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1/*
2 * kernel/workqueue.c - generic async execution with shared worker pool
3 *
4 * Copyright (C) 2002 Ingo Molnar
5 *
6 * Derived from the taskqueue/keventd code by:
7 * David Woodhouse <dwmw2@infradead.org>
8 * Andrew Morton
9 * Kai Petzke <wpp@marie.physik.tu-berlin.de>
10 * Theodore Ts'o <tytso@mit.edu>
11 *
12 * Made to use alloc_percpu by Christoph Lameter.
13 *
14 * Copyright (C) 2010 SUSE Linux Products GmbH
15 * Copyright (C) 2010 Tejun Heo <tj@kernel.org>
16 *
17 * This is the generic async execution mechanism. Work items as are
18 * executed in process context. The worker pool is shared and
19 * automatically managed. There are two worker pools for each CPU (one for
20 * normal work items and the other for high priority ones) and some extra
21 * pools for workqueues which are not bound to any specific CPU - the
22 * number of these backing pools is dynamic.
23 *
24 * Please read Documentation/workqueue.txt for details.
25 */
26
27#include <linux/export.h>
28#include <linux/kernel.h>
29#include <linux/sched.h>
30#include <linux/init.h>
31#include <linux/signal.h>
32#include <linux/completion.h>
33#include <linux/workqueue.h>
34#include <linux/slab.h>
35#include <linux/cpu.h>
36#include <linux/notifier.h>
37#include <linux/kthread.h>
38#include <linux/hardirq.h>
39#include <linux/mempolicy.h>
40#include <linux/freezer.h>
41#include <linux/kallsyms.h>
42#include <linux/debug_locks.h>
43#include <linux/lockdep.h>
44#include <linux/idr.h>
45#include <linux/jhash.h>
46#include <linux/hashtable.h>
47#include <linux/rculist.h>
48#include <linux/nodemask.h>
49#include <linux/moduleparam.h>
50#include <linux/uaccess.h>
51
52#include "workqueue_internal.h"
53
54enum {
55 /*
56 * worker_pool flags
57 *
58 * A bound pool is either associated or disassociated with its CPU.
59 * While associated (!DISASSOCIATED), all workers are bound to the
60 * CPU and none has %WORKER_UNBOUND set and concurrency management
61 * is in effect.
62 *
63 * While DISASSOCIATED, the cpu may be offline and all workers have
64 * %WORKER_UNBOUND set and concurrency management disabled, and may
65 * be executing on any CPU. The pool behaves as an unbound one.
66 *
67 * Note that DISASSOCIATED should be flipped only while holding
68 * attach_mutex to avoid changing binding state while
69 * worker_attach_to_pool() is in progress.
70 */
71 POOL_DISASSOCIATED = 1 << 2, /* cpu can't serve workers */
72
73 /* worker flags */
74 WORKER_DIE = 1 << 1, /* die die die */
75 WORKER_IDLE = 1 << 2, /* is idle */
76 WORKER_PREP = 1 << 3, /* preparing to run works */
77 WORKER_CPU_INTENSIVE = 1 << 6, /* cpu intensive */
78 WORKER_UNBOUND = 1 << 7, /* worker is unbound */
79 WORKER_REBOUND = 1 << 8, /* worker was rebound */
80
81 WORKER_NOT_RUNNING = WORKER_PREP | WORKER_CPU_INTENSIVE |
82 WORKER_UNBOUND | WORKER_REBOUND,
83
84 NR_STD_WORKER_POOLS = 2, /* # standard pools per cpu */
85
86 UNBOUND_POOL_HASH_ORDER = 6, /* hashed by pool->attrs */
87 BUSY_WORKER_HASH_ORDER = 6, /* 64 pointers */
88
89 MAX_IDLE_WORKERS_RATIO = 4, /* 1/4 of busy can be idle */
90 IDLE_WORKER_TIMEOUT = 300 * HZ, /* keep idle ones for 5 mins */
91
92 MAYDAY_INITIAL_TIMEOUT = HZ / 100 >= 2 ? HZ / 100 : 2,
93 /* call for help after 10ms
94 (min two ticks) */
95 MAYDAY_INTERVAL = HZ / 10, /* and then every 100ms */
96 CREATE_COOLDOWN = HZ, /* time to breath after fail */
97
98 /*
99 * Rescue workers are used only on emergencies and shared by
100 * all cpus. Give MIN_NICE.
101 */
102 RESCUER_NICE_LEVEL = MIN_NICE,
103 HIGHPRI_NICE_LEVEL = MIN_NICE,
104
105 WQ_NAME_LEN = 24,
106};
107
108/*
109 * Structure fields follow one of the following exclusion rules.
110 *
111 * I: Modifiable by initialization/destruction paths and read-only for
112 * everyone else.
113 *
114 * P: Preemption protected. Disabling preemption is enough and should
115 * only be modified and accessed from the local cpu.
116 *
117 * L: pool->lock protected. Access with pool->lock held.
118 *
119 * X: During normal operation, modification requires pool->lock and should
120 * be done only from local cpu. Either disabling preemption on local
121 * cpu or grabbing pool->lock is enough for read access. If
122 * POOL_DISASSOCIATED is set, it's identical to L.
123 *
124 * A: pool->attach_mutex protected.
125 *
126 * PL: wq_pool_mutex protected.
127 *
128 * PR: wq_pool_mutex protected for writes. Sched-RCU protected for reads.
129 *
130 * PW: wq_pool_mutex and wq->mutex protected for writes. Either for reads.
131 *
132 * PWR: wq_pool_mutex and wq->mutex protected for writes. Either or
133 * sched-RCU for reads.
134 *
135 * WQ: wq->mutex protected.
136 *
137 * WR: wq->mutex protected for writes. Sched-RCU protected for reads.
138 *
139 * MD: wq_mayday_lock protected.
140 */
141
142/* struct worker is defined in workqueue_internal.h */
143
144struct worker_pool {
145 spinlock_t lock; /* the pool lock */
146 int cpu; /* I: the associated cpu */
147 int node; /* I: the associated node ID */
148 int id; /* I: pool ID */
149 unsigned int flags; /* X: flags */
150
151 unsigned long watchdog_ts; /* L: watchdog timestamp */
152
153 struct list_head worklist; /* L: list of pending works */
154 int nr_workers; /* L: total number of workers */
155
156 /* nr_idle includes the ones off idle_list for rebinding */
157 int nr_idle; /* L: currently idle ones */
158
159 struct list_head idle_list; /* X: list of idle workers */
160 struct timer_list idle_timer; /* L: worker idle timeout */
161 struct timer_list mayday_timer; /* L: SOS timer for workers */
162
163 /* a workers is either on busy_hash or idle_list, or the manager */
164 DECLARE_HASHTABLE(busy_hash, BUSY_WORKER_HASH_ORDER);
165 /* L: hash of busy workers */
166
167 /* see manage_workers() for details on the two manager mutexes */
168 struct mutex manager_arb; /* manager arbitration */
169 struct worker *manager; /* L: purely informational */
170 struct mutex attach_mutex; /* attach/detach exclusion */
171 struct list_head workers; /* A: attached workers */
172 struct completion *detach_completion; /* all workers detached */
173
174 struct ida worker_ida; /* worker IDs for task name */
175
176 struct workqueue_attrs *attrs; /* I: worker attributes */
177 struct hlist_node hash_node; /* PL: unbound_pool_hash node */
178 int refcnt; /* PL: refcnt for unbound pools */
179
180 /*
181 * The current concurrency level. As it's likely to be accessed
182 * from other CPUs during try_to_wake_up(), put it in a separate
183 * cacheline.
184 */
185 atomic_t nr_running ____cacheline_aligned_in_smp;
186
187 /*
188 * Destruction of pool is sched-RCU protected to allow dereferences
189 * from get_work_pool().
190 */
191 struct rcu_head rcu;
192} ____cacheline_aligned_in_smp;
193
194/*
195 * The per-pool workqueue. While queued, the lower WORK_STRUCT_FLAG_BITS
196 * of work_struct->data are used for flags and the remaining high bits
197 * point to the pwq; thus, pwqs need to be aligned at two's power of the
198 * number of flag bits.
199 */
200struct pool_workqueue {
201 struct worker_pool *pool; /* I: the associated pool */
202 struct workqueue_struct *wq; /* I: the owning workqueue */
203 int work_color; /* L: current color */
204 int flush_color; /* L: flushing color */
205 int refcnt; /* L: reference count */
206 int nr_in_flight[WORK_NR_COLORS];
207 /* L: nr of in_flight works */
208 int nr_active; /* L: nr of active works */
209 int max_active; /* L: max active works */
210 struct list_head delayed_works; /* L: delayed works */
211 struct list_head pwqs_node; /* WR: node on wq->pwqs */
212 struct list_head mayday_node; /* MD: node on wq->maydays */
213
214 /*
215 * Release of unbound pwq is punted to system_wq. See put_pwq()
216 * and pwq_unbound_release_workfn() for details. pool_workqueue
217 * itself is also sched-RCU protected so that the first pwq can be
218 * determined without grabbing wq->mutex.
219 */
220 struct work_struct unbound_release_work;
221 struct rcu_head rcu;
222} __aligned(1 << WORK_STRUCT_FLAG_BITS);
223
224/*
225 * Structure used to wait for workqueue flush.
226 */
227struct wq_flusher {
228 struct list_head list; /* WQ: list of flushers */
229 int flush_color; /* WQ: flush color waiting for */
230 struct completion done; /* flush completion */
231};
232
233struct wq_device;
234
235/*
236 * The externally visible workqueue. It relays the issued work items to
237 * the appropriate worker_pool through its pool_workqueues.
238 */
239struct workqueue_struct {
240 struct list_head pwqs; /* WR: all pwqs of this wq */
241 struct list_head list; /* PR: list of all workqueues */
242
243 struct mutex mutex; /* protects this wq */
244 int work_color; /* WQ: current work color */
245 int flush_color; /* WQ: current flush color */
246 atomic_t nr_pwqs_to_flush; /* flush in progress */
247 struct wq_flusher *first_flusher; /* WQ: first flusher */
248 struct list_head flusher_queue; /* WQ: flush waiters */
249 struct list_head flusher_overflow; /* WQ: flush overflow list */
250
251 struct list_head maydays; /* MD: pwqs requesting rescue */
252 struct worker *rescuer; /* I: rescue worker */
253
254 int nr_drainers; /* WQ: drain in progress */
255 int saved_max_active; /* WQ: saved pwq max_active */
256
257 struct workqueue_attrs *unbound_attrs; /* PW: only for unbound wqs */
258 struct pool_workqueue *dfl_pwq; /* PW: only for unbound wqs */
259
260#ifdef CONFIG_SYSFS
261 struct wq_device *wq_dev; /* I: for sysfs interface */
262#endif
263#ifdef CONFIG_LOCKDEP
264 struct lockdep_map lockdep_map;
265#endif
266 char name[WQ_NAME_LEN]; /* I: workqueue name */
267
268 /*
269 * Destruction of workqueue_struct is sched-RCU protected to allow
270 * walking the workqueues list without grabbing wq_pool_mutex.
271 * This is used to dump all workqueues from sysrq.
272 */
273 struct rcu_head rcu;
274
275 /* hot fields used during command issue, aligned to cacheline */
276 unsigned int flags ____cacheline_aligned; /* WQ: WQ_* flags */
277 struct pool_workqueue __percpu *cpu_pwqs; /* I: per-cpu pwqs */
278 struct pool_workqueue __rcu *numa_pwq_tbl[]; /* PWR: unbound pwqs indexed by node */
279};
280
281static struct kmem_cache *pwq_cache;
282
283static cpumask_var_t *wq_numa_possible_cpumask;
284 /* possible CPUs of each node */
285
286static bool wq_disable_numa;
287module_param_named(disable_numa, wq_disable_numa, bool, 0444);
288
289/* see the comment above the definition of WQ_POWER_EFFICIENT */
290static bool wq_power_efficient = IS_ENABLED(CONFIG_WQ_POWER_EFFICIENT_DEFAULT);
291module_param_named(power_efficient, wq_power_efficient, bool, 0444);
292
293static bool wq_online; /* can kworkers be created yet? */
294
295static bool wq_numa_enabled; /* unbound NUMA affinity enabled */
296
297/* buf for wq_update_unbound_numa_attrs(), protected by CPU hotplug exclusion */
298static struct workqueue_attrs *wq_update_unbound_numa_attrs_buf;
299
300static DEFINE_MUTEX(wq_pool_mutex); /* protects pools and workqueues list */
301static DEFINE_SPINLOCK(wq_mayday_lock); /* protects wq->maydays list */
302
303static LIST_HEAD(workqueues); /* PR: list of all workqueues */
304static bool workqueue_freezing; /* PL: have wqs started freezing? */
305
306/* PL: allowable cpus for unbound wqs and work items */
307static cpumask_var_t wq_unbound_cpumask;
308
309/* CPU where unbound work was last round robin scheduled from this CPU */
310static DEFINE_PER_CPU(int, wq_rr_cpu_last);
311
312/*
313 * Local execution of unbound work items is no longer guaranteed. The
314 * following always forces round-robin CPU selection on unbound work items
315 * to uncover usages which depend on it.
316 */
317#ifdef CONFIG_DEBUG_WQ_FORCE_RR_CPU
318static bool wq_debug_force_rr_cpu = true;
319#else
320static bool wq_debug_force_rr_cpu = false;
321#endif
322module_param_named(debug_force_rr_cpu, wq_debug_force_rr_cpu, bool, 0644);
323
324/* the per-cpu worker pools */
325static DEFINE_PER_CPU_SHARED_ALIGNED(struct worker_pool [NR_STD_WORKER_POOLS], cpu_worker_pools);
326
327static DEFINE_IDR(worker_pool_idr); /* PR: idr of all pools */
328
329/* PL: hash of all unbound pools keyed by pool->attrs */
330static DEFINE_HASHTABLE(unbound_pool_hash, UNBOUND_POOL_HASH_ORDER);
331
332/* I: attributes used when instantiating standard unbound pools on demand */
333static struct workqueue_attrs *unbound_std_wq_attrs[NR_STD_WORKER_POOLS];
334
335/* I: attributes used when instantiating ordered pools on demand */
336static struct workqueue_attrs *ordered_wq_attrs[NR_STD_WORKER_POOLS];
337
338struct workqueue_struct *system_wq __read_mostly;
339EXPORT_SYMBOL(system_wq);
340struct workqueue_struct *system_highpri_wq __read_mostly;
341EXPORT_SYMBOL_GPL(system_highpri_wq);
342struct workqueue_struct *system_long_wq __read_mostly;
343EXPORT_SYMBOL_GPL(system_long_wq);
344struct workqueue_struct *system_unbound_wq __read_mostly;
345EXPORT_SYMBOL_GPL(system_unbound_wq);
346struct workqueue_struct *system_freezable_wq __read_mostly;
347EXPORT_SYMBOL_GPL(system_freezable_wq);
348struct workqueue_struct *system_power_efficient_wq __read_mostly;
349EXPORT_SYMBOL_GPL(system_power_efficient_wq);
350struct workqueue_struct *system_freezable_power_efficient_wq __read_mostly;
351EXPORT_SYMBOL_GPL(system_freezable_power_efficient_wq);
352
353static int worker_thread(void *__worker);
354static void workqueue_sysfs_unregister(struct workqueue_struct *wq);
355
356#define CREATE_TRACE_POINTS
357#include <trace/events/workqueue.h>
358
359#define assert_rcu_or_pool_mutex() \
360 RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held() && \
361 !lockdep_is_held(&wq_pool_mutex), \
362 "sched RCU or wq_pool_mutex should be held")
363
364#define assert_rcu_or_wq_mutex(wq) \
365 RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held() && \
366 !lockdep_is_held(&wq->mutex), \
367 "sched RCU or wq->mutex should be held")
368
369#define assert_rcu_or_wq_mutex_or_pool_mutex(wq) \
370 RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held() && \
371 !lockdep_is_held(&wq->mutex) && \
372 !lockdep_is_held(&wq_pool_mutex), \
373 "sched RCU, wq->mutex or wq_pool_mutex should be held")
374
375#define for_each_cpu_worker_pool(pool, cpu) \
376 for ((pool) = &per_cpu(cpu_worker_pools, cpu)[0]; \
377 (pool) < &per_cpu(cpu_worker_pools, cpu)[NR_STD_WORKER_POOLS]; \
378 (pool)++)
379
380/**
381 * for_each_pool - iterate through all worker_pools in the system
382 * @pool: iteration cursor
383 * @pi: integer used for iteration
384 *
385 * This must be called either with wq_pool_mutex held or sched RCU read
386 * locked. If the pool needs to be used beyond the locking in effect, the
387 * caller is responsible for guaranteeing that the pool stays online.
388 *
389 * The if/else clause exists only for the lockdep assertion and can be
390 * ignored.
391 */
392#define for_each_pool(pool, pi) \
393 idr_for_each_entry(&worker_pool_idr, pool, pi) \
394 if (({ assert_rcu_or_pool_mutex(); false; })) { } \
395 else
396
397/**
398 * for_each_pool_worker - iterate through all workers of a worker_pool
399 * @worker: iteration cursor
400 * @pool: worker_pool to iterate workers of
401 *
402 * This must be called with @pool->attach_mutex.
403 *
404 * The if/else clause exists only for the lockdep assertion and can be
405 * ignored.
406 */
407#define for_each_pool_worker(worker, pool) \
408 list_for_each_entry((worker), &(pool)->workers, node) \
409 if (({ lockdep_assert_held(&pool->attach_mutex); false; })) { } \
410 else
411
412/**
413 * for_each_pwq - iterate through all pool_workqueues of the specified workqueue
414 * @pwq: iteration cursor
415 * @wq: the target workqueue
416 *
417 * This must be called either with wq->mutex held or sched RCU read locked.
418 * If the pwq needs to be used beyond the locking in effect, the caller is
419 * responsible for guaranteeing that the pwq stays online.
420 *
421 * The if/else clause exists only for the lockdep assertion and can be
422 * ignored.
423 */
424#define for_each_pwq(pwq, wq) \
425 list_for_each_entry_rcu((pwq), &(wq)->pwqs, pwqs_node) \
426 if (({ assert_rcu_or_wq_mutex(wq); false; })) { } \
427 else
428
429#ifdef CONFIG_DEBUG_OBJECTS_WORK
430
431static struct debug_obj_descr work_debug_descr;
432
433static void *work_debug_hint(void *addr)
434{
435 return ((struct work_struct *) addr)->func;
436}
437
438static bool work_is_static_object(void *addr)
439{
440 struct work_struct *work = addr;
441
442 return test_bit(WORK_STRUCT_STATIC_BIT, work_data_bits(work));
443}
444
445/*
446 * fixup_init is called when:
447 * - an active object is initialized
448 */
449static bool work_fixup_init(void *addr, enum debug_obj_state state)
450{
451 struct work_struct *work = addr;
452
453 switch (state) {
454 case ODEBUG_STATE_ACTIVE:
455 cancel_work_sync(work);
456 debug_object_init(work, &work_debug_descr);
457 return true;
458 default:
459 return false;
460 }
461}
462
463/*
464 * fixup_free is called when:
465 * - an active object is freed
466 */
467static bool work_fixup_free(void *addr, enum debug_obj_state state)
468{
469 struct work_struct *work = addr;
470
471 switch (state) {
472 case ODEBUG_STATE_ACTIVE:
473 cancel_work_sync(work);
474 debug_object_free(work, &work_debug_descr);
475 return true;
476 default:
477 return false;
478 }
479}
480
481static struct debug_obj_descr work_debug_descr = {
482 .name = "work_struct",
483 .debug_hint = work_debug_hint,
484 .is_static_object = work_is_static_object,
485 .fixup_init = work_fixup_init,
486 .fixup_free = work_fixup_free,
487};
488
489static inline void debug_work_activate(struct work_struct *work)
490{
491 debug_object_activate(work, &work_debug_descr);
492}
493
494static inline void debug_work_deactivate(struct work_struct *work)
495{
496 debug_object_deactivate(work, &work_debug_descr);
497}
498
499void __init_work(struct work_struct *work, int onstack)
500{
501 if (onstack)
502 debug_object_init_on_stack(work, &work_debug_descr);
503 else
504 debug_object_init(work, &work_debug_descr);
505}
506EXPORT_SYMBOL_GPL(__init_work);
507
508void destroy_work_on_stack(struct work_struct *work)
509{
510 debug_object_free(work, &work_debug_descr);
511}
512EXPORT_SYMBOL_GPL(destroy_work_on_stack);
513
514void destroy_delayed_work_on_stack(struct delayed_work *work)
515{
516 destroy_timer_on_stack(&work->timer);
517 debug_object_free(&work->work, &work_debug_descr);
518}
519EXPORT_SYMBOL_GPL(destroy_delayed_work_on_stack);
520
521#else
522static inline void debug_work_activate(struct work_struct *work) { }
523static inline void debug_work_deactivate(struct work_struct *work) { }
524#endif
525
526/**
527 * worker_pool_assign_id - allocate ID and assing it to @pool
528 * @pool: the pool pointer of interest
529 *
530 * Returns 0 if ID in [0, WORK_OFFQ_POOL_NONE) is allocated and assigned
531 * successfully, -errno on failure.
532 */
533static int worker_pool_assign_id(struct worker_pool *pool)
534{
535 int ret;
536
537 lockdep_assert_held(&wq_pool_mutex);
538
539 ret = idr_alloc(&worker_pool_idr, pool, 0, WORK_OFFQ_POOL_NONE,
540 GFP_KERNEL);
541 if (ret >= 0) {
542 pool->id = ret;
543 return 0;
544 }
545 return ret;
546}
547
548/**
549 * unbound_pwq_by_node - return the unbound pool_workqueue for the given node
550 * @wq: the target workqueue
551 * @node: the node ID
552 *
553 * This must be called with any of wq_pool_mutex, wq->mutex or sched RCU
554 * read locked.
555 * If the pwq needs to be used beyond the locking in effect, the caller is
556 * responsible for guaranteeing that the pwq stays online.
557 *
558 * Return: The unbound pool_workqueue for @node.
559 */
560static struct pool_workqueue *unbound_pwq_by_node(struct workqueue_struct *wq,
561 int node)
562{
563 assert_rcu_or_wq_mutex_or_pool_mutex(wq);
564
565 /*
566 * XXX: @node can be NUMA_NO_NODE if CPU goes offline while a
567 * delayed item is pending. The plan is to keep CPU -> NODE
568 * mapping valid and stable across CPU on/offlines. Once that
569 * happens, this workaround can be removed.
570 */
571 if (unlikely(node == NUMA_NO_NODE))
572 return wq->dfl_pwq;
573
574 return rcu_dereference_raw(wq->numa_pwq_tbl[node]);
575}
576
577static unsigned int work_color_to_flags(int color)
578{
579 return color << WORK_STRUCT_COLOR_SHIFT;
580}
581
582static int get_work_color(struct work_struct *work)
583{
584 return (*work_data_bits(work) >> WORK_STRUCT_COLOR_SHIFT) &
585 ((1 << WORK_STRUCT_COLOR_BITS) - 1);
586}
587
588static int work_next_color(int color)
589{
590 return (color + 1) % WORK_NR_COLORS;
591}
592
593/*
594 * While queued, %WORK_STRUCT_PWQ is set and non flag bits of a work's data
595 * contain the pointer to the queued pwq. Once execution starts, the flag
596 * is cleared and the high bits contain OFFQ flags and pool ID.
597 *
598 * set_work_pwq(), set_work_pool_and_clear_pending(), mark_work_canceling()
599 * and clear_work_data() can be used to set the pwq, pool or clear
600 * work->data. These functions should only be called while the work is
601 * owned - ie. while the PENDING bit is set.
602 *
603 * get_work_pool() and get_work_pwq() can be used to obtain the pool or pwq
604 * corresponding to a work. Pool is available once the work has been
605 * queued anywhere after initialization until it is sync canceled. pwq is
606 * available only while the work item is queued.
607 *
608 * %WORK_OFFQ_CANCELING is used to mark a work item which is being
609 * canceled. While being canceled, a work item may have its PENDING set
610 * but stay off timer and worklist for arbitrarily long and nobody should
611 * try to steal the PENDING bit.
612 */
613static inline void set_work_data(struct work_struct *work, unsigned long data,
614 unsigned long flags)
615{
616 WARN_ON_ONCE(!work_pending(work));
617 atomic_long_set(&work->data, data | flags | work_static(work));
618}
619
620static void set_work_pwq(struct work_struct *work, struct pool_workqueue *pwq,
621 unsigned long extra_flags)
622{
623 set_work_data(work, (unsigned long)pwq,
624 WORK_STRUCT_PENDING | WORK_STRUCT_PWQ | extra_flags);
625}
626
627static void set_work_pool_and_keep_pending(struct work_struct *work,
628 int pool_id)
629{
630 set_work_data(work, (unsigned long)pool_id << WORK_OFFQ_POOL_SHIFT,
631 WORK_STRUCT_PENDING);
632}
633
634static void set_work_pool_and_clear_pending(struct work_struct *work,
635 int pool_id)
636{
637 /*
638 * The following wmb is paired with the implied mb in
639 * test_and_set_bit(PENDING) and ensures all updates to @work made
640 * here are visible to and precede any updates by the next PENDING
641 * owner.
642 */
643 smp_wmb();
644 set_work_data(work, (unsigned long)pool_id << WORK_OFFQ_POOL_SHIFT, 0);
645 /*
646 * The following mb guarantees that previous clear of a PENDING bit
647 * will not be reordered with any speculative LOADS or STORES from
648 * work->current_func, which is executed afterwards. This possible
649 * reordering can lead to a missed execution on attempt to qeueue
650 * the same @work. E.g. consider this case:
651 *
652 * CPU#0 CPU#1
653 * ---------------------------- --------------------------------
654 *
655 * 1 STORE event_indicated
656 * 2 queue_work_on() {
657 * 3 test_and_set_bit(PENDING)
658 * 4 } set_..._and_clear_pending() {
659 * 5 set_work_data() # clear bit
660 * 6 smp_mb()
661 * 7 work->current_func() {
662 * 8 LOAD event_indicated
663 * }
664 *
665 * Without an explicit full barrier speculative LOAD on line 8 can
666 * be executed before CPU#0 does STORE on line 1. If that happens,
667 * CPU#0 observes the PENDING bit is still set and new execution of
668 * a @work is not queued in a hope, that CPU#1 will eventually
669 * finish the queued @work. Meanwhile CPU#1 does not see
670 * event_indicated is set, because speculative LOAD was executed
671 * before actual STORE.
672 */
673 smp_mb();
674}
675
676static void clear_work_data(struct work_struct *work)
677{
678 smp_wmb(); /* see set_work_pool_and_clear_pending() */
679 set_work_data(work, WORK_STRUCT_NO_POOL, 0);
680}
681
682static struct pool_workqueue *get_work_pwq(struct work_struct *work)
683{
684 unsigned long data = atomic_long_read(&work->data);
685
686 if (data & WORK_STRUCT_PWQ)
687 return (void *)(data & WORK_STRUCT_WQ_DATA_MASK);
688 else
689 return NULL;
690}
691
692/**
693 * get_work_pool - return the worker_pool a given work was associated with
694 * @work: the work item of interest
695 *
696 * Pools are created and destroyed under wq_pool_mutex, and allows read
697 * access under sched-RCU read lock. As such, this function should be
698 * called under wq_pool_mutex or with preemption disabled.
699 *
700 * All fields of the returned pool are accessible as long as the above
701 * mentioned locking is in effect. If the returned pool needs to be used
702 * beyond the critical section, the caller is responsible for ensuring the
703 * returned pool is and stays online.
704 *
705 * Return: The worker_pool @work was last associated with. %NULL if none.
706 */
707static struct worker_pool *get_work_pool(struct work_struct *work)
708{
709 unsigned long data = atomic_long_read(&work->data);
710 int pool_id;
711
712 assert_rcu_or_pool_mutex();
713
714 if (data & WORK_STRUCT_PWQ)
715 return ((struct pool_workqueue *)
716 (data & WORK_STRUCT_WQ_DATA_MASK))->pool;
717
718 pool_id = data >> WORK_OFFQ_POOL_SHIFT;
719 if (pool_id == WORK_OFFQ_POOL_NONE)
720 return NULL;
721
722 return idr_find(&worker_pool_idr, pool_id);
723}
724
725/**
726 * get_work_pool_id - return the worker pool ID a given work is associated with
727 * @work: the work item of interest
728 *
729 * Return: The worker_pool ID @work was last associated with.
730 * %WORK_OFFQ_POOL_NONE if none.
731 */
732static int get_work_pool_id(struct work_struct *work)
733{
734 unsigned long data = atomic_long_read(&work->data);
735
736 if (data & WORK_STRUCT_PWQ)
737 return ((struct pool_workqueue *)
738 (data & WORK_STRUCT_WQ_DATA_MASK))->pool->id;
739
740 return data >> WORK_OFFQ_POOL_SHIFT;
741}
742
743static void mark_work_canceling(struct work_struct *work)
744{
745 unsigned long pool_id = get_work_pool_id(work);
746
747 pool_id <<= WORK_OFFQ_POOL_SHIFT;
748 set_work_data(work, pool_id | WORK_OFFQ_CANCELING, WORK_STRUCT_PENDING);
749}
750
751static bool work_is_canceling(struct work_struct *work)
752{
753 unsigned long data = atomic_long_read(&work->data);
754
755 return !(data & WORK_STRUCT_PWQ) && (data & WORK_OFFQ_CANCELING);
756}
757
758/*
759 * Policy functions. These define the policies on how the global worker
760 * pools are managed. Unless noted otherwise, these functions assume that
761 * they're being called with pool->lock held.
762 */
763
764static bool __need_more_worker(struct worker_pool *pool)
765{
766 return !atomic_read(&pool->nr_running);
767}
768
769/*
770 * Need to wake up a worker? Called from anything but currently
771 * running workers.
772 *
773 * Note that, because unbound workers never contribute to nr_running, this
774 * function will always return %true for unbound pools as long as the
775 * worklist isn't empty.
776 */
777static bool need_more_worker(struct worker_pool *pool)
778{
779 return !list_empty(&pool->worklist) && __need_more_worker(pool);
780}
781
782/* Can I start working? Called from busy but !running workers. */
783static bool may_start_working(struct worker_pool *pool)
784{
785 return pool->nr_idle;
786}
787
788/* Do I need to keep working? Called from currently running workers. */
789static bool keep_working(struct worker_pool *pool)
790{
791 return !list_empty(&pool->worklist) &&
792 atomic_read(&pool->nr_running) <= 1;
793}
794
795/* Do we need a new worker? Called from manager. */
796static bool need_to_create_worker(struct worker_pool *pool)
797{
798 return need_more_worker(pool) && !may_start_working(pool);
799}
800
801/* Do we have too many workers and should some go away? */
802static bool too_many_workers(struct worker_pool *pool)
803{
804 bool managing = mutex_is_locked(&pool->manager_arb);
805 int nr_idle = pool->nr_idle + managing; /* manager is considered idle */
806 int nr_busy = pool->nr_workers - nr_idle;
807
808 return nr_idle > 2 && (nr_idle - 2) * MAX_IDLE_WORKERS_RATIO >= nr_busy;
809}
810
811/*
812 * Wake up functions.
813 */
814
815/* Return the first idle worker. Safe with preemption disabled */
816static struct worker *first_idle_worker(struct worker_pool *pool)
817{
818 if (unlikely(list_empty(&pool->idle_list)))
819 return NULL;
820
821 return list_first_entry(&pool->idle_list, struct worker, entry);
822}
823
824/**
825 * wake_up_worker - wake up an idle worker
826 * @pool: worker pool to wake worker from
827 *
828 * Wake up the first idle worker of @pool.
829 *
830 * CONTEXT:
831 * spin_lock_irq(pool->lock).
832 */
833static void wake_up_worker(struct worker_pool *pool)
834{
835 struct worker *worker = first_idle_worker(pool);
836
837 if (likely(worker))
838 wake_up_process(worker->task);
839}
840
841/**
842 * wq_worker_waking_up - a worker is waking up
843 * @task: task waking up
844 * @cpu: CPU @task is waking up to
845 *
846 * This function is called during try_to_wake_up() when a worker is
847 * being awoken.
848 *
849 * CONTEXT:
850 * spin_lock_irq(rq->lock)
851 */
852void wq_worker_waking_up(struct task_struct *task, int cpu)
853{
854 struct worker *worker = kthread_data(task);
855
856 if (!(worker->flags & WORKER_NOT_RUNNING)) {
857 WARN_ON_ONCE(worker->pool->cpu != cpu);
858 atomic_inc(&worker->pool->nr_running);
859 }
860}
861
862/**
863 * wq_worker_sleeping - a worker is going to sleep
864 * @task: task going to sleep
865 *
866 * This function is called during schedule() when a busy worker is
867 * going to sleep. Worker on the same cpu can be woken up by
868 * returning pointer to its task.
869 *
870 * CONTEXT:
871 * spin_lock_irq(rq->lock)
872 *
873 * Return:
874 * Worker task on @cpu to wake up, %NULL if none.
875 */
876struct task_struct *wq_worker_sleeping(struct task_struct *task)
877{
878 struct worker *worker = kthread_data(task), *to_wakeup = NULL;
879 struct worker_pool *pool;
880
881 /*
882 * Rescuers, which may not have all the fields set up like normal
883 * workers, also reach here, let's not access anything before
884 * checking NOT_RUNNING.
885 */
886 if (worker->flags & WORKER_NOT_RUNNING)
887 return NULL;
888
889 pool = worker->pool;
890
891 /* this can only happen on the local cpu */
892 if (WARN_ON_ONCE(pool->cpu != raw_smp_processor_id()))
893 return NULL;
894
895 /*
896 * The counterpart of the following dec_and_test, implied mb,
897 * worklist not empty test sequence is in insert_work().
898 * Please read comment there.
899 *
900 * NOT_RUNNING is clear. This means that we're bound to and
901 * running on the local cpu w/ rq lock held and preemption
902 * disabled, which in turn means that none else could be
903 * manipulating idle_list, so dereferencing idle_list without pool
904 * lock is safe.
905 */
906 if (atomic_dec_and_test(&pool->nr_running) &&
907 !list_empty(&pool->worklist))
908 to_wakeup = first_idle_worker(pool);
909 return to_wakeup ? to_wakeup->task : NULL;
910}
911
912/**
913 * worker_set_flags - set worker flags and adjust nr_running accordingly
914 * @worker: self
915 * @flags: flags to set
916 *
917 * Set @flags in @worker->flags and adjust nr_running accordingly.
918 *
919 * CONTEXT:
920 * spin_lock_irq(pool->lock)
921 */
922static inline void worker_set_flags(struct worker *worker, unsigned int flags)
923{
924 struct worker_pool *pool = worker->pool;
925
926 WARN_ON_ONCE(worker->task != current);
927
928 /* If transitioning into NOT_RUNNING, adjust nr_running. */
929 if ((flags & WORKER_NOT_RUNNING) &&
930 !(worker->flags & WORKER_NOT_RUNNING)) {
931 atomic_dec(&pool->nr_running);
932 }
933
934 worker->flags |= flags;
935}
936
937/**
938 * worker_clr_flags - clear worker flags and adjust nr_running accordingly
939 * @worker: self
940 * @flags: flags to clear
941 *
942 * Clear @flags in @worker->flags and adjust nr_running accordingly.
943 *
944 * CONTEXT:
945 * spin_lock_irq(pool->lock)
946 */
947static inline void worker_clr_flags(struct worker *worker, unsigned int flags)
948{
949 struct worker_pool *pool = worker->pool;
950 unsigned int oflags = worker->flags;
951
952 WARN_ON_ONCE(worker->task != current);
953
954 worker->flags &= ~flags;
955
956 /*
957 * If transitioning out of NOT_RUNNING, increment nr_running. Note
958 * that the nested NOT_RUNNING is not a noop. NOT_RUNNING is mask
959 * of multiple flags, not a single flag.
960 */
961 if ((flags & WORKER_NOT_RUNNING) && (oflags & WORKER_NOT_RUNNING))
962 if (!(worker->flags & WORKER_NOT_RUNNING))
963 atomic_inc(&pool->nr_running);
964}
965
966/**
967 * find_worker_executing_work - find worker which is executing a work
968 * @pool: pool of interest
969 * @work: work to find worker for
970 *
971 * Find a worker which is executing @work on @pool by searching
972 * @pool->busy_hash which is keyed by the address of @work. For a worker
973 * to match, its current execution should match the address of @work and
974 * its work function. This is to avoid unwanted dependency between
975 * unrelated work executions through a work item being recycled while still
976 * being executed.
977 *
978 * This is a bit tricky. A work item may be freed once its execution
979 * starts and nothing prevents the freed area from being recycled for
980 * another work item. If the same work item address ends up being reused
981 * before the original execution finishes, workqueue will identify the
982 * recycled work item as currently executing and make it wait until the
983 * current execution finishes, introducing an unwanted dependency.
984 *
985 * This function checks the work item address and work function to avoid
986 * false positives. Note that this isn't complete as one may construct a
987 * work function which can introduce dependency onto itself through a
988 * recycled work item. Well, if somebody wants to shoot oneself in the
989 * foot that badly, there's only so much we can do, and if such deadlock
990 * actually occurs, it should be easy to locate the culprit work function.
991 *
992 * CONTEXT:
993 * spin_lock_irq(pool->lock).
994 *
995 * Return:
996 * Pointer to worker which is executing @work if found, %NULL
997 * otherwise.
998 */
999static struct worker *find_worker_executing_work(struct worker_pool *pool,
1000 struct work_struct *work)
1001{
1002 struct worker *worker;
1003
1004 hash_for_each_possible(pool->busy_hash, worker, hentry,
1005 (unsigned long)work)
1006 if (worker->current_work == work &&
1007 worker->current_func == work->func)
1008 return worker;
1009
1010 return NULL;
1011}
1012
1013/**
1014 * move_linked_works - move linked works to a list
1015 * @work: start of series of works to be scheduled
1016 * @head: target list to append @work to
1017 * @nextp: out parameter for nested worklist walking
1018 *
1019 * Schedule linked works starting from @work to @head. Work series to
1020 * be scheduled starts at @work and includes any consecutive work with
1021 * WORK_STRUCT_LINKED set in its predecessor.
1022 *
1023 * If @nextp is not NULL, it's updated to point to the next work of
1024 * the last scheduled work. This allows move_linked_works() to be
1025 * nested inside outer list_for_each_entry_safe().
1026 *
1027 * CONTEXT:
1028 * spin_lock_irq(pool->lock).
1029 */
1030static void move_linked_works(struct work_struct *work, struct list_head *head,
1031 struct work_struct **nextp)
1032{
1033 struct work_struct *n;
1034
1035 /*
1036 * Linked worklist will always end before the end of the list,
1037 * use NULL for list head.
1038 */
1039 list_for_each_entry_safe_from(work, n, NULL, entry) {
1040 list_move_tail(&work->entry, head);
1041 if (!(*work_data_bits(work) & WORK_STRUCT_LINKED))
1042 break;
1043 }
1044
1045 /*
1046 * If we're already inside safe list traversal and have moved
1047 * multiple works to the scheduled queue, the next position
1048 * needs to be updated.
1049 */
1050 if (nextp)
1051 *nextp = n;
1052}
1053
1054/**
1055 * get_pwq - get an extra reference on the specified pool_workqueue
1056 * @pwq: pool_workqueue to get
1057 *
1058 * Obtain an extra reference on @pwq. The caller should guarantee that
1059 * @pwq has positive refcnt and be holding the matching pool->lock.
1060 */
1061static void get_pwq(struct pool_workqueue *pwq)
1062{
1063 lockdep_assert_held(&pwq->pool->lock);
1064 WARN_ON_ONCE(pwq->refcnt <= 0);
1065 pwq->refcnt++;
1066}
1067
1068/**
1069 * put_pwq - put a pool_workqueue reference
1070 * @pwq: pool_workqueue to put
1071 *
1072 * Drop a reference of @pwq. If its refcnt reaches zero, schedule its
1073 * destruction. The caller should be holding the matching pool->lock.
1074 */
1075static void put_pwq(struct pool_workqueue *pwq)
1076{
1077 lockdep_assert_held(&pwq->pool->lock);
1078 if (likely(--pwq->refcnt))
1079 return;
1080 if (WARN_ON_ONCE(!(pwq->wq->flags & WQ_UNBOUND)))
1081 return;
1082 /*
1083 * @pwq can't be released under pool->lock, bounce to
1084 * pwq_unbound_release_workfn(). This never recurses on the same
1085 * pool->lock as this path is taken only for unbound workqueues and
1086 * the release work item is scheduled on a per-cpu workqueue. To
1087 * avoid lockdep warning, unbound pool->locks are given lockdep
1088 * subclass of 1 in get_unbound_pool().
1089 */
1090 schedule_work(&pwq->unbound_release_work);
1091}
1092
1093/**
1094 * put_pwq_unlocked - put_pwq() with surrounding pool lock/unlock
1095 * @pwq: pool_workqueue to put (can be %NULL)
1096 *
1097 * put_pwq() with locking. This function also allows %NULL @pwq.
1098 */
1099static void put_pwq_unlocked(struct pool_workqueue *pwq)
1100{
1101 if (pwq) {
1102 /*
1103 * As both pwqs and pools are sched-RCU protected, the
1104 * following lock operations are safe.
1105 */
1106 spin_lock_irq(&pwq->pool->lock);
1107 put_pwq(pwq);
1108 spin_unlock_irq(&pwq->pool->lock);
1109 }
1110}
1111
1112static void pwq_activate_delayed_work(struct work_struct *work)
1113{
1114 struct pool_workqueue *pwq = get_work_pwq(work);
1115
1116 trace_workqueue_activate_work(work);
1117 if (list_empty(&pwq->pool->worklist))
1118 pwq->pool->watchdog_ts = jiffies;
1119 move_linked_works(work, &pwq->pool->worklist, NULL);
1120 __clear_bit(WORK_STRUCT_DELAYED_BIT, work_data_bits(work));
1121 pwq->nr_active++;
1122}
1123
1124static void pwq_activate_first_delayed(struct pool_workqueue *pwq)
1125{
1126 struct work_struct *work = list_first_entry(&pwq->delayed_works,
1127 struct work_struct, entry);
1128
1129 pwq_activate_delayed_work(work);
1130}
1131
1132/**
1133 * pwq_dec_nr_in_flight - decrement pwq's nr_in_flight
1134 * @pwq: pwq of interest
1135 * @color: color of work which left the queue
1136 *
1137 * A work either has completed or is removed from pending queue,
1138 * decrement nr_in_flight of its pwq and handle workqueue flushing.
1139 *
1140 * CONTEXT:
1141 * spin_lock_irq(pool->lock).
1142 */
1143static void pwq_dec_nr_in_flight(struct pool_workqueue *pwq, int color)
1144{
1145 /* uncolored work items don't participate in flushing or nr_active */
1146 if (color == WORK_NO_COLOR)
1147 goto out_put;
1148
1149 pwq->nr_in_flight[color]--;
1150
1151 pwq->nr_active--;
1152 if (!list_empty(&pwq->delayed_works)) {
1153 /* one down, submit a delayed one */
1154 if (pwq->nr_active < pwq->max_active)
1155 pwq_activate_first_delayed(pwq);
1156 }
1157
1158 /* is flush in progress and are we at the flushing tip? */
1159 if (likely(pwq->flush_color != color))
1160 goto out_put;
1161
1162 /* are there still in-flight works? */
1163 if (pwq->nr_in_flight[color])
1164 goto out_put;
1165
1166 /* this pwq is done, clear flush_color */
1167 pwq->flush_color = -1;
1168
1169 /*
1170 * If this was the last pwq, wake up the first flusher. It
1171 * will handle the rest.
1172 */
1173 if (atomic_dec_and_test(&pwq->wq->nr_pwqs_to_flush))
1174 complete(&pwq->wq->first_flusher->done);
1175out_put:
1176 put_pwq(pwq);
1177}
1178
1179/**
1180 * try_to_grab_pending - steal work item from worklist and disable irq
1181 * @work: work item to steal
1182 * @is_dwork: @work is a delayed_work
1183 * @flags: place to store irq state
1184 *
1185 * Try to grab PENDING bit of @work. This function can handle @work in any
1186 * stable state - idle, on timer or on worklist.
1187 *
1188 * Return:
1189 * 1 if @work was pending and we successfully stole PENDING
1190 * 0 if @work was idle and we claimed PENDING
1191 * -EAGAIN if PENDING couldn't be grabbed at the moment, safe to busy-retry
1192 * -ENOENT if someone else is canceling @work, this state may persist
1193 * for arbitrarily long
1194 *
1195 * Note:
1196 * On >= 0 return, the caller owns @work's PENDING bit. To avoid getting
1197 * interrupted while holding PENDING and @work off queue, irq must be
1198 * disabled on entry. This, combined with delayed_work->timer being
1199 * irqsafe, ensures that we return -EAGAIN for finite short period of time.
1200 *
1201 * On successful return, >= 0, irq is disabled and the caller is
1202 * responsible for releasing it using local_irq_restore(*@flags).
1203 *
1204 * This function is safe to call from any context including IRQ handler.
1205 */
1206static int try_to_grab_pending(struct work_struct *work, bool is_dwork,
1207 unsigned long *flags)
1208{
1209 struct worker_pool *pool;
1210 struct pool_workqueue *pwq;
1211
1212 local_irq_save(*flags);
1213
1214 /* try to steal the timer if it exists */
1215 if (is_dwork) {
1216 struct delayed_work *dwork = to_delayed_work(work);
1217
1218 /*
1219 * dwork->timer is irqsafe. If del_timer() fails, it's
1220 * guaranteed that the timer is not queued anywhere and not
1221 * running on the local CPU.
1222 */
1223 if (likely(del_timer(&dwork->timer)))
1224 return 1;
1225 }
1226
1227 /* try to claim PENDING the normal way */
1228 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work)))
1229 return 0;
1230
1231 /*
1232 * The queueing is in progress, or it is already queued. Try to
1233 * steal it from ->worklist without clearing WORK_STRUCT_PENDING.
1234 */
1235 pool = get_work_pool(work);
1236 if (!pool)
1237 goto fail;
1238
1239 spin_lock(&pool->lock);
1240 /*
1241 * work->data is guaranteed to point to pwq only while the work
1242 * item is queued on pwq->wq, and both updating work->data to point
1243 * to pwq on queueing and to pool on dequeueing are done under
1244 * pwq->pool->lock. This in turn guarantees that, if work->data
1245 * points to pwq which is associated with a locked pool, the work
1246 * item is currently queued on that pool.
1247 */
1248 pwq = get_work_pwq(work);
1249 if (pwq && pwq->pool == pool) {
1250 debug_work_deactivate(work);
1251
1252 /*
1253 * A delayed work item cannot be grabbed directly because
1254 * it might have linked NO_COLOR work items which, if left
1255 * on the delayed_list, will confuse pwq->nr_active
1256 * management later on and cause stall. Make sure the work
1257 * item is activated before grabbing.
1258 */
1259 if (*work_data_bits(work) & WORK_STRUCT_DELAYED)
1260 pwq_activate_delayed_work(work);
1261
1262 list_del_init(&work->entry);
1263 pwq_dec_nr_in_flight(pwq, get_work_color(work));
1264
1265 /* work->data points to pwq iff queued, point to pool */
1266 set_work_pool_and_keep_pending(work, pool->id);
1267
1268 spin_unlock(&pool->lock);
1269 return 1;
1270 }
1271 spin_unlock(&pool->lock);
1272fail:
1273 local_irq_restore(*flags);
1274 if (work_is_canceling(work))
1275 return -ENOENT;
1276 cpu_relax();
1277 return -EAGAIN;
1278}
1279
1280/**
1281 * insert_work - insert a work into a pool
1282 * @pwq: pwq @work belongs to
1283 * @work: work to insert
1284 * @head: insertion point
1285 * @extra_flags: extra WORK_STRUCT_* flags to set
1286 *
1287 * Insert @work which belongs to @pwq after @head. @extra_flags is or'd to
1288 * work_struct flags.
1289 *
1290 * CONTEXT:
1291 * spin_lock_irq(pool->lock).
1292 */
1293static void insert_work(struct pool_workqueue *pwq, struct work_struct *work,
1294 struct list_head *head, unsigned int extra_flags)
1295{
1296 struct worker_pool *pool = pwq->pool;
1297
1298 /* we own @work, set data and link */
1299 set_work_pwq(work, pwq, extra_flags);
1300 list_add_tail(&work->entry, head);
1301 get_pwq(pwq);
1302
1303 /*
1304 * Ensure either wq_worker_sleeping() sees the above
1305 * list_add_tail() or we see zero nr_running to avoid workers lying
1306 * around lazily while there are works to be processed.
1307 */
1308 smp_mb();
1309
1310 if (__need_more_worker(pool))
1311 wake_up_worker(pool);
1312}
1313
1314/*
1315 * Test whether @work is being queued from another work executing on the
1316 * same workqueue.
1317 */
1318static bool is_chained_work(struct workqueue_struct *wq)
1319{
1320 struct worker *worker;
1321
1322 worker = current_wq_worker();
1323 /*
1324 * Return %true iff I'm a worker execuing a work item on @wq. If
1325 * I'm @worker, it's safe to dereference it without locking.
1326 */
1327 return worker && worker->current_pwq->wq == wq;
1328}
1329
1330/*
1331 * When queueing an unbound work item to a wq, prefer local CPU if allowed
1332 * by wq_unbound_cpumask. Otherwise, round robin among the allowed ones to
1333 * avoid perturbing sensitive tasks.
1334 */
1335static int wq_select_unbound_cpu(int cpu)
1336{
1337 static bool printed_dbg_warning;
1338 int new_cpu;
1339
1340 if (likely(!wq_debug_force_rr_cpu)) {
1341 if (cpumask_test_cpu(cpu, wq_unbound_cpumask))
1342 return cpu;
1343 } else if (!printed_dbg_warning) {
1344 pr_warn("workqueue: round-robin CPU selection forced, expect performance impact\n");
1345 printed_dbg_warning = true;
1346 }
1347
1348 if (cpumask_empty(wq_unbound_cpumask))
1349 return cpu;
1350
1351 new_cpu = __this_cpu_read(wq_rr_cpu_last);
1352 new_cpu = cpumask_next_and(new_cpu, wq_unbound_cpumask, cpu_online_mask);
1353 if (unlikely(new_cpu >= nr_cpu_ids)) {
1354 new_cpu = cpumask_first_and(wq_unbound_cpumask, cpu_online_mask);
1355 if (unlikely(new_cpu >= nr_cpu_ids))
1356 return cpu;
1357 }
1358 __this_cpu_write(wq_rr_cpu_last, new_cpu);
1359
1360 return new_cpu;
1361}
1362
1363static void __queue_work(int cpu, struct workqueue_struct *wq,
1364 struct work_struct *work)
1365{
1366 struct pool_workqueue *pwq;
1367 struct worker_pool *last_pool;
1368 struct list_head *worklist;
1369 unsigned int work_flags;
1370 unsigned int req_cpu = cpu;
1371
1372 /*
1373 * While a work item is PENDING && off queue, a task trying to
1374 * steal the PENDING will busy-loop waiting for it to either get
1375 * queued or lose PENDING. Grabbing PENDING and queueing should
1376 * happen with IRQ disabled.
1377 */
1378 WARN_ON_ONCE(!irqs_disabled());
1379
1380 debug_work_activate(work);
1381
1382 /* if draining, only works from the same workqueue are allowed */
1383 if (unlikely(wq->flags & __WQ_DRAINING) &&
1384 WARN_ON_ONCE(!is_chained_work(wq)))
1385 return;
1386retry:
1387 if (req_cpu == WORK_CPU_UNBOUND)
1388 cpu = wq_select_unbound_cpu(raw_smp_processor_id());
1389
1390 /* pwq which will be used unless @work is executing elsewhere */
1391 if (!(wq->flags & WQ_UNBOUND))
1392 pwq = per_cpu_ptr(wq->cpu_pwqs, cpu);
1393 else
1394 pwq = unbound_pwq_by_node(wq, cpu_to_node(cpu));
1395
1396 /*
1397 * If @work was previously on a different pool, it might still be
1398 * running there, in which case the work needs to be queued on that
1399 * pool to guarantee non-reentrancy.
1400 */
1401 last_pool = get_work_pool(work);
1402 if (last_pool && last_pool != pwq->pool) {
1403 struct worker *worker;
1404
1405 spin_lock(&last_pool->lock);
1406
1407 worker = find_worker_executing_work(last_pool, work);
1408
1409 if (worker && worker->current_pwq->wq == wq) {
1410 pwq = worker->current_pwq;
1411 } else {
1412 /* meh... not running there, queue here */
1413 spin_unlock(&last_pool->lock);
1414 spin_lock(&pwq->pool->lock);
1415 }
1416 } else {
1417 spin_lock(&pwq->pool->lock);
1418 }
1419
1420 /*
1421 * pwq is determined and locked. For unbound pools, we could have
1422 * raced with pwq release and it could already be dead. If its
1423 * refcnt is zero, repeat pwq selection. Note that pwqs never die
1424 * without another pwq replacing it in the numa_pwq_tbl or while
1425 * work items are executing on it, so the retrying is guaranteed to
1426 * make forward-progress.
1427 */
1428 if (unlikely(!pwq->refcnt)) {
1429 if (wq->flags & WQ_UNBOUND) {
1430 spin_unlock(&pwq->pool->lock);
1431 cpu_relax();
1432 goto retry;
1433 }
1434 /* oops */
1435 WARN_ONCE(true, "workqueue: per-cpu pwq for %s on cpu%d has 0 refcnt",
1436 wq->name, cpu);
1437 }
1438
1439 /* pwq determined, queue */
1440 trace_workqueue_queue_work(req_cpu, pwq, work);
1441
1442 if (WARN_ON(!list_empty(&work->entry))) {
1443 spin_unlock(&pwq->pool->lock);
1444 return;
1445 }
1446
1447 pwq->nr_in_flight[pwq->work_color]++;
1448 work_flags = work_color_to_flags(pwq->work_color);
1449
1450 if (likely(pwq->nr_active < pwq->max_active)) {
1451 trace_workqueue_activate_work(work);
1452 pwq->nr_active++;
1453 worklist = &pwq->pool->worklist;
1454 if (list_empty(worklist))
1455 pwq->pool->watchdog_ts = jiffies;
1456 } else {
1457 work_flags |= WORK_STRUCT_DELAYED;
1458 worklist = &pwq->delayed_works;
1459 }
1460
1461 insert_work(pwq, work, worklist, work_flags);
1462
1463 spin_unlock(&pwq->pool->lock);
1464}
1465
1466/**
1467 * queue_work_on - queue work on specific cpu
1468 * @cpu: CPU number to execute work on
1469 * @wq: workqueue to use
1470 * @work: work to queue
1471 *
1472 * We queue the work to a specific CPU, the caller must ensure it
1473 * can't go away.
1474 *
1475 * Return: %false if @work was already on a queue, %true otherwise.
1476 */
1477bool queue_work_on(int cpu, struct workqueue_struct *wq,
1478 struct work_struct *work)
1479{
1480 bool ret = false;
1481 unsigned long flags;
1482
1483 local_irq_save(flags);
1484
1485 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1486 __queue_work(cpu, wq, work);
1487 ret = true;
1488 }
1489
1490 local_irq_restore(flags);
1491 return ret;
1492}
1493EXPORT_SYMBOL(queue_work_on);
1494
1495void delayed_work_timer_fn(unsigned long __data)
1496{
1497 struct delayed_work *dwork = (struct delayed_work *)__data;
1498
1499 /* should have been called from irqsafe timer with irq already off */
1500 __queue_work(dwork->cpu, dwork->wq, &dwork->work);
1501}
1502EXPORT_SYMBOL(delayed_work_timer_fn);
1503
1504static void __queue_delayed_work(int cpu, struct workqueue_struct *wq,
1505 struct delayed_work *dwork, unsigned long delay)
1506{
1507 struct timer_list *timer = &dwork->timer;
1508 struct work_struct *work = &dwork->work;
1509
1510 WARN_ON_ONCE(timer->function != delayed_work_timer_fn ||
1511 timer->data != (unsigned long)dwork);
1512 WARN_ON_ONCE(timer_pending(timer));
1513 WARN_ON_ONCE(!list_empty(&work->entry));
1514
1515 /*
1516 * If @delay is 0, queue @dwork->work immediately. This is for
1517 * both optimization and correctness. The earliest @timer can
1518 * expire is on the closest next tick and delayed_work users depend
1519 * on that there's no such delay when @delay is 0.
1520 */
1521 if (!delay) {
1522 __queue_work(cpu, wq, &dwork->work);
1523 return;
1524 }
1525
1526 timer_stats_timer_set_start_info(&dwork->timer);
1527
1528 dwork->wq = wq;
1529 dwork->cpu = cpu;
1530 timer->expires = jiffies + delay;
1531
1532 if (unlikely(cpu != WORK_CPU_UNBOUND))
1533 add_timer_on(timer, cpu);
1534 else
1535 add_timer(timer);
1536}
1537
1538/**
1539 * queue_delayed_work_on - queue work on specific CPU after delay
1540 * @cpu: CPU number to execute work on
1541 * @wq: workqueue to use
1542 * @dwork: work to queue
1543 * @delay: number of jiffies to wait before queueing
1544 *
1545 * Return: %false if @work was already on a queue, %true otherwise. If
1546 * @delay is zero and @dwork is idle, it will be scheduled for immediate
1547 * execution.
1548 */
1549bool queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
1550 struct delayed_work *dwork, unsigned long delay)
1551{
1552 struct work_struct *work = &dwork->work;
1553 bool ret = false;
1554 unsigned long flags;
1555
1556 /* read the comment in __queue_work() */
1557 local_irq_save(flags);
1558
1559 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1560 __queue_delayed_work(cpu, wq, dwork, delay);
1561 ret = true;
1562 }
1563
1564 local_irq_restore(flags);
1565 return ret;
1566}
1567EXPORT_SYMBOL(queue_delayed_work_on);
1568
1569/**
1570 * mod_delayed_work_on - modify delay of or queue a delayed work on specific CPU
1571 * @cpu: CPU number to execute work on
1572 * @wq: workqueue to use
1573 * @dwork: work to queue
1574 * @delay: number of jiffies to wait before queueing
1575 *
1576 * If @dwork is idle, equivalent to queue_delayed_work_on(); otherwise,
1577 * modify @dwork's timer so that it expires after @delay. If @delay is
1578 * zero, @work is guaranteed to be scheduled immediately regardless of its
1579 * current state.
1580 *
1581 * Return: %false if @dwork was idle and queued, %true if @dwork was
1582 * pending and its timer was modified.
1583 *
1584 * This function is safe to call from any context including IRQ handler.
1585 * See try_to_grab_pending() for details.
1586 */
1587bool mod_delayed_work_on(int cpu, struct workqueue_struct *wq,
1588 struct delayed_work *dwork, unsigned long delay)
1589{
1590 unsigned long flags;
1591 int ret;
1592
1593 do {
1594 ret = try_to_grab_pending(&dwork->work, true, &flags);
1595 } while (unlikely(ret == -EAGAIN));
1596
1597 if (likely(ret >= 0)) {
1598 __queue_delayed_work(cpu, wq, dwork, delay);
1599 local_irq_restore(flags);
1600 }
1601
1602 /* -ENOENT from try_to_grab_pending() becomes %true */
1603 return ret;
1604}
1605EXPORT_SYMBOL_GPL(mod_delayed_work_on);
1606
1607/**
1608 * worker_enter_idle - enter idle state
1609 * @worker: worker which is entering idle state
1610 *
1611 * @worker is entering idle state. Update stats and idle timer if
1612 * necessary.
1613 *
1614 * LOCKING:
1615 * spin_lock_irq(pool->lock).
1616 */
1617static void worker_enter_idle(struct worker *worker)
1618{
1619 struct worker_pool *pool = worker->pool;
1620
1621 if (WARN_ON_ONCE(worker->flags & WORKER_IDLE) ||
1622 WARN_ON_ONCE(!list_empty(&worker->entry) &&
1623 (worker->hentry.next || worker->hentry.pprev)))
1624 return;
1625
1626 /* can't use worker_set_flags(), also called from create_worker() */
1627 worker->flags |= WORKER_IDLE;
1628 pool->nr_idle++;
1629 worker->last_active = jiffies;
1630
1631 /* idle_list is LIFO */
1632 list_add(&worker->entry, &pool->idle_list);
1633
1634 if (too_many_workers(pool) && !timer_pending(&pool->idle_timer))
1635 mod_timer(&pool->idle_timer, jiffies + IDLE_WORKER_TIMEOUT);
1636
1637 /*
1638 * Sanity check nr_running. Because wq_unbind_fn() releases
1639 * pool->lock between setting %WORKER_UNBOUND and zapping
1640 * nr_running, the warning may trigger spuriously. Check iff
1641 * unbind is not in progress.
1642 */
1643 WARN_ON_ONCE(!(pool->flags & POOL_DISASSOCIATED) &&
1644 pool->nr_workers == pool->nr_idle &&
1645 atomic_read(&pool->nr_running));
1646}
1647
1648/**
1649 * worker_leave_idle - leave idle state
1650 * @worker: worker which is leaving idle state
1651 *
1652 * @worker is leaving idle state. Update stats.
1653 *
1654 * LOCKING:
1655 * spin_lock_irq(pool->lock).
1656 */
1657static void worker_leave_idle(struct worker *worker)
1658{
1659 struct worker_pool *pool = worker->pool;
1660
1661 if (WARN_ON_ONCE(!(worker->flags & WORKER_IDLE)))
1662 return;
1663 worker_clr_flags(worker, WORKER_IDLE);
1664 pool->nr_idle--;
1665 list_del_init(&worker->entry);
1666}
1667
1668static struct worker *alloc_worker(int node)
1669{
1670 struct worker *worker;
1671
1672 worker = kzalloc_node(sizeof(*worker), GFP_KERNEL, node);
1673 if (worker) {
1674 INIT_LIST_HEAD(&worker->entry);
1675 INIT_LIST_HEAD(&worker->scheduled);
1676 INIT_LIST_HEAD(&worker->node);
1677 /* on creation a worker is in !idle && prep state */
1678 worker->flags = WORKER_PREP;
1679 }
1680 return worker;
1681}
1682
1683/**
1684 * worker_attach_to_pool() - attach a worker to a pool
1685 * @worker: worker to be attached
1686 * @pool: the target pool
1687 *
1688 * Attach @worker to @pool. Once attached, the %WORKER_UNBOUND flag and
1689 * cpu-binding of @worker are kept coordinated with the pool across
1690 * cpu-[un]hotplugs.
1691 */
1692static void worker_attach_to_pool(struct worker *worker,
1693 struct worker_pool *pool)
1694{
1695 mutex_lock(&pool->attach_mutex);
1696
1697 /*
1698 * set_cpus_allowed_ptr() will fail if the cpumask doesn't have any
1699 * online CPUs. It'll be re-applied when any of the CPUs come up.
1700 */
1701 set_cpus_allowed_ptr(worker->task, pool->attrs->cpumask);
1702
1703 /*
1704 * The pool->attach_mutex ensures %POOL_DISASSOCIATED remains
1705 * stable across this function. See the comments above the
1706 * flag definition for details.
1707 */
1708 if (pool->flags & POOL_DISASSOCIATED)
1709 worker->flags |= WORKER_UNBOUND;
1710
1711 list_add_tail(&worker->node, &pool->workers);
1712
1713 mutex_unlock(&pool->attach_mutex);
1714}
1715
1716/**
1717 * worker_detach_from_pool() - detach a worker from its pool
1718 * @worker: worker which is attached to its pool
1719 * @pool: the pool @worker is attached to
1720 *
1721 * Undo the attaching which had been done in worker_attach_to_pool(). The
1722 * caller worker shouldn't access to the pool after detached except it has
1723 * other reference to the pool.
1724 */
1725static void worker_detach_from_pool(struct worker *worker,
1726 struct worker_pool *pool)
1727{
1728 struct completion *detach_completion = NULL;
1729
1730 mutex_lock(&pool->attach_mutex);
1731 list_del(&worker->node);
1732 if (list_empty(&pool->workers))
1733 detach_completion = pool->detach_completion;
1734 mutex_unlock(&pool->attach_mutex);
1735
1736 /* clear leftover flags without pool->lock after it is detached */
1737 worker->flags &= ~(WORKER_UNBOUND | WORKER_REBOUND);
1738
1739 if (detach_completion)
1740 complete(detach_completion);
1741}
1742
1743/**
1744 * create_worker - create a new workqueue worker
1745 * @pool: pool the new worker will belong to
1746 *
1747 * Create and start a new worker which is attached to @pool.
1748 *
1749 * CONTEXT:
1750 * Might sleep. Does GFP_KERNEL allocations.
1751 *
1752 * Return:
1753 * Pointer to the newly created worker.
1754 */
1755static struct worker *create_worker(struct worker_pool *pool)
1756{
1757 struct worker *worker = NULL;
1758 int id = -1;
1759 char id_buf[16];
1760
1761 /* ID is needed to determine kthread name */
1762 id = ida_simple_get(&pool->worker_ida, 0, 0, GFP_KERNEL);
1763 if (id < 0)
1764 goto fail;
1765
1766 worker = alloc_worker(pool->node);
1767 if (!worker)
1768 goto fail;
1769
1770 worker->pool = pool;
1771 worker->id = id;
1772
1773 if (pool->cpu >= 0)
1774 snprintf(id_buf, sizeof(id_buf), "%d:%d%s", pool->cpu, id,
1775 pool->attrs->nice < 0 ? "H" : "");
1776 else
1777 snprintf(id_buf, sizeof(id_buf), "u%d:%d", pool->id, id);
1778
1779 worker->task = kthread_create_on_node(worker_thread, worker, pool->node,
1780 "kworker/%s", id_buf);
1781 if (IS_ERR(worker->task))
1782 goto fail;
1783
1784 set_user_nice(worker->task, pool->attrs->nice);
1785 kthread_bind_mask(worker->task, pool->attrs->cpumask);
1786
1787 /* successful, attach the worker to the pool */
1788 worker_attach_to_pool(worker, pool);
1789
1790 /* start the newly created worker */
1791 spin_lock_irq(&pool->lock);
1792 worker->pool->nr_workers++;
1793 worker_enter_idle(worker);
1794 wake_up_process(worker->task);
1795 spin_unlock_irq(&pool->lock);
1796
1797 return worker;
1798
1799fail:
1800 if (id >= 0)
1801 ida_simple_remove(&pool->worker_ida, id);
1802 kfree(worker);
1803 return NULL;
1804}
1805
1806/**
1807 * destroy_worker - destroy a workqueue worker
1808 * @worker: worker to be destroyed
1809 *
1810 * Destroy @worker and adjust @pool stats accordingly. The worker should
1811 * be idle.
1812 *
1813 * CONTEXT:
1814 * spin_lock_irq(pool->lock).
1815 */
1816static void destroy_worker(struct worker *worker)
1817{
1818 struct worker_pool *pool = worker->pool;
1819
1820 lockdep_assert_held(&pool->lock);
1821
1822 /* sanity check frenzy */
1823 if (WARN_ON(worker->current_work) ||
1824 WARN_ON(!list_empty(&worker->scheduled)) ||
1825 WARN_ON(!(worker->flags & WORKER_IDLE)))
1826 return;
1827
1828 pool->nr_workers--;
1829 pool->nr_idle--;
1830
1831 list_del_init(&worker->entry);
1832 worker->flags |= WORKER_DIE;
1833 wake_up_process(worker->task);
1834}
1835
1836static void idle_worker_timeout(unsigned long __pool)
1837{
1838 struct worker_pool *pool = (void *)__pool;
1839
1840 spin_lock_irq(&pool->lock);
1841
1842 while (too_many_workers(pool)) {
1843 struct worker *worker;
1844 unsigned long expires;
1845
1846 /* idle_list is kept in LIFO order, check the last one */
1847 worker = list_entry(pool->idle_list.prev, struct worker, entry);
1848 expires = worker->last_active + IDLE_WORKER_TIMEOUT;
1849
1850 if (time_before(jiffies, expires)) {
1851 mod_timer(&pool->idle_timer, expires);
1852 break;
1853 }
1854
1855 destroy_worker(worker);
1856 }
1857
1858 spin_unlock_irq(&pool->lock);
1859}
1860
1861static void send_mayday(struct work_struct *work)
1862{
1863 struct pool_workqueue *pwq = get_work_pwq(work);
1864 struct workqueue_struct *wq = pwq->wq;
1865
1866 lockdep_assert_held(&wq_mayday_lock);
1867
1868 if (!wq->rescuer)
1869 return;
1870
1871 /* mayday mayday mayday */
1872 if (list_empty(&pwq->mayday_node)) {
1873 /*
1874 * If @pwq is for an unbound wq, its base ref may be put at
1875 * any time due to an attribute change. Pin @pwq until the
1876 * rescuer is done with it.
1877 */
1878 get_pwq(pwq);
1879 list_add_tail(&pwq->mayday_node, &wq->maydays);
1880 wake_up_process(wq->rescuer->task);
1881 }
1882}
1883
1884static void pool_mayday_timeout(unsigned long __pool)
1885{
1886 struct worker_pool *pool = (void *)__pool;
1887 struct work_struct *work;
1888
1889 spin_lock_irq(&pool->lock);
1890 spin_lock(&wq_mayday_lock); /* for wq->maydays */
1891
1892 if (need_to_create_worker(pool)) {
1893 /*
1894 * We've been trying to create a new worker but
1895 * haven't been successful. We might be hitting an
1896 * allocation deadlock. Send distress signals to
1897 * rescuers.
1898 */
1899 list_for_each_entry(work, &pool->worklist, entry)
1900 send_mayday(work);
1901 }
1902
1903 spin_unlock(&wq_mayday_lock);
1904 spin_unlock_irq(&pool->lock);
1905
1906 mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INTERVAL);
1907}
1908
1909/**
1910 * maybe_create_worker - create a new worker if necessary
1911 * @pool: pool to create a new worker for
1912 *
1913 * Create a new worker for @pool if necessary. @pool is guaranteed to
1914 * have at least one idle worker on return from this function. If
1915 * creating a new worker takes longer than MAYDAY_INTERVAL, mayday is
1916 * sent to all rescuers with works scheduled on @pool to resolve
1917 * possible allocation deadlock.
1918 *
1919 * On return, need_to_create_worker() is guaranteed to be %false and
1920 * may_start_working() %true.
1921 *
1922 * LOCKING:
1923 * spin_lock_irq(pool->lock) which may be released and regrabbed
1924 * multiple times. Does GFP_KERNEL allocations. Called only from
1925 * manager.
1926 */
1927static void maybe_create_worker(struct worker_pool *pool)
1928__releases(&pool->lock)
1929__acquires(&pool->lock)
1930{
1931restart:
1932 spin_unlock_irq(&pool->lock);
1933
1934 /* if we don't make progress in MAYDAY_INITIAL_TIMEOUT, call for help */
1935 mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INITIAL_TIMEOUT);
1936
1937 while (true) {
1938 if (create_worker(pool) || !need_to_create_worker(pool))
1939 break;
1940
1941 schedule_timeout_interruptible(CREATE_COOLDOWN);
1942
1943 if (!need_to_create_worker(pool))
1944 break;
1945 }
1946
1947 del_timer_sync(&pool->mayday_timer);
1948 spin_lock_irq(&pool->lock);
1949 /*
1950 * This is necessary even after a new worker was just successfully
1951 * created as @pool->lock was dropped and the new worker might have
1952 * already become busy.
1953 */
1954 if (need_to_create_worker(pool))
1955 goto restart;
1956}
1957
1958/**
1959 * manage_workers - manage worker pool
1960 * @worker: self
1961 *
1962 * Assume the manager role and manage the worker pool @worker belongs
1963 * to. At any given time, there can be only zero or one manager per
1964 * pool. The exclusion is handled automatically by this function.
1965 *
1966 * The caller can safely start processing works on false return. On
1967 * true return, it's guaranteed that need_to_create_worker() is false
1968 * and may_start_working() is true.
1969 *
1970 * CONTEXT:
1971 * spin_lock_irq(pool->lock) which may be released and regrabbed
1972 * multiple times. Does GFP_KERNEL allocations.
1973 *
1974 * Return:
1975 * %false if the pool doesn't need management and the caller can safely
1976 * start processing works, %true if management function was performed and
1977 * the conditions that the caller verified before calling the function may
1978 * no longer be true.
1979 */
1980static bool manage_workers(struct worker *worker)
1981{
1982 struct worker_pool *pool = worker->pool;
1983
1984 /*
1985 * Anyone who successfully grabs manager_arb wins the arbitration
1986 * and becomes the manager. mutex_trylock() on pool->manager_arb
1987 * failure while holding pool->lock reliably indicates that someone
1988 * else is managing the pool and the worker which failed trylock
1989 * can proceed to executing work items. This means that anyone
1990 * grabbing manager_arb is responsible for actually performing
1991 * manager duties. If manager_arb is grabbed and released without
1992 * actual management, the pool may stall indefinitely.
1993 */
1994 if (!mutex_trylock(&pool->manager_arb))
1995 return false;
1996 pool->manager = worker;
1997
1998 maybe_create_worker(pool);
1999
2000 pool->manager = NULL;
2001 mutex_unlock(&pool->manager_arb);
2002 return true;
2003}
2004
2005/**
2006 * process_one_work - process single work
2007 * @worker: self
2008 * @work: work to process
2009 *
2010 * Process @work. This function contains all the logics necessary to
2011 * process a single work including synchronization against and
2012 * interaction with other workers on the same cpu, queueing and
2013 * flushing. As long as context requirement is met, any worker can
2014 * call this function to process a work.
2015 *
2016 * CONTEXT:
2017 * spin_lock_irq(pool->lock) which is released and regrabbed.
2018 */
2019static void process_one_work(struct worker *worker, struct work_struct *work)
2020__releases(&pool->lock)
2021__acquires(&pool->lock)
2022{
2023 struct pool_workqueue *pwq = get_work_pwq(work);
2024 struct worker_pool *pool = worker->pool;
2025 bool cpu_intensive = pwq->wq->flags & WQ_CPU_INTENSIVE;
2026 int work_color;
2027 struct worker *collision;
2028#ifdef CONFIG_LOCKDEP
2029 /*
2030 * It is permissible to free the struct work_struct from
2031 * inside the function that is called from it, this we need to
2032 * take into account for lockdep too. To avoid bogus "held
2033 * lock freed" warnings as well as problems when looking into
2034 * work->lockdep_map, make a copy and use that here.
2035 */
2036 struct lockdep_map lockdep_map;
2037
2038 lockdep_copy_map(&lockdep_map, &work->lockdep_map);
2039#endif
2040 /* ensure we're on the correct CPU */
2041 WARN_ON_ONCE(!(pool->flags & POOL_DISASSOCIATED) &&
2042 raw_smp_processor_id() != pool->cpu);
2043
2044 /*
2045 * A single work shouldn't be executed concurrently by
2046 * multiple workers on a single cpu. Check whether anyone is
2047 * already processing the work. If so, defer the work to the
2048 * currently executing one.
2049 */
2050 collision = find_worker_executing_work(pool, work);
2051 if (unlikely(collision)) {
2052 move_linked_works(work, &collision->scheduled, NULL);
2053 return;
2054 }
2055
2056 /* claim and dequeue */
2057 debug_work_deactivate(work);
2058 hash_add(pool->busy_hash, &worker->hentry, (unsigned long)work);
2059 worker->current_work = work;
2060 worker->current_func = work->func;
2061 worker->current_pwq = pwq;
2062 work_color = get_work_color(work);
2063
2064 list_del_init(&work->entry);
2065
2066 /*
2067 * CPU intensive works don't participate in concurrency management.
2068 * They're the scheduler's responsibility. This takes @worker out
2069 * of concurrency management and the next code block will chain
2070 * execution of the pending work items.
2071 */
2072 if (unlikely(cpu_intensive))
2073 worker_set_flags(worker, WORKER_CPU_INTENSIVE);
2074
2075 /*
2076 * Wake up another worker if necessary. The condition is always
2077 * false for normal per-cpu workers since nr_running would always
2078 * be >= 1 at this point. This is used to chain execution of the
2079 * pending work items for WORKER_NOT_RUNNING workers such as the
2080 * UNBOUND and CPU_INTENSIVE ones.
2081 */
2082 if (need_more_worker(pool))
2083 wake_up_worker(pool);
2084
2085 /*
2086 * Record the last pool and clear PENDING which should be the last
2087 * update to @work. Also, do this inside @pool->lock so that
2088 * PENDING and queued state changes happen together while IRQ is
2089 * disabled.
2090 */
2091 set_work_pool_and_clear_pending(work, pool->id);
2092
2093 spin_unlock_irq(&pool->lock);
2094
2095 lock_map_acquire_read(&pwq->wq->lockdep_map);
2096 lock_map_acquire(&lockdep_map);
2097 trace_workqueue_execute_start(work);
2098 worker->current_func(work);
2099 /*
2100 * While we must be careful to not use "work" after this, the trace
2101 * point will only record its address.
2102 */
2103 trace_workqueue_execute_end(work);
2104 lock_map_release(&lockdep_map);
2105 lock_map_release(&pwq->wq->lockdep_map);
2106
2107 if (unlikely(in_atomic() || lockdep_depth(current) > 0)) {
2108 pr_err("BUG: workqueue leaked lock or atomic: %s/0x%08x/%d\n"
2109 " last function: %pf\n",
2110 current->comm, preempt_count(), task_pid_nr(current),
2111 worker->current_func);
2112 debug_show_held_locks(current);
2113 dump_stack();
2114 }
2115
2116 /*
2117 * The following prevents a kworker from hogging CPU on !PREEMPT
2118 * kernels, where a requeueing work item waiting for something to
2119 * happen could deadlock with stop_machine as such work item could
2120 * indefinitely requeue itself while all other CPUs are trapped in
2121 * stop_machine. At the same time, report a quiescent RCU state so
2122 * the same condition doesn't freeze RCU.
2123 */
2124 cond_resched_rcu_qs();
2125
2126 spin_lock_irq(&pool->lock);
2127
2128 /* clear cpu intensive status */
2129 if (unlikely(cpu_intensive))
2130 worker_clr_flags(worker, WORKER_CPU_INTENSIVE);
2131
2132 /* we're done with it, release */
2133 hash_del(&worker->hentry);
2134 worker->current_work = NULL;
2135 worker->current_func = NULL;
2136 worker->current_pwq = NULL;
2137 worker->desc_valid = false;
2138 pwq_dec_nr_in_flight(pwq, work_color);
2139}
2140
2141/**
2142 * process_scheduled_works - process scheduled works
2143 * @worker: self
2144 *
2145 * Process all scheduled works. Please note that the scheduled list
2146 * may change while processing a work, so this function repeatedly
2147 * fetches a work from the top and executes it.
2148 *
2149 * CONTEXT:
2150 * spin_lock_irq(pool->lock) which may be released and regrabbed
2151 * multiple times.
2152 */
2153static void process_scheduled_works(struct worker *worker)
2154{
2155 while (!list_empty(&worker->scheduled)) {
2156 struct work_struct *work = list_first_entry(&worker->scheduled,
2157 struct work_struct, entry);
2158 process_one_work(worker, work);
2159 }
2160}
2161
2162/**
2163 * worker_thread - the worker thread function
2164 * @__worker: self
2165 *
2166 * The worker thread function. All workers belong to a worker_pool -
2167 * either a per-cpu one or dynamic unbound one. These workers process all
2168 * work items regardless of their specific target workqueue. The only
2169 * exception is work items which belong to workqueues with a rescuer which
2170 * will be explained in rescuer_thread().
2171 *
2172 * Return: 0
2173 */
2174static int worker_thread(void *__worker)
2175{
2176 struct worker *worker = __worker;
2177 struct worker_pool *pool = worker->pool;
2178
2179 /* tell the scheduler that this is a workqueue worker */
2180 worker->task->flags |= PF_WQ_WORKER;
2181woke_up:
2182 spin_lock_irq(&pool->lock);
2183
2184 /* am I supposed to die? */
2185 if (unlikely(worker->flags & WORKER_DIE)) {
2186 spin_unlock_irq(&pool->lock);
2187 WARN_ON_ONCE(!list_empty(&worker->entry));
2188 worker->task->flags &= ~PF_WQ_WORKER;
2189
2190 set_task_comm(worker->task, "kworker/dying");
2191 ida_simple_remove(&pool->worker_ida, worker->id);
2192 worker_detach_from_pool(worker, pool);
2193 kfree(worker);
2194 return 0;
2195 }
2196
2197 worker_leave_idle(worker);
2198recheck:
2199 /* no more worker necessary? */
2200 if (!need_more_worker(pool))
2201 goto sleep;
2202
2203 /* do we need to manage? */
2204 if (unlikely(!may_start_working(pool)) && manage_workers(worker))
2205 goto recheck;
2206
2207 /*
2208 * ->scheduled list can only be filled while a worker is
2209 * preparing to process a work or actually processing it.
2210 * Make sure nobody diddled with it while I was sleeping.
2211 */
2212 WARN_ON_ONCE(!list_empty(&worker->scheduled));
2213
2214 /*
2215 * Finish PREP stage. We're guaranteed to have at least one idle
2216 * worker or that someone else has already assumed the manager
2217 * role. This is where @worker starts participating in concurrency
2218 * management if applicable and concurrency management is restored
2219 * after being rebound. See rebind_workers() for details.
2220 */
2221 worker_clr_flags(worker, WORKER_PREP | WORKER_REBOUND);
2222
2223 do {
2224 struct work_struct *work =
2225 list_first_entry(&pool->worklist,
2226 struct work_struct, entry);
2227
2228 pool->watchdog_ts = jiffies;
2229
2230 if (likely(!(*work_data_bits(work) & WORK_STRUCT_LINKED))) {
2231 /* optimization path, not strictly necessary */
2232 process_one_work(worker, work);
2233 if (unlikely(!list_empty(&worker->scheduled)))
2234 process_scheduled_works(worker);
2235 } else {
2236 move_linked_works(work, &worker->scheduled, NULL);
2237 process_scheduled_works(worker);
2238 }
2239 } while (keep_working(pool));
2240
2241 worker_set_flags(worker, WORKER_PREP);
2242sleep:
2243 /*
2244 * pool->lock is held and there's no work to process and no need to
2245 * manage, sleep. Workers are woken up only while holding
2246 * pool->lock or from local cpu, so setting the current state
2247 * before releasing pool->lock is enough to prevent losing any
2248 * event.
2249 */
2250 worker_enter_idle(worker);
2251 __set_current_state(TASK_INTERRUPTIBLE);
2252 spin_unlock_irq(&pool->lock);
2253 schedule();
2254 goto woke_up;
2255}
2256
2257/**
2258 * rescuer_thread - the rescuer thread function
2259 * @__rescuer: self
2260 *
2261 * Workqueue rescuer thread function. There's one rescuer for each
2262 * workqueue which has WQ_MEM_RECLAIM set.
2263 *
2264 * Regular work processing on a pool may block trying to create a new
2265 * worker which uses GFP_KERNEL allocation which has slight chance of
2266 * developing into deadlock if some works currently on the same queue
2267 * need to be processed to satisfy the GFP_KERNEL allocation. This is
2268 * the problem rescuer solves.
2269 *
2270 * When such condition is possible, the pool summons rescuers of all
2271 * workqueues which have works queued on the pool and let them process
2272 * those works so that forward progress can be guaranteed.
2273 *
2274 * This should happen rarely.
2275 *
2276 * Return: 0
2277 */
2278static int rescuer_thread(void *__rescuer)
2279{
2280 struct worker *rescuer = __rescuer;
2281 struct workqueue_struct *wq = rescuer->rescue_wq;
2282 struct list_head *scheduled = &rescuer->scheduled;
2283 bool should_stop;
2284
2285 set_user_nice(current, RESCUER_NICE_LEVEL);
2286
2287 /*
2288 * Mark rescuer as worker too. As WORKER_PREP is never cleared, it
2289 * doesn't participate in concurrency management.
2290 */
2291 rescuer->task->flags |= PF_WQ_WORKER;
2292repeat:
2293 set_current_state(TASK_INTERRUPTIBLE);
2294
2295 /*
2296 * By the time the rescuer is requested to stop, the workqueue
2297 * shouldn't have any work pending, but @wq->maydays may still have
2298 * pwq(s) queued. This can happen by non-rescuer workers consuming
2299 * all the work items before the rescuer got to them. Go through
2300 * @wq->maydays processing before acting on should_stop so that the
2301 * list is always empty on exit.
2302 */
2303 should_stop = kthread_should_stop();
2304
2305 /* see whether any pwq is asking for help */
2306 spin_lock_irq(&wq_mayday_lock);
2307
2308 while (!list_empty(&wq->maydays)) {
2309 struct pool_workqueue *pwq = list_first_entry(&wq->maydays,
2310 struct pool_workqueue, mayday_node);
2311 struct worker_pool *pool = pwq->pool;
2312 struct work_struct *work, *n;
2313 bool first = true;
2314
2315 __set_current_state(TASK_RUNNING);
2316 list_del_init(&pwq->mayday_node);
2317
2318 spin_unlock_irq(&wq_mayday_lock);
2319
2320 worker_attach_to_pool(rescuer, pool);
2321
2322 spin_lock_irq(&pool->lock);
2323 rescuer->pool = pool;
2324
2325 /*
2326 * Slurp in all works issued via this workqueue and
2327 * process'em.
2328 */
2329 WARN_ON_ONCE(!list_empty(scheduled));
2330 list_for_each_entry_safe(work, n, &pool->worklist, entry) {
2331 if (get_work_pwq(work) == pwq) {
2332 if (first)
2333 pool->watchdog_ts = jiffies;
2334 move_linked_works(work, scheduled, &n);
2335 }
2336 first = false;
2337 }
2338
2339 if (!list_empty(scheduled)) {
2340 process_scheduled_works(rescuer);
2341
2342 /*
2343 * The above execution of rescued work items could
2344 * have created more to rescue through
2345 * pwq_activate_first_delayed() or chained
2346 * queueing. Let's put @pwq back on mayday list so
2347 * that such back-to-back work items, which may be
2348 * being used to relieve memory pressure, don't
2349 * incur MAYDAY_INTERVAL delay inbetween.
2350 */
2351 if (need_to_create_worker(pool)) {
2352 spin_lock(&wq_mayday_lock);
2353 get_pwq(pwq);
2354 list_move_tail(&pwq->mayday_node, &wq->maydays);
2355 spin_unlock(&wq_mayday_lock);
2356 }
2357 }
2358
2359 /*
2360 * Put the reference grabbed by send_mayday(). @pool won't
2361 * go away while we're still attached to it.
2362 */
2363 put_pwq(pwq);
2364
2365 /*
2366 * Leave this pool. If need_more_worker() is %true, notify a
2367 * regular worker; otherwise, we end up with 0 concurrency
2368 * and stalling the execution.
2369 */
2370 if (need_more_worker(pool))
2371 wake_up_worker(pool);
2372
2373 rescuer->pool = NULL;
2374 spin_unlock_irq(&pool->lock);
2375
2376 worker_detach_from_pool(rescuer, pool);
2377
2378 spin_lock_irq(&wq_mayday_lock);
2379 }
2380
2381 spin_unlock_irq(&wq_mayday_lock);
2382
2383 if (should_stop) {
2384 __set_current_state(TASK_RUNNING);
2385 rescuer->task->flags &= ~PF_WQ_WORKER;
2386 return 0;
2387 }
2388
2389 /* rescuers should never participate in concurrency management */
2390 WARN_ON_ONCE(!(rescuer->flags & WORKER_NOT_RUNNING));
2391 schedule();
2392 goto repeat;
2393}
2394
2395/**
2396 * check_flush_dependency - check for flush dependency sanity
2397 * @target_wq: workqueue being flushed
2398 * @target_work: work item being flushed (NULL for workqueue flushes)
2399 *
2400 * %current is trying to flush the whole @target_wq or @target_work on it.
2401 * If @target_wq doesn't have %WQ_MEM_RECLAIM, verify that %current is not
2402 * reclaiming memory or running on a workqueue which doesn't have
2403 * %WQ_MEM_RECLAIM as that can break forward-progress guarantee leading to
2404 * a deadlock.
2405 */
2406static void check_flush_dependency(struct workqueue_struct *target_wq,
2407 struct work_struct *target_work)
2408{
2409 work_func_t target_func = target_work ? target_work->func : NULL;
2410 struct worker *worker;
2411
2412 if (target_wq->flags & WQ_MEM_RECLAIM)
2413 return;
2414
2415 worker = current_wq_worker();
2416
2417 WARN_ONCE(current->flags & PF_MEMALLOC,
2418 "workqueue: PF_MEMALLOC task %d(%s) is flushing !WQ_MEM_RECLAIM %s:%pf",
2419 current->pid, current->comm, target_wq->name, target_func);
2420 WARN_ONCE(worker && ((worker->current_pwq->wq->flags &
2421 (WQ_MEM_RECLAIM | __WQ_LEGACY)) == WQ_MEM_RECLAIM),
2422 "workqueue: WQ_MEM_RECLAIM %s:%pf is flushing !WQ_MEM_RECLAIM %s:%pf",
2423 worker->current_pwq->wq->name, worker->current_func,
2424 target_wq->name, target_func);
2425}
2426
2427struct wq_barrier {
2428 struct work_struct work;
2429 struct completion done;
2430 struct task_struct *task; /* purely informational */
2431};
2432
2433static void wq_barrier_func(struct work_struct *work)
2434{
2435 struct wq_barrier *barr = container_of(work, struct wq_barrier, work);
2436 complete(&barr->done);
2437}
2438
2439/**
2440 * insert_wq_barrier - insert a barrier work
2441 * @pwq: pwq to insert barrier into
2442 * @barr: wq_barrier to insert
2443 * @target: target work to attach @barr to
2444 * @worker: worker currently executing @target, NULL if @target is not executing
2445 *
2446 * @barr is linked to @target such that @barr is completed only after
2447 * @target finishes execution. Please note that the ordering
2448 * guarantee is observed only with respect to @target and on the local
2449 * cpu.
2450 *
2451 * Currently, a queued barrier can't be canceled. This is because
2452 * try_to_grab_pending() can't determine whether the work to be
2453 * grabbed is at the head of the queue and thus can't clear LINKED
2454 * flag of the previous work while there must be a valid next work
2455 * after a work with LINKED flag set.
2456 *
2457 * Note that when @worker is non-NULL, @target may be modified
2458 * underneath us, so we can't reliably determine pwq from @target.
2459 *
2460 * CONTEXT:
2461 * spin_lock_irq(pool->lock).
2462 */
2463static void insert_wq_barrier(struct pool_workqueue *pwq,
2464 struct wq_barrier *barr,
2465 struct work_struct *target, struct worker *worker)
2466{
2467 struct list_head *head;
2468 unsigned int linked = 0;
2469
2470 /*
2471 * debugobject calls are safe here even with pool->lock locked
2472 * as we know for sure that this will not trigger any of the
2473 * checks and call back into the fixup functions where we
2474 * might deadlock.
2475 */
2476 INIT_WORK_ONSTACK(&barr->work, wq_barrier_func);
2477 __set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(&barr->work));
2478 init_completion(&barr->done);
2479 barr->task = current;
2480
2481 /*
2482 * If @target is currently being executed, schedule the
2483 * barrier to the worker; otherwise, put it after @target.
2484 */
2485 if (worker)
2486 head = worker->scheduled.next;
2487 else {
2488 unsigned long *bits = work_data_bits(target);
2489
2490 head = target->entry.next;
2491 /* there can already be other linked works, inherit and set */
2492 linked = *bits & WORK_STRUCT_LINKED;
2493 __set_bit(WORK_STRUCT_LINKED_BIT, bits);
2494 }
2495
2496 debug_work_activate(&barr->work);
2497 insert_work(pwq, &barr->work, head,
2498 work_color_to_flags(WORK_NO_COLOR) | linked);
2499}
2500
2501/**
2502 * flush_workqueue_prep_pwqs - prepare pwqs for workqueue flushing
2503 * @wq: workqueue being flushed
2504 * @flush_color: new flush color, < 0 for no-op
2505 * @work_color: new work color, < 0 for no-op
2506 *
2507 * Prepare pwqs for workqueue flushing.
2508 *
2509 * If @flush_color is non-negative, flush_color on all pwqs should be
2510 * -1. If no pwq has in-flight commands at the specified color, all
2511 * pwq->flush_color's stay at -1 and %false is returned. If any pwq
2512 * has in flight commands, its pwq->flush_color is set to
2513 * @flush_color, @wq->nr_pwqs_to_flush is updated accordingly, pwq
2514 * wakeup logic is armed and %true is returned.
2515 *
2516 * The caller should have initialized @wq->first_flusher prior to
2517 * calling this function with non-negative @flush_color. If
2518 * @flush_color is negative, no flush color update is done and %false
2519 * is returned.
2520 *
2521 * If @work_color is non-negative, all pwqs should have the same
2522 * work_color which is previous to @work_color and all will be
2523 * advanced to @work_color.
2524 *
2525 * CONTEXT:
2526 * mutex_lock(wq->mutex).
2527 *
2528 * Return:
2529 * %true if @flush_color >= 0 and there's something to flush. %false
2530 * otherwise.
2531 */
2532static bool flush_workqueue_prep_pwqs(struct workqueue_struct *wq,
2533 int flush_color, int work_color)
2534{
2535 bool wait = false;
2536 struct pool_workqueue *pwq;
2537
2538 if (flush_color >= 0) {
2539 WARN_ON_ONCE(atomic_read(&wq->nr_pwqs_to_flush));
2540 atomic_set(&wq->nr_pwqs_to_flush, 1);
2541 }
2542
2543 for_each_pwq(pwq, wq) {
2544 struct worker_pool *pool = pwq->pool;
2545
2546 spin_lock_irq(&pool->lock);
2547
2548 if (flush_color >= 0) {
2549 WARN_ON_ONCE(pwq->flush_color != -1);
2550
2551 if (pwq->nr_in_flight[flush_color]) {
2552 pwq->flush_color = flush_color;
2553 atomic_inc(&wq->nr_pwqs_to_flush);
2554 wait = true;
2555 }
2556 }
2557
2558 if (work_color >= 0) {
2559 WARN_ON_ONCE(work_color != work_next_color(pwq->work_color));
2560 pwq->work_color = work_color;
2561 }
2562
2563 spin_unlock_irq(&pool->lock);
2564 }
2565
2566 if (flush_color >= 0 && atomic_dec_and_test(&wq->nr_pwqs_to_flush))
2567 complete(&wq->first_flusher->done);
2568
2569 return wait;
2570}
2571
2572/**
2573 * flush_workqueue - ensure that any scheduled work has run to completion.
2574 * @wq: workqueue to flush
2575 *
2576 * This function sleeps until all work items which were queued on entry
2577 * have finished execution, but it is not livelocked by new incoming ones.
2578 */
2579void flush_workqueue(struct workqueue_struct *wq)
2580{
2581 struct wq_flusher this_flusher = {
2582 .list = LIST_HEAD_INIT(this_flusher.list),
2583 .flush_color = -1,
2584 .done = COMPLETION_INITIALIZER_ONSTACK(this_flusher.done),
2585 };
2586 int next_color;
2587
2588 if (WARN_ON(!wq_online))
2589 return;
2590
2591 lock_map_acquire(&wq->lockdep_map);
2592 lock_map_release(&wq->lockdep_map);
2593
2594 mutex_lock(&wq->mutex);
2595
2596 /*
2597 * Start-to-wait phase
2598 */
2599 next_color = work_next_color(wq->work_color);
2600
2601 if (next_color != wq->flush_color) {
2602 /*
2603 * Color space is not full. The current work_color
2604 * becomes our flush_color and work_color is advanced
2605 * by one.
2606 */
2607 WARN_ON_ONCE(!list_empty(&wq->flusher_overflow));
2608 this_flusher.flush_color = wq->work_color;
2609 wq->work_color = next_color;
2610
2611 if (!wq->first_flusher) {
2612 /* no flush in progress, become the first flusher */
2613 WARN_ON_ONCE(wq->flush_color != this_flusher.flush_color);
2614
2615 wq->first_flusher = &this_flusher;
2616
2617 if (!flush_workqueue_prep_pwqs(wq, wq->flush_color,
2618 wq->work_color)) {
2619 /* nothing to flush, done */
2620 wq->flush_color = next_color;
2621 wq->first_flusher = NULL;
2622 goto out_unlock;
2623 }
2624 } else {
2625 /* wait in queue */
2626 WARN_ON_ONCE(wq->flush_color == this_flusher.flush_color);
2627 list_add_tail(&this_flusher.list, &wq->flusher_queue);
2628 flush_workqueue_prep_pwqs(wq, -1, wq->work_color);
2629 }
2630 } else {
2631 /*
2632 * Oops, color space is full, wait on overflow queue.
2633 * The next flush completion will assign us
2634 * flush_color and transfer to flusher_queue.
2635 */
2636 list_add_tail(&this_flusher.list, &wq->flusher_overflow);
2637 }
2638
2639 check_flush_dependency(wq, NULL);
2640
2641 mutex_unlock(&wq->mutex);
2642
2643 wait_for_completion(&this_flusher.done);
2644
2645 /*
2646 * Wake-up-and-cascade phase
2647 *
2648 * First flushers are responsible for cascading flushes and
2649 * handling overflow. Non-first flushers can simply return.
2650 */
2651 if (wq->first_flusher != &this_flusher)
2652 return;
2653
2654 mutex_lock(&wq->mutex);
2655
2656 /* we might have raced, check again with mutex held */
2657 if (wq->first_flusher != &this_flusher)
2658 goto out_unlock;
2659
2660 wq->first_flusher = NULL;
2661
2662 WARN_ON_ONCE(!list_empty(&this_flusher.list));
2663 WARN_ON_ONCE(wq->flush_color != this_flusher.flush_color);
2664
2665 while (true) {
2666 struct wq_flusher *next, *tmp;
2667
2668 /* complete all the flushers sharing the current flush color */
2669 list_for_each_entry_safe(next, tmp, &wq->flusher_queue, list) {
2670 if (next->flush_color != wq->flush_color)
2671 break;
2672 list_del_init(&next->list);
2673 complete(&next->done);
2674 }
2675
2676 WARN_ON_ONCE(!list_empty(&wq->flusher_overflow) &&
2677 wq->flush_color != work_next_color(wq->work_color));
2678
2679 /* this flush_color is finished, advance by one */
2680 wq->flush_color = work_next_color(wq->flush_color);
2681
2682 /* one color has been freed, handle overflow queue */
2683 if (!list_empty(&wq->flusher_overflow)) {
2684 /*
2685 * Assign the same color to all overflowed
2686 * flushers, advance work_color and append to
2687 * flusher_queue. This is the start-to-wait
2688 * phase for these overflowed flushers.
2689 */
2690 list_for_each_entry(tmp, &wq->flusher_overflow, list)
2691 tmp->flush_color = wq->work_color;
2692
2693 wq->work_color = work_next_color(wq->work_color);
2694
2695 list_splice_tail_init(&wq->flusher_overflow,
2696 &wq->flusher_queue);
2697 flush_workqueue_prep_pwqs(wq, -1, wq->work_color);
2698 }
2699
2700 if (list_empty(&wq->flusher_queue)) {
2701 WARN_ON_ONCE(wq->flush_color != wq->work_color);
2702 break;
2703 }
2704
2705 /*
2706 * Need to flush more colors. Make the next flusher
2707 * the new first flusher and arm pwqs.
2708 */
2709 WARN_ON_ONCE(wq->flush_color == wq->work_color);
2710 WARN_ON_ONCE(wq->flush_color != next->flush_color);
2711
2712 list_del_init(&next->list);
2713 wq->first_flusher = next;
2714
2715 if (flush_workqueue_prep_pwqs(wq, wq->flush_color, -1))
2716 break;
2717
2718 /*
2719 * Meh... this color is already done, clear first
2720 * flusher and repeat cascading.
2721 */
2722 wq->first_flusher = NULL;
2723 }
2724
2725out_unlock:
2726 mutex_unlock(&wq->mutex);
2727}
2728EXPORT_SYMBOL(flush_workqueue);
2729
2730/**
2731 * drain_workqueue - drain a workqueue
2732 * @wq: workqueue to drain
2733 *
2734 * Wait until the workqueue becomes empty. While draining is in progress,
2735 * only chain queueing is allowed. IOW, only currently pending or running
2736 * work items on @wq can queue further work items on it. @wq is flushed
2737 * repeatedly until it becomes empty. The number of flushing is determined
2738 * by the depth of chaining and should be relatively short. Whine if it
2739 * takes too long.
2740 */
2741void drain_workqueue(struct workqueue_struct *wq)
2742{
2743 unsigned int flush_cnt = 0;
2744 struct pool_workqueue *pwq;
2745
2746 /*
2747 * __queue_work() needs to test whether there are drainers, is much
2748 * hotter than drain_workqueue() and already looks at @wq->flags.
2749 * Use __WQ_DRAINING so that queue doesn't have to check nr_drainers.
2750 */
2751 mutex_lock(&wq->mutex);
2752 if (!wq->nr_drainers++)
2753 wq->flags |= __WQ_DRAINING;
2754 mutex_unlock(&wq->mutex);
2755reflush:
2756 flush_workqueue(wq);
2757
2758 mutex_lock(&wq->mutex);
2759
2760 for_each_pwq(pwq, wq) {
2761 bool drained;
2762
2763 spin_lock_irq(&pwq->pool->lock);
2764 drained = !pwq->nr_active && list_empty(&pwq->delayed_works);
2765 spin_unlock_irq(&pwq->pool->lock);
2766
2767 if (drained)
2768 continue;
2769
2770 if (++flush_cnt == 10 ||
2771 (flush_cnt % 100 == 0 && flush_cnt <= 1000))
2772 pr_warn("workqueue %s: drain_workqueue() isn't complete after %u tries\n",
2773 wq->name, flush_cnt);
2774
2775 mutex_unlock(&wq->mutex);
2776 goto reflush;
2777 }
2778
2779 if (!--wq->nr_drainers)
2780 wq->flags &= ~__WQ_DRAINING;
2781 mutex_unlock(&wq->mutex);
2782}
2783EXPORT_SYMBOL_GPL(drain_workqueue);
2784
2785static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr)
2786{
2787 struct worker *worker = NULL;
2788 struct worker_pool *pool;
2789 struct pool_workqueue *pwq;
2790
2791 might_sleep();
2792
2793 local_irq_disable();
2794 pool = get_work_pool(work);
2795 if (!pool) {
2796 local_irq_enable();
2797 return false;
2798 }
2799
2800 spin_lock(&pool->lock);
2801 /* see the comment in try_to_grab_pending() with the same code */
2802 pwq = get_work_pwq(work);
2803 if (pwq) {
2804 if (unlikely(pwq->pool != pool))
2805 goto already_gone;
2806 } else {
2807 worker = find_worker_executing_work(pool, work);
2808 if (!worker)
2809 goto already_gone;
2810 pwq = worker->current_pwq;
2811 }
2812
2813 check_flush_dependency(pwq->wq, work);
2814
2815 insert_wq_barrier(pwq, barr, work, worker);
2816 spin_unlock_irq(&pool->lock);
2817
2818 /*
2819 * If @max_active is 1 or rescuer is in use, flushing another work
2820 * item on the same workqueue may lead to deadlock. Make sure the
2821 * flusher is not running on the same workqueue by verifying write
2822 * access.
2823 */
2824 if (pwq->wq->saved_max_active == 1 || pwq->wq->rescuer)
2825 lock_map_acquire(&pwq->wq->lockdep_map);
2826 else
2827 lock_map_acquire_read(&pwq->wq->lockdep_map);
2828 lock_map_release(&pwq->wq->lockdep_map);
2829
2830 return true;
2831already_gone:
2832 spin_unlock_irq(&pool->lock);
2833 return false;
2834}
2835
2836/**
2837 * flush_work - wait for a work to finish executing the last queueing instance
2838 * @work: the work to flush
2839 *
2840 * Wait until @work has finished execution. @work is guaranteed to be idle
2841 * on return if it hasn't been requeued since flush started.
2842 *
2843 * Return:
2844 * %true if flush_work() waited for the work to finish execution,
2845 * %false if it was already idle.
2846 */
2847bool flush_work(struct work_struct *work)
2848{
2849 struct wq_barrier barr;
2850
2851 if (WARN_ON(!wq_online))
2852 return false;
2853
2854 lock_map_acquire(&work->lockdep_map);
2855 lock_map_release(&work->lockdep_map);
2856
2857 if (start_flush_work(work, &barr)) {
2858 wait_for_completion(&barr.done);
2859 destroy_work_on_stack(&barr.work);
2860 return true;
2861 } else {
2862 return false;
2863 }
2864}
2865EXPORT_SYMBOL_GPL(flush_work);
2866
2867struct cwt_wait {
2868 wait_queue_t wait;
2869 struct work_struct *work;
2870};
2871
2872static int cwt_wakefn(wait_queue_t *wait, unsigned mode, int sync, void *key)
2873{
2874 struct cwt_wait *cwait = container_of(wait, struct cwt_wait, wait);
2875
2876 if (cwait->work != key)
2877 return 0;
2878 return autoremove_wake_function(wait, mode, sync, key);
2879}
2880
2881static bool __cancel_work_timer(struct work_struct *work, bool is_dwork)
2882{
2883 static DECLARE_WAIT_QUEUE_HEAD(cancel_waitq);
2884 unsigned long flags;
2885 int ret;
2886
2887 do {
2888 ret = try_to_grab_pending(work, is_dwork, &flags);
2889 /*
2890 * If someone else is already canceling, wait for it to
2891 * finish. flush_work() doesn't work for PREEMPT_NONE
2892 * because we may get scheduled between @work's completion
2893 * and the other canceling task resuming and clearing
2894 * CANCELING - flush_work() will return false immediately
2895 * as @work is no longer busy, try_to_grab_pending() will
2896 * return -ENOENT as @work is still being canceled and the
2897 * other canceling task won't be able to clear CANCELING as
2898 * we're hogging the CPU.
2899 *
2900 * Let's wait for completion using a waitqueue. As this
2901 * may lead to the thundering herd problem, use a custom
2902 * wake function which matches @work along with exclusive
2903 * wait and wakeup.
2904 */
2905 if (unlikely(ret == -ENOENT)) {
2906 struct cwt_wait cwait;
2907
2908 init_wait(&cwait.wait);
2909 cwait.wait.func = cwt_wakefn;
2910 cwait.work = work;
2911
2912 prepare_to_wait_exclusive(&cancel_waitq, &cwait.wait,
2913 TASK_UNINTERRUPTIBLE);
2914 if (work_is_canceling(work))
2915 schedule();
2916 finish_wait(&cancel_waitq, &cwait.wait);
2917 }
2918 } while (unlikely(ret < 0));
2919
2920 /* tell other tasks trying to grab @work to back off */
2921 mark_work_canceling(work);
2922 local_irq_restore(flags);
2923
2924 /*
2925 * This allows canceling during early boot. We know that @work
2926 * isn't executing.
2927 */
2928 if (wq_online)
2929 flush_work(work);
2930
2931 clear_work_data(work);
2932
2933 /*
2934 * Paired with prepare_to_wait() above so that either
2935 * waitqueue_active() is visible here or !work_is_canceling() is
2936 * visible there.
2937 */
2938 smp_mb();
2939 if (waitqueue_active(&cancel_waitq))
2940 __wake_up(&cancel_waitq, TASK_NORMAL, 1, work);
2941
2942 return ret;
2943}
2944
2945/**
2946 * cancel_work_sync - cancel a work and wait for it to finish
2947 * @work: the work to cancel
2948 *
2949 * Cancel @work and wait for its execution to finish. This function
2950 * can be used even if the work re-queues itself or migrates to
2951 * another workqueue. On return from this function, @work is
2952 * guaranteed to be not pending or executing on any CPU.
2953 *
2954 * cancel_work_sync(&delayed_work->work) must not be used for
2955 * delayed_work's. Use cancel_delayed_work_sync() instead.
2956 *
2957 * The caller must ensure that the workqueue on which @work was last
2958 * queued can't be destroyed before this function returns.
2959 *
2960 * Return:
2961 * %true if @work was pending, %false otherwise.
2962 */
2963bool cancel_work_sync(struct work_struct *work)
2964{
2965 return __cancel_work_timer(work, false);
2966}
2967EXPORT_SYMBOL_GPL(cancel_work_sync);
2968
2969/**
2970 * flush_delayed_work - wait for a dwork to finish executing the last queueing
2971 * @dwork: the delayed work to flush
2972 *
2973 * Delayed timer is cancelled and the pending work is queued for
2974 * immediate execution. Like flush_work(), this function only
2975 * considers the last queueing instance of @dwork.
2976 *
2977 * Return:
2978 * %true if flush_work() waited for the work to finish execution,
2979 * %false if it was already idle.
2980 */
2981bool flush_delayed_work(struct delayed_work *dwork)
2982{
2983 local_irq_disable();
2984 if (del_timer_sync(&dwork->timer))
2985 __queue_work(dwork->cpu, dwork->wq, &dwork->work);
2986 local_irq_enable();
2987 return flush_work(&dwork->work);
2988}
2989EXPORT_SYMBOL(flush_delayed_work);
2990
2991static bool __cancel_work(struct work_struct *work, bool is_dwork)
2992{
2993 unsigned long flags;
2994 int ret;
2995
2996 do {
2997 ret = try_to_grab_pending(work, is_dwork, &flags);
2998 } while (unlikely(ret == -EAGAIN));
2999
3000 if (unlikely(ret < 0))
3001 return false;
3002
3003 set_work_pool_and_clear_pending(work, get_work_pool_id(work));
3004 local_irq_restore(flags);
3005 return ret;
3006}
3007
3008/*
3009 * See cancel_delayed_work()
3010 */
3011bool cancel_work(struct work_struct *work)
3012{
3013 return __cancel_work(work, false);
3014}
3015
3016/**
3017 * cancel_delayed_work - cancel a delayed work
3018 * @dwork: delayed_work to cancel
3019 *
3020 * Kill off a pending delayed_work.
3021 *
3022 * Return: %true if @dwork was pending and canceled; %false if it wasn't
3023 * pending.
3024 *
3025 * Note:
3026 * The work callback function may still be running on return, unless
3027 * it returns %true and the work doesn't re-arm itself. Explicitly flush or
3028 * use cancel_delayed_work_sync() to wait on it.
3029 *
3030 * This function is safe to call from any context including IRQ handler.
3031 */
3032bool cancel_delayed_work(struct delayed_work *dwork)
3033{
3034 return __cancel_work(&dwork->work, true);
3035}
3036EXPORT_SYMBOL(cancel_delayed_work);
3037
3038/**
3039 * cancel_delayed_work_sync - cancel a delayed work and wait for it to finish
3040 * @dwork: the delayed work cancel
3041 *
3042 * This is cancel_work_sync() for delayed works.
3043 *
3044 * Return:
3045 * %true if @dwork was pending, %false otherwise.
3046 */
3047bool cancel_delayed_work_sync(struct delayed_work *dwork)
3048{
3049 return __cancel_work_timer(&dwork->work, true);
3050}
3051EXPORT_SYMBOL(cancel_delayed_work_sync);
3052
3053/**
3054 * schedule_on_each_cpu - execute a function synchronously on each online CPU
3055 * @func: the function to call
3056 *
3057 * schedule_on_each_cpu() executes @func on each online CPU using the
3058 * system workqueue and blocks until all CPUs have completed.
3059 * schedule_on_each_cpu() is very slow.
3060 *
3061 * Return:
3062 * 0 on success, -errno on failure.
3063 */
3064int schedule_on_each_cpu(work_func_t func)
3065{
3066 int cpu;
3067 struct work_struct __percpu *works;
3068
3069 works = alloc_percpu(struct work_struct);
3070 if (!works)
3071 return -ENOMEM;
3072
3073 get_online_cpus();
3074
3075 for_each_online_cpu(cpu) {
3076 struct work_struct *work = per_cpu_ptr(works, cpu);
3077
3078 INIT_WORK(work, func);
3079 schedule_work_on(cpu, work);
3080 }
3081
3082 for_each_online_cpu(cpu)
3083 flush_work(per_cpu_ptr(works, cpu));
3084
3085 put_online_cpus();
3086 free_percpu(works);
3087 return 0;
3088}
3089
3090/**
3091 * execute_in_process_context - reliably execute the routine with user context
3092 * @fn: the function to execute
3093 * @ew: guaranteed storage for the execute work structure (must
3094 * be available when the work executes)
3095 *
3096 * Executes the function immediately if process context is available,
3097 * otherwise schedules the function for delayed execution.
3098 *
3099 * Return: 0 - function was executed
3100 * 1 - function was scheduled for execution
3101 */
3102int execute_in_process_context(work_func_t fn, struct execute_work *ew)
3103{
3104 if (!in_interrupt()) {
3105 fn(&ew->work);
3106 return 0;
3107 }
3108
3109 INIT_WORK(&ew->work, fn);
3110 schedule_work(&ew->work);
3111
3112 return 1;
3113}
3114EXPORT_SYMBOL_GPL(execute_in_process_context);
3115
3116/**
3117 * free_workqueue_attrs - free a workqueue_attrs
3118 * @attrs: workqueue_attrs to free
3119 *
3120 * Undo alloc_workqueue_attrs().
3121 */
3122void free_workqueue_attrs(struct workqueue_attrs *attrs)
3123{
3124 if (attrs) {
3125 free_cpumask_var(attrs->cpumask);
3126 kfree(attrs);
3127 }
3128}
3129
3130/**
3131 * alloc_workqueue_attrs - allocate a workqueue_attrs
3132 * @gfp_mask: allocation mask to use
3133 *
3134 * Allocate a new workqueue_attrs, initialize with default settings and
3135 * return it.
3136 *
3137 * Return: The allocated new workqueue_attr on success. %NULL on failure.
3138 */
3139struct workqueue_attrs *alloc_workqueue_attrs(gfp_t gfp_mask)
3140{
3141 struct workqueue_attrs *attrs;
3142
3143 attrs = kzalloc(sizeof(*attrs), gfp_mask);
3144 if (!attrs)
3145 goto fail;
3146 if (!alloc_cpumask_var(&attrs->cpumask, gfp_mask))
3147 goto fail;
3148
3149 cpumask_copy(attrs->cpumask, cpu_possible_mask);
3150 return attrs;
3151fail:
3152 free_workqueue_attrs(attrs);
3153 return NULL;
3154}
3155
3156static void copy_workqueue_attrs(struct workqueue_attrs *to,
3157 const struct workqueue_attrs *from)
3158{
3159 to->nice = from->nice;
3160 cpumask_copy(to->cpumask, from->cpumask);
3161 /*
3162 * Unlike hash and equality test, this function doesn't ignore
3163 * ->no_numa as it is used for both pool and wq attrs. Instead,
3164 * get_unbound_pool() explicitly clears ->no_numa after copying.
3165 */
3166 to->no_numa = from->no_numa;
3167}
3168
3169/* hash value of the content of @attr */
3170static u32 wqattrs_hash(const struct workqueue_attrs *attrs)
3171{
3172 u32 hash = 0;
3173
3174 hash = jhash_1word(attrs->nice, hash);
3175 hash = jhash(cpumask_bits(attrs->cpumask),
3176 BITS_TO_LONGS(nr_cpumask_bits) * sizeof(long), hash);
3177 return hash;
3178}
3179
3180/* content equality test */
3181static bool wqattrs_equal(const struct workqueue_attrs *a,
3182 const struct workqueue_attrs *b)
3183{
3184 if (a->nice != b->nice)
3185 return false;
3186 if (!cpumask_equal(a->cpumask, b->cpumask))
3187 return false;
3188 return true;
3189}
3190
3191/**
3192 * init_worker_pool - initialize a newly zalloc'd worker_pool
3193 * @pool: worker_pool to initialize
3194 *
3195 * Initialize a newly zalloc'd @pool. It also allocates @pool->attrs.
3196 *
3197 * Return: 0 on success, -errno on failure. Even on failure, all fields
3198 * inside @pool proper are initialized and put_unbound_pool() can be called
3199 * on @pool safely to release it.
3200 */
3201static int init_worker_pool(struct worker_pool *pool)
3202{
3203 spin_lock_init(&pool->lock);
3204 pool->id = -1;
3205 pool->cpu = -1;
3206 pool->node = NUMA_NO_NODE;
3207 pool->flags |= POOL_DISASSOCIATED;
3208 pool->watchdog_ts = jiffies;
3209 INIT_LIST_HEAD(&pool->worklist);
3210 INIT_LIST_HEAD(&pool->idle_list);
3211 hash_init(pool->busy_hash);
3212
3213 init_timer_deferrable(&pool->idle_timer);
3214 pool->idle_timer.function = idle_worker_timeout;
3215 pool->idle_timer.data = (unsigned long)pool;
3216
3217 setup_timer(&pool->mayday_timer, pool_mayday_timeout,
3218 (unsigned long)pool);
3219
3220 mutex_init(&pool->manager_arb);
3221 mutex_init(&pool->attach_mutex);
3222 INIT_LIST_HEAD(&pool->workers);
3223
3224 ida_init(&pool->worker_ida);
3225 INIT_HLIST_NODE(&pool->hash_node);
3226 pool->refcnt = 1;
3227
3228 /* shouldn't fail above this point */
3229 pool->attrs = alloc_workqueue_attrs(GFP_KERNEL);
3230 if (!pool->attrs)
3231 return -ENOMEM;
3232 return 0;
3233}
3234
3235static void rcu_free_wq(struct rcu_head *rcu)
3236{
3237 struct workqueue_struct *wq =
3238 container_of(rcu, struct workqueue_struct, rcu);
3239
3240 if (!(wq->flags & WQ_UNBOUND))
3241 free_percpu(wq->cpu_pwqs);
3242 else
3243 free_workqueue_attrs(wq->unbound_attrs);
3244
3245 kfree(wq->rescuer);
3246 kfree(wq);
3247}
3248
3249static void rcu_free_pool(struct rcu_head *rcu)
3250{
3251 struct worker_pool *pool = container_of(rcu, struct worker_pool, rcu);
3252
3253 ida_destroy(&pool->worker_ida);
3254 free_workqueue_attrs(pool->attrs);
3255 kfree(pool);
3256}
3257
3258/**
3259 * put_unbound_pool - put a worker_pool
3260 * @pool: worker_pool to put
3261 *
3262 * Put @pool. If its refcnt reaches zero, it gets destroyed in sched-RCU
3263 * safe manner. get_unbound_pool() calls this function on its failure path
3264 * and this function should be able to release pools which went through,
3265 * successfully or not, init_worker_pool().
3266 *
3267 * Should be called with wq_pool_mutex held.
3268 */
3269static void put_unbound_pool(struct worker_pool *pool)
3270{
3271 DECLARE_COMPLETION_ONSTACK(detach_completion);
3272 struct worker *worker;
3273
3274 lockdep_assert_held(&wq_pool_mutex);
3275
3276 if (--pool->refcnt)
3277 return;
3278
3279 /* sanity checks */
3280 if (WARN_ON(!(pool->cpu < 0)) ||
3281 WARN_ON(!list_empty(&pool->worklist)))
3282 return;
3283
3284 /* release id and unhash */
3285 if (pool->id >= 0)
3286 idr_remove(&worker_pool_idr, pool->id);
3287 hash_del(&pool->hash_node);
3288
3289 /*
3290 * Become the manager and destroy all workers. Grabbing
3291 * manager_arb prevents @pool's workers from blocking on
3292 * attach_mutex.
3293 */
3294 mutex_lock(&pool->manager_arb);
3295
3296 spin_lock_irq(&pool->lock);
3297 while ((worker = first_idle_worker(pool)))
3298 destroy_worker(worker);
3299 WARN_ON(pool->nr_workers || pool->nr_idle);
3300 spin_unlock_irq(&pool->lock);
3301
3302 mutex_lock(&pool->attach_mutex);
3303 if (!list_empty(&pool->workers))
3304 pool->detach_completion = &detach_completion;
3305 mutex_unlock(&pool->attach_mutex);
3306
3307 if (pool->detach_completion)
3308 wait_for_completion(pool->detach_completion);
3309
3310 mutex_unlock(&pool->manager_arb);
3311
3312 /* shut down the timers */
3313 del_timer_sync(&pool->idle_timer);
3314 del_timer_sync(&pool->mayday_timer);
3315
3316 /* sched-RCU protected to allow dereferences from get_work_pool() */
3317 call_rcu_sched(&pool->rcu, rcu_free_pool);
3318}
3319
3320/**
3321 * get_unbound_pool - get a worker_pool with the specified attributes
3322 * @attrs: the attributes of the worker_pool to get
3323 *
3324 * Obtain a worker_pool which has the same attributes as @attrs, bump the
3325 * reference count and return it. If there already is a matching
3326 * worker_pool, it will be used; otherwise, this function attempts to
3327 * create a new one.
3328 *
3329 * Should be called with wq_pool_mutex held.
3330 *
3331 * Return: On success, a worker_pool with the same attributes as @attrs.
3332 * On failure, %NULL.
3333 */
3334static struct worker_pool *get_unbound_pool(const struct workqueue_attrs *attrs)
3335{
3336 u32 hash = wqattrs_hash(attrs);
3337 struct worker_pool *pool;
3338 int node;
3339 int target_node = NUMA_NO_NODE;
3340
3341 lockdep_assert_held(&wq_pool_mutex);
3342
3343 /* do we already have a matching pool? */
3344 hash_for_each_possible(unbound_pool_hash, pool, hash_node, hash) {
3345 if (wqattrs_equal(pool->attrs, attrs)) {
3346 pool->refcnt++;
3347 return pool;
3348 }
3349 }
3350
3351 /* if cpumask is contained inside a NUMA node, we belong to that node */
3352 if (wq_numa_enabled) {
3353 for_each_node(node) {
3354 if (cpumask_subset(attrs->cpumask,
3355 wq_numa_possible_cpumask[node])) {
3356 target_node = node;
3357 break;
3358 }
3359 }
3360 }
3361
3362 /* nope, create a new one */
3363 pool = kzalloc_node(sizeof(*pool), GFP_KERNEL, target_node);
3364 if (!pool || init_worker_pool(pool) < 0)
3365 goto fail;
3366
3367 lockdep_set_subclass(&pool->lock, 1); /* see put_pwq() */
3368 copy_workqueue_attrs(pool->attrs, attrs);
3369 pool->node = target_node;
3370
3371 /*
3372 * no_numa isn't a worker_pool attribute, always clear it. See
3373 * 'struct workqueue_attrs' comments for detail.
3374 */
3375 pool->attrs->no_numa = false;
3376
3377 if (worker_pool_assign_id(pool) < 0)
3378 goto fail;
3379
3380 /* create and start the initial worker */
3381 if (wq_online && !create_worker(pool))
3382 goto fail;
3383
3384 /* install */
3385 hash_add(unbound_pool_hash, &pool->hash_node, hash);
3386
3387 return pool;
3388fail:
3389 if (pool)
3390 put_unbound_pool(pool);
3391 return NULL;
3392}
3393
3394static void rcu_free_pwq(struct rcu_head *rcu)
3395{
3396 kmem_cache_free(pwq_cache,
3397 container_of(rcu, struct pool_workqueue, rcu));
3398}
3399
3400/*
3401 * Scheduled on system_wq by put_pwq() when an unbound pwq hits zero refcnt
3402 * and needs to be destroyed.
3403 */
3404static void pwq_unbound_release_workfn(struct work_struct *work)
3405{
3406 struct pool_workqueue *pwq = container_of(work, struct pool_workqueue,
3407 unbound_release_work);
3408 struct workqueue_struct *wq = pwq->wq;
3409 struct worker_pool *pool = pwq->pool;
3410 bool is_last;
3411
3412 if (WARN_ON_ONCE(!(wq->flags & WQ_UNBOUND)))
3413 return;
3414
3415 mutex_lock(&wq->mutex);
3416 list_del_rcu(&pwq->pwqs_node);
3417 is_last = list_empty(&wq->pwqs);
3418 mutex_unlock(&wq->mutex);
3419
3420 mutex_lock(&wq_pool_mutex);
3421 put_unbound_pool(pool);
3422 mutex_unlock(&wq_pool_mutex);
3423
3424 call_rcu_sched(&pwq->rcu, rcu_free_pwq);
3425
3426 /*
3427 * If we're the last pwq going away, @wq is already dead and no one
3428 * is gonna access it anymore. Schedule RCU free.
3429 */
3430 if (is_last)
3431 call_rcu_sched(&wq->rcu, rcu_free_wq);
3432}
3433
3434/**
3435 * pwq_adjust_max_active - update a pwq's max_active to the current setting
3436 * @pwq: target pool_workqueue
3437 *
3438 * If @pwq isn't freezing, set @pwq->max_active to the associated
3439 * workqueue's saved_max_active and activate delayed work items
3440 * accordingly. If @pwq is freezing, clear @pwq->max_active to zero.
3441 */
3442static void pwq_adjust_max_active(struct pool_workqueue *pwq)
3443{
3444 struct workqueue_struct *wq = pwq->wq;
3445 bool freezable = wq->flags & WQ_FREEZABLE;
3446 unsigned long flags;
3447
3448 /* for @wq->saved_max_active */
3449 lockdep_assert_held(&wq->mutex);
3450
3451 /* fast exit for non-freezable wqs */
3452 if (!freezable && pwq->max_active == wq->saved_max_active)
3453 return;
3454
3455 /* this function can be called during early boot w/ irq disabled */
3456 spin_lock_irqsave(&pwq->pool->lock, flags);
3457
3458 /*
3459 * During [un]freezing, the caller is responsible for ensuring that
3460 * this function is called at least once after @workqueue_freezing
3461 * is updated and visible.
3462 */
3463 if (!freezable || !workqueue_freezing) {
3464 pwq->max_active = wq->saved_max_active;
3465
3466 while (!list_empty(&pwq->delayed_works) &&
3467 pwq->nr_active < pwq->max_active)
3468 pwq_activate_first_delayed(pwq);
3469
3470 /*
3471 * Need to kick a worker after thawed or an unbound wq's
3472 * max_active is bumped. It's a slow path. Do it always.
3473 */
3474 wake_up_worker(pwq->pool);
3475 } else {
3476 pwq->max_active = 0;
3477 }
3478
3479 spin_unlock_irqrestore(&pwq->pool->lock, flags);
3480}
3481
3482/* initialize newly alloced @pwq which is associated with @wq and @pool */
3483static void init_pwq(struct pool_workqueue *pwq, struct workqueue_struct *wq,
3484 struct worker_pool *pool)
3485{
3486 BUG_ON((unsigned long)pwq & WORK_STRUCT_FLAG_MASK);
3487
3488 memset(pwq, 0, sizeof(*pwq));
3489
3490 pwq->pool = pool;
3491 pwq->wq = wq;
3492 pwq->flush_color = -1;
3493 pwq->refcnt = 1;
3494 INIT_LIST_HEAD(&pwq->delayed_works);
3495 INIT_LIST_HEAD(&pwq->pwqs_node);
3496 INIT_LIST_HEAD(&pwq->mayday_node);
3497 INIT_WORK(&pwq->unbound_release_work, pwq_unbound_release_workfn);
3498}
3499
3500/* sync @pwq with the current state of its associated wq and link it */
3501static void link_pwq(struct pool_workqueue *pwq)
3502{
3503 struct workqueue_struct *wq = pwq->wq;
3504
3505 lockdep_assert_held(&wq->mutex);
3506
3507 /* may be called multiple times, ignore if already linked */
3508 if (!list_empty(&pwq->pwqs_node))
3509 return;
3510
3511 /* set the matching work_color */
3512 pwq->work_color = wq->work_color;
3513
3514 /* sync max_active to the current setting */
3515 pwq_adjust_max_active(pwq);
3516
3517 /* link in @pwq */
3518 list_add_rcu(&pwq->pwqs_node, &wq->pwqs);
3519}
3520
3521/* obtain a pool matching @attr and create a pwq associating the pool and @wq */
3522static struct pool_workqueue *alloc_unbound_pwq(struct workqueue_struct *wq,
3523 const struct workqueue_attrs *attrs)
3524{
3525 struct worker_pool *pool;
3526 struct pool_workqueue *pwq;
3527
3528 lockdep_assert_held(&wq_pool_mutex);
3529
3530 pool = get_unbound_pool(attrs);
3531 if (!pool)
3532 return NULL;
3533
3534 pwq = kmem_cache_alloc_node(pwq_cache, GFP_KERNEL, pool->node);
3535 if (!pwq) {
3536 put_unbound_pool(pool);
3537 return NULL;
3538 }
3539
3540 init_pwq(pwq, wq, pool);
3541 return pwq;
3542}
3543
3544/**
3545 * wq_calc_node_cpumask - calculate a wq_attrs' cpumask for the specified node
3546 * @attrs: the wq_attrs of the default pwq of the target workqueue
3547 * @node: the target NUMA node
3548 * @cpu_going_down: if >= 0, the CPU to consider as offline
3549 * @cpumask: outarg, the resulting cpumask
3550 *
3551 * Calculate the cpumask a workqueue with @attrs should use on @node. If
3552 * @cpu_going_down is >= 0, that cpu is considered offline during
3553 * calculation. The result is stored in @cpumask.
3554 *
3555 * If NUMA affinity is not enabled, @attrs->cpumask is always used. If
3556 * enabled and @node has online CPUs requested by @attrs, the returned
3557 * cpumask is the intersection of the possible CPUs of @node and
3558 * @attrs->cpumask.
3559 *
3560 * The caller is responsible for ensuring that the cpumask of @node stays
3561 * stable.
3562 *
3563 * Return: %true if the resulting @cpumask is different from @attrs->cpumask,
3564 * %false if equal.
3565 */
3566static bool wq_calc_node_cpumask(const struct workqueue_attrs *attrs, int node,
3567 int cpu_going_down, cpumask_t *cpumask)
3568{
3569 if (!wq_numa_enabled || attrs->no_numa)
3570 goto use_dfl;
3571
3572 /* does @node have any online CPUs @attrs wants? */
3573 cpumask_and(cpumask, cpumask_of_node(node), attrs->cpumask);
3574 if (cpu_going_down >= 0)
3575 cpumask_clear_cpu(cpu_going_down, cpumask);
3576
3577 if (cpumask_empty(cpumask))
3578 goto use_dfl;
3579
3580 /* yeap, return possible CPUs in @node that @attrs wants */
3581 cpumask_and(cpumask, attrs->cpumask, wq_numa_possible_cpumask[node]);
3582 return !cpumask_equal(cpumask, attrs->cpumask);
3583
3584use_dfl:
3585 cpumask_copy(cpumask, attrs->cpumask);
3586 return false;
3587}
3588
3589/* install @pwq into @wq's numa_pwq_tbl[] for @node and return the old pwq */
3590static struct pool_workqueue *numa_pwq_tbl_install(struct workqueue_struct *wq,
3591 int node,
3592 struct pool_workqueue *pwq)
3593{
3594 struct pool_workqueue *old_pwq;
3595
3596 lockdep_assert_held(&wq_pool_mutex);
3597 lockdep_assert_held(&wq->mutex);
3598
3599 /* link_pwq() can handle duplicate calls */
3600 link_pwq(pwq);
3601
3602 old_pwq = rcu_access_pointer(wq->numa_pwq_tbl[node]);
3603 rcu_assign_pointer(wq->numa_pwq_tbl[node], pwq);
3604 return old_pwq;
3605}
3606
3607/* context to store the prepared attrs & pwqs before applying */
3608struct apply_wqattrs_ctx {
3609 struct workqueue_struct *wq; /* target workqueue */
3610 struct workqueue_attrs *attrs; /* attrs to apply */
3611 struct list_head list; /* queued for batching commit */
3612 struct pool_workqueue *dfl_pwq;
3613 struct pool_workqueue *pwq_tbl[];
3614};
3615
3616/* free the resources after success or abort */
3617static void apply_wqattrs_cleanup(struct apply_wqattrs_ctx *ctx)
3618{
3619 if (ctx) {
3620 int node;
3621
3622 for_each_node(node)
3623 put_pwq_unlocked(ctx->pwq_tbl[node]);
3624 put_pwq_unlocked(ctx->dfl_pwq);
3625
3626 free_workqueue_attrs(ctx->attrs);
3627
3628 kfree(ctx);
3629 }
3630}
3631
3632/* allocate the attrs and pwqs for later installation */
3633static struct apply_wqattrs_ctx *
3634apply_wqattrs_prepare(struct workqueue_struct *wq,
3635 const struct workqueue_attrs *attrs)
3636{
3637 struct apply_wqattrs_ctx *ctx;
3638 struct workqueue_attrs *new_attrs, *tmp_attrs;
3639 int node;
3640
3641 lockdep_assert_held(&wq_pool_mutex);
3642
3643 ctx = kzalloc(sizeof(*ctx) + nr_node_ids * sizeof(ctx->pwq_tbl[0]),
3644 GFP_KERNEL);
3645
3646 new_attrs = alloc_workqueue_attrs(GFP_KERNEL);
3647 tmp_attrs = alloc_workqueue_attrs(GFP_KERNEL);
3648 if (!ctx || !new_attrs || !tmp_attrs)
3649 goto out_free;
3650
3651 /*
3652 * Calculate the attrs of the default pwq.
3653 * If the user configured cpumask doesn't overlap with the
3654 * wq_unbound_cpumask, we fallback to the wq_unbound_cpumask.
3655 */
3656 copy_workqueue_attrs(new_attrs, attrs);
3657 cpumask_and(new_attrs->cpumask, new_attrs->cpumask, wq_unbound_cpumask);
3658 if (unlikely(cpumask_empty(new_attrs->cpumask)))
3659 cpumask_copy(new_attrs->cpumask, wq_unbound_cpumask);
3660
3661 /*
3662 * We may create multiple pwqs with differing cpumasks. Make a
3663 * copy of @new_attrs which will be modified and used to obtain
3664 * pools.
3665 */
3666 copy_workqueue_attrs(tmp_attrs, new_attrs);
3667
3668 /*
3669 * If something goes wrong during CPU up/down, we'll fall back to
3670 * the default pwq covering whole @attrs->cpumask. Always create
3671 * it even if we don't use it immediately.
3672 */
3673 ctx->dfl_pwq = alloc_unbound_pwq(wq, new_attrs);
3674 if (!ctx->dfl_pwq)
3675 goto out_free;
3676
3677 for_each_node(node) {
3678 if (wq_calc_node_cpumask(new_attrs, node, -1, tmp_attrs->cpumask)) {
3679 ctx->pwq_tbl[node] = alloc_unbound_pwq(wq, tmp_attrs);
3680 if (!ctx->pwq_tbl[node])
3681 goto out_free;
3682 } else {
3683 ctx->dfl_pwq->refcnt++;
3684 ctx->pwq_tbl[node] = ctx->dfl_pwq;
3685 }
3686 }
3687
3688 /* save the user configured attrs and sanitize it. */
3689 copy_workqueue_attrs(new_attrs, attrs);
3690 cpumask_and(new_attrs->cpumask, new_attrs->cpumask, cpu_possible_mask);
3691 ctx->attrs = new_attrs;
3692
3693 ctx->wq = wq;
3694 free_workqueue_attrs(tmp_attrs);
3695 return ctx;
3696
3697out_free:
3698 free_workqueue_attrs(tmp_attrs);
3699 free_workqueue_attrs(new_attrs);
3700 apply_wqattrs_cleanup(ctx);
3701 return NULL;
3702}
3703
3704/* set attrs and install prepared pwqs, @ctx points to old pwqs on return */
3705static void apply_wqattrs_commit(struct apply_wqattrs_ctx *ctx)
3706{
3707 int node;
3708
3709 /* all pwqs have been created successfully, let's install'em */
3710 mutex_lock(&ctx->wq->mutex);
3711
3712 copy_workqueue_attrs(ctx->wq->unbound_attrs, ctx->attrs);
3713
3714 /* save the previous pwq and install the new one */
3715 for_each_node(node)
3716 ctx->pwq_tbl[node] = numa_pwq_tbl_install(ctx->wq, node,
3717 ctx->pwq_tbl[node]);
3718
3719 /* @dfl_pwq might not have been used, ensure it's linked */
3720 link_pwq(ctx->dfl_pwq);
3721 swap(ctx->wq->dfl_pwq, ctx->dfl_pwq);
3722
3723 mutex_unlock(&ctx->wq->mutex);
3724}
3725
3726static void apply_wqattrs_lock(void)
3727{
3728 /* CPUs should stay stable across pwq creations and installations */
3729 get_online_cpus();
3730 mutex_lock(&wq_pool_mutex);
3731}
3732
3733static void apply_wqattrs_unlock(void)
3734{
3735 mutex_unlock(&wq_pool_mutex);
3736 put_online_cpus();
3737}
3738
3739static int apply_workqueue_attrs_locked(struct workqueue_struct *wq,
3740 const struct workqueue_attrs *attrs)
3741{
3742 struct apply_wqattrs_ctx *ctx;
3743
3744 /* only unbound workqueues can change attributes */
3745 if (WARN_ON(!(wq->flags & WQ_UNBOUND)))
3746 return -EINVAL;
3747
3748 /* creating multiple pwqs breaks ordering guarantee */
3749 if (WARN_ON((wq->flags & __WQ_ORDERED) && !list_empty(&wq->pwqs)))
3750 return -EINVAL;
3751
3752 ctx = apply_wqattrs_prepare(wq, attrs);
3753 if (!ctx)
3754 return -ENOMEM;
3755
3756 /* the ctx has been prepared successfully, let's commit it */
3757 apply_wqattrs_commit(ctx);
3758 apply_wqattrs_cleanup(ctx);
3759
3760 return 0;
3761}
3762
3763/**
3764 * apply_workqueue_attrs - apply new workqueue_attrs to an unbound workqueue
3765 * @wq: the target workqueue
3766 * @attrs: the workqueue_attrs to apply, allocated with alloc_workqueue_attrs()
3767 *
3768 * Apply @attrs to an unbound workqueue @wq. Unless disabled, on NUMA
3769 * machines, this function maps a separate pwq to each NUMA node with
3770 * possibles CPUs in @attrs->cpumask so that work items are affine to the
3771 * NUMA node it was issued on. Older pwqs are released as in-flight work
3772 * items finish. Note that a work item which repeatedly requeues itself
3773 * back-to-back will stay on its current pwq.
3774 *
3775 * Performs GFP_KERNEL allocations.
3776 *
3777 * Return: 0 on success and -errno on failure.
3778 */
3779int apply_workqueue_attrs(struct workqueue_struct *wq,
3780 const struct workqueue_attrs *attrs)
3781{
3782 int ret;
3783
3784 apply_wqattrs_lock();
3785 ret = apply_workqueue_attrs_locked(wq, attrs);
3786 apply_wqattrs_unlock();
3787
3788 return ret;
3789}
3790
3791/**
3792 * wq_update_unbound_numa - update NUMA affinity of a wq for CPU hot[un]plug
3793 * @wq: the target workqueue
3794 * @cpu: the CPU coming up or going down
3795 * @online: whether @cpu is coming up or going down
3796 *
3797 * This function is to be called from %CPU_DOWN_PREPARE, %CPU_ONLINE and
3798 * %CPU_DOWN_FAILED. @cpu is being hot[un]plugged, update NUMA affinity of
3799 * @wq accordingly.
3800 *
3801 * If NUMA affinity can't be adjusted due to memory allocation failure, it
3802 * falls back to @wq->dfl_pwq which may not be optimal but is always
3803 * correct.
3804 *
3805 * Note that when the last allowed CPU of a NUMA node goes offline for a
3806 * workqueue with a cpumask spanning multiple nodes, the workers which were
3807 * already executing the work items for the workqueue will lose their CPU
3808 * affinity and may execute on any CPU. This is similar to how per-cpu
3809 * workqueues behave on CPU_DOWN. If a workqueue user wants strict
3810 * affinity, it's the user's responsibility to flush the work item from
3811 * CPU_DOWN_PREPARE.
3812 */
3813static void wq_update_unbound_numa(struct workqueue_struct *wq, int cpu,
3814 bool online)
3815{
3816 int node = cpu_to_node(cpu);
3817 int cpu_off = online ? -1 : cpu;
3818 struct pool_workqueue *old_pwq = NULL, *pwq;
3819 struct workqueue_attrs *target_attrs;
3820 cpumask_t *cpumask;
3821
3822 lockdep_assert_held(&wq_pool_mutex);
3823
3824 if (!wq_numa_enabled || !(wq->flags & WQ_UNBOUND) ||
3825 wq->unbound_attrs->no_numa)
3826 return;
3827
3828 /*
3829 * We don't wanna alloc/free wq_attrs for each wq for each CPU.
3830 * Let's use a preallocated one. The following buf is protected by
3831 * CPU hotplug exclusion.
3832 */
3833 target_attrs = wq_update_unbound_numa_attrs_buf;
3834 cpumask = target_attrs->cpumask;
3835
3836 copy_workqueue_attrs(target_attrs, wq->unbound_attrs);
3837 pwq = unbound_pwq_by_node(wq, node);
3838
3839 /*
3840 * Let's determine what needs to be done. If the target cpumask is
3841 * different from the default pwq's, we need to compare it to @pwq's
3842 * and create a new one if they don't match. If the target cpumask
3843 * equals the default pwq's, the default pwq should be used.
3844 */
3845 if (wq_calc_node_cpumask(wq->dfl_pwq->pool->attrs, node, cpu_off, cpumask)) {
3846 if (cpumask_equal(cpumask, pwq->pool->attrs->cpumask))
3847 return;
3848 } else {
3849 goto use_dfl_pwq;
3850 }
3851
3852 /* create a new pwq */
3853 pwq = alloc_unbound_pwq(wq, target_attrs);
3854 if (!pwq) {
3855 pr_warn("workqueue: allocation failed while updating NUMA affinity of \"%s\"\n",
3856 wq->name);
3857 goto use_dfl_pwq;
3858 }
3859
3860 /* Install the new pwq. */
3861 mutex_lock(&wq->mutex);
3862 old_pwq = numa_pwq_tbl_install(wq, node, pwq);
3863 goto out_unlock;
3864
3865use_dfl_pwq:
3866 mutex_lock(&wq->mutex);
3867 spin_lock_irq(&wq->dfl_pwq->pool->lock);
3868 get_pwq(wq->dfl_pwq);
3869 spin_unlock_irq(&wq->dfl_pwq->pool->lock);
3870 old_pwq = numa_pwq_tbl_install(wq, node, wq->dfl_pwq);
3871out_unlock:
3872 mutex_unlock(&wq->mutex);
3873 put_pwq_unlocked(old_pwq);
3874}
3875
3876static int alloc_and_link_pwqs(struct workqueue_struct *wq)
3877{
3878 bool highpri = wq->flags & WQ_HIGHPRI;
3879 int cpu, ret;
3880
3881 if (!(wq->flags & WQ_UNBOUND)) {
3882 wq->cpu_pwqs = alloc_percpu(struct pool_workqueue);
3883 if (!wq->cpu_pwqs)
3884 return -ENOMEM;
3885
3886 for_each_possible_cpu(cpu) {
3887 struct pool_workqueue *pwq =
3888 per_cpu_ptr(wq->cpu_pwqs, cpu);
3889 struct worker_pool *cpu_pools =
3890 per_cpu(cpu_worker_pools, cpu);
3891
3892 init_pwq(pwq, wq, &cpu_pools[highpri]);
3893
3894 mutex_lock(&wq->mutex);
3895 link_pwq(pwq);
3896 mutex_unlock(&wq->mutex);
3897 }
3898 return 0;
3899 } else if (wq->flags & __WQ_ORDERED) {
3900 ret = apply_workqueue_attrs(wq, ordered_wq_attrs[highpri]);
3901 /* there should only be single pwq for ordering guarantee */
3902 WARN(!ret && (wq->pwqs.next != &wq->dfl_pwq->pwqs_node ||
3903 wq->pwqs.prev != &wq->dfl_pwq->pwqs_node),
3904 "ordering guarantee broken for workqueue %s\n", wq->name);
3905 return ret;
3906 } else {
3907 return apply_workqueue_attrs(wq, unbound_std_wq_attrs[highpri]);
3908 }
3909}
3910
3911static int wq_clamp_max_active(int max_active, unsigned int flags,
3912 const char *name)
3913{
3914 int lim = flags & WQ_UNBOUND ? WQ_UNBOUND_MAX_ACTIVE : WQ_MAX_ACTIVE;
3915
3916 if (max_active < 1 || max_active > lim)
3917 pr_warn("workqueue: max_active %d requested for %s is out of range, clamping between %d and %d\n",
3918 max_active, name, 1, lim);
3919
3920 return clamp_val(max_active, 1, lim);
3921}
3922
3923struct workqueue_struct *__alloc_workqueue_key(const char *fmt,
3924 unsigned int flags,
3925 int max_active,
3926 struct lock_class_key *key,
3927 const char *lock_name, ...)
3928{
3929 size_t tbl_size = 0;
3930 va_list args;
3931 struct workqueue_struct *wq;
3932 struct pool_workqueue *pwq;
3933
3934 /* see the comment above the definition of WQ_POWER_EFFICIENT */
3935 if ((flags & WQ_POWER_EFFICIENT) && wq_power_efficient)
3936 flags |= WQ_UNBOUND;
3937
3938 /* allocate wq and format name */
3939 if (flags & WQ_UNBOUND)
3940 tbl_size = nr_node_ids * sizeof(wq->numa_pwq_tbl[0]);
3941
3942 wq = kzalloc(sizeof(*wq) + tbl_size, GFP_KERNEL);
3943 if (!wq)
3944 return NULL;
3945
3946 if (flags & WQ_UNBOUND) {
3947 wq->unbound_attrs = alloc_workqueue_attrs(GFP_KERNEL);
3948 if (!wq->unbound_attrs)
3949 goto err_free_wq;
3950 }
3951
3952 va_start(args, lock_name);
3953 vsnprintf(wq->name, sizeof(wq->name), fmt, args);
3954 va_end(args);
3955
3956 max_active = max_active ?: WQ_DFL_ACTIVE;
3957 max_active = wq_clamp_max_active(max_active, flags, wq->name);
3958
3959 /* init wq */
3960 wq->flags = flags;
3961 wq->saved_max_active = max_active;
3962 mutex_init(&wq->mutex);
3963 atomic_set(&wq->nr_pwqs_to_flush, 0);
3964 INIT_LIST_HEAD(&wq->pwqs);
3965 INIT_LIST_HEAD(&wq->flusher_queue);
3966 INIT_LIST_HEAD(&wq->flusher_overflow);
3967 INIT_LIST_HEAD(&wq->maydays);
3968
3969 lockdep_init_map(&wq->lockdep_map, lock_name, key, 0);
3970 INIT_LIST_HEAD(&wq->list);
3971
3972 if (alloc_and_link_pwqs(wq) < 0)
3973 goto err_free_wq;
3974
3975 /*
3976 * Workqueues which may be used during memory reclaim should
3977 * have a rescuer to guarantee forward progress.
3978 */
3979 if (flags & WQ_MEM_RECLAIM) {
3980 struct worker *rescuer;
3981
3982 rescuer = alloc_worker(NUMA_NO_NODE);
3983 if (!rescuer)
3984 goto err_destroy;
3985
3986 rescuer->rescue_wq = wq;
3987 rescuer->task = kthread_create(rescuer_thread, rescuer, "%s",
3988 wq->name);
3989 if (IS_ERR(rescuer->task)) {
3990 kfree(rescuer);
3991 goto err_destroy;
3992 }
3993
3994 wq->rescuer = rescuer;
3995 kthread_bind_mask(rescuer->task, cpu_possible_mask);
3996 wake_up_process(rescuer->task);
3997 }
3998
3999 if ((wq->flags & WQ_SYSFS) && workqueue_sysfs_register(wq))
4000 goto err_destroy;
4001
4002 /*
4003 * wq_pool_mutex protects global freeze state and workqueues list.
4004 * Grab it, adjust max_active and add the new @wq to workqueues
4005 * list.
4006 */
4007 mutex_lock(&wq_pool_mutex);
4008
4009 mutex_lock(&wq->mutex);
4010 for_each_pwq(pwq, wq)
4011 pwq_adjust_max_active(pwq);
4012 mutex_unlock(&wq->mutex);
4013
4014 list_add_tail_rcu(&wq->list, &workqueues);
4015
4016 mutex_unlock(&wq_pool_mutex);
4017
4018 return wq;
4019
4020err_free_wq:
4021 free_workqueue_attrs(wq->unbound_attrs);
4022 kfree(wq);
4023 return NULL;
4024err_destroy:
4025 destroy_workqueue(wq);
4026 return NULL;
4027}
4028EXPORT_SYMBOL_GPL(__alloc_workqueue_key);
4029
4030/**
4031 * destroy_workqueue - safely terminate a workqueue
4032 * @wq: target workqueue
4033 *
4034 * Safely destroy a workqueue. All work currently pending will be done first.
4035 */
4036void destroy_workqueue(struct workqueue_struct *wq)
4037{
4038 struct pool_workqueue *pwq;
4039 int node;
4040
4041 /* drain it before proceeding with destruction */
4042 drain_workqueue(wq);
4043
4044 /* sanity checks */
4045 mutex_lock(&wq->mutex);
4046 for_each_pwq(pwq, wq) {
4047 int i;
4048
4049 for (i = 0; i < WORK_NR_COLORS; i++) {
4050 if (WARN_ON(pwq->nr_in_flight[i])) {
4051 mutex_unlock(&wq->mutex);
4052 show_workqueue_state();
4053 return;
4054 }
4055 }
4056
4057 if (WARN_ON((pwq != wq->dfl_pwq) && (pwq->refcnt > 1)) ||
4058 WARN_ON(pwq->nr_active) ||
4059 WARN_ON(!list_empty(&pwq->delayed_works))) {
4060 mutex_unlock(&wq->mutex);
4061 show_workqueue_state();
4062 return;
4063 }
4064 }
4065 mutex_unlock(&wq->mutex);
4066
4067 /*
4068 * wq list is used to freeze wq, remove from list after
4069 * flushing is complete in case freeze races us.
4070 */
4071 mutex_lock(&wq_pool_mutex);
4072 list_del_rcu(&wq->list);
4073 mutex_unlock(&wq_pool_mutex);
4074
4075 workqueue_sysfs_unregister(wq);
4076
4077 if (wq->rescuer)
4078 kthread_stop(wq->rescuer->task);
4079
4080 if (!(wq->flags & WQ_UNBOUND)) {
4081 /*
4082 * The base ref is never dropped on per-cpu pwqs. Directly
4083 * schedule RCU free.
4084 */
4085 call_rcu_sched(&wq->rcu, rcu_free_wq);
4086 } else {
4087 /*
4088 * We're the sole accessor of @wq at this point. Directly
4089 * access numa_pwq_tbl[] and dfl_pwq to put the base refs.
4090 * @wq will be freed when the last pwq is released.
4091 */
4092 for_each_node(node) {
4093 pwq = rcu_access_pointer(wq->numa_pwq_tbl[node]);
4094 RCU_INIT_POINTER(wq->numa_pwq_tbl[node], NULL);
4095 put_pwq_unlocked(pwq);
4096 }
4097
4098 /*
4099 * Put dfl_pwq. @wq may be freed any time after dfl_pwq is
4100 * put. Don't access it afterwards.
4101 */
4102 pwq = wq->dfl_pwq;
4103 wq->dfl_pwq = NULL;
4104 put_pwq_unlocked(pwq);
4105 }
4106}
4107EXPORT_SYMBOL_GPL(destroy_workqueue);
4108
4109/**
4110 * workqueue_set_max_active - adjust max_active of a workqueue
4111 * @wq: target workqueue
4112 * @max_active: new max_active value.
4113 *
4114 * Set max_active of @wq to @max_active.
4115 *
4116 * CONTEXT:
4117 * Don't call from IRQ context.
4118 */
4119void workqueue_set_max_active(struct workqueue_struct *wq, int max_active)
4120{
4121 struct pool_workqueue *pwq;
4122
4123 /* disallow meddling with max_active for ordered workqueues */
4124 if (WARN_ON(wq->flags & __WQ_ORDERED))
4125 return;
4126
4127 max_active = wq_clamp_max_active(max_active, wq->flags, wq->name);
4128
4129 mutex_lock(&wq->mutex);
4130
4131 wq->saved_max_active = max_active;
4132
4133 for_each_pwq(pwq, wq)
4134 pwq_adjust_max_active(pwq);
4135
4136 mutex_unlock(&wq->mutex);
4137}
4138EXPORT_SYMBOL_GPL(workqueue_set_max_active);
4139
4140/**
4141 * current_is_workqueue_rescuer - is %current workqueue rescuer?
4142 *
4143 * Determine whether %current is a workqueue rescuer. Can be used from
4144 * work functions to determine whether it's being run off the rescuer task.
4145 *
4146 * Return: %true if %current is a workqueue rescuer. %false otherwise.
4147 */
4148bool current_is_workqueue_rescuer(void)
4149{
4150 struct worker *worker = current_wq_worker();
4151
4152 return worker && worker->rescue_wq;
4153}
4154
4155/**
4156 * workqueue_congested - test whether a workqueue is congested
4157 * @cpu: CPU in question
4158 * @wq: target workqueue
4159 *
4160 * Test whether @wq's cpu workqueue for @cpu is congested. There is
4161 * no synchronization around this function and the test result is
4162 * unreliable and only useful as advisory hints or for debugging.
4163 *
4164 * If @cpu is WORK_CPU_UNBOUND, the test is performed on the local CPU.
4165 * Note that both per-cpu and unbound workqueues may be associated with
4166 * multiple pool_workqueues which have separate congested states. A
4167 * workqueue being congested on one CPU doesn't mean the workqueue is also
4168 * contested on other CPUs / NUMA nodes.
4169 *
4170 * Return:
4171 * %true if congested, %false otherwise.
4172 */
4173bool workqueue_congested(int cpu, struct workqueue_struct *wq)
4174{
4175 struct pool_workqueue *pwq;
4176 bool ret;
4177
4178 rcu_read_lock_sched();
4179
4180 if (cpu == WORK_CPU_UNBOUND)
4181 cpu = smp_processor_id();
4182
4183 if (!(wq->flags & WQ_UNBOUND))
4184 pwq = per_cpu_ptr(wq->cpu_pwqs, cpu);
4185 else
4186 pwq = unbound_pwq_by_node(wq, cpu_to_node(cpu));
4187
4188 ret = !list_empty(&pwq->delayed_works);
4189 rcu_read_unlock_sched();
4190
4191 return ret;
4192}
4193EXPORT_SYMBOL_GPL(workqueue_congested);
4194
4195/**
4196 * work_busy - test whether a work is currently pending or running
4197 * @work: the work to be tested
4198 *
4199 * Test whether @work is currently pending or running. There is no
4200 * synchronization around this function and the test result is
4201 * unreliable and only useful as advisory hints or for debugging.
4202 *
4203 * Return:
4204 * OR'd bitmask of WORK_BUSY_* bits.
4205 */
4206unsigned int work_busy(struct work_struct *work)
4207{
4208 struct worker_pool *pool;
4209 unsigned long flags;
4210 unsigned int ret = 0;
4211
4212 if (work_pending(work))
4213 ret |= WORK_BUSY_PENDING;
4214
4215 local_irq_save(flags);
4216 pool = get_work_pool(work);
4217 if (pool) {
4218 spin_lock(&pool->lock);
4219 if (find_worker_executing_work(pool, work))
4220 ret |= WORK_BUSY_RUNNING;
4221 spin_unlock(&pool->lock);
4222 }
4223 local_irq_restore(flags);
4224
4225 return ret;
4226}
4227EXPORT_SYMBOL_GPL(work_busy);
4228
4229/**
4230 * set_worker_desc - set description for the current work item
4231 * @fmt: printf-style format string
4232 * @...: arguments for the format string
4233 *
4234 * This function can be called by a running work function to describe what
4235 * the work item is about. If the worker task gets dumped, this
4236 * information will be printed out together to help debugging. The
4237 * description can be at most WORKER_DESC_LEN including the trailing '\0'.
4238 */
4239void set_worker_desc(const char *fmt, ...)
4240{
4241 struct worker *worker = current_wq_worker();
4242 va_list args;
4243
4244 if (worker) {
4245 va_start(args, fmt);
4246 vsnprintf(worker->desc, sizeof(worker->desc), fmt, args);
4247 va_end(args);
4248 worker->desc_valid = true;
4249 }
4250}
4251
4252/**
4253 * print_worker_info - print out worker information and description
4254 * @log_lvl: the log level to use when printing
4255 * @task: target task
4256 *
4257 * If @task is a worker and currently executing a work item, print out the
4258 * name of the workqueue being serviced and worker description set with
4259 * set_worker_desc() by the currently executing work item.
4260 *
4261 * This function can be safely called on any task as long as the
4262 * task_struct itself is accessible. While safe, this function isn't
4263 * synchronized and may print out mixups or garbages of limited length.
4264 */
4265void print_worker_info(const char *log_lvl, struct task_struct *task)
4266{
4267 work_func_t *fn = NULL;
4268 char name[WQ_NAME_LEN] = { };
4269 char desc[WORKER_DESC_LEN] = { };
4270 struct pool_workqueue *pwq = NULL;
4271 struct workqueue_struct *wq = NULL;
4272 bool desc_valid = false;
4273 struct worker *worker;
4274
4275 if (!(task->flags & PF_WQ_WORKER))
4276 return;
4277
4278 /*
4279 * This function is called without any synchronization and @task
4280 * could be in any state. Be careful with dereferences.
4281 */
4282 worker = kthread_probe_data(task);
4283
4284 /*
4285 * Carefully copy the associated workqueue's workfn and name. Keep
4286 * the original last '\0' in case the original contains garbage.
4287 */
4288 probe_kernel_read(&fn, &worker->current_func, sizeof(fn));
4289 probe_kernel_read(&pwq, &worker->current_pwq, sizeof(pwq));
4290 probe_kernel_read(&wq, &pwq->wq, sizeof(wq));
4291 probe_kernel_read(name, wq->name, sizeof(name) - 1);
4292
4293 /* copy worker description */
4294 probe_kernel_read(&desc_valid, &worker->desc_valid, sizeof(desc_valid));
4295 if (desc_valid)
4296 probe_kernel_read(desc, worker->desc, sizeof(desc) - 1);
4297
4298 if (fn || name[0] || desc[0]) {
4299 printk("%sWorkqueue: %s %pf", log_lvl, name, fn);
4300 if (desc[0])
4301 pr_cont(" (%s)", desc);
4302 pr_cont("\n");
4303 }
4304}
4305
4306static void pr_cont_pool_info(struct worker_pool *pool)
4307{
4308 pr_cont(" cpus=%*pbl", nr_cpumask_bits, pool->attrs->cpumask);
4309 if (pool->node != NUMA_NO_NODE)
4310 pr_cont(" node=%d", pool->node);
4311 pr_cont(" flags=0x%x nice=%d", pool->flags, pool->attrs->nice);
4312}
4313
4314static void pr_cont_work(bool comma, struct work_struct *work)
4315{
4316 if (work->func == wq_barrier_func) {
4317 struct wq_barrier *barr;
4318
4319 barr = container_of(work, struct wq_barrier, work);
4320
4321 pr_cont("%s BAR(%d)", comma ? "," : "",
4322 task_pid_nr(barr->task));
4323 } else {
4324 pr_cont("%s %pf", comma ? "," : "", work->func);
4325 }
4326}
4327
4328static void show_pwq(struct pool_workqueue *pwq)
4329{
4330 struct worker_pool *pool = pwq->pool;
4331 struct work_struct *work;
4332 struct worker *worker;
4333 bool has_in_flight = false, has_pending = false;
4334 int bkt;
4335
4336 pr_info(" pwq %d:", pool->id);
4337 pr_cont_pool_info(pool);
4338
4339 pr_cont(" active=%d/%d%s\n", pwq->nr_active, pwq->max_active,
4340 !list_empty(&pwq->mayday_node) ? " MAYDAY" : "");
4341
4342 hash_for_each(pool->busy_hash, bkt, worker, hentry) {
4343 if (worker->current_pwq == pwq) {
4344 has_in_flight = true;
4345 break;
4346 }
4347 }
4348 if (has_in_flight) {
4349 bool comma = false;
4350
4351 pr_info(" in-flight:");
4352 hash_for_each(pool->busy_hash, bkt, worker, hentry) {
4353 if (worker->current_pwq != pwq)
4354 continue;
4355
4356 pr_cont("%s %d%s:%pf", comma ? "," : "",
4357 task_pid_nr(worker->task),
4358 worker == pwq->wq->rescuer ? "(RESCUER)" : "",
4359 worker->current_func);
4360 list_for_each_entry(work, &worker->scheduled, entry)
4361 pr_cont_work(false, work);
4362 comma = true;
4363 }
4364 pr_cont("\n");
4365 }
4366
4367 list_for_each_entry(work, &pool->worklist, entry) {
4368 if (get_work_pwq(work) == pwq) {
4369 has_pending = true;
4370 break;
4371 }
4372 }
4373 if (has_pending) {
4374 bool comma = false;
4375
4376 pr_info(" pending:");
4377 list_for_each_entry(work, &pool->worklist, entry) {
4378 if (get_work_pwq(work) != pwq)
4379 continue;
4380
4381 pr_cont_work(comma, work);
4382 comma = !(*work_data_bits(work) & WORK_STRUCT_LINKED);
4383 }
4384 pr_cont("\n");
4385 }
4386
4387 if (!list_empty(&pwq->delayed_works)) {
4388 bool comma = false;
4389
4390 pr_info(" delayed:");
4391 list_for_each_entry(work, &pwq->delayed_works, entry) {
4392 pr_cont_work(comma, work);
4393 comma = !(*work_data_bits(work) & WORK_STRUCT_LINKED);
4394 }
4395 pr_cont("\n");
4396 }
4397}
4398
4399/**
4400 * show_workqueue_state - dump workqueue state
4401 *
4402 * Called from a sysrq handler or try_to_freeze_tasks() and prints out
4403 * all busy workqueues and pools.
4404 */
4405void show_workqueue_state(void)
4406{
4407 struct workqueue_struct *wq;
4408 struct worker_pool *pool;
4409 unsigned long flags;
4410 int pi;
4411
4412 rcu_read_lock_sched();
4413
4414 pr_info("Showing busy workqueues and worker pools:\n");
4415
4416 list_for_each_entry_rcu(wq, &workqueues, list) {
4417 struct pool_workqueue *pwq;
4418 bool idle = true;
4419
4420 for_each_pwq(pwq, wq) {
4421 if (pwq->nr_active || !list_empty(&pwq->delayed_works)) {
4422 idle = false;
4423 break;
4424 }
4425 }
4426 if (idle)
4427 continue;
4428
4429 pr_info("workqueue %s: flags=0x%x\n", wq->name, wq->flags);
4430
4431 for_each_pwq(pwq, wq) {
4432 spin_lock_irqsave(&pwq->pool->lock, flags);
4433 if (pwq->nr_active || !list_empty(&pwq->delayed_works))
4434 show_pwq(pwq);
4435 spin_unlock_irqrestore(&pwq->pool->lock, flags);
4436 }
4437 }
4438
4439 for_each_pool(pool, pi) {
4440 struct worker *worker;
4441 bool first = true;
4442
4443 spin_lock_irqsave(&pool->lock, flags);
4444 if (pool->nr_workers == pool->nr_idle)
4445 goto next_pool;
4446
4447 pr_info("pool %d:", pool->id);
4448 pr_cont_pool_info(pool);
4449 pr_cont(" hung=%us workers=%d",
4450 jiffies_to_msecs(jiffies - pool->watchdog_ts) / 1000,
4451 pool->nr_workers);
4452 if (pool->manager)
4453 pr_cont(" manager: %d",
4454 task_pid_nr(pool->manager->task));
4455 list_for_each_entry(worker, &pool->idle_list, entry) {
4456 pr_cont(" %s%d", first ? "idle: " : "",
4457 task_pid_nr(worker->task));
4458 first = false;
4459 }
4460 pr_cont("\n");
4461 next_pool:
4462 spin_unlock_irqrestore(&pool->lock, flags);
4463 }
4464
4465 rcu_read_unlock_sched();
4466}
4467
4468/*
4469 * CPU hotplug.
4470 *
4471 * There are two challenges in supporting CPU hotplug. Firstly, there
4472 * are a lot of assumptions on strong associations among work, pwq and
4473 * pool which make migrating pending and scheduled works very
4474 * difficult to implement without impacting hot paths. Secondly,
4475 * worker pools serve mix of short, long and very long running works making
4476 * blocked draining impractical.
4477 *
4478 * This is solved by allowing the pools to be disassociated from the CPU
4479 * running as an unbound one and allowing it to be reattached later if the
4480 * cpu comes back online.
4481 */
4482
4483static void wq_unbind_fn(struct work_struct *work)
4484{
4485 int cpu = smp_processor_id();
4486 struct worker_pool *pool;
4487 struct worker *worker;
4488
4489 for_each_cpu_worker_pool(pool, cpu) {
4490 mutex_lock(&pool->attach_mutex);
4491 spin_lock_irq(&pool->lock);
4492
4493 /*
4494 * We've blocked all attach/detach operations. Make all workers
4495 * unbound and set DISASSOCIATED. Before this, all workers
4496 * except for the ones which are still executing works from
4497 * before the last CPU down must be on the cpu. After
4498 * this, they may become diasporas.
4499 */
4500 for_each_pool_worker(worker, pool)
4501 worker->flags |= WORKER_UNBOUND;
4502
4503 pool->flags |= POOL_DISASSOCIATED;
4504
4505 spin_unlock_irq(&pool->lock);
4506 mutex_unlock(&pool->attach_mutex);
4507
4508 /*
4509 * Call schedule() so that we cross rq->lock and thus can
4510 * guarantee sched callbacks see the %WORKER_UNBOUND flag.
4511 * This is necessary as scheduler callbacks may be invoked
4512 * from other cpus.
4513 */
4514 schedule();
4515
4516 /*
4517 * Sched callbacks are disabled now. Zap nr_running.
4518 * After this, nr_running stays zero and need_more_worker()
4519 * and keep_working() are always true as long as the
4520 * worklist is not empty. This pool now behaves as an
4521 * unbound (in terms of concurrency management) pool which
4522 * are served by workers tied to the pool.
4523 */
4524 atomic_set(&pool->nr_running, 0);
4525
4526 /*
4527 * With concurrency management just turned off, a busy
4528 * worker blocking could lead to lengthy stalls. Kick off
4529 * unbound chain execution of currently pending work items.
4530 */
4531 spin_lock_irq(&pool->lock);
4532 wake_up_worker(pool);
4533 spin_unlock_irq(&pool->lock);
4534 }
4535}
4536
4537/**
4538 * rebind_workers - rebind all workers of a pool to the associated CPU
4539 * @pool: pool of interest
4540 *
4541 * @pool->cpu is coming online. Rebind all workers to the CPU.
4542 */
4543static void rebind_workers(struct worker_pool *pool)
4544{
4545 struct worker *worker;
4546
4547 lockdep_assert_held(&pool->attach_mutex);
4548
4549 /*
4550 * Restore CPU affinity of all workers. As all idle workers should
4551 * be on the run-queue of the associated CPU before any local
4552 * wake-ups for concurrency management happen, restore CPU affinity
4553 * of all workers first and then clear UNBOUND. As we're called
4554 * from CPU_ONLINE, the following shouldn't fail.
4555 */
4556 for_each_pool_worker(worker, pool)
4557 WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task,
4558 pool->attrs->cpumask) < 0);
4559
4560 spin_lock_irq(&pool->lock);
4561
4562 /*
4563 * XXX: CPU hotplug notifiers are weird and can call DOWN_FAILED
4564 * w/o preceding DOWN_PREPARE. Work around it. CPU hotplug is
4565 * being reworked and this can go away in time.
4566 */
4567 if (!(pool->flags & POOL_DISASSOCIATED)) {
4568 spin_unlock_irq(&pool->lock);
4569 return;
4570 }
4571
4572 pool->flags &= ~POOL_DISASSOCIATED;
4573
4574 for_each_pool_worker(worker, pool) {
4575 unsigned int worker_flags = worker->flags;
4576
4577 /*
4578 * A bound idle worker should actually be on the runqueue
4579 * of the associated CPU for local wake-ups targeting it to
4580 * work. Kick all idle workers so that they migrate to the
4581 * associated CPU. Doing this in the same loop as
4582 * replacing UNBOUND with REBOUND is safe as no worker will
4583 * be bound before @pool->lock is released.
4584 */
4585 if (worker_flags & WORKER_IDLE)
4586 wake_up_process(worker->task);
4587
4588 /*
4589 * We want to clear UNBOUND but can't directly call
4590 * worker_clr_flags() or adjust nr_running. Atomically
4591 * replace UNBOUND with another NOT_RUNNING flag REBOUND.
4592 * @worker will clear REBOUND using worker_clr_flags() when
4593 * it initiates the next execution cycle thus restoring
4594 * concurrency management. Note that when or whether
4595 * @worker clears REBOUND doesn't affect correctness.
4596 *
4597 * ACCESS_ONCE() is necessary because @worker->flags may be
4598 * tested without holding any lock in
4599 * wq_worker_waking_up(). Without it, NOT_RUNNING test may
4600 * fail incorrectly leading to premature concurrency
4601 * management operations.
4602 */
4603 WARN_ON_ONCE(!(worker_flags & WORKER_UNBOUND));
4604 worker_flags |= WORKER_REBOUND;
4605 worker_flags &= ~WORKER_UNBOUND;
4606 ACCESS_ONCE(worker->flags) = worker_flags;
4607 }
4608
4609 spin_unlock_irq(&pool->lock);
4610}
4611
4612/**
4613 * restore_unbound_workers_cpumask - restore cpumask of unbound workers
4614 * @pool: unbound pool of interest
4615 * @cpu: the CPU which is coming up
4616 *
4617 * An unbound pool may end up with a cpumask which doesn't have any online
4618 * CPUs. When a worker of such pool get scheduled, the scheduler resets
4619 * its cpus_allowed. If @cpu is in @pool's cpumask which didn't have any
4620 * online CPU before, cpus_allowed of all its workers should be restored.
4621 */
4622static void restore_unbound_workers_cpumask(struct worker_pool *pool, int cpu)
4623{
4624 static cpumask_t cpumask;
4625 struct worker *worker;
4626
4627 lockdep_assert_held(&pool->attach_mutex);
4628
4629 /* is @cpu allowed for @pool? */
4630 if (!cpumask_test_cpu(cpu, pool->attrs->cpumask))
4631 return;
4632
4633 cpumask_and(&cpumask, pool->attrs->cpumask, cpu_online_mask);
4634
4635 /* as we're called from CPU_ONLINE, the following shouldn't fail */
4636 for_each_pool_worker(worker, pool)
4637 WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task, &cpumask) < 0);
4638}
4639
4640int workqueue_prepare_cpu(unsigned int cpu)
4641{
4642 struct worker_pool *pool;
4643
4644 for_each_cpu_worker_pool(pool, cpu) {
4645 if (pool->nr_workers)
4646 continue;
4647 if (!create_worker(pool))
4648 return -ENOMEM;
4649 }
4650 return 0;
4651}
4652
4653int workqueue_online_cpu(unsigned int cpu)
4654{
4655 struct worker_pool *pool;
4656 struct workqueue_struct *wq;
4657 int pi;
4658
4659 mutex_lock(&wq_pool_mutex);
4660
4661 for_each_pool(pool, pi) {
4662 mutex_lock(&pool->attach_mutex);
4663
4664 if (pool->cpu == cpu)
4665 rebind_workers(pool);
4666 else if (pool->cpu < 0)
4667 restore_unbound_workers_cpumask(pool, cpu);
4668
4669 mutex_unlock(&pool->attach_mutex);
4670 }
4671
4672 /* update NUMA affinity of unbound workqueues */
4673 list_for_each_entry(wq, &workqueues, list)
4674 wq_update_unbound_numa(wq, cpu, true);
4675
4676 mutex_unlock(&wq_pool_mutex);
4677 return 0;
4678}
4679
4680int workqueue_offline_cpu(unsigned int cpu)
4681{
4682 struct work_struct unbind_work;
4683 struct workqueue_struct *wq;
4684
4685 /* unbinding per-cpu workers should happen on the local CPU */
4686 INIT_WORK_ONSTACK(&unbind_work, wq_unbind_fn);
4687 queue_work_on(cpu, system_highpri_wq, &unbind_work);
4688
4689 /* update NUMA affinity of unbound workqueues */
4690 mutex_lock(&wq_pool_mutex);
4691 list_for_each_entry(wq, &workqueues, list)
4692 wq_update_unbound_numa(wq, cpu, false);
4693 mutex_unlock(&wq_pool_mutex);
4694
4695 /* wait for per-cpu unbinding to finish */
4696 flush_work(&unbind_work);
4697 destroy_work_on_stack(&unbind_work);
4698 return 0;
4699}
4700
4701#ifdef CONFIG_SMP
4702
4703struct work_for_cpu {
4704 struct work_struct work;
4705 long (*fn)(void *);
4706 void *arg;
4707 long ret;
4708};
4709
4710static void work_for_cpu_fn(struct work_struct *work)
4711{
4712 struct work_for_cpu *wfc = container_of(work, struct work_for_cpu, work);
4713
4714 wfc->ret = wfc->fn(wfc->arg);
4715}
4716
4717/**
4718 * work_on_cpu - run a function in thread context on a particular cpu
4719 * @cpu: the cpu to run on
4720 * @fn: the function to run
4721 * @arg: the function arg
4722 *
4723 * It is up to the caller to ensure that the cpu doesn't go offline.
4724 * The caller must not hold any locks which would prevent @fn from completing.
4725 *
4726 * Return: The value @fn returns.
4727 */
4728long work_on_cpu(int cpu, long (*fn)(void *), void *arg)
4729{
4730 struct work_for_cpu wfc = { .fn = fn, .arg = arg };
4731
4732 INIT_WORK_ONSTACK(&wfc.work, work_for_cpu_fn);
4733 schedule_work_on(cpu, &wfc.work);
4734 flush_work(&wfc.work);
4735 destroy_work_on_stack(&wfc.work);
4736 return wfc.ret;
4737}
4738EXPORT_SYMBOL_GPL(work_on_cpu);
4739#endif /* CONFIG_SMP */
4740
4741#ifdef CONFIG_FREEZER
4742
4743/**
4744 * freeze_workqueues_begin - begin freezing workqueues
4745 *
4746 * Start freezing workqueues. After this function returns, all freezable
4747 * workqueues will queue new works to their delayed_works list instead of
4748 * pool->worklist.
4749 *
4750 * CONTEXT:
4751 * Grabs and releases wq_pool_mutex, wq->mutex and pool->lock's.
4752 */
4753void freeze_workqueues_begin(void)
4754{
4755 struct workqueue_struct *wq;
4756 struct pool_workqueue *pwq;
4757
4758 mutex_lock(&wq_pool_mutex);
4759
4760 WARN_ON_ONCE(workqueue_freezing);
4761 workqueue_freezing = true;
4762
4763 list_for_each_entry(wq, &workqueues, list) {
4764 mutex_lock(&wq->mutex);
4765 for_each_pwq(pwq, wq)
4766 pwq_adjust_max_active(pwq);
4767 mutex_unlock(&wq->mutex);
4768 }
4769
4770 mutex_unlock(&wq_pool_mutex);
4771}
4772
4773/**
4774 * freeze_workqueues_busy - are freezable workqueues still busy?
4775 *
4776 * Check whether freezing is complete. This function must be called
4777 * between freeze_workqueues_begin() and thaw_workqueues().
4778 *
4779 * CONTEXT:
4780 * Grabs and releases wq_pool_mutex.
4781 *
4782 * Return:
4783 * %true if some freezable workqueues are still busy. %false if freezing
4784 * is complete.
4785 */
4786bool freeze_workqueues_busy(void)
4787{
4788 bool busy = false;
4789 struct workqueue_struct *wq;
4790 struct pool_workqueue *pwq;
4791
4792 mutex_lock(&wq_pool_mutex);
4793
4794 WARN_ON_ONCE(!workqueue_freezing);
4795
4796 list_for_each_entry(wq, &workqueues, list) {
4797 if (!(wq->flags & WQ_FREEZABLE))
4798 continue;
4799 /*
4800 * nr_active is monotonically decreasing. It's safe
4801 * to peek without lock.
4802 */
4803 rcu_read_lock_sched();
4804 for_each_pwq(pwq, wq) {
4805 WARN_ON_ONCE(pwq->nr_active < 0);
4806 if (pwq->nr_active) {
4807 busy = true;
4808 rcu_read_unlock_sched();
4809 goto out_unlock;
4810 }
4811 }
4812 rcu_read_unlock_sched();
4813 }
4814out_unlock:
4815 mutex_unlock(&wq_pool_mutex);
4816 return busy;
4817}
4818
4819/**
4820 * thaw_workqueues - thaw workqueues
4821 *
4822 * Thaw workqueues. Normal queueing is restored and all collected
4823 * frozen works are transferred to their respective pool worklists.
4824 *
4825 * CONTEXT:
4826 * Grabs and releases wq_pool_mutex, wq->mutex and pool->lock's.
4827 */
4828void thaw_workqueues(void)
4829{
4830 struct workqueue_struct *wq;
4831 struct pool_workqueue *pwq;
4832
4833 mutex_lock(&wq_pool_mutex);
4834
4835 if (!workqueue_freezing)
4836 goto out_unlock;
4837
4838 workqueue_freezing = false;
4839
4840 /* restore max_active and repopulate worklist */
4841 list_for_each_entry(wq, &workqueues, list) {
4842 mutex_lock(&wq->mutex);
4843 for_each_pwq(pwq, wq)
4844 pwq_adjust_max_active(pwq);
4845 mutex_unlock(&wq->mutex);
4846 }
4847
4848out_unlock:
4849 mutex_unlock(&wq_pool_mutex);
4850}
4851#endif /* CONFIG_FREEZER */
4852
4853static int workqueue_apply_unbound_cpumask(void)
4854{
4855 LIST_HEAD(ctxs);
4856 int ret = 0;
4857 struct workqueue_struct *wq;
4858 struct apply_wqattrs_ctx *ctx, *n;
4859
4860 lockdep_assert_held(&wq_pool_mutex);
4861
4862 list_for_each_entry(wq, &workqueues, list) {
4863 if (!(wq->flags & WQ_UNBOUND))
4864 continue;
4865 /* creating multiple pwqs breaks ordering guarantee */
4866 if (wq->flags & __WQ_ORDERED)
4867 continue;
4868
4869 ctx = apply_wqattrs_prepare(wq, wq->unbound_attrs);
4870 if (!ctx) {
4871 ret = -ENOMEM;
4872 break;
4873 }
4874
4875 list_add_tail(&ctx->list, &ctxs);
4876 }
4877
4878 list_for_each_entry_safe(ctx, n, &ctxs, list) {
4879 if (!ret)
4880 apply_wqattrs_commit(ctx);
4881 apply_wqattrs_cleanup(ctx);
4882 }
4883
4884 return ret;
4885}
4886
4887/**
4888 * workqueue_set_unbound_cpumask - Set the low-level unbound cpumask
4889 * @cpumask: the cpumask to set
4890 *
4891 * The low-level workqueues cpumask is a global cpumask that limits
4892 * the affinity of all unbound workqueues. This function check the @cpumask
4893 * and apply it to all unbound workqueues and updates all pwqs of them.
4894 *
4895 * Retun: 0 - Success
4896 * -EINVAL - Invalid @cpumask
4897 * -ENOMEM - Failed to allocate memory for attrs or pwqs.
4898 */
4899int workqueue_set_unbound_cpumask(cpumask_var_t cpumask)
4900{
4901 int ret = -EINVAL;
4902 cpumask_var_t saved_cpumask;
4903
4904 if (!zalloc_cpumask_var(&saved_cpumask, GFP_KERNEL))
4905 return -ENOMEM;
4906
4907 cpumask_and(cpumask, cpumask, cpu_possible_mask);
4908 if (!cpumask_empty(cpumask)) {
4909 apply_wqattrs_lock();
4910
4911 /* save the old wq_unbound_cpumask. */
4912 cpumask_copy(saved_cpumask, wq_unbound_cpumask);
4913
4914 /* update wq_unbound_cpumask at first and apply it to wqs. */
4915 cpumask_copy(wq_unbound_cpumask, cpumask);
4916 ret = workqueue_apply_unbound_cpumask();
4917
4918 /* restore the wq_unbound_cpumask when failed. */
4919 if (ret < 0)
4920 cpumask_copy(wq_unbound_cpumask, saved_cpumask);
4921
4922 apply_wqattrs_unlock();
4923 }
4924
4925 free_cpumask_var(saved_cpumask);
4926 return ret;
4927}
4928
4929#ifdef CONFIG_SYSFS
4930/*
4931 * Workqueues with WQ_SYSFS flag set is visible to userland via
4932 * /sys/bus/workqueue/devices/WQ_NAME. All visible workqueues have the
4933 * following attributes.
4934 *
4935 * per_cpu RO bool : whether the workqueue is per-cpu or unbound
4936 * max_active RW int : maximum number of in-flight work items
4937 *
4938 * Unbound workqueues have the following extra attributes.
4939 *
4940 * id RO int : the associated pool ID
4941 * nice RW int : nice value of the workers
4942 * cpumask RW mask : bitmask of allowed CPUs for the workers
4943 */
4944struct wq_device {
4945 struct workqueue_struct *wq;
4946 struct device dev;
4947};
4948
4949static struct workqueue_struct *dev_to_wq(struct device *dev)
4950{
4951 struct wq_device *wq_dev = container_of(dev, struct wq_device, dev);
4952
4953 return wq_dev->wq;
4954}
4955
4956static ssize_t per_cpu_show(struct device *dev, struct device_attribute *attr,
4957 char *buf)
4958{
4959 struct workqueue_struct *wq = dev_to_wq(dev);
4960
4961 return scnprintf(buf, PAGE_SIZE, "%d\n", (bool)!(wq->flags & WQ_UNBOUND));
4962}
4963static DEVICE_ATTR_RO(per_cpu);
4964
4965static ssize_t max_active_show(struct device *dev,
4966 struct device_attribute *attr, char *buf)
4967{
4968 struct workqueue_struct *wq = dev_to_wq(dev);
4969
4970 return scnprintf(buf, PAGE_SIZE, "%d\n", wq->saved_max_active);
4971}
4972
4973static ssize_t max_active_store(struct device *dev,
4974 struct device_attribute *attr, const char *buf,
4975 size_t count)
4976{
4977 struct workqueue_struct *wq = dev_to_wq(dev);
4978 int val;
4979
4980 if (sscanf(buf, "%d", &val) != 1 || val <= 0)
4981 return -EINVAL;
4982
4983 workqueue_set_max_active(wq, val);
4984 return count;
4985}
4986static DEVICE_ATTR_RW(max_active);
4987
4988static struct attribute *wq_sysfs_attrs[] = {
4989 &dev_attr_per_cpu.attr,
4990 &dev_attr_max_active.attr,
4991 NULL,
4992};
4993ATTRIBUTE_GROUPS(wq_sysfs);
4994
4995static ssize_t wq_pool_ids_show(struct device *dev,
4996 struct device_attribute *attr, char *buf)
4997{
4998 struct workqueue_struct *wq = dev_to_wq(dev);
4999 const char *delim = "";
5000 int node, written = 0;
5001
5002 rcu_read_lock_sched();
5003 for_each_node(node) {
5004 written += scnprintf(buf + written, PAGE_SIZE - written,
5005 "%s%d:%d", delim, node,
5006 unbound_pwq_by_node(wq, node)->pool->id);
5007 delim = " ";
5008 }
5009 written += scnprintf(buf + written, PAGE_SIZE - written, "\n");
5010 rcu_read_unlock_sched();
5011
5012 return written;
5013}
5014
5015static ssize_t wq_nice_show(struct device *dev, struct device_attribute *attr,
5016 char *buf)
5017{
5018 struct workqueue_struct *wq = dev_to_wq(dev);
5019 int written;
5020
5021 mutex_lock(&wq->mutex);
5022 written = scnprintf(buf, PAGE_SIZE, "%d\n", wq->unbound_attrs->nice);
5023 mutex_unlock(&wq->mutex);
5024
5025 return written;
5026}
5027
5028/* prepare workqueue_attrs for sysfs store operations */
5029static struct workqueue_attrs *wq_sysfs_prep_attrs(struct workqueue_struct *wq)
5030{
5031 struct workqueue_attrs *attrs;
5032
5033 lockdep_assert_held(&wq_pool_mutex);
5034
5035 attrs = alloc_workqueue_attrs(GFP_KERNEL);
5036 if (!attrs)
5037 return NULL;
5038
5039 copy_workqueue_attrs(attrs, wq->unbound_attrs);
5040 return attrs;
5041}
5042
5043static ssize_t wq_nice_store(struct device *dev, struct device_attribute *attr,
5044 const char *buf, size_t count)
5045{
5046 struct workqueue_struct *wq = dev_to_wq(dev);
5047 struct workqueue_attrs *attrs;
5048 int ret = -ENOMEM;
5049
5050 apply_wqattrs_lock();
5051
5052 attrs = wq_sysfs_prep_attrs(wq);
5053 if (!attrs)
5054 goto out_unlock;
5055
5056 if (sscanf(buf, "%d", &attrs->nice) == 1 &&
5057 attrs->nice >= MIN_NICE && attrs->nice <= MAX_NICE)
5058 ret = apply_workqueue_attrs_locked(wq, attrs);
5059 else
5060 ret = -EINVAL;
5061
5062out_unlock:
5063 apply_wqattrs_unlock();
5064 free_workqueue_attrs(attrs);
5065 return ret ?: count;
5066}
5067
5068static ssize_t wq_cpumask_show(struct device *dev,
5069 struct device_attribute *attr, char *buf)
5070{
5071 struct workqueue_struct *wq = dev_to_wq(dev);
5072 int written;
5073
5074 mutex_lock(&wq->mutex);
5075 written = scnprintf(buf, PAGE_SIZE, "%*pb\n",
5076 cpumask_pr_args(wq->unbound_attrs->cpumask));
5077 mutex_unlock(&wq->mutex);
5078 return written;
5079}
5080
5081static ssize_t wq_cpumask_store(struct device *dev,
5082 struct device_attribute *attr,
5083 const char *buf, size_t count)
5084{
5085 struct workqueue_struct *wq = dev_to_wq(dev);
5086 struct workqueue_attrs *attrs;
5087 int ret = -ENOMEM;
5088
5089 apply_wqattrs_lock();
5090
5091 attrs = wq_sysfs_prep_attrs(wq);
5092 if (!attrs)
5093 goto out_unlock;
5094
5095 ret = cpumask_parse(buf, attrs->cpumask);
5096 if (!ret)
5097 ret = apply_workqueue_attrs_locked(wq, attrs);
5098
5099out_unlock:
5100 apply_wqattrs_unlock();
5101 free_workqueue_attrs(attrs);
5102 return ret ?: count;
5103}
5104
5105static ssize_t wq_numa_show(struct device *dev, struct device_attribute *attr,
5106 char *buf)
5107{
5108 struct workqueue_struct *wq = dev_to_wq(dev);
5109 int written;
5110
5111 mutex_lock(&wq->mutex);
5112 written = scnprintf(buf, PAGE_SIZE, "%d\n",
5113 !wq->unbound_attrs->no_numa);
5114 mutex_unlock(&wq->mutex);
5115
5116 return written;
5117}
5118
5119static ssize_t wq_numa_store(struct device *dev, struct device_attribute *attr,
5120 const char *buf, size_t count)
5121{
5122 struct workqueue_struct *wq = dev_to_wq(dev);
5123 struct workqueue_attrs *attrs;
5124 int v, ret = -ENOMEM;
5125
5126 apply_wqattrs_lock();
5127
5128 attrs = wq_sysfs_prep_attrs(wq);
5129 if (!attrs)
5130 goto out_unlock;
5131
5132 ret = -EINVAL;
5133 if (sscanf(buf, "%d", &v) == 1) {
5134 attrs->no_numa = !v;
5135 ret = apply_workqueue_attrs_locked(wq, attrs);
5136 }
5137
5138out_unlock:
5139 apply_wqattrs_unlock();
5140 free_workqueue_attrs(attrs);
5141 return ret ?: count;
5142}
5143
5144static struct device_attribute wq_sysfs_unbound_attrs[] = {
5145 __ATTR(pool_ids, 0444, wq_pool_ids_show, NULL),
5146 __ATTR(nice, 0644, wq_nice_show, wq_nice_store),
5147 __ATTR(cpumask, 0644, wq_cpumask_show, wq_cpumask_store),
5148 __ATTR(numa, 0644, wq_numa_show, wq_numa_store),
5149 __ATTR_NULL,
5150};
5151
5152static struct bus_type wq_subsys = {
5153 .name = "workqueue",
5154 .dev_groups = wq_sysfs_groups,
5155};
5156
5157static ssize_t wq_unbound_cpumask_show(struct device *dev,
5158 struct device_attribute *attr, char *buf)
5159{
5160 int written;
5161
5162 mutex_lock(&wq_pool_mutex);
5163 written = scnprintf(buf, PAGE_SIZE, "%*pb\n",
5164 cpumask_pr_args(wq_unbound_cpumask));
5165 mutex_unlock(&wq_pool_mutex);
5166
5167 return written;
5168}
5169
5170static ssize_t wq_unbound_cpumask_store(struct device *dev,
5171 struct device_attribute *attr, const char *buf, size_t count)
5172{
5173 cpumask_var_t cpumask;
5174 int ret;
5175
5176 if (!zalloc_cpumask_var(&cpumask, GFP_KERNEL))
5177 return -ENOMEM;
5178
5179 ret = cpumask_parse(buf, cpumask);
5180 if (!ret)
5181 ret = workqueue_set_unbound_cpumask(cpumask);
5182
5183 free_cpumask_var(cpumask);
5184 return ret ? ret : count;
5185}
5186
5187static struct device_attribute wq_sysfs_cpumask_attr =
5188 __ATTR(cpumask, 0644, wq_unbound_cpumask_show,
5189 wq_unbound_cpumask_store);
5190
5191static int __init wq_sysfs_init(void)
5192{
5193 int err;
5194
5195 err = subsys_virtual_register(&wq_subsys, NULL);
5196 if (err)
5197 return err;
5198
5199 return device_create_file(wq_subsys.dev_root, &wq_sysfs_cpumask_attr);
5200}
5201core_initcall(wq_sysfs_init);
5202
5203static void wq_device_release(struct device *dev)
5204{
5205 struct wq_device *wq_dev = container_of(dev, struct wq_device, dev);
5206
5207 kfree(wq_dev);
5208}
5209
5210/**
5211 * workqueue_sysfs_register - make a workqueue visible in sysfs
5212 * @wq: the workqueue to register
5213 *
5214 * Expose @wq in sysfs under /sys/bus/workqueue/devices.
5215 * alloc_workqueue*() automatically calls this function if WQ_SYSFS is set
5216 * which is the preferred method.
5217 *
5218 * Workqueue user should use this function directly iff it wants to apply
5219 * workqueue_attrs before making the workqueue visible in sysfs; otherwise,
5220 * apply_workqueue_attrs() may race against userland updating the
5221 * attributes.
5222 *
5223 * Return: 0 on success, -errno on failure.
5224 */
5225int workqueue_sysfs_register(struct workqueue_struct *wq)
5226{
5227 struct wq_device *wq_dev;
5228 int ret;
5229
5230 /*
5231 * Adjusting max_active or creating new pwqs by applying
5232 * attributes breaks ordering guarantee. Disallow exposing ordered
5233 * workqueues.
5234 */
5235 if (WARN_ON(wq->flags & __WQ_ORDERED))
5236 return -EINVAL;
5237
5238 wq->wq_dev = wq_dev = kzalloc(sizeof(*wq_dev), GFP_KERNEL);
5239 if (!wq_dev)
5240 return -ENOMEM;
5241
5242 wq_dev->wq = wq;
5243 wq_dev->dev.bus = &wq_subsys;
5244 wq_dev->dev.release = wq_device_release;
5245 dev_set_name(&wq_dev->dev, "%s", wq->name);
5246
5247 /*
5248 * unbound_attrs are created separately. Suppress uevent until
5249 * everything is ready.
5250 */
5251 dev_set_uevent_suppress(&wq_dev->dev, true);
5252
5253 ret = device_register(&wq_dev->dev);
5254 if (ret) {
5255 kfree(wq_dev);
5256 wq->wq_dev = NULL;
5257 return ret;
5258 }
5259
5260 if (wq->flags & WQ_UNBOUND) {
5261 struct device_attribute *attr;
5262
5263 for (attr = wq_sysfs_unbound_attrs; attr->attr.name; attr++) {
5264 ret = device_create_file(&wq_dev->dev, attr);
5265 if (ret) {
5266 device_unregister(&wq_dev->dev);
5267 wq->wq_dev = NULL;
5268 return ret;
5269 }
5270 }
5271 }
5272
5273 dev_set_uevent_suppress(&wq_dev->dev, false);
5274 kobject_uevent(&wq_dev->dev.kobj, KOBJ_ADD);
5275 return 0;
5276}
5277
5278/**
5279 * workqueue_sysfs_unregister - undo workqueue_sysfs_register()
5280 * @wq: the workqueue to unregister
5281 *
5282 * If @wq is registered to sysfs by workqueue_sysfs_register(), unregister.
5283 */
5284static void workqueue_sysfs_unregister(struct workqueue_struct *wq)
5285{
5286 struct wq_device *wq_dev = wq->wq_dev;
5287
5288 if (!wq->wq_dev)
5289 return;
5290
5291 wq->wq_dev = NULL;
5292 device_unregister(&wq_dev->dev);
5293}
5294#else /* CONFIG_SYSFS */
5295static void workqueue_sysfs_unregister(struct workqueue_struct *wq) { }
5296#endif /* CONFIG_SYSFS */
5297
5298/*
5299 * Workqueue watchdog.
5300 *
5301 * Stall may be caused by various bugs - missing WQ_MEM_RECLAIM, illegal
5302 * flush dependency, a concurrency managed work item which stays RUNNING
5303 * indefinitely. Workqueue stalls can be very difficult to debug as the
5304 * usual warning mechanisms don't trigger and internal workqueue state is
5305 * largely opaque.
5306 *
5307 * Workqueue watchdog monitors all worker pools periodically and dumps
5308 * state if some pools failed to make forward progress for a while where
5309 * forward progress is defined as the first item on ->worklist changing.
5310 *
5311 * This mechanism is controlled through the kernel parameter
5312 * "workqueue.watchdog_thresh" which can be updated at runtime through the
5313 * corresponding sysfs parameter file.
5314 */
5315#ifdef CONFIG_WQ_WATCHDOG
5316
5317static void wq_watchdog_timer_fn(unsigned long data);
5318
5319static unsigned long wq_watchdog_thresh = 30;
5320static struct timer_list wq_watchdog_timer =
5321 TIMER_DEFERRED_INITIALIZER(wq_watchdog_timer_fn, 0, 0);
5322
5323static unsigned long wq_watchdog_touched = INITIAL_JIFFIES;
5324static DEFINE_PER_CPU(unsigned long, wq_watchdog_touched_cpu) = INITIAL_JIFFIES;
5325
5326static void wq_watchdog_reset_touched(void)
5327{
5328 int cpu;
5329
5330 wq_watchdog_touched = jiffies;
5331 for_each_possible_cpu(cpu)
5332 per_cpu(wq_watchdog_touched_cpu, cpu) = jiffies;
5333}
5334
5335static void wq_watchdog_timer_fn(unsigned long data)
5336{
5337 unsigned long thresh = READ_ONCE(wq_watchdog_thresh) * HZ;
5338 bool lockup_detected = false;
5339 struct worker_pool *pool;
5340 int pi;
5341
5342 if (!thresh)
5343 return;
5344
5345 rcu_read_lock();
5346
5347 for_each_pool(pool, pi) {
5348 unsigned long pool_ts, touched, ts;
5349
5350 if (list_empty(&pool->worklist))
5351 continue;
5352
5353 /* get the latest of pool and touched timestamps */
5354 pool_ts = READ_ONCE(pool->watchdog_ts);
5355 touched = READ_ONCE(wq_watchdog_touched);
5356
5357 if (time_after(pool_ts, touched))
5358 ts = pool_ts;
5359 else
5360 ts = touched;
5361
5362 if (pool->cpu >= 0) {
5363 unsigned long cpu_touched =
5364 READ_ONCE(per_cpu(wq_watchdog_touched_cpu,
5365 pool->cpu));
5366 if (time_after(cpu_touched, ts))
5367 ts = cpu_touched;
5368 }
5369
5370 /* did we stall? */
5371 if (time_after(jiffies, ts + thresh)) {
5372 lockup_detected = true;
5373 pr_emerg("BUG: workqueue lockup - pool");
5374 pr_cont_pool_info(pool);
5375 pr_cont(" stuck for %us!\n",
5376 jiffies_to_msecs(jiffies - pool_ts) / 1000);
5377 }
5378 }
5379
5380 rcu_read_unlock();
5381
5382 if (lockup_detected)
5383 show_workqueue_state();
5384
5385 wq_watchdog_reset_touched();
5386 mod_timer(&wq_watchdog_timer, jiffies + thresh);
5387}
5388
5389void wq_watchdog_touch(int cpu)
5390{
5391 if (cpu >= 0)
5392 per_cpu(wq_watchdog_touched_cpu, cpu) = jiffies;
5393 else
5394 wq_watchdog_touched = jiffies;
5395}
5396
5397static void wq_watchdog_set_thresh(unsigned long thresh)
5398{
5399 wq_watchdog_thresh = 0;
5400 del_timer_sync(&wq_watchdog_timer);
5401
5402 if (thresh) {
5403 wq_watchdog_thresh = thresh;
5404 wq_watchdog_reset_touched();
5405 mod_timer(&wq_watchdog_timer, jiffies + thresh * HZ);
5406 }
5407}
5408
5409static int wq_watchdog_param_set_thresh(const char *val,
5410 const struct kernel_param *kp)
5411{
5412 unsigned long thresh;
5413 int ret;
5414
5415 ret = kstrtoul(val, 0, &thresh);
5416 if (ret)
5417 return ret;
5418
5419 if (system_wq)
5420 wq_watchdog_set_thresh(thresh);
5421 else
5422 wq_watchdog_thresh = thresh;
5423
5424 return 0;
5425}
5426
5427static const struct kernel_param_ops wq_watchdog_thresh_ops = {
5428 .set = wq_watchdog_param_set_thresh,
5429 .get = param_get_ulong,
5430};
5431
5432module_param_cb(watchdog_thresh, &wq_watchdog_thresh_ops, &wq_watchdog_thresh,
5433 0644);
5434
5435static void wq_watchdog_init(void)
5436{
5437 wq_watchdog_set_thresh(wq_watchdog_thresh);
5438}
5439
5440#else /* CONFIG_WQ_WATCHDOG */
5441
5442static inline void wq_watchdog_init(void) { }
5443
5444#endif /* CONFIG_WQ_WATCHDOG */
5445
5446static void __init wq_numa_init(void)
5447{
5448 cpumask_var_t *tbl;
5449 int node, cpu;
5450
5451 if (num_possible_nodes() <= 1)
5452 return;
5453
5454 if (wq_disable_numa) {
5455 pr_info("workqueue: NUMA affinity support disabled\n");
5456 return;
5457 }
5458
5459 wq_update_unbound_numa_attrs_buf = alloc_workqueue_attrs(GFP_KERNEL);
5460 BUG_ON(!wq_update_unbound_numa_attrs_buf);
5461
5462 /*
5463 * We want masks of possible CPUs of each node which isn't readily
5464 * available. Build one from cpu_to_node() which should have been
5465 * fully initialized by now.
5466 */
5467 tbl = kzalloc(nr_node_ids * sizeof(tbl[0]), GFP_KERNEL);
5468 BUG_ON(!tbl);
5469
5470 for_each_node(node)
5471 BUG_ON(!zalloc_cpumask_var_node(&tbl[node], GFP_KERNEL,
5472 node_online(node) ? node : NUMA_NO_NODE));
5473
5474 for_each_possible_cpu(cpu) {
5475 node = cpu_to_node(cpu);
5476 if (WARN_ON(node == NUMA_NO_NODE)) {
5477 pr_warn("workqueue: NUMA node mapping not available for cpu%d, disabling NUMA support\n", cpu);
5478 /* happens iff arch is bonkers, let's just proceed */
5479 return;
5480 }
5481 cpumask_set_cpu(cpu, tbl[node]);
5482 }
5483
5484 wq_numa_possible_cpumask = tbl;
5485 wq_numa_enabled = true;
5486}
5487
5488/**
5489 * workqueue_init_early - early init for workqueue subsystem
5490 *
5491 * This is the first half of two-staged workqueue subsystem initialization
5492 * and invoked as soon as the bare basics - memory allocation, cpumasks and
5493 * idr are up. It sets up all the data structures and system workqueues
5494 * and allows early boot code to create workqueues and queue/cancel work
5495 * items. Actual work item execution starts only after kthreads can be
5496 * created and scheduled right before early initcalls.
5497 */
5498int __init workqueue_init_early(void)
5499{
5500 int std_nice[NR_STD_WORKER_POOLS] = { 0, HIGHPRI_NICE_LEVEL };
5501 int i, cpu;
5502
5503 WARN_ON(__alignof__(struct pool_workqueue) < __alignof__(long long));
5504
5505 BUG_ON(!alloc_cpumask_var(&wq_unbound_cpumask, GFP_KERNEL));
5506 cpumask_copy(wq_unbound_cpumask, cpu_possible_mask);
5507
5508 pwq_cache = KMEM_CACHE(pool_workqueue, SLAB_PANIC);
5509
5510 /* initialize CPU pools */
5511 for_each_possible_cpu(cpu) {
5512 struct worker_pool *pool;
5513
5514 i = 0;
5515 for_each_cpu_worker_pool(pool, cpu) {
5516 BUG_ON(init_worker_pool(pool));
5517 pool->cpu = cpu;
5518 cpumask_copy(pool->attrs->cpumask, cpumask_of(cpu));
5519 pool->attrs->nice = std_nice[i++];
5520 pool->node = cpu_to_node(cpu);
5521
5522 /* alloc pool ID */
5523 mutex_lock(&wq_pool_mutex);
5524 BUG_ON(worker_pool_assign_id(pool));
5525 mutex_unlock(&wq_pool_mutex);
5526 }
5527 }
5528
5529 /* create default unbound and ordered wq attrs */
5530 for (i = 0; i < NR_STD_WORKER_POOLS; i++) {
5531 struct workqueue_attrs *attrs;
5532
5533 BUG_ON(!(attrs = alloc_workqueue_attrs(GFP_KERNEL)));
5534 attrs->nice = std_nice[i];
5535 unbound_std_wq_attrs[i] = attrs;
5536
5537 /*
5538 * An ordered wq should have only one pwq as ordering is
5539 * guaranteed by max_active which is enforced by pwqs.
5540 * Turn off NUMA so that dfl_pwq is used for all nodes.
5541 */
5542 BUG_ON(!(attrs = alloc_workqueue_attrs(GFP_KERNEL)));
5543 attrs->nice = std_nice[i];
5544 attrs->no_numa = true;
5545 ordered_wq_attrs[i] = attrs;
5546 }
5547
5548 system_wq = alloc_workqueue("events", 0, 0);
5549 system_highpri_wq = alloc_workqueue("events_highpri", WQ_HIGHPRI, 0);
5550 system_long_wq = alloc_workqueue("events_long", 0, 0);
5551 system_unbound_wq = alloc_workqueue("events_unbound", WQ_UNBOUND,
5552 WQ_UNBOUND_MAX_ACTIVE);
5553 system_freezable_wq = alloc_workqueue("events_freezable",
5554 WQ_FREEZABLE, 0);
5555 system_power_efficient_wq = alloc_workqueue("events_power_efficient",
5556 WQ_POWER_EFFICIENT, 0);
5557 system_freezable_power_efficient_wq = alloc_workqueue("events_freezable_power_efficient",
5558 WQ_FREEZABLE | WQ_POWER_EFFICIENT,
5559 0);
5560 BUG_ON(!system_wq || !system_highpri_wq || !system_long_wq ||
5561 !system_unbound_wq || !system_freezable_wq ||
5562 !system_power_efficient_wq ||
5563 !system_freezable_power_efficient_wq);
5564
5565 return 0;
5566}
5567
5568/**
5569 * workqueue_init - bring workqueue subsystem fully online
5570 *
5571 * This is the latter half of two-staged workqueue subsystem initialization
5572 * and invoked as soon as kthreads can be created and scheduled.
5573 * Workqueues have been created and work items queued on them, but there
5574 * are no kworkers executing the work items yet. Populate the worker pools
5575 * with the initial workers and enable future kworker creations.
5576 */
5577int __init workqueue_init(void)
5578{
5579 struct workqueue_struct *wq;
5580 struct worker_pool *pool;
5581 int cpu, bkt;
5582
5583 /*
5584 * It'd be simpler to initialize NUMA in workqueue_init_early() but
5585 * CPU to node mapping may not be available that early on some
5586 * archs such as power and arm64. As per-cpu pools created
5587 * previously could be missing node hint and unbound pools NUMA
5588 * affinity, fix them up.
5589 */
5590 wq_numa_init();
5591
5592 mutex_lock(&wq_pool_mutex);
5593
5594 for_each_possible_cpu(cpu) {
5595 for_each_cpu_worker_pool(pool, cpu) {
5596 pool->node = cpu_to_node(cpu);
5597 }
5598 }
5599
5600 list_for_each_entry(wq, &workqueues, list)
5601 wq_update_unbound_numa(wq, smp_processor_id(), true);
5602
5603 mutex_unlock(&wq_pool_mutex);
5604
5605 /* create the initial workers */
5606 for_each_online_cpu(cpu) {
5607 for_each_cpu_worker_pool(pool, cpu) {
5608 pool->flags &= ~POOL_DISASSOCIATED;
5609 BUG_ON(!create_worker(pool));
5610 }
5611 }
5612
5613 hash_for_each(unbound_pool_hash, bkt, pool, hash_node)
5614 BUG_ON(!create_worker(pool));
5615
5616 wq_online = true;
5617 wq_watchdog_init();
5618
5619 return 0;
5620}
1// 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/sched/debug.h>
53#include <linux/nmi.h>
54#include <linux/kvm_para.h>
55#include <linux/delay.h>
56
57#include "workqueue_internal.h"
58
59enum {
60 /*
61 * worker_pool flags
62 *
63 * A bound pool is either associated or disassociated with its CPU.
64 * While associated (!DISASSOCIATED), all workers are bound to the
65 * CPU and none has %WORKER_UNBOUND set and concurrency management
66 * is in effect.
67 *
68 * While DISASSOCIATED, the cpu may be offline and all workers have
69 * %WORKER_UNBOUND set and concurrency management disabled, and may
70 * be executing on any CPU. The pool behaves as an unbound one.
71 *
72 * Note that DISASSOCIATED should be flipped only while holding
73 * wq_pool_attach_mutex to avoid changing binding state while
74 * worker_attach_to_pool() is in progress.
75 */
76 POOL_MANAGER_ACTIVE = 1 << 0, /* being managed */
77 POOL_DISASSOCIATED = 1 << 2, /* cpu can't serve workers */
78
79 /* worker flags */
80 WORKER_DIE = 1 << 1, /* die die die */
81 WORKER_IDLE = 1 << 2, /* is idle */
82 WORKER_PREP = 1 << 3, /* preparing to run works */
83 WORKER_CPU_INTENSIVE = 1 << 6, /* cpu intensive */
84 WORKER_UNBOUND = 1 << 7, /* worker is unbound */
85 WORKER_REBOUND = 1 << 8, /* worker was rebound */
86
87 WORKER_NOT_RUNNING = WORKER_PREP | WORKER_CPU_INTENSIVE |
88 WORKER_UNBOUND | WORKER_REBOUND,
89
90 NR_STD_WORKER_POOLS = 2, /* # standard pools per cpu */
91
92 UNBOUND_POOL_HASH_ORDER = 6, /* hashed by pool->attrs */
93 BUSY_WORKER_HASH_ORDER = 6, /* 64 pointers */
94
95 MAX_IDLE_WORKERS_RATIO = 4, /* 1/4 of busy can be idle */
96 IDLE_WORKER_TIMEOUT = 300 * HZ, /* keep idle ones for 5 mins */
97
98 MAYDAY_INITIAL_TIMEOUT = HZ / 100 >= 2 ? HZ / 100 : 2,
99 /* call for help after 10ms
100 (min two ticks) */
101 MAYDAY_INTERVAL = HZ / 10, /* and then every 100ms */
102 CREATE_COOLDOWN = HZ, /* time to breath after fail */
103
104 /*
105 * Rescue workers are used only on emergencies and shared by
106 * all cpus. Give MIN_NICE.
107 */
108 RESCUER_NICE_LEVEL = MIN_NICE,
109 HIGHPRI_NICE_LEVEL = MIN_NICE,
110
111 WQ_NAME_LEN = 24,
112};
113
114/*
115 * Structure fields follow one of the following exclusion rules.
116 *
117 * I: Modifiable by initialization/destruction paths and read-only for
118 * everyone else.
119 *
120 * P: Preemption protected. Disabling preemption is enough and should
121 * only be modified and accessed from the local cpu.
122 *
123 * L: pool->lock protected. Access with pool->lock held.
124 *
125 * K: Only modified by worker while holding pool->lock. Can be safely read by
126 * self, while holding pool->lock or from IRQ context if %current is the
127 * kworker.
128 *
129 * S: Only modified by worker self.
130 *
131 * A: wq_pool_attach_mutex protected.
132 *
133 * PL: wq_pool_mutex protected.
134 *
135 * PR: wq_pool_mutex protected for writes. RCU protected for reads.
136 *
137 * PW: wq_pool_mutex and wq->mutex protected for writes. Either for reads.
138 *
139 * PWR: wq_pool_mutex and wq->mutex protected for writes. Either or
140 * RCU for reads.
141 *
142 * WQ: wq->mutex protected.
143 *
144 * WR: wq->mutex protected for writes. RCU protected for reads.
145 *
146 * MD: wq_mayday_lock protected.
147 *
148 * WD: Used internally by the watchdog.
149 */
150
151/* struct worker is defined in workqueue_internal.h */
152
153struct worker_pool {
154 raw_spinlock_t lock; /* the pool lock */
155 int cpu; /* I: the associated cpu */
156 int node; /* I: the associated node ID */
157 int id; /* I: pool ID */
158 unsigned int flags; /* L: flags */
159
160 unsigned long watchdog_ts; /* L: watchdog timestamp */
161 bool cpu_stall; /* WD: stalled cpu bound pool */
162
163 /*
164 * The counter is incremented in a process context on the associated CPU
165 * w/ preemption disabled, and decremented or reset in the same context
166 * but w/ pool->lock held. The readers grab pool->lock and are
167 * guaranteed to see if the counter reached zero.
168 */
169 int nr_running;
170
171 struct list_head worklist; /* L: list of pending works */
172
173 int nr_workers; /* L: total number of workers */
174 int nr_idle; /* L: currently idle workers */
175
176 struct list_head idle_list; /* L: list of idle workers */
177 struct timer_list idle_timer; /* L: worker idle timeout */
178 struct work_struct idle_cull_work; /* L: worker idle cleanup */
179
180 struct timer_list mayday_timer; /* L: SOS timer for workers */
181
182 /* a workers is either on busy_hash or idle_list, or the manager */
183 DECLARE_HASHTABLE(busy_hash, BUSY_WORKER_HASH_ORDER);
184 /* L: hash of busy workers */
185
186 struct worker *manager; /* L: purely informational */
187 struct list_head workers; /* A: attached workers */
188 struct list_head dying_workers; /* A: workers about to die */
189 struct completion *detach_completion; /* all workers detached */
190
191 struct ida worker_ida; /* worker IDs for task name */
192
193 struct workqueue_attrs *attrs; /* I: worker attributes */
194 struct hlist_node hash_node; /* PL: unbound_pool_hash node */
195 int refcnt; /* PL: refcnt for unbound pools */
196
197 /*
198 * Destruction of pool is RCU protected to allow dereferences
199 * from get_work_pool().
200 */
201 struct rcu_head rcu;
202};
203
204/*
205 * Per-pool_workqueue statistics. These can be monitored using
206 * tools/workqueue/wq_monitor.py.
207 */
208enum pool_workqueue_stats {
209 PWQ_STAT_STARTED, /* work items started execution */
210 PWQ_STAT_COMPLETED, /* work items completed execution */
211 PWQ_STAT_CPU_TIME, /* total CPU time consumed */
212 PWQ_STAT_CPU_INTENSIVE, /* wq_cpu_intensive_thresh_us violations */
213 PWQ_STAT_CM_WAKEUP, /* concurrency-management worker wakeups */
214 PWQ_STAT_REPATRIATED, /* unbound workers brought back into scope */
215 PWQ_STAT_MAYDAY, /* maydays to rescuer */
216 PWQ_STAT_RESCUED, /* linked work items executed by rescuer */
217
218 PWQ_NR_STATS,
219};
220
221/*
222 * The per-pool workqueue. While queued, the lower WORK_STRUCT_FLAG_BITS
223 * of work_struct->data are used for flags and the remaining high bits
224 * point to the pwq; thus, pwqs need to be aligned at two's power of the
225 * number of flag bits.
226 */
227struct pool_workqueue {
228 struct worker_pool *pool; /* I: the associated pool */
229 struct workqueue_struct *wq; /* I: the owning workqueue */
230 int work_color; /* L: current color */
231 int flush_color; /* L: flushing color */
232 int refcnt; /* L: reference count */
233 int nr_in_flight[WORK_NR_COLORS];
234 /* L: nr of in_flight works */
235
236 /*
237 * nr_active management and WORK_STRUCT_INACTIVE:
238 *
239 * When pwq->nr_active >= max_active, new work item is queued to
240 * pwq->inactive_works instead of pool->worklist and marked with
241 * WORK_STRUCT_INACTIVE.
242 *
243 * All work items marked with WORK_STRUCT_INACTIVE do not participate
244 * in pwq->nr_active and all work items in pwq->inactive_works are
245 * marked with WORK_STRUCT_INACTIVE. But not all WORK_STRUCT_INACTIVE
246 * work items are in pwq->inactive_works. Some of them are ready to
247 * run in pool->worklist or worker->scheduled. Those work itmes are
248 * only struct wq_barrier which is used for flush_work() and should
249 * not participate in pwq->nr_active. For non-barrier work item, it
250 * is marked with WORK_STRUCT_INACTIVE iff it is in pwq->inactive_works.
251 */
252 int nr_active; /* L: nr of active works */
253 int max_active; /* L: max active works */
254 struct list_head inactive_works; /* L: inactive works */
255 struct list_head pwqs_node; /* WR: node on wq->pwqs */
256 struct list_head mayday_node; /* MD: node on wq->maydays */
257
258 u64 stats[PWQ_NR_STATS];
259
260 /*
261 * Release of unbound pwq is punted to a kthread_worker. See put_pwq()
262 * and pwq_release_workfn() for details. pool_workqueue itself is also
263 * RCU protected so that the first pwq can be determined without
264 * grabbing wq->mutex.
265 */
266 struct kthread_work release_work;
267 struct rcu_head rcu;
268} __aligned(1 << WORK_STRUCT_FLAG_BITS);
269
270/*
271 * Structure used to wait for workqueue flush.
272 */
273struct wq_flusher {
274 struct list_head list; /* WQ: list of flushers */
275 int flush_color; /* WQ: flush color waiting for */
276 struct completion done; /* flush completion */
277};
278
279struct wq_device;
280
281/*
282 * The externally visible workqueue. It relays the issued work items to
283 * the appropriate worker_pool through its pool_workqueues.
284 */
285struct workqueue_struct {
286 struct list_head pwqs; /* WR: all pwqs of this wq */
287 struct list_head list; /* PR: list of all workqueues */
288
289 struct mutex mutex; /* protects this wq */
290 int work_color; /* WQ: current work color */
291 int flush_color; /* WQ: current flush color */
292 atomic_t nr_pwqs_to_flush; /* flush in progress */
293 struct wq_flusher *first_flusher; /* WQ: first flusher */
294 struct list_head flusher_queue; /* WQ: flush waiters */
295 struct list_head flusher_overflow; /* WQ: flush overflow list */
296
297 struct list_head maydays; /* MD: pwqs requesting rescue */
298 struct worker *rescuer; /* MD: rescue worker */
299
300 int nr_drainers; /* WQ: drain in progress */
301 int saved_max_active; /* WQ: saved pwq max_active */
302
303 struct workqueue_attrs *unbound_attrs; /* PW: only for unbound wqs */
304 struct pool_workqueue *dfl_pwq; /* PW: only for unbound wqs */
305
306#ifdef CONFIG_SYSFS
307 struct wq_device *wq_dev; /* I: for sysfs interface */
308#endif
309#ifdef CONFIG_LOCKDEP
310 char *lock_name;
311 struct lock_class_key key;
312 struct lockdep_map lockdep_map;
313#endif
314 char name[WQ_NAME_LEN]; /* I: workqueue name */
315
316 /*
317 * Destruction of workqueue_struct is RCU protected to allow walking
318 * the workqueues list without grabbing wq_pool_mutex.
319 * This is used to dump all workqueues from sysrq.
320 */
321 struct rcu_head rcu;
322
323 /* hot fields used during command issue, aligned to cacheline */
324 unsigned int flags ____cacheline_aligned; /* WQ: WQ_* flags */
325 struct pool_workqueue __percpu __rcu **cpu_pwq; /* I: per-cpu pwqs */
326};
327
328static struct kmem_cache *pwq_cache;
329
330/*
331 * Each pod type describes how CPUs should be grouped for unbound workqueues.
332 * See the comment above workqueue_attrs->affn_scope.
333 */
334struct wq_pod_type {
335 int nr_pods; /* number of pods */
336 cpumask_var_t *pod_cpus; /* pod -> cpus */
337 int *pod_node; /* pod -> node */
338 int *cpu_pod; /* cpu -> pod */
339};
340
341static struct wq_pod_type wq_pod_types[WQ_AFFN_NR_TYPES];
342static enum wq_affn_scope wq_affn_dfl = WQ_AFFN_CACHE;
343
344static const char *wq_affn_names[WQ_AFFN_NR_TYPES] = {
345 [WQ_AFFN_DFL] = "default",
346 [WQ_AFFN_CPU] = "cpu",
347 [WQ_AFFN_SMT] = "smt",
348 [WQ_AFFN_CACHE] = "cache",
349 [WQ_AFFN_NUMA] = "numa",
350 [WQ_AFFN_SYSTEM] = "system",
351};
352
353/*
354 * Per-cpu work items which run for longer than the following threshold are
355 * automatically considered CPU intensive and excluded from concurrency
356 * management to prevent them from noticeably delaying other per-cpu work items.
357 * ULONG_MAX indicates that the user hasn't overridden it with a boot parameter.
358 * The actual value is initialized in wq_cpu_intensive_thresh_init().
359 */
360static unsigned long wq_cpu_intensive_thresh_us = ULONG_MAX;
361module_param_named(cpu_intensive_thresh_us, wq_cpu_intensive_thresh_us, ulong, 0644);
362
363/* see the comment above the definition of WQ_POWER_EFFICIENT */
364static bool wq_power_efficient = IS_ENABLED(CONFIG_WQ_POWER_EFFICIENT_DEFAULT);
365module_param_named(power_efficient, wq_power_efficient, bool, 0444);
366
367static bool wq_online; /* can kworkers be created yet? */
368
369/* buf for wq_update_unbound_pod_attrs(), protected by CPU hotplug exclusion */
370static struct workqueue_attrs *wq_update_pod_attrs_buf;
371
372static DEFINE_MUTEX(wq_pool_mutex); /* protects pools and workqueues list */
373static DEFINE_MUTEX(wq_pool_attach_mutex); /* protects worker attach/detach */
374static DEFINE_RAW_SPINLOCK(wq_mayday_lock); /* protects wq->maydays list */
375/* wait for manager to go away */
376static struct rcuwait manager_wait = __RCUWAIT_INITIALIZER(manager_wait);
377
378static LIST_HEAD(workqueues); /* PR: list of all workqueues */
379static bool workqueue_freezing; /* PL: have wqs started freezing? */
380
381/* PL&A: allowable cpus for unbound wqs and work items */
382static cpumask_var_t wq_unbound_cpumask;
383
384/* PL: user requested unbound cpumask via sysfs */
385static cpumask_var_t wq_requested_unbound_cpumask;
386
387/* PL: isolated cpumask to be excluded from unbound cpumask */
388static cpumask_var_t wq_isolated_cpumask;
389
390/* for further constrain wq_unbound_cpumask by cmdline parameter*/
391static struct cpumask wq_cmdline_cpumask __initdata;
392
393/* CPU where unbound work was last round robin scheduled from this CPU */
394static DEFINE_PER_CPU(int, wq_rr_cpu_last);
395
396/*
397 * Local execution of unbound work items is no longer guaranteed. The
398 * following always forces round-robin CPU selection on unbound work items
399 * to uncover usages which depend on it.
400 */
401#ifdef CONFIG_DEBUG_WQ_FORCE_RR_CPU
402static bool wq_debug_force_rr_cpu = true;
403#else
404static bool wq_debug_force_rr_cpu = false;
405#endif
406module_param_named(debug_force_rr_cpu, wq_debug_force_rr_cpu, bool, 0644);
407
408/* the per-cpu worker pools */
409static DEFINE_PER_CPU_SHARED_ALIGNED(struct worker_pool [NR_STD_WORKER_POOLS], cpu_worker_pools);
410
411static DEFINE_IDR(worker_pool_idr); /* PR: idr of all pools */
412
413/* PL: hash of all unbound pools keyed by pool->attrs */
414static DEFINE_HASHTABLE(unbound_pool_hash, UNBOUND_POOL_HASH_ORDER);
415
416/* I: attributes used when instantiating standard unbound pools on demand */
417static struct workqueue_attrs *unbound_std_wq_attrs[NR_STD_WORKER_POOLS];
418
419/* I: attributes used when instantiating ordered pools on demand */
420static struct workqueue_attrs *ordered_wq_attrs[NR_STD_WORKER_POOLS];
421
422/*
423 * I: kthread_worker to release pwq's. pwq release needs to be bounced to a
424 * process context while holding a pool lock. Bounce to a dedicated kthread
425 * worker to avoid A-A deadlocks.
426 */
427static struct kthread_worker *pwq_release_worker __ro_after_init;
428
429struct workqueue_struct *system_wq __ro_after_init;
430EXPORT_SYMBOL(system_wq);
431struct workqueue_struct *system_highpri_wq __ro_after_init;
432EXPORT_SYMBOL_GPL(system_highpri_wq);
433struct workqueue_struct *system_long_wq __ro_after_init;
434EXPORT_SYMBOL_GPL(system_long_wq);
435struct workqueue_struct *system_unbound_wq __ro_after_init;
436EXPORT_SYMBOL_GPL(system_unbound_wq);
437struct workqueue_struct *system_freezable_wq __ro_after_init;
438EXPORT_SYMBOL_GPL(system_freezable_wq);
439struct workqueue_struct *system_power_efficient_wq __ro_after_init;
440EXPORT_SYMBOL_GPL(system_power_efficient_wq);
441struct workqueue_struct *system_freezable_power_efficient_wq __ro_after_init;
442EXPORT_SYMBOL_GPL(system_freezable_power_efficient_wq);
443
444static int worker_thread(void *__worker);
445static void workqueue_sysfs_unregister(struct workqueue_struct *wq);
446static void show_pwq(struct pool_workqueue *pwq);
447static void show_one_worker_pool(struct worker_pool *pool);
448
449#define CREATE_TRACE_POINTS
450#include <trace/events/workqueue.h>
451
452#define assert_rcu_or_pool_mutex() \
453 RCU_LOCKDEP_WARN(!rcu_read_lock_held() && \
454 !lockdep_is_held(&wq_pool_mutex), \
455 "RCU or wq_pool_mutex should be held")
456
457#define assert_rcu_or_wq_mutex_or_pool_mutex(wq) \
458 RCU_LOCKDEP_WARN(!rcu_read_lock_held() && \
459 !lockdep_is_held(&wq->mutex) && \
460 !lockdep_is_held(&wq_pool_mutex), \
461 "RCU, wq->mutex or wq_pool_mutex should be held")
462
463#define for_each_cpu_worker_pool(pool, cpu) \
464 for ((pool) = &per_cpu(cpu_worker_pools, cpu)[0]; \
465 (pool) < &per_cpu(cpu_worker_pools, cpu)[NR_STD_WORKER_POOLS]; \
466 (pool)++)
467
468/**
469 * for_each_pool - iterate through all worker_pools in the system
470 * @pool: iteration cursor
471 * @pi: integer used for iteration
472 *
473 * This must be called either with wq_pool_mutex held or RCU read
474 * locked. If the pool needs to be used beyond the locking in effect, the
475 * caller is responsible for guaranteeing that the pool stays online.
476 *
477 * The if/else clause exists only for the lockdep assertion and can be
478 * ignored.
479 */
480#define for_each_pool(pool, pi) \
481 idr_for_each_entry(&worker_pool_idr, pool, pi) \
482 if (({ assert_rcu_or_pool_mutex(); false; })) { } \
483 else
484
485/**
486 * for_each_pool_worker - iterate through all workers of a worker_pool
487 * @worker: iteration cursor
488 * @pool: worker_pool to iterate workers of
489 *
490 * This must be called with wq_pool_attach_mutex.
491 *
492 * The if/else clause exists only for the lockdep assertion and can be
493 * ignored.
494 */
495#define for_each_pool_worker(worker, pool) \
496 list_for_each_entry((worker), &(pool)->workers, node) \
497 if (({ lockdep_assert_held(&wq_pool_attach_mutex); false; })) { } \
498 else
499
500/**
501 * for_each_pwq - iterate through all pool_workqueues of the specified workqueue
502 * @pwq: iteration cursor
503 * @wq: the target workqueue
504 *
505 * This must be called either with wq->mutex held or RCU read locked.
506 * If the pwq needs to be used beyond the locking in effect, the caller is
507 * responsible for guaranteeing that the pwq stays online.
508 *
509 * The if/else clause exists only for the lockdep assertion and can be
510 * ignored.
511 */
512#define for_each_pwq(pwq, wq) \
513 list_for_each_entry_rcu((pwq), &(wq)->pwqs, pwqs_node, \
514 lockdep_is_held(&(wq->mutex)))
515
516#ifdef CONFIG_DEBUG_OBJECTS_WORK
517
518static const struct debug_obj_descr work_debug_descr;
519
520static void *work_debug_hint(void *addr)
521{
522 return ((struct work_struct *) addr)->func;
523}
524
525static bool work_is_static_object(void *addr)
526{
527 struct work_struct *work = addr;
528
529 return test_bit(WORK_STRUCT_STATIC_BIT, work_data_bits(work));
530}
531
532/*
533 * fixup_init is called when:
534 * - an active object is initialized
535 */
536static bool work_fixup_init(void *addr, enum debug_obj_state state)
537{
538 struct work_struct *work = addr;
539
540 switch (state) {
541 case ODEBUG_STATE_ACTIVE:
542 cancel_work_sync(work);
543 debug_object_init(work, &work_debug_descr);
544 return true;
545 default:
546 return false;
547 }
548}
549
550/*
551 * fixup_free is called when:
552 * - an active object is freed
553 */
554static bool work_fixup_free(void *addr, enum debug_obj_state state)
555{
556 struct work_struct *work = addr;
557
558 switch (state) {
559 case ODEBUG_STATE_ACTIVE:
560 cancel_work_sync(work);
561 debug_object_free(work, &work_debug_descr);
562 return true;
563 default:
564 return false;
565 }
566}
567
568static const struct debug_obj_descr work_debug_descr = {
569 .name = "work_struct",
570 .debug_hint = work_debug_hint,
571 .is_static_object = work_is_static_object,
572 .fixup_init = work_fixup_init,
573 .fixup_free = work_fixup_free,
574};
575
576static inline void debug_work_activate(struct work_struct *work)
577{
578 debug_object_activate(work, &work_debug_descr);
579}
580
581static inline void debug_work_deactivate(struct work_struct *work)
582{
583 debug_object_deactivate(work, &work_debug_descr);
584}
585
586void __init_work(struct work_struct *work, int onstack)
587{
588 if (onstack)
589 debug_object_init_on_stack(work, &work_debug_descr);
590 else
591 debug_object_init(work, &work_debug_descr);
592}
593EXPORT_SYMBOL_GPL(__init_work);
594
595void destroy_work_on_stack(struct work_struct *work)
596{
597 debug_object_free(work, &work_debug_descr);
598}
599EXPORT_SYMBOL_GPL(destroy_work_on_stack);
600
601void destroy_delayed_work_on_stack(struct delayed_work *work)
602{
603 destroy_timer_on_stack(&work->timer);
604 debug_object_free(&work->work, &work_debug_descr);
605}
606EXPORT_SYMBOL_GPL(destroy_delayed_work_on_stack);
607
608#else
609static inline void debug_work_activate(struct work_struct *work) { }
610static inline void debug_work_deactivate(struct work_struct *work) { }
611#endif
612
613/**
614 * worker_pool_assign_id - allocate ID and assign it to @pool
615 * @pool: the pool pointer of interest
616 *
617 * Returns 0 if ID in [0, WORK_OFFQ_POOL_NONE) is allocated and assigned
618 * successfully, -errno on failure.
619 */
620static int worker_pool_assign_id(struct worker_pool *pool)
621{
622 int ret;
623
624 lockdep_assert_held(&wq_pool_mutex);
625
626 ret = idr_alloc(&worker_pool_idr, pool, 0, WORK_OFFQ_POOL_NONE,
627 GFP_KERNEL);
628 if (ret >= 0) {
629 pool->id = ret;
630 return 0;
631 }
632 return ret;
633}
634
635static unsigned int work_color_to_flags(int color)
636{
637 return color << WORK_STRUCT_COLOR_SHIFT;
638}
639
640static int get_work_color(unsigned long work_data)
641{
642 return (work_data >> WORK_STRUCT_COLOR_SHIFT) &
643 ((1 << WORK_STRUCT_COLOR_BITS) - 1);
644}
645
646static int work_next_color(int color)
647{
648 return (color + 1) % WORK_NR_COLORS;
649}
650
651/*
652 * While queued, %WORK_STRUCT_PWQ is set and non flag bits of a work's data
653 * contain the pointer to the queued pwq. Once execution starts, the flag
654 * is cleared and the high bits contain OFFQ flags and pool ID.
655 *
656 * set_work_pwq(), set_work_pool_and_clear_pending(), mark_work_canceling()
657 * and clear_work_data() can be used to set the pwq, pool or clear
658 * work->data. These functions should only be called while the work is
659 * owned - ie. while the PENDING bit is set.
660 *
661 * get_work_pool() and get_work_pwq() can be used to obtain the pool or pwq
662 * corresponding to a work. Pool is available once the work has been
663 * queued anywhere after initialization until it is sync canceled. pwq is
664 * available only while the work item is queued.
665 *
666 * %WORK_OFFQ_CANCELING is used to mark a work item which is being
667 * canceled. While being canceled, a work item may have its PENDING set
668 * but stay off timer and worklist for arbitrarily long and nobody should
669 * try to steal the PENDING bit.
670 */
671static inline void set_work_data(struct work_struct *work, unsigned long data,
672 unsigned long flags)
673{
674 WARN_ON_ONCE(!work_pending(work));
675 atomic_long_set(&work->data, data | flags | work_static(work));
676}
677
678static void set_work_pwq(struct work_struct *work, struct pool_workqueue *pwq,
679 unsigned long extra_flags)
680{
681 set_work_data(work, (unsigned long)pwq,
682 WORK_STRUCT_PENDING | WORK_STRUCT_PWQ | extra_flags);
683}
684
685static void set_work_pool_and_keep_pending(struct work_struct *work,
686 int pool_id)
687{
688 set_work_data(work, (unsigned long)pool_id << WORK_OFFQ_POOL_SHIFT,
689 WORK_STRUCT_PENDING);
690}
691
692static void set_work_pool_and_clear_pending(struct work_struct *work,
693 int pool_id)
694{
695 /*
696 * The following wmb is paired with the implied mb in
697 * test_and_set_bit(PENDING) and ensures all updates to @work made
698 * here are visible to and precede any updates by the next PENDING
699 * owner.
700 */
701 smp_wmb();
702 set_work_data(work, (unsigned long)pool_id << WORK_OFFQ_POOL_SHIFT, 0);
703 /*
704 * The following mb guarantees that previous clear of a PENDING bit
705 * will not be reordered with any speculative LOADS or STORES from
706 * work->current_func, which is executed afterwards. This possible
707 * reordering can lead to a missed execution on attempt to queue
708 * the same @work. E.g. consider this case:
709 *
710 * CPU#0 CPU#1
711 * ---------------------------- --------------------------------
712 *
713 * 1 STORE event_indicated
714 * 2 queue_work_on() {
715 * 3 test_and_set_bit(PENDING)
716 * 4 } set_..._and_clear_pending() {
717 * 5 set_work_data() # clear bit
718 * 6 smp_mb()
719 * 7 work->current_func() {
720 * 8 LOAD event_indicated
721 * }
722 *
723 * Without an explicit full barrier speculative LOAD on line 8 can
724 * be executed before CPU#0 does STORE on line 1. If that happens,
725 * CPU#0 observes the PENDING bit is still set and new execution of
726 * a @work is not queued in a hope, that CPU#1 will eventually
727 * finish the queued @work. Meanwhile CPU#1 does not see
728 * event_indicated is set, because speculative LOAD was executed
729 * before actual STORE.
730 */
731 smp_mb();
732}
733
734static void clear_work_data(struct work_struct *work)
735{
736 smp_wmb(); /* see set_work_pool_and_clear_pending() */
737 set_work_data(work, WORK_STRUCT_NO_POOL, 0);
738}
739
740static inline struct pool_workqueue *work_struct_pwq(unsigned long data)
741{
742 return (struct pool_workqueue *)(data & WORK_STRUCT_WQ_DATA_MASK);
743}
744
745static struct pool_workqueue *get_work_pwq(struct work_struct *work)
746{
747 unsigned long data = atomic_long_read(&work->data);
748
749 if (data & WORK_STRUCT_PWQ)
750 return work_struct_pwq(data);
751 else
752 return NULL;
753}
754
755/**
756 * get_work_pool - return the worker_pool a given work was associated with
757 * @work: the work item of interest
758 *
759 * Pools are created and destroyed under wq_pool_mutex, and allows read
760 * access under RCU read lock. As such, this function should be
761 * called under wq_pool_mutex or inside of a rcu_read_lock() region.
762 *
763 * All fields of the returned pool are accessible as long as the above
764 * mentioned locking is in effect. If the returned pool needs to be used
765 * beyond the critical section, the caller is responsible for ensuring the
766 * returned pool is and stays online.
767 *
768 * Return: The worker_pool @work was last associated with. %NULL if none.
769 */
770static struct worker_pool *get_work_pool(struct work_struct *work)
771{
772 unsigned long data = atomic_long_read(&work->data);
773 int pool_id;
774
775 assert_rcu_or_pool_mutex();
776
777 if (data & WORK_STRUCT_PWQ)
778 return work_struct_pwq(data)->pool;
779
780 pool_id = data >> WORK_OFFQ_POOL_SHIFT;
781 if (pool_id == WORK_OFFQ_POOL_NONE)
782 return NULL;
783
784 return idr_find(&worker_pool_idr, pool_id);
785}
786
787/**
788 * get_work_pool_id - return the worker pool ID a given work is associated with
789 * @work: the work item of interest
790 *
791 * Return: The worker_pool ID @work was last associated with.
792 * %WORK_OFFQ_POOL_NONE if none.
793 */
794static int get_work_pool_id(struct work_struct *work)
795{
796 unsigned long data = atomic_long_read(&work->data);
797
798 if (data & WORK_STRUCT_PWQ)
799 return work_struct_pwq(data)->pool->id;
800
801 return data >> WORK_OFFQ_POOL_SHIFT;
802}
803
804static void mark_work_canceling(struct work_struct *work)
805{
806 unsigned long pool_id = get_work_pool_id(work);
807
808 pool_id <<= WORK_OFFQ_POOL_SHIFT;
809 set_work_data(work, pool_id | WORK_OFFQ_CANCELING, WORK_STRUCT_PENDING);
810}
811
812static bool work_is_canceling(struct work_struct *work)
813{
814 unsigned long data = atomic_long_read(&work->data);
815
816 return !(data & WORK_STRUCT_PWQ) && (data & WORK_OFFQ_CANCELING);
817}
818
819/*
820 * Policy functions. These define the policies on how the global worker
821 * pools are managed. Unless noted otherwise, these functions assume that
822 * they're being called with pool->lock held.
823 */
824
825/*
826 * Need to wake up a worker? Called from anything but currently
827 * running workers.
828 *
829 * Note that, because unbound workers never contribute to nr_running, this
830 * function will always return %true for unbound pools as long as the
831 * worklist isn't empty.
832 */
833static bool need_more_worker(struct worker_pool *pool)
834{
835 return !list_empty(&pool->worklist) && !pool->nr_running;
836}
837
838/* Can I start working? Called from busy but !running workers. */
839static bool may_start_working(struct worker_pool *pool)
840{
841 return pool->nr_idle;
842}
843
844/* Do I need to keep working? Called from currently running workers. */
845static bool keep_working(struct worker_pool *pool)
846{
847 return !list_empty(&pool->worklist) && (pool->nr_running <= 1);
848}
849
850/* Do we need a new worker? Called from manager. */
851static bool need_to_create_worker(struct worker_pool *pool)
852{
853 return need_more_worker(pool) && !may_start_working(pool);
854}
855
856/* Do we have too many workers and should some go away? */
857static bool too_many_workers(struct worker_pool *pool)
858{
859 bool managing = pool->flags & POOL_MANAGER_ACTIVE;
860 int nr_idle = pool->nr_idle + managing; /* manager is considered idle */
861 int nr_busy = pool->nr_workers - nr_idle;
862
863 return nr_idle > 2 && (nr_idle - 2) * MAX_IDLE_WORKERS_RATIO >= nr_busy;
864}
865
866/**
867 * worker_set_flags - set worker flags and adjust nr_running accordingly
868 * @worker: self
869 * @flags: flags to set
870 *
871 * Set @flags in @worker->flags and adjust nr_running accordingly.
872 */
873static inline void worker_set_flags(struct worker *worker, unsigned int flags)
874{
875 struct worker_pool *pool = worker->pool;
876
877 lockdep_assert_held(&pool->lock);
878
879 /* If transitioning into NOT_RUNNING, adjust nr_running. */
880 if ((flags & WORKER_NOT_RUNNING) &&
881 !(worker->flags & WORKER_NOT_RUNNING)) {
882 pool->nr_running--;
883 }
884
885 worker->flags |= flags;
886}
887
888/**
889 * worker_clr_flags - clear worker flags and adjust nr_running accordingly
890 * @worker: self
891 * @flags: flags to clear
892 *
893 * Clear @flags in @worker->flags and adjust nr_running accordingly.
894 */
895static inline void worker_clr_flags(struct worker *worker, unsigned int flags)
896{
897 struct worker_pool *pool = worker->pool;
898 unsigned int oflags = worker->flags;
899
900 lockdep_assert_held(&pool->lock);
901
902 worker->flags &= ~flags;
903
904 /*
905 * If transitioning out of NOT_RUNNING, increment nr_running. Note
906 * that the nested NOT_RUNNING is not a noop. NOT_RUNNING is mask
907 * of multiple flags, not a single flag.
908 */
909 if ((flags & WORKER_NOT_RUNNING) && (oflags & WORKER_NOT_RUNNING))
910 if (!(worker->flags & WORKER_NOT_RUNNING))
911 pool->nr_running++;
912}
913
914/* Return the first idle worker. Called with pool->lock held. */
915static struct worker *first_idle_worker(struct worker_pool *pool)
916{
917 if (unlikely(list_empty(&pool->idle_list)))
918 return NULL;
919
920 return list_first_entry(&pool->idle_list, struct worker, entry);
921}
922
923/**
924 * worker_enter_idle - enter idle state
925 * @worker: worker which is entering idle state
926 *
927 * @worker is entering idle state. Update stats and idle timer if
928 * necessary.
929 *
930 * LOCKING:
931 * raw_spin_lock_irq(pool->lock).
932 */
933static void worker_enter_idle(struct worker *worker)
934{
935 struct worker_pool *pool = worker->pool;
936
937 if (WARN_ON_ONCE(worker->flags & WORKER_IDLE) ||
938 WARN_ON_ONCE(!list_empty(&worker->entry) &&
939 (worker->hentry.next || worker->hentry.pprev)))
940 return;
941
942 /* can't use worker_set_flags(), also called from create_worker() */
943 worker->flags |= WORKER_IDLE;
944 pool->nr_idle++;
945 worker->last_active = jiffies;
946
947 /* idle_list is LIFO */
948 list_add(&worker->entry, &pool->idle_list);
949
950 if (too_many_workers(pool) && !timer_pending(&pool->idle_timer))
951 mod_timer(&pool->idle_timer, jiffies + IDLE_WORKER_TIMEOUT);
952
953 /* Sanity check nr_running. */
954 WARN_ON_ONCE(pool->nr_workers == pool->nr_idle && pool->nr_running);
955}
956
957/**
958 * worker_leave_idle - leave idle state
959 * @worker: worker which is leaving idle state
960 *
961 * @worker is leaving idle state. Update stats.
962 *
963 * LOCKING:
964 * raw_spin_lock_irq(pool->lock).
965 */
966static void worker_leave_idle(struct worker *worker)
967{
968 struct worker_pool *pool = worker->pool;
969
970 if (WARN_ON_ONCE(!(worker->flags & WORKER_IDLE)))
971 return;
972 worker_clr_flags(worker, WORKER_IDLE);
973 pool->nr_idle--;
974 list_del_init(&worker->entry);
975}
976
977/**
978 * find_worker_executing_work - find worker which is executing a work
979 * @pool: pool of interest
980 * @work: work to find worker for
981 *
982 * Find a worker which is executing @work on @pool by searching
983 * @pool->busy_hash which is keyed by the address of @work. For a worker
984 * to match, its current execution should match the address of @work and
985 * its work function. This is to avoid unwanted dependency between
986 * unrelated work executions through a work item being recycled while still
987 * being executed.
988 *
989 * This is a bit tricky. A work item may be freed once its execution
990 * starts and nothing prevents the freed area from being recycled for
991 * another work item. If the same work item address ends up being reused
992 * before the original execution finishes, workqueue will identify the
993 * recycled work item as currently executing and make it wait until the
994 * current execution finishes, introducing an unwanted dependency.
995 *
996 * This function checks the work item address and work function to avoid
997 * false positives. Note that this isn't complete as one may construct a
998 * work function which can introduce dependency onto itself through a
999 * recycled work item. Well, if somebody wants to shoot oneself in the
1000 * foot that badly, there's only so much we can do, and if such deadlock
1001 * actually occurs, it should be easy to locate the culprit work function.
1002 *
1003 * CONTEXT:
1004 * raw_spin_lock_irq(pool->lock).
1005 *
1006 * Return:
1007 * Pointer to worker which is executing @work if found, %NULL
1008 * otherwise.
1009 */
1010static struct worker *find_worker_executing_work(struct worker_pool *pool,
1011 struct work_struct *work)
1012{
1013 struct worker *worker;
1014
1015 hash_for_each_possible(pool->busy_hash, worker, hentry,
1016 (unsigned long)work)
1017 if (worker->current_work == work &&
1018 worker->current_func == work->func)
1019 return worker;
1020
1021 return NULL;
1022}
1023
1024/**
1025 * move_linked_works - move linked works to a list
1026 * @work: start of series of works to be scheduled
1027 * @head: target list to append @work to
1028 * @nextp: out parameter for nested worklist walking
1029 *
1030 * Schedule linked works starting from @work to @head. Work series to be
1031 * scheduled starts at @work and includes any consecutive work with
1032 * WORK_STRUCT_LINKED set in its predecessor. See assign_work() for details on
1033 * @nextp.
1034 *
1035 * CONTEXT:
1036 * raw_spin_lock_irq(pool->lock).
1037 */
1038static void move_linked_works(struct work_struct *work, struct list_head *head,
1039 struct work_struct **nextp)
1040{
1041 struct work_struct *n;
1042
1043 /*
1044 * Linked worklist will always end before the end of the list,
1045 * use NULL for list head.
1046 */
1047 list_for_each_entry_safe_from(work, n, NULL, entry) {
1048 list_move_tail(&work->entry, head);
1049 if (!(*work_data_bits(work) & WORK_STRUCT_LINKED))
1050 break;
1051 }
1052
1053 /*
1054 * If we're already inside safe list traversal and have moved
1055 * multiple works to the scheduled queue, the next position
1056 * needs to be updated.
1057 */
1058 if (nextp)
1059 *nextp = n;
1060}
1061
1062/**
1063 * assign_work - assign a work item and its linked work items to a worker
1064 * @work: work to assign
1065 * @worker: worker to assign to
1066 * @nextp: out parameter for nested worklist walking
1067 *
1068 * Assign @work and its linked work items to @worker. If @work is already being
1069 * executed by another worker in the same pool, it'll be punted there.
1070 *
1071 * If @nextp is not NULL, it's updated to point to the next work of the last
1072 * scheduled work. This allows assign_work() to be nested inside
1073 * list_for_each_entry_safe().
1074 *
1075 * Returns %true if @work was successfully assigned to @worker. %false if @work
1076 * was punted to another worker already executing it.
1077 */
1078static bool assign_work(struct work_struct *work, struct worker *worker,
1079 struct work_struct **nextp)
1080{
1081 struct worker_pool *pool = worker->pool;
1082 struct worker *collision;
1083
1084 lockdep_assert_held(&pool->lock);
1085
1086 /*
1087 * A single work shouldn't be executed concurrently by multiple workers.
1088 * __queue_work() ensures that @work doesn't jump to a different pool
1089 * while still running in the previous pool. Here, we should ensure that
1090 * @work is not executed concurrently by multiple workers from the same
1091 * pool. Check whether anyone is already processing the work. If so,
1092 * defer the work to the currently executing one.
1093 */
1094 collision = find_worker_executing_work(pool, work);
1095 if (unlikely(collision)) {
1096 move_linked_works(work, &collision->scheduled, nextp);
1097 return false;
1098 }
1099
1100 move_linked_works(work, &worker->scheduled, nextp);
1101 return true;
1102}
1103
1104/**
1105 * kick_pool - wake up an idle worker if necessary
1106 * @pool: pool to kick
1107 *
1108 * @pool may have pending work items. Wake up worker if necessary. Returns
1109 * whether a worker was woken up.
1110 */
1111static bool kick_pool(struct worker_pool *pool)
1112{
1113 struct worker *worker = first_idle_worker(pool);
1114 struct task_struct *p;
1115
1116 lockdep_assert_held(&pool->lock);
1117
1118 if (!need_more_worker(pool) || !worker)
1119 return false;
1120
1121 p = worker->task;
1122
1123#ifdef CONFIG_SMP
1124 /*
1125 * Idle @worker is about to execute @work and waking up provides an
1126 * opportunity to migrate @worker at a lower cost by setting the task's
1127 * wake_cpu field. Let's see if we want to move @worker to improve
1128 * execution locality.
1129 *
1130 * We're waking the worker that went idle the latest and there's some
1131 * chance that @worker is marked idle but hasn't gone off CPU yet. If
1132 * so, setting the wake_cpu won't do anything. As this is a best-effort
1133 * optimization and the race window is narrow, let's leave as-is for
1134 * now. If this becomes pronounced, we can skip over workers which are
1135 * still on cpu when picking an idle worker.
1136 *
1137 * If @pool has non-strict affinity, @worker might have ended up outside
1138 * its affinity scope. Repatriate.
1139 */
1140 if (!pool->attrs->affn_strict &&
1141 !cpumask_test_cpu(p->wake_cpu, pool->attrs->__pod_cpumask)) {
1142 struct work_struct *work = list_first_entry(&pool->worklist,
1143 struct work_struct, entry);
1144 p->wake_cpu = cpumask_any_distribute(pool->attrs->__pod_cpumask);
1145 get_work_pwq(work)->stats[PWQ_STAT_REPATRIATED]++;
1146 }
1147#endif
1148 wake_up_process(p);
1149 return true;
1150}
1151
1152#ifdef CONFIG_WQ_CPU_INTENSIVE_REPORT
1153
1154/*
1155 * Concurrency-managed per-cpu work items that hog CPU for longer than
1156 * wq_cpu_intensive_thresh_us trigger the automatic CPU_INTENSIVE mechanism,
1157 * which prevents them from stalling other concurrency-managed work items. If a
1158 * work function keeps triggering this mechanism, it's likely that the work item
1159 * should be using an unbound workqueue instead.
1160 *
1161 * wq_cpu_intensive_report() tracks work functions which trigger such conditions
1162 * and report them so that they can be examined and converted to use unbound
1163 * workqueues as appropriate. To avoid flooding the console, each violating work
1164 * function is tracked and reported with exponential backoff.
1165 */
1166#define WCI_MAX_ENTS 128
1167
1168struct wci_ent {
1169 work_func_t func;
1170 atomic64_t cnt;
1171 struct hlist_node hash_node;
1172};
1173
1174static struct wci_ent wci_ents[WCI_MAX_ENTS];
1175static int wci_nr_ents;
1176static DEFINE_RAW_SPINLOCK(wci_lock);
1177static DEFINE_HASHTABLE(wci_hash, ilog2(WCI_MAX_ENTS));
1178
1179static struct wci_ent *wci_find_ent(work_func_t func)
1180{
1181 struct wci_ent *ent;
1182
1183 hash_for_each_possible_rcu(wci_hash, ent, hash_node,
1184 (unsigned long)func) {
1185 if (ent->func == func)
1186 return ent;
1187 }
1188 return NULL;
1189}
1190
1191static void wq_cpu_intensive_report(work_func_t func)
1192{
1193 struct wci_ent *ent;
1194
1195restart:
1196 ent = wci_find_ent(func);
1197 if (ent) {
1198 u64 cnt;
1199
1200 /*
1201 * Start reporting from the fourth time and back off
1202 * exponentially.
1203 */
1204 cnt = atomic64_inc_return_relaxed(&ent->cnt);
1205 if (cnt >= 4 && is_power_of_2(cnt))
1206 printk_deferred(KERN_WARNING "workqueue: %ps hogged CPU for >%luus %llu times, consider switching to WQ_UNBOUND\n",
1207 ent->func, wq_cpu_intensive_thresh_us,
1208 atomic64_read(&ent->cnt));
1209 return;
1210 }
1211
1212 /*
1213 * @func is a new violation. Allocate a new entry for it. If wcn_ents[]
1214 * is exhausted, something went really wrong and we probably made enough
1215 * noise already.
1216 */
1217 if (wci_nr_ents >= WCI_MAX_ENTS)
1218 return;
1219
1220 raw_spin_lock(&wci_lock);
1221
1222 if (wci_nr_ents >= WCI_MAX_ENTS) {
1223 raw_spin_unlock(&wci_lock);
1224 return;
1225 }
1226
1227 if (wci_find_ent(func)) {
1228 raw_spin_unlock(&wci_lock);
1229 goto restart;
1230 }
1231
1232 ent = &wci_ents[wci_nr_ents++];
1233 ent->func = func;
1234 atomic64_set(&ent->cnt, 1);
1235 hash_add_rcu(wci_hash, &ent->hash_node, (unsigned long)func);
1236
1237 raw_spin_unlock(&wci_lock);
1238}
1239
1240#else /* CONFIG_WQ_CPU_INTENSIVE_REPORT */
1241static void wq_cpu_intensive_report(work_func_t func) {}
1242#endif /* CONFIG_WQ_CPU_INTENSIVE_REPORT */
1243
1244/**
1245 * wq_worker_running - a worker is running again
1246 * @task: task waking up
1247 *
1248 * This function is called when a worker returns from schedule()
1249 */
1250void wq_worker_running(struct task_struct *task)
1251{
1252 struct worker *worker = kthread_data(task);
1253
1254 if (!READ_ONCE(worker->sleeping))
1255 return;
1256
1257 /*
1258 * If preempted by unbind_workers() between the WORKER_NOT_RUNNING check
1259 * and the nr_running increment below, we may ruin the nr_running reset
1260 * and leave with an unexpected pool->nr_running == 1 on the newly unbound
1261 * pool. Protect against such race.
1262 */
1263 preempt_disable();
1264 if (!(worker->flags & WORKER_NOT_RUNNING))
1265 worker->pool->nr_running++;
1266 preempt_enable();
1267
1268 /*
1269 * CPU intensive auto-detection cares about how long a work item hogged
1270 * CPU without sleeping. Reset the starting timestamp on wakeup.
1271 */
1272 worker->current_at = worker->task->se.sum_exec_runtime;
1273
1274 WRITE_ONCE(worker->sleeping, 0);
1275}
1276
1277/**
1278 * wq_worker_sleeping - a worker is going to sleep
1279 * @task: task going to sleep
1280 *
1281 * This function is called from schedule() when a busy worker is
1282 * going to sleep.
1283 */
1284void wq_worker_sleeping(struct task_struct *task)
1285{
1286 struct worker *worker = kthread_data(task);
1287 struct worker_pool *pool;
1288
1289 /*
1290 * Rescuers, which may not have all the fields set up like normal
1291 * workers, also reach here, let's not access anything before
1292 * checking NOT_RUNNING.
1293 */
1294 if (worker->flags & WORKER_NOT_RUNNING)
1295 return;
1296
1297 pool = worker->pool;
1298
1299 /* Return if preempted before wq_worker_running() was reached */
1300 if (READ_ONCE(worker->sleeping))
1301 return;
1302
1303 WRITE_ONCE(worker->sleeping, 1);
1304 raw_spin_lock_irq(&pool->lock);
1305
1306 /*
1307 * Recheck in case unbind_workers() preempted us. We don't
1308 * want to decrement nr_running after the worker is unbound
1309 * and nr_running has been reset.
1310 */
1311 if (worker->flags & WORKER_NOT_RUNNING) {
1312 raw_spin_unlock_irq(&pool->lock);
1313 return;
1314 }
1315
1316 pool->nr_running--;
1317 if (kick_pool(pool))
1318 worker->current_pwq->stats[PWQ_STAT_CM_WAKEUP]++;
1319
1320 raw_spin_unlock_irq(&pool->lock);
1321}
1322
1323/**
1324 * wq_worker_tick - a scheduler tick occurred while a kworker is running
1325 * @task: task currently running
1326 *
1327 * Called from scheduler_tick(). We're in the IRQ context and the current
1328 * worker's fields which follow the 'K' locking rule can be accessed safely.
1329 */
1330void wq_worker_tick(struct task_struct *task)
1331{
1332 struct worker *worker = kthread_data(task);
1333 struct pool_workqueue *pwq = worker->current_pwq;
1334 struct worker_pool *pool = worker->pool;
1335
1336 if (!pwq)
1337 return;
1338
1339 pwq->stats[PWQ_STAT_CPU_TIME] += TICK_USEC;
1340
1341 if (!wq_cpu_intensive_thresh_us)
1342 return;
1343
1344 /*
1345 * If the current worker is concurrency managed and hogged the CPU for
1346 * longer than wq_cpu_intensive_thresh_us, it's automatically marked
1347 * CPU_INTENSIVE to avoid stalling other concurrency-managed work items.
1348 *
1349 * Set @worker->sleeping means that @worker is in the process of
1350 * switching out voluntarily and won't be contributing to
1351 * @pool->nr_running until it wakes up. As wq_worker_sleeping() also
1352 * decrements ->nr_running, setting CPU_INTENSIVE here can lead to
1353 * double decrements. The task is releasing the CPU anyway. Let's skip.
1354 * We probably want to make this prettier in the future.
1355 */
1356 if ((worker->flags & WORKER_NOT_RUNNING) || READ_ONCE(worker->sleeping) ||
1357 worker->task->se.sum_exec_runtime - worker->current_at <
1358 wq_cpu_intensive_thresh_us * NSEC_PER_USEC)
1359 return;
1360
1361 raw_spin_lock(&pool->lock);
1362
1363 worker_set_flags(worker, WORKER_CPU_INTENSIVE);
1364 wq_cpu_intensive_report(worker->current_func);
1365 pwq->stats[PWQ_STAT_CPU_INTENSIVE]++;
1366
1367 if (kick_pool(pool))
1368 pwq->stats[PWQ_STAT_CM_WAKEUP]++;
1369
1370 raw_spin_unlock(&pool->lock);
1371}
1372
1373/**
1374 * wq_worker_last_func - retrieve worker's last work function
1375 * @task: Task to retrieve last work function of.
1376 *
1377 * Determine the last function a worker executed. This is called from
1378 * the scheduler to get a worker's last known identity.
1379 *
1380 * CONTEXT:
1381 * raw_spin_lock_irq(rq->lock)
1382 *
1383 * This function is called during schedule() when a kworker is going
1384 * to sleep. It's used by psi to identify aggregation workers during
1385 * dequeuing, to allow periodic aggregation to shut-off when that
1386 * worker is the last task in the system or cgroup to go to sleep.
1387 *
1388 * As this function doesn't involve any workqueue-related locking, it
1389 * only returns stable values when called from inside the scheduler's
1390 * queuing and dequeuing paths, when @task, which must be a kworker,
1391 * is guaranteed to not be processing any works.
1392 *
1393 * Return:
1394 * The last work function %current executed as a worker, NULL if it
1395 * hasn't executed any work yet.
1396 */
1397work_func_t wq_worker_last_func(struct task_struct *task)
1398{
1399 struct worker *worker = kthread_data(task);
1400
1401 return worker->last_func;
1402}
1403
1404/**
1405 * get_pwq - get an extra reference on the specified pool_workqueue
1406 * @pwq: pool_workqueue to get
1407 *
1408 * Obtain an extra reference on @pwq. The caller should guarantee that
1409 * @pwq has positive refcnt and be holding the matching pool->lock.
1410 */
1411static void get_pwq(struct pool_workqueue *pwq)
1412{
1413 lockdep_assert_held(&pwq->pool->lock);
1414 WARN_ON_ONCE(pwq->refcnt <= 0);
1415 pwq->refcnt++;
1416}
1417
1418/**
1419 * put_pwq - put a pool_workqueue reference
1420 * @pwq: pool_workqueue to put
1421 *
1422 * Drop a reference of @pwq. If its refcnt reaches zero, schedule its
1423 * destruction. The caller should be holding the matching pool->lock.
1424 */
1425static void put_pwq(struct pool_workqueue *pwq)
1426{
1427 lockdep_assert_held(&pwq->pool->lock);
1428 if (likely(--pwq->refcnt))
1429 return;
1430 /*
1431 * @pwq can't be released under pool->lock, bounce to a dedicated
1432 * kthread_worker to avoid A-A deadlocks.
1433 */
1434 kthread_queue_work(pwq_release_worker, &pwq->release_work);
1435}
1436
1437/**
1438 * put_pwq_unlocked - put_pwq() with surrounding pool lock/unlock
1439 * @pwq: pool_workqueue to put (can be %NULL)
1440 *
1441 * put_pwq() with locking. This function also allows %NULL @pwq.
1442 */
1443static void put_pwq_unlocked(struct pool_workqueue *pwq)
1444{
1445 if (pwq) {
1446 /*
1447 * As both pwqs and pools are RCU protected, the
1448 * following lock operations are safe.
1449 */
1450 raw_spin_lock_irq(&pwq->pool->lock);
1451 put_pwq(pwq);
1452 raw_spin_unlock_irq(&pwq->pool->lock);
1453 }
1454}
1455
1456static void pwq_activate_inactive_work(struct work_struct *work)
1457{
1458 struct pool_workqueue *pwq = get_work_pwq(work);
1459
1460 trace_workqueue_activate_work(work);
1461 if (list_empty(&pwq->pool->worklist))
1462 pwq->pool->watchdog_ts = jiffies;
1463 move_linked_works(work, &pwq->pool->worklist, NULL);
1464 __clear_bit(WORK_STRUCT_INACTIVE_BIT, work_data_bits(work));
1465 pwq->nr_active++;
1466}
1467
1468static void pwq_activate_first_inactive(struct pool_workqueue *pwq)
1469{
1470 struct work_struct *work = list_first_entry(&pwq->inactive_works,
1471 struct work_struct, entry);
1472
1473 pwq_activate_inactive_work(work);
1474}
1475
1476/**
1477 * pwq_dec_nr_in_flight - decrement pwq's nr_in_flight
1478 * @pwq: pwq of interest
1479 * @work_data: work_data of work which left the queue
1480 *
1481 * A work either has completed or is removed from pending queue,
1482 * decrement nr_in_flight of its pwq and handle workqueue flushing.
1483 *
1484 * CONTEXT:
1485 * raw_spin_lock_irq(pool->lock).
1486 */
1487static void pwq_dec_nr_in_flight(struct pool_workqueue *pwq, unsigned long work_data)
1488{
1489 int color = get_work_color(work_data);
1490
1491 if (!(work_data & WORK_STRUCT_INACTIVE)) {
1492 pwq->nr_active--;
1493 if (!list_empty(&pwq->inactive_works)) {
1494 /* one down, submit an inactive one */
1495 if (pwq->nr_active < pwq->max_active)
1496 pwq_activate_first_inactive(pwq);
1497 }
1498 }
1499
1500 pwq->nr_in_flight[color]--;
1501
1502 /* is flush in progress and are we at the flushing tip? */
1503 if (likely(pwq->flush_color != color))
1504 goto out_put;
1505
1506 /* are there still in-flight works? */
1507 if (pwq->nr_in_flight[color])
1508 goto out_put;
1509
1510 /* this pwq is done, clear flush_color */
1511 pwq->flush_color = -1;
1512
1513 /*
1514 * If this was the last pwq, wake up the first flusher. It
1515 * will handle the rest.
1516 */
1517 if (atomic_dec_and_test(&pwq->wq->nr_pwqs_to_flush))
1518 complete(&pwq->wq->first_flusher->done);
1519out_put:
1520 put_pwq(pwq);
1521}
1522
1523/**
1524 * try_to_grab_pending - steal work item from worklist and disable irq
1525 * @work: work item to steal
1526 * @is_dwork: @work is a delayed_work
1527 * @flags: place to store irq state
1528 *
1529 * Try to grab PENDING bit of @work. This function can handle @work in any
1530 * stable state - idle, on timer or on worklist.
1531 *
1532 * Return:
1533 *
1534 * ======== ================================================================
1535 * 1 if @work was pending and we successfully stole PENDING
1536 * 0 if @work was idle and we claimed PENDING
1537 * -EAGAIN if PENDING couldn't be grabbed at the moment, safe to busy-retry
1538 * -ENOENT if someone else is canceling @work, this state may persist
1539 * for arbitrarily long
1540 * ======== ================================================================
1541 *
1542 * Note:
1543 * On >= 0 return, the caller owns @work's PENDING bit. To avoid getting
1544 * interrupted while holding PENDING and @work off queue, irq must be
1545 * disabled on entry. This, combined with delayed_work->timer being
1546 * irqsafe, ensures that we return -EAGAIN for finite short period of time.
1547 *
1548 * On successful return, >= 0, irq is disabled and the caller is
1549 * responsible for releasing it using local_irq_restore(*@flags).
1550 *
1551 * This function is safe to call from any context including IRQ handler.
1552 */
1553static int try_to_grab_pending(struct work_struct *work, bool is_dwork,
1554 unsigned long *flags)
1555{
1556 struct worker_pool *pool;
1557 struct pool_workqueue *pwq;
1558
1559 local_irq_save(*flags);
1560
1561 /* try to steal the timer if it exists */
1562 if (is_dwork) {
1563 struct delayed_work *dwork = to_delayed_work(work);
1564
1565 /*
1566 * dwork->timer is irqsafe. If del_timer() fails, it's
1567 * guaranteed that the timer is not queued anywhere and not
1568 * running on the local CPU.
1569 */
1570 if (likely(del_timer(&dwork->timer)))
1571 return 1;
1572 }
1573
1574 /* try to claim PENDING the normal way */
1575 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work)))
1576 return 0;
1577
1578 rcu_read_lock();
1579 /*
1580 * The queueing is in progress, or it is already queued. Try to
1581 * steal it from ->worklist without clearing WORK_STRUCT_PENDING.
1582 */
1583 pool = get_work_pool(work);
1584 if (!pool)
1585 goto fail;
1586
1587 raw_spin_lock(&pool->lock);
1588 /*
1589 * work->data is guaranteed to point to pwq only while the work
1590 * item is queued on pwq->wq, and both updating work->data to point
1591 * to pwq on queueing and to pool on dequeueing are done under
1592 * pwq->pool->lock. This in turn guarantees that, if work->data
1593 * points to pwq which is associated with a locked pool, the work
1594 * item is currently queued on that pool.
1595 */
1596 pwq = get_work_pwq(work);
1597 if (pwq && pwq->pool == pool) {
1598 debug_work_deactivate(work);
1599
1600 /*
1601 * A cancelable inactive work item must be in the
1602 * pwq->inactive_works since a queued barrier can't be
1603 * canceled (see the comments in insert_wq_barrier()).
1604 *
1605 * An inactive work item cannot be grabbed directly because
1606 * it might have linked barrier work items which, if left
1607 * on the inactive_works list, will confuse pwq->nr_active
1608 * management later on and cause stall. Make sure the work
1609 * item is activated before grabbing.
1610 */
1611 if (*work_data_bits(work) & WORK_STRUCT_INACTIVE)
1612 pwq_activate_inactive_work(work);
1613
1614 list_del_init(&work->entry);
1615 pwq_dec_nr_in_flight(pwq, *work_data_bits(work));
1616
1617 /* work->data points to pwq iff queued, point to pool */
1618 set_work_pool_and_keep_pending(work, pool->id);
1619
1620 raw_spin_unlock(&pool->lock);
1621 rcu_read_unlock();
1622 return 1;
1623 }
1624 raw_spin_unlock(&pool->lock);
1625fail:
1626 rcu_read_unlock();
1627 local_irq_restore(*flags);
1628 if (work_is_canceling(work))
1629 return -ENOENT;
1630 cpu_relax();
1631 return -EAGAIN;
1632}
1633
1634/**
1635 * insert_work - insert a work into a pool
1636 * @pwq: pwq @work belongs to
1637 * @work: work to insert
1638 * @head: insertion point
1639 * @extra_flags: extra WORK_STRUCT_* flags to set
1640 *
1641 * Insert @work which belongs to @pwq after @head. @extra_flags is or'd to
1642 * work_struct flags.
1643 *
1644 * CONTEXT:
1645 * raw_spin_lock_irq(pool->lock).
1646 */
1647static void insert_work(struct pool_workqueue *pwq, struct work_struct *work,
1648 struct list_head *head, unsigned int extra_flags)
1649{
1650 debug_work_activate(work);
1651
1652 /* record the work call stack in order to print it in KASAN reports */
1653 kasan_record_aux_stack_noalloc(work);
1654
1655 /* we own @work, set data and link */
1656 set_work_pwq(work, pwq, extra_flags);
1657 list_add_tail(&work->entry, head);
1658 get_pwq(pwq);
1659}
1660
1661/*
1662 * Test whether @work is being queued from another work executing on the
1663 * same workqueue.
1664 */
1665static bool is_chained_work(struct workqueue_struct *wq)
1666{
1667 struct worker *worker;
1668
1669 worker = current_wq_worker();
1670 /*
1671 * Return %true iff I'm a worker executing a work item on @wq. If
1672 * I'm @worker, it's safe to dereference it without locking.
1673 */
1674 return worker && worker->current_pwq->wq == wq;
1675}
1676
1677/*
1678 * When queueing an unbound work item to a wq, prefer local CPU if allowed
1679 * by wq_unbound_cpumask. Otherwise, round robin among the allowed ones to
1680 * avoid perturbing sensitive tasks.
1681 */
1682static int wq_select_unbound_cpu(int cpu)
1683{
1684 int new_cpu;
1685
1686 if (likely(!wq_debug_force_rr_cpu)) {
1687 if (cpumask_test_cpu(cpu, wq_unbound_cpumask))
1688 return cpu;
1689 } else {
1690 pr_warn_once("workqueue: round-robin CPU selection forced, expect performance impact\n");
1691 }
1692
1693 new_cpu = __this_cpu_read(wq_rr_cpu_last);
1694 new_cpu = cpumask_next_and(new_cpu, wq_unbound_cpumask, cpu_online_mask);
1695 if (unlikely(new_cpu >= nr_cpu_ids)) {
1696 new_cpu = cpumask_first_and(wq_unbound_cpumask, cpu_online_mask);
1697 if (unlikely(new_cpu >= nr_cpu_ids))
1698 return cpu;
1699 }
1700 __this_cpu_write(wq_rr_cpu_last, new_cpu);
1701
1702 return new_cpu;
1703}
1704
1705static void __queue_work(int cpu, struct workqueue_struct *wq,
1706 struct work_struct *work)
1707{
1708 struct pool_workqueue *pwq;
1709 struct worker_pool *last_pool, *pool;
1710 unsigned int work_flags;
1711 unsigned int req_cpu = cpu;
1712
1713 /*
1714 * While a work item is PENDING && off queue, a task trying to
1715 * steal the PENDING will busy-loop waiting for it to either get
1716 * queued or lose PENDING. Grabbing PENDING and queueing should
1717 * happen with IRQ disabled.
1718 */
1719 lockdep_assert_irqs_disabled();
1720
1721
1722 /*
1723 * For a draining wq, only works from the same workqueue are
1724 * allowed. The __WQ_DESTROYING helps to spot the issue that
1725 * queues a new work item to a wq after destroy_workqueue(wq).
1726 */
1727 if (unlikely(wq->flags & (__WQ_DESTROYING | __WQ_DRAINING) &&
1728 WARN_ON_ONCE(!is_chained_work(wq))))
1729 return;
1730 rcu_read_lock();
1731retry:
1732 /* pwq which will be used unless @work is executing elsewhere */
1733 if (req_cpu == WORK_CPU_UNBOUND) {
1734 if (wq->flags & WQ_UNBOUND)
1735 cpu = wq_select_unbound_cpu(raw_smp_processor_id());
1736 else
1737 cpu = raw_smp_processor_id();
1738 }
1739
1740 pwq = rcu_dereference(*per_cpu_ptr(wq->cpu_pwq, cpu));
1741 pool = pwq->pool;
1742
1743 /*
1744 * If @work was previously on a different pool, it might still be
1745 * running there, in which case the work needs to be queued on that
1746 * pool to guarantee non-reentrancy.
1747 */
1748 last_pool = get_work_pool(work);
1749 if (last_pool && last_pool != pool) {
1750 struct worker *worker;
1751
1752 raw_spin_lock(&last_pool->lock);
1753
1754 worker = find_worker_executing_work(last_pool, work);
1755
1756 if (worker && worker->current_pwq->wq == wq) {
1757 pwq = worker->current_pwq;
1758 pool = pwq->pool;
1759 WARN_ON_ONCE(pool != last_pool);
1760 } else {
1761 /* meh... not running there, queue here */
1762 raw_spin_unlock(&last_pool->lock);
1763 raw_spin_lock(&pool->lock);
1764 }
1765 } else {
1766 raw_spin_lock(&pool->lock);
1767 }
1768
1769 /*
1770 * pwq is determined and locked. For unbound pools, we could have raced
1771 * with pwq release and it could already be dead. If its refcnt is zero,
1772 * repeat pwq selection. Note that unbound pwqs never die without
1773 * another pwq replacing it in cpu_pwq or while work items are executing
1774 * on it, so the retrying is guaranteed to make forward-progress.
1775 */
1776 if (unlikely(!pwq->refcnt)) {
1777 if (wq->flags & WQ_UNBOUND) {
1778 raw_spin_unlock(&pool->lock);
1779 cpu_relax();
1780 goto retry;
1781 }
1782 /* oops */
1783 WARN_ONCE(true, "workqueue: per-cpu pwq for %s on cpu%d has 0 refcnt",
1784 wq->name, cpu);
1785 }
1786
1787 /* pwq determined, queue */
1788 trace_workqueue_queue_work(req_cpu, pwq, work);
1789
1790 if (WARN_ON(!list_empty(&work->entry)))
1791 goto out;
1792
1793 pwq->nr_in_flight[pwq->work_color]++;
1794 work_flags = work_color_to_flags(pwq->work_color);
1795
1796 if (likely(pwq->nr_active < pwq->max_active)) {
1797 if (list_empty(&pool->worklist))
1798 pool->watchdog_ts = jiffies;
1799
1800 trace_workqueue_activate_work(work);
1801 pwq->nr_active++;
1802 insert_work(pwq, work, &pool->worklist, work_flags);
1803 kick_pool(pool);
1804 } else {
1805 work_flags |= WORK_STRUCT_INACTIVE;
1806 insert_work(pwq, work, &pwq->inactive_works, work_flags);
1807 }
1808
1809out:
1810 raw_spin_unlock(&pool->lock);
1811 rcu_read_unlock();
1812}
1813
1814/**
1815 * queue_work_on - queue work on specific cpu
1816 * @cpu: CPU number to execute work on
1817 * @wq: workqueue to use
1818 * @work: work to queue
1819 *
1820 * We queue the work to a specific CPU, the caller must ensure it
1821 * can't go away. Callers that fail to ensure that the specified
1822 * CPU cannot go away will execute on a randomly chosen CPU.
1823 * But note well that callers specifying a CPU that never has been
1824 * online will get a splat.
1825 *
1826 * Return: %false if @work was already on a queue, %true otherwise.
1827 */
1828bool queue_work_on(int cpu, struct workqueue_struct *wq,
1829 struct work_struct *work)
1830{
1831 bool ret = false;
1832 unsigned long flags;
1833
1834 local_irq_save(flags);
1835
1836 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1837 __queue_work(cpu, wq, work);
1838 ret = true;
1839 }
1840
1841 local_irq_restore(flags);
1842 return ret;
1843}
1844EXPORT_SYMBOL(queue_work_on);
1845
1846/**
1847 * select_numa_node_cpu - Select a CPU based on NUMA node
1848 * @node: NUMA node ID that we want to select a CPU from
1849 *
1850 * This function will attempt to find a "random" cpu available on a given
1851 * node. If there are no CPUs available on the given node it will return
1852 * WORK_CPU_UNBOUND indicating that we should just schedule to any
1853 * available CPU if we need to schedule this work.
1854 */
1855static int select_numa_node_cpu(int node)
1856{
1857 int cpu;
1858
1859 /* Delay binding to CPU if node is not valid or online */
1860 if (node < 0 || node >= MAX_NUMNODES || !node_online(node))
1861 return WORK_CPU_UNBOUND;
1862
1863 /* Use local node/cpu if we are already there */
1864 cpu = raw_smp_processor_id();
1865 if (node == cpu_to_node(cpu))
1866 return cpu;
1867
1868 /* Use "random" otherwise know as "first" online CPU of node */
1869 cpu = cpumask_any_and(cpumask_of_node(node), cpu_online_mask);
1870
1871 /* If CPU is valid return that, otherwise just defer */
1872 return cpu < nr_cpu_ids ? cpu : WORK_CPU_UNBOUND;
1873}
1874
1875/**
1876 * queue_work_node - queue work on a "random" cpu for a given NUMA node
1877 * @node: NUMA node that we are targeting the work for
1878 * @wq: workqueue to use
1879 * @work: work to queue
1880 *
1881 * We queue the work to a "random" CPU within a given NUMA node. The basic
1882 * idea here is to provide a way to somehow associate work with a given
1883 * NUMA node.
1884 *
1885 * This function will only make a best effort attempt at getting this onto
1886 * the right NUMA node. If no node is requested or the requested node is
1887 * offline then we just fall back to standard queue_work behavior.
1888 *
1889 * Currently the "random" CPU ends up being the first available CPU in the
1890 * intersection of cpu_online_mask and the cpumask of the node, unless we
1891 * are running on the node. In that case we just use the current CPU.
1892 *
1893 * Return: %false if @work was already on a queue, %true otherwise.
1894 */
1895bool queue_work_node(int node, struct workqueue_struct *wq,
1896 struct work_struct *work)
1897{
1898 unsigned long flags;
1899 bool ret = false;
1900
1901 /*
1902 * This current implementation is specific to unbound workqueues.
1903 * Specifically we only return the first available CPU for a given
1904 * node instead of cycling through individual CPUs within the node.
1905 *
1906 * If this is used with a per-cpu workqueue then the logic in
1907 * workqueue_select_cpu_near would need to be updated to allow for
1908 * some round robin type logic.
1909 */
1910 WARN_ON_ONCE(!(wq->flags & WQ_UNBOUND));
1911
1912 local_irq_save(flags);
1913
1914 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1915 int cpu = select_numa_node_cpu(node);
1916
1917 __queue_work(cpu, wq, work);
1918 ret = true;
1919 }
1920
1921 local_irq_restore(flags);
1922 return ret;
1923}
1924EXPORT_SYMBOL_GPL(queue_work_node);
1925
1926void delayed_work_timer_fn(struct timer_list *t)
1927{
1928 struct delayed_work *dwork = from_timer(dwork, t, timer);
1929
1930 /* should have been called from irqsafe timer with irq already off */
1931 __queue_work(dwork->cpu, dwork->wq, &dwork->work);
1932}
1933EXPORT_SYMBOL(delayed_work_timer_fn);
1934
1935static void __queue_delayed_work(int cpu, struct workqueue_struct *wq,
1936 struct delayed_work *dwork, unsigned long delay)
1937{
1938 struct timer_list *timer = &dwork->timer;
1939 struct work_struct *work = &dwork->work;
1940
1941 WARN_ON_ONCE(!wq);
1942 WARN_ON_ONCE(timer->function != delayed_work_timer_fn);
1943 WARN_ON_ONCE(timer_pending(timer));
1944 WARN_ON_ONCE(!list_empty(&work->entry));
1945
1946 /*
1947 * If @delay is 0, queue @dwork->work immediately. This is for
1948 * both optimization and correctness. The earliest @timer can
1949 * expire is on the closest next tick and delayed_work users depend
1950 * on that there's no such delay when @delay is 0.
1951 */
1952 if (!delay) {
1953 __queue_work(cpu, wq, &dwork->work);
1954 return;
1955 }
1956
1957 dwork->wq = wq;
1958 dwork->cpu = cpu;
1959 timer->expires = jiffies + delay;
1960
1961 if (unlikely(cpu != WORK_CPU_UNBOUND))
1962 add_timer_on(timer, cpu);
1963 else
1964 add_timer(timer);
1965}
1966
1967/**
1968 * queue_delayed_work_on - queue work on specific CPU after delay
1969 * @cpu: CPU number to execute work on
1970 * @wq: workqueue to use
1971 * @dwork: work to queue
1972 * @delay: number of jiffies to wait before queueing
1973 *
1974 * Return: %false if @work was already on a queue, %true otherwise. If
1975 * @delay is zero and @dwork is idle, it will be scheduled for immediate
1976 * execution.
1977 */
1978bool queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
1979 struct delayed_work *dwork, unsigned long delay)
1980{
1981 struct work_struct *work = &dwork->work;
1982 bool ret = false;
1983 unsigned long flags;
1984
1985 /* read the comment in __queue_work() */
1986 local_irq_save(flags);
1987
1988 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1989 __queue_delayed_work(cpu, wq, dwork, delay);
1990 ret = true;
1991 }
1992
1993 local_irq_restore(flags);
1994 return ret;
1995}
1996EXPORT_SYMBOL(queue_delayed_work_on);
1997
1998/**
1999 * mod_delayed_work_on - modify delay of or queue a delayed work on specific CPU
2000 * @cpu: CPU number to execute work on
2001 * @wq: workqueue to use
2002 * @dwork: work to queue
2003 * @delay: number of jiffies to wait before queueing
2004 *
2005 * If @dwork is idle, equivalent to queue_delayed_work_on(); otherwise,
2006 * modify @dwork's timer so that it expires after @delay. If @delay is
2007 * zero, @work is guaranteed to be scheduled immediately regardless of its
2008 * current state.
2009 *
2010 * Return: %false if @dwork was idle and queued, %true if @dwork was
2011 * pending and its timer was modified.
2012 *
2013 * This function is safe to call from any context including IRQ handler.
2014 * See try_to_grab_pending() for details.
2015 */
2016bool mod_delayed_work_on(int cpu, struct workqueue_struct *wq,
2017 struct delayed_work *dwork, unsigned long delay)
2018{
2019 unsigned long flags;
2020 int ret;
2021
2022 do {
2023 ret = try_to_grab_pending(&dwork->work, true, &flags);
2024 } while (unlikely(ret == -EAGAIN));
2025
2026 if (likely(ret >= 0)) {
2027 __queue_delayed_work(cpu, wq, dwork, delay);
2028 local_irq_restore(flags);
2029 }
2030
2031 /* -ENOENT from try_to_grab_pending() becomes %true */
2032 return ret;
2033}
2034EXPORT_SYMBOL_GPL(mod_delayed_work_on);
2035
2036static void rcu_work_rcufn(struct rcu_head *rcu)
2037{
2038 struct rcu_work *rwork = container_of(rcu, struct rcu_work, rcu);
2039
2040 /* read the comment in __queue_work() */
2041 local_irq_disable();
2042 __queue_work(WORK_CPU_UNBOUND, rwork->wq, &rwork->work);
2043 local_irq_enable();
2044}
2045
2046/**
2047 * queue_rcu_work - queue work after a RCU grace period
2048 * @wq: workqueue to use
2049 * @rwork: work to queue
2050 *
2051 * Return: %false if @rwork was already pending, %true otherwise. Note
2052 * that a full RCU grace period is guaranteed only after a %true return.
2053 * While @rwork is guaranteed to be executed after a %false return, the
2054 * execution may happen before a full RCU grace period has passed.
2055 */
2056bool queue_rcu_work(struct workqueue_struct *wq, struct rcu_work *rwork)
2057{
2058 struct work_struct *work = &rwork->work;
2059
2060 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
2061 rwork->wq = wq;
2062 call_rcu_hurry(&rwork->rcu, rcu_work_rcufn);
2063 return true;
2064 }
2065
2066 return false;
2067}
2068EXPORT_SYMBOL(queue_rcu_work);
2069
2070static struct worker *alloc_worker(int node)
2071{
2072 struct worker *worker;
2073
2074 worker = kzalloc_node(sizeof(*worker), GFP_KERNEL, node);
2075 if (worker) {
2076 INIT_LIST_HEAD(&worker->entry);
2077 INIT_LIST_HEAD(&worker->scheduled);
2078 INIT_LIST_HEAD(&worker->node);
2079 /* on creation a worker is in !idle && prep state */
2080 worker->flags = WORKER_PREP;
2081 }
2082 return worker;
2083}
2084
2085static cpumask_t *pool_allowed_cpus(struct worker_pool *pool)
2086{
2087 if (pool->cpu < 0 && pool->attrs->affn_strict)
2088 return pool->attrs->__pod_cpumask;
2089 else
2090 return pool->attrs->cpumask;
2091}
2092
2093/**
2094 * worker_attach_to_pool() - attach a worker to a pool
2095 * @worker: worker to be attached
2096 * @pool: the target pool
2097 *
2098 * Attach @worker to @pool. Once attached, the %WORKER_UNBOUND flag and
2099 * cpu-binding of @worker are kept coordinated with the pool across
2100 * cpu-[un]hotplugs.
2101 */
2102static void worker_attach_to_pool(struct worker *worker,
2103 struct worker_pool *pool)
2104{
2105 mutex_lock(&wq_pool_attach_mutex);
2106
2107 /*
2108 * The wq_pool_attach_mutex ensures %POOL_DISASSOCIATED remains
2109 * stable across this function. See the comments above the flag
2110 * definition for details.
2111 */
2112 if (pool->flags & POOL_DISASSOCIATED)
2113 worker->flags |= WORKER_UNBOUND;
2114 else
2115 kthread_set_per_cpu(worker->task, pool->cpu);
2116
2117 if (worker->rescue_wq)
2118 set_cpus_allowed_ptr(worker->task, pool_allowed_cpus(pool));
2119
2120 list_add_tail(&worker->node, &pool->workers);
2121 worker->pool = pool;
2122
2123 mutex_unlock(&wq_pool_attach_mutex);
2124}
2125
2126/**
2127 * worker_detach_from_pool() - detach a worker from its pool
2128 * @worker: worker which is attached to its pool
2129 *
2130 * Undo the attaching which had been done in worker_attach_to_pool(). The
2131 * caller worker shouldn't access to the pool after detached except it has
2132 * other reference to the pool.
2133 */
2134static void worker_detach_from_pool(struct worker *worker)
2135{
2136 struct worker_pool *pool = worker->pool;
2137 struct completion *detach_completion = NULL;
2138
2139 mutex_lock(&wq_pool_attach_mutex);
2140
2141 kthread_set_per_cpu(worker->task, -1);
2142 list_del(&worker->node);
2143 worker->pool = NULL;
2144
2145 if (list_empty(&pool->workers) && list_empty(&pool->dying_workers))
2146 detach_completion = pool->detach_completion;
2147 mutex_unlock(&wq_pool_attach_mutex);
2148
2149 /* clear leftover flags without pool->lock after it is detached */
2150 worker->flags &= ~(WORKER_UNBOUND | WORKER_REBOUND);
2151
2152 if (detach_completion)
2153 complete(detach_completion);
2154}
2155
2156/**
2157 * create_worker - create a new workqueue worker
2158 * @pool: pool the new worker will belong to
2159 *
2160 * Create and start a new worker which is attached to @pool.
2161 *
2162 * CONTEXT:
2163 * Might sleep. Does GFP_KERNEL allocations.
2164 *
2165 * Return:
2166 * Pointer to the newly created worker.
2167 */
2168static struct worker *create_worker(struct worker_pool *pool)
2169{
2170 struct worker *worker;
2171 int id;
2172 char id_buf[23];
2173
2174 /* ID is needed to determine kthread name */
2175 id = ida_alloc(&pool->worker_ida, GFP_KERNEL);
2176 if (id < 0) {
2177 pr_err_once("workqueue: Failed to allocate a worker ID: %pe\n",
2178 ERR_PTR(id));
2179 return NULL;
2180 }
2181
2182 worker = alloc_worker(pool->node);
2183 if (!worker) {
2184 pr_err_once("workqueue: Failed to allocate a worker\n");
2185 goto fail;
2186 }
2187
2188 worker->id = id;
2189
2190 if (pool->cpu >= 0)
2191 snprintf(id_buf, sizeof(id_buf), "%d:%d%s", pool->cpu, id,
2192 pool->attrs->nice < 0 ? "H" : "");
2193 else
2194 snprintf(id_buf, sizeof(id_buf), "u%d:%d", pool->id, id);
2195
2196 worker->task = kthread_create_on_node(worker_thread, worker, pool->node,
2197 "kworker/%s", id_buf);
2198 if (IS_ERR(worker->task)) {
2199 if (PTR_ERR(worker->task) == -EINTR) {
2200 pr_err("workqueue: Interrupted when creating a worker thread \"kworker/%s\"\n",
2201 id_buf);
2202 } else {
2203 pr_err_once("workqueue: Failed to create a worker thread: %pe",
2204 worker->task);
2205 }
2206 goto fail;
2207 }
2208
2209 set_user_nice(worker->task, pool->attrs->nice);
2210 kthread_bind_mask(worker->task, pool_allowed_cpus(pool));
2211
2212 /* successful, attach the worker to the pool */
2213 worker_attach_to_pool(worker, pool);
2214
2215 /* start the newly created worker */
2216 raw_spin_lock_irq(&pool->lock);
2217
2218 worker->pool->nr_workers++;
2219 worker_enter_idle(worker);
2220 kick_pool(pool);
2221
2222 /*
2223 * @worker is waiting on a completion in kthread() and will trigger hung
2224 * check if not woken up soon. As kick_pool() might not have waken it
2225 * up, wake it up explicitly once more.
2226 */
2227 wake_up_process(worker->task);
2228
2229 raw_spin_unlock_irq(&pool->lock);
2230
2231 return worker;
2232
2233fail:
2234 ida_free(&pool->worker_ida, id);
2235 kfree(worker);
2236 return NULL;
2237}
2238
2239static void unbind_worker(struct worker *worker)
2240{
2241 lockdep_assert_held(&wq_pool_attach_mutex);
2242
2243 kthread_set_per_cpu(worker->task, -1);
2244 if (cpumask_intersects(wq_unbound_cpumask, cpu_active_mask))
2245 WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task, wq_unbound_cpumask) < 0);
2246 else
2247 WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task, cpu_possible_mask) < 0);
2248}
2249
2250static void wake_dying_workers(struct list_head *cull_list)
2251{
2252 struct worker *worker, *tmp;
2253
2254 list_for_each_entry_safe(worker, tmp, cull_list, entry) {
2255 list_del_init(&worker->entry);
2256 unbind_worker(worker);
2257 /*
2258 * If the worker was somehow already running, then it had to be
2259 * in pool->idle_list when set_worker_dying() happened or we
2260 * wouldn't have gotten here.
2261 *
2262 * Thus, the worker must either have observed the WORKER_DIE
2263 * flag, or have set its state to TASK_IDLE. Either way, the
2264 * below will be observed by the worker and is safe to do
2265 * outside of pool->lock.
2266 */
2267 wake_up_process(worker->task);
2268 }
2269}
2270
2271/**
2272 * set_worker_dying - Tag a worker for destruction
2273 * @worker: worker to be destroyed
2274 * @list: transfer worker away from its pool->idle_list and into list
2275 *
2276 * Tag @worker for destruction and adjust @pool stats accordingly. The worker
2277 * should be idle.
2278 *
2279 * CONTEXT:
2280 * raw_spin_lock_irq(pool->lock).
2281 */
2282static void set_worker_dying(struct worker *worker, struct list_head *list)
2283{
2284 struct worker_pool *pool = worker->pool;
2285
2286 lockdep_assert_held(&pool->lock);
2287 lockdep_assert_held(&wq_pool_attach_mutex);
2288
2289 /* sanity check frenzy */
2290 if (WARN_ON(worker->current_work) ||
2291 WARN_ON(!list_empty(&worker->scheduled)) ||
2292 WARN_ON(!(worker->flags & WORKER_IDLE)))
2293 return;
2294
2295 pool->nr_workers--;
2296 pool->nr_idle--;
2297
2298 worker->flags |= WORKER_DIE;
2299
2300 list_move(&worker->entry, list);
2301 list_move(&worker->node, &pool->dying_workers);
2302}
2303
2304/**
2305 * idle_worker_timeout - check if some idle workers can now be deleted.
2306 * @t: The pool's idle_timer that just expired
2307 *
2308 * The timer is armed in worker_enter_idle(). Note that it isn't disarmed in
2309 * worker_leave_idle(), as a worker flicking between idle and active while its
2310 * pool is at the too_many_workers() tipping point would cause too much timer
2311 * housekeeping overhead. Since IDLE_WORKER_TIMEOUT is long enough, we just let
2312 * it expire and re-evaluate things from there.
2313 */
2314static void idle_worker_timeout(struct timer_list *t)
2315{
2316 struct worker_pool *pool = from_timer(pool, t, idle_timer);
2317 bool do_cull = false;
2318
2319 if (work_pending(&pool->idle_cull_work))
2320 return;
2321
2322 raw_spin_lock_irq(&pool->lock);
2323
2324 if (too_many_workers(pool)) {
2325 struct worker *worker;
2326 unsigned long expires;
2327
2328 /* idle_list is kept in LIFO order, check the last one */
2329 worker = list_entry(pool->idle_list.prev, struct worker, entry);
2330 expires = worker->last_active + IDLE_WORKER_TIMEOUT;
2331 do_cull = !time_before(jiffies, expires);
2332
2333 if (!do_cull)
2334 mod_timer(&pool->idle_timer, expires);
2335 }
2336 raw_spin_unlock_irq(&pool->lock);
2337
2338 if (do_cull)
2339 queue_work(system_unbound_wq, &pool->idle_cull_work);
2340}
2341
2342/**
2343 * idle_cull_fn - cull workers that have been idle for too long.
2344 * @work: the pool's work for handling these idle workers
2345 *
2346 * This goes through a pool's idle workers and gets rid of those that have been
2347 * idle for at least IDLE_WORKER_TIMEOUT seconds.
2348 *
2349 * We don't want to disturb isolated CPUs because of a pcpu kworker being
2350 * culled, so this also resets worker affinity. This requires a sleepable
2351 * context, hence the split between timer callback and work item.
2352 */
2353static void idle_cull_fn(struct work_struct *work)
2354{
2355 struct worker_pool *pool = container_of(work, struct worker_pool, idle_cull_work);
2356 LIST_HEAD(cull_list);
2357
2358 /*
2359 * Grabbing wq_pool_attach_mutex here ensures an already-running worker
2360 * cannot proceed beyong worker_detach_from_pool() in its self-destruct
2361 * path. This is required as a previously-preempted worker could run after
2362 * set_worker_dying() has happened but before wake_dying_workers() did.
2363 */
2364 mutex_lock(&wq_pool_attach_mutex);
2365 raw_spin_lock_irq(&pool->lock);
2366
2367 while (too_many_workers(pool)) {
2368 struct worker *worker;
2369 unsigned long expires;
2370
2371 worker = list_entry(pool->idle_list.prev, struct worker, entry);
2372 expires = worker->last_active + IDLE_WORKER_TIMEOUT;
2373
2374 if (time_before(jiffies, expires)) {
2375 mod_timer(&pool->idle_timer, expires);
2376 break;
2377 }
2378
2379 set_worker_dying(worker, &cull_list);
2380 }
2381
2382 raw_spin_unlock_irq(&pool->lock);
2383 wake_dying_workers(&cull_list);
2384 mutex_unlock(&wq_pool_attach_mutex);
2385}
2386
2387static void send_mayday(struct work_struct *work)
2388{
2389 struct pool_workqueue *pwq = get_work_pwq(work);
2390 struct workqueue_struct *wq = pwq->wq;
2391
2392 lockdep_assert_held(&wq_mayday_lock);
2393
2394 if (!wq->rescuer)
2395 return;
2396
2397 /* mayday mayday mayday */
2398 if (list_empty(&pwq->mayday_node)) {
2399 /*
2400 * If @pwq is for an unbound wq, its base ref may be put at
2401 * any time due to an attribute change. Pin @pwq until the
2402 * rescuer is done with it.
2403 */
2404 get_pwq(pwq);
2405 list_add_tail(&pwq->mayday_node, &wq->maydays);
2406 wake_up_process(wq->rescuer->task);
2407 pwq->stats[PWQ_STAT_MAYDAY]++;
2408 }
2409}
2410
2411static void pool_mayday_timeout(struct timer_list *t)
2412{
2413 struct worker_pool *pool = from_timer(pool, t, mayday_timer);
2414 struct work_struct *work;
2415
2416 raw_spin_lock_irq(&pool->lock);
2417 raw_spin_lock(&wq_mayday_lock); /* for wq->maydays */
2418
2419 if (need_to_create_worker(pool)) {
2420 /*
2421 * We've been trying to create a new worker but
2422 * haven't been successful. We might be hitting an
2423 * allocation deadlock. Send distress signals to
2424 * rescuers.
2425 */
2426 list_for_each_entry(work, &pool->worklist, entry)
2427 send_mayday(work);
2428 }
2429
2430 raw_spin_unlock(&wq_mayday_lock);
2431 raw_spin_unlock_irq(&pool->lock);
2432
2433 mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INTERVAL);
2434}
2435
2436/**
2437 * maybe_create_worker - create a new worker if necessary
2438 * @pool: pool to create a new worker for
2439 *
2440 * Create a new worker for @pool if necessary. @pool is guaranteed to
2441 * have at least one idle worker on return from this function. If
2442 * creating a new worker takes longer than MAYDAY_INTERVAL, mayday is
2443 * sent to all rescuers with works scheduled on @pool to resolve
2444 * possible allocation deadlock.
2445 *
2446 * On return, need_to_create_worker() is guaranteed to be %false and
2447 * may_start_working() %true.
2448 *
2449 * LOCKING:
2450 * raw_spin_lock_irq(pool->lock) which may be released and regrabbed
2451 * multiple times. Does GFP_KERNEL allocations. Called only from
2452 * manager.
2453 */
2454static void maybe_create_worker(struct worker_pool *pool)
2455__releases(&pool->lock)
2456__acquires(&pool->lock)
2457{
2458restart:
2459 raw_spin_unlock_irq(&pool->lock);
2460
2461 /* if we don't make progress in MAYDAY_INITIAL_TIMEOUT, call for help */
2462 mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INITIAL_TIMEOUT);
2463
2464 while (true) {
2465 if (create_worker(pool) || !need_to_create_worker(pool))
2466 break;
2467
2468 schedule_timeout_interruptible(CREATE_COOLDOWN);
2469
2470 if (!need_to_create_worker(pool))
2471 break;
2472 }
2473
2474 del_timer_sync(&pool->mayday_timer);
2475 raw_spin_lock_irq(&pool->lock);
2476 /*
2477 * This is necessary even after a new worker was just successfully
2478 * created as @pool->lock was dropped and the new worker might have
2479 * already become busy.
2480 */
2481 if (need_to_create_worker(pool))
2482 goto restart;
2483}
2484
2485/**
2486 * manage_workers - manage worker pool
2487 * @worker: self
2488 *
2489 * Assume the manager role and manage the worker pool @worker belongs
2490 * to. At any given time, there can be only zero or one manager per
2491 * pool. The exclusion is handled automatically by this function.
2492 *
2493 * The caller can safely start processing works on false return. On
2494 * true return, it's guaranteed that need_to_create_worker() is false
2495 * and may_start_working() is true.
2496 *
2497 * CONTEXT:
2498 * raw_spin_lock_irq(pool->lock) which may be released and regrabbed
2499 * multiple times. Does GFP_KERNEL allocations.
2500 *
2501 * Return:
2502 * %false if the pool doesn't need management and the caller can safely
2503 * start processing works, %true if management function was performed and
2504 * the conditions that the caller verified before calling the function may
2505 * no longer be true.
2506 */
2507static bool manage_workers(struct worker *worker)
2508{
2509 struct worker_pool *pool = worker->pool;
2510
2511 if (pool->flags & POOL_MANAGER_ACTIVE)
2512 return false;
2513
2514 pool->flags |= POOL_MANAGER_ACTIVE;
2515 pool->manager = worker;
2516
2517 maybe_create_worker(pool);
2518
2519 pool->manager = NULL;
2520 pool->flags &= ~POOL_MANAGER_ACTIVE;
2521 rcuwait_wake_up(&manager_wait);
2522 return true;
2523}
2524
2525/**
2526 * process_one_work - process single work
2527 * @worker: self
2528 * @work: work to process
2529 *
2530 * Process @work. This function contains all the logics necessary to
2531 * process a single work including synchronization against and
2532 * interaction with other workers on the same cpu, queueing and
2533 * flushing. As long as context requirement is met, any worker can
2534 * call this function to process a work.
2535 *
2536 * CONTEXT:
2537 * raw_spin_lock_irq(pool->lock) which is released and regrabbed.
2538 */
2539static void process_one_work(struct worker *worker, struct work_struct *work)
2540__releases(&pool->lock)
2541__acquires(&pool->lock)
2542{
2543 struct pool_workqueue *pwq = get_work_pwq(work);
2544 struct worker_pool *pool = worker->pool;
2545 unsigned long work_data;
2546#ifdef CONFIG_LOCKDEP
2547 /*
2548 * It is permissible to free the struct work_struct from
2549 * inside the function that is called from it, this we need to
2550 * take into account for lockdep too. To avoid bogus "held
2551 * lock freed" warnings as well as problems when looking into
2552 * work->lockdep_map, make a copy and use that here.
2553 */
2554 struct lockdep_map lockdep_map;
2555
2556 lockdep_copy_map(&lockdep_map, &work->lockdep_map);
2557#endif
2558 /* ensure we're on the correct CPU */
2559 WARN_ON_ONCE(!(pool->flags & POOL_DISASSOCIATED) &&
2560 raw_smp_processor_id() != pool->cpu);
2561
2562 /* claim and dequeue */
2563 debug_work_deactivate(work);
2564 hash_add(pool->busy_hash, &worker->hentry, (unsigned long)work);
2565 worker->current_work = work;
2566 worker->current_func = work->func;
2567 worker->current_pwq = pwq;
2568 worker->current_at = worker->task->se.sum_exec_runtime;
2569 work_data = *work_data_bits(work);
2570 worker->current_color = get_work_color(work_data);
2571
2572 /*
2573 * Record wq name for cmdline and debug reporting, may get
2574 * overridden through set_worker_desc().
2575 */
2576 strscpy(worker->desc, pwq->wq->name, WORKER_DESC_LEN);
2577
2578 list_del_init(&work->entry);
2579
2580 /*
2581 * CPU intensive works don't participate in concurrency management.
2582 * They're the scheduler's responsibility. This takes @worker out
2583 * of concurrency management and the next code block will chain
2584 * execution of the pending work items.
2585 */
2586 if (unlikely(pwq->wq->flags & WQ_CPU_INTENSIVE))
2587 worker_set_flags(worker, WORKER_CPU_INTENSIVE);
2588
2589 /*
2590 * Kick @pool if necessary. It's always noop for per-cpu worker pools
2591 * since nr_running would always be >= 1 at this point. This is used to
2592 * chain execution of the pending work items for WORKER_NOT_RUNNING
2593 * workers such as the UNBOUND and CPU_INTENSIVE ones.
2594 */
2595 kick_pool(pool);
2596
2597 /*
2598 * Record the last pool and clear PENDING which should be the last
2599 * update to @work. Also, do this inside @pool->lock so that
2600 * PENDING and queued state changes happen together while IRQ is
2601 * disabled.
2602 */
2603 set_work_pool_and_clear_pending(work, pool->id);
2604
2605 pwq->stats[PWQ_STAT_STARTED]++;
2606 raw_spin_unlock_irq(&pool->lock);
2607
2608 lock_map_acquire(&pwq->wq->lockdep_map);
2609 lock_map_acquire(&lockdep_map);
2610 /*
2611 * Strictly speaking we should mark the invariant state without holding
2612 * any locks, that is, before these two lock_map_acquire()'s.
2613 *
2614 * However, that would result in:
2615 *
2616 * A(W1)
2617 * WFC(C)
2618 * A(W1)
2619 * C(C)
2620 *
2621 * Which would create W1->C->W1 dependencies, even though there is no
2622 * actual deadlock possible. There are two solutions, using a
2623 * read-recursive acquire on the work(queue) 'locks', but this will then
2624 * hit the lockdep limitation on recursive locks, or simply discard
2625 * these locks.
2626 *
2627 * AFAICT there is no possible deadlock scenario between the
2628 * flush_work() and complete() primitives (except for single-threaded
2629 * workqueues), so hiding them isn't a problem.
2630 */
2631 lockdep_invariant_state(true);
2632 trace_workqueue_execute_start(work);
2633 worker->current_func(work);
2634 /*
2635 * While we must be careful to not use "work" after this, the trace
2636 * point will only record its address.
2637 */
2638 trace_workqueue_execute_end(work, worker->current_func);
2639 pwq->stats[PWQ_STAT_COMPLETED]++;
2640 lock_map_release(&lockdep_map);
2641 lock_map_release(&pwq->wq->lockdep_map);
2642
2643 if (unlikely(in_atomic() || lockdep_depth(current) > 0)) {
2644 pr_err("BUG: workqueue leaked lock or atomic: %s/0x%08x/%d\n"
2645 " last function: %ps\n",
2646 current->comm, preempt_count(), task_pid_nr(current),
2647 worker->current_func);
2648 debug_show_held_locks(current);
2649 dump_stack();
2650 }
2651
2652 /*
2653 * The following prevents a kworker from hogging CPU on !PREEMPTION
2654 * kernels, where a requeueing work item waiting for something to
2655 * happen could deadlock with stop_machine as such work item could
2656 * indefinitely requeue itself while all other CPUs are trapped in
2657 * stop_machine. At the same time, report a quiescent RCU state so
2658 * the same condition doesn't freeze RCU.
2659 */
2660 cond_resched();
2661
2662 raw_spin_lock_irq(&pool->lock);
2663
2664 /*
2665 * In addition to %WQ_CPU_INTENSIVE, @worker may also have been marked
2666 * CPU intensive by wq_worker_tick() if @work hogged CPU longer than
2667 * wq_cpu_intensive_thresh_us. Clear it.
2668 */
2669 worker_clr_flags(worker, WORKER_CPU_INTENSIVE);
2670
2671 /* tag the worker for identification in schedule() */
2672 worker->last_func = worker->current_func;
2673
2674 /* we're done with it, release */
2675 hash_del(&worker->hentry);
2676 worker->current_work = NULL;
2677 worker->current_func = NULL;
2678 worker->current_pwq = NULL;
2679 worker->current_color = INT_MAX;
2680 pwq_dec_nr_in_flight(pwq, work_data);
2681}
2682
2683/**
2684 * process_scheduled_works - process scheduled works
2685 * @worker: self
2686 *
2687 * Process all scheduled works. Please note that the scheduled list
2688 * may change while processing a work, so this function repeatedly
2689 * fetches a work from the top and executes it.
2690 *
2691 * CONTEXT:
2692 * raw_spin_lock_irq(pool->lock) which may be released and regrabbed
2693 * multiple times.
2694 */
2695static void process_scheduled_works(struct worker *worker)
2696{
2697 struct work_struct *work;
2698 bool first = true;
2699
2700 while ((work = list_first_entry_or_null(&worker->scheduled,
2701 struct work_struct, entry))) {
2702 if (first) {
2703 worker->pool->watchdog_ts = jiffies;
2704 first = false;
2705 }
2706 process_one_work(worker, work);
2707 }
2708}
2709
2710static void set_pf_worker(bool val)
2711{
2712 mutex_lock(&wq_pool_attach_mutex);
2713 if (val)
2714 current->flags |= PF_WQ_WORKER;
2715 else
2716 current->flags &= ~PF_WQ_WORKER;
2717 mutex_unlock(&wq_pool_attach_mutex);
2718}
2719
2720/**
2721 * worker_thread - the worker thread function
2722 * @__worker: self
2723 *
2724 * The worker thread function. All workers belong to a worker_pool -
2725 * either a per-cpu one or dynamic unbound one. These workers process all
2726 * work items regardless of their specific target workqueue. The only
2727 * exception is work items which belong to workqueues with a rescuer which
2728 * will be explained in rescuer_thread().
2729 *
2730 * Return: 0
2731 */
2732static int worker_thread(void *__worker)
2733{
2734 struct worker *worker = __worker;
2735 struct worker_pool *pool = worker->pool;
2736
2737 /* tell the scheduler that this is a workqueue worker */
2738 set_pf_worker(true);
2739woke_up:
2740 raw_spin_lock_irq(&pool->lock);
2741
2742 /* am I supposed to die? */
2743 if (unlikely(worker->flags & WORKER_DIE)) {
2744 raw_spin_unlock_irq(&pool->lock);
2745 set_pf_worker(false);
2746
2747 set_task_comm(worker->task, "kworker/dying");
2748 ida_free(&pool->worker_ida, worker->id);
2749 worker_detach_from_pool(worker);
2750 WARN_ON_ONCE(!list_empty(&worker->entry));
2751 kfree(worker);
2752 return 0;
2753 }
2754
2755 worker_leave_idle(worker);
2756recheck:
2757 /* no more worker necessary? */
2758 if (!need_more_worker(pool))
2759 goto sleep;
2760
2761 /* do we need to manage? */
2762 if (unlikely(!may_start_working(pool)) && manage_workers(worker))
2763 goto recheck;
2764
2765 /*
2766 * ->scheduled list can only be filled while a worker is
2767 * preparing to process a work or actually processing it.
2768 * Make sure nobody diddled with it while I was sleeping.
2769 */
2770 WARN_ON_ONCE(!list_empty(&worker->scheduled));
2771
2772 /*
2773 * Finish PREP stage. We're guaranteed to have at least one idle
2774 * worker or that someone else has already assumed the manager
2775 * role. This is where @worker starts participating in concurrency
2776 * management if applicable and concurrency management is restored
2777 * after being rebound. See rebind_workers() for details.
2778 */
2779 worker_clr_flags(worker, WORKER_PREP | WORKER_REBOUND);
2780
2781 do {
2782 struct work_struct *work =
2783 list_first_entry(&pool->worklist,
2784 struct work_struct, entry);
2785
2786 if (assign_work(work, worker, NULL))
2787 process_scheduled_works(worker);
2788 } while (keep_working(pool));
2789
2790 worker_set_flags(worker, WORKER_PREP);
2791sleep:
2792 /*
2793 * pool->lock is held and there's no work to process and no need to
2794 * manage, sleep. Workers are woken up only while holding
2795 * pool->lock or from local cpu, so setting the current state
2796 * before releasing pool->lock is enough to prevent losing any
2797 * event.
2798 */
2799 worker_enter_idle(worker);
2800 __set_current_state(TASK_IDLE);
2801 raw_spin_unlock_irq(&pool->lock);
2802 schedule();
2803 goto woke_up;
2804}
2805
2806/**
2807 * rescuer_thread - the rescuer thread function
2808 * @__rescuer: self
2809 *
2810 * Workqueue rescuer thread function. There's one rescuer for each
2811 * workqueue which has WQ_MEM_RECLAIM set.
2812 *
2813 * Regular work processing on a pool may block trying to create a new
2814 * worker which uses GFP_KERNEL allocation which has slight chance of
2815 * developing into deadlock if some works currently on the same queue
2816 * need to be processed to satisfy the GFP_KERNEL allocation. This is
2817 * the problem rescuer solves.
2818 *
2819 * When such condition is possible, the pool summons rescuers of all
2820 * workqueues which have works queued on the pool and let them process
2821 * those works so that forward progress can be guaranteed.
2822 *
2823 * This should happen rarely.
2824 *
2825 * Return: 0
2826 */
2827static int rescuer_thread(void *__rescuer)
2828{
2829 struct worker *rescuer = __rescuer;
2830 struct workqueue_struct *wq = rescuer->rescue_wq;
2831 bool should_stop;
2832
2833 set_user_nice(current, RESCUER_NICE_LEVEL);
2834
2835 /*
2836 * Mark rescuer as worker too. As WORKER_PREP is never cleared, it
2837 * doesn't participate in concurrency management.
2838 */
2839 set_pf_worker(true);
2840repeat:
2841 set_current_state(TASK_IDLE);
2842
2843 /*
2844 * By the time the rescuer is requested to stop, the workqueue
2845 * shouldn't have any work pending, but @wq->maydays may still have
2846 * pwq(s) queued. This can happen by non-rescuer workers consuming
2847 * all the work items before the rescuer got to them. Go through
2848 * @wq->maydays processing before acting on should_stop so that the
2849 * list is always empty on exit.
2850 */
2851 should_stop = kthread_should_stop();
2852
2853 /* see whether any pwq is asking for help */
2854 raw_spin_lock_irq(&wq_mayday_lock);
2855
2856 while (!list_empty(&wq->maydays)) {
2857 struct pool_workqueue *pwq = list_first_entry(&wq->maydays,
2858 struct pool_workqueue, mayday_node);
2859 struct worker_pool *pool = pwq->pool;
2860 struct work_struct *work, *n;
2861
2862 __set_current_state(TASK_RUNNING);
2863 list_del_init(&pwq->mayday_node);
2864
2865 raw_spin_unlock_irq(&wq_mayday_lock);
2866
2867 worker_attach_to_pool(rescuer, pool);
2868
2869 raw_spin_lock_irq(&pool->lock);
2870
2871 /*
2872 * Slurp in all works issued via this workqueue and
2873 * process'em.
2874 */
2875 WARN_ON_ONCE(!list_empty(&rescuer->scheduled));
2876 list_for_each_entry_safe(work, n, &pool->worklist, entry) {
2877 if (get_work_pwq(work) == pwq &&
2878 assign_work(work, rescuer, &n))
2879 pwq->stats[PWQ_STAT_RESCUED]++;
2880 }
2881
2882 if (!list_empty(&rescuer->scheduled)) {
2883 process_scheduled_works(rescuer);
2884
2885 /*
2886 * The above execution of rescued work items could
2887 * have created more to rescue through
2888 * pwq_activate_first_inactive() or chained
2889 * queueing. Let's put @pwq back on mayday list so
2890 * that such back-to-back work items, which may be
2891 * being used to relieve memory pressure, don't
2892 * incur MAYDAY_INTERVAL delay inbetween.
2893 */
2894 if (pwq->nr_active && need_to_create_worker(pool)) {
2895 raw_spin_lock(&wq_mayday_lock);
2896 /*
2897 * Queue iff we aren't racing destruction
2898 * and somebody else hasn't queued it already.
2899 */
2900 if (wq->rescuer && list_empty(&pwq->mayday_node)) {
2901 get_pwq(pwq);
2902 list_add_tail(&pwq->mayday_node, &wq->maydays);
2903 }
2904 raw_spin_unlock(&wq_mayday_lock);
2905 }
2906 }
2907
2908 /*
2909 * Put the reference grabbed by send_mayday(). @pool won't
2910 * go away while we're still attached to it.
2911 */
2912 put_pwq(pwq);
2913
2914 /*
2915 * Leave this pool. Notify regular workers; otherwise, we end up
2916 * with 0 concurrency and stalling the execution.
2917 */
2918 kick_pool(pool);
2919
2920 raw_spin_unlock_irq(&pool->lock);
2921
2922 worker_detach_from_pool(rescuer);
2923
2924 raw_spin_lock_irq(&wq_mayday_lock);
2925 }
2926
2927 raw_spin_unlock_irq(&wq_mayday_lock);
2928
2929 if (should_stop) {
2930 __set_current_state(TASK_RUNNING);
2931 set_pf_worker(false);
2932 return 0;
2933 }
2934
2935 /* rescuers should never participate in concurrency management */
2936 WARN_ON_ONCE(!(rescuer->flags & WORKER_NOT_RUNNING));
2937 schedule();
2938 goto repeat;
2939}
2940
2941/**
2942 * check_flush_dependency - check for flush dependency sanity
2943 * @target_wq: workqueue being flushed
2944 * @target_work: work item being flushed (NULL for workqueue flushes)
2945 *
2946 * %current is trying to flush the whole @target_wq or @target_work on it.
2947 * If @target_wq doesn't have %WQ_MEM_RECLAIM, verify that %current is not
2948 * reclaiming memory or running on a workqueue which doesn't have
2949 * %WQ_MEM_RECLAIM as that can break forward-progress guarantee leading to
2950 * a deadlock.
2951 */
2952static void check_flush_dependency(struct workqueue_struct *target_wq,
2953 struct work_struct *target_work)
2954{
2955 work_func_t target_func = target_work ? target_work->func : NULL;
2956 struct worker *worker;
2957
2958 if (target_wq->flags & WQ_MEM_RECLAIM)
2959 return;
2960
2961 worker = current_wq_worker();
2962
2963 WARN_ONCE(current->flags & PF_MEMALLOC,
2964 "workqueue: PF_MEMALLOC task %d(%s) is flushing !WQ_MEM_RECLAIM %s:%ps",
2965 current->pid, current->comm, target_wq->name, target_func);
2966 WARN_ONCE(worker && ((worker->current_pwq->wq->flags &
2967 (WQ_MEM_RECLAIM | __WQ_LEGACY)) == WQ_MEM_RECLAIM),
2968 "workqueue: WQ_MEM_RECLAIM %s:%ps is flushing !WQ_MEM_RECLAIM %s:%ps",
2969 worker->current_pwq->wq->name, worker->current_func,
2970 target_wq->name, target_func);
2971}
2972
2973struct wq_barrier {
2974 struct work_struct work;
2975 struct completion done;
2976 struct task_struct *task; /* purely informational */
2977};
2978
2979static void wq_barrier_func(struct work_struct *work)
2980{
2981 struct wq_barrier *barr = container_of(work, struct wq_barrier, work);
2982 complete(&barr->done);
2983}
2984
2985/**
2986 * insert_wq_barrier - insert a barrier work
2987 * @pwq: pwq to insert barrier into
2988 * @barr: wq_barrier to insert
2989 * @target: target work to attach @barr to
2990 * @worker: worker currently executing @target, NULL if @target is not executing
2991 *
2992 * @barr is linked to @target such that @barr is completed only after
2993 * @target finishes execution. Please note that the ordering
2994 * guarantee is observed only with respect to @target and on the local
2995 * cpu.
2996 *
2997 * Currently, a queued barrier can't be canceled. This is because
2998 * try_to_grab_pending() can't determine whether the work to be
2999 * grabbed is at the head of the queue and thus can't clear LINKED
3000 * flag of the previous work while there must be a valid next work
3001 * after a work with LINKED flag set.
3002 *
3003 * Note that when @worker is non-NULL, @target may be modified
3004 * underneath us, so we can't reliably determine pwq from @target.
3005 *
3006 * CONTEXT:
3007 * raw_spin_lock_irq(pool->lock).
3008 */
3009static void insert_wq_barrier(struct pool_workqueue *pwq,
3010 struct wq_barrier *barr,
3011 struct work_struct *target, struct worker *worker)
3012{
3013 unsigned int work_flags = 0;
3014 unsigned int work_color;
3015 struct list_head *head;
3016
3017 /*
3018 * debugobject calls are safe here even with pool->lock locked
3019 * as we know for sure that this will not trigger any of the
3020 * checks and call back into the fixup functions where we
3021 * might deadlock.
3022 */
3023 INIT_WORK_ONSTACK(&barr->work, wq_barrier_func);
3024 __set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(&barr->work));
3025
3026 init_completion_map(&barr->done, &target->lockdep_map);
3027
3028 barr->task = current;
3029
3030 /* The barrier work item does not participate in pwq->nr_active. */
3031 work_flags |= WORK_STRUCT_INACTIVE;
3032
3033 /*
3034 * If @target is currently being executed, schedule the
3035 * barrier to the worker; otherwise, put it after @target.
3036 */
3037 if (worker) {
3038 head = worker->scheduled.next;
3039 work_color = worker->current_color;
3040 } else {
3041 unsigned long *bits = work_data_bits(target);
3042
3043 head = target->entry.next;
3044 /* there can already be other linked works, inherit and set */
3045 work_flags |= *bits & WORK_STRUCT_LINKED;
3046 work_color = get_work_color(*bits);
3047 __set_bit(WORK_STRUCT_LINKED_BIT, bits);
3048 }
3049
3050 pwq->nr_in_flight[work_color]++;
3051 work_flags |= work_color_to_flags(work_color);
3052
3053 insert_work(pwq, &barr->work, head, work_flags);
3054}
3055
3056/**
3057 * flush_workqueue_prep_pwqs - prepare pwqs for workqueue flushing
3058 * @wq: workqueue being flushed
3059 * @flush_color: new flush color, < 0 for no-op
3060 * @work_color: new work color, < 0 for no-op
3061 *
3062 * Prepare pwqs for workqueue flushing.
3063 *
3064 * If @flush_color is non-negative, flush_color on all pwqs should be
3065 * -1. If no pwq has in-flight commands at the specified color, all
3066 * pwq->flush_color's stay at -1 and %false is returned. If any pwq
3067 * has in flight commands, its pwq->flush_color is set to
3068 * @flush_color, @wq->nr_pwqs_to_flush is updated accordingly, pwq
3069 * wakeup logic is armed and %true is returned.
3070 *
3071 * The caller should have initialized @wq->first_flusher prior to
3072 * calling this function with non-negative @flush_color. If
3073 * @flush_color is negative, no flush color update is done and %false
3074 * is returned.
3075 *
3076 * If @work_color is non-negative, all pwqs should have the same
3077 * work_color which is previous to @work_color and all will be
3078 * advanced to @work_color.
3079 *
3080 * CONTEXT:
3081 * mutex_lock(wq->mutex).
3082 *
3083 * Return:
3084 * %true if @flush_color >= 0 and there's something to flush. %false
3085 * otherwise.
3086 */
3087static bool flush_workqueue_prep_pwqs(struct workqueue_struct *wq,
3088 int flush_color, int work_color)
3089{
3090 bool wait = false;
3091 struct pool_workqueue *pwq;
3092
3093 if (flush_color >= 0) {
3094 WARN_ON_ONCE(atomic_read(&wq->nr_pwqs_to_flush));
3095 atomic_set(&wq->nr_pwqs_to_flush, 1);
3096 }
3097
3098 for_each_pwq(pwq, wq) {
3099 struct worker_pool *pool = pwq->pool;
3100
3101 raw_spin_lock_irq(&pool->lock);
3102
3103 if (flush_color >= 0) {
3104 WARN_ON_ONCE(pwq->flush_color != -1);
3105
3106 if (pwq->nr_in_flight[flush_color]) {
3107 pwq->flush_color = flush_color;
3108 atomic_inc(&wq->nr_pwqs_to_flush);
3109 wait = true;
3110 }
3111 }
3112
3113 if (work_color >= 0) {
3114 WARN_ON_ONCE(work_color != work_next_color(pwq->work_color));
3115 pwq->work_color = work_color;
3116 }
3117
3118 raw_spin_unlock_irq(&pool->lock);
3119 }
3120
3121 if (flush_color >= 0 && atomic_dec_and_test(&wq->nr_pwqs_to_flush))
3122 complete(&wq->first_flusher->done);
3123
3124 return wait;
3125}
3126
3127/**
3128 * __flush_workqueue - ensure that any scheduled work has run to completion.
3129 * @wq: workqueue to flush
3130 *
3131 * This function sleeps until all work items which were queued on entry
3132 * have finished execution, but it is not livelocked by new incoming ones.
3133 */
3134void __flush_workqueue(struct workqueue_struct *wq)
3135{
3136 struct wq_flusher this_flusher = {
3137 .list = LIST_HEAD_INIT(this_flusher.list),
3138 .flush_color = -1,
3139 .done = COMPLETION_INITIALIZER_ONSTACK_MAP(this_flusher.done, wq->lockdep_map),
3140 };
3141 int next_color;
3142
3143 if (WARN_ON(!wq_online))
3144 return;
3145
3146 lock_map_acquire(&wq->lockdep_map);
3147 lock_map_release(&wq->lockdep_map);
3148
3149 mutex_lock(&wq->mutex);
3150
3151 /*
3152 * Start-to-wait phase
3153 */
3154 next_color = work_next_color(wq->work_color);
3155
3156 if (next_color != wq->flush_color) {
3157 /*
3158 * Color space is not full. The current work_color
3159 * becomes our flush_color and work_color is advanced
3160 * by one.
3161 */
3162 WARN_ON_ONCE(!list_empty(&wq->flusher_overflow));
3163 this_flusher.flush_color = wq->work_color;
3164 wq->work_color = next_color;
3165
3166 if (!wq->first_flusher) {
3167 /* no flush in progress, become the first flusher */
3168 WARN_ON_ONCE(wq->flush_color != this_flusher.flush_color);
3169
3170 wq->first_flusher = &this_flusher;
3171
3172 if (!flush_workqueue_prep_pwqs(wq, wq->flush_color,
3173 wq->work_color)) {
3174 /* nothing to flush, done */
3175 wq->flush_color = next_color;
3176 wq->first_flusher = NULL;
3177 goto out_unlock;
3178 }
3179 } else {
3180 /* wait in queue */
3181 WARN_ON_ONCE(wq->flush_color == this_flusher.flush_color);
3182 list_add_tail(&this_flusher.list, &wq->flusher_queue);
3183 flush_workqueue_prep_pwqs(wq, -1, wq->work_color);
3184 }
3185 } else {
3186 /*
3187 * Oops, color space is full, wait on overflow queue.
3188 * The next flush completion will assign us
3189 * flush_color and transfer to flusher_queue.
3190 */
3191 list_add_tail(&this_flusher.list, &wq->flusher_overflow);
3192 }
3193
3194 check_flush_dependency(wq, NULL);
3195
3196 mutex_unlock(&wq->mutex);
3197
3198 wait_for_completion(&this_flusher.done);
3199
3200 /*
3201 * Wake-up-and-cascade phase
3202 *
3203 * First flushers are responsible for cascading flushes and
3204 * handling overflow. Non-first flushers can simply return.
3205 */
3206 if (READ_ONCE(wq->first_flusher) != &this_flusher)
3207 return;
3208
3209 mutex_lock(&wq->mutex);
3210
3211 /* we might have raced, check again with mutex held */
3212 if (wq->first_flusher != &this_flusher)
3213 goto out_unlock;
3214
3215 WRITE_ONCE(wq->first_flusher, NULL);
3216
3217 WARN_ON_ONCE(!list_empty(&this_flusher.list));
3218 WARN_ON_ONCE(wq->flush_color != this_flusher.flush_color);
3219
3220 while (true) {
3221 struct wq_flusher *next, *tmp;
3222
3223 /* complete all the flushers sharing the current flush color */
3224 list_for_each_entry_safe(next, tmp, &wq->flusher_queue, list) {
3225 if (next->flush_color != wq->flush_color)
3226 break;
3227 list_del_init(&next->list);
3228 complete(&next->done);
3229 }
3230
3231 WARN_ON_ONCE(!list_empty(&wq->flusher_overflow) &&
3232 wq->flush_color != work_next_color(wq->work_color));
3233
3234 /* this flush_color is finished, advance by one */
3235 wq->flush_color = work_next_color(wq->flush_color);
3236
3237 /* one color has been freed, handle overflow queue */
3238 if (!list_empty(&wq->flusher_overflow)) {
3239 /*
3240 * Assign the same color to all overflowed
3241 * flushers, advance work_color and append to
3242 * flusher_queue. This is the start-to-wait
3243 * phase for these overflowed flushers.
3244 */
3245 list_for_each_entry(tmp, &wq->flusher_overflow, list)
3246 tmp->flush_color = wq->work_color;
3247
3248 wq->work_color = work_next_color(wq->work_color);
3249
3250 list_splice_tail_init(&wq->flusher_overflow,
3251 &wq->flusher_queue);
3252 flush_workqueue_prep_pwqs(wq, -1, wq->work_color);
3253 }
3254
3255 if (list_empty(&wq->flusher_queue)) {
3256 WARN_ON_ONCE(wq->flush_color != wq->work_color);
3257 break;
3258 }
3259
3260 /*
3261 * Need to flush more colors. Make the next flusher
3262 * the new first flusher and arm pwqs.
3263 */
3264 WARN_ON_ONCE(wq->flush_color == wq->work_color);
3265 WARN_ON_ONCE(wq->flush_color != next->flush_color);
3266
3267 list_del_init(&next->list);
3268 wq->first_flusher = next;
3269
3270 if (flush_workqueue_prep_pwqs(wq, wq->flush_color, -1))
3271 break;
3272
3273 /*
3274 * Meh... this color is already done, clear first
3275 * flusher and repeat cascading.
3276 */
3277 wq->first_flusher = NULL;
3278 }
3279
3280out_unlock:
3281 mutex_unlock(&wq->mutex);
3282}
3283EXPORT_SYMBOL(__flush_workqueue);
3284
3285/**
3286 * drain_workqueue - drain a workqueue
3287 * @wq: workqueue to drain
3288 *
3289 * Wait until the workqueue becomes empty. While draining is in progress,
3290 * only chain queueing is allowed. IOW, only currently pending or running
3291 * work items on @wq can queue further work items on it. @wq is flushed
3292 * repeatedly until it becomes empty. The number of flushing is determined
3293 * by the depth of chaining and should be relatively short. Whine if it
3294 * takes too long.
3295 */
3296void drain_workqueue(struct workqueue_struct *wq)
3297{
3298 unsigned int flush_cnt = 0;
3299 struct pool_workqueue *pwq;
3300
3301 /*
3302 * __queue_work() needs to test whether there are drainers, is much
3303 * hotter than drain_workqueue() and already looks at @wq->flags.
3304 * Use __WQ_DRAINING so that queue doesn't have to check nr_drainers.
3305 */
3306 mutex_lock(&wq->mutex);
3307 if (!wq->nr_drainers++)
3308 wq->flags |= __WQ_DRAINING;
3309 mutex_unlock(&wq->mutex);
3310reflush:
3311 __flush_workqueue(wq);
3312
3313 mutex_lock(&wq->mutex);
3314
3315 for_each_pwq(pwq, wq) {
3316 bool drained;
3317
3318 raw_spin_lock_irq(&pwq->pool->lock);
3319 drained = !pwq->nr_active && list_empty(&pwq->inactive_works);
3320 raw_spin_unlock_irq(&pwq->pool->lock);
3321
3322 if (drained)
3323 continue;
3324
3325 if (++flush_cnt == 10 ||
3326 (flush_cnt % 100 == 0 && flush_cnt <= 1000))
3327 pr_warn("workqueue %s: %s() isn't complete after %u tries\n",
3328 wq->name, __func__, flush_cnt);
3329
3330 mutex_unlock(&wq->mutex);
3331 goto reflush;
3332 }
3333
3334 if (!--wq->nr_drainers)
3335 wq->flags &= ~__WQ_DRAINING;
3336 mutex_unlock(&wq->mutex);
3337}
3338EXPORT_SYMBOL_GPL(drain_workqueue);
3339
3340static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr,
3341 bool from_cancel)
3342{
3343 struct worker *worker = NULL;
3344 struct worker_pool *pool;
3345 struct pool_workqueue *pwq;
3346
3347 might_sleep();
3348
3349 rcu_read_lock();
3350 pool = get_work_pool(work);
3351 if (!pool) {
3352 rcu_read_unlock();
3353 return false;
3354 }
3355
3356 raw_spin_lock_irq(&pool->lock);
3357 /* see the comment in try_to_grab_pending() with the same code */
3358 pwq = get_work_pwq(work);
3359 if (pwq) {
3360 if (unlikely(pwq->pool != pool))
3361 goto already_gone;
3362 } else {
3363 worker = find_worker_executing_work(pool, work);
3364 if (!worker)
3365 goto already_gone;
3366 pwq = worker->current_pwq;
3367 }
3368
3369 check_flush_dependency(pwq->wq, work);
3370
3371 insert_wq_barrier(pwq, barr, work, worker);
3372 raw_spin_unlock_irq(&pool->lock);
3373
3374 /*
3375 * Force a lock recursion deadlock when using flush_work() inside a
3376 * single-threaded or rescuer equipped workqueue.
3377 *
3378 * For single threaded workqueues the deadlock happens when the work
3379 * is after the work issuing the flush_work(). For rescuer equipped
3380 * workqueues the deadlock happens when the rescuer stalls, blocking
3381 * forward progress.
3382 */
3383 if (!from_cancel &&
3384 (pwq->wq->saved_max_active == 1 || pwq->wq->rescuer)) {
3385 lock_map_acquire(&pwq->wq->lockdep_map);
3386 lock_map_release(&pwq->wq->lockdep_map);
3387 }
3388 rcu_read_unlock();
3389 return true;
3390already_gone:
3391 raw_spin_unlock_irq(&pool->lock);
3392 rcu_read_unlock();
3393 return false;
3394}
3395
3396static bool __flush_work(struct work_struct *work, bool from_cancel)
3397{
3398 struct wq_barrier barr;
3399
3400 if (WARN_ON(!wq_online))
3401 return false;
3402
3403 if (WARN_ON(!work->func))
3404 return false;
3405
3406 lock_map_acquire(&work->lockdep_map);
3407 lock_map_release(&work->lockdep_map);
3408
3409 if (start_flush_work(work, &barr, from_cancel)) {
3410 wait_for_completion(&barr.done);
3411 destroy_work_on_stack(&barr.work);
3412 return true;
3413 } else {
3414 return false;
3415 }
3416}
3417
3418/**
3419 * flush_work - wait for a work to finish executing the last queueing instance
3420 * @work: the work to flush
3421 *
3422 * Wait until @work has finished execution. @work is guaranteed to be idle
3423 * on return if it hasn't been requeued since flush started.
3424 *
3425 * Return:
3426 * %true if flush_work() waited for the work to finish execution,
3427 * %false if it was already idle.
3428 */
3429bool flush_work(struct work_struct *work)
3430{
3431 return __flush_work(work, false);
3432}
3433EXPORT_SYMBOL_GPL(flush_work);
3434
3435struct cwt_wait {
3436 wait_queue_entry_t wait;
3437 struct work_struct *work;
3438};
3439
3440static int cwt_wakefn(wait_queue_entry_t *wait, unsigned mode, int sync, void *key)
3441{
3442 struct cwt_wait *cwait = container_of(wait, struct cwt_wait, wait);
3443
3444 if (cwait->work != key)
3445 return 0;
3446 return autoremove_wake_function(wait, mode, sync, key);
3447}
3448
3449static bool __cancel_work_timer(struct work_struct *work, bool is_dwork)
3450{
3451 static DECLARE_WAIT_QUEUE_HEAD(cancel_waitq);
3452 unsigned long flags;
3453 int ret;
3454
3455 do {
3456 ret = try_to_grab_pending(work, is_dwork, &flags);
3457 /*
3458 * If someone else is already canceling, wait for it to
3459 * finish. flush_work() doesn't work for PREEMPT_NONE
3460 * because we may get scheduled between @work's completion
3461 * and the other canceling task resuming and clearing
3462 * CANCELING - flush_work() will return false immediately
3463 * as @work is no longer busy, try_to_grab_pending() will
3464 * return -ENOENT as @work is still being canceled and the
3465 * other canceling task won't be able to clear CANCELING as
3466 * we're hogging the CPU.
3467 *
3468 * Let's wait for completion using a waitqueue. As this
3469 * may lead to the thundering herd problem, use a custom
3470 * wake function which matches @work along with exclusive
3471 * wait and wakeup.
3472 */
3473 if (unlikely(ret == -ENOENT)) {
3474 struct cwt_wait cwait;
3475
3476 init_wait(&cwait.wait);
3477 cwait.wait.func = cwt_wakefn;
3478 cwait.work = work;
3479
3480 prepare_to_wait_exclusive(&cancel_waitq, &cwait.wait,
3481 TASK_UNINTERRUPTIBLE);
3482 if (work_is_canceling(work))
3483 schedule();
3484 finish_wait(&cancel_waitq, &cwait.wait);
3485 }
3486 } while (unlikely(ret < 0));
3487
3488 /* tell other tasks trying to grab @work to back off */
3489 mark_work_canceling(work);
3490 local_irq_restore(flags);
3491
3492 /*
3493 * This allows canceling during early boot. We know that @work
3494 * isn't executing.
3495 */
3496 if (wq_online)
3497 __flush_work(work, true);
3498
3499 clear_work_data(work);
3500
3501 /*
3502 * Paired with prepare_to_wait() above so that either
3503 * waitqueue_active() is visible here or !work_is_canceling() is
3504 * visible there.
3505 */
3506 smp_mb();
3507 if (waitqueue_active(&cancel_waitq))
3508 __wake_up(&cancel_waitq, TASK_NORMAL, 1, work);
3509
3510 return ret;
3511}
3512
3513/**
3514 * cancel_work_sync - cancel a work and wait for it to finish
3515 * @work: the work to cancel
3516 *
3517 * Cancel @work and wait for its execution to finish. This function
3518 * can be used even if the work re-queues itself or migrates to
3519 * another workqueue. On return from this function, @work is
3520 * guaranteed to be not pending or executing on any CPU.
3521 *
3522 * cancel_work_sync(&delayed_work->work) must not be used for
3523 * delayed_work's. Use cancel_delayed_work_sync() instead.
3524 *
3525 * The caller must ensure that the workqueue on which @work was last
3526 * queued can't be destroyed before this function returns.
3527 *
3528 * Return:
3529 * %true if @work was pending, %false otherwise.
3530 */
3531bool cancel_work_sync(struct work_struct *work)
3532{
3533 return __cancel_work_timer(work, false);
3534}
3535EXPORT_SYMBOL_GPL(cancel_work_sync);
3536
3537/**
3538 * flush_delayed_work - wait for a dwork to finish executing the last queueing
3539 * @dwork: the delayed work to flush
3540 *
3541 * Delayed timer is cancelled and the pending work is queued for
3542 * immediate execution. Like flush_work(), this function only
3543 * considers the last queueing instance of @dwork.
3544 *
3545 * Return:
3546 * %true if flush_work() waited for the work to finish execution,
3547 * %false if it was already idle.
3548 */
3549bool flush_delayed_work(struct delayed_work *dwork)
3550{
3551 local_irq_disable();
3552 if (del_timer_sync(&dwork->timer))
3553 __queue_work(dwork->cpu, dwork->wq, &dwork->work);
3554 local_irq_enable();
3555 return flush_work(&dwork->work);
3556}
3557EXPORT_SYMBOL(flush_delayed_work);
3558
3559/**
3560 * flush_rcu_work - wait for a rwork to finish executing the last queueing
3561 * @rwork: the rcu work to flush
3562 *
3563 * Return:
3564 * %true if flush_rcu_work() waited for the work to finish execution,
3565 * %false if it was already idle.
3566 */
3567bool flush_rcu_work(struct rcu_work *rwork)
3568{
3569 if (test_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(&rwork->work))) {
3570 rcu_barrier();
3571 flush_work(&rwork->work);
3572 return true;
3573 } else {
3574 return flush_work(&rwork->work);
3575 }
3576}
3577EXPORT_SYMBOL(flush_rcu_work);
3578
3579static bool __cancel_work(struct work_struct *work, bool is_dwork)
3580{
3581 unsigned long flags;
3582 int ret;
3583
3584 do {
3585 ret = try_to_grab_pending(work, is_dwork, &flags);
3586 } while (unlikely(ret == -EAGAIN));
3587
3588 if (unlikely(ret < 0))
3589 return false;
3590
3591 set_work_pool_and_clear_pending(work, get_work_pool_id(work));
3592 local_irq_restore(flags);
3593 return ret;
3594}
3595
3596/*
3597 * See cancel_delayed_work()
3598 */
3599bool cancel_work(struct work_struct *work)
3600{
3601 return __cancel_work(work, false);
3602}
3603EXPORT_SYMBOL(cancel_work);
3604
3605/**
3606 * cancel_delayed_work - cancel a delayed work
3607 * @dwork: delayed_work to cancel
3608 *
3609 * Kill off a pending delayed_work.
3610 *
3611 * Return: %true if @dwork was pending and canceled; %false if it wasn't
3612 * pending.
3613 *
3614 * Note:
3615 * The work callback function may still be running on return, unless
3616 * it returns %true and the work doesn't re-arm itself. Explicitly flush or
3617 * use cancel_delayed_work_sync() to wait on it.
3618 *
3619 * This function is safe to call from any context including IRQ handler.
3620 */
3621bool cancel_delayed_work(struct delayed_work *dwork)
3622{
3623 return __cancel_work(&dwork->work, true);
3624}
3625EXPORT_SYMBOL(cancel_delayed_work);
3626
3627/**
3628 * cancel_delayed_work_sync - cancel a delayed work and wait for it to finish
3629 * @dwork: the delayed work cancel
3630 *
3631 * This is cancel_work_sync() for delayed works.
3632 *
3633 * Return:
3634 * %true if @dwork was pending, %false otherwise.
3635 */
3636bool cancel_delayed_work_sync(struct delayed_work *dwork)
3637{
3638 return __cancel_work_timer(&dwork->work, true);
3639}
3640EXPORT_SYMBOL(cancel_delayed_work_sync);
3641
3642/**
3643 * schedule_on_each_cpu - execute a function synchronously on each online CPU
3644 * @func: the function to call
3645 *
3646 * schedule_on_each_cpu() executes @func on each online CPU using the
3647 * system workqueue and blocks until all CPUs have completed.
3648 * schedule_on_each_cpu() is very slow.
3649 *
3650 * Return:
3651 * 0 on success, -errno on failure.
3652 */
3653int schedule_on_each_cpu(work_func_t func)
3654{
3655 int cpu;
3656 struct work_struct __percpu *works;
3657
3658 works = alloc_percpu(struct work_struct);
3659 if (!works)
3660 return -ENOMEM;
3661
3662 cpus_read_lock();
3663
3664 for_each_online_cpu(cpu) {
3665 struct work_struct *work = per_cpu_ptr(works, cpu);
3666
3667 INIT_WORK(work, func);
3668 schedule_work_on(cpu, work);
3669 }
3670
3671 for_each_online_cpu(cpu)
3672 flush_work(per_cpu_ptr(works, cpu));
3673
3674 cpus_read_unlock();
3675 free_percpu(works);
3676 return 0;
3677}
3678
3679/**
3680 * execute_in_process_context - reliably execute the routine with user context
3681 * @fn: the function to execute
3682 * @ew: guaranteed storage for the execute work structure (must
3683 * be available when the work executes)
3684 *
3685 * Executes the function immediately if process context is available,
3686 * otherwise schedules the function for delayed execution.
3687 *
3688 * Return: 0 - function was executed
3689 * 1 - function was scheduled for execution
3690 */
3691int execute_in_process_context(work_func_t fn, struct execute_work *ew)
3692{
3693 if (!in_interrupt()) {
3694 fn(&ew->work);
3695 return 0;
3696 }
3697
3698 INIT_WORK(&ew->work, fn);
3699 schedule_work(&ew->work);
3700
3701 return 1;
3702}
3703EXPORT_SYMBOL_GPL(execute_in_process_context);
3704
3705/**
3706 * free_workqueue_attrs - free a workqueue_attrs
3707 * @attrs: workqueue_attrs to free
3708 *
3709 * Undo alloc_workqueue_attrs().
3710 */
3711void free_workqueue_attrs(struct workqueue_attrs *attrs)
3712{
3713 if (attrs) {
3714 free_cpumask_var(attrs->cpumask);
3715 free_cpumask_var(attrs->__pod_cpumask);
3716 kfree(attrs);
3717 }
3718}
3719
3720/**
3721 * alloc_workqueue_attrs - allocate a workqueue_attrs
3722 *
3723 * Allocate a new workqueue_attrs, initialize with default settings and
3724 * return it.
3725 *
3726 * Return: The allocated new workqueue_attr on success. %NULL on failure.
3727 */
3728struct workqueue_attrs *alloc_workqueue_attrs(void)
3729{
3730 struct workqueue_attrs *attrs;
3731
3732 attrs = kzalloc(sizeof(*attrs), GFP_KERNEL);
3733 if (!attrs)
3734 goto fail;
3735 if (!alloc_cpumask_var(&attrs->cpumask, GFP_KERNEL))
3736 goto fail;
3737 if (!alloc_cpumask_var(&attrs->__pod_cpumask, GFP_KERNEL))
3738 goto fail;
3739
3740 cpumask_copy(attrs->cpumask, cpu_possible_mask);
3741 attrs->affn_scope = WQ_AFFN_DFL;
3742 return attrs;
3743fail:
3744 free_workqueue_attrs(attrs);
3745 return NULL;
3746}
3747
3748static void copy_workqueue_attrs(struct workqueue_attrs *to,
3749 const struct workqueue_attrs *from)
3750{
3751 to->nice = from->nice;
3752 cpumask_copy(to->cpumask, from->cpumask);
3753 cpumask_copy(to->__pod_cpumask, from->__pod_cpumask);
3754 to->affn_strict = from->affn_strict;
3755
3756 /*
3757 * Unlike hash and equality test, copying shouldn't ignore wq-only
3758 * fields as copying is used for both pool and wq attrs. Instead,
3759 * get_unbound_pool() explicitly clears the fields.
3760 */
3761 to->affn_scope = from->affn_scope;
3762 to->ordered = from->ordered;
3763}
3764
3765/*
3766 * Some attrs fields are workqueue-only. Clear them for worker_pool's. See the
3767 * comments in 'struct workqueue_attrs' definition.
3768 */
3769static void wqattrs_clear_for_pool(struct workqueue_attrs *attrs)
3770{
3771 attrs->affn_scope = WQ_AFFN_NR_TYPES;
3772 attrs->ordered = false;
3773}
3774
3775/* hash value of the content of @attr */
3776static u32 wqattrs_hash(const struct workqueue_attrs *attrs)
3777{
3778 u32 hash = 0;
3779
3780 hash = jhash_1word(attrs->nice, hash);
3781 hash = jhash(cpumask_bits(attrs->cpumask),
3782 BITS_TO_LONGS(nr_cpumask_bits) * sizeof(long), hash);
3783 hash = jhash(cpumask_bits(attrs->__pod_cpumask),
3784 BITS_TO_LONGS(nr_cpumask_bits) * sizeof(long), hash);
3785 hash = jhash_1word(attrs->affn_strict, hash);
3786 return hash;
3787}
3788
3789/* content equality test */
3790static bool wqattrs_equal(const struct workqueue_attrs *a,
3791 const struct workqueue_attrs *b)
3792{
3793 if (a->nice != b->nice)
3794 return false;
3795 if (!cpumask_equal(a->cpumask, b->cpumask))
3796 return false;
3797 if (!cpumask_equal(a->__pod_cpumask, b->__pod_cpumask))
3798 return false;
3799 if (a->affn_strict != b->affn_strict)
3800 return false;
3801 return true;
3802}
3803
3804/* Update @attrs with actually available CPUs */
3805static void wqattrs_actualize_cpumask(struct workqueue_attrs *attrs,
3806 const cpumask_t *unbound_cpumask)
3807{
3808 /*
3809 * Calculate the effective CPU mask of @attrs given @unbound_cpumask. If
3810 * @attrs->cpumask doesn't overlap with @unbound_cpumask, we fallback to
3811 * @unbound_cpumask.
3812 */
3813 cpumask_and(attrs->cpumask, attrs->cpumask, unbound_cpumask);
3814 if (unlikely(cpumask_empty(attrs->cpumask)))
3815 cpumask_copy(attrs->cpumask, unbound_cpumask);
3816}
3817
3818/* find wq_pod_type to use for @attrs */
3819static const struct wq_pod_type *
3820wqattrs_pod_type(const struct workqueue_attrs *attrs)
3821{
3822 enum wq_affn_scope scope;
3823 struct wq_pod_type *pt;
3824
3825 /* to synchronize access to wq_affn_dfl */
3826 lockdep_assert_held(&wq_pool_mutex);
3827
3828 if (attrs->affn_scope == WQ_AFFN_DFL)
3829 scope = wq_affn_dfl;
3830 else
3831 scope = attrs->affn_scope;
3832
3833 pt = &wq_pod_types[scope];
3834
3835 if (!WARN_ON_ONCE(attrs->affn_scope == WQ_AFFN_NR_TYPES) &&
3836 likely(pt->nr_pods))
3837 return pt;
3838
3839 /*
3840 * Before workqueue_init_topology(), only SYSTEM is available which is
3841 * initialized in workqueue_init_early().
3842 */
3843 pt = &wq_pod_types[WQ_AFFN_SYSTEM];
3844 BUG_ON(!pt->nr_pods);
3845 return pt;
3846}
3847
3848/**
3849 * init_worker_pool - initialize a newly zalloc'd worker_pool
3850 * @pool: worker_pool to initialize
3851 *
3852 * Initialize a newly zalloc'd @pool. It also allocates @pool->attrs.
3853 *
3854 * Return: 0 on success, -errno on failure. Even on failure, all fields
3855 * inside @pool proper are initialized and put_unbound_pool() can be called
3856 * on @pool safely to release it.
3857 */
3858static int init_worker_pool(struct worker_pool *pool)
3859{
3860 raw_spin_lock_init(&pool->lock);
3861 pool->id = -1;
3862 pool->cpu = -1;
3863 pool->node = NUMA_NO_NODE;
3864 pool->flags |= POOL_DISASSOCIATED;
3865 pool->watchdog_ts = jiffies;
3866 INIT_LIST_HEAD(&pool->worklist);
3867 INIT_LIST_HEAD(&pool->idle_list);
3868 hash_init(pool->busy_hash);
3869
3870 timer_setup(&pool->idle_timer, idle_worker_timeout, TIMER_DEFERRABLE);
3871 INIT_WORK(&pool->idle_cull_work, idle_cull_fn);
3872
3873 timer_setup(&pool->mayday_timer, pool_mayday_timeout, 0);
3874
3875 INIT_LIST_HEAD(&pool->workers);
3876 INIT_LIST_HEAD(&pool->dying_workers);
3877
3878 ida_init(&pool->worker_ida);
3879 INIT_HLIST_NODE(&pool->hash_node);
3880 pool->refcnt = 1;
3881
3882 /* shouldn't fail above this point */
3883 pool->attrs = alloc_workqueue_attrs();
3884 if (!pool->attrs)
3885 return -ENOMEM;
3886
3887 wqattrs_clear_for_pool(pool->attrs);
3888
3889 return 0;
3890}
3891
3892#ifdef CONFIG_LOCKDEP
3893static void wq_init_lockdep(struct workqueue_struct *wq)
3894{
3895 char *lock_name;
3896
3897 lockdep_register_key(&wq->key);
3898 lock_name = kasprintf(GFP_KERNEL, "%s%s", "(wq_completion)", wq->name);
3899 if (!lock_name)
3900 lock_name = wq->name;
3901
3902 wq->lock_name = lock_name;
3903 lockdep_init_map(&wq->lockdep_map, lock_name, &wq->key, 0);
3904}
3905
3906static void wq_unregister_lockdep(struct workqueue_struct *wq)
3907{
3908 lockdep_unregister_key(&wq->key);
3909}
3910
3911static void wq_free_lockdep(struct workqueue_struct *wq)
3912{
3913 if (wq->lock_name != wq->name)
3914 kfree(wq->lock_name);
3915}
3916#else
3917static void wq_init_lockdep(struct workqueue_struct *wq)
3918{
3919}
3920
3921static void wq_unregister_lockdep(struct workqueue_struct *wq)
3922{
3923}
3924
3925static void wq_free_lockdep(struct workqueue_struct *wq)
3926{
3927}
3928#endif
3929
3930static void rcu_free_wq(struct rcu_head *rcu)
3931{
3932 struct workqueue_struct *wq =
3933 container_of(rcu, struct workqueue_struct, rcu);
3934
3935 wq_free_lockdep(wq);
3936 free_percpu(wq->cpu_pwq);
3937 free_workqueue_attrs(wq->unbound_attrs);
3938 kfree(wq);
3939}
3940
3941static void rcu_free_pool(struct rcu_head *rcu)
3942{
3943 struct worker_pool *pool = container_of(rcu, struct worker_pool, rcu);
3944
3945 ida_destroy(&pool->worker_ida);
3946 free_workqueue_attrs(pool->attrs);
3947 kfree(pool);
3948}
3949
3950/**
3951 * put_unbound_pool - put a worker_pool
3952 * @pool: worker_pool to put
3953 *
3954 * Put @pool. If its refcnt reaches zero, it gets destroyed in RCU
3955 * safe manner. get_unbound_pool() calls this function on its failure path
3956 * and this function should be able to release pools which went through,
3957 * successfully or not, init_worker_pool().
3958 *
3959 * Should be called with wq_pool_mutex held.
3960 */
3961static void put_unbound_pool(struct worker_pool *pool)
3962{
3963 DECLARE_COMPLETION_ONSTACK(detach_completion);
3964 struct worker *worker;
3965 LIST_HEAD(cull_list);
3966
3967 lockdep_assert_held(&wq_pool_mutex);
3968
3969 if (--pool->refcnt)
3970 return;
3971
3972 /* sanity checks */
3973 if (WARN_ON(!(pool->cpu < 0)) ||
3974 WARN_ON(!list_empty(&pool->worklist)))
3975 return;
3976
3977 /* release id and unhash */
3978 if (pool->id >= 0)
3979 idr_remove(&worker_pool_idr, pool->id);
3980 hash_del(&pool->hash_node);
3981
3982 /*
3983 * Become the manager and destroy all workers. This prevents
3984 * @pool's workers from blocking on attach_mutex. We're the last
3985 * manager and @pool gets freed with the flag set.
3986 *
3987 * Having a concurrent manager is quite unlikely to happen as we can
3988 * only get here with
3989 * pwq->refcnt == pool->refcnt == 0
3990 * which implies no work queued to the pool, which implies no worker can
3991 * become the manager. However a worker could have taken the role of
3992 * manager before the refcnts dropped to 0, since maybe_create_worker()
3993 * drops pool->lock
3994 */
3995 while (true) {
3996 rcuwait_wait_event(&manager_wait,
3997 !(pool->flags & POOL_MANAGER_ACTIVE),
3998 TASK_UNINTERRUPTIBLE);
3999
4000 mutex_lock(&wq_pool_attach_mutex);
4001 raw_spin_lock_irq(&pool->lock);
4002 if (!(pool->flags & POOL_MANAGER_ACTIVE)) {
4003 pool->flags |= POOL_MANAGER_ACTIVE;
4004 break;
4005 }
4006 raw_spin_unlock_irq(&pool->lock);
4007 mutex_unlock(&wq_pool_attach_mutex);
4008 }
4009
4010 while ((worker = first_idle_worker(pool)))
4011 set_worker_dying(worker, &cull_list);
4012 WARN_ON(pool->nr_workers || pool->nr_idle);
4013 raw_spin_unlock_irq(&pool->lock);
4014
4015 wake_dying_workers(&cull_list);
4016
4017 if (!list_empty(&pool->workers) || !list_empty(&pool->dying_workers))
4018 pool->detach_completion = &detach_completion;
4019 mutex_unlock(&wq_pool_attach_mutex);
4020
4021 if (pool->detach_completion)
4022 wait_for_completion(pool->detach_completion);
4023
4024 /* shut down the timers */
4025 del_timer_sync(&pool->idle_timer);
4026 cancel_work_sync(&pool->idle_cull_work);
4027 del_timer_sync(&pool->mayday_timer);
4028
4029 /* RCU protected to allow dereferences from get_work_pool() */
4030 call_rcu(&pool->rcu, rcu_free_pool);
4031}
4032
4033/**
4034 * get_unbound_pool - get a worker_pool with the specified attributes
4035 * @attrs: the attributes of the worker_pool to get
4036 *
4037 * Obtain a worker_pool which has the same attributes as @attrs, bump the
4038 * reference count and return it. If there already is a matching
4039 * worker_pool, it will be used; otherwise, this function attempts to
4040 * create a new one.
4041 *
4042 * Should be called with wq_pool_mutex held.
4043 *
4044 * Return: On success, a worker_pool with the same attributes as @attrs.
4045 * On failure, %NULL.
4046 */
4047static struct worker_pool *get_unbound_pool(const struct workqueue_attrs *attrs)
4048{
4049 struct wq_pod_type *pt = &wq_pod_types[WQ_AFFN_NUMA];
4050 u32 hash = wqattrs_hash(attrs);
4051 struct worker_pool *pool;
4052 int pod, node = NUMA_NO_NODE;
4053
4054 lockdep_assert_held(&wq_pool_mutex);
4055
4056 /* do we already have a matching pool? */
4057 hash_for_each_possible(unbound_pool_hash, pool, hash_node, hash) {
4058 if (wqattrs_equal(pool->attrs, attrs)) {
4059 pool->refcnt++;
4060 return pool;
4061 }
4062 }
4063
4064 /* If __pod_cpumask is contained inside a NUMA pod, that's our node */
4065 for (pod = 0; pod < pt->nr_pods; pod++) {
4066 if (cpumask_subset(attrs->__pod_cpumask, pt->pod_cpus[pod])) {
4067 node = pt->pod_node[pod];
4068 break;
4069 }
4070 }
4071
4072 /* nope, create a new one */
4073 pool = kzalloc_node(sizeof(*pool), GFP_KERNEL, node);
4074 if (!pool || init_worker_pool(pool) < 0)
4075 goto fail;
4076
4077 pool->node = node;
4078 copy_workqueue_attrs(pool->attrs, attrs);
4079 wqattrs_clear_for_pool(pool->attrs);
4080
4081 if (worker_pool_assign_id(pool) < 0)
4082 goto fail;
4083
4084 /* create and start the initial worker */
4085 if (wq_online && !create_worker(pool))
4086 goto fail;
4087
4088 /* install */
4089 hash_add(unbound_pool_hash, &pool->hash_node, hash);
4090
4091 return pool;
4092fail:
4093 if (pool)
4094 put_unbound_pool(pool);
4095 return NULL;
4096}
4097
4098static void rcu_free_pwq(struct rcu_head *rcu)
4099{
4100 kmem_cache_free(pwq_cache,
4101 container_of(rcu, struct pool_workqueue, rcu));
4102}
4103
4104/*
4105 * Scheduled on pwq_release_worker by put_pwq() when an unbound pwq hits zero
4106 * refcnt and needs to be destroyed.
4107 */
4108static void pwq_release_workfn(struct kthread_work *work)
4109{
4110 struct pool_workqueue *pwq = container_of(work, struct pool_workqueue,
4111 release_work);
4112 struct workqueue_struct *wq = pwq->wq;
4113 struct worker_pool *pool = pwq->pool;
4114 bool is_last = false;
4115
4116 /*
4117 * When @pwq is not linked, it doesn't hold any reference to the
4118 * @wq, and @wq is invalid to access.
4119 */
4120 if (!list_empty(&pwq->pwqs_node)) {
4121 mutex_lock(&wq->mutex);
4122 list_del_rcu(&pwq->pwqs_node);
4123 is_last = list_empty(&wq->pwqs);
4124 mutex_unlock(&wq->mutex);
4125 }
4126
4127 if (wq->flags & WQ_UNBOUND) {
4128 mutex_lock(&wq_pool_mutex);
4129 put_unbound_pool(pool);
4130 mutex_unlock(&wq_pool_mutex);
4131 }
4132
4133 call_rcu(&pwq->rcu, rcu_free_pwq);
4134
4135 /*
4136 * If we're the last pwq going away, @wq is already dead and no one
4137 * is gonna access it anymore. Schedule RCU free.
4138 */
4139 if (is_last) {
4140 wq_unregister_lockdep(wq);
4141 call_rcu(&wq->rcu, rcu_free_wq);
4142 }
4143}
4144
4145/**
4146 * pwq_adjust_max_active - update a pwq's max_active to the current setting
4147 * @pwq: target pool_workqueue
4148 *
4149 * If @pwq isn't freezing, set @pwq->max_active to the associated
4150 * workqueue's saved_max_active and activate inactive work items
4151 * accordingly. If @pwq is freezing, clear @pwq->max_active to zero.
4152 */
4153static void pwq_adjust_max_active(struct pool_workqueue *pwq)
4154{
4155 struct workqueue_struct *wq = pwq->wq;
4156 bool freezable = wq->flags & WQ_FREEZABLE;
4157 unsigned long flags;
4158
4159 /* for @wq->saved_max_active */
4160 lockdep_assert_held(&wq->mutex);
4161
4162 /* fast exit for non-freezable wqs */
4163 if (!freezable && pwq->max_active == wq->saved_max_active)
4164 return;
4165
4166 /* this function can be called during early boot w/ irq disabled */
4167 raw_spin_lock_irqsave(&pwq->pool->lock, flags);
4168
4169 /*
4170 * During [un]freezing, the caller is responsible for ensuring that
4171 * this function is called at least once after @workqueue_freezing
4172 * is updated and visible.
4173 */
4174 if (!freezable || !workqueue_freezing) {
4175 pwq->max_active = wq->saved_max_active;
4176
4177 while (!list_empty(&pwq->inactive_works) &&
4178 pwq->nr_active < pwq->max_active)
4179 pwq_activate_first_inactive(pwq);
4180
4181 kick_pool(pwq->pool);
4182 } else {
4183 pwq->max_active = 0;
4184 }
4185
4186 raw_spin_unlock_irqrestore(&pwq->pool->lock, flags);
4187}
4188
4189/* initialize newly allocated @pwq which is associated with @wq and @pool */
4190static void init_pwq(struct pool_workqueue *pwq, struct workqueue_struct *wq,
4191 struct worker_pool *pool)
4192{
4193 BUG_ON((unsigned long)pwq & WORK_STRUCT_FLAG_MASK);
4194
4195 memset(pwq, 0, sizeof(*pwq));
4196
4197 pwq->pool = pool;
4198 pwq->wq = wq;
4199 pwq->flush_color = -1;
4200 pwq->refcnt = 1;
4201 INIT_LIST_HEAD(&pwq->inactive_works);
4202 INIT_LIST_HEAD(&pwq->pwqs_node);
4203 INIT_LIST_HEAD(&pwq->mayday_node);
4204 kthread_init_work(&pwq->release_work, pwq_release_workfn);
4205}
4206
4207/* sync @pwq with the current state of its associated wq and link it */
4208static void link_pwq(struct pool_workqueue *pwq)
4209{
4210 struct workqueue_struct *wq = pwq->wq;
4211
4212 lockdep_assert_held(&wq->mutex);
4213
4214 /* may be called multiple times, ignore if already linked */
4215 if (!list_empty(&pwq->pwqs_node))
4216 return;
4217
4218 /* set the matching work_color */
4219 pwq->work_color = wq->work_color;
4220
4221 /* sync max_active to the current setting */
4222 pwq_adjust_max_active(pwq);
4223
4224 /* link in @pwq */
4225 list_add_rcu(&pwq->pwqs_node, &wq->pwqs);
4226}
4227
4228/* obtain a pool matching @attr and create a pwq associating the pool and @wq */
4229static struct pool_workqueue *alloc_unbound_pwq(struct workqueue_struct *wq,
4230 const struct workqueue_attrs *attrs)
4231{
4232 struct worker_pool *pool;
4233 struct pool_workqueue *pwq;
4234
4235 lockdep_assert_held(&wq_pool_mutex);
4236
4237 pool = get_unbound_pool(attrs);
4238 if (!pool)
4239 return NULL;
4240
4241 pwq = kmem_cache_alloc_node(pwq_cache, GFP_KERNEL, pool->node);
4242 if (!pwq) {
4243 put_unbound_pool(pool);
4244 return NULL;
4245 }
4246
4247 init_pwq(pwq, wq, pool);
4248 return pwq;
4249}
4250
4251/**
4252 * wq_calc_pod_cpumask - calculate a wq_attrs' cpumask for a pod
4253 * @attrs: the wq_attrs of the default pwq of the target workqueue
4254 * @cpu: the target CPU
4255 * @cpu_going_down: if >= 0, the CPU to consider as offline
4256 *
4257 * Calculate the cpumask a workqueue with @attrs should use on @pod. If
4258 * @cpu_going_down is >= 0, that cpu is considered offline during calculation.
4259 * The result is stored in @attrs->__pod_cpumask.
4260 *
4261 * If pod affinity is not enabled, @attrs->cpumask is always used. If enabled
4262 * and @pod has online CPUs requested by @attrs, the returned cpumask is the
4263 * intersection of the possible CPUs of @pod and @attrs->cpumask.
4264 *
4265 * The caller is responsible for ensuring that the cpumask of @pod stays stable.
4266 */
4267static void wq_calc_pod_cpumask(struct workqueue_attrs *attrs, int cpu,
4268 int cpu_going_down)
4269{
4270 const struct wq_pod_type *pt = wqattrs_pod_type(attrs);
4271 int pod = pt->cpu_pod[cpu];
4272
4273 /* does @pod have any online CPUs @attrs wants? */
4274 cpumask_and(attrs->__pod_cpumask, pt->pod_cpus[pod], attrs->cpumask);
4275 cpumask_and(attrs->__pod_cpumask, attrs->__pod_cpumask, cpu_online_mask);
4276 if (cpu_going_down >= 0)
4277 cpumask_clear_cpu(cpu_going_down, attrs->__pod_cpumask);
4278
4279 if (cpumask_empty(attrs->__pod_cpumask)) {
4280 cpumask_copy(attrs->__pod_cpumask, attrs->cpumask);
4281 return;
4282 }
4283
4284 /* yeap, return possible CPUs in @pod that @attrs wants */
4285 cpumask_and(attrs->__pod_cpumask, attrs->cpumask, pt->pod_cpus[pod]);
4286
4287 if (cpumask_empty(attrs->__pod_cpumask))
4288 pr_warn_once("WARNING: workqueue cpumask: online intersect > "
4289 "possible intersect\n");
4290}
4291
4292/* install @pwq into @wq's cpu_pwq and return the old pwq */
4293static struct pool_workqueue *install_unbound_pwq(struct workqueue_struct *wq,
4294 int cpu, struct pool_workqueue *pwq)
4295{
4296 struct pool_workqueue *old_pwq;
4297
4298 lockdep_assert_held(&wq_pool_mutex);
4299 lockdep_assert_held(&wq->mutex);
4300
4301 /* link_pwq() can handle duplicate calls */
4302 link_pwq(pwq);
4303
4304 old_pwq = rcu_access_pointer(*per_cpu_ptr(wq->cpu_pwq, cpu));
4305 rcu_assign_pointer(*per_cpu_ptr(wq->cpu_pwq, cpu), pwq);
4306 return old_pwq;
4307}
4308
4309/* context to store the prepared attrs & pwqs before applying */
4310struct apply_wqattrs_ctx {
4311 struct workqueue_struct *wq; /* target workqueue */
4312 struct workqueue_attrs *attrs; /* attrs to apply */
4313 struct list_head list; /* queued for batching commit */
4314 struct pool_workqueue *dfl_pwq;
4315 struct pool_workqueue *pwq_tbl[];
4316};
4317
4318/* free the resources after success or abort */
4319static void apply_wqattrs_cleanup(struct apply_wqattrs_ctx *ctx)
4320{
4321 if (ctx) {
4322 int cpu;
4323
4324 for_each_possible_cpu(cpu)
4325 put_pwq_unlocked(ctx->pwq_tbl[cpu]);
4326 put_pwq_unlocked(ctx->dfl_pwq);
4327
4328 free_workqueue_attrs(ctx->attrs);
4329
4330 kfree(ctx);
4331 }
4332}
4333
4334/* allocate the attrs and pwqs for later installation */
4335static struct apply_wqattrs_ctx *
4336apply_wqattrs_prepare(struct workqueue_struct *wq,
4337 const struct workqueue_attrs *attrs,
4338 const cpumask_var_t unbound_cpumask)
4339{
4340 struct apply_wqattrs_ctx *ctx;
4341 struct workqueue_attrs *new_attrs;
4342 int cpu;
4343
4344 lockdep_assert_held(&wq_pool_mutex);
4345
4346 if (WARN_ON(attrs->affn_scope < 0 ||
4347 attrs->affn_scope >= WQ_AFFN_NR_TYPES))
4348 return ERR_PTR(-EINVAL);
4349
4350 ctx = kzalloc(struct_size(ctx, pwq_tbl, nr_cpu_ids), GFP_KERNEL);
4351
4352 new_attrs = alloc_workqueue_attrs();
4353 if (!ctx || !new_attrs)
4354 goto out_free;
4355
4356 /*
4357 * If something goes wrong during CPU up/down, we'll fall back to
4358 * the default pwq covering whole @attrs->cpumask. Always create
4359 * it even if we don't use it immediately.
4360 */
4361 copy_workqueue_attrs(new_attrs, attrs);
4362 wqattrs_actualize_cpumask(new_attrs, unbound_cpumask);
4363 cpumask_copy(new_attrs->__pod_cpumask, new_attrs->cpumask);
4364 ctx->dfl_pwq = alloc_unbound_pwq(wq, new_attrs);
4365 if (!ctx->dfl_pwq)
4366 goto out_free;
4367
4368 for_each_possible_cpu(cpu) {
4369 if (new_attrs->ordered) {
4370 ctx->dfl_pwq->refcnt++;
4371 ctx->pwq_tbl[cpu] = ctx->dfl_pwq;
4372 } else {
4373 wq_calc_pod_cpumask(new_attrs, cpu, -1);
4374 ctx->pwq_tbl[cpu] = alloc_unbound_pwq(wq, new_attrs);
4375 if (!ctx->pwq_tbl[cpu])
4376 goto out_free;
4377 }
4378 }
4379
4380 /* save the user configured attrs and sanitize it. */
4381 copy_workqueue_attrs(new_attrs, attrs);
4382 cpumask_and(new_attrs->cpumask, new_attrs->cpumask, cpu_possible_mask);
4383 cpumask_copy(new_attrs->__pod_cpumask, new_attrs->cpumask);
4384 ctx->attrs = new_attrs;
4385
4386 ctx->wq = wq;
4387 return ctx;
4388
4389out_free:
4390 free_workqueue_attrs(new_attrs);
4391 apply_wqattrs_cleanup(ctx);
4392 return ERR_PTR(-ENOMEM);
4393}
4394
4395/* set attrs and install prepared pwqs, @ctx points to old pwqs on return */
4396static void apply_wqattrs_commit(struct apply_wqattrs_ctx *ctx)
4397{
4398 int cpu;
4399
4400 /* all pwqs have been created successfully, let's install'em */
4401 mutex_lock(&ctx->wq->mutex);
4402
4403 copy_workqueue_attrs(ctx->wq->unbound_attrs, ctx->attrs);
4404
4405 /* save the previous pwq and install the new one */
4406 for_each_possible_cpu(cpu)
4407 ctx->pwq_tbl[cpu] = install_unbound_pwq(ctx->wq, cpu,
4408 ctx->pwq_tbl[cpu]);
4409
4410 /* @dfl_pwq might not have been used, ensure it's linked */
4411 link_pwq(ctx->dfl_pwq);
4412 swap(ctx->wq->dfl_pwq, ctx->dfl_pwq);
4413
4414 mutex_unlock(&ctx->wq->mutex);
4415}
4416
4417static int apply_workqueue_attrs_locked(struct workqueue_struct *wq,
4418 const struct workqueue_attrs *attrs)
4419{
4420 struct apply_wqattrs_ctx *ctx;
4421
4422 /* only unbound workqueues can change attributes */
4423 if (WARN_ON(!(wq->flags & WQ_UNBOUND)))
4424 return -EINVAL;
4425
4426 /* creating multiple pwqs breaks ordering guarantee */
4427 if (!list_empty(&wq->pwqs)) {
4428 if (WARN_ON(wq->flags & __WQ_ORDERED_EXPLICIT))
4429 return -EINVAL;
4430
4431 wq->flags &= ~__WQ_ORDERED;
4432 }
4433
4434 ctx = apply_wqattrs_prepare(wq, attrs, wq_unbound_cpumask);
4435 if (IS_ERR(ctx))
4436 return PTR_ERR(ctx);
4437
4438 /* the ctx has been prepared successfully, let's commit it */
4439 apply_wqattrs_commit(ctx);
4440 apply_wqattrs_cleanup(ctx);
4441
4442 return 0;
4443}
4444
4445/**
4446 * apply_workqueue_attrs - apply new workqueue_attrs to an unbound workqueue
4447 * @wq: the target workqueue
4448 * @attrs: the workqueue_attrs to apply, allocated with alloc_workqueue_attrs()
4449 *
4450 * Apply @attrs to an unbound workqueue @wq. Unless disabled, this function maps
4451 * a separate pwq to each CPU pod with possibles CPUs in @attrs->cpumask so that
4452 * work items are affine to the pod it was issued on. Older pwqs are released as
4453 * in-flight work items finish. Note that a work item which repeatedly requeues
4454 * itself back-to-back will stay on its current pwq.
4455 *
4456 * Performs GFP_KERNEL allocations.
4457 *
4458 * Assumes caller has CPU hotplug read exclusion, i.e. cpus_read_lock().
4459 *
4460 * Return: 0 on success and -errno on failure.
4461 */
4462int apply_workqueue_attrs(struct workqueue_struct *wq,
4463 const struct workqueue_attrs *attrs)
4464{
4465 int ret;
4466
4467 lockdep_assert_cpus_held();
4468
4469 mutex_lock(&wq_pool_mutex);
4470 ret = apply_workqueue_attrs_locked(wq, attrs);
4471 mutex_unlock(&wq_pool_mutex);
4472
4473 return ret;
4474}
4475
4476/**
4477 * wq_update_pod - update pod affinity of a wq for CPU hot[un]plug
4478 * @wq: the target workqueue
4479 * @cpu: the CPU to update pool association for
4480 * @hotplug_cpu: the CPU coming up or going down
4481 * @online: whether @cpu is coming up or going down
4482 *
4483 * This function is to be called from %CPU_DOWN_PREPARE, %CPU_ONLINE and
4484 * %CPU_DOWN_FAILED. @cpu is being hot[un]plugged, update pod affinity of
4485 * @wq accordingly.
4486 *
4487 *
4488 * If pod affinity can't be adjusted due to memory allocation failure, it falls
4489 * back to @wq->dfl_pwq which may not be optimal but is always correct.
4490 *
4491 * Note that when the last allowed CPU of a pod goes offline for a workqueue
4492 * with a cpumask spanning multiple pods, the workers which were already
4493 * executing the work items for the workqueue will lose their CPU affinity and
4494 * may execute on any CPU. This is similar to how per-cpu workqueues behave on
4495 * CPU_DOWN. If a workqueue user wants strict affinity, it's the user's
4496 * responsibility to flush the work item from CPU_DOWN_PREPARE.
4497 */
4498static void wq_update_pod(struct workqueue_struct *wq, int cpu,
4499 int hotplug_cpu, bool online)
4500{
4501 int off_cpu = online ? -1 : hotplug_cpu;
4502 struct pool_workqueue *old_pwq = NULL, *pwq;
4503 struct workqueue_attrs *target_attrs;
4504
4505 lockdep_assert_held(&wq_pool_mutex);
4506
4507 if (!(wq->flags & WQ_UNBOUND) || wq->unbound_attrs->ordered)
4508 return;
4509
4510 /*
4511 * We don't wanna alloc/free wq_attrs for each wq for each CPU.
4512 * Let's use a preallocated one. The following buf is protected by
4513 * CPU hotplug exclusion.
4514 */
4515 target_attrs = wq_update_pod_attrs_buf;
4516
4517 copy_workqueue_attrs(target_attrs, wq->unbound_attrs);
4518 wqattrs_actualize_cpumask(target_attrs, wq_unbound_cpumask);
4519
4520 /* nothing to do if the target cpumask matches the current pwq */
4521 wq_calc_pod_cpumask(target_attrs, cpu, off_cpu);
4522 pwq = rcu_dereference_protected(*per_cpu_ptr(wq->cpu_pwq, cpu),
4523 lockdep_is_held(&wq_pool_mutex));
4524 if (wqattrs_equal(target_attrs, pwq->pool->attrs))
4525 return;
4526
4527 /* create a new pwq */
4528 pwq = alloc_unbound_pwq(wq, target_attrs);
4529 if (!pwq) {
4530 pr_warn("workqueue: allocation failed while updating CPU pod affinity of \"%s\"\n",
4531 wq->name);
4532 goto use_dfl_pwq;
4533 }
4534
4535 /* Install the new pwq. */
4536 mutex_lock(&wq->mutex);
4537 old_pwq = install_unbound_pwq(wq, cpu, pwq);
4538 goto out_unlock;
4539
4540use_dfl_pwq:
4541 mutex_lock(&wq->mutex);
4542 raw_spin_lock_irq(&wq->dfl_pwq->pool->lock);
4543 get_pwq(wq->dfl_pwq);
4544 raw_spin_unlock_irq(&wq->dfl_pwq->pool->lock);
4545 old_pwq = install_unbound_pwq(wq, cpu, wq->dfl_pwq);
4546out_unlock:
4547 mutex_unlock(&wq->mutex);
4548 put_pwq_unlocked(old_pwq);
4549}
4550
4551static int alloc_and_link_pwqs(struct workqueue_struct *wq)
4552{
4553 bool highpri = wq->flags & WQ_HIGHPRI;
4554 int cpu, ret;
4555
4556 wq->cpu_pwq = alloc_percpu(struct pool_workqueue *);
4557 if (!wq->cpu_pwq)
4558 goto enomem;
4559
4560 if (!(wq->flags & WQ_UNBOUND)) {
4561 for_each_possible_cpu(cpu) {
4562 struct pool_workqueue **pwq_p =
4563 per_cpu_ptr(wq->cpu_pwq, cpu);
4564 struct worker_pool *pool =
4565 &(per_cpu_ptr(cpu_worker_pools, cpu)[highpri]);
4566
4567 *pwq_p = kmem_cache_alloc_node(pwq_cache, GFP_KERNEL,
4568 pool->node);
4569 if (!*pwq_p)
4570 goto enomem;
4571
4572 init_pwq(*pwq_p, wq, pool);
4573
4574 mutex_lock(&wq->mutex);
4575 link_pwq(*pwq_p);
4576 mutex_unlock(&wq->mutex);
4577 }
4578 return 0;
4579 }
4580
4581 cpus_read_lock();
4582 if (wq->flags & __WQ_ORDERED) {
4583 ret = apply_workqueue_attrs(wq, ordered_wq_attrs[highpri]);
4584 /* there should only be single pwq for ordering guarantee */
4585 WARN(!ret && (wq->pwqs.next != &wq->dfl_pwq->pwqs_node ||
4586 wq->pwqs.prev != &wq->dfl_pwq->pwqs_node),
4587 "ordering guarantee broken for workqueue %s\n", wq->name);
4588 } else {
4589 ret = apply_workqueue_attrs(wq, unbound_std_wq_attrs[highpri]);
4590 }
4591 cpus_read_unlock();
4592
4593 /* for unbound pwq, flush the pwq_release_worker ensures that the
4594 * pwq_release_workfn() completes before calling kfree(wq).
4595 */
4596 if (ret)
4597 kthread_flush_worker(pwq_release_worker);
4598
4599 return ret;
4600
4601enomem:
4602 if (wq->cpu_pwq) {
4603 for_each_possible_cpu(cpu) {
4604 struct pool_workqueue *pwq = *per_cpu_ptr(wq->cpu_pwq, cpu);
4605
4606 if (pwq)
4607 kmem_cache_free(pwq_cache, pwq);
4608 }
4609 free_percpu(wq->cpu_pwq);
4610 wq->cpu_pwq = NULL;
4611 }
4612 return -ENOMEM;
4613}
4614
4615static int wq_clamp_max_active(int max_active, unsigned int flags,
4616 const char *name)
4617{
4618 if (max_active < 1 || max_active > WQ_MAX_ACTIVE)
4619 pr_warn("workqueue: max_active %d requested for %s is out of range, clamping between %d and %d\n",
4620 max_active, name, 1, WQ_MAX_ACTIVE);
4621
4622 return clamp_val(max_active, 1, WQ_MAX_ACTIVE);
4623}
4624
4625/*
4626 * Workqueues which may be used during memory reclaim should have a rescuer
4627 * to guarantee forward progress.
4628 */
4629static int init_rescuer(struct workqueue_struct *wq)
4630{
4631 struct worker *rescuer;
4632 int ret;
4633
4634 if (!(wq->flags & WQ_MEM_RECLAIM))
4635 return 0;
4636
4637 rescuer = alloc_worker(NUMA_NO_NODE);
4638 if (!rescuer) {
4639 pr_err("workqueue: Failed to allocate a rescuer for wq \"%s\"\n",
4640 wq->name);
4641 return -ENOMEM;
4642 }
4643
4644 rescuer->rescue_wq = wq;
4645 rescuer->task = kthread_create(rescuer_thread, rescuer, "kworker/R-%s", wq->name);
4646 if (IS_ERR(rescuer->task)) {
4647 ret = PTR_ERR(rescuer->task);
4648 pr_err("workqueue: Failed to create a rescuer kthread for wq \"%s\": %pe",
4649 wq->name, ERR_PTR(ret));
4650 kfree(rescuer);
4651 return ret;
4652 }
4653
4654 wq->rescuer = rescuer;
4655 kthread_bind_mask(rescuer->task, cpu_possible_mask);
4656 wake_up_process(rescuer->task);
4657
4658 return 0;
4659}
4660
4661__printf(1, 4)
4662struct workqueue_struct *alloc_workqueue(const char *fmt,
4663 unsigned int flags,
4664 int max_active, ...)
4665{
4666 va_list args;
4667 struct workqueue_struct *wq;
4668 struct pool_workqueue *pwq;
4669
4670 /*
4671 * Unbound && max_active == 1 used to imply ordered, which is no longer
4672 * the case on many machines due to per-pod pools. While
4673 * alloc_ordered_workqueue() is the right way to create an ordered
4674 * workqueue, keep the previous behavior to avoid subtle breakages.
4675 */
4676 if ((flags & WQ_UNBOUND) && max_active == 1)
4677 flags |= __WQ_ORDERED;
4678
4679 /* see the comment above the definition of WQ_POWER_EFFICIENT */
4680 if ((flags & WQ_POWER_EFFICIENT) && wq_power_efficient)
4681 flags |= WQ_UNBOUND;
4682
4683 /* allocate wq and format name */
4684 wq = kzalloc(sizeof(*wq), GFP_KERNEL);
4685 if (!wq)
4686 return NULL;
4687
4688 if (flags & WQ_UNBOUND) {
4689 wq->unbound_attrs = alloc_workqueue_attrs();
4690 if (!wq->unbound_attrs)
4691 goto err_free_wq;
4692 }
4693
4694 va_start(args, max_active);
4695 vsnprintf(wq->name, sizeof(wq->name), fmt, args);
4696 va_end(args);
4697
4698 max_active = max_active ?: WQ_DFL_ACTIVE;
4699 max_active = wq_clamp_max_active(max_active, flags, wq->name);
4700
4701 /* init wq */
4702 wq->flags = flags;
4703 wq->saved_max_active = max_active;
4704 mutex_init(&wq->mutex);
4705 atomic_set(&wq->nr_pwqs_to_flush, 0);
4706 INIT_LIST_HEAD(&wq->pwqs);
4707 INIT_LIST_HEAD(&wq->flusher_queue);
4708 INIT_LIST_HEAD(&wq->flusher_overflow);
4709 INIT_LIST_HEAD(&wq->maydays);
4710
4711 wq_init_lockdep(wq);
4712 INIT_LIST_HEAD(&wq->list);
4713
4714 if (alloc_and_link_pwqs(wq) < 0)
4715 goto err_unreg_lockdep;
4716
4717 if (wq_online && init_rescuer(wq) < 0)
4718 goto err_destroy;
4719
4720 if ((wq->flags & WQ_SYSFS) && workqueue_sysfs_register(wq))
4721 goto err_destroy;
4722
4723 /*
4724 * wq_pool_mutex protects global freeze state and workqueues list.
4725 * Grab it, adjust max_active and add the new @wq to workqueues
4726 * list.
4727 */
4728 mutex_lock(&wq_pool_mutex);
4729
4730 mutex_lock(&wq->mutex);
4731 for_each_pwq(pwq, wq)
4732 pwq_adjust_max_active(pwq);
4733 mutex_unlock(&wq->mutex);
4734
4735 list_add_tail_rcu(&wq->list, &workqueues);
4736
4737 mutex_unlock(&wq_pool_mutex);
4738
4739 return wq;
4740
4741err_unreg_lockdep:
4742 wq_unregister_lockdep(wq);
4743 wq_free_lockdep(wq);
4744err_free_wq:
4745 free_workqueue_attrs(wq->unbound_attrs);
4746 kfree(wq);
4747 return NULL;
4748err_destroy:
4749 destroy_workqueue(wq);
4750 return NULL;
4751}
4752EXPORT_SYMBOL_GPL(alloc_workqueue);
4753
4754static bool pwq_busy(struct pool_workqueue *pwq)
4755{
4756 int i;
4757
4758 for (i = 0; i < WORK_NR_COLORS; i++)
4759 if (pwq->nr_in_flight[i])
4760 return true;
4761
4762 if ((pwq != pwq->wq->dfl_pwq) && (pwq->refcnt > 1))
4763 return true;
4764 if (pwq->nr_active || !list_empty(&pwq->inactive_works))
4765 return true;
4766
4767 return false;
4768}
4769
4770/**
4771 * destroy_workqueue - safely terminate a workqueue
4772 * @wq: target workqueue
4773 *
4774 * Safely destroy a workqueue. All work currently pending will be done first.
4775 */
4776void destroy_workqueue(struct workqueue_struct *wq)
4777{
4778 struct pool_workqueue *pwq;
4779 int cpu;
4780
4781 /*
4782 * Remove it from sysfs first so that sanity check failure doesn't
4783 * lead to sysfs name conflicts.
4784 */
4785 workqueue_sysfs_unregister(wq);
4786
4787 /* mark the workqueue destruction is in progress */
4788 mutex_lock(&wq->mutex);
4789 wq->flags |= __WQ_DESTROYING;
4790 mutex_unlock(&wq->mutex);
4791
4792 /* drain it before proceeding with destruction */
4793 drain_workqueue(wq);
4794
4795 /* kill rescuer, if sanity checks fail, leave it w/o rescuer */
4796 if (wq->rescuer) {
4797 struct worker *rescuer = wq->rescuer;
4798
4799 /* this prevents new queueing */
4800 raw_spin_lock_irq(&wq_mayday_lock);
4801 wq->rescuer = NULL;
4802 raw_spin_unlock_irq(&wq_mayday_lock);
4803
4804 /* rescuer will empty maydays list before exiting */
4805 kthread_stop(rescuer->task);
4806 kfree(rescuer);
4807 }
4808
4809 /*
4810 * Sanity checks - grab all the locks so that we wait for all
4811 * in-flight operations which may do put_pwq().
4812 */
4813 mutex_lock(&wq_pool_mutex);
4814 mutex_lock(&wq->mutex);
4815 for_each_pwq(pwq, wq) {
4816 raw_spin_lock_irq(&pwq->pool->lock);
4817 if (WARN_ON(pwq_busy(pwq))) {
4818 pr_warn("%s: %s has the following busy pwq\n",
4819 __func__, wq->name);
4820 show_pwq(pwq);
4821 raw_spin_unlock_irq(&pwq->pool->lock);
4822 mutex_unlock(&wq->mutex);
4823 mutex_unlock(&wq_pool_mutex);
4824 show_one_workqueue(wq);
4825 return;
4826 }
4827 raw_spin_unlock_irq(&pwq->pool->lock);
4828 }
4829 mutex_unlock(&wq->mutex);
4830
4831 /*
4832 * wq list is used to freeze wq, remove from list after
4833 * flushing is complete in case freeze races us.
4834 */
4835 list_del_rcu(&wq->list);
4836 mutex_unlock(&wq_pool_mutex);
4837
4838 /*
4839 * We're the sole accessor of @wq. Directly access cpu_pwq and dfl_pwq
4840 * to put the base refs. @wq will be auto-destroyed from the last
4841 * pwq_put. RCU read lock prevents @wq from going away from under us.
4842 */
4843 rcu_read_lock();
4844
4845 for_each_possible_cpu(cpu) {
4846 pwq = rcu_access_pointer(*per_cpu_ptr(wq->cpu_pwq, cpu));
4847 RCU_INIT_POINTER(*per_cpu_ptr(wq->cpu_pwq, cpu), NULL);
4848 put_pwq_unlocked(pwq);
4849 }
4850
4851 put_pwq_unlocked(wq->dfl_pwq);
4852 wq->dfl_pwq = NULL;
4853
4854 rcu_read_unlock();
4855}
4856EXPORT_SYMBOL_GPL(destroy_workqueue);
4857
4858/**
4859 * workqueue_set_max_active - adjust max_active of a workqueue
4860 * @wq: target workqueue
4861 * @max_active: new max_active value.
4862 *
4863 * Set max_active of @wq to @max_active.
4864 *
4865 * CONTEXT:
4866 * Don't call from IRQ context.
4867 */
4868void workqueue_set_max_active(struct workqueue_struct *wq, int max_active)
4869{
4870 struct pool_workqueue *pwq;
4871
4872 /* disallow meddling with max_active for ordered workqueues */
4873 if (WARN_ON(wq->flags & __WQ_ORDERED_EXPLICIT))
4874 return;
4875
4876 max_active = wq_clamp_max_active(max_active, wq->flags, wq->name);
4877
4878 mutex_lock(&wq->mutex);
4879
4880 wq->flags &= ~__WQ_ORDERED;
4881 wq->saved_max_active = max_active;
4882
4883 for_each_pwq(pwq, wq)
4884 pwq_adjust_max_active(pwq);
4885
4886 mutex_unlock(&wq->mutex);
4887}
4888EXPORT_SYMBOL_GPL(workqueue_set_max_active);
4889
4890/**
4891 * current_work - retrieve %current task's work struct
4892 *
4893 * Determine if %current task is a workqueue worker and what it's working on.
4894 * Useful to find out the context that the %current task is running in.
4895 *
4896 * Return: work struct if %current task is a workqueue worker, %NULL otherwise.
4897 */
4898struct work_struct *current_work(void)
4899{
4900 struct worker *worker = current_wq_worker();
4901
4902 return worker ? worker->current_work : NULL;
4903}
4904EXPORT_SYMBOL(current_work);
4905
4906/**
4907 * current_is_workqueue_rescuer - is %current workqueue rescuer?
4908 *
4909 * Determine whether %current is a workqueue rescuer. Can be used from
4910 * work functions to determine whether it's being run off the rescuer task.
4911 *
4912 * Return: %true if %current is a workqueue rescuer. %false otherwise.
4913 */
4914bool current_is_workqueue_rescuer(void)
4915{
4916 struct worker *worker = current_wq_worker();
4917
4918 return worker && worker->rescue_wq;
4919}
4920
4921/**
4922 * workqueue_congested - test whether a workqueue is congested
4923 * @cpu: CPU in question
4924 * @wq: target workqueue
4925 *
4926 * Test whether @wq's cpu workqueue for @cpu is congested. There is
4927 * no synchronization around this function and the test result is
4928 * unreliable and only useful as advisory hints or for debugging.
4929 *
4930 * If @cpu is WORK_CPU_UNBOUND, the test is performed on the local CPU.
4931 *
4932 * With the exception of ordered workqueues, all workqueues have per-cpu
4933 * pool_workqueues, each with its own congested state. A workqueue being
4934 * congested on one CPU doesn't mean that the workqueue is contested on any
4935 * other CPUs.
4936 *
4937 * Return:
4938 * %true if congested, %false otherwise.
4939 */
4940bool workqueue_congested(int cpu, struct workqueue_struct *wq)
4941{
4942 struct pool_workqueue *pwq;
4943 bool ret;
4944
4945 rcu_read_lock();
4946 preempt_disable();
4947
4948 if (cpu == WORK_CPU_UNBOUND)
4949 cpu = smp_processor_id();
4950
4951 pwq = *per_cpu_ptr(wq->cpu_pwq, cpu);
4952 ret = !list_empty(&pwq->inactive_works);
4953
4954 preempt_enable();
4955 rcu_read_unlock();
4956
4957 return ret;
4958}
4959EXPORT_SYMBOL_GPL(workqueue_congested);
4960
4961/**
4962 * work_busy - test whether a work is currently pending or running
4963 * @work: the work to be tested
4964 *
4965 * Test whether @work is currently pending or running. There is no
4966 * synchronization around this function and the test result is
4967 * unreliable and only useful as advisory hints or for debugging.
4968 *
4969 * Return:
4970 * OR'd bitmask of WORK_BUSY_* bits.
4971 */
4972unsigned int work_busy(struct work_struct *work)
4973{
4974 struct worker_pool *pool;
4975 unsigned long flags;
4976 unsigned int ret = 0;
4977
4978 if (work_pending(work))
4979 ret |= WORK_BUSY_PENDING;
4980
4981 rcu_read_lock();
4982 pool = get_work_pool(work);
4983 if (pool) {
4984 raw_spin_lock_irqsave(&pool->lock, flags);
4985 if (find_worker_executing_work(pool, work))
4986 ret |= WORK_BUSY_RUNNING;
4987 raw_spin_unlock_irqrestore(&pool->lock, flags);
4988 }
4989 rcu_read_unlock();
4990
4991 return ret;
4992}
4993EXPORT_SYMBOL_GPL(work_busy);
4994
4995/**
4996 * set_worker_desc - set description for the current work item
4997 * @fmt: printf-style format string
4998 * @...: arguments for the format string
4999 *
5000 * This function can be called by a running work function to describe what
5001 * the work item is about. If the worker task gets dumped, this
5002 * information will be printed out together to help debugging. The
5003 * description can be at most WORKER_DESC_LEN including the trailing '\0'.
5004 */
5005void set_worker_desc(const char *fmt, ...)
5006{
5007 struct worker *worker = current_wq_worker();
5008 va_list args;
5009
5010 if (worker) {
5011 va_start(args, fmt);
5012 vsnprintf(worker->desc, sizeof(worker->desc), fmt, args);
5013 va_end(args);
5014 }
5015}
5016EXPORT_SYMBOL_GPL(set_worker_desc);
5017
5018/**
5019 * print_worker_info - print out worker information and description
5020 * @log_lvl: the log level to use when printing
5021 * @task: target task
5022 *
5023 * If @task is a worker and currently executing a work item, print out the
5024 * name of the workqueue being serviced and worker description set with
5025 * set_worker_desc() by the currently executing work item.
5026 *
5027 * This function can be safely called on any task as long as the
5028 * task_struct itself is accessible. While safe, this function isn't
5029 * synchronized and may print out mixups or garbages of limited length.
5030 */
5031void print_worker_info(const char *log_lvl, struct task_struct *task)
5032{
5033 work_func_t *fn = NULL;
5034 char name[WQ_NAME_LEN] = { };
5035 char desc[WORKER_DESC_LEN] = { };
5036 struct pool_workqueue *pwq = NULL;
5037 struct workqueue_struct *wq = NULL;
5038 struct worker *worker;
5039
5040 if (!(task->flags & PF_WQ_WORKER))
5041 return;
5042
5043 /*
5044 * This function is called without any synchronization and @task
5045 * could be in any state. Be careful with dereferences.
5046 */
5047 worker = kthread_probe_data(task);
5048
5049 /*
5050 * Carefully copy the associated workqueue's workfn, name and desc.
5051 * Keep the original last '\0' in case the original is garbage.
5052 */
5053 copy_from_kernel_nofault(&fn, &worker->current_func, sizeof(fn));
5054 copy_from_kernel_nofault(&pwq, &worker->current_pwq, sizeof(pwq));
5055 copy_from_kernel_nofault(&wq, &pwq->wq, sizeof(wq));
5056 copy_from_kernel_nofault(name, wq->name, sizeof(name) - 1);
5057 copy_from_kernel_nofault(desc, worker->desc, sizeof(desc) - 1);
5058
5059 if (fn || name[0] || desc[0]) {
5060 printk("%sWorkqueue: %s %ps", log_lvl, name, fn);
5061 if (strcmp(name, desc))
5062 pr_cont(" (%s)", desc);
5063 pr_cont("\n");
5064 }
5065}
5066
5067static void pr_cont_pool_info(struct worker_pool *pool)
5068{
5069 pr_cont(" cpus=%*pbl", nr_cpumask_bits, pool->attrs->cpumask);
5070 if (pool->node != NUMA_NO_NODE)
5071 pr_cont(" node=%d", pool->node);
5072 pr_cont(" flags=0x%x nice=%d", pool->flags, pool->attrs->nice);
5073}
5074
5075struct pr_cont_work_struct {
5076 bool comma;
5077 work_func_t func;
5078 long ctr;
5079};
5080
5081static void pr_cont_work_flush(bool comma, work_func_t func, struct pr_cont_work_struct *pcwsp)
5082{
5083 if (!pcwsp->ctr)
5084 goto out_record;
5085 if (func == pcwsp->func) {
5086 pcwsp->ctr++;
5087 return;
5088 }
5089 if (pcwsp->ctr == 1)
5090 pr_cont("%s %ps", pcwsp->comma ? "," : "", pcwsp->func);
5091 else
5092 pr_cont("%s %ld*%ps", pcwsp->comma ? "," : "", pcwsp->ctr, pcwsp->func);
5093 pcwsp->ctr = 0;
5094out_record:
5095 if ((long)func == -1L)
5096 return;
5097 pcwsp->comma = comma;
5098 pcwsp->func = func;
5099 pcwsp->ctr = 1;
5100}
5101
5102static void pr_cont_work(bool comma, struct work_struct *work, struct pr_cont_work_struct *pcwsp)
5103{
5104 if (work->func == wq_barrier_func) {
5105 struct wq_barrier *barr;
5106
5107 barr = container_of(work, struct wq_barrier, work);
5108
5109 pr_cont_work_flush(comma, (work_func_t)-1, pcwsp);
5110 pr_cont("%s BAR(%d)", comma ? "," : "",
5111 task_pid_nr(barr->task));
5112 } else {
5113 if (!comma)
5114 pr_cont_work_flush(comma, (work_func_t)-1, pcwsp);
5115 pr_cont_work_flush(comma, work->func, pcwsp);
5116 }
5117}
5118
5119static void show_pwq(struct pool_workqueue *pwq)
5120{
5121 struct pr_cont_work_struct pcws = { .ctr = 0, };
5122 struct worker_pool *pool = pwq->pool;
5123 struct work_struct *work;
5124 struct worker *worker;
5125 bool has_in_flight = false, has_pending = false;
5126 int bkt;
5127
5128 pr_info(" pwq %d:", pool->id);
5129 pr_cont_pool_info(pool);
5130
5131 pr_cont(" active=%d/%d refcnt=%d%s\n",
5132 pwq->nr_active, pwq->max_active, pwq->refcnt,
5133 !list_empty(&pwq->mayday_node) ? " MAYDAY" : "");
5134
5135 hash_for_each(pool->busy_hash, bkt, worker, hentry) {
5136 if (worker->current_pwq == pwq) {
5137 has_in_flight = true;
5138 break;
5139 }
5140 }
5141 if (has_in_flight) {
5142 bool comma = false;
5143
5144 pr_info(" in-flight:");
5145 hash_for_each(pool->busy_hash, bkt, worker, hentry) {
5146 if (worker->current_pwq != pwq)
5147 continue;
5148
5149 pr_cont("%s %d%s:%ps", comma ? "," : "",
5150 task_pid_nr(worker->task),
5151 worker->rescue_wq ? "(RESCUER)" : "",
5152 worker->current_func);
5153 list_for_each_entry(work, &worker->scheduled, entry)
5154 pr_cont_work(false, work, &pcws);
5155 pr_cont_work_flush(comma, (work_func_t)-1L, &pcws);
5156 comma = true;
5157 }
5158 pr_cont("\n");
5159 }
5160
5161 list_for_each_entry(work, &pool->worklist, entry) {
5162 if (get_work_pwq(work) == pwq) {
5163 has_pending = true;
5164 break;
5165 }
5166 }
5167 if (has_pending) {
5168 bool comma = false;
5169
5170 pr_info(" pending:");
5171 list_for_each_entry(work, &pool->worklist, entry) {
5172 if (get_work_pwq(work) != pwq)
5173 continue;
5174
5175 pr_cont_work(comma, work, &pcws);
5176 comma = !(*work_data_bits(work) & WORK_STRUCT_LINKED);
5177 }
5178 pr_cont_work_flush(comma, (work_func_t)-1L, &pcws);
5179 pr_cont("\n");
5180 }
5181
5182 if (!list_empty(&pwq->inactive_works)) {
5183 bool comma = false;
5184
5185 pr_info(" inactive:");
5186 list_for_each_entry(work, &pwq->inactive_works, entry) {
5187 pr_cont_work(comma, work, &pcws);
5188 comma = !(*work_data_bits(work) & WORK_STRUCT_LINKED);
5189 }
5190 pr_cont_work_flush(comma, (work_func_t)-1L, &pcws);
5191 pr_cont("\n");
5192 }
5193}
5194
5195/**
5196 * show_one_workqueue - dump state of specified workqueue
5197 * @wq: workqueue whose state will be printed
5198 */
5199void show_one_workqueue(struct workqueue_struct *wq)
5200{
5201 struct pool_workqueue *pwq;
5202 bool idle = true;
5203 unsigned long flags;
5204
5205 for_each_pwq(pwq, wq) {
5206 if (pwq->nr_active || !list_empty(&pwq->inactive_works)) {
5207 idle = false;
5208 break;
5209 }
5210 }
5211 if (idle) /* Nothing to print for idle workqueue */
5212 return;
5213
5214 pr_info("workqueue %s: flags=0x%x\n", wq->name, wq->flags);
5215
5216 for_each_pwq(pwq, wq) {
5217 raw_spin_lock_irqsave(&pwq->pool->lock, flags);
5218 if (pwq->nr_active || !list_empty(&pwq->inactive_works)) {
5219 /*
5220 * Defer printing to avoid deadlocks in console
5221 * drivers that queue work while holding locks
5222 * also taken in their write paths.
5223 */
5224 printk_deferred_enter();
5225 show_pwq(pwq);
5226 printk_deferred_exit();
5227 }
5228 raw_spin_unlock_irqrestore(&pwq->pool->lock, flags);
5229 /*
5230 * We could be printing a lot from atomic context, e.g.
5231 * sysrq-t -> show_all_workqueues(). Avoid triggering
5232 * hard lockup.
5233 */
5234 touch_nmi_watchdog();
5235 }
5236
5237}
5238
5239/**
5240 * show_one_worker_pool - dump state of specified worker pool
5241 * @pool: worker pool whose state will be printed
5242 */
5243static void show_one_worker_pool(struct worker_pool *pool)
5244{
5245 struct worker *worker;
5246 bool first = true;
5247 unsigned long flags;
5248 unsigned long hung = 0;
5249
5250 raw_spin_lock_irqsave(&pool->lock, flags);
5251 if (pool->nr_workers == pool->nr_idle)
5252 goto next_pool;
5253
5254 /* How long the first pending work is waiting for a worker. */
5255 if (!list_empty(&pool->worklist))
5256 hung = jiffies_to_msecs(jiffies - pool->watchdog_ts) / 1000;
5257
5258 /*
5259 * Defer printing to avoid deadlocks in console drivers that
5260 * queue work while holding locks also taken in their write
5261 * paths.
5262 */
5263 printk_deferred_enter();
5264 pr_info("pool %d:", pool->id);
5265 pr_cont_pool_info(pool);
5266 pr_cont(" hung=%lus workers=%d", hung, pool->nr_workers);
5267 if (pool->manager)
5268 pr_cont(" manager: %d",
5269 task_pid_nr(pool->manager->task));
5270 list_for_each_entry(worker, &pool->idle_list, entry) {
5271 pr_cont(" %s%d", first ? "idle: " : "",
5272 task_pid_nr(worker->task));
5273 first = false;
5274 }
5275 pr_cont("\n");
5276 printk_deferred_exit();
5277next_pool:
5278 raw_spin_unlock_irqrestore(&pool->lock, flags);
5279 /*
5280 * We could be printing a lot from atomic context, e.g.
5281 * sysrq-t -> show_all_workqueues(). Avoid triggering
5282 * hard lockup.
5283 */
5284 touch_nmi_watchdog();
5285
5286}
5287
5288/**
5289 * show_all_workqueues - dump workqueue state
5290 *
5291 * Called from a sysrq handler and prints out all busy workqueues and pools.
5292 */
5293void show_all_workqueues(void)
5294{
5295 struct workqueue_struct *wq;
5296 struct worker_pool *pool;
5297 int pi;
5298
5299 rcu_read_lock();
5300
5301 pr_info("Showing busy workqueues and worker pools:\n");
5302
5303 list_for_each_entry_rcu(wq, &workqueues, list)
5304 show_one_workqueue(wq);
5305
5306 for_each_pool(pool, pi)
5307 show_one_worker_pool(pool);
5308
5309 rcu_read_unlock();
5310}
5311
5312/**
5313 * show_freezable_workqueues - dump freezable workqueue state
5314 *
5315 * Called from try_to_freeze_tasks() and prints out all freezable workqueues
5316 * still busy.
5317 */
5318void show_freezable_workqueues(void)
5319{
5320 struct workqueue_struct *wq;
5321
5322 rcu_read_lock();
5323
5324 pr_info("Showing freezable workqueues that are still busy:\n");
5325
5326 list_for_each_entry_rcu(wq, &workqueues, list) {
5327 if (!(wq->flags & WQ_FREEZABLE))
5328 continue;
5329 show_one_workqueue(wq);
5330 }
5331
5332 rcu_read_unlock();
5333}
5334
5335/* used to show worker information through /proc/PID/{comm,stat,status} */
5336void wq_worker_comm(char *buf, size_t size, struct task_struct *task)
5337{
5338 int off;
5339
5340 /* always show the actual comm */
5341 off = strscpy(buf, task->comm, size);
5342 if (off < 0)
5343 return;
5344
5345 /* stabilize PF_WQ_WORKER and worker pool association */
5346 mutex_lock(&wq_pool_attach_mutex);
5347
5348 if (task->flags & PF_WQ_WORKER) {
5349 struct worker *worker = kthread_data(task);
5350 struct worker_pool *pool = worker->pool;
5351
5352 if (pool) {
5353 raw_spin_lock_irq(&pool->lock);
5354 /*
5355 * ->desc tracks information (wq name or
5356 * set_worker_desc()) for the latest execution. If
5357 * current, prepend '+', otherwise '-'.
5358 */
5359 if (worker->desc[0] != '\0') {
5360 if (worker->current_work)
5361 scnprintf(buf + off, size - off, "+%s",
5362 worker->desc);
5363 else
5364 scnprintf(buf + off, size - off, "-%s",
5365 worker->desc);
5366 }
5367 raw_spin_unlock_irq(&pool->lock);
5368 }
5369 }
5370
5371 mutex_unlock(&wq_pool_attach_mutex);
5372}
5373
5374#ifdef CONFIG_SMP
5375
5376/*
5377 * CPU hotplug.
5378 *
5379 * There are two challenges in supporting CPU hotplug. Firstly, there
5380 * are a lot of assumptions on strong associations among work, pwq and
5381 * pool which make migrating pending and scheduled works very
5382 * difficult to implement without impacting hot paths. Secondly,
5383 * worker pools serve mix of short, long and very long running works making
5384 * blocked draining impractical.
5385 *
5386 * This is solved by allowing the pools to be disassociated from the CPU
5387 * running as an unbound one and allowing it to be reattached later if the
5388 * cpu comes back online.
5389 */
5390
5391static void unbind_workers(int cpu)
5392{
5393 struct worker_pool *pool;
5394 struct worker *worker;
5395
5396 for_each_cpu_worker_pool(pool, cpu) {
5397 mutex_lock(&wq_pool_attach_mutex);
5398 raw_spin_lock_irq(&pool->lock);
5399
5400 /*
5401 * We've blocked all attach/detach operations. Make all workers
5402 * unbound and set DISASSOCIATED. Before this, all workers
5403 * must be on the cpu. After this, they may become diasporas.
5404 * And the preemption disabled section in their sched callbacks
5405 * are guaranteed to see WORKER_UNBOUND since the code here
5406 * is on the same cpu.
5407 */
5408 for_each_pool_worker(worker, pool)
5409 worker->flags |= WORKER_UNBOUND;
5410
5411 pool->flags |= POOL_DISASSOCIATED;
5412
5413 /*
5414 * The handling of nr_running in sched callbacks are disabled
5415 * now. Zap nr_running. After this, nr_running stays zero and
5416 * need_more_worker() and keep_working() are always true as
5417 * long as the worklist is not empty. This pool now behaves as
5418 * an unbound (in terms of concurrency management) pool which
5419 * are served by workers tied to the pool.
5420 */
5421 pool->nr_running = 0;
5422
5423 /*
5424 * With concurrency management just turned off, a busy
5425 * worker blocking could lead to lengthy stalls. Kick off
5426 * unbound chain execution of currently pending work items.
5427 */
5428 kick_pool(pool);
5429
5430 raw_spin_unlock_irq(&pool->lock);
5431
5432 for_each_pool_worker(worker, pool)
5433 unbind_worker(worker);
5434
5435 mutex_unlock(&wq_pool_attach_mutex);
5436 }
5437}
5438
5439/**
5440 * rebind_workers - rebind all workers of a pool to the associated CPU
5441 * @pool: pool of interest
5442 *
5443 * @pool->cpu is coming online. Rebind all workers to the CPU.
5444 */
5445static void rebind_workers(struct worker_pool *pool)
5446{
5447 struct worker *worker;
5448
5449 lockdep_assert_held(&wq_pool_attach_mutex);
5450
5451 /*
5452 * Restore CPU affinity of all workers. As all idle workers should
5453 * be on the run-queue of the associated CPU before any local
5454 * wake-ups for concurrency management happen, restore CPU affinity
5455 * of all workers first and then clear UNBOUND. As we're called
5456 * from CPU_ONLINE, the following shouldn't fail.
5457 */
5458 for_each_pool_worker(worker, pool) {
5459 kthread_set_per_cpu(worker->task, pool->cpu);
5460 WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task,
5461 pool_allowed_cpus(pool)) < 0);
5462 }
5463
5464 raw_spin_lock_irq(&pool->lock);
5465
5466 pool->flags &= ~POOL_DISASSOCIATED;
5467
5468 for_each_pool_worker(worker, pool) {
5469 unsigned int worker_flags = worker->flags;
5470
5471 /*
5472 * We want to clear UNBOUND but can't directly call
5473 * worker_clr_flags() or adjust nr_running. Atomically
5474 * replace UNBOUND with another NOT_RUNNING flag REBOUND.
5475 * @worker will clear REBOUND using worker_clr_flags() when
5476 * it initiates the next execution cycle thus restoring
5477 * concurrency management. Note that when or whether
5478 * @worker clears REBOUND doesn't affect correctness.
5479 *
5480 * WRITE_ONCE() is necessary because @worker->flags may be
5481 * tested without holding any lock in
5482 * wq_worker_running(). Without it, NOT_RUNNING test may
5483 * fail incorrectly leading to premature concurrency
5484 * management operations.
5485 */
5486 WARN_ON_ONCE(!(worker_flags & WORKER_UNBOUND));
5487 worker_flags |= WORKER_REBOUND;
5488 worker_flags &= ~WORKER_UNBOUND;
5489 WRITE_ONCE(worker->flags, worker_flags);
5490 }
5491
5492 raw_spin_unlock_irq(&pool->lock);
5493}
5494
5495/**
5496 * restore_unbound_workers_cpumask - restore cpumask of unbound workers
5497 * @pool: unbound pool of interest
5498 * @cpu: the CPU which is coming up
5499 *
5500 * An unbound pool may end up with a cpumask which doesn't have any online
5501 * CPUs. When a worker of such pool get scheduled, the scheduler resets
5502 * its cpus_allowed. If @cpu is in @pool's cpumask which didn't have any
5503 * online CPU before, cpus_allowed of all its workers should be restored.
5504 */
5505static void restore_unbound_workers_cpumask(struct worker_pool *pool, int cpu)
5506{
5507 static cpumask_t cpumask;
5508 struct worker *worker;
5509
5510 lockdep_assert_held(&wq_pool_attach_mutex);
5511
5512 /* is @cpu allowed for @pool? */
5513 if (!cpumask_test_cpu(cpu, pool->attrs->cpumask))
5514 return;
5515
5516 cpumask_and(&cpumask, pool->attrs->cpumask, cpu_online_mask);
5517
5518 /* as we're called from CPU_ONLINE, the following shouldn't fail */
5519 for_each_pool_worker(worker, pool)
5520 WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task, &cpumask) < 0);
5521}
5522
5523int workqueue_prepare_cpu(unsigned int cpu)
5524{
5525 struct worker_pool *pool;
5526
5527 for_each_cpu_worker_pool(pool, cpu) {
5528 if (pool->nr_workers)
5529 continue;
5530 if (!create_worker(pool))
5531 return -ENOMEM;
5532 }
5533 return 0;
5534}
5535
5536int workqueue_online_cpu(unsigned int cpu)
5537{
5538 struct worker_pool *pool;
5539 struct workqueue_struct *wq;
5540 int pi;
5541
5542 mutex_lock(&wq_pool_mutex);
5543
5544 for_each_pool(pool, pi) {
5545 mutex_lock(&wq_pool_attach_mutex);
5546
5547 if (pool->cpu == cpu)
5548 rebind_workers(pool);
5549 else if (pool->cpu < 0)
5550 restore_unbound_workers_cpumask(pool, cpu);
5551
5552 mutex_unlock(&wq_pool_attach_mutex);
5553 }
5554
5555 /* update pod affinity of unbound workqueues */
5556 list_for_each_entry(wq, &workqueues, list) {
5557 struct workqueue_attrs *attrs = wq->unbound_attrs;
5558
5559 if (attrs) {
5560 const struct wq_pod_type *pt = wqattrs_pod_type(attrs);
5561 int tcpu;
5562
5563 for_each_cpu(tcpu, pt->pod_cpus[pt->cpu_pod[cpu]])
5564 wq_update_pod(wq, tcpu, cpu, true);
5565 }
5566 }
5567
5568 mutex_unlock(&wq_pool_mutex);
5569 return 0;
5570}
5571
5572int workqueue_offline_cpu(unsigned int cpu)
5573{
5574 struct workqueue_struct *wq;
5575
5576 /* unbinding per-cpu workers should happen on the local CPU */
5577 if (WARN_ON(cpu != smp_processor_id()))
5578 return -1;
5579
5580 unbind_workers(cpu);
5581
5582 /* update pod affinity of unbound workqueues */
5583 mutex_lock(&wq_pool_mutex);
5584 list_for_each_entry(wq, &workqueues, list) {
5585 struct workqueue_attrs *attrs = wq->unbound_attrs;
5586
5587 if (attrs) {
5588 const struct wq_pod_type *pt = wqattrs_pod_type(attrs);
5589 int tcpu;
5590
5591 for_each_cpu(tcpu, pt->pod_cpus[pt->cpu_pod[cpu]])
5592 wq_update_pod(wq, tcpu, cpu, false);
5593 }
5594 }
5595 mutex_unlock(&wq_pool_mutex);
5596
5597 return 0;
5598}
5599
5600struct work_for_cpu {
5601 struct work_struct work;
5602 long (*fn)(void *);
5603 void *arg;
5604 long ret;
5605};
5606
5607static void work_for_cpu_fn(struct work_struct *work)
5608{
5609 struct work_for_cpu *wfc = container_of(work, struct work_for_cpu, work);
5610
5611 wfc->ret = wfc->fn(wfc->arg);
5612}
5613
5614/**
5615 * work_on_cpu_key - run a function in thread context on a particular cpu
5616 * @cpu: the cpu to run on
5617 * @fn: the function to run
5618 * @arg: the function arg
5619 * @key: The lock class key for lock debugging purposes
5620 *
5621 * It is up to the caller to ensure that the cpu doesn't go offline.
5622 * The caller must not hold any locks which would prevent @fn from completing.
5623 *
5624 * Return: The value @fn returns.
5625 */
5626long work_on_cpu_key(int cpu, long (*fn)(void *),
5627 void *arg, struct lock_class_key *key)
5628{
5629 struct work_for_cpu wfc = { .fn = fn, .arg = arg };
5630
5631 INIT_WORK_ONSTACK_KEY(&wfc.work, work_for_cpu_fn, key);
5632 schedule_work_on(cpu, &wfc.work);
5633 flush_work(&wfc.work);
5634 destroy_work_on_stack(&wfc.work);
5635 return wfc.ret;
5636}
5637EXPORT_SYMBOL_GPL(work_on_cpu_key);
5638
5639/**
5640 * work_on_cpu_safe_key - run a function in thread context on a particular cpu
5641 * @cpu: the cpu to run on
5642 * @fn: the function to run
5643 * @arg: the function argument
5644 * @key: The lock class key for lock debugging purposes
5645 *
5646 * Disables CPU hotplug and calls work_on_cpu(). The caller must not hold
5647 * any locks which would prevent @fn from completing.
5648 *
5649 * Return: The value @fn returns.
5650 */
5651long work_on_cpu_safe_key(int cpu, long (*fn)(void *),
5652 void *arg, struct lock_class_key *key)
5653{
5654 long ret = -ENODEV;
5655
5656 cpus_read_lock();
5657 if (cpu_online(cpu))
5658 ret = work_on_cpu_key(cpu, fn, arg, key);
5659 cpus_read_unlock();
5660 return ret;
5661}
5662EXPORT_SYMBOL_GPL(work_on_cpu_safe_key);
5663#endif /* CONFIG_SMP */
5664
5665#ifdef CONFIG_FREEZER
5666
5667/**
5668 * freeze_workqueues_begin - begin freezing workqueues
5669 *
5670 * Start freezing workqueues. After this function returns, all freezable
5671 * workqueues will queue new works to their inactive_works list instead of
5672 * pool->worklist.
5673 *
5674 * CONTEXT:
5675 * Grabs and releases wq_pool_mutex, wq->mutex and pool->lock's.
5676 */
5677void freeze_workqueues_begin(void)
5678{
5679 struct workqueue_struct *wq;
5680 struct pool_workqueue *pwq;
5681
5682 mutex_lock(&wq_pool_mutex);
5683
5684 WARN_ON_ONCE(workqueue_freezing);
5685 workqueue_freezing = true;
5686
5687 list_for_each_entry(wq, &workqueues, list) {
5688 mutex_lock(&wq->mutex);
5689 for_each_pwq(pwq, wq)
5690 pwq_adjust_max_active(pwq);
5691 mutex_unlock(&wq->mutex);
5692 }
5693
5694 mutex_unlock(&wq_pool_mutex);
5695}
5696
5697/**
5698 * freeze_workqueues_busy - are freezable workqueues still busy?
5699 *
5700 * Check whether freezing is complete. This function must be called
5701 * between freeze_workqueues_begin() and thaw_workqueues().
5702 *
5703 * CONTEXT:
5704 * Grabs and releases wq_pool_mutex.
5705 *
5706 * Return:
5707 * %true if some freezable workqueues are still busy. %false if freezing
5708 * is complete.
5709 */
5710bool freeze_workqueues_busy(void)
5711{
5712 bool busy = false;
5713 struct workqueue_struct *wq;
5714 struct pool_workqueue *pwq;
5715
5716 mutex_lock(&wq_pool_mutex);
5717
5718 WARN_ON_ONCE(!workqueue_freezing);
5719
5720 list_for_each_entry(wq, &workqueues, list) {
5721 if (!(wq->flags & WQ_FREEZABLE))
5722 continue;
5723 /*
5724 * nr_active is monotonically decreasing. It's safe
5725 * to peek without lock.
5726 */
5727 rcu_read_lock();
5728 for_each_pwq(pwq, wq) {
5729 WARN_ON_ONCE(pwq->nr_active < 0);
5730 if (pwq->nr_active) {
5731 busy = true;
5732 rcu_read_unlock();
5733 goto out_unlock;
5734 }
5735 }
5736 rcu_read_unlock();
5737 }
5738out_unlock:
5739 mutex_unlock(&wq_pool_mutex);
5740 return busy;
5741}
5742
5743/**
5744 * thaw_workqueues - thaw workqueues
5745 *
5746 * Thaw workqueues. Normal queueing is restored and all collected
5747 * frozen works are transferred to their respective pool worklists.
5748 *
5749 * CONTEXT:
5750 * Grabs and releases wq_pool_mutex, wq->mutex and pool->lock's.
5751 */
5752void thaw_workqueues(void)
5753{
5754 struct workqueue_struct *wq;
5755 struct pool_workqueue *pwq;
5756
5757 mutex_lock(&wq_pool_mutex);
5758
5759 if (!workqueue_freezing)
5760 goto out_unlock;
5761
5762 workqueue_freezing = false;
5763
5764 /* restore max_active and repopulate worklist */
5765 list_for_each_entry(wq, &workqueues, list) {
5766 mutex_lock(&wq->mutex);
5767 for_each_pwq(pwq, wq)
5768 pwq_adjust_max_active(pwq);
5769 mutex_unlock(&wq->mutex);
5770 }
5771
5772out_unlock:
5773 mutex_unlock(&wq_pool_mutex);
5774}
5775#endif /* CONFIG_FREEZER */
5776
5777static int workqueue_apply_unbound_cpumask(const cpumask_var_t unbound_cpumask)
5778{
5779 LIST_HEAD(ctxs);
5780 int ret = 0;
5781 struct workqueue_struct *wq;
5782 struct apply_wqattrs_ctx *ctx, *n;
5783
5784 lockdep_assert_held(&wq_pool_mutex);
5785
5786 list_for_each_entry(wq, &workqueues, list) {
5787 if (!(wq->flags & WQ_UNBOUND))
5788 continue;
5789 /* creating multiple pwqs breaks ordering guarantee */
5790 if (wq->flags & __WQ_ORDERED)
5791 continue;
5792
5793 ctx = apply_wqattrs_prepare(wq, wq->unbound_attrs, unbound_cpumask);
5794 if (IS_ERR(ctx)) {
5795 ret = PTR_ERR(ctx);
5796 break;
5797 }
5798
5799 list_add_tail(&ctx->list, &ctxs);
5800 }
5801
5802 list_for_each_entry_safe(ctx, n, &ctxs, list) {
5803 if (!ret)
5804 apply_wqattrs_commit(ctx);
5805 apply_wqattrs_cleanup(ctx);
5806 }
5807
5808 if (!ret) {
5809 mutex_lock(&wq_pool_attach_mutex);
5810 cpumask_copy(wq_unbound_cpumask, unbound_cpumask);
5811 mutex_unlock(&wq_pool_attach_mutex);
5812 }
5813 return ret;
5814}
5815
5816/**
5817 * workqueue_unbound_exclude_cpumask - Exclude given CPUs from unbound cpumask
5818 * @exclude_cpumask: the cpumask to be excluded from wq_unbound_cpumask
5819 *
5820 * This function can be called from cpuset code to provide a set of isolated
5821 * CPUs that should be excluded from wq_unbound_cpumask. The caller must hold
5822 * either cpus_read_lock or cpus_write_lock.
5823 */
5824int workqueue_unbound_exclude_cpumask(cpumask_var_t exclude_cpumask)
5825{
5826 cpumask_var_t cpumask;
5827 int ret = 0;
5828
5829 if (!zalloc_cpumask_var(&cpumask, GFP_KERNEL))
5830 return -ENOMEM;
5831
5832 lockdep_assert_cpus_held();
5833 mutex_lock(&wq_pool_mutex);
5834
5835 /* Save the current isolated cpumask & export it via sysfs */
5836 cpumask_copy(wq_isolated_cpumask, exclude_cpumask);
5837
5838 /*
5839 * If the operation fails, it will fall back to
5840 * wq_requested_unbound_cpumask which is initially set to
5841 * (HK_TYPE_WQ ∩ HK_TYPE_DOMAIN) house keeping mask and rewritten
5842 * by any subsequent write to workqueue/cpumask sysfs file.
5843 */
5844 if (!cpumask_andnot(cpumask, wq_requested_unbound_cpumask, exclude_cpumask))
5845 cpumask_copy(cpumask, wq_requested_unbound_cpumask);
5846 if (!cpumask_equal(cpumask, wq_unbound_cpumask))
5847 ret = workqueue_apply_unbound_cpumask(cpumask);
5848
5849 mutex_unlock(&wq_pool_mutex);
5850 free_cpumask_var(cpumask);
5851 return ret;
5852}
5853
5854static int parse_affn_scope(const char *val)
5855{
5856 int i;
5857
5858 for (i = 0; i < ARRAY_SIZE(wq_affn_names); i++) {
5859 if (!strncasecmp(val, wq_affn_names[i], strlen(wq_affn_names[i])))
5860 return i;
5861 }
5862 return -EINVAL;
5863}
5864
5865static int wq_affn_dfl_set(const char *val, const struct kernel_param *kp)
5866{
5867 struct workqueue_struct *wq;
5868 int affn, cpu;
5869
5870 affn = parse_affn_scope(val);
5871 if (affn < 0)
5872 return affn;
5873 if (affn == WQ_AFFN_DFL)
5874 return -EINVAL;
5875
5876 cpus_read_lock();
5877 mutex_lock(&wq_pool_mutex);
5878
5879 wq_affn_dfl = affn;
5880
5881 list_for_each_entry(wq, &workqueues, list) {
5882 for_each_online_cpu(cpu) {
5883 wq_update_pod(wq, cpu, cpu, true);
5884 }
5885 }
5886
5887 mutex_unlock(&wq_pool_mutex);
5888 cpus_read_unlock();
5889
5890 return 0;
5891}
5892
5893static int wq_affn_dfl_get(char *buffer, const struct kernel_param *kp)
5894{
5895 return scnprintf(buffer, PAGE_SIZE, "%s\n", wq_affn_names[wq_affn_dfl]);
5896}
5897
5898static const struct kernel_param_ops wq_affn_dfl_ops = {
5899 .set = wq_affn_dfl_set,
5900 .get = wq_affn_dfl_get,
5901};
5902
5903module_param_cb(default_affinity_scope, &wq_affn_dfl_ops, NULL, 0644);
5904
5905#ifdef CONFIG_SYSFS
5906/*
5907 * Workqueues with WQ_SYSFS flag set is visible to userland via
5908 * /sys/bus/workqueue/devices/WQ_NAME. All visible workqueues have the
5909 * following attributes.
5910 *
5911 * per_cpu RO bool : whether the workqueue is per-cpu or unbound
5912 * max_active RW int : maximum number of in-flight work items
5913 *
5914 * Unbound workqueues have the following extra attributes.
5915 *
5916 * nice RW int : nice value of the workers
5917 * cpumask RW mask : bitmask of allowed CPUs for the workers
5918 * affinity_scope RW str : worker CPU affinity scope (cache, numa, none)
5919 * affinity_strict RW bool : worker CPU affinity is strict
5920 */
5921struct wq_device {
5922 struct workqueue_struct *wq;
5923 struct device dev;
5924};
5925
5926static struct workqueue_struct *dev_to_wq(struct device *dev)
5927{
5928 struct wq_device *wq_dev = container_of(dev, struct wq_device, dev);
5929
5930 return wq_dev->wq;
5931}
5932
5933static ssize_t per_cpu_show(struct device *dev, struct device_attribute *attr,
5934 char *buf)
5935{
5936 struct workqueue_struct *wq = dev_to_wq(dev);
5937
5938 return scnprintf(buf, PAGE_SIZE, "%d\n", (bool)!(wq->flags & WQ_UNBOUND));
5939}
5940static DEVICE_ATTR_RO(per_cpu);
5941
5942static ssize_t max_active_show(struct device *dev,
5943 struct device_attribute *attr, char *buf)
5944{
5945 struct workqueue_struct *wq = dev_to_wq(dev);
5946
5947 return scnprintf(buf, PAGE_SIZE, "%d\n", wq->saved_max_active);
5948}
5949
5950static ssize_t max_active_store(struct device *dev,
5951 struct device_attribute *attr, const char *buf,
5952 size_t count)
5953{
5954 struct workqueue_struct *wq = dev_to_wq(dev);
5955 int val;
5956
5957 if (sscanf(buf, "%d", &val) != 1 || val <= 0)
5958 return -EINVAL;
5959
5960 workqueue_set_max_active(wq, val);
5961 return count;
5962}
5963static DEVICE_ATTR_RW(max_active);
5964
5965static struct attribute *wq_sysfs_attrs[] = {
5966 &dev_attr_per_cpu.attr,
5967 &dev_attr_max_active.attr,
5968 NULL,
5969};
5970ATTRIBUTE_GROUPS(wq_sysfs);
5971
5972static void apply_wqattrs_lock(void)
5973{
5974 /* CPUs should stay stable across pwq creations and installations */
5975 cpus_read_lock();
5976 mutex_lock(&wq_pool_mutex);
5977}
5978
5979static void apply_wqattrs_unlock(void)
5980{
5981 mutex_unlock(&wq_pool_mutex);
5982 cpus_read_unlock();
5983}
5984
5985static ssize_t wq_nice_show(struct device *dev, struct device_attribute *attr,
5986 char *buf)
5987{
5988 struct workqueue_struct *wq = dev_to_wq(dev);
5989 int written;
5990
5991 mutex_lock(&wq->mutex);
5992 written = scnprintf(buf, PAGE_SIZE, "%d\n", wq->unbound_attrs->nice);
5993 mutex_unlock(&wq->mutex);
5994
5995 return written;
5996}
5997
5998/* prepare workqueue_attrs for sysfs store operations */
5999static struct workqueue_attrs *wq_sysfs_prep_attrs(struct workqueue_struct *wq)
6000{
6001 struct workqueue_attrs *attrs;
6002
6003 lockdep_assert_held(&wq_pool_mutex);
6004
6005 attrs = alloc_workqueue_attrs();
6006 if (!attrs)
6007 return NULL;
6008
6009 copy_workqueue_attrs(attrs, wq->unbound_attrs);
6010 return attrs;
6011}
6012
6013static ssize_t wq_nice_store(struct device *dev, struct device_attribute *attr,
6014 const char *buf, size_t count)
6015{
6016 struct workqueue_struct *wq = dev_to_wq(dev);
6017 struct workqueue_attrs *attrs;
6018 int ret = -ENOMEM;
6019
6020 apply_wqattrs_lock();
6021
6022 attrs = wq_sysfs_prep_attrs(wq);
6023 if (!attrs)
6024 goto out_unlock;
6025
6026 if (sscanf(buf, "%d", &attrs->nice) == 1 &&
6027 attrs->nice >= MIN_NICE && attrs->nice <= MAX_NICE)
6028 ret = apply_workqueue_attrs_locked(wq, attrs);
6029 else
6030 ret = -EINVAL;
6031
6032out_unlock:
6033 apply_wqattrs_unlock();
6034 free_workqueue_attrs(attrs);
6035 return ret ?: count;
6036}
6037
6038static ssize_t wq_cpumask_show(struct device *dev,
6039 struct device_attribute *attr, char *buf)
6040{
6041 struct workqueue_struct *wq = dev_to_wq(dev);
6042 int written;
6043
6044 mutex_lock(&wq->mutex);
6045 written = scnprintf(buf, PAGE_SIZE, "%*pb\n",
6046 cpumask_pr_args(wq->unbound_attrs->cpumask));
6047 mutex_unlock(&wq->mutex);
6048 return written;
6049}
6050
6051static ssize_t wq_cpumask_store(struct device *dev,
6052 struct device_attribute *attr,
6053 const char *buf, size_t count)
6054{
6055 struct workqueue_struct *wq = dev_to_wq(dev);
6056 struct workqueue_attrs *attrs;
6057 int ret = -ENOMEM;
6058
6059 apply_wqattrs_lock();
6060
6061 attrs = wq_sysfs_prep_attrs(wq);
6062 if (!attrs)
6063 goto out_unlock;
6064
6065 ret = cpumask_parse(buf, attrs->cpumask);
6066 if (!ret)
6067 ret = apply_workqueue_attrs_locked(wq, attrs);
6068
6069out_unlock:
6070 apply_wqattrs_unlock();
6071 free_workqueue_attrs(attrs);
6072 return ret ?: count;
6073}
6074
6075static ssize_t wq_affn_scope_show(struct device *dev,
6076 struct device_attribute *attr, char *buf)
6077{
6078 struct workqueue_struct *wq = dev_to_wq(dev);
6079 int written;
6080
6081 mutex_lock(&wq->mutex);
6082 if (wq->unbound_attrs->affn_scope == WQ_AFFN_DFL)
6083 written = scnprintf(buf, PAGE_SIZE, "%s (%s)\n",
6084 wq_affn_names[WQ_AFFN_DFL],
6085 wq_affn_names[wq_affn_dfl]);
6086 else
6087 written = scnprintf(buf, PAGE_SIZE, "%s\n",
6088 wq_affn_names[wq->unbound_attrs->affn_scope]);
6089 mutex_unlock(&wq->mutex);
6090
6091 return written;
6092}
6093
6094static ssize_t wq_affn_scope_store(struct device *dev,
6095 struct device_attribute *attr,
6096 const char *buf, size_t count)
6097{
6098 struct workqueue_struct *wq = dev_to_wq(dev);
6099 struct workqueue_attrs *attrs;
6100 int affn, ret = -ENOMEM;
6101
6102 affn = parse_affn_scope(buf);
6103 if (affn < 0)
6104 return affn;
6105
6106 apply_wqattrs_lock();
6107 attrs = wq_sysfs_prep_attrs(wq);
6108 if (attrs) {
6109 attrs->affn_scope = affn;
6110 ret = apply_workqueue_attrs_locked(wq, attrs);
6111 }
6112 apply_wqattrs_unlock();
6113 free_workqueue_attrs(attrs);
6114 return ret ?: count;
6115}
6116
6117static ssize_t wq_affinity_strict_show(struct device *dev,
6118 struct device_attribute *attr, char *buf)
6119{
6120 struct workqueue_struct *wq = dev_to_wq(dev);
6121
6122 return scnprintf(buf, PAGE_SIZE, "%d\n",
6123 wq->unbound_attrs->affn_strict);
6124}
6125
6126static ssize_t wq_affinity_strict_store(struct device *dev,
6127 struct device_attribute *attr,
6128 const char *buf, size_t count)
6129{
6130 struct workqueue_struct *wq = dev_to_wq(dev);
6131 struct workqueue_attrs *attrs;
6132 int v, ret = -ENOMEM;
6133
6134 if (sscanf(buf, "%d", &v) != 1)
6135 return -EINVAL;
6136
6137 apply_wqattrs_lock();
6138 attrs = wq_sysfs_prep_attrs(wq);
6139 if (attrs) {
6140 attrs->affn_strict = (bool)v;
6141 ret = apply_workqueue_attrs_locked(wq, attrs);
6142 }
6143 apply_wqattrs_unlock();
6144 free_workqueue_attrs(attrs);
6145 return ret ?: count;
6146}
6147
6148static struct device_attribute wq_sysfs_unbound_attrs[] = {
6149 __ATTR(nice, 0644, wq_nice_show, wq_nice_store),
6150 __ATTR(cpumask, 0644, wq_cpumask_show, wq_cpumask_store),
6151 __ATTR(affinity_scope, 0644, wq_affn_scope_show, wq_affn_scope_store),
6152 __ATTR(affinity_strict, 0644, wq_affinity_strict_show, wq_affinity_strict_store),
6153 __ATTR_NULL,
6154};
6155
6156static struct bus_type wq_subsys = {
6157 .name = "workqueue",
6158 .dev_groups = wq_sysfs_groups,
6159};
6160
6161/**
6162 * workqueue_set_unbound_cpumask - Set the low-level unbound cpumask
6163 * @cpumask: the cpumask to set
6164 *
6165 * The low-level workqueues cpumask is a global cpumask that limits
6166 * the affinity of all unbound workqueues. This function check the @cpumask
6167 * and apply it to all unbound workqueues and updates all pwqs of them.
6168 *
6169 * Return: 0 - Success
6170 * -EINVAL - Invalid @cpumask
6171 * -ENOMEM - Failed to allocate memory for attrs or pwqs.
6172 */
6173static int workqueue_set_unbound_cpumask(cpumask_var_t cpumask)
6174{
6175 int ret = -EINVAL;
6176
6177 /*
6178 * Not excluding isolated cpus on purpose.
6179 * If the user wishes to include them, we allow that.
6180 */
6181 cpumask_and(cpumask, cpumask, cpu_possible_mask);
6182 if (!cpumask_empty(cpumask)) {
6183 apply_wqattrs_lock();
6184 cpumask_copy(wq_requested_unbound_cpumask, cpumask);
6185 if (cpumask_equal(cpumask, wq_unbound_cpumask)) {
6186 ret = 0;
6187 goto out_unlock;
6188 }
6189
6190 ret = workqueue_apply_unbound_cpumask(cpumask);
6191
6192out_unlock:
6193 apply_wqattrs_unlock();
6194 }
6195
6196 return ret;
6197}
6198
6199static ssize_t __wq_cpumask_show(struct device *dev,
6200 struct device_attribute *attr, char *buf, cpumask_var_t mask)
6201{
6202 int written;
6203
6204 mutex_lock(&wq_pool_mutex);
6205 written = scnprintf(buf, PAGE_SIZE, "%*pb\n", cpumask_pr_args(mask));
6206 mutex_unlock(&wq_pool_mutex);
6207
6208 return written;
6209}
6210
6211static ssize_t wq_unbound_cpumask_show(struct device *dev,
6212 struct device_attribute *attr, char *buf)
6213{
6214 return __wq_cpumask_show(dev, attr, buf, wq_unbound_cpumask);
6215}
6216
6217static ssize_t wq_requested_cpumask_show(struct device *dev,
6218 struct device_attribute *attr, char *buf)
6219{
6220 return __wq_cpumask_show(dev, attr, buf, wq_requested_unbound_cpumask);
6221}
6222
6223static ssize_t wq_isolated_cpumask_show(struct device *dev,
6224 struct device_attribute *attr, char *buf)
6225{
6226 return __wq_cpumask_show(dev, attr, buf, wq_isolated_cpumask);
6227}
6228
6229static ssize_t wq_unbound_cpumask_store(struct device *dev,
6230 struct device_attribute *attr, const char *buf, size_t count)
6231{
6232 cpumask_var_t cpumask;
6233 int ret;
6234
6235 if (!zalloc_cpumask_var(&cpumask, GFP_KERNEL))
6236 return -ENOMEM;
6237
6238 ret = cpumask_parse(buf, cpumask);
6239 if (!ret)
6240 ret = workqueue_set_unbound_cpumask(cpumask);
6241
6242 free_cpumask_var(cpumask);
6243 return ret ? ret : count;
6244}
6245
6246static struct device_attribute wq_sysfs_cpumask_attrs[] = {
6247 __ATTR(cpumask, 0644, wq_unbound_cpumask_show,
6248 wq_unbound_cpumask_store),
6249 __ATTR(cpumask_requested, 0444, wq_requested_cpumask_show, NULL),
6250 __ATTR(cpumask_isolated, 0444, wq_isolated_cpumask_show, NULL),
6251 __ATTR_NULL,
6252};
6253
6254static int __init wq_sysfs_init(void)
6255{
6256 struct device *dev_root;
6257 int err;
6258
6259 err = subsys_virtual_register(&wq_subsys, NULL);
6260 if (err)
6261 return err;
6262
6263 dev_root = bus_get_dev_root(&wq_subsys);
6264 if (dev_root) {
6265 struct device_attribute *attr;
6266
6267 for (attr = wq_sysfs_cpumask_attrs; attr->attr.name; attr++) {
6268 err = device_create_file(dev_root, attr);
6269 if (err)
6270 break;
6271 }
6272 put_device(dev_root);
6273 }
6274 return err;
6275}
6276core_initcall(wq_sysfs_init);
6277
6278static void wq_device_release(struct device *dev)
6279{
6280 struct wq_device *wq_dev = container_of(dev, struct wq_device, dev);
6281
6282 kfree(wq_dev);
6283}
6284
6285/**
6286 * workqueue_sysfs_register - make a workqueue visible in sysfs
6287 * @wq: the workqueue to register
6288 *
6289 * Expose @wq in sysfs under /sys/bus/workqueue/devices.
6290 * alloc_workqueue*() automatically calls this function if WQ_SYSFS is set
6291 * which is the preferred method.
6292 *
6293 * Workqueue user should use this function directly iff it wants to apply
6294 * workqueue_attrs before making the workqueue visible in sysfs; otherwise,
6295 * apply_workqueue_attrs() may race against userland updating the
6296 * attributes.
6297 *
6298 * Return: 0 on success, -errno on failure.
6299 */
6300int workqueue_sysfs_register(struct workqueue_struct *wq)
6301{
6302 struct wq_device *wq_dev;
6303 int ret;
6304
6305 /*
6306 * Adjusting max_active or creating new pwqs by applying
6307 * attributes breaks ordering guarantee. Disallow exposing ordered
6308 * workqueues.
6309 */
6310 if (WARN_ON(wq->flags & __WQ_ORDERED_EXPLICIT))
6311 return -EINVAL;
6312
6313 wq->wq_dev = wq_dev = kzalloc(sizeof(*wq_dev), GFP_KERNEL);
6314 if (!wq_dev)
6315 return -ENOMEM;
6316
6317 wq_dev->wq = wq;
6318 wq_dev->dev.bus = &wq_subsys;
6319 wq_dev->dev.release = wq_device_release;
6320 dev_set_name(&wq_dev->dev, "%s", wq->name);
6321
6322 /*
6323 * unbound_attrs are created separately. Suppress uevent until
6324 * everything is ready.
6325 */
6326 dev_set_uevent_suppress(&wq_dev->dev, true);
6327
6328 ret = device_register(&wq_dev->dev);
6329 if (ret) {
6330 put_device(&wq_dev->dev);
6331 wq->wq_dev = NULL;
6332 return ret;
6333 }
6334
6335 if (wq->flags & WQ_UNBOUND) {
6336 struct device_attribute *attr;
6337
6338 for (attr = wq_sysfs_unbound_attrs; attr->attr.name; attr++) {
6339 ret = device_create_file(&wq_dev->dev, attr);
6340 if (ret) {
6341 device_unregister(&wq_dev->dev);
6342 wq->wq_dev = NULL;
6343 return ret;
6344 }
6345 }
6346 }
6347
6348 dev_set_uevent_suppress(&wq_dev->dev, false);
6349 kobject_uevent(&wq_dev->dev.kobj, KOBJ_ADD);
6350 return 0;
6351}
6352
6353/**
6354 * workqueue_sysfs_unregister - undo workqueue_sysfs_register()
6355 * @wq: the workqueue to unregister
6356 *
6357 * If @wq is registered to sysfs by workqueue_sysfs_register(), unregister.
6358 */
6359static void workqueue_sysfs_unregister(struct workqueue_struct *wq)
6360{
6361 struct wq_device *wq_dev = wq->wq_dev;
6362
6363 if (!wq->wq_dev)
6364 return;
6365
6366 wq->wq_dev = NULL;
6367 device_unregister(&wq_dev->dev);
6368}
6369#else /* CONFIG_SYSFS */
6370static void workqueue_sysfs_unregister(struct workqueue_struct *wq) { }
6371#endif /* CONFIG_SYSFS */
6372
6373/*
6374 * Workqueue watchdog.
6375 *
6376 * Stall may be caused by various bugs - missing WQ_MEM_RECLAIM, illegal
6377 * flush dependency, a concurrency managed work item which stays RUNNING
6378 * indefinitely. Workqueue stalls can be very difficult to debug as the
6379 * usual warning mechanisms don't trigger and internal workqueue state is
6380 * largely opaque.
6381 *
6382 * Workqueue watchdog monitors all worker pools periodically and dumps
6383 * state if some pools failed to make forward progress for a while where
6384 * forward progress is defined as the first item on ->worklist changing.
6385 *
6386 * This mechanism is controlled through the kernel parameter
6387 * "workqueue.watchdog_thresh" which can be updated at runtime through the
6388 * corresponding sysfs parameter file.
6389 */
6390#ifdef CONFIG_WQ_WATCHDOG
6391
6392static unsigned long wq_watchdog_thresh = 30;
6393static struct timer_list wq_watchdog_timer;
6394
6395static unsigned long wq_watchdog_touched = INITIAL_JIFFIES;
6396static DEFINE_PER_CPU(unsigned long, wq_watchdog_touched_cpu) = INITIAL_JIFFIES;
6397
6398/*
6399 * Show workers that might prevent the processing of pending work items.
6400 * The only candidates are CPU-bound workers in the running state.
6401 * Pending work items should be handled by another idle worker
6402 * in all other situations.
6403 */
6404static void show_cpu_pool_hog(struct worker_pool *pool)
6405{
6406 struct worker *worker;
6407 unsigned long flags;
6408 int bkt;
6409
6410 raw_spin_lock_irqsave(&pool->lock, flags);
6411
6412 hash_for_each(pool->busy_hash, bkt, worker, hentry) {
6413 if (task_is_running(worker->task)) {
6414 /*
6415 * Defer printing to avoid deadlocks in console
6416 * drivers that queue work while holding locks
6417 * also taken in their write paths.
6418 */
6419 printk_deferred_enter();
6420
6421 pr_info("pool %d:\n", pool->id);
6422 sched_show_task(worker->task);
6423
6424 printk_deferred_exit();
6425 }
6426 }
6427
6428 raw_spin_unlock_irqrestore(&pool->lock, flags);
6429}
6430
6431static void show_cpu_pools_hogs(void)
6432{
6433 struct worker_pool *pool;
6434 int pi;
6435
6436 pr_info("Showing backtraces of running workers in stalled CPU-bound worker pools:\n");
6437
6438 rcu_read_lock();
6439
6440 for_each_pool(pool, pi) {
6441 if (pool->cpu_stall)
6442 show_cpu_pool_hog(pool);
6443
6444 }
6445
6446 rcu_read_unlock();
6447}
6448
6449static void wq_watchdog_reset_touched(void)
6450{
6451 int cpu;
6452
6453 wq_watchdog_touched = jiffies;
6454 for_each_possible_cpu(cpu)
6455 per_cpu(wq_watchdog_touched_cpu, cpu) = jiffies;
6456}
6457
6458static void wq_watchdog_timer_fn(struct timer_list *unused)
6459{
6460 unsigned long thresh = READ_ONCE(wq_watchdog_thresh) * HZ;
6461 bool lockup_detected = false;
6462 bool cpu_pool_stall = false;
6463 unsigned long now = jiffies;
6464 struct worker_pool *pool;
6465 int pi;
6466
6467 if (!thresh)
6468 return;
6469
6470 rcu_read_lock();
6471
6472 for_each_pool(pool, pi) {
6473 unsigned long pool_ts, touched, ts;
6474
6475 pool->cpu_stall = false;
6476 if (list_empty(&pool->worklist))
6477 continue;
6478
6479 /*
6480 * If a virtual machine is stopped by the host it can look to
6481 * the watchdog like a stall.
6482 */
6483 kvm_check_and_clear_guest_paused();
6484
6485 /* get the latest of pool and touched timestamps */
6486 if (pool->cpu >= 0)
6487 touched = READ_ONCE(per_cpu(wq_watchdog_touched_cpu, pool->cpu));
6488 else
6489 touched = READ_ONCE(wq_watchdog_touched);
6490 pool_ts = READ_ONCE(pool->watchdog_ts);
6491
6492 if (time_after(pool_ts, touched))
6493 ts = pool_ts;
6494 else
6495 ts = touched;
6496
6497 /* did we stall? */
6498 if (time_after(now, ts + thresh)) {
6499 lockup_detected = true;
6500 if (pool->cpu >= 0) {
6501 pool->cpu_stall = true;
6502 cpu_pool_stall = true;
6503 }
6504 pr_emerg("BUG: workqueue lockup - pool");
6505 pr_cont_pool_info(pool);
6506 pr_cont(" stuck for %us!\n",
6507 jiffies_to_msecs(now - pool_ts) / 1000);
6508 }
6509
6510
6511 }
6512
6513 rcu_read_unlock();
6514
6515 if (lockup_detected)
6516 show_all_workqueues();
6517
6518 if (cpu_pool_stall)
6519 show_cpu_pools_hogs();
6520
6521 wq_watchdog_reset_touched();
6522 mod_timer(&wq_watchdog_timer, jiffies + thresh);
6523}
6524
6525notrace void wq_watchdog_touch(int cpu)
6526{
6527 if (cpu >= 0)
6528 per_cpu(wq_watchdog_touched_cpu, cpu) = jiffies;
6529
6530 wq_watchdog_touched = jiffies;
6531}
6532
6533static void wq_watchdog_set_thresh(unsigned long thresh)
6534{
6535 wq_watchdog_thresh = 0;
6536 del_timer_sync(&wq_watchdog_timer);
6537
6538 if (thresh) {
6539 wq_watchdog_thresh = thresh;
6540 wq_watchdog_reset_touched();
6541 mod_timer(&wq_watchdog_timer, jiffies + thresh * HZ);
6542 }
6543}
6544
6545static int wq_watchdog_param_set_thresh(const char *val,
6546 const struct kernel_param *kp)
6547{
6548 unsigned long thresh;
6549 int ret;
6550
6551 ret = kstrtoul(val, 0, &thresh);
6552 if (ret)
6553 return ret;
6554
6555 if (system_wq)
6556 wq_watchdog_set_thresh(thresh);
6557 else
6558 wq_watchdog_thresh = thresh;
6559
6560 return 0;
6561}
6562
6563static const struct kernel_param_ops wq_watchdog_thresh_ops = {
6564 .set = wq_watchdog_param_set_thresh,
6565 .get = param_get_ulong,
6566};
6567
6568module_param_cb(watchdog_thresh, &wq_watchdog_thresh_ops, &wq_watchdog_thresh,
6569 0644);
6570
6571static void wq_watchdog_init(void)
6572{
6573 timer_setup(&wq_watchdog_timer, wq_watchdog_timer_fn, TIMER_DEFERRABLE);
6574 wq_watchdog_set_thresh(wq_watchdog_thresh);
6575}
6576
6577#else /* CONFIG_WQ_WATCHDOG */
6578
6579static inline void wq_watchdog_init(void) { }
6580
6581#endif /* CONFIG_WQ_WATCHDOG */
6582
6583static void __init restrict_unbound_cpumask(const char *name, const struct cpumask *mask)
6584{
6585 if (!cpumask_intersects(wq_unbound_cpumask, mask)) {
6586 pr_warn("workqueue: Restricting unbound_cpumask (%*pb) with %s (%*pb) leaves no CPU, ignoring\n",
6587 cpumask_pr_args(wq_unbound_cpumask), name, cpumask_pr_args(mask));
6588 return;
6589 }
6590
6591 cpumask_and(wq_unbound_cpumask, wq_unbound_cpumask, mask);
6592}
6593
6594/**
6595 * workqueue_init_early - early init for workqueue subsystem
6596 *
6597 * This is the first step of three-staged workqueue subsystem initialization and
6598 * invoked as soon as the bare basics - memory allocation, cpumasks and idr are
6599 * up. It sets up all the data structures and system workqueues and allows early
6600 * boot code to create workqueues and queue/cancel work items. Actual work item
6601 * execution starts only after kthreads can be created and scheduled right
6602 * before early initcalls.
6603 */
6604void __init workqueue_init_early(void)
6605{
6606 struct wq_pod_type *pt = &wq_pod_types[WQ_AFFN_SYSTEM];
6607 int std_nice[NR_STD_WORKER_POOLS] = { 0, HIGHPRI_NICE_LEVEL };
6608 int i, cpu;
6609
6610 BUILD_BUG_ON(__alignof__(struct pool_workqueue) < __alignof__(long long));
6611
6612 BUG_ON(!alloc_cpumask_var(&wq_unbound_cpumask, GFP_KERNEL));
6613 BUG_ON(!alloc_cpumask_var(&wq_requested_unbound_cpumask, GFP_KERNEL));
6614 BUG_ON(!zalloc_cpumask_var(&wq_isolated_cpumask, GFP_KERNEL));
6615
6616 cpumask_copy(wq_unbound_cpumask, cpu_possible_mask);
6617 restrict_unbound_cpumask("HK_TYPE_WQ", housekeeping_cpumask(HK_TYPE_WQ));
6618 restrict_unbound_cpumask("HK_TYPE_DOMAIN", housekeeping_cpumask(HK_TYPE_DOMAIN));
6619 if (!cpumask_empty(&wq_cmdline_cpumask))
6620 restrict_unbound_cpumask("workqueue.unbound_cpus", &wq_cmdline_cpumask);
6621
6622 cpumask_copy(wq_requested_unbound_cpumask, wq_unbound_cpumask);
6623
6624 pwq_cache = KMEM_CACHE(pool_workqueue, SLAB_PANIC);
6625
6626 wq_update_pod_attrs_buf = alloc_workqueue_attrs();
6627 BUG_ON(!wq_update_pod_attrs_buf);
6628
6629 /* initialize WQ_AFFN_SYSTEM pods */
6630 pt->pod_cpus = kcalloc(1, sizeof(pt->pod_cpus[0]), GFP_KERNEL);
6631 pt->pod_node = kcalloc(1, sizeof(pt->pod_node[0]), GFP_KERNEL);
6632 pt->cpu_pod = kcalloc(nr_cpu_ids, sizeof(pt->cpu_pod[0]), GFP_KERNEL);
6633 BUG_ON(!pt->pod_cpus || !pt->pod_node || !pt->cpu_pod);
6634
6635 BUG_ON(!zalloc_cpumask_var_node(&pt->pod_cpus[0], GFP_KERNEL, NUMA_NO_NODE));
6636
6637 pt->nr_pods = 1;
6638 cpumask_copy(pt->pod_cpus[0], cpu_possible_mask);
6639 pt->pod_node[0] = NUMA_NO_NODE;
6640 pt->cpu_pod[0] = 0;
6641
6642 /* initialize CPU pools */
6643 for_each_possible_cpu(cpu) {
6644 struct worker_pool *pool;
6645
6646 i = 0;
6647 for_each_cpu_worker_pool(pool, cpu) {
6648 BUG_ON(init_worker_pool(pool));
6649 pool->cpu = cpu;
6650 cpumask_copy(pool->attrs->cpumask, cpumask_of(cpu));
6651 cpumask_copy(pool->attrs->__pod_cpumask, cpumask_of(cpu));
6652 pool->attrs->nice = std_nice[i++];
6653 pool->attrs->affn_strict = true;
6654 pool->node = cpu_to_node(cpu);
6655
6656 /* alloc pool ID */
6657 mutex_lock(&wq_pool_mutex);
6658 BUG_ON(worker_pool_assign_id(pool));
6659 mutex_unlock(&wq_pool_mutex);
6660 }
6661 }
6662
6663 /* create default unbound and ordered wq attrs */
6664 for (i = 0; i < NR_STD_WORKER_POOLS; i++) {
6665 struct workqueue_attrs *attrs;
6666
6667 BUG_ON(!(attrs = alloc_workqueue_attrs()));
6668 attrs->nice = std_nice[i];
6669 unbound_std_wq_attrs[i] = attrs;
6670
6671 /*
6672 * An ordered wq should have only one pwq as ordering is
6673 * guaranteed by max_active which is enforced by pwqs.
6674 */
6675 BUG_ON(!(attrs = alloc_workqueue_attrs()));
6676 attrs->nice = std_nice[i];
6677 attrs->ordered = true;
6678 ordered_wq_attrs[i] = attrs;
6679 }
6680
6681 system_wq = alloc_workqueue("events", 0, 0);
6682 system_highpri_wq = alloc_workqueue("events_highpri", WQ_HIGHPRI, 0);
6683 system_long_wq = alloc_workqueue("events_long", 0, 0);
6684 system_unbound_wq = alloc_workqueue("events_unbound", WQ_UNBOUND,
6685 WQ_MAX_ACTIVE);
6686 system_freezable_wq = alloc_workqueue("events_freezable",
6687 WQ_FREEZABLE, 0);
6688 system_power_efficient_wq = alloc_workqueue("events_power_efficient",
6689 WQ_POWER_EFFICIENT, 0);
6690 system_freezable_power_efficient_wq = alloc_workqueue("events_freezable_power_efficient",
6691 WQ_FREEZABLE | WQ_POWER_EFFICIENT,
6692 0);
6693 BUG_ON(!system_wq || !system_highpri_wq || !system_long_wq ||
6694 !system_unbound_wq || !system_freezable_wq ||
6695 !system_power_efficient_wq ||
6696 !system_freezable_power_efficient_wq);
6697}
6698
6699static void __init wq_cpu_intensive_thresh_init(void)
6700{
6701 unsigned long thresh;
6702 unsigned long bogo;
6703
6704 pwq_release_worker = kthread_create_worker(0, "pool_workqueue_release");
6705 BUG_ON(IS_ERR(pwq_release_worker));
6706
6707 /* if the user set it to a specific value, keep it */
6708 if (wq_cpu_intensive_thresh_us != ULONG_MAX)
6709 return;
6710
6711 /*
6712 * The default of 10ms is derived from the fact that most modern (as of
6713 * 2023) processors can do a lot in 10ms and that it's just below what
6714 * most consider human-perceivable. However, the kernel also runs on a
6715 * lot slower CPUs including microcontrollers where the threshold is way
6716 * too low.
6717 *
6718 * Let's scale up the threshold upto 1 second if BogoMips is below 4000.
6719 * This is by no means accurate but it doesn't have to be. The mechanism
6720 * is still useful even when the threshold is fully scaled up. Also, as
6721 * the reports would usually be applicable to everyone, some machines
6722 * operating on longer thresholds won't significantly diminish their
6723 * usefulness.
6724 */
6725 thresh = 10 * USEC_PER_MSEC;
6726
6727 /* see init/calibrate.c for lpj -> BogoMIPS calculation */
6728 bogo = max_t(unsigned long, loops_per_jiffy / 500000 * HZ, 1);
6729 if (bogo < 4000)
6730 thresh = min_t(unsigned long, thresh * 4000 / bogo, USEC_PER_SEC);
6731
6732 pr_debug("wq_cpu_intensive_thresh: lpj=%lu BogoMIPS=%lu thresh_us=%lu\n",
6733 loops_per_jiffy, bogo, thresh);
6734
6735 wq_cpu_intensive_thresh_us = thresh;
6736}
6737
6738/**
6739 * workqueue_init - bring workqueue subsystem fully online
6740 *
6741 * This is the second step of three-staged workqueue subsystem initialization
6742 * and invoked as soon as kthreads can be created and scheduled. Workqueues have
6743 * been created and work items queued on them, but there are no kworkers
6744 * executing the work items yet. Populate the worker pools with the initial
6745 * workers and enable future kworker creations.
6746 */
6747void __init workqueue_init(void)
6748{
6749 struct workqueue_struct *wq;
6750 struct worker_pool *pool;
6751 int cpu, bkt;
6752
6753 wq_cpu_intensive_thresh_init();
6754
6755 mutex_lock(&wq_pool_mutex);
6756
6757 /*
6758 * Per-cpu pools created earlier could be missing node hint. Fix them
6759 * up. Also, create a rescuer for workqueues that requested it.
6760 */
6761 for_each_possible_cpu(cpu) {
6762 for_each_cpu_worker_pool(pool, cpu) {
6763 pool->node = cpu_to_node(cpu);
6764 }
6765 }
6766
6767 list_for_each_entry(wq, &workqueues, list) {
6768 WARN(init_rescuer(wq),
6769 "workqueue: failed to create early rescuer for %s",
6770 wq->name);
6771 }
6772
6773 mutex_unlock(&wq_pool_mutex);
6774
6775 /* create the initial workers */
6776 for_each_online_cpu(cpu) {
6777 for_each_cpu_worker_pool(pool, cpu) {
6778 pool->flags &= ~POOL_DISASSOCIATED;
6779 BUG_ON(!create_worker(pool));
6780 }
6781 }
6782
6783 hash_for_each(unbound_pool_hash, bkt, pool, hash_node)
6784 BUG_ON(!create_worker(pool));
6785
6786 wq_online = true;
6787 wq_watchdog_init();
6788}
6789
6790/*
6791 * Initialize @pt by first initializing @pt->cpu_pod[] with pod IDs according to
6792 * @cpu_shares_pod(). Each subset of CPUs that share a pod is assigned a unique
6793 * and consecutive pod ID. The rest of @pt is initialized accordingly.
6794 */
6795static void __init init_pod_type(struct wq_pod_type *pt,
6796 bool (*cpus_share_pod)(int, int))
6797{
6798 int cur, pre, cpu, pod;
6799
6800 pt->nr_pods = 0;
6801
6802 /* init @pt->cpu_pod[] according to @cpus_share_pod() */
6803 pt->cpu_pod = kcalloc(nr_cpu_ids, sizeof(pt->cpu_pod[0]), GFP_KERNEL);
6804 BUG_ON(!pt->cpu_pod);
6805
6806 for_each_possible_cpu(cur) {
6807 for_each_possible_cpu(pre) {
6808 if (pre >= cur) {
6809 pt->cpu_pod[cur] = pt->nr_pods++;
6810 break;
6811 }
6812 if (cpus_share_pod(cur, pre)) {
6813 pt->cpu_pod[cur] = pt->cpu_pod[pre];
6814 break;
6815 }
6816 }
6817 }
6818
6819 /* init the rest to match @pt->cpu_pod[] */
6820 pt->pod_cpus = kcalloc(pt->nr_pods, sizeof(pt->pod_cpus[0]), GFP_KERNEL);
6821 pt->pod_node = kcalloc(pt->nr_pods, sizeof(pt->pod_node[0]), GFP_KERNEL);
6822 BUG_ON(!pt->pod_cpus || !pt->pod_node);
6823
6824 for (pod = 0; pod < pt->nr_pods; pod++)
6825 BUG_ON(!zalloc_cpumask_var(&pt->pod_cpus[pod], GFP_KERNEL));
6826
6827 for_each_possible_cpu(cpu) {
6828 cpumask_set_cpu(cpu, pt->pod_cpus[pt->cpu_pod[cpu]]);
6829 pt->pod_node[pt->cpu_pod[cpu]] = cpu_to_node(cpu);
6830 }
6831}
6832
6833static bool __init cpus_dont_share(int cpu0, int cpu1)
6834{
6835 return false;
6836}
6837
6838static bool __init cpus_share_smt(int cpu0, int cpu1)
6839{
6840#ifdef CONFIG_SCHED_SMT
6841 return cpumask_test_cpu(cpu0, cpu_smt_mask(cpu1));
6842#else
6843 return false;
6844#endif
6845}
6846
6847static bool __init cpus_share_numa(int cpu0, int cpu1)
6848{
6849 return cpu_to_node(cpu0) == cpu_to_node(cpu1);
6850}
6851
6852/**
6853 * workqueue_init_topology - initialize CPU pods for unbound workqueues
6854 *
6855 * This is the third step of there-staged workqueue subsystem initialization and
6856 * invoked after SMP and topology information are fully initialized. It
6857 * initializes the unbound CPU pods accordingly.
6858 */
6859void __init workqueue_init_topology(void)
6860{
6861 struct workqueue_struct *wq;
6862 int cpu;
6863
6864 init_pod_type(&wq_pod_types[WQ_AFFN_CPU], cpus_dont_share);
6865 init_pod_type(&wq_pod_types[WQ_AFFN_SMT], cpus_share_smt);
6866 init_pod_type(&wq_pod_types[WQ_AFFN_CACHE], cpus_share_cache);
6867 init_pod_type(&wq_pod_types[WQ_AFFN_NUMA], cpus_share_numa);
6868
6869 mutex_lock(&wq_pool_mutex);
6870
6871 /*
6872 * Workqueues allocated earlier would have all CPUs sharing the default
6873 * worker pool. Explicitly call wq_update_pod() on all workqueue and CPU
6874 * combinations to apply per-pod sharing.
6875 */
6876 list_for_each_entry(wq, &workqueues, list) {
6877 for_each_online_cpu(cpu) {
6878 wq_update_pod(wq, cpu, cpu, true);
6879 }
6880 }
6881
6882 mutex_unlock(&wq_pool_mutex);
6883}
6884
6885void __warn_flushing_systemwide_wq(void)
6886{
6887 pr_warn("WARNING: Flushing system-wide workqueues will be prohibited in near future.\n");
6888 dump_stack();
6889}
6890EXPORT_SYMBOL(__warn_flushing_systemwide_wq);
6891
6892static int __init workqueue_unbound_cpus_setup(char *str)
6893{
6894 if (cpulist_parse(str, &wq_cmdline_cpumask) < 0) {
6895 cpumask_clear(&wq_cmdline_cpumask);
6896 pr_warn("workqueue.unbound_cpus: incorrect CPU range, using default\n");
6897 }
6898
6899 return 1;
6900}
6901__setup("workqueue.unbound_cpus=", workqueue_unbound_cpus_setup);