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