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