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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_online; /* can kworkers be created yet? */
294
295static bool wq_numa_enabled; /* unbound NUMA affinity enabled */
296
297/* buf for wq_update_unbound_numa_attrs(), protected by CPU hotplug exclusion */
298static struct workqueue_attrs *wq_update_unbound_numa_attrs_buf;
299
300static DEFINE_MUTEX(wq_pool_mutex); /* protects pools and workqueues list */
301static DEFINE_SPINLOCK(wq_mayday_lock); /* protects wq->maydays list */
302
303static LIST_HEAD(workqueues); /* PR: list of all workqueues */
304static bool workqueue_freezing; /* PL: have wqs started freezing? */
305
306/* PL: allowable cpus for unbound wqs and work items */
307static cpumask_var_t wq_unbound_cpumask;
308
309/* CPU where unbound work was last round robin scheduled from this CPU */
310static DEFINE_PER_CPU(int, wq_rr_cpu_last);
311
312/*
313 * Local execution of unbound work items is no longer guaranteed. The
314 * following always forces round-robin CPU selection on unbound work items
315 * to uncover usages which depend on it.
316 */
317#ifdef CONFIG_DEBUG_WQ_FORCE_RR_CPU
318static bool wq_debug_force_rr_cpu = true;
319#else
320static bool wq_debug_force_rr_cpu = false;
321#endif
322module_param_named(debug_force_rr_cpu, wq_debug_force_rr_cpu, bool, 0644);
323
324/* the per-cpu worker pools */
325static DEFINE_PER_CPU_SHARED_ALIGNED(struct worker_pool [NR_STD_WORKER_POOLS], cpu_worker_pools);
326
327static DEFINE_IDR(worker_pool_idr); /* PR: idr of all pools */
328
329/* PL: hash of all unbound pools keyed by pool->attrs */
330static DEFINE_HASHTABLE(unbound_pool_hash, UNBOUND_POOL_HASH_ORDER);
331
332/* I: attributes used when instantiating standard unbound pools on demand */
333static struct workqueue_attrs *unbound_std_wq_attrs[NR_STD_WORKER_POOLS];
334
335/* I: attributes used when instantiating ordered pools on demand */
336static struct workqueue_attrs *ordered_wq_attrs[NR_STD_WORKER_POOLS];
337
338struct workqueue_struct *system_wq __read_mostly;
339EXPORT_SYMBOL(system_wq);
340struct workqueue_struct *system_highpri_wq __read_mostly;
341EXPORT_SYMBOL_GPL(system_highpri_wq);
342struct workqueue_struct *system_long_wq __read_mostly;
343EXPORT_SYMBOL_GPL(system_long_wq);
344struct workqueue_struct *system_unbound_wq __read_mostly;
345EXPORT_SYMBOL_GPL(system_unbound_wq);
346struct workqueue_struct *system_freezable_wq __read_mostly;
347EXPORT_SYMBOL_GPL(system_freezable_wq);
348struct workqueue_struct *system_power_efficient_wq __read_mostly;
349EXPORT_SYMBOL_GPL(system_power_efficient_wq);
350struct workqueue_struct *system_freezable_power_efficient_wq __read_mostly;
351EXPORT_SYMBOL_GPL(system_freezable_power_efficient_wq);
352
353static int worker_thread(void *__worker);
354static void workqueue_sysfs_unregister(struct workqueue_struct *wq);
355
356#define CREATE_TRACE_POINTS
357#include <trace/events/workqueue.h>
358
359#define assert_rcu_or_pool_mutex() \
360 RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held() && \
361 !lockdep_is_held(&wq_pool_mutex), \
362 "sched RCU or wq_pool_mutex should be held")
363
364#define assert_rcu_or_wq_mutex(wq) \
365 RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held() && \
366 !lockdep_is_held(&wq->mutex), \
367 "sched RCU or wq->mutex should be held")
368
369#define assert_rcu_or_wq_mutex_or_pool_mutex(wq) \
370 RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held() && \
371 !lockdep_is_held(&wq->mutex) && \
372 !lockdep_is_held(&wq_pool_mutex), \
373 "sched RCU, wq->mutex or wq_pool_mutex should be held")
374
375#define for_each_cpu_worker_pool(pool, cpu) \
376 for ((pool) = &per_cpu(cpu_worker_pools, cpu)[0]; \
377 (pool) < &per_cpu(cpu_worker_pools, cpu)[NR_STD_WORKER_POOLS]; \
378 (pool)++)
379
380/**
381 * for_each_pool - iterate through all worker_pools in the system
382 * @pool: iteration cursor
383 * @pi: integer used for iteration
384 *
385 * This must be called either with wq_pool_mutex held or sched RCU read
386 * locked. If the pool needs to be used beyond the locking in effect, the
387 * caller is responsible for guaranteeing that the pool stays online.
388 *
389 * The if/else clause exists only for the lockdep assertion and can be
390 * ignored.
391 */
392#define for_each_pool(pool, pi) \
393 idr_for_each_entry(&worker_pool_idr, pool, pi) \
394 if (({ assert_rcu_or_pool_mutex(); false; })) { } \
395 else
396
397/**
398 * for_each_pool_worker - iterate through all workers of a worker_pool
399 * @worker: iteration cursor
400 * @pool: worker_pool to iterate workers of
401 *
402 * This must be called with @pool->attach_mutex.
403 *
404 * The if/else clause exists only for the lockdep assertion and can be
405 * ignored.
406 */
407#define for_each_pool_worker(worker, pool) \
408 list_for_each_entry((worker), &(pool)->workers, node) \
409 if (({ lockdep_assert_held(&pool->attach_mutex); false; })) { } \
410 else
411
412/**
413 * for_each_pwq - iterate through all pool_workqueues of the specified workqueue
414 * @pwq: iteration cursor
415 * @wq: the target workqueue
416 *
417 * This must be called either with wq->mutex held or sched RCU read locked.
418 * If the pwq needs to be used beyond the locking in effect, the caller is
419 * responsible for guaranteeing that the pwq stays online.
420 *
421 * The if/else clause exists only for the lockdep assertion and can be
422 * ignored.
423 */
424#define for_each_pwq(pwq, wq) \
425 list_for_each_entry_rcu((pwq), &(wq)->pwqs, pwqs_node) \
426 if (({ assert_rcu_or_wq_mutex(wq); false; })) { } \
427 else
428
429#ifdef CONFIG_DEBUG_OBJECTS_WORK
430
431static struct debug_obj_descr work_debug_descr;
432
433static void *work_debug_hint(void *addr)
434{
435 return ((struct work_struct *) addr)->func;
436}
437
438static bool work_is_static_object(void *addr)
439{
440 struct work_struct *work = addr;
441
442 return test_bit(WORK_STRUCT_STATIC_BIT, work_data_bits(work));
443}
444
445/*
446 * fixup_init is called when:
447 * - an active object is initialized
448 */
449static bool work_fixup_init(void *addr, enum debug_obj_state state)
450{
451 struct work_struct *work = addr;
452
453 switch (state) {
454 case ODEBUG_STATE_ACTIVE:
455 cancel_work_sync(work);
456 debug_object_init(work, &work_debug_descr);
457 return true;
458 default:
459 return false;
460 }
461}
462
463/*
464 * fixup_free is called when:
465 * - an active object is freed
466 */
467static bool work_fixup_free(void *addr, enum debug_obj_state state)
468{
469 struct work_struct *work = addr;
470
471 switch (state) {
472 case ODEBUG_STATE_ACTIVE:
473 cancel_work_sync(work);
474 debug_object_free(work, &work_debug_descr);
475 return true;
476 default:
477 return false;
478 }
479}
480
481static struct debug_obj_descr work_debug_descr = {
482 .name = "work_struct",
483 .debug_hint = work_debug_hint,
484 .is_static_object = work_is_static_object,
485 .fixup_init = work_fixup_init,
486 .fixup_free = work_fixup_free,
487};
488
489static inline void debug_work_activate(struct work_struct *work)
490{
491 debug_object_activate(work, &work_debug_descr);
492}
493
494static inline void debug_work_deactivate(struct work_struct *work)
495{
496 debug_object_deactivate(work, &work_debug_descr);
497}
498
499void __init_work(struct work_struct *work, int onstack)
500{
501 if (onstack)
502 debug_object_init_on_stack(work, &work_debug_descr);
503 else
504 debug_object_init(work, &work_debug_descr);
505}
506EXPORT_SYMBOL_GPL(__init_work);
507
508void destroy_work_on_stack(struct work_struct *work)
509{
510 debug_object_free(work, &work_debug_descr);
511}
512EXPORT_SYMBOL_GPL(destroy_work_on_stack);
513
514void destroy_delayed_work_on_stack(struct delayed_work *work)
515{
516 destroy_timer_on_stack(&work->timer);
517 debug_object_free(&work->work, &work_debug_descr);
518}
519EXPORT_SYMBOL_GPL(destroy_delayed_work_on_stack);
520
521#else
522static inline void debug_work_activate(struct work_struct *work) { }
523static inline void debug_work_deactivate(struct work_struct *work) { }
524#endif
525
526/**
527 * worker_pool_assign_id - allocate ID and assing it to @pool
528 * @pool: the pool pointer of interest
529 *
530 * Returns 0 if ID in [0, WORK_OFFQ_POOL_NONE) is allocated and assigned
531 * successfully, -errno on failure.
532 */
533static int worker_pool_assign_id(struct worker_pool *pool)
534{
535 int ret;
536
537 lockdep_assert_held(&wq_pool_mutex);
538
539 ret = idr_alloc(&worker_pool_idr, pool, 0, WORK_OFFQ_POOL_NONE,
540 GFP_KERNEL);
541 if (ret >= 0) {
542 pool->id = ret;
543 return 0;
544 }
545 return ret;
546}
547
548/**
549 * unbound_pwq_by_node - return the unbound pool_workqueue for the given node
550 * @wq: the target workqueue
551 * @node: the node ID
552 *
553 * This must be called with any of wq_pool_mutex, wq->mutex or sched RCU
554 * read locked.
555 * If the pwq needs to be used beyond the locking in effect, the caller is
556 * responsible for guaranteeing that the pwq stays online.
557 *
558 * Return: The unbound pool_workqueue for @node.
559 */
560static struct pool_workqueue *unbound_pwq_by_node(struct workqueue_struct *wq,
561 int node)
562{
563 assert_rcu_or_wq_mutex_or_pool_mutex(wq);
564
565 /*
566 * XXX: @node can be NUMA_NO_NODE if CPU goes offline while a
567 * delayed item is pending. The plan is to keep CPU -> NODE
568 * mapping valid and stable across CPU on/offlines. Once that
569 * happens, this workaround can be removed.
570 */
571 if (unlikely(node == NUMA_NO_NODE))
572 return wq->dfl_pwq;
573
574 return rcu_dereference_raw(wq->numa_pwq_tbl[node]);
575}
576
577static unsigned int work_color_to_flags(int color)
578{
579 return color << WORK_STRUCT_COLOR_SHIFT;
580}
581
582static int get_work_color(struct work_struct *work)
583{
584 return (*work_data_bits(work) >> WORK_STRUCT_COLOR_SHIFT) &
585 ((1 << WORK_STRUCT_COLOR_BITS) - 1);
586}
587
588static int work_next_color(int color)
589{
590 return (color + 1) % WORK_NR_COLORS;
591}
592
593/*
594 * While queued, %WORK_STRUCT_PWQ is set and non flag bits of a work's data
595 * contain the pointer to the queued pwq. Once execution starts, the flag
596 * is cleared and the high bits contain OFFQ flags and pool ID.
597 *
598 * set_work_pwq(), set_work_pool_and_clear_pending(), mark_work_canceling()
599 * and clear_work_data() can be used to set the pwq, pool or clear
600 * work->data. These functions should only be called while the work is
601 * owned - ie. while the PENDING bit is set.
602 *
603 * get_work_pool() and get_work_pwq() can be used to obtain the pool or pwq
604 * corresponding to a work. Pool is available once the work has been
605 * queued anywhere after initialization until it is sync canceled. pwq is
606 * available only while the work item is queued.
607 *
608 * %WORK_OFFQ_CANCELING is used to mark a work item which is being
609 * canceled. While being canceled, a work item may have its PENDING set
610 * but stay off timer and worklist for arbitrarily long and nobody should
611 * try to steal the PENDING bit.
612 */
613static inline void set_work_data(struct work_struct *work, unsigned long data,
614 unsigned long flags)
615{
616 WARN_ON_ONCE(!work_pending(work));
617 atomic_long_set(&work->data, data | flags | work_static(work));
618}
619
620static void set_work_pwq(struct work_struct *work, struct pool_workqueue *pwq,
621 unsigned long extra_flags)
622{
623 set_work_data(work, (unsigned long)pwq,
624 WORK_STRUCT_PENDING | WORK_STRUCT_PWQ | extra_flags);
625}
626
627static void set_work_pool_and_keep_pending(struct work_struct *work,
628 int pool_id)
629{
630 set_work_data(work, (unsigned long)pool_id << WORK_OFFQ_POOL_SHIFT,
631 WORK_STRUCT_PENDING);
632}
633
634static void set_work_pool_and_clear_pending(struct work_struct *work,
635 int pool_id)
636{
637 /*
638 * The following wmb is paired with the implied mb in
639 * test_and_set_bit(PENDING) and ensures all updates to @work made
640 * here are visible to and precede any updates by the next PENDING
641 * owner.
642 */
643 smp_wmb();
644 set_work_data(work, (unsigned long)pool_id << WORK_OFFQ_POOL_SHIFT, 0);
645 /*
646 * The following mb guarantees that previous clear of a PENDING bit
647 * will not be reordered with any speculative LOADS or STORES from
648 * work->current_func, which is executed afterwards. This possible
649 * reordering can lead to a missed execution on attempt to qeueue
650 * the same @work. E.g. consider this case:
651 *
652 * CPU#0 CPU#1
653 * ---------------------------- --------------------------------
654 *
655 * 1 STORE event_indicated
656 * 2 queue_work_on() {
657 * 3 test_and_set_bit(PENDING)
658 * 4 } set_..._and_clear_pending() {
659 * 5 set_work_data() # clear bit
660 * 6 smp_mb()
661 * 7 work->current_func() {
662 * 8 LOAD event_indicated
663 * }
664 *
665 * Without an explicit full barrier speculative LOAD on line 8 can
666 * be executed before CPU#0 does STORE on line 1. If that happens,
667 * CPU#0 observes the PENDING bit is still set and new execution of
668 * a @work is not queued in a hope, that CPU#1 will eventually
669 * finish the queued @work. Meanwhile CPU#1 does not see
670 * event_indicated is set, because speculative LOAD was executed
671 * before actual STORE.
672 */
673 smp_mb();
674}
675
676static void clear_work_data(struct work_struct *work)
677{
678 smp_wmb(); /* see set_work_pool_and_clear_pending() */
679 set_work_data(work, WORK_STRUCT_NO_POOL, 0);
680}
681
682static struct pool_workqueue *get_work_pwq(struct work_struct *work)
683{
684 unsigned long data = atomic_long_read(&work->data);
685
686 if (data & WORK_STRUCT_PWQ)
687 return (void *)(data & WORK_STRUCT_WQ_DATA_MASK);
688 else
689 return NULL;
690}
691
692/**
693 * get_work_pool - return the worker_pool a given work was associated with
694 * @work: the work item of interest
695 *
696 * Pools are created and destroyed under wq_pool_mutex, and allows read
697 * access under sched-RCU read lock. As such, this function should be
698 * called under wq_pool_mutex or with preemption disabled.
699 *
700 * All fields of the returned pool are accessible as long as the above
701 * mentioned locking is in effect. If the returned pool needs to be used
702 * beyond the critical section, the caller is responsible for ensuring the
703 * returned pool is and stays online.
704 *
705 * Return: The worker_pool @work was last associated with. %NULL if none.
706 */
707static struct worker_pool *get_work_pool(struct work_struct *work)
708{
709 unsigned long data = atomic_long_read(&work->data);
710 int pool_id;
711
712 assert_rcu_or_pool_mutex();
713
714 if (data & WORK_STRUCT_PWQ)
715 return ((struct pool_workqueue *)
716 (data & WORK_STRUCT_WQ_DATA_MASK))->pool;
717
718 pool_id = data >> WORK_OFFQ_POOL_SHIFT;
719 if (pool_id == WORK_OFFQ_POOL_NONE)
720 return NULL;
721
722 return idr_find(&worker_pool_idr, pool_id);
723}
724
725/**
726 * get_work_pool_id - return the worker pool ID a given work is associated with
727 * @work: the work item of interest
728 *
729 * Return: The worker_pool ID @work was last associated with.
730 * %WORK_OFFQ_POOL_NONE if none.
731 */
732static int get_work_pool_id(struct work_struct *work)
733{
734 unsigned long data = atomic_long_read(&work->data);
735
736 if (data & WORK_STRUCT_PWQ)
737 return ((struct pool_workqueue *)
738 (data & WORK_STRUCT_WQ_DATA_MASK))->pool->id;
739
740 return data >> WORK_OFFQ_POOL_SHIFT;
741}
742
743static void mark_work_canceling(struct work_struct *work)
744{
745 unsigned long pool_id = get_work_pool_id(work);
746
747 pool_id <<= WORK_OFFQ_POOL_SHIFT;
748 set_work_data(work, pool_id | WORK_OFFQ_CANCELING, WORK_STRUCT_PENDING);
749}
750
751static bool work_is_canceling(struct work_struct *work)
752{
753 unsigned long data = atomic_long_read(&work->data);
754
755 return !(data & WORK_STRUCT_PWQ) && (data & WORK_OFFQ_CANCELING);
756}
757
758/*
759 * Policy functions. These define the policies on how the global worker
760 * pools are managed. Unless noted otherwise, these functions assume that
761 * they're being called with pool->lock held.
762 */
763
764static bool __need_more_worker(struct worker_pool *pool)
765{
766 return !atomic_read(&pool->nr_running);
767}
768
769/*
770 * Need to wake up a worker? Called from anything but currently
771 * running workers.
772 *
773 * Note that, because unbound workers never contribute to nr_running, this
774 * function will always return %true for unbound pools as long as the
775 * worklist isn't empty.
776 */
777static bool need_more_worker(struct worker_pool *pool)
778{
779 return !list_empty(&pool->worklist) && __need_more_worker(pool);
780}
781
782/* Can I start working? Called from busy but !running workers. */
783static bool may_start_working(struct worker_pool *pool)
784{
785 return pool->nr_idle;
786}
787
788/* Do I need to keep working? Called from currently running workers. */
789static bool keep_working(struct worker_pool *pool)
790{
791 return !list_empty(&pool->worklist) &&
792 atomic_read(&pool->nr_running) <= 1;
793}
794
795/* Do we need a new worker? Called from manager. */
796static bool need_to_create_worker(struct worker_pool *pool)
797{
798 return need_more_worker(pool) && !may_start_working(pool);
799}
800
801/* Do we have too many workers and should some go away? */
802static bool too_many_workers(struct worker_pool *pool)
803{
804 bool managing = mutex_is_locked(&pool->manager_arb);
805 int nr_idle = pool->nr_idle + managing; /* manager is considered idle */
806 int nr_busy = pool->nr_workers - nr_idle;
807
808 return nr_idle > 2 && (nr_idle - 2) * MAX_IDLE_WORKERS_RATIO >= nr_busy;
809}
810
811/*
812 * Wake up functions.
813 */
814
815/* Return the first idle worker. Safe with preemption disabled */
816static struct worker *first_idle_worker(struct worker_pool *pool)
817{
818 if (unlikely(list_empty(&pool->idle_list)))
819 return NULL;
820
821 return list_first_entry(&pool->idle_list, struct worker, entry);
822}
823
824/**
825 * wake_up_worker - wake up an idle worker
826 * @pool: worker pool to wake worker from
827 *
828 * Wake up the first idle worker of @pool.
829 *
830 * CONTEXT:
831 * spin_lock_irq(pool->lock).
832 */
833static void wake_up_worker(struct worker_pool *pool)
834{
835 struct worker *worker = first_idle_worker(pool);
836
837 if (likely(worker))
838 wake_up_process(worker->task);
839}
840
841/**
842 * wq_worker_waking_up - a worker is waking up
843 * @task: task waking up
844 * @cpu: CPU @task is waking up to
845 *
846 * This function is called during try_to_wake_up() when a worker is
847 * being awoken.
848 *
849 * CONTEXT:
850 * spin_lock_irq(rq->lock)
851 */
852void wq_worker_waking_up(struct task_struct *task, int cpu)
853{
854 struct worker *worker = kthread_data(task);
855
856 if (!(worker->flags & WORKER_NOT_RUNNING)) {
857 WARN_ON_ONCE(worker->pool->cpu != cpu);
858 atomic_inc(&worker->pool->nr_running);
859 }
860}
861
862/**
863 * wq_worker_sleeping - a worker is going to sleep
864 * @task: task going to sleep
865 *
866 * This function is called during schedule() when a busy worker is
867 * going to sleep. Worker on the same cpu can be woken up by
868 * returning pointer to its task.
869 *
870 * CONTEXT:
871 * spin_lock_irq(rq->lock)
872 *
873 * Return:
874 * Worker task on @cpu to wake up, %NULL if none.
875 */
876struct task_struct *wq_worker_sleeping(struct task_struct *task)
877{
878 struct worker *worker = kthread_data(task), *to_wakeup = NULL;
879 struct worker_pool *pool;
880
881 /*
882 * Rescuers, which may not have all the fields set up like normal
883 * workers, also reach here, let's not access anything before
884 * checking NOT_RUNNING.
885 */
886 if (worker->flags & WORKER_NOT_RUNNING)
887 return NULL;
888
889 pool = worker->pool;
890
891 /* this can only happen on the local cpu */
892 if (WARN_ON_ONCE(pool->cpu != raw_smp_processor_id()))
893 return NULL;
894
895 /*
896 * The counterpart of the following dec_and_test, implied mb,
897 * worklist not empty test sequence is in insert_work().
898 * Please read comment there.
899 *
900 * NOT_RUNNING is clear. This means that we're bound to and
901 * running on the local cpu w/ rq lock held and preemption
902 * disabled, which in turn means that none else could be
903 * manipulating idle_list, so dereferencing idle_list without pool
904 * lock is safe.
905 */
906 if (atomic_dec_and_test(&pool->nr_running) &&
907 !list_empty(&pool->worklist))
908 to_wakeup = first_idle_worker(pool);
909 return to_wakeup ? to_wakeup->task : NULL;
910}
911
912/**
913 * worker_set_flags - set worker flags and adjust nr_running accordingly
914 * @worker: self
915 * @flags: flags to set
916 *
917 * Set @flags in @worker->flags and adjust nr_running accordingly.
918 *
919 * CONTEXT:
920 * spin_lock_irq(pool->lock)
921 */
922static inline void worker_set_flags(struct worker *worker, unsigned int flags)
923{
924 struct worker_pool *pool = worker->pool;
925
926 WARN_ON_ONCE(worker->task != current);
927
928 /* If transitioning into NOT_RUNNING, adjust nr_running. */
929 if ((flags & WORKER_NOT_RUNNING) &&
930 !(worker->flags & WORKER_NOT_RUNNING)) {
931 atomic_dec(&pool->nr_running);
932 }
933
934 worker->flags |= flags;
935}
936
937/**
938 * worker_clr_flags - clear worker flags and adjust nr_running accordingly
939 * @worker: self
940 * @flags: flags to clear
941 *
942 * Clear @flags in @worker->flags and adjust nr_running accordingly.
943 *
944 * CONTEXT:
945 * spin_lock_irq(pool->lock)
946 */
947static inline void worker_clr_flags(struct worker *worker, unsigned int flags)
948{
949 struct worker_pool *pool = worker->pool;
950 unsigned int oflags = worker->flags;
951
952 WARN_ON_ONCE(worker->task != current);
953
954 worker->flags &= ~flags;
955
956 /*
957 * If transitioning out of NOT_RUNNING, increment nr_running. Note
958 * that the nested NOT_RUNNING is not a noop. NOT_RUNNING is mask
959 * of multiple flags, not a single flag.
960 */
961 if ((flags & WORKER_NOT_RUNNING) && (oflags & WORKER_NOT_RUNNING))
962 if (!(worker->flags & WORKER_NOT_RUNNING))
963 atomic_inc(&pool->nr_running);
964}
965
966/**
967 * find_worker_executing_work - find worker which is executing a work
968 * @pool: pool of interest
969 * @work: work to find worker for
970 *
971 * Find a worker which is executing @work on @pool by searching
972 * @pool->busy_hash which is keyed by the address of @work. For a worker
973 * to match, its current execution should match the address of @work and
974 * its work function. This is to avoid unwanted dependency between
975 * unrelated work executions through a work item being recycled while still
976 * being executed.
977 *
978 * This is a bit tricky. A work item may be freed once its execution
979 * starts and nothing prevents the freed area from being recycled for
980 * another work item. If the same work item address ends up being reused
981 * before the original execution finishes, workqueue will identify the
982 * recycled work item as currently executing and make it wait until the
983 * current execution finishes, introducing an unwanted dependency.
984 *
985 * This function checks the work item address and work function to avoid
986 * false positives. Note that this isn't complete as one may construct a
987 * work function which can introduce dependency onto itself through a
988 * recycled work item. Well, if somebody wants to shoot oneself in the
989 * foot that badly, there's only so much we can do, and if such deadlock
990 * actually occurs, it should be easy to locate the culprit work function.
991 *
992 * CONTEXT:
993 * spin_lock_irq(pool->lock).
994 *
995 * Return:
996 * Pointer to worker which is executing @work if found, %NULL
997 * otherwise.
998 */
999static struct worker *find_worker_executing_work(struct worker_pool *pool,
1000 struct work_struct *work)
1001{
1002 struct worker *worker;
1003
1004 hash_for_each_possible(pool->busy_hash, worker, hentry,
1005 (unsigned long)work)
1006 if (worker->current_work == work &&
1007 worker->current_func == work->func)
1008 return worker;
1009
1010 return NULL;
1011}
1012
1013/**
1014 * move_linked_works - move linked works to a list
1015 * @work: start of series of works to be scheduled
1016 * @head: target list to append @work to
1017 * @nextp: out parameter for nested worklist walking
1018 *
1019 * Schedule linked works starting from @work to @head. Work series to
1020 * be scheduled starts at @work and includes any consecutive work with
1021 * WORK_STRUCT_LINKED set in its predecessor.
1022 *
1023 * If @nextp is not NULL, it's updated to point to the next work of
1024 * the last scheduled work. This allows move_linked_works() to be
1025 * nested inside outer list_for_each_entry_safe().
1026 *
1027 * CONTEXT:
1028 * spin_lock_irq(pool->lock).
1029 */
1030static void move_linked_works(struct work_struct *work, struct list_head *head,
1031 struct work_struct **nextp)
1032{
1033 struct work_struct *n;
1034
1035 /*
1036 * Linked worklist will always end before the end of the list,
1037 * use NULL for list head.
1038 */
1039 list_for_each_entry_safe_from(work, n, NULL, entry) {
1040 list_move_tail(&work->entry, head);
1041 if (!(*work_data_bits(work) & WORK_STRUCT_LINKED))
1042 break;
1043 }
1044
1045 /*
1046 * If we're already inside safe list traversal and have moved
1047 * multiple works to the scheduled queue, the next position
1048 * needs to be updated.
1049 */
1050 if (nextp)
1051 *nextp = n;
1052}
1053
1054/**
1055 * get_pwq - get an extra reference on the specified pool_workqueue
1056 * @pwq: pool_workqueue to get
1057 *
1058 * Obtain an extra reference on @pwq. The caller should guarantee that
1059 * @pwq has positive refcnt and be holding the matching pool->lock.
1060 */
1061static void get_pwq(struct pool_workqueue *pwq)
1062{
1063 lockdep_assert_held(&pwq->pool->lock);
1064 WARN_ON_ONCE(pwq->refcnt <= 0);
1065 pwq->refcnt++;
1066}
1067
1068/**
1069 * put_pwq - put a pool_workqueue reference
1070 * @pwq: pool_workqueue to put
1071 *
1072 * Drop a reference of @pwq. If its refcnt reaches zero, schedule its
1073 * destruction. The caller should be holding the matching pool->lock.
1074 */
1075static void put_pwq(struct pool_workqueue *pwq)
1076{
1077 lockdep_assert_held(&pwq->pool->lock);
1078 if (likely(--pwq->refcnt))
1079 return;
1080 if (WARN_ON_ONCE(!(pwq->wq->flags & WQ_UNBOUND)))
1081 return;
1082 /*
1083 * @pwq can't be released under pool->lock, bounce to
1084 * pwq_unbound_release_workfn(). This never recurses on the same
1085 * pool->lock as this path is taken only for unbound workqueues and
1086 * the release work item is scheduled on a per-cpu workqueue. To
1087 * avoid lockdep warning, unbound pool->locks are given lockdep
1088 * subclass of 1 in get_unbound_pool().
1089 */
1090 schedule_work(&pwq->unbound_release_work);
1091}
1092
1093/**
1094 * put_pwq_unlocked - put_pwq() with surrounding pool lock/unlock
1095 * @pwq: pool_workqueue to put (can be %NULL)
1096 *
1097 * put_pwq() with locking. This function also allows %NULL @pwq.
1098 */
1099static void put_pwq_unlocked(struct pool_workqueue *pwq)
1100{
1101 if (pwq) {
1102 /*
1103 * As both pwqs and pools are sched-RCU protected, the
1104 * following lock operations are safe.
1105 */
1106 spin_lock_irq(&pwq->pool->lock);
1107 put_pwq(pwq);
1108 spin_unlock_irq(&pwq->pool->lock);
1109 }
1110}
1111
1112static void pwq_activate_delayed_work(struct work_struct *work)
1113{
1114 struct pool_workqueue *pwq = get_work_pwq(work);
1115
1116 trace_workqueue_activate_work(work);
1117 if (list_empty(&pwq->pool->worklist))
1118 pwq->pool->watchdog_ts = jiffies;
1119 move_linked_works(work, &pwq->pool->worklist, NULL);
1120 __clear_bit(WORK_STRUCT_DELAYED_BIT, work_data_bits(work));
1121 pwq->nr_active++;
1122}
1123
1124static void pwq_activate_first_delayed(struct pool_workqueue *pwq)
1125{
1126 struct work_struct *work = list_first_entry(&pwq->delayed_works,
1127 struct work_struct, entry);
1128
1129 pwq_activate_delayed_work(work);
1130}
1131
1132/**
1133 * pwq_dec_nr_in_flight - decrement pwq's nr_in_flight
1134 * @pwq: pwq of interest
1135 * @color: color of work which left the queue
1136 *
1137 * A work either has completed or is removed from pending queue,
1138 * decrement nr_in_flight of its pwq and handle workqueue flushing.
1139 *
1140 * CONTEXT:
1141 * spin_lock_irq(pool->lock).
1142 */
1143static void pwq_dec_nr_in_flight(struct pool_workqueue *pwq, int color)
1144{
1145 /* uncolored work items don't participate in flushing or nr_active */
1146 if (color == WORK_NO_COLOR)
1147 goto out_put;
1148
1149 pwq->nr_in_flight[color]--;
1150
1151 pwq->nr_active--;
1152 if (!list_empty(&pwq->delayed_works)) {
1153 /* one down, submit a delayed one */
1154 if (pwq->nr_active < pwq->max_active)
1155 pwq_activate_first_delayed(pwq);
1156 }
1157
1158 /* is flush in progress and are we at the flushing tip? */
1159 if (likely(pwq->flush_color != color))
1160 goto out_put;
1161
1162 /* are there still in-flight works? */
1163 if (pwq->nr_in_flight[color])
1164 goto out_put;
1165
1166 /* this pwq is done, clear flush_color */
1167 pwq->flush_color = -1;
1168
1169 /*
1170 * If this was the last pwq, wake up the first flusher. It
1171 * will handle the rest.
1172 */
1173 if (atomic_dec_and_test(&pwq->wq->nr_pwqs_to_flush))
1174 complete(&pwq->wq->first_flusher->done);
1175out_put:
1176 put_pwq(pwq);
1177}
1178
1179/**
1180 * try_to_grab_pending - steal work item from worklist and disable irq
1181 * @work: work item to steal
1182 * @is_dwork: @work is a delayed_work
1183 * @flags: place to store irq state
1184 *
1185 * Try to grab PENDING bit of @work. This function can handle @work in any
1186 * stable state - idle, on timer or on worklist.
1187 *
1188 * Return:
1189 * 1 if @work was pending and we successfully stole PENDING
1190 * 0 if @work was idle and we claimed PENDING
1191 * -EAGAIN if PENDING couldn't be grabbed at the moment, safe to busy-retry
1192 * -ENOENT if someone else is canceling @work, this state may persist
1193 * for arbitrarily long
1194 *
1195 * Note:
1196 * On >= 0 return, the caller owns @work's PENDING bit. To avoid getting
1197 * interrupted while holding PENDING and @work off queue, irq must be
1198 * disabled on entry. This, combined with delayed_work->timer being
1199 * irqsafe, ensures that we return -EAGAIN for finite short period of time.
1200 *
1201 * On successful return, >= 0, irq is disabled and the caller is
1202 * responsible for releasing it using local_irq_restore(*@flags).
1203 *
1204 * This function is safe to call from any context including IRQ handler.
1205 */
1206static int try_to_grab_pending(struct work_struct *work, bool is_dwork,
1207 unsigned long *flags)
1208{
1209 struct worker_pool *pool;
1210 struct pool_workqueue *pwq;
1211
1212 local_irq_save(*flags);
1213
1214 /* try to steal the timer if it exists */
1215 if (is_dwork) {
1216 struct delayed_work *dwork = to_delayed_work(work);
1217
1218 /*
1219 * dwork->timer is irqsafe. If del_timer() fails, it's
1220 * guaranteed that the timer is not queued anywhere and not
1221 * running on the local CPU.
1222 */
1223 if (likely(del_timer(&dwork->timer)))
1224 return 1;
1225 }
1226
1227 /* try to claim PENDING the normal way */
1228 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work)))
1229 return 0;
1230
1231 /*
1232 * The queueing is in progress, or it is already queued. Try to
1233 * steal it from ->worklist without clearing WORK_STRUCT_PENDING.
1234 */
1235 pool = get_work_pool(work);
1236 if (!pool)
1237 goto fail;
1238
1239 spin_lock(&pool->lock);
1240 /*
1241 * work->data is guaranteed to point to pwq only while the work
1242 * item is queued on pwq->wq, and both updating work->data to point
1243 * to pwq on queueing and to pool on dequeueing are done under
1244 * pwq->pool->lock. This in turn guarantees that, if work->data
1245 * points to pwq which is associated with a locked pool, the work
1246 * item is currently queued on that pool.
1247 */
1248 pwq = get_work_pwq(work);
1249 if (pwq && pwq->pool == pool) {
1250 debug_work_deactivate(work);
1251
1252 /*
1253 * A delayed work item cannot be grabbed directly because
1254 * it might have linked NO_COLOR work items which, if left
1255 * on the delayed_list, will confuse pwq->nr_active
1256 * management later on and cause stall. Make sure the work
1257 * item is activated before grabbing.
1258 */
1259 if (*work_data_bits(work) & WORK_STRUCT_DELAYED)
1260 pwq_activate_delayed_work(work);
1261
1262 list_del_init(&work->entry);
1263 pwq_dec_nr_in_flight(pwq, get_work_color(work));
1264
1265 /* work->data points to pwq iff queued, point to pool */
1266 set_work_pool_and_keep_pending(work, pool->id);
1267
1268 spin_unlock(&pool->lock);
1269 return 1;
1270 }
1271 spin_unlock(&pool->lock);
1272fail:
1273 local_irq_restore(*flags);
1274 if (work_is_canceling(work))
1275 return -ENOENT;
1276 cpu_relax();
1277 return -EAGAIN;
1278}
1279
1280/**
1281 * insert_work - insert a work into a pool
1282 * @pwq: pwq @work belongs to
1283 * @work: work to insert
1284 * @head: insertion point
1285 * @extra_flags: extra WORK_STRUCT_* flags to set
1286 *
1287 * Insert @work which belongs to @pwq after @head. @extra_flags is or'd to
1288 * work_struct flags.
1289 *
1290 * CONTEXT:
1291 * spin_lock_irq(pool->lock).
1292 */
1293static void insert_work(struct pool_workqueue *pwq, struct work_struct *work,
1294 struct list_head *head, unsigned int extra_flags)
1295{
1296 struct worker_pool *pool = pwq->pool;
1297
1298 /* we own @work, set data and link */
1299 set_work_pwq(work, pwq, extra_flags);
1300 list_add_tail(&work->entry, head);
1301 get_pwq(pwq);
1302
1303 /*
1304 * Ensure either wq_worker_sleeping() sees the above
1305 * list_add_tail() or we see zero nr_running to avoid workers lying
1306 * around lazily while there are works to be processed.
1307 */
1308 smp_mb();
1309
1310 if (__need_more_worker(pool))
1311 wake_up_worker(pool);
1312}
1313
1314/*
1315 * Test whether @work is being queued from another work executing on the
1316 * same workqueue.
1317 */
1318static bool is_chained_work(struct workqueue_struct *wq)
1319{
1320 struct worker *worker;
1321
1322 worker = current_wq_worker();
1323 /*
1324 * Return %true iff I'm a worker execuing a work item on @wq. If
1325 * I'm @worker, it's safe to dereference it without locking.
1326 */
1327 return worker && worker->current_pwq->wq == wq;
1328}
1329
1330/*
1331 * When queueing an unbound work item to a wq, prefer local CPU if allowed
1332 * by wq_unbound_cpumask. Otherwise, round robin among the allowed ones to
1333 * avoid perturbing sensitive tasks.
1334 */
1335static int wq_select_unbound_cpu(int cpu)
1336{
1337 static bool printed_dbg_warning;
1338 int new_cpu;
1339
1340 if (likely(!wq_debug_force_rr_cpu)) {
1341 if (cpumask_test_cpu(cpu, wq_unbound_cpumask))
1342 return cpu;
1343 } else if (!printed_dbg_warning) {
1344 pr_warn("workqueue: round-robin CPU selection forced, expect performance impact\n");
1345 printed_dbg_warning = true;
1346 }
1347
1348 if (cpumask_empty(wq_unbound_cpumask))
1349 return cpu;
1350
1351 new_cpu = __this_cpu_read(wq_rr_cpu_last);
1352 new_cpu = cpumask_next_and(new_cpu, wq_unbound_cpumask, cpu_online_mask);
1353 if (unlikely(new_cpu >= nr_cpu_ids)) {
1354 new_cpu = cpumask_first_and(wq_unbound_cpumask, cpu_online_mask);
1355 if (unlikely(new_cpu >= nr_cpu_ids))
1356 return cpu;
1357 }
1358 __this_cpu_write(wq_rr_cpu_last, new_cpu);
1359
1360 return new_cpu;
1361}
1362
1363static void __queue_work(int cpu, struct workqueue_struct *wq,
1364 struct work_struct *work)
1365{
1366 struct pool_workqueue *pwq;
1367 struct worker_pool *last_pool;
1368 struct list_head *worklist;
1369 unsigned int work_flags;
1370 unsigned int req_cpu = cpu;
1371
1372 /*
1373 * While a work item is PENDING && off queue, a task trying to
1374 * steal the PENDING will busy-loop waiting for it to either get
1375 * queued or lose PENDING. Grabbing PENDING and queueing should
1376 * happen with IRQ disabled.
1377 */
1378 WARN_ON_ONCE(!irqs_disabled());
1379
1380 debug_work_activate(work);
1381
1382 /* if draining, only works from the same workqueue are allowed */
1383 if (unlikely(wq->flags & __WQ_DRAINING) &&
1384 WARN_ON_ONCE(!is_chained_work(wq)))
1385 return;
1386retry:
1387 if (req_cpu == WORK_CPU_UNBOUND)
1388 cpu = wq_select_unbound_cpu(raw_smp_processor_id());
1389
1390 /* pwq which will be used unless @work is executing elsewhere */
1391 if (!(wq->flags & WQ_UNBOUND))
1392 pwq = per_cpu_ptr(wq->cpu_pwqs, cpu);
1393 else
1394 pwq = unbound_pwq_by_node(wq, cpu_to_node(cpu));
1395
1396 /*
1397 * If @work was previously on a different pool, it might still be
1398 * running there, in which case the work needs to be queued on that
1399 * pool to guarantee non-reentrancy.
1400 */
1401 last_pool = get_work_pool(work);
1402 if (last_pool && last_pool != pwq->pool) {
1403 struct worker *worker;
1404
1405 spin_lock(&last_pool->lock);
1406
1407 worker = find_worker_executing_work(last_pool, work);
1408
1409 if (worker && worker->current_pwq->wq == wq) {
1410 pwq = worker->current_pwq;
1411 } else {
1412 /* meh... not running there, queue here */
1413 spin_unlock(&last_pool->lock);
1414 spin_lock(&pwq->pool->lock);
1415 }
1416 } else {
1417 spin_lock(&pwq->pool->lock);
1418 }
1419
1420 /*
1421 * pwq is determined and locked. For unbound pools, we could have
1422 * raced with pwq release and it could already be dead. If its
1423 * refcnt is zero, repeat pwq selection. Note that pwqs never die
1424 * without another pwq replacing it in the numa_pwq_tbl or while
1425 * work items are executing on it, so the retrying is guaranteed to
1426 * make forward-progress.
1427 */
1428 if (unlikely(!pwq->refcnt)) {
1429 if (wq->flags & WQ_UNBOUND) {
1430 spin_unlock(&pwq->pool->lock);
1431 cpu_relax();
1432 goto retry;
1433 }
1434 /* oops */
1435 WARN_ONCE(true, "workqueue: per-cpu pwq for %s on cpu%d has 0 refcnt",
1436 wq->name, cpu);
1437 }
1438
1439 /* pwq determined, queue */
1440 trace_workqueue_queue_work(req_cpu, pwq, work);
1441
1442 if (WARN_ON(!list_empty(&work->entry))) {
1443 spin_unlock(&pwq->pool->lock);
1444 return;
1445 }
1446
1447 pwq->nr_in_flight[pwq->work_color]++;
1448 work_flags = work_color_to_flags(pwq->work_color);
1449
1450 if (likely(pwq->nr_active < pwq->max_active)) {
1451 trace_workqueue_activate_work(work);
1452 pwq->nr_active++;
1453 worklist = &pwq->pool->worklist;
1454 if (list_empty(worklist))
1455 pwq->pool->watchdog_ts = jiffies;
1456 } else {
1457 work_flags |= WORK_STRUCT_DELAYED;
1458 worklist = &pwq->delayed_works;
1459 }
1460
1461 insert_work(pwq, work, worklist, work_flags);
1462
1463 spin_unlock(&pwq->pool->lock);
1464}
1465
1466/**
1467 * queue_work_on - queue work on specific cpu
1468 * @cpu: CPU number to execute work on
1469 * @wq: workqueue to use
1470 * @work: work to queue
1471 *
1472 * We queue the work to a specific CPU, the caller must ensure it
1473 * can't go away.
1474 *
1475 * Return: %false if @work was already on a queue, %true otherwise.
1476 */
1477bool queue_work_on(int cpu, struct workqueue_struct *wq,
1478 struct work_struct *work)
1479{
1480 bool ret = false;
1481 unsigned long flags;
1482
1483 local_irq_save(flags);
1484
1485 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1486 __queue_work(cpu, wq, work);
1487 ret = true;
1488 }
1489
1490 local_irq_restore(flags);
1491 return ret;
1492}
1493EXPORT_SYMBOL(queue_work_on);
1494
1495void delayed_work_timer_fn(unsigned long __data)
1496{
1497 struct delayed_work *dwork = (struct delayed_work *)__data;
1498
1499 /* should have been called from irqsafe timer with irq already off */
1500 __queue_work(dwork->cpu, dwork->wq, &dwork->work);
1501}
1502EXPORT_SYMBOL(delayed_work_timer_fn);
1503
1504static void __queue_delayed_work(int cpu, struct workqueue_struct *wq,
1505 struct delayed_work *dwork, unsigned long delay)
1506{
1507 struct timer_list *timer = &dwork->timer;
1508 struct work_struct *work = &dwork->work;
1509
1510 WARN_ON_ONCE(timer->function != delayed_work_timer_fn ||
1511 timer->data != (unsigned long)dwork);
1512 WARN_ON_ONCE(timer_pending(timer));
1513 WARN_ON_ONCE(!list_empty(&work->entry));
1514
1515 /*
1516 * If @delay is 0, queue @dwork->work immediately. This is for
1517 * both optimization and correctness. The earliest @timer can
1518 * expire is on the closest next tick and delayed_work users depend
1519 * on that there's no such delay when @delay is 0.
1520 */
1521 if (!delay) {
1522 __queue_work(cpu, wq, &dwork->work);
1523 return;
1524 }
1525
1526 timer_stats_timer_set_start_info(&dwork->timer);
1527
1528 dwork->wq = wq;
1529 dwork->cpu = cpu;
1530 timer->expires = jiffies + delay;
1531
1532 if (unlikely(cpu != WORK_CPU_UNBOUND))
1533 add_timer_on(timer, cpu);
1534 else
1535 add_timer(timer);
1536}
1537
1538/**
1539 * queue_delayed_work_on - queue work on specific CPU after delay
1540 * @cpu: CPU number to execute work on
1541 * @wq: workqueue to use
1542 * @dwork: work to queue
1543 * @delay: number of jiffies to wait before queueing
1544 *
1545 * Return: %false if @work was already on a queue, %true otherwise. If
1546 * @delay is zero and @dwork is idle, it will be scheduled for immediate
1547 * execution.
1548 */
1549bool queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
1550 struct delayed_work *dwork, unsigned long delay)
1551{
1552 struct work_struct *work = &dwork->work;
1553 bool ret = false;
1554 unsigned long flags;
1555
1556 /* read the comment in __queue_work() */
1557 local_irq_save(flags);
1558
1559 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1560 __queue_delayed_work(cpu, wq, dwork, delay);
1561 ret = true;
1562 }
1563
1564 local_irq_restore(flags);
1565 return ret;
1566}
1567EXPORT_SYMBOL(queue_delayed_work_on);
1568
1569/**
1570 * mod_delayed_work_on - modify delay of or queue a delayed work on specific CPU
1571 * @cpu: CPU number to execute work on
1572 * @wq: workqueue to use
1573 * @dwork: work to queue
1574 * @delay: number of jiffies to wait before queueing
1575 *
1576 * If @dwork is idle, equivalent to queue_delayed_work_on(); otherwise,
1577 * modify @dwork's timer so that it expires after @delay. If @delay is
1578 * zero, @work is guaranteed to be scheduled immediately regardless of its
1579 * current state.
1580 *
1581 * Return: %false if @dwork was idle and queued, %true if @dwork was
1582 * pending and its timer was modified.
1583 *
1584 * This function is safe to call from any context including IRQ handler.
1585 * See try_to_grab_pending() for details.
1586 */
1587bool mod_delayed_work_on(int cpu, struct workqueue_struct *wq,
1588 struct delayed_work *dwork, unsigned long delay)
1589{
1590 unsigned long flags;
1591 int ret;
1592
1593 do {
1594 ret = try_to_grab_pending(&dwork->work, true, &flags);
1595 } while (unlikely(ret == -EAGAIN));
1596
1597 if (likely(ret >= 0)) {
1598 __queue_delayed_work(cpu, wq, dwork, delay);
1599 local_irq_restore(flags);
1600 }
1601
1602 /* -ENOENT from try_to_grab_pending() becomes %true */
1603 return ret;
1604}
1605EXPORT_SYMBOL_GPL(mod_delayed_work_on);
1606
1607/**
1608 * worker_enter_idle - enter idle state
1609 * @worker: worker which is entering idle state
1610 *
1611 * @worker is entering idle state. Update stats and idle timer if
1612 * necessary.
1613 *
1614 * LOCKING:
1615 * spin_lock_irq(pool->lock).
1616 */
1617static void worker_enter_idle(struct worker *worker)
1618{
1619 struct worker_pool *pool = worker->pool;
1620
1621 if (WARN_ON_ONCE(worker->flags & WORKER_IDLE) ||
1622 WARN_ON_ONCE(!list_empty(&worker->entry) &&
1623 (worker->hentry.next || worker->hentry.pprev)))
1624 return;
1625
1626 /* can't use worker_set_flags(), also called from create_worker() */
1627 worker->flags |= WORKER_IDLE;
1628 pool->nr_idle++;
1629 worker->last_active = jiffies;
1630
1631 /* idle_list is LIFO */
1632 list_add(&worker->entry, &pool->idle_list);
1633
1634 if (too_many_workers(pool) && !timer_pending(&pool->idle_timer))
1635 mod_timer(&pool->idle_timer, jiffies + IDLE_WORKER_TIMEOUT);
1636
1637 /*
1638 * Sanity check nr_running. Because wq_unbind_fn() releases
1639 * pool->lock between setting %WORKER_UNBOUND and zapping
1640 * nr_running, the warning may trigger spuriously. Check iff
1641 * unbind is not in progress.
1642 */
1643 WARN_ON_ONCE(!(pool->flags & POOL_DISASSOCIATED) &&
1644 pool->nr_workers == pool->nr_idle &&
1645 atomic_read(&pool->nr_running));
1646}
1647
1648/**
1649 * worker_leave_idle - leave idle state
1650 * @worker: worker which is leaving idle state
1651 *
1652 * @worker is leaving idle state. Update stats.
1653 *
1654 * LOCKING:
1655 * spin_lock_irq(pool->lock).
1656 */
1657static void worker_leave_idle(struct worker *worker)
1658{
1659 struct worker_pool *pool = worker->pool;
1660
1661 if (WARN_ON_ONCE(!(worker->flags & WORKER_IDLE)))
1662 return;
1663 worker_clr_flags(worker, WORKER_IDLE);
1664 pool->nr_idle--;
1665 list_del_init(&worker->entry);
1666}
1667
1668static struct worker *alloc_worker(int node)
1669{
1670 struct worker *worker;
1671
1672 worker = kzalloc_node(sizeof(*worker), GFP_KERNEL, node);
1673 if (worker) {
1674 INIT_LIST_HEAD(&worker->entry);
1675 INIT_LIST_HEAD(&worker->scheduled);
1676 INIT_LIST_HEAD(&worker->node);
1677 /* on creation a worker is in !idle && prep state */
1678 worker->flags = WORKER_PREP;
1679 }
1680 return worker;
1681}
1682
1683/**
1684 * worker_attach_to_pool() - attach a worker to a pool
1685 * @worker: worker to be attached
1686 * @pool: the target pool
1687 *
1688 * Attach @worker to @pool. Once attached, the %WORKER_UNBOUND flag and
1689 * cpu-binding of @worker are kept coordinated with the pool across
1690 * cpu-[un]hotplugs.
1691 */
1692static void worker_attach_to_pool(struct worker *worker,
1693 struct worker_pool *pool)
1694{
1695 mutex_lock(&pool->attach_mutex);
1696
1697 /*
1698 * set_cpus_allowed_ptr() will fail if the cpumask doesn't have any
1699 * online CPUs. It'll be re-applied when any of the CPUs come up.
1700 */
1701 set_cpus_allowed_ptr(worker->task, pool->attrs->cpumask);
1702
1703 /*
1704 * The pool->attach_mutex ensures %POOL_DISASSOCIATED remains
1705 * stable across this function. See the comments above the
1706 * flag definition for details.
1707 */
1708 if (pool->flags & POOL_DISASSOCIATED)
1709 worker->flags |= WORKER_UNBOUND;
1710
1711 list_add_tail(&worker->node, &pool->workers);
1712
1713 mutex_unlock(&pool->attach_mutex);
1714}
1715
1716/**
1717 * worker_detach_from_pool() - detach a worker from its pool
1718 * @worker: worker which is attached to its pool
1719 * @pool: the pool @worker is attached to
1720 *
1721 * Undo the attaching which had been done in worker_attach_to_pool(). The
1722 * caller worker shouldn't access to the pool after detached except it has
1723 * other reference to the pool.
1724 */
1725static void worker_detach_from_pool(struct worker *worker,
1726 struct worker_pool *pool)
1727{
1728 struct completion *detach_completion = NULL;
1729
1730 mutex_lock(&pool->attach_mutex);
1731 list_del(&worker->node);
1732 if (list_empty(&pool->workers))
1733 detach_completion = pool->detach_completion;
1734 mutex_unlock(&pool->attach_mutex);
1735
1736 /* clear leftover flags without pool->lock after it is detached */
1737 worker->flags &= ~(WORKER_UNBOUND | WORKER_REBOUND);
1738
1739 if (detach_completion)
1740 complete(detach_completion);
1741}
1742
1743/**
1744 * create_worker - create a new workqueue worker
1745 * @pool: pool the new worker will belong to
1746 *
1747 * Create and start a new worker which is attached to @pool.
1748 *
1749 * CONTEXT:
1750 * Might sleep. Does GFP_KERNEL allocations.
1751 *
1752 * Return:
1753 * Pointer to the newly created worker.
1754 */
1755static struct worker *create_worker(struct worker_pool *pool)
1756{
1757 struct worker *worker = NULL;
1758 int id = -1;
1759 char id_buf[16];
1760
1761 /* ID is needed to determine kthread name */
1762 id = ida_simple_get(&pool->worker_ida, 0, 0, GFP_KERNEL);
1763 if (id < 0)
1764 goto fail;
1765
1766 worker = alloc_worker(pool->node);
1767 if (!worker)
1768 goto fail;
1769
1770 worker->pool = pool;
1771 worker->id = id;
1772
1773 if (pool->cpu >= 0)
1774 snprintf(id_buf, sizeof(id_buf), "%d:%d%s", pool->cpu, id,
1775 pool->attrs->nice < 0 ? "H" : "");
1776 else
1777 snprintf(id_buf, sizeof(id_buf), "u%d:%d", pool->id, id);
1778
1779 worker->task = kthread_create_on_node(worker_thread, worker, pool->node,
1780 "kworker/%s", id_buf);
1781 if (IS_ERR(worker->task))
1782 goto fail;
1783
1784 set_user_nice(worker->task, pool->attrs->nice);
1785 kthread_bind_mask(worker->task, pool->attrs->cpumask);
1786
1787 /* successful, attach the worker to the pool */
1788 worker_attach_to_pool(worker, pool);
1789
1790 /* start the newly created worker */
1791 spin_lock_irq(&pool->lock);
1792 worker->pool->nr_workers++;
1793 worker_enter_idle(worker);
1794 wake_up_process(worker->task);
1795 spin_unlock_irq(&pool->lock);
1796
1797 return worker;
1798
1799fail:
1800 if (id >= 0)
1801 ida_simple_remove(&pool->worker_ida, id);
1802 kfree(worker);
1803 return NULL;
1804}
1805
1806/**
1807 * destroy_worker - destroy a workqueue worker
1808 * @worker: worker to be destroyed
1809 *
1810 * Destroy @worker and adjust @pool stats accordingly. The worker should
1811 * be idle.
1812 *
1813 * CONTEXT:
1814 * spin_lock_irq(pool->lock).
1815 */
1816static void destroy_worker(struct worker *worker)
1817{
1818 struct worker_pool *pool = worker->pool;
1819
1820 lockdep_assert_held(&pool->lock);
1821
1822 /* sanity check frenzy */
1823 if (WARN_ON(worker->current_work) ||
1824 WARN_ON(!list_empty(&worker->scheduled)) ||
1825 WARN_ON(!(worker->flags & WORKER_IDLE)))
1826 return;
1827
1828 pool->nr_workers--;
1829 pool->nr_idle--;
1830
1831 list_del_init(&worker->entry);
1832 worker->flags |= WORKER_DIE;
1833 wake_up_process(worker->task);
1834}
1835
1836static void idle_worker_timeout(unsigned long __pool)
1837{
1838 struct worker_pool *pool = (void *)__pool;
1839
1840 spin_lock_irq(&pool->lock);
1841
1842 while (too_many_workers(pool)) {
1843 struct worker *worker;
1844 unsigned long expires;
1845
1846 /* idle_list is kept in LIFO order, check the last one */
1847 worker = list_entry(pool->idle_list.prev, struct worker, entry);
1848 expires = worker->last_active + IDLE_WORKER_TIMEOUT;
1849
1850 if (time_before(jiffies, expires)) {
1851 mod_timer(&pool->idle_timer, expires);
1852 break;
1853 }
1854
1855 destroy_worker(worker);
1856 }
1857
1858 spin_unlock_irq(&pool->lock);
1859}
1860
1861static void send_mayday(struct work_struct *work)
1862{
1863 struct pool_workqueue *pwq = get_work_pwq(work);
1864 struct workqueue_struct *wq = pwq->wq;
1865
1866 lockdep_assert_held(&wq_mayday_lock);
1867
1868 if (!wq->rescuer)
1869 return;
1870
1871 /* mayday mayday mayday */
1872 if (list_empty(&pwq->mayday_node)) {
1873 /*
1874 * If @pwq is for an unbound wq, its base ref may be put at
1875 * any time due to an attribute change. Pin @pwq until the
1876 * rescuer is done with it.
1877 */
1878 get_pwq(pwq);
1879 list_add_tail(&pwq->mayday_node, &wq->maydays);
1880 wake_up_process(wq->rescuer->task);
1881 }
1882}
1883
1884static void pool_mayday_timeout(unsigned long __pool)
1885{
1886 struct worker_pool *pool = (void *)__pool;
1887 struct work_struct *work;
1888
1889 spin_lock_irq(&pool->lock);
1890 spin_lock(&wq_mayday_lock); /* for wq->maydays */
1891
1892 if (need_to_create_worker(pool)) {
1893 /*
1894 * We've been trying to create a new worker but
1895 * haven't been successful. We might be hitting an
1896 * allocation deadlock. Send distress signals to
1897 * rescuers.
1898 */
1899 list_for_each_entry(work, &pool->worklist, entry)
1900 send_mayday(work);
1901 }
1902
1903 spin_unlock(&wq_mayday_lock);
1904 spin_unlock_irq(&pool->lock);
1905
1906 mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INTERVAL);
1907}
1908
1909/**
1910 * maybe_create_worker - create a new worker if necessary
1911 * @pool: pool to create a new worker for
1912 *
1913 * Create a new worker for @pool if necessary. @pool is guaranteed to
1914 * have at least one idle worker on return from this function. If
1915 * creating a new worker takes longer than MAYDAY_INTERVAL, mayday is
1916 * sent to all rescuers with works scheduled on @pool to resolve
1917 * possible allocation deadlock.
1918 *
1919 * On return, need_to_create_worker() is guaranteed to be %false and
1920 * may_start_working() %true.
1921 *
1922 * LOCKING:
1923 * spin_lock_irq(pool->lock) which may be released and regrabbed
1924 * multiple times. Does GFP_KERNEL allocations. Called only from
1925 * manager.
1926 */
1927static void maybe_create_worker(struct worker_pool *pool)
1928__releases(&pool->lock)
1929__acquires(&pool->lock)
1930{
1931restart:
1932 spin_unlock_irq(&pool->lock);
1933
1934 /* if we don't make progress in MAYDAY_INITIAL_TIMEOUT, call for help */
1935 mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INITIAL_TIMEOUT);
1936
1937 while (true) {
1938 if (create_worker(pool) || !need_to_create_worker(pool))
1939 break;
1940
1941 schedule_timeout_interruptible(CREATE_COOLDOWN);
1942
1943 if (!need_to_create_worker(pool))
1944 break;
1945 }
1946
1947 del_timer_sync(&pool->mayday_timer);
1948 spin_lock_irq(&pool->lock);
1949 /*
1950 * This is necessary even after a new worker was just successfully
1951 * created as @pool->lock was dropped and the new worker might have
1952 * already become busy.
1953 */
1954 if (need_to_create_worker(pool))
1955 goto restart;
1956}
1957
1958/**
1959 * manage_workers - manage worker pool
1960 * @worker: self
1961 *
1962 * Assume the manager role and manage the worker pool @worker belongs
1963 * to. At any given time, there can be only zero or one manager per
1964 * pool. The exclusion is handled automatically by this function.
1965 *
1966 * The caller can safely start processing works on false return. On
1967 * true return, it's guaranteed that need_to_create_worker() is false
1968 * and may_start_working() is true.
1969 *
1970 * CONTEXT:
1971 * spin_lock_irq(pool->lock) which may be released and regrabbed
1972 * multiple times. Does GFP_KERNEL allocations.
1973 *
1974 * Return:
1975 * %false if the pool doesn't need management and the caller can safely
1976 * start processing works, %true if management function was performed and
1977 * the conditions that the caller verified before calling the function may
1978 * no longer be true.
1979 */
1980static bool manage_workers(struct worker *worker)
1981{
1982 struct worker_pool *pool = worker->pool;
1983
1984 /*
1985 * Anyone who successfully grabs manager_arb wins the arbitration
1986 * and becomes the manager. mutex_trylock() on pool->manager_arb
1987 * failure while holding pool->lock reliably indicates that someone
1988 * else is managing the pool and the worker which failed trylock
1989 * can proceed to executing work items. This means that anyone
1990 * grabbing manager_arb is responsible for actually performing
1991 * manager duties. If manager_arb is grabbed and released without
1992 * actual management, the pool may stall indefinitely.
1993 */
1994 if (!mutex_trylock(&pool->manager_arb))
1995 return false;
1996 pool->manager = worker;
1997
1998 maybe_create_worker(pool);
1999
2000 pool->manager = NULL;
2001 mutex_unlock(&pool->manager_arb);
2002 return true;
2003}
2004
2005/**
2006 * process_one_work - process single work
2007 * @worker: self
2008 * @work: work to process
2009 *
2010 * Process @work. This function contains all the logics necessary to
2011 * process a single work including synchronization against and
2012 * interaction with other workers on the same cpu, queueing and
2013 * flushing. As long as context requirement is met, any worker can
2014 * call this function to process a work.
2015 *
2016 * CONTEXT:
2017 * spin_lock_irq(pool->lock) which is released and regrabbed.
2018 */
2019static void process_one_work(struct worker *worker, struct work_struct *work)
2020__releases(&pool->lock)
2021__acquires(&pool->lock)
2022{
2023 struct pool_workqueue *pwq = get_work_pwq(work);
2024 struct worker_pool *pool = worker->pool;
2025 bool cpu_intensive = pwq->wq->flags & WQ_CPU_INTENSIVE;
2026 int work_color;
2027 struct worker *collision;
2028#ifdef CONFIG_LOCKDEP
2029 /*
2030 * It is permissible to free the struct work_struct from
2031 * inside the function that is called from it, this we need to
2032 * take into account for lockdep too. To avoid bogus "held
2033 * lock freed" warnings as well as problems when looking into
2034 * work->lockdep_map, make a copy and use that here.
2035 */
2036 struct lockdep_map lockdep_map;
2037
2038 lockdep_copy_map(&lockdep_map, &work->lockdep_map);
2039#endif
2040 /* ensure we're on the correct CPU */
2041 WARN_ON_ONCE(!(pool->flags & POOL_DISASSOCIATED) &&
2042 raw_smp_processor_id() != pool->cpu);
2043
2044 /*
2045 * A single work shouldn't be executed concurrently by
2046 * multiple workers on a single cpu. Check whether anyone is
2047 * already processing the work. If so, defer the work to the
2048 * currently executing one.
2049 */
2050 collision = find_worker_executing_work(pool, work);
2051 if (unlikely(collision)) {
2052 move_linked_works(work, &collision->scheduled, NULL);
2053 return;
2054 }
2055
2056 /* claim and dequeue */
2057 debug_work_deactivate(work);
2058 hash_add(pool->busy_hash, &worker->hentry, (unsigned long)work);
2059 worker->current_work = work;
2060 worker->current_func = work->func;
2061 worker->current_pwq = pwq;
2062 work_color = get_work_color(work);
2063
2064 list_del_init(&work->entry);
2065
2066 /*
2067 * CPU intensive works don't participate in concurrency management.
2068 * They're the scheduler's responsibility. This takes @worker out
2069 * of concurrency management and the next code block will chain
2070 * execution of the pending work items.
2071 */
2072 if (unlikely(cpu_intensive))
2073 worker_set_flags(worker, WORKER_CPU_INTENSIVE);
2074
2075 /*
2076 * Wake up another worker if necessary. The condition is always
2077 * false for normal per-cpu workers since nr_running would always
2078 * be >= 1 at this point. This is used to chain execution of the
2079 * pending work items for WORKER_NOT_RUNNING workers such as the
2080 * UNBOUND and CPU_INTENSIVE ones.
2081 */
2082 if (need_more_worker(pool))
2083 wake_up_worker(pool);
2084
2085 /*
2086 * Record the last pool and clear PENDING which should be the last
2087 * update to @work. Also, do this inside @pool->lock so that
2088 * PENDING and queued state changes happen together while IRQ is
2089 * disabled.
2090 */
2091 set_work_pool_and_clear_pending(work, pool->id);
2092
2093 spin_unlock_irq(&pool->lock);
2094
2095 lock_map_acquire_read(&pwq->wq->lockdep_map);
2096 lock_map_acquire(&lockdep_map);
2097 trace_workqueue_execute_start(work);
2098 worker->current_func(work);
2099 /*
2100 * While we must be careful to not use "work" after this, the trace
2101 * point will only record its address.
2102 */
2103 trace_workqueue_execute_end(work);
2104 lock_map_release(&lockdep_map);
2105 lock_map_release(&pwq->wq->lockdep_map);
2106
2107 if (unlikely(in_atomic() || lockdep_depth(current) > 0)) {
2108 pr_err("BUG: workqueue leaked lock or atomic: %s/0x%08x/%d\n"
2109 " last function: %pf\n",
2110 current->comm, preempt_count(), task_pid_nr(current),
2111 worker->current_func);
2112 debug_show_held_locks(current);
2113 dump_stack();
2114 }
2115
2116 /*
2117 * The following prevents a kworker from hogging CPU on !PREEMPT
2118 * kernels, where a requeueing work item waiting for something to
2119 * happen could deadlock with stop_machine as such work item could
2120 * indefinitely requeue itself while all other CPUs are trapped in
2121 * stop_machine. At the same time, report a quiescent RCU state so
2122 * the same condition doesn't freeze RCU.
2123 */
2124 cond_resched_rcu_qs();
2125
2126 spin_lock_irq(&pool->lock);
2127
2128 /* clear cpu intensive status */
2129 if (unlikely(cpu_intensive))
2130 worker_clr_flags(worker, WORKER_CPU_INTENSIVE);
2131
2132 /* we're done with it, release */
2133 hash_del(&worker->hentry);
2134 worker->current_work = NULL;
2135 worker->current_func = NULL;
2136 worker->current_pwq = NULL;
2137 worker->desc_valid = false;
2138 pwq_dec_nr_in_flight(pwq, work_color);
2139}
2140
2141/**
2142 * process_scheduled_works - process scheduled works
2143 * @worker: self
2144 *
2145 * Process all scheduled works. Please note that the scheduled list
2146 * may change while processing a work, so this function repeatedly
2147 * fetches a work from the top and executes it.
2148 *
2149 * CONTEXT:
2150 * spin_lock_irq(pool->lock) which may be released and regrabbed
2151 * multiple times.
2152 */
2153static void process_scheduled_works(struct worker *worker)
2154{
2155 while (!list_empty(&worker->scheduled)) {
2156 struct work_struct *work = list_first_entry(&worker->scheduled,
2157 struct work_struct, entry);
2158 process_one_work(worker, work);
2159 }
2160}
2161
2162/**
2163 * worker_thread - the worker thread function
2164 * @__worker: self
2165 *
2166 * The worker thread function. All workers belong to a worker_pool -
2167 * either a per-cpu one or dynamic unbound one. These workers process all
2168 * work items regardless of their specific target workqueue. The only
2169 * exception is work items which belong to workqueues with a rescuer which
2170 * will be explained in rescuer_thread().
2171 *
2172 * Return: 0
2173 */
2174static int worker_thread(void *__worker)
2175{
2176 struct worker *worker = __worker;
2177 struct worker_pool *pool = worker->pool;
2178
2179 /* tell the scheduler that this is a workqueue worker */
2180 worker->task->flags |= PF_WQ_WORKER;
2181woke_up:
2182 spin_lock_irq(&pool->lock);
2183
2184 /* am I supposed to die? */
2185 if (unlikely(worker->flags & WORKER_DIE)) {
2186 spin_unlock_irq(&pool->lock);
2187 WARN_ON_ONCE(!list_empty(&worker->entry));
2188 worker->task->flags &= ~PF_WQ_WORKER;
2189
2190 set_task_comm(worker->task, "kworker/dying");
2191 ida_simple_remove(&pool->worker_ida, worker->id);
2192 worker_detach_from_pool(worker, pool);
2193 kfree(worker);
2194 return 0;
2195 }
2196
2197 worker_leave_idle(worker);
2198recheck:
2199 /* no more worker necessary? */
2200 if (!need_more_worker(pool))
2201 goto sleep;
2202
2203 /* do we need to manage? */
2204 if (unlikely(!may_start_working(pool)) && manage_workers(worker))
2205 goto recheck;
2206
2207 /*
2208 * ->scheduled list can only be filled while a worker is
2209 * preparing to process a work or actually processing it.
2210 * Make sure nobody diddled with it while I was sleeping.
2211 */
2212 WARN_ON_ONCE(!list_empty(&worker->scheduled));
2213
2214 /*
2215 * Finish PREP stage. We're guaranteed to have at least one idle
2216 * worker or that someone else has already assumed the manager
2217 * role. This is where @worker starts participating in concurrency
2218 * management if applicable and concurrency management is restored
2219 * after being rebound. See rebind_workers() for details.
2220 */
2221 worker_clr_flags(worker, WORKER_PREP | WORKER_REBOUND);
2222
2223 do {
2224 struct work_struct *work =
2225 list_first_entry(&pool->worklist,
2226 struct work_struct, entry);
2227
2228 pool->watchdog_ts = jiffies;
2229
2230 if (likely(!(*work_data_bits(work) & WORK_STRUCT_LINKED))) {
2231 /* optimization path, not strictly necessary */
2232 process_one_work(worker, work);
2233 if (unlikely(!list_empty(&worker->scheduled)))
2234 process_scheduled_works(worker);
2235 } else {
2236 move_linked_works(work, &worker->scheduled, NULL);
2237 process_scheduled_works(worker);
2238 }
2239 } while (keep_working(pool));
2240
2241 worker_set_flags(worker, WORKER_PREP);
2242sleep:
2243 /*
2244 * pool->lock is held and there's no work to process and no need to
2245 * manage, sleep. Workers are woken up only while holding
2246 * pool->lock or from local cpu, so setting the current state
2247 * before releasing pool->lock is enough to prevent losing any
2248 * event.
2249 */
2250 worker_enter_idle(worker);
2251 __set_current_state(TASK_INTERRUPTIBLE);
2252 spin_unlock_irq(&pool->lock);
2253 schedule();
2254 goto woke_up;
2255}
2256
2257/**
2258 * rescuer_thread - the rescuer thread function
2259 * @__rescuer: self
2260 *
2261 * Workqueue rescuer thread function. There's one rescuer for each
2262 * workqueue which has WQ_MEM_RECLAIM set.
2263 *
2264 * Regular work processing on a pool may block trying to create a new
2265 * worker which uses GFP_KERNEL allocation which has slight chance of
2266 * developing into deadlock if some works currently on the same queue
2267 * need to be processed to satisfy the GFP_KERNEL allocation. This is
2268 * the problem rescuer solves.
2269 *
2270 * When such condition is possible, the pool summons rescuers of all
2271 * workqueues which have works queued on the pool and let them process
2272 * those works so that forward progress can be guaranteed.
2273 *
2274 * This should happen rarely.
2275 *
2276 * Return: 0
2277 */
2278static int rescuer_thread(void *__rescuer)
2279{
2280 struct worker *rescuer = __rescuer;
2281 struct workqueue_struct *wq = rescuer->rescue_wq;
2282 struct list_head *scheduled = &rescuer->scheduled;
2283 bool should_stop;
2284
2285 set_user_nice(current, RESCUER_NICE_LEVEL);
2286
2287 /*
2288 * Mark rescuer as worker too. As WORKER_PREP is never cleared, it
2289 * doesn't participate in concurrency management.
2290 */
2291 rescuer->task->flags |= PF_WQ_WORKER;
2292repeat:
2293 set_current_state(TASK_INTERRUPTIBLE);
2294
2295 /*
2296 * By the time the rescuer is requested to stop, the workqueue
2297 * shouldn't have any work pending, but @wq->maydays may still have
2298 * pwq(s) queued. This can happen by non-rescuer workers consuming
2299 * all the work items before the rescuer got to them. Go through
2300 * @wq->maydays processing before acting on should_stop so that the
2301 * list is always empty on exit.
2302 */
2303 should_stop = kthread_should_stop();
2304
2305 /* see whether any pwq is asking for help */
2306 spin_lock_irq(&wq_mayday_lock);
2307
2308 while (!list_empty(&wq->maydays)) {
2309 struct pool_workqueue *pwq = list_first_entry(&wq->maydays,
2310 struct pool_workqueue, mayday_node);
2311 struct worker_pool *pool = pwq->pool;
2312 struct work_struct *work, *n;
2313 bool first = true;
2314
2315 __set_current_state(TASK_RUNNING);
2316 list_del_init(&pwq->mayday_node);
2317
2318 spin_unlock_irq(&wq_mayday_lock);
2319
2320 worker_attach_to_pool(rescuer, pool);
2321
2322 spin_lock_irq(&pool->lock);
2323 rescuer->pool = pool;
2324
2325 /*
2326 * Slurp in all works issued via this workqueue and
2327 * process'em.
2328 */
2329 WARN_ON_ONCE(!list_empty(scheduled));
2330 list_for_each_entry_safe(work, n, &pool->worklist, entry) {
2331 if (get_work_pwq(work) == pwq) {
2332 if (first)
2333 pool->watchdog_ts = jiffies;
2334 move_linked_works(work, scheduled, &n);
2335 }
2336 first = false;
2337 }
2338
2339 if (!list_empty(scheduled)) {
2340 process_scheduled_works(rescuer);
2341
2342 /*
2343 * The above execution of rescued work items could
2344 * have created more to rescue through
2345 * pwq_activate_first_delayed() or chained
2346 * queueing. Let's put @pwq back on mayday list so
2347 * that such back-to-back work items, which may be
2348 * being used to relieve memory pressure, don't
2349 * incur MAYDAY_INTERVAL delay inbetween.
2350 */
2351 if (need_to_create_worker(pool)) {
2352 spin_lock(&wq_mayday_lock);
2353 get_pwq(pwq);
2354 list_move_tail(&pwq->mayday_node, &wq->maydays);
2355 spin_unlock(&wq_mayday_lock);
2356 }
2357 }
2358
2359 /*
2360 * Put the reference grabbed by send_mayday(). @pool won't
2361 * go away while we're still attached to it.
2362 */
2363 put_pwq(pwq);
2364
2365 /*
2366 * Leave this pool. If need_more_worker() is %true, notify a
2367 * regular worker; otherwise, we end up with 0 concurrency
2368 * and stalling the execution.
2369 */
2370 if (need_more_worker(pool))
2371 wake_up_worker(pool);
2372
2373 rescuer->pool = NULL;
2374 spin_unlock_irq(&pool->lock);
2375
2376 worker_detach_from_pool(rescuer, pool);
2377
2378 spin_lock_irq(&wq_mayday_lock);
2379 }
2380
2381 spin_unlock_irq(&wq_mayday_lock);
2382
2383 if (should_stop) {
2384 __set_current_state(TASK_RUNNING);
2385 rescuer->task->flags &= ~PF_WQ_WORKER;
2386 return 0;
2387 }
2388
2389 /* rescuers should never participate in concurrency management */
2390 WARN_ON_ONCE(!(rescuer->flags & WORKER_NOT_RUNNING));
2391 schedule();
2392 goto repeat;
2393}
2394
2395/**
2396 * check_flush_dependency - check for flush dependency sanity
2397 * @target_wq: workqueue being flushed
2398 * @target_work: work item being flushed (NULL for workqueue flushes)
2399 *
2400 * %current is trying to flush the whole @target_wq or @target_work on it.
2401 * If @target_wq doesn't have %WQ_MEM_RECLAIM, verify that %current is not
2402 * reclaiming memory or running on a workqueue which doesn't have
2403 * %WQ_MEM_RECLAIM as that can break forward-progress guarantee leading to
2404 * a deadlock.
2405 */
2406static void check_flush_dependency(struct workqueue_struct *target_wq,
2407 struct work_struct *target_work)
2408{
2409 work_func_t target_func = target_work ? target_work->func : NULL;
2410 struct worker *worker;
2411
2412 if (target_wq->flags & WQ_MEM_RECLAIM)
2413 return;
2414
2415 worker = current_wq_worker();
2416
2417 WARN_ONCE(current->flags & PF_MEMALLOC,
2418 "workqueue: PF_MEMALLOC task %d(%s) is flushing !WQ_MEM_RECLAIM %s:%pf",
2419 current->pid, current->comm, target_wq->name, target_func);
2420 WARN_ONCE(worker && ((worker->current_pwq->wq->flags &
2421 (WQ_MEM_RECLAIM | __WQ_LEGACY)) == WQ_MEM_RECLAIM),
2422 "workqueue: WQ_MEM_RECLAIM %s:%pf is flushing !WQ_MEM_RECLAIM %s:%pf",
2423 worker->current_pwq->wq->name, worker->current_func,
2424 target_wq->name, target_func);
2425}
2426
2427struct wq_barrier {
2428 struct work_struct work;
2429 struct completion done;
2430 struct task_struct *task; /* purely informational */
2431};
2432
2433static void wq_barrier_func(struct work_struct *work)
2434{
2435 struct wq_barrier *barr = container_of(work, struct wq_barrier, work);
2436 complete(&barr->done);
2437}
2438
2439/**
2440 * insert_wq_barrier - insert a barrier work
2441 * @pwq: pwq to insert barrier into
2442 * @barr: wq_barrier to insert
2443 * @target: target work to attach @barr to
2444 * @worker: worker currently executing @target, NULL if @target is not executing
2445 *
2446 * @barr is linked to @target such that @barr is completed only after
2447 * @target finishes execution. Please note that the ordering
2448 * guarantee is observed only with respect to @target and on the local
2449 * cpu.
2450 *
2451 * Currently, a queued barrier can't be canceled. This is because
2452 * try_to_grab_pending() can't determine whether the work to be
2453 * grabbed is at the head of the queue and thus can't clear LINKED
2454 * flag of the previous work while there must be a valid next work
2455 * after a work with LINKED flag set.
2456 *
2457 * Note that when @worker is non-NULL, @target may be modified
2458 * underneath us, so we can't reliably determine pwq from @target.
2459 *
2460 * CONTEXT:
2461 * spin_lock_irq(pool->lock).
2462 */
2463static void insert_wq_barrier(struct pool_workqueue *pwq,
2464 struct wq_barrier *barr,
2465 struct work_struct *target, struct worker *worker)
2466{
2467 struct list_head *head;
2468 unsigned int linked = 0;
2469
2470 /*
2471 * debugobject calls are safe here even with pool->lock locked
2472 * as we know for sure that this will not trigger any of the
2473 * checks and call back into the fixup functions where we
2474 * might deadlock.
2475 */
2476 INIT_WORK_ONSTACK(&barr->work, wq_barrier_func);
2477 __set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(&barr->work));
2478 init_completion(&barr->done);
2479 barr->task = current;
2480
2481 /*
2482 * If @target is currently being executed, schedule the
2483 * barrier to the worker; otherwise, put it after @target.
2484 */
2485 if (worker)
2486 head = worker->scheduled.next;
2487 else {
2488 unsigned long *bits = work_data_bits(target);
2489
2490 head = target->entry.next;
2491 /* there can already be other linked works, inherit and set */
2492 linked = *bits & WORK_STRUCT_LINKED;
2493 __set_bit(WORK_STRUCT_LINKED_BIT, bits);
2494 }
2495
2496 debug_work_activate(&barr->work);
2497 insert_work(pwq, &barr->work, head,
2498 work_color_to_flags(WORK_NO_COLOR) | linked);
2499}
2500
2501/**
2502 * flush_workqueue_prep_pwqs - prepare pwqs for workqueue flushing
2503 * @wq: workqueue being flushed
2504 * @flush_color: new flush color, < 0 for no-op
2505 * @work_color: new work color, < 0 for no-op
2506 *
2507 * Prepare pwqs for workqueue flushing.
2508 *
2509 * If @flush_color is non-negative, flush_color on all pwqs should be
2510 * -1. If no pwq has in-flight commands at the specified color, all
2511 * pwq->flush_color's stay at -1 and %false is returned. If any pwq
2512 * has in flight commands, its pwq->flush_color is set to
2513 * @flush_color, @wq->nr_pwqs_to_flush is updated accordingly, pwq
2514 * wakeup logic is armed and %true is returned.
2515 *
2516 * The caller should have initialized @wq->first_flusher prior to
2517 * calling this function with non-negative @flush_color. If
2518 * @flush_color is negative, no flush color update is done and %false
2519 * is returned.
2520 *
2521 * If @work_color is non-negative, all pwqs should have the same
2522 * work_color which is previous to @work_color and all will be
2523 * advanced to @work_color.
2524 *
2525 * CONTEXT:
2526 * mutex_lock(wq->mutex).
2527 *
2528 * Return:
2529 * %true if @flush_color >= 0 and there's something to flush. %false
2530 * otherwise.
2531 */
2532static bool flush_workqueue_prep_pwqs(struct workqueue_struct *wq,
2533 int flush_color, int work_color)
2534{
2535 bool wait = false;
2536 struct pool_workqueue *pwq;
2537
2538 if (flush_color >= 0) {
2539 WARN_ON_ONCE(atomic_read(&wq->nr_pwqs_to_flush));
2540 atomic_set(&wq->nr_pwqs_to_flush, 1);
2541 }
2542
2543 for_each_pwq(pwq, wq) {
2544 struct worker_pool *pool = pwq->pool;
2545
2546 spin_lock_irq(&pool->lock);
2547
2548 if (flush_color >= 0) {
2549 WARN_ON_ONCE(pwq->flush_color != -1);
2550
2551 if (pwq->nr_in_flight[flush_color]) {
2552 pwq->flush_color = flush_color;
2553 atomic_inc(&wq->nr_pwqs_to_flush);
2554 wait = true;
2555 }
2556 }
2557
2558 if (work_color >= 0) {
2559 WARN_ON_ONCE(work_color != work_next_color(pwq->work_color));
2560 pwq->work_color = work_color;
2561 }
2562
2563 spin_unlock_irq(&pool->lock);
2564 }
2565
2566 if (flush_color >= 0 && atomic_dec_and_test(&wq->nr_pwqs_to_flush))
2567 complete(&wq->first_flusher->done);
2568
2569 return wait;
2570}
2571
2572/**
2573 * flush_workqueue - ensure that any scheduled work has run to completion.
2574 * @wq: workqueue to flush
2575 *
2576 * This function sleeps until all work items which were queued on entry
2577 * have finished execution, but it is not livelocked by new incoming ones.
2578 */
2579void flush_workqueue(struct workqueue_struct *wq)
2580{
2581 struct wq_flusher this_flusher = {
2582 .list = LIST_HEAD_INIT(this_flusher.list),
2583 .flush_color = -1,
2584 .done = COMPLETION_INITIALIZER_ONSTACK(this_flusher.done),
2585 };
2586 int next_color;
2587
2588 if (WARN_ON(!wq_online))
2589 return;
2590
2591 lock_map_acquire(&wq->lockdep_map);
2592 lock_map_release(&wq->lockdep_map);
2593
2594 mutex_lock(&wq->mutex);
2595
2596 /*
2597 * Start-to-wait phase
2598 */
2599 next_color = work_next_color(wq->work_color);
2600
2601 if (next_color != wq->flush_color) {
2602 /*
2603 * Color space is not full. The current work_color
2604 * becomes our flush_color and work_color is advanced
2605 * by one.
2606 */
2607 WARN_ON_ONCE(!list_empty(&wq->flusher_overflow));
2608 this_flusher.flush_color = wq->work_color;
2609 wq->work_color = next_color;
2610
2611 if (!wq->first_flusher) {
2612 /* no flush in progress, become the first flusher */
2613 WARN_ON_ONCE(wq->flush_color != this_flusher.flush_color);
2614
2615 wq->first_flusher = &this_flusher;
2616
2617 if (!flush_workqueue_prep_pwqs(wq, wq->flush_color,
2618 wq->work_color)) {
2619 /* nothing to flush, done */
2620 wq->flush_color = next_color;
2621 wq->first_flusher = NULL;
2622 goto out_unlock;
2623 }
2624 } else {
2625 /* wait in queue */
2626 WARN_ON_ONCE(wq->flush_color == this_flusher.flush_color);
2627 list_add_tail(&this_flusher.list, &wq->flusher_queue);
2628 flush_workqueue_prep_pwqs(wq, -1, wq->work_color);
2629 }
2630 } else {
2631 /*
2632 * Oops, color space is full, wait on overflow queue.
2633 * The next flush completion will assign us
2634 * flush_color and transfer to flusher_queue.
2635 */
2636 list_add_tail(&this_flusher.list, &wq->flusher_overflow);
2637 }
2638
2639 check_flush_dependency(wq, NULL);
2640
2641 mutex_unlock(&wq->mutex);
2642
2643 wait_for_completion(&this_flusher.done);
2644
2645 /*
2646 * Wake-up-and-cascade phase
2647 *
2648 * First flushers are responsible for cascading flushes and
2649 * handling overflow. Non-first flushers can simply return.
2650 */
2651 if (wq->first_flusher != &this_flusher)
2652 return;
2653
2654 mutex_lock(&wq->mutex);
2655
2656 /* we might have raced, check again with mutex held */
2657 if (wq->first_flusher != &this_flusher)
2658 goto out_unlock;
2659
2660 wq->first_flusher = NULL;
2661
2662 WARN_ON_ONCE(!list_empty(&this_flusher.list));
2663 WARN_ON_ONCE(wq->flush_color != this_flusher.flush_color);
2664
2665 while (true) {
2666 struct wq_flusher *next, *tmp;
2667
2668 /* complete all the flushers sharing the current flush color */
2669 list_for_each_entry_safe(next, tmp, &wq->flusher_queue, list) {
2670 if (next->flush_color != wq->flush_color)
2671 break;
2672 list_del_init(&next->list);
2673 complete(&next->done);
2674 }
2675
2676 WARN_ON_ONCE(!list_empty(&wq->flusher_overflow) &&
2677 wq->flush_color != work_next_color(wq->work_color));
2678
2679 /* this flush_color is finished, advance by one */
2680 wq->flush_color = work_next_color(wq->flush_color);
2681
2682 /* one color has been freed, handle overflow queue */
2683 if (!list_empty(&wq->flusher_overflow)) {
2684 /*
2685 * Assign the same color to all overflowed
2686 * flushers, advance work_color and append to
2687 * flusher_queue. This is the start-to-wait
2688 * phase for these overflowed flushers.
2689 */
2690 list_for_each_entry(tmp, &wq->flusher_overflow, list)
2691 tmp->flush_color = wq->work_color;
2692
2693 wq->work_color = work_next_color(wq->work_color);
2694
2695 list_splice_tail_init(&wq->flusher_overflow,
2696 &wq->flusher_queue);
2697 flush_workqueue_prep_pwqs(wq, -1, wq->work_color);
2698 }
2699
2700 if (list_empty(&wq->flusher_queue)) {
2701 WARN_ON_ONCE(wq->flush_color != wq->work_color);
2702 break;
2703 }
2704
2705 /*
2706 * Need to flush more colors. Make the next flusher
2707 * the new first flusher and arm pwqs.
2708 */
2709 WARN_ON_ONCE(wq->flush_color == wq->work_color);
2710 WARN_ON_ONCE(wq->flush_color != next->flush_color);
2711
2712 list_del_init(&next->list);
2713 wq->first_flusher = next;
2714
2715 if (flush_workqueue_prep_pwqs(wq, wq->flush_color, -1))
2716 break;
2717
2718 /*
2719 * Meh... this color is already done, clear first
2720 * flusher and repeat cascading.
2721 */
2722 wq->first_flusher = NULL;
2723 }
2724
2725out_unlock:
2726 mutex_unlock(&wq->mutex);
2727}
2728EXPORT_SYMBOL(flush_workqueue);
2729
2730/**
2731 * drain_workqueue - drain a workqueue
2732 * @wq: workqueue to drain
2733 *
2734 * Wait until the workqueue becomes empty. While draining is in progress,
2735 * only chain queueing is allowed. IOW, only currently pending or running
2736 * work items on @wq can queue further work items on it. @wq is flushed
2737 * repeatedly until it becomes empty. The number of flushing is determined
2738 * by the depth of chaining and should be relatively short. Whine if it
2739 * takes too long.
2740 */
2741void drain_workqueue(struct workqueue_struct *wq)
2742{
2743 unsigned int flush_cnt = 0;
2744 struct pool_workqueue *pwq;
2745
2746 /*
2747 * __queue_work() needs to test whether there are drainers, is much
2748 * hotter than drain_workqueue() and already looks at @wq->flags.
2749 * Use __WQ_DRAINING so that queue doesn't have to check nr_drainers.
2750 */
2751 mutex_lock(&wq->mutex);
2752 if (!wq->nr_drainers++)
2753 wq->flags |= __WQ_DRAINING;
2754 mutex_unlock(&wq->mutex);
2755reflush:
2756 flush_workqueue(wq);
2757
2758 mutex_lock(&wq->mutex);
2759
2760 for_each_pwq(pwq, wq) {
2761 bool drained;
2762
2763 spin_lock_irq(&pwq->pool->lock);
2764 drained = !pwq->nr_active && list_empty(&pwq->delayed_works);
2765 spin_unlock_irq(&pwq->pool->lock);
2766
2767 if (drained)
2768 continue;
2769
2770 if (++flush_cnt == 10 ||
2771 (flush_cnt % 100 == 0 && flush_cnt <= 1000))
2772 pr_warn("workqueue %s: drain_workqueue() isn't complete after %u tries\n",
2773 wq->name, flush_cnt);
2774
2775 mutex_unlock(&wq->mutex);
2776 goto reflush;
2777 }
2778
2779 if (!--wq->nr_drainers)
2780 wq->flags &= ~__WQ_DRAINING;
2781 mutex_unlock(&wq->mutex);
2782}
2783EXPORT_SYMBOL_GPL(drain_workqueue);
2784
2785static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr)
2786{
2787 struct worker *worker = NULL;
2788 struct worker_pool *pool;
2789 struct pool_workqueue *pwq;
2790
2791 might_sleep();
2792
2793 local_irq_disable();
2794 pool = get_work_pool(work);
2795 if (!pool) {
2796 local_irq_enable();
2797 return false;
2798 }
2799
2800 spin_lock(&pool->lock);
2801 /* see the comment in try_to_grab_pending() with the same code */
2802 pwq = get_work_pwq(work);
2803 if (pwq) {
2804 if (unlikely(pwq->pool != pool))
2805 goto already_gone;
2806 } else {
2807 worker = find_worker_executing_work(pool, work);
2808 if (!worker)
2809 goto already_gone;
2810 pwq = worker->current_pwq;
2811 }
2812
2813 check_flush_dependency(pwq->wq, work);
2814
2815 insert_wq_barrier(pwq, barr, work, worker);
2816 spin_unlock_irq(&pool->lock);
2817
2818 /*
2819 * If @max_active is 1 or rescuer is in use, flushing another work
2820 * item on the same workqueue may lead to deadlock. Make sure the
2821 * flusher is not running on the same workqueue by verifying write
2822 * access.
2823 */
2824 if (pwq->wq->saved_max_active == 1 || pwq->wq->rescuer)
2825 lock_map_acquire(&pwq->wq->lockdep_map);
2826 else
2827 lock_map_acquire_read(&pwq->wq->lockdep_map);
2828 lock_map_release(&pwq->wq->lockdep_map);
2829
2830 return true;
2831already_gone:
2832 spin_unlock_irq(&pool->lock);
2833 return false;
2834}
2835
2836/**
2837 * flush_work - wait for a work to finish executing the last queueing instance
2838 * @work: the work to flush
2839 *
2840 * Wait until @work has finished execution. @work is guaranteed to be idle
2841 * on return if it hasn't been requeued since flush started.
2842 *
2843 * Return:
2844 * %true if flush_work() waited for the work to finish execution,
2845 * %false if it was already idle.
2846 */
2847bool flush_work(struct work_struct *work)
2848{
2849 struct wq_barrier barr;
2850
2851 if (WARN_ON(!wq_online))
2852 return false;
2853
2854 lock_map_acquire(&work->lockdep_map);
2855 lock_map_release(&work->lockdep_map);
2856
2857 if (start_flush_work(work, &barr)) {
2858 wait_for_completion(&barr.done);
2859 destroy_work_on_stack(&barr.work);
2860 return true;
2861 } else {
2862 return false;
2863 }
2864}
2865EXPORT_SYMBOL_GPL(flush_work);
2866
2867struct cwt_wait {
2868 wait_queue_t wait;
2869 struct work_struct *work;
2870};
2871
2872static int cwt_wakefn(wait_queue_t *wait, unsigned mode, int sync, void *key)
2873{
2874 struct cwt_wait *cwait = container_of(wait, struct cwt_wait, wait);
2875
2876 if (cwait->work != key)
2877 return 0;
2878 return autoremove_wake_function(wait, mode, sync, key);
2879}
2880
2881static bool __cancel_work_timer(struct work_struct *work, bool is_dwork)
2882{
2883 static DECLARE_WAIT_QUEUE_HEAD(cancel_waitq);
2884 unsigned long flags;
2885 int ret;
2886
2887 do {
2888 ret = try_to_grab_pending(work, is_dwork, &flags);
2889 /*
2890 * If someone else is already canceling, wait for it to
2891 * finish. flush_work() doesn't work for PREEMPT_NONE
2892 * because we may get scheduled between @work's completion
2893 * and the other canceling task resuming and clearing
2894 * CANCELING - flush_work() will return false immediately
2895 * as @work is no longer busy, try_to_grab_pending() will
2896 * return -ENOENT as @work is still being canceled and the
2897 * other canceling task won't be able to clear CANCELING as
2898 * we're hogging the CPU.
2899 *
2900 * Let's wait for completion using a waitqueue. As this
2901 * may lead to the thundering herd problem, use a custom
2902 * wake function which matches @work along with exclusive
2903 * wait and wakeup.
2904 */
2905 if (unlikely(ret == -ENOENT)) {
2906 struct cwt_wait cwait;
2907
2908 init_wait(&cwait.wait);
2909 cwait.wait.func = cwt_wakefn;
2910 cwait.work = work;
2911
2912 prepare_to_wait_exclusive(&cancel_waitq, &cwait.wait,
2913 TASK_UNINTERRUPTIBLE);
2914 if (work_is_canceling(work))
2915 schedule();
2916 finish_wait(&cancel_waitq, &cwait.wait);
2917 }
2918 } while (unlikely(ret < 0));
2919
2920 /* tell other tasks trying to grab @work to back off */
2921 mark_work_canceling(work);
2922 local_irq_restore(flags);
2923
2924 /*
2925 * This allows canceling during early boot. We know that @work
2926 * isn't executing.
2927 */
2928 if (wq_online)
2929 flush_work(work);
2930
2931 clear_work_data(work);
2932
2933 /*
2934 * Paired with prepare_to_wait() above so that either
2935 * waitqueue_active() is visible here or !work_is_canceling() is
2936 * visible there.
2937 */
2938 smp_mb();
2939 if (waitqueue_active(&cancel_waitq))
2940 __wake_up(&cancel_waitq, TASK_NORMAL, 1, work);
2941
2942 return ret;
2943}
2944
2945/**
2946 * cancel_work_sync - cancel a work and wait for it to finish
2947 * @work: the work to cancel
2948 *
2949 * Cancel @work and wait for its execution to finish. This function
2950 * can be used even if the work re-queues itself or migrates to
2951 * another workqueue. On return from this function, @work is
2952 * guaranteed to be not pending or executing on any CPU.
2953 *
2954 * cancel_work_sync(&delayed_work->work) must not be used for
2955 * delayed_work's. Use cancel_delayed_work_sync() instead.
2956 *
2957 * The caller must ensure that the workqueue on which @work was last
2958 * queued can't be destroyed before this function returns.
2959 *
2960 * Return:
2961 * %true if @work was pending, %false otherwise.
2962 */
2963bool cancel_work_sync(struct work_struct *work)
2964{
2965 return __cancel_work_timer(work, false);
2966}
2967EXPORT_SYMBOL_GPL(cancel_work_sync);
2968
2969/**
2970 * flush_delayed_work - wait for a dwork to finish executing the last queueing
2971 * @dwork: the delayed work to flush
2972 *
2973 * Delayed timer is cancelled and the pending work is queued for
2974 * immediate execution. Like flush_work(), this function only
2975 * considers the last queueing instance of @dwork.
2976 *
2977 * Return:
2978 * %true if flush_work() waited for the work to finish execution,
2979 * %false if it was already idle.
2980 */
2981bool flush_delayed_work(struct delayed_work *dwork)
2982{
2983 local_irq_disable();
2984 if (del_timer_sync(&dwork->timer))
2985 __queue_work(dwork->cpu, dwork->wq, &dwork->work);
2986 local_irq_enable();
2987 return flush_work(&dwork->work);
2988}
2989EXPORT_SYMBOL(flush_delayed_work);
2990
2991static bool __cancel_work(struct work_struct *work, bool is_dwork)
2992{
2993 unsigned long flags;
2994 int ret;
2995
2996 do {
2997 ret = try_to_grab_pending(work, is_dwork, &flags);
2998 } while (unlikely(ret == -EAGAIN));
2999
3000 if (unlikely(ret < 0))
3001 return false;
3002
3003 set_work_pool_and_clear_pending(work, get_work_pool_id(work));
3004 local_irq_restore(flags);
3005 return ret;
3006}
3007
3008/*
3009 * See cancel_delayed_work()
3010 */
3011bool cancel_work(struct work_struct *work)
3012{
3013 return __cancel_work(work, false);
3014}
3015
3016/**
3017 * cancel_delayed_work - cancel a delayed work
3018 * @dwork: delayed_work to cancel
3019 *
3020 * Kill off a pending delayed_work.
3021 *
3022 * Return: %true if @dwork was pending and canceled; %false if it wasn't
3023 * pending.
3024 *
3025 * Note:
3026 * The work callback function may still be running on return, unless
3027 * it returns %true and the work doesn't re-arm itself. Explicitly flush or
3028 * use cancel_delayed_work_sync() to wait on it.
3029 *
3030 * This function is safe to call from any context including IRQ handler.
3031 */
3032bool cancel_delayed_work(struct delayed_work *dwork)
3033{
3034 return __cancel_work(&dwork->work, true);
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 (wq_online && !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 unsigned long flags;
3447
3448 /* for @wq->saved_max_active */
3449 lockdep_assert_held(&wq->mutex);
3450
3451 /* fast exit for non-freezable wqs */
3452 if (!freezable && pwq->max_active == wq->saved_max_active)
3453 return;
3454
3455 /* this function can be called during early boot w/ irq disabled */
3456 spin_lock_irqsave(&pwq->pool->lock, flags);
3457
3458 /*
3459 * During [un]freezing, the caller is responsible for ensuring that
3460 * this function is called at least once after @workqueue_freezing
3461 * is updated and visible.
3462 */
3463 if (!freezable || !workqueue_freezing) {
3464 pwq->max_active = wq->saved_max_active;
3465
3466 while (!list_empty(&pwq->delayed_works) &&
3467 pwq->nr_active < pwq->max_active)
3468 pwq_activate_first_delayed(pwq);
3469
3470 /*
3471 * Need to kick a worker after thawed or an unbound wq's
3472 * max_active is bumped. It's a slow path. Do it always.
3473 */
3474 wake_up_worker(pwq->pool);
3475 } else {
3476 pwq->max_active = 0;
3477 }
3478
3479 spin_unlock_irqrestore(&pwq->pool->lock, flags);
3480}
3481
3482/* initialize newly alloced @pwq which is associated with @wq and @pool */
3483static void init_pwq(struct pool_workqueue *pwq, struct workqueue_struct *wq,
3484 struct worker_pool *pool)
3485{
3486 BUG_ON((unsigned long)pwq & WORK_STRUCT_FLAG_MASK);
3487
3488 memset(pwq, 0, sizeof(*pwq));
3489
3490 pwq->pool = pool;
3491 pwq->wq = wq;
3492 pwq->flush_color = -1;
3493 pwq->refcnt = 1;
3494 INIT_LIST_HEAD(&pwq->delayed_works);
3495 INIT_LIST_HEAD(&pwq->pwqs_node);
3496 INIT_LIST_HEAD(&pwq->mayday_node);
3497 INIT_WORK(&pwq->unbound_release_work, pwq_unbound_release_workfn);
3498}
3499
3500/* sync @pwq with the current state of its associated wq and link it */
3501static void link_pwq(struct pool_workqueue *pwq)
3502{
3503 struct workqueue_struct *wq = pwq->wq;
3504
3505 lockdep_assert_held(&wq->mutex);
3506
3507 /* may be called multiple times, ignore if already linked */
3508 if (!list_empty(&pwq->pwqs_node))
3509 return;
3510
3511 /* set the matching work_color */
3512 pwq->work_color = wq->work_color;
3513
3514 /* sync max_active to the current setting */
3515 pwq_adjust_max_active(pwq);
3516
3517 /* link in @pwq */
3518 list_add_rcu(&pwq->pwqs_node, &wq->pwqs);
3519}
3520
3521/* obtain a pool matching @attr and create a pwq associating the pool and @wq */
3522static struct pool_workqueue *alloc_unbound_pwq(struct workqueue_struct *wq,
3523 const struct workqueue_attrs *attrs)
3524{
3525 struct worker_pool *pool;
3526 struct pool_workqueue *pwq;
3527
3528 lockdep_assert_held(&wq_pool_mutex);
3529
3530 pool = get_unbound_pool(attrs);
3531 if (!pool)
3532 return NULL;
3533
3534 pwq = kmem_cache_alloc_node(pwq_cache, GFP_KERNEL, pool->node);
3535 if (!pwq) {
3536 put_unbound_pool(pool);
3537 return NULL;
3538 }
3539
3540 init_pwq(pwq, wq, pool);
3541 return pwq;
3542}
3543
3544/**
3545 * wq_calc_node_cpumask - calculate a wq_attrs' cpumask for the specified node
3546 * @attrs: the wq_attrs of the default pwq of the target workqueue
3547 * @node: the target NUMA node
3548 * @cpu_going_down: if >= 0, the CPU to consider as offline
3549 * @cpumask: outarg, the resulting cpumask
3550 *
3551 * Calculate the cpumask a workqueue with @attrs should use on @node. If
3552 * @cpu_going_down is >= 0, that cpu is considered offline during
3553 * calculation. The result is stored in @cpumask.
3554 *
3555 * If NUMA affinity is not enabled, @attrs->cpumask is always used. If
3556 * enabled and @node has online CPUs requested by @attrs, the returned
3557 * cpumask is the intersection of the possible CPUs of @node and
3558 * @attrs->cpumask.
3559 *
3560 * The caller is responsible for ensuring that the cpumask of @node stays
3561 * stable.
3562 *
3563 * Return: %true if the resulting @cpumask is different from @attrs->cpumask,
3564 * %false if equal.
3565 */
3566static bool wq_calc_node_cpumask(const struct workqueue_attrs *attrs, int node,
3567 int cpu_going_down, cpumask_t *cpumask)
3568{
3569 if (!wq_numa_enabled || attrs->no_numa)
3570 goto use_dfl;
3571
3572 /* does @node have any online CPUs @attrs wants? */
3573 cpumask_and(cpumask, cpumask_of_node(node), attrs->cpumask);
3574 if (cpu_going_down >= 0)
3575 cpumask_clear_cpu(cpu_going_down, cpumask);
3576
3577 if (cpumask_empty(cpumask))
3578 goto use_dfl;
3579
3580 /* yeap, return possible CPUs in @node that @attrs wants */
3581 cpumask_and(cpumask, attrs->cpumask, wq_numa_possible_cpumask[node]);
3582 return !cpumask_equal(cpumask, attrs->cpumask);
3583
3584use_dfl:
3585 cpumask_copy(cpumask, attrs->cpumask);
3586 return false;
3587}
3588
3589/* install @pwq into @wq's numa_pwq_tbl[] for @node and return the old pwq */
3590static struct pool_workqueue *numa_pwq_tbl_install(struct workqueue_struct *wq,
3591 int node,
3592 struct pool_workqueue *pwq)
3593{
3594 struct pool_workqueue *old_pwq;
3595
3596 lockdep_assert_held(&wq_pool_mutex);
3597 lockdep_assert_held(&wq->mutex);
3598
3599 /* link_pwq() can handle duplicate calls */
3600 link_pwq(pwq);
3601
3602 old_pwq = rcu_access_pointer(wq->numa_pwq_tbl[node]);
3603 rcu_assign_pointer(wq->numa_pwq_tbl[node], pwq);
3604 return old_pwq;
3605}
3606
3607/* context to store the prepared attrs & pwqs before applying */
3608struct apply_wqattrs_ctx {
3609 struct workqueue_struct *wq; /* target workqueue */
3610 struct workqueue_attrs *attrs; /* attrs to apply */
3611 struct list_head list; /* queued for batching commit */
3612 struct pool_workqueue *dfl_pwq;
3613 struct pool_workqueue *pwq_tbl[];
3614};
3615
3616/* free the resources after success or abort */
3617static void apply_wqattrs_cleanup(struct apply_wqattrs_ctx *ctx)
3618{
3619 if (ctx) {
3620 int node;
3621
3622 for_each_node(node)
3623 put_pwq_unlocked(ctx->pwq_tbl[node]);
3624 put_pwq_unlocked(ctx->dfl_pwq);
3625
3626 free_workqueue_attrs(ctx->attrs);
3627
3628 kfree(ctx);
3629 }
3630}
3631
3632/* allocate the attrs and pwqs for later installation */
3633static struct apply_wqattrs_ctx *
3634apply_wqattrs_prepare(struct workqueue_struct *wq,
3635 const struct workqueue_attrs *attrs)
3636{
3637 struct apply_wqattrs_ctx *ctx;
3638 struct workqueue_attrs *new_attrs, *tmp_attrs;
3639 int node;
3640
3641 lockdep_assert_held(&wq_pool_mutex);
3642
3643 ctx = kzalloc(sizeof(*ctx) + nr_node_ids * sizeof(ctx->pwq_tbl[0]),
3644 GFP_KERNEL);
3645
3646 new_attrs = alloc_workqueue_attrs(GFP_KERNEL);
3647 tmp_attrs = alloc_workqueue_attrs(GFP_KERNEL);
3648 if (!ctx || !new_attrs || !tmp_attrs)
3649 goto out_free;
3650
3651 /*
3652 * Calculate the attrs of the default pwq.
3653 * If the user configured cpumask doesn't overlap with the
3654 * wq_unbound_cpumask, we fallback to the wq_unbound_cpumask.
3655 */
3656 copy_workqueue_attrs(new_attrs, attrs);
3657 cpumask_and(new_attrs->cpumask, new_attrs->cpumask, wq_unbound_cpumask);
3658 if (unlikely(cpumask_empty(new_attrs->cpumask)))
3659 cpumask_copy(new_attrs->cpumask, wq_unbound_cpumask);
3660
3661 /*
3662 * We may create multiple pwqs with differing cpumasks. Make a
3663 * copy of @new_attrs which will be modified and used to obtain
3664 * pools.
3665 */
3666 copy_workqueue_attrs(tmp_attrs, new_attrs);
3667
3668 /*
3669 * If something goes wrong during CPU up/down, we'll fall back to
3670 * the default pwq covering whole @attrs->cpumask. Always create
3671 * it even if we don't use it immediately.
3672 */
3673 ctx->dfl_pwq = alloc_unbound_pwq(wq, new_attrs);
3674 if (!ctx->dfl_pwq)
3675 goto out_free;
3676
3677 for_each_node(node) {
3678 if (wq_calc_node_cpumask(new_attrs, node, -1, tmp_attrs->cpumask)) {
3679 ctx->pwq_tbl[node] = alloc_unbound_pwq(wq, tmp_attrs);
3680 if (!ctx->pwq_tbl[node])
3681 goto out_free;
3682 } else {
3683 ctx->dfl_pwq->refcnt++;
3684 ctx->pwq_tbl[node] = ctx->dfl_pwq;
3685 }
3686 }
3687
3688 /* save the user configured attrs and sanitize it. */
3689 copy_workqueue_attrs(new_attrs, attrs);
3690 cpumask_and(new_attrs->cpumask, new_attrs->cpumask, cpu_possible_mask);
3691 ctx->attrs = new_attrs;
3692
3693 ctx->wq = wq;
3694 free_workqueue_attrs(tmp_attrs);
3695 return ctx;
3696
3697out_free:
3698 free_workqueue_attrs(tmp_attrs);
3699 free_workqueue_attrs(new_attrs);
3700 apply_wqattrs_cleanup(ctx);
3701 return NULL;
3702}
3703
3704/* set attrs and install prepared pwqs, @ctx points to old pwqs on return */
3705static void apply_wqattrs_commit(struct apply_wqattrs_ctx *ctx)
3706{
3707 int node;
3708
3709 /* all pwqs have been created successfully, let's install'em */
3710 mutex_lock(&ctx->wq->mutex);
3711
3712 copy_workqueue_attrs(ctx->wq->unbound_attrs, ctx->attrs);
3713
3714 /* save the previous pwq and install the new one */
3715 for_each_node(node)
3716 ctx->pwq_tbl[node] = numa_pwq_tbl_install(ctx->wq, node,
3717 ctx->pwq_tbl[node]);
3718
3719 /* @dfl_pwq might not have been used, ensure it's linked */
3720 link_pwq(ctx->dfl_pwq);
3721 swap(ctx->wq->dfl_pwq, ctx->dfl_pwq);
3722
3723 mutex_unlock(&ctx->wq->mutex);
3724}
3725
3726static void apply_wqattrs_lock(void)
3727{
3728 /* CPUs should stay stable across pwq creations and installations */
3729 get_online_cpus();
3730 mutex_lock(&wq_pool_mutex);
3731}
3732
3733static void apply_wqattrs_unlock(void)
3734{
3735 mutex_unlock(&wq_pool_mutex);
3736 put_online_cpus();
3737}
3738
3739static int apply_workqueue_attrs_locked(struct workqueue_struct *wq,
3740 const struct workqueue_attrs *attrs)
3741{
3742 struct apply_wqattrs_ctx *ctx;
3743
3744 /* only unbound workqueues can change attributes */
3745 if (WARN_ON(!(wq->flags & WQ_UNBOUND)))
3746 return -EINVAL;
3747
3748 /* creating multiple pwqs breaks ordering guarantee */
3749 if (WARN_ON((wq->flags & __WQ_ORDERED) && !list_empty(&wq->pwqs)))
3750 return -EINVAL;
3751
3752 ctx = apply_wqattrs_prepare(wq, attrs);
3753 if (!ctx)
3754 return -ENOMEM;
3755
3756 /* the ctx has been prepared successfully, let's commit it */
3757 apply_wqattrs_commit(ctx);
3758 apply_wqattrs_cleanup(ctx);
3759
3760 return 0;
3761}
3762
3763/**
3764 * apply_workqueue_attrs - apply new workqueue_attrs to an unbound workqueue
3765 * @wq: the target workqueue
3766 * @attrs: the workqueue_attrs to apply, allocated with alloc_workqueue_attrs()
3767 *
3768 * Apply @attrs to an unbound workqueue @wq. Unless disabled, on NUMA
3769 * machines, this function maps a separate pwq to each NUMA node with
3770 * possibles CPUs in @attrs->cpumask so that work items are affine to the
3771 * NUMA node it was issued on. Older pwqs are released as in-flight work
3772 * items finish. Note that a work item which repeatedly requeues itself
3773 * back-to-back will stay on its current pwq.
3774 *
3775 * Performs GFP_KERNEL allocations.
3776 *
3777 * Return: 0 on success and -errno on failure.
3778 */
3779int apply_workqueue_attrs(struct workqueue_struct *wq,
3780 const struct workqueue_attrs *attrs)
3781{
3782 int ret;
3783
3784 apply_wqattrs_lock();
3785 ret = apply_workqueue_attrs_locked(wq, attrs);
3786 apply_wqattrs_unlock();
3787
3788 return ret;
3789}
3790
3791/**
3792 * wq_update_unbound_numa - update NUMA affinity of a wq for CPU hot[un]plug
3793 * @wq: the target workqueue
3794 * @cpu: the CPU coming up or going down
3795 * @online: whether @cpu is coming up or going down
3796 *
3797 * This function is to be called from %CPU_DOWN_PREPARE, %CPU_ONLINE and
3798 * %CPU_DOWN_FAILED. @cpu is being hot[un]plugged, update NUMA affinity of
3799 * @wq accordingly.
3800 *
3801 * If NUMA affinity can't be adjusted due to memory allocation failure, it
3802 * falls back to @wq->dfl_pwq which may not be optimal but is always
3803 * correct.
3804 *
3805 * Note that when the last allowed CPU of a NUMA node goes offline for a
3806 * workqueue with a cpumask spanning multiple nodes, the workers which were
3807 * already executing the work items for the workqueue will lose their CPU
3808 * affinity and may execute on any CPU. This is similar to how per-cpu
3809 * workqueues behave on CPU_DOWN. If a workqueue user wants strict
3810 * affinity, it's the user's responsibility to flush the work item from
3811 * CPU_DOWN_PREPARE.
3812 */
3813static void wq_update_unbound_numa(struct workqueue_struct *wq, int cpu,
3814 bool online)
3815{
3816 int node = cpu_to_node(cpu);
3817 int cpu_off = online ? -1 : cpu;
3818 struct pool_workqueue *old_pwq = NULL, *pwq;
3819 struct workqueue_attrs *target_attrs;
3820 cpumask_t *cpumask;
3821
3822 lockdep_assert_held(&wq_pool_mutex);
3823
3824 if (!wq_numa_enabled || !(wq->flags & WQ_UNBOUND) ||
3825 wq->unbound_attrs->no_numa)
3826 return;
3827
3828 /*
3829 * We don't wanna alloc/free wq_attrs for each wq for each CPU.
3830 * Let's use a preallocated one. The following buf is protected by
3831 * CPU hotplug exclusion.
3832 */
3833 target_attrs = wq_update_unbound_numa_attrs_buf;
3834 cpumask = target_attrs->cpumask;
3835
3836 copy_workqueue_attrs(target_attrs, wq->unbound_attrs);
3837 pwq = unbound_pwq_by_node(wq, node);
3838
3839 /*
3840 * Let's determine what needs to be done. If the target cpumask is
3841 * different from the default pwq's, we need to compare it to @pwq's
3842 * and create a new one if they don't match. If the target cpumask
3843 * equals the default pwq's, the default pwq should be used.
3844 */
3845 if (wq_calc_node_cpumask(wq->dfl_pwq->pool->attrs, node, cpu_off, cpumask)) {
3846 if (cpumask_equal(cpumask, pwq->pool->attrs->cpumask))
3847 return;
3848 } else {
3849 goto use_dfl_pwq;
3850 }
3851
3852 /* create a new pwq */
3853 pwq = alloc_unbound_pwq(wq, target_attrs);
3854 if (!pwq) {
3855 pr_warn("workqueue: allocation failed while updating NUMA affinity of \"%s\"\n",
3856 wq->name);
3857 goto use_dfl_pwq;
3858 }
3859
3860 /* Install the new pwq. */
3861 mutex_lock(&wq->mutex);
3862 old_pwq = numa_pwq_tbl_install(wq, node, pwq);
3863 goto out_unlock;
3864
3865use_dfl_pwq:
3866 mutex_lock(&wq->mutex);
3867 spin_lock_irq(&wq->dfl_pwq->pool->lock);
3868 get_pwq(wq->dfl_pwq);
3869 spin_unlock_irq(&wq->dfl_pwq->pool->lock);
3870 old_pwq = numa_pwq_tbl_install(wq, node, wq->dfl_pwq);
3871out_unlock:
3872 mutex_unlock(&wq->mutex);
3873 put_pwq_unlocked(old_pwq);
3874}
3875
3876static int alloc_and_link_pwqs(struct workqueue_struct *wq)
3877{
3878 bool highpri = wq->flags & WQ_HIGHPRI;
3879 int cpu, ret;
3880
3881 if (!(wq->flags & WQ_UNBOUND)) {
3882 wq->cpu_pwqs = alloc_percpu(struct pool_workqueue);
3883 if (!wq->cpu_pwqs)
3884 return -ENOMEM;
3885
3886 for_each_possible_cpu(cpu) {
3887 struct pool_workqueue *pwq =
3888 per_cpu_ptr(wq->cpu_pwqs, cpu);
3889 struct worker_pool *cpu_pools =
3890 per_cpu(cpu_worker_pools, cpu);
3891
3892 init_pwq(pwq, wq, &cpu_pools[highpri]);
3893
3894 mutex_lock(&wq->mutex);
3895 link_pwq(pwq);
3896 mutex_unlock(&wq->mutex);
3897 }
3898 return 0;
3899 } else if (wq->flags & __WQ_ORDERED) {
3900 ret = apply_workqueue_attrs(wq, ordered_wq_attrs[highpri]);
3901 /* there should only be single pwq for ordering guarantee */
3902 WARN(!ret && (wq->pwqs.next != &wq->dfl_pwq->pwqs_node ||
3903 wq->pwqs.prev != &wq->dfl_pwq->pwqs_node),
3904 "ordering guarantee broken for workqueue %s\n", wq->name);
3905 return ret;
3906 } else {
3907 return apply_workqueue_attrs(wq, unbound_std_wq_attrs[highpri]);
3908 }
3909}
3910
3911static int wq_clamp_max_active(int max_active, unsigned int flags,
3912 const char *name)
3913{
3914 int lim = flags & WQ_UNBOUND ? WQ_UNBOUND_MAX_ACTIVE : WQ_MAX_ACTIVE;
3915
3916 if (max_active < 1 || max_active > lim)
3917 pr_warn("workqueue: max_active %d requested for %s is out of range, clamping between %d and %d\n",
3918 max_active, name, 1, lim);
3919
3920 return clamp_val(max_active, 1, lim);
3921}
3922
3923struct workqueue_struct *__alloc_workqueue_key(const char *fmt,
3924 unsigned int flags,
3925 int max_active,
3926 struct lock_class_key *key,
3927 const char *lock_name, ...)
3928{
3929 size_t tbl_size = 0;
3930 va_list args;
3931 struct workqueue_struct *wq;
3932 struct pool_workqueue *pwq;
3933
3934 /* see the comment above the definition of WQ_POWER_EFFICIENT */
3935 if ((flags & WQ_POWER_EFFICIENT) && wq_power_efficient)
3936 flags |= WQ_UNBOUND;
3937
3938 /* allocate wq and format name */
3939 if (flags & WQ_UNBOUND)
3940 tbl_size = nr_node_ids * sizeof(wq->numa_pwq_tbl[0]);
3941
3942 wq = kzalloc(sizeof(*wq) + tbl_size, GFP_KERNEL);
3943 if (!wq)
3944 return NULL;
3945
3946 if (flags & WQ_UNBOUND) {
3947 wq->unbound_attrs = alloc_workqueue_attrs(GFP_KERNEL);
3948 if (!wq->unbound_attrs)
3949 goto err_free_wq;
3950 }
3951
3952 va_start(args, lock_name);
3953 vsnprintf(wq->name, sizeof(wq->name), fmt, args);
3954 va_end(args);
3955
3956 max_active = max_active ?: WQ_DFL_ACTIVE;
3957 max_active = wq_clamp_max_active(max_active, flags, wq->name);
3958
3959 /* init wq */
3960 wq->flags = flags;
3961 wq->saved_max_active = max_active;
3962 mutex_init(&wq->mutex);
3963 atomic_set(&wq->nr_pwqs_to_flush, 0);
3964 INIT_LIST_HEAD(&wq->pwqs);
3965 INIT_LIST_HEAD(&wq->flusher_queue);
3966 INIT_LIST_HEAD(&wq->flusher_overflow);
3967 INIT_LIST_HEAD(&wq->maydays);
3968
3969 lockdep_init_map(&wq->lockdep_map, lock_name, key, 0);
3970 INIT_LIST_HEAD(&wq->list);
3971
3972 if (alloc_and_link_pwqs(wq) < 0)
3973 goto err_free_wq;
3974
3975 /*
3976 * Workqueues which may be used during memory reclaim should
3977 * have a rescuer to guarantee forward progress.
3978 */
3979 if (flags & WQ_MEM_RECLAIM) {
3980 struct worker *rescuer;
3981
3982 rescuer = alloc_worker(NUMA_NO_NODE);
3983 if (!rescuer)
3984 goto err_destroy;
3985
3986 rescuer->rescue_wq = wq;
3987 rescuer->task = kthread_create(rescuer_thread, rescuer, "%s",
3988 wq->name);
3989 if (IS_ERR(rescuer->task)) {
3990 kfree(rescuer);
3991 goto err_destroy;
3992 }
3993
3994 wq->rescuer = rescuer;
3995 kthread_bind_mask(rescuer->task, cpu_possible_mask);
3996 wake_up_process(rescuer->task);
3997 }
3998
3999 if ((wq->flags & WQ_SYSFS) && workqueue_sysfs_register(wq))
4000 goto err_destroy;
4001
4002 /*
4003 * wq_pool_mutex protects global freeze state and workqueues list.
4004 * Grab it, adjust max_active and add the new @wq to workqueues
4005 * list.
4006 */
4007 mutex_lock(&wq_pool_mutex);
4008
4009 mutex_lock(&wq->mutex);
4010 for_each_pwq(pwq, wq)
4011 pwq_adjust_max_active(pwq);
4012 mutex_unlock(&wq->mutex);
4013
4014 list_add_tail_rcu(&wq->list, &workqueues);
4015
4016 mutex_unlock(&wq_pool_mutex);
4017
4018 return wq;
4019
4020err_free_wq:
4021 free_workqueue_attrs(wq->unbound_attrs);
4022 kfree(wq);
4023 return NULL;
4024err_destroy:
4025 destroy_workqueue(wq);
4026 return NULL;
4027}
4028EXPORT_SYMBOL_GPL(__alloc_workqueue_key);
4029
4030/**
4031 * destroy_workqueue - safely terminate a workqueue
4032 * @wq: target workqueue
4033 *
4034 * Safely destroy a workqueue. All work currently pending will be done first.
4035 */
4036void destroy_workqueue(struct workqueue_struct *wq)
4037{
4038 struct pool_workqueue *pwq;
4039 int node;
4040
4041 /* drain it before proceeding with destruction */
4042 drain_workqueue(wq);
4043
4044 /* sanity checks */
4045 mutex_lock(&wq->mutex);
4046 for_each_pwq(pwq, wq) {
4047 int i;
4048
4049 for (i = 0; i < WORK_NR_COLORS; i++) {
4050 if (WARN_ON(pwq->nr_in_flight[i])) {
4051 mutex_unlock(&wq->mutex);
4052 show_workqueue_state();
4053 return;
4054 }
4055 }
4056
4057 if (WARN_ON((pwq != wq->dfl_pwq) && (pwq->refcnt > 1)) ||
4058 WARN_ON(pwq->nr_active) ||
4059 WARN_ON(!list_empty(&pwq->delayed_works))) {
4060 mutex_unlock(&wq->mutex);
4061 show_workqueue_state();
4062 return;
4063 }
4064 }
4065 mutex_unlock(&wq->mutex);
4066
4067 /*
4068 * wq list is used to freeze wq, remove from list after
4069 * flushing is complete in case freeze races us.
4070 */
4071 mutex_lock(&wq_pool_mutex);
4072 list_del_rcu(&wq->list);
4073 mutex_unlock(&wq_pool_mutex);
4074
4075 workqueue_sysfs_unregister(wq);
4076
4077 if (wq->rescuer)
4078 kthread_stop(wq->rescuer->task);
4079
4080 if (!(wq->flags & WQ_UNBOUND)) {
4081 /*
4082 * The base ref is never dropped on per-cpu pwqs. Directly
4083 * schedule RCU free.
4084 */
4085 call_rcu_sched(&wq->rcu, rcu_free_wq);
4086 } else {
4087 /*
4088 * We're the sole accessor of @wq at this point. Directly
4089 * access numa_pwq_tbl[] and dfl_pwq to put the base refs.
4090 * @wq will be freed when the last pwq is released.
4091 */
4092 for_each_node(node) {
4093 pwq = rcu_access_pointer(wq->numa_pwq_tbl[node]);
4094 RCU_INIT_POINTER(wq->numa_pwq_tbl[node], NULL);
4095 put_pwq_unlocked(pwq);
4096 }
4097
4098 /*
4099 * Put dfl_pwq. @wq may be freed any time after dfl_pwq is
4100 * put. Don't access it afterwards.
4101 */
4102 pwq = wq->dfl_pwq;
4103 wq->dfl_pwq = NULL;
4104 put_pwq_unlocked(pwq);
4105 }
4106}
4107EXPORT_SYMBOL_GPL(destroy_workqueue);
4108
4109/**
4110 * workqueue_set_max_active - adjust max_active of a workqueue
4111 * @wq: target workqueue
4112 * @max_active: new max_active value.
4113 *
4114 * Set max_active of @wq to @max_active.
4115 *
4116 * CONTEXT:
4117 * Don't call from IRQ context.
4118 */
4119void workqueue_set_max_active(struct workqueue_struct *wq, int max_active)
4120{
4121 struct pool_workqueue *pwq;
4122
4123 /* disallow meddling with max_active for ordered workqueues */
4124 if (WARN_ON(wq->flags & __WQ_ORDERED))
4125 return;
4126
4127 max_active = wq_clamp_max_active(max_active, wq->flags, wq->name);
4128
4129 mutex_lock(&wq->mutex);
4130
4131 wq->saved_max_active = max_active;
4132
4133 for_each_pwq(pwq, wq)
4134 pwq_adjust_max_active(pwq);
4135
4136 mutex_unlock(&wq->mutex);
4137}
4138EXPORT_SYMBOL_GPL(workqueue_set_max_active);
4139
4140/**
4141 * current_is_workqueue_rescuer - is %current workqueue rescuer?
4142 *
4143 * Determine whether %current is a workqueue rescuer. Can be used from
4144 * work functions to determine whether it's being run off the rescuer task.
4145 *
4146 * Return: %true if %current is a workqueue rescuer. %false otherwise.
4147 */
4148bool current_is_workqueue_rescuer(void)
4149{
4150 struct worker *worker = current_wq_worker();
4151
4152 return worker && worker->rescue_wq;
4153}
4154
4155/**
4156 * workqueue_congested - test whether a workqueue is congested
4157 * @cpu: CPU in question
4158 * @wq: target workqueue
4159 *
4160 * Test whether @wq's cpu workqueue for @cpu is congested. There is
4161 * no synchronization around this function and the test result is
4162 * unreliable and only useful as advisory hints or for debugging.
4163 *
4164 * If @cpu is WORK_CPU_UNBOUND, the test is performed on the local CPU.
4165 * Note that both per-cpu and unbound workqueues may be associated with
4166 * multiple pool_workqueues which have separate congested states. A
4167 * workqueue being congested on one CPU doesn't mean the workqueue is also
4168 * contested on other CPUs / NUMA nodes.
4169 *
4170 * Return:
4171 * %true if congested, %false otherwise.
4172 */
4173bool workqueue_congested(int cpu, struct workqueue_struct *wq)
4174{
4175 struct pool_workqueue *pwq;
4176 bool ret;
4177
4178 rcu_read_lock_sched();
4179
4180 if (cpu == WORK_CPU_UNBOUND)
4181 cpu = smp_processor_id();
4182
4183 if (!(wq->flags & WQ_UNBOUND))
4184 pwq = per_cpu_ptr(wq->cpu_pwqs, cpu);
4185 else
4186 pwq = unbound_pwq_by_node(wq, cpu_to_node(cpu));
4187
4188 ret = !list_empty(&pwq->delayed_works);
4189 rcu_read_unlock_sched();
4190
4191 return ret;
4192}
4193EXPORT_SYMBOL_GPL(workqueue_congested);
4194
4195/**
4196 * work_busy - test whether a work is currently pending or running
4197 * @work: the work to be tested
4198 *
4199 * Test whether @work is currently pending or running. There is no
4200 * synchronization around this function and the test result is
4201 * unreliable and only useful as advisory hints or for debugging.
4202 *
4203 * Return:
4204 * OR'd bitmask of WORK_BUSY_* bits.
4205 */
4206unsigned int work_busy(struct work_struct *work)
4207{
4208 struct worker_pool *pool;
4209 unsigned long flags;
4210 unsigned int ret = 0;
4211
4212 if (work_pending(work))
4213 ret |= WORK_BUSY_PENDING;
4214
4215 local_irq_save(flags);
4216 pool = get_work_pool(work);
4217 if (pool) {
4218 spin_lock(&pool->lock);
4219 if (find_worker_executing_work(pool, work))
4220 ret |= WORK_BUSY_RUNNING;
4221 spin_unlock(&pool->lock);
4222 }
4223 local_irq_restore(flags);
4224
4225 return ret;
4226}
4227EXPORT_SYMBOL_GPL(work_busy);
4228
4229/**
4230 * set_worker_desc - set description for the current work item
4231 * @fmt: printf-style format string
4232 * @...: arguments for the format string
4233 *
4234 * This function can be called by a running work function to describe what
4235 * the work item is about. If the worker task gets dumped, this
4236 * information will be printed out together to help debugging. The
4237 * description can be at most WORKER_DESC_LEN including the trailing '\0'.
4238 */
4239void set_worker_desc(const char *fmt, ...)
4240{
4241 struct worker *worker = current_wq_worker();
4242 va_list args;
4243
4244 if (worker) {
4245 va_start(args, fmt);
4246 vsnprintf(worker->desc, sizeof(worker->desc), fmt, args);
4247 va_end(args);
4248 worker->desc_valid = true;
4249 }
4250}
4251
4252/**
4253 * print_worker_info - print out worker information and description
4254 * @log_lvl: the log level to use when printing
4255 * @task: target task
4256 *
4257 * If @task is a worker and currently executing a work item, print out the
4258 * name of the workqueue being serviced and worker description set with
4259 * set_worker_desc() by the currently executing work item.
4260 *
4261 * This function can be safely called on any task as long as the
4262 * task_struct itself is accessible. While safe, this function isn't
4263 * synchronized and may print out mixups or garbages of limited length.
4264 */
4265void print_worker_info(const char *log_lvl, struct task_struct *task)
4266{
4267 work_func_t *fn = NULL;
4268 char name[WQ_NAME_LEN] = { };
4269 char desc[WORKER_DESC_LEN] = { };
4270 struct pool_workqueue *pwq = NULL;
4271 struct workqueue_struct *wq = NULL;
4272 bool desc_valid = false;
4273 struct worker *worker;
4274
4275 if (!(task->flags & PF_WQ_WORKER))
4276 return;
4277
4278 /*
4279 * This function is called without any synchronization and @task
4280 * could be in any state. Be careful with dereferences.
4281 */
4282 worker = kthread_probe_data(task);
4283
4284 /*
4285 * Carefully copy the associated workqueue's workfn and name. Keep
4286 * the original last '\0' in case the original contains garbage.
4287 */
4288 probe_kernel_read(&fn, &worker->current_func, sizeof(fn));
4289 probe_kernel_read(&pwq, &worker->current_pwq, sizeof(pwq));
4290 probe_kernel_read(&wq, &pwq->wq, sizeof(wq));
4291 probe_kernel_read(name, wq->name, sizeof(name) - 1);
4292
4293 /* copy worker description */
4294 probe_kernel_read(&desc_valid, &worker->desc_valid, sizeof(desc_valid));
4295 if (desc_valid)
4296 probe_kernel_read(desc, worker->desc, sizeof(desc) - 1);
4297
4298 if (fn || name[0] || desc[0]) {
4299 printk("%sWorkqueue: %s %pf", log_lvl, name, fn);
4300 if (desc[0])
4301 pr_cont(" (%s)", desc);
4302 pr_cont("\n");
4303 }
4304}
4305
4306static void pr_cont_pool_info(struct worker_pool *pool)
4307{
4308 pr_cont(" cpus=%*pbl", nr_cpumask_bits, pool->attrs->cpumask);
4309 if (pool->node != NUMA_NO_NODE)
4310 pr_cont(" node=%d", pool->node);
4311 pr_cont(" flags=0x%x nice=%d", pool->flags, pool->attrs->nice);
4312}
4313
4314static void pr_cont_work(bool comma, struct work_struct *work)
4315{
4316 if (work->func == wq_barrier_func) {
4317 struct wq_barrier *barr;
4318
4319 barr = container_of(work, struct wq_barrier, work);
4320
4321 pr_cont("%s BAR(%d)", comma ? "," : "",
4322 task_pid_nr(barr->task));
4323 } else {
4324 pr_cont("%s %pf", comma ? "," : "", work->func);
4325 }
4326}
4327
4328static void show_pwq(struct pool_workqueue *pwq)
4329{
4330 struct worker_pool *pool = pwq->pool;
4331 struct work_struct *work;
4332 struct worker *worker;
4333 bool has_in_flight = false, has_pending = false;
4334 int bkt;
4335
4336 pr_info(" pwq %d:", pool->id);
4337 pr_cont_pool_info(pool);
4338
4339 pr_cont(" active=%d/%d%s\n", pwq->nr_active, pwq->max_active,
4340 !list_empty(&pwq->mayday_node) ? " MAYDAY" : "");
4341
4342 hash_for_each(pool->busy_hash, bkt, worker, hentry) {
4343 if (worker->current_pwq == pwq) {
4344 has_in_flight = true;
4345 break;
4346 }
4347 }
4348 if (has_in_flight) {
4349 bool comma = false;
4350
4351 pr_info(" in-flight:");
4352 hash_for_each(pool->busy_hash, bkt, worker, hentry) {
4353 if (worker->current_pwq != pwq)
4354 continue;
4355
4356 pr_cont("%s %d%s:%pf", comma ? "," : "",
4357 task_pid_nr(worker->task),
4358 worker == pwq->wq->rescuer ? "(RESCUER)" : "",
4359 worker->current_func);
4360 list_for_each_entry(work, &worker->scheduled, entry)
4361 pr_cont_work(false, work);
4362 comma = true;
4363 }
4364 pr_cont("\n");
4365 }
4366
4367 list_for_each_entry(work, &pool->worklist, entry) {
4368 if (get_work_pwq(work) == pwq) {
4369 has_pending = true;
4370 break;
4371 }
4372 }
4373 if (has_pending) {
4374 bool comma = false;
4375
4376 pr_info(" pending:");
4377 list_for_each_entry(work, &pool->worklist, entry) {
4378 if (get_work_pwq(work) != pwq)
4379 continue;
4380
4381 pr_cont_work(comma, work);
4382 comma = !(*work_data_bits(work) & WORK_STRUCT_LINKED);
4383 }
4384 pr_cont("\n");
4385 }
4386
4387 if (!list_empty(&pwq->delayed_works)) {
4388 bool comma = false;
4389
4390 pr_info(" delayed:");
4391 list_for_each_entry(work, &pwq->delayed_works, entry) {
4392 pr_cont_work(comma, work);
4393 comma = !(*work_data_bits(work) & WORK_STRUCT_LINKED);
4394 }
4395 pr_cont("\n");
4396 }
4397}
4398
4399/**
4400 * show_workqueue_state - dump workqueue state
4401 *
4402 * Called from a sysrq handler or try_to_freeze_tasks() and prints out
4403 * all busy workqueues and pools.
4404 */
4405void show_workqueue_state(void)
4406{
4407 struct workqueue_struct *wq;
4408 struct worker_pool *pool;
4409 unsigned long flags;
4410 int pi;
4411
4412 rcu_read_lock_sched();
4413
4414 pr_info("Showing busy workqueues and worker pools:\n");
4415
4416 list_for_each_entry_rcu(wq, &workqueues, list) {
4417 struct pool_workqueue *pwq;
4418 bool idle = true;
4419
4420 for_each_pwq(pwq, wq) {
4421 if (pwq->nr_active || !list_empty(&pwq->delayed_works)) {
4422 idle = false;
4423 break;
4424 }
4425 }
4426 if (idle)
4427 continue;
4428
4429 pr_info("workqueue %s: flags=0x%x\n", wq->name, wq->flags);
4430
4431 for_each_pwq(pwq, wq) {
4432 spin_lock_irqsave(&pwq->pool->lock, flags);
4433 if (pwq->nr_active || !list_empty(&pwq->delayed_works))
4434 show_pwq(pwq);
4435 spin_unlock_irqrestore(&pwq->pool->lock, flags);
4436 }
4437 }
4438
4439 for_each_pool(pool, pi) {
4440 struct worker *worker;
4441 bool first = true;
4442
4443 spin_lock_irqsave(&pool->lock, flags);
4444 if (pool->nr_workers == pool->nr_idle)
4445 goto next_pool;
4446
4447 pr_info("pool %d:", pool->id);
4448 pr_cont_pool_info(pool);
4449 pr_cont(" hung=%us workers=%d",
4450 jiffies_to_msecs(jiffies - pool->watchdog_ts) / 1000,
4451 pool->nr_workers);
4452 if (pool->manager)
4453 pr_cont(" manager: %d",
4454 task_pid_nr(pool->manager->task));
4455 list_for_each_entry(worker, &pool->idle_list, entry) {
4456 pr_cont(" %s%d", first ? "idle: " : "",
4457 task_pid_nr(worker->task));
4458 first = false;
4459 }
4460 pr_cont("\n");
4461 next_pool:
4462 spin_unlock_irqrestore(&pool->lock, flags);
4463 }
4464
4465 rcu_read_unlock_sched();
4466}
4467
4468/*
4469 * CPU hotplug.
4470 *
4471 * There are two challenges in supporting CPU hotplug. Firstly, there
4472 * are a lot of assumptions on strong associations among work, pwq and
4473 * pool which make migrating pending and scheduled works very
4474 * difficult to implement without impacting hot paths. Secondly,
4475 * worker pools serve mix of short, long and very long running works making
4476 * blocked draining impractical.
4477 *
4478 * This is solved by allowing the pools to be disassociated from the CPU
4479 * running as an unbound one and allowing it to be reattached later if the
4480 * cpu comes back online.
4481 */
4482
4483static void wq_unbind_fn(struct work_struct *work)
4484{
4485 int cpu = smp_processor_id();
4486 struct worker_pool *pool;
4487 struct worker *worker;
4488
4489 for_each_cpu_worker_pool(pool, cpu) {
4490 mutex_lock(&pool->attach_mutex);
4491 spin_lock_irq(&pool->lock);
4492
4493 /*
4494 * We've blocked all attach/detach operations. Make all workers
4495 * unbound and set DISASSOCIATED. Before this, all workers
4496 * except for the ones which are still executing works from
4497 * before the last CPU down must be on the cpu. After
4498 * this, they may become diasporas.
4499 */
4500 for_each_pool_worker(worker, pool)
4501 worker->flags |= WORKER_UNBOUND;
4502
4503 pool->flags |= POOL_DISASSOCIATED;
4504
4505 spin_unlock_irq(&pool->lock);
4506 mutex_unlock(&pool->attach_mutex);
4507
4508 /*
4509 * Call schedule() so that we cross rq->lock and thus can
4510 * guarantee sched callbacks see the %WORKER_UNBOUND flag.
4511 * This is necessary as scheduler callbacks may be invoked
4512 * from other cpus.
4513 */
4514 schedule();
4515
4516 /*
4517 * Sched callbacks are disabled now. Zap nr_running.
4518 * After this, nr_running stays zero and need_more_worker()
4519 * and keep_working() are always true as long as the
4520 * worklist is not empty. This pool now behaves as an
4521 * unbound (in terms of concurrency management) pool which
4522 * are served by workers tied to the pool.
4523 */
4524 atomic_set(&pool->nr_running, 0);
4525
4526 /*
4527 * With concurrency management just turned off, a busy
4528 * worker blocking could lead to lengthy stalls. Kick off
4529 * unbound chain execution of currently pending work items.
4530 */
4531 spin_lock_irq(&pool->lock);
4532 wake_up_worker(pool);
4533 spin_unlock_irq(&pool->lock);
4534 }
4535}
4536
4537/**
4538 * rebind_workers - rebind all workers of a pool to the associated CPU
4539 * @pool: pool of interest
4540 *
4541 * @pool->cpu is coming online. Rebind all workers to the CPU.
4542 */
4543static void rebind_workers(struct worker_pool *pool)
4544{
4545 struct worker *worker;
4546
4547 lockdep_assert_held(&pool->attach_mutex);
4548
4549 /*
4550 * Restore CPU affinity of all workers. As all idle workers should
4551 * be on the run-queue of the associated CPU before any local
4552 * wake-ups for concurrency management happen, restore CPU affinity
4553 * of all workers first and then clear UNBOUND. As we're called
4554 * from CPU_ONLINE, the following shouldn't fail.
4555 */
4556 for_each_pool_worker(worker, pool)
4557 WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task,
4558 pool->attrs->cpumask) < 0);
4559
4560 spin_lock_irq(&pool->lock);
4561
4562 /*
4563 * XXX: CPU hotplug notifiers are weird and can call DOWN_FAILED
4564 * w/o preceding DOWN_PREPARE. Work around it. CPU hotplug is
4565 * being reworked and this can go away in time.
4566 */
4567 if (!(pool->flags & POOL_DISASSOCIATED)) {
4568 spin_unlock_irq(&pool->lock);
4569 return;
4570 }
4571
4572 pool->flags &= ~POOL_DISASSOCIATED;
4573
4574 for_each_pool_worker(worker, pool) {
4575 unsigned int worker_flags = worker->flags;
4576
4577 /*
4578 * A bound idle worker should actually be on the runqueue
4579 * of the associated CPU for local wake-ups targeting it to
4580 * work. Kick all idle workers so that they migrate to the
4581 * associated CPU. Doing this in the same loop as
4582 * replacing UNBOUND with REBOUND is safe as no worker will
4583 * be bound before @pool->lock is released.
4584 */
4585 if (worker_flags & WORKER_IDLE)
4586 wake_up_process(worker->task);
4587
4588 /*
4589 * We want to clear UNBOUND but can't directly call
4590 * worker_clr_flags() or adjust nr_running. Atomically
4591 * replace UNBOUND with another NOT_RUNNING flag REBOUND.
4592 * @worker will clear REBOUND using worker_clr_flags() when
4593 * it initiates the next execution cycle thus restoring
4594 * concurrency management. Note that when or whether
4595 * @worker clears REBOUND doesn't affect correctness.
4596 *
4597 * ACCESS_ONCE() is necessary because @worker->flags may be
4598 * tested without holding any lock in
4599 * wq_worker_waking_up(). Without it, NOT_RUNNING test may
4600 * fail incorrectly leading to premature concurrency
4601 * management operations.
4602 */
4603 WARN_ON_ONCE(!(worker_flags & WORKER_UNBOUND));
4604 worker_flags |= WORKER_REBOUND;
4605 worker_flags &= ~WORKER_UNBOUND;
4606 ACCESS_ONCE(worker->flags) = worker_flags;
4607 }
4608
4609 spin_unlock_irq(&pool->lock);
4610}
4611
4612/**
4613 * restore_unbound_workers_cpumask - restore cpumask of unbound workers
4614 * @pool: unbound pool of interest
4615 * @cpu: the CPU which is coming up
4616 *
4617 * An unbound pool may end up with a cpumask which doesn't have any online
4618 * CPUs. When a worker of such pool get scheduled, the scheduler resets
4619 * its cpus_allowed. If @cpu is in @pool's cpumask which didn't have any
4620 * online CPU before, cpus_allowed of all its workers should be restored.
4621 */
4622static void restore_unbound_workers_cpumask(struct worker_pool *pool, int cpu)
4623{
4624 static cpumask_t cpumask;
4625 struct worker *worker;
4626
4627 lockdep_assert_held(&pool->attach_mutex);
4628
4629 /* is @cpu allowed for @pool? */
4630 if (!cpumask_test_cpu(cpu, pool->attrs->cpumask))
4631 return;
4632
4633 cpumask_and(&cpumask, pool->attrs->cpumask, cpu_online_mask);
4634
4635 /* as we're called from CPU_ONLINE, the following shouldn't fail */
4636 for_each_pool_worker(worker, pool)
4637 WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task, &cpumask) < 0);
4638}
4639
4640int workqueue_prepare_cpu(unsigned int cpu)
4641{
4642 struct worker_pool *pool;
4643
4644 for_each_cpu_worker_pool(pool, cpu) {
4645 if (pool->nr_workers)
4646 continue;
4647 if (!create_worker(pool))
4648 return -ENOMEM;
4649 }
4650 return 0;
4651}
4652
4653int workqueue_online_cpu(unsigned int cpu)
4654{
4655 struct worker_pool *pool;
4656 struct workqueue_struct *wq;
4657 int pi;
4658
4659 mutex_lock(&wq_pool_mutex);
4660
4661 for_each_pool(pool, pi) {
4662 mutex_lock(&pool->attach_mutex);
4663
4664 if (pool->cpu == cpu)
4665 rebind_workers(pool);
4666 else if (pool->cpu < 0)
4667 restore_unbound_workers_cpumask(pool, cpu);
4668
4669 mutex_unlock(&pool->attach_mutex);
4670 }
4671
4672 /* update NUMA affinity of unbound workqueues */
4673 list_for_each_entry(wq, &workqueues, list)
4674 wq_update_unbound_numa(wq, cpu, true);
4675
4676 mutex_unlock(&wq_pool_mutex);
4677 return 0;
4678}
4679
4680int workqueue_offline_cpu(unsigned int cpu)
4681{
4682 struct work_struct unbind_work;
4683 struct workqueue_struct *wq;
4684
4685 /* unbinding per-cpu workers should happen on the local CPU */
4686 INIT_WORK_ONSTACK(&unbind_work, wq_unbind_fn);
4687 queue_work_on(cpu, system_highpri_wq, &unbind_work);
4688
4689 /* update NUMA affinity of unbound workqueues */
4690 mutex_lock(&wq_pool_mutex);
4691 list_for_each_entry(wq, &workqueues, list)
4692 wq_update_unbound_numa(wq, cpu, false);
4693 mutex_unlock(&wq_pool_mutex);
4694
4695 /* wait for per-cpu unbinding to finish */
4696 flush_work(&unbind_work);
4697 destroy_work_on_stack(&unbind_work);
4698 return 0;
4699}
4700
4701#ifdef CONFIG_SMP
4702
4703struct work_for_cpu {
4704 struct work_struct work;
4705 long (*fn)(void *);
4706 void *arg;
4707 long ret;
4708};
4709
4710static void work_for_cpu_fn(struct work_struct *work)
4711{
4712 struct work_for_cpu *wfc = container_of(work, struct work_for_cpu, work);
4713
4714 wfc->ret = wfc->fn(wfc->arg);
4715}
4716
4717/**
4718 * work_on_cpu - run a function in thread context on a particular cpu
4719 * @cpu: the cpu to run on
4720 * @fn: the function to run
4721 * @arg: the function arg
4722 *
4723 * It is up to the caller to ensure that the cpu doesn't go offline.
4724 * The caller must not hold any locks which would prevent @fn from completing.
4725 *
4726 * Return: The value @fn returns.
4727 */
4728long work_on_cpu(int cpu, long (*fn)(void *), void *arg)
4729{
4730 struct work_for_cpu wfc = { .fn = fn, .arg = arg };
4731
4732 INIT_WORK_ONSTACK(&wfc.work, work_for_cpu_fn);
4733 schedule_work_on(cpu, &wfc.work);
4734 flush_work(&wfc.work);
4735 destroy_work_on_stack(&wfc.work);
4736 return wfc.ret;
4737}
4738EXPORT_SYMBOL_GPL(work_on_cpu);
4739#endif /* CONFIG_SMP */
4740
4741#ifdef CONFIG_FREEZER
4742
4743/**
4744 * freeze_workqueues_begin - begin freezing workqueues
4745 *
4746 * Start freezing workqueues. After this function returns, all freezable
4747 * workqueues will queue new works to their delayed_works list instead of
4748 * pool->worklist.
4749 *
4750 * CONTEXT:
4751 * Grabs and releases wq_pool_mutex, wq->mutex and pool->lock's.
4752 */
4753void freeze_workqueues_begin(void)
4754{
4755 struct workqueue_struct *wq;
4756 struct pool_workqueue *pwq;
4757
4758 mutex_lock(&wq_pool_mutex);
4759
4760 WARN_ON_ONCE(workqueue_freezing);
4761 workqueue_freezing = true;
4762
4763 list_for_each_entry(wq, &workqueues, list) {
4764 mutex_lock(&wq->mutex);
4765 for_each_pwq(pwq, wq)
4766 pwq_adjust_max_active(pwq);
4767 mutex_unlock(&wq->mutex);
4768 }
4769
4770 mutex_unlock(&wq_pool_mutex);
4771}
4772
4773/**
4774 * freeze_workqueues_busy - are freezable workqueues still busy?
4775 *
4776 * Check whether freezing is complete. This function must be called
4777 * between freeze_workqueues_begin() and thaw_workqueues().
4778 *
4779 * CONTEXT:
4780 * Grabs and releases wq_pool_mutex.
4781 *
4782 * Return:
4783 * %true if some freezable workqueues are still busy. %false if freezing
4784 * is complete.
4785 */
4786bool freeze_workqueues_busy(void)
4787{
4788 bool busy = false;
4789 struct workqueue_struct *wq;
4790 struct pool_workqueue *pwq;
4791
4792 mutex_lock(&wq_pool_mutex);
4793
4794 WARN_ON_ONCE(!workqueue_freezing);
4795
4796 list_for_each_entry(wq, &workqueues, list) {
4797 if (!(wq->flags & WQ_FREEZABLE))
4798 continue;
4799 /*
4800 * nr_active is monotonically decreasing. It's safe
4801 * to peek without lock.
4802 */
4803 rcu_read_lock_sched();
4804 for_each_pwq(pwq, wq) {
4805 WARN_ON_ONCE(pwq->nr_active < 0);
4806 if (pwq->nr_active) {
4807 busy = true;
4808 rcu_read_unlock_sched();
4809 goto out_unlock;
4810 }
4811 }
4812 rcu_read_unlock_sched();
4813 }
4814out_unlock:
4815 mutex_unlock(&wq_pool_mutex);
4816 return busy;
4817}
4818
4819/**
4820 * thaw_workqueues - thaw workqueues
4821 *
4822 * Thaw workqueues. Normal queueing is restored and all collected
4823 * frozen works are transferred to their respective pool worklists.
4824 *
4825 * CONTEXT:
4826 * Grabs and releases wq_pool_mutex, wq->mutex and pool->lock's.
4827 */
4828void thaw_workqueues(void)
4829{
4830 struct workqueue_struct *wq;
4831 struct pool_workqueue *pwq;
4832
4833 mutex_lock(&wq_pool_mutex);
4834
4835 if (!workqueue_freezing)
4836 goto out_unlock;
4837
4838 workqueue_freezing = false;
4839
4840 /* restore max_active and repopulate worklist */
4841 list_for_each_entry(wq, &workqueues, list) {
4842 mutex_lock(&wq->mutex);
4843 for_each_pwq(pwq, wq)
4844 pwq_adjust_max_active(pwq);
4845 mutex_unlock(&wq->mutex);
4846 }
4847
4848out_unlock:
4849 mutex_unlock(&wq_pool_mutex);
4850}
4851#endif /* CONFIG_FREEZER */
4852
4853static int workqueue_apply_unbound_cpumask(void)
4854{
4855 LIST_HEAD(ctxs);
4856 int ret = 0;
4857 struct workqueue_struct *wq;
4858 struct apply_wqattrs_ctx *ctx, *n;
4859
4860 lockdep_assert_held(&wq_pool_mutex);
4861
4862 list_for_each_entry(wq, &workqueues, list) {
4863 if (!(wq->flags & WQ_UNBOUND))
4864 continue;
4865 /* creating multiple pwqs breaks ordering guarantee */
4866 if (wq->flags & __WQ_ORDERED)
4867 continue;
4868
4869 ctx = apply_wqattrs_prepare(wq, wq->unbound_attrs);
4870 if (!ctx) {
4871 ret = -ENOMEM;
4872 break;
4873 }
4874
4875 list_add_tail(&ctx->list, &ctxs);
4876 }
4877
4878 list_for_each_entry_safe(ctx, n, &ctxs, list) {
4879 if (!ret)
4880 apply_wqattrs_commit(ctx);
4881 apply_wqattrs_cleanup(ctx);
4882 }
4883
4884 return ret;
4885}
4886
4887/**
4888 * workqueue_set_unbound_cpumask - Set the low-level unbound cpumask
4889 * @cpumask: the cpumask to set
4890 *
4891 * The low-level workqueues cpumask is a global cpumask that limits
4892 * the affinity of all unbound workqueues. This function check the @cpumask
4893 * and apply it to all unbound workqueues and updates all pwqs of them.
4894 *
4895 * Retun: 0 - Success
4896 * -EINVAL - Invalid @cpumask
4897 * -ENOMEM - Failed to allocate memory for attrs or pwqs.
4898 */
4899int workqueue_set_unbound_cpumask(cpumask_var_t cpumask)
4900{
4901 int ret = -EINVAL;
4902 cpumask_var_t saved_cpumask;
4903
4904 if (!zalloc_cpumask_var(&saved_cpumask, GFP_KERNEL))
4905 return -ENOMEM;
4906
4907 cpumask_and(cpumask, cpumask, cpu_possible_mask);
4908 if (!cpumask_empty(cpumask)) {
4909 apply_wqattrs_lock();
4910
4911 /* save the old wq_unbound_cpumask. */
4912 cpumask_copy(saved_cpumask, wq_unbound_cpumask);
4913
4914 /* update wq_unbound_cpumask at first and apply it to wqs. */
4915 cpumask_copy(wq_unbound_cpumask, cpumask);
4916 ret = workqueue_apply_unbound_cpumask();
4917
4918 /* restore the wq_unbound_cpumask when failed. */
4919 if (ret < 0)
4920 cpumask_copy(wq_unbound_cpumask, saved_cpumask);
4921
4922 apply_wqattrs_unlock();
4923 }
4924
4925 free_cpumask_var(saved_cpumask);
4926 return ret;
4927}
4928
4929#ifdef CONFIG_SYSFS
4930/*
4931 * Workqueues with WQ_SYSFS flag set is visible to userland via
4932 * /sys/bus/workqueue/devices/WQ_NAME. All visible workqueues have the
4933 * following attributes.
4934 *
4935 * per_cpu RO bool : whether the workqueue is per-cpu or unbound
4936 * max_active RW int : maximum number of in-flight work items
4937 *
4938 * Unbound workqueues have the following extra attributes.
4939 *
4940 * id RO int : the associated pool ID
4941 * nice RW int : nice value of the workers
4942 * cpumask RW mask : bitmask of allowed CPUs for the workers
4943 */
4944struct wq_device {
4945 struct workqueue_struct *wq;
4946 struct device dev;
4947};
4948
4949static struct workqueue_struct *dev_to_wq(struct device *dev)
4950{
4951 struct wq_device *wq_dev = container_of(dev, struct wq_device, dev);
4952
4953 return wq_dev->wq;
4954}
4955
4956static ssize_t per_cpu_show(struct device *dev, struct device_attribute *attr,
4957 char *buf)
4958{
4959 struct workqueue_struct *wq = dev_to_wq(dev);
4960
4961 return scnprintf(buf, PAGE_SIZE, "%d\n", (bool)!(wq->flags & WQ_UNBOUND));
4962}
4963static DEVICE_ATTR_RO(per_cpu);
4964
4965static ssize_t max_active_show(struct device *dev,
4966 struct device_attribute *attr, char *buf)
4967{
4968 struct workqueue_struct *wq = dev_to_wq(dev);
4969
4970 return scnprintf(buf, PAGE_SIZE, "%d\n", wq->saved_max_active);
4971}
4972
4973static ssize_t max_active_store(struct device *dev,
4974 struct device_attribute *attr, const char *buf,
4975 size_t count)
4976{
4977 struct workqueue_struct *wq = dev_to_wq(dev);
4978 int val;
4979
4980 if (sscanf(buf, "%d", &val) != 1 || val <= 0)
4981 return -EINVAL;
4982
4983 workqueue_set_max_active(wq, val);
4984 return count;
4985}
4986static DEVICE_ATTR_RW(max_active);
4987
4988static struct attribute *wq_sysfs_attrs[] = {
4989 &dev_attr_per_cpu.attr,
4990 &dev_attr_max_active.attr,
4991 NULL,
4992};
4993ATTRIBUTE_GROUPS(wq_sysfs);
4994
4995static ssize_t wq_pool_ids_show(struct device *dev,
4996 struct device_attribute *attr, char *buf)
4997{
4998 struct workqueue_struct *wq = dev_to_wq(dev);
4999 const char *delim = "";
5000 int node, written = 0;
5001
5002 rcu_read_lock_sched();
5003 for_each_node(node) {
5004 written += scnprintf(buf + written, PAGE_SIZE - written,
5005 "%s%d:%d", delim, node,
5006 unbound_pwq_by_node(wq, node)->pool->id);
5007 delim = " ";
5008 }
5009 written += scnprintf(buf + written, PAGE_SIZE - written, "\n");
5010 rcu_read_unlock_sched();
5011
5012 return written;
5013}
5014
5015static ssize_t wq_nice_show(struct device *dev, struct device_attribute *attr,
5016 char *buf)
5017{
5018 struct workqueue_struct *wq = dev_to_wq(dev);
5019 int written;
5020
5021 mutex_lock(&wq->mutex);
5022 written = scnprintf(buf, PAGE_SIZE, "%d\n", wq->unbound_attrs->nice);
5023 mutex_unlock(&wq->mutex);
5024
5025 return written;
5026}
5027
5028/* prepare workqueue_attrs for sysfs store operations */
5029static struct workqueue_attrs *wq_sysfs_prep_attrs(struct workqueue_struct *wq)
5030{
5031 struct workqueue_attrs *attrs;
5032
5033 lockdep_assert_held(&wq_pool_mutex);
5034
5035 attrs = alloc_workqueue_attrs(GFP_KERNEL);
5036 if (!attrs)
5037 return NULL;
5038
5039 copy_workqueue_attrs(attrs, wq->unbound_attrs);
5040 return attrs;
5041}
5042
5043static ssize_t wq_nice_store(struct device *dev, struct device_attribute *attr,
5044 const char *buf, size_t count)
5045{
5046 struct workqueue_struct *wq = dev_to_wq(dev);
5047 struct workqueue_attrs *attrs;
5048 int ret = -ENOMEM;
5049
5050 apply_wqattrs_lock();
5051
5052 attrs = wq_sysfs_prep_attrs(wq);
5053 if (!attrs)
5054 goto out_unlock;
5055
5056 if (sscanf(buf, "%d", &attrs->nice) == 1 &&
5057 attrs->nice >= MIN_NICE && attrs->nice <= MAX_NICE)
5058 ret = apply_workqueue_attrs_locked(wq, attrs);
5059 else
5060 ret = -EINVAL;
5061
5062out_unlock:
5063 apply_wqattrs_unlock();
5064 free_workqueue_attrs(attrs);
5065 return ret ?: count;
5066}
5067
5068static ssize_t wq_cpumask_show(struct device *dev,
5069 struct device_attribute *attr, char *buf)
5070{
5071 struct workqueue_struct *wq = dev_to_wq(dev);
5072 int written;
5073
5074 mutex_lock(&wq->mutex);
5075 written = scnprintf(buf, PAGE_SIZE, "%*pb\n",
5076 cpumask_pr_args(wq->unbound_attrs->cpumask));
5077 mutex_unlock(&wq->mutex);
5078 return written;
5079}
5080
5081static ssize_t wq_cpumask_store(struct device *dev,
5082 struct device_attribute *attr,
5083 const char *buf, size_t count)
5084{
5085 struct workqueue_struct *wq = dev_to_wq(dev);
5086 struct workqueue_attrs *attrs;
5087 int ret = -ENOMEM;
5088
5089 apply_wqattrs_lock();
5090
5091 attrs = wq_sysfs_prep_attrs(wq);
5092 if (!attrs)
5093 goto out_unlock;
5094
5095 ret = cpumask_parse(buf, attrs->cpumask);
5096 if (!ret)
5097 ret = apply_workqueue_attrs_locked(wq, attrs);
5098
5099out_unlock:
5100 apply_wqattrs_unlock();
5101 free_workqueue_attrs(attrs);
5102 return ret ?: count;
5103}
5104
5105static ssize_t wq_numa_show(struct device *dev, struct device_attribute *attr,
5106 char *buf)
5107{
5108 struct workqueue_struct *wq = dev_to_wq(dev);
5109 int written;
5110
5111 mutex_lock(&wq->mutex);
5112 written = scnprintf(buf, PAGE_SIZE, "%d\n",
5113 !wq->unbound_attrs->no_numa);
5114 mutex_unlock(&wq->mutex);
5115
5116 return written;
5117}
5118
5119static ssize_t wq_numa_store(struct device *dev, struct device_attribute *attr,
5120 const char *buf, size_t count)
5121{
5122 struct workqueue_struct *wq = dev_to_wq(dev);
5123 struct workqueue_attrs *attrs;
5124 int v, ret = -ENOMEM;
5125
5126 apply_wqattrs_lock();
5127
5128 attrs = wq_sysfs_prep_attrs(wq);
5129 if (!attrs)
5130 goto out_unlock;
5131
5132 ret = -EINVAL;
5133 if (sscanf(buf, "%d", &v) == 1) {
5134 attrs->no_numa = !v;
5135 ret = apply_workqueue_attrs_locked(wq, attrs);
5136 }
5137
5138out_unlock:
5139 apply_wqattrs_unlock();
5140 free_workqueue_attrs(attrs);
5141 return ret ?: count;
5142}
5143
5144static struct device_attribute wq_sysfs_unbound_attrs[] = {
5145 __ATTR(pool_ids, 0444, wq_pool_ids_show, NULL),
5146 __ATTR(nice, 0644, wq_nice_show, wq_nice_store),
5147 __ATTR(cpumask, 0644, wq_cpumask_show, wq_cpumask_store),
5148 __ATTR(numa, 0644, wq_numa_show, wq_numa_store),
5149 __ATTR_NULL,
5150};
5151
5152static struct bus_type wq_subsys = {
5153 .name = "workqueue",
5154 .dev_groups = wq_sysfs_groups,
5155};
5156
5157static ssize_t wq_unbound_cpumask_show(struct device *dev,
5158 struct device_attribute *attr, char *buf)
5159{
5160 int written;
5161
5162 mutex_lock(&wq_pool_mutex);
5163 written = scnprintf(buf, PAGE_SIZE, "%*pb\n",
5164 cpumask_pr_args(wq_unbound_cpumask));
5165 mutex_unlock(&wq_pool_mutex);
5166
5167 return written;
5168}
5169
5170static ssize_t wq_unbound_cpumask_store(struct device *dev,
5171 struct device_attribute *attr, const char *buf, size_t count)
5172{
5173 cpumask_var_t cpumask;
5174 int ret;
5175
5176 if (!zalloc_cpumask_var(&cpumask, GFP_KERNEL))
5177 return -ENOMEM;
5178
5179 ret = cpumask_parse(buf, cpumask);
5180 if (!ret)
5181 ret = workqueue_set_unbound_cpumask(cpumask);
5182
5183 free_cpumask_var(cpumask);
5184 return ret ? ret : count;
5185}
5186
5187static struct device_attribute wq_sysfs_cpumask_attr =
5188 __ATTR(cpumask, 0644, wq_unbound_cpumask_show,
5189 wq_unbound_cpumask_store);
5190
5191static int __init wq_sysfs_init(void)
5192{
5193 int err;
5194
5195 err = subsys_virtual_register(&wq_subsys, NULL);
5196 if (err)
5197 return err;
5198
5199 return device_create_file(wq_subsys.dev_root, &wq_sysfs_cpumask_attr);
5200}
5201core_initcall(wq_sysfs_init);
5202
5203static void wq_device_release(struct device *dev)
5204{
5205 struct wq_device *wq_dev = container_of(dev, struct wq_device, dev);
5206
5207 kfree(wq_dev);
5208}
5209
5210/**
5211 * workqueue_sysfs_register - make a workqueue visible in sysfs
5212 * @wq: the workqueue to register
5213 *
5214 * Expose @wq in sysfs under /sys/bus/workqueue/devices.
5215 * alloc_workqueue*() automatically calls this function if WQ_SYSFS is set
5216 * which is the preferred method.
5217 *
5218 * Workqueue user should use this function directly iff it wants to apply
5219 * workqueue_attrs before making the workqueue visible in sysfs; otherwise,
5220 * apply_workqueue_attrs() may race against userland updating the
5221 * attributes.
5222 *
5223 * Return: 0 on success, -errno on failure.
5224 */
5225int workqueue_sysfs_register(struct workqueue_struct *wq)
5226{
5227 struct wq_device *wq_dev;
5228 int ret;
5229
5230 /*
5231 * Adjusting max_active or creating new pwqs by applying
5232 * attributes breaks ordering guarantee. Disallow exposing ordered
5233 * workqueues.
5234 */
5235 if (WARN_ON(wq->flags & __WQ_ORDERED))
5236 return -EINVAL;
5237
5238 wq->wq_dev = wq_dev = kzalloc(sizeof(*wq_dev), GFP_KERNEL);
5239 if (!wq_dev)
5240 return -ENOMEM;
5241
5242 wq_dev->wq = wq;
5243 wq_dev->dev.bus = &wq_subsys;
5244 wq_dev->dev.release = wq_device_release;
5245 dev_set_name(&wq_dev->dev, "%s", wq->name);
5246
5247 /*
5248 * unbound_attrs are created separately. Suppress uevent until
5249 * everything is ready.
5250 */
5251 dev_set_uevent_suppress(&wq_dev->dev, true);
5252
5253 ret = device_register(&wq_dev->dev);
5254 if (ret) {
5255 kfree(wq_dev);
5256 wq->wq_dev = NULL;
5257 return ret;
5258 }
5259
5260 if (wq->flags & WQ_UNBOUND) {
5261 struct device_attribute *attr;
5262
5263 for (attr = wq_sysfs_unbound_attrs; attr->attr.name; attr++) {
5264 ret = device_create_file(&wq_dev->dev, attr);
5265 if (ret) {
5266 device_unregister(&wq_dev->dev);
5267 wq->wq_dev = NULL;
5268 return ret;
5269 }
5270 }
5271 }
5272
5273 dev_set_uevent_suppress(&wq_dev->dev, false);
5274 kobject_uevent(&wq_dev->dev.kobj, KOBJ_ADD);
5275 return 0;
5276}
5277
5278/**
5279 * workqueue_sysfs_unregister - undo workqueue_sysfs_register()
5280 * @wq: the workqueue to unregister
5281 *
5282 * If @wq is registered to sysfs by workqueue_sysfs_register(), unregister.
5283 */
5284static void workqueue_sysfs_unregister(struct workqueue_struct *wq)
5285{
5286 struct wq_device *wq_dev = wq->wq_dev;
5287
5288 if (!wq->wq_dev)
5289 return;
5290
5291 wq->wq_dev = NULL;
5292 device_unregister(&wq_dev->dev);
5293}
5294#else /* CONFIG_SYSFS */
5295static void workqueue_sysfs_unregister(struct workqueue_struct *wq) { }
5296#endif /* CONFIG_SYSFS */
5297
5298/*
5299 * Workqueue watchdog.
5300 *
5301 * Stall may be caused by various bugs - missing WQ_MEM_RECLAIM, illegal
5302 * flush dependency, a concurrency managed work item which stays RUNNING
5303 * indefinitely. Workqueue stalls can be very difficult to debug as the
5304 * usual warning mechanisms don't trigger and internal workqueue state is
5305 * largely opaque.
5306 *
5307 * Workqueue watchdog monitors all worker pools periodically and dumps
5308 * state if some pools failed to make forward progress for a while where
5309 * forward progress is defined as the first item on ->worklist changing.
5310 *
5311 * This mechanism is controlled through the kernel parameter
5312 * "workqueue.watchdog_thresh" which can be updated at runtime through the
5313 * corresponding sysfs parameter file.
5314 */
5315#ifdef CONFIG_WQ_WATCHDOG
5316
5317static void wq_watchdog_timer_fn(unsigned long data);
5318
5319static unsigned long wq_watchdog_thresh = 30;
5320static struct timer_list wq_watchdog_timer =
5321 TIMER_DEFERRED_INITIALIZER(wq_watchdog_timer_fn, 0, 0);
5322
5323static unsigned long wq_watchdog_touched = INITIAL_JIFFIES;
5324static DEFINE_PER_CPU(unsigned long, wq_watchdog_touched_cpu) = INITIAL_JIFFIES;
5325
5326static void wq_watchdog_reset_touched(void)
5327{
5328 int cpu;
5329
5330 wq_watchdog_touched = jiffies;
5331 for_each_possible_cpu(cpu)
5332 per_cpu(wq_watchdog_touched_cpu, cpu) = jiffies;
5333}
5334
5335static void wq_watchdog_timer_fn(unsigned long data)
5336{
5337 unsigned long thresh = READ_ONCE(wq_watchdog_thresh) * HZ;
5338 bool lockup_detected = false;
5339 struct worker_pool *pool;
5340 int pi;
5341
5342 if (!thresh)
5343 return;
5344
5345 rcu_read_lock();
5346
5347 for_each_pool(pool, pi) {
5348 unsigned long pool_ts, touched, ts;
5349
5350 if (list_empty(&pool->worklist))
5351 continue;
5352
5353 /* get the latest of pool and touched timestamps */
5354 pool_ts = READ_ONCE(pool->watchdog_ts);
5355 touched = READ_ONCE(wq_watchdog_touched);
5356
5357 if (time_after(pool_ts, touched))
5358 ts = pool_ts;
5359 else
5360 ts = touched;
5361
5362 if (pool->cpu >= 0) {
5363 unsigned long cpu_touched =
5364 READ_ONCE(per_cpu(wq_watchdog_touched_cpu,
5365 pool->cpu));
5366 if (time_after(cpu_touched, ts))
5367 ts = cpu_touched;
5368 }
5369
5370 /* did we stall? */
5371 if (time_after(jiffies, ts + thresh)) {
5372 lockup_detected = true;
5373 pr_emerg("BUG: workqueue lockup - pool");
5374 pr_cont_pool_info(pool);
5375 pr_cont(" stuck for %us!\n",
5376 jiffies_to_msecs(jiffies - pool_ts) / 1000);
5377 }
5378 }
5379
5380 rcu_read_unlock();
5381
5382 if (lockup_detected)
5383 show_workqueue_state();
5384
5385 wq_watchdog_reset_touched();
5386 mod_timer(&wq_watchdog_timer, jiffies + thresh);
5387}
5388
5389void wq_watchdog_touch(int cpu)
5390{
5391 if (cpu >= 0)
5392 per_cpu(wq_watchdog_touched_cpu, cpu) = jiffies;
5393 else
5394 wq_watchdog_touched = jiffies;
5395}
5396
5397static void wq_watchdog_set_thresh(unsigned long thresh)
5398{
5399 wq_watchdog_thresh = 0;
5400 del_timer_sync(&wq_watchdog_timer);
5401
5402 if (thresh) {
5403 wq_watchdog_thresh = thresh;
5404 wq_watchdog_reset_touched();
5405 mod_timer(&wq_watchdog_timer, jiffies + thresh * HZ);
5406 }
5407}
5408
5409static int wq_watchdog_param_set_thresh(const char *val,
5410 const struct kernel_param *kp)
5411{
5412 unsigned long thresh;
5413 int ret;
5414
5415 ret = kstrtoul(val, 0, &thresh);
5416 if (ret)
5417 return ret;
5418
5419 if (system_wq)
5420 wq_watchdog_set_thresh(thresh);
5421 else
5422 wq_watchdog_thresh = thresh;
5423
5424 return 0;
5425}
5426
5427static const struct kernel_param_ops wq_watchdog_thresh_ops = {
5428 .set = wq_watchdog_param_set_thresh,
5429 .get = param_get_ulong,
5430};
5431
5432module_param_cb(watchdog_thresh, &wq_watchdog_thresh_ops, &wq_watchdog_thresh,
5433 0644);
5434
5435static void wq_watchdog_init(void)
5436{
5437 wq_watchdog_set_thresh(wq_watchdog_thresh);
5438}
5439
5440#else /* CONFIG_WQ_WATCHDOG */
5441
5442static inline void wq_watchdog_init(void) { }
5443
5444#endif /* CONFIG_WQ_WATCHDOG */
5445
5446static void __init wq_numa_init(void)
5447{
5448 cpumask_var_t *tbl;
5449 int node, cpu;
5450
5451 if (num_possible_nodes() <= 1)
5452 return;
5453
5454 if (wq_disable_numa) {
5455 pr_info("workqueue: NUMA affinity support disabled\n");
5456 return;
5457 }
5458
5459 wq_update_unbound_numa_attrs_buf = alloc_workqueue_attrs(GFP_KERNEL);
5460 BUG_ON(!wq_update_unbound_numa_attrs_buf);
5461
5462 /*
5463 * We want masks of possible CPUs of each node which isn't readily
5464 * available. Build one from cpu_to_node() which should have been
5465 * fully initialized by now.
5466 */
5467 tbl = kzalloc(nr_node_ids * sizeof(tbl[0]), GFP_KERNEL);
5468 BUG_ON(!tbl);
5469
5470 for_each_node(node)
5471 BUG_ON(!zalloc_cpumask_var_node(&tbl[node], GFP_KERNEL,
5472 node_online(node) ? node : NUMA_NO_NODE));
5473
5474 for_each_possible_cpu(cpu) {
5475 node = cpu_to_node(cpu);
5476 if (WARN_ON(node == NUMA_NO_NODE)) {
5477 pr_warn("workqueue: NUMA node mapping not available for cpu%d, disabling NUMA support\n", cpu);
5478 /* happens iff arch is bonkers, let's just proceed */
5479 return;
5480 }
5481 cpumask_set_cpu(cpu, tbl[node]);
5482 }
5483
5484 wq_numa_possible_cpumask = tbl;
5485 wq_numa_enabled = true;
5486}
5487
5488/**
5489 * workqueue_init_early - early init for workqueue subsystem
5490 *
5491 * This is the first half of two-staged workqueue subsystem initialization
5492 * and invoked as soon as the bare basics - memory allocation, cpumasks and
5493 * idr are up. It sets up all the data structures and system workqueues
5494 * and allows early boot code to create workqueues and queue/cancel work
5495 * items. Actual work item execution starts only after kthreads can be
5496 * created and scheduled right before early initcalls.
5497 */
5498int __init workqueue_init_early(void)
5499{
5500 int std_nice[NR_STD_WORKER_POOLS] = { 0, HIGHPRI_NICE_LEVEL };
5501 int i, cpu;
5502
5503 WARN_ON(__alignof__(struct pool_workqueue) < __alignof__(long long));
5504
5505 BUG_ON(!alloc_cpumask_var(&wq_unbound_cpumask, GFP_KERNEL));
5506 cpumask_copy(wq_unbound_cpumask, cpu_possible_mask);
5507
5508 pwq_cache = KMEM_CACHE(pool_workqueue, SLAB_PANIC);
5509
5510 /* initialize CPU pools */
5511 for_each_possible_cpu(cpu) {
5512 struct worker_pool *pool;
5513
5514 i = 0;
5515 for_each_cpu_worker_pool(pool, cpu) {
5516 BUG_ON(init_worker_pool(pool));
5517 pool->cpu = cpu;
5518 cpumask_copy(pool->attrs->cpumask, cpumask_of(cpu));
5519 pool->attrs->nice = std_nice[i++];
5520 pool->node = cpu_to_node(cpu);
5521
5522 /* alloc pool ID */
5523 mutex_lock(&wq_pool_mutex);
5524 BUG_ON(worker_pool_assign_id(pool));
5525 mutex_unlock(&wq_pool_mutex);
5526 }
5527 }
5528
5529 /* create default unbound and ordered wq attrs */
5530 for (i = 0; i < NR_STD_WORKER_POOLS; i++) {
5531 struct workqueue_attrs *attrs;
5532
5533 BUG_ON(!(attrs = alloc_workqueue_attrs(GFP_KERNEL)));
5534 attrs->nice = std_nice[i];
5535 unbound_std_wq_attrs[i] = attrs;
5536
5537 /*
5538 * An ordered wq should have only one pwq as ordering is
5539 * guaranteed by max_active which is enforced by pwqs.
5540 * Turn off NUMA so that dfl_pwq is used for all nodes.
5541 */
5542 BUG_ON(!(attrs = alloc_workqueue_attrs(GFP_KERNEL)));
5543 attrs->nice = std_nice[i];
5544 attrs->no_numa = true;
5545 ordered_wq_attrs[i] = attrs;
5546 }
5547
5548 system_wq = alloc_workqueue("events", 0, 0);
5549 system_highpri_wq = alloc_workqueue("events_highpri", WQ_HIGHPRI, 0);
5550 system_long_wq = alloc_workqueue("events_long", 0, 0);
5551 system_unbound_wq = alloc_workqueue("events_unbound", WQ_UNBOUND,
5552 WQ_UNBOUND_MAX_ACTIVE);
5553 system_freezable_wq = alloc_workqueue("events_freezable",
5554 WQ_FREEZABLE, 0);
5555 system_power_efficient_wq = alloc_workqueue("events_power_efficient",
5556 WQ_POWER_EFFICIENT, 0);
5557 system_freezable_power_efficient_wq = alloc_workqueue("events_freezable_power_efficient",
5558 WQ_FREEZABLE | WQ_POWER_EFFICIENT,
5559 0);
5560 BUG_ON(!system_wq || !system_highpri_wq || !system_long_wq ||
5561 !system_unbound_wq || !system_freezable_wq ||
5562 !system_power_efficient_wq ||
5563 !system_freezable_power_efficient_wq);
5564
5565 return 0;
5566}
5567
5568/**
5569 * workqueue_init - bring workqueue subsystem fully online
5570 *
5571 * This is the latter half of two-staged workqueue subsystem initialization
5572 * and invoked as soon as kthreads can be created and scheduled.
5573 * Workqueues have been created and work items queued on them, but there
5574 * are no kworkers executing the work items yet. Populate the worker pools
5575 * with the initial workers and enable future kworker creations.
5576 */
5577int __init workqueue_init(void)
5578{
5579 struct workqueue_struct *wq;
5580 struct worker_pool *pool;
5581 int cpu, bkt;
5582
5583 /*
5584 * It'd be simpler to initialize NUMA in workqueue_init_early() but
5585 * CPU to node mapping may not be available that early on some
5586 * archs such as power and arm64. As per-cpu pools created
5587 * previously could be missing node hint and unbound pools NUMA
5588 * affinity, fix them up.
5589 */
5590 wq_numa_init();
5591
5592 mutex_lock(&wq_pool_mutex);
5593
5594 for_each_possible_cpu(cpu) {
5595 for_each_cpu_worker_pool(pool, cpu) {
5596 pool->node = cpu_to_node(cpu);
5597 }
5598 }
5599
5600 list_for_each_entry(wq, &workqueues, list)
5601 wq_update_unbound_numa(wq, smp_processor_id(), true);
5602
5603 mutex_unlock(&wq_pool_mutex);
5604
5605 /* create the initial workers */
5606 for_each_online_cpu(cpu) {
5607 for_each_cpu_worker_pool(pool, cpu) {
5608 pool->flags &= ~POOL_DISASSOCIATED;
5609 BUG_ON(!create_worker(pool));
5610 }
5611 }
5612
5613 hash_for_each(unbound_pool_hash, bkt, pool, hash_node)
5614 BUG_ON(!create_worker(pool));
5615
5616 wq_online = true;
5617 wq_watchdog_init();
5618
5619 return 0;
5620}
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 * manager_mutex to avoid changing binding state while
69 * create_worker() is in progress.
70 */
71 POOL_MANAGE_WORKERS = 1 << 0, /* need to manage workers */
72 POOL_DISASSOCIATED = 1 << 2, /* cpu can't serve workers */
73 POOL_FREEZING = 1 << 3, /* freeze in progress */
74
75 /* worker flags */
76 WORKER_STARTED = 1 << 0, /* started */
77 WORKER_DIE = 1 << 1, /* die die die */
78 WORKER_IDLE = 1 << 2, /* is idle */
79 WORKER_PREP = 1 << 3, /* preparing to run works */
80 WORKER_CPU_INTENSIVE = 1 << 6, /* cpu intensive */
81 WORKER_UNBOUND = 1 << 7, /* worker is unbound */
82 WORKER_REBOUND = 1 << 8, /* worker was rebound */
83
84 WORKER_NOT_RUNNING = WORKER_PREP | WORKER_CPU_INTENSIVE |
85 WORKER_UNBOUND | WORKER_REBOUND,
86
87 NR_STD_WORKER_POOLS = 2, /* # standard pools per cpu */
88
89 UNBOUND_POOL_HASH_ORDER = 6, /* hashed by pool->attrs */
90 BUSY_WORKER_HASH_ORDER = 6, /* 64 pointers */
91
92 MAX_IDLE_WORKERS_RATIO = 4, /* 1/4 of busy can be idle */
93 IDLE_WORKER_TIMEOUT = 300 * HZ, /* keep idle ones for 5 mins */
94
95 MAYDAY_INITIAL_TIMEOUT = HZ / 100 >= 2 ? HZ / 100 : 2,
96 /* call for help after 10ms
97 (min two ticks) */
98 MAYDAY_INTERVAL = HZ / 10, /* and then every 100ms */
99 CREATE_COOLDOWN = HZ, /* time to breath after fail */
100
101 /*
102 * Rescue workers are used only on emergencies and shared by
103 * all cpus. Give -20.
104 */
105 RESCUER_NICE_LEVEL = -20,
106 HIGHPRI_NICE_LEVEL = -20,
107
108 WQ_NAME_LEN = 24,
109};
110
111/*
112 * Structure fields follow one of the following exclusion rules.
113 *
114 * I: Modifiable by initialization/destruction paths and read-only for
115 * everyone else.
116 *
117 * P: Preemption protected. Disabling preemption is enough and should
118 * only be modified and accessed from the local cpu.
119 *
120 * L: pool->lock protected. Access with pool->lock held.
121 *
122 * X: During normal operation, modification requires pool->lock and should
123 * be done only from local cpu. Either disabling preemption on local
124 * cpu or grabbing pool->lock is enough for read access. If
125 * POOL_DISASSOCIATED is set, it's identical to L.
126 *
127 * MG: pool->manager_mutex and pool->lock protected. Writes require both
128 * locks. Reads can happen under either lock.
129 *
130 * PL: wq_pool_mutex protected.
131 *
132 * PR: wq_pool_mutex protected for writes. Sched-RCU protected for reads.
133 *
134 * WQ: wq->mutex protected.
135 *
136 * WR: wq->mutex protected for writes. Sched-RCU protected for reads.
137 *
138 * MD: wq_mayday_lock protected.
139 */
140
141/* struct worker is defined in workqueue_internal.h */
142
143struct worker_pool {
144 spinlock_t lock; /* the pool lock */
145 int cpu; /* I: the associated cpu */
146 int node; /* I: the associated node ID */
147 int id; /* I: pool ID */
148 unsigned int flags; /* X: flags */
149
150 struct list_head worklist; /* L: list of pending works */
151 int nr_workers; /* L: total number of workers */
152
153 /* nr_idle includes the ones off idle_list for rebinding */
154 int nr_idle; /* L: currently idle ones */
155
156 struct list_head idle_list; /* X: list of idle workers */
157 struct timer_list idle_timer; /* L: worker idle timeout */
158 struct timer_list mayday_timer; /* L: SOS timer for workers */
159
160 /* a workers is either on busy_hash or idle_list, or the manager */
161 DECLARE_HASHTABLE(busy_hash, BUSY_WORKER_HASH_ORDER);
162 /* L: hash of busy workers */
163
164 /* see manage_workers() for details on the two manager mutexes */
165 struct mutex manager_arb; /* manager arbitration */
166 struct mutex manager_mutex; /* manager exclusion */
167 struct idr worker_idr; /* MG: worker IDs and iteration */
168
169 struct workqueue_attrs *attrs; /* I: worker attributes */
170 struct hlist_node hash_node; /* PL: unbound_pool_hash node */
171 int refcnt; /* PL: refcnt for unbound pools */
172
173 /*
174 * The current concurrency level. As it's likely to be accessed
175 * from other CPUs during try_to_wake_up(), put it in a separate
176 * cacheline.
177 */
178 atomic_t nr_running ____cacheline_aligned_in_smp;
179
180 /*
181 * Destruction of pool is sched-RCU protected to allow dereferences
182 * from get_work_pool().
183 */
184 struct rcu_head rcu;
185} ____cacheline_aligned_in_smp;
186
187/*
188 * The per-pool workqueue. While queued, the lower WORK_STRUCT_FLAG_BITS
189 * of work_struct->data are used for flags and the remaining high bits
190 * point to the pwq; thus, pwqs need to be aligned at two's power of the
191 * number of flag bits.
192 */
193struct pool_workqueue {
194 struct worker_pool *pool; /* I: the associated pool */
195 struct workqueue_struct *wq; /* I: the owning workqueue */
196 int work_color; /* L: current color */
197 int flush_color; /* L: flushing color */
198 int refcnt; /* L: reference count */
199 int nr_in_flight[WORK_NR_COLORS];
200 /* L: nr of in_flight works */
201 int nr_active; /* L: nr of active works */
202 int max_active; /* L: max active works */
203 struct list_head delayed_works; /* L: delayed works */
204 struct list_head pwqs_node; /* WR: node on wq->pwqs */
205 struct list_head mayday_node; /* MD: node on wq->maydays */
206
207 /*
208 * Release of unbound pwq is punted to system_wq. See put_pwq()
209 * and pwq_unbound_release_workfn() for details. pool_workqueue
210 * itself is also sched-RCU protected so that the first pwq can be
211 * determined without grabbing wq->mutex.
212 */
213 struct work_struct unbound_release_work;
214 struct rcu_head rcu;
215} __aligned(1 << WORK_STRUCT_FLAG_BITS);
216
217/*
218 * Structure used to wait for workqueue flush.
219 */
220struct wq_flusher {
221 struct list_head list; /* WQ: list of flushers */
222 int flush_color; /* WQ: flush color waiting for */
223 struct completion done; /* flush completion */
224};
225
226struct wq_device;
227
228/*
229 * The externally visible workqueue. It relays the issued work items to
230 * the appropriate worker_pool through its pool_workqueues.
231 */
232struct workqueue_struct {
233 struct list_head pwqs; /* WR: all pwqs of this wq */
234 struct list_head list; /* PL: list of all workqueues */
235
236 struct mutex mutex; /* protects this wq */
237 int work_color; /* WQ: current work color */
238 int flush_color; /* WQ: current flush color */
239 atomic_t nr_pwqs_to_flush; /* flush in progress */
240 struct wq_flusher *first_flusher; /* WQ: first flusher */
241 struct list_head flusher_queue; /* WQ: flush waiters */
242 struct list_head flusher_overflow; /* WQ: flush overflow list */
243
244 struct list_head maydays; /* MD: pwqs requesting rescue */
245 struct worker *rescuer; /* I: rescue worker */
246
247 int nr_drainers; /* WQ: drain in progress */
248 int saved_max_active; /* WQ: saved pwq max_active */
249
250 struct workqueue_attrs *unbound_attrs; /* WQ: only for unbound wqs */
251 struct pool_workqueue *dfl_pwq; /* WQ: only for unbound wqs */
252
253#ifdef CONFIG_SYSFS
254 struct wq_device *wq_dev; /* I: for sysfs interface */
255#endif
256#ifdef CONFIG_LOCKDEP
257 struct lockdep_map lockdep_map;
258#endif
259 char name[WQ_NAME_LEN]; /* I: workqueue name */
260
261 /* hot fields used during command issue, aligned to cacheline */
262 unsigned int flags ____cacheline_aligned; /* WQ: WQ_* flags */
263 struct pool_workqueue __percpu *cpu_pwqs; /* I: per-cpu pwqs */
264 struct pool_workqueue __rcu *numa_pwq_tbl[]; /* FR: unbound pwqs indexed by node */
265};
266
267static struct kmem_cache *pwq_cache;
268
269static int wq_numa_tbl_len; /* highest possible NUMA node id + 1 */
270static cpumask_var_t *wq_numa_possible_cpumask;
271 /* possible CPUs of each node */
272
273static bool wq_disable_numa;
274module_param_named(disable_numa, wq_disable_numa, bool, 0444);
275
276/* see the comment above the definition of WQ_POWER_EFFICIENT */
277#ifdef CONFIG_WQ_POWER_EFFICIENT_DEFAULT
278static bool wq_power_efficient = true;
279#else
280static bool wq_power_efficient;
281#endif
282
283module_param_named(power_efficient, wq_power_efficient, bool, 0444);
284
285static bool wq_numa_enabled; /* unbound NUMA affinity enabled */
286
287/* buf for wq_update_unbound_numa_attrs(), protected by CPU hotplug exclusion */
288static struct workqueue_attrs *wq_update_unbound_numa_attrs_buf;
289
290static DEFINE_MUTEX(wq_pool_mutex); /* protects pools and workqueues list */
291static DEFINE_SPINLOCK(wq_mayday_lock); /* protects wq->maydays list */
292
293static LIST_HEAD(workqueues); /* PL: list of all workqueues */
294static bool workqueue_freezing; /* PL: have wqs started freezing? */
295
296/* the per-cpu worker pools */
297static DEFINE_PER_CPU_SHARED_ALIGNED(struct worker_pool [NR_STD_WORKER_POOLS],
298 cpu_worker_pools);
299
300static DEFINE_IDR(worker_pool_idr); /* PR: idr of all pools */
301
302/* PL: hash of all unbound pools keyed by pool->attrs */
303static DEFINE_HASHTABLE(unbound_pool_hash, UNBOUND_POOL_HASH_ORDER);
304
305/* I: attributes used when instantiating standard unbound pools on demand */
306static struct workqueue_attrs *unbound_std_wq_attrs[NR_STD_WORKER_POOLS];
307
308/* I: attributes used when instantiating ordered pools on demand */
309static struct workqueue_attrs *ordered_wq_attrs[NR_STD_WORKER_POOLS];
310
311struct workqueue_struct *system_wq __read_mostly;
312EXPORT_SYMBOL(system_wq);
313struct workqueue_struct *system_highpri_wq __read_mostly;
314EXPORT_SYMBOL_GPL(system_highpri_wq);
315struct workqueue_struct *system_long_wq __read_mostly;
316EXPORT_SYMBOL_GPL(system_long_wq);
317struct workqueue_struct *system_unbound_wq __read_mostly;
318EXPORT_SYMBOL_GPL(system_unbound_wq);
319struct workqueue_struct *system_freezable_wq __read_mostly;
320EXPORT_SYMBOL_GPL(system_freezable_wq);
321struct workqueue_struct *system_power_efficient_wq __read_mostly;
322EXPORT_SYMBOL_GPL(system_power_efficient_wq);
323struct workqueue_struct *system_freezable_power_efficient_wq __read_mostly;
324EXPORT_SYMBOL_GPL(system_freezable_power_efficient_wq);
325
326static int worker_thread(void *__worker);
327static void copy_workqueue_attrs(struct workqueue_attrs *to,
328 const struct workqueue_attrs *from);
329
330#define CREATE_TRACE_POINTS
331#include <trace/events/workqueue.h>
332
333#define assert_rcu_or_pool_mutex() \
334 rcu_lockdep_assert(rcu_read_lock_sched_held() || \
335 lockdep_is_held(&wq_pool_mutex), \
336 "sched RCU or wq_pool_mutex should be held")
337
338#define assert_rcu_or_wq_mutex(wq) \
339 rcu_lockdep_assert(rcu_read_lock_sched_held() || \
340 lockdep_is_held(&wq->mutex), \
341 "sched RCU or wq->mutex should be held")
342
343#ifdef CONFIG_LOCKDEP
344#define assert_manager_or_pool_lock(pool) \
345 WARN_ONCE(debug_locks && \
346 !lockdep_is_held(&(pool)->manager_mutex) && \
347 !lockdep_is_held(&(pool)->lock), \
348 "pool->manager_mutex or ->lock should be held")
349#else
350#define assert_manager_or_pool_lock(pool) do { } while (0)
351#endif
352
353#define for_each_cpu_worker_pool(pool, cpu) \
354 for ((pool) = &per_cpu(cpu_worker_pools, cpu)[0]; \
355 (pool) < &per_cpu(cpu_worker_pools, cpu)[NR_STD_WORKER_POOLS]; \
356 (pool)++)
357
358/**
359 * for_each_pool - iterate through all worker_pools in the system
360 * @pool: iteration cursor
361 * @pi: integer used for iteration
362 *
363 * This must be called either with wq_pool_mutex held or sched RCU read
364 * locked. If the pool needs to be used beyond the locking in effect, the
365 * caller is responsible for guaranteeing that the pool stays online.
366 *
367 * The if/else clause exists only for the lockdep assertion and can be
368 * ignored.
369 */
370#define for_each_pool(pool, pi) \
371 idr_for_each_entry(&worker_pool_idr, pool, pi) \
372 if (({ assert_rcu_or_pool_mutex(); false; })) { } \
373 else
374
375/**
376 * for_each_pool_worker - iterate through all workers of a worker_pool
377 * @worker: iteration cursor
378 * @wi: integer used for iteration
379 * @pool: worker_pool to iterate workers of
380 *
381 * This must be called with either @pool->manager_mutex or ->lock held.
382 *
383 * The if/else clause exists only for the lockdep assertion and can be
384 * ignored.
385 */
386#define for_each_pool_worker(worker, wi, pool) \
387 idr_for_each_entry(&(pool)->worker_idr, (worker), (wi)) \
388 if (({ assert_manager_or_pool_lock((pool)); false; })) { } \
389 else
390
391/**
392 * for_each_pwq - iterate through all pool_workqueues of the specified workqueue
393 * @pwq: iteration cursor
394 * @wq: the target workqueue
395 *
396 * This must be called either with wq->mutex held or sched RCU read locked.
397 * If the pwq needs to be used beyond the locking in effect, the caller is
398 * responsible for guaranteeing that the pwq stays online.
399 *
400 * The if/else clause exists only for the lockdep assertion and can be
401 * ignored.
402 */
403#define for_each_pwq(pwq, wq) \
404 list_for_each_entry_rcu((pwq), &(wq)->pwqs, pwqs_node) \
405 if (({ assert_rcu_or_wq_mutex(wq); false; })) { } \
406 else
407
408#ifdef CONFIG_DEBUG_OBJECTS_WORK
409
410static struct debug_obj_descr work_debug_descr;
411
412static void *work_debug_hint(void *addr)
413{
414 return ((struct work_struct *) addr)->func;
415}
416
417/*
418 * fixup_init is called when:
419 * - an active object is initialized
420 */
421static int work_fixup_init(void *addr, enum debug_obj_state state)
422{
423 struct work_struct *work = addr;
424
425 switch (state) {
426 case ODEBUG_STATE_ACTIVE:
427 cancel_work_sync(work);
428 debug_object_init(work, &work_debug_descr);
429 return 1;
430 default:
431 return 0;
432 }
433}
434
435/*
436 * fixup_activate is called when:
437 * - an active object is activated
438 * - an unknown object is activated (might be a statically initialized object)
439 */
440static int work_fixup_activate(void *addr, enum debug_obj_state state)
441{
442 struct work_struct *work = addr;
443
444 switch (state) {
445
446 case ODEBUG_STATE_NOTAVAILABLE:
447 /*
448 * This is not really a fixup. The work struct was
449 * statically initialized. We just make sure that it
450 * is tracked in the object tracker.
451 */
452 if (test_bit(WORK_STRUCT_STATIC_BIT, work_data_bits(work))) {
453 debug_object_init(work, &work_debug_descr);
454 debug_object_activate(work, &work_debug_descr);
455 return 0;
456 }
457 WARN_ON_ONCE(1);
458 return 0;
459
460 case ODEBUG_STATE_ACTIVE:
461 WARN_ON(1);
462
463 default:
464 return 0;
465 }
466}
467
468/*
469 * fixup_free is called when:
470 * - an active object is freed
471 */
472static int work_fixup_free(void *addr, enum debug_obj_state state)
473{
474 struct work_struct *work = addr;
475
476 switch (state) {
477 case ODEBUG_STATE_ACTIVE:
478 cancel_work_sync(work);
479 debug_object_free(work, &work_debug_descr);
480 return 1;
481 default:
482 return 0;
483 }
484}
485
486static struct debug_obj_descr work_debug_descr = {
487 .name = "work_struct",
488 .debug_hint = work_debug_hint,
489 .fixup_init = work_fixup_init,
490 .fixup_activate = work_fixup_activate,
491 .fixup_free = work_fixup_free,
492};
493
494static inline void debug_work_activate(struct work_struct *work)
495{
496 debug_object_activate(work, &work_debug_descr);
497}
498
499static inline void debug_work_deactivate(struct work_struct *work)
500{
501 debug_object_deactivate(work, &work_debug_descr);
502}
503
504void __init_work(struct work_struct *work, int onstack)
505{
506 if (onstack)
507 debug_object_init_on_stack(work, &work_debug_descr);
508 else
509 debug_object_init(work, &work_debug_descr);
510}
511EXPORT_SYMBOL_GPL(__init_work);
512
513void destroy_work_on_stack(struct work_struct *work)
514{
515 debug_object_free(work, &work_debug_descr);
516}
517EXPORT_SYMBOL_GPL(destroy_work_on_stack);
518
519void destroy_delayed_work_on_stack(struct delayed_work *work)
520{
521 destroy_timer_on_stack(&work->timer);
522 debug_object_free(&work->work, &work_debug_descr);
523}
524EXPORT_SYMBOL_GPL(destroy_delayed_work_on_stack);
525
526#else
527static inline void debug_work_activate(struct work_struct *work) { }
528static inline void debug_work_deactivate(struct work_struct *work) { }
529#endif
530
531/**
532 * worker_pool_assign_id - allocate ID and assing it to @pool
533 * @pool: the pool pointer of interest
534 *
535 * Returns 0 if ID in [0, WORK_OFFQ_POOL_NONE) is allocated and assigned
536 * successfully, -errno on failure.
537 */
538static int worker_pool_assign_id(struct worker_pool *pool)
539{
540 int ret;
541
542 lockdep_assert_held(&wq_pool_mutex);
543
544 ret = idr_alloc(&worker_pool_idr, pool, 0, WORK_OFFQ_POOL_NONE,
545 GFP_KERNEL);
546 if (ret >= 0) {
547 pool->id = ret;
548 return 0;
549 }
550 return ret;
551}
552
553/**
554 * unbound_pwq_by_node - return the unbound pool_workqueue for the given node
555 * @wq: the target workqueue
556 * @node: the node ID
557 *
558 * This must be called either with pwq_lock held or sched RCU read locked.
559 * If the pwq needs to be used beyond the locking in effect, the caller is
560 * responsible for guaranteeing that the pwq stays online.
561 *
562 * Return: The unbound pool_workqueue for @node.
563 */
564static struct pool_workqueue *unbound_pwq_by_node(struct workqueue_struct *wq,
565 int node)
566{
567 assert_rcu_or_wq_mutex(wq);
568 return rcu_dereference_raw(wq->numa_pwq_tbl[node]);
569}
570
571static unsigned int work_color_to_flags(int color)
572{
573 return color << WORK_STRUCT_COLOR_SHIFT;
574}
575
576static int get_work_color(struct work_struct *work)
577{
578 return (*work_data_bits(work) >> WORK_STRUCT_COLOR_SHIFT) &
579 ((1 << WORK_STRUCT_COLOR_BITS) - 1);
580}
581
582static int work_next_color(int color)
583{
584 return (color + 1) % WORK_NR_COLORS;
585}
586
587/*
588 * While queued, %WORK_STRUCT_PWQ is set and non flag bits of a work's data
589 * contain the pointer to the queued pwq. Once execution starts, the flag
590 * is cleared and the high bits contain OFFQ flags and pool ID.
591 *
592 * set_work_pwq(), set_work_pool_and_clear_pending(), mark_work_canceling()
593 * and clear_work_data() can be used to set the pwq, pool or clear
594 * work->data. These functions should only be called while the work is
595 * owned - ie. while the PENDING bit is set.
596 *
597 * get_work_pool() and get_work_pwq() can be used to obtain the pool or pwq
598 * corresponding to a work. Pool is available once the work has been
599 * queued anywhere after initialization until it is sync canceled. pwq is
600 * available only while the work item is queued.
601 *
602 * %WORK_OFFQ_CANCELING is used to mark a work item which is being
603 * canceled. While being canceled, a work item may have its PENDING set
604 * but stay off timer and worklist for arbitrarily long and nobody should
605 * try to steal the PENDING bit.
606 */
607static inline void set_work_data(struct work_struct *work, unsigned long data,
608 unsigned long flags)
609{
610 WARN_ON_ONCE(!work_pending(work));
611 atomic_long_set(&work->data, data | flags | work_static(work));
612}
613
614static void set_work_pwq(struct work_struct *work, struct pool_workqueue *pwq,
615 unsigned long extra_flags)
616{
617 set_work_data(work, (unsigned long)pwq,
618 WORK_STRUCT_PENDING | WORK_STRUCT_PWQ | extra_flags);
619}
620
621static void set_work_pool_and_keep_pending(struct work_struct *work,
622 int pool_id)
623{
624 set_work_data(work, (unsigned long)pool_id << WORK_OFFQ_POOL_SHIFT,
625 WORK_STRUCT_PENDING);
626}
627
628static void set_work_pool_and_clear_pending(struct work_struct *work,
629 int pool_id)
630{
631 /*
632 * The following wmb is paired with the implied mb in
633 * test_and_set_bit(PENDING) and ensures all updates to @work made
634 * here are visible to and precede any updates by the next PENDING
635 * owner.
636 */
637 smp_wmb();
638 set_work_data(work, (unsigned long)pool_id << WORK_OFFQ_POOL_SHIFT, 0);
639}
640
641static void clear_work_data(struct work_struct *work)
642{
643 smp_wmb(); /* see set_work_pool_and_clear_pending() */
644 set_work_data(work, WORK_STRUCT_NO_POOL, 0);
645}
646
647static struct pool_workqueue *get_work_pwq(struct work_struct *work)
648{
649 unsigned long data = atomic_long_read(&work->data);
650
651 if (data & WORK_STRUCT_PWQ)
652 return (void *)(data & WORK_STRUCT_WQ_DATA_MASK);
653 else
654 return NULL;
655}
656
657/**
658 * get_work_pool - return the worker_pool a given work was associated with
659 * @work: the work item of interest
660 *
661 * Pools are created and destroyed under wq_pool_mutex, and allows read
662 * access under sched-RCU read lock. As such, this function should be
663 * called under wq_pool_mutex or with preemption disabled.
664 *
665 * All fields of the returned pool are accessible as long as the above
666 * mentioned locking is in effect. If the returned pool needs to be used
667 * beyond the critical section, the caller is responsible for ensuring the
668 * returned pool is and stays online.
669 *
670 * Return: The worker_pool @work was last associated with. %NULL if none.
671 */
672static struct worker_pool *get_work_pool(struct work_struct *work)
673{
674 unsigned long data = atomic_long_read(&work->data);
675 int pool_id;
676
677 assert_rcu_or_pool_mutex();
678
679 if (data & WORK_STRUCT_PWQ)
680 return ((struct pool_workqueue *)
681 (data & WORK_STRUCT_WQ_DATA_MASK))->pool;
682
683 pool_id = data >> WORK_OFFQ_POOL_SHIFT;
684 if (pool_id == WORK_OFFQ_POOL_NONE)
685 return NULL;
686
687 return idr_find(&worker_pool_idr, pool_id);
688}
689
690/**
691 * get_work_pool_id - return the worker pool ID a given work is associated with
692 * @work: the work item of interest
693 *
694 * Return: The worker_pool ID @work was last associated with.
695 * %WORK_OFFQ_POOL_NONE if none.
696 */
697static int get_work_pool_id(struct work_struct *work)
698{
699 unsigned long data = atomic_long_read(&work->data);
700
701 if (data & WORK_STRUCT_PWQ)
702 return ((struct pool_workqueue *)
703 (data & WORK_STRUCT_WQ_DATA_MASK))->pool->id;
704
705 return data >> WORK_OFFQ_POOL_SHIFT;
706}
707
708static void mark_work_canceling(struct work_struct *work)
709{
710 unsigned long pool_id = get_work_pool_id(work);
711
712 pool_id <<= WORK_OFFQ_POOL_SHIFT;
713 set_work_data(work, pool_id | WORK_OFFQ_CANCELING, WORK_STRUCT_PENDING);
714}
715
716static bool work_is_canceling(struct work_struct *work)
717{
718 unsigned long data = atomic_long_read(&work->data);
719
720 return !(data & WORK_STRUCT_PWQ) && (data & WORK_OFFQ_CANCELING);
721}
722
723/*
724 * Policy functions. These define the policies on how the global worker
725 * pools are managed. Unless noted otherwise, these functions assume that
726 * they're being called with pool->lock held.
727 */
728
729static bool __need_more_worker(struct worker_pool *pool)
730{
731 return !atomic_read(&pool->nr_running);
732}
733
734/*
735 * Need to wake up a worker? Called from anything but currently
736 * running workers.
737 *
738 * Note that, because unbound workers never contribute to nr_running, this
739 * function will always return %true for unbound pools as long as the
740 * worklist isn't empty.
741 */
742static bool need_more_worker(struct worker_pool *pool)
743{
744 return !list_empty(&pool->worklist) && __need_more_worker(pool);
745}
746
747/* Can I start working? Called from busy but !running workers. */
748static bool may_start_working(struct worker_pool *pool)
749{
750 return pool->nr_idle;
751}
752
753/* Do I need to keep working? Called from currently running workers. */
754static bool keep_working(struct worker_pool *pool)
755{
756 return !list_empty(&pool->worklist) &&
757 atomic_read(&pool->nr_running) <= 1;
758}
759
760/* Do we need a new worker? Called from manager. */
761static bool need_to_create_worker(struct worker_pool *pool)
762{
763 return need_more_worker(pool) && !may_start_working(pool);
764}
765
766/* Do I need to be the manager? */
767static bool need_to_manage_workers(struct worker_pool *pool)
768{
769 return need_to_create_worker(pool) ||
770 (pool->flags & POOL_MANAGE_WORKERS);
771}
772
773/* Do we have too many workers and should some go away? */
774static bool too_many_workers(struct worker_pool *pool)
775{
776 bool managing = mutex_is_locked(&pool->manager_arb);
777 int nr_idle = pool->nr_idle + managing; /* manager is considered idle */
778 int nr_busy = pool->nr_workers - nr_idle;
779
780 /*
781 * nr_idle and idle_list may disagree if idle rebinding is in
782 * progress. Never return %true if idle_list is empty.
783 */
784 if (list_empty(&pool->idle_list))
785 return false;
786
787 return nr_idle > 2 && (nr_idle - 2) * MAX_IDLE_WORKERS_RATIO >= nr_busy;
788}
789
790/*
791 * Wake up functions.
792 */
793
794/* Return the first worker. Safe with preemption disabled */
795static struct worker *first_worker(struct worker_pool *pool)
796{
797 if (unlikely(list_empty(&pool->idle_list)))
798 return NULL;
799
800 return list_first_entry(&pool->idle_list, struct worker, entry);
801}
802
803/**
804 * wake_up_worker - wake up an idle worker
805 * @pool: worker pool to wake worker from
806 *
807 * Wake up the first idle worker of @pool.
808 *
809 * CONTEXT:
810 * spin_lock_irq(pool->lock).
811 */
812static void wake_up_worker(struct worker_pool *pool)
813{
814 struct worker *worker = first_worker(pool);
815
816 if (likely(worker))
817 wake_up_process(worker->task);
818}
819
820/**
821 * wq_worker_waking_up - a worker is waking up
822 * @task: task waking up
823 * @cpu: CPU @task is waking up to
824 *
825 * This function is called during try_to_wake_up() when a worker is
826 * being awoken.
827 *
828 * CONTEXT:
829 * spin_lock_irq(rq->lock)
830 */
831void wq_worker_waking_up(struct task_struct *task, int cpu)
832{
833 struct worker *worker = kthread_data(task);
834
835 if (!(worker->flags & WORKER_NOT_RUNNING)) {
836 WARN_ON_ONCE(worker->pool->cpu != cpu);
837 atomic_inc(&worker->pool->nr_running);
838 }
839}
840
841/**
842 * wq_worker_sleeping - a worker is going to sleep
843 * @task: task going to sleep
844 * @cpu: CPU in question, must be the current CPU number
845 *
846 * This function is called during schedule() when a busy worker is
847 * going to sleep. Worker on the same cpu can be woken up by
848 * returning pointer to its task.
849 *
850 * CONTEXT:
851 * spin_lock_irq(rq->lock)
852 *
853 * Return:
854 * Worker task on @cpu to wake up, %NULL if none.
855 */
856struct task_struct *wq_worker_sleeping(struct task_struct *task, int cpu)
857{
858 struct worker *worker = kthread_data(task), *to_wakeup = NULL;
859 struct worker_pool *pool;
860
861 /*
862 * Rescuers, which may not have all the fields set up like normal
863 * workers, also reach here, let's not access anything before
864 * checking NOT_RUNNING.
865 */
866 if (worker->flags & WORKER_NOT_RUNNING)
867 return NULL;
868
869 pool = worker->pool;
870
871 /* this can only happen on the local cpu */
872 if (WARN_ON_ONCE(cpu != raw_smp_processor_id()))
873 return NULL;
874
875 /*
876 * The counterpart of the following dec_and_test, implied mb,
877 * worklist not empty test sequence is in insert_work().
878 * Please read comment there.
879 *
880 * NOT_RUNNING is clear. This means that we're bound to and
881 * running on the local cpu w/ rq lock held and preemption
882 * disabled, which in turn means that none else could be
883 * manipulating idle_list, so dereferencing idle_list without pool
884 * lock is safe.
885 */
886 if (atomic_dec_and_test(&pool->nr_running) &&
887 !list_empty(&pool->worklist))
888 to_wakeup = first_worker(pool);
889 return to_wakeup ? to_wakeup->task : NULL;
890}
891
892/**
893 * worker_set_flags - set worker flags and adjust nr_running accordingly
894 * @worker: self
895 * @flags: flags to set
896 * @wakeup: wakeup an idle worker if necessary
897 *
898 * Set @flags in @worker->flags and adjust nr_running accordingly. If
899 * nr_running becomes zero and @wakeup is %true, an idle worker is
900 * woken up.
901 *
902 * CONTEXT:
903 * spin_lock_irq(pool->lock)
904 */
905static inline void worker_set_flags(struct worker *worker, unsigned int flags,
906 bool wakeup)
907{
908 struct worker_pool *pool = worker->pool;
909
910 WARN_ON_ONCE(worker->task != current);
911
912 /*
913 * If transitioning into NOT_RUNNING, adjust nr_running and
914 * wake up an idle worker as necessary if requested by
915 * @wakeup.
916 */
917 if ((flags & WORKER_NOT_RUNNING) &&
918 !(worker->flags & WORKER_NOT_RUNNING)) {
919 if (wakeup) {
920 if (atomic_dec_and_test(&pool->nr_running) &&
921 !list_empty(&pool->worklist))
922 wake_up_worker(pool);
923 } else
924 atomic_dec(&pool->nr_running);
925 }
926
927 worker->flags |= flags;
928}
929
930/**
931 * worker_clr_flags - clear worker flags and adjust nr_running accordingly
932 * @worker: self
933 * @flags: flags to clear
934 *
935 * Clear @flags in @worker->flags and adjust nr_running accordingly.
936 *
937 * CONTEXT:
938 * spin_lock_irq(pool->lock)
939 */
940static inline void worker_clr_flags(struct worker *worker, unsigned int flags)
941{
942 struct worker_pool *pool = worker->pool;
943 unsigned int oflags = worker->flags;
944
945 WARN_ON_ONCE(worker->task != current);
946
947 worker->flags &= ~flags;
948
949 /*
950 * If transitioning out of NOT_RUNNING, increment nr_running. Note
951 * that the nested NOT_RUNNING is not a noop. NOT_RUNNING is mask
952 * of multiple flags, not a single flag.
953 */
954 if ((flags & WORKER_NOT_RUNNING) && (oflags & WORKER_NOT_RUNNING))
955 if (!(worker->flags & WORKER_NOT_RUNNING))
956 atomic_inc(&pool->nr_running);
957}
958
959/**
960 * find_worker_executing_work - find worker which is executing a work
961 * @pool: pool of interest
962 * @work: work to find worker for
963 *
964 * Find a worker which is executing @work on @pool by searching
965 * @pool->busy_hash which is keyed by the address of @work. For a worker
966 * to match, its current execution should match the address of @work and
967 * its work function. This is to avoid unwanted dependency between
968 * unrelated work executions through a work item being recycled while still
969 * being executed.
970 *
971 * This is a bit tricky. A work item may be freed once its execution
972 * starts and nothing prevents the freed area from being recycled for
973 * another work item. If the same work item address ends up being reused
974 * before the original execution finishes, workqueue will identify the
975 * recycled work item as currently executing and make it wait until the
976 * current execution finishes, introducing an unwanted dependency.
977 *
978 * This function checks the work item address and work function to avoid
979 * false positives. Note that this isn't complete as one may construct a
980 * work function which can introduce dependency onto itself through a
981 * recycled work item. Well, if somebody wants to shoot oneself in the
982 * foot that badly, there's only so much we can do, and if such deadlock
983 * actually occurs, it should be easy to locate the culprit work function.
984 *
985 * CONTEXT:
986 * spin_lock_irq(pool->lock).
987 *
988 * Return:
989 * Pointer to worker which is executing @work if found, %NULL
990 * otherwise.
991 */
992static struct worker *find_worker_executing_work(struct worker_pool *pool,
993 struct work_struct *work)
994{
995 struct worker *worker;
996
997 hash_for_each_possible(pool->busy_hash, worker, hentry,
998 (unsigned long)work)
999 if (worker->current_work == work &&
1000 worker->current_func == work->func)
1001 return worker;
1002
1003 return NULL;
1004}
1005
1006/**
1007 * move_linked_works - move linked works to a list
1008 * @work: start of series of works to be scheduled
1009 * @head: target list to append @work to
1010 * @nextp: out paramter for nested worklist walking
1011 *
1012 * Schedule linked works starting from @work to @head. Work series to
1013 * be scheduled starts at @work and includes any consecutive work with
1014 * WORK_STRUCT_LINKED set in its predecessor.
1015 *
1016 * If @nextp is not NULL, it's updated to point to the next work of
1017 * the last scheduled work. This allows move_linked_works() to be
1018 * nested inside outer list_for_each_entry_safe().
1019 *
1020 * CONTEXT:
1021 * spin_lock_irq(pool->lock).
1022 */
1023static void move_linked_works(struct work_struct *work, struct list_head *head,
1024 struct work_struct **nextp)
1025{
1026 struct work_struct *n;
1027
1028 /*
1029 * Linked worklist will always end before the end of the list,
1030 * use NULL for list head.
1031 */
1032 list_for_each_entry_safe_from(work, n, NULL, entry) {
1033 list_move_tail(&work->entry, head);
1034 if (!(*work_data_bits(work) & WORK_STRUCT_LINKED))
1035 break;
1036 }
1037
1038 /*
1039 * If we're already inside safe list traversal and have moved
1040 * multiple works to the scheduled queue, the next position
1041 * needs to be updated.
1042 */
1043 if (nextp)
1044 *nextp = n;
1045}
1046
1047/**
1048 * get_pwq - get an extra reference on the specified pool_workqueue
1049 * @pwq: pool_workqueue to get
1050 *
1051 * Obtain an extra reference on @pwq. The caller should guarantee that
1052 * @pwq has positive refcnt and be holding the matching pool->lock.
1053 */
1054static void get_pwq(struct pool_workqueue *pwq)
1055{
1056 lockdep_assert_held(&pwq->pool->lock);
1057 WARN_ON_ONCE(pwq->refcnt <= 0);
1058 pwq->refcnt++;
1059}
1060
1061/**
1062 * put_pwq - put a pool_workqueue reference
1063 * @pwq: pool_workqueue to put
1064 *
1065 * Drop a reference of @pwq. If its refcnt reaches zero, schedule its
1066 * destruction. The caller should be holding the matching pool->lock.
1067 */
1068static void put_pwq(struct pool_workqueue *pwq)
1069{
1070 lockdep_assert_held(&pwq->pool->lock);
1071 if (likely(--pwq->refcnt))
1072 return;
1073 if (WARN_ON_ONCE(!(pwq->wq->flags & WQ_UNBOUND)))
1074 return;
1075 /*
1076 * @pwq can't be released under pool->lock, bounce to
1077 * pwq_unbound_release_workfn(). This never recurses on the same
1078 * pool->lock as this path is taken only for unbound workqueues and
1079 * the release work item is scheduled on a per-cpu workqueue. To
1080 * avoid lockdep warning, unbound pool->locks are given lockdep
1081 * subclass of 1 in get_unbound_pool().
1082 */
1083 schedule_work(&pwq->unbound_release_work);
1084}
1085
1086/**
1087 * put_pwq_unlocked - put_pwq() with surrounding pool lock/unlock
1088 * @pwq: pool_workqueue to put (can be %NULL)
1089 *
1090 * put_pwq() with locking. This function also allows %NULL @pwq.
1091 */
1092static void put_pwq_unlocked(struct pool_workqueue *pwq)
1093{
1094 if (pwq) {
1095 /*
1096 * As both pwqs and pools are sched-RCU protected, the
1097 * following lock operations are safe.
1098 */
1099 spin_lock_irq(&pwq->pool->lock);
1100 put_pwq(pwq);
1101 spin_unlock_irq(&pwq->pool->lock);
1102 }
1103}
1104
1105static void pwq_activate_delayed_work(struct work_struct *work)
1106{
1107 struct pool_workqueue *pwq = get_work_pwq(work);
1108
1109 trace_workqueue_activate_work(work);
1110 move_linked_works(work, &pwq->pool->worklist, NULL);
1111 __clear_bit(WORK_STRUCT_DELAYED_BIT, work_data_bits(work));
1112 pwq->nr_active++;
1113}
1114
1115static void pwq_activate_first_delayed(struct pool_workqueue *pwq)
1116{
1117 struct work_struct *work = list_first_entry(&pwq->delayed_works,
1118 struct work_struct, entry);
1119
1120 pwq_activate_delayed_work(work);
1121}
1122
1123/**
1124 * pwq_dec_nr_in_flight - decrement pwq's nr_in_flight
1125 * @pwq: pwq of interest
1126 * @color: color of work which left the queue
1127 *
1128 * A work either has completed or is removed from pending queue,
1129 * decrement nr_in_flight of its pwq and handle workqueue flushing.
1130 *
1131 * CONTEXT:
1132 * spin_lock_irq(pool->lock).
1133 */
1134static void pwq_dec_nr_in_flight(struct pool_workqueue *pwq, int color)
1135{
1136 /* uncolored work items don't participate in flushing or nr_active */
1137 if (color == WORK_NO_COLOR)
1138 goto out_put;
1139
1140 pwq->nr_in_flight[color]--;
1141
1142 pwq->nr_active--;
1143 if (!list_empty(&pwq->delayed_works)) {
1144 /* one down, submit a delayed one */
1145 if (pwq->nr_active < pwq->max_active)
1146 pwq_activate_first_delayed(pwq);
1147 }
1148
1149 /* is flush in progress and are we at the flushing tip? */
1150 if (likely(pwq->flush_color != color))
1151 goto out_put;
1152
1153 /* are there still in-flight works? */
1154 if (pwq->nr_in_flight[color])
1155 goto out_put;
1156
1157 /* this pwq is done, clear flush_color */
1158 pwq->flush_color = -1;
1159
1160 /*
1161 * If this was the last pwq, wake up the first flusher. It
1162 * will handle the rest.
1163 */
1164 if (atomic_dec_and_test(&pwq->wq->nr_pwqs_to_flush))
1165 complete(&pwq->wq->first_flusher->done);
1166out_put:
1167 put_pwq(pwq);
1168}
1169
1170/**
1171 * try_to_grab_pending - steal work item from worklist and disable irq
1172 * @work: work item to steal
1173 * @is_dwork: @work is a delayed_work
1174 * @flags: place to store irq state
1175 *
1176 * Try to grab PENDING bit of @work. This function can handle @work in any
1177 * stable state - idle, on timer or on worklist.
1178 *
1179 * Return:
1180 * 1 if @work was pending and we successfully stole PENDING
1181 * 0 if @work was idle and we claimed PENDING
1182 * -EAGAIN if PENDING couldn't be grabbed at the moment, safe to busy-retry
1183 * -ENOENT if someone else is canceling @work, this state may persist
1184 * for arbitrarily long
1185 *
1186 * Note:
1187 * On >= 0 return, the caller owns @work's PENDING bit. To avoid getting
1188 * interrupted while holding PENDING and @work off queue, irq must be
1189 * disabled on entry. This, combined with delayed_work->timer being
1190 * irqsafe, ensures that we return -EAGAIN for finite short period of time.
1191 *
1192 * On successful return, >= 0, irq is disabled and the caller is
1193 * responsible for releasing it using local_irq_restore(*@flags).
1194 *
1195 * This function is safe to call from any context including IRQ handler.
1196 */
1197static int try_to_grab_pending(struct work_struct *work, bool is_dwork,
1198 unsigned long *flags)
1199{
1200 struct worker_pool *pool;
1201 struct pool_workqueue *pwq;
1202
1203 local_irq_save(*flags);
1204
1205 /* try to steal the timer if it exists */
1206 if (is_dwork) {
1207 struct delayed_work *dwork = to_delayed_work(work);
1208
1209 /*
1210 * dwork->timer is irqsafe. If del_timer() fails, it's
1211 * guaranteed that the timer is not queued anywhere and not
1212 * running on the local CPU.
1213 */
1214 if (likely(del_timer(&dwork->timer)))
1215 return 1;
1216 }
1217
1218 /* try to claim PENDING the normal way */
1219 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work)))
1220 return 0;
1221
1222 /*
1223 * The queueing is in progress, or it is already queued. Try to
1224 * steal it from ->worklist without clearing WORK_STRUCT_PENDING.
1225 */
1226 pool = get_work_pool(work);
1227 if (!pool)
1228 goto fail;
1229
1230 spin_lock(&pool->lock);
1231 /*
1232 * work->data is guaranteed to point to pwq only while the work
1233 * item is queued on pwq->wq, and both updating work->data to point
1234 * to pwq on queueing and to pool on dequeueing are done under
1235 * pwq->pool->lock. This in turn guarantees that, if work->data
1236 * points to pwq which is associated with a locked pool, the work
1237 * item is currently queued on that pool.
1238 */
1239 pwq = get_work_pwq(work);
1240 if (pwq && pwq->pool == pool) {
1241 debug_work_deactivate(work);
1242
1243 /*
1244 * A delayed work item cannot be grabbed directly because
1245 * it might have linked NO_COLOR work items which, if left
1246 * on the delayed_list, will confuse pwq->nr_active
1247 * management later on and cause stall. Make sure the work
1248 * item is activated before grabbing.
1249 */
1250 if (*work_data_bits(work) & WORK_STRUCT_DELAYED)
1251 pwq_activate_delayed_work(work);
1252
1253 list_del_init(&work->entry);
1254 pwq_dec_nr_in_flight(get_work_pwq(work), get_work_color(work));
1255
1256 /* work->data points to pwq iff queued, point to pool */
1257 set_work_pool_and_keep_pending(work, pool->id);
1258
1259 spin_unlock(&pool->lock);
1260 return 1;
1261 }
1262 spin_unlock(&pool->lock);
1263fail:
1264 local_irq_restore(*flags);
1265 if (work_is_canceling(work))
1266 return -ENOENT;
1267 cpu_relax();
1268 return -EAGAIN;
1269}
1270
1271/**
1272 * insert_work - insert a work into a pool
1273 * @pwq: pwq @work belongs to
1274 * @work: work to insert
1275 * @head: insertion point
1276 * @extra_flags: extra WORK_STRUCT_* flags to set
1277 *
1278 * Insert @work which belongs to @pwq after @head. @extra_flags is or'd to
1279 * work_struct flags.
1280 *
1281 * CONTEXT:
1282 * spin_lock_irq(pool->lock).
1283 */
1284static void insert_work(struct pool_workqueue *pwq, struct work_struct *work,
1285 struct list_head *head, unsigned int extra_flags)
1286{
1287 struct worker_pool *pool = pwq->pool;
1288
1289 /* we own @work, set data and link */
1290 set_work_pwq(work, pwq, extra_flags);
1291 list_add_tail(&work->entry, head);
1292 get_pwq(pwq);
1293
1294 /*
1295 * Ensure either wq_worker_sleeping() sees the above
1296 * list_add_tail() or we see zero nr_running to avoid workers lying
1297 * around lazily while there are works to be processed.
1298 */
1299 smp_mb();
1300
1301 if (__need_more_worker(pool))
1302 wake_up_worker(pool);
1303}
1304
1305/*
1306 * Test whether @work is being queued from another work executing on the
1307 * same workqueue.
1308 */
1309static bool is_chained_work(struct workqueue_struct *wq)
1310{
1311 struct worker *worker;
1312
1313 worker = current_wq_worker();
1314 /*
1315 * Return %true iff I'm a worker execuing a work item on @wq. If
1316 * I'm @worker, it's safe to dereference it without locking.
1317 */
1318 return worker && worker->current_pwq->wq == wq;
1319}
1320
1321static void __queue_work(int cpu, struct workqueue_struct *wq,
1322 struct work_struct *work)
1323{
1324 struct pool_workqueue *pwq;
1325 struct worker_pool *last_pool;
1326 struct list_head *worklist;
1327 unsigned int work_flags;
1328 unsigned int req_cpu = cpu;
1329
1330 /*
1331 * While a work item is PENDING && off queue, a task trying to
1332 * steal the PENDING will busy-loop waiting for it to either get
1333 * queued or lose PENDING. Grabbing PENDING and queueing should
1334 * happen with IRQ disabled.
1335 */
1336 WARN_ON_ONCE(!irqs_disabled());
1337
1338 debug_work_activate(work);
1339
1340 /* if draining, only works from the same workqueue are allowed */
1341 if (unlikely(wq->flags & __WQ_DRAINING) &&
1342 WARN_ON_ONCE(!is_chained_work(wq)))
1343 return;
1344retry:
1345 if (req_cpu == WORK_CPU_UNBOUND)
1346 cpu = raw_smp_processor_id();
1347
1348 /* pwq which will be used unless @work is executing elsewhere */
1349 if (!(wq->flags & WQ_UNBOUND))
1350 pwq = per_cpu_ptr(wq->cpu_pwqs, cpu);
1351 else
1352 pwq = unbound_pwq_by_node(wq, cpu_to_node(cpu));
1353
1354 /*
1355 * If @work was previously on a different pool, it might still be
1356 * running there, in which case the work needs to be queued on that
1357 * pool to guarantee non-reentrancy.
1358 */
1359 last_pool = get_work_pool(work);
1360 if (last_pool && last_pool != pwq->pool) {
1361 struct worker *worker;
1362
1363 spin_lock(&last_pool->lock);
1364
1365 worker = find_worker_executing_work(last_pool, work);
1366
1367 if (worker && worker->current_pwq->wq == wq) {
1368 pwq = worker->current_pwq;
1369 } else {
1370 /* meh... not running there, queue here */
1371 spin_unlock(&last_pool->lock);
1372 spin_lock(&pwq->pool->lock);
1373 }
1374 } else {
1375 spin_lock(&pwq->pool->lock);
1376 }
1377
1378 /*
1379 * pwq is determined and locked. For unbound pools, we could have
1380 * raced with pwq release and it could already be dead. If its
1381 * refcnt is zero, repeat pwq selection. Note that pwqs never die
1382 * without another pwq replacing it in the numa_pwq_tbl or while
1383 * work items are executing on it, so the retrying is guaranteed to
1384 * make forward-progress.
1385 */
1386 if (unlikely(!pwq->refcnt)) {
1387 if (wq->flags & WQ_UNBOUND) {
1388 spin_unlock(&pwq->pool->lock);
1389 cpu_relax();
1390 goto retry;
1391 }
1392 /* oops */
1393 WARN_ONCE(true, "workqueue: per-cpu pwq for %s on cpu%d has 0 refcnt",
1394 wq->name, cpu);
1395 }
1396
1397 /* pwq determined, queue */
1398 trace_workqueue_queue_work(req_cpu, pwq, work);
1399
1400 if (WARN_ON(!list_empty(&work->entry))) {
1401 spin_unlock(&pwq->pool->lock);
1402 return;
1403 }
1404
1405 pwq->nr_in_flight[pwq->work_color]++;
1406 work_flags = work_color_to_flags(pwq->work_color);
1407
1408 if (likely(pwq->nr_active < pwq->max_active)) {
1409 trace_workqueue_activate_work(work);
1410 pwq->nr_active++;
1411 worklist = &pwq->pool->worklist;
1412 } else {
1413 work_flags |= WORK_STRUCT_DELAYED;
1414 worklist = &pwq->delayed_works;
1415 }
1416
1417 insert_work(pwq, work, worklist, work_flags);
1418
1419 spin_unlock(&pwq->pool->lock);
1420}
1421
1422/**
1423 * queue_work_on - queue work on specific cpu
1424 * @cpu: CPU number to execute work on
1425 * @wq: workqueue to use
1426 * @work: work to queue
1427 *
1428 * We queue the work to a specific CPU, the caller must ensure it
1429 * can't go away.
1430 *
1431 * Return: %false if @work was already on a queue, %true otherwise.
1432 */
1433bool queue_work_on(int cpu, struct workqueue_struct *wq,
1434 struct work_struct *work)
1435{
1436 bool ret = false;
1437 unsigned long flags;
1438
1439 local_irq_save(flags);
1440
1441 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1442 __queue_work(cpu, wq, work);
1443 ret = true;
1444 }
1445
1446 local_irq_restore(flags);
1447 return ret;
1448}
1449EXPORT_SYMBOL(queue_work_on);
1450
1451void delayed_work_timer_fn(unsigned long __data)
1452{
1453 struct delayed_work *dwork = (struct delayed_work *)__data;
1454
1455 /* should have been called from irqsafe timer with irq already off */
1456 __queue_work(dwork->cpu, dwork->wq, &dwork->work);
1457}
1458EXPORT_SYMBOL(delayed_work_timer_fn);
1459
1460static void __queue_delayed_work(int cpu, struct workqueue_struct *wq,
1461 struct delayed_work *dwork, unsigned long delay)
1462{
1463 struct timer_list *timer = &dwork->timer;
1464 struct work_struct *work = &dwork->work;
1465
1466 WARN_ON_ONCE(timer->function != delayed_work_timer_fn ||
1467 timer->data != (unsigned long)dwork);
1468 WARN_ON_ONCE(timer_pending(timer));
1469 WARN_ON_ONCE(!list_empty(&work->entry));
1470
1471 /*
1472 * If @delay is 0, queue @dwork->work immediately. This is for
1473 * both optimization and correctness. The earliest @timer can
1474 * expire is on the closest next tick and delayed_work users depend
1475 * on that there's no such delay when @delay is 0.
1476 */
1477 if (!delay) {
1478 __queue_work(cpu, wq, &dwork->work);
1479 return;
1480 }
1481
1482 timer_stats_timer_set_start_info(&dwork->timer);
1483
1484 dwork->wq = wq;
1485 dwork->cpu = cpu;
1486 timer->expires = jiffies + delay;
1487
1488 if (unlikely(cpu != WORK_CPU_UNBOUND))
1489 add_timer_on(timer, cpu);
1490 else
1491 add_timer(timer);
1492}
1493
1494/**
1495 * queue_delayed_work_on - queue work on specific CPU after delay
1496 * @cpu: CPU number to execute work on
1497 * @wq: workqueue to use
1498 * @dwork: work to queue
1499 * @delay: number of jiffies to wait before queueing
1500 *
1501 * Return: %false if @work was already on a queue, %true otherwise. If
1502 * @delay is zero and @dwork is idle, it will be scheduled for immediate
1503 * execution.
1504 */
1505bool queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
1506 struct delayed_work *dwork, unsigned long delay)
1507{
1508 struct work_struct *work = &dwork->work;
1509 bool ret = false;
1510 unsigned long flags;
1511
1512 /* read the comment in __queue_work() */
1513 local_irq_save(flags);
1514
1515 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1516 __queue_delayed_work(cpu, wq, dwork, delay);
1517 ret = true;
1518 }
1519
1520 local_irq_restore(flags);
1521 return ret;
1522}
1523EXPORT_SYMBOL(queue_delayed_work_on);
1524
1525/**
1526 * mod_delayed_work_on - modify delay of or queue a delayed work on specific CPU
1527 * @cpu: CPU number to execute work on
1528 * @wq: workqueue to use
1529 * @dwork: work to queue
1530 * @delay: number of jiffies to wait before queueing
1531 *
1532 * If @dwork is idle, equivalent to queue_delayed_work_on(); otherwise,
1533 * modify @dwork's timer so that it expires after @delay. If @delay is
1534 * zero, @work is guaranteed to be scheduled immediately regardless of its
1535 * current state.
1536 *
1537 * Return: %false if @dwork was idle and queued, %true if @dwork was
1538 * pending and its timer was modified.
1539 *
1540 * This function is safe to call from any context including IRQ handler.
1541 * See try_to_grab_pending() for details.
1542 */
1543bool mod_delayed_work_on(int cpu, struct workqueue_struct *wq,
1544 struct delayed_work *dwork, unsigned long delay)
1545{
1546 unsigned long flags;
1547 int ret;
1548
1549 do {
1550 ret = try_to_grab_pending(&dwork->work, true, &flags);
1551 } while (unlikely(ret == -EAGAIN));
1552
1553 if (likely(ret >= 0)) {
1554 __queue_delayed_work(cpu, wq, dwork, delay);
1555 local_irq_restore(flags);
1556 }
1557
1558 /* -ENOENT from try_to_grab_pending() becomes %true */
1559 return ret;
1560}
1561EXPORT_SYMBOL_GPL(mod_delayed_work_on);
1562
1563/**
1564 * worker_enter_idle - enter idle state
1565 * @worker: worker which is entering idle state
1566 *
1567 * @worker is entering idle state. Update stats and idle timer if
1568 * necessary.
1569 *
1570 * LOCKING:
1571 * spin_lock_irq(pool->lock).
1572 */
1573static void worker_enter_idle(struct worker *worker)
1574{
1575 struct worker_pool *pool = worker->pool;
1576
1577 if (WARN_ON_ONCE(worker->flags & WORKER_IDLE) ||
1578 WARN_ON_ONCE(!list_empty(&worker->entry) &&
1579 (worker->hentry.next || worker->hentry.pprev)))
1580 return;
1581
1582 /* can't use worker_set_flags(), also called from start_worker() */
1583 worker->flags |= WORKER_IDLE;
1584 pool->nr_idle++;
1585 worker->last_active = jiffies;
1586
1587 /* idle_list is LIFO */
1588 list_add(&worker->entry, &pool->idle_list);
1589
1590 if (too_many_workers(pool) && !timer_pending(&pool->idle_timer))
1591 mod_timer(&pool->idle_timer, jiffies + IDLE_WORKER_TIMEOUT);
1592
1593 /*
1594 * Sanity check nr_running. Because wq_unbind_fn() releases
1595 * pool->lock between setting %WORKER_UNBOUND and zapping
1596 * nr_running, the warning may trigger spuriously. Check iff
1597 * unbind is not in progress.
1598 */
1599 WARN_ON_ONCE(!(pool->flags & POOL_DISASSOCIATED) &&
1600 pool->nr_workers == pool->nr_idle &&
1601 atomic_read(&pool->nr_running));
1602}
1603
1604/**
1605 * worker_leave_idle - leave idle state
1606 * @worker: worker which is leaving idle state
1607 *
1608 * @worker is leaving idle state. Update stats.
1609 *
1610 * LOCKING:
1611 * spin_lock_irq(pool->lock).
1612 */
1613static void worker_leave_idle(struct worker *worker)
1614{
1615 struct worker_pool *pool = worker->pool;
1616
1617 if (WARN_ON_ONCE(!(worker->flags & WORKER_IDLE)))
1618 return;
1619 worker_clr_flags(worker, WORKER_IDLE);
1620 pool->nr_idle--;
1621 list_del_init(&worker->entry);
1622}
1623
1624/**
1625 * worker_maybe_bind_and_lock - try to bind %current to worker_pool and lock it
1626 * @pool: target worker_pool
1627 *
1628 * Bind %current to the cpu of @pool if it is associated and lock @pool.
1629 *
1630 * Works which are scheduled while the cpu is online must at least be
1631 * scheduled to a worker which is bound to the cpu so that if they are
1632 * flushed from cpu callbacks while cpu is going down, they are
1633 * guaranteed to execute on the cpu.
1634 *
1635 * This function is to be used by unbound workers and rescuers to bind
1636 * themselves to the target cpu and may race with cpu going down or
1637 * coming online. kthread_bind() can't be used because it may put the
1638 * worker to already dead cpu and set_cpus_allowed_ptr() can't be used
1639 * verbatim as it's best effort and blocking and pool may be
1640 * [dis]associated in the meantime.
1641 *
1642 * This function tries set_cpus_allowed() and locks pool and verifies the
1643 * binding against %POOL_DISASSOCIATED which is set during
1644 * %CPU_DOWN_PREPARE and cleared during %CPU_ONLINE, so if the worker
1645 * enters idle state or fetches works without dropping lock, it can
1646 * guarantee the scheduling requirement described in the first paragraph.
1647 *
1648 * CONTEXT:
1649 * Might sleep. Called without any lock but returns with pool->lock
1650 * held.
1651 *
1652 * Return:
1653 * %true if the associated pool is online (@worker is successfully
1654 * bound), %false if offline.
1655 */
1656static bool worker_maybe_bind_and_lock(struct worker_pool *pool)
1657__acquires(&pool->lock)
1658{
1659 while (true) {
1660 /*
1661 * The following call may fail, succeed or succeed
1662 * without actually migrating the task to the cpu if
1663 * it races with cpu hotunplug operation. Verify
1664 * against POOL_DISASSOCIATED.
1665 */
1666 if (!(pool->flags & POOL_DISASSOCIATED))
1667 set_cpus_allowed_ptr(current, pool->attrs->cpumask);
1668
1669 spin_lock_irq(&pool->lock);
1670 if (pool->flags & POOL_DISASSOCIATED)
1671 return false;
1672 if (task_cpu(current) == pool->cpu &&
1673 cpumask_equal(¤t->cpus_allowed, pool->attrs->cpumask))
1674 return true;
1675 spin_unlock_irq(&pool->lock);
1676
1677 /*
1678 * We've raced with CPU hot[un]plug. Give it a breather
1679 * and retry migration. cond_resched() is required here;
1680 * otherwise, we might deadlock against cpu_stop trying to
1681 * bring down the CPU on non-preemptive kernel.
1682 */
1683 cpu_relax();
1684 cond_resched();
1685 }
1686}
1687
1688static struct worker *alloc_worker(void)
1689{
1690 struct worker *worker;
1691
1692 worker = kzalloc(sizeof(*worker), GFP_KERNEL);
1693 if (worker) {
1694 INIT_LIST_HEAD(&worker->entry);
1695 INIT_LIST_HEAD(&worker->scheduled);
1696 /* on creation a worker is in !idle && prep state */
1697 worker->flags = WORKER_PREP;
1698 }
1699 return worker;
1700}
1701
1702/**
1703 * create_worker - create a new workqueue worker
1704 * @pool: pool the new worker will belong to
1705 *
1706 * Create a new worker which is bound to @pool. The returned worker
1707 * can be started by calling start_worker() or destroyed using
1708 * destroy_worker().
1709 *
1710 * CONTEXT:
1711 * Might sleep. Does GFP_KERNEL allocations.
1712 *
1713 * Return:
1714 * Pointer to the newly created worker.
1715 */
1716static struct worker *create_worker(struct worker_pool *pool)
1717{
1718 struct worker *worker = NULL;
1719 int id = -1;
1720 char id_buf[16];
1721
1722 lockdep_assert_held(&pool->manager_mutex);
1723
1724 /*
1725 * ID is needed to determine kthread name. Allocate ID first
1726 * without installing the pointer.
1727 */
1728 idr_preload(GFP_KERNEL);
1729 spin_lock_irq(&pool->lock);
1730
1731 id = idr_alloc(&pool->worker_idr, NULL, 0, 0, GFP_NOWAIT);
1732
1733 spin_unlock_irq(&pool->lock);
1734 idr_preload_end();
1735 if (id < 0)
1736 goto fail;
1737
1738 worker = alloc_worker();
1739 if (!worker)
1740 goto fail;
1741
1742 worker->pool = pool;
1743 worker->id = id;
1744
1745 if (pool->cpu >= 0)
1746 snprintf(id_buf, sizeof(id_buf), "%d:%d%s", pool->cpu, id,
1747 pool->attrs->nice < 0 ? "H" : "");
1748 else
1749 snprintf(id_buf, sizeof(id_buf), "u%d:%d", pool->id, id);
1750
1751 worker->task = kthread_create_on_node(worker_thread, worker, pool->node,
1752 "kworker/%s", id_buf);
1753 if (IS_ERR(worker->task))
1754 goto fail;
1755
1756 set_user_nice(worker->task, pool->attrs->nice);
1757
1758 /* prevent userland from meddling with cpumask of workqueue workers */
1759 worker->task->flags |= PF_NO_SETAFFINITY;
1760
1761 /*
1762 * set_cpus_allowed_ptr() will fail if the cpumask doesn't have any
1763 * online CPUs. It'll be re-applied when any of the CPUs come up.
1764 */
1765 set_cpus_allowed_ptr(worker->task, pool->attrs->cpumask);
1766
1767 /*
1768 * The caller is responsible for ensuring %POOL_DISASSOCIATED
1769 * remains stable across this function. See the comments above the
1770 * flag definition for details.
1771 */
1772 if (pool->flags & POOL_DISASSOCIATED)
1773 worker->flags |= WORKER_UNBOUND;
1774
1775 /* successful, commit the pointer to idr */
1776 spin_lock_irq(&pool->lock);
1777 idr_replace(&pool->worker_idr, worker, worker->id);
1778 spin_unlock_irq(&pool->lock);
1779
1780 return worker;
1781
1782fail:
1783 if (id >= 0) {
1784 spin_lock_irq(&pool->lock);
1785 idr_remove(&pool->worker_idr, id);
1786 spin_unlock_irq(&pool->lock);
1787 }
1788 kfree(worker);
1789 return NULL;
1790}
1791
1792/**
1793 * start_worker - start a newly created worker
1794 * @worker: worker to start
1795 *
1796 * Make the pool aware of @worker and start it.
1797 *
1798 * CONTEXT:
1799 * spin_lock_irq(pool->lock).
1800 */
1801static void start_worker(struct worker *worker)
1802{
1803 worker->flags |= WORKER_STARTED;
1804 worker->pool->nr_workers++;
1805 worker_enter_idle(worker);
1806 wake_up_process(worker->task);
1807}
1808
1809/**
1810 * create_and_start_worker - create and start a worker for a pool
1811 * @pool: the target pool
1812 *
1813 * Grab the managership of @pool and create and start a new worker for it.
1814 *
1815 * Return: 0 on success. A negative error code otherwise.
1816 */
1817static int create_and_start_worker(struct worker_pool *pool)
1818{
1819 struct worker *worker;
1820
1821 mutex_lock(&pool->manager_mutex);
1822
1823 worker = create_worker(pool);
1824 if (worker) {
1825 spin_lock_irq(&pool->lock);
1826 start_worker(worker);
1827 spin_unlock_irq(&pool->lock);
1828 }
1829
1830 mutex_unlock(&pool->manager_mutex);
1831
1832 return worker ? 0 : -ENOMEM;
1833}
1834
1835/**
1836 * destroy_worker - destroy a workqueue worker
1837 * @worker: worker to be destroyed
1838 *
1839 * Destroy @worker and adjust @pool stats accordingly.
1840 *
1841 * CONTEXT:
1842 * spin_lock_irq(pool->lock) which is released and regrabbed.
1843 */
1844static void destroy_worker(struct worker *worker)
1845{
1846 struct worker_pool *pool = worker->pool;
1847
1848 lockdep_assert_held(&pool->manager_mutex);
1849 lockdep_assert_held(&pool->lock);
1850
1851 /* sanity check frenzy */
1852 if (WARN_ON(worker->current_work) ||
1853 WARN_ON(!list_empty(&worker->scheduled)))
1854 return;
1855
1856 if (worker->flags & WORKER_STARTED)
1857 pool->nr_workers--;
1858 if (worker->flags & WORKER_IDLE)
1859 pool->nr_idle--;
1860
1861 /*
1862 * Once WORKER_DIE is set, the kworker may destroy itself at any
1863 * point. Pin to ensure the task stays until we're done with it.
1864 */
1865 get_task_struct(worker->task);
1866
1867 list_del_init(&worker->entry);
1868 worker->flags |= WORKER_DIE;
1869
1870 idr_remove(&pool->worker_idr, worker->id);
1871
1872 spin_unlock_irq(&pool->lock);
1873
1874 kthread_stop(worker->task);
1875 put_task_struct(worker->task);
1876 kfree(worker);
1877
1878 spin_lock_irq(&pool->lock);
1879}
1880
1881static void idle_worker_timeout(unsigned long __pool)
1882{
1883 struct worker_pool *pool = (void *)__pool;
1884
1885 spin_lock_irq(&pool->lock);
1886
1887 if (too_many_workers(pool)) {
1888 struct worker *worker;
1889 unsigned long expires;
1890
1891 /* idle_list is kept in LIFO order, check the last one */
1892 worker = list_entry(pool->idle_list.prev, struct worker, entry);
1893 expires = worker->last_active + IDLE_WORKER_TIMEOUT;
1894
1895 if (time_before(jiffies, expires))
1896 mod_timer(&pool->idle_timer, expires);
1897 else {
1898 /* it's been idle for too long, wake up manager */
1899 pool->flags |= POOL_MANAGE_WORKERS;
1900 wake_up_worker(pool);
1901 }
1902 }
1903
1904 spin_unlock_irq(&pool->lock);
1905}
1906
1907static void send_mayday(struct work_struct *work)
1908{
1909 struct pool_workqueue *pwq = get_work_pwq(work);
1910 struct workqueue_struct *wq = pwq->wq;
1911
1912 lockdep_assert_held(&wq_mayday_lock);
1913
1914 if (!wq->rescuer)
1915 return;
1916
1917 /* mayday mayday mayday */
1918 if (list_empty(&pwq->mayday_node)) {
1919 /*
1920 * If @pwq is for an unbound wq, its base ref may be put at
1921 * any time due to an attribute change. Pin @pwq until the
1922 * rescuer is done with it.
1923 */
1924 get_pwq(pwq);
1925 list_add_tail(&pwq->mayday_node, &wq->maydays);
1926 wake_up_process(wq->rescuer->task);
1927 }
1928}
1929
1930static void pool_mayday_timeout(unsigned long __pool)
1931{
1932 struct worker_pool *pool = (void *)__pool;
1933 struct work_struct *work;
1934
1935 spin_lock_irq(&wq_mayday_lock); /* for wq->maydays */
1936 spin_lock(&pool->lock);
1937
1938 if (need_to_create_worker(pool)) {
1939 /*
1940 * We've been trying to create a new worker but
1941 * haven't been successful. We might be hitting an
1942 * allocation deadlock. Send distress signals to
1943 * rescuers.
1944 */
1945 list_for_each_entry(work, &pool->worklist, entry)
1946 send_mayday(work);
1947 }
1948
1949 spin_unlock(&pool->lock);
1950 spin_unlock_irq(&wq_mayday_lock);
1951
1952 mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INTERVAL);
1953}
1954
1955/**
1956 * maybe_create_worker - create a new worker if necessary
1957 * @pool: pool to create a new worker for
1958 *
1959 * Create a new worker for @pool if necessary. @pool is guaranteed to
1960 * have at least one idle worker on return from this function. If
1961 * creating a new worker takes longer than MAYDAY_INTERVAL, mayday is
1962 * sent to all rescuers with works scheduled on @pool to resolve
1963 * possible allocation deadlock.
1964 *
1965 * On return, need_to_create_worker() is guaranteed to be %false and
1966 * may_start_working() %true.
1967 *
1968 * LOCKING:
1969 * spin_lock_irq(pool->lock) which may be released and regrabbed
1970 * multiple times. Does GFP_KERNEL allocations. Called only from
1971 * manager.
1972 *
1973 * Return:
1974 * %false if no action was taken and pool->lock stayed locked, %true
1975 * otherwise.
1976 */
1977static bool maybe_create_worker(struct worker_pool *pool)
1978__releases(&pool->lock)
1979__acquires(&pool->lock)
1980{
1981 if (!need_to_create_worker(pool))
1982 return false;
1983restart:
1984 spin_unlock_irq(&pool->lock);
1985
1986 /* if we don't make progress in MAYDAY_INITIAL_TIMEOUT, call for help */
1987 mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INITIAL_TIMEOUT);
1988
1989 while (true) {
1990 struct worker *worker;
1991
1992 worker = create_worker(pool);
1993 if (worker) {
1994 del_timer_sync(&pool->mayday_timer);
1995 spin_lock_irq(&pool->lock);
1996 start_worker(worker);
1997 if (WARN_ON_ONCE(need_to_create_worker(pool)))
1998 goto restart;
1999 return true;
2000 }
2001
2002 if (!need_to_create_worker(pool))
2003 break;
2004
2005 __set_current_state(TASK_INTERRUPTIBLE);
2006 schedule_timeout(CREATE_COOLDOWN);
2007
2008 if (!need_to_create_worker(pool))
2009 break;
2010 }
2011
2012 del_timer_sync(&pool->mayday_timer);
2013 spin_lock_irq(&pool->lock);
2014 if (need_to_create_worker(pool))
2015 goto restart;
2016 return true;
2017}
2018
2019/**
2020 * maybe_destroy_worker - destroy workers which have been idle for a while
2021 * @pool: pool to destroy workers for
2022 *
2023 * Destroy @pool workers which have been idle for longer than
2024 * IDLE_WORKER_TIMEOUT.
2025 *
2026 * LOCKING:
2027 * spin_lock_irq(pool->lock) which may be released and regrabbed
2028 * multiple times. Called only from manager.
2029 *
2030 * Return:
2031 * %false if no action was taken and pool->lock stayed locked, %true
2032 * otherwise.
2033 */
2034static bool maybe_destroy_workers(struct worker_pool *pool)
2035{
2036 bool ret = false;
2037
2038 while (too_many_workers(pool)) {
2039 struct worker *worker;
2040 unsigned long expires;
2041
2042 worker = list_entry(pool->idle_list.prev, struct worker, entry);
2043 expires = worker->last_active + IDLE_WORKER_TIMEOUT;
2044
2045 if (time_before(jiffies, expires)) {
2046 mod_timer(&pool->idle_timer, expires);
2047 break;
2048 }
2049
2050 destroy_worker(worker);
2051 ret = true;
2052 }
2053
2054 return ret;
2055}
2056
2057/**
2058 * manage_workers - manage worker pool
2059 * @worker: self
2060 *
2061 * Assume the manager role and manage the worker pool @worker belongs
2062 * to. At any given time, there can be only zero or one manager per
2063 * pool. The exclusion is handled automatically by this function.
2064 *
2065 * The caller can safely start processing works on false return. On
2066 * true return, it's guaranteed that need_to_create_worker() is false
2067 * and may_start_working() is true.
2068 *
2069 * CONTEXT:
2070 * spin_lock_irq(pool->lock) which may be released and regrabbed
2071 * multiple times. Does GFP_KERNEL allocations.
2072 *
2073 * Return:
2074 * %false if the pool don't need management and the caller can safely start
2075 * processing works, %true indicates that the function released pool->lock
2076 * and reacquired it to perform some management function and that the
2077 * conditions that the caller verified while holding the lock before
2078 * calling the function might no longer be true.
2079 */
2080static bool manage_workers(struct worker *worker)
2081{
2082 struct worker_pool *pool = worker->pool;
2083 bool ret = false;
2084
2085 /*
2086 * Managership is governed by two mutexes - manager_arb and
2087 * manager_mutex. manager_arb handles arbitration of manager role.
2088 * Anyone who successfully grabs manager_arb wins the arbitration
2089 * and becomes the manager. mutex_trylock() on pool->manager_arb
2090 * failure while holding pool->lock reliably indicates that someone
2091 * else is managing the pool and the worker which failed trylock
2092 * can proceed to executing work items. This means that anyone
2093 * grabbing manager_arb is responsible for actually performing
2094 * manager duties. If manager_arb is grabbed and released without
2095 * actual management, the pool may stall indefinitely.
2096 *
2097 * manager_mutex is used for exclusion of actual management
2098 * operations. The holder of manager_mutex can be sure that none
2099 * of management operations, including creation and destruction of
2100 * workers, won't take place until the mutex is released. Because
2101 * manager_mutex doesn't interfere with manager role arbitration,
2102 * it is guaranteed that the pool's management, while may be
2103 * delayed, won't be disturbed by someone else grabbing
2104 * manager_mutex.
2105 */
2106 if (!mutex_trylock(&pool->manager_arb))
2107 return ret;
2108
2109 /*
2110 * With manager arbitration won, manager_mutex would be free in
2111 * most cases. trylock first without dropping @pool->lock.
2112 */
2113 if (unlikely(!mutex_trylock(&pool->manager_mutex))) {
2114 spin_unlock_irq(&pool->lock);
2115 mutex_lock(&pool->manager_mutex);
2116 spin_lock_irq(&pool->lock);
2117 ret = true;
2118 }
2119
2120 pool->flags &= ~POOL_MANAGE_WORKERS;
2121
2122 /*
2123 * Destroy and then create so that may_start_working() is true
2124 * on return.
2125 */
2126 ret |= maybe_destroy_workers(pool);
2127 ret |= maybe_create_worker(pool);
2128
2129 mutex_unlock(&pool->manager_mutex);
2130 mutex_unlock(&pool->manager_arb);
2131 return ret;
2132}
2133
2134/**
2135 * process_one_work - process single work
2136 * @worker: self
2137 * @work: work to process
2138 *
2139 * Process @work. This function contains all the logics necessary to
2140 * process a single work including synchronization against and
2141 * interaction with other workers on the same cpu, queueing and
2142 * flushing. As long as context requirement is met, any worker can
2143 * call this function to process a work.
2144 *
2145 * CONTEXT:
2146 * spin_lock_irq(pool->lock) which is released and regrabbed.
2147 */
2148static void process_one_work(struct worker *worker, struct work_struct *work)
2149__releases(&pool->lock)
2150__acquires(&pool->lock)
2151{
2152 struct pool_workqueue *pwq = get_work_pwq(work);
2153 struct worker_pool *pool = worker->pool;
2154 bool cpu_intensive = pwq->wq->flags & WQ_CPU_INTENSIVE;
2155 int work_color;
2156 struct worker *collision;
2157#ifdef CONFIG_LOCKDEP
2158 /*
2159 * It is permissible to free the struct work_struct from
2160 * inside the function that is called from it, this we need to
2161 * take into account for lockdep too. To avoid bogus "held
2162 * lock freed" warnings as well as problems when looking into
2163 * work->lockdep_map, make a copy and use that here.
2164 */
2165 struct lockdep_map lockdep_map;
2166
2167 lockdep_copy_map(&lockdep_map, &work->lockdep_map);
2168#endif
2169 /*
2170 * Ensure we're on the correct CPU. DISASSOCIATED test is
2171 * necessary to avoid spurious warnings from rescuers servicing the
2172 * unbound or a disassociated pool.
2173 */
2174 WARN_ON_ONCE(!(worker->flags & WORKER_UNBOUND) &&
2175 !(pool->flags & POOL_DISASSOCIATED) &&
2176 raw_smp_processor_id() != pool->cpu);
2177
2178 /*
2179 * A single work shouldn't be executed concurrently by
2180 * multiple workers on a single cpu. Check whether anyone is
2181 * already processing the work. If so, defer the work to the
2182 * currently executing one.
2183 */
2184 collision = find_worker_executing_work(pool, work);
2185 if (unlikely(collision)) {
2186 move_linked_works(work, &collision->scheduled, NULL);
2187 return;
2188 }
2189
2190 /* claim and dequeue */
2191 debug_work_deactivate(work);
2192 hash_add(pool->busy_hash, &worker->hentry, (unsigned long)work);
2193 worker->current_work = work;
2194 worker->current_func = work->func;
2195 worker->current_pwq = pwq;
2196 work_color = get_work_color(work);
2197
2198 list_del_init(&work->entry);
2199
2200 /*
2201 * CPU intensive works don't participate in concurrency
2202 * management. They're the scheduler's responsibility.
2203 */
2204 if (unlikely(cpu_intensive))
2205 worker_set_flags(worker, WORKER_CPU_INTENSIVE, true);
2206
2207 /*
2208 * Unbound pool isn't concurrency managed and work items should be
2209 * executed ASAP. Wake up another worker if necessary.
2210 */
2211 if ((worker->flags & WORKER_UNBOUND) && need_more_worker(pool))
2212 wake_up_worker(pool);
2213
2214 /*
2215 * Record the last pool and clear PENDING which should be the last
2216 * update to @work. Also, do this inside @pool->lock so that
2217 * PENDING and queued state changes happen together while IRQ is
2218 * disabled.
2219 */
2220 set_work_pool_and_clear_pending(work, pool->id);
2221
2222 spin_unlock_irq(&pool->lock);
2223
2224 lock_map_acquire_read(&pwq->wq->lockdep_map);
2225 lock_map_acquire(&lockdep_map);
2226 trace_workqueue_execute_start(work);
2227 worker->current_func(work);
2228 /*
2229 * While we must be careful to not use "work" after this, the trace
2230 * point will only record its address.
2231 */
2232 trace_workqueue_execute_end(work);
2233 lock_map_release(&lockdep_map);
2234 lock_map_release(&pwq->wq->lockdep_map);
2235
2236 if (unlikely(in_atomic() || lockdep_depth(current) > 0)) {
2237 pr_err("BUG: workqueue leaked lock or atomic: %s/0x%08x/%d\n"
2238 " last function: %pf\n",
2239 current->comm, preempt_count(), task_pid_nr(current),
2240 worker->current_func);
2241 debug_show_held_locks(current);
2242 dump_stack();
2243 }
2244
2245 /*
2246 * The following prevents a kworker from hogging CPU on !PREEMPT
2247 * kernels, where a requeueing work item waiting for something to
2248 * happen could deadlock with stop_machine as such work item could
2249 * indefinitely requeue itself while all other CPUs are trapped in
2250 * stop_machine.
2251 */
2252 cond_resched();
2253
2254 spin_lock_irq(&pool->lock);
2255
2256 /* clear cpu intensive status */
2257 if (unlikely(cpu_intensive))
2258 worker_clr_flags(worker, WORKER_CPU_INTENSIVE);
2259
2260 /* we're done with it, release */
2261 hash_del(&worker->hentry);
2262 worker->current_work = NULL;
2263 worker->current_func = NULL;
2264 worker->current_pwq = NULL;
2265 worker->desc_valid = false;
2266 pwq_dec_nr_in_flight(pwq, work_color);
2267}
2268
2269/**
2270 * process_scheduled_works - process scheduled works
2271 * @worker: self
2272 *
2273 * Process all scheduled works. Please note that the scheduled list
2274 * may change while processing a work, so this function repeatedly
2275 * fetches a work from the top and executes it.
2276 *
2277 * CONTEXT:
2278 * spin_lock_irq(pool->lock) which may be released and regrabbed
2279 * multiple times.
2280 */
2281static void process_scheduled_works(struct worker *worker)
2282{
2283 while (!list_empty(&worker->scheduled)) {
2284 struct work_struct *work = list_first_entry(&worker->scheduled,
2285 struct work_struct, entry);
2286 process_one_work(worker, work);
2287 }
2288}
2289
2290/**
2291 * worker_thread - the worker thread function
2292 * @__worker: self
2293 *
2294 * The worker thread function. All workers belong to a worker_pool -
2295 * either a per-cpu one or dynamic unbound one. These workers process all
2296 * work items regardless of their specific target workqueue. The only
2297 * exception is work items which belong to workqueues with a rescuer which
2298 * will be explained in rescuer_thread().
2299 *
2300 * Return: 0
2301 */
2302static int worker_thread(void *__worker)
2303{
2304 struct worker *worker = __worker;
2305 struct worker_pool *pool = worker->pool;
2306
2307 /* tell the scheduler that this is a workqueue worker */
2308 worker->task->flags |= PF_WQ_WORKER;
2309woke_up:
2310 spin_lock_irq(&pool->lock);
2311
2312 /* am I supposed to die? */
2313 if (unlikely(worker->flags & WORKER_DIE)) {
2314 spin_unlock_irq(&pool->lock);
2315 WARN_ON_ONCE(!list_empty(&worker->entry));
2316 worker->task->flags &= ~PF_WQ_WORKER;
2317 return 0;
2318 }
2319
2320 worker_leave_idle(worker);
2321recheck:
2322 /* no more worker necessary? */
2323 if (!need_more_worker(pool))
2324 goto sleep;
2325
2326 /* do we need to manage? */
2327 if (unlikely(!may_start_working(pool)) && manage_workers(worker))
2328 goto recheck;
2329
2330 /*
2331 * ->scheduled list can only be filled while a worker is
2332 * preparing to process a work or actually processing it.
2333 * Make sure nobody diddled with it while I was sleeping.
2334 */
2335 WARN_ON_ONCE(!list_empty(&worker->scheduled));
2336
2337 /*
2338 * Finish PREP stage. We're guaranteed to have at least one idle
2339 * worker or that someone else has already assumed the manager
2340 * role. This is where @worker starts participating in concurrency
2341 * management if applicable and concurrency management is restored
2342 * after being rebound. See rebind_workers() for details.
2343 */
2344 worker_clr_flags(worker, WORKER_PREP | WORKER_REBOUND);
2345
2346 do {
2347 struct work_struct *work =
2348 list_first_entry(&pool->worklist,
2349 struct work_struct, entry);
2350
2351 if (likely(!(*work_data_bits(work) & WORK_STRUCT_LINKED))) {
2352 /* optimization path, not strictly necessary */
2353 process_one_work(worker, work);
2354 if (unlikely(!list_empty(&worker->scheduled)))
2355 process_scheduled_works(worker);
2356 } else {
2357 move_linked_works(work, &worker->scheduled, NULL);
2358 process_scheduled_works(worker);
2359 }
2360 } while (keep_working(pool));
2361
2362 worker_set_flags(worker, WORKER_PREP, false);
2363sleep:
2364 if (unlikely(need_to_manage_workers(pool)) && manage_workers(worker))
2365 goto recheck;
2366
2367 /*
2368 * pool->lock is held and there's no work to process and no need to
2369 * manage, sleep. Workers are woken up only while holding
2370 * pool->lock or from local cpu, so setting the current state
2371 * before releasing pool->lock is enough to prevent losing any
2372 * event.
2373 */
2374 worker_enter_idle(worker);
2375 __set_current_state(TASK_INTERRUPTIBLE);
2376 spin_unlock_irq(&pool->lock);
2377 schedule();
2378 goto woke_up;
2379}
2380
2381/**
2382 * rescuer_thread - the rescuer thread function
2383 * @__rescuer: self
2384 *
2385 * Workqueue rescuer thread function. There's one rescuer for each
2386 * workqueue which has WQ_MEM_RECLAIM set.
2387 *
2388 * Regular work processing on a pool may block trying to create a new
2389 * worker which uses GFP_KERNEL allocation which has slight chance of
2390 * developing into deadlock if some works currently on the same queue
2391 * need to be processed to satisfy the GFP_KERNEL allocation. This is
2392 * the problem rescuer solves.
2393 *
2394 * When such condition is possible, the pool summons rescuers of all
2395 * workqueues which have works queued on the pool and let them process
2396 * those works so that forward progress can be guaranteed.
2397 *
2398 * This should happen rarely.
2399 *
2400 * Return: 0
2401 */
2402static int rescuer_thread(void *__rescuer)
2403{
2404 struct worker *rescuer = __rescuer;
2405 struct workqueue_struct *wq = rescuer->rescue_wq;
2406 struct list_head *scheduled = &rescuer->scheduled;
2407 bool should_stop;
2408
2409 set_user_nice(current, RESCUER_NICE_LEVEL);
2410
2411 /*
2412 * Mark rescuer as worker too. As WORKER_PREP is never cleared, it
2413 * doesn't participate in concurrency management.
2414 */
2415 rescuer->task->flags |= PF_WQ_WORKER;
2416repeat:
2417 set_current_state(TASK_INTERRUPTIBLE);
2418
2419 /*
2420 * By the time the rescuer is requested to stop, the workqueue
2421 * shouldn't have any work pending, but @wq->maydays may still have
2422 * pwq(s) queued. This can happen by non-rescuer workers consuming
2423 * all the work items before the rescuer got to them. Go through
2424 * @wq->maydays processing before acting on should_stop so that the
2425 * list is always empty on exit.
2426 */
2427 should_stop = kthread_should_stop();
2428
2429 /* see whether any pwq is asking for help */
2430 spin_lock_irq(&wq_mayday_lock);
2431
2432 while (!list_empty(&wq->maydays)) {
2433 struct pool_workqueue *pwq = list_first_entry(&wq->maydays,
2434 struct pool_workqueue, mayday_node);
2435 struct worker_pool *pool = pwq->pool;
2436 struct work_struct *work, *n;
2437
2438 __set_current_state(TASK_RUNNING);
2439 list_del_init(&pwq->mayday_node);
2440
2441 spin_unlock_irq(&wq_mayday_lock);
2442
2443 /* migrate to the target cpu if possible */
2444 worker_maybe_bind_and_lock(pool);
2445 rescuer->pool = pool;
2446
2447 /*
2448 * Slurp in all works issued via this workqueue and
2449 * process'em.
2450 */
2451 WARN_ON_ONCE(!list_empty(&rescuer->scheduled));
2452 list_for_each_entry_safe(work, n, &pool->worklist, entry)
2453 if (get_work_pwq(work) == pwq)
2454 move_linked_works(work, scheduled, &n);
2455
2456 process_scheduled_works(rescuer);
2457
2458 /*
2459 * Put the reference grabbed by send_mayday(). @pool won't
2460 * go away while we're holding its lock.
2461 */
2462 put_pwq(pwq);
2463
2464 /*
2465 * Leave this pool. If keep_working() is %true, notify a
2466 * regular worker; otherwise, we end up with 0 concurrency
2467 * and stalling the execution.
2468 */
2469 if (keep_working(pool))
2470 wake_up_worker(pool);
2471
2472 rescuer->pool = NULL;
2473 spin_unlock(&pool->lock);
2474 spin_lock(&wq_mayday_lock);
2475 }
2476
2477 spin_unlock_irq(&wq_mayday_lock);
2478
2479 if (should_stop) {
2480 __set_current_state(TASK_RUNNING);
2481 rescuer->task->flags &= ~PF_WQ_WORKER;
2482 return 0;
2483 }
2484
2485 /* rescuers should never participate in concurrency management */
2486 WARN_ON_ONCE(!(rescuer->flags & WORKER_NOT_RUNNING));
2487 schedule();
2488 goto repeat;
2489}
2490
2491struct wq_barrier {
2492 struct work_struct work;
2493 struct completion done;
2494};
2495
2496static void wq_barrier_func(struct work_struct *work)
2497{
2498 struct wq_barrier *barr = container_of(work, struct wq_barrier, work);
2499 complete(&barr->done);
2500}
2501
2502/**
2503 * insert_wq_barrier - insert a barrier work
2504 * @pwq: pwq to insert barrier into
2505 * @barr: wq_barrier to insert
2506 * @target: target work to attach @barr to
2507 * @worker: worker currently executing @target, NULL if @target is not executing
2508 *
2509 * @barr is linked to @target such that @barr is completed only after
2510 * @target finishes execution. Please note that the ordering
2511 * guarantee is observed only with respect to @target and on the local
2512 * cpu.
2513 *
2514 * Currently, a queued barrier can't be canceled. This is because
2515 * try_to_grab_pending() can't determine whether the work to be
2516 * grabbed is at the head of the queue and thus can't clear LINKED
2517 * flag of the previous work while there must be a valid next work
2518 * after a work with LINKED flag set.
2519 *
2520 * Note that when @worker is non-NULL, @target may be modified
2521 * underneath us, so we can't reliably determine pwq from @target.
2522 *
2523 * CONTEXT:
2524 * spin_lock_irq(pool->lock).
2525 */
2526static void insert_wq_barrier(struct pool_workqueue *pwq,
2527 struct wq_barrier *barr,
2528 struct work_struct *target, struct worker *worker)
2529{
2530 struct list_head *head;
2531 unsigned int linked = 0;
2532
2533 /*
2534 * debugobject calls are safe here even with pool->lock locked
2535 * as we know for sure that this will not trigger any of the
2536 * checks and call back into the fixup functions where we
2537 * might deadlock.
2538 */
2539 INIT_WORK_ONSTACK(&barr->work, wq_barrier_func);
2540 __set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(&barr->work));
2541 init_completion(&barr->done);
2542
2543 /*
2544 * If @target is currently being executed, schedule the
2545 * barrier to the worker; otherwise, put it after @target.
2546 */
2547 if (worker)
2548 head = worker->scheduled.next;
2549 else {
2550 unsigned long *bits = work_data_bits(target);
2551
2552 head = target->entry.next;
2553 /* there can already be other linked works, inherit and set */
2554 linked = *bits & WORK_STRUCT_LINKED;
2555 __set_bit(WORK_STRUCT_LINKED_BIT, bits);
2556 }
2557
2558 debug_work_activate(&barr->work);
2559 insert_work(pwq, &barr->work, head,
2560 work_color_to_flags(WORK_NO_COLOR) | linked);
2561}
2562
2563/**
2564 * flush_workqueue_prep_pwqs - prepare pwqs for workqueue flushing
2565 * @wq: workqueue being flushed
2566 * @flush_color: new flush color, < 0 for no-op
2567 * @work_color: new work color, < 0 for no-op
2568 *
2569 * Prepare pwqs for workqueue flushing.
2570 *
2571 * If @flush_color is non-negative, flush_color on all pwqs should be
2572 * -1. If no pwq has in-flight commands at the specified color, all
2573 * pwq->flush_color's stay at -1 and %false is returned. If any pwq
2574 * has in flight commands, its pwq->flush_color is set to
2575 * @flush_color, @wq->nr_pwqs_to_flush is updated accordingly, pwq
2576 * wakeup logic is armed and %true is returned.
2577 *
2578 * The caller should have initialized @wq->first_flusher prior to
2579 * calling this function with non-negative @flush_color. If
2580 * @flush_color is negative, no flush color update is done and %false
2581 * is returned.
2582 *
2583 * If @work_color is non-negative, all pwqs should have the same
2584 * work_color which is previous to @work_color and all will be
2585 * advanced to @work_color.
2586 *
2587 * CONTEXT:
2588 * mutex_lock(wq->mutex).
2589 *
2590 * Return:
2591 * %true if @flush_color >= 0 and there's something to flush. %false
2592 * otherwise.
2593 */
2594static bool flush_workqueue_prep_pwqs(struct workqueue_struct *wq,
2595 int flush_color, int work_color)
2596{
2597 bool wait = false;
2598 struct pool_workqueue *pwq;
2599
2600 if (flush_color >= 0) {
2601 WARN_ON_ONCE(atomic_read(&wq->nr_pwqs_to_flush));
2602 atomic_set(&wq->nr_pwqs_to_flush, 1);
2603 }
2604
2605 for_each_pwq(pwq, wq) {
2606 struct worker_pool *pool = pwq->pool;
2607
2608 spin_lock_irq(&pool->lock);
2609
2610 if (flush_color >= 0) {
2611 WARN_ON_ONCE(pwq->flush_color != -1);
2612
2613 if (pwq->nr_in_flight[flush_color]) {
2614 pwq->flush_color = flush_color;
2615 atomic_inc(&wq->nr_pwqs_to_flush);
2616 wait = true;
2617 }
2618 }
2619
2620 if (work_color >= 0) {
2621 WARN_ON_ONCE(work_color != work_next_color(pwq->work_color));
2622 pwq->work_color = work_color;
2623 }
2624
2625 spin_unlock_irq(&pool->lock);
2626 }
2627
2628 if (flush_color >= 0 && atomic_dec_and_test(&wq->nr_pwqs_to_flush))
2629 complete(&wq->first_flusher->done);
2630
2631 return wait;
2632}
2633
2634/**
2635 * flush_workqueue - ensure that any scheduled work has run to completion.
2636 * @wq: workqueue to flush
2637 *
2638 * This function sleeps until all work items which were queued on entry
2639 * have finished execution, but it is not livelocked by new incoming ones.
2640 */
2641void flush_workqueue(struct workqueue_struct *wq)
2642{
2643 struct wq_flusher this_flusher = {
2644 .list = LIST_HEAD_INIT(this_flusher.list),
2645 .flush_color = -1,
2646 .done = COMPLETION_INITIALIZER_ONSTACK(this_flusher.done),
2647 };
2648 int next_color;
2649
2650 lock_map_acquire(&wq->lockdep_map);
2651 lock_map_release(&wq->lockdep_map);
2652
2653 mutex_lock(&wq->mutex);
2654
2655 /*
2656 * Start-to-wait phase
2657 */
2658 next_color = work_next_color(wq->work_color);
2659
2660 if (next_color != wq->flush_color) {
2661 /*
2662 * Color space is not full. The current work_color
2663 * becomes our flush_color and work_color is advanced
2664 * by one.
2665 */
2666 WARN_ON_ONCE(!list_empty(&wq->flusher_overflow));
2667 this_flusher.flush_color = wq->work_color;
2668 wq->work_color = next_color;
2669
2670 if (!wq->first_flusher) {
2671 /* no flush in progress, become the first flusher */
2672 WARN_ON_ONCE(wq->flush_color != this_flusher.flush_color);
2673
2674 wq->first_flusher = &this_flusher;
2675
2676 if (!flush_workqueue_prep_pwqs(wq, wq->flush_color,
2677 wq->work_color)) {
2678 /* nothing to flush, done */
2679 wq->flush_color = next_color;
2680 wq->first_flusher = NULL;
2681 goto out_unlock;
2682 }
2683 } else {
2684 /* wait in queue */
2685 WARN_ON_ONCE(wq->flush_color == this_flusher.flush_color);
2686 list_add_tail(&this_flusher.list, &wq->flusher_queue);
2687 flush_workqueue_prep_pwqs(wq, -1, wq->work_color);
2688 }
2689 } else {
2690 /*
2691 * Oops, color space is full, wait on overflow queue.
2692 * The next flush completion will assign us
2693 * flush_color and transfer to flusher_queue.
2694 */
2695 list_add_tail(&this_flusher.list, &wq->flusher_overflow);
2696 }
2697
2698 mutex_unlock(&wq->mutex);
2699
2700 wait_for_completion(&this_flusher.done);
2701
2702 /*
2703 * Wake-up-and-cascade phase
2704 *
2705 * First flushers are responsible for cascading flushes and
2706 * handling overflow. Non-first flushers can simply return.
2707 */
2708 if (wq->first_flusher != &this_flusher)
2709 return;
2710
2711 mutex_lock(&wq->mutex);
2712
2713 /* we might have raced, check again with mutex held */
2714 if (wq->first_flusher != &this_flusher)
2715 goto out_unlock;
2716
2717 wq->first_flusher = NULL;
2718
2719 WARN_ON_ONCE(!list_empty(&this_flusher.list));
2720 WARN_ON_ONCE(wq->flush_color != this_flusher.flush_color);
2721
2722 while (true) {
2723 struct wq_flusher *next, *tmp;
2724
2725 /* complete all the flushers sharing the current flush color */
2726 list_for_each_entry_safe(next, tmp, &wq->flusher_queue, list) {
2727 if (next->flush_color != wq->flush_color)
2728 break;
2729 list_del_init(&next->list);
2730 complete(&next->done);
2731 }
2732
2733 WARN_ON_ONCE(!list_empty(&wq->flusher_overflow) &&
2734 wq->flush_color != work_next_color(wq->work_color));
2735
2736 /* this flush_color is finished, advance by one */
2737 wq->flush_color = work_next_color(wq->flush_color);
2738
2739 /* one color has been freed, handle overflow queue */
2740 if (!list_empty(&wq->flusher_overflow)) {
2741 /*
2742 * Assign the same color to all overflowed
2743 * flushers, advance work_color and append to
2744 * flusher_queue. This is the start-to-wait
2745 * phase for these overflowed flushers.
2746 */
2747 list_for_each_entry(tmp, &wq->flusher_overflow, list)
2748 tmp->flush_color = wq->work_color;
2749
2750 wq->work_color = work_next_color(wq->work_color);
2751
2752 list_splice_tail_init(&wq->flusher_overflow,
2753 &wq->flusher_queue);
2754 flush_workqueue_prep_pwqs(wq, -1, wq->work_color);
2755 }
2756
2757 if (list_empty(&wq->flusher_queue)) {
2758 WARN_ON_ONCE(wq->flush_color != wq->work_color);
2759 break;
2760 }
2761
2762 /*
2763 * Need to flush more colors. Make the next flusher
2764 * the new first flusher and arm pwqs.
2765 */
2766 WARN_ON_ONCE(wq->flush_color == wq->work_color);
2767 WARN_ON_ONCE(wq->flush_color != next->flush_color);
2768
2769 list_del_init(&next->list);
2770 wq->first_flusher = next;
2771
2772 if (flush_workqueue_prep_pwqs(wq, wq->flush_color, -1))
2773 break;
2774
2775 /*
2776 * Meh... this color is already done, clear first
2777 * flusher and repeat cascading.
2778 */
2779 wq->first_flusher = NULL;
2780 }
2781
2782out_unlock:
2783 mutex_unlock(&wq->mutex);
2784}
2785EXPORT_SYMBOL_GPL(flush_workqueue);
2786
2787/**
2788 * drain_workqueue - drain a workqueue
2789 * @wq: workqueue to drain
2790 *
2791 * Wait until the workqueue becomes empty. While draining is in progress,
2792 * only chain queueing is allowed. IOW, only currently pending or running
2793 * work items on @wq can queue further work items on it. @wq is flushed
2794 * repeatedly until it becomes empty. The number of flushing is detemined
2795 * by the depth of chaining and should be relatively short. Whine if it
2796 * takes too long.
2797 */
2798void drain_workqueue(struct workqueue_struct *wq)
2799{
2800 unsigned int flush_cnt = 0;
2801 struct pool_workqueue *pwq;
2802
2803 /*
2804 * __queue_work() needs to test whether there are drainers, is much
2805 * hotter than drain_workqueue() and already looks at @wq->flags.
2806 * Use __WQ_DRAINING so that queue doesn't have to check nr_drainers.
2807 */
2808 mutex_lock(&wq->mutex);
2809 if (!wq->nr_drainers++)
2810 wq->flags |= __WQ_DRAINING;
2811 mutex_unlock(&wq->mutex);
2812reflush:
2813 flush_workqueue(wq);
2814
2815 mutex_lock(&wq->mutex);
2816
2817 for_each_pwq(pwq, wq) {
2818 bool drained;
2819
2820 spin_lock_irq(&pwq->pool->lock);
2821 drained = !pwq->nr_active && list_empty(&pwq->delayed_works);
2822 spin_unlock_irq(&pwq->pool->lock);
2823
2824 if (drained)
2825 continue;
2826
2827 if (++flush_cnt == 10 ||
2828 (flush_cnt % 100 == 0 && flush_cnt <= 1000))
2829 pr_warn("workqueue %s: drain_workqueue() isn't complete after %u tries\n",
2830 wq->name, flush_cnt);
2831
2832 mutex_unlock(&wq->mutex);
2833 goto reflush;
2834 }
2835
2836 if (!--wq->nr_drainers)
2837 wq->flags &= ~__WQ_DRAINING;
2838 mutex_unlock(&wq->mutex);
2839}
2840EXPORT_SYMBOL_GPL(drain_workqueue);
2841
2842static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr)
2843{
2844 struct worker *worker = NULL;
2845 struct worker_pool *pool;
2846 struct pool_workqueue *pwq;
2847
2848 might_sleep();
2849
2850 local_irq_disable();
2851 pool = get_work_pool(work);
2852 if (!pool) {
2853 local_irq_enable();
2854 return false;
2855 }
2856
2857 spin_lock(&pool->lock);
2858 /* see the comment in try_to_grab_pending() with the same code */
2859 pwq = get_work_pwq(work);
2860 if (pwq) {
2861 if (unlikely(pwq->pool != pool))
2862 goto already_gone;
2863 } else {
2864 worker = find_worker_executing_work(pool, work);
2865 if (!worker)
2866 goto already_gone;
2867 pwq = worker->current_pwq;
2868 }
2869
2870 insert_wq_barrier(pwq, barr, work, worker);
2871 spin_unlock_irq(&pool->lock);
2872
2873 /*
2874 * If @max_active is 1 or rescuer is in use, flushing another work
2875 * item on the same workqueue may lead to deadlock. Make sure the
2876 * flusher is not running on the same workqueue by verifying write
2877 * access.
2878 */
2879 if (pwq->wq->saved_max_active == 1 || pwq->wq->rescuer)
2880 lock_map_acquire(&pwq->wq->lockdep_map);
2881 else
2882 lock_map_acquire_read(&pwq->wq->lockdep_map);
2883 lock_map_release(&pwq->wq->lockdep_map);
2884
2885 return true;
2886already_gone:
2887 spin_unlock_irq(&pool->lock);
2888 return false;
2889}
2890
2891/**
2892 * flush_work - wait for a work to finish executing the last queueing instance
2893 * @work: the work to flush
2894 *
2895 * Wait until @work has finished execution. @work is guaranteed to be idle
2896 * on return if it hasn't been requeued since flush started.
2897 *
2898 * Return:
2899 * %true if flush_work() waited for the work to finish execution,
2900 * %false if it was already idle.
2901 */
2902bool flush_work(struct work_struct *work)
2903{
2904 struct wq_barrier barr;
2905
2906 lock_map_acquire(&work->lockdep_map);
2907 lock_map_release(&work->lockdep_map);
2908
2909 if (start_flush_work(work, &barr)) {
2910 wait_for_completion(&barr.done);
2911 destroy_work_on_stack(&barr.work);
2912 return true;
2913 } else {
2914 return false;
2915 }
2916}
2917EXPORT_SYMBOL_GPL(flush_work);
2918
2919static bool __cancel_work_timer(struct work_struct *work, bool is_dwork)
2920{
2921 unsigned long flags;
2922 int ret;
2923
2924 do {
2925 ret = try_to_grab_pending(work, is_dwork, &flags);
2926 /*
2927 * If someone else is canceling, wait for the same event it
2928 * would be waiting for before retrying.
2929 */
2930 if (unlikely(ret == -ENOENT))
2931 flush_work(work);
2932 } while (unlikely(ret < 0));
2933
2934 /* tell other tasks trying to grab @work to back off */
2935 mark_work_canceling(work);
2936 local_irq_restore(flags);
2937
2938 flush_work(work);
2939 clear_work_data(work);
2940 return ret;
2941}
2942
2943/**
2944 * cancel_work_sync - cancel a work and wait for it to finish
2945 * @work: the work to cancel
2946 *
2947 * Cancel @work and wait for its execution to finish. This function
2948 * can be used even if the work re-queues itself or migrates to
2949 * another workqueue. On return from this function, @work is
2950 * guaranteed to be not pending or executing on any CPU.
2951 *
2952 * cancel_work_sync(&delayed_work->work) must not be used for
2953 * delayed_work's. Use cancel_delayed_work_sync() instead.
2954 *
2955 * The caller must ensure that the workqueue on which @work was last
2956 * queued can't be destroyed before this function returns.
2957 *
2958 * Return:
2959 * %true if @work was pending, %false otherwise.
2960 */
2961bool cancel_work_sync(struct work_struct *work)
2962{
2963 return __cancel_work_timer(work, false);
2964}
2965EXPORT_SYMBOL_GPL(cancel_work_sync);
2966
2967/**
2968 * flush_delayed_work - wait for a dwork to finish executing the last queueing
2969 * @dwork: the delayed work to flush
2970 *
2971 * Delayed timer is cancelled and the pending work is queued for
2972 * immediate execution. Like flush_work(), this function only
2973 * considers the last queueing instance of @dwork.
2974 *
2975 * Return:
2976 * %true if flush_work() waited for the work to finish execution,
2977 * %false if it was already idle.
2978 */
2979bool flush_delayed_work(struct delayed_work *dwork)
2980{
2981 local_irq_disable();
2982 if (del_timer_sync(&dwork->timer))
2983 __queue_work(dwork->cpu, dwork->wq, &dwork->work);
2984 local_irq_enable();
2985 return flush_work(&dwork->work);
2986}
2987EXPORT_SYMBOL(flush_delayed_work);
2988
2989/**
2990 * cancel_delayed_work - cancel a delayed work
2991 * @dwork: delayed_work to cancel
2992 *
2993 * Kill off a pending delayed_work.
2994 *
2995 * Return: %true if @dwork was pending and canceled; %false if it wasn't
2996 * pending.
2997 *
2998 * Note:
2999 * The work callback function may still be running on return, unless
3000 * it returns %true and the work doesn't re-arm itself. Explicitly flush or
3001 * use cancel_delayed_work_sync() to wait on it.
3002 *
3003 * This function is safe to call from any context including IRQ handler.
3004 */
3005bool cancel_delayed_work(struct delayed_work *dwork)
3006{
3007 unsigned long flags;
3008 int ret;
3009
3010 do {
3011 ret = try_to_grab_pending(&dwork->work, true, &flags);
3012 } while (unlikely(ret == -EAGAIN));
3013
3014 if (unlikely(ret < 0))
3015 return false;
3016
3017 set_work_pool_and_clear_pending(&dwork->work,
3018 get_work_pool_id(&dwork->work));
3019 local_irq_restore(flags);
3020 return ret;
3021}
3022EXPORT_SYMBOL(cancel_delayed_work);
3023
3024/**
3025 * cancel_delayed_work_sync - cancel a delayed work and wait for it to finish
3026 * @dwork: the delayed work cancel
3027 *
3028 * This is cancel_work_sync() for delayed works.
3029 *
3030 * Return:
3031 * %true if @dwork was pending, %false otherwise.
3032 */
3033bool cancel_delayed_work_sync(struct delayed_work *dwork)
3034{
3035 return __cancel_work_timer(&dwork->work, true);
3036}
3037EXPORT_SYMBOL(cancel_delayed_work_sync);
3038
3039/**
3040 * schedule_on_each_cpu - execute a function synchronously on each online CPU
3041 * @func: the function to call
3042 *
3043 * schedule_on_each_cpu() executes @func on each online CPU using the
3044 * system workqueue and blocks until all CPUs have completed.
3045 * schedule_on_each_cpu() is very slow.
3046 *
3047 * Return:
3048 * 0 on success, -errno on failure.
3049 */
3050int schedule_on_each_cpu(work_func_t func)
3051{
3052 int cpu;
3053 struct work_struct __percpu *works;
3054
3055 works = alloc_percpu(struct work_struct);
3056 if (!works)
3057 return -ENOMEM;
3058
3059 get_online_cpus();
3060
3061 for_each_online_cpu(cpu) {
3062 struct work_struct *work = per_cpu_ptr(works, cpu);
3063
3064 INIT_WORK(work, func);
3065 schedule_work_on(cpu, work);
3066 }
3067
3068 for_each_online_cpu(cpu)
3069 flush_work(per_cpu_ptr(works, cpu));
3070
3071 put_online_cpus();
3072 free_percpu(works);
3073 return 0;
3074}
3075
3076/**
3077 * flush_scheduled_work - ensure that any scheduled work has run to completion.
3078 *
3079 * Forces execution of the kernel-global workqueue and blocks until its
3080 * completion.
3081 *
3082 * Think twice before calling this function! It's very easy to get into
3083 * trouble if you don't take great care. Either of the following situations
3084 * will lead to deadlock:
3085 *
3086 * One of the work items currently on the workqueue needs to acquire
3087 * a lock held by your code or its caller.
3088 *
3089 * Your code is running in the context of a work routine.
3090 *
3091 * They will be detected by lockdep when they occur, but the first might not
3092 * occur very often. It depends on what work items are on the workqueue and
3093 * what locks they need, which you have no control over.
3094 *
3095 * In most situations flushing the entire workqueue is overkill; you merely
3096 * need to know that a particular work item isn't queued and isn't running.
3097 * In such cases you should use cancel_delayed_work_sync() or
3098 * cancel_work_sync() instead.
3099 */
3100void flush_scheduled_work(void)
3101{
3102 flush_workqueue(system_wq);
3103}
3104EXPORT_SYMBOL(flush_scheduled_work);
3105
3106/**
3107 * execute_in_process_context - reliably execute the routine with user context
3108 * @fn: the function to execute
3109 * @ew: guaranteed storage for the execute work structure (must
3110 * be available when the work executes)
3111 *
3112 * Executes the function immediately if process context is available,
3113 * otherwise schedules the function for delayed execution.
3114 *
3115 * Return: 0 - function was executed
3116 * 1 - function was scheduled for execution
3117 */
3118int execute_in_process_context(work_func_t fn, struct execute_work *ew)
3119{
3120 if (!in_interrupt()) {
3121 fn(&ew->work);
3122 return 0;
3123 }
3124
3125 INIT_WORK(&ew->work, fn);
3126 schedule_work(&ew->work);
3127
3128 return 1;
3129}
3130EXPORT_SYMBOL_GPL(execute_in_process_context);
3131
3132#ifdef CONFIG_SYSFS
3133/*
3134 * Workqueues with WQ_SYSFS flag set is visible to userland via
3135 * /sys/bus/workqueue/devices/WQ_NAME. All visible workqueues have the
3136 * following attributes.
3137 *
3138 * per_cpu RO bool : whether the workqueue is per-cpu or unbound
3139 * max_active RW int : maximum number of in-flight work items
3140 *
3141 * Unbound workqueues have the following extra attributes.
3142 *
3143 * id RO int : the associated pool ID
3144 * nice RW int : nice value of the workers
3145 * cpumask RW mask : bitmask of allowed CPUs for the workers
3146 */
3147struct wq_device {
3148 struct workqueue_struct *wq;
3149 struct device dev;
3150};
3151
3152static struct workqueue_struct *dev_to_wq(struct device *dev)
3153{
3154 struct wq_device *wq_dev = container_of(dev, struct wq_device, dev);
3155
3156 return wq_dev->wq;
3157}
3158
3159static ssize_t per_cpu_show(struct device *dev, struct device_attribute *attr,
3160 char *buf)
3161{
3162 struct workqueue_struct *wq = dev_to_wq(dev);
3163
3164 return scnprintf(buf, PAGE_SIZE, "%d\n", (bool)!(wq->flags & WQ_UNBOUND));
3165}
3166static DEVICE_ATTR_RO(per_cpu);
3167
3168static ssize_t max_active_show(struct device *dev,
3169 struct device_attribute *attr, char *buf)
3170{
3171 struct workqueue_struct *wq = dev_to_wq(dev);
3172
3173 return scnprintf(buf, PAGE_SIZE, "%d\n", wq->saved_max_active);
3174}
3175
3176static ssize_t max_active_store(struct device *dev,
3177 struct device_attribute *attr, const char *buf,
3178 size_t count)
3179{
3180 struct workqueue_struct *wq = dev_to_wq(dev);
3181 int val;
3182
3183 if (sscanf(buf, "%d", &val) != 1 || val <= 0)
3184 return -EINVAL;
3185
3186 workqueue_set_max_active(wq, val);
3187 return count;
3188}
3189static DEVICE_ATTR_RW(max_active);
3190
3191static struct attribute *wq_sysfs_attrs[] = {
3192 &dev_attr_per_cpu.attr,
3193 &dev_attr_max_active.attr,
3194 NULL,
3195};
3196ATTRIBUTE_GROUPS(wq_sysfs);
3197
3198static ssize_t wq_pool_ids_show(struct device *dev,
3199 struct device_attribute *attr, char *buf)
3200{
3201 struct workqueue_struct *wq = dev_to_wq(dev);
3202 const char *delim = "";
3203 int node, written = 0;
3204
3205 rcu_read_lock_sched();
3206 for_each_node(node) {
3207 written += scnprintf(buf + written, PAGE_SIZE - written,
3208 "%s%d:%d", delim, node,
3209 unbound_pwq_by_node(wq, node)->pool->id);
3210 delim = " ";
3211 }
3212 written += scnprintf(buf + written, PAGE_SIZE - written, "\n");
3213 rcu_read_unlock_sched();
3214
3215 return written;
3216}
3217
3218static ssize_t wq_nice_show(struct device *dev, struct device_attribute *attr,
3219 char *buf)
3220{
3221 struct workqueue_struct *wq = dev_to_wq(dev);
3222 int written;
3223
3224 mutex_lock(&wq->mutex);
3225 written = scnprintf(buf, PAGE_SIZE, "%d\n", wq->unbound_attrs->nice);
3226 mutex_unlock(&wq->mutex);
3227
3228 return written;
3229}
3230
3231/* prepare workqueue_attrs for sysfs store operations */
3232static struct workqueue_attrs *wq_sysfs_prep_attrs(struct workqueue_struct *wq)
3233{
3234 struct workqueue_attrs *attrs;
3235
3236 attrs = alloc_workqueue_attrs(GFP_KERNEL);
3237 if (!attrs)
3238 return NULL;
3239
3240 mutex_lock(&wq->mutex);
3241 copy_workqueue_attrs(attrs, wq->unbound_attrs);
3242 mutex_unlock(&wq->mutex);
3243 return attrs;
3244}
3245
3246static ssize_t wq_nice_store(struct device *dev, struct device_attribute *attr,
3247 const char *buf, size_t count)
3248{
3249 struct workqueue_struct *wq = dev_to_wq(dev);
3250 struct workqueue_attrs *attrs;
3251 int ret;
3252
3253 attrs = wq_sysfs_prep_attrs(wq);
3254 if (!attrs)
3255 return -ENOMEM;
3256
3257 if (sscanf(buf, "%d", &attrs->nice) == 1 &&
3258 attrs->nice >= MIN_NICE && attrs->nice <= MAX_NICE)
3259 ret = apply_workqueue_attrs(wq, attrs);
3260 else
3261 ret = -EINVAL;
3262
3263 free_workqueue_attrs(attrs);
3264 return ret ?: count;
3265}
3266
3267static ssize_t wq_cpumask_show(struct device *dev,
3268 struct device_attribute *attr, char *buf)
3269{
3270 struct workqueue_struct *wq = dev_to_wq(dev);
3271 int written;
3272
3273 mutex_lock(&wq->mutex);
3274 written = cpumask_scnprintf(buf, PAGE_SIZE, wq->unbound_attrs->cpumask);
3275 mutex_unlock(&wq->mutex);
3276
3277 written += scnprintf(buf + written, PAGE_SIZE - written, "\n");
3278 return written;
3279}
3280
3281static ssize_t wq_cpumask_store(struct device *dev,
3282 struct device_attribute *attr,
3283 const char *buf, size_t count)
3284{
3285 struct workqueue_struct *wq = dev_to_wq(dev);
3286 struct workqueue_attrs *attrs;
3287 int ret;
3288
3289 attrs = wq_sysfs_prep_attrs(wq);
3290 if (!attrs)
3291 return -ENOMEM;
3292
3293 ret = cpumask_parse(buf, attrs->cpumask);
3294 if (!ret)
3295 ret = apply_workqueue_attrs(wq, attrs);
3296
3297 free_workqueue_attrs(attrs);
3298 return ret ?: count;
3299}
3300
3301static ssize_t wq_numa_show(struct device *dev, struct device_attribute *attr,
3302 char *buf)
3303{
3304 struct workqueue_struct *wq = dev_to_wq(dev);
3305 int written;
3306
3307 mutex_lock(&wq->mutex);
3308 written = scnprintf(buf, PAGE_SIZE, "%d\n",
3309 !wq->unbound_attrs->no_numa);
3310 mutex_unlock(&wq->mutex);
3311
3312 return written;
3313}
3314
3315static ssize_t wq_numa_store(struct device *dev, struct device_attribute *attr,
3316 const char *buf, size_t count)
3317{
3318 struct workqueue_struct *wq = dev_to_wq(dev);
3319 struct workqueue_attrs *attrs;
3320 int v, ret;
3321
3322 attrs = wq_sysfs_prep_attrs(wq);
3323 if (!attrs)
3324 return -ENOMEM;
3325
3326 ret = -EINVAL;
3327 if (sscanf(buf, "%d", &v) == 1) {
3328 attrs->no_numa = !v;
3329 ret = apply_workqueue_attrs(wq, attrs);
3330 }
3331
3332 free_workqueue_attrs(attrs);
3333 return ret ?: count;
3334}
3335
3336static struct device_attribute wq_sysfs_unbound_attrs[] = {
3337 __ATTR(pool_ids, 0444, wq_pool_ids_show, NULL),
3338 __ATTR(nice, 0644, wq_nice_show, wq_nice_store),
3339 __ATTR(cpumask, 0644, wq_cpumask_show, wq_cpumask_store),
3340 __ATTR(numa, 0644, wq_numa_show, wq_numa_store),
3341 __ATTR_NULL,
3342};
3343
3344static struct bus_type wq_subsys = {
3345 .name = "workqueue",
3346 .dev_groups = wq_sysfs_groups,
3347};
3348
3349static int __init wq_sysfs_init(void)
3350{
3351 return subsys_virtual_register(&wq_subsys, NULL);
3352}
3353core_initcall(wq_sysfs_init);
3354
3355static void wq_device_release(struct device *dev)
3356{
3357 struct wq_device *wq_dev = container_of(dev, struct wq_device, dev);
3358
3359 kfree(wq_dev);
3360}
3361
3362/**
3363 * workqueue_sysfs_register - make a workqueue visible in sysfs
3364 * @wq: the workqueue to register
3365 *
3366 * Expose @wq in sysfs under /sys/bus/workqueue/devices.
3367 * alloc_workqueue*() automatically calls this function if WQ_SYSFS is set
3368 * which is the preferred method.
3369 *
3370 * Workqueue user should use this function directly iff it wants to apply
3371 * workqueue_attrs before making the workqueue visible in sysfs; otherwise,
3372 * apply_workqueue_attrs() may race against userland updating the
3373 * attributes.
3374 *
3375 * Return: 0 on success, -errno on failure.
3376 */
3377int workqueue_sysfs_register(struct workqueue_struct *wq)
3378{
3379 struct wq_device *wq_dev;
3380 int ret;
3381
3382 /*
3383 * Adjusting max_active or creating new pwqs by applyting
3384 * attributes breaks ordering guarantee. Disallow exposing ordered
3385 * workqueues.
3386 */
3387 if (WARN_ON(wq->flags & __WQ_ORDERED))
3388 return -EINVAL;
3389
3390 wq->wq_dev = wq_dev = kzalloc(sizeof(*wq_dev), GFP_KERNEL);
3391 if (!wq_dev)
3392 return -ENOMEM;
3393
3394 wq_dev->wq = wq;
3395 wq_dev->dev.bus = &wq_subsys;
3396 wq_dev->dev.init_name = wq->name;
3397 wq_dev->dev.release = wq_device_release;
3398
3399 /*
3400 * unbound_attrs are created separately. Suppress uevent until
3401 * everything is ready.
3402 */
3403 dev_set_uevent_suppress(&wq_dev->dev, true);
3404
3405 ret = device_register(&wq_dev->dev);
3406 if (ret) {
3407 kfree(wq_dev);
3408 wq->wq_dev = NULL;
3409 return ret;
3410 }
3411
3412 if (wq->flags & WQ_UNBOUND) {
3413 struct device_attribute *attr;
3414
3415 for (attr = wq_sysfs_unbound_attrs; attr->attr.name; attr++) {
3416 ret = device_create_file(&wq_dev->dev, attr);
3417 if (ret) {
3418 device_unregister(&wq_dev->dev);
3419 wq->wq_dev = NULL;
3420 return ret;
3421 }
3422 }
3423 }
3424
3425 kobject_uevent(&wq_dev->dev.kobj, KOBJ_ADD);
3426 return 0;
3427}
3428
3429/**
3430 * workqueue_sysfs_unregister - undo workqueue_sysfs_register()
3431 * @wq: the workqueue to unregister
3432 *
3433 * If @wq is registered to sysfs by workqueue_sysfs_register(), unregister.
3434 */
3435static void workqueue_sysfs_unregister(struct workqueue_struct *wq)
3436{
3437 struct wq_device *wq_dev = wq->wq_dev;
3438
3439 if (!wq->wq_dev)
3440 return;
3441
3442 wq->wq_dev = NULL;
3443 device_unregister(&wq_dev->dev);
3444}
3445#else /* CONFIG_SYSFS */
3446static void workqueue_sysfs_unregister(struct workqueue_struct *wq) { }
3447#endif /* CONFIG_SYSFS */
3448
3449/**
3450 * free_workqueue_attrs - free a workqueue_attrs
3451 * @attrs: workqueue_attrs to free
3452 *
3453 * Undo alloc_workqueue_attrs().
3454 */
3455void free_workqueue_attrs(struct workqueue_attrs *attrs)
3456{
3457 if (attrs) {
3458 free_cpumask_var(attrs->cpumask);
3459 kfree(attrs);
3460 }
3461}
3462
3463/**
3464 * alloc_workqueue_attrs - allocate a workqueue_attrs
3465 * @gfp_mask: allocation mask to use
3466 *
3467 * Allocate a new workqueue_attrs, initialize with default settings and
3468 * return it.
3469 *
3470 * Return: The allocated new workqueue_attr on success. %NULL on failure.
3471 */
3472struct workqueue_attrs *alloc_workqueue_attrs(gfp_t gfp_mask)
3473{
3474 struct workqueue_attrs *attrs;
3475
3476 attrs = kzalloc(sizeof(*attrs), gfp_mask);
3477 if (!attrs)
3478 goto fail;
3479 if (!alloc_cpumask_var(&attrs->cpumask, gfp_mask))
3480 goto fail;
3481
3482 cpumask_copy(attrs->cpumask, cpu_possible_mask);
3483 return attrs;
3484fail:
3485 free_workqueue_attrs(attrs);
3486 return NULL;
3487}
3488
3489static void copy_workqueue_attrs(struct workqueue_attrs *to,
3490 const struct workqueue_attrs *from)
3491{
3492 to->nice = from->nice;
3493 cpumask_copy(to->cpumask, from->cpumask);
3494 /*
3495 * Unlike hash and equality test, this function doesn't ignore
3496 * ->no_numa as it is used for both pool and wq attrs. Instead,
3497 * get_unbound_pool() explicitly clears ->no_numa after copying.
3498 */
3499 to->no_numa = from->no_numa;
3500}
3501
3502/* hash value of the content of @attr */
3503static u32 wqattrs_hash(const struct workqueue_attrs *attrs)
3504{
3505 u32 hash = 0;
3506
3507 hash = jhash_1word(attrs->nice, hash);
3508 hash = jhash(cpumask_bits(attrs->cpumask),
3509 BITS_TO_LONGS(nr_cpumask_bits) * sizeof(long), hash);
3510 return hash;
3511}
3512
3513/* content equality test */
3514static bool wqattrs_equal(const struct workqueue_attrs *a,
3515 const struct workqueue_attrs *b)
3516{
3517 if (a->nice != b->nice)
3518 return false;
3519 if (!cpumask_equal(a->cpumask, b->cpumask))
3520 return false;
3521 return true;
3522}
3523
3524/**
3525 * init_worker_pool - initialize a newly zalloc'd worker_pool
3526 * @pool: worker_pool to initialize
3527 *
3528 * Initiailize a newly zalloc'd @pool. It also allocates @pool->attrs.
3529 *
3530 * Return: 0 on success, -errno on failure. Even on failure, all fields
3531 * inside @pool proper are initialized and put_unbound_pool() can be called
3532 * on @pool safely to release it.
3533 */
3534static int init_worker_pool(struct worker_pool *pool)
3535{
3536 spin_lock_init(&pool->lock);
3537 pool->id = -1;
3538 pool->cpu = -1;
3539 pool->node = NUMA_NO_NODE;
3540 pool->flags |= POOL_DISASSOCIATED;
3541 INIT_LIST_HEAD(&pool->worklist);
3542 INIT_LIST_HEAD(&pool->idle_list);
3543 hash_init(pool->busy_hash);
3544
3545 init_timer_deferrable(&pool->idle_timer);
3546 pool->idle_timer.function = idle_worker_timeout;
3547 pool->idle_timer.data = (unsigned long)pool;
3548
3549 setup_timer(&pool->mayday_timer, pool_mayday_timeout,
3550 (unsigned long)pool);
3551
3552 mutex_init(&pool->manager_arb);
3553 mutex_init(&pool->manager_mutex);
3554 idr_init(&pool->worker_idr);
3555
3556 INIT_HLIST_NODE(&pool->hash_node);
3557 pool->refcnt = 1;
3558
3559 /* shouldn't fail above this point */
3560 pool->attrs = alloc_workqueue_attrs(GFP_KERNEL);
3561 if (!pool->attrs)
3562 return -ENOMEM;
3563 return 0;
3564}
3565
3566static void rcu_free_pool(struct rcu_head *rcu)
3567{
3568 struct worker_pool *pool = container_of(rcu, struct worker_pool, rcu);
3569
3570 idr_destroy(&pool->worker_idr);
3571 free_workqueue_attrs(pool->attrs);
3572 kfree(pool);
3573}
3574
3575/**
3576 * put_unbound_pool - put a worker_pool
3577 * @pool: worker_pool to put
3578 *
3579 * Put @pool. If its refcnt reaches zero, it gets destroyed in sched-RCU
3580 * safe manner. get_unbound_pool() calls this function on its failure path
3581 * and this function should be able to release pools which went through,
3582 * successfully or not, init_worker_pool().
3583 *
3584 * Should be called with wq_pool_mutex held.
3585 */
3586static void put_unbound_pool(struct worker_pool *pool)
3587{
3588 struct worker *worker;
3589
3590 lockdep_assert_held(&wq_pool_mutex);
3591
3592 if (--pool->refcnt)
3593 return;
3594
3595 /* sanity checks */
3596 if (WARN_ON(!(pool->flags & POOL_DISASSOCIATED)) ||
3597 WARN_ON(!list_empty(&pool->worklist)))
3598 return;
3599
3600 /* release id and unhash */
3601 if (pool->id >= 0)
3602 idr_remove(&worker_pool_idr, pool->id);
3603 hash_del(&pool->hash_node);
3604
3605 /*
3606 * Become the manager and destroy all workers. Grabbing
3607 * manager_arb prevents @pool's workers from blocking on
3608 * manager_mutex.
3609 */
3610 mutex_lock(&pool->manager_arb);
3611 mutex_lock(&pool->manager_mutex);
3612 spin_lock_irq(&pool->lock);
3613
3614 while ((worker = first_worker(pool)))
3615 destroy_worker(worker);
3616 WARN_ON(pool->nr_workers || pool->nr_idle);
3617
3618 spin_unlock_irq(&pool->lock);
3619 mutex_unlock(&pool->manager_mutex);
3620 mutex_unlock(&pool->manager_arb);
3621
3622 /* shut down the timers */
3623 del_timer_sync(&pool->idle_timer);
3624 del_timer_sync(&pool->mayday_timer);
3625
3626 /* sched-RCU protected to allow dereferences from get_work_pool() */
3627 call_rcu_sched(&pool->rcu, rcu_free_pool);
3628}
3629
3630/**
3631 * get_unbound_pool - get a worker_pool with the specified attributes
3632 * @attrs: the attributes of the worker_pool to get
3633 *
3634 * Obtain a worker_pool which has the same attributes as @attrs, bump the
3635 * reference count and return it. If there already is a matching
3636 * worker_pool, it will be used; otherwise, this function attempts to
3637 * create a new one.
3638 *
3639 * Should be called with wq_pool_mutex held.
3640 *
3641 * Return: On success, a worker_pool with the same attributes as @attrs.
3642 * On failure, %NULL.
3643 */
3644static struct worker_pool *get_unbound_pool(const struct workqueue_attrs *attrs)
3645{
3646 u32 hash = wqattrs_hash(attrs);
3647 struct worker_pool *pool;
3648 int node;
3649
3650 lockdep_assert_held(&wq_pool_mutex);
3651
3652 /* do we already have a matching pool? */
3653 hash_for_each_possible(unbound_pool_hash, pool, hash_node, hash) {
3654 if (wqattrs_equal(pool->attrs, attrs)) {
3655 pool->refcnt++;
3656 goto out_unlock;
3657 }
3658 }
3659
3660 /* nope, create a new one */
3661 pool = kzalloc(sizeof(*pool), GFP_KERNEL);
3662 if (!pool || init_worker_pool(pool) < 0)
3663 goto fail;
3664
3665 if (workqueue_freezing)
3666 pool->flags |= POOL_FREEZING;
3667
3668 lockdep_set_subclass(&pool->lock, 1); /* see put_pwq() */
3669 copy_workqueue_attrs(pool->attrs, attrs);
3670
3671 /*
3672 * no_numa isn't a worker_pool attribute, always clear it. See
3673 * 'struct workqueue_attrs' comments for detail.
3674 */
3675 pool->attrs->no_numa = false;
3676
3677 /* if cpumask is contained inside a NUMA node, we belong to that node */
3678 if (wq_numa_enabled) {
3679 for_each_node(node) {
3680 if (cpumask_subset(pool->attrs->cpumask,
3681 wq_numa_possible_cpumask[node])) {
3682 pool->node = node;
3683 break;
3684 }
3685 }
3686 }
3687
3688 if (worker_pool_assign_id(pool) < 0)
3689 goto fail;
3690
3691 /* create and start the initial worker */
3692 if (create_and_start_worker(pool) < 0)
3693 goto fail;
3694
3695 /* install */
3696 hash_add(unbound_pool_hash, &pool->hash_node, hash);
3697out_unlock:
3698 return pool;
3699fail:
3700 if (pool)
3701 put_unbound_pool(pool);
3702 return NULL;
3703}
3704
3705static void rcu_free_pwq(struct rcu_head *rcu)
3706{
3707 kmem_cache_free(pwq_cache,
3708 container_of(rcu, struct pool_workqueue, rcu));
3709}
3710
3711/*
3712 * Scheduled on system_wq by put_pwq() when an unbound pwq hits zero refcnt
3713 * and needs to be destroyed.
3714 */
3715static void pwq_unbound_release_workfn(struct work_struct *work)
3716{
3717 struct pool_workqueue *pwq = container_of(work, struct pool_workqueue,
3718 unbound_release_work);
3719 struct workqueue_struct *wq = pwq->wq;
3720 struct worker_pool *pool = pwq->pool;
3721 bool is_last;
3722
3723 if (WARN_ON_ONCE(!(wq->flags & WQ_UNBOUND)))
3724 return;
3725
3726 /*
3727 * Unlink @pwq. Synchronization against wq->mutex isn't strictly
3728 * necessary on release but do it anyway. It's easier to verify
3729 * and consistent with the linking path.
3730 */
3731 mutex_lock(&wq->mutex);
3732 list_del_rcu(&pwq->pwqs_node);
3733 is_last = list_empty(&wq->pwqs);
3734 mutex_unlock(&wq->mutex);
3735
3736 mutex_lock(&wq_pool_mutex);
3737 put_unbound_pool(pool);
3738 mutex_unlock(&wq_pool_mutex);
3739
3740 call_rcu_sched(&pwq->rcu, rcu_free_pwq);
3741
3742 /*
3743 * If we're the last pwq going away, @wq is already dead and no one
3744 * is gonna access it anymore. Free it.
3745 */
3746 if (is_last) {
3747 free_workqueue_attrs(wq->unbound_attrs);
3748 kfree(wq);
3749 }
3750}
3751
3752/**
3753 * pwq_adjust_max_active - update a pwq's max_active to the current setting
3754 * @pwq: target pool_workqueue
3755 *
3756 * If @pwq isn't freezing, set @pwq->max_active to the associated
3757 * workqueue's saved_max_active and activate delayed work items
3758 * accordingly. If @pwq is freezing, clear @pwq->max_active to zero.
3759 */
3760static void pwq_adjust_max_active(struct pool_workqueue *pwq)
3761{
3762 struct workqueue_struct *wq = pwq->wq;
3763 bool freezable = wq->flags & WQ_FREEZABLE;
3764
3765 /* for @wq->saved_max_active */
3766 lockdep_assert_held(&wq->mutex);
3767
3768 /* fast exit for non-freezable wqs */
3769 if (!freezable && pwq->max_active == wq->saved_max_active)
3770 return;
3771
3772 spin_lock_irq(&pwq->pool->lock);
3773
3774 if (!freezable || !(pwq->pool->flags & POOL_FREEZING)) {
3775 pwq->max_active = wq->saved_max_active;
3776
3777 while (!list_empty(&pwq->delayed_works) &&
3778 pwq->nr_active < pwq->max_active)
3779 pwq_activate_first_delayed(pwq);
3780
3781 /*
3782 * Need to kick a worker after thawed or an unbound wq's
3783 * max_active is bumped. It's a slow path. Do it always.
3784 */
3785 wake_up_worker(pwq->pool);
3786 } else {
3787 pwq->max_active = 0;
3788 }
3789
3790 spin_unlock_irq(&pwq->pool->lock);
3791}
3792
3793/* initialize newly alloced @pwq which is associated with @wq and @pool */
3794static void init_pwq(struct pool_workqueue *pwq, struct workqueue_struct *wq,
3795 struct worker_pool *pool)
3796{
3797 BUG_ON((unsigned long)pwq & WORK_STRUCT_FLAG_MASK);
3798
3799 memset(pwq, 0, sizeof(*pwq));
3800
3801 pwq->pool = pool;
3802 pwq->wq = wq;
3803 pwq->flush_color = -1;
3804 pwq->refcnt = 1;
3805 INIT_LIST_HEAD(&pwq->delayed_works);
3806 INIT_LIST_HEAD(&pwq->pwqs_node);
3807 INIT_LIST_HEAD(&pwq->mayday_node);
3808 INIT_WORK(&pwq->unbound_release_work, pwq_unbound_release_workfn);
3809}
3810
3811/* sync @pwq with the current state of its associated wq and link it */
3812static void link_pwq(struct pool_workqueue *pwq)
3813{
3814 struct workqueue_struct *wq = pwq->wq;
3815
3816 lockdep_assert_held(&wq->mutex);
3817
3818 /* may be called multiple times, ignore if already linked */
3819 if (!list_empty(&pwq->pwqs_node))
3820 return;
3821
3822 /*
3823 * Set the matching work_color. This is synchronized with
3824 * wq->mutex to avoid confusing flush_workqueue().
3825 */
3826 pwq->work_color = wq->work_color;
3827
3828 /* sync max_active to the current setting */
3829 pwq_adjust_max_active(pwq);
3830
3831 /* link in @pwq */
3832 list_add_rcu(&pwq->pwqs_node, &wq->pwqs);
3833}
3834
3835/* obtain a pool matching @attr and create a pwq associating the pool and @wq */
3836static struct pool_workqueue *alloc_unbound_pwq(struct workqueue_struct *wq,
3837 const struct workqueue_attrs *attrs)
3838{
3839 struct worker_pool *pool;
3840 struct pool_workqueue *pwq;
3841
3842 lockdep_assert_held(&wq_pool_mutex);
3843
3844 pool = get_unbound_pool(attrs);
3845 if (!pool)
3846 return NULL;
3847
3848 pwq = kmem_cache_alloc_node(pwq_cache, GFP_KERNEL, pool->node);
3849 if (!pwq) {
3850 put_unbound_pool(pool);
3851 return NULL;
3852 }
3853
3854 init_pwq(pwq, wq, pool);
3855 return pwq;
3856}
3857
3858/* undo alloc_unbound_pwq(), used only in the error path */
3859static void free_unbound_pwq(struct pool_workqueue *pwq)
3860{
3861 lockdep_assert_held(&wq_pool_mutex);
3862
3863 if (pwq) {
3864 put_unbound_pool(pwq->pool);
3865 kmem_cache_free(pwq_cache, pwq);
3866 }
3867}
3868
3869/**
3870 * wq_calc_node_mask - calculate a wq_attrs' cpumask for the specified node
3871 * @attrs: the wq_attrs of interest
3872 * @node: the target NUMA node
3873 * @cpu_going_down: if >= 0, the CPU to consider as offline
3874 * @cpumask: outarg, the resulting cpumask
3875 *
3876 * Calculate the cpumask a workqueue with @attrs should use on @node. If
3877 * @cpu_going_down is >= 0, that cpu is considered offline during
3878 * calculation. The result is stored in @cpumask.
3879 *
3880 * If NUMA affinity is not enabled, @attrs->cpumask is always used. If
3881 * enabled and @node has online CPUs requested by @attrs, the returned
3882 * cpumask is the intersection of the possible CPUs of @node and
3883 * @attrs->cpumask.
3884 *
3885 * The caller is responsible for ensuring that the cpumask of @node stays
3886 * stable.
3887 *
3888 * Return: %true if the resulting @cpumask is different from @attrs->cpumask,
3889 * %false if equal.
3890 */
3891static bool wq_calc_node_cpumask(const struct workqueue_attrs *attrs, int node,
3892 int cpu_going_down, cpumask_t *cpumask)
3893{
3894 if (!wq_numa_enabled || attrs->no_numa)
3895 goto use_dfl;
3896
3897 /* does @node have any online CPUs @attrs wants? */
3898 cpumask_and(cpumask, cpumask_of_node(node), attrs->cpumask);
3899 if (cpu_going_down >= 0)
3900 cpumask_clear_cpu(cpu_going_down, cpumask);
3901
3902 if (cpumask_empty(cpumask))
3903 goto use_dfl;
3904
3905 /* yeap, return possible CPUs in @node that @attrs wants */
3906 cpumask_and(cpumask, attrs->cpumask, wq_numa_possible_cpumask[node]);
3907 return !cpumask_equal(cpumask, attrs->cpumask);
3908
3909use_dfl:
3910 cpumask_copy(cpumask, attrs->cpumask);
3911 return false;
3912}
3913
3914/* install @pwq into @wq's numa_pwq_tbl[] for @node and return the old pwq */
3915static struct pool_workqueue *numa_pwq_tbl_install(struct workqueue_struct *wq,
3916 int node,
3917 struct pool_workqueue *pwq)
3918{
3919 struct pool_workqueue *old_pwq;
3920
3921 lockdep_assert_held(&wq->mutex);
3922
3923 /* link_pwq() can handle duplicate calls */
3924 link_pwq(pwq);
3925
3926 old_pwq = rcu_access_pointer(wq->numa_pwq_tbl[node]);
3927 rcu_assign_pointer(wq->numa_pwq_tbl[node], pwq);
3928 return old_pwq;
3929}
3930
3931/**
3932 * apply_workqueue_attrs - apply new workqueue_attrs to an unbound workqueue
3933 * @wq: the target workqueue
3934 * @attrs: the workqueue_attrs to apply, allocated with alloc_workqueue_attrs()
3935 *
3936 * Apply @attrs to an unbound workqueue @wq. Unless disabled, on NUMA
3937 * machines, this function maps a separate pwq to each NUMA node with
3938 * possibles CPUs in @attrs->cpumask so that work items are affine to the
3939 * NUMA node it was issued on. Older pwqs are released as in-flight work
3940 * items finish. Note that a work item which repeatedly requeues itself
3941 * back-to-back will stay on its current pwq.
3942 *
3943 * Performs GFP_KERNEL allocations.
3944 *
3945 * Return: 0 on success and -errno on failure.
3946 */
3947int apply_workqueue_attrs(struct workqueue_struct *wq,
3948 const struct workqueue_attrs *attrs)
3949{
3950 struct workqueue_attrs *new_attrs, *tmp_attrs;
3951 struct pool_workqueue **pwq_tbl, *dfl_pwq;
3952 int node, ret;
3953
3954 /* only unbound workqueues can change attributes */
3955 if (WARN_ON(!(wq->flags & WQ_UNBOUND)))
3956 return -EINVAL;
3957
3958 /* creating multiple pwqs breaks ordering guarantee */
3959 if (WARN_ON((wq->flags & __WQ_ORDERED) && !list_empty(&wq->pwqs)))
3960 return -EINVAL;
3961
3962 pwq_tbl = kzalloc(wq_numa_tbl_len * sizeof(pwq_tbl[0]), GFP_KERNEL);
3963 new_attrs = alloc_workqueue_attrs(GFP_KERNEL);
3964 tmp_attrs = alloc_workqueue_attrs(GFP_KERNEL);
3965 if (!pwq_tbl || !new_attrs || !tmp_attrs)
3966 goto enomem;
3967
3968 /* make a copy of @attrs and sanitize it */
3969 copy_workqueue_attrs(new_attrs, attrs);
3970 cpumask_and(new_attrs->cpumask, new_attrs->cpumask, cpu_possible_mask);
3971
3972 /*
3973 * We may create multiple pwqs with differing cpumasks. Make a
3974 * copy of @new_attrs which will be modified and used to obtain
3975 * pools.
3976 */
3977 copy_workqueue_attrs(tmp_attrs, new_attrs);
3978
3979 /*
3980 * CPUs should stay stable across pwq creations and installations.
3981 * Pin CPUs, determine the target cpumask for each node and create
3982 * pwqs accordingly.
3983 */
3984 get_online_cpus();
3985
3986 mutex_lock(&wq_pool_mutex);
3987
3988 /*
3989 * If something goes wrong during CPU up/down, we'll fall back to
3990 * the default pwq covering whole @attrs->cpumask. Always create
3991 * it even if we don't use it immediately.
3992 */
3993 dfl_pwq = alloc_unbound_pwq(wq, new_attrs);
3994 if (!dfl_pwq)
3995 goto enomem_pwq;
3996
3997 for_each_node(node) {
3998 if (wq_calc_node_cpumask(attrs, node, -1, tmp_attrs->cpumask)) {
3999 pwq_tbl[node] = alloc_unbound_pwq(wq, tmp_attrs);
4000 if (!pwq_tbl[node])
4001 goto enomem_pwq;
4002 } else {
4003 dfl_pwq->refcnt++;
4004 pwq_tbl[node] = dfl_pwq;
4005 }
4006 }
4007
4008 mutex_unlock(&wq_pool_mutex);
4009
4010 /* all pwqs have been created successfully, let's install'em */
4011 mutex_lock(&wq->mutex);
4012
4013 copy_workqueue_attrs(wq->unbound_attrs, new_attrs);
4014
4015 /* save the previous pwq and install the new one */
4016 for_each_node(node)
4017 pwq_tbl[node] = numa_pwq_tbl_install(wq, node, pwq_tbl[node]);
4018
4019 /* @dfl_pwq might not have been used, ensure it's linked */
4020 link_pwq(dfl_pwq);
4021 swap(wq->dfl_pwq, dfl_pwq);
4022
4023 mutex_unlock(&wq->mutex);
4024
4025 /* put the old pwqs */
4026 for_each_node(node)
4027 put_pwq_unlocked(pwq_tbl[node]);
4028 put_pwq_unlocked(dfl_pwq);
4029
4030 put_online_cpus();
4031 ret = 0;
4032 /* fall through */
4033out_free:
4034 free_workqueue_attrs(tmp_attrs);
4035 free_workqueue_attrs(new_attrs);
4036 kfree(pwq_tbl);
4037 return ret;
4038
4039enomem_pwq:
4040 free_unbound_pwq(dfl_pwq);
4041 for_each_node(node)
4042 if (pwq_tbl && pwq_tbl[node] != dfl_pwq)
4043 free_unbound_pwq(pwq_tbl[node]);
4044 mutex_unlock(&wq_pool_mutex);
4045 put_online_cpus();
4046enomem:
4047 ret = -ENOMEM;
4048 goto out_free;
4049}
4050
4051/**
4052 * wq_update_unbound_numa - update NUMA affinity of a wq for CPU hot[un]plug
4053 * @wq: the target workqueue
4054 * @cpu: the CPU coming up or going down
4055 * @online: whether @cpu is coming up or going down
4056 *
4057 * This function is to be called from %CPU_DOWN_PREPARE, %CPU_ONLINE and
4058 * %CPU_DOWN_FAILED. @cpu is being hot[un]plugged, update NUMA affinity of
4059 * @wq accordingly.
4060 *
4061 * If NUMA affinity can't be adjusted due to memory allocation failure, it
4062 * falls back to @wq->dfl_pwq which may not be optimal but is always
4063 * correct.
4064 *
4065 * Note that when the last allowed CPU of a NUMA node goes offline for a
4066 * workqueue with a cpumask spanning multiple nodes, the workers which were
4067 * already executing the work items for the workqueue will lose their CPU
4068 * affinity and may execute on any CPU. This is similar to how per-cpu
4069 * workqueues behave on CPU_DOWN. If a workqueue user wants strict
4070 * affinity, it's the user's responsibility to flush the work item from
4071 * CPU_DOWN_PREPARE.
4072 */
4073static void wq_update_unbound_numa(struct workqueue_struct *wq, int cpu,
4074 bool online)
4075{
4076 int node = cpu_to_node(cpu);
4077 int cpu_off = online ? -1 : cpu;
4078 struct pool_workqueue *old_pwq = NULL, *pwq;
4079 struct workqueue_attrs *target_attrs;
4080 cpumask_t *cpumask;
4081
4082 lockdep_assert_held(&wq_pool_mutex);
4083
4084 if (!wq_numa_enabled || !(wq->flags & WQ_UNBOUND))
4085 return;
4086
4087 /*
4088 * We don't wanna alloc/free wq_attrs for each wq for each CPU.
4089 * Let's use a preallocated one. The following buf is protected by
4090 * CPU hotplug exclusion.
4091 */
4092 target_attrs = wq_update_unbound_numa_attrs_buf;
4093 cpumask = target_attrs->cpumask;
4094
4095 mutex_lock(&wq->mutex);
4096 if (wq->unbound_attrs->no_numa)
4097 goto out_unlock;
4098
4099 copy_workqueue_attrs(target_attrs, wq->unbound_attrs);
4100 pwq = unbound_pwq_by_node(wq, node);
4101
4102 /*
4103 * Let's determine what needs to be done. If the target cpumask is
4104 * different from wq's, we need to compare it to @pwq's and create
4105 * a new one if they don't match. If the target cpumask equals
4106 * wq's, the default pwq should be used. If @pwq is already the
4107 * default one, nothing to do; otherwise, install the default one.
4108 */
4109 if (wq_calc_node_cpumask(wq->unbound_attrs, node, cpu_off, cpumask)) {
4110 if (cpumask_equal(cpumask, pwq->pool->attrs->cpumask))
4111 goto out_unlock;
4112 } else {
4113 if (pwq == wq->dfl_pwq)
4114 goto out_unlock;
4115 else
4116 goto use_dfl_pwq;
4117 }
4118
4119 mutex_unlock(&wq->mutex);
4120
4121 /* create a new pwq */
4122 pwq = alloc_unbound_pwq(wq, target_attrs);
4123 if (!pwq) {
4124 pr_warning("workqueue: allocation failed while updating NUMA affinity of \"%s\"\n",
4125 wq->name);
4126 mutex_lock(&wq->mutex);
4127 goto use_dfl_pwq;
4128 }
4129
4130 /*
4131 * Install the new pwq. As this function is called only from CPU
4132 * hotplug callbacks and applying a new attrs is wrapped with
4133 * get/put_online_cpus(), @wq->unbound_attrs couldn't have changed
4134 * inbetween.
4135 */
4136 mutex_lock(&wq->mutex);
4137 old_pwq = numa_pwq_tbl_install(wq, node, pwq);
4138 goto out_unlock;
4139
4140use_dfl_pwq:
4141 spin_lock_irq(&wq->dfl_pwq->pool->lock);
4142 get_pwq(wq->dfl_pwq);
4143 spin_unlock_irq(&wq->dfl_pwq->pool->lock);
4144 old_pwq = numa_pwq_tbl_install(wq, node, wq->dfl_pwq);
4145out_unlock:
4146 mutex_unlock(&wq->mutex);
4147 put_pwq_unlocked(old_pwq);
4148}
4149
4150static int alloc_and_link_pwqs(struct workqueue_struct *wq)
4151{
4152 bool highpri = wq->flags & WQ_HIGHPRI;
4153 int cpu, ret;
4154
4155 if (!(wq->flags & WQ_UNBOUND)) {
4156 wq->cpu_pwqs = alloc_percpu(struct pool_workqueue);
4157 if (!wq->cpu_pwqs)
4158 return -ENOMEM;
4159
4160 for_each_possible_cpu(cpu) {
4161 struct pool_workqueue *pwq =
4162 per_cpu_ptr(wq->cpu_pwqs, cpu);
4163 struct worker_pool *cpu_pools =
4164 per_cpu(cpu_worker_pools, cpu);
4165
4166 init_pwq(pwq, wq, &cpu_pools[highpri]);
4167
4168 mutex_lock(&wq->mutex);
4169 link_pwq(pwq);
4170 mutex_unlock(&wq->mutex);
4171 }
4172 return 0;
4173 } else if (wq->flags & __WQ_ORDERED) {
4174 ret = apply_workqueue_attrs(wq, ordered_wq_attrs[highpri]);
4175 /* there should only be single pwq for ordering guarantee */
4176 WARN(!ret && (wq->pwqs.next != &wq->dfl_pwq->pwqs_node ||
4177 wq->pwqs.prev != &wq->dfl_pwq->pwqs_node),
4178 "ordering guarantee broken for workqueue %s\n", wq->name);
4179 return ret;
4180 } else {
4181 return apply_workqueue_attrs(wq, unbound_std_wq_attrs[highpri]);
4182 }
4183}
4184
4185static int wq_clamp_max_active(int max_active, unsigned int flags,
4186 const char *name)
4187{
4188 int lim = flags & WQ_UNBOUND ? WQ_UNBOUND_MAX_ACTIVE : WQ_MAX_ACTIVE;
4189
4190 if (max_active < 1 || max_active > lim)
4191 pr_warn("workqueue: max_active %d requested for %s is out of range, clamping between %d and %d\n",
4192 max_active, name, 1, lim);
4193
4194 return clamp_val(max_active, 1, lim);
4195}
4196
4197struct workqueue_struct *__alloc_workqueue_key(const char *fmt,
4198 unsigned int flags,
4199 int max_active,
4200 struct lock_class_key *key,
4201 const char *lock_name, ...)
4202{
4203 size_t tbl_size = 0;
4204 va_list args;
4205 struct workqueue_struct *wq;
4206 struct pool_workqueue *pwq;
4207
4208 /* see the comment above the definition of WQ_POWER_EFFICIENT */
4209 if ((flags & WQ_POWER_EFFICIENT) && wq_power_efficient)
4210 flags |= WQ_UNBOUND;
4211
4212 /* allocate wq and format name */
4213 if (flags & WQ_UNBOUND)
4214 tbl_size = wq_numa_tbl_len * sizeof(wq->numa_pwq_tbl[0]);
4215
4216 wq = kzalloc(sizeof(*wq) + tbl_size, GFP_KERNEL);
4217 if (!wq)
4218 return NULL;
4219
4220 if (flags & WQ_UNBOUND) {
4221 wq->unbound_attrs = alloc_workqueue_attrs(GFP_KERNEL);
4222 if (!wq->unbound_attrs)
4223 goto err_free_wq;
4224 }
4225
4226 va_start(args, lock_name);
4227 vsnprintf(wq->name, sizeof(wq->name), fmt, args);
4228 va_end(args);
4229
4230 max_active = max_active ?: WQ_DFL_ACTIVE;
4231 max_active = wq_clamp_max_active(max_active, flags, wq->name);
4232
4233 /* init wq */
4234 wq->flags = flags;
4235 wq->saved_max_active = max_active;
4236 mutex_init(&wq->mutex);
4237 atomic_set(&wq->nr_pwqs_to_flush, 0);
4238 INIT_LIST_HEAD(&wq->pwqs);
4239 INIT_LIST_HEAD(&wq->flusher_queue);
4240 INIT_LIST_HEAD(&wq->flusher_overflow);
4241 INIT_LIST_HEAD(&wq->maydays);
4242
4243 lockdep_init_map(&wq->lockdep_map, lock_name, key, 0);
4244 INIT_LIST_HEAD(&wq->list);
4245
4246 if (alloc_and_link_pwqs(wq) < 0)
4247 goto err_free_wq;
4248
4249 /*
4250 * Workqueues which may be used during memory reclaim should
4251 * have a rescuer to guarantee forward progress.
4252 */
4253 if (flags & WQ_MEM_RECLAIM) {
4254 struct worker *rescuer;
4255
4256 rescuer = alloc_worker();
4257 if (!rescuer)
4258 goto err_destroy;
4259
4260 rescuer->rescue_wq = wq;
4261 rescuer->task = kthread_create(rescuer_thread, rescuer, "%s",
4262 wq->name);
4263 if (IS_ERR(rescuer->task)) {
4264 kfree(rescuer);
4265 goto err_destroy;
4266 }
4267
4268 wq->rescuer = rescuer;
4269 rescuer->task->flags |= PF_NO_SETAFFINITY;
4270 wake_up_process(rescuer->task);
4271 }
4272
4273 if ((wq->flags & WQ_SYSFS) && workqueue_sysfs_register(wq))
4274 goto err_destroy;
4275
4276 /*
4277 * wq_pool_mutex protects global freeze state and workqueues list.
4278 * Grab it, adjust max_active and add the new @wq to workqueues
4279 * list.
4280 */
4281 mutex_lock(&wq_pool_mutex);
4282
4283 mutex_lock(&wq->mutex);
4284 for_each_pwq(pwq, wq)
4285 pwq_adjust_max_active(pwq);
4286 mutex_unlock(&wq->mutex);
4287
4288 list_add(&wq->list, &workqueues);
4289
4290 mutex_unlock(&wq_pool_mutex);
4291
4292 return wq;
4293
4294err_free_wq:
4295 free_workqueue_attrs(wq->unbound_attrs);
4296 kfree(wq);
4297 return NULL;
4298err_destroy:
4299 destroy_workqueue(wq);
4300 return NULL;
4301}
4302EXPORT_SYMBOL_GPL(__alloc_workqueue_key);
4303
4304/**
4305 * destroy_workqueue - safely terminate a workqueue
4306 * @wq: target workqueue
4307 *
4308 * Safely destroy a workqueue. All work currently pending will be done first.
4309 */
4310void destroy_workqueue(struct workqueue_struct *wq)
4311{
4312 struct pool_workqueue *pwq;
4313 int node;
4314
4315 /* drain it before proceeding with destruction */
4316 drain_workqueue(wq);
4317
4318 /* sanity checks */
4319 mutex_lock(&wq->mutex);
4320 for_each_pwq(pwq, wq) {
4321 int i;
4322
4323 for (i = 0; i < WORK_NR_COLORS; i++) {
4324 if (WARN_ON(pwq->nr_in_flight[i])) {
4325 mutex_unlock(&wq->mutex);
4326 return;
4327 }
4328 }
4329
4330 if (WARN_ON((pwq != wq->dfl_pwq) && (pwq->refcnt > 1)) ||
4331 WARN_ON(pwq->nr_active) ||
4332 WARN_ON(!list_empty(&pwq->delayed_works))) {
4333 mutex_unlock(&wq->mutex);
4334 return;
4335 }
4336 }
4337 mutex_unlock(&wq->mutex);
4338
4339 /*
4340 * wq list is used to freeze wq, remove from list after
4341 * flushing is complete in case freeze races us.
4342 */
4343 mutex_lock(&wq_pool_mutex);
4344 list_del_init(&wq->list);
4345 mutex_unlock(&wq_pool_mutex);
4346
4347 workqueue_sysfs_unregister(wq);
4348
4349 if (wq->rescuer) {
4350 kthread_stop(wq->rescuer->task);
4351 kfree(wq->rescuer);
4352 wq->rescuer = NULL;
4353 }
4354
4355 if (!(wq->flags & WQ_UNBOUND)) {
4356 /*
4357 * The base ref is never dropped on per-cpu pwqs. Directly
4358 * free the pwqs and wq.
4359 */
4360 free_percpu(wq->cpu_pwqs);
4361 kfree(wq);
4362 } else {
4363 /*
4364 * We're the sole accessor of @wq at this point. Directly
4365 * access numa_pwq_tbl[] and dfl_pwq to put the base refs.
4366 * @wq will be freed when the last pwq is released.
4367 */
4368 for_each_node(node) {
4369 pwq = rcu_access_pointer(wq->numa_pwq_tbl[node]);
4370 RCU_INIT_POINTER(wq->numa_pwq_tbl[node], NULL);
4371 put_pwq_unlocked(pwq);
4372 }
4373
4374 /*
4375 * Put dfl_pwq. @wq may be freed any time after dfl_pwq is
4376 * put. Don't access it afterwards.
4377 */
4378 pwq = wq->dfl_pwq;
4379 wq->dfl_pwq = NULL;
4380 put_pwq_unlocked(pwq);
4381 }
4382}
4383EXPORT_SYMBOL_GPL(destroy_workqueue);
4384
4385/**
4386 * workqueue_set_max_active - adjust max_active of a workqueue
4387 * @wq: target workqueue
4388 * @max_active: new max_active value.
4389 *
4390 * Set max_active of @wq to @max_active.
4391 *
4392 * CONTEXT:
4393 * Don't call from IRQ context.
4394 */
4395void workqueue_set_max_active(struct workqueue_struct *wq, int max_active)
4396{
4397 struct pool_workqueue *pwq;
4398
4399 /* disallow meddling with max_active for ordered workqueues */
4400 if (WARN_ON(wq->flags & __WQ_ORDERED))
4401 return;
4402
4403 max_active = wq_clamp_max_active(max_active, wq->flags, wq->name);
4404
4405 mutex_lock(&wq->mutex);
4406
4407 wq->saved_max_active = max_active;
4408
4409 for_each_pwq(pwq, wq)
4410 pwq_adjust_max_active(pwq);
4411
4412 mutex_unlock(&wq->mutex);
4413}
4414EXPORT_SYMBOL_GPL(workqueue_set_max_active);
4415
4416/**
4417 * current_is_workqueue_rescuer - is %current workqueue rescuer?
4418 *
4419 * Determine whether %current is a workqueue rescuer. Can be used from
4420 * work functions to determine whether it's being run off the rescuer task.
4421 *
4422 * Return: %true if %current is a workqueue rescuer. %false otherwise.
4423 */
4424bool current_is_workqueue_rescuer(void)
4425{
4426 struct worker *worker = current_wq_worker();
4427
4428 return worker && worker->rescue_wq;
4429}
4430
4431/**
4432 * workqueue_congested - test whether a workqueue is congested
4433 * @cpu: CPU in question
4434 * @wq: target workqueue
4435 *
4436 * Test whether @wq's cpu workqueue for @cpu is congested. There is
4437 * no synchronization around this function and the test result is
4438 * unreliable and only useful as advisory hints or for debugging.
4439 *
4440 * If @cpu is WORK_CPU_UNBOUND, the test is performed on the local CPU.
4441 * Note that both per-cpu and unbound workqueues may be associated with
4442 * multiple pool_workqueues which have separate congested states. A
4443 * workqueue being congested on one CPU doesn't mean the workqueue is also
4444 * contested on other CPUs / NUMA nodes.
4445 *
4446 * Return:
4447 * %true if congested, %false otherwise.
4448 */
4449bool workqueue_congested(int cpu, struct workqueue_struct *wq)
4450{
4451 struct pool_workqueue *pwq;
4452 bool ret;
4453
4454 rcu_read_lock_sched();
4455
4456 if (cpu == WORK_CPU_UNBOUND)
4457 cpu = smp_processor_id();
4458
4459 if (!(wq->flags & WQ_UNBOUND))
4460 pwq = per_cpu_ptr(wq->cpu_pwqs, cpu);
4461 else
4462 pwq = unbound_pwq_by_node(wq, cpu_to_node(cpu));
4463
4464 ret = !list_empty(&pwq->delayed_works);
4465 rcu_read_unlock_sched();
4466
4467 return ret;
4468}
4469EXPORT_SYMBOL_GPL(workqueue_congested);
4470
4471/**
4472 * work_busy - test whether a work is currently pending or running
4473 * @work: the work to be tested
4474 *
4475 * Test whether @work is currently pending or running. There is no
4476 * synchronization around this function and the test result is
4477 * unreliable and only useful as advisory hints or for debugging.
4478 *
4479 * Return:
4480 * OR'd bitmask of WORK_BUSY_* bits.
4481 */
4482unsigned int work_busy(struct work_struct *work)
4483{
4484 struct worker_pool *pool;
4485 unsigned long flags;
4486 unsigned int ret = 0;
4487
4488 if (work_pending(work))
4489 ret |= WORK_BUSY_PENDING;
4490
4491 local_irq_save(flags);
4492 pool = get_work_pool(work);
4493 if (pool) {
4494 spin_lock(&pool->lock);
4495 if (find_worker_executing_work(pool, work))
4496 ret |= WORK_BUSY_RUNNING;
4497 spin_unlock(&pool->lock);
4498 }
4499 local_irq_restore(flags);
4500
4501 return ret;
4502}
4503EXPORT_SYMBOL_GPL(work_busy);
4504
4505/**
4506 * set_worker_desc - set description for the current work item
4507 * @fmt: printf-style format string
4508 * @...: arguments for the format string
4509 *
4510 * This function can be called by a running work function to describe what
4511 * the work item is about. If the worker task gets dumped, this
4512 * information will be printed out together to help debugging. The
4513 * description can be at most WORKER_DESC_LEN including the trailing '\0'.
4514 */
4515void set_worker_desc(const char *fmt, ...)
4516{
4517 struct worker *worker = current_wq_worker();
4518 va_list args;
4519
4520 if (worker) {
4521 va_start(args, fmt);
4522 vsnprintf(worker->desc, sizeof(worker->desc), fmt, args);
4523 va_end(args);
4524 worker->desc_valid = true;
4525 }
4526}
4527
4528/**
4529 * print_worker_info - print out worker information and description
4530 * @log_lvl: the log level to use when printing
4531 * @task: target task
4532 *
4533 * If @task is a worker and currently executing a work item, print out the
4534 * name of the workqueue being serviced and worker description set with
4535 * set_worker_desc() by the currently executing work item.
4536 *
4537 * This function can be safely called on any task as long as the
4538 * task_struct itself is accessible. While safe, this function isn't
4539 * synchronized and may print out mixups or garbages of limited length.
4540 */
4541void print_worker_info(const char *log_lvl, struct task_struct *task)
4542{
4543 work_func_t *fn = NULL;
4544 char name[WQ_NAME_LEN] = { };
4545 char desc[WORKER_DESC_LEN] = { };
4546 struct pool_workqueue *pwq = NULL;
4547 struct workqueue_struct *wq = NULL;
4548 bool desc_valid = false;
4549 struct worker *worker;
4550
4551 if (!(task->flags & PF_WQ_WORKER))
4552 return;
4553
4554 /*
4555 * This function is called without any synchronization and @task
4556 * could be in any state. Be careful with dereferences.
4557 */
4558 worker = probe_kthread_data(task);
4559
4560 /*
4561 * Carefully copy the associated workqueue's workfn and name. Keep
4562 * the original last '\0' in case the original contains garbage.
4563 */
4564 probe_kernel_read(&fn, &worker->current_func, sizeof(fn));
4565 probe_kernel_read(&pwq, &worker->current_pwq, sizeof(pwq));
4566 probe_kernel_read(&wq, &pwq->wq, sizeof(wq));
4567 probe_kernel_read(name, wq->name, sizeof(name) - 1);
4568
4569 /* copy worker description */
4570 probe_kernel_read(&desc_valid, &worker->desc_valid, sizeof(desc_valid));
4571 if (desc_valid)
4572 probe_kernel_read(desc, worker->desc, sizeof(desc) - 1);
4573
4574 if (fn || name[0] || desc[0]) {
4575 printk("%sWorkqueue: %s %pf", log_lvl, name, fn);
4576 if (desc[0])
4577 pr_cont(" (%s)", desc);
4578 pr_cont("\n");
4579 }
4580}
4581
4582/*
4583 * CPU hotplug.
4584 *
4585 * There are two challenges in supporting CPU hotplug. Firstly, there
4586 * are a lot of assumptions on strong associations among work, pwq and
4587 * pool which make migrating pending and scheduled works very
4588 * difficult to implement without impacting hot paths. Secondly,
4589 * worker pools serve mix of short, long and very long running works making
4590 * blocked draining impractical.
4591 *
4592 * This is solved by allowing the pools to be disassociated from the CPU
4593 * running as an unbound one and allowing it to be reattached later if the
4594 * cpu comes back online.
4595 */
4596
4597static void wq_unbind_fn(struct work_struct *work)
4598{
4599 int cpu = smp_processor_id();
4600 struct worker_pool *pool;
4601 struct worker *worker;
4602 int wi;
4603
4604 for_each_cpu_worker_pool(pool, cpu) {
4605 WARN_ON_ONCE(cpu != smp_processor_id());
4606
4607 mutex_lock(&pool->manager_mutex);
4608 spin_lock_irq(&pool->lock);
4609
4610 /*
4611 * We've blocked all manager operations. Make all workers
4612 * unbound and set DISASSOCIATED. Before this, all workers
4613 * except for the ones which are still executing works from
4614 * before the last CPU down must be on the cpu. After
4615 * this, they may become diasporas.
4616 */
4617 for_each_pool_worker(worker, wi, pool)
4618 worker->flags |= WORKER_UNBOUND;
4619
4620 pool->flags |= POOL_DISASSOCIATED;
4621
4622 spin_unlock_irq(&pool->lock);
4623 mutex_unlock(&pool->manager_mutex);
4624
4625 /*
4626 * Call schedule() so that we cross rq->lock and thus can
4627 * guarantee sched callbacks see the %WORKER_UNBOUND flag.
4628 * This is necessary as scheduler callbacks may be invoked
4629 * from other cpus.
4630 */
4631 schedule();
4632
4633 /*
4634 * Sched callbacks are disabled now. Zap nr_running.
4635 * After this, nr_running stays zero and need_more_worker()
4636 * and keep_working() are always true as long as the
4637 * worklist is not empty. This pool now behaves as an
4638 * unbound (in terms of concurrency management) pool which
4639 * are served by workers tied to the pool.
4640 */
4641 atomic_set(&pool->nr_running, 0);
4642
4643 /*
4644 * With concurrency management just turned off, a busy
4645 * worker blocking could lead to lengthy stalls. Kick off
4646 * unbound chain execution of currently pending work items.
4647 */
4648 spin_lock_irq(&pool->lock);
4649 wake_up_worker(pool);
4650 spin_unlock_irq(&pool->lock);
4651 }
4652}
4653
4654/**
4655 * rebind_workers - rebind all workers of a pool to the associated CPU
4656 * @pool: pool of interest
4657 *
4658 * @pool->cpu is coming online. Rebind all workers to the CPU.
4659 */
4660static void rebind_workers(struct worker_pool *pool)
4661{
4662 struct worker *worker;
4663 int wi;
4664
4665 lockdep_assert_held(&pool->manager_mutex);
4666
4667 /*
4668 * Restore CPU affinity of all workers. As all idle workers should
4669 * be on the run-queue of the associated CPU before any local
4670 * wake-ups for concurrency management happen, restore CPU affinty
4671 * of all workers first and then clear UNBOUND. As we're called
4672 * from CPU_ONLINE, the following shouldn't fail.
4673 */
4674 for_each_pool_worker(worker, wi, pool)
4675 WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task,
4676 pool->attrs->cpumask) < 0);
4677
4678 spin_lock_irq(&pool->lock);
4679
4680 for_each_pool_worker(worker, wi, pool) {
4681 unsigned int worker_flags = worker->flags;
4682
4683 /*
4684 * A bound idle worker should actually be on the runqueue
4685 * of the associated CPU for local wake-ups targeting it to
4686 * work. Kick all idle workers so that they migrate to the
4687 * associated CPU. Doing this in the same loop as
4688 * replacing UNBOUND with REBOUND is safe as no worker will
4689 * be bound before @pool->lock is released.
4690 */
4691 if (worker_flags & WORKER_IDLE)
4692 wake_up_process(worker->task);
4693
4694 /*
4695 * We want to clear UNBOUND but can't directly call
4696 * worker_clr_flags() or adjust nr_running. Atomically
4697 * replace UNBOUND with another NOT_RUNNING flag REBOUND.
4698 * @worker will clear REBOUND using worker_clr_flags() when
4699 * it initiates the next execution cycle thus restoring
4700 * concurrency management. Note that when or whether
4701 * @worker clears REBOUND doesn't affect correctness.
4702 *
4703 * ACCESS_ONCE() is necessary because @worker->flags may be
4704 * tested without holding any lock in
4705 * wq_worker_waking_up(). Without it, NOT_RUNNING test may
4706 * fail incorrectly leading to premature concurrency
4707 * management operations.
4708 */
4709 WARN_ON_ONCE(!(worker_flags & WORKER_UNBOUND));
4710 worker_flags |= WORKER_REBOUND;
4711 worker_flags &= ~WORKER_UNBOUND;
4712 ACCESS_ONCE(worker->flags) = worker_flags;
4713 }
4714
4715 spin_unlock_irq(&pool->lock);
4716}
4717
4718/**
4719 * restore_unbound_workers_cpumask - restore cpumask of unbound workers
4720 * @pool: unbound pool of interest
4721 * @cpu: the CPU which is coming up
4722 *
4723 * An unbound pool may end up with a cpumask which doesn't have any online
4724 * CPUs. When a worker of such pool get scheduled, the scheduler resets
4725 * its cpus_allowed. If @cpu is in @pool's cpumask which didn't have any
4726 * online CPU before, cpus_allowed of all its workers should be restored.
4727 */
4728static void restore_unbound_workers_cpumask(struct worker_pool *pool, int cpu)
4729{
4730 static cpumask_t cpumask;
4731 struct worker *worker;
4732 int wi;
4733
4734 lockdep_assert_held(&pool->manager_mutex);
4735
4736 /* is @cpu allowed for @pool? */
4737 if (!cpumask_test_cpu(cpu, pool->attrs->cpumask))
4738 return;
4739
4740 /* is @cpu the only online CPU? */
4741 cpumask_and(&cpumask, pool->attrs->cpumask, cpu_online_mask);
4742 if (cpumask_weight(&cpumask) != 1)
4743 return;
4744
4745 /* as we're called from CPU_ONLINE, the following shouldn't fail */
4746 for_each_pool_worker(worker, wi, pool)
4747 WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task,
4748 pool->attrs->cpumask) < 0);
4749}
4750
4751/*
4752 * Workqueues should be brought up before normal priority CPU notifiers.
4753 * This will be registered high priority CPU notifier.
4754 */
4755static int workqueue_cpu_up_callback(struct notifier_block *nfb,
4756 unsigned long action,
4757 void *hcpu)
4758{
4759 int cpu = (unsigned long)hcpu;
4760 struct worker_pool *pool;
4761 struct workqueue_struct *wq;
4762 int pi;
4763
4764 switch (action & ~CPU_TASKS_FROZEN) {
4765 case CPU_UP_PREPARE:
4766 for_each_cpu_worker_pool(pool, cpu) {
4767 if (pool->nr_workers)
4768 continue;
4769 if (create_and_start_worker(pool) < 0)
4770 return NOTIFY_BAD;
4771 }
4772 break;
4773
4774 case CPU_DOWN_FAILED:
4775 case CPU_ONLINE:
4776 mutex_lock(&wq_pool_mutex);
4777
4778 for_each_pool(pool, pi) {
4779 mutex_lock(&pool->manager_mutex);
4780
4781 if (pool->cpu == cpu) {
4782 spin_lock_irq(&pool->lock);
4783 pool->flags &= ~POOL_DISASSOCIATED;
4784 spin_unlock_irq(&pool->lock);
4785
4786 rebind_workers(pool);
4787 } else if (pool->cpu < 0) {
4788 restore_unbound_workers_cpumask(pool, cpu);
4789 }
4790
4791 mutex_unlock(&pool->manager_mutex);
4792 }
4793
4794 /* update NUMA affinity of unbound workqueues */
4795 list_for_each_entry(wq, &workqueues, list)
4796 wq_update_unbound_numa(wq, cpu, true);
4797
4798 mutex_unlock(&wq_pool_mutex);
4799 break;
4800 }
4801 return NOTIFY_OK;
4802}
4803
4804/*
4805 * Workqueues should be brought down after normal priority CPU notifiers.
4806 * This will be registered as low priority CPU notifier.
4807 */
4808static int workqueue_cpu_down_callback(struct notifier_block *nfb,
4809 unsigned long action,
4810 void *hcpu)
4811{
4812 int cpu = (unsigned long)hcpu;
4813 struct work_struct unbind_work;
4814 struct workqueue_struct *wq;
4815
4816 switch (action & ~CPU_TASKS_FROZEN) {
4817 case CPU_DOWN_PREPARE:
4818 /* unbinding per-cpu workers should happen on the local CPU */
4819 INIT_WORK_ONSTACK(&unbind_work, wq_unbind_fn);
4820 queue_work_on(cpu, system_highpri_wq, &unbind_work);
4821
4822 /* update NUMA affinity of unbound workqueues */
4823 mutex_lock(&wq_pool_mutex);
4824 list_for_each_entry(wq, &workqueues, list)
4825 wq_update_unbound_numa(wq, cpu, false);
4826 mutex_unlock(&wq_pool_mutex);
4827
4828 /* wait for per-cpu unbinding to finish */
4829 flush_work(&unbind_work);
4830 destroy_work_on_stack(&unbind_work);
4831 break;
4832 }
4833 return NOTIFY_OK;
4834}
4835
4836#ifdef CONFIG_SMP
4837
4838struct work_for_cpu {
4839 struct work_struct work;
4840 long (*fn)(void *);
4841 void *arg;
4842 long ret;
4843};
4844
4845static void work_for_cpu_fn(struct work_struct *work)
4846{
4847 struct work_for_cpu *wfc = container_of(work, struct work_for_cpu, work);
4848
4849 wfc->ret = wfc->fn(wfc->arg);
4850}
4851
4852/**
4853 * work_on_cpu - run a function in user context on a particular cpu
4854 * @cpu: the cpu to run on
4855 * @fn: the function to run
4856 * @arg: the function arg
4857 *
4858 * It is up to the caller to ensure that the cpu doesn't go offline.
4859 * The caller must not hold any locks which would prevent @fn from completing.
4860 *
4861 * Return: The value @fn returns.
4862 */
4863long work_on_cpu(int cpu, long (*fn)(void *), void *arg)
4864{
4865 struct work_for_cpu wfc = { .fn = fn, .arg = arg };
4866
4867 INIT_WORK_ONSTACK(&wfc.work, work_for_cpu_fn);
4868 schedule_work_on(cpu, &wfc.work);
4869 flush_work(&wfc.work);
4870 destroy_work_on_stack(&wfc.work);
4871 return wfc.ret;
4872}
4873EXPORT_SYMBOL_GPL(work_on_cpu);
4874#endif /* CONFIG_SMP */
4875
4876#ifdef CONFIG_FREEZER
4877
4878/**
4879 * freeze_workqueues_begin - begin freezing workqueues
4880 *
4881 * Start freezing workqueues. After this function returns, all freezable
4882 * workqueues will queue new works to their delayed_works list instead of
4883 * pool->worklist.
4884 *
4885 * CONTEXT:
4886 * Grabs and releases wq_pool_mutex, wq->mutex and pool->lock's.
4887 */
4888void freeze_workqueues_begin(void)
4889{
4890 struct worker_pool *pool;
4891 struct workqueue_struct *wq;
4892 struct pool_workqueue *pwq;
4893 int pi;
4894
4895 mutex_lock(&wq_pool_mutex);
4896
4897 WARN_ON_ONCE(workqueue_freezing);
4898 workqueue_freezing = true;
4899
4900 /* set FREEZING */
4901 for_each_pool(pool, pi) {
4902 spin_lock_irq(&pool->lock);
4903 WARN_ON_ONCE(pool->flags & POOL_FREEZING);
4904 pool->flags |= POOL_FREEZING;
4905 spin_unlock_irq(&pool->lock);
4906 }
4907
4908 list_for_each_entry(wq, &workqueues, list) {
4909 mutex_lock(&wq->mutex);
4910 for_each_pwq(pwq, wq)
4911 pwq_adjust_max_active(pwq);
4912 mutex_unlock(&wq->mutex);
4913 }
4914
4915 mutex_unlock(&wq_pool_mutex);
4916}
4917
4918/**
4919 * freeze_workqueues_busy - are freezable workqueues still busy?
4920 *
4921 * Check whether freezing is complete. This function must be called
4922 * between freeze_workqueues_begin() and thaw_workqueues().
4923 *
4924 * CONTEXT:
4925 * Grabs and releases wq_pool_mutex.
4926 *
4927 * Return:
4928 * %true if some freezable workqueues are still busy. %false if freezing
4929 * is complete.
4930 */
4931bool freeze_workqueues_busy(void)
4932{
4933 bool busy = false;
4934 struct workqueue_struct *wq;
4935 struct pool_workqueue *pwq;
4936
4937 mutex_lock(&wq_pool_mutex);
4938
4939 WARN_ON_ONCE(!workqueue_freezing);
4940
4941 list_for_each_entry(wq, &workqueues, list) {
4942 if (!(wq->flags & WQ_FREEZABLE))
4943 continue;
4944 /*
4945 * nr_active is monotonically decreasing. It's safe
4946 * to peek without lock.
4947 */
4948 rcu_read_lock_sched();
4949 for_each_pwq(pwq, wq) {
4950 WARN_ON_ONCE(pwq->nr_active < 0);
4951 if (pwq->nr_active) {
4952 busy = true;
4953 rcu_read_unlock_sched();
4954 goto out_unlock;
4955 }
4956 }
4957 rcu_read_unlock_sched();
4958 }
4959out_unlock:
4960 mutex_unlock(&wq_pool_mutex);
4961 return busy;
4962}
4963
4964/**
4965 * thaw_workqueues - thaw workqueues
4966 *
4967 * Thaw workqueues. Normal queueing is restored and all collected
4968 * frozen works are transferred to their respective pool worklists.
4969 *
4970 * CONTEXT:
4971 * Grabs and releases wq_pool_mutex, wq->mutex and pool->lock's.
4972 */
4973void thaw_workqueues(void)
4974{
4975 struct workqueue_struct *wq;
4976 struct pool_workqueue *pwq;
4977 struct worker_pool *pool;
4978 int pi;
4979
4980 mutex_lock(&wq_pool_mutex);
4981
4982 if (!workqueue_freezing)
4983 goto out_unlock;
4984
4985 /* clear FREEZING */
4986 for_each_pool(pool, pi) {
4987 spin_lock_irq(&pool->lock);
4988 WARN_ON_ONCE(!(pool->flags & POOL_FREEZING));
4989 pool->flags &= ~POOL_FREEZING;
4990 spin_unlock_irq(&pool->lock);
4991 }
4992
4993 /* restore max_active and repopulate worklist */
4994 list_for_each_entry(wq, &workqueues, list) {
4995 mutex_lock(&wq->mutex);
4996 for_each_pwq(pwq, wq)
4997 pwq_adjust_max_active(pwq);
4998 mutex_unlock(&wq->mutex);
4999 }
5000
5001 workqueue_freezing = false;
5002out_unlock:
5003 mutex_unlock(&wq_pool_mutex);
5004}
5005#endif /* CONFIG_FREEZER */
5006
5007static void __init wq_numa_init(void)
5008{
5009 cpumask_var_t *tbl;
5010 int node, cpu;
5011
5012 /* determine NUMA pwq table len - highest node id + 1 */
5013 for_each_node(node)
5014 wq_numa_tbl_len = max(wq_numa_tbl_len, node + 1);
5015
5016 if (num_possible_nodes() <= 1)
5017 return;
5018
5019 if (wq_disable_numa) {
5020 pr_info("workqueue: NUMA affinity support disabled\n");
5021 return;
5022 }
5023
5024 wq_update_unbound_numa_attrs_buf = alloc_workqueue_attrs(GFP_KERNEL);
5025 BUG_ON(!wq_update_unbound_numa_attrs_buf);
5026
5027 /*
5028 * We want masks of possible CPUs of each node which isn't readily
5029 * available. Build one from cpu_to_node() which should have been
5030 * fully initialized by now.
5031 */
5032 tbl = kzalloc(wq_numa_tbl_len * sizeof(tbl[0]), GFP_KERNEL);
5033 BUG_ON(!tbl);
5034
5035 for_each_node(node)
5036 BUG_ON(!alloc_cpumask_var_node(&tbl[node], GFP_KERNEL,
5037 node_online(node) ? node : NUMA_NO_NODE));
5038
5039 for_each_possible_cpu(cpu) {
5040 node = cpu_to_node(cpu);
5041 if (WARN_ON(node == NUMA_NO_NODE)) {
5042 pr_warn("workqueue: NUMA node mapping not available for cpu%d, disabling NUMA support\n", cpu);
5043 /* happens iff arch is bonkers, let's just proceed */
5044 return;
5045 }
5046 cpumask_set_cpu(cpu, tbl[node]);
5047 }
5048
5049 wq_numa_possible_cpumask = tbl;
5050 wq_numa_enabled = true;
5051}
5052
5053static int __init init_workqueues(void)
5054{
5055 int std_nice[NR_STD_WORKER_POOLS] = { 0, HIGHPRI_NICE_LEVEL };
5056 int i, cpu;
5057
5058 WARN_ON(__alignof__(struct pool_workqueue) < __alignof__(long long));
5059
5060 pwq_cache = KMEM_CACHE(pool_workqueue, SLAB_PANIC);
5061
5062 cpu_notifier(workqueue_cpu_up_callback, CPU_PRI_WORKQUEUE_UP);
5063 hotcpu_notifier(workqueue_cpu_down_callback, CPU_PRI_WORKQUEUE_DOWN);
5064
5065 wq_numa_init();
5066
5067 /* initialize CPU pools */
5068 for_each_possible_cpu(cpu) {
5069 struct worker_pool *pool;
5070
5071 i = 0;
5072 for_each_cpu_worker_pool(pool, cpu) {
5073 BUG_ON(init_worker_pool(pool));
5074 pool->cpu = cpu;
5075 cpumask_copy(pool->attrs->cpumask, cpumask_of(cpu));
5076 pool->attrs->nice = std_nice[i++];
5077 pool->node = cpu_to_node(cpu);
5078
5079 /* alloc pool ID */
5080 mutex_lock(&wq_pool_mutex);
5081 BUG_ON(worker_pool_assign_id(pool));
5082 mutex_unlock(&wq_pool_mutex);
5083 }
5084 }
5085
5086 /* create the initial worker */
5087 for_each_online_cpu(cpu) {
5088 struct worker_pool *pool;
5089
5090 for_each_cpu_worker_pool(pool, cpu) {
5091 pool->flags &= ~POOL_DISASSOCIATED;
5092 BUG_ON(create_and_start_worker(pool) < 0);
5093 }
5094 }
5095
5096 /* create default unbound and ordered wq attrs */
5097 for (i = 0; i < NR_STD_WORKER_POOLS; i++) {
5098 struct workqueue_attrs *attrs;
5099
5100 BUG_ON(!(attrs = alloc_workqueue_attrs(GFP_KERNEL)));
5101 attrs->nice = std_nice[i];
5102 unbound_std_wq_attrs[i] = attrs;
5103
5104 /*
5105 * An ordered wq should have only one pwq as ordering is
5106 * guaranteed by max_active which is enforced by pwqs.
5107 * Turn off NUMA so that dfl_pwq is used for all nodes.
5108 */
5109 BUG_ON(!(attrs = alloc_workqueue_attrs(GFP_KERNEL)));
5110 attrs->nice = std_nice[i];
5111 attrs->no_numa = true;
5112 ordered_wq_attrs[i] = attrs;
5113 }
5114
5115 system_wq = alloc_workqueue("events", 0, 0);
5116 system_highpri_wq = alloc_workqueue("events_highpri", WQ_HIGHPRI, 0);
5117 system_long_wq = alloc_workqueue("events_long", 0, 0);
5118 system_unbound_wq = alloc_workqueue("events_unbound", WQ_UNBOUND,
5119 WQ_UNBOUND_MAX_ACTIVE);
5120 system_freezable_wq = alloc_workqueue("events_freezable",
5121 WQ_FREEZABLE, 0);
5122 system_power_efficient_wq = alloc_workqueue("events_power_efficient",
5123 WQ_POWER_EFFICIENT, 0);
5124 system_freezable_power_efficient_wq = alloc_workqueue("events_freezable_power_efficient",
5125 WQ_FREEZABLE | WQ_POWER_EFFICIENT,
5126 0);
5127 BUG_ON(!system_wq || !system_highpri_wq || !system_long_wq ||
5128 !system_unbound_wq || !system_freezable_wq ||
5129 !system_power_efficient_wq ||
5130 !system_freezable_power_efficient_wq);
5131 return 0;
5132}
5133early_initcall(init_workqueues);