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