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1/*
2 * kernel/workqueue.c - generic async execution with shared worker pool
3 *
4 * Copyright (C) 2002 Ingo Molnar
5 *
6 * Derived from the taskqueue/keventd code by:
7 * David Woodhouse <dwmw2@infradead.org>
8 * Andrew Morton
9 * Kai Petzke <wpp@marie.physik.tu-berlin.de>
10 * Theodore Ts'o <tytso@mit.edu>
11 *
12 * Made to use alloc_percpu by Christoph Lameter.
13 *
14 * Copyright (C) 2010 SUSE Linux Products GmbH
15 * Copyright (C) 2010 Tejun Heo <tj@kernel.org>
16 *
17 * This is the generic async execution mechanism. Work items as are
18 * executed in process context. The worker pool is shared and
19 * automatically managed. There are two worker pools for each CPU (one for
20 * normal work items and the other for high priority ones) and some extra
21 * pools for workqueues which are not bound to any specific CPU - the
22 * number of these backing pools is dynamic.
23 *
24 * Please read Documentation/workqueue.txt for details.
25 */
26
27#include <linux/export.h>
28#include <linux/kernel.h>
29#include <linux/sched.h>
30#include <linux/init.h>
31#include <linux/signal.h>
32#include <linux/completion.h>
33#include <linux/workqueue.h>
34#include <linux/slab.h>
35#include <linux/cpu.h>
36#include <linux/notifier.h>
37#include <linux/kthread.h>
38#include <linux/hardirq.h>
39#include <linux/mempolicy.h>
40#include <linux/freezer.h>
41#include <linux/kallsyms.h>
42#include <linux/debug_locks.h>
43#include <linux/lockdep.h>
44#include <linux/idr.h>
45#include <linux/jhash.h>
46#include <linux/hashtable.h>
47#include <linux/rculist.h>
48#include <linux/nodemask.h>
49#include <linux/moduleparam.h>
50#include <linux/uaccess.h>
51
52#include "workqueue_internal.h"
53
54enum {
55 /*
56 * worker_pool flags
57 *
58 * A bound pool is either associated or disassociated with its CPU.
59 * While associated (!DISASSOCIATED), all workers are bound to the
60 * CPU and none has %WORKER_UNBOUND set and concurrency management
61 * is in effect.
62 *
63 * While DISASSOCIATED, the cpu may be offline and all workers have
64 * %WORKER_UNBOUND set and concurrency management disabled, and may
65 * be executing on any CPU. The pool behaves as an unbound one.
66 *
67 * Note that DISASSOCIATED should be flipped only while holding
68 * attach_mutex to avoid changing binding state while
69 * worker_attach_to_pool() is in progress.
70 */
71 POOL_DISASSOCIATED = 1 << 2, /* cpu can't serve workers */
72
73 /* worker flags */
74 WORKER_DIE = 1 << 1, /* die die die */
75 WORKER_IDLE = 1 << 2, /* is idle */
76 WORKER_PREP = 1 << 3, /* preparing to run works */
77 WORKER_CPU_INTENSIVE = 1 << 6, /* cpu intensive */
78 WORKER_UNBOUND = 1 << 7, /* worker is unbound */
79 WORKER_REBOUND = 1 << 8, /* worker was rebound */
80
81 WORKER_NOT_RUNNING = WORKER_PREP | WORKER_CPU_INTENSIVE |
82 WORKER_UNBOUND | WORKER_REBOUND,
83
84 NR_STD_WORKER_POOLS = 2, /* # standard pools per cpu */
85
86 UNBOUND_POOL_HASH_ORDER = 6, /* hashed by pool->attrs */
87 BUSY_WORKER_HASH_ORDER = 6, /* 64 pointers */
88
89 MAX_IDLE_WORKERS_RATIO = 4, /* 1/4 of busy can be idle */
90 IDLE_WORKER_TIMEOUT = 300 * HZ, /* keep idle ones for 5 mins */
91
92 MAYDAY_INITIAL_TIMEOUT = HZ / 100 >= 2 ? HZ / 100 : 2,
93 /* call for help after 10ms
94 (min two ticks) */
95 MAYDAY_INTERVAL = HZ / 10, /* and then every 100ms */
96 CREATE_COOLDOWN = HZ, /* time to breath after fail */
97
98 /*
99 * Rescue workers are used only on emergencies and shared by
100 * all cpus. Give MIN_NICE.
101 */
102 RESCUER_NICE_LEVEL = MIN_NICE,
103 HIGHPRI_NICE_LEVEL = MIN_NICE,
104
105 WQ_NAME_LEN = 24,
106};
107
108/*
109 * Structure fields follow one of the following exclusion rules.
110 *
111 * I: Modifiable by initialization/destruction paths and read-only for
112 * everyone else.
113 *
114 * P: Preemption protected. Disabling preemption is enough and should
115 * only be modified and accessed from the local cpu.
116 *
117 * L: pool->lock protected. Access with pool->lock held.
118 *
119 * X: During normal operation, modification requires pool->lock and should
120 * be done only from local cpu. Either disabling preemption on local
121 * cpu or grabbing pool->lock is enough for read access. If
122 * POOL_DISASSOCIATED is set, it's identical to L.
123 *
124 * A: pool->attach_mutex protected.
125 *
126 * PL: wq_pool_mutex protected.
127 *
128 * PR: wq_pool_mutex protected for writes. Sched-RCU protected for reads.
129 *
130 * PW: wq_pool_mutex and wq->mutex protected for writes. Either for reads.
131 *
132 * PWR: wq_pool_mutex and wq->mutex protected for writes. Either or
133 * sched-RCU for reads.
134 *
135 * WQ: wq->mutex protected.
136 *
137 * WR: wq->mutex protected for writes. Sched-RCU protected for reads.
138 *
139 * MD: wq_mayday_lock protected.
140 */
141
142/* struct worker is defined in workqueue_internal.h */
143
144struct worker_pool {
145 spinlock_t lock; /* the pool lock */
146 int cpu; /* I: the associated cpu */
147 int node; /* I: the associated node ID */
148 int id; /* I: pool ID */
149 unsigned int flags; /* X: flags */
150
151 unsigned long watchdog_ts; /* L: watchdog timestamp */
152
153 struct list_head worklist; /* L: list of pending works */
154 int nr_workers; /* L: total number of workers */
155
156 /* nr_idle includes the ones off idle_list for rebinding */
157 int nr_idle; /* L: currently idle ones */
158
159 struct list_head idle_list; /* X: list of idle workers */
160 struct timer_list idle_timer; /* L: worker idle timeout */
161 struct timer_list mayday_timer; /* L: SOS timer for workers */
162
163 /* a workers is either on busy_hash or idle_list, or the manager */
164 DECLARE_HASHTABLE(busy_hash, BUSY_WORKER_HASH_ORDER);
165 /* L: hash of busy workers */
166
167 /* see manage_workers() for details on the two manager mutexes */
168 struct mutex manager_arb; /* manager arbitration */
169 struct worker *manager; /* L: purely informational */
170 struct mutex attach_mutex; /* attach/detach exclusion */
171 struct list_head workers; /* A: attached workers */
172 struct completion *detach_completion; /* all workers detached */
173
174 struct ida worker_ida; /* worker IDs for task name */
175
176 struct workqueue_attrs *attrs; /* I: worker attributes */
177 struct hlist_node hash_node; /* PL: unbound_pool_hash node */
178 int refcnt; /* PL: refcnt for unbound pools */
179
180 /*
181 * The current concurrency level. As it's likely to be accessed
182 * from other CPUs during try_to_wake_up(), put it in a separate
183 * cacheline.
184 */
185 atomic_t nr_running ____cacheline_aligned_in_smp;
186
187 /*
188 * Destruction of pool is sched-RCU protected to allow dereferences
189 * from get_work_pool().
190 */
191 struct rcu_head rcu;
192} ____cacheline_aligned_in_smp;
193
194/*
195 * The per-pool workqueue. While queued, the lower WORK_STRUCT_FLAG_BITS
196 * of work_struct->data are used for flags and the remaining high bits
197 * point to the pwq; thus, pwqs need to be aligned at two's power of the
198 * number of flag bits.
199 */
200struct pool_workqueue {
201 struct worker_pool *pool; /* I: the associated pool */
202 struct workqueue_struct *wq; /* I: the owning workqueue */
203 int work_color; /* L: current color */
204 int flush_color; /* L: flushing color */
205 int refcnt; /* L: reference count */
206 int nr_in_flight[WORK_NR_COLORS];
207 /* L: nr of in_flight works */
208 int nr_active; /* L: nr of active works */
209 int max_active; /* L: max active works */
210 struct list_head delayed_works; /* L: delayed works */
211 struct list_head pwqs_node; /* WR: node on wq->pwqs */
212 struct list_head mayday_node; /* MD: node on wq->maydays */
213
214 /*
215 * Release of unbound pwq is punted to system_wq. See put_pwq()
216 * and pwq_unbound_release_workfn() for details. pool_workqueue
217 * itself is also sched-RCU protected so that the first pwq can be
218 * determined without grabbing wq->mutex.
219 */
220 struct work_struct unbound_release_work;
221 struct rcu_head rcu;
222} __aligned(1 << WORK_STRUCT_FLAG_BITS);
223
224/*
225 * Structure used to wait for workqueue flush.
226 */
227struct wq_flusher {
228 struct list_head list; /* WQ: list of flushers */
229 int flush_color; /* WQ: flush color waiting for */
230 struct completion done; /* flush completion */
231};
232
233struct wq_device;
234
235/*
236 * The externally visible workqueue. It relays the issued work items to
237 * the appropriate worker_pool through its pool_workqueues.
238 */
239struct workqueue_struct {
240 struct list_head pwqs; /* WR: all pwqs of this wq */
241 struct list_head list; /* PR: list of all workqueues */
242
243 struct mutex mutex; /* protects this wq */
244 int work_color; /* WQ: current work color */
245 int flush_color; /* WQ: current flush color */
246 atomic_t nr_pwqs_to_flush; /* flush in progress */
247 struct wq_flusher *first_flusher; /* WQ: first flusher */
248 struct list_head flusher_queue; /* WQ: flush waiters */
249 struct list_head flusher_overflow; /* WQ: flush overflow list */
250
251 struct list_head maydays; /* MD: pwqs requesting rescue */
252 struct worker *rescuer; /* I: rescue worker */
253
254 int nr_drainers; /* WQ: drain in progress */
255 int saved_max_active; /* WQ: saved pwq max_active */
256
257 struct workqueue_attrs *unbound_attrs; /* PW: only for unbound wqs */
258 struct pool_workqueue *dfl_pwq; /* PW: only for unbound wqs */
259
260#ifdef CONFIG_SYSFS
261 struct wq_device *wq_dev; /* I: for sysfs interface */
262#endif
263#ifdef CONFIG_LOCKDEP
264 struct lockdep_map lockdep_map;
265#endif
266 char name[WQ_NAME_LEN]; /* I: workqueue name */
267
268 /*
269 * Destruction of workqueue_struct is sched-RCU protected to allow
270 * walking the workqueues list without grabbing wq_pool_mutex.
271 * This is used to dump all workqueues from sysrq.
272 */
273 struct rcu_head rcu;
274
275 /* hot fields used during command issue, aligned to cacheline */
276 unsigned int flags ____cacheline_aligned; /* WQ: WQ_* flags */
277 struct pool_workqueue __percpu *cpu_pwqs; /* I: per-cpu pwqs */
278 struct pool_workqueue __rcu *numa_pwq_tbl[]; /* PWR: unbound pwqs indexed by node */
279};
280
281static struct kmem_cache *pwq_cache;
282
283static cpumask_var_t *wq_numa_possible_cpumask;
284 /* possible CPUs of each node */
285
286static bool wq_disable_numa;
287module_param_named(disable_numa, wq_disable_numa, bool, 0444);
288
289/* see the comment above the definition of WQ_POWER_EFFICIENT */
290static bool wq_power_efficient = IS_ENABLED(CONFIG_WQ_POWER_EFFICIENT_DEFAULT);
291module_param_named(power_efficient, wq_power_efficient, bool, 0444);
292
293static bool wq_numa_enabled; /* unbound NUMA affinity enabled */
294
295/* buf for wq_update_unbound_numa_attrs(), protected by CPU hotplug exclusion */
296static struct workqueue_attrs *wq_update_unbound_numa_attrs_buf;
297
298static DEFINE_MUTEX(wq_pool_mutex); /* protects pools and workqueues list */
299static DEFINE_SPINLOCK(wq_mayday_lock); /* protects wq->maydays list */
300
301static LIST_HEAD(workqueues); /* PR: list of all workqueues */
302static bool workqueue_freezing; /* PL: have wqs started freezing? */
303
304/* PL: allowable cpus for unbound wqs and work items */
305static cpumask_var_t wq_unbound_cpumask;
306
307/* CPU where unbound work was last round robin scheduled from this CPU */
308static DEFINE_PER_CPU(int, wq_rr_cpu_last);
309
310/*
311 * Local execution of unbound work items is no longer guaranteed. The
312 * following always forces round-robin CPU selection on unbound work items
313 * to uncover usages which depend on it.
314 */
315#ifdef CONFIG_DEBUG_WQ_FORCE_RR_CPU
316static bool wq_debug_force_rr_cpu = true;
317#else
318static bool wq_debug_force_rr_cpu = false;
319#endif
320module_param_named(debug_force_rr_cpu, wq_debug_force_rr_cpu, bool, 0644);
321
322/* the per-cpu worker pools */
323static DEFINE_PER_CPU_SHARED_ALIGNED(struct worker_pool [NR_STD_WORKER_POOLS], cpu_worker_pools);
324
325static DEFINE_IDR(worker_pool_idr); /* PR: idr of all pools */
326
327/* PL: hash of all unbound pools keyed by pool->attrs */
328static DEFINE_HASHTABLE(unbound_pool_hash, UNBOUND_POOL_HASH_ORDER);
329
330/* I: attributes used when instantiating standard unbound pools on demand */
331static struct workqueue_attrs *unbound_std_wq_attrs[NR_STD_WORKER_POOLS];
332
333/* I: attributes used when instantiating ordered pools on demand */
334static struct workqueue_attrs *ordered_wq_attrs[NR_STD_WORKER_POOLS];
335
336struct workqueue_struct *system_wq __read_mostly;
337EXPORT_SYMBOL(system_wq);
338struct workqueue_struct *system_highpri_wq __read_mostly;
339EXPORT_SYMBOL_GPL(system_highpri_wq);
340struct workqueue_struct *system_long_wq __read_mostly;
341EXPORT_SYMBOL_GPL(system_long_wq);
342struct workqueue_struct *system_unbound_wq __read_mostly;
343EXPORT_SYMBOL_GPL(system_unbound_wq);
344struct workqueue_struct *system_freezable_wq __read_mostly;
345EXPORT_SYMBOL_GPL(system_freezable_wq);
346struct workqueue_struct *system_power_efficient_wq __read_mostly;
347EXPORT_SYMBOL_GPL(system_power_efficient_wq);
348struct workqueue_struct *system_freezable_power_efficient_wq __read_mostly;
349EXPORT_SYMBOL_GPL(system_freezable_power_efficient_wq);
350
351static int worker_thread(void *__worker);
352static void workqueue_sysfs_unregister(struct workqueue_struct *wq);
353
354#define CREATE_TRACE_POINTS
355#include <trace/events/workqueue.h>
356
357#define assert_rcu_or_pool_mutex() \
358 RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held() && \
359 !lockdep_is_held(&wq_pool_mutex), \
360 "sched RCU or wq_pool_mutex should be held")
361
362#define assert_rcu_or_wq_mutex(wq) \
363 RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held() && \
364 !lockdep_is_held(&wq->mutex), \
365 "sched RCU or wq->mutex should be held")
366
367#define assert_rcu_or_wq_mutex_or_pool_mutex(wq) \
368 RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held() && \
369 !lockdep_is_held(&wq->mutex) && \
370 !lockdep_is_held(&wq_pool_mutex), \
371 "sched RCU, wq->mutex or wq_pool_mutex should be held")
372
373#define for_each_cpu_worker_pool(pool, cpu) \
374 for ((pool) = &per_cpu(cpu_worker_pools, cpu)[0]; \
375 (pool) < &per_cpu(cpu_worker_pools, cpu)[NR_STD_WORKER_POOLS]; \
376 (pool)++)
377
378/**
379 * for_each_pool - iterate through all worker_pools in the system
380 * @pool: iteration cursor
381 * @pi: integer used for iteration
382 *
383 * This must be called either with wq_pool_mutex held or sched RCU read
384 * locked. If the pool needs to be used beyond the locking in effect, the
385 * caller is responsible for guaranteeing that the pool stays online.
386 *
387 * The if/else clause exists only for the lockdep assertion and can be
388 * ignored.
389 */
390#define for_each_pool(pool, pi) \
391 idr_for_each_entry(&worker_pool_idr, pool, pi) \
392 if (({ assert_rcu_or_pool_mutex(); false; })) { } \
393 else
394
395/**
396 * for_each_pool_worker - iterate through all workers of a worker_pool
397 * @worker: iteration cursor
398 * @pool: worker_pool to iterate workers of
399 *
400 * This must be called with @pool->attach_mutex.
401 *
402 * The if/else clause exists only for the lockdep assertion and can be
403 * ignored.
404 */
405#define for_each_pool_worker(worker, pool) \
406 list_for_each_entry((worker), &(pool)->workers, node) \
407 if (({ lockdep_assert_held(&pool->attach_mutex); false; })) { } \
408 else
409
410/**
411 * for_each_pwq - iterate through all pool_workqueues of the specified workqueue
412 * @pwq: iteration cursor
413 * @wq: the target workqueue
414 *
415 * This must be called either with wq->mutex held or sched RCU read locked.
416 * If the pwq needs to be used beyond the locking in effect, the caller is
417 * responsible for guaranteeing that the pwq stays online.
418 *
419 * The if/else clause exists only for the lockdep assertion and can be
420 * ignored.
421 */
422#define for_each_pwq(pwq, wq) \
423 list_for_each_entry_rcu((pwq), &(wq)->pwqs, pwqs_node) \
424 if (({ assert_rcu_or_wq_mutex(wq); false; })) { } \
425 else
426
427#ifdef CONFIG_DEBUG_OBJECTS_WORK
428
429static struct debug_obj_descr work_debug_descr;
430
431static void *work_debug_hint(void *addr)
432{
433 return ((struct work_struct *) addr)->func;
434}
435
436/*
437 * fixup_init is called when:
438 * - an active object is initialized
439 */
440static int work_fixup_init(void *addr, enum debug_obj_state state)
441{
442 struct work_struct *work = addr;
443
444 switch (state) {
445 case ODEBUG_STATE_ACTIVE:
446 cancel_work_sync(work);
447 debug_object_init(work, &work_debug_descr);
448 return 1;
449 default:
450 return 0;
451 }
452}
453
454/*
455 * fixup_activate is called when:
456 * - an active object is activated
457 * - an unknown object is activated (might be a statically initialized object)
458 */
459static int work_fixup_activate(void *addr, enum debug_obj_state state)
460{
461 struct work_struct *work = addr;
462
463 switch (state) {
464
465 case ODEBUG_STATE_NOTAVAILABLE:
466 /*
467 * This is not really a fixup. The work struct was
468 * statically initialized. We just make sure that it
469 * is tracked in the object tracker.
470 */
471 if (test_bit(WORK_STRUCT_STATIC_BIT, work_data_bits(work))) {
472 debug_object_init(work, &work_debug_descr);
473 debug_object_activate(work, &work_debug_descr);
474 return 0;
475 }
476 WARN_ON_ONCE(1);
477 return 0;
478
479 case ODEBUG_STATE_ACTIVE:
480 WARN_ON(1);
481
482 default:
483 return 0;
484 }
485}
486
487/*
488 * fixup_free is called when:
489 * - an active object is freed
490 */
491static int work_fixup_free(void *addr, enum debug_obj_state state)
492{
493 struct work_struct *work = addr;
494
495 switch (state) {
496 case ODEBUG_STATE_ACTIVE:
497 cancel_work_sync(work);
498 debug_object_free(work, &work_debug_descr);
499 return 1;
500 default:
501 return 0;
502 }
503}
504
505static struct debug_obj_descr work_debug_descr = {
506 .name = "work_struct",
507 .debug_hint = work_debug_hint,
508 .fixup_init = work_fixup_init,
509 .fixup_activate = work_fixup_activate,
510 .fixup_free = work_fixup_free,
511};
512
513static inline void debug_work_activate(struct work_struct *work)
514{
515 debug_object_activate(work, &work_debug_descr);
516}
517
518static inline void debug_work_deactivate(struct work_struct *work)
519{
520 debug_object_deactivate(work, &work_debug_descr);
521}
522
523void __init_work(struct work_struct *work, int onstack)
524{
525 if (onstack)
526 debug_object_init_on_stack(work, &work_debug_descr);
527 else
528 debug_object_init(work, &work_debug_descr);
529}
530EXPORT_SYMBOL_GPL(__init_work);
531
532void destroy_work_on_stack(struct work_struct *work)
533{
534 debug_object_free(work, &work_debug_descr);
535}
536EXPORT_SYMBOL_GPL(destroy_work_on_stack);
537
538void destroy_delayed_work_on_stack(struct delayed_work *work)
539{
540 destroy_timer_on_stack(&work->timer);
541 debug_object_free(&work->work, &work_debug_descr);
542}
543EXPORT_SYMBOL_GPL(destroy_delayed_work_on_stack);
544
545#else
546static inline void debug_work_activate(struct work_struct *work) { }
547static inline void debug_work_deactivate(struct work_struct *work) { }
548#endif
549
550/**
551 * worker_pool_assign_id - allocate ID and assing it to @pool
552 * @pool: the pool pointer of interest
553 *
554 * Returns 0 if ID in [0, WORK_OFFQ_POOL_NONE) is allocated and assigned
555 * successfully, -errno on failure.
556 */
557static int worker_pool_assign_id(struct worker_pool *pool)
558{
559 int ret;
560
561 lockdep_assert_held(&wq_pool_mutex);
562
563 ret = idr_alloc(&worker_pool_idr, pool, 0, WORK_OFFQ_POOL_NONE,
564 GFP_KERNEL);
565 if (ret >= 0) {
566 pool->id = ret;
567 return 0;
568 }
569 return ret;
570}
571
572/**
573 * unbound_pwq_by_node - return the unbound pool_workqueue for the given node
574 * @wq: the target workqueue
575 * @node: the node ID
576 *
577 * This must be called with any of wq_pool_mutex, wq->mutex or sched RCU
578 * read locked.
579 * If the pwq needs to be used beyond the locking in effect, the caller is
580 * responsible for guaranteeing that the pwq stays online.
581 *
582 * Return: The unbound pool_workqueue for @node.
583 */
584static struct pool_workqueue *unbound_pwq_by_node(struct workqueue_struct *wq,
585 int node)
586{
587 assert_rcu_or_wq_mutex_or_pool_mutex(wq);
588
589 /*
590 * XXX: @node can be NUMA_NO_NODE if CPU goes offline while a
591 * delayed item is pending. The plan is to keep CPU -> NODE
592 * mapping valid and stable across CPU on/offlines. Once that
593 * happens, this workaround can be removed.
594 */
595 if (unlikely(node == NUMA_NO_NODE))
596 return wq->dfl_pwq;
597
598 return rcu_dereference_raw(wq->numa_pwq_tbl[node]);
599}
600
601static unsigned int work_color_to_flags(int color)
602{
603 return color << WORK_STRUCT_COLOR_SHIFT;
604}
605
606static int get_work_color(struct work_struct *work)
607{
608 return (*work_data_bits(work) >> WORK_STRUCT_COLOR_SHIFT) &
609 ((1 << WORK_STRUCT_COLOR_BITS) - 1);
610}
611
612static int work_next_color(int color)
613{
614 return (color + 1) % WORK_NR_COLORS;
615}
616
617/*
618 * While queued, %WORK_STRUCT_PWQ is set and non flag bits of a work's data
619 * contain the pointer to the queued pwq. Once execution starts, the flag
620 * is cleared and the high bits contain OFFQ flags and pool ID.
621 *
622 * set_work_pwq(), set_work_pool_and_clear_pending(), mark_work_canceling()
623 * and clear_work_data() can be used to set the pwq, pool or clear
624 * work->data. These functions should only be called while the work is
625 * owned - ie. while the PENDING bit is set.
626 *
627 * get_work_pool() and get_work_pwq() can be used to obtain the pool or pwq
628 * corresponding to a work. Pool is available once the work has been
629 * queued anywhere after initialization until it is sync canceled. pwq is
630 * available only while the work item is queued.
631 *
632 * %WORK_OFFQ_CANCELING is used to mark a work item which is being
633 * canceled. While being canceled, a work item may have its PENDING set
634 * but stay off timer and worklist for arbitrarily long and nobody should
635 * try to steal the PENDING bit.
636 */
637static inline void set_work_data(struct work_struct *work, unsigned long data,
638 unsigned long flags)
639{
640 WARN_ON_ONCE(!work_pending(work));
641 atomic_long_set(&work->data, data | flags | work_static(work));
642}
643
644static void set_work_pwq(struct work_struct *work, struct pool_workqueue *pwq,
645 unsigned long extra_flags)
646{
647 set_work_data(work, (unsigned long)pwq,
648 WORK_STRUCT_PENDING | WORK_STRUCT_PWQ | extra_flags);
649}
650
651static void set_work_pool_and_keep_pending(struct work_struct *work,
652 int pool_id)
653{
654 set_work_data(work, (unsigned long)pool_id << WORK_OFFQ_POOL_SHIFT,
655 WORK_STRUCT_PENDING);
656}
657
658static void set_work_pool_and_clear_pending(struct work_struct *work,
659 int pool_id)
660{
661 /*
662 * The following wmb is paired with the implied mb in
663 * test_and_set_bit(PENDING) and ensures all updates to @work made
664 * here are visible to and precede any updates by the next PENDING
665 * owner.
666 */
667 smp_wmb();
668 set_work_data(work, (unsigned long)pool_id << WORK_OFFQ_POOL_SHIFT, 0);
669 /*
670 * The following mb guarantees that previous clear of a PENDING bit
671 * will not be reordered with any speculative LOADS or STORES from
672 * work->current_func, which is executed afterwards. This possible
673 * reordering can lead to a missed execution on attempt to qeueue
674 * the same @work. E.g. consider this case:
675 *
676 * CPU#0 CPU#1
677 * ---------------------------- --------------------------------
678 *
679 * 1 STORE event_indicated
680 * 2 queue_work_on() {
681 * 3 test_and_set_bit(PENDING)
682 * 4 } set_..._and_clear_pending() {
683 * 5 set_work_data() # clear bit
684 * 6 smp_mb()
685 * 7 work->current_func() {
686 * 8 LOAD event_indicated
687 * }
688 *
689 * Without an explicit full barrier speculative LOAD on line 8 can
690 * be executed before CPU#0 does STORE on line 1. If that happens,
691 * CPU#0 observes the PENDING bit is still set and new execution of
692 * a @work is not queued in a hope, that CPU#1 will eventually
693 * finish the queued @work. Meanwhile CPU#1 does not see
694 * event_indicated is set, because speculative LOAD was executed
695 * before actual STORE.
696 */
697 smp_mb();
698}
699
700static void clear_work_data(struct work_struct *work)
701{
702 smp_wmb(); /* see set_work_pool_and_clear_pending() */
703 set_work_data(work, WORK_STRUCT_NO_POOL, 0);
704}
705
706static struct pool_workqueue *get_work_pwq(struct work_struct *work)
707{
708 unsigned long data = atomic_long_read(&work->data);
709
710 if (data & WORK_STRUCT_PWQ)
711 return (void *)(data & WORK_STRUCT_WQ_DATA_MASK);
712 else
713 return NULL;
714}
715
716/**
717 * get_work_pool - return the worker_pool a given work was associated with
718 * @work: the work item of interest
719 *
720 * Pools are created and destroyed under wq_pool_mutex, and allows read
721 * access under sched-RCU read lock. As such, this function should be
722 * called under wq_pool_mutex or with preemption disabled.
723 *
724 * All fields of the returned pool are accessible as long as the above
725 * mentioned locking is in effect. If the returned pool needs to be used
726 * beyond the critical section, the caller is responsible for ensuring the
727 * returned pool is and stays online.
728 *
729 * Return: The worker_pool @work was last associated with. %NULL if none.
730 */
731static struct worker_pool *get_work_pool(struct work_struct *work)
732{
733 unsigned long data = atomic_long_read(&work->data);
734 int pool_id;
735
736 assert_rcu_or_pool_mutex();
737
738 if (data & WORK_STRUCT_PWQ)
739 return ((struct pool_workqueue *)
740 (data & WORK_STRUCT_WQ_DATA_MASK))->pool;
741
742 pool_id = data >> WORK_OFFQ_POOL_SHIFT;
743 if (pool_id == WORK_OFFQ_POOL_NONE)
744 return NULL;
745
746 return idr_find(&worker_pool_idr, pool_id);
747}
748
749/**
750 * get_work_pool_id - return the worker pool ID a given work is associated with
751 * @work: the work item of interest
752 *
753 * Return: The worker_pool ID @work was last associated with.
754 * %WORK_OFFQ_POOL_NONE if none.
755 */
756static int get_work_pool_id(struct work_struct *work)
757{
758 unsigned long data = atomic_long_read(&work->data);
759
760 if (data & WORK_STRUCT_PWQ)
761 return ((struct pool_workqueue *)
762 (data & WORK_STRUCT_WQ_DATA_MASK))->pool->id;
763
764 return data >> WORK_OFFQ_POOL_SHIFT;
765}
766
767static void mark_work_canceling(struct work_struct *work)
768{
769 unsigned long pool_id = get_work_pool_id(work);
770
771 pool_id <<= WORK_OFFQ_POOL_SHIFT;
772 set_work_data(work, pool_id | WORK_OFFQ_CANCELING, WORK_STRUCT_PENDING);
773}
774
775static bool work_is_canceling(struct work_struct *work)
776{
777 unsigned long data = atomic_long_read(&work->data);
778
779 return !(data & WORK_STRUCT_PWQ) && (data & WORK_OFFQ_CANCELING);
780}
781
782/*
783 * Policy functions. These define the policies on how the global worker
784 * pools are managed. Unless noted otherwise, these functions assume that
785 * they're being called with pool->lock held.
786 */
787
788static bool __need_more_worker(struct worker_pool *pool)
789{
790 return !atomic_read(&pool->nr_running);
791}
792
793/*
794 * Need to wake up a worker? Called from anything but currently
795 * running workers.
796 *
797 * Note that, because unbound workers never contribute to nr_running, this
798 * function will always return %true for unbound pools as long as the
799 * worklist isn't empty.
800 */
801static bool need_more_worker(struct worker_pool *pool)
802{
803 return !list_empty(&pool->worklist) && __need_more_worker(pool);
804}
805
806/* Can I start working? Called from busy but !running workers. */
807static bool may_start_working(struct worker_pool *pool)
808{
809 return pool->nr_idle;
810}
811
812/* Do I need to keep working? Called from currently running workers. */
813static bool keep_working(struct worker_pool *pool)
814{
815 return !list_empty(&pool->worklist) &&
816 atomic_read(&pool->nr_running) <= 1;
817}
818
819/* Do we need a new worker? Called from manager. */
820static bool need_to_create_worker(struct worker_pool *pool)
821{
822 return need_more_worker(pool) && !may_start_working(pool);
823}
824
825/* Do we have too many workers and should some go away? */
826static bool too_many_workers(struct worker_pool *pool)
827{
828 bool managing = mutex_is_locked(&pool->manager_arb);
829 int nr_idle = pool->nr_idle + managing; /* manager is considered idle */
830 int nr_busy = pool->nr_workers - nr_idle;
831
832 return nr_idle > 2 && (nr_idle - 2) * MAX_IDLE_WORKERS_RATIO >= nr_busy;
833}
834
835/*
836 * Wake up functions.
837 */
838
839/* Return the first idle worker. Safe with preemption disabled */
840static struct worker *first_idle_worker(struct worker_pool *pool)
841{
842 if (unlikely(list_empty(&pool->idle_list)))
843 return NULL;
844
845 return list_first_entry(&pool->idle_list, struct worker, entry);
846}
847
848/**
849 * wake_up_worker - wake up an idle worker
850 * @pool: worker pool to wake worker from
851 *
852 * Wake up the first idle worker of @pool.
853 *
854 * CONTEXT:
855 * spin_lock_irq(pool->lock).
856 */
857static void wake_up_worker(struct worker_pool *pool)
858{
859 struct worker *worker = first_idle_worker(pool);
860
861 if (likely(worker))
862 wake_up_process(worker->task);
863}
864
865/**
866 * wq_worker_waking_up - a worker is waking up
867 * @task: task waking up
868 * @cpu: CPU @task is waking up to
869 *
870 * This function is called during try_to_wake_up() when a worker is
871 * being awoken.
872 *
873 * CONTEXT:
874 * spin_lock_irq(rq->lock)
875 */
876void wq_worker_waking_up(struct task_struct *task, int cpu)
877{
878 struct worker *worker = kthread_data(task);
879
880 if (!(worker->flags & WORKER_NOT_RUNNING)) {
881 WARN_ON_ONCE(worker->pool->cpu != cpu);
882 atomic_inc(&worker->pool->nr_running);
883 }
884}
885
886/**
887 * wq_worker_sleeping - a worker is going to sleep
888 * @task: task going to sleep
889 *
890 * This function is called during schedule() when a busy worker is
891 * going to sleep. Worker on the same cpu can be woken up by
892 * returning pointer to its task.
893 *
894 * CONTEXT:
895 * spin_lock_irq(rq->lock)
896 *
897 * Return:
898 * Worker task on @cpu to wake up, %NULL if none.
899 */
900struct task_struct *wq_worker_sleeping(struct task_struct *task)
901{
902 struct worker *worker = kthread_data(task), *to_wakeup = NULL;
903 struct worker_pool *pool;
904
905 /*
906 * Rescuers, which may not have all the fields set up like normal
907 * workers, also reach here, let's not access anything before
908 * checking NOT_RUNNING.
909 */
910 if (worker->flags & WORKER_NOT_RUNNING)
911 return NULL;
912
913 pool = worker->pool;
914
915 /* this can only happen on the local cpu */
916 if (WARN_ON_ONCE(pool->cpu != raw_smp_processor_id()))
917 return NULL;
918
919 /*
920 * The counterpart of the following dec_and_test, implied mb,
921 * worklist not empty test sequence is in insert_work().
922 * Please read comment there.
923 *
924 * NOT_RUNNING is clear. This means that we're bound to and
925 * running on the local cpu w/ rq lock held and preemption
926 * disabled, which in turn means that none else could be
927 * manipulating idle_list, so dereferencing idle_list without pool
928 * lock is safe.
929 */
930 if (atomic_dec_and_test(&pool->nr_running) &&
931 !list_empty(&pool->worklist))
932 to_wakeup = first_idle_worker(pool);
933 return to_wakeup ? to_wakeup->task : NULL;
934}
935
936/**
937 * worker_set_flags - set worker flags and adjust nr_running accordingly
938 * @worker: self
939 * @flags: flags to set
940 *
941 * Set @flags in @worker->flags and adjust nr_running accordingly.
942 *
943 * CONTEXT:
944 * spin_lock_irq(pool->lock)
945 */
946static inline void worker_set_flags(struct worker *worker, unsigned int flags)
947{
948 struct worker_pool *pool = worker->pool;
949
950 WARN_ON_ONCE(worker->task != current);
951
952 /* If transitioning into NOT_RUNNING, adjust nr_running. */
953 if ((flags & WORKER_NOT_RUNNING) &&
954 !(worker->flags & WORKER_NOT_RUNNING)) {
955 atomic_dec(&pool->nr_running);
956 }
957
958 worker->flags |= flags;
959}
960
961/**
962 * worker_clr_flags - clear worker flags and adjust nr_running accordingly
963 * @worker: self
964 * @flags: flags to clear
965 *
966 * Clear @flags in @worker->flags and adjust nr_running accordingly.
967 *
968 * CONTEXT:
969 * spin_lock_irq(pool->lock)
970 */
971static inline void worker_clr_flags(struct worker *worker, unsigned int flags)
972{
973 struct worker_pool *pool = worker->pool;
974 unsigned int oflags = worker->flags;
975
976 WARN_ON_ONCE(worker->task != current);
977
978 worker->flags &= ~flags;
979
980 /*
981 * If transitioning out of NOT_RUNNING, increment nr_running. Note
982 * that the nested NOT_RUNNING is not a noop. NOT_RUNNING is mask
983 * of multiple flags, not a single flag.
984 */
985 if ((flags & WORKER_NOT_RUNNING) && (oflags & WORKER_NOT_RUNNING))
986 if (!(worker->flags & WORKER_NOT_RUNNING))
987 atomic_inc(&pool->nr_running);
988}
989
990/**
991 * find_worker_executing_work - find worker which is executing a work
992 * @pool: pool of interest
993 * @work: work to find worker for
994 *
995 * Find a worker which is executing @work on @pool by searching
996 * @pool->busy_hash which is keyed by the address of @work. For a worker
997 * to match, its current execution should match the address of @work and
998 * its work function. This is to avoid unwanted dependency between
999 * unrelated work executions through a work item being recycled while still
1000 * being executed.
1001 *
1002 * This is a bit tricky. A work item may be freed once its execution
1003 * starts and nothing prevents the freed area from being recycled for
1004 * another work item. If the same work item address ends up being reused
1005 * before the original execution finishes, workqueue will identify the
1006 * recycled work item as currently executing and make it wait until the
1007 * current execution finishes, introducing an unwanted dependency.
1008 *
1009 * This function checks the work item address and work function to avoid
1010 * false positives. Note that this isn't complete as one may construct a
1011 * work function which can introduce dependency onto itself through a
1012 * recycled work item. Well, if somebody wants to shoot oneself in the
1013 * foot that badly, there's only so much we can do, and if such deadlock
1014 * actually occurs, it should be easy to locate the culprit work function.
1015 *
1016 * CONTEXT:
1017 * spin_lock_irq(pool->lock).
1018 *
1019 * Return:
1020 * Pointer to worker which is executing @work if found, %NULL
1021 * otherwise.
1022 */
1023static struct worker *find_worker_executing_work(struct worker_pool *pool,
1024 struct work_struct *work)
1025{
1026 struct worker *worker;
1027
1028 hash_for_each_possible(pool->busy_hash, worker, hentry,
1029 (unsigned long)work)
1030 if (worker->current_work == work &&
1031 worker->current_func == work->func)
1032 return worker;
1033
1034 return NULL;
1035}
1036
1037/**
1038 * move_linked_works - move linked works to a list
1039 * @work: start of series of works to be scheduled
1040 * @head: target list to append @work to
1041 * @nextp: out parameter for nested worklist walking
1042 *
1043 * Schedule linked works starting from @work to @head. Work series to
1044 * be scheduled starts at @work and includes any consecutive work with
1045 * WORK_STRUCT_LINKED set in its predecessor.
1046 *
1047 * If @nextp is not NULL, it's updated to point to the next work of
1048 * the last scheduled work. This allows move_linked_works() to be
1049 * nested inside outer list_for_each_entry_safe().
1050 *
1051 * CONTEXT:
1052 * spin_lock_irq(pool->lock).
1053 */
1054static void move_linked_works(struct work_struct *work, struct list_head *head,
1055 struct work_struct **nextp)
1056{
1057 struct work_struct *n;
1058
1059 /*
1060 * Linked worklist will always end before the end of the list,
1061 * use NULL for list head.
1062 */
1063 list_for_each_entry_safe_from(work, n, NULL, entry) {
1064 list_move_tail(&work->entry, head);
1065 if (!(*work_data_bits(work) & WORK_STRUCT_LINKED))
1066 break;
1067 }
1068
1069 /*
1070 * If we're already inside safe list traversal and have moved
1071 * multiple works to the scheduled queue, the next position
1072 * needs to be updated.
1073 */
1074 if (nextp)
1075 *nextp = n;
1076}
1077
1078/**
1079 * get_pwq - get an extra reference on the specified pool_workqueue
1080 * @pwq: pool_workqueue to get
1081 *
1082 * Obtain an extra reference on @pwq. The caller should guarantee that
1083 * @pwq has positive refcnt and be holding the matching pool->lock.
1084 */
1085static void get_pwq(struct pool_workqueue *pwq)
1086{
1087 lockdep_assert_held(&pwq->pool->lock);
1088 WARN_ON_ONCE(pwq->refcnt <= 0);
1089 pwq->refcnt++;
1090}
1091
1092/**
1093 * put_pwq - put a pool_workqueue reference
1094 * @pwq: pool_workqueue to put
1095 *
1096 * Drop a reference of @pwq. If its refcnt reaches zero, schedule its
1097 * destruction. The caller should be holding the matching pool->lock.
1098 */
1099static void put_pwq(struct pool_workqueue *pwq)
1100{
1101 lockdep_assert_held(&pwq->pool->lock);
1102 if (likely(--pwq->refcnt))
1103 return;
1104 if (WARN_ON_ONCE(!(pwq->wq->flags & WQ_UNBOUND)))
1105 return;
1106 /*
1107 * @pwq can't be released under pool->lock, bounce to
1108 * pwq_unbound_release_workfn(). This never recurses on the same
1109 * pool->lock as this path is taken only for unbound workqueues and
1110 * the release work item is scheduled on a per-cpu workqueue. To
1111 * avoid lockdep warning, unbound pool->locks are given lockdep
1112 * subclass of 1 in get_unbound_pool().
1113 */
1114 schedule_work(&pwq->unbound_release_work);
1115}
1116
1117/**
1118 * put_pwq_unlocked - put_pwq() with surrounding pool lock/unlock
1119 * @pwq: pool_workqueue to put (can be %NULL)
1120 *
1121 * put_pwq() with locking. This function also allows %NULL @pwq.
1122 */
1123static void put_pwq_unlocked(struct pool_workqueue *pwq)
1124{
1125 if (pwq) {
1126 /*
1127 * As both pwqs and pools are sched-RCU protected, the
1128 * following lock operations are safe.
1129 */
1130 spin_lock_irq(&pwq->pool->lock);
1131 put_pwq(pwq);
1132 spin_unlock_irq(&pwq->pool->lock);
1133 }
1134}
1135
1136static void pwq_activate_delayed_work(struct work_struct *work)
1137{
1138 struct pool_workqueue *pwq = get_work_pwq(work);
1139
1140 trace_workqueue_activate_work(work);
1141 if (list_empty(&pwq->pool->worklist))
1142 pwq->pool->watchdog_ts = jiffies;
1143 move_linked_works(work, &pwq->pool->worklist, NULL);
1144 __clear_bit(WORK_STRUCT_DELAYED_BIT, work_data_bits(work));
1145 pwq->nr_active++;
1146}
1147
1148static void pwq_activate_first_delayed(struct pool_workqueue *pwq)
1149{
1150 struct work_struct *work = list_first_entry(&pwq->delayed_works,
1151 struct work_struct, entry);
1152
1153 pwq_activate_delayed_work(work);
1154}
1155
1156/**
1157 * pwq_dec_nr_in_flight - decrement pwq's nr_in_flight
1158 * @pwq: pwq of interest
1159 * @color: color of work which left the queue
1160 *
1161 * A work either has completed or is removed from pending queue,
1162 * decrement nr_in_flight of its pwq and handle workqueue flushing.
1163 *
1164 * CONTEXT:
1165 * spin_lock_irq(pool->lock).
1166 */
1167static void pwq_dec_nr_in_flight(struct pool_workqueue *pwq, int color)
1168{
1169 /* uncolored work items don't participate in flushing or nr_active */
1170 if (color == WORK_NO_COLOR)
1171 goto out_put;
1172
1173 pwq->nr_in_flight[color]--;
1174
1175 pwq->nr_active--;
1176 if (!list_empty(&pwq->delayed_works)) {
1177 /* one down, submit a delayed one */
1178 if (pwq->nr_active < pwq->max_active)
1179 pwq_activate_first_delayed(pwq);
1180 }
1181
1182 /* is flush in progress and are we at the flushing tip? */
1183 if (likely(pwq->flush_color != color))
1184 goto out_put;
1185
1186 /* are there still in-flight works? */
1187 if (pwq->nr_in_flight[color])
1188 goto out_put;
1189
1190 /* this pwq is done, clear flush_color */
1191 pwq->flush_color = -1;
1192
1193 /*
1194 * If this was the last pwq, wake up the first flusher. It
1195 * will handle the rest.
1196 */
1197 if (atomic_dec_and_test(&pwq->wq->nr_pwqs_to_flush))
1198 complete(&pwq->wq->first_flusher->done);
1199out_put:
1200 put_pwq(pwq);
1201}
1202
1203/**
1204 * try_to_grab_pending - steal work item from worklist and disable irq
1205 * @work: work item to steal
1206 * @is_dwork: @work is a delayed_work
1207 * @flags: place to store irq state
1208 *
1209 * Try to grab PENDING bit of @work. This function can handle @work in any
1210 * stable state - idle, on timer or on worklist.
1211 *
1212 * Return:
1213 * 1 if @work was pending and we successfully stole PENDING
1214 * 0 if @work was idle and we claimed PENDING
1215 * -EAGAIN if PENDING couldn't be grabbed at the moment, safe to busy-retry
1216 * -ENOENT if someone else is canceling @work, this state may persist
1217 * for arbitrarily long
1218 *
1219 * Note:
1220 * On >= 0 return, the caller owns @work's PENDING bit. To avoid getting
1221 * interrupted while holding PENDING and @work off queue, irq must be
1222 * disabled on entry. This, combined with delayed_work->timer being
1223 * irqsafe, ensures that we return -EAGAIN for finite short period of time.
1224 *
1225 * On successful return, >= 0, irq is disabled and the caller is
1226 * responsible for releasing it using local_irq_restore(*@flags).
1227 *
1228 * This function is safe to call from any context including IRQ handler.
1229 */
1230static int try_to_grab_pending(struct work_struct *work, bool is_dwork,
1231 unsigned long *flags)
1232{
1233 struct worker_pool *pool;
1234 struct pool_workqueue *pwq;
1235
1236 local_irq_save(*flags);
1237
1238 /* try to steal the timer if it exists */
1239 if (is_dwork) {
1240 struct delayed_work *dwork = to_delayed_work(work);
1241
1242 /*
1243 * dwork->timer is irqsafe. If del_timer() fails, it's
1244 * guaranteed that the timer is not queued anywhere and not
1245 * running on the local CPU.
1246 */
1247 if (likely(del_timer(&dwork->timer)))
1248 return 1;
1249 }
1250
1251 /* try to claim PENDING the normal way */
1252 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work)))
1253 return 0;
1254
1255 /*
1256 * The queueing is in progress, or it is already queued. Try to
1257 * steal it from ->worklist without clearing WORK_STRUCT_PENDING.
1258 */
1259 pool = get_work_pool(work);
1260 if (!pool)
1261 goto fail;
1262
1263 spin_lock(&pool->lock);
1264 /*
1265 * work->data is guaranteed to point to pwq only while the work
1266 * item is queued on pwq->wq, and both updating work->data to point
1267 * to pwq on queueing and to pool on dequeueing are done under
1268 * pwq->pool->lock. This in turn guarantees that, if work->data
1269 * points to pwq which is associated with a locked pool, the work
1270 * item is currently queued on that pool.
1271 */
1272 pwq = get_work_pwq(work);
1273 if (pwq && pwq->pool == pool) {
1274 debug_work_deactivate(work);
1275
1276 /*
1277 * A delayed work item cannot be grabbed directly because
1278 * it might have linked NO_COLOR work items which, if left
1279 * on the delayed_list, will confuse pwq->nr_active
1280 * management later on and cause stall. Make sure the work
1281 * item is activated before grabbing.
1282 */
1283 if (*work_data_bits(work) & WORK_STRUCT_DELAYED)
1284 pwq_activate_delayed_work(work);
1285
1286 list_del_init(&work->entry);
1287 pwq_dec_nr_in_flight(pwq, get_work_color(work));
1288
1289 /* work->data points to pwq iff queued, point to pool */
1290 set_work_pool_and_keep_pending(work, pool->id);
1291
1292 spin_unlock(&pool->lock);
1293 return 1;
1294 }
1295 spin_unlock(&pool->lock);
1296fail:
1297 local_irq_restore(*flags);
1298 if (work_is_canceling(work))
1299 return -ENOENT;
1300 cpu_relax();
1301 return -EAGAIN;
1302}
1303
1304/**
1305 * insert_work - insert a work into a pool
1306 * @pwq: pwq @work belongs to
1307 * @work: work to insert
1308 * @head: insertion point
1309 * @extra_flags: extra WORK_STRUCT_* flags to set
1310 *
1311 * Insert @work which belongs to @pwq after @head. @extra_flags is or'd to
1312 * work_struct flags.
1313 *
1314 * CONTEXT:
1315 * spin_lock_irq(pool->lock).
1316 */
1317static void insert_work(struct pool_workqueue *pwq, struct work_struct *work,
1318 struct list_head *head, unsigned int extra_flags)
1319{
1320 struct worker_pool *pool = pwq->pool;
1321
1322 /* we own @work, set data and link */
1323 set_work_pwq(work, pwq, extra_flags);
1324 list_add_tail(&work->entry, head);
1325 get_pwq(pwq);
1326
1327 /*
1328 * Ensure either wq_worker_sleeping() sees the above
1329 * list_add_tail() or we see zero nr_running to avoid workers lying
1330 * around lazily while there are works to be processed.
1331 */
1332 smp_mb();
1333
1334 if (__need_more_worker(pool))
1335 wake_up_worker(pool);
1336}
1337
1338/*
1339 * Test whether @work is being queued from another work executing on the
1340 * same workqueue.
1341 */
1342static bool is_chained_work(struct workqueue_struct *wq)
1343{
1344 struct worker *worker;
1345
1346 worker = current_wq_worker();
1347 /*
1348 * Return %true iff I'm a worker execuing a work item on @wq. If
1349 * I'm @worker, it's safe to dereference it without locking.
1350 */
1351 return worker && worker->current_pwq->wq == wq;
1352}
1353
1354/*
1355 * When queueing an unbound work item to a wq, prefer local CPU if allowed
1356 * by wq_unbound_cpumask. Otherwise, round robin among the allowed ones to
1357 * avoid perturbing sensitive tasks.
1358 */
1359static int wq_select_unbound_cpu(int cpu)
1360{
1361 static bool printed_dbg_warning;
1362 int new_cpu;
1363
1364 if (likely(!wq_debug_force_rr_cpu)) {
1365 if (cpumask_test_cpu(cpu, wq_unbound_cpumask))
1366 return cpu;
1367 } else if (!printed_dbg_warning) {
1368 pr_warn("workqueue: round-robin CPU selection forced, expect performance impact\n");
1369 printed_dbg_warning = true;
1370 }
1371
1372 if (cpumask_empty(wq_unbound_cpumask))
1373 return cpu;
1374
1375 new_cpu = __this_cpu_read(wq_rr_cpu_last);
1376 new_cpu = cpumask_next_and(new_cpu, wq_unbound_cpumask, cpu_online_mask);
1377 if (unlikely(new_cpu >= nr_cpu_ids)) {
1378 new_cpu = cpumask_first_and(wq_unbound_cpumask, cpu_online_mask);
1379 if (unlikely(new_cpu >= nr_cpu_ids))
1380 return cpu;
1381 }
1382 __this_cpu_write(wq_rr_cpu_last, new_cpu);
1383
1384 return new_cpu;
1385}
1386
1387static void __queue_work(int cpu, struct workqueue_struct *wq,
1388 struct work_struct *work)
1389{
1390 struct pool_workqueue *pwq;
1391 struct worker_pool *last_pool;
1392 struct list_head *worklist;
1393 unsigned int work_flags;
1394 unsigned int req_cpu = cpu;
1395
1396 /*
1397 * While a work item is PENDING && off queue, a task trying to
1398 * steal the PENDING will busy-loop waiting for it to either get
1399 * queued or lose PENDING. Grabbing PENDING and queueing should
1400 * happen with IRQ disabled.
1401 */
1402 WARN_ON_ONCE(!irqs_disabled());
1403
1404 debug_work_activate(work);
1405
1406 /* if draining, only works from the same workqueue are allowed */
1407 if (unlikely(wq->flags & __WQ_DRAINING) &&
1408 WARN_ON_ONCE(!is_chained_work(wq)))
1409 return;
1410retry:
1411 if (req_cpu == WORK_CPU_UNBOUND)
1412 cpu = wq_select_unbound_cpu(raw_smp_processor_id());
1413
1414 /* pwq which will be used unless @work is executing elsewhere */
1415 if (!(wq->flags & WQ_UNBOUND))
1416 pwq = per_cpu_ptr(wq->cpu_pwqs, cpu);
1417 else
1418 pwq = unbound_pwq_by_node(wq, cpu_to_node(cpu));
1419
1420 /*
1421 * If @work was previously on a different pool, it might still be
1422 * running there, in which case the work needs to be queued on that
1423 * pool to guarantee non-reentrancy.
1424 */
1425 last_pool = get_work_pool(work);
1426 if (last_pool && last_pool != pwq->pool) {
1427 struct worker *worker;
1428
1429 spin_lock(&last_pool->lock);
1430
1431 worker = find_worker_executing_work(last_pool, work);
1432
1433 if (worker && worker->current_pwq->wq == wq) {
1434 pwq = worker->current_pwq;
1435 } else {
1436 /* meh... not running there, queue here */
1437 spin_unlock(&last_pool->lock);
1438 spin_lock(&pwq->pool->lock);
1439 }
1440 } else {
1441 spin_lock(&pwq->pool->lock);
1442 }
1443
1444 /*
1445 * pwq is determined and locked. For unbound pools, we could have
1446 * raced with pwq release and it could already be dead. If its
1447 * refcnt is zero, repeat pwq selection. Note that pwqs never die
1448 * without another pwq replacing it in the numa_pwq_tbl or while
1449 * work items are executing on it, so the retrying is guaranteed to
1450 * make forward-progress.
1451 */
1452 if (unlikely(!pwq->refcnt)) {
1453 if (wq->flags & WQ_UNBOUND) {
1454 spin_unlock(&pwq->pool->lock);
1455 cpu_relax();
1456 goto retry;
1457 }
1458 /* oops */
1459 WARN_ONCE(true, "workqueue: per-cpu pwq for %s on cpu%d has 0 refcnt",
1460 wq->name, cpu);
1461 }
1462
1463 /* pwq determined, queue */
1464 trace_workqueue_queue_work(req_cpu, pwq, work);
1465
1466 if (WARN_ON(!list_empty(&work->entry))) {
1467 spin_unlock(&pwq->pool->lock);
1468 return;
1469 }
1470
1471 pwq->nr_in_flight[pwq->work_color]++;
1472 work_flags = work_color_to_flags(pwq->work_color);
1473
1474 if (likely(pwq->nr_active < pwq->max_active)) {
1475 trace_workqueue_activate_work(work);
1476 pwq->nr_active++;
1477 worklist = &pwq->pool->worklist;
1478 if (list_empty(worklist))
1479 pwq->pool->watchdog_ts = jiffies;
1480 } else {
1481 work_flags |= WORK_STRUCT_DELAYED;
1482 worklist = &pwq->delayed_works;
1483 }
1484
1485 insert_work(pwq, work, worklist, work_flags);
1486
1487 spin_unlock(&pwq->pool->lock);
1488}
1489
1490/**
1491 * queue_work_on - queue work on specific cpu
1492 * @cpu: CPU number to execute work on
1493 * @wq: workqueue to use
1494 * @work: work to queue
1495 *
1496 * We queue the work to a specific CPU, the caller must ensure it
1497 * can't go away.
1498 *
1499 * Return: %false if @work was already on a queue, %true otherwise.
1500 */
1501bool queue_work_on(int cpu, struct workqueue_struct *wq,
1502 struct work_struct *work)
1503{
1504 bool ret = false;
1505 unsigned long flags;
1506
1507 local_irq_save(flags);
1508
1509 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1510 __queue_work(cpu, wq, work);
1511 ret = true;
1512 }
1513
1514 local_irq_restore(flags);
1515 return ret;
1516}
1517EXPORT_SYMBOL(queue_work_on);
1518
1519void delayed_work_timer_fn(unsigned long __data)
1520{
1521 struct delayed_work *dwork = (struct delayed_work *)__data;
1522
1523 /* should have been called from irqsafe timer with irq already off */
1524 __queue_work(dwork->cpu, dwork->wq, &dwork->work);
1525}
1526EXPORT_SYMBOL(delayed_work_timer_fn);
1527
1528static void __queue_delayed_work(int cpu, struct workqueue_struct *wq,
1529 struct delayed_work *dwork, unsigned long delay)
1530{
1531 struct timer_list *timer = &dwork->timer;
1532 struct work_struct *work = &dwork->work;
1533
1534 WARN_ON_ONCE(timer->function != delayed_work_timer_fn ||
1535 timer->data != (unsigned long)dwork);
1536 WARN_ON_ONCE(timer_pending(timer));
1537 WARN_ON_ONCE(!list_empty(&work->entry));
1538
1539 /*
1540 * If @delay is 0, queue @dwork->work immediately. This is for
1541 * both optimization and correctness. The earliest @timer can
1542 * expire is on the closest next tick and delayed_work users depend
1543 * on that there's no such delay when @delay is 0.
1544 */
1545 if (!delay) {
1546 __queue_work(cpu, wq, &dwork->work);
1547 return;
1548 }
1549
1550 timer_stats_timer_set_start_info(&dwork->timer);
1551
1552 dwork->wq = wq;
1553 dwork->cpu = cpu;
1554 timer->expires = jiffies + delay;
1555
1556 if (unlikely(cpu != WORK_CPU_UNBOUND))
1557 add_timer_on(timer, cpu);
1558 else
1559 add_timer(timer);
1560}
1561
1562/**
1563 * queue_delayed_work_on - queue work on specific CPU after delay
1564 * @cpu: CPU number to execute work on
1565 * @wq: workqueue to use
1566 * @dwork: work to queue
1567 * @delay: number of jiffies to wait before queueing
1568 *
1569 * Return: %false if @work was already on a queue, %true otherwise. If
1570 * @delay is zero and @dwork is idle, it will be scheduled for immediate
1571 * execution.
1572 */
1573bool queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
1574 struct delayed_work *dwork, unsigned long delay)
1575{
1576 struct work_struct *work = &dwork->work;
1577 bool ret = false;
1578 unsigned long flags;
1579
1580 /* read the comment in __queue_work() */
1581 local_irq_save(flags);
1582
1583 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1584 __queue_delayed_work(cpu, wq, dwork, delay);
1585 ret = true;
1586 }
1587
1588 local_irq_restore(flags);
1589 return ret;
1590}
1591EXPORT_SYMBOL(queue_delayed_work_on);
1592
1593/**
1594 * mod_delayed_work_on - modify delay of or queue a delayed work on specific CPU
1595 * @cpu: CPU number to execute work on
1596 * @wq: workqueue to use
1597 * @dwork: work to queue
1598 * @delay: number of jiffies to wait before queueing
1599 *
1600 * If @dwork is idle, equivalent to queue_delayed_work_on(); otherwise,
1601 * modify @dwork's timer so that it expires after @delay. If @delay is
1602 * zero, @work is guaranteed to be scheduled immediately regardless of its
1603 * current state.
1604 *
1605 * Return: %false if @dwork was idle and queued, %true if @dwork was
1606 * pending and its timer was modified.
1607 *
1608 * This function is safe to call from any context including IRQ handler.
1609 * See try_to_grab_pending() for details.
1610 */
1611bool mod_delayed_work_on(int cpu, struct workqueue_struct *wq,
1612 struct delayed_work *dwork, unsigned long delay)
1613{
1614 unsigned long flags;
1615 int ret;
1616
1617 do {
1618 ret = try_to_grab_pending(&dwork->work, true, &flags);
1619 } while (unlikely(ret == -EAGAIN));
1620
1621 if (likely(ret >= 0)) {
1622 __queue_delayed_work(cpu, wq, dwork, delay);
1623 local_irq_restore(flags);
1624 }
1625
1626 /* -ENOENT from try_to_grab_pending() becomes %true */
1627 return ret;
1628}
1629EXPORT_SYMBOL_GPL(mod_delayed_work_on);
1630
1631/**
1632 * worker_enter_idle - enter idle state
1633 * @worker: worker which is entering idle state
1634 *
1635 * @worker is entering idle state. Update stats and idle timer if
1636 * necessary.
1637 *
1638 * LOCKING:
1639 * spin_lock_irq(pool->lock).
1640 */
1641static void worker_enter_idle(struct worker *worker)
1642{
1643 struct worker_pool *pool = worker->pool;
1644
1645 if (WARN_ON_ONCE(worker->flags & WORKER_IDLE) ||
1646 WARN_ON_ONCE(!list_empty(&worker->entry) &&
1647 (worker->hentry.next || worker->hentry.pprev)))
1648 return;
1649
1650 /* can't use worker_set_flags(), also called from create_worker() */
1651 worker->flags |= WORKER_IDLE;
1652 pool->nr_idle++;
1653 worker->last_active = jiffies;
1654
1655 /* idle_list is LIFO */
1656 list_add(&worker->entry, &pool->idle_list);
1657
1658 if (too_many_workers(pool) && !timer_pending(&pool->idle_timer))
1659 mod_timer(&pool->idle_timer, jiffies + IDLE_WORKER_TIMEOUT);
1660
1661 /*
1662 * Sanity check nr_running. Because wq_unbind_fn() releases
1663 * pool->lock between setting %WORKER_UNBOUND and zapping
1664 * nr_running, the warning may trigger spuriously. Check iff
1665 * unbind is not in progress.
1666 */
1667 WARN_ON_ONCE(!(pool->flags & POOL_DISASSOCIATED) &&
1668 pool->nr_workers == pool->nr_idle &&
1669 atomic_read(&pool->nr_running));
1670}
1671
1672/**
1673 * worker_leave_idle - leave idle state
1674 * @worker: worker which is leaving idle state
1675 *
1676 * @worker is leaving idle state. Update stats.
1677 *
1678 * LOCKING:
1679 * spin_lock_irq(pool->lock).
1680 */
1681static void worker_leave_idle(struct worker *worker)
1682{
1683 struct worker_pool *pool = worker->pool;
1684
1685 if (WARN_ON_ONCE(!(worker->flags & WORKER_IDLE)))
1686 return;
1687 worker_clr_flags(worker, WORKER_IDLE);
1688 pool->nr_idle--;
1689 list_del_init(&worker->entry);
1690}
1691
1692static struct worker *alloc_worker(int node)
1693{
1694 struct worker *worker;
1695
1696 worker = kzalloc_node(sizeof(*worker), GFP_KERNEL, node);
1697 if (worker) {
1698 INIT_LIST_HEAD(&worker->entry);
1699 INIT_LIST_HEAD(&worker->scheduled);
1700 INIT_LIST_HEAD(&worker->node);
1701 /* on creation a worker is in !idle && prep state */
1702 worker->flags = WORKER_PREP;
1703 }
1704 return worker;
1705}
1706
1707/**
1708 * worker_attach_to_pool() - attach a worker to a pool
1709 * @worker: worker to be attached
1710 * @pool: the target pool
1711 *
1712 * Attach @worker to @pool. Once attached, the %WORKER_UNBOUND flag and
1713 * cpu-binding of @worker are kept coordinated with the pool across
1714 * cpu-[un]hotplugs.
1715 */
1716static void worker_attach_to_pool(struct worker *worker,
1717 struct worker_pool *pool)
1718{
1719 mutex_lock(&pool->attach_mutex);
1720
1721 /*
1722 * set_cpus_allowed_ptr() will fail if the cpumask doesn't have any
1723 * online CPUs. It'll be re-applied when any of the CPUs come up.
1724 */
1725 set_cpus_allowed_ptr(worker->task, pool->attrs->cpumask);
1726
1727 /*
1728 * The pool->attach_mutex ensures %POOL_DISASSOCIATED remains
1729 * stable across this function. See the comments above the
1730 * flag definition for details.
1731 */
1732 if (pool->flags & POOL_DISASSOCIATED)
1733 worker->flags |= WORKER_UNBOUND;
1734
1735 list_add_tail(&worker->node, &pool->workers);
1736
1737 mutex_unlock(&pool->attach_mutex);
1738}
1739
1740/**
1741 * worker_detach_from_pool() - detach a worker from its pool
1742 * @worker: worker which is attached to its pool
1743 * @pool: the pool @worker is attached to
1744 *
1745 * Undo the attaching which had been done in worker_attach_to_pool(). The
1746 * caller worker shouldn't access to the pool after detached except it has
1747 * other reference to the pool.
1748 */
1749static void worker_detach_from_pool(struct worker *worker,
1750 struct worker_pool *pool)
1751{
1752 struct completion *detach_completion = NULL;
1753
1754 mutex_lock(&pool->attach_mutex);
1755 list_del(&worker->node);
1756 if (list_empty(&pool->workers))
1757 detach_completion = pool->detach_completion;
1758 mutex_unlock(&pool->attach_mutex);
1759
1760 /* clear leftover flags without pool->lock after it is detached */
1761 worker->flags &= ~(WORKER_UNBOUND | WORKER_REBOUND);
1762
1763 if (detach_completion)
1764 complete(detach_completion);
1765}
1766
1767/**
1768 * create_worker - create a new workqueue worker
1769 * @pool: pool the new worker will belong to
1770 *
1771 * Create and start a new worker which is attached to @pool.
1772 *
1773 * CONTEXT:
1774 * Might sleep. Does GFP_KERNEL allocations.
1775 *
1776 * Return:
1777 * Pointer to the newly created worker.
1778 */
1779static struct worker *create_worker(struct worker_pool *pool)
1780{
1781 struct worker *worker = NULL;
1782 int id = -1;
1783 char id_buf[16];
1784
1785 /* ID is needed to determine kthread name */
1786 id = ida_simple_get(&pool->worker_ida, 0, 0, GFP_KERNEL);
1787 if (id < 0)
1788 goto fail;
1789
1790 worker = alloc_worker(pool->node);
1791 if (!worker)
1792 goto fail;
1793
1794 worker->pool = pool;
1795 worker->id = id;
1796
1797 if (pool->cpu >= 0)
1798 snprintf(id_buf, sizeof(id_buf), "%d:%d%s", pool->cpu, id,
1799 pool->attrs->nice < 0 ? "H" : "");
1800 else
1801 snprintf(id_buf, sizeof(id_buf), "u%d:%d", pool->id, id);
1802
1803 worker->task = kthread_create_on_node(worker_thread, worker, pool->node,
1804 "kworker/%s", id_buf);
1805 if (IS_ERR(worker->task))
1806 goto fail;
1807
1808 set_user_nice(worker->task, pool->attrs->nice);
1809 kthread_bind_mask(worker->task, pool->attrs->cpumask);
1810
1811 /* successful, attach the worker to the pool */
1812 worker_attach_to_pool(worker, pool);
1813
1814 /* start the newly created worker */
1815 spin_lock_irq(&pool->lock);
1816 worker->pool->nr_workers++;
1817 worker_enter_idle(worker);
1818 wake_up_process(worker->task);
1819 spin_unlock_irq(&pool->lock);
1820
1821 return worker;
1822
1823fail:
1824 if (id >= 0)
1825 ida_simple_remove(&pool->worker_ida, id);
1826 kfree(worker);
1827 return NULL;
1828}
1829
1830/**
1831 * destroy_worker - destroy a workqueue worker
1832 * @worker: worker to be destroyed
1833 *
1834 * Destroy @worker and adjust @pool stats accordingly. The worker should
1835 * be idle.
1836 *
1837 * CONTEXT:
1838 * spin_lock_irq(pool->lock).
1839 */
1840static void destroy_worker(struct worker *worker)
1841{
1842 struct worker_pool *pool = worker->pool;
1843
1844 lockdep_assert_held(&pool->lock);
1845
1846 /* sanity check frenzy */
1847 if (WARN_ON(worker->current_work) ||
1848 WARN_ON(!list_empty(&worker->scheduled)) ||
1849 WARN_ON(!(worker->flags & WORKER_IDLE)))
1850 return;
1851
1852 pool->nr_workers--;
1853 pool->nr_idle--;
1854
1855 list_del_init(&worker->entry);
1856 worker->flags |= WORKER_DIE;
1857 wake_up_process(worker->task);
1858}
1859
1860static void idle_worker_timeout(unsigned long __pool)
1861{
1862 struct worker_pool *pool = (void *)__pool;
1863
1864 spin_lock_irq(&pool->lock);
1865
1866 while (too_many_workers(pool)) {
1867 struct worker *worker;
1868 unsigned long expires;
1869
1870 /* idle_list is kept in LIFO order, check the last one */
1871 worker = list_entry(pool->idle_list.prev, struct worker, entry);
1872 expires = worker->last_active + IDLE_WORKER_TIMEOUT;
1873
1874 if (time_before(jiffies, expires)) {
1875 mod_timer(&pool->idle_timer, expires);
1876 break;
1877 }
1878
1879 destroy_worker(worker);
1880 }
1881
1882 spin_unlock_irq(&pool->lock);
1883}
1884
1885static void send_mayday(struct work_struct *work)
1886{
1887 struct pool_workqueue *pwq = get_work_pwq(work);
1888 struct workqueue_struct *wq = pwq->wq;
1889
1890 lockdep_assert_held(&wq_mayday_lock);
1891
1892 if (!wq->rescuer)
1893 return;
1894
1895 /* mayday mayday mayday */
1896 if (list_empty(&pwq->mayday_node)) {
1897 /*
1898 * If @pwq is for an unbound wq, its base ref may be put at
1899 * any time due to an attribute change. Pin @pwq until the
1900 * rescuer is done with it.
1901 */
1902 get_pwq(pwq);
1903 list_add_tail(&pwq->mayday_node, &wq->maydays);
1904 wake_up_process(wq->rescuer->task);
1905 }
1906}
1907
1908static void pool_mayday_timeout(unsigned long __pool)
1909{
1910 struct worker_pool *pool = (void *)__pool;
1911 struct work_struct *work;
1912
1913 spin_lock_irq(&pool->lock);
1914 spin_lock(&wq_mayday_lock); /* for wq->maydays */
1915
1916 if (need_to_create_worker(pool)) {
1917 /*
1918 * We've been trying to create a new worker but
1919 * haven't been successful. We might be hitting an
1920 * allocation deadlock. Send distress signals to
1921 * rescuers.
1922 */
1923 list_for_each_entry(work, &pool->worklist, entry)
1924 send_mayday(work);
1925 }
1926
1927 spin_unlock(&wq_mayday_lock);
1928 spin_unlock_irq(&pool->lock);
1929
1930 mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INTERVAL);
1931}
1932
1933/**
1934 * maybe_create_worker - create a new worker if necessary
1935 * @pool: pool to create a new worker for
1936 *
1937 * Create a new worker for @pool if necessary. @pool is guaranteed to
1938 * have at least one idle worker on return from this function. If
1939 * creating a new worker takes longer than MAYDAY_INTERVAL, mayday is
1940 * sent to all rescuers with works scheduled on @pool to resolve
1941 * possible allocation deadlock.
1942 *
1943 * On return, need_to_create_worker() is guaranteed to be %false and
1944 * may_start_working() %true.
1945 *
1946 * LOCKING:
1947 * spin_lock_irq(pool->lock) which may be released and regrabbed
1948 * multiple times. Does GFP_KERNEL allocations. Called only from
1949 * manager.
1950 */
1951static void maybe_create_worker(struct worker_pool *pool)
1952__releases(&pool->lock)
1953__acquires(&pool->lock)
1954{
1955restart:
1956 spin_unlock_irq(&pool->lock);
1957
1958 /* if we don't make progress in MAYDAY_INITIAL_TIMEOUT, call for help */
1959 mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INITIAL_TIMEOUT);
1960
1961 while (true) {
1962 if (create_worker(pool) || !need_to_create_worker(pool))
1963 break;
1964
1965 schedule_timeout_interruptible(CREATE_COOLDOWN);
1966
1967 if (!need_to_create_worker(pool))
1968 break;
1969 }
1970
1971 del_timer_sync(&pool->mayday_timer);
1972 spin_lock_irq(&pool->lock);
1973 /*
1974 * This is necessary even after a new worker was just successfully
1975 * created as @pool->lock was dropped and the new worker might have
1976 * already become busy.
1977 */
1978 if (need_to_create_worker(pool))
1979 goto restart;
1980}
1981
1982/**
1983 * manage_workers - manage worker pool
1984 * @worker: self
1985 *
1986 * Assume the manager role and manage the worker pool @worker belongs
1987 * to. At any given time, there can be only zero or one manager per
1988 * pool. The exclusion is handled automatically by this function.
1989 *
1990 * The caller can safely start processing works on false return. On
1991 * true return, it's guaranteed that need_to_create_worker() is false
1992 * and may_start_working() is true.
1993 *
1994 * CONTEXT:
1995 * spin_lock_irq(pool->lock) which may be released and regrabbed
1996 * multiple times. Does GFP_KERNEL allocations.
1997 *
1998 * Return:
1999 * %false if the pool doesn't need management and the caller can safely
2000 * start processing works, %true if management function was performed and
2001 * the conditions that the caller verified before calling the function may
2002 * no longer be true.
2003 */
2004static bool manage_workers(struct worker *worker)
2005{
2006 struct worker_pool *pool = worker->pool;
2007
2008 /*
2009 * Anyone who successfully grabs manager_arb wins the arbitration
2010 * and becomes the manager. mutex_trylock() on pool->manager_arb
2011 * failure while holding pool->lock reliably indicates that someone
2012 * else is managing the pool and the worker which failed trylock
2013 * can proceed to executing work items. This means that anyone
2014 * grabbing manager_arb is responsible for actually performing
2015 * manager duties. If manager_arb is grabbed and released without
2016 * actual management, the pool may stall indefinitely.
2017 */
2018 if (!mutex_trylock(&pool->manager_arb))
2019 return false;
2020 pool->manager = worker;
2021
2022 maybe_create_worker(pool);
2023
2024 pool->manager = NULL;
2025 mutex_unlock(&pool->manager_arb);
2026 return true;
2027}
2028
2029/**
2030 * process_one_work - process single work
2031 * @worker: self
2032 * @work: work to process
2033 *
2034 * Process @work. This function contains all the logics necessary to
2035 * process a single work including synchronization against and
2036 * interaction with other workers on the same cpu, queueing and
2037 * flushing. As long as context requirement is met, any worker can
2038 * call this function to process a work.
2039 *
2040 * CONTEXT:
2041 * spin_lock_irq(pool->lock) which is released and regrabbed.
2042 */
2043static void process_one_work(struct worker *worker, struct work_struct *work)
2044__releases(&pool->lock)
2045__acquires(&pool->lock)
2046{
2047 struct pool_workqueue *pwq = get_work_pwq(work);
2048 struct worker_pool *pool = worker->pool;
2049 bool cpu_intensive = pwq->wq->flags & WQ_CPU_INTENSIVE;
2050 int work_color;
2051 struct worker *collision;
2052#ifdef CONFIG_LOCKDEP
2053 /*
2054 * It is permissible to free the struct work_struct from
2055 * inside the function that is called from it, this we need to
2056 * take into account for lockdep too. To avoid bogus "held
2057 * lock freed" warnings as well as problems when looking into
2058 * work->lockdep_map, make a copy and use that here.
2059 */
2060 struct lockdep_map lockdep_map;
2061
2062 lockdep_copy_map(&lockdep_map, &work->lockdep_map);
2063#endif
2064 /* ensure we're on the correct CPU */
2065 WARN_ON_ONCE(!(pool->flags & POOL_DISASSOCIATED) &&
2066 raw_smp_processor_id() != pool->cpu);
2067
2068 /*
2069 * A single work shouldn't be executed concurrently by
2070 * multiple workers on a single cpu. Check whether anyone is
2071 * already processing the work. If so, defer the work to the
2072 * currently executing one.
2073 */
2074 collision = find_worker_executing_work(pool, work);
2075 if (unlikely(collision)) {
2076 move_linked_works(work, &collision->scheduled, NULL);
2077 return;
2078 }
2079
2080 /* claim and dequeue */
2081 debug_work_deactivate(work);
2082 hash_add(pool->busy_hash, &worker->hentry, (unsigned long)work);
2083 worker->current_work = work;
2084 worker->current_func = work->func;
2085 worker->current_pwq = pwq;
2086 work_color = get_work_color(work);
2087
2088 list_del_init(&work->entry);
2089
2090 /*
2091 * CPU intensive works don't participate in concurrency management.
2092 * They're the scheduler's responsibility. This takes @worker out
2093 * of concurrency management and the next code block will chain
2094 * execution of the pending work items.
2095 */
2096 if (unlikely(cpu_intensive))
2097 worker_set_flags(worker, WORKER_CPU_INTENSIVE);
2098
2099 /*
2100 * Wake up another worker if necessary. The condition is always
2101 * false for normal per-cpu workers since nr_running would always
2102 * be >= 1 at this point. This is used to chain execution of the
2103 * pending work items for WORKER_NOT_RUNNING workers such as the
2104 * UNBOUND and CPU_INTENSIVE ones.
2105 */
2106 if (need_more_worker(pool))
2107 wake_up_worker(pool);
2108
2109 /*
2110 * Record the last pool and clear PENDING which should be the last
2111 * update to @work. Also, do this inside @pool->lock so that
2112 * PENDING and queued state changes happen together while IRQ is
2113 * disabled.
2114 */
2115 set_work_pool_and_clear_pending(work, pool->id);
2116
2117 spin_unlock_irq(&pool->lock);
2118
2119 lock_map_acquire_read(&pwq->wq->lockdep_map);
2120 lock_map_acquire(&lockdep_map);
2121 trace_workqueue_execute_start(work);
2122 worker->current_func(work);
2123 /*
2124 * While we must be careful to not use "work" after this, the trace
2125 * point will only record its address.
2126 */
2127 trace_workqueue_execute_end(work);
2128 lock_map_release(&lockdep_map);
2129 lock_map_release(&pwq->wq->lockdep_map);
2130
2131 if (unlikely(in_atomic() || lockdep_depth(current) > 0)) {
2132 pr_err("BUG: workqueue leaked lock or atomic: %s/0x%08x/%d\n"
2133 " last function: %pf\n",
2134 current->comm, preempt_count(), task_pid_nr(current),
2135 worker->current_func);
2136 debug_show_held_locks(current);
2137 dump_stack();
2138 }
2139
2140 /*
2141 * The following prevents a kworker from hogging CPU on !PREEMPT
2142 * kernels, where a requeueing work item waiting for something to
2143 * happen could deadlock with stop_machine as such work item could
2144 * indefinitely requeue itself while all other CPUs are trapped in
2145 * stop_machine. At the same time, report a quiescent RCU state so
2146 * the same condition doesn't freeze RCU.
2147 */
2148 cond_resched_rcu_qs();
2149
2150 spin_lock_irq(&pool->lock);
2151
2152 /* clear cpu intensive status */
2153 if (unlikely(cpu_intensive))
2154 worker_clr_flags(worker, WORKER_CPU_INTENSIVE);
2155
2156 /* we're done with it, release */
2157 hash_del(&worker->hentry);
2158 worker->current_work = NULL;
2159 worker->current_func = NULL;
2160 worker->current_pwq = NULL;
2161 worker->desc_valid = false;
2162 pwq_dec_nr_in_flight(pwq, work_color);
2163}
2164
2165/**
2166 * process_scheduled_works - process scheduled works
2167 * @worker: self
2168 *
2169 * Process all scheduled works. Please note that the scheduled list
2170 * may change while processing a work, so this function repeatedly
2171 * fetches a work from the top and executes it.
2172 *
2173 * CONTEXT:
2174 * spin_lock_irq(pool->lock) which may be released and regrabbed
2175 * multiple times.
2176 */
2177static void process_scheduled_works(struct worker *worker)
2178{
2179 while (!list_empty(&worker->scheduled)) {
2180 struct work_struct *work = list_first_entry(&worker->scheduled,
2181 struct work_struct, entry);
2182 process_one_work(worker, work);
2183 }
2184}
2185
2186/**
2187 * worker_thread - the worker thread function
2188 * @__worker: self
2189 *
2190 * The worker thread function. All workers belong to a worker_pool -
2191 * either a per-cpu one or dynamic unbound one. These workers process all
2192 * work items regardless of their specific target workqueue. The only
2193 * exception is work items which belong to workqueues with a rescuer which
2194 * will be explained in rescuer_thread().
2195 *
2196 * Return: 0
2197 */
2198static int worker_thread(void *__worker)
2199{
2200 struct worker *worker = __worker;
2201 struct worker_pool *pool = worker->pool;
2202
2203 /* tell the scheduler that this is a workqueue worker */
2204 worker->task->flags |= PF_WQ_WORKER;
2205woke_up:
2206 spin_lock_irq(&pool->lock);
2207
2208 /* am I supposed to die? */
2209 if (unlikely(worker->flags & WORKER_DIE)) {
2210 spin_unlock_irq(&pool->lock);
2211 WARN_ON_ONCE(!list_empty(&worker->entry));
2212 worker->task->flags &= ~PF_WQ_WORKER;
2213
2214 set_task_comm(worker->task, "kworker/dying");
2215 ida_simple_remove(&pool->worker_ida, worker->id);
2216 worker_detach_from_pool(worker, pool);
2217 kfree(worker);
2218 return 0;
2219 }
2220
2221 worker_leave_idle(worker);
2222recheck:
2223 /* no more worker necessary? */
2224 if (!need_more_worker(pool))
2225 goto sleep;
2226
2227 /* do we need to manage? */
2228 if (unlikely(!may_start_working(pool)) && manage_workers(worker))
2229 goto recheck;
2230
2231 /*
2232 * ->scheduled list can only be filled while a worker is
2233 * preparing to process a work or actually processing it.
2234 * Make sure nobody diddled with it while I was sleeping.
2235 */
2236 WARN_ON_ONCE(!list_empty(&worker->scheduled));
2237
2238 /*
2239 * Finish PREP stage. We're guaranteed to have at least one idle
2240 * worker or that someone else has already assumed the manager
2241 * role. This is where @worker starts participating in concurrency
2242 * management if applicable and concurrency management is restored
2243 * after being rebound. See rebind_workers() for details.
2244 */
2245 worker_clr_flags(worker, WORKER_PREP | WORKER_REBOUND);
2246
2247 do {
2248 struct work_struct *work =
2249 list_first_entry(&pool->worklist,
2250 struct work_struct, entry);
2251
2252 pool->watchdog_ts = jiffies;
2253
2254 if (likely(!(*work_data_bits(work) & WORK_STRUCT_LINKED))) {
2255 /* optimization path, not strictly necessary */
2256 process_one_work(worker, work);
2257 if (unlikely(!list_empty(&worker->scheduled)))
2258 process_scheduled_works(worker);
2259 } else {
2260 move_linked_works(work, &worker->scheduled, NULL);
2261 process_scheduled_works(worker);
2262 }
2263 } while (keep_working(pool));
2264
2265 worker_set_flags(worker, WORKER_PREP);
2266sleep:
2267 /*
2268 * pool->lock is held and there's no work to process and no need to
2269 * manage, sleep. Workers are woken up only while holding
2270 * pool->lock or from local cpu, so setting the current state
2271 * before releasing pool->lock is enough to prevent losing any
2272 * event.
2273 */
2274 worker_enter_idle(worker);
2275 __set_current_state(TASK_INTERRUPTIBLE);
2276 spin_unlock_irq(&pool->lock);
2277 schedule();
2278 goto woke_up;
2279}
2280
2281/**
2282 * rescuer_thread - the rescuer thread function
2283 * @__rescuer: self
2284 *
2285 * Workqueue rescuer thread function. There's one rescuer for each
2286 * workqueue which has WQ_MEM_RECLAIM set.
2287 *
2288 * Regular work processing on a pool may block trying to create a new
2289 * worker which uses GFP_KERNEL allocation which has slight chance of
2290 * developing into deadlock if some works currently on the same queue
2291 * need to be processed to satisfy the GFP_KERNEL allocation. This is
2292 * the problem rescuer solves.
2293 *
2294 * When such condition is possible, the pool summons rescuers of all
2295 * workqueues which have works queued on the pool and let them process
2296 * those works so that forward progress can be guaranteed.
2297 *
2298 * This should happen rarely.
2299 *
2300 * Return: 0
2301 */
2302static int rescuer_thread(void *__rescuer)
2303{
2304 struct worker *rescuer = __rescuer;
2305 struct workqueue_struct *wq = rescuer->rescue_wq;
2306 struct list_head *scheduled = &rescuer->scheduled;
2307 bool should_stop;
2308
2309 set_user_nice(current, RESCUER_NICE_LEVEL);
2310
2311 /*
2312 * Mark rescuer as worker too. As WORKER_PREP is never cleared, it
2313 * doesn't participate in concurrency management.
2314 */
2315 rescuer->task->flags |= PF_WQ_WORKER;
2316repeat:
2317 set_current_state(TASK_INTERRUPTIBLE);
2318
2319 /*
2320 * By the time the rescuer is requested to stop, the workqueue
2321 * shouldn't have any work pending, but @wq->maydays may still have
2322 * pwq(s) queued. This can happen by non-rescuer workers consuming
2323 * all the work items before the rescuer got to them. Go through
2324 * @wq->maydays processing before acting on should_stop so that the
2325 * list is always empty on exit.
2326 */
2327 should_stop = kthread_should_stop();
2328
2329 /* see whether any pwq is asking for help */
2330 spin_lock_irq(&wq_mayday_lock);
2331
2332 while (!list_empty(&wq->maydays)) {
2333 struct pool_workqueue *pwq = list_first_entry(&wq->maydays,
2334 struct pool_workqueue, mayday_node);
2335 struct worker_pool *pool = pwq->pool;
2336 struct work_struct *work, *n;
2337 bool first = true;
2338
2339 __set_current_state(TASK_RUNNING);
2340 list_del_init(&pwq->mayday_node);
2341
2342 spin_unlock_irq(&wq_mayday_lock);
2343
2344 worker_attach_to_pool(rescuer, pool);
2345
2346 spin_lock_irq(&pool->lock);
2347 rescuer->pool = pool;
2348
2349 /*
2350 * Slurp in all works issued via this workqueue and
2351 * process'em.
2352 */
2353 WARN_ON_ONCE(!list_empty(scheduled));
2354 list_for_each_entry_safe(work, n, &pool->worklist, entry) {
2355 if (get_work_pwq(work) == pwq) {
2356 if (first)
2357 pool->watchdog_ts = jiffies;
2358 move_linked_works(work, scheduled, &n);
2359 }
2360 first = false;
2361 }
2362
2363 if (!list_empty(scheduled)) {
2364 process_scheduled_works(rescuer);
2365
2366 /*
2367 * The above execution of rescued work items could
2368 * have created more to rescue through
2369 * pwq_activate_first_delayed() or chained
2370 * queueing. Let's put @pwq back on mayday list so
2371 * that such back-to-back work items, which may be
2372 * being used to relieve memory pressure, don't
2373 * incur MAYDAY_INTERVAL delay inbetween.
2374 */
2375 if (need_to_create_worker(pool)) {
2376 spin_lock(&wq_mayday_lock);
2377 get_pwq(pwq);
2378 list_move_tail(&pwq->mayday_node, &wq->maydays);
2379 spin_unlock(&wq_mayday_lock);
2380 }
2381 }
2382
2383 /*
2384 * Put the reference grabbed by send_mayday(). @pool won't
2385 * go away while we're still attached to it.
2386 */
2387 put_pwq(pwq);
2388
2389 /*
2390 * Leave this pool. If need_more_worker() is %true, notify a
2391 * regular worker; otherwise, we end up with 0 concurrency
2392 * and stalling the execution.
2393 */
2394 if (need_more_worker(pool))
2395 wake_up_worker(pool);
2396
2397 rescuer->pool = NULL;
2398 spin_unlock_irq(&pool->lock);
2399
2400 worker_detach_from_pool(rescuer, pool);
2401
2402 spin_lock_irq(&wq_mayday_lock);
2403 }
2404
2405 spin_unlock_irq(&wq_mayday_lock);
2406
2407 if (should_stop) {
2408 __set_current_state(TASK_RUNNING);
2409 rescuer->task->flags &= ~PF_WQ_WORKER;
2410 return 0;
2411 }
2412
2413 /* rescuers should never participate in concurrency management */
2414 WARN_ON_ONCE(!(rescuer->flags & WORKER_NOT_RUNNING));
2415 schedule();
2416 goto repeat;
2417}
2418
2419/**
2420 * check_flush_dependency - check for flush dependency sanity
2421 * @target_wq: workqueue being flushed
2422 * @target_work: work item being flushed (NULL for workqueue flushes)
2423 *
2424 * %current is trying to flush the whole @target_wq or @target_work on it.
2425 * If @target_wq doesn't have %WQ_MEM_RECLAIM, verify that %current is not
2426 * reclaiming memory or running on a workqueue which doesn't have
2427 * %WQ_MEM_RECLAIM as that can break forward-progress guarantee leading to
2428 * a deadlock.
2429 */
2430static void check_flush_dependency(struct workqueue_struct *target_wq,
2431 struct work_struct *target_work)
2432{
2433 work_func_t target_func = target_work ? target_work->func : NULL;
2434 struct worker *worker;
2435
2436 if (target_wq->flags & WQ_MEM_RECLAIM)
2437 return;
2438
2439 worker = current_wq_worker();
2440
2441 WARN_ONCE(current->flags & PF_MEMALLOC,
2442 "workqueue: PF_MEMALLOC task %d(%s) is flushing !WQ_MEM_RECLAIM %s:%pf",
2443 current->pid, current->comm, target_wq->name, target_func);
2444 WARN_ONCE(worker && ((worker->current_pwq->wq->flags &
2445 (WQ_MEM_RECLAIM | __WQ_LEGACY)) == WQ_MEM_RECLAIM),
2446 "workqueue: WQ_MEM_RECLAIM %s:%pf is flushing !WQ_MEM_RECLAIM %s:%pf",
2447 worker->current_pwq->wq->name, worker->current_func,
2448 target_wq->name, target_func);
2449}
2450
2451struct wq_barrier {
2452 struct work_struct work;
2453 struct completion done;
2454 struct task_struct *task; /* purely informational */
2455};
2456
2457static void wq_barrier_func(struct work_struct *work)
2458{
2459 struct wq_barrier *barr = container_of(work, struct wq_barrier, work);
2460 complete(&barr->done);
2461}
2462
2463/**
2464 * insert_wq_barrier - insert a barrier work
2465 * @pwq: pwq to insert barrier into
2466 * @barr: wq_barrier to insert
2467 * @target: target work to attach @barr to
2468 * @worker: worker currently executing @target, NULL if @target is not executing
2469 *
2470 * @barr is linked to @target such that @barr is completed only after
2471 * @target finishes execution. Please note that the ordering
2472 * guarantee is observed only with respect to @target and on the local
2473 * cpu.
2474 *
2475 * Currently, a queued barrier can't be canceled. This is because
2476 * try_to_grab_pending() can't determine whether the work to be
2477 * grabbed is at the head of the queue and thus can't clear LINKED
2478 * flag of the previous work while there must be a valid next work
2479 * after a work with LINKED flag set.
2480 *
2481 * Note that when @worker is non-NULL, @target may be modified
2482 * underneath us, so we can't reliably determine pwq from @target.
2483 *
2484 * CONTEXT:
2485 * spin_lock_irq(pool->lock).
2486 */
2487static void insert_wq_barrier(struct pool_workqueue *pwq,
2488 struct wq_barrier *barr,
2489 struct work_struct *target, struct worker *worker)
2490{
2491 struct list_head *head;
2492 unsigned int linked = 0;
2493
2494 /*
2495 * debugobject calls are safe here even with pool->lock locked
2496 * as we know for sure that this will not trigger any of the
2497 * checks and call back into the fixup functions where we
2498 * might deadlock.
2499 */
2500 INIT_WORK_ONSTACK(&barr->work, wq_barrier_func);
2501 __set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(&barr->work));
2502 init_completion(&barr->done);
2503 barr->task = current;
2504
2505 /*
2506 * If @target is currently being executed, schedule the
2507 * barrier to the worker; otherwise, put it after @target.
2508 */
2509 if (worker)
2510 head = worker->scheduled.next;
2511 else {
2512 unsigned long *bits = work_data_bits(target);
2513
2514 head = target->entry.next;
2515 /* there can already be other linked works, inherit and set */
2516 linked = *bits & WORK_STRUCT_LINKED;
2517 __set_bit(WORK_STRUCT_LINKED_BIT, bits);
2518 }
2519
2520 debug_work_activate(&barr->work);
2521 insert_work(pwq, &barr->work, head,
2522 work_color_to_flags(WORK_NO_COLOR) | linked);
2523}
2524
2525/**
2526 * flush_workqueue_prep_pwqs - prepare pwqs for workqueue flushing
2527 * @wq: workqueue being flushed
2528 * @flush_color: new flush color, < 0 for no-op
2529 * @work_color: new work color, < 0 for no-op
2530 *
2531 * Prepare pwqs for workqueue flushing.
2532 *
2533 * If @flush_color is non-negative, flush_color on all pwqs should be
2534 * -1. If no pwq has in-flight commands at the specified color, all
2535 * pwq->flush_color's stay at -1 and %false is returned. If any pwq
2536 * has in flight commands, its pwq->flush_color is set to
2537 * @flush_color, @wq->nr_pwqs_to_flush is updated accordingly, pwq
2538 * wakeup logic is armed and %true is returned.
2539 *
2540 * The caller should have initialized @wq->first_flusher prior to
2541 * calling this function with non-negative @flush_color. If
2542 * @flush_color is negative, no flush color update is done and %false
2543 * is returned.
2544 *
2545 * If @work_color is non-negative, all pwqs should have the same
2546 * work_color which is previous to @work_color and all will be
2547 * advanced to @work_color.
2548 *
2549 * CONTEXT:
2550 * mutex_lock(wq->mutex).
2551 *
2552 * Return:
2553 * %true if @flush_color >= 0 and there's something to flush. %false
2554 * otherwise.
2555 */
2556static bool flush_workqueue_prep_pwqs(struct workqueue_struct *wq,
2557 int flush_color, int work_color)
2558{
2559 bool wait = false;
2560 struct pool_workqueue *pwq;
2561
2562 if (flush_color >= 0) {
2563 WARN_ON_ONCE(atomic_read(&wq->nr_pwqs_to_flush));
2564 atomic_set(&wq->nr_pwqs_to_flush, 1);
2565 }
2566
2567 for_each_pwq(pwq, wq) {
2568 struct worker_pool *pool = pwq->pool;
2569
2570 spin_lock_irq(&pool->lock);
2571
2572 if (flush_color >= 0) {
2573 WARN_ON_ONCE(pwq->flush_color != -1);
2574
2575 if (pwq->nr_in_flight[flush_color]) {
2576 pwq->flush_color = flush_color;
2577 atomic_inc(&wq->nr_pwqs_to_flush);
2578 wait = true;
2579 }
2580 }
2581
2582 if (work_color >= 0) {
2583 WARN_ON_ONCE(work_color != work_next_color(pwq->work_color));
2584 pwq->work_color = work_color;
2585 }
2586
2587 spin_unlock_irq(&pool->lock);
2588 }
2589
2590 if (flush_color >= 0 && atomic_dec_and_test(&wq->nr_pwqs_to_flush))
2591 complete(&wq->first_flusher->done);
2592
2593 return wait;
2594}
2595
2596/**
2597 * flush_workqueue - ensure that any scheduled work has run to completion.
2598 * @wq: workqueue to flush
2599 *
2600 * This function sleeps until all work items which were queued on entry
2601 * have finished execution, but it is not livelocked by new incoming ones.
2602 */
2603void flush_workqueue(struct workqueue_struct *wq)
2604{
2605 struct wq_flusher this_flusher = {
2606 .list = LIST_HEAD_INIT(this_flusher.list),
2607 .flush_color = -1,
2608 .done = COMPLETION_INITIALIZER_ONSTACK(this_flusher.done),
2609 };
2610 int next_color;
2611
2612 lock_map_acquire(&wq->lockdep_map);
2613 lock_map_release(&wq->lockdep_map);
2614
2615 mutex_lock(&wq->mutex);
2616
2617 /*
2618 * Start-to-wait phase
2619 */
2620 next_color = work_next_color(wq->work_color);
2621
2622 if (next_color != wq->flush_color) {
2623 /*
2624 * Color space is not full. The current work_color
2625 * becomes our flush_color and work_color is advanced
2626 * by one.
2627 */
2628 WARN_ON_ONCE(!list_empty(&wq->flusher_overflow));
2629 this_flusher.flush_color = wq->work_color;
2630 wq->work_color = next_color;
2631
2632 if (!wq->first_flusher) {
2633 /* no flush in progress, become the first flusher */
2634 WARN_ON_ONCE(wq->flush_color != this_flusher.flush_color);
2635
2636 wq->first_flusher = &this_flusher;
2637
2638 if (!flush_workqueue_prep_pwqs(wq, wq->flush_color,
2639 wq->work_color)) {
2640 /* nothing to flush, done */
2641 wq->flush_color = next_color;
2642 wq->first_flusher = NULL;
2643 goto out_unlock;
2644 }
2645 } else {
2646 /* wait in queue */
2647 WARN_ON_ONCE(wq->flush_color == this_flusher.flush_color);
2648 list_add_tail(&this_flusher.list, &wq->flusher_queue);
2649 flush_workqueue_prep_pwqs(wq, -1, wq->work_color);
2650 }
2651 } else {
2652 /*
2653 * Oops, color space is full, wait on overflow queue.
2654 * The next flush completion will assign us
2655 * flush_color and transfer to flusher_queue.
2656 */
2657 list_add_tail(&this_flusher.list, &wq->flusher_overflow);
2658 }
2659
2660 check_flush_dependency(wq, NULL);
2661
2662 mutex_unlock(&wq->mutex);
2663
2664 wait_for_completion(&this_flusher.done);
2665
2666 /*
2667 * Wake-up-and-cascade phase
2668 *
2669 * First flushers are responsible for cascading flushes and
2670 * handling overflow. Non-first flushers can simply return.
2671 */
2672 if (wq->first_flusher != &this_flusher)
2673 return;
2674
2675 mutex_lock(&wq->mutex);
2676
2677 /* we might have raced, check again with mutex held */
2678 if (wq->first_flusher != &this_flusher)
2679 goto out_unlock;
2680
2681 wq->first_flusher = NULL;
2682
2683 WARN_ON_ONCE(!list_empty(&this_flusher.list));
2684 WARN_ON_ONCE(wq->flush_color != this_flusher.flush_color);
2685
2686 while (true) {
2687 struct wq_flusher *next, *tmp;
2688
2689 /* complete all the flushers sharing the current flush color */
2690 list_for_each_entry_safe(next, tmp, &wq->flusher_queue, list) {
2691 if (next->flush_color != wq->flush_color)
2692 break;
2693 list_del_init(&next->list);
2694 complete(&next->done);
2695 }
2696
2697 WARN_ON_ONCE(!list_empty(&wq->flusher_overflow) &&
2698 wq->flush_color != work_next_color(wq->work_color));
2699
2700 /* this flush_color is finished, advance by one */
2701 wq->flush_color = work_next_color(wq->flush_color);
2702
2703 /* one color has been freed, handle overflow queue */
2704 if (!list_empty(&wq->flusher_overflow)) {
2705 /*
2706 * Assign the same color to all overflowed
2707 * flushers, advance work_color and append to
2708 * flusher_queue. This is the start-to-wait
2709 * phase for these overflowed flushers.
2710 */
2711 list_for_each_entry(tmp, &wq->flusher_overflow, list)
2712 tmp->flush_color = wq->work_color;
2713
2714 wq->work_color = work_next_color(wq->work_color);
2715
2716 list_splice_tail_init(&wq->flusher_overflow,
2717 &wq->flusher_queue);
2718 flush_workqueue_prep_pwqs(wq, -1, wq->work_color);
2719 }
2720
2721 if (list_empty(&wq->flusher_queue)) {
2722 WARN_ON_ONCE(wq->flush_color != wq->work_color);
2723 break;
2724 }
2725
2726 /*
2727 * Need to flush more colors. Make the next flusher
2728 * the new first flusher and arm pwqs.
2729 */
2730 WARN_ON_ONCE(wq->flush_color == wq->work_color);
2731 WARN_ON_ONCE(wq->flush_color != next->flush_color);
2732
2733 list_del_init(&next->list);
2734 wq->first_flusher = next;
2735
2736 if (flush_workqueue_prep_pwqs(wq, wq->flush_color, -1))
2737 break;
2738
2739 /*
2740 * Meh... this color is already done, clear first
2741 * flusher and repeat cascading.
2742 */
2743 wq->first_flusher = NULL;
2744 }
2745
2746out_unlock:
2747 mutex_unlock(&wq->mutex);
2748}
2749EXPORT_SYMBOL(flush_workqueue);
2750
2751/**
2752 * drain_workqueue - drain a workqueue
2753 * @wq: workqueue to drain
2754 *
2755 * Wait until the workqueue becomes empty. While draining is in progress,
2756 * only chain queueing is allowed. IOW, only currently pending or running
2757 * work items on @wq can queue further work items on it. @wq is flushed
2758 * repeatedly until it becomes empty. The number of flushing is determined
2759 * by the depth of chaining and should be relatively short. Whine if it
2760 * takes too long.
2761 */
2762void drain_workqueue(struct workqueue_struct *wq)
2763{
2764 unsigned int flush_cnt = 0;
2765 struct pool_workqueue *pwq;
2766
2767 /*
2768 * __queue_work() needs to test whether there are drainers, is much
2769 * hotter than drain_workqueue() and already looks at @wq->flags.
2770 * Use __WQ_DRAINING so that queue doesn't have to check nr_drainers.
2771 */
2772 mutex_lock(&wq->mutex);
2773 if (!wq->nr_drainers++)
2774 wq->flags |= __WQ_DRAINING;
2775 mutex_unlock(&wq->mutex);
2776reflush:
2777 flush_workqueue(wq);
2778
2779 mutex_lock(&wq->mutex);
2780
2781 for_each_pwq(pwq, wq) {
2782 bool drained;
2783
2784 spin_lock_irq(&pwq->pool->lock);
2785 drained = !pwq->nr_active && list_empty(&pwq->delayed_works);
2786 spin_unlock_irq(&pwq->pool->lock);
2787
2788 if (drained)
2789 continue;
2790
2791 if (++flush_cnt == 10 ||
2792 (flush_cnt % 100 == 0 && flush_cnt <= 1000))
2793 pr_warn("workqueue %s: drain_workqueue() isn't complete after %u tries\n",
2794 wq->name, flush_cnt);
2795
2796 mutex_unlock(&wq->mutex);
2797 goto reflush;
2798 }
2799
2800 if (!--wq->nr_drainers)
2801 wq->flags &= ~__WQ_DRAINING;
2802 mutex_unlock(&wq->mutex);
2803}
2804EXPORT_SYMBOL_GPL(drain_workqueue);
2805
2806static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr)
2807{
2808 struct worker *worker = NULL;
2809 struct worker_pool *pool;
2810 struct pool_workqueue *pwq;
2811
2812 might_sleep();
2813
2814 local_irq_disable();
2815 pool = get_work_pool(work);
2816 if (!pool) {
2817 local_irq_enable();
2818 return false;
2819 }
2820
2821 spin_lock(&pool->lock);
2822 /* see the comment in try_to_grab_pending() with the same code */
2823 pwq = get_work_pwq(work);
2824 if (pwq) {
2825 if (unlikely(pwq->pool != pool))
2826 goto already_gone;
2827 } else {
2828 worker = find_worker_executing_work(pool, work);
2829 if (!worker)
2830 goto already_gone;
2831 pwq = worker->current_pwq;
2832 }
2833
2834 check_flush_dependency(pwq->wq, work);
2835
2836 insert_wq_barrier(pwq, barr, work, worker);
2837 spin_unlock_irq(&pool->lock);
2838
2839 /*
2840 * If @max_active is 1 or rescuer is in use, flushing another work
2841 * item on the same workqueue may lead to deadlock. Make sure the
2842 * flusher is not running on the same workqueue by verifying write
2843 * access.
2844 */
2845 if (pwq->wq->saved_max_active == 1 || pwq->wq->rescuer)
2846 lock_map_acquire(&pwq->wq->lockdep_map);
2847 else
2848 lock_map_acquire_read(&pwq->wq->lockdep_map);
2849 lock_map_release(&pwq->wq->lockdep_map);
2850
2851 return true;
2852already_gone:
2853 spin_unlock_irq(&pool->lock);
2854 return false;
2855}
2856
2857/**
2858 * flush_work - wait for a work to finish executing the last queueing instance
2859 * @work: the work to flush
2860 *
2861 * Wait until @work has finished execution. @work is guaranteed to be idle
2862 * on return if it hasn't been requeued since flush started.
2863 *
2864 * Return:
2865 * %true if flush_work() waited for the work to finish execution,
2866 * %false if it was already idle.
2867 */
2868bool flush_work(struct work_struct *work)
2869{
2870 struct wq_barrier barr;
2871
2872 lock_map_acquire(&work->lockdep_map);
2873 lock_map_release(&work->lockdep_map);
2874
2875 if (start_flush_work(work, &barr)) {
2876 wait_for_completion(&barr.done);
2877 destroy_work_on_stack(&barr.work);
2878 return true;
2879 } else {
2880 return false;
2881 }
2882}
2883EXPORT_SYMBOL_GPL(flush_work);
2884
2885struct cwt_wait {
2886 wait_queue_t wait;
2887 struct work_struct *work;
2888};
2889
2890static int cwt_wakefn(wait_queue_t *wait, unsigned mode, int sync, void *key)
2891{
2892 struct cwt_wait *cwait = container_of(wait, struct cwt_wait, wait);
2893
2894 if (cwait->work != key)
2895 return 0;
2896 return autoremove_wake_function(wait, mode, sync, key);
2897}
2898
2899static bool __cancel_work_timer(struct work_struct *work, bool is_dwork)
2900{
2901 static DECLARE_WAIT_QUEUE_HEAD(cancel_waitq);
2902 unsigned long flags;
2903 int ret;
2904
2905 do {
2906 ret = try_to_grab_pending(work, is_dwork, &flags);
2907 /*
2908 * If someone else is already canceling, wait for it to
2909 * finish. flush_work() doesn't work for PREEMPT_NONE
2910 * because we may get scheduled between @work's completion
2911 * and the other canceling task resuming and clearing
2912 * CANCELING - flush_work() will return false immediately
2913 * as @work is no longer busy, try_to_grab_pending() will
2914 * return -ENOENT as @work is still being canceled and the
2915 * other canceling task won't be able to clear CANCELING as
2916 * we're hogging the CPU.
2917 *
2918 * Let's wait for completion using a waitqueue. As this
2919 * may lead to the thundering herd problem, use a custom
2920 * wake function which matches @work along with exclusive
2921 * wait and wakeup.
2922 */
2923 if (unlikely(ret == -ENOENT)) {
2924 struct cwt_wait cwait;
2925
2926 init_wait(&cwait.wait);
2927 cwait.wait.func = cwt_wakefn;
2928 cwait.work = work;
2929
2930 prepare_to_wait_exclusive(&cancel_waitq, &cwait.wait,
2931 TASK_UNINTERRUPTIBLE);
2932 if (work_is_canceling(work))
2933 schedule();
2934 finish_wait(&cancel_waitq, &cwait.wait);
2935 }
2936 } while (unlikely(ret < 0));
2937
2938 /* tell other tasks trying to grab @work to back off */
2939 mark_work_canceling(work);
2940 local_irq_restore(flags);
2941
2942 flush_work(work);
2943 clear_work_data(work);
2944
2945 /*
2946 * Paired with prepare_to_wait() above so that either
2947 * waitqueue_active() is visible here or !work_is_canceling() is
2948 * visible there.
2949 */
2950 smp_mb();
2951 if (waitqueue_active(&cancel_waitq))
2952 __wake_up(&cancel_waitq, TASK_NORMAL, 1, work);
2953
2954 return ret;
2955}
2956
2957/**
2958 * cancel_work_sync - cancel a work and wait for it to finish
2959 * @work: the work to cancel
2960 *
2961 * Cancel @work and wait for its execution to finish. This function
2962 * can be used even if the work re-queues itself or migrates to
2963 * another workqueue. On return from this function, @work is
2964 * guaranteed to be not pending or executing on any CPU.
2965 *
2966 * cancel_work_sync(&delayed_work->work) must not be used for
2967 * delayed_work's. Use cancel_delayed_work_sync() instead.
2968 *
2969 * The caller must ensure that the workqueue on which @work was last
2970 * queued can't be destroyed before this function returns.
2971 *
2972 * Return:
2973 * %true if @work was pending, %false otherwise.
2974 */
2975bool cancel_work_sync(struct work_struct *work)
2976{
2977 return __cancel_work_timer(work, false);
2978}
2979EXPORT_SYMBOL_GPL(cancel_work_sync);
2980
2981/**
2982 * flush_delayed_work - wait for a dwork to finish executing the last queueing
2983 * @dwork: the delayed work to flush
2984 *
2985 * Delayed timer is cancelled and the pending work is queued for
2986 * immediate execution. Like flush_work(), this function only
2987 * considers the last queueing instance of @dwork.
2988 *
2989 * Return:
2990 * %true if flush_work() waited for the work to finish execution,
2991 * %false if it was already idle.
2992 */
2993bool flush_delayed_work(struct delayed_work *dwork)
2994{
2995 local_irq_disable();
2996 if (del_timer_sync(&dwork->timer))
2997 __queue_work(dwork->cpu, dwork->wq, &dwork->work);
2998 local_irq_enable();
2999 return flush_work(&dwork->work);
3000}
3001EXPORT_SYMBOL(flush_delayed_work);
3002
3003/**
3004 * cancel_delayed_work - cancel a delayed work
3005 * @dwork: delayed_work to cancel
3006 *
3007 * Kill off a pending delayed_work.
3008 *
3009 * Return: %true if @dwork was pending and canceled; %false if it wasn't
3010 * pending.
3011 *
3012 * Note:
3013 * The work callback function may still be running on return, unless
3014 * it returns %true and the work doesn't re-arm itself. Explicitly flush or
3015 * use cancel_delayed_work_sync() to wait on it.
3016 *
3017 * This function is safe to call from any context including IRQ handler.
3018 */
3019bool cancel_delayed_work(struct delayed_work *dwork)
3020{
3021 unsigned long flags;
3022 int ret;
3023
3024 do {
3025 ret = try_to_grab_pending(&dwork->work, true, &flags);
3026 } while (unlikely(ret == -EAGAIN));
3027
3028 if (unlikely(ret < 0))
3029 return false;
3030
3031 set_work_pool_and_clear_pending(&dwork->work,
3032 get_work_pool_id(&dwork->work));
3033 local_irq_restore(flags);
3034 return ret;
3035}
3036EXPORT_SYMBOL(cancel_delayed_work);
3037
3038/**
3039 * cancel_delayed_work_sync - cancel a delayed work and wait for it to finish
3040 * @dwork: the delayed work cancel
3041 *
3042 * This is cancel_work_sync() for delayed works.
3043 *
3044 * Return:
3045 * %true if @dwork was pending, %false otherwise.
3046 */
3047bool cancel_delayed_work_sync(struct delayed_work *dwork)
3048{
3049 return __cancel_work_timer(&dwork->work, true);
3050}
3051EXPORT_SYMBOL(cancel_delayed_work_sync);
3052
3053/**
3054 * schedule_on_each_cpu - execute a function synchronously on each online CPU
3055 * @func: the function to call
3056 *
3057 * schedule_on_each_cpu() executes @func on each online CPU using the
3058 * system workqueue and blocks until all CPUs have completed.
3059 * schedule_on_each_cpu() is very slow.
3060 *
3061 * Return:
3062 * 0 on success, -errno on failure.
3063 */
3064int schedule_on_each_cpu(work_func_t func)
3065{
3066 int cpu;
3067 struct work_struct __percpu *works;
3068
3069 works = alloc_percpu(struct work_struct);
3070 if (!works)
3071 return -ENOMEM;
3072
3073 get_online_cpus();
3074
3075 for_each_online_cpu(cpu) {
3076 struct work_struct *work = per_cpu_ptr(works, cpu);
3077
3078 INIT_WORK(work, func);
3079 schedule_work_on(cpu, work);
3080 }
3081
3082 for_each_online_cpu(cpu)
3083 flush_work(per_cpu_ptr(works, cpu));
3084
3085 put_online_cpus();
3086 free_percpu(works);
3087 return 0;
3088}
3089
3090/**
3091 * execute_in_process_context - reliably execute the routine with user context
3092 * @fn: the function to execute
3093 * @ew: guaranteed storage for the execute work structure (must
3094 * be available when the work executes)
3095 *
3096 * Executes the function immediately if process context is available,
3097 * otherwise schedules the function for delayed execution.
3098 *
3099 * Return: 0 - function was executed
3100 * 1 - function was scheduled for execution
3101 */
3102int execute_in_process_context(work_func_t fn, struct execute_work *ew)
3103{
3104 if (!in_interrupt()) {
3105 fn(&ew->work);
3106 return 0;
3107 }
3108
3109 INIT_WORK(&ew->work, fn);
3110 schedule_work(&ew->work);
3111
3112 return 1;
3113}
3114EXPORT_SYMBOL_GPL(execute_in_process_context);
3115
3116/**
3117 * free_workqueue_attrs - free a workqueue_attrs
3118 * @attrs: workqueue_attrs to free
3119 *
3120 * Undo alloc_workqueue_attrs().
3121 */
3122void free_workqueue_attrs(struct workqueue_attrs *attrs)
3123{
3124 if (attrs) {
3125 free_cpumask_var(attrs->cpumask);
3126 kfree(attrs);
3127 }
3128}
3129
3130/**
3131 * alloc_workqueue_attrs - allocate a workqueue_attrs
3132 * @gfp_mask: allocation mask to use
3133 *
3134 * Allocate a new workqueue_attrs, initialize with default settings and
3135 * return it.
3136 *
3137 * Return: The allocated new workqueue_attr on success. %NULL on failure.
3138 */
3139struct workqueue_attrs *alloc_workqueue_attrs(gfp_t gfp_mask)
3140{
3141 struct workqueue_attrs *attrs;
3142
3143 attrs = kzalloc(sizeof(*attrs), gfp_mask);
3144 if (!attrs)
3145 goto fail;
3146 if (!alloc_cpumask_var(&attrs->cpumask, gfp_mask))
3147 goto fail;
3148
3149 cpumask_copy(attrs->cpumask, cpu_possible_mask);
3150 return attrs;
3151fail:
3152 free_workqueue_attrs(attrs);
3153 return NULL;
3154}
3155
3156static void copy_workqueue_attrs(struct workqueue_attrs *to,
3157 const struct workqueue_attrs *from)
3158{
3159 to->nice = from->nice;
3160 cpumask_copy(to->cpumask, from->cpumask);
3161 /*
3162 * Unlike hash and equality test, this function doesn't ignore
3163 * ->no_numa as it is used for both pool and wq attrs. Instead,
3164 * get_unbound_pool() explicitly clears ->no_numa after copying.
3165 */
3166 to->no_numa = from->no_numa;
3167}
3168
3169/* hash value of the content of @attr */
3170static u32 wqattrs_hash(const struct workqueue_attrs *attrs)
3171{
3172 u32 hash = 0;
3173
3174 hash = jhash_1word(attrs->nice, hash);
3175 hash = jhash(cpumask_bits(attrs->cpumask),
3176 BITS_TO_LONGS(nr_cpumask_bits) * sizeof(long), hash);
3177 return hash;
3178}
3179
3180/* content equality test */
3181static bool wqattrs_equal(const struct workqueue_attrs *a,
3182 const struct workqueue_attrs *b)
3183{
3184 if (a->nice != b->nice)
3185 return false;
3186 if (!cpumask_equal(a->cpumask, b->cpumask))
3187 return false;
3188 return true;
3189}
3190
3191/**
3192 * init_worker_pool - initialize a newly zalloc'd worker_pool
3193 * @pool: worker_pool to initialize
3194 *
3195 * Initialize a newly zalloc'd @pool. It also allocates @pool->attrs.
3196 *
3197 * Return: 0 on success, -errno on failure. Even on failure, all fields
3198 * inside @pool proper are initialized and put_unbound_pool() can be called
3199 * on @pool safely to release it.
3200 */
3201static int init_worker_pool(struct worker_pool *pool)
3202{
3203 spin_lock_init(&pool->lock);
3204 pool->id = -1;
3205 pool->cpu = -1;
3206 pool->node = NUMA_NO_NODE;
3207 pool->flags |= POOL_DISASSOCIATED;
3208 pool->watchdog_ts = jiffies;
3209 INIT_LIST_HEAD(&pool->worklist);
3210 INIT_LIST_HEAD(&pool->idle_list);
3211 hash_init(pool->busy_hash);
3212
3213 init_timer_deferrable(&pool->idle_timer);
3214 pool->idle_timer.function = idle_worker_timeout;
3215 pool->idle_timer.data = (unsigned long)pool;
3216
3217 setup_timer(&pool->mayday_timer, pool_mayday_timeout,
3218 (unsigned long)pool);
3219
3220 mutex_init(&pool->manager_arb);
3221 mutex_init(&pool->attach_mutex);
3222 INIT_LIST_HEAD(&pool->workers);
3223
3224 ida_init(&pool->worker_ida);
3225 INIT_HLIST_NODE(&pool->hash_node);
3226 pool->refcnt = 1;
3227
3228 /* shouldn't fail above this point */
3229 pool->attrs = alloc_workqueue_attrs(GFP_KERNEL);
3230 if (!pool->attrs)
3231 return -ENOMEM;
3232 return 0;
3233}
3234
3235static void rcu_free_wq(struct rcu_head *rcu)
3236{
3237 struct workqueue_struct *wq =
3238 container_of(rcu, struct workqueue_struct, rcu);
3239
3240 if (!(wq->flags & WQ_UNBOUND))
3241 free_percpu(wq->cpu_pwqs);
3242 else
3243 free_workqueue_attrs(wq->unbound_attrs);
3244
3245 kfree(wq->rescuer);
3246 kfree(wq);
3247}
3248
3249static void rcu_free_pool(struct rcu_head *rcu)
3250{
3251 struct worker_pool *pool = container_of(rcu, struct worker_pool, rcu);
3252
3253 ida_destroy(&pool->worker_ida);
3254 free_workqueue_attrs(pool->attrs);
3255 kfree(pool);
3256}
3257
3258/**
3259 * put_unbound_pool - put a worker_pool
3260 * @pool: worker_pool to put
3261 *
3262 * Put @pool. If its refcnt reaches zero, it gets destroyed in sched-RCU
3263 * safe manner. get_unbound_pool() calls this function on its failure path
3264 * and this function should be able to release pools which went through,
3265 * successfully or not, init_worker_pool().
3266 *
3267 * Should be called with wq_pool_mutex held.
3268 */
3269static void put_unbound_pool(struct worker_pool *pool)
3270{
3271 DECLARE_COMPLETION_ONSTACK(detach_completion);
3272 struct worker *worker;
3273
3274 lockdep_assert_held(&wq_pool_mutex);
3275
3276 if (--pool->refcnt)
3277 return;
3278
3279 /* sanity checks */
3280 if (WARN_ON(!(pool->cpu < 0)) ||
3281 WARN_ON(!list_empty(&pool->worklist)))
3282 return;
3283
3284 /* release id and unhash */
3285 if (pool->id >= 0)
3286 idr_remove(&worker_pool_idr, pool->id);
3287 hash_del(&pool->hash_node);
3288
3289 /*
3290 * Become the manager and destroy all workers. Grabbing
3291 * manager_arb prevents @pool's workers from blocking on
3292 * attach_mutex.
3293 */
3294 mutex_lock(&pool->manager_arb);
3295
3296 spin_lock_irq(&pool->lock);
3297 while ((worker = first_idle_worker(pool)))
3298 destroy_worker(worker);
3299 WARN_ON(pool->nr_workers || pool->nr_idle);
3300 spin_unlock_irq(&pool->lock);
3301
3302 mutex_lock(&pool->attach_mutex);
3303 if (!list_empty(&pool->workers))
3304 pool->detach_completion = &detach_completion;
3305 mutex_unlock(&pool->attach_mutex);
3306
3307 if (pool->detach_completion)
3308 wait_for_completion(pool->detach_completion);
3309
3310 mutex_unlock(&pool->manager_arb);
3311
3312 /* shut down the timers */
3313 del_timer_sync(&pool->idle_timer);
3314 del_timer_sync(&pool->mayday_timer);
3315
3316 /* sched-RCU protected to allow dereferences from get_work_pool() */
3317 call_rcu_sched(&pool->rcu, rcu_free_pool);
3318}
3319
3320/**
3321 * get_unbound_pool - get a worker_pool with the specified attributes
3322 * @attrs: the attributes of the worker_pool to get
3323 *
3324 * Obtain a worker_pool which has the same attributes as @attrs, bump the
3325 * reference count and return it. If there already is a matching
3326 * worker_pool, it will be used; otherwise, this function attempts to
3327 * create a new one.
3328 *
3329 * Should be called with wq_pool_mutex held.
3330 *
3331 * Return: On success, a worker_pool with the same attributes as @attrs.
3332 * On failure, %NULL.
3333 */
3334static struct worker_pool *get_unbound_pool(const struct workqueue_attrs *attrs)
3335{
3336 u32 hash = wqattrs_hash(attrs);
3337 struct worker_pool *pool;
3338 int node;
3339 int target_node = NUMA_NO_NODE;
3340
3341 lockdep_assert_held(&wq_pool_mutex);
3342
3343 /* do we already have a matching pool? */
3344 hash_for_each_possible(unbound_pool_hash, pool, hash_node, hash) {
3345 if (wqattrs_equal(pool->attrs, attrs)) {
3346 pool->refcnt++;
3347 return pool;
3348 }
3349 }
3350
3351 /* if cpumask is contained inside a NUMA node, we belong to that node */
3352 if (wq_numa_enabled) {
3353 for_each_node(node) {
3354 if (cpumask_subset(attrs->cpumask,
3355 wq_numa_possible_cpumask[node])) {
3356 target_node = node;
3357 break;
3358 }
3359 }
3360 }
3361
3362 /* nope, create a new one */
3363 pool = kzalloc_node(sizeof(*pool), GFP_KERNEL, target_node);
3364 if (!pool || init_worker_pool(pool) < 0)
3365 goto fail;
3366
3367 lockdep_set_subclass(&pool->lock, 1); /* see put_pwq() */
3368 copy_workqueue_attrs(pool->attrs, attrs);
3369 pool->node = target_node;
3370
3371 /*
3372 * no_numa isn't a worker_pool attribute, always clear it. See
3373 * 'struct workqueue_attrs' comments for detail.
3374 */
3375 pool->attrs->no_numa = false;
3376
3377 if (worker_pool_assign_id(pool) < 0)
3378 goto fail;
3379
3380 /* create and start the initial worker */
3381 if (!create_worker(pool))
3382 goto fail;
3383
3384 /* install */
3385 hash_add(unbound_pool_hash, &pool->hash_node, hash);
3386
3387 return pool;
3388fail:
3389 if (pool)
3390 put_unbound_pool(pool);
3391 return NULL;
3392}
3393
3394static void rcu_free_pwq(struct rcu_head *rcu)
3395{
3396 kmem_cache_free(pwq_cache,
3397 container_of(rcu, struct pool_workqueue, rcu));
3398}
3399
3400/*
3401 * Scheduled on system_wq by put_pwq() when an unbound pwq hits zero refcnt
3402 * and needs to be destroyed.
3403 */
3404static void pwq_unbound_release_workfn(struct work_struct *work)
3405{
3406 struct pool_workqueue *pwq = container_of(work, struct pool_workqueue,
3407 unbound_release_work);
3408 struct workqueue_struct *wq = pwq->wq;
3409 struct worker_pool *pool = pwq->pool;
3410 bool is_last;
3411
3412 if (WARN_ON_ONCE(!(wq->flags & WQ_UNBOUND)))
3413 return;
3414
3415 mutex_lock(&wq->mutex);
3416 list_del_rcu(&pwq->pwqs_node);
3417 is_last = list_empty(&wq->pwqs);
3418 mutex_unlock(&wq->mutex);
3419
3420 mutex_lock(&wq_pool_mutex);
3421 put_unbound_pool(pool);
3422 mutex_unlock(&wq_pool_mutex);
3423
3424 call_rcu_sched(&pwq->rcu, rcu_free_pwq);
3425
3426 /*
3427 * If we're the last pwq going away, @wq is already dead and no one
3428 * is gonna access it anymore. Schedule RCU free.
3429 */
3430 if (is_last)
3431 call_rcu_sched(&wq->rcu, rcu_free_wq);
3432}
3433
3434/**
3435 * pwq_adjust_max_active - update a pwq's max_active to the current setting
3436 * @pwq: target pool_workqueue
3437 *
3438 * If @pwq isn't freezing, set @pwq->max_active to the associated
3439 * workqueue's saved_max_active and activate delayed work items
3440 * accordingly. If @pwq is freezing, clear @pwq->max_active to zero.
3441 */
3442static void pwq_adjust_max_active(struct pool_workqueue *pwq)
3443{
3444 struct workqueue_struct *wq = pwq->wq;
3445 bool freezable = wq->flags & WQ_FREEZABLE;
3446
3447 /* for @wq->saved_max_active */
3448 lockdep_assert_held(&wq->mutex);
3449
3450 /* fast exit for non-freezable wqs */
3451 if (!freezable && pwq->max_active == wq->saved_max_active)
3452 return;
3453
3454 spin_lock_irq(&pwq->pool->lock);
3455
3456 /*
3457 * During [un]freezing, the caller is responsible for ensuring that
3458 * this function is called at least once after @workqueue_freezing
3459 * is updated and visible.
3460 */
3461 if (!freezable || !workqueue_freezing) {
3462 pwq->max_active = wq->saved_max_active;
3463
3464 while (!list_empty(&pwq->delayed_works) &&
3465 pwq->nr_active < pwq->max_active)
3466 pwq_activate_first_delayed(pwq);
3467
3468 /*
3469 * Need to kick a worker after thawed or an unbound wq's
3470 * max_active is bumped. It's a slow path. Do it always.
3471 */
3472 wake_up_worker(pwq->pool);
3473 } else {
3474 pwq->max_active = 0;
3475 }
3476
3477 spin_unlock_irq(&pwq->pool->lock);
3478}
3479
3480/* initialize newly alloced @pwq which is associated with @wq and @pool */
3481static void init_pwq(struct pool_workqueue *pwq, struct workqueue_struct *wq,
3482 struct worker_pool *pool)
3483{
3484 BUG_ON((unsigned long)pwq & WORK_STRUCT_FLAG_MASK);
3485
3486 memset(pwq, 0, sizeof(*pwq));
3487
3488 pwq->pool = pool;
3489 pwq->wq = wq;
3490 pwq->flush_color = -1;
3491 pwq->refcnt = 1;
3492 INIT_LIST_HEAD(&pwq->delayed_works);
3493 INIT_LIST_HEAD(&pwq->pwqs_node);
3494 INIT_LIST_HEAD(&pwq->mayday_node);
3495 INIT_WORK(&pwq->unbound_release_work, pwq_unbound_release_workfn);
3496}
3497
3498/* sync @pwq with the current state of its associated wq and link it */
3499static void link_pwq(struct pool_workqueue *pwq)
3500{
3501 struct workqueue_struct *wq = pwq->wq;
3502
3503 lockdep_assert_held(&wq->mutex);
3504
3505 /* may be called multiple times, ignore if already linked */
3506 if (!list_empty(&pwq->pwqs_node))
3507 return;
3508
3509 /* set the matching work_color */
3510 pwq->work_color = wq->work_color;
3511
3512 /* sync max_active to the current setting */
3513 pwq_adjust_max_active(pwq);
3514
3515 /* link in @pwq */
3516 list_add_rcu(&pwq->pwqs_node, &wq->pwqs);
3517}
3518
3519/* obtain a pool matching @attr and create a pwq associating the pool and @wq */
3520static struct pool_workqueue *alloc_unbound_pwq(struct workqueue_struct *wq,
3521 const struct workqueue_attrs *attrs)
3522{
3523 struct worker_pool *pool;
3524 struct pool_workqueue *pwq;
3525
3526 lockdep_assert_held(&wq_pool_mutex);
3527
3528 pool = get_unbound_pool(attrs);
3529 if (!pool)
3530 return NULL;
3531
3532 pwq = kmem_cache_alloc_node(pwq_cache, GFP_KERNEL, pool->node);
3533 if (!pwq) {
3534 put_unbound_pool(pool);
3535 return NULL;
3536 }
3537
3538 init_pwq(pwq, wq, pool);
3539 return pwq;
3540}
3541
3542/**
3543 * wq_calc_node_cpumask - calculate a wq_attrs' cpumask for the specified node
3544 * @attrs: the wq_attrs of the default pwq of the target workqueue
3545 * @node: the target NUMA node
3546 * @cpu_going_down: if >= 0, the CPU to consider as offline
3547 * @cpumask: outarg, the resulting cpumask
3548 *
3549 * Calculate the cpumask a workqueue with @attrs should use on @node. If
3550 * @cpu_going_down is >= 0, that cpu is considered offline during
3551 * calculation. The result is stored in @cpumask.
3552 *
3553 * If NUMA affinity is not enabled, @attrs->cpumask is always used. If
3554 * enabled and @node has online CPUs requested by @attrs, the returned
3555 * cpumask is the intersection of the possible CPUs of @node and
3556 * @attrs->cpumask.
3557 *
3558 * The caller is responsible for ensuring that the cpumask of @node stays
3559 * stable.
3560 *
3561 * Return: %true if the resulting @cpumask is different from @attrs->cpumask,
3562 * %false if equal.
3563 */
3564static bool wq_calc_node_cpumask(const struct workqueue_attrs *attrs, int node,
3565 int cpu_going_down, cpumask_t *cpumask)
3566{
3567 if (!wq_numa_enabled || attrs->no_numa)
3568 goto use_dfl;
3569
3570 /* does @node have any online CPUs @attrs wants? */
3571 cpumask_and(cpumask, cpumask_of_node(node), attrs->cpumask);
3572 if (cpu_going_down >= 0)
3573 cpumask_clear_cpu(cpu_going_down, cpumask);
3574
3575 if (cpumask_empty(cpumask))
3576 goto use_dfl;
3577
3578 /* yeap, return possible CPUs in @node that @attrs wants */
3579 cpumask_and(cpumask, attrs->cpumask, wq_numa_possible_cpumask[node]);
3580 return !cpumask_equal(cpumask, attrs->cpumask);
3581
3582use_dfl:
3583 cpumask_copy(cpumask, attrs->cpumask);
3584 return false;
3585}
3586
3587/* install @pwq into @wq's numa_pwq_tbl[] for @node and return the old pwq */
3588static struct pool_workqueue *numa_pwq_tbl_install(struct workqueue_struct *wq,
3589 int node,
3590 struct pool_workqueue *pwq)
3591{
3592 struct pool_workqueue *old_pwq;
3593
3594 lockdep_assert_held(&wq_pool_mutex);
3595 lockdep_assert_held(&wq->mutex);
3596
3597 /* link_pwq() can handle duplicate calls */
3598 link_pwq(pwq);
3599
3600 old_pwq = rcu_access_pointer(wq->numa_pwq_tbl[node]);
3601 rcu_assign_pointer(wq->numa_pwq_tbl[node], pwq);
3602 return old_pwq;
3603}
3604
3605/* context to store the prepared attrs & pwqs before applying */
3606struct apply_wqattrs_ctx {
3607 struct workqueue_struct *wq; /* target workqueue */
3608 struct workqueue_attrs *attrs; /* attrs to apply */
3609 struct list_head list; /* queued for batching commit */
3610 struct pool_workqueue *dfl_pwq;
3611 struct pool_workqueue *pwq_tbl[];
3612};
3613
3614/* free the resources after success or abort */
3615static void apply_wqattrs_cleanup(struct apply_wqattrs_ctx *ctx)
3616{
3617 if (ctx) {
3618 int node;
3619
3620 for_each_node(node)
3621 put_pwq_unlocked(ctx->pwq_tbl[node]);
3622 put_pwq_unlocked(ctx->dfl_pwq);
3623
3624 free_workqueue_attrs(ctx->attrs);
3625
3626 kfree(ctx);
3627 }
3628}
3629
3630/* allocate the attrs and pwqs for later installation */
3631static struct apply_wqattrs_ctx *
3632apply_wqattrs_prepare(struct workqueue_struct *wq,
3633 const struct workqueue_attrs *attrs)
3634{
3635 struct apply_wqattrs_ctx *ctx;
3636 struct workqueue_attrs *new_attrs, *tmp_attrs;
3637 int node;
3638
3639 lockdep_assert_held(&wq_pool_mutex);
3640
3641 ctx = kzalloc(sizeof(*ctx) + nr_node_ids * sizeof(ctx->pwq_tbl[0]),
3642 GFP_KERNEL);
3643
3644 new_attrs = alloc_workqueue_attrs(GFP_KERNEL);
3645 tmp_attrs = alloc_workqueue_attrs(GFP_KERNEL);
3646 if (!ctx || !new_attrs || !tmp_attrs)
3647 goto out_free;
3648
3649 /*
3650 * Calculate the attrs of the default pwq.
3651 * If the user configured cpumask doesn't overlap with the
3652 * wq_unbound_cpumask, we fallback to the wq_unbound_cpumask.
3653 */
3654 copy_workqueue_attrs(new_attrs, attrs);
3655 cpumask_and(new_attrs->cpumask, new_attrs->cpumask, wq_unbound_cpumask);
3656 if (unlikely(cpumask_empty(new_attrs->cpumask)))
3657 cpumask_copy(new_attrs->cpumask, wq_unbound_cpumask);
3658
3659 /*
3660 * We may create multiple pwqs with differing cpumasks. Make a
3661 * copy of @new_attrs which will be modified and used to obtain
3662 * pools.
3663 */
3664 copy_workqueue_attrs(tmp_attrs, new_attrs);
3665
3666 /*
3667 * If something goes wrong during CPU up/down, we'll fall back to
3668 * the default pwq covering whole @attrs->cpumask. Always create
3669 * it even if we don't use it immediately.
3670 */
3671 ctx->dfl_pwq = alloc_unbound_pwq(wq, new_attrs);
3672 if (!ctx->dfl_pwq)
3673 goto out_free;
3674
3675 for_each_node(node) {
3676 if (wq_calc_node_cpumask(new_attrs, node, -1, tmp_attrs->cpumask)) {
3677 ctx->pwq_tbl[node] = alloc_unbound_pwq(wq, tmp_attrs);
3678 if (!ctx->pwq_tbl[node])
3679 goto out_free;
3680 } else {
3681 ctx->dfl_pwq->refcnt++;
3682 ctx->pwq_tbl[node] = ctx->dfl_pwq;
3683 }
3684 }
3685
3686 /* save the user configured attrs and sanitize it. */
3687 copy_workqueue_attrs(new_attrs, attrs);
3688 cpumask_and(new_attrs->cpumask, new_attrs->cpumask, cpu_possible_mask);
3689 ctx->attrs = new_attrs;
3690
3691 ctx->wq = wq;
3692 free_workqueue_attrs(tmp_attrs);
3693 return ctx;
3694
3695out_free:
3696 free_workqueue_attrs(tmp_attrs);
3697 free_workqueue_attrs(new_attrs);
3698 apply_wqattrs_cleanup(ctx);
3699 return NULL;
3700}
3701
3702/* set attrs and install prepared pwqs, @ctx points to old pwqs on return */
3703static void apply_wqattrs_commit(struct apply_wqattrs_ctx *ctx)
3704{
3705 int node;
3706
3707 /* all pwqs have been created successfully, let's install'em */
3708 mutex_lock(&ctx->wq->mutex);
3709
3710 copy_workqueue_attrs(ctx->wq->unbound_attrs, ctx->attrs);
3711
3712 /* save the previous pwq and install the new one */
3713 for_each_node(node)
3714 ctx->pwq_tbl[node] = numa_pwq_tbl_install(ctx->wq, node,
3715 ctx->pwq_tbl[node]);
3716
3717 /* @dfl_pwq might not have been used, ensure it's linked */
3718 link_pwq(ctx->dfl_pwq);
3719 swap(ctx->wq->dfl_pwq, ctx->dfl_pwq);
3720
3721 mutex_unlock(&ctx->wq->mutex);
3722}
3723
3724static void apply_wqattrs_lock(void)
3725{
3726 /* CPUs should stay stable across pwq creations and installations */
3727 get_online_cpus();
3728 mutex_lock(&wq_pool_mutex);
3729}
3730
3731static void apply_wqattrs_unlock(void)
3732{
3733 mutex_unlock(&wq_pool_mutex);
3734 put_online_cpus();
3735}
3736
3737static int apply_workqueue_attrs_locked(struct workqueue_struct *wq,
3738 const struct workqueue_attrs *attrs)
3739{
3740 struct apply_wqattrs_ctx *ctx;
3741
3742 /* only unbound workqueues can change attributes */
3743 if (WARN_ON(!(wq->flags & WQ_UNBOUND)))
3744 return -EINVAL;
3745
3746 /* creating multiple pwqs breaks ordering guarantee */
3747 if (WARN_ON((wq->flags & __WQ_ORDERED) && !list_empty(&wq->pwqs)))
3748 return -EINVAL;
3749
3750 ctx = apply_wqattrs_prepare(wq, attrs);
3751 if (!ctx)
3752 return -ENOMEM;
3753
3754 /* the ctx has been prepared successfully, let's commit it */
3755 apply_wqattrs_commit(ctx);
3756 apply_wqattrs_cleanup(ctx);
3757
3758 return 0;
3759}
3760
3761/**
3762 * apply_workqueue_attrs - apply new workqueue_attrs to an unbound workqueue
3763 * @wq: the target workqueue
3764 * @attrs: the workqueue_attrs to apply, allocated with alloc_workqueue_attrs()
3765 *
3766 * Apply @attrs to an unbound workqueue @wq. Unless disabled, on NUMA
3767 * machines, this function maps a separate pwq to each NUMA node with
3768 * possibles CPUs in @attrs->cpumask so that work items are affine to the
3769 * NUMA node it was issued on. Older pwqs are released as in-flight work
3770 * items finish. Note that a work item which repeatedly requeues itself
3771 * back-to-back will stay on its current pwq.
3772 *
3773 * Performs GFP_KERNEL allocations.
3774 *
3775 * Return: 0 on success and -errno on failure.
3776 */
3777int apply_workqueue_attrs(struct workqueue_struct *wq,
3778 const struct workqueue_attrs *attrs)
3779{
3780 int ret;
3781
3782 apply_wqattrs_lock();
3783 ret = apply_workqueue_attrs_locked(wq, attrs);
3784 apply_wqattrs_unlock();
3785
3786 return ret;
3787}
3788
3789/**
3790 * wq_update_unbound_numa - update NUMA affinity of a wq for CPU hot[un]plug
3791 * @wq: the target workqueue
3792 * @cpu: the CPU coming up or going down
3793 * @online: whether @cpu is coming up or going down
3794 *
3795 * This function is to be called from %CPU_DOWN_PREPARE, %CPU_ONLINE and
3796 * %CPU_DOWN_FAILED. @cpu is being hot[un]plugged, update NUMA affinity of
3797 * @wq accordingly.
3798 *
3799 * If NUMA affinity can't be adjusted due to memory allocation failure, it
3800 * falls back to @wq->dfl_pwq which may not be optimal but is always
3801 * correct.
3802 *
3803 * Note that when the last allowed CPU of a NUMA node goes offline for a
3804 * workqueue with a cpumask spanning multiple nodes, the workers which were
3805 * already executing the work items for the workqueue will lose their CPU
3806 * affinity and may execute on any CPU. This is similar to how per-cpu
3807 * workqueues behave on CPU_DOWN. If a workqueue user wants strict
3808 * affinity, it's the user's responsibility to flush the work item from
3809 * CPU_DOWN_PREPARE.
3810 */
3811static void wq_update_unbound_numa(struct workqueue_struct *wq, int cpu,
3812 bool online)
3813{
3814 int node = cpu_to_node(cpu);
3815 int cpu_off = online ? -1 : cpu;
3816 struct pool_workqueue *old_pwq = NULL, *pwq;
3817 struct workqueue_attrs *target_attrs;
3818 cpumask_t *cpumask;
3819
3820 lockdep_assert_held(&wq_pool_mutex);
3821
3822 if (!wq_numa_enabled || !(wq->flags & WQ_UNBOUND) ||
3823 wq->unbound_attrs->no_numa)
3824 return;
3825
3826 /*
3827 * We don't wanna alloc/free wq_attrs for each wq for each CPU.
3828 * Let's use a preallocated one. The following buf is protected by
3829 * CPU hotplug exclusion.
3830 */
3831 target_attrs = wq_update_unbound_numa_attrs_buf;
3832 cpumask = target_attrs->cpumask;
3833
3834 copy_workqueue_attrs(target_attrs, wq->unbound_attrs);
3835 pwq = unbound_pwq_by_node(wq, node);
3836
3837 /*
3838 * Let's determine what needs to be done. If the target cpumask is
3839 * different from the default pwq's, we need to compare it to @pwq's
3840 * and create a new one if they don't match. If the target cpumask
3841 * equals the default pwq's, the default pwq should be used.
3842 */
3843 if (wq_calc_node_cpumask(wq->dfl_pwq->pool->attrs, node, cpu_off, cpumask)) {
3844 if (cpumask_equal(cpumask, pwq->pool->attrs->cpumask))
3845 return;
3846 } else {
3847 goto use_dfl_pwq;
3848 }
3849
3850 /* create a new pwq */
3851 pwq = alloc_unbound_pwq(wq, target_attrs);
3852 if (!pwq) {
3853 pr_warn("workqueue: allocation failed while updating NUMA affinity of \"%s\"\n",
3854 wq->name);
3855 goto use_dfl_pwq;
3856 }
3857
3858 /* Install the new pwq. */
3859 mutex_lock(&wq->mutex);
3860 old_pwq = numa_pwq_tbl_install(wq, node, pwq);
3861 goto out_unlock;
3862
3863use_dfl_pwq:
3864 mutex_lock(&wq->mutex);
3865 spin_lock_irq(&wq->dfl_pwq->pool->lock);
3866 get_pwq(wq->dfl_pwq);
3867 spin_unlock_irq(&wq->dfl_pwq->pool->lock);
3868 old_pwq = numa_pwq_tbl_install(wq, node, wq->dfl_pwq);
3869out_unlock:
3870 mutex_unlock(&wq->mutex);
3871 put_pwq_unlocked(old_pwq);
3872}
3873
3874static int alloc_and_link_pwqs(struct workqueue_struct *wq)
3875{
3876 bool highpri = wq->flags & WQ_HIGHPRI;
3877 int cpu, ret;
3878
3879 if (!(wq->flags & WQ_UNBOUND)) {
3880 wq->cpu_pwqs = alloc_percpu(struct pool_workqueue);
3881 if (!wq->cpu_pwqs)
3882 return -ENOMEM;
3883
3884 for_each_possible_cpu(cpu) {
3885 struct pool_workqueue *pwq =
3886 per_cpu_ptr(wq->cpu_pwqs, cpu);
3887 struct worker_pool *cpu_pools =
3888 per_cpu(cpu_worker_pools, cpu);
3889
3890 init_pwq(pwq, wq, &cpu_pools[highpri]);
3891
3892 mutex_lock(&wq->mutex);
3893 link_pwq(pwq);
3894 mutex_unlock(&wq->mutex);
3895 }
3896 return 0;
3897 } else if (wq->flags & __WQ_ORDERED) {
3898 ret = apply_workqueue_attrs(wq, ordered_wq_attrs[highpri]);
3899 /* there should only be single pwq for ordering guarantee */
3900 WARN(!ret && (wq->pwqs.next != &wq->dfl_pwq->pwqs_node ||
3901 wq->pwqs.prev != &wq->dfl_pwq->pwqs_node),
3902 "ordering guarantee broken for workqueue %s\n", wq->name);
3903 return ret;
3904 } else {
3905 return apply_workqueue_attrs(wq, unbound_std_wq_attrs[highpri]);
3906 }
3907}
3908
3909static int wq_clamp_max_active(int max_active, unsigned int flags,
3910 const char *name)
3911{
3912 int lim = flags & WQ_UNBOUND ? WQ_UNBOUND_MAX_ACTIVE : WQ_MAX_ACTIVE;
3913
3914 if (max_active < 1 || max_active > lim)
3915 pr_warn("workqueue: max_active %d requested for %s is out of range, clamping between %d and %d\n",
3916 max_active, name, 1, lim);
3917
3918 return clamp_val(max_active, 1, lim);
3919}
3920
3921struct workqueue_struct *__alloc_workqueue_key(const char *fmt,
3922 unsigned int flags,
3923 int max_active,
3924 struct lock_class_key *key,
3925 const char *lock_name, ...)
3926{
3927 size_t tbl_size = 0;
3928 va_list args;
3929 struct workqueue_struct *wq;
3930 struct pool_workqueue *pwq;
3931
3932 /* see the comment above the definition of WQ_POWER_EFFICIENT */
3933 if ((flags & WQ_POWER_EFFICIENT) && wq_power_efficient)
3934 flags |= WQ_UNBOUND;
3935
3936 /* allocate wq and format name */
3937 if (flags & WQ_UNBOUND)
3938 tbl_size = nr_node_ids * sizeof(wq->numa_pwq_tbl[0]);
3939
3940 wq = kzalloc(sizeof(*wq) + tbl_size, GFP_KERNEL);
3941 if (!wq)
3942 return NULL;
3943
3944 if (flags & WQ_UNBOUND) {
3945 wq->unbound_attrs = alloc_workqueue_attrs(GFP_KERNEL);
3946 if (!wq->unbound_attrs)
3947 goto err_free_wq;
3948 }
3949
3950 va_start(args, lock_name);
3951 vsnprintf(wq->name, sizeof(wq->name), fmt, args);
3952 va_end(args);
3953
3954 max_active = max_active ?: WQ_DFL_ACTIVE;
3955 max_active = wq_clamp_max_active(max_active, flags, wq->name);
3956
3957 /* init wq */
3958 wq->flags = flags;
3959 wq->saved_max_active = max_active;
3960 mutex_init(&wq->mutex);
3961 atomic_set(&wq->nr_pwqs_to_flush, 0);
3962 INIT_LIST_HEAD(&wq->pwqs);
3963 INIT_LIST_HEAD(&wq->flusher_queue);
3964 INIT_LIST_HEAD(&wq->flusher_overflow);
3965 INIT_LIST_HEAD(&wq->maydays);
3966
3967 lockdep_init_map(&wq->lockdep_map, lock_name, key, 0);
3968 INIT_LIST_HEAD(&wq->list);
3969
3970 if (alloc_and_link_pwqs(wq) < 0)
3971 goto err_free_wq;
3972
3973 /*
3974 * Workqueues which may be used during memory reclaim should
3975 * have a rescuer to guarantee forward progress.
3976 */
3977 if (flags & WQ_MEM_RECLAIM) {
3978 struct worker *rescuer;
3979
3980 rescuer = alloc_worker(NUMA_NO_NODE);
3981 if (!rescuer)
3982 goto err_destroy;
3983
3984 rescuer->rescue_wq = wq;
3985 rescuer->task = kthread_create(rescuer_thread, rescuer, "%s",
3986 wq->name);
3987 if (IS_ERR(rescuer->task)) {
3988 kfree(rescuer);
3989 goto err_destroy;
3990 }
3991
3992 wq->rescuer = rescuer;
3993 kthread_bind_mask(rescuer->task, cpu_possible_mask);
3994 wake_up_process(rescuer->task);
3995 }
3996
3997 if ((wq->flags & WQ_SYSFS) && workqueue_sysfs_register(wq))
3998 goto err_destroy;
3999
4000 /*
4001 * wq_pool_mutex protects global freeze state and workqueues list.
4002 * Grab it, adjust max_active and add the new @wq to workqueues
4003 * list.
4004 */
4005 mutex_lock(&wq_pool_mutex);
4006
4007 mutex_lock(&wq->mutex);
4008 for_each_pwq(pwq, wq)
4009 pwq_adjust_max_active(pwq);
4010 mutex_unlock(&wq->mutex);
4011
4012 list_add_tail_rcu(&wq->list, &workqueues);
4013
4014 mutex_unlock(&wq_pool_mutex);
4015
4016 return wq;
4017
4018err_free_wq:
4019 free_workqueue_attrs(wq->unbound_attrs);
4020 kfree(wq);
4021 return NULL;
4022err_destroy:
4023 destroy_workqueue(wq);
4024 return NULL;
4025}
4026EXPORT_SYMBOL_GPL(__alloc_workqueue_key);
4027
4028/**
4029 * destroy_workqueue - safely terminate a workqueue
4030 * @wq: target workqueue
4031 *
4032 * Safely destroy a workqueue. All work currently pending will be done first.
4033 */
4034void destroy_workqueue(struct workqueue_struct *wq)
4035{
4036 struct pool_workqueue *pwq;
4037 int node;
4038
4039 /* drain it before proceeding with destruction */
4040 drain_workqueue(wq);
4041
4042 /* sanity checks */
4043 mutex_lock(&wq->mutex);
4044 for_each_pwq(pwq, wq) {
4045 int i;
4046
4047 for (i = 0; i < WORK_NR_COLORS; i++) {
4048 if (WARN_ON(pwq->nr_in_flight[i])) {
4049 mutex_unlock(&wq->mutex);
4050 return;
4051 }
4052 }
4053
4054 if (WARN_ON((pwq != wq->dfl_pwq) && (pwq->refcnt > 1)) ||
4055 WARN_ON(pwq->nr_active) ||
4056 WARN_ON(!list_empty(&pwq->delayed_works))) {
4057 mutex_unlock(&wq->mutex);
4058 return;
4059 }
4060 }
4061 mutex_unlock(&wq->mutex);
4062
4063 /*
4064 * wq list is used to freeze wq, remove from list after
4065 * flushing is complete in case freeze races us.
4066 */
4067 mutex_lock(&wq_pool_mutex);
4068 list_del_rcu(&wq->list);
4069 mutex_unlock(&wq_pool_mutex);
4070
4071 workqueue_sysfs_unregister(wq);
4072
4073 if (wq->rescuer)
4074 kthread_stop(wq->rescuer->task);
4075
4076 if (!(wq->flags & WQ_UNBOUND)) {
4077 /*
4078 * The base ref is never dropped on per-cpu pwqs. Directly
4079 * schedule RCU free.
4080 */
4081 call_rcu_sched(&wq->rcu, rcu_free_wq);
4082 } else {
4083 /*
4084 * We're the sole accessor of @wq at this point. Directly
4085 * access numa_pwq_tbl[] and dfl_pwq to put the base refs.
4086 * @wq will be freed when the last pwq is released.
4087 */
4088 for_each_node(node) {
4089 pwq = rcu_access_pointer(wq->numa_pwq_tbl[node]);
4090 RCU_INIT_POINTER(wq->numa_pwq_tbl[node], NULL);
4091 put_pwq_unlocked(pwq);
4092 }
4093
4094 /*
4095 * Put dfl_pwq. @wq may be freed any time after dfl_pwq is
4096 * put. Don't access it afterwards.
4097 */
4098 pwq = wq->dfl_pwq;
4099 wq->dfl_pwq = NULL;
4100 put_pwq_unlocked(pwq);
4101 }
4102}
4103EXPORT_SYMBOL_GPL(destroy_workqueue);
4104
4105/**
4106 * workqueue_set_max_active - adjust max_active of a workqueue
4107 * @wq: target workqueue
4108 * @max_active: new max_active value.
4109 *
4110 * Set max_active of @wq to @max_active.
4111 *
4112 * CONTEXT:
4113 * Don't call from IRQ context.
4114 */
4115void workqueue_set_max_active(struct workqueue_struct *wq, int max_active)
4116{
4117 struct pool_workqueue *pwq;
4118
4119 /* disallow meddling with max_active for ordered workqueues */
4120 if (WARN_ON(wq->flags & __WQ_ORDERED))
4121 return;
4122
4123 max_active = wq_clamp_max_active(max_active, wq->flags, wq->name);
4124
4125 mutex_lock(&wq->mutex);
4126
4127 wq->saved_max_active = max_active;
4128
4129 for_each_pwq(pwq, wq)
4130 pwq_adjust_max_active(pwq);
4131
4132 mutex_unlock(&wq->mutex);
4133}
4134EXPORT_SYMBOL_GPL(workqueue_set_max_active);
4135
4136/**
4137 * current_is_workqueue_rescuer - is %current workqueue rescuer?
4138 *
4139 * Determine whether %current is a workqueue rescuer. Can be used from
4140 * work functions to determine whether it's being run off the rescuer task.
4141 *
4142 * Return: %true if %current is a workqueue rescuer. %false otherwise.
4143 */
4144bool current_is_workqueue_rescuer(void)
4145{
4146 struct worker *worker = current_wq_worker();
4147
4148 return worker && worker->rescue_wq;
4149}
4150
4151/**
4152 * workqueue_congested - test whether a workqueue is congested
4153 * @cpu: CPU in question
4154 * @wq: target workqueue
4155 *
4156 * Test whether @wq's cpu workqueue for @cpu is congested. There is
4157 * no synchronization around this function and the test result is
4158 * unreliable and only useful as advisory hints or for debugging.
4159 *
4160 * If @cpu is WORK_CPU_UNBOUND, the test is performed on the local CPU.
4161 * Note that both per-cpu and unbound workqueues may be associated with
4162 * multiple pool_workqueues which have separate congested states. A
4163 * workqueue being congested on one CPU doesn't mean the workqueue is also
4164 * contested on other CPUs / NUMA nodes.
4165 *
4166 * Return:
4167 * %true if congested, %false otherwise.
4168 */
4169bool workqueue_congested(int cpu, struct workqueue_struct *wq)
4170{
4171 struct pool_workqueue *pwq;
4172 bool ret;
4173
4174 rcu_read_lock_sched();
4175
4176 if (cpu == WORK_CPU_UNBOUND)
4177 cpu = smp_processor_id();
4178
4179 if (!(wq->flags & WQ_UNBOUND))
4180 pwq = per_cpu_ptr(wq->cpu_pwqs, cpu);
4181 else
4182 pwq = unbound_pwq_by_node(wq, cpu_to_node(cpu));
4183
4184 ret = !list_empty(&pwq->delayed_works);
4185 rcu_read_unlock_sched();
4186
4187 return ret;
4188}
4189EXPORT_SYMBOL_GPL(workqueue_congested);
4190
4191/**
4192 * work_busy - test whether a work is currently pending or running
4193 * @work: the work to be tested
4194 *
4195 * Test whether @work is currently pending or running. There is no
4196 * synchronization around this function and the test result is
4197 * unreliable and only useful as advisory hints or for debugging.
4198 *
4199 * Return:
4200 * OR'd bitmask of WORK_BUSY_* bits.
4201 */
4202unsigned int work_busy(struct work_struct *work)
4203{
4204 struct worker_pool *pool;
4205 unsigned long flags;
4206 unsigned int ret = 0;
4207
4208 if (work_pending(work))
4209 ret |= WORK_BUSY_PENDING;
4210
4211 local_irq_save(flags);
4212 pool = get_work_pool(work);
4213 if (pool) {
4214 spin_lock(&pool->lock);
4215 if (find_worker_executing_work(pool, work))
4216 ret |= WORK_BUSY_RUNNING;
4217 spin_unlock(&pool->lock);
4218 }
4219 local_irq_restore(flags);
4220
4221 return ret;
4222}
4223EXPORT_SYMBOL_GPL(work_busy);
4224
4225/**
4226 * set_worker_desc - set description for the current work item
4227 * @fmt: printf-style format string
4228 * @...: arguments for the format string
4229 *
4230 * This function can be called by a running work function to describe what
4231 * the work item is about. If the worker task gets dumped, this
4232 * information will be printed out together to help debugging. The
4233 * description can be at most WORKER_DESC_LEN including the trailing '\0'.
4234 */
4235void set_worker_desc(const char *fmt, ...)
4236{
4237 struct worker *worker = current_wq_worker();
4238 va_list args;
4239
4240 if (worker) {
4241 va_start(args, fmt);
4242 vsnprintf(worker->desc, sizeof(worker->desc), fmt, args);
4243 va_end(args);
4244 worker->desc_valid = true;
4245 }
4246}
4247
4248/**
4249 * print_worker_info - print out worker information and description
4250 * @log_lvl: the log level to use when printing
4251 * @task: target task
4252 *
4253 * If @task is a worker and currently executing a work item, print out the
4254 * name of the workqueue being serviced and worker description set with
4255 * set_worker_desc() by the currently executing work item.
4256 *
4257 * This function can be safely called on any task as long as the
4258 * task_struct itself is accessible. While safe, this function isn't
4259 * synchronized and may print out mixups or garbages of limited length.
4260 */
4261void print_worker_info(const char *log_lvl, struct task_struct *task)
4262{
4263 work_func_t *fn = NULL;
4264 char name[WQ_NAME_LEN] = { };
4265 char desc[WORKER_DESC_LEN] = { };
4266 struct pool_workqueue *pwq = NULL;
4267 struct workqueue_struct *wq = NULL;
4268 bool desc_valid = false;
4269 struct worker *worker;
4270
4271 if (!(task->flags & PF_WQ_WORKER))
4272 return;
4273
4274 /*
4275 * This function is called without any synchronization and @task
4276 * could be in any state. Be careful with dereferences.
4277 */
4278 worker = probe_kthread_data(task);
4279
4280 /*
4281 * Carefully copy the associated workqueue's workfn and name. Keep
4282 * the original last '\0' in case the original contains garbage.
4283 */
4284 probe_kernel_read(&fn, &worker->current_func, sizeof(fn));
4285 probe_kernel_read(&pwq, &worker->current_pwq, sizeof(pwq));
4286 probe_kernel_read(&wq, &pwq->wq, sizeof(wq));
4287 probe_kernel_read(name, wq->name, sizeof(name) - 1);
4288
4289 /* copy worker description */
4290 probe_kernel_read(&desc_valid, &worker->desc_valid, sizeof(desc_valid));
4291 if (desc_valid)
4292 probe_kernel_read(desc, worker->desc, sizeof(desc) - 1);
4293
4294 if (fn || name[0] || desc[0]) {
4295 printk("%sWorkqueue: %s %pf", log_lvl, name, fn);
4296 if (desc[0])
4297 pr_cont(" (%s)", desc);
4298 pr_cont("\n");
4299 }
4300}
4301
4302static void pr_cont_pool_info(struct worker_pool *pool)
4303{
4304 pr_cont(" cpus=%*pbl", nr_cpumask_bits, pool->attrs->cpumask);
4305 if (pool->node != NUMA_NO_NODE)
4306 pr_cont(" node=%d", pool->node);
4307 pr_cont(" flags=0x%x nice=%d", pool->flags, pool->attrs->nice);
4308}
4309
4310static void pr_cont_work(bool comma, struct work_struct *work)
4311{
4312 if (work->func == wq_barrier_func) {
4313 struct wq_barrier *barr;
4314
4315 barr = container_of(work, struct wq_barrier, work);
4316
4317 pr_cont("%s BAR(%d)", comma ? "," : "",
4318 task_pid_nr(barr->task));
4319 } else {
4320 pr_cont("%s %pf", comma ? "," : "", work->func);
4321 }
4322}
4323
4324static void show_pwq(struct pool_workqueue *pwq)
4325{
4326 struct worker_pool *pool = pwq->pool;
4327 struct work_struct *work;
4328 struct worker *worker;
4329 bool has_in_flight = false, has_pending = false;
4330 int bkt;
4331
4332 pr_info(" pwq %d:", pool->id);
4333 pr_cont_pool_info(pool);
4334
4335 pr_cont(" active=%d/%d%s\n", pwq->nr_active, pwq->max_active,
4336 !list_empty(&pwq->mayday_node) ? " MAYDAY" : "");
4337
4338 hash_for_each(pool->busy_hash, bkt, worker, hentry) {
4339 if (worker->current_pwq == pwq) {
4340 has_in_flight = true;
4341 break;
4342 }
4343 }
4344 if (has_in_flight) {
4345 bool comma = false;
4346
4347 pr_info(" in-flight:");
4348 hash_for_each(pool->busy_hash, bkt, worker, hentry) {
4349 if (worker->current_pwq != pwq)
4350 continue;
4351
4352 pr_cont("%s %d%s:%pf", comma ? "," : "",
4353 task_pid_nr(worker->task),
4354 worker == pwq->wq->rescuer ? "(RESCUER)" : "",
4355 worker->current_func);
4356 list_for_each_entry(work, &worker->scheduled, entry)
4357 pr_cont_work(false, work);
4358 comma = true;
4359 }
4360 pr_cont("\n");
4361 }
4362
4363 list_for_each_entry(work, &pool->worklist, entry) {
4364 if (get_work_pwq(work) == pwq) {
4365 has_pending = true;
4366 break;
4367 }
4368 }
4369 if (has_pending) {
4370 bool comma = false;
4371
4372 pr_info(" pending:");
4373 list_for_each_entry(work, &pool->worklist, entry) {
4374 if (get_work_pwq(work) != pwq)
4375 continue;
4376
4377 pr_cont_work(comma, work);
4378 comma = !(*work_data_bits(work) & WORK_STRUCT_LINKED);
4379 }
4380 pr_cont("\n");
4381 }
4382
4383 if (!list_empty(&pwq->delayed_works)) {
4384 bool comma = false;
4385
4386 pr_info(" delayed:");
4387 list_for_each_entry(work, &pwq->delayed_works, entry) {
4388 pr_cont_work(comma, work);
4389 comma = !(*work_data_bits(work) & WORK_STRUCT_LINKED);
4390 }
4391 pr_cont("\n");
4392 }
4393}
4394
4395/**
4396 * show_workqueue_state - dump workqueue state
4397 *
4398 * Called from a sysrq handler and prints out all busy workqueues and
4399 * pools.
4400 */
4401void show_workqueue_state(void)
4402{
4403 struct workqueue_struct *wq;
4404 struct worker_pool *pool;
4405 unsigned long flags;
4406 int pi;
4407
4408 rcu_read_lock_sched();
4409
4410 pr_info("Showing busy workqueues and worker pools:\n");
4411
4412 list_for_each_entry_rcu(wq, &workqueues, list) {
4413 struct pool_workqueue *pwq;
4414 bool idle = true;
4415
4416 for_each_pwq(pwq, wq) {
4417 if (pwq->nr_active || !list_empty(&pwq->delayed_works)) {
4418 idle = false;
4419 break;
4420 }
4421 }
4422 if (idle)
4423 continue;
4424
4425 pr_info("workqueue %s: flags=0x%x\n", wq->name, wq->flags);
4426
4427 for_each_pwq(pwq, wq) {
4428 spin_lock_irqsave(&pwq->pool->lock, flags);
4429 if (pwq->nr_active || !list_empty(&pwq->delayed_works))
4430 show_pwq(pwq);
4431 spin_unlock_irqrestore(&pwq->pool->lock, flags);
4432 }
4433 }
4434
4435 for_each_pool(pool, pi) {
4436 struct worker *worker;
4437 bool first = true;
4438
4439 spin_lock_irqsave(&pool->lock, flags);
4440 if (pool->nr_workers == pool->nr_idle)
4441 goto next_pool;
4442
4443 pr_info("pool %d:", pool->id);
4444 pr_cont_pool_info(pool);
4445 pr_cont(" hung=%us workers=%d",
4446 jiffies_to_msecs(jiffies - pool->watchdog_ts) / 1000,
4447 pool->nr_workers);
4448 if (pool->manager)
4449 pr_cont(" manager: %d",
4450 task_pid_nr(pool->manager->task));
4451 list_for_each_entry(worker, &pool->idle_list, entry) {
4452 pr_cont(" %s%d", first ? "idle: " : "",
4453 task_pid_nr(worker->task));
4454 first = false;
4455 }
4456 pr_cont("\n");
4457 next_pool:
4458 spin_unlock_irqrestore(&pool->lock, flags);
4459 }
4460
4461 rcu_read_unlock_sched();
4462}
4463
4464/*
4465 * CPU hotplug.
4466 *
4467 * There are two challenges in supporting CPU hotplug. Firstly, there
4468 * are a lot of assumptions on strong associations among work, pwq and
4469 * pool which make migrating pending and scheduled works very
4470 * difficult to implement without impacting hot paths. Secondly,
4471 * worker pools serve mix of short, long and very long running works making
4472 * blocked draining impractical.
4473 *
4474 * This is solved by allowing the pools to be disassociated from the CPU
4475 * running as an unbound one and allowing it to be reattached later if the
4476 * cpu comes back online.
4477 */
4478
4479static void wq_unbind_fn(struct work_struct *work)
4480{
4481 int cpu = smp_processor_id();
4482 struct worker_pool *pool;
4483 struct worker *worker;
4484
4485 for_each_cpu_worker_pool(pool, cpu) {
4486 mutex_lock(&pool->attach_mutex);
4487 spin_lock_irq(&pool->lock);
4488
4489 /*
4490 * We've blocked all attach/detach operations. Make all workers
4491 * unbound and set DISASSOCIATED. Before this, all workers
4492 * except for the ones which are still executing works from
4493 * before the last CPU down must be on the cpu. After
4494 * this, they may become diasporas.
4495 */
4496 for_each_pool_worker(worker, pool)
4497 worker->flags |= WORKER_UNBOUND;
4498
4499 pool->flags |= POOL_DISASSOCIATED;
4500
4501 spin_unlock_irq(&pool->lock);
4502 mutex_unlock(&pool->attach_mutex);
4503
4504 /*
4505 * Call schedule() so that we cross rq->lock and thus can
4506 * guarantee sched callbacks see the %WORKER_UNBOUND flag.
4507 * This is necessary as scheduler callbacks may be invoked
4508 * from other cpus.
4509 */
4510 schedule();
4511
4512 /*
4513 * Sched callbacks are disabled now. Zap nr_running.
4514 * After this, nr_running stays zero and need_more_worker()
4515 * and keep_working() are always true as long as the
4516 * worklist is not empty. This pool now behaves as an
4517 * unbound (in terms of concurrency management) pool which
4518 * are served by workers tied to the pool.
4519 */
4520 atomic_set(&pool->nr_running, 0);
4521
4522 /*
4523 * With concurrency management just turned off, a busy
4524 * worker blocking could lead to lengthy stalls. Kick off
4525 * unbound chain execution of currently pending work items.
4526 */
4527 spin_lock_irq(&pool->lock);
4528 wake_up_worker(pool);
4529 spin_unlock_irq(&pool->lock);
4530 }
4531}
4532
4533/**
4534 * rebind_workers - rebind all workers of a pool to the associated CPU
4535 * @pool: pool of interest
4536 *
4537 * @pool->cpu is coming online. Rebind all workers to the CPU.
4538 */
4539static void rebind_workers(struct worker_pool *pool)
4540{
4541 struct worker *worker;
4542
4543 lockdep_assert_held(&pool->attach_mutex);
4544
4545 /*
4546 * Restore CPU affinity of all workers. As all idle workers should
4547 * be on the run-queue of the associated CPU before any local
4548 * wake-ups for concurrency management happen, restore CPU affinity
4549 * of all workers first and then clear UNBOUND. As we're called
4550 * from CPU_ONLINE, the following shouldn't fail.
4551 */
4552 for_each_pool_worker(worker, pool)
4553 WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task,
4554 pool->attrs->cpumask) < 0);
4555
4556 spin_lock_irq(&pool->lock);
4557
4558 /*
4559 * XXX: CPU hotplug notifiers are weird and can call DOWN_FAILED
4560 * w/o preceding DOWN_PREPARE. Work around it. CPU hotplug is
4561 * being reworked and this can go away in time.
4562 */
4563 if (!(pool->flags & POOL_DISASSOCIATED)) {
4564 spin_unlock_irq(&pool->lock);
4565 return;
4566 }
4567
4568 pool->flags &= ~POOL_DISASSOCIATED;
4569
4570 for_each_pool_worker(worker, pool) {
4571 unsigned int worker_flags = worker->flags;
4572
4573 /*
4574 * A bound idle worker should actually be on the runqueue
4575 * of the associated CPU for local wake-ups targeting it to
4576 * work. Kick all idle workers so that they migrate to the
4577 * associated CPU. Doing this in the same loop as
4578 * replacing UNBOUND with REBOUND is safe as no worker will
4579 * be bound before @pool->lock is released.
4580 */
4581 if (worker_flags & WORKER_IDLE)
4582 wake_up_process(worker->task);
4583
4584 /*
4585 * We want to clear UNBOUND but can't directly call
4586 * worker_clr_flags() or adjust nr_running. Atomically
4587 * replace UNBOUND with another NOT_RUNNING flag REBOUND.
4588 * @worker will clear REBOUND using worker_clr_flags() when
4589 * it initiates the next execution cycle thus restoring
4590 * concurrency management. Note that when or whether
4591 * @worker clears REBOUND doesn't affect correctness.
4592 *
4593 * ACCESS_ONCE() is necessary because @worker->flags may be
4594 * tested without holding any lock in
4595 * wq_worker_waking_up(). Without it, NOT_RUNNING test may
4596 * fail incorrectly leading to premature concurrency
4597 * management operations.
4598 */
4599 WARN_ON_ONCE(!(worker_flags & WORKER_UNBOUND));
4600 worker_flags |= WORKER_REBOUND;
4601 worker_flags &= ~WORKER_UNBOUND;
4602 ACCESS_ONCE(worker->flags) = worker_flags;
4603 }
4604
4605 spin_unlock_irq(&pool->lock);
4606}
4607
4608/**
4609 * restore_unbound_workers_cpumask - restore cpumask of unbound workers
4610 * @pool: unbound pool of interest
4611 * @cpu: the CPU which is coming up
4612 *
4613 * An unbound pool may end up with a cpumask which doesn't have any online
4614 * CPUs. When a worker of such pool get scheduled, the scheduler resets
4615 * its cpus_allowed. If @cpu is in @pool's cpumask which didn't have any
4616 * online CPU before, cpus_allowed of all its workers should be restored.
4617 */
4618static void restore_unbound_workers_cpumask(struct worker_pool *pool, int cpu)
4619{
4620 static cpumask_t cpumask;
4621 struct worker *worker;
4622
4623 lockdep_assert_held(&pool->attach_mutex);
4624
4625 /* is @cpu allowed for @pool? */
4626 if (!cpumask_test_cpu(cpu, pool->attrs->cpumask))
4627 return;
4628
4629 /* is @cpu the only online CPU? */
4630 cpumask_and(&cpumask, pool->attrs->cpumask, cpu_online_mask);
4631 if (cpumask_weight(&cpumask) != 1)
4632 return;
4633
4634 /* as we're called from CPU_ONLINE, the following shouldn't fail */
4635 for_each_pool_worker(worker, pool)
4636 WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task,
4637 pool->attrs->cpumask) < 0);
4638}
4639
4640/*
4641 * Workqueues should be brought up before normal priority CPU notifiers.
4642 * This will be registered high priority CPU notifier.
4643 */
4644static int workqueue_cpu_up_callback(struct notifier_block *nfb,
4645 unsigned long action,
4646 void *hcpu)
4647{
4648 int cpu = (unsigned long)hcpu;
4649 struct worker_pool *pool;
4650 struct workqueue_struct *wq;
4651 int pi;
4652
4653 switch (action & ~CPU_TASKS_FROZEN) {
4654 case CPU_UP_PREPARE:
4655 for_each_cpu_worker_pool(pool, cpu) {
4656 if (pool->nr_workers)
4657 continue;
4658 if (!create_worker(pool))
4659 return NOTIFY_BAD;
4660 }
4661 break;
4662
4663 case CPU_DOWN_FAILED:
4664 case CPU_ONLINE:
4665 mutex_lock(&wq_pool_mutex);
4666
4667 for_each_pool(pool, pi) {
4668 mutex_lock(&pool->attach_mutex);
4669
4670 if (pool->cpu == cpu)
4671 rebind_workers(pool);
4672 else if (pool->cpu < 0)
4673 restore_unbound_workers_cpumask(pool, cpu);
4674
4675 mutex_unlock(&pool->attach_mutex);
4676 }
4677
4678 /* update NUMA affinity of unbound workqueues */
4679 list_for_each_entry(wq, &workqueues, list)
4680 wq_update_unbound_numa(wq, cpu, true);
4681
4682 mutex_unlock(&wq_pool_mutex);
4683 break;
4684 }
4685 return NOTIFY_OK;
4686}
4687
4688/*
4689 * Workqueues should be brought down after normal priority CPU notifiers.
4690 * This will be registered as low priority CPU notifier.
4691 */
4692static int workqueue_cpu_down_callback(struct notifier_block *nfb,
4693 unsigned long action,
4694 void *hcpu)
4695{
4696 int cpu = (unsigned long)hcpu;
4697 struct work_struct unbind_work;
4698 struct workqueue_struct *wq;
4699
4700 switch (action & ~CPU_TASKS_FROZEN) {
4701 case CPU_DOWN_PREPARE:
4702 /* unbinding per-cpu workers should happen on the local CPU */
4703 INIT_WORK_ONSTACK(&unbind_work, wq_unbind_fn);
4704 queue_work_on(cpu, system_highpri_wq, &unbind_work);
4705
4706 /* update NUMA affinity of unbound workqueues */
4707 mutex_lock(&wq_pool_mutex);
4708 list_for_each_entry(wq, &workqueues, list)
4709 wq_update_unbound_numa(wq, cpu, false);
4710 mutex_unlock(&wq_pool_mutex);
4711
4712 /* wait for per-cpu unbinding to finish */
4713 flush_work(&unbind_work);
4714 destroy_work_on_stack(&unbind_work);
4715 break;
4716 }
4717 return NOTIFY_OK;
4718}
4719
4720#ifdef CONFIG_SMP
4721
4722struct work_for_cpu {
4723 struct work_struct work;
4724 long (*fn)(void *);
4725 void *arg;
4726 long ret;
4727};
4728
4729static void work_for_cpu_fn(struct work_struct *work)
4730{
4731 struct work_for_cpu *wfc = container_of(work, struct work_for_cpu, work);
4732
4733 wfc->ret = wfc->fn(wfc->arg);
4734}
4735
4736/**
4737 * work_on_cpu - run a function in thread context on a particular cpu
4738 * @cpu: the cpu to run on
4739 * @fn: the function to run
4740 * @arg: the function arg
4741 *
4742 * It is up to the caller to ensure that the cpu doesn't go offline.
4743 * The caller must not hold any locks which would prevent @fn from completing.
4744 *
4745 * Return: The value @fn returns.
4746 */
4747long work_on_cpu(int cpu, long (*fn)(void *), void *arg)
4748{
4749 struct work_for_cpu wfc = { .fn = fn, .arg = arg };
4750
4751 INIT_WORK_ONSTACK(&wfc.work, work_for_cpu_fn);
4752 schedule_work_on(cpu, &wfc.work);
4753 flush_work(&wfc.work);
4754 destroy_work_on_stack(&wfc.work);
4755 return wfc.ret;
4756}
4757EXPORT_SYMBOL_GPL(work_on_cpu);
4758#endif /* CONFIG_SMP */
4759
4760#ifdef CONFIG_FREEZER
4761
4762/**
4763 * freeze_workqueues_begin - begin freezing workqueues
4764 *
4765 * Start freezing workqueues. After this function returns, all freezable
4766 * workqueues will queue new works to their delayed_works list instead of
4767 * pool->worklist.
4768 *
4769 * CONTEXT:
4770 * Grabs and releases wq_pool_mutex, wq->mutex and pool->lock's.
4771 */
4772void freeze_workqueues_begin(void)
4773{
4774 struct workqueue_struct *wq;
4775 struct pool_workqueue *pwq;
4776
4777 mutex_lock(&wq_pool_mutex);
4778
4779 WARN_ON_ONCE(workqueue_freezing);
4780 workqueue_freezing = true;
4781
4782 list_for_each_entry(wq, &workqueues, list) {
4783 mutex_lock(&wq->mutex);
4784 for_each_pwq(pwq, wq)
4785 pwq_adjust_max_active(pwq);
4786 mutex_unlock(&wq->mutex);
4787 }
4788
4789 mutex_unlock(&wq_pool_mutex);
4790}
4791
4792/**
4793 * freeze_workqueues_busy - are freezable workqueues still busy?
4794 *
4795 * Check whether freezing is complete. This function must be called
4796 * between freeze_workqueues_begin() and thaw_workqueues().
4797 *
4798 * CONTEXT:
4799 * Grabs and releases wq_pool_mutex.
4800 *
4801 * Return:
4802 * %true if some freezable workqueues are still busy. %false if freezing
4803 * is complete.
4804 */
4805bool freeze_workqueues_busy(void)
4806{
4807 bool busy = false;
4808 struct workqueue_struct *wq;
4809 struct pool_workqueue *pwq;
4810
4811 mutex_lock(&wq_pool_mutex);
4812
4813 WARN_ON_ONCE(!workqueue_freezing);
4814
4815 list_for_each_entry(wq, &workqueues, list) {
4816 if (!(wq->flags & WQ_FREEZABLE))
4817 continue;
4818 /*
4819 * nr_active is monotonically decreasing. It's safe
4820 * to peek without lock.
4821 */
4822 rcu_read_lock_sched();
4823 for_each_pwq(pwq, wq) {
4824 WARN_ON_ONCE(pwq->nr_active < 0);
4825 if (pwq->nr_active) {
4826 busy = true;
4827 rcu_read_unlock_sched();
4828 goto out_unlock;
4829 }
4830 }
4831 rcu_read_unlock_sched();
4832 }
4833out_unlock:
4834 mutex_unlock(&wq_pool_mutex);
4835 return busy;
4836}
4837
4838/**
4839 * thaw_workqueues - thaw workqueues
4840 *
4841 * Thaw workqueues. Normal queueing is restored and all collected
4842 * frozen works are transferred to their respective pool worklists.
4843 *
4844 * CONTEXT:
4845 * Grabs and releases wq_pool_mutex, wq->mutex and pool->lock's.
4846 */
4847void thaw_workqueues(void)
4848{
4849 struct workqueue_struct *wq;
4850 struct pool_workqueue *pwq;
4851
4852 mutex_lock(&wq_pool_mutex);
4853
4854 if (!workqueue_freezing)
4855 goto out_unlock;
4856
4857 workqueue_freezing = false;
4858
4859 /* restore max_active and repopulate worklist */
4860 list_for_each_entry(wq, &workqueues, list) {
4861 mutex_lock(&wq->mutex);
4862 for_each_pwq(pwq, wq)
4863 pwq_adjust_max_active(pwq);
4864 mutex_unlock(&wq->mutex);
4865 }
4866
4867out_unlock:
4868 mutex_unlock(&wq_pool_mutex);
4869}
4870#endif /* CONFIG_FREEZER */
4871
4872static int workqueue_apply_unbound_cpumask(void)
4873{
4874 LIST_HEAD(ctxs);
4875 int ret = 0;
4876 struct workqueue_struct *wq;
4877 struct apply_wqattrs_ctx *ctx, *n;
4878
4879 lockdep_assert_held(&wq_pool_mutex);
4880
4881 list_for_each_entry(wq, &workqueues, list) {
4882 if (!(wq->flags & WQ_UNBOUND))
4883 continue;
4884 /* creating multiple pwqs breaks ordering guarantee */
4885 if (wq->flags & __WQ_ORDERED)
4886 continue;
4887
4888 ctx = apply_wqattrs_prepare(wq, wq->unbound_attrs);
4889 if (!ctx) {
4890 ret = -ENOMEM;
4891 break;
4892 }
4893
4894 list_add_tail(&ctx->list, &ctxs);
4895 }
4896
4897 list_for_each_entry_safe(ctx, n, &ctxs, list) {
4898 if (!ret)
4899 apply_wqattrs_commit(ctx);
4900 apply_wqattrs_cleanup(ctx);
4901 }
4902
4903 return ret;
4904}
4905
4906/**
4907 * workqueue_set_unbound_cpumask - Set the low-level unbound cpumask
4908 * @cpumask: the cpumask to set
4909 *
4910 * The low-level workqueues cpumask is a global cpumask that limits
4911 * the affinity of all unbound workqueues. This function check the @cpumask
4912 * and apply it to all unbound workqueues and updates all pwqs of them.
4913 *
4914 * Retun: 0 - Success
4915 * -EINVAL - Invalid @cpumask
4916 * -ENOMEM - Failed to allocate memory for attrs or pwqs.
4917 */
4918int workqueue_set_unbound_cpumask(cpumask_var_t cpumask)
4919{
4920 int ret = -EINVAL;
4921 cpumask_var_t saved_cpumask;
4922
4923 if (!zalloc_cpumask_var(&saved_cpumask, GFP_KERNEL))
4924 return -ENOMEM;
4925
4926 cpumask_and(cpumask, cpumask, cpu_possible_mask);
4927 if (!cpumask_empty(cpumask)) {
4928 apply_wqattrs_lock();
4929
4930 /* save the old wq_unbound_cpumask. */
4931 cpumask_copy(saved_cpumask, wq_unbound_cpumask);
4932
4933 /* update wq_unbound_cpumask at first and apply it to wqs. */
4934 cpumask_copy(wq_unbound_cpumask, cpumask);
4935 ret = workqueue_apply_unbound_cpumask();
4936
4937 /* restore the wq_unbound_cpumask when failed. */
4938 if (ret < 0)
4939 cpumask_copy(wq_unbound_cpumask, saved_cpumask);
4940
4941 apply_wqattrs_unlock();
4942 }
4943
4944 free_cpumask_var(saved_cpumask);
4945 return ret;
4946}
4947
4948#ifdef CONFIG_SYSFS
4949/*
4950 * Workqueues with WQ_SYSFS flag set is visible to userland via
4951 * /sys/bus/workqueue/devices/WQ_NAME. All visible workqueues have the
4952 * following attributes.
4953 *
4954 * per_cpu RO bool : whether the workqueue is per-cpu or unbound
4955 * max_active RW int : maximum number of in-flight work items
4956 *
4957 * Unbound workqueues have the following extra attributes.
4958 *
4959 * id RO int : the associated pool ID
4960 * nice RW int : nice value of the workers
4961 * cpumask RW mask : bitmask of allowed CPUs for the workers
4962 */
4963struct wq_device {
4964 struct workqueue_struct *wq;
4965 struct device dev;
4966};
4967
4968static struct workqueue_struct *dev_to_wq(struct device *dev)
4969{
4970 struct wq_device *wq_dev = container_of(dev, struct wq_device, dev);
4971
4972 return wq_dev->wq;
4973}
4974
4975static ssize_t per_cpu_show(struct device *dev, struct device_attribute *attr,
4976 char *buf)
4977{
4978 struct workqueue_struct *wq = dev_to_wq(dev);
4979
4980 return scnprintf(buf, PAGE_SIZE, "%d\n", (bool)!(wq->flags & WQ_UNBOUND));
4981}
4982static DEVICE_ATTR_RO(per_cpu);
4983
4984static ssize_t max_active_show(struct device *dev,
4985 struct device_attribute *attr, char *buf)
4986{
4987 struct workqueue_struct *wq = dev_to_wq(dev);
4988
4989 return scnprintf(buf, PAGE_SIZE, "%d\n", wq->saved_max_active);
4990}
4991
4992static ssize_t max_active_store(struct device *dev,
4993 struct device_attribute *attr, const char *buf,
4994 size_t count)
4995{
4996 struct workqueue_struct *wq = dev_to_wq(dev);
4997 int val;
4998
4999 if (sscanf(buf, "%d", &val) != 1 || val <= 0)
5000 return -EINVAL;
5001
5002 workqueue_set_max_active(wq, val);
5003 return count;
5004}
5005static DEVICE_ATTR_RW(max_active);
5006
5007static struct attribute *wq_sysfs_attrs[] = {
5008 &dev_attr_per_cpu.attr,
5009 &dev_attr_max_active.attr,
5010 NULL,
5011};
5012ATTRIBUTE_GROUPS(wq_sysfs);
5013
5014static ssize_t wq_pool_ids_show(struct device *dev,
5015 struct device_attribute *attr, char *buf)
5016{
5017 struct workqueue_struct *wq = dev_to_wq(dev);
5018 const char *delim = "";
5019 int node, written = 0;
5020
5021 rcu_read_lock_sched();
5022 for_each_node(node) {
5023 written += scnprintf(buf + written, PAGE_SIZE - written,
5024 "%s%d:%d", delim, node,
5025 unbound_pwq_by_node(wq, node)->pool->id);
5026 delim = " ";
5027 }
5028 written += scnprintf(buf + written, PAGE_SIZE - written, "\n");
5029 rcu_read_unlock_sched();
5030
5031 return written;
5032}
5033
5034static ssize_t wq_nice_show(struct device *dev, struct device_attribute *attr,
5035 char *buf)
5036{
5037 struct workqueue_struct *wq = dev_to_wq(dev);
5038 int written;
5039
5040 mutex_lock(&wq->mutex);
5041 written = scnprintf(buf, PAGE_SIZE, "%d\n", wq->unbound_attrs->nice);
5042 mutex_unlock(&wq->mutex);
5043
5044 return written;
5045}
5046
5047/* prepare workqueue_attrs for sysfs store operations */
5048static struct workqueue_attrs *wq_sysfs_prep_attrs(struct workqueue_struct *wq)
5049{
5050 struct workqueue_attrs *attrs;
5051
5052 lockdep_assert_held(&wq_pool_mutex);
5053
5054 attrs = alloc_workqueue_attrs(GFP_KERNEL);
5055 if (!attrs)
5056 return NULL;
5057
5058 copy_workqueue_attrs(attrs, wq->unbound_attrs);
5059 return attrs;
5060}
5061
5062static ssize_t wq_nice_store(struct device *dev, struct device_attribute *attr,
5063 const char *buf, size_t count)
5064{
5065 struct workqueue_struct *wq = dev_to_wq(dev);
5066 struct workqueue_attrs *attrs;
5067 int ret = -ENOMEM;
5068
5069 apply_wqattrs_lock();
5070
5071 attrs = wq_sysfs_prep_attrs(wq);
5072 if (!attrs)
5073 goto out_unlock;
5074
5075 if (sscanf(buf, "%d", &attrs->nice) == 1 &&
5076 attrs->nice >= MIN_NICE && attrs->nice <= MAX_NICE)
5077 ret = apply_workqueue_attrs_locked(wq, attrs);
5078 else
5079 ret = -EINVAL;
5080
5081out_unlock:
5082 apply_wqattrs_unlock();
5083 free_workqueue_attrs(attrs);
5084 return ret ?: count;
5085}
5086
5087static ssize_t wq_cpumask_show(struct device *dev,
5088 struct device_attribute *attr, char *buf)
5089{
5090 struct workqueue_struct *wq = dev_to_wq(dev);
5091 int written;
5092
5093 mutex_lock(&wq->mutex);
5094 written = scnprintf(buf, PAGE_SIZE, "%*pb\n",
5095 cpumask_pr_args(wq->unbound_attrs->cpumask));
5096 mutex_unlock(&wq->mutex);
5097 return written;
5098}
5099
5100static ssize_t wq_cpumask_store(struct device *dev,
5101 struct device_attribute *attr,
5102 const char *buf, size_t count)
5103{
5104 struct workqueue_struct *wq = dev_to_wq(dev);
5105 struct workqueue_attrs *attrs;
5106 int ret = -ENOMEM;
5107
5108 apply_wqattrs_lock();
5109
5110 attrs = wq_sysfs_prep_attrs(wq);
5111 if (!attrs)
5112 goto out_unlock;
5113
5114 ret = cpumask_parse(buf, attrs->cpumask);
5115 if (!ret)
5116 ret = apply_workqueue_attrs_locked(wq, attrs);
5117
5118out_unlock:
5119 apply_wqattrs_unlock();
5120 free_workqueue_attrs(attrs);
5121 return ret ?: count;
5122}
5123
5124static ssize_t wq_numa_show(struct device *dev, struct device_attribute *attr,
5125 char *buf)
5126{
5127 struct workqueue_struct *wq = dev_to_wq(dev);
5128 int written;
5129
5130 mutex_lock(&wq->mutex);
5131 written = scnprintf(buf, PAGE_SIZE, "%d\n",
5132 !wq->unbound_attrs->no_numa);
5133 mutex_unlock(&wq->mutex);
5134
5135 return written;
5136}
5137
5138static ssize_t wq_numa_store(struct device *dev, struct device_attribute *attr,
5139 const char *buf, size_t count)
5140{
5141 struct workqueue_struct *wq = dev_to_wq(dev);
5142 struct workqueue_attrs *attrs;
5143 int v, ret = -ENOMEM;
5144
5145 apply_wqattrs_lock();
5146
5147 attrs = wq_sysfs_prep_attrs(wq);
5148 if (!attrs)
5149 goto out_unlock;
5150
5151 ret = -EINVAL;
5152 if (sscanf(buf, "%d", &v) == 1) {
5153 attrs->no_numa = !v;
5154 ret = apply_workqueue_attrs_locked(wq, attrs);
5155 }
5156
5157out_unlock:
5158 apply_wqattrs_unlock();
5159 free_workqueue_attrs(attrs);
5160 return ret ?: count;
5161}
5162
5163static struct device_attribute wq_sysfs_unbound_attrs[] = {
5164 __ATTR(pool_ids, 0444, wq_pool_ids_show, NULL),
5165 __ATTR(nice, 0644, wq_nice_show, wq_nice_store),
5166 __ATTR(cpumask, 0644, wq_cpumask_show, wq_cpumask_store),
5167 __ATTR(numa, 0644, wq_numa_show, wq_numa_store),
5168 __ATTR_NULL,
5169};
5170
5171static struct bus_type wq_subsys = {
5172 .name = "workqueue",
5173 .dev_groups = wq_sysfs_groups,
5174};
5175
5176static ssize_t wq_unbound_cpumask_show(struct device *dev,
5177 struct device_attribute *attr, char *buf)
5178{
5179 int written;
5180
5181 mutex_lock(&wq_pool_mutex);
5182 written = scnprintf(buf, PAGE_SIZE, "%*pb\n",
5183 cpumask_pr_args(wq_unbound_cpumask));
5184 mutex_unlock(&wq_pool_mutex);
5185
5186 return written;
5187}
5188
5189static ssize_t wq_unbound_cpumask_store(struct device *dev,
5190 struct device_attribute *attr, const char *buf, size_t count)
5191{
5192 cpumask_var_t cpumask;
5193 int ret;
5194
5195 if (!zalloc_cpumask_var(&cpumask, GFP_KERNEL))
5196 return -ENOMEM;
5197
5198 ret = cpumask_parse(buf, cpumask);
5199 if (!ret)
5200 ret = workqueue_set_unbound_cpumask(cpumask);
5201
5202 free_cpumask_var(cpumask);
5203 return ret ? ret : count;
5204}
5205
5206static struct device_attribute wq_sysfs_cpumask_attr =
5207 __ATTR(cpumask, 0644, wq_unbound_cpumask_show,
5208 wq_unbound_cpumask_store);
5209
5210static int __init wq_sysfs_init(void)
5211{
5212 int err;
5213
5214 err = subsys_virtual_register(&wq_subsys, NULL);
5215 if (err)
5216 return err;
5217
5218 return device_create_file(wq_subsys.dev_root, &wq_sysfs_cpumask_attr);
5219}
5220core_initcall(wq_sysfs_init);
5221
5222static void wq_device_release(struct device *dev)
5223{
5224 struct wq_device *wq_dev = container_of(dev, struct wq_device, dev);
5225
5226 kfree(wq_dev);
5227}
5228
5229/**
5230 * workqueue_sysfs_register - make a workqueue visible in sysfs
5231 * @wq: the workqueue to register
5232 *
5233 * Expose @wq in sysfs under /sys/bus/workqueue/devices.
5234 * alloc_workqueue*() automatically calls this function if WQ_SYSFS is set
5235 * which is the preferred method.
5236 *
5237 * Workqueue user should use this function directly iff it wants to apply
5238 * workqueue_attrs before making the workqueue visible in sysfs; otherwise,
5239 * apply_workqueue_attrs() may race against userland updating the
5240 * attributes.
5241 *
5242 * Return: 0 on success, -errno on failure.
5243 */
5244int workqueue_sysfs_register(struct workqueue_struct *wq)
5245{
5246 struct wq_device *wq_dev;
5247 int ret;
5248
5249 /*
5250 * Adjusting max_active or creating new pwqs by applying
5251 * attributes breaks ordering guarantee. Disallow exposing ordered
5252 * workqueues.
5253 */
5254 if (WARN_ON(wq->flags & __WQ_ORDERED))
5255 return -EINVAL;
5256
5257 wq->wq_dev = wq_dev = kzalloc(sizeof(*wq_dev), GFP_KERNEL);
5258 if (!wq_dev)
5259 return -ENOMEM;
5260
5261 wq_dev->wq = wq;
5262 wq_dev->dev.bus = &wq_subsys;
5263 wq_dev->dev.release = wq_device_release;
5264 dev_set_name(&wq_dev->dev, "%s", wq->name);
5265
5266 /*
5267 * unbound_attrs are created separately. Suppress uevent until
5268 * everything is ready.
5269 */
5270 dev_set_uevent_suppress(&wq_dev->dev, true);
5271
5272 ret = device_register(&wq_dev->dev);
5273 if (ret) {
5274 kfree(wq_dev);
5275 wq->wq_dev = NULL;
5276 return ret;
5277 }
5278
5279 if (wq->flags & WQ_UNBOUND) {
5280 struct device_attribute *attr;
5281
5282 for (attr = wq_sysfs_unbound_attrs; attr->attr.name; attr++) {
5283 ret = device_create_file(&wq_dev->dev, attr);
5284 if (ret) {
5285 device_unregister(&wq_dev->dev);
5286 wq->wq_dev = NULL;
5287 return ret;
5288 }
5289 }
5290 }
5291
5292 dev_set_uevent_suppress(&wq_dev->dev, false);
5293 kobject_uevent(&wq_dev->dev.kobj, KOBJ_ADD);
5294 return 0;
5295}
5296
5297/**
5298 * workqueue_sysfs_unregister - undo workqueue_sysfs_register()
5299 * @wq: the workqueue to unregister
5300 *
5301 * If @wq is registered to sysfs by workqueue_sysfs_register(), unregister.
5302 */
5303static void workqueue_sysfs_unregister(struct workqueue_struct *wq)
5304{
5305 struct wq_device *wq_dev = wq->wq_dev;
5306
5307 if (!wq->wq_dev)
5308 return;
5309
5310 wq->wq_dev = NULL;
5311 device_unregister(&wq_dev->dev);
5312}
5313#else /* CONFIG_SYSFS */
5314static void workqueue_sysfs_unregister(struct workqueue_struct *wq) { }
5315#endif /* CONFIG_SYSFS */
5316
5317/*
5318 * Workqueue watchdog.
5319 *
5320 * Stall may be caused by various bugs - missing WQ_MEM_RECLAIM, illegal
5321 * flush dependency, a concurrency managed work item which stays RUNNING
5322 * indefinitely. Workqueue stalls can be very difficult to debug as the
5323 * usual warning mechanisms don't trigger and internal workqueue state is
5324 * largely opaque.
5325 *
5326 * Workqueue watchdog monitors all worker pools periodically and dumps
5327 * state if some pools failed to make forward progress for a while where
5328 * forward progress is defined as the first item on ->worklist changing.
5329 *
5330 * This mechanism is controlled through the kernel parameter
5331 * "workqueue.watchdog_thresh" which can be updated at runtime through the
5332 * corresponding sysfs parameter file.
5333 */
5334#ifdef CONFIG_WQ_WATCHDOG
5335
5336static void wq_watchdog_timer_fn(unsigned long data);
5337
5338static unsigned long wq_watchdog_thresh = 30;
5339static struct timer_list wq_watchdog_timer =
5340 TIMER_DEFERRED_INITIALIZER(wq_watchdog_timer_fn, 0, 0);
5341
5342static unsigned long wq_watchdog_touched = INITIAL_JIFFIES;
5343static DEFINE_PER_CPU(unsigned long, wq_watchdog_touched_cpu) = INITIAL_JIFFIES;
5344
5345static void wq_watchdog_reset_touched(void)
5346{
5347 int cpu;
5348
5349 wq_watchdog_touched = jiffies;
5350 for_each_possible_cpu(cpu)
5351 per_cpu(wq_watchdog_touched_cpu, cpu) = jiffies;
5352}
5353
5354static void wq_watchdog_timer_fn(unsigned long data)
5355{
5356 unsigned long thresh = READ_ONCE(wq_watchdog_thresh) * HZ;
5357 bool lockup_detected = false;
5358 struct worker_pool *pool;
5359 int pi;
5360
5361 if (!thresh)
5362 return;
5363
5364 rcu_read_lock();
5365
5366 for_each_pool(pool, pi) {
5367 unsigned long pool_ts, touched, ts;
5368
5369 if (list_empty(&pool->worklist))
5370 continue;
5371
5372 /* get the latest of pool and touched timestamps */
5373 pool_ts = READ_ONCE(pool->watchdog_ts);
5374 touched = READ_ONCE(wq_watchdog_touched);
5375
5376 if (time_after(pool_ts, touched))
5377 ts = pool_ts;
5378 else
5379 ts = touched;
5380
5381 if (pool->cpu >= 0) {
5382 unsigned long cpu_touched =
5383 READ_ONCE(per_cpu(wq_watchdog_touched_cpu,
5384 pool->cpu));
5385 if (time_after(cpu_touched, ts))
5386 ts = cpu_touched;
5387 }
5388
5389 /* did we stall? */
5390 if (time_after(jiffies, ts + thresh)) {
5391 lockup_detected = true;
5392 pr_emerg("BUG: workqueue lockup - pool");
5393 pr_cont_pool_info(pool);
5394 pr_cont(" stuck for %us!\n",
5395 jiffies_to_msecs(jiffies - pool_ts) / 1000);
5396 }
5397 }
5398
5399 rcu_read_unlock();
5400
5401 if (lockup_detected)
5402 show_workqueue_state();
5403
5404 wq_watchdog_reset_touched();
5405 mod_timer(&wq_watchdog_timer, jiffies + thresh);
5406}
5407
5408void wq_watchdog_touch(int cpu)
5409{
5410 if (cpu >= 0)
5411 per_cpu(wq_watchdog_touched_cpu, cpu) = jiffies;
5412 else
5413 wq_watchdog_touched = jiffies;
5414}
5415
5416static void wq_watchdog_set_thresh(unsigned long thresh)
5417{
5418 wq_watchdog_thresh = 0;
5419 del_timer_sync(&wq_watchdog_timer);
5420
5421 if (thresh) {
5422 wq_watchdog_thresh = thresh;
5423 wq_watchdog_reset_touched();
5424 mod_timer(&wq_watchdog_timer, jiffies + thresh * HZ);
5425 }
5426}
5427
5428static int wq_watchdog_param_set_thresh(const char *val,
5429 const struct kernel_param *kp)
5430{
5431 unsigned long thresh;
5432 int ret;
5433
5434 ret = kstrtoul(val, 0, &thresh);
5435 if (ret)
5436 return ret;
5437
5438 if (system_wq)
5439 wq_watchdog_set_thresh(thresh);
5440 else
5441 wq_watchdog_thresh = thresh;
5442
5443 return 0;
5444}
5445
5446static const struct kernel_param_ops wq_watchdog_thresh_ops = {
5447 .set = wq_watchdog_param_set_thresh,
5448 .get = param_get_ulong,
5449};
5450
5451module_param_cb(watchdog_thresh, &wq_watchdog_thresh_ops, &wq_watchdog_thresh,
5452 0644);
5453
5454static void wq_watchdog_init(void)
5455{
5456 wq_watchdog_set_thresh(wq_watchdog_thresh);
5457}
5458
5459#else /* CONFIG_WQ_WATCHDOG */
5460
5461static inline void wq_watchdog_init(void) { }
5462
5463#endif /* CONFIG_WQ_WATCHDOG */
5464
5465static void __init wq_numa_init(void)
5466{
5467 cpumask_var_t *tbl;
5468 int node, cpu;
5469
5470 if (num_possible_nodes() <= 1)
5471 return;
5472
5473 if (wq_disable_numa) {
5474 pr_info("workqueue: NUMA affinity support disabled\n");
5475 return;
5476 }
5477
5478 wq_update_unbound_numa_attrs_buf = alloc_workqueue_attrs(GFP_KERNEL);
5479 BUG_ON(!wq_update_unbound_numa_attrs_buf);
5480
5481 /*
5482 * We want masks of possible CPUs of each node which isn't readily
5483 * available. Build one from cpu_to_node() which should have been
5484 * fully initialized by now.
5485 */
5486 tbl = kzalloc(nr_node_ids * sizeof(tbl[0]), GFP_KERNEL);
5487 BUG_ON(!tbl);
5488
5489 for_each_node(node)
5490 BUG_ON(!zalloc_cpumask_var_node(&tbl[node], GFP_KERNEL,
5491 node_online(node) ? node : NUMA_NO_NODE));
5492
5493 for_each_possible_cpu(cpu) {
5494 node = cpu_to_node(cpu);
5495 if (WARN_ON(node == NUMA_NO_NODE)) {
5496 pr_warn("workqueue: NUMA node mapping not available for cpu%d, disabling NUMA support\n", cpu);
5497 /* happens iff arch is bonkers, let's just proceed */
5498 return;
5499 }
5500 cpumask_set_cpu(cpu, tbl[node]);
5501 }
5502
5503 wq_numa_possible_cpumask = tbl;
5504 wq_numa_enabled = true;
5505}
5506
5507static int __init init_workqueues(void)
5508{
5509 int std_nice[NR_STD_WORKER_POOLS] = { 0, HIGHPRI_NICE_LEVEL };
5510 int i, cpu;
5511
5512 WARN_ON(__alignof__(struct pool_workqueue) < __alignof__(long long));
5513
5514 BUG_ON(!alloc_cpumask_var(&wq_unbound_cpumask, GFP_KERNEL));
5515 cpumask_copy(wq_unbound_cpumask, cpu_possible_mask);
5516
5517 pwq_cache = KMEM_CACHE(pool_workqueue, SLAB_PANIC);
5518
5519 cpu_notifier(workqueue_cpu_up_callback, CPU_PRI_WORKQUEUE_UP);
5520 hotcpu_notifier(workqueue_cpu_down_callback, CPU_PRI_WORKQUEUE_DOWN);
5521
5522 wq_numa_init();
5523
5524 /* initialize CPU pools */
5525 for_each_possible_cpu(cpu) {
5526 struct worker_pool *pool;
5527
5528 i = 0;
5529 for_each_cpu_worker_pool(pool, cpu) {
5530 BUG_ON(init_worker_pool(pool));
5531 pool->cpu = cpu;
5532 cpumask_copy(pool->attrs->cpumask, cpumask_of(cpu));
5533 pool->attrs->nice = std_nice[i++];
5534 pool->node = cpu_to_node(cpu);
5535
5536 /* alloc pool ID */
5537 mutex_lock(&wq_pool_mutex);
5538 BUG_ON(worker_pool_assign_id(pool));
5539 mutex_unlock(&wq_pool_mutex);
5540 }
5541 }
5542
5543 /* create the initial worker */
5544 for_each_online_cpu(cpu) {
5545 struct worker_pool *pool;
5546
5547 for_each_cpu_worker_pool(pool, cpu) {
5548 pool->flags &= ~POOL_DISASSOCIATED;
5549 BUG_ON(!create_worker(pool));
5550 }
5551 }
5552
5553 /* create default unbound and ordered wq attrs */
5554 for (i = 0; i < NR_STD_WORKER_POOLS; i++) {
5555 struct workqueue_attrs *attrs;
5556
5557 BUG_ON(!(attrs = alloc_workqueue_attrs(GFP_KERNEL)));
5558 attrs->nice = std_nice[i];
5559 unbound_std_wq_attrs[i] = attrs;
5560
5561 /*
5562 * An ordered wq should have only one pwq as ordering is
5563 * guaranteed by max_active which is enforced by pwqs.
5564 * Turn off NUMA so that dfl_pwq is used for all nodes.
5565 */
5566 BUG_ON(!(attrs = alloc_workqueue_attrs(GFP_KERNEL)));
5567 attrs->nice = std_nice[i];
5568 attrs->no_numa = true;
5569 ordered_wq_attrs[i] = attrs;
5570 }
5571
5572 system_wq = alloc_workqueue("events", 0, 0);
5573 system_highpri_wq = alloc_workqueue("events_highpri", WQ_HIGHPRI, 0);
5574 system_long_wq = alloc_workqueue("events_long", 0, 0);
5575 system_unbound_wq = alloc_workqueue("events_unbound", WQ_UNBOUND,
5576 WQ_UNBOUND_MAX_ACTIVE);
5577 system_freezable_wq = alloc_workqueue("events_freezable",
5578 WQ_FREEZABLE, 0);
5579 system_power_efficient_wq = alloc_workqueue("events_power_efficient",
5580 WQ_POWER_EFFICIENT, 0);
5581 system_freezable_power_efficient_wq = alloc_workqueue("events_freezable_power_efficient",
5582 WQ_FREEZABLE | WQ_POWER_EFFICIENT,
5583 0);
5584 BUG_ON(!system_wq || !system_highpri_wq || !system_long_wq ||
5585 !system_unbound_wq || !system_freezable_wq ||
5586 !system_power_efficient_wq ||
5587 !system_freezable_power_efficient_wq);
5588
5589 wq_watchdog_init();
5590
5591 return 0;
5592}
5593early_initcall(init_workqueues);
1/*
2 * kernel/workqueue.c - generic async execution with shared worker pool
3 *
4 * Copyright (C) 2002 Ingo Molnar
5 *
6 * Derived from the taskqueue/keventd code by:
7 * David Woodhouse <dwmw2@infradead.org>
8 * Andrew Morton
9 * Kai Petzke <wpp@marie.physik.tu-berlin.de>
10 * Theodore Ts'o <tytso@mit.edu>
11 *
12 * Made to use alloc_percpu by Christoph Lameter.
13 *
14 * Copyright (C) 2010 SUSE Linux Products GmbH
15 * Copyright (C) 2010 Tejun Heo <tj@kernel.org>
16 *
17 * This is the generic async execution mechanism. Work items as are
18 * executed in process context. The worker pool is shared and
19 * automatically managed. There is one worker pool for each CPU and
20 * one extra for works which are better served by workers which are
21 * not bound to any specific CPU.
22 *
23 * Please read Documentation/workqueue.txt for details.
24 */
25
26#include <linux/module.h>
27#include <linux/kernel.h>
28#include <linux/sched.h>
29#include <linux/init.h>
30#include <linux/signal.h>
31#include <linux/completion.h>
32#include <linux/workqueue.h>
33#include <linux/slab.h>
34#include <linux/cpu.h>
35#include <linux/notifier.h>
36#include <linux/kthread.h>
37#include <linux/hardirq.h>
38#include <linux/mempolicy.h>
39#include <linux/freezer.h>
40#include <linux/kallsyms.h>
41#include <linux/debug_locks.h>
42#include <linux/lockdep.h>
43#include <linux/idr.h>
44
45#include "workqueue_sched.h"
46
47enum {
48 /* global_cwq flags */
49 GCWQ_MANAGE_WORKERS = 1 << 0, /* need to manage workers */
50 GCWQ_MANAGING_WORKERS = 1 << 1, /* managing workers */
51 GCWQ_DISASSOCIATED = 1 << 2, /* cpu can't serve workers */
52 GCWQ_FREEZING = 1 << 3, /* freeze in progress */
53 GCWQ_HIGHPRI_PENDING = 1 << 4, /* highpri works on queue */
54
55 /* worker flags */
56 WORKER_STARTED = 1 << 0, /* started */
57 WORKER_DIE = 1 << 1, /* die die die */
58 WORKER_IDLE = 1 << 2, /* is idle */
59 WORKER_PREP = 1 << 3, /* preparing to run works */
60 WORKER_ROGUE = 1 << 4, /* not bound to any cpu */
61 WORKER_REBIND = 1 << 5, /* mom is home, come back */
62 WORKER_CPU_INTENSIVE = 1 << 6, /* cpu intensive */
63 WORKER_UNBOUND = 1 << 7, /* worker is unbound */
64
65 WORKER_NOT_RUNNING = WORKER_PREP | WORKER_ROGUE | WORKER_REBIND |
66 WORKER_CPU_INTENSIVE | WORKER_UNBOUND,
67
68 /* gcwq->trustee_state */
69 TRUSTEE_START = 0, /* start */
70 TRUSTEE_IN_CHARGE = 1, /* trustee in charge of gcwq */
71 TRUSTEE_BUTCHER = 2, /* butcher workers */
72 TRUSTEE_RELEASE = 3, /* release workers */
73 TRUSTEE_DONE = 4, /* trustee is done */
74
75 BUSY_WORKER_HASH_ORDER = 6, /* 64 pointers */
76 BUSY_WORKER_HASH_SIZE = 1 << BUSY_WORKER_HASH_ORDER,
77 BUSY_WORKER_HASH_MASK = BUSY_WORKER_HASH_SIZE - 1,
78
79 MAX_IDLE_WORKERS_RATIO = 4, /* 1/4 of busy can be idle */
80 IDLE_WORKER_TIMEOUT = 300 * HZ, /* keep idle ones for 5 mins */
81
82 MAYDAY_INITIAL_TIMEOUT = HZ / 100 >= 2 ? HZ / 100 : 2,
83 /* call for help after 10ms
84 (min two ticks) */
85 MAYDAY_INTERVAL = HZ / 10, /* and then every 100ms */
86 CREATE_COOLDOWN = HZ, /* time to breath after fail */
87 TRUSTEE_COOLDOWN = HZ / 10, /* for trustee draining */
88
89 /*
90 * Rescue workers are used only on emergencies and shared by
91 * all cpus. Give -20.
92 */
93 RESCUER_NICE_LEVEL = -20,
94};
95
96/*
97 * Structure fields follow one of the following exclusion rules.
98 *
99 * I: Modifiable by initialization/destruction paths and read-only for
100 * everyone else.
101 *
102 * P: Preemption protected. Disabling preemption is enough and should
103 * only be modified and accessed from the local cpu.
104 *
105 * L: gcwq->lock protected. Access with gcwq->lock held.
106 *
107 * X: During normal operation, modification requires gcwq->lock and
108 * should be done only from local cpu. Either disabling preemption
109 * on local cpu or grabbing gcwq->lock is enough for read access.
110 * If GCWQ_DISASSOCIATED is set, it's identical to L.
111 *
112 * F: wq->flush_mutex protected.
113 *
114 * W: workqueue_lock protected.
115 */
116
117struct global_cwq;
118
119/*
120 * The poor guys doing the actual heavy lifting. All on-duty workers
121 * are either serving the manager role, on idle list or on busy hash.
122 */
123struct worker {
124 /* on idle list while idle, on busy hash table while busy */
125 union {
126 struct list_head entry; /* L: while idle */
127 struct hlist_node hentry; /* L: while busy */
128 };
129
130 struct work_struct *current_work; /* L: work being processed */
131 struct cpu_workqueue_struct *current_cwq; /* L: current_work's cwq */
132 struct list_head scheduled; /* L: scheduled works */
133 struct task_struct *task; /* I: worker task */
134 struct global_cwq *gcwq; /* I: the associated gcwq */
135 /* 64 bytes boundary on 64bit, 32 on 32bit */
136 unsigned long last_active; /* L: last active timestamp */
137 unsigned int flags; /* X: flags */
138 int id; /* I: worker id */
139 struct work_struct rebind_work; /* L: rebind worker to cpu */
140};
141
142/*
143 * Global per-cpu workqueue. There's one and only one for each cpu
144 * and all works are queued and processed here regardless of their
145 * target workqueues.
146 */
147struct global_cwq {
148 spinlock_t lock; /* the gcwq lock */
149 struct list_head worklist; /* L: list of pending works */
150 unsigned int cpu; /* I: the associated cpu */
151 unsigned int flags; /* L: GCWQ_* flags */
152
153 int nr_workers; /* L: total number of workers */
154 int nr_idle; /* L: currently idle ones */
155
156 /* workers are chained either in the idle_list or busy_hash */
157 struct list_head idle_list; /* X: list of idle workers */
158 struct hlist_head busy_hash[BUSY_WORKER_HASH_SIZE];
159 /* L: hash of busy workers */
160
161 struct timer_list idle_timer; /* L: worker idle timeout */
162 struct timer_list mayday_timer; /* L: SOS timer for dworkers */
163
164 struct ida worker_ida; /* L: for worker IDs */
165
166 struct task_struct *trustee; /* L: for gcwq shutdown */
167 unsigned int trustee_state; /* L: trustee state */
168 wait_queue_head_t trustee_wait; /* trustee wait */
169 struct worker *first_idle; /* L: first idle worker */
170} ____cacheline_aligned_in_smp;
171
172/*
173 * The per-CPU workqueue. The lower WORK_STRUCT_FLAG_BITS of
174 * work_struct->data are used for flags and thus cwqs need to be
175 * aligned at two's power of the number of flag bits.
176 */
177struct cpu_workqueue_struct {
178 struct global_cwq *gcwq; /* I: the associated gcwq */
179 struct workqueue_struct *wq; /* I: the owning workqueue */
180 int work_color; /* L: current color */
181 int flush_color; /* L: flushing color */
182 int nr_in_flight[WORK_NR_COLORS];
183 /* L: nr of in_flight works */
184 int nr_active; /* L: nr of active works */
185 int max_active; /* L: max active works */
186 struct list_head delayed_works; /* L: delayed works */
187};
188
189/*
190 * Structure used to wait for workqueue flush.
191 */
192struct wq_flusher {
193 struct list_head list; /* F: list of flushers */
194 int flush_color; /* F: flush color waiting for */
195 struct completion done; /* flush completion */
196};
197
198/*
199 * All cpumasks are assumed to be always set on UP and thus can't be
200 * used to determine whether there's something to be done.
201 */
202#ifdef CONFIG_SMP
203typedef cpumask_var_t mayday_mask_t;
204#define mayday_test_and_set_cpu(cpu, mask) \
205 cpumask_test_and_set_cpu((cpu), (mask))
206#define mayday_clear_cpu(cpu, mask) cpumask_clear_cpu((cpu), (mask))
207#define for_each_mayday_cpu(cpu, mask) for_each_cpu((cpu), (mask))
208#define alloc_mayday_mask(maskp, gfp) zalloc_cpumask_var((maskp), (gfp))
209#define free_mayday_mask(mask) free_cpumask_var((mask))
210#else
211typedef unsigned long mayday_mask_t;
212#define mayday_test_and_set_cpu(cpu, mask) test_and_set_bit(0, &(mask))
213#define mayday_clear_cpu(cpu, mask) clear_bit(0, &(mask))
214#define for_each_mayday_cpu(cpu, mask) if ((cpu) = 0, (mask))
215#define alloc_mayday_mask(maskp, gfp) true
216#define free_mayday_mask(mask) do { } while (0)
217#endif
218
219/*
220 * The externally visible workqueue abstraction is an array of
221 * per-CPU workqueues:
222 */
223struct workqueue_struct {
224 unsigned int flags; /* W: WQ_* flags */
225 union {
226 struct cpu_workqueue_struct __percpu *pcpu;
227 struct cpu_workqueue_struct *single;
228 unsigned long v;
229 } cpu_wq; /* I: cwq's */
230 struct list_head list; /* W: list of all workqueues */
231
232 struct mutex flush_mutex; /* protects wq flushing */
233 int work_color; /* F: current work color */
234 int flush_color; /* F: current flush color */
235 atomic_t nr_cwqs_to_flush; /* flush in progress */
236 struct wq_flusher *first_flusher; /* F: first flusher */
237 struct list_head flusher_queue; /* F: flush waiters */
238 struct list_head flusher_overflow; /* F: flush overflow list */
239
240 mayday_mask_t mayday_mask; /* cpus requesting rescue */
241 struct worker *rescuer; /* I: rescue worker */
242
243 int nr_drainers; /* W: drain in progress */
244 int saved_max_active; /* W: saved cwq max_active */
245 const char *name; /* I: workqueue name */
246#ifdef CONFIG_LOCKDEP
247 struct lockdep_map lockdep_map;
248#endif
249};
250
251struct workqueue_struct *system_wq __read_mostly;
252struct workqueue_struct *system_long_wq __read_mostly;
253struct workqueue_struct *system_nrt_wq __read_mostly;
254struct workqueue_struct *system_unbound_wq __read_mostly;
255struct workqueue_struct *system_freezable_wq __read_mostly;
256EXPORT_SYMBOL_GPL(system_wq);
257EXPORT_SYMBOL_GPL(system_long_wq);
258EXPORT_SYMBOL_GPL(system_nrt_wq);
259EXPORT_SYMBOL_GPL(system_unbound_wq);
260EXPORT_SYMBOL_GPL(system_freezable_wq);
261
262#define CREATE_TRACE_POINTS
263#include <trace/events/workqueue.h>
264
265#define for_each_busy_worker(worker, i, pos, gcwq) \
266 for (i = 0; i < BUSY_WORKER_HASH_SIZE; i++) \
267 hlist_for_each_entry(worker, pos, &gcwq->busy_hash[i], hentry)
268
269static inline int __next_gcwq_cpu(int cpu, const struct cpumask *mask,
270 unsigned int sw)
271{
272 if (cpu < nr_cpu_ids) {
273 if (sw & 1) {
274 cpu = cpumask_next(cpu, mask);
275 if (cpu < nr_cpu_ids)
276 return cpu;
277 }
278 if (sw & 2)
279 return WORK_CPU_UNBOUND;
280 }
281 return WORK_CPU_NONE;
282}
283
284static inline int __next_wq_cpu(int cpu, const struct cpumask *mask,
285 struct workqueue_struct *wq)
286{
287 return __next_gcwq_cpu(cpu, mask, !(wq->flags & WQ_UNBOUND) ? 1 : 2);
288}
289
290/*
291 * CPU iterators
292 *
293 * An extra gcwq is defined for an invalid cpu number
294 * (WORK_CPU_UNBOUND) to host workqueues which are not bound to any
295 * specific CPU. The following iterators are similar to
296 * for_each_*_cpu() iterators but also considers the unbound gcwq.
297 *
298 * for_each_gcwq_cpu() : possible CPUs + WORK_CPU_UNBOUND
299 * for_each_online_gcwq_cpu() : online CPUs + WORK_CPU_UNBOUND
300 * for_each_cwq_cpu() : possible CPUs for bound workqueues,
301 * WORK_CPU_UNBOUND for unbound workqueues
302 */
303#define for_each_gcwq_cpu(cpu) \
304 for ((cpu) = __next_gcwq_cpu(-1, cpu_possible_mask, 3); \
305 (cpu) < WORK_CPU_NONE; \
306 (cpu) = __next_gcwq_cpu((cpu), cpu_possible_mask, 3))
307
308#define for_each_online_gcwq_cpu(cpu) \
309 for ((cpu) = __next_gcwq_cpu(-1, cpu_online_mask, 3); \
310 (cpu) < WORK_CPU_NONE; \
311 (cpu) = __next_gcwq_cpu((cpu), cpu_online_mask, 3))
312
313#define for_each_cwq_cpu(cpu, wq) \
314 for ((cpu) = __next_wq_cpu(-1, cpu_possible_mask, (wq)); \
315 (cpu) < WORK_CPU_NONE; \
316 (cpu) = __next_wq_cpu((cpu), cpu_possible_mask, (wq)))
317
318#ifdef CONFIG_DEBUG_OBJECTS_WORK
319
320static struct debug_obj_descr work_debug_descr;
321
322static void *work_debug_hint(void *addr)
323{
324 return ((struct work_struct *) addr)->func;
325}
326
327/*
328 * fixup_init is called when:
329 * - an active object is initialized
330 */
331static int work_fixup_init(void *addr, enum debug_obj_state state)
332{
333 struct work_struct *work = addr;
334
335 switch (state) {
336 case ODEBUG_STATE_ACTIVE:
337 cancel_work_sync(work);
338 debug_object_init(work, &work_debug_descr);
339 return 1;
340 default:
341 return 0;
342 }
343}
344
345/*
346 * fixup_activate is called when:
347 * - an active object is activated
348 * - an unknown object is activated (might be a statically initialized object)
349 */
350static int work_fixup_activate(void *addr, enum debug_obj_state state)
351{
352 struct work_struct *work = addr;
353
354 switch (state) {
355
356 case ODEBUG_STATE_NOTAVAILABLE:
357 /*
358 * This is not really a fixup. The work struct was
359 * statically initialized. We just make sure that it
360 * is tracked in the object tracker.
361 */
362 if (test_bit(WORK_STRUCT_STATIC_BIT, work_data_bits(work))) {
363 debug_object_init(work, &work_debug_descr);
364 debug_object_activate(work, &work_debug_descr);
365 return 0;
366 }
367 WARN_ON_ONCE(1);
368 return 0;
369
370 case ODEBUG_STATE_ACTIVE:
371 WARN_ON(1);
372
373 default:
374 return 0;
375 }
376}
377
378/*
379 * fixup_free is called when:
380 * - an active object is freed
381 */
382static int work_fixup_free(void *addr, enum debug_obj_state state)
383{
384 struct work_struct *work = addr;
385
386 switch (state) {
387 case ODEBUG_STATE_ACTIVE:
388 cancel_work_sync(work);
389 debug_object_free(work, &work_debug_descr);
390 return 1;
391 default:
392 return 0;
393 }
394}
395
396static struct debug_obj_descr work_debug_descr = {
397 .name = "work_struct",
398 .debug_hint = work_debug_hint,
399 .fixup_init = work_fixup_init,
400 .fixup_activate = work_fixup_activate,
401 .fixup_free = work_fixup_free,
402};
403
404static inline void debug_work_activate(struct work_struct *work)
405{
406 debug_object_activate(work, &work_debug_descr);
407}
408
409static inline void debug_work_deactivate(struct work_struct *work)
410{
411 debug_object_deactivate(work, &work_debug_descr);
412}
413
414void __init_work(struct work_struct *work, int onstack)
415{
416 if (onstack)
417 debug_object_init_on_stack(work, &work_debug_descr);
418 else
419 debug_object_init(work, &work_debug_descr);
420}
421EXPORT_SYMBOL_GPL(__init_work);
422
423void destroy_work_on_stack(struct work_struct *work)
424{
425 debug_object_free(work, &work_debug_descr);
426}
427EXPORT_SYMBOL_GPL(destroy_work_on_stack);
428
429#else
430static inline void debug_work_activate(struct work_struct *work) { }
431static inline void debug_work_deactivate(struct work_struct *work) { }
432#endif
433
434/* Serializes the accesses to the list of workqueues. */
435static DEFINE_SPINLOCK(workqueue_lock);
436static LIST_HEAD(workqueues);
437static bool workqueue_freezing; /* W: have wqs started freezing? */
438
439/*
440 * The almighty global cpu workqueues. nr_running is the only field
441 * which is expected to be used frequently by other cpus via
442 * try_to_wake_up(). Put it in a separate cacheline.
443 */
444static DEFINE_PER_CPU(struct global_cwq, global_cwq);
445static DEFINE_PER_CPU_SHARED_ALIGNED(atomic_t, gcwq_nr_running);
446
447/*
448 * Global cpu workqueue and nr_running counter for unbound gcwq. The
449 * gcwq is always online, has GCWQ_DISASSOCIATED set, and all its
450 * workers have WORKER_UNBOUND set.
451 */
452static struct global_cwq unbound_global_cwq;
453static atomic_t unbound_gcwq_nr_running = ATOMIC_INIT(0); /* always 0 */
454
455static int worker_thread(void *__worker);
456
457static struct global_cwq *get_gcwq(unsigned int cpu)
458{
459 if (cpu != WORK_CPU_UNBOUND)
460 return &per_cpu(global_cwq, cpu);
461 else
462 return &unbound_global_cwq;
463}
464
465static atomic_t *get_gcwq_nr_running(unsigned int cpu)
466{
467 if (cpu != WORK_CPU_UNBOUND)
468 return &per_cpu(gcwq_nr_running, cpu);
469 else
470 return &unbound_gcwq_nr_running;
471}
472
473static struct cpu_workqueue_struct *get_cwq(unsigned int cpu,
474 struct workqueue_struct *wq)
475{
476 if (!(wq->flags & WQ_UNBOUND)) {
477 if (likely(cpu < nr_cpu_ids)) {
478#ifdef CONFIG_SMP
479 return per_cpu_ptr(wq->cpu_wq.pcpu, cpu);
480#else
481 return wq->cpu_wq.single;
482#endif
483 }
484 } else if (likely(cpu == WORK_CPU_UNBOUND))
485 return wq->cpu_wq.single;
486 return NULL;
487}
488
489static unsigned int work_color_to_flags(int color)
490{
491 return color << WORK_STRUCT_COLOR_SHIFT;
492}
493
494static int get_work_color(struct work_struct *work)
495{
496 return (*work_data_bits(work) >> WORK_STRUCT_COLOR_SHIFT) &
497 ((1 << WORK_STRUCT_COLOR_BITS) - 1);
498}
499
500static int work_next_color(int color)
501{
502 return (color + 1) % WORK_NR_COLORS;
503}
504
505/*
506 * A work's data points to the cwq with WORK_STRUCT_CWQ set while the
507 * work is on queue. Once execution starts, WORK_STRUCT_CWQ is
508 * cleared and the work data contains the cpu number it was last on.
509 *
510 * set_work_{cwq|cpu}() and clear_work_data() can be used to set the
511 * cwq, cpu or clear work->data. These functions should only be
512 * called while the work is owned - ie. while the PENDING bit is set.
513 *
514 * get_work_[g]cwq() can be used to obtain the gcwq or cwq
515 * corresponding to a work. gcwq is available once the work has been
516 * queued anywhere after initialization. cwq is available only from
517 * queueing until execution starts.
518 */
519static inline void set_work_data(struct work_struct *work, unsigned long data,
520 unsigned long flags)
521{
522 BUG_ON(!work_pending(work));
523 atomic_long_set(&work->data, data | flags | work_static(work));
524}
525
526static void set_work_cwq(struct work_struct *work,
527 struct cpu_workqueue_struct *cwq,
528 unsigned long extra_flags)
529{
530 set_work_data(work, (unsigned long)cwq,
531 WORK_STRUCT_PENDING | WORK_STRUCT_CWQ | extra_flags);
532}
533
534static void set_work_cpu(struct work_struct *work, unsigned int cpu)
535{
536 set_work_data(work, cpu << WORK_STRUCT_FLAG_BITS, WORK_STRUCT_PENDING);
537}
538
539static void clear_work_data(struct work_struct *work)
540{
541 set_work_data(work, WORK_STRUCT_NO_CPU, 0);
542}
543
544static struct cpu_workqueue_struct *get_work_cwq(struct work_struct *work)
545{
546 unsigned long data = atomic_long_read(&work->data);
547
548 if (data & WORK_STRUCT_CWQ)
549 return (void *)(data & WORK_STRUCT_WQ_DATA_MASK);
550 else
551 return NULL;
552}
553
554static struct global_cwq *get_work_gcwq(struct work_struct *work)
555{
556 unsigned long data = atomic_long_read(&work->data);
557 unsigned int cpu;
558
559 if (data & WORK_STRUCT_CWQ)
560 return ((struct cpu_workqueue_struct *)
561 (data & WORK_STRUCT_WQ_DATA_MASK))->gcwq;
562
563 cpu = data >> WORK_STRUCT_FLAG_BITS;
564 if (cpu == WORK_CPU_NONE)
565 return NULL;
566
567 BUG_ON(cpu >= nr_cpu_ids && cpu != WORK_CPU_UNBOUND);
568 return get_gcwq(cpu);
569}
570
571/*
572 * Policy functions. These define the policies on how the global
573 * worker pool is managed. Unless noted otherwise, these functions
574 * assume that they're being called with gcwq->lock held.
575 */
576
577static bool __need_more_worker(struct global_cwq *gcwq)
578{
579 return !atomic_read(get_gcwq_nr_running(gcwq->cpu)) ||
580 gcwq->flags & GCWQ_HIGHPRI_PENDING;
581}
582
583/*
584 * Need to wake up a worker? Called from anything but currently
585 * running workers.
586 */
587static bool need_more_worker(struct global_cwq *gcwq)
588{
589 return !list_empty(&gcwq->worklist) && __need_more_worker(gcwq);
590}
591
592/* Can I start working? Called from busy but !running workers. */
593static bool may_start_working(struct global_cwq *gcwq)
594{
595 return gcwq->nr_idle;
596}
597
598/* Do I need to keep working? Called from currently running workers. */
599static bool keep_working(struct global_cwq *gcwq)
600{
601 atomic_t *nr_running = get_gcwq_nr_running(gcwq->cpu);
602
603 return !list_empty(&gcwq->worklist) &&
604 (atomic_read(nr_running) <= 1 ||
605 gcwq->flags & GCWQ_HIGHPRI_PENDING);
606}
607
608/* Do we need a new worker? Called from manager. */
609static bool need_to_create_worker(struct global_cwq *gcwq)
610{
611 return need_more_worker(gcwq) && !may_start_working(gcwq);
612}
613
614/* Do I need to be the manager? */
615static bool need_to_manage_workers(struct global_cwq *gcwq)
616{
617 return need_to_create_worker(gcwq) || gcwq->flags & GCWQ_MANAGE_WORKERS;
618}
619
620/* Do we have too many workers and should some go away? */
621static bool too_many_workers(struct global_cwq *gcwq)
622{
623 bool managing = gcwq->flags & GCWQ_MANAGING_WORKERS;
624 int nr_idle = gcwq->nr_idle + managing; /* manager is considered idle */
625 int nr_busy = gcwq->nr_workers - nr_idle;
626
627 return nr_idle > 2 && (nr_idle - 2) * MAX_IDLE_WORKERS_RATIO >= nr_busy;
628}
629
630/*
631 * Wake up functions.
632 */
633
634/* Return the first worker. Safe with preemption disabled */
635static struct worker *first_worker(struct global_cwq *gcwq)
636{
637 if (unlikely(list_empty(&gcwq->idle_list)))
638 return NULL;
639
640 return list_first_entry(&gcwq->idle_list, struct worker, entry);
641}
642
643/**
644 * wake_up_worker - wake up an idle worker
645 * @gcwq: gcwq to wake worker for
646 *
647 * Wake up the first idle worker of @gcwq.
648 *
649 * CONTEXT:
650 * spin_lock_irq(gcwq->lock).
651 */
652static void wake_up_worker(struct global_cwq *gcwq)
653{
654 struct worker *worker = first_worker(gcwq);
655
656 if (likely(worker))
657 wake_up_process(worker->task);
658}
659
660/**
661 * wq_worker_waking_up - a worker is waking up
662 * @task: task waking up
663 * @cpu: CPU @task is waking up to
664 *
665 * This function is called during try_to_wake_up() when a worker is
666 * being awoken.
667 *
668 * CONTEXT:
669 * spin_lock_irq(rq->lock)
670 */
671void wq_worker_waking_up(struct task_struct *task, unsigned int cpu)
672{
673 struct worker *worker = kthread_data(task);
674
675 if (!(worker->flags & WORKER_NOT_RUNNING))
676 atomic_inc(get_gcwq_nr_running(cpu));
677}
678
679/**
680 * wq_worker_sleeping - a worker is going to sleep
681 * @task: task going to sleep
682 * @cpu: CPU in question, must be the current CPU number
683 *
684 * This function is called during schedule() when a busy worker is
685 * going to sleep. Worker on the same cpu can be woken up by
686 * returning pointer to its task.
687 *
688 * CONTEXT:
689 * spin_lock_irq(rq->lock)
690 *
691 * RETURNS:
692 * Worker task on @cpu to wake up, %NULL if none.
693 */
694struct task_struct *wq_worker_sleeping(struct task_struct *task,
695 unsigned int cpu)
696{
697 struct worker *worker = kthread_data(task), *to_wakeup = NULL;
698 struct global_cwq *gcwq = get_gcwq(cpu);
699 atomic_t *nr_running = get_gcwq_nr_running(cpu);
700
701 if (worker->flags & WORKER_NOT_RUNNING)
702 return NULL;
703
704 /* this can only happen on the local cpu */
705 BUG_ON(cpu != raw_smp_processor_id());
706
707 /*
708 * The counterpart of the following dec_and_test, implied mb,
709 * worklist not empty test sequence is in insert_work().
710 * Please read comment there.
711 *
712 * NOT_RUNNING is clear. This means that trustee is not in
713 * charge and we're running on the local cpu w/ rq lock held
714 * and preemption disabled, which in turn means that none else
715 * could be manipulating idle_list, so dereferencing idle_list
716 * without gcwq lock is safe.
717 */
718 if (atomic_dec_and_test(nr_running) && !list_empty(&gcwq->worklist))
719 to_wakeup = first_worker(gcwq);
720 return to_wakeup ? to_wakeup->task : NULL;
721}
722
723/**
724 * worker_set_flags - set worker flags and adjust nr_running accordingly
725 * @worker: self
726 * @flags: flags to set
727 * @wakeup: wakeup an idle worker if necessary
728 *
729 * Set @flags in @worker->flags and adjust nr_running accordingly. If
730 * nr_running becomes zero and @wakeup is %true, an idle worker is
731 * woken up.
732 *
733 * CONTEXT:
734 * spin_lock_irq(gcwq->lock)
735 */
736static inline void worker_set_flags(struct worker *worker, unsigned int flags,
737 bool wakeup)
738{
739 struct global_cwq *gcwq = worker->gcwq;
740
741 WARN_ON_ONCE(worker->task != current);
742
743 /*
744 * If transitioning into NOT_RUNNING, adjust nr_running and
745 * wake up an idle worker as necessary if requested by
746 * @wakeup.
747 */
748 if ((flags & WORKER_NOT_RUNNING) &&
749 !(worker->flags & WORKER_NOT_RUNNING)) {
750 atomic_t *nr_running = get_gcwq_nr_running(gcwq->cpu);
751
752 if (wakeup) {
753 if (atomic_dec_and_test(nr_running) &&
754 !list_empty(&gcwq->worklist))
755 wake_up_worker(gcwq);
756 } else
757 atomic_dec(nr_running);
758 }
759
760 worker->flags |= flags;
761}
762
763/**
764 * worker_clr_flags - clear worker flags and adjust nr_running accordingly
765 * @worker: self
766 * @flags: flags to clear
767 *
768 * Clear @flags in @worker->flags and adjust nr_running accordingly.
769 *
770 * CONTEXT:
771 * spin_lock_irq(gcwq->lock)
772 */
773static inline void worker_clr_flags(struct worker *worker, unsigned int flags)
774{
775 struct global_cwq *gcwq = worker->gcwq;
776 unsigned int oflags = worker->flags;
777
778 WARN_ON_ONCE(worker->task != current);
779
780 worker->flags &= ~flags;
781
782 /*
783 * If transitioning out of NOT_RUNNING, increment nr_running. Note
784 * that the nested NOT_RUNNING is not a noop. NOT_RUNNING is mask
785 * of multiple flags, not a single flag.
786 */
787 if ((flags & WORKER_NOT_RUNNING) && (oflags & WORKER_NOT_RUNNING))
788 if (!(worker->flags & WORKER_NOT_RUNNING))
789 atomic_inc(get_gcwq_nr_running(gcwq->cpu));
790}
791
792/**
793 * busy_worker_head - return the busy hash head for a work
794 * @gcwq: gcwq of interest
795 * @work: work to be hashed
796 *
797 * Return hash head of @gcwq for @work.
798 *
799 * CONTEXT:
800 * spin_lock_irq(gcwq->lock).
801 *
802 * RETURNS:
803 * Pointer to the hash head.
804 */
805static struct hlist_head *busy_worker_head(struct global_cwq *gcwq,
806 struct work_struct *work)
807{
808 const int base_shift = ilog2(sizeof(struct work_struct));
809 unsigned long v = (unsigned long)work;
810
811 /* simple shift and fold hash, do we need something better? */
812 v >>= base_shift;
813 v += v >> BUSY_WORKER_HASH_ORDER;
814 v &= BUSY_WORKER_HASH_MASK;
815
816 return &gcwq->busy_hash[v];
817}
818
819/**
820 * __find_worker_executing_work - find worker which is executing a work
821 * @gcwq: gcwq of interest
822 * @bwh: hash head as returned by busy_worker_head()
823 * @work: work to find worker for
824 *
825 * Find a worker which is executing @work on @gcwq. @bwh should be
826 * the hash head obtained by calling busy_worker_head() with the same
827 * work.
828 *
829 * CONTEXT:
830 * spin_lock_irq(gcwq->lock).
831 *
832 * RETURNS:
833 * Pointer to worker which is executing @work if found, NULL
834 * otherwise.
835 */
836static struct worker *__find_worker_executing_work(struct global_cwq *gcwq,
837 struct hlist_head *bwh,
838 struct work_struct *work)
839{
840 struct worker *worker;
841 struct hlist_node *tmp;
842
843 hlist_for_each_entry(worker, tmp, bwh, hentry)
844 if (worker->current_work == work)
845 return worker;
846 return NULL;
847}
848
849/**
850 * find_worker_executing_work - find worker which is executing a work
851 * @gcwq: gcwq of interest
852 * @work: work to find worker for
853 *
854 * Find a worker which is executing @work on @gcwq. This function is
855 * identical to __find_worker_executing_work() except that this
856 * function calculates @bwh itself.
857 *
858 * CONTEXT:
859 * spin_lock_irq(gcwq->lock).
860 *
861 * RETURNS:
862 * Pointer to worker which is executing @work if found, NULL
863 * otherwise.
864 */
865static struct worker *find_worker_executing_work(struct global_cwq *gcwq,
866 struct work_struct *work)
867{
868 return __find_worker_executing_work(gcwq, busy_worker_head(gcwq, work),
869 work);
870}
871
872/**
873 * gcwq_determine_ins_pos - find insertion position
874 * @gcwq: gcwq of interest
875 * @cwq: cwq a work is being queued for
876 *
877 * A work for @cwq is about to be queued on @gcwq, determine insertion
878 * position for the work. If @cwq is for HIGHPRI wq, the work is
879 * queued at the head of the queue but in FIFO order with respect to
880 * other HIGHPRI works; otherwise, at the end of the queue. This
881 * function also sets GCWQ_HIGHPRI_PENDING flag to hint @gcwq that
882 * there are HIGHPRI works pending.
883 *
884 * CONTEXT:
885 * spin_lock_irq(gcwq->lock).
886 *
887 * RETURNS:
888 * Pointer to inserstion position.
889 */
890static inline struct list_head *gcwq_determine_ins_pos(struct global_cwq *gcwq,
891 struct cpu_workqueue_struct *cwq)
892{
893 struct work_struct *twork;
894
895 if (likely(!(cwq->wq->flags & WQ_HIGHPRI)))
896 return &gcwq->worklist;
897
898 list_for_each_entry(twork, &gcwq->worklist, entry) {
899 struct cpu_workqueue_struct *tcwq = get_work_cwq(twork);
900
901 if (!(tcwq->wq->flags & WQ_HIGHPRI))
902 break;
903 }
904
905 gcwq->flags |= GCWQ_HIGHPRI_PENDING;
906 return &twork->entry;
907}
908
909/**
910 * insert_work - insert a work into gcwq
911 * @cwq: cwq @work belongs to
912 * @work: work to insert
913 * @head: insertion point
914 * @extra_flags: extra WORK_STRUCT_* flags to set
915 *
916 * Insert @work which belongs to @cwq into @gcwq after @head.
917 * @extra_flags is or'd to work_struct flags.
918 *
919 * CONTEXT:
920 * spin_lock_irq(gcwq->lock).
921 */
922static void insert_work(struct cpu_workqueue_struct *cwq,
923 struct work_struct *work, struct list_head *head,
924 unsigned int extra_flags)
925{
926 struct global_cwq *gcwq = cwq->gcwq;
927
928 /* we own @work, set data and link */
929 set_work_cwq(work, cwq, extra_flags);
930
931 /*
932 * Ensure that we get the right work->data if we see the
933 * result of list_add() below, see try_to_grab_pending().
934 */
935 smp_wmb();
936
937 list_add_tail(&work->entry, head);
938
939 /*
940 * Ensure either worker_sched_deactivated() sees the above
941 * list_add_tail() or we see zero nr_running to avoid workers
942 * lying around lazily while there are works to be processed.
943 */
944 smp_mb();
945
946 if (__need_more_worker(gcwq))
947 wake_up_worker(gcwq);
948}
949
950/*
951 * Test whether @work is being queued from another work executing on the
952 * same workqueue. This is rather expensive and should only be used from
953 * cold paths.
954 */
955static bool is_chained_work(struct workqueue_struct *wq)
956{
957 unsigned long flags;
958 unsigned int cpu;
959
960 for_each_gcwq_cpu(cpu) {
961 struct global_cwq *gcwq = get_gcwq(cpu);
962 struct worker *worker;
963 struct hlist_node *pos;
964 int i;
965
966 spin_lock_irqsave(&gcwq->lock, flags);
967 for_each_busy_worker(worker, i, pos, gcwq) {
968 if (worker->task != current)
969 continue;
970 spin_unlock_irqrestore(&gcwq->lock, flags);
971 /*
972 * I'm @worker, no locking necessary. See if @work
973 * is headed to the same workqueue.
974 */
975 return worker->current_cwq->wq == wq;
976 }
977 spin_unlock_irqrestore(&gcwq->lock, flags);
978 }
979 return false;
980}
981
982static void __queue_work(unsigned int cpu, struct workqueue_struct *wq,
983 struct work_struct *work)
984{
985 struct global_cwq *gcwq;
986 struct cpu_workqueue_struct *cwq;
987 struct list_head *worklist;
988 unsigned int work_flags;
989 unsigned long flags;
990
991 debug_work_activate(work);
992
993 /* if dying, only works from the same workqueue are allowed */
994 if (unlikely(wq->flags & WQ_DRAINING) &&
995 WARN_ON_ONCE(!is_chained_work(wq)))
996 return;
997
998 /* determine gcwq to use */
999 if (!(wq->flags & WQ_UNBOUND)) {
1000 struct global_cwq *last_gcwq;
1001
1002 if (unlikely(cpu == WORK_CPU_UNBOUND))
1003 cpu = raw_smp_processor_id();
1004
1005 /*
1006 * It's multi cpu. If @wq is non-reentrant and @work
1007 * was previously on a different cpu, it might still
1008 * be running there, in which case the work needs to
1009 * be queued on that cpu to guarantee non-reentrance.
1010 */
1011 gcwq = get_gcwq(cpu);
1012 if (wq->flags & WQ_NON_REENTRANT &&
1013 (last_gcwq = get_work_gcwq(work)) && last_gcwq != gcwq) {
1014 struct worker *worker;
1015
1016 spin_lock_irqsave(&last_gcwq->lock, flags);
1017
1018 worker = find_worker_executing_work(last_gcwq, work);
1019
1020 if (worker && worker->current_cwq->wq == wq)
1021 gcwq = last_gcwq;
1022 else {
1023 /* meh... not running there, queue here */
1024 spin_unlock_irqrestore(&last_gcwq->lock, flags);
1025 spin_lock_irqsave(&gcwq->lock, flags);
1026 }
1027 } else
1028 spin_lock_irqsave(&gcwq->lock, flags);
1029 } else {
1030 gcwq = get_gcwq(WORK_CPU_UNBOUND);
1031 spin_lock_irqsave(&gcwq->lock, flags);
1032 }
1033
1034 /* gcwq determined, get cwq and queue */
1035 cwq = get_cwq(gcwq->cpu, wq);
1036 trace_workqueue_queue_work(cpu, cwq, work);
1037
1038 BUG_ON(!list_empty(&work->entry));
1039
1040 cwq->nr_in_flight[cwq->work_color]++;
1041 work_flags = work_color_to_flags(cwq->work_color);
1042
1043 if (likely(cwq->nr_active < cwq->max_active)) {
1044 trace_workqueue_activate_work(work);
1045 cwq->nr_active++;
1046 worklist = gcwq_determine_ins_pos(gcwq, cwq);
1047 } else {
1048 work_flags |= WORK_STRUCT_DELAYED;
1049 worklist = &cwq->delayed_works;
1050 }
1051
1052 insert_work(cwq, work, worklist, work_flags);
1053
1054 spin_unlock_irqrestore(&gcwq->lock, flags);
1055}
1056
1057/**
1058 * queue_work - queue work on a workqueue
1059 * @wq: workqueue to use
1060 * @work: work to queue
1061 *
1062 * Returns 0 if @work was already on a queue, non-zero otherwise.
1063 *
1064 * We queue the work to the CPU on which it was submitted, but if the CPU dies
1065 * it can be processed by another CPU.
1066 */
1067int queue_work(struct workqueue_struct *wq, struct work_struct *work)
1068{
1069 int ret;
1070
1071 ret = queue_work_on(get_cpu(), wq, work);
1072 put_cpu();
1073
1074 return ret;
1075}
1076EXPORT_SYMBOL_GPL(queue_work);
1077
1078/**
1079 * queue_work_on - queue work on specific cpu
1080 * @cpu: CPU number to execute work on
1081 * @wq: workqueue to use
1082 * @work: work to queue
1083 *
1084 * Returns 0 if @work was already on a queue, non-zero otherwise.
1085 *
1086 * We queue the work to a specific CPU, the caller must ensure it
1087 * can't go away.
1088 */
1089int
1090queue_work_on(int cpu, struct workqueue_struct *wq, struct work_struct *work)
1091{
1092 int ret = 0;
1093
1094 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1095 __queue_work(cpu, wq, work);
1096 ret = 1;
1097 }
1098 return ret;
1099}
1100EXPORT_SYMBOL_GPL(queue_work_on);
1101
1102static void delayed_work_timer_fn(unsigned long __data)
1103{
1104 struct delayed_work *dwork = (struct delayed_work *)__data;
1105 struct cpu_workqueue_struct *cwq = get_work_cwq(&dwork->work);
1106
1107 __queue_work(smp_processor_id(), cwq->wq, &dwork->work);
1108}
1109
1110/**
1111 * queue_delayed_work - queue work on a workqueue after delay
1112 * @wq: workqueue to use
1113 * @dwork: delayable work to queue
1114 * @delay: number of jiffies to wait before queueing
1115 *
1116 * Returns 0 if @work was already on a queue, non-zero otherwise.
1117 */
1118int queue_delayed_work(struct workqueue_struct *wq,
1119 struct delayed_work *dwork, unsigned long delay)
1120{
1121 if (delay == 0)
1122 return queue_work(wq, &dwork->work);
1123
1124 return queue_delayed_work_on(-1, wq, dwork, delay);
1125}
1126EXPORT_SYMBOL_GPL(queue_delayed_work);
1127
1128/**
1129 * queue_delayed_work_on - queue work on specific CPU after delay
1130 * @cpu: CPU number to execute work on
1131 * @wq: workqueue to use
1132 * @dwork: work to queue
1133 * @delay: number of jiffies to wait before queueing
1134 *
1135 * Returns 0 if @work was already on a queue, non-zero otherwise.
1136 */
1137int queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
1138 struct delayed_work *dwork, unsigned long delay)
1139{
1140 int ret = 0;
1141 struct timer_list *timer = &dwork->timer;
1142 struct work_struct *work = &dwork->work;
1143
1144 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1145 unsigned int lcpu;
1146
1147 BUG_ON(timer_pending(timer));
1148 BUG_ON(!list_empty(&work->entry));
1149
1150 timer_stats_timer_set_start_info(&dwork->timer);
1151
1152 /*
1153 * This stores cwq for the moment, for the timer_fn.
1154 * Note that the work's gcwq is preserved to allow
1155 * reentrance detection for delayed works.
1156 */
1157 if (!(wq->flags & WQ_UNBOUND)) {
1158 struct global_cwq *gcwq = get_work_gcwq(work);
1159
1160 if (gcwq && gcwq->cpu != WORK_CPU_UNBOUND)
1161 lcpu = gcwq->cpu;
1162 else
1163 lcpu = raw_smp_processor_id();
1164 } else
1165 lcpu = WORK_CPU_UNBOUND;
1166
1167 set_work_cwq(work, get_cwq(lcpu, wq), 0);
1168
1169 timer->expires = jiffies + delay;
1170 timer->data = (unsigned long)dwork;
1171 timer->function = delayed_work_timer_fn;
1172
1173 if (unlikely(cpu >= 0))
1174 add_timer_on(timer, cpu);
1175 else
1176 add_timer(timer);
1177 ret = 1;
1178 }
1179 return ret;
1180}
1181EXPORT_SYMBOL_GPL(queue_delayed_work_on);
1182
1183/**
1184 * worker_enter_idle - enter idle state
1185 * @worker: worker which is entering idle state
1186 *
1187 * @worker is entering idle state. Update stats and idle timer if
1188 * necessary.
1189 *
1190 * LOCKING:
1191 * spin_lock_irq(gcwq->lock).
1192 */
1193static void worker_enter_idle(struct worker *worker)
1194{
1195 struct global_cwq *gcwq = worker->gcwq;
1196
1197 BUG_ON(worker->flags & WORKER_IDLE);
1198 BUG_ON(!list_empty(&worker->entry) &&
1199 (worker->hentry.next || worker->hentry.pprev));
1200
1201 /* can't use worker_set_flags(), also called from start_worker() */
1202 worker->flags |= WORKER_IDLE;
1203 gcwq->nr_idle++;
1204 worker->last_active = jiffies;
1205
1206 /* idle_list is LIFO */
1207 list_add(&worker->entry, &gcwq->idle_list);
1208
1209 if (likely(!(worker->flags & WORKER_ROGUE))) {
1210 if (too_many_workers(gcwq) && !timer_pending(&gcwq->idle_timer))
1211 mod_timer(&gcwq->idle_timer,
1212 jiffies + IDLE_WORKER_TIMEOUT);
1213 } else
1214 wake_up_all(&gcwq->trustee_wait);
1215
1216 /* sanity check nr_running */
1217 WARN_ON_ONCE(gcwq->nr_workers == gcwq->nr_idle &&
1218 atomic_read(get_gcwq_nr_running(gcwq->cpu)));
1219}
1220
1221/**
1222 * worker_leave_idle - leave idle state
1223 * @worker: worker which is leaving idle state
1224 *
1225 * @worker is leaving idle state. Update stats.
1226 *
1227 * LOCKING:
1228 * spin_lock_irq(gcwq->lock).
1229 */
1230static void worker_leave_idle(struct worker *worker)
1231{
1232 struct global_cwq *gcwq = worker->gcwq;
1233
1234 BUG_ON(!(worker->flags & WORKER_IDLE));
1235 worker_clr_flags(worker, WORKER_IDLE);
1236 gcwq->nr_idle--;
1237 list_del_init(&worker->entry);
1238}
1239
1240/**
1241 * worker_maybe_bind_and_lock - bind worker to its cpu if possible and lock gcwq
1242 * @worker: self
1243 *
1244 * Works which are scheduled while the cpu is online must at least be
1245 * scheduled to a worker which is bound to the cpu so that if they are
1246 * flushed from cpu callbacks while cpu is going down, they are
1247 * guaranteed to execute on the cpu.
1248 *
1249 * This function is to be used by rogue workers and rescuers to bind
1250 * themselves to the target cpu and may race with cpu going down or
1251 * coming online. kthread_bind() can't be used because it may put the
1252 * worker to already dead cpu and set_cpus_allowed_ptr() can't be used
1253 * verbatim as it's best effort and blocking and gcwq may be
1254 * [dis]associated in the meantime.
1255 *
1256 * This function tries set_cpus_allowed() and locks gcwq and verifies
1257 * the binding against GCWQ_DISASSOCIATED which is set during
1258 * CPU_DYING and cleared during CPU_ONLINE, so if the worker enters
1259 * idle state or fetches works without dropping lock, it can guarantee
1260 * the scheduling requirement described in the first paragraph.
1261 *
1262 * CONTEXT:
1263 * Might sleep. Called without any lock but returns with gcwq->lock
1264 * held.
1265 *
1266 * RETURNS:
1267 * %true if the associated gcwq is online (@worker is successfully
1268 * bound), %false if offline.
1269 */
1270static bool worker_maybe_bind_and_lock(struct worker *worker)
1271__acquires(&gcwq->lock)
1272{
1273 struct global_cwq *gcwq = worker->gcwq;
1274 struct task_struct *task = worker->task;
1275
1276 while (true) {
1277 /*
1278 * The following call may fail, succeed or succeed
1279 * without actually migrating the task to the cpu if
1280 * it races with cpu hotunplug operation. Verify
1281 * against GCWQ_DISASSOCIATED.
1282 */
1283 if (!(gcwq->flags & GCWQ_DISASSOCIATED))
1284 set_cpus_allowed_ptr(task, get_cpu_mask(gcwq->cpu));
1285
1286 spin_lock_irq(&gcwq->lock);
1287 if (gcwq->flags & GCWQ_DISASSOCIATED)
1288 return false;
1289 if (task_cpu(task) == gcwq->cpu &&
1290 cpumask_equal(¤t->cpus_allowed,
1291 get_cpu_mask(gcwq->cpu)))
1292 return true;
1293 spin_unlock_irq(&gcwq->lock);
1294
1295 /*
1296 * We've raced with CPU hot[un]plug. Give it a breather
1297 * and retry migration. cond_resched() is required here;
1298 * otherwise, we might deadlock against cpu_stop trying to
1299 * bring down the CPU on non-preemptive kernel.
1300 */
1301 cpu_relax();
1302 cond_resched();
1303 }
1304}
1305
1306/*
1307 * Function for worker->rebind_work used to rebind rogue busy workers
1308 * to the associated cpu which is coming back online. This is
1309 * scheduled by cpu up but can race with other cpu hotplug operations
1310 * and may be executed twice without intervening cpu down.
1311 */
1312static void worker_rebind_fn(struct work_struct *work)
1313{
1314 struct worker *worker = container_of(work, struct worker, rebind_work);
1315 struct global_cwq *gcwq = worker->gcwq;
1316
1317 if (worker_maybe_bind_and_lock(worker))
1318 worker_clr_flags(worker, WORKER_REBIND);
1319
1320 spin_unlock_irq(&gcwq->lock);
1321}
1322
1323static struct worker *alloc_worker(void)
1324{
1325 struct worker *worker;
1326
1327 worker = kzalloc(sizeof(*worker), GFP_KERNEL);
1328 if (worker) {
1329 INIT_LIST_HEAD(&worker->entry);
1330 INIT_LIST_HEAD(&worker->scheduled);
1331 INIT_WORK(&worker->rebind_work, worker_rebind_fn);
1332 /* on creation a worker is in !idle && prep state */
1333 worker->flags = WORKER_PREP;
1334 }
1335 return worker;
1336}
1337
1338/**
1339 * create_worker - create a new workqueue worker
1340 * @gcwq: gcwq the new worker will belong to
1341 * @bind: whether to set affinity to @cpu or not
1342 *
1343 * Create a new worker which is bound to @gcwq. The returned worker
1344 * can be started by calling start_worker() or destroyed using
1345 * destroy_worker().
1346 *
1347 * CONTEXT:
1348 * Might sleep. Does GFP_KERNEL allocations.
1349 *
1350 * RETURNS:
1351 * Pointer to the newly created worker.
1352 */
1353static struct worker *create_worker(struct global_cwq *gcwq, bool bind)
1354{
1355 bool on_unbound_cpu = gcwq->cpu == WORK_CPU_UNBOUND;
1356 struct worker *worker = NULL;
1357 int id = -1;
1358
1359 spin_lock_irq(&gcwq->lock);
1360 while (ida_get_new(&gcwq->worker_ida, &id)) {
1361 spin_unlock_irq(&gcwq->lock);
1362 if (!ida_pre_get(&gcwq->worker_ida, GFP_KERNEL))
1363 goto fail;
1364 spin_lock_irq(&gcwq->lock);
1365 }
1366 spin_unlock_irq(&gcwq->lock);
1367
1368 worker = alloc_worker();
1369 if (!worker)
1370 goto fail;
1371
1372 worker->gcwq = gcwq;
1373 worker->id = id;
1374
1375 if (!on_unbound_cpu)
1376 worker->task = kthread_create_on_node(worker_thread,
1377 worker,
1378 cpu_to_node(gcwq->cpu),
1379 "kworker/%u:%d", gcwq->cpu, id);
1380 else
1381 worker->task = kthread_create(worker_thread, worker,
1382 "kworker/u:%d", id);
1383 if (IS_ERR(worker->task))
1384 goto fail;
1385
1386 /*
1387 * A rogue worker will become a regular one if CPU comes
1388 * online later on. Make sure every worker has
1389 * PF_THREAD_BOUND set.
1390 */
1391 if (bind && !on_unbound_cpu)
1392 kthread_bind(worker->task, gcwq->cpu);
1393 else {
1394 worker->task->flags |= PF_THREAD_BOUND;
1395 if (on_unbound_cpu)
1396 worker->flags |= WORKER_UNBOUND;
1397 }
1398
1399 return worker;
1400fail:
1401 if (id >= 0) {
1402 spin_lock_irq(&gcwq->lock);
1403 ida_remove(&gcwq->worker_ida, id);
1404 spin_unlock_irq(&gcwq->lock);
1405 }
1406 kfree(worker);
1407 return NULL;
1408}
1409
1410/**
1411 * start_worker - start a newly created worker
1412 * @worker: worker to start
1413 *
1414 * Make the gcwq aware of @worker and start it.
1415 *
1416 * CONTEXT:
1417 * spin_lock_irq(gcwq->lock).
1418 */
1419static void start_worker(struct worker *worker)
1420{
1421 worker->flags |= WORKER_STARTED;
1422 worker->gcwq->nr_workers++;
1423 worker_enter_idle(worker);
1424 wake_up_process(worker->task);
1425}
1426
1427/**
1428 * destroy_worker - destroy a workqueue worker
1429 * @worker: worker to be destroyed
1430 *
1431 * Destroy @worker and adjust @gcwq stats accordingly.
1432 *
1433 * CONTEXT:
1434 * spin_lock_irq(gcwq->lock) which is released and regrabbed.
1435 */
1436static void destroy_worker(struct worker *worker)
1437{
1438 struct global_cwq *gcwq = worker->gcwq;
1439 int id = worker->id;
1440
1441 /* sanity check frenzy */
1442 BUG_ON(worker->current_work);
1443 BUG_ON(!list_empty(&worker->scheduled));
1444
1445 if (worker->flags & WORKER_STARTED)
1446 gcwq->nr_workers--;
1447 if (worker->flags & WORKER_IDLE)
1448 gcwq->nr_idle--;
1449
1450 list_del_init(&worker->entry);
1451 worker->flags |= WORKER_DIE;
1452
1453 spin_unlock_irq(&gcwq->lock);
1454
1455 kthread_stop(worker->task);
1456 kfree(worker);
1457
1458 spin_lock_irq(&gcwq->lock);
1459 ida_remove(&gcwq->worker_ida, id);
1460}
1461
1462static void idle_worker_timeout(unsigned long __gcwq)
1463{
1464 struct global_cwq *gcwq = (void *)__gcwq;
1465
1466 spin_lock_irq(&gcwq->lock);
1467
1468 if (too_many_workers(gcwq)) {
1469 struct worker *worker;
1470 unsigned long expires;
1471
1472 /* idle_list is kept in LIFO order, check the last one */
1473 worker = list_entry(gcwq->idle_list.prev, struct worker, entry);
1474 expires = worker->last_active + IDLE_WORKER_TIMEOUT;
1475
1476 if (time_before(jiffies, expires))
1477 mod_timer(&gcwq->idle_timer, expires);
1478 else {
1479 /* it's been idle for too long, wake up manager */
1480 gcwq->flags |= GCWQ_MANAGE_WORKERS;
1481 wake_up_worker(gcwq);
1482 }
1483 }
1484
1485 spin_unlock_irq(&gcwq->lock);
1486}
1487
1488static bool send_mayday(struct work_struct *work)
1489{
1490 struct cpu_workqueue_struct *cwq = get_work_cwq(work);
1491 struct workqueue_struct *wq = cwq->wq;
1492 unsigned int cpu;
1493
1494 if (!(wq->flags & WQ_RESCUER))
1495 return false;
1496
1497 /* mayday mayday mayday */
1498 cpu = cwq->gcwq->cpu;
1499 /* WORK_CPU_UNBOUND can't be set in cpumask, use cpu 0 instead */
1500 if (cpu == WORK_CPU_UNBOUND)
1501 cpu = 0;
1502 if (!mayday_test_and_set_cpu(cpu, wq->mayday_mask))
1503 wake_up_process(wq->rescuer->task);
1504 return true;
1505}
1506
1507static void gcwq_mayday_timeout(unsigned long __gcwq)
1508{
1509 struct global_cwq *gcwq = (void *)__gcwq;
1510 struct work_struct *work;
1511
1512 spin_lock_irq(&gcwq->lock);
1513
1514 if (need_to_create_worker(gcwq)) {
1515 /*
1516 * We've been trying to create a new worker but
1517 * haven't been successful. We might be hitting an
1518 * allocation deadlock. Send distress signals to
1519 * rescuers.
1520 */
1521 list_for_each_entry(work, &gcwq->worklist, entry)
1522 send_mayday(work);
1523 }
1524
1525 spin_unlock_irq(&gcwq->lock);
1526
1527 mod_timer(&gcwq->mayday_timer, jiffies + MAYDAY_INTERVAL);
1528}
1529
1530/**
1531 * maybe_create_worker - create a new worker if necessary
1532 * @gcwq: gcwq to create a new worker for
1533 *
1534 * Create a new worker for @gcwq if necessary. @gcwq is guaranteed to
1535 * have at least one idle worker on return from this function. If
1536 * creating a new worker takes longer than MAYDAY_INTERVAL, mayday is
1537 * sent to all rescuers with works scheduled on @gcwq to resolve
1538 * possible allocation deadlock.
1539 *
1540 * On return, need_to_create_worker() is guaranteed to be false and
1541 * may_start_working() true.
1542 *
1543 * LOCKING:
1544 * spin_lock_irq(gcwq->lock) which may be released and regrabbed
1545 * multiple times. Does GFP_KERNEL allocations. Called only from
1546 * manager.
1547 *
1548 * RETURNS:
1549 * false if no action was taken and gcwq->lock stayed locked, true
1550 * otherwise.
1551 */
1552static bool maybe_create_worker(struct global_cwq *gcwq)
1553__releases(&gcwq->lock)
1554__acquires(&gcwq->lock)
1555{
1556 if (!need_to_create_worker(gcwq))
1557 return false;
1558restart:
1559 spin_unlock_irq(&gcwq->lock);
1560
1561 /* if we don't make progress in MAYDAY_INITIAL_TIMEOUT, call for help */
1562 mod_timer(&gcwq->mayday_timer, jiffies + MAYDAY_INITIAL_TIMEOUT);
1563
1564 while (true) {
1565 struct worker *worker;
1566
1567 worker = create_worker(gcwq, true);
1568 if (worker) {
1569 del_timer_sync(&gcwq->mayday_timer);
1570 spin_lock_irq(&gcwq->lock);
1571 start_worker(worker);
1572 BUG_ON(need_to_create_worker(gcwq));
1573 return true;
1574 }
1575
1576 if (!need_to_create_worker(gcwq))
1577 break;
1578
1579 __set_current_state(TASK_INTERRUPTIBLE);
1580 schedule_timeout(CREATE_COOLDOWN);
1581
1582 if (!need_to_create_worker(gcwq))
1583 break;
1584 }
1585
1586 del_timer_sync(&gcwq->mayday_timer);
1587 spin_lock_irq(&gcwq->lock);
1588 if (need_to_create_worker(gcwq))
1589 goto restart;
1590 return true;
1591}
1592
1593/**
1594 * maybe_destroy_worker - destroy workers which have been idle for a while
1595 * @gcwq: gcwq to destroy workers for
1596 *
1597 * Destroy @gcwq workers which have been idle for longer than
1598 * IDLE_WORKER_TIMEOUT.
1599 *
1600 * LOCKING:
1601 * spin_lock_irq(gcwq->lock) which may be released and regrabbed
1602 * multiple times. Called only from manager.
1603 *
1604 * RETURNS:
1605 * false if no action was taken and gcwq->lock stayed locked, true
1606 * otherwise.
1607 */
1608static bool maybe_destroy_workers(struct global_cwq *gcwq)
1609{
1610 bool ret = false;
1611
1612 while (too_many_workers(gcwq)) {
1613 struct worker *worker;
1614 unsigned long expires;
1615
1616 worker = list_entry(gcwq->idle_list.prev, struct worker, entry);
1617 expires = worker->last_active + IDLE_WORKER_TIMEOUT;
1618
1619 if (time_before(jiffies, expires)) {
1620 mod_timer(&gcwq->idle_timer, expires);
1621 break;
1622 }
1623
1624 destroy_worker(worker);
1625 ret = true;
1626 }
1627
1628 return ret;
1629}
1630
1631/**
1632 * manage_workers - manage worker pool
1633 * @worker: self
1634 *
1635 * Assume the manager role and manage gcwq worker pool @worker belongs
1636 * to. At any given time, there can be only zero or one manager per
1637 * gcwq. The exclusion is handled automatically by this function.
1638 *
1639 * The caller can safely start processing works on false return. On
1640 * true return, it's guaranteed that need_to_create_worker() is false
1641 * and may_start_working() is true.
1642 *
1643 * CONTEXT:
1644 * spin_lock_irq(gcwq->lock) which may be released and regrabbed
1645 * multiple times. Does GFP_KERNEL allocations.
1646 *
1647 * RETURNS:
1648 * false if no action was taken and gcwq->lock stayed locked, true if
1649 * some action was taken.
1650 */
1651static bool manage_workers(struct worker *worker)
1652{
1653 struct global_cwq *gcwq = worker->gcwq;
1654 bool ret = false;
1655
1656 if (gcwq->flags & GCWQ_MANAGING_WORKERS)
1657 return ret;
1658
1659 gcwq->flags &= ~GCWQ_MANAGE_WORKERS;
1660 gcwq->flags |= GCWQ_MANAGING_WORKERS;
1661
1662 /*
1663 * Destroy and then create so that may_start_working() is true
1664 * on return.
1665 */
1666 ret |= maybe_destroy_workers(gcwq);
1667 ret |= maybe_create_worker(gcwq);
1668
1669 gcwq->flags &= ~GCWQ_MANAGING_WORKERS;
1670
1671 /*
1672 * The trustee might be waiting to take over the manager
1673 * position, tell it we're done.
1674 */
1675 if (unlikely(gcwq->trustee))
1676 wake_up_all(&gcwq->trustee_wait);
1677
1678 return ret;
1679}
1680
1681/**
1682 * move_linked_works - move linked works to a list
1683 * @work: start of series of works to be scheduled
1684 * @head: target list to append @work to
1685 * @nextp: out paramter for nested worklist walking
1686 *
1687 * Schedule linked works starting from @work to @head. Work series to
1688 * be scheduled starts at @work and includes any consecutive work with
1689 * WORK_STRUCT_LINKED set in its predecessor.
1690 *
1691 * If @nextp is not NULL, it's updated to point to the next work of
1692 * the last scheduled work. This allows move_linked_works() to be
1693 * nested inside outer list_for_each_entry_safe().
1694 *
1695 * CONTEXT:
1696 * spin_lock_irq(gcwq->lock).
1697 */
1698static void move_linked_works(struct work_struct *work, struct list_head *head,
1699 struct work_struct **nextp)
1700{
1701 struct work_struct *n;
1702
1703 /*
1704 * Linked worklist will always end before the end of the list,
1705 * use NULL for list head.
1706 */
1707 list_for_each_entry_safe_from(work, n, NULL, entry) {
1708 list_move_tail(&work->entry, head);
1709 if (!(*work_data_bits(work) & WORK_STRUCT_LINKED))
1710 break;
1711 }
1712
1713 /*
1714 * If we're already inside safe list traversal and have moved
1715 * multiple works to the scheduled queue, the next position
1716 * needs to be updated.
1717 */
1718 if (nextp)
1719 *nextp = n;
1720}
1721
1722static void cwq_activate_first_delayed(struct cpu_workqueue_struct *cwq)
1723{
1724 struct work_struct *work = list_first_entry(&cwq->delayed_works,
1725 struct work_struct, entry);
1726 struct list_head *pos = gcwq_determine_ins_pos(cwq->gcwq, cwq);
1727
1728 trace_workqueue_activate_work(work);
1729 move_linked_works(work, pos, NULL);
1730 __clear_bit(WORK_STRUCT_DELAYED_BIT, work_data_bits(work));
1731 cwq->nr_active++;
1732}
1733
1734/**
1735 * cwq_dec_nr_in_flight - decrement cwq's nr_in_flight
1736 * @cwq: cwq of interest
1737 * @color: color of work which left the queue
1738 * @delayed: for a delayed work
1739 *
1740 * A work either has completed or is removed from pending queue,
1741 * decrement nr_in_flight of its cwq and handle workqueue flushing.
1742 *
1743 * CONTEXT:
1744 * spin_lock_irq(gcwq->lock).
1745 */
1746static void cwq_dec_nr_in_flight(struct cpu_workqueue_struct *cwq, int color,
1747 bool delayed)
1748{
1749 /* ignore uncolored works */
1750 if (color == WORK_NO_COLOR)
1751 return;
1752
1753 cwq->nr_in_flight[color]--;
1754
1755 if (!delayed) {
1756 cwq->nr_active--;
1757 if (!list_empty(&cwq->delayed_works)) {
1758 /* one down, submit a delayed one */
1759 if (cwq->nr_active < cwq->max_active)
1760 cwq_activate_first_delayed(cwq);
1761 }
1762 }
1763
1764 /* is flush in progress and are we at the flushing tip? */
1765 if (likely(cwq->flush_color != color))
1766 return;
1767
1768 /* are there still in-flight works? */
1769 if (cwq->nr_in_flight[color])
1770 return;
1771
1772 /* this cwq is done, clear flush_color */
1773 cwq->flush_color = -1;
1774
1775 /*
1776 * If this was the last cwq, wake up the first flusher. It
1777 * will handle the rest.
1778 */
1779 if (atomic_dec_and_test(&cwq->wq->nr_cwqs_to_flush))
1780 complete(&cwq->wq->first_flusher->done);
1781}
1782
1783/**
1784 * process_one_work - process single work
1785 * @worker: self
1786 * @work: work to process
1787 *
1788 * Process @work. This function contains all the logics necessary to
1789 * process a single work including synchronization against and
1790 * interaction with other workers on the same cpu, queueing and
1791 * flushing. As long as context requirement is met, any worker can
1792 * call this function to process a work.
1793 *
1794 * CONTEXT:
1795 * spin_lock_irq(gcwq->lock) which is released and regrabbed.
1796 */
1797static void process_one_work(struct worker *worker, struct work_struct *work)
1798__releases(&gcwq->lock)
1799__acquires(&gcwq->lock)
1800{
1801 struct cpu_workqueue_struct *cwq = get_work_cwq(work);
1802 struct global_cwq *gcwq = cwq->gcwq;
1803 struct hlist_head *bwh = busy_worker_head(gcwq, work);
1804 bool cpu_intensive = cwq->wq->flags & WQ_CPU_INTENSIVE;
1805 work_func_t f = work->func;
1806 int work_color;
1807 struct worker *collision;
1808#ifdef CONFIG_LOCKDEP
1809 /*
1810 * It is permissible to free the struct work_struct from
1811 * inside the function that is called from it, this we need to
1812 * take into account for lockdep too. To avoid bogus "held
1813 * lock freed" warnings as well as problems when looking into
1814 * work->lockdep_map, make a copy and use that here.
1815 */
1816 struct lockdep_map lockdep_map = work->lockdep_map;
1817#endif
1818 /*
1819 * A single work shouldn't be executed concurrently by
1820 * multiple workers on a single cpu. Check whether anyone is
1821 * already processing the work. If so, defer the work to the
1822 * currently executing one.
1823 */
1824 collision = __find_worker_executing_work(gcwq, bwh, work);
1825 if (unlikely(collision)) {
1826 move_linked_works(work, &collision->scheduled, NULL);
1827 return;
1828 }
1829
1830 /* claim and process */
1831 debug_work_deactivate(work);
1832 hlist_add_head(&worker->hentry, bwh);
1833 worker->current_work = work;
1834 worker->current_cwq = cwq;
1835 work_color = get_work_color(work);
1836
1837 /* record the current cpu number in the work data and dequeue */
1838 set_work_cpu(work, gcwq->cpu);
1839 list_del_init(&work->entry);
1840
1841 /*
1842 * If HIGHPRI_PENDING, check the next work, and, if HIGHPRI,
1843 * wake up another worker; otherwise, clear HIGHPRI_PENDING.
1844 */
1845 if (unlikely(gcwq->flags & GCWQ_HIGHPRI_PENDING)) {
1846 struct work_struct *nwork = list_first_entry(&gcwq->worklist,
1847 struct work_struct, entry);
1848
1849 if (!list_empty(&gcwq->worklist) &&
1850 get_work_cwq(nwork)->wq->flags & WQ_HIGHPRI)
1851 wake_up_worker(gcwq);
1852 else
1853 gcwq->flags &= ~GCWQ_HIGHPRI_PENDING;
1854 }
1855
1856 /*
1857 * CPU intensive works don't participate in concurrency
1858 * management. They're the scheduler's responsibility.
1859 */
1860 if (unlikely(cpu_intensive))
1861 worker_set_flags(worker, WORKER_CPU_INTENSIVE, true);
1862
1863 spin_unlock_irq(&gcwq->lock);
1864
1865 work_clear_pending(work);
1866 lock_map_acquire_read(&cwq->wq->lockdep_map);
1867 lock_map_acquire(&lockdep_map);
1868 trace_workqueue_execute_start(work);
1869 f(work);
1870 /*
1871 * While we must be careful to not use "work" after this, the trace
1872 * point will only record its address.
1873 */
1874 trace_workqueue_execute_end(work);
1875 lock_map_release(&lockdep_map);
1876 lock_map_release(&cwq->wq->lockdep_map);
1877
1878 if (unlikely(in_atomic() || lockdep_depth(current) > 0)) {
1879 printk(KERN_ERR "BUG: workqueue leaked lock or atomic: "
1880 "%s/0x%08x/%d\n",
1881 current->comm, preempt_count(), task_pid_nr(current));
1882 printk(KERN_ERR " last function: ");
1883 print_symbol("%s\n", (unsigned long)f);
1884 debug_show_held_locks(current);
1885 dump_stack();
1886 }
1887
1888 spin_lock_irq(&gcwq->lock);
1889
1890 /* clear cpu intensive status */
1891 if (unlikely(cpu_intensive))
1892 worker_clr_flags(worker, WORKER_CPU_INTENSIVE);
1893
1894 /* we're done with it, release */
1895 hlist_del_init(&worker->hentry);
1896 worker->current_work = NULL;
1897 worker->current_cwq = NULL;
1898 cwq_dec_nr_in_flight(cwq, work_color, false);
1899}
1900
1901/**
1902 * process_scheduled_works - process scheduled works
1903 * @worker: self
1904 *
1905 * Process all scheduled works. Please note that the scheduled list
1906 * may change while processing a work, so this function repeatedly
1907 * fetches a work from the top and executes it.
1908 *
1909 * CONTEXT:
1910 * spin_lock_irq(gcwq->lock) which may be released and regrabbed
1911 * multiple times.
1912 */
1913static void process_scheduled_works(struct worker *worker)
1914{
1915 while (!list_empty(&worker->scheduled)) {
1916 struct work_struct *work = list_first_entry(&worker->scheduled,
1917 struct work_struct, entry);
1918 process_one_work(worker, work);
1919 }
1920}
1921
1922/**
1923 * worker_thread - the worker thread function
1924 * @__worker: self
1925 *
1926 * The gcwq worker thread function. There's a single dynamic pool of
1927 * these per each cpu. These workers process all works regardless of
1928 * their specific target workqueue. The only exception is works which
1929 * belong to workqueues with a rescuer which will be explained in
1930 * rescuer_thread().
1931 */
1932static int worker_thread(void *__worker)
1933{
1934 struct worker *worker = __worker;
1935 struct global_cwq *gcwq = worker->gcwq;
1936
1937 /* tell the scheduler that this is a workqueue worker */
1938 worker->task->flags |= PF_WQ_WORKER;
1939woke_up:
1940 spin_lock_irq(&gcwq->lock);
1941
1942 /* DIE can be set only while we're idle, checking here is enough */
1943 if (worker->flags & WORKER_DIE) {
1944 spin_unlock_irq(&gcwq->lock);
1945 worker->task->flags &= ~PF_WQ_WORKER;
1946 return 0;
1947 }
1948
1949 worker_leave_idle(worker);
1950recheck:
1951 /* no more worker necessary? */
1952 if (!need_more_worker(gcwq))
1953 goto sleep;
1954
1955 /* do we need to manage? */
1956 if (unlikely(!may_start_working(gcwq)) && manage_workers(worker))
1957 goto recheck;
1958
1959 /*
1960 * ->scheduled list can only be filled while a worker is
1961 * preparing to process a work or actually processing it.
1962 * Make sure nobody diddled with it while I was sleeping.
1963 */
1964 BUG_ON(!list_empty(&worker->scheduled));
1965
1966 /*
1967 * When control reaches this point, we're guaranteed to have
1968 * at least one idle worker or that someone else has already
1969 * assumed the manager role.
1970 */
1971 worker_clr_flags(worker, WORKER_PREP);
1972
1973 do {
1974 struct work_struct *work =
1975 list_first_entry(&gcwq->worklist,
1976 struct work_struct, entry);
1977
1978 if (likely(!(*work_data_bits(work) & WORK_STRUCT_LINKED))) {
1979 /* optimization path, not strictly necessary */
1980 process_one_work(worker, work);
1981 if (unlikely(!list_empty(&worker->scheduled)))
1982 process_scheduled_works(worker);
1983 } else {
1984 move_linked_works(work, &worker->scheduled, NULL);
1985 process_scheduled_works(worker);
1986 }
1987 } while (keep_working(gcwq));
1988
1989 worker_set_flags(worker, WORKER_PREP, false);
1990sleep:
1991 if (unlikely(need_to_manage_workers(gcwq)) && manage_workers(worker))
1992 goto recheck;
1993
1994 /*
1995 * gcwq->lock is held and there's no work to process and no
1996 * need to manage, sleep. Workers are woken up only while
1997 * holding gcwq->lock or from local cpu, so setting the
1998 * current state before releasing gcwq->lock is enough to
1999 * prevent losing any event.
2000 */
2001 worker_enter_idle(worker);
2002 __set_current_state(TASK_INTERRUPTIBLE);
2003 spin_unlock_irq(&gcwq->lock);
2004 schedule();
2005 goto woke_up;
2006}
2007
2008/**
2009 * rescuer_thread - the rescuer thread function
2010 * @__wq: the associated workqueue
2011 *
2012 * Workqueue rescuer thread function. There's one rescuer for each
2013 * workqueue which has WQ_RESCUER set.
2014 *
2015 * Regular work processing on a gcwq may block trying to create a new
2016 * worker which uses GFP_KERNEL allocation which has slight chance of
2017 * developing into deadlock if some works currently on the same queue
2018 * need to be processed to satisfy the GFP_KERNEL allocation. This is
2019 * the problem rescuer solves.
2020 *
2021 * When such condition is possible, the gcwq summons rescuers of all
2022 * workqueues which have works queued on the gcwq and let them process
2023 * those works so that forward progress can be guaranteed.
2024 *
2025 * This should happen rarely.
2026 */
2027static int rescuer_thread(void *__wq)
2028{
2029 struct workqueue_struct *wq = __wq;
2030 struct worker *rescuer = wq->rescuer;
2031 struct list_head *scheduled = &rescuer->scheduled;
2032 bool is_unbound = wq->flags & WQ_UNBOUND;
2033 unsigned int cpu;
2034
2035 set_user_nice(current, RESCUER_NICE_LEVEL);
2036repeat:
2037 set_current_state(TASK_INTERRUPTIBLE);
2038
2039 if (kthread_should_stop())
2040 return 0;
2041
2042 /*
2043 * See whether any cpu is asking for help. Unbounded
2044 * workqueues use cpu 0 in mayday_mask for CPU_UNBOUND.
2045 */
2046 for_each_mayday_cpu(cpu, wq->mayday_mask) {
2047 unsigned int tcpu = is_unbound ? WORK_CPU_UNBOUND : cpu;
2048 struct cpu_workqueue_struct *cwq = get_cwq(tcpu, wq);
2049 struct global_cwq *gcwq = cwq->gcwq;
2050 struct work_struct *work, *n;
2051
2052 __set_current_state(TASK_RUNNING);
2053 mayday_clear_cpu(cpu, wq->mayday_mask);
2054
2055 /* migrate to the target cpu if possible */
2056 rescuer->gcwq = gcwq;
2057 worker_maybe_bind_and_lock(rescuer);
2058
2059 /*
2060 * Slurp in all works issued via this workqueue and
2061 * process'em.
2062 */
2063 BUG_ON(!list_empty(&rescuer->scheduled));
2064 list_for_each_entry_safe(work, n, &gcwq->worklist, entry)
2065 if (get_work_cwq(work) == cwq)
2066 move_linked_works(work, scheduled, &n);
2067
2068 process_scheduled_works(rescuer);
2069
2070 /*
2071 * Leave this gcwq. If keep_working() is %true, notify a
2072 * regular worker; otherwise, we end up with 0 concurrency
2073 * and stalling the execution.
2074 */
2075 if (keep_working(gcwq))
2076 wake_up_worker(gcwq);
2077
2078 spin_unlock_irq(&gcwq->lock);
2079 }
2080
2081 schedule();
2082 goto repeat;
2083}
2084
2085struct wq_barrier {
2086 struct work_struct work;
2087 struct completion done;
2088};
2089
2090static void wq_barrier_func(struct work_struct *work)
2091{
2092 struct wq_barrier *barr = container_of(work, struct wq_barrier, work);
2093 complete(&barr->done);
2094}
2095
2096/**
2097 * insert_wq_barrier - insert a barrier work
2098 * @cwq: cwq to insert barrier into
2099 * @barr: wq_barrier to insert
2100 * @target: target work to attach @barr to
2101 * @worker: worker currently executing @target, NULL if @target is not executing
2102 *
2103 * @barr is linked to @target such that @barr is completed only after
2104 * @target finishes execution. Please note that the ordering
2105 * guarantee is observed only with respect to @target and on the local
2106 * cpu.
2107 *
2108 * Currently, a queued barrier can't be canceled. This is because
2109 * try_to_grab_pending() can't determine whether the work to be
2110 * grabbed is at the head of the queue and thus can't clear LINKED
2111 * flag of the previous work while there must be a valid next work
2112 * after a work with LINKED flag set.
2113 *
2114 * Note that when @worker is non-NULL, @target may be modified
2115 * underneath us, so we can't reliably determine cwq from @target.
2116 *
2117 * CONTEXT:
2118 * spin_lock_irq(gcwq->lock).
2119 */
2120static void insert_wq_barrier(struct cpu_workqueue_struct *cwq,
2121 struct wq_barrier *barr,
2122 struct work_struct *target, struct worker *worker)
2123{
2124 struct list_head *head;
2125 unsigned int linked = 0;
2126
2127 /*
2128 * debugobject calls are safe here even with gcwq->lock locked
2129 * as we know for sure that this will not trigger any of the
2130 * checks and call back into the fixup functions where we
2131 * might deadlock.
2132 */
2133 INIT_WORK_ONSTACK(&barr->work, wq_barrier_func);
2134 __set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(&barr->work));
2135 init_completion(&barr->done);
2136
2137 /*
2138 * If @target is currently being executed, schedule the
2139 * barrier to the worker; otherwise, put it after @target.
2140 */
2141 if (worker)
2142 head = worker->scheduled.next;
2143 else {
2144 unsigned long *bits = work_data_bits(target);
2145
2146 head = target->entry.next;
2147 /* there can already be other linked works, inherit and set */
2148 linked = *bits & WORK_STRUCT_LINKED;
2149 __set_bit(WORK_STRUCT_LINKED_BIT, bits);
2150 }
2151
2152 debug_work_activate(&barr->work);
2153 insert_work(cwq, &barr->work, head,
2154 work_color_to_flags(WORK_NO_COLOR) | linked);
2155}
2156
2157/**
2158 * flush_workqueue_prep_cwqs - prepare cwqs for workqueue flushing
2159 * @wq: workqueue being flushed
2160 * @flush_color: new flush color, < 0 for no-op
2161 * @work_color: new work color, < 0 for no-op
2162 *
2163 * Prepare cwqs for workqueue flushing.
2164 *
2165 * If @flush_color is non-negative, flush_color on all cwqs should be
2166 * -1. If no cwq has in-flight commands at the specified color, all
2167 * cwq->flush_color's stay at -1 and %false is returned. If any cwq
2168 * has in flight commands, its cwq->flush_color is set to
2169 * @flush_color, @wq->nr_cwqs_to_flush is updated accordingly, cwq
2170 * wakeup logic is armed and %true is returned.
2171 *
2172 * The caller should have initialized @wq->first_flusher prior to
2173 * calling this function with non-negative @flush_color. If
2174 * @flush_color is negative, no flush color update is done and %false
2175 * is returned.
2176 *
2177 * If @work_color is non-negative, all cwqs should have the same
2178 * work_color which is previous to @work_color and all will be
2179 * advanced to @work_color.
2180 *
2181 * CONTEXT:
2182 * mutex_lock(wq->flush_mutex).
2183 *
2184 * RETURNS:
2185 * %true if @flush_color >= 0 and there's something to flush. %false
2186 * otherwise.
2187 */
2188static bool flush_workqueue_prep_cwqs(struct workqueue_struct *wq,
2189 int flush_color, int work_color)
2190{
2191 bool wait = false;
2192 unsigned int cpu;
2193
2194 if (flush_color >= 0) {
2195 BUG_ON(atomic_read(&wq->nr_cwqs_to_flush));
2196 atomic_set(&wq->nr_cwqs_to_flush, 1);
2197 }
2198
2199 for_each_cwq_cpu(cpu, wq) {
2200 struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
2201 struct global_cwq *gcwq = cwq->gcwq;
2202
2203 spin_lock_irq(&gcwq->lock);
2204
2205 if (flush_color >= 0) {
2206 BUG_ON(cwq->flush_color != -1);
2207
2208 if (cwq->nr_in_flight[flush_color]) {
2209 cwq->flush_color = flush_color;
2210 atomic_inc(&wq->nr_cwqs_to_flush);
2211 wait = true;
2212 }
2213 }
2214
2215 if (work_color >= 0) {
2216 BUG_ON(work_color != work_next_color(cwq->work_color));
2217 cwq->work_color = work_color;
2218 }
2219
2220 spin_unlock_irq(&gcwq->lock);
2221 }
2222
2223 if (flush_color >= 0 && atomic_dec_and_test(&wq->nr_cwqs_to_flush))
2224 complete(&wq->first_flusher->done);
2225
2226 return wait;
2227}
2228
2229/**
2230 * flush_workqueue - ensure that any scheduled work has run to completion.
2231 * @wq: workqueue to flush
2232 *
2233 * Forces execution of the workqueue and blocks until its completion.
2234 * This is typically used in driver shutdown handlers.
2235 *
2236 * We sleep until all works which were queued on entry have been handled,
2237 * but we are not livelocked by new incoming ones.
2238 */
2239void flush_workqueue(struct workqueue_struct *wq)
2240{
2241 struct wq_flusher this_flusher = {
2242 .list = LIST_HEAD_INIT(this_flusher.list),
2243 .flush_color = -1,
2244 .done = COMPLETION_INITIALIZER_ONSTACK(this_flusher.done),
2245 };
2246 int next_color;
2247
2248 lock_map_acquire(&wq->lockdep_map);
2249 lock_map_release(&wq->lockdep_map);
2250
2251 mutex_lock(&wq->flush_mutex);
2252
2253 /*
2254 * Start-to-wait phase
2255 */
2256 next_color = work_next_color(wq->work_color);
2257
2258 if (next_color != wq->flush_color) {
2259 /*
2260 * Color space is not full. The current work_color
2261 * becomes our flush_color and work_color is advanced
2262 * by one.
2263 */
2264 BUG_ON(!list_empty(&wq->flusher_overflow));
2265 this_flusher.flush_color = wq->work_color;
2266 wq->work_color = next_color;
2267
2268 if (!wq->first_flusher) {
2269 /* no flush in progress, become the first flusher */
2270 BUG_ON(wq->flush_color != this_flusher.flush_color);
2271
2272 wq->first_flusher = &this_flusher;
2273
2274 if (!flush_workqueue_prep_cwqs(wq, wq->flush_color,
2275 wq->work_color)) {
2276 /* nothing to flush, done */
2277 wq->flush_color = next_color;
2278 wq->first_flusher = NULL;
2279 goto out_unlock;
2280 }
2281 } else {
2282 /* wait in queue */
2283 BUG_ON(wq->flush_color == this_flusher.flush_color);
2284 list_add_tail(&this_flusher.list, &wq->flusher_queue);
2285 flush_workqueue_prep_cwqs(wq, -1, wq->work_color);
2286 }
2287 } else {
2288 /*
2289 * Oops, color space is full, wait on overflow queue.
2290 * The next flush completion will assign us
2291 * flush_color and transfer to flusher_queue.
2292 */
2293 list_add_tail(&this_flusher.list, &wq->flusher_overflow);
2294 }
2295
2296 mutex_unlock(&wq->flush_mutex);
2297
2298 wait_for_completion(&this_flusher.done);
2299
2300 /*
2301 * Wake-up-and-cascade phase
2302 *
2303 * First flushers are responsible for cascading flushes and
2304 * handling overflow. Non-first flushers can simply return.
2305 */
2306 if (wq->first_flusher != &this_flusher)
2307 return;
2308
2309 mutex_lock(&wq->flush_mutex);
2310
2311 /* we might have raced, check again with mutex held */
2312 if (wq->first_flusher != &this_flusher)
2313 goto out_unlock;
2314
2315 wq->first_flusher = NULL;
2316
2317 BUG_ON(!list_empty(&this_flusher.list));
2318 BUG_ON(wq->flush_color != this_flusher.flush_color);
2319
2320 while (true) {
2321 struct wq_flusher *next, *tmp;
2322
2323 /* complete all the flushers sharing the current flush color */
2324 list_for_each_entry_safe(next, tmp, &wq->flusher_queue, list) {
2325 if (next->flush_color != wq->flush_color)
2326 break;
2327 list_del_init(&next->list);
2328 complete(&next->done);
2329 }
2330
2331 BUG_ON(!list_empty(&wq->flusher_overflow) &&
2332 wq->flush_color != work_next_color(wq->work_color));
2333
2334 /* this flush_color is finished, advance by one */
2335 wq->flush_color = work_next_color(wq->flush_color);
2336
2337 /* one color has been freed, handle overflow queue */
2338 if (!list_empty(&wq->flusher_overflow)) {
2339 /*
2340 * Assign the same color to all overflowed
2341 * flushers, advance work_color and append to
2342 * flusher_queue. This is the start-to-wait
2343 * phase for these overflowed flushers.
2344 */
2345 list_for_each_entry(tmp, &wq->flusher_overflow, list)
2346 tmp->flush_color = wq->work_color;
2347
2348 wq->work_color = work_next_color(wq->work_color);
2349
2350 list_splice_tail_init(&wq->flusher_overflow,
2351 &wq->flusher_queue);
2352 flush_workqueue_prep_cwqs(wq, -1, wq->work_color);
2353 }
2354
2355 if (list_empty(&wq->flusher_queue)) {
2356 BUG_ON(wq->flush_color != wq->work_color);
2357 break;
2358 }
2359
2360 /*
2361 * Need to flush more colors. Make the next flusher
2362 * the new first flusher and arm cwqs.
2363 */
2364 BUG_ON(wq->flush_color == wq->work_color);
2365 BUG_ON(wq->flush_color != next->flush_color);
2366
2367 list_del_init(&next->list);
2368 wq->first_flusher = next;
2369
2370 if (flush_workqueue_prep_cwqs(wq, wq->flush_color, -1))
2371 break;
2372
2373 /*
2374 * Meh... this color is already done, clear first
2375 * flusher and repeat cascading.
2376 */
2377 wq->first_flusher = NULL;
2378 }
2379
2380out_unlock:
2381 mutex_unlock(&wq->flush_mutex);
2382}
2383EXPORT_SYMBOL_GPL(flush_workqueue);
2384
2385/**
2386 * drain_workqueue - drain a workqueue
2387 * @wq: workqueue to drain
2388 *
2389 * Wait until the workqueue becomes empty. While draining is in progress,
2390 * only chain queueing is allowed. IOW, only currently pending or running
2391 * work items on @wq can queue further work items on it. @wq is flushed
2392 * repeatedly until it becomes empty. The number of flushing is detemined
2393 * by the depth of chaining and should be relatively short. Whine if it
2394 * takes too long.
2395 */
2396void drain_workqueue(struct workqueue_struct *wq)
2397{
2398 unsigned int flush_cnt = 0;
2399 unsigned int cpu;
2400
2401 /*
2402 * __queue_work() needs to test whether there are drainers, is much
2403 * hotter than drain_workqueue() and already looks at @wq->flags.
2404 * Use WQ_DRAINING so that queue doesn't have to check nr_drainers.
2405 */
2406 spin_lock(&workqueue_lock);
2407 if (!wq->nr_drainers++)
2408 wq->flags |= WQ_DRAINING;
2409 spin_unlock(&workqueue_lock);
2410reflush:
2411 flush_workqueue(wq);
2412
2413 for_each_cwq_cpu(cpu, wq) {
2414 struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
2415 bool drained;
2416
2417 spin_lock_irq(&cwq->gcwq->lock);
2418 drained = !cwq->nr_active && list_empty(&cwq->delayed_works);
2419 spin_unlock_irq(&cwq->gcwq->lock);
2420
2421 if (drained)
2422 continue;
2423
2424 if (++flush_cnt == 10 ||
2425 (flush_cnt % 100 == 0 && flush_cnt <= 1000))
2426 pr_warning("workqueue %s: flush on destruction isn't complete after %u tries\n",
2427 wq->name, flush_cnt);
2428 goto reflush;
2429 }
2430
2431 spin_lock(&workqueue_lock);
2432 if (!--wq->nr_drainers)
2433 wq->flags &= ~WQ_DRAINING;
2434 spin_unlock(&workqueue_lock);
2435}
2436EXPORT_SYMBOL_GPL(drain_workqueue);
2437
2438static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr,
2439 bool wait_executing)
2440{
2441 struct worker *worker = NULL;
2442 struct global_cwq *gcwq;
2443 struct cpu_workqueue_struct *cwq;
2444
2445 might_sleep();
2446 gcwq = get_work_gcwq(work);
2447 if (!gcwq)
2448 return false;
2449
2450 spin_lock_irq(&gcwq->lock);
2451 if (!list_empty(&work->entry)) {
2452 /*
2453 * See the comment near try_to_grab_pending()->smp_rmb().
2454 * If it was re-queued to a different gcwq under us, we
2455 * are not going to wait.
2456 */
2457 smp_rmb();
2458 cwq = get_work_cwq(work);
2459 if (unlikely(!cwq || gcwq != cwq->gcwq))
2460 goto already_gone;
2461 } else if (wait_executing) {
2462 worker = find_worker_executing_work(gcwq, work);
2463 if (!worker)
2464 goto already_gone;
2465 cwq = worker->current_cwq;
2466 } else
2467 goto already_gone;
2468
2469 insert_wq_barrier(cwq, barr, work, worker);
2470 spin_unlock_irq(&gcwq->lock);
2471
2472 /*
2473 * If @max_active is 1 or rescuer is in use, flushing another work
2474 * item on the same workqueue may lead to deadlock. Make sure the
2475 * flusher is not running on the same workqueue by verifying write
2476 * access.
2477 */
2478 if (cwq->wq->saved_max_active == 1 || cwq->wq->flags & WQ_RESCUER)
2479 lock_map_acquire(&cwq->wq->lockdep_map);
2480 else
2481 lock_map_acquire_read(&cwq->wq->lockdep_map);
2482 lock_map_release(&cwq->wq->lockdep_map);
2483
2484 return true;
2485already_gone:
2486 spin_unlock_irq(&gcwq->lock);
2487 return false;
2488}
2489
2490/**
2491 * flush_work - wait for a work to finish executing the last queueing instance
2492 * @work: the work to flush
2493 *
2494 * Wait until @work has finished execution. This function considers
2495 * only the last queueing instance of @work. If @work has been
2496 * enqueued across different CPUs on a non-reentrant workqueue or on
2497 * multiple workqueues, @work might still be executing on return on
2498 * some of the CPUs from earlier queueing.
2499 *
2500 * If @work was queued only on a non-reentrant, ordered or unbound
2501 * workqueue, @work is guaranteed to be idle on return if it hasn't
2502 * been requeued since flush started.
2503 *
2504 * RETURNS:
2505 * %true if flush_work() waited for the work to finish execution,
2506 * %false if it was already idle.
2507 */
2508bool flush_work(struct work_struct *work)
2509{
2510 struct wq_barrier barr;
2511
2512 if (start_flush_work(work, &barr, true)) {
2513 wait_for_completion(&barr.done);
2514 destroy_work_on_stack(&barr.work);
2515 return true;
2516 } else
2517 return false;
2518}
2519EXPORT_SYMBOL_GPL(flush_work);
2520
2521static bool wait_on_cpu_work(struct global_cwq *gcwq, struct work_struct *work)
2522{
2523 struct wq_barrier barr;
2524 struct worker *worker;
2525
2526 spin_lock_irq(&gcwq->lock);
2527
2528 worker = find_worker_executing_work(gcwq, work);
2529 if (unlikely(worker))
2530 insert_wq_barrier(worker->current_cwq, &barr, work, worker);
2531
2532 spin_unlock_irq(&gcwq->lock);
2533
2534 if (unlikely(worker)) {
2535 wait_for_completion(&barr.done);
2536 destroy_work_on_stack(&barr.work);
2537 return true;
2538 } else
2539 return false;
2540}
2541
2542static bool wait_on_work(struct work_struct *work)
2543{
2544 bool ret = false;
2545 int cpu;
2546
2547 might_sleep();
2548
2549 lock_map_acquire(&work->lockdep_map);
2550 lock_map_release(&work->lockdep_map);
2551
2552 for_each_gcwq_cpu(cpu)
2553 ret |= wait_on_cpu_work(get_gcwq(cpu), work);
2554 return ret;
2555}
2556
2557/**
2558 * flush_work_sync - wait until a work has finished execution
2559 * @work: the work to flush
2560 *
2561 * Wait until @work has finished execution. On return, it's
2562 * guaranteed that all queueing instances of @work which happened
2563 * before this function is called are finished. In other words, if
2564 * @work hasn't been requeued since this function was called, @work is
2565 * guaranteed to be idle on return.
2566 *
2567 * RETURNS:
2568 * %true if flush_work_sync() waited for the work to finish execution,
2569 * %false if it was already idle.
2570 */
2571bool flush_work_sync(struct work_struct *work)
2572{
2573 struct wq_barrier barr;
2574 bool pending, waited;
2575
2576 /* we'll wait for executions separately, queue barr only if pending */
2577 pending = start_flush_work(work, &barr, false);
2578
2579 /* wait for executions to finish */
2580 waited = wait_on_work(work);
2581
2582 /* wait for the pending one */
2583 if (pending) {
2584 wait_for_completion(&barr.done);
2585 destroy_work_on_stack(&barr.work);
2586 }
2587
2588 return pending || waited;
2589}
2590EXPORT_SYMBOL_GPL(flush_work_sync);
2591
2592/*
2593 * Upon a successful return (>= 0), the caller "owns" WORK_STRUCT_PENDING bit,
2594 * so this work can't be re-armed in any way.
2595 */
2596static int try_to_grab_pending(struct work_struct *work)
2597{
2598 struct global_cwq *gcwq;
2599 int ret = -1;
2600
2601 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work)))
2602 return 0;
2603
2604 /*
2605 * The queueing is in progress, or it is already queued. Try to
2606 * steal it from ->worklist without clearing WORK_STRUCT_PENDING.
2607 */
2608 gcwq = get_work_gcwq(work);
2609 if (!gcwq)
2610 return ret;
2611
2612 spin_lock_irq(&gcwq->lock);
2613 if (!list_empty(&work->entry)) {
2614 /*
2615 * This work is queued, but perhaps we locked the wrong gcwq.
2616 * In that case we must see the new value after rmb(), see
2617 * insert_work()->wmb().
2618 */
2619 smp_rmb();
2620 if (gcwq == get_work_gcwq(work)) {
2621 debug_work_deactivate(work);
2622 list_del_init(&work->entry);
2623 cwq_dec_nr_in_flight(get_work_cwq(work),
2624 get_work_color(work),
2625 *work_data_bits(work) & WORK_STRUCT_DELAYED);
2626 ret = 1;
2627 }
2628 }
2629 spin_unlock_irq(&gcwq->lock);
2630
2631 return ret;
2632}
2633
2634static bool __cancel_work_timer(struct work_struct *work,
2635 struct timer_list* timer)
2636{
2637 int ret;
2638
2639 do {
2640 ret = (timer && likely(del_timer(timer)));
2641 if (!ret)
2642 ret = try_to_grab_pending(work);
2643 wait_on_work(work);
2644 } while (unlikely(ret < 0));
2645
2646 clear_work_data(work);
2647 return ret;
2648}
2649
2650/**
2651 * cancel_work_sync - cancel a work and wait for it to finish
2652 * @work: the work to cancel
2653 *
2654 * Cancel @work and wait for its execution to finish. This function
2655 * can be used even if the work re-queues itself or migrates to
2656 * another workqueue. On return from this function, @work is
2657 * guaranteed to be not pending or executing on any CPU.
2658 *
2659 * cancel_work_sync(&delayed_work->work) must not be used for
2660 * delayed_work's. Use cancel_delayed_work_sync() instead.
2661 *
2662 * The caller must ensure that the workqueue on which @work was last
2663 * queued can't be destroyed before this function returns.
2664 *
2665 * RETURNS:
2666 * %true if @work was pending, %false otherwise.
2667 */
2668bool cancel_work_sync(struct work_struct *work)
2669{
2670 return __cancel_work_timer(work, NULL);
2671}
2672EXPORT_SYMBOL_GPL(cancel_work_sync);
2673
2674/**
2675 * flush_delayed_work - wait for a dwork to finish executing the last queueing
2676 * @dwork: the delayed work to flush
2677 *
2678 * Delayed timer is cancelled and the pending work is queued for
2679 * immediate execution. Like flush_work(), this function only
2680 * considers the last queueing instance of @dwork.
2681 *
2682 * RETURNS:
2683 * %true if flush_work() waited for the work to finish execution,
2684 * %false if it was already idle.
2685 */
2686bool flush_delayed_work(struct delayed_work *dwork)
2687{
2688 if (del_timer_sync(&dwork->timer))
2689 __queue_work(raw_smp_processor_id(),
2690 get_work_cwq(&dwork->work)->wq, &dwork->work);
2691 return flush_work(&dwork->work);
2692}
2693EXPORT_SYMBOL(flush_delayed_work);
2694
2695/**
2696 * flush_delayed_work_sync - wait for a dwork to finish
2697 * @dwork: the delayed work to flush
2698 *
2699 * Delayed timer is cancelled and the pending work is queued for
2700 * execution immediately. Other than timer handling, its behavior
2701 * is identical to flush_work_sync().
2702 *
2703 * RETURNS:
2704 * %true if flush_work_sync() waited for the work to finish execution,
2705 * %false if it was already idle.
2706 */
2707bool flush_delayed_work_sync(struct delayed_work *dwork)
2708{
2709 if (del_timer_sync(&dwork->timer))
2710 __queue_work(raw_smp_processor_id(),
2711 get_work_cwq(&dwork->work)->wq, &dwork->work);
2712 return flush_work_sync(&dwork->work);
2713}
2714EXPORT_SYMBOL(flush_delayed_work_sync);
2715
2716/**
2717 * cancel_delayed_work_sync - cancel a delayed work and wait for it to finish
2718 * @dwork: the delayed work cancel
2719 *
2720 * This is cancel_work_sync() for delayed works.
2721 *
2722 * RETURNS:
2723 * %true if @dwork was pending, %false otherwise.
2724 */
2725bool cancel_delayed_work_sync(struct delayed_work *dwork)
2726{
2727 return __cancel_work_timer(&dwork->work, &dwork->timer);
2728}
2729EXPORT_SYMBOL(cancel_delayed_work_sync);
2730
2731/**
2732 * schedule_work - put work task in global workqueue
2733 * @work: job to be done
2734 *
2735 * Returns zero if @work was already on the kernel-global workqueue and
2736 * non-zero otherwise.
2737 *
2738 * This puts a job in the kernel-global workqueue if it was not already
2739 * queued and leaves it in the same position on the kernel-global
2740 * workqueue otherwise.
2741 */
2742int schedule_work(struct work_struct *work)
2743{
2744 return queue_work(system_wq, work);
2745}
2746EXPORT_SYMBOL(schedule_work);
2747
2748/*
2749 * schedule_work_on - put work task on a specific cpu
2750 * @cpu: cpu to put the work task on
2751 * @work: job to be done
2752 *
2753 * This puts a job on a specific cpu
2754 */
2755int schedule_work_on(int cpu, struct work_struct *work)
2756{
2757 return queue_work_on(cpu, system_wq, work);
2758}
2759EXPORT_SYMBOL(schedule_work_on);
2760
2761/**
2762 * schedule_delayed_work - put work task in global workqueue after delay
2763 * @dwork: job to be done
2764 * @delay: number of jiffies to wait or 0 for immediate execution
2765 *
2766 * After waiting for a given time this puts a job in the kernel-global
2767 * workqueue.
2768 */
2769int schedule_delayed_work(struct delayed_work *dwork,
2770 unsigned long delay)
2771{
2772 return queue_delayed_work(system_wq, dwork, delay);
2773}
2774EXPORT_SYMBOL(schedule_delayed_work);
2775
2776/**
2777 * schedule_delayed_work_on - queue work in global workqueue on CPU after delay
2778 * @cpu: cpu to use
2779 * @dwork: job to be done
2780 * @delay: number of jiffies to wait
2781 *
2782 * After waiting for a given time this puts a job in the kernel-global
2783 * workqueue on the specified CPU.
2784 */
2785int schedule_delayed_work_on(int cpu,
2786 struct delayed_work *dwork, unsigned long delay)
2787{
2788 return queue_delayed_work_on(cpu, system_wq, dwork, delay);
2789}
2790EXPORT_SYMBOL(schedule_delayed_work_on);
2791
2792/**
2793 * schedule_on_each_cpu - execute a function synchronously on each online CPU
2794 * @func: the function to call
2795 *
2796 * schedule_on_each_cpu() executes @func on each online CPU using the
2797 * system workqueue and blocks until all CPUs have completed.
2798 * schedule_on_each_cpu() is very slow.
2799 *
2800 * RETURNS:
2801 * 0 on success, -errno on failure.
2802 */
2803int schedule_on_each_cpu(work_func_t func)
2804{
2805 int cpu;
2806 struct work_struct __percpu *works;
2807
2808 works = alloc_percpu(struct work_struct);
2809 if (!works)
2810 return -ENOMEM;
2811
2812 get_online_cpus();
2813
2814 for_each_online_cpu(cpu) {
2815 struct work_struct *work = per_cpu_ptr(works, cpu);
2816
2817 INIT_WORK(work, func);
2818 schedule_work_on(cpu, work);
2819 }
2820
2821 for_each_online_cpu(cpu)
2822 flush_work(per_cpu_ptr(works, cpu));
2823
2824 put_online_cpus();
2825 free_percpu(works);
2826 return 0;
2827}
2828
2829/**
2830 * flush_scheduled_work - ensure that any scheduled work has run to completion.
2831 *
2832 * Forces execution of the kernel-global workqueue and blocks until its
2833 * completion.
2834 *
2835 * Think twice before calling this function! It's very easy to get into
2836 * trouble if you don't take great care. Either of the following situations
2837 * will lead to deadlock:
2838 *
2839 * One of the work items currently on the workqueue needs to acquire
2840 * a lock held by your code or its caller.
2841 *
2842 * Your code is running in the context of a work routine.
2843 *
2844 * They will be detected by lockdep when they occur, but the first might not
2845 * occur very often. It depends on what work items are on the workqueue and
2846 * what locks they need, which you have no control over.
2847 *
2848 * In most situations flushing the entire workqueue is overkill; you merely
2849 * need to know that a particular work item isn't queued and isn't running.
2850 * In such cases you should use cancel_delayed_work_sync() or
2851 * cancel_work_sync() instead.
2852 */
2853void flush_scheduled_work(void)
2854{
2855 flush_workqueue(system_wq);
2856}
2857EXPORT_SYMBOL(flush_scheduled_work);
2858
2859/**
2860 * execute_in_process_context - reliably execute the routine with user context
2861 * @fn: the function to execute
2862 * @ew: guaranteed storage for the execute work structure (must
2863 * be available when the work executes)
2864 *
2865 * Executes the function immediately if process context is available,
2866 * otherwise schedules the function for delayed execution.
2867 *
2868 * Returns: 0 - function was executed
2869 * 1 - function was scheduled for execution
2870 */
2871int execute_in_process_context(work_func_t fn, struct execute_work *ew)
2872{
2873 if (!in_interrupt()) {
2874 fn(&ew->work);
2875 return 0;
2876 }
2877
2878 INIT_WORK(&ew->work, fn);
2879 schedule_work(&ew->work);
2880
2881 return 1;
2882}
2883EXPORT_SYMBOL_GPL(execute_in_process_context);
2884
2885int keventd_up(void)
2886{
2887 return system_wq != NULL;
2888}
2889
2890static int alloc_cwqs(struct workqueue_struct *wq)
2891{
2892 /*
2893 * cwqs are forced aligned according to WORK_STRUCT_FLAG_BITS.
2894 * Make sure that the alignment isn't lower than that of
2895 * unsigned long long.
2896 */
2897 const size_t size = sizeof(struct cpu_workqueue_struct);
2898 const size_t align = max_t(size_t, 1 << WORK_STRUCT_FLAG_BITS,
2899 __alignof__(unsigned long long));
2900#ifdef CONFIG_SMP
2901 bool percpu = !(wq->flags & WQ_UNBOUND);
2902#else
2903 bool percpu = false;
2904#endif
2905
2906 if (percpu)
2907 wq->cpu_wq.pcpu = __alloc_percpu(size, align);
2908 else {
2909 void *ptr;
2910
2911 /*
2912 * Allocate enough room to align cwq and put an extra
2913 * pointer at the end pointing back to the originally
2914 * allocated pointer which will be used for free.
2915 */
2916 ptr = kzalloc(size + align + sizeof(void *), GFP_KERNEL);
2917 if (ptr) {
2918 wq->cpu_wq.single = PTR_ALIGN(ptr, align);
2919 *(void **)(wq->cpu_wq.single + 1) = ptr;
2920 }
2921 }
2922
2923 /* just in case, make sure it's actually aligned */
2924 BUG_ON(!IS_ALIGNED(wq->cpu_wq.v, align));
2925 return wq->cpu_wq.v ? 0 : -ENOMEM;
2926}
2927
2928static void free_cwqs(struct workqueue_struct *wq)
2929{
2930#ifdef CONFIG_SMP
2931 bool percpu = !(wq->flags & WQ_UNBOUND);
2932#else
2933 bool percpu = false;
2934#endif
2935
2936 if (percpu)
2937 free_percpu(wq->cpu_wq.pcpu);
2938 else if (wq->cpu_wq.single) {
2939 /* the pointer to free is stored right after the cwq */
2940 kfree(*(void **)(wq->cpu_wq.single + 1));
2941 }
2942}
2943
2944static int wq_clamp_max_active(int max_active, unsigned int flags,
2945 const char *name)
2946{
2947 int lim = flags & WQ_UNBOUND ? WQ_UNBOUND_MAX_ACTIVE : WQ_MAX_ACTIVE;
2948
2949 if (max_active < 1 || max_active > lim)
2950 printk(KERN_WARNING "workqueue: max_active %d requested for %s "
2951 "is out of range, clamping between %d and %d\n",
2952 max_active, name, 1, lim);
2953
2954 return clamp_val(max_active, 1, lim);
2955}
2956
2957struct workqueue_struct *__alloc_workqueue_key(const char *name,
2958 unsigned int flags,
2959 int max_active,
2960 struct lock_class_key *key,
2961 const char *lock_name)
2962{
2963 struct workqueue_struct *wq;
2964 unsigned int cpu;
2965
2966 /*
2967 * Workqueues which may be used during memory reclaim should
2968 * have a rescuer to guarantee forward progress.
2969 */
2970 if (flags & WQ_MEM_RECLAIM)
2971 flags |= WQ_RESCUER;
2972
2973 /*
2974 * Unbound workqueues aren't concurrency managed and should be
2975 * dispatched to workers immediately.
2976 */
2977 if (flags & WQ_UNBOUND)
2978 flags |= WQ_HIGHPRI;
2979
2980 max_active = max_active ?: WQ_DFL_ACTIVE;
2981 max_active = wq_clamp_max_active(max_active, flags, name);
2982
2983 wq = kzalloc(sizeof(*wq), GFP_KERNEL);
2984 if (!wq)
2985 goto err;
2986
2987 wq->flags = flags;
2988 wq->saved_max_active = max_active;
2989 mutex_init(&wq->flush_mutex);
2990 atomic_set(&wq->nr_cwqs_to_flush, 0);
2991 INIT_LIST_HEAD(&wq->flusher_queue);
2992 INIT_LIST_HEAD(&wq->flusher_overflow);
2993
2994 wq->name = name;
2995 lockdep_init_map(&wq->lockdep_map, lock_name, key, 0);
2996 INIT_LIST_HEAD(&wq->list);
2997
2998 if (alloc_cwqs(wq) < 0)
2999 goto err;
3000
3001 for_each_cwq_cpu(cpu, wq) {
3002 struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
3003 struct global_cwq *gcwq = get_gcwq(cpu);
3004
3005 BUG_ON((unsigned long)cwq & WORK_STRUCT_FLAG_MASK);
3006 cwq->gcwq = gcwq;
3007 cwq->wq = wq;
3008 cwq->flush_color = -1;
3009 cwq->max_active = max_active;
3010 INIT_LIST_HEAD(&cwq->delayed_works);
3011 }
3012
3013 if (flags & WQ_RESCUER) {
3014 struct worker *rescuer;
3015
3016 if (!alloc_mayday_mask(&wq->mayday_mask, GFP_KERNEL))
3017 goto err;
3018
3019 wq->rescuer = rescuer = alloc_worker();
3020 if (!rescuer)
3021 goto err;
3022
3023 rescuer->task = kthread_create(rescuer_thread, wq, "%s", name);
3024 if (IS_ERR(rescuer->task))
3025 goto err;
3026
3027 rescuer->task->flags |= PF_THREAD_BOUND;
3028 wake_up_process(rescuer->task);
3029 }
3030
3031 /*
3032 * workqueue_lock protects global freeze state and workqueues
3033 * list. Grab it, set max_active accordingly and add the new
3034 * workqueue to workqueues list.
3035 */
3036 spin_lock(&workqueue_lock);
3037
3038 if (workqueue_freezing && wq->flags & WQ_FREEZABLE)
3039 for_each_cwq_cpu(cpu, wq)
3040 get_cwq(cpu, wq)->max_active = 0;
3041
3042 list_add(&wq->list, &workqueues);
3043
3044 spin_unlock(&workqueue_lock);
3045
3046 return wq;
3047err:
3048 if (wq) {
3049 free_cwqs(wq);
3050 free_mayday_mask(wq->mayday_mask);
3051 kfree(wq->rescuer);
3052 kfree(wq);
3053 }
3054 return NULL;
3055}
3056EXPORT_SYMBOL_GPL(__alloc_workqueue_key);
3057
3058/**
3059 * destroy_workqueue - safely terminate a workqueue
3060 * @wq: target workqueue
3061 *
3062 * Safely destroy a workqueue. All work currently pending will be done first.
3063 */
3064void destroy_workqueue(struct workqueue_struct *wq)
3065{
3066 unsigned int cpu;
3067
3068 /* drain it before proceeding with destruction */
3069 drain_workqueue(wq);
3070
3071 /*
3072 * wq list is used to freeze wq, remove from list after
3073 * flushing is complete in case freeze races us.
3074 */
3075 spin_lock(&workqueue_lock);
3076 list_del(&wq->list);
3077 spin_unlock(&workqueue_lock);
3078
3079 /* sanity check */
3080 for_each_cwq_cpu(cpu, wq) {
3081 struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
3082 int i;
3083
3084 for (i = 0; i < WORK_NR_COLORS; i++)
3085 BUG_ON(cwq->nr_in_flight[i]);
3086 BUG_ON(cwq->nr_active);
3087 BUG_ON(!list_empty(&cwq->delayed_works));
3088 }
3089
3090 if (wq->flags & WQ_RESCUER) {
3091 kthread_stop(wq->rescuer->task);
3092 free_mayday_mask(wq->mayday_mask);
3093 kfree(wq->rescuer);
3094 }
3095
3096 free_cwqs(wq);
3097 kfree(wq);
3098}
3099EXPORT_SYMBOL_GPL(destroy_workqueue);
3100
3101/**
3102 * workqueue_set_max_active - adjust max_active of a workqueue
3103 * @wq: target workqueue
3104 * @max_active: new max_active value.
3105 *
3106 * Set max_active of @wq to @max_active.
3107 *
3108 * CONTEXT:
3109 * Don't call from IRQ context.
3110 */
3111void workqueue_set_max_active(struct workqueue_struct *wq, int max_active)
3112{
3113 unsigned int cpu;
3114
3115 max_active = wq_clamp_max_active(max_active, wq->flags, wq->name);
3116
3117 spin_lock(&workqueue_lock);
3118
3119 wq->saved_max_active = max_active;
3120
3121 for_each_cwq_cpu(cpu, wq) {
3122 struct global_cwq *gcwq = get_gcwq(cpu);
3123
3124 spin_lock_irq(&gcwq->lock);
3125
3126 if (!(wq->flags & WQ_FREEZABLE) ||
3127 !(gcwq->flags & GCWQ_FREEZING))
3128 get_cwq(gcwq->cpu, wq)->max_active = max_active;
3129
3130 spin_unlock_irq(&gcwq->lock);
3131 }
3132
3133 spin_unlock(&workqueue_lock);
3134}
3135EXPORT_SYMBOL_GPL(workqueue_set_max_active);
3136
3137/**
3138 * workqueue_congested - test whether a workqueue is congested
3139 * @cpu: CPU in question
3140 * @wq: target workqueue
3141 *
3142 * Test whether @wq's cpu workqueue for @cpu is congested. There is
3143 * no synchronization around this function and the test result is
3144 * unreliable and only useful as advisory hints or for debugging.
3145 *
3146 * RETURNS:
3147 * %true if congested, %false otherwise.
3148 */
3149bool workqueue_congested(unsigned int cpu, struct workqueue_struct *wq)
3150{
3151 struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
3152
3153 return !list_empty(&cwq->delayed_works);
3154}
3155EXPORT_SYMBOL_GPL(workqueue_congested);
3156
3157/**
3158 * work_cpu - return the last known associated cpu for @work
3159 * @work: the work of interest
3160 *
3161 * RETURNS:
3162 * CPU number if @work was ever queued. WORK_CPU_NONE otherwise.
3163 */
3164unsigned int work_cpu(struct work_struct *work)
3165{
3166 struct global_cwq *gcwq = get_work_gcwq(work);
3167
3168 return gcwq ? gcwq->cpu : WORK_CPU_NONE;
3169}
3170EXPORT_SYMBOL_GPL(work_cpu);
3171
3172/**
3173 * work_busy - test whether a work is currently pending or running
3174 * @work: the work to be tested
3175 *
3176 * Test whether @work is currently pending or running. There is no
3177 * synchronization around this function and the test result is
3178 * unreliable and only useful as advisory hints or for debugging.
3179 * Especially for reentrant wqs, the pending state might hide the
3180 * running state.
3181 *
3182 * RETURNS:
3183 * OR'd bitmask of WORK_BUSY_* bits.
3184 */
3185unsigned int work_busy(struct work_struct *work)
3186{
3187 struct global_cwq *gcwq = get_work_gcwq(work);
3188 unsigned long flags;
3189 unsigned int ret = 0;
3190
3191 if (!gcwq)
3192 return false;
3193
3194 spin_lock_irqsave(&gcwq->lock, flags);
3195
3196 if (work_pending(work))
3197 ret |= WORK_BUSY_PENDING;
3198 if (find_worker_executing_work(gcwq, work))
3199 ret |= WORK_BUSY_RUNNING;
3200
3201 spin_unlock_irqrestore(&gcwq->lock, flags);
3202
3203 return ret;
3204}
3205EXPORT_SYMBOL_GPL(work_busy);
3206
3207/*
3208 * CPU hotplug.
3209 *
3210 * There are two challenges in supporting CPU hotplug. Firstly, there
3211 * are a lot of assumptions on strong associations among work, cwq and
3212 * gcwq which make migrating pending and scheduled works very
3213 * difficult to implement without impacting hot paths. Secondly,
3214 * gcwqs serve mix of short, long and very long running works making
3215 * blocked draining impractical.
3216 *
3217 * This is solved by allowing a gcwq to be detached from CPU, running
3218 * it with unbound (rogue) workers and allowing it to be reattached
3219 * later if the cpu comes back online. A separate thread is created
3220 * to govern a gcwq in such state and is called the trustee of the
3221 * gcwq.
3222 *
3223 * Trustee states and their descriptions.
3224 *
3225 * START Command state used on startup. On CPU_DOWN_PREPARE, a
3226 * new trustee is started with this state.
3227 *
3228 * IN_CHARGE Once started, trustee will enter this state after
3229 * assuming the manager role and making all existing
3230 * workers rogue. DOWN_PREPARE waits for trustee to
3231 * enter this state. After reaching IN_CHARGE, trustee
3232 * tries to execute the pending worklist until it's empty
3233 * and the state is set to BUTCHER, or the state is set
3234 * to RELEASE.
3235 *
3236 * BUTCHER Command state which is set by the cpu callback after
3237 * the cpu has went down. Once this state is set trustee
3238 * knows that there will be no new works on the worklist
3239 * and once the worklist is empty it can proceed to
3240 * killing idle workers.
3241 *
3242 * RELEASE Command state which is set by the cpu callback if the
3243 * cpu down has been canceled or it has come online
3244 * again. After recognizing this state, trustee stops
3245 * trying to drain or butcher and clears ROGUE, rebinds
3246 * all remaining workers back to the cpu and releases
3247 * manager role.
3248 *
3249 * DONE Trustee will enter this state after BUTCHER or RELEASE
3250 * is complete.
3251 *
3252 * trustee CPU draining
3253 * took over down complete
3254 * START -----------> IN_CHARGE -----------> BUTCHER -----------> DONE
3255 * | | ^
3256 * | CPU is back online v return workers |
3257 * ----------------> RELEASE --------------
3258 */
3259
3260/**
3261 * trustee_wait_event_timeout - timed event wait for trustee
3262 * @cond: condition to wait for
3263 * @timeout: timeout in jiffies
3264 *
3265 * wait_event_timeout() for trustee to use. Handles locking and
3266 * checks for RELEASE request.
3267 *
3268 * CONTEXT:
3269 * spin_lock_irq(gcwq->lock) which may be released and regrabbed
3270 * multiple times. To be used by trustee.
3271 *
3272 * RETURNS:
3273 * Positive indicating left time if @cond is satisfied, 0 if timed
3274 * out, -1 if canceled.
3275 */
3276#define trustee_wait_event_timeout(cond, timeout) ({ \
3277 long __ret = (timeout); \
3278 while (!((cond) || (gcwq->trustee_state == TRUSTEE_RELEASE)) && \
3279 __ret) { \
3280 spin_unlock_irq(&gcwq->lock); \
3281 __wait_event_timeout(gcwq->trustee_wait, (cond) || \
3282 (gcwq->trustee_state == TRUSTEE_RELEASE), \
3283 __ret); \
3284 spin_lock_irq(&gcwq->lock); \
3285 } \
3286 gcwq->trustee_state == TRUSTEE_RELEASE ? -1 : (__ret); \
3287})
3288
3289/**
3290 * trustee_wait_event - event wait for trustee
3291 * @cond: condition to wait for
3292 *
3293 * wait_event() for trustee to use. Automatically handles locking and
3294 * checks for CANCEL request.
3295 *
3296 * CONTEXT:
3297 * spin_lock_irq(gcwq->lock) which may be released and regrabbed
3298 * multiple times. To be used by trustee.
3299 *
3300 * RETURNS:
3301 * 0 if @cond is satisfied, -1 if canceled.
3302 */
3303#define trustee_wait_event(cond) ({ \
3304 long __ret1; \
3305 __ret1 = trustee_wait_event_timeout(cond, MAX_SCHEDULE_TIMEOUT);\
3306 __ret1 < 0 ? -1 : 0; \
3307})
3308
3309static int __cpuinit trustee_thread(void *__gcwq)
3310{
3311 struct global_cwq *gcwq = __gcwq;
3312 struct worker *worker;
3313 struct work_struct *work;
3314 struct hlist_node *pos;
3315 long rc;
3316 int i;
3317
3318 BUG_ON(gcwq->cpu != smp_processor_id());
3319
3320 spin_lock_irq(&gcwq->lock);
3321 /*
3322 * Claim the manager position and make all workers rogue.
3323 * Trustee must be bound to the target cpu and can't be
3324 * cancelled.
3325 */
3326 BUG_ON(gcwq->cpu != smp_processor_id());
3327 rc = trustee_wait_event(!(gcwq->flags & GCWQ_MANAGING_WORKERS));
3328 BUG_ON(rc < 0);
3329
3330 gcwq->flags |= GCWQ_MANAGING_WORKERS;
3331
3332 list_for_each_entry(worker, &gcwq->idle_list, entry)
3333 worker->flags |= WORKER_ROGUE;
3334
3335 for_each_busy_worker(worker, i, pos, gcwq)
3336 worker->flags |= WORKER_ROGUE;
3337
3338 /*
3339 * Call schedule() so that we cross rq->lock and thus can
3340 * guarantee sched callbacks see the rogue flag. This is
3341 * necessary as scheduler callbacks may be invoked from other
3342 * cpus.
3343 */
3344 spin_unlock_irq(&gcwq->lock);
3345 schedule();
3346 spin_lock_irq(&gcwq->lock);
3347
3348 /*
3349 * Sched callbacks are disabled now. Zap nr_running. After
3350 * this, nr_running stays zero and need_more_worker() and
3351 * keep_working() are always true as long as the worklist is
3352 * not empty.
3353 */
3354 atomic_set(get_gcwq_nr_running(gcwq->cpu), 0);
3355
3356 spin_unlock_irq(&gcwq->lock);
3357 del_timer_sync(&gcwq->idle_timer);
3358 spin_lock_irq(&gcwq->lock);
3359
3360 /*
3361 * We're now in charge. Notify and proceed to drain. We need
3362 * to keep the gcwq running during the whole CPU down
3363 * procedure as other cpu hotunplug callbacks may need to
3364 * flush currently running tasks.
3365 */
3366 gcwq->trustee_state = TRUSTEE_IN_CHARGE;
3367 wake_up_all(&gcwq->trustee_wait);
3368
3369 /*
3370 * The original cpu is in the process of dying and may go away
3371 * anytime now. When that happens, we and all workers would
3372 * be migrated to other cpus. Try draining any left work. We
3373 * want to get it over with ASAP - spam rescuers, wake up as
3374 * many idlers as necessary and create new ones till the
3375 * worklist is empty. Note that if the gcwq is frozen, there
3376 * may be frozen works in freezable cwqs. Don't declare
3377 * completion while frozen.
3378 */
3379 while (gcwq->nr_workers != gcwq->nr_idle ||
3380 gcwq->flags & GCWQ_FREEZING ||
3381 gcwq->trustee_state == TRUSTEE_IN_CHARGE) {
3382 int nr_works = 0;
3383
3384 list_for_each_entry(work, &gcwq->worklist, entry) {
3385 send_mayday(work);
3386 nr_works++;
3387 }
3388
3389 list_for_each_entry(worker, &gcwq->idle_list, entry) {
3390 if (!nr_works--)
3391 break;
3392 wake_up_process(worker->task);
3393 }
3394
3395 if (need_to_create_worker(gcwq)) {
3396 spin_unlock_irq(&gcwq->lock);
3397 worker = create_worker(gcwq, false);
3398 spin_lock_irq(&gcwq->lock);
3399 if (worker) {
3400 worker->flags |= WORKER_ROGUE;
3401 start_worker(worker);
3402 }
3403 }
3404
3405 /* give a breather */
3406 if (trustee_wait_event_timeout(false, TRUSTEE_COOLDOWN) < 0)
3407 break;
3408 }
3409
3410 /*
3411 * Either all works have been scheduled and cpu is down, or
3412 * cpu down has already been canceled. Wait for and butcher
3413 * all workers till we're canceled.
3414 */
3415 do {
3416 rc = trustee_wait_event(!list_empty(&gcwq->idle_list));
3417 while (!list_empty(&gcwq->idle_list))
3418 destroy_worker(list_first_entry(&gcwq->idle_list,
3419 struct worker, entry));
3420 } while (gcwq->nr_workers && rc >= 0);
3421
3422 /*
3423 * At this point, either draining has completed and no worker
3424 * is left, or cpu down has been canceled or the cpu is being
3425 * brought back up. There shouldn't be any idle one left.
3426 * Tell the remaining busy ones to rebind once it finishes the
3427 * currently scheduled works by scheduling the rebind_work.
3428 */
3429 WARN_ON(!list_empty(&gcwq->idle_list));
3430
3431 for_each_busy_worker(worker, i, pos, gcwq) {
3432 struct work_struct *rebind_work = &worker->rebind_work;
3433
3434 /*
3435 * Rebind_work may race with future cpu hotplug
3436 * operations. Use a separate flag to mark that
3437 * rebinding is scheduled.
3438 */
3439 worker->flags |= WORKER_REBIND;
3440 worker->flags &= ~WORKER_ROGUE;
3441
3442 /* queue rebind_work, wq doesn't matter, use the default one */
3443 if (test_and_set_bit(WORK_STRUCT_PENDING_BIT,
3444 work_data_bits(rebind_work)))
3445 continue;
3446
3447 debug_work_activate(rebind_work);
3448 insert_work(get_cwq(gcwq->cpu, system_wq), rebind_work,
3449 worker->scheduled.next,
3450 work_color_to_flags(WORK_NO_COLOR));
3451 }
3452
3453 /* relinquish manager role */
3454 gcwq->flags &= ~GCWQ_MANAGING_WORKERS;
3455
3456 /* notify completion */
3457 gcwq->trustee = NULL;
3458 gcwq->trustee_state = TRUSTEE_DONE;
3459 wake_up_all(&gcwq->trustee_wait);
3460 spin_unlock_irq(&gcwq->lock);
3461 return 0;
3462}
3463
3464/**
3465 * wait_trustee_state - wait for trustee to enter the specified state
3466 * @gcwq: gcwq the trustee of interest belongs to
3467 * @state: target state to wait for
3468 *
3469 * Wait for the trustee to reach @state. DONE is already matched.
3470 *
3471 * CONTEXT:
3472 * spin_lock_irq(gcwq->lock) which may be released and regrabbed
3473 * multiple times. To be used by cpu_callback.
3474 */
3475static void __cpuinit wait_trustee_state(struct global_cwq *gcwq, int state)
3476__releases(&gcwq->lock)
3477__acquires(&gcwq->lock)
3478{
3479 if (!(gcwq->trustee_state == state ||
3480 gcwq->trustee_state == TRUSTEE_DONE)) {
3481 spin_unlock_irq(&gcwq->lock);
3482 __wait_event(gcwq->trustee_wait,
3483 gcwq->trustee_state == state ||
3484 gcwq->trustee_state == TRUSTEE_DONE);
3485 spin_lock_irq(&gcwq->lock);
3486 }
3487}
3488
3489static int __devinit workqueue_cpu_callback(struct notifier_block *nfb,
3490 unsigned long action,
3491 void *hcpu)
3492{
3493 unsigned int cpu = (unsigned long)hcpu;
3494 struct global_cwq *gcwq = get_gcwq(cpu);
3495 struct task_struct *new_trustee = NULL;
3496 struct worker *uninitialized_var(new_worker);
3497 unsigned long flags;
3498
3499 action &= ~CPU_TASKS_FROZEN;
3500
3501 switch (action) {
3502 case CPU_DOWN_PREPARE:
3503 new_trustee = kthread_create(trustee_thread, gcwq,
3504 "workqueue_trustee/%d\n", cpu);
3505 if (IS_ERR(new_trustee))
3506 return notifier_from_errno(PTR_ERR(new_trustee));
3507 kthread_bind(new_trustee, cpu);
3508 /* fall through */
3509 case CPU_UP_PREPARE:
3510 BUG_ON(gcwq->first_idle);
3511 new_worker = create_worker(gcwq, false);
3512 if (!new_worker) {
3513 if (new_trustee)
3514 kthread_stop(new_trustee);
3515 return NOTIFY_BAD;
3516 }
3517 }
3518
3519 /* some are called w/ irq disabled, don't disturb irq status */
3520 spin_lock_irqsave(&gcwq->lock, flags);
3521
3522 switch (action) {
3523 case CPU_DOWN_PREPARE:
3524 /* initialize trustee and tell it to acquire the gcwq */
3525 BUG_ON(gcwq->trustee || gcwq->trustee_state != TRUSTEE_DONE);
3526 gcwq->trustee = new_trustee;
3527 gcwq->trustee_state = TRUSTEE_START;
3528 wake_up_process(gcwq->trustee);
3529 wait_trustee_state(gcwq, TRUSTEE_IN_CHARGE);
3530 /* fall through */
3531 case CPU_UP_PREPARE:
3532 BUG_ON(gcwq->first_idle);
3533 gcwq->first_idle = new_worker;
3534 break;
3535
3536 case CPU_DYING:
3537 /*
3538 * Before this, the trustee and all workers except for
3539 * the ones which are still executing works from
3540 * before the last CPU down must be on the cpu. After
3541 * this, they'll all be diasporas.
3542 */
3543 gcwq->flags |= GCWQ_DISASSOCIATED;
3544 break;
3545
3546 case CPU_POST_DEAD:
3547 gcwq->trustee_state = TRUSTEE_BUTCHER;
3548 /* fall through */
3549 case CPU_UP_CANCELED:
3550 destroy_worker(gcwq->first_idle);
3551 gcwq->first_idle = NULL;
3552 break;
3553
3554 case CPU_DOWN_FAILED:
3555 case CPU_ONLINE:
3556 gcwq->flags &= ~GCWQ_DISASSOCIATED;
3557 if (gcwq->trustee_state != TRUSTEE_DONE) {
3558 gcwq->trustee_state = TRUSTEE_RELEASE;
3559 wake_up_process(gcwq->trustee);
3560 wait_trustee_state(gcwq, TRUSTEE_DONE);
3561 }
3562
3563 /*
3564 * Trustee is done and there might be no worker left.
3565 * Put the first_idle in and request a real manager to
3566 * take a look.
3567 */
3568 spin_unlock_irq(&gcwq->lock);
3569 kthread_bind(gcwq->first_idle->task, cpu);
3570 spin_lock_irq(&gcwq->lock);
3571 gcwq->flags |= GCWQ_MANAGE_WORKERS;
3572 start_worker(gcwq->first_idle);
3573 gcwq->first_idle = NULL;
3574 break;
3575 }
3576
3577 spin_unlock_irqrestore(&gcwq->lock, flags);
3578
3579 return notifier_from_errno(0);
3580}
3581
3582#ifdef CONFIG_SMP
3583
3584struct work_for_cpu {
3585 struct completion completion;
3586 long (*fn)(void *);
3587 void *arg;
3588 long ret;
3589};
3590
3591static int do_work_for_cpu(void *_wfc)
3592{
3593 struct work_for_cpu *wfc = _wfc;
3594 wfc->ret = wfc->fn(wfc->arg);
3595 complete(&wfc->completion);
3596 return 0;
3597}
3598
3599/**
3600 * work_on_cpu - run a function in user context on a particular cpu
3601 * @cpu: the cpu to run on
3602 * @fn: the function to run
3603 * @arg: the function arg
3604 *
3605 * This will return the value @fn returns.
3606 * It is up to the caller to ensure that the cpu doesn't go offline.
3607 * The caller must not hold any locks which would prevent @fn from completing.
3608 */
3609long work_on_cpu(unsigned int cpu, long (*fn)(void *), void *arg)
3610{
3611 struct task_struct *sub_thread;
3612 struct work_for_cpu wfc = {
3613 .completion = COMPLETION_INITIALIZER_ONSTACK(wfc.completion),
3614 .fn = fn,
3615 .arg = arg,
3616 };
3617
3618 sub_thread = kthread_create(do_work_for_cpu, &wfc, "work_for_cpu");
3619 if (IS_ERR(sub_thread))
3620 return PTR_ERR(sub_thread);
3621 kthread_bind(sub_thread, cpu);
3622 wake_up_process(sub_thread);
3623 wait_for_completion(&wfc.completion);
3624 return wfc.ret;
3625}
3626EXPORT_SYMBOL_GPL(work_on_cpu);
3627#endif /* CONFIG_SMP */
3628
3629#ifdef CONFIG_FREEZER
3630
3631/**
3632 * freeze_workqueues_begin - begin freezing workqueues
3633 *
3634 * Start freezing workqueues. After this function returns, all freezable
3635 * workqueues will queue new works to their frozen_works list instead of
3636 * gcwq->worklist.
3637 *
3638 * CONTEXT:
3639 * Grabs and releases workqueue_lock and gcwq->lock's.
3640 */
3641void freeze_workqueues_begin(void)
3642{
3643 unsigned int cpu;
3644
3645 spin_lock(&workqueue_lock);
3646
3647 BUG_ON(workqueue_freezing);
3648 workqueue_freezing = true;
3649
3650 for_each_gcwq_cpu(cpu) {
3651 struct global_cwq *gcwq = get_gcwq(cpu);
3652 struct workqueue_struct *wq;
3653
3654 spin_lock_irq(&gcwq->lock);
3655
3656 BUG_ON(gcwq->flags & GCWQ_FREEZING);
3657 gcwq->flags |= GCWQ_FREEZING;
3658
3659 list_for_each_entry(wq, &workqueues, list) {
3660 struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
3661
3662 if (cwq && wq->flags & WQ_FREEZABLE)
3663 cwq->max_active = 0;
3664 }
3665
3666 spin_unlock_irq(&gcwq->lock);
3667 }
3668
3669 spin_unlock(&workqueue_lock);
3670}
3671
3672/**
3673 * freeze_workqueues_busy - are freezable workqueues still busy?
3674 *
3675 * Check whether freezing is complete. This function must be called
3676 * between freeze_workqueues_begin() and thaw_workqueues().
3677 *
3678 * CONTEXT:
3679 * Grabs and releases workqueue_lock.
3680 *
3681 * RETURNS:
3682 * %true if some freezable workqueues are still busy. %false if freezing
3683 * is complete.
3684 */
3685bool freeze_workqueues_busy(void)
3686{
3687 unsigned int cpu;
3688 bool busy = false;
3689
3690 spin_lock(&workqueue_lock);
3691
3692 BUG_ON(!workqueue_freezing);
3693
3694 for_each_gcwq_cpu(cpu) {
3695 struct workqueue_struct *wq;
3696 /*
3697 * nr_active is monotonically decreasing. It's safe
3698 * to peek without lock.
3699 */
3700 list_for_each_entry(wq, &workqueues, list) {
3701 struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
3702
3703 if (!cwq || !(wq->flags & WQ_FREEZABLE))
3704 continue;
3705
3706 BUG_ON(cwq->nr_active < 0);
3707 if (cwq->nr_active) {
3708 busy = true;
3709 goto out_unlock;
3710 }
3711 }
3712 }
3713out_unlock:
3714 spin_unlock(&workqueue_lock);
3715 return busy;
3716}
3717
3718/**
3719 * thaw_workqueues - thaw workqueues
3720 *
3721 * Thaw workqueues. Normal queueing is restored and all collected
3722 * frozen works are transferred to their respective gcwq worklists.
3723 *
3724 * CONTEXT:
3725 * Grabs and releases workqueue_lock and gcwq->lock's.
3726 */
3727void thaw_workqueues(void)
3728{
3729 unsigned int cpu;
3730
3731 spin_lock(&workqueue_lock);
3732
3733 if (!workqueue_freezing)
3734 goto out_unlock;
3735
3736 for_each_gcwq_cpu(cpu) {
3737 struct global_cwq *gcwq = get_gcwq(cpu);
3738 struct workqueue_struct *wq;
3739
3740 spin_lock_irq(&gcwq->lock);
3741
3742 BUG_ON(!(gcwq->flags & GCWQ_FREEZING));
3743 gcwq->flags &= ~GCWQ_FREEZING;
3744
3745 list_for_each_entry(wq, &workqueues, list) {
3746 struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
3747
3748 if (!cwq || !(wq->flags & WQ_FREEZABLE))
3749 continue;
3750
3751 /* restore max_active and repopulate worklist */
3752 cwq->max_active = wq->saved_max_active;
3753
3754 while (!list_empty(&cwq->delayed_works) &&
3755 cwq->nr_active < cwq->max_active)
3756 cwq_activate_first_delayed(cwq);
3757 }
3758
3759 wake_up_worker(gcwq);
3760
3761 spin_unlock_irq(&gcwq->lock);
3762 }
3763
3764 workqueue_freezing = false;
3765out_unlock:
3766 spin_unlock(&workqueue_lock);
3767}
3768#endif /* CONFIG_FREEZER */
3769
3770static int __init init_workqueues(void)
3771{
3772 unsigned int cpu;
3773 int i;
3774
3775 cpu_notifier(workqueue_cpu_callback, CPU_PRI_WORKQUEUE);
3776
3777 /* initialize gcwqs */
3778 for_each_gcwq_cpu(cpu) {
3779 struct global_cwq *gcwq = get_gcwq(cpu);
3780
3781 spin_lock_init(&gcwq->lock);
3782 INIT_LIST_HEAD(&gcwq->worklist);
3783 gcwq->cpu = cpu;
3784 gcwq->flags |= GCWQ_DISASSOCIATED;
3785
3786 INIT_LIST_HEAD(&gcwq->idle_list);
3787 for (i = 0; i < BUSY_WORKER_HASH_SIZE; i++)
3788 INIT_HLIST_HEAD(&gcwq->busy_hash[i]);
3789
3790 init_timer_deferrable(&gcwq->idle_timer);
3791 gcwq->idle_timer.function = idle_worker_timeout;
3792 gcwq->idle_timer.data = (unsigned long)gcwq;
3793
3794 setup_timer(&gcwq->mayday_timer, gcwq_mayday_timeout,
3795 (unsigned long)gcwq);
3796
3797 ida_init(&gcwq->worker_ida);
3798
3799 gcwq->trustee_state = TRUSTEE_DONE;
3800 init_waitqueue_head(&gcwq->trustee_wait);
3801 }
3802
3803 /* create the initial worker */
3804 for_each_online_gcwq_cpu(cpu) {
3805 struct global_cwq *gcwq = get_gcwq(cpu);
3806 struct worker *worker;
3807
3808 if (cpu != WORK_CPU_UNBOUND)
3809 gcwq->flags &= ~GCWQ_DISASSOCIATED;
3810 worker = create_worker(gcwq, true);
3811 BUG_ON(!worker);
3812 spin_lock_irq(&gcwq->lock);
3813 start_worker(worker);
3814 spin_unlock_irq(&gcwq->lock);
3815 }
3816
3817 system_wq = alloc_workqueue("events", 0, 0);
3818 system_long_wq = alloc_workqueue("events_long", 0, 0);
3819 system_nrt_wq = alloc_workqueue("events_nrt", WQ_NON_REENTRANT, 0);
3820 system_unbound_wq = alloc_workqueue("events_unbound", WQ_UNBOUND,
3821 WQ_UNBOUND_MAX_ACTIVE);
3822 system_freezable_wq = alloc_workqueue("events_freezable",
3823 WQ_FREEZABLE, 0);
3824 BUG_ON(!system_wq || !system_long_wq || !system_nrt_wq ||
3825 !system_unbound_wq || !system_freezable_wq);
3826 return 0;
3827}
3828early_initcall(init_workqueues);