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1/*
2 * kernel/workqueue.c - generic async execution with shared worker pool
3 *
4 * Copyright (C) 2002 Ingo Molnar
5 *
6 * Derived from the taskqueue/keventd code by:
7 * David Woodhouse <dwmw2@infradead.org>
8 * Andrew Morton
9 * Kai Petzke <wpp@marie.physik.tu-berlin.de>
10 * Theodore Ts'o <tytso@mit.edu>
11 *
12 * Made to use alloc_percpu by Christoph Lameter.
13 *
14 * Copyright (C) 2010 SUSE Linux Products GmbH
15 * Copyright (C) 2010 Tejun Heo <tj@kernel.org>
16 *
17 * This is the generic async execution mechanism. Work items as are
18 * executed in process context. The worker pool is shared and
19 * automatically managed. There is one worker pool for each CPU and
20 * one extra for works which are better served by workers which are
21 * not bound to any specific CPU.
22 *
23 * Please read Documentation/workqueue.txt for details.
24 */
25
26#include <linux/export.h>
27#include <linux/kernel.h>
28#include <linux/sched.h>
29#include <linux/init.h>
30#include <linux/signal.h>
31#include <linux/completion.h>
32#include <linux/workqueue.h>
33#include <linux/slab.h>
34#include <linux/cpu.h>
35#include <linux/notifier.h>
36#include <linux/kthread.h>
37#include <linux/hardirq.h>
38#include <linux/mempolicy.h>
39#include <linux/freezer.h>
40#include <linux/kallsyms.h>
41#include <linux/debug_locks.h>
42#include <linux/lockdep.h>
43#include <linux/idr.h>
44
45#include "workqueue_sched.h"
46
47enum {
48 /* global_cwq flags */
49 GCWQ_MANAGE_WORKERS = 1 << 0, /* need to manage workers */
50 GCWQ_MANAGING_WORKERS = 1 << 1, /* managing workers */
51 GCWQ_DISASSOCIATED = 1 << 2, /* cpu can't serve workers */
52 GCWQ_FREEZING = 1 << 3, /* freeze in progress */
53 GCWQ_HIGHPRI_PENDING = 1 << 4, /* highpri works on queue */
54
55 /* worker flags */
56 WORKER_STARTED = 1 << 0, /* started */
57 WORKER_DIE = 1 << 1, /* die die die */
58 WORKER_IDLE = 1 << 2, /* is idle */
59 WORKER_PREP = 1 << 3, /* preparing to run works */
60 WORKER_ROGUE = 1 << 4, /* not bound to any cpu */
61 WORKER_REBIND = 1 << 5, /* mom is home, come back */
62 WORKER_CPU_INTENSIVE = 1 << 6, /* cpu intensive */
63 WORKER_UNBOUND = 1 << 7, /* worker is unbound */
64
65 WORKER_NOT_RUNNING = WORKER_PREP | WORKER_ROGUE | WORKER_REBIND |
66 WORKER_CPU_INTENSIVE | WORKER_UNBOUND,
67
68 /* gcwq->trustee_state */
69 TRUSTEE_START = 0, /* start */
70 TRUSTEE_IN_CHARGE = 1, /* trustee in charge of gcwq */
71 TRUSTEE_BUTCHER = 2, /* butcher workers */
72 TRUSTEE_RELEASE = 3, /* release workers */
73 TRUSTEE_DONE = 4, /* trustee is done */
74
75 BUSY_WORKER_HASH_ORDER = 6, /* 64 pointers */
76 BUSY_WORKER_HASH_SIZE = 1 << BUSY_WORKER_HASH_ORDER,
77 BUSY_WORKER_HASH_MASK = BUSY_WORKER_HASH_SIZE - 1,
78
79 MAX_IDLE_WORKERS_RATIO = 4, /* 1/4 of busy can be idle */
80 IDLE_WORKER_TIMEOUT = 300 * HZ, /* keep idle ones for 5 mins */
81
82 MAYDAY_INITIAL_TIMEOUT = HZ / 100 >= 2 ? HZ / 100 : 2,
83 /* call for help after 10ms
84 (min two ticks) */
85 MAYDAY_INTERVAL = HZ / 10, /* and then every 100ms */
86 CREATE_COOLDOWN = HZ, /* time to breath after fail */
87 TRUSTEE_COOLDOWN = HZ / 10, /* for trustee draining */
88
89 /*
90 * Rescue workers are used only on emergencies and shared by
91 * all cpus. Give -20.
92 */
93 RESCUER_NICE_LEVEL = -20,
94};
95
96/*
97 * Structure fields follow one of the following exclusion rules.
98 *
99 * I: Modifiable by initialization/destruction paths and read-only for
100 * everyone else.
101 *
102 * P: Preemption protected. Disabling preemption is enough and should
103 * only be modified and accessed from the local cpu.
104 *
105 * L: gcwq->lock protected. Access with gcwq->lock held.
106 *
107 * X: During normal operation, modification requires gcwq->lock and
108 * should be done only from local cpu. Either disabling preemption
109 * on local cpu or grabbing gcwq->lock is enough for read access.
110 * If GCWQ_DISASSOCIATED is set, it's identical to L.
111 *
112 * F: wq->flush_mutex protected.
113 *
114 * W: workqueue_lock protected.
115 */
116
117struct global_cwq;
118
119/*
120 * The poor guys doing the actual heavy lifting. All on-duty workers
121 * are either serving the manager role, on idle list or on busy hash.
122 */
123struct worker {
124 /* on idle list while idle, on busy hash table while busy */
125 union {
126 struct list_head entry; /* L: while idle */
127 struct hlist_node hentry; /* L: while busy */
128 };
129
130 struct work_struct *current_work; /* L: work being processed */
131 struct cpu_workqueue_struct *current_cwq; /* L: current_work's cwq */
132 struct list_head scheduled; /* L: scheduled works */
133 struct task_struct *task; /* I: worker task */
134 struct global_cwq *gcwq; /* I: the associated gcwq */
135 /* 64 bytes boundary on 64bit, 32 on 32bit */
136 unsigned long last_active; /* L: last active timestamp */
137 unsigned int flags; /* X: flags */
138 int id; /* I: worker id */
139 struct work_struct rebind_work; /* L: rebind worker to cpu */
140};
141
142/*
143 * Global per-cpu workqueue. There's one and only one for each cpu
144 * and all works are queued and processed here regardless of their
145 * target workqueues.
146 */
147struct global_cwq {
148 spinlock_t lock; /* the gcwq lock */
149 struct list_head worklist; /* L: list of pending works */
150 unsigned int cpu; /* I: the associated cpu */
151 unsigned int flags; /* L: GCWQ_* flags */
152
153 int nr_workers; /* L: total number of workers */
154 int nr_idle; /* L: currently idle ones */
155
156 /* workers are chained either in the idle_list or busy_hash */
157 struct list_head idle_list; /* X: list of idle workers */
158 struct hlist_head busy_hash[BUSY_WORKER_HASH_SIZE];
159 /* L: hash of busy workers */
160
161 struct timer_list idle_timer; /* L: worker idle timeout */
162 struct timer_list mayday_timer; /* L: SOS timer for dworkers */
163
164 struct ida worker_ida; /* L: for worker IDs */
165
166 struct task_struct *trustee; /* L: for gcwq shutdown */
167 unsigned int trustee_state; /* L: trustee state */
168 wait_queue_head_t trustee_wait; /* trustee wait */
169 struct worker *first_idle; /* L: first idle worker */
170} ____cacheline_aligned_in_smp;
171
172/*
173 * The per-CPU workqueue. The lower WORK_STRUCT_FLAG_BITS of
174 * work_struct->data are used for flags and thus cwqs need to be
175 * aligned at two's power of the number of flag bits.
176 */
177struct cpu_workqueue_struct {
178 struct global_cwq *gcwq; /* I: the associated gcwq */
179 struct workqueue_struct *wq; /* I: the owning workqueue */
180 int work_color; /* L: current color */
181 int flush_color; /* L: flushing color */
182 int nr_in_flight[WORK_NR_COLORS];
183 /* L: nr of in_flight works */
184 int nr_active; /* L: nr of active works */
185 int max_active; /* L: max active works */
186 struct list_head delayed_works; /* L: delayed works */
187};
188
189/*
190 * Structure used to wait for workqueue flush.
191 */
192struct wq_flusher {
193 struct list_head list; /* F: list of flushers */
194 int flush_color; /* F: flush color waiting for */
195 struct completion done; /* flush completion */
196};
197
198/*
199 * All cpumasks are assumed to be always set on UP and thus can't be
200 * used to determine whether there's something to be done.
201 */
202#ifdef CONFIG_SMP
203typedef cpumask_var_t mayday_mask_t;
204#define mayday_test_and_set_cpu(cpu, mask) \
205 cpumask_test_and_set_cpu((cpu), (mask))
206#define mayday_clear_cpu(cpu, mask) cpumask_clear_cpu((cpu), (mask))
207#define for_each_mayday_cpu(cpu, mask) for_each_cpu((cpu), (mask))
208#define alloc_mayday_mask(maskp, gfp) zalloc_cpumask_var((maskp), (gfp))
209#define free_mayday_mask(mask) free_cpumask_var((mask))
210#else
211typedef unsigned long mayday_mask_t;
212#define mayday_test_and_set_cpu(cpu, mask) test_and_set_bit(0, &(mask))
213#define mayday_clear_cpu(cpu, mask) clear_bit(0, &(mask))
214#define for_each_mayday_cpu(cpu, mask) if ((cpu) = 0, (mask))
215#define alloc_mayday_mask(maskp, gfp) true
216#define free_mayday_mask(mask) do { } while (0)
217#endif
218
219/*
220 * The externally visible workqueue abstraction is an array of
221 * per-CPU workqueues:
222 */
223struct workqueue_struct {
224 unsigned int flags; /* W: WQ_* flags */
225 union {
226 struct cpu_workqueue_struct __percpu *pcpu;
227 struct cpu_workqueue_struct *single;
228 unsigned long v;
229 } cpu_wq; /* I: cwq's */
230 struct list_head list; /* W: list of all workqueues */
231
232 struct mutex flush_mutex; /* protects wq flushing */
233 int work_color; /* F: current work color */
234 int flush_color; /* F: current flush color */
235 atomic_t nr_cwqs_to_flush; /* flush in progress */
236 struct wq_flusher *first_flusher; /* F: first flusher */
237 struct list_head flusher_queue; /* F: flush waiters */
238 struct list_head flusher_overflow; /* F: flush overflow list */
239
240 mayday_mask_t mayday_mask; /* cpus requesting rescue */
241 struct worker *rescuer; /* I: rescue worker */
242
243 int nr_drainers; /* W: drain in progress */
244 int saved_max_active; /* W: saved cwq max_active */
245#ifdef CONFIG_LOCKDEP
246 struct lockdep_map lockdep_map;
247#endif
248 char name[]; /* I: workqueue name */
249};
250
251struct workqueue_struct *system_wq __read_mostly;
252struct workqueue_struct *system_long_wq __read_mostly;
253struct workqueue_struct *system_nrt_wq __read_mostly;
254struct workqueue_struct *system_unbound_wq __read_mostly;
255struct workqueue_struct *system_freezable_wq __read_mostly;
256struct workqueue_struct *system_nrt_freezable_wq __read_mostly;
257EXPORT_SYMBOL_GPL(system_wq);
258EXPORT_SYMBOL_GPL(system_long_wq);
259EXPORT_SYMBOL_GPL(system_nrt_wq);
260EXPORT_SYMBOL_GPL(system_unbound_wq);
261EXPORT_SYMBOL_GPL(system_freezable_wq);
262EXPORT_SYMBOL_GPL(system_nrt_freezable_wq);
263
264#define CREATE_TRACE_POINTS
265#include <trace/events/workqueue.h>
266
267#define for_each_busy_worker(worker, i, pos, gcwq) \
268 for (i = 0; i < BUSY_WORKER_HASH_SIZE; i++) \
269 hlist_for_each_entry(worker, pos, &gcwq->busy_hash[i], hentry)
270
271static inline int __next_gcwq_cpu(int cpu, const struct cpumask *mask,
272 unsigned int sw)
273{
274 if (cpu < nr_cpu_ids) {
275 if (sw & 1) {
276 cpu = cpumask_next(cpu, mask);
277 if (cpu < nr_cpu_ids)
278 return cpu;
279 }
280 if (sw & 2)
281 return WORK_CPU_UNBOUND;
282 }
283 return WORK_CPU_NONE;
284}
285
286static inline int __next_wq_cpu(int cpu, const struct cpumask *mask,
287 struct workqueue_struct *wq)
288{
289 return __next_gcwq_cpu(cpu, mask, !(wq->flags & WQ_UNBOUND) ? 1 : 2);
290}
291
292/*
293 * CPU iterators
294 *
295 * An extra gcwq is defined for an invalid cpu number
296 * (WORK_CPU_UNBOUND) to host workqueues which are not bound to any
297 * specific CPU. The following iterators are similar to
298 * for_each_*_cpu() iterators but also considers the unbound gcwq.
299 *
300 * for_each_gcwq_cpu() : possible CPUs + WORK_CPU_UNBOUND
301 * for_each_online_gcwq_cpu() : online CPUs + WORK_CPU_UNBOUND
302 * for_each_cwq_cpu() : possible CPUs for bound workqueues,
303 * WORK_CPU_UNBOUND for unbound workqueues
304 */
305#define for_each_gcwq_cpu(cpu) \
306 for ((cpu) = __next_gcwq_cpu(-1, cpu_possible_mask, 3); \
307 (cpu) < WORK_CPU_NONE; \
308 (cpu) = __next_gcwq_cpu((cpu), cpu_possible_mask, 3))
309
310#define for_each_online_gcwq_cpu(cpu) \
311 for ((cpu) = __next_gcwq_cpu(-1, cpu_online_mask, 3); \
312 (cpu) < WORK_CPU_NONE; \
313 (cpu) = __next_gcwq_cpu((cpu), cpu_online_mask, 3))
314
315#define for_each_cwq_cpu(cpu, wq) \
316 for ((cpu) = __next_wq_cpu(-1, cpu_possible_mask, (wq)); \
317 (cpu) < WORK_CPU_NONE; \
318 (cpu) = __next_wq_cpu((cpu), cpu_possible_mask, (wq)))
319
320#ifdef CONFIG_DEBUG_OBJECTS_WORK
321
322static struct debug_obj_descr work_debug_descr;
323
324static void *work_debug_hint(void *addr)
325{
326 return ((struct work_struct *) addr)->func;
327}
328
329/*
330 * fixup_init is called when:
331 * - an active object is initialized
332 */
333static int work_fixup_init(void *addr, enum debug_obj_state state)
334{
335 struct work_struct *work = addr;
336
337 switch (state) {
338 case ODEBUG_STATE_ACTIVE:
339 cancel_work_sync(work);
340 debug_object_init(work, &work_debug_descr);
341 return 1;
342 default:
343 return 0;
344 }
345}
346
347/*
348 * fixup_activate is called when:
349 * - an active object is activated
350 * - an unknown object is activated (might be a statically initialized object)
351 */
352static int work_fixup_activate(void *addr, enum debug_obj_state state)
353{
354 struct work_struct *work = addr;
355
356 switch (state) {
357
358 case ODEBUG_STATE_NOTAVAILABLE:
359 /*
360 * This is not really a fixup. The work struct was
361 * statically initialized. We just make sure that it
362 * is tracked in the object tracker.
363 */
364 if (test_bit(WORK_STRUCT_STATIC_BIT, work_data_bits(work))) {
365 debug_object_init(work, &work_debug_descr);
366 debug_object_activate(work, &work_debug_descr);
367 return 0;
368 }
369 WARN_ON_ONCE(1);
370 return 0;
371
372 case ODEBUG_STATE_ACTIVE:
373 WARN_ON(1);
374
375 default:
376 return 0;
377 }
378}
379
380/*
381 * fixup_free is called when:
382 * - an active object is freed
383 */
384static int work_fixup_free(void *addr, enum debug_obj_state state)
385{
386 struct work_struct *work = addr;
387
388 switch (state) {
389 case ODEBUG_STATE_ACTIVE:
390 cancel_work_sync(work);
391 debug_object_free(work, &work_debug_descr);
392 return 1;
393 default:
394 return 0;
395 }
396}
397
398static struct debug_obj_descr work_debug_descr = {
399 .name = "work_struct",
400 .debug_hint = work_debug_hint,
401 .fixup_init = work_fixup_init,
402 .fixup_activate = work_fixup_activate,
403 .fixup_free = work_fixup_free,
404};
405
406static inline void debug_work_activate(struct work_struct *work)
407{
408 debug_object_activate(work, &work_debug_descr);
409}
410
411static inline void debug_work_deactivate(struct work_struct *work)
412{
413 debug_object_deactivate(work, &work_debug_descr);
414}
415
416void __init_work(struct work_struct *work, int onstack)
417{
418 if (onstack)
419 debug_object_init_on_stack(work, &work_debug_descr);
420 else
421 debug_object_init(work, &work_debug_descr);
422}
423EXPORT_SYMBOL_GPL(__init_work);
424
425void destroy_work_on_stack(struct work_struct *work)
426{
427 debug_object_free(work, &work_debug_descr);
428}
429EXPORT_SYMBOL_GPL(destroy_work_on_stack);
430
431#else
432static inline void debug_work_activate(struct work_struct *work) { }
433static inline void debug_work_deactivate(struct work_struct *work) { }
434#endif
435
436/* Serializes the accesses to the list of workqueues. */
437static DEFINE_SPINLOCK(workqueue_lock);
438static LIST_HEAD(workqueues);
439static bool workqueue_freezing; /* W: have wqs started freezing? */
440
441/*
442 * The almighty global cpu workqueues. nr_running is the only field
443 * which is expected to be used frequently by other cpus via
444 * try_to_wake_up(). Put it in a separate cacheline.
445 */
446static DEFINE_PER_CPU(struct global_cwq, global_cwq);
447static DEFINE_PER_CPU_SHARED_ALIGNED(atomic_t, gcwq_nr_running);
448
449/*
450 * Global cpu workqueue and nr_running counter for unbound gcwq. The
451 * gcwq is always online, has GCWQ_DISASSOCIATED set, and all its
452 * workers have WORKER_UNBOUND set.
453 */
454static struct global_cwq unbound_global_cwq;
455static atomic_t unbound_gcwq_nr_running = ATOMIC_INIT(0); /* always 0 */
456
457static int worker_thread(void *__worker);
458
459static struct global_cwq *get_gcwq(unsigned int cpu)
460{
461 if (cpu != WORK_CPU_UNBOUND)
462 return &per_cpu(global_cwq, cpu);
463 else
464 return &unbound_global_cwq;
465}
466
467static atomic_t *get_gcwq_nr_running(unsigned int cpu)
468{
469 if (cpu != WORK_CPU_UNBOUND)
470 return &per_cpu(gcwq_nr_running, cpu);
471 else
472 return &unbound_gcwq_nr_running;
473}
474
475static struct cpu_workqueue_struct *get_cwq(unsigned int cpu,
476 struct workqueue_struct *wq)
477{
478 if (!(wq->flags & WQ_UNBOUND)) {
479 if (likely(cpu < nr_cpu_ids))
480 return per_cpu_ptr(wq->cpu_wq.pcpu, cpu);
481 } else if (likely(cpu == WORK_CPU_UNBOUND))
482 return wq->cpu_wq.single;
483 return NULL;
484}
485
486static unsigned int work_color_to_flags(int color)
487{
488 return color << WORK_STRUCT_COLOR_SHIFT;
489}
490
491static int get_work_color(struct work_struct *work)
492{
493 return (*work_data_bits(work) >> WORK_STRUCT_COLOR_SHIFT) &
494 ((1 << WORK_STRUCT_COLOR_BITS) - 1);
495}
496
497static int work_next_color(int color)
498{
499 return (color + 1) % WORK_NR_COLORS;
500}
501
502/*
503 * A work's data points to the cwq with WORK_STRUCT_CWQ set while the
504 * work is on queue. Once execution starts, WORK_STRUCT_CWQ is
505 * cleared and the work data contains the cpu number it was last on.
506 *
507 * set_work_{cwq|cpu}() and clear_work_data() can be used to set the
508 * cwq, cpu or clear work->data. These functions should only be
509 * called while the work is owned - ie. while the PENDING bit is set.
510 *
511 * get_work_[g]cwq() can be used to obtain the gcwq or cwq
512 * corresponding to a work. gcwq is available once the work has been
513 * queued anywhere after initialization. cwq is available only from
514 * queueing until execution starts.
515 */
516static inline void set_work_data(struct work_struct *work, unsigned long data,
517 unsigned long flags)
518{
519 BUG_ON(!work_pending(work));
520 atomic_long_set(&work->data, data | flags | work_static(work));
521}
522
523static void set_work_cwq(struct work_struct *work,
524 struct cpu_workqueue_struct *cwq,
525 unsigned long extra_flags)
526{
527 set_work_data(work, (unsigned long)cwq,
528 WORK_STRUCT_PENDING | WORK_STRUCT_CWQ | extra_flags);
529}
530
531static void set_work_cpu(struct work_struct *work, unsigned int cpu)
532{
533 set_work_data(work, cpu << WORK_STRUCT_FLAG_BITS, WORK_STRUCT_PENDING);
534}
535
536static void clear_work_data(struct work_struct *work)
537{
538 set_work_data(work, WORK_STRUCT_NO_CPU, 0);
539}
540
541static struct cpu_workqueue_struct *get_work_cwq(struct work_struct *work)
542{
543 unsigned long data = atomic_long_read(&work->data);
544
545 if (data & WORK_STRUCT_CWQ)
546 return (void *)(data & WORK_STRUCT_WQ_DATA_MASK);
547 else
548 return NULL;
549}
550
551static struct global_cwq *get_work_gcwq(struct work_struct *work)
552{
553 unsigned long data = atomic_long_read(&work->data);
554 unsigned int cpu;
555
556 if (data & WORK_STRUCT_CWQ)
557 return ((struct cpu_workqueue_struct *)
558 (data & WORK_STRUCT_WQ_DATA_MASK))->gcwq;
559
560 cpu = data >> WORK_STRUCT_FLAG_BITS;
561 if (cpu == WORK_CPU_NONE)
562 return NULL;
563
564 BUG_ON(cpu >= nr_cpu_ids && cpu != WORK_CPU_UNBOUND);
565 return get_gcwq(cpu);
566}
567
568/*
569 * Policy functions. These define the policies on how the global
570 * worker pool is managed. Unless noted otherwise, these functions
571 * assume that they're being called with gcwq->lock held.
572 */
573
574static bool __need_more_worker(struct global_cwq *gcwq)
575{
576 return !atomic_read(get_gcwq_nr_running(gcwq->cpu)) ||
577 gcwq->flags & GCWQ_HIGHPRI_PENDING;
578}
579
580/*
581 * Need to wake up a worker? Called from anything but currently
582 * running workers.
583 */
584static bool need_more_worker(struct global_cwq *gcwq)
585{
586 return !list_empty(&gcwq->worklist) && __need_more_worker(gcwq);
587}
588
589/* Can I start working? Called from busy but !running workers. */
590static bool may_start_working(struct global_cwq *gcwq)
591{
592 return gcwq->nr_idle;
593}
594
595/* Do I need to keep working? Called from currently running workers. */
596static bool keep_working(struct global_cwq *gcwq)
597{
598 atomic_t *nr_running = get_gcwq_nr_running(gcwq->cpu);
599
600 return !list_empty(&gcwq->worklist) &&
601 (atomic_read(nr_running) <= 1 ||
602 gcwq->flags & GCWQ_HIGHPRI_PENDING);
603}
604
605/* Do we need a new worker? Called from manager. */
606static bool need_to_create_worker(struct global_cwq *gcwq)
607{
608 return need_more_worker(gcwq) && !may_start_working(gcwq);
609}
610
611/* Do I need to be the manager? */
612static bool need_to_manage_workers(struct global_cwq *gcwq)
613{
614 return need_to_create_worker(gcwq) || gcwq->flags & GCWQ_MANAGE_WORKERS;
615}
616
617/* Do we have too many workers and should some go away? */
618static bool too_many_workers(struct global_cwq *gcwq)
619{
620 bool managing = gcwq->flags & GCWQ_MANAGING_WORKERS;
621 int nr_idle = gcwq->nr_idle + managing; /* manager is considered idle */
622 int nr_busy = gcwq->nr_workers - nr_idle;
623
624 return nr_idle > 2 && (nr_idle - 2) * MAX_IDLE_WORKERS_RATIO >= nr_busy;
625}
626
627/*
628 * Wake up functions.
629 */
630
631/* Return the first worker. Safe with preemption disabled */
632static struct worker *first_worker(struct global_cwq *gcwq)
633{
634 if (unlikely(list_empty(&gcwq->idle_list)))
635 return NULL;
636
637 return list_first_entry(&gcwq->idle_list, struct worker, entry);
638}
639
640/**
641 * wake_up_worker - wake up an idle worker
642 * @gcwq: gcwq to wake worker for
643 *
644 * Wake up the first idle worker of @gcwq.
645 *
646 * CONTEXT:
647 * spin_lock_irq(gcwq->lock).
648 */
649static void wake_up_worker(struct global_cwq *gcwq)
650{
651 struct worker *worker = first_worker(gcwq);
652
653 if (likely(worker))
654 wake_up_process(worker->task);
655}
656
657/**
658 * wq_worker_waking_up - a worker is waking up
659 * @task: task waking up
660 * @cpu: CPU @task is waking up to
661 *
662 * This function is called during try_to_wake_up() when a worker is
663 * being awoken.
664 *
665 * CONTEXT:
666 * spin_lock_irq(rq->lock)
667 */
668void wq_worker_waking_up(struct task_struct *task, unsigned int cpu)
669{
670 struct worker *worker = kthread_data(task);
671
672 if (!(worker->flags & WORKER_NOT_RUNNING))
673 atomic_inc(get_gcwq_nr_running(cpu));
674}
675
676/**
677 * wq_worker_sleeping - a worker is going to sleep
678 * @task: task going to sleep
679 * @cpu: CPU in question, must be the current CPU number
680 *
681 * This function is called during schedule() when a busy worker is
682 * going to sleep. Worker on the same cpu can be woken up by
683 * returning pointer to its task.
684 *
685 * CONTEXT:
686 * spin_lock_irq(rq->lock)
687 *
688 * RETURNS:
689 * Worker task on @cpu to wake up, %NULL if none.
690 */
691struct task_struct *wq_worker_sleeping(struct task_struct *task,
692 unsigned int cpu)
693{
694 struct worker *worker = kthread_data(task), *to_wakeup = NULL;
695 struct global_cwq *gcwq = get_gcwq(cpu);
696 atomic_t *nr_running = get_gcwq_nr_running(cpu);
697
698 if (worker->flags & WORKER_NOT_RUNNING)
699 return NULL;
700
701 /* this can only happen on the local cpu */
702 BUG_ON(cpu != raw_smp_processor_id());
703
704 /*
705 * The counterpart of the following dec_and_test, implied mb,
706 * worklist not empty test sequence is in insert_work().
707 * Please read comment there.
708 *
709 * NOT_RUNNING is clear. This means that trustee is not in
710 * charge and we're running on the local cpu w/ rq lock held
711 * and preemption disabled, which in turn means that none else
712 * could be manipulating idle_list, so dereferencing idle_list
713 * without gcwq lock is safe.
714 */
715 if (atomic_dec_and_test(nr_running) && !list_empty(&gcwq->worklist))
716 to_wakeup = first_worker(gcwq);
717 return to_wakeup ? to_wakeup->task : NULL;
718}
719
720/**
721 * worker_set_flags - set worker flags and adjust nr_running accordingly
722 * @worker: self
723 * @flags: flags to set
724 * @wakeup: wakeup an idle worker if necessary
725 *
726 * Set @flags in @worker->flags and adjust nr_running accordingly. If
727 * nr_running becomes zero and @wakeup is %true, an idle worker is
728 * woken up.
729 *
730 * CONTEXT:
731 * spin_lock_irq(gcwq->lock)
732 */
733static inline void worker_set_flags(struct worker *worker, unsigned int flags,
734 bool wakeup)
735{
736 struct global_cwq *gcwq = worker->gcwq;
737
738 WARN_ON_ONCE(worker->task != current);
739
740 /*
741 * If transitioning into NOT_RUNNING, adjust nr_running and
742 * wake up an idle worker as necessary if requested by
743 * @wakeup.
744 */
745 if ((flags & WORKER_NOT_RUNNING) &&
746 !(worker->flags & WORKER_NOT_RUNNING)) {
747 atomic_t *nr_running = get_gcwq_nr_running(gcwq->cpu);
748
749 if (wakeup) {
750 if (atomic_dec_and_test(nr_running) &&
751 !list_empty(&gcwq->worklist))
752 wake_up_worker(gcwq);
753 } else
754 atomic_dec(nr_running);
755 }
756
757 worker->flags |= flags;
758}
759
760/**
761 * worker_clr_flags - clear worker flags and adjust nr_running accordingly
762 * @worker: self
763 * @flags: flags to clear
764 *
765 * Clear @flags in @worker->flags and adjust nr_running accordingly.
766 *
767 * CONTEXT:
768 * spin_lock_irq(gcwq->lock)
769 */
770static inline void worker_clr_flags(struct worker *worker, unsigned int flags)
771{
772 struct global_cwq *gcwq = worker->gcwq;
773 unsigned int oflags = worker->flags;
774
775 WARN_ON_ONCE(worker->task != current);
776
777 worker->flags &= ~flags;
778
779 /*
780 * If transitioning out of NOT_RUNNING, increment nr_running. Note
781 * that the nested NOT_RUNNING is not a noop. NOT_RUNNING is mask
782 * of multiple flags, not a single flag.
783 */
784 if ((flags & WORKER_NOT_RUNNING) && (oflags & WORKER_NOT_RUNNING))
785 if (!(worker->flags & WORKER_NOT_RUNNING))
786 atomic_inc(get_gcwq_nr_running(gcwq->cpu));
787}
788
789/**
790 * busy_worker_head - return the busy hash head for a work
791 * @gcwq: gcwq of interest
792 * @work: work to be hashed
793 *
794 * Return hash head of @gcwq for @work.
795 *
796 * CONTEXT:
797 * spin_lock_irq(gcwq->lock).
798 *
799 * RETURNS:
800 * Pointer to the hash head.
801 */
802static struct hlist_head *busy_worker_head(struct global_cwq *gcwq,
803 struct work_struct *work)
804{
805 const int base_shift = ilog2(sizeof(struct work_struct));
806 unsigned long v = (unsigned long)work;
807
808 /* simple shift and fold hash, do we need something better? */
809 v >>= base_shift;
810 v += v >> BUSY_WORKER_HASH_ORDER;
811 v &= BUSY_WORKER_HASH_MASK;
812
813 return &gcwq->busy_hash[v];
814}
815
816/**
817 * __find_worker_executing_work - find worker which is executing a work
818 * @gcwq: gcwq of interest
819 * @bwh: hash head as returned by busy_worker_head()
820 * @work: work to find worker for
821 *
822 * Find a worker which is executing @work on @gcwq. @bwh should be
823 * the hash head obtained by calling busy_worker_head() with the same
824 * work.
825 *
826 * CONTEXT:
827 * spin_lock_irq(gcwq->lock).
828 *
829 * RETURNS:
830 * Pointer to worker which is executing @work if found, NULL
831 * otherwise.
832 */
833static struct worker *__find_worker_executing_work(struct global_cwq *gcwq,
834 struct hlist_head *bwh,
835 struct work_struct *work)
836{
837 struct worker *worker;
838 struct hlist_node *tmp;
839
840 hlist_for_each_entry(worker, tmp, bwh, hentry)
841 if (worker->current_work == work)
842 return worker;
843 return NULL;
844}
845
846/**
847 * find_worker_executing_work - find worker which is executing a work
848 * @gcwq: gcwq of interest
849 * @work: work to find worker for
850 *
851 * Find a worker which is executing @work on @gcwq. This function is
852 * identical to __find_worker_executing_work() except that this
853 * function calculates @bwh itself.
854 *
855 * CONTEXT:
856 * spin_lock_irq(gcwq->lock).
857 *
858 * RETURNS:
859 * Pointer to worker which is executing @work if found, NULL
860 * otherwise.
861 */
862static struct worker *find_worker_executing_work(struct global_cwq *gcwq,
863 struct work_struct *work)
864{
865 return __find_worker_executing_work(gcwq, busy_worker_head(gcwq, work),
866 work);
867}
868
869/**
870 * gcwq_determine_ins_pos - find insertion position
871 * @gcwq: gcwq of interest
872 * @cwq: cwq a work is being queued for
873 *
874 * A work for @cwq is about to be queued on @gcwq, determine insertion
875 * position for the work. If @cwq is for HIGHPRI wq, the work is
876 * queued at the head of the queue but in FIFO order with respect to
877 * other HIGHPRI works; otherwise, at the end of the queue. This
878 * function also sets GCWQ_HIGHPRI_PENDING flag to hint @gcwq that
879 * there are HIGHPRI works pending.
880 *
881 * CONTEXT:
882 * spin_lock_irq(gcwq->lock).
883 *
884 * RETURNS:
885 * Pointer to inserstion position.
886 */
887static inline struct list_head *gcwq_determine_ins_pos(struct global_cwq *gcwq,
888 struct cpu_workqueue_struct *cwq)
889{
890 struct work_struct *twork;
891
892 if (likely(!(cwq->wq->flags & WQ_HIGHPRI)))
893 return &gcwq->worklist;
894
895 list_for_each_entry(twork, &gcwq->worklist, entry) {
896 struct cpu_workqueue_struct *tcwq = get_work_cwq(twork);
897
898 if (!(tcwq->wq->flags & WQ_HIGHPRI))
899 break;
900 }
901
902 gcwq->flags |= GCWQ_HIGHPRI_PENDING;
903 return &twork->entry;
904}
905
906/**
907 * insert_work - insert a work into gcwq
908 * @cwq: cwq @work belongs to
909 * @work: work to insert
910 * @head: insertion point
911 * @extra_flags: extra WORK_STRUCT_* flags to set
912 *
913 * Insert @work which belongs to @cwq into @gcwq after @head.
914 * @extra_flags is or'd to work_struct flags.
915 *
916 * CONTEXT:
917 * spin_lock_irq(gcwq->lock).
918 */
919static void insert_work(struct cpu_workqueue_struct *cwq,
920 struct work_struct *work, struct list_head *head,
921 unsigned int extra_flags)
922{
923 struct global_cwq *gcwq = cwq->gcwq;
924
925 /* we own @work, set data and link */
926 set_work_cwq(work, cwq, extra_flags);
927
928 /*
929 * Ensure that we get the right work->data if we see the
930 * result of list_add() below, see try_to_grab_pending().
931 */
932 smp_wmb();
933
934 list_add_tail(&work->entry, head);
935
936 /*
937 * Ensure either worker_sched_deactivated() sees the above
938 * list_add_tail() or we see zero nr_running to avoid workers
939 * lying around lazily while there are works to be processed.
940 */
941 smp_mb();
942
943 if (__need_more_worker(gcwq))
944 wake_up_worker(gcwq);
945}
946
947/*
948 * Test whether @work is being queued from another work executing on the
949 * same workqueue. This is rather expensive and should only be used from
950 * cold paths.
951 */
952static bool is_chained_work(struct workqueue_struct *wq)
953{
954 unsigned long flags;
955 unsigned int cpu;
956
957 for_each_gcwq_cpu(cpu) {
958 struct global_cwq *gcwq = get_gcwq(cpu);
959 struct worker *worker;
960 struct hlist_node *pos;
961 int i;
962
963 spin_lock_irqsave(&gcwq->lock, flags);
964 for_each_busy_worker(worker, i, pos, gcwq) {
965 if (worker->task != current)
966 continue;
967 spin_unlock_irqrestore(&gcwq->lock, flags);
968 /*
969 * I'm @worker, no locking necessary. See if @work
970 * is headed to the same workqueue.
971 */
972 return worker->current_cwq->wq == wq;
973 }
974 spin_unlock_irqrestore(&gcwq->lock, flags);
975 }
976 return false;
977}
978
979static void __queue_work(unsigned int cpu, struct workqueue_struct *wq,
980 struct work_struct *work)
981{
982 struct global_cwq *gcwq;
983 struct cpu_workqueue_struct *cwq;
984 struct list_head *worklist;
985 unsigned int work_flags;
986 unsigned long flags;
987
988 debug_work_activate(work);
989
990 /* if dying, only works from the same workqueue are allowed */
991 if (unlikely(wq->flags & WQ_DRAINING) &&
992 WARN_ON_ONCE(!is_chained_work(wq)))
993 return;
994
995 /* determine gcwq to use */
996 if (!(wq->flags & WQ_UNBOUND)) {
997 struct global_cwq *last_gcwq;
998
999 if (unlikely(cpu == WORK_CPU_UNBOUND))
1000 cpu = raw_smp_processor_id();
1001
1002 /*
1003 * It's multi cpu. If @wq is non-reentrant and @work
1004 * was previously on a different cpu, it might still
1005 * be running there, in which case the work needs to
1006 * be queued on that cpu to guarantee non-reentrance.
1007 */
1008 gcwq = get_gcwq(cpu);
1009 if (wq->flags & WQ_NON_REENTRANT &&
1010 (last_gcwq = get_work_gcwq(work)) && last_gcwq != gcwq) {
1011 struct worker *worker;
1012
1013 spin_lock_irqsave(&last_gcwq->lock, flags);
1014
1015 worker = find_worker_executing_work(last_gcwq, work);
1016
1017 if (worker && worker->current_cwq->wq == wq)
1018 gcwq = last_gcwq;
1019 else {
1020 /* meh... not running there, queue here */
1021 spin_unlock_irqrestore(&last_gcwq->lock, flags);
1022 spin_lock_irqsave(&gcwq->lock, flags);
1023 }
1024 } else
1025 spin_lock_irqsave(&gcwq->lock, flags);
1026 } else {
1027 gcwq = get_gcwq(WORK_CPU_UNBOUND);
1028 spin_lock_irqsave(&gcwq->lock, flags);
1029 }
1030
1031 /* gcwq determined, get cwq and queue */
1032 cwq = get_cwq(gcwq->cpu, wq);
1033 trace_workqueue_queue_work(cpu, cwq, work);
1034
1035 if (WARN_ON(!list_empty(&work->entry))) {
1036 spin_unlock_irqrestore(&gcwq->lock, flags);
1037 return;
1038 }
1039
1040 cwq->nr_in_flight[cwq->work_color]++;
1041 work_flags = work_color_to_flags(cwq->work_color);
1042
1043 if (likely(cwq->nr_active < cwq->max_active)) {
1044 trace_workqueue_activate_work(work);
1045 cwq->nr_active++;
1046 worklist = gcwq_determine_ins_pos(gcwq, cwq);
1047 } else {
1048 work_flags |= WORK_STRUCT_DELAYED;
1049 worklist = &cwq->delayed_works;
1050 }
1051
1052 insert_work(cwq, work, worklist, work_flags);
1053
1054 spin_unlock_irqrestore(&gcwq->lock, flags);
1055}
1056
1057/**
1058 * queue_work - queue work on a workqueue
1059 * @wq: workqueue to use
1060 * @work: work to queue
1061 *
1062 * Returns 0 if @work was already on a queue, non-zero otherwise.
1063 *
1064 * We queue the work to the CPU on which it was submitted, but if the CPU dies
1065 * it can be processed by another CPU.
1066 */
1067int queue_work(struct workqueue_struct *wq, struct work_struct *work)
1068{
1069 int ret;
1070
1071 ret = queue_work_on(get_cpu(), wq, work);
1072 put_cpu();
1073
1074 return ret;
1075}
1076EXPORT_SYMBOL_GPL(queue_work);
1077
1078/**
1079 * queue_work_on - queue work on specific cpu
1080 * @cpu: CPU number to execute work on
1081 * @wq: workqueue to use
1082 * @work: work to queue
1083 *
1084 * Returns 0 if @work was already on a queue, non-zero otherwise.
1085 *
1086 * We queue the work to a specific CPU, the caller must ensure it
1087 * can't go away.
1088 */
1089int
1090queue_work_on(int cpu, struct workqueue_struct *wq, struct work_struct *work)
1091{
1092 int ret = 0;
1093
1094 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1095 __queue_work(cpu, wq, work);
1096 ret = 1;
1097 }
1098 return ret;
1099}
1100EXPORT_SYMBOL_GPL(queue_work_on);
1101
1102static void delayed_work_timer_fn(unsigned long __data)
1103{
1104 struct delayed_work *dwork = (struct delayed_work *)__data;
1105 struct cpu_workqueue_struct *cwq = get_work_cwq(&dwork->work);
1106
1107 __queue_work(smp_processor_id(), cwq->wq, &dwork->work);
1108}
1109
1110/**
1111 * queue_delayed_work - queue work on a workqueue after delay
1112 * @wq: workqueue to use
1113 * @dwork: delayable work to queue
1114 * @delay: number of jiffies to wait before queueing
1115 *
1116 * Returns 0 if @work was already on a queue, non-zero otherwise.
1117 */
1118int queue_delayed_work(struct workqueue_struct *wq,
1119 struct delayed_work *dwork, unsigned long delay)
1120{
1121 if (delay == 0)
1122 return queue_work(wq, &dwork->work);
1123
1124 return queue_delayed_work_on(-1, wq, dwork, delay);
1125}
1126EXPORT_SYMBOL_GPL(queue_delayed_work);
1127
1128/**
1129 * queue_delayed_work_on - queue work on specific CPU after delay
1130 * @cpu: CPU number to execute work on
1131 * @wq: workqueue to use
1132 * @dwork: work to queue
1133 * @delay: number of jiffies to wait before queueing
1134 *
1135 * Returns 0 if @work was already on a queue, non-zero otherwise.
1136 */
1137int queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
1138 struct delayed_work *dwork, unsigned long delay)
1139{
1140 int ret = 0;
1141 struct timer_list *timer = &dwork->timer;
1142 struct work_struct *work = &dwork->work;
1143
1144 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1145 unsigned int lcpu;
1146
1147 BUG_ON(timer_pending(timer));
1148 BUG_ON(!list_empty(&work->entry));
1149
1150 timer_stats_timer_set_start_info(&dwork->timer);
1151
1152 /*
1153 * This stores cwq for the moment, for the timer_fn.
1154 * Note that the work's gcwq is preserved to allow
1155 * reentrance detection for delayed works.
1156 */
1157 if (!(wq->flags & WQ_UNBOUND)) {
1158 struct global_cwq *gcwq = get_work_gcwq(work);
1159
1160 if (gcwq && gcwq->cpu != WORK_CPU_UNBOUND)
1161 lcpu = gcwq->cpu;
1162 else
1163 lcpu = raw_smp_processor_id();
1164 } else
1165 lcpu = WORK_CPU_UNBOUND;
1166
1167 set_work_cwq(work, get_cwq(lcpu, wq), 0);
1168
1169 timer->expires = jiffies + delay;
1170 timer->data = (unsigned long)dwork;
1171 timer->function = delayed_work_timer_fn;
1172
1173 if (unlikely(cpu >= 0))
1174 add_timer_on(timer, cpu);
1175 else
1176 add_timer(timer);
1177 ret = 1;
1178 }
1179 return ret;
1180}
1181EXPORT_SYMBOL_GPL(queue_delayed_work_on);
1182
1183/**
1184 * worker_enter_idle - enter idle state
1185 * @worker: worker which is entering idle state
1186 *
1187 * @worker is entering idle state. Update stats and idle timer if
1188 * necessary.
1189 *
1190 * LOCKING:
1191 * spin_lock_irq(gcwq->lock).
1192 */
1193static void worker_enter_idle(struct worker *worker)
1194{
1195 struct global_cwq *gcwq = worker->gcwq;
1196
1197 BUG_ON(worker->flags & WORKER_IDLE);
1198 BUG_ON(!list_empty(&worker->entry) &&
1199 (worker->hentry.next || worker->hentry.pprev));
1200
1201 /* can't use worker_set_flags(), also called from start_worker() */
1202 worker->flags |= WORKER_IDLE;
1203 gcwq->nr_idle++;
1204 worker->last_active = jiffies;
1205
1206 /* idle_list is LIFO */
1207 list_add(&worker->entry, &gcwq->idle_list);
1208
1209 if (likely(!(worker->flags & WORKER_ROGUE))) {
1210 if (too_many_workers(gcwq) && !timer_pending(&gcwq->idle_timer))
1211 mod_timer(&gcwq->idle_timer,
1212 jiffies + IDLE_WORKER_TIMEOUT);
1213 } else
1214 wake_up_all(&gcwq->trustee_wait);
1215
1216 /*
1217 * Sanity check nr_running. Because trustee releases gcwq->lock
1218 * between setting %WORKER_ROGUE and zapping nr_running, the
1219 * warning may trigger spuriously. Check iff trustee is idle.
1220 */
1221 WARN_ON_ONCE(gcwq->trustee_state == TRUSTEE_DONE &&
1222 gcwq->nr_workers == gcwq->nr_idle &&
1223 atomic_read(get_gcwq_nr_running(gcwq->cpu)));
1224}
1225
1226/**
1227 * worker_leave_idle - leave idle state
1228 * @worker: worker which is leaving idle state
1229 *
1230 * @worker is leaving idle state. Update stats.
1231 *
1232 * LOCKING:
1233 * spin_lock_irq(gcwq->lock).
1234 */
1235static void worker_leave_idle(struct worker *worker)
1236{
1237 struct global_cwq *gcwq = worker->gcwq;
1238
1239 BUG_ON(!(worker->flags & WORKER_IDLE));
1240 worker_clr_flags(worker, WORKER_IDLE);
1241 gcwq->nr_idle--;
1242 list_del_init(&worker->entry);
1243}
1244
1245/**
1246 * worker_maybe_bind_and_lock - bind worker to its cpu if possible and lock gcwq
1247 * @worker: self
1248 *
1249 * Works which are scheduled while the cpu is online must at least be
1250 * scheduled to a worker which is bound to the cpu so that if they are
1251 * flushed from cpu callbacks while cpu is going down, they are
1252 * guaranteed to execute on the cpu.
1253 *
1254 * This function is to be used by rogue workers and rescuers to bind
1255 * themselves to the target cpu and may race with cpu going down or
1256 * coming online. kthread_bind() can't be used because it may put the
1257 * worker to already dead cpu and set_cpus_allowed_ptr() can't be used
1258 * verbatim as it's best effort and blocking and gcwq may be
1259 * [dis]associated in the meantime.
1260 *
1261 * This function tries set_cpus_allowed() and locks gcwq and verifies
1262 * the binding against GCWQ_DISASSOCIATED which is set during
1263 * CPU_DYING and cleared during CPU_ONLINE, so if the worker enters
1264 * idle state or fetches works without dropping lock, it can guarantee
1265 * the scheduling requirement described in the first paragraph.
1266 *
1267 * CONTEXT:
1268 * Might sleep. Called without any lock but returns with gcwq->lock
1269 * held.
1270 *
1271 * RETURNS:
1272 * %true if the associated gcwq is online (@worker is successfully
1273 * bound), %false if offline.
1274 */
1275static bool worker_maybe_bind_and_lock(struct worker *worker)
1276__acquires(&gcwq->lock)
1277{
1278 struct global_cwq *gcwq = worker->gcwq;
1279 struct task_struct *task = worker->task;
1280
1281 while (true) {
1282 /*
1283 * The following call may fail, succeed or succeed
1284 * without actually migrating the task to the cpu if
1285 * it races with cpu hotunplug operation. Verify
1286 * against GCWQ_DISASSOCIATED.
1287 */
1288 if (!(gcwq->flags & GCWQ_DISASSOCIATED))
1289 set_cpus_allowed_ptr(task, get_cpu_mask(gcwq->cpu));
1290
1291 spin_lock_irq(&gcwq->lock);
1292 if (gcwq->flags & GCWQ_DISASSOCIATED)
1293 return false;
1294 if (task_cpu(task) == gcwq->cpu &&
1295 cpumask_equal(¤t->cpus_allowed,
1296 get_cpu_mask(gcwq->cpu)))
1297 return true;
1298 spin_unlock_irq(&gcwq->lock);
1299
1300 /*
1301 * We've raced with CPU hot[un]plug. Give it a breather
1302 * and retry migration. cond_resched() is required here;
1303 * otherwise, we might deadlock against cpu_stop trying to
1304 * bring down the CPU on non-preemptive kernel.
1305 */
1306 cpu_relax();
1307 cond_resched();
1308 }
1309}
1310
1311/*
1312 * Function for worker->rebind_work used to rebind rogue busy workers
1313 * to the associated cpu which is coming back online. This is
1314 * scheduled by cpu up but can race with other cpu hotplug operations
1315 * and may be executed twice without intervening cpu down.
1316 */
1317static void worker_rebind_fn(struct work_struct *work)
1318{
1319 struct worker *worker = container_of(work, struct worker, rebind_work);
1320 struct global_cwq *gcwq = worker->gcwq;
1321
1322 if (worker_maybe_bind_and_lock(worker))
1323 worker_clr_flags(worker, WORKER_REBIND);
1324
1325 spin_unlock_irq(&gcwq->lock);
1326}
1327
1328static struct worker *alloc_worker(void)
1329{
1330 struct worker *worker;
1331
1332 worker = kzalloc(sizeof(*worker), GFP_KERNEL);
1333 if (worker) {
1334 INIT_LIST_HEAD(&worker->entry);
1335 INIT_LIST_HEAD(&worker->scheduled);
1336 INIT_WORK(&worker->rebind_work, worker_rebind_fn);
1337 /* on creation a worker is in !idle && prep state */
1338 worker->flags = WORKER_PREP;
1339 }
1340 return worker;
1341}
1342
1343/**
1344 * create_worker - create a new workqueue worker
1345 * @gcwq: gcwq the new worker will belong to
1346 * @bind: whether to set affinity to @cpu or not
1347 *
1348 * Create a new worker which is bound to @gcwq. The returned worker
1349 * can be started by calling start_worker() or destroyed using
1350 * destroy_worker().
1351 *
1352 * CONTEXT:
1353 * Might sleep. Does GFP_KERNEL allocations.
1354 *
1355 * RETURNS:
1356 * Pointer to the newly created worker.
1357 */
1358static struct worker *create_worker(struct global_cwq *gcwq, bool bind)
1359{
1360 bool on_unbound_cpu = gcwq->cpu == WORK_CPU_UNBOUND;
1361 struct worker *worker = NULL;
1362 int id = -1;
1363
1364 spin_lock_irq(&gcwq->lock);
1365 while (ida_get_new(&gcwq->worker_ida, &id)) {
1366 spin_unlock_irq(&gcwq->lock);
1367 if (!ida_pre_get(&gcwq->worker_ida, GFP_KERNEL))
1368 goto fail;
1369 spin_lock_irq(&gcwq->lock);
1370 }
1371 spin_unlock_irq(&gcwq->lock);
1372
1373 worker = alloc_worker();
1374 if (!worker)
1375 goto fail;
1376
1377 worker->gcwq = gcwq;
1378 worker->id = id;
1379
1380 if (!on_unbound_cpu)
1381 worker->task = kthread_create_on_node(worker_thread,
1382 worker,
1383 cpu_to_node(gcwq->cpu),
1384 "kworker/%u:%d", gcwq->cpu, id);
1385 else
1386 worker->task = kthread_create(worker_thread, worker,
1387 "kworker/u:%d", id);
1388 if (IS_ERR(worker->task))
1389 goto fail;
1390
1391 /*
1392 * A rogue worker will become a regular one if CPU comes
1393 * online later on. Make sure every worker has
1394 * PF_THREAD_BOUND set.
1395 */
1396 if (bind && !on_unbound_cpu)
1397 kthread_bind(worker->task, gcwq->cpu);
1398 else {
1399 worker->task->flags |= PF_THREAD_BOUND;
1400 if (on_unbound_cpu)
1401 worker->flags |= WORKER_UNBOUND;
1402 }
1403
1404 return worker;
1405fail:
1406 if (id >= 0) {
1407 spin_lock_irq(&gcwq->lock);
1408 ida_remove(&gcwq->worker_ida, id);
1409 spin_unlock_irq(&gcwq->lock);
1410 }
1411 kfree(worker);
1412 return NULL;
1413}
1414
1415/**
1416 * start_worker - start a newly created worker
1417 * @worker: worker to start
1418 *
1419 * Make the gcwq aware of @worker and start it.
1420 *
1421 * CONTEXT:
1422 * spin_lock_irq(gcwq->lock).
1423 */
1424static void start_worker(struct worker *worker)
1425{
1426 worker->flags |= WORKER_STARTED;
1427 worker->gcwq->nr_workers++;
1428 worker_enter_idle(worker);
1429 wake_up_process(worker->task);
1430}
1431
1432/**
1433 * destroy_worker - destroy a workqueue worker
1434 * @worker: worker to be destroyed
1435 *
1436 * Destroy @worker and adjust @gcwq stats accordingly.
1437 *
1438 * CONTEXT:
1439 * spin_lock_irq(gcwq->lock) which is released and regrabbed.
1440 */
1441static void destroy_worker(struct worker *worker)
1442{
1443 struct global_cwq *gcwq = worker->gcwq;
1444 int id = worker->id;
1445
1446 /* sanity check frenzy */
1447 BUG_ON(worker->current_work);
1448 BUG_ON(!list_empty(&worker->scheduled));
1449
1450 if (worker->flags & WORKER_STARTED)
1451 gcwq->nr_workers--;
1452 if (worker->flags & WORKER_IDLE)
1453 gcwq->nr_idle--;
1454
1455 list_del_init(&worker->entry);
1456 worker->flags |= WORKER_DIE;
1457
1458 spin_unlock_irq(&gcwq->lock);
1459
1460 kthread_stop(worker->task);
1461 kfree(worker);
1462
1463 spin_lock_irq(&gcwq->lock);
1464 ida_remove(&gcwq->worker_ida, id);
1465}
1466
1467static void idle_worker_timeout(unsigned long __gcwq)
1468{
1469 struct global_cwq *gcwq = (void *)__gcwq;
1470
1471 spin_lock_irq(&gcwq->lock);
1472
1473 if (too_many_workers(gcwq)) {
1474 struct worker *worker;
1475 unsigned long expires;
1476
1477 /* idle_list is kept in LIFO order, check the last one */
1478 worker = list_entry(gcwq->idle_list.prev, struct worker, entry);
1479 expires = worker->last_active + IDLE_WORKER_TIMEOUT;
1480
1481 if (time_before(jiffies, expires))
1482 mod_timer(&gcwq->idle_timer, expires);
1483 else {
1484 /* it's been idle for too long, wake up manager */
1485 gcwq->flags |= GCWQ_MANAGE_WORKERS;
1486 wake_up_worker(gcwq);
1487 }
1488 }
1489
1490 spin_unlock_irq(&gcwq->lock);
1491}
1492
1493static bool send_mayday(struct work_struct *work)
1494{
1495 struct cpu_workqueue_struct *cwq = get_work_cwq(work);
1496 struct workqueue_struct *wq = cwq->wq;
1497 unsigned int cpu;
1498
1499 if (!(wq->flags & WQ_RESCUER))
1500 return false;
1501
1502 /* mayday mayday mayday */
1503 cpu = cwq->gcwq->cpu;
1504 /* WORK_CPU_UNBOUND can't be set in cpumask, use cpu 0 instead */
1505 if (cpu == WORK_CPU_UNBOUND)
1506 cpu = 0;
1507 if (!mayday_test_and_set_cpu(cpu, wq->mayday_mask))
1508 wake_up_process(wq->rescuer->task);
1509 return true;
1510}
1511
1512static void gcwq_mayday_timeout(unsigned long __gcwq)
1513{
1514 struct global_cwq *gcwq = (void *)__gcwq;
1515 struct work_struct *work;
1516
1517 spin_lock_irq(&gcwq->lock);
1518
1519 if (need_to_create_worker(gcwq)) {
1520 /*
1521 * We've been trying to create a new worker but
1522 * haven't been successful. We might be hitting an
1523 * allocation deadlock. Send distress signals to
1524 * rescuers.
1525 */
1526 list_for_each_entry(work, &gcwq->worklist, entry)
1527 send_mayday(work);
1528 }
1529
1530 spin_unlock_irq(&gcwq->lock);
1531
1532 mod_timer(&gcwq->mayday_timer, jiffies + MAYDAY_INTERVAL);
1533}
1534
1535/**
1536 * maybe_create_worker - create a new worker if necessary
1537 * @gcwq: gcwq to create a new worker for
1538 *
1539 * Create a new worker for @gcwq if necessary. @gcwq is guaranteed to
1540 * have at least one idle worker on return from this function. If
1541 * creating a new worker takes longer than MAYDAY_INTERVAL, mayday is
1542 * sent to all rescuers with works scheduled on @gcwq to resolve
1543 * possible allocation deadlock.
1544 *
1545 * On return, need_to_create_worker() is guaranteed to be false and
1546 * may_start_working() true.
1547 *
1548 * LOCKING:
1549 * spin_lock_irq(gcwq->lock) which may be released and regrabbed
1550 * multiple times. Does GFP_KERNEL allocations. Called only from
1551 * manager.
1552 *
1553 * RETURNS:
1554 * false if no action was taken and gcwq->lock stayed locked, true
1555 * otherwise.
1556 */
1557static bool maybe_create_worker(struct global_cwq *gcwq)
1558__releases(&gcwq->lock)
1559__acquires(&gcwq->lock)
1560{
1561 if (!need_to_create_worker(gcwq))
1562 return false;
1563restart:
1564 spin_unlock_irq(&gcwq->lock);
1565
1566 /* if we don't make progress in MAYDAY_INITIAL_TIMEOUT, call for help */
1567 mod_timer(&gcwq->mayday_timer, jiffies + MAYDAY_INITIAL_TIMEOUT);
1568
1569 while (true) {
1570 struct worker *worker;
1571
1572 worker = create_worker(gcwq, true);
1573 if (worker) {
1574 del_timer_sync(&gcwq->mayday_timer);
1575 spin_lock_irq(&gcwq->lock);
1576 start_worker(worker);
1577 BUG_ON(need_to_create_worker(gcwq));
1578 return true;
1579 }
1580
1581 if (!need_to_create_worker(gcwq))
1582 break;
1583
1584 __set_current_state(TASK_INTERRUPTIBLE);
1585 schedule_timeout(CREATE_COOLDOWN);
1586
1587 if (!need_to_create_worker(gcwq))
1588 break;
1589 }
1590
1591 del_timer_sync(&gcwq->mayday_timer);
1592 spin_lock_irq(&gcwq->lock);
1593 if (need_to_create_worker(gcwq))
1594 goto restart;
1595 return true;
1596}
1597
1598/**
1599 * maybe_destroy_worker - destroy workers which have been idle for a while
1600 * @gcwq: gcwq to destroy workers for
1601 *
1602 * Destroy @gcwq workers which have been idle for longer than
1603 * IDLE_WORKER_TIMEOUT.
1604 *
1605 * LOCKING:
1606 * spin_lock_irq(gcwq->lock) which may be released and regrabbed
1607 * multiple times. Called only from manager.
1608 *
1609 * RETURNS:
1610 * false if no action was taken and gcwq->lock stayed locked, true
1611 * otherwise.
1612 */
1613static bool maybe_destroy_workers(struct global_cwq *gcwq)
1614{
1615 bool ret = false;
1616
1617 while (too_many_workers(gcwq)) {
1618 struct worker *worker;
1619 unsigned long expires;
1620
1621 worker = list_entry(gcwq->idle_list.prev, struct worker, entry);
1622 expires = worker->last_active + IDLE_WORKER_TIMEOUT;
1623
1624 if (time_before(jiffies, expires)) {
1625 mod_timer(&gcwq->idle_timer, expires);
1626 break;
1627 }
1628
1629 destroy_worker(worker);
1630 ret = true;
1631 }
1632
1633 return ret;
1634}
1635
1636/**
1637 * manage_workers - manage worker pool
1638 * @worker: self
1639 *
1640 * Assume the manager role and manage gcwq worker pool @worker belongs
1641 * to. At any given time, there can be only zero or one manager per
1642 * gcwq. The exclusion is handled automatically by this function.
1643 *
1644 * The caller can safely start processing works on false return. On
1645 * true return, it's guaranteed that need_to_create_worker() is false
1646 * and may_start_working() is true.
1647 *
1648 * CONTEXT:
1649 * spin_lock_irq(gcwq->lock) which may be released and regrabbed
1650 * multiple times. Does GFP_KERNEL allocations.
1651 *
1652 * RETURNS:
1653 * false if no action was taken and gcwq->lock stayed locked, true if
1654 * some action was taken.
1655 */
1656static bool manage_workers(struct worker *worker)
1657{
1658 struct global_cwq *gcwq = worker->gcwq;
1659 bool ret = false;
1660
1661 if (gcwq->flags & GCWQ_MANAGING_WORKERS)
1662 return ret;
1663
1664 gcwq->flags &= ~GCWQ_MANAGE_WORKERS;
1665 gcwq->flags |= GCWQ_MANAGING_WORKERS;
1666
1667 /*
1668 * Destroy and then create so that may_start_working() is true
1669 * on return.
1670 */
1671 ret |= maybe_destroy_workers(gcwq);
1672 ret |= maybe_create_worker(gcwq);
1673
1674 gcwq->flags &= ~GCWQ_MANAGING_WORKERS;
1675
1676 /*
1677 * The trustee might be waiting to take over the manager
1678 * position, tell it we're done.
1679 */
1680 if (unlikely(gcwq->trustee))
1681 wake_up_all(&gcwq->trustee_wait);
1682
1683 return ret;
1684}
1685
1686/**
1687 * move_linked_works - move linked works to a list
1688 * @work: start of series of works to be scheduled
1689 * @head: target list to append @work to
1690 * @nextp: out paramter for nested worklist walking
1691 *
1692 * Schedule linked works starting from @work to @head. Work series to
1693 * be scheduled starts at @work and includes any consecutive work with
1694 * WORK_STRUCT_LINKED set in its predecessor.
1695 *
1696 * If @nextp is not NULL, it's updated to point to the next work of
1697 * the last scheduled work. This allows move_linked_works() to be
1698 * nested inside outer list_for_each_entry_safe().
1699 *
1700 * CONTEXT:
1701 * spin_lock_irq(gcwq->lock).
1702 */
1703static void move_linked_works(struct work_struct *work, struct list_head *head,
1704 struct work_struct **nextp)
1705{
1706 struct work_struct *n;
1707
1708 /*
1709 * Linked worklist will always end before the end of the list,
1710 * use NULL for list head.
1711 */
1712 list_for_each_entry_safe_from(work, n, NULL, entry) {
1713 list_move_tail(&work->entry, head);
1714 if (!(*work_data_bits(work) & WORK_STRUCT_LINKED))
1715 break;
1716 }
1717
1718 /*
1719 * If we're already inside safe list traversal and have moved
1720 * multiple works to the scheduled queue, the next position
1721 * needs to be updated.
1722 */
1723 if (nextp)
1724 *nextp = n;
1725}
1726
1727static void cwq_activate_first_delayed(struct cpu_workqueue_struct *cwq)
1728{
1729 struct work_struct *work = list_first_entry(&cwq->delayed_works,
1730 struct work_struct, entry);
1731 struct list_head *pos = gcwq_determine_ins_pos(cwq->gcwq, cwq);
1732
1733 trace_workqueue_activate_work(work);
1734 move_linked_works(work, pos, NULL);
1735 __clear_bit(WORK_STRUCT_DELAYED_BIT, work_data_bits(work));
1736 cwq->nr_active++;
1737}
1738
1739/**
1740 * cwq_dec_nr_in_flight - decrement cwq's nr_in_flight
1741 * @cwq: cwq of interest
1742 * @color: color of work which left the queue
1743 * @delayed: for a delayed work
1744 *
1745 * A work either has completed or is removed from pending queue,
1746 * decrement nr_in_flight of its cwq and handle workqueue flushing.
1747 *
1748 * CONTEXT:
1749 * spin_lock_irq(gcwq->lock).
1750 */
1751static void cwq_dec_nr_in_flight(struct cpu_workqueue_struct *cwq, int color,
1752 bool delayed)
1753{
1754 /* ignore uncolored works */
1755 if (color == WORK_NO_COLOR)
1756 return;
1757
1758 cwq->nr_in_flight[color]--;
1759
1760 if (!delayed) {
1761 cwq->nr_active--;
1762 if (!list_empty(&cwq->delayed_works)) {
1763 /* one down, submit a delayed one */
1764 if (cwq->nr_active < cwq->max_active)
1765 cwq_activate_first_delayed(cwq);
1766 }
1767 }
1768
1769 /* is flush in progress and are we at the flushing tip? */
1770 if (likely(cwq->flush_color != color))
1771 return;
1772
1773 /* are there still in-flight works? */
1774 if (cwq->nr_in_flight[color])
1775 return;
1776
1777 /* this cwq is done, clear flush_color */
1778 cwq->flush_color = -1;
1779
1780 /*
1781 * If this was the last cwq, wake up the first flusher. It
1782 * will handle the rest.
1783 */
1784 if (atomic_dec_and_test(&cwq->wq->nr_cwqs_to_flush))
1785 complete(&cwq->wq->first_flusher->done);
1786}
1787
1788/**
1789 * process_one_work - process single work
1790 * @worker: self
1791 * @work: work to process
1792 *
1793 * Process @work. This function contains all the logics necessary to
1794 * process a single work including synchronization against and
1795 * interaction with other workers on the same cpu, queueing and
1796 * flushing. As long as context requirement is met, any worker can
1797 * call this function to process a work.
1798 *
1799 * CONTEXT:
1800 * spin_lock_irq(gcwq->lock) which is released and regrabbed.
1801 */
1802static void process_one_work(struct worker *worker, struct work_struct *work)
1803__releases(&gcwq->lock)
1804__acquires(&gcwq->lock)
1805{
1806 struct cpu_workqueue_struct *cwq = get_work_cwq(work);
1807 struct global_cwq *gcwq = cwq->gcwq;
1808 struct hlist_head *bwh = busy_worker_head(gcwq, work);
1809 bool cpu_intensive = cwq->wq->flags & WQ_CPU_INTENSIVE;
1810 work_func_t f = work->func;
1811 int work_color;
1812 struct worker *collision;
1813#ifdef CONFIG_LOCKDEP
1814 /*
1815 * It is permissible to free the struct work_struct from
1816 * inside the function that is called from it, this we need to
1817 * take into account for lockdep too. To avoid bogus "held
1818 * lock freed" warnings as well as problems when looking into
1819 * work->lockdep_map, make a copy and use that here.
1820 */
1821 struct lockdep_map lockdep_map;
1822
1823 lockdep_copy_map(&lockdep_map, &work->lockdep_map);
1824#endif
1825 /*
1826 * A single work shouldn't be executed concurrently by
1827 * multiple workers on a single cpu. Check whether anyone is
1828 * already processing the work. If so, defer the work to the
1829 * currently executing one.
1830 */
1831 collision = __find_worker_executing_work(gcwq, bwh, work);
1832 if (unlikely(collision)) {
1833 move_linked_works(work, &collision->scheduled, NULL);
1834 return;
1835 }
1836
1837 /* claim and process */
1838 debug_work_deactivate(work);
1839 hlist_add_head(&worker->hentry, bwh);
1840 worker->current_work = work;
1841 worker->current_cwq = cwq;
1842 work_color = get_work_color(work);
1843
1844 /* record the current cpu number in the work data and dequeue */
1845 set_work_cpu(work, gcwq->cpu);
1846 list_del_init(&work->entry);
1847
1848 /*
1849 * If HIGHPRI_PENDING, check the next work, and, if HIGHPRI,
1850 * wake up another worker; otherwise, clear HIGHPRI_PENDING.
1851 */
1852 if (unlikely(gcwq->flags & GCWQ_HIGHPRI_PENDING)) {
1853 struct work_struct *nwork = list_first_entry(&gcwq->worklist,
1854 struct work_struct, entry);
1855
1856 if (!list_empty(&gcwq->worklist) &&
1857 get_work_cwq(nwork)->wq->flags & WQ_HIGHPRI)
1858 wake_up_worker(gcwq);
1859 else
1860 gcwq->flags &= ~GCWQ_HIGHPRI_PENDING;
1861 }
1862
1863 /*
1864 * CPU intensive works don't participate in concurrency
1865 * management. They're the scheduler's responsibility.
1866 */
1867 if (unlikely(cpu_intensive))
1868 worker_set_flags(worker, WORKER_CPU_INTENSIVE, true);
1869
1870 spin_unlock_irq(&gcwq->lock);
1871
1872 work_clear_pending(work);
1873 lock_map_acquire_read(&cwq->wq->lockdep_map);
1874 lock_map_acquire(&lockdep_map);
1875 trace_workqueue_execute_start(work);
1876 f(work);
1877 /*
1878 * While we must be careful to not use "work" after this, the trace
1879 * point will only record its address.
1880 */
1881 trace_workqueue_execute_end(work);
1882 lock_map_release(&lockdep_map);
1883 lock_map_release(&cwq->wq->lockdep_map);
1884
1885 if (unlikely(in_atomic() || lockdep_depth(current) > 0)) {
1886 printk(KERN_ERR "BUG: workqueue leaked lock or atomic: "
1887 "%s/0x%08x/%d\n",
1888 current->comm, preempt_count(), task_pid_nr(current));
1889 printk(KERN_ERR " last function: ");
1890 print_symbol("%s\n", (unsigned long)f);
1891 debug_show_held_locks(current);
1892 dump_stack();
1893 }
1894
1895 spin_lock_irq(&gcwq->lock);
1896
1897 /* clear cpu intensive status */
1898 if (unlikely(cpu_intensive))
1899 worker_clr_flags(worker, WORKER_CPU_INTENSIVE);
1900
1901 /* we're done with it, release */
1902 hlist_del_init(&worker->hentry);
1903 worker->current_work = NULL;
1904 worker->current_cwq = NULL;
1905 cwq_dec_nr_in_flight(cwq, work_color, false);
1906}
1907
1908/**
1909 * process_scheduled_works - process scheduled works
1910 * @worker: self
1911 *
1912 * Process all scheduled works. Please note that the scheduled list
1913 * may change while processing a work, so this function repeatedly
1914 * fetches a work from the top and executes it.
1915 *
1916 * CONTEXT:
1917 * spin_lock_irq(gcwq->lock) which may be released and regrabbed
1918 * multiple times.
1919 */
1920static void process_scheduled_works(struct worker *worker)
1921{
1922 while (!list_empty(&worker->scheduled)) {
1923 struct work_struct *work = list_first_entry(&worker->scheduled,
1924 struct work_struct, entry);
1925 process_one_work(worker, work);
1926 }
1927}
1928
1929/**
1930 * worker_thread - the worker thread function
1931 * @__worker: self
1932 *
1933 * The gcwq worker thread function. There's a single dynamic pool of
1934 * these per each cpu. These workers process all works regardless of
1935 * their specific target workqueue. The only exception is works which
1936 * belong to workqueues with a rescuer which will be explained in
1937 * rescuer_thread().
1938 */
1939static int worker_thread(void *__worker)
1940{
1941 struct worker *worker = __worker;
1942 struct global_cwq *gcwq = worker->gcwq;
1943
1944 /* tell the scheduler that this is a workqueue worker */
1945 worker->task->flags |= PF_WQ_WORKER;
1946woke_up:
1947 spin_lock_irq(&gcwq->lock);
1948
1949 /* DIE can be set only while we're idle, checking here is enough */
1950 if (worker->flags & WORKER_DIE) {
1951 spin_unlock_irq(&gcwq->lock);
1952 worker->task->flags &= ~PF_WQ_WORKER;
1953 return 0;
1954 }
1955
1956 worker_leave_idle(worker);
1957recheck:
1958 /* no more worker necessary? */
1959 if (!need_more_worker(gcwq))
1960 goto sleep;
1961
1962 /* do we need to manage? */
1963 if (unlikely(!may_start_working(gcwq)) && manage_workers(worker))
1964 goto recheck;
1965
1966 /*
1967 * ->scheduled list can only be filled while a worker is
1968 * preparing to process a work or actually processing it.
1969 * Make sure nobody diddled with it while I was sleeping.
1970 */
1971 BUG_ON(!list_empty(&worker->scheduled));
1972
1973 /*
1974 * When control reaches this point, we're guaranteed to have
1975 * at least one idle worker or that someone else has already
1976 * assumed the manager role.
1977 */
1978 worker_clr_flags(worker, WORKER_PREP);
1979
1980 do {
1981 struct work_struct *work =
1982 list_first_entry(&gcwq->worklist,
1983 struct work_struct, entry);
1984
1985 if (likely(!(*work_data_bits(work) & WORK_STRUCT_LINKED))) {
1986 /* optimization path, not strictly necessary */
1987 process_one_work(worker, work);
1988 if (unlikely(!list_empty(&worker->scheduled)))
1989 process_scheduled_works(worker);
1990 } else {
1991 move_linked_works(work, &worker->scheduled, NULL);
1992 process_scheduled_works(worker);
1993 }
1994 } while (keep_working(gcwq));
1995
1996 worker_set_flags(worker, WORKER_PREP, false);
1997sleep:
1998 if (unlikely(need_to_manage_workers(gcwq)) && manage_workers(worker))
1999 goto recheck;
2000
2001 /*
2002 * gcwq->lock is held and there's no work to process and no
2003 * need to manage, sleep. Workers are woken up only while
2004 * holding gcwq->lock or from local cpu, so setting the
2005 * current state before releasing gcwq->lock is enough to
2006 * prevent losing any event.
2007 */
2008 worker_enter_idle(worker);
2009 __set_current_state(TASK_INTERRUPTIBLE);
2010 spin_unlock_irq(&gcwq->lock);
2011 schedule();
2012 goto woke_up;
2013}
2014
2015/**
2016 * rescuer_thread - the rescuer thread function
2017 * @__wq: the associated workqueue
2018 *
2019 * Workqueue rescuer thread function. There's one rescuer for each
2020 * workqueue which has WQ_RESCUER set.
2021 *
2022 * Regular work processing on a gcwq may block trying to create a new
2023 * worker which uses GFP_KERNEL allocation which has slight chance of
2024 * developing into deadlock if some works currently on the same queue
2025 * need to be processed to satisfy the GFP_KERNEL allocation. This is
2026 * the problem rescuer solves.
2027 *
2028 * When such condition is possible, the gcwq summons rescuers of all
2029 * workqueues which have works queued on the gcwq and let them process
2030 * those works so that forward progress can be guaranteed.
2031 *
2032 * This should happen rarely.
2033 */
2034static int rescuer_thread(void *__wq)
2035{
2036 struct workqueue_struct *wq = __wq;
2037 struct worker *rescuer = wq->rescuer;
2038 struct list_head *scheduled = &rescuer->scheduled;
2039 bool is_unbound = wq->flags & WQ_UNBOUND;
2040 unsigned int cpu;
2041
2042 set_user_nice(current, RESCUER_NICE_LEVEL);
2043repeat:
2044 set_current_state(TASK_INTERRUPTIBLE);
2045
2046 if (kthread_should_stop())
2047 return 0;
2048
2049 /*
2050 * See whether any cpu is asking for help. Unbounded
2051 * workqueues use cpu 0 in mayday_mask for CPU_UNBOUND.
2052 */
2053 for_each_mayday_cpu(cpu, wq->mayday_mask) {
2054 unsigned int tcpu = is_unbound ? WORK_CPU_UNBOUND : cpu;
2055 struct cpu_workqueue_struct *cwq = get_cwq(tcpu, wq);
2056 struct global_cwq *gcwq = cwq->gcwq;
2057 struct work_struct *work, *n;
2058
2059 __set_current_state(TASK_RUNNING);
2060 mayday_clear_cpu(cpu, wq->mayday_mask);
2061
2062 /* migrate to the target cpu if possible */
2063 rescuer->gcwq = gcwq;
2064 worker_maybe_bind_and_lock(rescuer);
2065
2066 /*
2067 * Slurp in all works issued via this workqueue and
2068 * process'em.
2069 */
2070 BUG_ON(!list_empty(&rescuer->scheduled));
2071 list_for_each_entry_safe(work, n, &gcwq->worklist, entry)
2072 if (get_work_cwq(work) == cwq)
2073 move_linked_works(work, scheduled, &n);
2074
2075 process_scheduled_works(rescuer);
2076
2077 /*
2078 * Leave this gcwq. If keep_working() is %true, notify a
2079 * regular worker; otherwise, we end up with 0 concurrency
2080 * and stalling the execution.
2081 */
2082 if (keep_working(gcwq))
2083 wake_up_worker(gcwq);
2084
2085 spin_unlock_irq(&gcwq->lock);
2086 }
2087
2088 schedule();
2089 goto repeat;
2090}
2091
2092struct wq_barrier {
2093 struct work_struct work;
2094 struct completion done;
2095};
2096
2097static void wq_barrier_func(struct work_struct *work)
2098{
2099 struct wq_barrier *barr = container_of(work, struct wq_barrier, work);
2100 complete(&barr->done);
2101}
2102
2103/**
2104 * insert_wq_barrier - insert a barrier work
2105 * @cwq: cwq to insert barrier into
2106 * @barr: wq_barrier to insert
2107 * @target: target work to attach @barr to
2108 * @worker: worker currently executing @target, NULL if @target is not executing
2109 *
2110 * @barr is linked to @target such that @barr is completed only after
2111 * @target finishes execution. Please note that the ordering
2112 * guarantee is observed only with respect to @target and on the local
2113 * cpu.
2114 *
2115 * Currently, a queued barrier can't be canceled. This is because
2116 * try_to_grab_pending() can't determine whether the work to be
2117 * grabbed is at the head of the queue and thus can't clear LINKED
2118 * flag of the previous work while there must be a valid next work
2119 * after a work with LINKED flag set.
2120 *
2121 * Note that when @worker is non-NULL, @target may be modified
2122 * underneath us, so we can't reliably determine cwq from @target.
2123 *
2124 * CONTEXT:
2125 * spin_lock_irq(gcwq->lock).
2126 */
2127static void insert_wq_barrier(struct cpu_workqueue_struct *cwq,
2128 struct wq_barrier *barr,
2129 struct work_struct *target, struct worker *worker)
2130{
2131 struct list_head *head;
2132 unsigned int linked = 0;
2133
2134 /*
2135 * debugobject calls are safe here even with gcwq->lock locked
2136 * as we know for sure that this will not trigger any of the
2137 * checks and call back into the fixup functions where we
2138 * might deadlock.
2139 */
2140 INIT_WORK_ONSTACK(&barr->work, wq_barrier_func);
2141 __set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(&barr->work));
2142 init_completion(&barr->done);
2143
2144 /*
2145 * If @target is currently being executed, schedule the
2146 * barrier to the worker; otherwise, put it after @target.
2147 */
2148 if (worker)
2149 head = worker->scheduled.next;
2150 else {
2151 unsigned long *bits = work_data_bits(target);
2152
2153 head = target->entry.next;
2154 /* there can already be other linked works, inherit and set */
2155 linked = *bits & WORK_STRUCT_LINKED;
2156 __set_bit(WORK_STRUCT_LINKED_BIT, bits);
2157 }
2158
2159 debug_work_activate(&barr->work);
2160 insert_work(cwq, &barr->work, head,
2161 work_color_to_flags(WORK_NO_COLOR) | linked);
2162}
2163
2164/**
2165 * flush_workqueue_prep_cwqs - prepare cwqs for workqueue flushing
2166 * @wq: workqueue being flushed
2167 * @flush_color: new flush color, < 0 for no-op
2168 * @work_color: new work color, < 0 for no-op
2169 *
2170 * Prepare cwqs for workqueue flushing.
2171 *
2172 * If @flush_color is non-negative, flush_color on all cwqs should be
2173 * -1. If no cwq has in-flight commands at the specified color, all
2174 * cwq->flush_color's stay at -1 and %false is returned. If any cwq
2175 * has in flight commands, its cwq->flush_color is set to
2176 * @flush_color, @wq->nr_cwqs_to_flush is updated accordingly, cwq
2177 * wakeup logic is armed and %true is returned.
2178 *
2179 * The caller should have initialized @wq->first_flusher prior to
2180 * calling this function with non-negative @flush_color. If
2181 * @flush_color is negative, no flush color update is done and %false
2182 * is returned.
2183 *
2184 * If @work_color is non-negative, all cwqs should have the same
2185 * work_color which is previous to @work_color and all will be
2186 * advanced to @work_color.
2187 *
2188 * CONTEXT:
2189 * mutex_lock(wq->flush_mutex).
2190 *
2191 * RETURNS:
2192 * %true if @flush_color >= 0 and there's something to flush. %false
2193 * otherwise.
2194 */
2195static bool flush_workqueue_prep_cwqs(struct workqueue_struct *wq,
2196 int flush_color, int work_color)
2197{
2198 bool wait = false;
2199 unsigned int cpu;
2200
2201 if (flush_color >= 0) {
2202 BUG_ON(atomic_read(&wq->nr_cwqs_to_flush));
2203 atomic_set(&wq->nr_cwqs_to_flush, 1);
2204 }
2205
2206 for_each_cwq_cpu(cpu, wq) {
2207 struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
2208 struct global_cwq *gcwq = cwq->gcwq;
2209
2210 spin_lock_irq(&gcwq->lock);
2211
2212 if (flush_color >= 0) {
2213 BUG_ON(cwq->flush_color != -1);
2214
2215 if (cwq->nr_in_flight[flush_color]) {
2216 cwq->flush_color = flush_color;
2217 atomic_inc(&wq->nr_cwqs_to_flush);
2218 wait = true;
2219 }
2220 }
2221
2222 if (work_color >= 0) {
2223 BUG_ON(work_color != work_next_color(cwq->work_color));
2224 cwq->work_color = work_color;
2225 }
2226
2227 spin_unlock_irq(&gcwq->lock);
2228 }
2229
2230 if (flush_color >= 0 && atomic_dec_and_test(&wq->nr_cwqs_to_flush))
2231 complete(&wq->first_flusher->done);
2232
2233 return wait;
2234}
2235
2236/**
2237 * flush_workqueue - ensure that any scheduled work has run to completion.
2238 * @wq: workqueue to flush
2239 *
2240 * Forces execution of the workqueue and blocks until its completion.
2241 * This is typically used in driver shutdown handlers.
2242 *
2243 * We sleep until all works which were queued on entry have been handled,
2244 * but we are not livelocked by new incoming ones.
2245 */
2246void flush_workqueue(struct workqueue_struct *wq)
2247{
2248 struct wq_flusher this_flusher = {
2249 .list = LIST_HEAD_INIT(this_flusher.list),
2250 .flush_color = -1,
2251 .done = COMPLETION_INITIALIZER_ONSTACK(this_flusher.done),
2252 };
2253 int next_color;
2254
2255 lock_map_acquire(&wq->lockdep_map);
2256 lock_map_release(&wq->lockdep_map);
2257
2258 mutex_lock(&wq->flush_mutex);
2259
2260 /*
2261 * Start-to-wait phase
2262 */
2263 next_color = work_next_color(wq->work_color);
2264
2265 if (next_color != wq->flush_color) {
2266 /*
2267 * Color space is not full. The current work_color
2268 * becomes our flush_color and work_color is advanced
2269 * by one.
2270 */
2271 BUG_ON(!list_empty(&wq->flusher_overflow));
2272 this_flusher.flush_color = wq->work_color;
2273 wq->work_color = next_color;
2274
2275 if (!wq->first_flusher) {
2276 /* no flush in progress, become the first flusher */
2277 BUG_ON(wq->flush_color != this_flusher.flush_color);
2278
2279 wq->first_flusher = &this_flusher;
2280
2281 if (!flush_workqueue_prep_cwqs(wq, wq->flush_color,
2282 wq->work_color)) {
2283 /* nothing to flush, done */
2284 wq->flush_color = next_color;
2285 wq->first_flusher = NULL;
2286 goto out_unlock;
2287 }
2288 } else {
2289 /* wait in queue */
2290 BUG_ON(wq->flush_color == this_flusher.flush_color);
2291 list_add_tail(&this_flusher.list, &wq->flusher_queue);
2292 flush_workqueue_prep_cwqs(wq, -1, wq->work_color);
2293 }
2294 } else {
2295 /*
2296 * Oops, color space is full, wait on overflow queue.
2297 * The next flush completion will assign us
2298 * flush_color and transfer to flusher_queue.
2299 */
2300 list_add_tail(&this_flusher.list, &wq->flusher_overflow);
2301 }
2302
2303 mutex_unlock(&wq->flush_mutex);
2304
2305 wait_for_completion(&this_flusher.done);
2306
2307 /*
2308 * Wake-up-and-cascade phase
2309 *
2310 * First flushers are responsible for cascading flushes and
2311 * handling overflow. Non-first flushers can simply return.
2312 */
2313 if (wq->first_flusher != &this_flusher)
2314 return;
2315
2316 mutex_lock(&wq->flush_mutex);
2317
2318 /* we might have raced, check again with mutex held */
2319 if (wq->first_flusher != &this_flusher)
2320 goto out_unlock;
2321
2322 wq->first_flusher = NULL;
2323
2324 BUG_ON(!list_empty(&this_flusher.list));
2325 BUG_ON(wq->flush_color != this_flusher.flush_color);
2326
2327 while (true) {
2328 struct wq_flusher *next, *tmp;
2329
2330 /* complete all the flushers sharing the current flush color */
2331 list_for_each_entry_safe(next, tmp, &wq->flusher_queue, list) {
2332 if (next->flush_color != wq->flush_color)
2333 break;
2334 list_del_init(&next->list);
2335 complete(&next->done);
2336 }
2337
2338 BUG_ON(!list_empty(&wq->flusher_overflow) &&
2339 wq->flush_color != work_next_color(wq->work_color));
2340
2341 /* this flush_color is finished, advance by one */
2342 wq->flush_color = work_next_color(wq->flush_color);
2343
2344 /* one color has been freed, handle overflow queue */
2345 if (!list_empty(&wq->flusher_overflow)) {
2346 /*
2347 * Assign the same color to all overflowed
2348 * flushers, advance work_color and append to
2349 * flusher_queue. This is the start-to-wait
2350 * phase for these overflowed flushers.
2351 */
2352 list_for_each_entry(tmp, &wq->flusher_overflow, list)
2353 tmp->flush_color = wq->work_color;
2354
2355 wq->work_color = work_next_color(wq->work_color);
2356
2357 list_splice_tail_init(&wq->flusher_overflow,
2358 &wq->flusher_queue);
2359 flush_workqueue_prep_cwqs(wq, -1, wq->work_color);
2360 }
2361
2362 if (list_empty(&wq->flusher_queue)) {
2363 BUG_ON(wq->flush_color != wq->work_color);
2364 break;
2365 }
2366
2367 /*
2368 * Need to flush more colors. Make the next flusher
2369 * the new first flusher and arm cwqs.
2370 */
2371 BUG_ON(wq->flush_color == wq->work_color);
2372 BUG_ON(wq->flush_color != next->flush_color);
2373
2374 list_del_init(&next->list);
2375 wq->first_flusher = next;
2376
2377 if (flush_workqueue_prep_cwqs(wq, wq->flush_color, -1))
2378 break;
2379
2380 /*
2381 * Meh... this color is already done, clear first
2382 * flusher and repeat cascading.
2383 */
2384 wq->first_flusher = NULL;
2385 }
2386
2387out_unlock:
2388 mutex_unlock(&wq->flush_mutex);
2389}
2390EXPORT_SYMBOL_GPL(flush_workqueue);
2391
2392/**
2393 * drain_workqueue - drain a workqueue
2394 * @wq: workqueue to drain
2395 *
2396 * Wait until the workqueue becomes empty. While draining is in progress,
2397 * only chain queueing is allowed. IOW, only currently pending or running
2398 * work items on @wq can queue further work items on it. @wq is flushed
2399 * repeatedly until it becomes empty. The number of flushing is detemined
2400 * by the depth of chaining and should be relatively short. Whine if it
2401 * takes too long.
2402 */
2403void drain_workqueue(struct workqueue_struct *wq)
2404{
2405 unsigned int flush_cnt = 0;
2406 unsigned int cpu;
2407
2408 /*
2409 * __queue_work() needs to test whether there are drainers, is much
2410 * hotter than drain_workqueue() and already looks at @wq->flags.
2411 * Use WQ_DRAINING so that queue doesn't have to check nr_drainers.
2412 */
2413 spin_lock(&workqueue_lock);
2414 if (!wq->nr_drainers++)
2415 wq->flags |= WQ_DRAINING;
2416 spin_unlock(&workqueue_lock);
2417reflush:
2418 flush_workqueue(wq);
2419
2420 for_each_cwq_cpu(cpu, wq) {
2421 struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
2422 bool drained;
2423
2424 spin_lock_irq(&cwq->gcwq->lock);
2425 drained = !cwq->nr_active && list_empty(&cwq->delayed_works);
2426 spin_unlock_irq(&cwq->gcwq->lock);
2427
2428 if (drained)
2429 continue;
2430
2431 if (++flush_cnt == 10 ||
2432 (flush_cnt % 100 == 0 && flush_cnt <= 1000))
2433 pr_warning("workqueue %s: flush on destruction isn't complete after %u tries\n",
2434 wq->name, flush_cnt);
2435 goto reflush;
2436 }
2437
2438 spin_lock(&workqueue_lock);
2439 if (!--wq->nr_drainers)
2440 wq->flags &= ~WQ_DRAINING;
2441 spin_unlock(&workqueue_lock);
2442}
2443EXPORT_SYMBOL_GPL(drain_workqueue);
2444
2445static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr,
2446 bool wait_executing)
2447{
2448 struct worker *worker = NULL;
2449 struct global_cwq *gcwq;
2450 struct cpu_workqueue_struct *cwq;
2451
2452 might_sleep();
2453 gcwq = get_work_gcwq(work);
2454 if (!gcwq)
2455 return false;
2456
2457 spin_lock_irq(&gcwq->lock);
2458 if (!list_empty(&work->entry)) {
2459 /*
2460 * See the comment near try_to_grab_pending()->smp_rmb().
2461 * If it was re-queued to a different gcwq under us, we
2462 * are not going to wait.
2463 */
2464 smp_rmb();
2465 cwq = get_work_cwq(work);
2466 if (unlikely(!cwq || gcwq != cwq->gcwq))
2467 goto already_gone;
2468 } else if (wait_executing) {
2469 worker = find_worker_executing_work(gcwq, work);
2470 if (!worker)
2471 goto already_gone;
2472 cwq = worker->current_cwq;
2473 } else
2474 goto already_gone;
2475
2476 insert_wq_barrier(cwq, barr, work, worker);
2477 spin_unlock_irq(&gcwq->lock);
2478
2479 /*
2480 * If @max_active is 1 or rescuer is in use, flushing another work
2481 * item on the same workqueue may lead to deadlock. Make sure the
2482 * flusher is not running on the same workqueue by verifying write
2483 * access.
2484 */
2485 if (cwq->wq->saved_max_active == 1 || cwq->wq->flags & WQ_RESCUER)
2486 lock_map_acquire(&cwq->wq->lockdep_map);
2487 else
2488 lock_map_acquire_read(&cwq->wq->lockdep_map);
2489 lock_map_release(&cwq->wq->lockdep_map);
2490
2491 return true;
2492already_gone:
2493 spin_unlock_irq(&gcwq->lock);
2494 return false;
2495}
2496
2497/**
2498 * flush_work - wait for a work to finish executing the last queueing instance
2499 * @work: the work to flush
2500 *
2501 * Wait until @work has finished execution. This function considers
2502 * only the last queueing instance of @work. If @work has been
2503 * enqueued across different CPUs on a non-reentrant workqueue or on
2504 * multiple workqueues, @work might still be executing on return on
2505 * some of the CPUs from earlier queueing.
2506 *
2507 * If @work was queued only on a non-reentrant, ordered or unbound
2508 * workqueue, @work is guaranteed to be idle on return if it hasn't
2509 * been requeued since flush started.
2510 *
2511 * RETURNS:
2512 * %true if flush_work() waited for the work to finish execution,
2513 * %false if it was already idle.
2514 */
2515bool flush_work(struct work_struct *work)
2516{
2517 struct wq_barrier barr;
2518
2519 lock_map_acquire(&work->lockdep_map);
2520 lock_map_release(&work->lockdep_map);
2521
2522 if (start_flush_work(work, &barr, true)) {
2523 wait_for_completion(&barr.done);
2524 destroy_work_on_stack(&barr.work);
2525 return true;
2526 } else
2527 return false;
2528}
2529EXPORT_SYMBOL_GPL(flush_work);
2530
2531static bool wait_on_cpu_work(struct global_cwq *gcwq, struct work_struct *work)
2532{
2533 struct wq_barrier barr;
2534 struct worker *worker;
2535
2536 spin_lock_irq(&gcwq->lock);
2537
2538 worker = find_worker_executing_work(gcwq, work);
2539 if (unlikely(worker))
2540 insert_wq_barrier(worker->current_cwq, &barr, work, worker);
2541
2542 spin_unlock_irq(&gcwq->lock);
2543
2544 if (unlikely(worker)) {
2545 wait_for_completion(&barr.done);
2546 destroy_work_on_stack(&barr.work);
2547 return true;
2548 } else
2549 return false;
2550}
2551
2552static bool wait_on_work(struct work_struct *work)
2553{
2554 bool ret = false;
2555 int cpu;
2556
2557 might_sleep();
2558
2559 lock_map_acquire(&work->lockdep_map);
2560 lock_map_release(&work->lockdep_map);
2561
2562 for_each_gcwq_cpu(cpu)
2563 ret |= wait_on_cpu_work(get_gcwq(cpu), work);
2564 return ret;
2565}
2566
2567/**
2568 * flush_work_sync - wait until a work has finished execution
2569 * @work: the work to flush
2570 *
2571 * Wait until @work has finished execution. On return, it's
2572 * guaranteed that all queueing instances of @work which happened
2573 * before this function is called are finished. In other words, if
2574 * @work hasn't been requeued since this function was called, @work is
2575 * guaranteed to be idle on return.
2576 *
2577 * RETURNS:
2578 * %true if flush_work_sync() waited for the work to finish execution,
2579 * %false if it was already idle.
2580 */
2581bool flush_work_sync(struct work_struct *work)
2582{
2583 struct wq_barrier barr;
2584 bool pending, waited;
2585
2586 /* we'll wait for executions separately, queue barr only if pending */
2587 pending = start_flush_work(work, &barr, false);
2588
2589 /* wait for executions to finish */
2590 waited = wait_on_work(work);
2591
2592 /* wait for the pending one */
2593 if (pending) {
2594 wait_for_completion(&barr.done);
2595 destroy_work_on_stack(&barr.work);
2596 }
2597
2598 return pending || waited;
2599}
2600EXPORT_SYMBOL_GPL(flush_work_sync);
2601
2602/*
2603 * Upon a successful return (>= 0), the caller "owns" WORK_STRUCT_PENDING bit,
2604 * so this work can't be re-armed in any way.
2605 */
2606static int try_to_grab_pending(struct work_struct *work)
2607{
2608 struct global_cwq *gcwq;
2609 int ret = -1;
2610
2611 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work)))
2612 return 0;
2613
2614 /*
2615 * The queueing is in progress, or it is already queued. Try to
2616 * steal it from ->worklist without clearing WORK_STRUCT_PENDING.
2617 */
2618 gcwq = get_work_gcwq(work);
2619 if (!gcwq)
2620 return ret;
2621
2622 spin_lock_irq(&gcwq->lock);
2623 if (!list_empty(&work->entry)) {
2624 /*
2625 * This work is queued, but perhaps we locked the wrong gcwq.
2626 * In that case we must see the new value after rmb(), see
2627 * insert_work()->wmb().
2628 */
2629 smp_rmb();
2630 if (gcwq == get_work_gcwq(work)) {
2631 debug_work_deactivate(work);
2632 list_del_init(&work->entry);
2633 cwq_dec_nr_in_flight(get_work_cwq(work),
2634 get_work_color(work),
2635 *work_data_bits(work) & WORK_STRUCT_DELAYED);
2636 ret = 1;
2637 }
2638 }
2639 spin_unlock_irq(&gcwq->lock);
2640
2641 return ret;
2642}
2643
2644static bool __cancel_work_timer(struct work_struct *work,
2645 struct timer_list* timer)
2646{
2647 int ret;
2648
2649 do {
2650 ret = (timer && likely(del_timer(timer)));
2651 if (!ret)
2652 ret = try_to_grab_pending(work);
2653 wait_on_work(work);
2654 } while (unlikely(ret < 0));
2655
2656 clear_work_data(work);
2657 return ret;
2658}
2659
2660/**
2661 * cancel_work_sync - cancel a work and wait for it to finish
2662 * @work: the work to cancel
2663 *
2664 * Cancel @work and wait for its execution to finish. This function
2665 * can be used even if the work re-queues itself or migrates to
2666 * another workqueue. On return from this function, @work is
2667 * guaranteed to be not pending or executing on any CPU.
2668 *
2669 * cancel_work_sync(&delayed_work->work) must not be used for
2670 * delayed_work's. Use cancel_delayed_work_sync() instead.
2671 *
2672 * The caller must ensure that the workqueue on which @work was last
2673 * queued can't be destroyed before this function returns.
2674 *
2675 * RETURNS:
2676 * %true if @work was pending, %false otherwise.
2677 */
2678bool cancel_work_sync(struct work_struct *work)
2679{
2680 return __cancel_work_timer(work, NULL);
2681}
2682EXPORT_SYMBOL_GPL(cancel_work_sync);
2683
2684/**
2685 * flush_delayed_work - wait for a dwork to finish executing the last queueing
2686 * @dwork: the delayed work to flush
2687 *
2688 * Delayed timer is cancelled and the pending work is queued for
2689 * immediate execution. Like flush_work(), this function only
2690 * considers the last queueing instance of @dwork.
2691 *
2692 * RETURNS:
2693 * %true if flush_work() waited for the work to finish execution,
2694 * %false if it was already idle.
2695 */
2696bool flush_delayed_work(struct delayed_work *dwork)
2697{
2698 if (del_timer_sync(&dwork->timer))
2699 __queue_work(raw_smp_processor_id(),
2700 get_work_cwq(&dwork->work)->wq, &dwork->work);
2701 return flush_work(&dwork->work);
2702}
2703EXPORT_SYMBOL(flush_delayed_work);
2704
2705/**
2706 * flush_delayed_work_sync - wait for a dwork to finish
2707 * @dwork: the delayed work to flush
2708 *
2709 * Delayed timer is cancelled and the pending work is queued for
2710 * execution immediately. Other than timer handling, its behavior
2711 * is identical to flush_work_sync().
2712 *
2713 * RETURNS:
2714 * %true if flush_work_sync() waited for the work to finish execution,
2715 * %false if it was already idle.
2716 */
2717bool flush_delayed_work_sync(struct delayed_work *dwork)
2718{
2719 if (del_timer_sync(&dwork->timer))
2720 __queue_work(raw_smp_processor_id(),
2721 get_work_cwq(&dwork->work)->wq, &dwork->work);
2722 return flush_work_sync(&dwork->work);
2723}
2724EXPORT_SYMBOL(flush_delayed_work_sync);
2725
2726/**
2727 * cancel_delayed_work_sync - cancel a delayed work and wait for it to finish
2728 * @dwork: the delayed work cancel
2729 *
2730 * This is cancel_work_sync() for delayed works.
2731 *
2732 * RETURNS:
2733 * %true if @dwork was pending, %false otherwise.
2734 */
2735bool cancel_delayed_work_sync(struct delayed_work *dwork)
2736{
2737 return __cancel_work_timer(&dwork->work, &dwork->timer);
2738}
2739EXPORT_SYMBOL(cancel_delayed_work_sync);
2740
2741/**
2742 * schedule_work - put work task in global workqueue
2743 * @work: job to be done
2744 *
2745 * Returns zero if @work was already on the kernel-global workqueue and
2746 * non-zero otherwise.
2747 *
2748 * This puts a job in the kernel-global workqueue if it was not already
2749 * queued and leaves it in the same position on the kernel-global
2750 * workqueue otherwise.
2751 */
2752int schedule_work(struct work_struct *work)
2753{
2754 return queue_work(system_wq, work);
2755}
2756EXPORT_SYMBOL(schedule_work);
2757
2758/*
2759 * schedule_work_on - put work task on a specific cpu
2760 * @cpu: cpu to put the work task on
2761 * @work: job to be done
2762 *
2763 * This puts a job on a specific cpu
2764 */
2765int schedule_work_on(int cpu, struct work_struct *work)
2766{
2767 return queue_work_on(cpu, system_wq, work);
2768}
2769EXPORT_SYMBOL(schedule_work_on);
2770
2771/**
2772 * schedule_delayed_work - put work task in global workqueue after delay
2773 * @dwork: job to be done
2774 * @delay: number of jiffies to wait or 0 for immediate execution
2775 *
2776 * After waiting for a given time this puts a job in the kernel-global
2777 * workqueue.
2778 */
2779int schedule_delayed_work(struct delayed_work *dwork,
2780 unsigned long delay)
2781{
2782 return queue_delayed_work(system_wq, dwork, delay);
2783}
2784EXPORT_SYMBOL(schedule_delayed_work);
2785
2786/**
2787 * schedule_delayed_work_on - queue work in global workqueue on CPU after delay
2788 * @cpu: cpu to use
2789 * @dwork: job to be done
2790 * @delay: number of jiffies to wait
2791 *
2792 * After waiting for a given time this puts a job in the kernel-global
2793 * workqueue on the specified CPU.
2794 */
2795int schedule_delayed_work_on(int cpu,
2796 struct delayed_work *dwork, unsigned long delay)
2797{
2798 return queue_delayed_work_on(cpu, system_wq, dwork, delay);
2799}
2800EXPORT_SYMBOL(schedule_delayed_work_on);
2801
2802/**
2803 * schedule_on_each_cpu - execute a function synchronously on each online CPU
2804 * @func: the function to call
2805 *
2806 * schedule_on_each_cpu() executes @func on each online CPU using the
2807 * system workqueue and blocks until all CPUs have completed.
2808 * schedule_on_each_cpu() is very slow.
2809 *
2810 * RETURNS:
2811 * 0 on success, -errno on failure.
2812 */
2813int schedule_on_each_cpu(work_func_t func)
2814{
2815 int cpu;
2816 struct work_struct __percpu *works;
2817
2818 works = alloc_percpu(struct work_struct);
2819 if (!works)
2820 return -ENOMEM;
2821
2822 get_online_cpus();
2823
2824 for_each_online_cpu(cpu) {
2825 struct work_struct *work = per_cpu_ptr(works, cpu);
2826
2827 INIT_WORK(work, func);
2828 schedule_work_on(cpu, work);
2829 }
2830
2831 for_each_online_cpu(cpu)
2832 flush_work(per_cpu_ptr(works, cpu));
2833
2834 put_online_cpus();
2835 free_percpu(works);
2836 return 0;
2837}
2838
2839/**
2840 * flush_scheduled_work - ensure that any scheduled work has run to completion.
2841 *
2842 * Forces execution of the kernel-global workqueue and blocks until its
2843 * completion.
2844 *
2845 * Think twice before calling this function! It's very easy to get into
2846 * trouble if you don't take great care. Either of the following situations
2847 * will lead to deadlock:
2848 *
2849 * One of the work items currently on the workqueue needs to acquire
2850 * a lock held by your code or its caller.
2851 *
2852 * Your code is running in the context of a work routine.
2853 *
2854 * They will be detected by lockdep when they occur, but the first might not
2855 * occur very often. It depends on what work items are on the workqueue and
2856 * what locks they need, which you have no control over.
2857 *
2858 * In most situations flushing the entire workqueue is overkill; you merely
2859 * need to know that a particular work item isn't queued and isn't running.
2860 * In such cases you should use cancel_delayed_work_sync() or
2861 * cancel_work_sync() instead.
2862 */
2863void flush_scheduled_work(void)
2864{
2865 flush_workqueue(system_wq);
2866}
2867EXPORT_SYMBOL(flush_scheduled_work);
2868
2869/**
2870 * execute_in_process_context - reliably execute the routine with user context
2871 * @fn: the function to execute
2872 * @ew: guaranteed storage for the execute work structure (must
2873 * be available when the work executes)
2874 *
2875 * Executes the function immediately if process context is available,
2876 * otherwise schedules the function for delayed execution.
2877 *
2878 * Returns: 0 - function was executed
2879 * 1 - function was scheduled for execution
2880 */
2881int execute_in_process_context(work_func_t fn, struct execute_work *ew)
2882{
2883 if (!in_interrupt()) {
2884 fn(&ew->work);
2885 return 0;
2886 }
2887
2888 INIT_WORK(&ew->work, fn);
2889 schedule_work(&ew->work);
2890
2891 return 1;
2892}
2893EXPORT_SYMBOL_GPL(execute_in_process_context);
2894
2895int keventd_up(void)
2896{
2897 return system_wq != NULL;
2898}
2899
2900static int alloc_cwqs(struct workqueue_struct *wq)
2901{
2902 /*
2903 * cwqs are forced aligned according to WORK_STRUCT_FLAG_BITS.
2904 * Make sure that the alignment isn't lower than that of
2905 * unsigned long long.
2906 */
2907 const size_t size = sizeof(struct cpu_workqueue_struct);
2908 const size_t align = max_t(size_t, 1 << WORK_STRUCT_FLAG_BITS,
2909 __alignof__(unsigned long long));
2910
2911 if (!(wq->flags & WQ_UNBOUND))
2912 wq->cpu_wq.pcpu = __alloc_percpu(size, align);
2913 else {
2914 void *ptr;
2915
2916 /*
2917 * Allocate enough room to align cwq and put an extra
2918 * pointer at the end pointing back to the originally
2919 * allocated pointer which will be used for free.
2920 */
2921 ptr = kzalloc(size + align + sizeof(void *), GFP_KERNEL);
2922 if (ptr) {
2923 wq->cpu_wq.single = PTR_ALIGN(ptr, align);
2924 *(void **)(wq->cpu_wq.single + 1) = ptr;
2925 }
2926 }
2927
2928 /* just in case, make sure it's actually aligned */
2929 BUG_ON(!IS_ALIGNED(wq->cpu_wq.v, align));
2930 return wq->cpu_wq.v ? 0 : -ENOMEM;
2931}
2932
2933static void free_cwqs(struct workqueue_struct *wq)
2934{
2935 if (!(wq->flags & WQ_UNBOUND))
2936 free_percpu(wq->cpu_wq.pcpu);
2937 else if (wq->cpu_wq.single) {
2938 /* the pointer to free is stored right after the cwq */
2939 kfree(*(void **)(wq->cpu_wq.single + 1));
2940 }
2941}
2942
2943static int wq_clamp_max_active(int max_active, unsigned int flags,
2944 const char *name)
2945{
2946 int lim = flags & WQ_UNBOUND ? WQ_UNBOUND_MAX_ACTIVE : WQ_MAX_ACTIVE;
2947
2948 if (max_active < 1 || max_active > lim)
2949 printk(KERN_WARNING "workqueue: max_active %d requested for %s "
2950 "is out of range, clamping between %d and %d\n",
2951 max_active, name, 1, lim);
2952
2953 return clamp_val(max_active, 1, lim);
2954}
2955
2956struct workqueue_struct *__alloc_workqueue_key(const char *fmt,
2957 unsigned int flags,
2958 int max_active,
2959 struct lock_class_key *key,
2960 const char *lock_name, ...)
2961{
2962 va_list args, args1;
2963 struct workqueue_struct *wq;
2964 unsigned int cpu;
2965 size_t namelen;
2966
2967 /* determine namelen, allocate wq and format name */
2968 va_start(args, lock_name);
2969 va_copy(args1, args);
2970 namelen = vsnprintf(NULL, 0, fmt, args) + 1;
2971
2972 wq = kzalloc(sizeof(*wq) + namelen, GFP_KERNEL);
2973 if (!wq)
2974 goto err;
2975
2976 vsnprintf(wq->name, namelen, fmt, args1);
2977 va_end(args);
2978 va_end(args1);
2979
2980 /*
2981 * Workqueues which may be used during memory reclaim should
2982 * have a rescuer to guarantee forward progress.
2983 */
2984 if (flags & WQ_MEM_RECLAIM)
2985 flags |= WQ_RESCUER;
2986
2987 /*
2988 * Unbound workqueues aren't concurrency managed and should be
2989 * dispatched to workers immediately.
2990 */
2991 if (flags & WQ_UNBOUND)
2992 flags |= WQ_HIGHPRI;
2993
2994 max_active = max_active ?: WQ_DFL_ACTIVE;
2995 max_active = wq_clamp_max_active(max_active, flags, wq->name);
2996
2997 /* init wq */
2998 wq->flags = flags;
2999 wq->saved_max_active = max_active;
3000 mutex_init(&wq->flush_mutex);
3001 atomic_set(&wq->nr_cwqs_to_flush, 0);
3002 INIT_LIST_HEAD(&wq->flusher_queue);
3003 INIT_LIST_HEAD(&wq->flusher_overflow);
3004
3005 lockdep_init_map(&wq->lockdep_map, lock_name, key, 0);
3006 INIT_LIST_HEAD(&wq->list);
3007
3008 if (alloc_cwqs(wq) < 0)
3009 goto err;
3010
3011 for_each_cwq_cpu(cpu, wq) {
3012 struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
3013 struct global_cwq *gcwq = get_gcwq(cpu);
3014
3015 BUG_ON((unsigned long)cwq & WORK_STRUCT_FLAG_MASK);
3016 cwq->gcwq = gcwq;
3017 cwq->wq = wq;
3018 cwq->flush_color = -1;
3019 cwq->max_active = max_active;
3020 INIT_LIST_HEAD(&cwq->delayed_works);
3021 }
3022
3023 if (flags & WQ_RESCUER) {
3024 struct worker *rescuer;
3025
3026 if (!alloc_mayday_mask(&wq->mayday_mask, GFP_KERNEL))
3027 goto err;
3028
3029 wq->rescuer = rescuer = alloc_worker();
3030 if (!rescuer)
3031 goto err;
3032
3033 rescuer->task = kthread_create(rescuer_thread, wq, "%s",
3034 wq->name);
3035 if (IS_ERR(rescuer->task))
3036 goto err;
3037
3038 rescuer->task->flags |= PF_THREAD_BOUND;
3039 wake_up_process(rescuer->task);
3040 }
3041
3042 /*
3043 * workqueue_lock protects global freeze state and workqueues
3044 * list. Grab it, set max_active accordingly and add the new
3045 * workqueue to workqueues list.
3046 */
3047 spin_lock(&workqueue_lock);
3048
3049 if (workqueue_freezing && wq->flags & WQ_FREEZABLE)
3050 for_each_cwq_cpu(cpu, wq)
3051 get_cwq(cpu, wq)->max_active = 0;
3052
3053 list_add(&wq->list, &workqueues);
3054
3055 spin_unlock(&workqueue_lock);
3056
3057 return wq;
3058err:
3059 if (wq) {
3060 free_cwqs(wq);
3061 free_mayday_mask(wq->mayday_mask);
3062 kfree(wq->rescuer);
3063 kfree(wq);
3064 }
3065 return NULL;
3066}
3067EXPORT_SYMBOL_GPL(__alloc_workqueue_key);
3068
3069/**
3070 * destroy_workqueue - safely terminate a workqueue
3071 * @wq: target workqueue
3072 *
3073 * Safely destroy a workqueue. All work currently pending will be done first.
3074 */
3075void destroy_workqueue(struct workqueue_struct *wq)
3076{
3077 unsigned int cpu;
3078
3079 /* drain it before proceeding with destruction */
3080 drain_workqueue(wq);
3081
3082 /*
3083 * wq list is used to freeze wq, remove from list after
3084 * flushing is complete in case freeze races us.
3085 */
3086 spin_lock(&workqueue_lock);
3087 list_del(&wq->list);
3088 spin_unlock(&workqueue_lock);
3089
3090 /* sanity check */
3091 for_each_cwq_cpu(cpu, wq) {
3092 struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
3093 int i;
3094
3095 for (i = 0; i < WORK_NR_COLORS; i++)
3096 BUG_ON(cwq->nr_in_flight[i]);
3097 BUG_ON(cwq->nr_active);
3098 BUG_ON(!list_empty(&cwq->delayed_works));
3099 }
3100
3101 if (wq->flags & WQ_RESCUER) {
3102 kthread_stop(wq->rescuer->task);
3103 free_mayday_mask(wq->mayday_mask);
3104 kfree(wq->rescuer);
3105 }
3106
3107 free_cwqs(wq);
3108 kfree(wq);
3109}
3110EXPORT_SYMBOL_GPL(destroy_workqueue);
3111
3112/**
3113 * workqueue_set_max_active - adjust max_active of a workqueue
3114 * @wq: target workqueue
3115 * @max_active: new max_active value.
3116 *
3117 * Set max_active of @wq to @max_active.
3118 *
3119 * CONTEXT:
3120 * Don't call from IRQ context.
3121 */
3122void workqueue_set_max_active(struct workqueue_struct *wq, int max_active)
3123{
3124 unsigned int cpu;
3125
3126 max_active = wq_clamp_max_active(max_active, wq->flags, wq->name);
3127
3128 spin_lock(&workqueue_lock);
3129
3130 wq->saved_max_active = max_active;
3131
3132 for_each_cwq_cpu(cpu, wq) {
3133 struct global_cwq *gcwq = get_gcwq(cpu);
3134
3135 spin_lock_irq(&gcwq->lock);
3136
3137 if (!(wq->flags & WQ_FREEZABLE) ||
3138 !(gcwq->flags & GCWQ_FREEZING))
3139 get_cwq(gcwq->cpu, wq)->max_active = max_active;
3140
3141 spin_unlock_irq(&gcwq->lock);
3142 }
3143
3144 spin_unlock(&workqueue_lock);
3145}
3146EXPORT_SYMBOL_GPL(workqueue_set_max_active);
3147
3148/**
3149 * workqueue_congested - test whether a workqueue is congested
3150 * @cpu: CPU in question
3151 * @wq: target workqueue
3152 *
3153 * Test whether @wq's cpu workqueue for @cpu is congested. There is
3154 * no synchronization around this function and the test result is
3155 * unreliable and only useful as advisory hints or for debugging.
3156 *
3157 * RETURNS:
3158 * %true if congested, %false otherwise.
3159 */
3160bool workqueue_congested(unsigned int cpu, struct workqueue_struct *wq)
3161{
3162 struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
3163
3164 return !list_empty(&cwq->delayed_works);
3165}
3166EXPORT_SYMBOL_GPL(workqueue_congested);
3167
3168/**
3169 * work_cpu - return the last known associated cpu for @work
3170 * @work: the work of interest
3171 *
3172 * RETURNS:
3173 * CPU number if @work was ever queued. WORK_CPU_NONE otherwise.
3174 */
3175unsigned int work_cpu(struct work_struct *work)
3176{
3177 struct global_cwq *gcwq = get_work_gcwq(work);
3178
3179 return gcwq ? gcwq->cpu : WORK_CPU_NONE;
3180}
3181EXPORT_SYMBOL_GPL(work_cpu);
3182
3183/**
3184 * work_busy - test whether a work is currently pending or running
3185 * @work: the work to be tested
3186 *
3187 * Test whether @work is currently pending or running. There is no
3188 * synchronization around this function and the test result is
3189 * unreliable and only useful as advisory hints or for debugging.
3190 * Especially for reentrant wqs, the pending state might hide the
3191 * running state.
3192 *
3193 * RETURNS:
3194 * OR'd bitmask of WORK_BUSY_* bits.
3195 */
3196unsigned int work_busy(struct work_struct *work)
3197{
3198 struct global_cwq *gcwq = get_work_gcwq(work);
3199 unsigned long flags;
3200 unsigned int ret = 0;
3201
3202 if (!gcwq)
3203 return false;
3204
3205 spin_lock_irqsave(&gcwq->lock, flags);
3206
3207 if (work_pending(work))
3208 ret |= WORK_BUSY_PENDING;
3209 if (find_worker_executing_work(gcwq, work))
3210 ret |= WORK_BUSY_RUNNING;
3211
3212 spin_unlock_irqrestore(&gcwq->lock, flags);
3213
3214 return ret;
3215}
3216EXPORT_SYMBOL_GPL(work_busy);
3217
3218/*
3219 * CPU hotplug.
3220 *
3221 * There are two challenges in supporting CPU hotplug. Firstly, there
3222 * are a lot of assumptions on strong associations among work, cwq and
3223 * gcwq which make migrating pending and scheduled works very
3224 * difficult to implement without impacting hot paths. Secondly,
3225 * gcwqs serve mix of short, long and very long running works making
3226 * blocked draining impractical.
3227 *
3228 * This is solved by allowing a gcwq to be detached from CPU, running
3229 * it with unbound (rogue) workers and allowing it to be reattached
3230 * later if the cpu comes back online. A separate thread is created
3231 * to govern a gcwq in such state and is called the trustee of the
3232 * gcwq.
3233 *
3234 * Trustee states and their descriptions.
3235 *
3236 * START Command state used on startup. On CPU_DOWN_PREPARE, a
3237 * new trustee is started with this state.
3238 *
3239 * IN_CHARGE Once started, trustee will enter this state after
3240 * assuming the manager role and making all existing
3241 * workers rogue. DOWN_PREPARE waits for trustee to
3242 * enter this state. After reaching IN_CHARGE, trustee
3243 * tries to execute the pending worklist until it's empty
3244 * and the state is set to BUTCHER, or the state is set
3245 * to RELEASE.
3246 *
3247 * BUTCHER Command state which is set by the cpu callback after
3248 * the cpu has went down. Once this state is set trustee
3249 * knows that there will be no new works on the worklist
3250 * and once the worklist is empty it can proceed to
3251 * killing idle workers.
3252 *
3253 * RELEASE Command state which is set by the cpu callback if the
3254 * cpu down has been canceled or it has come online
3255 * again. After recognizing this state, trustee stops
3256 * trying to drain or butcher and clears ROGUE, rebinds
3257 * all remaining workers back to the cpu and releases
3258 * manager role.
3259 *
3260 * DONE Trustee will enter this state after BUTCHER or RELEASE
3261 * is complete.
3262 *
3263 * trustee CPU draining
3264 * took over down complete
3265 * START -----------> IN_CHARGE -----------> BUTCHER -----------> DONE
3266 * | | ^
3267 * | CPU is back online v return workers |
3268 * ----------------> RELEASE --------------
3269 */
3270
3271/**
3272 * trustee_wait_event_timeout - timed event wait for trustee
3273 * @cond: condition to wait for
3274 * @timeout: timeout in jiffies
3275 *
3276 * wait_event_timeout() for trustee to use. Handles locking and
3277 * checks for RELEASE request.
3278 *
3279 * CONTEXT:
3280 * spin_lock_irq(gcwq->lock) which may be released and regrabbed
3281 * multiple times. To be used by trustee.
3282 *
3283 * RETURNS:
3284 * Positive indicating left time if @cond is satisfied, 0 if timed
3285 * out, -1 if canceled.
3286 */
3287#define trustee_wait_event_timeout(cond, timeout) ({ \
3288 long __ret = (timeout); \
3289 while (!((cond) || (gcwq->trustee_state == TRUSTEE_RELEASE)) && \
3290 __ret) { \
3291 spin_unlock_irq(&gcwq->lock); \
3292 __wait_event_timeout(gcwq->trustee_wait, (cond) || \
3293 (gcwq->trustee_state == TRUSTEE_RELEASE), \
3294 __ret); \
3295 spin_lock_irq(&gcwq->lock); \
3296 } \
3297 gcwq->trustee_state == TRUSTEE_RELEASE ? -1 : (__ret); \
3298})
3299
3300/**
3301 * trustee_wait_event - event wait for trustee
3302 * @cond: condition to wait for
3303 *
3304 * wait_event() for trustee to use. Automatically handles locking and
3305 * checks for CANCEL request.
3306 *
3307 * CONTEXT:
3308 * spin_lock_irq(gcwq->lock) which may be released and regrabbed
3309 * multiple times. To be used by trustee.
3310 *
3311 * RETURNS:
3312 * 0 if @cond is satisfied, -1 if canceled.
3313 */
3314#define trustee_wait_event(cond) ({ \
3315 long __ret1; \
3316 __ret1 = trustee_wait_event_timeout(cond, MAX_SCHEDULE_TIMEOUT);\
3317 __ret1 < 0 ? -1 : 0; \
3318})
3319
3320static int __cpuinit trustee_thread(void *__gcwq)
3321{
3322 struct global_cwq *gcwq = __gcwq;
3323 struct worker *worker;
3324 struct work_struct *work;
3325 struct hlist_node *pos;
3326 long rc;
3327 int i;
3328
3329 BUG_ON(gcwq->cpu != smp_processor_id());
3330
3331 spin_lock_irq(&gcwq->lock);
3332 /*
3333 * Claim the manager position and make all workers rogue.
3334 * Trustee must be bound to the target cpu and can't be
3335 * cancelled.
3336 */
3337 BUG_ON(gcwq->cpu != smp_processor_id());
3338 rc = trustee_wait_event(!(gcwq->flags & GCWQ_MANAGING_WORKERS));
3339 BUG_ON(rc < 0);
3340
3341 gcwq->flags |= GCWQ_MANAGING_WORKERS;
3342
3343 list_for_each_entry(worker, &gcwq->idle_list, entry)
3344 worker->flags |= WORKER_ROGUE;
3345
3346 for_each_busy_worker(worker, i, pos, gcwq)
3347 worker->flags |= WORKER_ROGUE;
3348
3349 /*
3350 * Call schedule() so that we cross rq->lock and thus can
3351 * guarantee sched callbacks see the rogue flag. This is
3352 * necessary as scheduler callbacks may be invoked from other
3353 * cpus.
3354 */
3355 spin_unlock_irq(&gcwq->lock);
3356 schedule();
3357 spin_lock_irq(&gcwq->lock);
3358
3359 /*
3360 * Sched callbacks are disabled now. Zap nr_running. After
3361 * this, nr_running stays zero and need_more_worker() and
3362 * keep_working() are always true as long as the worklist is
3363 * not empty.
3364 */
3365 atomic_set(get_gcwq_nr_running(gcwq->cpu), 0);
3366
3367 spin_unlock_irq(&gcwq->lock);
3368 del_timer_sync(&gcwq->idle_timer);
3369 spin_lock_irq(&gcwq->lock);
3370
3371 /*
3372 * We're now in charge. Notify and proceed to drain. We need
3373 * to keep the gcwq running during the whole CPU down
3374 * procedure as other cpu hotunplug callbacks may need to
3375 * flush currently running tasks.
3376 */
3377 gcwq->trustee_state = TRUSTEE_IN_CHARGE;
3378 wake_up_all(&gcwq->trustee_wait);
3379
3380 /*
3381 * The original cpu is in the process of dying and may go away
3382 * anytime now. When that happens, we and all workers would
3383 * be migrated to other cpus. Try draining any left work. We
3384 * want to get it over with ASAP - spam rescuers, wake up as
3385 * many idlers as necessary and create new ones till the
3386 * worklist is empty. Note that if the gcwq is frozen, there
3387 * may be frozen works in freezable cwqs. Don't declare
3388 * completion while frozen.
3389 */
3390 while (gcwq->nr_workers != gcwq->nr_idle ||
3391 gcwq->flags & GCWQ_FREEZING ||
3392 gcwq->trustee_state == TRUSTEE_IN_CHARGE) {
3393 int nr_works = 0;
3394
3395 list_for_each_entry(work, &gcwq->worklist, entry) {
3396 send_mayday(work);
3397 nr_works++;
3398 }
3399
3400 list_for_each_entry(worker, &gcwq->idle_list, entry) {
3401 if (!nr_works--)
3402 break;
3403 wake_up_process(worker->task);
3404 }
3405
3406 if (need_to_create_worker(gcwq)) {
3407 spin_unlock_irq(&gcwq->lock);
3408 worker = create_worker(gcwq, false);
3409 spin_lock_irq(&gcwq->lock);
3410 if (worker) {
3411 worker->flags |= WORKER_ROGUE;
3412 start_worker(worker);
3413 }
3414 }
3415
3416 /* give a breather */
3417 if (trustee_wait_event_timeout(false, TRUSTEE_COOLDOWN) < 0)
3418 break;
3419 }
3420
3421 /*
3422 * Either all works have been scheduled and cpu is down, or
3423 * cpu down has already been canceled. Wait for and butcher
3424 * all workers till we're canceled.
3425 */
3426 do {
3427 rc = trustee_wait_event(!list_empty(&gcwq->idle_list));
3428 while (!list_empty(&gcwq->idle_list))
3429 destroy_worker(list_first_entry(&gcwq->idle_list,
3430 struct worker, entry));
3431 } while (gcwq->nr_workers && rc >= 0);
3432
3433 /*
3434 * At this point, either draining has completed and no worker
3435 * is left, or cpu down has been canceled or the cpu is being
3436 * brought back up. There shouldn't be any idle one left.
3437 * Tell the remaining busy ones to rebind once it finishes the
3438 * currently scheduled works by scheduling the rebind_work.
3439 */
3440 WARN_ON(!list_empty(&gcwq->idle_list));
3441
3442 for_each_busy_worker(worker, i, pos, gcwq) {
3443 struct work_struct *rebind_work = &worker->rebind_work;
3444 unsigned long worker_flags = worker->flags;
3445
3446 /*
3447 * Rebind_work may race with future cpu hotplug
3448 * operations. Use a separate flag to mark that
3449 * rebinding is scheduled. The morphing should
3450 * be atomic.
3451 */
3452 worker_flags |= WORKER_REBIND;
3453 worker_flags &= ~WORKER_ROGUE;
3454 ACCESS_ONCE(worker->flags) = worker_flags;
3455
3456 /* queue rebind_work, wq doesn't matter, use the default one */
3457 if (test_and_set_bit(WORK_STRUCT_PENDING_BIT,
3458 work_data_bits(rebind_work)))
3459 continue;
3460
3461 debug_work_activate(rebind_work);
3462 insert_work(get_cwq(gcwq->cpu, system_wq), rebind_work,
3463 worker->scheduled.next,
3464 work_color_to_flags(WORK_NO_COLOR));
3465 }
3466
3467 /* relinquish manager role */
3468 gcwq->flags &= ~GCWQ_MANAGING_WORKERS;
3469
3470 /* notify completion */
3471 gcwq->trustee = NULL;
3472 gcwq->trustee_state = TRUSTEE_DONE;
3473 wake_up_all(&gcwq->trustee_wait);
3474 spin_unlock_irq(&gcwq->lock);
3475 return 0;
3476}
3477
3478/**
3479 * wait_trustee_state - wait for trustee to enter the specified state
3480 * @gcwq: gcwq the trustee of interest belongs to
3481 * @state: target state to wait for
3482 *
3483 * Wait for the trustee to reach @state. DONE is already matched.
3484 *
3485 * CONTEXT:
3486 * spin_lock_irq(gcwq->lock) which may be released and regrabbed
3487 * multiple times. To be used by cpu_callback.
3488 */
3489static void __cpuinit wait_trustee_state(struct global_cwq *gcwq, int state)
3490__releases(&gcwq->lock)
3491__acquires(&gcwq->lock)
3492{
3493 if (!(gcwq->trustee_state == state ||
3494 gcwq->trustee_state == TRUSTEE_DONE)) {
3495 spin_unlock_irq(&gcwq->lock);
3496 __wait_event(gcwq->trustee_wait,
3497 gcwq->trustee_state == state ||
3498 gcwq->trustee_state == TRUSTEE_DONE);
3499 spin_lock_irq(&gcwq->lock);
3500 }
3501}
3502
3503static int __devinit workqueue_cpu_callback(struct notifier_block *nfb,
3504 unsigned long action,
3505 void *hcpu)
3506{
3507 unsigned int cpu = (unsigned long)hcpu;
3508 struct global_cwq *gcwq = get_gcwq(cpu);
3509 struct task_struct *new_trustee = NULL;
3510 struct worker *uninitialized_var(new_worker);
3511 unsigned long flags;
3512
3513 action &= ~CPU_TASKS_FROZEN;
3514
3515 switch (action) {
3516 case CPU_DOWN_PREPARE:
3517 new_trustee = kthread_create(trustee_thread, gcwq,
3518 "workqueue_trustee/%d\n", cpu);
3519 if (IS_ERR(new_trustee))
3520 return notifier_from_errno(PTR_ERR(new_trustee));
3521 kthread_bind(new_trustee, cpu);
3522 /* fall through */
3523 case CPU_UP_PREPARE:
3524 BUG_ON(gcwq->first_idle);
3525 new_worker = create_worker(gcwq, false);
3526 if (!new_worker) {
3527 if (new_trustee)
3528 kthread_stop(new_trustee);
3529 return NOTIFY_BAD;
3530 }
3531 }
3532
3533 /* some are called w/ irq disabled, don't disturb irq status */
3534 spin_lock_irqsave(&gcwq->lock, flags);
3535
3536 switch (action) {
3537 case CPU_DOWN_PREPARE:
3538 /* initialize trustee and tell it to acquire the gcwq */
3539 BUG_ON(gcwq->trustee || gcwq->trustee_state != TRUSTEE_DONE);
3540 gcwq->trustee = new_trustee;
3541 gcwq->trustee_state = TRUSTEE_START;
3542 wake_up_process(gcwq->trustee);
3543 wait_trustee_state(gcwq, TRUSTEE_IN_CHARGE);
3544 /* fall through */
3545 case CPU_UP_PREPARE:
3546 BUG_ON(gcwq->first_idle);
3547 gcwq->first_idle = new_worker;
3548 break;
3549
3550 case CPU_DYING:
3551 /*
3552 * Before this, the trustee and all workers except for
3553 * the ones which are still executing works from
3554 * before the last CPU down must be on the cpu. After
3555 * this, they'll all be diasporas.
3556 */
3557 gcwq->flags |= GCWQ_DISASSOCIATED;
3558 break;
3559
3560 case CPU_POST_DEAD:
3561 gcwq->trustee_state = TRUSTEE_BUTCHER;
3562 /* fall through */
3563 case CPU_UP_CANCELED:
3564 destroy_worker(gcwq->first_idle);
3565 gcwq->first_idle = NULL;
3566 break;
3567
3568 case CPU_DOWN_FAILED:
3569 case CPU_ONLINE:
3570 gcwq->flags &= ~GCWQ_DISASSOCIATED;
3571 if (gcwq->trustee_state != TRUSTEE_DONE) {
3572 gcwq->trustee_state = TRUSTEE_RELEASE;
3573 wake_up_process(gcwq->trustee);
3574 wait_trustee_state(gcwq, TRUSTEE_DONE);
3575 }
3576
3577 /*
3578 * Trustee is done and there might be no worker left.
3579 * Put the first_idle in and request a real manager to
3580 * take a look.
3581 */
3582 spin_unlock_irq(&gcwq->lock);
3583 kthread_bind(gcwq->first_idle->task, cpu);
3584 spin_lock_irq(&gcwq->lock);
3585 gcwq->flags |= GCWQ_MANAGE_WORKERS;
3586 start_worker(gcwq->first_idle);
3587 gcwq->first_idle = NULL;
3588 break;
3589 }
3590
3591 spin_unlock_irqrestore(&gcwq->lock, flags);
3592
3593 return notifier_from_errno(0);
3594}
3595
3596/*
3597 * Workqueues should be brought up before normal priority CPU notifiers.
3598 * This will be registered high priority CPU notifier.
3599 */
3600static int __devinit workqueue_cpu_up_callback(struct notifier_block *nfb,
3601 unsigned long action,
3602 void *hcpu)
3603{
3604 switch (action & ~CPU_TASKS_FROZEN) {
3605 case CPU_UP_PREPARE:
3606 case CPU_UP_CANCELED:
3607 case CPU_DOWN_FAILED:
3608 case CPU_ONLINE:
3609 return workqueue_cpu_callback(nfb, action, hcpu);
3610 }
3611 return NOTIFY_OK;
3612}
3613
3614/*
3615 * Workqueues should be brought down after normal priority CPU notifiers.
3616 * This will be registered as low priority CPU notifier.
3617 */
3618static int __devinit workqueue_cpu_down_callback(struct notifier_block *nfb,
3619 unsigned long action,
3620 void *hcpu)
3621{
3622 switch (action & ~CPU_TASKS_FROZEN) {
3623 case CPU_DOWN_PREPARE:
3624 case CPU_DYING:
3625 case CPU_POST_DEAD:
3626 return workqueue_cpu_callback(nfb, action, hcpu);
3627 }
3628 return NOTIFY_OK;
3629}
3630
3631#ifdef CONFIG_SMP
3632
3633struct work_for_cpu {
3634 struct work_struct work;
3635 long (*fn)(void *);
3636 void *arg;
3637 long ret;
3638};
3639
3640static void work_for_cpu_fn(struct work_struct *work)
3641{
3642 struct work_for_cpu *wfc = container_of(work, struct work_for_cpu, work);
3643
3644 wfc->ret = wfc->fn(wfc->arg);
3645}
3646
3647/**
3648 * work_on_cpu - run a function in user context on a particular cpu
3649 * @cpu: the cpu to run on
3650 * @fn: the function to run
3651 * @arg: the function arg
3652 *
3653 * This will return the value @fn returns.
3654 * It is up to the caller to ensure that the cpu doesn't go offline.
3655 * The caller must not hold any locks which would prevent @fn from completing.
3656 */
3657long work_on_cpu(unsigned int cpu, long (*fn)(void *), void *arg)
3658{
3659 struct work_for_cpu wfc = { .fn = fn, .arg = arg };
3660
3661 INIT_WORK_ONSTACK(&wfc.work, work_for_cpu_fn);
3662 schedule_work_on(cpu, &wfc.work);
3663 flush_work(&wfc.work);
3664 return wfc.ret;
3665}
3666EXPORT_SYMBOL_GPL(work_on_cpu);
3667#endif /* CONFIG_SMP */
3668
3669#ifdef CONFIG_FREEZER
3670
3671/**
3672 * freeze_workqueues_begin - begin freezing workqueues
3673 *
3674 * Start freezing workqueues. After this function returns, all freezable
3675 * workqueues will queue new works to their frozen_works list instead of
3676 * gcwq->worklist.
3677 *
3678 * CONTEXT:
3679 * Grabs and releases workqueue_lock and gcwq->lock's.
3680 */
3681void freeze_workqueues_begin(void)
3682{
3683 unsigned int cpu;
3684
3685 spin_lock(&workqueue_lock);
3686
3687 BUG_ON(workqueue_freezing);
3688 workqueue_freezing = true;
3689
3690 for_each_gcwq_cpu(cpu) {
3691 struct global_cwq *gcwq = get_gcwq(cpu);
3692 struct workqueue_struct *wq;
3693
3694 spin_lock_irq(&gcwq->lock);
3695
3696 BUG_ON(gcwq->flags & GCWQ_FREEZING);
3697 gcwq->flags |= GCWQ_FREEZING;
3698
3699 list_for_each_entry(wq, &workqueues, list) {
3700 struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
3701
3702 if (cwq && wq->flags & WQ_FREEZABLE)
3703 cwq->max_active = 0;
3704 }
3705
3706 spin_unlock_irq(&gcwq->lock);
3707 }
3708
3709 spin_unlock(&workqueue_lock);
3710}
3711
3712/**
3713 * freeze_workqueues_busy - are freezable workqueues still busy?
3714 *
3715 * Check whether freezing is complete. This function must be called
3716 * between freeze_workqueues_begin() and thaw_workqueues().
3717 *
3718 * CONTEXT:
3719 * Grabs and releases workqueue_lock.
3720 *
3721 * RETURNS:
3722 * %true if some freezable workqueues are still busy. %false if freezing
3723 * is complete.
3724 */
3725bool freeze_workqueues_busy(void)
3726{
3727 unsigned int cpu;
3728 bool busy = false;
3729
3730 spin_lock(&workqueue_lock);
3731
3732 BUG_ON(!workqueue_freezing);
3733
3734 for_each_gcwq_cpu(cpu) {
3735 struct workqueue_struct *wq;
3736 /*
3737 * nr_active is monotonically decreasing. It's safe
3738 * to peek without lock.
3739 */
3740 list_for_each_entry(wq, &workqueues, list) {
3741 struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
3742
3743 if (!cwq || !(wq->flags & WQ_FREEZABLE))
3744 continue;
3745
3746 BUG_ON(cwq->nr_active < 0);
3747 if (cwq->nr_active) {
3748 busy = true;
3749 goto out_unlock;
3750 }
3751 }
3752 }
3753out_unlock:
3754 spin_unlock(&workqueue_lock);
3755 return busy;
3756}
3757
3758/**
3759 * thaw_workqueues - thaw workqueues
3760 *
3761 * Thaw workqueues. Normal queueing is restored and all collected
3762 * frozen works are transferred to their respective gcwq worklists.
3763 *
3764 * CONTEXT:
3765 * Grabs and releases workqueue_lock and gcwq->lock's.
3766 */
3767void thaw_workqueues(void)
3768{
3769 unsigned int cpu;
3770
3771 spin_lock(&workqueue_lock);
3772
3773 if (!workqueue_freezing)
3774 goto out_unlock;
3775
3776 for_each_gcwq_cpu(cpu) {
3777 struct global_cwq *gcwq = get_gcwq(cpu);
3778 struct workqueue_struct *wq;
3779
3780 spin_lock_irq(&gcwq->lock);
3781
3782 BUG_ON(!(gcwq->flags & GCWQ_FREEZING));
3783 gcwq->flags &= ~GCWQ_FREEZING;
3784
3785 list_for_each_entry(wq, &workqueues, list) {
3786 struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
3787
3788 if (!cwq || !(wq->flags & WQ_FREEZABLE))
3789 continue;
3790
3791 /* restore max_active and repopulate worklist */
3792 cwq->max_active = wq->saved_max_active;
3793
3794 while (!list_empty(&cwq->delayed_works) &&
3795 cwq->nr_active < cwq->max_active)
3796 cwq_activate_first_delayed(cwq);
3797 }
3798
3799 wake_up_worker(gcwq);
3800
3801 spin_unlock_irq(&gcwq->lock);
3802 }
3803
3804 workqueue_freezing = false;
3805out_unlock:
3806 spin_unlock(&workqueue_lock);
3807}
3808#endif /* CONFIG_FREEZER */
3809
3810static int __init init_workqueues(void)
3811{
3812 unsigned int cpu;
3813 int i;
3814
3815 cpu_notifier(workqueue_cpu_up_callback, CPU_PRI_WORKQUEUE_UP);
3816 cpu_notifier(workqueue_cpu_down_callback, CPU_PRI_WORKQUEUE_DOWN);
3817
3818 /* initialize gcwqs */
3819 for_each_gcwq_cpu(cpu) {
3820 struct global_cwq *gcwq = get_gcwq(cpu);
3821
3822 spin_lock_init(&gcwq->lock);
3823 INIT_LIST_HEAD(&gcwq->worklist);
3824 gcwq->cpu = cpu;
3825 gcwq->flags |= GCWQ_DISASSOCIATED;
3826
3827 INIT_LIST_HEAD(&gcwq->idle_list);
3828 for (i = 0; i < BUSY_WORKER_HASH_SIZE; i++)
3829 INIT_HLIST_HEAD(&gcwq->busy_hash[i]);
3830
3831 init_timer_deferrable(&gcwq->idle_timer);
3832 gcwq->idle_timer.function = idle_worker_timeout;
3833 gcwq->idle_timer.data = (unsigned long)gcwq;
3834
3835 setup_timer(&gcwq->mayday_timer, gcwq_mayday_timeout,
3836 (unsigned long)gcwq);
3837
3838 ida_init(&gcwq->worker_ida);
3839
3840 gcwq->trustee_state = TRUSTEE_DONE;
3841 init_waitqueue_head(&gcwq->trustee_wait);
3842 }
3843
3844 /* create the initial worker */
3845 for_each_online_gcwq_cpu(cpu) {
3846 struct global_cwq *gcwq = get_gcwq(cpu);
3847 struct worker *worker;
3848
3849 if (cpu != WORK_CPU_UNBOUND)
3850 gcwq->flags &= ~GCWQ_DISASSOCIATED;
3851 worker = create_worker(gcwq, true);
3852 BUG_ON(!worker);
3853 spin_lock_irq(&gcwq->lock);
3854 start_worker(worker);
3855 spin_unlock_irq(&gcwq->lock);
3856 }
3857
3858 system_wq = alloc_workqueue("events", 0, 0);
3859 system_long_wq = alloc_workqueue("events_long", 0, 0);
3860 system_nrt_wq = alloc_workqueue("events_nrt", WQ_NON_REENTRANT, 0);
3861 system_unbound_wq = alloc_workqueue("events_unbound", WQ_UNBOUND,
3862 WQ_UNBOUND_MAX_ACTIVE);
3863 system_freezable_wq = alloc_workqueue("events_freezable",
3864 WQ_FREEZABLE, 0);
3865 system_nrt_freezable_wq = alloc_workqueue("events_nrt_freezable",
3866 WQ_NON_REENTRANT | WQ_FREEZABLE, 0);
3867 BUG_ON(!system_wq || !system_long_wq || !system_nrt_wq ||
3868 !system_unbound_wq || !system_freezable_wq ||
3869 !system_nrt_freezable_wq);
3870 return 0;
3871}
3872early_initcall(init_workqueues);
1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * kernel/workqueue.c - generic async execution with shared worker pool
4 *
5 * Copyright (C) 2002 Ingo Molnar
6 *
7 * Derived from the taskqueue/keventd code by:
8 * David Woodhouse <dwmw2@infradead.org>
9 * Andrew Morton
10 * Kai Petzke <wpp@marie.physik.tu-berlin.de>
11 * Theodore Ts'o <tytso@mit.edu>
12 *
13 * Made to use alloc_percpu by Christoph Lameter.
14 *
15 * Copyright (C) 2010 SUSE Linux Products GmbH
16 * Copyright (C) 2010 Tejun Heo <tj@kernel.org>
17 *
18 * This is the generic async execution mechanism. Work items as are
19 * executed in process context. The worker pool is shared and
20 * automatically managed. There are two worker pools for each CPU (one for
21 * normal work items and the other for high priority ones) and some extra
22 * pools for workqueues which are not bound to any specific CPU - the
23 * number of these backing pools is dynamic.
24 *
25 * Please read Documentation/core-api/workqueue.rst for details.
26 */
27
28#include <linux/export.h>
29#include <linux/kernel.h>
30#include <linux/sched.h>
31#include <linux/init.h>
32#include <linux/signal.h>
33#include <linux/completion.h>
34#include <linux/workqueue.h>
35#include <linux/slab.h>
36#include <linux/cpu.h>
37#include <linux/notifier.h>
38#include <linux/kthread.h>
39#include <linux/hardirq.h>
40#include <linux/mempolicy.h>
41#include <linux/freezer.h>
42#include <linux/debug_locks.h>
43#include <linux/lockdep.h>
44#include <linux/idr.h>
45#include <linux/jhash.h>
46#include <linux/hashtable.h>
47#include <linux/rculist.h>
48#include <linux/nodemask.h>
49#include <linux/moduleparam.h>
50#include <linux/uaccess.h>
51#include <linux/sched/isolation.h>
52#include <linux/nmi.h>
53#include <linux/kvm_para.h>
54
55#include "workqueue_internal.h"
56
57enum {
58 /*
59 * worker_pool flags
60 *
61 * A bound pool is either associated or disassociated with its CPU.
62 * While associated (!DISASSOCIATED), all workers are bound to the
63 * CPU and none has %WORKER_UNBOUND set and concurrency management
64 * is in effect.
65 *
66 * While DISASSOCIATED, the cpu may be offline and all workers have
67 * %WORKER_UNBOUND set and concurrency management disabled, and may
68 * be executing on any CPU. The pool behaves as an unbound one.
69 *
70 * Note that DISASSOCIATED should be flipped only while holding
71 * wq_pool_attach_mutex to avoid changing binding state while
72 * worker_attach_to_pool() is in progress.
73 */
74 POOL_MANAGER_ACTIVE = 1 << 0, /* being managed */
75 POOL_DISASSOCIATED = 1 << 2, /* cpu can't serve workers */
76
77 /* worker flags */
78 WORKER_DIE = 1 << 1, /* die die die */
79 WORKER_IDLE = 1 << 2, /* is idle */
80 WORKER_PREP = 1 << 3, /* preparing to run works */
81 WORKER_CPU_INTENSIVE = 1 << 6, /* cpu intensive */
82 WORKER_UNBOUND = 1 << 7, /* worker is unbound */
83 WORKER_REBOUND = 1 << 8, /* worker was rebound */
84
85 WORKER_NOT_RUNNING = WORKER_PREP | WORKER_CPU_INTENSIVE |
86 WORKER_UNBOUND | WORKER_REBOUND,
87
88 NR_STD_WORKER_POOLS = 2, /* # standard pools per cpu */
89
90 UNBOUND_POOL_HASH_ORDER = 6, /* hashed by pool->attrs */
91 BUSY_WORKER_HASH_ORDER = 6, /* 64 pointers */
92
93 MAX_IDLE_WORKERS_RATIO = 4, /* 1/4 of busy can be idle */
94 IDLE_WORKER_TIMEOUT = 300 * HZ, /* keep idle ones for 5 mins */
95
96 MAYDAY_INITIAL_TIMEOUT = HZ / 100 >= 2 ? HZ / 100 : 2,
97 /* call for help after 10ms
98 (min two ticks) */
99 MAYDAY_INTERVAL = HZ / 10, /* and then every 100ms */
100 CREATE_COOLDOWN = HZ, /* time to breath after fail */
101
102 /*
103 * Rescue workers are used only on emergencies and shared by
104 * all cpus. Give MIN_NICE.
105 */
106 RESCUER_NICE_LEVEL = MIN_NICE,
107 HIGHPRI_NICE_LEVEL = MIN_NICE,
108
109 WQ_NAME_LEN = 24,
110};
111
112/*
113 * Structure fields follow one of the following exclusion rules.
114 *
115 * I: Modifiable by initialization/destruction paths and read-only for
116 * everyone else.
117 *
118 * P: Preemption protected. Disabling preemption is enough and should
119 * only be modified and accessed from the local cpu.
120 *
121 * L: pool->lock protected. Access with pool->lock held.
122 *
123 * X: During normal operation, modification requires pool->lock and should
124 * be done only from local cpu. Either disabling preemption on local
125 * cpu or grabbing pool->lock is enough for read access. If
126 * POOL_DISASSOCIATED is set, it's identical to L.
127 *
128 * A: wq_pool_attach_mutex protected.
129 *
130 * PL: wq_pool_mutex protected.
131 *
132 * PR: wq_pool_mutex protected for writes. RCU protected for reads.
133 *
134 * PW: wq_pool_mutex and wq->mutex protected for writes. Either for reads.
135 *
136 * PWR: wq_pool_mutex and wq->mutex protected for writes. Either or
137 * RCU for reads.
138 *
139 * WQ: wq->mutex protected.
140 *
141 * WR: wq->mutex protected for writes. RCU protected for reads.
142 *
143 * MD: wq_mayday_lock protected.
144 */
145
146/* struct worker is defined in workqueue_internal.h */
147
148struct worker_pool {
149 raw_spinlock_t lock; /* the pool lock */
150 int cpu; /* I: the associated cpu */
151 int node; /* I: the associated node ID */
152 int id; /* I: pool ID */
153 unsigned int flags; /* X: flags */
154
155 unsigned long watchdog_ts; /* L: watchdog timestamp */
156
157 struct list_head worklist; /* L: list of pending works */
158
159 int nr_workers; /* L: total number of workers */
160 int nr_idle; /* L: currently idle workers */
161
162 struct list_head idle_list; /* X: list of idle workers */
163 struct timer_list idle_timer; /* L: worker idle timeout */
164 struct timer_list mayday_timer; /* L: SOS timer for workers */
165
166 /* a workers is either on busy_hash or idle_list, or the manager */
167 DECLARE_HASHTABLE(busy_hash, BUSY_WORKER_HASH_ORDER);
168 /* L: hash of busy workers */
169
170 struct worker *manager; /* L: purely informational */
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 RCU protected to allow dereferences
189 * from get_work_pool().
190 */
191 struct rcu_head rcu;
192} ____cacheline_aligned_in_smp;
193
194/*
195 * The per-pool workqueue. While queued, the lower WORK_STRUCT_FLAG_BITS
196 * of work_struct->data are used for flags and the remaining high bits
197 * point to the pwq; thus, pwqs need to be aligned at two's power of the
198 * number of flag bits.
199 */
200struct pool_workqueue {
201 struct worker_pool *pool; /* I: the associated pool */
202 struct workqueue_struct *wq; /* I: the owning workqueue */
203 int work_color; /* L: current color */
204 int flush_color; /* L: flushing color */
205 int refcnt; /* L: reference count */
206 int nr_in_flight[WORK_NR_COLORS];
207 /* L: nr of in_flight works */
208 int nr_active; /* L: nr of active works */
209 int max_active; /* L: max active works */
210 struct list_head delayed_works; /* L: delayed works */
211 struct list_head pwqs_node; /* WR: node on wq->pwqs */
212 struct list_head mayday_node; /* MD: node on wq->maydays */
213
214 /*
215 * Release of unbound pwq is punted to system_wq. See put_pwq()
216 * and pwq_unbound_release_workfn() for details. pool_workqueue
217 * itself is also RCU protected so that the first pwq can be
218 * determined without grabbing wq->mutex.
219 */
220 struct work_struct unbound_release_work;
221 struct rcu_head rcu;
222} __aligned(1 << WORK_STRUCT_FLAG_BITS);
223
224/*
225 * Structure used to wait for workqueue flush.
226 */
227struct wq_flusher {
228 struct list_head list; /* WQ: list of flushers */
229 int flush_color; /* WQ: flush color waiting for */
230 struct completion done; /* flush completion */
231};
232
233struct wq_device;
234
235/*
236 * The externally visible workqueue. It relays the issued work items to
237 * the appropriate worker_pool through its pool_workqueues.
238 */
239struct workqueue_struct {
240 struct list_head pwqs; /* WR: all pwqs of this wq */
241 struct list_head list; /* PR: list of all workqueues */
242
243 struct mutex mutex; /* protects this wq */
244 int work_color; /* WQ: current work color */
245 int flush_color; /* WQ: current flush color */
246 atomic_t nr_pwqs_to_flush; /* flush in progress */
247 struct wq_flusher *first_flusher; /* WQ: first flusher */
248 struct list_head flusher_queue; /* WQ: flush waiters */
249 struct list_head flusher_overflow; /* WQ: flush overflow list */
250
251 struct list_head maydays; /* MD: pwqs requesting rescue */
252 struct worker *rescuer; /* MD: 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 char *lock_name;
265 struct lock_class_key key;
266 struct lockdep_map lockdep_map;
267#endif
268 char name[WQ_NAME_LEN]; /* I: workqueue name */
269
270 /*
271 * Destruction of workqueue_struct is RCU protected to allow walking
272 * the workqueues list without grabbing wq_pool_mutex.
273 * This is used to dump all workqueues from sysrq.
274 */
275 struct rcu_head rcu;
276
277 /* hot fields used during command issue, aligned to cacheline */
278 unsigned int flags ____cacheline_aligned; /* WQ: WQ_* flags */
279 struct pool_workqueue __percpu *cpu_pwqs; /* I: per-cpu pwqs */
280 struct pool_workqueue __rcu *numa_pwq_tbl[]; /* PWR: unbound pwqs indexed by node */
281};
282
283static struct kmem_cache *pwq_cache;
284
285static cpumask_var_t *wq_numa_possible_cpumask;
286 /* possible CPUs of each node */
287
288static bool wq_disable_numa;
289module_param_named(disable_numa, wq_disable_numa, bool, 0444);
290
291/* see the comment above the definition of WQ_POWER_EFFICIENT */
292static bool wq_power_efficient = IS_ENABLED(CONFIG_WQ_POWER_EFFICIENT_DEFAULT);
293module_param_named(power_efficient, wq_power_efficient, bool, 0444);
294
295static bool wq_online; /* can kworkers be created yet? */
296
297static bool wq_numa_enabled; /* unbound NUMA affinity enabled */
298
299/* buf for wq_update_unbound_numa_attrs(), protected by CPU hotplug exclusion */
300static struct workqueue_attrs *wq_update_unbound_numa_attrs_buf;
301
302static DEFINE_MUTEX(wq_pool_mutex); /* protects pools and workqueues list */
303static DEFINE_MUTEX(wq_pool_attach_mutex); /* protects worker attach/detach */
304static DEFINE_RAW_SPINLOCK(wq_mayday_lock); /* protects wq->maydays list */
305/* wait for manager to go away */
306static struct rcuwait manager_wait = __RCUWAIT_INITIALIZER(manager_wait);
307
308static LIST_HEAD(workqueues); /* PR: list of all workqueues */
309static bool workqueue_freezing; /* PL: have wqs started freezing? */
310
311/* PL: allowable cpus for unbound wqs and work items */
312static cpumask_var_t wq_unbound_cpumask;
313
314/* CPU where unbound work was last round robin scheduled from this CPU */
315static DEFINE_PER_CPU(int, wq_rr_cpu_last);
316
317/*
318 * Local execution of unbound work items is no longer guaranteed. The
319 * following always forces round-robin CPU selection on unbound work items
320 * to uncover usages which depend on it.
321 */
322#ifdef CONFIG_DEBUG_WQ_FORCE_RR_CPU
323static bool wq_debug_force_rr_cpu = true;
324#else
325static bool wq_debug_force_rr_cpu = false;
326#endif
327module_param_named(debug_force_rr_cpu, wq_debug_force_rr_cpu, bool, 0644);
328
329/* the per-cpu worker pools */
330static DEFINE_PER_CPU_SHARED_ALIGNED(struct worker_pool [NR_STD_WORKER_POOLS], cpu_worker_pools);
331
332static DEFINE_IDR(worker_pool_idr); /* PR: idr of all pools */
333
334/* PL: hash of all unbound pools keyed by pool->attrs */
335static DEFINE_HASHTABLE(unbound_pool_hash, UNBOUND_POOL_HASH_ORDER);
336
337/* I: attributes used when instantiating standard unbound pools on demand */
338static struct workqueue_attrs *unbound_std_wq_attrs[NR_STD_WORKER_POOLS];
339
340/* I: attributes used when instantiating ordered pools on demand */
341static struct workqueue_attrs *ordered_wq_attrs[NR_STD_WORKER_POOLS];
342
343struct workqueue_struct *system_wq __read_mostly;
344EXPORT_SYMBOL(system_wq);
345struct workqueue_struct *system_highpri_wq __read_mostly;
346EXPORT_SYMBOL_GPL(system_highpri_wq);
347struct workqueue_struct *system_long_wq __read_mostly;
348EXPORT_SYMBOL_GPL(system_long_wq);
349struct workqueue_struct *system_unbound_wq __read_mostly;
350EXPORT_SYMBOL_GPL(system_unbound_wq);
351struct workqueue_struct *system_freezable_wq __read_mostly;
352EXPORT_SYMBOL_GPL(system_freezable_wq);
353struct workqueue_struct *system_power_efficient_wq __read_mostly;
354EXPORT_SYMBOL_GPL(system_power_efficient_wq);
355struct workqueue_struct *system_freezable_power_efficient_wq __read_mostly;
356EXPORT_SYMBOL_GPL(system_freezable_power_efficient_wq);
357
358static int worker_thread(void *__worker);
359static void workqueue_sysfs_unregister(struct workqueue_struct *wq);
360static void show_pwq(struct pool_workqueue *pwq);
361
362#define CREATE_TRACE_POINTS
363#include <trace/events/workqueue.h>
364
365#define assert_rcu_or_pool_mutex() \
366 RCU_LOCKDEP_WARN(!rcu_read_lock_held() && \
367 !lockdep_is_held(&wq_pool_mutex), \
368 "RCU or wq_pool_mutex should be held")
369
370#define assert_rcu_or_wq_mutex_or_pool_mutex(wq) \
371 RCU_LOCKDEP_WARN(!rcu_read_lock_held() && \
372 !lockdep_is_held(&wq->mutex) && \
373 !lockdep_is_held(&wq_pool_mutex), \
374 "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 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 wq_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(&wq_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 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 lockdep_is_held(&(wq->mutex)))
428
429#ifdef CONFIG_DEBUG_OBJECTS_WORK
430
431static const struct debug_obj_descr work_debug_descr;
432
433static void *work_debug_hint(void *addr)
434{
435 return ((struct work_struct *) addr)->func;
436}
437
438static bool work_is_static_object(void *addr)
439{
440 struct work_struct *work = addr;
441
442 return test_bit(WORK_STRUCT_STATIC_BIT, work_data_bits(work));
443}
444
445/*
446 * fixup_init is called when:
447 * - an active object is initialized
448 */
449static bool work_fixup_init(void *addr, enum debug_obj_state state)
450{
451 struct work_struct *work = addr;
452
453 switch (state) {
454 case ODEBUG_STATE_ACTIVE:
455 cancel_work_sync(work);
456 debug_object_init(work, &work_debug_descr);
457 return true;
458 default:
459 return false;
460 }
461}
462
463/*
464 * fixup_free is called when:
465 * - an active object is freed
466 */
467static bool work_fixup_free(void *addr, enum debug_obj_state state)
468{
469 struct work_struct *work = addr;
470
471 switch (state) {
472 case ODEBUG_STATE_ACTIVE:
473 cancel_work_sync(work);
474 debug_object_free(work, &work_debug_descr);
475 return true;
476 default:
477 return false;
478 }
479}
480
481static const struct debug_obj_descr work_debug_descr = {
482 .name = "work_struct",
483 .debug_hint = work_debug_hint,
484 .is_static_object = work_is_static_object,
485 .fixup_init = work_fixup_init,
486 .fixup_free = work_fixup_free,
487};
488
489static inline void debug_work_activate(struct work_struct *work)
490{
491 debug_object_activate(work, &work_debug_descr);
492}
493
494static inline void debug_work_deactivate(struct work_struct *work)
495{
496 debug_object_deactivate(work, &work_debug_descr);
497}
498
499void __init_work(struct work_struct *work, int onstack)
500{
501 if (onstack)
502 debug_object_init_on_stack(work, &work_debug_descr);
503 else
504 debug_object_init(work, &work_debug_descr);
505}
506EXPORT_SYMBOL_GPL(__init_work);
507
508void destroy_work_on_stack(struct work_struct *work)
509{
510 debug_object_free(work, &work_debug_descr);
511}
512EXPORT_SYMBOL_GPL(destroy_work_on_stack);
513
514void destroy_delayed_work_on_stack(struct delayed_work *work)
515{
516 destroy_timer_on_stack(&work->timer);
517 debug_object_free(&work->work, &work_debug_descr);
518}
519EXPORT_SYMBOL_GPL(destroy_delayed_work_on_stack);
520
521#else
522static inline void debug_work_activate(struct work_struct *work) { }
523static inline void debug_work_deactivate(struct work_struct *work) { }
524#endif
525
526/**
527 * worker_pool_assign_id - allocate ID and assing it to @pool
528 * @pool: the pool pointer of interest
529 *
530 * Returns 0 if ID in [0, WORK_OFFQ_POOL_NONE) is allocated and assigned
531 * successfully, -errno on failure.
532 */
533static int worker_pool_assign_id(struct worker_pool *pool)
534{
535 int ret;
536
537 lockdep_assert_held(&wq_pool_mutex);
538
539 ret = idr_alloc(&worker_pool_idr, pool, 0, WORK_OFFQ_POOL_NONE,
540 GFP_KERNEL);
541 if (ret >= 0) {
542 pool->id = ret;
543 return 0;
544 }
545 return ret;
546}
547
548/**
549 * unbound_pwq_by_node - return the unbound pool_workqueue for the given node
550 * @wq: the target workqueue
551 * @node: the node ID
552 *
553 * This must be called with any of wq_pool_mutex, wq->mutex or RCU
554 * read locked.
555 * If the pwq needs to be used beyond the locking in effect, the caller is
556 * responsible for guaranteeing that the pwq stays online.
557 *
558 * Return: The unbound pool_workqueue for @node.
559 */
560static struct pool_workqueue *unbound_pwq_by_node(struct workqueue_struct *wq,
561 int node)
562{
563 assert_rcu_or_wq_mutex_or_pool_mutex(wq);
564
565 /*
566 * XXX: @node can be NUMA_NO_NODE if CPU goes offline while a
567 * delayed item is pending. The plan is to keep CPU -> NODE
568 * mapping valid and stable across CPU on/offlines. Once that
569 * happens, this workaround can be removed.
570 */
571 if (unlikely(node == NUMA_NO_NODE))
572 return wq->dfl_pwq;
573
574 return rcu_dereference_raw(wq->numa_pwq_tbl[node]);
575}
576
577static unsigned int work_color_to_flags(int color)
578{
579 return color << WORK_STRUCT_COLOR_SHIFT;
580}
581
582static int get_work_color(struct work_struct *work)
583{
584 return (*work_data_bits(work) >> WORK_STRUCT_COLOR_SHIFT) &
585 ((1 << WORK_STRUCT_COLOR_BITS) - 1);
586}
587
588static int work_next_color(int color)
589{
590 return (color + 1) % WORK_NR_COLORS;
591}
592
593/*
594 * While queued, %WORK_STRUCT_PWQ is set and non flag bits of a work's data
595 * contain the pointer to the queued pwq. Once execution starts, the flag
596 * is cleared and the high bits contain OFFQ flags and pool ID.
597 *
598 * set_work_pwq(), set_work_pool_and_clear_pending(), mark_work_canceling()
599 * and clear_work_data() can be used to set the pwq, pool or clear
600 * work->data. These functions should only be called while the work is
601 * owned - ie. while the PENDING bit is set.
602 *
603 * get_work_pool() and get_work_pwq() can be used to obtain the pool or pwq
604 * corresponding to a work. Pool is available once the work has been
605 * queued anywhere after initialization until it is sync canceled. pwq is
606 * available only while the work item is queued.
607 *
608 * %WORK_OFFQ_CANCELING is used to mark a work item which is being
609 * canceled. While being canceled, a work item may have its PENDING set
610 * but stay off timer and worklist for arbitrarily long and nobody should
611 * try to steal the PENDING bit.
612 */
613static inline void set_work_data(struct work_struct *work, unsigned long data,
614 unsigned long flags)
615{
616 WARN_ON_ONCE(!work_pending(work));
617 atomic_long_set(&work->data, data | flags | work_static(work));
618}
619
620static void set_work_pwq(struct work_struct *work, struct pool_workqueue *pwq,
621 unsigned long extra_flags)
622{
623 set_work_data(work, (unsigned long)pwq,
624 WORK_STRUCT_PENDING | WORK_STRUCT_PWQ | extra_flags);
625}
626
627static void set_work_pool_and_keep_pending(struct work_struct *work,
628 int pool_id)
629{
630 set_work_data(work, (unsigned long)pool_id << WORK_OFFQ_POOL_SHIFT,
631 WORK_STRUCT_PENDING);
632}
633
634static void set_work_pool_and_clear_pending(struct work_struct *work,
635 int pool_id)
636{
637 /*
638 * The following wmb is paired with the implied mb in
639 * test_and_set_bit(PENDING) and ensures all updates to @work made
640 * here are visible to and precede any updates by the next PENDING
641 * owner.
642 */
643 smp_wmb();
644 set_work_data(work, (unsigned long)pool_id << WORK_OFFQ_POOL_SHIFT, 0);
645 /*
646 * The following mb guarantees that previous clear of a PENDING bit
647 * will not be reordered with any speculative LOADS or STORES from
648 * work->current_func, which is executed afterwards. This possible
649 * reordering can lead to a missed execution on attempt to queue
650 * the same @work. E.g. consider this case:
651 *
652 * CPU#0 CPU#1
653 * ---------------------------- --------------------------------
654 *
655 * 1 STORE event_indicated
656 * 2 queue_work_on() {
657 * 3 test_and_set_bit(PENDING)
658 * 4 } set_..._and_clear_pending() {
659 * 5 set_work_data() # clear bit
660 * 6 smp_mb()
661 * 7 work->current_func() {
662 * 8 LOAD event_indicated
663 * }
664 *
665 * Without an explicit full barrier speculative LOAD on line 8 can
666 * be executed before CPU#0 does STORE on line 1. If that happens,
667 * CPU#0 observes the PENDING bit is still set and new execution of
668 * a @work is not queued in a hope, that CPU#1 will eventually
669 * finish the queued @work. Meanwhile CPU#1 does not see
670 * event_indicated is set, because speculative LOAD was executed
671 * before actual STORE.
672 */
673 smp_mb();
674}
675
676static void clear_work_data(struct work_struct *work)
677{
678 smp_wmb(); /* see set_work_pool_and_clear_pending() */
679 set_work_data(work, WORK_STRUCT_NO_POOL, 0);
680}
681
682static struct pool_workqueue *get_work_pwq(struct work_struct *work)
683{
684 unsigned long data = atomic_long_read(&work->data);
685
686 if (data & WORK_STRUCT_PWQ)
687 return (void *)(data & WORK_STRUCT_WQ_DATA_MASK);
688 else
689 return NULL;
690}
691
692/**
693 * get_work_pool - return the worker_pool a given work was associated with
694 * @work: the work item of interest
695 *
696 * Pools are created and destroyed under wq_pool_mutex, and allows read
697 * access under RCU read lock. As such, this function should be
698 * called under wq_pool_mutex or inside of a rcu_read_lock() region.
699 *
700 * All fields of the returned pool are accessible as long as the above
701 * mentioned locking is in effect. If the returned pool needs to be used
702 * beyond the critical section, the caller is responsible for ensuring the
703 * returned pool is and stays online.
704 *
705 * Return: The worker_pool @work was last associated with. %NULL if none.
706 */
707static struct worker_pool *get_work_pool(struct work_struct *work)
708{
709 unsigned long data = atomic_long_read(&work->data);
710 int pool_id;
711
712 assert_rcu_or_pool_mutex();
713
714 if (data & WORK_STRUCT_PWQ)
715 return ((struct pool_workqueue *)
716 (data & WORK_STRUCT_WQ_DATA_MASK))->pool;
717
718 pool_id = data >> WORK_OFFQ_POOL_SHIFT;
719 if (pool_id == WORK_OFFQ_POOL_NONE)
720 return NULL;
721
722 return idr_find(&worker_pool_idr, pool_id);
723}
724
725/**
726 * get_work_pool_id - return the worker pool ID a given work is associated with
727 * @work: the work item of interest
728 *
729 * Return: The worker_pool ID @work was last associated with.
730 * %WORK_OFFQ_POOL_NONE if none.
731 */
732static int get_work_pool_id(struct work_struct *work)
733{
734 unsigned long data = atomic_long_read(&work->data);
735
736 if (data & WORK_STRUCT_PWQ)
737 return ((struct pool_workqueue *)
738 (data & WORK_STRUCT_WQ_DATA_MASK))->pool->id;
739
740 return data >> WORK_OFFQ_POOL_SHIFT;
741}
742
743static void mark_work_canceling(struct work_struct *work)
744{
745 unsigned long pool_id = get_work_pool_id(work);
746
747 pool_id <<= WORK_OFFQ_POOL_SHIFT;
748 set_work_data(work, pool_id | WORK_OFFQ_CANCELING, WORK_STRUCT_PENDING);
749}
750
751static bool work_is_canceling(struct work_struct *work)
752{
753 unsigned long data = atomic_long_read(&work->data);
754
755 return !(data & WORK_STRUCT_PWQ) && (data & WORK_OFFQ_CANCELING);
756}
757
758/*
759 * Policy functions. These define the policies on how the global worker
760 * pools are managed. Unless noted otherwise, these functions assume that
761 * they're being called with pool->lock held.
762 */
763
764static bool __need_more_worker(struct worker_pool *pool)
765{
766 return !atomic_read(&pool->nr_running);
767}
768
769/*
770 * Need to wake up a worker? Called from anything but currently
771 * running workers.
772 *
773 * Note that, because unbound workers never contribute to nr_running, this
774 * function will always return %true for unbound pools as long as the
775 * worklist isn't empty.
776 */
777static bool need_more_worker(struct worker_pool *pool)
778{
779 return !list_empty(&pool->worklist) && __need_more_worker(pool);
780}
781
782/* Can I start working? Called from busy but !running workers. */
783static bool may_start_working(struct worker_pool *pool)
784{
785 return pool->nr_idle;
786}
787
788/* Do I need to keep working? Called from currently running workers. */
789static bool keep_working(struct worker_pool *pool)
790{
791 return !list_empty(&pool->worklist) &&
792 atomic_read(&pool->nr_running) <= 1;
793}
794
795/* Do we need a new worker? Called from manager. */
796static bool need_to_create_worker(struct worker_pool *pool)
797{
798 return need_more_worker(pool) && !may_start_working(pool);
799}
800
801/* Do we have too many workers and should some go away? */
802static bool too_many_workers(struct worker_pool *pool)
803{
804 bool managing = pool->flags & POOL_MANAGER_ACTIVE;
805 int nr_idle = pool->nr_idle + managing; /* manager is considered idle */
806 int nr_busy = pool->nr_workers - nr_idle;
807
808 return nr_idle > 2 && (nr_idle - 2) * MAX_IDLE_WORKERS_RATIO >= nr_busy;
809}
810
811/*
812 * Wake up functions.
813 */
814
815/* Return the first idle worker. Safe with preemption disabled */
816static struct worker *first_idle_worker(struct worker_pool *pool)
817{
818 if (unlikely(list_empty(&pool->idle_list)))
819 return NULL;
820
821 return list_first_entry(&pool->idle_list, struct worker, entry);
822}
823
824/**
825 * wake_up_worker - wake up an idle worker
826 * @pool: worker pool to wake worker from
827 *
828 * Wake up the first idle worker of @pool.
829 *
830 * CONTEXT:
831 * raw_spin_lock_irq(pool->lock).
832 */
833static void wake_up_worker(struct worker_pool *pool)
834{
835 struct worker *worker = first_idle_worker(pool);
836
837 if (likely(worker))
838 wake_up_process(worker->task);
839}
840
841/**
842 * wq_worker_running - a worker is running again
843 * @task: task waking up
844 *
845 * This function is called when a worker returns from schedule()
846 */
847void wq_worker_running(struct task_struct *task)
848{
849 struct worker *worker = kthread_data(task);
850
851 if (!worker->sleeping)
852 return;
853 if (!(worker->flags & WORKER_NOT_RUNNING))
854 atomic_inc(&worker->pool->nr_running);
855 worker->sleeping = 0;
856}
857
858/**
859 * wq_worker_sleeping - a worker is going to sleep
860 * @task: task going to sleep
861 *
862 * This function is called from schedule() when a busy worker is
863 * going to sleep. Preemption needs to be disabled to protect ->sleeping
864 * assignment.
865 */
866void wq_worker_sleeping(struct task_struct *task)
867{
868 struct worker *next, *worker = kthread_data(task);
869 struct worker_pool *pool;
870
871 /*
872 * Rescuers, which may not have all the fields set up like normal
873 * workers, also reach here, let's not access anything before
874 * checking NOT_RUNNING.
875 */
876 if (worker->flags & WORKER_NOT_RUNNING)
877 return;
878
879 pool = worker->pool;
880
881 /* Return if preempted before wq_worker_running() was reached */
882 if (worker->sleeping)
883 return;
884
885 worker->sleeping = 1;
886 raw_spin_lock_irq(&pool->lock);
887
888 /*
889 * The counterpart of the following dec_and_test, implied mb,
890 * worklist not empty test sequence is in insert_work().
891 * Please read comment there.
892 *
893 * NOT_RUNNING is clear. This means that we're bound to and
894 * running on the local cpu w/ rq lock held and preemption
895 * disabled, which in turn means that none else could be
896 * manipulating idle_list, so dereferencing idle_list without pool
897 * lock is safe.
898 */
899 if (atomic_dec_and_test(&pool->nr_running) &&
900 !list_empty(&pool->worklist)) {
901 next = first_idle_worker(pool);
902 if (next)
903 wake_up_process(next->task);
904 }
905 raw_spin_unlock_irq(&pool->lock);
906}
907
908/**
909 * wq_worker_last_func - retrieve worker's last work function
910 * @task: Task to retrieve last work function of.
911 *
912 * Determine the last function a worker executed. This is called from
913 * the scheduler to get a worker's last known identity.
914 *
915 * CONTEXT:
916 * raw_spin_lock_irq(rq->lock)
917 *
918 * This function is called during schedule() when a kworker is going
919 * to sleep. It's used by psi to identify aggregation workers during
920 * dequeuing, to allow periodic aggregation to shut-off when that
921 * worker is the last task in the system or cgroup to go to sleep.
922 *
923 * As this function doesn't involve any workqueue-related locking, it
924 * only returns stable values when called from inside the scheduler's
925 * queuing and dequeuing paths, when @task, which must be a kworker,
926 * is guaranteed to not be processing any works.
927 *
928 * Return:
929 * The last work function %current executed as a worker, NULL if it
930 * hasn't executed any work yet.
931 */
932work_func_t wq_worker_last_func(struct task_struct *task)
933{
934 struct worker *worker = kthread_data(task);
935
936 return worker->last_func;
937}
938
939/**
940 * worker_set_flags - set worker flags and adjust nr_running accordingly
941 * @worker: self
942 * @flags: flags to set
943 *
944 * Set @flags in @worker->flags and adjust nr_running accordingly.
945 *
946 * CONTEXT:
947 * raw_spin_lock_irq(pool->lock)
948 */
949static inline void worker_set_flags(struct worker *worker, unsigned int flags)
950{
951 struct worker_pool *pool = worker->pool;
952
953 WARN_ON_ONCE(worker->task != current);
954
955 /* If transitioning into NOT_RUNNING, adjust nr_running. */
956 if ((flags & WORKER_NOT_RUNNING) &&
957 !(worker->flags & WORKER_NOT_RUNNING)) {
958 atomic_dec(&pool->nr_running);
959 }
960
961 worker->flags |= flags;
962}
963
964/**
965 * worker_clr_flags - clear worker flags and adjust nr_running accordingly
966 * @worker: self
967 * @flags: flags to clear
968 *
969 * Clear @flags in @worker->flags and adjust nr_running accordingly.
970 *
971 * CONTEXT:
972 * raw_spin_lock_irq(pool->lock)
973 */
974static inline void worker_clr_flags(struct worker *worker, unsigned int flags)
975{
976 struct worker_pool *pool = worker->pool;
977 unsigned int oflags = worker->flags;
978
979 WARN_ON_ONCE(worker->task != current);
980
981 worker->flags &= ~flags;
982
983 /*
984 * If transitioning out of NOT_RUNNING, increment nr_running. Note
985 * that the nested NOT_RUNNING is not a noop. NOT_RUNNING is mask
986 * of multiple flags, not a single flag.
987 */
988 if ((flags & WORKER_NOT_RUNNING) && (oflags & WORKER_NOT_RUNNING))
989 if (!(worker->flags & WORKER_NOT_RUNNING))
990 atomic_inc(&pool->nr_running);
991}
992
993/**
994 * find_worker_executing_work - find worker which is executing a work
995 * @pool: pool of interest
996 * @work: work to find worker for
997 *
998 * Find a worker which is executing @work on @pool by searching
999 * @pool->busy_hash which is keyed by the address of @work. For a worker
1000 * to match, its current execution should match the address of @work and
1001 * its work function. This is to avoid unwanted dependency between
1002 * unrelated work executions through a work item being recycled while still
1003 * being executed.
1004 *
1005 * This is a bit tricky. A work item may be freed once its execution
1006 * starts and nothing prevents the freed area from being recycled for
1007 * another work item. If the same work item address ends up being reused
1008 * before the original execution finishes, workqueue will identify the
1009 * recycled work item as currently executing and make it wait until the
1010 * current execution finishes, introducing an unwanted dependency.
1011 *
1012 * This function checks the work item address and work function to avoid
1013 * false positives. Note that this isn't complete as one may construct a
1014 * work function which can introduce dependency onto itself through a
1015 * recycled work item. Well, if somebody wants to shoot oneself in the
1016 * foot that badly, there's only so much we can do, and if such deadlock
1017 * actually occurs, it should be easy to locate the culprit work function.
1018 *
1019 * CONTEXT:
1020 * raw_spin_lock_irq(pool->lock).
1021 *
1022 * Return:
1023 * Pointer to worker which is executing @work if found, %NULL
1024 * otherwise.
1025 */
1026static struct worker *find_worker_executing_work(struct worker_pool *pool,
1027 struct work_struct *work)
1028{
1029 struct worker *worker;
1030
1031 hash_for_each_possible(pool->busy_hash, worker, hentry,
1032 (unsigned long)work)
1033 if (worker->current_work == work &&
1034 worker->current_func == work->func)
1035 return worker;
1036
1037 return NULL;
1038}
1039
1040/**
1041 * move_linked_works - move linked works to a list
1042 * @work: start of series of works to be scheduled
1043 * @head: target list to append @work to
1044 * @nextp: out parameter for nested worklist walking
1045 *
1046 * Schedule linked works starting from @work to @head. Work series to
1047 * be scheduled starts at @work and includes any consecutive work with
1048 * WORK_STRUCT_LINKED set in its predecessor.
1049 *
1050 * If @nextp is not NULL, it's updated to point to the next work of
1051 * the last scheduled work. This allows move_linked_works() to be
1052 * nested inside outer list_for_each_entry_safe().
1053 *
1054 * CONTEXT:
1055 * raw_spin_lock_irq(pool->lock).
1056 */
1057static void move_linked_works(struct work_struct *work, struct list_head *head,
1058 struct work_struct **nextp)
1059{
1060 struct work_struct *n;
1061
1062 /*
1063 * Linked worklist will always end before the end of the list,
1064 * use NULL for list head.
1065 */
1066 list_for_each_entry_safe_from(work, n, NULL, entry) {
1067 list_move_tail(&work->entry, head);
1068 if (!(*work_data_bits(work) & WORK_STRUCT_LINKED))
1069 break;
1070 }
1071
1072 /*
1073 * If we're already inside safe list traversal and have moved
1074 * multiple works to the scheduled queue, the next position
1075 * needs to be updated.
1076 */
1077 if (nextp)
1078 *nextp = n;
1079}
1080
1081/**
1082 * get_pwq - get an extra reference on the specified pool_workqueue
1083 * @pwq: pool_workqueue to get
1084 *
1085 * Obtain an extra reference on @pwq. The caller should guarantee that
1086 * @pwq has positive refcnt and be holding the matching pool->lock.
1087 */
1088static void get_pwq(struct pool_workqueue *pwq)
1089{
1090 lockdep_assert_held(&pwq->pool->lock);
1091 WARN_ON_ONCE(pwq->refcnt <= 0);
1092 pwq->refcnt++;
1093}
1094
1095/**
1096 * put_pwq - put a pool_workqueue reference
1097 * @pwq: pool_workqueue to put
1098 *
1099 * Drop a reference of @pwq. If its refcnt reaches zero, schedule its
1100 * destruction. The caller should be holding the matching pool->lock.
1101 */
1102static void put_pwq(struct pool_workqueue *pwq)
1103{
1104 lockdep_assert_held(&pwq->pool->lock);
1105 if (likely(--pwq->refcnt))
1106 return;
1107 if (WARN_ON_ONCE(!(pwq->wq->flags & WQ_UNBOUND)))
1108 return;
1109 /*
1110 * @pwq can't be released under pool->lock, bounce to
1111 * pwq_unbound_release_workfn(). This never recurses on the same
1112 * pool->lock as this path is taken only for unbound workqueues and
1113 * the release work item is scheduled on a per-cpu workqueue. To
1114 * avoid lockdep warning, unbound pool->locks are given lockdep
1115 * subclass of 1 in get_unbound_pool().
1116 */
1117 schedule_work(&pwq->unbound_release_work);
1118}
1119
1120/**
1121 * put_pwq_unlocked - put_pwq() with surrounding pool lock/unlock
1122 * @pwq: pool_workqueue to put (can be %NULL)
1123 *
1124 * put_pwq() with locking. This function also allows %NULL @pwq.
1125 */
1126static void put_pwq_unlocked(struct pool_workqueue *pwq)
1127{
1128 if (pwq) {
1129 /*
1130 * As both pwqs and pools are RCU protected, the
1131 * following lock operations are safe.
1132 */
1133 raw_spin_lock_irq(&pwq->pool->lock);
1134 put_pwq(pwq);
1135 raw_spin_unlock_irq(&pwq->pool->lock);
1136 }
1137}
1138
1139static void pwq_activate_delayed_work(struct work_struct *work)
1140{
1141 struct pool_workqueue *pwq = get_work_pwq(work);
1142
1143 trace_workqueue_activate_work(work);
1144 if (list_empty(&pwq->pool->worklist))
1145 pwq->pool->watchdog_ts = jiffies;
1146 move_linked_works(work, &pwq->pool->worklist, NULL);
1147 __clear_bit(WORK_STRUCT_DELAYED_BIT, work_data_bits(work));
1148 pwq->nr_active++;
1149}
1150
1151static void pwq_activate_first_delayed(struct pool_workqueue *pwq)
1152{
1153 struct work_struct *work = list_first_entry(&pwq->delayed_works,
1154 struct work_struct, entry);
1155
1156 pwq_activate_delayed_work(work);
1157}
1158
1159/**
1160 * pwq_dec_nr_in_flight - decrement pwq's nr_in_flight
1161 * @pwq: pwq of interest
1162 * @color: color of work which left the queue
1163 *
1164 * A work either has completed or is removed from pending queue,
1165 * decrement nr_in_flight of its pwq and handle workqueue flushing.
1166 *
1167 * CONTEXT:
1168 * raw_spin_lock_irq(pool->lock).
1169 */
1170static void pwq_dec_nr_in_flight(struct pool_workqueue *pwq, int color)
1171{
1172 /* uncolored work items don't participate in flushing or nr_active */
1173 if (color == WORK_NO_COLOR)
1174 goto out_put;
1175
1176 pwq->nr_in_flight[color]--;
1177
1178 pwq->nr_active--;
1179 if (!list_empty(&pwq->delayed_works)) {
1180 /* one down, submit a delayed one */
1181 if (pwq->nr_active < pwq->max_active)
1182 pwq_activate_first_delayed(pwq);
1183 }
1184
1185 /* is flush in progress and are we at the flushing tip? */
1186 if (likely(pwq->flush_color != color))
1187 goto out_put;
1188
1189 /* are there still in-flight works? */
1190 if (pwq->nr_in_flight[color])
1191 goto out_put;
1192
1193 /* this pwq is done, clear flush_color */
1194 pwq->flush_color = -1;
1195
1196 /*
1197 * If this was the last pwq, wake up the first flusher. It
1198 * will handle the rest.
1199 */
1200 if (atomic_dec_and_test(&pwq->wq->nr_pwqs_to_flush))
1201 complete(&pwq->wq->first_flusher->done);
1202out_put:
1203 put_pwq(pwq);
1204}
1205
1206/**
1207 * try_to_grab_pending - steal work item from worklist and disable irq
1208 * @work: work item to steal
1209 * @is_dwork: @work is a delayed_work
1210 * @flags: place to store irq state
1211 *
1212 * Try to grab PENDING bit of @work. This function can handle @work in any
1213 * stable state - idle, on timer or on worklist.
1214 *
1215 * Return:
1216 *
1217 * ======== ================================================================
1218 * 1 if @work was pending and we successfully stole PENDING
1219 * 0 if @work was idle and we claimed PENDING
1220 * -EAGAIN if PENDING couldn't be grabbed at the moment, safe to busy-retry
1221 * -ENOENT if someone else is canceling @work, this state may persist
1222 * for arbitrarily long
1223 * ======== ================================================================
1224 *
1225 * Note:
1226 * On >= 0 return, the caller owns @work's PENDING bit. To avoid getting
1227 * interrupted while holding PENDING and @work off queue, irq must be
1228 * disabled on entry. This, combined with delayed_work->timer being
1229 * irqsafe, ensures that we return -EAGAIN for finite short period of time.
1230 *
1231 * On successful return, >= 0, irq is disabled and the caller is
1232 * responsible for releasing it using local_irq_restore(*@flags).
1233 *
1234 * This function is safe to call from any context including IRQ handler.
1235 */
1236static int try_to_grab_pending(struct work_struct *work, bool is_dwork,
1237 unsigned long *flags)
1238{
1239 struct worker_pool *pool;
1240 struct pool_workqueue *pwq;
1241
1242 local_irq_save(*flags);
1243
1244 /* try to steal the timer if it exists */
1245 if (is_dwork) {
1246 struct delayed_work *dwork = to_delayed_work(work);
1247
1248 /*
1249 * dwork->timer is irqsafe. If del_timer() fails, it's
1250 * guaranteed that the timer is not queued anywhere and not
1251 * running on the local CPU.
1252 */
1253 if (likely(del_timer(&dwork->timer)))
1254 return 1;
1255 }
1256
1257 /* try to claim PENDING the normal way */
1258 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work)))
1259 return 0;
1260
1261 rcu_read_lock();
1262 /*
1263 * The queueing is in progress, or it is already queued. Try to
1264 * steal it from ->worklist without clearing WORK_STRUCT_PENDING.
1265 */
1266 pool = get_work_pool(work);
1267 if (!pool)
1268 goto fail;
1269
1270 raw_spin_lock(&pool->lock);
1271 /*
1272 * work->data is guaranteed to point to pwq only while the work
1273 * item is queued on pwq->wq, and both updating work->data to point
1274 * to pwq on queueing and to pool on dequeueing are done under
1275 * pwq->pool->lock. This in turn guarantees that, if work->data
1276 * points to pwq which is associated with a locked pool, the work
1277 * item is currently queued on that pool.
1278 */
1279 pwq = get_work_pwq(work);
1280 if (pwq && pwq->pool == pool) {
1281 debug_work_deactivate(work);
1282
1283 /*
1284 * A delayed work item cannot be grabbed directly because
1285 * it might have linked NO_COLOR work items which, if left
1286 * on the delayed_list, will confuse pwq->nr_active
1287 * management later on and cause stall. Make sure the work
1288 * item is activated before grabbing.
1289 */
1290 if (*work_data_bits(work) & WORK_STRUCT_DELAYED)
1291 pwq_activate_delayed_work(work);
1292
1293 list_del_init(&work->entry);
1294 pwq_dec_nr_in_flight(pwq, get_work_color(work));
1295
1296 /* work->data points to pwq iff queued, point to pool */
1297 set_work_pool_and_keep_pending(work, pool->id);
1298
1299 raw_spin_unlock(&pool->lock);
1300 rcu_read_unlock();
1301 return 1;
1302 }
1303 raw_spin_unlock(&pool->lock);
1304fail:
1305 rcu_read_unlock();
1306 local_irq_restore(*flags);
1307 if (work_is_canceling(work))
1308 return -ENOENT;
1309 cpu_relax();
1310 return -EAGAIN;
1311}
1312
1313/**
1314 * insert_work - insert a work into a pool
1315 * @pwq: pwq @work belongs to
1316 * @work: work to insert
1317 * @head: insertion point
1318 * @extra_flags: extra WORK_STRUCT_* flags to set
1319 *
1320 * Insert @work which belongs to @pwq after @head. @extra_flags is or'd to
1321 * work_struct flags.
1322 *
1323 * CONTEXT:
1324 * raw_spin_lock_irq(pool->lock).
1325 */
1326static void insert_work(struct pool_workqueue *pwq, struct work_struct *work,
1327 struct list_head *head, unsigned int extra_flags)
1328{
1329 struct worker_pool *pool = pwq->pool;
1330
1331 /* record the work call stack in order to print it in KASAN reports */
1332 kasan_record_aux_stack(work);
1333
1334 /* we own @work, set data and link */
1335 set_work_pwq(work, pwq, extra_flags);
1336 list_add_tail(&work->entry, head);
1337 get_pwq(pwq);
1338
1339 /*
1340 * Ensure either wq_worker_sleeping() sees the above
1341 * list_add_tail() or we see zero nr_running to avoid workers lying
1342 * around lazily while there are works to be processed.
1343 */
1344 smp_mb();
1345
1346 if (__need_more_worker(pool))
1347 wake_up_worker(pool);
1348}
1349
1350/*
1351 * Test whether @work is being queued from another work executing on the
1352 * same workqueue.
1353 */
1354static bool is_chained_work(struct workqueue_struct *wq)
1355{
1356 struct worker *worker;
1357
1358 worker = current_wq_worker();
1359 /*
1360 * Return %true iff I'm a worker executing a work item on @wq. If
1361 * I'm @worker, it's safe to dereference it without locking.
1362 */
1363 return worker && worker->current_pwq->wq == wq;
1364}
1365
1366/*
1367 * When queueing an unbound work item to a wq, prefer local CPU if allowed
1368 * by wq_unbound_cpumask. Otherwise, round robin among the allowed ones to
1369 * avoid perturbing sensitive tasks.
1370 */
1371static int wq_select_unbound_cpu(int cpu)
1372{
1373 static bool printed_dbg_warning;
1374 int new_cpu;
1375
1376 if (likely(!wq_debug_force_rr_cpu)) {
1377 if (cpumask_test_cpu(cpu, wq_unbound_cpumask))
1378 return cpu;
1379 } else if (!printed_dbg_warning) {
1380 pr_warn("workqueue: round-robin CPU selection forced, expect performance impact\n");
1381 printed_dbg_warning = true;
1382 }
1383
1384 if (cpumask_empty(wq_unbound_cpumask))
1385 return cpu;
1386
1387 new_cpu = __this_cpu_read(wq_rr_cpu_last);
1388 new_cpu = cpumask_next_and(new_cpu, wq_unbound_cpumask, cpu_online_mask);
1389 if (unlikely(new_cpu >= nr_cpu_ids)) {
1390 new_cpu = cpumask_first_and(wq_unbound_cpumask, cpu_online_mask);
1391 if (unlikely(new_cpu >= nr_cpu_ids))
1392 return cpu;
1393 }
1394 __this_cpu_write(wq_rr_cpu_last, new_cpu);
1395
1396 return new_cpu;
1397}
1398
1399static void __queue_work(int cpu, struct workqueue_struct *wq,
1400 struct work_struct *work)
1401{
1402 struct pool_workqueue *pwq;
1403 struct worker_pool *last_pool;
1404 struct list_head *worklist;
1405 unsigned int work_flags;
1406 unsigned int req_cpu = cpu;
1407
1408 /*
1409 * While a work item is PENDING && off queue, a task trying to
1410 * steal the PENDING will busy-loop waiting for it to either get
1411 * queued or lose PENDING. Grabbing PENDING and queueing should
1412 * happen with IRQ disabled.
1413 */
1414 lockdep_assert_irqs_disabled();
1415
1416
1417 /* if draining, only works from the same workqueue are allowed */
1418 if (unlikely(wq->flags & __WQ_DRAINING) &&
1419 WARN_ON_ONCE(!is_chained_work(wq)))
1420 return;
1421 rcu_read_lock();
1422retry:
1423 /* pwq which will be used unless @work is executing elsewhere */
1424 if (wq->flags & WQ_UNBOUND) {
1425 if (req_cpu == WORK_CPU_UNBOUND)
1426 cpu = wq_select_unbound_cpu(raw_smp_processor_id());
1427 pwq = unbound_pwq_by_node(wq, cpu_to_node(cpu));
1428 } else {
1429 if (req_cpu == WORK_CPU_UNBOUND)
1430 cpu = raw_smp_processor_id();
1431 pwq = per_cpu_ptr(wq->cpu_pwqs, cpu);
1432 }
1433
1434 /*
1435 * If @work was previously on a different pool, it might still be
1436 * running there, in which case the work needs to be queued on that
1437 * pool to guarantee non-reentrancy.
1438 */
1439 last_pool = get_work_pool(work);
1440 if (last_pool && last_pool != pwq->pool) {
1441 struct worker *worker;
1442
1443 raw_spin_lock(&last_pool->lock);
1444
1445 worker = find_worker_executing_work(last_pool, work);
1446
1447 if (worker && worker->current_pwq->wq == wq) {
1448 pwq = worker->current_pwq;
1449 } else {
1450 /* meh... not running there, queue here */
1451 raw_spin_unlock(&last_pool->lock);
1452 raw_spin_lock(&pwq->pool->lock);
1453 }
1454 } else {
1455 raw_spin_lock(&pwq->pool->lock);
1456 }
1457
1458 /*
1459 * pwq is determined and locked. For unbound pools, we could have
1460 * raced with pwq release and it could already be dead. If its
1461 * refcnt is zero, repeat pwq selection. Note that pwqs never die
1462 * without another pwq replacing it in the numa_pwq_tbl or while
1463 * work items are executing on it, so the retrying is guaranteed to
1464 * make forward-progress.
1465 */
1466 if (unlikely(!pwq->refcnt)) {
1467 if (wq->flags & WQ_UNBOUND) {
1468 raw_spin_unlock(&pwq->pool->lock);
1469 cpu_relax();
1470 goto retry;
1471 }
1472 /* oops */
1473 WARN_ONCE(true, "workqueue: per-cpu pwq for %s on cpu%d has 0 refcnt",
1474 wq->name, cpu);
1475 }
1476
1477 /* pwq determined, queue */
1478 trace_workqueue_queue_work(req_cpu, pwq, work);
1479
1480 if (WARN_ON(!list_empty(&work->entry)))
1481 goto out;
1482
1483 pwq->nr_in_flight[pwq->work_color]++;
1484 work_flags = work_color_to_flags(pwq->work_color);
1485
1486 if (likely(pwq->nr_active < pwq->max_active)) {
1487 trace_workqueue_activate_work(work);
1488 pwq->nr_active++;
1489 worklist = &pwq->pool->worklist;
1490 if (list_empty(worklist))
1491 pwq->pool->watchdog_ts = jiffies;
1492 } else {
1493 work_flags |= WORK_STRUCT_DELAYED;
1494 worklist = &pwq->delayed_works;
1495 }
1496
1497 debug_work_activate(work);
1498 insert_work(pwq, work, worklist, work_flags);
1499
1500out:
1501 raw_spin_unlock(&pwq->pool->lock);
1502 rcu_read_unlock();
1503}
1504
1505/**
1506 * queue_work_on - queue work on specific cpu
1507 * @cpu: CPU number to execute work on
1508 * @wq: workqueue to use
1509 * @work: work to queue
1510 *
1511 * We queue the work to a specific CPU, the caller must ensure it
1512 * can't go away.
1513 *
1514 * Return: %false if @work was already on a queue, %true otherwise.
1515 */
1516bool queue_work_on(int cpu, struct workqueue_struct *wq,
1517 struct work_struct *work)
1518{
1519 bool ret = false;
1520 unsigned long flags;
1521
1522 local_irq_save(flags);
1523
1524 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1525 __queue_work(cpu, wq, work);
1526 ret = true;
1527 }
1528
1529 local_irq_restore(flags);
1530 return ret;
1531}
1532EXPORT_SYMBOL(queue_work_on);
1533
1534/**
1535 * workqueue_select_cpu_near - Select a CPU based on NUMA node
1536 * @node: NUMA node ID that we want to select a CPU from
1537 *
1538 * This function will attempt to find a "random" cpu available on a given
1539 * node. If there are no CPUs available on the given node it will return
1540 * WORK_CPU_UNBOUND indicating that we should just schedule to any
1541 * available CPU if we need to schedule this work.
1542 */
1543static int workqueue_select_cpu_near(int node)
1544{
1545 int cpu;
1546
1547 /* No point in doing this if NUMA isn't enabled for workqueues */
1548 if (!wq_numa_enabled)
1549 return WORK_CPU_UNBOUND;
1550
1551 /* Delay binding to CPU if node is not valid or online */
1552 if (node < 0 || node >= MAX_NUMNODES || !node_online(node))
1553 return WORK_CPU_UNBOUND;
1554
1555 /* Use local node/cpu if we are already there */
1556 cpu = raw_smp_processor_id();
1557 if (node == cpu_to_node(cpu))
1558 return cpu;
1559
1560 /* Use "random" otherwise know as "first" online CPU of node */
1561 cpu = cpumask_any_and(cpumask_of_node(node), cpu_online_mask);
1562
1563 /* If CPU is valid return that, otherwise just defer */
1564 return cpu < nr_cpu_ids ? cpu : WORK_CPU_UNBOUND;
1565}
1566
1567/**
1568 * queue_work_node - queue work on a "random" cpu for a given NUMA node
1569 * @node: NUMA node that we are targeting the work for
1570 * @wq: workqueue to use
1571 * @work: work to queue
1572 *
1573 * We queue the work to a "random" CPU within a given NUMA node. The basic
1574 * idea here is to provide a way to somehow associate work with a given
1575 * NUMA node.
1576 *
1577 * This function will only make a best effort attempt at getting this onto
1578 * the right NUMA node. If no node is requested or the requested node is
1579 * offline then we just fall back to standard queue_work behavior.
1580 *
1581 * Currently the "random" CPU ends up being the first available CPU in the
1582 * intersection of cpu_online_mask and the cpumask of the node, unless we
1583 * are running on the node. In that case we just use the current CPU.
1584 *
1585 * Return: %false if @work was already on a queue, %true otherwise.
1586 */
1587bool queue_work_node(int node, struct workqueue_struct *wq,
1588 struct work_struct *work)
1589{
1590 unsigned long flags;
1591 bool ret = false;
1592
1593 /*
1594 * This current implementation is specific to unbound workqueues.
1595 * Specifically we only return the first available CPU for a given
1596 * node instead of cycling through individual CPUs within the node.
1597 *
1598 * If this is used with a per-cpu workqueue then the logic in
1599 * workqueue_select_cpu_near would need to be updated to allow for
1600 * some round robin type logic.
1601 */
1602 WARN_ON_ONCE(!(wq->flags & WQ_UNBOUND));
1603
1604 local_irq_save(flags);
1605
1606 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1607 int cpu = workqueue_select_cpu_near(node);
1608
1609 __queue_work(cpu, wq, work);
1610 ret = true;
1611 }
1612
1613 local_irq_restore(flags);
1614 return ret;
1615}
1616EXPORT_SYMBOL_GPL(queue_work_node);
1617
1618void delayed_work_timer_fn(struct timer_list *t)
1619{
1620 struct delayed_work *dwork = from_timer(dwork, t, timer);
1621
1622 /* should have been called from irqsafe timer with irq already off */
1623 __queue_work(dwork->cpu, dwork->wq, &dwork->work);
1624}
1625EXPORT_SYMBOL(delayed_work_timer_fn);
1626
1627static void __queue_delayed_work(int cpu, struct workqueue_struct *wq,
1628 struct delayed_work *dwork, unsigned long delay)
1629{
1630 struct timer_list *timer = &dwork->timer;
1631 struct work_struct *work = &dwork->work;
1632
1633 WARN_ON_ONCE(!wq);
1634 WARN_ON_FUNCTION_MISMATCH(timer->function, delayed_work_timer_fn);
1635 WARN_ON_ONCE(timer_pending(timer));
1636 WARN_ON_ONCE(!list_empty(&work->entry));
1637
1638 /*
1639 * If @delay is 0, queue @dwork->work immediately. This is for
1640 * both optimization and correctness. The earliest @timer can
1641 * expire is on the closest next tick and delayed_work users depend
1642 * on that there's no such delay when @delay is 0.
1643 */
1644 if (!delay) {
1645 __queue_work(cpu, wq, &dwork->work);
1646 return;
1647 }
1648
1649 dwork->wq = wq;
1650 dwork->cpu = cpu;
1651 timer->expires = jiffies + delay;
1652
1653 if (unlikely(cpu != WORK_CPU_UNBOUND))
1654 add_timer_on(timer, cpu);
1655 else
1656 add_timer(timer);
1657}
1658
1659/**
1660 * queue_delayed_work_on - queue work on specific CPU after delay
1661 * @cpu: CPU number to execute work on
1662 * @wq: workqueue to use
1663 * @dwork: work to queue
1664 * @delay: number of jiffies to wait before queueing
1665 *
1666 * Return: %false if @work was already on a queue, %true otherwise. If
1667 * @delay is zero and @dwork is idle, it will be scheduled for immediate
1668 * execution.
1669 */
1670bool queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
1671 struct delayed_work *dwork, unsigned long delay)
1672{
1673 struct work_struct *work = &dwork->work;
1674 bool ret = false;
1675 unsigned long flags;
1676
1677 /* read the comment in __queue_work() */
1678 local_irq_save(flags);
1679
1680 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1681 __queue_delayed_work(cpu, wq, dwork, delay);
1682 ret = true;
1683 }
1684
1685 local_irq_restore(flags);
1686 return ret;
1687}
1688EXPORT_SYMBOL(queue_delayed_work_on);
1689
1690/**
1691 * mod_delayed_work_on - modify delay of or queue a delayed work on specific CPU
1692 * @cpu: CPU number to execute work on
1693 * @wq: workqueue to use
1694 * @dwork: work to queue
1695 * @delay: number of jiffies to wait before queueing
1696 *
1697 * If @dwork is idle, equivalent to queue_delayed_work_on(); otherwise,
1698 * modify @dwork's timer so that it expires after @delay. If @delay is
1699 * zero, @work is guaranteed to be scheduled immediately regardless of its
1700 * current state.
1701 *
1702 * Return: %false if @dwork was idle and queued, %true if @dwork was
1703 * pending and its timer was modified.
1704 *
1705 * This function is safe to call from any context including IRQ handler.
1706 * See try_to_grab_pending() for details.
1707 */
1708bool mod_delayed_work_on(int cpu, struct workqueue_struct *wq,
1709 struct delayed_work *dwork, unsigned long delay)
1710{
1711 unsigned long flags;
1712 int ret;
1713
1714 do {
1715 ret = try_to_grab_pending(&dwork->work, true, &flags);
1716 } while (unlikely(ret == -EAGAIN));
1717
1718 if (likely(ret >= 0)) {
1719 __queue_delayed_work(cpu, wq, dwork, delay);
1720 local_irq_restore(flags);
1721 }
1722
1723 /* -ENOENT from try_to_grab_pending() becomes %true */
1724 return ret;
1725}
1726EXPORT_SYMBOL_GPL(mod_delayed_work_on);
1727
1728static void rcu_work_rcufn(struct rcu_head *rcu)
1729{
1730 struct rcu_work *rwork = container_of(rcu, struct rcu_work, rcu);
1731
1732 /* read the comment in __queue_work() */
1733 local_irq_disable();
1734 __queue_work(WORK_CPU_UNBOUND, rwork->wq, &rwork->work);
1735 local_irq_enable();
1736}
1737
1738/**
1739 * queue_rcu_work - queue work after a RCU grace period
1740 * @wq: workqueue to use
1741 * @rwork: work to queue
1742 *
1743 * Return: %false if @rwork was already pending, %true otherwise. Note
1744 * that a full RCU grace period is guaranteed only after a %true return.
1745 * While @rwork is guaranteed to be executed after a %false return, the
1746 * execution may happen before a full RCU grace period has passed.
1747 */
1748bool queue_rcu_work(struct workqueue_struct *wq, struct rcu_work *rwork)
1749{
1750 struct work_struct *work = &rwork->work;
1751
1752 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1753 rwork->wq = wq;
1754 call_rcu(&rwork->rcu, rcu_work_rcufn);
1755 return true;
1756 }
1757
1758 return false;
1759}
1760EXPORT_SYMBOL(queue_rcu_work);
1761
1762/**
1763 * worker_enter_idle - enter idle state
1764 * @worker: worker which is entering idle state
1765 *
1766 * @worker is entering idle state. Update stats and idle timer if
1767 * necessary.
1768 *
1769 * LOCKING:
1770 * raw_spin_lock_irq(pool->lock).
1771 */
1772static void worker_enter_idle(struct worker *worker)
1773{
1774 struct worker_pool *pool = worker->pool;
1775
1776 if (WARN_ON_ONCE(worker->flags & WORKER_IDLE) ||
1777 WARN_ON_ONCE(!list_empty(&worker->entry) &&
1778 (worker->hentry.next || worker->hentry.pprev)))
1779 return;
1780
1781 /* can't use worker_set_flags(), also called from create_worker() */
1782 worker->flags |= WORKER_IDLE;
1783 pool->nr_idle++;
1784 worker->last_active = jiffies;
1785
1786 /* idle_list is LIFO */
1787 list_add(&worker->entry, &pool->idle_list);
1788
1789 if (too_many_workers(pool) && !timer_pending(&pool->idle_timer))
1790 mod_timer(&pool->idle_timer, jiffies + IDLE_WORKER_TIMEOUT);
1791
1792 /*
1793 * Sanity check nr_running. Because unbind_workers() releases
1794 * pool->lock between setting %WORKER_UNBOUND and zapping
1795 * nr_running, the warning may trigger spuriously. Check iff
1796 * unbind is not in progress.
1797 */
1798 WARN_ON_ONCE(!(pool->flags & POOL_DISASSOCIATED) &&
1799 pool->nr_workers == pool->nr_idle &&
1800 atomic_read(&pool->nr_running));
1801}
1802
1803/**
1804 * worker_leave_idle - leave idle state
1805 * @worker: worker which is leaving idle state
1806 *
1807 * @worker is leaving idle state. Update stats.
1808 *
1809 * LOCKING:
1810 * raw_spin_lock_irq(pool->lock).
1811 */
1812static void worker_leave_idle(struct worker *worker)
1813{
1814 struct worker_pool *pool = worker->pool;
1815
1816 if (WARN_ON_ONCE(!(worker->flags & WORKER_IDLE)))
1817 return;
1818 worker_clr_flags(worker, WORKER_IDLE);
1819 pool->nr_idle--;
1820 list_del_init(&worker->entry);
1821}
1822
1823static struct worker *alloc_worker(int node)
1824{
1825 struct worker *worker;
1826
1827 worker = kzalloc_node(sizeof(*worker), GFP_KERNEL, node);
1828 if (worker) {
1829 INIT_LIST_HEAD(&worker->entry);
1830 INIT_LIST_HEAD(&worker->scheduled);
1831 INIT_LIST_HEAD(&worker->node);
1832 /* on creation a worker is in !idle && prep state */
1833 worker->flags = WORKER_PREP;
1834 }
1835 return worker;
1836}
1837
1838/**
1839 * worker_attach_to_pool() - attach a worker to a pool
1840 * @worker: worker to be attached
1841 * @pool: the target pool
1842 *
1843 * Attach @worker to @pool. Once attached, the %WORKER_UNBOUND flag and
1844 * cpu-binding of @worker are kept coordinated with the pool across
1845 * cpu-[un]hotplugs.
1846 */
1847static void worker_attach_to_pool(struct worker *worker,
1848 struct worker_pool *pool)
1849{
1850 mutex_lock(&wq_pool_attach_mutex);
1851
1852 /*
1853 * The wq_pool_attach_mutex ensures %POOL_DISASSOCIATED remains
1854 * stable across this function. See the comments above the flag
1855 * definition for details.
1856 */
1857 if (pool->flags & POOL_DISASSOCIATED)
1858 worker->flags |= WORKER_UNBOUND;
1859 else
1860 kthread_set_per_cpu(worker->task, pool->cpu);
1861
1862 if (worker->rescue_wq)
1863 set_cpus_allowed_ptr(worker->task, pool->attrs->cpumask);
1864
1865 list_add_tail(&worker->node, &pool->workers);
1866 worker->pool = pool;
1867
1868 mutex_unlock(&wq_pool_attach_mutex);
1869}
1870
1871/**
1872 * worker_detach_from_pool() - detach a worker from its pool
1873 * @worker: worker which is attached to its pool
1874 *
1875 * Undo the attaching which had been done in worker_attach_to_pool(). The
1876 * caller worker shouldn't access to the pool after detached except it has
1877 * other reference to the pool.
1878 */
1879static void worker_detach_from_pool(struct worker *worker)
1880{
1881 struct worker_pool *pool = worker->pool;
1882 struct completion *detach_completion = NULL;
1883
1884 mutex_lock(&wq_pool_attach_mutex);
1885
1886 kthread_set_per_cpu(worker->task, -1);
1887 list_del(&worker->node);
1888 worker->pool = NULL;
1889
1890 if (list_empty(&pool->workers))
1891 detach_completion = pool->detach_completion;
1892 mutex_unlock(&wq_pool_attach_mutex);
1893
1894 /* clear leftover flags without pool->lock after it is detached */
1895 worker->flags &= ~(WORKER_UNBOUND | WORKER_REBOUND);
1896
1897 if (detach_completion)
1898 complete(detach_completion);
1899}
1900
1901/**
1902 * create_worker - create a new workqueue worker
1903 * @pool: pool the new worker will belong to
1904 *
1905 * Create and start a new worker which is attached to @pool.
1906 *
1907 * CONTEXT:
1908 * Might sleep. Does GFP_KERNEL allocations.
1909 *
1910 * Return:
1911 * Pointer to the newly created worker.
1912 */
1913static struct worker *create_worker(struct worker_pool *pool)
1914{
1915 struct worker *worker = NULL;
1916 int id = -1;
1917 char id_buf[16];
1918
1919 /* ID is needed to determine kthread name */
1920 id = ida_simple_get(&pool->worker_ida, 0, 0, GFP_KERNEL);
1921 if (id < 0)
1922 goto fail;
1923
1924 worker = alloc_worker(pool->node);
1925 if (!worker)
1926 goto fail;
1927
1928 worker->id = id;
1929
1930 if (pool->cpu >= 0)
1931 snprintf(id_buf, sizeof(id_buf), "%d:%d%s", pool->cpu, id,
1932 pool->attrs->nice < 0 ? "H" : "");
1933 else
1934 snprintf(id_buf, sizeof(id_buf), "u%d:%d", pool->id, id);
1935
1936 worker->task = kthread_create_on_node(worker_thread, worker, pool->node,
1937 "kworker/%s", id_buf);
1938 if (IS_ERR(worker->task))
1939 goto fail;
1940
1941 set_user_nice(worker->task, pool->attrs->nice);
1942 kthread_bind_mask(worker->task, pool->attrs->cpumask);
1943
1944 /* successful, attach the worker to the pool */
1945 worker_attach_to_pool(worker, pool);
1946
1947 /* start the newly created worker */
1948 raw_spin_lock_irq(&pool->lock);
1949 worker->pool->nr_workers++;
1950 worker_enter_idle(worker);
1951 wake_up_process(worker->task);
1952 raw_spin_unlock_irq(&pool->lock);
1953
1954 return worker;
1955
1956fail:
1957 if (id >= 0)
1958 ida_simple_remove(&pool->worker_ida, id);
1959 kfree(worker);
1960 return NULL;
1961}
1962
1963/**
1964 * destroy_worker - destroy a workqueue worker
1965 * @worker: worker to be destroyed
1966 *
1967 * Destroy @worker and adjust @pool stats accordingly. The worker should
1968 * be idle.
1969 *
1970 * CONTEXT:
1971 * raw_spin_lock_irq(pool->lock).
1972 */
1973static void destroy_worker(struct worker *worker)
1974{
1975 struct worker_pool *pool = worker->pool;
1976
1977 lockdep_assert_held(&pool->lock);
1978
1979 /* sanity check frenzy */
1980 if (WARN_ON(worker->current_work) ||
1981 WARN_ON(!list_empty(&worker->scheduled)) ||
1982 WARN_ON(!(worker->flags & WORKER_IDLE)))
1983 return;
1984
1985 pool->nr_workers--;
1986 pool->nr_idle--;
1987
1988 list_del_init(&worker->entry);
1989 worker->flags |= WORKER_DIE;
1990 wake_up_process(worker->task);
1991}
1992
1993static void idle_worker_timeout(struct timer_list *t)
1994{
1995 struct worker_pool *pool = from_timer(pool, t, idle_timer);
1996
1997 raw_spin_lock_irq(&pool->lock);
1998
1999 while (too_many_workers(pool)) {
2000 struct worker *worker;
2001 unsigned long expires;
2002
2003 /* idle_list is kept in LIFO order, check the last one */
2004 worker = list_entry(pool->idle_list.prev, struct worker, entry);
2005 expires = worker->last_active + IDLE_WORKER_TIMEOUT;
2006
2007 if (time_before(jiffies, expires)) {
2008 mod_timer(&pool->idle_timer, expires);
2009 break;
2010 }
2011
2012 destroy_worker(worker);
2013 }
2014
2015 raw_spin_unlock_irq(&pool->lock);
2016}
2017
2018static void send_mayday(struct work_struct *work)
2019{
2020 struct pool_workqueue *pwq = get_work_pwq(work);
2021 struct workqueue_struct *wq = pwq->wq;
2022
2023 lockdep_assert_held(&wq_mayday_lock);
2024
2025 if (!wq->rescuer)
2026 return;
2027
2028 /* mayday mayday mayday */
2029 if (list_empty(&pwq->mayday_node)) {
2030 /*
2031 * If @pwq is for an unbound wq, its base ref may be put at
2032 * any time due to an attribute change. Pin @pwq until the
2033 * rescuer is done with it.
2034 */
2035 get_pwq(pwq);
2036 list_add_tail(&pwq->mayday_node, &wq->maydays);
2037 wake_up_process(wq->rescuer->task);
2038 }
2039}
2040
2041static void pool_mayday_timeout(struct timer_list *t)
2042{
2043 struct worker_pool *pool = from_timer(pool, t, mayday_timer);
2044 struct work_struct *work;
2045
2046 raw_spin_lock_irq(&pool->lock);
2047 raw_spin_lock(&wq_mayday_lock); /* for wq->maydays */
2048
2049 if (need_to_create_worker(pool)) {
2050 /*
2051 * We've been trying to create a new worker but
2052 * haven't been successful. We might be hitting an
2053 * allocation deadlock. Send distress signals to
2054 * rescuers.
2055 */
2056 list_for_each_entry(work, &pool->worklist, entry)
2057 send_mayday(work);
2058 }
2059
2060 raw_spin_unlock(&wq_mayday_lock);
2061 raw_spin_unlock_irq(&pool->lock);
2062
2063 mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INTERVAL);
2064}
2065
2066/**
2067 * maybe_create_worker - create a new worker if necessary
2068 * @pool: pool to create a new worker for
2069 *
2070 * Create a new worker for @pool if necessary. @pool is guaranteed to
2071 * have at least one idle worker on return from this function. If
2072 * creating a new worker takes longer than MAYDAY_INTERVAL, mayday is
2073 * sent to all rescuers with works scheduled on @pool to resolve
2074 * possible allocation deadlock.
2075 *
2076 * On return, need_to_create_worker() is guaranteed to be %false and
2077 * may_start_working() %true.
2078 *
2079 * LOCKING:
2080 * raw_spin_lock_irq(pool->lock) which may be released and regrabbed
2081 * multiple times. Does GFP_KERNEL allocations. Called only from
2082 * manager.
2083 */
2084static void maybe_create_worker(struct worker_pool *pool)
2085__releases(&pool->lock)
2086__acquires(&pool->lock)
2087{
2088restart:
2089 raw_spin_unlock_irq(&pool->lock);
2090
2091 /* if we don't make progress in MAYDAY_INITIAL_TIMEOUT, call for help */
2092 mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INITIAL_TIMEOUT);
2093
2094 while (true) {
2095 if (create_worker(pool) || !need_to_create_worker(pool))
2096 break;
2097
2098 schedule_timeout_interruptible(CREATE_COOLDOWN);
2099
2100 if (!need_to_create_worker(pool))
2101 break;
2102 }
2103
2104 del_timer_sync(&pool->mayday_timer);
2105 raw_spin_lock_irq(&pool->lock);
2106 /*
2107 * This is necessary even after a new worker was just successfully
2108 * created as @pool->lock was dropped and the new worker might have
2109 * already become busy.
2110 */
2111 if (need_to_create_worker(pool))
2112 goto restart;
2113}
2114
2115/**
2116 * manage_workers - manage worker pool
2117 * @worker: self
2118 *
2119 * Assume the manager role and manage the worker pool @worker belongs
2120 * to. At any given time, there can be only zero or one manager per
2121 * pool. The exclusion is handled automatically by this function.
2122 *
2123 * The caller can safely start processing works on false return. On
2124 * true return, it's guaranteed that need_to_create_worker() is false
2125 * and may_start_working() is true.
2126 *
2127 * CONTEXT:
2128 * raw_spin_lock_irq(pool->lock) which may be released and regrabbed
2129 * multiple times. Does GFP_KERNEL allocations.
2130 *
2131 * Return:
2132 * %false if the pool doesn't need management and the caller can safely
2133 * start processing works, %true if management function was performed and
2134 * the conditions that the caller verified before calling the function may
2135 * no longer be true.
2136 */
2137static bool manage_workers(struct worker *worker)
2138{
2139 struct worker_pool *pool = worker->pool;
2140
2141 if (pool->flags & POOL_MANAGER_ACTIVE)
2142 return false;
2143
2144 pool->flags |= POOL_MANAGER_ACTIVE;
2145 pool->manager = worker;
2146
2147 maybe_create_worker(pool);
2148
2149 pool->manager = NULL;
2150 pool->flags &= ~POOL_MANAGER_ACTIVE;
2151 rcuwait_wake_up(&manager_wait);
2152 return true;
2153}
2154
2155/**
2156 * process_one_work - process single work
2157 * @worker: self
2158 * @work: work to process
2159 *
2160 * Process @work. This function contains all the logics necessary to
2161 * process a single work including synchronization against and
2162 * interaction with other workers on the same cpu, queueing and
2163 * flushing. As long as context requirement is met, any worker can
2164 * call this function to process a work.
2165 *
2166 * CONTEXT:
2167 * raw_spin_lock_irq(pool->lock) which is released and regrabbed.
2168 */
2169static void process_one_work(struct worker *worker, struct work_struct *work)
2170__releases(&pool->lock)
2171__acquires(&pool->lock)
2172{
2173 struct pool_workqueue *pwq = get_work_pwq(work);
2174 struct worker_pool *pool = worker->pool;
2175 bool cpu_intensive = pwq->wq->flags & WQ_CPU_INTENSIVE;
2176 int work_color;
2177 struct worker *collision;
2178#ifdef CONFIG_LOCKDEP
2179 /*
2180 * It is permissible to free the struct work_struct from
2181 * inside the function that is called from it, this we need to
2182 * take into account for lockdep too. To avoid bogus "held
2183 * lock freed" warnings as well as problems when looking into
2184 * work->lockdep_map, make a copy and use that here.
2185 */
2186 struct lockdep_map lockdep_map;
2187
2188 lockdep_copy_map(&lockdep_map, &work->lockdep_map);
2189#endif
2190 /* ensure we're on the correct CPU */
2191 WARN_ON_ONCE(!(pool->flags & POOL_DISASSOCIATED) &&
2192 raw_smp_processor_id() != pool->cpu);
2193
2194 /*
2195 * A single work shouldn't be executed concurrently by
2196 * multiple workers on a single cpu. Check whether anyone is
2197 * already processing the work. If so, defer the work to the
2198 * currently executing one.
2199 */
2200 collision = find_worker_executing_work(pool, work);
2201 if (unlikely(collision)) {
2202 move_linked_works(work, &collision->scheduled, NULL);
2203 return;
2204 }
2205
2206 /* claim and dequeue */
2207 debug_work_deactivate(work);
2208 hash_add(pool->busy_hash, &worker->hentry, (unsigned long)work);
2209 worker->current_work = work;
2210 worker->current_func = work->func;
2211 worker->current_pwq = pwq;
2212 work_color = get_work_color(work);
2213
2214 /*
2215 * Record wq name for cmdline and debug reporting, may get
2216 * overridden through set_worker_desc().
2217 */
2218 strscpy(worker->desc, pwq->wq->name, WORKER_DESC_LEN);
2219
2220 list_del_init(&work->entry);
2221
2222 /*
2223 * CPU intensive works don't participate in concurrency management.
2224 * They're the scheduler's responsibility. This takes @worker out
2225 * of concurrency management and the next code block will chain
2226 * execution of the pending work items.
2227 */
2228 if (unlikely(cpu_intensive))
2229 worker_set_flags(worker, WORKER_CPU_INTENSIVE);
2230
2231 /*
2232 * Wake up another worker if necessary. The condition is always
2233 * false for normal per-cpu workers since nr_running would always
2234 * be >= 1 at this point. This is used to chain execution of the
2235 * pending work items for WORKER_NOT_RUNNING workers such as the
2236 * UNBOUND and CPU_INTENSIVE ones.
2237 */
2238 if (need_more_worker(pool))
2239 wake_up_worker(pool);
2240
2241 /*
2242 * Record the last pool and clear PENDING which should be the last
2243 * update to @work. Also, do this inside @pool->lock so that
2244 * PENDING and queued state changes happen together while IRQ is
2245 * disabled.
2246 */
2247 set_work_pool_and_clear_pending(work, pool->id);
2248
2249 raw_spin_unlock_irq(&pool->lock);
2250
2251 lock_map_acquire(&pwq->wq->lockdep_map);
2252 lock_map_acquire(&lockdep_map);
2253 /*
2254 * Strictly speaking we should mark the invariant state without holding
2255 * any locks, that is, before these two lock_map_acquire()'s.
2256 *
2257 * However, that would result in:
2258 *
2259 * A(W1)
2260 * WFC(C)
2261 * A(W1)
2262 * C(C)
2263 *
2264 * Which would create W1->C->W1 dependencies, even though there is no
2265 * actual deadlock possible. There are two solutions, using a
2266 * read-recursive acquire on the work(queue) 'locks', but this will then
2267 * hit the lockdep limitation on recursive locks, or simply discard
2268 * these locks.
2269 *
2270 * AFAICT there is no possible deadlock scenario between the
2271 * flush_work() and complete() primitives (except for single-threaded
2272 * workqueues), so hiding them isn't a problem.
2273 */
2274 lockdep_invariant_state(true);
2275 trace_workqueue_execute_start(work);
2276 worker->current_func(work);
2277 /*
2278 * While we must be careful to not use "work" after this, the trace
2279 * point will only record its address.
2280 */
2281 trace_workqueue_execute_end(work, worker->current_func);
2282 lock_map_release(&lockdep_map);
2283 lock_map_release(&pwq->wq->lockdep_map);
2284
2285 if (unlikely(in_atomic() || lockdep_depth(current) > 0)) {
2286 pr_err("BUG: workqueue leaked lock or atomic: %s/0x%08x/%d\n"
2287 " last function: %ps\n",
2288 current->comm, preempt_count(), task_pid_nr(current),
2289 worker->current_func);
2290 debug_show_held_locks(current);
2291 dump_stack();
2292 }
2293
2294 /*
2295 * The following prevents a kworker from hogging CPU on !PREEMPTION
2296 * kernels, where a requeueing work item waiting for something to
2297 * happen could deadlock with stop_machine as such work item could
2298 * indefinitely requeue itself while all other CPUs are trapped in
2299 * stop_machine. At the same time, report a quiescent RCU state so
2300 * the same condition doesn't freeze RCU.
2301 */
2302 cond_resched();
2303
2304 raw_spin_lock_irq(&pool->lock);
2305
2306 /* clear cpu intensive status */
2307 if (unlikely(cpu_intensive))
2308 worker_clr_flags(worker, WORKER_CPU_INTENSIVE);
2309
2310 /* tag the worker for identification in schedule() */
2311 worker->last_func = worker->current_func;
2312
2313 /* we're done with it, release */
2314 hash_del(&worker->hentry);
2315 worker->current_work = NULL;
2316 worker->current_func = NULL;
2317 worker->current_pwq = NULL;
2318 pwq_dec_nr_in_flight(pwq, work_color);
2319}
2320
2321/**
2322 * process_scheduled_works - process scheduled works
2323 * @worker: self
2324 *
2325 * Process all scheduled works. Please note that the scheduled list
2326 * may change while processing a work, so this function repeatedly
2327 * fetches a work from the top and executes it.
2328 *
2329 * CONTEXT:
2330 * raw_spin_lock_irq(pool->lock) which may be released and regrabbed
2331 * multiple times.
2332 */
2333static void process_scheduled_works(struct worker *worker)
2334{
2335 while (!list_empty(&worker->scheduled)) {
2336 struct work_struct *work = list_first_entry(&worker->scheduled,
2337 struct work_struct, entry);
2338 process_one_work(worker, work);
2339 }
2340}
2341
2342static void set_pf_worker(bool val)
2343{
2344 mutex_lock(&wq_pool_attach_mutex);
2345 if (val)
2346 current->flags |= PF_WQ_WORKER;
2347 else
2348 current->flags &= ~PF_WQ_WORKER;
2349 mutex_unlock(&wq_pool_attach_mutex);
2350}
2351
2352/**
2353 * worker_thread - the worker thread function
2354 * @__worker: self
2355 *
2356 * The worker thread function. All workers belong to a worker_pool -
2357 * either a per-cpu one or dynamic unbound one. These workers process all
2358 * work items regardless of their specific target workqueue. The only
2359 * exception is work items which belong to workqueues with a rescuer which
2360 * will be explained in rescuer_thread().
2361 *
2362 * Return: 0
2363 */
2364static int worker_thread(void *__worker)
2365{
2366 struct worker *worker = __worker;
2367 struct worker_pool *pool = worker->pool;
2368
2369 /* tell the scheduler that this is a workqueue worker */
2370 set_pf_worker(true);
2371woke_up:
2372 raw_spin_lock_irq(&pool->lock);
2373
2374 /* am I supposed to die? */
2375 if (unlikely(worker->flags & WORKER_DIE)) {
2376 raw_spin_unlock_irq(&pool->lock);
2377 WARN_ON_ONCE(!list_empty(&worker->entry));
2378 set_pf_worker(false);
2379
2380 set_task_comm(worker->task, "kworker/dying");
2381 ida_simple_remove(&pool->worker_ida, worker->id);
2382 worker_detach_from_pool(worker);
2383 kfree(worker);
2384 return 0;
2385 }
2386
2387 worker_leave_idle(worker);
2388recheck:
2389 /* no more worker necessary? */
2390 if (!need_more_worker(pool))
2391 goto sleep;
2392
2393 /* do we need to manage? */
2394 if (unlikely(!may_start_working(pool)) && manage_workers(worker))
2395 goto recheck;
2396
2397 /*
2398 * ->scheduled list can only be filled while a worker is
2399 * preparing to process a work or actually processing it.
2400 * Make sure nobody diddled with it while I was sleeping.
2401 */
2402 WARN_ON_ONCE(!list_empty(&worker->scheduled));
2403
2404 /*
2405 * Finish PREP stage. We're guaranteed to have at least one idle
2406 * worker or that someone else has already assumed the manager
2407 * role. This is where @worker starts participating in concurrency
2408 * management if applicable and concurrency management is restored
2409 * after being rebound. See rebind_workers() for details.
2410 */
2411 worker_clr_flags(worker, WORKER_PREP | WORKER_REBOUND);
2412
2413 do {
2414 struct work_struct *work =
2415 list_first_entry(&pool->worklist,
2416 struct work_struct, entry);
2417
2418 pool->watchdog_ts = jiffies;
2419
2420 if (likely(!(*work_data_bits(work) & WORK_STRUCT_LINKED))) {
2421 /* optimization path, not strictly necessary */
2422 process_one_work(worker, work);
2423 if (unlikely(!list_empty(&worker->scheduled)))
2424 process_scheduled_works(worker);
2425 } else {
2426 move_linked_works(work, &worker->scheduled, NULL);
2427 process_scheduled_works(worker);
2428 }
2429 } while (keep_working(pool));
2430
2431 worker_set_flags(worker, WORKER_PREP);
2432sleep:
2433 /*
2434 * pool->lock is held and there's no work to process and no need to
2435 * manage, sleep. Workers are woken up only while holding
2436 * pool->lock or from local cpu, so setting the current state
2437 * before releasing pool->lock is enough to prevent losing any
2438 * event.
2439 */
2440 worker_enter_idle(worker);
2441 __set_current_state(TASK_IDLE);
2442 raw_spin_unlock_irq(&pool->lock);
2443 schedule();
2444 goto woke_up;
2445}
2446
2447/**
2448 * rescuer_thread - the rescuer thread function
2449 * @__rescuer: self
2450 *
2451 * Workqueue rescuer thread function. There's one rescuer for each
2452 * workqueue which has WQ_MEM_RECLAIM set.
2453 *
2454 * Regular work processing on a pool may block trying to create a new
2455 * worker which uses GFP_KERNEL allocation which has slight chance of
2456 * developing into deadlock if some works currently on the same queue
2457 * need to be processed to satisfy the GFP_KERNEL allocation. This is
2458 * the problem rescuer solves.
2459 *
2460 * When such condition is possible, the pool summons rescuers of all
2461 * workqueues which have works queued on the pool and let them process
2462 * those works so that forward progress can be guaranteed.
2463 *
2464 * This should happen rarely.
2465 *
2466 * Return: 0
2467 */
2468static int rescuer_thread(void *__rescuer)
2469{
2470 struct worker *rescuer = __rescuer;
2471 struct workqueue_struct *wq = rescuer->rescue_wq;
2472 struct list_head *scheduled = &rescuer->scheduled;
2473 bool should_stop;
2474
2475 set_user_nice(current, RESCUER_NICE_LEVEL);
2476
2477 /*
2478 * Mark rescuer as worker too. As WORKER_PREP is never cleared, it
2479 * doesn't participate in concurrency management.
2480 */
2481 set_pf_worker(true);
2482repeat:
2483 set_current_state(TASK_IDLE);
2484
2485 /*
2486 * By the time the rescuer is requested to stop, the workqueue
2487 * shouldn't have any work pending, but @wq->maydays may still have
2488 * pwq(s) queued. This can happen by non-rescuer workers consuming
2489 * all the work items before the rescuer got to them. Go through
2490 * @wq->maydays processing before acting on should_stop so that the
2491 * list is always empty on exit.
2492 */
2493 should_stop = kthread_should_stop();
2494
2495 /* see whether any pwq is asking for help */
2496 raw_spin_lock_irq(&wq_mayday_lock);
2497
2498 while (!list_empty(&wq->maydays)) {
2499 struct pool_workqueue *pwq = list_first_entry(&wq->maydays,
2500 struct pool_workqueue, mayday_node);
2501 struct worker_pool *pool = pwq->pool;
2502 struct work_struct *work, *n;
2503 bool first = true;
2504
2505 __set_current_state(TASK_RUNNING);
2506 list_del_init(&pwq->mayday_node);
2507
2508 raw_spin_unlock_irq(&wq_mayday_lock);
2509
2510 worker_attach_to_pool(rescuer, pool);
2511
2512 raw_spin_lock_irq(&pool->lock);
2513
2514 /*
2515 * Slurp in all works issued via this workqueue and
2516 * process'em.
2517 */
2518 WARN_ON_ONCE(!list_empty(scheduled));
2519 list_for_each_entry_safe(work, n, &pool->worklist, entry) {
2520 if (get_work_pwq(work) == pwq) {
2521 if (first)
2522 pool->watchdog_ts = jiffies;
2523 move_linked_works(work, scheduled, &n);
2524 }
2525 first = false;
2526 }
2527
2528 if (!list_empty(scheduled)) {
2529 process_scheduled_works(rescuer);
2530
2531 /*
2532 * The above execution of rescued work items could
2533 * have created more to rescue through
2534 * pwq_activate_first_delayed() or chained
2535 * queueing. Let's put @pwq back on mayday list so
2536 * that such back-to-back work items, which may be
2537 * being used to relieve memory pressure, don't
2538 * incur MAYDAY_INTERVAL delay inbetween.
2539 */
2540 if (pwq->nr_active && need_to_create_worker(pool)) {
2541 raw_spin_lock(&wq_mayday_lock);
2542 /*
2543 * Queue iff we aren't racing destruction
2544 * and somebody else hasn't queued it already.
2545 */
2546 if (wq->rescuer && list_empty(&pwq->mayday_node)) {
2547 get_pwq(pwq);
2548 list_add_tail(&pwq->mayday_node, &wq->maydays);
2549 }
2550 raw_spin_unlock(&wq_mayday_lock);
2551 }
2552 }
2553
2554 /*
2555 * Put the reference grabbed by send_mayday(). @pool won't
2556 * go away while we're still attached to it.
2557 */
2558 put_pwq(pwq);
2559
2560 /*
2561 * Leave this pool. If need_more_worker() is %true, notify a
2562 * regular worker; otherwise, we end up with 0 concurrency
2563 * and stalling the execution.
2564 */
2565 if (need_more_worker(pool))
2566 wake_up_worker(pool);
2567
2568 raw_spin_unlock_irq(&pool->lock);
2569
2570 worker_detach_from_pool(rescuer);
2571
2572 raw_spin_lock_irq(&wq_mayday_lock);
2573 }
2574
2575 raw_spin_unlock_irq(&wq_mayday_lock);
2576
2577 if (should_stop) {
2578 __set_current_state(TASK_RUNNING);
2579 set_pf_worker(false);
2580 return 0;
2581 }
2582
2583 /* rescuers should never participate in concurrency management */
2584 WARN_ON_ONCE(!(rescuer->flags & WORKER_NOT_RUNNING));
2585 schedule();
2586 goto repeat;
2587}
2588
2589/**
2590 * check_flush_dependency - check for flush dependency sanity
2591 * @target_wq: workqueue being flushed
2592 * @target_work: work item being flushed (NULL for workqueue flushes)
2593 *
2594 * %current is trying to flush the whole @target_wq or @target_work on it.
2595 * If @target_wq doesn't have %WQ_MEM_RECLAIM, verify that %current is not
2596 * reclaiming memory or running on a workqueue which doesn't have
2597 * %WQ_MEM_RECLAIM as that can break forward-progress guarantee leading to
2598 * a deadlock.
2599 */
2600static void check_flush_dependency(struct workqueue_struct *target_wq,
2601 struct work_struct *target_work)
2602{
2603 work_func_t target_func = target_work ? target_work->func : NULL;
2604 struct worker *worker;
2605
2606 if (target_wq->flags & WQ_MEM_RECLAIM)
2607 return;
2608
2609 worker = current_wq_worker();
2610
2611 WARN_ONCE(current->flags & PF_MEMALLOC,
2612 "workqueue: PF_MEMALLOC task %d(%s) is flushing !WQ_MEM_RECLAIM %s:%ps",
2613 current->pid, current->comm, target_wq->name, target_func);
2614 WARN_ONCE(worker && ((worker->current_pwq->wq->flags &
2615 (WQ_MEM_RECLAIM | __WQ_LEGACY)) == WQ_MEM_RECLAIM),
2616 "workqueue: WQ_MEM_RECLAIM %s:%ps is flushing !WQ_MEM_RECLAIM %s:%ps",
2617 worker->current_pwq->wq->name, worker->current_func,
2618 target_wq->name, target_func);
2619}
2620
2621struct wq_barrier {
2622 struct work_struct work;
2623 struct completion done;
2624 struct task_struct *task; /* purely informational */
2625};
2626
2627static void wq_barrier_func(struct work_struct *work)
2628{
2629 struct wq_barrier *barr = container_of(work, struct wq_barrier, work);
2630 complete(&barr->done);
2631}
2632
2633/**
2634 * insert_wq_barrier - insert a barrier work
2635 * @pwq: pwq to insert barrier into
2636 * @barr: wq_barrier to insert
2637 * @target: target work to attach @barr to
2638 * @worker: worker currently executing @target, NULL if @target is not executing
2639 *
2640 * @barr is linked to @target such that @barr is completed only after
2641 * @target finishes execution. Please note that the ordering
2642 * guarantee is observed only with respect to @target and on the local
2643 * cpu.
2644 *
2645 * Currently, a queued barrier can't be canceled. This is because
2646 * try_to_grab_pending() can't determine whether the work to be
2647 * grabbed is at the head of the queue and thus can't clear LINKED
2648 * flag of the previous work while there must be a valid next work
2649 * after a work with LINKED flag set.
2650 *
2651 * Note that when @worker is non-NULL, @target may be modified
2652 * underneath us, so we can't reliably determine pwq from @target.
2653 *
2654 * CONTEXT:
2655 * raw_spin_lock_irq(pool->lock).
2656 */
2657static void insert_wq_barrier(struct pool_workqueue *pwq,
2658 struct wq_barrier *barr,
2659 struct work_struct *target, struct worker *worker)
2660{
2661 struct list_head *head;
2662 unsigned int linked = 0;
2663
2664 /*
2665 * debugobject calls are safe here even with pool->lock locked
2666 * as we know for sure that this will not trigger any of the
2667 * checks and call back into the fixup functions where we
2668 * might deadlock.
2669 */
2670 INIT_WORK_ONSTACK(&barr->work, wq_barrier_func);
2671 __set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(&barr->work));
2672
2673 init_completion_map(&barr->done, &target->lockdep_map);
2674
2675 barr->task = current;
2676
2677 /*
2678 * If @target is currently being executed, schedule the
2679 * barrier to the worker; otherwise, put it after @target.
2680 */
2681 if (worker)
2682 head = worker->scheduled.next;
2683 else {
2684 unsigned long *bits = work_data_bits(target);
2685
2686 head = target->entry.next;
2687 /* there can already be other linked works, inherit and set */
2688 linked = *bits & WORK_STRUCT_LINKED;
2689 __set_bit(WORK_STRUCT_LINKED_BIT, bits);
2690 }
2691
2692 debug_work_activate(&barr->work);
2693 insert_work(pwq, &barr->work, head,
2694 work_color_to_flags(WORK_NO_COLOR) | linked);
2695}
2696
2697/**
2698 * flush_workqueue_prep_pwqs - prepare pwqs for workqueue flushing
2699 * @wq: workqueue being flushed
2700 * @flush_color: new flush color, < 0 for no-op
2701 * @work_color: new work color, < 0 for no-op
2702 *
2703 * Prepare pwqs for workqueue flushing.
2704 *
2705 * If @flush_color is non-negative, flush_color on all pwqs should be
2706 * -1. If no pwq has in-flight commands at the specified color, all
2707 * pwq->flush_color's stay at -1 and %false is returned. If any pwq
2708 * has in flight commands, its pwq->flush_color is set to
2709 * @flush_color, @wq->nr_pwqs_to_flush is updated accordingly, pwq
2710 * wakeup logic is armed and %true is returned.
2711 *
2712 * The caller should have initialized @wq->first_flusher prior to
2713 * calling this function with non-negative @flush_color. If
2714 * @flush_color is negative, no flush color update is done and %false
2715 * is returned.
2716 *
2717 * If @work_color is non-negative, all pwqs should have the same
2718 * work_color which is previous to @work_color and all will be
2719 * advanced to @work_color.
2720 *
2721 * CONTEXT:
2722 * mutex_lock(wq->mutex).
2723 *
2724 * Return:
2725 * %true if @flush_color >= 0 and there's something to flush. %false
2726 * otherwise.
2727 */
2728static bool flush_workqueue_prep_pwqs(struct workqueue_struct *wq,
2729 int flush_color, int work_color)
2730{
2731 bool wait = false;
2732 struct pool_workqueue *pwq;
2733
2734 if (flush_color >= 0) {
2735 WARN_ON_ONCE(atomic_read(&wq->nr_pwqs_to_flush));
2736 atomic_set(&wq->nr_pwqs_to_flush, 1);
2737 }
2738
2739 for_each_pwq(pwq, wq) {
2740 struct worker_pool *pool = pwq->pool;
2741
2742 raw_spin_lock_irq(&pool->lock);
2743
2744 if (flush_color >= 0) {
2745 WARN_ON_ONCE(pwq->flush_color != -1);
2746
2747 if (pwq->nr_in_flight[flush_color]) {
2748 pwq->flush_color = flush_color;
2749 atomic_inc(&wq->nr_pwqs_to_flush);
2750 wait = true;
2751 }
2752 }
2753
2754 if (work_color >= 0) {
2755 WARN_ON_ONCE(work_color != work_next_color(pwq->work_color));
2756 pwq->work_color = work_color;
2757 }
2758
2759 raw_spin_unlock_irq(&pool->lock);
2760 }
2761
2762 if (flush_color >= 0 && atomic_dec_and_test(&wq->nr_pwqs_to_flush))
2763 complete(&wq->first_flusher->done);
2764
2765 return wait;
2766}
2767
2768/**
2769 * flush_workqueue - ensure that any scheduled work has run to completion.
2770 * @wq: workqueue to flush
2771 *
2772 * This function sleeps until all work items which were queued on entry
2773 * have finished execution, but it is not livelocked by new incoming ones.
2774 */
2775void flush_workqueue(struct workqueue_struct *wq)
2776{
2777 struct wq_flusher this_flusher = {
2778 .list = LIST_HEAD_INIT(this_flusher.list),
2779 .flush_color = -1,
2780 .done = COMPLETION_INITIALIZER_ONSTACK_MAP(this_flusher.done, wq->lockdep_map),
2781 };
2782 int next_color;
2783
2784 if (WARN_ON(!wq_online))
2785 return;
2786
2787 lock_map_acquire(&wq->lockdep_map);
2788 lock_map_release(&wq->lockdep_map);
2789
2790 mutex_lock(&wq->mutex);
2791
2792 /*
2793 * Start-to-wait phase
2794 */
2795 next_color = work_next_color(wq->work_color);
2796
2797 if (next_color != wq->flush_color) {
2798 /*
2799 * Color space is not full. The current work_color
2800 * becomes our flush_color and work_color is advanced
2801 * by one.
2802 */
2803 WARN_ON_ONCE(!list_empty(&wq->flusher_overflow));
2804 this_flusher.flush_color = wq->work_color;
2805 wq->work_color = next_color;
2806
2807 if (!wq->first_flusher) {
2808 /* no flush in progress, become the first flusher */
2809 WARN_ON_ONCE(wq->flush_color != this_flusher.flush_color);
2810
2811 wq->first_flusher = &this_flusher;
2812
2813 if (!flush_workqueue_prep_pwqs(wq, wq->flush_color,
2814 wq->work_color)) {
2815 /* nothing to flush, done */
2816 wq->flush_color = next_color;
2817 wq->first_flusher = NULL;
2818 goto out_unlock;
2819 }
2820 } else {
2821 /* wait in queue */
2822 WARN_ON_ONCE(wq->flush_color == this_flusher.flush_color);
2823 list_add_tail(&this_flusher.list, &wq->flusher_queue);
2824 flush_workqueue_prep_pwqs(wq, -1, wq->work_color);
2825 }
2826 } else {
2827 /*
2828 * Oops, color space is full, wait on overflow queue.
2829 * The next flush completion will assign us
2830 * flush_color and transfer to flusher_queue.
2831 */
2832 list_add_tail(&this_flusher.list, &wq->flusher_overflow);
2833 }
2834
2835 check_flush_dependency(wq, NULL);
2836
2837 mutex_unlock(&wq->mutex);
2838
2839 wait_for_completion(&this_flusher.done);
2840
2841 /*
2842 * Wake-up-and-cascade phase
2843 *
2844 * First flushers are responsible for cascading flushes and
2845 * handling overflow. Non-first flushers can simply return.
2846 */
2847 if (READ_ONCE(wq->first_flusher) != &this_flusher)
2848 return;
2849
2850 mutex_lock(&wq->mutex);
2851
2852 /* we might have raced, check again with mutex held */
2853 if (wq->first_flusher != &this_flusher)
2854 goto out_unlock;
2855
2856 WRITE_ONCE(wq->first_flusher, NULL);
2857
2858 WARN_ON_ONCE(!list_empty(&this_flusher.list));
2859 WARN_ON_ONCE(wq->flush_color != this_flusher.flush_color);
2860
2861 while (true) {
2862 struct wq_flusher *next, *tmp;
2863
2864 /* complete all the flushers sharing the current flush color */
2865 list_for_each_entry_safe(next, tmp, &wq->flusher_queue, list) {
2866 if (next->flush_color != wq->flush_color)
2867 break;
2868 list_del_init(&next->list);
2869 complete(&next->done);
2870 }
2871
2872 WARN_ON_ONCE(!list_empty(&wq->flusher_overflow) &&
2873 wq->flush_color != work_next_color(wq->work_color));
2874
2875 /* this flush_color is finished, advance by one */
2876 wq->flush_color = work_next_color(wq->flush_color);
2877
2878 /* one color has been freed, handle overflow queue */
2879 if (!list_empty(&wq->flusher_overflow)) {
2880 /*
2881 * Assign the same color to all overflowed
2882 * flushers, advance work_color and append to
2883 * flusher_queue. This is the start-to-wait
2884 * phase for these overflowed flushers.
2885 */
2886 list_for_each_entry(tmp, &wq->flusher_overflow, list)
2887 tmp->flush_color = wq->work_color;
2888
2889 wq->work_color = work_next_color(wq->work_color);
2890
2891 list_splice_tail_init(&wq->flusher_overflow,
2892 &wq->flusher_queue);
2893 flush_workqueue_prep_pwqs(wq, -1, wq->work_color);
2894 }
2895
2896 if (list_empty(&wq->flusher_queue)) {
2897 WARN_ON_ONCE(wq->flush_color != wq->work_color);
2898 break;
2899 }
2900
2901 /*
2902 * Need to flush more colors. Make the next flusher
2903 * the new first flusher and arm pwqs.
2904 */
2905 WARN_ON_ONCE(wq->flush_color == wq->work_color);
2906 WARN_ON_ONCE(wq->flush_color != next->flush_color);
2907
2908 list_del_init(&next->list);
2909 wq->first_flusher = next;
2910
2911 if (flush_workqueue_prep_pwqs(wq, wq->flush_color, -1))
2912 break;
2913
2914 /*
2915 * Meh... this color is already done, clear first
2916 * flusher and repeat cascading.
2917 */
2918 wq->first_flusher = NULL;
2919 }
2920
2921out_unlock:
2922 mutex_unlock(&wq->mutex);
2923}
2924EXPORT_SYMBOL(flush_workqueue);
2925
2926/**
2927 * drain_workqueue - drain a workqueue
2928 * @wq: workqueue to drain
2929 *
2930 * Wait until the workqueue becomes empty. While draining is in progress,
2931 * only chain queueing is allowed. IOW, only currently pending or running
2932 * work items on @wq can queue further work items on it. @wq is flushed
2933 * repeatedly until it becomes empty. The number of flushing is determined
2934 * by the depth of chaining and should be relatively short. Whine if it
2935 * takes too long.
2936 */
2937void drain_workqueue(struct workqueue_struct *wq)
2938{
2939 unsigned int flush_cnt = 0;
2940 struct pool_workqueue *pwq;
2941
2942 /*
2943 * __queue_work() needs to test whether there are drainers, is much
2944 * hotter than drain_workqueue() and already looks at @wq->flags.
2945 * Use __WQ_DRAINING so that queue doesn't have to check nr_drainers.
2946 */
2947 mutex_lock(&wq->mutex);
2948 if (!wq->nr_drainers++)
2949 wq->flags |= __WQ_DRAINING;
2950 mutex_unlock(&wq->mutex);
2951reflush:
2952 flush_workqueue(wq);
2953
2954 mutex_lock(&wq->mutex);
2955
2956 for_each_pwq(pwq, wq) {
2957 bool drained;
2958
2959 raw_spin_lock_irq(&pwq->pool->lock);
2960 drained = !pwq->nr_active && list_empty(&pwq->delayed_works);
2961 raw_spin_unlock_irq(&pwq->pool->lock);
2962
2963 if (drained)
2964 continue;
2965
2966 if (++flush_cnt == 10 ||
2967 (flush_cnt % 100 == 0 && flush_cnt <= 1000))
2968 pr_warn("workqueue %s: %s() isn't complete after %u tries\n",
2969 wq->name, __func__, flush_cnt);
2970
2971 mutex_unlock(&wq->mutex);
2972 goto reflush;
2973 }
2974
2975 if (!--wq->nr_drainers)
2976 wq->flags &= ~__WQ_DRAINING;
2977 mutex_unlock(&wq->mutex);
2978}
2979EXPORT_SYMBOL_GPL(drain_workqueue);
2980
2981static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr,
2982 bool from_cancel)
2983{
2984 struct worker *worker = NULL;
2985 struct worker_pool *pool;
2986 struct pool_workqueue *pwq;
2987
2988 might_sleep();
2989
2990 rcu_read_lock();
2991 pool = get_work_pool(work);
2992 if (!pool) {
2993 rcu_read_unlock();
2994 return false;
2995 }
2996
2997 raw_spin_lock_irq(&pool->lock);
2998 /* see the comment in try_to_grab_pending() with the same code */
2999 pwq = get_work_pwq(work);
3000 if (pwq) {
3001 if (unlikely(pwq->pool != pool))
3002 goto already_gone;
3003 } else {
3004 worker = find_worker_executing_work(pool, work);
3005 if (!worker)
3006 goto already_gone;
3007 pwq = worker->current_pwq;
3008 }
3009
3010 check_flush_dependency(pwq->wq, work);
3011
3012 insert_wq_barrier(pwq, barr, work, worker);
3013 raw_spin_unlock_irq(&pool->lock);
3014
3015 /*
3016 * Force a lock recursion deadlock when using flush_work() inside a
3017 * single-threaded or rescuer equipped workqueue.
3018 *
3019 * For single threaded workqueues the deadlock happens when the work
3020 * is after the work issuing the flush_work(). For rescuer equipped
3021 * workqueues the deadlock happens when the rescuer stalls, blocking
3022 * forward progress.
3023 */
3024 if (!from_cancel &&
3025 (pwq->wq->saved_max_active == 1 || pwq->wq->rescuer)) {
3026 lock_map_acquire(&pwq->wq->lockdep_map);
3027 lock_map_release(&pwq->wq->lockdep_map);
3028 }
3029 rcu_read_unlock();
3030 return true;
3031already_gone:
3032 raw_spin_unlock_irq(&pool->lock);
3033 rcu_read_unlock();
3034 return false;
3035}
3036
3037static bool __flush_work(struct work_struct *work, bool from_cancel)
3038{
3039 struct wq_barrier barr;
3040
3041 if (WARN_ON(!wq_online))
3042 return false;
3043
3044 if (WARN_ON(!work->func))
3045 return false;
3046
3047 if (!from_cancel) {
3048 lock_map_acquire(&work->lockdep_map);
3049 lock_map_release(&work->lockdep_map);
3050 }
3051
3052 if (start_flush_work(work, &barr, from_cancel)) {
3053 wait_for_completion(&barr.done);
3054 destroy_work_on_stack(&barr.work);
3055 return true;
3056 } else {
3057 return false;
3058 }
3059}
3060
3061/**
3062 * flush_work - wait for a work to finish executing the last queueing instance
3063 * @work: the work to flush
3064 *
3065 * Wait until @work has finished execution. @work is guaranteed to be idle
3066 * on return if it hasn't been requeued since flush started.
3067 *
3068 * Return:
3069 * %true if flush_work() waited for the work to finish execution,
3070 * %false if it was already idle.
3071 */
3072bool flush_work(struct work_struct *work)
3073{
3074 return __flush_work(work, false);
3075}
3076EXPORT_SYMBOL_GPL(flush_work);
3077
3078struct cwt_wait {
3079 wait_queue_entry_t wait;
3080 struct work_struct *work;
3081};
3082
3083static int cwt_wakefn(wait_queue_entry_t *wait, unsigned mode, int sync, void *key)
3084{
3085 struct cwt_wait *cwait = container_of(wait, struct cwt_wait, wait);
3086
3087 if (cwait->work != key)
3088 return 0;
3089 return autoremove_wake_function(wait, mode, sync, key);
3090}
3091
3092static bool __cancel_work_timer(struct work_struct *work, bool is_dwork)
3093{
3094 static DECLARE_WAIT_QUEUE_HEAD(cancel_waitq);
3095 unsigned long flags;
3096 int ret;
3097
3098 do {
3099 ret = try_to_grab_pending(work, is_dwork, &flags);
3100 /*
3101 * If someone else is already canceling, wait for it to
3102 * finish. flush_work() doesn't work for PREEMPT_NONE
3103 * because we may get scheduled between @work's completion
3104 * and the other canceling task resuming and clearing
3105 * CANCELING - flush_work() will return false immediately
3106 * as @work is no longer busy, try_to_grab_pending() will
3107 * return -ENOENT as @work is still being canceled and the
3108 * other canceling task won't be able to clear CANCELING as
3109 * we're hogging the CPU.
3110 *
3111 * Let's wait for completion using a waitqueue. As this
3112 * may lead to the thundering herd problem, use a custom
3113 * wake function which matches @work along with exclusive
3114 * wait and wakeup.
3115 */
3116 if (unlikely(ret == -ENOENT)) {
3117 struct cwt_wait cwait;
3118
3119 init_wait(&cwait.wait);
3120 cwait.wait.func = cwt_wakefn;
3121 cwait.work = work;
3122
3123 prepare_to_wait_exclusive(&cancel_waitq, &cwait.wait,
3124 TASK_UNINTERRUPTIBLE);
3125 if (work_is_canceling(work))
3126 schedule();
3127 finish_wait(&cancel_waitq, &cwait.wait);
3128 }
3129 } while (unlikely(ret < 0));
3130
3131 /* tell other tasks trying to grab @work to back off */
3132 mark_work_canceling(work);
3133 local_irq_restore(flags);
3134
3135 /*
3136 * This allows canceling during early boot. We know that @work
3137 * isn't executing.
3138 */
3139 if (wq_online)
3140 __flush_work(work, true);
3141
3142 clear_work_data(work);
3143
3144 /*
3145 * Paired with prepare_to_wait() above so that either
3146 * waitqueue_active() is visible here or !work_is_canceling() is
3147 * visible there.
3148 */
3149 smp_mb();
3150 if (waitqueue_active(&cancel_waitq))
3151 __wake_up(&cancel_waitq, TASK_NORMAL, 1, work);
3152
3153 return ret;
3154}
3155
3156/**
3157 * cancel_work_sync - cancel a work and wait for it to finish
3158 * @work: the work to cancel
3159 *
3160 * Cancel @work and wait for its execution to finish. This function
3161 * can be used even if the work re-queues itself or migrates to
3162 * another workqueue. On return from this function, @work is
3163 * guaranteed to be not pending or executing on any CPU.
3164 *
3165 * cancel_work_sync(&delayed_work->work) must not be used for
3166 * delayed_work's. Use cancel_delayed_work_sync() instead.
3167 *
3168 * The caller must ensure that the workqueue on which @work was last
3169 * queued can't be destroyed before this function returns.
3170 *
3171 * Return:
3172 * %true if @work was pending, %false otherwise.
3173 */
3174bool cancel_work_sync(struct work_struct *work)
3175{
3176 return __cancel_work_timer(work, false);
3177}
3178EXPORT_SYMBOL_GPL(cancel_work_sync);
3179
3180/**
3181 * flush_delayed_work - wait for a dwork to finish executing the last queueing
3182 * @dwork: the delayed work to flush
3183 *
3184 * Delayed timer is cancelled and the pending work is queued for
3185 * immediate execution. Like flush_work(), this function only
3186 * considers the last queueing instance of @dwork.
3187 *
3188 * Return:
3189 * %true if flush_work() waited for the work to finish execution,
3190 * %false if it was already idle.
3191 */
3192bool flush_delayed_work(struct delayed_work *dwork)
3193{
3194 local_irq_disable();
3195 if (del_timer_sync(&dwork->timer))
3196 __queue_work(dwork->cpu, dwork->wq, &dwork->work);
3197 local_irq_enable();
3198 return flush_work(&dwork->work);
3199}
3200EXPORT_SYMBOL(flush_delayed_work);
3201
3202/**
3203 * flush_rcu_work - wait for a rwork to finish executing the last queueing
3204 * @rwork: the rcu work to flush
3205 *
3206 * Return:
3207 * %true if flush_rcu_work() waited for the work to finish execution,
3208 * %false if it was already idle.
3209 */
3210bool flush_rcu_work(struct rcu_work *rwork)
3211{
3212 if (test_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(&rwork->work))) {
3213 rcu_barrier();
3214 flush_work(&rwork->work);
3215 return true;
3216 } else {
3217 return flush_work(&rwork->work);
3218 }
3219}
3220EXPORT_SYMBOL(flush_rcu_work);
3221
3222static bool __cancel_work(struct work_struct *work, bool is_dwork)
3223{
3224 unsigned long flags;
3225 int ret;
3226
3227 do {
3228 ret = try_to_grab_pending(work, is_dwork, &flags);
3229 } while (unlikely(ret == -EAGAIN));
3230
3231 if (unlikely(ret < 0))
3232 return false;
3233
3234 set_work_pool_and_clear_pending(work, get_work_pool_id(work));
3235 local_irq_restore(flags);
3236 return ret;
3237}
3238
3239/**
3240 * cancel_delayed_work - cancel a delayed work
3241 * @dwork: delayed_work to cancel
3242 *
3243 * Kill off a pending delayed_work.
3244 *
3245 * Return: %true if @dwork was pending and canceled; %false if it wasn't
3246 * pending.
3247 *
3248 * Note:
3249 * The work callback function may still be running on return, unless
3250 * it returns %true and the work doesn't re-arm itself. Explicitly flush or
3251 * use cancel_delayed_work_sync() to wait on it.
3252 *
3253 * This function is safe to call from any context including IRQ handler.
3254 */
3255bool cancel_delayed_work(struct delayed_work *dwork)
3256{
3257 return __cancel_work(&dwork->work, true);
3258}
3259EXPORT_SYMBOL(cancel_delayed_work);
3260
3261/**
3262 * cancel_delayed_work_sync - cancel a delayed work and wait for it to finish
3263 * @dwork: the delayed work cancel
3264 *
3265 * This is cancel_work_sync() for delayed works.
3266 *
3267 * Return:
3268 * %true if @dwork was pending, %false otherwise.
3269 */
3270bool cancel_delayed_work_sync(struct delayed_work *dwork)
3271{
3272 return __cancel_work_timer(&dwork->work, true);
3273}
3274EXPORT_SYMBOL(cancel_delayed_work_sync);
3275
3276/**
3277 * schedule_on_each_cpu - execute a function synchronously on each online CPU
3278 * @func: the function to call
3279 *
3280 * schedule_on_each_cpu() executes @func on each online CPU using the
3281 * system workqueue and blocks until all CPUs have completed.
3282 * schedule_on_each_cpu() is very slow.
3283 *
3284 * Return:
3285 * 0 on success, -errno on failure.
3286 */
3287int schedule_on_each_cpu(work_func_t func)
3288{
3289 int cpu;
3290 struct work_struct __percpu *works;
3291
3292 works = alloc_percpu(struct work_struct);
3293 if (!works)
3294 return -ENOMEM;
3295
3296 get_online_cpus();
3297
3298 for_each_online_cpu(cpu) {
3299 struct work_struct *work = per_cpu_ptr(works, cpu);
3300
3301 INIT_WORK(work, func);
3302 schedule_work_on(cpu, work);
3303 }
3304
3305 for_each_online_cpu(cpu)
3306 flush_work(per_cpu_ptr(works, cpu));
3307
3308 put_online_cpus();
3309 free_percpu(works);
3310 return 0;
3311}
3312
3313/**
3314 * execute_in_process_context - reliably execute the routine with user context
3315 * @fn: the function to execute
3316 * @ew: guaranteed storage for the execute work structure (must
3317 * be available when the work executes)
3318 *
3319 * Executes the function immediately if process context is available,
3320 * otherwise schedules the function for delayed execution.
3321 *
3322 * Return: 0 - function was executed
3323 * 1 - function was scheduled for execution
3324 */
3325int execute_in_process_context(work_func_t fn, struct execute_work *ew)
3326{
3327 if (!in_interrupt()) {
3328 fn(&ew->work);
3329 return 0;
3330 }
3331
3332 INIT_WORK(&ew->work, fn);
3333 schedule_work(&ew->work);
3334
3335 return 1;
3336}
3337EXPORT_SYMBOL_GPL(execute_in_process_context);
3338
3339/**
3340 * free_workqueue_attrs - free a workqueue_attrs
3341 * @attrs: workqueue_attrs to free
3342 *
3343 * Undo alloc_workqueue_attrs().
3344 */
3345void free_workqueue_attrs(struct workqueue_attrs *attrs)
3346{
3347 if (attrs) {
3348 free_cpumask_var(attrs->cpumask);
3349 kfree(attrs);
3350 }
3351}
3352
3353/**
3354 * alloc_workqueue_attrs - allocate a workqueue_attrs
3355 *
3356 * Allocate a new workqueue_attrs, initialize with default settings and
3357 * return it.
3358 *
3359 * Return: The allocated new workqueue_attr on success. %NULL on failure.
3360 */
3361struct workqueue_attrs *alloc_workqueue_attrs(void)
3362{
3363 struct workqueue_attrs *attrs;
3364
3365 attrs = kzalloc(sizeof(*attrs), GFP_KERNEL);
3366 if (!attrs)
3367 goto fail;
3368 if (!alloc_cpumask_var(&attrs->cpumask, GFP_KERNEL))
3369 goto fail;
3370
3371 cpumask_copy(attrs->cpumask, cpu_possible_mask);
3372 return attrs;
3373fail:
3374 free_workqueue_attrs(attrs);
3375 return NULL;
3376}
3377
3378static void copy_workqueue_attrs(struct workqueue_attrs *to,
3379 const struct workqueue_attrs *from)
3380{
3381 to->nice = from->nice;
3382 cpumask_copy(to->cpumask, from->cpumask);
3383 /*
3384 * Unlike hash and equality test, this function doesn't ignore
3385 * ->no_numa as it is used for both pool and wq attrs. Instead,
3386 * get_unbound_pool() explicitly clears ->no_numa after copying.
3387 */
3388 to->no_numa = from->no_numa;
3389}
3390
3391/* hash value of the content of @attr */
3392static u32 wqattrs_hash(const struct workqueue_attrs *attrs)
3393{
3394 u32 hash = 0;
3395
3396 hash = jhash_1word(attrs->nice, hash);
3397 hash = jhash(cpumask_bits(attrs->cpumask),
3398 BITS_TO_LONGS(nr_cpumask_bits) * sizeof(long), hash);
3399 return hash;
3400}
3401
3402/* content equality test */
3403static bool wqattrs_equal(const struct workqueue_attrs *a,
3404 const struct workqueue_attrs *b)
3405{
3406 if (a->nice != b->nice)
3407 return false;
3408 if (!cpumask_equal(a->cpumask, b->cpumask))
3409 return false;
3410 return true;
3411}
3412
3413/**
3414 * init_worker_pool - initialize a newly zalloc'd worker_pool
3415 * @pool: worker_pool to initialize
3416 *
3417 * Initialize a newly zalloc'd @pool. It also allocates @pool->attrs.
3418 *
3419 * Return: 0 on success, -errno on failure. Even on failure, all fields
3420 * inside @pool proper are initialized and put_unbound_pool() can be called
3421 * on @pool safely to release it.
3422 */
3423static int init_worker_pool(struct worker_pool *pool)
3424{
3425 raw_spin_lock_init(&pool->lock);
3426 pool->id = -1;
3427 pool->cpu = -1;
3428 pool->node = NUMA_NO_NODE;
3429 pool->flags |= POOL_DISASSOCIATED;
3430 pool->watchdog_ts = jiffies;
3431 INIT_LIST_HEAD(&pool->worklist);
3432 INIT_LIST_HEAD(&pool->idle_list);
3433 hash_init(pool->busy_hash);
3434
3435 timer_setup(&pool->idle_timer, idle_worker_timeout, TIMER_DEFERRABLE);
3436
3437 timer_setup(&pool->mayday_timer, pool_mayday_timeout, 0);
3438
3439 INIT_LIST_HEAD(&pool->workers);
3440
3441 ida_init(&pool->worker_ida);
3442 INIT_HLIST_NODE(&pool->hash_node);
3443 pool->refcnt = 1;
3444
3445 /* shouldn't fail above this point */
3446 pool->attrs = alloc_workqueue_attrs();
3447 if (!pool->attrs)
3448 return -ENOMEM;
3449 return 0;
3450}
3451
3452#ifdef CONFIG_LOCKDEP
3453static void wq_init_lockdep(struct workqueue_struct *wq)
3454{
3455 char *lock_name;
3456
3457 lockdep_register_key(&wq->key);
3458 lock_name = kasprintf(GFP_KERNEL, "%s%s", "(wq_completion)", wq->name);
3459 if (!lock_name)
3460 lock_name = wq->name;
3461
3462 wq->lock_name = lock_name;
3463 lockdep_init_map(&wq->lockdep_map, lock_name, &wq->key, 0);
3464}
3465
3466static void wq_unregister_lockdep(struct workqueue_struct *wq)
3467{
3468 lockdep_unregister_key(&wq->key);
3469}
3470
3471static void wq_free_lockdep(struct workqueue_struct *wq)
3472{
3473 if (wq->lock_name != wq->name)
3474 kfree(wq->lock_name);
3475}
3476#else
3477static void wq_init_lockdep(struct workqueue_struct *wq)
3478{
3479}
3480
3481static void wq_unregister_lockdep(struct workqueue_struct *wq)
3482{
3483}
3484
3485static void wq_free_lockdep(struct workqueue_struct *wq)
3486{
3487}
3488#endif
3489
3490static void rcu_free_wq(struct rcu_head *rcu)
3491{
3492 struct workqueue_struct *wq =
3493 container_of(rcu, struct workqueue_struct, rcu);
3494
3495 wq_free_lockdep(wq);
3496
3497 if (!(wq->flags & WQ_UNBOUND))
3498 free_percpu(wq->cpu_pwqs);
3499 else
3500 free_workqueue_attrs(wq->unbound_attrs);
3501
3502 kfree(wq);
3503}
3504
3505static void rcu_free_pool(struct rcu_head *rcu)
3506{
3507 struct worker_pool *pool = container_of(rcu, struct worker_pool, rcu);
3508
3509 ida_destroy(&pool->worker_ida);
3510 free_workqueue_attrs(pool->attrs);
3511 kfree(pool);
3512}
3513
3514/* This returns with the lock held on success (pool manager is inactive). */
3515static bool wq_manager_inactive(struct worker_pool *pool)
3516{
3517 raw_spin_lock_irq(&pool->lock);
3518
3519 if (pool->flags & POOL_MANAGER_ACTIVE) {
3520 raw_spin_unlock_irq(&pool->lock);
3521 return false;
3522 }
3523 return true;
3524}
3525
3526/**
3527 * put_unbound_pool - put a worker_pool
3528 * @pool: worker_pool to put
3529 *
3530 * Put @pool. If its refcnt reaches zero, it gets destroyed in RCU
3531 * safe manner. get_unbound_pool() calls this function on its failure path
3532 * and this function should be able to release pools which went through,
3533 * successfully or not, init_worker_pool().
3534 *
3535 * Should be called with wq_pool_mutex held.
3536 */
3537static void put_unbound_pool(struct worker_pool *pool)
3538{
3539 DECLARE_COMPLETION_ONSTACK(detach_completion);
3540 struct worker *worker;
3541
3542 lockdep_assert_held(&wq_pool_mutex);
3543
3544 if (--pool->refcnt)
3545 return;
3546
3547 /* sanity checks */
3548 if (WARN_ON(!(pool->cpu < 0)) ||
3549 WARN_ON(!list_empty(&pool->worklist)))
3550 return;
3551
3552 /* release id and unhash */
3553 if (pool->id >= 0)
3554 idr_remove(&worker_pool_idr, pool->id);
3555 hash_del(&pool->hash_node);
3556
3557 /*
3558 * Become the manager and destroy all workers. This prevents
3559 * @pool's workers from blocking on attach_mutex. We're the last
3560 * manager and @pool gets freed with the flag set.
3561 * Because of how wq_manager_inactive() works, we will hold the
3562 * spinlock after a successful wait.
3563 */
3564 rcuwait_wait_event(&manager_wait, wq_manager_inactive(pool),
3565 TASK_UNINTERRUPTIBLE);
3566 pool->flags |= POOL_MANAGER_ACTIVE;
3567
3568 while ((worker = first_idle_worker(pool)))
3569 destroy_worker(worker);
3570 WARN_ON(pool->nr_workers || pool->nr_idle);
3571 raw_spin_unlock_irq(&pool->lock);
3572
3573 mutex_lock(&wq_pool_attach_mutex);
3574 if (!list_empty(&pool->workers))
3575 pool->detach_completion = &detach_completion;
3576 mutex_unlock(&wq_pool_attach_mutex);
3577
3578 if (pool->detach_completion)
3579 wait_for_completion(pool->detach_completion);
3580
3581 /* shut down the timers */
3582 del_timer_sync(&pool->idle_timer);
3583 del_timer_sync(&pool->mayday_timer);
3584
3585 /* RCU protected to allow dereferences from get_work_pool() */
3586 call_rcu(&pool->rcu, rcu_free_pool);
3587}
3588
3589/**
3590 * get_unbound_pool - get a worker_pool with the specified attributes
3591 * @attrs: the attributes of the worker_pool to get
3592 *
3593 * Obtain a worker_pool which has the same attributes as @attrs, bump the
3594 * reference count and return it. If there already is a matching
3595 * worker_pool, it will be used; otherwise, this function attempts to
3596 * create a new one.
3597 *
3598 * Should be called with wq_pool_mutex held.
3599 *
3600 * Return: On success, a worker_pool with the same attributes as @attrs.
3601 * On failure, %NULL.
3602 */
3603static struct worker_pool *get_unbound_pool(const struct workqueue_attrs *attrs)
3604{
3605 u32 hash = wqattrs_hash(attrs);
3606 struct worker_pool *pool;
3607 int node;
3608 int target_node = NUMA_NO_NODE;
3609
3610 lockdep_assert_held(&wq_pool_mutex);
3611
3612 /* do we already have a matching pool? */
3613 hash_for_each_possible(unbound_pool_hash, pool, hash_node, hash) {
3614 if (wqattrs_equal(pool->attrs, attrs)) {
3615 pool->refcnt++;
3616 return pool;
3617 }
3618 }
3619
3620 /* if cpumask is contained inside a NUMA node, we belong to that node */
3621 if (wq_numa_enabled) {
3622 for_each_node(node) {
3623 if (cpumask_subset(attrs->cpumask,
3624 wq_numa_possible_cpumask[node])) {
3625 target_node = node;
3626 break;
3627 }
3628 }
3629 }
3630
3631 /* nope, create a new one */
3632 pool = kzalloc_node(sizeof(*pool), GFP_KERNEL, target_node);
3633 if (!pool || init_worker_pool(pool) < 0)
3634 goto fail;
3635
3636 lockdep_set_subclass(&pool->lock, 1); /* see put_pwq() */
3637 copy_workqueue_attrs(pool->attrs, attrs);
3638 pool->node = target_node;
3639
3640 /*
3641 * no_numa isn't a worker_pool attribute, always clear it. See
3642 * 'struct workqueue_attrs' comments for detail.
3643 */
3644 pool->attrs->no_numa = false;
3645
3646 if (worker_pool_assign_id(pool) < 0)
3647 goto fail;
3648
3649 /* create and start the initial worker */
3650 if (wq_online && !create_worker(pool))
3651 goto fail;
3652
3653 /* install */
3654 hash_add(unbound_pool_hash, &pool->hash_node, hash);
3655
3656 return pool;
3657fail:
3658 if (pool)
3659 put_unbound_pool(pool);
3660 return NULL;
3661}
3662
3663static void rcu_free_pwq(struct rcu_head *rcu)
3664{
3665 kmem_cache_free(pwq_cache,
3666 container_of(rcu, struct pool_workqueue, rcu));
3667}
3668
3669/*
3670 * Scheduled on system_wq by put_pwq() when an unbound pwq hits zero refcnt
3671 * and needs to be destroyed.
3672 */
3673static void pwq_unbound_release_workfn(struct work_struct *work)
3674{
3675 struct pool_workqueue *pwq = container_of(work, struct pool_workqueue,
3676 unbound_release_work);
3677 struct workqueue_struct *wq = pwq->wq;
3678 struct worker_pool *pool = pwq->pool;
3679 bool is_last = false;
3680
3681 /*
3682 * when @pwq is not linked, it doesn't hold any reference to the
3683 * @wq, and @wq is invalid to access.
3684 */
3685 if (!list_empty(&pwq->pwqs_node)) {
3686 if (WARN_ON_ONCE(!(wq->flags & WQ_UNBOUND)))
3687 return;
3688
3689 mutex_lock(&wq->mutex);
3690 list_del_rcu(&pwq->pwqs_node);
3691 is_last = list_empty(&wq->pwqs);
3692 mutex_unlock(&wq->mutex);
3693 }
3694
3695 mutex_lock(&wq_pool_mutex);
3696 put_unbound_pool(pool);
3697 mutex_unlock(&wq_pool_mutex);
3698
3699 call_rcu(&pwq->rcu, rcu_free_pwq);
3700
3701 /*
3702 * If we're the last pwq going away, @wq is already dead and no one
3703 * is gonna access it anymore. Schedule RCU free.
3704 */
3705 if (is_last) {
3706 wq_unregister_lockdep(wq);
3707 call_rcu(&wq->rcu, rcu_free_wq);
3708 }
3709}
3710
3711/**
3712 * pwq_adjust_max_active - update a pwq's max_active to the current setting
3713 * @pwq: target pool_workqueue
3714 *
3715 * If @pwq isn't freezing, set @pwq->max_active to the associated
3716 * workqueue's saved_max_active and activate delayed work items
3717 * accordingly. If @pwq is freezing, clear @pwq->max_active to zero.
3718 */
3719static void pwq_adjust_max_active(struct pool_workqueue *pwq)
3720{
3721 struct workqueue_struct *wq = pwq->wq;
3722 bool freezable = wq->flags & WQ_FREEZABLE;
3723 unsigned long flags;
3724
3725 /* for @wq->saved_max_active */
3726 lockdep_assert_held(&wq->mutex);
3727
3728 /* fast exit for non-freezable wqs */
3729 if (!freezable && pwq->max_active == wq->saved_max_active)
3730 return;
3731
3732 /* this function can be called during early boot w/ irq disabled */
3733 raw_spin_lock_irqsave(&pwq->pool->lock, flags);
3734
3735 /*
3736 * During [un]freezing, the caller is responsible for ensuring that
3737 * this function is called at least once after @workqueue_freezing
3738 * is updated and visible.
3739 */
3740 if (!freezable || !workqueue_freezing) {
3741 bool kick = false;
3742
3743 pwq->max_active = wq->saved_max_active;
3744
3745 while (!list_empty(&pwq->delayed_works) &&
3746 pwq->nr_active < pwq->max_active) {
3747 pwq_activate_first_delayed(pwq);
3748 kick = true;
3749 }
3750
3751 /*
3752 * Need to kick a worker after thawed or an unbound wq's
3753 * max_active is bumped. In realtime scenarios, always kicking a
3754 * worker will cause interference on the isolated cpu cores, so
3755 * let's kick iff work items were activated.
3756 */
3757 if (kick)
3758 wake_up_worker(pwq->pool);
3759 } else {
3760 pwq->max_active = 0;
3761 }
3762
3763 raw_spin_unlock_irqrestore(&pwq->pool->lock, flags);
3764}
3765
3766/* initialize newly alloced @pwq which is associated with @wq and @pool */
3767static void init_pwq(struct pool_workqueue *pwq, struct workqueue_struct *wq,
3768 struct worker_pool *pool)
3769{
3770 BUG_ON((unsigned long)pwq & WORK_STRUCT_FLAG_MASK);
3771
3772 memset(pwq, 0, sizeof(*pwq));
3773
3774 pwq->pool = pool;
3775 pwq->wq = wq;
3776 pwq->flush_color = -1;
3777 pwq->refcnt = 1;
3778 INIT_LIST_HEAD(&pwq->delayed_works);
3779 INIT_LIST_HEAD(&pwq->pwqs_node);
3780 INIT_LIST_HEAD(&pwq->mayday_node);
3781 INIT_WORK(&pwq->unbound_release_work, pwq_unbound_release_workfn);
3782}
3783
3784/* sync @pwq with the current state of its associated wq and link it */
3785static void link_pwq(struct pool_workqueue *pwq)
3786{
3787 struct workqueue_struct *wq = pwq->wq;
3788
3789 lockdep_assert_held(&wq->mutex);
3790
3791 /* may be called multiple times, ignore if already linked */
3792 if (!list_empty(&pwq->pwqs_node))
3793 return;
3794
3795 /* set the matching work_color */
3796 pwq->work_color = wq->work_color;
3797
3798 /* sync max_active to the current setting */
3799 pwq_adjust_max_active(pwq);
3800
3801 /* link in @pwq */
3802 list_add_rcu(&pwq->pwqs_node, &wq->pwqs);
3803}
3804
3805/* obtain a pool matching @attr and create a pwq associating the pool and @wq */
3806static struct pool_workqueue *alloc_unbound_pwq(struct workqueue_struct *wq,
3807 const struct workqueue_attrs *attrs)
3808{
3809 struct worker_pool *pool;
3810 struct pool_workqueue *pwq;
3811
3812 lockdep_assert_held(&wq_pool_mutex);
3813
3814 pool = get_unbound_pool(attrs);
3815 if (!pool)
3816 return NULL;
3817
3818 pwq = kmem_cache_alloc_node(pwq_cache, GFP_KERNEL, pool->node);
3819 if (!pwq) {
3820 put_unbound_pool(pool);
3821 return NULL;
3822 }
3823
3824 init_pwq(pwq, wq, pool);
3825 return pwq;
3826}
3827
3828/**
3829 * wq_calc_node_cpumask - calculate a wq_attrs' cpumask for the specified node
3830 * @attrs: the wq_attrs of the default pwq of the target workqueue
3831 * @node: the target NUMA node
3832 * @cpu_going_down: if >= 0, the CPU to consider as offline
3833 * @cpumask: outarg, the resulting cpumask
3834 *
3835 * Calculate the cpumask a workqueue with @attrs should use on @node. If
3836 * @cpu_going_down is >= 0, that cpu is considered offline during
3837 * calculation. The result is stored in @cpumask.
3838 *
3839 * If NUMA affinity is not enabled, @attrs->cpumask is always used. If
3840 * enabled and @node has online CPUs requested by @attrs, the returned
3841 * cpumask is the intersection of the possible CPUs of @node and
3842 * @attrs->cpumask.
3843 *
3844 * The caller is responsible for ensuring that the cpumask of @node stays
3845 * stable.
3846 *
3847 * Return: %true if the resulting @cpumask is different from @attrs->cpumask,
3848 * %false if equal.
3849 */
3850static bool wq_calc_node_cpumask(const struct workqueue_attrs *attrs, int node,
3851 int cpu_going_down, cpumask_t *cpumask)
3852{
3853 if (!wq_numa_enabled || attrs->no_numa)
3854 goto use_dfl;
3855
3856 /* does @node have any online CPUs @attrs wants? */
3857 cpumask_and(cpumask, cpumask_of_node(node), attrs->cpumask);
3858 if (cpu_going_down >= 0)
3859 cpumask_clear_cpu(cpu_going_down, cpumask);
3860
3861 if (cpumask_empty(cpumask))
3862 goto use_dfl;
3863
3864 /* yeap, return possible CPUs in @node that @attrs wants */
3865 cpumask_and(cpumask, attrs->cpumask, wq_numa_possible_cpumask[node]);
3866
3867 if (cpumask_empty(cpumask)) {
3868 pr_warn_once("WARNING: workqueue cpumask: online intersect > "
3869 "possible intersect\n");
3870 return false;
3871 }
3872
3873 return !cpumask_equal(cpumask, attrs->cpumask);
3874
3875use_dfl:
3876 cpumask_copy(cpumask, attrs->cpumask);
3877 return false;
3878}
3879
3880/* install @pwq into @wq's numa_pwq_tbl[] for @node and return the old pwq */
3881static struct pool_workqueue *numa_pwq_tbl_install(struct workqueue_struct *wq,
3882 int node,
3883 struct pool_workqueue *pwq)
3884{
3885 struct pool_workqueue *old_pwq;
3886
3887 lockdep_assert_held(&wq_pool_mutex);
3888 lockdep_assert_held(&wq->mutex);
3889
3890 /* link_pwq() can handle duplicate calls */
3891 link_pwq(pwq);
3892
3893 old_pwq = rcu_access_pointer(wq->numa_pwq_tbl[node]);
3894 rcu_assign_pointer(wq->numa_pwq_tbl[node], pwq);
3895 return old_pwq;
3896}
3897
3898/* context to store the prepared attrs & pwqs before applying */
3899struct apply_wqattrs_ctx {
3900 struct workqueue_struct *wq; /* target workqueue */
3901 struct workqueue_attrs *attrs; /* attrs to apply */
3902 struct list_head list; /* queued for batching commit */
3903 struct pool_workqueue *dfl_pwq;
3904 struct pool_workqueue *pwq_tbl[];
3905};
3906
3907/* free the resources after success or abort */
3908static void apply_wqattrs_cleanup(struct apply_wqattrs_ctx *ctx)
3909{
3910 if (ctx) {
3911 int node;
3912
3913 for_each_node(node)
3914 put_pwq_unlocked(ctx->pwq_tbl[node]);
3915 put_pwq_unlocked(ctx->dfl_pwq);
3916
3917 free_workqueue_attrs(ctx->attrs);
3918
3919 kfree(ctx);
3920 }
3921}
3922
3923/* allocate the attrs and pwqs for later installation */
3924static struct apply_wqattrs_ctx *
3925apply_wqattrs_prepare(struct workqueue_struct *wq,
3926 const struct workqueue_attrs *attrs)
3927{
3928 struct apply_wqattrs_ctx *ctx;
3929 struct workqueue_attrs *new_attrs, *tmp_attrs;
3930 int node;
3931
3932 lockdep_assert_held(&wq_pool_mutex);
3933
3934 ctx = kzalloc(struct_size(ctx, pwq_tbl, nr_node_ids), GFP_KERNEL);
3935
3936 new_attrs = alloc_workqueue_attrs();
3937 tmp_attrs = alloc_workqueue_attrs();
3938 if (!ctx || !new_attrs || !tmp_attrs)
3939 goto out_free;
3940
3941 /*
3942 * Calculate the attrs of the default pwq.
3943 * If the user configured cpumask doesn't overlap with the
3944 * wq_unbound_cpumask, we fallback to the wq_unbound_cpumask.
3945 */
3946 copy_workqueue_attrs(new_attrs, attrs);
3947 cpumask_and(new_attrs->cpumask, new_attrs->cpumask, wq_unbound_cpumask);
3948 if (unlikely(cpumask_empty(new_attrs->cpumask)))
3949 cpumask_copy(new_attrs->cpumask, wq_unbound_cpumask);
3950
3951 /*
3952 * We may create multiple pwqs with differing cpumasks. Make a
3953 * copy of @new_attrs which will be modified and used to obtain
3954 * pools.
3955 */
3956 copy_workqueue_attrs(tmp_attrs, new_attrs);
3957
3958 /*
3959 * If something goes wrong during CPU up/down, we'll fall back to
3960 * the default pwq covering whole @attrs->cpumask. Always create
3961 * it even if we don't use it immediately.
3962 */
3963 ctx->dfl_pwq = alloc_unbound_pwq(wq, new_attrs);
3964 if (!ctx->dfl_pwq)
3965 goto out_free;
3966
3967 for_each_node(node) {
3968 if (wq_calc_node_cpumask(new_attrs, node, -1, tmp_attrs->cpumask)) {
3969 ctx->pwq_tbl[node] = alloc_unbound_pwq(wq, tmp_attrs);
3970 if (!ctx->pwq_tbl[node])
3971 goto out_free;
3972 } else {
3973 ctx->dfl_pwq->refcnt++;
3974 ctx->pwq_tbl[node] = ctx->dfl_pwq;
3975 }
3976 }
3977
3978 /* save the user configured attrs and sanitize it. */
3979 copy_workqueue_attrs(new_attrs, attrs);
3980 cpumask_and(new_attrs->cpumask, new_attrs->cpumask, cpu_possible_mask);
3981 ctx->attrs = new_attrs;
3982
3983 ctx->wq = wq;
3984 free_workqueue_attrs(tmp_attrs);
3985 return ctx;
3986
3987out_free:
3988 free_workqueue_attrs(tmp_attrs);
3989 free_workqueue_attrs(new_attrs);
3990 apply_wqattrs_cleanup(ctx);
3991 return NULL;
3992}
3993
3994/* set attrs and install prepared pwqs, @ctx points to old pwqs on return */
3995static void apply_wqattrs_commit(struct apply_wqattrs_ctx *ctx)
3996{
3997 int node;
3998
3999 /* all pwqs have been created successfully, let's install'em */
4000 mutex_lock(&ctx->wq->mutex);
4001
4002 copy_workqueue_attrs(ctx->wq->unbound_attrs, ctx->attrs);
4003
4004 /* save the previous pwq and install the new one */
4005 for_each_node(node)
4006 ctx->pwq_tbl[node] = numa_pwq_tbl_install(ctx->wq, node,
4007 ctx->pwq_tbl[node]);
4008
4009 /* @dfl_pwq might not have been used, ensure it's linked */
4010 link_pwq(ctx->dfl_pwq);
4011 swap(ctx->wq->dfl_pwq, ctx->dfl_pwq);
4012
4013 mutex_unlock(&ctx->wq->mutex);
4014}
4015
4016static void apply_wqattrs_lock(void)
4017{
4018 /* CPUs should stay stable across pwq creations and installations */
4019 get_online_cpus();
4020 mutex_lock(&wq_pool_mutex);
4021}
4022
4023static void apply_wqattrs_unlock(void)
4024{
4025 mutex_unlock(&wq_pool_mutex);
4026 put_online_cpus();
4027}
4028
4029static int apply_workqueue_attrs_locked(struct workqueue_struct *wq,
4030 const struct workqueue_attrs *attrs)
4031{
4032 struct apply_wqattrs_ctx *ctx;
4033
4034 /* only unbound workqueues can change attributes */
4035 if (WARN_ON(!(wq->flags & WQ_UNBOUND)))
4036 return -EINVAL;
4037
4038 /* creating multiple pwqs breaks ordering guarantee */
4039 if (!list_empty(&wq->pwqs)) {
4040 if (WARN_ON(wq->flags & __WQ_ORDERED_EXPLICIT))
4041 return -EINVAL;
4042
4043 wq->flags &= ~__WQ_ORDERED;
4044 }
4045
4046 ctx = apply_wqattrs_prepare(wq, attrs);
4047 if (!ctx)
4048 return -ENOMEM;
4049
4050 /* the ctx has been prepared successfully, let's commit it */
4051 apply_wqattrs_commit(ctx);
4052 apply_wqattrs_cleanup(ctx);
4053
4054 return 0;
4055}
4056
4057/**
4058 * apply_workqueue_attrs - apply new workqueue_attrs to an unbound workqueue
4059 * @wq: the target workqueue
4060 * @attrs: the workqueue_attrs to apply, allocated with alloc_workqueue_attrs()
4061 *
4062 * Apply @attrs to an unbound workqueue @wq. Unless disabled, on NUMA
4063 * machines, this function maps a separate pwq to each NUMA node with
4064 * possibles CPUs in @attrs->cpumask so that work items are affine to the
4065 * NUMA node it was issued on. Older pwqs are released as in-flight work
4066 * items finish. Note that a work item which repeatedly requeues itself
4067 * back-to-back will stay on its current pwq.
4068 *
4069 * Performs GFP_KERNEL allocations.
4070 *
4071 * Assumes caller has CPU hotplug read exclusion, i.e. get_online_cpus().
4072 *
4073 * Return: 0 on success and -errno on failure.
4074 */
4075int apply_workqueue_attrs(struct workqueue_struct *wq,
4076 const struct workqueue_attrs *attrs)
4077{
4078 int ret;
4079
4080 lockdep_assert_cpus_held();
4081
4082 mutex_lock(&wq_pool_mutex);
4083 ret = apply_workqueue_attrs_locked(wq, attrs);
4084 mutex_unlock(&wq_pool_mutex);
4085
4086 return ret;
4087}
4088
4089/**
4090 * wq_update_unbound_numa - update NUMA affinity of a wq for CPU hot[un]plug
4091 * @wq: the target workqueue
4092 * @cpu: the CPU coming up or going down
4093 * @online: whether @cpu is coming up or going down
4094 *
4095 * This function is to be called from %CPU_DOWN_PREPARE, %CPU_ONLINE and
4096 * %CPU_DOWN_FAILED. @cpu is being hot[un]plugged, update NUMA affinity of
4097 * @wq accordingly.
4098 *
4099 * If NUMA affinity can't be adjusted due to memory allocation failure, it
4100 * falls back to @wq->dfl_pwq which may not be optimal but is always
4101 * correct.
4102 *
4103 * Note that when the last allowed CPU of a NUMA node goes offline for a
4104 * workqueue with a cpumask spanning multiple nodes, the workers which were
4105 * already executing the work items for the workqueue will lose their CPU
4106 * affinity and may execute on any CPU. This is similar to how per-cpu
4107 * workqueues behave on CPU_DOWN. If a workqueue user wants strict
4108 * affinity, it's the user's responsibility to flush the work item from
4109 * CPU_DOWN_PREPARE.
4110 */
4111static void wq_update_unbound_numa(struct workqueue_struct *wq, int cpu,
4112 bool online)
4113{
4114 int node = cpu_to_node(cpu);
4115 int cpu_off = online ? -1 : cpu;
4116 struct pool_workqueue *old_pwq = NULL, *pwq;
4117 struct workqueue_attrs *target_attrs;
4118 cpumask_t *cpumask;
4119
4120 lockdep_assert_held(&wq_pool_mutex);
4121
4122 if (!wq_numa_enabled || !(wq->flags & WQ_UNBOUND) ||
4123 wq->unbound_attrs->no_numa)
4124 return;
4125
4126 /*
4127 * We don't wanna alloc/free wq_attrs for each wq for each CPU.
4128 * Let's use a preallocated one. The following buf is protected by
4129 * CPU hotplug exclusion.
4130 */
4131 target_attrs = wq_update_unbound_numa_attrs_buf;
4132 cpumask = target_attrs->cpumask;
4133
4134 copy_workqueue_attrs(target_attrs, wq->unbound_attrs);
4135 pwq = unbound_pwq_by_node(wq, node);
4136
4137 /*
4138 * Let's determine what needs to be done. If the target cpumask is
4139 * different from the default pwq's, we need to compare it to @pwq's
4140 * and create a new one if they don't match. If the target cpumask
4141 * equals the default pwq's, the default pwq should be used.
4142 */
4143 if (wq_calc_node_cpumask(wq->dfl_pwq->pool->attrs, node, cpu_off, cpumask)) {
4144 if (cpumask_equal(cpumask, pwq->pool->attrs->cpumask))
4145 return;
4146 } else {
4147 goto use_dfl_pwq;
4148 }
4149
4150 /* create a new pwq */
4151 pwq = alloc_unbound_pwq(wq, target_attrs);
4152 if (!pwq) {
4153 pr_warn("workqueue: allocation failed while updating NUMA affinity of \"%s\"\n",
4154 wq->name);
4155 goto use_dfl_pwq;
4156 }
4157
4158 /* Install the new pwq. */
4159 mutex_lock(&wq->mutex);
4160 old_pwq = numa_pwq_tbl_install(wq, node, pwq);
4161 goto out_unlock;
4162
4163use_dfl_pwq:
4164 mutex_lock(&wq->mutex);
4165 raw_spin_lock_irq(&wq->dfl_pwq->pool->lock);
4166 get_pwq(wq->dfl_pwq);
4167 raw_spin_unlock_irq(&wq->dfl_pwq->pool->lock);
4168 old_pwq = numa_pwq_tbl_install(wq, node, wq->dfl_pwq);
4169out_unlock:
4170 mutex_unlock(&wq->mutex);
4171 put_pwq_unlocked(old_pwq);
4172}
4173
4174static int alloc_and_link_pwqs(struct workqueue_struct *wq)
4175{
4176 bool highpri = wq->flags & WQ_HIGHPRI;
4177 int cpu, ret;
4178
4179 if (!(wq->flags & WQ_UNBOUND)) {
4180 wq->cpu_pwqs = alloc_percpu(struct pool_workqueue);
4181 if (!wq->cpu_pwqs)
4182 return -ENOMEM;
4183
4184 for_each_possible_cpu(cpu) {
4185 struct pool_workqueue *pwq =
4186 per_cpu_ptr(wq->cpu_pwqs, cpu);
4187 struct worker_pool *cpu_pools =
4188 per_cpu(cpu_worker_pools, cpu);
4189
4190 init_pwq(pwq, wq, &cpu_pools[highpri]);
4191
4192 mutex_lock(&wq->mutex);
4193 link_pwq(pwq);
4194 mutex_unlock(&wq->mutex);
4195 }
4196 return 0;
4197 }
4198
4199 get_online_cpus();
4200 if (wq->flags & __WQ_ORDERED) {
4201 ret = apply_workqueue_attrs(wq, ordered_wq_attrs[highpri]);
4202 /* there should only be single pwq for ordering guarantee */
4203 WARN(!ret && (wq->pwqs.next != &wq->dfl_pwq->pwqs_node ||
4204 wq->pwqs.prev != &wq->dfl_pwq->pwqs_node),
4205 "ordering guarantee broken for workqueue %s\n", wq->name);
4206 } else {
4207 ret = apply_workqueue_attrs(wq, unbound_std_wq_attrs[highpri]);
4208 }
4209 put_online_cpus();
4210
4211 return ret;
4212}
4213
4214static int wq_clamp_max_active(int max_active, unsigned int flags,
4215 const char *name)
4216{
4217 int lim = flags & WQ_UNBOUND ? WQ_UNBOUND_MAX_ACTIVE : WQ_MAX_ACTIVE;
4218
4219 if (max_active < 1 || max_active > lim)
4220 pr_warn("workqueue: max_active %d requested for %s is out of range, clamping between %d and %d\n",
4221 max_active, name, 1, lim);
4222
4223 return clamp_val(max_active, 1, lim);
4224}
4225
4226/*
4227 * Workqueues which may be used during memory reclaim should have a rescuer
4228 * to guarantee forward progress.
4229 */
4230static int init_rescuer(struct workqueue_struct *wq)
4231{
4232 struct worker *rescuer;
4233 int ret;
4234
4235 if (!(wq->flags & WQ_MEM_RECLAIM))
4236 return 0;
4237
4238 rescuer = alloc_worker(NUMA_NO_NODE);
4239 if (!rescuer)
4240 return -ENOMEM;
4241
4242 rescuer->rescue_wq = wq;
4243 rescuer->task = kthread_create(rescuer_thread, rescuer, "%s", wq->name);
4244 if (IS_ERR(rescuer->task)) {
4245 ret = PTR_ERR(rescuer->task);
4246 kfree(rescuer);
4247 return ret;
4248 }
4249
4250 wq->rescuer = rescuer;
4251 kthread_bind_mask(rescuer->task, cpu_possible_mask);
4252 wake_up_process(rescuer->task);
4253
4254 return 0;
4255}
4256
4257__printf(1, 4)
4258struct workqueue_struct *alloc_workqueue(const char *fmt,
4259 unsigned int flags,
4260 int max_active, ...)
4261{
4262 size_t tbl_size = 0;
4263 va_list args;
4264 struct workqueue_struct *wq;
4265 struct pool_workqueue *pwq;
4266
4267 /*
4268 * Unbound && max_active == 1 used to imply ordered, which is no
4269 * longer the case on NUMA machines due to per-node pools. While
4270 * alloc_ordered_workqueue() is the right way to create an ordered
4271 * workqueue, keep the previous behavior to avoid subtle breakages
4272 * on NUMA.
4273 */
4274 if ((flags & WQ_UNBOUND) && max_active == 1)
4275 flags |= __WQ_ORDERED;
4276
4277 /* see the comment above the definition of WQ_POWER_EFFICIENT */
4278 if ((flags & WQ_POWER_EFFICIENT) && wq_power_efficient)
4279 flags |= WQ_UNBOUND;
4280
4281 /* allocate wq and format name */
4282 if (flags & WQ_UNBOUND)
4283 tbl_size = nr_node_ids * sizeof(wq->numa_pwq_tbl[0]);
4284
4285 wq = kzalloc(sizeof(*wq) + tbl_size, GFP_KERNEL);
4286 if (!wq)
4287 return NULL;
4288
4289 if (flags & WQ_UNBOUND) {
4290 wq->unbound_attrs = alloc_workqueue_attrs();
4291 if (!wq->unbound_attrs)
4292 goto err_free_wq;
4293 }
4294
4295 va_start(args, max_active);
4296 vsnprintf(wq->name, sizeof(wq->name), fmt, args);
4297 va_end(args);
4298
4299 max_active = max_active ?: WQ_DFL_ACTIVE;
4300 max_active = wq_clamp_max_active(max_active, flags, wq->name);
4301
4302 /* init wq */
4303 wq->flags = flags;
4304 wq->saved_max_active = max_active;
4305 mutex_init(&wq->mutex);
4306 atomic_set(&wq->nr_pwqs_to_flush, 0);
4307 INIT_LIST_HEAD(&wq->pwqs);
4308 INIT_LIST_HEAD(&wq->flusher_queue);
4309 INIT_LIST_HEAD(&wq->flusher_overflow);
4310 INIT_LIST_HEAD(&wq->maydays);
4311
4312 wq_init_lockdep(wq);
4313 INIT_LIST_HEAD(&wq->list);
4314
4315 if (alloc_and_link_pwqs(wq) < 0)
4316 goto err_unreg_lockdep;
4317
4318 if (wq_online && init_rescuer(wq) < 0)
4319 goto err_destroy;
4320
4321 if ((wq->flags & WQ_SYSFS) && workqueue_sysfs_register(wq))
4322 goto err_destroy;
4323
4324 /*
4325 * wq_pool_mutex protects global freeze state and workqueues list.
4326 * Grab it, adjust max_active and add the new @wq to workqueues
4327 * list.
4328 */
4329 mutex_lock(&wq_pool_mutex);
4330
4331 mutex_lock(&wq->mutex);
4332 for_each_pwq(pwq, wq)
4333 pwq_adjust_max_active(pwq);
4334 mutex_unlock(&wq->mutex);
4335
4336 list_add_tail_rcu(&wq->list, &workqueues);
4337
4338 mutex_unlock(&wq_pool_mutex);
4339
4340 return wq;
4341
4342err_unreg_lockdep:
4343 wq_unregister_lockdep(wq);
4344 wq_free_lockdep(wq);
4345err_free_wq:
4346 free_workqueue_attrs(wq->unbound_attrs);
4347 kfree(wq);
4348 return NULL;
4349err_destroy:
4350 destroy_workqueue(wq);
4351 return NULL;
4352}
4353EXPORT_SYMBOL_GPL(alloc_workqueue);
4354
4355static bool pwq_busy(struct pool_workqueue *pwq)
4356{
4357 int i;
4358
4359 for (i = 0; i < WORK_NR_COLORS; i++)
4360 if (pwq->nr_in_flight[i])
4361 return true;
4362
4363 if ((pwq != pwq->wq->dfl_pwq) && (pwq->refcnt > 1))
4364 return true;
4365 if (pwq->nr_active || !list_empty(&pwq->delayed_works))
4366 return true;
4367
4368 return false;
4369}
4370
4371/**
4372 * destroy_workqueue - safely terminate a workqueue
4373 * @wq: target workqueue
4374 *
4375 * Safely destroy a workqueue. All work currently pending will be done first.
4376 */
4377void destroy_workqueue(struct workqueue_struct *wq)
4378{
4379 struct pool_workqueue *pwq;
4380 int node;
4381
4382 /*
4383 * Remove it from sysfs first so that sanity check failure doesn't
4384 * lead to sysfs name conflicts.
4385 */
4386 workqueue_sysfs_unregister(wq);
4387
4388 /* drain it before proceeding with destruction */
4389 drain_workqueue(wq);
4390
4391 /* kill rescuer, if sanity checks fail, leave it w/o rescuer */
4392 if (wq->rescuer) {
4393 struct worker *rescuer = wq->rescuer;
4394
4395 /* this prevents new queueing */
4396 raw_spin_lock_irq(&wq_mayday_lock);
4397 wq->rescuer = NULL;
4398 raw_spin_unlock_irq(&wq_mayday_lock);
4399
4400 /* rescuer will empty maydays list before exiting */
4401 kthread_stop(rescuer->task);
4402 kfree(rescuer);
4403 }
4404
4405 /*
4406 * Sanity checks - grab all the locks so that we wait for all
4407 * in-flight operations which may do put_pwq().
4408 */
4409 mutex_lock(&wq_pool_mutex);
4410 mutex_lock(&wq->mutex);
4411 for_each_pwq(pwq, wq) {
4412 raw_spin_lock_irq(&pwq->pool->lock);
4413 if (WARN_ON(pwq_busy(pwq))) {
4414 pr_warn("%s: %s has the following busy pwq\n",
4415 __func__, wq->name);
4416 show_pwq(pwq);
4417 raw_spin_unlock_irq(&pwq->pool->lock);
4418 mutex_unlock(&wq->mutex);
4419 mutex_unlock(&wq_pool_mutex);
4420 show_workqueue_state();
4421 return;
4422 }
4423 raw_spin_unlock_irq(&pwq->pool->lock);
4424 }
4425 mutex_unlock(&wq->mutex);
4426
4427 /*
4428 * wq list is used to freeze wq, remove from list after
4429 * flushing is complete in case freeze races us.
4430 */
4431 list_del_rcu(&wq->list);
4432 mutex_unlock(&wq_pool_mutex);
4433
4434 if (!(wq->flags & WQ_UNBOUND)) {
4435 wq_unregister_lockdep(wq);
4436 /*
4437 * The base ref is never dropped on per-cpu pwqs. Directly
4438 * schedule RCU free.
4439 */
4440 call_rcu(&wq->rcu, rcu_free_wq);
4441 } else {
4442 /*
4443 * We're the sole accessor of @wq at this point. Directly
4444 * access numa_pwq_tbl[] and dfl_pwq to put the base refs.
4445 * @wq will be freed when the last pwq is released.
4446 */
4447 for_each_node(node) {
4448 pwq = rcu_access_pointer(wq->numa_pwq_tbl[node]);
4449 RCU_INIT_POINTER(wq->numa_pwq_tbl[node], NULL);
4450 put_pwq_unlocked(pwq);
4451 }
4452
4453 /*
4454 * Put dfl_pwq. @wq may be freed any time after dfl_pwq is
4455 * put. Don't access it afterwards.
4456 */
4457 pwq = wq->dfl_pwq;
4458 wq->dfl_pwq = NULL;
4459 put_pwq_unlocked(pwq);
4460 }
4461}
4462EXPORT_SYMBOL_GPL(destroy_workqueue);
4463
4464/**
4465 * workqueue_set_max_active - adjust max_active of a workqueue
4466 * @wq: target workqueue
4467 * @max_active: new max_active value.
4468 *
4469 * Set max_active of @wq to @max_active.
4470 *
4471 * CONTEXT:
4472 * Don't call from IRQ context.
4473 */
4474void workqueue_set_max_active(struct workqueue_struct *wq, int max_active)
4475{
4476 struct pool_workqueue *pwq;
4477
4478 /* disallow meddling with max_active for ordered workqueues */
4479 if (WARN_ON(wq->flags & __WQ_ORDERED_EXPLICIT))
4480 return;
4481
4482 max_active = wq_clamp_max_active(max_active, wq->flags, wq->name);
4483
4484 mutex_lock(&wq->mutex);
4485
4486 wq->flags &= ~__WQ_ORDERED;
4487 wq->saved_max_active = max_active;
4488
4489 for_each_pwq(pwq, wq)
4490 pwq_adjust_max_active(pwq);
4491
4492 mutex_unlock(&wq->mutex);
4493}
4494EXPORT_SYMBOL_GPL(workqueue_set_max_active);
4495
4496/**
4497 * current_work - retrieve %current task's work struct
4498 *
4499 * Determine if %current task is a workqueue worker and what it's working on.
4500 * Useful to find out the context that the %current task is running in.
4501 *
4502 * Return: work struct if %current task is a workqueue worker, %NULL otherwise.
4503 */
4504struct work_struct *current_work(void)
4505{
4506 struct worker *worker = current_wq_worker();
4507
4508 return worker ? worker->current_work : NULL;
4509}
4510EXPORT_SYMBOL(current_work);
4511
4512/**
4513 * current_is_workqueue_rescuer - is %current workqueue rescuer?
4514 *
4515 * Determine whether %current is a workqueue rescuer. Can be used from
4516 * work functions to determine whether it's being run off the rescuer task.
4517 *
4518 * Return: %true if %current is a workqueue rescuer. %false otherwise.
4519 */
4520bool current_is_workqueue_rescuer(void)
4521{
4522 struct worker *worker = current_wq_worker();
4523
4524 return worker && worker->rescue_wq;
4525}
4526
4527/**
4528 * workqueue_congested - test whether a workqueue is congested
4529 * @cpu: CPU in question
4530 * @wq: target workqueue
4531 *
4532 * Test whether @wq's cpu workqueue for @cpu is congested. There is
4533 * no synchronization around this function and the test result is
4534 * unreliable and only useful as advisory hints or for debugging.
4535 *
4536 * If @cpu is WORK_CPU_UNBOUND, the test is performed on the local CPU.
4537 * Note that both per-cpu and unbound workqueues may be associated with
4538 * multiple pool_workqueues which have separate congested states. A
4539 * workqueue being congested on one CPU doesn't mean the workqueue is also
4540 * contested on other CPUs / NUMA nodes.
4541 *
4542 * Return:
4543 * %true if congested, %false otherwise.
4544 */
4545bool workqueue_congested(int cpu, struct workqueue_struct *wq)
4546{
4547 struct pool_workqueue *pwq;
4548 bool ret;
4549
4550 rcu_read_lock();
4551 preempt_disable();
4552
4553 if (cpu == WORK_CPU_UNBOUND)
4554 cpu = smp_processor_id();
4555
4556 if (!(wq->flags & WQ_UNBOUND))
4557 pwq = per_cpu_ptr(wq->cpu_pwqs, cpu);
4558 else
4559 pwq = unbound_pwq_by_node(wq, cpu_to_node(cpu));
4560
4561 ret = !list_empty(&pwq->delayed_works);
4562 preempt_enable();
4563 rcu_read_unlock();
4564
4565 return ret;
4566}
4567EXPORT_SYMBOL_GPL(workqueue_congested);
4568
4569/**
4570 * work_busy - test whether a work is currently pending or running
4571 * @work: the work to be tested
4572 *
4573 * Test whether @work is currently pending or running. There is no
4574 * synchronization around this function and the test result is
4575 * unreliable and only useful as advisory hints or for debugging.
4576 *
4577 * Return:
4578 * OR'd bitmask of WORK_BUSY_* bits.
4579 */
4580unsigned int work_busy(struct work_struct *work)
4581{
4582 struct worker_pool *pool;
4583 unsigned long flags;
4584 unsigned int ret = 0;
4585
4586 if (work_pending(work))
4587 ret |= WORK_BUSY_PENDING;
4588
4589 rcu_read_lock();
4590 pool = get_work_pool(work);
4591 if (pool) {
4592 raw_spin_lock_irqsave(&pool->lock, flags);
4593 if (find_worker_executing_work(pool, work))
4594 ret |= WORK_BUSY_RUNNING;
4595 raw_spin_unlock_irqrestore(&pool->lock, flags);
4596 }
4597 rcu_read_unlock();
4598
4599 return ret;
4600}
4601EXPORT_SYMBOL_GPL(work_busy);
4602
4603/**
4604 * set_worker_desc - set description for the current work item
4605 * @fmt: printf-style format string
4606 * @...: arguments for the format string
4607 *
4608 * This function can be called by a running work function to describe what
4609 * the work item is about. If the worker task gets dumped, this
4610 * information will be printed out together to help debugging. The
4611 * description can be at most WORKER_DESC_LEN including the trailing '\0'.
4612 */
4613void set_worker_desc(const char *fmt, ...)
4614{
4615 struct worker *worker = current_wq_worker();
4616 va_list args;
4617
4618 if (worker) {
4619 va_start(args, fmt);
4620 vsnprintf(worker->desc, sizeof(worker->desc), fmt, args);
4621 va_end(args);
4622 }
4623}
4624EXPORT_SYMBOL_GPL(set_worker_desc);
4625
4626/**
4627 * print_worker_info - print out worker information and description
4628 * @log_lvl: the log level to use when printing
4629 * @task: target task
4630 *
4631 * If @task is a worker and currently executing a work item, print out the
4632 * name of the workqueue being serviced and worker description set with
4633 * set_worker_desc() by the currently executing work item.
4634 *
4635 * This function can be safely called on any task as long as the
4636 * task_struct itself is accessible. While safe, this function isn't
4637 * synchronized and may print out mixups or garbages of limited length.
4638 */
4639void print_worker_info(const char *log_lvl, struct task_struct *task)
4640{
4641 work_func_t *fn = NULL;
4642 char name[WQ_NAME_LEN] = { };
4643 char desc[WORKER_DESC_LEN] = { };
4644 struct pool_workqueue *pwq = NULL;
4645 struct workqueue_struct *wq = NULL;
4646 struct worker *worker;
4647
4648 if (!(task->flags & PF_WQ_WORKER))
4649 return;
4650
4651 /*
4652 * This function is called without any synchronization and @task
4653 * could be in any state. Be careful with dereferences.
4654 */
4655 worker = kthread_probe_data(task);
4656
4657 /*
4658 * Carefully copy the associated workqueue's workfn, name and desc.
4659 * Keep the original last '\0' in case the original is garbage.
4660 */
4661 copy_from_kernel_nofault(&fn, &worker->current_func, sizeof(fn));
4662 copy_from_kernel_nofault(&pwq, &worker->current_pwq, sizeof(pwq));
4663 copy_from_kernel_nofault(&wq, &pwq->wq, sizeof(wq));
4664 copy_from_kernel_nofault(name, wq->name, sizeof(name) - 1);
4665 copy_from_kernel_nofault(desc, worker->desc, sizeof(desc) - 1);
4666
4667 if (fn || name[0] || desc[0]) {
4668 printk("%sWorkqueue: %s %ps", log_lvl, name, fn);
4669 if (strcmp(name, desc))
4670 pr_cont(" (%s)", desc);
4671 pr_cont("\n");
4672 }
4673}
4674
4675static void pr_cont_pool_info(struct worker_pool *pool)
4676{
4677 pr_cont(" cpus=%*pbl", nr_cpumask_bits, pool->attrs->cpumask);
4678 if (pool->node != NUMA_NO_NODE)
4679 pr_cont(" node=%d", pool->node);
4680 pr_cont(" flags=0x%x nice=%d", pool->flags, pool->attrs->nice);
4681}
4682
4683static void pr_cont_work(bool comma, struct work_struct *work)
4684{
4685 if (work->func == wq_barrier_func) {
4686 struct wq_barrier *barr;
4687
4688 barr = container_of(work, struct wq_barrier, work);
4689
4690 pr_cont("%s BAR(%d)", comma ? "," : "",
4691 task_pid_nr(barr->task));
4692 } else {
4693 pr_cont("%s %ps", comma ? "," : "", work->func);
4694 }
4695}
4696
4697static void show_pwq(struct pool_workqueue *pwq)
4698{
4699 struct worker_pool *pool = pwq->pool;
4700 struct work_struct *work;
4701 struct worker *worker;
4702 bool has_in_flight = false, has_pending = false;
4703 int bkt;
4704
4705 pr_info(" pwq %d:", pool->id);
4706 pr_cont_pool_info(pool);
4707
4708 pr_cont(" active=%d/%d refcnt=%d%s\n",
4709 pwq->nr_active, pwq->max_active, pwq->refcnt,
4710 !list_empty(&pwq->mayday_node) ? " MAYDAY" : "");
4711
4712 hash_for_each(pool->busy_hash, bkt, worker, hentry) {
4713 if (worker->current_pwq == pwq) {
4714 has_in_flight = true;
4715 break;
4716 }
4717 }
4718 if (has_in_flight) {
4719 bool comma = false;
4720
4721 pr_info(" in-flight:");
4722 hash_for_each(pool->busy_hash, bkt, worker, hentry) {
4723 if (worker->current_pwq != pwq)
4724 continue;
4725
4726 pr_cont("%s %d%s:%ps", comma ? "," : "",
4727 task_pid_nr(worker->task),
4728 worker->rescue_wq ? "(RESCUER)" : "",
4729 worker->current_func);
4730 list_for_each_entry(work, &worker->scheduled, entry)
4731 pr_cont_work(false, work);
4732 comma = true;
4733 }
4734 pr_cont("\n");
4735 }
4736
4737 list_for_each_entry(work, &pool->worklist, entry) {
4738 if (get_work_pwq(work) == pwq) {
4739 has_pending = true;
4740 break;
4741 }
4742 }
4743 if (has_pending) {
4744 bool comma = false;
4745
4746 pr_info(" pending:");
4747 list_for_each_entry(work, &pool->worklist, entry) {
4748 if (get_work_pwq(work) != pwq)
4749 continue;
4750
4751 pr_cont_work(comma, work);
4752 comma = !(*work_data_bits(work) & WORK_STRUCT_LINKED);
4753 }
4754 pr_cont("\n");
4755 }
4756
4757 if (!list_empty(&pwq->delayed_works)) {
4758 bool comma = false;
4759
4760 pr_info(" delayed:");
4761 list_for_each_entry(work, &pwq->delayed_works, entry) {
4762 pr_cont_work(comma, work);
4763 comma = !(*work_data_bits(work) & WORK_STRUCT_LINKED);
4764 }
4765 pr_cont("\n");
4766 }
4767}
4768
4769/**
4770 * show_workqueue_state - dump workqueue state
4771 *
4772 * Called from a sysrq handler or try_to_freeze_tasks() and prints out
4773 * all busy workqueues and pools.
4774 */
4775void show_workqueue_state(void)
4776{
4777 struct workqueue_struct *wq;
4778 struct worker_pool *pool;
4779 unsigned long flags;
4780 int pi;
4781
4782 rcu_read_lock();
4783
4784 pr_info("Showing busy workqueues and worker pools:\n");
4785
4786 list_for_each_entry_rcu(wq, &workqueues, list) {
4787 struct pool_workqueue *pwq;
4788 bool idle = true;
4789
4790 for_each_pwq(pwq, wq) {
4791 if (pwq->nr_active || !list_empty(&pwq->delayed_works)) {
4792 idle = false;
4793 break;
4794 }
4795 }
4796 if (idle)
4797 continue;
4798
4799 pr_info("workqueue %s: flags=0x%x\n", wq->name, wq->flags);
4800
4801 for_each_pwq(pwq, wq) {
4802 raw_spin_lock_irqsave(&pwq->pool->lock, flags);
4803 if (pwq->nr_active || !list_empty(&pwq->delayed_works))
4804 show_pwq(pwq);
4805 raw_spin_unlock_irqrestore(&pwq->pool->lock, flags);
4806 /*
4807 * We could be printing a lot from atomic context, e.g.
4808 * sysrq-t -> show_workqueue_state(). Avoid triggering
4809 * hard lockup.
4810 */
4811 touch_nmi_watchdog();
4812 }
4813 }
4814
4815 for_each_pool(pool, pi) {
4816 struct worker *worker;
4817 bool first = true;
4818
4819 raw_spin_lock_irqsave(&pool->lock, flags);
4820 if (pool->nr_workers == pool->nr_idle)
4821 goto next_pool;
4822
4823 pr_info("pool %d:", pool->id);
4824 pr_cont_pool_info(pool);
4825 pr_cont(" hung=%us workers=%d",
4826 jiffies_to_msecs(jiffies - pool->watchdog_ts) / 1000,
4827 pool->nr_workers);
4828 if (pool->manager)
4829 pr_cont(" manager: %d",
4830 task_pid_nr(pool->manager->task));
4831 list_for_each_entry(worker, &pool->idle_list, entry) {
4832 pr_cont(" %s%d", first ? "idle: " : "",
4833 task_pid_nr(worker->task));
4834 first = false;
4835 }
4836 pr_cont("\n");
4837 next_pool:
4838 raw_spin_unlock_irqrestore(&pool->lock, flags);
4839 /*
4840 * We could be printing a lot from atomic context, e.g.
4841 * sysrq-t -> show_workqueue_state(). Avoid triggering
4842 * hard lockup.
4843 */
4844 touch_nmi_watchdog();
4845 }
4846
4847 rcu_read_unlock();
4848}
4849
4850/* used to show worker information through /proc/PID/{comm,stat,status} */
4851void wq_worker_comm(char *buf, size_t size, struct task_struct *task)
4852{
4853 int off;
4854
4855 /* always show the actual comm */
4856 off = strscpy(buf, task->comm, size);
4857 if (off < 0)
4858 return;
4859
4860 /* stabilize PF_WQ_WORKER and worker pool association */
4861 mutex_lock(&wq_pool_attach_mutex);
4862
4863 if (task->flags & PF_WQ_WORKER) {
4864 struct worker *worker = kthread_data(task);
4865 struct worker_pool *pool = worker->pool;
4866
4867 if (pool) {
4868 raw_spin_lock_irq(&pool->lock);
4869 /*
4870 * ->desc tracks information (wq name or
4871 * set_worker_desc()) for the latest execution. If
4872 * current, prepend '+', otherwise '-'.
4873 */
4874 if (worker->desc[0] != '\0') {
4875 if (worker->current_work)
4876 scnprintf(buf + off, size - off, "+%s",
4877 worker->desc);
4878 else
4879 scnprintf(buf + off, size - off, "-%s",
4880 worker->desc);
4881 }
4882 raw_spin_unlock_irq(&pool->lock);
4883 }
4884 }
4885
4886 mutex_unlock(&wq_pool_attach_mutex);
4887}
4888
4889#ifdef CONFIG_SMP
4890
4891/*
4892 * CPU hotplug.
4893 *
4894 * There are two challenges in supporting CPU hotplug. Firstly, there
4895 * are a lot of assumptions on strong associations among work, pwq and
4896 * pool which make migrating pending and scheduled works very
4897 * difficult to implement without impacting hot paths. Secondly,
4898 * worker pools serve mix of short, long and very long running works making
4899 * blocked draining impractical.
4900 *
4901 * This is solved by allowing the pools to be disassociated from the CPU
4902 * running as an unbound one and allowing it to be reattached later if the
4903 * cpu comes back online.
4904 */
4905
4906static void unbind_workers(int cpu)
4907{
4908 struct worker_pool *pool;
4909 struct worker *worker;
4910
4911 for_each_cpu_worker_pool(pool, cpu) {
4912 mutex_lock(&wq_pool_attach_mutex);
4913 raw_spin_lock_irq(&pool->lock);
4914
4915 /*
4916 * We've blocked all attach/detach operations. Make all workers
4917 * unbound and set DISASSOCIATED. Before this, all workers
4918 * except for the ones which are still executing works from
4919 * before the last CPU down must be on the cpu. After
4920 * this, they may become diasporas.
4921 */
4922 for_each_pool_worker(worker, pool)
4923 worker->flags |= WORKER_UNBOUND;
4924
4925 pool->flags |= POOL_DISASSOCIATED;
4926
4927 raw_spin_unlock_irq(&pool->lock);
4928
4929 for_each_pool_worker(worker, pool) {
4930 kthread_set_per_cpu(worker->task, -1);
4931 WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task, cpu_possible_mask) < 0);
4932 }
4933
4934 mutex_unlock(&wq_pool_attach_mutex);
4935
4936 /*
4937 * Call schedule() so that we cross rq->lock and thus can
4938 * guarantee sched callbacks see the %WORKER_UNBOUND flag.
4939 * This is necessary as scheduler callbacks may be invoked
4940 * from other cpus.
4941 */
4942 schedule();
4943
4944 /*
4945 * Sched callbacks are disabled now. Zap nr_running.
4946 * After this, nr_running stays zero and need_more_worker()
4947 * and keep_working() are always true as long as the
4948 * worklist is not empty. This pool now behaves as an
4949 * unbound (in terms of concurrency management) pool which
4950 * are served by workers tied to the pool.
4951 */
4952 atomic_set(&pool->nr_running, 0);
4953
4954 /*
4955 * With concurrency management just turned off, a busy
4956 * worker blocking could lead to lengthy stalls. Kick off
4957 * unbound chain execution of currently pending work items.
4958 */
4959 raw_spin_lock_irq(&pool->lock);
4960 wake_up_worker(pool);
4961 raw_spin_unlock_irq(&pool->lock);
4962 }
4963}
4964
4965/**
4966 * rebind_workers - rebind all workers of a pool to the associated CPU
4967 * @pool: pool of interest
4968 *
4969 * @pool->cpu is coming online. Rebind all workers to the CPU.
4970 */
4971static void rebind_workers(struct worker_pool *pool)
4972{
4973 struct worker *worker;
4974
4975 lockdep_assert_held(&wq_pool_attach_mutex);
4976
4977 /*
4978 * Restore CPU affinity of all workers. As all idle workers should
4979 * be on the run-queue of the associated CPU before any local
4980 * wake-ups for concurrency management happen, restore CPU affinity
4981 * of all workers first and then clear UNBOUND. As we're called
4982 * from CPU_ONLINE, the following shouldn't fail.
4983 */
4984 for_each_pool_worker(worker, pool) {
4985 kthread_set_per_cpu(worker->task, pool->cpu);
4986 WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task,
4987 pool->attrs->cpumask) < 0);
4988 }
4989
4990 raw_spin_lock_irq(&pool->lock);
4991
4992 pool->flags &= ~POOL_DISASSOCIATED;
4993
4994 for_each_pool_worker(worker, pool) {
4995 unsigned int worker_flags = worker->flags;
4996
4997 /*
4998 * A bound idle worker should actually be on the runqueue
4999 * of the associated CPU for local wake-ups targeting it to
5000 * work. Kick all idle workers so that they migrate to the
5001 * associated CPU. Doing this in the same loop as
5002 * replacing UNBOUND with REBOUND is safe as no worker will
5003 * be bound before @pool->lock is released.
5004 */
5005 if (worker_flags & WORKER_IDLE)
5006 wake_up_process(worker->task);
5007
5008 /*
5009 * We want to clear UNBOUND but can't directly call
5010 * worker_clr_flags() or adjust nr_running. Atomically
5011 * replace UNBOUND with another NOT_RUNNING flag REBOUND.
5012 * @worker will clear REBOUND using worker_clr_flags() when
5013 * it initiates the next execution cycle thus restoring
5014 * concurrency management. Note that when or whether
5015 * @worker clears REBOUND doesn't affect correctness.
5016 *
5017 * WRITE_ONCE() is necessary because @worker->flags may be
5018 * tested without holding any lock in
5019 * wq_worker_running(). Without it, NOT_RUNNING test may
5020 * fail incorrectly leading to premature concurrency
5021 * management operations.
5022 */
5023 WARN_ON_ONCE(!(worker_flags & WORKER_UNBOUND));
5024 worker_flags |= WORKER_REBOUND;
5025 worker_flags &= ~WORKER_UNBOUND;
5026 WRITE_ONCE(worker->flags, worker_flags);
5027 }
5028
5029 raw_spin_unlock_irq(&pool->lock);
5030}
5031
5032/**
5033 * restore_unbound_workers_cpumask - restore cpumask of unbound workers
5034 * @pool: unbound pool of interest
5035 * @cpu: the CPU which is coming up
5036 *
5037 * An unbound pool may end up with a cpumask which doesn't have any online
5038 * CPUs. When a worker of such pool get scheduled, the scheduler resets
5039 * its cpus_allowed. If @cpu is in @pool's cpumask which didn't have any
5040 * online CPU before, cpus_allowed of all its workers should be restored.
5041 */
5042static void restore_unbound_workers_cpumask(struct worker_pool *pool, int cpu)
5043{
5044 static cpumask_t cpumask;
5045 struct worker *worker;
5046
5047 lockdep_assert_held(&wq_pool_attach_mutex);
5048
5049 /* is @cpu allowed for @pool? */
5050 if (!cpumask_test_cpu(cpu, pool->attrs->cpumask))
5051 return;
5052
5053 cpumask_and(&cpumask, pool->attrs->cpumask, cpu_online_mask);
5054
5055 /* as we're called from CPU_ONLINE, the following shouldn't fail */
5056 for_each_pool_worker(worker, pool)
5057 WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task, &cpumask) < 0);
5058}
5059
5060int workqueue_prepare_cpu(unsigned int cpu)
5061{
5062 struct worker_pool *pool;
5063
5064 for_each_cpu_worker_pool(pool, cpu) {
5065 if (pool->nr_workers)
5066 continue;
5067 if (!create_worker(pool))
5068 return -ENOMEM;
5069 }
5070 return 0;
5071}
5072
5073int workqueue_online_cpu(unsigned int cpu)
5074{
5075 struct worker_pool *pool;
5076 struct workqueue_struct *wq;
5077 int pi;
5078
5079 mutex_lock(&wq_pool_mutex);
5080
5081 for_each_pool(pool, pi) {
5082 mutex_lock(&wq_pool_attach_mutex);
5083
5084 if (pool->cpu == cpu)
5085 rebind_workers(pool);
5086 else if (pool->cpu < 0)
5087 restore_unbound_workers_cpumask(pool, cpu);
5088
5089 mutex_unlock(&wq_pool_attach_mutex);
5090 }
5091
5092 /* update NUMA affinity of unbound workqueues */
5093 list_for_each_entry(wq, &workqueues, list)
5094 wq_update_unbound_numa(wq, cpu, true);
5095
5096 mutex_unlock(&wq_pool_mutex);
5097 return 0;
5098}
5099
5100int workqueue_offline_cpu(unsigned int cpu)
5101{
5102 struct workqueue_struct *wq;
5103
5104 /* unbinding per-cpu workers should happen on the local CPU */
5105 if (WARN_ON(cpu != smp_processor_id()))
5106 return -1;
5107
5108 unbind_workers(cpu);
5109
5110 /* update NUMA affinity of unbound workqueues */
5111 mutex_lock(&wq_pool_mutex);
5112 list_for_each_entry(wq, &workqueues, list)
5113 wq_update_unbound_numa(wq, cpu, false);
5114 mutex_unlock(&wq_pool_mutex);
5115
5116 return 0;
5117}
5118
5119struct work_for_cpu {
5120 struct work_struct work;
5121 long (*fn)(void *);
5122 void *arg;
5123 long ret;
5124};
5125
5126static void work_for_cpu_fn(struct work_struct *work)
5127{
5128 struct work_for_cpu *wfc = container_of(work, struct work_for_cpu, work);
5129
5130 wfc->ret = wfc->fn(wfc->arg);
5131}
5132
5133/**
5134 * work_on_cpu - run a function in thread context on a particular cpu
5135 * @cpu: the cpu to run on
5136 * @fn: the function to run
5137 * @arg: the function arg
5138 *
5139 * It is up to the caller to ensure that the cpu doesn't go offline.
5140 * The caller must not hold any locks which would prevent @fn from completing.
5141 *
5142 * Return: The value @fn returns.
5143 */
5144long work_on_cpu(int cpu, long (*fn)(void *), void *arg)
5145{
5146 struct work_for_cpu wfc = { .fn = fn, .arg = arg };
5147
5148 INIT_WORK_ONSTACK(&wfc.work, work_for_cpu_fn);
5149 schedule_work_on(cpu, &wfc.work);
5150 flush_work(&wfc.work);
5151 destroy_work_on_stack(&wfc.work);
5152 return wfc.ret;
5153}
5154EXPORT_SYMBOL_GPL(work_on_cpu);
5155
5156/**
5157 * work_on_cpu_safe - run a function in thread context on a particular cpu
5158 * @cpu: the cpu to run on
5159 * @fn: the function to run
5160 * @arg: the function argument
5161 *
5162 * Disables CPU hotplug and calls work_on_cpu(). The caller must not hold
5163 * any locks which would prevent @fn from completing.
5164 *
5165 * Return: The value @fn returns.
5166 */
5167long work_on_cpu_safe(int cpu, long (*fn)(void *), void *arg)
5168{
5169 long ret = -ENODEV;
5170
5171 get_online_cpus();
5172 if (cpu_online(cpu))
5173 ret = work_on_cpu(cpu, fn, arg);
5174 put_online_cpus();
5175 return ret;
5176}
5177EXPORT_SYMBOL_GPL(work_on_cpu_safe);
5178#endif /* CONFIG_SMP */
5179
5180#ifdef CONFIG_FREEZER
5181
5182/**
5183 * freeze_workqueues_begin - begin freezing workqueues
5184 *
5185 * Start freezing workqueues. After this function returns, all freezable
5186 * workqueues will queue new works to their delayed_works list instead of
5187 * pool->worklist.
5188 *
5189 * CONTEXT:
5190 * Grabs and releases wq_pool_mutex, wq->mutex and pool->lock's.
5191 */
5192void freeze_workqueues_begin(void)
5193{
5194 struct workqueue_struct *wq;
5195 struct pool_workqueue *pwq;
5196
5197 mutex_lock(&wq_pool_mutex);
5198
5199 WARN_ON_ONCE(workqueue_freezing);
5200 workqueue_freezing = true;
5201
5202 list_for_each_entry(wq, &workqueues, list) {
5203 mutex_lock(&wq->mutex);
5204 for_each_pwq(pwq, wq)
5205 pwq_adjust_max_active(pwq);
5206 mutex_unlock(&wq->mutex);
5207 }
5208
5209 mutex_unlock(&wq_pool_mutex);
5210}
5211
5212/**
5213 * freeze_workqueues_busy - are freezable workqueues still busy?
5214 *
5215 * Check whether freezing is complete. This function must be called
5216 * between freeze_workqueues_begin() and thaw_workqueues().
5217 *
5218 * CONTEXT:
5219 * Grabs and releases wq_pool_mutex.
5220 *
5221 * Return:
5222 * %true if some freezable workqueues are still busy. %false if freezing
5223 * is complete.
5224 */
5225bool freeze_workqueues_busy(void)
5226{
5227 bool busy = false;
5228 struct workqueue_struct *wq;
5229 struct pool_workqueue *pwq;
5230
5231 mutex_lock(&wq_pool_mutex);
5232
5233 WARN_ON_ONCE(!workqueue_freezing);
5234
5235 list_for_each_entry(wq, &workqueues, list) {
5236 if (!(wq->flags & WQ_FREEZABLE))
5237 continue;
5238 /*
5239 * nr_active is monotonically decreasing. It's safe
5240 * to peek without lock.
5241 */
5242 rcu_read_lock();
5243 for_each_pwq(pwq, wq) {
5244 WARN_ON_ONCE(pwq->nr_active < 0);
5245 if (pwq->nr_active) {
5246 busy = true;
5247 rcu_read_unlock();
5248 goto out_unlock;
5249 }
5250 }
5251 rcu_read_unlock();
5252 }
5253out_unlock:
5254 mutex_unlock(&wq_pool_mutex);
5255 return busy;
5256}
5257
5258/**
5259 * thaw_workqueues - thaw workqueues
5260 *
5261 * Thaw workqueues. Normal queueing is restored and all collected
5262 * frozen works are transferred to their respective pool worklists.
5263 *
5264 * CONTEXT:
5265 * Grabs and releases wq_pool_mutex, wq->mutex and pool->lock's.
5266 */
5267void thaw_workqueues(void)
5268{
5269 struct workqueue_struct *wq;
5270 struct pool_workqueue *pwq;
5271
5272 mutex_lock(&wq_pool_mutex);
5273
5274 if (!workqueue_freezing)
5275 goto out_unlock;
5276
5277 workqueue_freezing = false;
5278
5279 /* restore max_active and repopulate worklist */
5280 list_for_each_entry(wq, &workqueues, list) {
5281 mutex_lock(&wq->mutex);
5282 for_each_pwq(pwq, wq)
5283 pwq_adjust_max_active(pwq);
5284 mutex_unlock(&wq->mutex);
5285 }
5286
5287out_unlock:
5288 mutex_unlock(&wq_pool_mutex);
5289}
5290#endif /* CONFIG_FREEZER */
5291
5292static int workqueue_apply_unbound_cpumask(void)
5293{
5294 LIST_HEAD(ctxs);
5295 int ret = 0;
5296 struct workqueue_struct *wq;
5297 struct apply_wqattrs_ctx *ctx, *n;
5298
5299 lockdep_assert_held(&wq_pool_mutex);
5300
5301 list_for_each_entry(wq, &workqueues, list) {
5302 if (!(wq->flags & WQ_UNBOUND))
5303 continue;
5304 /* creating multiple pwqs breaks ordering guarantee */
5305 if (wq->flags & __WQ_ORDERED)
5306 continue;
5307
5308 ctx = apply_wqattrs_prepare(wq, wq->unbound_attrs);
5309 if (!ctx) {
5310 ret = -ENOMEM;
5311 break;
5312 }
5313
5314 list_add_tail(&ctx->list, &ctxs);
5315 }
5316
5317 list_for_each_entry_safe(ctx, n, &ctxs, list) {
5318 if (!ret)
5319 apply_wqattrs_commit(ctx);
5320 apply_wqattrs_cleanup(ctx);
5321 }
5322
5323 return ret;
5324}
5325
5326/**
5327 * workqueue_set_unbound_cpumask - Set the low-level unbound cpumask
5328 * @cpumask: the cpumask to set
5329 *
5330 * The low-level workqueues cpumask is a global cpumask that limits
5331 * the affinity of all unbound workqueues. This function check the @cpumask
5332 * and apply it to all unbound workqueues and updates all pwqs of them.
5333 *
5334 * Retun: 0 - Success
5335 * -EINVAL - Invalid @cpumask
5336 * -ENOMEM - Failed to allocate memory for attrs or pwqs.
5337 */
5338int workqueue_set_unbound_cpumask(cpumask_var_t cpumask)
5339{
5340 int ret = -EINVAL;
5341 cpumask_var_t saved_cpumask;
5342
5343 if (!zalloc_cpumask_var(&saved_cpumask, GFP_KERNEL))
5344 return -ENOMEM;
5345
5346 /*
5347 * Not excluding isolated cpus on purpose.
5348 * If the user wishes to include them, we allow that.
5349 */
5350 cpumask_and(cpumask, cpumask, cpu_possible_mask);
5351 if (!cpumask_empty(cpumask)) {
5352 apply_wqattrs_lock();
5353
5354 /* save the old wq_unbound_cpumask. */
5355 cpumask_copy(saved_cpumask, wq_unbound_cpumask);
5356
5357 /* update wq_unbound_cpumask at first and apply it to wqs. */
5358 cpumask_copy(wq_unbound_cpumask, cpumask);
5359 ret = workqueue_apply_unbound_cpumask();
5360
5361 /* restore the wq_unbound_cpumask when failed. */
5362 if (ret < 0)
5363 cpumask_copy(wq_unbound_cpumask, saved_cpumask);
5364
5365 apply_wqattrs_unlock();
5366 }
5367
5368 free_cpumask_var(saved_cpumask);
5369 return ret;
5370}
5371
5372#ifdef CONFIG_SYSFS
5373/*
5374 * Workqueues with WQ_SYSFS flag set is visible to userland via
5375 * /sys/bus/workqueue/devices/WQ_NAME. All visible workqueues have the
5376 * following attributes.
5377 *
5378 * per_cpu RO bool : whether the workqueue is per-cpu or unbound
5379 * max_active RW int : maximum number of in-flight work items
5380 *
5381 * Unbound workqueues have the following extra attributes.
5382 *
5383 * pool_ids RO int : the associated pool IDs for each node
5384 * nice RW int : nice value of the workers
5385 * cpumask RW mask : bitmask of allowed CPUs for the workers
5386 * numa RW bool : whether enable NUMA affinity
5387 */
5388struct wq_device {
5389 struct workqueue_struct *wq;
5390 struct device dev;
5391};
5392
5393static struct workqueue_struct *dev_to_wq(struct device *dev)
5394{
5395 struct wq_device *wq_dev = container_of(dev, struct wq_device, dev);
5396
5397 return wq_dev->wq;
5398}
5399
5400static ssize_t per_cpu_show(struct device *dev, struct device_attribute *attr,
5401 char *buf)
5402{
5403 struct workqueue_struct *wq = dev_to_wq(dev);
5404
5405 return scnprintf(buf, PAGE_SIZE, "%d\n", (bool)!(wq->flags & WQ_UNBOUND));
5406}
5407static DEVICE_ATTR_RO(per_cpu);
5408
5409static ssize_t max_active_show(struct device *dev,
5410 struct device_attribute *attr, char *buf)
5411{
5412 struct workqueue_struct *wq = dev_to_wq(dev);
5413
5414 return scnprintf(buf, PAGE_SIZE, "%d\n", wq->saved_max_active);
5415}
5416
5417static ssize_t max_active_store(struct device *dev,
5418 struct device_attribute *attr, const char *buf,
5419 size_t count)
5420{
5421 struct workqueue_struct *wq = dev_to_wq(dev);
5422 int val;
5423
5424 if (sscanf(buf, "%d", &val) != 1 || val <= 0)
5425 return -EINVAL;
5426
5427 workqueue_set_max_active(wq, val);
5428 return count;
5429}
5430static DEVICE_ATTR_RW(max_active);
5431
5432static struct attribute *wq_sysfs_attrs[] = {
5433 &dev_attr_per_cpu.attr,
5434 &dev_attr_max_active.attr,
5435 NULL,
5436};
5437ATTRIBUTE_GROUPS(wq_sysfs);
5438
5439static ssize_t wq_pool_ids_show(struct device *dev,
5440 struct device_attribute *attr, char *buf)
5441{
5442 struct workqueue_struct *wq = dev_to_wq(dev);
5443 const char *delim = "";
5444 int node, written = 0;
5445
5446 get_online_cpus();
5447 rcu_read_lock();
5448 for_each_node(node) {
5449 written += scnprintf(buf + written, PAGE_SIZE - written,
5450 "%s%d:%d", delim, node,
5451 unbound_pwq_by_node(wq, node)->pool->id);
5452 delim = " ";
5453 }
5454 written += scnprintf(buf + written, PAGE_SIZE - written, "\n");
5455 rcu_read_unlock();
5456 put_online_cpus();
5457
5458 return written;
5459}
5460
5461static ssize_t wq_nice_show(struct device *dev, struct device_attribute *attr,
5462 char *buf)
5463{
5464 struct workqueue_struct *wq = dev_to_wq(dev);
5465 int written;
5466
5467 mutex_lock(&wq->mutex);
5468 written = scnprintf(buf, PAGE_SIZE, "%d\n", wq->unbound_attrs->nice);
5469 mutex_unlock(&wq->mutex);
5470
5471 return written;
5472}
5473
5474/* prepare workqueue_attrs for sysfs store operations */
5475static struct workqueue_attrs *wq_sysfs_prep_attrs(struct workqueue_struct *wq)
5476{
5477 struct workqueue_attrs *attrs;
5478
5479 lockdep_assert_held(&wq_pool_mutex);
5480
5481 attrs = alloc_workqueue_attrs();
5482 if (!attrs)
5483 return NULL;
5484
5485 copy_workqueue_attrs(attrs, wq->unbound_attrs);
5486 return attrs;
5487}
5488
5489static ssize_t wq_nice_store(struct device *dev, struct device_attribute *attr,
5490 const char *buf, size_t count)
5491{
5492 struct workqueue_struct *wq = dev_to_wq(dev);
5493 struct workqueue_attrs *attrs;
5494 int ret = -ENOMEM;
5495
5496 apply_wqattrs_lock();
5497
5498 attrs = wq_sysfs_prep_attrs(wq);
5499 if (!attrs)
5500 goto out_unlock;
5501
5502 if (sscanf(buf, "%d", &attrs->nice) == 1 &&
5503 attrs->nice >= MIN_NICE && attrs->nice <= MAX_NICE)
5504 ret = apply_workqueue_attrs_locked(wq, attrs);
5505 else
5506 ret = -EINVAL;
5507
5508out_unlock:
5509 apply_wqattrs_unlock();
5510 free_workqueue_attrs(attrs);
5511 return ret ?: count;
5512}
5513
5514static ssize_t wq_cpumask_show(struct device *dev,
5515 struct device_attribute *attr, char *buf)
5516{
5517 struct workqueue_struct *wq = dev_to_wq(dev);
5518 int written;
5519
5520 mutex_lock(&wq->mutex);
5521 written = scnprintf(buf, PAGE_SIZE, "%*pb\n",
5522 cpumask_pr_args(wq->unbound_attrs->cpumask));
5523 mutex_unlock(&wq->mutex);
5524 return written;
5525}
5526
5527static ssize_t wq_cpumask_store(struct device *dev,
5528 struct device_attribute *attr,
5529 const char *buf, size_t count)
5530{
5531 struct workqueue_struct *wq = dev_to_wq(dev);
5532 struct workqueue_attrs *attrs;
5533 int ret = -ENOMEM;
5534
5535 apply_wqattrs_lock();
5536
5537 attrs = wq_sysfs_prep_attrs(wq);
5538 if (!attrs)
5539 goto out_unlock;
5540
5541 ret = cpumask_parse(buf, attrs->cpumask);
5542 if (!ret)
5543 ret = apply_workqueue_attrs_locked(wq, attrs);
5544
5545out_unlock:
5546 apply_wqattrs_unlock();
5547 free_workqueue_attrs(attrs);
5548 return ret ?: count;
5549}
5550
5551static ssize_t wq_numa_show(struct device *dev, struct device_attribute *attr,
5552 char *buf)
5553{
5554 struct workqueue_struct *wq = dev_to_wq(dev);
5555 int written;
5556
5557 mutex_lock(&wq->mutex);
5558 written = scnprintf(buf, PAGE_SIZE, "%d\n",
5559 !wq->unbound_attrs->no_numa);
5560 mutex_unlock(&wq->mutex);
5561
5562 return written;
5563}
5564
5565static ssize_t wq_numa_store(struct device *dev, struct device_attribute *attr,
5566 const char *buf, size_t count)
5567{
5568 struct workqueue_struct *wq = dev_to_wq(dev);
5569 struct workqueue_attrs *attrs;
5570 int v, ret = -ENOMEM;
5571
5572 apply_wqattrs_lock();
5573
5574 attrs = wq_sysfs_prep_attrs(wq);
5575 if (!attrs)
5576 goto out_unlock;
5577
5578 ret = -EINVAL;
5579 if (sscanf(buf, "%d", &v) == 1) {
5580 attrs->no_numa = !v;
5581 ret = apply_workqueue_attrs_locked(wq, attrs);
5582 }
5583
5584out_unlock:
5585 apply_wqattrs_unlock();
5586 free_workqueue_attrs(attrs);
5587 return ret ?: count;
5588}
5589
5590static struct device_attribute wq_sysfs_unbound_attrs[] = {
5591 __ATTR(pool_ids, 0444, wq_pool_ids_show, NULL),
5592 __ATTR(nice, 0644, wq_nice_show, wq_nice_store),
5593 __ATTR(cpumask, 0644, wq_cpumask_show, wq_cpumask_store),
5594 __ATTR(numa, 0644, wq_numa_show, wq_numa_store),
5595 __ATTR_NULL,
5596};
5597
5598static struct bus_type wq_subsys = {
5599 .name = "workqueue",
5600 .dev_groups = wq_sysfs_groups,
5601};
5602
5603static ssize_t wq_unbound_cpumask_show(struct device *dev,
5604 struct device_attribute *attr, char *buf)
5605{
5606 int written;
5607
5608 mutex_lock(&wq_pool_mutex);
5609 written = scnprintf(buf, PAGE_SIZE, "%*pb\n",
5610 cpumask_pr_args(wq_unbound_cpumask));
5611 mutex_unlock(&wq_pool_mutex);
5612
5613 return written;
5614}
5615
5616static ssize_t wq_unbound_cpumask_store(struct device *dev,
5617 struct device_attribute *attr, const char *buf, size_t count)
5618{
5619 cpumask_var_t cpumask;
5620 int ret;
5621
5622 if (!zalloc_cpumask_var(&cpumask, GFP_KERNEL))
5623 return -ENOMEM;
5624
5625 ret = cpumask_parse(buf, cpumask);
5626 if (!ret)
5627 ret = workqueue_set_unbound_cpumask(cpumask);
5628
5629 free_cpumask_var(cpumask);
5630 return ret ? ret : count;
5631}
5632
5633static struct device_attribute wq_sysfs_cpumask_attr =
5634 __ATTR(cpumask, 0644, wq_unbound_cpumask_show,
5635 wq_unbound_cpumask_store);
5636
5637static int __init wq_sysfs_init(void)
5638{
5639 int err;
5640
5641 err = subsys_virtual_register(&wq_subsys, NULL);
5642 if (err)
5643 return err;
5644
5645 return device_create_file(wq_subsys.dev_root, &wq_sysfs_cpumask_attr);
5646}
5647core_initcall(wq_sysfs_init);
5648
5649static void wq_device_release(struct device *dev)
5650{
5651 struct wq_device *wq_dev = container_of(dev, struct wq_device, dev);
5652
5653 kfree(wq_dev);
5654}
5655
5656/**
5657 * workqueue_sysfs_register - make a workqueue visible in sysfs
5658 * @wq: the workqueue to register
5659 *
5660 * Expose @wq in sysfs under /sys/bus/workqueue/devices.
5661 * alloc_workqueue*() automatically calls this function if WQ_SYSFS is set
5662 * which is the preferred method.
5663 *
5664 * Workqueue user should use this function directly iff it wants to apply
5665 * workqueue_attrs before making the workqueue visible in sysfs; otherwise,
5666 * apply_workqueue_attrs() may race against userland updating the
5667 * attributes.
5668 *
5669 * Return: 0 on success, -errno on failure.
5670 */
5671int workqueue_sysfs_register(struct workqueue_struct *wq)
5672{
5673 struct wq_device *wq_dev;
5674 int ret;
5675
5676 /*
5677 * Adjusting max_active or creating new pwqs by applying
5678 * attributes breaks ordering guarantee. Disallow exposing ordered
5679 * workqueues.
5680 */
5681 if (WARN_ON(wq->flags & __WQ_ORDERED_EXPLICIT))
5682 return -EINVAL;
5683
5684 wq->wq_dev = wq_dev = kzalloc(sizeof(*wq_dev), GFP_KERNEL);
5685 if (!wq_dev)
5686 return -ENOMEM;
5687
5688 wq_dev->wq = wq;
5689 wq_dev->dev.bus = &wq_subsys;
5690 wq_dev->dev.release = wq_device_release;
5691 dev_set_name(&wq_dev->dev, "%s", wq->name);
5692
5693 /*
5694 * unbound_attrs are created separately. Suppress uevent until
5695 * everything is ready.
5696 */
5697 dev_set_uevent_suppress(&wq_dev->dev, true);
5698
5699 ret = device_register(&wq_dev->dev);
5700 if (ret) {
5701 put_device(&wq_dev->dev);
5702 wq->wq_dev = NULL;
5703 return ret;
5704 }
5705
5706 if (wq->flags & WQ_UNBOUND) {
5707 struct device_attribute *attr;
5708
5709 for (attr = wq_sysfs_unbound_attrs; attr->attr.name; attr++) {
5710 ret = device_create_file(&wq_dev->dev, attr);
5711 if (ret) {
5712 device_unregister(&wq_dev->dev);
5713 wq->wq_dev = NULL;
5714 return ret;
5715 }
5716 }
5717 }
5718
5719 dev_set_uevent_suppress(&wq_dev->dev, false);
5720 kobject_uevent(&wq_dev->dev.kobj, KOBJ_ADD);
5721 return 0;
5722}
5723
5724/**
5725 * workqueue_sysfs_unregister - undo workqueue_sysfs_register()
5726 * @wq: the workqueue to unregister
5727 *
5728 * If @wq is registered to sysfs by workqueue_sysfs_register(), unregister.
5729 */
5730static void workqueue_sysfs_unregister(struct workqueue_struct *wq)
5731{
5732 struct wq_device *wq_dev = wq->wq_dev;
5733
5734 if (!wq->wq_dev)
5735 return;
5736
5737 wq->wq_dev = NULL;
5738 device_unregister(&wq_dev->dev);
5739}
5740#else /* CONFIG_SYSFS */
5741static void workqueue_sysfs_unregister(struct workqueue_struct *wq) { }
5742#endif /* CONFIG_SYSFS */
5743
5744/*
5745 * Workqueue watchdog.
5746 *
5747 * Stall may be caused by various bugs - missing WQ_MEM_RECLAIM, illegal
5748 * flush dependency, a concurrency managed work item which stays RUNNING
5749 * indefinitely. Workqueue stalls can be very difficult to debug as the
5750 * usual warning mechanisms don't trigger and internal workqueue state is
5751 * largely opaque.
5752 *
5753 * Workqueue watchdog monitors all worker pools periodically and dumps
5754 * state if some pools failed to make forward progress for a while where
5755 * forward progress is defined as the first item on ->worklist changing.
5756 *
5757 * This mechanism is controlled through the kernel parameter
5758 * "workqueue.watchdog_thresh" which can be updated at runtime through the
5759 * corresponding sysfs parameter file.
5760 */
5761#ifdef CONFIG_WQ_WATCHDOG
5762
5763static unsigned long wq_watchdog_thresh = 30;
5764static struct timer_list wq_watchdog_timer;
5765
5766static unsigned long wq_watchdog_touched = INITIAL_JIFFIES;
5767static DEFINE_PER_CPU(unsigned long, wq_watchdog_touched_cpu) = INITIAL_JIFFIES;
5768
5769static void wq_watchdog_reset_touched(void)
5770{
5771 int cpu;
5772
5773 wq_watchdog_touched = jiffies;
5774 for_each_possible_cpu(cpu)
5775 per_cpu(wq_watchdog_touched_cpu, cpu) = jiffies;
5776}
5777
5778static void wq_watchdog_timer_fn(struct timer_list *unused)
5779{
5780 unsigned long thresh = READ_ONCE(wq_watchdog_thresh) * HZ;
5781 bool lockup_detected = false;
5782 unsigned long now = jiffies;
5783 struct worker_pool *pool;
5784 int pi;
5785
5786 if (!thresh)
5787 return;
5788
5789 rcu_read_lock();
5790
5791 for_each_pool(pool, pi) {
5792 unsigned long pool_ts, touched, ts;
5793
5794 if (list_empty(&pool->worklist))
5795 continue;
5796
5797 /*
5798 * If a virtual machine is stopped by the host it can look to
5799 * the watchdog like a stall.
5800 */
5801 kvm_check_and_clear_guest_paused();
5802
5803 /* get the latest of pool and touched timestamps */
5804 if (pool->cpu >= 0)
5805 touched = READ_ONCE(per_cpu(wq_watchdog_touched_cpu, pool->cpu));
5806 else
5807 touched = READ_ONCE(wq_watchdog_touched);
5808 pool_ts = READ_ONCE(pool->watchdog_ts);
5809
5810 if (time_after(pool_ts, touched))
5811 ts = pool_ts;
5812 else
5813 ts = touched;
5814
5815 /* did we stall? */
5816 if (time_after(now, ts + thresh)) {
5817 lockup_detected = true;
5818 pr_emerg("BUG: workqueue lockup - pool");
5819 pr_cont_pool_info(pool);
5820 pr_cont(" stuck for %us!\n",
5821 jiffies_to_msecs(now - pool_ts) / 1000);
5822 }
5823 }
5824
5825 rcu_read_unlock();
5826
5827 if (lockup_detected)
5828 show_workqueue_state();
5829
5830 wq_watchdog_reset_touched();
5831 mod_timer(&wq_watchdog_timer, jiffies + thresh);
5832}
5833
5834notrace void wq_watchdog_touch(int cpu)
5835{
5836 if (cpu >= 0)
5837 per_cpu(wq_watchdog_touched_cpu, cpu) = jiffies;
5838
5839 wq_watchdog_touched = jiffies;
5840}
5841
5842static void wq_watchdog_set_thresh(unsigned long thresh)
5843{
5844 wq_watchdog_thresh = 0;
5845 del_timer_sync(&wq_watchdog_timer);
5846
5847 if (thresh) {
5848 wq_watchdog_thresh = thresh;
5849 wq_watchdog_reset_touched();
5850 mod_timer(&wq_watchdog_timer, jiffies + thresh * HZ);
5851 }
5852}
5853
5854static int wq_watchdog_param_set_thresh(const char *val,
5855 const struct kernel_param *kp)
5856{
5857 unsigned long thresh;
5858 int ret;
5859
5860 ret = kstrtoul(val, 0, &thresh);
5861 if (ret)
5862 return ret;
5863
5864 if (system_wq)
5865 wq_watchdog_set_thresh(thresh);
5866 else
5867 wq_watchdog_thresh = thresh;
5868
5869 return 0;
5870}
5871
5872static const struct kernel_param_ops wq_watchdog_thresh_ops = {
5873 .set = wq_watchdog_param_set_thresh,
5874 .get = param_get_ulong,
5875};
5876
5877module_param_cb(watchdog_thresh, &wq_watchdog_thresh_ops, &wq_watchdog_thresh,
5878 0644);
5879
5880static void wq_watchdog_init(void)
5881{
5882 timer_setup(&wq_watchdog_timer, wq_watchdog_timer_fn, TIMER_DEFERRABLE);
5883 wq_watchdog_set_thresh(wq_watchdog_thresh);
5884}
5885
5886#else /* CONFIG_WQ_WATCHDOG */
5887
5888static inline void wq_watchdog_init(void) { }
5889
5890#endif /* CONFIG_WQ_WATCHDOG */
5891
5892static void __init wq_numa_init(void)
5893{
5894 cpumask_var_t *tbl;
5895 int node, cpu;
5896
5897 if (num_possible_nodes() <= 1)
5898 return;
5899
5900 if (wq_disable_numa) {
5901 pr_info("workqueue: NUMA affinity support disabled\n");
5902 return;
5903 }
5904
5905 for_each_possible_cpu(cpu) {
5906 if (WARN_ON(cpu_to_node(cpu) == NUMA_NO_NODE)) {
5907 pr_warn("workqueue: NUMA node mapping not available for cpu%d, disabling NUMA support\n", cpu);
5908 return;
5909 }
5910 }
5911
5912 wq_update_unbound_numa_attrs_buf = alloc_workqueue_attrs();
5913 BUG_ON(!wq_update_unbound_numa_attrs_buf);
5914
5915 /*
5916 * We want masks of possible CPUs of each node which isn't readily
5917 * available. Build one from cpu_to_node() which should have been
5918 * fully initialized by now.
5919 */
5920 tbl = kcalloc(nr_node_ids, sizeof(tbl[0]), GFP_KERNEL);
5921 BUG_ON(!tbl);
5922
5923 for_each_node(node)
5924 BUG_ON(!zalloc_cpumask_var_node(&tbl[node], GFP_KERNEL,
5925 node_online(node) ? node : NUMA_NO_NODE));
5926
5927 for_each_possible_cpu(cpu) {
5928 node = cpu_to_node(cpu);
5929 cpumask_set_cpu(cpu, tbl[node]);
5930 }
5931
5932 wq_numa_possible_cpumask = tbl;
5933 wq_numa_enabled = true;
5934}
5935
5936/**
5937 * workqueue_init_early - early init for workqueue subsystem
5938 *
5939 * This is the first half of two-staged workqueue subsystem initialization
5940 * and invoked as soon as the bare basics - memory allocation, cpumasks and
5941 * idr are up. It sets up all the data structures and system workqueues
5942 * and allows early boot code to create workqueues and queue/cancel work
5943 * items. Actual work item execution starts only after kthreads can be
5944 * created and scheduled right before early initcalls.
5945 */
5946void __init workqueue_init_early(void)
5947{
5948 int std_nice[NR_STD_WORKER_POOLS] = { 0, HIGHPRI_NICE_LEVEL };
5949 int hk_flags = HK_FLAG_DOMAIN | HK_FLAG_WQ;
5950 int i, cpu;
5951
5952 BUILD_BUG_ON(__alignof__(struct pool_workqueue) < __alignof__(long long));
5953
5954 BUG_ON(!alloc_cpumask_var(&wq_unbound_cpumask, GFP_KERNEL));
5955 cpumask_copy(wq_unbound_cpumask, housekeeping_cpumask(hk_flags));
5956
5957 pwq_cache = KMEM_CACHE(pool_workqueue, SLAB_PANIC);
5958
5959 /* initialize CPU pools */
5960 for_each_possible_cpu(cpu) {
5961 struct worker_pool *pool;
5962
5963 i = 0;
5964 for_each_cpu_worker_pool(pool, cpu) {
5965 BUG_ON(init_worker_pool(pool));
5966 pool->cpu = cpu;
5967 cpumask_copy(pool->attrs->cpumask, cpumask_of(cpu));
5968 pool->attrs->nice = std_nice[i++];
5969 pool->node = cpu_to_node(cpu);
5970
5971 /* alloc pool ID */
5972 mutex_lock(&wq_pool_mutex);
5973 BUG_ON(worker_pool_assign_id(pool));
5974 mutex_unlock(&wq_pool_mutex);
5975 }
5976 }
5977
5978 /* create default unbound and ordered wq attrs */
5979 for (i = 0; i < NR_STD_WORKER_POOLS; i++) {
5980 struct workqueue_attrs *attrs;
5981
5982 BUG_ON(!(attrs = alloc_workqueue_attrs()));
5983 attrs->nice = std_nice[i];
5984 unbound_std_wq_attrs[i] = attrs;
5985
5986 /*
5987 * An ordered wq should have only one pwq as ordering is
5988 * guaranteed by max_active which is enforced by pwqs.
5989 * Turn off NUMA so that dfl_pwq is used for all nodes.
5990 */
5991 BUG_ON(!(attrs = alloc_workqueue_attrs()));
5992 attrs->nice = std_nice[i];
5993 attrs->no_numa = true;
5994 ordered_wq_attrs[i] = attrs;
5995 }
5996
5997 system_wq = alloc_workqueue("events", 0, 0);
5998 system_highpri_wq = alloc_workqueue("events_highpri", WQ_HIGHPRI, 0);
5999 system_long_wq = alloc_workqueue("events_long", 0, 0);
6000 system_unbound_wq = alloc_workqueue("events_unbound", WQ_UNBOUND,
6001 WQ_UNBOUND_MAX_ACTIVE);
6002 system_freezable_wq = alloc_workqueue("events_freezable",
6003 WQ_FREEZABLE, 0);
6004 system_power_efficient_wq = alloc_workqueue("events_power_efficient",
6005 WQ_POWER_EFFICIENT, 0);
6006 system_freezable_power_efficient_wq = alloc_workqueue("events_freezable_power_efficient",
6007 WQ_FREEZABLE | WQ_POWER_EFFICIENT,
6008 0);
6009 BUG_ON(!system_wq || !system_highpri_wq || !system_long_wq ||
6010 !system_unbound_wq || !system_freezable_wq ||
6011 !system_power_efficient_wq ||
6012 !system_freezable_power_efficient_wq);
6013}
6014
6015/**
6016 * workqueue_init - bring workqueue subsystem fully online
6017 *
6018 * This is the latter half of two-staged workqueue subsystem initialization
6019 * and invoked as soon as kthreads can be created and scheduled.
6020 * Workqueues have been created and work items queued on them, but there
6021 * are no kworkers executing the work items yet. Populate the worker pools
6022 * with the initial workers and enable future kworker creations.
6023 */
6024void __init workqueue_init(void)
6025{
6026 struct workqueue_struct *wq;
6027 struct worker_pool *pool;
6028 int cpu, bkt;
6029
6030 /*
6031 * It'd be simpler to initialize NUMA in workqueue_init_early() but
6032 * CPU to node mapping may not be available that early on some
6033 * archs such as power and arm64. As per-cpu pools created
6034 * previously could be missing node hint and unbound pools NUMA
6035 * affinity, fix them up.
6036 *
6037 * Also, while iterating workqueues, create rescuers if requested.
6038 */
6039 wq_numa_init();
6040
6041 mutex_lock(&wq_pool_mutex);
6042
6043 for_each_possible_cpu(cpu) {
6044 for_each_cpu_worker_pool(pool, cpu) {
6045 pool->node = cpu_to_node(cpu);
6046 }
6047 }
6048
6049 list_for_each_entry(wq, &workqueues, list) {
6050 wq_update_unbound_numa(wq, smp_processor_id(), true);
6051 WARN(init_rescuer(wq),
6052 "workqueue: failed to create early rescuer for %s",
6053 wq->name);
6054 }
6055
6056 mutex_unlock(&wq_pool_mutex);
6057
6058 /* create the initial workers */
6059 for_each_online_cpu(cpu) {
6060 for_each_cpu_worker_pool(pool, cpu) {
6061 pool->flags &= ~POOL_DISASSOCIATED;
6062 BUG_ON(!create_worker(pool));
6063 }
6064 }
6065
6066 hash_for_each(unbound_pool_hash, bkt, pool, hash_node)
6067 BUG_ON(!create_worker(pool));
6068
6069 wq_online = true;
6070 wq_watchdog_init();
6071}