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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/sched/debug.h>
53#include <linux/nmi.h>
54#include <linux/kvm_para.h>
55#include <linux/delay.h>
56
57#include "workqueue_internal.h"
58
59enum {
60 /*
61 * worker_pool flags
62 *
63 * A bound pool is either associated or disassociated with its CPU.
64 * While associated (!DISASSOCIATED), all workers are bound to the
65 * CPU and none has %WORKER_UNBOUND set and concurrency management
66 * is in effect.
67 *
68 * While DISASSOCIATED, the cpu may be offline and all workers have
69 * %WORKER_UNBOUND set and concurrency management disabled, and may
70 * be executing on any CPU. The pool behaves as an unbound one.
71 *
72 * Note that DISASSOCIATED should be flipped only while holding
73 * wq_pool_attach_mutex to avoid changing binding state while
74 * worker_attach_to_pool() is in progress.
75 */
76 POOL_MANAGER_ACTIVE = 1 << 0, /* being managed */
77 POOL_DISASSOCIATED = 1 << 2, /* cpu can't serve workers */
78
79 /* worker flags */
80 WORKER_DIE = 1 << 1, /* die die die */
81 WORKER_IDLE = 1 << 2, /* is idle */
82 WORKER_PREP = 1 << 3, /* preparing to run works */
83 WORKER_CPU_INTENSIVE = 1 << 6, /* cpu intensive */
84 WORKER_UNBOUND = 1 << 7, /* worker is unbound */
85 WORKER_REBOUND = 1 << 8, /* worker was rebound */
86
87 WORKER_NOT_RUNNING = WORKER_PREP | WORKER_CPU_INTENSIVE |
88 WORKER_UNBOUND | WORKER_REBOUND,
89
90 NR_STD_WORKER_POOLS = 2, /* # standard pools per cpu */
91
92 UNBOUND_POOL_HASH_ORDER = 6, /* hashed by pool->attrs */
93 BUSY_WORKER_HASH_ORDER = 6, /* 64 pointers */
94
95 MAX_IDLE_WORKERS_RATIO = 4, /* 1/4 of busy can be idle */
96 IDLE_WORKER_TIMEOUT = 300 * HZ, /* keep idle ones for 5 mins */
97
98 MAYDAY_INITIAL_TIMEOUT = HZ / 100 >= 2 ? HZ / 100 : 2,
99 /* call for help after 10ms
100 (min two ticks) */
101 MAYDAY_INTERVAL = HZ / 10, /* and then every 100ms */
102 CREATE_COOLDOWN = HZ, /* time to breath after fail */
103
104 /*
105 * Rescue workers are used only on emergencies and shared by
106 * all cpus. Give MIN_NICE.
107 */
108 RESCUER_NICE_LEVEL = MIN_NICE,
109 HIGHPRI_NICE_LEVEL = MIN_NICE,
110
111 WQ_NAME_LEN = 24,
112};
113
114/*
115 * Structure fields follow one of the following exclusion rules.
116 *
117 * I: Modifiable by initialization/destruction paths and read-only for
118 * everyone else.
119 *
120 * P: Preemption protected. Disabling preemption is enough and should
121 * only be modified and accessed from the local cpu.
122 *
123 * L: pool->lock protected. Access with pool->lock held.
124 *
125 * K: Only modified by worker while holding pool->lock. Can be safely read by
126 * self, while holding pool->lock or from IRQ context if %current is the
127 * kworker.
128 *
129 * S: Only modified by worker self.
130 *
131 * A: wq_pool_attach_mutex protected.
132 *
133 * PL: wq_pool_mutex protected.
134 *
135 * PR: wq_pool_mutex protected for writes. RCU protected for reads.
136 *
137 * PW: wq_pool_mutex and wq->mutex protected for writes. Either for reads.
138 *
139 * PWR: wq_pool_mutex and wq->mutex protected for writes. Either or
140 * RCU for reads.
141 *
142 * WQ: wq->mutex protected.
143 *
144 * WR: wq->mutex protected for writes. RCU protected for reads.
145 *
146 * MD: wq_mayday_lock protected.
147 *
148 * WD: Used internally by the watchdog.
149 */
150
151/* struct worker is defined in workqueue_internal.h */
152
153struct worker_pool {
154 raw_spinlock_t lock; /* the pool lock */
155 int cpu; /* I: the associated cpu */
156 int node; /* I: the associated node ID */
157 int id; /* I: pool ID */
158 unsigned int flags; /* L: flags */
159
160 unsigned long watchdog_ts; /* L: watchdog timestamp */
161 bool cpu_stall; /* WD: stalled cpu bound pool */
162
163 /*
164 * The counter is incremented in a process context on the associated CPU
165 * w/ preemption disabled, and decremented or reset in the same context
166 * but w/ pool->lock held. The readers grab pool->lock and are
167 * guaranteed to see if the counter reached zero.
168 */
169 int nr_running;
170
171 struct list_head worklist; /* L: list of pending works */
172
173 int nr_workers; /* L: total number of workers */
174 int nr_idle; /* L: currently idle workers */
175
176 struct list_head idle_list; /* L: list of idle workers */
177 struct timer_list idle_timer; /* L: worker idle timeout */
178 struct work_struct idle_cull_work; /* L: worker idle cleanup */
179
180 struct timer_list mayday_timer; /* L: SOS timer for workers */
181
182 /* a workers is either on busy_hash or idle_list, or the manager */
183 DECLARE_HASHTABLE(busy_hash, BUSY_WORKER_HASH_ORDER);
184 /* L: hash of busy workers */
185
186 struct worker *manager; /* L: purely informational */
187 struct list_head workers; /* A: attached workers */
188 struct list_head dying_workers; /* A: workers about to die */
189 struct completion *detach_completion; /* all workers detached */
190
191 struct ida worker_ida; /* worker IDs for task name */
192
193 struct workqueue_attrs *attrs; /* I: worker attributes */
194 struct hlist_node hash_node; /* PL: unbound_pool_hash node */
195 int refcnt; /* PL: refcnt for unbound pools */
196
197 /*
198 * Destruction of pool is RCU protected to allow dereferences
199 * from get_work_pool().
200 */
201 struct rcu_head rcu;
202};
203
204/*
205 * Per-pool_workqueue statistics. These can be monitored using
206 * tools/workqueue/wq_monitor.py.
207 */
208enum pool_workqueue_stats {
209 PWQ_STAT_STARTED, /* work items started execution */
210 PWQ_STAT_COMPLETED, /* work items completed execution */
211 PWQ_STAT_CPU_TIME, /* total CPU time consumed */
212 PWQ_STAT_CPU_INTENSIVE, /* wq_cpu_intensive_thresh_us violations */
213 PWQ_STAT_CM_WAKEUP, /* concurrency-management worker wakeups */
214 PWQ_STAT_REPATRIATED, /* unbound workers brought back into scope */
215 PWQ_STAT_MAYDAY, /* maydays to rescuer */
216 PWQ_STAT_RESCUED, /* linked work items executed by rescuer */
217
218 PWQ_NR_STATS,
219};
220
221/*
222 * The per-pool workqueue. While queued, the lower WORK_STRUCT_FLAG_BITS
223 * of work_struct->data are used for flags and the remaining high bits
224 * point to the pwq; thus, pwqs need to be aligned at two's power of the
225 * number of flag bits.
226 */
227struct pool_workqueue {
228 struct worker_pool *pool; /* I: the associated pool */
229 struct workqueue_struct *wq; /* I: the owning workqueue */
230 int work_color; /* L: current color */
231 int flush_color; /* L: flushing color */
232 int refcnt; /* L: reference count */
233 int nr_in_flight[WORK_NR_COLORS];
234 /* L: nr of in_flight works */
235
236 /*
237 * nr_active management and WORK_STRUCT_INACTIVE:
238 *
239 * When pwq->nr_active >= max_active, new work item is queued to
240 * pwq->inactive_works instead of pool->worklist and marked with
241 * WORK_STRUCT_INACTIVE.
242 *
243 * All work items marked with WORK_STRUCT_INACTIVE do not participate
244 * in pwq->nr_active and all work items in pwq->inactive_works are
245 * marked with WORK_STRUCT_INACTIVE. But not all WORK_STRUCT_INACTIVE
246 * work items are in pwq->inactive_works. Some of them are ready to
247 * run in pool->worklist or worker->scheduled. Those work itmes are
248 * only struct wq_barrier which is used for flush_work() and should
249 * not participate in pwq->nr_active. For non-barrier work item, it
250 * is marked with WORK_STRUCT_INACTIVE iff it is in pwq->inactive_works.
251 */
252 int nr_active; /* L: nr of active works */
253 int max_active; /* L: max active works */
254 struct list_head inactive_works; /* L: inactive works */
255 struct list_head pwqs_node; /* WR: node on wq->pwqs */
256 struct list_head mayday_node; /* MD: node on wq->maydays */
257
258 u64 stats[PWQ_NR_STATS];
259
260 /*
261 * Release of unbound pwq is punted to a kthread_worker. See put_pwq()
262 * and pwq_release_workfn() for details. pool_workqueue itself is also
263 * RCU protected so that the first pwq can be determined without
264 * grabbing wq->mutex.
265 */
266 struct kthread_work release_work;
267 struct rcu_head rcu;
268} __aligned(1 << WORK_STRUCT_FLAG_BITS);
269
270/*
271 * Structure used to wait for workqueue flush.
272 */
273struct wq_flusher {
274 struct list_head list; /* WQ: list of flushers */
275 int flush_color; /* WQ: flush color waiting for */
276 struct completion done; /* flush completion */
277};
278
279struct wq_device;
280
281/*
282 * The externally visible workqueue. It relays the issued work items to
283 * the appropriate worker_pool through its pool_workqueues.
284 */
285struct workqueue_struct {
286 struct list_head pwqs; /* WR: all pwqs of this wq */
287 struct list_head list; /* PR: list of all workqueues */
288
289 struct mutex mutex; /* protects this wq */
290 int work_color; /* WQ: current work color */
291 int flush_color; /* WQ: current flush color */
292 atomic_t nr_pwqs_to_flush; /* flush in progress */
293 struct wq_flusher *first_flusher; /* WQ: first flusher */
294 struct list_head flusher_queue; /* WQ: flush waiters */
295 struct list_head flusher_overflow; /* WQ: flush overflow list */
296
297 struct list_head maydays; /* MD: pwqs requesting rescue */
298 struct worker *rescuer; /* MD: rescue worker */
299
300 int nr_drainers; /* WQ: drain in progress */
301 int saved_max_active; /* WQ: saved pwq max_active */
302
303 struct workqueue_attrs *unbound_attrs; /* PW: only for unbound wqs */
304 struct pool_workqueue *dfl_pwq; /* PW: only for unbound wqs */
305
306#ifdef CONFIG_SYSFS
307 struct wq_device *wq_dev; /* I: for sysfs interface */
308#endif
309#ifdef CONFIG_LOCKDEP
310 char *lock_name;
311 struct lock_class_key key;
312 struct lockdep_map lockdep_map;
313#endif
314 char name[WQ_NAME_LEN]; /* I: workqueue name */
315
316 /*
317 * Destruction of workqueue_struct is RCU protected to allow walking
318 * the workqueues list without grabbing wq_pool_mutex.
319 * This is used to dump all workqueues from sysrq.
320 */
321 struct rcu_head rcu;
322
323 /* hot fields used during command issue, aligned to cacheline */
324 unsigned int flags ____cacheline_aligned; /* WQ: WQ_* flags */
325 struct pool_workqueue __percpu __rcu **cpu_pwq; /* I: per-cpu pwqs */
326};
327
328static struct kmem_cache *pwq_cache;
329
330/*
331 * Each pod type describes how CPUs should be grouped for unbound workqueues.
332 * See the comment above workqueue_attrs->affn_scope.
333 */
334struct wq_pod_type {
335 int nr_pods; /* number of pods */
336 cpumask_var_t *pod_cpus; /* pod -> cpus */
337 int *pod_node; /* pod -> node */
338 int *cpu_pod; /* cpu -> pod */
339};
340
341static struct wq_pod_type wq_pod_types[WQ_AFFN_NR_TYPES];
342static enum wq_affn_scope wq_affn_dfl = WQ_AFFN_CACHE;
343
344static const char *wq_affn_names[WQ_AFFN_NR_TYPES] = {
345 [WQ_AFFN_DFL] = "default",
346 [WQ_AFFN_CPU] = "cpu",
347 [WQ_AFFN_SMT] = "smt",
348 [WQ_AFFN_CACHE] = "cache",
349 [WQ_AFFN_NUMA] = "numa",
350 [WQ_AFFN_SYSTEM] = "system",
351};
352
353/*
354 * Per-cpu work items which run for longer than the following threshold are
355 * automatically considered CPU intensive and excluded from concurrency
356 * management to prevent them from noticeably delaying other per-cpu work items.
357 * ULONG_MAX indicates that the user hasn't overridden it with a boot parameter.
358 * The actual value is initialized in wq_cpu_intensive_thresh_init().
359 */
360static unsigned long wq_cpu_intensive_thresh_us = ULONG_MAX;
361module_param_named(cpu_intensive_thresh_us, wq_cpu_intensive_thresh_us, ulong, 0644);
362
363/* see the comment above the definition of WQ_POWER_EFFICIENT */
364static bool wq_power_efficient = IS_ENABLED(CONFIG_WQ_POWER_EFFICIENT_DEFAULT);
365module_param_named(power_efficient, wq_power_efficient, bool, 0444);
366
367static bool wq_online; /* can kworkers be created yet? */
368
369/* buf for wq_update_unbound_pod_attrs(), protected by CPU hotplug exclusion */
370static struct workqueue_attrs *wq_update_pod_attrs_buf;
371
372static DEFINE_MUTEX(wq_pool_mutex); /* protects pools and workqueues list */
373static DEFINE_MUTEX(wq_pool_attach_mutex); /* protects worker attach/detach */
374static DEFINE_RAW_SPINLOCK(wq_mayday_lock); /* protects wq->maydays list */
375/* wait for manager to go away */
376static struct rcuwait manager_wait = __RCUWAIT_INITIALIZER(manager_wait);
377
378static LIST_HEAD(workqueues); /* PR: list of all workqueues */
379static bool workqueue_freezing; /* PL: have wqs started freezing? */
380
381/* PL&A: allowable cpus for unbound wqs and work items */
382static cpumask_var_t wq_unbound_cpumask;
383
384/* PL: user requested unbound cpumask via sysfs */
385static cpumask_var_t wq_requested_unbound_cpumask;
386
387/* PL: isolated cpumask to be excluded from unbound cpumask */
388static cpumask_var_t wq_isolated_cpumask;
389
390/* for further constrain wq_unbound_cpumask by cmdline parameter*/
391static struct cpumask wq_cmdline_cpumask __initdata;
392
393/* CPU where unbound work was last round robin scheduled from this CPU */
394static DEFINE_PER_CPU(int, wq_rr_cpu_last);
395
396/*
397 * Local execution of unbound work items is no longer guaranteed. The
398 * following always forces round-robin CPU selection on unbound work items
399 * to uncover usages which depend on it.
400 */
401#ifdef CONFIG_DEBUG_WQ_FORCE_RR_CPU
402static bool wq_debug_force_rr_cpu = true;
403#else
404static bool wq_debug_force_rr_cpu = false;
405#endif
406module_param_named(debug_force_rr_cpu, wq_debug_force_rr_cpu, bool, 0644);
407
408/* the per-cpu worker pools */
409static DEFINE_PER_CPU_SHARED_ALIGNED(struct worker_pool [NR_STD_WORKER_POOLS], cpu_worker_pools);
410
411static DEFINE_IDR(worker_pool_idr); /* PR: idr of all pools */
412
413/* PL: hash of all unbound pools keyed by pool->attrs */
414static DEFINE_HASHTABLE(unbound_pool_hash, UNBOUND_POOL_HASH_ORDER);
415
416/* I: attributes used when instantiating standard unbound pools on demand */
417static struct workqueue_attrs *unbound_std_wq_attrs[NR_STD_WORKER_POOLS];
418
419/* I: attributes used when instantiating ordered pools on demand */
420static struct workqueue_attrs *ordered_wq_attrs[NR_STD_WORKER_POOLS];
421
422/*
423 * I: kthread_worker to release pwq's. pwq release needs to be bounced to a
424 * process context while holding a pool lock. Bounce to a dedicated kthread
425 * worker to avoid A-A deadlocks.
426 */
427static struct kthread_worker *pwq_release_worker __ro_after_init;
428
429struct workqueue_struct *system_wq __ro_after_init;
430EXPORT_SYMBOL(system_wq);
431struct workqueue_struct *system_highpri_wq __ro_after_init;
432EXPORT_SYMBOL_GPL(system_highpri_wq);
433struct workqueue_struct *system_long_wq __ro_after_init;
434EXPORT_SYMBOL_GPL(system_long_wq);
435struct workqueue_struct *system_unbound_wq __ro_after_init;
436EXPORT_SYMBOL_GPL(system_unbound_wq);
437struct workqueue_struct *system_freezable_wq __ro_after_init;
438EXPORT_SYMBOL_GPL(system_freezable_wq);
439struct workqueue_struct *system_power_efficient_wq __ro_after_init;
440EXPORT_SYMBOL_GPL(system_power_efficient_wq);
441struct workqueue_struct *system_freezable_power_efficient_wq __ro_after_init;
442EXPORT_SYMBOL_GPL(system_freezable_power_efficient_wq);
443
444static int worker_thread(void *__worker);
445static void workqueue_sysfs_unregister(struct workqueue_struct *wq);
446static void show_pwq(struct pool_workqueue *pwq);
447static void show_one_worker_pool(struct worker_pool *pool);
448
449#define CREATE_TRACE_POINTS
450#include <trace/events/workqueue.h>
451
452#define assert_rcu_or_pool_mutex() \
453 RCU_LOCKDEP_WARN(!rcu_read_lock_held() && \
454 !lockdep_is_held(&wq_pool_mutex), \
455 "RCU or wq_pool_mutex should be held")
456
457#define assert_rcu_or_wq_mutex_or_pool_mutex(wq) \
458 RCU_LOCKDEP_WARN(!rcu_read_lock_held() && \
459 !lockdep_is_held(&wq->mutex) && \
460 !lockdep_is_held(&wq_pool_mutex), \
461 "RCU, wq->mutex or wq_pool_mutex should be held")
462
463#define for_each_cpu_worker_pool(pool, cpu) \
464 for ((pool) = &per_cpu(cpu_worker_pools, cpu)[0]; \
465 (pool) < &per_cpu(cpu_worker_pools, cpu)[NR_STD_WORKER_POOLS]; \
466 (pool)++)
467
468/**
469 * for_each_pool - iterate through all worker_pools in the system
470 * @pool: iteration cursor
471 * @pi: integer used for iteration
472 *
473 * This must be called either with wq_pool_mutex held or RCU read
474 * locked. If the pool needs to be used beyond the locking in effect, the
475 * caller is responsible for guaranteeing that the pool stays online.
476 *
477 * The if/else clause exists only for the lockdep assertion and can be
478 * ignored.
479 */
480#define for_each_pool(pool, pi) \
481 idr_for_each_entry(&worker_pool_idr, pool, pi) \
482 if (({ assert_rcu_or_pool_mutex(); false; })) { } \
483 else
484
485/**
486 * for_each_pool_worker - iterate through all workers of a worker_pool
487 * @worker: iteration cursor
488 * @pool: worker_pool to iterate workers of
489 *
490 * This must be called with wq_pool_attach_mutex.
491 *
492 * The if/else clause exists only for the lockdep assertion and can be
493 * ignored.
494 */
495#define for_each_pool_worker(worker, pool) \
496 list_for_each_entry((worker), &(pool)->workers, node) \
497 if (({ lockdep_assert_held(&wq_pool_attach_mutex); false; })) { } \
498 else
499
500/**
501 * for_each_pwq - iterate through all pool_workqueues of the specified workqueue
502 * @pwq: iteration cursor
503 * @wq: the target workqueue
504 *
505 * This must be called either with wq->mutex held or RCU read locked.
506 * If the pwq needs to be used beyond the locking in effect, the caller is
507 * responsible for guaranteeing that the pwq stays online.
508 *
509 * The if/else clause exists only for the lockdep assertion and can be
510 * ignored.
511 */
512#define for_each_pwq(pwq, wq) \
513 list_for_each_entry_rcu((pwq), &(wq)->pwqs, pwqs_node, \
514 lockdep_is_held(&(wq->mutex)))
515
516#ifdef CONFIG_DEBUG_OBJECTS_WORK
517
518static const struct debug_obj_descr work_debug_descr;
519
520static void *work_debug_hint(void *addr)
521{
522 return ((struct work_struct *) addr)->func;
523}
524
525static bool work_is_static_object(void *addr)
526{
527 struct work_struct *work = addr;
528
529 return test_bit(WORK_STRUCT_STATIC_BIT, work_data_bits(work));
530}
531
532/*
533 * fixup_init is called when:
534 * - an active object is initialized
535 */
536static bool work_fixup_init(void *addr, enum debug_obj_state state)
537{
538 struct work_struct *work = addr;
539
540 switch (state) {
541 case ODEBUG_STATE_ACTIVE:
542 cancel_work_sync(work);
543 debug_object_init(work, &work_debug_descr);
544 return true;
545 default:
546 return false;
547 }
548}
549
550/*
551 * fixup_free is called when:
552 * - an active object is freed
553 */
554static bool work_fixup_free(void *addr, enum debug_obj_state state)
555{
556 struct work_struct *work = addr;
557
558 switch (state) {
559 case ODEBUG_STATE_ACTIVE:
560 cancel_work_sync(work);
561 debug_object_free(work, &work_debug_descr);
562 return true;
563 default:
564 return false;
565 }
566}
567
568static const struct debug_obj_descr work_debug_descr = {
569 .name = "work_struct",
570 .debug_hint = work_debug_hint,
571 .is_static_object = work_is_static_object,
572 .fixup_init = work_fixup_init,
573 .fixup_free = work_fixup_free,
574};
575
576static inline void debug_work_activate(struct work_struct *work)
577{
578 debug_object_activate(work, &work_debug_descr);
579}
580
581static inline void debug_work_deactivate(struct work_struct *work)
582{
583 debug_object_deactivate(work, &work_debug_descr);
584}
585
586void __init_work(struct work_struct *work, int onstack)
587{
588 if (onstack)
589 debug_object_init_on_stack(work, &work_debug_descr);
590 else
591 debug_object_init(work, &work_debug_descr);
592}
593EXPORT_SYMBOL_GPL(__init_work);
594
595void destroy_work_on_stack(struct work_struct *work)
596{
597 debug_object_free(work, &work_debug_descr);
598}
599EXPORT_SYMBOL_GPL(destroy_work_on_stack);
600
601void destroy_delayed_work_on_stack(struct delayed_work *work)
602{
603 destroy_timer_on_stack(&work->timer);
604 debug_object_free(&work->work, &work_debug_descr);
605}
606EXPORT_SYMBOL_GPL(destroy_delayed_work_on_stack);
607
608#else
609static inline void debug_work_activate(struct work_struct *work) { }
610static inline void debug_work_deactivate(struct work_struct *work) { }
611#endif
612
613/**
614 * worker_pool_assign_id - allocate ID and assign it to @pool
615 * @pool: the pool pointer of interest
616 *
617 * Returns 0 if ID in [0, WORK_OFFQ_POOL_NONE) is allocated and assigned
618 * successfully, -errno on failure.
619 */
620static int worker_pool_assign_id(struct worker_pool *pool)
621{
622 int ret;
623
624 lockdep_assert_held(&wq_pool_mutex);
625
626 ret = idr_alloc(&worker_pool_idr, pool, 0, WORK_OFFQ_POOL_NONE,
627 GFP_KERNEL);
628 if (ret >= 0) {
629 pool->id = ret;
630 return 0;
631 }
632 return ret;
633}
634
635static unsigned int work_color_to_flags(int color)
636{
637 return color << WORK_STRUCT_COLOR_SHIFT;
638}
639
640static int get_work_color(unsigned long work_data)
641{
642 return (work_data >> WORK_STRUCT_COLOR_SHIFT) &
643 ((1 << WORK_STRUCT_COLOR_BITS) - 1);
644}
645
646static int work_next_color(int color)
647{
648 return (color + 1) % WORK_NR_COLORS;
649}
650
651/*
652 * While queued, %WORK_STRUCT_PWQ is set and non flag bits of a work's data
653 * contain the pointer to the queued pwq. Once execution starts, the flag
654 * is cleared and the high bits contain OFFQ flags and pool ID.
655 *
656 * set_work_pwq(), set_work_pool_and_clear_pending(), mark_work_canceling()
657 * and clear_work_data() can be used to set the pwq, pool or clear
658 * work->data. These functions should only be called while the work is
659 * owned - ie. while the PENDING bit is set.
660 *
661 * get_work_pool() and get_work_pwq() can be used to obtain the pool or pwq
662 * corresponding to a work. Pool is available once the work has been
663 * queued anywhere after initialization until it is sync canceled. pwq is
664 * available only while the work item is queued.
665 *
666 * %WORK_OFFQ_CANCELING is used to mark a work item which is being
667 * canceled. While being canceled, a work item may have its PENDING set
668 * but stay off timer and worklist for arbitrarily long and nobody should
669 * try to steal the PENDING bit.
670 */
671static inline void set_work_data(struct work_struct *work, unsigned long data,
672 unsigned long flags)
673{
674 WARN_ON_ONCE(!work_pending(work));
675 atomic_long_set(&work->data, data | flags | work_static(work));
676}
677
678static void set_work_pwq(struct work_struct *work, struct pool_workqueue *pwq,
679 unsigned long extra_flags)
680{
681 set_work_data(work, (unsigned long)pwq,
682 WORK_STRUCT_PENDING | WORK_STRUCT_PWQ | extra_flags);
683}
684
685static void set_work_pool_and_keep_pending(struct work_struct *work,
686 int pool_id)
687{
688 set_work_data(work, (unsigned long)pool_id << WORK_OFFQ_POOL_SHIFT,
689 WORK_STRUCT_PENDING);
690}
691
692static void set_work_pool_and_clear_pending(struct work_struct *work,
693 int pool_id)
694{
695 /*
696 * The following wmb is paired with the implied mb in
697 * test_and_set_bit(PENDING) and ensures all updates to @work made
698 * here are visible to and precede any updates by the next PENDING
699 * owner.
700 */
701 smp_wmb();
702 set_work_data(work, (unsigned long)pool_id << WORK_OFFQ_POOL_SHIFT, 0);
703 /*
704 * The following mb guarantees that previous clear of a PENDING bit
705 * will not be reordered with any speculative LOADS or STORES from
706 * work->current_func, which is executed afterwards. This possible
707 * reordering can lead to a missed execution on attempt to queue
708 * the same @work. E.g. consider this case:
709 *
710 * CPU#0 CPU#1
711 * ---------------------------- --------------------------------
712 *
713 * 1 STORE event_indicated
714 * 2 queue_work_on() {
715 * 3 test_and_set_bit(PENDING)
716 * 4 } set_..._and_clear_pending() {
717 * 5 set_work_data() # clear bit
718 * 6 smp_mb()
719 * 7 work->current_func() {
720 * 8 LOAD event_indicated
721 * }
722 *
723 * Without an explicit full barrier speculative LOAD on line 8 can
724 * be executed before CPU#0 does STORE on line 1. If that happens,
725 * CPU#0 observes the PENDING bit is still set and new execution of
726 * a @work is not queued in a hope, that CPU#1 will eventually
727 * finish the queued @work. Meanwhile CPU#1 does not see
728 * event_indicated is set, because speculative LOAD was executed
729 * before actual STORE.
730 */
731 smp_mb();
732}
733
734static void clear_work_data(struct work_struct *work)
735{
736 smp_wmb(); /* see set_work_pool_and_clear_pending() */
737 set_work_data(work, WORK_STRUCT_NO_POOL, 0);
738}
739
740static inline struct pool_workqueue *work_struct_pwq(unsigned long data)
741{
742 return (struct pool_workqueue *)(data & WORK_STRUCT_WQ_DATA_MASK);
743}
744
745static struct pool_workqueue *get_work_pwq(struct work_struct *work)
746{
747 unsigned long data = atomic_long_read(&work->data);
748
749 if (data & WORK_STRUCT_PWQ)
750 return work_struct_pwq(data);
751 else
752 return NULL;
753}
754
755/**
756 * get_work_pool - return the worker_pool a given work was associated with
757 * @work: the work item of interest
758 *
759 * Pools are created and destroyed under wq_pool_mutex, and allows read
760 * access under RCU read lock. As such, this function should be
761 * called under wq_pool_mutex or inside of a rcu_read_lock() region.
762 *
763 * All fields of the returned pool are accessible as long as the above
764 * mentioned locking is in effect. If the returned pool needs to be used
765 * beyond the critical section, the caller is responsible for ensuring the
766 * returned pool is and stays online.
767 *
768 * Return: The worker_pool @work was last associated with. %NULL if none.
769 */
770static struct worker_pool *get_work_pool(struct work_struct *work)
771{
772 unsigned long data = atomic_long_read(&work->data);
773 int pool_id;
774
775 assert_rcu_or_pool_mutex();
776
777 if (data & WORK_STRUCT_PWQ)
778 return work_struct_pwq(data)->pool;
779
780 pool_id = data >> WORK_OFFQ_POOL_SHIFT;
781 if (pool_id == WORK_OFFQ_POOL_NONE)
782 return NULL;
783
784 return idr_find(&worker_pool_idr, pool_id);
785}
786
787/**
788 * get_work_pool_id - return the worker pool ID a given work is associated with
789 * @work: the work item of interest
790 *
791 * Return: The worker_pool ID @work was last associated with.
792 * %WORK_OFFQ_POOL_NONE if none.
793 */
794static int get_work_pool_id(struct work_struct *work)
795{
796 unsigned long data = atomic_long_read(&work->data);
797
798 if (data & WORK_STRUCT_PWQ)
799 return work_struct_pwq(data)->pool->id;
800
801 return data >> WORK_OFFQ_POOL_SHIFT;
802}
803
804static void mark_work_canceling(struct work_struct *work)
805{
806 unsigned long pool_id = get_work_pool_id(work);
807
808 pool_id <<= WORK_OFFQ_POOL_SHIFT;
809 set_work_data(work, pool_id | WORK_OFFQ_CANCELING, WORK_STRUCT_PENDING);
810}
811
812static bool work_is_canceling(struct work_struct *work)
813{
814 unsigned long data = atomic_long_read(&work->data);
815
816 return !(data & WORK_STRUCT_PWQ) && (data & WORK_OFFQ_CANCELING);
817}
818
819/*
820 * Policy functions. These define the policies on how the global worker
821 * pools are managed. Unless noted otherwise, these functions assume that
822 * they're being called with pool->lock held.
823 */
824
825/*
826 * Need to wake up a worker? Called from anything but currently
827 * running workers.
828 *
829 * Note that, because unbound workers never contribute to nr_running, this
830 * function will always return %true for unbound pools as long as the
831 * worklist isn't empty.
832 */
833static bool need_more_worker(struct worker_pool *pool)
834{
835 return !list_empty(&pool->worklist) && !pool->nr_running;
836}
837
838/* Can I start working? Called from busy but !running workers. */
839static bool may_start_working(struct worker_pool *pool)
840{
841 return pool->nr_idle;
842}
843
844/* Do I need to keep working? Called from currently running workers. */
845static bool keep_working(struct worker_pool *pool)
846{
847 return !list_empty(&pool->worklist) && (pool->nr_running <= 1);
848}
849
850/* Do we need a new worker? Called from manager. */
851static bool need_to_create_worker(struct worker_pool *pool)
852{
853 return need_more_worker(pool) && !may_start_working(pool);
854}
855
856/* Do we have too many workers and should some go away? */
857static bool too_many_workers(struct worker_pool *pool)
858{
859 bool managing = pool->flags & POOL_MANAGER_ACTIVE;
860 int nr_idle = pool->nr_idle + managing; /* manager is considered idle */
861 int nr_busy = pool->nr_workers - nr_idle;
862
863 return nr_idle > 2 && (nr_idle - 2) * MAX_IDLE_WORKERS_RATIO >= nr_busy;
864}
865
866/**
867 * worker_set_flags - set worker flags and adjust nr_running accordingly
868 * @worker: self
869 * @flags: flags to set
870 *
871 * Set @flags in @worker->flags and adjust nr_running accordingly.
872 */
873static inline void worker_set_flags(struct worker *worker, unsigned int flags)
874{
875 struct worker_pool *pool = worker->pool;
876
877 lockdep_assert_held(&pool->lock);
878
879 /* If transitioning into NOT_RUNNING, adjust nr_running. */
880 if ((flags & WORKER_NOT_RUNNING) &&
881 !(worker->flags & WORKER_NOT_RUNNING)) {
882 pool->nr_running--;
883 }
884
885 worker->flags |= flags;
886}
887
888/**
889 * worker_clr_flags - clear worker flags and adjust nr_running accordingly
890 * @worker: self
891 * @flags: flags to clear
892 *
893 * Clear @flags in @worker->flags and adjust nr_running accordingly.
894 */
895static inline void worker_clr_flags(struct worker *worker, unsigned int flags)
896{
897 struct worker_pool *pool = worker->pool;
898 unsigned int oflags = worker->flags;
899
900 lockdep_assert_held(&pool->lock);
901
902 worker->flags &= ~flags;
903
904 /*
905 * If transitioning out of NOT_RUNNING, increment nr_running. Note
906 * that the nested NOT_RUNNING is not a noop. NOT_RUNNING is mask
907 * of multiple flags, not a single flag.
908 */
909 if ((flags & WORKER_NOT_RUNNING) && (oflags & WORKER_NOT_RUNNING))
910 if (!(worker->flags & WORKER_NOT_RUNNING))
911 pool->nr_running++;
912}
913
914/* Return the first idle worker. Called with pool->lock held. */
915static struct worker *first_idle_worker(struct worker_pool *pool)
916{
917 if (unlikely(list_empty(&pool->idle_list)))
918 return NULL;
919
920 return list_first_entry(&pool->idle_list, struct worker, entry);
921}
922
923/**
924 * worker_enter_idle - enter idle state
925 * @worker: worker which is entering idle state
926 *
927 * @worker is entering idle state. Update stats and idle timer if
928 * necessary.
929 *
930 * LOCKING:
931 * raw_spin_lock_irq(pool->lock).
932 */
933static void worker_enter_idle(struct worker *worker)
934{
935 struct worker_pool *pool = worker->pool;
936
937 if (WARN_ON_ONCE(worker->flags & WORKER_IDLE) ||
938 WARN_ON_ONCE(!list_empty(&worker->entry) &&
939 (worker->hentry.next || worker->hentry.pprev)))
940 return;
941
942 /* can't use worker_set_flags(), also called from create_worker() */
943 worker->flags |= WORKER_IDLE;
944 pool->nr_idle++;
945 worker->last_active = jiffies;
946
947 /* idle_list is LIFO */
948 list_add(&worker->entry, &pool->idle_list);
949
950 if (too_many_workers(pool) && !timer_pending(&pool->idle_timer))
951 mod_timer(&pool->idle_timer, jiffies + IDLE_WORKER_TIMEOUT);
952
953 /* Sanity check nr_running. */
954 WARN_ON_ONCE(pool->nr_workers == pool->nr_idle && pool->nr_running);
955}
956
957/**
958 * worker_leave_idle - leave idle state
959 * @worker: worker which is leaving idle state
960 *
961 * @worker is leaving idle state. Update stats.
962 *
963 * LOCKING:
964 * raw_spin_lock_irq(pool->lock).
965 */
966static void worker_leave_idle(struct worker *worker)
967{
968 struct worker_pool *pool = worker->pool;
969
970 if (WARN_ON_ONCE(!(worker->flags & WORKER_IDLE)))
971 return;
972 worker_clr_flags(worker, WORKER_IDLE);
973 pool->nr_idle--;
974 list_del_init(&worker->entry);
975}
976
977/**
978 * find_worker_executing_work - find worker which is executing a work
979 * @pool: pool of interest
980 * @work: work to find worker for
981 *
982 * Find a worker which is executing @work on @pool by searching
983 * @pool->busy_hash which is keyed by the address of @work. For a worker
984 * to match, its current execution should match the address of @work and
985 * its work function. This is to avoid unwanted dependency between
986 * unrelated work executions through a work item being recycled while still
987 * being executed.
988 *
989 * This is a bit tricky. A work item may be freed once its execution
990 * starts and nothing prevents the freed area from being recycled for
991 * another work item. If the same work item address ends up being reused
992 * before the original execution finishes, workqueue will identify the
993 * recycled work item as currently executing and make it wait until the
994 * current execution finishes, introducing an unwanted dependency.
995 *
996 * This function checks the work item address and work function to avoid
997 * false positives. Note that this isn't complete as one may construct a
998 * work function which can introduce dependency onto itself through a
999 * recycled work item. Well, if somebody wants to shoot oneself in the
1000 * foot that badly, there's only so much we can do, and if such deadlock
1001 * actually occurs, it should be easy to locate the culprit work function.
1002 *
1003 * CONTEXT:
1004 * raw_spin_lock_irq(pool->lock).
1005 *
1006 * Return:
1007 * Pointer to worker which is executing @work if found, %NULL
1008 * otherwise.
1009 */
1010static struct worker *find_worker_executing_work(struct worker_pool *pool,
1011 struct work_struct *work)
1012{
1013 struct worker *worker;
1014
1015 hash_for_each_possible(pool->busy_hash, worker, hentry,
1016 (unsigned long)work)
1017 if (worker->current_work == work &&
1018 worker->current_func == work->func)
1019 return worker;
1020
1021 return NULL;
1022}
1023
1024/**
1025 * move_linked_works - move linked works to a list
1026 * @work: start of series of works to be scheduled
1027 * @head: target list to append @work to
1028 * @nextp: out parameter for nested worklist walking
1029 *
1030 * Schedule linked works starting from @work to @head. Work series to be
1031 * scheduled starts at @work and includes any consecutive work with
1032 * WORK_STRUCT_LINKED set in its predecessor. See assign_work() for details on
1033 * @nextp.
1034 *
1035 * CONTEXT:
1036 * raw_spin_lock_irq(pool->lock).
1037 */
1038static void move_linked_works(struct work_struct *work, struct list_head *head,
1039 struct work_struct **nextp)
1040{
1041 struct work_struct *n;
1042
1043 /*
1044 * Linked worklist will always end before the end of the list,
1045 * use NULL for list head.
1046 */
1047 list_for_each_entry_safe_from(work, n, NULL, entry) {
1048 list_move_tail(&work->entry, head);
1049 if (!(*work_data_bits(work) & WORK_STRUCT_LINKED))
1050 break;
1051 }
1052
1053 /*
1054 * If we're already inside safe list traversal and have moved
1055 * multiple works to the scheduled queue, the next position
1056 * needs to be updated.
1057 */
1058 if (nextp)
1059 *nextp = n;
1060}
1061
1062/**
1063 * assign_work - assign a work item and its linked work items to a worker
1064 * @work: work to assign
1065 * @worker: worker to assign to
1066 * @nextp: out parameter for nested worklist walking
1067 *
1068 * Assign @work and its linked work items to @worker. If @work is already being
1069 * executed by another worker in the same pool, it'll be punted there.
1070 *
1071 * If @nextp is not NULL, it's updated to point to the next work of the last
1072 * scheduled work. This allows assign_work() to be nested inside
1073 * list_for_each_entry_safe().
1074 *
1075 * Returns %true if @work was successfully assigned to @worker. %false if @work
1076 * was punted to another worker already executing it.
1077 */
1078static bool assign_work(struct work_struct *work, struct worker *worker,
1079 struct work_struct **nextp)
1080{
1081 struct worker_pool *pool = worker->pool;
1082 struct worker *collision;
1083
1084 lockdep_assert_held(&pool->lock);
1085
1086 /*
1087 * A single work shouldn't be executed concurrently by multiple workers.
1088 * __queue_work() ensures that @work doesn't jump to a different pool
1089 * while still running in the previous pool. Here, we should ensure that
1090 * @work is not executed concurrently by multiple workers from the same
1091 * pool. Check whether anyone is already processing the work. If so,
1092 * defer the work to the currently executing one.
1093 */
1094 collision = find_worker_executing_work(pool, work);
1095 if (unlikely(collision)) {
1096 move_linked_works(work, &collision->scheduled, nextp);
1097 return false;
1098 }
1099
1100 move_linked_works(work, &worker->scheduled, nextp);
1101 return true;
1102}
1103
1104/**
1105 * kick_pool - wake up an idle worker if necessary
1106 * @pool: pool to kick
1107 *
1108 * @pool may have pending work items. Wake up worker if necessary. Returns
1109 * whether a worker was woken up.
1110 */
1111static bool kick_pool(struct worker_pool *pool)
1112{
1113 struct worker *worker = first_idle_worker(pool);
1114 struct task_struct *p;
1115
1116 lockdep_assert_held(&pool->lock);
1117
1118 if (!need_more_worker(pool) || !worker)
1119 return false;
1120
1121 p = worker->task;
1122
1123#ifdef CONFIG_SMP
1124 /*
1125 * Idle @worker is about to execute @work and waking up provides an
1126 * opportunity to migrate @worker at a lower cost by setting the task's
1127 * wake_cpu field. Let's see if we want to move @worker to improve
1128 * execution locality.
1129 *
1130 * We're waking the worker that went idle the latest and there's some
1131 * chance that @worker is marked idle but hasn't gone off CPU yet. If
1132 * so, setting the wake_cpu won't do anything. As this is a best-effort
1133 * optimization and the race window is narrow, let's leave as-is for
1134 * now. If this becomes pronounced, we can skip over workers which are
1135 * still on cpu when picking an idle worker.
1136 *
1137 * If @pool has non-strict affinity, @worker might have ended up outside
1138 * its affinity scope. Repatriate.
1139 */
1140 if (!pool->attrs->affn_strict &&
1141 !cpumask_test_cpu(p->wake_cpu, pool->attrs->__pod_cpumask)) {
1142 struct work_struct *work = list_first_entry(&pool->worklist,
1143 struct work_struct, entry);
1144 p->wake_cpu = cpumask_any_distribute(pool->attrs->__pod_cpumask);
1145 get_work_pwq(work)->stats[PWQ_STAT_REPATRIATED]++;
1146 }
1147#endif
1148 wake_up_process(p);
1149 return true;
1150}
1151
1152#ifdef CONFIG_WQ_CPU_INTENSIVE_REPORT
1153
1154/*
1155 * Concurrency-managed per-cpu work items that hog CPU for longer than
1156 * wq_cpu_intensive_thresh_us trigger the automatic CPU_INTENSIVE mechanism,
1157 * which prevents them from stalling other concurrency-managed work items. If a
1158 * work function keeps triggering this mechanism, it's likely that the work item
1159 * should be using an unbound workqueue instead.
1160 *
1161 * wq_cpu_intensive_report() tracks work functions which trigger such conditions
1162 * and report them so that they can be examined and converted to use unbound
1163 * workqueues as appropriate. To avoid flooding the console, each violating work
1164 * function is tracked and reported with exponential backoff.
1165 */
1166#define WCI_MAX_ENTS 128
1167
1168struct wci_ent {
1169 work_func_t func;
1170 atomic64_t cnt;
1171 struct hlist_node hash_node;
1172};
1173
1174static struct wci_ent wci_ents[WCI_MAX_ENTS];
1175static int wci_nr_ents;
1176static DEFINE_RAW_SPINLOCK(wci_lock);
1177static DEFINE_HASHTABLE(wci_hash, ilog2(WCI_MAX_ENTS));
1178
1179static struct wci_ent *wci_find_ent(work_func_t func)
1180{
1181 struct wci_ent *ent;
1182
1183 hash_for_each_possible_rcu(wci_hash, ent, hash_node,
1184 (unsigned long)func) {
1185 if (ent->func == func)
1186 return ent;
1187 }
1188 return NULL;
1189}
1190
1191static void wq_cpu_intensive_report(work_func_t func)
1192{
1193 struct wci_ent *ent;
1194
1195restart:
1196 ent = wci_find_ent(func);
1197 if (ent) {
1198 u64 cnt;
1199
1200 /*
1201 * Start reporting from the fourth time and back off
1202 * exponentially.
1203 */
1204 cnt = atomic64_inc_return_relaxed(&ent->cnt);
1205 if (cnt >= 4 && is_power_of_2(cnt))
1206 printk_deferred(KERN_WARNING "workqueue: %ps hogged CPU for >%luus %llu times, consider switching to WQ_UNBOUND\n",
1207 ent->func, wq_cpu_intensive_thresh_us,
1208 atomic64_read(&ent->cnt));
1209 return;
1210 }
1211
1212 /*
1213 * @func is a new violation. Allocate a new entry for it. If wcn_ents[]
1214 * is exhausted, something went really wrong and we probably made enough
1215 * noise already.
1216 */
1217 if (wci_nr_ents >= WCI_MAX_ENTS)
1218 return;
1219
1220 raw_spin_lock(&wci_lock);
1221
1222 if (wci_nr_ents >= WCI_MAX_ENTS) {
1223 raw_spin_unlock(&wci_lock);
1224 return;
1225 }
1226
1227 if (wci_find_ent(func)) {
1228 raw_spin_unlock(&wci_lock);
1229 goto restart;
1230 }
1231
1232 ent = &wci_ents[wci_nr_ents++];
1233 ent->func = func;
1234 atomic64_set(&ent->cnt, 1);
1235 hash_add_rcu(wci_hash, &ent->hash_node, (unsigned long)func);
1236
1237 raw_spin_unlock(&wci_lock);
1238}
1239
1240#else /* CONFIG_WQ_CPU_INTENSIVE_REPORT */
1241static void wq_cpu_intensive_report(work_func_t func) {}
1242#endif /* CONFIG_WQ_CPU_INTENSIVE_REPORT */
1243
1244/**
1245 * wq_worker_running - a worker is running again
1246 * @task: task waking up
1247 *
1248 * This function is called when a worker returns from schedule()
1249 */
1250void wq_worker_running(struct task_struct *task)
1251{
1252 struct worker *worker = kthread_data(task);
1253
1254 if (!READ_ONCE(worker->sleeping))
1255 return;
1256
1257 /*
1258 * If preempted by unbind_workers() between the WORKER_NOT_RUNNING check
1259 * and the nr_running increment below, we may ruin the nr_running reset
1260 * and leave with an unexpected pool->nr_running == 1 on the newly unbound
1261 * pool. Protect against such race.
1262 */
1263 preempt_disable();
1264 if (!(worker->flags & WORKER_NOT_RUNNING))
1265 worker->pool->nr_running++;
1266 preempt_enable();
1267
1268 /*
1269 * CPU intensive auto-detection cares about how long a work item hogged
1270 * CPU without sleeping. Reset the starting timestamp on wakeup.
1271 */
1272 worker->current_at = worker->task->se.sum_exec_runtime;
1273
1274 WRITE_ONCE(worker->sleeping, 0);
1275}
1276
1277/**
1278 * wq_worker_sleeping - a worker is going to sleep
1279 * @task: task going to sleep
1280 *
1281 * This function is called from schedule() when a busy worker is
1282 * going to sleep.
1283 */
1284void wq_worker_sleeping(struct task_struct *task)
1285{
1286 struct worker *worker = kthread_data(task);
1287 struct worker_pool *pool;
1288
1289 /*
1290 * Rescuers, which may not have all the fields set up like normal
1291 * workers, also reach here, let's not access anything before
1292 * checking NOT_RUNNING.
1293 */
1294 if (worker->flags & WORKER_NOT_RUNNING)
1295 return;
1296
1297 pool = worker->pool;
1298
1299 /* Return if preempted before wq_worker_running() was reached */
1300 if (READ_ONCE(worker->sleeping))
1301 return;
1302
1303 WRITE_ONCE(worker->sleeping, 1);
1304 raw_spin_lock_irq(&pool->lock);
1305
1306 /*
1307 * Recheck in case unbind_workers() preempted us. We don't
1308 * want to decrement nr_running after the worker is unbound
1309 * and nr_running has been reset.
1310 */
1311 if (worker->flags & WORKER_NOT_RUNNING) {
1312 raw_spin_unlock_irq(&pool->lock);
1313 return;
1314 }
1315
1316 pool->nr_running--;
1317 if (kick_pool(pool))
1318 worker->current_pwq->stats[PWQ_STAT_CM_WAKEUP]++;
1319
1320 raw_spin_unlock_irq(&pool->lock);
1321}
1322
1323/**
1324 * wq_worker_tick - a scheduler tick occurred while a kworker is running
1325 * @task: task currently running
1326 *
1327 * Called from scheduler_tick(). We're in the IRQ context and the current
1328 * worker's fields which follow the 'K' locking rule can be accessed safely.
1329 */
1330void wq_worker_tick(struct task_struct *task)
1331{
1332 struct worker *worker = kthread_data(task);
1333 struct pool_workqueue *pwq = worker->current_pwq;
1334 struct worker_pool *pool = worker->pool;
1335
1336 if (!pwq)
1337 return;
1338
1339 pwq->stats[PWQ_STAT_CPU_TIME] += TICK_USEC;
1340
1341 if (!wq_cpu_intensive_thresh_us)
1342 return;
1343
1344 /*
1345 * If the current worker is concurrency managed and hogged the CPU for
1346 * longer than wq_cpu_intensive_thresh_us, it's automatically marked
1347 * CPU_INTENSIVE to avoid stalling other concurrency-managed work items.
1348 *
1349 * Set @worker->sleeping means that @worker is in the process of
1350 * switching out voluntarily and won't be contributing to
1351 * @pool->nr_running until it wakes up. As wq_worker_sleeping() also
1352 * decrements ->nr_running, setting CPU_INTENSIVE here can lead to
1353 * double decrements. The task is releasing the CPU anyway. Let's skip.
1354 * We probably want to make this prettier in the future.
1355 */
1356 if ((worker->flags & WORKER_NOT_RUNNING) || READ_ONCE(worker->sleeping) ||
1357 worker->task->se.sum_exec_runtime - worker->current_at <
1358 wq_cpu_intensive_thresh_us * NSEC_PER_USEC)
1359 return;
1360
1361 raw_spin_lock(&pool->lock);
1362
1363 worker_set_flags(worker, WORKER_CPU_INTENSIVE);
1364 wq_cpu_intensive_report(worker->current_func);
1365 pwq->stats[PWQ_STAT_CPU_INTENSIVE]++;
1366
1367 if (kick_pool(pool))
1368 pwq->stats[PWQ_STAT_CM_WAKEUP]++;
1369
1370 raw_spin_unlock(&pool->lock);
1371}
1372
1373/**
1374 * wq_worker_last_func - retrieve worker's last work function
1375 * @task: Task to retrieve last work function of.
1376 *
1377 * Determine the last function a worker executed. This is called from
1378 * the scheduler to get a worker's last known identity.
1379 *
1380 * CONTEXT:
1381 * raw_spin_lock_irq(rq->lock)
1382 *
1383 * This function is called during schedule() when a kworker is going
1384 * to sleep. It's used by psi to identify aggregation workers during
1385 * dequeuing, to allow periodic aggregation to shut-off when that
1386 * worker is the last task in the system or cgroup to go to sleep.
1387 *
1388 * As this function doesn't involve any workqueue-related locking, it
1389 * only returns stable values when called from inside the scheduler's
1390 * queuing and dequeuing paths, when @task, which must be a kworker,
1391 * is guaranteed to not be processing any works.
1392 *
1393 * Return:
1394 * The last work function %current executed as a worker, NULL if it
1395 * hasn't executed any work yet.
1396 */
1397work_func_t wq_worker_last_func(struct task_struct *task)
1398{
1399 struct worker *worker = kthread_data(task);
1400
1401 return worker->last_func;
1402}
1403
1404/**
1405 * get_pwq - get an extra reference on the specified pool_workqueue
1406 * @pwq: pool_workqueue to get
1407 *
1408 * Obtain an extra reference on @pwq. The caller should guarantee that
1409 * @pwq has positive refcnt and be holding the matching pool->lock.
1410 */
1411static void get_pwq(struct pool_workqueue *pwq)
1412{
1413 lockdep_assert_held(&pwq->pool->lock);
1414 WARN_ON_ONCE(pwq->refcnt <= 0);
1415 pwq->refcnt++;
1416}
1417
1418/**
1419 * put_pwq - put a pool_workqueue reference
1420 * @pwq: pool_workqueue to put
1421 *
1422 * Drop a reference of @pwq. If its refcnt reaches zero, schedule its
1423 * destruction. The caller should be holding the matching pool->lock.
1424 */
1425static void put_pwq(struct pool_workqueue *pwq)
1426{
1427 lockdep_assert_held(&pwq->pool->lock);
1428 if (likely(--pwq->refcnt))
1429 return;
1430 /*
1431 * @pwq can't be released under pool->lock, bounce to a dedicated
1432 * kthread_worker to avoid A-A deadlocks.
1433 */
1434 kthread_queue_work(pwq_release_worker, &pwq->release_work);
1435}
1436
1437/**
1438 * put_pwq_unlocked - put_pwq() with surrounding pool lock/unlock
1439 * @pwq: pool_workqueue to put (can be %NULL)
1440 *
1441 * put_pwq() with locking. This function also allows %NULL @pwq.
1442 */
1443static void put_pwq_unlocked(struct pool_workqueue *pwq)
1444{
1445 if (pwq) {
1446 /*
1447 * As both pwqs and pools are RCU protected, the
1448 * following lock operations are safe.
1449 */
1450 raw_spin_lock_irq(&pwq->pool->lock);
1451 put_pwq(pwq);
1452 raw_spin_unlock_irq(&pwq->pool->lock);
1453 }
1454}
1455
1456static void pwq_activate_inactive_work(struct work_struct *work)
1457{
1458 struct pool_workqueue *pwq = get_work_pwq(work);
1459
1460 trace_workqueue_activate_work(work);
1461 if (list_empty(&pwq->pool->worklist))
1462 pwq->pool->watchdog_ts = jiffies;
1463 move_linked_works(work, &pwq->pool->worklist, NULL);
1464 __clear_bit(WORK_STRUCT_INACTIVE_BIT, work_data_bits(work));
1465 pwq->nr_active++;
1466}
1467
1468static void pwq_activate_first_inactive(struct pool_workqueue *pwq)
1469{
1470 struct work_struct *work = list_first_entry(&pwq->inactive_works,
1471 struct work_struct, entry);
1472
1473 pwq_activate_inactive_work(work);
1474}
1475
1476/**
1477 * pwq_dec_nr_in_flight - decrement pwq's nr_in_flight
1478 * @pwq: pwq of interest
1479 * @work_data: work_data of work which left the queue
1480 *
1481 * A work either has completed or is removed from pending queue,
1482 * decrement nr_in_flight of its pwq and handle workqueue flushing.
1483 *
1484 * CONTEXT:
1485 * raw_spin_lock_irq(pool->lock).
1486 */
1487static void pwq_dec_nr_in_flight(struct pool_workqueue *pwq, unsigned long work_data)
1488{
1489 int color = get_work_color(work_data);
1490
1491 if (!(work_data & WORK_STRUCT_INACTIVE)) {
1492 pwq->nr_active--;
1493 if (!list_empty(&pwq->inactive_works)) {
1494 /* one down, submit an inactive one */
1495 if (pwq->nr_active < pwq->max_active)
1496 pwq_activate_first_inactive(pwq);
1497 }
1498 }
1499
1500 pwq->nr_in_flight[color]--;
1501
1502 /* is flush in progress and are we at the flushing tip? */
1503 if (likely(pwq->flush_color != color))
1504 goto out_put;
1505
1506 /* are there still in-flight works? */
1507 if (pwq->nr_in_flight[color])
1508 goto out_put;
1509
1510 /* this pwq is done, clear flush_color */
1511 pwq->flush_color = -1;
1512
1513 /*
1514 * If this was the last pwq, wake up the first flusher. It
1515 * will handle the rest.
1516 */
1517 if (atomic_dec_and_test(&pwq->wq->nr_pwqs_to_flush))
1518 complete(&pwq->wq->first_flusher->done);
1519out_put:
1520 put_pwq(pwq);
1521}
1522
1523/**
1524 * try_to_grab_pending - steal work item from worklist and disable irq
1525 * @work: work item to steal
1526 * @is_dwork: @work is a delayed_work
1527 * @flags: place to store irq state
1528 *
1529 * Try to grab PENDING bit of @work. This function can handle @work in any
1530 * stable state - idle, on timer or on worklist.
1531 *
1532 * Return:
1533 *
1534 * ======== ================================================================
1535 * 1 if @work was pending and we successfully stole PENDING
1536 * 0 if @work was idle and we claimed PENDING
1537 * -EAGAIN if PENDING couldn't be grabbed at the moment, safe to busy-retry
1538 * -ENOENT if someone else is canceling @work, this state may persist
1539 * for arbitrarily long
1540 * ======== ================================================================
1541 *
1542 * Note:
1543 * On >= 0 return, the caller owns @work's PENDING bit. To avoid getting
1544 * interrupted while holding PENDING and @work off queue, irq must be
1545 * disabled on entry. This, combined with delayed_work->timer being
1546 * irqsafe, ensures that we return -EAGAIN for finite short period of time.
1547 *
1548 * On successful return, >= 0, irq is disabled and the caller is
1549 * responsible for releasing it using local_irq_restore(*@flags).
1550 *
1551 * This function is safe to call from any context including IRQ handler.
1552 */
1553static int try_to_grab_pending(struct work_struct *work, bool is_dwork,
1554 unsigned long *flags)
1555{
1556 struct worker_pool *pool;
1557 struct pool_workqueue *pwq;
1558
1559 local_irq_save(*flags);
1560
1561 /* try to steal the timer if it exists */
1562 if (is_dwork) {
1563 struct delayed_work *dwork = to_delayed_work(work);
1564
1565 /*
1566 * dwork->timer is irqsafe. If del_timer() fails, it's
1567 * guaranteed that the timer is not queued anywhere and not
1568 * running on the local CPU.
1569 */
1570 if (likely(del_timer(&dwork->timer)))
1571 return 1;
1572 }
1573
1574 /* try to claim PENDING the normal way */
1575 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work)))
1576 return 0;
1577
1578 rcu_read_lock();
1579 /*
1580 * The queueing is in progress, or it is already queued. Try to
1581 * steal it from ->worklist without clearing WORK_STRUCT_PENDING.
1582 */
1583 pool = get_work_pool(work);
1584 if (!pool)
1585 goto fail;
1586
1587 raw_spin_lock(&pool->lock);
1588 /*
1589 * work->data is guaranteed to point to pwq only while the work
1590 * item is queued on pwq->wq, and both updating work->data to point
1591 * to pwq on queueing and to pool on dequeueing are done under
1592 * pwq->pool->lock. This in turn guarantees that, if work->data
1593 * points to pwq which is associated with a locked pool, the work
1594 * item is currently queued on that pool.
1595 */
1596 pwq = get_work_pwq(work);
1597 if (pwq && pwq->pool == pool) {
1598 debug_work_deactivate(work);
1599
1600 /*
1601 * A cancelable inactive work item must be in the
1602 * pwq->inactive_works since a queued barrier can't be
1603 * canceled (see the comments in insert_wq_barrier()).
1604 *
1605 * An inactive work item cannot be grabbed directly because
1606 * it might have linked barrier work items which, if left
1607 * on the inactive_works list, will confuse pwq->nr_active
1608 * management later on and cause stall. Make sure the work
1609 * item is activated before grabbing.
1610 */
1611 if (*work_data_bits(work) & WORK_STRUCT_INACTIVE)
1612 pwq_activate_inactive_work(work);
1613
1614 list_del_init(&work->entry);
1615 pwq_dec_nr_in_flight(pwq, *work_data_bits(work));
1616
1617 /* work->data points to pwq iff queued, point to pool */
1618 set_work_pool_and_keep_pending(work, pool->id);
1619
1620 raw_spin_unlock(&pool->lock);
1621 rcu_read_unlock();
1622 return 1;
1623 }
1624 raw_spin_unlock(&pool->lock);
1625fail:
1626 rcu_read_unlock();
1627 local_irq_restore(*flags);
1628 if (work_is_canceling(work))
1629 return -ENOENT;
1630 cpu_relax();
1631 return -EAGAIN;
1632}
1633
1634/**
1635 * insert_work - insert a work into a pool
1636 * @pwq: pwq @work belongs to
1637 * @work: work to insert
1638 * @head: insertion point
1639 * @extra_flags: extra WORK_STRUCT_* flags to set
1640 *
1641 * Insert @work which belongs to @pwq after @head. @extra_flags is or'd to
1642 * work_struct flags.
1643 *
1644 * CONTEXT:
1645 * raw_spin_lock_irq(pool->lock).
1646 */
1647static void insert_work(struct pool_workqueue *pwq, struct work_struct *work,
1648 struct list_head *head, unsigned int extra_flags)
1649{
1650 debug_work_activate(work);
1651
1652 /* record the work call stack in order to print it in KASAN reports */
1653 kasan_record_aux_stack_noalloc(work);
1654
1655 /* we own @work, set data and link */
1656 set_work_pwq(work, pwq, extra_flags);
1657 list_add_tail(&work->entry, head);
1658 get_pwq(pwq);
1659}
1660
1661/*
1662 * Test whether @work is being queued from another work executing on the
1663 * same workqueue.
1664 */
1665static bool is_chained_work(struct workqueue_struct *wq)
1666{
1667 struct worker *worker;
1668
1669 worker = current_wq_worker();
1670 /*
1671 * Return %true iff I'm a worker executing a work item on @wq. If
1672 * I'm @worker, it's safe to dereference it without locking.
1673 */
1674 return worker && worker->current_pwq->wq == wq;
1675}
1676
1677/*
1678 * When queueing an unbound work item to a wq, prefer local CPU if allowed
1679 * by wq_unbound_cpumask. Otherwise, round robin among the allowed ones to
1680 * avoid perturbing sensitive tasks.
1681 */
1682static int wq_select_unbound_cpu(int cpu)
1683{
1684 int new_cpu;
1685
1686 if (likely(!wq_debug_force_rr_cpu)) {
1687 if (cpumask_test_cpu(cpu, wq_unbound_cpumask))
1688 return cpu;
1689 } else {
1690 pr_warn_once("workqueue: round-robin CPU selection forced, expect performance impact\n");
1691 }
1692
1693 new_cpu = __this_cpu_read(wq_rr_cpu_last);
1694 new_cpu = cpumask_next_and(new_cpu, wq_unbound_cpumask, cpu_online_mask);
1695 if (unlikely(new_cpu >= nr_cpu_ids)) {
1696 new_cpu = cpumask_first_and(wq_unbound_cpumask, cpu_online_mask);
1697 if (unlikely(new_cpu >= nr_cpu_ids))
1698 return cpu;
1699 }
1700 __this_cpu_write(wq_rr_cpu_last, new_cpu);
1701
1702 return new_cpu;
1703}
1704
1705static void __queue_work(int cpu, struct workqueue_struct *wq,
1706 struct work_struct *work)
1707{
1708 struct pool_workqueue *pwq;
1709 struct worker_pool *last_pool, *pool;
1710 unsigned int work_flags;
1711 unsigned int req_cpu = cpu;
1712
1713 /*
1714 * While a work item is PENDING && off queue, a task trying to
1715 * steal the PENDING will busy-loop waiting for it to either get
1716 * queued or lose PENDING. Grabbing PENDING and queueing should
1717 * happen with IRQ disabled.
1718 */
1719 lockdep_assert_irqs_disabled();
1720
1721
1722 /*
1723 * For a draining wq, only works from the same workqueue are
1724 * allowed. The __WQ_DESTROYING helps to spot the issue that
1725 * queues a new work item to a wq after destroy_workqueue(wq).
1726 */
1727 if (unlikely(wq->flags & (__WQ_DESTROYING | __WQ_DRAINING) &&
1728 WARN_ON_ONCE(!is_chained_work(wq))))
1729 return;
1730 rcu_read_lock();
1731retry:
1732 /* pwq which will be used unless @work is executing elsewhere */
1733 if (req_cpu == WORK_CPU_UNBOUND) {
1734 if (wq->flags & WQ_UNBOUND)
1735 cpu = wq_select_unbound_cpu(raw_smp_processor_id());
1736 else
1737 cpu = raw_smp_processor_id();
1738 }
1739
1740 pwq = rcu_dereference(*per_cpu_ptr(wq->cpu_pwq, cpu));
1741 pool = pwq->pool;
1742
1743 /*
1744 * If @work was previously on a different pool, it might still be
1745 * running there, in which case the work needs to be queued on that
1746 * pool to guarantee non-reentrancy.
1747 */
1748 last_pool = get_work_pool(work);
1749 if (last_pool && last_pool != pool) {
1750 struct worker *worker;
1751
1752 raw_spin_lock(&last_pool->lock);
1753
1754 worker = find_worker_executing_work(last_pool, work);
1755
1756 if (worker && worker->current_pwq->wq == wq) {
1757 pwq = worker->current_pwq;
1758 pool = pwq->pool;
1759 WARN_ON_ONCE(pool != last_pool);
1760 } else {
1761 /* meh... not running there, queue here */
1762 raw_spin_unlock(&last_pool->lock);
1763 raw_spin_lock(&pool->lock);
1764 }
1765 } else {
1766 raw_spin_lock(&pool->lock);
1767 }
1768
1769 /*
1770 * pwq is determined and locked. For unbound pools, we could have raced
1771 * with pwq release and it could already be dead. If its refcnt is zero,
1772 * repeat pwq selection. Note that unbound pwqs never die without
1773 * another pwq replacing it in cpu_pwq or while work items are executing
1774 * on it, so the retrying is guaranteed to make forward-progress.
1775 */
1776 if (unlikely(!pwq->refcnt)) {
1777 if (wq->flags & WQ_UNBOUND) {
1778 raw_spin_unlock(&pool->lock);
1779 cpu_relax();
1780 goto retry;
1781 }
1782 /* oops */
1783 WARN_ONCE(true, "workqueue: per-cpu pwq for %s on cpu%d has 0 refcnt",
1784 wq->name, cpu);
1785 }
1786
1787 /* pwq determined, queue */
1788 trace_workqueue_queue_work(req_cpu, pwq, work);
1789
1790 if (WARN_ON(!list_empty(&work->entry)))
1791 goto out;
1792
1793 pwq->nr_in_flight[pwq->work_color]++;
1794 work_flags = work_color_to_flags(pwq->work_color);
1795
1796 if (likely(pwq->nr_active < pwq->max_active)) {
1797 if (list_empty(&pool->worklist))
1798 pool->watchdog_ts = jiffies;
1799
1800 trace_workqueue_activate_work(work);
1801 pwq->nr_active++;
1802 insert_work(pwq, work, &pool->worklist, work_flags);
1803 kick_pool(pool);
1804 } else {
1805 work_flags |= WORK_STRUCT_INACTIVE;
1806 insert_work(pwq, work, &pwq->inactive_works, work_flags);
1807 }
1808
1809out:
1810 raw_spin_unlock(&pool->lock);
1811 rcu_read_unlock();
1812}
1813
1814/**
1815 * queue_work_on - queue work on specific cpu
1816 * @cpu: CPU number to execute work on
1817 * @wq: workqueue to use
1818 * @work: work to queue
1819 *
1820 * We queue the work to a specific CPU, the caller must ensure it
1821 * can't go away. Callers that fail to ensure that the specified
1822 * CPU cannot go away will execute on a randomly chosen CPU.
1823 * But note well that callers specifying a CPU that never has been
1824 * online will get a splat.
1825 *
1826 * Return: %false if @work was already on a queue, %true otherwise.
1827 */
1828bool queue_work_on(int cpu, struct workqueue_struct *wq,
1829 struct work_struct *work)
1830{
1831 bool ret = false;
1832 unsigned long flags;
1833
1834 local_irq_save(flags);
1835
1836 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1837 __queue_work(cpu, wq, work);
1838 ret = true;
1839 }
1840
1841 local_irq_restore(flags);
1842 return ret;
1843}
1844EXPORT_SYMBOL(queue_work_on);
1845
1846/**
1847 * select_numa_node_cpu - Select a CPU based on NUMA node
1848 * @node: NUMA node ID that we want to select a CPU from
1849 *
1850 * This function will attempt to find a "random" cpu available on a given
1851 * node. If there are no CPUs available on the given node it will return
1852 * WORK_CPU_UNBOUND indicating that we should just schedule to any
1853 * available CPU if we need to schedule this work.
1854 */
1855static int select_numa_node_cpu(int node)
1856{
1857 int cpu;
1858
1859 /* Delay binding to CPU if node is not valid or online */
1860 if (node < 0 || node >= MAX_NUMNODES || !node_online(node))
1861 return WORK_CPU_UNBOUND;
1862
1863 /* Use local node/cpu if we are already there */
1864 cpu = raw_smp_processor_id();
1865 if (node == cpu_to_node(cpu))
1866 return cpu;
1867
1868 /* Use "random" otherwise know as "first" online CPU of node */
1869 cpu = cpumask_any_and(cpumask_of_node(node), cpu_online_mask);
1870
1871 /* If CPU is valid return that, otherwise just defer */
1872 return cpu < nr_cpu_ids ? cpu : WORK_CPU_UNBOUND;
1873}
1874
1875/**
1876 * queue_work_node - queue work on a "random" cpu for a given NUMA node
1877 * @node: NUMA node that we are targeting the work for
1878 * @wq: workqueue to use
1879 * @work: work to queue
1880 *
1881 * We queue the work to a "random" CPU within a given NUMA node. The basic
1882 * idea here is to provide a way to somehow associate work with a given
1883 * NUMA node.
1884 *
1885 * This function will only make a best effort attempt at getting this onto
1886 * the right NUMA node. If no node is requested or the requested node is
1887 * offline then we just fall back to standard queue_work behavior.
1888 *
1889 * Currently the "random" CPU ends up being the first available CPU in the
1890 * intersection of cpu_online_mask and the cpumask of the node, unless we
1891 * are running on the node. In that case we just use the current CPU.
1892 *
1893 * Return: %false if @work was already on a queue, %true otherwise.
1894 */
1895bool queue_work_node(int node, struct workqueue_struct *wq,
1896 struct work_struct *work)
1897{
1898 unsigned long flags;
1899 bool ret = false;
1900
1901 /*
1902 * This current implementation is specific to unbound workqueues.
1903 * Specifically we only return the first available CPU for a given
1904 * node instead of cycling through individual CPUs within the node.
1905 *
1906 * If this is used with a per-cpu workqueue then the logic in
1907 * workqueue_select_cpu_near would need to be updated to allow for
1908 * some round robin type logic.
1909 */
1910 WARN_ON_ONCE(!(wq->flags & WQ_UNBOUND));
1911
1912 local_irq_save(flags);
1913
1914 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1915 int cpu = select_numa_node_cpu(node);
1916
1917 __queue_work(cpu, wq, work);
1918 ret = true;
1919 }
1920
1921 local_irq_restore(flags);
1922 return ret;
1923}
1924EXPORT_SYMBOL_GPL(queue_work_node);
1925
1926void delayed_work_timer_fn(struct timer_list *t)
1927{
1928 struct delayed_work *dwork = from_timer(dwork, t, timer);
1929
1930 /* should have been called from irqsafe timer with irq already off */
1931 __queue_work(dwork->cpu, dwork->wq, &dwork->work);
1932}
1933EXPORT_SYMBOL(delayed_work_timer_fn);
1934
1935static void __queue_delayed_work(int cpu, struct workqueue_struct *wq,
1936 struct delayed_work *dwork, unsigned long delay)
1937{
1938 struct timer_list *timer = &dwork->timer;
1939 struct work_struct *work = &dwork->work;
1940
1941 WARN_ON_ONCE(!wq);
1942 WARN_ON_ONCE(timer->function != delayed_work_timer_fn);
1943 WARN_ON_ONCE(timer_pending(timer));
1944 WARN_ON_ONCE(!list_empty(&work->entry));
1945
1946 /*
1947 * If @delay is 0, queue @dwork->work immediately. This is for
1948 * both optimization and correctness. The earliest @timer can
1949 * expire is on the closest next tick and delayed_work users depend
1950 * on that there's no such delay when @delay is 0.
1951 */
1952 if (!delay) {
1953 __queue_work(cpu, wq, &dwork->work);
1954 return;
1955 }
1956
1957 dwork->wq = wq;
1958 dwork->cpu = cpu;
1959 timer->expires = jiffies + delay;
1960
1961 if (unlikely(cpu != WORK_CPU_UNBOUND))
1962 add_timer_on(timer, cpu);
1963 else
1964 add_timer(timer);
1965}
1966
1967/**
1968 * queue_delayed_work_on - queue work on specific CPU after delay
1969 * @cpu: CPU number to execute work on
1970 * @wq: workqueue to use
1971 * @dwork: work to queue
1972 * @delay: number of jiffies to wait before queueing
1973 *
1974 * Return: %false if @work was already on a queue, %true otherwise. If
1975 * @delay is zero and @dwork is idle, it will be scheduled for immediate
1976 * execution.
1977 */
1978bool queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
1979 struct delayed_work *dwork, unsigned long delay)
1980{
1981 struct work_struct *work = &dwork->work;
1982 bool ret = false;
1983 unsigned long flags;
1984
1985 /* read the comment in __queue_work() */
1986 local_irq_save(flags);
1987
1988 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1989 __queue_delayed_work(cpu, wq, dwork, delay);
1990 ret = true;
1991 }
1992
1993 local_irq_restore(flags);
1994 return ret;
1995}
1996EXPORT_SYMBOL(queue_delayed_work_on);
1997
1998/**
1999 * mod_delayed_work_on - modify delay of or queue a delayed work on specific CPU
2000 * @cpu: CPU number to execute work on
2001 * @wq: workqueue to use
2002 * @dwork: work to queue
2003 * @delay: number of jiffies to wait before queueing
2004 *
2005 * If @dwork is idle, equivalent to queue_delayed_work_on(); otherwise,
2006 * modify @dwork's timer so that it expires after @delay. If @delay is
2007 * zero, @work is guaranteed to be scheduled immediately regardless of its
2008 * current state.
2009 *
2010 * Return: %false if @dwork was idle and queued, %true if @dwork was
2011 * pending and its timer was modified.
2012 *
2013 * This function is safe to call from any context including IRQ handler.
2014 * See try_to_grab_pending() for details.
2015 */
2016bool mod_delayed_work_on(int cpu, struct workqueue_struct *wq,
2017 struct delayed_work *dwork, unsigned long delay)
2018{
2019 unsigned long flags;
2020 int ret;
2021
2022 do {
2023 ret = try_to_grab_pending(&dwork->work, true, &flags);
2024 } while (unlikely(ret == -EAGAIN));
2025
2026 if (likely(ret >= 0)) {
2027 __queue_delayed_work(cpu, wq, dwork, delay);
2028 local_irq_restore(flags);
2029 }
2030
2031 /* -ENOENT from try_to_grab_pending() becomes %true */
2032 return ret;
2033}
2034EXPORT_SYMBOL_GPL(mod_delayed_work_on);
2035
2036static void rcu_work_rcufn(struct rcu_head *rcu)
2037{
2038 struct rcu_work *rwork = container_of(rcu, struct rcu_work, rcu);
2039
2040 /* read the comment in __queue_work() */
2041 local_irq_disable();
2042 __queue_work(WORK_CPU_UNBOUND, rwork->wq, &rwork->work);
2043 local_irq_enable();
2044}
2045
2046/**
2047 * queue_rcu_work - queue work after a RCU grace period
2048 * @wq: workqueue to use
2049 * @rwork: work to queue
2050 *
2051 * Return: %false if @rwork was already pending, %true otherwise. Note
2052 * that a full RCU grace period is guaranteed only after a %true return.
2053 * While @rwork is guaranteed to be executed after a %false return, the
2054 * execution may happen before a full RCU grace period has passed.
2055 */
2056bool queue_rcu_work(struct workqueue_struct *wq, struct rcu_work *rwork)
2057{
2058 struct work_struct *work = &rwork->work;
2059
2060 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
2061 rwork->wq = wq;
2062 call_rcu_hurry(&rwork->rcu, rcu_work_rcufn);
2063 return true;
2064 }
2065
2066 return false;
2067}
2068EXPORT_SYMBOL(queue_rcu_work);
2069
2070static struct worker *alloc_worker(int node)
2071{
2072 struct worker *worker;
2073
2074 worker = kzalloc_node(sizeof(*worker), GFP_KERNEL, node);
2075 if (worker) {
2076 INIT_LIST_HEAD(&worker->entry);
2077 INIT_LIST_HEAD(&worker->scheduled);
2078 INIT_LIST_HEAD(&worker->node);
2079 /* on creation a worker is in !idle && prep state */
2080 worker->flags = WORKER_PREP;
2081 }
2082 return worker;
2083}
2084
2085static cpumask_t *pool_allowed_cpus(struct worker_pool *pool)
2086{
2087 if (pool->cpu < 0 && pool->attrs->affn_strict)
2088 return pool->attrs->__pod_cpumask;
2089 else
2090 return pool->attrs->cpumask;
2091}
2092
2093/**
2094 * worker_attach_to_pool() - attach a worker to a pool
2095 * @worker: worker to be attached
2096 * @pool: the target pool
2097 *
2098 * Attach @worker to @pool. Once attached, the %WORKER_UNBOUND flag and
2099 * cpu-binding of @worker are kept coordinated with the pool across
2100 * cpu-[un]hotplugs.
2101 */
2102static void worker_attach_to_pool(struct worker *worker,
2103 struct worker_pool *pool)
2104{
2105 mutex_lock(&wq_pool_attach_mutex);
2106
2107 /*
2108 * The wq_pool_attach_mutex ensures %POOL_DISASSOCIATED remains
2109 * stable across this function. See the comments above the flag
2110 * definition for details.
2111 */
2112 if (pool->flags & POOL_DISASSOCIATED)
2113 worker->flags |= WORKER_UNBOUND;
2114 else
2115 kthread_set_per_cpu(worker->task, pool->cpu);
2116
2117 if (worker->rescue_wq)
2118 set_cpus_allowed_ptr(worker->task, pool_allowed_cpus(pool));
2119
2120 list_add_tail(&worker->node, &pool->workers);
2121 worker->pool = pool;
2122
2123 mutex_unlock(&wq_pool_attach_mutex);
2124}
2125
2126/**
2127 * worker_detach_from_pool() - detach a worker from its pool
2128 * @worker: worker which is attached to its pool
2129 *
2130 * Undo the attaching which had been done in worker_attach_to_pool(). The
2131 * caller worker shouldn't access to the pool after detached except it has
2132 * other reference to the pool.
2133 */
2134static void worker_detach_from_pool(struct worker *worker)
2135{
2136 struct worker_pool *pool = worker->pool;
2137 struct completion *detach_completion = NULL;
2138
2139 mutex_lock(&wq_pool_attach_mutex);
2140
2141 kthread_set_per_cpu(worker->task, -1);
2142 list_del(&worker->node);
2143 worker->pool = NULL;
2144
2145 if (list_empty(&pool->workers) && list_empty(&pool->dying_workers))
2146 detach_completion = pool->detach_completion;
2147 mutex_unlock(&wq_pool_attach_mutex);
2148
2149 /* clear leftover flags without pool->lock after it is detached */
2150 worker->flags &= ~(WORKER_UNBOUND | WORKER_REBOUND);
2151
2152 if (detach_completion)
2153 complete(detach_completion);
2154}
2155
2156/**
2157 * create_worker - create a new workqueue worker
2158 * @pool: pool the new worker will belong to
2159 *
2160 * Create and start a new worker which is attached to @pool.
2161 *
2162 * CONTEXT:
2163 * Might sleep. Does GFP_KERNEL allocations.
2164 *
2165 * Return:
2166 * Pointer to the newly created worker.
2167 */
2168static struct worker *create_worker(struct worker_pool *pool)
2169{
2170 struct worker *worker;
2171 int id;
2172 char id_buf[23];
2173
2174 /* ID is needed to determine kthread name */
2175 id = ida_alloc(&pool->worker_ida, GFP_KERNEL);
2176 if (id < 0) {
2177 pr_err_once("workqueue: Failed to allocate a worker ID: %pe\n",
2178 ERR_PTR(id));
2179 return NULL;
2180 }
2181
2182 worker = alloc_worker(pool->node);
2183 if (!worker) {
2184 pr_err_once("workqueue: Failed to allocate a worker\n");
2185 goto fail;
2186 }
2187
2188 worker->id = id;
2189
2190 if (pool->cpu >= 0)
2191 snprintf(id_buf, sizeof(id_buf), "%d:%d%s", pool->cpu, id,
2192 pool->attrs->nice < 0 ? "H" : "");
2193 else
2194 snprintf(id_buf, sizeof(id_buf), "u%d:%d", pool->id, id);
2195
2196 worker->task = kthread_create_on_node(worker_thread, worker, pool->node,
2197 "kworker/%s", id_buf);
2198 if (IS_ERR(worker->task)) {
2199 if (PTR_ERR(worker->task) == -EINTR) {
2200 pr_err("workqueue: Interrupted when creating a worker thread \"kworker/%s\"\n",
2201 id_buf);
2202 } else {
2203 pr_err_once("workqueue: Failed to create a worker thread: %pe",
2204 worker->task);
2205 }
2206 goto fail;
2207 }
2208
2209 set_user_nice(worker->task, pool->attrs->nice);
2210 kthread_bind_mask(worker->task, pool_allowed_cpus(pool));
2211
2212 /* successful, attach the worker to the pool */
2213 worker_attach_to_pool(worker, pool);
2214
2215 /* start the newly created worker */
2216 raw_spin_lock_irq(&pool->lock);
2217
2218 worker->pool->nr_workers++;
2219 worker_enter_idle(worker);
2220 kick_pool(pool);
2221
2222 /*
2223 * @worker is waiting on a completion in kthread() and will trigger hung
2224 * check if not woken up soon. As kick_pool() might not have waken it
2225 * up, wake it up explicitly once more.
2226 */
2227 wake_up_process(worker->task);
2228
2229 raw_spin_unlock_irq(&pool->lock);
2230
2231 return worker;
2232
2233fail:
2234 ida_free(&pool->worker_ida, id);
2235 kfree(worker);
2236 return NULL;
2237}
2238
2239static void unbind_worker(struct worker *worker)
2240{
2241 lockdep_assert_held(&wq_pool_attach_mutex);
2242
2243 kthread_set_per_cpu(worker->task, -1);
2244 if (cpumask_intersects(wq_unbound_cpumask, cpu_active_mask))
2245 WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task, wq_unbound_cpumask) < 0);
2246 else
2247 WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task, cpu_possible_mask) < 0);
2248}
2249
2250static void wake_dying_workers(struct list_head *cull_list)
2251{
2252 struct worker *worker, *tmp;
2253
2254 list_for_each_entry_safe(worker, tmp, cull_list, entry) {
2255 list_del_init(&worker->entry);
2256 unbind_worker(worker);
2257 /*
2258 * If the worker was somehow already running, then it had to be
2259 * in pool->idle_list when set_worker_dying() happened or we
2260 * wouldn't have gotten here.
2261 *
2262 * Thus, the worker must either have observed the WORKER_DIE
2263 * flag, or have set its state to TASK_IDLE. Either way, the
2264 * below will be observed by the worker and is safe to do
2265 * outside of pool->lock.
2266 */
2267 wake_up_process(worker->task);
2268 }
2269}
2270
2271/**
2272 * set_worker_dying - Tag a worker for destruction
2273 * @worker: worker to be destroyed
2274 * @list: transfer worker away from its pool->idle_list and into list
2275 *
2276 * Tag @worker for destruction and adjust @pool stats accordingly. The worker
2277 * should be idle.
2278 *
2279 * CONTEXT:
2280 * raw_spin_lock_irq(pool->lock).
2281 */
2282static void set_worker_dying(struct worker *worker, struct list_head *list)
2283{
2284 struct worker_pool *pool = worker->pool;
2285
2286 lockdep_assert_held(&pool->lock);
2287 lockdep_assert_held(&wq_pool_attach_mutex);
2288
2289 /* sanity check frenzy */
2290 if (WARN_ON(worker->current_work) ||
2291 WARN_ON(!list_empty(&worker->scheduled)) ||
2292 WARN_ON(!(worker->flags & WORKER_IDLE)))
2293 return;
2294
2295 pool->nr_workers--;
2296 pool->nr_idle--;
2297
2298 worker->flags |= WORKER_DIE;
2299
2300 list_move(&worker->entry, list);
2301 list_move(&worker->node, &pool->dying_workers);
2302}
2303
2304/**
2305 * idle_worker_timeout - check if some idle workers can now be deleted.
2306 * @t: The pool's idle_timer that just expired
2307 *
2308 * The timer is armed in worker_enter_idle(). Note that it isn't disarmed in
2309 * worker_leave_idle(), as a worker flicking between idle and active while its
2310 * pool is at the too_many_workers() tipping point would cause too much timer
2311 * housekeeping overhead. Since IDLE_WORKER_TIMEOUT is long enough, we just let
2312 * it expire and re-evaluate things from there.
2313 */
2314static void idle_worker_timeout(struct timer_list *t)
2315{
2316 struct worker_pool *pool = from_timer(pool, t, idle_timer);
2317 bool do_cull = false;
2318
2319 if (work_pending(&pool->idle_cull_work))
2320 return;
2321
2322 raw_spin_lock_irq(&pool->lock);
2323
2324 if (too_many_workers(pool)) {
2325 struct worker *worker;
2326 unsigned long expires;
2327
2328 /* idle_list is kept in LIFO order, check the last one */
2329 worker = list_entry(pool->idle_list.prev, struct worker, entry);
2330 expires = worker->last_active + IDLE_WORKER_TIMEOUT;
2331 do_cull = !time_before(jiffies, expires);
2332
2333 if (!do_cull)
2334 mod_timer(&pool->idle_timer, expires);
2335 }
2336 raw_spin_unlock_irq(&pool->lock);
2337
2338 if (do_cull)
2339 queue_work(system_unbound_wq, &pool->idle_cull_work);
2340}
2341
2342/**
2343 * idle_cull_fn - cull workers that have been idle for too long.
2344 * @work: the pool's work for handling these idle workers
2345 *
2346 * This goes through a pool's idle workers and gets rid of those that have been
2347 * idle for at least IDLE_WORKER_TIMEOUT seconds.
2348 *
2349 * We don't want to disturb isolated CPUs because of a pcpu kworker being
2350 * culled, so this also resets worker affinity. This requires a sleepable
2351 * context, hence the split between timer callback and work item.
2352 */
2353static void idle_cull_fn(struct work_struct *work)
2354{
2355 struct worker_pool *pool = container_of(work, struct worker_pool, idle_cull_work);
2356 LIST_HEAD(cull_list);
2357
2358 /*
2359 * Grabbing wq_pool_attach_mutex here ensures an already-running worker
2360 * cannot proceed beyong worker_detach_from_pool() in its self-destruct
2361 * path. This is required as a previously-preempted worker could run after
2362 * set_worker_dying() has happened but before wake_dying_workers() did.
2363 */
2364 mutex_lock(&wq_pool_attach_mutex);
2365 raw_spin_lock_irq(&pool->lock);
2366
2367 while (too_many_workers(pool)) {
2368 struct worker *worker;
2369 unsigned long expires;
2370
2371 worker = list_entry(pool->idle_list.prev, struct worker, entry);
2372 expires = worker->last_active + IDLE_WORKER_TIMEOUT;
2373
2374 if (time_before(jiffies, expires)) {
2375 mod_timer(&pool->idle_timer, expires);
2376 break;
2377 }
2378
2379 set_worker_dying(worker, &cull_list);
2380 }
2381
2382 raw_spin_unlock_irq(&pool->lock);
2383 wake_dying_workers(&cull_list);
2384 mutex_unlock(&wq_pool_attach_mutex);
2385}
2386
2387static void send_mayday(struct work_struct *work)
2388{
2389 struct pool_workqueue *pwq = get_work_pwq(work);
2390 struct workqueue_struct *wq = pwq->wq;
2391
2392 lockdep_assert_held(&wq_mayday_lock);
2393
2394 if (!wq->rescuer)
2395 return;
2396
2397 /* mayday mayday mayday */
2398 if (list_empty(&pwq->mayday_node)) {
2399 /*
2400 * If @pwq is for an unbound wq, its base ref may be put at
2401 * any time due to an attribute change. Pin @pwq until the
2402 * rescuer is done with it.
2403 */
2404 get_pwq(pwq);
2405 list_add_tail(&pwq->mayday_node, &wq->maydays);
2406 wake_up_process(wq->rescuer->task);
2407 pwq->stats[PWQ_STAT_MAYDAY]++;
2408 }
2409}
2410
2411static void pool_mayday_timeout(struct timer_list *t)
2412{
2413 struct worker_pool *pool = from_timer(pool, t, mayday_timer);
2414 struct work_struct *work;
2415
2416 raw_spin_lock_irq(&pool->lock);
2417 raw_spin_lock(&wq_mayday_lock); /* for wq->maydays */
2418
2419 if (need_to_create_worker(pool)) {
2420 /*
2421 * We've been trying to create a new worker but
2422 * haven't been successful. We might be hitting an
2423 * allocation deadlock. Send distress signals to
2424 * rescuers.
2425 */
2426 list_for_each_entry(work, &pool->worklist, entry)
2427 send_mayday(work);
2428 }
2429
2430 raw_spin_unlock(&wq_mayday_lock);
2431 raw_spin_unlock_irq(&pool->lock);
2432
2433 mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INTERVAL);
2434}
2435
2436/**
2437 * maybe_create_worker - create a new worker if necessary
2438 * @pool: pool to create a new worker for
2439 *
2440 * Create a new worker for @pool if necessary. @pool is guaranteed to
2441 * have at least one idle worker on return from this function. If
2442 * creating a new worker takes longer than MAYDAY_INTERVAL, mayday is
2443 * sent to all rescuers with works scheduled on @pool to resolve
2444 * possible allocation deadlock.
2445 *
2446 * On return, need_to_create_worker() is guaranteed to be %false and
2447 * may_start_working() %true.
2448 *
2449 * LOCKING:
2450 * raw_spin_lock_irq(pool->lock) which may be released and regrabbed
2451 * multiple times. Does GFP_KERNEL allocations. Called only from
2452 * manager.
2453 */
2454static void maybe_create_worker(struct worker_pool *pool)
2455__releases(&pool->lock)
2456__acquires(&pool->lock)
2457{
2458restart:
2459 raw_spin_unlock_irq(&pool->lock);
2460
2461 /* if we don't make progress in MAYDAY_INITIAL_TIMEOUT, call for help */
2462 mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INITIAL_TIMEOUT);
2463
2464 while (true) {
2465 if (create_worker(pool) || !need_to_create_worker(pool))
2466 break;
2467
2468 schedule_timeout_interruptible(CREATE_COOLDOWN);
2469
2470 if (!need_to_create_worker(pool))
2471 break;
2472 }
2473
2474 del_timer_sync(&pool->mayday_timer);
2475 raw_spin_lock_irq(&pool->lock);
2476 /*
2477 * This is necessary even after a new worker was just successfully
2478 * created as @pool->lock was dropped and the new worker might have
2479 * already become busy.
2480 */
2481 if (need_to_create_worker(pool))
2482 goto restart;
2483}
2484
2485/**
2486 * manage_workers - manage worker pool
2487 * @worker: self
2488 *
2489 * Assume the manager role and manage the worker pool @worker belongs
2490 * to. At any given time, there can be only zero or one manager per
2491 * pool. The exclusion is handled automatically by this function.
2492 *
2493 * The caller can safely start processing works on false return. On
2494 * true return, it's guaranteed that need_to_create_worker() is false
2495 * and may_start_working() is true.
2496 *
2497 * CONTEXT:
2498 * raw_spin_lock_irq(pool->lock) which may be released and regrabbed
2499 * multiple times. Does GFP_KERNEL allocations.
2500 *
2501 * Return:
2502 * %false if the pool doesn't need management and the caller can safely
2503 * start processing works, %true if management function was performed and
2504 * the conditions that the caller verified before calling the function may
2505 * no longer be true.
2506 */
2507static bool manage_workers(struct worker *worker)
2508{
2509 struct worker_pool *pool = worker->pool;
2510
2511 if (pool->flags & POOL_MANAGER_ACTIVE)
2512 return false;
2513
2514 pool->flags |= POOL_MANAGER_ACTIVE;
2515 pool->manager = worker;
2516
2517 maybe_create_worker(pool);
2518
2519 pool->manager = NULL;
2520 pool->flags &= ~POOL_MANAGER_ACTIVE;
2521 rcuwait_wake_up(&manager_wait);
2522 return true;
2523}
2524
2525/**
2526 * process_one_work - process single work
2527 * @worker: self
2528 * @work: work to process
2529 *
2530 * Process @work. This function contains all the logics necessary to
2531 * process a single work including synchronization against and
2532 * interaction with other workers on the same cpu, queueing and
2533 * flushing. As long as context requirement is met, any worker can
2534 * call this function to process a work.
2535 *
2536 * CONTEXT:
2537 * raw_spin_lock_irq(pool->lock) which is released and regrabbed.
2538 */
2539static void process_one_work(struct worker *worker, struct work_struct *work)
2540__releases(&pool->lock)
2541__acquires(&pool->lock)
2542{
2543 struct pool_workqueue *pwq = get_work_pwq(work);
2544 struct worker_pool *pool = worker->pool;
2545 unsigned long work_data;
2546#ifdef CONFIG_LOCKDEP
2547 /*
2548 * It is permissible to free the struct work_struct from
2549 * inside the function that is called from it, this we need to
2550 * take into account for lockdep too. To avoid bogus "held
2551 * lock freed" warnings as well as problems when looking into
2552 * work->lockdep_map, make a copy and use that here.
2553 */
2554 struct lockdep_map lockdep_map;
2555
2556 lockdep_copy_map(&lockdep_map, &work->lockdep_map);
2557#endif
2558 /* ensure we're on the correct CPU */
2559 WARN_ON_ONCE(!(pool->flags & POOL_DISASSOCIATED) &&
2560 raw_smp_processor_id() != pool->cpu);
2561
2562 /* claim and dequeue */
2563 debug_work_deactivate(work);
2564 hash_add(pool->busy_hash, &worker->hentry, (unsigned long)work);
2565 worker->current_work = work;
2566 worker->current_func = work->func;
2567 worker->current_pwq = pwq;
2568 worker->current_at = worker->task->se.sum_exec_runtime;
2569 work_data = *work_data_bits(work);
2570 worker->current_color = get_work_color(work_data);
2571
2572 /*
2573 * Record wq name for cmdline and debug reporting, may get
2574 * overridden through set_worker_desc().
2575 */
2576 strscpy(worker->desc, pwq->wq->name, WORKER_DESC_LEN);
2577
2578 list_del_init(&work->entry);
2579
2580 /*
2581 * CPU intensive works don't participate in concurrency management.
2582 * They're the scheduler's responsibility. This takes @worker out
2583 * of concurrency management and the next code block will chain
2584 * execution of the pending work items.
2585 */
2586 if (unlikely(pwq->wq->flags & WQ_CPU_INTENSIVE))
2587 worker_set_flags(worker, WORKER_CPU_INTENSIVE);
2588
2589 /*
2590 * Kick @pool if necessary. It's always noop for per-cpu worker pools
2591 * since nr_running would always be >= 1 at this point. This is used to
2592 * chain execution of the pending work items for WORKER_NOT_RUNNING
2593 * workers such as the UNBOUND and CPU_INTENSIVE ones.
2594 */
2595 kick_pool(pool);
2596
2597 /*
2598 * Record the last pool and clear PENDING which should be the last
2599 * update to @work. Also, do this inside @pool->lock so that
2600 * PENDING and queued state changes happen together while IRQ is
2601 * disabled.
2602 */
2603 set_work_pool_and_clear_pending(work, pool->id);
2604
2605 pwq->stats[PWQ_STAT_STARTED]++;
2606 raw_spin_unlock_irq(&pool->lock);
2607
2608 lock_map_acquire(&pwq->wq->lockdep_map);
2609 lock_map_acquire(&lockdep_map);
2610 /*
2611 * Strictly speaking we should mark the invariant state without holding
2612 * any locks, that is, before these two lock_map_acquire()'s.
2613 *
2614 * However, that would result in:
2615 *
2616 * A(W1)
2617 * WFC(C)
2618 * A(W1)
2619 * C(C)
2620 *
2621 * Which would create W1->C->W1 dependencies, even though there is no
2622 * actual deadlock possible. There are two solutions, using a
2623 * read-recursive acquire on the work(queue) 'locks', but this will then
2624 * hit the lockdep limitation on recursive locks, or simply discard
2625 * these locks.
2626 *
2627 * AFAICT there is no possible deadlock scenario between the
2628 * flush_work() and complete() primitives (except for single-threaded
2629 * workqueues), so hiding them isn't a problem.
2630 */
2631 lockdep_invariant_state(true);
2632 trace_workqueue_execute_start(work);
2633 worker->current_func(work);
2634 /*
2635 * While we must be careful to not use "work" after this, the trace
2636 * point will only record its address.
2637 */
2638 trace_workqueue_execute_end(work, worker->current_func);
2639 pwq->stats[PWQ_STAT_COMPLETED]++;
2640 lock_map_release(&lockdep_map);
2641 lock_map_release(&pwq->wq->lockdep_map);
2642
2643 if (unlikely(in_atomic() || lockdep_depth(current) > 0)) {
2644 pr_err("BUG: workqueue leaked lock or atomic: %s/0x%08x/%d\n"
2645 " last function: %ps\n",
2646 current->comm, preempt_count(), task_pid_nr(current),
2647 worker->current_func);
2648 debug_show_held_locks(current);
2649 dump_stack();
2650 }
2651
2652 /*
2653 * The following prevents a kworker from hogging CPU on !PREEMPTION
2654 * kernels, where a requeueing work item waiting for something to
2655 * happen could deadlock with stop_machine as such work item could
2656 * indefinitely requeue itself while all other CPUs are trapped in
2657 * stop_machine. At the same time, report a quiescent RCU state so
2658 * the same condition doesn't freeze RCU.
2659 */
2660 cond_resched();
2661
2662 raw_spin_lock_irq(&pool->lock);
2663
2664 /*
2665 * In addition to %WQ_CPU_INTENSIVE, @worker may also have been marked
2666 * CPU intensive by wq_worker_tick() if @work hogged CPU longer than
2667 * wq_cpu_intensive_thresh_us. Clear it.
2668 */
2669 worker_clr_flags(worker, WORKER_CPU_INTENSIVE);
2670
2671 /* tag the worker for identification in schedule() */
2672 worker->last_func = worker->current_func;
2673
2674 /* we're done with it, release */
2675 hash_del(&worker->hentry);
2676 worker->current_work = NULL;
2677 worker->current_func = NULL;
2678 worker->current_pwq = NULL;
2679 worker->current_color = INT_MAX;
2680 pwq_dec_nr_in_flight(pwq, work_data);
2681}
2682
2683/**
2684 * process_scheduled_works - process scheduled works
2685 * @worker: self
2686 *
2687 * Process all scheduled works. Please note that the scheduled list
2688 * may change while processing a work, so this function repeatedly
2689 * fetches a work from the top and executes it.
2690 *
2691 * CONTEXT:
2692 * raw_spin_lock_irq(pool->lock) which may be released and regrabbed
2693 * multiple times.
2694 */
2695static void process_scheduled_works(struct worker *worker)
2696{
2697 struct work_struct *work;
2698 bool first = true;
2699
2700 while ((work = list_first_entry_or_null(&worker->scheduled,
2701 struct work_struct, entry))) {
2702 if (first) {
2703 worker->pool->watchdog_ts = jiffies;
2704 first = false;
2705 }
2706 process_one_work(worker, work);
2707 }
2708}
2709
2710static void set_pf_worker(bool val)
2711{
2712 mutex_lock(&wq_pool_attach_mutex);
2713 if (val)
2714 current->flags |= PF_WQ_WORKER;
2715 else
2716 current->flags &= ~PF_WQ_WORKER;
2717 mutex_unlock(&wq_pool_attach_mutex);
2718}
2719
2720/**
2721 * worker_thread - the worker thread function
2722 * @__worker: self
2723 *
2724 * The worker thread function. All workers belong to a worker_pool -
2725 * either a per-cpu one or dynamic unbound one. These workers process all
2726 * work items regardless of their specific target workqueue. The only
2727 * exception is work items which belong to workqueues with a rescuer which
2728 * will be explained in rescuer_thread().
2729 *
2730 * Return: 0
2731 */
2732static int worker_thread(void *__worker)
2733{
2734 struct worker *worker = __worker;
2735 struct worker_pool *pool = worker->pool;
2736
2737 /* tell the scheduler that this is a workqueue worker */
2738 set_pf_worker(true);
2739woke_up:
2740 raw_spin_lock_irq(&pool->lock);
2741
2742 /* am I supposed to die? */
2743 if (unlikely(worker->flags & WORKER_DIE)) {
2744 raw_spin_unlock_irq(&pool->lock);
2745 set_pf_worker(false);
2746
2747 set_task_comm(worker->task, "kworker/dying");
2748 ida_free(&pool->worker_ida, worker->id);
2749 worker_detach_from_pool(worker);
2750 WARN_ON_ONCE(!list_empty(&worker->entry));
2751 kfree(worker);
2752 return 0;
2753 }
2754
2755 worker_leave_idle(worker);
2756recheck:
2757 /* no more worker necessary? */
2758 if (!need_more_worker(pool))
2759 goto sleep;
2760
2761 /* do we need to manage? */
2762 if (unlikely(!may_start_working(pool)) && manage_workers(worker))
2763 goto recheck;
2764
2765 /*
2766 * ->scheduled list can only be filled while a worker is
2767 * preparing to process a work or actually processing it.
2768 * Make sure nobody diddled with it while I was sleeping.
2769 */
2770 WARN_ON_ONCE(!list_empty(&worker->scheduled));
2771
2772 /*
2773 * Finish PREP stage. We're guaranteed to have at least one idle
2774 * worker or that someone else has already assumed the manager
2775 * role. This is where @worker starts participating in concurrency
2776 * management if applicable and concurrency management is restored
2777 * after being rebound. See rebind_workers() for details.
2778 */
2779 worker_clr_flags(worker, WORKER_PREP | WORKER_REBOUND);
2780
2781 do {
2782 struct work_struct *work =
2783 list_first_entry(&pool->worklist,
2784 struct work_struct, entry);
2785
2786 if (assign_work(work, worker, NULL))
2787 process_scheduled_works(worker);
2788 } while (keep_working(pool));
2789
2790 worker_set_flags(worker, WORKER_PREP);
2791sleep:
2792 /*
2793 * pool->lock is held and there's no work to process and no need to
2794 * manage, sleep. Workers are woken up only while holding
2795 * pool->lock or from local cpu, so setting the current state
2796 * before releasing pool->lock is enough to prevent losing any
2797 * event.
2798 */
2799 worker_enter_idle(worker);
2800 __set_current_state(TASK_IDLE);
2801 raw_spin_unlock_irq(&pool->lock);
2802 schedule();
2803 goto woke_up;
2804}
2805
2806/**
2807 * rescuer_thread - the rescuer thread function
2808 * @__rescuer: self
2809 *
2810 * Workqueue rescuer thread function. There's one rescuer for each
2811 * workqueue which has WQ_MEM_RECLAIM set.
2812 *
2813 * Regular work processing on a pool may block trying to create a new
2814 * worker which uses GFP_KERNEL allocation which has slight chance of
2815 * developing into deadlock if some works currently on the same queue
2816 * need to be processed to satisfy the GFP_KERNEL allocation. This is
2817 * the problem rescuer solves.
2818 *
2819 * When such condition is possible, the pool summons rescuers of all
2820 * workqueues which have works queued on the pool and let them process
2821 * those works so that forward progress can be guaranteed.
2822 *
2823 * This should happen rarely.
2824 *
2825 * Return: 0
2826 */
2827static int rescuer_thread(void *__rescuer)
2828{
2829 struct worker *rescuer = __rescuer;
2830 struct workqueue_struct *wq = rescuer->rescue_wq;
2831 bool should_stop;
2832
2833 set_user_nice(current, RESCUER_NICE_LEVEL);
2834
2835 /*
2836 * Mark rescuer as worker too. As WORKER_PREP is never cleared, it
2837 * doesn't participate in concurrency management.
2838 */
2839 set_pf_worker(true);
2840repeat:
2841 set_current_state(TASK_IDLE);
2842
2843 /*
2844 * By the time the rescuer is requested to stop, the workqueue
2845 * shouldn't have any work pending, but @wq->maydays may still have
2846 * pwq(s) queued. This can happen by non-rescuer workers consuming
2847 * all the work items before the rescuer got to them. Go through
2848 * @wq->maydays processing before acting on should_stop so that the
2849 * list is always empty on exit.
2850 */
2851 should_stop = kthread_should_stop();
2852
2853 /* see whether any pwq is asking for help */
2854 raw_spin_lock_irq(&wq_mayday_lock);
2855
2856 while (!list_empty(&wq->maydays)) {
2857 struct pool_workqueue *pwq = list_first_entry(&wq->maydays,
2858 struct pool_workqueue, mayday_node);
2859 struct worker_pool *pool = pwq->pool;
2860 struct work_struct *work, *n;
2861
2862 __set_current_state(TASK_RUNNING);
2863 list_del_init(&pwq->mayday_node);
2864
2865 raw_spin_unlock_irq(&wq_mayday_lock);
2866
2867 worker_attach_to_pool(rescuer, pool);
2868
2869 raw_spin_lock_irq(&pool->lock);
2870
2871 /*
2872 * Slurp in all works issued via this workqueue and
2873 * process'em.
2874 */
2875 WARN_ON_ONCE(!list_empty(&rescuer->scheduled));
2876 list_for_each_entry_safe(work, n, &pool->worklist, entry) {
2877 if (get_work_pwq(work) == pwq &&
2878 assign_work(work, rescuer, &n))
2879 pwq->stats[PWQ_STAT_RESCUED]++;
2880 }
2881
2882 if (!list_empty(&rescuer->scheduled)) {
2883 process_scheduled_works(rescuer);
2884
2885 /*
2886 * The above execution of rescued work items could
2887 * have created more to rescue through
2888 * pwq_activate_first_inactive() or chained
2889 * queueing. Let's put @pwq back on mayday list so
2890 * that such back-to-back work items, which may be
2891 * being used to relieve memory pressure, don't
2892 * incur MAYDAY_INTERVAL delay inbetween.
2893 */
2894 if (pwq->nr_active && need_to_create_worker(pool)) {
2895 raw_spin_lock(&wq_mayday_lock);
2896 /*
2897 * Queue iff we aren't racing destruction
2898 * and somebody else hasn't queued it already.
2899 */
2900 if (wq->rescuer && list_empty(&pwq->mayday_node)) {
2901 get_pwq(pwq);
2902 list_add_tail(&pwq->mayday_node, &wq->maydays);
2903 }
2904 raw_spin_unlock(&wq_mayday_lock);
2905 }
2906 }
2907
2908 /*
2909 * Put the reference grabbed by send_mayday(). @pool won't
2910 * go away while we're still attached to it.
2911 */
2912 put_pwq(pwq);
2913
2914 /*
2915 * Leave this pool. Notify regular workers; otherwise, we end up
2916 * with 0 concurrency and stalling the execution.
2917 */
2918 kick_pool(pool);
2919
2920 raw_spin_unlock_irq(&pool->lock);
2921
2922 worker_detach_from_pool(rescuer);
2923
2924 raw_spin_lock_irq(&wq_mayday_lock);
2925 }
2926
2927 raw_spin_unlock_irq(&wq_mayday_lock);
2928
2929 if (should_stop) {
2930 __set_current_state(TASK_RUNNING);
2931 set_pf_worker(false);
2932 return 0;
2933 }
2934
2935 /* rescuers should never participate in concurrency management */
2936 WARN_ON_ONCE(!(rescuer->flags & WORKER_NOT_RUNNING));
2937 schedule();
2938 goto repeat;
2939}
2940
2941/**
2942 * check_flush_dependency - check for flush dependency sanity
2943 * @target_wq: workqueue being flushed
2944 * @target_work: work item being flushed (NULL for workqueue flushes)
2945 *
2946 * %current is trying to flush the whole @target_wq or @target_work on it.
2947 * If @target_wq doesn't have %WQ_MEM_RECLAIM, verify that %current is not
2948 * reclaiming memory or running on a workqueue which doesn't have
2949 * %WQ_MEM_RECLAIM as that can break forward-progress guarantee leading to
2950 * a deadlock.
2951 */
2952static void check_flush_dependency(struct workqueue_struct *target_wq,
2953 struct work_struct *target_work)
2954{
2955 work_func_t target_func = target_work ? target_work->func : NULL;
2956 struct worker *worker;
2957
2958 if (target_wq->flags & WQ_MEM_RECLAIM)
2959 return;
2960
2961 worker = current_wq_worker();
2962
2963 WARN_ONCE(current->flags & PF_MEMALLOC,
2964 "workqueue: PF_MEMALLOC task %d(%s) is flushing !WQ_MEM_RECLAIM %s:%ps",
2965 current->pid, current->comm, target_wq->name, target_func);
2966 WARN_ONCE(worker && ((worker->current_pwq->wq->flags &
2967 (WQ_MEM_RECLAIM | __WQ_LEGACY)) == WQ_MEM_RECLAIM),
2968 "workqueue: WQ_MEM_RECLAIM %s:%ps is flushing !WQ_MEM_RECLAIM %s:%ps",
2969 worker->current_pwq->wq->name, worker->current_func,
2970 target_wq->name, target_func);
2971}
2972
2973struct wq_barrier {
2974 struct work_struct work;
2975 struct completion done;
2976 struct task_struct *task; /* purely informational */
2977};
2978
2979static void wq_barrier_func(struct work_struct *work)
2980{
2981 struct wq_barrier *barr = container_of(work, struct wq_barrier, work);
2982 complete(&barr->done);
2983}
2984
2985/**
2986 * insert_wq_barrier - insert a barrier work
2987 * @pwq: pwq to insert barrier into
2988 * @barr: wq_barrier to insert
2989 * @target: target work to attach @barr to
2990 * @worker: worker currently executing @target, NULL if @target is not executing
2991 *
2992 * @barr is linked to @target such that @barr is completed only after
2993 * @target finishes execution. Please note that the ordering
2994 * guarantee is observed only with respect to @target and on the local
2995 * cpu.
2996 *
2997 * Currently, a queued barrier can't be canceled. This is because
2998 * try_to_grab_pending() can't determine whether the work to be
2999 * grabbed is at the head of the queue and thus can't clear LINKED
3000 * flag of the previous work while there must be a valid next work
3001 * after a work with LINKED flag set.
3002 *
3003 * Note that when @worker is non-NULL, @target may be modified
3004 * underneath us, so we can't reliably determine pwq from @target.
3005 *
3006 * CONTEXT:
3007 * raw_spin_lock_irq(pool->lock).
3008 */
3009static void insert_wq_barrier(struct pool_workqueue *pwq,
3010 struct wq_barrier *barr,
3011 struct work_struct *target, struct worker *worker)
3012{
3013 unsigned int work_flags = 0;
3014 unsigned int work_color;
3015 struct list_head *head;
3016
3017 /*
3018 * debugobject calls are safe here even with pool->lock locked
3019 * as we know for sure that this will not trigger any of the
3020 * checks and call back into the fixup functions where we
3021 * might deadlock.
3022 */
3023 INIT_WORK_ONSTACK(&barr->work, wq_barrier_func);
3024 __set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(&barr->work));
3025
3026 init_completion_map(&barr->done, &target->lockdep_map);
3027
3028 barr->task = current;
3029
3030 /* The barrier work item does not participate in pwq->nr_active. */
3031 work_flags |= WORK_STRUCT_INACTIVE;
3032
3033 /*
3034 * If @target is currently being executed, schedule the
3035 * barrier to the worker; otherwise, put it after @target.
3036 */
3037 if (worker) {
3038 head = worker->scheduled.next;
3039 work_color = worker->current_color;
3040 } else {
3041 unsigned long *bits = work_data_bits(target);
3042
3043 head = target->entry.next;
3044 /* there can already be other linked works, inherit and set */
3045 work_flags |= *bits & WORK_STRUCT_LINKED;
3046 work_color = get_work_color(*bits);
3047 __set_bit(WORK_STRUCT_LINKED_BIT, bits);
3048 }
3049
3050 pwq->nr_in_flight[work_color]++;
3051 work_flags |= work_color_to_flags(work_color);
3052
3053 insert_work(pwq, &barr->work, head, work_flags);
3054}
3055
3056/**
3057 * flush_workqueue_prep_pwqs - prepare pwqs for workqueue flushing
3058 * @wq: workqueue being flushed
3059 * @flush_color: new flush color, < 0 for no-op
3060 * @work_color: new work color, < 0 for no-op
3061 *
3062 * Prepare pwqs for workqueue flushing.
3063 *
3064 * If @flush_color is non-negative, flush_color on all pwqs should be
3065 * -1. If no pwq has in-flight commands at the specified color, all
3066 * pwq->flush_color's stay at -1 and %false is returned. If any pwq
3067 * has in flight commands, its pwq->flush_color is set to
3068 * @flush_color, @wq->nr_pwqs_to_flush is updated accordingly, pwq
3069 * wakeup logic is armed and %true is returned.
3070 *
3071 * The caller should have initialized @wq->first_flusher prior to
3072 * calling this function with non-negative @flush_color. If
3073 * @flush_color is negative, no flush color update is done and %false
3074 * is returned.
3075 *
3076 * If @work_color is non-negative, all pwqs should have the same
3077 * work_color which is previous to @work_color and all will be
3078 * advanced to @work_color.
3079 *
3080 * CONTEXT:
3081 * mutex_lock(wq->mutex).
3082 *
3083 * Return:
3084 * %true if @flush_color >= 0 and there's something to flush. %false
3085 * otherwise.
3086 */
3087static bool flush_workqueue_prep_pwqs(struct workqueue_struct *wq,
3088 int flush_color, int work_color)
3089{
3090 bool wait = false;
3091 struct pool_workqueue *pwq;
3092
3093 if (flush_color >= 0) {
3094 WARN_ON_ONCE(atomic_read(&wq->nr_pwqs_to_flush));
3095 atomic_set(&wq->nr_pwqs_to_flush, 1);
3096 }
3097
3098 for_each_pwq(pwq, wq) {
3099 struct worker_pool *pool = pwq->pool;
3100
3101 raw_spin_lock_irq(&pool->lock);
3102
3103 if (flush_color >= 0) {
3104 WARN_ON_ONCE(pwq->flush_color != -1);
3105
3106 if (pwq->nr_in_flight[flush_color]) {
3107 pwq->flush_color = flush_color;
3108 atomic_inc(&wq->nr_pwqs_to_flush);
3109 wait = true;
3110 }
3111 }
3112
3113 if (work_color >= 0) {
3114 WARN_ON_ONCE(work_color != work_next_color(pwq->work_color));
3115 pwq->work_color = work_color;
3116 }
3117
3118 raw_spin_unlock_irq(&pool->lock);
3119 }
3120
3121 if (flush_color >= 0 && atomic_dec_and_test(&wq->nr_pwqs_to_flush))
3122 complete(&wq->first_flusher->done);
3123
3124 return wait;
3125}
3126
3127/**
3128 * __flush_workqueue - ensure that any scheduled work has run to completion.
3129 * @wq: workqueue to flush
3130 *
3131 * This function sleeps until all work items which were queued on entry
3132 * have finished execution, but it is not livelocked by new incoming ones.
3133 */
3134void __flush_workqueue(struct workqueue_struct *wq)
3135{
3136 struct wq_flusher this_flusher = {
3137 .list = LIST_HEAD_INIT(this_flusher.list),
3138 .flush_color = -1,
3139 .done = COMPLETION_INITIALIZER_ONSTACK_MAP(this_flusher.done, wq->lockdep_map),
3140 };
3141 int next_color;
3142
3143 if (WARN_ON(!wq_online))
3144 return;
3145
3146 lock_map_acquire(&wq->lockdep_map);
3147 lock_map_release(&wq->lockdep_map);
3148
3149 mutex_lock(&wq->mutex);
3150
3151 /*
3152 * Start-to-wait phase
3153 */
3154 next_color = work_next_color(wq->work_color);
3155
3156 if (next_color != wq->flush_color) {
3157 /*
3158 * Color space is not full. The current work_color
3159 * becomes our flush_color and work_color is advanced
3160 * by one.
3161 */
3162 WARN_ON_ONCE(!list_empty(&wq->flusher_overflow));
3163 this_flusher.flush_color = wq->work_color;
3164 wq->work_color = next_color;
3165
3166 if (!wq->first_flusher) {
3167 /* no flush in progress, become the first flusher */
3168 WARN_ON_ONCE(wq->flush_color != this_flusher.flush_color);
3169
3170 wq->first_flusher = &this_flusher;
3171
3172 if (!flush_workqueue_prep_pwqs(wq, wq->flush_color,
3173 wq->work_color)) {
3174 /* nothing to flush, done */
3175 wq->flush_color = next_color;
3176 wq->first_flusher = NULL;
3177 goto out_unlock;
3178 }
3179 } else {
3180 /* wait in queue */
3181 WARN_ON_ONCE(wq->flush_color == this_flusher.flush_color);
3182 list_add_tail(&this_flusher.list, &wq->flusher_queue);
3183 flush_workqueue_prep_pwqs(wq, -1, wq->work_color);
3184 }
3185 } else {
3186 /*
3187 * Oops, color space is full, wait on overflow queue.
3188 * The next flush completion will assign us
3189 * flush_color and transfer to flusher_queue.
3190 */
3191 list_add_tail(&this_flusher.list, &wq->flusher_overflow);
3192 }
3193
3194 check_flush_dependency(wq, NULL);
3195
3196 mutex_unlock(&wq->mutex);
3197
3198 wait_for_completion(&this_flusher.done);
3199
3200 /*
3201 * Wake-up-and-cascade phase
3202 *
3203 * First flushers are responsible for cascading flushes and
3204 * handling overflow. Non-first flushers can simply return.
3205 */
3206 if (READ_ONCE(wq->first_flusher) != &this_flusher)
3207 return;
3208
3209 mutex_lock(&wq->mutex);
3210
3211 /* we might have raced, check again with mutex held */
3212 if (wq->first_flusher != &this_flusher)
3213 goto out_unlock;
3214
3215 WRITE_ONCE(wq->first_flusher, NULL);
3216
3217 WARN_ON_ONCE(!list_empty(&this_flusher.list));
3218 WARN_ON_ONCE(wq->flush_color != this_flusher.flush_color);
3219
3220 while (true) {
3221 struct wq_flusher *next, *tmp;
3222
3223 /* complete all the flushers sharing the current flush color */
3224 list_for_each_entry_safe(next, tmp, &wq->flusher_queue, list) {
3225 if (next->flush_color != wq->flush_color)
3226 break;
3227 list_del_init(&next->list);
3228 complete(&next->done);
3229 }
3230
3231 WARN_ON_ONCE(!list_empty(&wq->flusher_overflow) &&
3232 wq->flush_color != work_next_color(wq->work_color));
3233
3234 /* this flush_color is finished, advance by one */
3235 wq->flush_color = work_next_color(wq->flush_color);
3236
3237 /* one color has been freed, handle overflow queue */
3238 if (!list_empty(&wq->flusher_overflow)) {
3239 /*
3240 * Assign the same color to all overflowed
3241 * flushers, advance work_color and append to
3242 * flusher_queue. This is the start-to-wait
3243 * phase for these overflowed flushers.
3244 */
3245 list_for_each_entry(tmp, &wq->flusher_overflow, list)
3246 tmp->flush_color = wq->work_color;
3247
3248 wq->work_color = work_next_color(wq->work_color);
3249
3250 list_splice_tail_init(&wq->flusher_overflow,
3251 &wq->flusher_queue);
3252 flush_workqueue_prep_pwqs(wq, -1, wq->work_color);
3253 }
3254
3255 if (list_empty(&wq->flusher_queue)) {
3256 WARN_ON_ONCE(wq->flush_color != wq->work_color);
3257 break;
3258 }
3259
3260 /*
3261 * Need to flush more colors. Make the next flusher
3262 * the new first flusher and arm pwqs.
3263 */
3264 WARN_ON_ONCE(wq->flush_color == wq->work_color);
3265 WARN_ON_ONCE(wq->flush_color != next->flush_color);
3266
3267 list_del_init(&next->list);
3268 wq->first_flusher = next;
3269
3270 if (flush_workqueue_prep_pwqs(wq, wq->flush_color, -1))
3271 break;
3272
3273 /*
3274 * Meh... this color is already done, clear first
3275 * flusher and repeat cascading.
3276 */
3277 wq->first_flusher = NULL;
3278 }
3279
3280out_unlock:
3281 mutex_unlock(&wq->mutex);
3282}
3283EXPORT_SYMBOL(__flush_workqueue);
3284
3285/**
3286 * drain_workqueue - drain a workqueue
3287 * @wq: workqueue to drain
3288 *
3289 * Wait until the workqueue becomes empty. While draining is in progress,
3290 * only chain queueing is allowed. IOW, only currently pending or running
3291 * work items on @wq can queue further work items on it. @wq is flushed
3292 * repeatedly until it becomes empty. The number of flushing is determined
3293 * by the depth of chaining and should be relatively short. Whine if it
3294 * takes too long.
3295 */
3296void drain_workqueue(struct workqueue_struct *wq)
3297{
3298 unsigned int flush_cnt = 0;
3299 struct pool_workqueue *pwq;
3300
3301 /*
3302 * __queue_work() needs to test whether there are drainers, is much
3303 * hotter than drain_workqueue() and already looks at @wq->flags.
3304 * Use __WQ_DRAINING so that queue doesn't have to check nr_drainers.
3305 */
3306 mutex_lock(&wq->mutex);
3307 if (!wq->nr_drainers++)
3308 wq->flags |= __WQ_DRAINING;
3309 mutex_unlock(&wq->mutex);
3310reflush:
3311 __flush_workqueue(wq);
3312
3313 mutex_lock(&wq->mutex);
3314
3315 for_each_pwq(pwq, wq) {
3316 bool drained;
3317
3318 raw_spin_lock_irq(&pwq->pool->lock);
3319 drained = !pwq->nr_active && list_empty(&pwq->inactive_works);
3320 raw_spin_unlock_irq(&pwq->pool->lock);
3321
3322 if (drained)
3323 continue;
3324
3325 if (++flush_cnt == 10 ||
3326 (flush_cnt % 100 == 0 && flush_cnt <= 1000))
3327 pr_warn("workqueue %s: %s() isn't complete after %u tries\n",
3328 wq->name, __func__, flush_cnt);
3329
3330 mutex_unlock(&wq->mutex);
3331 goto reflush;
3332 }
3333
3334 if (!--wq->nr_drainers)
3335 wq->flags &= ~__WQ_DRAINING;
3336 mutex_unlock(&wq->mutex);
3337}
3338EXPORT_SYMBOL_GPL(drain_workqueue);
3339
3340static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr,
3341 bool from_cancel)
3342{
3343 struct worker *worker = NULL;
3344 struct worker_pool *pool;
3345 struct pool_workqueue *pwq;
3346
3347 might_sleep();
3348
3349 rcu_read_lock();
3350 pool = get_work_pool(work);
3351 if (!pool) {
3352 rcu_read_unlock();
3353 return false;
3354 }
3355
3356 raw_spin_lock_irq(&pool->lock);
3357 /* see the comment in try_to_grab_pending() with the same code */
3358 pwq = get_work_pwq(work);
3359 if (pwq) {
3360 if (unlikely(pwq->pool != pool))
3361 goto already_gone;
3362 } else {
3363 worker = find_worker_executing_work(pool, work);
3364 if (!worker)
3365 goto already_gone;
3366 pwq = worker->current_pwq;
3367 }
3368
3369 check_flush_dependency(pwq->wq, work);
3370
3371 insert_wq_barrier(pwq, barr, work, worker);
3372 raw_spin_unlock_irq(&pool->lock);
3373
3374 /*
3375 * Force a lock recursion deadlock when using flush_work() inside a
3376 * single-threaded or rescuer equipped workqueue.
3377 *
3378 * For single threaded workqueues the deadlock happens when the work
3379 * is after the work issuing the flush_work(). For rescuer equipped
3380 * workqueues the deadlock happens when the rescuer stalls, blocking
3381 * forward progress.
3382 */
3383 if (!from_cancel &&
3384 (pwq->wq->saved_max_active == 1 || pwq->wq->rescuer)) {
3385 lock_map_acquire(&pwq->wq->lockdep_map);
3386 lock_map_release(&pwq->wq->lockdep_map);
3387 }
3388 rcu_read_unlock();
3389 return true;
3390already_gone:
3391 raw_spin_unlock_irq(&pool->lock);
3392 rcu_read_unlock();
3393 return false;
3394}
3395
3396static bool __flush_work(struct work_struct *work, bool from_cancel)
3397{
3398 struct wq_barrier barr;
3399
3400 if (WARN_ON(!wq_online))
3401 return false;
3402
3403 if (WARN_ON(!work->func))
3404 return false;
3405
3406 lock_map_acquire(&work->lockdep_map);
3407 lock_map_release(&work->lockdep_map);
3408
3409 if (start_flush_work(work, &barr, from_cancel)) {
3410 wait_for_completion(&barr.done);
3411 destroy_work_on_stack(&barr.work);
3412 return true;
3413 } else {
3414 return false;
3415 }
3416}
3417
3418/**
3419 * flush_work - wait for a work to finish executing the last queueing instance
3420 * @work: the work to flush
3421 *
3422 * Wait until @work has finished execution. @work is guaranteed to be idle
3423 * on return if it hasn't been requeued since flush started.
3424 *
3425 * Return:
3426 * %true if flush_work() waited for the work to finish execution,
3427 * %false if it was already idle.
3428 */
3429bool flush_work(struct work_struct *work)
3430{
3431 return __flush_work(work, false);
3432}
3433EXPORT_SYMBOL_GPL(flush_work);
3434
3435struct cwt_wait {
3436 wait_queue_entry_t wait;
3437 struct work_struct *work;
3438};
3439
3440static int cwt_wakefn(wait_queue_entry_t *wait, unsigned mode, int sync, void *key)
3441{
3442 struct cwt_wait *cwait = container_of(wait, struct cwt_wait, wait);
3443
3444 if (cwait->work != key)
3445 return 0;
3446 return autoremove_wake_function(wait, mode, sync, key);
3447}
3448
3449static bool __cancel_work_timer(struct work_struct *work, bool is_dwork)
3450{
3451 static DECLARE_WAIT_QUEUE_HEAD(cancel_waitq);
3452 unsigned long flags;
3453 int ret;
3454
3455 do {
3456 ret = try_to_grab_pending(work, is_dwork, &flags);
3457 /*
3458 * If someone else is already canceling, wait for it to
3459 * finish. flush_work() doesn't work for PREEMPT_NONE
3460 * because we may get scheduled between @work's completion
3461 * and the other canceling task resuming and clearing
3462 * CANCELING - flush_work() will return false immediately
3463 * as @work is no longer busy, try_to_grab_pending() will
3464 * return -ENOENT as @work is still being canceled and the
3465 * other canceling task won't be able to clear CANCELING as
3466 * we're hogging the CPU.
3467 *
3468 * Let's wait for completion using a waitqueue. As this
3469 * may lead to the thundering herd problem, use a custom
3470 * wake function which matches @work along with exclusive
3471 * wait and wakeup.
3472 */
3473 if (unlikely(ret == -ENOENT)) {
3474 struct cwt_wait cwait;
3475
3476 init_wait(&cwait.wait);
3477 cwait.wait.func = cwt_wakefn;
3478 cwait.work = work;
3479
3480 prepare_to_wait_exclusive(&cancel_waitq, &cwait.wait,
3481 TASK_UNINTERRUPTIBLE);
3482 if (work_is_canceling(work))
3483 schedule();
3484 finish_wait(&cancel_waitq, &cwait.wait);
3485 }
3486 } while (unlikely(ret < 0));
3487
3488 /* tell other tasks trying to grab @work to back off */
3489 mark_work_canceling(work);
3490 local_irq_restore(flags);
3491
3492 /*
3493 * This allows canceling during early boot. We know that @work
3494 * isn't executing.
3495 */
3496 if (wq_online)
3497 __flush_work(work, true);
3498
3499 clear_work_data(work);
3500
3501 /*
3502 * Paired with prepare_to_wait() above so that either
3503 * waitqueue_active() is visible here or !work_is_canceling() is
3504 * visible there.
3505 */
3506 smp_mb();
3507 if (waitqueue_active(&cancel_waitq))
3508 __wake_up(&cancel_waitq, TASK_NORMAL, 1, work);
3509
3510 return ret;
3511}
3512
3513/**
3514 * cancel_work_sync - cancel a work and wait for it to finish
3515 * @work: the work to cancel
3516 *
3517 * Cancel @work and wait for its execution to finish. This function
3518 * can be used even if the work re-queues itself or migrates to
3519 * another workqueue. On return from this function, @work is
3520 * guaranteed to be not pending or executing on any CPU.
3521 *
3522 * cancel_work_sync(&delayed_work->work) must not be used for
3523 * delayed_work's. Use cancel_delayed_work_sync() instead.
3524 *
3525 * The caller must ensure that the workqueue on which @work was last
3526 * queued can't be destroyed before this function returns.
3527 *
3528 * Return:
3529 * %true if @work was pending, %false otherwise.
3530 */
3531bool cancel_work_sync(struct work_struct *work)
3532{
3533 return __cancel_work_timer(work, false);
3534}
3535EXPORT_SYMBOL_GPL(cancel_work_sync);
3536
3537/**
3538 * flush_delayed_work - wait for a dwork to finish executing the last queueing
3539 * @dwork: the delayed work to flush
3540 *
3541 * Delayed timer is cancelled and the pending work is queued for
3542 * immediate execution. Like flush_work(), this function only
3543 * considers the last queueing instance of @dwork.
3544 *
3545 * Return:
3546 * %true if flush_work() waited for the work to finish execution,
3547 * %false if it was already idle.
3548 */
3549bool flush_delayed_work(struct delayed_work *dwork)
3550{
3551 local_irq_disable();
3552 if (del_timer_sync(&dwork->timer))
3553 __queue_work(dwork->cpu, dwork->wq, &dwork->work);
3554 local_irq_enable();
3555 return flush_work(&dwork->work);
3556}
3557EXPORT_SYMBOL(flush_delayed_work);
3558
3559/**
3560 * flush_rcu_work - wait for a rwork to finish executing the last queueing
3561 * @rwork: the rcu work to flush
3562 *
3563 * Return:
3564 * %true if flush_rcu_work() waited for the work to finish execution,
3565 * %false if it was already idle.
3566 */
3567bool flush_rcu_work(struct rcu_work *rwork)
3568{
3569 if (test_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(&rwork->work))) {
3570 rcu_barrier();
3571 flush_work(&rwork->work);
3572 return true;
3573 } else {
3574 return flush_work(&rwork->work);
3575 }
3576}
3577EXPORT_SYMBOL(flush_rcu_work);
3578
3579static bool __cancel_work(struct work_struct *work, bool is_dwork)
3580{
3581 unsigned long flags;
3582 int ret;
3583
3584 do {
3585 ret = try_to_grab_pending(work, is_dwork, &flags);
3586 } while (unlikely(ret == -EAGAIN));
3587
3588 if (unlikely(ret < 0))
3589 return false;
3590
3591 set_work_pool_and_clear_pending(work, get_work_pool_id(work));
3592 local_irq_restore(flags);
3593 return ret;
3594}
3595
3596/*
3597 * See cancel_delayed_work()
3598 */
3599bool cancel_work(struct work_struct *work)
3600{
3601 return __cancel_work(work, false);
3602}
3603EXPORT_SYMBOL(cancel_work);
3604
3605/**
3606 * cancel_delayed_work - cancel a delayed work
3607 * @dwork: delayed_work to cancel
3608 *
3609 * Kill off a pending delayed_work.
3610 *
3611 * Return: %true if @dwork was pending and canceled; %false if it wasn't
3612 * pending.
3613 *
3614 * Note:
3615 * The work callback function may still be running on return, unless
3616 * it returns %true and the work doesn't re-arm itself. Explicitly flush or
3617 * use cancel_delayed_work_sync() to wait on it.
3618 *
3619 * This function is safe to call from any context including IRQ handler.
3620 */
3621bool cancel_delayed_work(struct delayed_work *dwork)
3622{
3623 return __cancel_work(&dwork->work, true);
3624}
3625EXPORT_SYMBOL(cancel_delayed_work);
3626
3627/**
3628 * cancel_delayed_work_sync - cancel a delayed work and wait for it to finish
3629 * @dwork: the delayed work cancel
3630 *
3631 * This is cancel_work_sync() for delayed works.
3632 *
3633 * Return:
3634 * %true if @dwork was pending, %false otherwise.
3635 */
3636bool cancel_delayed_work_sync(struct delayed_work *dwork)
3637{
3638 return __cancel_work_timer(&dwork->work, true);
3639}
3640EXPORT_SYMBOL(cancel_delayed_work_sync);
3641
3642/**
3643 * schedule_on_each_cpu - execute a function synchronously on each online CPU
3644 * @func: the function to call
3645 *
3646 * schedule_on_each_cpu() executes @func on each online CPU using the
3647 * system workqueue and blocks until all CPUs have completed.
3648 * schedule_on_each_cpu() is very slow.
3649 *
3650 * Return:
3651 * 0 on success, -errno on failure.
3652 */
3653int schedule_on_each_cpu(work_func_t func)
3654{
3655 int cpu;
3656 struct work_struct __percpu *works;
3657
3658 works = alloc_percpu(struct work_struct);
3659 if (!works)
3660 return -ENOMEM;
3661
3662 cpus_read_lock();
3663
3664 for_each_online_cpu(cpu) {
3665 struct work_struct *work = per_cpu_ptr(works, cpu);
3666
3667 INIT_WORK(work, func);
3668 schedule_work_on(cpu, work);
3669 }
3670
3671 for_each_online_cpu(cpu)
3672 flush_work(per_cpu_ptr(works, cpu));
3673
3674 cpus_read_unlock();
3675 free_percpu(works);
3676 return 0;
3677}
3678
3679/**
3680 * execute_in_process_context - reliably execute the routine with user context
3681 * @fn: the function to execute
3682 * @ew: guaranteed storage for the execute work structure (must
3683 * be available when the work executes)
3684 *
3685 * Executes the function immediately if process context is available,
3686 * otherwise schedules the function for delayed execution.
3687 *
3688 * Return: 0 - function was executed
3689 * 1 - function was scheduled for execution
3690 */
3691int execute_in_process_context(work_func_t fn, struct execute_work *ew)
3692{
3693 if (!in_interrupt()) {
3694 fn(&ew->work);
3695 return 0;
3696 }
3697
3698 INIT_WORK(&ew->work, fn);
3699 schedule_work(&ew->work);
3700
3701 return 1;
3702}
3703EXPORT_SYMBOL_GPL(execute_in_process_context);
3704
3705/**
3706 * free_workqueue_attrs - free a workqueue_attrs
3707 * @attrs: workqueue_attrs to free
3708 *
3709 * Undo alloc_workqueue_attrs().
3710 */
3711void free_workqueue_attrs(struct workqueue_attrs *attrs)
3712{
3713 if (attrs) {
3714 free_cpumask_var(attrs->cpumask);
3715 free_cpumask_var(attrs->__pod_cpumask);
3716 kfree(attrs);
3717 }
3718}
3719
3720/**
3721 * alloc_workqueue_attrs - allocate a workqueue_attrs
3722 *
3723 * Allocate a new workqueue_attrs, initialize with default settings and
3724 * return it.
3725 *
3726 * Return: The allocated new workqueue_attr on success. %NULL on failure.
3727 */
3728struct workqueue_attrs *alloc_workqueue_attrs(void)
3729{
3730 struct workqueue_attrs *attrs;
3731
3732 attrs = kzalloc(sizeof(*attrs), GFP_KERNEL);
3733 if (!attrs)
3734 goto fail;
3735 if (!alloc_cpumask_var(&attrs->cpumask, GFP_KERNEL))
3736 goto fail;
3737 if (!alloc_cpumask_var(&attrs->__pod_cpumask, GFP_KERNEL))
3738 goto fail;
3739
3740 cpumask_copy(attrs->cpumask, cpu_possible_mask);
3741 attrs->affn_scope = WQ_AFFN_DFL;
3742 return attrs;
3743fail:
3744 free_workqueue_attrs(attrs);
3745 return NULL;
3746}
3747
3748static void copy_workqueue_attrs(struct workqueue_attrs *to,
3749 const struct workqueue_attrs *from)
3750{
3751 to->nice = from->nice;
3752 cpumask_copy(to->cpumask, from->cpumask);
3753 cpumask_copy(to->__pod_cpumask, from->__pod_cpumask);
3754 to->affn_strict = from->affn_strict;
3755
3756 /*
3757 * Unlike hash and equality test, copying shouldn't ignore wq-only
3758 * fields as copying is used for both pool and wq attrs. Instead,
3759 * get_unbound_pool() explicitly clears the fields.
3760 */
3761 to->affn_scope = from->affn_scope;
3762 to->ordered = from->ordered;
3763}
3764
3765/*
3766 * Some attrs fields are workqueue-only. Clear them for worker_pool's. See the
3767 * comments in 'struct workqueue_attrs' definition.
3768 */
3769static void wqattrs_clear_for_pool(struct workqueue_attrs *attrs)
3770{
3771 attrs->affn_scope = WQ_AFFN_NR_TYPES;
3772 attrs->ordered = false;
3773}
3774
3775/* hash value of the content of @attr */
3776static u32 wqattrs_hash(const struct workqueue_attrs *attrs)
3777{
3778 u32 hash = 0;
3779
3780 hash = jhash_1word(attrs->nice, hash);
3781 hash = jhash(cpumask_bits(attrs->cpumask),
3782 BITS_TO_LONGS(nr_cpumask_bits) * sizeof(long), hash);
3783 hash = jhash(cpumask_bits(attrs->__pod_cpumask),
3784 BITS_TO_LONGS(nr_cpumask_bits) * sizeof(long), hash);
3785 hash = jhash_1word(attrs->affn_strict, hash);
3786 return hash;
3787}
3788
3789/* content equality test */
3790static bool wqattrs_equal(const struct workqueue_attrs *a,
3791 const struct workqueue_attrs *b)
3792{
3793 if (a->nice != b->nice)
3794 return false;
3795 if (!cpumask_equal(a->cpumask, b->cpumask))
3796 return false;
3797 if (!cpumask_equal(a->__pod_cpumask, b->__pod_cpumask))
3798 return false;
3799 if (a->affn_strict != b->affn_strict)
3800 return false;
3801 return true;
3802}
3803
3804/* Update @attrs with actually available CPUs */
3805static void wqattrs_actualize_cpumask(struct workqueue_attrs *attrs,
3806 const cpumask_t *unbound_cpumask)
3807{
3808 /*
3809 * Calculate the effective CPU mask of @attrs given @unbound_cpumask. If
3810 * @attrs->cpumask doesn't overlap with @unbound_cpumask, we fallback to
3811 * @unbound_cpumask.
3812 */
3813 cpumask_and(attrs->cpumask, attrs->cpumask, unbound_cpumask);
3814 if (unlikely(cpumask_empty(attrs->cpumask)))
3815 cpumask_copy(attrs->cpumask, unbound_cpumask);
3816}
3817
3818/* find wq_pod_type to use for @attrs */
3819static const struct wq_pod_type *
3820wqattrs_pod_type(const struct workqueue_attrs *attrs)
3821{
3822 enum wq_affn_scope scope;
3823 struct wq_pod_type *pt;
3824
3825 /* to synchronize access to wq_affn_dfl */
3826 lockdep_assert_held(&wq_pool_mutex);
3827
3828 if (attrs->affn_scope == WQ_AFFN_DFL)
3829 scope = wq_affn_dfl;
3830 else
3831 scope = attrs->affn_scope;
3832
3833 pt = &wq_pod_types[scope];
3834
3835 if (!WARN_ON_ONCE(attrs->affn_scope == WQ_AFFN_NR_TYPES) &&
3836 likely(pt->nr_pods))
3837 return pt;
3838
3839 /*
3840 * Before workqueue_init_topology(), only SYSTEM is available which is
3841 * initialized in workqueue_init_early().
3842 */
3843 pt = &wq_pod_types[WQ_AFFN_SYSTEM];
3844 BUG_ON(!pt->nr_pods);
3845 return pt;
3846}
3847
3848/**
3849 * init_worker_pool - initialize a newly zalloc'd worker_pool
3850 * @pool: worker_pool to initialize
3851 *
3852 * Initialize a newly zalloc'd @pool. It also allocates @pool->attrs.
3853 *
3854 * Return: 0 on success, -errno on failure. Even on failure, all fields
3855 * inside @pool proper are initialized and put_unbound_pool() can be called
3856 * on @pool safely to release it.
3857 */
3858static int init_worker_pool(struct worker_pool *pool)
3859{
3860 raw_spin_lock_init(&pool->lock);
3861 pool->id = -1;
3862 pool->cpu = -1;
3863 pool->node = NUMA_NO_NODE;
3864 pool->flags |= POOL_DISASSOCIATED;
3865 pool->watchdog_ts = jiffies;
3866 INIT_LIST_HEAD(&pool->worklist);
3867 INIT_LIST_HEAD(&pool->idle_list);
3868 hash_init(pool->busy_hash);
3869
3870 timer_setup(&pool->idle_timer, idle_worker_timeout, TIMER_DEFERRABLE);
3871 INIT_WORK(&pool->idle_cull_work, idle_cull_fn);
3872
3873 timer_setup(&pool->mayday_timer, pool_mayday_timeout, 0);
3874
3875 INIT_LIST_HEAD(&pool->workers);
3876 INIT_LIST_HEAD(&pool->dying_workers);
3877
3878 ida_init(&pool->worker_ida);
3879 INIT_HLIST_NODE(&pool->hash_node);
3880 pool->refcnt = 1;
3881
3882 /* shouldn't fail above this point */
3883 pool->attrs = alloc_workqueue_attrs();
3884 if (!pool->attrs)
3885 return -ENOMEM;
3886
3887 wqattrs_clear_for_pool(pool->attrs);
3888
3889 return 0;
3890}
3891
3892#ifdef CONFIG_LOCKDEP
3893static void wq_init_lockdep(struct workqueue_struct *wq)
3894{
3895 char *lock_name;
3896
3897 lockdep_register_key(&wq->key);
3898 lock_name = kasprintf(GFP_KERNEL, "%s%s", "(wq_completion)", wq->name);
3899 if (!lock_name)
3900 lock_name = wq->name;
3901
3902 wq->lock_name = lock_name;
3903 lockdep_init_map(&wq->lockdep_map, lock_name, &wq->key, 0);
3904}
3905
3906static void wq_unregister_lockdep(struct workqueue_struct *wq)
3907{
3908 lockdep_unregister_key(&wq->key);
3909}
3910
3911static void wq_free_lockdep(struct workqueue_struct *wq)
3912{
3913 if (wq->lock_name != wq->name)
3914 kfree(wq->lock_name);
3915}
3916#else
3917static void wq_init_lockdep(struct workqueue_struct *wq)
3918{
3919}
3920
3921static void wq_unregister_lockdep(struct workqueue_struct *wq)
3922{
3923}
3924
3925static void wq_free_lockdep(struct workqueue_struct *wq)
3926{
3927}
3928#endif
3929
3930static void rcu_free_wq(struct rcu_head *rcu)
3931{
3932 struct workqueue_struct *wq =
3933 container_of(rcu, struct workqueue_struct, rcu);
3934
3935 wq_free_lockdep(wq);
3936 free_percpu(wq->cpu_pwq);
3937 free_workqueue_attrs(wq->unbound_attrs);
3938 kfree(wq);
3939}
3940
3941static void rcu_free_pool(struct rcu_head *rcu)
3942{
3943 struct worker_pool *pool = container_of(rcu, struct worker_pool, rcu);
3944
3945 ida_destroy(&pool->worker_ida);
3946 free_workqueue_attrs(pool->attrs);
3947 kfree(pool);
3948}
3949
3950/**
3951 * put_unbound_pool - put a worker_pool
3952 * @pool: worker_pool to put
3953 *
3954 * Put @pool. If its refcnt reaches zero, it gets destroyed in RCU
3955 * safe manner. get_unbound_pool() calls this function on its failure path
3956 * and this function should be able to release pools which went through,
3957 * successfully or not, init_worker_pool().
3958 *
3959 * Should be called with wq_pool_mutex held.
3960 */
3961static void put_unbound_pool(struct worker_pool *pool)
3962{
3963 DECLARE_COMPLETION_ONSTACK(detach_completion);
3964 struct worker *worker;
3965 LIST_HEAD(cull_list);
3966
3967 lockdep_assert_held(&wq_pool_mutex);
3968
3969 if (--pool->refcnt)
3970 return;
3971
3972 /* sanity checks */
3973 if (WARN_ON(!(pool->cpu < 0)) ||
3974 WARN_ON(!list_empty(&pool->worklist)))
3975 return;
3976
3977 /* release id and unhash */
3978 if (pool->id >= 0)
3979 idr_remove(&worker_pool_idr, pool->id);
3980 hash_del(&pool->hash_node);
3981
3982 /*
3983 * Become the manager and destroy all workers. This prevents
3984 * @pool's workers from blocking on attach_mutex. We're the last
3985 * manager and @pool gets freed with the flag set.
3986 *
3987 * Having a concurrent manager is quite unlikely to happen as we can
3988 * only get here with
3989 * pwq->refcnt == pool->refcnt == 0
3990 * which implies no work queued to the pool, which implies no worker can
3991 * become the manager. However a worker could have taken the role of
3992 * manager before the refcnts dropped to 0, since maybe_create_worker()
3993 * drops pool->lock
3994 */
3995 while (true) {
3996 rcuwait_wait_event(&manager_wait,
3997 !(pool->flags & POOL_MANAGER_ACTIVE),
3998 TASK_UNINTERRUPTIBLE);
3999
4000 mutex_lock(&wq_pool_attach_mutex);
4001 raw_spin_lock_irq(&pool->lock);
4002 if (!(pool->flags & POOL_MANAGER_ACTIVE)) {
4003 pool->flags |= POOL_MANAGER_ACTIVE;
4004 break;
4005 }
4006 raw_spin_unlock_irq(&pool->lock);
4007 mutex_unlock(&wq_pool_attach_mutex);
4008 }
4009
4010 while ((worker = first_idle_worker(pool)))
4011 set_worker_dying(worker, &cull_list);
4012 WARN_ON(pool->nr_workers || pool->nr_idle);
4013 raw_spin_unlock_irq(&pool->lock);
4014
4015 wake_dying_workers(&cull_list);
4016
4017 if (!list_empty(&pool->workers) || !list_empty(&pool->dying_workers))
4018 pool->detach_completion = &detach_completion;
4019 mutex_unlock(&wq_pool_attach_mutex);
4020
4021 if (pool->detach_completion)
4022 wait_for_completion(pool->detach_completion);
4023
4024 /* shut down the timers */
4025 del_timer_sync(&pool->idle_timer);
4026 cancel_work_sync(&pool->idle_cull_work);
4027 del_timer_sync(&pool->mayday_timer);
4028
4029 /* RCU protected to allow dereferences from get_work_pool() */
4030 call_rcu(&pool->rcu, rcu_free_pool);
4031}
4032
4033/**
4034 * get_unbound_pool - get a worker_pool with the specified attributes
4035 * @attrs: the attributes of the worker_pool to get
4036 *
4037 * Obtain a worker_pool which has the same attributes as @attrs, bump the
4038 * reference count and return it. If there already is a matching
4039 * worker_pool, it will be used; otherwise, this function attempts to
4040 * create a new one.
4041 *
4042 * Should be called with wq_pool_mutex held.
4043 *
4044 * Return: On success, a worker_pool with the same attributes as @attrs.
4045 * On failure, %NULL.
4046 */
4047static struct worker_pool *get_unbound_pool(const struct workqueue_attrs *attrs)
4048{
4049 struct wq_pod_type *pt = &wq_pod_types[WQ_AFFN_NUMA];
4050 u32 hash = wqattrs_hash(attrs);
4051 struct worker_pool *pool;
4052 int pod, node = NUMA_NO_NODE;
4053
4054 lockdep_assert_held(&wq_pool_mutex);
4055
4056 /* do we already have a matching pool? */
4057 hash_for_each_possible(unbound_pool_hash, pool, hash_node, hash) {
4058 if (wqattrs_equal(pool->attrs, attrs)) {
4059 pool->refcnt++;
4060 return pool;
4061 }
4062 }
4063
4064 /* If __pod_cpumask is contained inside a NUMA pod, that's our node */
4065 for (pod = 0; pod < pt->nr_pods; pod++) {
4066 if (cpumask_subset(attrs->__pod_cpumask, pt->pod_cpus[pod])) {
4067 node = pt->pod_node[pod];
4068 break;
4069 }
4070 }
4071
4072 /* nope, create a new one */
4073 pool = kzalloc_node(sizeof(*pool), GFP_KERNEL, node);
4074 if (!pool || init_worker_pool(pool) < 0)
4075 goto fail;
4076
4077 pool->node = node;
4078 copy_workqueue_attrs(pool->attrs, attrs);
4079 wqattrs_clear_for_pool(pool->attrs);
4080
4081 if (worker_pool_assign_id(pool) < 0)
4082 goto fail;
4083
4084 /* create and start the initial worker */
4085 if (wq_online && !create_worker(pool))
4086 goto fail;
4087
4088 /* install */
4089 hash_add(unbound_pool_hash, &pool->hash_node, hash);
4090
4091 return pool;
4092fail:
4093 if (pool)
4094 put_unbound_pool(pool);
4095 return NULL;
4096}
4097
4098static void rcu_free_pwq(struct rcu_head *rcu)
4099{
4100 kmem_cache_free(pwq_cache,
4101 container_of(rcu, struct pool_workqueue, rcu));
4102}
4103
4104/*
4105 * Scheduled on pwq_release_worker by put_pwq() when an unbound pwq hits zero
4106 * refcnt and needs to be destroyed.
4107 */
4108static void pwq_release_workfn(struct kthread_work *work)
4109{
4110 struct pool_workqueue *pwq = container_of(work, struct pool_workqueue,
4111 release_work);
4112 struct workqueue_struct *wq = pwq->wq;
4113 struct worker_pool *pool = pwq->pool;
4114 bool is_last = false;
4115
4116 /*
4117 * When @pwq is not linked, it doesn't hold any reference to the
4118 * @wq, and @wq is invalid to access.
4119 */
4120 if (!list_empty(&pwq->pwqs_node)) {
4121 mutex_lock(&wq->mutex);
4122 list_del_rcu(&pwq->pwqs_node);
4123 is_last = list_empty(&wq->pwqs);
4124 mutex_unlock(&wq->mutex);
4125 }
4126
4127 if (wq->flags & WQ_UNBOUND) {
4128 mutex_lock(&wq_pool_mutex);
4129 put_unbound_pool(pool);
4130 mutex_unlock(&wq_pool_mutex);
4131 }
4132
4133 call_rcu(&pwq->rcu, rcu_free_pwq);
4134
4135 /*
4136 * If we're the last pwq going away, @wq is already dead and no one
4137 * is gonna access it anymore. Schedule RCU free.
4138 */
4139 if (is_last) {
4140 wq_unregister_lockdep(wq);
4141 call_rcu(&wq->rcu, rcu_free_wq);
4142 }
4143}
4144
4145/**
4146 * pwq_adjust_max_active - update a pwq's max_active to the current setting
4147 * @pwq: target pool_workqueue
4148 *
4149 * If @pwq isn't freezing, set @pwq->max_active to the associated
4150 * workqueue's saved_max_active and activate inactive work items
4151 * accordingly. If @pwq is freezing, clear @pwq->max_active to zero.
4152 */
4153static void pwq_adjust_max_active(struct pool_workqueue *pwq)
4154{
4155 struct workqueue_struct *wq = pwq->wq;
4156 bool freezable = wq->flags & WQ_FREEZABLE;
4157 unsigned long flags;
4158
4159 /* for @wq->saved_max_active */
4160 lockdep_assert_held(&wq->mutex);
4161
4162 /* fast exit for non-freezable wqs */
4163 if (!freezable && pwq->max_active == wq->saved_max_active)
4164 return;
4165
4166 /* this function can be called during early boot w/ irq disabled */
4167 raw_spin_lock_irqsave(&pwq->pool->lock, flags);
4168
4169 /*
4170 * During [un]freezing, the caller is responsible for ensuring that
4171 * this function is called at least once after @workqueue_freezing
4172 * is updated and visible.
4173 */
4174 if (!freezable || !workqueue_freezing) {
4175 pwq->max_active = wq->saved_max_active;
4176
4177 while (!list_empty(&pwq->inactive_works) &&
4178 pwq->nr_active < pwq->max_active)
4179 pwq_activate_first_inactive(pwq);
4180
4181 kick_pool(pwq->pool);
4182 } else {
4183 pwq->max_active = 0;
4184 }
4185
4186 raw_spin_unlock_irqrestore(&pwq->pool->lock, flags);
4187}
4188
4189/* initialize newly allocated @pwq which is associated with @wq and @pool */
4190static void init_pwq(struct pool_workqueue *pwq, struct workqueue_struct *wq,
4191 struct worker_pool *pool)
4192{
4193 BUG_ON((unsigned long)pwq & WORK_STRUCT_FLAG_MASK);
4194
4195 memset(pwq, 0, sizeof(*pwq));
4196
4197 pwq->pool = pool;
4198 pwq->wq = wq;
4199 pwq->flush_color = -1;
4200 pwq->refcnt = 1;
4201 INIT_LIST_HEAD(&pwq->inactive_works);
4202 INIT_LIST_HEAD(&pwq->pwqs_node);
4203 INIT_LIST_HEAD(&pwq->mayday_node);
4204 kthread_init_work(&pwq->release_work, pwq_release_workfn);
4205}
4206
4207/* sync @pwq with the current state of its associated wq and link it */
4208static void link_pwq(struct pool_workqueue *pwq)
4209{
4210 struct workqueue_struct *wq = pwq->wq;
4211
4212 lockdep_assert_held(&wq->mutex);
4213
4214 /* may be called multiple times, ignore if already linked */
4215 if (!list_empty(&pwq->pwqs_node))
4216 return;
4217
4218 /* set the matching work_color */
4219 pwq->work_color = wq->work_color;
4220
4221 /* sync max_active to the current setting */
4222 pwq_adjust_max_active(pwq);
4223
4224 /* link in @pwq */
4225 list_add_rcu(&pwq->pwqs_node, &wq->pwqs);
4226}
4227
4228/* obtain a pool matching @attr and create a pwq associating the pool and @wq */
4229static struct pool_workqueue *alloc_unbound_pwq(struct workqueue_struct *wq,
4230 const struct workqueue_attrs *attrs)
4231{
4232 struct worker_pool *pool;
4233 struct pool_workqueue *pwq;
4234
4235 lockdep_assert_held(&wq_pool_mutex);
4236
4237 pool = get_unbound_pool(attrs);
4238 if (!pool)
4239 return NULL;
4240
4241 pwq = kmem_cache_alloc_node(pwq_cache, GFP_KERNEL, pool->node);
4242 if (!pwq) {
4243 put_unbound_pool(pool);
4244 return NULL;
4245 }
4246
4247 init_pwq(pwq, wq, pool);
4248 return pwq;
4249}
4250
4251/**
4252 * wq_calc_pod_cpumask - calculate a wq_attrs' cpumask for a pod
4253 * @attrs: the wq_attrs of the default pwq of the target workqueue
4254 * @cpu: the target CPU
4255 * @cpu_going_down: if >= 0, the CPU to consider as offline
4256 *
4257 * Calculate the cpumask a workqueue with @attrs should use on @pod. If
4258 * @cpu_going_down is >= 0, that cpu is considered offline during calculation.
4259 * The result is stored in @attrs->__pod_cpumask.
4260 *
4261 * If pod affinity is not enabled, @attrs->cpumask is always used. If enabled
4262 * and @pod has online CPUs requested by @attrs, the returned cpumask is the
4263 * intersection of the possible CPUs of @pod and @attrs->cpumask.
4264 *
4265 * The caller is responsible for ensuring that the cpumask of @pod stays stable.
4266 */
4267static void wq_calc_pod_cpumask(struct workqueue_attrs *attrs, int cpu,
4268 int cpu_going_down)
4269{
4270 const struct wq_pod_type *pt = wqattrs_pod_type(attrs);
4271 int pod = pt->cpu_pod[cpu];
4272
4273 /* does @pod have any online CPUs @attrs wants? */
4274 cpumask_and(attrs->__pod_cpumask, pt->pod_cpus[pod], attrs->cpumask);
4275 cpumask_and(attrs->__pod_cpumask, attrs->__pod_cpumask, cpu_online_mask);
4276 if (cpu_going_down >= 0)
4277 cpumask_clear_cpu(cpu_going_down, attrs->__pod_cpumask);
4278
4279 if (cpumask_empty(attrs->__pod_cpumask)) {
4280 cpumask_copy(attrs->__pod_cpumask, attrs->cpumask);
4281 return;
4282 }
4283
4284 /* yeap, return possible CPUs in @pod that @attrs wants */
4285 cpumask_and(attrs->__pod_cpumask, attrs->cpumask, pt->pod_cpus[pod]);
4286
4287 if (cpumask_empty(attrs->__pod_cpumask))
4288 pr_warn_once("WARNING: workqueue cpumask: online intersect > "
4289 "possible intersect\n");
4290}
4291
4292/* install @pwq into @wq's cpu_pwq and return the old pwq */
4293static struct pool_workqueue *install_unbound_pwq(struct workqueue_struct *wq,
4294 int cpu, struct pool_workqueue *pwq)
4295{
4296 struct pool_workqueue *old_pwq;
4297
4298 lockdep_assert_held(&wq_pool_mutex);
4299 lockdep_assert_held(&wq->mutex);
4300
4301 /* link_pwq() can handle duplicate calls */
4302 link_pwq(pwq);
4303
4304 old_pwq = rcu_access_pointer(*per_cpu_ptr(wq->cpu_pwq, cpu));
4305 rcu_assign_pointer(*per_cpu_ptr(wq->cpu_pwq, cpu), pwq);
4306 return old_pwq;
4307}
4308
4309/* context to store the prepared attrs & pwqs before applying */
4310struct apply_wqattrs_ctx {
4311 struct workqueue_struct *wq; /* target workqueue */
4312 struct workqueue_attrs *attrs; /* attrs to apply */
4313 struct list_head list; /* queued for batching commit */
4314 struct pool_workqueue *dfl_pwq;
4315 struct pool_workqueue *pwq_tbl[];
4316};
4317
4318/* free the resources after success or abort */
4319static void apply_wqattrs_cleanup(struct apply_wqattrs_ctx *ctx)
4320{
4321 if (ctx) {
4322 int cpu;
4323
4324 for_each_possible_cpu(cpu)
4325 put_pwq_unlocked(ctx->pwq_tbl[cpu]);
4326 put_pwq_unlocked(ctx->dfl_pwq);
4327
4328 free_workqueue_attrs(ctx->attrs);
4329
4330 kfree(ctx);
4331 }
4332}
4333
4334/* allocate the attrs and pwqs for later installation */
4335static struct apply_wqattrs_ctx *
4336apply_wqattrs_prepare(struct workqueue_struct *wq,
4337 const struct workqueue_attrs *attrs,
4338 const cpumask_var_t unbound_cpumask)
4339{
4340 struct apply_wqattrs_ctx *ctx;
4341 struct workqueue_attrs *new_attrs;
4342 int cpu;
4343
4344 lockdep_assert_held(&wq_pool_mutex);
4345
4346 if (WARN_ON(attrs->affn_scope < 0 ||
4347 attrs->affn_scope >= WQ_AFFN_NR_TYPES))
4348 return ERR_PTR(-EINVAL);
4349
4350 ctx = kzalloc(struct_size(ctx, pwq_tbl, nr_cpu_ids), GFP_KERNEL);
4351
4352 new_attrs = alloc_workqueue_attrs();
4353 if (!ctx || !new_attrs)
4354 goto out_free;
4355
4356 /*
4357 * If something goes wrong during CPU up/down, we'll fall back to
4358 * the default pwq covering whole @attrs->cpumask. Always create
4359 * it even if we don't use it immediately.
4360 */
4361 copy_workqueue_attrs(new_attrs, attrs);
4362 wqattrs_actualize_cpumask(new_attrs, unbound_cpumask);
4363 cpumask_copy(new_attrs->__pod_cpumask, new_attrs->cpumask);
4364 ctx->dfl_pwq = alloc_unbound_pwq(wq, new_attrs);
4365 if (!ctx->dfl_pwq)
4366 goto out_free;
4367
4368 for_each_possible_cpu(cpu) {
4369 if (new_attrs->ordered) {
4370 ctx->dfl_pwq->refcnt++;
4371 ctx->pwq_tbl[cpu] = ctx->dfl_pwq;
4372 } else {
4373 wq_calc_pod_cpumask(new_attrs, cpu, -1);
4374 ctx->pwq_tbl[cpu] = alloc_unbound_pwq(wq, new_attrs);
4375 if (!ctx->pwq_tbl[cpu])
4376 goto out_free;
4377 }
4378 }
4379
4380 /* save the user configured attrs and sanitize it. */
4381 copy_workqueue_attrs(new_attrs, attrs);
4382 cpumask_and(new_attrs->cpumask, new_attrs->cpumask, cpu_possible_mask);
4383 cpumask_copy(new_attrs->__pod_cpumask, new_attrs->cpumask);
4384 ctx->attrs = new_attrs;
4385
4386 ctx->wq = wq;
4387 return ctx;
4388
4389out_free:
4390 free_workqueue_attrs(new_attrs);
4391 apply_wqattrs_cleanup(ctx);
4392 return ERR_PTR(-ENOMEM);
4393}
4394
4395/* set attrs and install prepared pwqs, @ctx points to old pwqs on return */
4396static void apply_wqattrs_commit(struct apply_wqattrs_ctx *ctx)
4397{
4398 int cpu;
4399
4400 /* all pwqs have been created successfully, let's install'em */
4401 mutex_lock(&ctx->wq->mutex);
4402
4403 copy_workqueue_attrs(ctx->wq->unbound_attrs, ctx->attrs);
4404
4405 /* save the previous pwq and install the new one */
4406 for_each_possible_cpu(cpu)
4407 ctx->pwq_tbl[cpu] = install_unbound_pwq(ctx->wq, cpu,
4408 ctx->pwq_tbl[cpu]);
4409
4410 /* @dfl_pwq might not have been used, ensure it's linked */
4411 link_pwq(ctx->dfl_pwq);
4412 swap(ctx->wq->dfl_pwq, ctx->dfl_pwq);
4413
4414 mutex_unlock(&ctx->wq->mutex);
4415}
4416
4417static int apply_workqueue_attrs_locked(struct workqueue_struct *wq,
4418 const struct workqueue_attrs *attrs)
4419{
4420 struct apply_wqattrs_ctx *ctx;
4421
4422 /* only unbound workqueues can change attributes */
4423 if (WARN_ON(!(wq->flags & WQ_UNBOUND)))
4424 return -EINVAL;
4425
4426 /* creating multiple pwqs breaks ordering guarantee */
4427 if (!list_empty(&wq->pwqs)) {
4428 if (WARN_ON(wq->flags & __WQ_ORDERED_EXPLICIT))
4429 return -EINVAL;
4430
4431 wq->flags &= ~__WQ_ORDERED;
4432 }
4433
4434 ctx = apply_wqattrs_prepare(wq, attrs, wq_unbound_cpumask);
4435 if (IS_ERR(ctx))
4436 return PTR_ERR(ctx);
4437
4438 /* the ctx has been prepared successfully, let's commit it */
4439 apply_wqattrs_commit(ctx);
4440 apply_wqattrs_cleanup(ctx);
4441
4442 return 0;
4443}
4444
4445/**
4446 * apply_workqueue_attrs - apply new workqueue_attrs to an unbound workqueue
4447 * @wq: the target workqueue
4448 * @attrs: the workqueue_attrs to apply, allocated with alloc_workqueue_attrs()
4449 *
4450 * Apply @attrs to an unbound workqueue @wq. Unless disabled, this function maps
4451 * a separate pwq to each CPU pod with possibles CPUs in @attrs->cpumask so that
4452 * work items are affine to the pod it was issued on. Older pwqs are released as
4453 * in-flight work items finish. Note that a work item which repeatedly requeues
4454 * itself back-to-back will stay on its current pwq.
4455 *
4456 * Performs GFP_KERNEL allocations.
4457 *
4458 * Assumes caller has CPU hotplug read exclusion, i.e. cpus_read_lock().
4459 *
4460 * Return: 0 on success and -errno on failure.
4461 */
4462int apply_workqueue_attrs(struct workqueue_struct *wq,
4463 const struct workqueue_attrs *attrs)
4464{
4465 int ret;
4466
4467 lockdep_assert_cpus_held();
4468
4469 mutex_lock(&wq_pool_mutex);
4470 ret = apply_workqueue_attrs_locked(wq, attrs);
4471 mutex_unlock(&wq_pool_mutex);
4472
4473 return ret;
4474}
4475
4476/**
4477 * wq_update_pod - update pod affinity of a wq for CPU hot[un]plug
4478 * @wq: the target workqueue
4479 * @cpu: the CPU to update pool association for
4480 * @hotplug_cpu: the CPU coming up or going down
4481 * @online: whether @cpu is coming up or going down
4482 *
4483 * This function is to be called from %CPU_DOWN_PREPARE, %CPU_ONLINE and
4484 * %CPU_DOWN_FAILED. @cpu is being hot[un]plugged, update pod affinity of
4485 * @wq accordingly.
4486 *
4487 *
4488 * If pod affinity can't be adjusted due to memory allocation failure, it falls
4489 * back to @wq->dfl_pwq which may not be optimal but is always correct.
4490 *
4491 * Note that when the last allowed CPU of a pod goes offline for a workqueue
4492 * with a cpumask spanning multiple pods, the workers which were already
4493 * executing the work items for the workqueue will lose their CPU affinity and
4494 * may execute on any CPU. This is similar to how per-cpu workqueues behave on
4495 * CPU_DOWN. If a workqueue user wants strict affinity, it's the user's
4496 * responsibility to flush the work item from CPU_DOWN_PREPARE.
4497 */
4498static void wq_update_pod(struct workqueue_struct *wq, int cpu,
4499 int hotplug_cpu, bool online)
4500{
4501 int off_cpu = online ? -1 : hotplug_cpu;
4502 struct pool_workqueue *old_pwq = NULL, *pwq;
4503 struct workqueue_attrs *target_attrs;
4504
4505 lockdep_assert_held(&wq_pool_mutex);
4506
4507 if (!(wq->flags & WQ_UNBOUND) || wq->unbound_attrs->ordered)
4508 return;
4509
4510 /*
4511 * We don't wanna alloc/free wq_attrs for each wq for each CPU.
4512 * Let's use a preallocated one. The following buf is protected by
4513 * CPU hotplug exclusion.
4514 */
4515 target_attrs = wq_update_pod_attrs_buf;
4516
4517 copy_workqueue_attrs(target_attrs, wq->unbound_attrs);
4518 wqattrs_actualize_cpumask(target_attrs, wq_unbound_cpumask);
4519
4520 /* nothing to do if the target cpumask matches the current pwq */
4521 wq_calc_pod_cpumask(target_attrs, cpu, off_cpu);
4522 pwq = rcu_dereference_protected(*per_cpu_ptr(wq->cpu_pwq, cpu),
4523 lockdep_is_held(&wq_pool_mutex));
4524 if (wqattrs_equal(target_attrs, pwq->pool->attrs))
4525 return;
4526
4527 /* create a new pwq */
4528 pwq = alloc_unbound_pwq(wq, target_attrs);
4529 if (!pwq) {
4530 pr_warn("workqueue: allocation failed while updating CPU pod affinity of \"%s\"\n",
4531 wq->name);
4532 goto use_dfl_pwq;
4533 }
4534
4535 /* Install the new pwq. */
4536 mutex_lock(&wq->mutex);
4537 old_pwq = install_unbound_pwq(wq, cpu, pwq);
4538 goto out_unlock;
4539
4540use_dfl_pwq:
4541 mutex_lock(&wq->mutex);
4542 raw_spin_lock_irq(&wq->dfl_pwq->pool->lock);
4543 get_pwq(wq->dfl_pwq);
4544 raw_spin_unlock_irq(&wq->dfl_pwq->pool->lock);
4545 old_pwq = install_unbound_pwq(wq, cpu, wq->dfl_pwq);
4546out_unlock:
4547 mutex_unlock(&wq->mutex);
4548 put_pwq_unlocked(old_pwq);
4549}
4550
4551static int alloc_and_link_pwqs(struct workqueue_struct *wq)
4552{
4553 bool highpri = wq->flags & WQ_HIGHPRI;
4554 int cpu, ret;
4555
4556 wq->cpu_pwq = alloc_percpu(struct pool_workqueue *);
4557 if (!wq->cpu_pwq)
4558 goto enomem;
4559
4560 if (!(wq->flags & WQ_UNBOUND)) {
4561 for_each_possible_cpu(cpu) {
4562 struct pool_workqueue **pwq_p =
4563 per_cpu_ptr(wq->cpu_pwq, cpu);
4564 struct worker_pool *pool =
4565 &(per_cpu_ptr(cpu_worker_pools, cpu)[highpri]);
4566
4567 *pwq_p = kmem_cache_alloc_node(pwq_cache, GFP_KERNEL,
4568 pool->node);
4569 if (!*pwq_p)
4570 goto enomem;
4571
4572 init_pwq(*pwq_p, wq, pool);
4573
4574 mutex_lock(&wq->mutex);
4575 link_pwq(*pwq_p);
4576 mutex_unlock(&wq->mutex);
4577 }
4578 return 0;
4579 }
4580
4581 cpus_read_lock();
4582 if (wq->flags & __WQ_ORDERED) {
4583 ret = apply_workqueue_attrs(wq, ordered_wq_attrs[highpri]);
4584 /* there should only be single pwq for ordering guarantee */
4585 WARN(!ret && (wq->pwqs.next != &wq->dfl_pwq->pwqs_node ||
4586 wq->pwqs.prev != &wq->dfl_pwq->pwqs_node),
4587 "ordering guarantee broken for workqueue %s\n", wq->name);
4588 } else {
4589 ret = apply_workqueue_attrs(wq, unbound_std_wq_attrs[highpri]);
4590 }
4591 cpus_read_unlock();
4592
4593 /* for unbound pwq, flush the pwq_release_worker ensures that the
4594 * pwq_release_workfn() completes before calling kfree(wq).
4595 */
4596 if (ret)
4597 kthread_flush_worker(pwq_release_worker);
4598
4599 return ret;
4600
4601enomem:
4602 if (wq->cpu_pwq) {
4603 for_each_possible_cpu(cpu) {
4604 struct pool_workqueue *pwq = *per_cpu_ptr(wq->cpu_pwq, cpu);
4605
4606 if (pwq)
4607 kmem_cache_free(pwq_cache, pwq);
4608 }
4609 free_percpu(wq->cpu_pwq);
4610 wq->cpu_pwq = NULL;
4611 }
4612 return -ENOMEM;
4613}
4614
4615static int wq_clamp_max_active(int max_active, unsigned int flags,
4616 const char *name)
4617{
4618 if (max_active < 1 || max_active > WQ_MAX_ACTIVE)
4619 pr_warn("workqueue: max_active %d requested for %s is out of range, clamping between %d and %d\n",
4620 max_active, name, 1, WQ_MAX_ACTIVE);
4621
4622 return clamp_val(max_active, 1, WQ_MAX_ACTIVE);
4623}
4624
4625/*
4626 * Workqueues which may be used during memory reclaim should have a rescuer
4627 * to guarantee forward progress.
4628 */
4629static int init_rescuer(struct workqueue_struct *wq)
4630{
4631 struct worker *rescuer;
4632 int ret;
4633
4634 if (!(wq->flags & WQ_MEM_RECLAIM))
4635 return 0;
4636
4637 rescuer = alloc_worker(NUMA_NO_NODE);
4638 if (!rescuer) {
4639 pr_err("workqueue: Failed to allocate a rescuer for wq \"%s\"\n",
4640 wq->name);
4641 return -ENOMEM;
4642 }
4643
4644 rescuer->rescue_wq = wq;
4645 rescuer->task = kthread_create(rescuer_thread, rescuer, "kworker/R-%s", wq->name);
4646 if (IS_ERR(rescuer->task)) {
4647 ret = PTR_ERR(rescuer->task);
4648 pr_err("workqueue: Failed to create a rescuer kthread for wq \"%s\": %pe",
4649 wq->name, ERR_PTR(ret));
4650 kfree(rescuer);
4651 return ret;
4652 }
4653
4654 wq->rescuer = rescuer;
4655 kthread_bind_mask(rescuer->task, cpu_possible_mask);
4656 wake_up_process(rescuer->task);
4657
4658 return 0;
4659}
4660
4661__printf(1, 4)
4662struct workqueue_struct *alloc_workqueue(const char *fmt,
4663 unsigned int flags,
4664 int max_active, ...)
4665{
4666 va_list args;
4667 struct workqueue_struct *wq;
4668 struct pool_workqueue *pwq;
4669
4670 /*
4671 * Unbound && max_active == 1 used to imply ordered, which is no longer
4672 * the case on many machines due to per-pod pools. While
4673 * alloc_ordered_workqueue() is the right way to create an ordered
4674 * workqueue, keep the previous behavior to avoid subtle breakages.
4675 */
4676 if ((flags & WQ_UNBOUND) && max_active == 1)
4677 flags |= __WQ_ORDERED;
4678
4679 /* see the comment above the definition of WQ_POWER_EFFICIENT */
4680 if ((flags & WQ_POWER_EFFICIENT) && wq_power_efficient)
4681 flags |= WQ_UNBOUND;
4682
4683 /* allocate wq and format name */
4684 wq = kzalloc(sizeof(*wq), GFP_KERNEL);
4685 if (!wq)
4686 return NULL;
4687
4688 if (flags & WQ_UNBOUND) {
4689 wq->unbound_attrs = alloc_workqueue_attrs();
4690 if (!wq->unbound_attrs)
4691 goto err_free_wq;
4692 }
4693
4694 va_start(args, max_active);
4695 vsnprintf(wq->name, sizeof(wq->name), fmt, args);
4696 va_end(args);
4697
4698 max_active = max_active ?: WQ_DFL_ACTIVE;
4699 max_active = wq_clamp_max_active(max_active, flags, wq->name);
4700
4701 /* init wq */
4702 wq->flags = flags;
4703 wq->saved_max_active = max_active;
4704 mutex_init(&wq->mutex);
4705 atomic_set(&wq->nr_pwqs_to_flush, 0);
4706 INIT_LIST_HEAD(&wq->pwqs);
4707 INIT_LIST_HEAD(&wq->flusher_queue);
4708 INIT_LIST_HEAD(&wq->flusher_overflow);
4709 INIT_LIST_HEAD(&wq->maydays);
4710
4711 wq_init_lockdep(wq);
4712 INIT_LIST_HEAD(&wq->list);
4713
4714 if (alloc_and_link_pwqs(wq) < 0)
4715 goto err_unreg_lockdep;
4716
4717 if (wq_online && init_rescuer(wq) < 0)
4718 goto err_destroy;
4719
4720 if ((wq->flags & WQ_SYSFS) && workqueue_sysfs_register(wq))
4721 goto err_destroy;
4722
4723 /*
4724 * wq_pool_mutex protects global freeze state and workqueues list.
4725 * Grab it, adjust max_active and add the new @wq to workqueues
4726 * list.
4727 */
4728 mutex_lock(&wq_pool_mutex);
4729
4730 mutex_lock(&wq->mutex);
4731 for_each_pwq(pwq, wq)
4732 pwq_adjust_max_active(pwq);
4733 mutex_unlock(&wq->mutex);
4734
4735 list_add_tail_rcu(&wq->list, &workqueues);
4736
4737 mutex_unlock(&wq_pool_mutex);
4738
4739 return wq;
4740
4741err_unreg_lockdep:
4742 wq_unregister_lockdep(wq);
4743 wq_free_lockdep(wq);
4744err_free_wq:
4745 free_workqueue_attrs(wq->unbound_attrs);
4746 kfree(wq);
4747 return NULL;
4748err_destroy:
4749 destroy_workqueue(wq);
4750 return NULL;
4751}
4752EXPORT_SYMBOL_GPL(alloc_workqueue);
4753
4754static bool pwq_busy(struct pool_workqueue *pwq)
4755{
4756 int i;
4757
4758 for (i = 0; i < WORK_NR_COLORS; i++)
4759 if (pwq->nr_in_flight[i])
4760 return true;
4761
4762 if ((pwq != pwq->wq->dfl_pwq) && (pwq->refcnt > 1))
4763 return true;
4764 if (pwq->nr_active || !list_empty(&pwq->inactive_works))
4765 return true;
4766
4767 return false;
4768}
4769
4770/**
4771 * destroy_workqueue - safely terminate a workqueue
4772 * @wq: target workqueue
4773 *
4774 * Safely destroy a workqueue. All work currently pending will be done first.
4775 */
4776void destroy_workqueue(struct workqueue_struct *wq)
4777{
4778 struct pool_workqueue *pwq;
4779 int cpu;
4780
4781 /*
4782 * Remove it from sysfs first so that sanity check failure doesn't
4783 * lead to sysfs name conflicts.
4784 */
4785 workqueue_sysfs_unregister(wq);
4786
4787 /* mark the workqueue destruction is in progress */
4788 mutex_lock(&wq->mutex);
4789 wq->flags |= __WQ_DESTROYING;
4790 mutex_unlock(&wq->mutex);
4791
4792 /* drain it before proceeding with destruction */
4793 drain_workqueue(wq);
4794
4795 /* kill rescuer, if sanity checks fail, leave it w/o rescuer */
4796 if (wq->rescuer) {
4797 struct worker *rescuer = wq->rescuer;
4798
4799 /* this prevents new queueing */
4800 raw_spin_lock_irq(&wq_mayday_lock);
4801 wq->rescuer = NULL;
4802 raw_spin_unlock_irq(&wq_mayday_lock);
4803
4804 /* rescuer will empty maydays list before exiting */
4805 kthread_stop(rescuer->task);
4806 kfree(rescuer);
4807 }
4808
4809 /*
4810 * Sanity checks - grab all the locks so that we wait for all
4811 * in-flight operations which may do put_pwq().
4812 */
4813 mutex_lock(&wq_pool_mutex);
4814 mutex_lock(&wq->mutex);
4815 for_each_pwq(pwq, wq) {
4816 raw_spin_lock_irq(&pwq->pool->lock);
4817 if (WARN_ON(pwq_busy(pwq))) {
4818 pr_warn("%s: %s has the following busy pwq\n",
4819 __func__, wq->name);
4820 show_pwq(pwq);
4821 raw_spin_unlock_irq(&pwq->pool->lock);
4822 mutex_unlock(&wq->mutex);
4823 mutex_unlock(&wq_pool_mutex);
4824 show_one_workqueue(wq);
4825 return;
4826 }
4827 raw_spin_unlock_irq(&pwq->pool->lock);
4828 }
4829 mutex_unlock(&wq->mutex);
4830
4831 /*
4832 * wq list is used to freeze wq, remove from list after
4833 * flushing is complete in case freeze races us.
4834 */
4835 list_del_rcu(&wq->list);
4836 mutex_unlock(&wq_pool_mutex);
4837
4838 /*
4839 * We're the sole accessor of @wq. Directly access cpu_pwq and dfl_pwq
4840 * to put the base refs. @wq will be auto-destroyed from the last
4841 * pwq_put. RCU read lock prevents @wq from going away from under us.
4842 */
4843 rcu_read_lock();
4844
4845 for_each_possible_cpu(cpu) {
4846 pwq = rcu_access_pointer(*per_cpu_ptr(wq->cpu_pwq, cpu));
4847 RCU_INIT_POINTER(*per_cpu_ptr(wq->cpu_pwq, cpu), NULL);
4848 put_pwq_unlocked(pwq);
4849 }
4850
4851 put_pwq_unlocked(wq->dfl_pwq);
4852 wq->dfl_pwq = NULL;
4853
4854 rcu_read_unlock();
4855}
4856EXPORT_SYMBOL_GPL(destroy_workqueue);
4857
4858/**
4859 * workqueue_set_max_active - adjust max_active of a workqueue
4860 * @wq: target workqueue
4861 * @max_active: new max_active value.
4862 *
4863 * Set max_active of @wq to @max_active.
4864 *
4865 * CONTEXT:
4866 * Don't call from IRQ context.
4867 */
4868void workqueue_set_max_active(struct workqueue_struct *wq, int max_active)
4869{
4870 struct pool_workqueue *pwq;
4871
4872 /* disallow meddling with max_active for ordered workqueues */
4873 if (WARN_ON(wq->flags & __WQ_ORDERED_EXPLICIT))
4874 return;
4875
4876 max_active = wq_clamp_max_active(max_active, wq->flags, wq->name);
4877
4878 mutex_lock(&wq->mutex);
4879
4880 wq->flags &= ~__WQ_ORDERED;
4881 wq->saved_max_active = max_active;
4882
4883 for_each_pwq(pwq, wq)
4884 pwq_adjust_max_active(pwq);
4885
4886 mutex_unlock(&wq->mutex);
4887}
4888EXPORT_SYMBOL_GPL(workqueue_set_max_active);
4889
4890/**
4891 * current_work - retrieve %current task's work struct
4892 *
4893 * Determine if %current task is a workqueue worker and what it's working on.
4894 * Useful to find out the context that the %current task is running in.
4895 *
4896 * Return: work struct if %current task is a workqueue worker, %NULL otherwise.
4897 */
4898struct work_struct *current_work(void)
4899{
4900 struct worker *worker = current_wq_worker();
4901
4902 return worker ? worker->current_work : NULL;
4903}
4904EXPORT_SYMBOL(current_work);
4905
4906/**
4907 * current_is_workqueue_rescuer - is %current workqueue rescuer?
4908 *
4909 * Determine whether %current is a workqueue rescuer. Can be used from
4910 * work functions to determine whether it's being run off the rescuer task.
4911 *
4912 * Return: %true if %current is a workqueue rescuer. %false otherwise.
4913 */
4914bool current_is_workqueue_rescuer(void)
4915{
4916 struct worker *worker = current_wq_worker();
4917
4918 return worker && worker->rescue_wq;
4919}
4920
4921/**
4922 * workqueue_congested - test whether a workqueue is congested
4923 * @cpu: CPU in question
4924 * @wq: target workqueue
4925 *
4926 * Test whether @wq's cpu workqueue for @cpu is congested. There is
4927 * no synchronization around this function and the test result is
4928 * unreliable and only useful as advisory hints or for debugging.
4929 *
4930 * If @cpu is WORK_CPU_UNBOUND, the test is performed on the local CPU.
4931 *
4932 * With the exception of ordered workqueues, all workqueues have per-cpu
4933 * pool_workqueues, each with its own congested state. A workqueue being
4934 * congested on one CPU doesn't mean that the workqueue is contested on any
4935 * other CPUs.
4936 *
4937 * Return:
4938 * %true if congested, %false otherwise.
4939 */
4940bool workqueue_congested(int cpu, struct workqueue_struct *wq)
4941{
4942 struct pool_workqueue *pwq;
4943 bool ret;
4944
4945 rcu_read_lock();
4946 preempt_disable();
4947
4948 if (cpu == WORK_CPU_UNBOUND)
4949 cpu = smp_processor_id();
4950
4951 pwq = *per_cpu_ptr(wq->cpu_pwq, cpu);
4952 ret = !list_empty(&pwq->inactive_works);
4953
4954 preempt_enable();
4955 rcu_read_unlock();
4956
4957 return ret;
4958}
4959EXPORT_SYMBOL_GPL(workqueue_congested);
4960
4961/**
4962 * work_busy - test whether a work is currently pending or running
4963 * @work: the work to be tested
4964 *
4965 * Test whether @work is currently pending or running. There is no
4966 * synchronization around this function and the test result is
4967 * unreliable and only useful as advisory hints or for debugging.
4968 *
4969 * Return:
4970 * OR'd bitmask of WORK_BUSY_* bits.
4971 */
4972unsigned int work_busy(struct work_struct *work)
4973{
4974 struct worker_pool *pool;
4975 unsigned long flags;
4976 unsigned int ret = 0;
4977
4978 if (work_pending(work))
4979 ret |= WORK_BUSY_PENDING;
4980
4981 rcu_read_lock();
4982 pool = get_work_pool(work);
4983 if (pool) {
4984 raw_spin_lock_irqsave(&pool->lock, flags);
4985 if (find_worker_executing_work(pool, work))
4986 ret |= WORK_BUSY_RUNNING;
4987 raw_spin_unlock_irqrestore(&pool->lock, flags);
4988 }
4989 rcu_read_unlock();
4990
4991 return ret;
4992}
4993EXPORT_SYMBOL_GPL(work_busy);
4994
4995/**
4996 * set_worker_desc - set description for the current work item
4997 * @fmt: printf-style format string
4998 * @...: arguments for the format string
4999 *
5000 * This function can be called by a running work function to describe what
5001 * the work item is about. If the worker task gets dumped, this
5002 * information will be printed out together to help debugging. The
5003 * description can be at most WORKER_DESC_LEN including the trailing '\0'.
5004 */
5005void set_worker_desc(const char *fmt, ...)
5006{
5007 struct worker *worker = current_wq_worker();
5008 va_list args;
5009
5010 if (worker) {
5011 va_start(args, fmt);
5012 vsnprintf(worker->desc, sizeof(worker->desc), fmt, args);
5013 va_end(args);
5014 }
5015}
5016EXPORT_SYMBOL_GPL(set_worker_desc);
5017
5018/**
5019 * print_worker_info - print out worker information and description
5020 * @log_lvl: the log level to use when printing
5021 * @task: target task
5022 *
5023 * If @task is a worker and currently executing a work item, print out the
5024 * name of the workqueue being serviced and worker description set with
5025 * set_worker_desc() by the currently executing work item.
5026 *
5027 * This function can be safely called on any task as long as the
5028 * task_struct itself is accessible. While safe, this function isn't
5029 * synchronized and may print out mixups or garbages of limited length.
5030 */
5031void print_worker_info(const char *log_lvl, struct task_struct *task)
5032{
5033 work_func_t *fn = NULL;
5034 char name[WQ_NAME_LEN] = { };
5035 char desc[WORKER_DESC_LEN] = { };
5036 struct pool_workqueue *pwq = NULL;
5037 struct workqueue_struct *wq = NULL;
5038 struct worker *worker;
5039
5040 if (!(task->flags & PF_WQ_WORKER))
5041 return;
5042
5043 /*
5044 * This function is called without any synchronization and @task
5045 * could be in any state. Be careful with dereferences.
5046 */
5047 worker = kthread_probe_data(task);
5048
5049 /*
5050 * Carefully copy the associated workqueue's workfn, name and desc.
5051 * Keep the original last '\0' in case the original is garbage.
5052 */
5053 copy_from_kernel_nofault(&fn, &worker->current_func, sizeof(fn));
5054 copy_from_kernel_nofault(&pwq, &worker->current_pwq, sizeof(pwq));
5055 copy_from_kernel_nofault(&wq, &pwq->wq, sizeof(wq));
5056 copy_from_kernel_nofault(name, wq->name, sizeof(name) - 1);
5057 copy_from_kernel_nofault(desc, worker->desc, sizeof(desc) - 1);
5058
5059 if (fn || name[0] || desc[0]) {
5060 printk("%sWorkqueue: %s %ps", log_lvl, name, fn);
5061 if (strcmp(name, desc))
5062 pr_cont(" (%s)", desc);
5063 pr_cont("\n");
5064 }
5065}
5066
5067static void pr_cont_pool_info(struct worker_pool *pool)
5068{
5069 pr_cont(" cpus=%*pbl", nr_cpumask_bits, pool->attrs->cpumask);
5070 if (pool->node != NUMA_NO_NODE)
5071 pr_cont(" node=%d", pool->node);
5072 pr_cont(" flags=0x%x nice=%d", pool->flags, pool->attrs->nice);
5073}
5074
5075struct pr_cont_work_struct {
5076 bool comma;
5077 work_func_t func;
5078 long ctr;
5079};
5080
5081static void pr_cont_work_flush(bool comma, work_func_t func, struct pr_cont_work_struct *pcwsp)
5082{
5083 if (!pcwsp->ctr)
5084 goto out_record;
5085 if (func == pcwsp->func) {
5086 pcwsp->ctr++;
5087 return;
5088 }
5089 if (pcwsp->ctr == 1)
5090 pr_cont("%s %ps", pcwsp->comma ? "," : "", pcwsp->func);
5091 else
5092 pr_cont("%s %ld*%ps", pcwsp->comma ? "," : "", pcwsp->ctr, pcwsp->func);
5093 pcwsp->ctr = 0;
5094out_record:
5095 if ((long)func == -1L)
5096 return;
5097 pcwsp->comma = comma;
5098 pcwsp->func = func;
5099 pcwsp->ctr = 1;
5100}
5101
5102static void pr_cont_work(bool comma, struct work_struct *work, struct pr_cont_work_struct *pcwsp)
5103{
5104 if (work->func == wq_barrier_func) {
5105 struct wq_barrier *barr;
5106
5107 barr = container_of(work, struct wq_barrier, work);
5108
5109 pr_cont_work_flush(comma, (work_func_t)-1, pcwsp);
5110 pr_cont("%s BAR(%d)", comma ? "," : "",
5111 task_pid_nr(barr->task));
5112 } else {
5113 if (!comma)
5114 pr_cont_work_flush(comma, (work_func_t)-1, pcwsp);
5115 pr_cont_work_flush(comma, work->func, pcwsp);
5116 }
5117}
5118
5119static void show_pwq(struct pool_workqueue *pwq)
5120{
5121 struct pr_cont_work_struct pcws = { .ctr = 0, };
5122 struct worker_pool *pool = pwq->pool;
5123 struct work_struct *work;
5124 struct worker *worker;
5125 bool has_in_flight = false, has_pending = false;
5126 int bkt;
5127
5128 pr_info(" pwq %d:", pool->id);
5129 pr_cont_pool_info(pool);
5130
5131 pr_cont(" active=%d/%d refcnt=%d%s\n",
5132 pwq->nr_active, pwq->max_active, pwq->refcnt,
5133 !list_empty(&pwq->mayday_node) ? " MAYDAY" : "");
5134
5135 hash_for_each(pool->busy_hash, bkt, worker, hentry) {
5136 if (worker->current_pwq == pwq) {
5137 has_in_flight = true;
5138 break;
5139 }
5140 }
5141 if (has_in_flight) {
5142 bool comma = false;
5143
5144 pr_info(" in-flight:");
5145 hash_for_each(pool->busy_hash, bkt, worker, hentry) {
5146 if (worker->current_pwq != pwq)
5147 continue;
5148
5149 pr_cont("%s %d%s:%ps", comma ? "," : "",
5150 task_pid_nr(worker->task),
5151 worker->rescue_wq ? "(RESCUER)" : "",
5152 worker->current_func);
5153 list_for_each_entry(work, &worker->scheduled, entry)
5154 pr_cont_work(false, work, &pcws);
5155 pr_cont_work_flush(comma, (work_func_t)-1L, &pcws);
5156 comma = true;
5157 }
5158 pr_cont("\n");
5159 }
5160
5161 list_for_each_entry(work, &pool->worklist, entry) {
5162 if (get_work_pwq(work) == pwq) {
5163 has_pending = true;
5164 break;
5165 }
5166 }
5167 if (has_pending) {
5168 bool comma = false;
5169
5170 pr_info(" pending:");
5171 list_for_each_entry(work, &pool->worklist, entry) {
5172 if (get_work_pwq(work) != pwq)
5173 continue;
5174
5175 pr_cont_work(comma, work, &pcws);
5176 comma = !(*work_data_bits(work) & WORK_STRUCT_LINKED);
5177 }
5178 pr_cont_work_flush(comma, (work_func_t)-1L, &pcws);
5179 pr_cont("\n");
5180 }
5181
5182 if (!list_empty(&pwq->inactive_works)) {
5183 bool comma = false;
5184
5185 pr_info(" inactive:");
5186 list_for_each_entry(work, &pwq->inactive_works, entry) {
5187 pr_cont_work(comma, work, &pcws);
5188 comma = !(*work_data_bits(work) & WORK_STRUCT_LINKED);
5189 }
5190 pr_cont_work_flush(comma, (work_func_t)-1L, &pcws);
5191 pr_cont("\n");
5192 }
5193}
5194
5195/**
5196 * show_one_workqueue - dump state of specified workqueue
5197 * @wq: workqueue whose state will be printed
5198 */
5199void show_one_workqueue(struct workqueue_struct *wq)
5200{
5201 struct pool_workqueue *pwq;
5202 bool idle = true;
5203 unsigned long flags;
5204
5205 for_each_pwq(pwq, wq) {
5206 if (pwq->nr_active || !list_empty(&pwq->inactive_works)) {
5207 idle = false;
5208 break;
5209 }
5210 }
5211 if (idle) /* Nothing to print for idle workqueue */
5212 return;
5213
5214 pr_info("workqueue %s: flags=0x%x\n", wq->name, wq->flags);
5215
5216 for_each_pwq(pwq, wq) {
5217 raw_spin_lock_irqsave(&pwq->pool->lock, flags);
5218 if (pwq->nr_active || !list_empty(&pwq->inactive_works)) {
5219 /*
5220 * Defer printing to avoid deadlocks in console
5221 * drivers that queue work while holding locks
5222 * also taken in their write paths.
5223 */
5224 printk_deferred_enter();
5225 show_pwq(pwq);
5226 printk_deferred_exit();
5227 }
5228 raw_spin_unlock_irqrestore(&pwq->pool->lock, flags);
5229 /*
5230 * We could be printing a lot from atomic context, e.g.
5231 * sysrq-t -> show_all_workqueues(). Avoid triggering
5232 * hard lockup.
5233 */
5234 touch_nmi_watchdog();
5235 }
5236
5237}
5238
5239/**
5240 * show_one_worker_pool - dump state of specified worker pool
5241 * @pool: worker pool whose state will be printed
5242 */
5243static void show_one_worker_pool(struct worker_pool *pool)
5244{
5245 struct worker *worker;
5246 bool first = true;
5247 unsigned long flags;
5248 unsigned long hung = 0;
5249
5250 raw_spin_lock_irqsave(&pool->lock, flags);
5251 if (pool->nr_workers == pool->nr_idle)
5252 goto next_pool;
5253
5254 /* How long the first pending work is waiting for a worker. */
5255 if (!list_empty(&pool->worklist))
5256 hung = jiffies_to_msecs(jiffies - pool->watchdog_ts) / 1000;
5257
5258 /*
5259 * Defer printing to avoid deadlocks in console drivers that
5260 * queue work while holding locks also taken in their write
5261 * paths.
5262 */
5263 printk_deferred_enter();
5264 pr_info("pool %d:", pool->id);
5265 pr_cont_pool_info(pool);
5266 pr_cont(" hung=%lus workers=%d", hung, pool->nr_workers);
5267 if (pool->manager)
5268 pr_cont(" manager: %d",
5269 task_pid_nr(pool->manager->task));
5270 list_for_each_entry(worker, &pool->idle_list, entry) {
5271 pr_cont(" %s%d", first ? "idle: " : "",
5272 task_pid_nr(worker->task));
5273 first = false;
5274 }
5275 pr_cont("\n");
5276 printk_deferred_exit();
5277next_pool:
5278 raw_spin_unlock_irqrestore(&pool->lock, flags);
5279 /*
5280 * We could be printing a lot from atomic context, e.g.
5281 * sysrq-t -> show_all_workqueues(). Avoid triggering
5282 * hard lockup.
5283 */
5284 touch_nmi_watchdog();
5285
5286}
5287
5288/**
5289 * show_all_workqueues - dump workqueue state
5290 *
5291 * Called from a sysrq handler and prints out all busy workqueues and pools.
5292 */
5293void show_all_workqueues(void)
5294{
5295 struct workqueue_struct *wq;
5296 struct worker_pool *pool;
5297 int pi;
5298
5299 rcu_read_lock();
5300
5301 pr_info("Showing busy workqueues and worker pools:\n");
5302
5303 list_for_each_entry_rcu(wq, &workqueues, list)
5304 show_one_workqueue(wq);
5305
5306 for_each_pool(pool, pi)
5307 show_one_worker_pool(pool);
5308
5309 rcu_read_unlock();
5310}
5311
5312/**
5313 * show_freezable_workqueues - dump freezable workqueue state
5314 *
5315 * Called from try_to_freeze_tasks() and prints out all freezable workqueues
5316 * still busy.
5317 */
5318void show_freezable_workqueues(void)
5319{
5320 struct workqueue_struct *wq;
5321
5322 rcu_read_lock();
5323
5324 pr_info("Showing freezable workqueues that are still busy:\n");
5325
5326 list_for_each_entry_rcu(wq, &workqueues, list) {
5327 if (!(wq->flags & WQ_FREEZABLE))
5328 continue;
5329 show_one_workqueue(wq);
5330 }
5331
5332 rcu_read_unlock();
5333}
5334
5335/* used to show worker information through /proc/PID/{comm,stat,status} */
5336void wq_worker_comm(char *buf, size_t size, struct task_struct *task)
5337{
5338 int off;
5339
5340 /* always show the actual comm */
5341 off = strscpy(buf, task->comm, size);
5342 if (off < 0)
5343 return;
5344
5345 /* stabilize PF_WQ_WORKER and worker pool association */
5346 mutex_lock(&wq_pool_attach_mutex);
5347
5348 if (task->flags & PF_WQ_WORKER) {
5349 struct worker *worker = kthread_data(task);
5350 struct worker_pool *pool = worker->pool;
5351
5352 if (pool) {
5353 raw_spin_lock_irq(&pool->lock);
5354 /*
5355 * ->desc tracks information (wq name or
5356 * set_worker_desc()) for the latest execution. If
5357 * current, prepend '+', otherwise '-'.
5358 */
5359 if (worker->desc[0] != '\0') {
5360 if (worker->current_work)
5361 scnprintf(buf + off, size - off, "+%s",
5362 worker->desc);
5363 else
5364 scnprintf(buf + off, size - off, "-%s",
5365 worker->desc);
5366 }
5367 raw_spin_unlock_irq(&pool->lock);
5368 }
5369 }
5370
5371 mutex_unlock(&wq_pool_attach_mutex);
5372}
5373
5374#ifdef CONFIG_SMP
5375
5376/*
5377 * CPU hotplug.
5378 *
5379 * There are two challenges in supporting CPU hotplug. Firstly, there
5380 * are a lot of assumptions on strong associations among work, pwq and
5381 * pool which make migrating pending and scheduled works very
5382 * difficult to implement without impacting hot paths. Secondly,
5383 * worker pools serve mix of short, long and very long running works making
5384 * blocked draining impractical.
5385 *
5386 * This is solved by allowing the pools to be disassociated from the CPU
5387 * running as an unbound one and allowing it to be reattached later if the
5388 * cpu comes back online.
5389 */
5390
5391static void unbind_workers(int cpu)
5392{
5393 struct worker_pool *pool;
5394 struct worker *worker;
5395
5396 for_each_cpu_worker_pool(pool, cpu) {
5397 mutex_lock(&wq_pool_attach_mutex);
5398 raw_spin_lock_irq(&pool->lock);
5399
5400 /*
5401 * We've blocked all attach/detach operations. Make all workers
5402 * unbound and set DISASSOCIATED. Before this, all workers
5403 * must be on the cpu. After this, they may become diasporas.
5404 * And the preemption disabled section in their sched callbacks
5405 * are guaranteed to see WORKER_UNBOUND since the code here
5406 * is on the same cpu.
5407 */
5408 for_each_pool_worker(worker, pool)
5409 worker->flags |= WORKER_UNBOUND;
5410
5411 pool->flags |= POOL_DISASSOCIATED;
5412
5413 /*
5414 * The handling of nr_running in sched callbacks are disabled
5415 * now. Zap nr_running. After this, nr_running stays zero and
5416 * need_more_worker() and keep_working() are always true as
5417 * long as the worklist is not empty. This pool now behaves as
5418 * an unbound (in terms of concurrency management) pool which
5419 * are served by workers tied to the pool.
5420 */
5421 pool->nr_running = 0;
5422
5423 /*
5424 * With concurrency management just turned off, a busy
5425 * worker blocking could lead to lengthy stalls. Kick off
5426 * unbound chain execution of currently pending work items.
5427 */
5428 kick_pool(pool);
5429
5430 raw_spin_unlock_irq(&pool->lock);
5431
5432 for_each_pool_worker(worker, pool)
5433 unbind_worker(worker);
5434
5435 mutex_unlock(&wq_pool_attach_mutex);
5436 }
5437}
5438
5439/**
5440 * rebind_workers - rebind all workers of a pool to the associated CPU
5441 * @pool: pool of interest
5442 *
5443 * @pool->cpu is coming online. Rebind all workers to the CPU.
5444 */
5445static void rebind_workers(struct worker_pool *pool)
5446{
5447 struct worker *worker;
5448
5449 lockdep_assert_held(&wq_pool_attach_mutex);
5450
5451 /*
5452 * Restore CPU affinity of all workers. As all idle workers should
5453 * be on the run-queue of the associated CPU before any local
5454 * wake-ups for concurrency management happen, restore CPU affinity
5455 * of all workers first and then clear UNBOUND. As we're called
5456 * from CPU_ONLINE, the following shouldn't fail.
5457 */
5458 for_each_pool_worker(worker, pool) {
5459 kthread_set_per_cpu(worker->task, pool->cpu);
5460 WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task,
5461 pool_allowed_cpus(pool)) < 0);
5462 }
5463
5464 raw_spin_lock_irq(&pool->lock);
5465
5466 pool->flags &= ~POOL_DISASSOCIATED;
5467
5468 for_each_pool_worker(worker, pool) {
5469 unsigned int worker_flags = worker->flags;
5470
5471 /*
5472 * We want to clear UNBOUND but can't directly call
5473 * worker_clr_flags() or adjust nr_running. Atomically
5474 * replace UNBOUND with another NOT_RUNNING flag REBOUND.
5475 * @worker will clear REBOUND using worker_clr_flags() when
5476 * it initiates the next execution cycle thus restoring
5477 * concurrency management. Note that when or whether
5478 * @worker clears REBOUND doesn't affect correctness.
5479 *
5480 * WRITE_ONCE() is necessary because @worker->flags may be
5481 * tested without holding any lock in
5482 * wq_worker_running(). Without it, NOT_RUNNING test may
5483 * fail incorrectly leading to premature concurrency
5484 * management operations.
5485 */
5486 WARN_ON_ONCE(!(worker_flags & WORKER_UNBOUND));
5487 worker_flags |= WORKER_REBOUND;
5488 worker_flags &= ~WORKER_UNBOUND;
5489 WRITE_ONCE(worker->flags, worker_flags);
5490 }
5491
5492 raw_spin_unlock_irq(&pool->lock);
5493}
5494
5495/**
5496 * restore_unbound_workers_cpumask - restore cpumask of unbound workers
5497 * @pool: unbound pool of interest
5498 * @cpu: the CPU which is coming up
5499 *
5500 * An unbound pool may end up with a cpumask which doesn't have any online
5501 * CPUs. When a worker of such pool get scheduled, the scheduler resets
5502 * its cpus_allowed. If @cpu is in @pool's cpumask which didn't have any
5503 * online CPU before, cpus_allowed of all its workers should be restored.
5504 */
5505static void restore_unbound_workers_cpumask(struct worker_pool *pool, int cpu)
5506{
5507 static cpumask_t cpumask;
5508 struct worker *worker;
5509
5510 lockdep_assert_held(&wq_pool_attach_mutex);
5511
5512 /* is @cpu allowed for @pool? */
5513 if (!cpumask_test_cpu(cpu, pool->attrs->cpumask))
5514 return;
5515
5516 cpumask_and(&cpumask, pool->attrs->cpumask, cpu_online_mask);
5517
5518 /* as we're called from CPU_ONLINE, the following shouldn't fail */
5519 for_each_pool_worker(worker, pool)
5520 WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task, &cpumask) < 0);
5521}
5522
5523int workqueue_prepare_cpu(unsigned int cpu)
5524{
5525 struct worker_pool *pool;
5526
5527 for_each_cpu_worker_pool(pool, cpu) {
5528 if (pool->nr_workers)
5529 continue;
5530 if (!create_worker(pool))
5531 return -ENOMEM;
5532 }
5533 return 0;
5534}
5535
5536int workqueue_online_cpu(unsigned int cpu)
5537{
5538 struct worker_pool *pool;
5539 struct workqueue_struct *wq;
5540 int pi;
5541
5542 mutex_lock(&wq_pool_mutex);
5543
5544 for_each_pool(pool, pi) {
5545 mutex_lock(&wq_pool_attach_mutex);
5546
5547 if (pool->cpu == cpu)
5548 rebind_workers(pool);
5549 else if (pool->cpu < 0)
5550 restore_unbound_workers_cpumask(pool, cpu);
5551
5552 mutex_unlock(&wq_pool_attach_mutex);
5553 }
5554
5555 /* update pod affinity of unbound workqueues */
5556 list_for_each_entry(wq, &workqueues, list) {
5557 struct workqueue_attrs *attrs = wq->unbound_attrs;
5558
5559 if (attrs) {
5560 const struct wq_pod_type *pt = wqattrs_pod_type(attrs);
5561 int tcpu;
5562
5563 for_each_cpu(tcpu, pt->pod_cpus[pt->cpu_pod[cpu]])
5564 wq_update_pod(wq, tcpu, cpu, true);
5565 }
5566 }
5567
5568 mutex_unlock(&wq_pool_mutex);
5569 return 0;
5570}
5571
5572int workqueue_offline_cpu(unsigned int cpu)
5573{
5574 struct workqueue_struct *wq;
5575
5576 /* unbinding per-cpu workers should happen on the local CPU */
5577 if (WARN_ON(cpu != smp_processor_id()))
5578 return -1;
5579
5580 unbind_workers(cpu);
5581
5582 /* update pod affinity of unbound workqueues */
5583 mutex_lock(&wq_pool_mutex);
5584 list_for_each_entry(wq, &workqueues, list) {
5585 struct workqueue_attrs *attrs = wq->unbound_attrs;
5586
5587 if (attrs) {
5588 const struct wq_pod_type *pt = wqattrs_pod_type(attrs);
5589 int tcpu;
5590
5591 for_each_cpu(tcpu, pt->pod_cpus[pt->cpu_pod[cpu]])
5592 wq_update_pod(wq, tcpu, cpu, false);
5593 }
5594 }
5595 mutex_unlock(&wq_pool_mutex);
5596
5597 return 0;
5598}
5599
5600struct work_for_cpu {
5601 struct work_struct work;
5602 long (*fn)(void *);
5603 void *arg;
5604 long ret;
5605};
5606
5607static void work_for_cpu_fn(struct work_struct *work)
5608{
5609 struct work_for_cpu *wfc = container_of(work, struct work_for_cpu, work);
5610
5611 wfc->ret = wfc->fn(wfc->arg);
5612}
5613
5614/**
5615 * work_on_cpu_key - run a function in thread context on a particular cpu
5616 * @cpu: the cpu to run on
5617 * @fn: the function to run
5618 * @arg: the function arg
5619 * @key: The lock class key for lock debugging purposes
5620 *
5621 * It is up to the caller to ensure that the cpu doesn't go offline.
5622 * The caller must not hold any locks which would prevent @fn from completing.
5623 *
5624 * Return: The value @fn returns.
5625 */
5626long work_on_cpu_key(int cpu, long (*fn)(void *),
5627 void *arg, struct lock_class_key *key)
5628{
5629 struct work_for_cpu wfc = { .fn = fn, .arg = arg };
5630
5631 INIT_WORK_ONSTACK_KEY(&wfc.work, work_for_cpu_fn, key);
5632 schedule_work_on(cpu, &wfc.work);
5633 flush_work(&wfc.work);
5634 destroy_work_on_stack(&wfc.work);
5635 return wfc.ret;
5636}
5637EXPORT_SYMBOL_GPL(work_on_cpu_key);
5638
5639/**
5640 * work_on_cpu_safe_key - run a function in thread context on a particular cpu
5641 * @cpu: the cpu to run on
5642 * @fn: the function to run
5643 * @arg: the function argument
5644 * @key: The lock class key for lock debugging purposes
5645 *
5646 * Disables CPU hotplug and calls work_on_cpu(). The caller must not hold
5647 * any locks which would prevent @fn from completing.
5648 *
5649 * Return: The value @fn returns.
5650 */
5651long work_on_cpu_safe_key(int cpu, long (*fn)(void *),
5652 void *arg, struct lock_class_key *key)
5653{
5654 long ret = -ENODEV;
5655
5656 cpus_read_lock();
5657 if (cpu_online(cpu))
5658 ret = work_on_cpu_key(cpu, fn, arg, key);
5659 cpus_read_unlock();
5660 return ret;
5661}
5662EXPORT_SYMBOL_GPL(work_on_cpu_safe_key);
5663#endif /* CONFIG_SMP */
5664
5665#ifdef CONFIG_FREEZER
5666
5667/**
5668 * freeze_workqueues_begin - begin freezing workqueues
5669 *
5670 * Start freezing workqueues. After this function returns, all freezable
5671 * workqueues will queue new works to their inactive_works list instead of
5672 * pool->worklist.
5673 *
5674 * CONTEXT:
5675 * Grabs and releases wq_pool_mutex, wq->mutex and pool->lock's.
5676 */
5677void freeze_workqueues_begin(void)
5678{
5679 struct workqueue_struct *wq;
5680 struct pool_workqueue *pwq;
5681
5682 mutex_lock(&wq_pool_mutex);
5683
5684 WARN_ON_ONCE(workqueue_freezing);
5685 workqueue_freezing = true;
5686
5687 list_for_each_entry(wq, &workqueues, list) {
5688 mutex_lock(&wq->mutex);
5689 for_each_pwq(pwq, wq)
5690 pwq_adjust_max_active(pwq);
5691 mutex_unlock(&wq->mutex);
5692 }
5693
5694 mutex_unlock(&wq_pool_mutex);
5695}
5696
5697/**
5698 * freeze_workqueues_busy - are freezable workqueues still busy?
5699 *
5700 * Check whether freezing is complete. This function must be called
5701 * between freeze_workqueues_begin() and thaw_workqueues().
5702 *
5703 * CONTEXT:
5704 * Grabs and releases wq_pool_mutex.
5705 *
5706 * Return:
5707 * %true if some freezable workqueues are still busy. %false if freezing
5708 * is complete.
5709 */
5710bool freeze_workqueues_busy(void)
5711{
5712 bool busy = false;
5713 struct workqueue_struct *wq;
5714 struct pool_workqueue *pwq;
5715
5716 mutex_lock(&wq_pool_mutex);
5717
5718 WARN_ON_ONCE(!workqueue_freezing);
5719
5720 list_for_each_entry(wq, &workqueues, list) {
5721 if (!(wq->flags & WQ_FREEZABLE))
5722 continue;
5723 /*
5724 * nr_active is monotonically decreasing. It's safe
5725 * to peek without lock.
5726 */
5727 rcu_read_lock();
5728 for_each_pwq(pwq, wq) {
5729 WARN_ON_ONCE(pwq->nr_active < 0);
5730 if (pwq->nr_active) {
5731 busy = true;
5732 rcu_read_unlock();
5733 goto out_unlock;
5734 }
5735 }
5736 rcu_read_unlock();
5737 }
5738out_unlock:
5739 mutex_unlock(&wq_pool_mutex);
5740 return busy;
5741}
5742
5743/**
5744 * thaw_workqueues - thaw workqueues
5745 *
5746 * Thaw workqueues. Normal queueing is restored and all collected
5747 * frozen works are transferred to their respective pool worklists.
5748 *
5749 * CONTEXT:
5750 * Grabs and releases wq_pool_mutex, wq->mutex and pool->lock's.
5751 */
5752void thaw_workqueues(void)
5753{
5754 struct workqueue_struct *wq;
5755 struct pool_workqueue *pwq;
5756
5757 mutex_lock(&wq_pool_mutex);
5758
5759 if (!workqueue_freezing)
5760 goto out_unlock;
5761
5762 workqueue_freezing = false;
5763
5764 /* restore max_active and repopulate worklist */
5765 list_for_each_entry(wq, &workqueues, list) {
5766 mutex_lock(&wq->mutex);
5767 for_each_pwq(pwq, wq)
5768 pwq_adjust_max_active(pwq);
5769 mutex_unlock(&wq->mutex);
5770 }
5771
5772out_unlock:
5773 mutex_unlock(&wq_pool_mutex);
5774}
5775#endif /* CONFIG_FREEZER */
5776
5777static int workqueue_apply_unbound_cpumask(const cpumask_var_t unbound_cpumask)
5778{
5779 LIST_HEAD(ctxs);
5780 int ret = 0;
5781 struct workqueue_struct *wq;
5782 struct apply_wqattrs_ctx *ctx, *n;
5783
5784 lockdep_assert_held(&wq_pool_mutex);
5785
5786 list_for_each_entry(wq, &workqueues, list) {
5787 if (!(wq->flags & WQ_UNBOUND))
5788 continue;
5789 /* creating multiple pwqs breaks ordering guarantee */
5790 if (wq->flags & __WQ_ORDERED)
5791 continue;
5792
5793 ctx = apply_wqattrs_prepare(wq, wq->unbound_attrs, unbound_cpumask);
5794 if (IS_ERR(ctx)) {
5795 ret = PTR_ERR(ctx);
5796 break;
5797 }
5798
5799 list_add_tail(&ctx->list, &ctxs);
5800 }
5801
5802 list_for_each_entry_safe(ctx, n, &ctxs, list) {
5803 if (!ret)
5804 apply_wqattrs_commit(ctx);
5805 apply_wqattrs_cleanup(ctx);
5806 }
5807
5808 if (!ret) {
5809 mutex_lock(&wq_pool_attach_mutex);
5810 cpumask_copy(wq_unbound_cpumask, unbound_cpumask);
5811 mutex_unlock(&wq_pool_attach_mutex);
5812 }
5813 return ret;
5814}
5815
5816/**
5817 * workqueue_unbound_exclude_cpumask - Exclude given CPUs from unbound cpumask
5818 * @exclude_cpumask: the cpumask to be excluded from wq_unbound_cpumask
5819 *
5820 * This function can be called from cpuset code to provide a set of isolated
5821 * CPUs that should be excluded from wq_unbound_cpumask. The caller must hold
5822 * either cpus_read_lock or cpus_write_lock.
5823 */
5824int workqueue_unbound_exclude_cpumask(cpumask_var_t exclude_cpumask)
5825{
5826 cpumask_var_t cpumask;
5827 int ret = 0;
5828
5829 if (!zalloc_cpumask_var(&cpumask, GFP_KERNEL))
5830 return -ENOMEM;
5831
5832 lockdep_assert_cpus_held();
5833 mutex_lock(&wq_pool_mutex);
5834
5835 /* Save the current isolated cpumask & export it via sysfs */
5836 cpumask_copy(wq_isolated_cpumask, exclude_cpumask);
5837
5838 /*
5839 * If the operation fails, it will fall back to
5840 * wq_requested_unbound_cpumask which is initially set to
5841 * (HK_TYPE_WQ ∩ HK_TYPE_DOMAIN) house keeping mask and rewritten
5842 * by any subsequent write to workqueue/cpumask sysfs file.
5843 */
5844 if (!cpumask_andnot(cpumask, wq_requested_unbound_cpumask, exclude_cpumask))
5845 cpumask_copy(cpumask, wq_requested_unbound_cpumask);
5846 if (!cpumask_equal(cpumask, wq_unbound_cpumask))
5847 ret = workqueue_apply_unbound_cpumask(cpumask);
5848
5849 mutex_unlock(&wq_pool_mutex);
5850 free_cpumask_var(cpumask);
5851 return ret;
5852}
5853
5854static int parse_affn_scope(const char *val)
5855{
5856 int i;
5857
5858 for (i = 0; i < ARRAY_SIZE(wq_affn_names); i++) {
5859 if (!strncasecmp(val, wq_affn_names[i], strlen(wq_affn_names[i])))
5860 return i;
5861 }
5862 return -EINVAL;
5863}
5864
5865static int wq_affn_dfl_set(const char *val, const struct kernel_param *kp)
5866{
5867 struct workqueue_struct *wq;
5868 int affn, cpu;
5869
5870 affn = parse_affn_scope(val);
5871 if (affn < 0)
5872 return affn;
5873 if (affn == WQ_AFFN_DFL)
5874 return -EINVAL;
5875
5876 cpus_read_lock();
5877 mutex_lock(&wq_pool_mutex);
5878
5879 wq_affn_dfl = affn;
5880
5881 list_for_each_entry(wq, &workqueues, list) {
5882 for_each_online_cpu(cpu) {
5883 wq_update_pod(wq, cpu, cpu, true);
5884 }
5885 }
5886
5887 mutex_unlock(&wq_pool_mutex);
5888 cpus_read_unlock();
5889
5890 return 0;
5891}
5892
5893static int wq_affn_dfl_get(char *buffer, const struct kernel_param *kp)
5894{
5895 return scnprintf(buffer, PAGE_SIZE, "%s\n", wq_affn_names[wq_affn_dfl]);
5896}
5897
5898static const struct kernel_param_ops wq_affn_dfl_ops = {
5899 .set = wq_affn_dfl_set,
5900 .get = wq_affn_dfl_get,
5901};
5902
5903module_param_cb(default_affinity_scope, &wq_affn_dfl_ops, NULL, 0644);
5904
5905#ifdef CONFIG_SYSFS
5906/*
5907 * Workqueues with WQ_SYSFS flag set is visible to userland via
5908 * /sys/bus/workqueue/devices/WQ_NAME. All visible workqueues have the
5909 * following attributes.
5910 *
5911 * per_cpu RO bool : whether the workqueue is per-cpu or unbound
5912 * max_active RW int : maximum number of in-flight work items
5913 *
5914 * Unbound workqueues have the following extra attributes.
5915 *
5916 * nice RW int : nice value of the workers
5917 * cpumask RW mask : bitmask of allowed CPUs for the workers
5918 * affinity_scope RW str : worker CPU affinity scope (cache, numa, none)
5919 * affinity_strict RW bool : worker CPU affinity is strict
5920 */
5921struct wq_device {
5922 struct workqueue_struct *wq;
5923 struct device dev;
5924};
5925
5926static struct workqueue_struct *dev_to_wq(struct device *dev)
5927{
5928 struct wq_device *wq_dev = container_of(dev, struct wq_device, dev);
5929
5930 return wq_dev->wq;
5931}
5932
5933static ssize_t per_cpu_show(struct device *dev, struct device_attribute *attr,
5934 char *buf)
5935{
5936 struct workqueue_struct *wq = dev_to_wq(dev);
5937
5938 return scnprintf(buf, PAGE_SIZE, "%d\n", (bool)!(wq->flags & WQ_UNBOUND));
5939}
5940static DEVICE_ATTR_RO(per_cpu);
5941
5942static ssize_t max_active_show(struct device *dev,
5943 struct device_attribute *attr, char *buf)
5944{
5945 struct workqueue_struct *wq = dev_to_wq(dev);
5946
5947 return scnprintf(buf, PAGE_SIZE, "%d\n", wq->saved_max_active);
5948}
5949
5950static ssize_t max_active_store(struct device *dev,
5951 struct device_attribute *attr, const char *buf,
5952 size_t count)
5953{
5954 struct workqueue_struct *wq = dev_to_wq(dev);
5955 int val;
5956
5957 if (sscanf(buf, "%d", &val) != 1 || val <= 0)
5958 return -EINVAL;
5959
5960 workqueue_set_max_active(wq, val);
5961 return count;
5962}
5963static DEVICE_ATTR_RW(max_active);
5964
5965static struct attribute *wq_sysfs_attrs[] = {
5966 &dev_attr_per_cpu.attr,
5967 &dev_attr_max_active.attr,
5968 NULL,
5969};
5970ATTRIBUTE_GROUPS(wq_sysfs);
5971
5972static void apply_wqattrs_lock(void)
5973{
5974 /* CPUs should stay stable across pwq creations and installations */
5975 cpus_read_lock();
5976 mutex_lock(&wq_pool_mutex);
5977}
5978
5979static void apply_wqattrs_unlock(void)
5980{
5981 mutex_unlock(&wq_pool_mutex);
5982 cpus_read_unlock();
5983}
5984
5985static ssize_t wq_nice_show(struct device *dev, struct device_attribute *attr,
5986 char *buf)
5987{
5988 struct workqueue_struct *wq = dev_to_wq(dev);
5989 int written;
5990
5991 mutex_lock(&wq->mutex);
5992 written = scnprintf(buf, PAGE_SIZE, "%d\n", wq->unbound_attrs->nice);
5993 mutex_unlock(&wq->mutex);
5994
5995 return written;
5996}
5997
5998/* prepare workqueue_attrs for sysfs store operations */
5999static struct workqueue_attrs *wq_sysfs_prep_attrs(struct workqueue_struct *wq)
6000{
6001 struct workqueue_attrs *attrs;
6002
6003 lockdep_assert_held(&wq_pool_mutex);
6004
6005 attrs = alloc_workqueue_attrs();
6006 if (!attrs)
6007 return NULL;
6008
6009 copy_workqueue_attrs(attrs, wq->unbound_attrs);
6010 return attrs;
6011}
6012
6013static ssize_t wq_nice_store(struct device *dev, struct device_attribute *attr,
6014 const char *buf, size_t count)
6015{
6016 struct workqueue_struct *wq = dev_to_wq(dev);
6017 struct workqueue_attrs *attrs;
6018 int ret = -ENOMEM;
6019
6020 apply_wqattrs_lock();
6021
6022 attrs = wq_sysfs_prep_attrs(wq);
6023 if (!attrs)
6024 goto out_unlock;
6025
6026 if (sscanf(buf, "%d", &attrs->nice) == 1 &&
6027 attrs->nice >= MIN_NICE && attrs->nice <= MAX_NICE)
6028 ret = apply_workqueue_attrs_locked(wq, attrs);
6029 else
6030 ret = -EINVAL;
6031
6032out_unlock:
6033 apply_wqattrs_unlock();
6034 free_workqueue_attrs(attrs);
6035 return ret ?: count;
6036}
6037
6038static ssize_t wq_cpumask_show(struct device *dev,
6039 struct device_attribute *attr, char *buf)
6040{
6041 struct workqueue_struct *wq = dev_to_wq(dev);
6042 int written;
6043
6044 mutex_lock(&wq->mutex);
6045 written = scnprintf(buf, PAGE_SIZE, "%*pb\n",
6046 cpumask_pr_args(wq->unbound_attrs->cpumask));
6047 mutex_unlock(&wq->mutex);
6048 return written;
6049}
6050
6051static ssize_t wq_cpumask_store(struct device *dev,
6052 struct device_attribute *attr,
6053 const char *buf, size_t count)
6054{
6055 struct workqueue_struct *wq = dev_to_wq(dev);
6056 struct workqueue_attrs *attrs;
6057 int ret = -ENOMEM;
6058
6059 apply_wqattrs_lock();
6060
6061 attrs = wq_sysfs_prep_attrs(wq);
6062 if (!attrs)
6063 goto out_unlock;
6064
6065 ret = cpumask_parse(buf, attrs->cpumask);
6066 if (!ret)
6067 ret = apply_workqueue_attrs_locked(wq, attrs);
6068
6069out_unlock:
6070 apply_wqattrs_unlock();
6071 free_workqueue_attrs(attrs);
6072 return ret ?: count;
6073}
6074
6075static ssize_t wq_affn_scope_show(struct device *dev,
6076 struct device_attribute *attr, char *buf)
6077{
6078 struct workqueue_struct *wq = dev_to_wq(dev);
6079 int written;
6080
6081 mutex_lock(&wq->mutex);
6082 if (wq->unbound_attrs->affn_scope == WQ_AFFN_DFL)
6083 written = scnprintf(buf, PAGE_SIZE, "%s (%s)\n",
6084 wq_affn_names[WQ_AFFN_DFL],
6085 wq_affn_names[wq_affn_dfl]);
6086 else
6087 written = scnprintf(buf, PAGE_SIZE, "%s\n",
6088 wq_affn_names[wq->unbound_attrs->affn_scope]);
6089 mutex_unlock(&wq->mutex);
6090
6091 return written;
6092}
6093
6094static ssize_t wq_affn_scope_store(struct device *dev,
6095 struct device_attribute *attr,
6096 const char *buf, size_t count)
6097{
6098 struct workqueue_struct *wq = dev_to_wq(dev);
6099 struct workqueue_attrs *attrs;
6100 int affn, ret = -ENOMEM;
6101
6102 affn = parse_affn_scope(buf);
6103 if (affn < 0)
6104 return affn;
6105
6106 apply_wqattrs_lock();
6107 attrs = wq_sysfs_prep_attrs(wq);
6108 if (attrs) {
6109 attrs->affn_scope = affn;
6110 ret = apply_workqueue_attrs_locked(wq, attrs);
6111 }
6112 apply_wqattrs_unlock();
6113 free_workqueue_attrs(attrs);
6114 return ret ?: count;
6115}
6116
6117static ssize_t wq_affinity_strict_show(struct device *dev,
6118 struct device_attribute *attr, char *buf)
6119{
6120 struct workqueue_struct *wq = dev_to_wq(dev);
6121
6122 return scnprintf(buf, PAGE_SIZE, "%d\n",
6123 wq->unbound_attrs->affn_strict);
6124}
6125
6126static ssize_t wq_affinity_strict_store(struct device *dev,
6127 struct device_attribute *attr,
6128 const char *buf, size_t count)
6129{
6130 struct workqueue_struct *wq = dev_to_wq(dev);
6131 struct workqueue_attrs *attrs;
6132 int v, ret = -ENOMEM;
6133
6134 if (sscanf(buf, "%d", &v) != 1)
6135 return -EINVAL;
6136
6137 apply_wqattrs_lock();
6138 attrs = wq_sysfs_prep_attrs(wq);
6139 if (attrs) {
6140 attrs->affn_strict = (bool)v;
6141 ret = apply_workqueue_attrs_locked(wq, attrs);
6142 }
6143 apply_wqattrs_unlock();
6144 free_workqueue_attrs(attrs);
6145 return ret ?: count;
6146}
6147
6148static struct device_attribute wq_sysfs_unbound_attrs[] = {
6149 __ATTR(nice, 0644, wq_nice_show, wq_nice_store),
6150 __ATTR(cpumask, 0644, wq_cpumask_show, wq_cpumask_store),
6151 __ATTR(affinity_scope, 0644, wq_affn_scope_show, wq_affn_scope_store),
6152 __ATTR(affinity_strict, 0644, wq_affinity_strict_show, wq_affinity_strict_store),
6153 __ATTR_NULL,
6154};
6155
6156static struct bus_type wq_subsys = {
6157 .name = "workqueue",
6158 .dev_groups = wq_sysfs_groups,
6159};
6160
6161/**
6162 * workqueue_set_unbound_cpumask - Set the low-level unbound cpumask
6163 * @cpumask: the cpumask to set
6164 *
6165 * The low-level workqueues cpumask is a global cpumask that limits
6166 * the affinity of all unbound workqueues. This function check the @cpumask
6167 * and apply it to all unbound workqueues and updates all pwqs of them.
6168 *
6169 * Return: 0 - Success
6170 * -EINVAL - Invalid @cpumask
6171 * -ENOMEM - Failed to allocate memory for attrs or pwqs.
6172 */
6173static int workqueue_set_unbound_cpumask(cpumask_var_t cpumask)
6174{
6175 int ret = -EINVAL;
6176
6177 /*
6178 * Not excluding isolated cpus on purpose.
6179 * If the user wishes to include them, we allow that.
6180 */
6181 cpumask_and(cpumask, cpumask, cpu_possible_mask);
6182 if (!cpumask_empty(cpumask)) {
6183 apply_wqattrs_lock();
6184 cpumask_copy(wq_requested_unbound_cpumask, cpumask);
6185 if (cpumask_equal(cpumask, wq_unbound_cpumask)) {
6186 ret = 0;
6187 goto out_unlock;
6188 }
6189
6190 ret = workqueue_apply_unbound_cpumask(cpumask);
6191
6192out_unlock:
6193 apply_wqattrs_unlock();
6194 }
6195
6196 return ret;
6197}
6198
6199static ssize_t __wq_cpumask_show(struct device *dev,
6200 struct device_attribute *attr, char *buf, cpumask_var_t mask)
6201{
6202 int written;
6203
6204 mutex_lock(&wq_pool_mutex);
6205 written = scnprintf(buf, PAGE_SIZE, "%*pb\n", cpumask_pr_args(mask));
6206 mutex_unlock(&wq_pool_mutex);
6207
6208 return written;
6209}
6210
6211static ssize_t wq_unbound_cpumask_show(struct device *dev,
6212 struct device_attribute *attr, char *buf)
6213{
6214 return __wq_cpumask_show(dev, attr, buf, wq_unbound_cpumask);
6215}
6216
6217static ssize_t wq_requested_cpumask_show(struct device *dev,
6218 struct device_attribute *attr, char *buf)
6219{
6220 return __wq_cpumask_show(dev, attr, buf, wq_requested_unbound_cpumask);
6221}
6222
6223static ssize_t wq_isolated_cpumask_show(struct device *dev,
6224 struct device_attribute *attr, char *buf)
6225{
6226 return __wq_cpumask_show(dev, attr, buf, wq_isolated_cpumask);
6227}
6228
6229static ssize_t wq_unbound_cpumask_store(struct device *dev,
6230 struct device_attribute *attr, const char *buf, size_t count)
6231{
6232 cpumask_var_t cpumask;
6233 int ret;
6234
6235 if (!zalloc_cpumask_var(&cpumask, GFP_KERNEL))
6236 return -ENOMEM;
6237
6238 ret = cpumask_parse(buf, cpumask);
6239 if (!ret)
6240 ret = workqueue_set_unbound_cpumask(cpumask);
6241
6242 free_cpumask_var(cpumask);
6243 return ret ? ret : count;
6244}
6245
6246static struct device_attribute wq_sysfs_cpumask_attrs[] = {
6247 __ATTR(cpumask, 0644, wq_unbound_cpumask_show,
6248 wq_unbound_cpumask_store),
6249 __ATTR(cpumask_requested, 0444, wq_requested_cpumask_show, NULL),
6250 __ATTR(cpumask_isolated, 0444, wq_isolated_cpumask_show, NULL),
6251 __ATTR_NULL,
6252};
6253
6254static int __init wq_sysfs_init(void)
6255{
6256 struct device *dev_root;
6257 int err;
6258
6259 err = subsys_virtual_register(&wq_subsys, NULL);
6260 if (err)
6261 return err;
6262
6263 dev_root = bus_get_dev_root(&wq_subsys);
6264 if (dev_root) {
6265 struct device_attribute *attr;
6266
6267 for (attr = wq_sysfs_cpumask_attrs; attr->attr.name; attr++) {
6268 err = device_create_file(dev_root, attr);
6269 if (err)
6270 break;
6271 }
6272 put_device(dev_root);
6273 }
6274 return err;
6275}
6276core_initcall(wq_sysfs_init);
6277
6278static void wq_device_release(struct device *dev)
6279{
6280 struct wq_device *wq_dev = container_of(dev, struct wq_device, dev);
6281
6282 kfree(wq_dev);
6283}
6284
6285/**
6286 * workqueue_sysfs_register - make a workqueue visible in sysfs
6287 * @wq: the workqueue to register
6288 *
6289 * Expose @wq in sysfs under /sys/bus/workqueue/devices.
6290 * alloc_workqueue*() automatically calls this function if WQ_SYSFS is set
6291 * which is the preferred method.
6292 *
6293 * Workqueue user should use this function directly iff it wants to apply
6294 * workqueue_attrs before making the workqueue visible in sysfs; otherwise,
6295 * apply_workqueue_attrs() may race against userland updating the
6296 * attributes.
6297 *
6298 * Return: 0 on success, -errno on failure.
6299 */
6300int workqueue_sysfs_register(struct workqueue_struct *wq)
6301{
6302 struct wq_device *wq_dev;
6303 int ret;
6304
6305 /*
6306 * Adjusting max_active or creating new pwqs by applying
6307 * attributes breaks ordering guarantee. Disallow exposing ordered
6308 * workqueues.
6309 */
6310 if (WARN_ON(wq->flags & __WQ_ORDERED_EXPLICIT))
6311 return -EINVAL;
6312
6313 wq->wq_dev = wq_dev = kzalloc(sizeof(*wq_dev), GFP_KERNEL);
6314 if (!wq_dev)
6315 return -ENOMEM;
6316
6317 wq_dev->wq = wq;
6318 wq_dev->dev.bus = &wq_subsys;
6319 wq_dev->dev.release = wq_device_release;
6320 dev_set_name(&wq_dev->dev, "%s", wq->name);
6321
6322 /*
6323 * unbound_attrs are created separately. Suppress uevent until
6324 * everything is ready.
6325 */
6326 dev_set_uevent_suppress(&wq_dev->dev, true);
6327
6328 ret = device_register(&wq_dev->dev);
6329 if (ret) {
6330 put_device(&wq_dev->dev);
6331 wq->wq_dev = NULL;
6332 return ret;
6333 }
6334
6335 if (wq->flags & WQ_UNBOUND) {
6336 struct device_attribute *attr;
6337
6338 for (attr = wq_sysfs_unbound_attrs; attr->attr.name; attr++) {
6339 ret = device_create_file(&wq_dev->dev, attr);
6340 if (ret) {
6341 device_unregister(&wq_dev->dev);
6342 wq->wq_dev = NULL;
6343 return ret;
6344 }
6345 }
6346 }
6347
6348 dev_set_uevent_suppress(&wq_dev->dev, false);
6349 kobject_uevent(&wq_dev->dev.kobj, KOBJ_ADD);
6350 return 0;
6351}
6352
6353/**
6354 * workqueue_sysfs_unregister - undo workqueue_sysfs_register()
6355 * @wq: the workqueue to unregister
6356 *
6357 * If @wq is registered to sysfs by workqueue_sysfs_register(), unregister.
6358 */
6359static void workqueue_sysfs_unregister(struct workqueue_struct *wq)
6360{
6361 struct wq_device *wq_dev = wq->wq_dev;
6362
6363 if (!wq->wq_dev)
6364 return;
6365
6366 wq->wq_dev = NULL;
6367 device_unregister(&wq_dev->dev);
6368}
6369#else /* CONFIG_SYSFS */
6370static void workqueue_sysfs_unregister(struct workqueue_struct *wq) { }
6371#endif /* CONFIG_SYSFS */
6372
6373/*
6374 * Workqueue watchdog.
6375 *
6376 * Stall may be caused by various bugs - missing WQ_MEM_RECLAIM, illegal
6377 * flush dependency, a concurrency managed work item which stays RUNNING
6378 * indefinitely. Workqueue stalls can be very difficult to debug as the
6379 * usual warning mechanisms don't trigger and internal workqueue state is
6380 * largely opaque.
6381 *
6382 * Workqueue watchdog monitors all worker pools periodically and dumps
6383 * state if some pools failed to make forward progress for a while where
6384 * forward progress is defined as the first item on ->worklist changing.
6385 *
6386 * This mechanism is controlled through the kernel parameter
6387 * "workqueue.watchdog_thresh" which can be updated at runtime through the
6388 * corresponding sysfs parameter file.
6389 */
6390#ifdef CONFIG_WQ_WATCHDOG
6391
6392static unsigned long wq_watchdog_thresh = 30;
6393static struct timer_list wq_watchdog_timer;
6394
6395static unsigned long wq_watchdog_touched = INITIAL_JIFFIES;
6396static DEFINE_PER_CPU(unsigned long, wq_watchdog_touched_cpu) = INITIAL_JIFFIES;
6397
6398/*
6399 * Show workers that might prevent the processing of pending work items.
6400 * The only candidates are CPU-bound workers in the running state.
6401 * Pending work items should be handled by another idle worker
6402 * in all other situations.
6403 */
6404static void show_cpu_pool_hog(struct worker_pool *pool)
6405{
6406 struct worker *worker;
6407 unsigned long flags;
6408 int bkt;
6409
6410 raw_spin_lock_irqsave(&pool->lock, flags);
6411
6412 hash_for_each(pool->busy_hash, bkt, worker, hentry) {
6413 if (task_is_running(worker->task)) {
6414 /*
6415 * Defer printing to avoid deadlocks in console
6416 * drivers that queue work while holding locks
6417 * also taken in their write paths.
6418 */
6419 printk_deferred_enter();
6420
6421 pr_info("pool %d:\n", pool->id);
6422 sched_show_task(worker->task);
6423
6424 printk_deferred_exit();
6425 }
6426 }
6427
6428 raw_spin_unlock_irqrestore(&pool->lock, flags);
6429}
6430
6431static void show_cpu_pools_hogs(void)
6432{
6433 struct worker_pool *pool;
6434 int pi;
6435
6436 pr_info("Showing backtraces of running workers in stalled CPU-bound worker pools:\n");
6437
6438 rcu_read_lock();
6439
6440 for_each_pool(pool, pi) {
6441 if (pool->cpu_stall)
6442 show_cpu_pool_hog(pool);
6443
6444 }
6445
6446 rcu_read_unlock();
6447}
6448
6449static void wq_watchdog_reset_touched(void)
6450{
6451 int cpu;
6452
6453 wq_watchdog_touched = jiffies;
6454 for_each_possible_cpu(cpu)
6455 per_cpu(wq_watchdog_touched_cpu, cpu) = jiffies;
6456}
6457
6458static void wq_watchdog_timer_fn(struct timer_list *unused)
6459{
6460 unsigned long thresh = READ_ONCE(wq_watchdog_thresh) * HZ;
6461 bool lockup_detected = false;
6462 bool cpu_pool_stall = false;
6463 unsigned long now = jiffies;
6464 struct worker_pool *pool;
6465 int pi;
6466
6467 if (!thresh)
6468 return;
6469
6470 rcu_read_lock();
6471
6472 for_each_pool(pool, pi) {
6473 unsigned long pool_ts, touched, ts;
6474
6475 pool->cpu_stall = false;
6476 if (list_empty(&pool->worklist))
6477 continue;
6478
6479 /*
6480 * If a virtual machine is stopped by the host it can look to
6481 * the watchdog like a stall.
6482 */
6483 kvm_check_and_clear_guest_paused();
6484
6485 /* get the latest of pool and touched timestamps */
6486 if (pool->cpu >= 0)
6487 touched = READ_ONCE(per_cpu(wq_watchdog_touched_cpu, pool->cpu));
6488 else
6489 touched = READ_ONCE(wq_watchdog_touched);
6490 pool_ts = READ_ONCE(pool->watchdog_ts);
6491
6492 if (time_after(pool_ts, touched))
6493 ts = pool_ts;
6494 else
6495 ts = touched;
6496
6497 /* did we stall? */
6498 if (time_after(now, ts + thresh)) {
6499 lockup_detected = true;
6500 if (pool->cpu >= 0) {
6501 pool->cpu_stall = true;
6502 cpu_pool_stall = true;
6503 }
6504 pr_emerg("BUG: workqueue lockup - pool");
6505 pr_cont_pool_info(pool);
6506 pr_cont(" stuck for %us!\n",
6507 jiffies_to_msecs(now - pool_ts) / 1000);
6508 }
6509
6510
6511 }
6512
6513 rcu_read_unlock();
6514
6515 if (lockup_detected)
6516 show_all_workqueues();
6517
6518 if (cpu_pool_stall)
6519 show_cpu_pools_hogs();
6520
6521 wq_watchdog_reset_touched();
6522 mod_timer(&wq_watchdog_timer, jiffies + thresh);
6523}
6524
6525notrace void wq_watchdog_touch(int cpu)
6526{
6527 if (cpu >= 0)
6528 per_cpu(wq_watchdog_touched_cpu, cpu) = jiffies;
6529
6530 wq_watchdog_touched = jiffies;
6531}
6532
6533static void wq_watchdog_set_thresh(unsigned long thresh)
6534{
6535 wq_watchdog_thresh = 0;
6536 del_timer_sync(&wq_watchdog_timer);
6537
6538 if (thresh) {
6539 wq_watchdog_thresh = thresh;
6540 wq_watchdog_reset_touched();
6541 mod_timer(&wq_watchdog_timer, jiffies + thresh * HZ);
6542 }
6543}
6544
6545static int wq_watchdog_param_set_thresh(const char *val,
6546 const struct kernel_param *kp)
6547{
6548 unsigned long thresh;
6549 int ret;
6550
6551 ret = kstrtoul(val, 0, &thresh);
6552 if (ret)
6553 return ret;
6554
6555 if (system_wq)
6556 wq_watchdog_set_thresh(thresh);
6557 else
6558 wq_watchdog_thresh = thresh;
6559
6560 return 0;
6561}
6562
6563static const struct kernel_param_ops wq_watchdog_thresh_ops = {
6564 .set = wq_watchdog_param_set_thresh,
6565 .get = param_get_ulong,
6566};
6567
6568module_param_cb(watchdog_thresh, &wq_watchdog_thresh_ops, &wq_watchdog_thresh,
6569 0644);
6570
6571static void wq_watchdog_init(void)
6572{
6573 timer_setup(&wq_watchdog_timer, wq_watchdog_timer_fn, TIMER_DEFERRABLE);
6574 wq_watchdog_set_thresh(wq_watchdog_thresh);
6575}
6576
6577#else /* CONFIG_WQ_WATCHDOG */
6578
6579static inline void wq_watchdog_init(void) { }
6580
6581#endif /* CONFIG_WQ_WATCHDOG */
6582
6583static void __init restrict_unbound_cpumask(const char *name, const struct cpumask *mask)
6584{
6585 if (!cpumask_intersects(wq_unbound_cpumask, mask)) {
6586 pr_warn("workqueue: Restricting unbound_cpumask (%*pb) with %s (%*pb) leaves no CPU, ignoring\n",
6587 cpumask_pr_args(wq_unbound_cpumask), name, cpumask_pr_args(mask));
6588 return;
6589 }
6590
6591 cpumask_and(wq_unbound_cpumask, wq_unbound_cpumask, mask);
6592}
6593
6594/**
6595 * workqueue_init_early - early init for workqueue subsystem
6596 *
6597 * This is the first step of three-staged workqueue subsystem initialization and
6598 * invoked as soon as the bare basics - memory allocation, cpumasks and idr are
6599 * up. It sets up all the data structures and system workqueues and allows early
6600 * boot code to create workqueues and queue/cancel work items. Actual work item
6601 * execution starts only after kthreads can be created and scheduled right
6602 * before early initcalls.
6603 */
6604void __init workqueue_init_early(void)
6605{
6606 struct wq_pod_type *pt = &wq_pod_types[WQ_AFFN_SYSTEM];
6607 int std_nice[NR_STD_WORKER_POOLS] = { 0, HIGHPRI_NICE_LEVEL };
6608 int i, cpu;
6609
6610 BUILD_BUG_ON(__alignof__(struct pool_workqueue) < __alignof__(long long));
6611
6612 BUG_ON(!alloc_cpumask_var(&wq_unbound_cpumask, GFP_KERNEL));
6613 BUG_ON(!alloc_cpumask_var(&wq_requested_unbound_cpumask, GFP_KERNEL));
6614 BUG_ON(!zalloc_cpumask_var(&wq_isolated_cpumask, GFP_KERNEL));
6615
6616 cpumask_copy(wq_unbound_cpumask, cpu_possible_mask);
6617 restrict_unbound_cpumask("HK_TYPE_WQ", housekeeping_cpumask(HK_TYPE_WQ));
6618 restrict_unbound_cpumask("HK_TYPE_DOMAIN", housekeeping_cpumask(HK_TYPE_DOMAIN));
6619 if (!cpumask_empty(&wq_cmdline_cpumask))
6620 restrict_unbound_cpumask("workqueue.unbound_cpus", &wq_cmdline_cpumask);
6621
6622 cpumask_copy(wq_requested_unbound_cpumask, wq_unbound_cpumask);
6623
6624 pwq_cache = KMEM_CACHE(pool_workqueue, SLAB_PANIC);
6625
6626 wq_update_pod_attrs_buf = alloc_workqueue_attrs();
6627 BUG_ON(!wq_update_pod_attrs_buf);
6628
6629 /* initialize WQ_AFFN_SYSTEM pods */
6630 pt->pod_cpus = kcalloc(1, sizeof(pt->pod_cpus[0]), GFP_KERNEL);
6631 pt->pod_node = kcalloc(1, sizeof(pt->pod_node[0]), GFP_KERNEL);
6632 pt->cpu_pod = kcalloc(nr_cpu_ids, sizeof(pt->cpu_pod[0]), GFP_KERNEL);
6633 BUG_ON(!pt->pod_cpus || !pt->pod_node || !pt->cpu_pod);
6634
6635 BUG_ON(!zalloc_cpumask_var_node(&pt->pod_cpus[0], GFP_KERNEL, NUMA_NO_NODE));
6636
6637 pt->nr_pods = 1;
6638 cpumask_copy(pt->pod_cpus[0], cpu_possible_mask);
6639 pt->pod_node[0] = NUMA_NO_NODE;
6640 pt->cpu_pod[0] = 0;
6641
6642 /* initialize CPU pools */
6643 for_each_possible_cpu(cpu) {
6644 struct worker_pool *pool;
6645
6646 i = 0;
6647 for_each_cpu_worker_pool(pool, cpu) {
6648 BUG_ON(init_worker_pool(pool));
6649 pool->cpu = cpu;
6650 cpumask_copy(pool->attrs->cpumask, cpumask_of(cpu));
6651 cpumask_copy(pool->attrs->__pod_cpumask, cpumask_of(cpu));
6652 pool->attrs->nice = std_nice[i++];
6653 pool->attrs->affn_strict = true;
6654 pool->node = cpu_to_node(cpu);
6655
6656 /* alloc pool ID */
6657 mutex_lock(&wq_pool_mutex);
6658 BUG_ON(worker_pool_assign_id(pool));
6659 mutex_unlock(&wq_pool_mutex);
6660 }
6661 }
6662
6663 /* create default unbound and ordered wq attrs */
6664 for (i = 0; i < NR_STD_WORKER_POOLS; i++) {
6665 struct workqueue_attrs *attrs;
6666
6667 BUG_ON(!(attrs = alloc_workqueue_attrs()));
6668 attrs->nice = std_nice[i];
6669 unbound_std_wq_attrs[i] = attrs;
6670
6671 /*
6672 * An ordered wq should have only one pwq as ordering is
6673 * guaranteed by max_active which is enforced by pwqs.
6674 */
6675 BUG_ON(!(attrs = alloc_workqueue_attrs()));
6676 attrs->nice = std_nice[i];
6677 attrs->ordered = true;
6678 ordered_wq_attrs[i] = attrs;
6679 }
6680
6681 system_wq = alloc_workqueue("events", 0, 0);
6682 system_highpri_wq = alloc_workqueue("events_highpri", WQ_HIGHPRI, 0);
6683 system_long_wq = alloc_workqueue("events_long", 0, 0);
6684 system_unbound_wq = alloc_workqueue("events_unbound", WQ_UNBOUND,
6685 WQ_MAX_ACTIVE);
6686 system_freezable_wq = alloc_workqueue("events_freezable",
6687 WQ_FREEZABLE, 0);
6688 system_power_efficient_wq = alloc_workqueue("events_power_efficient",
6689 WQ_POWER_EFFICIENT, 0);
6690 system_freezable_power_efficient_wq = alloc_workqueue("events_freezable_power_efficient",
6691 WQ_FREEZABLE | WQ_POWER_EFFICIENT,
6692 0);
6693 BUG_ON(!system_wq || !system_highpri_wq || !system_long_wq ||
6694 !system_unbound_wq || !system_freezable_wq ||
6695 !system_power_efficient_wq ||
6696 !system_freezable_power_efficient_wq);
6697}
6698
6699static void __init wq_cpu_intensive_thresh_init(void)
6700{
6701 unsigned long thresh;
6702 unsigned long bogo;
6703
6704 pwq_release_worker = kthread_create_worker(0, "pool_workqueue_release");
6705 BUG_ON(IS_ERR(pwq_release_worker));
6706
6707 /* if the user set it to a specific value, keep it */
6708 if (wq_cpu_intensive_thresh_us != ULONG_MAX)
6709 return;
6710
6711 /*
6712 * The default of 10ms is derived from the fact that most modern (as of
6713 * 2023) processors can do a lot in 10ms and that it's just below what
6714 * most consider human-perceivable. However, the kernel also runs on a
6715 * lot slower CPUs including microcontrollers where the threshold is way
6716 * too low.
6717 *
6718 * Let's scale up the threshold upto 1 second if BogoMips is below 4000.
6719 * This is by no means accurate but it doesn't have to be. The mechanism
6720 * is still useful even when the threshold is fully scaled up. Also, as
6721 * the reports would usually be applicable to everyone, some machines
6722 * operating on longer thresholds won't significantly diminish their
6723 * usefulness.
6724 */
6725 thresh = 10 * USEC_PER_MSEC;
6726
6727 /* see init/calibrate.c for lpj -> BogoMIPS calculation */
6728 bogo = max_t(unsigned long, loops_per_jiffy / 500000 * HZ, 1);
6729 if (bogo < 4000)
6730 thresh = min_t(unsigned long, thresh * 4000 / bogo, USEC_PER_SEC);
6731
6732 pr_debug("wq_cpu_intensive_thresh: lpj=%lu BogoMIPS=%lu thresh_us=%lu\n",
6733 loops_per_jiffy, bogo, thresh);
6734
6735 wq_cpu_intensive_thresh_us = thresh;
6736}
6737
6738/**
6739 * workqueue_init - bring workqueue subsystem fully online
6740 *
6741 * This is the second step of three-staged workqueue subsystem initialization
6742 * and invoked as soon as kthreads can be created and scheduled. Workqueues have
6743 * been created and work items queued on them, but there are no kworkers
6744 * executing the work items yet. Populate the worker pools with the initial
6745 * workers and enable future kworker creations.
6746 */
6747void __init workqueue_init(void)
6748{
6749 struct workqueue_struct *wq;
6750 struct worker_pool *pool;
6751 int cpu, bkt;
6752
6753 wq_cpu_intensive_thresh_init();
6754
6755 mutex_lock(&wq_pool_mutex);
6756
6757 /*
6758 * Per-cpu pools created earlier could be missing node hint. Fix them
6759 * up. Also, create a rescuer for workqueues that requested it.
6760 */
6761 for_each_possible_cpu(cpu) {
6762 for_each_cpu_worker_pool(pool, cpu) {
6763 pool->node = cpu_to_node(cpu);
6764 }
6765 }
6766
6767 list_for_each_entry(wq, &workqueues, list) {
6768 WARN(init_rescuer(wq),
6769 "workqueue: failed to create early rescuer for %s",
6770 wq->name);
6771 }
6772
6773 mutex_unlock(&wq_pool_mutex);
6774
6775 /* create the initial workers */
6776 for_each_online_cpu(cpu) {
6777 for_each_cpu_worker_pool(pool, cpu) {
6778 pool->flags &= ~POOL_DISASSOCIATED;
6779 BUG_ON(!create_worker(pool));
6780 }
6781 }
6782
6783 hash_for_each(unbound_pool_hash, bkt, pool, hash_node)
6784 BUG_ON(!create_worker(pool));
6785
6786 wq_online = true;
6787 wq_watchdog_init();
6788}
6789
6790/*
6791 * Initialize @pt by first initializing @pt->cpu_pod[] with pod IDs according to
6792 * @cpu_shares_pod(). Each subset of CPUs that share a pod is assigned a unique
6793 * and consecutive pod ID. The rest of @pt is initialized accordingly.
6794 */
6795static void __init init_pod_type(struct wq_pod_type *pt,
6796 bool (*cpus_share_pod)(int, int))
6797{
6798 int cur, pre, cpu, pod;
6799
6800 pt->nr_pods = 0;
6801
6802 /* init @pt->cpu_pod[] according to @cpus_share_pod() */
6803 pt->cpu_pod = kcalloc(nr_cpu_ids, sizeof(pt->cpu_pod[0]), GFP_KERNEL);
6804 BUG_ON(!pt->cpu_pod);
6805
6806 for_each_possible_cpu(cur) {
6807 for_each_possible_cpu(pre) {
6808 if (pre >= cur) {
6809 pt->cpu_pod[cur] = pt->nr_pods++;
6810 break;
6811 }
6812 if (cpus_share_pod(cur, pre)) {
6813 pt->cpu_pod[cur] = pt->cpu_pod[pre];
6814 break;
6815 }
6816 }
6817 }
6818
6819 /* init the rest to match @pt->cpu_pod[] */
6820 pt->pod_cpus = kcalloc(pt->nr_pods, sizeof(pt->pod_cpus[0]), GFP_KERNEL);
6821 pt->pod_node = kcalloc(pt->nr_pods, sizeof(pt->pod_node[0]), GFP_KERNEL);
6822 BUG_ON(!pt->pod_cpus || !pt->pod_node);
6823
6824 for (pod = 0; pod < pt->nr_pods; pod++)
6825 BUG_ON(!zalloc_cpumask_var(&pt->pod_cpus[pod], GFP_KERNEL));
6826
6827 for_each_possible_cpu(cpu) {
6828 cpumask_set_cpu(cpu, pt->pod_cpus[pt->cpu_pod[cpu]]);
6829 pt->pod_node[pt->cpu_pod[cpu]] = cpu_to_node(cpu);
6830 }
6831}
6832
6833static bool __init cpus_dont_share(int cpu0, int cpu1)
6834{
6835 return false;
6836}
6837
6838static bool __init cpus_share_smt(int cpu0, int cpu1)
6839{
6840#ifdef CONFIG_SCHED_SMT
6841 return cpumask_test_cpu(cpu0, cpu_smt_mask(cpu1));
6842#else
6843 return false;
6844#endif
6845}
6846
6847static bool __init cpus_share_numa(int cpu0, int cpu1)
6848{
6849 return cpu_to_node(cpu0) == cpu_to_node(cpu1);
6850}
6851
6852/**
6853 * workqueue_init_topology - initialize CPU pods for unbound workqueues
6854 *
6855 * This is the third step of there-staged workqueue subsystem initialization and
6856 * invoked after SMP and topology information are fully initialized. It
6857 * initializes the unbound CPU pods accordingly.
6858 */
6859void __init workqueue_init_topology(void)
6860{
6861 struct workqueue_struct *wq;
6862 int cpu;
6863
6864 init_pod_type(&wq_pod_types[WQ_AFFN_CPU], cpus_dont_share);
6865 init_pod_type(&wq_pod_types[WQ_AFFN_SMT], cpus_share_smt);
6866 init_pod_type(&wq_pod_types[WQ_AFFN_CACHE], cpus_share_cache);
6867 init_pod_type(&wq_pod_types[WQ_AFFN_NUMA], cpus_share_numa);
6868
6869 mutex_lock(&wq_pool_mutex);
6870
6871 /*
6872 * Workqueues allocated earlier would have all CPUs sharing the default
6873 * worker pool. Explicitly call wq_update_pod() on all workqueue and CPU
6874 * combinations to apply per-pod sharing.
6875 */
6876 list_for_each_entry(wq, &workqueues, list) {
6877 for_each_online_cpu(cpu) {
6878 wq_update_pod(wq, cpu, cpu, true);
6879 }
6880 }
6881
6882 mutex_unlock(&wq_pool_mutex);
6883}
6884
6885void __warn_flushing_systemwide_wq(void)
6886{
6887 pr_warn("WARNING: Flushing system-wide workqueues will be prohibited in near future.\n");
6888 dump_stack();
6889}
6890EXPORT_SYMBOL(__warn_flushing_systemwide_wq);
6891
6892static int __init workqueue_unbound_cpus_setup(char *str)
6893{
6894 if (cpulist_parse(str, &wq_cmdline_cpumask) < 0) {
6895 cpumask_clear(&wq_cmdline_cpumask);
6896 pr_warn("workqueue.unbound_cpus: incorrect CPU range, using default\n");
6897 }
6898
6899 return 1;
6900}
6901__setup("workqueue.unbound_cpus=", workqueue_unbound_cpus_setup);