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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/interrupt.h>
33#include <linux/signal.h>
34#include <linux/completion.h>
35#include <linux/workqueue.h>
36#include <linux/slab.h>
37#include <linux/cpu.h>
38#include <linux/notifier.h>
39#include <linux/kthread.h>
40#include <linux/hardirq.h>
41#include <linux/mempolicy.h>
42#include <linux/freezer.h>
43#include <linux/debug_locks.h>
44#include <linux/lockdep.h>
45#include <linux/idr.h>
46#include <linux/jhash.h>
47#include <linux/hashtable.h>
48#include <linux/rculist.h>
49#include <linux/nodemask.h>
50#include <linux/moduleparam.h>
51#include <linux/uaccess.h>
52#include <linux/sched/isolation.h>
53#include <linux/sched/debug.h>
54#include <linux/nmi.h>
55#include <linux/kvm_para.h>
56#include <linux/delay.h>
57#include <linux/irq_work.h>
58
59#include "workqueue_internal.h"
60
61enum worker_pool_flags {
62 /*
63 * worker_pool flags
64 *
65 * A bound pool is either associated or disassociated with its CPU.
66 * While associated (!DISASSOCIATED), all workers are bound to the
67 * CPU and none has %WORKER_UNBOUND set and concurrency management
68 * is in effect.
69 *
70 * While DISASSOCIATED, the cpu may be offline and all workers have
71 * %WORKER_UNBOUND set and concurrency management disabled, and may
72 * be executing on any CPU. The pool behaves as an unbound one.
73 *
74 * Note that DISASSOCIATED should be flipped only while holding
75 * wq_pool_attach_mutex to avoid changing binding state while
76 * worker_attach_to_pool() is in progress.
77 *
78 * As there can only be one concurrent BH execution context per CPU, a
79 * BH pool is per-CPU and always DISASSOCIATED.
80 */
81 POOL_BH = 1 << 0, /* is a BH pool */
82 POOL_MANAGER_ACTIVE = 1 << 1, /* being managed */
83 POOL_DISASSOCIATED = 1 << 2, /* cpu can't serve workers */
84 POOL_BH_DRAINING = 1 << 3, /* draining after CPU offline */
85};
86
87enum worker_flags {
88 /* worker flags */
89 WORKER_DIE = 1 << 1, /* die die die */
90 WORKER_IDLE = 1 << 2, /* is idle */
91 WORKER_PREP = 1 << 3, /* preparing to run works */
92 WORKER_CPU_INTENSIVE = 1 << 6, /* cpu intensive */
93 WORKER_UNBOUND = 1 << 7, /* worker is unbound */
94 WORKER_REBOUND = 1 << 8, /* worker was rebound */
95
96 WORKER_NOT_RUNNING = WORKER_PREP | WORKER_CPU_INTENSIVE |
97 WORKER_UNBOUND | WORKER_REBOUND,
98};
99
100enum work_cancel_flags {
101 WORK_CANCEL_DELAYED = 1 << 0, /* canceling a delayed_work */
102};
103
104enum wq_internal_consts {
105 NR_STD_WORKER_POOLS = 2, /* # standard pools per cpu */
106
107 UNBOUND_POOL_HASH_ORDER = 6, /* hashed by pool->attrs */
108 BUSY_WORKER_HASH_ORDER = 6, /* 64 pointers */
109
110 MAX_IDLE_WORKERS_RATIO = 4, /* 1/4 of busy can be idle */
111 IDLE_WORKER_TIMEOUT = 300 * HZ, /* keep idle ones for 5 mins */
112
113 MAYDAY_INITIAL_TIMEOUT = HZ / 100 >= 2 ? HZ / 100 : 2,
114 /* call for help after 10ms
115 (min two ticks) */
116 MAYDAY_INTERVAL = HZ / 10, /* and then every 100ms */
117 CREATE_COOLDOWN = HZ, /* time to breath after fail */
118
119 /*
120 * Rescue workers are used only on emergencies and shared by
121 * all cpus. Give MIN_NICE.
122 */
123 RESCUER_NICE_LEVEL = MIN_NICE,
124 HIGHPRI_NICE_LEVEL = MIN_NICE,
125
126 WQ_NAME_LEN = 32,
127};
128
129/*
130 * We don't want to trap softirq for too long. See MAX_SOFTIRQ_TIME and
131 * MAX_SOFTIRQ_RESTART in kernel/softirq.c. These are macros because
132 * msecs_to_jiffies() can't be an initializer.
133 */
134#define BH_WORKER_JIFFIES msecs_to_jiffies(2)
135#define BH_WORKER_RESTARTS 10
136
137/*
138 * Structure fields follow one of the following exclusion rules.
139 *
140 * I: Modifiable by initialization/destruction paths and read-only for
141 * everyone else.
142 *
143 * P: Preemption protected. Disabling preemption is enough and should
144 * only be modified and accessed from the local cpu.
145 *
146 * L: pool->lock protected. Access with pool->lock held.
147 *
148 * LN: pool->lock and wq_node_nr_active->lock protected for writes. Either for
149 * reads.
150 *
151 * K: Only modified by worker while holding pool->lock. Can be safely read by
152 * self, while holding pool->lock or from IRQ context if %current is the
153 * kworker.
154 *
155 * S: Only modified by worker self.
156 *
157 * A: wq_pool_attach_mutex protected.
158 *
159 * PL: wq_pool_mutex protected.
160 *
161 * PR: wq_pool_mutex protected for writes. RCU protected for reads.
162 *
163 * PW: wq_pool_mutex and wq->mutex protected for writes. Either for reads.
164 *
165 * PWR: wq_pool_mutex and wq->mutex protected for writes. Either or
166 * RCU for reads.
167 *
168 * WQ: wq->mutex protected.
169 *
170 * WR: wq->mutex protected for writes. RCU protected for reads.
171 *
172 * WO: wq->mutex protected for writes. Updated with WRITE_ONCE() and can be read
173 * with READ_ONCE() without locking.
174 *
175 * MD: wq_mayday_lock protected.
176 *
177 * WD: Used internally by the watchdog.
178 */
179
180/* struct worker is defined in workqueue_internal.h */
181
182struct worker_pool {
183 raw_spinlock_t lock; /* the pool lock */
184 int cpu; /* I: the associated cpu */
185 int node; /* I: the associated node ID */
186 int id; /* I: pool ID */
187 unsigned int flags; /* L: flags */
188
189 unsigned long watchdog_ts; /* L: watchdog timestamp */
190 bool cpu_stall; /* WD: stalled cpu bound pool */
191
192 /*
193 * The counter is incremented in a process context on the associated CPU
194 * w/ preemption disabled, and decremented or reset in the same context
195 * but w/ pool->lock held. The readers grab pool->lock and are
196 * guaranteed to see if the counter reached zero.
197 */
198 int nr_running;
199
200 struct list_head worklist; /* L: list of pending works */
201
202 int nr_workers; /* L: total number of workers */
203 int nr_idle; /* L: currently idle workers */
204
205 struct list_head idle_list; /* L: list of idle workers */
206 struct timer_list idle_timer; /* L: worker idle timeout */
207 struct work_struct idle_cull_work; /* L: worker idle cleanup */
208
209 struct timer_list mayday_timer; /* L: SOS timer for workers */
210
211 /* a workers is either on busy_hash or idle_list, or the manager */
212 DECLARE_HASHTABLE(busy_hash, BUSY_WORKER_HASH_ORDER);
213 /* L: hash of busy workers */
214
215 struct worker *manager; /* L: purely informational */
216 struct list_head workers; /* A: attached workers */
217 struct list_head dying_workers; /* A: workers about to die */
218 struct completion *detach_completion; /* all workers detached */
219
220 struct ida worker_ida; /* worker IDs for task name */
221
222 struct workqueue_attrs *attrs; /* I: worker attributes */
223 struct hlist_node hash_node; /* PL: unbound_pool_hash node */
224 int refcnt; /* PL: refcnt for unbound pools */
225
226 /*
227 * Destruction of pool is RCU protected to allow dereferences
228 * from get_work_pool().
229 */
230 struct rcu_head rcu;
231};
232
233/*
234 * Per-pool_workqueue statistics. These can be monitored using
235 * tools/workqueue/wq_monitor.py.
236 */
237enum pool_workqueue_stats {
238 PWQ_STAT_STARTED, /* work items started execution */
239 PWQ_STAT_COMPLETED, /* work items completed execution */
240 PWQ_STAT_CPU_TIME, /* total CPU time consumed */
241 PWQ_STAT_CPU_INTENSIVE, /* wq_cpu_intensive_thresh_us violations */
242 PWQ_STAT_CM_WAKEUP, /* concurrency-management worker wakeups */
243 PWQ_STAT_REPATRIATED, /* unbound workers brought back into scope */
244 PWQ_STAT_MAYDAY, /* maydays to rescuer */
245 PWQ_STAT_RESCUED, /* linked work items executed by rescuer */
246
247 PWQ_NR_STATS,
248};
249
250/*
251 * The per-pool workqueue. While queued, bits below WORK_PWQ_SHIFT
252 * of work_struct->data are used for flags and the remaining high bits
253 * point to the pwq; thus, pwqs need to be aligned at two's power of the
254 * number of flag bits.
255 */
256struct pool_workqueue {
257 struct worker_pool *pool; /* I: the associated pool */
258 struct workqueue_struct *wq; /* I: the owning workqueue */
259 int work_color; /* L: current color */
260 int flush_color; /* L: flushing color */
261 int refcnt; /* L: reference count */
262 int nr_in_flight[WORK_NR_COLORS];
263 /* L: nr of in_flight works */
264 bool plugged; /* L: execution suspended */
265
266 /*
267 * nr_active management and WORK_STRUCT_INACTIVE:
268 *
269 * When pwq->nr_active >= max_active, new work item is queued to
270 * pwq->inactive_works instead of pool->worklist and marked with
271 * WORK_STRUCT_INACTIVE.
272 *
273 * All work items marked with WORK_STRUCT_INACTIVE do not participate in
274 * nr_active and all work items in pwq->inactive_works are marked with
275 * WORK_STRUCT_INACTIVE. But not all WORK_STRUCT_INACTIVE work items are
276 * in pwq->inactive_works. Some of them are ready to run in
277 * pool->worklist or worker->scheduled. Those work itmes are only struct
278 * wq_barrier which is used for flush_work() and should not participate
279 * in nr_active. For non-barrier work item, it is marked with
280 * WORK_STRUCT_INACTIVE iff it is in pwq->inactive_works.
281 */
282 int nr_active; /* L: nr of active works */
283 struct list_head inactive_works; /* L: inactive works */
284 struct list_head pending_node; /* LN: node on wq_node_nr_active->pending_pwqs */
285 struct list_head pwqs_node; /* WR: node on wq->pwqs */
286 struct list_head mayday_node; /* MD: node on wq->maydays */
287
288 u64 stats[PWQ_NR_STATS];
289
290 /*
291 * Release of unbound pwq is punted to a kthread_worker. See put_pwq()
292 * and pwq_release_workfn() for details. pool_workqueue itself is also
293 * RCU protected so that the first pwq can be determined without
294 * grabbing wq->mutex.
295 */
296 struct kthread_work release_work;
297 struct rcu_head rcu;
298} __aligned(1 << WORK_STRUCT_PWQ_SHIFT);
299
300/*
301 * Structure used to wait for workqueue flush.
302 */
303struct wq_flusher {
304 struct list_head list; /* WQ: list of flushers */
305 int flush_color; /* WQ: flush color waiting for */
306 struct completion done; /* flush completion */
307};
308
309struct wq_device;
310
311/*
312 * Unlike in a per-cpu workqueue where max_active limits its concurrency level
313 * on each CPU, in an unbound workqueue, max_active applies to the whole system.
314 * As sharing a single nr_active across multiple sockets can be very expensive,
315 * the counting and enforcement is per NUMA node.
316 *
317 * The following struct is used to enforce per-node max_active. When a pwq wants
318 * to start executing a work item, it should increment ->nr using
319 * tryinc_node_nr_active(). If acquisition fails due to ->nr already being over
320 * ->max, the pwq is queued on ->pending_pwqs. As in-flight work items finish
321 * and decrement ->nr, node_activate_pending_pwq() activates the pending pwqs in
322 * round-robin order.
323 */
324struct wq_node_nr_active {
325 int max; /* per-node max_active */
326 atomic_t nr; /* per-node nr_active */
327 raw_spinlock_t lock; /* nests inside pool locks */
328 struct list_head pending_pwqs; /* LN: pwqs with inactive works */
329};
330
331/*
332 * The externally visible workqueue. It relays the issued work items to
333 * the appropriate worker_pool through its pool_workqueues.
334 */
335struct workqueue_struct {
336 struct list_head pwqs; /* WR: all pwqs of this wq */
337 struct list_head list; /* PR: list of all workqueues */
338
339 struct mutex mutex; /* protects this wq */
340 int work_color; /* WQ: current work color */
341 int flush_color; /* WQ: current flush color */
342 atomic_t nr_pwqs_to_flush; /* flush in progress */
343 struct wq_flusher *first_flusher; /* WQ: first flusher */
344 struct list_head flusher_queue; /* WQ: flush waiters */
345 struct list_head flusher_overflow; /* WQ: flush overflow list */
346
347 struct list_head maydays; /* MD: pwqs requesting rescue */
348 struct worker *rescuer; /* MD: rescue worker */
349
350 int nr_drainers; /* WQ: drain in progress */
351
352 /* See alloc_workqueue() function comment for info on min/max_active */
353 int max_active; /* WO: max active works */
354 int min_active; /* WO: min active works */
355 int saved_max_active; /* WQ: saved max_active */
356 int saved_min_active; /* WQ: saved min_active */
357
358 struct workqueue_attrs *unbound_attrs; /* PW: only for unbound wqs */
359 struct pool_workqueue __rcu *dfl_pwq; /* PW: only for unbound wqs */
360
361#ifdef CONFIG_SYSFS
362 struct wq_device *wq_dev; /* I: for sysfs interface */
363#endif
364#ifdef CONFIG_LOCKDEP
365 char *lock_name;
366 struct lock_class_key key;
367 struct lockdep_map lockdep_map;
368#endif
369 char name[WQ_NAME_LEN]; /* I: workqueue name */
370
371 /*
372 * Destruction of workqueue_struct is RCU protected to allow walking
373 * the workqueues list without grabbing wq_pool_mutex.
374 * This is used to dump all workqueues from sysrq.
375 */
376 struct rcu_head rcu;
377
378 /* hot fields used during command issue, aligned to cacheline */
379 unsigned int flags ____cacheline_aligned; /* WQ: WQ_* flags */
380 struct pool_workqueue __percpu __rcu **cpu_pwq; /* I: per-cpu pwqs */
381 struct wq_node_nr_active *node_nr_active[]; /* I: per-node nr_active */
382};
383
384/*
385 * Each pod type describes how CPUs should be grouped for unbound workqueues.
386 * See the comment above workqueue_attrs->affn_scope.
387 */
388struct wq_pod_type {
389 int nr_pods; /* number of pods */
390 cpumask_var_t *pod_cpus; /* pod -> cpus */
391 int *pod_node; /* pod -> node */
392 int *cpu_pod; /* cpu -> pod */
393};
394
395static const char *wq_affn_names[WQ_AFFN_NR_TYPES] = {
396 [WQ_AFFN_DFL] = "default",
397 [WQ_AFFN_CPU] = "cpu",
398 [WQ_AFFN_SMT] = "smt",
399 [WQ_AFFN_CACHE] = "cache",
400 [WQ_AFFN_NUMA] = "numa",
401 [WQ_AFFN_SYSTEM] = "system",
402};
403
404/*
405 * Per-cpu work items which run for longer than the following threshold are
406 * automatically considered CPU intensive and excluded from concurrency
407 * management to prevent them from noticeably delaying other per-cpu work items.
408 * ULONG_MAX indicates that the user hasn't overridden it with a boot parameter.
409 * The actual value is initialized in wq_cpu_intensive_thresh_init().
410 */
411static unsigned long wq_cpu_intensive_thresh_us = ULONG_MAX;
412module_param_named(cpu_intensive_thresh_us, wq_cpu_intensive_thresh_us, ulong, 0644);
413#ifdef CONFIG_WQ_CPU_INTENSIVE_REPORT
414static unsigned int wq_cpu_intensive_warning_thresh = 4;
415module_param_named(cpu_intensive_warning_thresh, wq_cpu_intensive_warning_thresh, uint, 0644);
416#endif
417
418/* see the comment above the definition of WQ_POWER_EFFICIENT */
419static bool wq_power_efficient = IS_ENABLED(CONFIG_WQ_POWER_EFFICIENT_DEFAULT);
420module_param_named(power_efficient, wq_power_efficient, bool, 0444);
421
422static bool wq_online; /* can kworkers be created yet? */
423static bool wq_topo_initialized __read_mostly = false;
424
425static struct kmem_cache *pwq_cache;
426
427static struct wq_pod_type wq_pod_types[WQ_AFFN_NR_TYPES];
428static enum wq_affn_scope wq_affn_dfl = WQ_AFFN_CACHE;
429
430/* buf for wq_update_unbound_pod_attrs(), protected by CPU hotplug exclusion */
431static struct workqueue_attrs *wq_update_pod_attrs_buf;
432
433static DEFINE_MUTEX(wq_pool_mutex); /* protects pools and workqueues list */
434static DEFINE_MUTEX(wq_pool_attach_mutex); /* protects worker attach/detach */
435static DEFINE_RAW_SPINLOCK(wq_mayday_lock); /* protects wq->maydays list */
436/* wait for manager to go away */
437static struct rcuwait manager_wait = __RCUWAIT_INITIALIZER(manager_wait);
438
439static LIST_HEAD(workqueues); /* PR: list of all workqueues */
440static bool workqueue_freezing; /* PL: have wqs started freezing? */
441
442/* PL&A: allowable cpus for unbound wqs and work items */
443static cpumask_var_t wq_unbound_cpumask;
444
445/* PL: user requested unbound cpumask via sysfs */
446static cpumask_var_t wq_requested_unbound_cpumask;
447
448/* PL: isolated cpumask to be excluded from unbound cpumask */
449static cpumask_var_t wq_isolated_cpumask;
450
451/* for further constrain wq_unbound_cpumask by cmdline parameter*/
452static struct cpumask wq_cmdline_cpumask __initdata;
453
454/* CPU where unbound work was last round robin scheduled from this CPU */
455static DEFINE_PER_CPU(int, wq_rr_cpu_last);
456
457/*
458 * Local execution of unbound work items is no longer guaranteed. The
459 * following always forces round-robin CPU selection on unbound work items
460 * to uncover usages which depend on it.
461 */
462#ifdef CONFIG_DEBUG_WQ_FORCE_RR_CPU
463static bool wq_debug_force_rr_cpu = true;
464#else
465static bool wq_debug_force_rr_cpu = false;
466#endif
467module_param_named(debug_force_rr_cpu, wq_debug_force_rr_cpu, bool, 0644);
468
469/* to raise softirq for the BH worker pools on other CPUs */
470static DEFINE_PER_CPU_SHARED_ALIGNED(struct irq_work [NR_STD_WORKER_POOLS],
471 bh_pool_irq_works);
472
473/* the BH worker pools */
474static DEFINE_PER_CPU_SHARED_ALIGNED(struct worker_pool [NR_STD_WORKER_POOLS],
475 bh_worker_pools);
476
477/* the per-cpu worker pools */
478static DEFINE_PER_CPU_SHARED_ALIGNED(struct worker_pool [NR_STD_WORKER_POOLS],
479 cpu_worker_pools);
480
481static DEFINE_IDR(worker_pool_idr); /* PR: idr of all pools */
482
483/* PL: hash of all unbound pools keyed by pool->attrs */
484static DEFINE_HASHTABLE(unbound_pool_hash, UNBOUND_POOL_HASH_ORDER);
485
486/* I: attributes used when instantiating standard unbound pools on demand */
487static struct workqueue_attrs *unbound_std_wq_attrs[NR_STD_WORKER_POOLS];
488
489/* I: attributes used when instantiating ordered pools on demand */
490static struct workqueue_attrs *ordered_wq_attrs[NR_STD_WORKER_POOLS];
491
492/*
493 * Used to synchronize multiple cancel_sync attempts on the same work item. See
494 * work_grab_pending() and __cancel_work_sync().
495 */
496static DECLARE_WAIT_QUEUE_HEAD(wq_cancel_waitq);
497
498/*
499 * I: kthread_worker to release pwq's. pwq release needs to be bounced to a
500 * process context while holding a pool lock. Bounce to a dedicated kthread
501 * worker to avoid A-A deadlocks.
502 */
503static struct kthread_worker *pwq_release_worker __ro_after_init;
504
505struct workqueue_struct *system_wq __ro_after_init;
506EXPORT_SYMBOL(system_wq);
507struct workqueue_struct *system_highpri_wq __ro_after_init;
508EXPORT_SYMBOL_GPL(system_highpri_wq);
509struct workqueue_struct *system_long_wq __ro_after_init;
510EXPORT_SYMBOL_GPL(system_long_wq);
511struct workqueue_struct *system_unbound_wq __ro_after_init;
512EXPORT_SYMBOL_GPL(system_unbound_wq);
513struct workqueue_struct *system_freezable_wq __ro_after_init;
514EXPORT_SYMBOL_GPL(system_freezable_wq);
515struct workqueue_struct *system_power_efficient_wq __ro_after_init;
516EXPORT_SYMBOL_GPL(system_power_efficient_wq);
517struct workqueue_struct *system_freezable_power_efficient_wq __ro_after_init;
518EXPORT_SYMBOL_GPL(system_freezable_power_efficient_wq);
519struct workqueue_struct *system_bh_wq;
520EXPORT_SYMBOL_GPL(system_bh_wq);
521struct workqueue_struct *system_bh_highpri_wq;
522EXPORT_SYMBOL_GPL(system_bh_highpri_wq);
523
524static int worker_thread(void *__worker);
525static void workqueue_sysfs_unregister(struct workqueue_struct *wq);
526static void show_pwq(struct pool_workqueue *pwq);
527static void show_one_worker_pool(struct worker_pool *pool);
528
529#define CREATE_TRACE_POINTS
530#include <trace/events/workqueue.h>
531
532#define assert_rcu_or_pool_mutex() \
533 RCU_LOCKDEP_WARN(!rcu_read_lock_any_held() && \
534 !lockdep_is_held(&wq_pool_mutex), \
535 "RCU or wq_pool_mutex should be held")
536
537#define assert_rcu_or_wq_mutex_or_pool_mutex(wq) \
538 RCU_LOCKDEP_WARN(!rcu_read_lock_any_held() && \
539 !lockdep_is_held(&wq->mutex) && \
540 !lockdep_is_held(&wq_pool_mutex), \
541 "RCU, wq->mutex or wq_pool_mutex should be held")
542
543#define for_each_bh_worker_pool(pool, cpu) \
544 for ((pool) = &per_cpu(bh_worker_pools, cpu)[0]; \
545 (pool) < &per_cpu(bh_worker_pools, cpu)[NR_STD_WORKER_POOLS]; \
546 (pool)++)
547
548#define for_each_cpu_worker_pool(pool, cpu) \
549 for ((pool) = &per_cpu(cpu_worker_pools, cpu)[0]; \
550 (pool) < &per_cpu(cpu_worker_pools, cpu)[NR_STD_WORKER_POOLS]; \
551 (pool)++)
552
553/**
554 * for_each_pool - iterate through all worker_pools in the system
555 * @pool: iteration cursor
556 * @pi: integer used for iteration
557 *
558 * This must be called either with wq_pool_mutex held or RCU read
559 * locked. If the pool needs to be used beyond the locking in effect, the
560 * caller is responsible for guaranteeing that the pool stays online.
561 *
562 * The if/else clause exists only for the lockdep assertion and can be
563 * ignored.
564 */
565#define for_each_pool(pool, pi) \
566 idr_for_each_entry(&worker_pool_idr, pool, pi) \
567 if (({ assert_rcu_or_pool_mutex(); false; })) { } \
568 else
569
570/**
571 * for_each_pool_worker - iterate through all workers of a worker_pool
572 * @worker: iteration cursor
573 * @pool: worker_pool to iterate workers of
574 *
575 * This must be called with wq_pool_attach_mutex.
576 *
577 * The if/else clause exists only for the lockdep assertion and can be
578 * ignored.
579 */
580#define for_each_pool_worker(worker, pool) \
581 list_for_each_entry((worker), &(pool)->workers, node) \
582 if (({ lockdep_assert_held(&wq_pool_attach_mutex); false; })) { } \
583 else
584
585/**
586 * for_each_pwq - iterate through all pool_workqueues of the specified workqueue
587 * @pwq: iteration cursor
588 * @wq: the target workqueue
589 *
590 * This must be called either with wq->mutex held or RCU read locked.
591 * If the pwq needs to be used beyond the locking in effect, the caller is
592 * responsible for guaranteeing that the pwq stays online.
593 *
594 * The if/else clause exists only for the lockdep assertion and can be
595 * ignored.
596 */
597#define for_each_pwq(pwq, wq) \
598 list_for_each_entry_rcu((pwq), &(wq)->pwqs, pwqs_node, \
599 lockdep_is_held(&(wq->mutex)))
600
601#ifdef CONFIG_DEBUG_OBJECTS_WORK
602
603static const struct debug_obj_descr work_debug_descr;
604
605static void *work_debug_hint(void *addr)
606{
607 return ((struct work_struct *) addr)->func;
608}
609
610static bool work_is_static_object(void *addr)
611{
612 struct work_struct *work = addr;
613
614 return test_bit(WORK_STRUCT_STATIC_BIT, work_data_bits(work));
615}
616
617/*
618 * fixup_init is called when:
619 * - an active object is initialized
620 */
621static bool work_fixup_init(void *addr, enum debug_obj_state state)
622{
623 struct work_struct *work = addr;
624
625 switch (state) {
626 case ODEBUG_STATE_ACTIVE:
627 cancel_work_sync(work);
628 debug_object_init(work, &work_debug_descr);
629 return true;
630 default:
631 return false;
632 }
633}
634
635/*
636 * fixup_free is called when:
637 * - an active object is freed
638 */
639static bool work_fixup_free(void *addr, enum debug_obj_state state)
640{
641 struct work_struct *work = addr;
642
643 switch (state) {
644 case ODEBUG_STATE_ACTIVE:
645 cancel_work_sync(work);
646 debug_object_free(work, &work_debug_descr);
647 return true;
648 default:
649 return false;
650 }
651}
652
653static const struct debug_obj_descr work_debug_descr = {
654 .name = "work_struct",
655 .debug_hint = work_debug_hint,
656 .is_static_object = work_is_static_object,
657 .fixup_init = work_fixup_init,
658 .fixup_free = work_fixup_free,
659};
660
661static inline void debug_work_activate(struct work_struct *work)
662{
663 debug_object_activate(work, &work_debug_descr);
664}
665
666static inline void debug_work_deactivate(struct work_struct *work)
667{
668 debug_object_deactivate(work, &work_debug_descr);
669}
670
671void __init_work(struct work_struct *work, int onstack)
672{
673 if (onstack)
674 debug_object_init_on_stack(work, &work_debug_descr);
675 else
676 debug_object_init(work, &work_debug_descr);
677}
678EXPORT_SYMBOL_GPL(__init_work);
679
680void destroy_work_on_stack(struct work_struct *work)
681{
682 debug_object_free(work, &work_debug_descr);
683}
684EXPORT_SYMBOL_GPL(destroy_work_on_stack);
685
686void destroy_delayed_work_on_stack(struct delayed_work *work)
687{
688 destroy_timer_on_stack(&work->timer);
689 debug_object_free(&work->work, &work_debug_descr);
690}
691EXPORT_SYMBOL_GPL(destroy_delayed_work_on_stack);
692
693#else
694static inline void debug_work_activate(struct work_struct *work) { }
695static inline void debug_work_deactivate(struct work_struct *work) { }
696#endif
697
698/**
699 * worker_pool_assign_id - allocate ID and assign it to @pool
700 * @pool: the pool pointer of interest
701 *
702 * Returns 0 if ID in [0, WORK_OFFQ_POOL_NONE) is allocated and assigned
703 * successfully, -errno on failure.
704 */
705static int worker_pool_assign_id(struct worker_pool *pool)
706{
707 int ret;
708
709 lockdep_assert_held(&wq_pool_mutex);
710
711 ret = idr_alloc(&worker_pool_idr, pool, 0, WORK_OFFQ_POOL_NONE,
712 GFP_KERNEL);
713 if (ret >= 0) {
714 pool->id = ret;
715 return 0;
716 }
717 return ret;
718}
719
720static struct pool_workqueue __rcu **
721unbound_pwq_slot(struct workqueue_struct *wq, int cpu)
722{
723 if (cpu >= 0)
724 return per_cpu_ptr(wq->cpu_pwq, cpu);
725 else
726 return &wq->dfl_pwq;
727}
728
729/* @cpu < 0 for dfl_pwq */
730static struct pool_workqueue *unbound_pwq(struct workqueue_struct *wq, int cpu)
731{
732 return rcu_dereference_check(*unbound_pwq_slot(wq, cpu),
733 lockdep_is_held(&wq_pool_mutex) ||
734 lockdep_is_held(&wq->mutex));
735}
736
737/**
738 * unbound_effective_cpumask - effective cpumask of an unbound workqueue
739 * @wq: workqueue of interest
740 *
741 * @wq->unbound_attrs->cpumask contains the cpumask requested by the user which
742 * is masked with wq_unbound_cpumask to determine the effective cpumask. The
743 * default pwq is always mapped to the pool with the current effective cpumask.
744 */
745static struct cpumask *unbound_effective_cpumask(struct workqueue_struct *wq)
746{
747 return unbound_pwq(wq, -1)->pool->attrs->__pod_cpumask;
748}
749
750static unsigned int work_color_to_flags(int color)
751{
752 return color << WORK_STRUCT_COLOR_SHIFT;
753}
754
755static int get_work_color(unsigned long work_data)
756{
757 return (work_data >> WORK_STRUCT_COLOR_SHIFT) &
758 ((1 << WORK_STRUCT_COLOR_BITS) - 1);
759}
760
761static int work_next_color(int color)
762{
763 return (color + 1) % WORK_NR_COLORS;
764}
765
766/*
767 * While queued, %WORK_STRUCT_PWQ is set and non flag bits of a work's data
768 * contain the pointer to the queued pwq. Once execution starts, the flag
769 * is cleared and the high bits contain OFFQ flags and pool ID.
770 *
771 * set_work_pwq(), set_work_pool_and_clear_pending() and mark_work_canceling()
772 * can be used to set the pwq, pool or clear work->data. These functions should
773 * only be called while the work is owned - ie. while the PENDING bit is set.
774 *
775 * get_work_pool() and get_work_pwq() can be used to obtain the pool or pwq
776 * corresponding to a work. Pool is available once the work has been
777 * queued anywhere after initialization until it is sync canceled. pwq is
778 * available only while the work item is queued.
779 *
780 * %WORK_OFFQ_CANCELING is used to mark a work item which is being
781 * canceled. While being canceled, a work item may have its PENDING set
782 * but stay off timer and worklist for arbitrarily long and nobody should
783 * try to steal the PENDING bit.
784 */
785static inline void set_work_data(struct work_struct *work, unsigned long data)
786{
787 WARN_ON_ONCE(!work_pending(work));
788 atomic_long_set(&work->data, data | work_static(work));
789}
790
791static void set_work_pwq(struct work_struct *work, struct pool_workqueue *pwq,
792 unsigned long flags)
793{
794 set_work_data(work, (unsigned long)pwq | WORK_STRUCT_PENDING |
795 WORK_STRUCT_PWQ | flags);
796}
797
798static void set_work_pool_and_keep_pending(struct work_struct *work,
799 int pool_id, unsigned long flags)
800{
801 set_work_data(work, ((unsigned long)pool_id << WORK_OFFQ_POOL_SHIFT) |
802 WORK_STRUCT_PENDING | flags);
803}
804
805static void set_work_pool_and_clear_pending(struct work_struct *work,
806 int pool_id, unsigned long flags)
807{
808 /*
809 * The following wmb is paired with the implied mb in
810 * test_and_set_bit(PENDING) and ensures all updates to @work made
811 * here are visible to and precede any updates by the next PENDING
812 * owner.
813 */
814 smp_wmb();
815 set_work_data(work, ((unsigned long)pool_id << WORK_OFFQ_POOL_SHIFT) |
816 flags);
817 /*
818 * The following mb guarantees that previous clear of a PENDING bit
819 * will not be reordered with any speculative LOADS or STORES from
820 * work->current_func, which is executed afterwards. This possible
821 * reordering can lead to a missed execution on attempt to queue
822 * the same @work. E.g. consider this case:
823 *
824 * CPU#0 CPU#1
825 * ---------------------------- --------------------------------
826 *
827 * 1 STORE event_indicated
828 * 2 queue_work_on() {
829 * 3 test_and_set_bit(PENDING)
830 * 4 } set_..._and_clear_pending() {
831 * 5 set_work_data() # clear bit
832 * 6 smp_mb()
833 * 7 work->current_func() {
834 * 8 LOAD event_indicated
835 * }
836 *
837 * Without an explicit full barrier speculative LOAD on line 8 can
838 * be executed before CPU#0 does STORE on line 1. If that happens,
839 * CPU#0 observes the PENDING bit is still set and new execution of
840 * a @work is not queued in a hope, that CPU#1 will eventually
841 * finish the queued @work. Meanwhile CPU#1 does not see
842 * event_indicated is set, because speculative LOAD was executed
843 * before actual STORE.
844 */
845 smp_mb();
846}
847
848static inline struct pool_workqueue *work_struct_pwq(unsigned long data)
849{
850 return (struct pool_workqueue *)(data & WORK_STRUCT_PWQ_MASK);
851}
852
853static struct pool_workqueue *get_work_pwq(struct work_struct *work)
854{
855 unsigned long data = atomic_long_read(&work->data);
856
857 if (data & WORK_STRUCT_PWQ)
858 return work_struct_pwq(data);
859 else
860 return NULL;
861}
862
863/**
864 * get_work_pool - return the worker_pool a given work was associated with
865 * @work: the work item of interest
866 *
867 * Pools are created and destroyed under wq_pool_mutex, and allows read
868 * access under RCU read lock. As such, this function should be
869 * called under wq_pool_mutex or inside of a rcu_read_lock() region.
870 *
871 * All fields of the returned pool are accessible as long as the above
872 * mentioned locking is in effect. If the returned pool needs to be used
873 * beyond the critical section, the caller is responsible for ensuring the
874 * returned pool is and stays online.
875 *
876 * Return: The worker_pool @work was last associated with. %NULL if none.
877 */
878static struct worker_pool *get_work_pool(struct work_struct *work)
879{
880 unsigned long data = atomic_long_read(&work->data);
881 int pool_id;
882
883 assert_rcu_or_pool_mutex();
884
885 if (data & WORK_STRUCT_PWQ)
886 return work_struct_pwq(data)->pool;
887
888 pool_id = data >> WORK_OFFQ_POOL_SHIFT;
889 if (pool_id == WORK_OFFQ_POOL_NONE)
890 return NULL;
891
892 return idr_find(&worker_pool_idr, pool_id);
893}
894
895/**
896 * get_work_pool_id - return the worker pool ID a given work is associated with
897 * @work: the work item of interest
898 *
899 * Return: The worker_pool ID @work was last associated with.
900 * %WORK_OFFQ_POOL_NONE if none.
901 */
902static int get_work_pool_id(struct work_struct *work)
903{
904 unsigned long data = atomic_long_read(&work->data);
905
906 if (data & WORK_STRUCT_PWQ)
907 return work_struct_pwq(data)->pool->id;
908
909 return data >> WORK_OFFQ_POOL_SHIFT;
910}
911
912static void mark_work_canceling(struct work_struct *work)
913{
914 unsigned long pool_id = get_work_pool_id(work);
915
916 pool_id <<= WORK_OFFQ_POOL_SHIFT;
917 set_work_data(work, pool_id | WORK_STRUCT_PENDING | WORK_OFFQ_CANCELING);
918}
919
920static bool work_is_canceling(struct work_struct *work)
921{
922 unsigned long data = atomic_long_read(&work->data);
923
924 return !(data & WORK_STRUCT_PWQ) && (data & WORK_OFFQ_CANCELING);
925}
926
927/*
928 * Policy functions. These define the policies on how the global worker
929 * pools are managed. Unless noted otherwise, these functions assume that
930 * they're being called with pool->lock held.
931 */
932
933/*
934 * Need to wake up a worker? Called from anything but currently
935 * running workers.
936 *
937 * Note that, because unbound workers never contribute to nr_running, this
938 * function will always return %true for unbound pools as long as the
939 * worklist isn't empty.
940 */
941static bool need_more_worker(struct worker_pool *pool)
942{
943 return !list_empty(&pool->worklist) && !pool->nr_running;
944}
945
946/* Can I start working? Called from busy but !running workers. */
947static bool may_start_working(struct worker_pool *pool)
948{
949 return pool->nr_idle;
950}
951
952/* Do I need to keep working? Called from currently running workers. */
953static bool keep_working(struct worker_pool *pool)
954{
955 return !list_empty(&pool->worklist) && (pool->nr_running <= 1);
956}
957
958/* Do we need a new worker? Called from manager. */
959static bool need_to_create_worker(struct worker_pool *pool)
960{
961 return need_more_worker(pool) && !may_start_working(pool);
962}
963
964/* Do we have too many workers and should some go away? */
965static bool too_many_workers(struct worker_pool *pool)
966{
967 bool managing = pool->flags & POOL_MANAGER_ACTIVE;
968 int nr_idle = pool->nr_idle + managing; /* manager is considered idle */
969 int nr_busy = pool->nr_workers - nr_idle;
970
971 return nr_idle > 2 && (nr_idle - 2) * MAX_IDLE_WORKERS_RATIO >= nr_busy;
972}
973
974/**
975 * worker_set_flags - set worker flags and adjust nr_running accordingly
976 * @worker: self
977 * @flags: flags to set
978 *
979 * Set @flags in @worker->flags and adjust nr_running accordingly.
980 */
981static inline void worker_set_flags(struct worker *worker, unsigned int flags)
982{
983 struct worker_pool *pool = worker->pool;
984
985 lockdep_assert_held(&pool->lock);
986
987 /* If transitioning into NOT_RUNNING, adjust nr_running. */
988 if ((flags & WORKER_NOT_RUNNING) &&
989 !(worker->flags & WORKER_NOT_RUNNING)) {
990 pool->nr_running--;
991 }
992
993 worker->flags |= flags;
994}
995
996/**
997 * worker_clr_flags - clear worker flags and adjust nr_running accordingly
998 * @worker: self
999 * @flags: flags to clear
1000 *
1001 * Clear @flags in @worker->flags and adjust nr_running accordingly.
1002 */
1003static inline void worker_clr_flags(struct worker *worker, unsigned int flags)
1004{
1005 struct worker_pool *pool = worker->pool;
1006 unsigned int oflags = worker->flags;
1007
1008 lockdep_assert_held(&pool->lock);
1009
1010 worker->flags &= ~flags;
1011
1012 /*
1013 * If transitioning out of NOT_RUNNING, increment nr_running. Note
1014 * that the nested NOT_RUNNING is not a noop. NOT_RUNNING is mask
1015 * of multiple flags, not a single flag.
1016 */
1017 if ((flags & WORKER_NOT_RUNNING) && (oflags & WORKER_NOT_RUNNING))
1018 if (!(worker->flags & WORKER_NOT_RUNNING))
1019 pool->nr_running++;
1020}
1021
1022/* Return the first idle worker. Called with pool->lock held. */
1023static struct worker *first_idle_worker(struct worker_pool *pool)
1024{
1025 if (unlikely(list_empty(&pool->idle_list)))
1026 return NULL;
1027
1028 return list_first_entry(&pool->idle_list, struct worker, entry);
1029}
1030
1031/**
1032 * worker_enter_idle - enter idle state
1033 * @worker: worker which is entering idle state
1034 *
1035 * @worker is entering idle state. Update stats and idle timer if
1036 * necessary.
1037 *
1038 * LOCKING:
1039 * raw_spin_lock_irq(pool->lock).
1040 */
1041static void worker_enter_idle(struct worker *worker)
1042{
1043 struct worker_pool *pool = worker->pool;
1044
1045 if (WARN_ON_ONCE(worker->flags & WORKER_IDLE) ||
1046 WARN_ON_ONCE(!list_empty(&worker->entry) &&
1047 (worker->hentry.next || worker->hentry.pprev)))
1048 return;
1049
1050 /* can't use worker_set_flags(), also called from create_worker() */
1051 worker->flags |= WORKER_IDLE;
1052 pool->nr_idle++;
1053 worker->last_active = jiffies;
1054
1055 /* idle_list is LIFO */
1056 list_add(&worker->entry, &pool->idle_list);
1057
1058 if (too_many_workers(pool) && !timer_pending(&pool->idle_timer))
1059 mod_timer(&pool->idle_timer, jiffies + IDLE_WORKER_TIMEOUT);
1060
1061 /* Sanity check nr_running. */
1062 WARN_ON_ONCE(pool->nr_workers == pool->nr_idle && pool->nr_running);
1063}
1064
1065/**
1066 * worker_leave_idle - leave idle state
1067 * @worker: worker which is leaving idle state
1068 *
1069 * @worker is leaving idle state. Update stats.
1070 *
1071 * LOCKING:
1072 * raw_spin_lock_irq(pool->lock).
1073 */
1074static void worker_leave_idle(struct worker *worker)
1075{
1076 struct worker_pool *pool = worker->pool;
1077
1078 if (WARN_ON_ONCE(!(worker->flags & WORKER_IDLE)))
1079 return;
1080 worker_clr_flags(worker, WORKER_IDLE);
1081 pool->nr_idle--;
1082 list_del_init(&worker->entry);
1083}
1084
1085/**
1086 * find_worker_executing_work - find worker which is executing a work
1087 * @pool: pool of interest
1088 * @work: work to find worker for
1089 *
1090 * Find a worker which is executing @work on @pool by searching
1091 * @pool->busy_hash which is keyed by the address of @work. For a worker
1092 * to match, its current execution should match the address of @work and
1093 * its work function. This is to avoid unwanted dependency between
1094 * unrelated work executions through a work item being recycled while still
1095 * being executed.
1096 *
1097 * This is a bit tricky. A work item may be freed once its execution
1098 * starts and nothing prevents the freed area from being recycled for
1099 * another work item. If the same work item address ends up being reused
1100 * before the original execution finishes, workqueue will identify the
1101 * recycled work item as currently executing and make it wait until the
1102 * current execution finishes, introducing an unwanted dependency.
1103 *
1104 * This function checks the work item address and work function to avoid
1105 * false positives. Note that this isn't complete as one may construct a
1106 * work function which can introduce dependency onto itself through a
1107 * recycled work item. Well, if somebody wants to shoot oneself in the
1108 * foot that badly, there's only so much we can do, and if such deadlock
1109 * actually occurs, it should be easy to locate the culprit work function.
1110 *
1111 * CONTEXT:
1112 * raw_spin_lock_irq(pool->lock).
1113 *
1114 * Return:
1115 * Pointer to worker which is executing @work if found, %NULL
1116 * otherwise.
1117 */
1118static struct worker *find_worker_executing_work(struct worker_pool *pool,
1119 struct work_struct *work)
1120{
1121 struct worker *worker;
1122
1123 hash_for_each_possible(pool->busy_hash, worker, hentry,
1124 (unsigned long)work)
1125 if (worker->current_work == work &&
1126 worker->current_func == work->func)
1127 return worker;
1128
1129 return NULL;
1130}
1131
1132/**
1133 * move_linked_works - move linked works to a list
1134 * @work: start of series of works to be scheduled
1135 * @head: target list to append @work to
1136 * @nextp: out parameter for nested worklist walking
1137 *
1138 * Schedule linked works starting from @work to @head. Work series to be
1139 * scheduled starts at @work and includes any consecutive work with
1140 * WORK_STRUCT_LINKED set in its predecessor. See assign_work() for details on
1141 * @nextp.
1142 *
1143 * CONTEXT:
1144 * raw_spin_lock_irq(pool->lock).
1145 */
1146static void move_linked_works(struct work_struct *work, struct list_head *head,
1147 struct work_struct **nextp)
1148{
1149 struct work_struct *n;
1150
1151 /*
1152 * Linked worklist will always end before the end of the list,
1153 * use NULL for list head.
1154 */
1155 list_for_each_entry_safe_from(work, n, NULL, entry) {
1156 list_move_tail(&work->entry, head);
1157 if (!(*work_data_bits(work) & WORK_STRUCT_LINKED))
1158 break;
1159 }
1160
1161 /*
1162 * If we're already inside safe list traversal and have moved
1163 * multiple works to the scheduled queue, the next position
1164 * needs to be updated.
1165 */
1166 if (nextp)
1167 *nextp = n;
1168}
1169
1170/**
1171 * assign_work - assign a work item and its linked work items to a worker
1172 * @work: work to assign
1173 * @worker: worker to assign to
1174 * @nextp: out parameter for nested worklist walking
1175 *
1176 * Assign @work and its linked work items to @worker. If @work is already being
1177 * executed by another worker in the same pool, it'll be punted there.
1178 *
1179 * If @nextp is not NULL, it's updated to point to the next work of the last
1180 * scheduled work. This allows assign_work() to be nested inside
1181 * list_for_each_entry_safe().
1182 *
1183 * Returns %true if @work was successfully assigned to @worker. %false if @work
1184 * was punted to another worker already executing it.
1185 */
1186static bool assign_work(struct work_struct *work, struct worker *worker,
1187 struct work_struct **nextp)
1188{
1189 struct worker_pool *pool = worker->pool;
1190 struct worker *collision;
1191
1192 lockdep_assert_held(&pool->lock);
1193
1194 /*
1195 * A single work shouldn't be executed concurrently by multiple workers.
1196 * __queue_work() ensures that @work doesn't jump to a different pool
1197 * while still running in the previous pool. Here, we should ensure that
1198 * @work is not executed concurrently by multiple workers from the same
1199 * pool. Check whether anyone is already processing the work. If so,
1200 * defer the work to the currently executing one.
1201 */
1202 collision = find_worker_executing_work(pool, work);
1203 if (unlikely(collision)) {
1204 move_linked_works(work, &collision->scheduled, nextp);
1205 return false;
1206 }
1207
1208 move_linked_works(work, &worker->scheduled, nextp);
1209 return true;
1210}
1211
1212static struct irq_work *bh_pool_irq_work(struct worker_pool *pool)
1213{
1214 int high = pool->attrs->nice == HIGHPRI_NICE_LEVEL ? 1 : 0;
1215
1216 return &per_cpu(bh_pool_irq_works, pool->cpu)[high];
1217}
1218
1219static void kick_bh_pool(struct worker_pool *pool)
1220{
1221#ifdef CONFIG_SMP
1222 /* see drain_dead_softirq_workfn() for BH_DRAINING */
1223 if (unlikely(pool->cpu != smp_processor_id() &&
1224 !(pool->flags & POOL_BH_DRAINING))) {
1225 irq_work_queue_on(bh_pool_irq_work(pool), pool->cpu);
1226 return;
1227 }
1228#endif
1229 if (pool->attrs->nice == HIGHPRI_NICE_LEVEL)
1230 raise_softirq_irqoff(HI_SOFTIRQ);
1231 else
1232 raise_softirq_irqoff(TASKLET_SOFTIRQ);
1233}
1234
1235/**
1236 * kick_pool - wake up an idle worker if necessary
1237 * @pool: pool to kick
1238 *
1239 * @pool may have pending work items. Wake up worker if necessary. Returns
1240 * whether a worker was woken up.
1241 */
1242static bool kick_pool(struct worker_pool *pool)
1243{
1244 struct worker *worker = first_idle_worker(pool);
1245 struct task_struct *p;
1246
1247 lockdep_assert_held(&pool->lock);
1248
1249 if (!need_more_worker(pool) || !worker)
1250 return false;
1251
1252 if (pool->flags & POOL_BH) {
1253 kick_bh_pool(pool);
1254 return true;
1255 }
1256
1257 p = worker->task;
1258
1259#ifdef CONFIG_SMP
1260 /*
1261 * Idle @worker is about to execute @work and waking up provides an
1262 * opportunity to migrate @worker at a lower cost by setting the task's
1263 * wake_cpu field. Let's see if we want to move @worker to improve
1264 * execution locality.
1265 *
1266 * We're waking the worker that went idle the latest and there's some
1267 * chance that @worker is marked idle but hasn't gone off CPU yet. If
1268 * so, setting the wake_cpu won't do anything. As this is a best-effort
1269 * optimization and the race window is narrow, let's leave as-is for
1270 * now. If this becomes pronounced, we can skip over workers which are
1271 * still on cpu when picking an idle worker.
1272 *
1273 * If @pool has non-strict affinity, @worker might have ended up outside
1274 * its affinity scope. Repatriate.
1275 */
1276 if (!pool->attrs->affn_strict &&
1277 !cpumask_test_cpu(p->wake_cpu, pool->attrs->__pod_cpumask)) {
1278 struct work_struct *work = list_first_entry(&pool->worklist,
1279 struct work_struct, entry);
1280 int wake_cpu = cpumask_any_and_distribute(pool->attrs->__pod_cpumask,
1281 cpu_online_mask);
1282 if (wake_cpu < nr_cpu_ids) {
1283 p->wake_cpu = wake_cpu;
1284 get_work_pwq(work)->stats[PWQ_STAT_REPATRIATED]++;
1285 }
1286 }
1287#endif
1288 wake_up_process(p);
1289 return true;
1290}
1291
1292#ifdef CONFIG_WQ_CPU_INTENSIVE_REPORT
1293
1294/*
1295 * Concurrency-managed per-cpu work items that hog CPU for longer than
1296 * wq_cpu_intensive_thresh_us trigger the automatic CPU_INTENSIVE mechanism,
1297 * which prevents them from stalling other concurrency-managed work items. If a
1298 * work function keeps triggering this mechanism, it's likely that the work item
1299 * should be using an unbound workqueue instead.
1300 *
1301 * wq_cpu_intensive_report() tracks work functions which trigger such conditions
1302 * and report them so that they can be examined and converted to use unbound
1303 * workqueues as appropriate. To avoid flooding the console, each violating work
1304 * function is tracked and reported with exponential backoff.
1305 */
1306#define WCI_MAX_ENTS 128
1307
1308struct wci_ent {
1309 work_func_t func;
1310 atomic64_t cnt;
1311 struct hlist_node hash_node;
1312};
1313
1314static struct wci_ent wci_ents[WCI_MAX_ENTS];
1315static int wci_nr_ents;
1316static DEFINE_RAW_SPINLOCK(wci_lock);
1317static DEFINE_HASHTABLE(wci_hash, ilog2(WCI_MAX_ENTS));
1318
1319static struct wci_ent *wci_find_ent(work_func_t func)
1320{
1321 struct wci_ent *ent;
1322
1323 hash_for_each_possible_rcu(wci_hash, ent, hash_node,
1324 (unsigned long)func) {
1325 if (ent->func == func)
1326 return ent;
1327 }
1328 return NULL;
1329}
1330
1331static void wq_cpu_intensive_report(work_func_t func)
1332{
1333 struct wci_ent *ent;
1334
1335restart:
1336 ent = wci_find_ent(func);
1337 if (ent) {
1338 u64 cnt;
1339
1340 /*
1341 * Start reporting from the warning_thresh and back off
1342 * exponentially.
1343 */
1344 cnt = atomic64_inc_return_relaxed(&ent->cnt);
1345 if (wq_cpu_intensive_warning_thresh &&
1346 cnt >= wq_cpu_intensive_warning_thresh &&
1347 is_power_of_2(cnt + 1 - wq_cpu_intensive_warning_thresh))
1348 printk_deferred(KERN_WARNING "workqueue: %ps hogged CPU for >%luus %llu times, consider switching to WQ_UNBOUND\n",
1349 ent->func, wq_cpu_intensive_thresh_us,
1350 atomic64_read(&ent->cnt));
1351 return;
1352 }
1353
1354 /*
1355 * @func is a new violation. Allocate a new entry for it. If wcn_ents[]
1356 * is exhausted, something went really wrong and we probably made enough
1357 * noise already.
1358 */
1359 if (wci_nr_ents >= WCI_MAX_ENTS)
1360 return;
1361
1362 raw_spin_lock(&wci_lock);
1363
1364 if (wci_nr_ents >= WCI_MAX_ENTS) {
1365 raw_spin_unlock(&wci_lock);
1366 return;
1367 }
1368
1369 if (wci_find_ent(func)) {
1370 raw_spin_unlock(&wci_lock);
1371 goto restart;
1372 }
1373
1374 ent = &wci_ents[wci_nr_ents++];
1375 ent->func = func;
1376 atomic64_set(&ent->cnt, 0);
1377 hash_add_rcu(wci_hash, &ent->hash_node, (unsigned long)func);
1378
1379 raw_spin_unlock(&wci_lock);
1380
1381 goto restart;
1382}
1383
1384#else /* CONFIG_WQ_CPU_INTENSIVE_REPORT */
1385static void wq_cpu_intensive_report(work_func_t func) {}
1386#endif /* CONFIG_WQ_CPU_INTENSIVE_REPORT */
1387
1388/**
1389 * wq_worker_running - a worker is running again
1390 * @task: task waking up
1391 *
1392 * This function is called when a worker returns from schedule()
1393 */
1394void wq_worker_running(struct task_struct *task)
1395{
1396 struct worker *worker = kthread_data(task);
1397
1398 if (!READ_ONCE(worker->sleeping))
1399 return;
1400
1401 /*
1402 * If preempted by unbind_workers() between the WORKER_NOT_RUNNING check
1403 * and the nr_running increment below, we may ruin the nr_running reset
1404 * and leave with an unexpected pool->nr_running == 1 on the newly unbound
1405 * pool. Protect against such race.
1406 */
1407 preempt_disable();
1408 if (!(worker->flags & WORKER_NOT_RUNNING))
1409 worker->pool->nr_running++;
1410 preempt_enable();
1411
1412 /*
1413 * CPU intensive auto-detection cares about how long a work item hogged
1414 * CPU without sleeping. Reset the starting timestamp on wakeup.
1415 */
1416 worker->current_at = worker->task->se.sum_exec_runtime;
1417
1418 WRITE_ONCE(worker->sleeping, 0);
1419}
1420
1421/**
1422 * wq_worker_sleeping - a worker is going to sleep
1423 * @task: task going to sleep
1424 *
1425 * This function is called from schedule() when a busy worker is
1426 * going to sleep.
1427 */
1428void wq_worker_sleeping(struct task_struct *task)
1429{
1430 struct worker *worker = kthread_data(task);
1431 struct worker_pool *pool;
1432
1433 /*
1434 * Rescuers, which may not have all the fields set up like normal
1435 * workers, also reach here, let's not access anything before
1436 * checking NOT_RUNNING.
1437 */
1438 if (worker->flags & WORKER_NOT_RUNNING)
1439 return;
1440
1441 pool = worker->pool;
1442
1443 /* Return if preempted before wq_worker_running() was reached */
1444 if (READ_ONCE(worker->sleeping))
1445 return;
1446
1447 WRITE_ONCE(worker->sleeping, 1);
1448 raw_spin_lock_irq(&pool->lock);
1449
1450 /*
1451 * Recheck in case unbind_workers() preempted us. We don't
1452 * want to decrement nr_running after the worker is unbound
1453 * and nr_running has been reset.
1454 */
1455 if (worker->flags & WORKER_NOT_RUNNING) {
1456 raw_spin_unlock_irq(&pool->lock);
1457 return;
1458 }
1459
1460 pool->nr_running--;
1461 if (kick_pool(pool))
1462 worker->current_pwq->stats[PWQ_STAT_CM_WAKEUP]++;
1463
1464 raw_spin_unlock_irq(&pool->lock);
1465}
1466
1467/**
1468 * wq_worker_tick - a scheduler tick occurred while a kworker is running
1469 * @task: task currently running
1470 *
1471 * Called from scheduler_tick(). We're in the IRQ context and the current
1472 * worker's fields which follow the 'K' locking rule can be accessed safely.
1473 */
1474void wq_worker_tick(struct task_struct *task)
1475{
1476 struct worker *worker = kthread_data(task);
1477 struct pool_workqueue *pwq = worker->current_pwq;
1478 struct worker_pool *pool = worker->pool;
1479
1480 if (!pwq)
1481 return;
1482
1483 pwq->stats[PWQ_STAT_CPU_TIME] += TICK_USEC;
1484
1485 if (!wq_cpu_intensive_thresh_us)
1486 return;
1487
1488 /*
1489 * If the current worker is concurrency managed and hogged the CPU for
1490 * longer than wq_cpu_intensive_thresh_us, it's automatically marked
1491 * CPU_INTENSIVE to avoid stalling other concurrency-managed work items.
1492 *
1493 * Set @worker->sleeping means that @worker is in the process of
1494 * switching out voluntarily and won't be contributing to
1495 * @pool->nr_running until it wakes up. As wq_worker_sleeping() also
1496 * decrements ->nr_running, setting CPU_INTENSIVE here can lead to
1497 * double decrements. The task is releasing the CPU anyway. Let's skip.
1498 * We probably want to make this prettier in the future.
1499 */
1500 if ((worker->flags & WORKER_NOT_RUNNING) || READ_ONCE(worker->sleeping) ||
1501 worker->task->se.sum_exec_runtime - worker->current_at <
1502 wq_cpu_intensive_thresh_us * NSEC_PER_USEC)
1503 return;
1504
1505 raw_spin_lock(&pool->lock);
1506
1507 worker_set_flags(worker, WORKER_CPU_INTENSIVE);
1508 wq_cpu_intensive_report(worker->current_func);
1509 pwq->stats[PWQ_STAT_CPU_INTENSIVE]++;
1510
1511 if (kick_pool(pool))
1512 pwq->stats[PWQ_STAT_CM_WAKEUP]++;
1513
1514 raw_spin_unlock(&pool->lock);
1515}
1516
1517/**
1518 * wq_worker_last_func - retrieve worker's last work function
1519 * @task: Task to retrieve last work function of.
1520 *
1521 * Determine the last function a worker executed. This is called from
1522 * the scheduler to get a worker's last known identity.
1523 *
1524 * CONTEXT:
1525 * raw_spin_lock_irq(rq->lock)
1526 *
1527 * This function is called during schedule() when a kworker is going
1528 * to sleep. It's used by psi to identify aggregation workers during
1529 * dequeuing, to allow periodic aggregation to shut-off when that
1530 * worker is the last task in the system or cgroup to go to sleep.
1531 *
1532 * As this function doesn't involve any workqueue-related locking, it
1533 * only returns stable values when called from inside the scheduler's
1534 * queuing and dequeuing paths, when @task, which must be a kworker,
1535 * is guaranteed to not be processing any works.
1536 *
1537 * Return:
1538 * The last work function %current executed as a worker, NULL if it
1539 * hasn't executed any work yet.
1540 */
1541work_func_t wq_worker_last_func(struct task_struct *task)
1542{
1543 struct worker *worker = kthread_data(task);
1544
1545 return worker->last_func;
1546}
1547
1548/**
1549 * wq_node_nr_active - Determine wq_node_nr_active to use
1550 * @wq: workqueue of interest
1551 * @node: NUMA node, can be %NUMA_NO_NODE
1552 *
1553 * Determine wq_node_nr_active to use for @wq on @node. Returns:
1554 *
1555 * - %NULL for per-cpu workqueues as they don't need to use shared nr_active.
1556 *
1557 * - node_nr_active[nr_node_ids] if @node is %NUMA_NO_NODE.
1558 *
1559 * - Otherwise, node_nr_active[@node].
1560 */
1561static struct wq_node_nr_active *wq_node_nr_active(struct workqueue_struct *wq,
1562 int node)
1563{
1564 if (!(wq->flags & WQ_UNBOUND))
1565 return NULL;
1566
1567 if (node == NUMA_NO_NODE)
1568 node = nr_node_ids;
1569
1570 return wq->node_nr_active[node];
1571}
1572
1573/**
1574 * wq_update_node_max_active - Update per-node max_actives to use
1575 * @wq: workqueue to update
1576 * @off_cpu: CPU that's going down, -1 if a CPU is not going down
1577 *
1578 * Update @wq->node_nr_active[]->max. @wq must be unbound. max_active is
1579 * distributed among nodes according to the proportions of numbers of online
1580 * cpus. The result is always between @wq->min_active and max_active.
1581 */
1582static void wq_update_node_max_active(struct workqueue_struct *wq, int off_cpu)
1583{
1584 struct cpumask *effective = unbound_effective_cpumask(wq);
1585 int min_active = READ_ONCE(wq->min_active);
1586 int max_active = READ_ONCE(wq->max_active);
1587 int total_cpus, node;
1588
1589 lockdep_assert_held(&wq->mutex);
1590
1591 if (!wq_topo_initialized)
1592 return;
1593
1594 if (off_cpu >= 0 && !cpumask_test_cpu(off_cpu, effective))
1595 off_cpu = -1;
1596
1597 total_cpus = cpumask_weight_and(effective, cpu_online_mask);
1598 if (off_cpu >= 0)
1599 total_cpus--;
1600
1601 /* If all CPUs of the wq get offline, use the default values */
1602 if (unlikely(!total_cpus)) {
1603 for_each_node(node)
1604 wq_node_nr_active(wq, node)->max = min_active;
1605
1606 wq_node_nr_active(wq, NUMA_NO_NODE)->max = max_active;
1607 return;
1608 }
1609
1610 for_each_node(node) {
1611 int node_cpus;
1612
1613 node_cpus = cpumask_weight_and(effective, cpumask_of_node(node));
1614 if (off_cpu >= 0 && cpu_to_node(off_cpu) == node)
1615 node_cpus--;
1616
1617 wq_node_nr_active(wq, node)->max =
1618 clamp(DIV_ROUND_UP(max_active * node_cpus, total_cpus),
1619 min_active, max_active);
1620 }
1621
1622 wq_node_nr_active(wq, NUMA_NO_NODE)->max = max_active;
1623}
1624
1625/**
1626 * get_pwq - get an extra reference on the specified pool_workqueue
1627 * @pwq: pool_workqueue to get
1628 *
1629 * Obtain an extra reference on @pwq. The caller should guarantee that
1630 * @pwq has positive refcnt and be holding the matching pool->lock.
1631 */
1632static void get_pwq(struct pool_workqueue *pwq)
1633{
1634 lockdep_assert_held(&pwq->pool->lock);
1635 WARN_ON_ONCE(pwq->refcnt <= 0);
1636 pwq->refcnt++;
1637}
1638
1639/**
1640 * put_pwq - put a pool_workqueue reference
1641 * @pwq: pool_workqueue to put
1642 *
1643 * Drop a reference of @pwq. If its refcnt reaches zero, schedule its
1644 * destruction. The caller should be holding the matching pool->lock.
1645 */
1646static void put_pwq(struct pool_workqueue *pwq)
1647{
1648 lockdep_assert_held(&pwq->pool->lock);
1649 if (likely(--pwq->refcnt))
1650 return;
1651 /*
1652 * @pwq can't be released under pool->lock, bounce to a dedicated
1653 * kthread_worker to avoid A-A deadlocks.
1654 */
1655 kthread_queue_work(pwq_release_worker, &pwq->release_work);
1656}
1657
1658/**
1659 * put_pwq_unlocked - put_pwq() with surrounding pool lock/unlock
1660 * @pwq: pool_workqueue to put (can be %NULL)
1661 *
1662 * put_pwq() with locking. This function also allows %NULL @pwq.
1663 */
1664static void put_pwq_unlocked(struct pool_workqueue *pwq)
1665{
1666 if (pwq) {
1667 /*
1668 * As both pwqs and pools are RCU protected, the
1669 * following lock operations are safe.
1670 */
1671 raw_spin_lock_irq(&pwq->pool->lock);
1672 put_pwq(pwq);
1673 raw_spin_unlock_irq(&pwq->pool->lock);
1674 }
1675}
1676
1677static bool pwq_is_empty(struct pool_workqueue *pwq)
1678{
1679 return !pwq->nr_active && list_empty(&pwq->inactive_works);
1680}
1681
1682static void __pwq_activate_work(struct pool_workqueue *pwq,
1683 struct work_struct *work)
1684{
1685 unsigned long *wdb = work_data_bits(work);
1686
1687 WARN_ON_ONCE(!(*wdb & WORK_STRUCT_INACTIVE));
1688 trace_workqueue_activate_work(work);
1689 if (list_empty(&pwq->pool->worklist))
1690 pwq->pool->watchdog_ts = jiffies;
1691 move_linked_works(work, &pwq->pool->worklist, NULL);
1692 __clear_bit(WORK_STRUCT_INACTIVE_BIT, wdb);
1693}
1694
1695/**
1696 * pwq_activate_work - Activate a work item if inactive
1697 * @pwq: pool_workqueue @work belongs to
1698 * @work: work item to activate
1699 *
1700 * Returns %true if activated. %false if already active.
1701 */
1702static bool pwq_activate_work(struct pool_workqueue *pwq,
1703 struct work_struct *work)
1704{
1705 struct worker_pool *pool = pwq->pool;
1706 struct wq_node_nr_active *nna;
1707
1708 lockdep_assert_held(&pool->lock);
1709
1710 if (!(*work_data_bits(work) & WORK_STRUCT_INACTIVE))
1711 return false;
1712
1713 nna = wq_node_nr_active(pwq->wq, pool->node);
1714 if (nna)
1715 atomic_inc(&nna->nr);
1716
1717 pwq->nr_active++;
1718 __pwq_activate_work(pwq, work);
1719 return true;
1720}
1721
1722static bool tryinc_node_nr_active(struct wq_node_nr_active *nna)
1723{
1724 int max = READ_ONCE(nna->max);
1725
1726 while (true) {
1727 int old, tmp;
1728
1729 old = atomic_read(&nna->nr);
1730 if (old >= max)
1731 return false;
1732 tmp = atomic_cmpxchg_relaxed(&nna->nr, old, old + 1);
1733 if (tmp == old)
1734 return true;
1735 }
1736}
1737
1738/**
1739 * pwq_tryinc_nr_active - Try to increment nr_active for a pwq
1740 * @pwq: pool_workqueue of interest
1741 * @fill: max_active may have increased, try to increase concurrency level
1742 *
1743 * Try to increment nr_active for @pwq. Returns %true if an nr_active count is
1744 * successfully obtained. %false otherwise.
1745 */
1746static bool pwq_tryinc_nr_active(struct pool_workqueue *pwq, bool fill)
1747{
1748 struct workqueue_struct *wq = pwq->wq;
1749 struct worker_pool *pool = pwq->pool;
1750 struct wq_node_nr_active *nna = wq_node_nr_active(wq, pool->node);
1751 bool obtained = false;
1752
1753 lockdep_assert_held(&pool->lock);
1754
1755 if (!nna) {
1756 /* BH or per-cpu workqueue, pwq->nr_active is sufficient */
1757 obtained = pwq->nr_active < READ_ONCE(wq->max_active);
1758 goto out;
1759 }
1760
1761 if (unlikely(pwq->plugged))
1762 return false;
1763
1764 /*
1765 * Unbound workqueue uses per-node shared nr_active $nna. If @pwq is
1766 * already waiting on $nna, pwq_dec_nr_active() will maintain the
1767 * concurrency level. Don't jump the line.
1768 *
1769 * We need to ignore the pending test after max_active has increased as
1770 * pwq_dec_nr_active() can only maintain the concurrency level but not
1771 * increase it. This is indicated by @fill.
1772 */
1773 if (!list_empty(&pwq->pending_node) && likely(!fill))
1774 goto out;
1775
1776 obtained = tryinc_node_nr_active(nna);
1777 if (obtained)
1778 goto out;
1779
1780 /*
1781 * Lockless acquisition failed. Lock, add ourself to $nna->pending_pwqs
1782 * and try again. The smp_mb() is paired with the implied memory barrier
1783 * of atomic_dec_return() in pwq_dec_nr_active() to ensure that either
1784 * we see the decremented $nna->nr or they see non-empty
1785 * $nna->pending_pwqs.
1786 */
1787 raw_spin_lock(&nna->lock);
1788
1789 if (list_empty(&pwq->pending_node))
1790 list_add_tail(&pwq->pending_node, &nna->pending_pwqs);
1791 else if (likely(!fill))
1792 goto out_unlock;
1793
1794 smp_mb();
1795
1796 obtained = tryinc_node_nr_active(nna);
1797
1798 /*
1799 * If @fill, @pwq might have already been pending. Being spuriously
1800 * pending in cold paths doesn't affect anything. Let's leave it be.
1801 */
1802 if (obtained && likely(!fill))
1803 list_del_init(&pwq->pending_node);
1804
1805out_unlock:
1806 raw_spin_unlock(&nna->lock);
1807out:
1808 if (obtained)
1809 pwq->nr_active++;
1810 return obtained;
1811}
1812
1813/**
1814 * pwq_activate_first_inactive - Activate the first inactive work item on a pwq
1815 * @pwq: pool_workqueue of interest
1816 * @fill: max_active may have increased, try to increase concurrency level
1817 *
1818 * Activate the first inactive work item of @pwq if available and allowed by
1819 * max_active limit.
1820 *
1821 * Returns %true if an inactive work item has been activated. %false if no
1822 * inactive work item is found or max_active limit is reached.
1823 */
1824static bool pwq_activate_first_inactive(struct pool_workqueue *pwq, bool fill)
1825{
1826 struct work_struct *work =
1827 list_first_entry_or_null(&pwq->inactive_works,
1828 struct work_struct, entry);
1829
1830 if (work && pwq_tryinc_nr_active(pwq, fill)) {
1831 __pwq_activate_work(pwq, work);
1832 return true;
1833 } else {
1834 return false;
1835 }
1836}
1837
1838/**
1839 * unplug_oldest_pwq - unplug the oldest pool_workqueue
1840 * @wq: workqueue_struct where its oldest pwq is to be unplugged
1841 *
1842 * This function should only be called for ordered workqueues where only the
1843 * oldest pwq is unplugged, the others are plugged to suspend execution to
1844 * ensure proper work item ordering::
1845 *
1846 * dfl_pwq --------------+ [P] - plugged
1847 * |
1848 * v
1849 * pwqs -> A -> B [P] -> C [P] (newest)
1850 * | | |
1851 * 1 3 5
1852 * | | |
1853 * 2 4 6
1854 *
1855 * When the oldest pwq is drained and removed, this function should be called
1856 * to unplug the next oldest one to start its work item execution. Note that
1857 * pwq's are linked into wq->pwqs with the oldest first, so the first one in
1858 * the list is the oldest.
1859 */
1860static void unplug_oldest_pwq(struct workqueue_struct *wq)
1861{
1862 struct pool_workqueue *pwq;
1863
1864 lockdep_assert_held(&wq->mutex);
1865
1866 /* Caller should make sure that pwqs isn't empty before calling */
1867 pwq = list_first_entry_or_null(&wq->pwqs, struct pool_workqueue,
1868 pwqs_node);
1869 raw_spin_lock_irq(&pwq->pool->lock);
1870 if (pwq->plugged) {
1871 pwq->plugged = false;
1872 if (pwq_activate_first_inactive(pwq, true))
1873 kick_pool(pwq->pool);
1874 }
1875 raw_spin_unlock_irq(&pwq->pool->lock);
1876}
1877
1878/**
1879 * node_activate_pending_pwq - Activate a pending pwq on a wq_node_nr_active
1880 * @nna: wq_node_nr_active to activate a pending pwq for
1881 * @caller_pool: worker_pool the caller is locking
1882 *
1883 * Activate a pwq in @nna->pending_pwqs. Called with @caller_pool locked.
1884 * @caller_pool may be unlocked and relocked to lock other worker_pools.
1885 */
1886static void node_activate_pending_pwq(struct wq_node_nr_active *nna,
1887 struct worker_pool *caller_pool)
1888{
1889 struct worker_pool *locked_pool = caller_pool;
1890 struct pool_workqueue *pwq;
1891 struct work_struct *work;
1892
1893 lockdep_assert_held(&caller_pool->lock);
1894
1895 raw_spin_lock(&nna->lock);
1896retry:
1897 pwq = list_first_entry_or_null(&nna->pending_pwqs,
1898 struct pool_workqueue, pending_node);
1899 if (!pwq)
1900 goto out_unlock;
1901
1902 /*
1903 * If @pwq is for a different pool than @locked_pool, we need to lock
1904 * @pwq->pool->lock. Let's trylock first. If unsuccessful, do the unlock
1905 * / lock dance. For that, we also need to release @nna->lock as it's
1906 * nested inside pool locks.
1907 */
1908 if (pwq->pool != locked_pool) {
1909 raw_spin_unlock(&locked_pool->lock);
1910 locked_pool = pwq->pool;
1911 if (!raw_spin_trylock(&locked_pool->lock)) {
1912 raw_spin_unlock(&nna->lock);
1913 raw_spin_lock(&locked_pool->lock);
1914 raw_spin_lock(&nna->lock);
1915 goto retry;
1916 }
1917 }
1918
1919 /*
1920 * $pwq may not have any inactive work items due to e.g. cancellations.
1921 * Drop it from pending_pwqs and see if there's another one.
1922 */
1923 work = list_first_entry_or_null(&pwq->inactive_works,
1924 struct work_struct, entry);
1925 if (!work) {
1926 list_del_init(&pwq->pending_node);
1927 goto retry;
1928 }
1929
1930 /*
1931 * Acquire an nr_active count and activate the inactive work item. If
1932 * $pwq still has inactive work items, rotate it to the end of the
1933 * pending_pwqs so that we round-robin through them. This means that
1934 * inactive work items are not activated in queueing order which is fine
1935 * given that there has never been any ordering across different pwqs.
1936 */
1937 if (likely(tryinc_node_nr_active(nna))) {
1938 pwq->nr_active++;
1939 __pwq_activate_work(pwq, work);
1940
1941 if (list_empty(&pwq->inactive_works))
1942 list_del_init(&pwq->pending_node);
1943 else
1944 list_move_tail(&pwq->pending_node, &nna->pending_pwqs);
1945
1946 /* if activating a foreign pool, make sure it's running */
1947 if (pwq->pool != caller_pool)
1948 kick_pool(pwq->pool);
1949 }
1950
1951out_unlock:
1952 raw_spin_unlock(&nna->lock);
1953 if (locked_pool != caller_pool) {
1954 raw_spin_unlock(&locked_pool->lock);
1955 raw_spin_lock(&caller_pool->lock);
1956 }
1957}
1958
1959/**
1960 * pwq_dec_nr_active - Retire an active count
1961 * @pwq: pool_workqueue of interest
1962 *
1963 * Decrement @pwq's nr_active and try to activate the first inactive work item.
1964 * For unbound workqueues, this function may temporarily drop @pwq->pool->lock.
1965 */
1966static void pwq_dec_nr_active(struct pool_workqueue *pwq)
1967{
1968 struct worker_pool *pool = pwq->pool;
1969 struct wq_node_nr_active *nna = wq_node_nr_active(pwq->wq, pool->node);
1970
1971 lockdep_assert_held(&pool->lock);
1972
1973 /*
1974 * @pwq->nr_active should be decremented for both percpu and unbound
1975 * workqueues.
1976 */
1977 pwq->nr_active--;
1978
1979 /*
1980 * For a percpu workqueue, it's simple. Just need to kick the first
1981 * inactive work item on @pwq itself.
1982 */
1983 if (!nna) {
1984 pwq_activate_first_inactive(pwq, false);
1985 return;
1986 }
1987
1988 /*
1989 * If @pwq is for an unbound workqueue, it's more complicated because
1990 * multiple pwqs and pools may be sharing the nr_active count. When a
1991 * pwq needs to wait for an nr_active count, it puts itself on
1992 * $nna->pending_pwqs. The following atomic_dec_return()'s implied
1993 * memory barrier is paired with smp_mb() in pwq_tryinc_nr_active() to
1994 * guarantee that either we see non-empty pending_pwqs or they see
1995 * decremented $nna->nr.
1996 *
1997 * $nna->max may change as CPUs come online/offline and @pwq->wq's
1998 * max_active gets updated. However, it is guaranteed to be equal to or
1999 * larger than @pwq->wq->min_active which is above zero unless freezing.
2000 * This maintains the forward progress guarantee.
2001 */
2002 if (atomic_dec_return(&nna->nr) >= READ_ONCE(nna->max))
2003 return;
2004
2005 if (!list_empty(&nna->pending_pwqs))
2006 node_activate_pending_pwq(nna, pool);
2007}
2008
2009/**
2010 * pwq_dec_nr_in_flight - decrement pwq's nr_in_flight
2011 * @pwq: pwq of interest
2012 * @work_data: work_data of work which left the queue
2013 *
2014 * A work either has completed or is removed from pending queue,
2015 * decrement nr_in_flight of its pwq and handle workqueue flushing.
2016 *
2017 * NOTE:
2018 * For unbound workqueues, this function may temporarily drop @pwq->pool->lock
2019 * and thus should be called after all other state updates for the in-flight
2020 * work item is complete.
2021 *
2022 * CONTEXT:
2023 * raw_spin_lock_irq(pool->lock).
2024 */
2025static void pwq_dec_nr_in_flight(struct pool_workqueue *pwq, unsigned long work_data)
2026{
2027 int color = get_work_color(work_data);
2028
2029 if (!(work_data & WORK_STRUCT_INACTIVE))
2030 pwq_dec_nr_active(pwq);
2031
2032 pwq->nr_in_flight[color]--;
2033
2034 /* is flush in progress and are we at the flushing tip? */
2035 if (likely(pwq->flush_color != color))
2036 goto out_put;
2037
2038 /* are there still in-flight works? */
2039 if (pwq->nr_in_flight[color])
2040 goto out_put;
2041
2042 /* this pwq is done, clear flush_color */
2043 pwq->flush_color = -1;
2044
2045 /*
2046 * If this was the last pwq, wake up the first flusher. It
2047 * will handle the rest.
2048 */
2049 if (atomic_dec_and_test(&pwq->wq->nr_pwqs_to_flush))
2050 complete(&pwq->wq->first_flusher->done);
2051out_put:
2052 put_pwq(pwq);
2053}
2054
2055/**
2056 * try_to_grab_pending - steal work item from worklist and disable irq
2057 * @work: work item to steal
2058 * @cflags: %WORK_CANCEL_ flags
2059 * @irq_flags: place to store irq state
2060 *
2061 * Try to grab PENDING bit of @work. This function can handle @work in any
2062 * stable state - idle, on timer or on worklist.
2063 *
2064 * Return:
2065 *
2066 * ======== ================================================================
2067 * 1 if @work was pending and we successfully stole PENDING
2068 * 0 if @work was idle and we claimed PENDING
2069 * -EAGAIN if PENDING couldn't be grabbed at the moment, safe to busy-retry
2070 * -ENOENT if someone else is canceling @work, this state may persist
2071 * for arbitrarily long
2072 * ======== ================================================================
2073 *
2074 * Note:
2075 * On >= 0 return, the caller owns @work's PENDING bit. To avoid getting
2076 * interrupted while holding PENDING and @work off queue, irq must be
2077 * disabled on entry. This, combined with delayed_work->timer being
2078 * irqsafe, ensures that we return -EAGAIN for finite short period of time.
2079 *
2080 * On successful return, >= 0, irq is disabled and the caller is
2081 * responsible for releasing it using local_irq_restore(*@irq_flags).
2082 *
2083 * This function is safe to call from any context including IRQ handler.
2084 */
2085static int try_to_grab_pending(struct work_struct *work, u32 cflags,
2086 unsigned long *irq_flags)
2087{
2088 struct worker_pool *pool;
2089 struct pool_workqueue *pwq;
2090
2091 local_irq_save(*irq_flags);
2092
2093 /* try to steal the timer if it exists */
2094 if (cflags & WORK_CANCEL_DELAYED) {
2095 struct delayed_work *dwork = to_delayed_work(work);
2096
2097 /*
2098 * dwork->timer is irqsafe. If del_timer() fails, it's
2099 * guaranteed that the timer is not queued anywhere and not
2100 * running on the local CPU.
2101 */
2102 if (likely(del_timer(&dwork->timer)))
2103 return 1;
2104 }
2105
2106 /* try to claim PENDING the normal way */
2107 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work)))
2108 return 0;
2109
2110 rcu_read_lock();
2111 /*
2112 * The queueing is in progress, or it is already queued. Try to
2113 * steal it from ->worklist without clearing WORK_STRUCT_PENDING.
2114 */
2115 pool = get_work_pool(work);
2116 if (!pool)
2117 goto fail;
2118
2119 raw_spin_lock(&pool->lock);
2120 /*
2121 * work->data is guaranteed to point to pwq only while the work
2122 * item is queued on pwq->wq, and both updating work->data to point
2123 * to pwq on queueing and to pool on dequeueing are done under
2124 * pwq->pool->lock. This in turn guarantees that, if work->data
2125 * points to pwq which is associated with a locked pool, the work
2126 * item is currently queued on that pool.
2127 */
2128 pwq = get_work_pwq(work);
2129 if (pwq && pwq->pool == pool) {
2130 unsigned long work_data;
2131
2132 debug_work_deactivate(work);
2133
2134 /*
2135 * A cancelable inactive work item must be in the
2136 * pwq->inactive_works since a queued barrier can't be
2137 * canceled (see the comments in insert_wq_barrier()).
2138 *
2139 * An inactive work item cannot be grabbed directly because
2140 * it might have linked barrier work items which, if left
2141 * on the inactive_works list, will confuse pwq->nr_active
2142 * management later on and cause stall. Make sure the work
2143 * item is activated before grabbing.
2144 */
2145 pwq_activate_work(pwq, work);
2146
2147 list_del_init(&work->entry);
2148
2149 /*
2150 * work->data points to pwq iff queued. Let's point to pool. As
2151 * this destroys work->data needed by the next step, stash it.
2152 */
2153 work_data = *work_data_bits(work);
2154 set_work_pool_and_keep_pending(work, pool->id, 0);
2155
2156 /* must be the last step, see the function comment */
2157 pwq_dec_nr_in_flight(pwq, work_data);
2158
2159 raw_spin_unlock(&pool->lock);
2160 rcu_read_unlock();
2161 return 1;
2162 }
2163 raw_spin_unlock(&pool->lock);
2164fail:
2165 rcu_read_unlock();
2166 local_irq_restore(*irq_flags);
2167 if (work_is_canceling(work))
2168 return -ENOENT;
2169 cpu_relax();
2170 return -EAGAIN;
2171}
2172
2173struct cwt_wait {
2174 wait_queue_entry_t wait;
2175 struct work_struct *work;
2176};
2177
2178static int cwt_wakefn(wait_queue_entry_t *wait, unsigned mode, int sync, void *key)
2179{
2180 struct cwt_wait *cwait = container_of(wait, struct cwt_wait, wait);
2181
2182 if (cwait->work != key)
2183 return 0;
2184 return autoremove_wake_function(wait, mode, sync, key);
2185}
2186
2187/**
2188 * work_grab_pending - steal work item from worklist and disable irq
2189 * @work: work item to steal
2190 * @cflags: %WORK_CANCEL_ flags
2191 * @irq_flags: place to store IRQ state
2192 *
2193 * Grab PENDING bit of @work. @work can be in any stable state - idle, on timer
2194 * or on worklist.
2195 *
2196 * Must be called in process context. IRQ is disabled on return with IRQ state
2197 * stored in *@irq_flags. The caller is responsible for re-enabling it using
2198 * local_irq_restore().
2199 *
2200 * Returns %true if @work was pending. %false if idle.
2201 */
2202static bool work_grab_pending(struct work_struct *work, u32 cflags,
2203 unsigned long *irq_flags)
2204{
2205 struct cwt_wait cwait;
2206 int ret;
2207
2208 might_sleep();
2209repeat:
2210 ret = try_to_grab_pending(work, cflags, irq_flags);
2211 if (likely(ret >= 0))
2212 return ret;
2213 if (ret != -ENOENT)
2214 goto repeat;
2215
2216 /*
2217 * Someone is already canceling. Wait for it to finish. flush_work()
2218 * doesn't work for PREEMPT_NONE because we may get woken up between
2219 * @work's completion and the other canceling task resuming and clearing
2220 * CANCELING - flush_work() will return false immediately as @work is no
2221 * longer busy, try_to_grab_pending() will return -ENOENT as @work is
2222 * still being canceled and the other canceling task won't be able to
2223 * clear CANCELING as we're hogging the CPU.
2224 *
2225 * Let's wait for completion using a waitqueue. As this may lead to the
2226 * thundering herd problem, use a custom wake function which matches
2227 * @work along with exclusive wait and wakeup.
2228 */
2229 init_wait(&cwait.wait);
2230 cwait.wait.func = cwt_wakefn;
2231 cwait.work = work;
2232
2233 prepare_to_wait_exclusive(&wq_cancel_waitq, &cwait.wait,
2234 TASK_UNINTERRUPTIBLE);
2235 if (work_is_canceling(work))
2236 schedule();
2237 finish_wait(&wq_cancel_waitq, &cwait.wait);
2238
2239 goto repeat;
2240}
2241
2242/**
2243 * insert_work - insert a work into a pool
2244 * @pwq: pwq @work belongs to
2245 * @work: work to insert
2246 * @head: insertion point
2247 * @extra_flags: extra WORK_STRUCT_* flags to set
2248 *
2249 * Insert @work which belongs to @pwq after @head. @extra_flags is or'd to
2250 * work_struct flags.
2251 *
2252 * CONTEXT:
2253 * raw_spin_lock_irq(pool->lock).
2254 */
2255static void insert_work(struct pool_workqueue *pwq, struct work_struct *work,
2256 struct list_head *head, unsigned int extra_flags)
2257{
2258 debug_work_activate(work);
2259
2260 /* record the work call stack in order to print it in KASAN reports */
2261 kasan_record_aux_stack_noalloc(work);
2262
2263 /* we own @work, set data and link */
2264 set_work_pwq(work, pwq, extra_flags);
2265 list_add_tail(&work->entry, head);
2266 get_pwq(pwq);
2267}
2268
2269/*
2270 * Test whether @work is being queued from another work executing on the
2271 * same workqueue.
2272 */
2273static bool is_chained_work(struct workqueue_struct *wq)
2274{
2275 struct worker *worker;
2276
2277 worker = current_wq_worker();
2278 /*
2279 * Return %true iff I'm a worker executing a work item on @wq. If
2280 * I'm @worker, it's safe to dereference it without locking.
2281 */
2282 return worker && worker->current_pwq->wq == wq;
2283}
2284
2285/*
2286 * When queueing an unbound work item to a wq, prefer local CPU if allowed
2287 * by wq_unbound_cpumask. Otherwise, round robin among the allowed ones to
2288 * avoid perturbing sensitive tasks.
2289 */
2290static int wq_select_unbound_cpu(int cpu)
2291{
2292 int new_cpu;
2293
2294 if (likely(!wq_debug_force_rr_cpu)) {
2295 if (cpumask_test_cpu(cpu, wq_unbound_cpumask))
2296 return cpu;
2297 } else {
2298 pr_warn_once("workqueue: round-robin CPU selection forced, expect performance impact\n");
2299 }
2300
2301 new_cpu = __this_cpu_read(wq_rr_cpu_last);
2302 new_cpu = cpumask_next_and(new_cpu, wq_unbound_cpumask, cpu_online_mask);
2303 if (unlikely(new_cpu >= nr_cpu_ids)) {
2304 new_cpu = cpumask_first_and(wq_unbound_cpumask, cpu_online_mask);
2305 if (unlikely(new_cpu >= nr_cpu_ids))
2306 return cpu;
2307 }
2308 __this_cpu_write(wq_rr_cpu_last, new_cpu);
2309
2310 return new_cpu;
2311}
2312
2313static void __queue_work(int cpu, struct workqueue_struct *wq,
2314 struct work_struct *work)
2315{
2316 struct pool_workqueue *pwq;
2317 struct worker_pool *last_pool, *pool;
2318 unsigned int work_flags;
2319 unsigned int req_cpu = cpu;
2320
2321 /*
2322 * While a work item is PENDING && off queue, a task trying to
2323 * steal the PENDING will busy-loop waiting for it to either get
2324 * queued or lose PENDING. Grabbing PENDING and queueing should
2325 * happen with IRQ disabled.
2326 */
2327 lockdep_assert_irqs_disabled();
2328
2329 /*
2330 * For a draining wq, only works from the same workqueue are
2331 * allowed. The __WQ_DESTROYING helps to spot the issue that
2332 * queues a new work item to a wq after destroy_workqueue(wq).
2333 */
2334 if (unlikely(wq->flags & (__WQ_DESTROYING | __WQ_DRAINING) &&
2335 WARN_ON_ONCE(!is_chained_work(wq))))
2336 return;
2337 rcu_read_lock();
2338retry:
2339 /* pwq which will be used unless @work is executing elsewhere */
2340 if (req_cpu == WORK_CPU_UNBOUND) {
2341 if (wq->flags & WQ_UNBOUND)
2342 cpu = wq_select_unbound_cpu(raw_smp_processor_id());
2343 else
2344 cpu = raw_smp_processor_id();
2345 }
2346
2347 pwq = rcu_dereference(*per_cpu_ptr(wq->cpu_pwq, cpu));
2348 pool = pwq->pool;
2349
2350 /*
2351 * If @work was previously on a different pool, it might still be
2352 * running there, in which case the work needs to be queued on that
2353 * pool to guarantee non-reentrancy.
2354 */
2355 last_pool = get_work_pool(work);
2356 if (last_pool && last_pool != pool) {
2357 struct worker *worker;
2358
2359 raw_spin_lock(&last_pool->lock);
2360
2361 worker = find_worker_executing_work(last_pool, work);
2362
2363 if (worker && worker->current_pwq->wq == wq) {
2364 pwq = worker->current_pwq;
2365 pool = pwq->pool;
2366 WARN_ON_ONCE(pool != last_pool);
2367 } else {
2368 /* meh... not running there, queue here */
2369 raw_spin_unlock(&last_pool->lock);
2370 raw_spin_lock(&pool->lock);
2371 }
2372 } else {
2373 raw_spin_lock(&pool->lock);
2374 }
2375
2376 /*
2377 * pwq is determined and locked. For unbound pools, we could have raced
2378 * with pwq release and it could already be dead. If its refcnt is zero,
2379 * repeat pwq selection. Note that unbound pwqs never die without
2380 * another pwq replacing it in cpu_pwq or while work items are executing
2381 * on it, so the retrying is guaranteed to make forward-progress.
2382 */
2383 if (unlikely(!pwq->refcnt)) {
2384 if (wq->flags & WQ_UNBOUND) {
2385 raw_spin_unlock(&pool->lock);
2386 cpu_relax();
2387 goto retry;
2388 }
2389 /* oops */
2390 WARN_ONCE(true, "workqueue: per-cpu pwq for %s on cpu%d has 0 refcnt",
2391 wq->name, cpu);
2392 }
2393
2394 /* pwq determined, queue */
2395 trace_workqueue_queue_work(req_cpu, pwq, work);
2396
2397 if (WARN_ON(!list_empty(&work->entry)))
2398 goto out;
2399
2400 pwq->nr_in_flight[pwq->work_color]++;
2401 work_flags = work_color_to_flags(pwq->work_color);
2402
2403 /*
2404 * Limit the number of concurrently active work items to max_active.
2405 * @work must also queue behind existing inactive work items to maintain
2406 * ordering when max_active changes. See wq_adjust_max_active().
2407 */
2408 if (list_empty(&pwq->inactive_works) && pwq_tryinc_nr_active(pwq, false)) {
2409 if (list_empty(&pool->worklist))
2410 pool->watchdog_ts = jiffies;
2411
2412 trace_workqueue_activate_work(work);
2413 insert_work(pwq, work, &pool->worklist, work_flags);
2414 kick_pool(pool);
2415 } else {
2416 work_flags |= WORK_STRUCT_INACTIVE;
2417 insert_work(pwq, work, &pwq->inactive_works, work_flags);
2418 }
2419
2420out:
2421 raw_spin_unlock(&pool->lock);
2422 rcu_read_unlock();
2423}
2424
2425/**
2426 * queue_work_on - queue work on specific cpu
2427 * @cpu: CPU number to execute work on
2428 * @wq: workqueue to use
2429 * @work: work to queue
2430 *
2431 * We queue the work to a specific CPU, the caller must ensure it
2432 * can't go away. Callers that fail to ensure that the specified
2433 * CPU cannot go away will execute on a randomly chosen CPU.
2434 * But note well that callers specifying a CPU that never has been
2435 * online will get a splat.
2436 *
2437 * Return: %false if @work was already on a queue, %true otherwise.
2438 */
2439bool queue_work_on(int cpu, struct workqueue_struct *wq,
2440 struct work_struct *work)
2441{
2442 bool ret = false;
2443 unsigned long irq_flags;
2444
2445 local_irq_save(irq_flags);
2446
2447 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
2448 __queue_work(cpu, wq, work);
2449 ret = true;
2450 }
2451
2452 local_irq_restore(irq_flags);
2453 return ret;
2454}
2455EXPORT_SYMBOL(queue_work_on);
2456
2457/**
2458 * select_numa_node_cpu - Select a CPU based on NUMA node
2459 * @node: NUMA node ID that we want to select a CPU from
2460 *
2461 * This function will attempt to find a "random" cpu available on a given
2462 * node. If there are no CPUs available on the given node it will return
2463 * WORK_CPU_UNBOUND indicating that we should just schedule to any
2464 * available CPU if we need to schedule this work.
2465 */
2466static int select_numa_node_cpu(int node)
2467{
2468 int cpu;
2469
2470 /* Delay binding to CPU if node is not valid or online */
2471 if (node < 0 || node >= MAX_NUMNODES || !node_online(node))
2472 return WORK_CPU_UNBOUND;
2473
2474 /* Use local node/cpu if we are already there */
2475 cpu = raw_smp_processor_id();
2476 if (node == cpu_to_node(cpu))
2477 return cpu;
2478
2479 /* Use "random" otherwise know as "first" online CPU of node */
2480 cpu = cpumask_any_and(cpumask_of_node(node), cpu_online_mask);
2481
2482 /* If CPU is valid return that, otherwise just defer */
2483 return cpu < nr_cpu_ids ? cpu : WORK_CPU_UNBOUND;
2484}
2485
2486/**
2487 * queue_work_node - queue work on a "random" cpu for a given NUMA node
2488 * @node: NUMA node that we are targeting the work for
2489 * @wq: workqueue to use
2490 * @work: work to queue
2491 *
2492 * We queue the work to a "random" CPU within a given NUMA node. The basic
2493 * idea here is to provide a way to somehow associate work with a given
2494 * NUMA node.
2495 *
2496 * This function will only make a best effort attempt at getting this onto
2497 * the right NUMA node. If no node is requested or the requested node is
2498 * offline then we just fall back to standard queue_work behavior.
2499 *
2500 * Currently the "random" CPU ends up being the first available CPU in the
2501 * intersection of cpu_online_mask and the cpumask of the node, unless we
2502 * are running on the node. In that case we just use the current CPU.
2503 *
2504 * Return: %false if @work was already on a queue, %true otherwise.
2505 */
2506bool queue_work_node(int node, struct workqueue_struct *wq,
2507 struct work_struct *work)
2508{
2509 unsigned long irq_flags;
2510 bool ret = false;
2511
2512 /*
2513 * This current implementation is specific to unbound workqueues.
2514 * Specifically we only return the first available CPU for a given
2515 * node instead of cycling through individual CPUs within the node.
2516 *
2517 * If this is used with a per-cpu workqueue then the logic in
2518 * workqueue_select_cpu_near would need to be updated to allow for
2519 * some round robin type logic.
2520 */
2521 WARN_ON_ONCE(!(wq->flags & WQ_UNBOUND));
2522
2523 local_irq_save(irq_flags);
2524
2525 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
2526 int cpu = select_numa_node_cpu(node);
2527
2528 __queue_work(cpu, wq, work);
2529 ret = true;
2530 }
2531
2532 local_irq_restore(irq_flags);
2533 return ret;
2534}
2535EXPORT_SYMBOL_GPL(queue_work_node);
2536
2537void delayed_work_timer_fn(struct timer_list *t)
2538{
2539 struct delayed_work *dwork = from_timer(dwork, t, timer);
2540
2541 /* should have been called from irqsafe timer with irq already off */
2542 __queue_work(dwork->cpu, dwork->wq, &dwork->work);
2543}
2544EXPORT_SYMBOL(delayed_work_timer_fn);
2545
2546static void __queue_delayed_work(int cpu, struct workqueue_struct *wq,
2547 struct delayed_work *dwork, unsigned long delay)
2548{
2549 struct timer_list *timer = &dwork->timer;
2550 struct work_struct *work = &dwork->work;
2551
2552 WARN_ON_ONCE(!wq);
2553 WARN_ON_ONCE(timer->function != delayed_work_timer_fn);
2554 WARN_ON_ONCE(timer_pending(timer));
2555 WARN_ON_ONCE(!list_empty(&work->entry));
2556
2557 /*
2558 * If @delay is 0, queue @dwork->work immediately. This is for
2559 * both optimization and correctness. The earliest @timer can
2560 * expire is on the closest next tick and delayed_work users depend
2561 * on that there's no such delay when @delay is 0.
2562 */
2563 if (!delay) {
2564 __queue_work(cpu, wq, &dwork->work);
2565 return;
2566 }
2567
2568 dwork->wq = wq;
2569 dwork->cpu = cpu;
2570 timer->expires = jiffies + delay;
2571
2572 if (housekeeping_enabled(HK_TYPE_TIMER)) {
2573 /* If the current cpu is a housekeeping cpu, use it. */
2574 cpu = smp_processor_id();
2575 if (!housekeeping_test_cpu(cpu, HK_TYPE_TIMER))
2576 cpu = housekeeping_any_cpu(HK_TYPE_TIMER);
2577 add_timer_on(timer, cpu);
2578 } else {
2579 if (likely(cpu == WORK_CPU_UNBOUND))
2580 add_timer_global(timer);
2581 else
2582 add_timer_on(timer, cpu);
2583 }
2584}
2585
2586/**
2587 * queue_delayed_work_on - queue work on specific CPU after delay
2588 * @cpu: CPU number to execute work on
2589 * @wq: workqueue to use
2590 * @dwork: work to queue
2591 * @delay: number of jiffies to wait before queueing
2592 *
2593 * Return: %false if @work was already on a queue, %true otherwise. If
2594 * @delay is zero and @dwork is idle, it will be scheduled for immediate
2595 * execution.
2596 */
2597bool queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
2598 struct delayed_work *dwork, unsigned long delay)
2599{
2600 struct work_struct *work = &dwork->work;
2601 bool ret = false;
2602 unsigned long irq_flags;
2603
2604 /* read the comment in __queue_work() */
2605 local_irq_save(irq_flags);
2606
2607 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
2608 __queue_delayed_work(cpu, wq, dwork, delay);
2609 ret = true;
2610 }
2611
2612 local_irq_restore(irq_flags);
2613 return ret;
2614}
2615EXPORT_SYMBOL(queue_delayed_work_on);
2616
2617/**
2618 * mod_delayed_work_on - modify delay of or queue a delayed work on specific CPU
2619 * @cpu: CPU number to execute work on
2620 * @wq: workqueue to use
2621 * @dwork: work to queue
2622 * @delay: number of jiffies to wait before queueing
2623 *
2624 * If @dwork is idle, equivalent to queue_delayed_work_on(); otherwise,
2625 * modify @dwork's timer so that it expires after @delay. If @delay is
2626 * zero, @work is guaranteed to be scheduled immediately regardless of its
2627 * current state.
2628 *
2629 * Return: %false if @dwork was idle and queued, %true if @dwork was
2630 * pending and its timer was modified.
2631 *
2632 * This function is safe to call from any context including IRQ handler.
2633 * See try_to_grab_pending() for details.
2634 */
2635bool mod_delayed_work_on(int cpu, struct workqueue_struct *wq,
2636 struct delayed_work *dwork, unsigned long delay)
2637{
2638 unsigned long irq_flags;
2639 int ret;
2640
2641 do {
2642 ret = try_to_grab_pending(&dwork->work, WORK_CANCEL_DELAYED,
2643 &irq_flags);
2644 } while (unlikely(ret == -EAGAIN));
2645
2646 if (likely(ret >= 0)) {
2647 __queue_delayed_work(cpu, wq, dwork, delay);
2648 local_irq_restore(irq_flags);
2649 }
2650
2651 /* -ENOENT from try_to_grab_pending() becomes %true */
2652 return ret;
2653}
2654EXPORT_SYMBOL_GPL(mod_delayed_work_on);
2655
2656static void rcu_work_rcufn(struct rcu_head *rcu)
2657{
2658 struct rcu_work *rwork = container_of(rcu, struct rcu_work, rcu);
2659
2660 /* read the comment in __queue_work() */
2661 local_irq_disable();
2662 __queue_work(WORK_CPU_UNBOUND, rwork->wq, &rwork->work);
2663 local_irq_enable();
2664}
2665
2666/**
2667 * queue_rcu_work - queue work after a RCU grace period
2668 * @wq: workqueue to use
2669 * @rwork: work to queue
2670 *
2671 * Return: %false if @rwork was already pending, %true otherwise. Note
2672 * that a full RCU grace period is guaranteed only after a %true return.
2673 * While @rwork is guaranteed to be executed after a %false return, the
2674 * execution may happen before a full RCU grace period has passed.
2675 */
2676bool queue_rcu_work(struct workqueue_struct *wq, struct rcu_work *rwork)
2677{
2678 struct work_struct *work = &rwork->work;
2679
2680 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
2681 rwork->wq = wq;
2682 call_rcu_hurry(&rwork->rcu, rcu_work_rcufn);
2683 return true;
2684 }
2685
2686 return false;
2687}
2688EXPORT_SYMBOL(queue_rcu_work);
2689
2690static struct worker *alloc_worker(int node)
2691{
2692 struct worker *worker;
2693
2694 worker = kzalloc_node(sizeof(*worker), GFP_KERNEL, node);
2695 if (worker) {
2696 INIT_LIST_HEAD(&worker->entry);
2697 INIT_LIST_HEAD(&worker->scheduled);
2698 INIT_LIST_HEAD(&worker->node);
2699 /* on creation a worker is in !idle && prep state */
2700 worker->flags = WORKER_PREP;
2701 }
2702 return worker;
2703}
2704
2705static cpumask_t *pool_allowed_cpus(struct worker_pool *pool)
2706{
2707 if (pool->cpu < 0 && pool->attrs->affn_strict)
2708 return pool->attrs->__pod_cpumask;
2709 else
2710 return pool->attrs->cpumask;
2711}
2712
2713/**
2714 * worker_attach_to_pool() - attach a worker to a pool
2715 * @worker: worker to be attached
2716 * @pool: the target pool
2717 *
2718 * Attach @worker to @pool. Once attached, the %WORKER_UNBOUND flag and
2719 * cpu-binding of @worker are kept coordinated with the pool across
2720 * cpu-[un]hotplugs.
2721 */
2722static void worker_attach_to_pool(struct worker *worker,
2723 struct worker_pool *pool)
2724{
2725 mutex_lock(&wq_pool_attach_mutex);
2726
2727 /*
2728 * The wq_pool_attach_mutex ensures %POOL_DISASSOCIATED remains stable
2729 * across this function. See the comments above the flag definition for
2730 * details. BH workers are, while per-CPU, always DISASSOCIATED.
2731 */
2732 if (pool->flags & POOL_DISASSOCIATED) {
2733 worker->flags |= WORKER_UNBOUND;
2734 } else {
2735 WARN_ON_ONCE(pool->flags & POOL_BH);
2736 kthread_set_per_cpu(worker->task, pool->cpu);
2737 }
2738
2739 if (worker->rescue_wq)
2740 set_cpus_allowed_ptr(worker->task, pool_allowed_cpus(pool));
2741
2742 list_add_tail(&worker->node, &pool->workers);
2743 worker->pool = pool;
2744
2745 mutex_unlock(&wq_pool_attach_mutex);
2746}
2747
2748/**
2749 * worker_detach_from_pool() - detach a worker from its pool
2750 * @worker: worker which is attached to its pool
2751 *
2752 * Undo the attaching which had been done in worker_attach_to_pool(). The
2753 * caller worker shouldn't access to the pool after detached except it has
2754 * other reference to the pool.
2755 */
2756static void worker_detach_from_pool(struct worker *worker)
2757{
2758 struct worker_pool *pool = worker->pool;
2759 struct completion *detach_completion = NULL;
2760
2761 /* there is one permanent BH worker per CPU which should never detach */
2762 WARN_ON_ONCE(pool->flags & POOL_BH);
2763
2764 mutex_lock(&wq_pool_attach_mutex);
2765
2766 kthread_set_per_cpu(worker->task, -1);
2767 list_del(&worker->node);
2768 worker->pool = NULL;
2769
2770 if (list_empty(&pool->workers) && list_empty(&pool->dying_workers))
2771 detach_completion = pool->detach_completion;
2772 mutex_unlock(&wq_pool_attach_mutex);
2773
2774 /* clear leftover flags without pool->lock after it is detached */
2775 worker->flags &= ~(WORKER_UNBOUND | WORKER_REBOUND);
2776
2777 if (detach_completion)
2778 complete(detach_completion);
2779}
2780
2781/**
2782 * create_worker - create a new workqueue worker
2783 * @pool: pool the new worker will belong to
2784 *
2785 * Create and start a new worker which is attached to @pool.
2786 *
2787 * CONTEXT:
2788 * Might sleep. Does GFP_KERNEL allocations.
2789 *
2790 * Return:
2791 * Pointer to the newly created worker.
2792 */
2793static struct worker *create_worker(struct worker_pool *pool)
2794{
2795 struct worker *worker;
2796 int id;
2797 char id_buf[23];
2798
2799 /* ID is needed to determine kthread name */
2800 id = ida_alloc(&pool->worker_ida, GFP_KERNEL);
2801 if (id < 0) {
2802 pr_err_once("workqueue: Failed to allocate a worker ID: %pe\n",
2803 ERR_PTR(id));
2804 return NULL;
2805 }
2806
2807 worker = alloc_worker(pool->node);
2808 if (!worker) {
2809 pr_err_once("workqueue: Failed to allocate a worker\n");
2810 goto fail;
2811 }
2812
2813 worker->id = id;
2814
2815 if (!(pool->flags & POOL_BH)) {
2816 if (pool->cpu >= 0)
2817 snprintf(id_buf, sizeof(id_buf), "%d:%d%s", pool->cpu, id,
2818 pool->attrs->nice < 0 ? "H" : "");
2819 else
2820 snprintf(id_buf, sizeof(id_buf), "u%d:%d", pool->id, id);
2821
2822 worker->task = kthread_create_on_node(worker_thread, worker,
2823 pool->node, "kworker/%s", id_buf);
2824 if (IS_ERR(worker->task)) {
2825 if (PTR_ERR(worker->task) == -EINTR) {
2826 pr_err("workqueue: Interrupted when creating a worker thread \"kworker/%s\"\n",
2827 id_buf);
2828 } else {
2829 pr_err_once("workqueue: Failed to create a worker thread: %pe",
2830 worker->task);
2831 }
2832 goto fail;
2833 }
2834
2835 set_user_nice(worker->task, pool->attrs->nice);
2836 kthread_bind_mask(worker->task, pool_allowed_cpus(pool));
2837 }
2838
2839 /* successful, attach the worker to the pool */
2840 worker_attach_to_pool(worker, pool);
2841
2842 /* start the newly created worker */
2843 raw_spin_lock_irq(&pool->lock);
2844
2845 worker->pool->nr_workers++;
2846 worker_enter_idle(worker);
2847
2848 /*
2849 * @worker is waiting on a completion in kthread() and will trigger hung
2850 * check if not woken up soon. As kick_pool() is noop if @pool is empty,
2851 * wake it up explicitly.
2852 */
2853 if (worker->task)
2854 wake_up_process(worker->task);
2855
2856 raw_spin_unlock_irq(&pool->lock);
2857
2858 return worker;
2859
2860fail:
2861 ida_free(&pool->worker_ida, id);
2862 kfree(worker);
2863 return NULL;
2864}
2865
2866static void unbind_worker(struct worker *worker)
2867{
2868 lockdep_assert_held(&wq_pool_attach_mutex);
2869
2870 kthread_set_per_cpu(worker->task, -1);
2871 if (cpumask_intersects(wq_unbound_cpumask, cpu_active_mask))
2872 WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task, wq_unbound_cpumask) < 0);
2873 else
2874 WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task, cpu_possible_mask) < 0);
2875}
2876
2877static void wake_dying_workers(struct list_head *cull_list)
2878{
2879 struct worker *worker, *tmp;
2880
2881 list_for_each_entry_safe(worker, tmp, cull_list, entry) {
2882 list_del_init(&worker->entry);
2883 unbind_worker(worker);
2884 /*
2885 * If the worker was somehow already running, then it had to be
2886 * in pool->idle_list when set_worker_dying() happened or we
2887 * wouldn't have gotten here.
2888 *
2889 * Thus, the worker must either have observed the WORKER_DIE
2890 * flag, or have set its state to TASK_IDLE. Either way, the
2891 * below will be observed by the worker and is safe to do
2892 * outside of pool->lock.
2893 */
2894 wake_up_process(worker->task);
2895 }
2896}
2897
2898/**
2899 * set_worker_dying - Tag a worker for destruction
2900 * @worker: worker to be destroyed
2901 * @list: transfer worker away from its pool->idle_list and into list
2902 *
2903 * Tag @worker for destruction and adjust @pool stats accordingly. The worker
2904 * should be idle.
2905 *
2906 * CONTEXT:
2907 * raw_spin_lock_irq(pool->lock).
2908 */
2909static void set_worker_dying(struct worker *worker, struct list_head *list)
2910{
2911 struct worker_pool *pool = worker->pool;
2912
2913 lockdep_assert_held(&pool->lock);
2914 lockdep_assert_held(&wq_pool_attach_mutex);
2915
2916 /* sanity check frenzy */
2917 if (WARN_ON(worker->current_work) ||
2918 WARN_ON(!list_empty(&worker->scheduled)) ||
2919 WARN_ON(!(worker->flags & WORKER_IDLE)))
2920 return;
2921
2922 pool->nr_workers--;
2923 pool->nr_idle--;
2924
2925 worker->flags |= WORKER_DIE;
2926
2927 list_move(&worker->entry, list);
2928 list_move(&worker->node, &pool->dying_workers);
2929}
2930
2931/**
2932 * idle_worker_timeout - check if some idle workers can now be deleted.
2933 * @t: The pool's idle_timer that just expired
2934 *
2935 * The timer is armed in worker_enter_idle(). Note that it isn't disarmed in
2936 * worker_leave_idle(), as a worker flicking between idle and active while its
2937 * pool is at the too_many_workers() tipping point would cause too much timer
2938 * housekeeping overhead. Since IDLE_WORKER_TIMEOUT is long enough, we just let
2939 * it expire and re-evaluate things from there.
2940 */
2941static void idle_worker_timeout(struct timer_list *t)
2942{
2943 struct worker_pool *pool = from_timer(pool, t, idle_timer);
2944 bool do_cull = false;
2945
2946 if (work_pending(&pool->idle_cull_work))
2947 return;
2948
2949 raw_spin_lock_irq(&pool->lock);
2950
2951 if (too_many_workers(pool)) {
2952 struct worker *worker;
2953 unsigned long expires;
2954
2955 /* idle_list is kept in LIFO order, check the last one */
2956 worker = list_entry(pool->idle_list.prev, struct worker, entry);
2957 expires = worker->last_active + IDLE_WORKER_TIMEOUT;
2958 do_cull = !time_before(jiffies, expires);
2959
2960 if (!do_cull)
2961 mod_timer(&pool->idle_timer, expires);
2962 }
2963 raw_spin_unlock_irq(&pool->lock);
2964
2965 if (do_cull)
2966 queue_work(system_unbound_wq, &pool->idle_cull_work);
2967}
2968
2969/**
2970 * idle_cull_fn - cull workers that have been idle for too long.
2971 * @work: the pool's work for handling these idle workers
2972 *
2973 * This goes through a pool's idle workers and gets rid of those that have been
2974 * idle for at least IDLE_WORKER_TIMEOUT seconds.
2975 *
2976 * We don't want to disturb isolated CPUs because of a pcpu kworker being
2977 * culled, so this also resets worker affinity. This requires a sleepable
2978 * context, hence the split between timer callback and work item.
2979 */
2980static void idle_cull_fn(struct work_struct *work)
2981{
2982 struct worker_pool *pool = container_of(work, struct worker_pool, idle_cull_work);
2983 LIST_HEAD(cull_list);
2984
2985 /*
2986 * Grabbing wq_pool_attach_mutex here ensures an already-running worker
2987 * cannot proceed beyong worker_detach_from_pool() in its self-destruct
2988 * path. This is required as a previously-preempted worker could run after
2989 * set_worker_dying() has happened but before wake_dying_workers() did.
2990 */
2991 mutex_lock(&wq_pool_attach_mutex);
2992 raw_spin_lock_irq(&pool->lock);
2993
2994 while (too_many_workers(pool)) {
2995 struct worker *worker;
2996 unsigned long expires;
2997
2998 worker = list_entry(pool->idle_list.prev, struct worker, entry);
2999 expires = worker->last_active + IDLE_WORKER_TIMEOUT;
3000
3001 if (time_before(jiffies, expires)) {
3002 mod_timer(&pool->idle_timer, expires);
3003 break;
3004 }
3005
3006 set_worker_dying(worker, &cull_list);
3007 }
3008
3009 raw_spin_unlock_irq(&pool->lock);
3010 wake_dying_workers(&cull_list);
3011 mutex_unlock(&wq_pool_attach_mutex);
3012}
3013
3014static void send_mayday(struct work_struct *work)
3015{
3016 struct pool_workqueue *pwq = get_work_pwq(work);
3017 struct workqueue_struct *wq = pwq->wq;
3018
3019 lockdep_assert_held(&wq_mayday_lock);
3020
3021 if (!wq->rescuer)
3022 return;
3023
3024 /* mayday mayday mayday */
3025 if (list_empty(&pwq->mayday_node)) {
3026 /*
3027 * If @pwq is for an unbound wq, its base ref may be put at
3028 * any time due to an attribute change. Pin @pwq until the
3029 * rescuer is done with it.
3030 */
3031 get_pwq(pwq);
3032 list_add_tail(&pwq->mayday_node, &wq->maydays);
3033 wake_up_process(wq->rescuer->task);
3034 pwq->stats[PWQ_STAT_MAYDAY]++;
3035 }
3036}
3037
3038static void pool_mayday_timeout(struct timer_list *t)
3039{
3040 struct worker_pool *pool = from_timer(pool, t, mayday_timer);
3041 struct work_struct *work;
3042
3043 raw_spin_lock_irq(&pool->lock);
3044 raw_spin_lock(&wq_mayday_lock); /* for wq->maydays */
3045
3046 if (need_to_create_worker(pool)) {
3047 /*
3048 * We've been trying to create a new worker but
3049 * haven't been successful. We might be hitting an
3050 * allocation deadlock. Send distress signals to
3051 * rescuers.
3052 */
3053 list_for_each_entry(work, &pool->worklist, entry)
3054 send_mayday(work);
3055 }
3056
3057 raw_spin_unlock(&wq_mayday_lock);
3058 raw_spin_unlock_irq(&pool->lock);
3059
3060 mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INTERVAL);
3061}
3062
3063/**
3064 * maybe_create_worker - create a new worker if necessary
3065 * @pool: pool to create a new worker for
3066 *
3067 * Create a new worker for @pool if necessary. @pool is guaranteed to
3068 * have at least one idle worker on return from this function. If
3069 * creating a new worker takes longer than MAYDAY_INTERVAL, mayday is
3070 * sent to all rescuers with works scheduled on @pool to resolve
3071 * possible allocation deadlock.
3072 *
3073 * On return, need_to_create_worker() is guaranteed to be %false and
3074 * may_start_working() %true.
3075 *
3076 * LOCKING:
3077 * raw_spin_lock_irq(pool->lock) which may be released and regrabbed
3078 * multiple times. Does GFP_KERNEL allocations. Called only from
3079 * manager.
3080 */
3081static void maybe_create_worker(struct worker_pool *pool)
3082__releases(&pool->lock)
3083__acquires(&pool->lock)
3084{
3085restart:
3086 raw_spin_unlock_irq(&pool->lock);
3087
3088 /* if we don't make progress in MAYDAY_INITIAL_TIMEOUT, call for help */
3089 mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INITIAL_TIMEOUT);
3090
3091 while (true) {
3092 if (create_worker(pool) || !need_to_create_worker(pool))
3093 break;
3094
3095 schedule_timeout_interruptible(CREATE_COOLDOWN);
3096
3097 if (!need_to_create_worker(pool))
3098 break;
3099 }
3100
3101 del_timer_sync(&pool->mayday_timer);
3102 raw_spin_lock_irq(&pool->lock);
3103 /*
3104 * This is necessary even after a new worker was just successfully
3105 * created as @pool->lock was dropped and the new worker might have
3106 * already become busy.
3107 */
3108 if (need_to_create_worker(pool))
3109 goto restart;
3110}
3111
3112/**
3113 * manage_workers - manage worker pool
3114 * @worker: self
3115 *
3116 * Assume the manager role and manage the worker pool @worker belongs
3117 * to. At any given time, there can be only zero or one manager per
3118 * pool. The exclusion is handled automatically by this function.
3119 *
3120 * The caller can safely start processing works on false return. On
3121 * true return, it's guaranteed that need_to_create_worker() is false
3122 * and may_start_working() is true.
3123 *
3124 * CONTEXT:
3125 * raw_spin_lock_irq(pool->lock) which may be released and regrabbed
3126 * multiple times. Does GFP_KERNEL allocations.
3127 *
3128 * Return:
3129 * %false if the pool doesn't need management and the caller can safely
3130 * start processing works, %true if management function was performed and
3131 * the conditions that the caller verified before calling the function may
3132 * no longer be true.
3133 */
3134static bool manage_workers(struct worker *worker)
3135{
3136 struct worker_pool *pool = worker->pool;
3137
3138 if (pool->flags & POOL_MANAGER_ACTIVE)
3139 return false;
3140
3141 pool->flags |= POOL_MANAGER_ACTIVE;
3142 pool->manager = worker;
3143
3144 maybe_create_worker(pool);
3145
3146 pool->manager = NULL;
3147 pool->flags &= ~POOL_MANAGER_ACTIVE;
3148 rcuwait_wake_up(&manager_wait);
3149 return true;
3150}
3151
3152/**
3153 * process_one_work - process single work
3154 * @worker: self
3155 * @work: work to process
3156 *
3157 * Process @work. This function contains all the logics necessary to
3158 * process a single work including synchronization against and
3159 * interaction with other workers on the same cpu, queueing and
3160 * flushing. As long as context requirement is met, any worker can
3161 * call this function to process a work.
3162 *
3163 * CONTEXT:
3164 * raw_spin_lock_irq(pool->lock) which is released and regrabbed.
3165 */
3166static void process_one_work(struct worker *worker, struct work_struct *work)
3167__releases(&pool->lock)
3168__acquires(&pool->lock)
3169{
3170 struct pool_workqueue *pwq = get_work_pwq(work);
3171 struct worker_pool *pool = worker->pool;
3172 unsigned long work_data;
3173 int lockdep_start_depth, rcu_start_depth;
3174 bool bh_draining = pool->flags & POOL_BH_DRAINING;
3175#ifdef CONFIG_LOCKDEP
3176 /*
3177 * It is permissible to free the struct work_struct from
3178 * inside the function that is called from it, this we need to
3179 * take into account for lockdep too. To avoid bogus "held
3180 * lock freed" warnings as well as problems when looking into
3181 * work->lockdep_map, make a copy and use that here.
3182 */
3183 struct lockdep_map lockdep_map;
3184
3185 lockdep_copy_map(&lockdep_map, &work->lockdep_map);
3186#endif
3187 /* ensure we're on the correct CPU */
3188 WARN_ON_ONCE(!(pool->flags & POOL_DISASSOCIATED) &&
3189 raw_smp_processor_id() != pool->cpu);
3190
3191 /* claim and dequeue */
3192 debug_work_deactivate(work);
3193 hash_add(pool->busy_hash, &worker->hentry, (unsigned long)work);
3194 worker->current_work = work;
3195 worker->current_func = work->func;
3196 worker->current_pwq = pwq;
3197 if (worker->task)
3198 worker->current_at = worker->task->se.sum_exec_runtime;
3199 work_data = *work_data_bits(work);
3200 worker->current_color = get_work_color(work_data);
3201
3202 /*
3203 * Record wq name for cmdline and debug reporting, may get
3204 * overridden through set_worker_desc().
3205 */
3206 strscpy(worker->desc, pwq->wq->name, WORKER_DESC_LEN);
3207
3208 list_del_init(&work->entry);
3209
3210 /*
3211 * CPU intensive works don't participate in concurrency management.
3212 * They're the scheduler's responsibility. This takes @worker out
3213 * of concurrency management and the next code block will chain
3214 * execution of the pending work items.
3215 */
3216 if (unlikely(pwq->wq->flags & WQ_CPU_INTENSIVE))
3217 worker_set_flags(worker, WORKER_CPU_INTENSIVE);
3218
3219 /*
3220 * Kick @pool if necessary. It's always noop for per-cpu worker pools
3221 * since nr_running would always be >= 1 at this point. This is used to
3222 * chain execution of the pending work items for WORKER_NOT_RUNNING
3223 * workers such as the UNBOUND and CPU_INTENSIVE ones.
3224 */
3225 kick_pool(pool);
3226
3227 /*
3228 * Record the last pool and clear PENDING which should be the last
3229 * update to @work. Also, do this inside @pool->lock so that
3230 * PENDING and queued state changes happen together while IRQ is
3231 * disabled.
3232 */
3233 set_work_pool_and_clear_pending(work, pool->id, 0);
3234
3235 pwq->stats[PWQ_STAT_STARTED]++;
3236 raw_spin_unlock_irq(&pool->lock);
3237
3238 rcu_start_depth = rcu_preempt_depth();
3239 lockdep_start_depth = lockdep_depth(current);
3240 /* see drain_dead_softirq_workfn() */
3241 if (!bh_draining)
3242 lock_map_acquire(&pwq->wq->lockdep_map);
3243 lock_map_acquire(&lockdep_map);
3244 /*
3245 * Strictly speaking we should mark the invariant state without holding
3246 * any locks, that is, before these two lock_map_acquire()'s.
3247 *
3248 * However, that would result in:
3249 *
3250 * A(W1)
3251 * WFC(C)
3252 * A(W1)
3253 * C(C)
3254 *
3255 * Which would create W1->C->W1 dependencies, even though there is no
3256 * actual deadlock possible. There are two solutions, using a
3257 * read-recursive acquire on the work(queue) 'locks', but this will then
3258 * hit the lockdep limitation on recursive locks, or simply discard
3259 * these locks.
3260 *
3261 * AFAICT there is no possible deadlock scenario between the
3262 * flush_work() and complete() primitives (except for single-threaded
3263 * workqueues), so hiding them isn't a problem.
3264 */
3265 lockdep_invariant_state(true);
3266 trace_workqueue_execute_start(work);
3267 worker->current_func(work);
3268 /*
3269 * While we must be careful to not use "work" after this, the trace
3270 * point will only record its address.
3271 */
3272 trace_workqueue_execute_end(work, worker->current_func);
3273 pwq->stats[PWQ_STAT_COMPLETED]++;
3274 lock_map_release(&lockdep_map);
3275 if (!bh_draining)
3276 lock_map_release(&pwq->wq->lockdep_map);
3277
3278 if (unlikely((worker->task && in_atomic()) ||
3279 lockdep_depth(current) != lockdep_start_depth ||
3280 rcu_preempt_depth() != rcu_start_depth)) {
3281 pr_err("BUG: workqueue leaked atomic, lock or RCU: %s[%d]\n"
3282 " preempt=0x%08x lock=%d->%d RCU=%d->%d workfn=%ps\n",
3283 current->comm, task_pid_nr(current), preempt_count(),
3284 lockdep_start_depth, lockdep_depth(current),
3285 rcu_start_depth, rcu_preempt_depth(),
3286 worker->current_func);
3287 debug_show_held_locks(current);
3288 dump_stack();
3289 }
3290
3291 /*
3292 * The following prevents a kworker from hogging CPU on !PREEMPTION
3293 * kernels, where a requeueing work item waiting for something to
3294 * happen could deadlock with stop_machine as such work item could
3295 * indefinitely requeue itself while all other CPUs are trapped in
3296 * stop_machine. At the same time, report a quiescent RCU state so
3297 * the same condition doesn't freeze RCU.
3298 */
3299 if (worker->task)
3300 cond_resched();
3301
3302 raw_spin_lock_irq(&pool->lock);
3303
3304 /*
3305 * In addition to %WQ_CPU_INTENSIVE, @worker may also have been marked
3306 * CPU intensive by wq_worker_tick() if @work hogged CPU longer than
3307 * wq_cpu_intensive_thresh_us. Clear it.
3308 */
3309 worker_clr_flags(worker, WORKER_CPU_INTENSIVE);
3310
3311 /* tag the worker for identification in schedule() */
3312 worker->last_func = worker->current_func;
3313
3314 /* we're done with it, release */
3315 hash_del(&worker->hentry);
3316 worker->current_work = NULL;
3317 worker->current_func = NULL;
3318 worker->current_pwq = NULL;
3319 worker->current_color = INT_MAX;
3320
3321 /* must be the last step, see the function comment */
3322 pwq_dec_nr_in_flight(pwq, work_data);
3323}
3324
3325/**
3326 * process_scheduled_works - process scheduled works
3327 * @worker: self
3328 *
3329 * Process all scheduled works. Please note that the scheduled list
3330 * may change while processing a work, so this function repeatedly
3331 * fetches a work from the top and executes it.
3332 *
3333 * CONTEXT:
3334 * raw_spin_lock_irq(pool->lock) which may be released and regrabbed
3335 * multiple times.
3336 */
3337static void process_scheduled_works(struct worker *worker)
3338{
3339 struct work_struct *work;
3340 bool first = true;
3341
3342 while ((work = list_first_entry_or_null(&worker->scheduled,
3343 struct work_struct, entry))) {
3344 if (first) {
3345 worker->pool->watchdog_ts = jiffies;
3346 first = false;
3347 }
3348 process_one_work(worker, work);
3349 }
3350}
3351
3352static void set_pf_worker(bool val)
3353{
3354 mutex_lock(&wq_pool_attach_mutex);
3355 if (val)
3356 current->flags |= PF_WQ_WORKER;
3357 else
3358 current->flags &= ~PF_WQ_WORKER;
3359 mutex_unlock(&wq_pool_attach_mutex);
3360}
3361
3362/**
3363 * worker_thread - the worker thread function
3364 * @__worker: self
3365 *
3366 * The worker thread function. All workers belong to a worker_pool -
3367 * either a per-cpu one or dynamic unbound one. These workers process all
3368 * work items regardless of their specific target workqueue. The only
3369 * exception is work items which belong to workqueues with a rescuer which
3370 * will be explained in rescuer_thread().
3371 *
3372 * Return: 0
3373 */
3374static int worker_thread(void *__worker)
3375{
3376 struct worker *worker = __worker;
3377 struct worker_pool *pool = worker->pool;
3378
3379 /* tell the scheduler that this is a workqueue worker */
3380 set_pf_worker(true);
3381woke_up:
3382 raw_spin_lock_irq(&pool->lock);
3383
3384 /* am I supposed to die? */
3385 if (unlikely(worker->flags & WORKER_DIE)) {
3386 raw_spin_unlock_irq(&pool->lock);
3387 set_pf_worker(false);
3388
3389 set_task_comm(worker->task, "kworker/dying");
3390 ida_free(&pool->worker_ida, worker->id);
3391 worker_detach_from_pool(worker);
3392 WARN_ON_ONCE(!list_empty(&worker->entry));
3393 kfree(worker);
3394 return 0;
3395 }
3396
3397 worker_leave_idle(worker);
3398recheck:
3399 /* no more worker necessary? */
3400 if (!need_more_worker(pool))
3401 goto sleep;
3402
3403 /* do we need to manage? */
3404 if (unlikely(!may_start_working(pool)) && manage_workers(worker))
3405 goto recheck;
3406
3407 /*
3408 * ->scheduled list can only be filled while a worker is
3409 * preparing to process a work or actually processing it.
3410 * Make sure nobody diddled with it while I was sleeping.
3411 */
3412 WARN_ON_ONCE(!list_empty(&worker->scheduled));
3413
3414 /*
3415 * Finish PREP stage. We're guaranteed to have at least one idle
3416 * worker or that someone else has already assumed the manager
3417 * role. This is where @worker starts participating in concurrency
3418 * management if applicable and concurrency management is restored
3419 * after being rebound. See rebind_workers() for details.
3420 */
3421 worker_clr_flags(worker, WORKER_PREP | WORKER_REBOUND);
3422
3423 do {
3424 struct work_struct *work =
3425 list_first_entry(&pool->worklist,
3426 struct work_struct, entry);
3427
3428 if (assign_work(work, worker, NULL))
3429 process_scheduled_works(worker);
3430 } while (keep_working(pool));
3431
3432 worker_set_flags(worker, WORKER_PREP);
3433sleep:
3434 /*
3435 * pool->lock is held and there's no work to process and no need to
3436 * manage, sleep. Workers are woken up only while holding
3437 * pool->lock or from local cpu, so setting the current state
3438 * before releasing pool->lock is enough to prevent losing any
3439 * event.
3440 */
3441 worker_enter_idle(worker);
3442 __set_current_state(TASK_IDLE);
3443 raw_spin_unlock_irq(&pool->lock);
3444 schedule();
3445 goto woke_up;
3446}
3447
3448/**
3449 * rescuer_thread - the rescuer thread function
3450 * @__rescuer: self
3451 *
3452 * Workqueue rescuer thread function. There's one rescuer for each
3453 * workqueue which has WQ_MEM_RECLAIM set.
3454 *
3455 * Regular work processing on a pool may block trying to create a new
3456 * worker which uses GFP_KERNEL allocation which has slight chance of
3457 * developing into deadlock if some works currently on the same queue
3458 * need to be processed to satisfy the GFP_KERNEL allocation. This is
3459 * the problem rescuer solves.
3460 *
3461 * When such condition is possible, the pool summons rescuers of all
3462 * workqueues which have works queued on the pool and let them process
3463 * those works so that forward progress can be guaranteed.
3464 *
3465 * This should happen rarely.
3466 *
3467 * Return: 0
3468 */
3469static int rescuer_thread(void *__rescuer)
3470{
3471 struct worker *rescuer = __rescuer;
3472 struct workqueue_struct *wq = rescuer->rescue_wq;
3473 bool should_stop;
3474
3475 set_user_nice(current, RESCUER_NICE_LEVEL);
3476
3477 /*
3478 * Mark rescuer as worker too. As WORKER_PREP is never cleared, it
3479 * doesn't participate in concurrency management.
3480 */
3481 set_pf_worker(true);
3482repeat:
3483 set_current_state(TASK_IDLE);
3484
3485 /*
3486 * By the time the rescuer is requested to stop, the workqueue
3487 * shouldn't have any work pending, but @wq->maydays may still have
3488 * pwq(s) queued. This can happen by non-rescuer workers consuming
3489 * all the work items before the rescuer got to them. Go through
3490 * @wq->maydays processing before acting on should_stop so that the
3491 * list is always empty on exit.
3492 */
3493 should_stop = kthread_should_stop();
3494
3495 /* see whether any pwq is asking for help */
3496 raw_spin_lock_irq(&wq_mayday_lock);
3497
3498 while (!list_empty(&wq->maydays)) {
3499 struct pool_workqueue *pwq = list_first_entry(&wq->maydays,
3500 struct pool_workqueue, mayday_node);
3501 struct worker_pool *pool = pwq->pool;
3502 struct work_struct *work, *n;
3503
3504 __set_current_state(TASK_RUNNING);
3505 list_del_init(&pwq->mayday_node);
3506
3507 raw_spin_unlock_irq(&wq_mayday_lock);
3508
3509 worker_attach_to_pool(rescuer, pool);
3510
3511 raw_spin_lock_irq(&pool->lock);
3512
3513 /*
3514 * Slurp in all works issued via this workqueue and
3515 * process'em.
3516 */
3517 WARN_ON_ONCE(!list_empty(&rescuer->scheduled));
3518 list_for_each_entry_safe(work, n, &pool->worklist, entry) {
3519 if (get_work_pwq(work) == pwq &&
3520 assign_work(work, rescuer, &n))
3521 pwq->stats[PWQ_STAT_RESCUED]++;
3522 }
3523
3524 if (!list_empty(&rescuer->scheduled)) {
3525 process_scheduled_works(rescuer);
3526
3527 /*
3528 * The above execution of rescued work items could
3529 * have created more to rescue through
3530 * pwq_activate_first_inactive() or chained
3531 * queueing. Let's put @pwq back on mayday list so
3532 * that such back-to-back work items, which may be
3533 * being used to relieve memory pressure, don't
3534 * incur MAYDAY_INTERVAL delay inbetween.
3535 */
3536 if (pwq->nr_active && need_to_create_worker(pool)) {
3537 raw_spin_lock(&wq_mayday_lock);
3538 /*
3539 * Queue iff we aren't racing destruction
3540 * and somebody else hasn't queued it already.
3541 */
3542 if (wq->rescuer && list_empty(&pwq->mayday_node)) {
3543 get_pwq(pwq);
3544 list_add_tail(&pwq->mayday_node, &wq->maydays);
3545 }
3546 raw_spin_unlock(&wq_mayday_lock);
3547 }
3548 }
3549
3550 /*
3551 * Put the reference grabbed by send_mayday(). @pool won't
3552 * go away while we're still attached to it.
3553 */
3554 put_pwq(pwq);
3555
3556 /*
3557 * Leave this pool. Notify regular workers; otherwise, we end up
3558 * with 0 concurrency and stalling the execution.
3559 */
3560 kick_pool(pool);
3561
3562 raw_spin_unlock_irq(&pool->lock);
3563
3564 worker_detach_from_pool(rescuer);
3565
3566 raw_spin_lock_irq(&wq_mayday_lock);
3567 }
3568
3569 raw_spin_unlock_irq(&wq_mayday_lock);
3570
3571 if (should_stop) {
3572 __set_current_state(TASK_RUNNING);
3573 set_pf_worker(false);
3574 return 0;
3575 }
3576
3577 /* rescuers should never participate in concurrency management */
3578 WARN_ON_ONCE(!(rescuer->flags & WORKER_NOT_RUNNING));
3579 schedule();
3580 goto repeat;
3581}
3582
3583static void bh_worker(struct worker *worker)
3584{
3585 struct worker_pool *pool = worker->pool;
3586 int nr_restarts = BH_WORKER_RESTARTS;
3587 unsigned long end = jiffies + BH_WORKER_JIFFIES;
3588
3589 raw_spin_lock_irq(&pool->lock);
3590 worker_leave_idle(worker);
3591
3592 /*
3593 * This function follows the structure of worker_thread(). See there for
3594 * explanations on each step.
3595 */
3596 if (!need_more_worker(pool))
3597 goto done;
3598
3599 WARN_ON_ONCE(!list_empty(&worker->scheduled));
3600 worker_clr_flags(worker, WORKER_PREP | WORKER_REBOUND);
3601
3602 do {
3603 struct work_struct *work =
3604 list_first_entry(&pool->worklist,
3605 struct work_struct, entry);
3606
3607 if (assign_work(work, worker, NULL))
3608 process_scheduled_works(worker);
3609 } while (keep_working(pool) &&
3610 --nr_restarts && time_before(jiffies, end));
3611
3612 worker_set_flags(worker, WORKER_PREP);
3613done:
3614 worker_enter_idle(worker);
3615 kick_pool(pool);
3616 raw_spin_unlock_irq(&pool->lock);
3617}
3618
3619/*
3620 * TODO: Convert all tasklet users to workqueue and use softirq directly.
3621 *
3622 * This is currently called from tasklet[_hi]action() and thus is also called
3623 * whenever there are tasklets to run. Let's do an early exit if there's nothing
3624 * queued. Once conversion from tasklet is complete, the need_more_worker() test
3625 * can be dropped.
3626 *
3627 * After full conversion, we'll add worker->softirq_action, directly use the
3628 * softirq action and obtain the worker pointer from the softirq_action pointer.
3629 */
3630void workqueue_softirq_action(bool highpri)
3631{
3632 struct worker_pool *pool =
3633 &per_cpu(bh_worker_pools, smp_processor_id())[highpri];
3634 if (need_more_worker(pool))
3635 bh_worker(list_first_entry(&pool->workers, struct worker, node));
3636}
3637
3638struct wq_drain_dead_softirq_work {
3639 struct work_struct work;
3640 struct worker_pool *pool;
3641 struct completion done;
3642};
3643
3644static void drain_dead_softirq_workfn(struct work_struct *work)
3645{
3646 struct wq_drain_dead_softirq_work *dead_work =
3647 container_of(work, struct wq_drain_dead_softirq_work, work);
3648 struct worker_pool *pool = dead_work->pool;
3649 bool repeat;
3650
3651 /*
3652 * @pool's CPU is dead and we want to execute its still pending work
3653 * items from this BH work item which is running on a different CPU. As
3654 * its CPU is dead, @pool can't be kicked and, as work execution path
3655 * will be nested, a lockdep annotation needs to be suppressed. Mark
3656 * @pool with %POOL_BH_DRAINING for the special treatments.
3657 */
3658 raw_spin_lock_irq(&pool->lock);
3659 pool->flags |= POOL_BH_DRAINING;
3660 raw_spin_unlock_irq(&pool->lock);
3661
3662 bh_worker(list_first_entry(&pool->workers, struct worker, node));
3663
3664 raw_spin_lock_irq(&pool->lock);
3665 pool->flags &= ~POOL_BH_DRAINING;
3666 repeat = need_more_worker(pool);
3667 raw_spin_unlock_irq(&pool->lock);
3668
3669 /*
3670 * bh_worker() might hit consecutive execution limit and bail. If there
3671 * still are pending work items, reschedule self and return so that we
3672 * don't hog this CPU's BH.
3673 */
3674 if (repeat) {
3675 if (pool->attrs->nice == HIGHPRI_NICE_LEVEL)
3676 queue_work(system_bh_highpri_wq, work);
3677 else
3678 queue_work(system_bh_wq, work);
3679 } else {
3680 complete(&dead_work->done);
3681 }
3682}
3683
3684/*
3685 * @cpu is dead. Drain the remaining BH work items on the current CPU. It's
3686 * possible to allocate dead_work per CPU and avoid flushing. However, then we
3687 * have to worry about draining overlapping with CPU coming back online or
3688 * nesting (one CPU's dead_work queued on another CPU which is also dead and so
3689 * on). Let's keep it simple and drain them synchronously. These are BH work
3690 * items which shouldn't be requeued on the same pool. Shouldn't take long.
3691 */
3692void workqueue_softirq_dead(unsigned int cpu)
3693{
3694 int i;
3695
3696 for (i = 0; i < NR_STD_WORKER_POOLS; i++) {
3697 struct worker_pool *pool = &per_cpu(bh_worker_pools, cpu)[i];
3698 struct wq_drain_dead_softirq_work dead_work;
3699
3700 if (!need_more_worker(pool))
3701 continue;
3702
3703 INIT_WORK(&dead_work.work, drain_dead_softirq_workfn);
3704 dead_work.pool = pool;
3705 init_completion(&dead_work.done);
3706
3707 if (pool->attrs->nice == HIGHPRI_NICE_LEVEL)
3708 queue_work(system_bh_highpri_wq, &dead_work.work);
3709 else
3710 queue_work(system_bh_wq, &dead_work.work);
3711
3712 wait_for_completion(&dead_work.done);
3713 }
3714}
3715
3716/**
3717 * check_flush_dependency - check for flush dependency sanity
3718 * @target_wq: workqueue being flushed
3719 * @target_work: work item being flushed (NULL for workqueue flushes)
3720 *
3721 * %current is trying to flush the whole @target_wq or @target_work on it.
3722 * If @target_wq doesn't have %WQ_MEM_RECLAIM, verify that %current is not
3723 * reclaiming memory or running on a workqueue which doesn't have
3724 * %WQ_MEM_RECLAIM as that can break forward-progress guarantee leading to
3725 * a deadlock.
3726 */
3727static void check_flush_dependency(struct workqueue_struct *target_wq,
3728 struct work_struct *target_work)
3729{
3730 work_func_t target_func = target_work ? target_work->func : NULL;
3731 struct worker *worker;
3732
3733 if (target_wq->flags & WQ_MEM_RECLAIM)
3734 return;
3735
3736 worker = current_wq_worker();
3737
3738 WARN_ONCE(current->flags & PF_MEMALLOC,
3739 "workqueue: PF_MEMALLOC task %d(%s) is flushing !WQ_MEM_RECLAIM %s:%ps",
3740 current->pid, current->comm, target_wq->name, target_func);
3741 WARN_ONCE(worker && ((worker->current_pwq->wq->flags &
3742 (WQ_MEM_RECLAIM | __WQ_LEGACY)) == WQ_MEM_RECLAIM),
3743 "workqueue: WQ_MEM_RECLAIM %s:%ps is flushing !WQ_MEM_RECLAIM %s:%ps",
3744 worker->current_pwq->wq->name, worker->current_func,
3745 target_wq->name, target_func);
3746}
3747
3748struct wq_barrier {
3749 struct work_struct work;
3750 struct completion done;
3751 struct task_struct *task; /* purely informational */
3752};
3753
3754static void wq_barrier_func(struct work_struct *work)
3755{
3756 struct wq_barrier *barr = container_of(work, struct wq_barrier, work);
3757 complete(&barr->done);
3758}
3759
3760/**
3761 * insert_wq_barrier - insert a barrier work
3762 * @pwq: pwq to insert barrier into
3763 * @barr: wq_barrier to insert
3764 * @target: target work to attach @barr to
3765 * @worker: worker currently executing @target, NULL if @target is not executing
3766 *
3767 * @barr is linked to @target such that @barr is completed only after
3768 * @target finishes execution. Please note that the ordering
3769 * guarantee is observed only with respect to @target and on the local
3770 * cpu.
3771 *
3772 * Currently, a queued barrier can't be canceled. This is because
3773 * try_to_grab_pending() can't determine whether the work to be
3774 * grabbed is at the head of the queue and thus can't clear LINKED
3775 * flag of the previous work while there must be a valid next work
3776 * after a work with LINKED flag set.
3777 *
3778 * Note that when @worker is non-NULL, @target may be modified
3779 * underneath us, so we can't reliably determine pwq from @target.
3780 *
3781 * CONTEXT:
3782 * raw_spin_lock_irq(pool->lock).
3783 */
3784static void insert_wq_barrier(struct pool_workqueue *pwq,
3785 struct wq_barrier *barr,
3786 struct work_struct *target, struct worker *worker)
3787{
3788 static __maybe_unused struct lock_class_key bh_key, thr_key;
3789 unsigned int work_flags = 0;
3790 unsigned int work_color;
3791 struct list_head *head;
3792
3793 /*
3794 * debugobject calls are safe here even with pool->lock locked
3795 * as we know for sure that this will not trigger any of the
3796 * checks and call back into the fixup functions where we
3797 * might deadlock.
3798 *
3799 * BH and threaded workqueues need separate lockdep keys to avoid
3800 * spuriously triggering "inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W}
3801 * usage".
3802 */
3803 INIT_WORK_ONSTACK_KEY(&barr->work, wq_barrier_func,
3804 (pwq->wq->flags & WQ_BH) ? &bh_key : &thr_key);
3805 __set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(&barr->work));
3806
3807 init_completion_map(&barr->done, &target->lockdep_map);
3808
3809 barr->task = current;
3810
3811 /* The barrier work item does not participate in nr_active. */
3812 work_flags |= WORK_STRUCT_INACTIVE;
3813
3814 /*
3815 * If @target is currently being executed, schedule the
3816 * barrier to the worker; otherwise, put it after @target.
3817 */
3818 if (worker) {
3819 head = worker->scheduled.next;
3820 work_color = worker->current_color;
3821 } else {
3822 unsigned long *bits = work_data_bits(target);
3823
3824 head = target->entry.next;
3825 /* there can already be other linked works, inherit and set */
3826 work_flags |= *bits & WORK_STRUCT_LINKED;
3827 work_color = get_work_color(*bits);
3828 __set_bit(WORK_STRUCT_LINKED_BIT, bits);
3829 }
3830
3831 pwq->nr_in_flight[work_color]++;
3832 work_flags |= work_color_to_flags(work_color);
3833
3834 insert_work(pwq, &barr->work, head, work_flags);
3835}
3836
3837/**
3838 * flush_workqueue_prep_pwqs - prepare pwqs for workqueue flushing
3839 * @wq: workqueue being flushed
3840 * @flush_color: new flush color, < 0 for no-op
3841 * @work_color: new work color, < 0 for no-op
3842 *
3843 * Prepare pwqs for workqueue flushing.
3844 *
3845 * If @flush_color is non-negative, flush_color on all pwqs should be
3846 * -1. If no pwq has in-flight commands at the specified color, all
3847 * pwq->flush_color's stay at -1 and %false is returned. If any pwq
3848 * has in flight commands, its pwq->flush_color is set to
3849 * @flush_color, @wq->nr_pwqs_to_flush is updated accordingly, pwq
3850 * wakeup logic is armed and %true is returned.
3851 *
3852 * The caller should have initialized @wq->first_flusher prior to
3853 * calling this function with non-negative @flush_color. If
3854 * @flush_color is negative, no flush color update is done and %false
3855 * is returned.
3856 *
3857 * If @work_color is non-negative, all pwqs should have the same
3858 * work_color which is previous to @work_color and all will be
3859 * advanced to @work_color.
3860 *
3861 * CONTEXT:
3862 * mutex_lock(wq->mutex).
3863 *
3864 * Return:
3865 * %true if @flush_color >= 0 and there's something to flush. %false
3866 * otherwise.
3867 */
3868static bool flush_workqueue_prep_pwqs(struct workqueue_struct *wq,
3869 int flush_color, int work_color)
3870{
3871 bool wait = false;
3872 struct pool_workqueue *pwq;
3873
3874 if (flush_color >= 0) {
3875 WARN_ON_ONCE(atomic_read(&wq->nr_pwqs_to_flush));
3876 atomic_set(&wq->nr_pwqs_to_flush, 1);
3877 }
3878
3879 for_each_pwq(pwq, wq) {
3880 struct worker_pool *pool = pwq->pool;
3881
3882 raw_spin_lock_irq(&pool->lock);
3883
3884 if (flush_color >= 0) {
3885 WARN_ON_ONCE(pwq->flush_color != -1);
3886
3887 if (pwq->nr_in_flight[flush_color]) {
3888 pwq->flush_color = flush_color;
3889 atomic_inc(&wq->nr_pwqs_to_flush);
3890 wait = true;
3891 }
3892 }
3893
3894 if (work_color >= 0) {
3895 WARN_ON_ONCE(work_color != work_next_color(pwq->work_color));
3896 pwq->work_color = work_color;
3897 }
3898
3899 raw_spin_unlock_irq(&pool->lock);
3900 }
3901
3902 if (flush_color >= 0 && atomic_dec_and_test(&wq->nr_pwqs_to_flush))
3903 complete(&wq->first_flusher->done);
3904
3905 return wait;
3906}
3907
3908static void touch_wq_lockdep_map(struct workqueue_struct *wq)
3909{
3910#ifdef CONFIG_LOCKDEP
3911 if (wq->flags & WQ_BH)
3912 local_bh_disable();
3913
3914 lock_map_acquire(&wq->lockdep_map);
3915 lock_map_release(&wq->lockdep_map);
3916
3917 if (wq->flags & WQ_BH)
3918 local_bh_enable();
3919#endif
3920}
3921
3922static void touch_work_lockdep_map(struct work_struct *work,
3923 struct workqueue_struct *wq)
3924{
3925#ifdef CONFIG_LOCKDEP
3926 if (wq->flags & WQ_BH)
3927 local_bh_disable();
3928
3929 lock_map_acquire(&work->lockdep_map);
3930 lock_map_release(&work->lockdep_map);
3931
3932 if (wq->flags & WQ_BH)
3933 local_bh_enable();
3934#endif
3935}
3936
3937/**
3938 * __flush_workqueue - ensure that any scheduled work has run to completion.
3939 * @wq: workqueue to flush
3940 *
3941 * This function sleeps until all work items which were queued on entry
3942 * have finished execution, but it is not livelocked by new incoming ones.
3943 */
3944void __flush_workqueue(struct workqueue_struct *wq)
3945{
3946 struct wq_flusher this_flusher = {
3947 .list = LIST_HEAD_INIT(this_flusher.list),
3948 .flush_color = -1,
3949 .done = COMPLETION_INITIALIZER_ONSTACK_MAP(this_flusher.done, wq->lockdep_map),
3950 };
3951 int next_color;
3952
3953 if (WARN_ON(!wq_online))
3954 return;
3955
3956 touch_wq_lockdep_map(wq);
3957
3958 mutex_lock(&wq->mutex);
3959
3960 /*
3961 * Start-to-wait phase
3962 */
3963 next_color = work_next_color(wq->work_color);
3964
3965 if (next_color != wq->flush_color) {
3966 /*
3967 * Color space is not full. The current work_color
3968 * becomes our flush_color and work_color is advanced
3969 * by one.
3970 */
3971 WARN_ON_ONCE(!list_empty(&wq->flusher_overflow));
3972 this_flusher.flush_color = wq->work_color;
3973 wq->work_color = next_color;
3974
3975 if (!wq->first_flusher) {
3976 /* no flush in progress, become the first flusher */
3977 WARN_ON_ONCE(wq->flush_color != this_flusher.flush_color);
3978
3979 wq->first_flusher = &this_flusher;
3980
3981 if (!flush_workqueue_prep_pwqs(wq, wq->flush_color,
3982 wq->work_color)) {
3983 /* nothing to flush, done */
3984 wq->flush_color = next_color;
3985 wq->first_flusher = NULL;
3986 goto out_unlock;
3987 }
3988 } else {
3989 /* wait in queue */
3990 WARN_ON_ONCE(wq->flush_color == this_flusher.flush_color);
3991 list_add_tail(&this_flusher.list, &wq->flusher_queue);
3992 flush_workqueue_prep_pwqs(wq, -1, wq->work_color);
3993 }
3994 } else {
3995 /*
3996 * Oops, color space is full, wait on overflow queue.
3997 * The next flush completion will assign us
3998 * flush_color and transfer to flusher_queue.
3999 */
4000 list_add_tail(&this_flusher.list, &wq->flusher_overflow);
4001 }
4002
4003 check_flush_dependency(wq, NULL);
4004
4005 mutex_unlock(&wq->mutex);
4006
4007 wait_for_completion(&this_flusher.done);
4008
4009 /*
4010 * Wake-up-and-cascade phase
4011 *
4012 * First flushers are responsible for cascading flushes and
4013 * handling overflow. Non-first flushers can simply return.
4014 */
4015 if (READ_ONCE(wq->first_flusher) != &this_flusher)
4016 return;
4017
4018 mutex_lock(&wq->mutex);
4019
4020 /* we might have raced, check again with mutex held */
4021 if (wq->first_flusher != &this_flusher)
4022 goto out_unlock;
4023
4024 WRITE_ONCE(wq->first_flusher, NULL);
4025
4026 WARN_ON_ONCE(!list_empty(&this_flusher.list));
4027 WARN_ON_ONCE(wq->flush_color != this_flusher.flush_color);
4028
4029 while (true) {
4030 struct wq_flusher *next, *tmp;
4031
4032 /* complete all the flushers sharing the current flush color */
4033 list_for_each_entry_safe(next, tmp, &wq->flusher_queue, list) {
4034 if (next->flush_color != wq->flush_color)
4035 break;
4036 list_del_init(&next->list);
4037 complete(&next->done);
4038 }
4039
4040 WARN_ON_ONCE(!list_empty(&wq->flusher_overflow) &&
4041 wq->flush_color != work_next_color(wq->work_color));
4042
4043 /* this flush_color is finished, advance by one */
4044 wq->flush_color = work_next_color(wq->flush_color);
4045
4046 /* one color has been freed, handle overflow queue */
4047 if (!list_empty(&wq->flusher_overflow)) {
4048 /*
4049 * Assign the same color to all overflowed
4050 * flushers, advance work_color and append to
4051 * flusher_queue. This is the start-to-wait
4052 * phase for these overflowed flushers.
4053 */
4054 list_for_each_entry(tmp, &wq->flusher_overflow, list)
4055 tmp->flush_color = wq->work_color;
4056
4057 wq->work_color = work_next_color(wq->work_color);
4058
4059 list_splice_tail_init(&wq->flusher_overflow,
4060 &wq->flusher_queue);
4061 flush_workqueue_prep_pwqs(wq, -1, wq->work_color);
4062 }
4063
4064 if (list_empty(&wq->flusher_queue)) {
4065 WARN_ON_ONCE(wq->flush_color != wq->work_color);
4066 break;
4067 }
4068
4069 /*
4070 * Need to flush more colors. Make the next flusher
4071 * the new first flusher and arm pwqs.
4072 */
4073 WARN_ON_ONCE(wq->flush_color == wq->work_color);
4074 WARN_ON_ONCE(wq->flush_color != next->flush_color);
4075
4076 list_del_init(&next->list);
4077 wq->first_flusher = next;
4078
4079 if (flush_workqueue_prep_pwqs(wq, wq->flush_color, -1))
4080 break;
4081
4082 /*
4083 * Meh... this color is already done, clear first
4084 * flusher and repeat cascading.
4085 */
4086 wq->first_flusher = NULL;
4087 }
4088
4089out_unlock:
4090 mutex_unlock(&wq->mutex);
4091}
4092EXPORT_SYMBOL(__flush_workqueue);
4093
4094/**
4095 * drain_workqueue - drain a workqueue
4096 * @wq: workqueue to drain
4097 *
4098 * Wait until the workqueue becomes empty. While draining is in progress,
4099 * only chain queueing is allowed. IOW, only currently pending or running
4100 * work items on @wq can queue further work items on it. @wq is flushed
4101 * repeatedly until it becomes empty. The number of flushing is determined
4102 * by the depth of chaining and should be relatively short. Whine if it
4103 * takes too long.
4104 */
4105void drain_workqueue(struct workqueue_struct *wq)
4106{
4107 unsigned int flush_cnt = 0;
4108 struct pool_workqueue *pwq;
4109
4110 /*
4111 * __queue_work() needs to test whether there are drainers, is much
4112 * hotter than drain_workqueue() and already looks at @wq->flags.
4113 * Use __WQ_DRAINING so that queue doesn't have to check nr_drainers.
4114 */
4115 mutex_lock(&wq->mutex);
4116 if (!wq->nr_drainers++)
4117 wq->flags |= __WQ_DRAINING;
4118 mutex_unlock(&wq->mutex);
4119reflush:
4120 __flush_workqueue(wq);
4121
4122 mutex_lock(&wq->mutex);
4123
4124 for_each_pwq(pwq, wq) {
4125 bool drained;
4126
4127 raw_spin_lock_irq(&pwq->pool->lock);
4128 drained = pwq_is_empty(pwq);
4129 raw_spin_unlock_irq(&pwq->pool->lock);
4130
4131 if (drained)
4132 continue;
4133
4134 if (++flush_cnt == 10 ||
4135 (flush_cnt % 100 == 0 && flush_cnt <= 1000))
4136 pr_warn("workqueue %s: %s() isn't complete after %u tries\n",
4137 wq->name, __func__, flush_cnt);
4138
4139 mutex_unlock(&wq->mutex);
4140 goto reflush;
4141 }
4142
4143 if (!--wq->nr_drainers)
4144 wq->flags &= ~__WQ_DRAINING;
4145 mutex_unlock(&wq->mutex);
4146}
4147EXPORT_SYMBOL_GPL(drain_workqueue);
4148
4149static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr,
4150 bool from_cancel)
4151{
4152 struct worker *worker = NULL;
4153 struct worker_pool *pool;
4154 struct pool_workqueue *pwq;
4155 struct workqueue_struct *wq;
4156
4157 might_sleep();
4158
4159 rcu_read_lock();
4160 pool = get_work_pool(work);
4161 if (!pool) {
4162 rcu_read_unlock();
4163 return false;
4164 }
4165
4166 raw_spin_lock_irq(&pool->lock);
4167 /* see the comment in try_to_grab_pending() with the same code */
4168 pwq = get_work_pwq(work);
4169 if (pwq) {
4170 if (unlikely(pwq->pool != pool))
4171 goto already_gone;
4172 } else {
4173 worker = find_worker_executing_work(pool, work);
4174 if (!worker)
4175 goto already_gone;
4176 pwq = worker->current_pwq;
4177 }
4178
4179 wq = pwq->wq;
4180 check_flush_dependency(wq, work);
4181
4182 insert_wq_barrier(pwq, barr, work, worker);
4183 raw_spin_unlock_irq(&pool->lock);
4184
4185 touch_work_lockdep_map(work, wq);
4186
4187 /*
4188 * Force a lock recursion deadlock when using flush_work() inside a
4189 * single-threaded or rescuer equipped workqueue.
4190 *
4191 * For single threaded workqueues the deadlock happens when the work
4192 * is after the work issuing the flush_work(). For rescuer equipped
4193 * workqueues the deadlock happens when the rescuer stalls, blocking
4194 * forward progress.
4195 */
4196 if (!from_cancel && (wq->saved_max_active == 1 || wq->rescuer))
4197 touch_wq_lockdep_map(wq);
4198
4199 rcu_read_unlock();
4200 return true;
4201already_gone:
4202 raw_spin_unlock_irq(&pool->lock);
4203 rcu_read_unlock();
4204 return false;
4205}
4206
4207static bool __flush_work(struct work_struct *work, bool from_cancel)
4208{
4209 struct wq_barrier barr;
4210
4211 if (WARN_ON(!wq_online))
4212 return false;
4213
4214 if (WARN_ON(!work->func))
4215 return false;
4216
4217 if (start_flush_work(work, &barr, from_cancel)) {
4218 wait_for_completion(&barr.done);
4219 destroy_work_on_stack(&barr.work);
4220 return true;
4221 } else {
4222 return false;
4223 }
4224}
4225
4226/**
4227 * flush_work - wait for a work to finish executing the last queueing instance
4228 * @work: the work to flush
4229 *
4230 * Wait until @work has finished execution. @work is guaranteed to be idle
4231 * on return if it hasn't been requeued since flush started.
4232 *
4233 * Return:
4234 * %true if flush_work() waited for the work to finish execution,
4235 * %false if it was already idle.
4236 */
4237bool flush_work(struct work_struct *work)
4238{
4239 return __flush_work(work, false);
4240}
4241EXPORT_SYMBOL_GPL(flush_work);
4242
4243/**
4244 * flush_delayed_work - wait for a dwork to finish executing the last queueing
4245 * @dwork: the delayed work to flush
4246 *
4247 * Delayed timer is cancelled and the pending work is queued for
4248 * immediate execution. Like flush_work(), this function only
4249 * considers the last queueing instance of @dwork.
4250 *
4251 * Return:
4252 * %true if flush_work() waited for the work to finish execution,
4253 * %false if it was already idle.
4254 */
4255bool flush_delayed_work(struct delayed_work *dwork)
4256{
4257 local_irq_disable();
4258 if (del_timer_sync(&dwork->timer))
4259 __queue_work(dwork->cpu, dwork->wq, &dwork->work);
4260 local_irq_enable();
4261 return flush_work(&dwork->work);
4262}
4263EXPORT_SYMBOL(flush_delayed_work);
4264
4265/**
4266 * flush_rcu_work - wait for a rwork to finish executing the last queueing
4267 * @rwork: the rcu work to flush
4268 *
4269 * Return:
4270 * %true if flush_rcu_work() waited for the work to finish execution,
4271 * %false if it was already idle.
4272 */
4273bool flush_rcu_work(struct rcu_work *rwork)
4274{
4275 if (test_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(&rwork->work))) {
4276 rcu_barrier();
4277 flush_work(&rwork->work);
4278 return true;
4279 } else {
4280 return flush_work(&rwork->work);
4281 }
4282}
4283EXPORT_SYMBOL(flush_rcu_work);
4284
4285static bool __cancel_work(struct work_struct *work, u32 cflags)
4286{
4287 unsigned long irq_flags;
4288 int ret;
4289
4290 do {
4291 ret = try_to_grab_pending(work, cflags, &irq_flags);
4292 } while (unlikely(ret == -EAGAIN));
4293
4294 if (unlikely(ret < 0))
4295 return false;
4296
4297 set_work_pool_and_clear_pending(work, get_work_pool_id(work), 0);
4298 local_irq_restore(irq_flags);
4299 return ret;
4300}
4301
4302static bool __cancel_work_sync(struct work_struct *work, u32 cflags)
4303{
4304 unsigned long irq_flags;
4305 bool ret;
4306
4307 /* claim @work and tell other tasks trying to grab @work to back off */
4308 ret = work_grab_pending(work, cflags, &irq_flags);
4309 mark_work_canceling(work);
4310 local_irq_restore(irq_flags);
4311
4312 /*
4313 * Skip __flush_work() during early boot when we know that @work isn't
4314 * executing. This allows canceling during early boot.
4315 */
4316 if (wq_online)
4317 __flush_work(work, true);
4318
4319 /*
4320 * smp_mb() at the end of set_work_pool_and_clear_pending() is paired
4321 * with prepare_to_wait() above so that either waitqueue_active() is
4322 * visible here or !work_is_canceling() is visible there.
4323 */
4324 set_work_pool_and_clear_pending(work, WORK_OFFQ_POOL_NONE, 0);
4325
4326 if (waitqueue_active(&wq_cancel_waitq))
4327 __wake_up(&wq_cancel_waitq, TASK_NORMAL, 1, work);
4328
4329 return ret;
4330}
4331
4332/*
4333 * See cancel_delayed_work()
4334 */
4335bool cancel_work(struct work_struct *work)
4336{
4337 return __cancel_work(work, 0);
4338}
4339EXPORT_SYMBOL(cancel_work);
4340
4341/**
4342 * cancel_work_sync - cancel a work and wait for it to finish
4343 * @work: the work to cancel
4344 *
4345 * Cancel @work and wait for its execution to finish. This function
4346 * can be used even if the work re-queues itself or migrates to
4347 * another workqueue. On return from this function, @work is
4348 * guaranteed to be not pending or executing on any CPU.
4349 *
4350 * cancel_work_sync(&delayed_work->work) must not be used for
4351 * delayed_work's. Use cancel_delayed_work_sync() instead.
4352 *
4353 * The caller must ensure that the workqueue on which @work was last
4354 * queued can't be destroyed before this function returns.
4355 *
4356 * Return:
4357 * %true if @work was pending, %false otherwise.
4358 */
4359bool cancel_work_sync(struct work_struct *work)
4360{
4361 return __cancel_work_sync(work, 0);
4362}
4363EXPORT_SYMBOL_GPL(cancel_work_sync);
4364
4365/**
4366 * cancel_delayed_work - cancel a delayed work
4367 * @dwork: delayed_work to cancel
4368 *
4369 * Kill off a pending delayed_work.
4370 *
4371 * Return: %true if @dwork was pending and canceled; %false if it wasn't
4372 * pending.
4373 *
4374 * Note:
4375 * The work callback function may still be running on return, unless
4376 * it returns %true and the work doesn't re-arm itself. Explicitly flush or
4377 * use cancel_delayed_work_sync() to wait on it.
4378 *
4379 * This function is safe to call from any context including IRQ handler.
4380 */
4381bool cancel_delayed_work(struct delayed_work *dwork)
4382{
4383 return __cancel_work(&dwork->work, WORK_CANCEL_DELAYED);
4384}
4385EXPORT_SYMBOL(cancel_delayed_work);
4386
4387/**
4388 * cancel_delayed_work_sync - cancel a delayed work and wait for it to finish
4389 * @dwork: the delayed work cancel
4390 *
4391 * This is cancel_work_sync() for delayed works.
4392 *
4393 * Return:
4394 * %true if @dwork was pending, %false otherwise.
4395 */
4396bool cancel_delayed_work_sync(struct delayed_work *dwork)
4397{
4398 return __cancel_work_sync(&dwork->work, WORK_CANCEL_DELAYED);
4399}
4400EXPORT_SYMBOL(cancel_delayed_work_sync);
4401
4402/**
4403 * schedule_on_each_cpu - execute a function synchronously on each online CPU
4404 * @func: the function to call
4405 *
4406 * schedule_on_each_cpu() executes @func on each online CPU using the
4407 * system workqueue and blocks until all CPUs have completed.
4408 * schedule_on_each_cpu() is very slow.
4409 *
4410 * Return:
4411 * 0 on success, -errno on failure.
4412 */
4413int schedule_on_each_cpu(work_func_t func)
4414{
4415 int cpu;
4416 struct work_struct __percpu *works;
4417
4418 works = alloc_percpu(struct work_struct);
4419 if (!works)
4420 return -ENOMEM;
4421
4422 cpus_read_lock();
4423
4424 for_each_online_cpu(cpu) {
4425 struct work_struct *work = per_cpu_ptr(works, cpu);
4426
4427 INIT_WORK(work, func);
4428 schedule_work_on(cpu, work);
4429 }
4430
4431 for_each_online_cpu(cpu)
4432 flush_work(per_cpu_ptr(works, cpu));
4433
4434 cpus_read_unlock();
4435 free_percpu(works);
4436 return 0;
4437}
4438
4439/**
4440 * execute_in_process_context - reliably execute the routine with user context
4441 * @fn: the function to execute
4442 * @ew: guaranteed storage for the execute work structure (must
4443 * be available when the work executes)
4444 *
4445 * Executes the function immediately if process context is available,
4446 * otherwise schedules the function for delayed execution.
4447 *
4448 * Return: 0 - function was executed
4449 * 1 - function was scheduled for execution
4450 */
4451int execute_in_process_context(work_func_t fn, struct execute_work *ew)
4452{
4453 if (!in_interrupt()) {
4454 fn(&ew->work);
4455 return 0;
4456 }
4457
4458 INIT_WORK(&ew->work, fn);
4459 schedule_work(&ew->work);
4460
4461 return 1;
4462}
4463EXPORT_SYMBOL_GPL(execute_in_process_context);
4464
4465/**
4466 * free_workqueue_attrs - free a workqueue_attrs
4467 * @attrs: workqueue_attrs to free
4468 *
4469 * Undo alloc_workqueue_attrs().
4470 */
4471void free_workqueue_attrs(struct workqueue_attrs *attrs)
4472{
4473 if (attrs) {
4474 free_cpumask_var(attrs->cpumask);
4475 free_cpumask_var(attrs->__pod_cpumask);
4476 kfree(attrs);
4477 }
4478}
4479
4480/**
4481 * alloc_workqueue_attrs - allocate a workqueue_attrs
4482 *
4483 * Allocate a new workqueue_attrs, initialize with default settings and
4484 * return it.
4485 *
4486 * Return: The allocated new workqueue_attr on success. %NULL on failure.
4487 */
4488struct workqueue_attrs *alloc_workqueue_attrs(void)
4489{
4490 struct workqueue_attrs *attrs;
4491
4492 attrs = kzalloc(sizeof(*attrs), GFP_KERNEL);
4493 if (!attrs)
4494 goto fail;
4495 if (!alloc_cpumask_var(&attrs->cpumask, GFP_KERNEL))
4496 goto fail;
4497 if (!alloc_cpumask_var(&attrs->__pod_cpumask, GFP_KERNEL))
4498 goto fail;
4499
4500 cpumask_copy(attrs->cpumask, cpu_possible_mask);
4501 attrs->affn_scope = WQ_AFFN_DFL;
4502 return attrs;
4503fail:
4504 free_workqueue_attrs(attrs);
4505 return NULL;
4506}
4507
4508static void copy_workqueue_attrs(struct workqueue_attrs *to,
4509 const struct workqueue_attrs *from)
4510{
4511 to->nice = from->nice;
4512 cpumask_copy(to->cpumask, from->cpumask);
4513 cpumask_copy(to->__pod_cpumask, from->__pod_cpumask);
4514 to->affn_strict = from->affn_strict;
4515
4516 /*
4517 * Unlike hash and equality test, copying shouldn't ignore wq-only
4518 * fields as copying is used for both pool and wq attrs. Instead,
4519 * get_unbound_pool() explicitly clears the fields.
4520 */
4521 to->affn_scope = from->affn_scope;
4522 to->ordered = from->ordered;
4523}
4524
4525/*
4526 * Some attrs fields are workqueue-only. Clear them for worker_pool's. See the
4527 * comments in 'struct workqueue_attrs' definition.
4528 */
4529static void wqattrs_clear_for_pool(struct workqueue_attrs *attrs)
4530{
4531 attrs->affn_scope = WQ_AFFN_NR_TYPES;
4532 attrs->ordered = false;
4533}
4534
4535/* hash value of the content of @attr */
4536static u32 wqattrs_hash(const struct workqueue_attrs *attrs)
4537{
4538 u32 hash = 0;
4539
4540 hash = jhash_1word(attrs->nice, hash);
4541 hash = jhash(cpumask_bits(attrs->cpumask),
4542 BITS_TO_LONGS(nr_cpumask_bits) * sizeof(long), hash);
4543 hash = jhash(cpumask_bits(attrs->__pod_cpumask),
4544 BITS_TO_LONGS(nr_cpumask_bits) * sizeof(long), hash);
4545 hash = jhash_1word(attrs->affn_strict, hash);
4546 return hash;
4547}
4548
4549/* content equality test */
4550static bool wqattrs_equal(const struct workqueue_attrs *a,
4551 const struct workqueue_attrs *b)
4552{
4553 if (a->nice != b->nice)
4554 return false;
4555 if (!cpumask_equal(a->cpumask, b->cpumask))
4556 return false;
4557 if (!cpumask_equal(a->__pod_cpumask, b->__pod_cpumask))
4558 return false;
4559 if (a->affn_strict != b->affn_strict)
4560 return false;
4561 return true;
4562}
4563
4564/* Update @attrs with actually available CPUs */
4565static void wqattrs_actualize_cpumask(struct workqueue_attrs *attrs,
4566 const cpumask_t *unbound_cpumask)
4567{
4568 /*
4569 * Calculate the effective CPU mask of @attrs given @unbound_cpumask. If
4570 * @attrs->cpumask doesn't overlap with @unbound_cpumask, we fallback to
4571 * @unbound_cpumask.
4572 */
4573 cpumask_and(attrs->cpumask, attrs->cpumask, unbound_cpumask);
4574 if (unlikely(cpumask_empty(attrs->cpumask)))
4575 cpumask_copy(attrs->cpumask, unbound_cpumask);
4576}
4577
4578/* find wq_pod_type to use for @attrs */
4579static const struct wq_pod_type *
4580wqattrs_pod_type(const struct workqueue_attrs *attrs)
4581{
4582 enum wq_affn_scope scope;
4583 struct wq_pod_type *pt;
4584
4585 /* to synchronize access to wq_affn_dfl */
4586 lockdep_assert_held(&wq_pool_mutex);
4587
4588 if (attrs->affn_scope == WQ_AFFN_DFL)
4589 scope = wq_affn_dfl;
4590 else
4591 scope = attrs->affn_scope;
4592
4593 pt = &wq_pod_types[scope];
4594
4595 if (!WARN_ON_ONCE(attrs->affn_scope == WQ_AFFN_NR_TYPES) &&
4596 likely(pt->nr_pods))
4597 return pt;
4598
4599 /*
4600 * Before workqueue_init_topology(), only SYSTEM is available which is
4601 * initialized in workqueue_init_early().
4602 */
4603 pt = &wq_pod_types[WQ_AFFN_SYSTEM];
4604 BUG_ON(!pt->nr_pods);
4605 return pt;
4606}
4607
4608/**
4609 * init_worker_pool - initialize a newly zalloc'd worker_pool
4610 * @pool: worker_pool to initialize
4611 *
4612 * Initialize a newly zalloc'd @pool. It also allocates @pool->attrs.
4613 *
4614 * Return: 0 on success, -errno on failure. Even on failure, all fields
4615 * inside @pool proper are initialized and put_unbound_pool() can be called
4616 * on @pool safely to release it.
4617 */
4618static int init_worker_pool(struct worker_pool *pool)
4619{
4620 raw_spin_lock_init(&pool->lock);
4621 pool->id = -1;
4622 pool->cpu = -1;
4623 pool->node = NUMA_NO_NODE;
4624 pool->flags |= POOL_DISASSOCIATED;
4625 pool->watchdog_ts = jiffies;
4626 INIT_LIST_HEAD(&pool->worklist);
4627 INIT_LIST_HEAD(&pool->idle_list);
4628 hash_init(pool->busy_hash);
4629
4630 timer_setup(&pool->idle_timer, idle_worker_timeout, TIMER_DEFERRABLE);
4631 INIT_WORK(&pool->idle_cull_work, idle_cull_fn);
4632
4633 timer_setup(&pool->mayday_timer, pool_mayday_timeout, 0);
4634
4635 INIT_LIST_HEAD(&pool->workers);
4636 INIT_LIST_HEAD(&pool->dying_workers);
4637
4638 ida_init(&pool->worker_ida);
4639 INIT_HLIST_NODE(&pool->hash_node);
4640 pool->refcnt = 1;
4641
4642 /* shouldn't fail above this point */
4643 pool->attrs = alloc_workqueue_attrs();
4644 if (!pool->attrs)
4645 return -ENOMEM;
4646
4647 wqattrs_clear_for_pool(pool->attrs);
4648
4649 return 0;
4650}
4651
4652#ifdef CONFIG_LOCKDEP
4653static void wq_init_lockdep(struct workqueue_struct *wq)
4654{
4655 char *lock_name;
4656
4657 lockdep_register_key(&wq->key);
4658 lock_name = kasprintf(GFP_KERNEL, "%s%s", "(wq_completion)", wq->name);
4659 if (!lock_name)
4660 lock_name = wq->name;
4661
4662 wq->lock_name = lock_name;
4663 lockdep_init_map(&wq->lockdep_map, lock_name, &wq->key, 0);
4664}
4665
4666static void wq_unregister_lockdep(struct workqueue_struct *wq)
4667{
4668 lockdep_unregister_key(&wq->key);
4669}
4670
4671static void wq_free_lockdep(struct workqueue_struct *wq)
4672{
4673 if (wq->lock_name != wq->name)
4674 kfree(wq->lock_name);
4675}
4676#else
4677static void wq_init_lockdep(struct workqueue_struct *wq)
4678{
4679}
4680
4681static void wq_unregister_lockdep(struct workqueue_struct *wq)
4682{
4683}
4684
4685static void wq_free_lockdep(struct workqueue_struct *wq)
4686{
4687}
4688#endif
4689
4690static void free_node_nr_active(struct wq_node_nr_active **nna_ar)
4691{
4692 int node;
4693
4694 for_each_node(node) {
4695 kfree(nna_ar[node]);
4696 nna_ar[node] = NULL;
4697 }
4698
4699 kfree(nna_ar[nr_node_ids]);
4700 nna_ar[nr_node_ids] = NULL;
4701}
4702
4703static void init_node_nr_active(struct wq_node_nr_active *nna)
4704{
4705 nna->max = WQ_DFL_MIN_ACTIVE;
4706 atomic_set(&nna->nr, 0);
4707 raw_spin_lock_init(&nna->lock);
4708 INIT_LIST_HEAD(&nna->pending_pwqs);
4709}
4710
4711/*
4712 * Each node's nr_active counter will be accessed mostly from its own node and
4713 * should be allocated in the node.
4714 */
4715static int alloc_node_nr_active(struct wq_node_nr_active **nna_ar)
4716{
4717 struct wq_node_nr_active *nna;
4718 int node;
4719
4720 for_each_node(node) {
4721 nna = kzalloc_node(sizeof(*nna), GFP_KERNEL, node);
4722 if (!nna)
4723 goto err_free;
4724 init_node_nr_active(nna);
4725 nna_ar[node] = nna;
4726 }
4727
4728 /* [nr_node_ids] is used as the fallback */
4729 nna = kzalloc_node(sizeof(*nna), GFP_KERNEL, NUMA_NO_NODE);
4730 if (!nna)
4731 goto err_free;
4732 init_node_nr_active(nna);
4733 nna_ar[nr_node_ids] = nna;
4734
4735 return 0;
4736
4737err_free:
4738 free_node_nr_active(nna_ar);
4739 return -ENOMEM;
4740}
4741
4742static void rcu_free_wq(struct rcu_head *rcu)
4743{
4744 struct workqueue_struct *wq =
4745 container_of(rcu, struct workqueue_struct, rcu);
4746
4747 if (wq->flags & WQ_UNBOUND)
4748 free_node_nr_active(wq->node_nr_active);
4749
4750 wq_free_lockdep(wq);
4751 free_percpu(wq->cpu_pwq);
4752 free_workqueue_attrs(wq->unbound_attrs);
4753 kfree(wq);
4754}
4755
4756static void rcu_free_pool(struct rcu_head *rcu)
4757{
4758 struct worker_pool *pool = container_of(rcu, struct worker_pool, rcu);
4759
4760 ida_destroy(&pool->worker_ida);
4761 free_workqueue_attrs(pool->attrs);
4762 kfree(pool);
4763}
4764
4765/**
4766 * put_unbound_pool - put a worker_pool
4767 * @pool: worker_pool to put
4768 *
4769 * Put @pool. If its refcnt reaches zero, it gets destroyed in RCU
4770 * safe manner. get_unbound_pool() calls this function on its failure path
4771 * and this function should be able to release pools which went through,
4772 * successfully or not, init_worker_pool().
4773 *
4774 * Should be called with wq_pool_mutex held.
4775 */
4776static void put_unbound_pool(struct worker_pool *pool)
4777{
4778 DECLARE_COMPLETION_ONSTACK(detach_completion);
4779 struct worker *worker;
4780 LIST_HEAD(cull_list);
4781
4782 lockdep_assert_held(&wq_pool_mutex);
4783
4784 if (--pool->refcnt)
4785 return;
4786
4787 /* sanity checks */
4788 if (WARN_ON(!(pool->cpu < 0)) ||
4789 WARN_ON(!list_empty(&pool->worklist)))
4790 return;
4791
4792 /* release id and unhash */
4793 if (pool->id >= 0)
4794 idr_remove(&worker_pool_idr, pool->id);
4795 hash_del(&pool->hash_node);
4796
4797 /*
4798 * Become the manager and destroy all workers. This prevents
4799 * @pool's workers from blocking on attach_mutex. We're the last
4800 * manager and @pool gets freed with the flag set.
4801 *
4802 * Having a concurrent manager is quite unlikely to happen as we can
4803 * only get here with
4804 * pwq->refcnt == pool->refcnt == 0
4805 * which implies no work queued to the pool, which implies no worker can
4806 * become the manager. However a worker could have taken the role of
4807 * manager before the refcnts dropped to 0, since maybe_create_worker()
4808 * drops pool->lock
4809 */
4810 while (true) {
4811 rcuwait_wait_event(&manager_wait,
4812 !(pool->flags & POOL_MANAGER_ACTIVE),
4813 TASK_UNINTERRUPTIBLE);
4814
4815 mutex_lock(&wq_pool_attach_mutex);
4816 raw_spin_lock_irq(&pool->lock);
4817 if (!(pool->flags & POOL_MANAGER_ACTIVE)) {
4818 pool->flags |= POOL_MANAGER_ACTIVE;
4819 break;
4820 }
4821 raw_spin_unlock_irq(&pool->lock);
4822 mutex_unlock(&wq_pool_attach_mutex);
4823 }
4824
4825 while ((worker = first_idle_worker(pool)))
4826 set_worker_dying(worker, &cull_list);
4827 WARN_ON(pool->nr_workers || pool->nr_idle);
4828 raw_spin_unlock_irq(&pool->lock);
4829
4830 wake_dying_workers(&cull_list);
4831
4832 if (!list_empty(&pool->workers) || !list_empty(&pool->dying_workers))
4833 pool->detach_completion = &detach_completion;
4834 mutex_unlock(&wq_pool_attach_mutex);
4835
4836 if (pool->detach_completion)
4837 wait_for_completion(pool->detach_completion);
4838
4839 /* shut down the timers */
4840 del_timer_sync(&pool->idle_timer);
4841 cancel_work_sync(&pool->idle_cull_work);
4842 del_timer_sync(&pool->mayday_timer);
4843
4844 /* RCU protected to allow dereferences from get_work_pool() */
4845 call_rcu(&pool->rcu, rcu_free_pool);
4846}
4847
4848/**
4849 * get_unbound_pool - get a worker_pool with the specified attributes
4850 * @attrs: the attributes of the worker_pool to get
4851 *
4852 * Obtain a worker_pool which has the same attributes as @attrs, bump the
4853 * reference count and return it. If there already is a matching
4854 * worker_pool, it will be used; otherwise, this function attempts to
4855 * create a new one.
4856 *
4857 * Should be called with wq_pool_mutex held.
4858 *
4859 * Return: On success, a worker_pool with the same attributes as @attrs.
4860 * On failure, %NULL.
4861 */
4862static struct worker_pool *get_unbound_pool(const struct workqueue_attrs *attrs)
4863{
4864 struct wq_pod_type *pt = &wq_pod_types[WQ_AFFN_NUMA];
4865 u32 hash = wqattrs_hash(attrs);
4866 struct worker_pool *pool;
4867 int pod, node = NUMA_NO_NODE;
4868
4869 lockdep_assert_held(&wq_pool_mutex);
4870
4871 /* do we already have a matching pool? */
4872 hash_for_each_possible(unbound_pool_hash, pool, hash_node, hash) {
4873 if (wqattrs_equal(pool->attrs, attrs)) {
4874 pool->refcnt++;
4875 return pool;
4876 }
4877 }
4878
4879 /* If __pod_cpumask is contained inside a NUMA pod, that's our node */
4880 for (pod = 0; pod < pt->nr_pods; pod++) {
4881 if (cpumask_subset(attrs->__pod_cpumask, pt->pod_cpus[pod])) {
4882 node = pt->pod_node[pod];
4883 break;
4884 }
4885 }
4886
4887 /* nope, create a new one */
4888 pool = kzalloc_node(sizeof(*pool), GFP_KERNEL, node);
4889 if (!pool || init_worker_pool(pool) < 0)
4890 goto fail;
4891
4892 pool->node = node;
4893 copy_workqueue_attrs(pool->attrs, attrs);
4894 wqattrs_clear_for_pool(pool->attrs);
4895
4896 if (worker_pool_assign_id(pool) < 0)
4897 goto fail;
4898
4899 /* create and start the initial worker */
4900 if (wq_online && !create_worker(pool))
4901 goto fail;
4902
4903 /* install */
4904 hash_add(unbound_pool_hash, &pool->hash_node, hash);
4905
4906 return pool;
4907fail:
4908 if (pool)
4909 put_unbound_pool(pool);
4910 return NULL;
4911}
4912
4913static void rcu_free_pwq(struct rcu_head *rcu)
4914{
4915 kmem_cache_free(pwq_cache,
4916 container_of(rcu, struct pool_workqueue, rcu));
4917}
4918
4919/*
4920 * Scheduled on pwq_release_worker by put_pwq() when an unbound pwq hits zero
4921 * refcnt and needs to be destroyed.
4922 */
4923static void pwq_release_workfn(struct kthread_work *work)
4924{
4925 struct pool_workqueue *pwq = container_of(work, struct pool_workqueue,
4926 release_work);
4927 struct workqueue_struct *wq = pwq->wq;
4928 struct worker_pool *pool = pwq->pool;
4929 bool is_last = false;
4930
4931 /*
4932 * When @pwq is not linked, it doesn't hold any reference to the
4933 * @wq, and @wq is invalid to access.
4934 */
4935 if (!list_empty(&pwq->pwqs_node)) {
4936 mutex_lock(&wq->mutex);
4937 list_del_rcu(&pwq->pwqs_node);
4938 is_last = list_empty(&wq->pwqs);
4939
4940 /*
4941 * For ordered workqueue with a plugged dfl_pwq, restart it now.
4942 */
4943 if (!is_last && (wq->flags & __WQ_ORDERED))
4944 unplug_oldest_pwq(wq);
4945
4946 mutex_unlock(&wq->mutex);
4947 }
4948
4949 if (wq->flags & WQ_UNBOUND) {
4950 mutex_lock(&wq_pool_mutex);
4951 put_unbound_pool(pool);
4952 mutex_unlock(&wq_pool_mutex);
4953 }
4954
4955 if (!list_empty(&pwq->pending_node)) {
4956 struct wq_node_nr_active *nna =
4957 wq_node_nr_active(pwq->wq, pwq->pool->node);
4958
4959 raw_spin_lock_irq(&nna->lock);
4960 list_del_init(&pwq->pending_node);
4961 raw_spin_unlock_irq(&nna->lock);
4962 }
4963
4964 call_rcu(&pwq->rcu, rcu_free_pwq);
4965
4966 /*
4967 * If we're the last pwq going away, @wq is already dead and no one
4968 * is gonna access it anymore. Schedule RCU free.
4969 */
4970 if (is_last) {
4971 wq_unregister_lockdep(wq);
4972 call_rcu(&wq->rcu, rcu_free_wq);
4973 }
4974}
4975
4976/* initialize newly allocated @pwq which is associated with @wq and @pool */
4977static void init_pwq(struct pool_workqueue *pwq, struct workqueue_struct *wq,
4978 struct worker_pool *pool)
4979{
4980 BUG_ON((unsigned long)pwq & ~WORK_STRUCT_PWQ_MASK);
4981
4982 memset(pwq, 0, sizeof(*pwq));
4983
4984 pwq->pool = pool;
4985 pwq->wq = wq;
4986 pwq->flush_color = -1;
4987 pwq->refcnt = 1;
4988 INIT_LIST_HEAD(&pwq->inactive_works);
4989 INIT_LIST_HEAD(&pwq->pending_node);
4990 INIT_LIST_HEAD(&pwq->pwqs_node);
4991 INIT_LIST_HEAD(&pwq->mayday_node);
4992 kthread_init_work(&pwq->release_work, pwq_release_workfn);
4993}
4994
4995/* sync @pwq with the current state of its associated wq and link it */
4996static void link_pwq(struct pool_workqueue *pwq)
4997{
4998 struct workqueue_struct *wq = pwq->wq;
4999
5000 lockdep_assert_held(&wq->mutex);
5001
5002 /* may be called multiple times, ignore if already linked */
5003 if (!list_empty(&pwq->pwqs_node))
5004 return;
5005
5006 /* set the matching work_color */
5007 pwq->work_color = wq->work_color;
5008
5009 /* link in @pwq */
5010 list_add_tail_rcu(&pwq->pwqs_node, &wq->pwqs);
5011}
5012
5013/* obtain a pool matching @attr and create a pwq associating the pool and @wq */
5014static struct pool_workqueue *alloc_unbound_pwq(struct workqueue_struct *wq,
5015 const struct workqueue_attrs *attrs)
5016{
5017 struct worker_pool *pool;
5018 struct pool_workqueue *pwq;
5019
5020 lockdep_assert_held(&wq_pool_mutex);
5021
5022 pool = get_unbound_pool(attrs);
5023 if (!pool)
5024 return NULL;
5025
5026 pwq = kmem_cache_alloc_node(pwq_cache, GFP_KERNEL, pool->node);
5027 if (!pwq) {
5028 put_unbound_pool(pool);
5029 return NULL;
5030 }
5031
5032 init_pwq(pwq, wq, pool);
5033 return pwq;
5034}
5035
5036/**
5037 * wq_calc_pod_cpumask - calculate a wq_attrs' cpumask for a pod
5038 * @attrs: the wq_attrs of the default pwq of the target workqueue
5039 * @cpu: the target CPU
5040 * @cpu_going_down: if >= 0, the CPU to consider as offline
5041 *
5042 * Calculate the cpumask a workqueue with @attrs should use on @pod. If
5043 * @cpu_going_down is >= 0, that cpu is considered offline during calculation.
5044 * The result is stored in @attrs->__pod_cpumask.
5045 *
5046 * If pod affinity is not enabled, @attrs->cpumask is always used. If enabled
5047 * and @pod has online CPUs requested by @attrs, the returned cpumask is the
5048 * intersection of the possible CPUs of @pod and @attrs->cpumask.
5049 *
5050 * The caller is responsible for ensuring that the cpumask of @pod stays stable.
5051 */
5052static void wq_calc_pod_cpumask(struct workqueue_attrs *attrs, int cpu,
5053 int cpu_going_down)
5054{
5055 const struct wq_pod_type *pt = wqattrs_pod_type(attrs);
5056 int pod = pt->cpu_pod[cpu];
5057
5058 /* does @pod have any online CPUs @attrs wants? */
5059 cpumask_and(attrs->__pod_cpumask, pt->pod_cpus[pod], attrs->cpumask);
5060 cpumask_and(attrs->__pod_cpumask, attrs->__pod_cpumask, cpu_online_mask);
5061 if (cpu_going_down >= 0)
5062 cpumask_clear_cpu(cpu_going_down, attrs->__pod_cpumask);
5063
5064 if (cpumask_empty(attrs->__pod_cpumask)) {
5065 cpumask_copy(attrs->__pod_cpumask, attrs->cpumask);
5066 return;
5067 }
5068
5069 /* yeap, return possible CPUs in @pod that @attrs wants */
5070 cpumask_and(attrs->__pod_cpumask, attrs->cpumask, pt->pod_cpus[pod]);
5071
5072 if (cpumask_empty(attrs->__pod_cpumask))
5073 pr_warn_once("WARNING: workqueue cpumask: online intersect > "
5074 "possible intersect\n");
5075}
5076
5077/* install @pwq into @wq and return the old pwq, @cpu < 0 for dfl_pwq */
5078static struct pool_workqueue *install_unbound_pwq(struct workqueue_struct *wq,
5079 int cpu, struct pool_workqueue *pwq)
5080{
5081 struct pool_workqueue __rcu **slot = unbound_pwq_slot(wq, cpu);
5082 struct pool_workqueue *old_pwq;
5083
5084 lockdep_assert_held(&wq_pool_mutex);
5085 lockdep_assert_held(&wq->mutex);
5086
5087 /* link_pwq() can handle duplicate calls */
5088 link_pwq(pwq);
5089
5090 old_pwq = rcu_access_pointer(*slot);
5091 rcu_assign_pointer(*slot, pwq);
5092 return old_pwq;
5093}
5094
5095/* context to store the prepared attrs & pwqs before applying */
5096struct apply_wqattrs_ctx {
5097 struct workqueue_struct *wq; /* target workqueue */
5098 struct workqueue_attrs *attrs; /* attrs to apply */
5099 struct list_head list; /* queued for batching commit */
5100 struct pool_workqueue *dfl_pwq;
5101 struct pool_workqueue *pwq_tbl[];
5102};
5103
5104/* free the resources after success or abort */
5105static void apply_wqattrs_cleanup(struct apply_wqattrs_ctx *ctx)
5106{
5107 if (ctx) {
5108 int cpu;
5109
5110 for_each_possible_cpu(cpu)
5111 put_pwq_unlocked(ctx->pwq_tbl[cpu]);
5112 put_pwq_unlocked(ctx->dfl_pwq);
5113
5114 free_workqueue_attrs(ctx->attrs);
5115
5116 kfree(ctx);
5117 }
5118}
5119
5120/* allocate the attrs and pwqs for later installation */
5121static struct apply_wqattrs_ctx *
5122apply_wqattrs_prepare(struct workqueue_struct *wq,
5123 const struct workqueue_attrs *attrs,
5124 const cpumask_var_t unbound_cpumask)
5125{
5126 struct apply_wqattrs_ctx *ctx;
5127 struct workqueue_attrs *new_attrs;
5128 int cpu;
5129
5130 lockdep_assert_held(&wq_pool_mutex);
5131
5132 if (WARN_ON(attrs->affn_scope < 0 ||
5133 attrs->affn_scope >= WQ_AFFN_NR_TYPES))
5134 return ERR_PTR(-EINVAL);
5135
5136 ctx = kzalloc(struct_size(ctx, pwq_tbl, nr_cpu_ids), GFP_KERNEL);
5137
5138 new_attrs = alloc_workqueue_attrs();
5139 if (!ctx || !new_attrs)
5140 goto out_free;
5141
5142 /*
5143 * If something goes wrong during CPU up/down, we'll fall back to
5144 * the default pwq covering whole @attrs->cpumask. Always create
5145 * it even if we don't use it immediately.
5146 */
5147 copy_workqueue_attrs(new_attrs, attrs);
5148 wqattrs_actualize_cpumask(new_attrs, unbound_cpumask);
5149 cpumask_copy(new_attrs->__pod_cpumask, new_attrs->cpumask);
5150 ctx->dfl_pwq = alloc_unbound_pwq(wq, new_attrs);
5151 if (!ctx->dfl_pwq)
5152 goto out_free;
5153
5154 for_each_possible_cpu(cpu) {
5155 if (new_attrs->ordered) {
5156 ctx->dfl_pwq->refcnt++;
5157 ctx->pwq_tbl[cpu] = ctx->dfl_pwq;
5158 } else {
5159 wq_calc_pod_cpumask(new_attrs, cpu, -1);
5160 ctx->pwq_tbl[cpu] = alloc_unbound_pwq(wq, new_attrs);
5161 if (!ctx->pwq_tbl[cpu])
5162 goto out_free;
5163 }
5164 }
5165
5166 /* save the user configured attrs and sanitize it. */
5167 copy_workqueue_attrs(new_attrs, attrs);
5168 cpumask_and(new_attrs->cpumask, new_attrs->cpumask, cpu_possible_mask);
5169 cpumask_copy(new_attrs->__pod_cpumask, new_attrs->cpumask);
5170 ctx->attrs = new_attrs;
5171
5172 /*
5173 * For initialized ordered workqueues, there should only be one pwq
5174 * (dfl_pwq). Set the plugged flag of ctx->dfl_pwq to suspend execution
5175 * of newly queued work items until execution of older work items in
5176 * the old pwq's have completed.
5177 */
5178 if ((wq->flags & __WQ_ORDERED) && !list_empty(&wq->pwqs))
5179 ctx->dfl_pwq->plugged = true;
5180
5181 ctx->wq = wq;
5182 return ctx;
5183
5184out_free:
5185 free_workqueue_attrs(new_attrs);
5186 apply_wqattrs_cleanup(ctx);
5187 return ERR_PTR(-ENOMEM);
5188}
5189
5190/* set attrs and install prepared pwqs, @ctx points to old pwqs on return */
5191static void apply_wqattrs_commit(struct apply_wqattrs_ctx *ctx)
5192{
5193 int cpu;
5194
5195 /* all pwqs have been created successfully, let's install'em */
5196 mutex_lock(&ctx->wq->mutex);
5197
5198 copy_workqueue_attrs(ctx->wq->unbound_attrs, ctx->attrs);
5199
5200 /* save the previous pwqs and install the new ones */
5201 for_each_possible_cpu(cpu)
5202 ctx->pwq_tbl[cpu] = install_unbound_pwq(ctx->wq, cpu,
5203 ctx->pwq_tbl[cpu]);
5204 ctx->dfl_pwq = install_unbound_pwq(ctx->wq, -1, ctx->dfl_pwq);
5205
5206 /* update node_nr_active->max */
5207 wq_update_node_max_active(ctx->wq, -1);
5208
5209 /* rescuer needs to respect wq cpumask changes */
5210 if (ctx->wq->rescuer)
5211 set_cpus_allowed_ptr(ctx->wq->rescuer->task,
5212 unbound_effective_cpumask(ctx->wq));
5213
5214 mutex_unlock(&ctx->wq->mutex);
5215}
5216
5217static int apply_workqueue_attrs_locked(struct workqueue_struct *wq,
5218 const struct workqueue_attrs *attrs)
5219{
5220 struct apply_wqattrs_ctx *ctx;
5221
5222 /* only unbound workqueues can change attributes */
5223 if (WARN_ON(!(wq->flags & WQ_UNBOUND)))
5224 return -EINVAL;
5225
5226 ctx = apply_wqattrs_prepare(wq, attrs, wq_unbound_cpumask);
5227 if (IS_ERR(ctx))
5228 return PTR_ERR(ctx);
5229
5230 /* the ctx has been prepared successfully, let's commit it */
5231 apply_wqattrs_commit(ctx);
5232 apply_wqattrs_cleanup(ctx);
5233
5234 return 0;
5235}
5236
5237/**
5238 * apply_workqueue_attrs - apply new workqueue_attrs to an unbound workqueue
5239 * @wq: the target workqueue
5240 * @attrs: the workqueue_attrs to apply, allocated with alloc_workqueue_attrs()
5241 *
5242 * Apply @attrs to an unbound workqueue @wq. Unless disabled, this function maps
5243 * a separate pwq to each CPU pod with possibles CPUs in @attrs->cpumask so that
5244 * work items are affine to the pod it was issued on. Older pwqs are released as
5245 * in-flight work items finish. Note that a work item which repeatedly requeues
5246 * itself back-to-back will stay on its current pwq.
5247 *
5248 * Performs GFP_KERNEL allocations.
5249 *
5250 * Assumes caller has CPU hotplug read exclusion, i.e. cpus_read_lock().
5251 *
5252 * Return: 0 on success and -errno on failure.
5253 */
5254int apply_workqueue_attrs(struct workqueue_struct *wq,
5255 const struct workqueue_attrs *attrs)
5256{
5257 int ret;
5258
5259 lockdep_assert_cpus_held();
5260
5261 mutex_lock(&wq_pool_mutex);
5262 ret = apply_workqueue_attrs_locked(wq, attrs);
5263 mutex_unlock(&wq_pool_mutex);
5264
5265 return ret;
5266}
5267
5268/**
5269 * wq_update_pod - update pod affinity of a wq for CPU hot[un]plug
5270 * @wq: the target workqueue
5271 * @cpu: the CPU to update pool association for
5272 * @hotplug_cpu: the CPU coming up or going down
5273 * @online: whether @cpu is coming up or going down
5274 *
5275 * This function is to be called from %CPU_DOWN_PREPARE, %CPU_ONLINE and
5276 * %CPU_DOWN_FAILED. @cpu is being hot[un]plugged, update pod affinity of
5277 * @wq accordingly.
5278 *
5279 *
5280 * If pod affinity can't be adjusted due to memory allocation failure, it falls
5281 * back to @wq->dfl_pwq which may not be optimal but is always correct.
5282 *
5283 * Note that when the last allowed CPU of a pod goes offline for a workqueue
5284 * with a cpumask spanning multiple pods, the workers which were already
5285 * executing the work items for the workqueue will lose their CPU affinity and
5286 * may execute on any CPU. This is similar to how per-cpu workqueues behave on
5287 * CPU_DOWN. If a workqueue user wants strict affinity, it's the user's
5288 * responsibility to flush the work item from CPU_DOWN_PREPARE.
5289 */
5290static void wq_update_pod(struct workqueue_struct *wq, int cpu,
5291 int hotplug_cpu, bool online)
5292{
5293 int off_cpu = online ? -1 : hotplug_cpu;
5294 struct pool_workqueue *old_pwq = NULL, *pwq;
5295 struct workqueue_attrs *target_attrs;
5296
5297 lockdep_assert_held(&wq_pool_mutex);
5298
5299 if (!(wq->flags & WQ_UNBOUND) || wq->unbound_attrs->ordered)
5300 return;
5301
5302 /*
5303 * We don't wanna alloc/free wq_attrs for each wq for each CPU.
5304 * Let's use a preallocated one. The following buf is protected by
5305 * CPU hotplug exclusion.
5306 */
5307 target_attrs = wq_update_pod_attrs_buf;
5308
5309 copy_workqueue_attrs(target_attrs, wq->unbound_attrs);
5310 wqattrs_actualize_cpumask(target_attrs, wq_unbound_cpumask);
5311
5312 /* nothing to do if the target cpumask matches the current pwq */
5313 wq_calc_pod_cpumask(target_attrs, cpu, off_cpu);
5314 if (wqattrs_equal(target_attrs, unbound_pwq(wq, cpu)->pool->attrs))
5315 return;
5316
5317 /* create a new pwq */
5318 pwq = alloc_unbound_pwq(wq, target_attrs);
5319 if (!pwq) {
5320 pr_warn("workqueue: allocation failed while updating CPU pod affinity of \"%s\"\n",
5321 wq->name);
5322 goto use_dfl_pwq;
5323 }
5324
5325 /* Install the new pwq. */
5326 mutex_lock(&wq->mutex);
5327 old_pwq = install_unbound_pwq(wq, cpu, pwq);
5328 goto out_unlock;
5329
5330use_dfl_pwq:
5331 mutex_lock(&wq->mutex);
5332 pwq = unbound_pwq(wq, -1);
5333 raw_spin_lock_irq(&pwq->pool->lock);
5334 get_pwq(pwq);
5335 raw_spin_unlock_irq(&pwq->pool->lock);
5336 old_pwq = install_unbound_pwq(wq, cpu, pwq);
5337out_unlock:
5338 mutex_unlock(&wq->mutex);
5339 put_pwq_unlocked(old_pwq);
5340}
5341
5342static int alloc_and_link_pwqs(struct workqueue_struct *wq)
5343{
5344 bool highpri = wq->flags & WQ_HIGHPRI;
5345 int cpu, ret;
5346
5347 wq->cpu_pwq = alloc_percpu(struct pool_workqueue *);
5348 if (!wq->cpu_pwq)
5349 goto enomem;
5350
5351 if (!(wq->flags & WQ_UNBOUND)) {
5352 for_each_possible_cpu(cpu) {
5353 struct pool_workqueue **pwq_p;
5354 struct worker_pool __percpu *pools;
5355 struct worker_pool *pool;
5356
5357 if (wq->flags & WQ_BH)
5358 pools = bh_worker_pools;
5359 else
5360 pools = cpu_worker_pools;
5361
5362 pool = &(per_cpu_ptr(pools, cpu)[highpri]);
5363 pwq_p = per_cpu_ptr(wq->cpu_pwq, cpu);
5364
5365 *pwq_p = kmem_cache_alloc_node(pwq_cache, GFP_KERNEL,
5366 pool->node);
5367 if (!*pwq_p)
5368 goto enomem;
5369
5370 init_pwq(*pwq_p, wq, pool);
5371
5372 mutex_lock(&wq->mutex);
5373 link_pwq(*pwq_p);
5374 mutex_unlock(&wq->mutex);
5375 }
5376 return 0;
5377 }
5378
5379 cpus_read_lock();
5380 if (wq->flags & __WQ_ORDERED) {
5381 struct pool_workqueue *dfl_pwq;
5382
5383 ret = apply_workqueue_attrs(wq, ordered_wq_attrs[highpri]);
5384 /* there should only be single pwq for ordering guarantee */
5385 dfl_pwq = rcu_access_pointer(wq->dfl_pwq);
5386 WARN(!ret && (wq->pwqs.next != &dfl_pwq->pwqs_node ||
5387 wq->pwqs.prev != &dfl_pwq->pwqs_node),
5388 "ordering guarantee broken for workqueue %s\n", wq->name);
5389 } else {
5390 ret = apply_workqueue_attrs(wq, unbound_std_wq_attrs[highpri]);
5391 }
5392 cpus_read_unlock();
5393
5394 /* for unbound pwq, flush the pwq_release_worker ensures that the
5395 * pwq_release_workfn() completes before calling kfree(wq).
5396 */
5397 if (ret)
5398 kthread_flush_worker(pwq_release_worker);
5399
5400 return ret;
5401
5402enomem:
5403 if (wq->cpu_pwq) {
5404 for_each_possible_cpu(cpu) {
5405 struct pool_workqueue *pwq = *per_cpu_ptr(wq->cpu_pwq, cpu);
5406
5407 if (pwq)
5408 kmem_cache_free(pwq_cache, pwq);
5409 }
5410 free_percpu(wq->cpu_pwq);
5411 wq->cpu_pwq = NULL;
5412 }
5413 return -ENOMEM;
5414}
5415
5416static int wq_clamp_max_active(int max_active, unsigned int flags,
5417 const char *name)
5418{
5419 if (max_active < 1 || max_active > WQ_MAX_ACTIVE)
5420 pr_warn("workqueue: max_active %d requested for %s is out of range, clamping between %d and %d\n",
5421 max_active, name, 1, WQ_MAX_ACTIVE);
5422
5423 return clamp_val(max_active, 1, WQ_MAX_ACTIVE);
5424}
5425
5426/*
5427 * Workqueues which may be used during memory reclaim should have a rescuer
5428 * to guarantee forward progress.
5429 */
5430static int init_rescuer(struct workqueue_struct *wq)
5431{
5432 struct worker *rescuer;
5433 int ret;
5434
5435 if (!(wq->flags & WQ_MEM_RECLAIM))
5436 return 0;
5437
5438 rescuer = alloc_worker(NUMA_NO_NODE);
5439 if (!rescuer) {
5440 pr_err("workqueue: Failed to allocate a rescuer for wq \"%s\"\n",
5441 wq->name);
5442 return -ENOMEM;
5443 }
5444
5445 rescuer->rescue_wq = wq;
5446 rescuer->task = kthread_create(rescuer_thread, rescuer, "kworker/R-%s", wq->name);
5447 if (IS_ERR(rescuer->task)) {
5448 ret = PTR_ERR(rescuer->task);
5449 pr_err("workqueue: Failed to create a rescuer kthread for wq \"%s\": %pe",
5450 wq->name, ERR_PTR(ret));
5451 kfree(rescuer);
5452 return ret;
5453 }
5454
5455 wq->rescuer = rescuer;
5456 if (wq->flags & WQ_UNBOUND)
5457 kthread_bind_mask(rescuer->task, wq_unbound_cpumask);
5458 else
5459 kthread_bind_mask(rescuer->task, cpu_possible_mask);
5460 wake_up_process(rescuer->task);
5461
5462 return 0;
5463}
5464
5465/**
5466 * wq_adjust_max_active - update a wq's max_active to the current setting
5467 * @wq: target workqueue
5468 *
5469 * If @wq isn't freezing, set @wq->max_active to the saved_max_active and
5470 * activate inactive work items accordingly. If @wq is freezing, clear
5471 * @wq->max_active to zero.
5472 */
5473static void wq_adjust_max_active(struct workqueue_struct *wq)
5474{
5475 bool activated;
5476 int new_max, new_min;
5477
5478 lockdep_assert_held(&wq->mutex);
5479
5480 if ((wq->flags & WQ_FREEZABLE) && workqueue_freezing) {
5481 new_max = 0;
5482 new_min = 0;
5483 } else {
5484 new_max = wq->saved_max_active;
5485 new_min = wq->saved_min_active;
5486 }
5487
5488 if (wq->max_active == new_max && wq->min_active == new_min)
5489 return;
5490
5491 /*
5492 * Update @wq->max/min_active and then kick inactive work items if more
5493 * active work items are allowed. This doesn't break work item ordering
5494 * because new work items are always queued behind existing inactive
5495 * work items if there are any.
5496 */
5497 WRITE_ONCE(wq->max_active, new_max);
5498 WRITE_ONCE(wq->min_active, new_min);
5499
5500 if (wq->flags & WQ_UNBOUND)
5501 wq_update_node_max_active(wq, -1);
5502
5503 if (new_max == 0)
5504 return;
5505
5506 /*
5507 * Round-robin through pwq's activating the first inactive work item
5508 * until max_active is filled.
5509 */
5510 do {
5511 struct pool_workqueue *pwq;
5512
5513 activated = false;
5514 for_each_pwq(pwq, wq) {
5515 unsigned long irq_flags;
5516
5517 /* can be called during early boot w/ irq disabled */
5518 raw_spin_lock_irqsave(&pwq->pool->lock, irq_flags);
5519 if (pwq_activate_first_inactive(pwq, true)) {
5520 activated = true;
5521 kick_pool(pwq->pool);
5522 }
5523 raw_spin_unlock_irqrestore(&pwq->pool->lock, irq_flags);
5524 }
5525 } while (activated);
5526}
5527
5528__printf(1, 4)
5529struct workqueue_struct *alloc_workqueue(const char *fmt,
5530 unsigned int flags,
5531 int max_active, ...)
5532{
5533 va_list args;
5534 struct workqueue_struct *wq;
5535 size_t wq_size;
5536 int name_len;
5537
5538 if (flags & WQ_BH) {
5539 if (WARN_ON_ONCE(flags & ~__WQ_BH_ALLOWS))
5540 return NULL;
5541 if (WARN_ON_ONCE(max_active))
5542 return NULL;
5543 }
5544
5545 /* see the comment above the definition of WQ_POWER_EFFICIENT */
5546 if ((flags & WQ_POWER_EFFICIENT) && wq_power_efficient)
5547 flags |= WQ_UNBOUND;
5548
5549 /* allocate wq and format name */
5550 if (flags & WQ_UNBOUND)
5551 wq_size = struct_size(wq, node_nr_active, nr_node_ids + 1);
5552 else
5553 wq_size = sizeof(*wq);
5554
5555 wq = kzalloc(wq_size, GFP_KERNEL);
5556 if (!wq)
5557 return NULL;
5558
5559 if (flags & WQ_UNBOUND) {
5560 wq->unbound_attrs = alloc_workqueue_attrs();
5561 if (!wq->unbound_attrs)
5562 goto err_free_wq;
5563 }
5564
5565 va_start(args, max_active);
5566 name_len = vsnprintf(wq->name, sizeof(wq->name), fmt, args);
5567 va_end(args);
5568
5569 if (name_len >= WQ_NAME_LEN)
5570 pr_warn_once("workqueue: name exceeds WQ_NAME_LEN. Truncating to: %s\n",
5571 wq->name);
5572
5573 if (flags & WQ_BH) {
5574 /*
5575 * BH workqueues always share a single execution context per CPU
5576 * and don't impose any max_active limit.
5577 */
5578 max_active = INT_MAX;
5579 } else {
5580 max_active = max_active ?: WQ_DFL_ACTIVE;
5581 max_active = wq_clamp_max_active(max_active, flags, wq->name);
5582 }
5583
5584 /* init wq */
5585 wq->flags = flags;
5586 wq->max_active = max_active;
5587 wq->min_active = min(max_active, WQ_DFL_MIN_ACTIVE);
5588 wq->saved_max_active = wq->max_active;
5589 wq->saved_min_active = wq->min_active;
5590 mutex_init(&wq->mutex);
5591 atomic_set(&wq->nr_pwqs_to_flush, 0);
5592 INIT_LIST_HEAD(&wq->pwqs);
5593 INIT_LIST_HEAD(&wq->flusher_queue);
5594 INIT_LIST_HEAD(&wq->flusher_overflow);
5595 INIT_LIST_HEAD(&wq->maydays);
5596
5597 wq_init_lockdep(wq);
5598 INIT_LIST_HEAD(&wq->list);
5599
5600 if (flags & WQ_UNBOUND) {
5601 if (alloc_node_nr_active(wq->node_nr_active) < 0)
5602 goto err_unreg_lockdep;
5603 }
5604
5605 if (alloc_and_link_pwqs(wq) < 0)
5606 goto err_free_node_nr_active;
5607
5608 if (wq_online && init_rescuer(wq) < 0)
5609 goto err_destroy;
5610
5611 if ((wq->flags & WQ_SYSFS) && workqueue_sysfs_register(wq))
5612 goto err_destroy;
5613
5614 /*
5615 * wq_pool_mutex protects global freeze state and workqueues list.
5616 * Grab it, adjust max_active and add the new @wq to workqueues
5617 * list.
5618 */
5619 mutex_lock(&wq_pool_mutex);
5620
5621 mutex_lock(&wq->mutex);
5622 wq_adjust_max_active(wq);
5623 mutex_unlock(&wq->mutex);
5624
5625 list_add_tail_rcu(&wq->list, &workqueues);
5626
5627 mutex_unlock(&wq_pool_mutex);
5628
5629 return wq;
5630
5631err_free_node_nr_active:
5632 if (wq->flags & WQ_UNBOUND)
5633 free_node_nr_active(wq->node_nr_active);
5634err_unreg_lockdep:
5635 wq_unregister_lockdep(wq);
5636 wq_free_lockdep(wq);
5637err_free_wq:
5638 free_workqueue_attrs(wq->unbound_attrs);
5639 kfree(wq);
5640 return NULL;
5641err_destroy:
5642 destroy_workqueue(wq);
5643 return NULL;
5644}
5645EXPORT_SYMBOL_GPL(alloc_workqueue);
5646
5647static bool pwq_busy(struct pool_workqueue *pwq)
5648{
5649 int i;
5650
5651 for (i = 0; i < WORK_NR_COLORS; i++)
5652 if (pwq->nr_in_flight[i])
5653 return true;
5654
5655 if ((pwq != rcu_access_pointer(pwq->wq->dfl_pwq)) && (pwq->refcnt > 1))
5656 return true;
5657 if (!pwq_is_empty(pwq))
5658 return true;
5659
5660 return false;
5661}
5662
5663/**
5664 * destroy_workqueue - safely terminate a workqueue
5665 * @wq: target workqueue
5666 *
5667 * Safely destroy a workqueue. All work currently pending will be done first.
5668 */
5669void destroy_workqueue(struct workqueue_struct *wq)
5670{
5671 struct pool_workqueue *pwq;
5672 int cpu;
5673
5674 /*
5675 * Remove it from sysfs first so that sanity check failure doesn't
5676 * lead to sysfs name conflicts.
5677 */
5678 workqueue_sysfs_unregister(wq);
5679
5680 /* mark the workqueue destruction is in progress */
5681 mutex_lock(&wq->mutex);
5682 wq->flags |= __WQ_DESTROYING;
5683 mutex_unlock(&wq->mutex);
5684
5685 /* drain it before proceeding with destruction */
5686 drain_workqueue(wq);
5687
5688 /* kill rescuer, if sanity checks fail, leave it w/o rescuer */
5689 if (wq->rescuer) {
5690 struct worker *rescuer = wq->rescuer;
5691
5692 /* this prevents new queueing */
5693 raw_spin_lock_irq(&wq_mayday_lock);
5694 wq->rescuer = NULL;
5695 raw_spin_unlock_irq(&wq_mayday_lock);
5696
5697 /* rescuer will empty maydays list before exiting */
5698 kthread_stop(rescuer->task);
5699 kfree(rescuer);
5700 }
5701
5702 /*
5703 * Sanity checks - grab all the locks so that we wait for all
5704 * in-flight operations which may do put_pwq().
5705 */
5706 mutex_lock(&wq_pool_mutex);
5707 mutex_lock(&wq->mutex);
5708 for_each_pwq(pwq, wq) {
5709 raw_spin_lock_irq(&pwq->pool->lock);
5710 if (WARN_ON(pwq_busy(pwq))) {
5711 pr_warn("%s: %s has the following busy pwq\n",
5712 __func__, wq->name);
5713 show_pwq(pwq);
5714 raw_spin_unlock_irq(&pwq->pool->lock);
5715 mutex_unlock(&wq->mutex);
5716 mutex_unlock(&wq_pool_mutex);
5717 show_one_workqueue(wq);
5718 return;
5719 }
5720 raw_spin_unlock_irq(&pwq->pool->lock);
5721 }
5722 mutex_unlock(&wq->mutex);
5723
5724 /*
5725 * wq list is used to freeze wq, remove from list after
5726 * flushing is complete in case freeze races us.
5727 */
5728 list_del_rcu(&wq->list);
5729 mutex_unlock(&wq_pool_mutex);
5730
5731 /*
5732 * We're the sole accessor of @wq. Directly access cpu_pwq and dfl_pwq
5733 * to put the base refs. @wq will be auto-destroyed from the last
5734 * pwq_put. RCU read lock prevents @wq from going away from under us.
5735 */
5736 rcu_read_lock();
5737
5738 for_each_possible_cpu(cpu) {
5739 put_pwq_unlocked(unbound_pwq(wq, cpu));
5740 RCU_INIT_POINTER(*unbound_pwq_slot(wq, cpu), NULL);
5741 }
5742
5743 put_pwq_unlocked(unbound_pwq(wq, -1));
5744 RCU_INIT_POINTER(*unbound_pwq_slot(wq, -1), NULL);
5745
5746 rcu_read_unlock();
5747}
5748EXPORT_SYMBOL_GPL(destroy_workqueue);
5749
5750/**
5751 * workqueue_set_max_active - adjust max_active of a workqueue
5752 * @wq: target workqueue
5753 * @max_active: new max_active value.
5754 *
5755 * Set max_active of @wq to @max_active. See the alloc_workqueue() function
5756 * comment.
5757 *
5758 * CONTEXT:
5759 * Don't call from IRQ context.
5760 */
5761void workqueue_set_max_active(struct workqueue_struct *wq, int max_active)
5762{
5763 /* max_active doesn't mean anything for BH workqueues */
5764 if (WARN_ON(wq->flags & WQ_BH))
5765 return;
5766 /* disallow meddling with max_active for ordered workqueues */
5767 if (WARN_ON(wq->flags & __WQ_ORDERED))
5768 return;
5769
5770 max_active = wq_clamp_max_active(max_active, wq->flags, wq->name);
5771
5772 mutex_lock(&wq->mutex);
5773
5774 wq->saved_max_active = max_active;
5775 if (wq->flags & WQ_UNBOUND)
5776 wq->saved_min_active = min(wq->saved_min_active, max_active);
5777
5778 wq_adjust_max_active(wq);
5779
5780 mutex_unlock(&wq->mutex);
5781}
5782EXPORT_SYMBOL_GPL(workqueue_set_max_active);
5783
5784/**
5785 * workqueue_set_min_active - adjust min_active of an unbound workqueue
5786 * @wq: target unbound workqueue
5787 * @min_active: new min_active value
5788 *
5789 * Set min_active of an unbound workqueue. Unlike other types of workqueues, an
5790 * unbound workqueue is not guaranteed to be able to process max_active
5791 * interdependent work items. Instead, an unbound workqueue is guaranteed to be
5792 * able to process min_active number of interdependent work items which is
5793 * %WQ_DFL_MIN_ACTIVE by default.
5794 *
5795 * Use this function to adjust the min_active value between 0 and the current
5796 * max_active.
5797 */
5798void workqueue_set_min_active(struct workqueue_struct *wq, int min_active)
5799{
5800 /* min_active is only meaningful for non-ordered unbound workqueues */
5801 if (WARN_ON((wq->flags & (WQ_BH | WQ_UNBOUND | __WQ_ORDERED)) !=
5802 WQ_UNBOUND))
5803 return;
5804
5805 mutex_lock(&wq->mutex);
5806 wq->saved_min_active = clamp(min_active, 0, wq->saved_max_active);
5807 wq_adjust_max_active(wq);
5808 mutex_unlock(&wq->mutex);
5809}
5810
5811/**
5812 * current_work - retrieve %current task's work struct
5813 *
5814 * Determine if %current task is a workqueue worker and what it's working on.
5815 * Useful to find out the context that the %current task is running in.
5816 *
5817 * Return: work struct if %current task is a workqueue worker, %NULL otherwise.
5818 */
5819struct work_struct *current_work(void)
5820{
5821 struct worker *worker = current_wq_worker();
5822
5823 return worker ? worker->current_work : NULL;
5824}
5825EXPORT_SYMBOL(current_work);
5826
5827/**
5828 * current_is_workqueue_rescuer - is %current workqueue rescuer?
5829 *
5830 * Determine whether %current is a workqueue rescuer. Can be used from
5831 * work functions to determine whether it's being run off the rescuer task.
5832 *
5833 * Return: %true if %current is a workqueue rescuer. %false otherwise.
5834 */
5835bool current_is_workqueue_rescuer(void)
5836{
5837 struct worker *worker = current_wq_worker();
5838
5839 return worker && worker->rescue_wq;
5840}
5841
5842/**
5843 * workqueue_congested - test whether a workqueue is congested
5844 * @cpu: CPU in question
5845 * @wq: target workqueue
5846 *
5847 * Test whether @wq's cpu workqueue for @cpu is congested. There is
5848 * no synchronization around this function and the test result is
5849 * unreliable and only useful as advisory hints or for debugging.
5850 *
5851 * If @cpu is WORK_CPU_UNBOUND, the test is performed on the local CPU.
5852 *
5853 * With the exception of ordered workqueues, all workqueues have per-cpu
5854 * pool_workqueues, each with its own congested state. A workqueue being
5855 * congested on one CPU doesn't mean that the workqueue is contested on any
5856 * other CPUs.
5857 *
5858 * Return:
5859 * %true if congested, %false otherwise.
5860 */
5861bool workqueue_congested(int cpu, struct workqueue_struct *wq)
5862{
5863 struct pool_workqueue *pwq;
5864 bool ret;
5865
5866 rcu_read_lock();
5867 preempt_disable();
5868
5869 if (cpu == WORK_CPU_UNBOUND)
5870 cpu = smp_processor_id();
5871
5872 pwq = *per_cpu_ptr(wq->cpu_pwq, cpu);
5873 ret = !list_empty(&pwq->inactive_works);
5874
5875 preempt_enable();
5876 rcu_read_unlock();
5877
5878 return ret;
5879}
5880EXPORT_SYMBOL_GPL(workqueue_congested);
5881
5882/**
5883 * work_busy - test whether a work is currently pending or running
5884 * @work: the work to be tested
5885 *
5886 * Test whether @work is currently pending or running. There is no
5887 * synchronization around this function and the test result is
5888 * unreliable and only useful as advisory hints or for debugging.
5889 *
5890 * Return:
5891 * OR'd bitmask of WORK_BUSY_* bits.
5892 */
5893unsigned int work_busy(struct work_struct *work)
5894{
5895 struct worker_pool *pool;
5896 unsigned long irq_flags;
5897 unsigned int ret = 0;
5898
5899 if (work_pending(work))
5900 ret |= WORK_BUSY_PENDING;
5901
5902 rcu_read_lock();
5903 pool = get_work_pool(work);
5904 if (pool) {
5905 raw_spin_lock_irqsave(&pool->lock, irq_flags);
5906 if (find_worker_executing_work(pool, work))
5907 ret |= WORK_BUSY_RUNNING;
5908 raw_spin_unlock_irqrestore(&pool->lock, irq_flags);
5909 }
5910 rcu_read_unlock();
5911
5912 return ret;
5913}
5914EXPORT_SYMBOL_GPL(work_busy);
5915
5916/**
5917 * set_worker_desc - set description for the current work item
5918 * @fmt: printf-style format string
5919 * @...: arguments for the format string
5920 *
5921 * This function can be called by a running work function to describe what
5922 * the work item is about. If the worker task gets dumped, this
5923 * information will be printed out together to help debugging. The
5924 * description can be at most WORKER_DESC_LEN including the trailing '\0'.
5925 */
5926void set_worker_desc(const char *fmt, ...)
5927{
5928 struct worker *worker = current_wq_worker();
5929 va_list args;
5930
5931 if (worker) {
5932 va_start(args, fmt);
5933 vsnprintf(worker->desc, sizeof(worker->desc), fmt, args);
5934 va_end(args);
5935 }
5936}
5937EXPORT_SYMBOL_GPL(set_worker_desc);
5938
5939/**
5940 * print_worker_info - print out worker information and description
5941 * @log_lvl: the log level to use when printing
5942 * @task: target task
5943 *
5944 * If @task is a worker and currently executing a work item, print out the
5945 * name of the workqueue being serviced and worker description set with
5946 * set_worker_desc() by the currently executing work item.
5947 *
5948 * This function can be safely called on any task as long as the
5949 * task_struct itself is accessible. While safe, this function isn't
5950 * synchronized and may print out mixups or garbages of limited length.
5951 */
5952void print_worker_info(const char *log_lvl, struct task_struct *task)
5953{
5954 work_func_t *fn = NULL;
5955 char name[WQ_NAME_LEN] = { };
5956 char desc[WORKER_DESC_LEN] = { };
5957 struct pool_workqueue *pwq = NULL;
5958 struct workqueue_struct *wq = NULL;
5959 struct worker *worker;
5960
5961 if (!(task->flags & PF_WQ_WORKER))
5962 return;
5963
5964 /*
5965 * This function is called without any synchronization and @task
5966 * could be in any state. Be careful with dereferences.
5967 */
5968 worker = kthread_probe_data(task);
5969
5970 /*
5971 * Carefully copy the associated workqueue's workfn, name and desc.
5972 * Keep the original last '\0' in case the original is garbage.
5973 */
5974 copy_from_kernel_nofault(&fn, &worker->current_func, sizeof(fn));
5975 copy_from_kernel_nofault(&pwq, &worker->current_pwq, sizeof(pwq));
5976 copy_from_kernel_nofault(&wq, &pwq->wq, sizeof(wq));
5977 copy_from_kernel_nofault(name, wq->name, sizeof(name) - 1);
5978 copy_from_kernel_nofault(desc, worker->desc, sizeof(desc) - 1);
5979
5980 if (fn || name[0] || desc[0]) {
5981 printk("%sWorkqueue: %s %ps", log_lvl, name, fn);
5982 if (strcmp(name, desc))
5983 pr_cont(" (%s)", desc);
5984 pr_cont("\n");
5985 }
5986}
5987
5988static void pr_cont_pool_info(struct worker_pool *pool)
5989{
5990 pr_cont(" cpus=%*pbl", nr_cpumask_bits, pool->attrs->cpumask);
5991 if (pool->node != NUMA_NO_NODE)
5992 pr_cont(" node=%d", pool->node);
5993 pr_cont(" flags=0x%x", pool->flags);
5994 if (pool->flags & POOL_BH)
5995 pr_cont(" bh%s",
5996 pool->attrs->nice == HIGHPRI_NICE_LEVEL ? "-hi" : "");
5997 else
5998 pr_cont(" nice=%d", pool->attrs->nice);
5999}
6000
6001static void pr_cont_worker_id(struct worker *worker)
6002{
6003 struct worker_pool *pool = worker->pool;
6004
6005 if (pool->flags & WQ_BH)
6006 pr_cont("bh%s",
6007 pool->attrs->nice == HIGHPRI_NICE_LEVEL ? "-hi" : "");
6008 else
6009 pr_cont("%d%s", task_pid_nr(worker->task),
6010 worker->rescue_wq ? "(RESCUER)" : "");
6011}
6012
6013struct pr_cont_work_struct {
6014 bool comma;
6015 work_func_t func;
6016 long ctr;
6017};
6018
6019static void pr_cont_work_flush(bool comma, work_func_t func, struct pr_cont_work_struct *pcwsp)
6020{
6021 if (!pcwsp->ctr)
6022 goto out_record;
6023 if (func == pcwsp->func) {
6024 pcwsp->ctr++;
6025 return;
6026 }
6027 if (pcwsp->ctr == 1)
6028 pr_cont("%s %ps", pcwsp->comma ? "," : "", pcwsp->func);
6029 else
6030 pr_cont("%s %ld*%ps", pcwsp->comma ? "," : "", pcwsp->ctr, pcwsp->func);
6031 pcwsp->ctr = 0;
6032out_record:
6033 if ((long)func == -1L)
6034 return;
6035 pcwsp->comma = comma;
6036 pcwsp->func = func;
6037 pcwsp->ctr = 1;
6038}
6039
6040static void pr_cont_work(bool comma, struct work_struct *work, struct pr_cont_work_struct *pcwsp)
6041{
6042 if (work->func == wq_barrier_func) {
6043 struct wq_barrier *barr;
6044
6045 barr = container_of(work, struct wq_barrier, work);
6046
6047 pr_cont_work_flush(comma, (work_func_t)-1, pcwsp);
6048 pr_cont("%s BAR(%d)", comma ? "," : "",
6049 task_pid_nr(barr->task));
6050 } else {
6051 if (!comma)
6052 pr_cont_work_flush(comma, (work_func_t)-1, pcwsp);
6053 pr_cont_work_flush(comma, work->func, pcwsp);
6054 }
6055}
6056
6057static void show_pwq(struct pool_workqueue *pwq)
6058{
6059 struct pr_cont_work_struct pcws = { .ctr = 0, };
6060 struct worker_pool *pool = pwq->pool;
6061 struct work_struct *work;
6062 struct worker *worker;
6063 bool has_in_flight = false, has_pending = false;
6064 int bkt;
6065
6066 pr_info(" pwq %d:", pool->id);
6067 pr_cont_pool_info(pool);
6068
6069 pr_cont(" active=%d refcnt=%d%s\n",
6070 pwq->nr_active, pwq->refcnt,
6071 !list_empty(&pwq->mayday_node) ? " MAYDAY" : "");
6072
6073 hash_for_each(pool->busy_hash, bkt, worker, hentry) {
6074 if (worker->current_pwq == pwq) {
6075 has_in_flight = true;
6076 break;
6077 }
6078 }
6079 if (has_in_flight) {
6080 bool comma = false;
6081
6082 pr_info(" in-flight:");
6083 hash_for_each(pool->busy_hash, bkt, worker, hentry) {
6084 if (worker->current_pwq != pwq)
6085 continue;
6086
6087 pr_cont(" %s", comma ? "," : "");
6088 pr_cont_worker_id(worker);
6089 pr_cont(":%ps", worker->current_func);
6090 list_for_each_entry(work, &worker->scheduled, entry)
6091 pr_cont_work(false, work, &pcws);
6092 pr_cont_work_flush(comma, (work_func_t)-1L, &pcws);
6093 comma = true;
6094 }
6095 pr_cont("\n");
6096 }
6097
6098 list_for_each_entry(work, &pool->worklist, entry) {
6099 if (get_work_pwq(work) == pwq) {
6100 has_pending = true;
6101 break;
6102 }
6103 }
6104 if (has_pending) {
6105 bool comma = false;
6106
6107 pr_info(" pending:");
6108 list_for_each_entry(work, &pool->worklist, entry) {
6109 if (get_work_pwq(work) != pwq)
6110 continue;
6111
6112 pr_cont_work(comma, work, &pcws);
6113 comma = !(*work_data_bits(work) & WORK_STRUCT_LINKED);
6114 }
6115 pr_cont_work_flush(comma, (work_func_t)-1L, &pcws);
6116 pr_cont("\n");
6117 }
6118
6119 if (!list_empty(&pwq->inactive_works)) {
6120 bool comma = false;
6121
6122 pr_info(" inactive:");
6123 list_for_each_entry(work, &pwq->inactive_works, entry) {
6124 pr_cont_work(comma, work, &pcws);
6125 comma = !(*work_data_bits(work) & WORK_STRUCT_LINKED);
6126 }
6127 pr_cont_work_flush(comma, (work_func_t)-1L, &pcws);
6128 pr_cont("\n");
6129 }
6130}
6131
6132/**
6133 * show_one_workqueue - dump state of specified workqueue
6134 * @wq: workqueue whose state will be printed
6135 */
6136void show_one_workqueue(struct workqueue_struct *wq)
6137{
6138 struct pool_workqueue *pwq;
6139 bool idle = true;
6140 unsigned long irq_flags;
6141
6142 for_each_pwq(pwq, wq) {
6143 if (!pwq_is_empty(pwq)) {
6144 idle = false;
6145 break;
6146 }
6147 }
6148 if (idle) /* Nothing to print for idle workqueue */
6149 return;
6150
6151 pr_info("workqueue %s: flags=0x%x\n", wq->name, wq->flags);
6152
6153 for_each_pwq(pwq, wq) {
6154 raw_spin_lock_irqsave(&pwq->pool->lock, irq_flags);
6155 if (!pwq_is_empty(pwq)) {
6156 /*
6157 * Defer printing to avoid deadlocks in console
6158 * drivers that queue work while holding locks
6159 * also taken in their write paths.
6160 */
6161 printk_deferred_enter();
6162 show_pwq(pwq);
6163 printk_deferred_exit();
6164 }
6165 raw_spin_unlock_irqrestore(&pwq->pool->lock, irq_flags);
6166 /*
6167 * We could be printing a lot from atomic context, e.g.
6168 * sysrq-t -> show_all_workqueues(). Avoid triggering
6169 * hard lockup.
6170 */
6171 touch_nmi_watchdog();
6172 }
6173
6174}
6175
6176/**
6177 * show_one_worker_pool - dump state of specified worker pool
6178 * @pool: worker pool whose state will be printed
6179 */
6180static void show_one_worker_pool(struct worker_pool *pool)
6181{
6182 struct worker *worker;
6183 bool first = true;
6184 unsigned long irq_flags;
6185 unsigned long hung = 0;
6186
6187 raw_spin_lock_irqsave(&pool->lock, irq_flags);
6188 if (pool->nr_workers == pool->nr_idle)
6189 goto next_pool;
6190
6191 /* How long the first pending work is waiting for a worker. */
6192 if (!list_empty(&pool->worklist))
6193 hung = jiffies_to_msecs(jiffies - pool->watchdog_ts) / 1000;
6194
6195 /*
6196 * Defer printing to avoid deadlocks in console drivers that
6197 * queue work while holding locks also taken in their write
6198 * paths.
6199 */
6200 printk_deferred_enter();
6201 pr_info("pool %d:", pool->id);
6202 pr_cont_pool_info(pool);
6203 pr_cont(" hung=%lus workers=%d", hung, pool->nr_workers);
6204 if (pool->manager)
6205 pr_cont(" manager: %d",
6206 task_pid_nr(pool->manager->task));
6207 list_for_each_entry(worker, &pool->idle_list, entry) {
6208 pr_cont(" %s", first ? "idle: " : "");
6209 pr_cont_worker_id(worker);
6210 first = false;
6211 }
6212 pr_cont("\n");
6213 printk_deferred_exit();
6214next_pool:
6215 raw_spin_unlock_irqrestore(&pool->lock, irq_flags);
6216 /*
6217 * We could be printing a lot from atomic context, e.g.
6218 * sysrq-t -> show_all_workqueues(). Avoid triggering
6219 * hard lockup.
6220 */
6221 touch_nmi_watchdog();
6222
6223}
6224
6225/**
6226 * show_all_workqueues - dump workqueue state
6227 *
6228 * Called from a sysrq handler and prints out all busy workqueues and pools.
6229 */
6230void show_all_workqueues(void)
6231{
6232 struct workqueue_struct *wq;
6233 struct worker_pool *pool;
6234 int pi;
6235
6236 rcu_read_lock();
6237
6238 pr_info("Showing busy workqueues and worker pools:\n");
6239
6240 list_for_each_entry_rcu(wq, &workqueues, list)
6241 show_one_workqueue(wq);
6242
6243 for_each_pool(pool, pi)
6244 show_one_worker_pool(pool);
6245
6246 rcu_read_unlock();
6247}
6248
6249/**
6250 * show_freezable_workqueues - dump freezable workqueue state
6251 *
6252 * Called from try_to_freeze_tasks() and prints out all freezable workqueues
6253 * still busy.
6254 */
6255void show_freezable_workqueues(void)
6256{
6257 struct workqueue_struct *wq;
6258
6259 rcu_read_lock();
6260
6261 pr_info("Showing freezable workqueues that are still busy:\n");
6262
6263 list_for_each_entry_rcu(wq, &workqueues, list) {
6264 if (!(wq->flags & WQ_FREEZABLE))
6265 continue;
6266 show_one_workqueue(wq);
6267 }
6268
6269 rcu_read_unlock();
6270}
6271
6272/* used to show worker information through /proc/PID/{comm,stat,status} */
6273void wq_worker_comm(char *buf, size_t size, struct task_struct *task)
6274{
6275 int off;
6276
6277 /* always show the actual comm */
6278 off = strscpy(buf, task->comm, size);
6279 if (off < 0)
6280 return;
6281
6282 /* stabilize PF_WQ_WORKER and worker pool association */
6283 mutex_lock(&wq_pool_attach_mutex);
6284
6285 if (task->flags & PF_WQ_WORKER) {
6286 struct worker *worker = kthread_data(task);
6287 struct worker_pool *pool = worker->pool;
6288
6289 if (pool) {
6290 raw_spin_lock_irq(&pool->lock);
6291 /*
6292 * ->desc tracks information (wq name or
6293 * set_worker_desc()) for the latest execution. If
6294 * current, prepend '+', otherwise '-'.
6295 */
6296 if (worker->desc[0] != '\0') {
6297 if (worker->current_work)
6298 scnprintf(buf + off, size - off, "+%s",
6299 worker->desc);
6300 else
6301 scnprintf(buf + off, size - off, "-%s",
6302 worker->desc);
6303 }
6304 raw_spin_unlock_irq(&pool->lock);
6305 }
6306 }
6307
6308 mutex_unlock(&wq_pool_attach_mutex);
6309}
6310
6311#ifdef CONFIG_SMP
6312
6313/*
6314 * CPU hotplug.
6315 *
6316 * There are two challenges in supporting CPU hotplug. Firstly, there
6317 * are a lot of assumptions on strong associations among work, pwq and
6318 * pool which make migrating pending and scheduled works very
6319 * difficult to implement without impacting hot paths. Secondly,
6320 * worker pools serve mix of short, long and very long running works making
6321 * blocked draining impractical.
6322 *
6323 * This is solved by allowing the pools to be disassociated from the CPU
6324 * running as an unbound one and allowing it to be reattached later if the
6325 * cpu comes back online.
6326 */
6327
6328static void unbind_workers(int cpu)
6329{
6330 struct worker_pool *pool;
6331 struct worker *worker;
6332
6333 for_each_cpu_worker_pool(pool, cpu) {
6334 mutex_lock(&wq_pool_attach_mutex);
6335 raw_spin_lock_irq(&pool->lock);
6336
6337 /*
6338 * We've blocked all attach/detach operations. Make all workers
6339 * unbound and set DISASSOCIATED. Before this, all workers
6340 * must be on the cpu. After this, they may become diasporas.
6341 * And the preemption disabled section in their sched callbacks
6342 * are guaranteed to see WORKER_UNBOUND since the code here
6343 * is on the same cpu.
6344 */
6345 for_each_pool_worker(worker, pool)
6346 worker->flags |= WORKER_UNBOUND;
6347
6348 pool->flags |= POOL_DISASSOCIATED;
6349
6350 /*
6351 * The handling of nr_running in sched callbacks are disabled
6352 * now. Zap nr_running. After this, nr_running stays zero and
6353 * need_more_worker() and keep_working() are always true as
6354 * long as the worklist is not empty. This pool now behaves as
6355 * an unbound (in terms of concurrency management) pool which
6356 * are served by workers tied to the pool.
6357 */
6358 pool->nr_running = 0;
6359
6360 /*
6361 * With concurrency management just turned off, a busy
6362 * worker blocking could lead to lengthy stalls. Kick off
6363 * unbound chain execution of currently pending work items.
6364 */
6365 kick_pool(pool);
6366
6367 raw_spin_unlock_irq(&pool->lock);
6368
6369 for_each_pool_worker(worker, pool)
6370 unbind_worker(worker);
6371
6372 mutex_unlock(&wq_pool_attach_mutex);
6373 }
6374}
6375
6376/**
6377 * rebind_workers - rebind all workers of a pool to the associated CPU
6378 * @pool: pool of interest
6379 *
6380 * @pool->cpu is coming online. Rebind all workers to the CPU.
6381 */
6382static void rebind_workers(struct worker_pool *pool)
6383{
6384 struct worker *worker;
6385
6386 lockdep_assert_held(&wq_pool_attach_mutex);
6387
6388 /*
6389 * Restore CPU affinity of all workers. As all idle workers should
6390 * be on the run-queue of the associated CPU before any local
6391 * wake-ups for concurrency management happen, restore CPU affinity
6392 * of all workers first and then clear UNBOUND. As we're called
6393 * from CPU_ONLINE, the following shouldn't fail.
6394 */
6395 for_each_pool_worker(worker, pool) {
6396 kthread_set_per_cpu(worker->task, pool->cpu);
6397 WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task,
6398 pool_allowed_cpus(pool)) < 0);
6399 }
6400
6401 raw_spin_lock_irq(&pool->lock);
6402
6403 pool->flags &= ~POOL_DISASSOCIATED;
6404
6405 for_each_pool_worker(worker, pool) {
6406 unsigned int worker_flags = worker->flags;
6407
6408 /*
6409 * We want to clear UNBOUND but can't directly call
6410 * worker_clr_flags() or adjust nr_running. Atomically
6411 * replace UNBOUND with another NOT_RUNNING flag REBOUND.
6412 * @worker will clear REBOUND using worker_clr_flags() when
6413 * it initiates the next execution cycle thus restoring
6414 * concurrency management. Note that when or whether
6415 * @worker clears REBOUND doesn't affect correctness.
6416 *
6417 * WRITE_ONCE() is necessary because @worker->flags may be
6418 * tested without holding any lock in
6419 * wq_worker_running(). Without it, NOT_RUNNING test may
6420 * fail incorrectly leading to premature concurrency
6421 * management operations.
6422 */
6423 WARN_ON_ONCE(!(worker_flags & WORKER_UNBOUND));
6424 worker_flags |= WORKER_REBOUND;
6425 worker_flags &= ~WORKER_UNBOUND;
6426 WRITE_ONCE(worker->flags, worker_flags);
6427 }
6428
6429 raw_spin_unlock_irq(&pool->lock);
6430}
6431
6432/**
6433 * restore_unbound_workers_cpumask - restore cpumask of unbound workers
6434 * @pool: unbound pool of interest
6435 * @cpu: the CPU which is coming up
6436 *
6437 * An unbound pool may end up with a cpumask which doesn't have any online
6438 * CPUs. When a worker of such pool get scheduled, the scheduler resets
6439 * its cpus_allowed. If @cpu is in @pool's cpumask which didn't have any
6440 * online CPU before, cpus_allowed of all its workers should be restored.
6441 */
6442static void restore_unbound_workers_cpumask(struct worker_pool *pool, int cpu)
6443{
6444 static cpumask_t cpumask;
6445 struct worker *worker;
6446
6447 lockdep_assert_held(&wq_pool_attach_mutex);
6448
6449 /* is @cpu allowed for @pool? */
6450 if (!cpumask_test_cpu(cpu, pool->attrs->cpumask))
6451 return;
6452
6453 cpumask_and(&cpumask, pool->attrs->cpumask, cpu_online_mask);
6454
6455 /* as we're called from CPU_ONLINE, the following shouldn't fail */
6456 for_each_pool_worker(worker, pool)
6457 WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task, &cpumask) < 0);
6458}
6459
6460int workqueue_prepare_cpu(unsigned int cpu)
6461{
6462 struct worker_pool *pool;
6463
6464 for_each_cpu_worker_pool(pool, cpu) {
6465 if (pool->nr_workers)
6466 continue;
6467 if (!create_worker(pool))
6468 return -ENOMEM;
6469 }
6470 return 0;
6471}
6472
6473int workqueue_online_cpu(unsigned int cpu)
6474{
6475 struct worker_pool *pool;
6476 struct workqueue_struct *wq;
6477 int pi;
6478
6479 mutex_lock(&wq_pool_mutex);
6480
6481 for_each_pool(pool, pi) {
6482 /* BH pools aren't affected by hotplug */
6483 if (pool->flags & POOL_BH)
6484 continue;
6485
6486 mutex_lock(&wq_pool_attach_mutex);
6487 if (pool->cpu == cpu)
6488 rebind_workers(pool);
6489 else if (pool->cpu < 0)
6490 restore_unbound_workers_cpumask(pool, cpu);
6491 mutex_unlock(&wq_pool_attach_mutex);
6492 }
6493
6494 /* update pod affinity of unbound workqueues */
6495 list_for_each_entry(wq, &workqueues, list) {
6496 struct workqueue_attrs *attrs = wq->unbound_attrs;
6497
6498 if (attrs) {
6499 const struct wq_pod_type *pt = wqattrs_pod_type(attrs);
6500 int tcpu;
6501
6502 for_each_cpu(tcpu, pt->pod_cpus[pt->cpu_pod[cpu]])
6503 wq_update_pod(wq, tcpu, cpu, true);
6504
6505 mutex_lock(&wq->mutex);
6506 wq_update_node_max_active(wq, -1);
6507 mutex_unlock(&wq->mutex);
6508 }
6509 }
6510
6511 mutex_unlock(&wq_pool_mutex);
6512 return 0;
6513}
6514
6515int workqueue_offline_cpu(unsigned int cpu)
6516{
6517 struct workqueue_struct *wq;
6518
6519 /* unbinding per-cpu workers should happen on the local CPU */
6520 if (WARN_ON(cpu != smp_processor_id()))
6521 return -1;
6522
6523 unbind_workers(cpu);
6524
6525 /* update pod affinity of unbound workqueues */
6526 mutex_lock(&wq_pool_mutex);
6527 list_for_each_entry(wq, &workqueues, list) {
6528 struct workqueue_attrs *attrs = wq->unbound_attrs;
6529
6530 if (attrs) {
6531 const struct wq_pod_type *pt = wqattrs_pod_type(attrs);
6532 int tcpu;
6533
6534 for_each_cpu(tcpu, pt->pod_cpus[pt->cpu_pod[cpu]])
6535 wq_update_pod(wq, tcpu, cpu, false);
6536
6537 mutex_lock(&wq->mutex);
6538 wq_update_node_max_active(wq, cpu);
6539 mutex_unlock(&wq->mutex);
6540 }
6541 }
6542 mutex_unlock(&wq_pool_mutex);
6543
6544 return 0;
6545}
6546
6547struct work_for_cpu {
6548 struct work_struct work;
6549 long (*fn)(void *);
6550 void *arg;
6551 long ret;
6552};
6553
6554static void work_for_cpu_fn(struct work_struct *work)
6555{
6556 struct work_for_cpu *wfc = container_of(work, struct work_for_cpu, work);
6557
6558 wfc->ret = wfc->fn(wfc->arg);
6559}
6560
6561/**
6562 * work_on_cpu_key - run a function in thread context on a particular cpu
6563 * @cpu: the cpu to run on
6564 * @fn: the function to run
6565 * @arg: the function arg
6566 * @key: The lock class key for lock debugging purposes
6567 *
6568 * It is up to the caller to ensure that the cpu doesn't go offline.
6569 * The caller must not hold any locks which would prevent @fn from completing.
6570 *
6571 * Return: The value @fn returns.
6572 */
6573long work_on_cpu_key(int cpu, long (*fn)(void *),
6574 void *arg, struct lock_class_key *key)
6575{
6576 struct work_for_cpu wfc = { .fn = fn, .arg = arg };
6577
6578 INIT_WORK_ONSTACK_KEY(&wfc.work, work_for_cpu_fn, key);
6579 schedule_work_on(cpu, &wfc.work);
6580 flush_work(&wfc.work);
6581 destroy_work_on_stack(&wfc.work);
6582 return wfc.ret;
6583}
6584EXPORT_SYMBOL_GPL(work_on_cpu_key);
6585
6586/**
6587 * work_on_cpu_safe_key - run a function in thread context on a particular cpu
6588 * @cpu: the cpu to run on
6589 * @fn: the function to run
6590 * @arg: the function argument
6591 * @key: The lock class key for lock debugging purposes
6592 *
6593 * Disables CPU hotplug and calls work_on_cpu(). The caller must not hold
6594 * any locks which would prevent @fn from completing.
6595 *
6596 * Return: The value @fn returns.
6597 */
6598long work_on_cpu_safe_key(int cpu, long (*fn)(void *),
6599 void *arg, struct lock_class_key *key)
6600{
6601 long ret = -ENODEV;
6602
6603 cpus_read_lock();
6604 if (cpu_online(cpu))
6605 ret = work_on_cpu_key(cpu, fn, arg, key);
6606 cpus_read_unlock();
6607 return ret;
6608}
6609EXPORT_SYMBOL_GPL(work_on_cpu_safe_key);
6610#endif /* CONFIG_SMP */
6611
6612#ifdef CONFIG_FREEZER
6613
6614/**
6615 * freeze_workqueues_begin - begin freezing workqueues
6616 *
6617 * Start freezing workqueues. After this function returns, all freezable
6618 * workqueues will queue new works to their inactive_works list instead of
6619 * pool->worklist.
6620 *
6621 * CONTEXT:
6622 * Grabs and releases wq_pool_mutex, wq->mutex and pool->lock's.
6623 */
6624void freeze_workqueues_begin(void)
6625{
6626 struct workqueue_struct *wq;
6627
6628 mutex_lock(&wq_pool_mutex);
6629
6630 WARN_ON_ONCE(workqueue_freezing);
6631 workqueue_freezing = true;
6632
6633 list_for_each_entry(wq, &workqueues, list) {
6634 mutex_lock(&wq->mutex);
6635 wq_adjust_max_active(wq);
6636 mutex_unlock(&wq->mutex);
6637 }
6638
6639 mutex_unlock(&wq_pool_mutex);
6640}
6641
6642/**
6643 * freeze_workqueues_busy - are freezable workqueues still busy?
6644 *
6645 * Check whether freezing is complete. This function must be called
6646 * between freeze_workqueues_begin() and thaw_workqueues().
6647 *
6648 * CONTEXT:
6649 * Grabs and releases wq_pool_mutex.
6650 *
6651 * Return:
6652 * %true if some freezable workqueues are still busy. %false if freezing
6653 * is complete.
6654 */
6655bool freeze_workqueues_busy(void)
6656{
6657 bool busy = false;
6658 struct workqueue_struct *wq;
6659 struct pool_workqueue *pwq;
6660
6661 mutex_lock(&wq_pool_mutex);
6662
6663 WARN_ON_ONCE(!workqueue_freezing);
6664
6665 list_for_each_entry(wq, &workqueues, list) {
6666 if (!(wq->flags & WQ_FREEZABLE))
6667 continue;
6668 /*
6669 * nr_active is monotonically decreasing. It's safe
6670 * to peek without lock.
6671 */
6672 rcu_read_lock();
6673 for_each_pwq(pwq, wq) {
6674 WARN_ON_ONCE(pwq->nr_active < 0);
6675 if (pwq->nr_active) {
6676 busy = true;
6677 rcu_read_unlock();
6678 goto out_unlock;
6679 }
6680 }
6681 rcu_read_unlock();
6682 }
6683out_unlock:
6684 mutex_unlock(&wq_pool_mutex);
6685 return busy;
6686}
6687
6688/**
6689 * thaw_workqueues - thaw workqueues
6690 *
6691 * Thaw workqueues. Normal queueing is restored and all collected
6692 * frozen works are transferred to their respective pool worklists.
6693 *
6694 * CONTEXT:
6695 * Grabs and releases wq_pool_mutex, wq->mutex and pool->lock's.
6696 */
6697void thaw_workqueues(void)
6698{
6699 struct workqueue_struct *wq;
6700
6701 mutex_lock(&wq_pool_mutex);
6702
6703 if (!workqueue_freezing)
6704 goto out_unlock;
6705
6706 workqueue_freezing = false;
6707
6708 /* restore max_active and repopulate worklist */
6709 list_for_each_entry(wq, &workqueues, list) {
6710 mutex_lock(&wq->mutex);
6711 wq_adjust_max_active(wq);
6712 mutex_unlock(&wq->mutex);
6713 }
6714
6715out_unlock:
6716 mutex_unlock(&wq_pool_mutex);
6717}
6718#endif /* CONFIG_FREEZER */
6719
6720static int workqueue_apply_unbound_cpumask(const cpumask_var_t unbound_cpumask)
6721{
6722 LIST_HEAD(ctxs);
6723 int ret = 0;
6724 struct workqueue_struct *wq;
6725 struct apply_wqattrs_ctx *ctx, *n;
6726
6727 lockdep_assert_held(&wq_pool_mutex);
6728
6729 list_for_each_entry(wq, &workqueues, list) {
6730 if (!(wq->flags & WQ_UNBOUND) || (wq->flags & __WQ_DESTROYING))
6731 continue;
6732
6733 ctx = apply_wqattrs_prepare(wq, wq->unbound_attrs, unbound_cpumask);
6734 if (IS_ERR(ctx)) {
6735 ret = PTR_ERR(ctx);
6736 break;
6737 }
6738
6739 list_add_tail(&ctx->list, &ctxs);
6740 }
6741
6742 list_for_each_entry_safe(ctx, n, &ctxs, list) {
6743 if (!ret)
6744 apply_wqattrs_commit(ctx);
6745 apply_wqattrs_cleanup(ctx);
6746 }
6747
6748 if (!ret) {
6749 mutex_lock(&wq_pool_attach_mutex);
6750 cpumask_copy(wq_unbound_cpumask, unbound_cpumask);
6751 mutex_unlock(&wq_pool_attach_mutex);
6752 }
6753 return ret;
6754}
6755
6756/**
6757 * workqueue_unbound_exclude_cpumask - Exclude given CPUs from unbound cpumask
6758 * @exclude_cpumask: the cpumask to be excluded from wq_unbound_cpumask
6759 *
6760 * This function can be called from cpuset code to provide a set of isolated
6761 * CPUs that should be excluded from wq_unbound_cpumask. The caller must hold
6762 * either cpus_read_lock or cpus_write_lock.
6763 */
6764int workqueue_unbound_exclude_cpumask(cpumask_var_t exclude_cpumask)
6765{
6766 cpumask_var_t cpumask;
6767 int ret = 0;
6768
6769 if (!zalloc_cpumask_var(&cpumask, GFP_KERNEL))
6770 return -ENOMEM;
6771
6772 lockdep_assert_cpus_held();
6773 mutex_lock(&wq_pool_mutex);
6774
6775 /* Save the current isolated cpumask & export it via sysfs */
6776 cpumask_copy(wq_isolated_cpumask, exclude_cpumask);
6777
6778 /*
6779 * If the operation fails, it will fall back to
6780 * wq_requested_unbound_cpumask which is initially set to
6781 * (HK_TYPE_WQ ∩ HK_TYPE_DOMAIN) house keeping mask and rewritten
6782 * by any subsequent write to workqueue/cpumask sysfs file.
6783 */
6784 if (!cpumask_andnot(cpumask, wq_requested_unbound_cpumask, exclude_cpumask))
6785 cpumask_copy(cpumask, wq_requested_unbound_cpumask);
6786 if (!cpumask_equal(cpumask, wq_unbound_cpumask))
6787 ret = workqueue_apply_unbound_cpumask(cpumask);
6788
6789 mutex_unlock(&wq_pool_mutex);
6790 free_cpumask_var(cpumask);
6791 return ret;
6792}
6793
6794static int parse_affn_scope(const char *val)
6795{
6796 int i;
6797
6798 for (i = 0; i < ARRAY_SIZE(wq_affn_names); i++) {
6799 if (!strncasecmp(val, wq_affn_names[i], strlen(wq_affn_names[i])))
6800 return i;
6801 }
6802 return -EINVAL;
6803}
6804
6805static int wq_affn_dfl_set(const char *val, const struct kernel_param *kp)
6806{
6807 struct workqueue_struct *wq;
6808 int affn, cpu;
6809
6810 affn = parse_affn_scope(val);
6811 if (affn < 0)
6812 return affn;
6813 if (affn == WQ_AFFN_DFL)
6814 return -EINVAL;
6815
6816 cpus_read_lock();
6817 mutex_lock(&wq_pool_mutex);
6818
6819 wq_affn_dfl = affn;
6820
6821 list_for_each_entry(wq, &workqueues, list) {
6822 for_each_online_cpu(cpu) {
6823 wq_update_pod(wq, cpu, cpu, true);
6824 }
6825 }
6826
6827 mutex_unlock(&wq_pool_mutex);
6828 cpus_read_unlock();
6829
6830 return 0;
6831}
6832
6833static int wq_affn_dfl_get(char *buffer, const struct kernel_param *kp)
6834{
6835 return scnprintf(buffer, PAGE_SIZE, "%s\n", wq_affn_names[wq_affn_dfl]);
6836}
6837
6838static const struct kernel_param_ops wq_affn_dfl_ops = {
6839 .set = wq_affn_dfl_set,
6840 .get = wq_affn_dfl_get,
6841};
6842
6843module_param_cb(default_affinity_scope, &wq_affn_dfl_ops, NULL, 0644);
6844
6845#ifdef CONFIG_SYSFS
6846/*
6847 * Workqueues with WQ_SYSFS flag set is visible to userland via
6848 * /sys/bus/workqueue/devices/WQ_NAME. All visible workqueues have the
6849 * following attributes.
6850 *
6851 * per_cpu RO bool : whether the workqueue is per-cpu or unbound
6852 * max_active RW int : maximum number of in-flight work items
6853 *
6854 * Unbound workqueues have the following extra attributes.
6855 *
6856 * nice RW int : nice value of the workers
6857 * cpumask RW mask : bitmask of allowed CPUs for the workers
6858 * affinity_scope RW str : worker CPU affinity scope (cache, numa, none)
6859 * affinity_strict RW bool : worker CPU affinity is strict
6860 */
6861struct wq_device {
6862 struct workqueue_struct *wq;
6863 struct device dev;
6864};
6865
6866static struct workqueue_struct *dev_to_wq(struct device *dev)
6867{
6868 struct wq_device *wq_dev = container_of(dev, struct wq_device, dev);
6869
6870 return wq_dev->wq;
6871}
6872
6873static ssize_t per_cpu_show(struct device *dev, struct device_attribute *attr,
6874 char *buf)
6875{
6876 struct workqueue_struct *wq = dev_to_wq(dev);
6877
6878 return scnprintf(buf, PAGE_SIZE, "%d\n", (bool)!(wq->flags & WQ_UNBOUND));
6879}
6880static DEVICE_ATTR_RO(per_cpu);
6881
6882static ssize_t max_active_show(struct device *dev,
6883 struct device_attribute *attr, char *buf)
6884{
6885 struct workqueue_struct *wq = dev_to_wq(dev);
6886
6887 return scnprintf(buf, PAGE_SIZE, "%d\n", wq->saved_max_active);
6888}
6889
6890static ssize_t max_active_store(struct device *dev,
6891 struct device_attribute *attr, const char *buf,
6892 size_t count)
6893{
6894 struct workqueue_struct *wq = dev_to_wq(dev);
6895 int val;
6896
6897 if (sscanf(buf, "%d", &val) != 1 || val <= 0)
6898 return -EINVAL;
6899
6900 workqueue_set_max_active(wq, val);
6901 return count;
6902}
6903static DEVICE_ATTR_RW(max_active);
6904
6905static struct attribute *wq_sysfs_attrs[] = {
6906 &dev_attr_per_cpu.attr,
6907 &dev_attr_max_active.attr,
6908 NULL,
6909};
6910ATTRIBUTE_GROUPS(wq_sysfs);
6911
6912static void apply_wqattrs_lock(void)
6913{
6914 /* CPUs should stay stable across pwq creations and installations */
6915 cpus_read_lock();
6916 mutex_lock(&wq_pool_mutex);
6917}
6918
6919static void apply_wqattrs_unlock(void)
6920{
6921 mutex_unlock(&wq_pool_mutex);
6922 cpus_read_unlock();
6923}
6924
6925static ssize_t wq_nice_show(struct device *dev, struct device_attribute *attr,
6926 char *buf)
6927{
6928 struct workqueue_struct *wq = dev_to_wq(dev);
6929 int written;
6930
6931 mutex_lock(&wq->mutex);
6932 written = scnprintf(buf, PAGE_SIZE, "%d\n", wq->unbound_attrs->nice);
6933 mutex_unlock(&wq->mutex);
6934
6935 return written;
6936}
6937
6938/* prepare workqueue_attrs for sysfs store operations */
6939static struct workqueue_attrs *wq_sysfs_prep_attrs(struct workqueue_struct *wq)
6940{
6941 struct workqueue_attrs *attrs;
6942
6943 lockdep_assert_held(&wq_pool_mutex);
6944
6945 attrs = alloc_workqueue_attrs();
6946 if (!attrs)
6947 return NULL;
6948
6949 copy_workqueue_attrs(attrs, wq->unbound_attrs);
6950 return attrs;
6951}
6952
6953static ssize_t wq_nice_store(struct device *dev, struct device_attribute *attr,
6954 const char *buf, size_t count)
6955{
6956 struct workqueue_struct *wq = dev_to_wq(dev);
6957 struct workqueue_attrs *attrs;
6958 int ret = -ENOMEM;
6959
6960 apply_wqattrs_lock();
6961
6962 attrs = wq_sysfs_prep_attrs(wq);
6963 if (!attrs)
6964 goto out_unlock;
6965
6966 if (sscanf(buf, "%d", &attrs->nice) == 1 &&
6967 attrs->nice >= MIN_NICE && attrs->nice <= MAX_NICE)
6968 ret = apply_workqueue_attrs_locked(wq, attrs);
6969 else
6970 ret = -EINVAL;
6971
6972out_unlock:
6973 apply_wqattrs_unlock();
6974 free_workqueue_attrs(attrs);
6975 return ret ?: count;
6976}
6977
6978static ssize_t wq_cpumask_show(struct device *dev,
6979 struct device_attribute *attr, char *buf)
6980{
6981 struct workqueue_struct *wq = dev_to_wq(dev);
6982 int written;
6983
6984 mutex_lock(&wq->mutex);
6985 written = scnprintf(buf, PAGE_SIZE, "%*pb\n",
6986 cpumask_pr_args(wq->unbound_attrs->cpumask));
6987 mutex_unlock(&wq->mutex);
6988 return written;
6989}
6990
6991static ssize_t wq_cpumask_store(struct device *dev,
6992 struct device_attribute *attr,
6993 const char *buf, size_t count)
6994{
6995 struct workqueue_struct *wq = dev_to_wq(dev);
6996 struct workqueue_attrs *attrs;
6997 int ret = -ENOMEM;
6998
6999 apply_wqattrs_lock();
7000
7001 attrs = wq_sysfs_prep_attrs(wq);
7002 if (!attrs)
7003 goto out_unlock;
7004
7005 ret = cpumask_parse(buf, attrs->cpumask);
7006 if (!ret)
7007 ret = apply_workqueue_attrs_locked(wq, attrs);
7008
7009out_unlock:
7010 apply_wqattrs_unlock();
7011 free_workqueue_attrs(attrs);
7012 return ret ?: count;
7013}
7014
7015static ssize_t wq_affn_scope_show(struct device *dev,
7016 struct device_attribute *attr, char *buf)
7017{
7018 struct workqueue_struct *wq = dev_to_wq(dev);
7019 int written;
7020
7021 mutex_lock(&wq->mutex);
7022 if (wq->unbound_attrs->affn_scope == WQ_AFFN_DFL)
7023 written = scnprintf(buf, PAGE_SIZE, "%s (%s)\n",
7024 wq_affn_names[WQ_AFFN_DFL],
7025 wq_affn_names[wq_affn_dfl]);
7026 else
7027 written = scnprintf(buf, PAGE_SIZE, "%s\n",
7028 wq_affn_names[wq->unbound_attrs->affn_scope]);
7029 mutex_unlock(&wq->mutex);
7030
7031 return written;
7032}
7033
7034static ssize_t wq_affn_scope_store(struct device *dev,
7035 struct device_attribute *attr,
7036 const char *buf, size_t count)
7037{
7038 struct workqueue_struct *wq = dev_to_wq(dev);
7039 struct workqueue_attrs *attrs;
7040 int affn, ret = -ENOMEM;
7041
7042 affn = parse_affn_scope(buf);
7043 if (affn < 0)
7044 return affn;
7045
7046 apply_wqattrs_lock();
7047 attrs = wq_sysfs_prep_attrs(wq);
7048 if (attrs) {
7049 attrs->affn_scope = affn;
7050 ret = apply_workqueue_attrs_locked(wq, attrs);
7051 }
7052 apply_wqattrs_unlock();
7053 free_workqueue_attrs(attrs);
7054 return ret ?: count;
7055}
7056
7057static ssize_t wq_affinity_strict_show(struct device *dev,
7058 struct device_attribute *attr, char *buf)
7059{
7060 struct workqueue_struct *wq = dev_to_wq(dev);
7061
7062 return scnprintf(buf, PAGE_SIZE, "%d\n",
7063 wq->unbound_attrs->affn_strict);
7064}
7065
7066static ssize_t wq_affinity_strict_store(struct device *dev,
7067 struct device_attribute *attr,
7068 const char *buf, size_t count)
7069{
7070 struct workqueue_struct *wq = dev_to_wq(dev);
7071 struct workqueue_attrs *attrs;
7072 int v, ret = -ENOMEM;
7073
7074 if (sscanf(buf, "%d", &v) != 1)
7075 return -EINVAL;
7076
7077 apply_wqattrs_lock();
7078 attrs = wq_sysfs_prep_attrs(wq);
7079 if (attrs) {
7080 attrs->affn_strict = (bool)v;
7081 ret = apply_workqueue_attrs_locked(wq, attrs);
7082 }
7083 apply_wqattrs_unlock();
7084 free_workqueue_attrs(attrs);
7085 return ret ?: count;
7086}
7087
7088static struct device_attribute wq_sysfs_unbound_attrs[] = {
7089 __ATTR(nice, 0644, wq_nice_show, wq_nice_store),
7090 __ATTR(cpumask, 0644, wq_cpumask_show, wq_cpumask_store),
7091 __ATTR(affinity_scope, 0644, wq_affn_scope_show, wq_affn_scope_store),
7092 __ATTR(affinity_strict, 0644, wq_affinity_strict_show, wq_affinity_strict_store),
7093 __ATTR_NULL,
7094};
7095
7096static const struct bus_type wq_subsys = {
7097 .name = "workqueue",
7098 .dev_groups = wq_sysfs_groups,
7099};
7100
7101/**
7102 * workqueue_set_unbound_cpumask - Set the low-level unbound cpumask
7103 * @cpumask: the cpumask to set
7104 *
7105 * The low-level workqueues cpumask is a global cpumask that limits
7106 * the affinity of all unbound workqueues. This function check the @cpumask
7107 * and apply it to all unbound workqueues and updates all pwqs of them.
7108 *
7109 * Return: 0 - Success
7110 * -EINVAL - Invalid @cpumask
7111 * -ENOMEM - Failed to allocate memory for attrs or pwqs.
7112 */
7113static int workqueue_set_unbound_cpumask(cpumask_var_t cpumask)
7114{
7115 int ret = -EINVAL;
7116
7117 /*
7118 * Not excluding isolated cpus on purpose.
7119 * If the user wishes to include them, we allow that.
7120 */
7121 cpumask_and(cpumask, cpumask, cpu_possible_mask);
7122 if (!cpumask_empty(cpumask)) {
7123 apply_wqattrs_lock();
7124 cpumask_copy(wq_requested_unbound_cpumask, cpumask);
7125 if (cpumask_equal(cpumask, wq_unbound_cpumask)) {
7126 ret = 0;
7127 goto out_unlock;
7128 }
7129
7130 ret = workqueue_apply_unbound_cpumask(cpumask);
7131
7132out_unlock:
7133 apply_wqattrs_unlock();
7134 }
7135
7136 return ret;
7137}
7138
7139static ssize_t __wq_cpumask_show(struct device *dev,
7140 struct device_attribute *attr, char *buf, cpumask_var_t mask)
7141{
7142 int written;
7143
7144 mutex_lock(&wq_pool_mutex);
7145 written = scnprintf(buf, PAGE_SIZE, "%*pb\n", cpumask_pr_args(mask));
7146 mutex_unlock(&wq_pool_mutex);
7147
7148 return written;
7149}
7150
7151static ssize_t wq_unbound_cpumask_show(struct device *dev,
7152 struct device_attribute *attr, char *buf)
7153{
7154 return __wq_cpumask_show(dev, attr, buf, wq_unbound_cpumask);
7155}
7156
7157static ssize_t wq_requested_cpumask_show(struct device *dev,
7158 struct device_attribute *attr, char *buf)
7159{
7160 return __wq_cpumask_show(dev, attr, buf, wq_requested_unbound_cpumask);
7161}
7162
7163static ssize_t wq_isolated_cpumask_show(struct device *dev,
7164 struct device_attribute *attr, char *buf)
7165{
7166 return __wq_cpumask_show(dev, attr, buf, wq_isolated_cpumask);
7167}
7168
7169static ssize_t wq_unbound_cpumask_store(struct device *dev,
7170 struct device_attribute *attr, const char *buf, size_t count)
7171{
7172 cpumask_var_t cpumask;
7173 int ret;
7174
7175 if (!zalloc_cpumask_var(&cpumask, GFP_KERNEL))
7176 return -ENOMEM;
7177
7178 ret = cpumask_parse(buf, cpumask);
7179 if (!ret)
7180 ret = workqueue_set_unbound_cpumask(cpumask);
7181
7182 free_cpumask_var(cpumask);
7183 return ret ? ret : count;
7184}
7185
7186static struct device_attribute wq_sysfs_cpumask_attrs[] = {
7187 __ATTR(cpumask, 0644, wq_unbound_cpumask_show,
7188 wq_unbound_cpumask_store),
7189 __ATTR(cpumask_requested, 0444, wq_requested_cpumask_show, NULL),
7190 __ATTR(cpumask_isolated, 0444, wq_isolated_cpumask_show, NULL),
7191 __ATTR_NULL,
7192};
7193
7194static int __init wq_sysfs_init(void)
7195{
7196 struct device *dev_root;
7197 int err;
7198
7199 err = subsys_virtual_register(&wq_subsys, NULL);
7200 if (err)
7201 return err;
7202
7203 dev_root = bus_get_dev_root(&wq_subsys);
7204 if (dev_root) {
7205 struct device_attribute *attr;
7206
7207 for (attr = wq_sysfs_cpumask_attrs; attr->attr.name; attr++) {
7208 err = device_create_file(dev_root, attr);
7209 if (err)
7210 break;
7211 }
7212 put_device(dev_root);
7213 }
7214 return err;
7215}
7216core_initcall(wq_sysfs_init);
7217
7218static void wq_device_release(struct device *dev)
7219{
7220 struct wq_device *wq_dev = container_of(dev, struct wq_device, dev);
7221
7222 kfree(wq_dev);
7223}
7224
7225/**
7226 * workqueue_sysfs_register - make a workqueue visible in sysfs
7227 * @wq: the workqueue to register
7228 *
7229 * Expose @wq in sysfs under /sys/bus/workqueue/devices.
7230 * alloc_workqueue*() automatically calls this function if WQ_SYSFS is set
7231 * which is the preferred method.
7232 *
7233 * Workqueue user should use this function directly iff it wants to apply
7234 * workqueue_attrs before making the workqueue visible in sysfs; otherwise,
7235 * apply_workqueue_attrs() may race against userland updating the
7236 * attributes.
7237 *
7238 * Return: 0 on success, -errno on failure.
7239 */
7240int workqueue_sysfs_register(struct workqueue_struct *wq)
7241{
7242 struct wq_device *wq_dev;
7243 int ret;
7244
7245 /*
7246 * Adjusting max_active breaks ordering guarantee. Disallow exposing
7247 * ordered workqueues.
7248 */
7249 if (WARN_ON(wq->flags & __WQ_ORDERED))
7250 return -EINVAL;
7251
7252 wq->wq_dev = wq_dev = kzalloc(sizeof(*wq_dev), GFP_KERNEL);
7253 if (!wq_dev)
7254 return -ENOMEM;
7255
7256 wq_dev->wq = wq;
7257 wq_dev->dev.bus = &wq_subsys;
7258 wq_dev->dev.release = wq_device_release;
7259 dev_set_name(&wq_dev->dev, "%s", wq->name);
7260
7261 /*
7262 * unbound_attrs are created separately. Suppress uevent until
7263 * everything is ready.
7264 */
7265 dev_set_uevent_suppress(&wq_dev->dev, true);
7266
7267 ret = device_register(&wq_dev->dev);
7268 if (ret) {
7269 put_device(&wq_dev->dev);
7270 wq->wq_dev = NULL;
7271 return ret;
7272 }
7273
7274 if (wq->flags & WQ_UNBOUND) {
7275 struct device_attribute *attr;
7276
7277 for (attr = wq_sysfs_unbound_attrs; attr->attr.name; attr++) {
7278 ret = device_create_file(&wq_dev->dev, attr);
7279 if (ret) {
7280 device_unregister(&wq_dev->dev);
7281 wq->wq_dev = NULL;
7282 return ret;
7283 }
7284 }
7285 }
7286
7287 dev_set_uevent_suppress(&wq_dev->dev, false);
7288 kobject_uevent(&wq_dev->dev.kobj, KOBJ_ADD);
7289 return 0;
7290}
7291
7292/**
7293 * workqueue_sysfs_unregister - undo workqueue_sysfs_register()
7294 * @wq: the workqueue to unregister
7295 *
7296 * If @wq is registered to sysfs by workqueue_sysfs_register(), unregister.
7297 */
7298static void workqueue_sysfs_unregister(struct workqueue_struct *wq)
7299{
7300 struct wq_device *wq_dev = wq->wq_dev;
7301
7302 if (!wq->wq_dev)
7303 return;
7304
7305 wq->wq_dev = NULL;
7306 device_unregister(&wq_dev->dev);
7307}
7308#else /* CONFIG_SYSFS */
7309static void workqueue_sysfs_unregister(struct workqueue_struct *wq) { }
7310#endif /* CONFIG_SYSFS */
7311
7312/*
7313 * Workqueue watchdog.
7314 *
7315 * Stall may be caused by various bugs - missing WQ_MEM_RECLAIM, illegal
7316 * flush dependency, a concurrency managed work item which stays RUNNING
7317 * indefinitely. Workqueue stalls can be very difficult to debug as the
7318 * usual warning mechanisms don't trigger and internal workqueue state is
7319 * largely opaque.
7320 *
7321 * Workqueue watchdog monitors all worker pools periodically and dumps
7322 * state if some pools failed to make forward progress for a while where
7323 * forward progress is defined as the first item on ->worklist changing.
7324 *
7325 * This mechanism is controlled through the kernel parameter
7326 * "workqueue.watchdog_thresh" which can be updated at runtime through the
7327 * corresponding sysfs parameter file.
7328 */
7329#ifdef CONFIG_WQ_WATCHDOG
7330
7331static unsigned long wq_watchdog_thresh = 30;
7332static struct timer_list wq_watchdog_timer;
7333
7334static unsigned long wq_watchdog_touched = INITIAL_JIFFIES;
7335static DEFINE_PER_CPU(unsigned long, wq_watchdog_touched_cpu) = INITIAL_JIFFIES;
7336
7337/*
7338 * Show workers that might prevent the processing of pending work items.
7339 * The only candidates are CPU-bound workers in the running state.
7340 * Pending work items should be handled by another idle worker
7341 * in all other situations.
7342 */
7343static void show_cpu_pool_hog(struct worker_pool *pool)
7344{
7345 struct worker *worker;
7346 unsigned long irq_flags;
7347 int bkt;
7348
7349 raw_spin_lock_irqsave(&pool->lock, irq_flags);
7350
7351 hash_for_each(pool->busy_hash, bkt, worker, hentry) {
7352 if (task_is_running(worker->task)) {
7353 /*
7354 * Defer printing to avoid deadlocks in console
7355 * drivers that queue work while holding locks
7356 * also taken in their write paths.
7357 */
7358 printk_deferred_enter();
7359
7360 pr_info("pool %d:\n", pool->id);
7361 sched_show_task(worker->task);
7362
7363 printk_deferred_exit();
7364 }
7365 }
7366
7367 raw_spin_unlock_irqrestore(&pool->lock, irq_flags);
7368}
7369
7370static void show_cpu_pools_hogs(void)
7371{
7372 struct worker_pool *pool;
7373 int pi;
7374
7375 pr_info("Showing backtraces of running workers in stalled CPU-bound worker pools:\n");
7376
7377 rcu_read_lock();
7378
7379 for_each_pool(pool, pi) {
7380 if (pool->cpu_stall)
7381 show_cpu_pool_hog(pool);
7382
7383 }
7384
7385 rcu_read_unlock();
7386}
7387
7388static void wq_watchdog_reset_touched(void)
7389{
7390 int cpu;
7391
7392 wq_watchdog_touched = jiffies;
7393 for_each_possible_cpu(cpu)
7394 per_cpu(wq_watchdog_touched_cpu, cpu) = jiffies;
7395}
7396
7397static void wq_watchdog_timer_fn(struct timer_list *unused)
7398{
7399 unsigned long thresh = READ_ONCE(wq_watchdog_thresh) * HZ;
7400 bool lockup_detected = false;
7401 bool cpu_pool_stall = false;
7402 unsigned long now = jiffies;
7403 struct worker_pool *pool;
7404 int pi;
7405
7406 if (!thresh)
7407 return;
7408
7409 rcu_read_lock();
7410
7411 for_each_pool(pool, pi) {
7412 unsigned long pool_ts, touched, ts;
7413
7414 pool->cpu_stall = false;
7415 if (list_empty(&pool->worklist))
7416 continue;
7417
7418 /*
7419 * If a virtual machine is stopped by the host it can look to
7420 * the watchdog like a stall.
7421 */
7422 kvm_check_and_clear_guest_paused();
7423
7424 /* get the latest of pool and touched timestamps */
7425 if (pool->cpu >= 0)
7426 touched = READ_ONCE(per_cpu(wq_watchdog_touched_cpu, pool->cpu));
7427 else
7428 touched = READ_ONCE(wq_watchdog_touched);
7429 pool_ts = READ_ONCE(pool->watchdog_ts);
7430
7431 if (time_after(pool_ts, touched))
7432 ts = pool_ts;
7433 else
7434 ts = touched;
7435
7436 /* did we stall? */
7437 if (time_after(now, ts + thresh)) {
7438 lockup_detected = true;
7439 if (pool->cpu >= 0 && !(pool->flags & POOL_BH)) {
7440 pool->cpu_stall = true;
7441 cpu_pool_stall = true;
7442 }
7443 pr_emerg("BUG: workqueue lockup - pool");
7444 pr_cont_pool_info(pool);
7445 pr_cont(" stuck for %us!\n",
7446 jiffies_to_msecs(now - pool_ts) / 1000);
7447 }
7448
7449
7450 }
7451
7452 rcu_read_unlock();
7453
7454 if (lockup_detected)
7455 show_all_workqueues();
7456
7457 if (cpu_pool_stall)
7458 show_cpu_pools_hogs();
7459
7460 wq_watchdog_reset_touched();
7461 mod_timer(&wq_watchdog_timer, jiffies + thresh);
7462}
7463
7464notrace void wq_watchdog_touch(int cpu)
7465{
7466 if (cpu >= 0)
7467 per_cpu(wq_watchdog_touched_cpu, cpu) = jiffies;
7468
7469 wq_watchdog_touched = jiffies;
7470}
7471
7472static void wq_watchdog_set_thresh(unsigned long thresh)
7473{
7474 wq_watchdog_thresh = 0;
7475 del_timer_sync(&wq_watchdog_timer);
7476
7477 if (thresh) {
7478 wq_watchdog_thresh = thresh;
7479 wq_watchdog_reset_touched();
7480 mod_timer(&wq_watchdog_timer, jiffies + thresh * HZ);
7481 }
7482}
7483
7484static int wq_watchdog_param_set_thresh(const char *val,
7485 const struct kernel_param *kp)
7486{
7487 unsigned long thresh;
7488 int ret;
7489
7490 ret = kstrtoul(val, 0, &thresh);
7491 if (ret)
7492 return ret;
7493
7494 if (system_wq)
7495 wq_watchdog_set_thresh(thresh);
7496 else
7497 wq_watchdog_thresh = thresh;
7498
7499 return 0;
7500}
7501
7502static const struct kernel_param_ops wq_watchdog_thresh_ops = {
7503 .set = wq_watchdog_param_set_thresh,
7504 .get = param_get_ulong,
7505};
7506
7507module_param_cb(watchdog_thresh, &wq_watchdog_thresh_ops, &wq_watchdog_thresh,
7508 0644);
7509
7510static void wq_watchdog_init(void)
7511{
7512 timer_setup(&wq_watchdog_timer, wq_watchdog_timer_fn, TIMER_DEFERRABLE);
7513 wq_watchdog_set_thresh(wq_watchdog_thresh);
7514}
7515
7516#else /* CONFIG_WQ_WATCHDOG */
7517
7518static inline void wq_watchdog_init(void) { }
7519
7520#endif /* CONFIG_WQ_WATCHDOG */
7521
7522static void bh_pool_kick_normal(struct irq_work *irq_work)
7523{
7524 raise_softirq_irqoff(TASKLET_SOFTIRQ);
7525}
7526
7527static void bh_pool_kick_highpri(struct irq_work *irq_work)
7528{
7529 raise_softirq_irqoff(HI_SOFTIRQ);
7530}
7531
7532static void __init restrict_unbound_cpumask(const char *name, const struct cpumask *mask)
7533{
7534 if (!cpumask_intersects(wq_unbound_cpumask, mask)) {
7535 pr_warn("workqueue: Restricting unbound_cpumask (%*pb) with %s (%*pb) leaves no CPU, ignoring\n",
7536 cpumask_pr_args(wq_unbound_cpumask), name, cpumask_pr_args(mask));
7537 return;
7538 }
7539
7540 cpumask_and(wq_unbound_cpumask, wq_unbound_cpumask, mask);
7541}
7542
7543static void __init init_cpu_worker_pool(struct worker_pool *pool, int cpu, int nice)
7544{
7545 BUG_ON(init_worker_pool(pool));
7546 pool->cpu = cpu;
7547 cpumask_copy(pool->attrs->cpumask, cpumask_of(cpu));
7548 cpumask_copy(pool->attrs->__pod_cpumask, cpumask_of(cpu));
7549 pool->attrs->nice = nice;
7550 pool->attrs->affn_strict = true;
7551 pool->node = cpu_to_node(cpu);
7552
7553 /* alloc pool ID */
7554 mutex_lock(&wq_pool_mutex);
7555 BUG_ON(worker_pool_assign_id(pool));
7556 mutex_unlock(&wq_pool_mutex);
7557}
7558
7559/**
7560 * workqueue_init_early - early init for workqueue subsystem
7561 *
7562 * This is the first step of three-staged workqueue subsystem initialization and
7563 * invoked as soon as the bare basics - memory allocation, cpumasks and idr are
7564 * up. It sets up all the data structures and system workqueues and allows early
7565 * boot code to create workqueues and queue/cancel work items. Actual work item
7566 * execution starts only after kthreads can be created and scheduled right
7567 * before early initcalls.
7568 */
7569void __init workqueue_init_early(void)
7570{
7571 struct wq_pod_type *pt = &wq_pod_types[WQ_AFFN_SYSTEM];
7572 int std_nice[NR_STD_WORKER_POOLS] = { 0, HIGHPRI_NICE_LEVEL };
7573 void (*irq_work_fns[2])(struct irq_work *) = { bh_pool_kick_normal,
7574 bh_pool_kick_highpri };
7575 int i, cpu;
7576
7577 BUILD_BUG_ON(__alignof__(struct pool_workqueue) < __alignof__(long long));
7578
7579 BUG_ON(!alloc_cpumask_var(&wq_unbound_cpumask, GFP_KERNEL));
7580 BUG_ON(!alloc_cpumask_var(&wq_requested_unbound_cpumask, GFP_KERNEL));
7581 BUG_ON(!zalloc_cpumask_var(&wq_isolated_cpumask, GFP_KERNEL));
7582
7583 cpumask_copy(wq_unbound_cpumask, cpu_possible_mask);
7584 restrict_unbound_cpumask("HK_TYPE_WQ", housekeeping_cpumask(HK_TYPE_WQ));
7585 restrict_unbound_cpumask("HK_TYPE_DOMAIN", housekeeping_cpumask(HK_TYPE_DOMAIN));
7586 if (!cpumask_empty(&wq_cmdline_cpumask))
7587 restrict_unbound_cpumask("workqueue.unbound_cpus", &wq_cmdline_cpumask);
7588
7589 cpumask_copy(wq_requested_unbound_cpumask, wq_unbound_cpumask);
7590
7591 pwq_cache = KMEM_CACHE(pool_workqueue, SLAB_PANIC);
7592
7593 wq_update_pod_attrs_buf = alloc_workqueue_attrs();
7594 BUG_ON(!wq_update_pod_attrs_buf);
7595
7596 /*
7597 * If nohz_full is enabled, set power efficient workqueue as unbound.
7598 * This allows workqueue items to be moved to HK CPUs.
7599 */
7600 if (housekeeping_enabled(HK_TYPE_TICK))
7601 wq_power_efficient = true;
7602
7603 /* initialize WQ_AFFN_SYSTEM pods */
7604 pt->pod_cpus = kcalloc(1, sizeof(pt->pod_cpus[0]), GFP_KERNEL);
7605 pt->pod_node = kcalloc(1, sizeof(pt->pod_node[0]), GFP_KERNEL);
7606 pt->cpu_pod = kcalloc(nr_cpu_ids, sizeof(pt->cpu_pod[0]), GFP_KERNEL);
7607 BUG_ON(!pt->pod_cpus || !pt->pod_node || !pt->cpu_pod);
7608
7609 BUG_ON(!zalloc_cpumask_var_node(&pt->pod_cpus[0], GFP_KERNEL, NUMA_NO_NODE));
7610
7611 pt->nr_pods = 1;
7612 cpumask_copy(pt->pod_cpus[0], cpu_possible_mask);
7613 pt->pod_node[0] = NUMA_NO_NODE;
7614 pt->cpu_pod[0] = 0;
7615
7616 /* initialize BH and CPU pools */
7617 for_each_possible_cpu(cpu) {
7618 struct worker_pool *pool;
7619
7620 i = 0;
7621 for_each_bh_worker_pool(pool, cpu) {
7622 init_cpu_worker_pool(pool, cpu, std_nice[i]);
7623 pool->flags |= POOL_BH;
7624 init_irq_work(bh_pool_irq_work(pool), irq_work_fns[i]);
7625 i++;
7626 }
7627
7628 i = 0;
7629 for_each_cpu_worker_pool(pool, cpu)
7630 init_cpu_worker_pool(pool, cpu, std_nice[i++]);
7631 }
7632
7633 /* create default unbound and ordered wq attrs */
7634 for (i = 0; i < NR_STD_WORKER_POOLS; i++) {
7635 struct workqueue_attrs *attrs;
7636
7637 BUG_ON(!(attrs = alloc_workqueue_attrs()));
7638 attrs->nice = std_nice[i];
7639 unbound_std_wq_attrs[i] = attrs;
7640
7641 /*
7642 * An ordered wq should have only one pwq as ordering is
7643 * guaranteed by max_active which is enforced by pwqs.
7644 */
7645 BUG_ON(!(attrs = alloc_workqueue_attrs()));
7646 attrs->nice = std_nice[i];
7647 attrs->ordered = true;
7648 ordered_wq_attrs[i] = attrs;
7649 }
7650
7651 system_wq = alloc_workqueue("events", 0, 0);
7652 system_highpri_wq = alloc_workqueue("events_highpri", WQ_HIGHPRI, 0);
7653 system_long_wq = alloc_workqueue("events_long", 0, 0);
7654 system_unbound_wq = alloc_workqueue("events_unbound", WQ_UNBOUND,
7655 WQ_MAX_ACTIVE);
7656 system_freezable_wq = alloc_workqueue("events_freezable",
7657 WQ_FREEZABLE, 0);
7658 system_power_efficient_wq = alloc_workqueue("events_power_efficient",
7659 WQ_POWER_EFFICIENT, 0);
7660 system_freezable_power_efficient_wq = alloc_workqueue("events_freezable_pwr_efficient",
7661 WQ_FREEZABLE | WQ_POWER_EFFICIENT,
7662 0);
7663 system_bh_wq = alloc_workqueue("events_bh", WQ_BH, 0);
7664 system_bh_highpri_wq = alloc_workqueue("events_bh_highpri",
7665 WQ_BH | WQ_HIGHPRI, 0);
7666 BUG_ON(!system_wq || !system_highpri_wq || !system_long_wq ||
7667 !system_unbound_wq || !system_freezable_wq ||
7668 !system_power_efficient_wq ||
7669 !system_freezable_power_efficient_wq ||
7670 !system_bh_wq || !system_bh_highpri_wq);
7671}
7672
7673static void __init wq_cpu_intensive_thresh_init(void)
7674{
7675 unsigned long thresh;
7676 unsigned long bogo;
7677
7678 pwq_release_worker = kthread_create_worker(0, "pool_workqueue_release");
7679 BUG_ON(IS_ERR(pwq_release_worker));
7680
7681 /* if the user set it to a specific value, keep it */
7682 if (wq_cpu_intensive_thresh_us != ULONG_MAX)
7683 return;
7684
7685 /*
7686 * The default of 10ms is derived from the fact that most modern (as of
7687 * 2023) processors can do a lot in 10ms and that it's just below what
7688 * most consider human-perceivable. However, the kernel also runs on a
7689 * lot slower CPUs including microcontrollers where the threshold is way
7690 * too low.
7691 *
7692 * Let's scale up the threshold upto 1 second if BogoMips is below 4000.
7693 * This is by no means accurate but it doesn't have to be. The mechanism
7694 * is still useful even when the threshold is fully scaled up. Also, as
7695 * the reports would usually be applicable to everyone, some machines
7696 * operating on longer thresholds won't significantly diminish their
7697 * usefulness.
7698 */
7699 thresh = 10 * USEC_PER_MSEC;
7700
7701 /* see init/calibrate.c for lpj -> BogoMIPS calculation */
7702 bogo = max_t(unsigned long, loops_per_jiffy / 500000 * HZ, 1);
7703 if (bogo < 4000)
7704 thresh = min_t(unsigned long, thresh * 4000 / bogo, USEC_PER_SEC);
7705
7706 pr_debug("wq_cpu_intensive_thresh: lpj=%lu BogoMIPS=%lu thresh_us=%lu\n",
7707 loops_per_jiffy, bogo, thresh);
7708
7709 wq_cpu_intensive_thresh_us = thresh;
7710}
7711
7712/**
7713 * workqueue_init - bring workqueue subsystem fully online
7714 *
7715 * This is the second step of three-staged workqueue subsystem initialization
7716 * and invoked as soon as kthreads can be created and scheduled. Workqueues have
7717 * been created and work items queued on them, but there are no kworkers
7718 * executing the work items yet. Populate the worker pools with the initial
7719 * workers and enable future kworker creations.
7720 */
7721void __init workqueue_init(void)
7722{
7723 struct workqueue_struct *wq;
7724 struct worker_pool *pool;
7725 int cpu, bkt;
7726
7727 wq_cpu_intensive_thresh_init();
7728
7729 mutex_lock(&wq_pool_mutex);
7730
7731 /*
7732 * Per-cpu pools created earlier could be missing node hint. Fix them
7733 * up. Also, create a rescuer for workqueues that requested it.
7734 */
7735 for_each_possible_cpu(cpu) {
7736 for_each_bh_worker_pool(pool, cpu)
7737 pool->node = cpu_to_node(cpu);
7738 for_each_cpu_worker_pool(pool, cpu)
7739 pool->node = cpu_to_node(cpu);
7740 }
7741
7742 list_for_each_entry(wq, &workqueues, list) {
7743 WARN(init_rescuer(wq),
7744 "workqueue: failed to create early rescuer for %s",
7745 wq->name);
7746 }
7747
7748 mutex_unlock(&wq_pool_mutex);
7749
7750 /*
7751 * Create the initial workers. A BH pool has one pseudo worker that
7752 * represents the shared BH execution context and thus doesn't get
7753 * affected by hotplug events. Create the BH pseudo workers for all
7754 * possible CPUs here.
7755 */
7756 for_each_possible_cpu(cpu)
7757 for_each_bh_worker_pool(pool, cpu)
7758 BUG_ON(!create_worker(pool));
7759
7760 for_each_online_cpu(cpu) {
7761 for_each_cpu_worker_pool(pool, cpu) {
7762 pool->flags &= ~POOL_DISASSOCIATED;
7763 BUG_ON(!create_worker(pool));
7764 }
7765 }
7766
7767 hash_for_each(unbound_pool_hash, bkt, pool, hash_node)
7768 BUG_ON(!create_worker(pool));
7769
7770 wq_online = true;
7771 wq_watchdog_init();
7772}
7773
7774/*
7775 * Initialize @pt by first initializing @pt->cpu_pod[] with pod IDs according to
7776 * @cpu_shares_pod(). Each subset of CPUs that share a pod is assigned a unique
7777 * and consecutive pod ID. The rest of @pt is initialized accordingly.
7778 */
7779static void __init init_pod_type(struct wq_pod_type *pt,
7780 bool (*cpus_share_pod)(int, int))
7781{
7782 int cur, pre, cpu, pod;
7783
7784 pt->nr_pods = 0;
7785
7786 /* init @pt->cpu_pod[] according to @cpus_share_pod() */
7787 pt->cpu_pod = kcalloc(nr_cpu_ids, sizeof(pt->cpu_pod[0]), GFP_KERNEL);
7788 BUG_ON(!pt->cpu_pod);
7789
7790 for_each_possible_cpu(cur) {
7791 for_each_possible_cpu(pre) {
7792 if (pre >= cur) {
7793 pt->cpu_pod[cur] = pt->nr_pods++;
7794 break;
7795 }
7796 if (cpus_share_pod(cur, pre)) {
7797 pt->cpu_pod[cur] = pt->cpu_pod[pre];
7798 break;
7799 }
7800 }
7801 }
7802
7803 /* init the rest to match @pt->cpu_pod[] */
7804 pt->pod_cpus = kcalloc(pt->nr_pods, sizeof(pt->pod_cpus[0]), GFP_KERNEL);
7805 pt->pod_node = kcalloc(pt->nr_pods, sizeof(pt->pod_node[0]), GFP_KERNEL);
7806 BUG_ON(!pt->pod_cpus || !pt->pod_node);
7807
7808 for (pod = 0; pod < pt->nr_pods; pod++)
7809 BUG_ON(!zalloc_cpumask_var(&pt->pod_cpus[pod], GFP_KERNEL));
7810
7811 for_each_possible_cpu(cpu) {
7812 cpumask_set_cpu(cpu, pt->pod_cpus[pt->cpu_pod[cpu]]);
7813 pt->pod_node[pt->cpu_pod[cpu]] = cpu_to_node(cpu);
7814 }
7815}
7816
7817static bool __init cpus_dont_share(int cpu0, int cpu1)
7818{
7819 return false;
7820}
7821
7822static bool __init cpus_share_smt(int cpu0, int cpu1)
7823{
7824#ifdef CONFIG_SCHED_SMT
7825 return cpumask_test_cpu(cpu0, cpu_smt_mask(cpu1));
7826#else
7827 return false;
7828#endif
7829}
7830
7831static bool __init cpus_share_numa(int cpu0, int cpu1)
7832{
7833 return cpu_to_node(cpu0) == cpu_to_node(cpu1);
7834}
7835
7836/**
7837 * workqueue_init_topology - initialize CPU pods for unbound workqueues
7838 *
7839 * This is the third step of three-staged workqueue subsystem initialization and
7840 * invoked after SMP and topology information are fully initialized. It
7841 * initializes the unbound CPU pods accordingly.
7842 */
7843void __init workqueue_init_topology(void)
7844{
7845 struct workqueue_struct *wq;
7846 int cpu;
7847
7848 init_pod_type(&wq_pod_types[WQ_AFFN_CPU], cpus_dont_share);
7849 init_pod_type(&wq_pod_types[WQ_AFFN_SMT], cpus_share_smt);
7850 init_pod_type(&wq_pod_types[WQ_AFFN_CACHE], cpus_share_cache);
7851 init_pod_type(&wq_pod_types[WQ_AFFN_NUMA], cpus_share_numa);
7852
7853 wq_topo_initialized = true;
7854
7855 mutex_lock(&wq_pool_mutex);
7856
7857 /*
7858 * Workqueues allocated earlier would have all CPUs sharing the default
7859 * worker pool. Explicitly call wq_update_pod() on all workqueue and CPU
7860 * combinations to apply per-pod sharing.
7861 */
7862 list_for_each_entry(wq, &workqueues, list) {
7863 for_each_online_cpu(cpu)
7864 wq_update_pod(wq, cpu, cpu, true);
7865 if (wq->flags & WQ_UNBOUND) {
7866 mutex_lock(&wq->mutex);
7867 wq_update_node_max_active(wq, -1);
7868 mutex_unlock(&wq->mutex);
7869 }
7870 }
7871
7872 mutex_unlock(&wq_pool_mutex);
7873}
7874
7875void __warn_flushing_systemwide_wq(void)
7876{
7877 pr_warn("WARNING: Flushing system-wide workqueues will be prohibited in near future.\n");
7878 dump_stack();
7879}
7880EXPORT_SYMBOL(__warn_flushing_systemwide_wq);
7881
7882static int __init workqueue_unbound_cpus_setup(char *str)
7883{
7884 if (cpulist_parse(str, &wq_cmdline_cpumask) < 0) {
7885 cpumask_clear(&wq_cmdline_cpumask);
7886 pr_warn("workqueue.unbound_cpus: incorrect CPU range, using default\n");
7887 }
7888
7889 return 1;
7890}
7891__setup("workqueue.unbound_cpus=", workqueue_unbound_cpus_setup);