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