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