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