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