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1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * kernel/workqueue.c - generic async execution with shared worker pool
4 *
5 * Copyright (C) 2002 Ingo Molnar
6 *
7 * Derived from the taskqueue/keventd code by:
8 * David Woodhouse <dwmw2@infradead.org>
9 * Andrew Morton
10 * Kai Petzke <wpp@marie.physik.tu-berlin.de>
11 * Theodore Ts'o <tytso@mit.edu>
12 *
13 * Made to use alloc_percpu by Christoph Lameter.
14 *
15 * Copyright (C) 2010 SUSE Linux Products GmbH
16 * Copyright (C) 2010 Tejun Heo <tj@kernel.org>
17 *
18 * This is the generic async execution mechanism. Work items as are
19 * executed in process context. The worker pool is shared and
20 * automatically managed. There are two worker pools for each CPU (one for
21 * normal work items and the other for high priority ones) and some extra
22 * pools for workqueues which are not bound to any specific CPU - the
23 * number of these backing pools is dynamic.
24 *
25 * Please read Documentation/core-api/workqueue.rst for details.
26 */
27
28#include <linux/export.h>
29#include <linux/kernel.h>
30#include <linux/sched.h>
31#include <linux/init.h>
32#include <linux/signal.h>
33#include <linux/completion.h>
34#include <linux/workqueue.h>
35#include <linux/slab.h>
36#include <linux/cpu.h>
37#include <linux/notifier.h>
38#include <linux/kthread.h>
39#include <linux/hardirq.h>
40#include <linux/mempolicy.h>
41#include <linux/freezer.h>
42#include <linux/debug_locks.h>
43#include <linux/lockdep.h>
44#include <linux/idr.h>
45#include <linux/jhash.h>
46#include <linux/hashtable.h>
47#include <linux/rculist.h>
48#include <linux/nodemask.h>
49#include <linux/moduleparam.h>
50#include <linux/uaccess.h>
51#include <linux/sched/isolation.h>
52#include <linux/nmi.h>
53
54#include "workqueue_internal.h"
55
56enum {
57 /*
58 * worker_pool flags
59 *
60 * A bound pool is either associated or disassociated with its CPU.
61 * While associated (!DISASSOCIATED), all workers are bound to the
62 * CPU and none has %WORKER_UNBOUND set and concurrency management
63 * is in effect.
64 *
65 * While DISASSOCIATED, the cpu may be offline and all workers have
66 * %WORKER_UNBOUND set and concurrency management disabled, and may
67 * be executing on any CPU. The pool behaves as an unbound one.
68 *
69 * Note that DISASSOCIATED should be flipped only while holding
70 * wq_pool_attach_mutex to avoid changing binding state while
71 * worker_attach_to_pool() is in progress.
72 */
73 POOL_MANAGER_ACTIVE = 1 << 0, /* being managed */
74 POOL_DISASSOCIATED = 1 << 2, /* cpu can't serve workers */
75
76 /* worker flags */
77 WORKER_DIE = 1 << 1, /* die die die */
78 WORKER_IDLE = 1 << 2, /* is idle */
79 WORKER_PREP = 1 << 3, /* preparing to run works */
80 WORKER_CPU_INTENSIVE = 1 << 6, /* cpu intensive */
81 WORKER_UNBOUND = 1 << 7, /* worker is unbound */
82 WORKER_REBOUND = 1 << 8, /* worker was rebound */
83
84 WORKER_NOT_RUNNING = WORKER_PREP | WORKER_CPU_INTENSIVE |
85 WORKER_UNBOUND | WORKER_REBOUND,
86
87 NR_STD_WORKER_POOLS = 2, /* # standard pools per cpu */
88
89 UNBOUND_POOL_HASH_ORDER = 6, /* hashed by pool->attrs */
90 BUSY_WORKER_HASH_ORDER = 6, /* 64 pointers */
91
92 MAX_IDLE_WORKERS_RATIO = 4, /* 1/4 of busy can be idle */
93 IDLE_WORKER_TIMEOUT = 300 * HZ, /* keep idle ones for 5 mins */
94
95 MAYDAY_INITIAL_TIMEOUT = HZ / 100 >= 2 ? HZ / 100 : 2,
96 /* call for help after 10ms
97 (min two ticks) */
98 MAYDAY_INTERVAL = HZ / 10, /* and then every 100ms */
99 CREATE_COOLDOWN = HZ, /* time to breath after fail */
100
101 /*
102 * Rescue workers are used only on emergencies and shared by
103 * all cpus. Give MIN_NICE.
104 */
105 RESCUER_NICE_LEVEL = MIN_NICE,
106 HIGHPRI_NICE_LEVEL = MIN_NICE,
107
108 WQ_NAME_LEN = 24,
109};
110
111/*
112 * Structure fields follow one of the following exclusion rules.
113 *
114 * I: Modifiable by initialization/destruction paths and read-only for
115 * everyone else.
116 *
117 * P: Preemption protected. Disabling preemption is enough and should
118 * only be modified and accessed from the local cpu.
119 *
120 * L: pool->lock protected. Access with pool->lock held.
121 *
122 * X: During normal operation, modification requires pool->lock and should
123 * be done only from local cpu. Either disabling preemption on local
124 * cpu or grabbing pool->lock is enough for read access. If
125 * POOL_DISASSOCIATED is set, it's identical to L.
126 *
127 * A: wq_pool_attach_mutex protected.
128 *
129 * PL: wq_pool_mutex protected.
130 *
131 * PR: wq_pool_mutex protected for writes. RCU protected for reads.
132 *
133 * PW: wq_pool_mutex and wq->mutex protected for writes. Either for reads.
134 *
135 * PWR: wq_pool_mutex and wq->mutex protected for writes. Either or
136 * RCU for reads.
137 *
138 * WQ: wq->mutex protected.
139 *
140 * WR: wq->mutex protected for writes. RCU protected for reads.
141 *
142 * MD: wq_mayday_lock protected.
143 */
144
145/* struct worker is defined in workqueue_internal.h */
146
147struct worker_pool {
148 spinlock_t lock; /* the pool lock */
149 int cpu; /* I: the associated cpu */
150 int node; /* I: the associated node ID */
151 int id; /* I: pool ID */
152 unsigned int flags; /* X: flags */
153
154 unsigned long watchdog_ts; /* L: watchdog timestamp */
155
156 struct list_head worklist; /* L: list of pending works */
157
158 int nr_workers; /* L: total number of workers */
159 int nr_idle; /* L: currently idle workers */
160
161 struct list_head idle_list; /* X: list of idle workers */
162 struct timer_list idle_timer; /* L: worker idle timeout */
163 struct timer_list mayday_timer; /* L: SOS timer for workers */
164
165 /* a workers is either on busy_hash or idle_list, or the manager */
166 DECLARE_HASHTABLE(busy_hash, BUSY_WORKER_HASH_ORDER);
167 /* L: hash of busy workers */
168
169 struct worker *manager; /* L: purely informational */
170 struct list_head workers; /* A: attached workers */
171 struct completion *detach_completion; /* all workers detached */
172
173 struct ida worker_ida; /* worker IDs for task name */
174
175 struct workqueue_attrs *attrs; /* I: worker attributes */
176 struct hlist_node hash_node; /* PL: unbound_pool_hash node */
177 int refcnt; /* PL: refcnt for unbound pools */
178
179 /*
180 * The current concurrency level. As it's likely to be accessed
181 * from other CPUs during try_to_wake_up(), put it in a separate
182 * cacheline.
183 */
184 atomic_t nr_running ____cacheline_aligned_in_smp;
185
186 /*
187 * Destruction of pool is RCU protected to allow dereferences
188 * from get_work_pool().
189 */
190 struct rcu_head rcu;
191} ____cacheline_aligned_in_smp;
192
193/*
194 * The per-pool workqueue. While queued, the lower WORK_STRUCT_FLAG_BITS
195 * of work_struct->data are used for flags and the remaining high bits
196 * point to the pwq; thus, pwqs need to be aligned at two's power of the
197 * number of flag bits.
198 */
199struct pool_workqueue {
200 struct worker_pool *pool; /* I: the associated pool */
201 struct workqueue_struct *wq; /* I: the owning workqueue */
202 int work_color; /* L: current color */
203 int flush_color; /* L: flushing color */
204 int refcnt; /* L: reference count */
205 int nr_in_flight[WORK_NR_COLORS];
206 /* L: nr of in_flight works */
207 int nr_active; /* L: nr of active works */
208 int max_active; /* L: max active works */
209 struct list_head delayed_works; /* L: delayed works */
210 struct list_head pwqs_node; /* WR: node on wq->pwqs */
211 struct list_head mayday_node; /* MD: node on wq->maydays */
212
213 /*
214 * Release of unbound pwq is punted to system_wq. See put_pwq()
215 * and pwq_unbound_release_workfn() for details. pool_workqueue
216 * itself is also RCU protected so that the first pwq can be
217 * determined without grabbing wq->mutex.
218 */
219 struct work_struct unbound_release_work;
220 struct rcu_head rcu;
221} __aligned(1 << WORK_STRUCT_FLAG_BITS);
222
223/*
224 * Structure used to wait for workqueue flush.
225 */
226struct wq_flusher {
227 struct list_head list; /* WQ: list of flushers */
228 int flush_color; /* WQ: flush color waiting for */
229 struct completion done; /* flush completion */
230};
231
232struct wq_device;
233
234/*
235 * The externally visible workqueue. It relays the issued work items to
236 * the appropriate worker_pool through its pool_workqueues.
237 */
238struct workqueue_struct {
239 struct list_head pwqs; /* WR: all pwqs of this wq */
240 struct list_head list; /* PR: list of all workqueues */
241
242 struct mutex mutex; /* protects this wq */
243 int work_color; /* WQ: current work color */
244 int flush_color; /* WQ: current flush color */
245 atomic_t nr_pwqs_to_flush; /* flush in progress */
246 struct wq_flusher *first_flusher; /* WQ: first flusher */
247 struct list_head flusher_queue; /* WQ: flush waiters */
248 struct list_head flusher_overflow; /* WQ: flush overflow list */
249
250 struct list_head maydays; /* MD: pwqs requesting rescue */
251 struct worker *rescuer; /* I: rescue worker */
252
253 int nr_drainers; /* WQ: drain in progress */
254 int saved_max_active; /* WQ: saved pwq max_active */
255
256 struct workqueue_attrs *unbound_attrs; /* PW: only for unbound wqs */
257 struct pool_workqueue *dfl_pwq; /* PW: only for unbound wqs */
258
259#ifdef CONFIG_SYSFS
260 struct wq_device *wq_dev; /* I: for sysfs interface */
261#endif
262#ifdef CONFIG_LOCKDEP
263 char *lock_name;
264 struct lock_class_key key;
265 struct lockdep_map lockdep_map;
266#endif
267 char name[WQ_NAME_LEN]; /* I: workqueue name */
268
269 /*
270 * Destruction of workqueue_struct is RCU protected to allow walking
271 * the workqueues list without grabbing wq_pool_mutex.
272 * This is used to dump all workqueues from sysrq.
273 */
274 struct rcu_head rcu;
275
276 /* hot fields used during command issue, aligned to cacheline */
277 unsigned int flags ____cacheline_aligned; /* WQ: WQ_* flags */
278 struct pool_workqueue __percpu *cpu_pwqs; /* I: per-cpu pwqs */
279 struct pool_workqueue __rcu *numa_pwq_tbl[]; /* PWR: unbound pwqs indexed by node */
280};
281
282static struct kmem_cache *pwq_cache;
283
284static cpumask_var_t *wq_numa_possible_cpumask;
285 /* possible CPUs of each node */
286
287static bool wq_disable_numa;
288module_param_named(disable_numa, wq_disable_numa, bool, 0444);
289
290/* see the comment above the definition of WQ_POWER_EFFICIENT */
291static bool wq_power_efficient = IS_ENABLED(CONFIG_WQ_POWER_EFFICIENT_DEFAULT);
292module_param_named(power_efficient, wq_power_efficient, bool, 0444);
293
294static bool wq_online; /* can kworkers be created yet? */
295
296static bool wq_numa_enabled; /* unbound NUMA affinity enabled */
297
298/* buf for wq_update_unbound_numa_attrs(), protected by CPU hotplug exclusion */
299static struct workqueue_attrs *wq_update_unbound_numa_attrs_buf;
300
301static DEFINE_MUTEX(wq_pool_mutex); /* protects pools and workqueues list */
302static DEFINE_MUTEX(wq_pool_attach_mutex); /* protects worker attach/detach */
303static DEFINE_SPINLOCK(wq_mayday_lock); /* protects wq->maydays list */
304static DECLARE_WAIT_QUEUE_HEAD(wq_manager_wait); /* wait for manager to go away */
305
306static LIST_HEAD(workqueues); /* PR: list of all workqueues */
307static bool workqueue_freezing; /* PL: have wqs started freezing? */
308
309/* PL: allowable cpus for unbound wqs and work items */
310static cpumask_var_t wq_unbound_cpumask;
311
312/* CPU where unbound work was last round robin scheduled from this CPU */
313static DEFINE_PER_CPU(int, wq_rr_cpu_last);
314
315/*
316 * Local execution of unbound work items is no longer guaranteed. The
317 * following always forces round-robin CPU selection on unbound work items
318 * to uncover usages which depend on it.
319 */
320#ifdef CONFIG_DEBUG_WQ_FORCE_RR_CPU
321static bool wq_debug_force_rr_cpu = true;
322#else
323static bool wq_debug_force_rr_cpu = false;
324#endif
325module_param_named(debug_force_rr_cpu, wq_debug_force_rr_cpu, bool, 0644);
326
327/* the per-cpu worker pools */
328static DEFINE_PER_CPU_SHARED_ALIGNED(struct worker_pool [NR_STD_WORKER_POOLS], cpu_worker_pools);
329
330static DEFINE_IDR(worker_pool_idr); /* PR: idr of all pools */
331
332/* PL: hash of all unbound pools keyed by pool->attrs */
333static DEFINE_HASHTABLE(unbound_pool_hash, UNBOUND_POOL_HASH_ORDER);
334
335/* I: attributes used when instantiating standard unbound pools on demand */
336static struct workqueue_attrs *unbound_std_wq_attrs[NR_STD_WORKER_POOLS];
337
338/* I: attributes used when instantiating ordered pools on demand */
339static struct workqueue_attrs *ordered_wq_attrs[NR_STD_WORKER_POOLS];
340
341struct workqueue_struct *system_wq __read_mostly;
342EXPORT_SYMBOL(system_wq);
343struct workqueue_struct *system_highpri_wq __read_mostly;
344EXPORT_SYMBOL_GPL(system_highpri_wq);
345struct workqueue_struct *system_long_wq __read_mostly;
346EXPORT_SYMBOL_GPL(system_long_wq);
347struct workqueue_struct *system_unbound_wq __read_mostly;
348EXPORT_SYMBOL_GPL(system_unbound_wq);
349struct workqueue_struct *system_freezable_wq __read_mostly;
350EXPORT_SYMBOL_GPL(system_freezable_wq);
351struct workqueue_struct *system_power_efficient_wq __read_mostly;
352EXPORT_SYMBOL_GPL(system_power_efficient_wq);
353struct workqueue_struct *system_freezable_power_efficient_wq __read_mostly;
354EXPORT_SYMBOL_GPL(system_freezable_power_efficient_wq);
355
356static int worker_thread(void *__worker);
357static void workqueue_sysfs_unregister(struct workqueue_struct *wq);
358
359#define CREATE_TRACE_POINTS
360#include <trace/events/workqueue.h>
361
362#define assert_rcu_or_pool_mutex() \
363 RCU_LOCKDEP_WARN(!rcu_read_lock_held() && \
364 !lockdep_is_held(&wq_pool_mutex), \
365 "RCU or wq_pool_mutex should be held")
366
367#define assert_rcu_or_wq_mutex(wq) \
368 RCU_LOCKDEP_WARN(!rcu_read_lock_held() && \
369 !lockdep_is_held(&wq->mutex), \
370 "RCU or wq->mutex should be held")
371
372#define assert_rcu_or_wq_mutex_or_pool_mutex(wq) \
373 RCU_LOCKDEP_WARN(!rcu_read_lock_held() && \
374 !lockdep_is_held(&wq->mutex) && \
375 !lockdep_is_held(&wq_pool_mutex), \
376 "RCU, wq->mutex or wq_pool_mutex should be held")
377
378#define for_each_cpu_worker_pool(pool, cpu) \
379 for ((pool) = &per_cpu(cpu_worker_pools, cpu)[0]; \
380 (pool) < &per_cpu(cpu_worker_pools, cpu)[NR_STD_WORKER_POOLS]; \
381 (pool)++)
382
383/**
384 * for_each_pool - iterate through all worker_pools in the system
385 * @pool: iteration cursor
386 * @pi: integer used for iteration
387 *
388 * This must be called either with wq_pool_mutex held or RCU read
389 * locked. If the pool needs to be used beyond the locking in effect, the
390 * caller is responsible for guaranteeing that the pool stays online.
391 *
392 * The if/else clause exists only for the lockdep assertion and can be
393 * ignored.
394 */
395#define for_each_pool(pool, pi) \
396 idr_for_each_entry(&worker_pool_idr, pool, pi) \
397 if (({ assert_rcu_or_pool_mutex(); false; })) { } \
398 else
399
400/**
401 * for_each_pool_worker - iterate through all workers of a worker_pool
402 * @worker: iteration cursor
403 * @pool: worker_pool to iterate workers of
404 *
405 * This must be called with wq_pool_attach_mutex.
406 *
407 * The if/else clause exists only for the lockdep assertion and can be
408 * ignored.
409 */
410#define for_each_pool_worker(worker, pool) \
411 list_for_each_entry((worker), &(pool)->workers, node) \
412 if (({ lockdep_assert_held(&wq_pool_attach_mutex); false; })) { } \
413 else
414
415/**
416 * for_each_pwq - iterate through all pool_workqueues of the specified workqueue
417 * @pwq: iteration cursor
418 * @wq: the target workqueue
419 *
420 * This must be called either with wq->mutex held or RCU read locked.
421 * If the pwq needs to be used beyond the locking in effect, the caller is
422 * responsible for guaranteeing that the pwq stays online.
423 *
424 * The if/else clause exists only for the lockdep assertion and can be
425 * ignored.
426 */
427#define for_each_pwq(pwq, wq) \
428 list_for_each_entry_rcu((pwq), &(wq)->pwqs, pwqs_node) \
429 if (({ assert_rcu_or_wq_mutex(wq); false; })) { } \
430 else
431
432#ifdef CONFIG_DEBUG_OBJECTS_WORK
433
434static struct debug_obj_descr work_debug_descr;
435
436static void *work_debug_hint(void *addr)
437{
438 return ((struct work_struct *) addr)->func;
439}
440
441static bool work_is_static_object(void *addr)
442{
443 struct work_struct *work = addr;
444
445 return test_bit(WORK_STRUCT_STATIC_BIT, work_data_bits(work));
446}
447
448/*
449 * fixup_init is called when:
450 * - an active object is initialized
451 */
452static bool work_fixup_init(void *addr, enum debug_obj_state state)
453{
454 struct work_struct *work = addr;
455
456 switch (state) {
457 case ODEBUG_STATE_ACTIVE:
458 cancel_work_sync(work);
459 debug_object_init(work, &work_debug_descr);
460 return true;
461 default:
462 return false;
463 }
464}
465
466/*
467 * fixup_free is called when:
468 * - an active object is freed
469 */
470static bool work_fixup_free(void *addr, enum debug_obj_state state)
471{
472 struct work_struct *work = addr;
473
474 switch (state) {
475 case ODEBUG_STATE_ACTIVE:
476 cancel_work_sync(work);
477 debug_object_free(work, &work_debug_descr);
478 return true;
479 default:
480 return false;
481 }
482}
483
484static struct debug_obj_descr work_debug_descr = {
485 .name = "work_struct",
486 .debug_hint = work_debug_hint,
487 .is_static_object = work_is_static_object,
488 .fixup_init = work_fixup_init,
489 .fixup_free = work_fixup_free,
490};
491
492static inline void debug_work_activate(struct work_struct *work)
493{
494 debug_object_activate(work, &work_debug_descr);
495}
496
497static inline void debug_work_deactivate(struct work_struct *work)
498{
499 debug_object_deactivate(work, &work_debug_descr);
500}
501
502void __init_work(struct work_struct *work, int onstack)
503{
504 if (onstack)
505 debug_object_init_on_stack(work, &work_debug_descr);
506 else
507 debug_object_init(work, &work_debug_descr);
508}
509EXPORT_SYMBOL_GPL(__init_work);
510
511void destroy_work_on_stack(struct work_struct *work)
512{
513 debug_object_free(work, &work_debug_descr);
514}
515EXPORT_SYMBOL_GPL(destroy_work_on_stack);
516
517void destroy_delayed_work_on_stack(struct delayed_work *work)
518{
519 destroy_timer_on_stack(&work->timer);
520 debug_object_free(&work->work, &work_debug_descr);
521}
522EXPORT_SYMBOL_GPL(destroy_delayed_work_on_stack);
523
524#else
525static inline void debug_work_activate(struct work_struct *work) { }
526static inline void debug_work_deactivate(struct work_struct *work) { }
527#endif
528
529/**
530 * worker_pool_assign_id - allocate ID and assing it to @pool
531 * @pool: the pool pointer of interest
532 *
533 * Returns 0 if ID in [0, WORK_OFFQ_POOL_NONE) is allocated and assigned
534 * successfully, -errno on failure.
535 */
536static int worker_pool_assign_id(struct worker_pool *pool)
537{
538 int ret;
539
540 lockdep_assert_held(&wq_pool_mutex);
541
542 ret = idr_alloc(&worker_pool_idr, pool, 0, WORK_OFFQ_POOL_NONE,
543 GFP_KERNEL);
544 if (ret >= 0) {
545 pool->id = ret;
546 return 0;
547 }
548 return ret;
549}
550
551/**
552 * unbound_pwq_by_node - return the unbound pool_workqueue for the given node
553 * @wq: the target workqueue
554 * @node: the node ID
555 *
556 * This must be called with any of wq_pool_mutex, wq->mutex or RCU
557 * read locked.
558 * If the pwq needs to be used beyond the locking in effect, the caller is
559 * responsible for guaranteeing that the pwq stays online.
560 *
561 * Return: The unbound pool_workqueue for @node.
562 */
563static struct pool_workqueue *unbound_pwq_by_node(struct workqueue_struct *wq,
564 int node)
565{
566 assert_rcu_or_wq_mutex_or_pool_mutex(wq);
567
568 /*
569 * XXX: @node can be NUMA_NO_NODE if CPU goes offline while a
570 * delayed item is pending. The plan is to keep CPU -> NODE
571 * mapping valid and stable across CPU on/offlines. Once that
572 * happens, this workaround can be removed.
573 */
574 if (unlikely(node == NUMA_NO_NODE))
575 return wq->dfl_pwq;
576
577 return rcu_dereference_raw(wq->numa_pwq_tbl[node]);
578}
579
580static unsigned int work_color_to_flags(int color)
581{
582 return color << WORK_STRUCT_COLOR_SHIFT;
583}
584
585static int get_work_color(struct work_struct *work)
586{
587 return (*work_data_bits(work) >> WORK_STRUCT_COLOR_SHIFT) &
588 ((1 << WORK_STRUCT_COLOR_BITS) - 1);
589}
590
591static int work_next_color(int color)
592{
593 return (color + 1) % WORK_NR_COLORS;
594}
595
596/*
597 * While queued, %WORK_STRUCT_PWQ is set and non flag bits of a work's data
598 * contain the pointer to the queued pwq. Once execution starts, the flag
599 * is cleared and the high bits contain OFFQ flags and pool ID.
600 *
601 * set_work_pwq(), set_work_pool_and_clear_pending(), mark_work_canceling()
602 * and clear_work_data() can be used to set the pwq, pool or clear
603 * work->data. These functions should only be called while the work is
604 * owned - ie. while the PENDING bit is set.
605 *
606 * get_work_pool() and get_work_pwq() can be used to obtain the pool or pwq
607 * corresponding to a work. Pool is available once the work has been
608 * queued anywhere after initialization until it is sync canceled. pwq is
609 * available only while the work item is queued.
610 *
611 * %WORK_OFFQ_CANCELING is used to mark a work item which is being
612 * canceled. While being canceled, a work item may have its PENDING set
613 * but stay off timer and worklist for arbitrarily long and nobody should
614 * try to steal the PENDING bit.
615 */
616static inline void set_work_data(struct work_struct *work, unsigned long data,
617 unsigned long flags)
618{
619 WARN_ON_ONCE(!work_pending(work));
620 atomic_long_set(&work->data, data | flags | work_static(work));
621}
622
623static void set_work_pwq(struct work_struct *work, struct pool_workqueue *pwq,
624 unsigned long extra_flags)
625{
626 set_work_data(work, (unsigned long)pwq,
627 WORK_STRUCT_PENDING | WORK_STRUCT_PWQ | extra_flags);
628}
629
630static void set_work_pool_and_keep_pending(struct work_struct *work,
631 int pool_id)
632{
633 set_work_data(work, (unsigned long)pool_id << WORK_OFFQ_POOL_SHIFT,
634 WORK_STRUCT_PENDING);
635}
636
637static void set_work_pool_and_clear_pending(struct work_struct *work,
638 int pool_id)
639{
640 /*
641 * The following wmb is paired with the implied mb in
642 * test_and_set_bit(PENDING) and ensures all updates to @work made
643 * here are visible to and precede any updates by the next PENDING
644 * owner.
645 */
646 smp_wmb();
647 set_work_data(work, (unsigned long)pool_id << WORK_OFFQ_POOL_SHIFT, 0);
648 /*
649 * The following mb guarantees that previous clear of a PENDING bit
650 * will not be reordered with any speculative LOADS or STORES from
651 * work->current_func, which is executed afterwards. This possible
652 * reordering can lead to a missed execution on attempt to queue
653 * the same @work. E.g. consider this case:
654 *
655 * CPU#0 CPU#1
656 * ---------------------------- --------------------------------
657 *
658 * 1 STORE event_indicated
659 * 2 queue_work_on() {
660 * 3 test_and_set_bit(PENDING)
661 * 4 } set_..._and_clear_pending() {
662 * 5 set_work_data() # clear bit
663 * 6 smp_mb()
664 * 7 work->current_func() {
665 * 8 LOAD event_indicated
666 * }
667 *
668 * Without an explicit full barrier speculative LOAD on line 8 can
669 * be executed before CPU#0 does STORE on line 1. If that happens,
670 * CPU#0 observes the PENDING bit is still set and new execution of
671 * a @work is not queued in a hope, that CPU#1 will eventually
672 * finish the queued @work. Meanwhile CPU#1 does not see
673 * event_indicated is set, because speculative LOAD was executed
674 * before actual STORE.
675 */
676 smp_mb();
677}
678
679static void clear_work_data(struct work_struct *work)
680{
681 smp_wmb(); /* see set_work_pool_and_clear_pending() */
682 set_work_data(work, WORK_STRUCT_NO_POOL, 0);
683}
684
685static struct pool_workqueue *get_work_pwq(struct work_struct *work)
686{
687 unsigned long data = atomic_long_read(&work->data);
688
689 if (data & WORK_STRUCT_PWQ)
690 return (void *)(data & WORK_STRUCT_WQ_DATA_MASK);
691 else
692 return NULL;
693}
694
695/**
696 * get_work_pool - return the worker_pool a given work was associated with
697 * @work: the work item of interest
698 *
699 * Pools are created and destroyed under wq_pool_mutex, and allows read
700 * access under RCU read lock. As such, this function should be
701 * called under wq_pool_mutex or inside of a rcu_read_lock() region.
702 *
703 * All fields of the returned pool are accessible as long as the above
704 * mentioned locking is in effect. If the returned pool needs to be used
705 * beyond the critical section, the caller is responsible for ensuring the
706 * returned pool is and stays online.
707 *
708 * Return: The worker_pool @work was last associated with. %NULL if none.
709 */
710static struct worker_pool *get_work_pool(struct work_struct *work)
711{
712 unsigned long data = atomic_long_read(&work->data);
713 int pool_id;
714
715 assert_rcu_or_pool_mutex();
716
717 if (data & WORK_STRUCT_PWQ)
718 return ((struct pool_workqueue *)
719 (data & WORK_STRUCT_WQ_DATA_MASK))->pool;
720
721 pool_id = data >> WORK_OFFQ_POOL_SHIFT;
722 if (pool_id == WORK_OFFQ_POOL_NONE)
723 return NULL;
724
725 return idr_find(&worker_pool_idr, pool_id);
726}
727
728/**
729 * get_work_pool_id - return the worker pool ID a given work is associated with
730 * @work: the work item of interest
731 *
732 * Return: The worker_pool ID @work was last associated with.
733 * %WORK_OFFQ_POOL_NONE if none.
734 */
735static int get_work_pool_id(struct work_struct *work)
736{
737 unsigned long data = atomic_long_read(&work->data);
738
739 if (data & WORK_STRUCT_PWQ)
740 return ((struct pool_workqueue *)
741 (data & WORK_STRUCT_WQ_DATA_MASK))->pool->id;
742
743 return data >> WORK_OFFQ_POOL_SHIFT;
744}
745
746static void mark_work_canceling(struct work_struct *work)
747{
748 unsigned long pool_id = get_work_pool_id(work);
749
750 pool_id <<= WORK_OFFQ_POOL_SHIFT;
751 set_work_data(work, pool_id | WORK_OFFQ_CANCELING, WORK_STRUCT_PENDING);
752}
753
754static bool work_is_canceling(struct work_struct *work)
755{
756 unsigned long data = atomic_long_read(&work->data);
757
758 return !(data & WORK_STRUCT_PWQ) && (data & WORK_OFFQ_CANCELING);
759}
760
761/*
762 * Policy functions. These define the policies on how the global worker
763 * pools are managed. Unless noted otherwise, these functions assume that
764 * they're being called with pool->lock held.
765 */
766
767static bool __need_more_worker(struct worker_pool *pool)
768{
769 return !atomic_read(&pool->nr_running);
770}
771
772/*
773 * Need to wake up a worker? Called from anything but currently
774 * running workers.
775 *
776 * Note that, because unbound workers never contribute to nr_running, this
777 * function will always return %true for unbound pools as long as the
778 * worklist isn't empty.
779 */
780static bool need_more_worker(struct worker_pool *pool)
781{
782 return !list_empty(&pool->worklist) && __need_more_worker(pool);
783}
784
785/* Can I start working? Called from busy but !running workers. */
786static bool may_start_working(struct worker_pool *pool)
787{
788 return pool->nr_idle;
789}
790
791/* Do I need to keep working? Called from currently running workers. */
792static bool keep_working(struct worker_pool *pool)
793{
794 return !list_empty(&pool->worklist) &&
795 atomic_read(&pool->nr_running) <= 1;
796}
797
798/* Do we need a new worker? Called from manager. */
799static bool need_to_create_worker(struct worker_pool *pool)
800{
801 return need_more_worker(pool) && !may_start_working(pool);
802}
803
804/* Do we have too many workers and should some go away? */
805static bool too_many_workers(struct worker_pool *pool)
806{
807 bool managing = pool->flags & POOL_MANAGER_ACTIVE;
808 int nr_idle = pool->nr_idle + managing; /* manager is considered idle */
809 int nr_busy = pool->nr_workers - nr_idle;
810
811 return nr_idle > 2 && (nr_idle - 2) * MAX_IDLE_WORKERS_RATIO >= nr_busy;
812}
813
814/*
815 * Wake up functions.
816 */
817
818/* Return the first idle worker. Safe with preemption disabled */
819static struct worker *first_idle_worker(struct worker_pool *pool)
820{
821 if (unlikely(list_empty(&pool->idle_list)))
822 return NULL;
823
824 return list_first_entry(&pool->idle_list, struct worker, entry);
825}
826
827/**
828 * wake_up_worker - wake up an idle worker
829 * @pool: worker pool to wake worker from
830 *
831 * Wake up the first idle worker of @pool.
832 *
833 * CONTEXT:
834 * spin_lock_irq(pool->lock).
835 */
836static void wake_up_worker(struct worker_pool *pool)
837{
838 struct worker *worker = first_idle_worker(pool);
839
840 if (likely(worker))
841 wake_up_process(worker->task);
842}
843
844/**
845 * wq_worker_running - a worker is running again
846 * @task: task waking up
847 *
848 * This function is called when a worker returns from schedule()
849 */
850void wq_worker_running(struct task_struct *task)
851{
852 struct worker *worker = kthread_data(task);
853
854 if (!worker->sleeping)
855 return;
856 if (!(worker->flags & WORKER_NOT_RUNNING))
857 atomic_inc(&worker->pool->nr_running);
858 worker->sleeping = 0;
859}
860
861/**
862 * wq_worker_sleeping - a worker is going to sleep
863 * @task: task going to sleep
864 *
865 * This function is called from schedule() when a busy worker is
866 * going to sleep.
867 */
868void wq_worker_sleeping(struct task_struct *task)
869{
870 struct worker *next, *worker = kthread_data(task);
871 struct worker_pool *pool;
872
873 /*
874 * Rescuers, which may not have all the fields set up like normal
875 * workers, also reach here, let's not access anything before
876 * checking NOT_RUNNING.
877 */
878 if (worker->flags & WORKER_NOT_RUNNING)
879 return;
880
881 pool = worker->pool;
882
883 if (WARN_ON_ONCE(worker->sleeping))
884 return;
885
886 worker->sleeping = 1;
887 spin_lock_irq(&pool->lock);
888
889 /*
890 * The counterpart of the following dec_and_test, implied mb,
891 * worklist not empty test sequence is in insert_work().
892 * Please read comment there.
893 *
894 * NOT_RUNNING is clear. This means that we're bound to and
895 * running on the local cpu w/ rq lock held and preemption
896 * disabled, which in turn means that none else could be
897 * manipulating idle_list, so dereferencing idle_list without pool
898 * lock is safe.
899 */
900 if (atomic_dec_and_test(&pool->nr_running) &&
901 !list_empty(&pool->worklist)) {
902 next = first_idle_worker(pool);
903 if (next)
904 wake_up_process(next->task);
905 }
906 spin_unlock_irq(&pool->lock);
907}
908
909/**
910 * wq_worker_last_func - retrieve worker's last work function
911 * @task: Task to retrieve last work function of.
912 *
913 * Determine the last function a worker executed. This is called from
914 * the scheduler to get a worker's last known identity.
915 *
916 * CONTEXT:
917 * spin_lock_irq(rq->lock)
918 *
919 * This function is called during schedule() when a kworker is going
920 * to sleep. It's used by psi to identify aggregation workers during
921 * dequeuing, to allow periodic aggregation to shut-off when that
922 * worker is the last task in the system or cgroup to go to sleep.
923 *
924 * As this function doesn't involve any workqueue-related locking, it
925 * only returns stable values when called from inside the scheduler's
926 * queuing and dequeuing paths, when @task, which must be a kworker,
927 * is guaranteed to not be processing any works.
928 *
929 * Return:
930 * The last work function %current executed as a worker, NULL if it
931 * hasn't executed any work yet.
932 */
933work_func_t wq_worker_last_func(struct task_struct *task)
934{
935 struct worker *worker = kthread_data(task);
936
937 return worker->last_func;
938}
939
940/**
941 * worker_set_flags - set worker flags and adjust nr_running accordingly
942 * @worker: self
943 * @flags: flags to set
944 *
945 * Set @flags in @worker->flags and adjust nr_running accordingly.
946 *
947 * CONTEXT:
948 * spin_lock_irq(pool->lock)
949 */
950static inline void worker_set_flags(struct worker *worker, unsigned int flags)
951{
952 struct worker_pool *pool = worker->pool;
953
954 WARN_ON_ONCE(worker->task != current);
955
956 /* If transitioning into NOT_RUNNING, adjust nr_running. */
957 if ((flags & WORKER_NOT_RUNNING) &&
958 !(worker->flags & WORKER_NOT_RUNNING)) {
959 atomic_dec(&pool->nr_running);
960 }
961
962 worker->flags |= flags;
963}
964
965/**
966 * worker_clr_flags - clear worker flags and adjust nr_running accordingly
967 * @worker: self
968 * @flags: flags to clear
969 *
970 * Clear @flags in @worker->flags and adjust nr_running accordingly.
971 *
972 * CONTEXT:
973 * spin_lock_irq(pool->lock)
974 */
975static inline void worker_clr_flags(struct worker *worker, unsigned int flags)
976{
977 struct worker_pool *pool = worker->pool;
978 unsigned int oflags = worker->flags;
979
980 WARN_ON_ONCE(worker->task != current);
981
982 worker->flags &= ~flags;
983
984 /*
985 * If transitioning out of NOT_RUNNING, increment nr_running. Note
986 * that the nested NOT_RUNNING is not a noop. NOT_RUNNING is mask
987 * of multiple flags, not a single flag.
988 */
989 if ((flags & WORKER_NOT_RUNNING) && (oflags & WORKER_NOT_RUNNING))
990 if (!(worker->flags & WORKER_NOT_RUNNING))
991 atomic_inc(&pool->nr_running);
992}
993
994/**
995 * find_worker_executing_work - find worker which is executing a work
996 * @pool: pool of interest
997 * @work: work to find worker for
998 *
999 * Find a worker which is executing @work on @pool by searching
1000 * @pool->busy_hash which is keyed by the address of @work. For a worker
1001 * to match, its current execution should match the address of @work and
1002 * its work function. This is to avoid unwanted dependency between
1003 * unrelated work executions through a work item being recycled while still
1004 * being executed.
1005 *
1006 * This is a bit tricky. A work item may be freed once its execution
1007 * starts and nothing prevents the freed area from being recycled for
1008 * another work item. If the same work item address ends up being reused
1009 * before the original execution finishes, workqueue will identify the
1010 * recycled work item as currently executing and make it wait until the
1011 * current execution finishes, introducing an unwanted dependency.
1012 *
1013 * This function checks the work item address and work function to avoid
1014 * false positives. Note that this isn't complete as one may construct a
1015 * work function which can introduce dependency onto itself through a
1016 * recycled work item. Well, if somebody wants to shoot oneself in the
1017 * foot that badly, there's only so much we can do, and if such deadlock
1018 * actually occurs, it should be easy to locate the culprit work function.
1019 *
1020 * CONTEXT:
1021 * spin_lock_irq(pool->lock).
1022 *
1023 * Return:
1024 * Pointer to worker which is executing @work if found, %NULL
1025 * otherwise.
1026 */
1027static struct worker *find_worker_executing_work(struct worker_pool *pool,
1028 struct work_struct *work)
1029{
1030 struct worker *worker;
1031
1032 hash_for_each_possible(pool->busy_hash, worker, hentry,
1033 (unsigned long)work)
1034 if (worker->current_work == work &&
1035 worker->current_func == work->func)
1036 return worker;
1037
1038 return NULL;
1039}
1040
1041/**
1042 * move_linked_works - move linked works to a list
1043 * @work: start of series of works to be scheduled
1044 * @head: target list to append @work to
1045 * @nextp: out parameter for nested worklist walking
1046 *
1047 * Schedule linked works starting from @work to @head. Work series to
1048 * be scheduled starts at @work and includes any consecutive work with
1049 * WORK_STRUCT_LINKED set in its predecessor.
1050 *
1051 * If @nextp is not NULL, it's updated to point to the next work of
1052 * the last scheduled work. This allows move_linked_works() to be
1053 * nested inside outer list_for_each_entry_safe().
1054 *
1055 * CONTEXT:
1056 * spin_lock_irq(pool->lock).
1057 */
1058static void move_linked_works(struct work_struct *work, struct list_head *head,
1059 struct work_struct **nextp)
1060{
1061 struct work_struct *n;
1062
1063 /*
1064 * Linked worklist will always end before the end of the list,
1065 * use NULL for list head.
1066 */
1067 list_for_each_entry_safe_from(work, n, NULL, entry) {
1068 list_move_tail(&work->entry, head);
1069 if (!(*work_data_bits(work) & WORK_STRUCT_LINKED))
1070 break;
1071 }
1072
1073 /*
1074 * If we're already inside safe list traversal and have moved
1075 * multiple works to the scheduled queue, the next position
1076 * needs to be updated.
1077 */
1078 if (nextp)
1079 *nextp = n;
1080}
1081
1082/**
1083 * get_pwq - get an extra reference on the specified pool_workqueue
1084 * @pwq: pool_workqueue to get
1085 *
1086 * Obtain an extra reference on @pwq. The caller should guarantee that
1087 * @pwq has positive refcnt and be holding the matching pool->lock.
1088 */
1089static void get_pwq(struct pool_workqueue *pwq)
1090{
1091 lockdep_assert_held(&pwq->pool->lock);
1092 WARN_ON_ONCE(pwq->refcnt <= 0);
1093 pwq->refcnt++;
1094}
1095
1096/**
1097 * put_pwq - put a pool_workqueue reference
1098 * @pwq: pool_workqueue to put
1099 *
1100 * Drop a reference of @pwq. If its refcnt reaches zero, schedule its
1101 * destruction. The caller should be holding the matching pool->lock.
1102 */
1103static void put_pwq(struct pool_workqueue *pwq)
1104{
1105 lockdep_assert_held(&pwq->pool->lock);
1106 if (likely(--pwq->refcnt))
1107 return;
1108 if (WARN_ON_ONCE(!(pwq->wq->flags & WQ_UNBOUND)))
1109 return;
1110 /*
1111 * @pwq can't be released under pool->lock, bounce to
1112 * pwq_unbound_release_workfn(). This never recurses on the same
1113 * pool->lock as this path is taken only for unbound workqueues and
1114 * the release work item is scheduled on a per-cpu workqueue. To
1115 * avoid lockdep warning, unbound pool->locks are given lockdep
1116 * subclass of 1 in get_unbound_pool().
1117 */
1118 schedule_work(&pwq->unbound_release_work);
1119}
1120
1121/**
1122 * put_pwq_unlocked - put_pwq() with surrounding pool lock/unlock
1123 * @pwq: pool_workqueue to put (can be %NULL)
1124 *
1125 * put_pwq() with locking. This function also allows %NULL @pwq.
1126 */
1127static void put_pwq_unlocked(struct pool_workqueue *pwq)
1128{
1129 if (pwq) {
1130 /*
1131 * As both pwqs and pools are RCU protected, the
1132 * following lock operations are safe.
1133 */
1134 spin_lock_irq(&pwq->pool->lock);
1135 put_pwq(pwq);
1136 spin_unlock_irq(&pwq->pool->lock);
1137 }
1138}
1139
1140static void pwq_activate_delayed_work(struct work_struct *work)
1141{
1142 struct pool_workqueue *pwq = get_work_pwq(work);
1143
1144 trace_workqueue_activate_work(work);
1145 if (list_empty(&pwq->pool->worklist))
1146 pwq->pool->watchdog_ts = jiffies;
1147 move_linked_works(work, &pwq->pool->worklist, NULL);
1148 __clear_bit(WORK_STRUCT_DELAYED_BIT, work_data_bits(work));
1149 pwq->nr_active++;
1150}
1151
1152static void pwq_activate_first_delayed(struct pool_workqueue *pwq)
1153{
1154 struct work_struct *work = list_first_entry(&pwq->delayed_works,
1155 struct work_struct, entry);
1156
1157 pwq_activate_delayed_work(work);
1158}
1159
1160/**
1161 * pwq_dec_nr_in_flight - decrement pwq's nr_in_flight
1162 * @pwq: pwq of interest
1163 * @color: color of work which left the queue
1164 *
1165 * A work either has completed or is removed from pending queue,
1166 * decrement nr_in_flight of its pwq and handle workqueue flushing.
1167 *
1168 * CONTEXT:
1169 * spin_lock_irq(pool->lock).
1170 */
1171static void pwq_dec_nr_in_flight(struct pool_workqueue *pwq, int color)
1172{
1173 /* uncolored work items don't participate in flushing or nr_active */
1174 if (color == WORK_NO_COLOR)
1175 goto out_put;
1176
1177 pwq->nr_in_flight[color]--;
1178
1179 pwq->nr_active--;
1180 if (!list_empty(&pwq->delayed_works)) {
1181 /* one down, submit a delayed one */
1182 if (pwq->nr_active < pwq->max_active)
1183 pwq_activate_first_delayed(pwq);
1184 }
1185
1186 /* is flush in progress and are we at the flushing tip? */
1187 if (likely(pwq->flush_color != color))
1188 goto out_put;
1189
1190 /* are there still in-flight works? */
1191 if (pwq->nr_in_flight[color])
1192 goto out_put;
1193
1194 /* this pwq is done, clear flush_color */
1195 pwq->flush_color = -1;
1196
1197 /*
1198 * If this was the last pwq, wake up the first flusher. It
1199 * will handle the rest.
1200 */
1201 if (atomic_dec_and_test(&pwq->wq->nr_pwqs_to_flush))
1202 complete(&pwq->wq->first_flusher->done);
1203out_put:
1204 put_pwq(pwq);
1205}
1206
1207/**
1208 * try_to_grab_pending - steal work item from worklist and disable irq
1209 * @work: work item to steal
1210 * @is_dwork: @work is a delayed_work
1211 * @flags: place to store irq state
1212 *
1213 * Try to grab PENDING bit of @work. This function can handle @work in any
1214 * stable state - idle, on timer or on worklist.
1215 *
1216 * Return:
1217 * 1 if @work was pending and we successfully stole PENDING
1218 * 0 if @work was idle and we claimed PENDING
1219 * -EAGAIN if PENDING couldn't be grabbed at the moment, safe to busy-retry
1220 * -ENOENT if someone else is canceling @work, this state may persist
1221 * for arbitrarily long
1222 *
1223 * Note:
1224 * On >= 0 return, the caller owns @work's PENDING bit. To avoid getting
1225 * interrupted while holding PENDING and @work off queue, irq must be
1226 * disabled on entry. This, combined with delayed_work->timer being
1227 * irqsafe, ensures that we return -EAGAIN for finite short period of time.
1228 *
1229 * On successful return, >= 0, irq is disabled and the caller is
1230 * responsible for releasing it using local_irq_restore(*@flags).
1231 *
1232 * This function is safe to call from any context including IRQ handler.
1233 */
1234static int try_to_grab_pending(struct work_struct *work, bool is_dwork,
1235 unsigned long *flags)
1236{
1237 struct worker_pool *pool;
1238 struct pool_workqueue *pwq;
1239
1240 local_irq_save(*flags);
1241
1242 /* try to steal the timer if it exists */
1243 if (is_dwork) {
1244 struct delayed_work *dwork = to_delayed_work(work);
1245
1246 /*
1247 * dwork->timer is irqsafe. If del_timer() fails, it's
1248 * guaranteed that the timer is not queued anywhere and not
1249 * running on the local CPU.
1250 */
1251 if (likely(del_timer(&dwork->timer)))
1252 return 1;
1253 }
1254
1255 /* try to claim PENDING the normal way */
1256 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work)))
1257 return 0;
1258
1259 rcu_read_lock();
1260 /*
1261 * The queueing is in progress, or it is already queued. Try to
1262 * steal it from ->worklist without clearing WORK_STRUCT_PENDING.
1263 */
1264 pool = get_work_pool(work);
1265 if (!pool)
1266 goto fail;
1267
1268 spin_lock(&pool->lock);
1269 /*
1270 * work->data is guaranteed to point to pwq only while the work
1271 * item is queued on pwq->wq, and both updating work->data to point
1272 * to pwq on queueing and to pool on dequeueing are done under
1273 * pwq->pool->lock. This in turn guarantees that, if work->data
1274 * points to pwq which is associated with a locked pool, the work
1275 * item is currently queued on that pool.
1276 */
1277 pwq = get_work_pwq(work);
1278 if (pwq && pwq->pool == pool) {
1279 debug_work_deactivate(work);
1280
1281 /*
1282 * A delayed work item cannot be grabbed directly because
1283 * it might have linked NO_COLOR work items which, if left
1284 * on the delayed_list, will confuse pwq->nr_active
1285 * management later on and cause stall. Make sure the work
1286 * item is activated before grabbing.
1287 */
1288 if (*work_data_bits(work) & WORK_STRUCT_DELAYED)
1289 pwq_activate_delayed_work(work);
1290
1291 list_del_init(&work->entry);
1292 pwq_dec_nr_in_flight(pwq, get_work_color(work));
1293
1294 /* work->data points to pwq iff queued, point to pool */
1295 set_work_pool_and_keep_pending(work, pool->id);
1296
1297 spin_unlock(&pool->lock);
1298 rcu_read_unlock();
1299 return 1;
1300 }
1301 spin_unlock(&pool->lock);
1302fail:
1303 rcu_read_unlock();
1304 local_irq_restore(*flags);
1305 if (work_is_canceling(work))
1306 return -ENOENT;
1307 cpu_relax();
1308 return -EAGAIN;
1309}
1310
1311/**
1312 * insert_work - insert a work into a pool
1313 * @pwq: pwq @work belongs to
1314 * @work: work to insert
1315 * @head: insertion point
1316 * @extra_flags: extra WORK_STRUCT_* flags to set
1317 *
1318 * Insert @work which belongs to @pwq after @head. @extra_flags is or'd to
1319 * work_struct flags.
1320 *
1321 * CONTEXT:
1322 * spin_lock_irq(pool->lock).
1323 */
1324static void insert_work(struct pool_workqueue *pwq, struct work_struct *work,
1325 struct list_head *head, unsigned int extra_flags)
1326{
1327 struct worker_pool *pool = pwq->pool;
1328
1329 /* we own @work, set data and link */
1330 set_work_pwq(work, pwq, extra_flags);
1331 list_add_tail(&work->entry, head);
1332 get_pwq(pwq);
1333
1334 /*
1335 * Ensure either wq_worker_sleeping() sees the above
1336 * list_add_tail() or we see zero nr_running to avoid workers lying
1337 * around lazily while there are works to be processed.
1338 */
1339 smp_mb();
1340
1341 if (__need_more_worker(pool))
1342 wake_up_worker(pool);
1343}
1344
1345/*
1346 * Test whether @work is being queued from another work executing on the
1347 * same workqueue.
1348 */
1349static bool is_chained_work(struct workqueue_struct *wq)
1350{
1351 struct worker *worker;
1352
1353 worker = current_wq_worker();
1354 /*
1355 * Return %true iff I'm a worker executing a work item on @wq. If
1356 * I'm @worker, it's safe to dereference it without locking.
1357 */
1358 return worker && worker->current_pwq->wq == wq;
1359}
1360
1361/*
1362 * When queueing an unbound work item to a wq, prefer local CPU if allowed
1363 * by wq_unbound_cpumask. Otherwise, round robin among the allowed ones to
1364 * avoid perturbing sensitive tasks.
1365 */
1366static int wq_select_unbound_cpu(int cpu)
1367{
1368 static bool printed_dbg_warning;
1369 int new_cpu;
1370
1371 if (likely(!wq_debug_force_rr_cpu)) {
1372 if (cpumask_test_cpu(cpu, wq_unbound_cpumask))
1373 return cpu;
1374 } else if (!printed_dbg_warning) {
1375 pr_warn("workqueue: round-robin CPU selection forced, expect performance impact\n");
1376 printed_dbg_warning = true;
1377 }
1378
1379 if (cpumask_empty(wq_unbound_cpumask))
1380 return cpu;
1381
1382 new_cpu = __this_cpu_read(wq_rr_cpu_last);
1383 new_cpu = cpumask_next_and(new_cpu, wq_unbound_cpumask, cpu_online_mask);
1384 if (unlikely(new_cpu >= nr_cpu_ids)) {
1385 new_cpu = cpumask_first_and(wq_unbound_cpumask, cpu_online_mask);
1386 if (unlikely(new_cpu >= nr_cpu_ids))
1387 return cpu;
1388 }
1389 __this_cpu_write(wq_rr_cpu_last, new_cpu);
1390
1391 return new_cpu;
1392}
1393
1394static void __queue_work(int cpu, struct workqueue_struct *wq,
1395 struct work_struct *work)
1396{
1397 struct pool_workqueue *pwq;
1398 struct worker_pool *last_pool;
1399 struct list_head *worklist;
1400 unsigned int work_flags;
1401 unsigned int req_cpu = cpu;
1402
1403 /*
1404 * While a work item is PENDING && off queue, a task trying to
1405 * steal the PENDING will busy-loop waiting for it to either get
1406 * queued or lose PENDING. Grabbing PENDING and queueing should
1407 * happen with IRQ disabled.
1408 */
1409 lockdep_assert_irqs_disabled();
1410
1411 debug_work_activate(work);
1412
1413 /* if draining, only works from the same workqueue are allowed */
1414 if (unlikely(wq->flags & __WQ_DRAINING) &&
1415 WARN_ON_ONCE(!is_chained_work(wq)))
1416 return;
1417 rcu_read_lock();
1418retry:
1419 if (req_cpu == WORK_CPU_UNBOUND)
1420 cpu = wq_select_unbound_cpu(raw_smp_processor_id());
1421
1422 /* pwq which will be used unless @work is executing elsewhere */
1423 if (!(wq->flags & WQ_UNBOUND))
1424 pwq = per_cpu_ptr(wq->cpu_pwqs, cpu);
1425 else
1426 pwq = unbound_pwq_by_node(wq, cpu_to_node(cpu));
1427
1428 /*
1429 * If @work was previously on a different pool, it might still be
1430 * running there, in which case the work needs to be queued on that
1431 * pool to guarantee non-reentrancy.
1432 */
1433 last_pool = get_work_pool(work);
1434 if (last_pool && last_pool != pwq->pool) {
1435 struct worker *worker;
1436
1437 spin_lock(&last_pool->lock);
1438
1439 worker = find_worker_executing_work(last_pool, work);
1440
1441 if (worker && worker->current_pwq->wq == wq) {
1442 pwq = worker->current_pwq;
1443 } else {
1444 /* meh... not running there, queue here */
1445 spin_unlock(&last_pool->lock);
1446 spin_lock(&pwq->pool->lock);
1447 }
1448 } else {
1449 spin_lock(&pwq->pool->lock);
1450 }
1451
1452 /*
1453 * pwq is determined and locked. For unbound pools, we could have
1454 * raced with pwq release and it could already be dead. If its
1455 * refcnt is zero, repeat pwq selection. Note that pwqs never die
1456 * without another pwq replacing it in the numa_pwq_tbl or while
1457 * work items are executing on it, so the retrying is guaranteed to
1458 * make forward-progress.
1459 */
1460 if (unlikely(!pwq->refcnt)) {
1461 if (wq->flags & WQ_UNBOUND) {
1462 spin_unlock(&pwq->pool->lock);
1463 cpu_relax();
1464 goto retry;
1465 }
1466 /* oops */
1467 WARN_ONCE(true, "workqueue: per-cpu pwq for %s on cpu%d has 0 refcnt",
1468 wq->name, cpu);
1469 }
1470
1471 /* pwq determined, queue */
1472 trace_workqueue_queue_work(req_cpu, pwq, work);
1473
1474 if (WARN_ON(!list_empty(&work->entry)))
1475 goto out;
1476
1477 pwq->nr_in_flight[pwq->work_color]++;
1478 work_flags = work_color_to_flags(pwq->work_color);
1479
1480 if (likely(pwq->nr_active < pwq->max_active)) {
1481 trace_workqueue_activate_work(work);
1482 pwq->nr_active++;
1483 worklist = &pwq->pool->worklist;
1484 if (list_empty(worklist))
1485 pwq->pool->watchdog_ts = jiffies;
1486 } else {
1487 work_flags |= WORK_STRUCT_DELAYED;
1488 worklist = &pwq->delayed_works;
1489 }
1490
1491 insert_work(pwq, work, worklist, work_flags);
1492
1493out:
1494 spin_unlock(&pwq->pool->lock);
1495 rcu_read_unlock();
1496}
1497
1498/**
1499 * queue_work_on - queue work on specific cpu
1500 * @cpu: CPU number to execute work on
1501 * @wq: workqueue to use
1502 * @work: work to queue
1503 *
1504 * We queue the work to a specific CPU, the caller must ensure it
1505 * can't go away.
1506 *
1507 * Return: %false if @work was already on a queue, %true otherwise.
1508 */
1509bool queue_work_on(int cpu, struct workqueue_struct *wq,
1510 struct work_struct *work)
1511{
1512 bool ret = false;
1513 unsigned long flags;
1514
1515 local_irq_save(flags);
1516
1517 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1518 __queue_work(cpu, wq, work);
1519 ret = true;
1520 }
1521
1522 local_irq_restore(flags);
1523 return ret;
1524}
1525EXPORT_SYMBOL(queue_work_on);
1526
1527/**
1528 * workqueue_select_cpu_near - Select a CPU based on NUMA node
1529 * @node: NUMA node ID that we want to select a CPU from
1530 *
1531 * This function will attempt to find a "random" cpu available on a given
1532 * node. If there are no CPUs available on the given node it will return
1533 * WORK_CPU_UNBOUND indicating that we should just schedule to any
1534 * available CPU if we need to schedule this work.
1535 */
1536static int workqueue_select_cpu_near(int node)
1537{
1538 int cpu;
1539
1540 /* No point in doing this if NUMA isn't enabled for workqueues */
1541 if (!wq_numa_enabled)
1542 return WORK_CPU_UNBOUND;
1543
1544 /* Delay binding to CPU if node is not valid or online */
1545 if (node < 0 || node >= MAX_NUMNODES || !node_online(node))
1546 return WORK_CPU_UNBOUND;
1547
1548 /* Use local node/cpu if we are already there */
1549 cpu = raw_smp_processor_id();
1550 if (node == cpu_to_node(cpu))
1551 return cpu;
1552
1553 /* Use "random" otherwise know as "first" online CPU of node */
1554 cpu = cpumask_any_and(cpumask_of_node(node), cpu_online_mask);
1555
1556 /* If CPU is valid return that, otherwise just defer */
1557 return cpu < nr_cpu_ids ? cpu : WORK_CPU_UNBOUND;
1558}
1559
1560/**
1561 * queue_work_node - queue work on a "random" cpu for a given NUMA node
1562 * @node: NUMA node that we are targeting the work for
1563 * @wq: workqueue to use
1564 * @work: work to queue
1565 *
1566 * We queue the work to a "random" CPU within a given NUMA node. The basic
1567 * idea here is to provide a way to somehow associate work with a given
1568 * NUMA node.
1569 *
1570 * This function will only make a best effort attempt at getting this onto
1571 * the right NUMA node. If no node is requested or the requested node is
1572 * offline then we just fall back to standard queue_work behavior.
1573 *
1574 * Currently the "random" CPU ends up being the first available CPU in the
1575 * intersection of cpu_online_mask and the cpumask of the node, unless we
1576 * are running on the node. In that case we just use the current CPU.
1577 *
1578 * Return: %false if @work was already on a queue, %true otherwise.
1579 */
1580bool queue_work_node(int node, struct workqueue_struct *wq,
1581 struct work_struct *work)
1582{
1583 unsigned long flags;
1584 bool ret = false;
1585
1586 /*
1587 * This current implementation is specific to unbound workqueues.
1588 * Specifically we only return the first available CPU for a given
1589 * node instead of cycling through individual CPUs within the node.
1590 *
1591 * If this is used with a per-cpu workqueue then the logic in
1592 * workqueue_select_cpu_near would need to be updated to allow for
1593 * some round robin type logic.
1594 */
1595 WARN_ON_ONCE(!(wq->flags & WQ_UNBOUND));
1596
1597 local_irq_save(flags);
1598
1599 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1600 int cpu = workqueue_select_cpu_near(node);
1601
1602 __queue_work(cpu, wq, work);
1603 ret = true;
1604 }
1605
1606 local_irq_restore(flags);
1607 return ret;
1608}
1609EXPORT_SYMBOL_GPL(queue_work_node);
1610
1611void delayed_work_timer_fn(struct timer_list *t)
1612{
1613 struct delayed_work *dwork = from_timer(dwork, t, timer);
1614
1615 /* should have been called from irqsafe timer with irq already off */
1616 __queue_work(dwork->cpu, dwork->wq, &dwork->work);
1617}
1618EXPORT_SYMBOL(delayed_work_timer_fn);
1619
1620static void __queue_delayed_work(int cpu, struct workqueue_struct *wq,
1621 struct delayed_work *dwork, unsigned long delay)
1622{
1623 struct timer_list *timer = &dwork->timer;
1624 struct work_struct *work = &dwork->work;
1625
1626 WARN_ON_ONCE(!wq);
1627 WARN_ON_ONCE(timer->function != delayed_work_timer_fn);
1628 WARN_ON_ONCE(timer_pending(timer));
1629 WARN_ON_ONCE(!list_empty(&work->entry));
1630
1631 /*
1632 * If @delay is 0, queue @dwork->work immediately. This is for
1633 * both optimization and correctness. The earliest @timer can
1634 * expire is on the closest next tick and delayed_work users depend
1635 * on that there's no such delay when @delay is 0.
1636 */
1637 if (!delay) {
1638 __queue_work(cpu, wq, &dwork->work);
1639 return;
1640 }
1641
1642 dwork->wq = wq;
1643 dwork->cpu = cpu;
1644 timer->expires = jiffies + delay;
1645
1646 if (unlikely(cpu != WORK_CPU_UNBOUND))
1647 add_timer_on(timer, cpu);
1648 else
1649 add_timer(timer);
1650}
1651
1652/**
1653 * queue_delayed_work_on - queue work on specific CPU after delay
1654 * @cpu: CPU number to execute work on
1655 * @wq: workqueue to use
1656 * @dwork: work to queue
1657 * @delay: number of jiffies to wait before queueing
1658 *
1659 * Return: %false if @work was already on a queue, %true otherwise. If
1660 * @delay is zero and @dwork is idle, it will be scheduled for immediate
1661 * execution.
1662 */
1663bool queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
1664 struct delayed_work *dwork, unsigned long delay)
1665{
1666 struct work_struct *work = &dwork->work;
1667 bool ret = false;
1668 unsigned long flags;
1669
1670 /* read the comment in __queue_work() */
1671 local_irq_save(flags);
1672
1673 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1674 __queue_delayed_work(cpu, wq, dwork, delay);
1675 ret = true;
1676 }
1677
1678 local_irq_restore(flags);
1679 return ret;
1680}
1681EXPORT_SYMBOL(queue_delayed_work_on);
1682
1683/**
1684 * mod_delayed_work_on - modify delay of or queue a delayed work on specific CPU
1685 * @cpu: CPU number to execute work on
1686 * @wq: workqueue to use
1687 * @dwork: work to queue
1688 * @delay: number of jiffies to wait before queueing
1689 *
1690 * If @dwork is idle, equivalent to queue_delayed_work_on(); otherwise,
1691 * modify @dwork's timer so that it expires after @delay. If @delay is
1692 * zero, @work is guaranteed to be scheduled immediately regardless of its
1693 * current state.
1694 *
1695 * Return: %false if @dwork was idle and queued, %true if @dwork was
1696 * pending and its timer was modified.
1697 *
1698 * This function is safe to call from any context including IRQ handler.
1699 * See try_to_grab_pending() for details.
1700 */
1701bool mod_delayed_work_on(int cpu, struct workqueue_struct *wq,
1702 struct delayed_work *dwork, unsigned long delay)
1703{
1704 unsigned long flags;
1705 int ret;
1706
1707 do {
1708 ret = try_to_grab_pending(&dwork->work, true, &flags);
1709 } while (unlikely(ret == -EAGAIN));
1710
1711 if (likely(ret >= 0)) {
1712 __queue_delayed_work(cpu, wq, dwork, delay);
1713 local_irq_restore(flags);
1714 }
1715
1716 /* -ENOENT from try_to_grab_pending() becomes %true */
1717 return ret;
1718}
1719EXPORT_SYMBOL_GPL(mod_delayed_work_on);
1720
1721static void rcu_work_rcufn(struct rcu_head *rcu)
1722{
1723 struct rcu_work *rwork = container_of(rcu, struct rcu_work, rcu);
1724
1725 /* read the comment in __queue_work() */
1726 local_irq_disable();
1727 __queue_work(WORK_CPU_UNBOUND, rwork->wq, &rwork->work);
1728 local_irq_enable();
1729}
1730
1731/**
1732 * queue_rcu_work - queue work after a RCU grace period
1733 * @wq: workqueue to use
1734 * @rwork: work to queue
1735 *
1736 * Return: %false if @rwork was already pending, %true otherwise. Note
1737 * that a full RCU grace period is guaranteed only after a %true return.
1738 * While @rwork is guaranteed to be executed after a %false return, the
1739 * execution may happen before a full RCU grace period has passed.
1740 */
1741bool queue_rcu_work(struct workqueue_struct *wq, struct rcu_work *rwork)
1742{
1743 struct work_struct *work = &rwork->work;
1744
1745 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1746 rwork->wq = wq;
1747 call_rcu(&rwork->rcu, rcu_work_rcufn);
1748 return true;
1749 }
1750
1751 return false;
1752}
1753EXPORT_SYMBOL(queue_rcu_work);
1754
1755/**
1756 * worker_enter_idle - enter idle state
1757 * @worker: worker which is entering idle state
1758 *
1759 * @worker is entering idle state. Update stats and idle timer if
1760 * necessary.
1761 *
1762 * LOCKING:
1763 * spin_lock_irq(pool->lock).
1764 */
1765static void worker_enter_idle(struct worker *worker)
1766{
1767 struct worker_pool *pool = worker->pool;
1768
1769 if (WARN_ON_ONCE(worker->flags & WORKER_IDLE) ||
1770 WARN_ON_ONCE(!list_empty(&worker->entry) &&
1771 (worker->hentry.next || worker->hentry.pprev)))
1772 return;
1773
1774 /* can't use worker_set_flags(), also called from create_worker() */
1775 worker->flags |= WORKER_IDLE;
1776 pool->nr_idle++;
1777 worker->last_active = jiffies;
1778
1779 /* idle_list is LIFO */
1780 list_add(&worker->entry, &pool->idle_list);
1781
1782 if (too_many_workers(pool) && !timer_pending(&pool->idle_timer))
1783 mod_timer(&pool->idle_timer, jiffies + IDLE_WORKER_TIMEOUT);
1784
1785 /*
1786 * Sanity check nr_running. Because unbind_workers() releases
1787 * pool->lock between setting %WORKER_UNBOUND and zapping
1788 * nr_running, the warning may trigger spuriously. Check iff
1789 * unbind is not in progress.
1790 */
1791 WARN_ON_ONCE(!(pool->flags & POOL_DISASSOCIATED) &&
1792 pool->nr_workers == pool->nr_idle &&
1793 atomic_read(&pool->nr_running));
1794}
1795
1796/**
1797 * worker_leave_idle - leave idle state
1798 * @worker: worker which is leaving idle state
1799 *
1800 * @worker is leaving idle state. Update stats.
1801 *
1802 * LOCKING:
1803 * spin_lock_irq(pool->lock).
1804 */
1805static void worker_leave_idle(struct worker *worker)
1806{
1807 struct worker_pool *pool = worker->pool;
1808
1809 if (WARN_ON_ONCE(!(worker->flags & WORKER_IDLE)))
1810 return;
1811 worker_clr_flags(worker, WORKER_IDLE);
1812 pool->nr_idle--;
1813 list_del_init(&worker->entry);
1814}
1815
1816static struct worker *alloc_worker(int node)
1817{
1818 struct worker *worker;
1819
1820 worker = kzalloc_node(sizeof(*worker), GFP_KERNEL, node);
1821 if (worker) {
1822 INIT_LIST_HEAD(&worker->entry);
1823 INIT_LIST_HEAD(&worker->scheduled);
1824 INIT_LIST_HEAD(&worker->node);
1825 /* on creation a worker is in !idle && prep state */
1826 worker->flags = WORKER_PREP;
1827 }
1828 return worker;
1829}
1830
1831/**
1832 * worker_attach_to_pool() - attach a worker to a pool
1833 * @worker: worker to be attached
1834 * @pool: the target pool
1835 *
1836 * Attach @worker to @pool. Once attached, the %WORKER_UNBOUND flag and
1837 * cpu-binding of @worker are kept coordinated with the pool across
1838 * cpu-[un]hotplugs.
1839 */
1840static void worker_attach_to_pool(struct worker *worker,
1841 struct worker_pool *pool)
1842{
1843 mutex_lock(&wq_pool_attach_mutex);
1844
1845 /*
1846 * set_cpus_allowed_ptr() will fail if the cpumask doesn't have any
1847 * online CPUs. It'll be re-applied when any of the CPUs come up.
1848 */
1849 set_cpus_allowed_ptr(worker->task, pool->attrs->cpumask);
1850
1851 /*
1852 * The wq_pool_attach_mutex ensures %POOL_DISASSOCIATED remains
1853 * stable across this function. See the comments above the flag
1854 * definition for details.
1855 */
1856 if (pool->flags & POOL_DISASSOCIATED)
1857 worker->flags |= WORKER_UNBOUND;
1858
1859 list_add_tail(&worker->node, &pool->workers);
1860 worker->pool = pool;
1861
1862 mutex_unlock(&wq_pool_attach_mutex);
1863}
1864
1865/**
1866 * worker_detach_from_pool() - detach a worker from its pool
1867 * @worker: worker which is attached to its pool
1868 *
1869 * Undo the attaching which had been done in worker_attach_to_pool(). The
1870 * caller worker shouldn't access to the pool after detached except it has
1871 * other reference to the pool.
1872 */
1873static void worker_detach_from_pool(struct worker *worker)
1874{
1875 struct worker_pool *pool = worker->pool;
1876 struct completion *detach_completion = NULL;
1877
1878 mutex_lock(&wq_pool_attach_mutex);
1879
1880 list_del(&worker->node);
1881 worker->pool = NULL;
1882
1883 if (list_empty(&pool->workers))
1884 detach_completion = pool->detach_completion;
1885 mutex_unlock(&wq_pool_attach_mutex);
1886
1887 /* clear leftover flags without pool->lock after it is detached */
1888 worker->flags &= ~(WORKER_UNBOUND | WORKER_REBOUND);
1889
1890 if (detach_completion)
1891 complete(detach_completion);
1892}
1893
1894/**
1895 * create_worker - create a new workqueue worker
1896 * @pool: pool the new worker will belong to
1897 *
1898 * Create and start a new worker which is attached to @pool.
1899 *
1900 * CONTEXT:
1901 * Might sleep. Does GFP_KERNEL allocations.
1902 *
1903 * Return:
1904 * Pointer to the newly created worker.
1905 */
1906static struct worker *create_worker(struct worker_pool *pool)
1907{
1908 struct worker *worker = NULL;
1909 int id = -1;
1910 char id_buf[16];
1911
1912 /* ID is needed to determine kthread name */
1913 id = ida_simple_get(&pool->worker_ida, 0, 0, GFP_KERNEL);
1914 if (id < 0)
1915 goto fail;
1916
1917 worker = alloc_worker(pool->node);
1918 if (!worker)
1919 goto fail;
1920
1921 worker->id = id;
1922
1923 if (pool->cpu >= 0)
1924 snprintf(id_buf, sizeof(id_buf), "%d:%d%s", pool->cpu, id,
1925 pool->attrs->nice < 0 ? "H" : "");
1926 else
1927 snprintf(id_buf, sizeof(id_buf), "u%d:%d", pool->id, id);
1928
1929 worker->task = kthread_create_on_node(worker_thread, worker, pool->node,
1930 "kworker/%s", id_buf);
1931 if (IS_ERR(worker->task))
1932 goto fail;
1933
1934 set_user_nice(worker->task, pool->attrs->nice);
1935 kthread_bind_mask(worker->task, pool->attrs->cpumask);
1936
1937 /* successful, attach the worker to the pool */
1938 worker_attach_to_pool(worker, pool);
1939
1940 /* start the newly created worker */
1941 spin_lock_irq(&pool->lock);
1942 worker->pool->nr_workers++;
1943 worker_enter_idle(worker);
1944 wake_up_process(worker->task);
1945 spin_unlock_irq(&pool->lock);
1946
1947 return worker;
1948
1949fail:
1950 if (id >= 0)
1951 ida_simple_remove(&pool->worker_ida, id);
1952 kfree(worker);
1953 return NULL;
1954}
1955
1956/**
1957 * destroy_worker - destroy a workqueue worker
1958 * @worker: worker to be destroyed
1959 *
1960 * Destroy @worker and adjust @pool stats accordingly. The worker should
1961 * be idle.
1962 *
1963 * CONTEXT:
1964 * spin_lock_irq(pool->lock).
1965 */
1966static void destroy_worker(struct worker *worker)
1967{
1968 struct worker_pool *pool = worker->pool;
1969
1970 lockdep_assert_held(&pool->lock);
1971
1972 /* sanity check frenzy */
1973 if (WARN_ON(worker->current_work) ||
1974 WARN_ON(!list_empty(&worker->scheduled)) ||
1975 WARN_ON(!(worker->flags & WORKER_IDLE)))
1976 return;
1977
1978 pool->nr_workers--;
1979 pool->nr_idle--;
1980
1981 list_del_init(&worker->entry);
1982 worker->flags |= WORKER_DIE;
1983 wake_up_process(worker->task);
1984}
1985
1986static void idle_worker_timeout(struct timer_list *t)
1987{
1988 struct worker_pool *pool = from_timer(pool, t, idle_timer);
1989
1990 spin_lock_irq(&pool->lock);
1991
1992 while (too_many_workers(pool)) {
1993 struct worker *worker;
1994 unsigned long expires;
1995
1996 /* idle_list is kept in LIFO order, check the last one */
1997 worker = list_entry(pool->idle_list.prev, struct worker, entry);
1998 expires = worker->last_active + IDLE_WORKER_TIMEOUT;
1999
2000 if (time_before(jiffies, expires)) {
2001 mod_timer(&pool->idle_timer, expires);
2002 break;
2003 }
2004
2005 destroy_worker(worker);
2006 }
2007
2008 spin_unlock_irq(&pool->lock);
2009}
2010
2011static void send_mayday(struct work_struct *work)
2012{
2013 struct pool_workqueue *pwq = get_work_pwq(work);
2014 struct workqueue_struct *wq = pwq->wq;
2015
2016 lockdep_assert_held(&wq_mayday_lock);
2017
2018 if (!wq->rescuer)
2019 return;
2020
2021 /* mayday mayday mayday */
2022 if (list_empty(&pwq->mayday_node)) {
2023 /*
2024 * If @pwq is for an unbound wq, its base ref may be put at
2025 * any time due to an attribute change. Pin @pwq until the
2026 * rescuer is done with it.
2027 */
2028 get_pwq(pwq);
2029 list_add_tail(&pwq->mayday_node, &wq->maydays);
2030 wake_up_process(wq->rescuer->task);
2031 }
2032}
2033
2034static void pool_mayday_timeout(struct timer_list *t)
2035{
2036 struct worker_pool *pool = from_timer(pool, t, mayday_timer);
2037 struct work_struct *work;
2038
2039 spin_lock_irq(&pool->lock);
2040 spin_lock(&wq_mayday_lock); /* for wq->maydays */
2041
2042 if (need_to_create_worker(pool)) {
2043 /*
2044 * We've been trying to create a new worker but
2045 * haven't been successful. We might be hitting an
2046 * allocation deadlock. Send distress signals to
2047 * rescuers.
2048 */
2049 list_for_each_entry(work, &pool->worklist, entry)
2050 send_mayday(work);
2051 }
2052
2053 spin_unlock(&wq_mayday_lock);
2054 spin_unlock_irq(&pool->lock);
2055
2056 mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INTERVAL);
2057}
2058
2059/**
2060 * maybe_create_worker - create a new worker if necessary
2061 * @pool: pool to create a new worker for
2062 *
2063 * Create a new worker for @pool if necessary. @pool is guaranteed to
2064 * have at least one idle worker on return from this function. If
2065 * creating a new worker takes longer than MAYDAY_INTERVAL, mayday is
2066 * sent to all rescuers with works scheduled on @pool to resolve
2067 * possible allocation deadlock.
2068 *
2069 * On return, need_to_create_worker() is guaranteed to be %false and
2070 * may_start_working() %true.
2071 *
2072 * LOCKING:
2073 * spin_lock_irq(pool->lock) which may be released and regrabbed
2074 * multiple times. Does GFP_KERNEL allocations. Called only from
2075 * manager.
2076 */
2077static void maybe_create_worker(struct worker_pool *pool)
2078__releases(&pool->lock)
2079__acquires(&pool->lock)
2080{
2081restart:
2082 spin_unlock_irq(&pool->lock);
2083
2084 /* if we don't make progress in MAYDAY_INITIAL_TIMEOUT, call for help */
2085 mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INITIAL_TIMEOUT);
2086
2087 while (true) {
2088 if (create_worker(pool) || !need_to_create_worker(pool))
2089 break;
2090
2091 schedule_timeout_interruptible(CREATE_COOLDOWN);
2092
2093 if (!need_to_create_worker(pool))
2094 break;
2095 }
2096
2097 del_timer_sync(&pool->mayday_timer);
2098 spin_lock_irq(&pool->lock);
2099 /*
2100 * This is necessary even after a new worker was just successfully
2101 * created as @pool->lock was dropped and the new worker might have
2102 * already become busy.
2103 */
2104 if (need_to_create_worker(pool))
2105 goto restart;
2106}
2107
2108/**
2109 * manage_workers - manage worker pool
2110 * @worker: self
2111 *
2112 * Assume the manager role and manage the worker pool @worker belongs
2113 * to. At any given time, there can be only zero or one manager per
2114 * pool. The exclusion is handled automatically by this function.
2115 *
2116 * The caller can safely start processing works on false return. On
2117 * true return, it's guaranteed that need_to_create_worker() is false
2118 * and may_start_working() is true.
2119 *
2120 * CONTEXT:
2121 * spin_lock_irq(pool->lock) which may be released and regrabbed
2122 * multiple times. Does GFP_KERNEL allocations.
2123 *
2124 * Return:
2125 * %false if the pool doesn't need management and the caller can safely
2126 * start processing works, %true if management function was performed and
2127 * the conditions that the caller verified before calling the function may
2128 * no longer be true.
2129 */
2130static bool manage_workers(struct worker *worker)
2131{
2132 struct worker_pool *pool = worker->pool;
2133
2134 if (pool->flags & POOL_MANAGER_ACTIVE)
2135 return false;
2136
2137 pool->flags |= POOL_MANAGER_ACTIVE;
2138 pool->manager = worker;
2139
2140 maybe_create_worker(pool);
2141
2142 pool->manager = NULL;
2143 pool->flags &= ~POOL_MANAGER_ACTIVE;
2144 wake_up(&wq_manager_wait);
2145 return true;
2146}
2147
2148/**
2149 * process_one_work - process single work
2150 * @worker: self
2151 * @work: work to process
2152 *
2153 * Process @work. This function contains all the logics necessary to
2154 * process a single work including synchronization against and
2155 * interaction with other workers on the same cpu, queueing and
2156 * flushing. As long as context requirement is met, any worker can
2157 * call this function to process a work.
2158 *
2159 * CONTEXT:
2160 * spin_lock_irq(pool->lock) which is released and regrabbed.
2161 */
2162static void process_one_work(struct worker *worker, struct work_struct *work)
2163__releases(&pool->lock)
2164__acquires(&pool->lock)
2165{
2166 struct pool_workqueue *pwq = get_work_pwq(work);
2167 struct worker_pool *pool = worker->pool;
2168 bool cpu_intensive = pwq->wq->flags & WQ_CPU_INTENSIVE;
2169 int work_color;
2170 struct worker *collision;
2171#ifdef CONFIG_LOCKDEP
2172 /*
2173 * It is permissible to free the struct work_struct from
2174 * inside the function that is called from it, this we need to
2175 * take into account for lockdep too. To avoid bogus "held
2176 * lock freed" warnings as well as problems when looking into
2177 * work->lockdep_map, make a copy and use that here.
2178 */
2179 struct lockdep_map lockdep_map;
2180
2181 lockdep_copy_map(&lockdep_map, &work->lockdep_map);
2182#endif
2183 /* ensure we're on the correct CPU */
2184 WARN_ON_ONCE(!(pool->flags & POOL_DISASSOCIATED) &&
2185 raw_smp_processor_id() != pool->cpu);
2186
2187 /*
2188 * A single work shouldn't be executed concurrently by
2189 * multiple workers on a single cpu. Check whether anyone is
2190 * already processing the work. If so, defer the work to the
2191 * currently executing one.
2192 */
2193 collision = find_worker_executing_work(pool, work);
2194 if (unlikely(collision)) {
2195 move_linked_works(work, &collision->scheduled, NULL);
2196 return;
2197 }
2198
2199 /* claim and dequeue */
2200 debug_work_deactivate(work);
2201 hash_add(pool->busy_hash, &worker->hentry, (unsigned long)work);
2202 worker->current_work = work;
2203 worker->current_func = work->func;
2204 worker->current_pwq = pwq;
2205 work_color = get_work_color(work);
2206
2207 /*
2208 * Record wq name for cmdline and debug reporting, may get
2209 * overridden through set_worker_desc().
2210 */
2211 strscpy(worker->desc, pwq->wq->name, WORKER_DESC_LEN);
2212
2213 list_del_init(&work->entry);
2214
2215 /*
2216 * CPU intensive works don't participate in concurrency management.
2217 * They're the scheduler's responsibility. This takes @worker out
2218 * of concurrency management and the next code block will chain
2219 * execution of the pending work items.
2220 */
2221 if (unlikely(cpu_intensive))
2222 worker_set_flags(worker, WORKER_CPU_INTENSIVE);
2223
2224 /*
2225 * Wake up another worker if necessary. The condition is always
2226 * false for normal per-cpu workers since nr_running would always
2227 * be >= 1 at this point. This is used to chain execution of the
2228 * pending work items for WORKER_NOT_RUNNING workers such as the
2229 * UNBOUND and CPU_INTENSIVE ones.
2230 */
2231 if (need_more_worker(pool))
2232 wake_up_worker(pool);
2233
2234 /*
2235 * Record the last pool and clear PENDING which should be the last
2236 * update to @work. Also, do this inside @pool->lock so that
2237 * PENDING and queued state changes happen together while IRQ is
2238 * disabled.
2239 */
2240 set_work_pool_and_clear_pending(work, pool->id);
2241
2242 spin_unlock_irq(&pool->lock);
2243
2244 lock_map_acquire(&pwq->wq->lockdep_map);
2245 lock_map_acquire(&lockdep_map);
2246 /*
2247 * Strictly speaking we should mark the invariant state without holding
2248 * any locks, that is, before these two lock_map_acquire()'s.
2249 *
2250 * However, that would result in:
2251 *
2252 * A(W1)
2253 * WFC(C)
2254 * A(W1)
2255 * C(C)
2256 *
2257 * Which would create W1->C->W1 dependencies, even though there is no
2258 * actual deadlock possible. There are two solutions, using a
2259 * read-recursive acquire on the work(queue) 'locks', but this will then
2260 * hit the lockdep limitation on recursive locks, or simply discard
2261 * these locks.
2262 *
2263 * AFAICT there is no possible deadlock scenario between the
2264 * flush_work() and complete() primitives (except for single-threaded
2265 * workqueues), so hiding them isn't a problem.
2266 */
2267 lockdep_invariant_state(true);
2268 trace_workqueue_execute_start(work);
2269 worker->current_func(work);
2270 /*
2271 * While we must be careful to not use "work" after this, the trace
2272 * point will only record its address.
2273 */
2274 trace_workqueue_execute_end(work);
2275 lock_map_release(&lockdep_map);
2276 lock_map_release(&pwq->wq->lockdep_map);
2277
2278 if (unlikely(in_atomic() || lockdep_depth(current) > 0)) {
2279 pr_err("BUG: workqueue leaked lock or atomic: %s/0x%08x/%d\n"
2280 " last function: %ps\n",
2281 current->comm, preempt_count(), task_pid_nr(current),
2282 worker->current_func);
2283 debug_show_held_locks(current);
2284 dump_stack();
2285 }
2286
2287 /*
2288 * The following prevents a kworker from hogging CPU on !PREEMPT
2289 * kernels, where a requeueing work item waiting for something to
2290 * happen could deadlock with stop_machine as such work item could
2291 * indefinitely requeue itself while all other CPUs are trapped in
2292 * stop_machine. At the same time, report a quiescent RCU state so
2293 * the same condition doesn't freeze RCU.
2294 */
2295 cond_resched();
2296
2297 spin_lock_irq(&pool->lock);
2298
2299 /* clear cpu intensive status */
2300 if (unlikely(cpu_intensive))
2301 worker_clr_flags(worker, WORKER_CPU_INTENSIVE);
2302
2303 /* tag the worker for identification in schedule() */
2304 worker->last_func = worker->current_func;
2305
2306 /* we're done with it, release */
2307 hash_del(&worker->hentry);
2308 worker->current_work = NULL;
2309 worker->current_func = NULL;
2310 worker->current_pwq = NULL;
2311 pwq_dec_nr_in_flight(pwq, work_color);
2312}
2313
2314/**
2315 * process_scheduled_works - process scheduled works
2316 * @worker: self
2317 *
2318 * Process all scheduled works. Please note that the scheduled list
2319 * may change while processing a work, so this function repeatedly
2320 * fetches a work from the top and executes it.
2321 *
2322 * CONTEXT:
2323 * spin_lock_irq(pool->lock) which may be released and regrabbed
2324 * multiple times.
2325 */
2326static void process_scheduled_works(struct worker *worker)
2327{
2328 while (!list_empty(&worker->scheduled)) {
2329 struct work_struct *work = list_first_entry(&worker->scheduled,
2330 struct work_struct, entry);
2331 process_one_work(worker, work);
2332 }
2333}
2334
2335static void set_pf_worker(bool val)
2336{
2337 mutex_lock(&wq_pool_attach_mutex);
2338 if (val)
2339 current->flags |= PF_WQ_WORKER;
2340 else
2341 current->flags &= ~PF_WQ_WORKER;
2342 mutex_unlock(&wq_pool_attach_mutex);
2343}
2344
2345/**
2346 * worker_thread - the worker thread function
2347 * @__worker: self
2348 *
2349 * The worker thread function. All workers belong to a worker_pool -
2350 * either a per-cpu one or dynamic unbound one. These workers process all
2351 * work items regardless of their specific target workqueue. The only
2352 * exception is work items which belong to workqueues with a rescuer which
2353 * will be explained in rescuer_thread().
2354 *
2355 * Return: 0
2356 */
2357static int worker_thread(void *__worker)
2358{
2359 struct worker *worker = __worker;
2360 struct worker_pool *pool = worker->pool;
2361
2362 /* tell the scheduler that this is a workqueue worker */
2363 set_pf_worker(true);
2364woke_up:
2365 spin_lock_irq(&pool->lock);
2366
2367 /* am I supposed to die? */
2368 if (unlikely(worker->flags & WORKER_DIE)) {
2369 spin_unlock_irq(&pool->lock);
2370 WARN_ON_ONCE(!list_empty(&worker->entry));
2371 set_pf_worker(false);
2372
2373 set_task_comm(worker->task, "kworker/dying");
2374 ida_simple_remove(&pool->worker_ida, worker->id);
2375 worker_detach_from_pool(worker);
2376 kfree(worker);
2377 return 0;
2378 }
2379
2380 worker_leave_idle(worker);
2381recheck:
2382 /* no more worker necessary? */
2383 if (!need_more_worker(pool))
2384 goto sleep;
2385
2386 /* do we need to manage? */
2387 if (unlikely(!may_start_working(pool)) && manage_workers(worker))
2388 goto recheck;
2389
2390 /*
2391 * ->scheduled list can only be filled while a worker is
2392 * preparing to process a work or actually processing it.
2393 * Make sure nobody diddled with it while I was sleeping.
2394 */
2395 WARN_ON_ONCE(!list_empty(&worker->scheduled));
2396
2397 /*
2398 * Finish PREP stage. We're guaranteed to have at least one idle
2399 * worker or that someone else has already assumed the manager
2400 * role. This is where @worker starts participating in concurrency
2401 * management if applicable and concurrency management is restored
2402 * after being rebound. See rebind_workers() for details.
2403 */
2404 worker_clr_flags(worker, WORKER_PREP | WORKER_REBOUND);
2405
2406 do {
2407 struct work_struct *work =
2408 list_first_entry(&pool->worklist,
2409 struct work_struct, entry);
2410
2411 pool->watchdog_ts = jiffies;
2412
2413 if (likely(!(*work_data_bits(work) & WORK_STRUCT_LINKED))) {
2414 /* optimization path, not strictly necessary */
2415 process_one_work(worker, work);
2416 if (unlikely(!list_empty(&worker->scheduled)))
2417 process_scheduled_works(worker);
2418 } else {
2419 move_linked_works(work, &worker->scheduled, NULL);
2420 process_scheduled_works(worker);
2421 }
2422 } while (keep_working(pool));
2423
2424 worker_set_flags(worker, WORKER_PREP);
2425sleep:
2426 /*
2427 * pool->lock is held and there's no work to process and no need to
2428 * manage, sleep. Workers are woken up only while holding
2429 * pool->lock or from local cpu, so setting the current state
2430 * before releasing pool->lock is enough to prevent losing any
2431 * event.
2432 */
2433 worker_enter_idle(worker);
2434 __set_current_state(TASK_IDLE);
2435 spin_unlock_irq(&pool->lock);
2436 schedule();
2437 goto woke_up;
2438}
2439
2440/**
2441 * rescuer_thread - the rescuer thread function
2442 * @__rescuer: self
2443 *
2444 * Workqueue rescuer thread function. There's one rescuer for each
2445 * workqueue which has WQ_MEM_RECLAIM set.
2446 *
2447 * Regular work processing on a pool may block trying to create a new
2448 * worker which uses GFP_KERNEL allocation which has slight chance of
2449 * developing into deadlock if some works currently on the same queue
2450 * need to be processed to satisfy the GFP_KERNEL allocation. This is
2451 * the problem rescuer solves.
2452 *
2453 * When such condition is possible, the pool summons rescuers of all
2454 * workqueues which have works queued on the pool and let them process
2455 * those works so that forward progress can be guaranteed.
2456 *
2457 * This should happen rarely.
2458 *
2459 * Return: 0
2460 */
2461static int rescuer_thread(void *__rescuer)
2462{
2463 struct worker *rescuer = __rescuer;
2464 struct workqueue_struct *wq = rescuer->rescue_wq;
2465 struct list_head *scheduled = &rescuer->scheduled;
2466 bool should_stop;
2467
2468 set_user_nice(current, RESCUER_NICE_LEVEL);
2469
2470 /*
2471 * Mark rescuer as worker too. As WORKER_PREP is never cleared, it
2472 * doesn't participate in concurrency management.
2473 */
2474 set_pf_worker(true);
2475repeat:
2476 set_current_state(TASK_IDLE);
2477
2478 /*
2479 * By the time the rescuer is requested to stop, the workqueue
2480 * shouldn't have any work pending, but @wq->maydays may still have
2481 * pwq(s) queued. This can happen by non-rescuer workers consuming
2482 * all the work items before the rescuer got to them. Go through
2483 * @wq->maydays processing before acting on should_stop so that the
2484 * list is always empty on exit.
2485 */
2486 should_stop = kthread_should_stop();
2487
2488 /* see whether any pwq is asking for help */
2489 spin_lock_irq(&wq_mayday_lock);
2490
2491 while (!list_empty(&wq->maydays)) {
2492 struct pool_workqueue *pwq = list_first_entry(&wq->maydays,
2493 struct pool_workqueue, mayday_node);
2494 struct worker_pool *pool = pwq->pool;
2495 struct work_struct *work, *n;
2496 bool first = true;
2497
2498 __set_current_state(TASK_RUNNING);
2499 list_del_init(&pwq->mayday_node);
2500
2501 spin_unlock_irq(&wq_mayday_lock);
2502
2503 worker_attach_to_pool(rescuer, pool);
2504
2505 spin_lock_irq(&pool->lock);
2506
2507 /*
2508 * Slurp in all works issued via this workqueue and
2509 * process'em.
2510 */
2511 WARN_ON_ONCE(!list_empty(scheduled));
2512 list_for_each_entry_safe(work, n, &pool->worklist, entry) {
2513 if (get_work_pwq(work) == pwq) {
2514 if (first)
2515 pool->watchdog_ts = jiffies;
2516 move_linked_works(work, scheduled, &n);
2517 }
2518 first = false;
2519 }
2520
2521 if (!list_empty(scheduled)) {
2522 process_scheduled_works(rescuer);
2523
2524 /*
2525 * The above execution of rescued work items could
2526 * have created more to rescue through
2527 * pwq_activate_first_delayed() or chained
2528 * queueing. Let's put @pwq back on mayday list so
2529 * that such back-to-back work items, which may be
2530 * being used to relieve memory pressure, don't
2531 * incur MAYDAY_INTERVAL delay inbetween.
2532 */
2533 if (need_to_create_worker(pool)) {
2534 spin_lock(&wq_mayday_lock);
2535 get_pwq(pwq);
2536 list_move_tail(&pwq->mayday_node, &wq->maydays);
2537 spin_unlock(&wq_mayday_lock);
2538 }
2539 }
2540
2541 /*
2542 * Put the reference grabbed by send_mayday(). @pool won't
2543 * go away while we're still attached to it.
2544 */
2545 put_pwq(pwq);
2546
2547 /*
2548 * Leave this pool. If need_more_worker() is %true, notify a
2549 * regular worker; otherwise, we end up with 0 concurrency
2550 * and stalling the execution.
2551 */
2552 if (need_more_worker(pool))
2553 wake_up_worker(pool);
2554
2555 spin_unlock_irq(&pool->lock);
2556
2557 worker_detach_from_pool(rescuer);
2558
2559 spin_lock_irq(&wq_mayday_lock);
2560 }
2561
2562 spin_unlock_irq(&wq_mayday_lock);
2563
2564 if (should_stop) {
2565 __set_current_state(TASK_RUNNING);
2566 set_pf_worker(false);
2567 return 0;
2568 }
2569
2570 /* rescuers should never participate in concurrency management */
2571 WARN_ON_ONCE(!(rescuer->flags & WORKER_NOT_RUNNING));
2572 schedule();
2573 goto repeat;
2574}
2575
2576/**
2577 * check_flush_dependency - check for flush dependency sanity
2578 * @target_wq: workqueue being flushed
2579 * @target_work: work item being flushed (NULL for workqueue flushes)
2580 *
2581 * %current is trying to flush the whole @target_wq or @target_work on it.
2582 * If @target_wq doesn't have %WQ_MEM_RECLAIM, verify that %current is not
2583 * reclaiming memory or running on a workqueue which doesn't have
2584 * %WQ_MEM_RECLAIM as that can break forward-progress guarantee leading to
2585 * a deadlock.
2586 */
2587static void check_flush_dependency(struct workqueue_struct *target_wq,
2588 struct work_struct *target_work)
2589{
2590 work_func_t target_func = target_work ? target_work->func : NULL;
2591 struct worker *worker;
2592
2593 if (target_wq->flags & WQ_MEM_RECLAIM)
2594 return;
2595
2596 worker = current_wq_worker();
2597
2598 WARN_ONCE(current->flags & PF_MEMALLOC,
2599 "workqueue: PF_MEMALLOC task %d(%s) is flushing !WQ_MEM_RECLAIM %s:%ps",
2600 current->pid, current->comm, target_wq->name, target_func);
2601 WARN_ONCE(worker && ((worker->current_pwq->wq->flags &
2602 (WQ_MEM_RECLAIM | __WQ_LEGACY)) == WQ_MEM_RECLAIM),
2603 "workqueue: WQ_MEM_RECLAIM %s:%ps is flushing !WQ_MEM_RECLAIM %s:%ps",
2604 worker->current_pwq->wq->name, worker->current_func,
2605 target_wq->name, target_func);
2606}
2607
2608struct wq_barrier {
2609 struct work_struct work;
2610 struct completion done;
2611 struct task_struct *task; /* purely informational */
2612};
2613
2614static void wq_barrier_func(struct work_struct *work)
2615{
2616 struct wq_barrier *barr = container_of(work, struct wq_barrier, work);
2617 complete(&barr->done);
2618}
2619
2620/**
2621 * insert_wq_barrier - insert a barrier work
2622 * @pwq: pwq to insert barrier into
2623 * @barr: wq_barrier to insert
2624 * @target: target work to attach @barr to
2625 * @worker: worker currently executing @target, NULL if @target is not executing
2626 *
2627 * @barr is linked to @target such that @barr is completed only after
2628 * @target finishes execution. Please note that the ordering
2629 * guarantee is observed only with respect to @target and on the local
2630 * cpu.
2631 *
2632 * Currently, a queued barrier can't be canceled. This is because
2633 * try_to_grab_pending() can't determine whether the work to be
2634 * grabbed is at the head of the queue and thus can't clear LINKED
2635 * flag of the previous work while there must be a valid next work
2636 * after a work with LINKED flag set.
2637 *
2638 * Note that when @worker is non-NULL, @target may be modified
2639 * underneath us, so we can't reliably determine pwq from @target.
2640 *
2641 * CONTEXT:
2642 * spin_lock_irq(pool->lock).
2643 */
2644static void insert_wq_barrier(struct pool_workqueue *pwq,
2645 struct wq_barrier *barr,
2646 struct work_struct *target, struct worker *worker)
2647{
2648 struct list_head *head;
2649 unsigned int linked = 0;
2650
2651 /*
2652 * debugobject calls are safe here even with pool->lock locked
2653 * as we know for sure that this will not trigger any of the
2654 * checks and call back into the fixup functions where we
2655 * might deadlock.
2656 */
2657 INIT_WORK_ONSTACK(&barr->work, wq_barrier_func);
2658 __set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(&barr->work));
2659
2660 init_completion_map(&barr->done, &target->lockdep_map);
2661
2662 barr->task = current;
2663
2664 /*
2665 * If @target is currently being executed, schedule the
2666 * barrier to the worker; otherwise, put it after @target.
2667 */
2668 if (worker)
2669 head = worker->scheduled.next;
2670 else {
2671 unsigned long *bits = work_data_bits(target);
2672
2673 head = target->entry.next;
2674 /* there can already be other linked works, inherit and set */
2675 linked = *bits & WORK_STRUCT_LINKED;
2676 __set_bit(WORK_STRUCT_LINKED_BIT, bits);
2677 }
2678
2679 debug_work_activate(&barr->work);
2680 insert_work(pwq, &barr->work, head,
2681 work_color_to_flags(WORK_NO_COLOR) | linked);
2682}
2683
2684/**
2685 * flush_workqueue_prep_pwqs - prepare pwqs for workqueue flushing
2686 * @wq: workqueue being flushed
2687 * @flush_color: new flush color, < 0 for no-op
2688 * @work_color: new work color, < 0 for no-op
2689 *
2690 * Prepare pwqs for workqueue flushing.
2691 *
2692 * If @flush_color is non-negative, flush_color on all pwqs should be
2693 * -1. If no pwq has in-flight commands at the specified color, all
2694 * pwq->flush_color's stay at -1 and %false is returned. If any pwq
2695 * has in flight commands, its pwq->flush_color is set to
2696 * @flush_color, @wq->nr_pwqs_to_flush is updated accordingly, pwq
2697 * wakeup logic is armed and %true is returned.
2698 *
2699 * The caller should have initialized @wq->first_flusher prior to
2700 * calling this function with non-negative @flush_color. If
2701 * @flush_color is negative, no flush color update is done and %false
2702 * is returned.
2703 *
2704 * If @work_color is non-negative, all pwqs should have the same
2705 * work_color which is previous to @work_color and all will be
2706 * advanced to @work_color.
2707 *
2708 * CONTEXT:
2709 * mutex_lock(wq->mutex).
2710 *
2711 * Return:
2712 * %true if @flush_color >= 0 and there's something to flush. %false
2713 * otherwise.
2714 */
2715static bool flush_workqueue_prep_pwqs(struct workqueue_struct *wq,
2716 int flush_color, int work_color)
2717{
2718 bool wait = false;
2719 struct pool_workqueue *pwq;
2720
2721 if (flush_color >= 0) {
2722 WARN_ON_ONCE(atomic_read(&wq->nr_pwqs_to_flush));
2723 atomic_set(&wq->nr_pwqs_to_flush, 1);
2724 }
2725
2726 for_each_pwq(pwq, wq) {
2727 struct worker_pool *pool = pwq->pool;
2728
2729 spin_lock_irq(&pool->lock);
2730
2731 if (flush_color >= 0) {
2732 WARN_ON_ONCE(pwq->flush_color != -1);
2733
2734 if (pwq->nr_in_flight[flush_color]) {
2735 pwq->flush_color = flush_color;
2736 atomic_inc(&wq->nr_pwqs_to_flush);
2737 wait = true;
2738 }
2739 }
2740
2741 if (work_color >= 0) {
2742 WARN_ON_ONCE(work_color != work_next_color(pwq->work_color));
2743 pwq->work_color = work_color;
2744 }
2745
2746 spin_unlock_irq(&pool->lock);
2747 }
2748
2749 if (flush_color >= 0 && atomic_dec_and_test(&wq->nr_pwqs_to_flush))
2750 complete(&wq->first_flusher->done);
2751
2752 return wait;
2753}
2754
2755/**
2756 * flush_workqueue - ensure that any scheduled work has run to completion.
2757 * @wq: workqueue to flush
2758 *
2759 * This function sleeps until all work items which were queued on entry
2760 * have finished execution, but it is not livelocked by new incoming ones.
2761 */
2762void flush_workqueue(struct workqueue_struct *wq)
2763{
2764 struct wq_flusher this_flusher = {
2765 .list = LIST_HEAD_INIT(this_flusher.list),
2766 .flush_color = -1,
2767 .done = COMPLETION_INITIALIZER_ONSTACK_MAP(this_flusher.done, wq->lockdep_map),
2768 };
2769 int next_color;
2770
2771 if (WARN_ON(!wq_online))
2772 return;
2773
2774 lock_map_acquire(&wq->lockdep_map);
2775 lock_map_release(&wq->lockdep_map);
2776
2777 mutex_lock(&wq->mutex);
2778
2779 /*
2780 * Start-to-wait phase
2781 */
2782 next_color = work_next_color(wq->work_color);
2783
2784 if (next_color != wq->flush_color) {
2785 /*
2786 * Color space is not full. The current work_color
2787 * becomes our flush_color and work_color is advanced
2788 * by one.
2789 */
2790 WARN_ON_ONCE(!list_empty(&wq->flusher_overflow));
2791 this_flusher.flush_color = wq->work_color;
2792 wq->work_color = next_color;
2793
2794 if (!wq->first_flusher) {
2795 /* no flush in progress, become the first flusher */
2796 WARN_ON_ONCE(wq->flush_color != this_flusher.flush_color);
2797
2798 wq->first_flusher = &this_flusher;
2799
2800 if (!flush_workqueue_prep_pwqs(wq, wq->flush_color,
2801 wq->work_color)) {
2802 /* nothing to flush, done */
2803 wq->flush_color = next_color;
2804 wq->first_flusher = NULL;
2805 goto out_unlock;
2806 }
2807 } else {
2808 /* wait in queue */
2809 WARN_ON_ONCE(wq->flush_color == this_flusher.flush_color);
2810 list_add_tail(&this_flusher.list, &wq->flusher_queue);
2811 flush_workqueue_prep_pwqs(wq, -1, wq->work_color);
2812 }
2813 } else {
2814 /*
2815 * Oops, color space is full, wait on overflow queue.
2816 * The next flush completion will assign us
2817 * flush_color and transfer to flusher_queue.
2818 */
2819 list_add_tail(&this_flusher.list, &wq->flusher_overflow);
2820 }
2821
2822 check_flush_dependency(wq, NULL);
2823
2824 mutex_unlock(&wq->mutex);
2825
2826 wait_for_completion(&this_flusher.done);
2827
2828 /*
2829 * Wake-up-and-cascade phase
2830 *
2831 * First flushers are responsible for cascading flushes and
2832 * handling overflow. Non-first flushers can simply return.
2833 */
2834 if (wq->first_flusher != &this_flusher)
2835 return;
2836
2837 mutex_lock(&wq->mutex);
2838
2839 /* we might have raced, check again with mutex held */
2840 if (wq->first_flusher != &this_flusher)
2841 goto out_unlock;
2842
2843 wq->first_flusher = NULL;
2844
2845 WARN_ON_ONCE(!list_empty(&this_flusher.list));
2846 WARN_ON_ONCE(wq->flush_color != this_flusher.flush_color);
2847
2848 while (true) {
2849 struct wq_flusher *next, *tmp;
2850
2851 /* complete all the flushers sharing the current flush color */
2852 list_for_each_entry_safe(next, tmp, &wq->flusher_queue, list) {
2853 if (next->flush_color != wq->flush_color)
2854 break;
2855 list_del_init(&next->list);
2856 complete(&next->done);
2857 }
2858
2859 WARN_ON_ONCE(!list_empty(&wq->flusher_overflow) &&
2860 wq->flush_color != work_next_color(wq->work_color));
2861
2862 /* this flush_color is finished, advance by one */
2863 wq->flush_color = work_next_color(wq->flush_color);
2864
2865 /* one color has been freed, handle overflow queue */
2866 if (!list_empty(&wq->flusher_overflow)) {
2867 /*
2868 * Assign the same color to all overflowed
2869 * flushers, advance work_color and append to
2870 * flusher_queue. This is the start-to-wait
2871 * phase for these overflowed flushers.
2872 */
2873 list_for_each_entry(tmp, &wq->flusher_overflow, list)
2874 tmp->flush_color = wq->work_color;
2875
2876 wq->work_color = work_next_color(wq->work_color);
2877
2878 list_splice_tail_init(&wq->flusher_overflow,
2879 &wq->flusher_queue);
2880 flush_workqueue_prep_pwqs(wq, -1, wq->work_color);
2881 }
2882
2883 if (list_empty(&wq->flusher_queue)) {
2884 WARN_ON_ONCE(wq->flush_color != wq->work_color);
2885 break;
2886 }
2887
2888 /*
2889 * Need to flush more colors. Make the next flusher
2890 * the new first flusher and arm pwqs.
2891 */
2892 WARN_ON_ONCE(wq->flush_color == wq->work_color);
2893 WARN_ON_ONCE(wq->flush_color != next->flush_color);
2894
2895 list_del_init(&next->list);
2896 wq->first_flusher = next;
2897
2898 if (flush_workqueue_prep_pwqs(wq, wq->flush_color, -1))
2899 break;
2900
2901 /*
2902 * Meh... this color is already done, clear first
2903 * flusher and repeat cascading.
2904 */
2905 wq->first_flusher = NULL;
2906 }
2907
2908out_unlock:
2909 mutex_unlock(&wq->mutex);
2910}
2911EXPORT_SYMBOL(flush_workqueue);
2912
2913/**
2914 * drain_workqueue - drain a workqueue
2915 * @wq: workqueue to drain
2916 *
2917 * Wait until the workqueue becomes empty. While draining is in progress,
2918 * only chain queueing is allowed. IOW, only currently pending or running
2919 * work items on @wq can queue further work items on it. @wq is flushed
2920 * repeatedly until it becomes empty. The number of flushing is determined
2921 * by the depth of chaining and should be relatively short. Whine if it
2922 * takes too long.
2923 */
2924void drain_workqueue(struct workqueue_struct *wq)
2925{
2926 unsigned int flush_cnt = 0;
2927 struct pool_workqueue *pwq;
2928
2929 /*
2930 * __queue_work() needs to test whether there are drainers, is much
2931 * hotter than drain_workqueue() and already looks at @wq->flags.
2932 * Use __WQ_DRAINING so that queue doesn't have to check nr_drainers.
2933 */
2934 mutex_lock(&wq->mutex);
2935 if (!wq->nr_drainers++)
2936 wq->flags |= __WQ_DRAINING;
2937 mutex_unlock(&wq->mutex);
2938reflush:
2939 flush_workqueue(wq);
2940
2941 mutex_lock(&wq->mutex);
2942
2943 for_each_pwq(pwq, wq) {
2944 bool drained;
2945
2946 spin_lock_irq(&pwq->pool->lock);
2947 drained = !pwq->nr_active && list_empty(&pwq->delayed_works);
2948 spin_unlock_irq(&pwq->pool->lock);
2949
2950 if (drained)
2951 continue;
2952
2953 if (++flush_cnt == 10 ||
2954 (flush_cnt % 100 == 0 && flush_cnt <= 1000))
2955 pr_warn("workqueue %s: drain_workqueue() isn't complete after %u tries\n",
2956 wq->name, flush_cnt);
2957
2958 mutex_unlock(&wq->mutex);
2959 goto reflush;
2960 }
2961
2962 if (!--wq->nr_drainers)
2963 wq->flags &= ~__WQ_DRAINING;
2964 mutex_unlock(&wq->mutex);
2965}
2966EXPORT_SYMBOL_GPL(drain_workqueue);
2967
2968static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr,
2969 bool from_cancel)
2970{
2971 struct worker *worker = NULL;
2972 struct worker_pool *pool;
2973 struct pool_workqueue *pwq;
2974
2975 might_sleep();
2976
2977 rcu_read_lock();
2978 pool = get_work_pool(work);
2979 if (!pool) {
2980 rcu_read_unlock();
2981 return false;
2982 }
2983
2984 spin_lock_irq(&pool->lock);
2985 /* see the comment in try_to_grab_pending() with the same code */
2986 pwq = get_work_pwq(work);
2987 if (pwq) {
2988 if (unlikely(pwq->pool != pool))
2989 goto already_gone;
2990 } else {
2991 worker = find_worker_executing_work(pool, work);
2992 if (!worker)
2993 goto already_gone;
2994 pwq = worker->current_pwq;
2995 }
2996
2997 check_flush_dependency(pwq->wq, work);
2998
2999 insert_wq_barrier(pwq, barr, work, worker);
3000 spin_unlock_irq(&pool->lock);
3001
3002 /*
3003 * Force a lock recursion deadlock when using flush_work() inside a
3004 * single-threaded or rescuer equipped workqueue.
3005 *
3006 * For single threaded workqueues the deadlock happens when the work
3007 * is after the work issuing the flush_work(). For rescuer equipped
3008 * workqueues the deadlock happens when the rescuer stalls, blocking
3009 * forward progress.
3010 */
3011 if (!from_cancel &&
3012 (pwq->wq->saved_max_active == 1 || pwq->wq->rescuer)) {
3013 lock_map_acquire(&pwq->wq->lockdep_map);
3014 lock_map_release(&pwq->wq->lockdep_map);
3015 }
3016 rcu_read_unlock();
3017 return true;
3018already_gone:
3019 spin_unlock_irq(&pool->lock);
3020 rcu_read_unlock();
3021 return false;
3022}
3023
3024static bool __flush_work(struct work_struct *work, bool from_cancel)
3025{
3026 struct wq_barrier barr;
3027
3028 if (WARN_ON(!wq_online))
3029 return false;
3030
3031 if (WARN_ON(!work->func))
3032 return false;
3033
3034 if (!from_cancel) {
3035 lock_map_acquire(&work->lockdep_map);
3036 lock_map_release(&work->lockdep_map);
3037 }
3038
3039 if (start_flush_work(work, &barr, from_cancel)) {
3040 wait_for_completion(&barr.done);
3041 destroy_work_on_stack(&barr.work);
3042 return true;
3043 } else {
3044 return false;
3045 }
3046}
3047
3048/**
3049 * flush_work - wait for a work to finish executing the last queueing instance
3050 * @work: the work to flush
3051 *
3052 * Wait until @work has finished execution. @work is guaranteed to be idle
3053 * on return if it hasn't been requeued since flush started.
3054 *
3055 * Return:
3056 * %true if flush_work() waited for the work to finish execution,
3057 * %false if it was already idle.
3058 */
3059bool flush_work(struct work_struct *work)
3060{
3061 return __flush_work(work, false);
3062}
3063EXPORT_SYMBOL_GPL(flush_work);
3064
3065struct cwt_wait {
3066 wait_queue_entry_t wait;
3067 struct work_struct *work;
3068};
3069
3070static int cwt_wakefn(wait_queue_entry_t *wait, unsigned mode, int sync, void *key)
3071{
3072 struct cwt_wait *cwait = container_of(wait, struct cwt_wait, wait);
3073
3074 if (cwait->work != key)
3075 return 0;
3076 return autoremove_wake_function(wait, mode, sync, key);
3077}
3078
3079static bool __cancel_work_timer(struct work_struct *work, bool is_dwork)
3080{
3081 static DECLARE_WAIT_QUEUE_HEAD(cancel_waitq);
3082 unsigned long flags;
3083 int ret;
3084
3085 do {
3086 ret = try_to_grab_pending(work, is_dwork, &flags);
3087 /*
3088 * If someone else is already canceling, wait for it to
3089 * finish. flush_work() doesn't work for PREEMPT_NONE
3090 * because we may get scheduled between @work's completion
3091 * and the other canceling task resuming and clearing
3092 * CANCELING - flush_work() will return false immediately
3093 * as @work is no longer busy, try_to_grab_pending() will
3094 * return -ENOENT as @work is still being canceled and the
3095 * other canceling task won't be able to clear CANCELING as
3096 * we're hogging the CPU.
3097 *
3098 * Let's wait for completion using a waitqueue. As this
3099 * may lead to the thundering herd problem, use a custom
3100 * wake function which matches @work along with exclusive
3101 * wait and wakeup.
3102 */
3103 if (unlikely(ret == -ENOENT)) {
3104 struct cwt_wait cwait;
3105
3106 init_wait(&cwait.wait);
3107 cwait.wait.func = cwt_wakefn;
3108 cwait.work = work;
3109
3110 prepare_to_wait_exclusive(&cancel_waitq, &cwait.wait,
3111 TASK_UNINTERRUPTIBLE);
3112 if (work_is_canceling(work))
3113 schedule();
3114 finish_wait(&cancel_waitq, &cwait.wait);
3115 }
3116 } while (unlikely(ret < 0));
3117
3118 /* tell other tasks trying to grab @work to back off */
3119 mark_work_canceling(work);
3120 local_irq_restore(flags);
3121
3122 /*
3123 * This allows canceling during early boot. We know that @work
3124 * isn't executing.
3125 */
3126 if (wq_online)
3127 __flush_work(work, true);
3128
3129 clear_work_data(work);
3130
3131 /*
3132 * Paired with prepare_to_wait() above so that either
3133 * waitqueue_active() is visible here or !work_is_canceling() is
3134 * visible there.
3135 */
3136 smp_mb();
3137 if (waitqueue_active(&cancel_waitq))
3138 __wake_up(&cancel_waitq, TASK_NORMAL, 1, work);
3139
3140 return ret;
3141}
3142
3143/**
3144 * cancel_work_sync - cancel a work and wait for it to finish
3145 * @work: the work to cancel
3146 *
3147 * Cancel @work and wait for its execution to finish. This function
3148 * can be used even if the work re-queues itself or migrates to
3149 * another workqueue. On return from this function, @work is
3150 * guaranteed to be not pending or executing on any CPU.
3151 *
3152 * cancel_work_sync(&delayed_work->work) must not be used for
3153 * delayed_work's. Use cancel_delayed_work_sync() instead.
3154 *
3155 * The caller must ensure that the workqueue on which @work was last
3156 * queued can't be destroyed before this function returns.
3157 *
3158 * Return:
3159 * %true if @work was pending, %false otherwise.
3160 */
3161bool cancel_work_sync(struct work_struct *work)
3162{
3163 return __cancel_work_timer(work, false);
3164}
3165EXPORT_SYMBOL_GPL(cancel_work_sync);
3166
3167/**
3168 * flush_delayed_work - wait for a dwork to finish executing the last queueing
3169 * @dwork: the delayed work to flush
3170 *
3171 * Delayed timer is cancelled and the pending work is queued for
3172 * immediate execution. Like flush_work(), this function only
3173 * considers the last queueing instance of @dwork.
3174 *
3175 * Return:
3176 * %true if flush_work() waited for the work to finish execution,
3177 * %false if it was already idle.
3178 */
3179bool flush_delayed_work(struct delayed_work *dwork)
3180{
3181 local_irq_disable();
3182 if (del_timer_sync(&dwork->timer))
3183 __queue_work(dwork->cpu, dwork->wq, &dwork->work);
3184 local_irq_enable();
3185 return flush_work(&dwork->work);
3186}
3187EXPORT_SYMBOL(flush_delayed_work);
3188
3189/**
3190 * flush_rcu_work - wait for a rwork to finish executing the last queueing
3191 * @rwork: the rcu work to flush
3192 *
3193 * Return:
3194 * %true if flush_rcu_work() waited for the work to finish execution,
3195 * %false if it was already idle.
3196 */
3197bool flush_rcu_work(struct rcu_work *rwork)
3198{
3199 if (test_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(&rwork->work))) {
3200 rcu_barrier();
3201 flush_work(&rwork->work);
3202 return true;
3203 } else {
3204 return flush_work(&rwork->work);
3205 }
3206}
3207EXPORT_SYMBOL(flush_rcu_work);
3208
3209static bool __cancel_work(struct work_struct *work, bool is_dwork)
3210{
3211 unsigned long flags;
3212 int ret;
3213
3214 do {
3215 ret = try_to_grab_pending(work, is_dwork, &flags);
3216 } while (unlikely(ret == -EAGAIN));
3217
3218 if (unlikely(ret < 0))
3219 return false;
3220
3221 set_work_pool_and_clear_pending(work, get_work_pool_id(work));
3222 local_irq_restore(flags);
3223 return ret;
3224}
3225
3226/**
3227 * cancel_delayed_work - cancel a delayed work
3228 * @dwork: delayed_work to cancel
3229 *
3230 * Kill off a pending delayed_work.
3231 *
3232 * Return: %true if @dwork was pending and canceled; %false if it wasn't
3233 * pending.
3234 *
3235 * Note:
3236 * The work callback function may still be running on return, unless
3237 * it returns %true and the work doesn't re-arm itself. Explicitly flush or
3238 * use cancel_delayed_work_sync() to wait on it.
3239 *
3240 * This function is safe to call from any context including IRQ handler.
3241 */
3242bool cancel_delayed_work(struct delayed_work *dwork)
3243{
3244 return __cancel_work(&dwork->work, true);
3245}
3246EXPORT_SYMBOL(cancel_delayed_work);
3247
3248/**
3249 * cancel_delayed_work_sync - cancel a delayed work and wait for it to finish
3250 * @dwork: the delayed work cancel
3251 *
3252 * This is cancel_work_sync() for delayed works.
3253 *
3254 * Return:
3255 * %true if @dwork was pending, %false otherwise.
3256 */
3257bool cancel_delayed_work_sync(struct delayed_work *dwork)
3258{
3259 return __cancel_work_timer(&dwork->work, true);
3260}
3261EXPORT_SYMBOL(cancel_delayed_work_sync);
3262
3263/**
3264 * schedule_on_each_cpu - execute a function synchronously on each online CPU
3265 * @func: the function to call
3266 *
3267 * schedule_on_each_cpu() executes @func on each online CPU using the
3268 * system workqueue and blocks until all CPUs have completed.
3269 * schedule_on_each_cpu() is very slow.
3270 *
3271 * Return:
3272 * 0 on success, -errno on failure.
3273 */
3274int schedule_on_each_cpu(work_func_t func)
3275{
3276 int cpu;
3277 struct work_struct __percpu *works;
3278
3279 works = alloc_percpu(struct work_struct);
3280 if (!works)
3281 return -ENOMEM;
3282
3283 get_online_cpus();
3284
3285 for_each_online_cpu(cpu) {
3286 struct work_struct *work = per_cpu_ptr(works, cpu);
3287
3288 INIT_WORK(work, func);
3289 schedule_work_on(cpu, work);
3290 }
3291
3292 for_each_online_cpu(cpu)
3293 flush_work(per_cpu_ptr(works, cpu));
3294
3295 put_online_cpus();
3296 free_percpu(works);
3297 return 0;
3298}
3299
3300/**
3301 * execute_in_process_context - reliably execute the routine with user context
3302 * @fn: the function to execute
3303 * @ew: guaranteed storage for the execute work structure (must
3304 * be available when the work executes)
3305 *
3306 * Executes the function immediately if process context is available,
3307 * otherwise schedules the function for delayed execution.
3308 *
3309 * Return: 0 - function was executed
3310 * 1 - function was scheduled for execution
3311 */
3312int execute_in_process_context(work_func_t fn, struct execute_work *ew)
3313{
3314 if (!in_interrupt()) {
3315 fn(&ew->work);
3316 return 0;
3317 }
3318
3319 INIT_WORK(&ew->work, fn);
3320 schedule_work(&ew->work);
3321
3322 return 1;
3323}
3324EXPORT_SYMBOL_GPL(execute_in_process_context);
3325
3326/**
3327 * free_workqueue_attrs - free a workqueue_attrs
3328 * @attrs: workqueue_attrs to free
3329 *
3330 * Undo alloc_workqueue_attrs().
3331 */
3332void free_workqueue_attrs(struct workqueue_attrs *attrs)
3333{
3334 if (attrs) {
3335 free_cpumask_var(attrs->cpumask);
3336 kfree(attrs);
3337 }
3338}
3339
3340/**
3341 * alloc_workqueue_attrs - allocate a workqueue_attrs
3342 *
3343 * Allocate a new workqueue_attrs, initialize with default settings and
3344 * return it.
3345 *
3346 * Return: The allocated new workqueue_attr on success. %NULL on failure.
3347 */
3348struct workqueue_attrs *alloc_workqueue_attrs(void)
3349{
3350 struct workqueue_attrs *attrs;
3351
3352 attrs = kzalloc(sizeof(*attrs), GFP_KERNEL);
3353 if (!attrs)
3354 goto fail;
3355 if (!alloc_cpumask_var(&attrs->cpumask, GFP_KERNEL))
3356 goto fail;
3357
3358 cpumask_copy(attrs->cpumask, cpu_possible_mask);
3359 return attrs;
3360fail:
3361 free_workqueue_attrs(attrs);
3362 return NULL;
3363}
3364
3365static void copy_workqueue_attrs(struct workqueue_attrs *to,
3366 const struct workqueue_attrs *from)
3367{
3368 to->nice = from->nice;
3369 cpumask_copy(to->cpumask, from->cpumask);
3370 /*
3371 * Unlike hash and equality test, this function doesn't ignore
3372 * ->no_numa as it is used for both pool and wq attrs. Instead,
3373 * get_unbound_pool() explicitly clears ->no_numa after copying.
3374 */
3375 to->no_numa = from->no_numa;
3376}
3377
3378/* hash value of the content of @attr */
3379static u32 wqattrs_hash(const struct workqueue_attrs *attrs)
3380{
3381 u32 hash = 0;
3382
3383 hash = jhash_1word(attrs->nice, hash);
3384 hash = jhash(cpumask_bits(attrs->cpumask),
3385 BITS_TO_LONGS(nr_cpumask_bits) * sizeof(long), hash);
3386 return hash;
3387}
3388
3389/* content equality test */
3390static bool wqattrs_equal(const struct workqueue_attrs *a,
3391 const struct workqueue_attrs *b)
3392{
3393 if (a->nice != b->nice)
3394 return false;
3395 if (!cpumask_equal(a->cpumask, b->cpumask))
3396 return false;
3397 return true;
3398}
3399
3400/**
3401 * init_worker_pool - initialize a newly zalloc'd worker_pool
3402 * @pool: worker_pool to initialize
3403 *
3404 * Initialize a newly zalloc'd @pool. It also allocates @pool->attrs.
3405 *
3406 * Return: 0 on success, -errno on failure. Even on failure, all fields
3407 * inside @pool proper are initialized and put_unbound_pool() can be called
3408 * on @pool safely to release it.
3409 */
3410static int init_worker_pool(struct worker_pool *pool)
3411{
3412 spin_lock_init(&pool->lock);
3413 pool->id = -1;
3414 pool->cpu = -1;
3415 pool->node = NUMA_NO_NODE;
3416 pool->flags |= POOL_DISASSOCIATED;
3417 pool->watchdog_ts = jiffies;
3418 INIT_LIST_HEAD(&pool->worklist);
3419 INIT_LIST_HEAD(&pool->idle_list);
3420 hash_init(pool->busy_hash);
3421
3422 timer_setup(&pool->idle_timer, idle_worker_timeout, TIMER_DEFERRABLE);
3423
3424 timer_setup(&pool->mayday_timer, pool_mayday_timeout, 0);
3425
3426 INIT_LIST_HEAD(&pool->workers);
3427
3428 ida_init(&pool->worker_ida);
3429 INIT_HLIST_NODE(&pool->hash_node);
3430 pool->refcnt = 1;
3431
3432 /* shouldn't fail above this point */
3433 pool->attrs = alloc_workqueue_attrs();
3434 if (!pool->attrs)
3435 return -ENOMEM;
3436 return 0;
3437}
3438
3439#ifdef CONFIG_LOCKDEP
3440static void wq_init_lockdep(struct workqueue_struct *wq)
3441{
3442 char *lock_name;
3443
3444 lockdep_register_key(&wq->key);
3445 lock_name = kasprintf(GFP_KERNEL, "%s%s", "(wq_completion)", wq->name);
3446 if (!lock_name)
3447 lock_name = wq->name;
3448
3449 wq->lock_name = lock_name;
3450 lockdep_init_map(&wq->lockdep_map, lock_name, &wq->key, 0);
3451}
3452
3453static void wq_unregister_lockdep(struct workqueue_struct *wq)
3454{
3455 lockdep_unregister_key(&wq->key);
3456}
3457
3458static void wq_free_lockdep(struct workqueue_struct *wq)
3459{
3460 if (wq->lock_name != wq->name)
3461 kfree(wq->lock_name);
3462}
3463#else
3464static void wq_init_lockdep(struct workqueue_struct *wq)
3465{
3466}
3467
3468static void wq_unregister_lockdep(struct workqueue_struct *wq)
3469{
3470}
3471
3472static void wq_free_lockdep(struct workqueue_struct *wq)
3473{
3474}
3475#endif
3476
3477static void rcu_free_wq(struct rcu_head *rcu)
3478{
3479 struct workqueue_struct *wq =
3480 container_of(rcu, struct workqueue_struct, rcu);
3481
3482 wq_free_lockdep(wq);
3483
3484 if (!(wq->flags & WQ_UNBOUND))
3485 free_percpu(wq->cpu_pwqs);
3486 else
3487 free_workqueue_attrs(wq->unbound_attrs);
3488
3489 kfree(wq->rescuer);
3490 kfree(wq);
3491}
3492
3493static void rcu_free_pool(struct rcu_head *rcu)
3494{
3495 struct worker_pool *pool = container_of(rcu, struct worker_pool, rcu);
3496
3497 ida_destroy(&pool->worker_ida);
3498 free_workqueue_attrs(pool->attrs);
3499 kfree(pool);
3500}
3501
3502/**
3503 * put_unbound_pool - put a worker_pool
3504 * @pool: worker_pool to put
3505 *
3506 * Put @pool. If its refcnt reaches zero, it gets destroyed in RCU
3507 * safe manner. get_unbound_pool() calls this function on its failure path
3508 * and this function should be able to release pools which went through,
3509 * successfully or not, init_worker_pool().
3510 *
3511 * Should be called with wq_pool_mutex held.
3512 */
3513static void put_unbound_pool(struct worker_pool *pool)
3514{
3515 DECLARE_COMPLETION_ONSTACK(detach_completion);
3516 struct worker *worker;
3517
3518 lockdep_assert_held(&wq_pool_mutex);
3519
3520 if (--pool->refcnt)
3521 return;
3522
3523 /* sanity checks */
3524 if (WARN_ON(!(pool->cpu < 0)) ||
3525 WARN_ON(!list_empty(&pool->worklist)))
3526 return;
3527
3528 /* release id and unhash */
3529 if (pool->id >= 0)
3530 idr_remove(&worker_pool_idr, pool->id);
3531 hash_del(&pool->hash_node);
3532
3533 /*
3534 * Become the manager and destroy all workers. This prevents
3535 * @pool's workers from blocking on attach_mutex. We're the last
3536 * manager and @pool gets freed with the flag set.
3537 */
3538 spin_lock_irq(&pool->lock);
3539 wait_event_lock_irq(wq_manager_wait,
3540 !(pool->flags & POOL_MANAGER_ACTIVE), pool->lock);
3541 pool->flags |= POOL_MANAGER_ACTIVE;
3542
3543 while ((worker = first_idle_worker(pool)))
3544 destroy_worker(worker);
3545 WARN_ON(pool->nr_workers || pool->nr_idle);
3546 spin_unlock_irq(&pool->lock);
3547
3548 mutex_lock(&wq_pool_attach_mutex);
3549 if (!list_empty(&pool->workers))
3550 pool->detach_completion = &detach_completion;
3551 mutex_unlock(&wq_pool_attach_mutex);
3552
3553 if (pool->detach_completion)
3554 wait_for_completion(pool->detach_completion);
3555
3556 /* shut down the timers */
3557 del_timer_sync(&pool->idle_timer);
3558 del_timer_sync(&pool->mayday_timer);
3559
3560 /* RCU protected to allow dereferences from get_work_pool() */
3561 call_rcu(&pool->rcu, rcu_free_pool);
3562}
3563
3564/**
3565 * get_unbound_pool - get a worker_pool with the specified attributes
3566 * @attrs: the attributes of the worker_pool to get
3567 *
3568 * Obtain a worker_pool which has the same attributes as @attrs, bump the
3569 * reference count and return it. If there already is a matching
3570 * worker_pool, it will be used; otherwise, this function attempts to
3571 * create a new one.
3572 *
3573 * Should be called with wq_pool_mutex held.
3574 *
3575 * Return: On success, a worker_pool with the same attributes as @attrs.
3576 * On failure, %NULL.
3577 */
3578static struct worker_pool *get_unbound_pool(const struct workqueue_attrs *attrs)
3579{
3580 u32 hash = wqattrs_hash(attrs);
3581 struct worker_pool *pool;
3582 int node;
3583 int target_node = NUMA_NO_NODE;
3584
3585 lockdep_assert_held(&wq_pool_mutex);
3586
3587 /* do we already have a matching pool? */
3588 hash_for_each_possible(unbound_pool_hash, pool, hash_node, hash) {
3589 if (wqattrs_equal(pool->attrs, attrs)) {
3590 pool->refcnt++;
3591 return pool;
3592 }
3593 }
3594
3595 /* if cpumask is contained inside a NUMA node, we belong to that node */
3596 if (wq_numa_enabled) {
3597 for_each_node(node) {
3598 if (cpumask_subset(attrs->cpumask,
3599 wq_numa_possible_cpumask[node])) {
3600 target_node = node;
3601 break;
3602 }
3603 }
3604 }
3605
3606 /* nope, create a new one */
3607 pool = kzalloc_node(sizeof(*pool), GFP_KERNEL, target_node);
3608 if (!pool || init_worker_pool(pool) < 0)
3609 goto fail;
3610
3611 lockdep_set_subclass(&pool->lock, 1); /* see put_pwq() */
3612 copy_workqueue_attrs(pool->attrs, attrs);
3613 pool->node = target_node;
3614
3615 /*
3616 * no_numa isn't a worker_pool attribute, always clear it. See
3617 * 'struct workqueue_attrs' comments for detail.
3618 */
3619 pool->attrs->no_numa = false;
3620
3621 if (worker_pool_assign_id(pool) < 0)
3622 goto fail;
3623
3624 /* create and start the initial worker */
3625 if (wq_online && !create_worker(pool))
3626 goto fail;
3627
3628 /* install */
3629 hash_add(unbound_pool_hash, &pool->hash_node, hash);
3630
3631 return pool;
3632fail:
3633 if (pool)
3634 put_unbound_pool(pool);
3635 return NULL;
3636}
3637
3638static void rcu_free_pwq(struct rcu_head *rcu)
3639{
3640 kmem_cache_free(pwq_cache,
3641 container_of(rcu, struct pool_workqueue, rcu));
3642}
3643
3644/*
3645 * Scheduled on system_wq by put_pwq() when an unbound pwq hits zero refcnt
3646 * and needs to be destroyed.
3647 */
3648static void pwq_unbound_release_workfn(struct work_struct *work)
3649{
3650 struct pool_workqueue *pwq = container_of(work, struct pool_workqueue,
3651 unbound_release_work);
3652 struct workqueue_struct *wq = pwq->wq;
3653 struct worker_pool *pool = pwq->pool;
3654 bool is_last;
3655
3656 if (WARN_ON_ONCE(!(wq->flags & WQ_UNBOUND)))
3657 return;
3658
3659 mutex_lock(&wq->mutex);
3660 list_del_rcu(&pwq->pwqs_node);
3661 is_last = list_empty(&wq->pwqs);
3662 mutex_unlock(&wq->mutex);
3663
3664 mutex_lock(&wq_pool_mutex);
3665 put_unbound_pool(pool);
3666 mutex_unlock(&wq_pool_mutex);
3667
3668 call_rcu(&pwq->rcu, rcu_free_pwq);
3669
3670 /*
3671 * If we're the last pwq going away, @wq is already dead and no one
3672 * is gonna access it anymore. Schedule RCU free.
3673 */
3674 if (is_last) {
3675 wq_unregister_lockdep(wq);
3676 call_rcu(&wq->rcu, rcu_free_wq);
3677 }
3678}
3679
3680/**
3681 * pwq_adjust_max_active - update a pwq's max_active to the current setting
3682 * @pwq: target pool_workqueue
3683 *
3684 * If @pwq isn't freezing, set @pwq->max_active to the associated
3685 * workqueue's saved_max_active and activate delayed work items
3686 * accordingly. If @pwq is freezing, clear @pwq->max_active to zero.
3687 */
3688static void pwq_adjust_max_active(struct pool_workqueue *pwq)
3689{
3690 struct workqueue_struct *wq = pwq->wq;
3691 bool freezable = wq->flags & WQ_FREEZABLE;
3692 unsigned long flags;
3693
3694 /* for @wq->saved_max_active */
3695 lockdep_assert_held(&wq->mutex);
3696
3697 /* fast exit for non-freezable wqs */
3698 if (!freezable && pwq->max_active == wq->saved_max_active)
3699 return;
3700
3701 /* this function can be called during early boot w/ irq disabled */
3702 spin_lock_irqsave(&pwq->pool->lock, flags);
3703
3704 /*
3705 * During [un]freezing, the caller is responsible for ensuring that
3706 * this function is called at least once after @workqueue_freezing
3707 * is updated and visible.
3708 */
3709 if (!freezable || !workqueue_freezing) {
3710 pwq->max_active = wq->saved_max_active;
3711
3712 while (!list_empty(&pwq->delayed_works) &&
3713 pwq->nr_active < pwq->max_active)
3714 pwq_activate_first_delayed(pwq);
3715
3716 /*
3717 * Need to kick a worker after thawed or an unbound wq's
3718 * max_active is bumped. It's a slow path. Do it always.
3719 */
3720 wake_up_worker(pwq->pool);
3721 } else {
3722 pwq->max_active = 0;
3723 }
3724
3725 spin_unlock_irqrestore(&pwq->pool->lock, flags);
3726}
3727
3728/* initialize newly alloced @pwq which is associated with @wq and @pool */
3729static void init_pwq(struct pool_workqueue *pwq, struct workqueue_struct *wq,
3730 struct worker_pool *pool)
3731{
3732 BUG_ON((unsigned long)pwq & WORK_STRUCT_FLAG_MASK);
3733
3734 memset(pwq, 0, sizeof(*pwq));
3735
3736 pwq->pool = pool;
3737 pwq->wq = wq;
3738 pwq->flush_color = -1;
3739 pwq->refcnt = 1;
3740 INIT_LIST_HEAD(&pwq->delayed_works);
3741 INIT_LIST_HEAD(&pwq->pwqs_node);
3742 INIT_LIST_HEAD(&pwq->mayday_node);
3743 INIT_WORK(&pwq->unbound_release_work, pwq_unbound_release_workfn);
3744}
3745
3746/* sync @pwq with the current state of its associated wq and link it */
3747static void link_pwq(struct pool_workqueue *pwq)
3748{
3749 struct workqueue_struct *wq = pwq->wq;
3750
3751 lockdep_assert_held(&wq->mutex);
3752
3753 /* may be called multiple times, ignore if already linked */
3754 if (!list_empty(&pwq->pwqs_node))
3755 return;
3756
3757 /* set the matching work_color */
3758 pwq->work_color = wq->work_color;
3759
3760 /* sync max_active to the current setting */
3761 pwq_adjust_max_active(pwq);
3762
3763 /* link in @pwq */
3764 list_add_rcu(&pwq->pwqs_node, &wq->pwqs);
3765}
3766
3767/* obtain a pool matching @attr and create a pwq associating the pool and @wq */
3768static struct pool_workqueue *alloc_unbound_pwq(struct workqueue_struct *wq,
3769 const struct workqueue_attrs *attrs)
3770{
3771 struct worker_pool *pool;
3772 struct pool_workqueue *pwq;
3773
3774 lockdep_assert_held(&wq_pool_mutex);
3775
3776 pool = get_unbound_pool(attrs);
3777 if (!pool)
3778 return NULL;
3779
3780 pwq = kmem_cache_alloc_node(pwq_cache, GFP_KERNEL, pool->node);
3781 if (!pwq) {
3782 put_unbound_pool(pool);
3783 return NULL;
3784 }
3785
3786 init_pwq(pwq, wq, pool);
3787 return pwq;
3788}
3789
3790/**
3791 * wq_calc_node_cpumask - calculate a wq_attrs' cpumask for the specified node
3792 * @attrs: the wq_attrs of the default pwq of the target workqueue
3793 * @node: the target NUMA node
3794 * @cpu_going_down: if >= 0, the CPU to consider as offline
3795 * @cpumask: outarg, the resulting cpumask
3796 *
3797 * Calculate the cpumask a workqueue with @attrs should use on @node. If
3798 * @cpu_going_down is >= 0, that cpu is considered offline during
3799 * calculation. The result is stored in @cpumask.
3800 *
3801 * If NUMA affinity is not enabled, @attrs->cpumask is always used. If
3802 * enabled and @node has online CPUs requested by @attrs, the returned
3803 * cpumask is the intersection of the possible CPUs of @node and
3804 * @attrs->cpumask.
3805 *
3806 * The caller is responsible for ensuring that the cpumask of @node stays
3807 * stable.
3808 *
3809 * Return: %true if the resulting @cpumask is different from @attrs->cpumask,
3810 * %false if equal.
3811 */
3812static bool wq_calc_node_cpumask(const struct workqueue_attrs *attrs, int node,
3813 int cpu_going_down, cpumask_t *cpumask)
3814{
3815 if (!wq_numa_enabled || attrs->no_numa)
3816 goto use_dfl;
3817
3818 /* does @node have any online CPUs @attrs wants? */
3819 cpumask_and(cpumask, cpumask_of_node(node), attrs->cpumask);
3820 if (cpu_going_down >= 0)
3821 cpumask_clear_cpu(cpu_going_down, cpumask);
3822
3823 if (cpumask_empty(cpumask))
3824 goto use_dfl;
3825
3826 /* yeap, return possible CPUs in @node that @attrs wants */
3827 cpumask_and(cpumask, attrs->cpumask, wq_numa_possible_cpumask[node]);
3828
3829 if (cpumask_empty(cpumask)) {
3830 pr_warn_once("WARNING: workqueue cpumask: online intersect > "
3831 "possible intersect\n");
3832 return false;
3833 }
3834
3835 return !cpumask_equal(cpumask, attrs->cpumask);
3836
3837use_dfl:
3838 cpumask_copy(cpumask, attrs->cpumask);
3839 return false;
3840}
3841
3842/* install @pwq into @wq's numa_pwq_tbl[] for @node and return the old pwq */
3843static struct pool_workqueue *numa_pwq_tbl_install(struct workqueue_struct *wq,
3844 int node,
3845 struct pool_workqueue *pwq)
3846{
3847 struct pool_workqueue *old_pwq;
3848
3849 lockdep_assert_held(&wq_pool_mutex);
3850 lockdep_assert_held(&wq->mutex);
3851
3852 /* link_pwq() can handle duplicate calls */
3853 link_pwq(pwq);
3854
3855 old_pwq = rcu_access_pointer(wq->numa_pwq_tbl[node]);
3856 rcu_assign_pointer(wq->numa_pwq_tbl[node], pwq);
3857 return old_pwq;
3858}
3859
3860/* context to store the prepared attrs & pwqs before applying */
3861struct apply_wqattrs_ctx {
3862 struct workqueue_struct *wq; /* target workqueue */
3863 struct workqueue_attrs *attrs; /* attrs to apply */
3864 struct list_head list; /* queued for batching commit */
3865 struct pool_workqueue *dfl_pwq;
3866 struct pool_workqueue *pwq_tbl[];
3867};
3868
3869/* free the resources after success or abort */
3870static void apply_wqattrs_cleanup(struct apply_wqattrs_ctx *ctx)
3871{
3872 if (ctx) {
3873 int node;
3874
3875 for_each_node(node)
3876 put_pwq_unlocked(ctx->pwq_tbl[node]);
3877 put_pwq_unlocked(ctx->dfl_pwq);
3878
3879 free_workqueue_attrs(ctx->attrs);
3880
3881 kfree(ctx);
3882 }
3883}
3884
3885/* allocate the attrs and pwqs for later installation */
3886static struct apply_wqattrs_ctx *
3887apply_wqattrs_prepare(struct workqueue_struct *wq,
3888 const struct workqueue_attrs *attrs)
3889{
3890 struct apply_wqattrs_ctx *ctx;
3891 struct workqueue_attrs *new_attrs, *tmp_attrs;
3892 int node;
3893
3894 lockdep_assert_held(&wq_pool_mutex);
3895
3896 ctx = kzalloc(struct_size(ctx, pwq_tbl, nr_node_ids), GFP_KERNEL);
3897
3898 new_attrs = alloc_workqueue_attrs();
3899 tmp_attrs = alloc_workqueue_attrs();
3900 if (!ctx || !new_attrs || !tmp_attrs)
3901 goto out_free;
3902
3903 /*
3904 * Calculate the attrs of the default pwq.
3905 * If the user configured cpumask doesn't overlap with the
3906 * wq_unbound_cpumask, we fallback to the wq_unbound_cpumask.
3907 */
3908 copy_workqueue_attrs(new_attrs, attrs);
3909 cpumask_and(new_attrs->cpumask, new_attrs->cpumask, wq_unbound_cpumask);
3910 if (unlikely(cpumask_empty(new_attrs->cpumask)))
3911 cpumask_copy(new_attrs->cpumask, wq_unbound_cpumask);
3912
3913 /*
3914 * We may create multiple pwqs with differing cpumasks. Make a
3915 * copy of @new_attrs which will be modified and used to obtain
3916 * pools.
3917 */
3918 copy_workqueue_attrs(tmp_attrs, new_attrs);
3919
3920 /*
3921 * If something goes wrong during CPU up/down, we'll fall back to
3922 * the default pwq covering whole @attrs->cpumask. Always create
3923 * it even if we don't use it immediately.
3924 */
3925 ctx->dfl_pwq = alloc_unbound_pwq(wq, new_attrs);
3926 if (!ctx->dfl_pwq)
3927 goto out_free;
3928
3929 for_each_node(node) {
3930 if (wq_calc_node_cpumask(new_attrs, node, -1, tmp_attrs->cpumask)) {
3931 ctx->pwq_tbl[node] = alloc_unbound_pwq(wq, tmp_attrs);
3932 if (!ctx->pwq_tbl[node])
3933 goto out_free;
3934 } else {
3935 ctx->dfl_pwq->refcnt++;
3936 ctx->pwq_tbl[node] = ctx->dfl_pwq;
3937 }
3938 }
3939
3940 /* save the user configured attrs and sanitize it. */
3941 copy_workqueue_attrs(new_attrs, attrs);
3942 cpumask_and(new_attrs->cpumask, new_attrs->cpumask, cpu_possible_mask);
3943 ctx->attrs = new_attrs;
3944
3945 ctx->wq = wq;
3946 free_workqueue_attrs(tmp_attrs);
3947 return ctx;
3948
3949out_free:
3950 free_workqueue_attrs(tmp_attrs);
3951 free_workqueue_attrs(new_attrs);
3952 apply_wqattrs_cleanup(ctx);
3953 return NULL;
3954}
3955
3956/* set attrs and install prepared pwqs, @ctx points to old pwqs on return */
3957static void apply_wqattrs_commit(struct apply_wqattrs_ctx *ctx)
3958{
3959 int node;
3960
3961 /* all pwqs have been created successfully, let's install'em */
3962 mutex_lock(&ctx->wq->mutex);
3963
3964 copy_workqueue_attrs(ctx->wq->unbound_attrs, ctx->attrs);
3965
3966 /* save the previous pwq and install the new one */
3967 for_each_node(node)
3968 ctx->pwq_tbl[node] = numa_pwq_tbl_install(ctx->wq, node,
3969 ctx->pwq_tbl[node]);
3970
3971 /* @dfl_pwq might not have been used, ensure it's linked */
3972 link_pwq(ctx->dfl_pwq);
3973 swap(ctx->wq->dfl_pwq, ctx->dfl_pwq);
3974
3975 mutex_unlock(&ctx->wq->mutex);
3976}
3977
3978static void apply_wqattrs_lock(void)
3979{
3980 /* CPUs should stay stable across pwq creations and installations */
3981 get_online_cpus();
3982 mutex_lock(&wq_pool_mutex);
3983}
3984
3985static void apply_wqattrs_unlock(void)
3986{
3987 mutex_unlock(&wq_pool_mutex);
3988 put_online_cpus();
3989}
3990
3991static int apply_workqueue_attrs_locked(struct workqueue_struct *wq,
3992 const struct workqueue_attrs *attrs)
3993{
3994 struct apply_wqattrs_ctx *ctx;
3995
3996 /* only unbound workqueues can change attributes */
3997 if (WARN_ON(!(wq->flags & WQ_UNBOUND)))
3998 return -EINVAL;
3999
4000 /* creating multiple pwqs breaks ordering guarantee */
4001 if (!list_empty(&wq->pwqs)) {
4002 if (WARN_ON(wq->flags & __WQ_ORDERED_EXPLICIT))
4003 return -EINVAL;
4004
4005 wq->flags &= ~__WQ_ORDERED;
4006 }
4007
4008 ctx = apply_wqattrs_prepare(wq, attrs);
4009 if (!ctx)
4010 return -ENOMEM;
4011
4012 /* the ctx has been prepared successfully, let's commit it */
4013 apply_wqattrs_commit(ctx);
4014 apply_wqattrs_cleanup(ctx);
4015
4016 return 0;
4017}
4018
4019/**
4020 * apply_workqueue_attrs - apply new workqueue_attrs to an unbound workqueue
4021 * @wq: the target workqueue
4022 * @attrs: the workqueue_attrs to apply, allocated with alloc_workqueue_attrs()
4023 *
4024 * Apply @attrs to an unbound workqueue @wq. Unless disabled, on NUMA
4025 * machines, this function maps a separate pwq to each NUMA node with
4026 * possibles CPUs in @attrs->cpumask so that work items are affine to the
4027 * NUMA node it was issued on. Older pwqs are released as in-flight work
4028 * items finish. Note that a work item which repeatedly requeues itself
4029 * back-to-back will stay on its current pwq.
4030 *
4031 * Performs GFP_KERNEL allocations.
4032 *
4033 * Assumes caller has CPU hotplug read exclusion, i.e. get_online_cpus().
4034 *
4035 * Return: 0 on success and -errno on failure.
4036 */
4037int apply_workqueue_attrs(struct workqueue_struct *wq,
4038 const struct workqueue_attrs *attrs)
4039{
4040 int ret;
4041
4042 lockdep_assert_cpus_held();
4043
4044 mutex_lock(&wq_pool_mutex);
4045 ret = apply_workqueue_attrs_locked(wq, attrs);
4046 mutex_unlock(&wq_pool_mutex);
4047
4048 return ret;
4049}
4050
4051/**
4052 * wq_update_unbound_numa - update NUMA affinity of a wq for CPU hot[un]plug
4053 * @wq: the target workqueue
4054 * @cpu: the CPU coming up or going down
4055 * @online: whether @cpu is coming up or going down
4056 *
4057 * This function is to be called from %CPU_DOWN_PREPARE, %CPU_ONLINE and
4058 * %CPU_DOWN_FAILED. @cpu is being hot[un]plugged, update NUMA affinity of
4059 * @wq accordingly.
4060 *
4061 * If NUMA affinity can't be adjusted due to memory allocation failure, it
4062 * falls back to @wq->dfl_pwq which may not be optimal but is always
4063 * correct.
4064 *
4065 * Note that when the last allowed CPU of a NUMA node goes offline for a
4066 * workqueue with a cpumask spanning multiple nodes, the workers which were
4067 * already executing the work items for the workqueue will lose their CPU
4068 * affinity and may execute on any CPU. This is similar to how per-cpu
4069 * workqueues behave on CPU_DOWN. If a workqueue user wants strict
4070 * affinity, it's the user's responsibility to flush the work item from
4071 * CPU_DOWN_PREPARE.
4072 */
4073static void wq_update_unbound_numa(struct workqueue_struct *wq, int cpu,
4074 bool online)
4075{
4076 int node = cpu_to_node(cpu);
4077 int cpu_off = online ? -1 : cpu;
4078 struct pool_workqueue *old_pwq = NULL, *pwq;
4079 struct workqueue_attrs *target_attrs;
4080 cpumask_t *cpumask;
4081
4082 lockdep_assert_held(&wq_pool_mutex);
4083
4084 if (!wq_numa_enabled || !(wq->flags & WQ_UNBOUND) ||
4085 wq->unbound_attrs->no_numa)
4086 return;
4087
4088 /*
4089 * We don't wanna alloc/free wq_attrs for each wq for each CPU.
4090 * Let's use a preallocated one. The following buf is protected by
4091 * CPU hotplug exclusion.
4092 */
4093 target_attrs = wq_update_unbound_numa_attrs_buf;
4094 cpumask = target_attrs->cpumask;
4095
4096 copy_workqueue_attrs(target_attrs, wq->unbound_attrs);
4097 pwq = unbound_pwq_by_node(wq, node);
4098
4099 /*
4100 * Let's determine what needs to be done. If the target cpumask is
4101 * different from the default pwq's, we need to compare it to @pwq's
4102 * and create a new one if they don't match. If the target cpumask
4103 * equals the default pwq's, the default pwq should be used.
4104 */
4105 if (wq_calc_node_cpumask(wq->dfl_pwq->pool->attrs, node, cpu_off, cpumask)) {
4106 if (cpumask_equal(cpumask, pwq->pool->attrs->cpumask))
4107 return;
4108 } else {
4109 goto use_dfl_pwq;
4110 }
4111
4112 /* create a new pwq */
4113 pwq = alloc_unbound_pwq(wq, target_attrs);
4114 if (!pwq) {
4115 pr_warn("workqueue: allocation failed while updating NUMA affinity of \"%s\"\n",
4116 wq->name);
4117 goto use_dfl_pwq;
4118 }
4119
4120 /* Install the new pwq. */
4121 mutex_lock(&wq->mutex);
4122 old_pwq = numa_pwq_tbl_install(wq, node, pwq);
4123 goto out_unlock;
4124
4125use_dfl_pwq:
4126 mutex_lock(&wq->mutex);
4127 spin_lock_irq(&wq->dfl_pwq->pool->lock);
4128 get_pwq(wq->dfl_pwq);
4129 spin_unlock_irq(&wq->dfl_pwq->pool->lock);
4130 old_pwq = numa_pwq_tbl_install(wq, node, wq->dfl_pwq);
4131out_unlock:
4132 mutex_unlock(&wq->mutex);
4133 put_pwq_unlocked(old_pwq);
4134}
4135
4136static int alloc_and_link_pwqs(struct workqueue_struct *wq)
4137{
4138 bool highpri = wq->flags & WQ_HIGHPRI;
4139 int cpu, ret;
4140
4141 if (!(wq->flags & WQ_UNBOUND)) {
4142 wq->cpu_pwqs = alloc_percpu(struct pool_workqueue);
4143 if (!wq->cpu_pwqs)
4144 return -ENOMEM;
4145
4146 for_each_possible_cpu(cpu) {
4147 struct pool_workqueue *pwq =
4148 per_cpu_ptr(wq->cpu_pwqs, cpu);
4149 struct worker_pool *cpu_pools =
4150 per_cpu(cpu_worker_pools, cpu);
4151
4152 init_pwq(pwq, wq, &cpu_pools[highpri]);
4153
4154 mutex_lock(&wq->mutex);
4155 link_pwq(pwq);
4156 mutex_unlock(&wq->mutex);
4157 }
4158 return 0;
4159 }
4160
4161 get_online_cpus();
4162 if (wq->flags & __WQ_ORDERED) {
4163 ret = apply_workqueue_attrs(wq, ordered_wq_attrs[highpri]);
4164 /* there should only be single pwq for ordering guarantee */
4165 WARN(!ret && (wq->pwqs.next != &wq->dfl_pwq->pwqs_node ||
4166 wq->pwqs.prev != &wq->dfl_pwq->pwqs_node),
4167 "ordering guarantee broken for workqueue %s\n", wq->name);
4168 } else {
4169 ret = apply_workqueue_attrs(wq, unbound_std_wq_attrs[highpri]);
4170 }
4171 put_online_cpus();
4172
4173 return ret;
4174}
4175
4176static int wq_clamp_max_active(int max_active, unsigned int flags,
4177 const char *name)
4178{
4179 int lim = flags & WQ_UNBOUND ? WQ_UNBOUND_MAX_ACTIVE : WQ_MAX_ACTIVE;
4180
4181 if (max_active < 1 || max_active > lim)
4182 pr_warn("workqueue: max_active %d requested for %s is out of range, clamping between %d and %d\n",
4183 max_active, name, 1, lim);
4184
4185 return clamp_val(max_active, 1, lim);
4186}
4187
4188/*
4189 * Workqueues which may be used during memory reclaim should have a rescuer
4190 * to guarantee forward progress.
4191 */
4192static int init_rescuer(struct workqueue_struct *wq)
4193{
4194 struct worker *rescuer;
4195 int ret;
4196
4197 if (!(wq->flags & WQ_MEM_RECLAIM))
4198 return 0;
4199
4200 rescuer = alloc_worker(NUMA_NO_NODE);
4201 if (!rescuer)
4202 return -ENOMEM;
4203
4204 rescuer->rescue_wq = wq;
4205 rescuer->task = kthread_create(rescuer_thread, rescuer, "%s", wq->name);
4206 ret = PTR_ERR_OR_ZERO(rescuer->task);
4207 if (ret) {
4208 kfree(rescuer);
4209 return ret;
4210 }
4211
4212 wq->rescuer = rescuer;
4213 kthread_bind_mask(rescuer->task, cpu_possible_mask);
4214 wake_up_process(rescuer->task);
4215
4216 return 0;
4217}
4218
4219__printf(1, 4)
4220struct workqueue_struct *alloc_workqueue(const char *fmt,
4221 unsigned int flags,
4222 int max_active, ...)
4223{
4224 size_t tbl_size = 0;
4225 va_list args;
4226 struct workqueue_struct *wq;
4227 struct pool_workqueue *pwq;
4228
4229 /*
4230 * Unbound && max_active == 1 used to imply ordered, which is no
4231 * longer the case on NUMA machines due to per-node pools. While
4232 * alloc_ordered_workqueue() is the right way to create an ordered
4233 * workqueue, keep the previous behavior to avoid subtle breakages
4234 * on NUMA.
4235 */
4236 if ((flags & WQ_UNBOUND) && max_active == 1)
4237 flags |= __WQ_ORDERED;
4238
4239 /* see the comment above the definition of WQ_POWER_EFFICIENT */
4240 if ((flags & WQ_POWER_EFFICIENT) && wq_power_efficient)
4241 flags |= WQ_UNBOUND;
4242
4243 /* allocate wq and format name */
4244 if (flags & WQ_UNBOUND)
4245 tbl_size = nr_node_ids * sizeof(wq->numa_pwq_tbl[0]);
4246
4247 wq = kzalloc(sizeof(*wq) + tbl_size, GFP_KERNEL);
4248 if (!wq)
4249 return NULL;
4250
4251 if (flags & WQ_UNBOUND) {
4252 wq->unbound_attrs = alloc_workqueue_attrs();
4253 if (!wq->unbound_attrs)
4254 goto err_free_wq;
4255 }
4256
4257 va_start(args, max_active);
4258 vsnprintf(wq->name, sizeof(wq->name), fmt, args);
4259 va_end(args);
4260
4261 max_active = max_active ?: WQ_DFL_ACTIVE;
4262 max_active = wq_clamp_max_active(max_active, flags, wq->name);
4263
4264 /* init wq */
4265 wq->flags = flags;
4266 wq->saved_max_active = max_active;
4267 mutex_init(&wq->mutex);
4268 atomic_set(&wq->nr_pwqs_to_flush, 0);
4269 INIT_LIST_HEAD(&wq->pwqs);
4270 INIT_LIST_HEAD(&wq->flusher_queue);
4271 INIT_LIST_HEAD(&wq->flusher_overflow);
4272 INIT_LIST_HEAD(&wq->maydays);
4273
4274 wq_init_lockdep(wq);
4275 INIT_LIST_HEAD(&wq->list);
4276
4277 if (alloc_and_link_pwqs(wq) < 0)
4278 goto err_unreg_lockdep;
4279
4280 if (wq_online && init_rescuer(wq) < 0)
4281 goto err_destroy;
4282
4283 if ((wq->flags & WQ_SYSFS) && workqueue_sysfs_register(wq))
4284 goto err_destroy;
4285
4286 /*
4287 * wq_pool_mutex protects global freeze state and workqueues list.
4288 * Grab it, adjust max_active and add the new @wq to workqueues
4289 * list.
4290 */
4291 mutex_lock(&wq_pool_mutex);
4292
4293 mutex_lock(&wq->mutex);
4294 for_each_pwq(pwq, wq)
4295 pwq_adjust_max_active(pwq);
4296 mutex_unlock(&wq->mutex);
4297
4298 list_add_tail_rcu(&wq->list, &workqueues);
4299
4300 mutex_unlock(&wq_pool_mutex);
4301
4302 return wq;
4303
4304err_unreg_lockdep:
4305 wq_unregister_lockdep(wq);
4306 wq_free_lockdep(wq);
4307err_free_wq:
4308 free_workqueue_attrs(wq->unbound_attrs);
4309 kfree(wq);
4310 return NULL;
4311err_destroy:
4312 destroy_workqueue(wq);
4313 return NULL;
4314}
4315EXPORT_SYMBOL_GPL(alloc_workqueue);
4316
4317/**
4318 * destroy_workqueue - safely terminate a workqueue
4319 * @wq: target workqueue
4320 *
4321 * Safely destroy a workqueue. All work currently pending will be done first.
4322 */
4323void destroy_workqueue(struct workqueue_struct *wq)
4324{
4325 struct pool_workqueue *pwq;
4326 int node;
4327
4328 /* drain it before proceeding with destruction */
4329 drain_workqueue(wq);
4330
4331 /* sanity checks */
4332 mutex_lock(&wq->mutex);
4333 for_each_pwq(pwq, wq) {
4334 int i;
4335
4336 for (i = 0; i < WORK_NR_COLORS; i++) {
4337 if (WARN_ON(pwq->nr_in_flight[i])) {
4338 mutex_unlock(&wq->mutex);
4339 show_workqueue_state();
4340 return;
4341 }
4342 }
4343
4344 if (WARN_ON((pwq != wq->dfl_pwq) && (pwq->refcnt > 1)) ||
4345 WARN_ON(pwq->nr_active) ||
4346 WARN_ON(!list_empty(&pwq->delayed_works))) {
4347 mutex_unlock(&wq->mutex);
4348 show_workqueue_state();
4349 return;
4350 }
4351 }
4352 mutex_unlock(&wq->mutex);
4353
4354 /*
4355 * wq list is used to freeze wq, remove from list after
4356 * flushing is complete in case freeze races us.
4357 */
4358 mutex_lock(&wq_pool_mutex);
4359 list_del_rcu(&wq->list);
4360 mutex_unlock(&wq_pool_mutex);
4361
4362 workqueue_sysfs_unregister(wq);
4363
4364 if (wq->rescuer)
4365 kthread_stop(wq->rescuer->task);
4366
4367 if (!(wq->flags & WQ_UNBOUND)) {
4368 wq_unregister_lockdep(wq);
4369 /*
4370 * The base ref is never dropped on per-cpu pwqs. Directly
4371 * schedule RCU free.
4372 */
4373 call_rcu(&wq->rcu, rcu_free_wq);
4374 } else {
4375 /*
4376 * We're the sole accessor of @wq at this point. Directly
4377 * access numa_pwq_tbl[] and dfl_pwq to put the base refs.
4378 * @wq will be freed when the last pwq is released.
4379 */
4380 for_each_node(node) {
4381 pwq = rcu_access_pointer(wq->numa_pwq_tbl[node]);
4382 RCU_INIT_POINTER(wq->numa_pwq_tbl[node], NULL);
4383 put_pwq_unlocked(pwq);
4384 }
4385
4386 /*
4387 * Put dfl_pwq. @wq may be freed any time after dfl_pwq is
4388 * put. Don't access it afterwards.
4389 */
4390 pwq = wq->dfl_pwq;
4391 wq->dfl_pwq = NULL;
4392 put_pwq_unlocked(pwq);
4393 }
4394}
4395EXPORT_SYMBOL_GPL(destroy_workqueue);
4396
4397/**
4398 * workqueue_set_max_active - adjust max_active of a workqueue
4399 * @wq: target workqueue
4400 * @max_active: new max_active value.
4401 *
4402 * Set max_active of @wq to @max_active.
4403 *
4404 * CONTEXT:
4405 * Don't call from IRQ context.
4406 */
4407void workqueue_set_max_active(struct workqueue_struct *wq, int max_active)
4408{
4409 struct pool_workqueue *pwq;
4410
4411 /* disallow meddling with max_active for ordered workqueues */
4412 if (WARN_ON(wq->flags & __WQ_ORDERED_EXPLICIT))
4413 return;
4414
4415 max_active = wq_clamp_max_active(max_active, wq->flags, wq->name);
4416
4417 mutex_lock(&wq->mutex);
4418
4419 wq->flags &= ~__WQ_ORDERED;
4420 wq->saved_max_active = max_active;
4421
4422 for_each_pwq(pwq, wq)
4423 pwq_adjust_max_active(pwq);
4424
4425 mutex_unlock(&wq->mutex);
4426}
4427EXPORT_SYMBOL_GPL(workqueue_set_max_active);
4428
4429/**
4430 * current_work - retrieve %current task's work struct
4431 *
4432 * Determine if %current task is a workqueue worker and what it's working on.
4433 * Useful to find out the context that the %current task is running in.
4434 *
4435 * Return: work struct if %current task is a workqueue worker, %NULL otherwise.
4436 */
4437struct work_struct *current_work(void)
4438{
4439 struct worker *worker = current_wq_worker();
4440
4441 return worker ? worker->current_work : NULL;
4442}
4443EXPORT_SYMBOL(current_work);
4444
4445/**
4446 * current_is_workqueue_rescuer - is %current workqueue rescuer?
4447 *
4448 * Determine whether %current is a workqueue rescuer. Can be used from
4449 * work functions to determine whether it's being run off the rescuer task.
4450 *
4451 * Return: %true if %current is a workqueue rescuer. %false otherwise.
4452 */
4453bool current_is_workqueue_rescuer(void)
4454{
4455 struct worker *worker = current_wq_worker();
4456
4457 return worker && worker->rescue_wq;
4458}
4459
4460/**
4461 * workqueue_congested - test whether a workqueue is congested
4462 * @cpu: CPU in question
4463 * @wq: target workqueue
4464 *
4465 * Test whether @wq's cpu workqueue for @cpu is congested. There is
4466 * no synchronization around this function and the test result is
4467 * unreliable and only useful as advisory hints or for debugging.
4468 *
4469 * If @cpu is WORK_CPU_UNBOUND, the test is performed on the local CPU.
4470 * Note that both per-cpu and unbound workqueues may be associated with
4471 * multiple pool_workqueues which have separate congested states. A
4472 * workqueue being congested on one CPU doesn't mean the workqueue is also
4473 * contested on other CPUs / NUMA nodes.
4474 *
4475 * Return:
4476 * %true if congested, %false otherwise.
4477 */
4478bool workqueue_congested(int cpu, struct workqueue_struct *wq)
4479{
4480 struct pool_workqueue *pwq;
4481 bool ret;
4482
4483 rcu_read_lock();
4484 preempt_disable();
4485
4486 if (cpu == WORK_CPU_UNBOUND)
4487 cpu = smp_processor_id();
4488
4489 if (!(wq->flags & WQ_UNBOUND))
4490 pwq = per_cpu_ptr(wq->cpu_pwqs, cpu);
4491 else
4492 pwq = unbound_pwq_by_node(wq, cpu_to_node(cpu));
4493
4494 ret = !list_empty(&pwq->delayed_works);
4495 preempt_enable();
4496 rcu_read_unlock();
4497
4498 return ret;
4499}
4500EXPORT_SYMBOL_GPL(workqueue_congested);
4501
4502/**
4503 * work_busy - test whether a work is currently pending or running
4504 * @work: the work to be tested
4505 *
4506 * Test whether @work is currently pending or running. There is no
4507 * synchronization around this function and the test result is
4508 * unreliable and only useful as advisory hints or for debugging.
4509 *
4510 * Return:
4511 * OR'd bitmask of WORK_BUSY_* bits.
4512 */
4513unsigned int work_busy(struct work_struct *work)
4514{
4515 struct worker_pool *pool;
4516 unsigned long flags;
4517 unsigned int ret = 0;
4518
4519 if (work_pending(work))
4520 ret |= WORK_BUSY_PENDING;
4521
4522 rcu_read_lock();
4523 pool = get_work_pool(work);
4524 if (pool) {
4525 spin_lock_irqsave(&pool->lock, flags);
4526 if (find_worker_executing_work(pool, work))
4527 ret |= WORK_BUSY_RUNNING;
4528 spin_unlock_irqrestore(&pool->lock, flags);
4529 }
4530 rcu_read_unlock();
4531
4532 return ret;
4533}
4534EXPORT_SYMBOL_GPL(work_busy);
4535
4536/**
4537 * set_worker_desc - set description for the current work item
4538 * @fmt: printf-style format string
4539 * @...: arguments for the format string
4540 *
4541 * This function can be called by a running work function to describe what
4542 * the work item is about. If the worker task gets dumped, this
4543 * information will be printed out together to help debugging. The
4544 * description can be at most WORKER_DESC_LEN including the trailing '\0'.
4545 */
4546void set_worker_desc(const char *fmt, ...)
4547{
4548 struct worker *worker = current_wq_worker();
4549 va_list args;
4550
4551 if (worker) {
4552 va_start(args, fmt);
4553 vsnprintf(worker->desc, sizeof(worker->desc), fmt, args);
4554 va_end(args);
4555 }
4556}
4557EXPORT_SYMBOL_GPL(set_worker_desc);
4558
4559/**
4560 * print_worker_info - print out worker information and description
4561 * @log_lvl: the log level to use when printing
4562 * @task: target task
4563 *
4564 * If @task is a worker and currently executing a work item, print out the
4565 * name of the workqueue being serviced and worker description set with
4566 * set_worker_desc() by the currently executing work item.
4567 *
4568 * This function can be safely called on any task as long as the
4569 * task_struct itself is accessible. While safe, this function isn't
4570 * synchronized and may print out mixups or garbages of limited length.
4571 */
4572void print_worker_info(const char *log_lvl, struct task_struct *task)
4573{
4574 work_func_t *fn = NULL;
4575 char name[WQ_NAME_LEN] = { };
4576 char desc[WORKER_DESC_LEN] = { };
4577 struct pool_workqueue *pwq = NULL;
4578 struct workqueue_struct *wq = NULL;
4579 struct worker *worker;
4580
4581 if (!(task->flags & PF_WQ_WORKER))
4582 return;
4583
4584 /*
4585 * This function is called without any synchronization and @task
4586 * could be in any state. Be careful with dereferences.
4587 */
4588 worker = kthread_probe_data(task);
4589
4590 /*
4591 * Carefully copy the associated workqueue's workfn, name and desc.
4592 * Keep the original last '\0' in case the original is garbage.
4593 */
4594 probe_kernel_read(&fn, &worker->current_func, sizeof(fn));
4595 probe_kernel_read(&pwq, &worker->current_pwq, sizeof(pwq));
4596 probe_kernel_read(&wq, &pwq->wq, sizeof(wq));
4597 probe_kernel_read(name, wq->name, sizeof(name) - 1);
4598 probe_kernel_read(desc, worker->desc, sizeof(desc) - 1);
4599
4600 if (fn || name[0] || desc[0]) {
4601 printk("%sWorkqueue: %s %ps", log_lvl, name, fn);
4602 if (strcmp(name, desc))
4603 pr_cont(" (%s)", desc);
4604 pr_cont("\n");
4605 }
4606}
4607
4608static void pr_cont_pool_info(struct worker_pool *pool)
4609{
4610 pr_cont(" cpus=%*pbl", nr_cpumask_bits, pool->attrs->cpumask);
4611 if (pool->node != NUMA_NO_NODE)
4612 pr_cont(" node=%d", pool->node);
4613 pr_cont(" flags=0x%x nice=%d", pool->flags, pool->attrs->nice);
4614}
4615
4616static void pr_cont_work(bool comma, struct work_struct *work)
4617{
4618 if (work->func == wq_barrier_func) {
4619 struct wq_barrier *barr;
4620
4621 barr = container_of(work, struct wq_barrier, work);
4622
4623 pr_cont("%s BAR(%d)", comma ? "," : "",
4624 task_pid_nr(barr->task));
4625 } else {
4626 pr_cont("%s %ps", comma ? "," : "", work->func);
4627 }
4628}
4629
4630static void show_pwq(struct pool_workqueue *pwq)
4631{
4632 struct worker_pool *pool = pwq->pool;
4633 struct work_struct *work;
4634 struct worker *worker;
4635 bool has_in_flight = false, has_pending = false;
4636 int bkt;
4637
4638 pr_info(" pwq %d:", pool->id);
4639 pr_cont_pool_info(pool);
4640
4641 pr_cont(" active=%d/%d%s\n", pwq->nr_active, pwq->max_active,
4642 !list_empty(&pwq->mayday_node) ? " MAYDAY" : "");
4643
4644 hash_for_each(pool->busy_hash, bkt, worker, hentry) {
4645 if (worker->current_pwq == pwq) {
4646 has_in_flight = true;
4647 break;
4648 }
4649 }
4650 if (has_in_flight) {
4651 bool comma = false;
4652
4653 pr_info(" in-flight:");
4654 hash_for_each(pool->busy_hash, bkt, worker, hentry) {
4655 if (worker->current_pwq != pwq)
4656 continue;
4657
4658 pr_cont("%s %d%s:%ps", comma ? "," : "",
4659 task_pid_nr(worker->task),
4660 worker == pwq->wq->rescuer ? "(RESCUER)" : "",
4661 worker->current_func);
4662 list_for_each_entry(work, &worker->scheduled, entry)
4663 pr_cont_work(false, work);
4664 comma = true;
4665 }
4666 pr_cont("\n");
4667 }
4668
4669 list_for_each_entry(work, &pool->worklist, entry) {
4670 if (get_work_pwq(work) == pwq) {
4671 has_pending = true;
4672 break;
4673 }
4674 }
4675 if (has_pending) {
4676 bool comma = false;
4677
4678 pr_info(" pending:");
4679 list_for_each_entry(work, &pool->worklist, entry) {
4680 if (get_work_pwq(work) != pwq)
4681 continue;
4682
4683 pr_cont_work(comma, work);
4684 comma = !(*work_data_bits(work) & WORK_STRUCT_LINKED);
4685 }
4686 pr_cont("\n");
4687 }
4688
4689 if (!list_empty(&pwq->delayed_works)) {
4690 bool comma = false;
4691
4692 pr_info(" delayed:");
4693 list_for_each_entry(work, &pwq->delayed_works, entry) {
4694 pr_cont_work(comma, work);
4695 comma = !(*work_data_bits(work) & WORK_STRUCT_LINKED);
4696 }
4697 pr_cont("\n");
4698 }
4699}
4700
4701/**
4702 * show_workqueue_state - dump workqueue state
4703 *
4704 * Called from a sysrq handler or try_to_freeze_tasks() and prints out
4705 * all busy workqueues and pools.
4706 */
4707void show_workqueue_state(void)
4708{
4709 struct workqueue_struct *wq;
4710 struct worker_pool *pool;
4711 unsigned long flags;
4712 int pi;
4713
4714 rcu_read_lock();
4715
4716 pr_info("Showing busy workqueues and worker pools:\n");
4717
4718 list_for_each_entry_rcu(wq, &workqueues, list) {
4719 struct pool_workqueue *pwq;
4720 bool idle = true;
4721
4722 for_each_pwq(pwq, wq) {
4723 if (pwq->nr_active || !list_empty(&pwq->delayed_works)) {
4724 idle = false;
4725 break;
4726 }
4727 }
4728 if (idle)
4729 continue;
4730
4731 pr_info("workqueue %s: flags=0x%x\n", wq->name, wq->flags);
4732
4733 for_each_pwq(pwq, wq) {
4734 spin_lock_irqsave(&pwq->pool->lock, flags);
4735 if (pwq->nr_active || !list_empty(&pwq->delayed_works))
4736 show_pwq(pwq);
4737 spin_unlock_irqrestore(&pwq->pool->lock, flags);
4738 /*
4739 * We could be printing a lot from atomic context, e.g.
4740 * sysrq-t -> show_workqueue_state(). Avoid triggering
4741 * hard lockup.
4742 */
4743 touch_nmi_watchdog();
4744 }
4745 }
4746
4747 for_each_pool(pool, pi) {
4748 struct worker *worker;
4749 bool first = true;
4750
4751 spin_lock_irqsave(&pool->lock, flags);
4752 if (pool->nr_workers == pool->nr_idle)
4753 goto next_pool;
4754
4755 pr_info("pool %d:", pool->id);
4756 pr_cont_pool_info(pool);
4757 pr_cont(" hung=%us workers=%d",
4758 jiffies_to_msecs(jiffies - pool->watchdog_ts) / 1000,
4759 pool->nr_workers);
4760 if (pool->manager)
4761 pr_cont(" manager: %d",
4762 task_pid_nr(pool->manager->task));
4763 list_for_each_entry(worker, &pool->idle_list, entry) {
4764 pr_cont(" %s%d", first ? "idle: " : "",
4765 task_pid_nr(worker->task));
4766 first = false;
4767 }
4768 pr_cont("\n");
4769 next_pool:
4770 spin_unlock_irqrestore(&pool->lock, flags);
4771 /*
4772 * We could be printing a lot from atomic context, e.g.
4773 * sysrq-t -> show_workqueue_state(). Avoid triggering
4774 * hard lockup.
4775 */
4776 touch_nmi_watchdog();
4777 }
4778
4779 rcu_read_unlock();
4780}
4781
4782/* used to show worker information through /proc/PID/{comm,stat,status} */
4783void wq_worker_comm(char *buf, size_t size, struct task_struct *task)
4784{
4785 int off;
4786
4787 /* always show the actual comm */
4788 off = strscpy(buf, task->comm, size);
4789 if (off < 0)
4790 return;
4791
4792 /* stabilize PF_WQ_WORKER and worker pool association */
4793 mutex_lock(&wq_pool_attach_mutex);
4794
4795 if (task->flags & PF_WQ_WORKER) {
4796 struct worker *worker = kthread_data(task);
4797 struct worker_pool *pool = worker->pool;
4798
4799 if (pool) {
4800 spin_lock_irq(&pool->lock);
4801 /*
4802 * ->desc tracks information (wq name or
4803 * set_worker_desc()) for the latest execution. If
4804 * current, prepend '+', otherwise '-'.
4805 */
4806 if (worker->desc[0] != '\0') {
4807 if (worker->current_work)
4808 scnprintf(buf + off, size - off, "+%s",
4809 worker->desc);
4810 else
4811 scnprintf(buf + off, size - off, "-%s",
4812 worker->desc);
4813 }
4814 spin_unlock_irq(&pool->lock);
4815 }
4816 }
4817
4818 mutex_unlock(&wq_pool_attach_mutex);
4819}
4820
4821#ifdef CONFIG_SMP
4822
4823/*
4824 * CPU hotplug.
4825 *
4826 * There are two challenges in supporting CPU hotplug. Firstly, there
4827 * are a lot of assumptions on strong associations among work, pwq and
4828 * pool which make migrating pending and scheduled works very
4829 * difficult to implement without impacting hot paths. Secondly,
4830 * worker pools serve mix of short, long and very long running works making
4831 * blocked draining impractical.
4832 *
4833 * This is solved by allowing the pools to be disassociated from the CPU
4834 * running as an unbound one and allowing it to be reattached later if the
4835 * cpu comes back online.
4836 */
4837
4838static void unbind_workers(int cpu)
4839{
4840 struct worker_pool *pool;
4841 struct worker *worker;
4842
4843 for_each_cpu_worker_pool(pool, cpu) {
4844 mutex_lock(&wq_pool_attach_mutex);
4845 spin_lock_irq(&pool->lock);
4846
4847 /*
4848 * We've blocked all attach/detach operations. Make all workers
4849 * unbound and set DISASSOCIATED. Before this, all workers
4850 * except for the ones which are still executing works from
4851 * before the last CPU down must be on the cpu. After
4852 * this, they may become diasporas.
4853 */
4854 for_each_pool_worker(worker, pool)
4855 worker->flags |= WORKER_UNBOUND;
4856
4857 pool->flags |= POOL_DISASSOCIATED;
4858
4859 spin_unlock_irq(&pool->lock);
4860 mutex_unlock(&wq_pool_attach_mutex);
4861
4862 /*
4863 * Call schedule() so that we cross rq->lock and thus can
4864 * guarantee sched callbacks see the %WORKER_UNBOUND flag.
4865 * This is necessary as scheduler callbacks may be invoked
4866 * from other cpus.
4867 */
4868 schedule();
4869
4870 /*
4871 * Sched callbacks are disabled now. Zap nr_running.
4872 * After this, nr_running stays zero and need_more_worker()
4873 * and keep_working() are always true as long as the
4874 * worklist is not empty. This pool now behaves as an
4875 * unbound (in terms of concurrency management) pool which
4876 * are served by workers tied to the pool.
4877 */
4878 atomic_set(&pool->nr_running, 0);
4879
4880 /*
4881 * With concurrency management just turned off, a busy
4882 * worker blocking could lead to lengthy stalls. Kick off
4883 * unbound chain execution of currently pending work items.
4884 */
4885 spin_lock_irq(&pool->lock);
4886 wake_up_worker(pool);
4887 spin_unlock_irq(&pool->lock);
4888 }
4889}
4890
4891/**
4892 * rebind_workers - rebind all workers of a pool to the associated CPU
4893 * @pool: pool of interest
4894 *
4895 * @pool->cpu is coming online. Rebind all workers to the CPU.
4896 */
4897static void rebind_workers(struct worker_pool *pool)
4898{
4899 struct worker *worker;
4900
4901 lockdep_assert_held(&wq_pool_attach_mutex);
4902
4903 /*
4904 * Restore CPU affinity of all workers. As all idle workers should
4905 * be on the run-queue of the associated CPU before any local
4906 * wake-ups for concurrency management happen, restore CPU affinity
4907 * of all workers first and then clear UNBOUND. As we're called
4908 * from CPU_ONLINE, the following shouldn't fail.
4909 */
4910 for_each_pool_worker(worker, pool)
4911 WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task,
4912 pool->attrs->cpumask) < 0);
4913
4914 spin_lock_irq(&pool->lock);
4915
4916 pool->flags &= ~POOL_DISASSOCIATED;
4917
4918 for_each_pool_worker(worker, pool) {
4919 unsigned int worker_flags = worker->flags;
4920
4921 /*
4922 * A bound idle worker should actually be on the runqueue
4923 * of the associated CPU for local wake-ups targeting it to
4924 * work. Kick all idle workers so that they migrate to the
4925 * associated CPU. Doing this in the same loop as
4926 * replacing UNBOUND with REBOUND is safe as no worker will
4927 * be bound before @pool->lock is released.
4928 */
4929 if (worker_flags & WORKER_IDLE)
4930 wake_up_process(worker->task);
4931
4932 /*
4933 * We want to clear UNBOUND but can't directly call
4934 * worker_clr_flags() or adjust nr_running. Atomically
4935 * replace UNBOUND with another NOT_RUNNING flag REBOUND.
4936 * @worker will clear REBOUND using worker_clr_flags() when
4937 * it initiates the next execution cycle thus restoring
4938 * concurrency management. Note that when or whether
4939 * @worker clears REBOUND doesn't affect correctness.
4940 *
4941 * WRITE_ONCE() is necessary because @worker->flags may be
4942 * tested without holding any lock in
4943 * wq_worker_running(). Without it, NOT_RUNNING test may
4944 * fail incorrectly leading to premature concurrency
4945 * management operations.
4946 */
4947 WARN_ON_ONCE(!(worker_flags & WORKER_UNBOUND));
4948 worker_flags |= WORKER_REBOUND;
4949 worker_flags &= ~WORKER_UNBOUND;
4950 WRITE_ONCE(worker->flags, worker_flags);
4951 }
4952
4953 spin_unlock_irq(&pool->lock);
4954}
4955
4956/**
4957 * restore_unbound_workers_cpumask - restore cpumask of unbound workers
4958 * @pool: unbound pool of interest
4959 * @cpu: the CPU which is coming up
4960 *
4961 * An unbound pool may end up with a cpumask which doesn't have any online
4962 * CPUs. When a worker of such pool get scheduled, the scheduler resets
4963 * its cpus_allowed. If @cpu is in @pool's cpumask which didn't have any
4964 * online CPU before, cpus_allowed of all its workers should be restored.
4965 */
4966static void restore_unbound_workers_cpumask(struct worker_pool *pool, int cpu)
4967{
4968 static cpumask_t cpumask;
4969 struct worker *worker;
4970
4971 lockdep_assert_held(&wq_pool_attach_mutex);
4972
4973 /* is @cpu allowed for @pool? */
4974 if (!cpumask_test_cpu(cpu, pool->attrs->cpumask))
4975 return;
4976
4977 cpumask_and(&cpumask, pool->attrs->cpumask, cpu_online_mask);
4978
4979 /* as we're called from CPU_ONLINE, the following shouldn't fail */
4980 for_each_pool_worker(worker, pool)
4981 WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task, &cpumask) < 0);
4982}
4983
4984int workqueue_prepare_cpu(unsigned int cpu)
4985{
4986 struct worker_pool *pool;
4987
4988 for_each_cpu_worker_pool(pool, cpu) {
4989 if (pool->nr_workers)
4990 continue;
4991 if (!create_worker(pool))
4992 return -ENOMEM;
4993 }
4994 return 0;
4995}
4996
4997int workqueue_online_cpu(unsigned int cpu)
4998{
4999 struct worker_pool *pool;
5000 struct workqueue_struct *wq;
5001 int pi;
5002
5003 mutex_lock(&wq_pool_mutex);
5004
5005 for_each_pool(pool, pi) {
5006 mutex_lock(&wq_pool_attach_mutex);
5007
5008 if (pool->cpu == cpu)
5009 rebind_workers(pool);
5010 else if (pool->cpu < 0)
5011 restore_unbound_workers_cpumask(pool, cpu);
5012
5013 mutex_unlock(&wq_pool_attach_mutex);
5014 }
5015
5016 /* update NUMA affinity of unbound workqueues */
5017 list_for_each_entry(wq, &workqueues, list)
5018 wq_update_unbound_numa(wq, cpu, true);
5019
5020 mutex_unlock(&wq_pool_mutex);
5021 return 0;
5022}
5023
5024int workqueue_offline_cpu(unsigned int cpu)
5025{
5026 struct workqueue_struct *wq;
5027
5028 /* unbinding per-cpu workers should happen on the local CPU */
5029 if (WARN_ON(cpu != smp_processor_id()))
5030 return -1;
5031
5032 unbind_workers(cpu);
5033
5034 /* update NUMA affinity of unbound workqueues */
5035 mutex_lock(&wq_pool_mutex);
5036 list_for_each_entry(wq, &workqueues, list)
5037 wq_update_unbound_numa(wq, cpu, false);
5038 mutex_unlock(&wq_pool_mutex);
5039
5040 return 0;
5041}
5042
5043struct work_for_cpu {
5044 struct work_struct work;
5045 long (*fn)(void *);
5046 void *arg;
5047 long ret;
5048};
5049
5050static void work_for_cpu_fn(struct work_struct *work)
5051{
5052 struct work_for_cpu *wfc = container_of(work, struct work_for_cpu, work);
5053
5054 wfc->ret = wfc->fn(wfc->arg);
5055}
5056
5057/**
5058 * work_on_cpu - run a function in thread context on a particular cpu
5059 * @cpu: the cpu to run on
5060 * @fn: the function to run
5061 * @arg: the function arg
5062 *
5063 * It is up to the caller to ensure that the cpu doesn't go offline.
5064 * The caller must not hold any locks which would prevent @fn from completing.
5065 *
5066 * Return: The value @fn returns.
5067 */
5068long work_on_cpu(int cpu, long (*fn)(void *), void *arg)
5069{
5070 struct work_for_cpu wfc = { .fn = fn, .arg = arg };
5071
5072 INIT_WORK_ONSTACK(&wfc.work, work_for_cpu_fn);
5073 schedule_work_on(cpu, &wfc.work);
5074 flush_work(&wfc.work);
5075 destroy_work_on_stack(&wfc.work);
5076 return wfc.ret;
5077}
5078EXPORT_SYMBOL_GPL(work_on_cpu);
5079
5080/**
5081 * work_on_cpu_safe - run a function in thread context on a particular cpu
5082 * @cpu: the cpu to run on
5083 * @fn: the function to run
5084 * @arg: the function argument
5085 *
5086 * Disables CPU hotplug and calls work_on_cpu(). The caller must not hold
5087 * any locks which would prevent @fn from completing.
5088 *
5089 * Return: The value @fn returns.
5090 */
5091long work_on_cpu_safe(int cpu, long (*fn)(void *), void *arg)
5092{
5093 long ret = -ENODEV;
5094
5095 get_online_cpus();
5096 if (cpu_online(cpu))
5097 ret = work_on_cpu(cpu, fn, arg);
5098 put_online_cpus();
5099 return ret;
5100}
5101EXPORT_SYMBOL_GPL(work_on_cpu_safe);
5102#endif /* CONFIG_SMP */
5103
5104#ifdef CONFIG_FREEZER
5105
5106/**
5107 * freeze_workqueues_begin - begin freezing workqueues
5108 *
5109 * Start freezing workqueues. After this function returns, all freezable
5110 * workqueues will queue new works to their delayed_works list instead of
5111 * pool->worklist.
5112 *
5113 * CONTEXT:
5114 * Grabs and releases wq_pool_mutex, wq->mutex and pool->lock's.
5115 */
5116void freeze_workqueues_begin(void)
5117{
5118 struct workqueue_struct *wq;
5119 struct pool_workqueue *pwq;
5120
5121 mutex_lock(&wq_pool_mutex);
5122
5123 WARN_ON_ONCE(workqueue_freezing);
5124 workqueue_freezing = true;
5125
5126 list_for_each_entry(wq, &workqueues, list) {
5127 mutex_lock(&wq->mutex);
5128 for_each_pwq(pwq, wq)
5129 pwq_adjust_max_active(pwq);
5130 mutex_unlock(&wq->mutex);
5131 }
5132
5133 mutex_unlock(&wq_pool_mutex);
5134}
5135
5136/**
5137 * freeze_workqueues_busy - are freezable workqueues still busy?
5138 *
5139 * Check whether freezing is complete. This function must be called
5140 * between freeze_workqueues_begin() and thaw_workqueues().
5141 *
5142 * CONTEXT:
5143 * Grabs and releases wq_pool_mutex.
5144 *
5145 * Return:
5146 * %true if some freezable workqueues are still busy. %false if freezing
5147 * is complete.
5148 */
5149bool freeze_workqueues_busy(void)
5150{
5151 bool busy = false;
5152 struct workqueue_struct *wq;
5153 struct pool_workqueue *pwq;
5154
5155 mutex_lock(&wq_pool_mutex);
5156
5157 WARN_ON_ONCE(!workqueue_freezing);
5158
5159 list_for_each_entry(wq, &workqueues, list) {
5160 if (!(wq->flags & WQ_FREEZABLE))
5161 continue;
5162 /*
5163 * nr_active is monotonically decreasing. It's safe
5164 * to peek without lock.
5165 */
5166 rcu_read_lock();
5167 for_each_pwq(pwq, wq) {
5168 WARN_ON_ONCE(pwq->nr_active < 0);
5169 if (pwq->nr_active) {
5170 busy = true;
5171 rcu_read_unlock();
5172 goto out_unlock;
5173 }
5174 }
5175 rcu_read_unlock();
5176 }
5177out_unlock:
5178 mutex_unlock(&wq_pool_mutex);
5179 return busy;
5180}
5181
5182/**
5183 * thaw_workqueues - thaw workqueues
5184 *
5185 * Thaw workqueues. Normal queueing is restored and all collected
5186 * frozen works are transferred to their respective pool worklists.
5187 *
5188 * CONTEXT:
5189 * Grabs and releases wq_pool_mutex, wq->mutex and pool->lock's.
5190 */
5191void thaw_workqueues(void)
5192{
5193 struct workqueue_struct *wq;
5194 struct pool_workqueue *pwq;
5195
5196 mutex_lock(&wq_pool_mutex);
5197
5198 if (!workqueue_freezing)
5199 goto out_unlock;
5200
5201 workqueue_freezing = false;
5202
5203 /* restore max_active and repopulate worklist */
5204 list_for_each_entry(wq, &workqueues, list) {
5205 mutex_lock(&wq->mutex);
5206 for_each_pwq(pwq, wq)
5207 pwq_adjust_max_active(pwq);
5208 mutex_unlock(&wq->mutex);
5209 }
5210
5211out_unlock:
5212 mutex_unlock(&wq_pool_mutex);
5213}
5214#endif /* CONFIG_FREEZER */
5215
5216static int workqueue_apply_unbound_cpumask(void)
5217{
5218 LIST_HEAD(ctxs);
5219 int ret = 0;
5220 struct workqueue_struct *wq;
5221 struct apply_wqattrs_ctx *ctx, *n;
5222
5223 lockdep_assert_held(&wq_pool_mutex);
5224
5225 list_for_each_entry(wq, &workqueues, list) {
5226 if (!(wq->flags & WQ_UNBOUND))
5227 continue;
5228 /* creating multiple pwqs breaks ordering guarantee */
5229 if (wq->flags & __WQ_ORDERED)
5230 continue;
5231
5232 ctx = apply_wqattrs_prepare(wq, wq->unbound_attrs);
5233 if (!ctx) {
5234 ret = -ENOMEM;
5235 break;
5236 }
5237
5238 list_add_tail(&ctx->list, &ctxs);
5239 }
5240
5241 list_for_each_entry_safe(ctx, n, &ctxs, list) {
5242 if (!ret)
5243 apply_wqattrs_commit(ctx);
5244 apply_wqattrs_cleanup(ctx);
5245 }
5246
5247 return ret;
5248}
5249
5250/**
5251 * workqueue_set_unbound_cpumask - Set the low-level unbound cpumask
5252 * @cpumask: the cpumask to set
5253 *
5254 * The low-level workqueues cpumask is a global cpumask that limits
5255 * the affinity of all unbound workqueues. This function check the @cpumask
5256 * and apply it to all unbound workqueues and updates all pwqs of them.
5257 *
5258 * Retun: 0 - Success
5259 * -EINVAL - Invalid @cpumask
5260 * -ENOMEM - Failed to allocate memory for attrs or pwqs.
5261 */
5262int workqueue_set_unbound_cpumask(cpumask_var_t cpumask)
5263{
5264 int ret = -EINVAL;
5265 cpumask_var_t saved_cpumask;
5266
5267 if (!zalloc_cpumask_var(&saved_cpumask, GFP_KERNEL))
5268 return -ENOMEM;
5269
5270 /*
5271 * Not excluding isolated cpus on purpose.
5272 * If the user wishes to include them, we allow that.
5273 */
5274 cpumask_and(cpumask, cpumask, cpu_possible_mask);
5275 if (!cpumask_empty(cpumask)) {
5276 apply_wqattrs_lock();
5277
5278 /* save the old wq_unbound_cpumask. */
5279 cpumask_copy(saved_cpumask, wq_unbound_cpumask);
5280
5281 /* update wq_unbound_cpumask at first and apply it to wqs. */
5282 cpumask_copy(wq_unbound_cpumask, cpumask);
5283 ret = workqueue_apply_unbound_cpumask();
5284
5285 /* restore the wq_unbound_cpumask when failed. */
5286 if (ret < 0)
5287 cpumask_copy(wq_unbound_cpumask, saved_cpumask);
5288
5289 apply_wqattrs_unlock();
5290 }
5291
5292 free_cpumask_var(saved_cpumask);
5293 return ret;
5294}
5295
5296#ifdef CONFIG_SYSFS
5297/*
5298 * Workqueues with WQ_SYSFS flag set is visible to userland via
5299 * /sys/bus/workqueue/devices/WQ_NAME. All visible workqueues have the
5300 * following attributes.
5301 *
5302 * per_cpu RO bool : whether the workqueue is per-cpu or unbound
5303 * max_active RW int : maximum number of in-flight work items
5304 *
5305 * Unbound workqueues have the following extra attributes.
5306 *
5307 * pool_ids RO int : the associated pool IDs for each node
5308 * nice RW int : nice value of the workers
5309 * cpumask RW mask : bitmask of allowed CPUs for the workers
5310 * numa RW bool : whether enable NUMA affinity
5311 */
5312struct wq_device {
5313 struct workqueue_struct *wq;
5314 struct device dev;
5315};
5316
5317static struct workqueue_struct *dev_to_wq(struct device *dev)
5318{
5319 struct wq_device *wq_dev = container_of(dev, struct wq_device, dev);
5320
5321 return wq_dev->wq;
5322}
5323
5324static ssize_t per_cpu_show(struct device *dev, struct device_attribute *attr,
5325 char *buf)
5326{
5327 struct workqueue_struct *wq = dev_to_wq(dev);
5328
5329 return scnprintf(buf, PAGE_SIZE, "%d\n", (bool)!(wq->flags & WQ_UNBOUND));
5330}
5331static DEVICE_ATTR_RO(per_cpu);
5332
5333static ssize_t max_active_show(struct device *dev,
5334 struct device_attribute *attr, char *buf)
5335{
5336 struct workqueue_struct *wq = dev_to_wq(dev);
5337
5338 return scnprintf(buf, PAGE_SIZE, "%d\n", wq->saved_max_active);
5339}
5340
5341static ssize_t max_active_store(struct device *dev,
5342 struct device_attribute *attr, const char *buf,
5343 size_t count)
5344{
5345 struct workqueue_struct *wq = dev_to_wq(dev);
5346 int val;
5347
5348 if (sscanf(buf, "%d", &val) != 1 || val <= 0)
5349 return -EINVAL;
5350
5351 workqueue_set_max_active(wq, val);
5352 return count;
5353}
5354static DEVICE_ATTR_RW(max_active);
5355
5356static struct attribute *wq_sysfs_attrs[] = {
5357 &dev_attr_per_cpu.attr,
5358 &dev_attr_max_active.attr,
5359 NULL,
5360};
5361ATTRIBUTE_GROUPS(wq_sysfs);
5362
5363static ssize_t wq_pool_ids_show(struct device *dev,
5364 struct device_attribute *attr, char *buf)
5365{
5366 struct workqueue_struct *wq = dev_to_wq(dev);
5367 const char *delim = "";
5368 int node, written = 0;
5369
5370 get_online_cpus();
5371 rcu_read_lock();
5372 for_each_node(node) {
5373 written += scnprintf(buf + written, PAGE_SIZE - written,
5374 "%s%d:%d", delim, node,
5375 unbound_pwq_by_node(wq, node)->pool->id);
5376 delim = " ";
5377 }
5378 written += scnprintf(buf + written, PAGE_SIZE - written, "\n");
5379 rcu_read_unlock();
5380 put_online_cpus();
5381
5382 return written;
5383}
5384
5385static ssize_t wq_nice_show(struct device *dev, struct device_attribute *attr,
5386 char *buf)
5387{
5388 struct workqueue_struct *wq = dev_to_wq(dev);
5389 int written;
5390
5391 mutex_lock(&wq->mutex);
5392 written = scnprintf(buf, PAGE_SIZE, "%d\n", wq->unbound_attrs->nice);
5393 mutex_unlock(&wq->mutex);
5394
5395 return written;
5396}
5397
5398/* prepare workqueue_attrs for sysfs store operations */
5399static struct workqueue_attrs *wq_sysfs_prep_attrs(struct workqueue_struct *wq)
5400{
5401 struct workqueue_attrs *attrs;
5402
5403 lockdep_assert_held(&wq_pool_mutex);
5404
5405 attrs = alloc_workqueue_attrs();
5406 if (!attrs)
5407 return NULL;
5408
5409 copy_workqueue_attrs(attrs, wq->unbound_attrs);
5410 return attrs;
5411}
5412
5413static ssize_t wq_nice_store(struct device *dev, struct device_attribute *attr,
5414 const char *buf, size_t count)
5415{
5416 struct workqueue_struct *wq = dev_to_wq(dev);
5417 struct workqueue_attrs *attrs;
5418 int ret = -ENOMEM;
5419
5420 apply_wqattrs_lock();
5421
5422 attrs = wq_sysfs_prep_attrs(wq);
5423 if (!attrs)
5424 goto out_unlock;
5425
5426 if (sscanf(buf, "%d", &attrs->nice) == 1 &&
5427 attrs->nice >= MIN_NICE && attrs->nice <= MAX_NICE)
5428 ret = apply_workqueue_attrs_locked(wq, attrs);
5429 else
5430 ret = -EINVAL;
5431
5432out_unlock:
5433 apply_wqattrs_unlock();
5434 free_workqueue_attrs(attrs);
5435 return ret ?: count;
5436}
5437
5438static ssize_t wq_cpumask_show(struct device *dev,
5439 struct device_attribute *attr, char *buf)
5440{
5441 struct workqueue_struct *wq = dev_to_wq(dev);
5442 int written;
5443
5444 mutex_lock(&wq->mutex);
5445 written = scnprintf(buf, PAGE_SIZE, "%*pb\n",
5446 cpumask_pr_args(wq->unbound_attrs->cpumask));
5447 mutex_unlock(&wq->mutex);
5448 return written;
5449}
5450
5451static ssize_t wq_cpumask_store(struct device *dev,
5452 struct device_attribute *attr,
5453 const char *buf, size_t count)
5454{
5455 struct workqueue_struct *wq = dev_to_wq(dev);
5456 struct workqueue_attrs *attrs;
5457 int ret = -ENOMEM;
5458
5459 apply_wqattrs_lock();
5460
5461 attrs = wq_sysfs_prep_attrs(wq);
5462 if (!attrs)
5463 goto out_unlock;
5464
5465 ret = cpumask_parse(buf, attrs->cpumask);
5466 if (!ret)
5467 ret = apply_workqueue_attrs_locked(wq, attrs);
5468
5469out_unlock:
5470 apply_wqattrs_unlock();
5471 free_workqueue_attrs(attrs);
5472 return ret ?: count;
5473}
5474
5475static ssize_t wq_numa_show(struct device *dev, struct device_attribute *attr,
5476 char *buf)
5477{
5478 struct workqueue_struct *wq = dev_to_wq(dev);
5479 int written;
5480
5481 mutex_lock(&wq->mutex);
5482 written = scnprintf(buf, PAGE_SIZE, "%d\n",
5483 !wq->unbound_attrs->no_numa);
5484 mutex_unlock(&wq->mutex);
5485
5486 return written;
5487}
5488
5489static ssize_t wq_numa_store(struct device *dev, struct device_attribute *attr,
5490 const char *buf, size_t count)
5491{
5492 struct workqueue_struct *wq = dev_to_wq(dev);
5493 struct workqueue_attrs *attrs;
5494 int v, ret = -ENOMEM;
5495
5496 apply_wqattrs_lock();
5497
5498 attrs = wq_sysfs_prep_attrs(wq);
5499 if (!attrs)
5500 goto out_unlock;
5501
5502 ret = -EINVAL;
5503 if (sscanf(buf, "%d", &v) == 1) {
5504 attrs->no_numa = !v;
5505 ret = apply_workqueue_attrs_locked(wq, attrs);
5506 }
5507
5508out_unlock:
5509 apply_wqattrs_unlock();
5510 free_workqueue_attrs(attrs);
5511 return ret ?: count;
5512}
5513
5514static struct device_attribute wq_sysfs_unbound_attrs[] = {
5515 __ATTR(pool_ids, 0444, wq_pool_ids_show, NULL),
5516 __ATTR(nice, 0644, wq_nice_show, wq_nice_store),
5517 __ATTR(cpumask, 0644, wq_cpumask_show, wq_cpumask_store),
5518 __ATTR(numa, 0644, wq_numa_show, wq_numa_store),
5519 __ATTR_NULL,
5520};
5521
5522static struct bus_type wq_subsys = {
5523 .name = "workqueue",
5524 .dev_groups = wq_sysfs_groups,
5525};
5526
5527static ssize_t wq_unbound_cpumask_show(struct device *dev,
5528 struct device_attribute *attr, char *buf)
5529{
5530 int written;
5531
5532 mutex_lock(&wq_pool_mutex);
5533 written = scnprintf(buf, PAGE_SIZE, "%*pb\n",
5534 cpumask_pr_args(wq_unbound_cpumask));
5535 mutex_unlock(&wq_pool_mutex);
5536
5537 return written;
5538}
5539
5540static ssize_t wq_unbound_cpumask_store(struct device *dev,
5541 struct device_attribute *attr, const char *buf, size_t count)
5542{
5543 cpumask_var_t cpumask;
5544 int ret;
5545
5546 if (!zalloc_cpumask_var(&cpumask, GFP_KERNEL))
5547 return -ENOMEM;
5548
5549 ret = cpumask_parse(buf, cpumask);
5550 if (!ret)
5551 ret = workqueue_set_unbound_cpumask(cpumask);
5552
5553 free_cpumask_var(cpumask);
5554 return ret ? ret : count;
5555}
5556
5557static struct device_attribute wq_sysfs_cpumask_attr =
5558 __ATTR(cpumask, 0644, wq_unbound_cpumask_show,
5559 wq_unbound_cpumask_store);
5560
5561static int __init wq_sysfs_init(void)
5562{
5563 int err;
5564
5565 err = subsys_virtual_register(&wq_subsys, NULL);
5566 if (err)
5567 return err;
5568
5569 return device_create_file(wq_subsys.dev_root, &wq_sysfs_cpumask_attr);
5570}
5571core_initcall(wq_sysfs_init);
5572
5573static void wq_device_release(struct device *dev)
5574{
5575 struct wq_device *wq_dev = container_of(dev, struct wq_device, dev);
5576
5577 kfree(wq_dev);
5578}
5579
5580/**
5581 * workqueue_sysfs_register - make a workqueue visible in sysfs
5582 * @wq: the workqueue to register
5583 *
5584 * Expose @wq in sysfs under /sys/bus/workqueue/devices.
5585 * alloc_workqueue*() automatically calls this function if WQ_SYSFS is set
5586 * which is the preferred method.
5587 *
5588 * Workqueue user should use this function directly iff it wants to apply
5589 * workqueue_attrs before making the workqueue visible in sysfs; otherwise,
5590 * apply_workqueue_attrs() may race against userland updating the
5591 * attributes.
5592 *
5593 * Return: 0 on success, -errno on failure.
5594 */
5595int workqueue_sysfs_register(struct workqueue_struct *wq)
5596{
5597 struct wq_device *wq_dev;
5598 int ret;
5599
5600 /*
5601 * Adjusting max_active or creating new pwqs by applying
5602 * attributes breaks ordering guarantee. Disallow exposing ordered
5603 * workqueues.
5604 */
5605 if (WARN_ON(wq->flags & __WQ_ORDERED_EXPLICIT))
5606 return -EINVAL;
5607
5608 wq->wq_dev = wq_dev = kzalloc(sizeof(*wq_dev), GFP_KERNEL);
5609 if (!wq_dev)
5610 return -ENOMEM;
5611
5612 wq_dev->wq = wq;
5613 wq_dev->dev.bus = &wq_subsys;
5614 wq_dev->dev.release = wq_device_release;
5615 dev_set_name(&wq_dev->dev, "%s", wq->name);
5616
5617 /*
5618 * unbound_attrs are created separately. Suppress uevent until
5619 * everything is ready.
5620 */
5621 dev_set_uevent_suppress(&wq_dev->dev, true);
5622
5623 ret = device_register(&wq_dev->dev);
5624 if (ret) {
5625 put_device(&wq_dev->dev);
5626 wq->wq_dev = NULL;
5627 return ret;
5628 }
5629
5630 if (wq->flags & WQ_UNBOUND) {
5631 struct device_attribute *attr;
5632
5633 for (attr = wq_sysfs_unbound_attrs; attr->attr.name; attr++) {
5634 ret = device_create_file(&wq_dev->dev, attr);
5635 if (ret) {
5636 device_unregister(&wq_dev->dev);
5637 wq->wq_dev = NULL;
5638 return ret;
5639 }
5640 }
5641 }
5642
5643 dev_set_uevent_suppress(&wq_dev->dev, false);
5644 kobject_uevent(&wq_dev->dev.kobj, KOBJ_ADD);
5645 return 0;
5646}
5647
5648/**
5649 * workqueue_sysfs_unregister - undo workqueue_sysfs_register()
5650 * @wq: the workqueue to unregister
5651 *
5652 * If @wq is registered to sysfs by workqueue_sysfs_register(), unregister.
5653 */
5654static void workqueue_sysfs_unregister(struct workqueue_struct *wq)
5655{
5656 struct wq_device *wq_dev = wq->wq_dev;
5657
5658 if (!wq->wq_dev)
5659 return;
5660
5661 wq->wq_dev = NULL;
5662 device_unregister(&wq_dev->dev);
5663}
5664#else /* CONFIG_SYSFS */
5665static void workqueue_sysfs_unregister(struct workqueue_struct *wq) { }
5666#endif /* CONFIG_SYSFS */
5667
5668/*
5669 * Workqueue watchdog.
5670 *
5671 * Stall may be caused by various bugs - missing WQ_MEM_RECLAIM, illegal
5672 * flush dependency, a concurrency managed work item which stays RUNNING
5673 * indefinitely. Workqueue stalls can be very difficult to debug as the
5674 * usual warning mechanisms don't trigger and internal workqueue state is
5675 * largely opaque.
5676 *
5677 * Workqueue watchdog monitors all worker pools periodically and dumps
5678 * state if some pools failed to make forward progress for a while where
5679 * forward progress is defined as the first item on ->worklist changing.
5680 *
5681 * This mechanism is controlled through the kernel parameter
5682 * "workqueue.watchdog_thresh" which can be updated at runtime through the
5683 * corresponding sysfs parameter file.
5684 */
5685#ifdef CONFIG_WQ_WATCHDOG
5686
5687static unsigned long wq_watchdog_thresh = 30;
5688static struct timer_list wq_watchdog_timer;
5689
5690static unsigned long wq_watchdog_touched = INITIAL_JIFFIES;
5691static DEFINE_PER_CPU(unsigned long, wq_watchdog_touched_cpu) = INITIAL_JIFFIES;
5692
5693static void wq_watchdog_reset_touched(void)
5694{
5695 int cpu;
5696
5697 wq_watchdog_touched = jiffies;
5698 for_each_possible_cpu(cpu)
5699 per_cpu(wq_watchdog_touched_cpu, cpu) = jiffies;
5700}
5701
5702static void wq_watchdog_timer_fn(struct timer_list *unused)
5703{
5704 unsigned long thresh = READ_ONCE(wq_watchdog_thresh) * HZ;
5705 bool lockup_detected = false;
5706 struct worker_pool *pool;
5707 int pi;
5708
5709 if (!thresh)
5710 return;
5711
5712 rcu_read_lock();
5713
5714 for_each_pool(pool, pi) {
5715 unsigned long pool_ts, touched, ts;
5716
5717 if (list_empty(&pool->worklist))
5718 continue;
5719
5720 /* get the latest of pool and touched timestamps */
5721 pool_ts = READ_ONCE(pool->watchdog_ts);
5722 touched = READ_ONCE(wq_watchdog_touched);
5723
5724 if (time_after(pool_ts, touched))
5725 ts = pool_ts;
5726 else
5727 ts = touched;
5728
5729 if (pool->cpu >= 0) {
5730 unsigned long cpu_touched =
5731 READ_ONCE(per_cpu(wq_watchdog_touched_cpu,
5732 pool->cpu));
5733 if (time_after(cpu_touched, ts))
5734 ts = cpu_touched;
5735 }
5736
5737 /* did we stall? */
5738 if (time_after(jiffies, ts + thresh)) {
5739 lockup_detected = true;
5740 pr_emerg("BUG: workqueue lockup - pool");
5741 pr_cont_pool_info(pool);
5742 pr_cont(" stuck for %us!\n",
5743 jiffies_to_msecs(jiffies - pool_ts) / 1000);
5744 }
5745 }
5746
5747 rcu_read_unlock();
5748
5749 if (lockup_detected)
5750 show_workqueue_state();
5751
5752 wq_watchdog_reset_touched();
5753 mod_timer(&wq_watchdog_timer, jiffies + thresh);
5754}
5755
5756notrace void wq_watchdog_touch(int cpu)
5757{
5758 if (cpu >= 0)
5759 per_cpu(wq_watchdog_touched_cpu, cpu) = jiffies;
5760 else
5761 wq_watchdog_touched = jiffies;
5762}
5763
5764static void wq_watchdog_set_thresh(unsigned long thresh)
5765{
5766 wq_watchdog_thresh = 0;
5767 del_timer_sync(&wq_watchdog_timer);
5768
5769 if (thresh) {
5770 wq_watchdog_thresh = thresh;
5771 wq_watchdog_reset_touched();
5772 mod_timer(&wq_watchdog_timer, jiffies + thresh * HZ);
5773 }
5774}
5775
5776static int wq_watchdog_param_set_thresh(const char *val,
5777 const struct kernel_param *kp)
5778{
5779 unsigned long thresh;
5780 int ret;
5781
5782 ret = kstrtoul(val, 0, &thresh);
5783 if (ret)
5784 return ret;
5785
5786 if (system_wq)
5787 wq_watchdog_set_thresh(thresh);
5788 else
5789 wq_watchdog_thresh = thresh;
5790
5791 return 0;
5792}
5793
5794static const struct kernel_param_ops wq_watchdog_thresh_ops = {
5795 .set = wq_watchdog_param_set_thresh,
5796 .get = param_get_ulong,
5797};
5798
5799module_param_cb(watchdog_thresh, &wq_watchdog_thresh_ops, &wq_watchdog_thresh,
5800 0644);
5801
5802static void wq_watchdog_init(void)
5803{
5804 timer_setup(&wq_watchdog_timer, wq_watchdog_timer_fn, TIMER_DEFERRABLE);
5805 wq_watchdog_set_thresh(wq_watchdog_thresh);
5806}
5807
5808#else /* CONFIG_WQ_WATCHDOG */
5809
5810static inline void wq_watchdog_init(void) { }
5811
5812#endif /* CONFIG_WQ_WATCHDOG */
5813
5814static void __init wq_numa_init(void)
5815{
5816 cpumask_var_t *tbl;
5817 int node, cpu;
5818
5819 if (num_possible_nodes() <= 1)
5820 return;
5821
5822 if (wq_disable_numa) {
5823 pr_info("workqueue: NUMA affinity support disabled\n");
5824 return;
5825 }
5826
5827 wq_update_unbound_numa_attrs_buf = alloc_workqueue_attrs();
5828 BUG_ON(!wq_update_unbound_numa_attrs_buf);
5829
5830 /*
5831 * We want masks of possible CPUs of each node which isn't readily
5832 * available. Build one from cpu_to_node() which should have been
5833 * fully initialized by now.
5834 */
5835 tbl = kcalloc(nr_node_ids, sizeof(tbl[0]), GFP_KERNEL);
5836 BUG_ON(!tbl);
5837
5838 for_each_node(node)
5839 BUG_ON(!zalloc_cpumask_var_node(&tbl[node], GFP_KERNEL,
5840 node_online(node) ? node : NUMA_NO_NODE));
5841
5842 for_each_possible_cpu(cpu) {
5843 node = cpu_to_node(cpu);
5844 if (WARN_ON(node == NUMA_NO_NODE)) {
5845 pr_warn("workqueue: NUMA node mapping not available for cpu%d, disabling NUMA support\n", cpu);
5846 /* happens iff arch is bonkers, let's just proceed */
5847 return;
5848 }
5849 cpumask_set_cpu(cpu, tbl[node]);
5850 }
5851
5852 wq_numa_possible_cpumask = tbl;
5853 wq_numa_enabled = true;
5854}
5855
5856/**
5857 * workqueue_init_early - early init for workqueue subsystem
5858 *
5859 * This is the first half of two-staged workqueue subsystem initialization
5860 * and invoked as soon as the bare basics - memory allocation, cpumasks and
5861 * idr are up. It sets up all the data structures and system workqueues
5862 * and allows early boot code to create workqueues and queue/cancel work
5863 * items. Actual work item execution starts only after kthreads can be
5864 * created and scheduled right before early initcalls.
5865 */
5866int __init workqueue_init_early(void)
5867{
5868 int std_nice[NR_STD_WORKER_POOLS] = { 0, HIGHPRI_NICE_LEVEL };
5869 int hk_flags = HK_FLAG_DOMAIN | HK_FLAG_WQ;
5870 int i, cpu;
5871
5872 WARN_ON(__alignof__(struct pool_workqueue) < __alignof__(long long));
5873
5874 BUG_ON(!alloc_cpumask_var(&wq_unbound_cpumask, GFP_KERNEL));
5875 cpumask_copy(wq_unbound_cpumask, housekeeping_cpumask(hk_flags));
5876
5877 pwq_cache = KMEM_CACHE(pool_workqueue, SLAB_PANIC);
5878
5879 /* initialize CPU pools */
5880 for_each_possible_cpu(cpu) {
5881 struct worker_pool *pool;
5882
5883 i = 0;
5884 for_each_cpu_worker_pool(pool, cpu) {
5885 BUG_ON(init_worker_pool(pool));
5886 pool->cpu = cpu;
5887 cpumask_copy(pool->attrs->cpumask, cpumask_of(cpu));
5888 pool->attrs->nice = std_nice[i++];
5889 pool->node = cpu_to_node(cpu);
5890
5891 /* alloc pool ID */
5892 mutex_lock(&wq_pool_mutex);
5893 BUG_ON(worker_pool_assign_id(pool));
5894 mutex_unlock(&wq_pool_mutex);
5895 }
5896 }
5897
5898 /* create default unbound and ordered wq attrs */
5899 for (i = 0; i < NR_STD_WORKER_POOLS; i++) {
5900 struct workqueue_attrs *attrs;
5901
5902 BUG_ON(!(attrs = alloc_workqueue_attrs()));
5903 attrs->nice = std_nice[i];
5904 unbound_std_wq_attrs[i] = attrs;
5905
5906 /*
5907 * An ordered wq should have only one pwq as ordering is
5908 * guaranteed by max_active which is enforced by pwqs.
5909 * Turn off NUMA so that dfl_pwq is used for all nodes.
5910 */
5911 BUG_ON(!(attrs = alloc_workqueue_attrs()));
5912 attrs->nice = std_nice[i];
5913 attrs->no_numa = true;
5914 ordered_wq_attrs[i] = attrs;
5915 }
5916
5917 system_wq = alloc_workqueue("events", 0, 0);
5918 system_highpri_wq = alloc_workqueue("events_highpri", WQ_HIGHPRI, 0);
5919 system_long_wq = alloc_workqueue("events_long", 0, 0);
5920 system_unbound_wq = alloc_workqueue("events_unbound", WQ_UNBOUND,
5921 WQ_UNBOUND_MAX_ACTIVE);
5922 system_freezable_wq = alloc_workqueue("events_freezable",
5923 WQ_FREEZABLE, 0);
5924 system_power_efficient_wq = alloc_workqueue("events_power_efficient",
5925 WQ_POWER_EFFICIENT, 0);
5926 system_freezable_power_efficient_wq = alloc_workqueue("events_freezable_power_efficient",
5927 WQ_FREEZABLE | WQ_POWER_EFFICIENT,
5928 0);
5929 BUG_ON(!system_wq || !system_highpri_wq || !system_long_wq ||
5930 !system_unbound_wq || !system_freezable_wq ||
5931 !system_power_efficient_wq ||
5932 !system_freezable_power_efficient_wq);
5933
5934 return 0;
5935}
5936
5937/**
5938 * workqueue_init - bring workqueue subsystem fully online
5939 *
5940 * This is the latter half of two-staged workqueue subsystem initialization
5941 * and invoked as soon as kthreads can be created and scheduled.
5942 * Workqueues have been created and work items queued on them, but there
5943 * are no kworkers executing the work items yet. Populate the worker pools
5944 * with the initial workers and enable future kworker creations.
5945 */
5946int __init workqueue_init(void)
5947{
5948 struct workqueue_struct *wq;
5949 struct worker_pool *pool;
5950 int cpu, bkt;
5951
5952 /*
5953 * It'd be simpler to initialize NUMA in workqueue_init_early() but
5954 * CPU to node mapping may not be available that early on some
5955 * archs such as power and arm64. As per-cpu pools created
5956 * previously could be missing node hint and unbound pools NUMA
5957 * affinity, fix them up.
5958 *
5959 * Also, while iterating workqueues, create rescuers if requested.
5960 */
5961 wq_numa_init();
5962
5963 mutex_lock(&wq_pool_mutex);
5964
5965 for_each_possible_cpu(cpu) {
5966 for_each_cpu_worker_pool(pool, cpu) {
5967 pool->node = cpu_to_node(cpu);
5968 }
5969 }
5970
5971 list_for_each_entry(wq, &workqueues, list) {
5972 wq_update_unbound_numa(wq, smp_processor_id(), true);
5973 WARN(init_rescuer(wq),
5974 "workqueue: failed to create early rescuer for %s",
5975 wq->name);
5976 }
5977
5978 mutex_unlock(&wq_pool_mutex);
5979
5980 /* create the initial workers */
5981 for_each_online_cpu(cpu) {
5982 for_each_cpu_worker_pool(pool, cpu) {
5983 pool->flags &= ~POOL_DISASSOCIATED;
5984 BUG_ON(!create_worker(pool));
5985 }
5986 }
5987
5988 hash_for_each(unbound_pool_hash, bkt, pool, hash_node)
5989 BUG_ON(!create_worker(pool));
5990
5991 wq_online = true;
5992 wq_watchdog_init();
5993
5994 return 0;
5995}
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 is one worker pool for each CPU and
20 * one extra for works which are better served by workers which are
21 * not bound to any specific CPU.
22 *
23 * Please read Documentation/workqueue.txt for details.
24 */
25
26#include <linux/module.h>
27#include <linux/kernel.h>
28#include <linux/sched.h>
29#include <linux/init.h>
30#include <linux/signal.h>
31#include <linux/completion.h>
32#include <linux/workqueue.h>
33#include <linux/slab.h>
34#include <linux/cpu.h>
35#include <linux/notifier.h>
36#include <linux/kthread.h>
37#include <linux/hardirq.h>
38#include <linux/mempolicy.h>
39#include <linux/freezer.h>
40#include <linux/kallsyms.h>
41#include <linux/debug_locks.h>
42#include <linux/lockdep.h>
43#include <linux/idr.h>
44
45#include "workqueue_sched.h"
46
47enum {
48 /* global_cwq flags */
49 GCWQ_MANAGE_WORKERS = 1 << 0, /* need to manage workers */
50 GCWQ_MANAGING_WORKERS = 1 << 1, /* managing workers */
51 GCWQ_DISASSOCIATED = 1 << 2, /* cpu can't serve workers */
52 GCWQ_FREEZING = 1 << 3, /* freeze in progress */
53 GCWQ_HIGHPRI_PENDING = 1 << 4, /* highpri works on queue */
54
55 /* worker flags */
56 WORKER_STARTED = 1 << 0, /* started */
57 WORKER_DIE = 1 << 1, /* die die die */
58 WORKER_IDLE = 1 << 2, /* is idle */
59 WORKER_PREP = 1 << 3, /* preparing to run works */
60 WORKER_ROGUE = 1 << 4, /* not bound to any cpu */
61 WORKER_REBIND = 1 << 5, /* mom is home, come back */
62 WORKER_CPU_INTENSIVE = 1 << 6, /* cpu intensive */
63 WORKER_UNBOUND = 1 << 7, /* worker is unbound */
64
65 WORKER_NOT_RUNNING = WORKER_PREP | WORKER_ROGUE | WORKER_REBIND |
66 WORKER_CPU_INTENSIVE | WORKER_UNBOUND,
67
68 /* gcwq->trustee_state */
69 TRUSTEE_START = 0, /* start */
70 TRUSTEE_IN_CHARGE = 1, /* trustee in charge of gcwq */
71 TRUSTEE_BUTCHER = 2, /* butcher workers */
72 TRUSTEE_RELEASE = 3, /* release workers */
73 TRUSTEE_DONE = 4, /* trustee is done */
74
75 BUSY_WORKER_HASH_ORDER = 6, /* 64 pointers */
76 BUSY_WORKER_HASH_SIZE = 1 << BUSY_WORKER_HASH_ORDER,
77 BUSY_WORKER_HASH_MASK = BUSY_WORKER_HASH_SIZE - 1,
78
79 MAX_IDLE_WORKERS_RATIO = 4, /* 1/4 of busy can be idle */
80 IDLE_WORKER_TIMEOUT = 300 * HZ, /* keep idle ones for 5 mins */
81
82 MAYDAY_INITIAL_TIMEOUT = HZ / 100 >= 2 ? HZ / 100 : 2,
83 /* call for help after 10ms
84 (min two ticks) */
85 MAYDAY_INTERVAL = HZ / 10, /* and then every 100ms */
86 CREATE_COOLDOWN = HZ, /* time to breath after fail */
87 TRUSTEE_COOLDOWN = HZ / 10, /* for trustee draining */
88
89 /*
90 * Rescue workers are used only on emergencies and shared by
91 * all cpus. Give -20.
92 */
93 RESCUER_NICE_LEVEL = -20,
94};
95
96/*
97 * Structure fields follow one of the following exclusion rules.
98 *
99 * I: Modifiable by initialization/destruction paths and read-only for
100 * everyone else.
101 *
102 * P: Preemption protected. Disabling preemption is enough and should
103 * only be modified and accessed from the local cpu.
104 *
105 * L: gcwq->lock protected. Access with gcwq->lock held.
106 *
107 * X: During normal operation, modification requires gcwq->lock and
108 * should be done only from local cpu. Either disabling preemption
109 * on local cpu or grabbing gcwq->lock is enough for read access.
110 * If GCWQ_DISASSOCIATED is set, it's identical to L.
111 *
112 * F: wq->flush_mutex protected.
113 *
114 * W: workqueue_lock protected.
115 */
116
117struct global_cwq;
118
119/*
120 * The poor guys doing the actual heavy lifting. All on-duty workers
121 * are either serving the manager role, on idle list or on busy hash.
122 */
123struct worker {
124 /* on idle list while idle, on busy hash table while busy */
125 union {
126 struct list_head entry; /* L: while idle */
127 struct hlist_node hentry; /* L: while busy */
128 };
129
130 struct work_struct *current_work; /* L: work being processed */
131 struct cpu_workqueue_struct *current_cwq; /* L: current_work's cwq */
132 struct list_head scheduled; /* L: scheduled works */
133 struct task_struct *task; /* I: worker task */
134 struct global_cwq *gcwq; /* I: the associated gcwq */
135 /* 64 bytes boundary on 64bit, 32 on 32bit */
136 unsigned long last_active; /* L: last active timestamp */
137 unsigned int flags; /* X: flags */
138 int id; /* I: worker id */
139 struct work_struct rebind_work; /* L: rebind worker to cpu */
140};
141
142/*
143 * Global per-cpu workqueue. There's one and only one for each cpu
144 * and all works are queued and processed here regardless of their
145 * target workqueues.
146 */
147struct global_cwq {
148 spinlock_t lock; /* the gcwq lock */
149 struct list_head worklist; /* L: list of pending works */
150 unsigned int cpu; /* I: the associated cpu */
151 unsigned int flags; /* L: GCWQ_* flags */
152
153 int nr_workers; /* L: total number of workers */
154 int nr_idle; /* L: currently idle ones */
155
156 /* workers are chained either in the idle_list or busy_hash */
157 struct list_head idle_list; /* X: list of idle workers */
158 struct hlist_head busy_hash[BUSY_WORKER_HASH_SIZE];
159 /* L: hash of busy workers */
160
161 struct timer_list idle_timer; /* L: worker idle timeout */
162 struct timer_list mayday_timer; /* L: SOS timer for dworkers */
163
164 struct ida worker_ida; /* L: for worker IDs */
165
166 struct task_struct *trustee; /* L: for gcwq shutdown */
167 unsigned int trustee_state; /* L: trustee state */
168 wait_queue_head_t trustee_wait; /* trustee wait */
169 struct worker *first_idle; /* L: first idle worker */
170} ____cacheline_aligned_in_smp;
171
172/*
173 * The per-CPU workqueue. The lower WORK_STRUCT_FLAG_BITS of
174 * work_struct->data are used for flags and thus cwqs need to be
175 * aligned at two's power of the number of flag bits.
176 */
177struct cpu_workqueue_struct {
178 struct global_cwq *gcwq; /* I: the associated gcwq */
179 struct workqueue_struct *wq; /* I: the owning workqueue */
180 int work_color; /* L: current color */
181 int flush_color; /* L: flushing color */
182 int nr_in_flight[WORK_NR_COLORS];
183 /* L: nr of in_flight works */
184 int nr_active; /* L: nr of active works */
185 int max_active; /* L: max active works */
186 struct list_head delayed_works; /* L: delayed works */
187};
188
189/*
190 * Structure used to wait for workqueue flush.
191 */
192struct wq_flusher {
193 struct list_head list; /* F: list of flushers */
194 int flush_color; /* F: flush color waiting for */
195 struct completion done; /* flush completion */
196};
197
198/*
199 * All cpumasks are assumed to be always set on UP and thus can't be
200 * used to determine whether there's something to be done.
201 */
202#ifdef CONFIG_SMP
203typedef cpumask_var_t mayday_mask_t;
204#define mayday_test_and_set_cpu(cpu, mask) \
205 cpumask_test_and_set_cpu((cpu), (mask))
206#define mayday_clear_cpu(cpu, mask) cpumask_clear_cpu((cpu), (mask))
207#define for_each_mayday_cpu(cpu, mask) for_each_cpu((cpu), (mask))
208#define alloc_mayday_mask(maskp, gfp) zalloc_cpumask_var((maskp), (gfp))
209#define free_mayday_mask(mask) free_cpumask_var((mask))
210#else
211typedef unsigned long mayday_mask_t;
212#define mayday_test_and_set_cpu(cpu, mask) test_and_set_bit(0, &(mask))
213#define mayday_clear_cpu(cpu, mask) clear_bit(0, &(mask))
214#define for_each_mayday_cpu(cpu, mask) if ((cpu) = 0, (mask))
215#define alloc_mayday_mask(maskp, gfp) true
216#define free_mayday_mask(mask) do { } while (0)
217#endif
218
219/*
220 * The externally visible workqueue abstraction is an array of
221 * per-CPU workqueues:
222 */
223struct workqueue_struct {
224 unsigned int flags; /* W: WQ_* flags */
225 union {
226 struct cpu_workqueue_struct __percpu *pcpu;
227 struct cpu_workqueue_struct *single;
228 unsigned long v;
229 } cpu_wq; /* I: cwq's */
230 struct list_head list; /* W: list of all workqueues */
231
232 struct mutex flush_mutex; /* protects wq flushing */
233 int work_color; /* F: current work color */
234 int flush_color; /* F: current flush color */
235 atomic_t nr_cwqs_to_flush; /* flush in progress */
236 struct wq_flusher *first_flusher; /* F: first flusher */
237 struct list_head flusher_queue; /* F: flush waiters */
238 struct list_head flusher_overflow; /* F: flush overflow list */
239
240 mayday_mask_t mayday_mask; /* cpus requesting rescue */
241 struct worker *rescuer; /* I: rescue worker */
242
243 int nr_drainers; /* W: drain in progress */
244 int saved_max_active; /* W: saved cwq max_active */
245 const char *name; /* I: workqueue name */
246#ifdef CONFIG_LOCKDEP
247 struct lockdep_map lockdep_map;
248#endif
249};
250
251struct workqueue_struct *system_wq __read_mostly;
252struct workqueue_struct *system_long_wq __read_mostly;
253struct workqueue_struct *system_nrt_wq __read_mostly;
254struct workqueue_struct *system_unbound_wq __read_mostly;
255struct workqueue_struct *system_freezable_wq __read_mostly;
256EXPORT_SYMBOL_GPL(system_wq);
257EXPORT_SYMBOL_GPL(system_long_wq);
258EXPORT_SYMBOL_GPL(system_nrt_wq);
259EXPORT_SYMBOL_GPL(system_unbound_wq);
260EXPORT_SYMBOL_GPL(system_freezable_wq);
261
262#define CREATE_TRACE_POINTS
263#include <trace/events/workqueue.h>
264
265#define for_each_busy_worker(worker, i, pos, gcwq) \
266 for (i = 0; i < BUSY_WORKER_HASH_SIZE; i++) \
267 hlist_for_each_entry(worker, pos, &gcwq->busy_hash[i], hentry)
268
269static inline int __next_gcwq_cpu(int cpu, const struct cpumask *mask,
270 unsigned int sw)
271{
272 if (cpu < nr_cpu_ids) {
273 if (sw & 1) {
274 cpu = cpumask_next(cpu, mask);
275 if (cpu < nr_cpu_ids)
276 return cpu;
277 }
278 if (sw & 2)
279 return WORK_CPU_UNBOUND;
280 }
281 return WORK_CPU_NONE;
282}
283
284static inline int __next_wq_cpu(int cpu, const struct cpumask *mask,
285 struct workqueue_struct *wq)
286{
287 return __next_gcwq_cpu(cpu, mask, !(wq->flags & WQ_UNBOUND) ? 1 : 2);
288}
289
290/*
291 * CPU iterators
292 *
293 * An extra gcwq is defined for an invalid cpu number
294 * (WORK_CPU_UNBOUND) to host workqueues which are not bound to any
295 * specific CPU. The following iterators are similar to
296 * for_each_*_cpu() iterators but also considers the unbound gcwq.
297 *
298 * for_each_gcwq_cpu() : possible CPUs + WORK_CPU_UNBOUND
299 * for_each_online_gcwq_cpu() : online CPUs + WORK_CPU_UNBOUND
300 * for_each_cwq_cpu() : possible CPUs for bound workqueues,
301 * WORK_CPU_UNBOUND for unbound workqueues
302 */
303#define for_each_gcwq_cpu(cpu) \
304 for ((cpu) = __next_gcwq_cpu(-1, cpu_possible_mask, 3); \
305 (cpu) < WORK_CPU_NONE; \
306 (cpu) = __next_gcwq_cpu((cpu), cpu_possible_mask, 3))
307
308#define for_each_online_gcwq_cpu(cpu) \
309 for ((cpu) = __next_gcwq_cpu(-1, cpu_online_mask, 3); \
310 (cpu) < WORK_CPU_NONE; \
311 (cpu) = __next_gcwq_cpu((cpu), cpu_online_mask, 3))
312
313#define for_each_cwq_cpu(cpu, wq) \
314 for ((cpu) = __next_wq_cpu(-1, cpu_possible_mask, (wq)); \
315 (cpu) < WORK_CPU_NONE; \
316 (cpu) = __next_wq_cpu((cpu), cpu_possible_mask, (wq)))
317
318#ifdef CONFIG_DEBUG_OBJECTS_WORK
319
320static struct debug_obj_descr work_debug_descr;
321
322static void *work_debug_hint(void *addr)
323{
324 return ((struct work_struct *) addr)->func;
325}
326
327/*
328 * fixup_init is called when:
329 * - an active object is initialized
330 */
331static int work_fixup_init(void *addr, enum debug_obj_state state)
332{
333 struct work_struct *work = addr;
334
335 switch (state) {
336 case ODEBUG_STATE_ACTIVE:
337 cancel_work_sync(work);
338 debug_object_init(work, &work_debug_descr);
339 return 1;
340 default:
341 return 0;
342 }
343}
344
345/*
346 * fixup_activate is called when:
347 * - an active object is activated
348 * - an unknown object is activated (might be a statically initialized object)
349 */
350static int work_fixup_activate(void *addr, enum debug_obj_state state)
351{
352 struct work_struct *work = addr;
353
354 switch (state) {
355
356 case ODEBUG_STATE_NOTAVAILABLE:
357 /*
358 * This is not really a fixup. The work struct was
359 * statically initialized. We just make sure that it
360 * is tracked in the object tracker.
361 */
362 if (test_bit(WORK_STRUCT_STATIC_BIT, work_data_bits(work))) {
363 debug_object_init(work, &work_debug_descr);
364 debug_object_activate(work, &work_debug_descr);
365 return 0;
366 }
367 WARN_ON_ONCE(1);
368 return 0;
369
370 case ODEBUG_STATE_ACTIVE:
371 WARN_ON(1);
372
373 default:
374 return 0;
375 }
376}
377
378/*
379 * fixup_free is called when:
380 * - an active object is freed
381 */
382static int work_fixup_free(void *addr, enum debug_obj_state state)
383{
384 struct work_struct *work = addr;
385
386 switch (state) {
387 case ODEBUG_STATE_ACTIVE:
388 cancel_work_sync(work);
389 debug_object_free(work, &work_debug_descr);
390 return 1;
391 default:
392 return 0;
393 }
394}
395
396static struct debug_obj_descr work_debug_descr = {
397 .name = "work_struct",
398 .debug_hint = work_debug_hint,
399 .fixup_init = work_fixup_init,
400 .fixup_activate = work_fixup_activate,
401 .fixup_free = work_fixup_free,
402};
403
404static inline void debug_work_activate(struct work_struct *work)
405{
406 debug_object_activate(work, &work_debug_descr);
407}
408
409static inline void debug_work_deactivate(struct work_struct *work)
410{
411 debug_object_deactivate(work, &work_debug_descr);
412}
413
414void __init_work(struct work_struct *work, int onstack)
415{
416 if (onstack)
417 debug_object_init_on_stack(work, &work_debug_descr);
418 else
419 debug_object_init(work, &work_debug_descr);
420}
421EXPORT_SYMBOL_GPL(__init_work);
422
423void destroy_work_on_stack(struct work_struct *work)
424{
425 debug_object_free(work, &work_debug_descr);
426}
427EXPORT_SYMBOL_GPL(destroy_work_on_stack);
428
429#else
430static inline void debug_work_activate(struct work_struct *work) { }
431static inline void debug_work_deactivate(struct work_struct *work) { }
432#endif
433
434/* Serializes the accesses to the list of workqueues. */
435static DEFINE_SPINLOCK(workqueue_lock);
436static LIST_HEAD(workqueues);
437static bool workqueue_freezing; /* W: have wqs started freezing? */
438
439/*
440 * The almighty global cpu workqueues. nr_running is the only field
441 * which is expected to be used frequently by other cpus via
442 * try_to_wake_up(). Put it in a separate cacheline.
443 */
444static DEFINE_PER_CPU(struct global_cwq, global_cwq);
445static DEFINE_PER_CPU_SHARED_ALIGNED(atomic_t, gcwq_nr_running);
446
447/*
448 * Global cpu workqueue and nr_running counter for unbound gcwq. The
449 * gcwq is always online, has GCWQ_DISASSOCIATED set, and all its
450 * workers have WORKER_UNBOUND set.
451 */
452static struct global_cwq unbound_global_cwq;
453static atomic_t unbound_gcwq_nr_running = ATOMIC_INIT(0); /* always 0 */
454
455static int worker_thread(void *__worker);
456
457static struct global_cwq *get_gcwq(unsigned int cpu)
458{
459 if (cpu != WORK_CPU_UNBOUND)
460 return &per_cpu(global_cwq, cpu);
461 else
462 return &unbound_global_cwq;
463}
464
465static atomic_t *get_gcwq_nr_running(unsigned int cpu)
466{
467 if (cpu != WORK_CPU_UNBOUND)
468 return &per_cpu(gcwq_nr_running, cpu);
469 else
470 return &unbound_gcwq_nr_running;
471}
472
473static struct cpu_workqueue_struct *get_cwq(unsigned int cpu,
474 struct workqueue_struct *wq)
475{
476 if (!(wq->flags & WQ_UNBOUND)) {
477 if (likely(cpu < nr_cpu_ids)) {
478#ifdef CONFIG_SMP
479 return per_cpu_ptr(wq->cpu_wq.pcpu, cpu);
480#else
481 return wq->cpu_wq.single;
482#endif
483 }
484 } else if (likely(cpu == WORK_CPU_UNBOUND))
485 return wq->cpu_wq.single;
486 return NULL;
487}
488
489static unsigned int work_color_to_flags(int color)
490{
491 return color << WORK_STRUCT_COLOR_SHIFT;
492}
493
494static int get_work_color(struct work_struct *work)
495{
496 return (*work_data_bits(work) >> WORK_STRUCT_COLOR_SHIFT) &
497 ((1 << WORK_STRUCT_COLOR_BITS) - 1);
498}
499
500static int work_next_color(int color)
501{
502 return (color + 1) % WORK_NR_COLORS;
503}
504
505/*
506 * A work's data points to the cwq with WORK_STRUCT_CWQ set while the
507 * work is on queue. Once execution starts, WORK_STRUCT_CWQ is
508 * cleared and the work data contains the cpu number it was last on.
509 *
510 * set_work_{cwq|cpu}() and clear_work_data() can be used to set the
511 * cwq, cpu or clear work->data. These functions should only be
512 * called while the work is owned - ie. while the PENDING bit is set.
513 *
514 * get_work_[g]cwq() can be used to obtain the gcwq or cwq
515 * corresponding to a work. gcwq is available once the work has been
516 * queued anywhere after initialization. cwq is available only from
517 * queueing until execution starts.
518 */
519static inline void set_work_data(struct work_struct *work, unsigned long data,
520 unsigned long flags)
521{
522 BUG_ON(!work_pending(work));
523 atomic_long_set(&work->data, data | flags | work_static(work));
524}
525
526static void set_work_cwq(struct work_struct *work,
527 struct cpu_workqueue_struct *cwq,
528 unsigned long extra_flags)
529{
530 set_work_data(work, (unsigned long)cwq,
531 WORK_STRUCT_PENDING | WORK_STRUCT_CWQ | extra_flags);
532}
533
534static void set_work_cpu(struct work_struct *work, unsigned int cpu)
535{
536 set_work_data(work, cpu << WORK_STRUCT_FLAG_BITS, WORK_STRUCT_PENDING);
537}
538
539static void clear_work_data(struct work_struct *work)
540{
541 set_work_data(work, WORK_STRUCT_NO_CPU, 0);
542}
543
544static struct cpu_workqueue_struct *get_work_cwq(struct work_struct *work)
545{
546 unsigned long data = atomic_long_read(&work->data);
547
548 if (data & WORK_STRUCT_CWQ)
549 return (void *)(data & WORK_STRUCT_WQ_DATA_MASK);
550 else
551 return NULL;
552}
553
554static struct global_cwq *get_work_gcwq(struct work_struct *work)
555{
556 unsigned long data = atomic_long_read(&work->data);
557 unsigned int cpu;
558
559 if (data & WORK_STRUCT_CWQ)
560 return ((struct cpu_workqueue_struct *)
561 (data & WORK_STRUCT_WQ_DATA_MASK))->gcwq;
562
563 cpu = data >> WORK_STRUCT_FLAG_BITS;
564 if (cpu == WORK_CPU_NONE)
565 return NULL;
566
567 BUG_ON(cpu >= nr_cpu_ids && cpu != WORK_CPU_UNBOUND);
568 return get_gcwq(cpu);
569}
570
571/*
572 * Policy functions. These define the policies on how the global
573 * worker pool is managed. Unless noted otherwise, these functions
574 * assume that they're being called with gcwq->lock held.
575 */
576
577static bool __need_more_worker(struct global_cwq *gcwq)
578{
579 return !atomic_read(get_gcwq_nr_running(gcwq->cpu)) ||
580 gcwq->flags & GCWQ_HIGHPRI_PENDING;
581}
582
583/*
584 * Need to wake up a worker? Called from anything but currently
585 * running workers.
586 */
587static bool need_more_worker(struct global_cwq *gcwq)
588{
589 return !list_empty(&gcwq->worklist) && __need_more_worker(gcwq);
590}
591
592/* Can I start working? Called from busy but !running workers. */
593static bool may_start_working(struct global_cwq *gcwq)
594{
595 return gcwq->nr_idle;
596}
597
598/* Do I need to keep working? Called from currently running workers. */
599static bool keep_working(struct global_cwq *gcwq)
600{
601 atomic_t *nr_running = get_gcwq_nr_running(gcwq->cpu);
602
603 return !list_empty(&gcwq->worklist) &&
604 (atomic_read(nr_running) <= 1 ||
605 gcwq->flags & GCWQ_HIGHPRI_PENDING);
606}
607
608/* Do we need a new worker? Called from manager. */
609static bool need_to_create_worker(struct global_cwq *gcwq)
610{
611 return need_more_worker(gcwq) && !may_start_working(gcwq);
612}
613
614/* Do I need to be the manager? */
615static bool need_to_manage_workers(struct global_cwq *gcwq)
616{
617 return need_to_create_worker(gcwq) || gcwq->flags & GCWQ_MANAGE_WORKERS;
618}
619
620/* Do we have too many workers and should some go away? */
621static bool too_many_workers(struct global_cwq *gcwq)
622{
623 bool managing = gcwq->flags & GCWQ_MANAGING_WORKERS;
624 int nr_idle = gcwq->nr_idle + managing; /* manager is considered idle */
625 int nr_busy = gcwq->nr_workers - nr_idle;
626
627 return nr_idle > 2 && (nr_idle - 2) * MAX_IDLE_WORKERS_RATIO >= nr_busy;
628}
629
630/*
631 * Wake up functions.
632 */
633
634/* Return the first worker. Safe with preemption disabled */
635static struct worker *first_worker(struct global_cwq *gcwq)
636{
637 if (unlikely(list_empty(&gcwq->idle_list)))
638 return NULL;
639
640 return list_first_entry(&gcwq->idle_list, struct worker, entry);
641}
642
643/**
644 * wake_up_worker - wake up an idle worker
645 * @gcwq: gcwq to wake worker for
646 *
647 * Wake up the first idle worker of @gcwq.
648 *
649 * CONTEXT:
650 * spin_lock_irq(gcwq->lock).
651 */
652static void wake_up_worker(struct global_cwq *gcwq)
653{
654 struct worker *worker = first_worker(gcwq);
655
656 if (likely(worker))
657 wake_up_process(worker->task);
658}
659
660/**
661 * wq_worker_waking_up - a worker is waking up
662 * @task: task waking up
663 * @cpu: CPU @task is waking up to
664 *
665 * This function is called during try_to_wake_up() when a worker is
666 * being awoken.
667 *
668 * CONTEXT:
669 * spin_lock_irq(rq->lock)
670 */
671void wq_worker_waking_up(struct task_struct *task, unsigned int cpu)
672{
673 struct worker *worker = kthread_data(task);
674
675 if (!(worker->flags & WORKER_NOT_RUNNING))
676 atomic_inc(get_gcwq_nr_running(cpu));
677}
678
679/**
680 * wq_worker_sleeping - a worker is going to sleep
681 * @task: task going to sleep
682 * @cpu: CPU in question, must be the current CPU number
683 *
684 * This function is called during schedule() when a busy worker is
685 * going to sleep. Worker on the same cpu can be woken up by
686 * returning pointer to its task.
687 *
688 * CONTEXT:
689 * spin_lock_irq(rq->lock)
690 *
691 * RETURNS:
692 * Worker task on @cpu to wake up, %NULL if none.
693 */
694struct task_struct *wq_worker_sleeping(struct task_struct *task,
695 unsigned int cpu)
696{
697 struct worker *worker = kthread_data(task), *to_wakeup = NULL;
698 struct global_cwq *gcwq = get_gcwq(cpu);
699 atomic_t *nr_running = get_gcwq_nr_running(cpu);
700
701 if (worker->flags & WORKER_NOT_RUNNING)
702 return NULL;
703
704 /* this can only happen on the local cpu */
705 BUG_ON(cpu != raw_smp_processor_id());
706
707 /*
708 * The counterpart of the following dec_and_test, implied mb,
709 * worklist not empty test sequence is in insert_work().
710 * Please read comment there.
711 *
712 * NOT_RUNNING is clear. This means that trustee is not in
713 * charge and we're running on the local cpu w/ rq lock held
714 * and preemption disabled, which in turn means that none else
715 * could be manipulating idle_list, so dereferencing idle_list
716 * without gcwq lock is safe.
717 */
718 if (atomic_dec_and_test(nr_running) && !list_empty(&gcwq->worklist))
719 to_wakeup = first_worker(gcwq);
720 return to_wakeup ? to_wakeup->task : NULL;
721}
722
723/**
724 * worker_set_flags - set worker flags and adjust nr_running accordingly
725 * @worker: self
726 * @flags: flags to set
727 * @wakeup: wakeup an idle worker if necessary
728 *
729 * Set @flags in @worker->flags and adjust nr_running accordingly. If
730 * nr_running becomes zero and @wakeup is %true, an idle worker is
731 * woken up.
732 *
733 * CONTEXT:
734 * spin_lock_irq(gcwq->lock)
735 */
736static inline void worker_set_flags(struct worker *worker, unsigned int flags,
737 bool wakeup)
738{
739 struct global_cwq *gcwq = worker->gcwq;
740
741 WARN_ON_ONCE(worker->task != current);
742
743 /*
744 * If transitioning into NOT_RUNNING, adjust nr_running and
745 * wake up an idle worker as necessary if requested by
746 * @wakeup.
747 */
748 if ((flags & WORKER_NOT_RUNNING) &&
749 !(worker->flags & WORKER_NOT_RUNNING)) {
750 atomic_t *nr_running = get_gcwq_nr_running(gcwq->cpu);
751
752 if (wakeup) {
753 if (atomic_dec_and_test(nr_running) &&
754 !list_empty(&gcwq->worklist))
755 wake_up_worker(gcwq);
756 } else
757 atomic_dec(nr_running);
758 }
759
760 worker->flags |= flags;
761}
762
763/**
764 * worker_clr_flags - clear worker flags and adjust nr_running accordingly
765 * @worker: self
766 * @flags: flags to clear
767 *
768 * Clear @flags in @worker->flags and adjust nr_running accordingly.
769 *
770 * CONTEXT:
771 * spin_lock_irq(gcwq->lock)
772 */
773static inline void worker_clr_flags(struct worker *worker, unsigned int flags)
774{
775 struct global_cwq *gcwq = worker->gcwq;
776 unsigned int oflags = worker->flags;
777
778 WARN_ON_ONCE(worker->task != current);
779
780 worker->flags &= ~flags;
781
782 /*
783 * If transitioning out of NOT_RUNNING, increment nr_running. Note
784 * that the nested NOT_RUNNING is not a noop. NOT_RUNNING is mask
785 * of multiple flags, not a single flag.
786 */
787 if ((flags & WORKER_NOT_RUNNING) && (oflags & WORKER_NOT_RUNNING))
788 if (!(worker->flags & WORKER_NOT_RUNNING))
789 atomic_inc(get_gcwq_nr_running(gcwq->cpu));
790}
791
792/**
793 * busy_worker_head - return the busy hash head for a work
794 * @gcwq: gcwq of interest
795 * @work: work to be hashed
796 *
797 * Return hash head of @gcwq for @work.
798 *
799 * CONTEXT:
800 * spin_lock_irq(gcwq->lock).
801 *
802 * RETURNS:
803 * Pointer to the hash head.
804 */
805static struct hlist_head *busy_worker_head(struct global_cwq *gcwq,
806 struct work_struct *work)
807{
808 const int base_shift = ilog2(sizeof(struct work_struct));
809 unsigned long v = (unsigned long)work;
810
811 /* simple shift and fold hash, do we need something better? */
812 v >>= base_shift;
813 v += v >> BUSY_WORKER_HASH_ORDER;
814 v &= BUSY_WORKER_HASH_MASK;
815
816 return &gcwq->busy_hash[v];
817}
818
819/**
820 * __find_worker_executing_work - find worker which is executing a work
821 * @gcwq: gcwq of interest
822 * @bwh: hash head as returned by busy_worker_head()
823 * @work: work to find worker for
824 *
825 * Find a worker which is executing @work on @gcwq. @bwh should be
826 * the hash head obtained by calling busy_worker_head() with the same
827 * work.
828 *
829 * CONTEXT:
830 * spin_lock_irq(gcwq->lock).
831 *
832 * RETURNS:
833 * Pointer to worker which is executing @work if found, NULL
834 * otherwise.
835 */
836static struct worker *__find_worker_executing_work(struct global_cwq *gcwq,
837 struct hlist_head *bwh,
838 struct work_struct *work)
839{
840 struct worker *worker;
841 struct hlist_node *tmp;
842
843 hlist_for_each_entry(worker, tmp, bwh, hentry)
844 if (worker->current_work == work)
845 return worker;
846 return NULL;
847}
848
849/**
850 * find_worker_executing_work - find worker which is executing a work
851 * @gcwq: gcwq of interest
852 * @work: work to find worker for
853 *
854 * Find a worker which is executing @work on @gcwq. This function is
855 * identical to __find_worker_executing_work() except that this
856 * function calculates @bwh itself.
857 *
858 * CONTEXT:
859 * spin_lock_irq(gcwq->lock).
860 *
861 * RETURNS:
862 * Pointer to worker which is executing @work if found, NULL
863 * otherwise.
864 */
865static struct worker *find_worker_executing_work(struct global_cwq *gcwq,
866 struct work_struct *work)
867{
868 return __find_worker_executing_work(gcwq, busy_worker_head(gcwq, work),
869 work);
870}
871
872/**
873 * gcwq_determine_ins_pos - find insertion position
874 * @gcwq: gcwq of interest
875 * @cwq: cwq a work is being queued for
876 *
877 * A work for @cwq is about to be queued on @gcwq, determine insertion
878 * position for the work. If @cwq is for HIGHPRI wq, the work is
879 * queued at the head of the queue but in FIFO order with respect to
880 * other HIGHPRI works; otherwise, at the end of the queue. This
881 * function also sets GCWQ_HIGHPRI_PENDING flag to hint @gcwq that
882 * there are HIGHPRI works pending.
883 *
884 * CONTEXT:
885 * spin_lock_irq(gcwq->lock).
886 *
887 * RETURNS:
888 * Pointer to inserstion position.
889 */
890static inline struct list_head *gcwq_determine_ins_pos(struct global_cwq *gcwq,
891 struct cpu_workqueue_struct *cwq)
892{
893 struct work_struct *twork;
894
895 if (likely(!(cwq->wq->flags & WQ_HIGHPRI)))
896 return &gcwq->worklist;
897
898 list_for_each_entry(twork, &gcwq->worklist, entry) {
899 struct cpu_workqueue_struct *tcwq = get_work_cwq(twork);
900
901 if (!(tcwq->wq->flags & WQ_HIGHPRI))
902 break;
903 }
904
905 gcwq->flags |= GCWQ_HIGHPRI_PENDING;
906 return &twork->entry;
907}
908
909/**
910 * insert_work - insert a work into gcwq
911 * @cwq: cwq @work belongs to
912 * @work: work to insert
913 * @head: insertion point
914 * @extra_flags: extra WORK_STRUCT_* flags to set
915 *
916 * Insert @work which belongs to @cwq into @gcwq after @head.
917 * @extra_flags is or'd to work_struct flags.
918 *
919 * CONTEXT:
920 * spin_lock_irq(gcwq->lock).
921 */
922static void insert_work(struct cpu_workqueue_struct *cwq,
923 struct work_struct *work, struct list_head *head,
924 unsigned int extra_flags)
925{
926 struct global_cwq *gcwq = cwq->gcwq;
927
928 /* we own @work, set data and link */
929 set_work_cwq(work, cwq, extra_flags);
930
931 /*
932 * Ensure that we get the right work->data if we see the
933 * result of list_add() below, see try_to_grab_pending().
934 */
935 smp_wmb();
936
937 list_add_tail(&work->entry, head);
938
939 /*
940 * Ensure either worker_sched_deactivated() sees the above
941 * list_add_tail() or we see zero nr_running to avoid workers
942 * lying around lazily while there are works to be processed.
943 */
944 smp_mb();
945
946 if (__need_more_worker(gcwq))
947 wake_up_worker(gcwq);
948}
949
950/*
951 * Test whether @work is being queued from another work executing on the
952 * same workqueue. This is rather expensive and should only be used from
953 * cold paths.
954 */
955static bool is_chained_work(struct workqueue_struct *wq)
956{
957 unsigned long flags;
958 unsigned int cpu;
959
960 for_each_gcwq_cpu(cpu) {
961 struct global_cwq *gcwq = get_gcwq(cpu);
962 struct worker *worker;
963 struct hlist_node *pos;
964 int i;
965
966 spin_lock_irqsave(&gcwq->lock, flags);
967 for_each_busy_worker(worker, i, pos, gcwq) {
968 if (worker->task != current)
969 continue;
970 spin_unlock_irqrestore(&gcwq->lock, flags);
971 /*
972 * I'm @worker, no locking necessary. See if @work
973 * is headed to the same workqueue.
974 */
975 return worker->current_cwq->wq == wq;
976 }
977 spin_unlock_irqrestore(&gcwq->lock, flags);
978 }
979 return false;
980}
981
982static void __queue_work(unsigned int cpu, struct workqueue_struct *wq,
983 struct work_struct *work)
984{
985 struct global_cwq *gcwq;
986 struct cpu_workqueue_struct *cwq;
987 struct list_head *worklist;
988 unsigned int work_flags;
989 unsigned long flags;
990
991 debug_work_activate(work);
992
993 /* if dying, only works from the same workqueue are allowed */
994 if (unlikely(wq->flags & WQ_DRAINING) &&
995 WARN_ON_ONCE(!is_chained_work(wq)))
996 return;
997
998 /* determine gcwq to use */
999 if (!(wq->flags & WQ_UNBOUND)) {
1000 struct global_cwq *last_gcwq;
1001
1002 if (unlikely(cpu == WORK_CPU_UNBOUND))
1003 cpu = raw_smp_processor_id();
1004
1005 /*
1006 * It's multi cpu. If @wq is non-reentrant and @work
1007 * was previously on a different cpu, it might still
1008 * be running there, in which case the work needs to
1009 * be queued on that cpu to guarantee non-reentrance.
1010 */
1011 gcwq = get_gcwq(cpu);
1012 if (wq->flags & WQ_NON_REENTRANT &&
1013 (last_gcwq = get_work_gcwq(work)) && last_gcwq != gcwq) {
1014 struct worker *worker;
1015
1016 spin_lock_irqsave(&last_gcwq->lock, flags);
1017
1018 worker = find_worker_executing_work(last_gcwq, work);
1019
1020 if (worker && worker->current_cwq->wq == wq)
1021 gcwq = last_gcwq;
1022 else {
1023 /* meh... not running there, queue here */
1024 spin_unlock_irqrestore(&last_gcwq->lock, flags);
1025 spin_lock_irqsave(&gcwq->lock, flags);
1026 }
1027 } else
1028 spin_lock_irqsave(&gcwq->lock, flags);
1029 } else {
1030 gcwq = get_gcwq(WORK_CPU_UNBOUND);
1031 spin_lock_irqsave(&gcwq->lock, flags);
1032 }
1033
1034 /* gcwq determined, get cwq and queue */
1035 cwq = get_cwq(gcwq->cpu, wq);
1036 trace_workqueue_queue_work(cpu, cwq, work);
1037
1038 BUG_ON(!list_empty(&work->entry));
1039
1040 cwq->nr_in_flight[cwq->work_color]++;
1041 work_flags = work_color_to_flags(cwq->work_color);
1042
1043 if (likely(cwq->nr_active < cwq->max_active)) {
1044 trace_workqueue_activate_work(work);
1045 cwq->nr_active++;
1046 worklist = gcwq_determine_ins_pos(gcwq, cwq);
1047 } else {
1048 work_flags |= WORK_STRUCT_DELAYED;
1049 worklist = &cwq->delayed_works;
1050 }
1051
1052 insert_work(cwq, work, worklist, work_flags);
1053
1054 spin_unlock_irqrestore(&gcwq->lock, flags);
1055}
1056
1057/**
1058 * queue_work - queue work on a workqueue
1059 * @wq: workqueue to use
1060 * @work: work to queue
1061 *
1062 * Returns 0 if @work was already on a queue, non-zero otherwise.
1063 *
1064 * We queue the work to the CPU on which it was submitted, but if the CPU dies
1065 * it can be processed by another CPU.
1066 */
1067int queue_work(struct workqueue_struct *wq, struct work_struct *work)
1068{
1069 int ret;
1070
1071 ret = queue_work_on(get_cpu(), wq, work);
1072 put_cpu();
1073
1074 return ret;
1075}
1076EXPORT_SYMBOL_GPL(queue_work);
1077
1078/**
1079 * queue_work_on - queue work on specific cpu
1080 * @cpu: CPU number to execute work on
1081 * @wq: workqueue to use
1082 * @work: work to queue
1083 *
1084 * Returns 0 if @work was already on a queue, non-zero otherwise.
1085 *
1086 * We queue the work to a specific CPU, the caller must ensure it
1087 * can't go away.
1088 */
1089int
1090queue_work_on(int cpu, struct workqueue_struct *wq, struct work_struct *work)
1091{
1092 int ret = 0;
1093
1094 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1095 __queue_work(cpu, wq, work);
1096 ret = 1;
1097 }
1098 return ret;
1099}
1100EXPORT_SYMBOL_GPL(queue_work_on);
1101
1102static void delayed_work_timer_fn(unsigned long __data)
1103{
1104 struct delayed_work *dwork = (struct delayed_work *)__data;
1105 struct cpu_workqueue_struct *cwq = get_work_cwq(&dwork->work);
1106
1107 __queue_work(smp_processor_id(), cwq->wq, &dwork->work);
1108}
1109
1110/**
1111 * queue_delayed_work - queue work on a workqueue after delay
1112 * @wq: workqueue to use
1113 * @dwork: delayable work to queue
1114 * @delay: number of jiffies to wait before queueing
1115 *
1116 * Returns 0 if @work was already on a queue, non-zero otherwise.
1117 */
1118int queue_delayed_work(struct workqueue_struct *wq,
1119 struct delayed_work *dwork, unsigned long delay)
1120{
1121 if (delay == 0)
1122 return queue_work(wq, &dwork->work);
1123
1124 return queue_delayed_work_on(-1, wq, dwork, delay);
1125}
1126EXPORT_SYMBOL_GPL(queue_delayed_work);
1127
1128/**
1129 * queue_delayed_work_on - queue work on specific CPU after delay
1130 * @cpu: CPU number to execute work on
1131 * @wq: workqueue to use
1132 * @dwork: work to queue
1133 * @delay: number of jiffies to wait before queueing
1134 *
1135 * Returns 0 if @work was already on a queue, non-zero otherwise.
1136 */
1137int queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
1138 struct delayed_work *dwork, unsigned long delay)
1139{
1140 int ret = 0;
1141 struct timer_list *timer = &dwork->timer;
1142 struct work_struct *work = &dwork->work;
1143
1144 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1145 unsigned int lcpu;
1146
1147 BUG_ON(timer_pending(timer));
1148 BUG_ON(!list_empty(&work->entry));
1149
1150 timer_stats_timer_set_start_info(&dwork->timer);
1151
1152 /*
1153 * This stores cwq for the moment, for the timer_fn.
1154 * Note that the work's gcwq is preserved to allow
1155 * reentrance detection for delayed works.
1156 */
1157 if (!(wq->flags & WQ_UNBOUND)) {
1158 struct global_cwq *gcwq = get_work_gcwq(work);
1159
1160 if (gcwq && gcwq->cpu != WORK_CPU_UNBOUND)
1161 lcpu = gcwq->cpu;
1162 else
1163 lcpu = raw_smp_processor_id();
1164 } else
1165 lcpu = WORK_CPU_UNBOUND;
1166
1167 set_work_cwq(work, get_cwq(lcpu, wq), 0);
1168
1169 timer->expires = jiffies + delay;
1170 timer->data = (unsigned long)dwork;
1171 timer->function = delayed_work_timer_fn;
1172
1173 if (unlikely(cpu >= 0))
1174 add_timer_on(timer, cpu);
1175 else
1176 add_timer(timer);
1177 ret = 1;
1178 }
1179 return ret;
1180}
1181EXPORT_SYMBOL_GPL(queue_delayed_work_on);
1182
1183/**
1184 * worker_enter_idle - enter idle state
1185 * @worker: worker which is entering idle state
1186 *
1187 * @worker is entering idle state. Update stats and idle timer if
1188 * necessary.
1189 *
1190 * LOCKING:
1191 * spin_lock_irq(gcwq->lock).
1192 */
1193static void worker_enter_idle(struct worker *worker)
1194{
1195 struct global_cwq *gcwq = worker->gcwq;
1196
1197 BUG_ON(worker->flags & WORKER_IDLE);
1198 BUG_ON(!list_empty(&worker->entry) &&
1199 (worker->hentry.next || worker->hentry.pprev));
1200
1201 /* can't use worker_set_flags(), also called from start_worker() */
1202 worker->flags |= WORKER_IDLE;
1203 gcwq->nr_idle++;
1204 worker->last_active = jiffies;
1205
1206 /* idle_list is LIFO */
1207 list_add(&worker->entry, &gcwq->idle_list);
1208
1209 if (likely(!(worker->flags & WORKER_ROGUE))) {
1210 if (too_many_workers(gcwq) && !timer_pending(&gcwq->idle_timer))
1211 mod_timer(&gcwq->idle_timer,
1212 jiffies + IDLE_WORKER_TIMEOUT);
1213 } else
1214 wake_up_all(&gcwq->trustee_wait);
1215
1216 /* sanity check nr_running */
1217 WARN_ON_ONCE(gcwq->nr_workers == gcwq->nr_idle &&
1218 atomic_read(get_gcwq_nr_running(gcwq->cpu)));
1219}
1220
1221/**
1222 * worker_leave_idle - leave idle state
1223 * @worker: worker which is leaving idle state
1224 *
1225 * @worker is leaving idle state. Update stats.
1226 *
1227 * LOCKING:
1228 * spin_lock_irq(gcwq->lock).
1229 */
1230static void worker_leave_idle(struct worker *worker)
1231{
1232 struct global_cwq *gcwq = worker->gcwq;
1233
1234 BUG_ON(!(worker->flags & WORKER_IDLE));
1235 worker_clr_flags(worker, WORKER_IDLE);
1236 gcwq->nr_idle--;
1237 list_del_init(&worker->entry);
1238}
1239
1240/**
1241 * worker_maybe_bind_and_lock - bind worker to its cpu if possible and lock gcwq
1242 * @worker: self
1243 *
1244 * Works which are scheduled while the cpu is online must at least be
1245 * scheduled to a worker which is bound to the cpu so that if they are
1246 * flushed from cpu callbacks while cpu is going down, they are
1247 * guaranteed to execute on the cpu.
1248 *
1249 * This function is to be used by rogue workers and rescuers to bind
1250 * themselves to the target cpu and may race with cpu going down or
1251 * coming online. kthread_bind() can't be used because it may put the
1252 * worker to already dead cpu and set_cpus_allowed_ptr() can't be used
1253 * verbatim as it's best effort and blocking and gcwq may be
1254 * [dis]associated in the meantime.
1255 *
1256 * This function tries set_cpus_allowed() and locks gcwq and verifies
1257 * the binding against GCWQ_DISASSOCIATED which is set during
1258 * CPU_DYING and cleared during CPU_ONLINE, so if the worker enters
1259 * idle state or fetches works without dropping lock, it can guarantee
1260 * the scheduling requirement described in the first paragraph.
1261 *
1262 * CONTEXT:
1263 * Might sleep. Called without any lock but returns with gcwq->lock
1264 * held.
1265 *
1266 * RETURNS:
1267 * %true if the associated gcwq is online (@worker is successfully
1268 * bound), %false if offline.
1269 */
1270static bool worker_maybe_bind_and_lock(struct worker *worker)
1271__acquires(&gcwq->lock)
1272{
1273 struct global_cwq *gcwq = worker->gcwq;
1274 struct task_struct *task = worker->task;
1275
1276 while (true) {
1277 /*
1278 * The following call may fail, succeed or succeed
1279 * without actually migrating the task to the cpu if
1280 * it races with cpu hotunplug operation. Verify
1281 * against GCWQ_DISASSOCIATED.
1282 */
1283 if (!(gcwq->flags & GCWQ_DISASSOCIATED))
1284 set_cpus_allowed_ptr(task, get_cpu_mask(gcwq->cpu));
1285
1286 spin_lock_irq(&gcwq->lock);
1287 if (gcwq->flags & GCWQ_DISASSOCIATED)
1288 return false;
1289 if (task_cpu(task) == gcwq->cpu &&
1290 cpumask_equal(¤t->cpus_allowed,
1291 get_cpu_mask(gcwq->cpu)))
1292 return true;
1293 spin_unlock_irq(&gcwq->lock);
1294
1295 /*
1296 * We've raced with CPU hot[un]plug. Give it a breather
1297 * and retry migration. cond_resched() is required here;
1298 * otherwise, we might deadlock against cpu_stop trying to
1299 * bring down the CPU on non-preemptive kernel.
1300 */
1301 cpu_relax();
1302 cond_resched();
1303 }
1304}
1305
1306/*
1307 * Function for worker->rebind_work used to rebind rogue busy workers
1308 * to the associated cpu which is coming back online. This is
1309 * scheduled by cpu up but can race with other cpu hotplug operations
1310 * and may be executed twice without intervening cpu down.
1311 */
1312static void worker_rebind_fn(struct work_struct *work)
1313{
1314 struct worker *worker = container_of(work, struct worker, rebind_work);
1315 struct global_cwq *gcwq = worker->gcwq;
1316
1317 if (worker_maybe_bind_and_lock(worker))
1318 worker_clr_flags(worker, WORKER_REBIND);
1319
1320 spin_unlock_irq(&gcwq->lock);
1321}
1322
1323static struct worker *alloc_worker(void)
1324{
1325 struct worker *worker;
1326
1327 worker = kzalloc(sizeof(*worker), GFP_KERNEL);
1328 if (worker) {
1329 INIT_LIST_HEAD(&worker->entry);
1330 INIT_LIST_HEAD(&worker->scheduled);
1331 INIT_WORK(&worker->rebind_work, worker_rebind_fn);
1332 /* on creation a worker is in !idle && prep state */
1333 worker->flags = WORKER_PREP;
1334 }
1335 return worker;
1336}
1337
1338/**
1339 * create_worker - create a new workqueue worker
1340 * @gcwq: gcwq the new worker will belong to
1341 * @bind: whether to set affinity to @cpu or not
1342 *
1343 * Create a new worker which is bound to @gcwq. The returned worker
1344 * can be started by calling start_worker() or destroyed using
1345 * destroy_worker().
1346 *
1347 * CONTEXT:
1348 * Might sleep. Does GFP_KERNEL allocations.
1349 *
1350 * RETURNS:
1351 * Pointer to the newly created worker.
1352 */
1353static struct worker *create_worker(struct global_cwq *gcwq, bool bind)
1354{
1355 bool on_unbound_cpu = gcwq->cpu == WORK_CPU_UNBOUND;
1356 struct worker *worker = NULL;
1357 int id = -1;
1358
1359 spin_lock_irq(&gcwq->lock);
1360 while (ida_get_new(&gcwq->worker_ida, &id)) {
1361 spin_unlock_irq(&gcwq->lock);
1362 if (!ida_pre_get(&gcwq->worker_ida, GFP_KERNEL))
1363 goto fail;
1364 spin_lock_irq(&gcwq->lock);
1365 }
1366 spin_unlock_irq(&gcwq->lock);
1367
1368 worker = alloc_worker();
1369 if (!worker)
1370 goto fail;
1371
1372 worker->gcwq = gcwq;
1373 worker->id = id;
1374
1375 if (!on_unbound_cpu)
1376 worker->task = kthread_create_on_node(worker_thread,
1377 worker,
1378 cpu_to_node(gcwq->cpu),
1379 "kworker/%u:%d", gcwq->cpu, id);
1380 else
1381 worker->task = kthread_create(worker_thread, worker,
1382 "kworker/u:%d", id);
1383 if (IS_ERR(worker->task))
1384 goto fail;
1385
1386 /*
1387 * A rogue worker will become a regular one if CPU comes
1388 * online later on. Make sure every worker has
1389 * PF_THREAD_BOUND set.
1390 */
1391 if (bind && !on_unbound_cpu)
1392 kthread_bind(worker->task, gcwq->cpu);
1393 else {
1394 worker->task->flags |= PF_THREAD_BOUND;
1395 if (on_unbound_cpu)
1396 worker->flags |= WORKER_UNBOUND;
1397 }
1398
1399 return worker;
1400fail:
1401 if (id >= 0) {
1402 spin_lock_irq(&gcwq->lock);
1403 ida_remove(&gcwq->worker_ida, id);
1404 spin_unlock_irq(&gcwq->lock);
1405 }
1406 kfree(worker);
1407 return NULL;
1408}
1409
1410/**
1411 * start_worker - start a newly created worker
1412 * @worker: worker to start
1413 *
1414 * Make the gcwq aware of @worker and start it.
1415 *
1416 * CONTEXT:
1417 * spin_lock_irq(gcwq->lock).
1418 */
1419static void start_worker(struct worker *worker)
1420{
1421 worker->flags |= WORKER_STARTED;
1422 worker->gcwq->nr_workers++;
1423 worker_enter_idle(worker);
1424 wake_up_process(worker->task);
1425}
1426
1427/**
1428 * destroy_worker - destroy a workqueue worker
1429 * @worker: worker to be destroyed
1430 *
1431 * Destroy @worker and adjust @gcwq stats accordingly.
1432 *
1433 * CONTEXT:
1434 * spin_lock_irq(gcwq->lock) which is released and regrabbed.
1435 */
1436static void destroy_worker(struct worker *worker)
1437{
1438 struct global_cwq *gcwq = worker->gcwq;
1439 int id = worker->id;
1440
1441 /* sanity check frenzy */
1442 BUG_ON(worker->current_work);
1443 BUG_ON(!list_empty(&worker->scheduled));
1444
1445 if (worker->flags & WORKER_STARTED)
1446 gcwq->nr_workers--;
1447 if (worker->flags & WORKER_IDLE)
1448 gcwq->nr_idle--;
1449
1450 list_del_init(&worker->entry);
1451 worker->flags |= WORKER_DIE;
1452
1453 spin_unlock_irq(&gcwq->lock);
1454
1455 kthread_stop(worker->task);
1456 kfree(worker);
1457
1458 spin_lock_irq(&gcwq->lock);
1459 ida_remove(&gcwq->worker_ida, id);
1460}
1461
1462static void idle_worker_timeout(unsigned long __gcwq)
1463{
1464 struct global_cwq *gcwq = (void *)__gcwq;
1465
1466 spin_lock_irq(&gcwq->lock);
1467
1468 if (too_many_workers(gcwq)) {
1469 struct worker *worker;
1470 unsigned long expires;
1471
1472 /* idle_list is kept in LIFO order, check the last one */
1473 worker = list_entry(gcwq->idle_list.prev, struct worker, entry);
1474 expires = worker->last_active + IDLE_WORKER_TIMEOUT;
1475
1476 if (time_before(jiffies, expires))
1477 mod_timer(&gcwq->idle_timer, expires);
1478 else {
1479 /* it's been idle for too long, wake up manager */
1480 gcwq->flags |= GCWQ_MANAGE_WORKERS;
1481 wake_up_worker(gcwq);
1482 }
1483 }
1484
1485 spin_unlock_irq(&gcwq->lock);
1486}
1487
1488static bool send_mayday(struct work_struct *work)
1489{
1490 struct cpu_workqueue_struct *cwq = get_work_cwq(work);
1491 struct workqueue_struct *wq = cwq->wq;
1492 unsigned int cpu;
1493
1494 if (!(wq->flags & WQ_RESCUER))
1495 return false;
1496
1497 /* mayday mayday mayday */
1498 cpu = cwq->gcwq->cpu;
1499 /* WORK_CPU_UNBOUND can't be set in cpumask, use cpu 0 instead */
1500 if (cpu == WORK_CPU_UNBOUND)
1501 cpu = 0;
1502 if (!mayday_test_and_set_cpu(cpu, wq->mayday_mask))
1503 wake_up_process(wq->rescuer->task);
1504 return true;
1505}
1506
1507static void gcwq_mayday_timeout(unsigned long __gcwq)
1508{
1509 struct global_cwq *gcwq = (void *)__gcwq;
1510 struct work_struct *work;
1511
1512 spin_lock_irq(&gcwq->lock);
1513
1514 if (need_to_create_worker(gcwq)) {
1515 /*
1516 * We've been trying to create a new worker but
1517 * haven't been successful. We might be hitting an
1518 * allocation deadlock. Send distress signals to
1519 * rescuers.
1520 */
1521 list_for_each_entry(work, &gcwq->worklist, entry)
1522 send_mayday(work);
1523 }
1524
1525 spin_unlock_irq(&gcwq->lock);
1526
1527 mod_timer(&gcwq->mayday_timer, jiffies + MAYDAY_INTERVAL);
1528}
1529
1530/**
1531 * maybe_create_worker - create a new worker if necessary
1532 * @gcwq: gcwq to create a new worker for
1533 *
1534 * Create a new worker for @gcwq if necessary. @gcwq is guaranteed to
1535 * have at least one idle worker on return from this function. If
1536 * creating a new worker takes longer than MAYDAY_INTERVAL, mayday is
1537 * sent to all rescuers with works scheduled on @gcwq to resolve
1538 * possible allocation deadlock.
1539 *
1540 * On return, need_to_create_worker() is guaranteed to be false and
1541 * may_start_working() true.
1542 *
1543 * LOCKING:
1544 * spin_lock_irq(gcwq->lock) which may be released and regrabbed
1545 * multiple times. Does GFP_KERNEL allocations. Called only from
1546 * manager.
1547 *
1548 * RETURNS:
1549 * false if no action was taken and gcwq->lock stayed locked, true
1550 * otherwise.
1551 */
1552static bool maybe_create_worker(struct global_cwq *gcwq)
1553__releases(&gcwq->lock)
1554__acquires(&gcwq->lock)
1555{
1556 if (!need_to_create_worker(gcwq))
1557 return false;
1558restart:
1559 spin_unlock_irq(&gcwq->lock);
1560
1561 /* if we don't make progress in MAYDAY_INITIAL_TIMEOUT, call for help */
1562 mod_timer(&gcwq->mayday_timer, jiffies + MAYDAY_INITIAL_TIMEOUT);
1563
1564 while (true) {
1565 struct worker *worker;
1566
1567 worker = create_worker(gcwq, true);
1568 if (worker) {
1569 del_timer_sync(&gcwq->mayday_timer);
1570 spin_lock_irq(&gcwq->lock);
1571 start_worker(worker);
1572 BUG_ON(need_to_create_worker(gcwq));
1573 return true;
1574 }
1575
1576 if (!need_to_create_worker(gcwq))
1577 break;
1578
1579 __set_current_state(TASK_INTERRUPTIBLE);
1580 schedule_timeout(CREATE_COOLDOWN);
1581
1582 if (!need_to_create_worker(gcwq))
1583 break;
1584 }
1585
1586 del_timer_sync(&gcwq->mayday_timer);
1587 spin_lock_irq(&gcwq->lock);
1588 if (need_to_create_worker(gcwq))
1589 goto restart;
1590 return true;
1591}
1592
1593/**
1594 * maybe_destroy_worker - destroy workers which have been idle for a while
1595 * @gcwq: gcwq to destroy workers for
1596 *
1597 * Destroy @gcwq workers which have been idle for longer than
1598 * IDLE_WORKER_TIMEOUT.
1599 *
1600 * LOCKING:
1601 * spin_lock_irq(gcwq->lock) which may be released and regrabbed
1602 * multiple times. Called only from manager.
1603 *
1604 * RETURNS:
1605 * false if no action was taken and gcwq->lock stayed locked, true
1606 * otherwise.
1607 */
1608static bool maybe_destroy_workers(struct global_cwq *gcwq)
1609{
1610 bool ret = false;
1611
1612 while (too_many_workers(gcwq)) {
1613 struct worker *worker;
1614 unsigned long expires;
1615
1616 worker = list_entry(gcwq->idle_list.prev, struct worker, entry);
1617 expires = worker->last_active + IDLE_WORKER_TIMEOUT;
1618
1619 if (time_before(jiffies, expires)) {
1620 mod_timer(&gcwq->idle_timer, expires);
1621 break;
1622 }
1623
1624 destroy_worker(worker);
1625 ret = true;
1626 }
1627
1628 return ret;
1629}
1630
1631/**
1632 * manage_workers - manage worker pool
1633 * @worker: self
1634 *
1635 * Assume the manager role and manage gcwq worker pool @worker belongs
1636 * to. At any given time, there can be only zero or one manager per
1637 * gcwq. The exclusion is handled automatically by this function.
1638 *
1639 * The caller can safely start processing works on false return. On
1640 * true return, it's guaranteed that need_to_create_worker() is false
1641 * and may_start_working() is true.
1642 *
1643 * CONTEXT:
1644 * spin_lock_irq(gcwq->lock) which may be released and regrabbed
1645 * multiple times. Does GFP_KERNEL allocations.
1646 *
1647 * RETURNS:
1648 * false if no action was taken and gcwq->lock stayed locked, true if
1649 * some action was taken.
1650 */
1651static bool manage_workers(struct worker *worker)
1652{
1653 struct global_cwq *gcwq = worker->gcwq;
1654 bool ret = false;
1655
1656 if (gcwq->flags & GCWQ_MANAGING_WORKERS)
1657 return ret;
1658
1659 gcwq->flags &= ~GCWQ_MANAGE_WORKERS;
1660 gcwq->flags |= GCWQ_MANAGING_WORKERS;
1661
1662 /*
1663 * Destroy and then create so that may_start_working() is true
1664 * on return.
1665 */
1666 ret |= maybe_destroy_workers(gcwq);
1667 ret |= maybe_create_worker(gcwq);
1668
1669 gcwq->flags &= ~GCWQ_MANAGING_WORKERS;
1670
1671 /*
1672 * The trustee might be waiting to take over the manager
1673 * position, tell it we're done.
1674 */
1675 if (unlikely(gcwq->trustee))
1676 wake_up_all(&gcwq->trustee_wait);
1677
1678 return ret;
1679}
1680
1681/**
1682 * move_linked_works - move linked works to a list
1683 * @work: start of series of works to be scheduled
1684 * @head: target list to append @work to
1685 * @nextp: out paramter for nested worklist walking
1686 *
1687 * Schedule linked works starting from @work to @head. Work series to
1688 * be scheduled starts at @work and includes any consecutive work with
1689 * WORK_STRUCT_LINKED set in its predecessor.
1690 *
1691 * If @nextp is not NULL, it's updated to point to the next work of
1692 * the last scheduled work. This allows move_linked_works() to be
1693 * nested inside outer list_for_each_entry_safe().
1694 *
1695 * CONTEXT:
1696 * spin_lock_irq(gcwq->lock).
1697 */
1698static void move_linked_works(struct work_struct *work, struct list_head *head,
1699 struct work_struct **nextp)
1700{
1701 struct work_struct *n;
1702
1703 /*
1704 * Linked worklist will always end before the end of the list,
1705 * use NULL for list head.
1706 */
1707 list_for_each_entry_safe_from(work, n, NULL, entry) {
1708 list_move_tail(&work->entry, head);
1709 if (!(*work_data_bits(work) & WORK_STRUCT_LINKED))
1710 break;
1711 }
1712
1713 /*
1714 * If we're already inside safe list traversal and have moved
1715 * multiple works to the scheduled queue, the next position
1716 * needs to be updated.
1717 */
1718 if (nextp)
1719 *nextp = n;
1720}
1721
1722static void cwq_activate_first_delayed(struct cpu_workqueue_struct *cwq)
1723{
1724 struct work_struct *work = list_first_entry(&cwq->delayed_works,
1725 struct work_struct, entry);
1726 struct list_head *pos = gcwq_determine_ins_pos(cwq->gcwq, cwq);
1727
1728 trace_workqueue_activate_work(work);
1729 move_linked_works(work, pos, NULL);
1730 __clear_bit(WORK_STRUCT_DELAYED_BIT, work_data_bits(work));
1731 cwq->nr_active++;
1732}
1733
1734/**
1735 * cwq_dec_nr_in_flight - decrement cwq's nr_in_flight
1736 * @cwq: cwq of interest
1737 * @color: color of work which left the queue
1738 * @delayed: for a delayed work
1739 *
1740 * A work either has completed or is removed from pending queue,
1741 * decrement nr_in_flight of its cwq and handle workqueue flushing.
1742 *
1743 * CONTEXT:
1744 * spin_lock_irq(gcwq->lock).
1745 */
1746static void cwq_dec_nr_in_flight(struct cpu_workqueue_struct *cwq, int color,
1747 bool delayed)
1748{
1749 /* ignore uncolored works */
1750 if (color == WORK_NO_COLOR)
1751 return;
1752
1753 cwq->nr_in_flight[color]--;
1754
1755 if (!delayed) {
1756 cwq->nr_active--;
1757 if (!list_empty(&cwq->delayed_works)) {
1758 /* one down, submit a delayed one */
1759 if (cwq->nr_active < cwq->max_active)
1760 cwq_activate_first_delayed(cwq);
1761 }
1762 }
1763
1764 /* is flush in progress and are we at the flushing tip? */
1765 if (likely(cwq->flush_color != color))
1766 return;
1767
1768 /* are there still in-flight works? */
1769 if (cwq->nr_in_flight[color])
1770 return;
1771
1772 /* this cwq is done, clear flush_color */
1773 cwq->flush_color = -1;
1774
1775 /*
1776 * If this was the last cwq, wake up the first flusher. It
1777 * will handle the rest.
1778 */
1779 if (atomic_dec_and_test(&cwq->wq->nr_cwqs_to_flush))
1780 complete(&cwq->wq->first_flusher->done);
1781}
1782
1783/**
1784 * process_one_work - process single work
1785 * @worker: self
1786 * @work: work to process
1787 *
1788 * Process @work. This function contains all the logics necessary to
1789 * process a single work including synchronization against and
1790 * interaction with other workers on the same cpu, queueing and
1791 * flushing. As long as context requirement is met, any worker can
1792 * call this function to process a work.
1793 *
1794 * CONTEXT:
1795 * spin_lock_irq(gcwq->lock) which is released and regrabbed.
1796 */
1797static void process_one_work(struct worker *worker, struct work_struct *work)
1798__releases(&gcwq->lock)
1799__acquires(&gcwq->lock)
1800{
1801 struct cpu_workqueue_struct *cwq = get_work_cwq(work);
1802 struct global_cwq *gcwq = cwq->gcwq;
1803 struct hlist_head *bwh = busy_worker_head(gcwq, work);
1804 bool cpu_intensive = cwq->wq->flags & WQ_CPU_INTENSIVE;
1805 work_func_t f = work->func;
1806 int work_color;
1807 struct worker *collision;
1808#ifdef CONFIG_LOCKDEP
1809 /*
1810 * It is permissible to free the struct work_struct from
1811 * inside the function that is called from it, this we need to
1812 * take into account for lockdep too. To avoid bogus "held
1813 * lock freed" warnings as well as problems when looking into
1814 * work->lockdep_map, make a copy and use that here.
1815 */
1816 struct lockdep_map lockdep_map = work->lockdep_map;
1817#endif
1818 /*
1819 * A single work shouldn't be executed concurrently by
1820 * multiple workers on a single cpu. Check whether anyone is
1821 * already processing the work. If so, defer the work to the
1822 * currently executing one.
1823 */
1824 collision = __find_worker_executing_work(gcwq, bwh, work);
1825 if (unlikely(collision)) {
1826 move_linked_works(work, &collision->scheduled, NULL);
1827 return;
1828 }
1829
1830 /* claim and process */
1831 debug_work_deactivate(work);
1832 hlist_add_head(&worker->hentry, bwh);
1833 worker->current_work = work;
1834 worker->current_cwq = cwq;
1835 work_color = get_work_color(work);
1836
1837 /* record the current cpu number in the work data and dequeue */
1838 set_work_cpu(work, gcwq->cpu);
1839 list_del_init(&work->entry);
1840
1841 /*
1842 * If HIGHPRI_PENDING, check the next work, and, if HIGHPRI,
1843 * wake up another worker; otherwise, clear HIGHPRI_PENDING.
1844 */
1845 if (unlikely(gcwq->flags & GCWQ_HIGHPRI_PENDING)) {
1846 struct work_struct *nwork = list_first_entry(&gcwq->worklist,
1847 struct work_struct, entry);
1848
1849 if (!list_empty(&gcwq->worklist) &&
1850 get_work_cwq(nwork)->wq->flags & WQ_HIGHPRI)
1851 wake_up_worker(gcwq);
1852 else
1853 gcwq->flags &= ~GCWQ_HIGHPRI_PENDING;
1854 }
1855
1856 /*
1857 * CPU intensive works don't participate in concurrency
1858 * management. They're the scheduler's responsibility.
1859 */
1860 if (unlikely(cpu_intensive))
1861 worker_set_flags(worker, WORKER_CPU_INTENSIVE, true);
1862
1863 spin_unlock_irq(&gcwq->lock);
1864
1865 work_clear_pending(work);
1866 lock_map_acquire_read(&cwq->wq->lockdep_map);
1867 lock_map_acquire(&lockdep_map);
1868 trace_workqueue_execute_start(work);
1869 f(work);
1870 /*
1871 * While we must be careful to not use "work" after this, the trace
1872 * point will only record its address.
1873 */
1874 trace_workqueue_execute_end(work);
1875 lock_map_release(&lockdep_map);
1876 lock_map_release(&cwq->wq->lockdep_map);
1877
1878 if (unlikely(in_atomic() || lockdep_depth(current) > 0)) {
1879 printk(KERN_ERR "BUG: workqueue leaked lock or atomic: "
1880 "%s/0x%08x/%d\n",
1881 current->comm, preempt_count(), task_pid_nr(current));
1882 printk(KERN_ERR " last function: ");
1883 print_symbol("%s\n", (unsigned long)f);
1884 debug_show_held_locks(current);
1885 dump_stack();
1886 }
1887
1888 spin_lock_irq(&gcwq->lock);
1889
1890 /* clear cpu intensive status */
1891 if (unlikely(cpu_intensive))
1892 worker_clr_flags(worker, WORKER_CPU_INTENSIVE);
1893
1894 /* we're done with it, release */
1895 hlist_del_init(&worker->hentry);
1896 worker->current_work = NULL;
1897 worker->current_cwq = NULL;
1898 cwq_dec_nr_in_flight(cwq, work_color, false);
1899}
1900
1901/**
1902 * process_scheduled_works - process scheduled works
1903 * @worker: self
1904 *
1905 * Process all scheduled works. Please note that the scheduled list
1906 * may change while processing a work, so this function repeatedly
1907 * fetches a work from the top and executes it.
1908 *
1909 * CONTEXT:
1910 * spin_lock_irq(gcwq->lock) which may be released and regrabbed
1911 * multiple times.
1912 */
1913static void process_scheduled_works(struct worker *worker)
1914{
1915 while (!list_empty(&worker->scheduled)) {
1916 struct work_struct *work = list_first_entry(&worker->scheduled,
1917 struct work_struct, entry);
1918 process_one_work(worker, work);
1919 }
1920}
1921
1922/**
1923 * worker_thread - the worker thread function
1924 * @__worker: self
1925 *
1926 * The gcwq worker thread function. There's a single dynamic pool of
1927 * these per each cpu. These workers process all works regardless of
1928 * their specific target workqueue. The only exception is works which
1929 * belong to workqueues with a rescuer which will be explained in
1930 * rescuer_thread().
1931 */
1932static int worker_thread(void *__worker)
1933{
1934 struct worker *worker = __worker;
1935 struct global_cwq *gcwq = worker->gcwq;
1936
1937 /* tell the scheduler that this is a workqueue worker */
1938 worker->task->flags |= PF_WQ_WORKER;
1939woke_up:
1940 spin_lock_irq(&gcwq->lock);
1941
1942 /* DIE can be set only while we're idle, checking here is enough */
1943 if (worker->flags & WORKER_DIE) {
1944 spin_unlock_irq(&gcwq->lock);
1945 worker->task->flags &= ~PF_WQ_WORKER;
1946 return 0;
1947 }
1948
1949 worker_leave_idle(worker);
1950recheck:
1951 /* no more worker necessary? */
1952 if (!need_more_worker(gcwq))
1953 goto sleep;
1954
1955 /* do we need to manage? */
1956 if (unlikely(!may_start_working(gcwq)) && manage_workers(worker))
1957 goto recheck;
1958
1959 /*
1960 * ->scheduled list can only be filled while a worker is
1961 * preparing to process a work or actually processing it.
1962 * Make sure nobody diddled with it while I was sleeping.
1963 */
1964 BUG_ON(!list_empty(&worker->scheduled));
1965
1966 /*
1967 * When control reaches this point, we're guaranteed to have
1968 * at least one idle worker or that someone else has already
1969 * assumed the manager role.
1970 */
1971 worker_clr_flags(worker, WORKER_PREP);
1972
1973 do {
1974 struct work_struct *work =
1975 list_first_entry(&gcwq->worklist,
1976 struct work_struct, entry);
1977
1978 if (likely(!(*work_data_bits(work) & WORK_STRUCT_LINKED))) {
1979 /* optimization path, not strictly necessary */
1980 process_one_work(worker, work);
1981 if (unlikely(!list_empty(&worker->scheduled)))
1982 process_scheduled_works(worker);
1983 } else {
1984 move_linked_works(work, &worker->scheduled, NULL);
1985 process_scheduled_works(worker);
1986 }
1987 } while (keep_working(gcwq));
1988
1989 worker_set_flags(worker, WORKER_PREP, false);
1990sleep:
1991 if (unlikely(need_to_manage_workers(gcwq)) && manage_workers(worker))
1992 goto recheck;
1993
1994 /*
1995 * gcwq->lock is held and there's no work to process and no
1996 * need to manage, sleep. Workers are woken up only while
1997 * holding gcwq->lock or from local cpu, so setting the
1998 * current state before releasing gcwq->lock is enough to
1999 * prevent losing any event.
2000 */
2001 worker_enter_idle(worker);
2002 __set_current_state(TASK_INTERRUPTIBLE);
2003 spin_unlock_irq(&gcwq->lock);
2004 schedule();
2005 goto woke_up;
2006}
2007
2008/**
2009 * rescuer_thread - the rescuer thread function
2010 * @__wq: the associated workqueue
2011 *
2012 * Workqueue rescuer thread function. There's one rescuer for each
2013 * workqueue which has WQ_RESCUER set.
2014 *
2015 * Regular work processing on a gcwq may block trying to create a new
2016 * worker which uses GFP_KERNEL allocation which has slight chance of
2017 * developing into deadlock if some works currently on the same queue
2018 * need to be processed to satisfy the GFP_KERNEL allocation. This is
2019 * the problem rescuer solves.
2020 *
2021 * When such condition is possible, the gcwq summons rescuers of all
2022 * workqueues which have works queued on the gcwq and let them process
2023 * those works so that forward progress can be guaranteed.
2024 *
2025 * This should happen rarely.
2026 */
2027static int rescuer_thread(void *__wq)
2028{
2029 struct workqueue_struct *wq = __wq;
2030 struct worker *rescuer = wq->rescuer;
2031 struct list_head *scheduled = &rescuer->scheduled;
2032 bool is_unbound = wq->flags & WQ_UNBOUND;
2033 unsigned int cpu;
2034
2035 set_user_nice(current, RESCUER_NICE_LEVEL);
2036repeat:
2037 set_current_state(TASK_INTERRUPTIBLE);
2038
2039 if (kthread_should_stop())
2040 return 0;
2041
2042 /*
2043 * See whether any cpu is asking for help. Unbounded
2044 * workqueues use cpu 0 in mayday_mask for CPU_UNBOUND.
2045 */
2046 for_each_mayday_cpu(cpu, wq->mayday_mask) {
2047 unsigned int tcpu = is_unbound ? WORK_CPU_UNBOUND : cpu;
2048 struct cpu_workqueue_struct *cwq = get_cwq(tcpu, wq);
2049 struct global_cwq *gcwq = cwq->gcwq;
2050 struct work_struct *work, *n;
2051
2052 __set_current_state(TASK_RUNNING);
2053 mayday_clear_cpu(cpu, wq->mayday_mask);
2054
2055 /* migrate to the target cpu if possible */
2056 rescuer->gcwq = gcwq;
2057 worker_maybe_bind_and_lock(rescuer);
2058
2059 /*
2060 * Slurp in all works issued via this workqueue and
2061 * process'em.
2062 */
2063 BUG_ON(!list_empty(&rescuer->scheduled));
2064 list_for_each_entry_safe(work, n, &gcwq->worklist, entry)
2065 if (get_work_cwq(work) == cwq)
2066 move_linked_works(work, scheduled, &n);
2067
2068 process_scheduled_works(rescuer);
2069
2070 /*
2071 * Leave this gcwq. If keep_working() is %true, notify a
2072 * regular worker; otherwise, we end up with 0 concurrency
2073 * and stalling the execution.
2074 */
2075 if (keep_working(gcwq))
2076 wake_up_worker(gcwq);
2077
2078 spin_unlock_irq(&gcwq->lock);
2079 }
2080
2081 schedule();
2082 goto repeat;
2083}
2084
2085struct wq_barrier {
2086 struct work_struct work;
2087 struct completion done;
2088};
2089
2090static void wq_barrier_func(struct work_struct *work)
2091{
2092 struct wq_barrier *barr = container_of(work, struct wq_barrier, work);
2093 complete(&barr->done);
2094}
2095
2096/**
2097 * insert_wq_barrier - insert a barrier work
2098 * @cwq: cwq to insert barrier into
2099 * @barr: wq_barrier to insert
2100 * @target: target work to attach @barr to
2101 * @worker: worker currently executing @target, NULL if @target is not executing
2102 *
2103 * @barr is linked to @target such that @barr is completed only after
2104 * @target finishes execution. Please note that the ordering
2105 * guarantee is observed only with respect to @target and on the local
2106 * cpu.
2107 *
2108 * Currently, a queued barrier can't be canceled. This is because
2109 * try_to_grab_pending() can't determine whether the work to be
2110 * grabbed is at the head of the queue and thus can't clear LINKED
2111 * flag of the previous work while there must be a valid next work
2112 * after a work with LINKED flag set.
2113 *
2114 * Note that when @worker is non-NULL, @target may be modified
2115 * underneath us, so we can't reliably determine cwq from @target.
2116 *
2117 * CONTEXT:
2118 * spin_lock_irq(gcwq->lock).
2119 */
2120static void insert_wq_barrier(struct cpu_workqueue_struct *cwq,
2121 struct wq_barrier *barr,
2122 struct work_struct *target, struct worker *worker)
2123{
2124 struct list_head *head;
2125 unsigned int linked = 0;
2126
2127 /*
2128 * debugobject calls are safe here even with gcwq->lock locked
2129 * as we know for sure that this will not trigger any of the
2130 * checks and call back into the fixup functions where we
2131 * might deadlock.
2132 */
2133 INIT_WORK_ONSTACK(&barr->work, wq_barrier_func);
2134 __set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(&barr->work));
2135 init_completion(&barr->done);
2136
2137 /*
2138 * If @target is currently being executed, schedule the
2139 * barrier to the worker; otherwise, put it after @target.
2140 */
2141 if (worker)
2142 head = worker->scheduled.next;
2143 else {
2144 unsigned long *bits = work_data_bits(target);
2145
2146 head = target->entry.next;
2147 /* there can already be other linked works, inherit and set */
2148 linked = *bits & WORK_STRUCT_LINKED;
2149 __set_bit(WORK_STRUCT_LINKED_BIT, bits);
2150 }
2151
2152 debug_work_activate(&barr->work);
2153 insert_work(cwq, &barr->work, head,
2154 work_color_to_flags(WORK_NO_COLOR) | linked);
2155}
2156
2157/**
2158 * flush_workqueue_prep_cwqs - prepare cwqs for workqueue flushing
2159 * @wq: workqueue being flushed
2160 * @flush_color: new flush color, < 0 for no-op
2161 * @work_color: new work color, < 0 for no-op
2162 *
2163 * Prepare cwqs for workqueue flushing.
2164 *
2165 * If @flush_color is non-negative, flush_color on all cwqs should be
2166 * -1. If no cwq has in-flight commands at the specified color, all
2167 * cwq->flush_color's stay at -1 and %false is returned. If any cwq
2168 * has in flight commands, its cwq->flush_color is set to
2169 * @flush_color, @wq->nr_cwqs_to_flush is updated accordingly, cwq
2170 * wakeup logic is armed and %true is returned.
2171 *
2172 * The caller should have initialized @wq->first_flusher prior to
2173 * calling this function with non-negative @flush_color. If
2174 * @flush_color is negative, no flush color update is done and %false
2175 * is returned.
2176 *
2177 * If @work_color is non-negative, all cwqs should have the same
2178 * work_color which is previous to @work_color and all will be
2179 * advanced to @work_color.
2180 *
2181 * CONTEXT:
2182 * mutex_lock(wq->flush_mutex).
2183 *
2184 * RETURNS:
2185 * %true if @flush_color >= 0 and there's something to flush. %false
2186 * otherwise.
2187 */
2188static bool flush_workqueue_prep_cwqs(struct workqueue_struct *wq,
2189 int flush_color, int work_color)
2190{
2191 bool wait = false;
2192 unsigned int cpu;
2193
2194 if (flush_color >= 0) {
2195 BUG_ON(atomic_read(&wq->nr_cwqs_to_flush));
2196 atomic_set(&wq->nr_cwqs_to_flush, 1);
2197 }
2198
2199 for_each_cwq_cpu(cpu, wq) {
2200 struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
2201 struct global_cwq *gcwq = cwq->gcwq;
2202
2203 spin_lock_irq(&gcwq->lock);
2204
2205 if (flush_color >= 0) {
2206 BUG_ON(cwq->flush_color != -1);
2207
2208 if (cwq->nr_in_flight[flush_color]) {
2209 cwq->flush_color = flush_color;
2210 atomic_inc(&wq->nr_cwqs_to_flush);
2211 wait = true;
2212 }
2213 }
2214
2215 if (work_color >= 0) {
2216 BUG_ON(work_color != work_next_color(cwq->work_color));
2217 cwq->work_color = work_color;
2218 }
2219
2220 spin_unlock_irq(&gcwq->lock);
2221 }
2222
2223 if (flush_color >= 0 && atomic_dec_and_test(&wq->nr_cwqs_to_flush))
2224 complete(&wq->first_flusher->done);
2225
2226 return wait;
2227}
2228
2229/**
2230 * flush_workqueue - ensure that any scheduled work has run to completion.
2231 * @wq: workqueue to flush
2232 *
2233 * Forces execution of the workqueue and blocks until its completion.
2234 * This is typically used in driver shutdown handlers.
2235 *
2236 * We sleep until all works which were queued on entry have been handled,
2237 * but we are not livelocked by new incoming ones.
2238 */
2239void flush_workqueue(struct workqueue_struct *wq)
2240{
2241 struct wq_flusher this_flusher = {
2242 .list = LIST_HEAD_INIT(this_flusher.list),
2243 .flush_color = -1,
2244 .done = COMPLETION_INITIALIZER_ONSTACK(this_flusher.done),
2245 };
2246 int next_color;
2247
2248 lock_map_acquire(&wq->lockdep_map);
2249 lock_map_release(&wq->lockdep_map);
2250
2251 mutex_lock(&wq->flush_mutex);
2252
2253 /*
2254 * Start-to-wait phase
2255 */
2256 next_color = work_next_color(wq->work_color);
2257
2258 if (next_color != wq->flush_color) {
2259 /*
2260 * Color space is not full. The current work_color
2261 * becomes our flush_color and work_color is advanced
2262 * by one.
2263 */
2264 BUG_ON(!list_empty(&wq->flusher_overflow));
2265 this_flusher.flush_color = wq->work_color;
2266 wq->work_color = next_color;
2267
2268 if (!wq->first_flusher) {
2269 /* no flush in progress, become the first flusher */
2270 BUG_ON(wq->flush_color != this_flusher.flush_color);
2271
2272 wq->first_flusher = &this_flusher;
2273
2274 if (!flush_workqueue_prep_cwqs(wq, wq->flush_color,
2275 wq->work_color)) {
2276 /* nothing to flush, done */
2277 wq->flush_color = next_color;
2278 wq->first_flusher = NULL;
2279 goto out_unlock;
2280 }
2281 } else {
2282 /* wait in queue */
2283 BUG_ON(wq->flush_color == this_flusher.flush_color);
2284 list_add_tail(&this_flusher.list, &wq->flusher_queue);
2285 flush_workqueue_prep_cwqs(wq, -1, wq->work_color);
2286 }
2287 } else {
2288 /*
2289 * Oops, color space is full, wait on overflow queue.
2290 * The next flush completion will assign us
2291 * flush_color and transfer to flusher_queue.
2292 */
2293 list_add_tail(&this_flusher.list, &wq->flusher_overflow);
2294 }
2295
2296 mutex_unlock(&wq->flush_mutex);
2297
2298 wait_for_completion(&this_flusher.done);
2299
2300 /*
2301 * Wake-up-and-cascade phase
2302 *
2303 * First flushers are responsible for cascading flushes and
2304 * handling overflow. Non-first flushers can simply return.
2305 */
2306 if (wq->first_flusher != &this_flusher)
2307 return;
2308
2309 mutex_lock(&wq->flush_mutex);
2310
2311 /* we might have raced, check again with mutex held */
2312 if (wq->first_flusher != &this_flusher)
2313 goto out_unlock;
2314
2315 wq->first_flusher = NULL;
2316
2317 BUG_ON(!list_empty(&this_flusher.list));
2318 BUG_ON(wq->flush_color != this_flusher.flush_color);
2319
2320 while (true) {
2321 struct wq_flusher *next, *tmp;
2322
2323 /* complete all the flushers sharing the current flush color */
2324 list_for_each_entry_safe(next, tmp, &wq->flusher_queue, list) {
2325 if (next->flush_color != wq->flush_color)
2326 break;
2327 list_del_init(&next->list);
2328 complete(&next->done);
2329 }
2330
2331 BUG_ON(!list_empty(&wq->flusher_overflow) &&
2332 wq->flush_color != work_next_color(wq->work_color));
2333
2334 /* this flush_color is finished, advance by one */
2335 wq->flush_color = work_next_color(wq->flush_color);
2336
2337 /* one color has been freed, handle overflow queue */
2338 if (!list_empty(&wq->flusher_overflow)) {
2339 /*
2340 * Assign the same color to all overflowed
2341 * flushers, advance work_color and append to
2342 * flusher_queue. This is the start-to-wait
2343 * phase for these overflowed flushers.
2344 */
2345 list_for_each_entry(tmp, &wq->flusher_overflow, list)
2346 tmp->flush_color = wq->work_color;
2347
2348 wq->work_color = work_next_color(wq->work_color);
2349
2350 list_splice_tail_init(&wq->flusher_overflow,
2351 &wq->flusher_queue);
2352 flush_workqueue_prep_cwqs(wq, -1, wq->work_color);
2353 }
2354
2355 if (list_empty(&wq->flusher_queue)) {
2356 BUG_ON(wq->flush_color != wq->work_color);
2357 break;
2358 }
2359
2360 /*
2361 * Need to flush more colors. Make the next flusher
2362 * the new first flusher and arm cwqs.
2363 */
2364 BUG_ON(wq->flush_color == wq->work_color);
2365 BUG_ON(wq->flush_color != next->flush_color);
2366
2367 list_del_init(&next->list);
2368 wq->first_flusher = next;
2369
2370 if (flush_workqueue_prep_cwqs(wq, wq->flush_color, -1))
2371 break;
2372
2373 /*
2374 * Meh... this color is already done, clear first
2375 * flusher and repeat cascading.
2376 */
2377 wq->first_flusher = NULL;
2378 }
2379
2380out_unlock:
2381 mutex_unlock(&wq->flush_mutex);
2382}
2383EXPORT_SYMBOL_GPL(flush_workqueue);
2384
2385/**
2386 * drain_workqueue - drain a workqueue
2387 * @wq: workqueue to drain
2388 *
2389 * Wait until the workqueue becomes empty. While draining is in progress,
2390 * only chain queueing is allowed. IOW, only currently pending or running
2391 * work items on @wq can queue further work items on it. @wq is flushed
2392 * repeatedly until it becomes empty. The number of flushing is detemined
2393 * by the depth of chaining and should be relatively short. Whine if it
2394 * takes too long.
2395 */
2396void drain_workqueue(struct workqueue_struct *wq)
2397{
2398 unsigned int flush_cnt = 0;
2399 unsigned int cpu;
2400
2401 /*
2402 * __queue_work() needs to test whether there are drainers, is much
2403 * hotter than drain_workqueue() and already looks at @wq->flags.
2404 * Use WQ_DRAINING so that queue doesn't have to check nr_drainers.
2405 */
2406 spin_lock(&workqueue_lock);
2407 if (!wq->nr_drainers++)
2408 wq->flags |= WQ_DRAINING;
2409 spin_unlock(&workqueue_lock);
2410reflush:
2411 flush_workqueue(wq);
2412
2413 for_each_cwq_cpu(cpu, wq) {
2414 struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
2415 bool drained;
2416
2417 spin_lock_irq(&cwq->gcwq->lock);
2418 drained = !cwq->nr_active && list_empty(&cwq->delayed_works);
2419 spin_unlock_irq(&cwq->gcwq->lock);
2420
2421 if (drained)
2422 continue;
2423
2424 if (++flush_cnt == 10 ||
2425 (flush_cnt % 100 == 0 && flush_cnt <= 1000))
2426 pr_warning("workqueue %s: flush on destruction isn't complete after %u tries\n",
2427 wq->name, flush_cnt);
2428 goto reflush;
2429 }
2430
2431 spin_lock(&workqueue_lock);
2432 if (!--wq->nr_drainers)
2433 wq->flags &= ~WQ_DRAINING;
2434 spin_unlock(&workqueue_lock);
2435}
2436EXPORT_SYMBOL_GPL(drain_workqueue);
2437
2438static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr,
2439 bool wait_executing)
2440{
2441 struct worker *worker = NULL;
2442 struct global_cwq *gcwq;
2443 struct cpu_workqueue_struct *cwq;
2444
2445 might_sleep();
2446 gcwq = get_work_gcwq(work);
2447 if (!gcwq)
2448 return false;
2449
2450 spin_lock_irq(&gcwq->lock);
2451 if (!list_empty(&work->entry)) {
2452 /*
2453 * See the comment near try_to_grab_pending()->smp_rmb().
2454 * If it was re-queued to a different gcwq under us, we
2455 * are not going to wait.
2456 */
2457 smp_rmb();
2458 cwq = get_work_cwq(work);
2459 if (unlikely(!cwq || gcwq != cwq->gcwq))
2460 goto already_gone;
2461 } else if (wait_executing) {
2462 worker = find_worker_executing_work(gcwq, work);
2463 if (!worker)
2464 goto already_gone;
2465 cwq = worker->current_cwq;
2466 } else
2467 goto already_gone;
2468
2469 insert_wq_barrier(cwq, barr, work, worker);
2470 spin_unlock_irq(&gcwq->lock);
2471
2472 /*
2473 * If @max_active is 1 or rescuer is in use, flushing another work
2474 * item on the same workqueue may lead to deadlock. Make sure the
2475 * flusher is not running on the same workqueue by verifying write
2476 * access.
2477 */
2478 if (cwq->wq->saved_max_active == 1 || cwq->wq->flags & WQ_RESCUER)
2479 lock_map_acquire(&cwq->wq->lockdep_map);
2480 else
2481 lock_map_acquire_read(&cwq->wq->lockdep_map);
2482 lock_map_release(&cwq->wq->lockdep_map);
2483
2484 return true;
2485already_gone:
2486 spin_unlock_irq(&gcwq->lock);
2487 return false;
2488}
2489
2490/**
2491 * flush_work - wait for a work to finish executing the last queueing instance
2492 * @work: the work to flush
2493 *
2494 * Wait until @work has finished execution. This function considers
2495 * only the last queueing instance of @work. If @work has been
2496 * enqueued across different CPUs on a non-reentrant workqueue or on
2497 * multiple workqueues, @work might still be executing on return on
2498 * some of the CPUs from earlier queueing.
2499 *
2500 * If @work was queued only on a non-reentrant, ordered or unbound
2501 * workqueue, @work is guaranteed to be idle on return if it hasn't
2502 * been requeued since flush started.
2503 *
2504 * RETURNS:
2505 * %true if flush_work() waited for the work to finish execution,
2506 * %false if it was already idle.
2507 */
2508bool flush_work(struct work_struct *work)
2509{
2510 struct wq_barrier barr;
2511
2512 if (start_flush_work(work, &barr, true)) {
2513 wait_for_completion(&barr.done);
2514 destroy_work_on_stack(&barr.work);
2515 return true;
2516 } else
2517 return false;
2518}
2519EXPORT_SYMBOL_GPL(flush_work);
2520
2521static bool wait_on_cpu_work(struct global_cwq *gcwq, struct work_struct *work)
2522{
2523 struct wq_barrier barr;
2524 struct worker *worker;
2525
2526 spin_lock_irq(&gcwq->lock);
2527
2528 worker = find_worker_executing_work(gcwq, work);
2529 if (unlikely(worker))
2530 insert_wq_barrier(worker->current_cwq, &barr, work, worker);
2531
2532 spin_unlock_irq(&gcwq->lock);
2533
2534 if (unlikely(worker)) {
2535 wait_for_completion(&barr.done);
2536 destroy_work_on_stack(&barr.work);
2537 return true;
2538 } else
2539 return false;
2540}
2541
2542static bool wait_on_work(struct work_struct *work)
2543{
2544 bool ret = false;
2545 int cpu;
2546
2547 might_sleep();
2548
2549 lock_map_acquire(&work->lockdep_map);
2550 lock_map_release(&work->lockdep_map);
2551
2552 for_each_gcwq_cpu(cpu)
2553 ret |= wait_on_cpu_work(get_gcwq(cpu), work);
2554 return ret;
2555}
2556
2557/**
2558 * flush_work_sync - wait until a work has finished execution
2559 * @work: the work to flush
2560 *
2561 * Wait until @work has finished execution. On return, it's
2562 * guaranteed that all queueing instances of @work which happened
2563 * before this function is called are finished. In other words, if
2564 * @work hasn't been requeued since this function was called, @work is
2565 * guaranteed to be idle on return.
2566 *
2567 * RETURNS:
2568 * %true if flush_work_sync() waited for the work to finish execution,
2569 * %false if it was already idle.
2570 */
2571bool flush_work_sync(struct work_struct *work)
2572{
2573 struct wq_barrier barr;
2574 bool pending, waited;
2575
2576 /* we'll wait for executions separately, queue barr only if pending */
2577 pending = start_flush_work(work, &barr, false);
2578
2579 /* wait for executions to finish */
2580 waited = wait_on_work(work);
2581
2582 /* wait for the pending one */
2583 if (pending) {
2584 wait_for_completion(&barr.done);
2585 destroy_work_on_stack(&barr.work);
2586 }
2587
2588 return pending || waited;
2589}
2590EXPORT_SYMBOL_GPL(flush_work_sync);
2591
2592/*
2593 * Upon a successful return (>= 0), the caller "owns" WORK_STRUCT_PENDING bit,
2594 * so this work can't be re-armed in any way.
2595 */
2596static int try_to_grab_pending(struct work_struct *work)
2597{
2598 struct global_cwq *gcwq;
2599 int ret = -1;
2600
2601 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work)))
2602 return 0;
2603
2604 /*
2605 * The queueing is in progress, or it is already queued. Try to
2606 * steal it from ->worklist without clearing WORK_STRUCT_PENDING.
2607 */
2608 gcwq = get_work_gcwq(work);
2609 if (!gcwq)
2610 return ret;
2611
2612 spin_lock_irq(&gcwq->lock);
2613 if (!list_empty(&work->entry)) {
2614 /*
2615 * This work is queued, but perhaps we locked the wrong gcwq.
2616 * In that case we must see the new value after rmb(), see
2617 * insert_work()->wmb().
2618 */
2619 smp_rmb();
2620 if (gcwq == get_work_gcwq(work)) {
2621 debug_work_deactivate(work);
2622 list_del_init(&work->entry);
2623 cwq_dec_nr_in_flight(get_work_cwq(work),
2624 get_work_color(work),
2625 *work_data_bits(work) & WORK_STRUCT_DELAYED);
2626 ret = 1;
2627 }
2628 }
2629 spin_unlock_irq(&gcwq->lock);
2630
2631 return ret;
2632}
2633
2634static bool __cancel_work_timer(struct work_struct *work,
2635 struct timer_list* timer)
2636{
2637 int ret;
2638
2639 do {
2640 ret = (timer && likely(del_timer(timer)));
2641 if (!ret)
2642 ret = try_to_grab_pending(work);
2643 wait_on_work(work);
2644 } while (unlikely(ret < 0));
2645
2646 clear_work_data(work);
2647 return ret;
2648}
2649
2650/**
2651 * cancel_work_sync - cancel a work and wait for it to finish
2652 * @work: the work to cancel
2653 *
2654 * Cancel @work and wait for its execution to finish. This function
2655 * can be used even if the work re-queues itself or migrates to
2656 * another workqueue. On return from this function, @work is
2657 * guaranteed to be not pending or executing on any CPU.
2658 *
2659 * cancel_work_sync(&delayed_work->work) must not be used for
2660 * delayed_work's. Use cancel_delayed_work_sync() instead.
2661 *
2662 * The caller must ensure that the workqueue on which @work was last
2663 * queued can't be destroyed before this function returns.
2664 *
2665 * RETURNS:
2666 * %true if @work was pending, %false otherwise.
2667 */
2668bool cancel_work_sync(struct work_struct *work)
2669{
2670 return __cancel_work_timer(work, NULL);
2671}
2672EXPORT_SYMBOL_GPL(cancel_work_sync);
2673
2674/**
2675 * flush_delayed_work - wait for a dwork to finish executing the last queueing
2676 * @dwork: the delayed work to flush
2677 *
2678 * Delayed timer is cancelled and the pending work is queued for
2679 * immediate execution. Like flush_work(), this function only
2680 * considers the last queueing instance of @dwork.
2681 *
2682 * RETURNS:
2683 * %true if flush_work() waited for the work to finish execution,
2684 * %false if it was already idle.
2685 */
2686bool flush_delayed_work(struct delayed_work *dwork)
2687{
2688 if (del_timer_sync(&dwork->timer))
2689 __queue_work(raw_smp_processor_id(),
2690 get_work_cwq(&dwork->work)->wq, &dwork->work);
2691 return flush_work(&dwork->work);
2692}
2693EXPORT_SYMBOL(flush_delayed_work);
2694
2695/**
2696 * flush_delayed_work_sync - wait for a dwork to finish
2697 * @dwork: the delayed work to flush
2698 *
2699 * Delayed timer is cancelled and the pending work is queued for
2700 * execution immediately. Other than timer handling, its behavior
2701 * is identical to flush_work_sync().
2702 *
2703 * RETURNS:
2704 * %true if flush_work_sync() waited for the work to finish execution,
2705 * %false if it was already idle.
2706 */
2707bool flush_delayed_work_sync(struct delayed_work *dwork)
2708{
2709 if (del_timer_sync(&dwork->timer))
2710 __queue_work(raw_smp_processor_id(),
2711 get_work_cwq(&dwork->work)->wq, &dwork->work);
2712 return flush_work_sync(&dwork->work);
2713}
2714EXPORT_SYMBOL(flush_delayed_work_sync);
2715
2716/**
2717 * cancel_delayed_work_sync - cancel a delayed work and wait for it to finish
2718 * @dwork: the delayed work cancel
2719 *
2720 * This is cancel_work_sync() for delayed works.
2721 *
2722 * RETURNS:
2723 * %true if @dwork was pending, %false otherwise.
2724 */
2725bool cancel_delayed_work_sync(struct delayed_work *dwork)
2726{
2727 return __cancel_work_timer(&dwork->work, &dwork->timer);
2728}
2729EXPORT_SYMBOL(cancel_delayed_work_sync);
2730
2731/**
2732 * schedule_work - put work task in global workqueue
2733 * @work: job to be done
2734 *
2735 * Returns zero if @work was already on the kernel-global workqueue and
2736 * non-zero otherwise.
2737 *
2738 * This puts a job in the kernel-global workqueue if it was not already
2739 * queued and leaves it in the same position on the kernel-global
2740 * workqueue otherwise.
2741 */
2742int schedule_work(struct work_struct *work)
2743{
2744 return queue_work(system_wq, work);
2745}
2746EXPORT_SYMBOL(schedule_work);
2747
2748/*
2749 * schedule_work_on - put work task on a specific cpu
2750 * @cpu: cpu to put the work task on
2751 * @work: job to be done
2752 *
2753 * This puts a job on a specific cpu
2754 */
2755int schedule_work_on(int cpu, struct work_struct *work)
2756{
2757 return queue_work_on(cpu, system_wq, work);
2758}
2759EXPORT_SYMBOL(schedule_work_on);
2760
2761/**
2762 * schedule_delayed_work - put work task in global workqueue after delay
2763 * @dwork: job to be done
2764 * @delay: number of jiffies to wait or 0 for immediate execution
2765 *
2766 * After waiting for a given time this puts a job in the kernel-global
2767 * workqueue.
2768 */
2769int schedule_delayed_work(struct delayed_work *dwork,
2770 unsigned long delay)
2771{
2772 return queue_delayed_work(system_wq, dwork, delay);
2773}
2774EXPORT_SYMBOL(schedule_delayed_work);
2775
2776/**
2777 * schedule_delayed_work_on - queue work in global workqueue on CPU after delay
2778 * @cpu: cpu to use
2779 * @dwork: job to be done
2780 * @delay: number of jiffies to wait
2781 *
2782 * After waiting for a given time this puts a job in the kernel-global
2783 * workqueue on the specified CPU.
2784 */
2785int schedule_delayed_work_on(int cpu,
2786 struct delayed_work *dwork, unsigned long delay)
2787{
2788 return queue_delayed_work_on(cpu, system_wq, dwork, delay);
2789}
2790EXPORT_SYMBOL(schedule_delayed_work_on);
2791
2792/**
2793 * schedule_on_each_cpu - execute a function synchronously on each online CPU
2794 * @func: the function to call
2795 *
2796 * schedule_on_each_cpu() executes @func on each online CPU using the
2797 * system workqueue and blocks until all CPUs have completed.
2798 * schedule_on_each_cpu() is very slow.
2799 *
2800 * RETURNS:
2801 * 0 on success, -errno on failure.
2802 */
2803int schedule_on_each_cpu(work_func_t func)
2804{
2805 int cpu;
2806 struct work_struct __percpu *works;
2807
2808 works = alloc_percpu(struct work_struct);
2809 if (!works)
2810 return -ENOMEM;
2811
2812 get_online_cpus();
2813
2814 for_each_online_cpu(cpu) {
2815 struct work_struct *work = per_cpu_ptr(works, cpu);
2816
2817 INIT_WORK(work, func);
2818 schedule_work_on(cpu, work);
2819 }
2820
2821 for_each_online_cpu(cpu)
2822 flush_work(per_cpu_ptr(works, cpu));
2823
2824 put_online_cpus();
2825 free_percpu(works);
2826 return 0;
2827}
2828
2829/**
2830 * flush_scheduled_work - ensure that any scheduled work has run to completion.
2831 *
2832 * Forces execution of the kernel-global workqueue and blocks until its
2833 * completion.
2834 *
2835 * Think twice before calling this function! It's very easy to get into
2836 * trouble if you don't take great care. Either of the following situations
2837 * will lead to deadlock:
2838 *
2839 * One of the work items currently on the workqueue needs to acquire
2840 * a lock held by your code or its caller.
2841 *
2842 * Your code is running in the context of a work routine.
2843 *
2844 * They will be detected by lockdep when they occur, but the first might not
2845 * occur very often. It depends on what work items are on the workqueue and
2846 * what locks they need, which you have no control over.
2847 *
2848 * In most situations flushing the entire workqueue is overkill; you merely
2849 * need to know that a particular work item isn't queued and isn't running.
2850 * In such cases you should use cancel_delayed_work_sync() or
2851 * cancel_work_sync() instead.
2852 */
2853void flush_scheduled_work(void)
2854{
2855 flush_workqueue(system_wq);
2856}
2857EXPORT_SYMBOL(flush_scheduled_work);
2858
2859/**
2860 * execute_in_process_context - reliably execute the routine with user context
2861 * @fn: the function to execute
2862 * @ew: guaranteed storage for the execute work structure (must
2863 * be available when the work executes)
2864 *
2865 * Executes the function immediately if process context is available,
2866 * otherwise schedules the function for delayed execution.
2867 *
2868 * Returns: 0 - function was executed
2869 * 1 - function was scheduled for execution
2870 */
2871int execute_in_process_context(work_func_t fn, struct execute_work *ew)
2872{
2873 if (!in_interrupt()) {
2874 fn(&ew->work);
2875 return 0;
2876 }
2877
2878 INIT_WORK(&ew->work, fn);
2879 schedule_work(&ew->work);
2880
2881 return 1;
2882}
2883EXPORT_SYMBOL_GPL(execute_in_process_context);
2884
2885int keventd_up(void)
2886{
2887 return system_wq != NULL;
2888}
2889
2890static int alloc_cwqs(struct workqueue_struct *wq)
2891{
2892 /*
2893 * cwqs are forced aligned according to WORK_STRUCT_FLAG_BITS.
2894 * Make sure that the alignment isn't lower than that of
2895 * unsigned long long.
2896 */
2897 const size_t size = sizeof(struct cpu_workqueue_struct);
2898 const size_t align = max_t(size_t, 1 << WORK_STRUCT_FLAG_BITS,
2899 __alignof__(unsigned long long));
2900#ifdef CONFIG_SMP
2901 bool percpu = !(wq->flags & WQ_UNBOUND);
2902#else
2903 bool percpu = false;
2904#endif
2905
2906 if (percpu)
2907 wq->cpu_wq.pcpu = __alloc_percpu(size, align);
2908 else {
2909 void *ptr;
2910
2911 /*
2912 * Allocate enough room to align cwq and put an extra
2913 * pointer at the end pointing back to the originally
2914 * allocated pointer which will be used for free.
2915 */
2916 ptr = kzalloc(size + align + sizeof(void *), GFP_KERNEL);
2917 if (ptr) {
2918 wq->cpu_wq.single = PTR_ALIGN(ptr, align);
2919 *(void **)(wq->cpu_wq.single + 1) = ptr;
2920 }
2921 }
2922
2923 /* just in case, make sure it's actually aligned */
2924 BUG_ON(!IS_ALIGNED(wq->cpu_wq.v, align));
2925 return wq->cpu_wq.v ? 0 : -ENOMEM;
2926}
2927
2928static void free_cwqs(struct workqueue_struct *wq)
2929{
2930#ifdef CONFIG_SMP
2931 bool percpu = !(wq->flags & WQ_UNBOUND);
2932#else
2933 bool percpu = false;
2934#endif
2935
2936 if (percpu)
2937 free_percpu(wq->cpu_wq.pcpu);
2938 else if (wq->cpu_wq.single) {
2939 /* the pointer to free is stored right after the cwq */
2940 kfree(*(void **)(wq->cpu_wq.single + 1));
2941 }
2942}
2943
2944static int wq_clamp_max_active(int max_active, unsigned int flags,
2945 const char *name)
2946{
2947 int lim = flags & WQ_UNBOUND ? WQ_UNBOUND_MAX_ACTIVE : WQ_MAX_ACTIVE;
2948
2949 if (max_active < 1 || max_active > lim)
2950 printk(KERN_WARNING "workqueue: max_active %d requested for %s "
2951 "is out of range, clamping between %d and %d\n",
2952 max_active, name, 1, lim);
2953
2954 return clamp_val(max_active, 1, lim);
2955}
2956
2957struct workqueue_struct *__alloc_workqueue_key(const char *name,
2958 unsigned int flags,
2959 int max_active,
2960 struct lock_class_key *key,
2961 const char *lock_name)
2962{
2963 struct workqueue_struct *wq;
2964 unsigned int cpu;
2965
2966 /*
2967 * Workqueues which may be used during memory reclaim should
2968 * have a rescuer to guarantee forward progress.
2969 */
2970 if (flags & WQ_MEM_RECLAIM)
2971 flags |= WQ_RESCUER;
2972
2973 /*
2974 * Unbound workqueues aren't concurrency managed and should be
2975 * dispatched to workers immediately.
2976 */
2977 if (flags & WQ_UNBOUND)
2978 flags |= WQ_HIGHPRI;
2979
2980 max_active = max_active ?: WQ_DFL_ACTIVE;
2981 max_active = wq_clamp_max_active(max_active, flags, name);
2982
2983 wq = kzalloc(sizeof(*wq), GFP_KERNEL);
2984 if (!wq)
2985 goto err;
2986
2987 wq->flags = flags;
2988 wq->saved_max_active = max_active;
2989 mutex_init(&wq->flush_mutex);
2990 atomic_set(&wq->nr_cwqs_to_flush, 0);
2991 INIT_LIST_HEAD(&wq->flusher_queue);
2992 INIT_LIST_HEAD(&wq->flusher_overflow);
2993
2994 wq->name = name;
2995 lockdep_init_map(&wq->lockdep_map, lock_name, key, 0);
2996 INIT_LIST_HEAD(&wq->list);
2997
2998 if (alloc_cwqs(wq) < 0)
2999 goto err;
3000
3001 for_each_cwq_cpu(cpu, wq) {
3002 struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
3003 struct global_cwq *gcwq = get_gcwq(cpu);
3004
3005 BUG_ON((unsigned long)cwq & WORK_STRUCT_FLAG_MASK);
3006 cwq->gcwq = gcwq;
3007 cwq->wq = wq;
3008 cwq->flush_color = -1;
3009 cwq->max_active = max_active;
3010 INIT_LIST_HEAD(&cwq->delayed_works);
3011 }
3012
3013 if (flags & WQ_RESCUER) {
3014 struct worker *rescuer;
3015
3016 if (!alloc_mayday_mask(&wq->mayday_mask, GFP_KERNEL))
3017 goto err;
3018
3019 wq->rescuer = rescuer = alloc_worker();
3020 if (!rescuer)
3021 goto err;
3022
3023 rescuer->task = kthread_create(rescuer_thread, wq, "%s", name);
3024 if (IS_ERR(rescuer->task))
3025 goto err;
3026
3027 rescuer->task->flags |= PF_THREAD_BOUND;
3028 wake_up_process(rescuer->task);
3029 }
3030
3031 /*
3032 * workqueue_lock protects global freeze state and workqueues
3033 * list. Grab it, set max_active accordingly and add the new
3034 * workqueue to workqueues list.
3035 */
3036 spin_lock(&workqueue_lock);
3037
3038 if (workqueue_freezing && wq->flags & WQ_FREEZABLE)
3039 for_each_cwq_cpu(cpu, wq)
3040 get_cwq(cpu, wq)->max_active = 0;
3041
3042 list_add(&wq->list, &workqueues);
3043
3044 spin_unlock(&workqueue_lock);
3045
3046 return wq;
3047err:
3048 if (wq) {
3049 free_cwqs(wq);
3050 free_mayday_mask(wq->mayday_mask);
3051 kfree(wq->rescuer);
3052 kfree(wq);
3053 }
3054 return NULL;
3055}
3056EXPORT_SYMBOL_GPL(__alloc_workqueue_key);
3057
3058/**
3059 * destroy_workqueue - safely terminate a workqueue
3060 * @wq: target workqueue
3061 *
3062 * Safely destroy a workqueue. All work currently pending will be done first.
3063 */
3064void destroy_workqueue(struct workqueue_struct *wq)
3065{
3066 unsigned int cpu;
3067
3068 /* drain it before proceeding with destruction */
3069 drain_workqueue(wq);
3070
3071 /*
3072 * wq list is used to freeze wq, remove from list after
3073 * flushing is complete in case freeze races us.
3074 */
3075 spin_lock(&workqueue_lock);
3076 list_del(&wq->list);
3077 spin_unlock(&workqueue_lock);
3078
3079 /* sanity check */
3080 for_each_cwq_cpu(cpu, wq) {
3081 struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
3082 int i;
3083
3084 for (i = 0; i < WORK_NR_COLORS; i++)
3085 BUG_ON(cwq->nr_in_flight[i]);
3086 BUG_ON(cwq->nr_active);
3087 BUG_ON(!list_empty(&cwq->delayed_works));
3088 }
3089
3090 if (wq->flags & WQ_RESCUER) {
3091 kthread_stop(wq->rescuer->task);
3092 free_mayday_mask(wq->mayday_mask);
3093 kfree(wq->rescuer);
3094 }
3095
3096 free_cwqs(wq);
3097 kfree(wq);
3098}
3099EXPORT_SYMBOL_GPL(destroy_workqueue);
3100
3101/**
3102 * workqueue_set_max_active - adjust max_active of a workqueue
3103 * @wq: target workqueue
3104 * @max_active: new max_active value.
3105 *
3106 * Set max_active of @wq to @max_active.
3107 *
3108 * CONTEXT:
3109 * Don't call from IRQ context.
3110 */
3111void workqueue_set_max_active(struct workqueue_struct *wq, int max_active)
3112{
3113 unsigned int cpu;
3114
3115 max_active = wq_clamp_max_active(max_active, wq->flags, wq->name);
3116
3117 spin_lock(&workqueue_lock);
3118
3119 wq->saved_max_active = max_active;
3120
3121 for_each_cwq_cpu(cpu, wq) {
3122 struct global_cwq *gcwq = get_gcwq(cpu);
3123
3124 spin_lock_irq(&gcwq->lock);
3125
3126 if (!(wq->flags & WQ_FREEZABLE) ||
3127 !(gcwq->flags & GCWQ_FREEZING))
3128 get_cwq(gcwq->cpu, wq)->max_active = max_active;
3129
3130 spin_unlock_irq(&gcwq->lock);
3131 }
3132
3133 spin_unlock(&workqueue_lock);
3134}
3135EXPORT_SYMBOL_GPL(workqueue_set_max_active);
3136
3137/**
3138 * workqueue_congested - test whether a workqueue is congested
3139 * @cpu: CPU in question
3140 * @wq: target workqueue
3141 *
3142 * Test whether @wq's cpu workqueue for @cpu is congested. There is
3143 * no synchronization around this function and the test result is
3144 * unreliable and only useful as advisory hints or for debugging.
3145 *
3146 * RETURNS:
3147 * %true if congested, %false otherwise.
3148 */
3149bool workqueue_congested(unsigned int cpu, struct workqueue_struct *wq)
3150{
3151 struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
3152
3153 return !list_empty(&cwq->delayed_works);
3154}
3155EXPORT_SYMBOL_GPL(workqueue_congested);
3156
3157/**
3158 * work_cpu - return the last known associated cpu for @work
3159 * @work: the work of interest
3160 *
3161 * RETURNS:
3162 * CPU number if @work was ever queued. WORK_CPU_NONE otherwise.
3163 */
3164unsigned int work_cpu(struct work_struct *work)
3165{
3166 struct global_cwq *gcwq = get_work_gcwq(work);
3167
3168 return gcwq ? gcwq->cpu : WORK_CPU_NONE;
3169}
3170EXPORT_SYMBOL_GPL(work_cpu);
3171
3172/**
3173 * work_busy - test whether a work is currently pending or running
3174 * @work: the work to be tested
3175 *
3176 * Test whether @work is currently pending or running. There is no
3177 * synchronization around this function and the test result is
3178 * unreliable and only useful as advisory hints or for debugging.
3179 * Especially for reentrant wqs, the pending state might hide the
3180 * running state.
3181 *
3182 * RETURNS:
3183 * OR'd bitmask of WORK_BUSY_* bits.
3184 */
3185unsigned int work_busy(struct work_struct *work)
3186{
3187 struct global_cwq *gcwq = get_work_gcwq(work);
3188 unsigned long flags;
3189 unsigned int ret = 0;
3190
3191 if (!gcwq)
3192 return false;
3193
3194 spin_lock_irqsave(&gcwq->lock, flags);
3195
3196 if (work_pending(work))
3197 ret |= WORK_BUSY_PENDING;
3198 if (find_worker_executing_work(gcwq, work))
3199 ret |= WORK_BUSY_RUNNING;
3200
3201 spin_unlock_irqrestore(&gcwq->lock, flags);
3202
3203 return ret;
3204}
3205EXPORT_SYMBOL_GPL(work_busy);
3206
3207/*
3208 * CPU hotplug.
3209 *
3210 * There are two challenges in supporting CPU hotplug. Firstly, there
3211 * are a lot of assumptions on strong associations among work, cwq and
3212 * gcwq which make migrating pending and scheduled works very
3213 * difficult to implement without impacting hot paths. Secondly,
3214 * gcwqs serve mix of short, long and very long running works making
3215 * blocked draining impractical.
3216 *
3217 * This is solved by allowing a gcwq to be detached from CPU, running
3218 * it with unbound (rogue) workers and allowing it to be reattached
3219 * later if the cpu comes back online. A separate thread is created
3220 * to govern a gcwq in such state and is called the trustee of the
3221 * gcwq.
3222 *
3223 * Trustee states and their descriptions.
3224 *
3225 * START Command state used on startup. On CPU_DOWN_PREPARE, a
3226 * new trustee is started with this state.
3227 *
3228 * IN_CHARGE Once started, trustee will enter this state after
3229 * assuming the manager role and making all existing
3230 * workers rogue. DOWN_PREPARE waits for trustee to
3231 * enter this state. After reaching IN_CHARGE, trustee
3232 * tries to execute the pending worklist until it's empty
3233 * and the state is set to BUTCHER, or the state is set
3234 * to RELEASE.
3235 *
3236 * BUTCHER Command state which is set by the cpu callback after
3237 * the cpu has went down. Once this state is set trustee
3238 * knows that there will be no new works on the worklist
3239 * and once the worklist is empty it can proceed to
3240 * killing idle workers.
3241 *
3242 * RELEASE Command state which is set by the cpu callback if the
3243 * cpu down has been canceled or it has come online
3244 * again. After recognizing this state, trustee stops
3245 * trying to drain or butcher and clears ROGUE, rebinds
3246 * all remaining workers back to the cpu and releases
3247 * manager role.
3248 *
3249 * DONE Trustee will enter this state after BUTCHER or RELEASE
3250 * is complete.
3251 *
3252 * trustee CPU draining
3253 * took over down complete
3254 * START -----------> IN_CHARGE -----------> BUTCHER -----------> DONE
3255 * | | ^
3256 * | CPU is back online v return workers |
3257 * ----------------> RELEASE --------------
3258 */
3259
3260/**
3261 * trustee_wait_event_timeout - timed event wait for trustee
3262 * @cond: condition to wait for
3263 * @timeout: timeout in jiffies
3264 *
3265 * wait_event_timeout() for trustee to use. Handles locking and
3266 * checks for RELEASE request.
3267 *
3268 * CONTEXT:
3269 * spin_lock_irq(gcwq->lock) which may be released and regrabbed
3270 * multiple times. To be used by trustee.
3271 *
3272 * RETURNS:
3273 * Positive indicating left time if @cond is satisfied, 0 if timed
3274 * out, -1 if canceled.
3275 */
3276#define trustee_wait_event_timeout(cond, timeout) ({ \
3277 long __ret = (timeout); \
3278 while (!((cond) || (gcwq->trustee_state == TRUSTEE_RELEASE)) && \
3279 __ret) { \
3280 spin_unlock_irq(&gcwq->lock); \
3281 __wait_event_timeout(gcwq->trustee_wait, (cond) || \
3282 (gcwq->trustee_state == TRUSTEE_RELEASE), \
3283 __ret); \
3284 spin_lock_irq(&gcwq->lock); \
3285 } \
3286 gcwq->trustee_state == TRUSTEE_RELEASE ? -1 : (__ret); \
3287})
3288
3289/**
3290 * trustee_wait_event - event wait for trustee
3291 * @cond: condition to wait for
3292 *
3293 * wait_event() for trustee to use. Automatically handles locking and
3294 * checks for CANCEL request.
3295 *
3296 * CONTEXT:
3297 * spin_lock_irq(gcwq->lock) which may be released and regrabbed
3298 * multiple times. To be used by trustee.
3299 *
3300 * RETURNS:
3301 * 0 if @cond is satisfied, -1 if canceled.
3302 */
3303#define trustee_wait_event(cond) ({ \
3304 long __ret1; \
3305 __ret1 = trustee_wait_event_timeout(cond, MAX_SCHEDULE_TIMEOUT);\
3306 __ret1 < 0 ? -1 : 0; \
3307})
3308
3309static int __cpuinit trustee_thread(void *__gcwq)
3310{
3311 struct global_cwq *gcwq = __gcwq;
3312 struct worker *worker;
3313 struct work_struct *work;
3314 struct hlist_node *pos;
3315 long rc;
3316 int i;
3317
3318 BUG_ON(gcwq->cpu != smp_processor_id());
3319
3320 spin_lock_irq(&gcwq->lock);
3321 /*
3322 * Claim the manager position and make all workers rogue.
3323 * Trustee must be bound to the target cpu and can't be
3324 * cancelled.
3325 */
3326 BUG_ON(gcwq->cpu != smp_processor_id());
3327 rc = trustee_wait_event(!(gcwq->flags & GCWQ_MANAGING_WORKERS));
3328 BUG_ON(rc < 0);
3329
3330 gcwq->flags |= GCWQ_MANAGING_WORKERS;
3331
3332 list_for_each_entry(worker, &gcwq->idle_list, entry)
3333 worker->flags |= WORKER_ROGUE;
3334
3335 for_each_busy_worker(worker, i, pos, gcwq)
3336 worker->flags |= WORKER_ROGUE;
3337
3338 /*
3339 * Call schedule() so that we cross rq->lock and thus can
3340 * guarantee sched callbacks see the rogue flag. This is
3341 * necessary as scheduler callbacks may be invoked from other
3342 * cpus.
3343 */
3344 spin_unlock_irq(&gcwq->lock);
3345 schedule();
3346 spin_lock_irq(&gcwq->lock);
3347
3348 /*
3349 * Sched callbacks are disabled now. Zap nr_running. After
3350 * this, nr_running stays zero and need_more_worker() and
3351 * keep_working() are always true as long as the worklist is
3352 * not empty.
3353 */
3354 atomic_set(get_gcwq_nr_running(gcwq->cpu), 0);
3355
3356 spin_unlock_irq(&gcwq->lock);
3357 del_timer_sync(&gcwq->idle_timer);
3358 spin_lock_irq(&gcwq->lock);
3359
3360 /*
3361 * We're now in charge. Notify and proceed to drain. We need
3362 * to keep the gcwq running during the whole CPU down
3363 * procedure as other cpu hotunplug callbacks may need to
3364 * flush currently running tasks.
3365 */
3366 gcwq->trustee_state = TRUSTEE_IN_CHARGE;
3367 wake_up_all(&gcwq->trustee_wait);
3368
3369 /*
3370 * The original cpu is in the process of dying and may go away
3371 * anytime now. When that happens, we and all workers would
3372 * be migrated to other cpus. Try draining any left work. We
3373 * want to get it over with ASAP - spam rescuers, wake up as
3374 * many idlers as necessary and create new ones till the
3375 * worklist is empty. Note that if the gcwq is frozen, there
3376 * may be frozen works in freezable cwqs. Don't declare
3377 * completion while frozen.
3378 */
3379 while (gcwq->nr_workers != gcwq->nr_idle ||
3380 gcwq->flags & GCWQ_FREEZING ||
3381 gcwq->trustee_state == TRUSTEE_IN_CHARGE) {
3382 int nr_works = 0;
3383
3384 list_for_each_entry(work, &gcwq->worklist, entry) {
3385 send_mayday(work);
3386 nr_works++;
3387 }
3388
3389 list_for_each_entry(worker, &gcwq->idle_list, entry) {
3390 if (!nr_works--)
3391 break;
3392 wake_up_process(worker->task);
3393 }
3394
3395 if (need_to_create_worker(gcwq)) {
3396 spin_unlock_irq(&gcwq->lock);
3397 worker = create_worker(gcwq, false);
3398 spin_lock_irq(&gcwq->lock);
3399 if (worker) {
3400 worker->flags |= WORKER_ROGUE;
3401 start_worker(worker);
3402 }
3403 }
3404
3405 /* give a breather */
3406 if (trustee_wait_event_timeout(false, TRUSTEE_COOLDOWN) < 0)
3407 break;
3408 }
3409
3410 /*
3411 * Either all works have been scheduled and cpu is down, or
3412 * cpu down has already been canceled. Wait for and butcher
3413 * all workers till we're canceled.
3414 */
3415 do {
3416 rc = trustee_wait_event(!list_empty(&gcwq->idle_list));
3417 while (!list_empty(&gcwq->idle_list))
3418 destroy_worker(list_first_entry(&gcwq->idle_list,
3419 struct worker, entry));
3420 } while (gcwq->nr_workers && rc >= 0);
3421
3422 /*
3423 * At this point, either draining has completed and no worker
3424 * is left, or cpu down has been canceled or the cpu is being
3425 * brought back up. There shouldn't be any idle one left.
3426 * Tell the remaining busy ones to rebind once it finishes the
3427 * currently scheduled works by scheduling the rebind_work.
3428 */
3429 WARN_ON(!list_empty(&gcwq->idle_list));
3430
3431 for_each_busy_worker(worker, i, pos, gcwq) {
3432 struct work_struct *rebind_work = &worker->rebind_work;
3433
3434 /*
3435 * Rebind_work may race with future cpu hotplug
3436 * operations. Use a separate flag to mark that
3437 * rebinding is scheduled.
3438 */
3439 worker->flags |= WORKER_REBIND;
3440 worker->flags &= ~WORKER_ROGUE;
3441
3442 /* queue rebind_work, wq doesn't matter, use the default one */
3443 if (test_and_set_bit(WORK_STRUCT_PENDING_BIT,
3444 work_data_bits(rebind_work)))
3445 continue;
3446
3447 debug_work_activate(rebind_work);
3448 insert_work(get_cwq(gcwq->cpu, system_wq), rebind_work,
3449 worker->scheduled.next,
3450 work_color_to_flags(WORK_NO_COLOR));
3451 }
3452
3453 /* relinquish manager role */
3454 gcwq->flags &= ~GCWQ_MANAGING_WORKERS;
3455
3456 /* notify completion */
3457 gcwq->trustee = NULL;
3458 gcwq->trustee_state = TRUSTEE_DONE;
3459 wake_up_all(&gcwq->trustee_wait);
3460 spin_unlock_irq(&gcwq->lock);
3461 return 0;
3462}
3463
3464/**
3465 * wait_trustee_state - wait for trustee to enter the specified state
3466 * @gcwq: gcwq the trustee of interest belongs to
3467 * @state: target state to wait for
3468 *
3469 * Wait for the trustee to reach @state. DONE is already matched.
3470 *
3471 * CONTEXT:
3472 * spin_lock_irq(gcwq->lock) which may be released and regrabbed
3473 * multiple times. To be used by cpu_callback.
3474 */
3475static void __cpuinit wait_trustee_state(struct global_cwq *gcwq, int state)
3476__releases(&gcwq->lock)
3477__acquires(&gcwq->lock)
3478{
3479 if (!(gcwq->trustee_state == state ||
3480 gcwq->trustee_state == TRUSTEE_DONE)) {
3481 spin_unlock_irq(&gcwq->lock);
3482 __wait_event(gcwq->trustee_wait,
3483 gcwq->trustee_state == state ||
3484 gcwq->trustee_state == TRUSTEE_DONE);
3485 spin_lock_irq(&gcwq->lock);
3486 }
3487}
3488
3489static int __devinit workqueue_cpu_callback(struct notifier_block *nfb,
3490 unsigned long action,
3491 void *hcpu)
3492{
3493 unsigned int cpu = (unsigned long)hcpu;
3494 struct global_cwq *gcwq = get_gcwq(cpu);
3495 struct task_struct *new_trustee = NULL;
3496 struct worker *uninitialized_var(new_worker);
3497 unsigned long flags;
3498
3499 action &= ~CPU_TASKS_FROZEN;
3500
3501 switch (action) {
3502 case CPU_DOWN_PREPARE:
3503 new_trustee = kthread_create(trustee_thread, gcwq,
3504 "workqueue_trustee/%d\n", cpu);
3505 if (IS_ERR(new_trustee))
3506 return notifier_from_errno(PTR_ERR(new_trustee));
3507 kthread_bind(new_trustee, cpu);
3508 /* fall through */
3509 case CPU_UP_PREPARE:
3510 BUG_ON(gcwq->first_idle);
3511 new_worker = create_worker(gcwq, false);
3512 if (!new_worker) {
3513 if (new_trustee)
3514 kthread_stop(new_trustee);
3515 return NOTIFY_BAD;
3516 }
3517 }
3518
3519 /* some are called w/ irq disabled, don't disturb irq status */
3520 spin_lock_irqsave(&gcwq->lock, flags);
3521
3522 switch (action) {
3523 case CPU_DOWN_PREPARE:
3524 /* initialize trustee and tell it to acquire the gcwq */
3525 BUG_ON(gcwq->trustee || gcwq->trustee_state != TRUSTEE_DONE);
3526 gcwq->trustee = new_trustee;
3527 gcwq->trustee_state = TRUSTEE_START;
3528 wake_up_process(gcwq->trustee);
3529 wait_trustee_state(gcwq, TRUSTEE_IN_CHARGE);
3530 /* fall through */
3531 case CPU_UP_PREPARE:
3532 BUG_ON(gcwq->first_idle);
3533 gcwq->first_idle = new_worker;
3534 break;
3535
3536 case CPU_DYING:
3537 /*
3538 * Before this, the trustee and all workers except for
3539 * the ones which are still executing works from
3540 * before the last CPU down must be on the cpu. After
3541 * this, they'll all be diasporas.
3542 */
3543 gcwq->flags |= GCWQ_DISASSOCIATED;
3544 break;
3545
3546 case CPU_POST_DEAD:
3547 gcwq->trustee_state = TRUSTEE_BUTCHER;
3548 /* fall through */
3549 case CPU_UP_CANCELED:
3550 destroy_worker(gcwq->first_idle);
3551 gcwq->first_idle = NULL;
3552 break;
3553
3554 case CPU_DOWN_FAILED:
3555 case CPU_ONLINE:
3556 gcwq->flags &= ~GCWQ_DISASSOCIATED;
3557 if (gcwq->trustee_state != TRUSTEE_DONE) {
3558 gcwq->trustee_state = TRUSTEE_RELEASE;
3559 wake_up_process(gcwq->trustee);
3560 wait_trustee_state(gcwq, TRUSTEE_DONE);
3561 }
3562
3563 /*
3564 * Trustee is done and there might be no worker left.
3565 * Put the first_idle in and request a real manager to
3566 * take a look.
3567 */
3568 spin_unlock_irq(&gcwq->lock);
3569 kthread_bind(gcwq->first_idle->task, cpu);
3570 spin_lock_irq(&gcwq->lock);
3571 gcwq->flags |= GCWQ_MANAGE_WORKERS;
3572 start_worker(gcwq->first_idle);
3573 gcwq->first_idle = NULL;
3574 break;
3575 }
3576
3577 spin_unlock_irqrestore(&gcwq->lock, flags);
3578
3579 return notifier_from_errno(0);
3580}
3581
3582#ifdef CONFIG_SMP
3583
3584struct work_for_cpu {
3585 struct completion completion;
3586 long (*fn)(void *);
3587 void *arg;
3588 long ret;
3589};
3590
3591static int do_work_for_cpu(void *_wfc)
3592{
3593 struct work_for_cpu *wfc = _wfc;
3594 wfc->ret = wfc->fn(wfc->arg);
3595 complete(&wfc->completion);
3596 return 0;
3597}
3598
3599/**
3600 * work_on_cpu - run a function in user context on a particular cpu
3601 * @cpu: the cpu to run on
3602 * @fn: the function to run
3603 * @arg: the function arg
3604 *
3605 * This will return the value @fn returns.
3606 * It is up to the caller to ensure that the cpu doesn't go offline.
3607 * The caller must not hold any locks which would prevent @fn from completing.
3608 */
3609long work_on_cpu(unsigned int cpu, long (*fn)(void *), void *arg)
3610{
3611 struct task_struct *sub_thread;
3612 struct work_for_cpu wfc = {
3613 .completion = COMPLETION_INITIALIZER_ONSTACK(wfc.completion),
3614 .fn = fn,
3615 .arg = arg,
3616 };
3617
3618 sub_thread = kthread_create(do_work_for_cpu, &wfc, "work_for_cpu");
3619 if (IS_ERR(sub_thread))
3620 return PTR_ERR(sub_thread);
3621 kthread_bind(sub_thread, cpu);
3622 wake_up_process(sub_thread);
3623 wait_for_completion(&wfc.completion);
3624 return wfc.ret;
3625}
3626EXPORT_SYMBOL_GPL(work_on_cpu);
3627#endif /* CONFIG_SMP */
3628
3629#ifdef CONFIG_FREEZER
3630
3631/**
3632 * freeze_workqueues_begin - begin freezing workqueues
3633 *
3634 * Start freezing workqueues. After this function returns, all freezable
3635 * workqueues will queue new works to their frozen_works list instead of
3636 * gcwq->worklist.
3637 *
3638 * CONTEXT:
3639 * Grabs and releases workqueue_lock and gcwq->lock's.
3640 */
3641void freeze_workqueues_begin(void)
3642{
3643 unsigned int cpu;
3644
3645 spin_lock(&workqueue_lock);
3646
3647 BUG_ON(workqueue_freezing);
3648 workqueue_freezing = true;
3649
3650 for_each_gcwq_cpu(cpu) {
3651 struct global_cwq *gcwq = get_gcwq(cpu);
3652 struct workqueue_struct *wq;
3653
3654 spin_lock_irq(&gcwq->lock);
3655
3656 BUG_ON(gcwq->flags & GCWQ_FREEZING);
3657 gcwq->flags |= GCWQ_FREEZING;
3658
3659 list_for_each_entry(wq, &workqueues, list) {
3660 struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
3661
3662 if (cwq && wq->flags & WQ_FREEZABLE)
3663 cwq->max_active = 0;
3664 }
3665
3666 spin_unlock_irq(&gcwq->lock);
3667 }
3668
3669 spin_unlock(&workqueue_lock);
3670}
3671
3672/**
3673 * freeze_workqueues_busy - are freezable workqueues still busy?
3674 *
3675 * Check whether freezing is complete. This function must be called
3676 * between freeze_workqueues_begin() and thaw_workqueues().
3677 *
3678 * CONTEXT:
3679 * Grabs and releases workqueue_lock.
3680 *
3681 * RETURNS:
3682 * %true if some freezable workqueues are still busy. %false if freezing
3683 * is complete.
3684 */
3685bool freeze_workqueues_busy(void)
3686{
3687 unsigned int cpu;
3688 bool busy = false;
3689
3690 spin_lock(&workqueue_lock);
3691
3692 BUG_ON(!workqueue_freezing);
3693
3694 for_each_gcwq_cpu(cpu) {
3695 struct workqueue_struct *wq;
3696 /*
3697 * nr_active is monotonically decreasing. It's safe
3698 * to peek without lock.
3699 */
3700 list_for_each_entry(wq, &workqueues, list) {
3701 struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
3702
3703 if (!cwq || !(wq->flags & WQ_FREEZABLE))
3704 continue;
3705
3706 BUG_ON(cwq->nr_active < 0);
3707 if (cwq->nr_active) {
3708 busy = true;
3709 goto out_unlock;
3710 }
3711 }
3712 }
3713out_unlock:
3714 spin_unlock(&workqueue_lock);
3715 return busy;
3716}
3717
3718/**
3719 * thaw_workqueues - thaw workqueues
3720 *
3721 * Thaw workqueues. Normal queueing is restored and all collected
3722 * frozen works are transferred to their respective gcwq worklists.
3723 *
3724 * CONTEXT:
3725 * Grabs and releases workqueue_lock and gcwq->lock's.
3726 */
3727void thaw_workqueues(void)
3728{
3729 unsigned int cpu;
3730
3731 spin_lock(&workqueue_lock);
3732
3733 if (!workqueue_freezing)
3734 goto out_unlock;
3735
3736 for_each_gcwq_cpu(cpu) {
3737 struct global_cwq *gcwq = get_gcwq(cpu);
3738 struct workqueue_struct *wq;
3739
3740 spin_lock_irq(&gcwq->lock);
3741
3742 BUG_ON(!(gcwq->flags & GCWQ_FREEZING));
3743 gcwq->flags &= ~GCWQ_FREEZING;
3744
3745 list_for_each_entry(wq, &workqueues, list) {
3746 struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
3747
3748 if (!cwq || !(wq->flags & WQ_FREEZABLE))
3749 continue;
3750
3751 /* restore max_active and repopulate worklist */
3752 cwq->max_active = wq->saved_max_active;
3753
3754 while (!list_empty(&cwq->delayed_works) &&
3755 cwq->nr_active < cwq->max_active)
3756 cwq_activate_first_delayed(cwq);
3757 }
3758
3759 wake_up_worker(gcwq);
3760
3761 spin_unlock_irq(&gcwq->lock);
3762 }
3763
3764 workqueue_freezing = false;
3765out_unlock:
3766 spin_unlock(&workqueue_lock);
3767}
3768#endif /* CONFIG_FREEZER */
3769
3770static int __init init_workqueues(void)
3771{
3772 unsigned int cpu;
3773 int i;
3774
3775 cpu_notifier(workqueue_cpu_callback, CPU_PRI_WORKQUEUE);
3776
3777 /* initialize gcwqs */
3778 for_each_gcwq_cpu(cpu) {
3779 struct global_cwq *gcwq = get_gcwq(cpu);
3780
3781 spin_lock_init(&gcwq->lock);
3782 INIT_LIST_HEAD(&gcwq->worklist);
3783 gcwq->cpu = cpu;
3784 gcwq->flags |= GCWQ_DISASSOCIATED;
3785
3786 INIT_LIST_HEAD(&gcwq->idle_list);
3787 for (i = 0; i < BUSY_WORKER_HASH_SIZE; i++)
3788 INIT_HLIST_HEAD(&gcwq->busy_hash[i]);
3789
3790 init_timer_deferrable(&gcwq->idle_timer);
3791 gcwq->idle_timer.function = idle_worker_timeout;
3792 gcwq->idle_timer.data = (unsigned long)gcwq;
3793
3794 setup_timer(&gcwq->mayday_timer, gcwq_mayday_timeout,
3795 (unsigned long)gcwq);
3796
3797 ida_init(&gcwq->worker_ida);
3798
3799 gcwq->trustee_state = TRUSTEE_DONE;
3800 init_waitqueue_head(&gcwq->trustee_wait);
3801 }
3802
3803 /* create the initial worker */
3804 for_each_online_gcwq_cpu(cpu) {
3805 struct global_cwq *gcwq = get_gcwq(cpu);
3806 struct worker *worker;
3807
3808 if (cpu != WORK_CPU_UNBOUND)
3809 gcwq->flags &= ~GCWQ_DISASSOCIATED;
3810 worker = create_worker(gcwq, true);
3811 BUG_ON(!worker);
3812 spin_lock_irq(&gcwq->lock);
3813 start_worker(worker);
3814 spin_unlock_irq(&gcwq->lock);
3815 }
3816
3817 system_wq = alloc_workqueue("events", 0, 0);
3818 system_long_wq = alloc_workqueue("events_long", 0, 0);
3819 system_nrt_wq = alloc_workqueue("events_nrt", WQ_NON_REENTRANT, 0);
3820 system_unbound_wq = alloc_workqueue("events_unbound", WQ_UNBOUND,
3821 WQ_UNBOUND_MAX_ACTIVE);
3822 system_freezable_wq = alloc_workqueue("events_freezable",
3823 WQ_FREEZABLE, 0);
3824 BUG_ON(!system_wq || !system_long_wq || !system_nrt_wq ||
3825 !system_unbound_wq || !system_freezable_wq);
3826 return 0;
3827}
3828early_initcall(init_workqueues);