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