Loading...
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 WORK_CANCEL_DISABLE = 1 << 1, /* canceling to disable */
103};
104
105enum wq_internal_consts {
106 NR_STD_WORKER_POOLS = 2, /* # standard pools per cpu */
107
108 UNBOUND_POOL_HASH_ORDER = 6, /* hashed by pool->attrs */
109 BUSY_WORKER_HASH_ORDER = 6, /* 64 pointers */
110
111 MAX_IDLE_WORKERS_RATIO = 4, /* 1/4 of busy can be idle */
112 IDLE_WORKER_TIMEOUT = 300 * HZ, /* keep idle ones for 5 mins */
113
114 MAYDAY_INITIAL_TIMEOUT = HZ / 100 >= 2 ? HZ / 100 : 2,
115 /* call for help after 10ms
116 (min two ticks) */
117 MAYDAY_INTERVAL = HZ / 10, /* and then every 100ms */
118 CREATE_COOLDOWN = HZ, /* time to breath after fail */
119
120 /*
121 * Rescue workers are used only on emergencies and shared by
122 * all cpus. Give MIN_NICE.
123 */
124 RESCUER_NICE_LEVEL = MIN_NICE,
125 HIGHPRI_NICE_LEVEL = MIN_NICE,
126
127 WQ_NAME_LEN = 32,
128 WORKER_ID_LEN = 10 + WQ_NAME_LEN, /* "kworker/R-" + WQ_NAME_LEN */
129};
130
131/*
132 * We don't want to trap softirq for too long. See MAX_SOFTIRQ_TIME and
133 * MAX_SOFTIRQ_RESTART in kernel/softirq.c. These are macros because
134 * msecs_to_jiffies() can't be an initializer.
135 */
136#define BH_WORKER_JIFFIES msecs_to_jiffies(2)
137#define BH_WORKER_RESTARTS 10
138
139/*
140 * Structure fields follow one of the following exclusion rules.
141 *
142 * I: Modifiable by initialization/destruction paths and read-only for
143 * everyone else.
144 *
145 * P: Preemption protected. Disabling preemption is enough and should
146 * only be modified and accessed from the local cpu.
147 *
148 * L: pool->lock protected. Access with pool->lock held.
149 *
150 * LN: pool->lock and wq_node_nr_active->lock protected for writes. Either for
151 * reads.
152 *
153 * K: Only modified by worker while holding pool->lock. Can be safely read by
154 * self, while holding pool->lock or from IRQ context if %current is the
155 * kworker.
156 *
157 * S: Only modified by worker self.
158 *
159 * A: wq_pool_attach_mutex protected.
160 *
161 * PL: wq_pool_mutex protected.
162 *
163 * PR: wq_pool_mutex protected for writes. RCU protected for reads.
164 *
165 * PW: wq_pool_mutex and wq->mutex protected for writes. Either for reads.
166 *
167 * PWR: wq_pool_mutex and wq->mutex protected for writes. Either or
168 * RCU for reads.
169 *
170 * WQ: wq->mutex protected.
171 *
172 * WR: wq->mutex protected for writes. RCU protected for reads.
173 *
174 * WO: wq->mutex protected for writes. Updated with WRITE_ONCE() and can be read
175 * with READ_ONCE() without locking.
176 *
177 * MD: wq_mayday_lock protected.
178 *
179 * WD: Used internally by the watchdog.
180 */
181
182/* struct worker is defined in workqueue_internal.h */
183
184struct worker_pool {
185 raw_spinlock_t lock; /* the pool lock */
186 int cpu; /* I: the associated cpu */
187 int node; /* I: the associated node ID */
188 int id; /* I: pool ID */
189 unsigned int flags; /* L: flags */
190
191 unsigned long watchdog_ts; /* L: watchdog timestamp */
192 bool cpu_stall; /* WD: stalled cpu bound pool */
193
194 /*
195 * The counter is incremented in a process context on the associated CPU
196 * w/ preemption disabled, and decremented or reset in the same context
197 * but w/ pool->lock held. The readers grab pool->lock and are
198 * guaranteed to see if the counter reached zero.
199 */
200 int nr_running;
201
202 struct list_head worklist; /* L: list of pending works */
203
204 int nr_workers; /* L: total number of workers */
205 int nr_idle; /* L: currently idle workers */
206
207 struct list_head idle_list; /* L: list of idle workers */
208 struct timer_list idle_timer; /* L: worker idle timeout */
209 struct work_struct idle_cull_work; /* L: worker idle cleanup */
210
211 struct timer_list mayday_timer; /* L: SOS timer for workers */
212
213 /* a workers is either on busy_hash or idle_list, or the manager */
214 DECLARE_HASHTABLE(busy_hash, BUSY_WORKER_HASH_ORDER);
215 /* L: hash of busy workers */
216
217 struct worker *manager; /* L: purely informational */
218 struct list_head workers; /* A: attached workers */
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 struct lockdep_map *lockdep_map;
369#endif
370 char name[WQ_NAME_LEN]; /* I: workqueue name */
371
372 /*
373 * Destruction of workqueue_struct is RCU protected to allow walking
374 * the workqueues list without grabbing wq_pool_mutex.
375 * This is used to dump all workqueues from sysrq.
376 */
377 struct rcu_head rcu;
378
379 /* hot fields used during command issue, aligned to cacheline */
380 unsigned int flags ____cacheline_aligned; /* WQ: WQ_* flags */
381 struct pool_workqueue __rcu * __percpu *cpu_pwq; /* I: per-cpu pwqs */
382 struct wq_node_nr_active *node_nr_active[]; /* I: per-node nr_active */
383};
384
385/*
386 * Each pod type describes how CPUs should be grouped for unbound workqueues.
387 * See the comment above workqueue_attrs->affn_scope.
388 */
389struct wq_pod_type {
390 int nr_pods; /* number of pods */
391 cpumask_var_t *pod_cpus; /* pod -> cpus */
392 int *pod_node; /* pod -> node */
393 int *cpu_pod; /* cpu -> pod */
394};
395
396struct work_offq_data {
397 u32 pool_id;
398 u32 disable;
399 u32 flags;
400};
401
402static const char *wq_affn_names[WQ_AFFN_NR_TYPES] = {
403 [WQ_AFFN_DFL] = "default",
404 [WQ_AFFN_CPU] = "cpu",
405 [WQ_AFFN_SMT] = "smt",
406 [WQ_AFFN_CACHE] = "cache",
407 [WQ_AFFN_NUMA] = "numa",
408 [WQ_AFFN_SYSTEM] = "system",
409};
410
411/*
412 * Per-cpu work items which run for longer than the following threshold are
413 * automatically considered CPU intensive and excluded from concurrency
414 * management to prevent them from noticeably delaying other per-cpu work items.
415 * ULONG_MAX indicates that the user hasn't overridden it with a boot parameter.
416 * The actual value is initialized in wq_cpu_intensive_thresh_init().
417 */
418static unsigned long wq_cpu_intensive_thresh_us = ULONG_MAX;
419module_param_named(cpu_intensive_thresh_us, wq_cpu_intensive_thresh_us, ulong, 0644);
420#ifdef CONFIG_WQ_CPU_INTENSIVE_REPORT
421static unsigned int wq_cpu_intensive_warning_thresh = 4;
422module_param_named(cpu_intensive_warning_thresh, wq_cpu_intensive_warning_thresh, uint, 0644);
423#endif
424
425/* see the comment above the definition of WQ_POWER_EFFICIENT */
426static bool wq_power_efficient = IS_ENABLED(CONFIG_WQ_POWER_EFFICIENT_DEFAULT);
427module_param_named(power_efficient, wq_power_efficient, bool, 0444);
428
429static bool wq_online; /* can kworkers be created yet? */
430static bool wq_topo_initialized __read_mostly = false;
431
432static struct kmem_cache *pwq_cache;
433
434static struct wq_pod_type wq_pod_types[WQ_AFFN_NR_TYPES];
435static enum wq_affn_scope wq_affn_dfl = WQ_AFFN_CACHE;
436
437/* buf for wq_update_unbound_pod_attrs(), protected by CPU hotplug exclusion */
438static struct workqueue_attrs *unbound_wq_update_pwq_attrs_buf;
439
440static DEFINE_MUTEX(wq_pool_mutex); /* protects pools and workqueues list */
441static DEFINE_MUTEX(wq_pool_attach_mutex); /* protects worker attach/detach */
442static DEFINE_RAW_SPINLOCK(wq_mayday_lock); /* protects wq->maydays list */
443/* wait for manager to go away */
444static struct rcuwait manager_wait = __RCUWAIT_INITIALIZER(manager_wait);
445
446static LIST_HEAD(workqueues); /* PR: list of all workqueues */
447static bool workqueue_freezing; /* PL: have wqs started freezing? */
448
449/* PL: mirror the cpu_online_mask excluding the CPU in the midst of hotplugging */
450static cpumask_var_t wq_online_cpumask;
451
452/* PL&A: allowable cpus for unbound wqs and work items */
453static cpumask_var_t wq_unbound_cpumask;
454
455/* PL: user requested unbound cpumask via sysfs */
456static cpumask_var_t wq_requested_unbound_cpumask;
457
458/* PL: isolated cpumask to be excluded from unbound cpumask */
459static cpumask_var_t wq_isolated_cpumask;
460
461/* for further constrain wq_unbound_cpumask by cmdline parameter*/
462static struct cpumask wq_cmdline_cpumask __initdata;
463
464/* CPU where unbound work was last round robin scheduled from this CPU */
465static DEFINE_PER_CPU(int, wq_rr_cpu_last);
466
467/*
468 * Local execution of unbound work items is no longer guaranteed. The
469 * following always forces round-robin CPU selection on unbound work items
470 * to uncover usages which depend on it.
471 */
472#ifdef CONFIG_DEBUG_WQ_FORCE_RR_CPU
473static bool wq_debug_force_rr_cpu = true;
474#else
475static bool wq_debug_force_rr_cpu = false;
476#endif
477module_param_named(debug_force_rr_cpu, wq_debug_force_rr_cpu, bool, 0644);
478
479/* to raise softirq for the BH worker pools on other CPUs */
480static DEFINE_PER_CPU_SHARED_ALIGNED(struct irq_work [NR_STD_WORKER_POOLS], bh_pool_irq_works);
481
482/* the BH worker pools */
483static DEFINE_PER_CPU_SHARED_ALIGNED(struct worker_pool [NR_STD_WORKER_POOLS], bh_worker_pools);
484
485/* the per-cpu worker pools */
486static DEFINE_PER_CPU_SHARED_ALIGNED(struct worker_pool [NR_STD_WORKER_POOLS], cpu_worker_pools);
487
488static DEFINE_IDR(worker_pool_idr); /* PR: idr of all pools */
489
490/* PL: hash of all unbound pools keyed by pool->attrs */
491static DEFINE_HASHTABLE(unbound_pool_hash, UNBOUND_POOL_HASH_ORDER);
492
493/* I: attributes used when instantiating standard unbound pools on demand */
494static struct workqueue_attrs *unbound_std_wq_attrs[NR_STD_WORKER_POOLS];
495
496/* I: attributes used when instantiating ordered pools on demand */
497static struct workqueue_attrs *ordered_wq_attrs[NR_STD_WORKER_POOLS];
498
499/*
500 * I: kthread_worker to release pwq's. pwq release needs to be bounced to a
501 * process context while holding a pool lock. Bounce to a dedicated kthread
502 * worker to avoid A-A deadlocks.
503 */
504static struct kthread_worker *pwq_release_worker __ro_after_init;
505
506struct workqueue_struct *system_wq __ro_after_init;
507EXPORT_SYMBOL(system_wq);
508struct workqueue_struct *system_highpri_wq __ro_after_init;
509EXPORT_SYMBOL_GPL(system_highpri_wq);
510struct workqueue_struct *system_long_wq __ro_after_init;
511EXPORT_SYMBOL_GPL(system_long_wq);
512struct workqueue_struct *system_unbound_wq __ro_after_init;
513EXPORT_SYMBOL_GPL(system_unbound_wq);
514struct workqueue_struct *system_freezable_wq __ro_after_init;
515EXPORT_SYMBOL_GPL(system_freezable_wq);
516struct workqueue_struct *system_power_efficient_wq __ro_after_init;
517EXPORT_SYMBOL_GPL(system_power_efficient_wq);
518struct workqueue_struct *system_freezable_power_efficient_wq __ro_after_init;
519EXPORT_SYMBOL_GPL(system_freezable_power_efficient_wq);
520struct workqueue_struct *system_bh_wq;
521EXPORT_SYMBOL_GPL(system_bh_wq);
522struct workqueue_struct *system_bh_highpri_wq;
523EXPORT_SYMBOL_GPL(system_bh_highpri_wq);
524
525static int worker_thread(void *__worker);
526static void workqueue_sysfs_unregister(struct workqueue_struct *wq);
527static void show_pwq(struct pool_workqueue *pwq);
528static void show_one_worker_pool(struct worker_pool *pool);
529
530#define CREATE_TRACE_POINTS
531#include <trace/events/workqueue.h>
532
533#define assert_rcu_or_pool_mutex() \
534 RCU_LOCKDEP_WARN(!rcu_read_lock_any_held() && \
535 !lockdep_is_held(&wq_pool_mutex), \
536 "RCU or wq_pool_mutex should be held")
537
538#define assert_rcu_or_wq_mutex_or_pool_mutex(wq) \
539 RCU_LOCKDEP_WARN(!rcu_read_lock_any_held() && \
540 !lockdep_is_held(&wq->mutex) && \
541 !lockdep_is_held(&wq_pool_mutex), \
542 "RCU, wq->mutex or wq_pool_mutex should be held")
543
544#define for_each_bh_worker_pool(pool, cpu) \
545 for ((pool) = &per_cpu(bh_worker_pools, cpu)[0]; \
546 (pool) < &per_cpu(bh_worker_pools, cpu)[NR_STD_WORKER_POOLS]; \
547 (pool)++)
548
549#define for_each_cpu_worker_pool(pool, cpu) \
550 for ((pool) = &per_cpu(cpu_worker_pools, cpu)[0]; \
551 (pool) < &per_cpu(cpu_worker_pools, cpu)[NR_STD_WORKER_POOLS]; \
552 (pool)++)
553
554/**
555 * for_each_pool - iterate through all worker_pools in the system
556 * @pool: iteration cursor
557 * @pi: integer used for iteration
558 *
559 * This must be called either with wq_pool_mutex held or RCU read
560 * locked. If the pool needs to be used beyond the locking in effect, the
561 * caller is responsible for guaranteeing that the pool stays online.
562 *
563 * The if/else clause exists only for the lockdep assertion and can be
564 * ignored.
565 */
566#define for_each_pool(pool, pi) \
567 idr_for_each_entry(&worker_pool_idr, pool, pi) \
568 if (({ assert_rcu_or_pool_mutex(); false; })) { } \
569 else
570
571/**
572 * for_each_pool_worker - iterate through all workers of a worker_pool
573 * @worker: iteration cursor
574 * @pool: worker_pool to iterate workers of
575 *
576 * This must be called with wq_pool_attach_mutex.
577 *
578 * The if/else clause exists only for the lockdep assertion and can be
579 * ignored.
580 */
581#define for_each_pool_worker(worker, pool) \
582 list_for_each_entry((worker), &(pool)->workers, node) \
583 if (({ lockdep_assert_held(&wq_pool_attach_mutex); false; })) { } \
584 else
585
586/**
587 * for_each_pwq - iterate through all pool_workqueues of the specified workqueue
588 * @pwq: iteration cursor
589 * @wq: the target workqueue
590 *
591 * This must be called either with wq->mutex held or RCU read locked.
592 * If the pwq needs to be used beyond the locking in effect, the caller is
593 * responsible for guaranteeing that the pwq stays online.
594 *
595 * The if/else clause exists only for the lockdep assertion and can be
596 * ignored.
597 */
598#define for_each_pwq(pwq, wq) \
599 list_for_each_entry_rcu((pwq), &(wq)->pwqs, pwqs_node, \
600 lockdep_is_held(&(wq->mutex)))
601
602#ifdef CONFIG_DEBUG_OBJECTS_WORK
603
604static const struct debug_obj_descr work_debug_descr;
605
606static void *work_debug_hint(void *addr)
607{
608 return ((struct work_struct *) addr)->func;
609}
610
611static bool work_is_static_object(void *addr)
612{
613 struct work_struct *work = addr;
614
615 return test_bit(WORK_STRUCT_STATIC_BIT, work_data_bits(work));
616}
617
618/*
619 * fixup_init is called when:
620 * - an active object is initialized
621 */
622static bool work_fixup_init(void *addr, enum debug_obj_state state)
623{
624 struct work_struct *work = addr;
625
626 switch (state) {
627 case ODEBUG_STATE_ACTIVE:
628 cancel_work_sync(work);
629 debug_object_init(work, &work_debug_descr);
630 return true;
631 default:
632 return false;
633 }
634}
635
636/*
637 * fixup_free is called when:
638 * - an active object is freed
639 */
640static bool work_fixup_free(void *addr, enum debug_obj_state state)
641{
642 struct work_struct *work = addr;
643
644 switch (state) {
645 case ODEBUG_STATE_ACTIVE:
646 cancel_work_sync(work);
647 debug_object_free(work, &work_debug_descr);
648 return true;
649 default:
650 return false;
651 }
652}
653
654static const struct debug_obj_descr work_debug_descr = {
655 .name = "work_struct",
656 .debug_hint = work_debug_hint,
657 .is_static_object = work_is_static_object,
658 .fixup_init = work_fixup_init,
659 .fixup_free = work_fixup_free,
660};
661
662static inline void debug_work_activate(struct work_struct *work)
663{
664 debug_object_activate(work, &work_debug_descr);
665}
666
667static inline void debug_work_deactivate(struct work_struct *work)
668{
669 debug_object_deactivate(work, &work_debug_descr);
670}
671
672void __init_work(struct work_struct *work, int onstack)
673{
674 if (onstack)
675 debug_object_init_on_stack(work, &work_debug_descr);
676 else
677 debug_object_init(work, &work_debug_descr);
678}
679EXPORT_SYMBOL_GPL(__init_work);
680
681void destroy_work_on_stack(struct work_struct *work)
682{
683 debug_object_free(work, &work_debug_descr);
684}
685EXPORT_SYMBOL_GPL(destroy_work_on_stack);
686
687void destroy_delayed_work_on_stack(struct delayed_work *work)
688{
689 destroy_timer_on_stack(&work->timer);
690 debug_object_free(&work->work, &work_debug_descr);
691}
692EXPORT_SYMBOL_GPL(destroy_delayed_work_on_stack);
693
694#else
695static inline void debug_work_activate(struct work_struct *work) { }
696static inline void debug_work_deactivate(struct work_struct *work) { }
697#endif
698
699/**
700 * worker_pool_assign_id - allocate ID and assign it to @pool
701 * @pool: the pool pointer of interest
702 *
703 * Returns 0 if ID in [0, WORK_OFFQ_POOL_NONE) is allocated and assigned
704 * successfully, -errno on failure.
705 */
706static int worker_pool_assign_id(struct worker_pool *pool)
707{
708 int ret;
709
710 lockdep_assert_held(&wq_pool_mutex);
711
712 ret = idr_alloc(&worker_pool_idr, pool, 0, WORK_OFFQ_POOL_NONE,
713 GFP_KERNEL);
714 if (ret >= 0) {
715 pool->id = ret;
716 return 0;
717 }
718 return ret;
719}
720
721static struct pool_workqueue __rcu **
722unbound_pwq_slot(struct workqueue_struct *wq, int cpu)
723{
724 if (cpu >= 0)
725 return per_cpu_ptr(wq->cpu_pwq, cpu);
726 else
727 return &wq->dfl_pwq;
728}
729
730/* @cpu < 0 for dfl_pwq */
731static struct pool_workqueue *unbound_pwq(struct workqueue_struct *wq, int cpu)
732{
733 return rcu_dereference_check(*unbound_pwq_slot(wq, cpu),
734 lockdep_is_held(&wq_pool_mutex) ||
735 lockdep_is_held(&wq->mutex));
736}
737
738/**
739 * unbound_effective_cpumask - effective cpumask of an unbound workqueue
740 * @wq: workqueue of interest
741 *
742 * @wq->unbound_attrs->cpumask contains the cpumask requested by the user which
743 * is masked with wq_unbound_cpumask to determine the effective cpumask. The
744 * default pwq is always mapped to the pool with the current effective cpumask.
745 */
746static struct cpumask *unbound_effective_cpumask(struct workqueue_struct *wq)
747{
748 return unbound_pwq(wq, -1)->pool->attrs->__pod_cpumask;
749}
750
751static unsigned int work_color_to_flags(int color)
752{
753 return color << WORK_STRUCT_COLOR_SHIFT;
754}
755
756static int get_work_color(unsigned long work_data)
757{
758 return (work_data >> WORK_STRUCT_COLOR_SHIFT) &
759 ((1 << WORK_STRUCT_COLOR_BITS) - 1);
760}
761
762static int work_next_color(int color)
763{
764 return (color + 1) % WORK_NR_COLORS;
765}
766
767static unsigned long pool_offq_flags(struct worker_pool *pool)
768{
769 return (pool->flags & POOL_BH) ? WORK_OFFQ_BH : 0;
770}
771
772/*
773 * While queued, %WORK_STRUCT_PWQ is set and non flag bits of a work's data
774 * contain the pointer to the queued pwq. Once execution starts, the flag
775 * is cleared and the high bits contain OFFQ flags and pool ID.
776 *
777 * set_work_pwq(), set_work_pool_and_clear_pending() and mark_work_canceling()
778 * can be used to set the pwq, pool or clear work->data. These functions should
779 * only be called while the work is owned - ie. while the PENDING bit is set.
780 *
781 * get_work_pool() and get_work_pwq() can be used to obtain the pool or pwq
782 * corresponding to a work. Pool is available once the work has been
783 * queued anywhere after initialization until it is sync canceled. pwq is
784 * available only while the work item is queued.
785 */
786static inline void set_work_data(struct work_struct *work, unsigned long data)
787{
788 WARN_ON_ONCE(!work_pending(work));
789 atomic_long_set(&work->data, data | work_static(work));
790}
791
792static void set_work_pwq(struct work_struct *work, struct pool_workqueue *pwq,
793 unsigned long flags)
794{
795 set_work_data(work, (unsigned long)pwq | WORK_STRUCT_PENDING |
796 WORK_STRUCT_PWQ | flags);
797}
798
799static void set_work_pool_and_keep_pending(struct work_struct *work,
800 int pool_id, unsigned long flags)
801{
802 set_work_data(work, ((unsigned long)pool_id << WORK_OFFQ_POOL_SHIFT) |
803 WORK_STRUCT_PENDING | flags);
804}
805
806static void set_work_pool_and_clear_pending(struct work_struct *work,
807 int pool_id, unsigned long flags)
808{
809 /*
810 * The following wmb is paired with the implied mb in
811 * test_and_set_bit(PENDING) and ensures all updates to @work made
812 * here are visible to and precede any updates by the next PENDING
813 * owner.
814 */
815 smp_wmb();
816 set_work_data(work, ((unsigned long)pool_id << WORK_OFFQ_POOL_SHIFT) |
817 flags);
818 /*
819 * The following mb guarantees that previous clear of a PENDING bit
820 * will not be reordered with any speculative LOADS or STORES from
821 * work->current_func, which is executed afterwards. This possible
822 * reordering can lead to a missed execution on attempt to queue
823 * the same @work. E.g. consider this case:
824 *
825 * CPU#0 CPU#1
826 * ---------------------------- --------------------------------
827 *
828 * 1 STORE event_indicated
829 * 2 queue_work_on() {
830 * 3 test_and_set_bit(PENDING)
831 * 4 } set_..._and_clear_pending() {
832 * 5 set_work_data() # clear bit
833 * 6 smp_mb()
834 * 7 work->current_func() {
835 * 8 LOAD event_indicated
836 * }
837 *
838 * Without an explicit full barrier speculative LOAD on line 8 can
839 * be executed before CPU#0 does STORE on line 1. If that happens,
840 * CPU#0 observes the PENDING bit is still set and new execution of
841 * a @work is not queued in a hope, that CPU#1 will eventually
842 * finish the queued @work. Meanwhile CPU#1 does not see
843 * event_indicated is set, because speculative LOAD was executed
844 * before actual STORE.
845 */
846 smp_mb();
847}
848
849static inline struct pool_workqueue *work_struct_pwq(unsigned long data)
850{
851 return (struct pool_workqueue *)(data & WORK_STRUCT_PWQ_MASK);
852}
853
854static struct pool_workqueue *get_work_pwq(struct work_struct *work)
855{
856 unsigned long data = atomic_long_read(&work->data);
857
858 if (data & WORK_STRUCT_PWQ)
859 return work_struct_pwq(data);
860 else
861 return NULL;
862}
863
864/**
865 * get_work_pool - return the worker_pool a given work was associated with
866 * @work: the work item of interest
867 *
868 * Pools are created and destroyed under wq_pool_mutex, and allows read
869 * access under RCU read lock. As such, this function should be
870 * called under wq_pool_mutex or inside of a rcu_read_lock() region.
871 *
872 * All fields of the returned pool are accessible as long as the above
873 * mentioned locking is in effect. If the returned pool needs to be used
874 * beyond the critical section, the caller is responsible for ensuring the
875 * returned pool is and stays online.
876 *
877 * Return: The worker_pool @work was last associated with. %NULL if none.
878 */
879static struct worker_pool *get_work_pool(struct work_struct *work)
880{
881 unsigned long data = atomic_long_read(&work->data);
882 int pool_id;
883
884 assert_rcu_or_pool_mutex();
885
886 if (data & WORK_STRUCT_PWQ)
887 return work_struct_pwq(data)->pool;
888
889 pool_id = data >> WORK_OFFQ_POOL_SHIFT;
890 if (pool_id == WORK_OFFQ_POOL_NONE)
891 return NULL;
892
893 return idr_find(&worker_pool_idr, pool_id);
894}
895
896static unsigned long shift_and_mask(unsigned long v, u32 shift, u32 bits)
897{
898 return (v >> shift) & ((1U << bits) - 1);
899}
900
901static void work_offqd_unpack(struct work_offq_data *offqd, unsigned long data)
902{
903 WARN_ON_ONCE(data & WORK_STRUCT_PWQ);
904
905 offqd->pool_id = shift_and_mask(data, WORK_OFFQ_POOL_SHIFT,
906 WORK_OFFQ_POOL_BITS);
907 offqd->disable = shift_and_mask(data, WORK_OFFQ_DISABLE_SHIFT,
908 WORK_OFFQ_DISABLE_BITS);
909 offqd->flags = data & WORK_OFFQ_FLAG_MASK;
910}
911
912static unsigned long work_offqd_pack_flags(struct work_offq_data *offqd)
913{
914 return ((unsigned long)offqd->disable << WORK_OFFQ_DISABLE_SHIFT) |
915 ((unsigned long)offqd->flags);
916}
917
918/*
919 * Policy functions. These define the policies on how the global worker
920 * pools are managed. Unless noted otherwise, these functions assume that
921 * they're being called with pool->lock held.
922 */
923
924/*
925 * Need to wake up a worker? Called from anything but currently
926 * running workers.
927 *
928 * Note that, because unbound workers never contribute to nr_running, this
929 * function will always return %true for unbound pools as long as the
930 * worklist isn't empty.
931 */
932static bool need_more_worker(struct worker_pool *pool)
933{
934 return !list_empty(&pool->worklist) && !pool->nr_running;
935}
936
937/* Can I start working? Called from busy but !running workers. */
938static bool may_start_working(struct worker_pool *pool)
939{
940 return pool->nr_idle;
941}
942
943/* Do I need to keep working? Called from currently running workers. */
944static bool keep_working(struct worker_pool *pool)
945{
946 return !list_empty(&pool->worklist) && (pool->nr_running <= 1);
947}
948
949/* Do we need a new worker? Called from manager. */
950static bool need_to_create_worker(struct worker_pool *pool)
951{
952 return need_more_worker(pool) && !may_start_working(pool);
953}
954
955/* Do we have too many workers and should some go away? */
956static bool too_many_workers(struct worker_pool *pool)
957{
958 bool managing = pool->flags & POOL_MANAGER_ACTIVE;
959 int nr_idle = pool->nr_idle + managing; /* manager is considered idle */
960 int nr_busy = pool->nr_workers - nr_idle;
961
962 return nr_idle > 2 && (nr_idle - 2) * MAX_IDLE_WORKERS_RATIO >= nr_busy;
963}
964
965/**
966 * worker_set_flags - set worker flags and adjust nr_running accordingly
967 * @worker: self
968 * @flags: flags to set
969 *
970 * Set @flags in @worker->flags and adjust nr_running accordingly.
971 */
972static inline void worker_set_flags(struct worker *worker, unsigned int flags)
973{
974 struct worker_pool *pool = worker->pool;
975
976 lockdep_assert_held(&pool->lock);
977
978 /* If transitioning into NOT_RUNNING, adjust nr_running. */
979 if ((flags & WORKER_NOT_RUNNING) &&
980 !(worker->flags & WORKER_NOT_RUNNING)) {
981 pool->nr_running--;
982 }
983
984 worker->flags |= flags;
985}
986
987/**
988 * worker_clr_flags - clear worker flags and adjust nr_running accordingly
989 * @worker: self
990 * @flags: flags to clear
991 *
992 * Clear @flags in @worker->flags and adjust nr_running accordingly.
993 */
994static inline void worker_clr_flags(struct worker *worker, unsigned int flags)
995{
996 struct worker_pool *pool = worker->pool;
997 unsigned int oflags = worker->flags;
998
999 lockdep_assert_held(&pool->lock);
1000
1001 worker->flags &= ~flags;
1002
1003 /*
1004 * If transitioning out of NOT_RUNNING, increment nr_running. Note
1005 * that the nested NOT_RUNNING is not a noop. NOT_RUNNING is mask
1006 * of multiple flags, not a single flag.
1007 */
1008 if ((flags & WORKER_NOT_RUNNING) && (oflags & WORKER_NOT_RUNNING))
1009 if (!(worker->flags & WORKER_NOT_RUNNING))
1010 pool->nr_running++;
1011}
1012
1013/* Return the first idle worker. Called with pool->lock held. */
1014static struct worker *first_idle_worker(struct worker_pool *pool)
1015{
1016 if (unlikely(list_empty(&pool->idle_list)))
1017 return NULL;
1018
1019 return list_first_entry(&pool->idle_list, struct worker, entry);
1020}
1021
1022/**
1023 * worker_enter_idle - enter idle state
1024 * @worker: worker which is entering idle state
1025 *
1026 * @worker is entering idle state. Update stats and idle timer if
1027 * necessary.
1028 *
1029 * LOCKING:
1030 * raw_spin_lock_irq(pool->lock).
1031 */
1032static void worker_enter_idle(struct worker *worker)
1033{
1034 struct worker_pool *pool = worker->pool;
1035
1036 if (WARN_ON_ONCE(worker->flags & WORKER_IDLE) ||
1037 WARN_ON_ONCE(!list_empty(&worker->entry) &&
1038 (worker->hentry.next || worker->hentry.pprev)))
1039 return;
1040
1041 /* can't use worker_set_flags(), also called from create_worker() */
1042 worker->flags |= WORKER_IDLE;
1043 pool->nr_idle++;
1044 worker->last_active = jiffies;
1045
1046 /* idle_list is LIFO */
1047 list_add(&worker->entry, &pool->idle_list);
1048
1049 if (too_many_workers(pool) && !timer_pending(&pool->idle_timer))
1050 mod_timer(&pool->idle_timer, jiffies + IDLE_WORKER_TIMEOUT);
1051
1052 /* Sanity check nr_running. */
1053 WARN_ON_ONCE(pool->nr_workers == pool->nr_idle && pool->nr_running);
1054}
1055
1056/**
1057 * worker_leave_idle - leave idle state
1058 * @worker: worker which is leaving idle state
1059 *
1060 * @worker is leaving idle state. Update stats.
1061 *
1062 * LOCKING:
1063 * raw_spin_lock_irq(pool->lock).
1064 */
1065static void worker_leave_idle(struct worker *worker)
1066{
1067 struct worker_pool *pool = worker->pool;
1068
1069 if (WARN_ON_ONCE(!(worker->flags & WORKER_IDLE)))
1070 return;
1071 worker_clr_flags(worker, WORKER_IDLE);
1072 pool->nr_idle--;
1073 list_del_init(&worker->entry);
1074}
1075
1076/**
1077 * find_worker_executing_work - find worker which is executing a work
1078 * @pool: pool of interest
1079 * @work: work to find worker for
1080 *
1081 * Find a worker which is executing @work on @pool by searching
1082 * @pool->busy_hash which is keyed by the address of @work. For a worker
1083 * to match, its current execution should match the address of @work and
1084 * its work function. This is to avoid unwanted dependency between
1085 * unrelated work executions through a work item being recycled while still
1086 * being executed.
1087 *
1088 * This is a bit tricky. A work item may be freed once its execution
1089 * starts and nothing prevents the freed area from being recycled for
1090 * another work item. If the same work item address ends up being reused
1091 * before the original execution finishes, workqueue will identify the
1092 * recycled work item as currently executing and make it wait until the
1093 * current execution finishes, introducing an unwanted dependency.
1094 *
1095 * This function checks the work item address and work function to avoid
1096 * false positives. Note that this isn't complete as one may construct a
1097 * work function which can introduce dependency onto itself through a
1098 * recycled work item. Well, if somebody wants to shoot oneself in the
1099 * foot that badly, there's only so much we can do, and if such deadlock
1100 * actually occurs, it should be easy to locate the culprit work function.
1101 *
1102 * CONTEXT:
1103 * raw_spin_lock_irq(pool->lock).
1104 *
1105 * Return:
1106 * Pointer to worker which is executing @work if found, %NULL
1107 * otherwise.
1108 */
1109static struct worker *find_worker_executing_work(struct worker_pool *pool,
1110 struct work_struct *work)
1111{
1112 struct worker *worker;
1113
1114 hash_for_each_possible(pool->busy_hash, worker, hentry,
1115 (unsigned long)work)
1116 if (worker->current_work == work &&
1117 worker->current_func == work->func)
1118 return worker;
1119
1120 return NULL;
1121}
1122
1123/**
1124 * move_linked_works - move linked works to a list
1125 * @work: start of series of works to be scheduled
1126 * @head: target list to append @work to
1127 * @nextp: out parameter for nested worklist walking
1128 *
1129 * Schedule linked works starting from @work to @head. Work series to be
1130 * scheduled starts at @work and includes any consecutive work with
1131 * WORK_STRUCT_LINKED set in its predecessor. See assign_work() for details on
1132 * @nextp.
1133 *
1134 * CONTEXT:
1135 * raw_spin_lock_irq(pool->lock).
1136 */
1137static void move_linked_works(struct work_struct *work, struct list_head *head,
1138 struct work_struct **nextp)
1139{
1140 struct work_struct *n;
1141
1142 /*
1143 * Linked worklist will always end before the end of the list,
1144 * use NULL for list head.
1145 */
1146 list_for_each_entry_safe_from(work, n, NULL, entry) {
1147 list_move_tail(&work->entry, head);
1148 if (!(*work_data_bits(work) & WORK_STRUCT_LINKED))
1149 break;
1150 }
1151
1152 /*
1153 * If we're already inside safe list traversal and have moved
1154 * multiple works to the scheduled queue, the next position
1155 * needs to be updated.
1156 */
1157 if (nextp)
1158 *nextp = n;
1159}
1160
1161/**
1162 * assign_work - assign a work item and its linked work items to a worker
1163 * @work: work to assign
1164 * @worker: worker to assign to
1165 * @nextp: out parameter for nested worklist walking
1166 *
1167 * Assign @work and its linked work items to @worker. If @work is already being
1168 * executed by another worker in the same pool, it'll be punted there.
1169 *
1170 * If @nextp is not NULL, it's updated to point to the next work of the last
1171 * scheduled work. This allows assign_work() to be nested inside
1172 * list_for_each_entry_safe().
1173 *
1174 * Returns %true if @work was successfully assigned to @worker. %false if @work
1175 * was punted to another worker already executing it.
1176 */
1177static bool assign_work(struct work_struct *work, struct worker *worker,
1178 struct work_struct **nextp)
1179{
1180 struct worker_pool *pool = worker->pool;
1181 struct worker *collision;
1182
1183 lockdep_assert_held(&pool->lock);
1184
1185 /*
1186 * A single work shouldn't be executed concurrently by multiple workers.
1187 * __queue_work() ensures that @work doesn't jump to a different pool
1188 * while still running in the previous pool. Here, we should ensure that
1189 * @work is not executed concurrently by multiple workers from the same
1190 * pool. Check whether anyone is already processing the work. If so,
1191 * defer the work to the currently executing one.
1192 */
1193 collision = find_worker_executing_work(pool, work);
1194 if (unlikely(collision)) {
1195 move_linked_works(work, &collision->scheduled, nextp);
1196 return false;
1197 }
1198
1199 move_linked_works(work, &worker->scheduled, nextp);
1200 return true;
1201}
1202
1203static struct irq_work *bh_pool_irq_work(struct worker_pool *pool)
1204{
1205 int high = pool->attrs->nice == HIGHPRI_NICE_LEVEL ? 1 : 0;
1206
1207 return &per_cpu(bh_pool_irq_works, pool->cpu)[high];
1208}
1209
1210static void kick_bh_pool(struct worker_pool *pool)
1211{
1212#ifdef CONFIG_SMP
1213 /* see drain_dead_softirq_workfn() for BH_DRAINING */
1214 if (unlikely(pool->cpu != smp_processor_id() &&
1215 !(pool->flags & POOL_BH_DRAINING))) {
1216 irq_work_queue_on(bh_pool_irq_work(pool), pool->cpu);
1217 return;
1218 }
1219#endif
1220 if (pool->attrs->nice == HIGHPRI_NICE_LEVEL)
1221 raise_softirq_irqoff(HI_SOFTIRQ);
1222 else
1223 raise_softirq_irqoff(TASKLET_SOFTIRQ);
1224}
1225
1226/**
1227 * kick_pool - wake up an idle worker if necessary
1228 * @pool: pool to kick
1229 *
1230 * @pool may have pending work items. Wake up worker if necessary. Returns
1231 * whether a worker was woken up.
1232 */
1233static bool kick_pool(struct worker_pool *pool)
1234{
1235 struct worker *worker = first_idle_worker(pool);
1236 struct task_struct *p;
1237
1238 lockdep_assert_held(&pool->lock);
1239
1240 if (!need_more_worker(pool) || !worker)
1241 return false;
1242
1243 if (pool->flags & POOL_BH) {
1244 kick_bh_pool(pool);
1245 return true;
1246 }
1247
1248 p = worker->task;
1249
1250#ifdef CONFIG_SMP
1251 /*
1252 * Idle @worker is about to execute @work and waking up provides an
1253 * opportunity to migrate @worker at a lower cost by setting the task's
1254 * wake_cpu field. Let's see if we want to move @worker to improve
1255 * execution locality.
1256 *
1257 * We're waking the worker that went idle the latest and there's some
1258 * chance that @worker is marked idle but hasn't gone off CPU yet. If
1259 * so, setting the wake_cpu won't do anything. As this is a best-effort
1260 * optimization and the race window is narrow, let's leave as-is for
1261 * now. If this becomes pronounced, we can skip over workers which are
1262 * still on cpu when picking an idle worker.
1263 *
1264 * If @pool has non-strict affinity, @worker might have ended up outside
1265 * its affinity scope. Repatriate.
1266 */
1267 if (!pool->attrs->affn_strict &&
1268 !cpumask_test_cpu(p->wake_cpu, pool->attrs->__pod_cpumask)) {
1269 struct work_struct *work = list_first_entry(&pool->worklist,
1270 struct work_struct, entry);
1271 int wake_cpu = cpumask_any_and_distribute(pool->attrs->__pod_cpumask,
1272 cpu_online_mask);
1273 if (wake_cpu < nr_cpu_ids) {
1274 p->wake_cpu = wake_cpu;
1275 get_work_pwq(work)->stats[PWQ_STAT_REPATRIATED]++;
1276 }
1277 }
1278#endif
1279 wake_up_process(p);
1280 return true;
1281}
1282
1283#ifdef CONFIG_WQ_CPU_INTENSIVE_REPORT
1284
1285/*
1286 * Concurrency-managed per-cpu work items that hog CPU for longer than
1287 * wq_cpu_intensive_thresh_us trigger the automatic CPU_INTENSIVE mechanism,
1288 * which prevents them from stalling other concurrency-managed work items. If a
1289 * work function keeps triggering this mechanism, it's likely that the work item
1290 * should be using an unbound workqueue instead.
1291 *
1292 * wq_cpu_intensive_report() tracks work functions which trigger such conditions
1293 * and report them so that they can be examined and converted to use unbound
1294 * workqueues as appropriate. To avoid flooding the console, each violating work
1295 * function is tracked and reported with exponential backoff.
1296 */
1297#define WCI_MAX_ENTS 128
1298
1299struct wci_ent {
1300 work_func_t func;
1301 atomic64_t cnt;
1302 struct hlist_node hash_node;
1303};
1304
1305static struct wci_ent wci_ents[WCI_MAX_ENTS];
1306static int wci_nr_ents;
1307static DEFINE_RAW_SPINLOCK(wci_lock);
1308static DEFINE_HASHTABLE(wci_hash, ilog2(WCI_MAX_ENTS));
1309
1310static struct wci_ent *wci_find_ent(work_func_t func)
1311{
1312 struct wci_ent *ent;
1313
1314 hash_for_each_possible_rcu(wci_hash, ent, hash_node,
1315 (unsigned long)func) {
1316 if (ent->func == func)
1317 return ent;
1318 }
1319 return NULL;
1320}
1321
1322static void wq_cpu_intensive_report(work_func_t func)
1323{
1324 struct wci_ent *ent;
1325
1326restart:
1327 ent = wci_find_ent(func);
1328 if (ent) {
1329 u64 cnt;
1330
1331 /*
1332 * Start reporting from the warning_thresh and back off
1333 * exponentially.
1334 */
1335 cnt = atomic64_inc_return_relaxed(&ent->cnt);
1336 if (wq_cpu_intensive_warning_thresh &&
1337 cnt >= wq_cpu_intensive_warning_thresh &&
1338 is_power_of_2(cnt + 1 - wq_cpu_intensive_warning_thresh))
1339 printk_deferred(KERN_WARNING "workqueue: %ps hogged CPU for >%luus %llu times, consider switching to WQ_UNBOUND\n",
1340 ent->func, wq_cpu_intensive_thresh_us,
1341 atomic64_read(&ent->cnt));
1342 return;
1343 }
1344
1345 /*
1346 * @func is a new violation. Allocate a new entry for it. If wcn_ents[]
1347 * is exhausted, something went really wrong and we probably made enough
1348 * noise already.
1349 */
1350 if (wci_nr_ents >= WCI_MAX_ENTS)
1351 return;
1352
1353 raw_spin_lock(&wci_lock);
1354
1355 if (wci_nr_ents >= WCI_MAX_ENTS) {
1356 raw_spin_unlock(&wci_lock);
1357 return;
1358 }
1359
1360 if (wci_find_ent(func)) {
1361 raw_spin_unlock(&wci_lock);
1362 goto restart;
1363 }
1364
1365 ent = &wci_ents[wci_nr_ents++];
1366 ent->func = func;
1367 atomic64_set(&ent->cnt, 0);
1368 hash_add_rcu(wci_hash, &ent->hash_node, (unsigned long)func);
1369
1370 raw_spin_unlock(&wci_lock);
1371
1372 goto restart;
1373}
1374
1375#else /* CONFIG_WQ_CPU_INTENSIVE_REPORT */
1376static void wq_cpu_intensive_report(work_func_t func) {}
1377#endif /* CONFIG_WQ_CPU_INTENSIVE_REPORT */
1378
1379/**
1380 * wq_worker_running - a worker is running again
1381 * @task: task waking up
1382 *
1383 * This function is called when a worker returns from schedule()
1384 */
1385void wq_worker_running(struct task_struct *task)
1386{
1387 struct worker *worker = kthread_data(task);
1388
1389 if (!READ_ONCE(worker->sleeping))
1390 return;
1391
1392 /*
1393 * If preempted by unbind_workers() between the WORKER_NOT_RUNNING check
1394 * and the nr_running increment below, we may ruin the nr_running reset
1395 * and leave with an unexpected pool->nr_running == 1 on the newly unbound
1396 * pool. Protect against such race.
1397 */
1398 preempt_disable();
1399 if (!(worker->flags & WORKER_NOT_RUNNING))
1400 worker->pool->nr_running++;
1401 preempt_enable();
1402
1403 /*
1404 * CPU intensive auto-detection cares about how long a work item hogged
1405 * CPU without sleeping. Reset the starting timestamp on wakeup.
1406 */
1407 worker->current_at = worker->task->se.sum_exec_runtime;
1408
1409 WRITE_ONCE(worker->sleeping, 0);
1410}
1411
1412/**
1413 * wq_worker_sleeping - a worker is going to sleep
1414 * @task: task going to sleep
1415 *
1416 * This function is called from schedule() when a busy worker is
1417 * going to sleep.
1418 */
1419void wq_worker_sleeping(struct task_struct *task)
1420{
1421 struct worker *worker = kthread_data(task);
1422 struct worker_pool *pool;
1423
1424 /*
1425 * Rescuers, which may not have all the fields set up like normal
1426 * workers, also reach here, let's not access anything before
1427 * checking NOT_RUNNING.
1428 */
1429 if (worker->flags & WORKER_NOT_RUNNING)
1430 return;
1431
1432 pool = worker->pool;
1433
1434 /* Return if preempted before wq_worker_running() was reached */
1435 if (READ_ONCE(worker->sleeping))
1436 return;
1437
1438 WRITE_ONCE(worker->sleeping, 1);
1439 raw_spin_lock_irq(&pool->lock);
1440
1441 /*
1442 * Recheck in case unbind_workers() preempted us. We don't
1443 * want to decrement nr_running after the worker is unbound
1444 * and nr_running has been reset.
1445 */
1446 if (worker->flags & WORKER_NOT_RUNNING) {
1447 raw_spin_unlock_irq(&pool->lock);
1448 return;
1449 }
1450
1451 pool->nr_running--;
1452 if (kick_pool(pool))
1453 worker->current_pwq->stats[PWQ_STAT_CM_WAKEUP]++;
1454
1455 raw_spin_unlock_irq(&pool->lock);
1456}
1457
1458/**
1459 * wq_worker_tick - a scheduler tick occurred while a kworker is running
1460 * @task: task currently running
1461 *
1462 * Called from sched_tick(). We're in the IRQ context and the current
1463 * worker's fields which follow the 'K' locking rule can be accessed safely.
1464 */
1465void wq_worker_tick(struct task_struct *task)
1466{
1467 struct worker *worker = kthread_data(task);
1468 struct pool_workqueue *pwq = worker->current_pwq;
1469 struct worker_pool *pool = worker->pool;
1470
1471 if (!pwq)
1472 return;
1473
1474 pwq->stats[PWQ_STAT_CPU_TIME] += TICK_USEC;
1475
1476 if (!wq_cpu_intensive_thresh_us)
1477 return;
1478
1479 /*
1480 * If the current worker is concurrency managed and hogged the CPU for
1481 * longer than wq_cpu_intensive_thresh_us, it's automatically marked
1482 * CPU_INTENSIVE to avoid stalling other concurrency-managed work items.
1483 *
1484 * Set @worker->sleeping means that @worker is in the process of
1485 * switching out voluntarily and won't be contributing to
1486 * @pool->nr_running until it wakes up. As wq_worker_sleeping() also
1487 * decrements ->nr_running, setting CPU_INTENSIVE here can lead to
1488 * double decrements. The task is releasing the CPU anyway. Let's skip.
1489 * We probably want to make this prettier in the future.
1490 */
1491 if ((worker->flags & WORKER_NOT_RUNNING) || READ_ONCE(worker->sleeping) ||
1492 worker->task->se.sum_exec_runtime - worker->current_at <
1493 wq_cpu_intensive_thresh_us * NSEC_PER_USEC)
1494 return;
1495
1496 raw_spin_lock(&pool->lock);
1497
1498 worker_set_flags(worker, WORKER_CPU_INTENSIVE);
1499 wq_cpu_intensive_report(worker->current_func);
1500 pwq->stats[PWQ_STAT_CPU_INTENSIVE]++;
1501
1502 if (kick_pool(pool))
1503 pwq->stats[PWQ_STAT_CM_WAKEUP]++;
1504
1505 raw_spin_unlock(&pool->lock);
1506}
1507
1508/**
1509 * wq_worker_last_func - retrieve worker's last work function
1510 * @task: Task to retrieve last work function of.
1511 *
1512 * Determine the last function a worker executed. This is called from
1513 * the scheduler to get a worker's last known identity.
1514 *
1515 * CONTEXT:
1516 * raw_spin_lock_irq(rq->lock)
1517 *
1518 * This function is called during schedule() when a kworker is going
1519 * to sleep. It's used by psi to identify aggregation workers during
1520 * dequeuing, to allow periodic aggregation to shut-off when that
1521 * worker is the last task in the system or cgroup to go to sleep.
1522 *
1523 * As this function doesn't involve any workqueue-related locking, it
1524 * only returns stable values when called from inside the scheduler's
1525 * queuing and dequeuing paths, when @task, which must be a kworker,
1526 * is guaranteed to not be processing any works.
1527 *
1528 * Return:
1529 * The last work function %current executed as a worker, NULL if it
1530 * hasn't executed any work yet.
1531 */
1532work_func_t wq_worker_last_func(struct task_struct *task)
1533{
1534 struct worker *worker = kthread_data(task);
1535
1536 return worker->last_func;
1537}
1538
1539/**
1540 * wq_node_nr_active - Determine wq_node_nr_active to use
1541 * @wq: workqueue of interest
1542 * @node: NUMA node, can be %NUMA_NO_NODE
1543 *
1544 * Determine wq_node_nr_active to use for @wq on @node. Returns:
1545 *
1546 * - %NULL for per-cpu workqueues as they don't need to use shared nr_active.
1547 *
1548 * - node_nr_active[nr_node_ids] if @node is %NUMA_NO_NODE.
1549 *
1550 * - Otherwise, node_nr_active[@node].
1551 */
1552static struct wq_node_nr_active *wq_node_nr_active(struct workqueue_struct *wq,
1553 int node)
1554{
1555 if (!(wq->flags & WQ_UNBOUND))
1556 return NULL;
1557
1558 if (node == NUMA_NO_NODE)
1559 node = nr_node_ids;
1560
1561 return wq->node_nr_active[node];
1562}
1563
1564/**
1565 * wq_update_node_max_active - Update per-node max_actives to use
1566 * @wq: workqueue to update
1567 * @off_cpu: CPU that's going down, -1 if a CPU is not going down
1568 *
1569 * Update @wq->node_nr_active[]->max. @wq must be unbound. max_active is
1570 * distributed among nodes according to the proportions of numbers of online
1571 * cpus. The result is always between @wq->min_active and max_active.
1572 */
1573static void wq_update_node_max_active(struct workqueue_struct *wq, int off_cpu)
1574{
1575 struct cpumask *effective = unbound_effective_cpumask(wq);
1576 int min_active = READ_ONCE(wq->min_active);
1577 int max_active = READ_ONCE(wq->max_active);
1578 int total_cpus, node;
1579
1580 lockdep_assert_held(&wq->mutex);
1581
1582 if (!wq_topo_initialized)
1583 return;
1584
1585 if (off_cpu >= 0 && !cpumask_test_cpu(off_cpu, effective))
1586 off_cpu = -1;
1587
1588 total_cpus = cpumask_weight_and(effective, cpu_online_mask);
1589 if (off_cpu >= 0)
1590 total_cpus--;
1591
1592 /* If all CPUs of the wq get offline, use the default values */
1593 if (unlikely(!total_cpus)) {
1594 for_each_node(node)
1595 wq_node_nr_active(wq, node)->max = min_active;
1596
1597 wq_node_nr_active(wq, NUMA_NO_NODE)->max = max_active;
1598 return;
1599 }
1600
1601 for_each_node(node) {
1602 int node_cpus;
1603
1604 node_cpus = cpumask_weight_and(effective, cpumask_of_node(node));
1605 if (off_cpu >= 0 && cpu_to_node(off_cpu) == node)
1606 node_cpus--;
1607
1608 wq_node_nr_active(wq, node)->max =
1609 clamp(DIV_ROUND_UP(max_active * node_cpus, total_cpus),
1610 min_active, max_active);
1611 }
1612
1613 wq_node_nr_active(wq, NUMA_NO_NODE)->max = max_active;
1614}
1615
1616/**
1617 * get_pwq - get an extra reference on the specified pool_workqueue
1618 * @pwq: pool_workqueue to get
1619 *
1620 * Obtain an extra reference on @pwq. The caller should guarantee that
1621 * @pwq has positive refcnt and be holding the matching pool->lock.
1622 */
1623static void get_pwq(struct pool_workqueue *pwq)
1624{
1625 lockdep_assert_held(&pwq->pool->lock);
1626 WARN_ON_ONCE(pwq->refcnt <= 0);
1627 pwq->refcnt++;
1628}
1629
1630/**
1631 * put_pwq - put a pool_workqueue reference
1632 * @pwq: pool_workqueue to put
1633 *
1634 * Drop a reference of @pwq. If its refcnt reaches zero, schedule its
1635 * destruction. The caller should be holding the matching pool->lock.
1636 */
1637static void put_pwq(struct pool_workqueue *pwq)
1638{
1639 lockdep_assert_held(&pwq->pool->lock);
1640 if (likely(--pwq->refcnt))
1641 return;
1642 /*
1643 * @pwq can't be released under pool->lock, bounce to a dedicated
1644 * kthread_worker to avoid A-A deadlocks.
1645 */
1646 kthread_queue_work(pwq_release_worker, &pwq->release_work);
1647}
1648
1649/**
1650 * put_pwq_unlocked - put_pwq() with surrounding pool lock/unlock
1651 * @pwq: pool_workqueue to put (can be %NULL)
1652 *
1653 * put_pwq() with locking. This function also allows %NULL @pwq.
1654 */
1655static void put_pwq_unlocked(struct pool_workqueue *pwq)
1656{
1657 if (pwq) {
1658 /*
1659 * As both pwqs and pools are RCU protected, the
1660 * following lock operations are safe.
1661 */
1662 raw_spin_lock_irq(&pwq->pool->lock);
1663 put_pwq(pwq);
1664 raw_spin_unlock_irq(&pwq->pool->lock);
1665 }
1666}
1667
1668static bool pwq_is_empty(struct pool_workqueue *pwq)
1669{
1670 return !pwq->nr_active && list_empty(&pwq->inactive_works);
1671}
1672
1673static void __pwq_activate_work(struct pool_workqueue *pwq,
1674 struct work_struct *work)
1675{
1676 unsigned long *wdb = work_data_bits(work);
1677
1678 WARN_ON_ONCE(!(*wdb & WORK_STRUCT_INACTIVE));
1679 trace_workqueue_activate_work(work);
1680 if (list_empty(&pwq->pool->worklist))
1681 pwq->pool->watchdog_ts = jiffies;
1682 move_linked_works(work, &pwq->pool->worklist, NULL);
1683 __clear_bit(WORK_STRUCT_INACTIVE_BIT, wdb);
1684}
1685
1686static bool tryinc_node_nr_active(struct wq_node_nr_active *nna)
1687{
1688 int max = READ_ONCE(nna->max);
1689
1690 while (true) {
1691 int old, tmp;
1692
1693 old = atomic_read(&nna->nr);
1694 if (old >= max)
1695 return false;
1696 tmp = atomic_cmpxchg_relaxed(&nna->nr, old, old + 1);
1697 if (tmp == old)
1698 return true;
1699 }
1700}
1701
1702/**
1703 * pwq_tryinc_nr_active - Try to increment nr_active for a pwq
1704 * @pwq: pool_workqueue of interest
1705 * @fill: max_active may have increased, try to increase concurrency level
1706 *
1707 * Try to increment nr_active for @pwq. Returns %true if an nr_active count is
1708 * successfully obtained. %false otherwise.
1709 */
1710static bool pwq_tryinc_nr_active(struct pool_workqueue *pwq, bool fill)
1711{
1712 struct workqueue_struct *wq = pwq->wq;
1713 struct worker_pool *pool = pwq->pool;
1714 struct wq_node_nr_active *nna = wq_node_nr_active(wq, pool->node);
1715 bool obtained = false;
1716
1717 lockdep_assert_held(&pool->lock);
1718
1719 if (!nna) {
1720 /* BH or per-cpu workqueue, pwq->nr_active is sufficient */
1721 obtained = pwq->nr_active < READ_ONCE(wq->max_active);
1722 goto out;
1723 }
1724
1725 if (unlikely(pwq->plugged))
1726 return false;
1727
1728 /*
1729 * Unbound workqueue uses per-node shared nr_active $nna. If @pwq is
1730 * already waiting on $nna, pwq_dec_nr_active() will maintain the
1731 * concurrency level. Don't jump the line.
1732 *
1733 * We need to ignore the pending test after max_active has increased as
1734 * pwq_dec_nr_active() can only maintain the concurrency level but not
1735 * increase it. This is indicated by @fill.
1736 */
1737 if (!list_empty(&pwq->pending_node) && likely(!fill))
1738 goto out;
1739
1740 obtained = tryinc_node_nr_active(nna);
1741 if (obtained)
1742 goto out;
1743
1744 /*
1745 * Lockless acquisition failed. Lock, add ourself to $nna->pending_pwqs
1746 * and try again. The smp_mb() is paired with the implied memory barrier
1747 * of atomic_dec_return() in pwq_dec_nr_active() to ensure that either
1748 * we see the decremented $nna->nr or they see non-empty
1749 * $nna->pending_pwqs.
1750 */
1751 raw_spin_lock(&nna->lock);
1752
1753 if (list_empty(&pwq->pending_node))
1754 list_add_tail(&pwq->pending_node, &nna->pending_pwqs);
1755 else if (likely(!fill))
1756 goto out_unlock;
1757
1758 smp_mb();
1759
1760 obtained = tryinc_node_nr_active(nna);
1761
1762 /*
1763 * If @fill, @pwq might have already been pending. Being spuriously
1764 * pending in cold paths doesn't affect anything. Let's leave it be.
1765 */
1766 if (obtained && likely(!fill))
1767 list_del_init(&pwq->pending_node);
1768
1769out_unlock:
1770 raw_spin_unlock(&nna->lock);
1771out:
1772 if (obtained)
1773 pwq->nr_active++;
1774 return obtained;
1775}
1776
1777/**
1778 * pwq_activate_first_inactive - Activate the first inactive work item on a pwq
1779 * @pwq: pool_workqueue of interest
1780 * @fill: max_active may have increased, try to increase concurrency level
1781 *
1782 * Activate the first inactive work item of @pwq if available and allowed by
1783 * max_active limit.
1784 *
1785 * Returns %true if an inactive work item has been activated. %false if no
1786 * inactive work item is found or max_active limit is reached.
1787 */
1788static bool pwq_activate_first_inactive(struct pool_workqueue *pwq, bool fill)
1789{
1790 struct work_struct *work =
1791 list_first_entry_or_null(&pwq->inactive_works,
1792 struct work_struct, entry);
1793
1794 if (work && pwq_tryinc_nr_active(pwq, fill)) {
1795 __pwq_activate_work(pwq, work);
1796 return true;
1797 } else {
1798 return false;
1799 }
1800}
1801
1802/**
1803 * unplug_oldest_pwq - unplug the oldest pool_workqueue
1804 * @wq: workqueue_struct where its oldest pwq is to be unplugged
1805 *
1806 * This function should only be called for ordered workqueues where only the
1807 * oldest pwq is unplugged, the others are plugged to suspend execution to
1808 * ensure proper work item ordering::
1809 *
1810 * dfl_pwq --------------+ [P] - plugged
1811 * |
1812 * v
1813 * pwqs -> A -> B [P] -> C [P] (newest)
1814 * | | |
1815 * 1 3 5
1816 * | | |
1817 * 2 4 6
1818 *
1819 * When the oldest pwq is drained and removed, this function should be called
1820 * to unplug the next oldest one to start its work item execution. Note that
1821 * pwq's are linked into wq->pwqs with the oldest first, so the first one in
1822 * the list is the oldest.
1823 */
1824static void unplug_oldest_pwq(struct workqueue_struct *wq)
1825{
1826 struct pool_workqueue *pwq;
1827
1828 lockdep_assert_held(&wq->mutex);
1829
1830 /* Caller should make sure that pwqs isn't empty before calling */
1831 pwq = list_first_entry_or_null(&wq->pwqs, struct pool_workqueue,
1832 pwqs_node);
1833 raw_spin_lock_irq(&pwq->pool->lock);
1834 if (pwq->plugged) {
1835 pwq->plugged = false;
1836 if (pwq_activate_first_inactive(pwq, true))
1837 kick_pool(pwq->pool);
1838 }
1839 raw_spin_unlock_irq(&pwq->pool->lock);
1840}
1841
1842/**
1843 * node_activate_pending_pwq - Activate a pending pwq on a wq_node_nr_active
1844 * @nna: wq_node_nr_active to activate a pending pwq for
1845 * @caller_pool: worker_pool the caller is locking
1846 *
1847 * Activate a pwq in @nna->pending_pwqs. Called with @caller_pool locked.
1848 * @caller_pool may be unlocked and relocked to lock other worker_pools.
1849 */
1850static void node_activate_pending_pwq(struct wq_node_nr_active *nna,
1851 struct worker_pool *caller_pool)
1852{
1853 struct worker_pool *locked_pool = caller_pool;
1854 struct pool_workqueue *pwq;
1855 struct work_struct *work;
1856
1857 lockdep_assert_held(&caller_pool->lock);
1858
1859 raw_spin_lock(&nna->lock);
1860retry:
1861 pwq = list_first_entry_or_null(&nna->pending_pwqs,
1862 struct pool_workqueue, pending_node);
1863 if (!pwq)
1864 goto out_unlock;
1865
1866 /*
1867 * If @pwq is for a different pool than @locked_pool, we need to lock
1868 * @pwq->pool->lock. Let's trylock first. If unsuccessful, do the unlock
1869 * / lock dance. For that, we also need to release @nna->lock as it's
1870 * nested inside pool locks.
1871 */
1872 if (pwq->pool != locked_pool) {
1873 raw_spin_unlock(&locked_pool->lock);
1874 locked_pool = pwq->pool;
1875 if (!raw_spin_trylock(&locked_pool->lock)) {
1876 raw_spin_unlock(&nna->lock);
1877 raw_spin_lock(&locked_pool->lock);
1878 raw_spin_lock(&nna->lock);
1879 goto retry;
1880 }
1881 }
1882
1883 /*
1884 * $pwq may not have any inactive work items due to e.g. cancellations.
1885 * Drop it from pending_pwqs and see if there's another one.
1886 */
1887 work = list_first_entry_or_null(&pwq->inactive_works,
1888 struct work_struct, entry);
1889 if (!work) {
1890 list_del_init(&pwq->pending_node);
1891 goto retry;
1892 }
1893
1894 /*
1895 * Acquire an nr_active count and activate the inactive work item. If
1896 * $pwq still has inactive work items, rotate it to the end of the
1897 * pending_pwqs so that we round-robin through them. This means that
1898 * inactive work items are not activated in queueing order which is fine
1899 * given that there has never been any ordering across different pwqs.
1900 */
1901 if (likely(tryinc_node_nr_active(nna))) {
1902 pwq->nr_active++;
1903 __pwq_activate_work(pwq, work);
1904
1905 if (list_empty(&pwq->inactive_works))
1906 list_del_init(&pwq->pending_node);
1907 else
1908 list_move_tail(&pwq->pending_node, &nna->pending_pwqs);
1909
1910 /* if activating a foreign pool, make sure it's running */
1911 if (pwq->pool != caller_pool)
1912 kick_pool(pwq->pool);
1913 }
1914
1915out_unlock:
1916 raw_spin_unlock(&nna->lock);
1917 if (locked_pool != caller_pool) {
1918 raw_spin_unlock(&locked_pool->lock);
1919 raw_spin_lock(&caller_pool->lock);
1920 }
1921}
1922
1923/**
1924 * pwq_dec_nr_active - Retire an active count
1925 * @pwq: pool_workqueue of interest
1926 *
1927 * Decrement @pwq's nr_active and try to activate the first inactive work item.
1928 * For unbound workqueues, this function may temporarily drop @pwq->pool->lock.
1929 */
1930static void pwq_dec_nr_active(struct pool_workqueue *pwq)
1931{
1932 struct worker_pool *pool = pwq->pool;
1933 struct wq_node_nr_active *nna = wq_node_nr_active(pwq->wq, pool->node);
1934
1935 lockdep_assert_held(&pool->lock);
1936
1937 /*
1938 * @pwq->nr_active should be decremented for both percpu and unbound
1939 * workqueues.
1940 */
1941 pwq->nr_active--;
1942
1943 /*
1944 * For a percpu workqueue, it's simple. Just need to kick the first
1945 * inactive work item on @pwq itself.
1946 */
1947 if (!nna) {
1948 pwq_activate_first_inactive(pwq, false);
1949 return;
1950 }
1951
1952 /*
1953 * If @pwq is for an unbound workqueue, it's more complicated because
1954 * multiple pwqs and pools may be sharing the nr_active count. When a
1955 * pwq needs to wait for an nr_active count, it puts itself on
1956 * $nna->pending_pwqs. The following atomic_dec_return()'s implied
1957 * memory barrier is paired with smp_mb() in pwq_tryinc_nr_active() to
1958 * guarantee that either we see non-empty pending_pwqs or they see
1959 * decremented $nna->nr.
1960 *
1961 * $nna->max may change as CPUs come online/offline and @pwq->wq's
1962 * max_active gets updated. However, it is guaranteed to be equal to or
1963 * larger than @pwq->wq->min_active which is above zero unless freezing.
1964 * This maintains the forward progress guarantee.
1965 */
1966 if (atomic_dec_return(&nna->nr) >= READ_ONCE(nna->max))
1967 return;
1968
1969 if (!list_empty(&nna->pending_pwqs))
1970 node_activate_pending_pwq(nna, pool);
1971}
1972
1973/**
1974 * pwq_dec_nr_in_flight - decrement pwq's nr_in_flight
1975 * @pwq: pwq of interest
1976 * @work_data: work_data of work which left the queue
1977 *
1978 * A work either has completed or is removed from pending queue,
1979 * decrement nr_in_flight of its pwq and handle workqueue flushing.
1980 *
1981 * NOTE:
1982 * For unbound workqueues, this function may temporarily drop @pwq->pool->lock
1983 * and thus should be called after all other state updates for the in-flight
1984 * work item is complete.
1985 *
1986 * CONTEXT:
1987 * raw_spin_lock_irq(pool->lock).
1988 */
1989static void pwq_dec_nr_in_flight(struct pool_workqueue *pwq, unsigned long work_data)
1990{
1991 int color = get_work_color(work_data);
1992
1993 if (!(work_data & WORK_STRUCT_INACTIVE))
1994 pwq_dec_nr_active(pwq);
1995
1996 pwq->nr_in_flight[color]--;
1997
1998 /* is flush in progress and are we at the flushing tip? */
1999 if (likely(pwq->flush_color != color))
2000 goto out_put;
2001
2002 /* are there still in-flight works? */
2003 if (pwq->nr_in_flight[color])
2004 goto out_put;
2005
2006 /* this pwq is done, clear flush_color */
2007 pwq->flush_color = -1;
2008
2009 /*
2010 * If this was the last pwq, wake up the first flusher. It
2011 * will handle the rest.
2012 */
2013 if (atomic_dec_and_test(&pwq->wq->nr_pwqs_to_flush))
2014 complete(&pwq->wq->first_flusher->done);
2015out_put:
2016 put_pwq(pwq);
2017}
2018
2019/**
2020 * try_to_grab_pending - steal work item from worklist and disable irq
2021 * @work: work item to steal
2022 * @cflags: %WORK_CANCEL_ flags
2023 * @irq_flags: place to store irq state
2024 *
2025 * Try to grab PENDING bit of @work. This function can handle @work in any
2026 * stable state - idle, on timer or on worklist.
2027 *
2028 * Return:
2029 *
2030 * ======== ================================================================
2031 * 1 if @work was pending and we successfully stole PENDING
2032 * 0 if @work was idle and we claimed PENDING
2033 * -EAGAIN if PENDING couldn't be grabbed at the moment, safe to busy-retry
2034 * ======== ================================================================
2035 *
2036 * Note:
2037 * On >= 0 return, the caller owns @work's PENDING bit. To avoid getting
2038 * interrupted while holding PENDING and @work off queue, irq must be
2039 * disabled on entry. This, combined with delayed_work->timer being
2040 * irqsafe, ensures that we return -EAGAIN for finite short period of time.
2041 *
2042 * On successful return, >= 0, irq is disabled and the caller is
2043 * responsible for releasing it using local_irq_restore(*@irq_flags).
2044 *
2045 * This function is safe to call from any context including IRQ handler.
2046 */
2047static int try_to_grab_pending(struct work_struct *work, u32 cflags,
2048 unsigned long *irq_flags)
2049{
2050 struct worker_pool *pool;
2051 struct pool_workqueue *pwq;
2052
2053 local_irq_save(*irq_flags);
2054
2055 /* try to steal the timer if it exists */
2056 if (cflags & WORK_CANCEL_DELAYED) {
2057 struct delayed_work *dwork = to_delayed_work(work);
2058
2059 /*
2060 * dwork->timer is irqsafe. If del_timer() fails, it's
2061 * guaranteed that the timer is not queued anywhere and not
2062 * running on the local CPU.
2063 */
2064 if (likely(del_timer(&dwork->timer)))
2065 return 1;
2066 }
2067
2068 /* try to claim PENDING the normal way */
2069 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work)))
2070 return 0;
2071
2072 rcu_read_lock();
2073 /*
2074 * The queueing is in progress, or it is already queued. Try to
2075 * steal it from ->worklist without clearing WORK_STRUCT_PENDING.
2076 */
2077 pool = get_work_pool(work);
2078 if (!pool)
2079 goto fail;
2080
2081 raw_spin_lock(&pool->lock);
2082 /*
2083 * work->data is guaranteed to point to pwq only while the work
2084 * item is queued on pwq->wq, and both updating work->data to point
2085 * to pwq on queueing and to pool on dequeueing are done under
2086 * pwq->pool->lock. This in turn guarantees that, if work->data
2087 * points to pwq which is associated with a locked pool, the work
2088 * item is currently queued on that pool.
2089 */
2090 pwq = get_work_pwq(work);
2091 if (pwq && pwq->pool == pool) {
2092 unsigned long work_data = *work_data_bits(work);
2093
2094 debug_work_deactivate(work);
2095
2096 /*
2097 * A cancelable inactive work item must be in the
2098 * pwq->inactive_works since a queued barrier can't be
2099 * canceled (see the comments in insert_wq_barrier()).
2100 *
2101 * An inactive work item cannot be deleted directly because
2102 * it might have linked barrier work items which, if left
2103 * on the inactive_works list, will confuse pwq->nr_active
2104 * management later on and cause stall. Move the linked
2105 * barrier work items to the worklist when deleting the grabbed
2106 * item. Also keep WORK_STRUCT_INACTIVE in work_data, so that
2107 * it doesn't participate in nr_active management in later
2108 * pwq_dec_nr_in_flight().
2109 */
2110 if (work_data & WORK_STRUCT_INACTIVE)
2111 move_linked_works(work, &pwq->pool->worklist, NULL);
2112
2113 list_del_init(&work->entry);
2114
2115 /*
2116 * work->data points to pwq iff queued. Let's point to pool. As
2117 * this destroys work->data needed by the next step, stash it.
2118 */
2119 set_work_pool_and_keep_pending(work, pool->id,
2120 pool_offq_flags(pool));
2121
2122 /* must be the last step, see the function comment */
2123 pwq_dec_nr_in_flight(pwq, work_data);
2124
2125 raw_spin_unlock(&pool->lock);
2126 rcu_read_unlock();
2127 return 1;
2128 }
2129 raw_spin_unlock(&pool->lock);
2130fail:
2131 rcu_read_unlock();
2132 local_irq_restore(*irq_flags);
2133 return -EAGAIN;
2134}
2135
2136/**
2137 * work_grab_pending - steal work item from worklist and disable irq
2138 * @work: work item to steal
2139 * @cflags: %WORK_CANCEL_ flags
2140 * @irq_flags: place to store IRQ state
2141 *
2142 * Grab PENDING bit of @work. @work can be in any stable state - idle, on timer
2143 * or on worklist.
2144 *
2145 * Can be called from any context. IRQ is disabled on return with IRQ state
2146 * stored in *@irq_flags. The caller is responsible for re-enabling it using
2147 * local_irq_restore().
2148 *
2149 * Returns %true if @work was pending. %false if idle.
2150 */
2151static bool work_grab_pending(struct work_struct *work, u32 cflags,
2152 unsigned long *irq_flags)
2153{
2154 int ret;
2155
2156 while (true) {
2157 ret = try_to_grab_pending(work, cflags, irq_flags);
2158 if (ret >= 0)
2159 return ret;
2160 cpu_relax();
2161 }
2162}
2163
2164/**
2165 * insert_work - insert a work into a pool
2166 * @pwq: pwq @work belongs to
2167 * @work: work to insert
2168 * @head: insertion point
2169 * @extra_flags: extra WORK_STRUCT_* flags to set
2170 *
2171 * Insert @work which belongs to @pwq after @head. @extra_flags is or'd to
2172 * work_struct flags.
2173 *
2174 * CONTEXT:
2175 * raw_spin_lock_irq(pool->lock).
2176 */
2177static void insert_work(struct pool_workqueue *pwq, struct work_struct *work,
2178 struct list_head *head, unsigned int extra_flags)
2179{
2180 debug_work_activate(work);
2181
2182 /* record the work call stack in order to print it in KASAN reports */
2183 kasan_record_aux_stack_noalloc(work);
2184
2185 /* we own @work, set data and link */
2186 set_work_pwq(work, pwq, extra_flags);
2187 list_add_tail(&work->entry, head);
2188 get_pwq(pwq);
2189}
2190
2191/*
2192 * Test whether @work is being queued from another work executing on the
2193 * same workqueue.
2194 */
2195static bool is_chained_work(struct workqueue_struct *wq)
2196{
2197 struct worker *worker;
2198
2199 worker = current_wq_worker();
2200 /*
2201 * Return %true iff I'm a worker executing a work item on @wq. If
2202 * I'm @worker, it's safe to dereference it without locking.
2203 */
2204 return worker && worker->current_pwq->wq == wq;
2205}
2206
2207/*
2208 * When queueing an unbound work item to a wq, prefer local CPU if allowed
2209 * by wq_unbound_cpumask. Otherwise, round robin among the allowed ones to
2210 * avoid perturbing sensitive tasks.
2211 */
2212static int wq_select_unbound_cpu(int cpu)
2213{
2214 int new_cpu;
2215
2216 if (likely(!wq_debug_force_rr_cpu)) {
2217 if (cpumask_test_cpu(cpu, wq_unbound_cpumask))
2218 return cpu;
2219 } else {
2220 pr_warn_once("workqueue: round-robin CPU selection forced, expect performance impact\n");
2221 }
2222
2223 new_cpu = __this_cpu_read(wq_rr_cpu_last);
2224 new_cpu = cpumask_next_and(new_cpu, wq_unbound_cpumask, cpu_online_mask);
2225 if (unlikely(new_cpu >= nr_cpu_ids)) {
2226 new_cpu = cpumask_first_and(wq_unbound_cpumask, cpu_online_mask);
2227 if (unlikely(new_cpu >= nr_cpu_ids))
2228 return cpu;
2229 }
2230 __this_cpu_write(wq_rr_cpu_last, new_cpu);
2231
2232 return new_cpu;
2233}
2234
2235static void __queue_work(int cpu, struct workqueue_struct *wq,
2236 struct work_struct *work)
2237{
2238 struct pool_workqueue *pwq;
2239 struct worker_pool *last_pool, *pool;
2240 unsigned int work_flags;
2241 unsigned int req_cpu = cpu;
2242
2243 /*
2244 * While a work item is PENDING && off queue, a task trying to
2245 * steal the PENDING will busy-loop waiting for it to either get
2246 * queued or lose PENDING. Grabbing PENDING and queueing should
2247 * happen with IRQ disabled.
2248 */
2249 lockdep_assert_irqs_disabled();
2250
2251 /*
2252 * For a draining wq, only works from the same workqueue are
2253 * allowed. The __WQ_DESTROYING helps to spot the issue that
2254 * queues a new work item to a wq after destroy_workqueue(wq).
2255 */
2256 if (unlikely(wq->flags & (__WQ_DESTROYING | __WQ_DRAINING) &&
2257 WARN_ON_ONCE(!is_chained_work(wq))))
2258 return;
2259 rcu_read_lock();
2260retry:
2261 /* pwq which will be used unless @work is executing elsewhere */
2262 if (req_cpu == WORK_CPU_UNBOUND) {
2263 if (wq->flags & WQ_UNBOUND)
2264 cpu = wq_select_unbound_cpu(raw_smp_processor_id());
2265 else
2266 cpu = raw_smp_processor_id();
2267 }
2268
2269 pwq = rcu_dereference(*per_cpu_ptr(wq->cpu_pwq, cpu));
2270 pool = pwq->pool;
2271
2272 /*
2273 * If @work was previously on a different pool, it might still be
2274 * running there, in which case the work needs to be queued on that
2275 * pool to guarantee non-reentrancy.
2276 *
2277 * For ordered workqueue, work items must be queued on the newest pwq
2278 * for accurate order management. Guaranteed order also guarantees
2279 * non-reentrancy. See the comments above unplug_oldest_pwq().
2280 */
2281 last_pool = get_work_pool(work);
2282 if (last_pool && last_pool != pool && !(wq->flags & __WQ_ORDERED)) {
2283 struct worker *worker;
2284
2285 raw_spin_lock(&last_pool->lock);
2286
2287 worker = find_worker_executing_work(last_pool, work);
2288
2289 if (worker && worker->current_pwq->wq == wq) {
2290 pwq = worker->current_pwq;
2291 pool = pwq->pool;
2292 WARN_ON_ONCE(pool != last_pool);
2293 } else {
2294 /* meh... not running there, queue here */
2295 raw_spin_unlock(&last_pool->lock);
2296 raw_spin_lock(&pool->lock);
2297 }
2298 } else {
2299 raw_spin_lock(&pool->lock);
2300 }
2301
2302 /*
2303 * pwq is determined and locked. For unbound pools, we could have raced
2304 * with pwq release and it could already be dead. If its refcnt is zero,
2305 * repeat pwq selection. Note that unbound pwqs never die without
2306 * another pwq replacing it in cpu_pwq or while work items are executing
2307 * on it, so the retrying is guaranteed to make forward-progress.
2308 */
2309 if (unlikely(!pwq->refcnt)) {
2310 if (wq->flags & WQ_UNBOUND) {
2311 raw_spin_unlock(&pool->lock);
2312 cpu_relax();
2313 goto retry;
2314 }
2315 /* oops */
2316 WARN_ONCE(true, "workqueue: per-cpu pwq for %s on cpu%d has 0 refcnt",
2317 wq->name, cpu);
2318 }
2319
2320 /* pwq determined, queue */
2321 trace_workqueue_queue_work(req_cpu, pwq, work);
2322
2323 if (WARN_ON(!list_empty(&work->entry)))
2324 goto out;
2325
2326 pwq->nr_in_flight[pwq->work_color]++;
2327 work_flags = work_color_to_flags(pwq->work_color);
2328
2329 /*
2330 * Limit the number of concurrently active work items to max_active.
2331 * @work must also queue behind existing inactive work items to maintain
2332 * ordering when max_active changes. See wq_adjust_max_active().
2333 */
2334 if (list_empty(&pwq->inactive_works) && pwq_tryinc_nr_active(pwq, false)) {
2335 if (list_empty(&pool->worklist))
2336 pool->watchdog_ts = jiffies;
2337
2338 trace_workqueue_activate_work(work);
2339 insert_work(pwq, work, &pool->worklist, work_flags);
2340 kick_pool(pool);
2341 } else {
2342 work_flags |= WORK_STRUCT_INACTIVE;
2343 insert_work(pwq, work, &pwq->inactive_works, work_flags);
2344 }
2345
2346out:
2347 raw_spin_unlock(&pool->lock);
2348 rcu_read_unlock();
2349}
2350
2351static bool clear_pending_if_disabled(struct work_struct *work)
2352{
2353 unsigned long data = *work_data_bits(work);
2354 struct work_offq_data offqd;
2355
2356 if (likely((data & WORK_STRUCT_PWQ) ||
2357 !(data & WORK_OFFQ_DISABLE_MASK)))
2358 return false;
2359
2360 work_offqd_unpack(&offqd, data);
2361 set_work_pool_and_clear_pending(work, offqd.pool_id,
2362 work_offqd_pack_flags(&offqd));
2363 return true;
2364}
2365
2366/**
2367 * queue_work_on - queue work on specific cpu
2368 * @cpu: CPU number to execute work on
2369 * @wq: workqueue to use
2370 * @work: work to queue
2371 *
2372 * We queue the work to a specific CPU, the caller must ensure it
2373 * can't go away. Callers that fail to ensure that the specified
2374 * CPU cannot go away will execute on a randomly chosen CPU.
2375 * But note well that callers specifying a CPU that never has been
2376 * online will get a splat.
2377 *
2378 * Return: %false if @work was already on a queue, %true otherwise.
2379 */
2380bool queue_work_on(int cpu, struct workqueue_struct *wq,
2381 struct work_struct *work)
2382{
2383 bool ret = false;
2384 unsigned long irq_flags;
2385
2386 local_irq_save(irq_flags);
2387
2388 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work)) &&
2389 !clear_pending_if_disabled(work)) {
2390 __queue_work(cpu, wq, work);
2391 ret = true;
2392 }
2393
2394 local_irq_restore(irq_flags);
2395 return ret;
2396}
2397EXPORT_SYMBOL(queue_work_on);
2398
2399/**
2400 * select_numa_node_cpu - Select a CPU based on NUMA node
2401 * @node: NUMA node ID that we want to select a CPU from
2402 *
2403 * This function will attempt to find a "random" cpu available on a given
2404 * node. If there are no CPUs available on the given node it will return
2405 * WORK_CPU_UNBOUND indicating that we should just schedule to any
2406 * available CPU if we need to schedule this work.
2407 */
2408static int select_numa_node_cpu(int node)
2409{
2410 int cpu;
2411
2412 /* Delay binding to CPU if node is not valid or online */
2413 if (node < 0 || node >= MAX_NUMNODES || !node_online(node))
2414 return WORK_CPU_UNBOUND;
2415
2416 /* Use local node/cpu if we are already there */
2417 cpu = raw_smp_processor_id();
2418 if (node == cpu_to_node(cpu))
2419 return cpu;
2420
2421 /* Use "random" otherwise know as "first" online CPU of node */
2422 cpu = cpumask_any_and(cpumask_of_node(node), cpu_online_mask);
2423
2424 /* If CPU is valid return that, otherwise just defer */
2425 return cpu < nr_cpu_ids ? cpu : WORK_CPU_UNBOUND;
2426}
2427
2428/**
2429 * queue_work_node - queue work on a "random" cpu for a given NUMA node
2430 * @node: NUMA node that we are targeting the work for
2431 * @wq: workqueue to use
2432 * @work: work to queue
2433 *
2434 * We queue the work to a "random" CPU within a given NUMA node. The basic
2435 * idea here is to provide a way to somehow associate work with a given
2436 * NUMA node.
2437 *
2438 * This function will only make a best effort attempt at getting this onto
2439 * the right NUMA node. If no node is requested or the requested node is
2440 * offline then we just fall back to standard queue_work behavior.
2441 *
2442 * Currently the "random" CPU ends up being the first available CPU in the
2443 * intersection of cpu_online_mask and the cpumask of the node, unless we
2444 * are running on the node. In that case we just use the current CPU.
2445 *
2446 * Return: %false if @work was already on a queue, %true otherwise.
2447 */
2448bool queue_work_node(int node, struct workqueue_struct *wq,
2449 struct work_struct *work)
2450{
2451 unsigned long irq_flags;
2452 bool ret = false;
2453
2454 /*
2455 * This current implementation is specific to unbound workqueues.
2456 * Specifically we only return the first available CPU for a given
2457 * node instead of cycling through individual CPUs within the node.
2458 *
2459 * If this is used with a per-cpu workqueue then the logic in
2460 * workqueue_select_cpu_near would need to be updated to allow for
2461 * some round robin type logic.
2462 */
2463 WARN_ON_ONCE(!(wq->flags & WQ_UNBOUND));
2464
2465 local_irq_save(irq_flags);
2466
2467 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work)) &&
2468 !clear_pending_if_disabled(work)) {
2469 int cpu = select_numa_node_cpu(node);
2470
2471 __queue_work(cpu, wq, work);
2472 ret = true;
2473 }
2474
2475 local_irq_restore(irq_flags);
2476 return ret;
2477}
2478EXPORT_SYMBOL_GPL(queue_work_node);
2479
2480void delayed_work_timer_fn(struct timer_list *t)
2481{
2482 struct delayed_work *dwork = from_timer(dwork, t, timer);
2483
2484 /* should have been called from irqsafe timer with irq already off */
2485 __queue_work(dwork->cpu, dwork->wq, &dwork->work);
2486}
2487EXPORT_SYMBOL(delayed_work_timer_fn);
2488
2489static void __queue_delayed_work(int cpu, struct workqueue_struct *wq,
2490 struct delayed_work *dwork, unsigned long delay)
2491{
2492 struct timer_list *timer = &dwork->timer;
2493 struct work_struct *work = &dwork->work;
2494
2495 WARN_ON_ONCE(!wq);
2496 WARN_ON_ONCE(timer->function != delayed_work_timer_fn);
2497 WARN_ON_ONCE(timer_pending(timer));
2498 WARN_ON_ONCE(!list_empty(&work->entry));
2499
2500 /*
2501 * If @delay is 0, queue @dwork->work immediately. This is for
2502 * both optimization and correctness. The earliest @timer can
2503 * expire is on the closest next tick and delayed_work users depend
2504 * on that there's no such delay when @delay is 0.
2505 */
2506 if (!delay) {
2507 __queue_work(cpu, wq, &dwork->work);
2508 return;
2509 }
2510
2511 WARN_ON_ONCE(cpu != WORK_CPU_UNBOUND && !cpu_online(cpu));
2512 dwork->wq = wq;
2513 dwork->cpu = cpu;
2514 timer->expires = jiffies + delay;
2515
2516 if (housekeeping_enabled(HK_TYPE_TIMER)) {
2517 /* If the current cpu is a housekeeping cpu, use it. */
2518 cpu = smp_processor_id();
2519 if (!housekeeping_test_cpu(cpu, HK_TYPE_TIMER))
2520 cpu = housekeeping_any_cpu(HK_TYPE_TIMER);
2521 add_timer_on(timer, cpu);
2522 } else {
2523 if (likely(cpu == WORK_CPU_UNBOUND))
2524 add_timer_global(timer);
2525 else
2526 add_timer_on(timer, cpu);
2527 }
2528}
2529
2530/**
2531 * queue_delayed_work_on - queue work on specific CPU after delay
2532 * @cpu: CPU number to execute work on
2533 * @wq: workqueue to use
2534 * @dwork: work to queue
2535 * @delay: number of jiffies to wait before queueing
2536 *
2537 * We queue the delayed_work to a specific CPU, for non-zero delays the
2538 * caller must ensure it is online and can't go away. Callers that fail
2539 * to ensure this, may get @dwork->timer queued to an offlined CPU and
2540 * this will prevent queueing of @dwork->work unless the offlined CPU
2541 * becomes online again.
2542 *
2543 * Return: %false if @work was already on a queue, %true otherwise. If
2544 * @delay is zero and @dwork is idle, it will be scheduled for immediate
2545 * execution.
2546 */
2547bool queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
2548 struct delayed_work *dwork, unsigned long delay)
2549{
2550 struct work_struct *work = &dwork->work;
2551 bool ret = false;
2552 unsigned long irq_flags;
2553
2554 /* read the comment in __queue_work() */
2555 local_irq_save(irq_flags);
2556
2557 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work)) &&
2558 !clear_pending_if_disabled(work)) {
2559 __queue_delayed_work(cpu, wq, dwork, delay);
2560 ret = true;
2561 }
2562
2563 local_irq_restore(irq_flags);
2564 return ret;
2565}
2566EXPORT_SYMBOL(queue_delayed_work_on);
2567
2568/**
2569 * mod_delayed_work_on - modify delay of or queue a delayed work on specific CPU
2570 * @cpu: CPU number to execute work on
2571 * @wq: workqueue to use
2572 * @dwork: work to queue
2573 * @delay: number of jiffies to wait before queueing
2574 *
2575 * If @dwork is idle, equivalent to queue_delayed_work_on(); otherwise,
2576 * modify @dwork's timer so that it expires after @delay. If @delay is
2577 * zero, @work is guaranteed to be scheduled immediately regardless of its
2578 * current state.
2579 *
2580 * Return: %false if @dwork was idle and queued, %true if @dwork was
2581 * pending and its timer was modified.
2582 *
2583 * This function is safe to call from any context including IRQ handler.
2584 * See try_to_grab_pending() for details.
2585 */
2586bool mod_delayed_work_on(int cpu, struct workqueue_struct *wq,
2587 struct delayed_work *dwork, unsigned long delay)
2588{
2589 unsigned long irq_flags;
2590 bool ret;
2591
2592 ret = work_grab_pending(&dwork->work, WORK_CANCEL_DELAYED, &irq_flags);
2593
2594 if (!clear_pending_if_disabled(&dwork->work))
2595 __queue_delayed_work(cpu, wq, dwork, delay);
2596
2597 local_irq_restore(irq_flags);
2598 return ret;
2599}
2600EXPORT_SYMBOL_GPL(mod_delayed_work_on);
2601
2602static void rcu_work_rcufn(struct rcu_head *rcu)
2603{
2604 struct rcu_work *rwork = container_of(rcu, struct rcu_work, rcu);
2605
2606 /* read the comment in __queue_work() */
2607 local_irq_disable();
2608 __queue_work(WORK_CPU_UNBOUND, rwork->wq, &rwork->work);
2609 local_irq_enable();
2610}
2611
2612/**
2613 * queue_rcu_work - queue work after a RCU grace period
2614 * @wq: workqueue to use
2615 * @rwork: work to queue
2616 *
2617 * Return: %false if @rwork was already pending, %true otherwise. Note
2618 * that a full RCU grace period is guaranteed only after a %true return.
2619 * While @rwork is guaranteed to be executed after a %false return, the
2620 * execution may happen before a full RCU grace period has passed.
2621 */
2622bool queue_rcu_work(struct workqueue_struct *wq, struct rcu_work *rwork)
2623{
2624 struct work_struct *work = &rwork->work;
2625
2626 /*
2627 * rcu_work can't be canceled or disabled. Warn if the user reached
2628 * inside @rwork and disabled the inner work.
2629 */
2630 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work)) &&
2631 !WARN_ON_ONCE(clear_pending_if_disabled(work))) {
2632 rwork->wq = wq;
2633 call_rcu_hurry(&rwork->rcu, rcu_work_rcufn);
2634 return true;
2635 }
2636
2637 return false;
2638}
2639EXPORT_SYMBOL(queue_rcu_work);
2640
2641static struct worker *alloc_worker(int node)
2642{
2643 struct worker *worker;
2644
2645 worker = kzalloc_node(sizeof(*worker), GFP_KERNEL, node);
2646 if (worker) {
2647 INIT_LIST_HEAD(&worker->entry);
2648 INIT_LIST_HEAD(&worker->scheduled);
2649 INIT_LIST_HEAD(&worker->node);
2650 /* on creation a worker is in !idle && prep state */
2651 worker->flags = WORKER_PREP;
2652 }
2653 return worker;
2654}
2655
2656static cpumask_t *pool_allowed_cpus(struct worker_pool *pool)
2657{
2658 if (pool->cpu < 0 && pool->attrs->affn_strict)
2659 return pool->attrs->__pod_cpumask;
2660 else
2661 return pool->attrs->cpumask;
2662}
2663
2664/**
2665 * worker_attach_to_pool() - attach a worker to a pool
2666 * @worker: worker to be attached
2667 * @pool: the target pool
2668 *
2669 * Attach @worker to @pool. Once attached, the %WORKER_UNBOUND flag and
2670 * cpu-binding of @worker are kept coordinated with the pool across
2671 * cpu-[un]hotplugs.
2672 */
2673static void worker_attach_to_pool(struct worker *worker,
2674 struct worker_pool *pool)
2675{
2676 mutex_lock(&wq_pool_attach_mutex);
2677
2678 /*
2679 * The wq_pool_attach_mutex ensures %POOL_DISASSOCIATED remains stable
2680 * across this function. See the comments above the flag definition for
2681 * details. BH workers are, while per-CPU, always DISASSOCIATED.
2682 */
2683 if (pool->flags & POOL_DISASSOCIATED) {
2684 worker->flags |= WORKER_UNBOUND;
2685 } else {
2686 WARN_ON_ONCE(pool->flags & POOL_BH);
2687 kthread_set_per_cpu(worker->task, pool->cpu);
2688 }
2689
2690 if (worker->rescue_wq)
2691 set_cpus_allowed_ptr(worker->task, pool_allowed_cpus(pool));
2692
2693 list_add_tail(&worker->node, &pool->workers);
2694 worker->pool = pool;
2695
2696 mutex_unlock(&wq_pool_attach_mutex);
2697}
2698
2699static void unbind_worker(struct worker *worker)
2700{
2701 lockdep_assert_held(&wq_pool_attach_mutex);
2702
2703 kthread_set_per_cpu(worker->task, -1);
2704 if (cpumask_intersects(wq_unbound_cpumask, cpu_active_mask))
2705 WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task, wq_unbound_cpumask) < 0);
2706 else
2707 WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task, cpu_possible_mask) < 0);
2708}
2709
2710
2711static void detach_worker(struct worker *worker)
2712{
2713 lockdep_assert_held(&wq_pool_attach_mutex);
2714
2715 unbind_worker(worker);
2716 list_del(&worker->node);
2717}
2718
2719/**
2720 * worker_detach_from_pool() - detach a worker from its pool
2721 * @worker: worker which is attached to its pool
2722 *
2723 * Undo the attaching which had been done in worker_attach_to_pool(). The
2724 * caller worker shouldn't access to the pool after detached except it has
2725 * other reference to the pool.
2726 */
2727static void worker_detach_from_pool(struct worker *worker)
2728{
2729 struct worker_pool *pool = worker->pool;
2730
2731 /* there is one permanent BH worker per CPU which should never detach */
2732 WARN_ON_ONCE(pool->flags & POOL_BH);
2733
2734 mutex_lock(&wq_pool_attach_mutex);
2735 detach_worker(worker);
2736 worker->pool = NULL;
2737 mutex_unlock(&wq_pool_attach_mutex);
2738
2739 /* clear leftover flags without pool->lock after it is detached */
2740 worker->flags &= ~(WORKER_UNBOUND | WORKER_REBOUND);
2741}
2742
2743static int format_worker_id(char *buf, size_t size, struct worker *worker,
2744 struct worker_pool *pool)
2745{
2746 if (worker->rescue_wq)
2747 return scnprintf(buf, size, "kworker/R-%s",
2748 worker->rescue_wq->name);
2749
2750 if (pool) {
2751 if (pool->cpu >= 0)
2752 return scnprintf(buf, size, "kworker/%d:%d%s",
2753 pool->cpu, worker->id,
2754 pool->attrs->nice < 0 ? "H" : "");
2755 else
2756 return scnprintf(buf, size, "kworker/u%d:%d",
2757 pool->id, worker->id);
2758 } else {
2759 return scnprintf(buf, size, "kworker/dying");
2760 }
2761}
2762
2763/**
2764 * create_worker - create a new workqueue worker
2765 * @pool: pool the new worker will belong to
2766 *
2767 * Create and start a new worker which is attached to @pool.
2768 *
2769 * CONTEXT:
2770 * Might sleep. Does GFP_KERNEL allocations.
2771 *
2772 * Return:
2773 * Pointer to the newly created worker.
2774 */
2775static struct worker *create_worker(struct worker_pool *pool)
2776{
2777 struct worker *worker;
2778 int id;
2779
2780 /* ID is needed to determine kthread name */
2781 id = ida_alloc(&pool->worker_ida, GFP_KERNEL);
2782 if (id < 0) {
2783 pr_err_once("workqueue: Failed to allocate a worker ID: %pe\n",
2784 ERR_PTR(id));
2785 return NULL;
2786 }
2787
2788 worker = alloc_worker(pool->node);
2789 if (!worker) {
2790 pr_err_once("workqueue: Failed to allocate a worker\n");
2791 goto fail;
2792 }
2793
2794 worker->id = id;
2795
2796 if (!(pool->flags & POOL_BH)) {
2797 char id_buf[WORKER_ID_LEN];
2798
2799 format_worker_id(id_buf, sizeof(id_buf), worker, pool);
2800 worker->task = kthread_create_on_node(worker_thread, worker,
2801 pool->node, "%s", id_buf);
2802 if (IS_ERR(worker->task)) {
2803 if (PTR_ERR(worker->task) == -EINTR) {
2804 pr_err("workqueue: Interrupted when creating a worker thread \"%s\"\n",
2805 id_buf);
2806 } else {
2807 pr_err_once("workqueue: Failed to create a worker thread: %pe",
2808 worker->task);
2809 }
2810 goto fail;
2811 }
2812
2813 set_user_nice(worker->task, pool->attrs->nice);
2814 kthread_bind_mask(worker->task, pool_allowed_cpus(pool));
2815 }
2816
2817 /* successful, attach the worker to the pool */
2818 worker_attach_to_pool(worker, pool);
2819
2820 /* start the newly created worker */
2821 raw_spin_lock_irq(&pool->lock);
2822
2823 worker->pool->nr_workers++;
2824 worker_enter_idle(worker);
2825
2826 /*
2827 * @worker is waiting on a completion in kthread() and will trigger hung
2828 * check if not woken up soon. As kick_pool() is noop if @pool is empty,
2829 * wake it up explicitly.
2830 */
2831 if (worker->task)
2832 wake_up_process(worker->task);
2833
2834 raw_spin_unlock_irq(&pool->lock);
2835
2836 return worker;
2837
2838fail:
2839 ida_free(&pool->worker_ida, id);
2840 kfree(worker);
2841 return NULL;
2842}
2843
2844static void detach_dying_workers(struct list_head *cull_list)
2845{
2846 struct worker *worker;
2847
2848 list_for_each_entry(worker, cull_list, entry)
2849 detach_worker(worker);
2850}
2851
2852static void reap_dying_workers(struct list_head *cull_list)
2853{
2854 struct worker *worker, *tmp;
2855
2856 list_for_each_entry_safe(worker, tmp, cull_list, entry) {
2857 list_del_init(&worker->entry);
2858 kthread_stop_put(worker->task);
2859 kfree(worker);
2860 }
2861}
2862
2863/**
2864 * set_worker_dying - Tag a worker for destruction
2865 * @worker: worker to be destroyed
2866 * @list: transfer worker away from its pool->idle_list and into list
2867 *
2868 * Tag @worker for destruction and adjust @pool stats accordingly. The worker
2869 * should be idle.
2870 *
2871 * CONTEXT:
2872 * raw_spin_lock_irq(pool->lock).
2873 */
2874static void set_worker_dying(struct worker *worker, struct list_head *list)
2875{
2876 struct worker_pool *pool = worker->pool;
2877
2878 lockdep_assert_held(&pool->lock);
2879 lockdep_assert_held(&wq_pool_attach_mutex);
2880
2881 /* sanity check frenzy */
2882 if (WARN_ON(worker->current_work) ||
2883 WARN_ON(!list_empty(&worker->scheduled)) ||
2884 WARN_ON(!(worker->flags & WORKER_IDLE)))
2885 return;
2886
2887 pool->nr_workers--;
2888 pool->nr_idle--;
2889
2890 worker->flags |= WORKER_DIE;
2891
2892 list_move(&worker->entry, list);
2893
2894 /* get an extra task struct reference for later kthread_stop_put() */
2895 get_task_struct(worker->task);
2896}
2897
2898/**
2899 * idle_worker_timeout - check if some idle workers can now be deleted.
2900 * @t: The pool's idle_timer that just expired
2901 *
2902 * The timer is armed in worker_enter_idle(). Note that it isn't disarmed in
2903 * worker_leave_idle(), as a worker flicking between idle and active while its
2904 * pool is at the too_many_workers() tipping point would cause too much timer
2905 * housekeeping overhead. Since IDLE_WORKER_TIMEOUT is long enough, we just let
2906 * it expire and re-evaluate things from there.
2907 */
2908static void idle_worker_timeout(struct timer_list *t)
2909{
2910 struct worker_pool *pool = from_timer(pool, t, idle_timer);
2911 bool do_cull = false;
2912
2913 if (work_pending(&pool->idle_cull_work))
2914 return;
2915
2916 raw_spin_lock_irq(&pool->lock);
2917
2918 if (too_many_workers(pool)) {
2919 struct worker *worker;
2920 unsigned long expires;
2921
2922 /* idle_list is kept in LIFO order, check the last one */
2923 worker = list_last_entry(&pool->idle_list, struct worker, entry);
2924 expires = worker->last_active + IDLE_WORKER_TIMEOUT;
2925 do_cull = !time_before(jiffies, expires);
2926
2927 if (!do_cull)
2928 mod_timer(&pool->idle_timer, expires);
2929 }
2930 raw_spin_unlock_irq(&pool->lock);
2931
2932 if (do_cull)
2933 queue_work(system_unbound_wq, &pool->idle_cull_work);
2934}
2935
2936/**
2937 * idle_cull_fn - cull workers that have been idle for too long.
2938 * @work: the pool's work for handling these idle workers
2939 *
2940 * This goes through a pool's idle workers and gets rid of those that have been
2941 * idle for at least IDLE_WORKER_TIMEOUT seconds.
2942 *
2943 * We don't want to disturb isolated CPUs because of a pcpu kworker being
2944 * culled, so this also resets worker affinity. This requires a sleepable
2945 * context, hence the split between timer callback and work item.
2946 */
2947static void idle_cull_fn(struct work_struct *work)
2948{
2949 struct worker_pool *pool = container_of(work, struct worker_pool, idle_cull_work);
2950 LIST_HEAD(cull_list);
2951
2952 /*
2953 * Grabbing wq_pool_attach_mutex here ensures an already-running worker
2954 * cannot proceed beyong set_pf_worker() in its self-destruct path.
2955 * This is required as a previously-preempted worker could run after
2956 * set_worker_dying() has happened but before detach_dying_workers() did.
2957 */
2958 mutex_lock(&wq_pool_attach_mutex);
2959 raw_spin_lock_irq(&pool->lock);
2960
2961 while (too_many_workers(pool)) {
2962 struct worker *worker;
2963 unsigned long expires;
2964
2965 worker = list_last_entry(&pool->idle_list, struct worker, entry);
2966 expires = worker->last_active + IDLE_WORKER_TIMEOUT;
2967
2968 if (time_before(jiffies, expires)) {
2969 mod_timer(&pool->idle_timer, expires);
2970 break;
2971 }
2972
2973 set_worker_dying(worker, &cull_list);
2974 }
2975
2976 raw_spin_unlock_irq(&pool->lock);
2977 detach_dying_workers(&cull_list);
2978 mutex_unlock(&wq_pool_attach_mutex);
2979
2980 reap_dying_workers(&cull_list);
2981}
2982
2983static void send_mayday(struct work_struct *work)
2984{
2985 struct pool_workqueue *pwq = get_work_pwq(work);
2986 struct workqueue_struct *wq = pwq->wq;
2987
2988 lockdep_assert_held(&wq_mayday_lock);
2989
2990 if (!wq->rescuer)
2991 return;
2992
2993 /* mayday mayday mayday */
2994 if (list_empty(&pwq->mayday_node)) {
2995 /*
2996 * If @pwq is for an unbound wq, its base ref may be put at
2997 * any time due to an attribute change. Pin @pwq until the
2998 * rescuer is done with it.
2999 */
3000 get_pwq(pwq);
3001 list_add_tail(&pwq->mayday_node, &wq->maydays);
3002 wake_up_process(wq->rescuer->task);
3003 pwq->stats[PWQ_STAT_MAYDAY]++;
3004 }
3005}
3006
3007static void pool_mayday_timeout(struct timer_list *t)
3008{
3009 struct worker_pool *pool = from_timer(pool, t, mayday_timer);
3010 struct work_struct *work;
3011
3012 raw_spin_lock_irq(&pool->lock);
3013 raw_spin_lock(&wq_mayday_lock); /* for wq->maydays */
3014
3015 if (need_to_create_worker(pool)) {
3016 /*
3017 * We've been trying to create a new worker but
3018 * haven't been successful. We might be hitting an
3019 * allocation deadlock. Send distress signals to
3020 * rescuers.
3021 */
3022 list_for_each_entry(work, &pool->worklist, entry)
3023 send_mayday(work);
3024 }
3025
3026 raw_spin_unlock(&wq_mayday_lock);
3027 raw_spin_unlock_irq(&pool->lock);
3028
3029 mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INTERVAL);
3030}
3031
3032/**
3033 * maybe_create_worker - create a new worker if necessary
3034 * @pool: pool to create a new worker for
3035 *
3036 * Create a new worker for @pool if necessary. @pool is guaranteed to
3037 * have at least one idle worker on return from this function. If
3038 * creating a new worker takes longer than MAYDAY_INTERVAL, mayday is
3039 * sent to all rescuers with works scheduled on @pool to resolve
3040 * possible allocation deadlock.
3041 *
3042 * On return, need_to_create_worker() is guaranteed to be %false and
3043 * may_start_working() %true.
3044 *
3045 * LOCKING:
3046 * raw_spin_lock_irq(pool->lock) which may be released and regrabbed
3047 * multiple times. Does GFP_KERNEL allocations. Called only from
3048 * manager.
3049 */
3050static void maybe_create_worker(struct worker_pool *pool)
3051__releases(&pool->lock)
3052__acquires(&pool->lock)
3053{
3054restart:
3055 raw_spin_unlock_irq(&pool->lock);
3056
3057 /* if we don't make progress in MAYDAY_INITIAL_TIMEOUT, call for help */
3058 mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INITIAL_TIMEOUT);
3059
3060 while (true) {
3061 if (create_worker(pool) || !need_to_create_worker(pool))
3062 break;
3063
3064 schedule_timeout_interruptible(CREATE_COOLDOWN);
3065
3066 if (!need_to_create_worker(pool))
3067 break;
3068 }
3069
3070 del_timer_sync(&pool->mayday_timer);
3071 raw_spin_lock_irq(&pool->lock);
3072 /*
3073 * This is necessary even after a new worker was just successfully
3074 * created as @pool->lock was dropped and the new worker might have
3075 * already become busy.
3076 */
3077 if (need_to_create_worker(pool))
3078 goto restart;
3079}
3080
3081/**
3082 * manage_workers - manage worker pool
3083 * @worker: self
3084 *
3085 * Assume the manager role and manage the worker pool @worker belongs
3086 * to. At any given time, there can be only zero or one manager per
3087 * pool. The exclusion is handled automatically by this function.
3088 *
3089 * The caller can safely start processing works on false return. On
3090 * true return, it's guaranteed that need_to_create_worker() is false
3091 * and may_start_working() is true.
3092 *
3093 * CONTEXT:
3094 * raw_spin_lock_irq(pool->lock) which may be released and regrabbed
3095 * multiple times. Does GFP_KERNEL allocations.
3096 *
3097 * Return:
3098 * %false if the pool doesn't need management and the caller can safely
3099 * start processing works, %true if management function was performed and
3100 * the conditions that the caller verified before calling the function may
3101 * no longer be true.
3102 */
3103static bool manage_workers(struct worker *worker)
3104{
3105 struct worker_pool *pool = worker->pool;
3106
3107 if (pool->flags & POOL_MANAGER_ACTIVE)
3108 return false;
3109
3110 pool->flags |= POOL_MANAGER_ACTIVE;
3111 pool->manager = worker;
3112
3113 maybe_create_worker(pool);
3114
3115 pool->manager = NULL;
3116 pool->flags &= ~POOL_MANAGER_ACTIVE;
3117 rcuwait_wake_up(&manager_wait);
3118 return true;
3119}
3120
3121/**
3122 * process_one_work - process single work
3123 * @worker: self
3124 * @work: work to process
3125 *
3126 * Process @work. This function contains all the logics necessary to
3127 * process a single work including synchronization against and
3128 * interaction with other workers on the same cpu, queueing and
3129 * flushing. As long as context requirement is met, any worker can
3130 * call this function to process a work.
3131 *
3132 * CONTEXT:
3133 * raw_spin_lock_irq(pool->lock) which is released and regrabbed.
3134 */
3135static void process_one_work(struct worker *worker, struct work_struct *work)
3136__releases(&pool->lock)
3137__acquires(&pool->lock)
3138{
3139 struct pool_workqueue *pwq = get_work_pwq(work);
3140 struct worker_pool *pool = worker->pool;
3141 unsigned long work_data;
3142 int lockdep_start_depth, rcu_start_depth;
3143 bool bh_draining = pool->flags & POOL_BH_DRAINING;
3144#ifdef CONFIG_LOCKDEP
3145 /*
3146 * It is permissible to free the struct work_struct from
3147 * inside the function that is called from it, this we need to
3148 * take into account for lockdep too. To avoid bogus "held
3149 * lock freed" warnings as well as problems when looking into
3150 * work->lockdep_map, make a copy and use that here.
3151 */
3152 struct lockdep_map lockdep_map;
3153
3154 lockdep_copy_map(&lockdep_map, &work->lockdep_map);
3155#endif
3156 /* ensure we're on the correct CPU */
3157 WARN_ON_ONCE(!(pool->flags & POOL_DISASSOCIATED) &&
3158 raw_smp_processor_id() != pool->cpu);
3159
3160 /* claim and dequeue */
3161 debug_work_deactivate(work);
3162 hash_add(pool->busy_hash, &worker->hentry, (unsigned long)work);
3163 worker->current_work = work;
3164 worker->current_func = work->func;
3165 worker->current_pwq = pwq;
3166 if (worker->task)
3167 worker->current_at = worker->task->se.sum_exec_runtime;
3168 work_data = *work_data_bits(work);
3169 worker->current_color = get_work_color(work_data);
3170
3171 /*
3172 * Record wq name for cmdline and debug reporting, may get
3173 * overridden through set_worker_desc().
3174 */
3175 strscpy(worker->desc, pwq->wq->name, WORKER_DESC_LEN);
3176
3177 list_del_init(&work->entry);
3178
3179 /*
3180 * CPU intensive works don't participate in concurrency management.
3181 * They're the scheduler's responsibility. This takes @worker out
3182 * of concurrency management and the next code block will chain
3183 * execution of the pending work items.
3184 */
3185 if (unlikely(pwq->wq->flags & WQ_CPU_INTENSIVE))
3186 worker_set_flags(worker, WORKER_CPU_INTENSIVE);
3187
3188 /*
3189 * Kick @pool if necessary. It's always noop for per-cpu worker pools
3190 * since nr_running would always be >= 1 at this point. This is used to
3191 * chain execution of the pending work items for WORKER_NOT_RUNNING
3192 * workers such as the UNBOUND and CPU_INTENSIVE ones.
3193 */
3194 kick_pool(pool);
3195
3196 /*
3197 * Record the last pool and clear PENDING which should be the last
3198 * update to @work. Also, do this inside @pool->lock so that
3199 * PENDING and queued state changes happen together while IRQ is
3200 * disabled.
3201 */
3202 set_work_pool_and_clear_pending(work, pool->id, pool_offq_flags(pool));
3203
3204 pwq->stats[PWQ_STAT_STARTED]++;
3205 raw_spin_unlock_irq(&pool->lock);
3206
3207 rcu_start_depth = rcu_preempt_depth();
3208 lockdep_start_depth = lockdep_depth(current);
3209 /* see drain_dead_softirq_workfn() */
3210 if (!bh_draining)
3211 lock_map_acquire(pwq->wq->lockdep_map);
3212 lock_map_acquire(&lockdep_map);
3213 /*
3214 * Strictly speaking we should mark the invariant state without holding
3215 * any locks, that is, before these two lock_map_acquire()'s.
3216 *
3217 * However, that would result in:
3218 *
3219 * A(W1)
3220 * WFC(C)
3221 * A(W1)
3222 * C(C)
3223 *
3224 * Which would create W1->C->W1 dependencies, even though there is no
3225 * actual deadlock possible. There are two solutions, using a
3226 * read-recursive acquire on the work(queue) 'locks', but this will then
3227 * hit the lockdep limitation on recursive locks, or simply discard
3228 * these locks.
3229 *
3230 * AFAICT there is no possible deadlock scenario between the
3231 * flush_work() and complete() primitives (except for single-threaded
3232 * workqueues), so hiding them isn't a problem.
3233 */
3234 lockdep_invariant_state(true);
3235 trace_workqueue_execute_start(work);
3236 worker->current_func(work);
3237 /*
3238 * While we must be careful to not use "work" after this, the trace
3239 * point will only record its address.
3240 */
3241 trace_workqueue_execute_end(work, worker->current_func);
3242 pwq->stats[PWQ_STAT_COMPLETED]++;
3243 lock_map_release(&lockdep_map);
3244 if (!bh_draining)
3245 lock_map_release(pwq->wq->lockdep_map);
3246
3247 if (unlikely((worker->task && in_atomic()) ||
3248 lockdep_depth(current) != lockdep_start_depth ||
3249 rcu_preempt_depth() != rcu_start_depth)) {
3250 pr_err("BUG: workqueue leaked atomic, lock or RCU: %s[%d]\n"
3251 " preempt=0x%08x lock=%d->%d RCU=%d->%d workfn=%ps\n",
3252 current->comm, task_pid_nr(current), preempt_count(),
3253 lockdep_start_depth, lockdep_depth(current),
3254 rcu_start_depth, rcu_preempt_depth(),
3255 worker->current_func);
3256 debug_show_held_locks(current);
3257 dump_stack();
3258 }
3259
3260 /*
3261 * The following prevents a kworker from hogging CPU on !PREEMPTION
3262 * kernels, where a requeueing work item waiting for something to
3263 * happen could deadlock with stop_machine as such work item could
3264 * indefinitely requeue itself while all other CPUs are trapped in
3265 * stop_machine. At the same time, report a quiescent RCU state so
3266 * the same condition doesn't freeze RCU.
3267 */
3268 if (worker->task)
3269 cond_resched();
3270
3271 raw_spin_lock_irq(&pool->lock);
3272
3273 /*
3274 * In addition to %WQ_CPU_INTENSIVE, @worker may also have been marked
3275 * CPU intensive by wq_worker_tick() if @work hogged CPU longer than
3276 * wq_cpu_intensive_thresh_us. Clear it.
3277 */
3278 worker_clr_flags(worker, WORKER_CPU_INTENSIVE);
3279
3280 /* tag the worker for identification in schedule() */
3281 worker->last_func = worker->current_func;
3282
3283 /* we're done with it, release */
3284 hash_del(&worker->hentry);
3285 worker->current_work = NULL;
3286 worker->current_func = NULL;
3287 worker->current_pwq = NULL;
3288 worker->current_color = INT_MAX;
3289
3290 /* must be the last step, see the function comment */
3291 pwq_dec_nr_in_flight(pwq, work_data);
3292}
3293
3294/**
3295 * process_scheduled_works - process scheduled works
3296 * @worker: self
3297 *
3298 * Process all scheduled works. Please note that the scheduled list
3299 * may change while processing a work, so this function repeatedly
3300 * fetches a work from the top and executes it.
3301 *
3302 * CONTEXT:
3303 * raw_spin_lock_irq(pool->lock) which may be released and regrabbed
3304 * multiple times.
3305 */
3306static void process_scheduled_works(struct worker *worker)
3307{
3308 struct work_struct *work;
3309 bool first = true;
3310
3311 while ((work = list_first_entry_or_null(&worker->scheduled,
3312 struct work_struct, entry))) {
3313 if (first) {
3314 worker->pool->watchdog_ts = jiffies;
3315 first = false;
3316 }
3317 process_one_work(worker, work);
3318 }
3319}
3320
3321static void set_pf_worker(bool val)
3322{
3323 mutex_lock(&wq_pool_attach_mutex);
3324 if (val)
3325 current->flags |= PF_WQ_WORKER;
3326 else
3327 current->flags &= ~PF_WQ_WORKER;
3328 mutex_unlock(&wq_pool_attach_mutex);
3329}
3330
3331/**
3332 * worker_thread - the worker thread function
3333 * @__worker: self
3334 *
3335 * The worker thread function. All workers belong to a worker_pool -
3336 * either a per-cpu one or dynamic unbound one. These workers process all
3337 * work items regardless of their specific target workqueue. The only
3338 * exception is work items which belong to workqueues with a rescuer which
3339 * will be explained in rescuer_thread().
3340 *
3341 * Return: 0
3342 */
3343static int worker_thread(void *__worker)
3344{
3345 struct worker *worker = __worker;
3346 struct worker_pool *pool = worker->pool;
3347
3348 /* tell the scheduler that this is a workqueue worker */
3349 set_pf_worker(true);
3350woke_up:
3351 raw_spin_lock_irq(&pool->lock);
3352
3353 /* am I supposed to die? */
3354 if (unlikely(worker->flags & WORKER_DIE)) {
3355 raw_spin_unlock_irq(&pool->lock);
3356 set_pf_worker(false);
3357 /*
3358 * The worker is dead and PF_WQ_WORKER is cleared, worker->pool
3359 * shouldn't be accessed, reset it to NULL in case otherwise.
3360 */
3361 worker->pool = NULL;
3362 ida_free(&pool->worker_ida, worker->id);
3363 return 0;
3364 }
3365
3366 worker_leave_idle(worker);
3367recheck:
3368 /* no more worker necessary? */
3369 if (!need_more_worker(pool))
3370 goto sleep;
3371
3372 /* do we need to manage? */
3373 if (unlikely(!may_start_working(pool)) && manage_workers(worker))
3374 goto recheck;
3375
3376 /*
3377 * ->scheduled list can only be filled while a worker is
3378 * preparing to process a work or actually processing it.
3379 * Make sure nobody diddled with it while I was sleeping.
3380 */
3381 WARN_ON_ONCE(!list_empty(&worker->scheduled));
3382
3383 /*
3384 * Finish PREP stage. We're guaranteed to have at least one idle
3385 * worker or that someone else has already assumed the manager
3386 * role. This is where @worker starts participating in concurrency
3387 * management if applicable and concurrency management is restored
3388 * after being rebound. See rebind_workers() for details.
3389 */
3390 worker_clr_flags(worker, WORKER_PREP | WORKER_REBOUND);
3391
3392 do {
3393 struct work_struct *work =
3394 list_first_entry(&pool->worklist,
3395 struct work_struct, entry);
3396
3397 if (assign_work(work, worker, NULL))
3398 process_scheduled_works(worker);
3399 } while (keep_working(pool));
3400
3401 worker_set_flags(worker, WORKER_PREP);
3402sleep:
3403 /*
3404 * pool->lock is held and there's no work to process and no need to
3405 * manage, sleep. Workers are woken up only while holding
3406 * pool->lock or from local cpu, so setting the current state
3407 * before releasing pool->lock is enough to prevent losing any
3408 * event.
3409 */
3410 worker_enter_idle(worker);
3411 __set_current_state(TASK_IDLE);
3412 raw_spin_unlock_irq(&pool->lock);
3413 schedule();
3414 goto woke_up;
3415}
3416
3417/**
3418 * rescuer_thread - the rescuer thread function
3419 * @__rescuer: self
3420 *
3421 * Workqueue rescuer thread function. There's one rescuer for each
3422 * workqueue which has WQ_MEM_RECLAIM set.
3423 *
3424 * Regular work processing on a pool may block trying to create a new
3425 * worker which uses GFP_KERNEL allocation which has slight chance of
3426 * developing into deadlock if some works currently on the same queue
3427 * need to be processed to satisfy the GFP_KERNEL allocation. This is
3428 * the problem rescuer solves.
3429 *
3430 * When such condition is possible, the pool summons rescuers of all
3431 * workqueues which have works queued on the pool and let them process
3432 * those works so that forward progress can be guaranteed.
3433 *
3434 * This should happen rarely.
3435 *
3436 * Return: 0
3437 */
3438static int rescuer_thread(void *__rescuer)
3439{
3440 struct worker *rescuer = __rescuer;
3441 struct workqueue_struct *wq = rescuer->rescue_wq;
3442 bool should_stop;
3443
3444 set_user_nice(current, RESCUER_NICE_LEVEL);
3445
3446 /*
3447 * Mark rescuer as worker too. As WORKER_PREP is never cleared, it
3448 * doesn't participate in concurrency management.
3449 */
3450 set_pf_worker(true);
3451repeat:
3452 set_current_state(TASK_IDLE);
3453
3454 /*
3455 * By the time the rescuer is requested to stop, the workqueue
3456 * shouldn't have any work pending, but @wq->maydays may still have
3457 * pwq(s) queued. This can happen by non-rescuer workers consuming
3458 * all the work items before the rescuer got to them. Go through
3459 * @wq->maydays processing before acting on should_stop so that the
3460 * list is always empty on exit.
3461 */
3462 should_stop = kthread_should_stop();
3463
3464 /* see whether any pwq is asking for help */
3465 raw_spin_lock_irq(&wq_mayday_lock);
3466
3467 while (!list_empty(&wq->maydays)) {
3468 struct pool_workqueue *pwq = list_first_entry(&wq->maydays,
3469 struct pool_workqueue, mayday_node);
3470 struct worker_pool *pool = pwq->pool;
3471 struct work_struct *work, *n;
3472
3473 __set_current_state(TASK_RUNNING);
3474 list_del_init(&pwq->mayday_node);
3475
3476 raw_spin_unlock_irq(&wq_mayday_lock);
3477
3478 worker_attach_to_pool(rescuer, pool);
3479
3480 raw_spin_lock_irq(&pool->lock);
3481
3482 /*
3483 * Slurp in all works issued via this workqueue and
3484 * process'em.
3485 */
3486 WARN_ON_ONCE(!list_empty(&rescuer->scheduled));
3487 list_for_each_entry_safe(work, n, &pool->worklist, entry) {
3488 if (get_work_pwq(work) == pwq &&
3489 assign_work(work, rescuer, &n))
3490 pwq->stats[PWQ_STAT_RESCUED]++;
3491 }
3492
3493 if (!list_empty(&rescuer->scheduled)) {
3494 process_scheduled_works(rescuer);
3495
3496 /*
3497 * The above execution of rescued work items could
3498 * have created more to rescue through
3499 * pwq_activate_first_inactive() or chained
3500 * queueing. Let's put @pwq back on mayday list so
3501 * that such back-to-back work items, which may be
3502 * being used to relieve memory pressure, don't
3503 * incur MAYDAY_INTERVAL delay inbetween.
3504 */
3505 if (pwq->nr_active && need_to_create_worker(pool)) {
3506 raw_spin_lock(&wq_mayday_lock);
3507 /*
3508 * Queue iff we aren't racing destruction
3509 * and somebody else hasn't queued it already.
3510 */
3511 if (wq->rescuer && list_empty(&pwq->mayday_node)) {
3512 get_pwq(pwq);
3513 list_add_tail(&pwq->mayday_node, &wq->maydays);
3514 }
3515 raw_spin_unlock(&wq_mayday_lock);
3516 }
3517 }
3518
3519 /*
3520 * Leave this pool. Notify regular workers; otherwise, we end up
3521 * with 0 concurrency and stalling the execution.
3522 */
3523 kick_pool(pool);
3524
3525 raw_spin_unlock_irq(&pool->lock);
3526
3527 worker_detach_from_pool(rescuer);
3528
3529 /*
3530 * Put the reference grabbed by send_mayday(). @pool might
3531 * go away any time after it.
3532 */
3533 put_pwq_unlocked(pwq);
3534
3535 raw_spin_lock_irq(&wq_mayday_lock);
3536 }
3537
3538 raw_spin_unlock_irq(&wq_mayday_lock);
3539
3540 if (should_stop) {
3541 __set_current_state(TASK_RUNNING);
3542 set_pf_worker(false);
3543 return 0;
3544 }
3545
3546 /* rescuers should never participate in concurrency management */
3547 WARN_ON_ONCE(!(rescuer->flags & WORKER_NOT_RUNNING));
3548 schedule();
3549 goto repeat;
3550}
3551
3552static void bh_worker(struct worker *worker)
3553{
3554 struct worker_pool *pool = worker->pool;
3555 int nr_restarts = BH_WORKER_RESTARTS;
3556 unsigned long end = jiffies + BH_WORKER_JIFFIES;
3557
3558 raw_spin_lock_irq(&pool->lock);
3559 worker_leave_idle(worker);
3560
3561 /*
3562 * This function follows the structure of worker_thread(). See there for
3563 * explanations on each step.
3564 */
3565 if (!need_more_worker(pool))
3566 goto done;
3567
3568 WARN_ON_ONCE(!list_empty(&worker->scheduled));
3569 worker_clr_flags(worker, WORKER_PREP | WORKER_REBOUND);
3570
3571 do {
3572 struct work_struct *work =
3573 list_first_entry(&pool->worklist,
3574 struct work_struct, entry);
3575
3576 if (assign_work(work, worker, NULL))
3577 process_scheduled_works(worker);
3578 } while (keep_working(pool) &&
3579 --nr_restarts && time_before(jiffies, end));
3580
3581 worker_set_flags(worker, WORKER_PREP);
3582done:
3583 worker_enter_idle(worker);
3584 kick_pool(pool);
3585 raw_spin_unlock_irq(&pool->lock);
3586}
3587
3588/*
3589 * TODO: Convert all tasklet users to workqueue and use softirq directly.
3590 *
3591 * This is currently called from tasklet[_hi]action() and thus is also called
3592 * whenever there are tasklets to run. Let's do an early exit if there's nothing
3593 * queued. Once conversion from tasklet is complete, the need_more_worker() test
3594 * can be dropped.
3595 *
3596 * After full conversion, we'll add worker->softirq_action, directly use the
3597 * softirq action and obtain the worker pointer from the softirq_action pointer.
3598 */
3599void workqueue_softirq_action(bool highpri)
3600{
3601 struct worker_pool *pool =
3602 &per_cpu(bh_worker_pools, smp_processor_id())[highpri];
3603 if (need_more_worker(pool))
3604 bh_worker(list_first_entry(&pool->workers, struct worker, node));
3605}
3606
3607struct wq_drain_dead_softirq_work {
3608 struct work_struct work;
3609 struct worker_pool *pool;
3610 struct completion done;
3611};
3612
3613static void drain_dead_softirq_workfn(struct work_struct *work)
3614{
3615 struct wq_drain_dead_softirq_work *dead_work =
3616 container_of(work, struct wq_drain_dead_softirq_work, work);
3617 struct worker_pool *pool = dead_work->pool;
3618 bool repeat;
3619
3620 /*
3621 * @pool's CPU is dead and we want to execute its still pending work
3622 * items from this BH work item which is running on a different CPU. As
3623 * its CPU is dead, @pool can't be kicked and, as work execution path
3624 * will be nested, a lockdep annotation needs to be suppressed. Mark
3625 * @pool with %POOL_BH_DRAINING for the special treatments.
3626 */
3627 raw_spin_lock_irq(&pool->lock);
3628 pool->flags |= POOL_BH_DRAINING;
3629 raw_spin_unlock_irq(&pool->lock);
3630
3631 bh_worker(list_first_entry(&pool->workers, struct worker, node));
3632
3633 raw_spin_lock_irq(&pool->lock);
3634 pool->flags &= ~POOL_BH_DRAINING;
3635 repeat = need_more_worker(pool);
3636 raw_spin_unlock_irq(&pool->lock);
3637
3638 /*
3639 * bh_worker() might hit consecutive execution limit and bail. If there
3640 * still are pending work items, reschedule self and return so that we
3641 * don't hog this CPU's BH.
3642 */
3643 if (repeat) {
3644 if (pool->attrs->nice == HIGHPRI_NICE_LEVEL)
3645 queue_work(system_bh_highpri_wq, work);
3646 else
3647 queue_work(system_bh_wq, work);
3648 } else {
3649 complete(&dead_work->done);
3650 }
3651}
3652
3653/*
3654 * @cpu is dead. Drain the remaining BH work items on the current CPU. It's
3655 * possible to allocate dead_work per CPU and avoid flushing. However, then we
3656 * have to worry about draining overlapping with CPU coming back online or
3657 * nesting (one CPU's dead_work queued on another CPU which is also dead and so
3658 * on). Let's keep it simple and drain them synchronously. These are BH work
3659 * items which shouldn't be requeued on the same pool. Shouldn't take long.
3660 */
3661void workqueue_softirq_dead(unsigned int cpu)
3662{
3663 int i;
3664
3665 for (i = 0; i < NR_STD_WORKER_POOLS; i++) {
3666 struct worker_pool *pool = &per_cpu(bh_worker_pools, cpu)[i];
3667 struct wq_drain_dead_softirq_work dead_work;
3668
3669 if (!need_more_worker(pool))
3670 continue;
3671
3672 INIT_WORK_ONSTACK(&dead_work.work, drain_dead_softirq_workfn);
3673 dead_work.pool = pool;
3674 init_completion(&dead_work.done);
3675
3676 if (pool->attrs->nice == HIGHPRI_NICE_LEVEL)
3677 queue_work(system_bh_highpri_wq, &dead_work.work);
3678 else
3679 queue_work(system_bh_wq, &dead_work.work);
3680
3681 wait_for_completion(&dead_work.done);
3682 destroy_work_on_stack(&dead_work.work);
3683 }
3684}
3685
3686/**
3687 * check_flush_dependency - check for flush dependency sanity
3688 * @target_wq: workqueue being flushed
3689 * @target_work: work item being flushed (NULL for workqueue flushes)
3690 * @from_cancel: are we called from the work cancel path
3691 *
3692 * %current is trying to flush the whole @target_wq or @target_work on it.
3693 * If this is not the cancel path (which implies work being flushed is either
3694 * already running, or will not be at all), check if @target_wq doesn't have
3695 * %WQ_MEM_RECLAIM and verify that %current is not reclaiming memory or running
3696 * on a workqueue which doesn't have %WQ_MEM_RECLAIM as that can break forward-
3697 * progress guarantee leading to a deadlock.
3698 */
3699static void check_flush_dependency(struct workqueue_struct *target_wq,
3700 struct work_struct *target_work,
3701 bool from_cancel)
3702{
3703 work_func_t target_func;
3704 struct worker *worker;
3705
3706 if (from_cancel || target_wq->flags & WQ_MEM_RECLAIM)
3707 return;
3708
3709 worker = current_wq_worker();
3710 target_func = target_work ? target_work->func : NULL;
3711
3712 WARN_ONCE(current->flags & PF_MEMALLOC,
3713 "workqueue: PF_MEMALLOC task %d(%s) is flushing !WQ_MEM_RECLAIM %s:%ps",
3714 current->pid, current->comm, target_wq->name, target_func);
3715 WARN_ONCE(worker && ((worker->current_pwq->wq->flags &
3716 (WQ_MEM_RECLAIM | __WQ_LEGACY)) == WQ_MEM_RECLAIM),
3717 "workqueue: WQ_MEM_RECLAIM %s:%ps is flushing !WQ_MEM_RECLAIM %s:%ps",
3718 worker->current_pwq->wq->name, worker->current_func,
3719 target_wq->name, target_func);
3720}
3721
3722struct wq_barrier {
3723 struct work_struct work;
3724 struct completion done;
3725 struct task_struct *task; /* purely informational */
3726};
3727
3728static void wq_barrier_func(struct work_struct *work)
3729{
3730 struct wq_barrier *barr = container_of(work, struct wq_barrier, work);
3731 complete(&barr->done);
3732}
3733
3734/**
3735 * insert_wq_barrier - insert a barrier work
3736 * @pwq: pwq to insert barrier into
3737 * @barr: wq_barrier to insert
3738 * @target: target work to attach @barr to
3739 * @worker: worker currently executing @target, NULL if @target is not executing
3740 *
3741 * @barr is linked to @target such that @barr is completed only after
3742 * @target finishes execution. Please note that the ordering
3743 * guarantee is observed only with respect to @target and on the local
3744 * cpu.
3745 *
3746 * Currently, a queued barrier can't be canceled. This is because
3747 * try_to_grab_pending() can't determine whether the work to be
3748 * grabbed is at the head of the queue and thus can't clear LINKED
3749 * flag of the previous work while there must be a valid next work
3750 * after a work with LINKED flag set.
3751 *
3752 * Note that when @worker is non-NULL, @target may be modified
3753 * underneath us, so we can't reliably determine pwq from @target.
3754 *
3755 * CONTEXT:
3756 * raw_spin_lock_irq(pool->lock).
3757 */
3758static void insert_wq_barrier(struct pool_workqueue *pwq,
3759 struct wq_barrier *barr,
3760 struct work_struct *target, struct worker *worker)
3761{
3762 static __maybe_unused struct lock_class_key bh_key, thr_key;
3763 unsigned int work_flags = 0;
3764 unsigned int work_color;
3765 struct list_head *head;
3766
3767 /*
3768 * debugobject calls are safe here even with pool->lock locked
3769 * as we know for sure that this will not trigger any of the
3770 * checks and call back into the fixup functions where we
3771 * might deadlock.
3772 *
3773 * BH and threaded workqueues need separate lockdep keys to avoid
3774 * spuriously triggering "inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W}
3775 * usage".
3776 */
3777 INIT_WORK_ONSTACK_KEY(&barr->work, wq_barrier_func,
3778 (pwq->wq->flags & WQ_BH) ? &bh_key : &thr_key);
3779 __set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(&barr->work));
3780
3781 init_completion_map(&barr->done, &target->lockdep_map);
3782
3783 barr->task = current;
3784
3785 /* The barrier work item does not participate in nr_active. */
3786 work_flags |= WORK_STRUCT_INACTIVE;
3787
3788 /*
3789 * If @target is currently being executed, schedule the
3790 * barrier to the worker; otherwise, put it after @target.
3791 */
3792 if (worker) {
3793 head = worker->scheduled.next;
3794 work_color = worker->current_color;
3795 } else {
3796 unsigned long *bits = work_data_bits(target);
3797
3798 head = target->entry.next;
3799 /* there can already be other linked works, inherit and set */
3800 work_flags |= *bits & WORK_STRUCT_LINKED;
3801 work_color = get_work_color(*bits);
3802 __set_bit(WORK_STRUCT_LINKED_BIT, bits);
3803 }
3804
3805 pwq->nr_in_flight[work_color]++;
3806 work_flags |= work_color_to_flags(work_color);
3807
3808 insert_work(pwq, &barr->work, head, work_flags);
3809}
3810
3811/**
3812 * flush_workqueue_prep_pwqs - prepare pwqs for workqueue flushing
3813 * @wq: workqueue being flushed
3814 * @flush_color: new flush color, < 0 for no-op
3815 * @work_color: new work color, < 0 for no-op
3816 *
3817 * Prepare pwqs for workqueue flushing.
3818 *
3819 * If @flush_color is non-negative, flush_color on all pwqs should be
3820 * -1. If no pwq has in-flight commands at the specified color, all
3821 * pwq->flush_color's stay at -1 and %false is returned. If any pwq
3822 * has in flight commands, its pwq->flush_color is set to
3823 * @flush_color, @wq->nr_pwqs_to_flush is updated accordingly, pwq
3824 * wakeup logic is armed and %true is returned.
3825 *
3826 * The caller should have initialized @wq->first_flusher prior to
3827 * calling this function with non-negative @flush_color. If
3828 * @flush_color is negative, no flush color update is done and %false
3829 * is returned.
3830 *
3831 * If @work_color is non-negative, all pwqs should have the same
3832 * work_color which is previous to @work_color and all will be
3833 * advanced to @work_color.
3834 *
3835 * CONTEXT:
3836 * mutex_lock(wq->mutex).
3837 *
3838 * Return:
3839 * %true if @flush_color >= 0 and there's something to flush. %false
3840 * otherwise.
3841 */
3842static bool flush_workqueue_prep_pwqs(struct workqueue_struct *wq,
3843 int flush_color, int work_color)
3844{
3845 bool wait = false;
3846 struct pool_workqueue *pwq;
3847 struct worker_pool *current_pool = NULL;
3848
3849 if (flush_color >= 0) {
3850 WARN_ON_ONCE(atomic_read(&wq->nr_pwqs_to_flush));
3851 atomic_set(&wq->nr_pwqs_to_flush, 1);
3852 }
3853
3854 /*
3855 * For unbound workqueue, pwqs will map to only a few pools.
3856 * Most of the time, pwqs within the same pool will be linked
3857 * sequentially to wq->pwqs by cpu index. So in the majority
3858 * of pwq iters, the pool is the same, only doing lock/unlock
3859 * if the pool has changed. This can largely reduce expensive
3860 * lock operations.
3861 */
3862 for_each_pwq(pwq, wq) {
3863 if (current_pool != pwq->pool) {
3864 if (likely(current_pool))
3865 raw_spin_unlock_irq(¤t_pool->lock);
3866 current_pool = pwq->pool;
3867 raw_spin_lock_irq(¤t_pool->lock);
3868 }
3869
3870 if (flush_color >= 0) {
3871 WARN_ON_ONCE(pwq->flush_color != -1);
3872
3873 if (pwq->nr_in_flight[flush_color]) {
3874 pwq->flush_color = flush_color;
3875 atomic_inc(&wq->nr_pwqs_to_flush);
3876 wait = true;
3877 }
3878 }
3879
3880 if (work_color >= 0) {
3881 WARN_ON_ONCE(work_color != work_next_color(pwq->work_color));
3882 pwq->work_color = work_color;
3883 }
3884
3885 }
3886
3887 if (current_pool)
3888 raw_spin_unlock_irq(¤t_pool->lock);
3889
3890 if (flush_color >= 0 && atomic_dec_and_test(&wq->nr_pwqs_to_flush))
3891 complete(&wq->first_flusher->done);
3892
3893 return wait;
3894}
3895
3896static void touch_wq_lockdep_map(struct workqueue_struct *wq)
3897{
3898#ifdef CONFIG_LOCKDEP
3899 if (unlikely(!wq->lockdep_map))
3900 return;
3901
3902 if (wq->flags & WQ_BH)
3903 local_bh_disable();
3904
3905 lock_map_acquire(wq->lockdep_map);
3906 lock_map_release(wq->lockdep_map);
3907
3908 if (wq->flags & WQ_BH)
3909 local_bh_enable();
3910#endif
3911}
3912
3913static void touch_work_lockdep_map(struct work_struct *work,
3914 struct workqueue_struct *wq)
3915{
3916#ifdef CONFIG_LOCKDEP
3917 if (wq->flags & WQ_BH)
3918 local_bh_disable();
3919
3920 lock_map_acquire(&work->lockdep_map);
3921 lock_map_release(&work->lockdep_map);
3922
3923 if (wq->flags & WQ_BH)
3924 local_bh_enable();
3925#endif
3926}
3927
3928/**
3929 * __flush_workqueue - ensure that any scheduled work has run to completion.
3930 * @wq: workqueue to flush
3931 *
3932 * This function sleeps until all work items which were queued on entry
3933 * have finished execution, but it is not livelocked by new incoming ones.
3934 */
3935void __flush_workqueue(struct workqueue_struct *wq)
3936{
3937 struct wq_flusher this_flusher = {
3938 .list = LIST_HEAD_INIT(this_flusher.list),
3939 .flush_color = -1,
3940 .done = COMPLETION_INITIALIZER_ONSTACK_MAP(this_flusher.done, (*wq->lockdep_map)),
3941 };
3942 int next_color;
3943
3944 if (WARN_ON(!wq_online))
3945 return;
3946
3947 touch_wq_lockdep_map(wq);
3948
3949 mutex_lock(&wq->mutex);
3950
3951 /*
3952 * Start-to-wait phase
3953 */
3954 next_color = work_next_color(wq->work_color);
3955
3956 if (next_color != wq->flush_color) {
3957 /*
3958 * Color space is not full. The current work_color
3959 * becomes our flush_color and work_color is advanced
3960 * by one.
3961 */
3962 WARN_ON_ONCE(!list_empty(&wq->flusher_overflow));
3963 this_flusher.flush_color = wq->work_color;
3964 wq->work_color = next_color;
3965
3966 if (!wq->first_flusher) {
3967 /* no flush in progress, become the first flusher */
3968 WARN_ON_ONCE(wq->flush_color != this_flusher.flush_color);
3969
3970 wq->first_flusher = &this_flusher;
3971
3972 if (!flush_workqueue_prep_pwqs(wq, wq->flush_color,
3973 wq->work_color)) {
3974 /* nothing to flush, done */
3975 wq->flush_color = next_color;
3976 wq->first_flusher = NULL;
3977 goto out_unlock;
3978 }
3979 } else {
3980 /* wait in queue */
3981 WARN_ON_ONCE(wq->flush_color == this_flusher.flush_color);
3982 list_add_tail(&this_flusher.list, &wq->flusher_queue);
3983 flush_workqueue_prep_pwqs(wq, -1, wq->work_color);
3984 }
3985 } else {
3986 /*
3987 * Oops, color space is full, wait on overflow queue.
3988 * The next flush completion will assign us
3989 * flush_color and transfer to flusher_queue.
3990 */
3991 list_add_tail(&this_flusher.list, &wq->flusher_overflow);
3992 }
3993
3994 check_flush_dependency(wq, NULL, false);
3995
3996 mutex_unlock(&wq->mutex);
3997
3998 wait_for_completion(&this_flusher.done);
3999
4000 /*
4001 * Wake-up-and-cascade phase
4002 *
4003 * First flushers are responsible for cascading flushes and
4004 * handling overflow. Non-first flushers can simply return.
4005 */
4006 if (READ_ONCE(wq->first_flusher) != &this_flusher)
4007 return;
4008
4009 mutex_lock(&wq->mutex);
4010
4011 /* we might have raced, check again with mutex held */
4012 if (wq->first_flusher != &this_flusher)
4013 goto out_unlock;
4014
4015 WRITE_ONCE(wq->first_flusher, NULL);
4016
4017 WARN_ON_ONCE(!list_empty(&this_flusher.list));
4018 WARN_ON_ONCE(wq->flush_color != this_flusher.flush_color);
4019
4020 while (true) {
4021 struct wq_flusher *next, *tmp;
4022
4023 /* complete all the flushers sharing the current flush color */
4024 list_for_each_entry_safe(next, tmp, &wq->flusher_queue, list) {
4025 if (next->flush_color != wq->flush_color)
4026 break;
4027 list_del_init(&next->list);
4028 complete(&next->done);
4029 }
4030
4031 WARN_ON_ONCE(!list_empty(&wq->flusher_overflow) &&
4032 wq->flush_color != work_next_color(wq->work_color));
4033
4034 /* this flush_color is finished, advance by one */
4035 wq->flush_color = work_next_color(wq->flush_color);
4036
4037 /* one color has been freed, handle overflow queue */
4038 if (!list_empty(&wq->flusher_overflow)) {
4039 /*
4040 * Assign the same color to all overflowed
4041 * flushers, advance work_color and append to
4042 * flusher_queue. This is the start-to-wait
4043 * phase for these overflowed flushers.
4044 */
4045 list_for_each_entry(tmp, &wq->flusher_overflow, list)
4046 tmp->flush_color = wq->work_color;
4047
4048 wq->work_color = work_next_color(wq->work_color);
4049
4050 list_splice_tail_init(&wq->flusher_overflow,
4051 &wq->flusher_queue);
4052 flush_workqueue_prep_pwqs(wq, -1, wq->work_color);
4053 }
4054
4055 if (list_empty(&wq->flusher_queue)) {
4056 WARN_ON_ONCE(wq->flush_color != wq->work_color);
4057 break;
4058 }
4059
4060 /*
4061 * Need to flush more colors. Make the next flusher
4062 * the new first flusher and arm pwqs.
4063 */
4064 WARN_ON_ONCE(wq->flush_color == wq->work_color);
4065 WARN_ON_ONCE(wq->flush_color != next->flush_color);
4066
4067 list_del_init(&next->list);
4068 wq->first_flusher = next;
4069
4070 if (flush_workqueue_prep_pwqs(wq, wq->flush_color, -1))
4071 break;
4072
4073 /*
4074 * Meh... this color is already done, clear first
4075 * flusher and repeat cascading.
4076 */
4077 wq->first_flusher = NULL;
4078 }
4079
4080out_unlock:
4081 mutex_unlock(&wq->mutex);
4082}
4083EXPORT_SYMBOL(__flush_workqueue);
4084
4085/**
4086 * drain_workqueue - drain a workqueue
4087 * @wq: workqueue to drain
4088 *
4089 * Wait until the workqueue becomes empty. While draining is in progress,
4090 * only chain queueing is allowed. IOW, only currently pending or running
4091 * work items on @wq can queue further work items on it. @wq is flushed
4092 * repeatedly until it becomes empty. The number of flushing is determined
4093 * by the depth of chaining and should be relatively short. Whine if it
4094 * takes too long.
4095 */
4096void drain_workqueue(struct workqueue_struct *wq)
4097{
4098 unsigned int flush_cnt = 0;
4099 struct pool_workqueue *pwq;
4100
4101 /*
4102 * __queue_work() needs to test whether there are drainers, is much
4103 * hotter than drain_workqueue() and already looks at @wq->flags.
4104 * Use __WQ_DRAINING so that queue doesn't have to check nr_drainers.
4105 */
4106 mutex_lock(&wq->mutex);
4107 if (!wq->nr_drainers++)
4108 wq->flags |= __WQ_DRAINING;
4109 mutex_unlock(&wq->mutex);
4110reflush:
4111 __flush_workqueue(wq);
4112
4113 mutex_lock(&wq->mutex);
4114
4115 for_each_pwq(pwq, wq) {
4116 bool drained;
4117
4118 raw_spin_lock_irq(&pwq->pool->lock);
4119 drained = pwq_is_empty(pwq);
4120 raw_spin_unlock_irq(&pwq->pool->lock);
4121
4122 if (drained)
4123 continue;
4124
4125 if (++flush_cnt == 10 ||
4126 (flush_cnt % 100 == 0 && flush_cnt <= 1000))
4127 pr_warn("workqueue %s: %s() isn't complete after %u tries\n",
4128 wq->name, __func__, flush_cnt);
4129
4130 mutex_unlock(&wq->mutex);
4131 goto reflush;
4132 }
4133
4134 if (!--wq->nr_drainers)
4135 wq->flags &= ~__WQ_DRAINING;
4136 mutex_unlock(&wq->mutex);
4137}
4138EXPORT_SYMBOL_GPL(drain_workqueue);
4139
4140static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr,
4141 bool from_cancel)
4142{
4143 struct worker *worker = NULL;
4144 struct worker_pool *pool;
4145 struct pool_workqueue *pwq;
4146 struct workqueue_struct *wq;
4147
4148 rcu_read_lock();
4149 pool = get_work_pool(work);
4150 if (!pool) {
4151 rcu_read_unlock();
4152 return false;
4153 }
4154
4155 raw_spin_lock_irq(&pool->lock);
4156 /* see the comment in try_to_grab_pending() with the same code */
4157 pwq = get_work_pwq(work);
4158 if (pwq) {
4159 if (unlikely(pwq->pool != pool))
4160 goto already_gone;
4161 } else {
4162 worker = find_worker_executing_work(pool, work);
4163 if (!worker)
4164 goto already_gone;
4165 pwq = worker->current_pwq;
4166 }
4167
4168 wq = pwq->wq;
4169 check_flush_dependency(wq, work, from_cancel);
4170
4171 insert_wq_barrier(pwq, barr, work, worker);
4172 raw_spin_unlock_irq(&pool->lock);
4173
4174 touch_work_lockdep_map(work, wq);
4175
4176 /*
4177 * Force a lock recursion deadlock when using flush_work() inside a
4178 * single-threaded or rescuer equipped workqueue.
4179 *
4180 * For single threaded workqueues the deadlock happens when the work
4181 * is after the work issuing the flush_work(). For rescuer equipped
4182 * workqueues the deadlock happens when the rescuer stalls, blocking
4183 * forward progress.
4184 */
4185 if (!from_cancel && (wq->saved_max_active == 1 || wq->rescuer))
4186 touch_wq_lockdep_map(wq);
4187
4188 rcu_read_unlock();
4189 return true;
4190already_gone:
4191 raw_spin_unlock_irq(&pool->lock);
4192 rcu_read_unlock();
4193 return false;
4194}
4195
4196static bool __flush_work(struct work_struct *work, bool from_cancel)
4197{
4198 struct wq_barrier barr;
4199
4200 if (WARN_ON(!wq_online))
4201 return false;
4202
4203 if (WARN_ON(!work->func))
4204 return false;
4205
4206 if (!start_flush_work(work, &barr, from_cancel))
4207 return false;
4208
4209 /*
4210 * start_flush_work() returned %true. If @from_cancel is set, we know
4211 * that @work must have been executing during start_flush_work() and
4212 * can't currently be queued. Its data must contain OFFQ bits. If @work
4213 * was queued on a BH workqueue, we also know that it was running in the
4214 * BH context and thus can be busy-waited.
4215 */
4216 if (from_cancel) {
4217 unsigned long data = *work_data_bits(work);
4218
4219 if (!WARN_ON_ONCE(data & WORK_STRUCT_PWQ) &&
4220 (data & WORK_OFFQ_BH)) {
4221 /*
4222 * On RT, prevent a live lock when %current preempted
4223 * soft interrupt processing or prevents ksoftirqd from
4224 * running by keeping flipping BH. If the BH work item
4225 * runs on a different CPU then this has no effect other
4226 * than doing the BH disable/enable dance for nothing.
4227 * This is copied from
4228 * kernel/softirq.c::tasklet_unlock_spin_wait().
4229 */
4230 while (!try_wait_for_completion(&barr.done)) {
4231 if (IS_ENABLED(CONFIG_PREEMPT_RT)) {
4232 local_bh_disable();
4233 local_bh_enable();
4234 } else {
4235 cpu_relax();
4236 }
4237 }
4238 goto out_destroy;
4239 }
4240 }
4241
4242 wait_for_completion(&barr.done);
4243
4244out_destroy:
4245 destroy_work_on_stack(&barr.work);
4246 return true;
4247}
4248
4249/**
4250 * flush_work - wait for a work to finish executing the last queueing instance
4251 * @work: the work to flush
4252 *
4253 * Wait until @work has finished execution. @work is guaranteed to be idle
4254 * on return if it hasn't been requeued since flush started.
4255 *
4256 * Return:
4257 * %true if flush_work() waited for the work to finish execution,
4258 * %false if it was already idle.
4259 */
4260bool flush_work(struct work_struct *work)
4261{
4262 might_sleep();
4263 return __flush_work(work, false);
4264}
4265EXPORT_SYMBOL_GPL(flush_work);
4266
4267/**
4268 * flush_delayed_work - wait for a dwork to finish executing the last queueing
4269 * @dwork: the delayed work to flush
4270 *
4271 * Delayed timer is cancelled and the pending work is queued for
4272 * immediate execution. Like flush_work(), this function only
4273 * considers the last queueing instance of @dwork.
4274 *
4275 * Return:
4276 * %true if flush_work() waited for the work to finish execution,
4277 * %false if it was already idle.
4278 */
4279bool flush_delayed_work(struct delayed_work *dwork)
4280{
4281 local_irq_disable();
4282 if (del_timer_sync(&dwork->timer))
4283 __queue_work(dwork->cpu, dwork->wq, &dwork->work);
4284 local_irq_enable();
4285 return flush_work(&dwork->work);
4286}
4287EXPORT_SYMBOL(flush_delayed_work);
4288
4289/**
4290 * flush_rcu_work - wait for a rwork to finish executing the last queueing
4291 * @rwork: the rcu work to flush
4292 *
4293 * Return:
4294 * %true if flush_rcu_work() waited for the work to finish execution,
4295 * %false if it was already idle.
4296 */
4297bool flush_rcu_work(struct rcu_work *rwork)
4298{
4299 if (test_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(&rwork->work))) {
4300 rcu_barrier();
4301 flush_work(&rwork->work);
4302 return true;
4303 } else {
4304 return flush_work(&rwork->work);
4305 }
4306}
4307EXPORT_SYMBOL(flush_rcu_work);
4308
4309static void work_offqd_disable(struct work_offq_data *offqd)
4310{
4311 const unsigned long max = (1lu << WORK_OFFQ_DISABLE_BITS) - 1;
4312
4313 if (likely(offqd->disable < max))
4314 offqd->disable++;
4315 else
4316 WARN_ONCE(true, "workqueue: work disable count overflowed\n");
4317}
4318
4319static void work_offqd_enable(struct work_offq_data *offqd)
4320{
4321 if (likely(offqd->disable > 0))
4322 offqd->disable--;
4323 else
4324 WARN_ONCE(true, "workqueue: work disable count underflowed\n");
4325}
4326
4327static bool __cancel_work(struct work_struct *work, u32 cflags)
4328{
4329 struct work_offq_data offqd;
4330 unsigned long irq_flags;
4331 int ret;
4332
4333 ret = work_grab_pending(work, cflags, &irq_flags);
4334
4335 work_offqd_unpack(&offqd, *work_data_bits(work));
4336
4337 if (cflags & WORK_CANCEL_DISABLE)
4338 work_offqd_disable(&offqd);
4339
4340 set_work_pool_and_clear_pending(work, offqd.pool_id,
4341 work_offqd_pack_flags(&offqd));
4342 local_irq_restore(irq_flags);
4343 return ret;
4344}
4345
4346static bool __cancel_work_sync(struct work_struct *work, u32 cflags)
4347{
4348 bool ret;
4349
4350 ret = __cancel_work(work, cflags | WORK_CANCEL_DISABLE);
4351
4352 if (*work_data_bits(work) & WORK_OFFQ_BH)
4353 WARN_ON_ONCE(in_hardirq());
4354 else
4355 might_sleep();
4356
4357 /*
4358 * Skip __flush_work() during early boot when we know that @work isn't
4359 * executing. This allows canceling during early boot.
4360 */
4361 if (wq_online)
4362 __flush_work(work, true);
4363
4364 if (!(cflags & WORK_CANCEL_DISABLE))
4365 enable_work(work);
4366
4367 return ret;
4368}
4369
4370/*
4371 * See cancel_delayed_work()
4372 */
4373bool cancel_work(struct work_struct *work)
4374{
4375 return __cancel_work(work, 0);
4376}
4377EXPORT_SYMBOL(cancel_work);
4378
4379/**
4380 * cancel_work_sync - cancel a work and wait for it to finish
4381 * @work: the work to cancel
4382 *
4383 * Cancel @work and wait for its execution to finish. This function can be used
4384 * even if the work re-queues itself or migrates to another workqueue. On return
4385 * from this function, @work is guaranteed to be not pending or executing on any
4386 * CPU as long as there aren't racing enqueues.
4387 *
4388 * cancel_work_sync(&delayed_work->work) must not be used for delayed_work's.
4389 * Use cancel_delayed_work_sync() instead.
4390 *
4391 * Must be called from a sleepable context if @work was last queued on a non-BH
4392 * workqueue. Can also be called from non-hardirq atomic contexts including BH
4393 * if @work was last queued on a BH workqueue.
4394 *
4395 * Returns %true if @work was pending, %false otherwise.
4396 */
4397bool cancel_work_sync(struct work_struct *work)
4398{
4399 return __cancel_work_sync(work, 0);
4400}
4401EXPORT_SYMBOL_GPL(cancel_work_sync);
4402
4403/**
4404 * cancel_delayed_work - cancel a delayed work
4405 * @dwork: delayed_work to cancel
4406 *
4407 * Kill off a pending delayed_work.
4408 *
4409 * Return: %true if @dwork was pending and canceled; %false if it wasn't
4410 * pending.
4411 *
4412 * Note:
4413 * The work callback function may still be running on return, unless
4414 * it returns %true and the work doesn't re-arm itself. Explicitly flush or
4415 * use cancel_delayed_work_sync() to wait on it.
4416 *
4417 * This function is safe to call from any context including IRQ handler.
4418 */
4419bool cancel_delayed_work(struct delayed_work *dwork)
4420{
4421 return __cancel_work(&dwork->work, WORK_CANCEL_DELAYED);
4422}
4423EXPORT_SYMBOL(cancel_delayed_work);
4424
4425/**
4426 * cancel_delayed_work_sync - cancel a delayed work and wait for it to finish
4427 * @dwork: the delayed work cancel
4428 *
4429 * This is cancel_work_sync() for delayed works.
4430 *
4431 * Return:
4432 * %true if @dwork was pending, %false otherwise.
4433 */
4434bool cancel_delayed_work_sync(struct delayed_work *dwork)
4435{
4436 return __cancel_work_sync(&dwork->work, WORK_CANCEL_DELAYED);
4437}
4438EXPORT_SYMBOL(cancel_delayed_work_sync);
4439
4440/**
4441 * disable_work - Disable and cancel a work item
4442 * @work: work item to disable
4443 *
4444 * Disable @work by incrementing its disable count and cancel it if currently
4445 * pending. As long as the disable count is non-zero, any attempt to queue @work
4446 * will fail and return %false. The maximum supported disable depth is 2 to the
4447 * power of %WORK_OFFQ_DISABLE_BITS, currently 65536.
4448 *
4449 * Can be called from any context. Returns %true if @work was pending, %false
4450 * otherwise.
4451 */
4452bool disable_work(struct work_struct *work)
4453{
4454 return __cancel_work(work, WORK_CANCEL_DISABLE);
4455}
4456EXPORT_SYMBOL_GPL(disable_work);
4457
4458/**
4459 * disable_work_sync - Disable, cancel and drain a work item
4460 * @work: work item to disable
4461 *
4462 * Similar to disable_work() but also wait for @work to finish if currently
4463 * executing.
4464 *
4465 * Must be called from a sleepable context if @work was last queued on a non-BH
4466 * workqueue. Can also be called from non-hardirq atomic contexts including BH
4467 * if @work was last queued on a BH workqueue.
4468 *
4469 * Returns %true if @work was pending, %false otherwise.
4470 */
4471bool disable_work_sync(struct work_struct *work)
4472{
4473 return __cancel_work_sync(work, WORK_CANCEL_DISABLE);
4474}
4475EXPORT_SYMBOL_GPL(disable_work_sync);
4476
4477/**
4478 * enable_work - Enable a work item
4479 * @work: work item to enable
4480 *
4481 * Undo disable_work[_sync]() by decrementing @work's disable count. @work can
4482 * only be queued if its disable count is 0.
4483 *
4484 * Can be called from any context. Returns %true if the disable count reached 0.
4485 * Otherwise, %false.
4486 */
4487bool enable_work(struct work_struct *work)
4488{
4489 struct work_offq_data offqd;
4490 unsigned long irq_flags;
4491
4492 work_grab_pending(work, 0, &irq_flags);
4493
4494 work_offqd_unpack(&offqd, *work_data_bits(work));
4495 work_offqd_enable(&offqd);
4496 set_work_pool_and_clear_pending(work, offqd.pool_id,
4497 work_offqd_pack_flags(&offqd));
4498 local_irq_restore(irq_flags);
4499
4500 return !offqd.disable;
4501}
4502EXPORT_SYMBOL_GPL(enable_work);
4503
4504/**
4505 * disable_delayed_work - Disable and cancel a delayed work item
4506 * @dwork: delayed work item to disable
4507 *
4508 * disable_work() for delayed work items.
4509 */
4510bool disable_delayed_work(struct delayed_work *dwork)
4511{
4512 return __cancel_work(&dwork->work,
4513 WORK_CANCEL_DELAYED | WORK_CANCEL_DISABLE);
4514}
4515EXPORT_SYMBOL_GPL(disable_delayed_work);
4516
4517/**
4518 * disable_delayed_work_sync - Disable, cancel and drain a delayed work item
4519 * @dwork: delayed work item to disable
4520 *
4521 * disable_work_sync() for delayed work items.
4522 */
4523bool disable_delayed_work_sync(struct delayed_work *dwork)
4524{
4525 return __cancel_work_sync(&dwork->work,
4526 WORK_CANCEL_DELAYED | WORK_CANCEL_DISABLE);
4527}
4528EXPORT_SYMBOL_GPL(disable_delayed_work_sync);
4529
4530/**
4531 * enable_delayed_work - Enable a delayed work item
4532 * @dwork: delayed work item to enable
4533 *
4534 * enable_work() for delayed work items.
4535 */
4536bool enable_delayed_work(struct delayed_work *dwork)
4537{
4538 return enable_work(&dwork->work);
4539}
4540EXPORT_SYMBOL_GPL(enable_delayed_work);
4541
4542/**
4543 * schedule_on_each_cpu - execute a function synchronously on each online CPU
4544 * @func: the function to call
4545 *
4546 * schedule_on_each_cpu() executes @func on each online CPU using the
4547 * system workqueue and blocks until all CPUs have completed.
4548 * schedule_on_each_cpu() is very slow.
4549 *
4550 * Return:
4551 * 0 on success, -errno on failure.
4552 */
4553int schedule_on_each_cpu(work_func_t func)
4554{
4555 int cpu;
4556 struct work_struct __percpu *works;
4557
4558 works = alloc_percpu(struct work_struct);
4559 if (!works)
4560 return -ENOMEM;
4561
4562 cpus_read_lock();
4563
4564 for_each_online_cpu(cpu) {
4565 struct work_struct *work = per_cpu_ptr(works, cpu);
4566
4567 INIT_WORK(work, func);
4568 schedule_work_on(cpu, work);
4569 }
4570
4571 for_each_online_cpu(cpu)
4572 flush_work(per_cpu_ptr(works, cpu));
4573
4574 cpus_read_unlock();
4575 free_percpu(works);
4576 return 0;
4577}
4578
4579/**
4580 * execute_in_process_context - reliably execute the routine with user context
4581 * @fn: the function to execute
4582 * @ew: guaranteed storage for the execute work structure (must
4583 * be available when the work executes)
4584 *
4585 * Executes the function immediately if process context is available,
4586 * otherwise schedules the function for delayed execution.
4587 *
4588 * Return: 0 - function was executed
4589 * 1 - function was scheduled for execution
4590 */
4591int execute_in_process_context(work_func_t fn, struct execute_work *ew)
4592{
4593 if (!in_interrupt()) {
4594 fn(&ew->work);
4595 return 0;
4596 }
4597
4598 INIT_WORK(&ew->work, fn);
4599 schedule_work(&ew->work);
4600
4601 return 1;
4602}
4603EXPORT_SYMBOL_GPL(execute_in_process_context);
4604
4605/**
4606 * free_workqueue_attrs - free a workqueue_attrs
4607 * @attrs: workqueue_attrs to free
4608 *
4609 * Undo alloc_workqueue_attrs().
4610 */
4611void free_workqueue_attrs(struct workqueue_attrs *attrs)
4612{
4613 if (attrs) {
4614 free_cpumask_var(attrs->cpumask);
4615 free_cpumask_var(attrs->__pod_cpumask);
4616 kfree(attrs);
4617 }
4618}
4619
4620/**
4621 * alloc_workqueue_attrs - allocate a workqueue_attrs
4622 *
4623 * Allocate a new workqueue_attrs, initialize with default settings and
4624 * return it.
4625 *
4626 * Return: The allocated new workqueue_attr on success. %NULL on failure.
4627 */
4628struct workqueue_attrs *alloc_workqueue_attrs(void)
4629{
4630 struct workqueue_attrs *attrs;
4631
4632 attrs = kzalloc(sizeof(*attrs), GFP_KERNEL);
4633 if (!attrs)
4634 goto fail;
4635 if (!alloc_cpumask_var(&attrs->cpumask, GFP_KERNEL))
4636 goto fail;
4637 if (!alloc_cpumask_var(&attrs->__pod_cpumask, GFP_KERNEL))
4638 goto fail;
4639
4640 cpumask_copy(attrs->cpumask, cpu_possible_mask);
4641 attrs->affn_scope = WQ_AFFN_DFL;
4642 return attrs;
4643fail:
4644 free_workqueue_attrs(attrs);
4645 return NULL;
4646}
4647
4648static void copy_workqueue_attrs(struct workqueue_attrs *to,
4649 const struct workqueue_attrs *from)
4650{
4651 to->nice = from->nice;
4652 cpumask_copy(to->cpumask, from->cpumask);
4653 cpumask_copy(to->__pod_cpumask, from->__pod_cpumask);
4654 to->affn_strict = from->affn_strict;
4655
4656 /*
4657 * Unlike hash and equality test, copying shouldn't ignore wq-only
4658 * fields as copying is used for both pool and wq attrs. Instead,
4659 * get_unbound_pool() explicitly clears the fields.
4660 */
4661 to->affn_scope = from->affn_scope;
4662 to->ordered = from->ordered;
4663}
4664
4665/*
4666 * Some attrs fields are workqueue-only. Clear them for worker_pool's. See the
4667 * comments in 'struct workqueue_attrs' definition.
4668 */
4669static void wqattrs_clear_for_pool(struct workqueue_attrs *attrs)
4670{
4671 attrs->affn_scope = WQ_AFFN_NR_TYPES;
4672 attrs->ordered = false;
4673 if (attrs->affn_strict)
4674 cpumask_copy(attrs->cpumask, cpu_possible_mask);
4675}
4676
4677/* hash value of the content of @attr */
4678static u32 wqattrs_hash(const struct workqueue_attrs *attrs)
4679{
4680 u32 hash = 0;
4681
4682 hash = jhash_1word(attrs->nice, hash);
4683 hash = jhash_1word(attrs->affn_strict, hash);
4684 hash = jhash(cpumask_bits(attrs->__pod_cpumask),
4685 BITS_TO_LONGS(nr_cpumask_bits) * sizeof(long), hash);
4686 if (!attrs->affn_strict)
4687 hash = jhash(cpumask_bits(attrs->cpumask),
4688 BITS_TO_LONGS(nr_cpumask_bits) * sizeof(long), hash);
4689 return hash;
4690}
4691
4692/* content equality test */
4693static bool wqattrs_equal(const struct workqueue_attrs *a,
4694 const struct workqueue_attrs *b)
4695{
4696 if (a->nice != b->nice)
4697 return false;
4698 if (a->affn_strict != b->affn_strict)
4699 return false;
4700 if (!cpumask_equal(a->__pod_cpumask, b->__pod_cpumask))
4701 return false;
4702 if (!a->affn_strict && !cpumask_equal(a->cpumask, b->cpumask))
4703 return false;
4704 return true;
4705}
4706
4707/* Update @attrs with actually available CPUs */
4708static void wqattrs_actualize_cpumask(struct workqueue_attrs *attrs,
4709 const cpumask_t *unbound_cpumask)
4710{
4711 /*
4712 * Calculate the effective CPU mask of @attrs given @unbound_cpumask. If
4713 * @attrs->cpumask doesn't overlap with @unbound_cpumask, we fallback to
4714 * @unbound_cpumask.
4715 */
4716 cpumask_and(attrs->cpumask, attrs->cpumask, unbound_cpumask);
4717 if (unlikely(cpumask_empty(attrs->cpumask)))
4718 cpumask_copy(attrs->cpumask, unbound_cpumask);
4719}
4720
4721/* find wq_pod_type to use for @attrs */
4722static const struct wq_pod_type *
4723wqattrs_pod_type(const struct workqueue_attrs *attrs)
4724{
4725 enum wq_affn_scope scope;
4726 struct wq_pod_type *pt;
4727
4728 /* to synchronize access to wq_affn_dfl */
4729 lockdep_assert_held(&wq_pool_mutex);
4730
4731 if (attrs->affn_scope == WQ_AFFN_DFL)
4732 scope = wq_affn_dfl;
4733 else
4734 scope = attrs->affn_scope;
4735
4736 pt = &wq_pod_types[scope];
4737
4738 if (!WARN_ON_ONCE(attrs->affn_scope == WQ_AFFN_NR_TYPES) &&
4739 likely(pt->nr_pods))
4740 return pt;
4741
4742 /*
4743 * Before workqueue_init_topology(), only SYSTEM is available which is
4744 * initialized in workqueue_init_early().
4745 */
4746 pt = &wq_pod_types[WQ_AFFN_SYSTEM];
4747 BUG_ON(!pt->nr_pods);
4748 return pt;
4749}
4750
4751/**
4752 * init_worker_pool - initialize a newly zalloc'd worker_pool
4753 * @pool: worker_pool to initialize
4754 *
4755 * Initialize a newly zalloc'd @pool. It also allocates @pool->attrs.
4756 *
4757 * Return: 0 on success, -errno on failure. Even on failure, all fields
4758 * inside @pool proper are initialized and put_unbound_pool() can be called
4759 * on @pool safely to release it.
4760 */
4761static int init_worker_pool(struct worker_pool *pool)
4762{
4763 raw_spin_lock_init(&pool->lock);
4764 pool->id = -1;
4765 pool->cpu = -1;
4766 pool->node = NUMA_NO_NODE;
4767 pool->flags |= POOL_DISASSOCIATED;
4768 pool->watchdog_ts = jiffies;
4769 INIT_LIST_HEAD(&pool->worklist);
4770 INIT_LIST_HEAD(&pool->idle_list);
4771 hash_init(pool->busy_hash);
4772
4773 timer_setup(&pool->idle_timer, idle_worker_timeout, TIMER_DEFERRABLE);
4774 INIT_WORK(&pool->idle_cull_work, idle_cull_fn);
4775
4776 timer_setup(&pool->mayday_timer, pool_mayday_timeout, 0);
4777
4778 INIT_LIST_HEAD(&pool->workers);
4779
4780 ida_init(&pool->worker_ida);
4781 INIT_HLIST_NODE(&pool->hash_node);
4782 pool->refcnt = 1;
4783
4784 /* shouldn't fail above this point */
4785 pool->attrs = alloc_workqueue_attrs();
4786 if (!pool->attrs)
4787 return -ENOMEM;
4788
4789 wqattrs_clear_for_pool(pool->attrs);
4790
4791 return 0;
4792}
4793
4794#ifdef CONFIG_LOCKDEP
4795static void wq_init_lockdep(struct workqueue_struct *wq)
4796{
4797 char *lock_name;
4798
4799 lockdep_register_key(&wq->key);
4800 lock_name = kasprintf(GFP_KERNEL, "%s%s", "(wq_completion)", wq->name);
4801 if (!lock_name)
4802 lock_name = wq->name;
4803
4804 wq->lock_name = lock_name;
4805 wq->lockdep_map = &wq->__lockdep_map;
4806 lockdep_init_map(wq->lockdep_map, lock_name, &wq->key, 0);
4807}
4808
4809static void wq_unregister_lockdep(struct workqueue_struct *wq)
4810{
4811 if (wq->lockdep_map != &wq->__lockdep_map)
4812 return;
4813
4814 lockdep_unregister_key(&wq->key);
4815}
4816
4817static void wq_free_lockdep(struct workqueue_struct *wq)
4818{
4819 if (wq->lockdep_map != &wq->__lockdep_map)
4820 return;
4821
4822 if (wq->lock_name != wq->name)
4823 kfree(wq->lock_name);
4824}
4825#else
4826static void wq_init_lockdep(struct workqueue_struct *wq)
4827{
4828}
4829
4830static void wq_unregister_lockdep(struct workqueue_struct *wq)
4831{
4832}
4833
4834static void wq_free_lockdep(struct workqueue_struct *wq)
4835{
4836}
4837#endif
4838
4839static void free_node_nr_active(struct wq_node_nr_active **nna_ar)
4840{
4841 int node;
4842
4843 for_each_node(node) {
4844 kfree(nna_ar[node]);
4845 nna_ar[node] = NULL;
4846 }
4847
4848 kfree(nna_ar[nr_node_ids]);
4849 nna_ar[nr_node_ids] = NULL;
4850}
4851
4852static void init_node_nr_active(struct wq_node_nr_active *nna)
4853{
4854 nna->max = WQ_DFL_MIN_ACTIVE;
4855 atomic_set(&nna->nr, 0);
4856 raw_spin_lock_init(&nna->lock);
4857 INIT_LIST_HEAD(&nna->pending_pwqs);
4858}
4859
4860/*
4861 * Each node's nr_active counter will be accessed mostly from its own node and
4862 * should be allocated in the node.
4863 */
4864static int alloc_node_nr_active(struct wq_node_nr_active **nna_ar)
4865{
4866 struct wq_node_nr_active *nna;
4867 int node;
4868
4869 for_each_node(node) {
4870 nna = kzalloc_node(sizeof(*nna), GFP_KERNEL, node);
4871 if (!nna)
4872 goto err_free;
4873 init_node_nr_active(nna);
4874 nna_ar[node] = nna;
4875 }
4876
4877 /* [nr_node_ids] is used as the fallback */
4878 nna = kzalloc_node(sizeof(*nna), GFP_KERNEL, NUMA_NO_NODE);
4879 if (!nna)
4880 goto err_free;
4881 init_node_nr_active(nna);
4882 nna_ar[nr_node_ids] = nna;
4883
4884 return 0;
4885
4886err_free:
4887 free_node_nr_active(nna_ar);
4888 return -ENOMEM;
4889}
4890
4891static void rcu_free_wq(struct rcu_head *rcu)
4892{
4893 struct workqueue_struct *wq =
4894 container_of(rcu, struct workqueue_struct, rcu);
4895
4896 if (wq->flags & WQ_UNBOUND)
4897 free_node_nr_active(wq->node_nr_active);
4898
4899 wq_free_lockdep(wq);
4900 free_percpu(wq->cpu_pwq);
4901 free_workqueue_attrs(wq->unbound_attrs);
4902 kfree(wq);
4903}
4904
4905static void rcu_free_pool(struct rcu_head *rcu)
4906{
4907 struct worker_pool *pool = container_of(rcu, struct worker_pool, rcu);
4908
4909 ida_destroy(&pool->worker_ida);
4910 free_workqueue_attrs(pool->attrs);
4911 kfree(pool);
4912}
4913
4914/**
4915 * put_unbound_pool - put a worker_pool
4916 * @pool: worker_pool to put
4917 *
4918 * Put @pool. If its refcnt reaches zero, it gets destroyed in RCU
4919 * safe manner. get_unbound_pool() calls this function on its failure path
4920 * and this function should be able to release pools which went through,
4921 * successfully or not, init_worker_pool().
4922 *
4923 * Should be called with wq_pool_mutex held.
4924 */
4925static void put_unbound_pool(struct worker_pool *pool)
4926{
4927 struct worker *worker;
4928 LIST_HEAD(cull_list);
4929
4930 lockdep_assert_held(&wq_pool_mutex);
4931
4932 if (--pool->refcnt)
4933 return;
4934
4935 /* sanity checks */
4936 if (WARN_ON(!(pool->cpu < 0)) ||
4937 WARN_ON(!list_empty(&pool->worklist)))
4938 return;
4939
4940 /* release id and unhash */
4941 if (pool->id >= 0)
4942 idr_remove(&worker_pool_idr, pool->id);
4943 hash_del(&pool->hash_node);
4944
4945 /*
4946 * Become the manager and destroy all workers. This prevents
4947 * @pool's workers from blocking on attach_mutex. We're the last
4948 * manager and @pool gets freed with the flag set.
4949 *
4950 * Having a concurrent manager is quite unlikely to happen as we can
4951 * only get here with
4952 * pwq->refcnt == pool->refcnt == 0
4953 * which implies no work queued to the pool, which implies no worker can
4954 * become the manager. However a worker could have taken the role of
4955 * manager before the refcnts dropped to 0, since maybe_create_worker()
4956 * drops pool->lock
4957 */
4958 while (true) {
4959 rcuwait_wait_event(&manager_wait,
4960 !(pool->flags & POOL_MANAGER_ACTIVE),
4961 TASK_UNINTERRUPTIBLE);
4962
4963 mutex_lock(&wq_pool_attach_mutex);
4964 raw_spin_lock_irq(&pool->lock);
4965 if (!(pool->flags & POOL_MANAGER_ACTIVE)) {
4966 pool->flags |= POOL_MANAGER_ACTIVE;
4967 break;
4968 }
4969 raw_spin_unlock_irq(&pool->lock);
4970 mutex_unlock(&wq_pool_attach_mutex);
4971 }
4972
4973 while ((worker = first_idle_worker(pool)))
4974 set_worker_dying(worker, &cull_list);
4975 WARN_ON(pool->nr_workers || pool->nr_idle);
4976 raw_spin_unlock_irq(&pool->lock);
4977
4978 detach_dying_workers(&cull_list);
4979
4980 mutex_unlock(&wq_pool_attach_mutex);
4981
4982 reap_dying_workers(&cull_list);
4983
4984 /* shut down the timers */
4985 del_timer_sync(&pool->idle_timer);
4986 cancel_work_sync(&pool->idle_cull_work);
4987 del_timer_sync(&pool->mayday_timer);
4988
4989 /* RCU protected to allow dereferences from get_work_pool() */
4990 call_rcu(&pool->rcu, rcu_free_pool);
4991}
4992
4993/**
4994 * get_unbound_pool - get a worker_pool with the specified attributes
4995 * @attrs: the attributes of the worker_pool to get
4996 *
4997 * Obtain a worker_pool which has the same attributes as @attrs, bump the
4998 * reference count and return it. If there already is a matching
4999 * worker_pool, it will be used; otherwise, this function attempts to
5000 * create a new one.
5001 *
5002 * Should be called with wq_pool_mutex held.
5003 *
5004 * Return: On success, a worker_pool with the same attributes as @attrs.
5005 * On failure, %NULL.
5006 */
5007static struct worker_pool *get_unbound_pool(const struct workqueue_attrs *attrs)
5008{
5009 struct wq_pod_type *pt = &wq_pod_types[WQ_AFFN_NUMA];
5010 u32 hash = wqattrs_hash(attrs);
5011 struct worker_pool *pool;
5012 int pod, node = NUMA_NO_NODE;
5013
5014 lockdep_assert_held(&wq_pool_mutex);
5015
5016 /* do we already have a matching pool? */
5017 hash_for_each_possible(unbound_pool_hash, pool, hash_node, hash) {
5018 if (wqattrs_equal(pool->attrs, attrs)) {
5019 pool->refcnt++;
5020 return pool;
5021 }
5022 }
5023
5024 /* If __pod_cpumask is contained inside a NUMA pod, that's our node */
5025 for (pod = 0; pod < pt->nr_pods; pod++) {
5026 if (cpumask_subset(attrs->__pod_cpumask, pt->pod_cpus[pod])) {
5027 node = pt->pod_node[pod];
5028 break;
5029 }
5030 }
5031
5032 /* nope, create a new one */
5033 pool = kzalloc_node(sizeof(*pool), GFP_KERNEL, node);
5034 if (!pool || init_worker_pool(pool) < 0)
5035 goto fail;
5036
5037 pool->node = node;
5038 copy_workqueue_attrs(pool->attrs, attrs);
5039 wqattrs_clear_for_pool(pool->attrs);
5040
5041 if (worker_pool_assign_id(pool) < 0)
5042 goto fail;
5043
5044 /* create and start the initial worker */
5045 if (wq_online && !create_worker(pool))
5046 goto fail;
5047
5048 /* install */
5049 hash_add(unbound_pool_hash, &pool->hash_node, hash);
5050
5051 return pool;
5052fail:
5053 if (pool)
5054 put_unbound_pool(pool);
5055 return NULL;
5056}
5057
5058/*
5059 * Scheduled on pwq_release_worker by put_pwq() when an unbound pwq hits zero
5060 * refcnt and needs to be destroyed.
5061 */
5062static void pwq_release_workfn(struct kthread_work *work)
5063{
5064 struct pool_workqueue *pwq = container_of(work, struct pool_workqueue,
5065 release_work);
5066 struct workqueue_struct *wq = pwq->wq;
5067 struct worker_pool *pool = pwq->pool;
5068 bool is_last = false;
5069
5070 /*
5071 * When @pwq is not linked, it doesn't hold any reference to the
5072 * @wq, and @wq is invalid to access.
5073 */
5074 if (!list_empty(&pwq->pwqs_node)) {
5075 mutex_lock(&wq->mutex);
5076 list_del_rcu(&pwq->pwqs_node);
5077 is_last = list_empty(&wq->pwqs);
5078
5079 /*
5080 * For ordered workqueue with a plugged dfl_pwq, restart it now.
5081 */
5082 if (!is_last && (wq->flags & __WQ_ORDERED))
5083 unplug_oldest_pwq(wq);
5084
5085 mutex_unlock(&wq->mutex);
5086 }
5087
5088 if (wq->flags & WQ_UNBOUND) {
5089 mutex_lock(&wq_pool_mutex);
5090 put_unbound_pool(pool);
5091 mutex_unlock(&wq_pool_mutex);
5092 }
5093
5094 if (!list_empty(&pwq->pending_node)) {
5095 struct wq_node_nr_active *nna =
5096 wq_node_nr_active(pwq->wq, pwq->pool->node);
5097
5098 raw_spin_lock_irq(&nna->lock);
5099 list_del_init(&pwq->pending_node);
5100 raw_spin_unlock_irq(&nna->lock);
5101 }
5102
5103 kfree_rcu(pwq, rcu);
5104
5105 /*
5106 * If we're the last pwq going away, @wq is already dead and no one
5107 * is gonna access it anymore. Schedule RCU free.
5108 */
5109 if (is_last) {
5110 wq_unregister_lockdep(wq);
5111 call_rcu(&wq->rcu, rcu_free_wq);
5112 }
5113}
5114
5115/* initialize newly allocated @pwq which is associated with @wq and @pool */
5116static void init_pwq(struct pool_workqueue *pwq, struct workqueue_struct *wq,
5117 struct worker_pool *pool)
5118{
5119 BUG_ON((unsigned long)pwq & ~WORK_STRUCT_PWQ_MASK);
5120
5121 memset(pwq, 0, sizeof(*pwq));
5122
5123 pwq->pool = pool;
5124 pwq->wq = wq;
5125 pwq->flush_color = -1;
5126 pwq->refcnt = 1;
5127 INIT_LIST_HEAD(&pwq->inactive_works);
5128 INIT_LIST_HEAD(&pwq->pending_node);
5129 INIT_LIST_HEAD(&pwq->pwqs_node);
5130 INIT_LIST_HEAD(&pwq->mayday_node);
5131 kthread_init_work(&pwq->release_work, pwq_release_workfn);
5132}
5133
5134/* sync @pwq with the current state of its associated wq and link it */
5135static void link_pwq(struct pool_workqueue *pwq)
5136{
5137 struct workqueue_struct *wq = pwq->wq;
5138
5139 lockdep_assert_held(&wq->mutex);
5140
5141 /* may be called multiple times, ignore if already linked */
5142 if (!list_empty(&pwq->pwqs_node))
5143 return;
5144
5145 /* set the matching work_color */
5146 pwq->work_color = wq->work_color;
5147
5148 /* link in @pwq */
5149 list_add_tail_rcu(&pwq->pwqs_node, &wq->pwqs);
5150}
5151
5152/* obtain a pool matching @attr and create a pwq associating the pool and @wq */
5153static struct pool_workqueue *alloc_unbound_pwq(struct workqueue_struct *wq,
5154 const struct workqueue_attrs *attrs)
5155{
5156 struct worker_pool *pool;
5157 struct pool_workqueue *pwq;
5158
5159 lockdep_assert_held(&wq_pool_mutex);
5160
5161 pool = get_unbound_pool(attrs);
5162 if (!pool)
5163 return NULL;
5164
5165 pwq = kmem_cache_alloc_node(pwq_cache, GFP_KERNEL, pool->node);
5166 if (!pwq) {
5167 put_unbound_pool(pool);
5168 return NULL;
5169 }
5170
5171 init_pwq(pwq, wq, pool);
5172 return pwq;
5173}
5174
5175static void apply_wqattrs_lock(void)
5176{
5177 mutex_lock(&wq_pool_mutex);
5178}
5179
5180static void apply_wqattrs_unlock(void)
5181{
5182 mutex_unlock(&wq_pool_mutex);
5183}
5184
5185/**
5186 * wq_calc_pod_cpumask - calculate a wq_attrs' cpumask for a pod
5187 * @attrs: the wq_attrs of the default pwq of the target workqueue
5188 * @cpu: the target CPU
5189 *
5190 * Calculate the cpumask a workqueue with @attrs should use on @pod.
5191 * The result is stored in @attrs->__pod_cpumask.
5192 *
5193 * If pod affinity is not enabled, @attrs->cpumask is always used. If enabled
5194 * and @pod has online CPUs requested by @attrs, the returned cpumask is the
5195 * intersection of the possible CPUs of @pod and @attrs->cpumask.
5196 *
5197 * The caller is responsible for ensuring that the cpumask of @pod stays stable.
5198 */
5199static void wq_calc_pod_cpumask(struct workqueue_attrs *attrs, int cpu)
5200{
5201 const struct wq_pod_type *pt = wqattrs_pod_type(attrs);
5202 int pod = pt->cpu_pod[cpu];
5203
5204 /* calculate possible CPUs in @pod that @attrs wants */
5205 cpumask_and(attrs->__pod_cpumask, pt->pod_cpus[pod], attrs->cpumask);
5206 /* does @pod have any online CPUs @attrs wants? */
5207 if (!cpumask_intersects(attrs->__pod_cpumask, wq_online_cpumask)) {
5208 cpumask_copy(attrs->__pod_cpumask, attrs->cpumask);
5209 return;
5210 }
5211}
5212
5213/* install @pwq into @wq and return the old pwq, @cpu < 0 for dfl_pwq */
5214static struct pool_workqueue *install_unbound_pwq(struct workqueue_struct *wq,
5215 int cpu, struct pool_workqueue *pwq)
5216{
5217 struct pool_workqueue __rcu **slot = unbound_pwq_slot(wq, cpu);
5218 struct pool_workqueue *old_pwq;
5219
5220 lockdep_assert_held(&wq_pool_mutex);
5221 lockdep_assert_held(&wq->mutex);
5222
5223 /* link_pwq() can handle duplicate calls */
5224 link_pwq(pwq);
5225
5226 old_pwq = rcu_access_pointer(*slot);
5227 rcu_assign_pointer(*slot, pwq);
5228 return old_pwq;
5229}
5230
5231/* context to store the prepared attrs & pwqs before applying */
5232struct apply_wqattrs_ctx {
5233 struct workqueue_struct *wq; /* target workqueue */
5234 struct workqueue_attrs *attrs; /* attrs to apply */
5235 struct list_head list; /* queued for batching commit */
5236 struct pool_workqueue *dfl_pwq;
5237 struct pool_workqueue *pwq_tbl[];
5238};
5239
5240/* free the resources after success or abort */
5241static void apply_wqattrs_cleanup(struct apply_wqattrs_ctx *ctx)
5242{
5243 if (ctx) {
5244 int cpu;
5245
5246 for_each_possible_cpu(cpu)
5247 put_pwq_unlocked(ctx->pwq_tbl[cpu]);
5248 put_pwq_unlocked(ctx->dfl_pwq);
5249
5250 free_workqueue_attrs(ctx->attrs);
5251
5252 kfree(ctx);
5253 }
5254}
5255
5256/* allocate the attrs and pwqs for later installation */
5257static struct apply_wqattrs_ctx *
5258apply_wqattrs_prepare(struct workqueue_struct *wq,
5259 const struct workqueue_attrs *attrs,
5260 const cpumask_var_t unbound_cpumask)
5261{
5262 struct apply_wqattrs_ctx *ctx;
5263 struct workqueue_attrs *new_attrs;
5264 int cpu;
5265
5266 lockdep_assert_held(&wq_pool_mutex);
5267
5268 if (WARN_ON(attrs->affn_scope < 0 ||
5269 attrs->affn_scope >= WQ_AFFN_NR_TYPES))
5270 return ERR_PTR(-EINVAL);
5271
5272 ctx = kzalloc(struct_size(ctx, pwq_tbl, nr_cpu_ids), GFP_KERNEL);
5273
5274 new_attrs = alloc_workqueue_attrs();
5275 if (!ctx || !new_attrs)
5276 goto out_free;
5277
5278 /*
5279 * If something goes wrong during CPU up/down, we'll fall back to
5280 * the default pwq covering whole @attrs->cpumask. Always create
5281 * it even if we don't use it immediately.
5282 */
5283 copy_workqueue_attrs(new_attrs, attrs);
5284 wqattrs_actualize_cpumask(new_attrs, unbound_cpumask);
5285 cpumask_copy(new_attrs->__pod_cpumask, new_attrs->cpumask);
5286 ctx->dfl_pwq = alloc_unbound_pwq(wq, new_attrs);
5287 if (!ctx->dfl_pwq)
5288 goto out_free;
5289
5290 for_each_possible_cpu(cpu) {
5291 if (new_attrs->ordered) {
5292 ctx->dfl_pwq->refcnt++;
5293 ctx->pwq_tbl[cpu] = ctx->dfl_pwq;
5294 } else {
5295 wq_calc_pod_cpumask(new_attrs, cpu);
5296 ctx->pwq_tbl[cpu] = alloc_unbound_pwq(wq, new_attrs);
5297 if (!ctx->pwq_tbl[cpu])
5298 goto out_free;
5299 }
5300 }
5301
5302 /* save the user configured attrs and sanitize it. */
5303 copy_workqueue_attrs(new_attrs, attrs);
5304 cpumask_and(new_attrs->cpumask, new_attrs->cpumask, cpu_possible_mask);
5305 cpumask_copy(new_attrs->__pod_cpumask, new_attrs->cpumask);
5306 ctx->attrs = new_attrs;
5307
5308 /*
5309 * For initialized ordered workqueues, there should only be one pwq
5310 * (dfl_pwq). Set the plugged flag of ctx->dfl_pwq to suspend execution
5311 * of newly queued work items until execution of older work items in
5312 * the old pwq's have completed.
5313 */
5314 if ((wq->flags & __WQ_ORDERED) && !list_empty(&wq->pwqs))
5315 ctx->dfl_pwq->plugged = true;
5316
5317 ctx->wq = wq;
5318 return ctx;
5319
5320out_free:
5321 free_workqueue_attrs(new_attrs);
5322 apply_wqattrs_cleanup(ctx);
5323 return ERR_PTR(-ENOMEM);
5324}
5325
5326/* set attrs and install prepared pwqs, @ctx points to old pwqs on return */
5327static void apply_wqattrs_commit(struct apply_wqattrs_ctx *ctx)
5328{
5329 int cpu;
5330
5331 /* all pwqs have been created successfully, let's install'em */
5332 mutex_lock(&ctx->wq->mutex);
5333
5334 copy_workqueue_attrs(ctx->wq->unbound_attrs, ctx->attrs);
5335
5336 /* save the previous pwqs and install the new ones */
5337 for_each_possible_cpu(cpu)
5338 ctx->pwq_tbl[cpu] = install_unbound_pwq(ctx->wq, cpu,
5339 ctx->pwq_tbl[cpu]);
5340 ctx->dfl_pwq = install_unbound_pwq(ctx->wq, -1, ctx->dfl_pwq);
5341
5342 /* update node_nr_active->max */
5343 wq_update_node_max_active(ctx->wq, -1);
5344
5345 /* rescuer needs to respect wq cpumask changes */
5346 if (ctx->wq->rescuer)
5347 set_cpus_allowed_ptr(ctx->wq->rescuer->task,
5348 unbound_effective_cpumask(ctx->wq));
5349
5350 mutex_unlock(&ctx->wq->mutex);
5351}
5352
5353static int apply_workqueue_attrs_locked(struct workqueue_struct *wq,
5354 const struct workqueue_attrs *attrs)
5355{
5356 struct apply_wqattrs_ctx *ctx;
5357
5358 /* only unbound workqueues can change attributes */
5359 if (WARN_ON(!(wq->flags & WQ_UNBOUND)))
5360 return -EINVAL;
5361
5362 ctx = apply_wqattrs_prepare(wq, attrs, wq_unbound_cpumask);
5363 if (IS_ERR(ctx))
5364 return PTR_ERR(ctx);
5365
5366 /* the ctx has been prepared successfully, let's commit it */
5367 apply_wqattrs_commit(ctx);
5368 apply_wqattrs_cleanup(ctx);
5369
5370 return 0;
5371}
5372
5373/**
5374 * apply_workqueue_attrs - apply new workqueue_attrs to an unbound workqueue
5375 * @wq: the target workqueue
5376 * @attrs: the workqueue_attrs to apply, allocated with alloc_workqueue_attrs()
5377 *
5378 * Apply @attrs to an unbound workqueue @wq. Unless disabled, this function maps
5379 * a separate pwq to each CPU pod with possibles CPUs in @attrs->cpumask so that
5380 * work items are affine to the pod it was issued on. Older pwqs are released as
5381 * in-flight work items finish. Note that a work item which repeatedly requeues
5382 * itself back-to-back will stay on its current pwq.
5383 *
5384 * Performs GFP_KERNEL allocations.
5385 *
5386 * Return: 0 on success and -errno on failure.
5387 */
5388int apply_workqueue_attrs(struct workqueue_struct *wq,
5389 const struct workqueue_attrs *attrs)
5390{
5391 int ret;
5392
5393 mutex_lock(&wq_pool_mutex);
5394 ret = apply_workqueue_attrs_locked(wq, attrs);
5395 mutex_unlock(&wq_pool_mutex);
5396
5397 return ret;
5398}
5399
5400/**
5401 * unbound_wq_update_pwq - update a pwq slot for CPU hot[un]plug
5402 * @wq: the target workqueue
5403 * @cpu: the CPU to update the pwq slot for
5404 *
5405 * This function is to be called from %CPU_DOWN_PREPARE, %CPU_ONLINE and
5406 * %CPU_DOWN_FAILED. @cpu is in the same pod of the CPU being hot[un]plugged.
5407 *
5408 *
5409 * If pod affinity can't be adjusted due to memory allocation failure, it falls
5410 * back to @wq->dfl_pwq which may not be optimal but is always correct.
5411 *
5412 * Note that when the last allowed CPU of a pod goes offline for a workqueue
5413 * with a cpumask spanning multiple pods, the workers which were already
5414 * executing the work items for the workqueue will lose their CPU affinity and
5415 * may execute on any CPU. This is similar to how per-cpu workqueues behave on
5416 * CPU_DOWN. If a workqueue user wants strict affinity, it's the user's
5417 * responsibility to flush the work item from CPU_DOWN_PREPARE.
5418 */
5419static void unbound_wq_update_pwq(struct workqueue_struct *wq, int cpu)
5420{
5421 struct pool_workqueue *old_pwq = NULL, *pwq;
5422 struct workqueue_attrs *target_attrs;
5423
5424 lockdep_assert_held(&wq_pool_mutex);
5425
5426 if (!(wq->flags & WQ_UNBOUND) || wq->unbound_attrs->ordered)
5427 return;
5428
5429 /*
5430 * We don't wanna alloc/free wq_attrs for each wq for each CPU.
5431 * Let's use a preallocated one. The following buf is protected by
5432 * CPU hotplug exclusion.
5433 */
5434 target_attrs = unbound_wq_update_pwq_attrs_buf;
5435
5436 copy_workqueue_attrs(target_attrs, wq->unbound_attrs);
5437 wqattrs_actualize_cpumask(target_attrs, wq_unbound_cpumask);
5438
5439 /* nothing to do if the target cpumask matches the current pwq */
5440 wq_calc_pod_cpumask(target_attrs, cpu);
5441 if (wqattrs_equal(target_attrs, unbound_pwq(wq, cpu)->pool->attrs))
5442 return;
5443
5444 /* create a new pwq */
5445 pwq = alloc_unbound_pwq(wq, target_attrs);
5446 if (!pwq) {
5447 pr_warn("workqueue: allocation failed while updating CPU pod affinity of \"%s\"\n",
5448 wq->name);
5449 goto use_dfl_pwq;
5450 }
5451
5452 /* Install the new pwq. */
5453 mutex_lock(&wq->mutex);
5454 old_pwq = install_unbound_pwq(wq, cpu, pwq);
5455 goto out_unlock;
5456
5457use_dfl_pwq:
5458 mutex_lock(&wq->mutex);
5459 pwq = unbound_pwq(wq, -1);
5460 raw_spin_lock_irq(&pwq->pool->lock);
5461 get_pwq(pwq);
5462 raw_spin_unlock_irq(&pwq->pool->lock);
5463 old_pwq = install_unbound_pwq(wq, cpu, pwq);
5464out_unlock:
5465 mutex_unlock(&wq->mutex);
5466 put_pwq_unlocked(old_pwq);
5467}
5468
5469static int alloc_and_link_pwqs(struct workqueue_struct *wq)
5470{
5471 bool highpri = wq->flags & WQ_HIGHPRI;
5472 int cpu, ret;
5473
5474 lockdep_assert_held(&wq_pool_mutex);
5475
5476 wq->cpu_pwq = alloc_percpu(struct pool_workqueue *);
5477 if (!wq->cpu_pwq)
5478 goto enomem;
5479
5480 if (!(wq->flags & WQ_UNBOUND)) {
5481 struct worker_pool __percpu *pools;
5482
5483 if (wq->flags & WQ_BH)
5484 pools = bh_worker_pools;
5485 else
5486 pools = cpu_worker_pools;
5487
5488 for_each_possible_cpu(cpu) {
5489 struct pool_workqueue **pwq_p;
5490 struct worker_pool *pool;
5491
5492 pool = &(per_cpu_ptr(pools, cpu)[highpri]);
5493 pwq_p = per_cpu_ptr(wq->cpu_pwq, cpu);
5494
5495 *pwq_p = kmem_cache_alloc_node(pwq_cache, GFP_KERNEL,
5496 pool->node);
5497 if (!*pwq_p)
5498 goto enomem;
5499
5500 init_pwq(*pwq_p, wq, pool);
5501
5502 mutex_lock(&wq->mutex);
5503 link_pwq(*pwq_p);
5504 mutex_unlock(&wq->mutex);
5505 }
5506 return 0;
5507 }
5508
5509 if (wq->flags & __WQ_ORDERED) {
5510 struct pool_workqueue *dfl_pwq;
5511
5512 ret = apply_workqueue_attrs_locked(wq, ordered_wq_attrs[highpri]);
5513 /* there should only be single pwq for ordering guarantee */
5514 dfl_pwq = rcu_access_pointer(wq->dfl_pwq);
5515 WARN(!ret && (wq->pwqs.next != &dfl_pwq->pwqs_node ||
5516 wq->pwqs.prev != &dfl_pwq->pwqs_node),
5517 "ordering guarantee broken for workqueue %s\n", wq->name);
5518 } else {
5519 ret = apply_workqueue_attrs_locked(wq, unbound_std_wq_attrs[highpri]);
5520 }
5521
5522 return ret;
5523
5524enomem:
5525 if (wq->cpu_pwq) {
5526 for_each_possible_cpu(cpu) {
5527 struct pool_workqueue *pwq = *per_cpu_ptr(wq->cpu_pwq, cpu);
5528
5529 if (pwq)
5530 kmem_cache_free(pwq_cache, pwq);
5531 }
5532 free_percpu(wq->cpu_pwq);
5533 wq->cpu_pwq = NULL;
5534 }
5535 return -ENOMEM;
5536}
5537
5538static int wq_clamp_max_active(int max_active, unsigned int flags,
5539 const char *name)
5540{
5541 if (max_active < 1 || max_active > WQ_MAX_ACTIVE)
5542 pr_warn("workqueue: max_active %d requested for %s is out of range, clamping between %d and %d\n",
5543 max_active, name, 1, WQ_MAX_ACTIVE);
5544
5545 return clamp_val(max_active, 1, WQ_MAX_ACTIVE);
5546}
5547
5548/*
5549 * Workqueues which may be used during memory reclaim should have a rescuer
5550 * to guarantee forward progress.
5551 */
5552static int init_rescuer(struct workqueue_struct *wq)
5553{
5554 struct worker *rescuer;
5555 char id_buf[WORKER_ID_LEN];
5556 int ret;
5557
5558 lockdep_assert_held(&wq_pool_mutex);
5559
5560 if (!(wq->flags & WQ_MEM_RECLAIM))
5561 return 0;
5562
5563 rescuer = alloc_worker(NUMA_NO_NODE);
5564 if (!rescuer) {
5565 pr_err("workqueue: Failed to allocate a rescuer for wq \"%s\"\n",
5566 wq->name);
5567 return -ENOMEM;
5568 }
5569
5570 rescuer->rescue_wq = wq;
5571 format_worker_id(id_buf, sizeof(id_buf), rescuer, NULL);
5572
5573 rescuer->task = kthread_create(rescuer_thread, rescuer, "%s", id_buf);
5574 if (IS_ERR(rescuer->task)) {
5575 ret = PTR_ERR(rescuer->task);
5576 pr_err("workqueue: Failed to create a rescuer kthread for wq \"%s\": %pe",
5577 wq->name, ERR_PTR(ret));
5578 kfree(rescuer);
5579 return ret;
5580 }
5581
5582 wq->rescuer = rescuer;
5583 if (wq->flags & WQ_UNBOUND)
5584 kthread_bind_mask(rescuer->task, unbound_effective_cpumask(wq));
5585 else
5586 kthread_bind_mask(rescuer->task, cpu_possible_mask);
5587 wake_up_process(rescuer->task);
5588
5589 return 0;
5590}
5591
5592/**
5593 * wq_adjust_max_active - update a wq's max_active to the current setting
5594 * @wq: target workqueue
5595 *
5596 * If @wq isn't freezing, set @wq->max_active to the saved_max_active and
5597 * activate inactive work items accordingly. If @wq is freezing, clear
5598 * @wq->max_active to zero.
5599 */
5600static void wq_adjust_max_active(struct workqueue_struct *wq)
5601{
5602 bool activated;
5603 int new_max, new_min;
5604
5605 lockdep_assert_held(&wq->mutex);
5606
5607 if ((wq->flags & WQ_FREEZABLE) && workqueue_freezing) {
5608 new_max = 0;
5609 new_min = 0;
5610 } else {
5611 new_max = wq->saved_max_active;
5612 new_min = wq->saved_min_active;
5613 }
5614
5615 if (wq->max_active == new_max && wq->min_active == new_min)
5616 return;
5617
5618 /*
5619 * Update @wq->max/min_active and then kick inactive work items if more
5620 * active work items are allowed. This doesn't break work item ordering
5621 * because new work items are always queued behind existing inactive
5622 * work items if there are any.
5623 */
5624 WRITE_ONCE(wq->max_active, new_max);
5625 WRITE_ONCE(wq->min_active, new_min);
5626
5627 if (wq->flags & WQ_UNBOUND)
5628 wq_update_node_max_active(wq, -1);
5629
5630 if (new_max == 0)
5631 return;
5632
5633 /*
5634 * Round-robin through pwq's activating the first inactive work item
5635 * until max_active is filled.
5636 */
5637 do {
5638 struct pool_workqueue *pwq;
5639
5640 activated = false;
5641 for_each_pwq(pwq, wq) {
5642 unsigned long irq_flags;
5643
5644 /* can be called during early boot w/ irq disabled */
5645 raw_spin_lock_irqsave(&pwq->pool->lock, irq_flags);
5646 if (pwq_activate_first_inactive(pwq, true)) {
5647 activated = true;
5648 kick_pool(pwq->pool);
5649 }
5650 raw_spin_unlock_irqrestore(&pwq->pool->lock, irq_flags);
5651 }
5652 } while (activated);
5653}
5654
5655__printf(1, 0)
5656static struct workqueue_struct *__alloc_workqueue(const char *fmt,
5657 unsigned int flags,
5658 int max_active, va_list args)
5659{
5660 struct workqueue_struct *wq;
5661 size_t wq_size;
5662 int name_len;
5663
5664 if (flags & WQ_BH) {
5665 if (WARN_ON_ONCE(flags & ~__WQ_BH_ALLOWS))
5666 return NULL;
5667 if (WARN_ON_ONCE(max_active))
5668 return NULL;
5669 }
5670
5671 /* see the comment above the definition of WQ_POWER_EFFICIENT */
5672 if ((flags & WQ_POWER_EFFICIENT) && wq_power_efficient)
5673 flags |= WQ_UNBOUND;
5674
5675 /* allocate wq and format name */
5676 if (flags & WQ_UNBOUND)
5677 wq_size = struct_size(wq, node_nr_active, nr_node_ids + 1);
5678 else
5679 wq_size = sizeof(*wq);
5680
5681 wq = kzalloc(wq_size, GFP_KERNEL);
5682 if (!wq)
5683 return NULL;
5684
5685 if (flags & WQ_UNBOUND) {
5686 wq->unbound_attrs = alloc_workqueue_attrs();
5687 if (!wq->unbound_attrs)
5688 goto err_free_wq;
5689 }
5690
5691 name_len = vsnprintf(wq->name, sizeof(wq->name), fmt, args);
5692
5693 if (name_len >= WQ_NAME_LEN)
5694 pr_warn_once("workqueue: name exceeds WQ_NAME_LEN. Truncating to: %s\n",
5695 wq->name);
5696
5697 if (flags & WQ_BH) {
5698 /*
5699 * BH workqueues always share a single execution context per CPU
5700 * and don't impose any max_active limit.
5701 */
5702 max_active = INT_MAX;
5703 } else {
5704 max_active = max_active ?: WQ_DFL_ACTIVE;
5705 max_active = wq_clamp_max_active(max_active, flags, wq->name);
5706 }
5707
5708 /* init wq */
5709 wq->flags = flags;
5710 wq->max_active = max_active;
5711 wq->min_active = min(max_active, WQ_DFL_MIN_ACTIVE);
5712 wq->saved_max_active = wq->max_active;
5713 wq->saved_min_active = wq->min_active;
5714 mutex_init(&wq->mutex);
5715 atomic_set(&wq->nr_pwqs_to_flush, 0);
5716 INIT_LIST_HEAD(&wq->pwqs);
5717 INIT_LIST_HEAD(&wq->flusher_queue);
5718 INIT_LIST_HEAD(&wq->flusher_overflow);
5719 INIT_LIST_HEAD(&wq->maydays);
5720
5721 INIT_LIST_HEAD(&wq->list);
5722
5723 if (flags & WQ_UNBOUND) {
5724 if (alloc_node_nr_active(wq->node_nr_active) < 0)
5725 goto err_free_wq;
5726 }
5727
5728 /*
5729 * wq_pool_mutex protects the workqueues list, allocations of PWQs,
5730 * and the global freeze state.
5731 */
5732 apply_wqattrs_lock();
5733
5734 if (alloc_and_link_pwqs(wq) < 0)
5735 goto err_unlock_free_node_nr_active;
5736
5737 mutex_lock(&wq->mutex);
5738 wq_adjust_max_active(wq);
5739 mutex_unlock(&wq->mutex);
5740
5741 list_add_tail_rcu(&wq->list, &workqueues);
5742
5743 if (wq_online && init_rescuer(wq) < 0)
5744 goto err_unlock_destroy;
5745
5746 apply_wqattrs_unlock();
5747
5748 if ((wq->flags & WQ_SYSFS) && workqueue_sysfs_register(wq))
5749 goto err_destroy;
5750
5751 return wq;
5752
5753err_unlock_free_node_nr_active:
5754 apply_wqattrs_unlock();
5755 /*
5756 * Failed alloc_and_link_pwqs() may leave pending pwq->release_work,
5757 * flushing the pwq_release_worker ensures that the pwq_release_workfn()
5758 * completes before calling kfree(wq).
5759 */
5760 if (wq->flags & WQ_UNBOUND) {
5761 kthread_flush_worker(pwq_release_worker);
5762 free_node_nr_active(wq->node_nr_active);
5763 }
5764err_free_wq:
5765 free_workqueue_attrs(wq->unbound_attrs);
5766 kfree(wq);
5767 return NULL;
5768err_unlock_destroy:
5769 apply_wqattrs_unlock();
5770err_destroy:
5771 destroy_workqueue(wq);
5772 return NULL;
5773}
5774
5775__printf(1, 4)
5776struct workqueue_struct *alloc_workqueue(const char *fmt,
5777 unsigned int flags,
5778 int max_active, ...)
5779{
5780 struct workqueue_struct *wq;
5781 va_list args;
5782
5783 va_start(args, max_active);
5784 wq = __alloc_workqueue(fmt, flags, max_active, args);
5785 va_end(args);
5786 if (!wq)
5787 return NULL;
5788
5789 wq_init_lockdep(wq);
5790
5791 return wq;
5792}
5793EXPORT_SYMBOL_GPL(alloc_workqueue);
5794
5795#ifdef CONFIG_LOCKDEP
5796__printf(1, 5)
5797struct workqueue_struct *
5798alloc_workqueue_lockdep_map(const char *fmt, unsigned int flags,
5799 int max_active, struct lockdep_map *lockdep_map, ...)
5800{
5801 struct workqueue_struct *wq;
5802 va_list args;
5803
5804 va_start(args, lockdep_map);
5805 wq = __alloc_workqueue(fmt, flags, max_active, args);
5806 va_end(args);
5807 if (!wq)
5808 return NULL;
5809
5810 wq->lockdep_map = lockdep_map;
5811
5812 return wq;
5813}
5814EXPORT_SYMBOL_GPL(alloc_workqueue_lockdep_map);
5815#endif
5816
5817static bool pwq_busy(struct pool_workqueue *pwq)
5818{
5819 int i;
5820
5821 for (i = 0; i < WORK_NR_COLORS; i++)
5822 if (pwq->nr_in_flight[i])
5823 return true;
5824
5825 if ((pwq != rcu_access_pointer(pwq->wq->dfl_pwq)) && (pwq->refcnt > 1))
5826 return true;
5827 if (!pwq_is_empty(pwq))
5828 return true;
5829
5830 return false;
5831}
5832
5833/**
5834 * destroy_workqueue - safely terminate a workqueue
5835 * @wq: target workqueue
5836 *
5837 * Safely destroy a workqueue. All work currently pending will be done first.
5838 */
5839void destroy_workqueue(struct workqueue_struct *wq)
5840{
5841 struct pool_workqueue *pwq;
5842 int cpu;
5843
5844 /*
5845 * Remove it from sysfs first so that sanity check failure doesn't
5846 * lead to sysfs name conflicts.
5847 */
5848 workqueue_sysfs_unregister(wq);
5849
5850 /* mark the workqueue destruction is in progress */
5851 mutex_lock(&wq->mutex);
5852 wq->flags |= __WQ_DESTROYING;
5853 mutex_unlock(&wq->mutex);
5854
5855 /* drain it before proceeding with destruction */
5856 drain_workqueue(wq);
5857
5858 /* kill rescuer, if sanity checks fail, leave it w/o rescuer */
5859 if (wq->rescuer) {
5860 struct worker *rescuer = wq->rescuer;
5861
5862 /* this prevents new queueing */
5863 raw_spin_lock_irq(&wq_mayday_lock);
5864 wq->rescuer = NULL;
5865 raw_spin_unlock_irq(&wq_mayday_lock);
5866
5867 /* rescuer will empty maydays list before exiting */
5868 kthread_stop(rescuer->task);
5869 kfree(rescuer);
5870 }
5871
5872 /*
5873 * Sanity checks - grab all the locks so that we wait for all
5874 * in-flight operations which may do put_pwq().
5875 */
5876 mutex_lock(&wq_pool_mutex);
5877 mutex_lock(&wq->mutex);
5878 for_each_pwq(pwq, wq) {
5879 raw_spin_lock_irq(&pwq->pool->lock);
5880 if (WARN_ON(pwq_busy(pwq))) {
5881 pr_warn("%s: %s has the following busy pwq\n",
5882 __func__, wq->name);
5883 show_pwq(pwq);
5884 raw_spin_unlock_irq(&pwq->pool->lock);
5885 mutex_unlock(&wq->mutex);
5886 mutex_unlock(&wq_pool_mutex);
5887 show_one_workqueue(wq);
5888 return;
5889 }
5890 raw_spin_unlock_irq(&pwq->pool->lock);
5891 }
5892 mutex_unlock(&wq->mutex);
5893
5894 /*
5895 * wq list is used to freeze wq, remove from list after
5896 * flushing is complete in case freeze races us.
5897 */
5898 list_del_rcu(&wq->list);
5899 mutex_unlock(&wq_pool_mutex);
5900
5901 /*
5902 * We're the sole accessor of @wq. Directly access cpu_pwq and dfl_pwq
5903 * to put the base refs. @wq will be auto-destroyed from the last
5904 * pwq_put. RCU read lock prevents @wq from going away from under us.
5905 */
5906 rcu_read_lock();
5907
5908 for_each_possible_cpu(cpu) {
5909 put_pwq_unlocked(unbound_pwq(wq, cpu));
5910 RCU_INIT_POINTER(*unbound_pwq_slot(wq, cpu), NULL);
5911 }
5912
5913 put_pwq_unlocked(unbound_pwq(wq, -1));
5914 RCU_INIT_POINTER(*unbound_pwq_slot(wq, -1), NULL);
5915
5916 rcu_read_unlock();
5917}
5918EXPORT_SYMBOL_GPL(destroy_workqueue);
5919
5920/**
5921 * workqueue_set_max_active - adjust max_active of a workqueue
5922 * @wq: target workqueue
5923 * @max_active: new max_active value.
5924 *
5925 * Set max_active of @wq to @max_active. See the alloc_workqueue() function
5926 * comment.
5927 *
5928 * CONTEXT:
5929 * Don't call from IRQ context.
5930 */
5931void workqueue_set_max_active(struct workqueue_struct *wq, int max_active)
5932{
5933 /* max_active doesn't mean anything for BH workqueues */
5934 if (WARN_ON(wq->flags & WQ_BH))
5935 return;
5936 /* disallow meddling with max_active for ordered workqueues */
5937 if (WARN_ON(wq->flags & __WQ_ORDERED))
5938 return;
5939
5940 max_active = wq_clamp_max_active(max_active, wq->flags, wq->name);
5941
5942 mutex_lock(&wq->mutex);
5943
5944 wq->saved_max_active = max_active;
5945 if (wq->flags & WQ_UNBOUND)
5946 wq->saved_min_active = min(wq->saved_min_active, max_active);
5947
5948 wq_adjust_max_active(wq);
5949
5950 mutex_unlock(&wq->mutex);
5951}
5952EXPORT_SYMBOL_GPL(workqueue_set_max_active);
5953
5954/**
5955 * workqueue_set_min_active - adjust min_active of an unbound workqueue
5956 * @wq: target unbound workqueue
5957 * @min_active: new min_active value
5958 *
5959 * Set min_active of an unbound workqueue. Unlike other types of workqueues, an
5960 * unbound workqueue is not guaranteed to be able to process max_active
5961 * interdependent work items. Instead, an unbound workqueue is guaranteed to be
5962 * able to process min_active number of interdependent work items which is
5963 * %WQ_DFL_MIN_ACTIVE by default.
5964 *
5965 * Use this function to adjust the min_active value between 0 and the current
5966 * max_active.
5967 */
5968void workqueue_set_min_active(struct workqueue_struct *wq, int min_active)
5969{
5970 /* min_active is only meaningful for non-ordered unbound workqueues */
5971 if (WARN_ON((wq->flags & (WQ_BH | WQ_UNBOUND | __WQ_ORDERED)) !=
5972 WQ_UNBOUND))
5973 return;
5974
5975 mutex_lock(&wq->mutex);
5976 wq->saved_min_active = clamp(min_active, 0, wq->saved_max_active);
5977 wq_adjust_max_active(wq);
5978 mutex_unlock(&wq->mutex);
5979}
5980
5981/**
5982 * current_work - retrieve %current task's work struct
5983 *
5984 * Determine if %current task is a workqueue worker and what it's working on.
5985 * Useful to find out the context that the %current task is running in.
5986 *
5987 * Return: work struct if %current task is a workqueue worker, %NULL otherwise.
5988 */
5989struct work_struct *current_work(void)
5990{
5991 struct worker *worker = current_wq_worker();
5992
5993 return worker ? worker->current_work : NULL;
5994}
5995EXPORT_SYMBOL(current_work);
5996
5997/**
5998 * current_is_workqueue_rescuer - is %current workqueue rescuer?
5999 *
6000 * Determine whether %current is a workqueue rescuer. Can be used from
6001 * work functions to determine whether it's being run off the rescuer task.
6002 *
6003 * Return: %true if %current is a workqueue rescuer. %false otherwise.
6004 */
6005bool current_is_workqueue_rescuer(void)
6006{
6007 struct worker *worker = current_wq_worker();
6008
6009 return worker && worker->rescue_wq;
6010}
6011
6012/**
6013 * workqueue_congested - test whether a workqueue is congested
6014 * @cpu: CPU in question
6015 * @wq: target workqueue
6016 *
6017 * Test whether @wq's cpu workqueue for @cpu is congested. There is
6018 * no synchronization around this function and the test result is
6019 * unreliable and only useful as advisory hints or for debugging.
6020 *
6021 * If @cpu is WORK_CPU_UNBOUND, the test is performed on the local CPU.
6022 *
6023 * With the exception of ordered workqueues, all workqueues have per-cpu
6024 * pool_workqueues, each with its own congested state. A workqueue being
6025 * congested on one CPU doesn't mean that the workqueue is contested on any
6026 * other CPUs.
6027 *
6028 * Return:
6029 * %true if congested, %false otherwise.
6030 */
6031bool workqueue_congested(int cpu, struct workqueue_struct *wq)
6032{
6033 struct pool_workqueue *pwq;
6034 bool ret;
6035
6036 rcu_read_lock();
6037 preempt_disable();
6038
6039 if (cpu == WORK_CPU_UNBOUND)
6040 cpu = smp_processor_id();
6041
6042 pwq = *per_cpu_ptr(wq->cpu_pwq, cpu);
6043 ret = !list_empty(&pwq->inactive_works);
6044
6045 preempt_enable();
6046 rcu_read_unlock();
6047
6048 return ret;
6049}
6050EXPORT_SYMBOL_GPL(workqueue_congested);
6051
6052/**
6053 * work_busy - test whether a work is currently pending or running
6054 * @work: the work to be tested
6055 *
6056 * Test whether @work is currently pending or running. There is no
6057 * synchronization around this function and the test result is
6058 * unreliable and only useful as advisory hints or for debugging.
6059 *
6060 * Return:
6061 * OR'd bitmask of WORK_BUSY_* bits.
6062 */
6063unsigned int work_busy(struct work_struct *work)
6064{
6065 struct worker_pool *pool;
6066 unsigned long irq_flags;
6067 unsigned int ret = 0;
6068
6069 if (work_pending(work))
6070 ret |= WORK_BUSY_PENDING;
6071
6072 rcu_read_lock();
6073 pool = get_work_pool(work);
6074 if (pool) {
6075 raw_spin_lock_irqsave(&pool->lock, irq_flags);
6076 if (find_worker_executing_work(pool, work))
6077 ret |= WORK_BUSY_RUNNING;
6078 raw_spin_unlock_irqrestore(&pool->lock, irq_flags);
6079 }
6080 rcu_read_unlock();
6081
6082 return ret;
6083}
6084EXPORT_SYMBOL_GPL(work_busy);
6085
6086/**
6087 * set_worker_desc - set description for the current work item
6088 * @fmt: printf-style format string
6089 * @...: arguments for the format string
6090 *
6091 * This function can be called by a running work function to describe what
6092 * the work item is about. If the worker task gets dumped, this
6093 * information will be printed out together to help debugging. The
6094 * description can be at most WORKER_DESC_LEN including the trailing '\0'.
6095 */
6096void set_worker_desc(const char *fmt, ...)
6097{
6098 struct worker *worker = current_wq_worker();
6099 va_list args;
6100
6101 if (worker) {
6102 va_start(args, fmt);
6103 vsnprintf(worker->desc, sizeof(worker->desc), fmt, args);
6104 va_end(args);
6105 }
6106}
6107EXPORT_SYMBOL_GPL(set_worker_desc);
6108
6109/**
6110 * print_worker_info - print out worker information and description
6111 * @log_lvl: the log level to use when printing
6112 * @task: target task
6113 *
6114 * If @task is a worker and currently executing a work item, print out the
6115 * name of the workqueue being serviced and worker description set with
6116 * set_worker_desc() by the currently executing work item.
6117 *
6118 * This function can be safely called on any task as long as the
6119 * task_struct itself is accessible. While safe, this function isn't
6120 * synchronized and may print out mixups or garbages of limited length.
6121 */
6122void print_worker_info(const char *log_lvl, struct task_struct *task)
6123{
6124 work_func_t *fn = NULL;
6125 char name[WQ_NAME_LEN] = { };
6126 char desc[WORKER_DESC_LEN] = { };
6127 struct pool_workqueue *pwq = NULL;
6128 struct workqueue_struct *wq = NULL;
6129 struct worker *worker;
6130
6131 if (!(task->flags & PF_WQ_WORKER))
6132 return;
6133
6134 /*
6135 * This function is called without any synchronization and @task
6136 * could be in any state. Be careful with dereferences.
6137 */
6138 worker = kthread_probe_data(task);
6139
6140 /*
6141 * Carefully copy the associated workqueue's workfn, name and desc.
6142 * Keep the original last '\0' in case the original is garbage.
6143 */
6144 copy_from_kernel_nofault(&fn, &worker->current_func, sizeof(fn));
6145 copy_from_kernel_nofault(&pwq, &worker->current_pwq, sizeof(pwq));
6146 copy_from_kernel_nofault(&wq, &pwq->wq, sizeof(wq));
6147 copy_from_kernel_nofault(name, wq->name, sizeof(name) - 1);
6148 copy_from_kernel_nofault(desc, worker->desc, sizeof(desc) - 1);
6149
6150 if (fn || name[0] || desc[0]) {
6151 printk("%sWorkqueue: %s %ps", log_lvl, name, fn);
6152 if (strcmp(name, desc))
6153 pr_cont(" (%s)", desc);
6154 pr_cont("\n");
6155 }
6156}
6157
6158static void pr_cont_pool_info(struct worker_pool *pool)
6159{
6160 pr_cont(" cpus=%*pbl", nr_cpumask_bits, pool->attrs->cpumask);
6161 if (pool->node != NUMA_NO_NODE)
6162 pr_cont(" node=%d", pool->node);
6163 pr_cont(" flags=0x%x", pool->flags);
6164 if (pool->flags & POOL_BH)
6165 pr_cont(" bh%s",
6166 pool->attrs->nice == HIGHPRI_NICE_LEVEL ? "-hi" : "");
6167 else
6168 pr_cont(" nice=%d", pool->attrs->nice);
6169}
6170
6171static void pr_cont_worker_id(struct worker *worker)
6172{
6173 struct worker_pool *pool = worker->pool;
6174
6175 if (pool->flags & WQ_BH)
6176 pr_cont("bh%s",
6177 pool->attrs->nice == HIGHPRI_NICE_LEVEL ? "-hi" : "");
6178 else
6179 pr_cont("%d%s", task_pid_nr(worker->task),
6180 worker->rescue_wq ? "(RESCUER)" : "");
6181}
6182
6183struct pr_cont_work_struct {
6184 bool comma;
6185 work_func_t func;
6186 long ctr;
6187};
6188
6189static void pr_cont_work_flush(bool comma, work_func_t func, struct pr_cont_work_struct *pcwsp)
6190{
6191 if (!pcwsp->ctr)
6192 goto out_record;
6193 if (func == pcwsp->func) {
6194 pcwsp->ctr++;
6195 return;
6196 }
6197 if (pcwsp->ctr == 1)
6198 pr_cont("%s %ps", pcwsp->comma ? "," : "", pcwsp->func);
6199 else
6200 pr_cont("%s %ld*%ps", pcwsp->comma ? "," : "", pcwsp->ctr, pcwsp->func);
6201 pcwsp->ctr = 0;
6202out_record:
6203 if ((long)func == -1L)
6204 return;
6205 pcwsp->comma = comma;
6206 pcwsp->func = func;
6207 pcwsp->ctr = 1;
6208}
6209
6210static void pr_cont_work(bool comma, struct work_struct *work, struct pr_cont_work_struct *pcwsp)
6211{
6212 if (work->func == wq_barrier_func) {
6213 struct wq_barrier *barr;
6214
6215 barr = container_of(work, struct wq_barrier, work);
6216
6217 pr_cont_work_flush(comma, (work_func_t)-1, pcwsp);
6218 pr_cont("%s BAR(%d)", comma ? "," : "",
6219 task_pid_nr(barr->task));
6220 } else {
6221 if (!comma)
6222 pr_cont_work_flush(comma, (work_func_t)-1, pcwsp);
6223 pr_cont_work_flush(comma, work->func, pcwsp);
6224 }
6225}
6226
6227static void show_pwq(struct pool_workqueue *pwq)
6228{
6229 struct pr_cont_work_struct pcws = { .ctr = 0, };
6230 struct worker_pool *pool = pwq->pool;
6231 struct work_struct *work;
6232 struct worker *worker;
6233 bool has_in_flight = false, has_pending = false;
6234 int bkt;
6235
6236 pr_info(" pwq %d:", pool->id);
6237 pr_cont_pool_info(pool);
6238
6239 pr_cont(" active=%d refcnt=%d%s\n",
6240 pwq->nr_active, pwq->refcnt,
6241 !list_empty(&pwq->mayday_node) ? " MAYDAY" : "");
6242
6243 hash_for_each(pool->busy_hash, bkt, worker, hentry) {
6244 if (worker->current_pwq == pwq) {
6245 has_in_flight = true;
6246 break;
6247 }
6248 }
6249 if (has_in_flight) {
6250 bool comma = false;
6251
6252 pr_info(" in-flight:");
6253 hash_for_each(pool->busy_hash, bkt, worker, hentry) {
6254 if (worker->current_pwq != pwq)
6255 continue;
6256
6257 pr_cont(" %s", comma ? "," : "");
6258 pr_cont_worker_id(worker);
6259 pr_cont(":%ps", worker->current_func);
6260 list_for_each_entry(work, &worker->scheduled, entry)
6261 pr_cont_work(false, work, &pcws);
6262 pr_cont_work_flush(comma, (work_func_t)-1L, &pcws);
6263 comma = true;
6264 }
6265 pr_cont("\n");
6266 }
6267
6268 list_for_each_entry(work, &pool->worklist, entry) {
6269 if (get_work_pwq(work) == pwq) {
6270 has_pending = true;
6271 break;
6272 }
6273 }
6274 if (has_pending) {
6275 bool comma = false;
6276
6277 pr_info(" pending:");
6278 list_for_each_entry(work, &pool->worklist, entry) {
6279 if (get_work_pwq(work) != pwq)
6280 continue;
6281
6282 pr_cont_work(comma, work, &pcws);
6283 comma = !(*work_data_bits(work) & WORK_STRUCT_LINKED);
6284 }
6285 pr_cont_work_flush(comma, (work_func_t)-1L, &pcws);
6286 pr_cont("\n");
6287 }
6288
6289 if (!list_empty(&pwq->inactive_works)) {
6290 bool comma = false;
6291
6292 pr_info(" inactive:");
6293 list_for_each_entry(work, &pwq->inactive_works, entry) {
6294 pr_cont_work(comma, work, &pcws);
6295 comma = !(*work_data_bits(work) & WORK_STRUCT_LINKED);
6296 }
6297 pr_cont_work_flush(comma, (work_func_t)-1L, &pcws);
6298 pr_cont("\n");
6299 }
6300}
6301
6302/**
6303 * show_one_workqueue - dump state of specified workqueue
6304 * @wq: workqueue whose state will be printed
6305 */
6306void show_one_workqueue(struct workqueue_struct *wq)
6307{
6308 struct pool_workqueue *pwq;
6309 bool idle = true;
6310 unsigned long irq_flags;
6311
6312 for_each_pwq(pwq, wq) {
6313 if (!pwq_is_empty(pwq)) {
6314 idle = false;
6315 break;
6316 }
6317 }
6318 if (idle) /* Nothing to print for idle workqueue */
6319 return;
6320
6321 pr_info("workqueue %s: flags=0x%x\n", wq->name, wq->flags);
6322
6323 for_each_pwq(pwq, wq) {
6324 raw_spin_lock_irqsave(&pwq->pool->lock, irq_flags);
6325 if (!pwq_is_empty(pwq)) {
6326 /*
6327 * Defer printing to avoid deadlocks in console
6328 * drivers that queue work while holding locks
6329 * also taken in their write paths.
6330 */
6331 printk_deferred_enter();
6332 show_pwq(pwq);
6333 printk_deferred_exit();
6334 }
6335 raw_spin_unlock_irqrestore(&pwq->pool->lock, irq_flags);
6336 /*
6337 * We could be printing a lot from atomic context, e.g.
6338 * sysrq-t -> show_all_workqueues(). Avoid triggering
6339 * hard lockup.
6340 */
6341 touch_nmi_watchdog();
6342 }
6343
6344}
6345
6346/**
6347 * show_one_worker_pool - dump state of specified worker pool
6348 * @pool: worker pool whose state will be printed
6349 */
6350static void show_one_worker_pool(struct worker_pool *pool)
6351{
6352 struct worker *worker;
6353 bool first = true;
6354 unsigned long irq_flags;
6355 unsigned long hung = 0;
6356
6357 raw_spin_lock_irqsave(&pool->lock, irq_flags);
6358 if (pool->nr_workers == pool->nr_idle)
6359 goto next_pool;
6360
6361 /* How long the first pending work is waiting for a worker. */
6362 if (!list_empty(&pool->worklist))
6363 hung = jiffies_to_msecs(jiffies - pool->watchdog_ts) / 1000;
6364
6365 /*
6366 * Defer printing to avoid deadlocks in console drivers that
6367 * queue work while holding locks also taken in their write
6368 * paths.
6369 */
6370 printk_deferred_enter();
6371 pr_info("pool %d:", pool->id);
6372 pr_cont_pool_info(pool);
6373 pr_cont(" hung=%lus workers=%d", hung, pool->nr_workers);
6374 if (pool->manager)
6375 pr_cont(" manager: %d",
6376 task_pid_nr(pool->manager->task));
6377 list_for_each_entry(worker, &pool->idle_list, entry) {
6378 pr_cont(" %s", first ? "idle: " : "");
6379 pr_cont_worker_id(worker);
6380 first = false;
6381 }
6382 pr_cont("\n");
6383 printk_deferred_exit();
6384next_pool:
6385 raw_spin_unlock_irqrestore(&pool->lock, irq_flags);
6386 /*
6387 * We could be printing a lot from atomic context, e.g.
6388 * sysrq-t -> show_all_workqueues(). Avoid triggering
6389 * hard lockup.
6390 */
6391 touch_nmi_watchdog();
6392
6393}
6394
6395/**
6396 * show_all_workqueues - dump workqueue state
6397 *
6398 * Called from a sysrq handler and prints out all busy workqueues and pools.
6399 */
6400void show_all_workqueues(void)
6401{
6402 struct workqueue_struct *wq;
6403 struct worker_pool *pool;
6404 int pi;
6405
6406 rcu_read_lock();
6407
6408 pr_info("Showing busy workqueues and worker pools:\n");
6409
6410 list_for_each_entry_rcu(wq, &workqueues, list)
6411 show_one_workqueue(wq);
6412
6413 for_each_pool(pool, pi)
6414 show_one_worker_pool(pool);
6415
6416 rcu_read_unlock();
6417}
6418
6419/**
6420 * show_freezable_workqueues - dump freezable workqueue state
6421 *
6422 * Called from try_to_freeze_tasks() and prints out all freezable workqueues
6423 * still busy.
6424 */
6425void show_freezable_workqueues(void)
6426{
6427 struct workqueue_struct *wq;
6428
6429 rcu_read_lock();
6430
6431 pr_info("Showing freezable workqueues that are still busy:\n");
6432
6433 list_for_each_entry_rcu(wq, &workqueues, list) {
6434 if (!(wq->flags & WQ_FREEZABLE))
6435 continue;
6436 show_one_workqueue(wq);
6437 }
6438
6439 rcu_read_unlock();
6440}
6441
6442/* used to show worker information through /proc/PID/{comm,stat,status} */
6443void wq_worker_comm(char *buf, size_t size, struct task_struct *task)
6444{
6445 /* stabilize PF_WQ_WORKER and worker pool association */
6446 mutex_lock(&wq_pool_attach_mutex);
6447
6448 if (task->flags & PF_WQ_WORKER) {
6449 struct worker *worker = kthread_data(task);
6450 struct worker_pool *pool = worker->pool;
6451 int off;
6452
6453 off = format_worker_id(buf, size, worker, pool);
6454
6455 if (pool) {
6456 raw_spin_lock_irq(&pool->lock);
6457 /*
6458 * ->desc tracks information (wq name or
6459 * set_worker_desc()) for the latest execution. If
6460 * current, prepend '+', otherwise '-'.
6461 */
6462 if (worker->desc[0] != '\0') {
6463 if (worker->current_work)
6464 scnprintf(buf + off, size - off, "+%s",
6465 worker->desc);
6466 else
6467 scnprintf(buf + off, size - off, "-%s",
6468 worker->desc);
6469 }
6470 raw_spin_unlock_irq(&pool->lock);
6471 }
6472 } else {
6473 strscpy(buf, task->comm, size);
6474 }
6475
6476 mutex_unlock(&wq_pool_attach_mutex);
6477}
6478
6479#ifdef CONFIG_SMP
6480
6481/*
6482 * CPU hotplug.
6483 *
6484 * There are two challenges in supporting CPU hotplug. Firstly, there
6485 * are a lot of assumptions on strong associations among work, pwq and
6486 * pool which make migrating pending and scheduled works very
6487 * difficult to implement without impacting hot paths. Secondly,
6488 * worker pools serve mix of short, long and very long running works making
6489 * blocked draining impractical.
6490 *
6491 * This is solved by allowing the pools to be disassociated from the CPU
6492 * running as an unbound one and allowing it to be reattached later if the
6493 * cpu comes back online.
6494 */
6495
6496static void unbind_workers(int cpu)
6497{
6498 struct worker_pool *pool;
6499 struct worker *worker;
6500
6501 for_each_cpu_worker_pool(pool, cpu) {
6502 mutex_lock(&wq_pool_attach_mutex);
6503 raw_spin_lock_irq(&pool->lock);
6504
6505 /*
6506 * We've blocked all attach/detach operations. Make all workers
6507 * unbound and set DISASSOCIATED. Before this, all workers
6508 * must be on the cpu. After this, they may become diasporas.
6509 * And the preemption disabled section in their sched callbacks
6510 * are guaranteed to see WORKER_UNBOUND since the code here
6511 * is on the same cpu.
6512 */
6513 for_each_pool_worker(worker, pool)
6514 worker->flags |= WORKER_UNBOUND;
6515
6516 pool->flags |= POOL_DISASSOCIATED;
6517
6518 /*
6519 * The handling of nr_running in sched callbacks are disabled
6520 * now. Zap nr_running. After this, nr_running stays zero and
6521 * need_more_worker() and keep_working() are always true as
6522 * long as the worklist is not empty. This pool now behaves as
6523 * an unbound (in terms of concurrency management) pool which
6524 * are served by workers tied to the pool.
6525 */
6526 pool->nr_running = 0;
6527
6528 /*
6529 * With concurrency management just turned off, a busy
6530 * worker blocking could lead to lengthy stalls. Kick off
6531 * unbound chain execution of currently pending work items.
6532 */
6533 kick_pool(pool);
6534
6535 raw_spin_unlock_irq(&pool->lock);
6536
6537 for_each_pool_worker(worker, pool)
6538 unbind_worker(worker);
6539
6540 mutex_unlock(&wq_pool_attach_mutex);
6541 }
6542}
6543
6544/**
6545 * rebind_workers - rebind all workers of a pool to the associated CPU
6546 * @pool: pool of interest
6547 *
6548 * @pool->cpu is coming online. Rebind all workers to the CPU.
6549 */
6550static void rebind_workers(struct worker_pool *pool)
6551{
6552 struct worker *worker;
6553
6554 lockdep_assert_held(&wq_pool_attach_mutex);
6555
6556 /*
6557 * Restore CPU affinity of all workers. As all idle workers should
6558 * be on the run-queue of the associated CPU before any local
6559 * wake-ups for concurrency management happen, restore CPU affinity
6560 * of all workers first and then clear UNBOUND. As we're called
6561 * from CPU_ONLINE, the following shouldn't fail.
6562 */
6563 for_each_pool_worker(worker, pool) {
6564 kthread_set_per_cpu(worker->task, pool->cpu);
6565 WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task,
6566 pool_allowed_cpus(pool)) < 0);
6567 }
6568
6569 raw_spin_lock_irq(&pool->lock);
6570
6571 pool->flags &= ~POOL_DISASSOCIATED;
6572
6573 for_each_pool_worker(worker, pool) {
6574 unsigned int worker_flags = worker->flags;
6575
6576 /*
6577 * We want to clear UNBOUND but can't directly call
6578 * worker_clr_flags() or adjust nr_running. Atomically
6579 * replace UNBOUND with another NOT_RUNNING flag REBOUND.
6580 * @worker will clear REBOUND using worker_clr_flags() when
6581 * it initiates the next execution cycle thus restoring
6582 * concurrency management. Note that when or whether
6583 * @worker clears REBOUND doesn't affect correctness.
6584 *
6585 * WRITE_ONCE() is necessary because @worker->flags may be
6586 * tested without holding any lock in
6587 * wq_worker_running(). Without it, NOT_RUNNING test may
6588 * fail incorrectly leading to premature concurrency
6589 * management operations.
6590 */
6591 WARN_ON_ONCE(!(worker_flags & WORKER_UNBOUND));
6592 worker_flags |= WORKER_REBOUND;
6593 worker_flags &= ~WORKER_UNBOUND;
6594 WRITE_ONCE(worker->flags, worker_flags);
6595 }
6596
6597 raw_spin_unlock_irq(&pool->lock);
6598}
6599
6600/**
6601 * restore_unbound_workers_cpumask - restore cpumask of unbound workers
6602 * @pool: unbound pool of interest
6603 * @cpu: the CPU which is coming up
6604 *
6605 * An unbound pool may end up with a cpumask which doesn't have any online
6606 * CPUs. When a worker of such pool get scheduled, the scheduler resets
6607 * its cpus_allowed. If @cpu is in @pool's cpumask which didn't have any
6608 * online CPU before, cpus_allowed of all its workers should be restored.
6609 */
6610static void restore_unbound_workers_cpumask(struct worker_pool *pool, int cpu)
6611{
6612 static cpumask_t cpumask;
6613 struct worker *worker;
6614
6615 lockdep_assert_held(&wq_pool_attach_mutex);
6616
6617 /* is @cpu allowed for @pool? */
6618 if (!cpumask_test_cpu(cpu, pool->attrs->cpumask))
6619 return;
6620
6621 cpumask_and(&cpumask, pool->attrs->cpumask, cpu_online_mask);
6622
6623 /* as we're called from CPU_ONLINE, the following shouldn't fail */
6624 for_each_pool_worker(worker, pool)
6625 WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task, &cpumask) < 0);
6626}
6627
6628int workqueue_prepare_cpu(unsigned int cpu)
6629{
6630 struct worker_pool *pool;
6631
6632 for_each_cpu_worker_pool(pool, cpu) {
6633 if (pool->nr_workers)
6634 continue;
6635 if (!create_worker(pool))
6636 return -ENOMEM;
6637 }
6638 return 0;
6639}
6640
6641int workqueue_online_cpu(unsigned int cpu)
6642{
6643 struct worker_pool *pool;
6644 struct workqueue_struct *wq;
6645 int pi;
6646
6647 mutex_lock(&wq_pool_mutex);
6648
6649 cpumask_set_cpu(cpu, wq_online_cpumask);
6650
6651 for_each_pool(pool, pi) {
6652 /* BH pools aren't affected by hotplug */
6653 if (pool->flags & POOL_BH)
6654 continue;
6655
6656 mutex_lock(&wq_pool_attach_mutex);
6657 if (pool->cpu == cpu)
6658 rebind_workers(pool);
6659 else if (pool->cpu < 0)
6660 restore_unbound_workers_cpumask(pool, cpu);
6661 mutex_unlock(&wq_pool_attach_mutex);
6662 }
6663
6664 /* update pod affinity of unbound workqueues */
6665 list_for_each_entry(wq, &workqueues, list) {
6666 struct workqueue_attrs *attrs = wq->unbound_attrs;
6667
6668 if (attrs) {
6669 const struct wq_pod_type *pt = wqattrs_pod_type(attrs);
6670 int tcpu;
6671
6672 for_each_cpu(tcpu, pt->pod_cpus[pt->cpu_pod[cpu]])
6673 unbound_wq_update_pwq(wq, tcpu);
6674
6675 mutex_lock(&wq->mutex);
6676 wq_update_node_max_active(wq, -1);
6677 mutex_unlock(&wq->mutex);
6678 }
6679 }
6680
6681 mutex_unlock(&wq_pool_mutex);
6682 return 0;
6683}
6684
6685int workqueue_offline_cpu(unsigned int cpu)
6686{
6687 struct workqueue_struct *wq;
6688
6689 /* unbinding per-cpu workers should happen on the local CPU */
6690 if (WARN_ON(cpu != smp_processor_id()))
6691 return -1;
6692
6693 unbind_workers(cpu);
6694
6695 /* update pod affinity of unbound workqueues */
6696 mutex_lock(&wq_pool_mutex);
6697
6698 cpumask_clear_cpu(cpu, wq_online_cpumask);
6699
6700 list_for_each_entry(wq, &workqueues, list) {
6701 struct workqueue_attrs *attrs = wq->unbound_attrs;
6702
6703 if (attrs) {
6704 const struct wq_pod_type *pt = wqattrs_pod_type(attrs);
6705 int tcpu;
6706
6707 for_each_cpu(tcpu, pt->pod_cpus[pt->cpu_pod[cpu]])
6708 unbound_wq_update_pwq(wq, tcpu);
6709
6710 mutex_lock(&wq->mutex);
6711 wq_update_node_max_active(wq, cpu);
6712 mutex_unlock(&wq->mutex);
6713 }
6714 }
6715 mutex_unlock(&wq_pool_mutex);
6716
6717 return 0;
6718}
6719
6720struct work_for_cpu {
6721 struct work_struct work;
6722 long (*fn)(void *);
6723 void *arg;
6724 long ret;
6725};
6726
6727static void work_for_cpu_fn(struct work_struct *work)
6728{
6729 struct work_for_cpu *wfc = container_of(work, struct work_for_cpu, work);
6730
6731 wfc->ret = wfc->fn(wfc->arg);
6732}
6733
6734/**
6735 * work_on_cpu_key - run a function in thread context on a particular cpu
6736 * @cpu: the cpu to run on
6737 * @fn: the function to run
6738 * @arg: the function arg
6739 * @key: The lock class key for lock debugging purposes
6740 *
6741 * It is up to the caller to ensure that the cpu doesn't go offline.
6742 * The caller must not hold any locks which would prevent @fn from completing.
6743 *
6744 * Return: The value @fn returns.
6745 */
6746long work_on_cpu_key(int cpu, long (*fn)(void *),
6747 void *arg, struct lock_class_key *key)
6748{
6749 struct work_for_cpu wfc = { .fn = fn, .arg = arg };
6750
6751 INIT_WORK_ONSTACK_KEY(&wfc.work, work_for_cpu_fn, key);
6752 schedule_work_on(cpu, &wfc.work);
6753 flush_work(&wfc.work);
6754 destroy_work_on_stack(&wfc.work);
6755 return wfc.ret;
6756}
6757EXPORT_SYMBOL_GPL(work_on_cpu_key);
6758
6759/**
6760 * work_on_cpu_safe_key - run a function in thread context on a particular cpu
6761 * @cpu: the cpu to run on
6762 * @fn: the function to run
6763 * @arg: the function argument
6764 * @key: The lock class key for lock debugging purposes
6765 *
6766 * Disables CPU hotplug and calls work_on_cpu(). The caller must not hold
6767 * any locks which would prevent @fn from completing.
6768 *
6769 * Return: The value @fn returns.
6770 */
6771long work_on_cpu_safe_key(int cpu, long (*fn)(void *),
6772 void *arg, struct lock_class_key *key)
6773{
6774 long ret = -ENODEV;
6775
6776 cpus_read_lock();
6777 if (cpu_online(cpu))
6778 ret = work_on_cpu_key(cpu, fn, arg, key);
6779 cpus_read_unlock();
6780 return ret;
6781}
6782EXPORT_SYMBOL_GPL(work_on_cpu_safe_key);
6783#endif /* CONFIG_SMP */
6784
6785#ifdef CONFIG_FREEZER
6786
6787/**
6788 * freeze_workqueues_begin - begin freezing workqueues
6789 *
6790 * Start freezing workqueues. After this function returns, all freezable
6791 * workqueues will queue new works to their inactive_works list instead of
6792 * pool->worklist.
6793 *
6794 * CONTEXT:
6795 * Grabs and releases wq_pool_mutex, wq->mutex and pool->lock's.
6796 */
6797void freeze_workqueues_begin(void)
6798{
6799 struct workqueue_struct *wq;
6800
6801 mutex_lock(&wq_pool_mutex);
6802
6803 WARN_ON_ONCE(workqueue_freezing);
6804 workqueue_freezing = true;
6805
6806 list_for_each_entry(wq, &workqueues, list) {
6807 mutex_lock(&wq->mutex);
6808 wq_adjust_max_active(wq);
6809 mutex_unlock(&wq->mutex);
6810 }
6811
6812 mutex_unlock(&wq_pool_mutex);
6813}
6814
6815/**
6816 * freeze_workqueues_busy - are freezable workqueues still busy?
6817 *
6818 * Check whether freezing is complete. This function must be called
6819 * between freeze_workqueues_begin() and thaw_workqueues().
6820 *
6821 * CONTEXT:
6822 * Grabs and releases wq_pool_mutex.
6823 *
6824 * Return:
6825 * %true if some freezable workqueues are still busy. %false if freezing
6826 * is complete.
6827 */
6828bool freeze_workqueues_busy(void)
6829{
6830 bool busy = false;
6831 struct workqueue_struct *wq;
6832 struct pool_workqueue *pwq;
6833
6834 mutex_lock(&wq_pool_mutex);
6835
6836 WARN_ON_ONCE(!workqueue_freezing);
6837
6838 list_for_each_entry(wq, &workqueues, list) {
6839 if (!(wq->flags & WQ_FREEZABLE))
6840 continue;
6841 /*
6842 * nr_active is monotonically decreasing. It's safe
6843 * to peek without lock.
6844 */
6845 rcu_read_lock();
6846 for_each_pwq(pwq, wq) {
6847 WARN_ON_ONCE(pwq->nr_active < 0);
6848 if (pwq->nr_active) {
6849 busy = true;
6850 rcu_read_unlock();
6851 goto out_unlock;
6852 }
6853 }
6854 rcu_read_unlock();
6855 }
6856out_unlock:
6857 mutex_unlock(&wq_pool_mutex);
6858 return busy;
6859}
6860
6861/**
6862 * thaw_workqueues - thaw workqueues
6863 *
6864 * Thaw workqueues. Normal queueing is restored and all collected
6865 * frozen works are transferred to their respective pool worklists.
6866 *
6867 * CONTEXT:
6868 * Grabs and releases wq_pool_mutex, wq->mutex and pool->lock's.
6869 */
6870void thaw_workqueues(void)
6871{
6872 struct workqueue_struct *wq;
6873
6874 mutex_lock(&wq_pool_mutex);
6875
6876 if (!workqueue_freezing)
6877 goto out_unlock;
6878
6879 workqueue_freezing = false;
6880
6881 /* restore max_active and repopulate worklist */
6882 list_for_each_entry(wq, &workqueues, list) {
6883 mutex_lock(&wq->mutex);
6884 wq_adjust_max_active(wq);
6885 mutex_unlock(&wq->mutex);
6886 }
6887
6888out_unlock:
6889 mutex_unlock(&wq_pool_mutex);
6890}
6891#endif /* CONFIG_FREEZER */
6892
6893static int workqueue_apply_unbound_cpumask(const cpumask_var_t unbound_cpumask)
6894{
6895 LIST_HEAD(ctxs);
6896 int ret = 0;
6897 struct workqueue_struct *wq;
6898 struct apply_wqattrs_ctx *ctx, *n;
6899
6900 lockdep_assert_held(&wq_pool_mutex);
6901
6902 list_for_each_entry(wq, &workqueues, list) {
6903 if (!(wq->flags & WQ_UNBOUND) || (wq->flags & __WQ_DESTROYING))
6904 continue;
6905
6906 ctx = apply_wqattrs_prepare(wq, wq->unbound_attrs, unbound_cpumask);
6907 if (IS_ERR(ctx)) {
6908 ret = PTR_ERR(ctx);
6909 break;
6910 }
6911
6912 list_add_tail(&ctx->list, &ctxs);
6913 }
6914
6915 list_for_each_entry_safe(ctx, n, &ctxs, list) {
6916 if (!ret)
6917 apply_wqattrs_commit(ctx);
6918 apply_wqattrs_cleanup(ctx);
6919 }
6920
6921 if (!ret) {
6922 mutex_lock(&wq_pool_attach_mutex);
6923 cpumask_copy(wq_unbound_cpumask, unbound_cpumask);
6924 mutex_unlock(&wq_pool_attach_mutex);
6925 }
6926 return ret;
6927}
6928
6929/**
6930 * workqueue_unbound_exclude_cpumask - Exclude given CPUs from unbound cpumask
6931 * @exclude_cpumask: the cpumask to be excluded from wq_unbound_cpumask
6932 *
6933 * This function can be called from cpuset code to provide a set of isolated
6934 * CPUs that should be excluded from wq_unbound_cpumask.
6935 */
6936int workqueue_unbound_exclude_cpumask(cpumask_var_t exclude_cpumask)
6937{
6938 cpumask_var_t cpumask;
6939 int ret = 0;
6940
6941 if (!zalloc_cpumask_var(&cpumask, GFP_KERNEL))
6942 return -ENOMEM;
6943
6944 mutex_lock(&wq_pool_mutex);
6945
6946 /*
6947 * If the operation fails, it will fall back to
6948 * wq_requested_unbound_cpumask which is initially set to
6949 * (HK_TYPE_WQ ∩ HK_TYPE_DOMAIN) house keeping mask and rewritten
6950 * by any subsequent write to workqueue/cpumask sysfs file.
6951 */
6952 if (!cpumask_andnot(cpumask, wq_requested_unbound_cpumask, exclude_cpumask))
6953 cpumask_copy(cpumask, wq_requested_unbound_cpumask);
6954 if (!cpumask_equal(cpumask, wq_unbound_cpumask))
6955 ret = workqueue_apply_unbound_cpumask(cpumask);
6956
6957 /* Save the current isolated cpumask & export it via sysfs */
6958 if (!ret)
6959 cpumask_copy(wq_isolated_cpumask, exclude_cpumask);
6960
6961 mutex_unlock(&wq_pool_mutex);
6962 free_cpumask_var(cpumask);
6963 return ret;
6964}
6965
6966static int parse_affn_scope(const char *val)
6967{
6968 int i;
6969
6970 for (i = 0; i < ARRAY_SIZE(wq_affn_names); i++) {
6971 if (!strncasecmp(val, wq_affn_names[i], strlen(wq_affn_names[i])))
6972 return i;
6973 }
6974 return -EINVAL;
6975}
6976
6977static int wq_affn_dfl_set(const char *val, const struct kernel_param *kp)
6978{
6979 struct workqueue_struct *wq;
6980 int affn, cpu;
6981
6982 affn = parse_affn_scope(val);
6983 if (affn < 0)
6984 return affn;
6985 if (affn == WQ_AFFN_DFL)
6986 return -EINVAL;
6987
6988 cpus_read_lock();
6989 mutex_lock(&wq_pool_mutex);
6990
6991 wq_affn_dfl = affn;
6992
6993 list_for_each_entry(wq, &workqueues, list) {
6994 for_each_online_cpu(cpu)
6995 unbound_wq_update_pwq(wq, cpu);
6996 }
6997
6998 mutex_unlock(&wq_pool_mutex);
6999 cpus_read_unlock();
7000
7001 return 0;
7002}
7003
7004static int wq_affn_dfl_get(char *buffer, const struct kernel_param *kp)
7005{
7006 return scnprintf(buffer, PAGE_SIZE, "%s\n", wq_affn_names[wq_affn_dfl]);
7007}
7008
7009static const struct kernel_param_ops wq_affn_dfl_ops = {
7010 .set = wq_affn_dfl_set,
7011 .get = wq_affn_dfl_get,
7012};
7013
7014module_param_cb(default_affinity_scope, &wq_affn_dfl_ops, NULL, 0644);
7015
7016#ifdef CONFIG_SYSFS
7017/*
7018 * Workqueues with WQ_SYSFS flag set is visible to userland via
7019 * /sys/bus/workqueue/devices/WQ_NAME. All visible workqueues have the
7020 * following attributes.
7021 *
7022 * per_cpu RO bool : whether the workqueue is per-cpu or unbound
7023 * max_active RW int : maximum number of in-flight work items
7024 *
7025 * Unbound workqueues have the following extra attributes.
7026 *
7027 * nice RW int : nice value of the workers
7028 * cpumask RW mask : bitmask of allowed CPUs for the workers
7029 * affinity_scope RW str : worker CPU affinity scope (cache, numa, none)
7030 * affinity_strict RW bool : worker CPU affinity is strict
7031 */
7032struct wq_device {
7033 struct workqueue_struct *wq;
7034 struct device dev;
7035};
7036
7037static struct workqueue_struct *dev_to_wq(struct device *dev)
7038{
7039 struct wq_device *wq_dev = container_of(dev, struct wq_device, dev);
7040
7041 return wq_dev->wq;
7042}
7043
7044static ssize_t per_cpu_show(struct device *dev, struct device_attribute *attr,
7045 char *buf)
7046{
7047 struct workqueue_struct *wq = dev_to_wq(dev);
7048
7049 return scnprintf(buf, PAGE_SIZE, "%d\n", (bool)!(wq->flags & WQ_UNBOUND));
7050}
7051static DEVICE_ATTR_RO(per_cpu);
7052
7053static ssize_t max_active_show(struct device *dev,
7054 struct device_attribute *attr, char *buf)
7055{
7056 struct workqueue_struct *wq = dev_to_wq(dev);
7057
7058 return scnprintf(buf, PAGE_SIZE, "%d\n", wq->saved_max_active);
7059}
7060
7061static ssize_t max_active_store(struct device *dev,
7062 struct device_attribute *attr, const char *buf,
7063 size_t count)
7064{
7065 struct workqueue_struct *wq = dev_to_wq(dev);
7066 int val;
7067
7068 if (sscanf(buf, "%d", &val) != 1 || val <= 0)
7069 return -EINVAL;
7070
7071 workqueue_set_max_active(wq, val);
7072 return count;
7073}
7074static DEVICE_ATTR_RW(max_active);
7075
7076static struct attribute *wq_sysfs_attrs[] = {
7077 &dev_attr_per_cpu.attr,
7078 &dev_attr_max_active.attr,
7079 NULL,
7080};
7081ATTRIBUTE_GROUPS(wq_sysfs);
7082
7083static ssize_t wq_nice_show(struct device *dev, struct device_attribute *attr,
7084 char *buf)
7085{
7086 struct workqueue_struct *wq = dev_to_wq(dev);
7087 int written;
7088
7089 mutex_lock(&wq->mutex);
7090 written = scnprintf(buf, PAGE_SIZE, "%d\n", wq->unbound_attrs->nice);
7091 mutex_unlock(&wq->mutex);
7092
7093 return written;
7094}
7095
7096/* prepare workqueue_attrs for sysfs store operations */
7097static struct workqueue_attrs *wq_sysfs_prep_attrs(struct workqueue_struct *wq)
7098{
7099 struct workqueue_attrs *attrs;
7100
7101 lockdep_assert_held(&wq_pool_mutex);
7102
7103 attrs = alloc_workqueue_attrs();
7104 if (!attrs)
7105 return NULL;
7106
7107 copy_workqueue_attrs(attrs, wq->unbound_attrs);
7108 return attrs;
7109}
7110
7111static ssize_t wq_nice_store(struct device *dev, struct device_attribute *attr,
7112 const char *buf, size_t count)
7113{
7114 struct workqueue_struct *wq = dev_to_wq(dev);
7115 struct workqueue_attrs *attrs;
7116 int ret = -ENOMEM;
7117
7118 apply_wqattrs_lock();
7119
7120 attrs = wq_sysfs_prep_attrs(wq);
7121 if (!attrs)
7122 goto out_unlock;
7123
7124 if (sscanf(buf, "%d", &attrs->nice) == 1 &&
7125 attrs->nice >= MIN_NICE && attrs->nice <= MAX_NICE)
7126 ret = apply_workqueue_attrs_locked(wq, attrs);
7127 else
7128 ret = -EINVAL;
7129
7130out_unlock:
7131 apply_wqattrs_unlock();
7132 free_workqueue_attrs(attrs);
7133 return ret ?: count;
7134}
7135
7136static ssize_t wq_cpumask_show(struct device *dev,
7137 struct device_attribute *attr, char *buf)
7138{
7139 struct workqueue_struct *wq = dev_to_wq(dev);
7140 int written;
7141
7142 mutex_lock(&wq->mutex);
7143 written = scnprintf(buf, PAGE_SIZE, "%*pb\n",
7144 cpumask_pr_args(wq->unbound_attrs->cpumask));
7145 mutex_unlock(&wq->mutex);
7146 return written;
7147}
7148
7149static ssize_t wq_cpumask_store(struct device *dev,
7150 struct device_attribute *attr,
7151 const char *buf, size_t count)
7152{
7153 struct workqueue_struct *wq = dev_to_wq(dev);
7154 struct workqueue_attrs *attrs;
7155 int ret = -ENOMEM;
7156
7157 apply_wqattrs_lock();
7158
7159 attrs = wq_sysfs_prep_attrs(wq);
7160 if (!attrs)
7161 goto out_unlock;
7162
7163 ret = cpumask_parse(buf, attrs->cpumask);
7164 if (!ret)
7165 ret = apply_workqueue_attrs_locked(wq, attrs);
7166
7167out_unlock:
7168 apply_wqattrs_unlock();
7169 free_workqueue_attrs(attrs);
7170 return ret ?: count;
7171}
7172
7173static ssize_t wq_affn_scope_show(struct device *dev,
7174 struct device_attribute *attr, char *buf)
7175{
7176 struct workqueue_struct *wq = dev_to_wq(dev);
7177 int written;
7178
7179 mutex_lock(&wq->mutex);
7180 if (wq->unbound_attrs->affn_scope == WQ_AFFN_DFL)
7181 written = scnprintf(buf, PAGE_SIZE, "%s (%s)\n",
7182 wq_affn_names[WQ_AFFN_DFL],
7183 wq_affn_names[wq_affn_dfl]);
7184 else
7185 written = scnprintf(buf, PAGE_SIZE, "%s\n",
7186 wq_affn_names[wq->unbound_attrs->affn_scope]);
7187 mutex_unlock(&wq->mutex);
7188
7189 return written;
7190}
7191
7192static ssize_t wq_affn_scope_store(struct device *dev,
7193 struct device_attribute *attr,
7194 const char *buf, size_t count)
7195{
7196 struct workqueue_struct *wq = dev_to_wq(dev);
7197 struct workqueue_attrs *attrs;
7198 int affn, ret = -ENOMEM;
7199
7200 affn = parse_affn_scope(buf);
7201 if (affn < 0)
7202 return affn;
7203
7204 apply_wqattrs_lock();
7205 attrs = wq_sysfs_prep_attrs(wq);
7206 if (attrs) {
7207 attrs->affn_scope = affn;
7208 ret = apply_workqueue_attrs_locked(wq, attrs);
7209 }
7210 apply_wqattrs_unlock();
7211 free_workqueue_attrs(attrs);
7212 return ret ?: count;
7213}
7214
7215static ssize_t wq_affinity_strict_show(struct device *dev,
7216 struct device_attribute *attr, char *buf)
7217{
7218 struct workqueue_struct *wq = dev_to_wq(dev);
7219
7220 return scnprintf(buf, PAGE_SIZE, "%d\n",
7221 wq->unbound_attrs->affn_strict);
7222}
7223
7224static ssize_t wq_affinity_strict_store(struct device *dev,
7225 struct device_attribute *attr,
7226 const char *buf, size_t count)
7227{
7228 struct workqueue_struct *wq = dev_to_wq(dev);
7229 struct workqueue_attrs *attrs;
7230 int v, ret = -ENOMEM;
7231
7232 if (sscanf(buf, "%d", &v) != 1)
7233 return -EINVAL;
7234
7235 apply_wqattrs_lock();
7236 attrs = wq_sysfs_prep_attrs(wq);
7237 if (attrs) {
7238 attrs->affn_strict = (bool)v;
7239 ret = apply_workqueue_attrs_locked(wq, attrs);
7240 }
7241 apply_wqattrs_unlock();
7242 free_workqueue_attrs(attrs);
7243 return ret ?: count;
7244}
7245
7246static struct device_attribute wq_sysfs_unbound_attrs[] = {
7247 __ATTR(nice, 0644, wq_nice_show, wq_nice_store),
7248 __ATTR(cpumask, 0644, wq_cpumask_show, wq_cpumask_store),
7249 __ATTR(affinity_scope, 0644, wq_affn_scope_show, wq_affn_scope_store),
7250 __ATTR(affinity_strict, 0644, wq_affinity_strict_show, wq_affinity_strict_store),
7251 __ATTR_NULL,
7252};
7253
7254static const struct bus_type wq_subsys = {
7255 .name = "workqueue",
7256 .dev_groups = wq_sysfs_groups,
7257};
7258
7259/**
7260 * workqueue_set_unbound_cpumask - Set the low-level unbound cpumask
7261 * @cpumask: the cpumask to set
7262 *
7263 * The low-level workqueues cpumask is a global cpumask that limits
7264 * the affinity of all unbound workqueues. This function check the @cpumask
7265 * and apply it to all unbound workqueues and updates all pwqs of them.
7266 *
7267 * Return: 0 - Success
7268 * -EINVAL - Invalid @cpumask
7269 * -ENOMEM - Failed to allocate memory for attrs or pwqs.
7270 */
7271static int workqueue_set_unbound_cpumask(cpumask_var_t cpumask)
7272{
7273 int ret = -EINVAL;
7274
7275 /*
7276 * Not excluding isolated cpus on purpose.
7277 * If the user wishes to include them, we allow that.
7278 */
7279 cpumask_and(cpumask, cpumask, cpu_possible_mask);
7280 if (!cpumask_empty(cpumask)) {
7281 ret = 0;
7282 apply_wqattrs_lock();
7283 if (!cpumask_equal(cpumask, wq_unbound_cpumask))
7284 ret = workqueue_apply_unbound_cpumask(cpumask);
7285 if (!ret)
7286 cpumask_copy(wq_requested_unbound_cpumask, cpumask);
7287 apply_wqattrs_unlock();
7288 }
7289
7290 return ret;
7291}
7292
7293static ssize_t __wq_cpumask_show(struct device *dev,
7294 struct device_attribute *attr, char *buf, cpumask_var_t mask)
7295{
7296 int written;
7297
7298 mutex_lock(&wq_pool_mutex);
7299 written = scnprintf(buf, PAGE_SIZE, "%*pb\n", cpumask_pr_args(mask));
7300 mutex_unlock(&wq_pool_mutex);
7301
7302 return written;
7303}
7304
7305static ssize_t cpumask_requested_show(struct device *dev,
7306 struct device_attribute *attr, char *buf)
7307{
7308 return __wq_cpumask_show(dev, attr, buf, wq_requested_unbound_cpumask);
7309}
7310static DEVICE_ATTR_RO(cpumask_requested);
7311
7312static ssize_t cpumask_isolated_show(struct device *dev,
7313 struct device_attribute *attr, char *buf)
7314{
7315 return __wq_cpumask_show(dev, attr, buf, wq_isolated_cpumask);
7316}
7317static DEVICE_ATTR_RO(cpumask_isolated);
7318
7319static ssize_t cpumask_show(struct device *dev,
7320 struct device_attribute *attr, char *buf)
7321{
7322 return __wq_cpumask_show(dev, attr, buf, wq_unbound_cpumask);
7323}
7324
7325static ssize_t cpumask_store(struct device *dev,
7326 struct device_attribute *attr, const char *buf, size_t count)
7327{
7328 cpumask_var_t cpumask;
7329 int ret;
7330
7331 if (!zalloc_cpumask_var(&cpumask, GFP_KERNEL))
7332 return -ENOMEM;
7333
7334 ret = cpumask_parse(buf, cpumask);
7335 if (!ret)
7336 ret = workqueue_set_unbound_cpumask(cpumask);
7337
7338 free_cpumask_var(cpumask);
7339 return ret ? ret : count;
7340}
7341static DEVICE_ATTR_RW(cpumask);
7342
7343static struct attribute *wq_sysfs_cpumask_attrs[] = {
7344 &dev_attr_cpumask.attr,
7345 &dev_attr_cpumask_requested.attr,
7346 &dev_attr_cpumask_isolated.attr,
7347 NULL,
7348};
7349ATTRIBUTE_GROUPS(wq_sysfs_cpumask);
7350
7351static int __init wq_sysfs_init(void)
7352{
7353 return subsys_virtual_register(&wq_subsys, wq_sysfs_cpumask_groups);
7354}
7355core_initcall(wq_sysfs_init);
7356
7357static void wq_device_release(struct device *dev)
7358{
7359 struct wq_device *wq_dev = container_of(dev, struct wq_device, dev);
7360
7361 kfree(wq_dev);
7362}
7363
7364/**
7365 * workqueue_sysfs_register - make a workqueue visible in sysfs
7366 * @wq: the workqueue to register
7367 *
7368 * Expose @wq in sysfs under /sys/bus/workqueue/devices.
7369 * alloc_workqueue*() automatically calls this function if WQ_SYSFS is set
7370 * which is the preferred method.
7371 *
7372 * Workqueue user should use this function directly iff it wants to apply
7373 * workqueue_attrs before making the workqueue visible in sysfs; otherwise,
7374 * apply_workqueue_attrs() may race against userland updating the
7375 * attributes.
7376 *
7377 * Return: 0 on success, -errno on failure.
7378 */
7379int workqueue_sysfs_register(struct workqueue_struct *wq)
7380{
7381 struct wq_device *wq_dev;
7382 int ret;
7383
7384 /*
7385 * Adjusting max_active breaks ordering guarantee. Disallow exposing
7386 * ordered workqueues.
7387 */
7388 if (WARN_ON(wq->flags & __WQ_ORDERED))
7389 return -EINVAL;
7390
7391 wq->wq_dev = wq_dev = kzalloc(sizeof(*wq_dev), GFP_KERNEL);
7392 if (!wq_dev)
7393 return -ENOMEM;
7394
7395 wq_dev->wq = wq;
7396 wq_dev->dev.bus = &wq_subsys;
7397 wq_dev->dev.release = wq_device_release;
7398 dev_set_name(&wq_dev->dev, "%s", wq->name);
7399
7400 /*
7401 * unbound_attrs are created separately. Suppress uevent until
7402 * everything is ready.
7403 */
7404 dev_set_uevent_suppress(&wq_dev->dev, true);
7405
7406 ret = device_register(&wq_dev->dev);
7407 if (ret) {
7408 put_device(&wq_dev->dev);
7409 wq->wq_dev = NULL;
7410 return ret;
7411 }
7412
7413 if (wq->flags & WQ_UNBOUND) {
7414 struct device_attribute *attr;
7415
7416 for (attr = wq_sysfs_unbound_attrs; attr->attr.name; attr++) {
7417 ret = device_create_file(&wq_dev->dev, attr);
7418 if (ret) {
7419 device_unregister(&wq_dev->dev);
7420 wq->wq_dev = NULL;
7421 return ret;
7422 }
7423 }
7424 }
7425
7426 dev_set_uevent_suppress(&wq_dev->dev, false);
7427 kobject_uevent(&wq_dev->dev.kobj, KOBJ_ADD);
7428 return 0;
7429}
7430
7431/**
7432 * workqueue_sysfs_unregister - undo workqueue_sysfs_register()
7433 * @wq: the workqueue to unregister
7434 *
7435 * If @wq is registered to sysfs by workqueue_sysfs_register(), unregister.
7436 */
7437static void workqueue_sysfs_unregister(struct workqueue_struct *wq)
7438{
7439 struct wq_device *wq_dev = wq->wq_dev;
7440
7441 if (!wq->wq_dev)
7442 return;
7443
7444 wq->wq_dev = NULL;
7445 device_unregister(&wq_dev->dev);
7446}
7447#else /* CONFIG_SYSFS */
7448static void workqueue_sysfs_unregister(struct workqueue_struct *wq) { }
7449#endif /* CONFIG_SYSFS */
7450
7451/*
7452 * Workqueue watchdog.
7453 *
7454 * Stall may be caused by various bugs - missing WQ_MEM_RECLAIM, illegal
7455 * flush dependency, a concurrency managed work item which stays RUNNING
7456 * indefinitely. Workqueue stalls can be very difficult to debug as the
7457 * usual warning mechanisms don't trigger and internal workqueue state is
7458 * largely opaque.
7459 *
7460 * Workqueue watchdog monitors all worker pools periodically and dumps
7461 * state if some pools failed to make forward progress for a while where
7462 * forward progress is defined as the first item on ->worklist changing.
7463 *
7464 * This mechanism is controlled through the kernel parameter
7465 * "workqueue.watchdog_thresh" which can be updated at runtime through the
7466 * corresponding sysfs parameter file.
7467 */
7468#ifdef CONFIG_WQ_WATCHDOG
7469
7470static unsigned long wq_watchdog_thresh = 30;
7471static struct timer_list wq_watchdog_timer;
7472
7473static unsigned long wq_watchdog_touched = INITIAL_JIFFIES;
7474static DEFINE_PER_CPU(unsigned long, wq_watchdog_touched_cpu) = INITIAL_JIFFIES;
7475
7476static unsigned int wq_panic_on_stall;
7477module_param_named(panic_on_stall, wq_panic_on_stall, uint, 0644);
7478
7479/*
7480 * Show workers that might prevent the processing of pending work items.
7481 * The only candidates are CPU-bound workers in the running state.
7482 * Pending work items should be handled by another idle worker
7483 * in all other situations.
7484 */
7485static void show_cpu_pool_hog(struct worker_pool *pool)
7486{
7487 struct worker *worker;
7488 unsigned long irq_flags;
7489 int bkt;
7490
7491 raw_spin_lock_irqsave(&pool->lock, irq_flags);
7492
7493 hash_for_each(pool->busy_hash, bkt, worker, hentry) {
7494 if (task_is_running(worker->task)) {
7495 /*
7496 * Defer printing to avoid deadlocks in console
7497 * drivers that queue work while holding locks
7498 * also taken in their write paths.
7499 */
7500 printk_deferred_enter();
7501
7502 pr_info("pool %d:\n", pool->id);
7503 sched_show_task(worker->task);
7504
7505 printk_deferred_exit();
7506 }
7507 }
7508
7509 raw_spin_unlock_irqrestore(&pool->lock, irq_flags);
7510}
7511
7512static void show_cpu_pools_hogs(void)
7513{
7514 struct worker_pool *pool;
7515 int pi;
7516
7517 pr_info("Showing backtraces of running workers in stalled CPU-bound worker pools:\n");
7518
7519 rcu_read_lock();
7520
7521 for_each_pool(pool, pi) {
7522 if (pool->cpu_stall)
7523 show_cpu_pool_hog(pool);
7524
7525 }
7526
7527 rcu_read_unlock();
7528}
7529
7530static void panic_on_wq_watchdog(void)
7531{
7532 static unsigned int wq_stall;
7533
7534 if (wq_panic_on_stall) {
7535 wq_stall++;
7536 BUG_ON(wq_stall >= wq_panic_on_stall);
7537 }
7538}
7539
7540static void wq_watchdog_reset_touched(void)
7541{
7542 int cpu;
7543
7544 wq_watchdog_touched = jiffies;
7545 for_each_possible_cpu(cpu)
7546 per_cpu(wq_watchdog_touched_cpu, cpu) = jiffies;
7547}
7548
7549static void wq_watchdog_timer_fn(struct timer_list *unused)
7550{
7551 unsigned long thresh = READ_ONCE(wq_watchdog_thresh) * HZ;
7552 bool lockup_detected = false;
7553 bool cpu_pool_stall = false;
7554 unsigned long now = jiffies;
7555 struct worker_pool *pool;
7556 int pi;
7557
7558 if (!thresh)
7559 return;
7560
7561 rcu_read_lock();
7562
7563 for_each_pool(pool, pi) {
7564 unsigned long pool_ts, touched, ts;
7565
7566 pool->cpu_stall = false;
7567 if (list_empty(&pool->worklist))
7568 continue;
7569
7570 /*
7571 * If a virtual machine is stopped by the host it can look to
7572 * the watchdog like a stall.
7573 */
7574 kvm_check_and_clear_guest_paused();
7575
7576 /* get the latest of pool and touched timestamps */
7577 if (pool->cpu >= 0)
7578 touched = READ_ONCE(per_cpu(wq_watchdog_touched_cpu, pool->cpu));
7579 else
7580 touched = READ_ONCE(wq_watchdog_touched);
7581 pool_ts = READ_ONCE(pool->watchdog_ts);
7582
7583 if (time_after(pool_ts, touched))
7584 ts = pool_ts;
7585 else
7586 ts = touched;
7587
7588 /* did we stall? */
7589 if (time_after(now, ts + thresh)) {
7590 lockup_detected = true;
7591 if (pool->cpu >= 0 && !(pool->flags & POOL_BH)) {
7592 pool->cpu_stall = true;
7593 cpu_pool_stall = true;
7594 }
7595 pr_emerg("BUG: workqueue lockup - pool");
7596 pr_cont_pool_info(pool);
7597 pr_cont(" stuck for %us!\n",
7598 jiffies_to_msecs(now - pool_ts) / 1000);
7599 }
7600
7601
7602 }
7603
7604 rcu_read_unlock();
7605
7606 if (lockup_detected)
7607 show_all_workqueues();
7608
7609 if (cpu_pool_stall)
7610 show_cpu_pools_hogs();
7611
7612 if (lockup_detected)
7613 panic_on_wq_watchdog();
7614
7615 wq_watchdog_reset_touched();
7616 mod_timer(&wq_watchdog_timer, jiffies + thresh);
7617}
7618
7619notrace void wq_watchdog_touch(int cpu)
7620{
7621 unsigned long thresh = READ_ONCE(wq_watchdog_thresh) * HZ;
7622 unsigned long touch_ts = READ_ONCE(wq_watchdog_touched);
7623 unsigned long now = jiffies;
7624
7625 if (cpu >= 0)
7626 per_cpu(wq_watchdog_touched_cpu, cpu) = now;
7627 else
7628 WARN_ONCE(1, "%s should be called with valid CPU", __func__);
7629
7630 /* Don't unnecessarily store to global cacheline */
7631 if (time_after(now, touch_ts + thresh / 4))
7632 WRITE_ONCE(wq_watchdog_touched, jiffies);
7633}
7634
7635static void wq_watchdog_set_thresh(unsigned long thresh)
7636{
7637 wq_watchdog_thresh = 0;
7638 del_timer_sync(&wq_watchdog_timer);
7639
7640 if (thresh) {
7641 wq_watchdog_thresh = thresh;
7642 wq_watchdog_reset_touched();
7643 mod_timer(&wq_watchdog_timer, jiffies + thresh * HZ);
7644 }
7645}
7646
7647static int wq_watchdog_param_set_thresh(const char *val,
7648 const struct kernel_param *kp)
7649{
7650 unsigned long thresh;
7651 int ret;
7652
7653 ret = kstrtoul(val, 0, &thresh);
7654 if (ret)
7655 return ret;
7656
7657 if (system_wq)
7658 wq_watchdog_set_thresh(thresh);
7659 else
7660 wq_watchdog_thresh = thresh;
7661
7662 return 0;
7663}
7664
7665static const struct kernel_param_ops wq_watchdog_thresh_ops = {
7666 .set = wq_watchdog_param_set_thresh,
7667 .get = param_get_ulong,
7668};
7669
7670module_param_cb(watchdog_thresh, &wq_watchdog_thresh_ops, &wq_watchdog_thresh,
7671 0644);
7672
7673static void wq_watchdog_init(void)
7674{
7675 timer_setup(&wq_watchdog_timer, wq_watchdog_timer_fn, TIMER_DEFERRABLE);
7676 wq_watchdog_set_thresh(wq_watchdog_thresh);
7677}
7678
7679#else /* CONFIG_WQ_WATCHDOG */
7680
7681static inline void wq_watchdog_init(void) { }
7682
7683#endif /* CONFIG_WQ_WATCHDOG */
7684
7685static void bh_pool_kick_normal(struct irq_work *irq_work)
7686{
7687 raise_softirq_irqoff(TASKLET_SOFTIRQ);
7688}
7689
7690static void bh_pool_kick_highpri(struct irq_work *irq_work)
7691{
7692 raise_softirq_irqoff(HI_SOFTIRQ);
7693}
7694
7695static void __init restrict_unbound_cpumask(const char *name, const struct cpumask *mask)
7696{
7697 if (!cpumask_intersects(wq_unbound_cpumask, mask)) {
7698 pr_warn("workqueue: Restricting unbound_cpumask (%*pb) with %s (%*pb) leaves no CPU, ignoring\n",
7699 cpumask_pr_args(wq_unbound_cpumask), name, cpumask_pr_args(mask));
7700 return;
7701 }
7702
7703 cpumask_and(wq_unbound_cpumask, wq_unbound_cpumask, mask);
7704}
7705
7706static void __init init_cpu_worker_pool(struct worker_pool *pool, int cpu, int nice)
7707{
7708 BUG_ON(init_worker_pool(pool));
7709 pool->cpu = cpu;
7710 cpumask_copy(pool->attrs->cpumask, cpumask_of(cpu));
7711 cpumask_copy(pool->attrs->__pod_cpumask, cpumask_of(cpu));
7712 pool->attrs->nice = nice;
7713 pool->attrs->affn_strict = true;
7714 pool->node = cpu_to_node(cpu);
7715
7716 /* alloc pool ID */
7717 mutex_lock(&wq_pool_mutex);
7718 BUG_ON(worker_pool_assign_id(pool));
7719 mutex_unlock(&wq_pool_mutex);
7720}
7721
7722/**
7723 * workqueue_init_early - early init for workqueue subsystem
7724 *
7725 * This is the first step of three-staged workqueue subsystem initialization and
7726 * invoked as soon as the bare basics - memory allocation, cpumasks and idr are
7727 * up. It sets up all the data structures and system workqueues and allows early
7728 * boot code to create workqueues and queue/cancel work items. Actual work item
7729 * execution starts only after kthreads can be created and scheduled right
7730 * before early initcalls.
7731 */
7732void __init workqueue_init_early(void)
7733{
7734 struct wq_pod_type *pt = &wq_pod_types[WQ_AFFN_SYSTEM];
7735 int std_nice[NR_STD_WORKER_POOLS] = { 0, HIGHPRI_NICE_LEVEL };
7736 void (*irq_work_fns[2])(struct irq_work *) = { bh_pool_kick_normal,
7737 bh_pool_kick_highpri };
7738 int i, cpu;
7739
7740 BUILD_BUG_ON(__alignof__(struct pool_workqueue) < __alignof__(long long));
7741
7742 BUG_ON(!alloc_cpumask_var(&wq_online_cpumask, GFP_KERNEL));
7743 BUG_ON(!alloc_cpumask_var(&wq_unbound_cpumask, GFP_KERNEL));
7744 BUG_ON(!alloc_cpumask_var(&wq_requested_unbound_cpumask, GFP_KERNEL));
7745 BUG_ON(!zalloc_cpumask_var(&wq_isolated_cpumask, GFP_KERNEL));
7746
7747 cpumask_copy(wq_online_cpumask, cpu_online_mask);
7748 cpumask_copy(wq_unbound_cpumask, cpu_possible_mask);
7749 restrict_unbound_cpumask("HK_TYPE_WQ", housekeeping_cpumask(HK_TYPE_WQ));
7750 restrict_unbound_cpumask("HK_TYPE_DOMAIN", housekeeping_cpumask(HK_TYPE_DOMAIN));
7751 if (!cpumask_empty(&wq_cmdline_cpumask))
7752 restrict_unbound_cpumask("workqueue.unbound_cpus", &wq_cmdline_cpumask);
7753
7754 cpumask_copy(wq_requested_unbound_cpumask, wq_unbound_cpumask);
7755
7756 pwq_cache = KMEM_CACHE(pool_workqueue, SLAB_PANIC);
7757
7758 unbound_wq_update_pwq_attrs_buf = alloc_workqueue_attrs();
7759 BUG_ON(!unbound_wq_update_pwq_attrs_buf);
7760
7761 /*
7762 * If nohz_full is enabled, set power efficient workqueue as unbound.
7763 * This allows workqueue items to be moved to HK CPUs.
7764 */
7765 if (housekeeping_enabled(HK_TYPE_TICK))
7766 wq_power_efficient = true;
7767
7768 /* initialize WQ_AFFN_SYSTEM pods */
7769 pt->pod_cpus = kcalloc(1, sizeof(pt->pod_cpus[0]), GFP_KERNEL);
7770 pt->pod_node = kcalloc(1, sizeof(pt->pod_node[0]), GFP_KERNEL);
7771 pt->cpu_pod = kcalloc(nr_cpu_ids, sizeof(pt->cpu_pod[0]), GFP_KERNEL);
7772 BUG_ON(!pt->pod_cpus || !pt->pod_node || !pt->cpu_pod);
7773
7774 BUG_ON(!zalloc_cpumask_var_node(&pt->pod_cpus[0], GFP_KERNEL, NUMA_NO_NODE));
7775
7776 pt->nr_pods = 1;
7777 cpumask_copy(pt->pod_cpus[0], cpu_possible_mask);
7778 pt->pod_node[0] = NUMA_NO_NODE;
7779 pt->cpu_pod[0] = 0;
7780
7781 /* initialize BH and CPU pools */
7782 for_each_possible_cpu(cpu) {
7783 struct worker_pool *pool;
7784
7785 i = 0;
7786 for_each_bh_worker_pool(pool, cpu) {
7787 init_cpu_worker_pool(pool, cpu, std_nice[i]);
7788 pool->flags |= POOL_BH;
7789 init_irq_work(bh_pool_irq_work(pool), irq_work_fns[i]);
7790 i++;
7791 }
7792
7793 i = 0;
7794 for_each_cpu_worker_pool(pool, cpu)
7795 init_cpu_worker_pool(pool, cpu, std_nice[i++]);
7796 }
7797
7798 /* create default unbound and ordered wq attrs */
7799 for (i = 0; i < NR_STD_WORKER_POOLS; i++) {
7800 struct workqueue_attrs *attrs;
7801
7802 BUG_ON(!(attrs = alloc_workqueue_attrs()));
7803 attrs->nice = std_nice[i];
7804 unbound_std_wq_attrs[i] = attrs;
7805
7806 /*
7807 * An ordered wq should have only one pwq as ordering is
7808 * guaranteed by max_active which is enforced by pwqs.
7809 */
7810 BUG_ON(!(attrs = alloc_workqueue_attrs()));
7811 attrs->nice = std_nice[i];
7812 attrs->ordered = true;
7813 ordered_wq_attrs[i] = attrs;
7814 }
7815
7816 system_wq = alloc_workqueue("events", 0, 0);
7817 system_highpri_wq = alloc_workqueue("events_highpri", WQ_HIGHPRI, 0);
7818 system_long_wq = alloc_workqueue("events_long", 0, 0);
7819 system_unbound_wq = alloc_workqueue("events_unbound", WQ_UNBOUND,
7820 WQ_MAX_ACTIVE);
7821 system_freezable_wq = alloc_workqueue("events_freezable",
7822 WQ_FREEZABLE, 0);
7823 system_power_efficient_wq = alloc_workqueue("events_power_efficient",
7824 WQ_POWER_EFFICIENT, 0);
7825 system_freezable_power_efficient_wq = alloc_workqueue("events_freezable_pwr_efficient",
7826 WQ_FREEZABLE | WQ_POWER_EFFICIENT,
7827 0);
7828 system_bh_wq = alloc_workqueue("events_bh", WQ_BH, 0);
7829 system_bh_highpri_wq = alloc_workqueue("events_bh_highpri",
7830 WQ_BH | WQ_HIGHPRI, 0);
7831 BUG_ON(!system_wq || !system_highpri_wq || !system_long_wq ||
7832 !system_unbound_wq || !system_freezable_wq ||
7833 !system_power_efficient_wq ||
7834 !system_freezable_power_efficient_wq ||
7835 !system_bh_wq || !system_bh_highpri_wq);
7836}
7837
7838static void __init wq_cpu_intensive_thresh_init(void)
7839{
7840 unsigned long thresh;
7841 unsigned long bogo;
7842
7843 pwq_release_worker = kthread_create_worker(0, "pool_workqueue_release");
7844 BUG_ON(IS_ERR(pwq_release_worker));
7845
7846 /* if the user set it to a specific value, keep it */
7847 if (wq_cpu_intensive_thresh_us != ULONG_MAX)
7848 return;
7849
7850 /*
7851 * The default of 10ms is derived from the fact that most modern (as of
7852 * 2023) processors can do a lot in 10ms and that it's just below what
7853 * most consider human-perceivable. However, the kernel also runs on a
7854 * lot slower CPUs including microcontrollers where the threshold is way
7855 * too low.
7856 *
7857 * Let's scale up the threshold upto 1 second if BogoMips is below 4000.
7858 * This is by no means accurate but it doesn't have to be. The mechanism
7859 * is still useful even when the threshold is fully scaled up. Also, as
7860 * the reports would usually be applicable to everyone, some machines
7861 * operating on longer thresholds won't significantly diminish their
7862 * usefulness.
7863 */
7864 thresh = 10 * USEC_PER_MSEC;
7865
7866 /* see init/calibrate.c for lpj -> BogoMIPS calculation */
7867 bogo = max_t(unsigned long, loops_per_jiffy / 500000 * HZ, 1);
7868 if (bogo < 4000)
7869 thresh = min_t(unsigned long, thresh * 4000 / bogo, USEC_PER_SEC);
7870
7871 pr_debug("wq_cpu_intensive_thresh: lpj=%lu BogoMIPS=%lu thresh_us=%lu\n",
7872 loops_per_jiffy, bogo, thresh);
7873
7874 wq_cpu_intensive_thresh_us = thresh;
7875}
7876
7877/**
7878 * workqueue_init - bring workqueue subsystem fully online
7879 *
7880 * This is the second step of three-staged workqueue subsystem initialization
7881 * and invoked as soon as kthreads can be created and scheduled. Workqueues have
7882 * been created and work items queued on them, but there are no kworkers
7883 * executing the work items yet. Populate the worker pools with the initial
7884 * workers and enable future kworker creations.
7885 */
7886void __init workqueue_init(void)
7887{
7888 struct workqueue_struct *wq;
7889 struct worker_pool *pool;
7890 int cpu, bkt;
7891
7892 wq_cpu_intensive_thresh_init();
7893
7894 mutex_lock(&wq_pool_mutex);
7895
7896 /*
7897 * Per-cpu pools created earlier could be missing node hint. Fix them
7898 * up. Also, create a rescuer for workqueues that requested it.
7899 */
7900 for_each_possible_cpu(cpu) {
7901 for_each_bh_worker_pool(pool, cpu)
7902 pool->node = cpu_to_node(cpu);
7903 for_each_cpu_worker_pool(pool, cpu)
7904 pool->node = cpu_to_node(cpu);
7905 }
7906
7907 list_for_each_entry(wq, &workqueues, list) {
7908 WARN(init_rescuer(wq),
7909 "workqueue: failed to create early rescuer for %s",
7910 wq->name);
7911 }
7912
7913 mutex_unlock(&wq_pool_mutex);
7914
7915 /*
7916 * Create the initial workers. A BH pool has one pseudo worker that
7917 * represents the shared BH execution context and thus doesn't get
7918 * affected by hotplug events. Create the BH pseudo workers for all
7919 * possible CPUs here.
7920 */
7921 for_each_possible_cpu(cpu)
7922 for_each_bh_worker_pool(pool, cpu)
7923 BUG_ON(!create_worker(pool));
7924
7925 for_each_online_cpu(cpu) {
7926 for_each_cpu_worker_pool(pool, cpu) {
7927 pool->flags &= ~POOL_DISASSOCIATED;
7928 BUG_ON(!create_worker(pool));
7929 }
7930 }
7931
7932 hash_for_each(unbound_pool_hash, bkt, pool, hash_node)
7933 BUG_ON(!create_worker(pool));
7934
7935 wq_online = true;
7936 wq_watchdog_init();
7937}
7938
7939/*
7940 * Initialize @pt by first initializing @pt->cpu_pod[] with pod IDs according to
7941 * @cpu_shares_pod(). Each subset of CPUs that share a pod is assigned a unique
7942 * and consecutive pod ID. The rest of @pt is initialized accordingly.
7943 */
7944static void __init init_pod_type(struct wq_pod_type *pt,
7945 bool (*cpus_share_pod)(int, int))
7946{
7947 int cur, pre, cpu, pod;
7948
7949 pt->nr_pods = 0;
7950
7951 /* init @pt->cpu_pod[] according to @cpus_share_pod() */
7952 pt->cpu_pod = kcalloc(nr_cpu_ids, sizeof(pt->cpu_pod[0]), GFP_KERNEL);
7953 BUG_ON(!pt->cpu_pod);
7954
7955 for_each_possible_cpu(cur) {
7956 for_each_possible_cpu(pre) {
7957 if (pre >= cur) {
7958 pt->cpu_pod[cur] = pt->nr_pods++;
7959 break;
7960 }
7961 if (cpus_share_pod(cur, pre)) {
7962 pt->cpu_pod[cur] = pt->cpu_pod[pre];
7963 break;
7964 }
7965 }
7966 }
7967
7968 /* init the rest to match @pt->cpu_pod[] */
7969 pt->pod_cpus = kcalloc(pt->nr_pods, sizeof(pt->pod_cpus[0]), GFP_KERNEL);
7970 pt->pod_node = kcalloc(pt->nr_pods, sizeof(pt->pod_node[0]), GFP_KERNEL);
7971 BUG_ON(!pt->pod_cpus || !pt->pod_node);
7972
7973 for (pod = 0; pod < pt->nr_pods; pod++)
7974 BUG_ON(!zalloc_cpumask_var(&pt->pod_cpus[pod], GFP_KERNEL));
7975
7976 for_each_possible_cpu(cpu) {
7977 cpumask_set_cpu(cpu, pt->pod_cpus[pt->cpu_pod[cpu]]);
7978 pt->pod_node[pt->cpu_pod[cpu]] = cpu_to_node(cpu);
7979 }
7980}
7981
7982static bool __init cpus_dont_share(int cpu0, int cpu1)
7983{
7984 return false;
7985}
7986
7987static bool __init cpus_share_smt(int cpu0, int cpu1)
7988{
7989#ifdef CONFIG_SCHED_SMT
7990 return cpumask_test_cpu(cpu0, cpu_smt_mask(cpu1));
7991#else
7992 return false;
7993#endif
7994}
7995
7996static bool __init cpus_share_numa(int cpu0, int cpu1)
7997{
7998 return cpu_to_node(cpu0) == cpu_to_node(cpu1);
7999}
8000
8001/**
8002 * workqueue_init_topology - initialize CPU pods for unbound workqueues
8003 *
8004 * This is the third step of three-staged workqueue subsystem initialization and
8005 * invoked after SMP and topology information are fully initialized. It
8006 * initializes the unbound CPU pods accordingly.
8007 */
8008void __init workqueue_init_topology(void)
8009{
8010 struct workqueue_struct *wq;
8011 int cpu;
8012
8013 init_pod_type(&wq_pod_types[WQ_AFFN_CPU], cpus_dont_share);
8014 init_pod_type(&wq_pod_types[WQ_AFFN_SMT], cpus_share_smt);
8015 init_pod_type(&wq_pod_types[WQ_AFFN_CACHE], cpus_share_cache);
8016 init_pod_type(&wq_pod_types[WQ_AFFN_NUMA], cpus_share_numa);
8017
8018 wq_topo_initialized = true;
8019
8020 mutex_lock(&wq_pool_mutex);
8021
8022 /*
8023 * Workqueues allocated earlier would have all CPUs sharing the default
8024 * worker pool. Explicitly call unbound_wq_update_pwq() on all workqueue
8025 * and CPU combinations to apply per-pod sharing.
8026 */
8027 list_for_each_entry(wq, &workqueues, list) {
8028 for_each_online_cpu(cpu)
8029 unbound_wq_update_pwq(wq, cpu);
8030 if (wq->flags & WQ_UNBOUND) {
8031 mutex_lock(&wq->mutex);
8032 wq_update_node_max_active(wq, -1);
8033 mutex_unlock(&wq->mutex);
8034 }
8035 }
8036
8037 mutex_unlock(&wq_pool_mutex);
8038}
8039
8040void __warn_flushing_systemwide_wq(void)
8041{
8042 pr_warn("WARNING: Flushing system-wide workqueues will be prohibited in near future.\n");
8043 dump_stack();
8044}
8045EXPORT_SYMBOL(__warn_flushing_systemwide_wq);
8046
8047static int __init workqueue_unbound_cpus_setup(char *str)
8048{
8049 if (cpulist_parse(str, &wq_cmdline_cpumask) < 0) {
8050 cpumask_clear(&wq_cmdline_cpumask);
8051 pr_warn("workqueue.unbound_cpus: incorrect CPU range, using default\n");
8052 }
8053
8054 return 1;
8055}
8056__setup("workqueue.unbound_cpus=", workqueue_unbound_cpus_setup);