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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 is one worker pool for each CPU and
20 * one extra for works which are better served by workers which are
21 * not bound to any specific CPU.
22 *
23 * Please read Documentation/workqueue.txt for details.
24 */
25
26#include <linux/module.h>
27#include <linux/kernel.h>
28#include <linux/sched.h>
29#include <linux/init.h>
30#include <linux/signal.h>
31#include <linux/completion.h>
32#include <linux/workqueue.h>
33#include <linux/slab.h>
34#include <linux/cpu.h>
35#include <linux/notifier.h>
36#include <linux/kthread.h>
37#include <linux/hardirq.h>
38#include <linux/mempolicy.h>
39#include <linux/freezer.h>
40#include <linux/kallsyms.h>
41#include <linux/debug_locks.h>
42#include <linux/lockdep.h>
43#include <linux/idr.h>
44
45#include "workqueue_sched.h"
46
47enum {
48 /* global_cwq flags */
49 GCWQ_MANAGE_WORKERS = 1 << 0, /* need to manage workers */
50 GCWQ_MANAGING_WORKERS = 1 << 1, /* managing workers */
51 GCWQ_DISASSOCIATED = 1 << 2, /* cpu can't serve workers */
52 GCWQ_FREEZING = 1 << 3, /* freeze in progress */
53 GCWQ_HIGHPRI_PENDING = 1 << 4, /* highpri works on queue */
54
55 /* worker flags */
56 WORKER_STARTED = 1 << 0, /* started */
57 WORKER_DIE = 1 << 1, /* die die die */
58 WORKER_IDLE = 1 << 2, /* is idle */
59 WORKER_PREP = 1 << 3, /* preparing to run works */
60 WORKER_ROGUE = 1 << 4, /* not bound to any cpu */
61 WORKER_REBIND = 1 << 5, /* mom is home, come back */
62 WORKER_CPU_INTENSIVE = 1 << 6, /* cpu intensive */
63 WORKER_UNBOUND = 1 << 7, /* worker is unbound */
64
65 WORKER_NOT_RUNNING = WORKER_PREP | WORKER_ROGUE | WORKER_REBIND |
66 WORKER_CPU_INTENSIVE | WORKER_UNBOUND,
67
68 /* gcwq->trustee_state */
69 TRUSTEE_START = 0, /* start */
70 TRUSTEE_IN_CHARGE = 1, /* trustee in charge of gcwq */
71 TRUSTEE_BUTCHER = 2, /* butcher workers */
72 TRUSTEE_RELEASE = 3, /* release workers */
73 TRUSTEE_DONE = 4, /* trustee is done */
74
75 BUSY_WORKER_HASH_ORDER = 6, /* 64 pointers */
76 BUSY_WORKER_HASH_SIZE = 1 << BUSY_WORKER_HASH_ORDER,
77 BUSY_WORKER_HASH_MASK = BUSY_WORKER_HASH_SIZE - 1,
78
79 MAX_IDLE_WORKERS_RATIO = 4, /* 1/4 of busy can be idle */
80 IDLE_WORKER_TIMEOUT = 300 * HZ, /* keep idle ones for 5 mins */
81
82 MAYDAY_INITIAL_TIMEOUT = HZ / 100 >= 2 ? HZ / 100 : 2,
83 /* call for help after 10ms
84 (min two ticks) */
85 MAYDAY_INTERVAL = HZ / 10, /* and then every 100ms */
86 CREATE_COOLDOWN = HZ, /* time to breath after fail */
87 TRUSTEE_COOLDOWN = HZ / 10, /* for trustee draining */
88
89 /*
90 * Rescue workers are used only on emergencies and shared by
91 * all cpus. Give -20.
92 */
93 RESCUER_NICE_LEVEL = -20,
94};
95
96/*
97 * Structure fields follow one of the following exclusion rules.
98 *
99 * I: Modifiable by initialization/destruction paths and read-only for
100 * everyone else.
101 *
102 * P: Preemption protected. Disabling preemption is enough and should
103 * only be modified and accessed from the local cpu.
104 *
105 * L: gcwq->lock protected. Access with gcwq->lock held.
106 *
107 * X: During normal operation, modification requires gcwq->lock and
108 * should be done only from local cpu. Either disabling preemption
109 * on local cpu or grabbing gcwq->lock is enough for read access.
110 * If GCWQ_DISASSOCIATED is set, it's identical to L.
111 *
112 * F: wq->flush_mutex protected.
113 *
114 * W: workqueue_lock protected.
115 */
116
117struct global_cwq;
118
119/*
120 * The poor guys doing the actual heavy lifting. All on-duty workers
121 * are either serving the manager role, on idle list or on busy hash.
122 */
123struct worker {
124 /* on idle list while idle, on busy hash table while busy */
125 union {
126 struct list_head entry; /* L: while idle */
127 struct hlist_node hentry; /* L: while busy */
128 };
129
130 struct work_struct *current_work; /* L: work being processed */
131 struct cpu_workqueue_struct *current_cwq; /* L: current_work's cwq */
132 struct list_head scheduled; /* L: scheduled works */
133 struct task_struct *task; /* I: worker task */
134 struct global_cwq *gcwq; /* I: the associated gcwq */
135 /* 64 bytes boundary on 64bit, 32 on 32bit */
136 unsigned long last_active; /* L: last active timestamp */
137 unsigned int flags; /* X: flags */
138 int id; /* I: worker id */
139 struct work_struct rebind_work; /* L: rebind worker to cpu */
140};
141
142/*
143 * Global per-cpu workqueue. There's one and only one for each cpu
144 * and all works are queued and processed here regardless of their
145 * target workqueues.
146 */
147struct global_cwq {
148 spinlock_t lock; /* the gcwq lock */
149 struct list_head worklist; /* L: list of pending works */
150 unsigned int cpu; /* I: the associated cpu */
151 unsigned int flags; /* L: GCWQ_* flags */
152
153 int nr_workers; /* L: total number of workers */
154 int nr_idle; /* L: currently idle ones */
155
156 /* workers are chained either in the idle_list or busy_hash */
157 struct list_head idle_list; /* X: list of idle workers */
158 struct hlist_head busy_hash[BUSY_WORKER_HASH_SIZE];
159 /* L: hash of busy workers */
160
161 struct timer_list idle_timer; /* L: worker idle timeout */
162 struct timer_list mayday_timer; /* L: SOS timer for dworkers */
163
164 struct ida worker_ida; /* L: for worker IDs */
165
166 struct task_struct *trustee; /* L: for gcwq shutdown */
167 unsigned int trustee_state; /* L: trustee state */
168 wait_queue_head_t trustee_wait; /* trustee wait */
169 struct worker *first_idle; /* L: first idle worker */
170} ____cacheline_aligned_in_smp;
171
172/*
173 * The per-CPU workqueue. The lower WORK_STRUCT_FLAG_BITS of
174 * work_struct->data are used for flags and thus cwqs need to be
175 * aligned at two's power of the number of flag bits.
176 */
177struct cpu_workqueue_struct {
178 struct global_cwq *gcwq; /* I: the associated gcwq */
179 struct workqueue_struct *wq; /* I: the owning workqueue */
180 int work_color; /* L: current color */
181 int flush_color; /* L: flushing color */
182 int nr_in_flight[WORK_NR_COLORS];
183 /* L: nr of in_flight works */
184 int nr_active; /* L: nr of active works */
185 int max_active; /* L: max active works */
186 struct list_head delayed_works; /* L: delayed works */
187};
188
189/*
190 * Structure used to wait for workqueue flush.
191 */
192struct wq_flusher {
193 struct list_head list; /* F: list of flushers */
194 int flush_color; /* F: flush color waiting for */
195 struct completion done; /* flush completion */
196};
197
198/*
199 * All cpumasks are assumed to be always set on UP and thus can't be
200 * used to determine whether there's something to be done.
201 */
202#ifdef CONFIG_SMP
203typedef cpumask_var_t mayday_mask_t;
204#define mayday_test_and_set_cpu(cpu, mask) \
205 cpumask_test_and_set_cpu((cpu), (mask))
206#define mayday_clear_cpu(cpu, mask) cpumask_clear_cpu((cpu), (mask))
207#define for_each_mayday_cpu(cpu, mask) for_each_cpu((cpu), (mask))
208#define alloc_mayday_mask(maskp, gfp) zalloc_cpumask_var((maskp), (gfp))
209#define free_mayday_mask(mask) free_cpumask_var((mask))
210#else
211typedef unsigned long mayday_mask_t;
212#define mayday_test_and_set_cpu(cpu, mask) test_and_set_bit(0, &(mask))
213#define mayday_clear_cpu(cpu, mask) clear_bit(0, &(mask))
214#define for_each_mayday_cpu(cpu, mask) if ((cpu) = 0, (mask))
215#define alloc_mayday_mask(maskp, gfp) true
216#define free_mayday_mask(mask) do { } while (0)
217#endif
218
219/*
220 * The externally visible workqueue abstraction is an array of
221 * per-CPU workqueues:
222 */
223struct workqueue_struct {
224 unsigned int flags; /* W: WQ_* flags */
225 union {
226 struct cpu_workqueue_struct __percpu *pcpu;
227 struct cpu_workqueue_struct *single;
228 unsigned long v;
229 } cpu_wq; /* I: cwq's */
230 struct list_head list; /* W: list of all workqueues */
231
232 struct mutex flush_mutex; /* protects wq flushing */
233 int work_color; /* F: current work color */
234 int flush_color; /* F: current flush color */
235 atomic_t nr_cwqs_to_flush; /* flush in progress */
236 struct wq_flusher *first_flusher; /* F: first flusher */
237 struct list_head flusher_queue; /* F: flush waiters */
238 struct list_head flusher_overflow; /* F: flush overflow list */
239
240 mayday_mask_t mayday_mask; /* cpus requesting rescue */
241 struct worker *rescuer; /* I: rescue worker */
242
243 int nr_drainers; /* W: drain in progress */
244 int saved_max_active; /* W: saved cwq max_active */
245 const char *name; /* I: workqueue name */
246#ifdef CONFIG_LOCKDEP
247 struct lockdep_map lockdep_map;
248#endif
249};
250
251struct workqueue_struct *system_wq __read_mostly;
252struct workqueue_struct *system_long_wq __read_mostly;
253struct workqueue_struct *system_nrt_wq __read_mostly;
254struct workqueue_struct *system_unbound_wq __read_mostly;
255struct workqueue_struct *system_freezable_wq __read_mostly;
256EXPORT_SYMBOL_GPL(system_wq);
257EXPORT_SYMBOL_GPL(system_long_wq);
258EXPORT_SYMBOL_GPL(system_nrt_wq);
259EXPORT_SYMBOL_GPL(system_unbound_wq);
260EXPORT_SYMBOL_GPL(system_freezable_wq);
261
262#define CREATE_TRACE_POINTS
263#include <trace/events/workqueue.h>
264
265#define for_each_busy_worker(worker, i, pos, gcwq) \
266 for (i = 0; i < BUSY_WORKER_HASH_SIZE; i++) \
267 hlist_for_each_entry(worker, pos, &gcwq->busy_hash[i], hentry)
268
269static inline int __next_gcwq_cpu(int cpu, const struct cpumask *mask,
270 unsigned int sw)
271{
272 if (cpu < nr_cpu_ids) {
273 if (sw & 1) {
274 cpu = cpumask_next(cpu, mask);
275 if (cpu < nr_cpu_ids)
276 return cpu;
277 }
278 if (sw & 2)
279 return WORK_CPU_UNBOUND;
280 }
281 return WORK_CPU_NONE;
282}
283
284static inline int __next_wq_cpu(int cpu, const struct cpumask *mask,
285 struct workqueue_struct *wq)
286{
287 return __next_gcwq_cpu(cpu, mask, !(wq->flags & WQ_UNBOUND) ? 1 : 2);
288}
289
290/*
291 * CPU iterators
292 *
293 * An extra gcwq is defined for an invalid cpu number
294 * (WORK_CPU_UNBOUND) to host workqueues which are not bound to any
295 * specific CPU. The following iterators are similar to
296 * for_each_*_cpu() iterators but also considers the unbound gcwq.
297 *
298 * for_each_gcwq_cpu() : possible CPUs + WORK_CPU_UNBOUND
299 * for_each_online_gcwq_cpu() : online CPUs + WORK_CPU_UNBOUND
300 * for_each_cwq_cpu() : possible CPUs for bound workqueues,
301 * WORK_CPU_UNBOUND for unbound workqueues
302 */
303#define for_each_gcwq_cpu(cpu) \
304 for ((cpu) = __next_gcwq_cpu(-1, cpu_possible_mask, 3); \
305 (cpu) < WORK_CPU_NONE; \
306 (cpu) = __next_gcwq_cpu((cpu), cpu_possible_mask, 3))
307
308#define for_each_online_gcwq_cpu(cpu) \
309 for ((cpu) = __next_gcwq_cpu(-1, cpu_online_mask, 3); \
310 (cpu) < WORK_CPU_NONE; \
311 (cpu) = __next_gcwq_cpu((cpu), cpu_online_mask, 3))
312
313#define for_each_cwq_cpu(cpu, wq) \
314 for ((cpu) = __next_wq_cpu(-1, cpu_possible_mask, (wq)); \
315 (cpu) < WORK_CPU_NONE; \
316 (cpu) = __next_wq_cpu((cpu), cpu_possible_mask, (wq)))
317
318#ifdef CONFIG_DEBUG_OBJECTS_WORK
319
320static struct debug_obj_descr work_debug_descr;
321
322static void *work_debug_hint(void *addr)
323{
324 return ((struct work_struct *) addr)->func;
325}
326
327/*
328 * fixup_init is called when:
329 * - an active object is initialized
330 */
331static int work_fixup_init(void *addr, enum debug_obj_state state)
332{
333 struct work_struct *work = addr;
334
335 switch (state) {
336 case ODEBUG_STATE_ACTIVE:
337 cancel_work_sync(work);
338 debug_object_init(work, &work_debug_descr);
339 return 1;
340 default:
341 return 0;
342 }
343}
344
345/*
346 * fixup_activate is called when:
347 * - an active object is activated
348 * - an unknown object is activated (might be a statically initialized object)
349 */
350static int work_fixup_activate(void *addr, enum debug_obj_state state)
351{
352 struct work_struct *work = addr;
353
354 switch (state) {
355
356 case ODEBUG_STATE_NOTAVAILABLE:
357 /*
358 * This is not really a fixup. The work struct was
359 * statically initialized. We just make sure that it
360 * is tracked in the object tracker.
361 */
362 if (test_bit(WORK_STRUCT_STATIC_BIT, work_data_bits(work))) {
363 debug_object_init(work, &work_debug_descr);
364 debug_object_activate(work, &work_debug_descr);
365 return 0;
366 }
367 WARN_ON_ONCE(1);
368 return 0;
369
370 case ODEBUG_STATE_ACTIVE:
371 WARN_ON(1);
372
373 default:
374 return 0;
375 }
376}
377
378/*
379 * fixup_free is called when:
380 * - an active object is freed
381 */
382static int work_fixup_free(void *addr, enum debug_obj_state state)
383{
384 struct work_struct *work = addr;
385
386 switch (state) {
387 case ODEBUG_STATE_ACTIVE:
388 cancel_work_sync(work);
389 debug_object_free(work, &work_debug_descr);
390 return 1;
391 default:
392 return 0;
393 }
394}
395
396static struct debug_obj_descr work_debug_descr = {
397 .name = "work_struct",
398 .debug_hint = work_debug_hint,
399 .fixup_init = work_fixup_init,
400 .fixup_activate = work_fixup_activate,
401 .fixup_free = work_fixup_free,
402};
403
404static inline void debug_work_activate(struct work_struct *work)
405{
406 debug_object_activate(work, &work_debug_descr);
407}
408
409static inline void debug_work_deactivate(struct work_struct *work)
410{
411 debug_object_deactivate(work, &work_debug_descr);
412}
413
414void __init_work(struct work_struct *work, int onstack)
415{
416 if (onstack)
417 debug_object_init_on_stack(work, &work_debug_descr);
418 else
419 debug_object_init(work, &work_debug_descr);
420}
421EXPORT_SYMBOL_GPL(__init_work);
422
423void destroy_work_on_stack(struct work_struct *work)
424{
425 debug_object_free(work, &work_debug_descr);
426}
427EXPORT_SYMBOL_GPL(destroy_work_on_stack);
428
429#else
430static inline void debug_work_activate(struct work_struct *work) { }
431static inline void debug_work_deactivate(struct work_struct *work) { }
432#endif
433
434/* Serializes the accesses to the list of workqueues. */
435static DEFINE_SPINLOCK(workqueue_lock);
436static LIST_HEAD(workqueues);
437static bool workqueue_freezing; /* W: have wqs started freezing? */
438
439/*
440 * The almighty global cpu workqueues. nr_running is the only field
441 * which is expected to be used frequently by other cpus via
442 * try_to_wake_up(). Put it in a separate cacheline.
443 */
444static DEFINE_PER_CPU(struct global_cwq, global_cwq);
445static DEFINE_PER_CPU_SHARED_ALIGNED(atomic_t, gcwq_nr_running);
446
447/*
448 * Global cpu workqueue and nr_running counter for unbound gcwq. The
449 * gcwq is always online, has GCWQ_DISASSOCIATED set, and all its
450 * workers have WORKER_UNBOUND set.
451 */
452static struct global_cwq unbound_global_cwq;
453static atomic_t unbound_gcwq_nr_running = ATOMIC_INIT(0); /* always 0 */
454
455static int worker_thread(void *__worker);
456
457static struct global_cwq *get_gcwq(unsigned int cpu)
458{
459 if (cpu != WORK_CPU_UNBOUND)
460 return &per_cpu(global_cwq, cpu);
461 else
462 return &unbound_global_cwq;
463}
464
465static atomic_t *get_gcwq_nr_running(unsigned int cpu)
466{
467 if (cpu != WORK_CPU_UNBOUND)
468 return &per_cpu(gcwq_nr_running, cpu);
469 else
470 return &unbound_gcwq_nr_running;
471}
472
473static struct cpu_workqueue_struct *get_cwq(unsigned int cpu,
474 struct workqueue_struct *wq)
475{
476 if (!(wq->flags & WQ_UNBOUND)) {
477 if (likely(cpu < nr_cpu_ids)) {
478#ifdef CONFIG_SMP
479 return per_cpu_ptr(wq->cpu_wq.pcpu, cpu);
480#else
481 return wq->cpu_wq.single;
482#endif
483 }
484 } else if (likely(cpu == WORK_CPU_UNBOUND))
485 return wq->cpu_wq.single;
486 return NULL;
487}
488
489static unsigned int work_color_to_flags(int color)
490{
491 return color << WORK_STRUCT_COLOR_SHIFT;
492}
493
494static int get_work_color(struct work_struct *work)
495{
496 return (*work_data_bits(work) >> WORK_STRUCT_COLOR_SHIFT) &
497 ((1 << WORK_STRUCT_COLOR_BITS) - 1);
498}
499
500static int work_next_color(int color)
501{
502 return (color + 1) % WORK_NR_COLORS;
503}
504
505/*
506 * A work's data points to the cwq with WORK_STRUCT_CWQ set while the
507 * work is on queue. Once execution starts, WORK_STRUCT_CWQ is
508 * cleared and the work data contains the cpu number it was last on.
509 *
510 * set_work_{cwq|cpu}() and clear_work_data() can be used to set the
511 * cwq, cpu or clear work->data. These functions should only be
512 * called while the work is owned - ie. while the PENDING bit is set.
513 *
514 * get_work_[g]cwq() can be used to obtain the gcwq or cwq
515 * corresponding to a work. gcwq is available once the work has been
516 * queued anywhere after initialization. cwq is available only from
517 * queueing until execution starts.
518 */
519static inline void set_work_data(struct work_struct *work, unsigned long data,
520 unsigned long flags)
521{
522 BUG_ON(!work_pending(work));
523 atomic_long_set(&work->data, data | flags | work_static(work));
524}
525
526static void set_work_cwq(struct work_struct *work,
527 struct cpu_workqueue_struct *cwq,
528 unsigned long extra_flags)
529{
530 set_work_data(work, (unsigned long)cwq,
531 WORK_STRUCT_PENDING | WORK_STRUCT_CWQ | extra_flags);
532}
533
534static void set_work_cpu(struct work_struct *work, unsigned int cpu)
535{
536 set_work_data(work, cpu << WORK_STRUCT_FLAG_BITS, WORK_STRUCT_PENDING);
537}
538
539static void clear_work_data(struct work_struct *work)
540{
541 set_work_data(work, WORK_STRUCT_NO_CPU, 0);
542}
543
544static struct cpu_workqueue_struct *get_work_cwq(struct work_struct *work)
545{
546 unsigned long data = atomic_long_read(&work->data);
547
548 if (data & WORK_STRUCT_CWQ)
549 return (void *)(data & WORK_STRUCT_WQ_DATA_MASK);
550 else
551 return NULL;
552}
553
554static struct global_cwq *get_work_gcwq(struct work_struct *work)
555{
556 unsigned long data = atomic_long_read(&work->data);
557 unsigned int cpu;
558
559 if (data & WORK_STRUCT_CWQ)
560 return ((struct cpu_workqueue_struct *)
561 (data & WORK_STRUCT_WQ_DATA_MASK))->gcwq;
562
563 cpu = data >> WORK_STRUCT_FLAG_BITS;
564 if (cpu == WORK_CPU_NONE)
565 return NULL;
566
567 BUG_ON(cpu >= nr_cpu_ids && cpu != WORK_CPU_UNBOUND);
568 return get_gcwq(cpu);
569}
570
571/*
572 * Policy functions. These define the policies on how the global
573 * worker pool is managed. Unless noted otherwise, these functions
574 * assume that they're being called with gcwq->lock held.
575 */
576
577static bool __need_more_worker(struct global_cwq *gcwq)
578{
579 return !atomic_read(get_gcwq_nr_running(gcwq->cpu)) ||
580 gcwq->flags & GCWQ_HIGHPRI_PENDING;
581}
582
583/*
584 * Need to wake up a worker? Called from anything but currently
585 * running workers.
586 */
587static bool need_more_worker(struct global_cwq *gcwq)
588{
589 return !list_empty(&gcwq->worklist) && __need_more_worker(gcwq);
590}
591
592/* Can I start working? Called from busy but !running workers. */
593static bool may_start_working(struct global_cwq *gcwq)
594{
595 return gcwq->nr_idle;
596}
597
598/* Do I need to keep working? Called from currently running workers. */
599static bool keep_working(struct global_cwq *gcwq)
600{
601 atomic_t *nr_running = get_gcwq_nr_running(gcwq->cpu);
602
603 return !list_empty(&gcwq->worklist) &&
604 (atomic_read(nr_running) <= 1 ||
605 gcwq->flags & GCWQ_HIGHPRI_PENDING);
606}
607
608/* Do we need a new worker? Called from manager. */
609static bool need_to_create_worker(struct global_cwq *gcwq)
610{
611 return need_more_worker(gcwq) && !may_start_working(gcwq);
612}
613
614/* Do I need to be the manager? */
615static bool need_to_manage_workers(struct global_cwq *gcwq)
616{
617 return need_to_create_worker(gcwq) || gcwq->flags & GCWQ_MANAGE_WORKERS;
618}
619
620/* Do we have too many workers and should some go away? */
621static bool too_many_workers(struct global_cwq *gcwq)
622{
623 bool managing = gcwq->flags & GCWQ_MANAGING_WORKERS;
624 int nr_idle = gcwq->nr_idle + managing; /* manager is considered idle */
625 int nr_busy = gcwq->nr_workers - nr_idle;
626
627 return nr_idle > 2 && (nr_idle - 2) * MAX_IDLE_WORKERS_RATIO >= nr_busy;
628}
629
630/*
631 * Wake up functions.
632 */
633
634/* Return the first worker. Safe with preemption disabled */
635static struct worker *first_worker(struct global_cwq *gcwq)
636{
637 if (unlikely(list_empty(&gcwq->idle_list)))
638 return NULL;
639
640 return list_first_entry(&gcwq->idle_list, struct worker, entry);
641}
642
643/**
644 * wake_up_worker - wake up an idle worker
645 * @gcwq: gcwq to wake worker for
646 *
647 * Wake up the first idle worker of @gcwq.
648 *
649 * CONTEXT:
650 * spin_lock_irq(gcwq->lock).
651 */
652static void wake_up_worker(struct global_cwq *gcwq)
653{
654 struct worker *worker = first_worker(gcwq);
655
656 if (likely(worker))
657 wake_up_process(worker->task);
658}
659
660/**
661 * wq_worker_waking_up - a worker is waking up
662 * @task: task waking up
663 * @cpu: CPU @task is waking up to
664 *
665 * This function is called during try_to_wake_up() when a worker is
666 * being awoken.
667 *
668 * CONTEXT:
669 * spin_lock_irq(rq->lock)
670 */
671void wq_worker_waking_up(struct task_struct *task, unsigned int cpu)
672{
673 struct worker *worker = kthread_data(task);
674
675 if (!(worker->flags & WORKER_NOT_RUNNING))
676 atomic_inc(get_gcwq_nr_running(cpu));
677}
678
679/**
680 * wq_worker_sleeping - a worker is going to sleep
681 * @task: task going to sleep
682 * @cpu: CPU in question, must be the current CPU number
683 *
684 * This function is called during schedule() when a busy worker is
685 * going to sleep. Worker on the same cpu can be woken up by
686 * returning pointer to its task.
687 *
688 * CONTEXT:
689 * spin_lock_irq(rq->lock)
690 *
691 * RETURNS:
692 * Worker task on @cpu to wake up, %NULL if none.
693 */
694struct task_struct *wq_worker_sleeping(struct task_struct *task,
695 unsigned int cpu)
696{
697 struct worker *worker = kthread_data(task), *to_wakeup = NULL;
698 struct global_cwq *gcwq = get_gcwq(cpu);
699 atomic_t *nr_running = get_gcwq_nr_running(cpu);
700
701 if (worker->flags & WORKER_NOT_RUNNING)
702 return NULL;
703
704 /* this can only happen on the local cpu */
705 BUG_ON(cpu != raw_smp_processor_id());
706
707 /*
708 * The counterpart of the following dec_and_test, implied mb,
709 * worklist not empty test sequence is in insert_work().
710 * Please read comment there.
711 *
712 * NOT_RUNNING is clear. This means that trustee is not in
713 * charge and we're running on the local cpu w/ rq lock held
714 * and preemption disabled, which in turn means that none else
715 * could be manipulating idle_list, so dereferencing idle_list
716 * without gcwq lock is safe.
717 */
718 if (atomic_dec_and_test(nr_running) && !list_empty(&gcwq->worklist))
719 to_wakeup = first_worker(gcwq);
720 return to_wakeup ? to_wakeup->task : NULL;
721}
722
723/**
724 * worker_set_flags - set worker flags and adjust nr_running accordingly
725 * @worker: self
726 * @flags: flags to set
727 * @wakeup: wakeup an idle worker if necessary
728 *
729 * Set @flags in @worker->flags and adjust nr_running accordingly. If
730 * nr_running becomes zero and @wakeup is %true, an idle worker is
731 * woken up.
732 *
733 * CONTEXT:
734 * spin_lock_irq(gcwq->lock)
735 */
736static inline void worker_set_flags(struct worker *worker, unsigned int flags,
737 bool wakeup)
738{
739 struct global_cwq *gcwq = worker->gcwq;
740
741 WARN_ON_ONCE(worker->task != current);
742
743 /*
744 * If transitioning into NOT_RUNNING, adjust nr_running and
745 * wake up an idle worker as necessary if requested by
746 * @wakeup.
747 */
748 if ((flags & WORKER_NOT_RUNNING) &&
749 !(worker->flags & WORKER_NOT_RUNNING)) {
750 atomic_t *nr_running = get_gcwq_nr_running(gcwq->cpu);
751
752 if (wakeup) {
753 if (atomic_dec_and_test(nr_running) &&
754 !list_empty(&gcwq->worklist))
755 wake_up_worker(gcwq);
756 } else
757 atomic_dec(nr_running);
758 }
759
760 worker->flags |= flags;
761}
762
763/**
764 * worker_clr_flags - clear worker flags and adjust nr_running accordingly
765 * @worker: self
766 * @flags: flags to clear
767 *
768 * Clear @flags in @worker->flags and adjust nr_running accordingly.
769 *
770 * CONTEXT:
771 * spin_lock_irq(gcwq->lock)
772 */
773static inline void worker_clr_flags(struct worker *worker, unsigned int flags)
774{
775 struct global_cwq *gcwq = worker->gcwq;
776 unsigned int oflags = worker->flags;
777
778 WARN_ON_ONCE(worker->task != current);
779
780 worker->flags &= ~flags;
781
782 /*
783 * If transitioning out of NOT_RUNNING, increment nr_running. Note
784 * that the nested NOT_RUNNING is not a noop. NOT_RUNNING is mask
785 * of multiple flags, not a single flag.
786 */
787 if ((flags & WORKER_NOT_RUNNING) && (oflags & WORKER_NOT_RUNNING))
788 if (!(worker->flags & WORKER_NOT_RUNNING))
789 atomic_inc(get_gcwq_nr_running(gcwq->cpu));
790}
791
792/**
793 * busy_worker_head - return the busy hash head for a work
794 * @gcwq: gcwq of interest
795 * @work: work to be hashed
796 *
797 * Return hash head of @gcwq for @work.
798 *
799 * CONTEXT:
800 * spin_lock_irq(gcwq->lock).
801 *
802 * RETURNS:
803 * Pointer to the hash head.
804 */
805static struct hlist_head *busy_worker_head(struct global_cwq *gcwq,
806 struct work_struct *work)
807{
808 const int base_shift = ilog2(sizeof(struct work_struct));
809 unsigned long v = (unsigned long)work;
810
811 /* simple shift and fold hash, do we need something better? */
812 v >>= base_shift;
813 v += v >> BUSY_WORKER_HASH_ORDER;
814 v &= BUSY_WORKER_HASH_MASK;
815
816 return &gcwq->busy_hash[v];
817}
818
819/**
820 * __find_worker_executing_work - find worker which is executing a work
821 * @gcwq: gcwq of interest
822 * @bwh: hash head as returned by busy_worker_head()
823 * @work: work to find worker for
824 *
825 * Find a worker which is executing @work on @gcwq. @bwh should be
826 * the hash head obtained by calling busy_worker_head() with the same
827 * work.
828 *
829 * CONTEXT:
830 * spin_lock_irq(gcwq->lock).
831 *
832 * RETURNS:
833 * Pointer to worker which is executing @work if found, NULL
834 * otherwise.
835 */
836static struct worker *__find_worker_executing_work(struct global_cwq *gcwq,
837 struct hlist_head *bwh,
838 struct work_struct *work)
839{
840 struct worker *worker;
841 struct hlist_node *tmp;
842
843 hlist_for_each_entry(worker, tmp, bwh, hentry)
844 if (worker->current_work == work)
845 return worker;
846 return NULL;
847}
848
849/**
850 * find_worker_executing_work - find worker which is executing a work
851 * @gcwq: gcwq of interest
852 * @work: work to find worker for
853 *
854 * Find a worker which is executing @work on @gcwq. This function is
855 * identical to __find_worker_executing_work() except that this
856 * function calculates @bwh itself.
857 *
858 * CONTEXT:
859 * spin_lock_irq(gcwq->lock).
860 *
861 * RETURNS:
862 * Pointer to worker which is executing @work if found, NULL
863 * otherwise.
864 */
865static struct worker *find_worker_executing_work(struct global_cwq *gcwq,
866 struct work_struct *work)
867{
868 return __find_worker_executing_work(gcwq, busy_worker_head(gcwq, work),
869 work);
870}
871
872/**
873 * gcwq_determine_ins_pos - find insertion position
874 * @gcwq: gcwq of interest
875 * @cwq: cwq a work is being queued for
876 *
877 * A work for @cwq is about to be queued on @gcwq, determine insertion
878 * position for the work. If @cwq is for HIGHPRI wq, the work is
879 * queued at the head of the queue but in FIFO order with respect to
880 * other HIGHPRI works; otherwise, at the end of the queue. This
881 * function also sets GCWQ_HIGHPRI_PENDING flag to hint @gcwq that
882 * there are HIGHPRI works pending.
883 *
884 * CONTEXT:
885 * spin_lock_irq(gcwq->lock).
886 *
887 * RETURNS:
888 * Pointer to inserstion position.
889 */
890static inline struct list_head *gcwq_determine_ins_pos(struct global_cwq *gcwq,
891 struct cpu_workqueue_struct *cwq)
892{
893 struct work_struct *twork;
894
895 if (likely(!(cwq->wq->flags & WQ_HIGHPRI)))
896 return &gcwq->worklist;
897
898 list_for_each_entry(twork, &gcwq->worklist, entry) {
899 struct cpu_workqueue_struct *tcwq = get_work_cwq(twork);
900
901 if (!(tcwq->wq->flags & WQ_HIGHPRI))
902 break;
903 }
904
905 gcwq->flags |= GCWQ_HIGHPRI_PENDING;
906 return &twork->entry;
907}
908
909/**
910 * insert_work - insert a work into gcwq
911 * @cwq: cwq @work belongs to
912 * @work: work to insert
913 * @head: insertion point
914 * @extra_flags: extra WORK_STRUCT_* flags to set
915 *
916 * Insert @work which belongs to @cwq into @gcwq after @head.
917 * @extra_flags is or'd to work_struct flags.
918 *
919 * CONTEXT:
920 * spin_lock_irq(gcwq->lock).
921 */
922static void insert_work(struct cpu_workqueue_struct *cwq,
923 struct work_struct *work, struct list_head *head,
924 unsigned int extra_flags)
925{
926 struct global_cwq *gcwq = cwq->gcwq;
927
928 /* we own @work, set data and link */
929 set_work_cwq(work, cwq, extra_flags);
930
931 /*
932 * Ensure that we get the right work->data if we see the
933 * result of list_add() below, see try_to_grab_pending().
934 */
935 smp_wmb();
936
937 list_add_tail(&work->entry, head);
938
939 /*
940 * Ensure either worker_sched_deactivated() sees the above
941 * list_add_tail() or we see zero nr_running to avoid workers
942 * lying around lazily while there are works to be processed.
943 */
944 smp_mb();
945
946 if (__need_more_worker(gcwq))
947 wake_up_worker(gcwq);
948}
949
950/*
951 * Test whether @work is being queued from another work executing on the
952 * same workqueue. This is rather expensive and should only be used from
953 * cold paths.
954 */
955static bool is_chained_work(struct workqueue_struct *wq)
956{
957 unsigned long flags;
958 unsigned int cpu;
959
960 for_each_gcwq_cpu(cpu) {
961 struct global_cwq *gcwq = get_gcwq(cpu);
962 struct worker *worker;
963 struct hlist_node *pos;
964 int i;
965
966 spin_lock_irqsave(&gcwq->lock, flags);
967 for_each_busy_worker(worker, i, pos, gcwq) {
968 if (worker->task != current)
969 continue;
970 spin_unlock_irqrestore(&gcwq->lock, flags);
971 /*
972 * I'm @worker, no locking necessary. See if @work
973 * is headed to the same workqueue.
974 */
975 return worker->current_cwq->wq == wq;
976 }
977 spin_unlock_irqrestore(&gcwq->lock, flags);
978 }
979 return false;
980}
981
982static void __queue_work(unsigned int cpu, struct workqueue_struct *wq,
983 struct work_struct *work)
984{
985 struct global_cwq *gcwq;
986 struct cpu_workqueue_struct *cwq;
987 struct list_head *worklist;
988 unsigned int work_flags;
989 unsigned long flags;
990
991 debug_work_activate(work);
992
993 /* if dying, only works from the same workqueue are allowed */
994 if (unlikely(wq->flags & WQ_DRAINING) &&
995 WARN_ON_ONCE(!is_chained_work(wq)))
996 return;
997
998 /* determine gcwq to use */
999 if (!(wq->flags & WQ_UNBOUND)) {
1000 struct global_cwq *last_gcwq;
1001
1002 if (unlikely(cpu == WORK_CPU_UNBOUND))
1003 cpu = raw_smp_processor_id();
1004
1005 /*
1006 * It's multi cpu. If @wq is non-reentrant and @work
1007 * was previously on a different cpu, it might still
1008 * be running there, in which case the work needs to
1009 * be queued on that cpu to guarantee non-reentrance.
1010 */
1011 gcwq = get_gcwq(cpu);
1012 if (wq->flags & WQ_NON_REENTRANT &&
1013 (last_gcwq = get_work_gcwq(work)) && last_gcwq != gcwq) {
1014 struct worker *worker;
1015
1016 spin_lock_irqsave(&last_gcwq->lock, flags);
1017
1018 worker = find_worker_executing_work(last_gcwq, work);
1019
1020 if (worker && worker->current_cwq->wq == wq)
1021 gcwq = last_gcwq;
1022 else {
1023 /* meh... not running there, queue here */
1024 spin_unlock_irqrestore(&last_gcwq->lock, flags);
1025 spin_lock_irqsave(&gcwq->lock, flags);
1026 }
1027 } else
1028 spin_lock_irqsave(&gcwq->lock, flags);
1029 } else {
1030 gcwq = get_gcwq(WORK_CPU_UNBOUND);
1031 spin_lock_irqsave(&gcwq->lock, flags);
1032 }
1033
1034 /* gcwq determined, get cwq and queue */
1035 cwq = get_cwq(gcwq->cpu, wq);
1036 trace_workqueue_queue_work(cpu, cwq, work);
1037
1038 BUG_ON(!list_empty(&work->entry));
1039
1040 cwq->nr_in_flight[cwq->work_color]++;
1041 work_flags = work_color_to_flags(cwq->work_color);
1042
1043 if (likely(cwq->nr_active < cwq->max_active)) {
1044 trace_workqueue_activate_work(work);
1045 cwq->nr_active++;
1046 worklist = gcwq_determine_ins_pos(gcwq, cwq);
1047 } else {
1048 work_flags |= WORK_STRUCT_DELAYED;
1049 worklist = &cwq->delayed_works;
1050 }
1051
1052 insert_work(cwq, work, worklist, work_flags);
1053
1054 spin_unlock_irqrestore(&gcwq->lock, flags);
1055}
1056
1057/**
1058 * queue_work - queue work on a workqueue
1059 * @wq: workqueue to use
1060 * @work: work to queue
1061 *
1062 * Returns 0 if @work was already on a queue, non-zero otherwise.
1063 *
1064 * We queue the work to the CPU on which it was submitted, but if the CPU dies
1065 * it can be processed by another CPU.
1066 */
1067int queue_work(struct workqueue_struct *wq, struct work_struct *work)
1068{
1069 int ret;
1070
1071 ret = queue_work_on(get_cpu(), wq, work);
1072 put_cpu();
1073
1074 return ret;
1075}
1076EXPORT_SYMBOL_GPL(queue_work);
1077
1078/**
1079 * queue_work_on - queue work on specific cpu
1080 * @cpu: CPU number to execute work on
1081 * @wq: workqueue to use
1082 * @work: work to queue
1083 *
1084 * Returns 0 if @work was already on a queue, non-zero otherwise.
1085 *
1086 * We queue the work to a specific CPU, the caller must ensure it
1087 * can't go away.
1088 */
1089int
1090queue_work_on(int cpu, struct workqueue_struct *wq, struct work_struct *work)
1091{
1092 int ret = 0;
1093
1094 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1095 __queue_work(cpu, wq, work);
1096 ret = 1;
1097 }
1098 return ret;
1099}
1100EXPORT_SYMBOL_GPL(queue_work_on);
1101
1102static void delayed_work_timer_fn(unsigned long __data)
1103{
1104 struct delayed_work *dwork = (struct delayed_work *)__data;
1105 struct cpu_workqueue_struct *cwq = get_work_cwq(&dwork->work);
1106
1107 __queue_work(smp_processor_id(), cwq->wq, &dwork->work);
1108}
1109
1110/**
1111 * queue_delayed_work - queue work on a workqueue after delay
1112 * @wq: workqueue to use
1113 * @dwork: delayable work to queue
1114 * @delay: number of jiffies to wait before queueing
1115 *
1116 * Returns 0 if @work was already on a queue, non-zero otherwise.
1117 */
1118int queue_delayed_work(struct workqueue_struct *wq,
1119 struct delayed_work *dwork, unsigned long delay)
1120{
1121 if (delay == 0)
1122 return queue_work(wq, &dwork->work);
1123
1124 return queue_delayed_work_on(-1, wq, dwork, delay);
1125}
1126EXPORT_SYMBOL_GPL(queue_delayed_work);
1127
1128/**
1129 * queue_delayed_work_on - queue work on specific CPU after delay
1130 * @cpu: CPU number to execute work on
1131 * @wq: workqueue to use
1132 * @dwork: work to queue
1133 * @delay: number of jiffies to wait before queueing
1134 *
1135 * Returns 0 if @work was already on a queue, non-zero otherwise.
1136 */
1137int queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
1138 struct delayed_work *dwork, unsigned long delay)
1139{
1140 int ret = 0;
1141 struct timer_list *timer = &dwork->timer;
1142 struct work_struct *work = &dwork->work;
1143
1144 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1145 unsigned int lcpu;
1146
1147 BUG_ON(timer_pending(timer));
1148 BUG_ON(!list_empty(&work->entry));
1149
1150 timer_stats_timer_set_start_info(&dwork->timer);
1151
1152 /*
1153 * This stores cwq for the moment, for the timer_fn.
1154 * Note that the work's gcwq is preserved to allow
1155 * reentrance detection for delayed works.
1156 */
1157 if (!(wq->flags & WQ_UNBOUND)) {
1158 struct global_cwq *gcwq = get_work_gcwq(work);
1159
1160 if (gcwq && gcwq->cpu != WORK_CPU_UNBOUND)
1161 lcpu = gcwq->cpu;
1162 else
1163 lcpu = raw_smp_processor_id();
1164 } else
1165 lcpu = WORK_CPU_UNBOUND;
1166
1167 set_work_cwq(work, get_cwq(lcpu, wq), 0);
1168
1169 timer->expires = jiffies + delay;
1170 timer->data = (unsigned long)dwork;
1171 timer->function = delayed_work_timer_fn;
1172
1173 if (unlikely(cpu >= 0))
1174 add_timer_on(timer, cpu);
1175 else
1176 add_timer(timer);
1177 ret = 1;
1178 }
1179 return ret;
1180}
1181EXPORT_SYMBOL_GPL(queue_delayed_work_on);
1182
1183/**
1184 * worker_enter_idle - enter idle state
1185 * @worker: worker which is entering idle state
1186 *
1187 * @worker is entering idle state. Update stats and idle timer if
1188 * necessary.
1189 *
1190 * LOCKING:
1191 * spin_lock_irq(gcwq->lock).
1192 */
1193static void worker_enter_idle(struct worker *worker)
1194{
1195 struct global_cwq *gcwq = worker->gcwq;
1196
1197 BUG_ON(worker->flags & WORKER_IDLE);
1198 BUG_ON(!list_empty(&worker->entry) &&
1199 (worker->hentry.next || worker->hentry.pprev));
1200
1201 /* can't use worker_set_flags(), also called from start_worker() */
1202 worker->flags |= WORKER_IDLE;
1203 gcwq->nr_idle++;
1204 worker->last_active = jiffies;
1205
1206 /* idle_list is LIFO */
1207 list_add(&worker->entry, &gcwq->idle_list);
1208
1209 if (likely(!(worker->flags & WORKER_ROGUE))) {
1210 if (too_many_workers(gcwq) && !timer_pending(&gcwq->idle_timer))
1211 mod_timer(&gcwq->idle_timer,
1212 jiffies + IDLE_WORKER_TIMEOUT);
1213 } else
1214 wake_up_all(&gcwq->trustee_wait);
1215
1216 /* sanity check nr_running */
1217 WARN_ON_ONCE(gcwq->nr_workers == gcwq->nr_idle &&
1218 atomic_read(get_gcwq_nr_running(gcwq->cpu)));
1219}
1220
1221/**
1222 * worker_leave_idle - leave idle state
1223 * @worker: worker which is leaving idle state
1224 *
1225 * @worker is leaving idle state. Update stats.
1226 *
1227 * LOCKING:
1228 * spin_lock_irq(gcwq->lock).
1229 */
1230static void worker_leave_idle(struct worker *worker)
1231{
1232 struct global_cwq *gcwq = worker->gcwq;
1233
1234 BUG_ON(!(worker->flags & WORKER_IDLE));
1235 worker_clr_flags(worker, WORKER_IDLE);
1236 gcwq->nr_idle--;
1237 list_del_init(&worker->entry);
1238}
1239
1240/**
1241 * worker_maybe_bind_and_lock - bind worker to its cpu if possible and lock gcwq
1242 * @worker: self
1243 *
1244 * Works which are scheduled while the cpu is online must at least be
1245 * scheduled to a worker which is bound to the cpu so that if they are
1246 * flushed from cpu callbacks while cpu is going down, they are
1247 * guaranteed to execute on the cpu.
1248 *
1249 * This function is to be used by rogue workers and rescuers to bind
1250 * themselves to the target cpu and may race with cpu going down or
1251 * coming online. kthread_bind() can't be used because it may put the
1252 * worker to already dead cpu and set_cpus_allowed_ptr() can't be used
1253 * verbatim as it's best effort and blocking and gcwq may be
1254 * [dis]associated in the meantime.
1255 *
1256 * This function tries set_cpus_allowed() and locks gcwq and verifies
1257 * the binding against GCWQ_DISASSOCIATED which is set during
1258 * CPU_DYING and cleared during CPU_ONLINE, so if the worker enters
1259 * idle state or fetches works without dropping lock, it can guarantee
1260 * the scheduling requirement described in the first paragraph.
1261 *
1262 * CONTEXT:
1263 * Might sleep. Called without any lock but returns with gcwq->lock
1264 * held.
1265 *
1266 * RETURNS:
1267 * %true if the associated gcwq is online (@worker is successfully
1268 * bound), %false if offline.
1269 */
1270static bool worker_maybe_bind_and_lock(struct worker *worker)
1271__acquires(&gcwq->lock)
1272{
1273 struct global_cwq *gcwq = worker->gcwq;
1274 struct task_struct *task = worker->task;
1275
1276 while (true) {
1277 /*
1278 * The following call may fail, succeed or succeed
1279 * without actually migrating the task to the cpu if
1280 * it races with cpu hotunplug operation. Verify
1281 * against GCWQ_DISASSOCIATED.
1282 */
1283 if (!(gcwq->flags & GCWQ_DISASSOCIATED))
1284 set_cpus_allowed_ptr(task, get_cpu_mask(gcwq->cpu));
1285
1286 spin_lock_irq(&gcwq->lock);
1287 if (gcwq->flags & GCWQ_DISASSOCIATED)
1288 return false;
1289 if (task_cpu(task) == gcwq->cpu &&
1290 cpumask_equal(¤t->cpus_allowed,
1291 get_cpu_mask(gcwq->cpu)))
1292 return true;
1293 spin_unlock_irq(&gcwq->lock);
1294
1295 /*
1296 * We've raced with CPU hot[un]plug. Give it a breather
1297 * and retry migration. cond_resched() is required here;
1298 * otherwise, we might deadlock against cpu_stop trying to
1299 * bring down the CPU on non-preemptive kernel.
1300 */
1301 cpu_relax();
1302 cond_resched();
1303 }
1304}
1305
1306/*
1307 * Function for worker->rebind_work used to rebind rogue busy workers
1308 * to the associated cpu which is coming back online. This is
1309 * scheduled by cpu up but can race with other cpu hotplug operations
1310 * and may be executed twice without intervening cpu down.
1311 */
1312static void worker_rebind_fn(struct work_struct *work)
1313{
1314 struct worker *worker = container_of(work, struct worker, rebind_work);
1315 struct global_cwq *gcwq = worker->gcwq;
1316
1317 if (worker_maybe_bind_and_lock(worker))
1318 worker_clr_flags(worker, WORKER_REBIND);
1319
1320 spin_unlock_irq(&gcwq->lock);
1321}
1322
1323static struct worker *alloc_worker(void)
1324{
1325 struct worker *worker;
1326
1327 worker = kzalloc(sizeof(*worker), GFP_KERNEL);
1328 if (worker) {
1329 INIT_LIST_HEAD(&worker->entry);
1330 INIT_LIST_HEAD(&worker->scheduled);
1331 INIT_WORK(&worker->rebind_work, worker_rebind_fn);
1332 /* on creation a worker is in !idle && prep state */
1333 worker->flags = WORKER_PREP;
1334 }
1335 return worker;
1336}
1337
1338/**
1339 * create_worker - create a new workqueue worker
1340 * @gcwq: gcwq the new worker will belong to
1341 * @bind: whether to set affinity to @cpu or not
1342 *
1343 * Create a new worker which is bound to @gcwq. The returned worker
1344 * can be started by calling start_worker() or destroyed using
1345 * destroy_worker().
1346 *
1347 * CONTEXT:
1348 * Might sleep. Does GFP_KERNEL allocations.
1349 *
1350 * RETURNS:
1351 * Pointer to the newly created worker.
1352 */
1353static struct worker *create_worker(struct global_cwq *gcwq, bool bind)
1354{
1355 bool on_unbound_cpu = gcwq->cpu == WORK_CPU_UNBOUND;
1356 struct worker *worker = NULL;
1357 int id = -1;
1358
1359 spin_lock_irq(&gcwq->lock);
1360 while (ida_get_new(&gcwq->worker_ida, &id)) {
1361 spin_unlock_irq(&gcwq->lock);
1362 if (!ida_pre_get(&gcwq->worker_ida, GFP_KERNEL))
1363 goto fail;
1364 spin_lock_irq(&gcwq->lock);
1365 }
1366 spin_unlock_irq(&gcwq->lock);
1367
1368 worker = alloc_worker();
1369 if (!worker)
1370 goto fail;
1371
1372 worker->gcwq = gcwq;
1373 worker->id = id;
1374
1375 if (!on_unbound_cpu)
1376 worker->task = kthread_create_on_node(worker_thread,
1377 worker,
1378 cpu_to_node(gcwq->cpu),
1379 "kworker/%u:%d", gcwq->cpu, id);
1380 else
1381 worker->task = kthread_create(worker_thread, worker,
1382 "kworker/u:%d", id);
1383 if (IS_ERR(worker->task))
1384 goto fail;
1385
1386 /*
1387 * A rogue worker will become a regular one if CPU comes
1388 * online later on. Make sure every worker has
1389 * PF_THREAD_BOUND set.
1390 */
1391 if (bind && !on_unbound_cpu)
1392 kthread_bind(worker->task, gcwq->cpu);
1393 else {
1394 worker->task->flags |= PF_THREAD_BOUND;
1395 if (on_unbound_cpu)
1396 worker->flags |= WORKER_UNBOUND;
1397 }
1398
1399 return worker;
1400fail:
1401 if (id >= 0) {
1402 spin_lock_irq(&gcwq->lock);
1403 ida_remove(&gcwq->worker_ida, id);
1404 spin_unlock_irq(&gcwq->lock);
1405 }
1406 kfree(worker);
1407 return NULL;
1408}
1409
1410/**
1411 * start_worker - start a newly created worker
1412 * @worker: worker to start
1413 *
1414 * Make the gcwq aware of @worker and start it.
1415 *
1416 * CONTEXT:
1417 * spin_lock_irq(gcwq->lock).
1418 */
1419static void start_worker(struct worker *worker)
1420{
1421 worker->flags |= WORKER_STARTED;
1422 worker->gcwq->nr_workers++;
1423 worker_enter_idle(worker);
1424 wake_up_process(worker->task);
1425}
1426
1427/**
1428 * destroy_worker - destroy a workqueue worker
1429 * @worker: worker to be destroyed
1430 *
1431 * Destroy @worker and adjust @gcwq stats accordingly.
1432 *
1433 * CONTEXT:
1434 * spin_lock_irq(gcwq->lock) which is released and regrabbed.
1435 */
1436static void destroy_worker(struct worker *worker)
1437{
1438 struct global_cwq *gcwq = worker->gcwq;
1439 int id = worker->id;
1440
1441 /* sanity check frenzy */
1442 BUG_ON(worker->current_work);
1443 BUG_ON(!list_empty(&worker->scheduled));
1444
1445 if (worker->flags & WORKER_STARTED)
1446 gcwq->nr_workers--;
1447 if (worker->flags & WORKER_IDLE)
1448 gcwq->nr_idle--;
1449
1450 list_del_init(&worker->entry);
1451 worker->flags |= WORKER_DIE;
1452
1453 spin_unlock_irq(&gcwq->lock);
1454
1455 kthread_stop(worker->task);
1456 kfree(worker);
1457
1458 spin_lock_irq(&gcwq->lock);
1459 ida_remove(&gcwq->worker_ida, id);
1460}
1461
1462static void idle_worker_timeout(unsigned long __gcwq)
1463{
1464 struct global_cwq *gcwq = (void *)__gcwq;
1465
1466 spin_lock_irq(&gcwq->lock);
1467
1468 if (too_many_workers(gcwq)) {
1469 struct worker *worker;
1470 unsigned long expires;
1471
1472 /* idle_list is kept in LIFO order, check the last one */
1473 worker = list_entry(gcwq->idle_list.prev, struct worker, entry);
1474 expires = worker->last_active + IDLE_WORKER_TIMEOUT;
1475
1476 if (time_before(jiffies, expires))
1477 mod_timer(&gcwq->idle_timer, expires);
1478 else {
1479 /* it's been idle for too long, wake up manager */
1480 gcwq->flags |= GCWQ_MANAGE_WORKERS;
1481 wake_up_worker(gcwq);
1482 }
1483 }
1484
1485 spin_unlock_irq(&gcwq->lock);
1486}
1487
1488static bool send_mayday(struct work_struct *work)
1489{
1490 struct cpu_workqueue_struct *cwq = get_work_cwq(work);
1491 struct workqueue_struct *wq = cwq->wq;
1492 unsigned int cpu;
1493
1494 if (!(wq->flags & WQ_RESCUER))
1495 return false;
1496
1497 /* mayday mayday mayday */
1498 cpu = cwq->gcwq->cpu;
1499 /* WORK_CPU_UNBOUND can't be set in cpumask, use cpu 0 instead */
1500 if (cpu == WORK_CPU_UNBOUND)
1501 cpu = 0;
1502 if (!mayday_test_and_set_cpu(cpu, wq->mayday_mask))
1503 wake_up_process(wq->rescuer->task);
1504 return true;
1505}
1506
1507static void gcwq_mayday_timeout(unsigned long __gcwq)
1508{
1509 struct global_cwq *gcwq = (void *)__gcwq;
1510 struct work_struct *work;
1511
1512 spin_lock_irq(&gcwq->lock);
1513
1514 if (need_to_create_worker(gcwq)) {
1515 /*
1516 * We've been trying to create a new worker but
1517 * haven't been successful. We might be hitting an
1518 * allocation deadlock. Send distress signals to
1519 * rescuers.
1520 */
1521 list_for_each_entry(work, &gcwq->worklist, entry)
1522 send_mayday(work);
1523 }
1524
1525 spin_unlock_irq(&gcwq->lock);
1526
1527 mod_timer(&gcwq->mayday_timer, jiffies + MAYDAY_INTERVAL);
1528}
1529
1530/**
1531 * maybe_create_worker - create a new worker if necessary
1532 * @gcwq: gcwq to create a new worker for
1533 *
1534 * Create a new worker for @gcwq if necessary. @gcwq is guaranteed to
1535 * have at least one idle worker on return from this function. If
1536 * creating a new worker takes longer than MAYDAY_INTERVAL, mayday is
1537 * sent to all rescuers with works scheduled on @gcwq to resolve
1538 * possible allocation deadlock.
1539 *
1540 * On return, need_to_create_worker() is guaranteed to be false and
1541 * may_start_working() true.
1542 *
1543 * LOCKING:
1544 * spin_lock_irq(gcwq->lock) which may be released and regrabbed
1545 * multiple times. Does GFP_KERNEL allocations. Called only from
1546 * manager.
1547 *
1548 * RETURNS:
1549 * false if no action was taken and gcwq->lock stayed locked, true
1550 * otherwise.
1551 */
1552static bool maybe_create_worker(struct global_cwq *gcwq)
1553__releases(&gcwq->lock)
1554__acquires(&gcwq->lock)
1555{
1556 if (!need_to_create_worker(gcwq))
1557 return false;
1558restart:
1559 spin_unlock_irq(&gcwq->lock);
1560
1561 /* if we don't make progress in MAYDAY_INITIAL_TIMEOUT, call for help */
1562 mod_timer(&gcwq->mayday_timer, jiffies + MAYDAY_INITIAL_TIMEOUT);
1563
1564 while (true) {
1565 struct worker *worker;
1566
1567 worker = create_worker(gcwq, true);
1568 if (worker) {
1569 del_timer_sync(&gcwq->mayday_timer);
1570 spin_lock_irq(&gcwq->lock);
1571 start_worker(worker);
1572 BUG_ON(need_to_create_worker(gcwq));
1573 return true;
1574 }
1575
1576 if (!need_to_create_worker(gcwq))
1577 break;
1578
1579 __set_current_state(TASK_INTERRUPTIBLE);
1580 schedule_timeout(CREATE_COOLDOWN);
1581
1582 if (!need_to_create_worker(gcwq))
1583 break;
1584 }
1585
1586 del_timer_sync(&gcwq->mayday_timer);
1587 spin_lock_irq(&gcwq->lock);
1588 if (need_to_create_worker(gcwq))
1589 goto restart;
1590 return true;
1591}
1592
1593/**
1594 * maybe_destroy_worker - destroy workers which have been idle for a while
1595 * @gcwq: gcwq to destroy workers for
1596 *
1597 * Destroy @gcwq workers which have been idle for longer than
1598 * IDLE_WORKER_TIMEOUT.
1599 *
1600 * LOCKING:
1601 * spin_lock_irq(gcwq->lock) which may be released and regrabbed
1602 * multiple times. Called only from manager.
1603 *
1604 * RETURNS:
1605 * false if no action was taken and gcwq->lock stayed locked, true
1606 * otherwise.
1607 */
1608static bool maybe_destroy_workers(struct global_cwq *gcwq)
1609{
1610 bool ret = false;
1611
1612 while (too_many_workers(gcwq)) {
1613 struct worker *worker;
1614 unsigned long expires;
1615
1616 worker = list_entry(gcwq->idle_list.prev, struct worker, entry);
1617 expires = worker->last_active + IDLE_WORKER_TIMEOUT;
1618
1619 if (time_before(jiffies, expires)) {
1620 mod_timer(&gcwq->idle_timer, expires);
1621 break;
1622 }
1623
1624 destroy_worker(worker);
1625 ret = true;
1626 }
1627
1628 return ret;
1629}
1630
1631/**
1632 * manage_workers - manage worker pool
1633 * @worker: self
1634 *
1635 * Assume the manager role and manage gcwq worker pool @worker belongs
1636 * to. At any given time, there can be only zero or one manager per
1637 * gcwq. The exclusion is handled automatically by this function.
1638 *
1639 * The caller can safely start processing works on false return. On
1640 * true return, it's guaranteed that need_to_create_worker() is false
1641 * and may_start_working() is true.
1642 *
1643 * CONTEXT:
1644 * spin_lock_irq(gcwq->lock) which may be released and regrabbed
1645 * multiple times. Does GFP_KERNEL allocations.
1646 *
1647 * RETURNS:
1648 * false if no action was taken and gcwq->lock stayed locked, true if
1649 * some action was taken.
1650 */
1651static bool manage_workers(struct worker *worker)
1652{
1653 struct global_cwq *gcwq = worker->gcwq;
1654 bool ret = false;
1655
1656 if (gcwq->flags & GCWQ_MANAGING_WORKERS)
1657 return ret;
1658
1659 gcwq->flags &= ~GCWQ_MANAGE_WORKERS;
1660 gcwq->flags |= GCWQ_MANAGING_WORKERS;
1661
1662 /*
1663 * Destroy and then create so that may_start_working() is true
1664 * on return.
1665 */
1666 ret |= maybe_destroy_workers(gcwq);
1667 ret |= maybe_create_worker(gcwq);
1668
1669 gcwq->flags &= ~GCWQ_MANAGING_WORKERS;
1670
1671 /*
1672 * The trustee might be waiting to take over the manager
1673 * position, tell it we're done.
1674 */
1675 if (unlikely(gcwq->trustee))
1676 wake_up_all(&gcwq->trustee_wait);
1677
1678 return ret;
1679}
1680
1681/**
1682 * move_linked_works - move linked works to a list
1683 * @work: start of series of works to be scheduled
1684 * @head: target list to append @work to
1685 * @nextp: out paramter for nested worklist walking
1686 *
1687 * Schedule linked works starting from @work to @head. Work series to
1688 * be scheduled starts at @work and includes any consecutive work with
1689 * WORK_STRUCT_LINKED set in its predecessor.
1690 *
1691 * If @nextp is not NULL, it's updated to point to the next work of
1692 * the last scheduled work. This allows move_linked_works() to be
1693 * nested inside outer list_for_each_entry_safe().
1694 *
1695 * CONTEXT:
1696 * spin_lock_irq(gcwq->lock).
1697 */
1698static void move_linked_works(struct work_struct *work, struct list_head *head,
1699 struct work_struct **nextp)
1700{
1701 struct work_struct *n;
1702
1703 /*
1704 * Linked worklist will always end before the end of the list,
1705 * use NULL for list head.
1706 */
1707 list_for_each_entry_safe_from(work, n, NULL, entry) {
1708 list_move_tail(&work->entry, head);
1709 if (!(*work_data_bits(work) & WORK_STRUCT_LINKED))
1710 break;
1711 }
1712
1713 /*
1714 * If we're already inside safe list traversal and have moved
1715 * multiple works to the scheduled queue, the next position
1716 * needs to be updated.
1717 */
1718 if (nextp)
1719 *nextp = n;
1720}
1721
1722static void cwq_activate_first_delayed(struct cpu_workqueue_struct *cwq)
1723{
1724 struct work_struct *work = list_first_entry(&cwq->delayed_works,
1725 struct work_struct, entry);
1726 struct list_head *pos = gcwq_determine_ins_pos(cwq->gcwq, cwq);
1727
1728 trace_workqueue_activate_work(work);
1729 move_linked_works(work, pos, NULL);
1730 __clear_bit(WORK_STRUCT_DELAYED_BIT, work_data_bits(work));
1731 cwq->nr_active++;
1732}
1733
1734/**
1735 * cwq_dec_nr_in_flight - decrement cwq's nr_in_flight
1736 * @cwq: cwq of interest
1737 * @color: color of work which left the queue
1738 * @delayed: for a delayed work
1739 *
1740 * A work either has completed or is removed from pending queue,
1741 * decrement nr_in_flight of its cwq and handle workqueue flushing.
1742 *
1743 * CONTEXT:
1744 * spin_lock_irq(gcwq->lock).
1745 */
1746static void cwq_dec_nr_in_flight(struct cpu_workqueue_struct *cwq, int color,
1747 bool delayed)
1748{
1749 /* ignore uncolored works */
1750 if (color == WORK_NO_COLOR)
1751 return;
1752
1753 cwq->nr_in_flight[color]--;
1754
1755 if (!delayed) {
1756 cwq->nr_active--;
1757 if (!list_empty(&cwq->delayed_works)) {
1758 /* one down, submit a delayed one */
1759 if (cwq->nr_active < cwq->max_active)
1760 cwq_activate_first_delayed(cwq);
1761 }
1762 }
1763
1764 /* is flush in progress and are we at the flushing tip? */
1765 if (likely(cwq->flush_color != color))
1766 return;
1767
1768 /* are there still in-flight works? */
1769 if (cwq->nr_in_flight[color])
1770 return;
1771
1772 /* this cwq is done, clear flush_color */
1773 cwq->flush_color = -1;
1774
1775 /*
1776 * If this was the last cwq, wake up the first flusher. It
1777 * will handle the rest.
1778 */
1779 if (atomic_dec_and_test(&cwq->wq->nr_cwqs_to_flush))
1780 complete(&cwq->wq->first_flusher->done);
1781}
1782
1783/**
1784 * process_one_work - process single work
1785 * @worker: self
1786 * @work: work to process
1787 *
1788 * Process @work. This function contains all the logics necessary to
1789 * process a single work including synchronization against and
1790 * interaction with other workers on the same cpu, queueing and
1791 * flushing. As long as context requirement is met, any worker can
1792 * call this function to process a work.
1793 *
1794 * CONTEXT:
1795 * spin_lock_irq(gcwq->lock) which is released and regrabbed.
1796 */
1797static void process_one_work(struct worker *worker, struct work_struct *work)
1798__releases(&gcwq->lock)
1799__acquires(&gcwq->lock)
1800{
1801 struct cpu_workqueue_struct *cwq = get_work_cwq(work);
1802 struct global_cwq *gcwq = cwq->gcwq;
1803 struct hlist_head *bwh = busy_worker_head(gcwq, work);
1804 bool cpu_intensive = cwq->wq->flags & WQ_CPU_INTENSIVE;
1805 work_func_t f = work->func;
1806 int work_color;
1807 struct worker *collision;
1808#ifdef CONFIG_LOCKDEP
1809 /*
1810 * It is permissible to free the struct work_struct from
1811 * inside the function that is called from it, this we need to
1812 * take into account for lockdep too. To avoid bogus "held
1813 * lock freed" warnings as well as problems when looking into
1814 * work->lockdep_map, make a copy and use that here.
1815 */
1816 struct lockdep_map lockdep_map = work->lockdep_map;
1817#endif
1818 /*
1819 * A single work shouldn't be executed concurrently by
1820 * multiple workers on a single cpu. Check whether anyone is
1821 * already processing the work. If so, defer the work to the
1822 * currently executing one.
1823 */
1824 collision = __find_worker_executing_work(gcwq, bwh, work);
1825 if (unlikely(collision)) {
1826 move_linked_works(work, &collision->scheduled, NULL);
1827 return;
1828 }
1829
1830 /* claim and process */
1831 debug_work_deactivate(work);
1832 hlist_add_head(&worker->hentry, bwh);
1833 worker->current_work = work;
1834 worker->current_cwq = cwq;
1835 work_color = get_work_color(work);
1836
1837 /* record the current cpu number in the work data and dequeue */
1838 set_work_cpu(work, gcwq->cpu);
1839 list_del_init(&work->entry);
1840
1841 /*
1842 * If HIGHPRI_PENDING, check the next work, and, if HIGHPRI,
1843 * wake up another worker; otherwise, clear HIGHPRI_PENDING.
1844 */
1845 if (unlikely(gcwq->flags & GCWQ_HIGHPRI_PENDING)) {
1846 struct work_struct *nwork = list_first_entry(&gcwq->worklist,
1847 struct work_struct, entry);
1848
1849 if (!list_empty(&gcwq->worklist) &&
1850 get_work_cwq(nwork)->wq->flags & WQ_HIGHPRI)
1851 wake_up_worker(gcwq);
1852 else
1853 gcwq->flags &= ~GCWQ_HIGHPRI_PENDING;
1854 }
1855
1856 /*
1857 * CPU intensive works don't participate in concurrency
1858 * management. They're the scheduler's responsibility.
1859 */
1860 if (unlikely(cpu_intensive))
1861 worker_set_flags(worker, WORKER_CPU_INTENSIVE, true);
1862
1863 spin_unlock_irq(&gcwq->lock);
1864
1865 work_clear_pending(work);
1866 lock_map_acquire_read(&cwq->wq->lockdep_map);
1867 lock_map_acquire(&lockdep_map);
1868 trace_workqueue_execute_start(work);
1869 f(work);
1870 /*
1871 * While we must be careful to not use "work" after this, the trace
1872 * point will only record its address.
1873 */
1874 trace_workqueue_execute_end(work);
1875 lock_map_release(&lockdep_map);
1876 lock_map_release(&cwq->wq->lockdep_map);
1877
1878 if (unlikely(in_atomic() || lockdep_depth(current) > 0)) {
1879 printk(KERN_ERR "BUG: workqueue leaked lock or atomic: "
1880 "%s/0x%08x/%d\n",
1881 current->comm, preempt_count(), task_pid_nr(current));
1882 printk(KERN_ERR " last function: ");
1883 print_symbol("%s\n", (unsigned long)f);
1884 debug_show_held_locks(current);
1885 dump_stack();
1886 }
1887
1888 spin_lock_irq(&gcwq->lock);
1889
1890 /* clear cpu intensive status */
1891 if (unlikely(cpu_intensive))
1892 worker_clr_flags(worker, WORKER_CPU_INTENSIVE);
1893
1894 /* we're done with it, release */
1895 hlist_del_init(&worker->hentry);
1896 worker->current_work = NULL;
1897 worker->current_cwq = NULL;
1898 cwq_dec_nr_in_flight(cwq, work_color, false);
1899}
1900
1901/**
1902 * process_scheduled_works - process scheduled works
1903 * @worker: self
1904 *
1905 * Process all scheduled works. Please note that the scheduled list
1906 * may change while processing a work, so this function repeatedly
1907 * fetches a work from the top and executes it.
1908 *
1909 * CONTEXT:
1910 * spin_lock_irq(gcwq->lock) which may be released and regrabbed
1911 * multiple times.
1912 */
1913static void process_scheduled_works(struct worker *worker)
1914{
1915 while (!list_empty(&worker->scheduled)) {
1916 struct work_struct *work = list_first_entry(&worker->scheduled,
1917 struct work_struct, entry);
1918 process_one_work(worker, work);
1919 }
1920}
1921
1922/**
1923 * worker_thread - the worker thread function
1924 * @__worker: self
1925 *
1926 * The gcwq worker thread function. There's a single dynamic pool of
1927 * these per each cpu. These workers process all works regardless of
1928 * their specific target workqueue. The only exception is works which
1929 * belong to workqueues with a rescuer which will be explained in
1930 * rescuer_thread().
1931 */
1932static int worker_thread(void *__worker)
1933{
1934 struct worker *worker = __worker;
1935 struct global_cwq *gcwq = worker->gcwq;
1936
1937 /* tell the scheduler that this is a workqueue worker */
1938 worker->task->flags |= PF_WQ_WORKER;
1939woke_up:
1940 spin_lock_irq(&gcwq->lock);
1941
1942 /* DIE can be set only while we're idle, checking here is enough */
1943 if (worker->flags & WORKER_DIE) {
1944 spin_unlock_irq(&gcwq->lock);
1945 worker->task->flags &= ~PF_WQ_WORKER;
1946 return 0;
1947 }
1948
1949 worker_leave_idle(worker);
1950recheck:
1951 /* no more worker necessary? */
1952 if (!need_more_worker(gcwq))
1953 goto sleep;
1954
1955 /* do we need to manage? */
1956 if (unlikely(!may_start_working(gcwq)) && manage_workers(worker))
1957 goto recheck;
1958
1959 /*
1960 * ->scheduled list can only be filled while a worker is
1961 * preparing to process a work or actually processing it.
1962 * Make sure nobody diddled with it while I was sleeping.
1963 */
1964 BUG_ON(!list_empty(&worker->scheduled));
1965
1966 /*
1967 * When control reaches this point, we're guaranteed to have
1968 * at least one idle worker or that someone else has already
1969 * assumed the manager role.
1970 */
1971 worker_clr_flags(worker, WORKER_PREP);
1972
1973 do {
1974 struct work_struct *work =
1975 list_first_entry(&gcwq->worklist,
1976 struct work_struct, entry);
1977
1978 if (likely(!(*work_data_bits(work) & WORK_STRUCT_LINKED))) {
1979 /* optimization path, not strictly necessary */
1980 process_one_work(worker, work);
1981 if (unlikely(!list_empty(&worker->scheduled)))
1982 process_scheduled_works(worker);
1983 } else {
1984 move_linked_works(work, &worker->scheduled, NULL);
1985 process_scheduled_works(worker);
1986 }
1987 } while (keep_working(gcwq));
1988
1989 worker_set_flags(worker, WORKER_PREP, false);
1990sleep:
1991 if (unlikely(need_to_manage_workers(gcwq)) && manage_workers(worker))
1992 goto recheck;
1993
1994 /*
1995 * gcwq->lock is held and there's no work to process and no
1996 * need to manage, sleep. Workers are woken up only while
1997 * holding gcwq->lock or from local cpu, so setting the
1998 * current state before releasing gcwq->lock is enough to
1999 * prevent losing any event.
2000 */
2001 worker_enter_idle(worker);
2002 __set_current_state(TASK_INTERRUPTIBLE);
2003 spin_unlock_irq(&gcwq->lock);
2004 schedule();
2005 goto woke_up;
2006}
2007
2008/**
2009 * rescuer_thread - the rescuer thread function
2010 * @__wq: the associated workqueue
2011 *
2012 * Workqueue rescuer thread function. There's one rescuer for each
2013 * workqueue which has WQ_RESCUER set.
2014 *
2015 * Regular work processing on a gcwq may block trying to create a new
2016 * worker which uses GFP_KERNEL allocation which has slight chance of
2017 * developing into deadlock if some works currently on the same queue
2018 * need to be processed to satisfy the GFP_KERNEL allocation. This is
2019 * the problem rescuer solves.
2020 *
2021 * When such condition is possible, the gcwq summons rescuers of all
2022 * workqueues which have works queued on the gcwq and let them process
2023 * those works so that forward progress can be guaranteed.
2024 *
2025 * This should happen rarely.
2026 */
2027static int rescuer_thread(void *__wq)
2028{
2029 struct workqueue_struct *wq = __wq;
2030 struct worker *rescuer = wq->rescuer;
2031 struct list_head *scheduled = &rescuer->scheduled;
2032 bool is_unbound = wq->flags & WQ_UNBOUND;
2033 unsigned int cpu;
2034
2035 set_user_nice(current, RESCUER_NICE_LEVEL);
2036repeat:
2037 set_current_state(TASK_INTERRUPTIBLE);
2038
2039 if (kthread_should_stop())
2040 return 0;
2041
2042 /*
2043 * See whether any cpu is asking for help. Unbounded
2044 * workqueues use cpu 0 in mayday_mask for CPU_UNBOUND.
2045 */
2046 for_each_mayday_cpu(cpu, wq->mayday_mask) {
2047 unsigned int tcpu = is_unbound ? WORK_CPU_UNBOUND : cpu;
2048 struct cpu_workqueue_struct *cwq = get_cwq(tcpu, wq);
2049 struct global_cwq *gcwq = cwq->gcwq;
2050 struct work_struct *work, *n;
2051
2052 __set_current_state(TASK_RUNNING);
2053 mayday_clear_cpu(cpu, wq->mayday_mask);
2054
2055 /* migrate to the target cpu if possible */
2056 rescuer->gcwq = gcwq;
2057 worker_maybe_bind_and_lock(rescuer);
2058
2059 /*
2060 * Slurp in all works issued via this workqueue and
2061 * process'em.
2062 */
2063 BUG_ON(!list_empty(&rescuer->scheduled));
2064 list_for_each_entry_safe(work, n, &gcwq->worklist, entry)
2065 if (get_work_cwq(work) == cwq)
2066 move_linked_works(work, scheduled, &n);
2067
2068 process_scheduled_works(rescuer);
2069
2070 /*
2071 * Leave this gcwq. If keep_working() is %true, notify a
2072 * regular worker; otherwise, we end up with 0 concurrency
2073 * and stalling the execution.
2074 */
2075 if (keep_working(gcwq))
2076 wake_up_worker(gcwq);
2077
2078 spin_unlock_irq(&gcwq->lock);
2079 }
2080
2081 schedule();
2082 goto repeat;
2083}
2084
2085struct wq_barrier {
2086 struct work_struct work;
2087 struct completion done;
2088};
2089
2090static void wq_barrier_func(struct work_struct *work)
2091{
2092 struct wq_barrier *barr = container_of(work, struct wq_barrier, work);
2093 complete(&barr->done);
2094}
2095
2096/**
2097 * insert_wq_barrier - insert a barrier work
2098 * @cwq: cwq to insert barrier into
2099 * @barr: wq_barrier to insert
2100 * @target: target work to attach @barr to
2101 * @worker: worker currently executing @target, NULL if @target is not executing
2102 *
2103 * @barr is linked to @target such that @barr is completed only after
2104 * @target finishes execution. Please note that the ordering
2105 * guarantee is observed only with respect to @target and on the local
2106 * cpu.
2107 *
2108 * Currently, a queued barrier can't be canceled. This is because
2109 * try_to_grab_pending() can't determine whether the work to be
2110 * grabbed is at the head of the queue and thus can't clear LINKED
2111 * flag of the previous work while there must be a valid next work
2112 * after a work with LINKED flag set.
2113 *
2114 * Note that when @worker is non-NULL, @target may be modified
2115 * underneath us, so we can't reliably determine cwq from @target.
2116 *
2117 * CONTEXT:
2118 * spin_lock_irq(gcwq->lock).
2119 */
2120static void insert_wq_barrier(struct cpu_workqueue_struct *cwq,
2121 struct wq_barrier *barr,
2122 struct work_struct *target, struct worker *worker)
2123{
2124 struct list_head *head;
2125 unsigned int linked = 0;
2126
2127 /*
2128 * debugobject calls are safe here even with gcwq->lock locked
2129 * as we know for sure that this will not trigger any of the
2130 * checks and call back into the fixup functions where we
2131 * might deadlock.
2132 */
2133 INIT_WORK_ONSTACK(&barr->work, wq_barrier_func);
2134 __set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(&barr->work));
2135 init_completion(&barr->done);
2136
2137 /*
2138 * If @target is currently being executed, schedule the
2139 * barrier to the worker; otherwise, put it after @target.
2140 */
2141 if (worker)
2142 head = worker->scheduled.next;
2143 else {
2144 unsigned long *bits = work_data_bits(target);
2145
2146 head = target->entry.next;
2147 /* there can already be other linked works, inherit and set */
2148 linked = *bits & WORK_STRUCT_LINKED;
2149 __set_bit(WORK_STRUCT_LINKED_BIT, bits);
2150 }
2151
2152 debug_work_activate(&barr->work);
2153 insert_work(cwq, &barr->work, head,
2154 work_color_to_flags(WORK_NO_COLOR) | linked);
2155}
2156
2157/**
2158 * flush_workqueue_prep_cwqs - prepare cwqs for workqueue flushing
2159 * @wq: workqueue being flushed
2160 * @flush_color: new flush color, < 0 for no-op
2161 * @work_color: new work color, < 0 for no-op
2162 *
2163 * Prepare cwqs for workqueue flushing.
2164 *
2165 * If @flush_color is non-negative, flush_color on all cwqs should be
2166 * -1. If no cwq has in-flight commands at the specified color, all
2167 * cwq->flush_color's stay at -1 and %false is returned. If any cwq
2168 * has in flight commands, its cwq->flush_color is set to
2169 * @flush_color, @wq->nr_cwqs_to_flush is updated accordingly, cwq
2170 * wakeup logic is armed and %true is returned.
2171 *
2172 * The caller should have initialized @wq->first_flusher prior to
2173 * calling this function with non-negative @flush_color. If
2174 * @flush_color is negative, no flush color update is done and %false
2175 * is returned.
2176 *
2177 * If @work_color is non-negative, all cwqs should have the same
2178 * work_color which is previous to @work_color and all will be
2179 * advanced to @work_color.
2180 *
2181 * CONTEXT:
2182 * mutex_lock(wq->flush_mutex).
2183 *
2184 * RETURNS:
2185 * %true if @flush_color >= 0 and there's something to flush. %false
2186 * otherwise.
2187 */
2188static bool flush_workqueue_prep_cwqs(struct workqueue_struct *wq,
2189 int flush_color, int work_color)
2190{
2191 bool wait = false;
2192 unsigned int cpu;
2193
2194 if (flush_color >= 0) {
2195 BUG_ON(atomic_read(&wq->nr_cwqs_to_flush));
2196 atomic_set(&wq->nr_cwqs_to_flush, 1);
2197 }
2198
2199 for_each_cwq_cpu(cpu, wq) {
2200 struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
2201 struct global_cwq *gcwq = cwq->gcwq;
2202
2203 spin_lock_irq(&gcwq->lock);
2204
2205 if (flush_color >= 0) {
2206 BUG_ON(cwq->flush_color != -1);
2207
2208 if (cwq->nr_in_flight[flush_color]) {
2209 cwq->flush_color = flush_color;
2210 atomic_inc(&wq->nr_cwqs_to_flush);
2211 wait = true;
2212 }
2213 }
2214
2215 if (work_color >= 0) {
2216 BUG_ON(work_color != work_next_color(cwq->work_color));
2217 cwq->work_color = work_color;
2218 }
2219
2220 spin_unlock_irq(&gcwq->lock);
2221 }
2222
2223 if (flush_color >= 0 && atomic_dec_and_test(&wq->nr_cwqs_to_flush))
2224 complete(&wq->first_flusher->done);
2225
2226 return wait;
2227}
2228
2229/**
2230 * flush_workqueue - ensure that any scheduled work has run to completion.
2231 * @wq: workqueue to flush
2232 *
2233 * Forces execution of the workqueue and blocks until its completion.
2234 * This is typically used in driver shutdown handlers.
2235 *
2236 * We sleep until all works which were queued on entry have been handled,
2237 * but we are not livelocked by new incoming ones.
2238 */
2239void flush_workqueue(struct workqueue_struct *wq)
2240{
2241 struct wq_flusher this_flusher = {
2242 .list = LIST_HEAD_INIT(this_flusher.list),
2243 .flush_color = -1,
2244 .done = COMPLETION_INITIALIZER_ONSTACK(this_flusher.done),
2245 };
2246 int next_color;
2247
2248 lock_map_acquire(&wq->lockdep_map);
2249 lock_map_release(&wq->lockdep_map);
2250
2251 mutex_lock(&wq->flush_mutex);
2252
2253 /*
2254 * Start-to-wait phase
2255 */
2256 next_color = work_next_color(wq->work_color);
2257
2258 if (next_color != wq->flush_color) {
2259 /*
2260 * Color space is not full. The current work_color
2261 * becomes our flush_color and work_color is advanced
2262 * by one.
2263 */
2264 BUG_ON(!list_empty(&wq->flusher_overflow));
2265 this_flusher.flush_color = wq->work_color;
2266 wq->work_color = next_color;
2267
2268 if (!wq->first_flusher) {
2269 /* no flush in progress, become the first flusher */
2270 BUG_ON(wq->flush_color != this_flusher.flush_color);
2271
2272 wq->first_flusher = &this_flusher;
2273
2274 if (!flush_workqueue_prep_cwqs(wq, wq->flush_color,
2275 wq->work_color)) {
2276 /* nothing to flush, done */
2277 wq->flush_color = next_color;
2278 wq->first_flusher = NULL;
2279 goto out_unlock;
2280 }
2281 } else {
2282 /* wait in queue */
2283 BUG_ON(wq->flush_color == this_flusher.flush_color);
2284 list_add_tail(&this_flusher.list, &wq->flusher_queue);
2285 flush_workqueue_prep_cwqs(wq, -1, wq->work_color);
2286 }
2287 } else {
2288 /*
2289 * Oops, color space is full, wait on overflow queue.
2290 * The next flush completion will assign us
2291 * flush_color and transfer to flusher_queue.
2292 */
2293 list_add_tail(&this_flusher.list, &wq->flusher_overflow);
2294 }
2295
2296 mutex_unlock(&wq->flush_mutex);
2297
2298 wait_for_completion(&this_flusher.done);
2299
2300 /*
2301 * Wake-up-and-cascade phase
2302 *
2303 * First flushers are responsible for cascading flushes and
2304 * handling overflow. Non-first flushers can simply return.
2305 */
2306 if (wq->first_flusher != &this_flusher)
2307 return;
2308
2309 mutex_lock(&wq->flush_mutex);
2310
2311 /* we might have raced, check again with mutex held */
2312 if (wq->first_flusher != &this_flusher)
2313 goto out_unlock;
2314
2315 wq->first_flusher = NULL;
2316
2317 BUG_ON(!list_empty(&this_flusher.list));
2318 BUG_ON(wq->flush_color != this_flusher.flush_color);
2319
2320 while (true) {
2321 struct wq_flusher *next, *tmp;
2322
2323 /* complete all the flushers sharing the current flush color */
2324 list_for_each_entry_safe(next, tmp, &wq->flusher_queue, list) {
2325 if (next->flush_color != wq->flush_color)
2326 break;
2327 list_del_init(&next->list);
2328 complete(&next->done);
2329 }
2330
2331 BUG_ON(!list_empty(&wq->flusher_overflow) &&
2332 wq->flush_color != work_next_color(wq->work_color));
2333
2334 /* this flush_color is finished, advance by one */
2335 wq->flush_color = work_next_color(wq->flush_color);
2336
2337 /* one color has been freed, handle overflow queue */
2338 if (!list_empty(&wq->flusher_overflow)) {
2339 /*
2340 * Assign the same color to all overflowed
2341 * flushers, advance work_color and append to
2342 * flusher_queue. This is the start-to-wait
2343 * phase for these overflowed flushers.
2344 */
2345 list_for_each_entry(tmp, &wq->flusher_overflow, list)
2346 tmp->flush_color = wq->work_color;
2347
2348 wq->work_color = work_next_color(wq->work_color);
2349
2350 list_splice_tail_init(&wq->flusher_overflow,
2351 &wq->flusher_queue);
2352 flush_workqueue_prep_cwqs(wq, -1, wq->work_color);
2353 }
2354
2355 if (list_empty(&wq->flusher_queue)) {
2356 BUG_ON(wq->flush_color != wq->work_color);
2357 break;
2358 }
2359
2360 /*
2361 * Need to flush more colors. Make the next flusher
2362 * the new first flusher and arm cwqs.
2363 */
2364 BUG_ON(wq->flush_color == wq->work_color);
2365 BUG_ON(wq->flush_color != next->flush_color);
2366
2367 list_del_init(&next->list);
2368 wq->first_flusher = next;
2369
2370 if (flush_workqueue_prep_cwqs(wq, wq->flush_color, -1))
2371 break;
2372
2373 /*
2374 * Meh... this color is already done, clear first
2375 * flusher and repeat cascading.
2376 */
2377 wq->first_flusher = NULL;
2378 }
2379
2380out_unlock:
2381 mutex_unlock(&wq->flush_mutex);
2382}
2383EXPORT_SYMBOL_GPL(flush_workqueue);
2384
2385/**
2386 * drain_workqueue - drain a workqueue
2387 * @wq: workqueue to drain
2388 *
2389 * Wait until the workqueue becomes empty. While draining is in progress,
2390 * only chain queueing is allowed. IOW, only currently pending or running
2391 * work items on @wq can queue further work items on it. @wq is flushed
2392 * repeatedly until it becomes empty. The number of flushing is detemined
2393 * by the depth of chaining and should be relatively short. Whine if it
2394 * takes too long.
2395 */
2396void drain_workqueue(struct workqueue_struct *wq)
2397{
2398 unsigned int flush_cnt = 0;
2399 unsigned int cpu;
2400
2401 /*
2402 * __queue_work() needs to test whether there are drainers, is much
2403 * hotter than drain_workqueue() and already looks at @wq->flags.
2404 * Use WQ_DRAINING so that queue doesn't have to check nr_drainers.
2405 */
2406 spin_lock(&workqueue_lock);
2407 if (!wq->nr_drainers++)
2408 wq->flags |= WQ_DRAINING;
2409 spin_unlock(&workqueue_lock);
2410reflush:
2411 flush_workqueue(wq);
2412
2413 for_each_cwq_cpu(cpu, wq) {
2414 struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
2415 bool drained;
2416
2417 spin_lock_irq(&cwq->gcwq->lock);
2418 drained = !cwq->nr_active && list_empty(&cwq->delayed_works);
2419 spin_unlock_irq(&cwq->gcwq->lock);
2420
2421 if (drained)
2422 continue;
2423
2424 if (++flush_cnt == 10 ||
2425 (flush_cnt % 100 == 0 && flush_cnt <= 1000))
2426 pr_warning("workqueue %s: flush on destruction isn't complete after %u tries\n",
2427 wq->name, flush_cnt);
2428 goto reflush;
2429 }
2430
2431 spin_lock(&workqueue_lock);
2432 if (!--wq->nr_drainers)
2433 wq->flags &= ~WQ_DRAINING;
2434 spin_unlock(&workqueue_lock);
2435}
2436EXPORT_SYMBOL_GPL(drain_workqueue);
2437
2438static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr,
2439 bool wait_executing)
2440{
2441 struct worker *worker = NULL;
2442 struct global_cwq *gcwq;
2443 struct cpu_workqueue_struct *cwq;
2444
2445 might_sleep();
2446 gcwq = get_work_gcwq(work);
2447 if (!gcwq)
2448 return false;
2449
2450 spin_lock_irq(&gcwq->lock);
2451 if (!list_empty(&work->entry)) {
2452 /*
2453 * See the comment near try_to_grab_pending()->smp_rmb().
2454 * If it was re-queued to a different gcwq under us, we
2455 * are not going to wait.
2456 */
2457 smp_rmb();
2458 cwq = get_work_cwq(work);
2459 if (unlikely(!cwq || gcwq != cwq->gcwq))
2460 goto already_gone;
2461 } else if (wait_executing) {
2462 worker = find_worker_executing_work(gcwq, work);
2463 if (!worker)
2464 goto already_gone;
2465 cwq = worker->current_cwq;
2466 } else
2467 goto already_gone;
2468
2469 insert_wq_barrier(cwq, barr, work, worker);
2470 spin_unlock_irq(&gcwq->lock);
2471
2472 /*
2473 * If @max_active is 1 or rescuer is in use, flushing another work
2474 * item on the same workqueue may lead to deadlock. Make sure the
2475 * flusher is not running on the same workqueue by verifying write
2476 * access.
2477 */
2478 if (cwq->wq->saved_max_active == 1 || cwq->wq->flags & WQ_RESCUER)
2479 lock_map_acquire(&cwq->wq->lockdep_map);
2480 else
2481 lock_map_acquire_read(&cwq->wq->lockdep_map);
2482 lock_map_release(&cwq->wq->lockdep_map);
2483
2484 return true;
2485already_gone:
2486 spin_unlock_irq(&gcwq->lock);
2487 return false;
2488}
2489
2490/**
2491 * flush_work - wait for a work to finish executing the last queueing instance
2492 * @work: the work to flush
2493 *
2494 * Wait until @work has finished execution. This function considers
2495 * only the last queueing instance of @work. If @work has been
2496 * enqueued across different CPUs on a non-reentrant workqueue or on
2497 * multiple workqueues, @work might still be executing on return on
2498 * some of the CPUs from earlier queueing.
2499 *
2500 * If @work was queued only on a non-reentrant, ordered or unbound
2501 * workqueue, @work is guaranteed to be idle on return if it hasn't
2502 * been requeued since flush started.
2503 *
2504 * RETURNS:
2505 * %true if flush_work() waited for the work to finish execution,
2506 * %false if it was already idle.
2507 */
2508bool flush_work(struct work_struct *work)
2509{
2510 struct wq_barrier barr;
2511
2512 if (start_flush_work(work, &barr, true)) {
2513 wait_for_completion(&barr.done);
2514 destroy_work_on_stack(&barr.work);
2515 return true;
2516 } else
2517 return false;
2518}
2519EXPORT_SYMBOL_GPL(flush_work);
2520
2521static bool wait_on_cpu_work(struct global_cwq *gcwq, struct work_struct *work)
2522{
2523 struct wq_barrier barr;
2524 struct worker *worker;
2525
2526 spin_lock_irq(&gcwq->lock);
2527
2528 worker = find_worker_executing_work(gcwq, work);
2529 if (unlikely(worker))
2530 insert_wq_barrier(worker->current_cwq, &barr, work, worker);
2531
2532 spin_unlock_irq(&gcwq->lock);
2533
2534 if (unlikely(worker)) {
2535 wait_for_completion(&barr.done);
2536 destroy_work_on_stack(&barr.work);
2537 return true;
2538 } else
2539 return false;
2540}
2541
2542static bool wait_on_work(struct work_struct *work)
2543{
2544 bool ret = false;
2545 int cpu;
2546
2547 might_sleep();
2548
2549 lock_map_acquire(&work->lockdep_map);
2550 lock_map_release(&work->lockdep_map);
2551
2552 for_each_gcwq_cpu(cpu)
2553 ret |= wait_on_cpu_work(get_gcwq(cpu), work);
2554 return ret;
2555}
2556
2557/**
2558 * flush_work_sync - wait until a work has finished execution
2559 * @work: the work to flush
2560 *
2561 * Wait until @work has finished execution. On return, it's
2562 * guaranteed that all queueing instances of @work which happened
2563 * before this function is called are finished. In other words, if
2564 * @work hasn't been requeued since this function was called, @work is
2565 * guaranteed to be idle on return.
2566 *
2567 * RETURNS:
2568 * %true if flush_work_sync() waited for the work to finish execution,
2569 * %false if it was already idle.
2570 */
2571bool flush_work_sync(struct work_struct *work)
2572{
2573 struct wq_barrier barr;
2574 bool pending, waited;
2575
2576 /* we'll wait for executions separately, queue barr only if pending */
2577 pending = start_flush_work(work, &barr, false);
2578
2579 /* wait for executions to finish */
2580 waited = wait_on_work(work);
2581
2582 /* wait for the pending one */
2583 if (pending) {
2584 wait_for_completion(&barr.done);
2585 destroy_work_on_stack(&barr.work);
2586 }
2587
2588 return pending || waited;
2589}
2590EXPORT_SYMBOL_GPL(flush_work_sync);
2591
2592/*
2593 * Upon a successful return (>= 0), the caller "owns" WORK_STRUCT_PENDING bit,
2594 * so this work can't be re-armed in any way.
2595 */
2596static int try_to_grab_pending(struct work_struct *work)
2597{
2598 struct global_cwq *gcwq;
2599 int ret = -1;
2600
2601 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work)))
2602 return 0;
2603
2604 /*
2605 * The queueing is in progress, or it is already queued. Try to
2606 * steal it from ->worklist without clearing WORK_STRUCT_PENDING.
2607 */
2608 gcwq = get_work_gcwq(work);
2609 if (!gcwq)
2610 return ret;
2611
2612 spin_lock_irq(&gcwq->lock);
2613 if (!list_empty(&work->entry)) {
2614 /*
2615 * This work is queued, but perhaps we locked the wrong gcwq.
2616 * In that case we must see the new value after rmb(), see
2617 * insert_work()->wmb().
2618 */
2619 smp_rmb();
2620 if (gcwq == get_work_gcwq(work)) {
2621 debug_work_deactivate(work);
2622 list_del_init(&work->entry);
2623 cwq_dec_nr_in_flight(get_work_cwq(work),
2624 get_work_color(work),
2625 *work_data_bits(work) & WORK_STRUCT_DELAYED);
2626 ret = 1;
2627 }
2628 }
2629 spin_unlock_irq(&gcwq->lock);
2630
2631 return ret;
2632}
2633
2634static bool __cancel_work_timer(struct work_struct *work,
2635 struct timer_list* timer)
2636{
2637 int ret;
2638
2639 do {
2640 ret = (timer && likely(del_timer(timer)));
2641 if (!ret)
2642 ret = try_to_grab_pending(work);
2643 wait_on_work(work);
2644 } while (unlikely(ret < 0));
2645
2646 clear_work_data(work);
2647 return ret;
2648}
2649
2650/**
2651 * cancel_work_sync - cancel a work and wait for it to finish
2652 * @work: the work to cancel
2653 *
2654 * Cancel @work and wait for its execution to finish. This function
2655 * can be used even if the work re-queues itself or migrates to
2656 * another workqueue. On return from this function, @work is
2657 * guaranteed to be not pending or executing on any CPU.
2658 *
2659 * cancel_work_sync(&delayed_work->work) must not be used for
2660 * delayed_work's. Use cancel_delayed_work_sync() instead.
2661 *
2662 * The caller must ensure that the workqueue on which @work was last
2663 * queued can't be destroyed before this function returns.
2664 *
2665 * RETURNS:
2666 * %true if @work was pending, %false otherwise.
2667 */
2668bool cancel_work_sync(struct work_struct *work)
2669{
2670 return __cancel_work_timer(work, NULL);
2671}
2672EXPORT_SYMBOL_GPL(cancel_work_sync);
2673
2674/**
2675 * flush_delayed_work - wait for a dwork to finish executing the last queueing
2676 * @dwork: the delayed work to flush
2677 *
2678 * Delayed timer is cancelled and the pending work is queued for
2679 * immediate execution. Like flush_work(), this function only
2680 * considers the last queueing instance of @dwork.
2681 *
2682 * RETURNS:
2683 * %true if flush_work() waited for the work to finish execution,
2684 * %false if it was already idle.
2685 */
2686bool flush_delayed_work(struct delayed_work *dwork)
2687{
2688 if (del_timer_sync(&dwork->timer))
2689 __queue_work(raw_smp_processor_id(),
2690 get_work_cwq(&dwork->work)->wq, &dwork->work);
2691 return flush_work(&dwork->work);
2692}
2693EXPORT_SYMBOL(flush_delayed_work);
2694
2695/**
2696 * flush_delayed_work_sync - wait for a dwork to finish
2697 * @dwork: the delayed work to flush
2698 *
2699 * Delayed timer is cancelled and the pending work is queued for
2700 * execution immediately. Other than timer handling, its behavior
2701 * is identical to flush_work_sync().
2702 *
2703 * RETURNS:
2704 * %true if flush_work_sync() waited for the work to finish execution,
2705 * %false if it was already idle.
2706 */
2707bool flush_delayed_work_sync(struct delayed_work *dwork)
2708{
2709 if (del_timer_sync(&dwork->timer))
2710 __queue_work(raw_smp_processor_id(),
2711 get_work_cwq(&dwork->work)->wq, &dwork->work);
2712 return flush_work_sync(&dwork->work);
2713}
2714EXPORT_SYMBOL(flush_delayed_work_sync);
2715
2716/**
2717 * cancel_delayed_work_sync - cancel a delayed work and wait for it to finish
2718 * @dwork: the delayed work cancel
2719 *
2720 * This is cancel_work_sync() for delayed works.
2721 *
2722 * RETURNS:
2723 * %true if @dwork was pending, %false otherwise.
2724 */
2725bool cancel_delayed_work_sync(struct delayed_work *dwork)
2726{
2727 return __cancel_work_timer(&dwork->work, &dwork->timer);
2728}
2729EXPORT_SYMBOL(cancel_delayed_work_sync);
2730
2731/**
2732 * schedule_work - put work task in global workqueue
2733 * @work: job to be done
2734 *
2735 * Returns zero if @work was already on the kernel-global workqueue and
2736 * non-zero otherwise.
2737 *
2738 * This puts a job in the kernel-global workqueue if it was not already
2739 * queued and leaves it in the same position on the kernel-global
2740 * workqueue otherwise.
2741 */
2742int schedule_work(struct work_struct *work)
2743{
2744 return queue_work(system_wq, work);
2745}
2746EXPORT_SYMBOL(schedule_work);
2747
2748/*
2749 * schedule_work_on - put work task on a specific cpu
2750 * @cpu: cpu to put the work task on
2751 * @work: job to be done
2752 *
2753 * This puts a job on a specific cpu
2754 */
2755int schedule_work_on(int cpu, struct work_struct *work)
2756{
2757 return queue_work_on(cpu, system_wq, work);
2758}
2759EXPORT_SYMBOL(schedule_work_on);
2760
2761/**
2762 * schedule_delayed_work - put work task in global workqueue after delay
2763 * @dwork: job to be done
2764 * @delay: number of jiffies to wait or 0 for immediate execution
2765 *
2766 * After waiting for a given time this puts a job in the kernel-global
2767 * workqueue.
2768 */
2769int schedule_delayed_work(struct delayed_work *dwork,
2770 unsigned long delay)
2771{
2772 return queue_delayed_work(system_wq, dwork, delay);
2773}
2774EXPORT_SYMBOL(schedule_delayed_work);
2775
2776/**
2777 * schedule_delayed_work_on - queue work in global workqueue on CPU after delay
2778 * @cpu: cpu to use
2779 * @dwork: job to be done
2780 * @delay: number of jiffies to wait
2781 *
2782 * After waiting for a given time this puts a job in the kernel-global
2783 * workqueue on the specified CPU.
2784 */
2785int schedule_delayed_work_on(int cpu,
2786 struct delayed_work *dwork, unsigned long delay)
2787{
2788 return queue_delayed_work_on(cpu, system_wq, dwork, delay);
2789}
2790EXPORT_SYMBOL(schedule_delayed_work_on);
2791
2792/**
2793 * schedule_on_each_cpu - execute a function synchronously on each online CPU
2794 * @func: the function to call
2795 *
2796 * schedule_on_each_cpu() executes @func on each online CPU using the
2797 * system workqueue and blocks until all CPUs have completed.
2798 * schedule_on_each_cpu() is very slow.
2799 *
2800 * RETURNS:
2801 * 0 on success, -errno on failure.
2802 */
2803int schedule_on_each_cpu(work_func_t func)
2804{
2805 int cpu;
2806 struct work_struct __percpu *works;
2807
2808 works = alloc_percpu(struct work_struct);
2809 if (!works)
2810 return -ENOMEM;
2811
2812 get_online_cpus();
2813
2814 for_each_online_cpu(cpu) {
2815 struct work_struct *work = per_cpu_ptr(works, cpu);
2816
2817 INIT_WORK(work, func);
2818 schedule_work_on(cpu, work);
2819 }
2820
2821 for_each_online_cpu(cpu)
2822 flush_work(per_cpu_ptr(works, cpu));
2823
2824 put_online_cpus();
2825 free_percpu(works);
2826 return 0;
2827}
2828
2829/**
2830 * flush_scheduled_work - ensure that any scheduled work has run to completion.
2831 *
2832 * Forces execution of the kernel-global workqueue and blocks until its
2833 * completion.
2834 *
2835 * Think twice before calling this function! It's very easy to get into
2836 * trouble if you don't take great care. Either of the following situations
2837 * will lead to deadlock:
2838 *
2839 * One of the work items currently on the workqueue needs to acquire
2840 * a lock held by your code or its caller.
2841 *
2842 * Your code is running in the context of a work routine.
2843 *
2844 * They will be detected by lockdep when they occur, but the first might not
2845 * occur very often. It depends on what work items are on the workqueue and
2846 * what locks they need, which you have no control over.
2847 *
2848 * In most situations flushing the entire workqueue is overkill; you merely
2849 * need to know that a particular work item isn't queued and isn't running.
2850 * In such cases you should use cancel_delayed_work_sync() or
2851 * cancel_work_sync() instead.
2852 */
2853void flush_scheduled_work(void)
2854{
2855 flush_workqueue(system_wq);
2856}
2857EXPORT_SYMBOL(flush_scheduled_work);
2858
2859/**
2860 * execute_in_process_context - reliably execute the routine with user context
2861 * @fn: the function to execute
2862 * @ew: guaranteed storage for the execute work structure (must
2863 * be available when the work executes)
2864 *
2865 * Executes the function immediately if process context is available,
2866 * otherwise schedules the function for delayed execution.
2867 *
2868 * Returns: 0 - function was executed
2869 * 1 - function was scheduled for execution
2870 */
2871int execute_in_process_context(work_func_t fn, struct execute_work *ew)
2872{
2873 if (!in_interrupt()) {
2874 fn(&ew->work);
2875 return 0;
2876 }
2877
2878 INIT_WORK(&ew->work, fn);
2879 schedule_work(&ew->work);
2880
2881 return 1;
2882}
2883EXPORT_SYMBOL_GPL(execute_in_process_context);
2884
2885int keventd_up(void)
2886{
2887 return system_wq != NULL;
2888}
2889
2890static int alloc_cwqs(struct workqueue_struct *wq)
2891{
2892 /*
2893 * cwqs are forced aligned according to WORK_STRUCT_FLAG_BITS.
2894 * Make sure that the alignment isn't lower than that of
2895 * unsigned long long.
2896 */
2897 const size_t size = sizeof(struct cpu_workqueue_struct);
2898 const size_t align = max_t(size_t, 1 << WORK_STRUCT_FLAG_BITS,
2899 __alignof__(unsigned long long));
2900#ifdef CONFIG_SMP
2901 bool percpu = !(wq->flags & WQ_UNBOUND);
2902#else
2903 bool percpu = false;
2904#endif
2905
2906 if (percpu)
2907 wq->cpu_wq.pcpu = __alloc_percpu(size, align);
2908 else {
2909 void *ptr;
2910
2911 /*
2912 * Allocate enough room to align cwq and put an extra
2913 * pointer at the end pointing back to the originally
2914 * allocated pointer which will be used for free.
2915 */
2916 ptr = kzalloc(size + align + sizeof(void *), GFP_KERNEL);
2917 if (ptr) {
2918 wq->cpu_wq.single = PTR_ALIGN(ptr, align);
2919 *(void **)(wq->cpu_wq.single + 1) = ptr;
2920 }
2921 }
2922
2923 /* just in case, make sure it's actually aligned */
2924 BUG_ON(!IS_ALIGNED(wq->cpu_wq.v, align));
2925 return wq->cpu_wq.v ? 0 : -ENOMEM;
2926}
2927
2928static void free_cwqs(struct workqueue_struct *wq)
2929{
2930#ifdef CONFIG_SMP
2931 bool percpu = !(wq->flags & WQ_UNBOUND);
2932#else
2933 bool percpu = false;
2934#endif
2935
2936 if (percpu)
2937 free_percpu(wq->cpu_wq.pcpu);
2938 else if (wq->cpu_wq.single) {
2939 /* the pointer to free is stored right after the cwq */
2940 kfree(*(void **)(wq->cpu_wq.single + 1));
2941 }
2942}
2943
2944static int wq_clamp_max_active(int max_active, unsigned int flags,
2945 const char *name)
2946{
2947 int lim = flags & WQ_UNBOUND ? WQ_UNBOUND_MAX_ACTIVE : WQ_MAX_ACTIVE;
2948
2949 if (max_active < 1 || max_active > lim)
2950 printk(KERN_WARNING "workqueue: max_active %d requested for %s "
2951 "is out of range, clamping between %d and %d\n",
2952 max_active, name, 1, lim);
2953
2954 return clamp_val(max_active, 1, lim);
2955}
2956
2957struct workqueue_struct *__alloc_workqueue_key(const char *name,
2958 unsigned int flags,
2959 int max_active,
2960 struct lock_class_key *key,
2961 const char *lock_name)
2962{
2963 struct workqueue_struct *wq;
2964 unsigned int cpu;
2965
2966 /*
2967 * Workqueues which may be used during memory reclaim should
2968 * have a rescuer to guarantee forward progress.
2969 */
2970 if (flags & WQ_MEM_RECLAIM)
2971 flags |= WQ_RESCUER;
2972
2973 /*
2974 * Unbound workqueues aren't concurrency managed and should be
2975 * dispatched to workers immediately.
2976 */
2977 if (flags & WQ_UNBOUND)
2978 flags |= WQ_HIGHPRI;
2979
2980 max_active = max_active ?: WQ_DFL_ACTIVE;
2981 max_active = wq_clamp_max_active(max_active, flags, name);
2982
2983 wq = kzalloc(sizeof(*wq), GFP_KERNEL);
2984 if (!wq)
2985 goto err;
2986
2987 wq->flags = flags;
2988 wq->saved_max_active = max_active;
2989 mutex_init(&wq->flush_mutex);
2990 atomic_set(&wq->nr_cwqs_to_flush, 0);
2991 INIT_LIST_HEAD(&wq->flusher_queue);
2992 INIT_LIST_HEAD(&wq->flusher_overflow);
2993
2994 wq->name = name;
2995 lockdep_init_map(&wq->lockdep_map, lock_name, key, 0);
2996 INIT_LIST_HEAD(&wq->list);
2997
2998 if (alloc_cwqs(wq) < 0)
2999 goto err;
3000
3001 for_each_cwq_cpu(cpu, wq) {
3002 struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
3003 struct global_cwq *gcwq = get_gcwq(cpu);
3004
3005 BUG_ON((unsigned long)cwq & WORK_STRUCT_FLAG_MASK);
3006 cwq->gcwq = gcwq;
3007 cwq->wq = wq;
3008 cwq->flush_color = -1;
3009 cwq->max_active = max_active;
3010 INIT_LIST_HEAD(&cwq->delayed_works);
3011 }
3012
3013 if (flags & WQ_RESCUER) {
3014 struct worker *rescuer;
3015
3016 if (!alloc_mayday_mask(&wq->mayday_mask, GFP_KERNEL))
3017 goto err;
3018
3019 wq->rescuer = rescuer = alloc_worker();
3020 if (!rescuer)
3021 goto err;
3022
3023 rescuer->task = kthread_create(rescuer_thread, wq, "%s", name);
3024 if (IS_ERR(rescuer->task))
3025 goto err;
3026
3027 rescuer->task->flags |= PF_THREAD_BOUND;
3028 wake_up_process(rescuer->task);
3029 }
3030
3031 /*
3032 * workqueue_lock protects global freeze state and workqueues
3033 * list. Grab it, set max_active accordingly and add the new
3034 * workqueue to workqueues list.
3035 */
3036 spin_lock(&workqueue_lock);
3037
3038 if (workqueue_freezing && wq->flags & WQ_FREEZABLE)
3039 for_each_cwq_cpu(cpu, wq)
3040 get_cwq(cpu, wq)->max_active = 0;
3041
3042 list_add(&wq->list, &workqueues);
3043
3044 spin_unlock(&workqueue_lock);
3045
3046 return wq;
3047err:
3048 if (wq) {
3049 free_cwqs(wq);
3050 free_mayday_mask(wq->mayday_mask);
3051 kfree(wq->rescuer);
3052 kfree(wq);
3053 }
3054 return NULL;
3055}
3056EXPORT_SYMBOL_GPL(__alloc_workqueue_key);
3057
3058/**
3059 * destroy_workqueue - safely terminate a workqueue
3060 * @wq: target workqueue
3061 *
3062 * Safely destroy a workqueue. All work currently pending will be done first.
3063 */
3064void destroy_workqueue(struct workqueue_struct *wq)
3065{
3066 unsigned int cpu;
3067
3068 /* drain it before proceeding with destruction */
3069 drain_workqueue(wq);
3070
3071 /*
3072 * wq list is used to freeze wq, remove from list after
3073 * flushing is complete in case freeze races us.
3074 */
3075 spin_lock(&workqueue_lock);
3076 list_del(&wq->list);
3077 spin_unlock(&workqueue_lock);
3078
3079 /* sanity check */
3080 for_each_cwq_cpu(cpu, wq) {
3081 struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
3082 int i;
3083
3084 for (i = 0; i < WORK_NR_COLORS; i++)
3085 BUG_ON(cwq->nr_in_flight[i]);
3086 BUG_ON(cwq->nr_active);
3087 BUG_ON(!list_empty(&cwq->delayed_works));
3088 }
3089
3090 if (wq->flags & WQ_RESCUER) {
3091 kthread_stop(wq->rescuer->task);
3092 free_mayday_mask(wq->mayday_mask);
3093 kfree(wq->rescuer);
3094 }
3095
3096 free_cwqs(wq);
3097 kfree(wq);
3098}
3099EXPORT_SYMBOL_GPL(destroy_workqueue);
3100
3101/**
3102 * workqueue_set_max_active - adjust max_active of a workqueue
3103 * @wq: target workqueue
3104 * @max_active: new max_active value.
3105 *
3106 * Set max_active of @wq to @max_active.
3107 *
3108 * CONTEXT:
3109 * Don't call from IRQ context.
3110 */
3111void workqueue_set_max_active(struct workqueue_struct *wq, int max_active)
3112{
3113 unsigned int cpu;
3114
3115 max_active = wq_clamp_max_active(max_active, wq->flags, wq->name);
3116
3117 spin_lock(&workqueue_lock);
3118
3119 wq->saved_max_active = max_active;
3120
3121 for_each_cwq_cpu(cpu, wq) {
3122 struct global_cwq *gcwq = get_gcwq(cpu);
3123
3124 spin_lock_irq(&gcwq->lock);
3125
3126 if (!(wq->flags & WQ_FREEZABLE) ||
3127 !(gcwq->flags & GCWQ_FREEZING))
3128 get_cwq(gcwq->cpu, wq)->max_active = max_active;
3129
3130 spin_unlock_irq(&gcwq->lock);
3131 }
3132
3133 spin_unlock(&workqueue_lock);
3134}
3135EXPORT_SYMBOL_GPL(workqueue_set_max_active);
3136
3137/**
3138 * workqueue_congested - test whether a workqueue is congested
3139 * @cpu: CPU in question
3140 * @wq: target workqueue
3141 *
3142 * Test whether @wq's cpu workqueue for @cpu is congested. There is
3143 * no synchronization around this function and the test result is
3144 * unreliable and only useful as advisory hints or for debugging.
3145 *
3146 * RETURNS:
3147 * %true if congested, %false otherwise.
3148 */
3149bool workqueue_congested(unsigned int cpu, struct workqueue_struct *wq)
3150{
3151 struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
3152
3153 return !list_empty(&cwq->delayed_works);
3154}
3155EXPORT_SYMBOL_GPL(workqueue_congested);
3156
3157/**
3158 * work_cpu - return the last known associated cpu for @work
3159 * @work: the work of interest
3160 *
3161 * RETURNS:
3162 * CPU number if @work was ever queued. WORK_CPU_NONE otherwise.
3163 */
3164unsigned int work_cpu(struct work_struct *work)
3165{
3166 struct global_cwq *gcwq = get_work_gcwq(work);
3167
3168 return gcwq ? gcwq->cpu : WORK_CPU_NONE;
3169}
3170EXPORT_SYMBOL_GPL(work_cpu);
3171
3172/**
3173 * work_busy - test whether a work is currently pending or running
3174 * @work: the work to be tested
3175 *
3176 * Test whether @work is currently pending or running. There is no
3177 * synchronization around this function and the test result is
3178 * unreliable and only useful as advisory hints or for debugging.
3179 * Especially for reentrant wqs, the pending state might hide the
3180 * running state.
3181 *
3182 * RETURNS:
3183 * OR'd bitmask of WORK_BUSY_* bits.
3184 */
3185unsigned int work_busy(struct work_struct *work)
3186{
3187 struct global_cwq *gcwq = get_work_gcwq(work);
3188 unsigned long flags;
3189 unsigned int ret = 0;
3190
3191 if (!gcwq)
3192 return false;
3193
3194 spin_lock_irqsave(&gcwq->lock, flags);
3195
3196 if (work_pending(work))
3197 ret |= WORK_BUSY_PENDING;
3198 if (find_worker_executing_work(gcwq, work))
3199 ret |= WORK_BUSY_RUNNING;
3200
3201 spin_unlock_irqrestore(&gcwq->lock, flags);
3202
3203 return ret;
3204}
3205EXPORT_SYMBOL_GPL(work_busy);
3206
3207/*
3208 * CPU hotplug.
3209 *
3210 * There are two challenges in supporting CPU hotplug. Firstly, there
3211 * are a lot of assumptions on strong associations among work, cwq and
3212 * gcwq which make migrating pending and scheduled works very
3213 * difficult to implement without impacting hot paths. Secondly,
3214 * gcwqs serve mix of short, long and very long running works making
3215 * blocked draining impractical.
3216 *
3217 * This is solved by allowing a gcwq to be detached from CPU, running
3218 * it with unbound (rogue) workers and allowing it to be reattached
3219 * later if the cpu comes back online. A separate thread is created
3220 * to govern a gcwq in such state and is called the trustee of the
3221 * gcwq.
3222 *
3223 * Trustee states and their descriptions.
3224 *
3225 * START Command state used on startup. On CPU_DOWN_PREPARE, a
3226 * new trustee is started with this state.
3227 *
3228 * IN_CHARGE Once started, trustee will enter this state after
3229 * assuming the manager role and making all existing
3230 * workers rogue. DOWN_PREPARE waits for trustee to
3231 * enter this state. After reaching IN_CHARGE, trustee
3232 * tries to execute the pending worklist until it's empty
3233 * and the state is set to BUTCHER, or the state is set
3234 * to RELEASE.
3235 *
3236 * BUTCHER Command state which is set by the cpu callback after
3237 * the cpu has went down. Once this state is set trustee
3238 * knows that there will be no new works on the worklist
3239 * and once the worklist is empty it can proceed to
3240 * killing idle workers.
3241 *
3242 * RELEASE Command state which is set by the cpu callback if the
3243 * cpu down has been canceled or it has come online
3244 * again. After recognizing this state, trustee stops
3245 * trying to drain or butcher and clears ROGUE, rebinds
3246 * all remaining workers back to the cpu and releases
3247 * manager role.
3248 *
3249 * DONE Trustee will enter this state after BUTCHER or RELEASE
3250 * is complete.
3251 *
3252 * trustee CPU draining
3253 * took over down complete
3254 * START -----------> IN_CHARGE -----------> BUTCHER -----------> DONE
3255 * | | ^
3256 * | CPU is back online v return workers |
3257 * ----------------> RELEASE --------------
3258 */
3259
3260/**
3261 * trustee_wait_event_timeout - timed event wait for trustee
3262 * @cond: condition to wait for
3263 * @timeout: timeout in jiffies
3264 *
3265 * wait_event_timeout() for trustee to use. Handles locking and
3266 * checks for RELEASE request.
3267 *
3268 * CONTEXT:
3269 * spin_lock_irq(gcwq->lock) which may be released and regrabbed
3270 * multiple times. To be used by trustee.
3271 *
3272 * RETURNS:
3273 * Positive indicating left time if @cond is satisfied, 0 if timed
3274 * out, -1 if canceled.
3275 */
3276#define trustee_wait_event_timeout(cond, timeout) ({ \
3277 long __ret = (timeout); \
3278 while (!((cond) || (gcwq->trustee_state == TRUSTEE_RELEASE)) && \
3279 __ret) { \
3280 spin_unlock_irq(&gcwq->lock); \
3281 __wait_event_timeout(gcwq->trustee_wait, (cond) || \
3282 (gcwq->trustee_state == TRUSTEE_RELEASE), \
3283 __ret); \
3284 spin_lock_irq(&gcwq->lock); \
3285 } \
3286 gcwq->trustee_state == TRUSTEE_RELEASE ? -1 : (__ret); \
3287})
3288
3289/**
3290 * trustee_wait_event - event wait for trustee
3291 * @cond: condition to wait for
3292 *
3293 * wait_event() for trustee to use. Automatically handles locking and
3294 * checks for CANCEL request.
3295 *
3296 * CONTEXT:
3297 * spin_lock_irq(gcwq->lock) which may be released and regrabbed
3298 * multiple times. To be used by trustee.
3299 *
3300 * RETURNS:
3301 * 0 if @cond is satisfied, -1 if canceled.
3302 */
3303#define trustee_wait_event(cond) ({ \
3304 long __ret1; \
3305 __ret1 = trustee_wait_event_timeout(cond, MAX_SCHEDULE_TIMEOUT);\
3306 __ret1 < 0 ? -1 : 0; \
3307})
3308
3309static int __cpuinit trustee_thread(void *__gcwq)
3310{
3311 struct global_cwq *gcwq = __gcwq;
3312 struct worker *worker;
3313 struct work_struct *work;
3314 struct hlist_node *pos;
3315 long rc;
3316 int i;
3317
3318 BUG_ON(gcwq->cpu != smp_processor_id());
3319
3320 spin_lock_irq(&gcwq->lock);
3321 /*
3322 * Claim the manager position and make all workers rogue.
3323 * Trustee must be bound to the target cpu and can't be
3324 * cancelled.
3325 */
3326 BUG_ON(gcwq->cpu != smp_processor_id());
3327 rc = trustee_wait_event(!(gcwq->flags & GCWQ_MANAGING_WORKERS));
3328 BUG_ON(rc < 0);
3329
3330 gcwq->flags |= GCWQ_MANAGING_WORKERS;
3331
3332 list_for_each_entry(worker, &gcwq->idle_list, entry)
3333 worker->flags |= WORKER_ROGUE;
3334
3335 for_each_busy_worker(worker, i, pos, gcwq)
3336 worker->flags |= WORKER_ROGUE;
3337
3338 /*
3339 * Call schedule() so that we cross rq->lock and thus can
3340 * guarantee sched callbacks see the rogue flag. This is
3341 * necessary as scheduler callbacks may be invoked from other
3342 * cpus.
3343 */
3344 spin_unlock_irq(&gcwq->lock);
3345 schedule();
3346 spin_lock_irq(&gcwq->lock);
3347
3348 /*
3349 * Sched callbacks are disabled now. Zap nr_running. After
3350 * this, nr_running stays zero and need_more_worker() and
3351 * keep_working() are always true as long as the worklist is
3352 * not empty.
3353 */
3354 atomic_set(get_gcwq_nr_running(gcwq->cpu), 0);
3355
3356 spin_unlock_irq(&gcwq->lock);
3357 del_timer_sync(&gcwq->idle_timer);
3358 spin_lock_irq(&gcwq->lock);
3359
3360 /*
3361 * We're now in charge. Notify and proceed to drain. We need
3362 * to keep the gcwq running during the whole CPU down
3363 * procedure as other cpu hotunplug callbacks may need to
3364 * flush currently running tasks.
3365 */
3366 gcwq->trustee_state = TRUSTEE_IN_CHARGE;
3367 wake_up_all(&gcwq->trustee_wait);
3368
3369 /*
3370 * The original cpu is in the process of dying and may go away
3371 * anytime now. When that happens, we and all workers would
3372 * be migrated to other cpus. Try draining any left work. We
3373 * want to get it over with ASAP - spam rescuers, wake up as
3374 * many idlers as necessary and create new ones till the
3375 * worklist is empty. Note that if the gcwq is frozen, there
3376 * may be frozen works in freezable cwqs. Don't declare
3377 * completion while frozen.
3378 */
3379 while (gcwq->nr_workers != gcwq->nr_idle ||
3380 gcwq->flags & GCWQ_FREEZING ||
3381 gcwq->trustee_state == TRUSTEE_IN_CHARGE) {
3382 int nr_works = 0;
3383
3384 list_for_each_entry(work, &gcwq->worklist, entry) {
3385 send_mayday(work);
3386 nr_works++;
3387 }
3388
3389 list_for_each_entry(worker, &gcwq->idle_list, entry) {
3390 if (!nr_works--)
3391 break;
3392 wake_up_process(worker->task);
3393 }
3394
3395 if (need_to_create_worker(gcwq)) {
3396 spin_unlock_irq(&gcwq->lock);
3397 worker = create_worker(gcwq, false);
3398 spin_lock_irq(&gcwq->lock);
3399 if (worker) {
3400 worker->flags |= WORKER_ROGUE;
3401 start_worker(worker);
3402 }
3403 }
3404
3405 /* give a breather */
3406 if (trustee_wait_event_timeout(false, TRUSTEE_COOLDOWN) < 0)
3407 break;
3408 }
3409
3410 /*
3411 * Either all works have been scheduled and cpu is down, or
3412 * cpu down has already been canceled. Wait for and butcher
3413 * all workers till we're canceled.
3414 */
3415 do {
3416 rc = trustee_wait_event(!list_empty(&gcwq->idle_list));
3417 while (!list_empty(&gcwq->idle_list))
3418 destroy_worker(list_first_entry(&gcwq->idle_list,
3419 struct worker, entry));
3420 } while (gcwq->nr_workers && rc >= 0);
3421
3422 /*
3423 * At this point, either draining has completed and no worker
3424 * is left, or cpu down has been canceled or the cpu is being
3425 * brought back up. There shouldn't be any idle one left.
3426 * Tell the remaining busy ones to rebind once it finishes the
3427 * currently scheduled works by scheduling the rebind_work.
3428 */
3429 WARN_ON(!list_empty(&gcwq->idle_list));
3430
3431 for_each_busy_worker(worker, i, pos, gcwq) {
3432 struct work_struct *rebind_work = &worker->rebind_work;
3433
3434 /*
3435 * Rebind_work may race with future cpu hotplug
3436 * operations. Use a separate flag to mark that
3437 * rebinding is scheduled.
3438 */
3439 worker->flags |= WORKER_REBIND;
3440 worker->flags &= ~WORKER_ROGUE;
3441
3442 /* queue rebind_work, wq doesn't matter, use the default one */
3443 if (test_and_set_bit(WORK_STRUCT_PENDING_BIT,
3444 work_data_bits(rebind_work)))
3445 continue;
3446
3447 debug_work_activate(rebind_work);
3448 insert_work(get_cwq(gcwq->cpu, system_wq), rebind_work,
3449 worker->scheduled.next,
3450 work_color_to_flags(WORK_NO_COLOR));
3451 }
3452
3453 /* relinquish manager role */
3454 gcwq->flags &= ~GCWQ_MANAGING_WORKERS;
3455
3456 /* notify completion */
3457 gcwq->trustee = NULL;
3458 gcwq->trustee_state = TRUSTEE_DONE;
3459 wake_up_all(&gcwq->trustee_wait);
3460 spin_unlock_irq(&gcwq->lock);
3461 return 0;
3462}
3463
3464/**
3465 * wait_trustee_state - wait for trustee to enter the specified state
3466 * @gcwq: gcwq the trustee of interest belongs to
3467 * @state: target state to wait for
3468 *
3469 * Wait for the trustee to reach @state. DONE is already matched.
3470 *
3471 * CONTEXT:
3472 * spin_lock_irq(gcwq->lock) which may be released and regrabbed
3473 * multiple times. To be used by cpu_callback.
3474 */
3475static void __cpuinit wait_trustee_state(struct global_cwq *gcwq, int state)
3476__releases(&gcwq->lock)
3477__acquires(&gcwq->lock)
3478{
3479 if (!(gcwq->trustee_state == state ||
3480 gcwq->trustee_state == TRUSTEE_DONE)) {
3481 spin_unlock_irq(&gcwq->lock);
3482 __wait_event(gcwq->trustee_wait,
3483 gcwq->trustee_state == state ||
3484 gcwq->trustee_state == TRUSTEE_DONE);
3485 spin_lock_irq(&gcwq->lock);
3486 }
3487}
3488
3489static int __devinit workqueue_cpu_callback(struct notifier_block *nfb,
3490 unsigned long action,
3491 void *hcpu)
3492{
3493 unsigned int cpu = (unsigned long)hcpu;
3494 struct global_cwq *gcwq = get_gcwq(cpu);
3495 struct task_struct *new_trustee = NULL;
3496 struct worker *uninitialized_var(new_worker);
3497 unsigned long flags;
3498
3499 action &= ~CPU_TASKS_FROZEN;
3500
3501 switch (action) {
3502 case CPU_DOWN_PREPARE:
3503 new_trustee = kthread_create(trustee_thread, gcwq,
3504 "workqueue_trustee/%d\n", cpu);
3505 if (IS_ERR(new_trustee))
3506 return notifier_from_errno(PTR_ERR(new_trustee));
3507 kthread_bind(new_trustee, cpu);
3508 /* fall through */
3509 case CPU_UP_PREPARE:
3510 BUG_ON(gcwq->first_idle);
3511 new_worker = create_worker(gcwq, false);
3512 if (!new_worker) {
3513 if (new_trustee)
3514 kthread_stop(new_trustee);
3515 return NOTIFY_BAD;
3516 }
3517 }
3518
3519 /* some are called w/ irq disabled, don't disturb irq status */
3520 spin_lock_irqsave(&gcwq->lock, flags);
3521
3522 switch (action) {
3523 case CPU_DOWN_PREPARE:
3524 /* initialize trustee and tell it to acquire the gcwq */
3525 BUG_ON(gcwq->trustee || gcwq->trustee_state != TRUSTEE_DONE);
3526 gcwq->trustee = new_trustee;
3527 gcwq->trustee_state = TRUSTEE_START;
3528 wake_up_process(gcwq->trustee);
3529 wait_trustee_state(gcwq, TRUSTEE_IN_CHARGE);
3530 /* fall through */
3531 case CPU_UP_PREPARE:
3532 BUG_ON(gcwq->first_idle);
3533 gcwq->first_idle = new_worker;
3534 break;
3535
3536 case CPU_DYING:
3537 /*
3538 * Before this, the trustee and all workers except for
3539 * the ones which are still executing works from
3540 * before the last CPU down must be on the cpu. After
3541 * this, they'll all be diasporas.
3542 */
3543 gcwq->flags |= GCWQ_DISASSOCIATED;
3544 break;
3545
3546 case CPU_POST_DEAD:
3547 gcwq->trustee_state = TRUSTEE_BUTCHER;
3548 /* fall through */
3549 case CPU_UP_CANCELED:
3550 destroy_worker(gcwq->first_idle);
3551 gcwq->first_idle = NULL;
3552 break;
3553
3554 case CPU_DOWN_FAILED:
3555 case CPU_ONLINE:
3556 gcwq->flags &= ~GCWQ_DISASSOCIATED;
3557 if (gcwq->trustee_state != TRUSTEE_DONE) {
3558 gcwq->trustee_state = TRUSTEE_RELEASE;
3559 wake_up_process(gcwq->trustee);
3560 wait_trustee_state(gcwq, TRUSTEE_DONE);
3561 }
3562
3563 /*
3564 * Trustee is done and there might be no worker left.
3565 * Put the first_idle in and request a real manager to
3566 * take a look.
3567 */
3568 spin_unlock_irq(&gcwq->lock);
3569 kthread_bind(gcwq->first_idle->task, cpu);
3570 spin_lock_irq(&gcwq->lock);
3571 gcwq->flags |= GCWQ_MANAGE_WORKERS;
3572 start_worker(gcwq->first_idle);
3573 gcwq->first_idle = NULL;
3574 break;
3575 }
3576
3577 spin_unlock_irqrestore(&gcwq->lock, flags);
3578
3579 return notifier_from_errno(0);
3580}
3581
3582#ifdef CONFIG_SMP
3583
3584struct work_for_cpu {
3585 struct completion completion;
3586 long (*fn)(void *);
3587 void *arg;
3588 long ret;
3589};
3590
3591static int do_work_for_cpu(void *_wfc)
3592{
3593 struct work_for_cpu *wfc = _wfc;
3594 wfc->ret = wfc->fn(wfc->arg);
3595 complete(&wfc->completion);
3596 return 0;
3597}
3598
3599/**
3600 * work_on_cpu - run a function in user context on a particular cpu
3601 * @cpu: the cpu to run on
3602 * @fn: the function to run
3603 * @arg: the function arg
3604 *
3605 * This will return the value @fn returns.
3606 * It is up to the caller to ensure that the cpu doesn't go offline.
3607 * The caller must not hold any locks which would prevent @fn from completing.
3608 */
3609long work_on_cpu(unsigned int cpu, long (*fn)(void *), void *arg)
3610{
3611 struct task_struct *sub_thread;
3612 struct work_for_cpu wfc = {
3613 .completion = COMPLETION_INITIALIZER_ONSTACK(wfc.completion),
3614 .fn = fn,
3615 .arg = arg,
3616 };
3617
3618 sub_thread = kthread_create(do_work_for_cpu, &wfc, "work_for_cpu");
3619 if (IS_ERR(sub_thread))
3620 return PTR_ERR(sub_thread);
3621 kthread_bind(sub_thread, cpu);
3622 wake_up_process(sub_thread);
3623 wait_for_completion(&wfc.completion);
3624 return wfc.ret;
3625}
3626EXPORT_SYMBOL_GPL(work_on_cpu);
3627#endif /* CONFIG_SMP */
3628
3629#ifdef CONFIG_FREEZER
3630
3631/**
3632 * freeze_workqueues_begin - begin freezing workqueues
3633 *
3634 * Start freezing workqueues. After this function returns, all freezable
3635 * workqueues will queue new works to their frozen_works list instead of
3636 * gcwq->worklist.
3637 *
3638 * CONTEXT:
3639 * Grabs and releases workqueue_lock and gcwq->lock's.
3640 */
3641void freeze_workqueues_begin(void)
3642{
3643 unsigned int cpu;
3644
3645 spin_lock(&workqueue_lock);
3646
3647 BUG_ON(workqueue_freezing);
3648 workqueue_freezing = true;
3649
3650 for_each_gcwq_cpu(cpu) {
3651 struct global_cwq *gcwq = get_gcwq(cpu);
3652 struct workqueue_struct *wq;
3653
3654 spin_lock_irq(&gcwq->lock);
3655
3656 BUG_ON(gcwq->flags & GCWQ_FREEZING);
3657 gcwq->flags |= GCWQ_FREEZING;
3658
3659 list_for_each_entry(wq, &workqueues, list) {
3660 struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
3661
3662 if (cwq && wq->flags & WQ_FREEZABLE)
3663 cwq->max_active = 0;
3664 }
3665
3666 spin_unlock_irq(&gcwq->lock);
3667 }
3668
3669 spin_unlock(&workqueue_lock);
3670}
3671
3672/**
3673 * freeze_workqueues_busy - are freezable workqueues still busy?
3674 *
3675 * Check whether freezing is complete. This function must be called
3676 * between freeze_workqueues_begin() and thaw_workqueues().
3677 *
3678 * CONTEXT:
3679 * Grabs and releases workqueue_lock.
3680 *
3681 * RETURNS:
3682 * %true if some freezable workqueues are still busy. %false if freezing
3683 * is complete.
3684 */
3685bool freeze_workqueues_busy(void)
3686{
3687 unsigned int cpu;
3688 bool busy = false;
3689
3690 spin_lock(&workqueue_lock);
3691
3692 BUG_ON(!workqueue_freezing);
3693
3694 for_each_gcwq_cpu(cpu) {
3695 struct workqueue_struct *wq;
3696 /*
3697 * nr_active is monotonically decreasing. It's safe
3698 * to peek without lock.
3699 */
3700 list_for_each_entry(wq, &workqueues, list) {
3701 struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
3702
3703 if (!cwq || !(wq->flags & WQ_FREEZABLE))
3704 continue;
3705
3706 BUG_ON(cwq->nr_active < 0);
3707 if (cwq->nr_active) {
3708 busy = true;
3709 goto out_unlock;
3710 }
3711 }
3712 }
3713out_unlock:
3714 spin_unlock(&workqueue_lock);
3715 return busy;
3716}
3717
3718/**
3719 * thaw_workqueues - thaw workqueues
3720 *
3721 * Thaw workqueues. Normal queueing is restored and all collected
3722 * frozen works are transferred to their respective gcwq worklists.
3723 *
3724 * CONTEXT:
3725 * Grabs and releases workqueue_lock and gcwq->lock's.
3726 */
3727void thaw_workqueues(void)
3728{
3729 unsigned int cpu;
3730
3731 spin_lock(&workqueue_lock);
3732
3733 if (!workqueue_freezing)
3734 goto out_unlock;
3735
3736 for_each_gcwq_cpu(cpu) {
3737 struct global_cwq *gcwq = get_gcwq(cpu);
3738 struct workqueue_struct *wq;
3739
3740 spin_lock_irq(&gcwq->lock);
3741
3742 BUG_ON(!(gcwq->flags & GCWQ_FREEZING));
3743 gcwq->flags &= ~GCWQ_FREEZING;
3744
3745 list_for_each_entry(wq, &workqueues, list) {
3746 struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
3747
3748 if (!cwq || !(wq->flags & WQ_FREEZABLE))
3749 continue;
3750
3751 /* restore max_active and repopulate worklist */
3752 cwq->max_active = wq->saved_max_active;
3753
3754 while (!list_empty(&cwq->delayed_works) &&
3755 cwq->nr_active < cwq->max_active)
3756 cwq_activate_first_delayed(cwq);
3757 }
3758
3759 wake_up_worker(gcwq);
3760
3761 spin_unlock_irq(&gcwq->lock);
3762 }
3763
3764 workqueue_freezing = false;
3765out_unlock:
3766 spin_unlock(&workqueue_lock);
3767}
3768#endif /* CONFIG_FREEZER */
3769
3770static int __init init_workqueues(void)
3771{
3772 unsigned int cpu;
3773 int i;
3774
3775 cpu_notifier(workqueue_cpu_callback, CPU_PRI_WORKQUEUE);
3776
3777 /* initialize gcwqs */
3778 for_each_gcwq_cpu(cpu) {
3779 struct global_cwq *gcwq = get_gcwq(cpu);
3780
3781 spin_lock_init(&gcwq->lock);
3782 INIT_LIST_HEAD(&gcwq->worklist);
3783 gcwq->cpu = cpu;
3784 gcwq->flags |= GCWQ_DISASSOCIATED;
3785
3786 INIT_LIST_HEAD(&gcwq->idle_list);
3787 for (i = 0; i < BUSY_WORKER_HASH_SIZE; i++)
3788 INIT_HLIST_HEAD(&gcwq->busy_hash[i]);
3789
3790 init_timer_deferrable(&gcwq->idle_timer);
3791 gcwq->idle_timer.function = idle_worker_timeout;
3792 gcwq->idle_timer.data = (unsigned long)gcwq;
3793
3794 setup_timer(&gcwq->mayday_timer, gcwq_mayday_timeout,
3795 (unsigned long)gcwq);
3796
3797 ida_init(&gcwq->worker_ida);
3798
3799 gcwq->trustee_state = TRUSTEE_DONE;
3800 init_waitqueue_head(&gcwq->trustee_wait);
3801 }
3802
3803 /* create the initial worker */
3804 for_each_online_gcwq_cpu(cpu) {
3805 struct global_cwq *gcwq = get_gcwq(cpu);
3806 struct worker *worker;
3807
3808 if (cpu != WORK_CPU_UNBOUND)
3809 gcwq->flags &= ~GCWQ_DISASSOCIATED;
3810 worker = create_worker(gcwq, true);
3811 BUG_ON(!worker);
3812 spin_lock_irq(&gcwq->lock);
3813 start_worker(worker);
3814 spin_unlock_irq(&gcwq->lock);
3815 }
3816
3817 system_wq = alloc_workqueue("events", 0, 0);
3818 system_long_wq = alloc_workqueue("events_long", 0, 0);
3819 system_nrt_wq = alloc_workqueue("events_nrt", WQ_NON_REENTRANT, 0);
3820 system_unbound_wq = alloc_workqueue("events_unbound", WQ_UNBOUND,
3821 WQ_UNBOUND_MAX_ACTIVE);
3822 system_freezable_wq = alloc_workqueue("events_freezable",
3823 WQ_FREEZABLE, 0);
3824 BUG_ON(!system_wq || !system_long_wq || !system_nrt_wq ||
3825 !system_unbound_wq || !system_freezable_wq);
3826 return 0;
3827}
3828early_initcall(init_workqueues);