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