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