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1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * kernel/workqueue.c - generic async execution with shared worker pool
4 *
5 * Copyright (C) 2002 Ingo Molnar
6 *
7 * Derived from the taskqueue/keventd code by:
8 * David Woodhouse <dwmw2@infradead.org>
9 * Andrew Morton
10 * Kai Petzke <wpp@marie.physik.tu-berlin.de>
11 * Theodore Ts'o <tytso@mit.edu>
12 *
13 * Made to use alloc_percpu by Christoph Lameter.
14 *
15 * Copyright (C) 2010 SUSE Linux Products GmbH
16 * Copyright (C) 2010 Tejun Heo <tj@kernel.org>
17 *
18 * This is the generic async execution mechanism. Work items as are
19 * executed in process context. The worker pool is shared and
20 * automatically managed. There are two worker pools for each CPU (one for
21 * normal work items and the other for high priority ones) and some extra
22 * pools for workqueues which are not bound to any specific CPU - the
23 * number of these backing pools is dynamic.
24 *
25 * Please read Documentation/core-api/workqueue.rst for details.
26 */
27
28#include <linux/export.h>
29#include <linux/kernel.h>
30#include <linux/sched.h>
31#include <linux/init.h>
32#include <linux/signal.h>
33#include <linux/completion.h>
34#include <linux/workqueue.h>
35#include <linux/slab.h>
36#include <linux/cpu.h>
37#include <linux/notifier.h>
38#include <linux/kthread.h>
39#include <linux/hardirq.h>
40#include <linux/mempolicy.h>
41#include <linux/freezer.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#include <linux/sched/isolation.h>
52#include <linux/nmi.h>
53#include <linux/kvm_para.h>
54
55#include "workqueue_internal.h"
56
57enum {
58 /*
59 * worker_pool flags
60 *
61 * A bound pool is either associated or disassociated with its CPU.
62 * While associated (!DISASSOCIATED), all workers are bound to the
63 * CPU and none has %WORKER_UNBOUND set and concurrency management
64 * is in effect.
65 *
66 * While DISASSOCIATED, the cpu may be offline and all workers have
67 * %WORKER_UNBOUND set and concurrency management disabled, and may
68 * be executing on any CPU. The pool behaves as an unbound one.
69 *
70 * Note that DISASSOCIATED should be flipped only while holding
71 * wq_pool_attach_mutex to avoid changing binding state while
72 * worker_attach_to_pool() is in progress.
73 */
74 POOL_MANAGER_ACTIVE = 1 << 0, /* being managed */
75 POOL_DISASSOCIATED = 1 << 2, /* cpu can't serve workers */
76
77 /* worker flags */
78 WORKER_DIE = 1 << 1, /* die die die */
79 WORKER_IDLE = 1 << 2, /* is idle */
80 WORKER_PREP = 1 << 3, /* preparing to run works */
81 WORKER_CPU_INTENSIVE = 1 << 6, /* cpu intensive */
82 WORKER_UNBOUND = 1 << 7, /* worker is unbound */
83 WORKER_REBOUND = 1 << 8, /* worker was rebound */
84
85 WORKER_NOT_RUNNING = WORKER_PREP | WORKER_CPU_INTENSIVE |
86 WORKER_UNBOUND | WORKER_REBOUND,
87
88 NR_STD_WORKER_POOLS = 2, /* # standard pools per cpu */
89
90 UNBOUND_POOL_HASH_ORDER = 6, /* hashed by pool->attrs */
91 BUSY_WORKER_HASH_ORDER = 6, /* 64 pointers */
92
93 MAX_IDLE_WORKERS_RATIO = 4, /* 1/4 of busy can be idle */
94 IDLE_WORKER_TIMEOUT = 300 * HZ, /* keep idle ones for 5 mins */
95
96 MAYDAY_INITIAL_TIMEOUT = HZ / 100 >= 2 ? HZ / 100 : 2,
97 /* call for help after 10ms
98 (min two ticks) */
99 MAYDAY_INTERVAL = HZ / 10, /* and then every 100ms */
100 CREATE_COOLDOWN = HZ, /* time to breath after fail */
101
102 /*
103 * Rescue workers are used only on emergencies and shared by
104 * all cpus. Give MIN_NICE.
105 */
106 RESCUER_NICE_LEVEL = MIN_NICE,
107 HIGHPRI_NICE_LEVEL = MIN_NICE,
108
109 WQ_NAME_LEN = 24,
110};
111
112/*
113 * Structure fields follow one of the following exclusion rules.
114 *
115 * I: Modifiable by initialization/destruction paths and read-only for
116 * everyone else.
117 *
118 * P: Preemption protected. Disabling preemption is enough and should
119 * only be modified and accessed from the local cpu.
120 *
121 * L: pool->lock protected. Access with pool->lock held.
122 *
123 * X: During normal operation, modification requires pool->lock and should
124 * be done only from local cpu. Either disabling preemption on local
125 * cpu or grabbing pool->lock is enough for read access. If
126 * POOL_DISASSOCIATED is set, it's identical to L.
127 *
128 * A: wq_pool_attach_mutex protected.
129 *
130 * PL: wq_pool_mutex protected.
131 *
132 * PR: wq_pool_mutex protected for writes. RCU protected for reads.
133 *
134 * PW: wq_pool_mutex and wq->mutex protected for writes. Either for reads.
135 *
136 * PWR: wq_pool_mutex and wq->mutex protected for writes. Either or
137 * RCU for reads.
138 *
139 * WQ: wq->mutex protected.
140 *
141 * WR: wq->mutex protected for writes. RCU protected for reads.
142 *
143 * MD: wq_mayday_lock protected.
144 */
145
146/* struct worker is defined in workqueue_internal.h */
147
148struct worker_pool {
149 raw_spinlock_t lock; /* the pool lock */
150 int cpu; /* I: the associated cpu */
151 int node; /* I: the associated node ID */
152 int id; /* I: pool ID */
153 unsigned int flags; /* X: flags */
154
155 unsigned long watchdog_ts; /* L: watchdog timestamp */
156
157 /*
158 * The counter is incremented in a process context on the associated CPU
159 * w/ preemption disabled, and decremented or reset in the same context
160 * but w/ pool->lock held. The readers grab pool->lock and are
161 * guaranteed to see if the counter reached zero.
162 */
163 int nr_running;
164
165 struct list_head worklist; /* L: list of pending works */
166
167 int nr_workers; /* L: total number of workers */
168 int nr_idle; /* L: currently idle workers */
169
170 struct list_head idle_list; /* L: list of idle workers */
171 struct timer_list idle_timer; /* L: worker idle timeout */
172 struct timer_list mayday_timer; /* L: SOS timer for workers */
173
174 /* a workers is either on busy_hash or idle_list, or the manager */
175 DECLARE_HASHTABLE(busy_hash, BUSY_WORKER_HASH_ORDER);
176 /* L: hash of busy workers */
177
178 struct worker *manager; /* L: purely informational */
179 struct list_head workers; /* A: attached workers */
180 struct completion *detach_completion; /* all workers detached */
181
182 struct ida worker_ida; /* worker IDs for task name */
183
184 struct workqueue_attrs *attrs; /* I: worker attributes */
185 struct hlist_node hash_node; /* PL: unbound_pool_hash node */
186 int refcnt; /* PL: refcnt for unbound pools */
187
188 /*
189 * Destruction of pool is RCU protected to allow dereferences
190 * from get_work_pool().
191 */
192 struct rcu_head rcu;
193};
194
195/*
196 * The per-pool workqueue. While queued, the lower WORK_STRUCT_FLAG_BITS
197 * of work_struct->data are used for flags and the remaining high bits
198 * point to the pwq; thus, pwqs need to be aligned at two's power of the
199 * number of flag bits.
200 */
201struct pool_workqueue {
202 struct worker_pool *pool; /* I: the associated pool */
203 struct workqueue_struct *wq; /* I: the owning workqueue */
204 int work_color; /* L: current color */
205 int flush_color; /* L: flushing color */
206 int refcnt; /* L: reference count */
207 int nr_in_flight[WORK_NR_COLORS];
208 /* L: nr of in_flight works */
209
210 /*
211 * nr_active management and WORK_STRUCT_INACTIVE:
212 *
213 * When pwq->nr_active >= max_active, new work item is queued to
214 * pwq->inactive_works instead of pool->worklist and marked with
215 * WORK_STRUCT_INACTIVE.
216 *
217 * All work items marked with WORK_STRUCT_INACTIVE do not participate
218 * in pwq->nr_active and all work items in pwq->inactive_works are
219 * marked with WORK_STRUCT_INACTIVE. But not all WORK_STRUCT_INACTIVE
220 * work items are in pwq->inactive_works. Some of them are ready to
221 * run in pool->worklist or worker->scheduled. Those work itmes are
222 * only struct wq_barrier which is used for flush_work() and should
223 * not participate in pwq->nr_active. For non-barrier work item, it
224 * is marked with WORK_STRUCT_INACTIVE iff it is in pwq->inactive_works.
225 */
226 int nr_active; /* L: nr of active works */
227 int max_active; /* L: max active works */
228 struct list_head inactive_works; /* L: inactive works */
229 struct list_head pwqs_node; /* WR: node on wq->pwqs */
230 struct list_head mayday_node; /* MD: node on wq->maydays */
231
232 /*
233 * Release of unbound pwq is punted to system_wq. See put_pwq()
234 * and pwq_unbound_release_workfn() for details. pool_workqueue
235 * itself is also RCU protected so that the first pwq can be
236 * determined without grabbing wq->mutex.
237 */
238 struct work_struct unbound_release_work;
239 struct rcu_head rcu;
240} __aligned(1 << WORK_STRUCT_FLAG_BITS);
241
242/*
243 * Structure used to wait for workqueue flush.
244 */
245struct wq_flusher {
246 struct list_head list; /* WQ: list of flushers */
247 int flush_color; /* WQ: flush color waiting for */
248 struct completion done; /* flush completion */
249};
250
251struct wq_device;
252
253/*
254 * The externally visible workqueue. It relays the issued work items to
255 * the appropriate worker_pool through its pool_workqueues.
256 */
257struct workqueue_struct {
258 struct list_head pwqs; /* WR: all pwqs of this wq */
259 struct list_head list; /* PR: list of all workqueues */
260
261 struct mutex mutex; /* protects this wq */
262 int work_color; /* WQ: current work color */
263 int flush_color; /* WQ: current flush color */
264 atomic_t nr_pwqs_to_flush; /* flush in progress */
265 struct wq_flusher *first_flusher; /* WQ: first flusher */
266 struct list_head flusher_queue; /* WQ: flush waiters */
267 struct list_head flusher_overflow; /* WQ: flush overflow list */
268
269 struct list_head maydays; /* MD: pwqs requesting rescue */
270 struct worker *rescuer; /* MD: rescue worker */
271
272 int nr_drainers; /* WQ: drain in progress */
273 int saved_max_active; /* WQ: saved pwq max_active */
274
275 struct workqueue_attrs *unbound_attrs; /* PW: only for unbound wqs */
276 struct pool_workqueue *dfl_pwq; /* PW: only for unbound wqs */
277
278#ifdef CONFIG_SYSFS
279 struct wq_device *wq_dev; /* I: for sysfs interface */
280#endif
281#ifdef CONFIG_LOCKDEP
282 char *lock_name;
283 struct lock_class_key key;
284 struct lockdep_map lockdep_map;
285#endif
286 char name[WQ_NAME_LEN]; /* I: workqueue name */
287
288 /*
289 * Destruction of workqueue_struct is RCU protected to allow walking
290 * the workqueues list without grabbing wq_pool_mutex.
291 * This is used to dump all workqueues from sysrq.
292 */
293 struct rcu_head rcu;
294
295 /* hot fields used during command issue, aligned to cacheline */
296 unsigned int flags ____cacheline_aligned; /* WQ: WQ_* flags */
297 struct pool_workqueue __percpu *cpu_pwqs; /* I: per-cpu pwqs */
298 struct pool_workqueue __rcu *numa_pwq_tbl[]; /* PWR: unbound pwqs indexed by node */
299};
300
301static struct kmem_cache *pwq_cache;
302
303static cpumask_var_t *wq_numa_possible_cpumask;
304 /* possible CPUs of each node */
305
306static bool wq_disable_numa;
307module_param_named(disable_numa, wq_disable_numa, bool, 0444);
308
309/* see the comment above the definition of WQ_POWER_EFFICIENT */
310static bool wq_power_efficient = IS_ENABLED(CONFIG_WQ_POWER_EFFICIENT_DEFAULT);
311module_param_named(power_efficient, wq_power_efficient, bool, 0444);
312
313static bool wq_online; /* can kworkers be created yet? */
314
315static bool wq_numa_enabled; /* unbound NUMA affinity enabled */
316
317/* buf for wq_update_unbound_numa_attrs(), protected by CPU hotplug exclusion */
318static struct workqueue_attrs *wq_update_unbound_numa_attrs_buf;
319
320static DEFINE_MUTEX(wq_pool_mutex); /* protects pools and workqueues list */
321static DEFINE_MUTEX(wq_pool_attach_mutex); /* protects worker attach/detach */
322static DEFINE_RAW_SPINLOCK(wq_mayday_lock); /* protects wq->maydays list */
323/* wait for manager to go away */
324static struct rcuwait manager_wait = __RCUWAIT_INITIALIZER(manager_wait);
325
326static LIST_HEAD(workqueues); /* PR: list of all workqueues */
327static bool workqueue_freezing; /* PL: have wqs started freezing? */
328
329/* PL: allowable cpus for unbound wqs and work items */
330static cpumask_var_t wq_unbound_cpumask;
331
332/* CPU where unbound work was last round robin scheduled from this CPU */
333static DEFINE_PER_CPU(int, wq_rr_cpu_last);
334
335/*
336 * Local execution of unbound work items is no longer guaranteed. The
337 * following always forces round-robin CPU selection on unbound work items
338 * to uncover usages which depend on it.
339 */
340#ifdef CONFIG_DEBUG_WQ_FORCE_RR_CPU
341static bool wq_debug_force_rr_cpu = true;
342#else
343static bool wq_debug_force_rr_cpu = false;
344#endif
345module_param_named(debug_force_rr_cpu, wq_debug_force_rr_cpu, bool, 0644);
346
347/* the per-cpu worker pools */
348static DEFINE_PER_CPU_SHARED_ALIGNED(struct worker_pool [NR_STD_WORKER_POOLS], cpu_worker_pools);
349
350static DEFINE_IDR(worker_pool_idr); /* PR: idr of all pools */
351
352/* PL: hash of all unbound pools keyed by pool->attrs */
353static DEFINE_HASHTABLE(unbound_pool_hash, UNBOUND_POOL_HASH_ORDER);
354
355/* I: attributes used when instantiating standard unbound pools on demand */
356static struct workqueue_attrs *unbound_std_wq_attrs[NR_STD_WORKER_POOLS];
357
358/* I: attributes used when instantiating ordered pools on demand */
359static struct workqueue_attrs *ordered_wq_attrs[NR_STD_WORKER_POOLS];
360
361struct workqueue_struct *system_wq __read_mostly;
362EXPORT_SYMBOL(system_wq);
363struct workqueue_struct *system_highpri_wq __read_mostly;
364EXPORT_SYMBOL_GPL(system_highpri_wq);
365struct workqueue_struct *system_long_wq __read_mostly;
366EXPORT_SYMBOL_GPL(system_long_wq);
367struct workqueue_struct *system_unbound_wq __read_mostly;
368EXPORT_SYMBOL_GPL(system_unbound_wq);
369struct workqueue_struct *system_freezable_wq __read_mostly;
370EXPORT_SYMBOL_GPL(system_freezable_wq);
371struct workqueue_struct *system_power_efficient_wq __read_mostly;
372EXPORT_SYMBOL_GPL(system_power_efficient_wq);
373struct workqueue_struct *system_freezable_power_efficient_wq __read_mostly;
374EXPORT_SYMBOL_GPL(system_freezable_power_efficient_wq);
375
376static int worker_thread(void *__worker);
377static void workqueue_sysfs_unregister(struct workqueue_struct *wq);
378static void show_pwq(struct pool_workqueue *pwq);
379static void show_one_worker_pool(struct worker_pool *pool);
380
381#define CREATE_TRACE_POINTS
382#include <trace/events/workqueue.h>
383
384#define assert_rcu_or_pool_mutex() \
385 RCU_LOCKDEP_WARN(!rcu_read_lock_held() && \
386 !lockdep_is_held(&wq_pool_mutex), \
387 "RCU or wq_pool_mutex should be held")
388
389#define assert_rcu_or_wq_mutex_or_pool_mutex(wq) \
390 RCU_LOCKDEP_WARN(!rcu_read_lock_held() && \
391 !lockdep_is_held(&wq->mutex) && \
392 !lockdep_is_held(&wq_pool_mutex), \
393 "RCU, wq->mutex or wq_pool_mutex should be held")
394
395#define for_each_cpu_worker_pool(pool, cpu) \
396 for ((pool) = &per_cpu(cpu_worker_pools, cpu)[0]; \
397 (pool) < &per_cpu(cpu_worker_pools, cpu)[NR_STD_WORKER_POOLS]; \
398 (pool)++)
399
400/**
401 * for_each_pool - iterate through all worker_pools in the system
402 * @pool: iteration cursor
403 * @pi: integer used for iteration
404 *
405 * This must be called either with wq_pool_mutex held or RCU read
406 * locked. If the pool needs to be used beyond the locking in effect, the
407 * caller is responsible for guaranteeing that the pool stays online.
408 *
409 * The if/else clause exists only for the lockdep assertion and can be
410 * ignored.
411 */
412#define for_each_pool(pool, pi) \
413 idr_for_each_entry(&worker_pool_idr, pool, pi) \
414 if (({ assert_rcu_or_pool_mutex(); false; })) { } \
415 else
416
417/**
418 * for_each_pool_worker - iterate through all workers of a worker_pool
419 * @worker: iteration cursor
420 * @pool: worker_pool to iterate workers of
421 *
422 * This must be called with wq_pool_attach_mutex.
423 *
424 * The if/else clause exists only for the lockdep assertion and can be
425 * ignored.
426 */
427#define for_each_pool_worker(worker, pool) \
428 list_for_each_entry((worker), &(pool)->workers, node) \
429 if (({ lockdep_assert_held(&wq_pool_attach_mutex); false; })) { } \
430 else
431
432/**
433 * for_each_pwq - iterate through all pool_workqueues of the specified workqueue
434 * @pwq: iteration cursor
435 * @wq: the target workqueue
436 *
437 * This must be called either with wq->mutex held or RCU read locked.
438 * If the pwq needs to be used beyond the locking in effect, the caller is
439 * responsible for guaranteeing that the pwq stays online.
440 *
441 * The if/else clause exists only for the lockdep assertion and can be
442 * ignored.
443 */
444#define for_each_pwq(pwq, wq) \
445 list_for_each_entry_rcu((pwq), &(wq)->pwqs, pwqs_node, \
446 lockdep_is_held(&(wq->mutex)))
447
448#ifdef CONFIG_DEBUG_OBJECTS_WORK
449
450static const struct debug_obj_descr work_debug_descr;
451
452static void *work_debug_hint(void *addr)
453{
454 return ((struct work_struct *) addr)->func;
455}
456
457static bool work_is_static_object(void *addr)
458{
459 struct work_struct *work = addr;
460
461 return test_bit(WORK_STRUCT_STATIC_BIT, work_data_bits(work));
462}
463
464/*
465 * fixup_init is called when:
466 * - an active object is initialized
467 */
468static bool work_fixup_init(void *addr, enum debug_obj_state state)
469{
470 struct work_struct *work = addr;
471
472 switch (state) {
473 case ODEBUG_STATE_ACTIVE:
474 cancel_work_sync(work);
475 debug_object_init(work, &work_debug_descr);
476 return true;
477 default:
478 return false;
479 }
480}
481
482/*
483 * fixup_free is called when:
484 * - an active object is freed
485 */
486static bool work_fixup_free(void *addr, enum debug_obj_state state)
487{
488 struct work_struct *work = addr;
489
490 switch (state) {
491 case ODEBUG_STATE_ACTIVE:
492 cancel_work_sync(work);
493 debug_object_free(work, &work_debug_descr);
494 return true;
495 default:
496 return false;
497 }
498}
499
500static const struct debug_obj_descr work_debug_descr = {
501 .name = "work_struct",
502 .debug_hint = work_debug_hint,
503 .is_static_object = work_is_static_object,
504 .fixup_init = work_fixup_init,
505 .fixup_free = work_fixup_free,
506};
507
508static inline void debug_work_activate(struct work_struct *work)
509{
510 debug_object_activate(work, &work_debug_descr);
511}
512
513static inline void debug_work_deactivate(struct work_struct *work)
514{
515 debug_object_deactivate(work, &work_debug_descr);
516}
517
518void __init_work(struct work_struct *work, int onstack)
519{
520 if (onstack)
521 debug_object_init_on_stack(work, &work_debug_descr);
522 else
523 debug_object_init(work, &work_debug_descr);
524}
525EXPORT_SYMBOL_GPL(__init_work);
526
527void destroy_work_on_stack(struct work_struct *work)
528{
529 debug_object_free(work, &work_debug_descr);
530}
531EXPORT_SYMBOL_GPL(destroy_work_on_stack);
532
533void destroy_delayed_work_on_stack(struct delayed_work *work)
534{
535 destroy_timer_on_stack(&work->timer);
536 debug_object_free(&work->work, &work_debug_descr);
537}
538EXPORT_SYMBOL_GPL(destroy_delayed_work_on_stack);
539
540#else
541static inline void debug_work_activate(struct work_struct *work) { }
542static inline void debug_work_deactivate(struct work_struct *work) { }
543#endif
544
545/**
546 * worker_pool_assign_id - allocate ID and assign it to @pool
547 * @pool: the pool pointer of interest
548 *
549 * Returns 0 if ID in [0, WORK_OFFQ_POOL_NONE) is allocated and assigned
550 * successfully, -errno on failure.
551 */
552static int worker_pool_assign_id(struct worker_pool *pool)
553{
554 int ret;
555
556 lockdep_assert_held(&wq_pool_mutex);
557
558 ret = idr_alloc(&worker_pool_idr, pool, 0, WORK_OFFQ_POOL_NONE,
559 GFP_KERNEL);
560 if (ret >= 0) {
561 pool->id = ret;
562 return 0;
563 }
564 return ret;
565}
566
567/**
568 * unbound_pwq_by_node - return the unbound pool_workqueue for the given node
569 * @wq: the target workqueue
570 * @node: the node ID
571 *
572 * This must be called with any of wq_pool_mutex, wq->mutex or RCU
573 * read locked.
574 * If the pwq needs to be used beyond the locking in effect, the caller is
575 * responsible for guaranteeing that the pwq stays online.
576 *
577 * Return: The unbound pool_workqueue for @node.
578 */
579static struct pool_workqueue *unbound_pwq_by_node(struct workqueue_struct *wq,
580 int node)
581{
582 assert_rcu_or_wq_mutex_or_pool_mutex(wq);
583
584 /*
585 * XXX: @node can be NUMA_NO_NODE if CPU goes offline while a
586 * delayed item is pending. The plan is to keep CPU -> NODE
587 * mapping valid and stable across CPU on/offlines. Once that
588 * happens, this workaround can be removed.
589 */
590 if (unlikely(node == NUMA_NO_NODE))
591 return wq->dfl_pwq;
592
593 return rcu_dereference_raw(wq->numa_pwq_tbl[node]);
594}
595
596static unsigned int work_color_to_flags(int color)
597{
598 return color << WORK_STRUCT_COLOR_SHIFT;
599}
600
601static int get_work_color(unsigned long work_data)
602{
603 return (work_data >> WORK_STRUCT_COLOR_SHIFT) &
604 ((1 << WORK_STRUCT_COLOR_BITS) - 1);
605}
606
607static int work_next_color(int color)
608{
609 return (color + 1) % WORK_NR_COLORS;
610}
611
612/*
613 * While queued, %WORK_STRUCT_PWQ is set and non flag bits of a work's data
614 * contain the pointer to the queued pwq. Once execution starts, the flag
615 * is cleared and the high bits contain OFFQ flags and pool ID.
616 *
617 * set_work_pwq(), set_work_pool_and_clear_pending(), mark_work_canceling()
618 * and clear_work_data() can be used to set the pwq, pool or clear
619 * work->data. These functions should only be called while the work is
620 * owned - ie. while the PENDING bit is set.
621 *
622 * get_work_pool() and get_work_pwq() can be used to obtain the pool or pwq
623 * corresponding to a work. Pool is available once the work has been
624 * queued anywhere after initialization until it is sync canceled. pwq is
625 * available only while the work item is queued.
626 *
627 * %WORK_OFFQ_CANCELING is used to mark a work item which is being
628 * canceled. While being canceled, a work item may have its PENDING set
629 * but stay off timer and worklist for arbitrarily long and nobody should
630 * try to steal the PENDING bit.
631 */
632static inline void set_work_data(struct work_struct *work, unsigned long data,
633 unsigned long flags)
634{
635 WARN_ON_ONCE(!work_pending(work));
636 atomic_long_set(&work->data, data | flags | work_static(work));
637}
638
639static void set_work_pwq(struct work_struct *work, struct pool_workqueue *pwq,
640 unsigned long extra_flags)
641{
642 set_work_data(work, (unsigned long)pwq,
643 WORK_STRUCT_PENDING | WORK_STRUCT_PWQ | extra_flags);
644}
645
646static void set_work_pool_and_keep_pending(struct work_struct *work,
647 int pool_id)
648{
649 set_work_data(work, (unsigned long)pool_id << WORK_OFFQ_POOL_SHIFT,
650 WORK_STRUCT_PENDING);
651}
652
653static void set_work_pool_and_clear_pending(struct work_struct *work,
654 int pool_id)
655{
656 /*
657 * The following wmb is paired with the implied mb in
658 * test_and_set_bit(PENDING) and ensures all updates to @work made
659 * here are visible to and precede any updates by the next PENDING
660 * owner.
661 */
662 smp_wmb();
663 set_work_data(work, (unsigned long)pool_id << WORK_OFFQ_POOL_SHIFT, 0);
664 /*
665 * The following mb guarantees that previous clear of a PENDING bit
666 * will not be reordered with any speculative LOADS or STORES from
667 * work->current_func, which is executed afterwards. This possible
668 * reordering can lead to a missed execution on attempt to queue
669 * the same @work. E.g. consider this case:
670 *
671 * CPU#0 CPU#1
672 * ---------------------------- --------------------------------
673 *
674 * 1 STORE event_indicated
675 * 2 queue_work_on() {
676 * 3 test_and_set_bit(PENDING)
677 * 4 } set_..._and_clear_pending() {
678 * 5 set_work_data() # clear bit
679 * 6 smp_mb()
680 * 7 work->current_func() {
681 * 8 LOAD event_indicated
682 * }
683 *
684 * Without an explicit full barrier speculative LOAD on line 8 can
685 * be executed before CPU#0 does STORE on line 1. If that happens,
686 * CPU#0 observes the PENDING bit is still set and new execution of
687 * a @work is not queued in a hope, that CPU#1 will eventually
688 * finish the queued @work. Meanwhile CPU#1 does not see
689 * event_indicated is set, because speculative LOAD was executed
690 * before actual STORE.
691 */
692 smp_mb();
693}
694
695static void clear_work_data(struct work_struct *work)
696{
697 smp_wmb(); /* see set_work_pool_and_clear_pending() */
698 set_work_data(work, WORK_STRUCT_NO_POOL, 0);
699}
700
701static struct pool_workqueue *get_work_pwq(struct work_struct *work)
702{
703 unsigned long data = atomic_long_read(&work->data);
704
705 if (data & WORK_STRUCT_PWQ)
706 return (void *)(data & WORK_STRUCT_WQ_DATA_MASK);
707 else
708 return NULL;
709}
710
711/**
712 * get_work_pool - return the worker_pool a given work was associated with
713 * @work: the work item of interest
714 *
715 * Pools are created and destroyed under wq_pool_mutex, and allows read
716 * access under RCU read lock. As such, this function should be
717 * called under wq_pool_mutex or inside of a rcu_read_lock() region.
718 *
719 * All fields of the returned pool are accessible as long as the above
720 * mentioned locking is in effect. If the returned pool needs to be used
721 * beyond the critical section, the caller is responsible for ensuring the
722 * returned pool is and stays online.
723 *
724 * Return: The worker_pool @work was last associated with. %NULL if none.
725 */
726static struct worker_pool *get_work_pool(struct work_struct *work)
727{
728 unsigned long data = atomic_long_read(&work->data);
729 int pool_id;
730
731 assert_rcu_or_pool_mutex();
732
733 if (data & WORK_STRUCT_PWQ)
734 return ((struct pool_workqueue *)
735 (data & WORK_STRUCT_WQ_DATA_MASK))->pool;
736
737 pool_id = data >> WORK_OFFQ_POOL_SHIFT;
738 if (pool_id == WORK_OFFQ_POOL_NONE)
739 return NULL;
740
741 return idr_find(&worker_pool_idr, pool_id);
742}
743
744/**
745 * get_work_pool_id - return the worker pool ID a given work is associated with
746 * @work: the work item of interest
747 *
748 * Return: The worker_pool ID @work was last associated with.
749 * %WORK_OFFQ_POOL_NONE if none.
750 */
751static int get_work_pool_id(struct work_struct *work)
752{
753 unsigned long data = atomic_long_read(&work->data);
754
755 if (data & WORK_STRUCT_PWQ)
756 return ((struct pool_workqueue *)
757 (data & WORK_STRUCT_WQ_DATA_MASK))->pool->id;
758
759 return data >> WORK_OFFQ_POOL_SHIFT;
760}
761
762static void mark_work_canceling(struct work_struct *work)
763{
764 unsigned long pool_id = get_work_pool_id(work);
765
766 pool_id <<= WORK_OFFQ_POOL_SHIFT;
767 set_work_data(work, pool_id | WORK_OFFQ_CANCELING, WORK_STRUCT_PENDING);
768}
769
770static bool work_is_canceling(struct work_struct *work)
771{
772 unsigned long data = atomic_long_read(&work->data);
773
774 return !(data & WORK_STRUCT_PWQ) && (data & WORK_OFFQ_CANCELING);
775}
776
777/*
778 * Policy functions. These define the policies on how the global worker
779 * pools are managed. Unless noted otherwise, these functions assume that
780 * they're being called with pool->lock held.
781 */
782
783static bool __need_more_worker(struct worker_pool *pool)
784{
785 return !pool->nr_running;
786}
787
788/*
789 * Need to wake up a worker? Called from anything but currently
790 * running workers.
791 *
792 * Note that, because unbound workers never contribute to nr_running, this
793 * function will always return %true for unbound pools as long as the
794 * worklist isn't empty.
795 */
796static bool need_more_worker(struct worker_pool *pool)
797{
798 return !list_empty(&pool->worklist) && __need_more_worker(pool);
799}
800
801/* Can I start working? Called from busy but !running workers. */
802static bool may_start_working(struct worker_pool *pool)
803{
804 return pool->nr_idle;
805}
806
807/* Do I need to keep working? Called from currently running workers. */
808static bool keep_working(struct worker_pool *pool)
809{
810 return !list_empty(&pool->worklist) && (pool->nr_running <= 1);
811}
812
813/* Do we need a new worker? Called from manager. */
814static bool need_to_create_worker(struct worker_pool *pool)
815{
816 return need_more_worker(pool) && !may_start_working(pool);
817}
818
819/* Do we have too many workers and should some go away? */
820static bool too_many_workers(struct worker_pool *pool)
821{
822 bool managing = pool->flags & POOL_MANAGER_ACTIVE;
823 int nr_idle = pool->nr_idle + managing; /* manager is considered idle */
824 int nr_busy = pool->nr_workers - nr_idle;
825
826 return nr_idle > 2 && (nr_idle - 2) * MAX_IDLE_WORKERS_RATIO >= nr_busy;
827}
828
829/*
830 * Wake up functions.
831 */
832
833/* Return the first idle worker. Called with pool->lock held. */
834static struct worker *first_idle_worker(struct worker_pool *pool)
835{
836 if (unlikely(list_empty(&pool->idle_list)))
837 return NULL;
838
839 return list_first_entry(&pool->idle_list, struct worker, entry);
840}
841
842/**
843 * wake_up_worker - wake up an idle worker
844 * @pool: worker pool to wake worker from
845 *
846 * Wake up the first idle worker of @pool.
847 *
848 * CONTEXT:
849 * raw_spin_lock_irq(pool->lock).
850 */
851static void wake_up_worker(struct worker_pool *pool)
852{
853 struct worker *worker = first_idle_worker(pool);
854
855 if (likely(worker))
856 wake_up_process(worker->task);
857}
858
859/**
860 * wq_worker_running - a worker is running again
861 * @task: task waking up
862 *
863 * This function is called when a worker returns from schedule()
864 */
865void wq_worker_running(struct task_struct *task)
866{
867 struct worker *worker = kthread_data(task);
868
869 if (!worker->sleeping)
870 return;
871
872 /*
873 * If preempted by unbind_workers() between the WORKER_NOT_RUNNING check
874 * and the nr_running increment below, we may ruin the nr_running reset
875 * and leave with an unexpected pool->nr_running == 1 on the newly unbound
876 * pool. Protect against such race.
877 */
878 preempt_disable();
879 if (!(worker->flags & WORKER_NOT_RUNNING))
880 worker->pool->nr_running++;
881 preempt_enable();
882 worker->sleeping = 0;
883}
884
885/**
886 * wq_worker_sleeping - a worker is going to sleep
887 * @task: task going to sleep
888 *
889 * This function is called from schedule() when a busy worker is
890 * going to sleep.
891 */
892void wq_worker_sleeping(struct task_struct *task)
893{
894 struct worker *worker = kthread_data(task);
895 struct worker_pool *pool;
896
897 /*
898 * Rescuers, which may not have all the fields set up like normal
899 * workers, also reach here, let's not access anything before
900 * checking NOT_RUNNING.
901 */
902 if (worker->flags & WORKER_NOT_RUNNING)
903 return;
904
905 pool = worker->pool;
906
907 /* Return if preempted before wq_worker_running() was reached */
908 if (worker->sleeping)
909 return;
910
911 worker->sleeping = 1;
912 raw_spin_lock_irq(&pool->lock);
913
914 /*
915 * Recheck in case unbind_workers() preempted us. We don't
916 * want to decrement nr_running after the worker is unbound
917 * and nr_running has been reset.
918 */
919 if (worker->flags & WORKER_NOT_RUNNING) {
920 raw_spin_unlock_irq(&pool->lock);
921 return;
922 }
923
924 pool->nr_running--;
925 if (need_more_worker(pool))
926 wake_up_worker(pool);
927 raw_spin_unlock_irq(&pool->lock);
928}
929
930/**
931 * wq_worker_last_func - retrieve worker's last work function
932 * @task: Task to retrieve last work function of.
933 *
934 * Determine the last function a worker executed. This is called from
935 * the scheduler to get a worker's last known identity.
936 *
937 * CONTEXT:
938 * raw_spin_lock_irq(rq->lock)
939 *
940 * This function is called during schedule() when a kworker is going
941 * to sleep. It's used by psi to identify aggregation workers during
942 * dequeuing, to allow periodic aggregation to shut-off when that
943 * worker is the last task in the system or cgroup to go to sleep.
944 *
945 * As this function doesn't involve any workqueue-related locking, it
946 * only returns stable values when called from inside the scheduler's
947 * queuing and dequeuing paths, when @task, which must be a kworker,
948 * is guaranteed to not be processing any works.
949 *
950 * Return:
951 * The last work function %current executed as a worker, NULL if it
952 * hasn't executed any work yet.
953 */
954work_func_t wq_worker_last_func(struct task_struct *task)
955{
956 struct worker *worker = kthread_data(task);
957
958 return worker->last_func;
959}
960
961/**
962 * worker_set_flags - set worker flags and adjust nr_running accordingly
963 * @worker: self
964 * @flags: flags to set
965 *
966 * Set @flags in @worker->flags and adjust nr_running accordingly.
967 *
968 * CONTEXT:
969 * raw_spin_lock_irq(pool->lock)
970 */
971static inline void worker_set_flags(struct worker *worker, unsigned int flags)
972{
973 struct worker_pool *pool = worker->pool;
974
975 WARN_ON_ONCE(worker->task != current);
976
977 /* If transitioning into NOT_RUNNING, adjust nr_running. */
978 if ((flags & WORKER_NOT_RUNNING) &&
979 !(worker->flags & WORKER_NOT_RUNNING)) {
980 pool->nr_running--;
981 }
982
983 worker->flags |= flags;
984}
985
986/**
987 * worker_clr_flags - clear worker flags and adjust nr_running accordingly
988 * @worker: self
989 * @flags: flags to clear
990 *
991 * Clear @flags in @worker->flags and adjust nr_running accordingly.
992 *
993 * CONTEXT:
994 * raw_spin_lock_irq(pool->lock)
995 */
996static inline void worker_clr_flags(struct worker *worker, unsigned int flags)
997{
998 struct worker_pool *pool = worker->pool;
999 unsigned int oflags = worker->flags;
1000
1001 WARN_ON_ONCE(worker->task != current);
1002
1003 worker->flags &= ~flags;
1004
1005 /*
1006 * If transitioning out of NOT_RUNNING, increment nr_running. Note
1007 * that the nested NOT_RUNNING is not a noop. NOT_RUNNING is mask
1008 * of multiple flags, not a single flag.
1009 */
1010 if ((flags & WORKER_NOT_RUNNING) && (oflags & WORKER_NOT_RUNNING))
1011 if (!(worker->flags & WORKER_NOT_RUNNING))
1012 pool->nr_running++;
1013}
1014
1015/**
1016 * find_worker_executing_work - find worker which is executing a work
1017 * @pool: pool of interest
1018 * @work: work to find worker for
1019 *
1020 * Find a worker which is executing @work on @pool by searching
1021 * @pool->busy_hash which is keyed by the address of @work. For a worker
1022 * to match, its current execution should match the address of @work and
1023 * its work function. This is to avoid unwanted dependency between
1024 * unrelated work executions through a work item being recycled while still
1025 * being executed.
1026 *
1027 * This is a bit tricky. A work item may be freed once its execution
1028 * starts and nothing prevents the freed area from being recycled for
1029 * another work item. If the same work item address ends up being reused
1030 * before the original execution finishes, workqueue will identify the
1031 * recycled work item as currently executing and make it wait until the
1032 * current execution finishes, introducing an unwanted dependency.
1033 *
1034 * This function checks the work item address and work function to avoid
1035 * false positives. Note that this isn't complete as one may construct a
1036 * work function which can introduce dependency onto itself through a
1037 * recycled work item. Well, if somebody wants to shoot oneself in the
1038 * foot that badly, there's only so much we can do, and if such deadlock
1039 * actually occurs, it should be easy to locate the culprit work function.
1040 *
1041 * CONTEXT:
1042 * raw_spin_lock_irq(pool->lock).
1043 *
1044 * Return:
1045 * Pointer to worker which is executing @work if found, %NULL
1046 * otherwise.
1047 */
1048static struct worker *find_worker_executing_work(struct worker_pool *pool,
1049 struct work_struct *work)
1050{
1051 struct worker *worker;
1052
1053 hash_for_each_possible(pool->busy_hash, worker, hentry,
1054 (unsigned long)work)
1055 if (worker->current_work == work &&
1056 worker->current_func == work->func)
1057 return worker;
1058
1059 return NULL;
1060}
1061
1062/**
1063 * move_linked_works - move linked works to a list
1064 * @work: start of series of works to be scheduled
1065 * @head: target list to append @work to
1066 * @nextp: out parameter for nested worklist walking
1067 *
1068 * Schedule linked works starting from @work to @head. Work series to
1069 * be scheduled starts at @work and includes any consecutive work with
1070 * WORK_STRUCT_LINKED set in its predecessor.
1071 *
1072 * If @nextp is not NULL, it's updated to point to the next work of
1073 * the last scheduled work. This allows move_linked_works() to be
1074 * nested inside outer list_for_each_entry_safe().
1075 *
1076 * CONTEXT:
1077 * raw_spin_lock_irq(pool->lock).
1078 */
1079static void move_linked_works(struct work_struct *work, struct list_head *head,
1080 struct work_struct **nextp)
1081{
1082 struct work_struct *n;
1083
1084 /*
1085 * Linked worklist will always end before the end of the list,
1086 * use NULL for list head.
1087 */
1088 list_for_each_entry_safe_from(work, n, NULL, entry) {
1089 list_move_tail(&work->entry, head);
1090 if (!(*work_data_bits(work) & WORK_STRUCT_LINKED))
1091 break;
1092 }
1093
1094 /*
1095 * If we're already inside safe list traversal and have moved
1096 * multiple works to the scheduled queue, the next position
1097 * needs to be updated.
1098 */
1099 if (nextp)
1100 *nextp = n;
1101}
1102
1103/**
1104 * get_pwq - get an extra reference on the specified pool_workqueue
1105 * @pwq: pool_workqueue to get
1106 *
1107 * Obtain an extra reference on @pwq. The caller should guarantee that
1108 * @pwq has positive refcnt and be holding the matching pool->lock.
1109 */
1110static void get_pwq(struct pool_workqueue *pwq)
1111{
1112 lockdep_assert_held(&pwq->pool->lock);
1113 WARN_ON_ONCE(pwq->refcnt <= 0);
1114 pwq->refcnt++;
1115}
1116
1117/**
1118 * put_pwq - put a pool_workqueue reference
1119 * @pwq: pool_workqueue to put
1120 *
1121 * Drop a reference of @pwq. If its refcnt reaches zero, schedule its
1122 * destruction. The caller should be holding the matching pool->lock.
1123 */
1124static void put_pwq(struct pool_workqueue *pwq)
1125{
1126 lockdep_assert_held(&pwq->pool->lock);
1127 if (likely(--pwq->refcnt))
1128 return;
1129 if (WARN_ON_ONCE(!(pwq->wq->flags & WQ_UNBOUND)))
1130 return;
1131 /*
1132 * @pwq can't be released under pool->lock, bounce to
1133 * pwq_unbound_release_workfn(). This never recurses on the same
1134 * pool->lock as this path is taken only for unbound workqueues and
1135 * the release work item is scheduled on a per-cpu workqueue. To
1136 * avoid lockdep warning, unbound pool->locks are given lockdep
1137 * subclass of 1 in get_unbound_pool().
1138 */
1139 schedule_work(&pwq->unbound_release_work);
1140}
1141
1142/**
1143 * put_pwq_unlocked - put_pwq() with surrounding pool lock/unlock
1144 * @pwq: pool_workqueue to put (can be %NULL)
1145 *
1146 * put_pwq() with locking. This function also allows %NULL @pwq.
1147 */
1148static void put_pwq_unlocked(struct pool_workqueue *pwq)
1149{
1150 if (pwq) {
1151 /*
1152 * As both pwqs and pools are RCU protected, the
1153 * following lock operations are safe.
1154 */
1155 raw_spin_lock_irq(&pwq->pool->lock);
1156 put_pwq(pwq);
1157 raw_spin_unlock_irq(&pwq->pool->lock);
1158 }
1159}
1160
1161static void pwq_activate_inactive_work(struct work_struct *work)
1162{
1163 struct pool_workqueue *pwq = get_work_pwq(work);
1164
1165 trace_workqueue_activate_work(work);
1166 if (list_empty(&pwq->pool->worklist))
1167 pwq->pool->watchdog_ts = jiffies;
1168 move_linked_works(work, &pwq->pool->worklist, NULL);
1169 __clear_bit(WORK_STRUCT_INACTIVE_BIT, work_data_bits(work));
1170 pwq->nr_active++;
1171}
1172
1173static void pwq_activate_first_inactive(struct pool_workqueue *pwq)
1174{
1175 struct work_struct *work = list_first_entry(&pwq->inactive_works,
1176 struct work_struct, entry);
1177
1178 pwq_activate_inactive_work(work);
1179}
1180
1181/**
1182 * pwq_dec_nr_in_flight - decrement pwq's nr_in_flight
1183 * @pwq: pwq of interest
1184 * @work_data: work_data of work which left the queue
1185 *
1186 * A work either has completed or is removed from pending queue,
1187 * decrement nr_in_flight of its pwq and handle workqueue flushing.
1188 *
1189 * CONTEXT:
1190 * raw_spin_lock_irq(pool->lock).
1191 */
1192static void pwq_dec_nr_in_flight(struct pool_workqueue *pwq, unsigned long work_data)
1193{
1194 int color = get_work_color(work_data);
1195
1196 if (!(work_data & WORK_STRUCT_INACTIVE)) {
1197 pwq->nr_active--;
1198 if (!list_empty(&pwq->inactive_works)) {
1199 /* one down, submit an inactive one */
1200 if (pwq->nr_active < pwq->max_active)
1201 pwq_activate_first_inactive(pwq);
1202 }
1203 }
1204
1205 pwq->nr_in_flight[color]--;
1206
1207 /* is flush in progress and are we at the flushing tip? */
1208 if (likely(pwq->flush_color != color))
1209 goto out_put;
1210
1211 /* are there still in-flight works? */
1212 if (pwq->nr_in_flight[color])
1213 goto out_put;
1214
1215 /* this pwq is done, clear flush_color */
1216 pwq->flush_color = -1;
1217
1218 /*
1219 * If this was the last pwq, wake up the first flusher. It
1220 * will handle the rest.
1221 */
1222 if (atomic_dec_and_test(&pwq->wq->nr_pwqs_to_flush))
1223 complete(&pwq->wq->first_flusher->done);
1224out_put:
1225 put_pwq(pwq);
1226}
1227
1228/**
1229 * try_to_grab_pending - steal work item from worklist and disable irq
1230 * @work: work item to steal
1231 * @is_dwork: @work is a delayed_work
1232 * @flags: place to store irq state
1233 *
1234 * Try to grab PENDING bit of @work. This function can handle @work in any
1235 * stable state - idle, on timer or on worklist.
1236 *
1237 * Return:
1238 *
1239 * ======== ================================================================
1240 * 1 if @work was pending and we successfully stole PENDING
1241 * 0 if @work was idle and we claimed PENDING
1242 * -EAGAIN if PENDING couldn't be grabbed at the moment, safe to busy-retry
1243 * -ENOENT if someone else is canceling @work, this state may persist
1244 * for arbitrarily long
1245 * ======== ================================================================
1246 *
1247 * Note:
1248 * On >= 0 return, the caller owns @work's PENDING bit. To avoid getting
1249 * interrupted while holding PENDING and @work off queue, irq must be
1250 * disabled on entry. This, combined with delayed_work->timer being
1251 * irqsafe, ensures that we return -EAGAIN for finite short period of time.
1252 *
1253 * On successful return, >= 0, irq is disabled and the caller is
1254 * responsible for releasing it using local_irq_restore(*@flags).
1255 *
1256 * This function is safe to call from any context including IRQ handler.
1257 */
1258static int try_to_grab_pending(struct work_struct *work, bool is_dwork,
1259 unsigned long *flags)
1260{
1261 struct worker_pool *pool;
1262 struct pool_workqueue *pwq;
1263
1264 local_irq_save(*flags);
1265
1266 /* try to steal the timer if it exists */
1267 if (is_dwork) {
1268 struct delayed_work *dwork = to_delayed_work(work);
1269
1270 /*
1271 * dwork->timer is irqsafe. If del_timer() fails, it's
1272 * guaranteed that the timer is not queued anywhere and not
1273 * running on the local CPU.
1274 */
1275 if (likely(del_timer(&dwork->timer)))
1276 return 1;
1277 }
1278
1279 /* try to claim PENDING the normal way */
1280 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work)))
1281 return 0;
1282
1283 rcu_read_lock();
1284 /*
1285 * The queueing is in progress, or it is already queued. Try to
1286 * steal it from ->worklist without clearing WORK_STRUCT_PENDING.
1287 */
1288 pool = get_work_pool(work);
1289 if (!pool)
1290 goto fail;
1291
1292 raw_spin_lock(&pool->lock);
1293 /*
1294 * work->data is guaranteed to point to pwq only while the work
1295 * item is queued on pwq->wq, and both updating work->data to point
1296 * to pwq on queueing and to pool on dequeueing are done under
1297 * pwq->pool->lock. This in turn guarantees that, if work->data
1298 * points to pwq which is associated with a locked pool, the work
1299 * item is currently queued on that pool.
1300 */
1301 pwq = get_work_pwq(work);
1302 if (pwq && pwq->pool == pool) {
1303 debug_work_deactivate(work);
1304
1305 /*
1306 * A cancelable inactive work item must be in the
1307 * pwq->inactive_works since a queued barrier can't be
1308 * canceled (see the comments in insert_wq_barrier()).
1309 *
1310 * An inactive work item cannot be grabbed directly because
1311 * it might have linked barrier work items which, if left
1312 * on the inactive_works list, will confuse pwq->nr_active
1313 * management later on and cause stall. Make sure the work
1314 * item is activated before grabbing.
1315 */
1316 if (*work_data_bits(work) & WORK_STRUCT_INACTIVE)
1317 pwq_activate_inactive_work(work);
1318
1319 list_del_init(&work->entry);
1320 pwq_dec_nr_in_flight(pwq, *work_data_bits(work));
1321
1322 /* work->data points to pwq iff queued, point to pool */
1323 set_work_pool_and_keep_pending(work, pool->id);
1324
1325 raw_spin_unlock(&pool->lock);
1326 rcu_read_unlock();
1327 return 1;
1328 }
1329 raw_spin_unlock(&pool->lock);
1330fail:
1331 rcu_read_unlock();
1332 local_irq_restore(*flags);
1333 if (work_is_canceling(work))
1334 return -ENOENT;
1335 cpu_relax();
1336 return -EAGAIN;
1337}
1338
1339/**
1340 * insert_work - insert a work into a pool
1341 * @pwq: pwq @work belongs to
1342 * @work: work to insert
1343 * @head: insertion point
1344 * @extra_flags: extra WORK_STRUCT_* flags to set
1345 *
1346 * Insert @work which belongs to @pwq after @head. @extra_flags is or'd to
1347 * work_struct flags.
1348 *
1349 * CONTEXT:
1350 * raw_spin_lock_irq(pool->lock).
1351 */
1352static void insert_work(struct pool_workqueue *pwq, struct work_struct *work,
1353 struct list_head *head, unsigned int extra_flags)
1354{
1355 struct worker_pool *pool = pwq->pool;
1356
1357 /* record the work call stack in order to print it in KASAN reports */
1358 kasan_record_aux_stack_noalloc(work);
1359
1360 /* we own @work, set data and link */
1361 set_work_pwq(work, pwq, extra_flags);
1362 list_add_tail(&work->entry, head);
1363 get_pwq(pwq);
1364
1365 if (__need_more_worker(pool))
1366 wake_up_worker(pool);
1367}
1368
1369/*
1370 * Test whether @work is being queued from another work executing on the
1371 * same workqueue.
1372 */
1373static bool is_chained_work(struct workqueue_struct *wq)
1374{
1375 struct worker *worker;
1376
1377 worker = current_wq_worker();
1378 /*
1379 * Return %true iff I'm a worker executing a work item on @wq. If
1380 * I'm @worker, it's safe to dereference it without locking.
1381 */
1382 return worker && worker->current_pwq->wq == wq;
1383}
1384
1385/*
1386 * When queueing an unbound work item to a wq, prefer local CPU if allowed
1387 * by wq_unbound_cpumask. Otherwise, round robin among the allowed ones to
1388 * avoid perturbing sensitive tasks.
1389 */
1390static int wq_select_unbound_cpu(int cpu)
1391{
1392 static bool printed_dbg_warning;
1393 int new_cpu;
1394
1395 if (likely(!wq_debug_force_rr_cpu)) {
1396 if (cpumask_test_cpu(cpu, wq_unbound_cpumask))
1397 return cpu;
1398 } else if (!printed_dbg_warning) {
1399 pr_warn("workqueue: round-robin CPU selection forced, expect performance impact\n");
1400 printed_dbg_warning = true;
1401 }
1402
1403 if (cpumask_empty(wq_unbound_cpumask))
1404 return cpu;
1405
1406 new_cpu = __this_cpu_read(wq_rr_cpu_last);
1407 new_cpu = cpumask_next_and(new_cpu, wq_unbound_cpumask, cpu_online_mask);
1408 if (unlikely(new_cpu >= nr_cpu_ids)) {
1409 new_cpu = cpumask_first_and(wq_unbound_cpumask, cpu_online_mask);
1410 if (unlikely(new_cpu >= nr_cpu_ids))
1411 return cpu;
1412 }
1413 __this_cpu_write(wq_rr_cpu_last, new_cpu);
1414
1415 return new_cpu;
1416}
1417
1418static void __queue_work(int cpu, struct workqueue_struct *wq,
1419 struct work_struct *work)
1420{
1421 struct pool_workqueue *pwq;
1422 struct worker_pool *last_pool;
1423 struct list_head *worklist;
1424 unsigned int work_flags;
1425 unsigned int req_cpu = cpu;
1426
1427 /*
1428 * While a work item is PENDING && off queue, a task trying to
1429 * steal the PENDING will busy-loop waiting for it to either get
1430 * queued or lose PENDING. Grabbing PENDING and queueing should
1431 * happen with IRQ disabled.
1432 */
1433 lockdep_assert_irqs_disabled();
1434
1435
1436 /* if draining, only works from the same workqueue are allowed */
1437 if (unlikely(wq->flags & __WQ_DRAINING) &&
1438 WARN_ON_ONCE(!is_chained_work(wq)))
1439 return;
1440 rcu_read_lock();
1441retry:
1442 /* pwq which will be used unless @work is executing elsewhere */
1443 if (wq->flags & WQ_UNBOUND) {
1444 if (req_cpu == WORK_CPU_UNBOUND)
1445 cpu = wq_select_unbound_cpu(raw_smp_processor_id());
1446 pwq = unbound_pwq_by_node(wq, cpu_to_node(cpu));
1447 } else {
1448 if (req_cpu == WORK_CPU_UNBOUND)
1449 cpu = raw_smp_processor_id();
1450 pwq = per_cpu_ptr(wq->cpu_pwqs, cpu);
1451 }
1452
1453 /*
1454 * If @work was previously on a different pool, it might still be
1455 * running there, in which case the work needs to be queued on that
1456 * pool to guarantee non-reentrancy.
1457 */
1458 last_pool = get_work_pool(work);
1459 if (last_pool && last_pool != pwq->pool) {
1460 struct worker *worker;
1461
1462 raw_spin_lock(&last_pool->lock);
1463
1464 worker = find_worker_executing_work(last_pool, work);
1465
1466 if (worker && worker->current_pwq->wq == wq) {
1467 pwq = worker->current_pwq;
1468 } else {
1469 /* meh... not running there, queue here */
1470 raw_spin_unlock(&last_pool->lock);
1471 raw_spin_lock(&pwq->pool->lock);
1472 }
1473 } else {
1474 raw_spin_lock(&pwq->pool->lock);
1475 }
1476
1477 /*
1478 * pwq is determined and locked. For unbound pools, we could have
1479 * raced with pwq release and it could already be dead. If its
1480 * refcnt is zero, repeat pwq selection. Note that pwqs never die
1481 * without another pwq replacing it in the numa_pwq_tbl or while
1482 * work items are executing on it, so the retrying is guaranteed to
1483 * make forward-progress.
1484 */
1485 if (unlikely(!pwq->refcnt)) {
1486 if (wq->flags & WQ_UNBOUND) {
1487 raw_spin_unlock(&pwq->pool->lock);
1488 cpu_relax();
1489 goto retry;
1490 }
1491 /* oops */
1492 WARN_ONCE(true, "workqueue: per-cpu pwq for %s on cpu%d has 0 refcnt",
1493 wq->name, cpu);
1494 }
1495
1496 /* pwq determined, queue */
1497 trace_workqueue_queue_work(req_cpu, pwq, work);
1498
1499 if (WARN_ON(!list_empty(&work->entry)))
1500 goto out;
1501
1502 pwq->nr_in_flight[pwq->work_color]++;
1503 work_flags = work_color_to_flags(pwq->work_color);
1504
1505 if (likely(pwq->nr_active < pwq->max_active)) {
1506 trace_workqueue_activate_work(work);
1507 pwq->nr_active++;
1508 worklist = &pwq->pool->worklist;
1509 if (list_empty(worklist))
1510 pwq->pool->watchdog_ts = jiffies;
1511 } else {
1512 work_flags |= WORK_STRUCT_INACTIVE;
1513 worklist = &pwq->inactive_works;
1514 }
1515
1516 debug_work_activate(work);
1517 insert_work(pwq, work, worklist, work_flags);
1518
1519out:
1520 raw_spin_unlock(&pwq->pool->lock);
1521 rcu_read_unlock();
1522}
1523
1524/**
1525 * queue_work_on - queue work on specific cpu
1526 * @cpu: CPU number to execute work on
1527 * @wq: workqueue to use
1528 * @work: work to queue
1529 *
1530 * We queue the work to a specific CPU, the caller must ensure it
1531 * can't go away. Callers that fail to ensure that the specified
1532 * CPU cannot go away will execute on a randomly chosen CPU.
1533 *
1534 * Return: %false if @work was already on a queue, %true otherwise.
1535 */
1536bool queue_work_on(int cpu, struct workqueue_struct *wq,
1537 struct work_struct *work)
1538{
1539 bool ret = false;
1540 unsigned long flags;
1541
1542 local_irq_save(flags);
1543
1544 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1545 __queue_work(cpu, wq, work);
1546 ret = true;
1547 }
1548
1549 local_irq_restore(flags);
1550 return ret;
1551}
1552EXPORT_SYMBOL(queue_work_on);
1553
1554/**
1555 * workqueue_select_cpu_near - Select a CPU based on NUMA node
1556 * @node: NUMA node ID that we want to select a CPU from
1557 *
1558 * This function will attempt to find a "random" cpu available on a given
1559 * node. If there are no CPUs available on the given node it will return
1560 * WORK_CPU_UNBOUND indicating that we should just schedule to any
1561 * available CPU if we need to schedule this work.
1562 */
1563static int workqueue_select_cpu_near(int node)
1564{
1565 int cpu;
1566
1567 /* No point in doing this if NUMA isn't enabled for workqueues */
1568 if (!wq_numa_enabled)
1569 return WORK_CPU_UNBOUND;
1570
1571 /* Delay binding to CPU if node is not valid or online */
1572 if (node < 0 || node >= MAX_NUMNODES || !node_online(node))
1573 return WORK_CPU_UNBOUND;
1574
1575 /* Use local node/cpu if we are already there */
1576 cpu = raw_smp_processor_id();
1577 if (node == cpu_to_node(cpu))
1578 return cpu;
1579
1580 /* Use "random" otherwise know as "first" online CPU of node */
1581 cpu = cpumask_any_and(cpumask_of_node(node), cpu_online_mask);
1582
1583 /* If CPU is valid return that, otherwise just defer */
1584 return cpu < nr_cpu_ids ? cpu : WORK_CPU_UNBOUND;
1585}
1586
1587/**
1588 * queue_work_node - queue work on a "random" cpu for a given NUMA node
1589 * @node: NUMA node that we are targeting the work for
1590 * @wq: workqueue to use
1591 * @work: work to queue
1592 *
1593 * We queue the work to a "random" CPU within a given NUMA node. The basic
1594 * idea here is to provide a way to somehow associate work with a given
1595 * NUMA node.
1596 *
1597 * This function will only make a best effort attempt at getting this onto
1598 * the right NUMA node. If no node is requested or the requested node is
1599 * offline then we just fall back to standard queue_work behavior.
1600 *
1601 * Currently the "random" CPU ends up being the first available CPU in the
1602 * intersection of cpu_online_mask and the cpumask of the node, unless we
1603 * are running on the node. In that case we just use the current CPU.
1604 *
1605 * Return: %false if @work was already on a queue, %true otherwise.
1606 */
1607bool queue_work_node(int node, struct workqueue_struct *wq,
1608 struct work_struct *work)
1609{
1610 unsigned long flags;
1611 bool ret = false;
1612
1613 /*
1614 * This current implementation is specific to unbound workqueues.
1615 * Specifically we only return the first available CPU for a given
1616 * node instead of cycling through individual CPUs within the node.
1617 *
1618 * If this is used with a per-cpu workqueue then the logic in
1619 * workqueue_select_cpu_near would need to be updated to allow for
1620 * some round robin type logic.
1621 */
1622 WARN_ON_ONCE(!(wq->flags & WQ_UNBOUND));
1623
1624 local_irq_save(flags);
1625
1626 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1627 int cpu = workqueue_select_cpu_near(node);
1628
1629 __queue_work(cpu, wq, work);
1630 ret = true;
1631 }
1632
1633 local_irq_restore(flags);
1634 return ret;
1635}
1636EXPORT_SYMBOL_GPL(queue_work_node);
1637
1638void delayed_work_timer_fn(struct timer_list *t)
1639{
1640 struct delayed_work *dwork = from_timer(dwork, t, timer);
1641
1642 /* should have been called from irqsafe timer with irq already off */
1643 __queue_work(dwork->cpu, dwork->wq, &dwork->work);
1644}
1645EXPORT_SYMBOL(delayed_work_timer_fn);
1646
1647static void __queue_delayed_work(int cpu, struct workqueue_struct *wq,
1648 struct delayed_work *dwork, unsigned long delay)
1649{
1650 struct timer_list *timer = &dwork->timer;
1651 struct work_struct *work = &dwork->work;
1652
1653 WARN_ON_ONCE(!wq);
1654 WARN_ON_ONCE(timer->function != delayed_work_timer_fn);
1655 WARN_ON_ONCE(timer_pending(timer));
1656 WARN_ON_ONCE(!list_empty(&work->entry));
1657
1658 /*
1659 * If @delay is 0, queue @dwork->work immediately. This is for
1660 * both optimization and correctness. The earliest @timer can
1661 * expire is on the closest next tick and delayed_work users depend
1662 * on that there's no such delay when @delay is 0.
1663 */
1664 if (!delay) {
1665 __queue_work(cpu, wq, &dwork->work);
1666 return;
1667 }
1668
1669 dwork->wq = wq;
1670 dwork->cpu = cpu;
1671 timer->expires = jiffies + delay;
1672
1673 if (unlikely(cpu != WORK_CPU_UNBOUND))
1674 add_timer_on(timer, cpu);
1675 else
1676 add_timer(timer);
1677}
1678
1679/**
1680 * queue_delayed_work_on - queue work on specific CPU after delay
1681 * @cpu: CPU number to execute work on
1682 * @wq: workqueue to use
1683 * @dwork: work to queue
1684 * @delay: number of jiffies to wait before queueing
1685 *
1686 * Return: %false if @work was already on a queue, %true otherwise. If
1687 * @delay is zero and @dwork is idle, it will be scheduled for immediate
1688 * execution.
1689 */
1690bool queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
1691 struct delayed_work *dwork, unsigned long delay)
1692{
1693 struct work_struct *work = &dwork->work;
1694 bool ret = false;
1695 unsigned long flags;
1696
1697 /* read the comment in __queue_work() */
1698 local_irq_save(flags);
1699
1700 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1701 __queue_delayed_work(cpu, wq, dwork, delay);
1702 ret = true;
1703 }
1704
1705 local_irq_restore(flags);
1706 return ret;
1707}
1708EXPORT_SYMBOL(queue_delayed_work_on);
1709
1710/**
1711 * mod_delayed_work_on - modify delay of or queue a delayed work on specific CPU
1712 * @cpu: CPU number to execute work on
1713 * @wq: workqueue to use
1714 * @dwork: work to queue
1715 * @delay: number of jiffies to wait before queueing
1716 *
1717 * If @dwork is idle, equivalent to queue_delayed_work_on(); otherwise,
1718 * modify @dwork's timer so that it expires after @delay. If @delay is
1719 * zero, @work is guaranteed to be scheduled immediately regardless of its
1720 * current state.
1721 *
1722 * Return: %false if @dwork was idle and queued, %true if @dwork was
1723 * pending and its timer was modified.
1724 *
1725 * This function is safe to call from any context including IRQ handler.
1726 * See try_to_grab_pending() for details.
1727 */
1728bool mod_delayed_work_on(int cpu, struct workqueue_struct *wq,
1729 struct delayed_work *dwork, unsigned long delay)
1730{
1731 unsigned long flags;
1732 int ret;
1733
1734 do {
1735 ret = try_to_grab_pending(&dwork->work, true, &flags);
1736 } while (unlikely(ret == -EAGAIN));
1737
1738 if (likely(ret >= 0)) {
1739 __queue_delayed_work(cpu, wq, dwork, delay);
1740 local_irq_restore(flags);
1741 }
1742
1743 /* -ENOENT from try_to_grab_pending() becomes %true */
1744 return ret;
1745}
1746EXPORT_SYMBOL_GPL(mod_delayed_work_on);
1747
1748static void rcu_work_rcufn(struct rcu_head *rcu)
1749{
1750 struct rcu_work *rwork = container_of(rcu, struct rcu_work, rcu);
1751
1752 /* read the comment in __queue_work() */
1753 local_irq_disable();
1754 __queue_work(WORK_CPU_UNBOUND, rwork->wq, &rwork->work);
1755 local_irq_enable();
1756}
1757
1758/**
1759 * queue_rcu_work - queue work after a RCU grace period
1760 * @wq: workqueue to use
1761 * @rwork: work to queue
1762 *
1763 * Return: %false if @rwork was already pending, %true otherwise. Note
1764 * that a full RCU grace period is guaranteed only after a %true return.
1765 * While @rwork is guaranteed to be executed after a %false return, the
1766 * execution may happen before a full RCU grace period has passed.
1767 */
1768bool queue_rcu_work(struct workqueue_struct *wq, struct rcu_work *rwork)
1769{
1770 struct work_struct *work = &rwork->work;
1771
1772 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1773 rwork->wq = wq;
1774 call_rcu_hurry(&rwork->rcu, rcu_work_rcufn);
1775 return true;
1776 }
1777
1778 return false;
1779}
1780EXPORT_SYMBOL(queue_rcu_work);
1781
1782/**
1783 * worker_enter_idle - enter idle state
1784 * @worker: worker which is entering idle state
1785 *
1786 * @worker is entering idle state. Update stats and idle timer if
1787 * necessary.
1788 *
1789 * LOCKING:
1790 * raw_spin_lock_irq(pool->lock).
1791 */
1792static void worker_enter_idle(struct worker *worker)
1793{
1794 struct worker_pool *pool = worker->pool;
1795
1796 if (WARN_ON_ONCE(worker->flags & WORKER_IDLE) ||
1797 WARN_ON_ONCE(!list_empty(&worker->entry) &&
1798 (worker->hentry.next || worker->hentry.pprev)))
1799 return;
1800
1801 /* can't use worker_set_flags(), also called from create_worker() */
1802 worker->flags |= WORKER_IDLE;
1803 pool->nr_idle++;
1804 worker->last_active = jiffies;
1805
1806 /* idle_list is LIFO */
1807 list_add(&worker->entry, &pool->idle_list);
1808
1809 if (too_many_workers(pool) && !timer_pending(&pool->idle_timer))
1810 mod_timer(&pool->idle_timer, jiffies + IDLE_WORKER_TIMEOUT);
1811
1812 /* Sanity check nr_running. */
1813 WARN_ON_ONCE(pool->nr_workers == pool->nr_idle && pool->nr_running);
1814}
1815
1816/**
1817 * worker_leave_idle - leave idle state
1818 * @worker: worker which is leaving idle state
1819 *
1820 * @worker is leaving idle state. Update stats.
1821 *
1822 * LOCKING:
1823 * raw_spin_lock_irq(pool->lock).
1824 */
1825static void worker_leave_idle(struct worker *worker)
1826{
1827 struct worker_pool *pool = worker->pool;
1828
1829 if (WARN_ON_ONCE(!(worker->flags & WORKER_IDLE)))
1830 return;
1831 worker_clr_flags(worker, WORKER_IDLE);
1832 pool->nr_idle--;
1833 list_del_init(&worker->entry);
1834}
1835
1836static struct worker *alloc_worker(int node)
1837{
1838 struct worker *worker;
1839
1840 worker = kzalloc_node(sizeof(*worker), GFP_KERNEL, node);
1841 if (worker) {
1842 INIT_LIST_HEAD(&worker->entry);
1843 INIT_LIST_HEAD(&worker->scheduled);
1844 INIT_LIST_HEAD(&worker->node);
1845 /* on creation a worker is in !idle && prep state */
1846 worker->flags = WORKER_PREP;
1847 }
1848 return worker;
1849}
1850
1851/**
1852 * worker_attach_to_pool() - attach a worker to a pool
1853 * @worker: worker to be attached
1854 * @pool: the target pool
1855 *
1856 * Attach @worker to @pool. Once attached, the %WORKER_UNBOUND flag and
1857 * cpu-binding of @worker are kept coordinated with the pool across
1858 * cpu-[un]hotplugs.
1859 */
1860static void worker_attach_to_pool(struct worker *worker,
1861 struct worker_pool *pool)
1862{
1863 mutex_lock(&wq_pool_attach_mutex);
1864
1865 /*
1866 * The wq_pool_attach_mutex ensures %POOL_DISASSOCIATED remains
1867 * stable across this function. See the comments above the flag
1868 * definition for details.
1869 */
1870 if (pool->flags & POOL_DISASSOCIATED)
1871 worker->flags |= WORKER_UNBOUND;
1872 else
1873 kthread_set_per_cpu(worker->task, pool->cpu);
1874
1875 if (worker->rescue_wq)
1876 set_cpus_allowed_ptr(worker->task, pool->attrs->cpumask);
1877
1878 list_add_tail(&worker->node, &pool->workers);
1879 worker->pool = pool;
1880
1881 mutex_unlock(&wq_pool_attach_mutex);
1882}
1883
1884/**
1885 * worker_detach_from_pool() - detach a worker from its pool
1886 * @worker: worker which is attached to its pool
1887 *
1888 * Undo the attaching which had been done in worker_attach_to_pool(). The
1889 * caller worker shouldn't access to the pool after detached except it has
1890 * other reference to the pool.
1891 */
1892static void worker_detach_from_pool(struct worker *worker)
1893{
1894 struct worker_pool *pool = worker->pool;
1895 struct completion *detach_completion = NULL;
1896
1897 mutex_lock(&wq_pool_attach_mutex);
1898
1899 kthread_set_per_cpu(worker->task, -1);
1900 list_del(&worker->node);
1901 worker->pool = NULL;
1902
1903 if (list_empty(&pool->workers))
1904 detach_completion = pool->detach_completion;
1905 mutex_unlock(&wq_pool_attach_mutex);
1906
1907 /* clear leftover flags without pool->lock after it is detached */
1908 worker->flags &= ~(WORKER_UNBOUND | WORKER_REBOUND);
1909
1910 if (detach_completion)
1911 complete(detach_completion);
1912}
1913
1914/**
1915 * create_worker - create a new workqueue worker
1916 * @pool: pool the new worker will belong to
1917 *
1918 * Create and start a new worker which is attached to @pool.
1919 *
1920 * CONTEXT:
1921 * Might sleep. Does GFP_KERNEL allocations.
1922 *
1923 * Return:
1924 * Pointer to the newly created worker.
1925 */
1926static struct worker *create_worker(struct worker_pool *pool)
1927{
1928 struct worker *worker;
1929 int id;
1930 char id_buf[16];
1931
1932 /* ID is needed to determine kthread name */
1933 id = ida_alloc(&pool->worker_ida, GFP_KERNEL);
1934 if (id < 0)
1935 return NULL;
1936
1937 worker = alloc_worker(pool->node);
1938 if (!worker)
1939 goto fail;
1940
1941 worker->id = id;
1942
1943 if (pool->cpu >= 0)
1944 snprintf(id_buf, sizeof(id_buf), "%d:%d%s", pool->cpu, id,
1945 pool->attrs->nice < 0 ? "H" : "");
1946 else
1947 snprintf(id_buf, sizeof(id_buf), "u%d:%d", pool->id, id);
1948
1949 worker->task = kthread_create_on_node(worker_thread, worker, pool->node,
1950 "kworker/%s", id_buf);
1951 if (IS_ERR(worker->task))
1952 goto fail;
1953
1954 set_user_nice(worker->task, pool->attrs->nice);
1955 kthread_bind_mask(worker->task, pool->attrs->cpumask);
1956
1957 /* successful, attach the worker to the pool */
1958 worker_attach_to_pool(worker, pool);
1959
1960 /* start the newly created worker */
1961 raw_spin_lock_irq(&pool->lock);
1962 worker->pool->nr_workers++;
1963 worker_enter_idle(worker);
1964 wake_up_process(worker->task);
1965 raw_spin_unlock_irq(&pool->lock);
1966
1967 return worker;
1968
1969fail:
1970 ida_free(&pool->worker_ida, id);
1971 kfree(worker);
1972 return NULL;
1973}
1974
1975/**
1976 * destroy_worker - destroy a workqueue worker
1977 * @worker: worker to be destroyed
1978 *
1979 * Destroy @worker and adjust @pool stats accordingly. The worker should
1980 * be idle.
1981 *
1982 * CONTEXT:
1983 * raw_spin_lock_irq(pool->lock).
1984 */
1985static void destroy_worker(struct worker *worker)
1986{
1987 struct worker_pool *pool = worker->pool;
1988
1989 lockdep_assert_held(&pool->lock);
1990
1991 /* sanity check frenzy */
1992 if (WARN_ON(worker->current_work) ||
1993 WARN_ON(!list_empty(&worker->scheduled)) ||
1994 WARN_ON(!(worker->flags & WORKER_IDLE)))
1995 return;
1996
1997 pool->nr_workers--;
1998 pool->nr_idle--;
1999
2000 list_del_init(&worker->entry);
2001 worker->flags |= WORKER_DIE;
2002 wake_up_process(worker->task);
2003}
2004
2005static void idle_worker_timeout(struct timer_list *t)
2006{
2007 struct worker_pool *pool = from_timer(pool, t, idle_timer);
2008
2009 raw_spin_lock_irq(&pool->lock);
2010
2011 while (too_many_workers(pool)) {
2012 struct worker *worker;
2013 unsigned long expires;
2014
2015 /* idle_list is kept in LIFO order, check the last one */
2016 worker = list_entry(pool->idle_list.prev, struct worker, entry);
2017 expires = worker->last_active + IDLE_WORKER_TIMEOUT;
2018
2019 if (time_before(jiffies, expires)) {
2020 mod_timer(&pool->idle_timer, expires);
2021 break;
2022 }
2023
2024 destroy_worker(worker);
2025 }
2026
2027 raw_spin_unlock_irq(&pool->lock);
2028}
2029
2030static void send_mayday(struct work_struct *work)
2031{
2032 struct pool_workqueue *pwq = get_work_pwq(work);
2033 struct workqueue_struct *wq = pwq->wq;
2034
2035 lockdep_assert_held(&wq_mayday_lock);
2036
2037 if (!wq->rescuer)
2038 return;
2039
2040 /* mayday mayday mayday */
2041 if (list_empty(&pwq->mayday_node)) {
2042 /*
2043 * If @pwq is for an unbound wq, its base ref may be put at
2044 * any time due to an attribute change. Pin @pwq until the
2045 * rescuer is done with it.
2046 */
2047 get_pwq(pwq);
2048 list_add_tail(&pwq->mayday_node, &wq->maydays);
2049 wake_up_process(wq->rescuer->task);
2050 }
2051}
2052
2053static void pool_mayday_timeout(struct timer_list *t)
2054{
2055 struct worker_pool *pool = from_timer(pool, t, mayday_timer);
2056 struct work_struct *work;
2057
2058 raw_spin_lock_irq(&pool->lock);
2059 raw_spin_lock(&wq_mayday_lock); /* for wq->maydays */
2060
2061 if (need_to_create_worker(pool)) {
2062 /*
2063 * We've been trying to create a new worker but
2064 * haven't been successful. We might be hitting an
2065 * allocation deadlock. Send distress signals to
2066 * rescuers.
2067 */
2068 list_for_each_entry(work, &pool->worklist, entry)
2069 send_mayday(work);
2070 }
2071
2072 raw_spin_unlock(&wq_mayday_lock);
2073 raw_spin_unlock_irq(&pool->lock);
2074
2075 mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INTERVAL);
2076}
2077
2078/**
2079 * maybe_create_worker - create a new worker if necessary
2080 * @pool: pool to create a new worker for
2081 *
2082 * Create a new worker for @pool if necessary. @pool is guaranteed to
2083 * have at least one idle worker on return from this function. If
2084 * creating a new worker takes longer than MAYDAY_INTERVAL, mayday is
2085 * sent to all rescuers with works scheduled on @pool to resolve
2086 * possible allocation deadlock.
2087 *
2088 * On return, need_to_create_worker() is guaranteed to be %false and
2089 * may_start_working() %true.
2090 *
2091 * LOCKING:
2092 * raw_spin_lock_irq(pool->lock) which may be released and regrabbed
2093 * multiple times. Does GFP_KERNEL allocations. Called only from
2094 * manager.
2095 */
2096static void maybe_create_worker(struct worker_pool *pool)
2097__releases(&pool->lock)
2098__acquires(&pool->lock)
2099{
2100restart:
2101 raw_spin_unlock_irq(&pool->lock);
2102
2103 /* if we don't make progress in MAYDAY_INITIAL_TIMEOUT, call for help */
2104 mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INITIAL_TIMEOUT);
2105
2106 while (true) {
2107 if (create_worker(pool) || !need_to_create_worker(pool))
2108 break;
2109
2110 schedule_timeout_interruptible(CREATE_COOLDOWN);
2111
2112 if (!need_to_create_worker(pool))
2113 break;
2114 }
2115
2116 del_timer_sync(&pool->mayday_timer);
2117 raw_spin_lock_irq(&pool->lock);
2118 /*
2119 * This is necessary even after a new worker was just successfully
2120 * created as @pool->lock was dropped and the new worker might have
2121 * already become busy.
2122 */
2123 if (need_to_create_worker(pool))
2124 goto restart;
2125}
2126
2127/**
2128 * manage_workers - manage worker pool
2129 * @worker: self
2130 *
2131 * Assume the manager role and manage the worker pool @worker belongs
2132 * to. At any given time, there can be only zero or one manager per
2133 * pool. The exclusion is handled automatically by this function.
2134 *
2135 * The caller can safely start processing works on false return. On
2136 * true return, it's guaranteed that need_to_create_worker() is false
2137 * and may_start_working() is true.
2138 *
2139 * CONTEXT:
2140 * raw_spin_lock_irq(pool->lock) which may be released and regrabbed
2141 * multiple times. Does GFP_KERNEL allocations.
2142 *
2143 * Return:
2144 * %false if the pool doesn't need management and the caller can safely
2145 * start processing works, %true if management function was performed and
2146 * the conditions that the caller verified before calling the function may
2147 * no longer be true.
2148 */
2149static bool manage_workers(struct worker *worker)
2150{
2151 struct worker_pool *pool = worker->pool;
2152
2153 if (pool->flags & POOL_MANAGER_ACTIVE)
2154 return false;
2155
2156 pool->flags |= POOL_MANAGER_ACTIVE;
2157 pool->manager = worker;
2158
2159 maybe_create_worker(pool);
2160
2161 pool->manager = NULL;
2162 pool->flags &= ~POOL_MANAGER_ACTIVE;
2163 rcuwait_wake_up(&manager_wait);
2164 return true;
2165}
2166
2167/**
2168 * process_one_work - process single work
2169 * @worker: self
2170 * @work: work to process
2171 *
2172 * Process @work. This function contains all the logics necessary to
2173 * process a single work including synchronization against and
2174 * interaction with other workers on the same cpu, queueing and
2175 * flushing. As long as context requirement is met, any worker can
2176 * call this function to process a work.
2177 *
2178 * CONTEXT:
2179 * raw_spin_lock_irq(pool->lock) which is released and regrabbed.
2180 */
2181static void process_one_work(struct worker *worker, struct work_struct *work)
2182__releases(&pool->lock)
2183__acquires(&pool->lock)
2184{
2185 struct pool_workqueue *pwq = get_work_pwq(work);
2186 struct worker_pool *pool = worker->pool;
2187 bool cpu_intensive = pwq->wq->flags & WQ_CPU_INTENSIVE;
2188 unsigned long work_data;
2189 struct worker *collision;
2190#ifdef CONFIG_LOCKDEP
2191 /*
2192 * It is permissible to free the struct work_struct from
2193 * inside the function that is called from it, this we need to
2194 * take into account for lockdep too. To avoid bogus "held
2195 * lock freed" warnings as well as problems when looking into
2196 * work->lockdep_map, make a copy and use that here.
2197 */
2198 struct lockdep_map lockdep_map;
2199
2200 lockdep_copy_map(&lockdep_map, &work->lockdep_map);
2201#endif
2202 /* ensure we're on the correct CPU */
2203 WARN_ON_ONCE(!(pool->flags & POOL_DISASSOCIATED) &&
2204 raw_smp_processor_id() != pool->cpu);
2205
2206 /*
2207 * A single work shouldn't be executed concurrently by
2208 * multiple workers on a single cpu. Check whether anyone is
2209 * already processing the work. If so, defer the work to the
2210 * currently executing one.
2211 */
2212 collision = find_worker_executing_work(pool, work);
2213 if (unlikely(collision)) {
2214 move_linked_works(work, &collision->scheduled, NULL);
2215 return;
2216 }
2217
2218 /* claim and dequeue */
2219 debug_work_deactivate(work);
2220 hash_add(pool->busy_hash, &worker->hentry, (unsigned long)work);
2221 worker->current_work = work;
2222 worker->current_func = work->func;
2223 worker->current_pwq = pwq;
2224 work_data = *work_data_bits(work);
2225 worker->current_color = get_work_color(work_data);
2226
2227 /*
2228 * Record wq name for cmdline and debug reporting, may get
2229 * overridden through set_worker_desc().
2230 */
2231 strscpy(worker->desc, pwq->wq->name, WORKER_DESC_LEN);
2232
2233 list_del_init(&work->entry);
2234
2235 /*
2236 * CPU intensive works don't participate in concurrency management.
2237 * They're the scheduler's responsibility. This takes @worker out
2238 * of concurrency management and the next code block will chain
2239 * execution of the pending work items.
2240 */
2241 if (unlikely(cpu_intensive))
2242 worker_set_flags(worker, WORKER_CPU_INTENSIVE);
2243
2244 /*
2245 * Wake up another worker if necessary. The condition is always
2246 * false for normal per-cpu workers since nr_running would always
2247 * be >= 1 at this point. This is used to chain execution of the
2248 * pending work items for WORKER_NOT_RUNNING workers such as the
2249 * UNBOUND and CPU_INTENSIVE ones.
2250 */
2251 if (need_more_worker(pool))
2252 wake_up_worker(pool);
2253
2254 /*
2255 * Record the last pool and clear PENDING which should be the last
2256 * update to @work. Also, do this inside @pool->lock so that
2257 * PENDING and queued state changes happen together while IRQ is
2258 * disabled.
2259 */
2260 set_work_pool_and_clear_pending(work, pool->id);
2261
2262 raw_spin_unlock_irq(&pool->lock);
2263
2264 lock_map_acquire(&pwq->wq->lockdep_map);
2265 lock_map_acquire(&lockdep_map);
2266 /*
2267 * Strictly speaking we should mark the invariant state without holding
2268 * any locks, that is, before these two lock_map_acquire()'s.
2269 *
2270 * However, that would result in:
2271 *
2272 * A(W1)
2273 * WFC(C)
2274 * A(W1)
2275 * C(C)
2276 *
2277 * Which would create W1->C->W1 dependencies, even though there is no
2278 * actual deadlock possible. There are two solutions, using a
2279 * read-recursive acquire on the work(queue) 'locks', but this will then
2280 * hit the lockdep limitation on recursive locks, or simply discard
2281 * these locks.
2282 *
2283 * AFAICT there is no possible deadlock scenario between the
2284 * flush_work() and complete() primitives (except for single-threaded
2285 * workqueues), so hiding them isn't a problem.
2286 */
2287 lockdep_invariant_state(true);
2288 trace_workqueue_execute_start(work);
2289 worker->current_func(work);
2290 /*
2291 * While we must be careful to not use "work" after this, the trace
2292 * point will only record its address.
2293 */
2294 trace_workqueue_execute_end(work, worker->current_func);
2295 lock_map_release(&lockdep_map);
2296 lock_map_release(&pwq->wq->lockdep_map);
2297
2298 if (unlikely(in_atomic() || lockdep_depth(current) > 0)) {
2299 pr_err("BUG: workqueue leaked lock or atomic: %s/0x%08x/%d\n"
2300 " last function: %ps\n",
2301 current->comm, preempt_count(), task_pid_nr(current),
2302 worker->current_func);
2303 debug_show_held_locks(current);
2304 dump_stack();
2305 }
2306
2307 /*
2308 * The following prevents a kworker from hogging CPU on !PREEMPTION
2309 * kernels, where a requeueing work item waiting for something to
2310 * happen could deadlock with stop_machine as such work item could
2311 * indefinitely requeue itself while all other CPUs are trapped in
2312 * stop_machine. At the same time, report a quiescent RCU state so
2313 * the same condition doesn't freeze RCU.
2314 */
2315 cond_resched();
2316
2317 raw_spin_lock_irq(&pool->lock);
2318
2319 /* clear cpu intensive status */
2320 if (unlikely(cpu_intensive))
2321 worker_clr_flags(worker, WORKER_CPU_INTENSIVE);
2322
2323 /* tag the worker for identification in schedule() */
2324 worker->last_func = worker->current_func;
2325
2326 /* we're done with it, release */
2327 hash_del(&worker->hentry);
2328 worker->current_work = NULL;
2329 worker->current_func = NULL;
2330 worker->current_pwq = NULL;
2331 worker->current_color = INT_MAX;
2332 pwq_dec_nr_in_flight(pwq, work_data);
2333}
2334
2335/**
2336 * process_scheduled_works - process scheduled works
2337 * @worker: self
2338 *
2339 * Process all scheduled works. Please note that the scheduled list
2340 * may change while processing a work, so this function repeatedly
2341 * fetches a work from the top and executes it.
2342 *
2343 * CONTEXT:
2344 * raw_spin_lock_irq(pool->lock) which may be released and regrabbed
2345 * multiple times.
2346 */
2347static void process_scheduled_works(struct worker *worker)
2348{
2349 while (!list_empty(&worker->scheduled)) {
2350 struct work_struct *work = list_first_entry(&worker->scheduled,
2351 struct work_struct, entry);
2352 process_one_work(worker, work);
2353 }
2354}
2355
2356static void set_pf_worker(bool val)
2357{
2358 mutex_lock(&wq_pool_attach_mutex);
2359 if (val)
2360 current->flags |= PF_WQ_WORKER;
2361 else
2362 current->flags &= ~PF_WQ_WORKER;
2363 mutex_unlock(&wq_pool_attach_mutex);
2364}
2365
2366/**
2367 * worker_thread - the worker thread function
2368 * @__worker: self
2369 *
2370 * The worker thread function. All workers belong to a worker_pool -
2371 * either a per-cpu one or dynamic unbound one. These workers process all
2372 * work items regardless of their specific target workqueue. The only
2373 * exception is work items which belong to workqueues with a rescuer which
2374 * will be explained in rescuer_thread().
2375 *
2376 * Return: 0
2377 */
2378static int worker_thread(void *__worker)
2379{
2380 struct worker *worker = __worker;
2381 struct worker_pool *pool = worker->pool;
2382
2383 /* tell the scheduler that this is a workqueue worker */
2384 set_pf_worker(true);
2385woke_up:
2386 raw_spin_lock_irq(&pool->lock);
2387
2388 /* am I supposed to die? */
2389 if (unlikely(worker->flags & WORKER_DIE)) {
2390 raw_spin_unlock_irq(&pool->lock);
2391 WARN_ON_ONCE(!list_empty(&worker->entry));
2392 set_pf_worker(false);
2393
2394 set_task_comm(worker->task, "kworker/dying");
2395 ida_free(&pool->worker_ida, worker->id);
2396 worker_detach_from_pool(worker);
2397 kfree(worker);
2398 return 0;
2399 }
2400
2401 worker_leave_idle(worker);
2402recheck:
2403 /* no more worker necessary? */
2404 if (!need_more_worker(pool))
2405 goto sleep;
2406
2407 /* do we need to manage? */
2408 if (unlikely(!may_start_working(pool)) && manage_workers(worker))
2409 goto recheck;
2410
2411 /*
2412 * ->scheduled list can only be filled while a worker is
2413 * preparing to process a work or actually processing it.
2414 * Make sure nobody diddled with it while I was sleeping.
2415 */
2416 WARN_ON_ONCE(!list_empty(&worker->scheduled));
2417
2418 /*
2419 * Finish PREP stage. We're guaranteed to have at least one idle
2420 * worker or that someone else has already assumed the manager
2421 * role. This is where @worker starts participating in concurrency
2422 * management if applicable and concurrency management is restored
2423 * after being rebound. See rebind_workers() for details.
2424 */
2425 worker_clr_flags(worker, WORKER_PREP | WORKER_REBOUND);
2426
2427 do {
2428 struct work_struct *work =
2429 list_first_entry(&pool->worklist,
2430 struct work_struct, entry);
2431
2432 pool->watchdog_ts = jiffies;
2433
2434 if (likely(!(*work_data_bits(work) & WORK_STRUCT_LINKED))) {
2435 /* optimization path, not strictly necessary */
2436 process_one_work(worker, work);
2437 if (unlikely(!list_empty(&worker->scheduled)))
2438 process_scheduled_works(worker);
2439 } else {
2440 move_linked_works(work, &worker->scheduled, NULL);
2441 process_scheduled_works(worker);
2442 }
2443 } while (keep_working(pool));
2444
2445 worker_set_flags(worker, WORKER_PREP);
2446sleep:
2447 /*
2448 * pool->lock is held and there's no work to process and no need to
2449 * manage, sleep. Workers are woken up only while holding
2450 * pool->lock or from local cpu, so setting the current state
2451 * before releasing pool->lock is enough to prevent losing any
2452 * event.
2453 */
2454 worker_enter_idle(worker);
2455 __set_current_state(TASK_IDLE);
2456 raw_spin_unlock_irq(&pool->lock);
2457 schedule();
2458 goto woke_up;
2459}
2460
2461/**
2462 * rescuer_thread - the rescuer thread function
2463 * @__rescuer: self
2464 *
2465 * Workqueue rescuer thread function. There's one rescuer for each
2466 * workqueue which has WQ_MEM_RECLAIM set.
2467 *
2468 * Regular work processing on a pool may block trying to create a new
2469 * worker which uses GFP_KERNEL allocation which has slight chance of
2470 * developing into deadlock if some works currently on the same queue
2471 * need to be processed to satisfy the GFP_KERNEL allocation. This is
2472 * the problem rescuer solves.
2473 *
2474 * When such condition is possible, the pool summons rescuers of all
2475 * workqueues which have works queued on the pool and let them process
2476 * those works so that forward progress can be guaranteed.
2477 *
2478 * This should happen rarely.
2479 *
2480 * Return: 0
2481 */
2482static int rescuer_thread(void *__rescuer)
2483{
2484 struct worker *rescuer = __rescuer;
2485 struct workqueue_struct *wq = rescuer->rescue_wq;
2486 struct list_head *scheduled = &rescuer->scheduled;
2487 bool should_stop;
2488
2489 set_user_nice(current, RESCUER_NICE_LEVEL);
2490
2491 /*
2492 * Mark rescuer as worker too. As WORKER_PREP is never cleared, it
2493 * doesn't participate in concurrency management.
2494 */
2495 set_pf_worker(true);
2496repeat:
2497 set_current_state(TASK_IDLE);
2498
2499 /*
2500 * By the time the rescuer is requested to stop, the workqueue
2501 * shouldn't have any work pending, but @wq->maydays may still have
2502 * pwq(s) queued. This can happen by non-rescuer workers consuming
2503 * all the work items before the rescuer got to them. Go through
2504 * @wq->maydays processing before acting on should_stop so that the
2505 * list is always empty on exit.
2506 */
2507 should_stop = kthread_should_stop();
2508
2509 /* see whether any pwq is asking for help */
2510 raw_spin_lock_irq(&wq_mayday_lock);
2511
2512 while (!list_empty(&wq->maydays)) {
2513 struct pool_workqueue *pwq = list_first_entry(&wq->maydays,
2514 struct pool_workqueue, mayday_node);
2515 struct worker_pool *pool = pwq->pool;
2516 struct work_struct *work, *n;
2517 bool first = true;
2518
2519 __set_current_state(TASK_RUNNING);
2520 list_del_init(&pwq->mayday_node);
2521
2522 raw_spin_unlock_irq(&wq_mayday_lock);
2523
2524 worker_attach_to_pool(rescuer, pool);
2525
2526 raw_spin_lock_irq(&pool->lock);
2527
2528 /*
2529 * Slurp in all works issued via this workqueue and
2530 * process'em.
2531 */
2532 WARN_ON_ONCE(!list_empty(scheduled));
2533 list_for_each_entry_safe(work, n, &pool->worklist, entry) {
2534 if (get_work_pwq(work) == pwq) {
2535 if (first)
2536 pool->watchdog_ts = jiffies;
2537 move_linked_works(work, scheduled, &n);
2538 }
2539 first = false;
2540 }
2541
2542 if (!list_empty(scheduled)) {
2543 process_scheduled_works(rescuer);
2544
2545 /*
2546 * The above execution of rescued work items could
2547 * have created more to rescue through
2548 * pwq_activate_first_inactive() or chained
2549 * queueing. Let's put @pwq back on mayday list so
2550 * that such back-to-back work items, which may be
2551 * being used to relieve memory pressure, don't
2552 * incur MAYDAY_INTERVAL delay inbetween.
2553 */
2554 if (pwq->nr_active && need_to_create_worker(pool)) {
2555 raw_spin_lock(&wq_mayday_lock);
2556 /*
2557 * Queue iff we aren't racing destruction
2558 * and somebody else hasn't queued it already.
2559 */
2560 if (wq->rescuer && list_empty(&pwq->mayday_node)) {
2561 get_pwq(pwq);
2562 list_add_tail(&pwq->mayday_node, &wq->maydays);
2563 }
2564 raw_spin_unlock(&wq_mayday_lock);
2565 }
2566 }
2567
2568 /*
2569 * Put the reference grabbed by send_mayday(). @pool won't
2570 * go away while we're still attached to it.
2571 */
2572 put_pwq(pwq);
2573
2574 /*
2575 * Leave this pool. If need_more_worker() is %true, notify a
2576 * regular worker; otherwise, we end up with 0 concurrency
2577 * and stalling the execution.
2578 */
2579 if (need_more_worker(pool))
2580 wake_up_worker(pool);
2581
2582 raw_spin_unlock_irq(&pool->lock);
2583
2584 worker_detach_from_pool(rescuer);
2585
2586 raw_spin_lock_irq(&wq_mayday_lock);
2587 }
2588
2589 raw_spin_unlock_irq(&wq_mayday_lock);
2590
2591 if (should_stop) {
2592 __set_current_state(TASK_RUNNING);
2593 set_pf_worker(false);
2594 return 0;
2595 }
2596
2597 /* rescuers should never participate in concurrency management */
2598 WARN_ON_ONCE(!(rescuer->flags & WORKER_NOT_RUNNING));
2599 schedule();
2600 goto repeat;
2601}
2602
2603/**
2604 * check_flush_dependency - check for flush dependency sanity
2605 * @target_wq: workqueue being flushed
2606 * @target_work: work item being flushed (NULL for workqueue flushes)
2607 *
2608 * %current is trying to flush the whole @target_wq or @target_work on it.
2609 * If @target_wq doesn't have %WQ_MEM_RECLAIM, verify that %current is not
2610 * reclaiming memory or running on a workqueue which doesn't have
2611 * %WQ_MEM_RECLAIM as that can break forward-progress guarantee leading to
2612 * a deadlock.
2613 */
2614static void check_flush_dependency(struct workqueue_struct *target_wq,
2615 struct work_struct *target_work)
2616{
2617 work_func_t target_func = target_work ? target_work->func : NULL;
2618 struct worker *worker;
2619
2620 if (target_wq->flags & WQ_MEM_RECLAIM)
2621 return;
2622
2623 worker = current_wq_worker();
2624
2625 WARN_ONCE(current->flags & PF_MEMALLOC,
2626 "workqueue: PF_MEMALLOC task %d(%s) is flushing !WQ_MEM_RECLAIM %s:%ps",
2627 current->pid, current->comm, target_wq->name, target_func);
2628 WARN_ONCE(worker && ((worker->current_pwq->wq->flags &
2629 (WQ_MEM_RECLAIM | __WQ_LEGACY)) == WQ_MEM_RECLAIM),
2630 "workqueue: WQ_MEM_RECLAIM %s:%ps is flushing !WQ_MEM_RECLAIM %s:%ps",
2631 worker->current_pwq->wq->name, worker->current_func,
2632 target_wq->name, target_func);
2633}
2634
2635struct wq_barrier {
2636 struct work_struct work;
2637 struct completion done;
2638 struct task_struct *task; /* purely informational */
2639};
2640
2641static void wq_barrier_func(struct work_struct *work)
2642{
2643 struct wq_barrier *barr = container_of(work, struct wq_barrier, work);
2644 complete(&barr->done);
2645}
2646
2647/**
2648 * insert_wq_barrier - insert a barrier work
2649 * @pwq: pwq to insert barrier into
2650 * @barr: wq_barrier to insert
2651 * @target: target work to attach @barr to
2652 * @worker: worker currently executing @target, NULL if @target is not executing
2653 *
2654 * @barr is linked to @target such that @barr is completed only after
2655 * @target finishes execution. Please note that the ordering
2656 * guarantee is observed only with respect to @target and on the local
2657 * cpu.
2658 *
2659 * Currently, a queued barrier can't be canceled. This is because
2660 * try_to_grab_pending() can't determine whether the work to be
2661 * grabbed is at the head of the queue and thus can't clear LINKED
2662 * flag of the previous work while there must be a valid next work
2663 * after a work with LINKED flag set.
2664 *
2665 * Note that when @worker is non-NULL, @target may be modified
2666 * underneath us, so we can't reliably determine pwq from @target.
2667 *
2668 * CONTEXT:
2669 * raw_spin_lock_irq(pool->lock).
2670 */
2671static void insert_wq_barrier(struct pool_workqueue *pwq,
2672 struct wq_barrier *barr,
2673 struct work_struct *target, struct worker *worker)
2674{
2675 unsigned int work_flags = 0;
2676 unsigned int work_color;
2677 struct list_head *head;
2678
2679 /*
2680 * debugobject calls are safe here even with pool->lock locked
2681 * as we know for sure that this will not trigger any of the
2682 * checks and call back into the fixup functions where we
2683 * might deadlock.
2684 */
2685 INIT_WORK_ONSTACK(&barr->work, wq_barrier_func);
2686 __set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(&barr->work));
2687
2688 init_completion_map(&barr->done, &target->lockdep_map);
2689
2690 barr->task = current;
2691
2692 /* The barrier work item does not participate in pwq->nr_active. */
2693 work_flags |= WORK_STRUCT_INACTIVE;
2694
2695 /*
2696 * If @target is currently being executed, schedule the
2697 * barrier to the worker; otherwise, put it after @target.
2698 */
2699 if (worker) {
2700 head = worker->scheduled.next;
2701 work_color = worker->current_color;
2702 } else {
2703 unsigned long *bits = work_data_bits(target);
2704
2705 head = target->entry.next;
2706 /* there can already be other linked works, inherit and set */
2707 work_flags |= *bits & WORK_STRUCT_LINKED;
2708 work_color = get_work_color(*bits);
2709 __set_bit(WORK_STRUCT_LINKED_BIT, bits);
2710 }
2711
2712 pwq->nr_in_flight[work_color]++;
2713 work_flags |= work_color_to_flags(work_color);
2714
2715 debug_work_activate(&barr->work);
2716 insert_work(pwq, &barr->work, head, work_flags);
2717}
2718
2719/**
2720 * flush_workqueue_prep_pwqs - prepare pwqs for workqueue flushing
2721 * @wq: workqueue being flushed
2722 * @flush_color: new flush color, < 0 for no-op
2723 * @work_color: new work color, < 0 for no-op
2724 *
2725 * Prepare pwqs for workqueue flushing.
2726 *
2727 * If @flush_color is non-negative, flush_color on all pwqs should be
2728 * -1. If no pwq has in-flight commands at the specified color, all
2729 * pwq->flush_color's stay at -1 and %false is returned. If any pwq
2730 * has in flight commands, its pwq->flush_color is set to
2731 * @flush_color, @wq->nr_pwqs_to_flush is updated accordingly, pwq
2732 * wakeup logic is armed and %true is returned.
2733 *
2734 * The caller should have initialized @wq->first_flusher prior to
2735 * calling this function with non-negative @flush_color. If
2736 * @flush_color is negative, no flush color update is done and %false
2737 * is returned.
2738 *
2739 * If @work_color is non-negative, all pwqs should have the same
2740 * work_color which is previous to @work_color and all will be
2741 * advanced to @work_color.
2742 *
2743 * CONTEXT:
2744 * mutex_lock(wq->mutex).
2745 *
2746 * Return:
2747 * %true if @flush_color >= 0 and there's something to flush. %false
2748 * otherwise.
2749 */
2750static bool flush_workqueue_prep_pwqs(struct workqueue_struct *wq,
2751 int flush_color, int work_color)
2752{
2753 bool wait = false;
2754 struct pool_workqueue *pwq;
2755
2756 if (flush_color >= 0) {
2757 WARN_ON_ONCE(atomic_read(&wq->nr_pwqs_to_flush));
2758 atomic_set(&wq->nr_pwqs_to_flush, 1);
2759 }
2760
2761 for_each_pwq(pwq, wq) {
2762 struct worker_pool *pool = pwq->pool;
2763
2764 raw_spin_lock_irq(&pool->lock);
2765
2766 if (flush_color >= 0) {
2767 WARN_ON_ONCE(pwq->flush_color != -1);
2768
2769 if (pwq->nr_in_flight[flush_color]) {
2770 pwq->flush_color = flush_color;
2771 atomic_inc(&wq->nr_pwqs_to_flush);
2772 wait = true;
2773 }
2774 }
2775
2776 if (work_color >= 0) {
2777 WARN_ON_ONCE(work_color != work_next_color(pwq->work_color));
2778 pwq->work_color = work_color;
2779 }
2780
2781 raw_spin_unlock_irq(&pool->lock);
2782 }
2783
2784 if (flush_color >= 0 && atomic_dec_and_test(&wq->nr_pwqs_to_flush))
2785 complete(&wq->first_flusher->done);
2786
2787 return wait;
2788}
2789
2790/**
2791 * __flush_workqueue - ensure that any scheduled work has run to completion.
2792 * @wq: workqueue to flush
2793 *
2794 * This function sleeps until all work items which were queued on entry
2795 * have finished execution, but it is not livelocked by new incoming ones.
2796 */
2797void __flush_workqueue(struct workqueue_struct *wq)
2798{
2799 struct wq_flusher this_flusher = {
2800 .list = LIST_HEAD_INIT(this_flusher.list),
2801 .flush_color = -1,
2802 .done = COMPLETION_INITIALIZER_ONSTACK_MAP(this_flusher.done, wq->lockdep_map),
2803 };
2804 int next_color;
2805
2806 if (WARN_ON(!wq_online))
2807 return;
2808
2809 lock_map_acquire(&wq->lockdep_map);
2810 lock_map_release(&wq->lockdep_map);
2811
2812 mutex_lock(&wq->mutex);
2813
2814 /*
2815 * Start-to-wait phase
2816 */
2817 next_color = work_next_color(wq->work_color);
2818
2819 if (next_color != wq->flush_color) {
2820 /*
2821 * Color space is not full. The current work_color
2822 * becomes our flush_color and work_color is advanced
2823 * by one.
2824 */
2825 WARN_ON_ONCE(!list_empty(&wq->flusher_overflow));
2826 this_flusher.flush_color = wq->work_color;
2827 wq->work_color = next_color;
2828
2829 if (!wq->first_flusher) {
2830 /* no flush in progress, become the first flusher */
2831 WARN_ON_ONCE(wq->flush_color != this_flusher.flush_color);
2832
2833 wq->first_flusher = &this_flusher;
2834
2835 if (!flush_workqueue_prep_pwqs(wq, wq->flush_color,
2836 wq->work_color)) {
2837 /* nothing to flush, done */
2838 wq->flush_color = next_color;
2839 wq->first_flusher = NULL;
2840 goto out_unlock;
2841 }
2842 } else {
2843 /* wait in queue */
2844 WARN_ON_ONCE(wq->flush_color == this_flusher.flush_color);
2845 list_add_tail(&this_flusher.list, &wq->flusher_queue);
2846 flush_workqueue_prep_pwqs(wq, -1, wq->work_color);
2847 }
2848 } else {
2849 /*
2850 * Oops, color space is full, wait on overflow queue.
2851 * The next flush completion will assign us
2852 * flush_color and transfer to flusher_queue.
2853 */
2854 list_add_tail(&this_flusher.list, &wq->flusher_overflow);
2855 }
2856
2857 check_flush_dependency(wq, NULL);
2858
2859 mutex_unlock(&wq->mutex);
2860
2861 wait_for_completion(&this_flusher.done);
2862
2863 /*
2864 * Wake-up-and-cascade phase
2865 *
2866 * First flushers are responsible for cascading flushes and
2867 * handling overflow. Non-first flushers can simply return.
2868 */
2869 if (READ_ONCE(wq->first_flusher) != &this_flusher)
2870 return;
2871
2872 mutex_lock(&wq->mutex);
2873
2874 /* we might have raced, check again with mutex held */
2875 if (wq->first_flusher != &this_flusher)
2876 goto out_unlock;
2877
2878 WRITE_ONCE(wq->first_flusher, NULL);
2879
2880 WARN_ON_ONCE(!list_empty(&this_flusher.list));
2881 WARN_ON_ONCE(wq->flush_color != this_flusher.flush_color);
2882
2883 while (true) {
2884 struct wq_flusher *next, *tmp;
2885
2886 /* complete all the flushers sharing the current flush color */
2887 list_for_each_entry_safe(next, tmp, &wq->flusher_queue, list) {
2888 if (next->flush_color != wq->flush_color)
2889 break;
2890 list_del_init(&next->list);
2891 complete(&next->done);
2892 }
2893
2894 WARN_ON_ONCE(!list_empty(&wq->flusher_overflow) &&
2895 wq->flush_color != work_next_color(wq->work_color));
2896
2897 /* this flush_color is finished, advance by one */
2898 wq->flush_color = work_next_color(wq->flush_color);
2899
2900 /* one color has been freed, handle overflow queue */
2901 if (!list_empty(&wq->flusher_overflow)) {
2902 /*
2903 * Assign the same color to all overflowed
2904 * flushers, advance work_color and append to
2905 * flusher_queue. This is the start-to-wait
2906 * phase for these overflowed flushers.
2907 */
2908 list_for_each_entry(tmp, &wq->flusher_overflow, list)
2909 tmp->flush_color = wq->work_color;
2910
2911 wq->work_color = work_next_color(wq->work_color);
2912
2913 list_splice_tail_init(&wq->flusher_overflow,
2914 &wq->flusher_queue);
2915 flush_workqueue_prep_pwqs(wq, -1, wq->work_color);
2916 }
2917
2918 if (list_empty(&wq->flusher_queue)) {
2919 WARN_ON_ONCE(wq->flush_color != wq->work_color);
2920 break;
2921 }
2922
2923 /*
2924 * Need to flush more colors. Make the next flusher
2925 * the new first flusher and arm pwqs.
2926 */
2927 WARN_ON_ONCE(wq->flush_color == wq->work_color);
2928 WARN_ON_ONCE(wq->flush_color != next->flush_color);
2929
2930 list_del_init(&next->list);
2931 wq->first_flusher = next;
2932
2933 if (flush_workqueue_prep_pwqs(wq, wq->flush_color, -1))
2934 break;
2935
2936 /*
2937 * Meh... this color is already done, clear first
2938 * flusher and repeat cascading.
2939 */
2940 wq->first_flusher = NULL;
2941 }
2942
2943out_unlock:
2944 mutex_unlock(&wq->mutex);
2945}
2946EXPORT_SYMBOL(__flush_workqueue);
2947
2948/**
2949 * drain_workqueue - drain a workqueue
2950 * @wq: workqueue to drain
2951 *
2952 * Wait until the workqueue becomes empty. While draining is in progress,
2953 * only chain queueing is allowed. IOW, only currently pending or running
2954 * work items on @wq can queue further work items on it. @wq is flushed
2955 * repeatedly until it becomes empty. The number of flushing is determined
2956 * by the depth of chaining and should be relatively short. Whine if it
2957 * takes too long.
2958 */
2959void drain_workqueue(struct workqueue_struct *wq)
2960{
2961 unsigned int flush_cnt = 0;
2962 struct pool_workqueue *pwq;
2963
2964 /*
2965 * __queue_work() needs to test whether there are drainers, is much
2966 * hotter than drain_workqueue() and already looks at @wq->flags.
2967 * Use __WQ_DRAINING so that queue doesn't have to check nr_drainers.
2968 */
2969 mutex_lock(&wq->mutex);
2970 if (!wq->nr_drainers++)
2971 wq->flags |= __WQ_DRAINING;
2972 mutex_unlock(&wq->mutex);
2973reflush:
2974 __flush_workqueue(wq);
2975
2976 mutex_lock(&wq->mutex);
2977
2978 for_each_pwq(pwq, wq) {
2979 bool drained;
2980
2981 raw_spin_lock_irq(&pwq->pool->lock);
2982 drained = !pwq->nr_active && list_empty(&pwq->inactive_works);
2983 raw_spin_unlock_irq(&pwq->pool->lock);
2984
2985 if (drained)
2986 continue;
2987
2988 if (++flush_cnt == 10 ||
2989 (flush_cnt % 100 == 0 && flush_cnt <= 1000))
2990 pr_warn("workqueue %s: %s() isn't complete after %u tries\n",
2991 wq->name, __func__, flush_cnt);
2992
2993 mutex_unlock(&wq->mutex);
2994 goto reflush;
2995 }
2996
2997 if (!--wq->nr_drainers)
2998 wq->flags &= ~__WQ_DRAINING;
2999 mutex_unlock(&wq->mutex);
3000}
3001EXPORT_SYMBOL_GPL(drain_workqueue);
3002
3003static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr,
3004 bool from_cancel)
3005{
3006 struct worker *worker = NULL;
3007 struct worker_pool *pool;
3008 struct pool_workqueue *pwq;
3009
3010 might_sleep();
3011
3012 rcu_read_lock();
3013 pool = get_work_pool(work);
3014 if (!pool) {
3015 rcu_read_unlock();
3016 return false;
3017 }
3018
3019 raw_spin_lock_irq(&pool->lock);
3020 /* see the comment in try_to_grab_pending() with the same code */
3021 pwq = get_work_pwq(work);
3022 if (pwq) {
3023 if (unlikely(pwq->pool != pool))
3024 goto already_gone;
3025 } else {
3026 worker = find_worker_executing_work(pool, work);
3027 if (!worker)
3028 goto already_gone;
3029 pwq = worker->current_pwq;
3030 }
3031
3032 check_flush_dependency(pwq->wq, work);
3033
3034 insert_wq_barrier(pwq, barr, work, worker);
3035 raw_spin_unlock_irq(&pool->lock);
3036
3037 /*
3038 * Force a lock recursion deadlock when using flush_work() inside a
3039 * single-threaded or rescuer equipped workqueue.
3040 *
3041 * For single threaded workqueues the deadlock happens when the work
3042 * is after the work issuing the flush_work(). For rescuer equipped
3043 * workqueues the deadlock happens when the rescuer stalls, blocking
3044 * forward progress.
3045 */
3046 if (!from_cancel &&
3047 (pwq->wq->saved_max_active == 1 || pwq->wq->rescuer)) {
3048 lock_map_acquire(&pwq->wq->lockdep_map);
3049 lock_map_release(&pwq->wq->lockdep_map);
3050 }
3051 rcu_read_unlock();
3052 return true;
3053already_gone:
3054 raw_spin_unlock_irq(&pool->lock);
3055 rcu_read_unlock();
3056 return false;
3057}
3058
3059static bool __flush_work(struct work_struct *work, bool from_cancel)
3060{
3061 struct wq_barrier barr;
3062
3063 if (WARN_ON(!wq_online))
3064 return false;
3065
3066 if (WARN_ON(!work->func))
3067 return false;
3068
3069 lock_map_acquire(&work->lockdep_map);
3070 lock_map_release(&work->lockdep_map);
3071
3072 if (start_flush_work(work, &barr, from_cancel)) {
3073 wait_for_completion(&barr.done);
3074 destroy_work_on_stack(&barr.work);
3075 return true;
3076 } else {
3077 return false;
3078 }
3079}
3080
3081/**
3082 * flush_work - wait for a work to finish executing the last queueing instance
3083 * @work: the work to flush
3084 *
3085 * Wait until @work has finished execution. @work is guaranteed to be idle
3086 * on return if it hasn't been requeued since flush started.
3087 *
3088 * Return:
3089 * %true if flush_work() waited for the work to finish execution,
3090 * %false if it was already idle.
3091 */
3092bool flush_work(struct work_struct *work)
3093{
3094 return __flush_work(work, false);
3095}
3096EXPORT_SYMBOL_GPL(flush_work);
3097
3098struct cwt_wait {
3099 wait_queue_entry_t wait;
3100 struct work_struct *work;
3101};
3102
3103static int cwt_wakefn(wait_queue_entry_t *wait, unsigned mode, int sync, void *key)
3104{
3105 struct cwt_wait *cwait = container_of(wait, struct cwt_wait, wait);
3106
3107 if (cwait->work != key)
3108 return 0;
3109 return autoremove_wake_function(wait, mode, sync, key);
3110}
3111
3112static bool __cancel_work_timer(struct work_struct *work, bool is_dwork)
3113{
3114 static DECLARE_WAIT_QUEUE_HEAD(cancel_waitq);
3115 unsigned long flags;
3116 int ret;
3117
3118 do {
3119 ret = try_to_grab_pending(work, is_dwork, &flags);
3120 /*
3121 * If someone else is already canceling, wait for it to
3122 * finish. flush_work() doesn't work for PREEMPT_NONE
3123 * because we may get scheduled between @work's completion
3124 * and the other canceling task resuming and clearing
3125 * CANCELING - flush_work() will return false immediately
3126 * as @work is no longer busy, try_to_grab_pending() will
3127 * return -ENOENT as @work is still being canceled and the
3128 * other canceling task won't be able to clear CANCELING as
3129 * we're hogging the CPU.
3130 *
3131 * Let's wait for completion using a waitqueue. As this
3132 * may lead to the thundering herd problem, use a custom
3133 * wake function which matches @work along with exclusive
3134 * wait and wakeup.
3135 */
3136 if (unlikely(ret == -ENOENT)) {
3137 struct cwt_wait cwait;
3138
3139 init_wait(&cwait.wait);
3140 cwait.wait.func = cwt_wakefn;
3141 cwait.work = work;
3142
3143 prepare_to_wait_exclusive(&cancel_waitq, &cwait.wait,
3144 TASK_UNINTERRUPTIBLE);
3145 if (work_is_canceling(work))
3146 schedule();
3147 finish_wait(&cancel_waitq, &cwait.wait);
3148 }
3149 } while (unlikely(ret < 0));
3150
3151 /* tell other tasks trying to grab @work to back off */
3152 mark_work_canceling(work);
3153 local_irq_restore(flags);
3154
3155 /*
3156 * This allows canceling during early boot. We know that @work
3157 * isn't executing.
3158 */
3159 if (wq_online)
3160 __flush_work(work, true);
3161
3162 clear_work_data(work);
3163
3164 /*
3165 * Paired with prepare_to_wait() above so that either
3166 * waitqueue_active() is visible here or !work_is_canceling() is
3167 * visible there.
3168 */
3169 smp_mb();
3170 if (waitqueue_active(&cancel_waitq))
3171 __wake_up(&cancel_waitq, TASK_NORMAL, 1, work);
3172
3173 return ret;
3174}
3175
3176/**
3177 * cancel_work_sync - cancel a work and wait for it to finish
3178 * @work: the work to cancel
3179 *
3180 * Cancel @work and wait for its execution to finish. This function
3181 * can be used even if the work re-queues itself or migrates to
3182 * another workqueue. On return from this function, @work is
3183 * guaranteed to be not pending or executing on any CPU.
3184 *
3185 * cancel_work_sync(&delayed_work->work) must not be used for
3186 * delayed_work's. Use cancel_delayed_work_sync() instead.
3187 *
3188 * The caller must ensure that the workqueue on which @work was last
3189 * queued can't be destroyed before this function returns.
3190 *
3191 * Return:
3192 * %true if @work was pending, %false otherwise.
3193 */
3194bool cancel_work_sync(struct work_struct *work)
3195{
3196 return __cancel_work_timer(work, false);
3197}
3198EXPORT_SYMBOL_GPL(cancel_work_sync);
3199
3200/**
3201 * flush_delayed_work - wait for a dwork to finish executing the last queueing
3202 * @dwork: the delayed work to flush
3203 *
3204 * Delayed timer is cancelled and the pending work is queued for
3205 * immediate execution. Like flush_work(), this function only
3206 * considers the last queueing instance of @dwork.
3207 *
3208 * Return:
3209 * %true if flush_work() waited for the work to finish execution,
3210 * %false if it was already idle.
3211 */
3212bool flush_delayed_work(struct delayed_work *dwork)
3213{
3214 local_irq_disable();
3215 if (del_timer_sync(&dwork->timer))
3216 __queue_work(dwork->cpu, dwork->wq, &dwork->work);
3217 local_irq_enable();
3218 return flush_work(&dwork->work);
3219}
3220EXPORT_SYMBOL(flush_delayed_work);
3221
3222/**
3223 * flush_rcu_work - wait for a rwork to finish executing the last queueing
3224 * @rwork: the rcu work to flush
3225 *
3226 * Return:
3227 * %true if flush_rcu_work() waited for the work to finish execution,
3228 * %false if it was already idle.
3229 */
3230bool flush_rcu_work(struct rcu_work *rwork)
3231{
3232 if (test_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(&rwork->work))) {
3233 rcu_barrier();
3234 flush_work(&rwork->work);
3235 return true;
3236 } else {
3237 return flush_work(&rwork->work);
3238 }
3239}
3240EXPORT_SYMBOL(flush_rcu_work);
3241
3242static bool __cancel_work(struct work_struct *work, bool is_dwork)
3243{
3244 unsigned long flags;
3245 int ret;
3246
3247 do {
3248 ret = try_to_grab_pending(work, is_dwork, &flags);
3249 } while (unlikely(ret == -EAGAIN));
3250
3251 if (unlikely(ret < 0))
3252 return false;
3253
3254 set_work_pool_and_clear_pending(work, get_work_pool_id(work));
3255 local_irq_restore(flags);
3256 return ret;
3257}
3258
3259/*
3260 * See cancel_delayed_work()
3261 */
3262bool cancel_work(struct work_struct *work)
3263{
3264 return __cancel_work(work, false);
3265}
3266EXPORT_SYMBOL(cancel_work);
3267
3268/**
3269 * cancel_delayed_work - cancel a delayed work
3270 * @dwork: delayed_work to cancel
3271 *
3272 * Kill off a pending delayed_work.
3273 *
3274 * Return: %true if @dwork was pending and canceled; %false if it wasn't
3275 * pending.
3276 *
3277 * Note:
3278 * The work callback function may still be running on return, unless
3279 * it returns %true and the work doesn't re-arm itself. Explicitly flush or
3280 * use cancel_delayed_work_sync() to wait on it.
3281 *
3282 * This function is safe to call from any context including IRQ handler.
3283 */
3284bool cancel_delayed_work(struct delayed_work *dwork)
3285{
3286 return __cancel_work(&dwork->work, true);
3287}
3288EXPORT_SYMBOL(cancel_delayed_work);
3289
3290/**
3291 * cancel_delayed_work_sync - cancel a delayed work and wait for it to finish
3292 * @dwork: the delayed work cancel
3293 *
3294 * This is cancel_work_sync() for delayed works.
3295 *
3296 * Return:
3297 * %true if @dwork was pending, %false otherwise.
3298 */
3299bool cancel_delayed_work_sync(struct delayed_work *dwork)
3300{
3301 return __cancel_work_timer(&dwork->work, true);
3302}
3303EXPORT_SYMBOL(cancel_delayed_work_sync);
3304
3305/**
3306 * schedule_on_each_cpu - execute a function synchronously on each online CPU
3307 * @func: the function to call
3308 *
3309 * schedule_on_each_cpu() executes @func on each online CPU using the
3310 * system workqueue and blocks until all CPUs have completed.
3311 * schedule_on_each_cpu() is very slow.
3312 *
3313 * Return:
3314 * 0 on success, -errno on failure.
3315 */
3316int schedule_on_each_cpu(work_func_t func)
3317{
3318 int cpu;
3319 struct work_struct __percpu *works;
3320
3321 works = alloc_percpu(struct work_struct);
3322 if (!works)
3323 return -ENOMEM;
3324
3325 cpus_read_lock();
3326
3327 for_each_online_cpu(cpu) {
3328 struct work_struct *work = per_cpu_ptr(works, cpu);
3329
3330 INIT_WORK(work, func);
3331 schedule_work_on(cpu, work);
3332 }
3333
3334 for_each_online_cpu(cpu)
3335 flush_work(per_cpu_ptr(works, cpu));
3336
3337 cpus_read_unlock();
3338 free_percpu(works);
3339 return 0;
3340}
3341
3342/**
3343 * execute_in_process_context - reliably execute the routine with user context
3344 * @fn: the function to execute
3345 * @ew: guaranteed storage for the execute work structure (must
3346 * be available when the work executes)
3347 *
3348 * Executes the function immediately if process context is available,
3349 * otherwise schedules the function for delayed execution.
3350 *
3351 * Return: 0 - function was executed
3352 * 1 - function was scheduled for execution
3353 */
3354int execute_in_process_context(work_func_t fn, struct execute_work *ew)
3355{
3356 if (!in_interrupt()) {
3357 fn(&ew->work);
3358 return 0;
3359 }
3360
3361 INIT_WORK(&ew->work, fn);
3362 schedule_work(&ew->work);
3363
3364 return 1;
3365}
3366EXPORT_SYMBOL_GPL(execute_in_process_context);
3367
3368/**
3369 * free_workqueue_attrs - free a workqueue_attrs
3370 * @attrs: workqueue_attrs to free
3371 *
3372 * Undo alloc_workqueue_attrs().
3373 */
3374void free_workqueue_attrs(struct workqueue_attrs *attrs)
3375{
3376 if (attrs) {
3377 free_cpumask_var(attrs->cpumask);
3378 kfree(attrs);
3379 }
3380}
3381
3382/**
3383 * alloc_workqueue_attrs - allocate a workqueue_attrs
3384 *
3385 * Allocate a new workqueue_attrs, initialize with default settings and
3386 * return it.
3387 *
3388 * Return: The allocated new workqueue_attr on success. %NULL on failure.
3389 */
3390struct workqueue_attrs *alloc_workqueue_attrs(void)
3391{
3392 struct workqueue_attrs *attrs;
3393
3394 attrs = kzalloc(sizeof(*attrs), GFP_KERNEL);
3395 if (!attrs)
3396 goto fail;
3397 if (!alloc_cpumask_var(&attrs->cpumask, GFP_KERNEL))
3398 goto fail;
3399
3400 cpumask_copy(attrs->cpumask, cpu_possible_mask);
3401 return attrs;
3402fail:
3403 free_workqueue_attrs(attrs);
3404 return NULL;
3405}
3406
3407static void copy_workqueue_attrs(struct workqueue_attrs *to,
3408 const struct workqueue_attrs *from)
3409{
3410 to->nice = from->nice;
3411 cpumask_copy(to->cpumask, from->cpumask);
3412 /*
3413 * Unlike hash and equality test, this function doesn't ignore
3414 * ->no_numa as it is used for both pool and wq attrs. Instead,
3415 * get_unbound_pool() explicitly clears ->no_numa after copying.
3416 */
3417 to->no_numa = from->no_numa;
3418}
3419
3420/* hash value of the content of @attr */
3421static u32 wqattrs_hash(const struct workqueue_attrs *attrs)
3422{
3423 u32 hash = 0;
3424
3425 hash = jhash_1word(attrs->nice, hash);
3426 hash = jhash(cpumask_bits(attrs->cpumask),
3427 BITS_TO_LONGS(nr_cpumask_bits) * sizeof(long), hash);
3428 return hash;
3429}
3430
3431/* content equality test */
3432static bool wqattrs_equal(const struct workqueue_attrs *a,
3433 const struct workqueue_attrs *b)
3434{
3435 if (a->nice != b->nice)
3436 return false;
3437 if (!cpumask_equal(a->cpumask, b->cpumask))
3438 return false;
3439 return true;
3440}
3441
3442/**
3443 * init_worker_pool - initialize a newly zalloc'd worker_pool
3444 * @pool: worker_pool to initialize
3445 *
3446 * Initialize a newly zalloc'd @pool. It also allocates @pool->attrs.
3447 *
3448 * Return: 0 on success, -errno on failure. Even on failure, all fields
3449 * inside @pool proper are initialized and put_unbound_pool() can be called
3450 * on @pool safely to release it.
3451 */
3452static int init_worker_pool(struct worker_pool *pool)
3453{
3454 raw_spin_lock_init(&pool->lock);
3455 pool->id = -1;
3456 pool->cpu = -1;
3457 pool->node = NUMA_NO_NODE;
3458 pool->flags |= POOL_DISASSOCIATED;
3459 pool->watchdog_ts = jiffies;
3460 INIT_LIST_HEAD(&pool->worklist);
3461 INIT_LIST_HEAD(&pool->idle_list);
3462 hash_init(pool->busy_hash);
3463
3464 timer_setup(&pool->idle_timer, idle_worker_timeout, TIMER_DEFERRABLE);
3465
3466 timer_setup(&pool->mayday_timer, pool_mayday_timeout, 0);
3467
3468 INIT_LIST_HEAD(&pool->workers);
3469
3470 ida_init(&pool->worker_ida);
3471 INIT_HLIST_NODE(&pool->hash_node);
3472 pool->refcnt = 1;
3473
3474 /* shouldn't fail above this point */
3475 pool->attrs = alloc_workqueue_attrs();
3476 if (!pool->attrs)
3477 return -ENOMEM;
3478 return 0;
3479}
3480
3481#ifdef CONFIG_LOCKDEP
3482static void wq_init_lockdep(struct workqueue_struct *wq)
3483{
3484 char *lock_name;
3485
3486 lockdep_register_key(&wq->key);
3487 lock_name = kasprintf(GFP_KERNEL, "%s%s", "(wq_completion)", wq->name);
3488 if (!lock_name)
3489 lock_name = wq->name;
3490
3491 wq->lock_name = lock_name;
3492 lockdep_init_map(&wq->lockdep_map, lock_name, &wq->key, 0);
3493}
3494
3495static void wq_unregister_lockdep(struct workqueue_struct *wq)
3496{
3497 lockdep_unregister_key(&wq->key);
3498}
3499
3500static void wq_free_lockdep(struct workqueue_struct *wq)
3501{
3502 if (wq->lock_name != wq->name)
3503 kfree(wq->lock_name);
3504}
3505#else
3506static void wq_init_lockdep(struct workqueue_struct *wq)
3507{
3508}
3509
3510static void wq_unregister_lockdep(struct workqueue_struct *wq)
3511{
3512}
3513
3514static void wq_free_lockdep(struct workqueue_struct *wq)
3515{
3516}
3517#endif
3518
3519static void rcu_free_wq(struct rcu_head *rcu)
3520{
3521 struct workqueue_struct *wq =
3522 container_of(rcu, struct workqueue_struct, rcu);
3523
3524 wq_free_lockdep(wq);
3525
3526 if (!(wq->flags & WQ_UNBOUND))
3527 free_percpu(wq->cpu_pwqs);
3528 else
3529 free_workqueue_attrs(wq->unbound_attrs);
3530
3531 kfree(wq);
3532}
3533
3534static void rcu_free_pool(struct rcu_head *rcu)
3535{
3536 struct worker_pool *pool = container_of(rcu, struct worker_pool, rcu);
3537
3538 ida_destroy(&pool->worker_ida);
3539 free_workqueue_attrs(pool->attrs);
3540 kfree(pool);
3541}
3542
3543/* This returns with the lock held on success (pool manager is inactive). */
3544static bool wq_manager_inactive(struct worker_pool *pool)
3545{
3546 raw_spin_lock_irq(&pool->lock);
3547
3548 if (pool->flags & POOL_MANAGER_ACTIVE) {
3549 raw_spin_unlock_irq(&pool->lock);
3550 return false;
3551 }
3552 return true;
3553}
3554
3555/**
3556 * put_unbound_pool - put a worker_pool
3557 * @pool: worker_pool to put
3558 *
3559 * Put @pool. If its refcnt reaches zero, it gets destroyed in RCU
3560 * safe manner. get_unbound_pool() calls this function on its failure path
3561 * and this function should be able to release pools which went through,
3562 * successfully or not, init_worker_pool().
3563 *
3564 * Should be called with wq_pool_mutex held.
3565 */
3566static void put_unbound_pool(struct worker_pool *pool)
3567{
3568 DECLARE_COMPLETION_ONSTACK(detach_completion);
3569 struct worker *worker;
3570
3571 lockdep_assert_held(&wq_pool_mutex);
3572
3573 if (--pool->refcnt)
3574 return;
3575
3576 /* sanity checks */
3577 if (WARN_ON(!(pool->cpu < 0)) ||
3578 WARN_ON(!list_empty(&pool->worklist)))
3579 return;
3580
3581 /* release id and unhash */
3582 if (pool->id >= 0)
3583 idr_remove(&worker_pool_idr, pool->id);
3584 hash_del(&pool->hash_node);
3585
3586 /*
3587 * Become the manager and destroy all workers. This prevents
3588 * @pool's workers from blocking on attach_mutex. We're the last
3589 * manager and @pool gets freed with the flag set.
3590 * Because of how wq_manager_inactive() works, we will hold the
3591 * spinlock after a successful wait.
3592 */
3593 rcuwait_wait_event(&manager_wait, wq_manager_inactive(pool),
3594 TASK_UNINTERRUPTIBLE);
3595 pool->flags |= POOL_MANAGER_ACTIVE;
3596
3597 while ((worker = first_idle_worker(pool)))
3598 destroy_worker(worker);
3599 WARN_ON(pool->nr_workers || pool->nr_idle);
3600 raw_spin_unlock_irq(&pool->lock);
3601
3602 mutex_lock(&wq_pool_attach_mutex);
3603 if (!list_empty(&pool->workers))
3604 pool->detach_completion = &detach_completion;
3605 mutex_unlock(&wq_pool_attach_mutex);
3606
3607 if (pool->detach_completion)
3608 wait_for_completion(pool->detach_completion);
3609
3610 /* shut down the timers */
3611 del_timer_sync(&pool->idle_timer);
3612 del_timer_sync(&pool->mayday_timer);
3613
3614 /* RCU protected to allow dereferences from get_work_pool() */
3615 call_rcu(&pool->rcu, rcu_free_pool);
3616}
3617
3618/**
3619 * get_unbound_pool - get a worker_pool with the specified attributes
3620 * @attrs: the attributes of the worker_pool to get
3621 *
3622 * Obtain a worker_pool which has the same attributes as @attrs, bump the
3623 * reference count and return it. If there already is a matching
3624 * worker_pool, it will be used; otherwise, this function attempts to
3625 * create a new one.
3626 *
3627 * Should be called with wq_pool_mutex held.
3628 *
3629 * Return: On success, a worker_pool with the same attributes as @attrs.
3630 * On failure, %NULL.
3631 */
3632static struct worker_pool *get_unbound_pool(const struct workqueue_attrs *attrs)
3633{
3634 u32 hash = wqattrs_hash(attrs);
3635 struct worker_pool *pool;
3636 int node;
3637 int target_node = NUMA_NO_NODE;
3638
3639 lockdep_assert_held(&wq_pool_mutex);
3640
3641 /* do we already have a matching pool? */
3642 hash_for_each_possible(unbound_pool_hash, pool, hash_node, hash) {
3643 if (wqattrs_equal(pool->attrs, attrs)) {
3644 pool->refcnt++;
3645 return pool;
3646 }
3647 }
3648
3649 /* if cpumask is contained inside a NUMA node, we belong to that node */
3650 if (wq_numa_enabled) {
3651 for_each_node(node) {
3652 if (cpumask_subset(attrs->cpumask,
3653 wq_numa_possible_cpumask[node])) {
3654 target_node = node;
3655 break;
3656 }
3657 }
3658 }
3659
3660 /* nope, create a new one */
3661 pool = kzalloc_node(sizeof(*pool), GFP_KERNEL, target_node);
3662 if (!pool || init_worker_pool(pool) < 0)
3663 goto fail;
3664
3665 lockdep_set_subclass(&pool->lock, 1); /* see put_pwq() */
3666 copy_workqueue_attrs(pool->attrs, attrs);
3667 pool->node = target_node;
3668
3669 /*
3670 * no_numa isn't a worker_pool attribute, always clear it. See
3671 * 'struct workqueue_attrs' comments for detail.
3672 */
3673 pool->attrs->no_numa = false;
3674
3675 if (worker_pool_assign_id(pool) < 0)
3676 goto fail;
3677
3678 /* create and start the initial worker */
3679 if (wq_online && !create_worker(pool))
3680 goto fail;
3681
3682 /* install */
3683 hash_add(unbound_pool_hash, &pool->hash_node, hash);
3684
3685 return pool;
3686fail:
3687 if (pool)
3688 put_unbound_pool(pool);
3689 return NULL;
3690}
3691
3692static void rcu_free_pwq(struct rcu_head *rcu)
3693{
3694 kmem_cache_free(pwq_cache,
3695 container_of(rcu, struct pool_workqueue, rcu));
3696}
3697
3698/*
3699 * Scheduled on system_wq by put_pwq() when an unbound pwq hits zero refcnt
3700 * and needs to be destroyed.
3701 */
3702static void pwq_unbound_release_workfn(struct work_struct *work)
3703{
3704 struct pool_workqueue *pwq = container_of(work, struct pool_workqueue,
3705 unbound_release_work);
3706 struct workqueue_struct *wq = pwq->wq;
3707 struct worker_pool *pool = pwq->pool;
3708 bool is_last = false;
3709
3710 /*
3711 * when @pwq is not linked, it doesn't hold any reference to the
3712 * @wq, and @wq is invalid to access.
3713 */
3714 if (!list_empty(&pwq->pwqs_node)) {
3715 if (WARN_ON_ONCE(!(wq->flags & WQ_UNBOUND)))
3716 return;
3717
3718 mutex_lock(&wq->mutex);
3719 list_del_rcu(&pwq->pwqs_node);
3720 is_last = list_empty(&wq->pwqs);
3721 mutex_unlock(&wq->mutex);
3722 }
3723
3724 mutex_lock(&wq_pool_mutex);
3725 put_unbound_pool(pool);
3726 mutex_unlock(&wq_pool_mutex);
3727
3728 call_rcu(&pwq->rcu, rcu_free_pwq);
3729
3730 /*
3731 * If we're the last pwq going away, @wq is already dead and no one
3732 * is gonna access it anymore. Schedule RCU free.
3733 */
3734 if (is_last) {
3735 wq_unregister_lockdep(wq);
3736 call_rcu(&wq->rcu, rcu_free_wq);
3737 }
3738}
3739
3740/**
3741 * pwq_adjust_max_active - update a pwq's max_active to the current setting
3742 * @pwq: target pool_workqueue
3743 *
3744 * If @pwq isn't freezing, set @pwq->max_active to the associated
3745 * workqueue's saved_max_active and activate inactive work items
3746 * accordingly. If @pwq is freezing, clear @pwq->max_active to zero.
3747 */
3748static void pwq_adjust_max_active(struct pool_workqueue *pwq)
3749{
3750 struct workqueue_struct *wq = pwq->wq;
3751 bool freezable = wq->flags & WQ_FREEZABLE;
3752 unsigned long flags;
3753
3754 /* for @wq->saved_max_active */
3755 lockdep_assert_held(&wq->mutex);
3756
3757 /* fast exit for non-freezable wqs */
3758 if (!freezable && pwq->max_active == wq->saved_max_active)
3759 return;
3760
3761 /* this function can be called during early boot w/ irq disabled */
3762 raw_spin_lock_irqsave(&pwq->pool->lock, flags);
3763
3764 /*
3765 * During [un]freezing, the caller is responsible for ensuring that
3766 * this function is called at least once after @workqueue_freezing
3767 * is updated and visible.
3768 */
3769 if (!freezable || !workqueue_freezing) {
3770 bool kick = false;
3771
3772 pwq->max_active = wq->saved_max_active;
3773
3774 while (!list_empty(&pwq->inactive_works) &&
3775 pwq->nr_active < pwq->max_active) {
3776 pwq_activate_first_inactive(pwq);
3777 kick = true;
3778 }
3779
3780 /*
3781 * Need to kick a worker after thawed or an unbound wq's
3782 * max_active is bumped. In realtime scenarios, always kicking a
3783 * worker will cause interference on the isolated cpu cores, so
3784 * let's kick iff work items were activated.
3785 */
3786 if (kick)
3787 wake_up_worker(pwq->pool);
3788 } else {
3789 pwq->max_active = 0;
3790 }
3791
3792 raw_spin_unlock_irqrestore(&pwq->pool->lock, flags);
3793}
3794
3795/* initialize newly allocated @pwq which is associated with @wq and @pool */
3796static void init_pwq(struct pool_workqueue *pwq, struct workqueue_struct *wq,
3797 struct worker_pool *pool)
3798{
3799 BUG_ON((unsigned long)pwq & WORK_STRUCT_FLAG_MASK);
3800
3801 memset(pwq, 0, sizeof(*pwq));
3802
3803 pwq->pool = pool;
3804 pwq->wq = wq;
3805 pwq->flush_color = -1;
3806 pwq->refcnt = 1;
3807 INIT_LIST_HEAD(&pwq->inactive_works);
3808 INIT_LIST_HEAD(&pwq->pwqs_node);
3809 INIT_LIST_HEAD(&pwq->mayday_node);
3810 INIT_WORK(&pwq->unbound_release_work, pwq_unbound_release_workfn);
3811}
3812
3813/* sync @pwq with the current state of its associated wq and link it */
3814static void link_pwq(struct pool_workqueue *pwq)
3815{
3816 struct workqueue_struct *wq = pwq->wq;
3817
3818 lockdep_assert_held(&wq->mutex);
3819
3820 /* may be called multiple times, ignore if already linked */
3821 if (!list_empty(&pwq->pwqs_node))
3822 return;
3823
3824 /* set the matching work_color */
3825 pwq->work_color = wq->work_color;
3826
3827 /* sync max_active to the current setting */
3828 pwq_adjust_max_active(pwq);
3829
3830 /* link in @pwq */
3831 list_add_rcu(&pwq->pwqs_node, &wq->pwqs);
3832}
3833
3834/* obtain a pool matching @attr and create a pwq associating the pool and @wq */
3835static struct pool_workqueue *alloc_unbound_pwq(struct workqueue_struct *wq,
3836 const struct workqueue_attrs *attrs)
3837{
3838 struct worker_pool *pool;
3839 struct pool_workqueue *pwq;
3840
3841 lockdep_assert_held(&wq_pool_mutex);
3842
3843 pool = get_unbound_pool(attrs);
3844 if (!pool)
3845 return NULL;
3846
3847 pwq = kmem_cache_alloc_node(pwq_cache, GFP_KERNEL, pool->node);
3848 if (!pwq) {
3849 put_unbound_pool(pool);
3850 return NULL;
3851 }
3852
3853 init_pwq(pwq, wq, pool);
3854 return pwq;
3855}
3856
3857/**
3858 * wq_calc_node_cpumask - calculate a wq_attrs' cpumask for the specified node
3859 * @attrs: the wq_attrs of the default pwq of the target workqueue
3860 * @node: the target NUMA node
3861 * @cpu_going_down: if >= 0, the CPU to consider as offline
3862 * @cpumask: outarg, the resulting cpumask
3863 *
3864 * Calculate the cpumask a workqueue with @attrs should use on @node. If
3865 * @cpu_going_down is >= 0, that cpu is considered offline during
3866 * calculation. The result is stored in @cpumask.
3867 *
3868 * If NUMA affinity is not enabled, @attrs->cpumask is always used. If
3869 * enabled and @node has online CPUs requested by @attrs, the returned
3870 * cpumask is the intersection of the possible CPUs of @node and
3871 * @attrs->cpumask.
3872 *
3873 * The caller is responsible for ensuring that the cpumask of @node stays
3874 * stable.
3875 *
3876 * Return: %true if the resulting @cpumask is different from @attrs->cpumask,
3877 * %false if equal.
3878 */
3879static bool wq_calc_node_cpumask(const struct workqueue_attrs *attrs, int node,
3880 int cpu_going_down, cpumask_t *cpumask)
3881{
3882 if (!wq_numa_enabled || attrs->no_numa)
3883 goto use_dfl;
3884
3885 /* does @node have any online CPUs @attrs wants? */
3886 cpumask_and(cpumask, cpumask_of_node(node), attrs->cpumask);
3887 if (cpu_going_down >= 0)
3888 cpumask_clear_cpu(cpu_going_down, cpumask);
3889
3890 if (cpumask_empty(cpumask))
3891 goto use_dfl;
3892
3893 /* yeap, return possible CPUs in @node that @attrs wants */
3894 cpumask_and(cpumask, attrs->cpumask, wq_numa_possible_cpumask[node]);
3895
3896 if (cpumask_empty(cpumask)) {
3897 pr_warn_once("WARNING: workqueue cpumask: online intersect > "
3898 "possible intersect\n");
3899 return false;
3900 }
3901
3902 return !cpumask_equal(cpumask, attrs->cpumask);
3903
3904use_dfl:
3905 cpumask_copy(cpumask, attrs->cpumask);
3906 return false;
3907}
3908
3909/* install @pwq into @wq's numa_pwq_tbl[] for @node and return the old pwq */
3910static struct pool_workqueue *numa_pwq_tbl_install(struct workqueue_struct *wq,
3911 int node,
3912 struct pool_workqueue *pwq)
3913{
3914 struct pool_workqueue *old_pwq;
3915
3916 lockdep_assert_held(&wq_pool_mutex);
3917 lockdep_assert_held(&wq->mutex);
3918
3919 /* link_pwq() can handle duplicate calls */
3920 link_pwq(pwq);
3921
3922 old_pwq = rcu_access_pointer(wq->numa_pwq_tbl[node]);
3923 rcu_assign_pointer(wq->numa_pwq_tbl[node], pwq);
3924 return old_pwq;
3925}
3926
3927/* context to store the prepared attrs & pwqs before applying */
3928struct apply_wqattrs_ctx {
3929 struct workqueue_struct *wq; /* target workqueue */
3930 struct workqueue_attrs *attrs; /* attrs to apply */
3931 struct list_head list; /* queued for batching commit */
3932 struct pool_workqueue *dfl_pwq;
3933 struct pool_workqueue *pwq_tbl[];
3934};
3935
3936/* free the resources after success or abort */
3937static void apply_wqattrs_cleanup(struct apply_wqattrs_ctx *ctx)
3938{
3939 if (ctx) {
3940 int node;
3941
3942 for_each_node(node)
3943 put_pwq_unlocked(ctx->pwq_tbl[node]);
3944 put_pwq_unlocked(ctx->dfl_pwq);
3945
3946 free_workqueue_attrs(ctx->attrs);
3947
3948 kfree(ctx);
3949 }
3950}
3951
3952/* allocate the attrs and pwqs for later installation */
3953static struct apply_wqattrs_ctx *
3954apply_wqattrs_prepare(struct workqueue_struct *wq,
3955 const struct workqueue_attrs *attrs)
3956{
3957 struct apply_wqattrs_ctx *ctx;
3958 struct workqueue_attrs *new_attrs, *tmp_attrs;
3959 int node;
3960
3961 lockdep_assert_held(&wq_pool_mutex);
3962
3963 ctx = kzalloc(struct_size(ctx, pwq_tbl, nr_node_ids), GFP_KERNEL);
3964
3965 new_attrs = alloc_workqueue_attrs();
3966 tmp_attrs = alloc_workqueue_attrs();
3967 if (!ctx || !new_attrs || !tmp_attrs)
3968 goto out_free;
3969
3970 /*
3971 * Calculate the attrs of the default pwq.
3972 * If the user configured cpumask doesn't overlap with the
3973 * wq_unbound_cpumask, we fallback to the wq_unbound_cpumask.
3974 */
3975 copy_workqueue_attrs(new_attrs, attrs);
3976 cpumask_and(new_attrs->cpumask, new_attrs->cpumask, wq_unbound_cpumask);
3977 if (unlikely(cpumask_empty(new_attrs->cpumask)))
3978 cpumask_copy(new_attrs->cpumask, wq_unbound_cpumask);
3979
3980 /*
3981 * We may create multiple pwqs with differing cpumasks. Make a
3982 * copy of @new_attrs which will be modified and used to obtain
3983 * pools.
3984 */
3985 copy_workqueue_attrs(tmp_attrs, new_attrs);
3986
3987 /*
3988 * If something goes wrong during CPU up/down, we'll fall back to
3989 * the default pwq covering whole @attrs->cpumask. Always create
3990 * it even if we don't use it immediately.
3991 */
3992 ctx->dfl_pwq = alloc_unbound_pwq(wq, new_attrs);
3993 if (!ctx->dfl_pwq)
3994 goto out_free;
3995
3996 for_each_node(node) {
3997 if (wq_calc_node_cpumask(new_attrs, node, -1, tmp_attrs->cpumask)) {
3998 ctx->pwq_tbl[node] = alloc_unbound_pwq(wq, tmp_attrs);
3999 if (!ctx->pwq_tbl[node])
4000 goto out_free;
4001 } else {
4002 ctx->dfl_pwq->refcnt++;
4003 ctx->pwq_tbl[node] = ctx->dfl_pwq;
4004 }
4005 }
4006
4007 /* save the user configured attrs and sanitize it. */
4008 copy_workqueue_attrs(new_attrs, attrs);
4009 cpumask_and(new_attrs->cpumask, new_attrs->cpumask, cpu_possible_mask);
4010 ctx->attrs = new_attrs;
4011
4012 ctx->wq = wq;
4013 free_workqueue_attrs(tmp_attrs);
4014 return ctx;
4015
4016out_free:
4017 free_workqueue_attrs(tmp_attrs);
4018 free_workqueue_attrs(new_attrs);
4019 apply_wqattrs_cleanup(ctx);
4020 return NULL;
4021}
4022
4023/* set attrs and install prepared pwqs, @ctx points to old pwqs on return */
4024static void apply_wqattrs_commit(struct apply_wqattrs_ctx *ctx)
4025{
4026 int node;
4027
4028 /* all pwqs have been created successfully, let's install'em */
4029 mutex_lock(&ctx->wq->mutex);
4030
4031 copy_workqueue_attrs(ctx->wq->unbound_attrs, ctx->attrs);
4032
4033 /* save the previous pwq and install the new one */
4034 for_each_node(node)
4035 ctx->pwq_tbl[node] = numa_pwq_tbl_install(ctx->wq, node,
4036 ctx->pwq_tbl[node]);
4037
4038 /* @dfl_pwq might not have been used, ensure it's linked */
4039 link_pwq(ctx->dfl_pwq);
4040 swap(ctx->wq->dfl_pwq, ctx->dfl_pwq);
4041
4042 mutex_unlock(&ctx->wq->mutex);
4043}
4044
4045static void apply_wqattrs_lock(void)
4046{
4047 /* CPUs should stay stable across pwq creations and installations */
4048 cpus_read_lock();
4049 mutex_lock(&wq_pool_mutex);
4050}
4051
4052static void apply_wqattrs_unlock(void)
4053{
4054 mutex_unlock(&wq_pool_mutex);
4055 cpus_read_unlock();
4056}
4057
4058static int apply_workqueue_attrs_locked(struct workqueue_struct *wq,
4059 const struct workqueue_attrs *attrs)
4060{
4061 struct apply_wqattrs_ctx *ctx;
4062
4063 /* only unbound workqueues can change attributes */
4064 if (WARN_ON(!(wq->flags & WQ_UNBOUND)))
4065 return -EINVAL;
4066
4067 /* creating multiple pwqs breaks ordering guarantee */
4068 if (!list_empty(&wq->pwqs)) {
4069 if (WARN_ON(wq->flags & __WQ_ORDERED_EXPLICIT))
4070 return -EINVAL;
4071
4072 wq->flags &= ~__WQ_ORDERED;
4073 }
4074
4075 ctx = apply_wqattrs_prepare(wq, attrs);
4076 if (!ctx)
4077 return -ENOMEM;
4078
4079 /* the ctx has been prepared successfully, let's commit it */
4080 apply_wqattrs_commit(ctx);
4081 apply_wqattrs_cleanup(ctx);
4082
4083 return 0;
4084}
4085
4086/**
4087 * apply_workqueue_attrs - apply new workqueue_attrs to an unbound workqueue
4088 * @wq: the target workqueue
4089 * @attrs: the workqueue_attrs to apply, allocated with alloc_workqueue_attrs()
4090 *
4091 * Apply @attrs to an unbound workqueue @wq. Unless disabled, on NUMA
4092 * machines, this function maps a separate pwq to each NUMA node with
4093 * possibles CPUs in @attrs->cpumask so that work items are affine to the
4094 * NUMA node it was issued on. Older pwqs are released as in-flight work
4095 * items finish. Note that a work item which repeatedly requeues itself
4096 * back-to-back will stay on its current pwq.
4097 *
4098 * Performs GFP_KERNEL allocations.
4099 *
4100 * Assumes caller has CPU hotplug read exclusion, i.e. cpus_read_lock().
4101 *
4102 * Return: 0 on success and -errno on failure.
4103 */
4104int apply_workqueue_attrs(struct workqueue_struct *wq,
4105 const struct workqueue_attrs *attrs)
4106{
4107 int ret;
4108
4109 lockdep_assert_cpus_held();
4110
4111 mutex_lock(&wq_pool_mutex);
4112 ret = apply_workqueue_attrs_locked(wq, attrs);
4113 mutex_unlock(&wq_pool_mutex);
4114
4115 return ret;
4116}
4117
4118/**
4119 * wq_update_unbound_numa - update NUMA affinity of a wq for CPU hot[un]plug
4120 * @wq: the target workqueue
4121 * @cpu: the CPU coming up or going down
4122 * @online: whether @cpu is coming up or going down
4123 *
4124 * This function is to be called from %CPU_DOWN_PREPARE, %CPU_ONLINE and
4125 * %CPU_DOWN_FAILED. @cpu is being hot[un]plugged, update NUMA affinity of
4126 * @wq accordingly.
4127 *
4128 * If NUMA affinity can't be adjusted due to memory allocation failure, it
4129 * falls back to @wq->dfl_pwq which may not be optimal but is always
4130 * correct.
4131 *
4132 * Note that when the last allowed CPU of a NUMA node goes offline for a
4133 * workqueue with a cpumask spanning multiple nodes, the workers which were
4134 * already executing the work items for the workqueue will lose their CPU
4135 * affinity and may execute on any CPU. This is similar to how per-cpu
4136 * workqueues behave on CPU_DOWN. If a workqueue user wants strict
4137 * affinity, it's the user's responsibility to flush the work item from
4138 * CPU_DOWN_PREPARE.
4139 */
4140static void wq_update_unbound_numa(struct workqueue_struct *wq, int cpu,
4141 bool online)
4142{
4143 int node = cpu_to_node(cpu);
4144 int cpu_off = online ? -1 : cpu;
4145 struct pool_workqueue *old_pwq = NULL, *pwq;
4146 struct workqueue_attrs *target_attrs;
4147 cpumask_t *cpumask;
4148
4149 lockdep_assert_held(&wq_pool_mutex);
4150
4151 if (!wq_numa_enabled || !(wq->flags & WQ_UNBOUND) ||
4152 wq->unbound_attrs->no_numa)
4153 return;
4154
4155 /*
4156 * We don't wanna alloc/free wq_attrs for each wq for each CPU.
4157 * Let's use a preallocated one. The following buf is protected by
4158 * CPU hotplug exclusion.
4159 */
4160 target_attrs = wq_update_unbound_numa_attrs_buf;
4161 cpumask = target_attrs->cpumask;
4162
4163 copy_workqueue_attrs(target_attrs, wq->unbound_attrs);
4164 pwq = unbound_pwq_by_node(wq, node);
4165
4166 /*
4167 * Let's determine what needs to be done. If the target cpumask is
4168 * different from the default pwq's, we need to compare it to @pwq's
4169 * and create a new one if they don't match. If the target cpumask
4170 * equals the default pwq's, the default pwq should be used.
4171 */
4172 if (wq_calc_node_cpumask(wq->dfl_pwq->pool->attrs, node, cpu_off, cpumask)) {
4173 if (cpumask_equal(cpumask, pwq->pool->attrs->cpumask))
4174 return;
4175 } else {
4176 goto use_dfl_pwq;
4177 }
4178
4179 /* create a new pwq */
4180 pwq = alloc_unbound_pwq(wq, target_attrs);
4181 if (!pwq) {
4182 pr_warn("workqueue: allocation failed while updating NUMA affinity of \"%s\"\n",
4183 wq->name);
4184 goto use_dfl_pwq;
4185 }
4186
4187 /* Install the new pwq. */
4188 mutex_lock(&wq->mutex);
4189 old_pwq = numa_pwq_tbl_install(wq, node, pwq);
4190 goto out_unlock;
4191
4192use_dfl_pwq:
4193 mutex_lock(&wq->mutex);
4194 raw_spin_lock_irq(&wq->dfl_pwq->pool->lock);
4195 get_pwq(wq->dfl_pwq);
4196 raw_spin_unlock_irq(&wq->dfl_pwq->pool->lock);
4197 old_pwq = numa_pwq_tbl_install(wq, node, wq->dfl_pwq);
4198out_unlock:
4199 mutex_unlock(&wq->mutex);
4200 put_pwq_unlocked(old_pwq);
4201}
4202
4203static int alloc_and_link_pwqs(struct workqueue_struct *wq)
4204{
4205 bool highpri = wq->flags & WQ_HIGHPRI;
4206 int cpu, ret;
4207
4208 if (!(wq->flags & WQ_UNBOUND)) {
4209 wq->cpu_pwqs = alloc_percpu(struct pool_workqueue);
4210 if (!wq->cpu_pwqs)
4211 return -ENOMEM;
4212
4213 for_each_possible_cpu(cpu) {
4214 struct pool_workqueue *pwq =
4215 per_cpu_ptr(wq->cpu_pwqs, cpu);
4216 struct worker_pool *cpu_pools =
4217 per_cpu(cpu_worker_pools, cpu);
4218
4219 init_pwq(pwq, wq, &cpu_pools[highpri]);
4220
4221 mutex_lock(&wq->mutex);
4222 link_pwq(pwq);
4223 mutex_unlock(&wq->mutex);
4224 }
4225 return 0;
4226 }
4227
4228 cpus_read_lock();
4229 if (wq->flags & __WQ_ORDERED) {
4230 ret = apply_workqueue_attrs(wq, ordered_wq_attrs[highpri]);
4231 /* there should only be single pwq for ordering guarantee */
4232 WARN(!ret && (wq->pwqs.next != &wq->dfl_pwq->pwqs_node ||
4233 wq->pwqs.prev != &wq->dfl_pwq->pwqs_node),
4234 "ordering guarantee broken for workqueue %s\n", wq->name);
4235 } else {
4236 ret = apply_workqueue_attrs(wq, unbound_std_wq_attrs[highpri]);
4237 }
4238 cpus_read_unlock();
4239
4240 return ret;
4241}
4242
4243static int wq_clamp_max_active(int max_active, unsigned int flags,
4244 const char *name)
4245{
4246 int lim = flags & WQ_UNBOUND ? WQ_UNBOUND_MAX_ACTIVE : WQ_MAX_ACTIVE;
4247
4248 if (max_active < 1 || max_active > lim)
4249 pr_warn("workqueue: max_active %d requested for %s is out of range, clamping between %d and %d\n",
4250 max_active, name, 1, lim);
4251
4252 return clamp_val(max_active, 1, lim);
4253}
4254
4255/*
4256 * Workqueues which may be used during memory reclaim should have a rescuer
4257 * to guarantee forward progress.
4258 */
4259static int init_rescuer(struct workqueue_struct *wq)
4260{
4261 struct worker *rescuer;
4262 int ret;
4263
4264 if (!(wq->flags & WQ_MEM_RECLAIM))
4265 return 0;
4266
4267 rescuer = alloc_worker(NUMA_NO_NODE);
4268 if (!rescuer)
4269 return -ENOMEM;
4270
4271 rescuer->rescue_wq = wq;
4272 rescuer->task = kthread_create(rescuer_thread, rescuer, "%s", wq->name);
4273 if (IS_ERR(rescuer->task)) {
4274 ret = PTR_ERR(rescuer->task);
4275 kfree(rescuer);
4276 return ret;
4277 }
4278
4279 wq->rescuer = rescuer;
4280 kthread_bind_mask(rescuer->task, cpu_possible_mask);
4281 wake_up_process(rescuer->task);
4282
4283 return 0;
4284}
4285
4286__printf(1, 4)
4287struct workqueue_struct *alloc_workqueue(const char *fmt,
4288 unsigned int flags,
4289 int max_active, ...)
4290{
4291 size_t tbl_size = 0;
4292 va_list args;
4293 struct workqueue_struct *wq;
4294 struct pool_workqueue *pwq;
4295
4296 /*
4297 * Unbound && max_active == 1 used to imply ordered, which is no
4298 * longer the case on NUMA machines due to per-node pools. While
4299 * alloc_ordered_workqueue() is the right way to create an ordered
4300 * workqueue, keep the previous behavior to avoid subtle breakages
4301 * on NUMA.
4302 */
4303 if ((flags & WQ_UNBOUND) && max_active == 1)
4304 flags |= __WQ_ORDERED;
4305
4306 /* see the comment above the definition of WQ_POWER_EFFICIENT */
4307 if ((flags & WQ_POWER_EFFICIENT) && wq_power_efficient)
4308 flags |= WQ_UNBOUND;
4309
4310 /* allocate wq and format name */
4311 if (flags & WQ_UNBOUND)
4312 tbl_size = nr_node_ids * sizeof(wq->numa_pwq_tbl[0]);
4313
4314 wq = kzalloc(sizeof(*wq) + tbl_size, GFP_KERNEL);
4315 if (!wq)
4316 return NULL;
4317
4318 if (flags & WQ_UNBOUND) {
4319 wq->unbound_attrs = alloc_workqueue_attrs();
4320 if (!wq->unbound_attrs)
4321 goto err_free_wq;
4322 }
4323
4324 va_start(args, max_active);
4325 vsnprintf(wq->name, sizeof(wq->name), fmt, args);
4326 va_end(args);
4327
4328 max_active = max_active ?: WQ_DFL_ACTIVE;
4329 max_active = wq_clamp_max_active(max_active, flags, wq->name);
4330
4331 /* init wq */
4332 wq->flags = flags;
4333 wq->saved_max_active = max_active;
4334 mutex_init(&wq->mutex);
4335 atomic_set(&wq->nr_pwqs_to_flush, 0);
4336 INIT_LIST_HEAD(&wq->pwqs);
4337 INIT_LIST_HEAD(&wq->flusher_queue);
4338 INIT_LIST_HEAD(&wq->flusher_overflow);
4339 INIT_LIST_HEAD(&wq->maydays);
4340
4341 wq_init_lockdep(wq);
4342 INIT_LIST_HEAD(&wq->list);
4343
4344 if (alloc_and_link_pwqs(wq) < 0)
4345 goto err_unreg_lockdep;
4346
4347 if (wq_online && init_rescuer(wq) < 0)
4348 goto err_destroy;
4349
4350 if ((wq->flags & WQ_SYSFS) && workqueue_sysfs_register(wq))
4351 goto err_destroy;
4352
4353 /*
4354 * wq_pool_mutex protects global freeze state and workqueues list.
4355 * Grab it, adjust max_active and add the new @wq to workqueues
4356 * list.
4357 */
4358 mutex_lock(&wq_pool_mutex);
4359
4360 mutex_lock(&wq->mutex);
4361 for_each_pwq(pwq, wq)
4362 pwq_adjust_max_active(pwq);
4363 mutex_unlock(&wq->mutex);
4364
4365 list_add_tail_rcu(&wq->list, &workqueues);
4366
4367 mutex_unlock(&wq_pool_mutex);
4368
4369 return wq;
4370
4371err_unreg_lockdep:
4372 wq_unregister_lockdep(wq);
4373 wq_free_lockdep(wq);
4374err_free_wq:
4375 free_workqueue_attrs(wq->unbound_attrs);
4376 kfree(wq);
4377 return NULL;
4378err_destroy:
4379 destroy_workqueue(wq);
4380 return NULL;
4381}
4382EXPORT_SYMBOL_GPL(alloc_workqueue);
4383
4384static bool pwq_busy(struct pool_workqueue *pwq)
4385{
4386 int i;
4387
4388 for (i = 0; i < WORK_NR_COLORS; i++)
4389 if (pwq->nr_in_flight[i])
4390 return true;
4391
4392 if ((pwq != pwq->wq->dfl_pwq) && (pwq->refcnt > 1))
4393 return true;
4394 if (pwq->nr_active || !list_empty(&pwq->inactive_works))
4395 return true;
4396
4397 return false;
4398}
4399
4400/**
4401 * destroy_workqueue - safely terminate a workqueue
4402 * @wq: target workqueue
4403 *
4404 * Safely destroy a workqueue. All work currently pending will be done first.
4405 */
4406void destroy_workqueue(struct workqueue_struct *wq)
4407{
4408 struct pool_workqueue *pwq;
4409 int node;
4410
4411 /*
4412 * Remove it from sysfs first so that sanity check failure doesn't
4413 * lead to sysfs name conflicts.
4414 */
4415 workqueue_sysfs_unregister(wq);
4416
4417 /* drain it before proceeding with destruction */
4418 drain_workqueue(wq);
4419
4420 /* kill rescuer, if sanity checks fail, leave it w/o rescuer */
4421 if (wq->rescuer) {
4422 struct worker *rescuer = wq->rescuer;
4423
4424 /* this prevents new queueing */
4425 raw_spin_lock_irq(&wq_mayday_lock);
4426 wq->rescuer = NULL;
4427 raw_spin_unlock_irq(&wq_mayday_lock);
4428
4429 /* rescuer will empty maydays list before exiting */
4430 kthread_stop(rescuer->task);
4431 kfree(rescuer);
4432 }
4433
4434 /*
4435 * Sanity checks - grab all the locks so that we wait for all
4436 * in-flight operations which may do put_pwq().
4437 */
4438 mutex_lock(&wq_pool_mutex);
4439 mutex_lock(&wq->mutex);
4440 for_each_pwq(pwq, wq) {
4441 raw_spin_lock_irq(&pwq->pool->lock);
4442 if (WARN_ON(pwq_busy(pwq))) {
4443 pr_warn("%s: %s has the following busy pwq\n",
4444 __func__, wq->name);
4445 show_pwq(pwq);
4446 raw_spin_unlock_irq(&pwq->pool->lock);
4447 mutex_unlock(&wq->mutex);
4448 mutex_unlock(&wq_pool_mutex);
4449 show_one_workqueue(wq);
4450 return;
4451 }
4452 raw_spin_unlock_irq(&pwq->pool->lock);
4453 }
4454 mutex_unlock(&wq->mutex);
4455
4456 /*
4457 * wq list is used to freeze wq, remove from list after
4458 * flushing is complete in case freeze races us.
4459 */
4460 list_del_rcu(&wq->list);
4461 mutex_unlock(&wq_pool_mutex);
4462
4463 if (!(wq->flags & WQ_UNBOUND)) {
4464 wq_unregister_lockdep(wq);
4465 /*
4466 * The base ref is never dropped on per-cpu pwqs. Directly
4467 * schedule RCU free.
4468 */
4469 call_rcu(&wq->rcu, rcu_free_wq);
4470 } else {
4471 /*
4472 * We're the sole accessor of @wq at this point. Directly
4473 * access numa_pwq_tbl[] and dfl_pwq to put the base refs.
4474 * @wq will be freed when the last pwq is released.
4475 */
4476 for_each_node(node) {
4477 pwq = rcu_access_pointer(wq->numa_pwq_tbl[node]);
4478 RCU_INIT_POINTER(wq->numa_pwq_tbl[node], NULL);
4479 put_pwq_unlocked(pwq);
4480 }
4481
4482 /*
4483 * Put dfl_pwq. @wq may be freed any time after dfl_pwq is
4484 * put. Don't access it afterwards.
4485 */
4486 pwq = wq->dfl_pwq;
4487 wq->dfl_pwq = NULL;
4488 put_pwq_unlocked(pwq);
4489 }
4490}
4491EXPORT_SYMBOL_GPL(destroy_workqueue);
4492
4493/**
4494 * workqueue_set_max_active - adjust max_active of a workqueue
4495 * @wq: target workqueue
4496 * @max_active: new max_active value.
4497 *
4498 * Set max_active of @wq to @max_active.
4499 *
4500 * CONTEXT:
4501 * Don't call from IRQ context.
4502 */
4503void workqueue_set_max_active(struct workqueue_struct *wq, int max_active)
4504{
4505 struct pool_workqueue *pwq;
4506
4507 /* disallow meddling with max_active for ordered workqueues */
4508 if (WARN_ON(wq->flags & __WQ_ORDERED_EXPLICIT))
4509 return;
4510
4511 max_active = wq_clamp_max_active(max_active, wq->flags, wq->name);
4512
4513 mutex_lock(&wq->mutex);
4514
4515 wq->flags &= ~__WQ_ORDERED;
4516 wq->saved_max_active = max_active;
4517
4518 for_each_pwq(pwq, wq)
4519 pwq_adjust_max_active(pwq);
4520
4521 mutex_unlock(&wq->mutex);
4522}
4523EXPORT_SYMBOL_GPL(workqueue_set_max_active);
4524
4525/**
4526 * current_work - retrieve %current task's work struct
4527 *
4528 * Determine if %current task is a workqueue worker and what it's working on.
4529 * Useful to find out the context that the %current task is running in.
4530 *
4531 * Return: work struct if %current task is a workqueue worker, %NULL otherwise.
4532 */
4533struct work_struct *current_work(void)
4534{
4535 struct worker *worker = current_wq_worker();
4536
4537 return worker ? worker->current_work : NULL;
4538}
4539EXPORT_SYMBOL(current_work);
4540
4541/**
4542 * current_is_workqueue_rescuer - is %current workqueue rescuer?
4543 *
4544 * Determine whether %current is a workqueue rescuer. Can be used from
4545 * work functions to determine whether it's being run off the rescuer task.
4546 *
4547 * Return: %true if %current is a workqueue rescuer. %false otherwise.
4548 */
4549bool current_is_workqueue_rescuer(void)
4550{
4551 struct worker *worker = current_wq_worker();
4552
4553 return worker && worker->rescue_wq;
4554}
4555
4556/**
4557 * workqueue_congested - test whether a workqueue is congested
4558 * @cpu: CPU in question
4559 * @wq: target workqueue
4560 *
4561 * Test whether @wq's cpu workqueue for @cpu is congested. There is
4562 * no synchronization around this function and the test result is
4563 * unreliable and only useful as advisory hints or for debugging.
4564 *
4565 * If @cpu is WORK_CPU_UNBOUND, the test is performed on the local CPU.
4566 * Note that both per-cpu and unbound workqueues may be associated with
4567 * multiple pool_workqueues which have separate congested states. A
4568 * workqueue being congested on one CPU doesn't mean the workqueue is also
4569 * contested on other CPUs / NUMA nodes.
4570 *
4571 * Return:
4572 * %true if congested, %false otherwise.
4573 */
4574bool workqueue_congested(int cpu, struct workqueue_struct *wq)
4575{
4576 struct pool_workqueue *pwq;
4577 bool ret;
4578
4579 rcu_read_lock();
4580 preempt_disable();
4581
4582 if (cpu == WORK_CPU_UNBOUND)
4583 cpu = smp_processor_id();
4584
4585 if (!(wq->flags & WQ_UNBOUND))
4586 pwq = per_cpu_ptr(wq->cpu_pwqs, cpu);
4587 else
4588 pwq = unbound_pwq_by_node(wq, cpu_to_node(cpu));
4589
4590 ret = !list_empty(&pwq->inactive_works);
4591 preempt_enable();
4592 rcu_read_unlock();
4593
4594 return ret;
4595}
4596EXPORT_SYMBOL_GPL(workqueue_congested);
4597
4598/**
4599 * work_busy - test whether a work is currently pending or running
4600 * @work: the work to be tested
4601 *
4602 * Test whether @work is currently pending or running. There is no
4603 * synchronization around this function and the test result is
4604 * unreliable and only useful as advisory hints or for debugging.
4605 *
4606 * Return:
4607 * OR'd bitmask of WORK_BUSY_* bits.
4608 */
4609unsigned int work_busy(struct work_struct *work)
4610{
4611 struct worker_pool *pool;
4612 unsigned long flags;
4613 unsigned int ret = 0;
4614
4615 if (work_pending(work))
4616 ret |= WORK_BUSY_PENDING;
4617
4618 rcu_read_lock();
4619 pool = get_work_pool(work);
4620 if (pool) {
4621 raw_spin_lock_irqsave(&pool->lock, flags);
4622 if (find_worker_executing_work(pool, work))
4623 ret |= WORK_BUSY_RUNNING;
4624 raw_spin_unlock_irqrestore(&pool->lock, flags);
4625 }
4626 rcu_read_unlock();
4627
4628 return ret;
4629}
4630EXPORT_SYMBOL_GPL(work_busy);
4631
4632/**
4633 * set_worker_desc - set description for the current work item
4634 * @fmt: printf-style format string
4635 * @...: arguments for the format string
4636 *
4637 * This function can be called by a running work function to describe what
4638 * the work item is about. If the worker task gets dumped, this
4639 * information will be printed out together to help debugging. The
4640 * description can be at most WORKER_DESC_LEN including the trailing '\0'.
4641 */
4642void set_worker_desc(const char *fmt, ...)
4643{
4644 struct worker *worker = current_wq_worker();
4645 va_list args;
4646
4647 if (worker) {
4648 va_start(args, fmt);
4649 vsnprintf(worker->desc, sizeof(worker->desc), fmt, args);
4650 va_end(args);
4651 }
4652}
4653EXPORT_SYMBOL_GPL(set_worker_desc);
4654
4655/**
4656 * print_worker_info - print out worker information and description
4657 * @log_lvl: the log level to use when printing
4658 * @task: target task
4659 *
4660 * If @task is a worker and currently executing a work item, print out the
4661 * name of the workqueue being serviced and worker description set with
4662 * set_worker_desc() by the currently executing work item.
4663 *
4664 * This function can be safely called on any task as long as the
4665 * task_struct itself is accessible. While safe, this function isn't
4666 * synchronized and may print out mixups or garbages of limited length.
4667 */
4668void print_worker_info(const char *log_lvl, struct task_struct *task)
4669{
4670 work_func_t *fn = NULL;
4671 char name[WQ_NAME_LEN] = { };
4672 char desc[WORKER_DESC_LEN] = { };
4673 struct pool_workqueue *pwq = NULL;
4674 struct workqueue_struct *wq = NULL;
4675 struct worker *worker;
4676
4677 if (!(task->flags & PF_WQ_WORKER))
4678 return;
4679
4680 /*
4681 * This function is called without any synchronization and @task
4682 * could be in any state. Be careful with dereferences.
4683 */
4684 worker = kthread_probe_data(task);
4685
4686 /*
4687 * Carefully copy the associated workqueue's workfn, name and desc.
4688 * Keep the original last '\0' in case the original is garbage.
4689 */
4690 copy_from_kernel_nofault(&fn, &worker->current_func, sizeof(fn));
4691 copy_from_kernel_nofault(&pwq, &worker->current_pwq, sizeof(pwq));
4692 copy_from_kernel_nofault(&wq, &pwq->wq, sizeof(wq));
4693 copy_from_kernel_nofault(name, wq->name, sizeof(name) - 1);
4694 copy_from_kernel_nofault(desc, worker->desc, sizeof(desc) - 1);
4695
4696 if (fn || name[0] || desc[0]) {
4697 printk("%sWorkqueue: %s %ps", log_lvl, name, fn);
4698 if (strcmp(name, desc))
4699 pr_cont(" (%s)", desc);
4700 pr_cont("\n");
4701 }
4702}
4703
4704static void pr_cont_pool_info(struct worker_pool *pool)
4705{
4706 pr_cont(" cpus=%*pbl", nr_cpumask_bits, pool->attrs->cpumask);
4707 if (pool->node != NUMA_NO_NODE)
4708 pr_cont(" node=%d", pool->node);
4709 pr_cont(" flags=0x%x nice=%d", pool->flags, pool->attrs->nice);
4710}
4711
4712static void pr_cont_work(bool comma, struct work_struct *work)
4713{
4714 if (work->func == wq_barrier_func) {
4715 struct wq_barrier *barr;
4716
4717 barr = container_of(work, struct wq_barrier, work);
4718
4719 pr_cont("%s BAR(%d)", comma ? "," : "",
4720 task_pid_nr(barr->task));
4721 } else {
4722 pr_cont("%s %ps", comma ? "," : "", work->func);
4723 }
4724}
4725
4726static void show_pwq(struct pool_workqueue *pwq)
4727{
4728 struct worker_pool *pool = pwq->pool;
4729 struct work_struct *work;
4730 struct worker *worker;
4731 bool has_in_flight = false, has_pending = false;
4732 int bkt;
4733
4734 pr_info(" pwq %d:", pool->id);
4735 pr_cont_pool_info(pool);
4736
4737 pr_cont(" active=%d/%d refcnt=%d%s\n",
4738 pwq->nr_active, pwq->max_active, pwq->refcnt,
4739 !list_empty(&pwq->mayday_node) ? " MAYDAY" : "");
4740
4741 hash_for_each(pool->busy_hash, bkt, worker, hentry) {
4742 if (worker->current_pwq == pwq) {
4743 has_in_flight = true;
4744 break;
4745 }
4746 }
4747 if (has_in_flight) {
4748 bool comma = false;
4749
4750 pr_info(" in-flight:");
4751 hash_for_each(pool->busy_hash, bkt, worker, hentry) {
4752 if (worker->current_pwq != pwq)
4753 continue;
4754
4755 pr_cont("%s %d%s:%ps", comma ? "," : "",
4756 task_pid_nr(worker->task),
4757 worker->rescue_wq ? "(RESCUER)" : "",
4758 worker->current_func);
4759 list_for_each_entry(work, &worker->scheduled, entry)
4760 pr_cont_work(false, work);
4761 comma = true;
4762 }
4763 pr_cont("\n");
4764 }
4765
4766 list_for_each_entry(work, &pool->worklist, entry) {
4767 if (get_work_pwq(work) == pwq) {
4768 has_pending = true;
4769 break;
4770 }
4771 }
4772 if (has_pending) {
4773 bool comma = false;
4774
4775 pr_info(" pending:");
4776 list_for_each_entry(work, &pool->worklist, entry) {
4777 if (get_work_pwq(work) != pwq)
4778 continue;
4779
4780 pr_cont_work(comma, work);
4781 comma = !(*work_data_bits(work) & WORK_STRUCT_LINKED);
4782 }
4783 pr_cont("\n");
4784 }
4785
4786 if (!list_empty(&pwq->inactive_works)) {
4787 bool comma = false;
4788
4789 pr_info(" inactive:");
4790 list_for_each_entry(work, &pwq->inactive_works, entry) {
4791 pr_cont_work(comma, work);
4792 comma = !(*work_data_bits(work) & WORK_STRUCT_LINKED);
4793 }
4794 pr_cont("\n");
4795 }
4796}
4797
4798/**
4799 * show_one_workqueue - dump state of specified workqueue
4800 * @wq: workqueue whose state will be printed
4801 */
4802void show_one_workqueue(struct workqueue_struct *wq)
4803{
4804 struct pool_workqueue *pwq;
4805 bool idle = true;
4806 unsigned long flags;
4807
4808 for_each_pwq(pwq, wq) {
4809 if (pwq->nr_active || !list_empty(&pwq->inactive_works)) {
4810 idle = false;
4811 break;
4812 }
4813 }
4814 if (idle) /* Nothing to print for idle workqueue */
4815 return;
4816
4817 pr_info("workqueue %s: flags=0x%x\n", wq->name, wq->flags);
4818
4819 for_each_pwq(pwq, wq) {
4820 raw_spin_lock_irqsave(&pwq->pool->lock, flags);
4821 if (pwq->nr_active || !list_empty(&pwq->inactive_works)) {
4822 /*
4823 * Defer printing to avoid deadlocks in console
4824 * drivers that queue work while holding locks
4825 * also taken in their write paths.
4826 */
4827 printk_deferred_enter();
4828 show_pwq(pwq);
4829 printk_deferred_exit();
4830 }
4831 raw_spin_unlock_irqrestore(&pwq->pool->lock, flags);
4832 /*
4833 * We could be printing a lot from atomic context, e.g.
4834 * sysrq-t -> show_all_workqueues(). Avoid triggering
4835 * hard lockup.
4836 */
4837 touch_nmi_watchdog();
4838 }
4839
4840}
4841
4842/**
4843 * show_one_worker_pool - dump state of specified worker pool
4844 * @pool: worker pool whose state will be printed
4845 */
4846static void show_one_worker_pool(struct worker_pool *pool)
4847{
4848 struct worker *worker;
4849 bool first = true;
4850 unsigned long flags;
4851
4852 raw_spin_lock_irqsave(&pool->lock, flags);
4853 if (pool->nr_workers == pool->nr_idle)
4854 goto next_pool;
4855 /*
4856 * Defer printing to avoid deadlocks in console drivers that
4857 * queue work while holding locks also taken in their write
4858 * paths.
4859 */
4860 printk_deferred_enter();
4861 pr_info("pool %d:", pool->id);
4862 pr_cont_pool_info(pool);
4863 pr_cont(" hung=%us workers=%d",
4864 jiffies_to_msecs(jiffies - pool->watchdog_ts) / 1000,
4865 pool->nr_workers);
4866 if (pool->manager)
4867 pr_cont(" manager: %d",
4868 task_pid_nr(pool->manager->task));
4869 list_for_each_entry(worker, &pool->idle_list, entry) {
4870 pr_cont(" %s%d", first ? "idle: " : "",
4871 task_pid_nr(worker->task));
4872 first = false;
4873 }
4874 pr_cont("\n");
4875 printk_deferred_exit();
4876next_pool:
4877 raw_spin_unlock_irqrestore(&pool->lock, flags);
4878 /*
4879 * We could be printing a lot from atomic context, e.g.
4880 * sysrq-t -> show_all_workqueues(). Avoid triggering
4881 * hard lockup.
4882 */
4883 touch_nmi_watchdog();
4884
4885}
4886
4887/**
4888 * show_all_workqueues - dump workqueue state
4889 *
4890 * Called from a sysrq handler or try_to_freeze_tasks() and prints out
4891 * all busy workqueues and pools.
4892 */
4893void show_all_workqueues(void)
4894{
4895 struct workqueue_struct *wq;
4896 struct worker_pool *pool;
4897 int pi;
4898
4899 rcu_read_lock();
4900
4901 pr_info("Showing busy workqueues and worker pools:\n");
4902
4903 list_for_each_entry_rcu(wq, &workqueues, list)
4904 show_one_workqueue(wq);
4905
4906 for_each_pool(pool, pi)
4907 show_one_worker_pool(pool);
4908
4909 rcu_read_unlock();
4910}
4911
4912/* used to show worker information through /proc/PID/{comm,stat,status} */
4913void wq_worker_comm(char *buf, size_t size, struct task_struct *task)
4914{
4915 int off;
4916
4917 /* always show the actual comm */
4918 off = strscpy(buf, task->comm, size);
4919 if (off < 0)
4920 return;
4921
4922 /* stabilize PF_WQ_WORKER and worker pool association */
4923 mutex_lock(&wq_pool_attach_mutex);
4924
4925 if (task->flags & PF_WQ_WORKER) {
4926 struct worker *worker = kthread_data(task);
4927 struct worker_pool *pool = worker->pool;
4928
4929 if (pool) {
4930 raw_spin_lock_irq(&pool->lock);
4931 /*
4932 * ->desc tracks information (wq name or
4933 * set_worker_desc()) for the latest execution. If
4934 * current, prepend '+', otherwise '-'.
4935 */
4936 if (worker->desc[0] != '\0') {
4937 if (worker->current_work)
4938 scnprintf(buf + off, size - off, "+%s",
4939 worker->desc);
4940 else
4941 scnprintf(buf + off, size - off, "-%s",
4942 worker->desc);
4943 }
4944 raw_spin_unlock_irq(&pool->lock);
4945 }
4946 }
4947
4948 mutex_unlock(&wq_pool_attach_mutex);
4949}
4950
4951#ifdef CONFIG_SMP
4952
4953/*
4954 * CPU hotplug.
4955 *
4956 * There are two challenges in supporting CPU hotplug. Firstly, there
4957 * are a lot of assumptions on strong associations among work, pwq and
4958 * pool which make migrating pending and scheduled works very
4959 * difficult to implement without impacting hot paths. Secondly,
4960 * worker pools serve mix of short, long and very long running works making
4961 * blocked draining impractical.
4962 *
4963 * This is solved by allowing the pools to be disassociated from the CPU
4964 * running as an unbound one and allowing it to be reattached later if the
4965 * cpu comes back online.
4966 */
4967
4968static void unbind_workers(int cpu)
4969{
4970 struct worker_pool *pool;
4971 struct worker *worker;
4972
4973 for_each_cpu_worker_pool(pool, cpu) {
4974 mutex_lock(&wq_pool_attach_mutex);
4975 raw_spin_lock_irq(&pool->lock);
4976
4977 /*
4978 * We've blocked all attach/detach operations. Make all workers
4979 * unbound and set DISASSOCIATED. Before this, all workers
4980 * must be on the cpu. After this, they may become diasporas.
4981 * And the preemption disabled section in their sched callbacks
4982 * are guaranteed to see WORKER_UNBOUND since the code here
4983 * is on the same cpu.
4984 */
4985 for_each_pool_worker(worker, pool)
4986 worker->flags |= WORKER_UNBOUND;
4987
4988 pool->flags |= POOL_DISASSOCIATED;
4989
4990 /*
4991 * The handling of nr_running in sched callbacks are disabled
4992 * now. Zap nr_running. After this, nr_running stays zero and
4993 * need_more_worker() and keep_working() are always true as
4994 * long as the worklist is not empty. This pool now behaves as
4995 * an unbound (in terms of concurrency management) pool which
4996 * are served by workers tied to the pool.
4997 */
4998 pool->nr_running = 0;
4999
5000 /*
5001 * With concurrency management just turned off, a busy
5002 * worker blocking could lead to lengthy stalls. Kick off
5003 * unbound chain execution of currently pending work items.
5004 */
5005 wake_up_worker(pool);
5006
5007 raw_spin_unlock_irq(&pool->lock);
5008
5009 for_each_pool_worker(worker, pool) {
5010 kthread_set_per_cpu(worker->task, -1);
5011 if (cpumask_intersects(wq_unbound_cpumask, cpu_active_mask))
5012 WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task, wq_unbound_cpumask) < 0);
5013 else
5014 WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task, cpu_possible_mask) < 0);
5015 }
5016
5017 mutex_unlock(&wq_pool_attach_mutex);
5018 }
5019}
5020
5021/**
5022 * rebind_workers - rebind all workers of a pool to the associated CPU
5023 * @pool: pool of interest
5024 *
5025 * @pool->cpu is coming online. Rebind all workers to the CPU.
5026 */
5027static void rebind_workers(struct worker_pool *pool)
5028{
5029 struct worker *worker;
5030
5031 lockdep_assert_held(&wq_pool_attach_mutex);
5032
5033 /*
5034 * Restore CPU affinity of all workers. As all idle workers should
5035 * be on the run-queue of the associated CPU before any local
5036 * wake-ups for concurrency management happen, restore CPU affinity
5037 * of all workers first and then clear UNBOUND. As we're called
5038 * from CPU_ONLINE, the following shouldn't fail.
5039 */
5040 for_each_pool_worker(worker, pool) {
5041 kthread_set_per_cpu(worker->task, pool->cpu);
5042 WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task,
5043 pool->attrs->cpumask) < 0);
5044 }
5045
5046 raw_spin_lock_irq(&pool->lock);
5047
5048 pool->flags &= ~POOL_DISASSOCIATED;
5049
5050 for_each_pool_worker(worker, pool) {
5051 unsigned int worker_flags = worker->flags;
5052
5053 /*
5054 * We want to clear UNBOUND but can't directly call
5055 * worker_clr_flags() or adjust nr_running. Atomically
5056 * replace UNBOUND with another NOT_RUNNING flag REBOUND.
5057 * @worker will clear REBOUND using worker_clr_flags() when
5058 * it initiates the next execution cycle thus restoring
5059 * concurrency management. Note that when or whether
5060 * @worker clears REBOUND doesn't affect correctness.
5061 *
5062 * WRITE_ONCE() is necessary because @worker->flags may be
5063 * tested without holding any lock in
5064 * wq_worker_running(). Without it, NOT_RUNNING test may
5065 * fail incorrectly leading to premature concurrency
5066 * management operations.
5067 */
5068 WARN_ON_ONCE(!(worker_flags & WORKER_UNBOUND));
5069 worker_flags |= WORKER_REBOUND;
5070 worker_flags &= ~WORKER_UNBOUND;
5071 WRITE_ONCE(worker->flags, worker_flags);
5072 }
5073
5074 raw_spin_unlock_irq(&pool->lock);
5075}
5076
5077/**
5078 * restore_unbound_workers_cpumask - restore cpumask of unbound workers
5079 * @pool: unbound pool of interest
5080 * @cpu: the CPU which is coming up
5081 *
5082 * An unbound pool may end up with a cpumask which doesn't have any online
5083 * CPUs. When a worker of such pool get scheduled, the scheduler resets
5084 * its cpus_allowed. If @cpu is in @pool's cpumask which didn't have any
5085 * online CPU before, cpus_allowed of all its workers should be restored.
5086 */
5087static void restore_unbound_workers_cpumask(struct worker_pool *pool, int cpu)
5088{
5089 static cpumask_t cpumask;
5090 struct worker *worker;
5091
5092 lockdep_assert_held(&wq_pool_attach_mutex);
5093
5094 /* is @cpu allowed for @pool? */
5095 if (!cpumask_test_cpu(cpu, pool->attrs->cpumask))
5096 return;
5097
5098 cpumask_and(&cpumask, pool->attrs->cpumask, cpu_online_mask);
5099
5100 /* as we're called from CPU_ONLINE, the following shouldn't fail */
5101 for_each_pool_worker(worker, pool)
5102 WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task, &cpumask) < 0);
5103}
5104
5105int workqueue_prepare_cpu(unsigned int cpu)
5106{
5107 struct worker_pool *pool;
5108
5109 for_each_cpu_worker_pool(pool, cpu) {
5110 if (pool->nr_workers)
5111 continue;
5112 if (!create_worker(pool))
5113 return -ENOMEM;
5114 }
5115 return 0;
5116}
5117
5118int workqueue_online_cpu(unsigned int cpu)
5119{
5120 struct worker_pool *pool;
5121 struct workqueue_struct *wq;
5122 int pi;
5123
5124 mutex_lock(&wq_pool_mutex);
5125
5126 for_each_pool(pool, pi) {
5127 mutex_lock(&wq_pool_attach_mutex);
5128
5129 if (pool->cpu == cpu)
5130 rebind_workers(pool);
5131 else if (pool->cpu < 0)
5132 restore_unbound_workers_cpumask(pool, cpu);
5133
5134 mutex_unlock(&wq_pool_attach_mutex);
5135 }
5136
5137 /* update NUMA affinity of unbound workqueues */
5138 list_for_each_entry(wq, &workqueues, list)
5139 wq_update_unbound_numa(wq, cpu, true);
5140
5141 mutex_unlock(&wq_pool_mutex);
5142 return 0;
5143}
5144
5145int workqueue_offline_cpu(unsigned int cpu)
5146{
5147 struct workqueue_struct *wq;
5148
5149 /* unbinding per-cpu workers should happen on the local CPU */
5150 if (WARN_ON(cpu != smp_processor_id()))
5151 return -1;
5152
5153 unbind_workers(cpu);
5154
5155 /* update NUMA affinity of unbound workqueues */
5156 mutex_lock(&wq_pool_mutex);
5157 list_for_each_entry(wq, &workqueues, list)
5158 wq_update_unbound_numa(wq, cpu, false);
5159 mutex_unlock(&wq_pool_mutex);
5160
5161 return 0;
5162}
5163
5164struct work_for_cpu {
5165 struct work_struct work;
5166 long (*fn)(void *);
5167 void *arg;
5168 long ret;
5169};
5170
5171static void work_for_cpu_fn(struct work_struct *work)
5172{
5173 struct work_for_cpu *wfc = container_of(work, struct work_for_cpu, work);
5174
5175 wfc->ret = wfc->fn(wfc->arg);
5176}
5177
5178/**
5179 * work_on_cpu - run a function in thread context on a particular cpu
5180 * @cpu: the cpu to run on
5181 * @fn: the function to run
5182 * @arg: the function arg
5183 *
5184 * It is up to the caller to ensure that the cpu doesn't go offline.
5185 * The caller must not hold any locks which would prevent @fn from completing.
5186 *
5187 * Return: The value @fn returns.
5188 */
5189long work_on_cpu(int cpu, long (*fn)(void *), void *arg)
5190{
5191 struct work_for_cpu wfc = { .fn = fn, .arg = arg };
5192
5193 INIT_WORK_ONSTACK(&wfc.work, work_for_cpu_fn);
5194 schedule_work_on(cpu, &wfc.work);
5195 flush_work(&wfc.work);
5196 destroy_work_on_stack(&wfc.work);
5197 return wfc.ret;
5198}
5199EXPORT_SYMBOL_GPL(work_on_cpu);
5200
5201/**
5202 * work_on_cpu_safe - run a function in thread context on a particular cpu
5203 * @cpu: the cpu to run on
5204 * @fn: the function to run
5205 * @arg: the function argument
5206 *
5207 * Disables CPU hotplug and calls work_on_cpu(). The caller must not hold
5208 * any locks which would prevent @fn from completing.
5209 *
5210 * Return: The value @fn returns.
5211 */
5212long work_on_cpu_safe(int cpu, long (*fn)(void *), void *arg)
5213{
5214 long ret = -ENODEV;
5215
5216 cpus_read_lock();
5217 if (cpu_online(cpu))
5218 ret = work_on_cpu(cpu, fn, arg);
5219 cpus_read_unlock();
5220 return ret;
5221}
5222EXPORT_SYMBOL_GPL(work_on_cpu_safe);
5223#endif /* CONFIG_SMP */
5224
5225#ifdef CONFIG_FREEZER
5226
5227/**
5228 * freeze_workqueues_begin - begin freezing workqueues
5229 *
5230 * Start freezing workqueues. After this function returns, all freezable
5231 * workqueues will queue new works to their inactive_works list instead of
5232 * pool->worklist.
5233 *
5234 * CONTEXT:
5235 * Grabs and releases wq_pool_mutex, wq->mutex and pool->lock's.
5236 */
5237void freeze_workqueues_begin(void)
5238{
5239 struct workqueue_struct *wq;
5240 struct pool_workqueue *pwq;
5241
5242 mutex_lock(&wq_pool_mutex);
5243
5244 WARN_ON_ONCE(workqueue_freezing);
5245 workqueue_freezing = true;
5246
5247 list_for_each_entry(wq, &workqueues, list) {
5248 mutex_lock(&wq->mutex);
5249 for_each_pwq(pwq, wq)
5250 pwq_adjust_max_active(pwq);
5251 mutex_unlock(&wq->mutex);
5252 }
5253
5254 mutex_unlock(&wq_pool_mutex);
5255}
5256
5257/**
5258 * freeze_workqueues_busy - are freezable workqueues still busy?
5259 *
5260 * Check whether freezing is complete. This function must be called
5261 * between freeze_workqueues_begin() and thaw_workqueues().
5262 *
5263 * CONTEXT:
5264 * Grabs and releases wq_pool_mutex.
5265 *
5266 * Return:
5267 * %true if some freezable workqueues are still busy. %false if freezing
5268 * is complete.
5269 */
5270bool freeze_workqueues_busy(void)
5271{
5272 bool busy = false;
5273 struct workqueue_struct *wq;
5274 struct pool_workqueue *pwq;
5275
5276 mutex_lock(&wq_pool_mutex);
5277
5278 WARN_ON_ONCE(!workqueue_freezing);
5279
5280 list_for_each_entry(wq, &workqueues, list) {
5281 if (!(wq->flags & WQ_FREEZABLE))
5282 continue;
5283 /*
5284 * nr_active is monotonically decreasing. It's safe
5285 * to peek without lock.
5286 */
5287 rcu_read_lock();
5288 for_each_pwq(pwq, wq) {
5289 WARN_ON_ONCE(pwq->nr_active < 0);
5290 if (pwq->nr_active) {
5291 busy = true;
5292 rcu_read_unlock();
5293 goto out_unlock;
5294 }
5295 }
5296 rcu_read_unlock();
5297 }
5298out_unlock:
5299 mutex_unlock(&wq_pool_mutex);
5300 return busy;
5301}
5302
5303/**
5304 * thaw_workqueues - thaw workqueues
5305 *
5306 * Thaw workqueues. Normal queueing is restored and all collected
5307 * frozen works are transferred to their respective pool worklists.
5308 *
5309 * CONTEXT:
5310 * Grabs and releases wq_pool_mutex, wq->mutex and pool->lock's.
5311 */
5312void thaw_workqueues(void)
5313{
5314 struct workqueue_struct *wq;
5315 struct pool_workqueue *pwq;
5316
5317 mutex_lock(&wq_pool_mutex);
5318
5319 if (!workqueue_freezing)
5320 goto out_unlock;
5321
5322 workqueue_freezing = false;
5323
5324 /* restore max_active and repopulate worklist */
5325 list_for_each_entry(wq, &workqueues, list) {
5326 mutex_lock(&wq->mutex);
5327 for_each_pwq(pwq, wq)
5328 pwq_adjust_max_active(pwq);
5329 mutex_unlock(&wq->mutex);
5330 }
5331
5332out_unlock:
5333 mutex_unlock(&wq_pool_mutex);
5334}
5335#endif /* CONFIG_FREEZER */
5336
5337static int workqueue_apply_unbound_cpumask(void)
5338{
5339 LIST_HEAD(ctxs);
5340 int ret = 0;
5341 struct workqueue_struct *wq;
5342 struct apply_wqattrs_ctx *ctx, *n;
5343
5344 lockdep_assert_held(&wq_pool_mutex);
5345
5346 list_for_each_entry(wq, &workqueues, list) {
5347 if (!(wq->flags & WQ_UNBOUND))
5348 continue;
5349 /* creating multiple pwqs breaks ordering guarantee */
5350 if (wq->flags & __WQ_ORDERED)
5351 continue;
5352
5353 ctx = apply_wqattrs_prepare(wq, wq->unbound_attrs);
5354 if (!ctx) {
5355 ret = -ENOMEM;
5356 break;
5357 }
5358
5359 list_add_tail(&ctx->list, &ctxs);
5360 }
5361
5362 list_for_each_entry_safe(ctx, n, &ctxs, list) {
5363 if (!ret)
5364 apply_wqattrs_commit(ctx);
5365 apply_wqattrs_cleanup(ctx);
5366 }
5367
5368 return ret;
5369}
5370
5371/**
5372 * workqueue_set_unbound_cpumask - Set the low-level unbound cpumask
5373 * @cpumask: the cpumask to set
5374 *
5375 * The low-level workqueues cpumask is a global cpumask that limits
5376 * the affinity of all unbound workqueues. This function check the @cpumask
5377 * and apply it to all unbound workqueues and updates all pwqs of them.
5378 *
5379 * Return: 0 - Success
5380 * -EINVAL - Invalid @cpumask
5381 * -ENOMEM - Failed to allocate memory for attrs or pwqs.
5382 */
5383int workqueue_set_unbound_cpumask(cpumask_var_t cpumask)
5384{
5385 int ret = -EINVAL;
5386 cpumask_var_t saved_cpumask;
5387
5388 /*
5389 * Not excluding isolated cpus on purpose.
5390 * If the user wishes to include them, we allow that.
5391 */
5392 cpumask_and(cpumask, cpumask, cpu_possible_mask);
5393 if (!cpumask_empty(cpumask)) {
5394 apply_wqattrs_lock();
5395 if (cpumask_equal(cpumask, wq_unbound_cpumask)) {
5396 ret = 0;
5397 goto out_unlock;
5398 }
5399
5400 if (!zalloc_cpumask_var(&saved_cpumask, GFP_KERNEL)) {
5401 ret = -ENOMEM;
5402 goto out_unlock;
5403 }
5404
5405 /* save the old wq_unbound_cpumask. */
5406 cpumask_copy(saved_cpumask, wq_unbound_cpumask);
5407
5408 /* update wq_unbound_cpumask at first and apply it to wqs. */
5409 cpumask_copy(wq_unbound_cpumask, cpumask);
5410 ret = workqueue_apply_unbound_cpumask();
5411
5412 /* restore the wq_unbound_cpumask when failed. */
5413 if (ret < 0)
5414 cpumask_copy(wq_unbound_cpumask, saved_cpumask);
5415
5416 free_cpumask_var(saved_cpumask);
5417out_unlock:
5418 apply_wqattrs_unlock();
5419 }
5420
5421 return ret;
5422}
5423
5424#ifdef CONFIG_SYSFS
5425/*
5426 * Workqueues with WQ_SYSFS flag set is visible to userland via
5427 * /sys/bus/workqueue/devices/WQ_NAME. All visible workqueues have the
5428 * following attributes.
5429 *
5430 * per_cpu RO bool : whether the workqueue is per-cpu or unbound
5431 * max_active RW int : maximum number of in-flight work items
5432 *
5433 * Unbound workqueues have the following extra attributes.
5434 *
5435 * pool_ids RO int : the associated pool IDs for each node
5436 * nice RW int : nice value of the workers
5437 * cpumask RW mask : bitmask of allowed CPUs for the workers
5438 * numa RW bool : whether enable NUMA affinity
5439 */
5440struct wq_device {
5441 struct workqueue_struct *wq;
5442 struct device dev;
5443};
5444
5445static struct workqueue_struct *dev_to_wq(struct device *dev)
5446{
5447 struct wq_device *wq_dev = container_of(dev, struct wq_device, dev);
5448
5449 return wq_dev->wq;
5450}
5451
5452static ssize_t per_cpu_show(struct device *dev, struct device_attribute *attr,
5453 char *buf)
5454{
5455 struct workqueue_struct *wq = dev_to_wq(dev);
5456
5457 return scnprintf(buf, PAGE_SIZE, "%d\n", (bool)!(wq->flags & WQ_UNBOUND));
5458}
5459static DEVICE_ATTR_RO(per_cpu);
5460
5461static ssize_t max_active_show(struct device *dev,
5462 struct device_attribute *attr, char *buf)
5463{
5464 struct workqueue_struct *wq = dev_to_wq(dev);
5465
5466 return scnprintf(buf, PAGE_SIZE, "%d\n", wq->saved_max_active);
5467}
5468
5469static ssize_t max_active_store(struct device *dev,
5470 struct device_attribute *attr, const char *buf,
5471 size_t count)
5472{
5473 struct workqueue_struct *wq = dev_to_wq(dev);
5474 int val;
5475
5476 if (sscanf(buf, "%d", &val) != 1 || val <= 0)
5477 return -EINVAL;
5478
5479 workqueue_set_max_active(wq, val);
5480 return count;
5481}
5482static DEVICE_ATTR_RW(max_active);
5483
5484static struct attribute *wq_sysfs_attrs[] = {
5485 &dev_attr_per_cpu.attr,
5486 &dev_attr_max_active.attr,
5487 NULL,
5488};
5489ATTRIBUTE_GROUPS(wq_sysfs);
5490
5491static ssize_t wq_pool_ids_show(struct device *dev,
5492 struct device_attribute *attr, char *buf)
5493{
5494 struct workqueue_struct *wq = dev_to_wq(dev);
5495 const char *delim = "";
5496 int node, written = 0;
5497
5498 cpus_read_lock();
5499 rcu_read_lock();
5500 for_each_node(node) {
5501 written += scnprintf(buf + written, PAGE_SIZE - written,
5502 "%s%d:%d", delim, node,
5503 unbound_pwq_by_node(wq, node)->pool->id);
5504 delim = " ";
5505 }
5506 written += scnprintf(buf + written, PAGE_SIZE - written, "\n");
5507 rcu_read_unlock();
5508 cpus_read_unlock();
5509
5510 return written;
5511}
5512
5513static ssize_t wq_nice_show(struct device *dev, struct device_attribute *attr,
5514 char *buf)
5515{
5516 struct workqueue_struct *wq = dev_to_wq(dev);
5517 int written;
5518
5519 mutex_lock(&wq->mutex);
5520 written = scnprintf(buf, PAGE_SIZE, "%d\n", wq->unbound_attrs->nice);
5521 mutex_unlock(&wq->mutex);
5522
5523 return written;
5524}
5525
5526/* prepare workqueue_attrs for sysfs store operations */
5527static struct workqueue_attrs *wq_sysfs_prep_attrs(struct workqueue_struct *wq)
5528{
5529 struct workqueue_attrs *attrs;
5530
5531 lockdep_assert_held(&wq_pool_mutex);
5532
5533 attrs = alloc_workqueue_attrs();
5534 if (!attrs)
5535 return NULL;
5536
5537 copy_workqueue_attrs(attrs, wq->unbound_attrs);
5538 return attrs;
5539}
5540
5541static ssize_t wq_nice_store(struct device *dev, struct device_attribute *attr,
5542 const char *buf, size_t count)
5543{
5544 struct workqueue_struct *wq = dev_to_wq(dev);
5545 struct workqueue_attrs *attrs;
5546 int ret = -ENOMEM;
5547
5548 apply_wqattrs_lock();
5549
5550 attrs = wq_sysfs_prep_attrs(wq);
5551 if (!attrs)
5552 goto out_unlock;
5553
5554 if (sscanf(buf, "%d", &attrs->nice) == 1 &&
5555 attrs->nice >= MIN_NICE && attrs->nice <= MAX_NICE)
5556 ret = apply_workqueue_attrs_locked(wq, attrs);
5557 else
5558 ret = -EINVAL;
5559
5560out_unlock:
5561 apply_wqattrs_unlock();
5562 free_workqueue_attrs(attrs);
5563 return ret ?: count;
5564}
5565
5566static ssize_t wq_cpumask_show(struct device *dev,
5567 struct device_attribute *attr, char *buf)
5568{
5569 struct workqueue_struct *wq = dev_to_wq(dev);
5570 int written;
5571
5572 mutex_lock(&wq->mutex);
5573 written = scnprintf(buf, PAGE_SIZE, "%*pb\n",
5574 cpumask_pr_args(wq->unbound_attrs->cpumask));
5575 mutex_unlock(&wq->mutex);
5576 return written;
5577}
5578
5579static ssize_t wq_cpumask_store(struct device *dev,
5580 struct device_attribute *attr,
5581 const char *buf, size_t count)
5582{
5583 struct workqueue_struct *wq = dev_to_wq(dev);
5584 struct workqueue_attrs *attrs;
5585 int ret = -ENOMEM;
5586
5587 apply_wqattrs_lock();
5588
5589 attrs = wq_sysfs_prep_attrs(wq);
5590 if (!attrs)
5591 goto out_unlock;
5592
5593 ret = cpumask_parse(buf, attrs->cpumask);
5594 if (!ret)
5595 ret = apply_workqueue_attrs_locked(wq, attrs);
5596
5597out_unlock:
5598 apply_wqattrs_unlock();
5599 free_workqueue_attrs(attrs);
5600 return ret ?: count;
5601}
5602
5603static ssize_t wq_numa_show(struct device *dev, struct device_attribute *attr,
5604 char *buf)
5605{
5606 struct workqueue_struct *wq = dev_to_wq(dev);
5607 int written;
5608
5609 mutex_lock(&wq->mutex);
5610 written = scnprintf(buf, PAGE_SIZE, "%d\n",
5611 !wq->unbound_attrs->no_numa);
5612 mutex_unlock(&wq->mutex);
5613
5614 return written;
5615}
5616
5617static ssize_t wq_numa_store(struct device *dev, struct device_attribute *attr,
5618 const char *buf, size_t count)
5619{
5620 struct workqueue_struct *wq = dev_to_wq(dev);
5621 struct workqueue_attrs *attrs;
5622 int v, ret = -ENOMEM;
5623
5624 apply_wqattrs_lock();
5625
5626 attrs = wq_sysfs_prep_attrs(wq);
5627 if (!attrs)
5628 goto out_unlock;
5629
5630 ret = -EINVAL;
5631 if (sscanf(buf, "%d", &v) == 1) {
5632 attrs->no_numa = !v;
5633 ret = apply_workqueue_attrs_locked(wq, attrs);
5634 }
5635
5636out_unlock:
5637 apply_wqattrs_unlock();
5638 free_workqueue_attrs(attrs);
5639 return ret ?: count;
5640}
5641
5642static struct device_attribute wq_sysfs_unbound_attrs[] = {
5643 __ATTR(pool_ids, 0444, wq_pool_ids_show, NULL),
5644 __ATTR(nice, 0644, wq_nice_show, wq_nice_store),
5645 __ATTR(cpumask, 0644, wq_cpumask_show, wq_cpumask_store),
5646 __ATTR(numa, 0644, wq_numa_show, wq_numa_store),
5647 __ATTR_NULL,
5648};
5649
5650static struct bus_type wq_subsys = {
5651 .name = "workqueue",
5652 .dev_groups = wq_sysfs_groups,
5653};
5654
5655static ssize_t wq_unbound_cpumask_show(struct device *dev,
5656 struct device_attribute *attr, char *buf)
5657{
5658 int written;
5659
5660 mutex_lock(&wq_pool_mutex);
5661 written = scnprintf(buf, PAGE_SIZE, "%*pb\n",
5662 cpumask_pr_args(wq_unbound_cpumask));
5663 mutex_unlock(&wq_pool_mutex);
5664
5665 return written;
5666}
5667
5668static ssize_t wq_unbound_cpumask_store(struct device *dev,
5669 struct device_attribute *attr, const char *buf, size_t count)
5670{
5671 cpumask_var_t cpumask;
5672 int ret;
5673
5674 if (!zalloc_cpumask_var(&cpumask, GFP_KERNEL))
5675 return -ENOMEM;
5676
5677 ret = cpumask_parse(buf, cpumask);
5678 if (!ret)
5679 ret = workqueue_set_unbound_cpumask(cpumask);
5680
5681 free_cpumask_var(cpumask);
5682 return ret ? ret : count;
5683}
5684
5685static struct device_attribute wq_sysfs_cpumask_attr =
5686 __ATTR(cpumask, 0644, wq_unbound_cpumask_show,
5687 wq_unbound_cpumask_store);
5688
5689static int __init wq_sysfs_init(void)
5690{
5691 int err;
5692
5693 err = subsys_virtual_register(&wq_subsys, NULL);
5694 if (err)
5695 return err;
5696
5697 return device_create_file(wq_subsys.dev_root, &wq_sysfs_cpumask_attr);
5698}
5699core_initcall(wq_sysfs_init);
5700
5701static void wq_device_release(struct device *dev)
5702{
5703 struct wq_device *wq_dev = container_of(dev, struct wq_device, dev);
5704
5705 kfree(wq_dev);
5706}
5707
5708/**
5709 * workqueue_sysfs_register - make a workqueue visible in sysfs
5710 * @wq: the workqueue to register
5711 *
5712 * Expose @wq in sysfs under /sys/bus/workqueue/devices.
5713 * alloc_workqueue*() automatically calls this function if WQ_SYSFS is set
5714 * which is the preferred method.
5715 *
5716 * Workqueue user should use this function directly iff it wants to apply
5717 * workqueue_attrs before making the workqueue visible in sysfs; otherwise,
5718 * apply_workqueue_attrs() may race against userland updating the
5719 * attributes.
5720 *
5721 * Return: 0 on success, -errno on failure.
5722 */
5723int workqueue_sysfs_register(struct workqueue_struct *wq)
5724{
5725 struct wq_device *wq_dev;
5726 int ret;
5727
5728 /*
5729 * Adjusting max_active or creating new pwqs by applying
5730 * attributes breaks ordering guarantee. Disallow exposing ordered
5731 * workqueues.
5732 */
5733 if (WARN_ON(wq->flags & __WQ_ORDERED_EXPLICIT))
5734 return -EINVAL;
5735
5736 wq->wq_dev = wq_dev = kzalloc(sizeof(*wq_dev), GFP_KERNEL);
5737 if (!wq_dev)
5738 return -ENOMEM;
5739
5740 wq_dev->wq = wq;
5741 wq_dev->dev.bus = &wq_subsys;
5742 wq_dev->dev.release = wq_device_release;
5743 dev_set_name(&wq_dev->dev, "%s", wq->name);
5744
5745 /*
5746 * unbound_attrs are created separately. Suppress uevent until
5747 * everything is ready.
5748 */
5749 dev_set_uevent_suppress(&wq_dev->dev, true);
5750
5751 ret = device_register(&wq_dev->dev);
5752 if (ret) {
5753 put_device(&wq_dev->dev);
5754 wq->wq_dev = NULL;
5755 return ret;
5756 }
5757
5758 if (wq->flags & WQ_UNBOUND) {
5759 struct device_attribute *attr;
5760
5761 for (attr = wq_sysfs_unbound_attrs; attr->attr.name; attr++) {
5762 ret = device_create_file(&wq_dev->dev, attr);
5763 if (ret) {
5764 device_unregister(&wq_dev->dev);
5765 wq->wq_dev = NULL;
5766 return ret;
5767 }
5768 }
5769 }
5770
5771 dev_set_uevent_suppress(&wq_dev->dev, false);
5772 kobject_uevent(&wq_dev->dev.kobj, KOBJ_ADD);
5773 return 0;
5774}
5775
5776/**
5777 * workqueue_sysfs_unregister - undo workqueue_sysfs_register()
5778 * @wq: the workqueue to unregister
5779 *
5780 * If @wq is registered to sysfs by workqueue_sysfs_register(), unregister.
5781 */
5782static void workqueue_sysfs_unregister(struct workqueue_struct *wq)
5783{
5784 struct wq_device *wq_dev = wq->wq_dev;
5785
5786 if (!wq->wq_dev)
5787 return;
5788
5789 wq->wq_dev = NULL;
5790 device_unregister(&wq_dev->dev);
5791}
5792#else /* CONFIG_SYSFS */
5793static void workqueue_sysfs_unregister(struct workqueue_struct *wq) { }
5794#endif /* CONFIG_SYSFS */
5795
5796/*
5797 * Workqueue watchdog.
5798 *
5799 * Stall may be caused by various bugs - missing WQ_MEM_RECLAIM, illegal
5800 * flush dependency, a concurrency managed work item which stays RUNNING
5801 * indefinitely. Workqueue stalls can be very difficult to debug as the
5802 * usual warning mechanisms don't trigger and internal workqueue state is
5803 * largely opaque.
5804 *
5805 * Workqueue watchdog monitors all worker pools periodically and dumps
5806 * state if some pools failed to make forward progress for a while where
5807 * forward progress is defined as the first item on ->worklist changing.
5808 *
5809 * This mechanism is controlled through the kernel parameter
5810 * "workqueue.watchdog_thresh" which can be updated at runtime through the
5811 * corresponding sysfs parameter file.
5812 */
5813#ifdef CONFIG_WQ_WATCHDOG
5814
5815static unsigned long wq_watchdog_thresh = 30;
5816static struct timer_list wq_watchdog_timer;
5817
5818static unsigned long wq_watchdog_touched = INITIAL_JIFFIES;
5819static DEFINE_PER_CPU(unsigned long, wq_watchdog_touched_cpu) = INITIAL_JIFFIES;
5820
5821static void wq_watchdog_reset_touched(void)
5822{
5823 int cpu;
5824
5825 wq_watchdog_touched = jiffies;
5826 for_each_possible_cpu(cpu)
5827 per_cpu(wq_watchdog_touched_cpu, cpu) = jiffies;
5828}
5829
5830static void wq_watchdog_timer_fn(struct timer_list *unused)
5831{
5832 unsigned long thresh = READ_ONCE(wq_watchdog_thresh) * HZ;
5833 bool lockup_detected = false;
5834 unsigned long now = jiffies;
5835 struct worker_pool *pool;
5836 int pi;
5837
5838 if (!thresh)
5839 return;
5840
5841 rcu_read_lock();
5842
5843 for_each_pool(pool, pi) {
5844 unsigned long pool_ts, touched, ts;
5845
5846 if (list_empty(&pool->worklist))
5847 continue;
5848
5849 /*
5850 * If a virtual machine is stopped by the host it can look to
5851 * the watchdog like a stall.
5852 */
5853 kvm_check_and_clear_guest_paused();
5854
5855 /* get the latest of pool and touched timestamps */
5856 if (pool->cpu >= 0)
5857 touched = READ_ONCE(per_cpu(wq_watchdog_touched_cpu, pool->cpu));
5858 else
5859 touched = READ_ONCE(wq_watchdog_touched);
5860 pool_ts = READ_ONCE(pool->watchdog_ts);
5861
5862 if (time_after(pool_ts, touched))
5863 ts = pool_ts;
5864 else
5865 ts = touched;
5866
5867 /* did we stall? */
5868 if (time_after(now, ts + thresh)) {
5869 lockup_detected = true;
5870 pr_emerg("BUG: workqueue lockup - pool");
5871 pr_cont_pool_info(pool);
5872 pr_cont(" stuck for %us!\n",
5873 jiffies_to_msecs(now - pool_ts) / 1000);
5874 }
5875 }
5876
5877 rcu_read_unlock();
5878
5879 if (lockup_detected)
5880 show_all_workqueues();
5881
5882 wq_watchdog_reset_touched();
5883 mod_timer(&wq_watchdog_timer, jiffies + thresh);
5884}
5885
5886notrace void wq_watchdog_touch(int cpu)
5887{
5888 if (cpu >= 0)
5889 per_cpu(wq_watchdog_touched_cpu, cpu) = jiffies;
5890
5891 wq_watchdog_touched = jiffies;
5892}
5893
5894static void wq_watchdog_set_thresh(unsigned long thresh)
5895{
5896 wq_watchdog_thresh = 0;
5897 del_timer_sync(&wq_watchdog_timer);
5898
5899 if (thresh) {
5900 wq_watchdog_thresh = thresh;
5901 wq_watchdog_reset_touched();
5902 mod_timer(&wq_watchdog_timer, jiffies + thresh * HZ);
5903 }
5904}
5905
5906static int wq_watchdog_param_set_thresh(const char *val,
5907 const struct kernel_param *kp)
5908{
5909 unsigned long thresh;
5910 int ret;
5911
5912 ret = kstrtoul(val, 0, &thresh);
5913 if (ret)
5914 return ret;
5915
5916 if (system_wq)
5917 wq_watchdog_set_thresh(thresh);
5918 else
5919 wq_watchdog_thresh = thresh;
5920
5921 return 0;
5922}
5923
5924static const struct kernel_param_ops wq_watchdog_thresh_ops = {
5925 .set = wq_watchdog_param_set_thresh,
5926 .get = param_get_ulong,
5927};
5928
5929module_param_cb(watchdog_thresh, &wq_watchdog_thresh_ops, &wq_watchdog_thresh,
5930 0644);
5931
5932static void wq_watchdog_init(void)
5933{
5934 timer_setup(&wq_watchdog_timer, wq_watchdog_timer_fn, TIMER_DEFERRABLE);
5935 wq_watchdog_set_thresh(wq_watchdog_thresh);
5936}
5937
5938#else /* CONFIG_WQ_WATCHDOG */
5939
5940static inline void wq_watchdog_init(void) { }
5941
5942#endif /* CONFIG_WQ_WATCHDOG */
5943
5944static void __init wq_numa_init(void)
5945{
5946 cpumask_var_t *tbl;
5947 int node, cpu;
5948
5949 if (num_possible_nodes() <= 1)
5950 return;
5951
5952 if (wq_disable_numa) {
5953 pr_info("workqueue: NUMA affinity support disabled\n");
5954 return;
5955 }
5956
5957 for_each_possible_cpu(cpu) {
5958 if (WARN_ON(cpu_to_node(cpu) == NUMA_NO_NODE)) {
5959 pr_warn("workqueue: NUMA node mapping not available for cpu%d, disabling NUMA support\n", cpu);
5960 return;
5961 }
5962 }
5963
5964 wq_update_unbound_numa_attrs_buf = alloc_workqueue_attrs();
5965 BUG_ON(!wq_update_unbound_numa_attrs_buf);
5966
5967 /*
5968 * We want masks of possible CPUs of each node which isn't readily
5969 * available. Build one from cpu_to_node() which should have been
5970 * fully initialized by now.
5971 */
5972 tbl = kcalloc(nr_node_ids, sizeof(tbl[0]), GFP_KERNEL);
5973 BUG_ON(!tbl);
5974
5975 for_each_node(node)
5976 BUG_ON(!zalloc_cpumask_var_node(&tbl[node], GFP_KERNEL,
5977 node_online(node) ? node : NUMA_NO_NODE));
5978
5979 for_each_possible_cpu(cpu) {
5980 node = cpu_to_node(cpu);
5981 cpumask_set_cpu(cpu, tbl[node]);
5982 }
5983
5984 wq_numa_possible_cpumask = tbl;
5985 wq_numa_enabled = true;
5986}
5987
5988/**
5989 * workqueue_init_early - early init for workqueue subsystem
5990 *
5991 * This is the first half of two-staged workqueue subsystem initialization
5992 * and invoked as soon as the bare basics - memory allocation, cpumasks and
5993 * idr are up. It sets up all the data structures and system workqueues
5994 * and allows early boot code to create workqueues and queue/cancel work
5995 * items. Actual work item execution starts only after kthreads can be
5996 * created and scheduled right before early initcalls.
5997 */
5998void __init workqueue_init_early(void)
5999{
6000 int std_nice[NR_STD_WORKER_POOLS] = { 0, HIGHPRI_NICE_LEVEL };
6001 int i, cpu;
6002
6003 BUILD_BUG_ON(__alignof__(struct pool_workqueue) < __alignof__(long long));
6004
6005 BUG_ON(!alloc_cpumask_var(&wq_unbound_cpumask, GFP_KERNEL));
6006 cpumask_copy(wq_unbound_cpumask, housekeeping_cpumask(HK_TYPE_WQ));
6007 cpumask_and(wq_unbound_cpumask, wq_unbound_cpumask, housekeeping_cpumask(HK_TYPE_DOMAIN));
6008
6009 pwq_cache = KMEM_CACHE(pool_workqueue, SLAB_PANIC);
6010
6011 /* initialize CPU pools */
6012 for_each_possible_cpu(cpu) {
6013 struct worker_pool *pool;
6014
6015 i = 0;
6016 for_each_cpu_worker_pool(pool, cpu) {
6017 BUG_ON(init_worker_pool(pool));
6018 pool->cpu = cpu;
6019 cpumask_copy(pool->attrs->cpumask, cpumask_of(cpu));
6020 pool->attrs->nice = std_nice[i++];
6021 pool->node = cpu_to_node(cpu);
6022
6023 /* alloc pool ID */
6024 mutex_lock(&wq_pool_mutex);
6025 BUG_ON(worker_pool_assign_id(pool));
6026 mutex_unlock(&wq_pool_mutex);
6027 }
6028 }
6029
6030 /* create default unbound and ordered wq attrs */
6031 for (i = 0; i < NR_STD_WORKER_POOLS; i++) {
6032 struct workqueue_attrs *attrs;
6033
6034 BUG_ON(!(attrs = alloc_workqueue_attrs()));
6035 attrs->nice = std_nice[i];
6036 unbound_std_wq_attrs[i] = attrs;
6037
6038 /*
6039 * An ordered wq should have only one pwq as ordering is
6040 * guaranteed by max_active which is enforced by pwqs.
6041 * Turn off NUMA so that dfl_pwq is used for all nodes.
6042 */
6043 BUG_ON(!(attrs = alloc_workqueue_attrs()));
6044 attrs->nice = std_nice[i];
6045 attrs->no_numa = true;
6046 ordered_wq_attrs[i] = attrs;
6047 }
6048
6049 system_wq = alloc_workqueue("events", 0, 0);
6050 system_highpri_wq = alloc_workqueue("events_highpri", WQ_HIGHPRI, 0);
6051 system_long_wq = alloc_workqueue("events_long", 0, 0);
6052 system_unbound_wq = alloc_workqueue("events_unbound", WQ_UNBOUND,
6053 WQ_UNBOUND_MAX_ACTIVE);
6054 system_freezable_wq = alloc_workqueue("events_freezable",
6055 WQ_FREEZABLE, 0);
6056 system_power_efficient_wq = alloc_workqueue("events_power_efficient",
6057 WQ_POWER_EFFICIENT, 0);
6058 system_freezable_power_efficient_wq = alloc_workqueue("events_freezable_power_efficient",
6059 WQ_FREEZABLE | WQ_POWER_EFFICIENT,
6060 0);
6061 BUG_ON(!system_wq || !system_highpri_wq || !system_long_wq ||
6062 !system_unbound_wq || !system_freezable_wq ||
6063 !system_power_efficient_wq ||
6064 !system_freezable_power_efficient_wq);
6065}
6066
6067/**
6068 * workqueue_init - bring workqueue subsystem fully online
6069 *
6070 * This is the latter half of two-staged workqueue subsystem initialization
6071 * and invoked as soon as kthreads can be created and scheduled.
6072 * Workqueues have been created and work items queued on them, but there
6073 * are no kworkers executing the work items yet. Populate the worker pools
6074 * with the initial workers and enable future kworker creations.
6075 */
6076void __init workqueue_init(void)
6077{
6078 struct workqueue_struct *wq;
6079 struct worker_pool *pool;
6080 int cpu, bkt;
6081
6082 /*
6083 * It'd be simpler to initialize NUMA in workqueue_init_early() but
6084 * CPU to node mapping may not be available that early on some
6085 * archs such as power and arm64. As per-cpu pools created
6086 * previously could be missing node hint and unbound pools NUMA
6087 * affinity, fix them up.
6088 *
6089 * Also, while iterating workqueues, create rescuers if requested.
6090 */
6091 wq_numa_init();
6092
6093 mutex_lock(&wq_pool_mutex);
6094
6095 for_each_possible_cpu(cpu) {
6096 for_each_cpu_worker_pool(pool, cpu) {
6097 pool->node = cpu_to_node(cpu);
6098 }
6099 }
6100
6101 list_for_each_entry(wq, &workqueues, list) {
6102 wq_update_unbound_numa(wq, smp_processor_id(), true);
6103 WARN(init_rescuer(wq),
6104 "workqueue: failed to create early rescuer for %s",
6105 wq->name);
6106 }
6107
6108 mutex_unlock(&wq_pool_mutex);
6109
6110 /* create the initial workers */
6111 for_each_online_cpu(cpu) {
6112 for_each_cpu_worker_pool(pool, cpu) {
6113 pool->flags &= ~POOL_DISASSOCIATED;
6114 BUG_ON(!create_worker(pool));
6115 }
6116 }
6117
6118 hash_for_each(unbound_pool_hash, bkt, pool, hash_node)
6119 BUG_ON(!create_worker(pool));
6120
6121 wq_online = true;
6122 wq_watchdog_init();
6123}
6124
6125/*
6126 * Despite the naming, this is a no-op function which is here only for avoiding
6127 * link error. Since compile-time warning may fail to catch, we will need to
6128 * emit run-time warning from __flush_workqueue().
6129 */
6130void __warn_flushing_systemwide_wq(void) { }
6131EXPORT_SYMBOL(__warn_flushing_systemwide_wq);
1/*
2 * kernel/workqueue.c - generic async execution with shared worker pool
3 *
4 * Copyright (C) 2002 Ingo Molnar
5 *
6 * Derived from the taskqueue/keventd code by:
7 * David Woodhouse <dwmw2@infradead.org>
8 * Andrew Morton
9 * Kai Petzke <wpp@marie.physik.tu-berlin.de>
10 * Theodore Ts'o <tytso@mit.edu>
11 *
12 * Made to use alloc_percpu by Christoph Lameter.
13 *
14 * Copyright (C) 2010 SUSE Linux Products GmbH
15 * Copyright (C) 2010 Tejun Heo <tj@kernel.org>
16 *
17 * This is the generic async execution mechanism. Work items as are
18 * executed in process context. The worker pool is shared and
19 * automatically managed. There is one worker pool for each CPU and
20 * one extra for works which are better served by workers which are
21 * not bound to any specific CPU.
22 *
23 * Please read Documentation/workqueue.txt for details.
24 */
25
26#include <linux/module.h>
27#include <linux/kernel.h>
28#include <linux/sched.h>
29#include <linux/init.h>
30#include <linux/signal.h>
31#include <linux/completion.h>
32#include <linux/workqueue.h>
33#include <linux/slab.h>
34#include <linux/cpu.h>
35#include <linux/notifier.h>
36#include <linux/kthread.h>
37#include <linux/hardirq.h>
38#include <linux/mempolicy.h>
39#include <linux/freezer.h>
40#include <linux/kallsyms.h>
41#include <linux/debug_locks.h>
42#include <linux/lockdep.h>
43#include <linux/idr.h>
44
45#include "workqueue_sched.h"
46
47enum {
48 /* global_cwq flags */
49 GCWQ_MANAGE_WORKERS = 1 << 0, /* need to manage workers */
50 GCWQ_MANAGING_WORKERS = 1 << 1, /* managing workers */
51 GCWQ_DISASSOCIATED = 1 << 2, /* cpu can't serve workers */
52 GCWQ_FREEZING = 1 << 3, /* freeze in progress */
53 GCWQ_HIGHPRI_PENDING = 1 << 4, /* highpri works on queue */
54
55 /* worker flags */
56 WORKER_STARTED = 1 << 0, /* started */
57 WORKER_DIE = 1 << 1, /* die die die */
58 WORKER_IDLE = 1 << 2, /* is idle */
59 WORKER_PREP = 1 << 3, /* preparing to run works */
60 WORKER_ROGUE = 1 << 4, /* not bound to any cpu */
61 WORKER_REBIND = 1 << 5, /* mom is home, come back */
62 WORKER_CPU_INTENSIVE = 1 << 6, /* cpu intensive */
63 WORKER_UNBOUND = 1 << 7, /* worker is unbound */
64
65 WORKER_NOT_RUNNING = WORKER_PREP | WORKER_ROGUE | WORKER_REBIND |
66 WORKER_CPU_INTENSIVE | WORKER_UNBOUND,
67
68 /* gcwq->trustee_state */
69 TRUSTEE_START = 0, /* start */
70 TRUSTEE_IN_CHARGE = 1, /* trustee in charge of gcwq */
71 TRUSTEE_BUTCHER = 2, /* butcher workers */
72 TRUSTEE_RELEASE = 3, /* release workers */
73 TRUSTEE_DONE = 4, /* trustee is done */
74
75 BUSY_WORKER_HASH_ORDER = 6, /* 64 pointers */
76 BUSY_WORKER_HASH_SIZE = 1 << BUSY_WORKER_HASH_ORDER,
77 BUSY_WORKER_HASH_MASK = BUSY_WORKER_HASH_SIZE - 1,
78
79 MAX_IDLE_WORKERS_RATIO = 4, /* 1/4 of busy can be idle */
80 IDLE_WORKER_TIMEOUT = 300 * HZ, /* keep idle ones for 5 mins */
81
82 MAYDAY_INITIAL_TIMEOUT = HZ / 100 >= 2 ? HZ / 100 : 2,
83 /* call for help after 10ms
84 (min two ticks) */
85 MAYDAY_INTERVAL = HZ / 10, /* and then every 100ms */
86 CREATE_COOLDOWN = HZ, /* time to breath after fail */
87 TRUSTEE_COOLDOWN = HZ / 10, /* for trustee draining */
88
89 /*
90 * Rescue workers are used only on emergencies and shared by
91 * all cpus. Give -20.
92 */
93 RESCUER_NICE_LEVEL = -20,
94};
95
96/*
97 * Structure fields follow one of the following exclusion rules.
98 *
99 * I: Modifiable by initialization/destruction paths and read-only for
100 * everyone else.
101 *
102 * P: Preemption protected. Disabling preemption is enough and should
103 * only be modified and accessed from the local cpu.
104 *
105 * L: gcwq->lock protected. Access with gcwq->lock held.
106 *
107 * X: During normal operation, modification requires gcwq->lock and
108 * should be done only from local cpu. Either disabling preemption
109 * on local cpu or grabbing gcwq->lock is enough for read access.
110 * If GCWQ_DISASSOCIATED is set, it's identical to L.
111 *
112 * F: wq->flush_mutex protected.
113 *
114 * W: workqueue_lock protected.
115 */
116
117struct global_cwq;
118
119/*
120 * The poor guys doing the actual heavy lifting. All on-duty workers
121 * are either serving the manager role, on idle list or on busy hash.
122 */
123struct worker {
124 /* on idle list while idle, on busy hash table while busy */
125 union {
126 struct list_head entry; /* L: while idle */
127 struct hlist_node hentry; /* L: while busy */
128 };
129
130 struct work_struct *current_work; /* L: work being processed */
131 struct cpu_workqueue_struct *current_cwq; /* L: current_work's cwq */
132 struct list_head scheduled; /* L: scheduled works */
133 struct task_struct *task; /* I: worker task */
134 struct global_cwq *gcwq; /* I: the associated gcwq */
135 /* 64 bytes boundary on 64bit, 32 on 32bit */
136 unsigned long last_active; /* L: last active timestamp */
137 unsigned int flags; /* X: flags */
138 int id; /* I: worker id */
139 struct work_struct rebind_work; /* L: rebind worker to cpu */
140};
141
142/*
143 * Global per-cpu workqueue. There's one and only one for each cpu
144 * and all works are queued and processed here regardless of their
145 * target workqueues.
146 */
147struct global_cwq {
148 spinlock_t lock; /* the gcwq lock */
149 struct list_head worklist; /* L: list of pending works */
150 unsigned int cpu; /* I: the associated cpu */
151 unsigned int flags; /* L: GCWQ_* flags */
152
153 int nr_workers; /* L: total number of workers */
154 int nr_idle; /* L: currently idle ones */
155
156 /* workers are chained either in the idle_list or busy_hash */
157 struct list_head idle_list; /* X: list of idle workers */
158 struct hlist_head busy_hash[BUSY_WORKER_HASH_SIZE];
159 /* L: hash of busy workers */
160
161 struct timer_list idle_timer; /* L: worker idle timeout */
162 struct timer_list mayday_timer; /* L: SOS timer for dworkers */
163
164 struct ida worker_ida; /* L: for worker IDs */
165
166 struct task_struct *trustee; /* L: for gcwq shutdown */
167 unsigned int trustee_state; /* L: trustee state */
168 wait_queue_head_t trustee_wait; /* trustee wait */
169 struct worker *first_idle; /* L: first idle worker */
170} ____cacheline_aligned_in_smp;
171
172/*
173 * The per-CPU workqueue. The lower WORK_STRUCT_FLAG_BITS of
174 * work_struct->data are used for flags and thus cwqs need to be
175 * aligned at two's power of the number of flag bits.
176 */
177struct cpu_workqueue_struct {
178 struct global_cwq *gcwq; /* I: the associated gcwq */
179 struct workqueue_struct *wq; /* I: the owning workqueue */
180 int work_color; /* L: current color */
181 int flush_color; /* L: flushing color */
182 int nr_in_flight[WORK_NR_COLORS];
183 /* L: nr of in_flight works */
184 int nr_active; /* L: nr of active works */
185 int max_active; /* L: max active works */
186 struct list_head delayed_works; /* L: delayed works */
187};
188
189/*
190 * Structure used to wait for workqueue flush.
191 */
192struct wq_flusher {
193 struct list_head list; /* F: list of flushers */
194 int flush_color; /* F: flush color waiting for */
195 struct completion done; /* flush completion */
196};
197
198/*
199 * All cpumasks are assumed to be always set on UP and thus can't be
200 * used to determine whether there's something to be done.
201 */
202#ifdef CONFIG_SMP
203typedef cpumask_var_t mayday_mask_t;
204#define mayday_test_and_set_cpu(cpu, mask) \
205 cpumask_test_and_set_cpu((cpu), (mask))
206#define mayday_clear_cpu(cpu, mask) cpumask_clear_cpu((cpu), (mask))
207#define for_each_mayday_cpu(cpu, mask) for_each_cpu((cpu), (mask))
208#define alloc_mayday_mask(maskp, gfp) zalloc_cpumask_var((maskp), (gfp))
209#define free_mayday_mask(mask) free_cpumask_var((mask))
210#else
211typedef unsigned long mayday_mask_t;
212#define mayday_test_and_set_cpu(cpu, mask) test_and_set_bit(0, &(mask))
213#define mayday_clear_cpu(cpu, mask) clear_bit(0, &(mask))
214#define for_each_mayday_cpu(cpu, mask) if ((cpu) = 0, (mask))
215#define alloc_mayday_mask(maskp, gfp) true
216#define free_mayday_mask(mask) do { } while (0)
217#endif
218
219/*
220 * The externally visible workqueue abstraction is an array of
221 * per-CPU workqueues:
222 */
223struct workqueue_struct {
224 unsigned int flags; /* W: WQ_* flags */
225 union {
226 struct cpu_workqueue_struct __percpu *pcpu;
227 struct cpu_workqueue_struct *single;
228 unsigned long v;
229 } cpu_wq; /* I: cwq's */
230 struct list_head list; /* W: list of all workqueues */
231
232 struct mutex flush_mutex; /* protects wq flushing */
233 int work_color; /* F: current work color */
234 int flush_color; /* F: current flush color */
235 atomic_t nr_cwqs_to_flush; /* flush in progress */
236 struct wq_flusher *first_flusher; /* F: first flusher */
237 struct list_head flusher_queue; /* F: flush waiters */
238 struct list_head flusher_overflow; /* F: flush overflow list */
239
240 mayday_mask_t mayday_mask; /* cpus requesting rescue */
241 struct worker *rescuer; /* I: rescue worker */
242
243 int nr_drainers; /* W: drain in progress */
244 int saved_max_active; /* W: saved cwq max_active */
245 const char *name; /* I: workqueue name */
246#ifdef CONFIG_LOCKDEP
247 struct lockdep_map lockdep_map;
248#endif
249};
250
251struct workqueue_struct *system_wq __read_mostly;
252struct workqueue_struct *system_long_wq __read_mostly;
253struct workqueue_struct *system_nrt_wq __read_mostly;
254struct workqueue_struct *system_unbound_wq __read_mostly;
255struct workqueue_struct *system_freezable_wq __read_mostly;
256EXPORT_SYMBOL_GPL(system_wq);
257EXPORT_SYMBOL_GPL(system_long_wq);
258EXPORT_SYMBOL_GPL(system_nrt_wq);
259EXPORT_SYMBOL_GPL(system_unbound_wq);
260EXPORT_SYMBOL_GPL(system_freezable_wq);
261
262#define CREATE_TRACE_POINTS
263#include <trace/events/workqueue.h>
264
265#define for_each_busy_worker(worker, i, pos, gcwq) \
266 for (i = 0; i < BUSY_WORKER_HASH_SIZE; i++) \
267 hlist_for_each_entry(worker, pos, &gcwq->busy_hash[i], hentry)
268
269static inline int __next_gcwq_cpu(int cpu, const struct cpumask *mask,
270 unsigned int sw)
271{
272 if (cpu < nr_cpu_ids) {
273 if (sw & 1) {
274 cpu = cpumask_next(cpu, mask);
275 if (cpu < nr_cpu_ids)
276 return cpu;
277 }
278 if (sw & 2)
279 return WORK_CPU_UNBOUND;
280 }
281 return WORK_CPU_NONE;
282}
283
284static inline int __next_wq_cpu(int cpu, const struct cpumask *mask,
285 struct workqueue_struct *wq)
286{
287 return __next_gcwq_cpu(cpu, mask, !(wq->flags & WQ_UNBOUND) ? 1 : 2);
288}
289
290/*
291 * CPU iterators
292 *
293 * An extra gcwq is defined for an invalid cpu number
294 * (WORK_CPU_UNBOUND) to host workqueues which are not bound to any
295 * specific CPU. The following iterators are similar to
296 * for_each_*_cpu() iterators but also considers the unbound gcwq.
297 *
298 * for_each_gcwq_cpu() : possible CPUs + WORK_CPU_UNBOUND
299 * for_each_online_gcwq_cpu() : online CPUs + WORK_CPU_UNBOUND
300 * for_each_cwq_cpu() : possible CPUs for bound workqueues,
301 * WORK_CPU_UNBOUND for unbound workqueues
302 */
303#define for_each_gcwq_cpu(cpu) \
304 for ((cpu) = __next_gcwq_cpu(-1, cpu_possible_mask, 3); \
305 (cpu) < WORK_CPU_NONE; \
306 (cpu) = __next_gcwq_cpu((cpu), cpu_possible_mask, 3))
307
308#define for_each_online_gcwq_cpu(cpu) \
309 for ((cpu) = __next_gcwq_cpu(-1, cpu_online_mask, 3); \
310 (cpu) < WORK_CPU_NONE; \
311 (cpu) = __next_gcwq_cpu((cpu), cpu_online_mask, 3))
312
313#define for_each_cwq_cpu(cpu, wq) \
314 for ((cpu) = __next_wq_cpu(-1, cpu_possible_mask, (wq)); \
315 (cpu) < WORK_CPU_NONE; \
316 (cpu) = __next_wq_cpu((cpu), cpu_possible_mask, (wq)))
317
318#ifdef CONFIG_DEBUG_OBJECTS_WORK
319
320static struct debug_obj_descr work_debug_descr;
321
322static void *work_debug_hint(void *addr)
323{
324 return ((struct work_struct *) addr)->func;
325}
326
327/*
328 * fixup_init is called when:
329 * - an active object is initialized
330 */
331static int work_fixup_init(void *addr, enum debug_obj_state state)
332{
333 struct work_struct *work = addr;
334
335 switch (state) {
336 case ODEBUG_STATE_ACTIVE:
337 cancel_work_sync(work);
338 debug_object_init(work, &work_debug_descr);
339 return 1;
340 default:
341 return 0;
342 }
343}
344
345/*
346 * fixup_activate is called when:
347 * - an active object is activated
348 * - an unknown object is activated (might be a statically initialized object)
349 */
350static int work_fixup_activate(void *addr, enum debug_obj_state state)
351{
352 struct work_struct *work = addr;
353
354 switch (state) {
355
356 case ODEBUG_STATE_NOTAVAILABLE:
357 /*
358 * This is not really a fixup. The work struct was
359 * statically initialized. We just make sure that it
360 * is tracked in the object tracker.
361 */
362 if (test_bit(WORK_STRUCT_STATIC_BIT, work_data_bits(work))) {
363 debug_object_init(work, &work_debug_descr);
364 debug_object_activate(work, &work_debug_descr);
365 return 0;
366 }
367 WARN_ON_ONCE(1);
368 return 0;
369
370 case ODEBUG_STATE_ACTIVE:
371 WARN_ON(1);
372
373 default:
374 return 0;
375 }
376}
377
378/*
379 * fixup_free is called when:
380 * - an active object is freed
381 */
382static int work_fixup_free(void *addr, enum debug_obj_state state)
383{
384 struct work_struct *work = addr;
385
386 switch (state) {
387 case ODEBUG_STATE_ACTIVE:
388 cancel_work_sync(work);
389 debug_object_free(work, &work_debug_descr);
390 return 1;
391 default:
392 return 0;
393 }
394}
395
396static struct debug_obj_descr work_debug_descr = {
397 .name = "work_struct",
398 .debug_hint = work_debug_hint,
399 .fixup_init = work_fixup_init,
400 .fixup_activate = work_fixup_activate,
401 .fixup_free = work_fixup_free,
402};
403
404static inline void debug_work_activate(struct work_struct *work)
405{
406 debug_object_activate(work, &work_debug_descr);
407}
408
409static inline void debug_work_deactivate(struct work_struct *work)
410{
411 debug_object_deactivate(work, &work_debug_descr);
412}
413
414void __init_work(struct work_struct *work, int onstack)
415{
416 if (onstack)
417 debug_object_init_on_stack(work, &work_debug_descr);
418 else
419 debug_object_init(work, &work_debug_descr);
420}
421EXPORT_SYMBOL_GPL(__init_work);
422
423void destroy_work_on_stack(struct work_struct *work)
424{
425 debug_object_free(work, &work_debug_descr);
426}
427EXPORT_SYMBOL_GPL(destroy_work_on_stack);
428
429#else
430static inline void debug_work_activate(struct work_struct *work) { }
431static inline void debug_work_deactivate(struct work_struct *work) { }
432#endif
433
434/* Serializes the accesses to the list of workqueues. */
435static DEFINE_SPINLOCK(workqueue_lock);
436static LIST_HEAD(workqueues);
437static bool workqueue_freezing; /* W: have wqs started freezing? */
438
439/*
440 * The almighty global cpu workqueues. nr_running is the only field
441 * which is expected to be used frequently by other cpus via
442 * try_to_wake_up(). Put it in a separate cacheline.
443 */
444static DEFINE_PER_CPU(struct global_cwq, global_cwq);
445static DEFINE_PER_CPU_SHARED_ALIGNED(atomic_t, gcwq_nr_running);
446
447/*
448 * Global cpu workqueue and nr_running counter for unbound gcwq. The
449 * gcwq is always online, has GCWQ_DISASSOCIATED set, and all its
450 * workers have WORKER_UNBOUND set.
451 */
452static struct global_cwq unbound_global_cwq;
453static atomic_t unbound_gcwq_nr_running = ATOMIC_INIT(0); /* always 0 */
454
455static int worker_thread(void *__worker);
456
457static struct global_cwq *get_gcwq(unsigned int cpu)
458{
459 if (cpu != WORK_CPU_UNBOUND)
460 return &per_cpu(global_cwq, cpu);
461 else
462 return &unbound_global_cwq;
463}
464
465static atomic_t *get_gcwq_nr_running(unsigned int cpu)
466{
467 if (cpu != WORK_CPU_UNBOUND)
468 return &per_cpu(gcwq_nr_running, cpu);
469 else
470 return &unbound_gcwq_nr_running;
471}
472
473static struct cpu_workqueue_struct *get_cwq(unsigned int cpu,
474 struct workqueue_struct *wq)
475{
476 if (!(wq->flags & WQ_UNBOUND)) {
477 if (likely(cpu < nr_cpu_ids)) {
478#ifdef CONFIG_SMP
479 return per_cpu_ptr(wq->cpu_wq.pcpu, cpu);
480#else
481 return wq->cpu_wq.single;
482#endif
483 }
484 } else if (likely(cpu == WORK_CPU_UNBOUND))
485 return wq->cpu_wq.single;
486 return NULL;
487}
488
489static unsigned int work_color_to_flags(int color)
490{
491 return color << WORK_STRUCT_COLOR_SHIFT;
492}
493
494static int get_work_color(struct work_struct *work)
495{
496 return (*work_data_bits(work) >> WORK_STRUCT_COLOR_SHIFT) &
497 ((1 << WORK_STRUCT_COLOR_BITS) - 1);
498}
499
500static int work_next_color(int color)
501{
502 return (color + 1) % WORK_NR_COLORS;
503}
504
505/*
506 * A work's data points to the cwq with WORK_STRUCT_CWQ set while the
507 * work is on queue. Once execution starts, WORK_STRUCT_CWQ is
508 * cleared and the work data contains the cpu number it was last on.
509 *
510 * set_work_{cwq|cpu}() and clear_work_data() can be used to set the
511 * cwq, cpu or clear work->data. These functions should only be
512 * called while the work is owned - ie. while the PENDING bit is set.
513 *
514 * get_work_[g]cwq() can be used to obtain the gcwq or cwq
515 * corresponding to a work. gcwq is available once the work has been
516 * queued anywhere after initialization. cwq is available only from
517 * queueing until execution starts.
518 */
519static inline void set_work_data(struct work_struct *work, unsigned long data,
520 unsigned long flags)
521{
522 BUG_ON(!work_pending(work));
523 atomic_long_set(&work->data, data | flags | work_static(work));
524}
525
526static void set_work_cwq(struct work_struct *work,
527 struct cpu_workqueue_struct *cwq,
528 unsigned long extra_flags)
529{
530 set_work_data(work, (unsigned long)cwq,
531 WORK_STRUCT_PENDING | WORK_STRUCT_CWQ | extra_flags);
532}
533
534static void set_work_cpu(struct work_struct *work, unsigned int cpu)
535{
536 set_work_data(work, cpu << WORK_STRUCT_FLAG_BITS, WORK_STRUCT_PENDING);
537}
538
539static void clear_work_data(struct work_struct *work)
540{
541 set_work_data(work, WORK_STRUCT_NO_CPU, 0);
542}
543
544static struct cpu_workqueue_struct *get_work_cwq(struct work_struct *work)
545{
546 unsigned long data = atomic_long_read(&work->data);
547
548 if (data & WORK_STRUCT_CWQ)
549 return (void *)(data & WORK_STRUCT_WQ_DATA_MASK);
550 else
551 return NULL;
552}
553
554static struct global_cwq *get_work_gcwq(struct work_struct *work)
555{
556 unsigned long data = atomic_long_read(&work->data);
557 unsigned int cpu;
558
559 if (data & WORK_STRUCT_CWQ)
560 return ((struct cpu_workqueue_struct *)
561 (data & WORK_STRUCT_WQ_DATA_MASK))->gcwq;
562
563 cpu = data >> WORK_STRUCT_FLAG_BITS;
564 if (cpu == WORK_CPU_NONE)
565 return NULL;
566
567 BUG_ON(cpu >= nr_cpu_ids && cpu != WORK_CPU_UNBOUND);
568 return get_gcwq(cpu);
569}
570
571/*
572 * Policy functions. These define the policies on how the global
573 * worker pool is managed. Unless noted otherwise, these functions
574 * assume that they're being called with gcwq->lock held.
575 */
576
577static bool __need_more_worker(struct global_cwq *gcwq)
578{
579 return !atomic_read(get_gcwq_nr_running(gcwq->cpu)) ||
580 gcwq->flags & GCWQ_HIGHPRI_PENDING;
581}
582
583/*
584 * Need to wake up a worker? Called from anything but currently
585 * running workers.
586 */
587static bool need_more_worker(struct global_cwq *gcwq)
588{
589 return !list_empty(&gcwq->worklist) && __need_more_worker(gcwq);
590}
591
592/* Can I start working? Called from busy but !running workers. */
593static bool may_start_working(struct global_cwq *gcwq)
594{
595 return gcwq->nr_idle;
596}
597
598/* Do I need to keep working? Called from currently running workers. */
599static bool keep_working(struct global_cwq *gcwq)
600{
601 atomic_t *nr_running = get_gcwq_nr_running(gcwq->cpu);
602
603 return !list_empty(&gcwq->worklist) &&
604 (atomic_read(nr_running) <= 1 ||
605 gcwq->flags & GCWQ_HIGHPRI_PENDING);
606}
607
608/* Do we need a new worker? Called from manager. */
609static bool need_to_create_worker(struct global_cwq *gcwq)
610{
611 return need_more_worker(gcwq) && !may_start_working(gcwq);
612}
613
614/* Do I need to be the manager? */
615static bool need_to_manage_workers(struct global_cwq *gcwq)
616{
617 return need_to_create_worker(gcwq) || gcwq->flags & GCWQ_MANAGE_WORKERS;
618}
619
620/* Do we have too many workers and should some go away? */
621static bool too_many_workers(struct global_cwq *gcwq)
622{
623 bool managing = gcwq->flags & GCWQ_MANAGING_WORKERS;
624 int nr_idle = gcwq->nr_idle + managing; /* manager is considered idle */
625 int nr_busy = gcwq->nr_workers - nr_idle;
626
627 return nr_idle > 2 && (nr_idle - 2) * MAX_IDLE_WORKERS_RATIO >= nr_busy;
628}
629
630/*
631 * Wake up functions.
632 */
633
634/* Return the first worker. Safe with preemption disabled */
635static struct worker *first_worker(struct global_cwq *gcwq)
636{
637 if (unlikely(list_empty(&gcwq->idle_list)))
638 return NULL;
639
640 return list_first_entry(&gcwq->idle_list, struct worker, entry);
641}
642
643/**
644 * wake_up_worker - wake up an idle worker
645 * @gcwq: gcwq to wake worker for
646 *
647 * Wake up the first idle worker of @gcwq.
648 *
649 * CONTEXT:
650 * spin_lock_irq(gcwq->lock).
651 */
652static void wake_up_worker(struct global_cwq *gcwq)
653{
654 struct worker *worker = first_worker(gcwq);
655
656 if (likely(worker))
657 wake_up_process(worker->task);
658}
659
660/**
661 * wq_worker_waking_up - a worker is waking up
662 * @task: task waking up
663 * @cpu: CPU @task is waking up to
664 *
665 * This function is called during try_to_wake_up() when a worker is
666 * being awoken.
667 *
668 * CONTEXT:
669 * spin_lock_irq(rq->lock)
670 */
671void wq_worker_waking_up(struct task_struct *task, unsigned int cpu)
672{
673 struct worker *worker = kthread_data(task);
674
675 if (!(worker->flags & WORKER_NOT_RUNNING))
676 atomic_inc(get_gcwq_nr_running(cpu));
677}
678
679/**
680 * wq_worker_sleeping - a worker is going to sleep
681 * @task: task going to sleep
682 * @cpu: CPU in question, must be the current CPU number
683 *
684 * This function is called during schedule() when a busy worker is
685 * going to sleep. Worker on the same cpu can be woken up by
686 * returning pointer to its task.
687 *
688 * CONTEXT:
689 * spin_lock_irq(rq->lock)
690 *
691 * RETURNS:
692 * Worker task on @cpu to wake up, %NULL if none.
693 */
694struct task_struct *wq_worker_sleeping(struct task_struct *task,
695 unsigned int cpu)
696{
697 struct worker *worker = kthread_data(task), *to_wakeup = NULL;
698 struct global_cwq *gcwq = get_gcwq(cpu);
699 atomic_t *nr_running = get_gcwq_nr_running(cpu);
700
701 if (worker->flags & WORKER_NOT_RUNNING)
702 return NULL;
703
704 /* this can only happen on the local cpu */
705 BUG_ON(cpu != raw_smp_processor_id());
706
707 /*
708 * The counterpart of the following dec_and_test, implied mb,
709 * worklist not empty test sequence is in insert_work().
710 * Please read comment there.
711 *
712 * NOT_RUNNING is clear. This means that trustee is not in
713 * charge and we're running on the local cpu w/ rq lock held
714 * and preemption disabled, which in turn means that none else
715 * could be manipulating idle_list, so dereferencing idle_list
716 * without gcwq lock is safe.
717 */
718 if (atomic_dec_and_test(nr_running) && !list_empty(&gcwq->worklist))
719 to_wakeup = first_worker(gcwq);
720 return to_wakeup ? to_wakeup->task : NULL;
721}
722
723/**
724 * worker_set_flags - set worker flags and adjust nr_running accordingly
725 * @worker: self
726 * @flags: flags to set
727 * @wakeup: wakeup an idle worker if necessary
728 *
729 * Set @flags in @worker->flags and adjust nr_running accordingly. If
730 * nr_running becomes zero and @wakeup is %true, an idle worker is
731 * woken up.
732 *
733 * CONTEXT:
734 * spin_lock_irq(gcwq->lock)
735 */
736static inline void worker_set_flags(struct worker *worker, unsigned int flags,
737 bool wakeup)
738{
739 struct global_cwq *gcwq = worker->gcwq;
740
741 WARN_ON_ONCE(worker->task != current);
742
743 /*
744 * If transitioning into NOT_RUNNING, adjust nr_running and
745 * wake up an idle worker as necessary if requested by
746 * @wakeup.
747 */
748 if ((flags & WORKER_NOT_RUNNING) &&
749 !(worker->flags & WORKER_NOT_RUNNING)) {
750 atomic_t *nr_running = get_gcwq_nr_running(gcwq->cpu);
751
752 if (wakeup) {
753 if (atomic_dec_and_test(nr_running) &&
754 !list_empty(&gcwq->worklist))
755 wake_up_worker(gcwq);
756 } else
757 atomic_dec(nr_running);
758 }
759
760 worker->flags |= flags;
761}
762
763/**
764 * worker_clr_flags - clear worker flags and adjust nr_running accordingly
765 * @worker: self
766 * @flags: flags to clear
767 *
768 * Clear @flags in @worker->flags and adjust nr_running accordingly.
769 *
770 * CONTEXT:
771 * spin_lock_irq(gcwq->lock)
772 */
773static inline void worker_clr_flags(struct worker *worker, unsigned int flags)
774{
775 struct global_cwq *gcwq = worker->gcwq;
776 unsigned int oflags = worker->flags;
777
778 WARN_ON_ONCE(worker->task != current);
779
780 worker->flags &= ~flags;
781
782 /*
783 * If transitioning out of NOT_RUNNING, increment nr_running. Note
784 * that the nested NOT_RUNNING is not a noop. NOT_RUNNING is mask
785 * of multiple flags, not a single flag.
786 */
787 if ((flags & WORKER_NOT_RUNNING) && (oflags & WORKER_NOT_RUNNING))
788 if (!(worker->flags & WORKER_NOT_RUNNING))
789 atomic_inc(get_gcwq_nr_running(gcwq->cpu));
790}
791
792/**
793 * busy_worker_head - return the busy hash head for a work
794 * @gcwq: gcwq of interest
795 * @work: work to be hashed
796 *
797 * Return hash head of @gcwq for @work.
798 *
799 * CONTEXT:
800 * spin_lock_irq(gcwq->lock).
801 *
802 * RETURNS:
803 * Pointer to the hash head.
804 */
805static struct hlist_head *busy_worker_head(struct global_cwq *gcwq,
806 struct work_struct *work)
807{
808 const int base_shift = ilog2(sizeof(struct work_struct));
809 unsigned long v = (unsigned long)work;
810
811 /* simple shift and fold hash, do we need something better? */
812 v >>= base_shift;
813 v += v >> BUSY_WORKER_HASH_ORDER;
814 v &= BUSY_WORKER_HASH_MASK;
815
816 return &gcwq->busy_hash[v];
817}
818
819/**
820 * __find_worker_executing_work - find worker which is executing a work
821 * @gcwq: gcwq of interest
822 * @bwh: hash head as returned by busy_worker_head()
823 * @work: work to find worker for
824 *
825 * Find a worker which is executing @work on @gcwq. @bwh should be
826 * the hash head obtained by calling busy_worker_head() with the same
827 * work.
828 *
829 * CONTEXT:
830 * spin_lock_irq(gcwq->lock).
831 *
832 * RETURNS:
833 * Pointer to worker which is executing @work if found, NULL
834 * otherwise.
835 */
836static struct worker *__find_worker_executing_work(struct global_cwq *gcwq,
837 struct hlist_head *bwh,
838 struct work_struct *work)
839{
840 struct worker *worker;
841 struct hlist_node *tmp;
842
843 hlist_for_each_entry(worker, tmp, bwh, hentry)
844 if (worker->current_work == work)
845 return worker;
846 return NULL;
847}
848
849/**
850 * find_worker_executing_work - find worker which is executing a work
851 * @gcwq: gcwq of interest
852 * @work: work to find worker for
853 *
854 * Find a worker which is executing @work on @gcwq. This function is
855 * identical to __find_worker_executing_work() except that this
856 * function calculates @bwh itself.
857 *
858 * CONTEXT:
859 * spin_lock_irq(gcwq->lock).
860 *
861 * RETURNS:
862 * Pointer to worker which is executing @work if found, NULL
863 * otherwise.
864 */
865static struct worker *find_worker_executing_work(struct global_cwq *gcwq,
866 struct work_struct *work)
867{
868 return __find_worker_executing_work(gcwq, busy_worker_head(gcwq, work),
869 work);
870}
871
872/**
873 * gcwq_determine_ins_pos - find insertion position
874 * @gcwq: gcwq of interest
875 * @cwq: cwq a work is being queued for
876 *
877 * A work for @cwq is about to be queued on @gcwq, determine insertion
878 * position for the work. If @cwq is for HIGHPRI wq, the work is
879 * queued at the head of the queue but in FIFO order with respect to
880 * other HIGHPRI works; otherwise, at the end of the queue. This
881 * function also sets GCWQ_HIGHPRI_PENDING flag to hint @gcwq that
882 * there are HIGHPRI works pending.
883 *
884 * CONTEXT:
885 * spin_lock_irq(gcwq->lock).
886 *
887 * RETURNS:
888 * Pointer to inserstion position.
889 */
890static inline struct list_head *gcwq_determine_ins_pos(struct global_cwq *gcwq,
891 struct cpu_workqueue_struct *cwq)
892{
893 struct work_struct *twork;
894
895 if (likely(!(cwq->wq->flags & WQ_HIGHPRI)))
896 return &gcwq->worklist;
897
898 list_for_each_entry(twork, &gcwq->worklist, entry) {
899 struct cpu_workqueue_struct *tcwq = get_work_cwq(twork);
900
901 if (!(tcwq->wq->flags & WQ_HIGHPRI))
902 break;
903 }
904
905 gcwq->flags |= GCWQ_HIGHPRI_PENDING;
906 return &twork->entry;
907}
908
909/**
910 * insert_work - insert a work into gcwq
911 * @cwq: cwq @work belongs to
912 * @work: work to insert
913 * @head: insertion point
914 * @extra_flags: extra WORK_STRUCT_* flags to set
915 *
916 * Insert @work which belongs to @cwq into @gcwq after @head.
917 * @extra_flags is or'd to work_struct flags.
918 *
919 * CONTEXT:
920 * spin_lock_irq(gcwq->lock).
921 */
922static void insert_work(struct cpu_workqueue_struct *cwq,
923 struct work_struct *work, struct list_head *head,
924 unsigned int extra_flags)
925{
926 struct global_cwq *gcwq = cwq->gcwq;
927
928 /* we own @work, set data and link */
929 set_work_cwq(work, cwq, extra_flags);
930
931 /*
932 * Ensure that we get the right work->data if we see the
933 * result of list_add() below, see try_to_grab_pending().
934 */
935 smp_wmb();
936
937 list_add_tail(&work->entry, head);
938
939 /*
940 * Ensure either worker_sched_deactivated() sees the above
941 * list_add_tail() or we see zero nr_running to avoid workers
942 * lying around lazily while there are works to be processed.
943 */
944 smp_mb();
945
946 if (__need_more_worker(gcwq))
947 wake_up_worker(gcwq);
948}
949
950/*
951 * Test whether @work is being queued from another work executing on the
952 * same workqueue. This is rather expensive and should only be used from
953 * cold paths.
954 */
955static bool is_chained_work(struct workqueue_struct *wq)
956{
957 unsigned long flags;
958 unsigned int cpu;
959
960 for_each_gcwq_cpu(cpu) {
961 struct global_cwq *gcwq = get_gcwq(cpu);
962 struct worker *worker;
963 struct hlist_node *pos;
964 int i;
965
966 spin_lock_irqsave(&gcwq->lock, flags);
967 for_each_busy_worker(worker, i, pos, gcwq) {
968 if (worker->task != current)
969 continue;
970 spin_unlock_irqrestore(&gcwq->lock, flags);
971 /*
972 * I'm @worker, no locking necessary. See if @work
973 * is headed to the same workqueue.
974 */
975 return worker->current_cwq->wq == wq;
976 }
977 spin_unlock_irqrestore(&gcwq->lock, flags);
978 }
979 return false;
980}
981
982static void __queue_work(unsigned int cpu, struct workqueue_struct *wq,
983 struct work_struct *work)
984{
985 struct global_cwq *gcwq;
986 struct cpu_workqueue_struct *cwq;
987 struct list_head *worklist;
988 unsigned int work_flags;
989 unsigned long flags;
990
991 debug_work_activate(work);
992
993 /* if dying, only works from the same workqueue are allowed */
994 if (unlikely(wq->flags & WQ_DRAINING) &&
995 WARN_ON_ONCE(!is_chained_work(wq)))
996 return;
997
998 /* determine gcwq to use */
999 if (!(wq->flags & WQ_UNBOUND)) {
1000 struct global_cwq *last_gcwq;
1001
1002 if (unlikely(cpu == WORK_CPU_UNBOUND))
1003 cpu = raw_smp_processor_id();
1004
1005 /*
1006 * It's multi cpu. If @wq is non-reentrant and @work
1007 * was previously on a different cpu, it might still
1008 * be running there, in which case the work needs to
1009 * be queued on that cpu to guarantee non-reentrance.
1010 */
1011 gcwq = get_gcwq(cpu);
1012 if (wq->flags & WQ_NON_REENTRANT &&
1013 (last_gcwq = get_work_gcwq(work)) && last_gcwq != gcwq) {
1014 struct worker *worker;
1015
1016 spin_lock_irqsave(&last_gcwq->lock, flags);
1017
1018 worker = find_worker_executing_work(last_gcwq, work);
1019
1020 if (worker && worker->current_cwq->wq == wq)
1021 gcwq = last_gcwq;
1022 else {
1023 /* meh... not running there, queue here */
1024 spin_unlock_irqrestore(&last_gcwq->lock, flags);
1025 spin_lock_irqsave(&gcwq->lock, flags);
1026 }
1027 } else
1028 spin_lock_irqsave(&gcwq->lock, flags);
1029 } else {
1030 gcwq = get_gcwq(WORK_CPU_UNBOUND);
1031 spin_lock_irqsave(&gcwq->lock, flags);
1032 }
1033
1034 /* gcwq determined, get cwq and queue */
1035 cwq = get_cwq(gcwq->cpu, wq);
1036 trace_workqueue_queue_work(cpu, cwq, work);
1037
1038 BUG_ON(!list_empty(&work->entry));
1039
1040 cwq->nr_in_flight[cwq->work_color]++;
1041 work_flags = work_color_to_flags(cwq->work_color);
1042
1043 if (likely(cwq->nr_active < cwq->max_active)) {
1044 trace_workqueue_activate_work(work);
1045 cwq->nr_active++;
1046 worklist = gcwq_determine_ins_pos(gcwq, cwq);
1047 } else {
1048 work_flags |= WORK_STRUCT_DELAYED;
1049 worklist = &cwq->delayed_works;
1050 }
1051
1052 insert_work(cwq, work, worklist, work_flags);
1053
1054 spin_unlock_irqrestore(&gcwq->lock, flags);
1055}
1056
1057/**
1058 * queue_work - queue work on a workqueue
1059 * @wq: workqueue to use
1060 * @work: work to queue
1061 *
1062 * Returns 0 if @work was already on a queue, non-zero otherwise.
1063 *
1064 * We queue the work to the CPU on which it was submitted, but if the CPU dies
1065 * it can be processed by another CPU.
1066 */
1067int queue_work(struct workqueue_struct *wq, struct work_struct *work)
1068{
1069 int ret;
1070
1071 ret = queue_work_on(get_cpu(), wq, work);
1072 put_cpu();
1073
1074 return ret;
1075}
1076EXPORT_SYMBOL_GPL(queue_work);
1077
1078/**
1079 * queue_work_on - queue work on specific cpu
1080 * @cpu: CPU number to execute work on
1081 * @wq: workqueue to use
1082 * @work: work to queue
1083 *
1084 * Returns 0 if @work was already on a queue, non-zero otherwise.
1085 *
1086 * We queue the work to a specific CPU, the caller must ensure it
1087 * can't go away.
1088 */
1089int
1090queue_work_on(int cpu, struct workqueue_struct *wq, struct work_struct *work)
1091{
1092 int ret = 0;
1093
1094 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1095 __queue_work(cpu, wq, work);
1096 ret = 1;
1097 }
1098 return ret;
1099}
1100EXPORT_SYMBOL_GPL(queue_work_on);
1101
1102static void delayed_work_timer_fn(unsigned long __data)
1103{
1104 struct delayed_work *dwork = (struct delayed_work *)__data;
1105 struct cpu_workqueue_struct *cwq = get_work_cwq(&dwork->work);
1106
1107 __queue_work(smp_processor_id(), cwq->wq, &dwork->work);
1108}
1109
1110/**
1111 * queue_delayed_work - queue work on a workqueue after delay
1112 * @wq: workqueue to use
1113 * @dwork: delayable work to queue
1114 * @delay: number of jiffies to wait before queueing
1115 *
1116 * Returns 0 if @work was already on a queue, non-zero otherwise.
1117 */
1118int queue_delayed_work(struct workqueue_struct *wq,
1119 struct delayed_work *dwork, unsigned long delay)
1120{
1121 if (delay == 0)
1122 return queue_work(wq, &dwork->work);
1123
1124 return queue_delayed_work_on(-1, wq, dwork, delay);
1125}
1126EXPORT_SYMBOL_GPL(queue_delayed_work);
1127
1128/**
1129 * queue_delayed_work_on - queue work on specific CPU after delay
1130 * @cpu: CPU number to execute work on
1131 * @wq: workqueue to use
1132 * @dwork: work to queue
1133 * @delay: number of jiffies to wait before queueing
1134 *
1135 * Returns 0 if @work was already on a queue, non-zero otherwise.
1136 */
1137int queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
1138 struct delayed_work *dwork, unsigned long delay)
1139{
1140 int ret = 0;
1141 struct timer_list *timer = &dwork->timer;
1142 struct work_struct *work = &dwork->work;
1143
1144 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1145 unsigned int lcpu;
1146
1147 BUG_ON(timer_pending(timer));
1148 BUG_ON(!list_empty(&work->entry));
1149
1150 timer_stats_timer_set_start_info(&dwork->timer);
1151
1152 /*
1153 * This stores cwq for the moment, for the timer_fn.
1154 * Note that the work's gcwq is preserved to allow
1155 * reentrance detection for delayed works.
1156 */
1157 if (!(wq->flags & WQ_UNBOUND)) {
1158 struct global_cwq *gcwq = get_work_gcwq(work);
1159
1160 if (gcwq && gcwq->cpu != WORK_CPU_UNBOUND)
1161 lcpu = gcwq->cpu;
1162 else
1163 lcpu = raw_smp_processor_id();
1164 } else
1165 lcpu = WORK_CPU_UNBOUND;
1166
1167 set_work_cwq(work, get_cwq(lcpu, wq), 0);
1168
1169 timer->expires = jiffies + delay;
1170 timer->data = (unsigned long)dwork;
1171 timer->function = delayed_work_timer_fn;
1172
1173 if (unlikely(cpu >= 0))
1174 add_timer_on(timer, cpu);
1175 else
1176 add_timer(timer);
1177 ret = 1;
1178 }
1179 return ret;
1180}
1181EXPORT_SYMBOL_GPL(queue_delayed_work_on);
1182
1183/**
1184 * worker_enter_idle - enter idle state
1185 * @worker: worker which is entering idle state
1186 *
1187 * @worker is entering idle state. Update stats and idle timer if
1188 * necessary.
1189 *
1190 * LOCKING:
1191 * spin_lock_irq(gcwq->lock).
1192 */
1193static void worker_enter_idle(struct worker *worker)
1194{
1195 struct global_cwq *gcwq = worker->gcwq;
1196
1197 BUG_ON(worker->flags & WORKER_IDLE);
1198 BUG_ON(!list_empty(&worker->entry) &&
1199 (worker->hentry.next || worker->hentry.pprev));
1200
1201 /* can't use worker_set_flags(), also called from start_worker() */
1202 worker->flags |= WORKER_IDLE;
1203 gcwq->nr_idle++;
1204 worker->last_active = jiffies;
1205
1206 /* idle_list is LIFO */
1207 list_add(&worker->entry, &gcwq->idle_list);
1208
1209 if (likely(!(worker->flags & WORKER_ROGUE))) {
1210 if (too_many_workers(gcwq) && !timer_pending(&gcwq->idle_timer))
1211 mod_timer(&gcwq->idle_timer,
1212 jiffies + IDLE_WORKER_TIMEOUT);
1213 } else
1214 wake_up_all(&gcwq->trustee_wait);
1215
1216 /* sanity check nr_running */
1217 WARN_ON_ONCE(gcwq->nr_workers == gcwq->nr_idle &&
1218 atomic_read(get_gcwq_nr_running(gcwq->cpu)));
1219}
1220
1221/**
1222 * worker_leave_idle - leave idle state
1223 * @worker: worker which is leaving idle state
1224 *
1225 * @worker is leaving idle state. Update stats.
1226 *
1227 * LOCKING:
1228 * spin_lock_irq(gcwq->lock).
1229 */
1230static void worker_leave_idle(struct worker *worker)
1231{
1232 struct global_cwq *gcwq = worker->gcwq;
1233
1234 BUG_ON(!(worker->flags & WORKER_IDLE));
1235 worker_clr_flags(worker, WORKER_IDLE);
1236 gcwq->nr_idle--;
1237 list_del_init(&worker->entry);
1238}
1239
1240/**
1241 * worker_maybe_bind_and_lock - bind worker to its cpu if possible and lock gcwq
1242 * @worker: self
1243 *
1244 * Works which are scheduled while the cpu is online must at least be
1245 * scheduled to a worker which is bound to the cpu so that if they are
1246 * flushed from cpu callbacks while cpu is going down, they are
1247 * guaranteed to execute on the cpu.
1248 *
1249 * This function is to be used by rogue workers and rescuers to bind
1250 * themselves to the target cpu and may race with cpu going down or
1251 * coming online. kthread_bind() can't be used because it may put the
1252 * worker to already dead cpu and set_cpus_allowed_ptr() can't be used
1253 * verbatim as it's best effort and blocking and gcwq may be
1254 * [dis]associated in the meantime.
1255 *
1256 * This function tries set_cpus_allowed() and locks gcwq and verifies
1257 * the binding against GCWQ_DISASSOCIATED which is set during
1258 * CPU_DYING and cleared during CPU_ONLINE, so if the worker enters
1259 * idle state or fetches works without dropping lock, it can guarantee
1260 * the scheduling requirement described in the first paragraph.
1261 *
1262 * CONTEXT:
1263 * Might sleep. Called without any lock but returns with gcwq->lock
1264 * held.
1265 *
1266 * RETURNS:
1267 * %true if the associated gcwq is online (@worker is successfully
1268 * bound), %false if offline.
1269 */
1270static bool worker_maybe_bind_and_lock(struct worker *worker)
1271__acquires(&gcwq->lock)
1272{
1273 struct global_cwq *gcwq = worker->gcwq;
1274 struct task_struct *task = worker->task;
1275
1276 while (true) {
1277 /*
1278 * The following call may fail, succeed or succeed
1279 * without actually migrating the task to the cpu if
1280 * it races with cpu hotunplug operation. Verify
1281 * against GCWQ_DISASSOCIATED.
1282 */
1283 if (!(gcwq->flags & GCWQ_DISASSOCIATED))
1284 set_cpus_allowed_ptr(task, get_cpu_mask(gcwq->cpu));
1285
1286 spin_lock_irq(&gcwq->lock);
1287 if (gcwq->flags & GCWQ_DISASSOCIATED)
1288 return false;
1289 if (task_cpu(task) == gcwq->cpu &&
1290 cpumask_equal(¤t->cpus_allowed,
1291 get_cpu_mask(gcwq->cpu)))
1292 return true;
1293 spin_unlock_irq(&gcwq->lock);
1294
1295 /*
1296 * We've raced with CPU hot[un]plug. Give it a breather
1297 * and retry migration. cond_resched() is required here;
1298 * otherwise, we might deadlock against cpu_stop trying to
1299 * bring down the CPU on non-preemptive kernel.
1300 */
1301 cpu_relax();
1302 cond_resched();
1303 }
1304}
1305
1306/*
1307 * Function for worker->rebind_work used to rebind rogue busy workers
1308 * to the associated cpu which is coming back online. This is
1309 * scheduled by cpu up but can race with other cpu hotplug operations
1310 * and may be executed twice without intervening cpu down.
1311 */
1312static void worker_rebind_fn(struct work_struct *work)
1313{
1314 struct worker *worker = container_of(work, struct worker, rebind_work);
1315 struct global_cwq *gcwq = worker->gcwq;
1316
1317 if (worker_maybe_bind_and_lock(worker))
1318 worker_clr_flags(worker, WORKER_REBIND);
1319
1320 spin_unlock_irq(&gcwq->lock);
1321}
1322
1323static struct worker *alloc_worker(void)
1324{
1325 struct worker *worker;
1326
1327 worker = kzalloc(sizeof(*worker), GFP_KERNEL);
1328 if (worker) {
1329 INIT_LIST_HEAD(&worker->entry);
1330 INIT_LIST_HEAD(&worker->scheduled);
1331 INIT_WORK(&worker->rebind_work, worker_rebind_fn);
1332 /* on creation a worker is in !idle && prep state */
1333 worker->flags = WORKER_PREP;
1334 }
1335 return worker;
1336}
1337
1338/**
1339 * create_worker - create a new workqueue worker
1340 * @gcwq: gcwq the new worker will belong to
1341 * @bind: whether to set affinity to @cpu or not
1342 *
1343 * Create a new worker which is bound to @gcwq. The returned worker
1344 * can be started by calling start_worker() or destroyed using
1345 * destroy_worker().
1346 *
1347 * CONTEXT:
1348 * Might sleep. Does GFP_KERNEL allocations.
1349 *
1350 * RETURNS:
1351 * Pointer to the newly created worker.
1352 */
1353static struct worker *create_worker(struct global_cwq *gcwq, bool bind)
1354{
1355 bool on_unbound_cpu = gcwq->cpu == WORK_CPU_UNBOUND;
1356 struct worker *worker = NULL;
1357 int id = -1;
1358
1359 spin_lock_irq(&gcwq->lock);
1360 while (ida_get_new(&gcwq->worker_ida, &id)) {
1361 spin_unlock_irq(&gcwq->lock);
1362 if (!ida_pre_get(&gcwq->worker_ida, GFP_KERNEL))
1363 goto fail;
1364 spin_lock_irq(&gcwq->lock);
1365 }
1366 spin_unlock_irq(&gcwq->lock);
1367
1368 worker = alloc_worker();
1369 if (!worker)
1370 goto fail;
1371
1372 worker->gcwq = gcwq;
1373 worker->id = id;
1374
1375 if (!on_unbound_cpu)
1376 worker->task = kthread_create_on_node(worker_thread,
1377 worker,
1378 cpu_to_node(gcwq->cpu),
1379 "kworker/%u:%d", gcwq->cpu, id);
1380 else
1381 worker->task = kthread_create(worker_thread, worker,
1382 "kworker/u:%d", id);
1383 if (IS_ERR(worker->task))
1384 goto fail;
1385
1386 /*
1387 * A rogue worker will become a regular one if CPU comes
1388 * online later on. Make sure every worker has
1389 * PF_THREAD_BOUND set.
1390 */
1391 if (bind && !on_unbound_cpu)
1392 kthread_bind(worker->task, gcwq->cpu);
1393 else {
1394 worker->task->flags |= PF_THREAD_BOUND;
1395 if (on_unbound_cpu)
1396 worker->flags |= WORKER_UNBOUND;
1397 }
1398
1399 return worker;
1400fail:
1401 if (id >= 0) {
1402 spin_lock_irq(&gcwq->lock);
1403 ida_remove(&gcwq->worker_ida, id);
1404 spin_unlock_irq(&gcwq->lock);
1405 }
1406 kfree(worker);
1407 return NULL;
1408}
1409
1410/**
1411 * start_worker - start a newly created worker
1412 * @worker: worker to start
1413 *
1414 * Make the gcwq aware of @worker and start it.
1415 *
1416 * CONTEXT:
1417 * spin_lock_irq(gcwq->lock).
1418 */
1419static void start_worker(struct worker *worker)
1420{
1421 worker->flags |= WORKER_STARTED;
1422 worker->gcwq->nr_workers++;
1423 worker_enter_idle(worker);
1424 wake_up_process(worker->task);
1425}
1426
1427/**
1428 * destroy_worker - destroy a workqueue worker
1429 * @worker: worker to be destroyed
1430 *
1431 * Destroy @worker and adjust @gcwq stats accordingly.
1432 *
1433 * CONTEXT:
1434 * spin_lock_irq(gcwq->lock) which is released and regrabbed.
1435 */
1436static void destroy_worker(struct worker *worker)
1437{
1438 struct global_cwq *gcwq = worker->gcwq;
1439 int id = worker->id;
1440
1441 /* sanity check frenzy */
1442 BUG_ON(worker->current_work);
1443 BUG_ON(!list_empty(&worker->scheduled));
1444
1445 if (worker->flags & WORKER_STARTED)
1446 gcwq->nr_workers--;
1447 if (worker->flags & WORKER_IDLE)
1448 gcwq->nr_idle--;
1449
1450 list_del_init(&worker->entry);
1451 worker->flags |= WORKER_DIE;
1452
1453 spin_unlock_irq(&gcwq->lock);
1454
1455 kthread_stop(worker->task);
1456 kfree(worker);
1457
1458 spin_lock_irq(&gcwq->lock);
1459 ida_remove(&gcwq->worker_ida, id);
1460}
1461
1462static void idle_worker_timeout(unsigned long __gcwq)
1463{
1464 struct global_cwq *gcwq = (void *)__gcwq;
1465
1466 spin_lock_irq(&gcwq->lock);
1467
1468 if (too_many_workers(gcwq)) {
1469 struct worker *worker;
1470 unsigned long expires;
1471
1472 /* idle_list is kept in LIFO order, check the last one */
1473 worker = list_entry(gcwq->idle_list.prev, struct worker, entry);
1474 expires = worker->last_active + IDLE_WORKER_TIMEOUT;
1475
1476 if (time_before(jiffies, expires))
1477 mod_timer(&gcwq->idle_timer, expires);
1478 else {
1479 /* it's been idle for too long, wake up manager */
1480 gcwq->flags |= GCWQ_MANAGE_WORKERS;
1481 wake_up_worker(gcwq);
1482 }
1483 }
1484
1485 spin_unlock_irq(&gcwq->lock);
1486}
1487
1488static bool send_mayday(struct work_struct *work)
1489{
1490 struct cpu_workqueue_struct *cwq = get_work_cwq(work);
1491 struct workqueue_struct *wq = cwq->wq;
1492 unsigned int cpu;
1493
1494 if (!(wq->flags & WQ_RESCUER))
1495 return false;
1496
1497 /* mayday mayday mayday */
1498 cpu = cwq->gcwq->cpu;
1499 /* WORK_CPU_UNBOUND can't be set in cpumask, use cpu 0 instead */
1500 if (cpu == WORK_CPU_UNBOUND)
1501 cpu = 0;
1502 if (!mayday_test_and_set_cpu(cpu, wq->mayday_mask))
1503 wake_up_process(wq->rescuer->task);
1504 return true;
1505}
1506
1507static void gcwq_mayday_timeout(unsigned long __gcwq)
1508{
1509 struct global_cwq *gcwq = (void *)__gcwq;
1510 struct work_struct *work;
1511
1512 spin_lock_irq(&gcwq->lock);
1513
1514 if (need_to_create_worker(gcwq)) {
1515 /*
1516 * We've been trying to create a new worker but
1517 * haven't been successful. We might be hitting an
1518 * allocation deadlock. Send distress signals to
1519 * rescuers.
1520 */
1521 list_for_each_entry(work, &gcwq->worklist, entry)
1522 send_mayday(work);
1523 }
1524
1525 spin_unlock_irq(&gcwq->lock);
1526
1527 mod_timer(&gcwq->mayday_timer, jiffies + MAYDAY_INTERVAL);
1528}
1529
1530/**
1531 * maybe_create_worker - create a new worker if necessary
1532 * @gcwq: gcwq to create a new worker for
1533 *
1534 * Create a new worker for @gcwq if necessary. @gcwq is guaranteed to
1535 * have at least one idle worker on return from this function. If
1536 * creating a new worker takes longer than MAYDAY_INTERVAL, mayday is
1537 * sent to all rescuers with works scheduled on @gcwq to resolve
1538 * possible allocation deadlock.
1539 *
1540 * On return, need_to_create_worker() is guaranteed to be false and
1541 * may_start_working() true.
1542 *
1543 * LOCKING:
1544 * spin_lock_irq(gcwq->lock) which may be released and regrabbed
1545 * multiple times. Does GFP_KERNEL allocations. Called only from
1546 * manager.
1547 *
1548 * RETURNS:
1549 * false if no action was taken and gcwq->lock stayed locked, true
1550 * otherwise.
1551 */
1552static bool maybe_create_worker(struct global_cwq *gcwq)
1553__releases(&gcwq->lock)
1554__acquires(&gcwq->lock)
1555{
1556 if (!need_to_create_worker(gcwq))
1557 return false;
1558restart:
1559 spin_unlock_irq(&gcwq->lock);
1560
1561 /* if we don't make progress in MAYDAY_INITIAL_TIMEOUT, call for help */
1562 mod_timer(&gcwq->mayday_timer, jiffies + MAYDAY_INITIAL_TIMEOUT);
1563
1564 while (true) {
1565 struct worker *worker;
1566
1567 worker = create_worker(gcwq, true);
1568 if (worker) {
1569 del_timer_sync(&gcwq->mayday_timer);
1570 spin_lock_irq(&gcwq->lock);
1571 start_worker(worker);
1572 BUG_ON(need_to_create_worker(gcwq));
1573 return true;
1574 }
1575
1576 if (!need_to_create_worker(gcwq))
1577 break;
1578
1579 __set_current_state(TASK_INTERRUPTIBLE);
1580 schedule_timeout(CREATE_COOLDOWN);
1581
1582 if (!need_to_create_worker(gcwq))
1583 break;
1584 }
1585
1586 del_timer_sync(&gcwq->mayday_timer);
1587 spin_lock_irq(&gcwq->lock);
1588 if (need_to_create_worker(gcwq))
1589 goto restart;
1590 return true;
1591}
1592
1593/**
1594 * maybe_destroy_worker - destroy workers which have been idle for a while
1595 * @gcwq: gcwq to destroy workers for
1596 *
1597 * Destroy @gcwq workers which have been idle for longer than
1598 * IDLE_WORKER_TIMEOUT.
1599 *
1600 * LOCKING:
1601 * spin_lock_irq(gcwq->lock) which may be released and regrabbed
1602 * multiple times. Called only from manager.
1603 *
1604 * RETURNS:
1605 * false if no action was taken and gcwq->lock stayed locked, true
1606 * otherwise.
1607 */
1608static bool maybe_destroy_workers(struct global_cwq *gcwq)
1609{
1610 bool ret = false;
1611
1612 while (too_many_workers(gcwq)) {
1613 struct worker *worker;
1614 unsigned long expires;
1615
1616 worker = list_entry(gcwq->idle_list.prev, struct worker, entry);
1617 expires = worker->last_active + IDLE_WORKER_TIMEOUT;
1618
1619 if (time_before(jiffies, expires)) {
1620 mod_timer(&gcwq->idle_timer, expires);
1621 break;
1622 }
1623
1624 destroy_worker(worker);
1625 ret = true;
1626 }
1627
1628 return ret;
1629}
1630
1631/**
1632 * manage_workers - manage worker pool
1633 * @worker: self
1634 *
1635 * Assume the manager role and manage gcwq worker pool @worker belongs
1636 * to. At any given time, there can be only zero or one manager per
1637 * gcwq. The exclusion is handled automatically by this function.
1638 *
1639 * The caller can safely start processing works on false return. On
1640 * true return, it's guaranteed that need_to_create_worker() is false
1641 * and may_start_working() is true.
1642 *
1643 * CONTEXT:
1644 * spin_lock_irq(gcwq->lock) which may be released and regrabbed
1645 * multiple times. Does GFP_KERNEL allocations.
1646 *
1647 * RETURNS:
1648 * false if no action was taken and gcwq->lock stayed locked, true if
1649 * some action was taken.
1650 */
1651static bool manage_workers(struct worker *worker)
1652{
1653 struct global_cwq *gcwq = worker->gcwq;
1654 bool ret = false;
1655
1656 if (gcwq->flags & GCWQ_MANAGING_WORKERS)
1657 return ret;
1658
1659 gcwq->flags &= ~GCWQ_MANAGE_WORKERS;
1660 gcwq->flags |= GCWQ_MANAGING_WORKERS;
1661
1662 /*
1663 * Destroy and then create so that may_start_working() is true
1664 * on return.
1665 */
1666 ret |= maybe_destroy_workers(gcwq);
1667 ret |= maybe_create_worker(gcwq);
1668
1669 gcwq->flags &= ~GCWQ_MANAGING_WORKERS;
1670
1671 /*
1672 * The trustee might be waiting to take over the manager
1673 * position, tell it we're done.
1674 */
1675 if (unlikely(gcwq->trustee))
1676 wake_up_all(&gcwq->trustee_wait);
1677
1678 return ret;
1679}
1680
1681/**
1682 * move_linked_works - move linked works to a list
1683 * @work: start of series of works to be scheduled
1684 * @head: target list to append @work to
1685 * @nextp: out paramter for nested worklist walking
1686 *
1687 * Schedule linked works starting from @work to @head. Work series to
1688 * be scheduled starts at @work and includes any consecutive work with
1689 * WORK_STRUCT_LINKED set in its predecessor.
1690 *
1691 * If @nextp is not NULL, it's updated to point to the next work of
1692 * the last scheduled work. This allows move_linked_works() to be
1693 * nested inside outer list_for_each_entry_safe().
1694 *
1695 * CONTEXT:
1696 * spin_lock_irq(gcwq->lock).
1697 */
1698static void move_linked_works(struct work_struct *work, struct list_head *head,
1699 struct work_struct **nextp)
1700{
1701 struct work_struct *n;
1702
1703 /*
1704 * Linked worklist will always end before the end of the list,
1705 * use NULL for list head.
1706 */
1707 list_for_each_entry_safe_from(work, n, NULL, entry) {
1708 list_move_tail(&work->entry, head);
1709 if (!(*work_data_bits(work) & WORK_STRUCT_LINKED))
1710 break;
1711 }
1712
1713 /*
1714 * If we're already inside safe list traversal and have moved
1715 * multiple works to the scheduled queue, the next position
1716 * needs to be updated.
1717 */
1718 if (nextp)
1719 *nextp = n;
1720}
1721
1722static void cwq_activate_first_delayed(struct cpu_workqueue_struct *cwq)
1723{
1724 struct work_struct *work = list_first_entry(&cwq->delayed_works,
1725 struct work_struct, entry);
1726 struct list_head *pos = gcwq_determine_ins_pos(cwq->gcwq, cwq);
1727
1728 trace_workqueue_activate_work(work);
1729 move_linked_works(work, pos, NULL);
1730 __clear_bit(WORK_STRUCT_DELAYED_BIT, work_data_bits(work));
1731 cwq->nr_active++;
1732}
1733
1734/**
1735 * cwq_dec_nr_in_flight - decrement cwq's nr_in_flight
1736 * @cwq: cwq of interest
1737 * @color: color of work which left the queue
1738 * @delayed: for a delayed work
1739 *
1740 * A work either has completed or is removed from pending queue,
1741 * decrement nr_in_flight of its cwq and handle workqueue flushing.
1742 *
1743 * CONTEXT:
1744 * spin_lock_irq(gcwq->lock).
1745 */
1746static void cwq_dec_nr_in_flight(struct cpu_workqueue_struct *cwq, int color,
1747 bool delayed)
1748{
1749 /* ignore uncolored works */
1750 if (color == WORK_NO_COLOR)
1751 return;
1752
1753 cwq->nr_in_flight[color]--;
1754
1755 if (!delayed) {
1756 cwq->nr_active--;
1757 if (!list_empty(&cwq->delayed_works)) {
1758 /* one down, submit a delayed one */
1759 if (cwq->nr_active < cwq->max_active)
1760 cwq_activate_first_delayed(cwq);
1761 }
1762 }
1763
1764 /* is flush in progress and are we at the flushing tip? */
1765 if (likely(cwq->flush_color != color))
1766 return;
1767
1768 /* are there still in-flight works? */
1769 if (cwq->nr_in_flight[color])
1770 return;
1771
1772 /* this cwq is done, clear flush_color */
1773 cwq->flush_color = -1;
1774
1775 /*
1776 * If this was the last cwq, wake up the first flusher. It
1777 * will handle the rest.
1778 */
1779 if (atomic_dec_and_test(&cwq->wq->nr_cwqs_to_flush))
1780 complete(&cwq->wq->first_flusher->done);
1781}
1782
1783/**
1784 * process_one_work - process single work
1785 * @worker: self
1786 * @work: work to process
1787 *
1788 * Process @work. This function contains all the logics necessary to
1789 * process a single work including synchronization against and
1790 * interaction with other workers on the same cpu, queueing and
1791 * flushing. As long as context requirement is met, any worker can
1792 * call this function to process a work.
1793 *
1794 * CONTEXT:
1795 * spin_lock_irq(gcwq->lock) which is released and regrabbed.
1796 */
1797static void process_one_work(struct worker *worker, struct work_struct *work)
1798__releases(&gcwq->lock)
1799__acquires(&gcwq->lock)
1800{
1801 struct cpu_workqueue_struct *cwq = get_work_cwq(work);
1802 struct global_cwq *gcwq = cwq->gcwq;
1803 struct hlist_head *bwh = busy_worker_head(gcwq, work);
1804 bool cpu_intensive = cwq->wq->flags & WQ_CPU_INTENSIVE;
1805 work_func_t f = work->func;
1806 int work_color;
1807 struct worker *collision;
1808#ifdef CONFIG_LOCKDEP
1809 /*
1810 * It is permissible to free the struct work_struct from
1811 * inside the function that is called from it, this we need to
1812 * take into account for lockdep too. To avoid bogus "held
1813 * lock freed" warnings as well as problems when looking into
1814 * work->lockdep_map, make a copy and use that here.
1815 */
1816 struct lockdep_map lockdep_map = work->lockdep_map;
1817#endif
1818 /*
1819 * A single work shouldn't be executed concurrently by
1820 * multiple workers on a single cpu. Check whether anyone is
1821 * already processing the work. If so, defer the work to the
1822 * currently executing one.
1823 */
1824 collision = __find_worker_executing_work(gcwq, bwh, work);
1825 if (unlikely(collision)) {
1826 move_linked_works(work, &collision->scheduled, NULL);
1827 return;
1828 }
1829
1830 /* claim and process */
1831 debug_work_deactivate(work);
1832 hlist_add_head(&worker->hentry, bwh);
1833 worker->current_work = work;
1834 worker->current_cwq = cwq;
1835 work_color = get_work_color(work);
1836
1837 /* record the current cpu number in the work data and dequeue */
1838 set_work_cpu(work, gcwq->cpu);
1839 list_del_init(&work->entry);
1840
1841 /*
1842 * If HIGHPRI_PENDING, check the next work, and, if HIGHPRI,
1843 * wake up another worker; otherwise, clear HIGHPRI_PENDING.
1844 */
1845 if (unlikely(gcwq->flags & GCWQ_HIGHPRI_PENDING)) {
1846 struct work_struct *nwork = list_first_entry(&gcwq->worklist,
1847 struct work_struct, entry);
1848
1849 if (!list_empty(&gcwq->worklist) &&
1850 get_work_cwq(nwork)->wq->flags & WQ_HIGHPRI)
1851 wake_up_worker(gcwq);
1852 else
1853 gcwq->flags &= ~GCWQ_HIGHPRI_PENDING;
1854 }
1855
1856 /*
1857 * CPU intensive works don't participate in concurrency
1858 * management. They're the scheduler's responsibility.
1859 */
1860 if (unlikely(cpu_intensive))
1861 worker_set_flags(worker, WORKER_CPU_INTENSIVE, true);
1862
1863 spin_unlock_irq(&gcwq->lock);
1864
1865 work_clear_pending(work);
1866 lock_map_acquire_read(&cwq->wq->lockdep_map);
1867 lock_map_acquire(&lockdep_map);
1868 trace_workqueue_execute_start(work);
1869 f(work);
1870 /*
1871 * While we must be careful to not use "work" after this, the trace
1872 * point will only record its address.
1873 */
1874 trace_workqueue_execute_end(work);
1875 lock_map_release(&lockdep_map);
1876 lock_map_release(&cwq->wq->lockdep_map);
1877
1878 if (unlikely(in_atomic() || lockdep_depth(current) > 0)) {
1879 printk(KERN_ERR "BUG: workqueue leaked lock or atomic: "
1880 "%s/0x%08x/%d\n",
1881 current->comm, preempt_count(), task_pid_nr(current));
1882 printk(KERN_ERR " last function: ");
1883 print_symbol("%s\n", (unsigned long)f);
1884 debug_show_held_locks(current);
1885 dump_stack();
1886 }
1887
1888 spin_lock_irq(&gcwq->lock);
1889
1890 /* clear cpu intensive status */
1891 if (unlikely(cpu_intensive))
1892 worker_clr_flags(worker, WORKER_CPU_INTENSIVE);
1893
1894 /* we're done with it, release */
1895 hlist_del_init(&worker->hentry);
1896 worker->current_work = NULL;
1897 worker->current_cwq = NULL;
1898 cwq_dec_nr_in_flight(cwq, work_color, false);
1899}
1900
1901/**
1902 * process_scheduled_works - process scheduled works
1903 * @worker: self
1904 *
1905 * Process all scheduled works. Please note that the scheduled list
1906 * may change while processing a work, so this function repeatedly
1907 * fetches a work from the top and executes it.
1908 *
1909 * CONTEXT:
1910 * spin_lock_irq(gcwq->lock) which may be released and regrabbed
1911 * multiple times.
1912 */
1913static void process_scheduled_works(struct worker *worker)
1914{
1915 while (!list_empty(&worker->scheduled)) {
1916 struct work_struct *work = list_first_entry(&worker->scheduled,
1917 struct work_struct, entry);
1918 process_one_work(worker, work);
1919 }
1920}
1921
1922/**
1923 * worker_thread - the worker thread function
1924 * @__worker: self
1925 *
1926 * The gcwq worker thread function. There's a single dynamic pool of
1927 * these per each cpu. These workers process all works regardless of
1928 * their specific target workqueue. The only exception is works which
1929 * belong to workqueues with a rescuer which will be explained in
1930 * rescuer_thread().
1931 */
1932static int worker_thread(void *__worker)
1933{
1934 struct worker *worker = __worker;
1935 struct global_cwq *gcwq = worker->gcwq;
1936
1937 /* tell the scheduler that this is a workqueue worker */
1938 worker->task->flags |= PF_WQ_WORKER;
1939woke_up:
1940 spin_lock_irq(&gcwq->lock);
1941
1942 /* DIE can be set only while we're idle, checking here is enough */
1943 if (worker->flags & WORKER_DIE) {
1944 spin_unlock_irq(&gcwq->lock);
1945 worker->task->flags &= ~PF_WQ_WORKER;
1946 return 0;
1947 }
1948
1949 worker_leave_idle(worker);
1950recheck:
1951 /* no more worker necessary? */
1952 if (!need_more_worker(gcwq))
1953 goto sleep;
1954
1955 /* do we need to manage? */
1956 if (unlikely(!may_start_working(gcwq)) && manage_workers(worker))
1957 goto recheck;
1958
1959 /*
1960 * ->scheduled list can only be filled while a worker is
1961 * preparing to process a work or actually processing it.
1962 * Make sure nobody diddled with it while I was sleeping.
1963 */
1964 BUG_ON(!list_empty(&worker->scheduled));
1965
1966 /*
1967 * When control reaches this point, we're guaranteed to have
1968 * at least one idle worker or that someone else has already
1969 * assumed the manager role.
1970 */
1971 worker_clr_flags(worker, WORKER_PREP);
1972
1973 do {
1974 struct work_struct *work =
1975 list_first_entry(&gcwq->worklist,
1976 struct work_struct, entry);
1977
1978 if (likely(!(*work_data_bits(work) & WORK_STRUCT_LINKED))) {
1979 /* optimization path, not strictly necessary */
1980 process_one_work(worker, work);
1981 if (unlikely(!list_empty(&worker->scheduled)))
1982 process_scheduled_works(worker);
1983 } else {
1984 move_linked_works(work, &worker->scheduled, NULL);
1985 process_scheduled_works(worker);
1986 }
1987 } while (keep_working(gcwq));
1988
1989 worker_set_flags(worker, WORKER_PREP, false);
1990sleep:
1991 if (unlikely(need_to_manage_workers(gcwq)) && manage_workers(worker))
1992 goto recheck;
1993
1994 /*
1995 * gcwq->lock is held and there's no work to process and no
1996 * need to manage, sleep. Workers are woken up only while
1997 * holding gcwq->lock or from local cpu, so setting the
1998 * current state before releasing gcwq->lock is enough to
1999 * prevent losing any event.
2000 */
2001 worker_enter_idle(worker);
2002 __set_current_state(TASK_INTERRUPTIBLE);
2003 spin_unlock_irq(&gcwq->lock);
2004 schedule();
2005 goto woke_up;
2006}
2007
2008/**
2009 * rescuer_thread - the rescuer thread function
2010 * @__wq: the associated workqueue
2011 *
2012 * Workqueue rescuer thread function. There's one rescuer for each
2013 * workqueue which has WQ_RESCUER set.
2014 *
2015 * Regular work processing on a gcwq may block trying to create a new
2016 * worker which uses GFP_KERNEL allocation which has slight chance of
2017 * developing into deadlock if some works currently on the same queue
2018 * need to be processed to satisfy the GFP_KERNEL allocation. This is
2019 * the problem rescuer solves.
2020 *
2021 * When such condition is possible, the gcwq summons rescuers of all
2022 * workqueues which have works queued on the gcwq and let them process
2023 * those works so that forward progress can be guaranteed.
2024 *
2025 * This should happen rarely.
2026 */
2027static int rescuer_thread(void *__wq)
2028{
2029 struct workqueue_struct *wq = __wq;
2030 struct worker *rescuer = wq->rescuer;
2031 struct list_head *scheduled = &rescuer->scheduled;
2032 bool is_unbound = wq->flags & WQ_UNBOUND;
2033 unsigned int cpu;
2034
2035 set_user_nice(current, RESCUER_NICE_LEVEL);
2036repeat:
2037 set_current_state(TASK_INTERRUPTIBLE);
2038
2039 if (kthread_should_stop())
2040 return 0;
2041
2042 /*
2043 * See whether any cpu is asking for help. Unbounded
2044 * workqueues use cpu 0 in mayday_mask for CPU_UNBOUND.
2045 */
2046 for_each_mayday_cpu(cpu, wq->mayday_mask) {
2047 unsigned int tcpu = is_unbound ? WORK_CPU_UNBOUND : cpu;
2048 struct cpu_workqueue_struct *cwq = get_cwq(tcpu, wq);
2049 struct global_cwq *gcwq = cwq->gcwq;
2050 struct work_struct *work, *n;
2051
2052 __set_current_state(TASK_RUNNING);
2053 mayday_clear_cpu(cpu, wq->mayday_mask);
2054
2055 /* migrate to the target cpu if possible */
2056 rescuer->gcwq = gcwq;
2057 worker_maybe_bind_and_lock(rescuer);
2058
2059 /*
2060 * Slurp in all works issued via this workqueue and
2061 * process'em.
2062 */
2063 BUG_ON(!list_empty(&rescuer->scheduled));
2064 list_for_each_entry_safe(work, n, &gcwq->worklist, entry)
2065 if (get_work_cwq(work) == cwq)
2066 move_linked_works(work, scheduled, &n);
2067
2068 process_scheduled_works(rescuer);
2069
2070 /*
2071 * Leave this gcwq. If keep_working() is %true, notify a
2072 * regular worker; otherwise, we end up with 0 concurrency
2073 * and stalling the execution.
2074 */
2075 if (keep_working(gcwq))
2076 wake_up_worker(gcwq);
2077
2078 spin_unlock_irq(&gcwq->lock);
2079 }
2080
2081 schedule();
2082 goto repeat;
2083}
2084
2085struct wq_barrier {
2086 struct work_struct work;
2087 struct completion done;
2088};
2089
2090static void wq_barrier_func(struct work_struct *work)
2091{
2092 struct wq_barrier *barr = container_of(work, struct wq_barrier, work);
2093 complete(&barr->done);
2094}
2095
2096/**
2097 * insert_wq_barrier - insert a barrier work
2098 * @cwq: cwq to insert barrier into
2099 * @barr: wq_barrier to insert
2100 * @target: target work to attach @barr to
2101 * @worker: worker currently executing @target, NULL if @target is not executing
2102 *
2103 * @barr is linked to @target such that @barr is completed only after
2104 * @target finishes execution. Please note that the ordering
2105 * guarantee is observed only with respect to @target and on the local
2106 * cpu.
2107 *
2108 * Currently, a queued barrier can't be canceled. This is because
2109 * try_to_grab_pending() can't determine whether the work to be
2110 * grabbed is at the head of the queue and thus can't clear LINKED
2111 * flag of the previous work while there must be a valid next work
2112 * after a work with LINKED flag set.
2113 *
2114 * Note that when @worker is non-NULL, @target may be modified
2115 * underneath us, so we can't reliably determine cwq from @target.
2116 *
2117 * CONTEXT:
2118 * spin_lock_irq(gcwq->lock).
2119 */
2120static void insert_wq_barrier(struct cpu_workqueue_struct *cwq,
2121 struct wq_barrier *barr,
2122 struct work_struct *target, struct worker *worker)
2123{
2124 struct list_head *head;
2125 unsigned int linked = 0;
2126
2127 /*
2128 * debugobject calls are safe here even with gcwq->lock locked
2129 * as we know for sure that this will not trigger any of the
2130 * checks and call back into the fixup functions where we
2131 * might deadlock.
2132 */
2133 INIT_WORK_ONSTACK(&barr->work, wq_barrier_func);
2134 __set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(&barr->work));
2135 init_completion(&barr->done);
2136
2137 /*
2138 * If @target is currently being executed, schedule the
2139 * barrier to the worker; otherwise, put it after @target.
2140 */
2141 if (worker)
2142 head = worker->scheduled.next;
2143 else {
2144 unsigned long *bits = work_data_bits(target);
2145
2146 head = target->entry.next;
2147 /* there can already be other linked works, inherit and set */
2148 linked = *bits & WORK_STRUCT_LINKED;
2149 __set_bit(WORK_STRUCT_LINKED_BIT, bits);
2150 }
2151
2152 debug_work_activate(&barr->work);
2153 insert_work(cwq, &barr->work, head,
2154 work_color_to_flags(WORK_NO_COLOR) | linked);
2155}
2156
2157/**
2158 * flush_workqueue_prep_cwqs - prepare cwqs for workqueue flushing
2159 * @wq: workqueue being flushed
2160 * @flush_color: new flush color, < 0 for no-op
2161 * @work_color: new work color, < 0 for no-op
2162 *
2163 * Prepare cwqs for workqueue flushing.
2164 *
2165 * If @flush_color is non-negative, flush_color on all cwqs should be
2166 * -1. If no cwq has in-flight commands at the specified color, all
2167 * cwq->flush_color's stay at -1 and %false is returned. If any cwq
2168 * has in flight commands, its cwq->flush_color is set to
2169 * @flush_color, @wq->nr_cwqs_to_flush is updated accordingly, cwq
2170 * wakeup logic is armed and %true is returned.
2171 *
2172 * The caller should have initialized @wq->first_flusher prior to
2173 * calling this function with non-negative @flush_color. If
2174 * @flush_color is negative, no flush color update is done and %false
2175 * is returned.
2176 *
2177 * If @work_color is non-negative, all cwqs should have the same
2178 * work_color which is previous to @work_color and all will be
2179 * advanced to @work_color.
2180 *
2181 * CONTEXT:
2182 * mutex_lock(wq->flush_mutex).
2183 *
2184 * RETURNS:
2185 * %true if @flush_color >= 0 and there's something to flush. %false
2186 * otherwise.
2187 */
2188static bool flush_workqueue_prep_cwqs(struct workqueue_struct *wq,
2189 int flush_color, int work_color)
2190{
2191 bool wait = false;
2192 unsigned int cpu;
2193
2194 if (flush_color >= 0) {
2195 BUG_ON(atomic_read(&wq->nr_cwqs_to_flush));
2196 atomic_set(&wq->nr_cwqs_to_flush, 1);
2197 }
2198
2199 for_each_cwq_cpu(cpu, wq) {
2200 struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
2201 struct global_cwq *gcwq = cwq->gcwq;
2202
2203 spin_lock_irq(&gcwq->lock);
2204
2205 if (flush_color >= 0) {
2206 BUG_ON(cwq->flush_color != -1);
2207
2208 if (cwq->nr_in_flight[flush_color]) {
2209 cwq->flush_color = flush_color;
2210 atomic_inc(&wq->nr_cwqs_to_flush);
2211 wait = true;
2212 }
2213 }
2214
2215 if (work_color >= 0) {
2216 BUG_ON(work_color != work_next_color(cwq->work_color));
2217 cwq->work_color = work_color;
2218 }
2219
2220 spin_unlock_irq(&gcwq->lock);
2221 }
2222
2223 if (flush_color >= 0 && atomic_dec_and_test(&wq->nr_cwqs_to_flush))
2224 complete(&wq->first_flusher->done);
2225
2226 return wait;
2227}
2228
2229/**
2230 * flush_workqueue - ensure that any scheduled work has run to completion.
2231 * @wq: workqueue to flush
2232 *
2233 * Forces execution of the workqueue and blocks until its completion.
2234 * This is typically used in driver shutdown handlers.
2235 *
2236 * We sleep until all works which were queued on entry have been handled,
2237 * but we are not livelocked by new incoming ones.
2238 */
2239void flush_workqueue(struct workqueue_struct *wq)
2240{
2241 struct wq_flusher this_flusher = {
2242 .list = LIST_HEAD_INIT(this_flusher.list),
2243 .flush_color = -1,
2244 .done = COMPLETION_INITIALIZER_ONSTACK(this_flusher.done),
2245 };
2246 int next_color;
2247
2248 lock_map_acquire(&wq->lockdep_map);
2249 lock_map_release(&wq->lockdep_map);
2250
2251 mutex_lock(&wq->flush_mutex);
2252
2253 /*
2254 * Start-to-wait phase
2255 */
2256 next_color = work_next_color(wq->work_color);
2257
2258 if (next_color != wq->flush_color) {
2259 /*
2260 * Color space is not full. The current work_color
2261 * becomes our flush_color and work_color is advanced
2262 * by one.
2263 */
2264 BUG_ON(!list_empty(&wq->flusher_overflow));
2265 this_flusher.flush_color = wq->work_color;
2266 wq->work_color = next_color;
2267
2268 if (!wq->first_flusher) {
2269 /* no flush in progress, become the first flusher */
2270 BUG_ON(wq->flush_color != this_flusher.flush_color);
2271
2272 wq->first_flusher = &this_flusher;
2273
2274 if (!flush_workqueue_prep_cwqs(wq, wq->flush_color,
2275 wq->work_color)) {
2276 /* nothing to flush, done */
2277 wq->flush_color = next_color;
2278 wq->first_flusher = NULL;
2279 goto out_unlock;
2280 }
2281 } else {
2282 /* wait in queue */
2283 BUG_ON(wq->flush_color == this_flusher.flush_color);
2284 list_add_tail(&this_flusher.list, &wq->flusher_queue);
2285 flush_workqueue_prep_cwqs(wq, -1, wq->work_color);
2286 }
2287 } else {
2288 /*
2289 * Oops, color space is full, wait on overflow queue.
2290 * The next flush completion will assign us
2291 * flush_color and transfer to flusher_queue.
2292 */
2293 list_add_tail(&this_flusher.list, &wq->flusher_overflow);
2294 }
2295
2296 mutex_unlock(&wq->flush_mutex);
2297
2298 wait_for_completion(&this_flusher.done);
2299
2300 /*
2301 * Wake-up-and-cascade phase
2302 *
2303 * First flushers are responsible for cascading flushes and
2304 * handling overflow. Non-first flushers can simply return.
2305 */
2306 if (wq->first_flusher != &this_flusher)
2307 return;
2308
2309 mutex_lock(&wq->flush_mutex);
2310
2311 /* we might have raced, check again with mutex held */
2312 if (wq->first_flusher != &this_flusher)
2313 goto out_unlock;
2314
2315 wq->first_flusher = NULL;
2316
2317 BUG_ON(!list_empty(&this_flusher.list));
2318 BUG_ON(wq->flush_color != this_flusher.flush_color);
2319
2320 while (true) {
2321 struct wq_flusher *next, *tmp;
2322
2323 /* complete all the flushers sharing the current flush color */
2324 list_for_each_entry_safe(next, tmp, &wq->flusher_queue, list) {
2325 if (next->flush_color != wq->flush_color)
2326 break;
2327 list_del_init(&next->list);
2328 complete(&next->done);
2329 }
2330
2331 BUG_ON(!list_empty(&wq->flusher_overflow) &&
2332 wq->flush_color != work_next_color(wq->work_color));
2333
2334 /* this flush_color is finished, advance by one */
2335 wq->flush_color = work_next_color(wq->flush_color);
2336
2337 /* one color has been freed, handle overflow queue */
2338 if (!list_empty(&wq->flusher_overflow)) {
2339 /*
2340 * Assign the same color to all overflowed
2341 * flushers, advance work_color and append to
2342 * flusher_queue. This is the start-to-wait
2343 * phase for these overflowed flushers.
2344 */
2345 list_for_each_entry(tmp, &wq->flusher_overflow, list)
2346 tmp->flush_color = wq->work_color;
2347
2348 wq->work_color = work_next_color(wq->work_color);
2349
2350 list_splice_tail_init(&wq->flusher_overflow,
2351 &wq->flusher_queue);
2352 flush_workqueue_prep_cwqs(wq, -1, wq->work_color);
2353 }
2354
2355 if (list_empty(&wq->flusher_queue)) {
2356 BUG_ON(wq->flush_color != wq->work_color);
2357 break;
2358 }
2359
2360 /*
2361 * Need to flush more colors. Make the next flusher
2362 * the new first flusher and arm cwqs.
2363 */
2364 BUG_ON(wq->flush_color == wq->work_color);
2365 BUG_ON(wq->flush_color != next->flush_color);
2366
2367 list_del_init(&next->list);
2368 wq->first_flusher = next;
2369
2370 if (flush_workqueue_prep_cwqs(wq, wq->flush_color, -1))
2371 break;
2372
2373 /*
2374 * Meh... this color is already done, clear first
2375 * flusher and repeat cascading.
2376 */
2377 wq->first_flusher = NULL;
2378 }
2379
2380out_unlock:
2381 mutex_unlock(&wq->flush_mutex);
2382}
2383EXPORT_SYMBOL_GPL(flush_workqueue);
2384
2385/**
2386 * drain_workqueue - drain a workqueue
2387 * @wq: workqueue to drain
2388 *
2389 * Wait until the workqueue becomes empty. While draining is in progress,
2390 * only chain queueing is allowed. IOW, only currently pending or running
2391 * work items on @wq can queue further work items on it. @wq is flushed
2392 * repeatedly until it becomes empty. The number of flushing is detemined
2393 * by the depth of chaining and should be relatively short. Whine if it
2394 * takes too long.
2395 */
2396void drain_workqueue(struct workqueue_struct *wq)
2397{
2398 unsigned int flush_cnt = 0;
2399 unsigned int cpu;
2400
2401 /*
2402 * __queue_work() needs to test whether there are drainers, is much
2403 * hotter than drain_workqueue() and already looks at @wq->flags.
2404 * Use WQ_DRAINING so that queue doesn't have to check nr_drainers.
2405 */
2406 spin_lock(&workqueue_lock);
2407 if (!wq->nr_drainers++)
2408 wq->flags |= WQ_DRAINING;
2409 spin_unlock(&workqueue_lock);
2410reflush:
2411 flush_workqueue(wq);
2412
2413 for_each_cwq_cpu(cpu, wq) {
2414 struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
2415 bool drained;
2416
2417 spin_lock_irq(&cwq->gcwq->lock);
2418 drained = !cwq->nr_active && list_empty(&cwq->delayed_works);
2419 spin_unlock_irq(&cwq->gcwq->lock);
2420
2421 if (drained)
2422 continue;
2423
2424 if (++flush_cnt == 10 ||
2425 (flush_cnt % 100 == 0 && flush_cnt <= 1000))
2426 pr_warning("workqueue %s: flush on destruction isn't complete after %u tries\n",
2427 wq->name, flush_cnt);
2428 goto reflush;
2429 }
2430
2431 spin_lock(&workqueue_lock);
2432 if (!--wq->nr_drainers)
2433 wq->flags &= ~WQ_DRAINING;
2434 spin_unlock(&workqueue_lock);
2435}
2436EXPORT_SYMBOL_GPL(drain_workqueue);
2437
2438static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr,
2439 bool wait_executing)
2440{
2441 struct worker *worker = NULL;
2442 struct global_cwq *gcwq;
2443 struct cpu_workqueue_struct *cwq;
2444
2445 might_sleep();
2446 gcwq = get_work_gcwq(work);
2447 if (!gcwq)
2448 return false;
2449
2450 spin_lock_irq(&gcwq->lock);
2451 if (!list_empty(&work->entry)) {
2452 /*
2453 * See the comment near try_to_grab_pending()->smp_rmb().
2454 * If it was re-queued to a different gcwq under us, we
2455 * are not going to wait.
2456 */
2457 smp_rmb();
2458 cwq = get_work_cwq(work);
2459 if (unlikely(!cwq || gcwq != cwq->gcwq))
2460 goto already_gone;
2461 } else if (wait_executing) {
2462 worker = find_worker_executing_work(gcwq, work);
2463 if (!worker)
2464 goto already_gone;
2465 cwq = worker->current_cwq;
2466 } else
2467 goto already_gone;
2468
2469 insert_wq_barrier(cwq, barr, work, worker);
2470 spin_unlock_irq(&gcwq->lock);
2471
2472 /*
2473 * If @max_active is 1 or rescuer is in use, flushing another work
2474 * item on the same workqueue may lead to deadlock. Make sure the
2475 * flusher is not running on the same workqueue by verifying write
2476 * access.
2477 */
2478 if (cwq->wq->saved_max_active == 1 || cwq->wq->flags & WQ_RESCUER)
2479 lock_map_acquire(&cwq->wq->lockdep_map);
2480 else
2481 lock_map_acquire_read(&cwq->wq->lockdep_map);
2482 lock_map_release(&cwq->wq->lockdep_map);
2483
2484 return true;
2485already_gone:
2486 spin_unlock_irq(&gcwq->lock);
2487 return false;
2488}
2489
2490/**
2491 * flush_work - wait for a work to finish executing the last queueing instance
2492 * @work: the work to flush
2493 *
2494 * Wait until @work has finished execution. This function considers
2495 * only the last queueing instance of @work. If @work has been
2496 * enqueued across different CPUs on a non-reentrant workqueue or on
2497 * multiple workqueues, @work might still be executing on return on
2498 * some of the CPUs from earlier queueing.
2499 *
2500 * If @work was queued only on a non-reentrant, ordered or unbound
2501 * workqueue, @work is guaranteed to be idle on return if it hasn't
2502 * been requeued since flush started.
2503 *
2504 * RETURNS:
2505 * %true if flush_work() waited for the work to finish execution,
2506 * %false if it was already idle.
2507 */
2508bool flush_work(struct work_struct *work)
2509{
2510 struct wq_barrier barr;
2511
2512 if (start_flush_work(work, &barr, true)) {
2513 wait_for_completion(&barr.done);
2514 destroy_work_on_stack(&barr.work);
2515 return true;
2516 } else
2517 return false;
2518}
2519EXPORT_SYMBOL_GPL(flush_work);
2520
2521static bool wait_on_cpu_work(struct global_cwq *gcwq, struct work_struct *work)
2522{
2523 struct wq_barrier barr;
2524 struct worker *worker;
2525
2526 spin_lock_irq(&gcwq->lock);
2527
2528 worker = find_worker_executing_work(gcwq, work);
2529 if (unlikely(worker))
2530 insert_wq_barrier(worker->current_cwq, &barr, work, worker);
2531
2532 spin_unlock_irq(&gcwq->lock);
2533
2534 if (unlikely(worker)) {
2535 wait_for_completion(&barr.done);
2536 destroy_work_on_stack(&barr.work);
2537 return true;
2538 } else
2539 return false;
2540}
2541
2542static bool wait_on_work(struct work_struct *work)
2543{
2544 bool ret = false;
2545 int cpu;
2546
2547 might_sleep();
2548
2549 lock_map_acquire(&work->lockdep_map);
2550 lock_map_release(&work->lockdep_map);
2551
2552 for_each_gcwq_cpu(cpu)
2553 ret |= wait_on_cpu_work(get_gcwq(cpu), work);
2554 return ret;
2555}
2556
2557/**
2558 * flush_work_sync - wait until a work has finished execution
2559 * @work: the work to flush
2560 *
2561 * Wait until @work has finished execution. On return, it's
2562 * guaranteed that all queueing instances of @work which happened
2563 * before this function is called are finished. In other words, if
2564 * @work hasn't been requeued since this function was called, @work is
2565 * guaranteed to be idle on return.
2566 *
2567 * RETURNS:
2568 * %true if flush_work_sync() waited for the work to finish execution,
2569 * %false if it was already idle.
2570 */
2571bool flush_work_sync(struct work_struct *work)
2572{
2573 struct wq_barrier barr;
2574 bool pending, waited;
2575
2576 /* we'll wait for executions separately, queue barr only if pending */
2577 pending = start_flush_work(work, &barr, false);
2578
2579 /* wait for executions to finish */
2580 waited = wait_on_work(work);
2581
2582 /* wait for the pending one */
2583 if (pending) {
2584 wait_for_completion(&barr.done);
2585 destroy_work_on_stack(&barr.work);
2586 }
2587
2588 return pending || waited;
2589}
2590EXPORT_SYMBOL_GPL(flush_work_sync);
2591
2592/*
2593 * Upon a successful return (>= 0), the caller "owns" WORK_STRUCT_PENDING bit,
2594 * so this work can't be re-armed in any way.
2595 */
2596static int try_to_grab_pending(struct work_struct *work)
2597{
2598 struct global_cwq *gcwq;
2599 int ret = -1;
2600
2601 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work)))
2602 return 0;
2603
2604 /*
2605 * The queueing is in progress, or it is already queued. Try to
2606 * steal it from ->worklist without clearing WORK_STRUCT_PENDING.
2607 */
2608 gcwq = get_work_gcwq(work);
2609 if (!gcwq)
2610 return ret;
2611
2612 spin_lock_irq(&gcwq->lock);
2613 if (!list_empty(&work->entry)) {
2614 /*
2615 * This work is queued, but perhaps we locked the wrong gcwq.
2616 * In that case we must see the new value after rmb(), see
2617 * insert_work()->wmb().
2618 */
2619 smp_rmb();
2620 if (gcwq == get_work_gcwq(work)) {
2621 debug_work_deactivate(work);
2622 list_del_init(&work->entry);
2623 cwq_dec_nr_in_flight(get_work_cwq(work),
2624 get_work_color(work),
2625 *work_data_bits(work) & WORK_STRUCT_DELAYED);
2626 ret = 1;
2627 }
2628 }
2629 spin_unlock_irq(&gcwq->lock);
2630
2631 return ret;
2632}
2633
2634static bool __cancel_work_timer(struct work_struct *work,
2635 struct timer_list* timer)
2636{
2637 int ret;
2638
2639 do {
2640 ret = (timer && likely(del_timer(timer)));
2641 if (!ret)
2642 ret = try_to_grab_pending(work);
2643 wait_on_work(work);
2644 } while (unlikely(ret < 0));
2645
2646 clear_work_data(work);
2647 return ret;
2648}
2649
2650/**
2651 * cancel_work_sync - cancel a work and wait for it to finish
2652 * @work: the work to cancel
2653 *
2654 * Cancel @work and wait for its execution to finish. This function
2655 * can be used even if the work re-queues itself or migrates to
2656 * another workqueue. On return from this function, @work is
2657 * guaranteed to be not pending or executing on any CPU.
2658 *
2659 * cancel_work_sync(&delayed_work->work) must not be used for
2660 * delayed_work's. Use cancel_delayed_work_sync() instead.
2661 *
2662 * The caller must ensure that the workqueue on which @work was last
2663 * queued can't be destroyed before this function returns.
2664 *
2665 * RETURNS:
2666 * %true if @work was pending, %false otherwise.
2667 */
2668bool cancel_work_sync(struct work_struct *work)
2669{
2670 return __cancel_work_timer(work, NULL);
2671}
2672EXPORT_SYMBOL_GPL(cancel_work_sync);
2673
2674/**
2675 * flush_delayed_work - wait for a dwork to finish executing the last queueing
2676 * @dwork: the delayed work to flush
2677 *
2678 * Delayed timer is cancelled and the pending work is queued for
2679 * immediate execution. Like flush_work(), this function only
2680 * considers the last queueing instance of @dwork.
2681 *
2682 * RETURNS:
2683 * %true if flush_work() waited for the work to finish execution,
2684 * %false if it was already idle.
2685 */
2686bool flush_delayed_work(struct delayed_work *dwork)
2687{
2688 if (del_timer_sync(&dwork->timer))
2689 __queue_work(raw_smp_processor_id(),
2690 get_work_cwq(&dwork->work)->wq, &dwork->work);
2691 return flush_work(&dwork->work);
2692}
2693EXPORT_SYMBOL(flush_delayed_work);
2694
2695/**
2696 * flush_delayed_work_sync - wait for a dwork to finish
2697 * @dwork: the delayed work to flush
2698 *
2699 * Delayed timer is cancelled and the pending work is queued for
2700 * execution immediately. Other than timer handling, its behavior
2701 * is identical to flush_work_sync().
2702 *
2703 * RETURNS:
2704 * %true if flush_work_sync() waited for the work to finish execution,
2705 * %false if it was already idle.
2706 */
2707bool flush_delayed_work_sync(struct delayed_work *dwork)
2708{
2709 if (del_timer_sync(&dwork->timer))
2710 __queue_work(raw_smp_processor_id(),
2711 get_work_cwq(&dwork->work)->wq, &dwork->work);
2712 return flush_work_sync(&dwork->work);
2713}
2714EXPORT_SYMBOL(flush_delayed_work_sync);
2715
2716/**
2717 * cancel_delayed_work_sync - cancel a delayed work and wait for it to finish
2718 * @dwork: the delayed work cancel
2719 *
2720 * This is cancel_work_sync() for delayed works.
2721 *
2722 * RETURNS:
2723 * %true if @dwork was pending, %false otherwise.
2724 */
2725bool cancel_delayed_work_sync(struct delayed_work *dwork)
2726{
2727 return __cancel_work_timer(&dwork->work, &dwork->timer);
2728}
2729EXPORT_SYMBOL(cancel_delayed_work_sync);
2730
2731/**
2732 * schedule_work - put work task in global workqueue
2733 * @work: job to be done
2734 *
2735 * Returns zero if @work was already on the kernel-global workqueue and
2736 * non-zero otherwise.
2737 *
2738 * This puts a job in the kernel-global workqueue if it was not already
2739 * queued and leaves it in the same position on the kernel-global
2740 * workqueue otherwise.
2741 */
2742int schedule_work(struct work_struct *work)
2743{
2744 return queue_work(system_wq, work);
2745}
2746EXPORT_SYMBOL(schedule_work);
2747
2748/*
2749 * schedule_work_on - put work task on a specific cpu
2750 * @cpu: cpu to put the work task on
2751 * @work: job to be done
2752 *
2753 * This puts a job on a specific cpu
2754 */
2755int schedule_work_on(int cpu, struct work_struct *work)
2756{
2757 return queue_work_on(cpu, system_wq, work);
2758}
2759EXPORT_SYMBOL(schedule_work_on);
2760
2761/**
2762 * schedule_delayed_work - put work task in global workqueue after delay
2763 * @dwork: job to be done
2764 * @delay: number of jiffies to wait or 0 for immediate execution
2765 *
2766 * After waiting for a given time this puts a job in the kernel-global
2767 * workqueue.
2768 */
2769int schedule_delayed_work(struct delayed_work *dwork,
2770 unsigned long delay)
2771{
2772 return queue_delayed_work(system_wq, dwork, delay);
2773}
2774EXPORT_SYMBOL(schedule_delayed_work);
2775
2776/**
2777 * schedule_delayed_work_on - queue work in global workqueue on CPU after delay
2778 * @cpu: cpu to use
2779 * @dwork: job to be done
2780 * @delay: number of jiffies to wait
2781 *
2782 * After waiting for a given time this puts a job in the kernel-global
2783 * workqueue on the specified CPU.
2784 */
2785int schedule_delayed_work_on(int cpu,
2786 struct delayed_work *dwork, unsigned long delay)
2787{
2788 return queue_delayed_work_on(cpu, system_wq, dwork, delay);
2789}
2790EXPORT_SYMBOL(schedule_delayed_work_on);
2791
2792/**
2793 * schedule_on_each_cpu - execute a function synchronously on each online CPU
2794 * @func: the function to call
2795 *
2796 * schedule_on_each_cpu() executes @func on each online CPU using the
2797 * system workqueue and blocks until all CPUs have completed.
2798 * schedule_on_each_cpu() is very slow.
2799 *
2800 * RETURNS:
2801 * 0 on success, -errno on failure.
2802 */
2803int schedule_on_each_cpu(work_func_t func)
2804{
2805 int cpu;
2806 struct work_struct __percpu *works;
2807
2808 works = alloc_percpu(struct work_struct);
2809 if (!works)
2810 return -ENOMEM;
2811
2812 get_online_cpus();
2813
2814 for_each_online_cpu(cpu) {
2815 struct work_struct *work = per_cpu_ptr(works, cpu);
2816
2817 INIT_WORK(work, func);
2818 schedule_work_on(cpu, work);
2819 }
2820
2821 for_each_online_cpu(cpu)
2822 flush_work(per_cpu_ptr(works, cpu));
2823
2824 put_online_cpus();
2825 free_percpu(works);
2826 return 0;
2827}
2828
2829/**
2830 * flush_scheduled_work - ensure that any scheduled work has run to completion.
2831 *
2832 * Forces execution of the kernel-global workqueue and blocks until its
2833 * completion.
2834 *
2835 * Think twice before calling this function! It's very easy to get into
2836 * trouble if you don't take great care. Either of the following situations
2837 * will lead to deadlock:
2838 *
2839 * One of the work items currently on the workqueue needs to acquire
2840 * a lock held by your code or its caller.
2841 *
2842 * Your code is running in the context of a work routine.
2843 *
2844 * They will be detected by lockdep when they occur, but the first might not
2845 * occur very often. It depends on what work items are on the workqueue and
2846 * what locks they need, which you have no control over.
2847 *
2848 * In most situations flushing the entire workqueue is overkill; you merely
2849 * need to know that a particular work item isn't queued and isn't running.
2850 * In such cases you should use cancel_delayed_work_sync() or
2851 * cancel_work_sync() instead.
2852 */
2853void flush_scheduled_work(void)
2854{
2855 flush_workqueue(system_wq);
2856}
2857EXPORT_SYMBOL(flush_scheduled_work);
2858
2859/**
2860 * execute_in_process_context - reliably execute the routine with user context
2861 * @fn: the function to execute
2862 * @ew: guaranteed storage for the execute work structure (must
2863 * be available when the work executes)
2864 *
2865 * Executes the function immediately if process context is available,
2866 * otherwise schedules the function for delayed execution.
2867 *
2868 * Returns: 0 - function was executed
2869 * 1 - function was scheduled for execution
2870 */
2871int execute_in_process_context(work_func_t fn, struct execute_work *ew)
2872{
2873 if (!in_interrupt()) {
2874 fn(&ew->work);
2875 return 0;
2876 }
2877
2878 INIT_WORK(&ew->work, fn);
2879 schedule_work(&ew->work);
2880
2881 return 1;
2882}
2883EXPORT_SYMBOL_GPL(execute_in_process_context);
2884
2885int keventd_up(void)
2886{
2887 return system_wq != NULL;
2888}
2889
2890static int alloc_cwqs(struct workqueue_struct *wq)
2891{
2892 /*
2893 * cwqs are forced aligned according to WORK_STRUCT_FLAG_BITS.
2894 * Make sure that the alignment isn't lower than that of
2895 * unsigned long long.
2896 */
2897 const size_t size = sizeof(struct cpu_workqueue_struct);
2898 const size_t align = max_t(size_t, 1 << WORK_STRUCT_FLAG_BITS,
2899 __alignof__(unsigned long long));
2900#ifdef CONFIG_SMP
2901 bool percpu = !(wq->flags & WQ_UNBOUND);
2902#else
2903 bool percpu = false;
2904#endif
2905
2906 if (percpu)
2907 wq->cpu_wq.pcpu = __alloc_percpu(size, align);
2908 else {
2909 void *ptr;
2910
2911 /*
2912 * Allocate enough room to align cwq and put an extra
2913 * pointer at the end pointing back to the originally
2914 * allocated pointer which will be used for free.
2915 */
2916 ptr = kzalloc(size + align + sizeof(void *), GFP_KERNEL);
2917 if (ptr) {
2918 wq->cpu_wq.single = PTR_ALIGN(ptr, align);
2919 *(void **)(wq->cpu_wq.single + 1) = ptr;
2920 }
2921 }
2922
2923 /* just in case, make sure it's actually aligned */
2924 BUG_ON(!IS_ALIGNED(wq->cpu_wq.v, align));
2925 return wq->cpu_wq.v ? 0 : -ENOMEM;
2926}
2927
2928static void free_cwqs(struct workqueue_struct *wq)
2929{
2930#ifdef CONFIG_SMP
2931 bool percpu = !(wq->flags & WQ_UNBOUND);
2932#else
2933 bool percpu = false;
2934#endif
2935
2936 if (percpu)
2937 free_percpu(wq->cpu_wq.pcpu);
2938 else if (wq->cpu_wq.single) {
2939 /* the pointer to free is stored right after the cwq */
2940 kfree(*(void **)(wq->cpu_wq.single + 1));
2941 }
2942}
2943
2944static int wq_clamp_max_active(int max_active, unsigned int flags,
2945 const char *name)
2946{
2947 int lim = flags & WQ_UNBOUND ? WQ_UNBOUND_MAX_ACTIVE : WQ_MAX_ACTIVE;
2948
2949 if (max_active < 1 || max_active > lim)
2950 printk(KERN_WARNING "workqueue: max_active %d requested for %s "
2951 "is out of range, clamping between %d and %d\n",
2952 max_active, name, 1, lim);
2953
2954 return clamp_val(max_active, 1, lim);
2955}
2956
2957struct workqueue_struct *__alloc_workqueue_key(const char *name,
2958 unsigned int flags,
2959 int max_active,
2960 struct lock_class_key *key,
2961 const char *lock_name)
2962{
2963 struct workqueue_struct *wq;
2964 unsigned int cpu;
2965
2966 /*
2967 * Workqueues which may be used during memory reclaim should
2968 * have a rescuer to guarantee forward progress.
2969 */
2970 if (flags & WQ_MEM_RECLAIM)
2971 flags |= WQ_RESCUER;
2972
2973 /*
2974 * Unbound workqueues aren't concurrency managed and should be
2975 * dispatched to workers immediately.
2976 */
2977 if (flags & WQ_UNBOUND)
2978 flags |= WQ_HIGHPRI;
2979
2980 max_active = max_active ?: WQ_DFL_ACTIVE;
2981 max_active = wq_clamp_max_active(max_active, flags, name);
2982
2983 wq = kzalloc(sizeof(*wq), GFP_KERNEL);
2984 if (!wq)
2985 goto err;
2986
2987 wq->flags = flags;
2988 wq->saved_max_active = max_active;
2989 mutex_init(&wq->flush_mutex);
2990 atomic_set(&wq->nr_cwqs_to_flush, 0);
2991 INIT_LIST_HEAD(&wq->flusher_queue);
2992 INIT_LIST_HEAD(&wq->flusher_overflow);
2993
2994 wq->name = name;
2995 lockdep_init_map(&wq->lockdep_map, lock_name, key, 0);
2996 INIT_LIST_HEAD(&wq->list);
2997
2998 if (alloc_cwqs(wq) < 0)
2999 goto err;
3000
3001 for_each_cwq_cpu(cpu, wq) {
3002 struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
3003 struct global_cwq *gcwq = get_gcwq(cpu);
3004
3005 BUG_ON((unsigned long)cwq & WORK_STRUCT_FLAG_MASK);
3006 cwq->gcwq = gcwq;
3007 cwq->wq = wq;
3008 cwq->flush_color = -1;
3009 cwq->max_active = max_active;
3010 INIT_LIST_HEAD(&cwq->delayed_works);
3011 }
3012
3013 if (flags & WQ_RESCUER) {
3014 struct worker *rescuer;
3015
3016 if (!alloc_mayday_mask(&wq->mayday_mask, GFP_KERNEL))
3017 goto err;
3018
3019 wq->rescuer = rescuer = alloc_worker();
3020 if (!rescuer)
3021 goto err;
3022
3023 rescuer->task = kthread_create(rescuer_thread, wq, "%s", name);
3024 if (IS_ERR(rescuer->task))
3025 goto err;
3026
3027 rescuer->task->flags |= PF_THREAD_BOUND;
3028 wake_up_process(rescuer->task);
3029 }
3030
3031 /*
3032 * workqueue_lock protects global freeze state and workqueues
3033 * list. Grab it, set max_active accordingly and add the new
3034 * workqueue to workqueues list.
3035 */
3036 spin_lock(&workqueue_lock);
3037
3038 if (workqueue_freezing && wq->flags & WQ_FREEZABLE)
3039 for_each_cwq_cpu(cpu, wq)
3040 get_cwq(cpu, wq)->max_active = 0;
3041
3042 list_add(&wq->list, &workqueues);
3043
3044 spin_unlock(&workqueue_lock);
3045
3046 return wq;
3047err:
3048 if (wq) {
3049 free_cwqs(wq);
3050 free_mayday_mask(wq->mayday_mask);
3051 kfree(wq->rescuer);
3052 kfree(wq);
3053 }
3054 return NULL;
3055}
3056EXPORT_SYMBOL_GPL(__alloc_workqueue_key);
3057
3058/**
3059 * destroy_workqueue - safely terminate a workqueue
3060 * @wq: target workqueue
3061 *
3062 * Safely destroy a workqueue. All work currently pending will be done first.
3063 */
3064void destroy_workqueue(struct workqueue_struct *wq)
3065{
3066 unsigned int cpu;
3067
3068 /* drain it before proceeding with destruction */
3069 drain_workqueue(wq);
3070
3071 /*
3072 * wq list is used to freeze wq, remove from list after
3073 * flushing is complete in case freeze races us.
3074 */
3075 spin_lock(&workqueue_lock);
3076 list_del(&wq->list);
3077 spin_unlock(&workqueue_lock);
3078
3079 /* sanity check */
3080 for_each_cwq_cpu(cpu, wq) {
3081 struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
3082 int i;
3083
3084 for (i = 0; i < WORK_NR_COLORS; i++)
3085 BUG_ON(cwq->nr_in_flight[i]);
3086 BUG_ON(cwq->nr_active);
3087 BUG_ON(!list_empty(&cwq->delayed_works));
3088 }
3089
3090 if (wq->flags & WQ_RESCUER) {
3091 kthread_stop(wq->rescuer->task);
3092 free_mayday_mask(wq->mayday_mask);
3093 kfree(wq->rescuer);
3094 }
3095
3096 free_cwqs(wq);
3097 kfree(wq);
3098}
3099EXPORT_SYMBOL_GPL(destroy_workqueue);
3100
3101/**
3102 * workqueue_set_max_active - adjust max_active of a workqueue
3103 * @wq: target workqueue
3104 * @max_active: new max_active value.
3105 *
3106 * Set max_active of @wq to @max_active.
3107 *
3108 * CONTEXT:
3109 * Don't call from IRQ context.
3110 */
3111void workqueue_set_max_active(struct workqueue_struct *wq, int max_active)
3112{
3113 unsigned int cpu;
3114
3115 max_active = wq_clamp_max_active(max_active, wq->flags, wq->name);
3116
3117 spin_lock(&workqueue_lock);
3118
3119 wq->saved_max_active = max_active;
3120
3121 for_each_cwq_cpu(cpu, wq) {
3122 struct global_cwq *gcwq = get_gcwq(cpu);
3123
3124 spin_lock_irq(&gcwq->lock);
3125
3126 if (!(wq->flags & WQ_FREEZABLE) ||
3127 !(gcwq->flags & GCWQ_FREEZING))
3128 get_cwq(gcwq->cpu, wq)->max_active = max_active;
3129
3130 spin_unlock_irq(&gcwq->lock);
3131 }
3132
3133 spin_unlock(&workqueue_lock);
3134}
3135EXPORT_SYMBOL_GPL(workqueue_set_max_active);
3136
3137/**
3138 * workqueue_congested - test whether a workqueue is congested
3139 * @cpu: CPU in question
3140 * @wq: target workqueue
3141 *
3142 * Test whether @wq's cpu workqueue for @cpu is congested. There is
3143 * no synchronization around this function and the test result is
3144 * unreliable and only useful as advisory hints or for debugging.
3145 *
3146 * RETURNS:
3147 * %true if congested, %false otherwise.
3148 */
3149bool workqueue_congested(unsigned int cpu, struct workqueue_struct *wq)
3150{
3151 struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
3152
3153 return !list_empty(&cwq->delayed_works);
3154}
3155EXPORT_SYMBOL_GPL(workqueue_congested);
3156
3157/**
3158 * work_cpu - return the last known associated cpu for @work
3159 * @work: the work of interest
3160 *
3161 * RETURNS:
3162 * CPU number if @work was ever queued. WORK_CPU_NONE otherwise.
3163 */
3164unsigned int work_cpu(struct work_struct *work)
3165{
3166 struct global_cwq *gcwq = get_work_gcwq(work);
3167
3168 return gcwq ? gcwq->cpu : WORK_CPU_NONE;
3169}
3170EXPORT_SYMBOL_GPL(work_cpu);
3171
3172/**
3173 * work_busy - test whether a work is currently pending or running
3174 * @work: the work to be tested
3175 *
3176 * Test whether @work is currently pending or running. There is no
3177 * synchronization around this function and the test result is
3178 * unreliable and only useful as advisory hints or for debugging.
3179 * Especially for reentrant wqs, the pending state might hide the
3180 * running state.
3181 *
3182 * RETURNS:
3183 * OR'd bitmask of WORK_BUSY_* bits.
3184 */
3185unsigned int work_busy(struct work_struct *work)
3186{
3187 struct global_cwq *gcwq = get_work_gcwq(work);
3188 unsigned long flags;
3189 unsigned int ret = 0;
3190
3191 if (!gcwq)
3192 return false;
3193
3194 spin_lock_irqsave(&gcwq->lock, flags);
3195
3196 if (work_pending(work))
3197 ret |= WORK_BUSY_PENDING;
3198 if (find_worker_executing_work(gcwq, work))
3199 ret |= WORK_BUSY_RUNNING;
3200
3201 spin_unlock_irqrestore(&gcwq->lock, flags);
3202
3203 return ret;
3204}
3205EXPORT_SYMBOL_GPL(work_busy);
3206
3207/*
3208 * CPU hotplug.
3209 *
3210 * There are two challenges in supporting CPU hotplug. Firstly, there
3211 * are a lot of assumptions on strong associations among work, cwq and
3212 * gcwq which make migrating pending and scheduled works very
3213 * difficult to implement without impacting hot paths. Secondly,
3214 * gcwqs serve mix of short, long and very long running works making
3215 * blocked draining impractical.
3216 *
3217 * This is solved by allowing a gcwq to be detached from CPU, running
3218 * it with unbound (rogue) workers and allowing it to be reattached
3219 * later if the cpu comes back online. A separate thread is created
3220 * to govern a gcwq in such state and is called the trustee of the
3221 * gcwq.
3222 *
3223 * Trustee states and their descriptions.
3224 *
3225 * START Command state used on startup. On CPU_DOWN_PREPARE, a
3226 * new trustee is started with this state.
3227 *
3228 * IN_CHARGE Once started, trustee will enter this state after
3229 * assuming the manager role and making all existing
3230 * workers rogue. DOWN_PREPARE waits for trustee to
3231 * enter this state. After reaching IN_CHARGE, trustee
3232 * tries to execute the pending worklist until it's empty
3233 * and the state is set to BUTCHER, or the state is set
3234 * to RELEASE.
3235 *
3236 * BUTCHER Command state which is set by the cpu callback after
3237 * the cpu has went down. Once this state is set trustee
3238 * knows that there will be no new works on the worklist
3239 * and once the worklist is empty it can proceed to
3240 * killing idle workers.
3241 *
3242 * RELEASE Command state which is set by the cpu callback if the
3243 * cpu down has been canceled or it has come online
3244 * again. After recognizing this state, trustee stops
3245 * trying to drain or butcher and clears ROGUE, rebinds
3246 * all remaining workers back to the cpu and releases
3247 * manager role.
3248 *
3249 * DONE Trustee will enter this state after BUTCHER or RELEASE
3250 * is complete.
3251 *
3252 * trustee CPU draining
3253 * took over down complete
3254 * START -----------> IN_CHARGE -----------> BUTCHER -----------> DONE
3255 * | | ^
3256 * | CPU is back online v return workers |
3257 * ----------------> RELEASE --------------
3258 */
3259
3260/**
3261 * trustee_wait_event_timeout - timed event wait for trustee
3262 * @cond: condition to wait for
3263 * @timeout: timeout in jiffies
3264 *
3265 * wait_event_timeout() for trustee to use. Handles locking and
3266 * checks for RELEASE request.
3267 *
3268 * CONTEXT:
3269 * spin_lock_irq(gcwq->lock) which may be released and regrabbed
3270 * multiple times. To be used by trustee.
3271 *
3272 * RETURNS:
3273 * Positive indicating left time if @cond is satisfied, 0 if timed
3274 * out, -1 if canceled.
3275 */
3276#define trustee_wait_event_timeout(cond, timeout) ({ \
3277 long __ret = (timeout); \
3278 while (!((cond) || (gcwq->trustee_state == TRUSTEE_RELEASE)) && \
3279 __ret) { \
3280 spin_unlock_irq(&gcwq->lock); \
3281 __wait_event_timeout(gcwq->trustee_wait, (cond) || \
3282 (gcwq->trustee_state == TRUSTEE_RELEASE), \
3283 __ret); \
3284 spin_lock_irq(&gcwq->lock); \
3285 } \
3286 gcwq->trustee_state == TRUSTEE_RELEASE ? -1 : (__ret); \
3287})
3288
3289/**
3290 * trustee_wait_event - event wait for trustee
3291 * @cond: condition to wait for
3292 *
3293 * wait_event() for trustee to use. Automatically handles locking and
3294 * checks for CANCEL request.
3295 *
3296 * CONTEXT:
3297 * spin_lock_irq(gcwq->lock) which may be released and regrabbed
3298 * multiple times. To be used by trustee.
3299 *
3300 * RETURNS:
3301 * 0 if @cond is satisfied, -1 if canceled.
3302 */
3303#define trustee_wait_event(cond) ({ \
3304 long __ret1; \
3305 __ret1 = trustee_wait_event_timeout(cond, MAX_SCHEDULE_TIMEOUT);\
3306 __ret1 < 0 ? -1 : 0; \
3307})
3308
3309static int __cpuinit trustee_thread(void *__gcwq)
3310{
3311 struct global_cwq *gcwq = __gcwq;
3312 struct worker *worker;
3313 struct work_struct *work;
3314 struct hlist_node *pos;
3315 long rc;
3316 int i;
3317
3318 BUG_ON(gcwq->cpu != smp_processor_id());
3319
3320 spin_lock_irq(&gcwq->lock);
3321 /*
3322 * Claim the manager position and make all workers rogue.
3323 * Trustee must be bound to the target cpu and can't be
3324 * cancelled.
3325 */
3326 BUG_ON(gcwq->cpu != smp_processor_id());
3327 rc = trustee_wait_event(!(gcwq->flags & GCWQ_MANAGING_WORKERS));
3328 BUG_ON(rc < 0);
3329
3330 gcwq->flags |= GCWQ_MANAGING_WORKERS;
3331
3332 list_for_each_entry(worker, &gcwq->idle_list, entry)
3333 worker->flags |= WORKER_ROGUE;
3334
3335 for_each_busy_worker(worker, i, pos, gcwq)
3336 worker->flags |= WORKER_ROGUE;
3337
3338 /*
3339 * Call schedule() so that we cross rq->lock and thus can
3340 * guarantee sched callbacks see the rogue flag. This is
3341 * necessary as scheduler callbacks may be invoked from other
3342 * cpus.
3343 */
3344 spin_unlock_irq(&gcwq->lock);
3345 schedule();
3346 spin_lock_irq(&gcwq->lock);
3347
3348 /*
3349 * Sched callbacks are disabled now. Zap nr_running. After
3350 * this, nr_running stays zero and need_more_worker() and
3351 * keep_working() are always true as long as the worklist is
3352 * not empty.
3353 */
3354 atomic_set(get_gcwq_nr_running(gcwq->cpu), 0);
3355
3356 spin_unlock_irq(&gcwq->lock);
3357 del_timer_sync(&gcwq->idle_timer);
3358 spin_lock_irq(&gcwq->lock);
3359
3360 /*
3361 * We're now in charge. Notify and proceed to drain. We need
3362 * to keep the gcwq running during the whole CPU down
3363 * procedure as other cpu hotunplug callbacks may need to
3364 * flush currently running tasks.
3365 */
3366 gcwq->trustee_state = TRUSTEE_IN_CHARGE;
3367 wake_up_all(&gcwq->trustee_wait);
3368
3369 /*
3370 * The original cpu is in the process of dying and may go away
3371 * anytime now. When that happens, we and all workers would
3372 * be migrated to other cpus. Try draining any left work. We
3373 * want to get it over with ASAP - spam rescuers, wake up as
3374 * many idlers as necessary and create new ones till the
3375 * worklist is empty. Note that if the gcwq is frozen, there
3376 * may be frozen works in freezable cwqs. Don't declare
3377 * completion while frozen.
3378 */
3379 while (gcwq->nr_workers != gcwq->nr_idle ||
3380 gcwq->flags & GCWQ_FREEZING ||
3381 gcwq->trustee_state == TRUSTEE_IN_CHARGE) {
3382 int nr_works = 0;
3383
3384 list_for_each_entry(work, &gcwq->worklist, entry) {
3385 send_mayday(work);
3386 nr_works++;
3387 }
3388
3389 list_for_each_entry(worker, &gcwq->idle_list, entry) {
3390 if (!nr_works--)
3391 break;
3392 wake_up_process(worker->task);
3393 }
3394
3395 if (need_to_create_worker(gcwq)) {
3396 spin_unlock_irq(&gcwq->lock);
3397 worker = create_worker(gcwq, false);
3398 spin_lock_irq(&gcwq->lock);
3399 if (worker) {
3400 worker->flags |= WORKER_ROGUE;
3401 start_worker(worker);
3402 }
3403 }
3404
3405 /* give a breather */
3406 if (trustee_wait_event_timeout(false, TRUSTEE_COOLDOWN) < 0)
3407 break;
3408 }
3409
3410 /*
3411 * Either all works have been scheduled and cpu is down, or
3412 * cpu down has already been canceled. Wait for and butcher
3413 * all workers till we're canceled.
3414 */
3415 do {
3416 rc = trustee_wait_event(!list_empty(&gcwq->idle_list));
3417 while (!list_empty(&gcwq->idle_list))
3418 destroy_worker(list_first_entry(&gcwq->idle_list,
3419 struct worker, entry));
3420 } while (gcwq->nr_workers && rc >= 0);
3421
3422 /*
3423 * At this point, either draining has completed and no worker
3424 * is left, or cpu down has been canceled or the cpu is being
3425 * brought back up. There shouldn't be any idle one left.
3426 * Tell the remaining busy ones to rebind once it finishes the
3427 * currently scheduled works by scheduling the rebind_work.
3428 */
3429 WARN_ON(!list_empty(&gcwq->idle_list));
3430
3431 for_each_busy_worker(worker, i, pos, gcwq) {
3432 struct work_struct *rebind_work = &worker->rebind_work;
3433
3434 /*
3435 * Rebind_work may race with future cpu hotplug
3436 * operations. Use a separate flag to mark that
3437 * rebinding is scheduled.
3438 */
3439 worker->flags |= WORKER_REBIND;
3440 worker->flags &= ~WORKER_ROGUE;
3441
3442 /* queue rebind_work, wq doesn't matter, use the default one */
3443 if (test_and_set_bit(WORK_STRUCT_PENDING_BIT,
3444 work_data_bits(rebind_work)))
3445 continue;
3446
3447 debug_work_activate(rebind_work);
3448 insert_work(get_cwq(gcwq->cpu, system_wq), rebind_work,
3449 worker->scheduled.next,
3450 work_color_to_flags(WORK_NO_COLOR));
3451 }
3452
3453 /* relinquish manager role */
3454 gcwq->flags &= ~GCWQ_MANAGING_WORKERS;
3455
3456 /* notify completion */
3457 gcwq->trustee = NULL;
3458 gcwq->trustee_state = TRUSTEE_DONE;
3459 wake_up_all(&gcwq->trustee_wait);
3460 spin_unlock_irq(&gcwq->lock);
3461 return 0;
3462}
3463
3464/**
3465 * wait_trustee_state - wait for trustee to enter the specified state
3466 * @gcwq: gcwq the trustee of interest belongs to
3467 * @state: target state to wait for
3468 *
3469 * Wait for the trustee to reach @state. DONE is already matched.
3470 *
3471 * CONTEXT:
3472 * spin_lock_irq(gcwq->lock) which may be released and regrabbed
3473 * multiple times. To be used by cpu_callback.
3474 */
3475static void __cpuinit wait_trustee_state(struct global_cwq *gcwq, int state)
3476__releases(&gcwq->lock)
3477__acquires(&gcwq->lock)
3478{
3479 if (!(gcwq->trustee_state == state ||
3480 gcwq->trustee_state == TRUSTEE_DONE)) {
3481 spin_unlock_irq(&gcwq->lock);
3482 __wait_event(gcwq->trustee_wait,
3483 gcwq->trustee_state == state ||
3484 gcwq->trustee_state == TRUSTEE_DONE);
3485 spin_lock_irq(&gcwq->lock);
3486 }
3487}
3488
3489static int __devinit workqueue_cpu_callback(struct notifier_block *nfb,
3490 unsigned long action,
3491 void *hcpu)
3492{
3493 unsigned int cpu = (unsigned long)hcpu;
3494 struct global_cwq *gcwq = get_gcwq(cpu);
3495 struct task_struct *new_trustee = NULL;
3496 struct worker *uninitialized_var(new_worker);
3497 unsigned long flags;
3498
3499 action &= ~CPU_TASKS_FROZEN;
3500
3501 switch (action) {
3502 case CPU_DOWN_PREPARE:
3503 new_trustee = kthread_create(trustee_thread, gcwq,
3504 "workqueue_trustee/%d\n", cpu);
3505 if (IS_ERR(new_trustee))
3506 return notifier_from_errno(PTR_ERR(new_trustee));
3507 kthread_bind(new_trustee, cpu);
3508 /* fall through */
3509 case CPU_UP_PREPARE:
3510 BUG_ON(gcwq->first_idle);
3511 new_worker = create_worker(gcwq, false);
3512 if (!new_worker) {
3513 if (new_trustee)
3514 kthread_stop(new_trustee);
3515 return NOTIFY_BAD;
3516 }
3517 }
3518
3519 /* some are called w/ irq disabled, don't disturb irq status */
3520 spin_lock_irqsave(&gcwq->lock, flags);
3521
3522 switch (action) {
3523 case CPU_DOWN_PREPARE:
3524 /* initialize trustee and tell it to acquire the gcwq */
3525 BUG_ON(gcwq->trustee || gcwq->trustee_state != TRUSTEE_DONE);
3526 gcwq->trustee = new_trustee;
3527 gcwq->trustee_state = TRUSTEE_START;
3528 wake_up_process(gcwq->trustee);
3529 wait_trustee_state(gcwq, TRUSTEE_IN_CHARGE);
3530 /* fall through */
3531 case CPU_UP_PREPARE:
3532 BUG_ON(gcwq->first_idle);
3533 gcwq->first_idle = new_worker;
3534 break;
3535
3536 case CPU_DYING:
3537 /*
3538 * Before this, the trustee and all workers except for
3539 * the ones which are still executing works from
3540 * before the last CPU down must be on the cpu. After
3541 * this, they'll all be diasporas.
3542 */
3543 gcwq->flags |= GCWQ_DISASSOCIATED;
3544 break;
3545
3546 case CPU_POST_DEAD:
3547 gcwq->trustee_state = TRUSTEE_BUTCHER;
3548 /* fall through */
3549 case CPU_UP_CANCELED:
3550 destroy_worker(gcwq->first_idle);
3551 gcwq->first_idle = NULL;
3552 break;
3553
3554 case CPU_DOWN_FAILED:
3555 case CPU_ONLINE:
3556 gcwq->flags &= ~GCWQ_DISASSOCIATED;
3557 if (gcwq->trustee_state != TRUSTEE_DONE) {
3558 gcwq->trustee_state = TRUSTEE_RELEASE;
3559 wake_up_process(gcwq->trustee);
3560 wait_trustee_state(gcwq, TRUSTEE_DONE);
3561 }
3562
3563 /*
3564 * Trustee is done and there might be no worker left.
3565 * Put the first_idle in and request a real manager to
3566 * take a look.
3567 */
3568 spin_unlock_irq(&gcwq->lock);
3569 kthread_bind(gcwq->first_idle->task, cpu);
3570 spin_lock_irq(&gcwq->lock);
3571 gcwq->flags |= GCWQ_MANAGE_WORKERS;
3572 start_worker(gcwq->first_idle);
3573 gcwq->first_idle = NULL;
3574 break;
3575 }
3576
3577 spin_unlock_irqrestore(&gcwq->lock, flags);
3578
3579 return notifier_from_errno(0);
3580}
3581
3582#ifdef CONFIG_SMP
3583
3584struct work_for_cpu {
3585 struct completion completion;
3586 long (*fn)(void *);
3587 void *arg;
3588 long ret;
3589};
3590
3591static int do_work_for_cpu(void *_wfc)
3592{
3593 struct work_for_cpu *wfc = _wfc;
3594 wfc->ret = wfc->fn(wfc->arg);
3595 complete(&wfc->completion);
3596 return 0;
3597}
3598
3599/**
3600 * work_on_cpu - run a function in user context on a particular cpu
3601 * @cpu: the cpu to run on
3602 * @fn: the function to run
3603 * @arg: the function arg
3604 *
3605 * This will return the value @fn returns.
3606 * It is up to the caller to ensure that the cpu doesn't go offline.
3607 * The caller must not hold any locks which would prevent @fn from completing.
3608 */
3609long work_on_cpu(unsigned int cpu, long (*fn)(void *), void *arg)
3610{
3611 struct task_struct *sub_thread;
3612 struct work_for_cpu wfc = {
3613 .completion = COMPLETION_INITIALIZER_ONSTACK(wfc.completion),
3614 .fn = fn,
3615 .arg = arg,
3616 };
3617
3618 sub_thread = kthread_create(do_work_for_cpu, &wfc, "work_for_cpu");
3619 if (IS_ERR(sub_thread))
3620 return PTR_ERR(sub_thread);
3621 kthread_bind(sub_thread, cpu);
3622 wake_up_process(sub_thread);
3623 wait_for_completion(&wfc.completion);
3624 return wfc.ret;
3625}
3626EXPORT_SYMBOL_GPL(work_on_cpu);
3627#endif /* CONFIG_SMP */
3628
3629#ifdef CONFIG_FREEZER
3630
3631/**
3632 * freeze_workqueues_begin - begin freezing workqueues
3633 *
3634 * Start freezing workqueues. After this function returns, all freezable
3635 * workqueues will queue new works to their frozen_works list instead of
3636 * gcwq->worklist.
3637 *
3638 * CONTEXT:
3639 * Grabs and releases workqueue_lock and gcwq->lock's.
3640 */
3641void freeze_workqueues_begin(void)
3642{
3643 unsigned int cpu;
3644
3645 spin_lock(&workqueue_lock);
3646
3647 BUG_ON(workqueue_freezing);
3648 workqueue_freezing = true;
3649
3650 for_each_gcwq_cpu(cpu) {
3651 struct global_cwq *gcwq = get_gcwq(cpu);
3652 struct workqueue_struct *wq;
3653
3654 spin_lock_irq(&gcwq->lock);
3655
3656 BUG_ON(gcwq->flags & GCWQ_FREEZING);
3657 gcwq->flags |= GCWQ_FREEZING;
3658
3659 list_for_each_entry(wq, &workqueues, list) {
3660 struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
3661
3662 if (cwq && wq->flags & WQ_FREEZABLE)
3663 cwq->max_active = 0;
3664 }
3665
3666 spin_unlock_irq(&gcwq->lock);
3667 }
3668
3669 spin_unlock(&workqueue_lock);
3670}
3671
3672/**
3673 * freeze_workqueues_busy - are freezable workqueues still busy?
3674 *
3675 * Check whether freezing is complete. This function must be called
3676 * between freeze_workqueues_begin() and thaw_workqueues().
3677 *
3678 * CONTEXT:
3679 * Grabs and releases workqueue_lock.
3680 *
3681 * RETURNS:
3682 * %true if some freezable workqueues are still busy. %false if freezing
3683 * is complete.
3684 */
3685bool freeze_workqueues_busy(void)
3686{
3687 unsigned int cpu;
3688 bool busy = false;
3689
3690 spin_lock(&workqueue_lock);
3691
3692 BUG_ON(!workqueue_freezing);
3693
3694 for_each_gcwq_cpu(cpu) {
3695 struct workqueue_struct *wq;
3696 /*
3697 * nr_active is monotonically decreasing. It's safe
3698 * to peek without lock.
3699 */
3700 list_for_each_entry(wq, &workqueues, list) {
3701 struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
3702
3703 if (!cwq || !(wq->flags & WQ_FREEZABLE))
3704 continue;
3705
3706 BUG_ON(cwq->nr_active < 0);
3707 if (cwq->nr_active) {
3708 busy = true;
3709 goto out_unlock;
3710 }
3711 }
3712 }
3713out_unlock:
3714 spin_unlock(&workqueue_lock);
3715 return busy;
3716}
3717
3718/**
3719 * thaw_workqueues - thaw workqueues
3720 *
3721 * Thaw workqueues. Normal queueing is restored and all collected
3722 * frozen works are transferred to their respective gcwq worklists.
3723 *
3724 * CONTEXT:
3725 * Grabs and releases workqueue_lock and gcwq->lock's.
3726 */
3727void thaw_workqueues(void)
3728{
3729 unsigned int cpu;
3730
3731 spin_lock(&workqueue_lock);
3732
3733 if (!workqueue_freezing)
3734 goto out_unlock;
3735
3736 for_each_gcwq_cpu(cpu) {
3737 struct global_cwq *gcwq = get_gcwq(cpu);
3738 struct workqueue_struct *wq;
3739
3740 spin_lock_irq(&gcwq->lock);
3741
3742 BUG_ON(!(gcwq->flags & GCWQ_FREEZING));
3743 gcwq->flags &= ~GCWQ_FREEZING;
3744
3745 list_for_each_entry(wq, &workqueues, list) {
3746 struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
3747
3748 if (!cwq || !(wq->flags & WQ_FREEZABLE))
3749 continue;
3750
3751 /* restore max_active and repopulate worklist */
3752 cwq->max_active = wq->saved_max_active;
3753
3754 while (!list_empty(&cwq->delayed_works) &&
3755 cwq->nr_active < cwq->max_active)
3756 cwq_activate_first_delayed(cwq);
3757 }
3758
3759 wake_up_worker(gcwq);
3760
3761 spin_unlock_irq(&gcwq->lock);
3762 }
3763
3764 workqueue_freezing = false;
3765out_unlock:
3766 spin_unlock(&workqueue_lock);
3767}
3768#endif /* CONFIG_FREEZER */
3769
3770static int __init init_workqueues(void)
3771{
3772 unsigned int cpu;
3773 int i;
3774
3775 cpu_notifier(workqueue_cpu_callback, CPU_PRI_WORKQUEUE);
3776
3777 /* initialize gcwqs */
3778 for_each_gcwq_cpu(cpu) {
3779 struct global_cwq *gcwq = get_gcwq(cpu);
3780
3781 spin_lock_init(&gcwq->lock);
3782 INIT_LIST_HEAD(&gcwq->worklist);
3783 gcwq->cpu = cpu;
3784 gcwq->flags |= GCWQ_DISASSOCIATED;
3785
3786 INIT_LIST_HEAD(&gcwq->idle_list);
3787 for (i = 0; i < BUSY_WORKER_HASH_SIZE; i++)
3788 INIT_HLIST_HEAD(&gcwq->busy_hash[i]);
3789
3790 init_timer_deferrable(&gcwq->idle_timer);
3791 gcwq->idle_timer.function = idle_worker_timeout;
3792 gcwq->idle_timer.data = (unsigned long)gcwq;
3793
3794 setup_timer(&gcwq->mayday_timer, gcwq_mayday_timeout,
3795 (unsigned long)gcwq);
3796
3797 ida_init(&gcwq->worker_ida);
3798
3799 gcwq->trustee_state = TRUSTEE_DONE;
3800 init_waitqueue_head(&gcwq->trustee_wait);
3801 }
3802
3803 /* create the initial worker */
3804 for_each_online_gcwq_cpu(cpu) {
3805 struct global_cwq *gcwq = get_gcwq(cpu);
3806 struct worker *worker;
3807
3808 if (cpu != WORK_CPU_UNBOUND)
3809 gcwq->flags &= ~GCWQ_DISASSOCIATED;
3810 worker = create_worker(gcwq, true);
3811 BUG_ON(!worker);
3812 spin_lock_irq(&gcwq->lock);
3813 start_worker(worker);
3814 spin_unlock_irq(&gcwq->lock);
3815 }
3816
3817 system_wq = alloc_workqueue("events", 0, 0);
3818 system_long_wq = alloc_workqueue("events_long", 0, 0);
3819 system_nrt_wq = alloc_workqueue("events_nrt", WQ_NON_REENTRANT, 0);
3820 system_unbound_wq = alloc_workqueue("events_unbound", WQ_UNBOUND,
3821 WQ_UNBOUND_MAX_ACTIVE);
3822 system_freezable_wq = alloc_workqueue("events_freezable",
3823 WQ_FREEZABLE, 0);
3824 BUG_ON(!system_wq || !system_long_wq || !system_nrt_wq ||
3825 !system_unbound_wq || !system_freezable_wq);
3826 return 0;
3827}
3828early_initcall(init_workqueues);