct global_cwq
*gcwq
)
602 return need_more_worker(gcwq
) && !may_start_working(gcwq
);
605 /* Do I need to be the manager? */
606 static bool need_to_manage_workers(struct global_cwq
*gcwq
)
608 return need_to_create_worker(gcwq
) || gcwq
->flags
& GCWQ_MANAGE_WORKERS
;
611 /* Do we have too many workers and should some go away? */
612 static bool too_many_workers(struct global_cwq
*gcwq
)
614 bool managing
= gcwq
->flags
& GCWQ_MANAGING_WORKERS
;
615 int nr_idle
= gcwq
->nr_idle
+ managing
; /* manager is considered idle */
616 int nr_busy
= gcwq
->nr_workers
- nr_idle
;
618 return nr_idle
> 2 && (nr_idle
- 2) * MAX_IDLE_WORKERS_RATIO
>= nr_busy
;
625 /* Return the first worker. Safe with preemption disabled */
626 static struct worker
*first_worker(struct global_cwq
*gcwq
)
628 if (unlikely(list_empty(&gcwq
->idle_list
)))
631 return list_first_entry(&gcwq
->idle_list
, struct worker
, entry
);
635 * wake_up_worker - wake up an idle worker
636 * @gcwq: gcwq to wake worker for
638 * Wake up the first idle worker of @gcwq.
641 * spin_lock_irq(gcwq->lock).
643 static void wake_up_worker(struct global_cwq
*gcwq
)
645 struct worker
*worker
= first_worker(gcwq
);
648 wake_up_process(worker
->task
);
652 * wq_worker_waking_up - a worker is waking up
653 * @task: task waking up
654 * @cpu: CPU @task is waking up to
656 * This function is called during try_to_wake_up() when a worker is
660 * spin_lock_irq(rq->lock)
662 void wq_worker_waking_up(struct task_struct
*task
, unsigned int cpu
)
664 struct worker
*worker
= kthread_data(task
);
666 if (likely(!(worker
->flags
& WORKER_NOT_RUNNING
)))
667 atomic_inc(get_gcwq_nr_running(cpu
));
671 * wq_worker_sleeping - a worker is going to sleep
672 * @task: task going to sleep
673 * @cpu: CPU in question, must be the current CPU number
675 * This function is called during schedule() when a busy worker is
676 * going to sleep. Worker on the same cpu can be woken up by
677 * returning pointer to its task.
680 * spin_lock_irq(rq->lock)
683 * Worker task on @cpu to wake up, %NULL if none.
685 struct task_struct
*wq_worker_sleeping(struct task_struct
*task
,
688 struct worker
*worker
= kthread_data(task
), *to_wakeup
= NULL
;
689 struct global_cwq
*gcwq
= get_gcwq(cpu
);
690 atomic_t
*nr_running
= get_gcwq_nr_running(cpu
);
692 if (unlikely(worker
->flags
& WORKER_NOT_RUNNING
))
695 /* this can only happen on the local cpu */
696 BUG_ON(cpu
!= raw_smp_processor_id());
699 * The counterpart of the following dec_and_test, implied mb,
700 * worklist not empty test sequence is in insert_work().
701 * Please read comment there.
703 * NOT_RUNNING is clear. This means that trustee is not in
704 * charge and we're running on the local cpu w/ rq lock held
705 * and preemption disabled, which in turn means that none else
706 * could be manipulating idle_list, so dereferencing idle_list
707 * without gcwq lock is safe.
709 if (atomic_dec_and_test(nr_running
) && !list_empty(&gcwq
->worklist
))
710 to_wakeup
= first_worker(gcwq
);
711 return to_wakeup
? to_wakeup
->task
: NULL
;
715 * worker_set_flags - set worker flags and adjust nr_running accordingly
717 * @flags: flags to set
718 * @wakeup: wakeup an idle worker if necessary
720 * Set @flags in @worker->flags and adjust nr_running accordingly. If
721 * nr_running becomes zero and @wakeup is %true, an idle worker is
725 * spin_lock_irq(gcwq->lock)
727 static inline void worker_set_flags(struct worker
*worker
, unsigned int flags
,
730 struct global_cwq
*gcwq
= worker
->gcwq
;
732 WARN_ON_ONCE(worker
->task
!= current
);
735 * If transitioning into NOT_RUNNING, adjust nr_running and
736 * wake up an idle worker as necessary if requested by
739 if ((flags
& WORKER_NOT_RUNNING
) &&
740 !(worker
->flags
& WORKER_NOT_RUNNING
)) {
741 atomic_t
*nr_running
= get_gcwq_nr_running(gcwq
->cpu
);
744 if (atomic_dec_and_test(nr_running
) &&
745 !list_empty(&gcwq
->worklist
))
746 wake_up_worker(gcwq
);
748 atomic_dec(nr_running
);
751 worker
->flags
|= flags
;
755 * worker_clr_flags - clear worker flags and adjust nr_running accordingly
757 * @flags: flags to clear
759 * Clear @flags in @worker->flags and adjust nr_running accordingly.
762 * spin_lock_irq(gcwq->lock)
764 static inline void worker_clr_flags(struct worker
*worker
, unsigned int flags
)
766 struct global_cwq
*gcwq
= worker
->gcwq
;
767 unsigned int oflags
= worker
->flags
;
769 WARN_ON_ONCE(worker
->task
!= current
);
771 worker
->flags
&= ~flags
;
773 /* if transitioning out of NOT_RUNNING, increment nr_running */
774 if ((flags
& WORKER_NOT_RUNNING
) && (oflags
& WORKER_NOT_RUNNING
))
775 if (!(worker
->flags
& WORKER_NOT_RUNNING
))
776 atomic_inc(get_gcwq_nr_running(gcwq
->cpu
));
780 * busy_worker_head - return the busy hash head for a work
781 * @gcwq: gcwq of interest
782 * @work: work to be hashed
784 * Return hash head of @gcwq for @work.
787 * spin_lock_irq(gcwq->lock).
790 * Pointer to the hash head.
792 static struct hlist_head
*busy_worker_head(struct global_cwq
*gcwq
,
793 struct work_struct
*work
)
795 const int base_shift
= ilog2(sizeof(struct work_struct
));
796 unsigned long v
= (unsigned long)work
;
798 /* simple shift and fold hash, do we need something better? */
800 v
+= v
>> BUSY_WORKER_HASH_ORDER
;
801 v
&= BUSY_WORKER_HASH_MASK
;
803 return &gcwq
->busy_hash
[v
];
807 * __find_worker_executing_work - find worker which is executing a work
808 * @gcwq: gcwq of interest
809 * @bwh: hash head as returned by busy_worker_head()
810 * @work: work to find worker for
812 * Find a worker which is executing @work on @gcwq. @bwh should be
813 * the hash head obtained by calling busy_worker_head() with the same
817 * spin_lock_irq(gcwq->lock).
820 * Pointer to worker which is executing @work if found, NULL
823 static struct worker
*__find_worker_executing_work(struct global_cwq
*gcwq
,
824 struct hlist_head
*bwh
,
825 struct work_struct
*work
)
827 struct worker
*worker
;
828 struct hlist_node
*tmp
;
830 hlist_for_each_entry(worker
, tmp
, bwh
, hentry
)
831 if (worker
->current_work
== work
)
837 * find_worker_executing_work - find worker which is executing a work
838 * @gcwq: gcwq of interest
839 * @work: work to find worker for
841 * Find a worker which is executing @work on @gcwq. This function is
842 * identical to __find_worker_executing_work() except that this
843 * function calculates @bwh itself.
846 * spin_lock_irq(gcwq->lock).
849 * Pointer to worker which is executing @work if found, NULL
852 static struct worker
*find_worker_executing_work(struct global_cwq
*gcwq
,
853 struct work_struct
*work
)
855 return __find_worker_executing_work(gcwq
, busy_worker_head(gcwq
, work
),
860 * gcwq_determine_ins_pos - find insertion position
861 * @gcwq: gcwq of interest
862 * @cwq: cwq a work is being queued for
864 * A work for @cwq is about to be queued on @gcwq, determine insertion
865 * position for the work. If @cwq is for HIGHPRI wq, the work is
866 * queued at the head of the queue but in FIFO order with respect to
867 * other HIGHPRI works; otherwise, at the end of the queue. This
868 * function also sets GCWQ_HIGHPRI_PENDING flag to hint @gcwq that
869 * there are HIGHPRI works pending.
872 * spin_lock_irq(gcwq->lock).
875 * Pointer to inserstion position.
877 static inline struct list_head
*gcwq_determine_ins_pos(struct global_cwq
*gcwq
,
878 struct cpu_workqueue_struct
*cwq
)
880 struct work_struct
*twork
;
882 if (likely(!(cwq
->wq
->flags
& WQ_HIGHPRI
)))
883 return &gcwq
->worklist
;
885 list_for_each_entry(twork
, &gcwq
->worklist
, entry
) {
886 struct cpu_workqueue_struct
*tcwq
= get_work_cwq(twork
);
888 if (!(tcwq
->wq
->flags
& WQ_HIGHPRI
))
892 gcwq
->flags
|= GCWQ_HIGHPRI_PENDING
;
893 return &twork
->entry
;
897 * insert_work - insert a work into gcwq
898 * @cwq: cwq @work belongs to
899 * @work: work to insert
900 * @head: insertion point
901 * @extra_flags: extra WORK_STRUCT_* flags to set
903 * Insert @work which belongs to @cwq into @gcwq after @head.
904 * @extra_flags is or'd to work_struct flags.
907 * spin_lock_irq(gcwq->lock).
909 static void insert_work(struct cpu_workqueue_struct
*cwq
,
910 struct work_struct
*work
, struct list_head
*head
,
911 unsigned int extra_flags
)
913 struct global_cwq
*gcwq
= cwq
->gcwq
;
915 /* we own @work, set data and link */
916 set_work_cwq(work
, cwq
, extra_flags
);
919 * Ensure that we get the right work->data if we see the
920 * result of list_add() below, see try_to_grab_pending().
924 list_add_tail(&work
->entry
, head
);
927 * Ensure either worker_sched_deactivated() sees the above
928 * list_add_tail() or we see zero nr_running to avoid workers
929 * lying around lazily while there are works to be processed.
933 if (__need_more_worker(gcwq
))
934 wake_up_worker(gcwq
);
937 static void __queue_work(unsigned int cpu
, struct workqueue_struct
*wq
,
938 struct work_struct
*work
)
940 struct global_cwq
*gcwq
;
941 struct cpu_workqueue_struct
*cwq
;
942 struct list_head
*worklist
;
945 debug_work_activate(work
);
947 /* determine gcwq to use */
948 if (!(wq
->flags
& WQ_UNBOUND
)) {
949 struct global_cwq
*last_gcwq
;
951 if (unlikely(cpu
== WORK_CPU_UNBOUND
))
952 cpu
= raw_smp_processor_id();
955 * It's multi cpu. If @wq is non-reentrant and @work
956 * was previously on a different cpu, it might still
957 * be running there, in which case the work needs to
958 * be queued on that cpu to guarantee non-reentrance.
960 gcwq
= get_gcwq(cpu
);
961 if (wq
->flags
& WQ_NON_REENTRANT
&&
962 (last_gcwq
= get_work_gcwq(work
)) && last_gcwq
!= gcwq
) {
963 struct worker
*worker
;
965 spin_lock_irqsave(&last_gcwq
->lock
, flags
);
967 worker
= find_worker_executing_work(last_gcwq
, work
);
969 if (worker
&& worker
->current_cwq
->wq
== wq
)
972 /* meh... not running there, queue here */
973 spin_unlock_irqrestore(&last_gcwq
->lock
, flags
);
974 spin_lock_irqsave(&gcwq
->lock
, flags
);
977 spin_lock_irqsave(&gcwq
->lock
, flags
);
979 gcwq
= get_gcwq(WORK_CPU_UNBOUND
);
980 spin_lock_irqsave(&gcwq
->lock
, flags
);
983 /* gcwq determined, get cwq and queue */
984 cwq
= get_cwq(gcwq
->cpu
, wq
);
986 BUG_ON(!list_empty(&work
->entry
));
988 cwq
->nr_in_flight
[cwq
->work_color
]++;
990 if (likely(cwq
->nr_active
< cwq
->max_active
)) {
992 worklist
= gcwq_determine_ins_pos(gcwq
, cwq
);
994 worklist
= &cwq
->delayed_works
;
996 insert_work(cwq
, work
, worklist
, work_color_to_flags(cwq
->work_color
));
998 spin_unlock_irqrestore(&gcwq
->lock
, flags
);
1002 * queue_work - queue work on a workqueue
1003 * @wq: workqueue to use
1004 * @work: work to queue
1006 * Returns 0 if @work was already on a queue, non-zero otherwise.
1008 * We queue the work to the CPU on which it was submitted, but if the CPU dies
1009 * it can be processed by another CPU.
1011 int queue_work(struct workqueue_struct
*wq
, struct work_struct
*work
)
1015 ret
= queue_work_on(get_cpu(), wq
, work
);
1020 EXPORT_SYMBOL_GPL(queue_work
);
1023 * queue_work_on - queue work on specific cpu
1024 * @cpu: CPU number to execute work on
1025 * @wq: workqueue to use
1026 * @work: work to queue
1028 * Returns 0 if @work was already on a queue, non-zero otherwise.
1030 * We queue the work to a specific CPU, the caller must ensure it
1034 queue_work_on(int cpu
, struct workqueue_struct
*wq
, struct work_struct
*work
)
1038 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT
, work_data_bits(work
))) {
1039 __queue_work(cpu
, wq
, work
);
1044 EXPORT_SYMBOL_GPL(queue_work_on
);
1046 static void delayed_work_timer_fn(unsigned long __data
)
1048 struct delayed_work
*dwork
= (struct delayed_work
*)__data
;
1049 struct cpu_workqueue_struct
*cwq
= get_work_cwq(&dwork
->work
);
1051 __queue_work(smp_processor_id(), cwq
->wq
, &dwork
->work
);
1055 * queue_delayed_work - queue work on a workqueue after delay
1056 * @wq: workqueue to use
1057 * @dwork: delayable work to queue
1058 * @delay: number of jiffies to wait before queueing
1060 * Returns 0 if @work was already on a queue, non-zero otherwise.
1062 int queue_delayed_work(struct workqueue_struct
*wq
,
1063 struct delayed_work
*dwork
, unsigned long delay
)
1066 return queue_work(wq
, &dwork
->work
);
1068 return queue_delayed_work_on(-1, wq
, dwork
, delay
);
1070 EXPORT_SYMBOL_GPL(queue_delayed_work
);
1073 * queue_delayed_work_on - queue work on specific CPU after delay
1074 * @cpu: CPU number to execute work on
1075 * @wq: workqueue to use
1076 * @dwork: work to queue
1077 * @delay: number of jiffies to wait before queueing
1079 * Returns 0 if @work was already on a queue, non-zero otherwise.
1081 int queue_delayed_work_on(int cpu
, struct workqueue_struct
*wq
,
1082 struct delayed_work
*dwork
, unsigned long delay
)
1085 struct timer_list
*timer
= &dwork
->timer
;
1086 struct work_struct
*work
= &dwork
->work
;
1088 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT
, work_data_bits(work
))) {
1091 BUG_ON(timer_pending(timer
));
1092 BUG_ON(!list_empty(&work
->entry
));
1094 timer_stats_timer_set_start_info(&dwork
->timer
);
1097 * This stores cwq for the moment, for the timer_fn.
1098 * Note that the work's gcwq is preserved to allow
1099 * reentrance detection for delayed works.
1101 if (!(wq
->flags
& WQ_UNBOUND
)) {
1102 struct global_cwq
*gcwq
= get_work_gcwq(work
);
1104 if (gcwq
&& gcwq
->cpu
!= WORK_CPU_UNBOUND
)
1107 lcpu
= raw_smp_processor_id();
1109 lcpu
= WORK_CPU_UNBOUND
;
1111 set_work_cwq(work
, get_cwq(lcpu
, wq
), 0);
1113 timer
->expires
= jiffies
+ delay
;
1114 timer
->data
= (unsigned long)dwork
;
1115 timer
->function
= delayed_work_timer_fn
;
1117 if (unlikely(cpu
>= 0))
1118 add_timer_on(timer
, cpu
);
1125 EXPORT_SYMBOL_GPL(queue_delayed_work_on
);
1128 * worker_enter_idle - enter idle state
1129 * @worker: worker which is entering idle state
1131 * @worker is entering idle state. Update stats and idle timer if
1135 * spin_lock_irq(gcwq->lock).
1137 static void worker_enter_idle(struct worker
*worker
)
1139 struct global_cwq
*gcwq
= worker
->gcwq
;
1141 BUG_ON(worker
->flags
& WORKER_IDLE
);
1142 BUG_ON(!list_empty(&worker
->entry
) &&
1143 (worker
->hentry
.next
|| worker
->hentry
.pprev
));
1145 /* can't use worker_set_flags(), also called from start_worker() */
1146 worker
->flags
|= WORKER_IDLE
;
1148 worker
->last_active
= jiffies
;
1150 /* idle_list is LIFO */
1151 list_add(&worker
->entry
, &gcwq
->idle_list
);
1153 if (likely(!(worker
->flags
& WORKER_ROGUE
))) {
1154 if (too_many_workers(gcwq
) && !timer_pending(&gcwq
->idle_timer
))
1155 mod_timer(&gcwq
->idle_timer
,
1156 jiffies
+ IDLE_WORKER_TIMEOUT
);
1158 wake_up_all(&gcwq
->trustee_wait
);
1160 /* sanity check nr_running */
1161 WARN_ON_ONCE(gcwq
->nr_workers
== gcwq
->nr_idle
&&
1162 atomic_read(get_gcwq_nr_running(gcwq
->cpu
)));
1166 * worker_leave_idle - leave idle state
1167 * @worker: worker which is leaving idle state
1169 * @worker is leaving idle state. Update stats.
1172 * spin_lock_irq(gcwq->lock).
1174 static void worker_leave_idle(struct worker
*worker
)
1176 struct global_cwq
*gcwq
= worker
->gcwq
;
1178 BUG_ON(!(worker
->flags
& WORKER_IDLE
));
1179 worker_clr_flags(worker
, WORKER_IDLE
);
1181 list_del_init(&worker
->entry
);
1185 * worker_maybe_bind_and_lock - bind worker to its cpu if possible and lock gcwq
1188 * Works which are scheduled while the cpu is online must at least be
1189 * scheduled to a worker which is bound to the cpu so that if they are
1190 * flushed from cpu callbacks while cpu is going down, they are
1191 * guaranteed to execute on the cpu.
1193 * This function is to be used by rogue workers and rescuers to bind
1194 * themselves to the target cpu and may race with cpu going down or
1195 * coming online. kthread_bind() can't be used because it may put the
1196 * worker to already dead cpu and set_cpus_allowed_ptr() can't be used
1197 * verbatim as it's best effort and blocking and gcwq may be
1198 * [dis]associated in the meantime.
1200 * This function tries set_cpus_allowed() and locks gcwq and verifies
1201 * the binding against GCWQ_DISASSOCIATED which is set during
1202 * CPU_DYING and cleared during CPU_ONLINE, so if the worker enters
1203 * idle state or fetches works without dropping lock, it can guarantee
1204 * the scheduling requirement described in the first paragraph.
1207 * Might sleep. Called without any lock but returns with gcwq->lock
1211 * %true if the associated gcwq is online (@worker is successfully
1212 * bound), %false if offline.
1214 static bool worker_maybe_bind_and_lock(struct worker
*worker
)
1216 struct global_cwq
*gcwq
= worker
->gcwq
;
1217 struct task_struct
*task
= worker
->task
;
1221 * The following call may fail, succeed or succeed
1222 * without actually migrating the task to the cpu if
1223 * it races with cpu hotunplug operation. Verify
1224 * against GCWQ_DISASSOCIATED.
1226 if (!(gcwq
->flags
& GCWQ_DISASSOCIATED
))
1227 set_cpus_allowed_ptr(task
, get_cpu_mask(gcwq
->cpu
));
1229 spin_lock_irq(&gcwq
->lock
);
1230 if (gcwq
->flags
& GCWQ_DISASSOCIATED
)
1232 if (task_cpu(task
) == gcwq
->cpu
&&
1233 cpumask_equal(¤t
->cpus_allowed
,
1234 get_cpu_mask(gcwq
->cpu
)))
1236 spin_unlock_irq(&gcwq
->lock
);
1238 /* CPU has come up inbetween, retry migration */
1244 * Function for worker->rebind_work used to rebind rogue busy workers
1245 * to the associated cpu which is coming back online. This is
1246 * scheduled by cpu up but can race with other cpu hotplug operations
1247 * and may be executed twice without intervening cpu down.
1249 static void worker_rebind_fn(struct work_struct
*work
)
1251 struct worker
*worker
= container_of(work
, struct worker
, rebind_work
);
1252 struct global_cwq
*gcwq
= worker
->gcwq
;
1254 if (worker_maybe_bind_and_lock(worker
))
1255 worker_clr_flags(worker
, WORKER_REBIND
);
1257 spin_unlock_irq(&gcwq
->lock
);
1260 static struct worker
*alloc_worker(void)
1262 struct worker
*worker
;
1264 worker
= kzalloc(sizeof(*worker
), GFP_KERNEL
);
1266 INIT_LIST_HEAD(&worker
->entry
);
1267 INIT_LIST_HEAD(&worker
->scheduled
);
1268 INIT_WORK(&worker
->rebind_work
, worker_rebind_fn
);
1269 /* on creation a worker is in !idle && prep state */
1270 worker
->flags
= WORKER_PREP
;
1276 * create_worker - create a new workqueue worker
1277 * @gcwq: gcwq the new worker will belong to
1278 * @bind: whether to set affinity to @cpu or not
1280 * Create a new worker which is bound to @gcwq. The returned worker
1281 * can be started by calling start_worker() or destroyed using
1285 * Might sleep. Does GFP_KERNEL allocations.
1288 * Pointer to the newly created worker.
1290 static struct worker
*create_worker(struct global_cwq
*gcwq
, bool bind
)
1292 bool on_unbound_cpu
= gcwq
->cpu
== WORK_CPU_UNBOUND
;
1293 struct worker
*worker
= NULL
;
1296 spin_lock_irq(&gcwq
->lock
);
1297 while (ida_get_new(&gcwq
->worker_ida
, &id
)) {
1298 spin_unlock_irq(&gcwq
->lock
);
1299 if (!ida_pre_get(&gcwq
->worker_ida
, GFP_KERNEL
))
1301 spin_lock_irq(&gcwq
->lock
);
1303 spin_unlock_irq(&gcwq
->lock
);
1305 worker
= alloc_worker();
1309 worker
->gcwq
= gcwq
;
1312 if (!on_unbound_cpu
)
1313 worker
->task
= kthread_create(worker_thread
, worker
,
1314 "kworker/%u:%d", gcwq
->cpu
, id
);
1316 worker
->task
= kthread_create(worker_thread
, worker
,
1317 "kworker/u:%d", id
);
1318 if (IS_ERR(worker
->task
))
1322 * A rogue worker will become a regular one if CPU comes
1323 * online later on. Make sure every worker has
1324 * PF_THREAD_BOUND set.
1326 if (bind
&& !on_unbound_cpu
)
1327 kthread_bind(worker
->task
, gcwq
->cpu
);
1329 worker
->task
->flags
|= PF_THREAD_BOUND
;
1331 worker
->flags
|= WORKER_UNBOUND
;
1337 spin_lock_irq(&gcwq
->lock
);
1338 ida_remove(&gcwq
->worker_ida
, id
);
1339 spin_unlock_irq(&gcwq
->lock
);
1346 * start_worker - start a newly created worker
1347 * @worker: worker to start
1349 * Make the gcwq aware of @worker and start it.
1352 * spin_lock_irq(gcwq->lock).
1354 static void start_worker(struct worker
*worker
)
1356 worker
->flags
|= WORKER_STARTED
;
1357 worker
->gcwq
->nr_workers
++;
1358 worker_enter_idle(worker
);
1359 wake_up_process(worker
->task
);
1363 * destroy_worker - destroy a workqueue worker
1364 * @worker: worker to be destroyed
1366 * Destroy @worker and adjust @gcwq stats accordingly.
1369 * spin_lock_irq(gcwq->lock) which is released and regrabbed.
1371 static void destroy_worker(struct worker
*worker
)
1373 struct global_cwq
*gcwq
= worker
->gcwq
;
1374 int id
= worker
->id
;
1376 /* sanity check frenzy */
1377 BUG_ON(worker
->current_work
);
1378 BUG_ON(!list_empty(&worker
->scheduled
));
1380 if (worker
->flags
& WORKER_STARTED
)
1382 if (worker
->flags
& WORKER_IDLE
)
1385 list_del_init(&worker
->entry
);
1386 worker
->flags
|= WORKER_DIE
;
1388 spin_unlock_irq(&gcwq
->lock
);
1390 kthread_stop(worker
->task
);
1393 spin_lock_irq(&gcwq
->lock
);
1394 ida_remove(&gcwq
->worker_ida
, id
);
1397 static void idle_worker_timeout(unsigned long __gcwq
)
1399 struct global_cwq
*gcwq
= (void *)__gcwq
;
1401 spin_lock_irq(&gcwq
->lock
);
1403 if (too_many_workers(gcwq
)) {
1404 struct worker
*worker
;
1405 unsigned long expires
;
1407 /* idle_list is kept in LIFO order, check the last one */
1408 worker
= list_entry(gcwq
->idle_list
.prev
, struct worker
, entry
);
1409 expires
= worker
->last_active
+ IDLE_WORKER_TIMEOUT
;
1411 if (time_before(jiffies
, expires
))
1412 mod_timer(&gcwq
->idle_timer
, expires
);
1414 /* it's been idle for too long, wake up manager */
1415 gcwq
->flags
|= GCWQ_MANAGE_WORKERS
;
1416 wake_up_worker(gcwq
);
1420 spin_unlock_irq(&gcwq
->lock
);
1423 static bool send_mayday(struct work_struct
*work
)
1425 struct cpu_workqueue_struct
*cwq
= get_work_cwq(work
);
1426 struct workqueue_struct
*wq
= cwq
->wq
;
1429 if (!(wq
->flags
& WQ_RESCUER
))
1432 /* mayday mayday mayday */
1433 cpu
= cwq
->gcwq
->cpu
;
1434 /* WORK_CPU_UNBOUND can't be set in cpumask, use cpu 0 instead */
1435 if (cpu
== WORK_CPU_UNBOUND
)
1437 if (!mayday_test_and_set_cpu(cpu
, wq
->mayday_mask
))
1438 wake_up_process(wq
->rescuer
->task
);
1442 static void gcwq_mayday_timeout(unsigned long __gcwq
)
1444 struct global_cwq
*gcwq
= (void *)__gcwq
;
1445 struct work_struct
*work
;
1447 spin_lock_irq(&gcwq
->lock
);
1449 if (need_to_create_worker(gcwq
)) {
1451 * We've been trying to create a new worker but
1452 * haven't been successful. We might be hitting an
1453 * allocation deadlock. Send distress signals to
1456 list_for_each_entry(work
, &gcwq
->worklist
, entry
)
1460 spin_unlock_irq(&gcwq
->lock
);
1462 mod_timer(&gcwq
->mayday_timer
, jiffies
+ MAYDAY_INTERVAL
);
1466 * maybe_create_worker - create a new worker if necessary
1467 * @gcwq: gcwq to create a new worker for
1469 * Create a new worker for @gcwq if necessary. @gcwq is guaranteed to
1470 * have at least one idle worker on return from this function. If
1471 * creating a new worker takes longer than MAYDAY_INTERVAL, mayday is
1472 * sent to all rescuers with works scheduled on @gcwq to resolve
1473 * possible allocation deadlock.
1475 * On return, need_to_create_worker() is guaranteed to be false and
1476 * may_start_working() true.
1479 * spin_lock_irq(gcwq->lock) which may be released and regrabbed
1480 * multiple times. Does GFP_KERNEL allocations. Called only from
1484 * false if no action was taken and gcwq->lock stayed locked, true
1487 static bool maybe_create_worker(struct global_cwq
*gcwq
)
1489 if (!need_to_create_worker(gcwq
))
1492 spin_unlock_irq(&gcwq
->lock
);
1494 /* if we don't make progress in MAYDAY_INITIAL_TIMEOUT, call for help */
1495 mod_timer(&gcwq
->mayday_timer
, jiffies
+ MAYDAY_INITIAL_TIMEOUT
);
1498 struct worker
*worker
;
1500 worker
= create_worker(gcwq
, true);
1502 del_timer_sync(&gcwq
->mayday_timer
);
1503 spin_lock_irq(&gcwq
->lock
);
1504 start_worker(worker
);
1505 BUG_ON(need_to_create_worker(gcwq
));
1509 if (!need_to_create_worker(gcwq
))
1512 __set_current_state(TASK_INTERRUPTIBLE
);
1513 schedule_timeout(CREATE_COOLDOWN
);
1515 if (!need_to_create_worker(gcwq
))
1519 del_timer_sync(&gcwq
->mayday_timer
);
1520 spin_lock_irq(&gcwq
->lock
);
1521 if (need_to_create_worker(gcwq
))
1527 * maybe_destroy_worker - destroy workers which have been idle for a while
1528 * @gcwq: gcwq to destroy workers for
1530 * Destroy @gcwq workers which have been idle for longer than
1531 * IDLE_WORKER_TIMEOUT.
1534 * spin_lock_irq(gcwq->lock) which may be released and regrabbed
1535 * multiple times. Called only from manager.
1538 * false if no action was taken and gcwq->lock stayed locked, true
1541 static bool maybe_destroy_workers(struct global_cwq
*gcwq
)
1545 while (too_many_workers(gcwq
)) {
1546 struct worker
*worker
;
1547 unsigned long expires
;
1549 worker
= list_entry(gcwq
->idle_list
.prev
, struct worker
, entry
);
1550 expires
= worker
->last_active
+ IDLE_WORKER_TIMEOUT
;
1552 if (time_before(jiffies
, expires
)) {
1553 mod_timer(&gcwq
->idle_timer
, expires
);
1557 destroy_worker(worker
);
1565 * manage_workers - manage worker pool
1568 * Assume the manager role and manage gcwq worker pool @worker belongs
1569 * to. At any given time, there can be only zero or one manager per
1570 * gcwq. The exclusion is handled automatically by this function.
1572 * The caller can safely start processing works on false return. On
1573 * true return, it's guaranteed that need_to_create_worker() is false
1574 * and may_start_working() is true.
1577 * spin_lock_irq(gcwq->lock) which may be released and regrabbed
1578 * multiple times. Does GFP_KERNEL allocations.
1581 * false if no action was taken and gcwq->lock stayed locked, true if
1582 * some action was taken.
1584 static bool manage_workers(struct worker
*worker
)
1586 struct global_cwq
*gcwq
= worker
->gcwq
;
1589 if (gcwq
->flags
& GCWQ_MANAGING_WORKERS
)
1592 gcwq
->flags
&= ~GCWQ_MANAGE_WORKERS
;
1593 gcwq
->flags
|= GCWQ_MANAGING_WORKERS
;
1596 * Destroy and then create so that may_start_working() is true
1599 ret
|= maybe_destroy_workers(gcwq
);
1600 ret
|= maybe_create_worker(gcwq
);
1602 gcwq
->flags
&= ~GCWQ_MANAGING_WORKERS
;
1605 * The trustee might be waiting to take over the manager
1606 * position, tell it we're done.
1608 if (unlikely(gcwq
->trustee
))
1609 wake_up_all(&gcwq
->trustee_wait
);
1615 * move_linked_works - move linked works to a list
1616 * @work: start of series of works to be scheduled
1617 * @head: target list to append @work to
1618 * @nextp: out paramter for nested worklist walking
1620 * Schedule linked works starting from @work to @head. Work series to
1621 * be scheduled starts at @work and includes any consecutive work with
1622 * WORK_STRUCT_LINKED set in its predecessor.
1624 * If @nextp is not NULL, it's updated to point to the next work of
1625 * the last scheduled work. This allows move_linked_works() to be
1626 * nested inside outer list_for_each_entry_safe().
1629 * spin_lock_irq(gcwq->lock).
1631 static void move_linked_works(struct work_struct
*work
, struct list_head
*head
,
1632 struct work_struct
**nextp
)
1634 struct work_struct
*n
;
1637 * Linked worklist will always end before the end of the list,
1638 * use NULL for list head.
1640 list_for_each_entry_safe_from(work
, n
, NULL
, entry
) {
1641 list_move_tail(&work
->entry
, head
);
1642 if (!(*work_data_bits(work
) & WORK_STRUCT_LINKED
))
1647 * If we're already inside safe list traversal and have moved
1648 * multiple works to the scheduled queue, the next position
1649 * needs to be updated.
1655 static void cwq_activate_first_delayed(struct cpu_workqueue_struct
*cwq
)
1657 struct work_struct
*work
= list_first_entry(&cwq
->delayed_works
,
1658 struct work_struct
, entry
);
1659 struct list_head
*pos
= gcwq_determine_ins_pos(cwq
->gcwq
, cwq
);
1661 move_linked_works(work
, pos
, NULL
);
1666 * cwq_dec_nr_in_flight - decrement cwq's nr_in_flight
1667 * @cwq: cwq of interest
1668 * @color: color of work which left the queue
1670 * A work either has completed or is removed from pending queue,
1671 * decrement nr_in_flight of its cwq and handle workqueue flushing.
1674 * spin_lock_irq(gcwq->lock).
1676 static void cwq_dec_nr_in_flight(struct cpu_workqueue_struct
*cwq
, int color
)
1678 /* ignore uncolored works */
1679 if (color
== WORK_NO_COLOR
)
1682 cwq
->nr_in_flight
[color
]--;
1685 if (!list_empty(&cwq
->delayed_works
)) {
1686 /* one down, submit a delayed one */
1687 if (cwq
->nr_active
< cwq
->max_active
)
1688 cwq_activate_first_delayed(cwq
);
1691 /* is flush in progress and are we at the flushing tip? */
1692 if (likely(cwq
->flush_color
!= color
))
1695 /* are there still in-flight works? */
1696 if (cwq
->nr_in_flight
[color
])
1699 /* this cwq is done, clear flush_color */
1700 cwq
->flush_color
= -1;
1703 * If this was the last cwq, wake up the first flusher. It
1704 * will handle the rest.
1706 if (atomic_dec_and_test(&cwq
->wq
->nr_cwqs_to_flush
))
1707 complete(&cwq
->wq
->first_flusher
->done
);
1711 * process_one_work - process single work
1713 * @work: work to process
1715 * Process @work. This function contains all the logics necessary to
1716 * process a single work including synchronization against and
1717 * interaction with other workers on the same cpu, queueing and
1718 * flushing. As long as context requirement is met, any worker can
1719 * call this function to process a work.
1722 * spin_lock_irq(gcwq->lock) which is released and regrabbed.
1724 static void process_one_work(struct worker
*worker
, struct work_struct
*work
)
1726 struct cpu_workqueue_struct
*cwq
= get_work_cwq(work
);
1727 struct global_cwq
*gcwq
= cwq
->gcwq
;
1728 struct hlist_head
*bwh
= busy_worker_head(gcwq
, work
);
1729 bool cpu_intensive
= cwq
->wq
->flags
& WQ_CPU_INTENSIVE
;
1730 work_func_t f
= work
->func
;
1732 struct worker
*collision
;
1733 #ifdef CONFIG_LOCKDEP
1735 * It is permissible to free the struct work_struct from
1736 * inside the function that is called from it, this we need to
1737 * take into account for lockdep too. To avoid bogus "held
1738 * lock freed" warnings as well as problems when looking into
1739 * work->lockdep_map, make a copy and use that here.
1741 struct lockdep_map lockdep_map
= work
->lockdep_map
;
1744 * A single work shouldn't be executed concurrently by
1745 * multiple workers on a single cpu. Check whether anyone is
1746 * already processing the work. If so, defer the work to the
1747 * currently executing one.
1749 collision
= __find_worker_executing_work(gcwq
, bwh
, work
);
1750 if (unlikely(collision
)) {
1751 move_linked_works(work
, &collision
->scheduled
, NULL
);
1755 /* claim and process */
1756 debug_work_deactivate(work
);
1757 hlist_add_head(&worker
->hentry
, bwh
);
1758 worker
->current_work
= work
;
1759 worker
->current_cwq
= cwq
;
1760 work_color
= get_work_color(work
);
1762 /* record the current cpu number in the work data and dequeue */
1763 set_work_cpu(work
, gcwq
->cpu
);
1764 list_del_init(&work
->entry
);
1767 * If HIGHPRI_PENDING, check the next work, and, if HIGHPRI,
1768 * wake up another worker; otherwise, clear HIGHPRI_PENDING.
1770 if (unlikely(gcwq
->flags
& GCWQ_HIGHPRI_PENDING
)) {
1771 struct work_struct
*nwork
= list_first_entry(&gcwq
->worklist
,
1772 struct work_struct
, entry
);
1774 if (!list_empty(&gcwq
->worklist
) &&
1775 get_work_cwq(nwork
)->wq
->flags
& WQ_HIGHPRI
)
1776 wake_up_worker(gcwq
);
1778 gcwq
->flags
&= ~GCWQ_HIGHPRI_PENDING
;
1782 * CPU intensive works don't participate in concurrency
1783 * management. They're the scheduler's responsibility.
1785 if (unlikely(cpu_intensive
))
1786 worker_set_flags(worker
, WORKER_CPU_INTENSIVE
, true);
1788 spin_unlock_irq(&gcwq
->lock
);
1790 work_clear_pending(work
);
1791 lock_map_acquire(&cwq
->wq
->lockdep_map
);
1792 lock_map_acquire(&lockdep_map
);
1794 lock_map_release(&lockdep_map
);
1795 lock_map_release(&cwq
->wq
->lockdep_map
);
1797 if (unlikely(in_atomic() || lockdep_depth(current
) > 0)) {
1798 printk(KERN_ERR
"BUG: workqueue leaked lock or atomic: "
1800 current
->comm
, preempt_count(), task_pid_nr(current
));
1801 printk(KERN_ERR
" last function: ");
1802 print_symbol("%s\n", (unsigned long)f
);
1803 debug_show_held_locks(current
);
1807 spin_lock_irq(&gcwq
->lock
);
1809 /* clear cpu intensive status */
1810 if (unlikely(cpu_intensive
))
1811 worker_clr_flags(worker
, WORKER_CPU_INTENSIVE
);
1813 /* we're done with it, release */
1814 hlist_del_init(&worker
->hentry
);
1815 worker
->current_work
= NULL
;
1816 worker
->current_cwq
= NULL
;
1817 cwq_dec_nr_in_flight(cwq
, work_color
);
1821 * process_scheduled_works - process scheduled works
1824 * Process all scheduled works. Please note that the scheduled list
1825 * may change while processing a work, so this function repeatedly
1826 * fetches a work from the top and executes it.
1829 * spin_lock_irq(gcwq->lock) which may be released and regrabbed
1832 static void process_scheduled_works(struct worker
*worker
)
1834 while (!list_empty(&worker
->scheduled
)) {
1835 struct work_struct
*work
= list_first_entry(&worker
->scheduled
,
1836 struct work_struct
, entry
);
1837 process_one_work(worker
, work
);
1842 * worker_thread - the worker thread function
1845 * The gcwq worker thread function. There's a single dynamic pool of
1846 * these per each cpu. These workers process all works regardless of
1847 * their specific target workqueue. The only exception is works which
1848 * belong to workqueues with a rescuer which will be explained in
1851 static int worker_thread(void *__worker
)
1853 struct worker
*worker
= __worker
;
1854 struct global_cwq
*gcwq
= worker
->gcwq
;
1856 /* tell the scheduler that this is a workqueue worker */
1857 worker
->task
->flags
|= PF_WQ_WORKER
;
1859 spin_lock_irq(&gcwq
->lock
);
1861 /* DIE can be set only while we're idle, checking here is enough */
1862 if (worker
->flags
& WORKER_DIE
) {
1863 spin_unlock_irq(&gcwq
->lock
);
1864 worker
->task
->flags
&= ~PF_WQ_WORKER
;
1868 worker_leave_idle(worker
);
1870 /* no more worker necessary? */
1871 if (!need_more_worker(gcwq
))
1874 /* do we need to manage? */
1875 if (unlikely(!may_start_working(gcwq
)) && manage_workers(worker
))
1879 * ->scheduled list can only be filled while a worker is
1880 * preparing to process a work or actually processing it.
1881 * Make sure nobody diddled with it while I was sleeping.
1883 BUG_ON(!list_empty(&worker
->scheduled
));
1886 * When control reaches this point, we're guaranteed to have
1887 * at least one idle worker or that someone else has already
1888 * assumed the manager role.
1890 worker_clr_flags(worker
, WORKER_PREP
);
1893 struct work_struct
*work
=
1894 list_first_entry(&gcwq
->worklist
,
1895 struct work_struct
, entry
);
1897 if (likely(!(*work_data_bits(work
) & WORK_STRUCT_LINKED
))) {
1898 /* optimization path, not strictly necessary */
1899 process_one_work(worker
, work
);
1900 if (unlikely(!list_empty(&worker
->scheduled
)))
1901 process_scheduled_works(worker
);
1903 move_linked_works(work
, &worker
->scheduled
, NULL
);
1904 process_scheduled_works(worker
);
1906 } while (keep_working(gcwq
));
1908 worker_set_flags(worker
, WORKER_PREP
, false);
1910 if (unlikely(need_to_manage_workers(gcwq
)) && manage_workers(worker
))
1914 * gcwq->lock is held and there's no work to process and no
1915 * need to manage, sleep. Workers are woken up only while
1916 * holding gcwq->lock or from local cpu, so setting the
1917 * current state before releasing gcwq->lock is enough to
1918 * prevent losing any event.
1920 worker_enter_idle(worker
);
1921 __set_current_state(TASK_INTERRUPTIBLE
);
1922 spin_unlock_irq(&gcwq
->lock
);
1928 * rescuer_thread - the rescuer thread function
1929 * @__wq: the associated workqueue
1931 * Workqueue rescuer thread function. There's one rescuer for each
1932 * workqueue which has WQ_RESCUER set.
1934 * Regular work processing on a gcwq may block trying to create a new
1935 * worker which uses GFP_KERNEL allocation which has slight chance of
1936 * developing into deadlock if some works currently on the same queue
1937 * need to be processed to satisfy the GFP_KERNEL allocation. This is
1938 * the problem rescuer solves.
1940 * When such condition is possible, the gcwq summons rescuers of all
1941 * workqueues which have works queued on the gcwq and let them process
1942 * those works so that forward progress can be guaranteed.
1944 * This should happen rarely.
1946 static int rescuer_thread(void *__wq
)
1948 struct workqueue_struct
*wq
= __wq
;
1949 struct worker
*rescuer
= wq
->rescuer
;
1950 struct list_head
*scheduled
= &rescuer
->scheduled
;
1951 bool is_unbound
= wq
->flags
& WQ_UNBOUND
;
1954 set_user_nice(current
, RESCUER_NICE_LEVEL
);
1956 set_current_state(TASK_INTERRUPTIBLE
);
1958 if (kthread_should_stop())
1962 * See whether any cpu is asking for help. Unbounded
1963 * workqueues use cpu 0 in mayday_mask for CPU_UNBOUND.
1965 for_each_mayday_cpu(cpu
, wq
->mayday_mask
) {
1966 unsigned int tcpu
= is_unbound
? WORK_CPU_UNBOUND
: cpu
;
1967 struct cpu_workqueue_struct
*cwq
= get_cwq(tcpu
, wq
);
1968 struct global_cwq
*gcwq
= cwq
->gcwq
;
1969 struct work_struct
*work
, *n
;
1971 __set_current_state(TASK_RUNNING
);
1972 mayday_clear_cpu(cpu
, wq
->mayday_mask
);
1974 /* migrate to the target cpu if possible */
1975 rescuer
->gcwq
= gcwq
;
1976 worker_maybe_bind_and_lock(rescuer
);
1979 * Slurp in all works issued via this workqueue and
1982 BUG_ON(!list_empty(&rescuer
->scheduled
));
1983 list_for_each_entry_safe(work
, n
, &gcwq
->worklist
, entry
)
1984 if (get_work_cwq(work
) == cwq
)
1985 move_linked_works(work
, scheduled
, &n
);
1987 process_scheduled_works(rescuer
);
1988 spin_unlock_irq(&gcwq
->lock
);
1996 struct work_struct work
;
1997 struct completion done
;
2000 static void wq_barrier_func(struct work_struct
*work
)
2002 struct wq_barrier
*barr
= container_of(work
, struct wq_barrier
, work
);
2003 complete(&barr
->done
);
2007 * insert_wq_barrier - insert a barrier work
2008 * @cwq: cwq to insert barrier into
2009 * @barr: wq_barrier to insert
2010 * @target: target work to attach @barr to
2011 * @worker: worker currently executing @target, NULL if @target is not executing
2013 * @barr is linked to @target such that @barr is completed only after
2014 * @target finishes execution. Please note that the ordering
2015 * guarantee is observed only with respect to @target and on the local
2018 * Currently, a queued barrier can't be canceled. This is because
2019 * try_to_grab_pending() can't determine whether the work to be
2020 * grabbed is at the head of the queue and thus can't clear LINKED
2021 * flag of the previous work while there must be a valid next work
2022 * after a work with LINKED flag set.
2024 * Note that when @worker is non-NULL, @target may be modified
2025 * underneath us, so we can't reliably determine cwq from @target.
2028 * spin_lock_irq(gcwq->lock).
2030 static void insert_wq_barrier(struct cpu_workqueue_struct
*cwq
,
2031 struct wq_barrier
*barr
,
2032 struct work_struct
*target
, struct worker
*worker
)
2034 struct list_head
*head
;
2035 unsigned int linked
= 0;
2038 * debugobject calls are safe here even with gcwq->lock locked
2039 * as we know for sure that this will not trigger any of the
2040 * checks and call back into the fixup functions where we
2043 INIT_WORK_ON_STACK(&barr
->work
, wq_barrier_func
);
2044 __set_bit(WORK_STRUCT_PENDING_BIT
, work_data_bits(&barr
->work
));
2045 init_completion(&barr
->done
);
2048 * If @target is currently being executed, schedule the
2049 * barrier to the worker; otherwise, put it after @target.
2052 head
= worker
->scheduled
.next
;
2054 unsigned long *bits
= work_data_bits(target
);
2056 head
= target
->entry
.next
;
2057 /* there can already be other linked works, inherit and set */
2058 linked
= *bits
& WORK_STRUCT_LINKED
;
2059 __set_bit(WORK_STRUCT_LINKED_BIT
, bits
);
2062 debug_work_activate(&barr
->work
);
2063 insert_work(cwq
, &barr
->work
, head
,
2064 work_color_to_flags(WORK_NO_COLOR
) | linked
);
2068 * flush_workqueue_prep_cwqs - prepare cwqs for workqueue flushing
2069 * @wq: workqueue being flushed
2070 * @flush_color: new flush color, < 0 for no-op
2071 * @work_color: new work color, < 0 for no-op
2073 * Prepare cwqs for workqueue flushing.
2075 * If @flush_color is non-negative, flush_color on all cwqs should be
2076 * -1. If no cwq has in-flight commands at the specified color, all
2077 * cwq->flush_color's stay at -1 and %false is returned. If any cwq
2078 * has in flight commands, its cwq->flush_color is set to
2079 * @flush_color, @wq->nr_cwqs_to_flush is updated accordingly, cwq
2080 * wakeup logic is armed and %true is returned.
2082 * The caller should have initialized @wq->first_flusher prior to
2083 * calling this function with non-negative @flush_color. If
2084 * @flush_color is negative, no flush color update is done and %false
2087 * If @work_color is non-negative, all cwqs should have the same
2088 * work_color which is previous to @work_color and all will be
2089 * advanced to @work_color.
2092 * mutex_lock(wq->flush_mutex).
2095 * %true if @flush_color >= 0 and there's something to flush. %false
2098 static bool flush_workqueue_prep_cwqs(struct workqueue_struct
*wq
,
2099 int flush_color
, int work_color
)
2104 if (flush_color
>= 0) {
2105 BUG_ON(atomic_read(&wq
->nr_cwqs_to_flush
));
2106 atomic_set(&wq
->nr_cwqs_to_flush
, 1);
2109 for_each_cwq_cpu(cpu
, wq
) {
2110 struct cpu_workqueue_struct
*cwq
= get_cwq(cpu
, wq
);
2111 struct global_cwq
*gcwq
= cwq
->gcwq
;
2113 spin_lock_irq(&gcwq
->lock
);
2115 if (flush_color
>= 0) {
2116 BUG_ON(cwq
->flush_color
!= -1);
2118 if (cwq
->nr_in_flight
[flush_color
]) {
2119 cwq
->flush_color
= flush_color
;
2120 atomic_inc(&wq
->nr_cwqs_to_flush
);
2125 if (work_color
>= 0) {
2126 BUG_ON(work_color
!= work_next_color(cwq
->work_color
));
2127 cwq
->work_color
= work_color
;
2130 spin_unlock_irq(&gcwq
->lock
);
2133 if (flush_color
>= 0 && atomic_dec_and_test(&wq
->nr_cwqs_to_flush
))
2134 complete(&wq
->first_flusher
->done
);
2140 * flush_workqueue - ensure that any scheduled work has run to completion.
2141 * @wq: workqueue to flush
2143 * Forces execution of the workqueue and blocks until its completion.
2144 * This is typically used in driver shutdown handlers.
2146 * We sleep until all works which were queued on entry have been handled,
2147 * but we are not livelocked by new incoming ones.
2149 void flush_workqueue(struct workqueue_struct
*wq
)
2151 struct wq_flusher this_flusher
= {
2152 .list
= LIST_HEAD_INIT(this_flusher
.list
),
2154 .done
= COMPLETION_INITIALIZER_ONSTACK(this_flusher
.done
),
2158 lock_map_acquire(&wq
->lockdep_map
);
2159 lock_map_release(&wq
->lockdep_map
);
2161 mutex_lock(&wq
->flush_mutex
);
2164 * Start-to-wait phase
2166 next_color
= work_next_color(wq
->work_color
);
2168 if (next_color
!= wq
->flush_color
) {
2170 * Color space is not full. The current work_color
2171 * becomes our flush_color and work_color is advanced
2174 BUG_ON(!list_empty(&wq
->flusher_overflow
));
2175 this_flusher
.flush_color
= wq
->work_color
;
2176 wq
->work_color
= next_color
;
2178 if (!wq
->first_flusher
) {
2179 /* no flush in progress, become the first flusher */
2180 BUG_ON(wq
->flush_color
!= this_flusher
.flush_color
);
2182 wq
->first_flusher
= &this_flusher
;
2184 if (!flush_workqueue_prep_cwqs(wq
, wq
->flush_color
,
2186 /* nothing to flush, done */
2187 wq
->flush_color
= next_color
;
2188 wq
->first_flusher
= NULL
;
2193 BUG_ON(wq
->flush_color
== this_flusher
.flush_color
);
2194 list_add_tail(&this_flusher
.list
, &wq
->flusher_queue
);
2195 flush_workqueue_prep_cwqs(wq
, -1, wq
->work_color
);
2199 * Oops, color space is full, wait on overflow queue.
2200 * The next flush completion will assign us
2201 * flush_color and transfer to flusher_queue.
2203 list_add_tail(&this_flusher
.list
, &wq
->flusher_overflow
);
2206 mutex_unlock(&wq
->flush_mutex
);
2208 wait_for_completion(&this_flusher
.done
);
2211 * Wake-up-and-cascade phase
2213 * First flushers are responsible for cascading flushes and
2214 * handling overflow. Non-first flushers can simply return.
2216 if (wq
->first_flusher
!= &this_flusher
)
2219 mutex_lock(&wq
->flush_mutex
);
2221 /* we might have raced, check again with mutex held */
2222 if (wq
->first_flusher
!= &this_flusher
)
2225 wq
->first_flusher
= NULL
;
2227 BUG_ON(!list_empty(&this_flusher
.list
));
2228 BUG_ON(wq
->flush_color
!= this_flusher
.flush_color
);
2231 struct wq_flusher
*next
, *tmp
;
2233 /* complete all the flushers sharing the current flush color */
2234 list_for_each_entry_safe(next
, tmp
, &wq
->flusher_queue
, list
) {
2235 if (next
->flush_color
!= wq
->flush_color
)
2237 list_del_init(&next
->list
);
2238 complete(&next
->done
);
2241 BUG_ON(!list_empty(&wq
->flusher_overflow
) &&
2242 wq
->flush_color
!= work_next_color(wq
->work_color
));
2244 /* this flush_color is finished, advance by one */
2245 wq
->flush_color
= work_next_color(wq
->flush_color
);
2247 /* one color has been freed, handle overflow queue */
2248 if (!list_empty(&wq
->flusher_overflow
)) {
2250 * Assign the same color to all overflowed
2251 * flushers, advance work_color and append to
2252 * flusher_queue. This is the start-to-wait
2253 * phase for these overflowed flushers.
2255 list_for_each_entry(tmp
, &wq
->flusher_overflow
, list
)
2256 tmp
->flush_color
= wq
->work_color
;
2258 wq
->work_color
= work_next_color(wq
->work_color
);
2260 list_splice_tail_init(&wq
->flusher_overflow
,
2261 &wq
->flusher_queue
);
2262 flush_workqueue_prep_cwqs(wq
, -1, wq
->work_color
);
2265 if (list_empty(&wq
->flusher_queue
)) {
2266 BUG_ON(wq
->flush_color
!= wq
->work_color
);
2271 * Need to flush more colors. Make the next flusher
2272 * the new first flusher and arm cwqs.
2274 BUG_ON(wq
->flush_color
== wq
->work_color
);
2275 BUG_ON(wq
->flush_color
!= next
->flush_color
);
2277 list_del_init(&next
->list
);
2278 wq
->first_flusher
= next
;
2280 if (flush_workqueue_prep_cwqs(wq
, wq
->flush_color
, -1))
2284 * Meh... this color is already done, clear first
2285 * flusher and repeat cascading.
2287 wq
->first_flusher
= NULL
;
2291 mutex_unlock(&wq
->flush_mutex
);
2293 EXPORT_SYMBOL_GPL(flush_workqueue
);
2296 * flush_work - block until a work_struct's callback has terminated
2297 * @work: the work which is to be flushed
2299 * Returns false if @work has already terminated.
2301 * It is expected that, prior to calling flush_work(), the caller has
2302 * arranged for the work to not be requeued, otherwise it doesn't make
2303 * sense to use this function.
2305 int flush_work(struct work_struct
*work
)
2307 struct worker
*worker
= NULL
;
2308 struct global_cwq
*gcwq
;
2309 struct cpu_workqueue_struct
*cwq
;
2310 struct wq_barrier barr
;
2313 gcwq
= get_work_gcwq(work
);
2317 spin_lock_irq(&gcwq
->lock
);
2318 if (!list_empty(&work
->entry
)) {
2320 * See the comment near try_to_grab_pending()->smp_rmb().
2321 * If it was re-queued to a different gcwq under us, we
2322 * are not going to wait.
2325 cwq
= get_work_cwq(work
);
2326 if (unlikely(!cwq
|| gcwq
!= cwq
->gcwq
))
2329 worker
= find_worker_executing_work(gcwq
, work
);
2332 cwq
= worker
->current_cwq
;
2335 insert_wq_barrier(cwq
, &barr
, work
, worker
);
2336 spin_unlock_irq(&gcwq
->lock
);
2338 lock_map_acquire(&cwq
->wq
->lockdep_map
);
2339 lock_map_release(&cwq
->wq
->lockdep_map
);
2341 wait_for_completion(&barr
.done
);
2342 destroy_work_on_stack(&barr
.work
);
2345 spin_unlock_irq(&gcwq
->lock
);
2348 EXPORT_SYMBOL_GPL(flush_work
);
2351 * Upon a successful return (>= 0), the caller "owns" WORK_STRUCT_PENDING bit,
2352 * so this work can't be re-armed in any way.
2354 static int try_to_grab_pending(struct work_struct
*work
)
2356 struct global_cwq
*gcwq
;
2359 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT
, work_data_bits(work
)))
2363 * The queueing is in progress, or it is already queued. Try to
2364 * steal it from ->worklist without clearing WORK_STRUCT_PENDING.
2366 gcwq
= get_work_gcwq(work
);
2370 spin_lock_irq(&gcwq
->lock
);
2371 if (!list_empty(&work
->entry
)) {
2373 * This work is queued, but perhaps we locked the wrong gcwq.
2374 * In that case we must see the new value after rmb(), see
2375 * insert_work()->wmb().
2378 if (gcwq
== get_work_gcwq(work
)) {
2379 debug_work_deactivate(work
);
2380 list_del_init(&work
->entry
);
2381 cwq_dec_nr_in_flight(get_work_cwq(work
),
2382 get_work_color(work
));
2386 spin_unlock_irq(&gcwq
->lock
);
2391 static void wait_on_cpu_work(struct global_cwq
*gcwq
, struct work_struct
*work
)
2393 struct wq_barrier barr
;
2394 struct worker
*worker
;
2396 spin_lock_irq(&gcwq
->lock
);
2398 worker
= find_worker_executing_work(gcwq
, work
);
2399 if (unlikely(worker
))
2400 insert_wq_barrier(worker
->current_cwq
, &barr
, work
, worker
);
2402 spin_unlock_irq(&gcwq
->lock
);
2404 if (unlikely(worker
)) {
2405 wait_for_completion(&barr
.done
);
2406 destroy_work_on_stack(&barr
.work
);
2410 static void wait_on_work(struct work_struct
*work
)
2416 lock_map_acquire(&work
->lockdep_map
);
2417 lock_map_release(&work
->lockdep_map
);
2419 for_each_gcwq_cpu(cpu
)
2420 wait_on_cpu_work(get_gcwq(cpu
), work
);
2423 static int __cancel_work_timer(struct work_struct
*work
,
2424 struct timer_list
* timer
)
2429 ret
= (timer
&& likely(del_timer(timer
)));
2431 ret
= try_to_grab_pending(work
);
2433 } while (unlikely(ret
< 0));
2435 clear_work_data(work
);
2440 * cancel_work_sync - block until a work_struct's callback has terminated
2441 * @work: the work which is to be flushed
2443 * Returns true if @work was pending.
2445 * cancel_work_sync() will cancel the work if it is queued. If the work's
2446 * callback appears to be running, cancel_work_sync() will block until it
2449 * It is possible to use this function if the work re-queues itself. It can
2450 * cancel the work even if it migrates to another workqueue, however in that
2451 * case it only guarantees that work->func() has completed on the last queued
2454 * cancel_work_sync(&delayed_work->work) should be used only if ->timer is not
2455 * pending, otherwise it goes into a busy-wait loop until the timer expires.
2457 * The caller must ensure that workqueue_struct on which this work was last
2458 * queued can't be destroyed before this function returns.
2460 int cancel_work_sync(struct work_struct
*work
)
2462 return __cancel_work_timer(work
, NULL
);
2464 EXPORT_SYMBOL_GPL(cancel_work_sync
);
2467 * cancel_delayed_work_sync - reliably kill off a delayed work.
2468 * @dwork: the delayed work struct
2470 * Returns true if @dwork was pending.
2472 * It is possible to use this function if @dwork rearms itself via queue_work()
2473 * or queue_delayed_work(). See also the comment for cancel_work_sync().
2475 int cancel_delayed_work_sync(struct delayed_work
*dwork
)
2477 return __cancel_work_timer(&dwork
->work
, &dwork
->timer
);
2479 EXPORT_SYMBOL(cancel_delayed_work_sync
);
2482 * schedule_work - put work task in global workqueue
2483 * @work: job to be done
2485 * Returns zero if @work was already on the kernel-global workqueue and
2486 * non-zero otherwise.
2488 * This puts a job in the kernel-global workqueue if it was not already
2489 * queued and leaves it in the same position on the kernel-global
2490 * workqueue otherwise.
2492 int schedule_work(struct work_struct
*work
)
2494 return queue_work(system_wq
, work
);
2496 EXPORT_SYMBOL(schedule_work
);
2499 * schedule_work_on - put work task on a specific cpu
2500 * @cpu: cpu to put the work task on
2501 * @work: job to be done
2503 * This puts a job on a specific cpu
2505 int schedule_work_on(int cpu
, struct work_struct
*work
)
2507 return queue_work_on(cpu
, system_wq
, work
);
2509 EXPORT_SYMBOL(schedule_work_on
);
2512 * schedule_delayed_work - put work task in global workqueue after delay
2513 * @dwork: job to be done
2514 * @delay: number of jiffies to wait or 0 for immediate execution
2516 * After waiting for a given time this puts a job in the kernel-global
2519 int schedule_delayed_work(struct delayed_work
*dwork
,
2520 unsigned long delay
)
2522 return queue_delayed_work(system_wq
, dwork
, delay
);
2524 EXPORT_SYMBOL(schedule_delayed_work
);
2527 * flush_delayed_work - block until a dwork_struct's callback has terminated
2528 * @dwork: the delayed work which is to be flushed
2530 * Any timeout is cancelled, and any pending work is run immediately.
2532 void flush_delayed_work(struct delayed_work
*dwork
)
2534 if (del_timer_sync(&dwork
->timer
)) {
2535 __queue_work(get_cpu(), get_work_cwq(&dwork
->work
)->wq
,
2539 flush_work(&dwork
->work
);
2541 EXPORT_SYMBOL(flush_delayed_work
);
2544 * schedule_delayed_work_on - queue work in global workqueue on CPU after delay
2546 * @dwork: job to be done
2547 * @delay: number of jiffies to wait
2549 * After waiting for a given time this puts a job in the kernel-global
2550 * workqueue on the specified CPU.
2552 int schedule_delayed_work_on(int cpu
,
2553 struct delayed_work
*dwork
, unsigned long delay
)
2555 return queue_delayed_work_on(cpu
, system_wq
, dwork
, delay
);
2557 EXPORT_SYMBOL(schedule_delayed_work_on
);
2560 * schedule_on_each_cpu - call a function on each online CPU from keventd
2561 * @func: the function to call
2563 * Returns zero on success.
2564 * Returns -ve errno on failure.
2566 * schedule_on_each_cpu() is very slow.
2568 int schedule_on_each_cpu(work_func_t func
)
2571 struct work_struct
*works
;
2573 works
= alloc_percpu(struct work_struct
);
2579 for_each_online_cpu(cpu
) {
2580 struct work_struct
*work
= per_cpu_ptr(works
, cpu
);
2582 INIT_WORK(work
, func
);
2583 schedule_work_on(cpu
, work
);
2586 for_each_online_cpu(cpu
)
2587 flush_work(per_cpu_ptr(works
, cpu
));
2595 * flush_scheduled_work - ensure that any scheduled work has run to completion.
2597 * Forces execution of the kernel-global workqueue and blocks until its
2600 * Think twice before calling this function! It's very easy to get into
2601 * trouble if you don't take great care. Either of the following situations
2602 * will lead to deadlock:
2604 * One of the work items currently on the workqueue needs to acquire
2605 * a lock held by your code or its caller.
2607 * Your code is running in the context of a work routine.
2609 * They will be detected by lockdep when they occur, but the first might not
2610 * occur very often. It depends on what work items are on the workqueue and
2611 * what locks they need, which you have no control over.
2613 * In most situations flushing the entire workqueue is overkill; you merely
2614 * need to know that a particular work item isn't queued and isn't running.
2615 * In such cases you should use cancel_delayed_work_sync() or
2616 * cancel_work_sync() instead.
2618 void flush_scheduled_work(void)
2620 flush_workqueue(system_wq
);
2622 EXPORT_SYMBOL(flush_scheduled_work
);
2625 * execute_in_process_context - reliably execute the routine with user context
2626 * @fn: the function to execute
2627 * @ew: guaranteed storage for the execute work structure (must
2628 * be available when the work executes)
2630 * Executes the function immediately if process context is available,
2631 * otherwise schedules the function for delayed execution.
2633 * Returns: 0 - function was executed
2634 * 1 - function was scheduled for execution
2636 int execute_in_process_context(work_func_t fn
, struct execute_work
*ew
)
2638 if (!in_interrupt()) {
2643 INIT_WORK(&ew
->work
, fn
);
2644 schedule_work(&ew
->work
);
2648 EXPORT_SYMBOL_GPL(execute_in_process_context
);
2650 int keventd_up(void)
2652 return system_wq
!= NULL
;
2655 static int alloc_cwqs(struct workqueue_struct
*wq
)
2658 * cwqs are forced aligned according to WORK_STRUCT_FLAG_BITS.
2659 * Make sure that the alignment isn't lower than that of
2660 * unsigned long long.
2662 const size_t size
= sizeof(struct cpu_workqueue_struct
);
2663 const size_t align
= max_t(size_t, 1 << WORK_STRUCT_FLAG_BITS
,
2664 __alignof__(unsigned long long));
2666 bool percpu
= !(wq
->flags
& WQ_UNBOUND
);
2668 bool percpu
= false;
2672 wq
->cpu_wq
.pcpu
= __alloc_percpu(size
, align
);
2677 * Allocate enough room to align cwq and put an extra
2678 * pointer at the end pointing back to the originally
2679 * allocated pointer which will be used for free.
2681 ptr
= kzalloc(size
+ align
+ sizeof(void *), GFP_KERNEL
);
2683 wq
->cpu_wq
.single
= PTR_ALIGN(ptr
, align
);
2684 *(void **)(wq
->cpu_wq
.single
+ 1) = ptr
;
2688 /* just in case, make sure it's actually aligned */
2689 BUG_ON(!IS_ALIGNED(wq
->cpu_wq
.v
, align
));
2690 return wq
->cpu_wq
.v
? 0 : -ENOMEM
;
2693 static void free_cwqs(struct workqueue_struct
*wq
)
2696 bool percpu
= !(wq
->flags
& WQ_UNBOUND
);
2698 bool percpu
= false;
2702 free_percpu(wq
->cpu_wq
.pcpu
);
2703 else if (wq
->cpu_wq
.single
) {
2704 /* the pointer to free is stored right after the cwq */
2705 kfree(*(void **)(wq
->cpu_wq
.single
+ 1));
2709 static int wq_clamp_max_active(int max_active
, unsigned int flags
,
2712 int lim
= flags
& WQ_UNBOUND
? WQ_UNBOUND_MAX_ACTIVE
: WQ_MAX_ACTIVE
;
2714 if (max_active
< 1 || max_active
> lim
)
2715 printk(KERN_WARNING
"workqueue: max_active %d requested for %s "
2716 "is out of range, clamping between %d and %d\n",
2717 max_active
, name
, 1, lim
);
2719 return clamp_val(max_active
, 1, lim
);
2722 struct workqueue_struct
*__alloc_workqueue_key(const char *name
,
2725 struct lock_class_key
*key
,
2726 const char *lock_name
)
2728 struct workqueue_struct
*wq
;
2732 * Unbound workqueues aren't concurrency managed and should be
2733 * dispatched to workers immediately.
2735 if (flags
& WQ_UNBOUND
)
2736 flags
|= WQ_HIGHPRI
;
2738 max_active
= max_active
?: WQ_DFL_ACTIVE
;
2739 max_active
= wq_clamp_max_active(max_active
, flags
, name
);
2741 wq
= kzalloc(sizeof(*wq
), GFP_KERNEL
);
2746 wq
->saved_max_active
= max_active
;
2747 mutex_init(&wq
->flush_mutex
);
2748 atomic_set(&wq
->nr_cwqs_to_flush
, 0);
2749 INIT_LIST_HEAD(&wq
->flusher_queue
);
2750 INIT_LIST_HEAD(&wq
->flusher_overflow
);
2753 lockdep_init_map(&wq
->lockdep_map
, lock_name
, key
, 0);
2754 INIT_LIST_HEAD(&wq
->list
);
2756 if (alloc_cwqs(wq
) < 0)
2759 for_each_cwq_cpu(cpu
, wq
) {
2760 struct cpu_workqueue_struct
*cwq
= get_cwq(cpu
, wq
);
2761 struct global_cwq
*gcwq
= get_gcwq(cpu
);
2763 BUG_ON((unsigned long)cwq
& WORK_STRUCT_FLAG_MASK
);
2766 cwq
->flush_color
= -1;
2767 cwq
->max_active
= max_active
;
2768 INIT_LIST_HEAD(&cwq
->delayed_works
);
2771 if (flags
& WQ_RESCUER
) {
2772 struct worker
*rescuer
;
2774 if (!alloc_mayday_mask(&wq
->mayday_mask
, GFP_KERNEL
))
2777 wq
->rescuer
= rescuer
= alloc_worker();
2781 rescuer
->task
= kthread_create(rescuer_thread
, wq
, "%s", name
);
2782 if (IS_ERR(rescuer
->task
))
2785 wq
->rescuer
= rescuer
;
2786 rescuer
->task
->flags
|= PF_THREAD_BOUND
;
2787 wake_up_process(rescuer
->task
);
2791 * workqueue_lock protects global freeze state and workqueues
2792 * list. Grab it, set max_active accordingly and add the new
2793 * workqueue to workqueues list.
2795 spin_lock(&workqueue_lock
);
2797 if (workqueue_freezing
&& wq
->flags
& WQ_FREEZEABLE
)
2798 for_each_cwq_cpu(cpu
, wq
)
2799 get_cwq(cpu
, wq
)->max_active
= 0;
2801 list_add(&wq
->list
, &workqueues
);
2803 spin_unlock(&workqueue_lock
);
2809 free_mayday_mask(wq
->mayday_mask
);
2815 EXPORT_SYMBOL_GPL(__alloc_workqueue_key
);
2818 * destroy_workqueue - safely terminate a workqueue
2819 * @wq: target workqueue
2821 * Safely destroy a workqueue. All work currently pending will be done first.
2823 void destroy_workqueue(struct workqueue_struct
*wq
)
2827 flush_workqueue(wq
);
2830 * wq list is used to freeze wq, remove from list after
2831 * flushing is complete in case freeze races us.
2833 spin_lock(&workqueue_lock
);
2834 list_del(&wq
->list
);
2835 spin_unlock(&workqueue_lock
);
2838 for_each_cwq_cpu(cpu
, wq
) {
2839 struct cpu_workqueue_struct
*cwq
= get_cwq(cpu
, wq
);
2842 for (i
= 0; i
< WORK_NR_COLORS
; i
++)
2843 BUG_ON(cwq
->nr_in_flight
[i
]);
2844 BUG_ON(cwq
->nr_active
);
2845 BUG_ON(!list_empty(&cwq
->delayed_works
));
2848 if (wq
->flags
& WQ_RESCUER
) {
2849 kthread_stop(wq
->rescuer
->task
);
2850 free_mayday_mask(wq
->mayday_mask
);
2856 EXPORT_SYMBOL_GPL(destroy_workqueue
);
2859 * workqueue_set_max_active - adjust max_active of a workqueue
2860 * @wq: target workqueue
2861 * @max_active: new max_active value.
2863 * Set max_active of @wq to @max_active.
2866 * Don't call from IRQ context.
2868 void workqueue_set_max_active(struct workqueue_struct
*wq
, int max_active
)
2872 max_active
= wq_clamp_max_active(max_active
, wq
->flags
, wq
->name
);
2874 spin_lock(&workqueue_lock
);
2876 wq
->saved_max_active
= max_active
;
2878 for_each_cwq_cpu(cpu
, wq
) {
2879 struct global_cwq
*gcwq
= get_gcwq(cpu
);
2881 spin_lock_irq(&gcwq
->lock
);
2883 if (!(wq
->flags
& WQ_FREEZEABLE
) ||
2884 !(gcwq
->flags
& GCWQ_FREEZING
))
2885 get_cwq(gcwq
->cpu
, wq
)->max_active
= max_active
;
2887 spin_unlock_irq(&gcwq
->lock
);
2890 spin_unlock(&workqueue_lock
);
2892 EXPORT_SYMBOL_GPL(workqueue_set_max_active
);
2895 * workqueue_congested - test whether a workqueue is congested
2896 * @cpu: CPU in question
2897 * @wq: target workqueue
2899 * Test whether @wq's cpu workqueue for @cpu is congested. There is
2900 * no synchronization around this function and the test result is
2901 * unreliable and only useful as advisory hints or for debugging.
2904 * %true if congested, %false otherwise.
2906 bool workqueue_congested(unsigned int cpu
, struct workqueue_struct
*wq
)
2908 struct cpu_workqueue_struct
*cwq
= get_cwq(cpu
, wq
);
2910 return !list_empty(&cwq
->delayed_works
);
2912 EXPORT_SYMBOL_GPL(workqueue_congested
);
2915 * work_cpu - return the last known associated cpu for @work
2916 * @work: the work of interest
2919 * CPU number if @work was ever queued. WORK_CPU_NONE otherwise.
2921 unsigned int work_cpu(struct work_struct
*work
)
2923 struct global_cwq
*gcwq
= get_work_gcwq(work
);
2925 return gcwq
? gcwq
->cpu
: WORK_CPU_NONE
;
2927 EXPORT_SYMBOL_GPL(work_cpu
);
2930 * work_busy - test whether a work is currently pending or running
2931 * @work: the work to be tested
2933 * Test whether @work is currently pending or running. There is no
2934 * synchronization around this function and the test result is
2935 * unreliable and only useful as advisory hints or for debugging.
2936 * Especially for reentrant wqs, the pending state might hide the
2940 * OR'd bitmask of WORK_BUSY_* bits.
2942 unsigned int work_busy(struct work_struct
*work
)
2944 struct global_cwq
*gcwq
= get_work_gcwq(work
);
2945 unsigned long flags
;
2946 unsigned int ret
= 0;
2951 spin_lock_irqsave(&gcwq
->lock
, flags
);
2953 if (work_pending(work
))
2954 ret
|= WORK_BUSY_PENDING
;
2955 if (find_worker_executing_work(gcwq
, work
))
2956 ret
|= WORK_BUSY_RUNNING
;
2958 spin_unlock_irqrestore(&gcwq
->lock
, flags
);
2962 EXPORT_SYMBOL_GPL(work_busy
);
2967 * There are two challenges in supporting CPU hotplug. Firstly, there
2968 * are a lot of assumptions on strong associations among work, cwq and
2969 * gcwq which make migrating pending and scheduled works very
2970 * difficult to implement without impacting hot paths. Secondly,
2971 * gcwqs serve mix of short, long and very long running works making
2972 * blocked draining impractical.
2974 * This is solved by allowing a gcwq to be detached from CPU, running
2975 * it with unbound (rogue) workers and allowing it to be reattached
2976 * later if the cpu comes back online. A separate thread is created
2977 * to govern a gcwq in such state and is called the trustee of the
2980 * Trustee states and their descriptions.
2982 * START Command state used on startup. On CPU_DOWN_PREPARE, a
2983 * new trustee is started with this state.
2985 * IN_CHARGE Once started, trustee will enter this state after
2986 * assuming the manager role and making all existing
2987 * workers rogue. DOWN_PREPARE waits for trustee to
2988 * enter this state. After reaching IN_CHARGE, trustee
2989 * tries to execute the pending worklist until it's empty
2990 * and the state is set to BUTCHER, or the state is set
2993 * BUTCHER Command state which is set by the cpu callback after
2994 * the cpu has went down. Once this state is set trustee
2995 * knows that there will be no new works on the worklist
2996 * and once the worklist is empty it can proceed to
2997 * killing idle workers.
2999 * RELEASE Command state which is set by the cpu callback if the
3000 * cpu down has been canceled or it has come online
3001 * again. After recognizing this state, trustee stops
3002 * trying to drain or butcher and clears ROGUE, rebinds
3003 * all remaining workers back to the cpu and releases
3006 * DONE Trustee will enter this state after BUTCHER or RELEASE
3009 * trustee CPU draining
3010 * took over down complete
3011 * START -----------> IN_CHARGE -----------> BUTCHER -----------> DONE
3013 * | CPU is back online v return workers |
3014 * ----------------> RELEASE --------------
3018 * trustee_wait_event_timeout - timed event wait for trustee
3019 * @cond: condition to wait for
3020 * @timeout: timeout in jiffies
3022 * wait_event_timeout() for trustee to use. Handles locking and
3023 * checks for RELEASE request.
3026 * spin_lock_irq(gcwq->lock) which may be released and regrabbed
3027 * multiple times. To be used by trustee.
3030 * Positive indicating left time if @cond is satisfied, 0 if timed
3031 * out, -1 if canceled.
3033 #define trustee_wait_event_timeout(cond, timeout) ({ \
3034 long __ret = (timeout); \
3035 while (!((cond) || (gcwq->trustee_state == TRUSTEE_RELEASE)) && \
3037 spin_unlock_irq(&gcwq->lock); \
3038 __wait_event_timeout(gcwq->trustee_wait, (cond) || \
3039 (gcwq->trustee_state == TRUSTEE_RELEASE), \
3041 spin_lock_irq(&gcwq->lock); \
3043 gcwq->trustee_state == TRUSTEE_RELEASE ? -1 : (__ret); \
3047 * trustee_wait_event - event wait for trustee
3048 * @cond: condition to wait for
3050 * wait_event() for trustee to use. Automatically handles locking and
3051 * checks for CANCEL request.
3054 * spin_lock_irq(gcwq->lock) which may be released and regrabbed
3055 * multiple times. To be used by trustee.
3058 * 0 if @cond is satisfied, -1 if canceled.
3060 #define trustee_wait_event(cond) ({ \
3062 __ret1 = trustee_wait_event_timeout(cond, MAX_SCHEDULE_TIMEOUT);\
3063 __ret1 < 0 ? -1 : 0; \
3066 static int __cpuinit
trustee_thread(void *__gcwq
)
3068 struct global_cwq
*gcwq
= __gcwq
;
3069 struct worker
*worker
;
3070 struct work_struct
*work
;
3071 struct hlist_node
*pos
;
3075 BUG_ON(gcwq
->cpu
!= smp_processor_id());
3077 spin_lock_irq(&gcwq
->lock
);
3079 * Claim the manager position and make all workers rogue.
3080 * Trustee must be bound to the target cpu and can't be
3083 BUG_ON(gcwq
->cpu
!= smp_processor_id());
3084 rc
= trustee_wait_event(!(gcwq
->flags
& GCWQ_MANAGING_WORKERS
));
3087 gcwq
->flags
|= GCWQ_MANAGING_WORKERS
;
3089 list_for_each_entry(worker
, &gcwq
->idle_list
, entry
)
3090 worker
->flags
|= WORKER_ROGUE
;
3092 for_each_busy_worker(worker
, i
, pos
, gcwq
)
3093 worker
->flags
|= WORKER_ROGUE
;
3096 * Call schedule() so that we cross rq->lock and thus can
3097 * guarantee sched callbacks see the rogue flag. This is
3098 * necessary as scheduler callbacks may be invoked from other
3101 spin_unlock_irq(&gcwq
->lock
);
3103 spin_lock_irq(&gcwq
->lock
);
3106 * Sched callbacks are disabled now. Zap nr_running. After
3107 * this, nr_running stays zero and need_more_worker() and
3108 * keep_working() are always true as long as the worklist is
3111 atomic_set(get_gcwq_nr_running(gcwq
->cpu
), 0);
3113 spin_unlock_irq(&gcwq
->lock
);
3114 del_timer_sync(&gcwq
->idle_timer
);
3115 spin_lock_irq(&gcwq
->lock
);
3118 * We're now in charge. Notify and proceed to drain. We need
3119 * to keep the gcwq running during the whole CPU down
3120 * procedure as other cpu hotunplug callbacks may need to
3121 * flush currently running tasks.
3123 gcwq
->trustee_state
= TRUSTEE_IN_CHARGE
;
3124 wake_up_all(&gcwq
->trustee_wait
);
3127 * The original cpu is in the process of dying and may go away
3128 * anytime now. When that happens, we and all workers would
3129 * be migrated to other cpus. Try draining any left work. We
3130 * want to get it over with ASAP - spam rescuers, wake up as
3131 * many idlers as necessary and create new ones till the
3132 * worklist is empty. Note that if the gcwq is frozen, there
3133 * may be frozen works in freezeable cwqs. Don't declare
3134 * completion while frozen.
3136 while (gcwq
->nr_workers
!= gcwq
->nr_idle
||
3137 gcwq
->flags
& GCWQ_FREEZING
||
3138 gcwq
->trustee_state
== TRUSTEE_IN_CHARGE
) {
3141 list_for_each_entry(work
, &gcwq
->worklist
, entry
) {
3146 list_for_each_entry(worker
, &gcwq
->idle_list
, entry
) {
3149 wake_up_process(worker
->task
);
3152 if (need_to_create_worker(gcwq
)) {
3153 spin_unlock_irq(&gcwq
->lock
);
3154 worker
= create_worker(gcwq
, false);
3155 spin_lock_irq(&gcwq
->lock
);
3157 worker
->flags
|= WORKER_ROGUE
;
3158 start_worker(worker
);
3162 /* give a breather */
3163 if (trustee_wait_event_timeout(false, TRUSTEE_COOLDOWN
) < 0)
3168 * Either all works have been scheduled and cpu is down, or
3169 * cpu down has already been canceled. Wait for and butcher
3170 * all workers till we're canceled.
3173 rc
= trustee_wait_event(!list_empty(&gcwq
->idle_list
));
3174 while (!list_empty(&gcwq
->idle_list
))
3175 destroy_worker(list_first_entry(&gcwq
->idle_list
,
3176 struct worker
, entry
));
3177 } while (gcwq
->nr_workers
&& rc
>= 0);
3180 * At this point, either draining has completed and no worker
3181 * is left, or cpu down has been canceled or the cpu is being
3182 * brought back up. There shouldn't be any idle one left.
3183 * Tell the remaining busy ones to rebind once it finishes the
3184 * currently scheduled works by scheduling the rebind_work.
3186 WARN_ON(!list_empty(&gcwq
->idle_list
));
3188 for_each_busy_worker(worker
, i
, pos
, gcwq
) {
3189 struct work_struct
*rebind_work
= &worker
->rebind_work
;
3192 * Rebind_work may race with future cpu hotplug
3193 * operations. Use a separate flag to mark that
3194 * rebinding is scheduled.
3196 worker
->flags
|= WORKER_REBIND
;
3197 worker
->flags
&= ~WORKER_ROGUE
;
3199 /* queue rebind_work, wq doesn't matter, use the default one */
3200 if (test_and_set_bit(WORK_STRUCT_PENDING_BIT
,
3201 work_data_bits(rebind_work
)))
3204 debug_work_activate(rebind_work
);
3205 insert_work(get_cwq(gcwq
->cpu
, system_wq
), rebind_work
,
3206 worker
->scheduled
.next
,
3207 work_color_to_flags(WORK_NO_COLOR
));
3210 /* relinquish manager role */
3211 gcwq
->flags
&= ~GCWQ_MANAGING_WORKERS
;
3213 /* notify completion */
3214 gcwq
->trustee
= NULL
;
3215 gcwq
->trustee_state
= TRUSTEE_DONE
;
3216 wake_up_all(&gcwq
->trustee_wait
);
3217 spin_unlock_irq(&gcwq
->lock
);
3222 * wait_trustee_state - wait for trustee to enter the specified state
3223 * @gcwq: gcwq the trustee of interest belongs to
3224 * @state: target state to wait for
3226 * Wait for the trustee to reach @state. DONE is already matched.
3229 * spin_lock_irq(gcwq->lock) which may be released and regrabbed
3230 * multiple times. To be used by cpu_callback.
3232 static void __cpuinit
wait_trustee_state(struct global_cwq
*gcwq
, int state
)
3234 if (!(gcwq
->trustee_state
== state
||
3235 gcwq
->trustee_state
== TRUSTEE_DONE
)) {
3236 spin_unlock_irq(&gcwq
->lock
);
3237 __wait_event(gcwq
->trustee_wait
,
3238 gcwq
->trustee_state
== state
||
3239 gcwq
->trustee_state
== TRUSTEE_DONE
);
3240 spin_lock_irq(&gcwq
->lock
);
3244 static int __devinit
workqueue_cpu_callback(struct notifier_block
*nfb
,
3245 unsigned long action
,
3248 unsigned int cpu
= (unsigned long)hcpu
;
3249 struct global_cwq
*gcwq
= get_gcwq(cpu
);
3250 struct task_struct
*new_trustee
= NULL
;
3251 struct worker
*uninitialized_var(new_worker
);
3252 unsigned long flags
;
3254 action
&= ~CPU_TASKS_FROZEN
;
3257 case CPU_DOWN_PREPARE
:
3258 new_trustee
= kthread_create(trustee_thread
, gcwq
,
3259 "workqueue_trustee/%d\n", cpu
);
3260 if (IS_ERR(new_trustee
))
3261 return notifier_from_errno(PTR_ERR(new_trustee
));
3262 kthread_bind(new_trustee
, cpu
);
3264 case CPU_UP_PREPARE
:
3265 BUG_ON(gcwq
->first_idle
);
3266 new_worker
= create_worker(gcwq
, false);
3269 kthread_stop(new_trustee
);
3274 /* some are called w/ irq disabled, don't disturb irq status */
3275 spin_lock_irqsave(&gcwq
->lock
, flags
);
3278 case CPU_DOWN_PREPARE
:
3279 /* initialize trustee and tell it to acquire the gcwq */
3280 BUG_ON(gcwq
->trustee
|| gcwq
->trustee_state
!= TRUSTEE_DONE
);
3281 gcwq
->trustee
= new_trustee
;
3282 gcwq
->trustee_state
= TRUSTEE_START
;
3283 wake_up_process(gcwq
->trustee
);
3284 wait_trustee_state(gcwq
, TRUSTEE_IN_CHARGE
);
3286 case CPU_UP_PREPARE
:
3287 BUG_ON(gcwq
->first_idle
);
3288 gcwq
->first_idle
= new_worker
;
3293 * Before this, the trustee and all workers except for
3294 * the ones which are still executing works from
3295 * before the last CPU down must be on the cpu. After
3296 * this, they'll all be diasporas.
3298 gcwq
->flags
|= GCWQ_DISASSOCIATED
;
3302 gcwq
->trustee_state
= TRUSTEE_BUTCHER
;
3304 case CPU_UP_CANCELED
:
3305 destroy_worker(gcwq
->first_idle
);
3306 gcwq
->first_idle
= NULL
;
3309 case CPU_DOWN_FAILED
:
3311 gcwq
->flags
&= ~GCWQ_DISASSOCIATED
;
3312 if (gcwq
->trustee_state
!= TRUSTEE_DONE
) {
3313 gcwq
->trustee_state
= TRUSTEE_RELEASE
;
3314 wake_up_process(gcwq
->trustee
);
3315 wait_trustee_state(gcwq
, TRUSTEE_DONE
);
3319 * Trustee is done and there might be no worker left.
3320 * Put the first_idle in and request a real manager to
3323 spin_unlock_irq(&gcwq
->lock
);
3324 kthread_bind(gcwq
->first_idle
->task
, cpu
);
3325 spin_lock_irq(&gcwq
->lock
);
3326 gcwq
->flags
|= GCWQ_MANAGE_WORKERS
;
3327 start_worker(gcwq
->first_idle
);
3328 gcwq
->first_idle
= NULL
;
3332 spin_unlock_irqrestore(&gcwq
->lock
, flags
);
3334 return notifier_from_errno(0);
3339 struct work_for_cpu
{
3340 struct completion completion
;
3346 static int do_work_for_cpu(void *_wfc
)
3348 struct work_for_cpu
*wfc
= _wfc
;
3349 wfc
->ret
= wfc
->fn(wfc
->arg
);
3350 complete(&wfc
->completion
);
3355 * work_on_cpu - run a function in user context on a particular cpu
3356 * @cpu: the cpu to run on
3357 * @fn: the function to run
3358 * @arg: the function arg
3360 * This will return the value @fn returns.
3361 * It is up to the caller to ensure that the cpu doesn't go offline.
3362 * The caller must not hold any locks which would prevent @fn from completing.
3364 long work_on_cpu(unsigned int cpu
, long (*fn
)(void *), void *arg
)
3366 struct task_struct
*sub_thread
;
3367 struct work_for_cpu wfc
= {
3368 .completion
= COMPLETION_INITIALIZER_ONSTACK(wfc
.completion
),
3373 sub_thread
= kthread_create(do_work_for_cpu
, &wfc
, "work_for_cpu");
3374 if (IS_ERR(sub_thread
))
3375 return PTR_ERR(sub_thread
);
3376 kthread_bind(sub_thread
, cpu
);
3377 wake_up_process(sub_thread
);
3378 wait_for_completion(&wfc
.completion
);
3381 EXPORT_SYMBOL_GPL(work_on_cpu
);
3382 #endif /* CONFIG_SMP */
3384 #ifdef CONFIG_FREEZER
3387 * freeze_workqueues_begin - begin freezing workqueues
3389 * Start freezing workqueues. After this function returns, all
3390 * freezeable workqueues will queue new works to their frozen_works
3391 * list instead of gcwq->worklist.
3394 * Grabs and releases workqueue_lock and gcwq->lock's.
3396 void freeze_workqueues_begin(void)
3400 spin_lock(&workqueue_lock
);
3402 BUG_ON(workqueue_freezing
);
3403 workqueue_freezing
= true;
3405 for_each_gcwq_cpu(cpu
) {
3406 struct global_cwq
*gcwq
= get_gcwq(cpu
);
3407 struct workqueue_struct
*wq
;
3409 spin_lock_irq(&gcwq
->lock
);
3411 BUG_ON(gcwq
->flags
& GCWQ_FREEZING
);
3412 gcwq
->flags
|= GCWQ_FREEZING
;
3414 list_for_each_entry(wq
, &workqueues
, list
) {
3415 struct cpu_workqueue_struct
*cwq
= get_cwq(cpu
, wq
);
3417 if (cwq
&& wq
->flags
& WQ_FREEZEABLE
)
3418 cwq
->max_active
= 0;
3421 spin_unlock_irq(&gcwq
->lock
);
3424 spin_unlock(&workqueue_lock
);
3428 * freeze_workqueues_busy - are freezeable workqueues still busy?
3430 * Check whether freezing is complete. This function must be called
3431 * between freeze_workqueues_begin() and thaw_workqueues().
3434 * Grabs and releases workqueue_lock.
3437 * %true if some freezeable workqueues are still busy. %false if
3438 * freezing is complete.
3440 bool freeze_workqueues_busy(void)
3445 spin_lock(&workqueue_lock
);
3447 BUG_ON(!workqueue_freezing
);
3449 for_each_gcwq_cpu(cpu
) {
3450 struct workqueue_struct
*wq
;
3452 * nr_active is monotonically decreasing. It's safe
3453 * to peek without lock.
3455 list_for_each_entry(wq
, &workqueues
, list
) {
3456 struct cpu_workqueue_struct
*cwq
= get_cwq(cpu
, wq
);
3458 if (!cwq
|| !(wq
->flags
& WQ_FREEZEABLE
))
3461 BUG_ON(cwq
->nr_active
< 0);
3462 if (cwq
->nr_active
) {
3469 spin_unlock(&workqueue_lock
);
3474 * thaw_workqueues - thaw workqueues
3476 * Thaw workqueues. Normal queueing is restored and all collected
3477 * frozen works are transferred to their respective gcwq worklists.
3480 * Grabs and releases workqueue_lock and gcwq->lock's.
3482 void thaw_workqueues(void)
3486 spin_lock(&workqueue_lock
);
3488 if (!workqueue_freezing
)
3491 for_each_gcwq_cpu(cpu
) {
3492 struct global_cwq
*gcwq
= get_gcwq(cpu
);
3493 struct workqueue_struct
*wq
;
3495 spin_lock_irq(&gcwq
->lock
);
3497 BUG_ON(!(gcwq
->flags
& GCWQ_FREEZING
));
3498 gcwq
->flags
&= ~GCWQ_FREEZING
;
3500 list_for_each_entry(wq
, &workqueues
, list
) {
3501 struct cpu_workqueue_struct
*cwq
= get_cwq(cpu
, wq
);
3503 if (!cwq
|| !(wq
->flags
& WQ_FREEZEABLE
))
3506 /* restore max_active and repopulate worklist */
3507 cwq
->max_active
= wq
->saved_max_active
;
3509 while (!list_empty(&cwq
->delayed_works
) &&
3510 cwq
->nr_active
< cwq
->max_active
)
3511 cwq_activate_first_delayed(cwq
);
3514 wake_up_worker(gcwq
);
3516 spin_unlock_irq(&gcwq
->lock
);
3519 workqueue_freezing
= false;
3521 spin_unlock(&workqueue_lock
);
3523 #endif /* CONFIG_FREEZER */
3525 static int __init
init_workqueues(void)
3530 hotcpu_notifier(workqueue_cpu_callback
, CPU_PRI_WORKQUEUE
);
3532 /* initialize gcwqs */
3533 for_each_gcwq_cpu(cpu
) {
3534 struct global_cwq
*gcwq
= get_gcwq(cpu
);
3536 spin_lock_init(&gcwq
->lock
);
3537 INIT_LIST_HEAD(&gcwq
->worklist
);
3539 if (cpu
== WORK_CPU_UNBOUND
)
3540 gcwq
->flags
|= GCWQ_DISASSOCIATED
;
3542 INIT_LIST_HEAD(&gcwq
->idle_list
);
3543 for (i
= 0; i
< BUSY_WORKER_HASH_SIZE
; i
++)
3544 INIT_HLIST_HEAD(&gcwq
->busy_hash
[i
]);
3546 init_timer_deferrable(&gcwq
->idle_timer
);
3547 gcwq
->idle_timer
.function
= idle_worker_timeout
;
3548 gcwq
->idle_timer
.data
= (unsigned long)gcwq
;
3550 setup_timer(&gcwq
->mayday_timer
, gcwq_mayday_timeout
,
3551 (unsigned long)gcwq
);
3553 ida_init(&gcwq
->worker_ida
);
3555 gcwq
->trustee_state
= TRUSTEE_DONE
;
3556 init_waitqueue_head(&gcwq
->trustee_wait
);
3559 /* create the initial worker */
3560 for_each_online_gcwq_cpu(cpu
) {
3561 struct global_cwq
*gcwq
= get_gcwq(cpu
);
3562 struct worker
*worker
;
3564 worker
= create_worker(gcwq
, true);
3566 spin_lock_irq(&gcwq
->lock
);
3567 start_worker(worker
);
3568 spin_unlock_irq(&gcwq
->lock
);
3571 system_wq
= alloc_workqueue("events", 0, 0);
3572 system_long_wq
= alloc_workqueue("events_long", 0, 0);
3573 system_nrt_wq
= alloc_workqueue("events_nrt", WQ_NON_REENTRANT
, 0);
3574 system_unbound_wq
= alloc_workqueue("events_unbound", WQ_UNBOUND
,
3575 WQ_UNBOUND_MAX_ACTIVE
);
3576 BUG_ON(!system_wq
|| !system_long_wq
|| !system_nrt_wq
);
3579 early_initcall(init_workqueues
);