2 * kernel/workqueue.c - generic async execution with shared worker pool
4 * Copyright (C) 2002 Ingo Molnar
6 * Derived from the taskqueue/keventd code by:
7 * David Woodhouse <dwmw2@infradead.org>
9 * Kai Petzke <wpp@marie.physik.tu-berlin.de>
10 * Theodore Ts'o <tytso@mit.edu>
12 * Made to use alloc_percpu by Christoph Lameter.
14 * Copyright (C) 2010 SUSE Linux Products GmbH
15 * Copyright (C) 2010 Tejun Heo <tj@kernel.org>
17 * This is the generic async execution mechanism. Work items as are
18 * executed in process context. The worker pool is shared and
19 * automatically managed. There are two worker pools for each CPU (one for
20 * normal work items and the other for high priority ones) and some extra
21 * pools for workqueues which are not bound to any specific CPU - the
22 * number of these backing pools is dynamic.
24 * Please read Documentation/core-api/workqueue.rst for details.
27 #include <linux/export.h>
28 #include <linux/kernel.h>
29 #include <linux/sched.h>
30 #include <linux/init.h>
31 #include <linux/signal.h>
32 #include <linux/completion.h>
33 #include <linux/workqueue.h>
34 #include <linux/slab.h>
35 #include <linux/cpu.h>
36 #include <linux/notifier.h>
37 #include <linux/kthread.h>
38 #include <linux/hardirq.h>
39 #include <linux/mempolicy.h>
40 #include <linux/freezer.h>
41 #include <linux/debug_locks.h>
42 #include <linux/lockdep.h>
43 #include <linux/idr.h>
44 #include <linux/jhash.h>
45 #include <linux/hashtable.h>
46 #include <linux/rculist.h>
47 #include <linux/nodemask.h>
48 #include <linux/moduleparam.h>
49 #include <linux/uaccess.h>
50 #include <linux/sched/isolation.h>
51 #include <linux/nmi.h>
53 #include "workqueue_internal.h"
59 * A bound pool is either associated or disassociated with its CPU.
60 * While associated (!DISASSOCIATED), all workers are bound to the
61 * CPU and none has %WORKER_UNBOUND set and concurrency management
64 * While DISASSOCIATED, the cpu may be offline and all workers have
65 * %WORKER_UNBOUND set and concurrency management disabled, and may
66 * be executing on any CPU. The pool behaves as an unbound one.
68 * Note that DISASSOCIATED should be flipped only while holding
69 * attach_mutex to avoid changing binding state while
70 * worker_attach_to_pool() is in progress.
72 POOL_MANAGER_ACTIVE
= 1 << 0, /* being managed */
73 POOL_DISASSOCIATED
= 1 << 2, /* cpu can't serve workers */
76 WORKER_DIE
= 1 << 1, /* die die die */
77 WORKER_IDLE
= 1 << 2, /* is idle */
78 WORKER_PREP
= 1 << 3, /* preparing to run works */
79 WORKER_CPU_INTENSIVE
= 1 << 6, /* cpu intensive */
80 WORKER_UNBOUND
= 1 << 7, /* worker is unbound */
81 WORKER_REBOUND
= 1 << 8, /* worker was rebound */
83 WORKER_NOT_RUNNING
= WORKER_PREP
| WORKER_CPU_INTENSIVE
|
84 WORKER_UNBOUND
| WORKER_REBOUND
,
86 NR_STD_WORKER_POOLS
= 2, /* # standard pools per cpu */
88 UNBOUND_POOL_HASH_ORDER
= 6, /* hashed by pool->attrs */
89 BUSY_WORKER_HASH_ORDER
= 6, /* 64 pointers */
91 MAX_IDLE_WORKERS_RATIO
= 4, /* 1/4 of busy can be idle */
92 IDLE_WORKER_TIMEOUT
= 300 * HZ
, /* keep idle ones for 5 mins */
94 MAYDAY_INITIAL_TIMEOUT
= HZ
/ 100 >= 2 ? HZ
/ 100 : 2,
95 /* call for help after 10ms
97 MAYDAY_INTERVAL
= HZ
/ 10, /* and then every 100ms */
98 CREATE_COOLDOWN
= HZ
, /* time to breath after fail */
101 * Rescue workers are used only on emergencies and shared by
102 * all cpus. Give MIN_NICE.
104 RESCUER_NICE_LEVEL
= MIN_NICE
,
105 HIGHPRI_NICE_LEVEL
= MIN_NICE
,
111 * Structure fields follow one of the following exclusion rules.
113 * I: Modifiable by initialization/destruction paths and read-only for
116 * P: Preemption protected. Disabling preemption is enough and should
117 * only be modified and accessed from the local cpu.
119 * L: pool->lock protected. Access with pool->lock held.
121 * X: During normal operation, modification requires pool->lock and should
122 * be done only from local cpu. Either disabling preemption on local
123 * cpu or grabbing pool->lock is enough for read access. If
124 * POOL_DISASSOCIATED is set, it's identical to L.
126 * A: pool->attach_mutex protected.
128 * PL: wq_pool_mutex protected.
130 * PR: wq_pool_mutex protected for writes. Sched-RCU protected for reads.
132 * PW: wq_pool_mutex and wq->mutex protected for writes. Either for reads.
134 * PWR: wq_pool_mutex and wq->mutex protected for writes. Either or
135 * sched-RCU for reads.
137 * WQ: wq->mutex protected.
139 * WR: wq->mutex protected for writes. Sched-RCU protected for reads.
141 * MD: wq_mayday_lock protected.
144 /* struct worker is defined in workqueue_internal.h */
147 spinlock_t lock
; /* the pool lock */
148 int cpu
; /* I: the associated cpu */
149 int node
; /* I: the associated node ID */
150 int id
; /* I: pool ID */
151 unsigned int flags
; /* X: flags */
153 unsigned long watchdog_ts
; /* L: watchdog timestamp */
155 struct list_head worklist
; /* L: list of pending works */
156 int nr_workers
; /* L: total number of workers */
158 /* nr_idle includes the ones off idle_list for rebinding */
159 int nr_idle
; /* L: currently idle ones */
161 struct list_head idle_list
; /* X: list of idle workers */
162 struct timer_list idle_timer
; /* L: worker idle timeout */
163 struct timer_list mayday_timer
; /* L: SOS timer for workers */
165 /* a workers is either on busy_hash or idle_list, or the manager */
166 DECLARE_HASHTABLE(busy_hash
, BUSY_WORKER_HASH_ORDER
);
167 /* L: hash of busy workers */
169 /* see manage_workers() for details on the two manager mutexes */
170 struct worker
*manager
; /* L: purely informational */
171 struct mutex attach_mutex
; /* attach/detach exclusion */
172 struct list_head workers
; /* A: attached workers */
173 struct completion
*detach_completion
; /* all workers detached */
175 struct ida worker_ida
; /* worker IDs for task name */
177 struct workqueue_attrs
*attrs
; /* I: worker attributes */
178 struct hlist_node hash_node
; /* PL: unbound_pool_hash node */
179 int refcnt
; /* PL: refcnt for unbound pools */
182 * The current concurrency level. As it's likely to be accessed
183 * from other CPUs during try_to_wake_up(), put it in a separate
186 atomic_t nr_running ____cacheline_aligned_in_smp
;
189 * Destruction of pool is sched-RCU protected to allow dereferences
190 * from get_work_pool().
193 } ____cacheline_aligned_in_smp
;
196 * The per-pool workqueue. While queued, the lower WORK_STRUCT_FLAG_BITS
197 * of work_struct->data are used for flags and the remaining high bits
198 * point to the pwq; thus, pwqs need to be aligned at two's power of the
199 * number of flag bits.
201 struct pool_workqueue
{
202 struct worker_pool
*pool
; /* I: the associated pool */
203 struct workqueue_struct
*wq
; /* I: the owning workqueue */
204 int work_color
; /* L: current color */
205 int flush_color
; /* L: flushing color */
206 int refcnt
; /* L: reference count */
207 int nr_in_flight
[WORK_NR_COLORS
];
208 /* L: nr of in_flight works */
209 int nr_active
; /* L: nr of active works */
210 int max_active
; /* L: max active works */
211 struct list_head delayed_works
; /* L: delayed works */
212 struct list_head pwqs_node
; /* WR: node on wq->pwqs */
213 struct list_head mayday_node
; /* MD: node on wq->maydays */
216 * Release of unbound pwq is punted to system_wq. See put_pwq()
217 * and pwq_unbound_release_workfn() for details. pool_workqueue
218 * itself is also sched-RCU protected so that the first pwq can be
219 * determined without grabbing wq->mutex.
221 struct work_struct unbound_release_work
;
223 } __aligned(1 << WORK_STRUCT_FLAG_BITS
);
226 * Structure used to wait for workqueue flush.
229 struct list_head list
; /* WQ: list of flushers */
230 int flush_color
; /* WQ: flush color waiting for */
231 struct completion done
; /* flush completion */
237 * The externally visible workqueue. It relays the issued work items to
238 * the appropriate worker_pool through its pool_workqueues.
240 struct workqueue_struct
{
241 struct list_head pwqs
; /* WR: all pwqs of this wq */
242 struct list_head list
; /* PR: list of all workqueues */
244 struct mutex mutex
; /* protects this wq */
245 int work_color
; /* WQ: current work color */
246 int flush_color
; /* WQ: current flush color */
247 atomic_t nr_pwqs_to_flush
; /* flush in progress */
248 struct wq_flusher
*first_flusher
; /* WQ: first flusher */
249 struct list_head flusher_queue
; /* WQ: flush waiters */
250 struct list_head flusher_overflow
; /* WQ: flush overflow list */
252 struct list_head maydays
; /* MD: pwqs requesting rescue */
253 struct worker
*rescuer
; /* I: rescue worker */
255 int nr_drainers
; /* WQ: drain in progress */
256 int saved_max_active
; /* WQ: saved pwq max_active */
258 struct workqueue_attrs
*unbound_attrs
; /* PW: only for unbound wqs */
259 struct pool_workqueue
*dfl_pwq
; /* PW: only for unbound wqs */
262 struct wq_device
*wq_dev
; /* I: for sysfs interface */
264 #ifdef CONFIG_LOCKDEP
265 struct lockdep_map lockdep_map
;
267 char name
[WQ_NAME_LEN
]; /* I: workqueue name */
270 * Destruction of workqueue_struct is sched-RCU protected to allow
271 * walking the workqueues list without grabbing wq_pool_mutex.
272 * This is used to dump all workqueues from sysrq.
276 /* hot fields used during command issue, aligned to cacheline */
277 unsigned int flags ____cacheline_aligned
; /* WQ: WQ_* flags */
278 struct pool_workqueue __percpu
*cpu_pwqs
; /* I: per-cpu pwqs */
279 struct pool_workqueue __rcu
*numa_pwq_tbl
[]; /* PWR: unbound pwqs indexed by node */
282 static struct kmem_cache
*pwq_cache
;
284 static cpumask_var_t
*wq_numa_possible_cpumask
;
285 /* possible CPUs of each node */
287 static bool wq_disable_numa
;
288 module_param_named(disable_numa
, wq_disable_numa
, bool, 0444);
290 /* see the comment above the definition of WQ_POWER_EFFICIENT */
291 static bool wq_power_efficient
= IS_ENABLED(CONFIG_WQ_POWER_EFFICIENT_DEFAULT
);
292 module_param_named(power_efficient
, wq_power_efficient
, bool, 0444);
294 static bool wq_online
; /* can kworkers be created yet? */
296 static bool wq_numa_enabled
; /* unbound NUMA affinity enabled */
298 /* buf for wq_update_unbound_numa_attrs(), protected by CPU hotplug exclusion */
299 static struct workqueue_attrs
*wq_update_unbound_numa_attrs_buf
;
301 static DEFINE_MUTEX(wq_pool_mutex
); /* protects pools and workqueues list */
302 static DEFINE_SPINLOCK(wq_mayday_lock
); /* protects wq->maydays list */
303 static DECLARE_WAIT_QUEUE_HEAD(wq_manager_wait
); /* wait for manager to go away */
305 static LIST_HEAD(workqueues
); /* PR: list of all workqueues */
306 static bool workqueue_freezing
; /* PL: have wqs started freezing? */
308 /* PL: allowable cpus for unbound wqs and work items */
309 static cpumask_var_t wq_unbound_cpumask
;
311 /* CPU where unbound work was last round robin scheduled from this CPU */
312 static DEFINE_PER_CPU(int, wq_rr_cpu_last
);
315 * Local execution of unbound work items is no longer guaranteed. The
316 * following always forces round-robin CPU selection on unbound work items
317 * to uncover usages which depend on it.
319 #ifdef CONFIG_DEBUG_WQ_FORCE_RR_CPU
320 static bool wq_debug_force_rr_cpu
= true;
322 static bool wq_debug_force_rr_cpu
= false;
324 module_param_named(debug_force_rr_cpu
, wq_debug_force_rr_cpu
, bool, 0644);
326 /* the per-cpu worker pools */
327 static DEFINE_PER_CPU_SHARED_ALIGNED(struct worker_pool
[NR_STD_WORKER_POOLS
], cpu_worker_pools
);
329 static DEFINE_IDR(worker_pool_idr
); /* PR: idr of all pools */
331 /* PL: hash of all unbound pools keyed by pool->attrs */
332 static DEFINE_HASHTABLE(unbound_pool_hash
, UNBOUND_POOL_HASH_ORDER
);
334 /* I: attributes used when instantiating standard unbound pools on demand */
335 static struct workqueue_attrs
*unbound_std_wq_attrs
[NR_STD_WORKER_POOLS
];
337 /* I: attributes used when instantiating ordered pools on demand */
338 static struct workqueue_attrs
*ordered_wq_attrs
[NR_STD_WORKER_POOLS
];
340 struct workqueue_struct
*system_wq __read_mostly
;
341 EXPORT_SYMBOL(system_wq
);
342 struct workqueue_struct
*system_highpri_wq __read_mostly
;
343 EXPORT_SYMBOL_GPL(system_highpri_wq
);
344 struct workqueue_struct
*system_long_wq __read_mostly
;
345 EXPORT_SYMBOL_GPL(system_long_wq
);
346 struct workqueue_struct
*system_unbound_wq __read_mostly
;
347 EXPORT_SYMBOL_GPL(system_unbound_wq
);
348 struct workqueue_struct
*system_freezable_wq __read_mostly
;
349 EXPORT_SYMBOL_GPL(system_freezable_wq
);
350 struct workqueue_struct
*system_power_efficient_wq __read_mostly
;
351 EXPORT_SYMBOL_GPL(system_power_efficient_wq
);
352 struct workqueue_struct
*system_freezable_power_efficient_wq __read_mostly
;
353 EXPORT_SYMBOL_GPL(system_freezable_power_efficient_wq
);
355 static int worker_thread(void *__worker
);
356 static void workqueue_sysfs_unregister(struct workqueue_struct
*wq
);
358 #define CREATE_TRACE_POINTS
359 #include <trace/events/workqueue.h>
361 #define assert_rcu_or_pool_mutex() \
362 RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held() && \
363 !lockdep_is_held(&wq_pool_mutex), \
364 "sched RCU or wq_pool_mutex should be held")
366 #define assert_rcu_or_wq_mutex(wq) \
367 RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held() && \
368 !lockdep_is_held(&wq->mutex), \
369 "sched RCU or wq->mutex should be held")
371 #define assert_rcu_or_wq_mutex_or_pool_mutex(wq) \
372 RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held() && \
373 !lockdep_is_held(&wq->mutex) && \
374 !lockdep_is_held(&wq_pool_mutex), \
375 "sched RCU, wq->mutex or wq_pool_mutex should be held")
377 #define for_each_cpu_worker_pool(pool, cpu) \
378 for ((pool) = &per_cpu(cpu_worker_pools, cpu)[0]; \
379 (pool) < &per_cpu(cpu_worker_pools, cpu)[NR_STD_WORKER_POOLS]; \
383 * for_each_pool - iterate through all worker_pools in the system
384 * @pool: iteration cursor
385 * @pi: integer used for iteration
387 * This must be called either with wq_pool_mutex held or sched RCU read
388 * locked. If the pool needs to be used beyond the locking in effect, the
389 * caller is responsible for guaranteeing that the pool stays online.
391 * The if/else clause exists only for the lockdep assertion and can be
394 #define for_each_pool(pool, pi) \
395 idr_for_each_entry(&worker_pool_idr, pool, pi) \
396 if (({ assert_rcu_or_pool_mutex(); false; })) { } \
400 * for_each_pool_worker - iterate through all workers of a worker_pool
401 * @worker: iteration cursor
402 * @pool: worker_pool to iterate workers of
404 * This must be called with @pool->attach_mutex.
406 * The if/else clause exists only for the lockdep assertion and can be
409 #define for_each_pool_worker(worker, pool) \
410 list_for_each_entry((worker), &(pool)->workers, node) \
411 if (({ lockdep_assert_held(&pool->attach_mutex); false; })) { } \
415 * for_each_pwq - iterate through all pool_workqueues of the specified workqueue
416 * @pwq: iteration cursor
417 * @wq: the target workqueue
419 * This must be called either with wq->mutex held or sched RCU read locked.
420 * If the pwq needs to be used beyond the locking in effect, the caller is
421 * responsible for guaranteeing that the pwq stays online.
423 * The if/else clause exists only for the lockdep assertion and can be
426 #define for_each_pwq(pwq, wq) \
427 list_for_each_entry_rcu((pwq), &(wq)->pwqs, pwqs_node) \
428 if (({ assert_rcu_or_wq_mutex(wq); false; })) { } \
431 #ifdef CONFIG_DEBUG_OBJECTS_WORK
433 static struct debug_obj_descr work_debug_descr
;
435 static void *work_debug_hint(void *addr
)
437 return ((struct work_struct
*) addr
)->func
;
440 static bool work_is_static_object(void *addr
)
442 struct work_struct
*work
= addr
;
444 return test_bit(WORK_STRUCT_STATIC_BIT
, work_data_bits(work
));
448 * fixup_init is called when:
449 * - an active object is initialized
451 static bool work_fixup_init(void *addr
, enum debug_obj_state state
)
453 struct work_struct
*work
= addr
;
456 case ODEBUG_STATE_ACTIVE
:
457 cancel_work_sync(work
);
458 debug_object_init(work
, &work_debug_descr
);
466 * fixup_free is called when:
467 * - an active object is freed
469 static bool work_fixup_free(void *addr
, enum debug_obj_state state
)
471 struct work_struct
*work
= addr
;
474 case ODEBUG_STATE_ACTIVE
:
475 cancel_work_sync(work
);
476 debug_object_free(work
, &work_debug_descr
);
483 static struct debug_obj_descr work_debug_descr
= {
484 .name
= "work_struct",
485 .debug_hint
= work_debug_hint
,
486 .is_static_object
= work_is_static_object
,
487 .fixup_init
= work_fixup_init
,
488 .fixup_free
= work_fixup_free
,
491 static inline void debug_work_activate(struct work_struct
*work
)
493 debug_object_activate(work
, &work_debug_descr
);
496 static inline void debug_work_deactivate(struct work_struct
*work
)
498 debug_object_deactivate(work
, &work_debug_descr
);
501 void __init_work(struct work_struct
*work
, int onstack
)
504 debug_object_init_on_stack(work
, &work_debug_descr
);
506 debug_object_init(work
, &work_debug_descr
);
508 EXPORT_SYMBOL_GPL(__init_work
);
510 void destroy_work_on_stack(struct work_struct
*work
)
512 debug_object_free(work
, &work_debug_descr
);
514 EXPORT_SYMBOL_GPL(destroy_work_on_stack
);
516 void destroy_delayed_work_on_stack(struct delayed_work
*work
)
518 destroy_timer_on_stack(&work
->timer
);
519 debug_object_free(&work
->work
, &work_debug_descr
);
521 EXPORT_SYMBOL_GPL(destroy_delayed_work_on_stack
);
524 static inline void debug_work_activate(struct work_struct
*work
) { }
525 static inline void debug_work_deactivate(struct work_struct
*work
) { }
529 * worker_pool_assign_id - allocate ID and assing it to @pool
530 * @pool: the pool pointer of interest
532 * Returns 0 if ID in [0, WORK_OFFQ_POOL_NONE) is allocated and assigned
533 * successfully, -errno on failure.
535 static int worker_pool_assign_id(struct worker_pool
*pool
)
539 lockdep_assert_held(&wq_pool_mutex
);
541 ret
= idr_alloc(&worker_pool_idr
, pool
, 0, WORK_OFFQ_POOL_NONE
,
551 * unbound_pwq_by_node - return the unbound pool_workqueue for the given node
552 * @wq: the target workqueue
555 * This must be called with any of wq_pool_mutex, wq->mutex or sched RCU
557 * If the pwq needs to be used beyond the locking in effect, the caller is
558 * responsible for guaranteeing that the pwq stays online.
560 * Return: The unbound pool_workqueue for @node.
562 static struct pool_workqueue
*unbound_pwq_by_node(struct workqueue_struct
*wq
,
565 assert_rcu_or_wq_mutex_or_pool_mutex(wq
);
568 * XXX: @node can be NUMA_NO_NODE if CPU goes offline while a
569 * delayed item is pending. The plan is to keep CPU -> NODE
570 * mapping valid and stable across CPU on/offlines. Once that
571 * happens, this workaround can be removed.
573 if (unlikely(node
== NUMA_NO_NODE
))
576 return rcu_dereference_raw(wq
->numa_pwq_tbl
[node
]);
579 static unsigned int work_color_to_flags(int color
)
581 return color
<< WORK_STRUCT_COLOR_SHIFT
;
584 static int get_work_color(struct work_struct
*work
)
586 return (*work_data_bits(work
) >> WORK_STRUCT_COLOR_SHIFT
) &
587 ((1 << WORK_STRUCT_COLOR_BITS
) - 1);
590 static int work_next_color(int color
)
592 return (color
+ 1) % WORK_NR_COLORS
;
596 * While queued, %WORK_STRUCT_PWQ is set and non flag bits of a work's data
597 * contain the pointer to the queued pwq. Once execution starts, the flag
598 * is cleared and the high bits contain OFFQ flags and pool ID.
600 * set_work_pwq(), set_work_pool_and_clear_pending(), mark_work_canceling()
601 * and clear_work_data() can be used to set the pwq, pool or clear
602 * work->data. These functions should only be called while the work is
603 * owned - ie. while the PENDING bit is set.
605 * get_work_pool() and get_work_pwq() can be used to obtain the pool or pwq
606 * corresponding to a work. Pool is available once the work has been
607 * queued anywhere after initialization until it is sync canceled. pwq is
608 * available only while the work item is queued.
610 * %WORK_OFFQ_CANCELING is used to mark a work item which is being
611 * canceled. While being canceled, a work item may have its PENDING set
612 * but stay off timer and worklist for arbitrarily long and nobody should
613 * try to steal the PENDING bit.
615 static inline void set_work_data(struct work_struct
*work
, unsigned long data
,
618 WARN_ON_ONCE(!work_pending(work
));
619 atomic_long_set(&work
->data
, data
| flags
| work_static(work
));
622 static void set_work_pwq(struct work_struct
*work
, struct pool_workqueue
*pwq
,
623 unsigned long extra_flags
)
625 set_work_data(work
, (unsigned long)pwq
,
626 WORK_STRUCT_PENDING
| WORK_STRUCT_PWQ
| extra_flags
);
629 static void set_work_pool_and_keep_pending(struct work_struct
*work
,
632 set_work_data(work
, (unsigned long)pool_id
<< WORK_OFFQ_POOL_SHIFT
,
633 WORK_STRUCT_PENDING
);
636 static void set_work_pool_and_clear_pending(struct work_struct
*work
,
640 * The following wmb is paired with the implied mb in
641 * test_and_set_bit(PENDING) and ensures all updates to @work made
642 * here are visible to and precede any updates by the next PENDING
646 set_work_data(work
, (unsigned long)pool_id
<< WORK_OFFQ_POOL_SHIFT
, 0);
648 * The following mb guarantees that previous clear of a PENDING bit
649 * will not be reordered with any speculative LOADS or STORES from
650 * work->current_func, which is executed afterwards. This possible
651 * reordering can lead to a missed execution on attempt to qeueue
652 * the same @work. E.g. consider this case:
655 * ---------------------------- --------------------------------
657 * 1 STORE event_indicated
658 * 2 queue_work_on() {
659 * 3 test_and_set_bit(PENDING)
660 * 4 } set_..._and_clear_pending() {
661 * 5 set_work_data() # clear bit
663 * 7 work->current_func() {
664 * 8 LOAD event_indicated
667 * Without an explicit full barrier speculative LOAD on line 8 can
668 * be executed before CPU#0 does STORE on line 1. If that happens,
669 * CPU#0 observes the PENDING bit is still set and new execution of
670 * a @work is not queued in a hope, that CPU#1 will eventually
671 * finish the queued @work. Meanwhile CPU#1 does not see
672 * event_indicated is set, because speculative LOAD was executed
673 * before actual STORE.
678 static void clear_work_data(struct work_struct
*work
)
680 smp_wmb(); /* see set_work_pool_and_clear_pending() */
681 set_work_data(work
, WORK_STRUCT_NO_POOL
, 0);
684 static struct pool_workqueue
*get_work_pwq(struct work_struct
*work
)
686 unsigned long data
= atomic_long_read(&work
->data
);
688 if (data
& WORK_STRUCT_PWQ
)
689 return (void *)(data
& WORK_STRUCT_WQ_DATA_MASK
);
695 * get_work_pool - return the worker_pool a given work was associated with
696 * @work: the work item of interest
698 * Pools are created and destroyed under wq_pool_mutex, and allows read
699 * access under sched-RCU read lock. As such, this function should be
700 * called under wq_pool_mutex or with preemption disabled.
702 * All fields of the returned pool are accessible as long as the above
703 * mentioned locking is in effect. If the returned pool needs to be used
704 * beyond the critical section, the caller is responsible for ensuring the
705 * returned pool is and stays online.
707 * Return: The worker_pool @work was last associated with. %NULL if none.
709 static struct worker_pool
*get_work_pool(struct work_struct
*work
)
711 unsigned long data
= atomic_long_read(&work
->data
);
714 assert_rcu_or_pool_mutex();
716 if (data
& WORK_STRUCT_PWQ
)
717 return ((struct pool_workqueue
*)
718 (data
& WORK_STRUCT_WQ_DATA_MASK
))->pool
;
720 pool_id
= data
>> WORK_OFFQ_POOL_SHIFT
;
721 if (pool_id
== WORK_OFFQ_POOL_NONE
)
724 return idr_find(&worker_pool_idr
, pool_id
);
728 * get_work_pool_id - return the worker pool ID a given work is associated with
729 * @work: the work item of interest
731 * Return: The worker_pool ID @work was last associated with.
732 * %WORK_OFFQ_POOL_NONE if none.
734 static int get_work_pool_id(struct work_struct
*work
)
736 unsigned long data
= atomic_long_read(&work
->data
);
738 if (data
& WORK_STRUCT_PWQ
)
739 return ((struct pool_workqueue
*)
740 (data
& WORK_STRUCT_WQ_DATA_MASK
))->pool
->id
;
742 return data
>> WORK_OFFQ_POOL_SHIFT
;
745 static void mark_work_canceling(struct work_struct
*work
)
747 unsigned long pool_id
= get_work_pool_id(work
);
749 pool_id
<<= WORK_OFFQ_POOL_SHIFT
;
750 set_work_data(work
, pool_id
| WORK_OFFQ_CANCELING
, WORK_STRUCT_PENDING
);
753 static bool work_is_canceling(struct work_struct
*work
)
755 unsigned long data
= atomic_long_read(&work
->data
);
757 return !(data
& WORK_STRUCT_PWQ
) && (data
& WORK_OFFQ_CANCELING
);
761 * Policy functions. These define the policies on how the global worker
762 * pools are managed. Unless noted otherwise, these functions assume that
763 * they're being called with pool->lock held.
766 static bool __need_more_worker(struct worker_pool
*pool
)
768 return !atomic_read(&pool
->nr_running
);
772 * Need to wake up a worker? Called from anything but currently
775 * Note that, because unbound workers never contribute to nr_running, this
776 * function will always return %true for unbound pools as long as the
777 * worklist isn't empty.
779 static bool need_more_worker(struct worker_pool
*pool
)
781 return !list_empty(&pool
->worklist
) && __need_more_worker(pool
);
784 /* Can I start working? Called from busy but !running workers. */
785 static bool may_start_working(struct worker_pool
*pool
)
787 return pool
->nr_idle
;
790 /* Do I need to keep working? Called from currently running workers. */
791 static bool keep_working(struct worker_pool
*pool
)
793 return !list_empty(&pool
->worklist
) &&
794 atomic_read(&pool
->nr_running
) <= 1;
797 /* Do we need a new worker? Called from manager. */
798 static bool need_to_create_worker(struct worker_pool
*pool
)
800 return need_more_worker(pool
) && !may_start_working(pool
);
803 /* Do we have too many workers and should some go away? */
804 static bool too_many_workers(struct worker_pool
*pool
)
806 bool managing
= pool
->flags
& POOL_MANAGER_ACTIVE
;
807 int nr_idle
= pool
->nr_idle
+ managing
; /* manager is considered idle */
808 int nr_busy
= pool
->nr_workers
- nr_idle
;
810 return nr_idle
> 2 && (nr_idle
- 2) * MAX_IDLE_WORKERS_RATIO
>= nr_busy
;
817 /* Return the first idle worker. Safe with preemption disabled */
818 static struct worker
*first_idle_worker(struct worker_pool
*pool
)
820 if (unlikely(list_empty(&pool
->idle_list
)))
823 return list_first_entry(&pool
->idle_list
, struct worker
, entry
);
827 * wake_up_worker - wake up an idle worker
828 * @pool: worker pool to wake worker from
830 * Wake up the first idle worker of @pool.
833 * spin_lock_irq(pool->lock).
835 static void wake_up_worker(struct worker_pool
*pool
)
837 struct worker
*worker
= first_idle_worker(pool
);
840 wake_up_process(worker
->task
);
844 * wq_worker_waking_up - a worker is waking up
845 * @task: task waking up
846 * @cpu: CPU @task is waking up to
848 * This function is called during try_to_wake_up() when a worker is
852 * spin_lock_irq(rq->lock)
854 void wq_worker_waking_up(struct task_struct
*task
, int cpu
)
856 struct worker
*worker
= kthread_data(task
);
858 if (!(worker
->flags
& WORKER_NOT_RUNNING
)) {
859 WARN_ON_ONCE(worker
->pool
->cpu
!= cpu
);
860 atomic_inc(&worker
->pool
->nr_running
);
865 * wq_worker_sleeping - a worker is going to sleep
866 * @task: task going to sleep
868 * This function is called during schedule() when a busy worker is
869 * going to sleep. Worker on the same cpu can be woken up by
870 * returning pointer to its task.
873 * spin_lock_irq(rq->lock)
876 * Worker task on @cpu to wake up, %NULL if none.
878 struct task_struct
*wq_worker_sleeping(struct task_struct
*task
)
880 struct worker
*worker
= kthread_data(task
), *to_wakeup
= NULL
;
881 struct worker_pool
*pool
;
884 * Rescuers, which may not have all the fields set up like normal
885 * workers, also reach here, let's not access anything before
886 * checking NOT_RUNNING.
888 if (worker
->flags
& WORKER_NOT_RUNNING
)
893 /* this can only happen on the local cpu */
894 if (WARN_ON_ONCE(pool
->cpu
!= raw_smp_processor_id()))
898 * The counterpart of the following dec_and_test, implied mb,
899 * worklist not empty test sequence is in insert_work().
900 * Please read comment there.
902 * NOT_RUNNING is clear. This means that we're bound to and
903 * running on the local cpu w/ rq lock held and preemption
904 * disabled, which in turn means that none else could be
905 * manipulating idle_list, so dereferencing idle_list without pool
908 if (atomic_dec_and_test(&pool
->nr_running
) &&
909 !list_empty(&pool
->worklist
))
910 to_wakeup
= first_idle_worker(pool
);
911 return to_wakeup
? to_wakeup
->task
: NULL
;
915 * worker_set_flags - set worker flags and adjust nr_running accordingly
917 * @flags: flags to set
919 * Set @flags in @worker->flags and adjust nr_running accordingly.
922 * spin_lock_irq(pool->lock)
924 static inline void worker_set_flags(struct worker
*worker
, unsigned int flags
)
926 struct worker_pool
*pool
= worker
->pool
;
928 WARN_ON_ONCE(worker
->task
!= current
);
930 /* If transitioning into NOT_RUNNING, adjust nr_running. */
931 if ((flags
& WORKER_NOT_RUNNING
) &&
932 !(worker
->flags
& WORKER_NOT_RUNNING
)) {
933 atomic_dec(&pool
->nr_running
);
936 worker
->flags
|= flags
;
940 * worker_clr_flags - clear worker flags and adjust nr_running accordingly
942 * @flags: flags to clear
944 * Clear @flags in @worker->flags and adjust nr_running accordingly.
947 * spin_lock_irq(pool->lock)
949 static inline void worker_clr_flags(struct worker
*worker
, unsigned int flags
)
951 struct worker_pool
*pool
= worker
->pool
;
952 unsigned int oflags
= worker
->flags
;
954 WARN_ON_ONCE(worker
->task
!= current
);
956 worker
->flags
&= ~flags
;
959 * If transitioning out of NOT_RUNNING, increment nr_running. Note
960 * that the nested NOT_RUNNING is not a noop. NOT_RUNNING is mask
961 * of multiple flags, not a single flag.
963 if ((flags
& WORKER_NOT_RUNNING
) && (oflags
& WORKER_NOT_RUNNING
))
964 if (!(worker
->flags
& WORKER_NOT_RUNNING
))
965 atomic_inc(&pool
->nr_running
);
969 * find_worker_executing_work - find worker which is executing a work
970 * @pool: pool of interest
971 * @work: work to find worker for
973 * Find a worker which is executing @work on @pool by searching
974 * @pool->busy_hash which is keyed by the address of @work. For a worker
975 * to match, its current execution should match the address of @work and
976 * its work function. This is to avoid unwanted dependency between
977 * unrelated work executions through a work item being recycled while still
980 * This is a bit tricky. A work item may be freed once its execution
981 * starts and nothing prevents the freed area from being recycled for
982 * another work item. If the same work item address ends up being reused
983 * before the original execution finishes, workqueue will identify the
984 * recycled work item as currently executing and make it wait until the
985 * current execution finishes, introducing an unwanted dependency.
987 * This function checks the work item address and work function to avoid
988 * false positives. Note that this isn't complete as one may construct a
989 * work function which can introduce dependency onto itself through a
990 * recycled work item. Well, if somebody wants to shoot oneself in the
991 * foot that badly, there's only so much we can do, and if such deadlock
992 * actually occurs, it should be easy to locate the culprit work function.
995 * spin_lock_irq(pool->lock).
998 * Pointer to worker which is executing @work if found, %NULL
1001 static struct worker
*find_worker_executing_work(struct worker_pool
*pool
,
1002 struct work_struct
*work
)
1004 struct worker
*worker
;
1006 hash_for_each_possible(pool
->busy_hash
, worker
, hentry
,
1007 (unsigned long)work
)
1008 if (worker
->current_work
== work
&&
1009 worker
->current_func
== work
->func
)
1016 * move_linked_works - move linked works to a list
1017 * @work: start of series of works to be scheduled
1018 * @head: target list to append @work to
1019 * @nextp: out parameter for nested worklist walking
1021 * Schedule linked works starting from @work to @head. Work series to
1022 * be scheduled starts at @work and includes any consecutive work with
1023 * WORK_STRUCT_LINKED set in its predecessor.
1025 * If @nextp is not NULL, it's updated to point to the next work of
1026 * the last scheduled work. This allows move_linked_works() to be
1027 * nested inside outer list_for_each_entry_safe().
1030 * spin_lock_irq(pool->lock).
1032 static void move_linked_works(struct work_struct
*work
, struct list_head
*head
,
1033 struct work_struct
**nextp
)
1035 struct work_struct
*n
;
1038 * Linked worklist will always end before the end of the list,
1039 * use NULL for list head.
1041 list_for_each_entry_safe_from(work
, n
, NULL
, entry
) {
1042 list_move_tail(&work
->entry
, head
);
1043 if (!(*work_data_bits(work
) & WORK_STRUCT_LINKED
))
1048 * If we're already inside safe list traversal and have moved
1049 * multiple works to the scheduled queue, the next position
1050 * needs to be updated.
1057 * get_pwq - get an extra reference on the specified pool_workqueue
1058 * @pwq: pool_workqueue to get
1060 * Obtain an extra reference on @pwq. The caller should guarantee that
1061 * @pwq has positive refcnt and be holding the matching pool->lock.
1063 static void get_pwq(struct pool_workqueue
*pwq
)
1065 lockdep_assert_held(&pwq
->pool
->lock
);
1066 WARN_ON_ONCE(pwq
->refcnt
<= 0);
1071 * put_pwq - put a pool_workqueue reference
1072 * @pwq: pool_workqueue to put
1074 * Drop a reference of @pwq. If its refcnt reaches zero, schedule its
1075 * destruction. The caller should be holding the matching pool->lock.
1077 static void put_pwq(struct pool_workqueue
*pwq
)
1079 lockdep_assert_held(&pwq
->pool
->lock
);
1080 if (likely(--pwq
->refcnt
))
1082 if (WARN_ON_ONCE(!(pwq
->wq
->flags
& WQ_UNBOUND
)))
1085 * @pwq can't be released under pool->lock, bounce to
1086 * pwq_unbound_release_workfn(). This never recurses on the same
1087 * pool->lock as this path is taken only for unbound workqueues and
1088 * the release work item is scheduled on a per-cpu workqueue. To
1089 * avoid lockdep warning, unbound pool->locks are given lockdep
1090 * subclass of 1 in get_unbound_pool().
1092 schedule_work(&pwq
->unbound_release_work
);
1096 * put_pwq_unlocked - put_pwq() with surrounding pool lock/unlock
1097 * @pwq: pool_workqueue to put (can be %NULL)
1099 * put_pwq() with locking. This function also allows %NULL @pwq.
1101 static void put_pwq_unlocked(struct pool_workqueue
*pwq
)
1105 * As both pwqs and pools are sched-RCU protected, the
1106 * following lock operations are safe.
1108 spin_lock_irq(&pwq
->pool
->lock
);
1110 spin_unlock_irq(&pwq
->pool
->lock
);
1114 static void pwq_activate_delayed_work(struct work_struct
*work
)
1116 struct pool_workqueue
*pwq
= get_work_pwq(work
);
1118 trace_workqueue_activate_work(work
);
1119 if (list_empty(&pwq
->pool
->worklist
))
1120 pwq
->pool
->watchdog_ts
= jiffies
;
1121 move_linked_works(work
, &pwq
->pool
->worklist
, NULL
);
1122 __clear_bit(WORK_STRUCT_DELAYED_BIT
, work_data_bits(work
));
1126 static void pwq_activate_first_delayed(struct pool_workqueue
*pwq
)
1128 struct work_struct
*work
= list_first_entry(&pwq
->delayed_works
,
1129 struct work_struct
, entry
);
1131 pwq_activate_delayed_work(work
);
1135 * pwq_dec_nr_in_flight - decrement pwq's nr_in_flight
1136 * @pwq: pwq of interest
1137 * @color: color of work which left the queue
1139 * A work either has completed or is removed from pending queue,
1140 * decrement nr_in_flight of its pwq and handle workqueue flushing.
1143 * spin_lock_irq(pool->lock).
1145 static void pwq_dec_nr_in_flight(struct pool_workqueue
*pwq
, int color
)
1147 /* uncolored work items don't participate in flushing or nr_active */
1148 if (color
== WORK_NO_COLOR
)
1151 pwq
->nr_in_flight
[color
]--;
1154 if (!list_empty(&pwq
->delayed_works
)) {
1155 /* one down, submit a delayed one */
1156 if (pwq
->nr_active
< pwq
->max_active
)
1157 pwq_activate_first_delayed(pwq
);
1160 /* is flush in progress and are we at the flushing tip? */
1161 if (likely(pwq
->flush_color
!= color
))
1164 /* are there still in-flight works? */
1165 if (pwq
->nr_in_flight
[color
])
1168 /* this pwq is done, clear flush_color */
1169 pwq
->flush_color
= -1;
1172 * If this was the last pwq, wake up the first flusher. It
1173 * will handle the rest.
1175 if (atomic_dec_and_test(&pwq
->wq
->nr_pwqs_to_flush
))
1176 complete(&pwq
->wq
->first_flusher
->done
);
1182 * try_to_grab_pending - steal work item from worklist and disable irq
1183 * @work: work item to steal
1184 * @is_dwork: @work is a delayed_work
1185 * @flags: place to store irq state
1187 * Try to grab PENDING bit of @work. This function can handle @work in any
1188 * stable state - idle, on timer or on worklist.
1191 * 1 if @work was pending and we successfully stole PENDING
1192 * 0 if @work was idle and we claimed PENDING
1193 * -EAGAIN if PENDING couldn't be grabbed at the moment, safe to busy-retry
1194 * -ENOENT if someone else is canceling @work, this state may persist
1195 * for arbitrarily long
1198 * On >= 0 return, the caller owns @work's PENDING bit. To avoid getting
1199 * interrupted while holding PENDING and @work off queue, irq must be
1200 * disabled on entry. This, combined with delayed_work->timer being
1201 * irqsafe, ensures that we return -EAGAIN for finite short period of time.
1203 * On successful return, >= 0, irq is disabled and the caller is
1204 * responsible for releasing it using local_irq_restore(*@flags).
1206 * This function is safe to call from any context including IRQ handler.
1208 static int try_to_grab_pending(struct work_struct
*work
, bool is_dwork
,
1209 unsigned long *flags
)
1211 struct worker_pool
*pool
;
1212 struct pool_workqueue
*pwq
;
1214 local_irq_save(*flags
);
1216 /* try to steal the timer if it exists */
1218 struct delayed_work
*dwork
= to_delayed_work(work
);
1221 * dwork->timer is irqsafe. If del_timer() fails, it's
1222 * guaranteed that the timer is not queued anywhere and not
1223 * running on the local CPU.
1225 if (likely(del_timer(&dwork
->timer
)))
1229 /* try to claim PENDING the normal way */
1230 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT
, work_data_bits(work
)))
1234 * The queueing is in progress, or it is already queued. Try to
1235 * steal it from ->worklist without clearing WORK_STRUCT_PENDING.
1237 pool
= get_work_pool(work
);
1241 spin_lock(&pool
->lock
);
1243 * work->data is guaranteed to point to pwq only while the work
1244 * item is queued on pwq->wq, and both updating work->data to point
1245 * to pwq on queueing and to pool on dequeueing are done under
1246 * pwq->pool->lock. This in turn guarantees that, if work->data
1247 * points to pwq which is associated with a locked pool, the work
1248 * item is currently queued on that pool.
1250 pwq
= get_work_pwq(work
);
1251 if (pwq
&& pwq
->pool
== pool
) {
1252 debug_work_deactivate(work
);
1255 * A delayed work item cannot be grabbed directly because
1256 * it might have linked NO_COLOR work items which, if left
1257 * on the delayed_list, will confuse pwq->nr_active
1258 * management later on and cause stall. Make sure the work
1259 * item is activated before grabbing.
1261 if (*work_data_bits(work
) & WORK_STRUCT_DELAYED
)
1262 pwq_activate_delayed_work(work
);
1264 list_del_init(&work
->entry
);
1265 pwq_dec_nr_in_flight(pwq
, get_work_color(work
));
1267 /* work->data points to pwq iff queued, point to pool */
1268 set_work_pool_and_keep_pending(work
, pool
->id
);
1270 spin_unlock(&pool
->lock
);
1273 spin_unlock(&pool
->lock
);
1275 local_irq_restore(*flags
);
1276 if (work_is_canceling(work
))
1283 * insert_work - insert a work into a pool
1284 * @pwq: pwq @work belongs to
1285 * @work: work to insert
1286 * @head: insertion point
1287 * @extra_flags: extra WORK_STRUCT_* flags to set
1289 * Insert @work which belongs to @pwq after @head. @extra_flags is or'd to
1290 * work_struct flags.
1293 * spin_lock_irq(pool->lock).
1295 static void insert_work(struct pool_workqueue
*pwq
, struct work_struct
*work
,
1296 struct list_head
*head
, unsigned int extra_flags
)
1298 struct worker_pool
*pool
= pwq
->pool
;
1300 /* we own @work, set data and link */
1301 set_work_pwq(work
, pwq
, extra_flags
);
1302 list_add_tail(&work
->entry
, head
);
1306 * Ensure either wq_worker_sleeping() sees the above
1307 * list_add_tail() or we see zero nr_running to avoid workers lying
1308 * around lazily while there are works to be processed.
1312 if (__need_more_worker(pool
))
1313 wake_up_worker(pool
);
1317 * Test whether @work is being queued from another work executing on the
1320 static bool is_chained_work(struct workqueue_struct
*wq
)
1322 struct worker
*worker
;
1324 worker
= current_wq_worker();
1326 * Return %true iff I'm a worker execuing a work item on @wq. If
1327 * I'm @worker, it's safe to dereference it without locking.
1329 return worker
&& worker
->current_pwq
->wq
== wq
;
1333 * When queueing an unbound work item to a wq, prefer local CPU if allowed
1334 * by wq_unbound_cpumask. Otherwise, round robin among the allowed ones to
1335 * avoid perturbing sensitive tasks.
1337 static int wq_select_unbound_cpu(int cpu
)
1339 static bool printed_dbg_warning
;
1342 if (likely(!wq_debug_force_rr_cpu
)) {
1343 if (cpumask_test_cpu(cpu
, wq_unbound_cpumask
))
1345 } else if (!printed_dbg_warning
) {
1346 pr_warn("workqueue: round-robin CPU selection forced, expect performance impact\n");
1347 printed_dbg_warning
= true;
1350 if (cpumask_empty(wq_unbound_cpumask
))
1353 new_cpu
= __this_cpu_read(wq_rr_cpu_last
);
1354 new_cpu
= cpumask_next_and(new_cpu
, wq_unbound_cpumask
, cpu_online_mask
);
1355 if (unlikely(new_cpu
>= nr_cpu_ids
)) {
1356 new_cpu
= cpumask_first_and(wq_unbound_cpumask
, cpu_online_mask
);
1357 if (unlikely(new_cpu
>= nr_cpu_ids
))
1360 __this_cpu_write(wq_rr_cpu_last
, new_cpu
);
1365 static void __queue_work(int cpu
, struct workqueue_struct
*wq
,
1366 struct work_struct
*work
)
1368 struct pool_workqueue
*pwq
;
1369 struct worker_pool
*last_pool
;
1370 struct list_head
*worklist
;
1371 unsigned int work_flags
;
1372 unsigned int req_cpu
= cpu
;
1375 * While a work item is PENDING && off queue, a task trying to
1376 * steal the PENDING will busy-loop waiting for it to either get
1377 * queued or lose PENDING. Grabbing PENDING and queueing should
1378 * happen with IRQ disabled.
1380 lockdep_assert_irqs_disabled();
1382 debug_work_activate(work
);
1384 /* if draining, only works from the same workqueue are allowed */
1385 if (unlikely(wq
->flags
& __WQ_DRAINING
) &&
1386 WARN_ON_ONCE(!is_chained_work(wq
)))
1389 if (req_cpu
== WORK_CPU_UNBOUND
)
1390 cpu
= wq_select_unbound_cpu(raw_smp_processor_id());
1392 /* pwq which will be used unless @work is executing elsewhere */
1393 if (!(wq
->flags
& WQ_UNBOUND
))
1394 pwq
= per_cpu_ptr(wq
->cpu_pwqs
, cpu
);
1396 pwq
= unbound_pwq_by_node(wq
, cpu_to_node(cpu
));
1399 * If @work was previously on a different pool, it might still be
1400 * running there, in which case the work needs to be queued on that
1401 * pool to guarantee non-reentrancy.
1403 last_pool
= get_work_pool(work
);
1404 if (last_pool
&& last_pool
!= pwq
->pool
) {
1405 struct worker
*worker
;
1407 spin_lock(&last_pool
->lock
);
1409 worker
= find_worker_executing_work(last_pool
, work
);
1411 if (worker
&& worker
->current_pwq
->wq
== wq
) {
1412 pwq
= worker
->current_pwq
;
1414 /* meh... not running there, queue here */
1415 spin_unlock(&last_pool
->lock
);
1416 spin_lock(&pwq
->pool
->lock
);
1419 spin_lock(&pwq
->pool
->lock
);
1423 * pwq is determined and locked. For unbound pools, we could have
1424 * raced with pwq release and it could already be dead. If its
1425 * refcnt is zero, repeat pwq selection. Note that pwqs never die
1426 * without another pwq replacing it in the numa_pwq_tbl or while
1427 * work items are executing on it, so the retrying is guaranteed to
1428 * make forward-progress.
1430 if (unlikely(!pwq
->refcnt
)) {
1431 if (wq
->flags
& WQ_UNBOUND
) {
1432 spin_unlock(&pwq
->pool
->lock
);
1437 WARN_ONCE(true, "workqueue: per-cpu pwq for %s on cpu%d has 0 refcnt",
1441 /* pwq determined, queue */
1442 trace_workqueue_queue_work(req_cpu
, pwq
, work
);
1444 if (WARN_ON(!list_empty(&work
->entry
))) {
1445 spin_unlock(&pwq
->pool
->lock
);
1449 pwq
->nr_in_flight
[pwq
->work_color
]++;
1450 work_flags
= work_color_to_flags(pwq
->work_color
);
1452 if (likely(pwq
->nr_active
< pwq
->max_active
)) {
1453 trace_workqueue_activate_work(work
);
1455 worklist
= &pwq
->pool
->worklist
;
1456 if (list_empty(worklist
))
1457 pwq
->pool
->watchdog_ts
= jiffies
;
1459 work_flags
|= WORK_STRUCT_DELAYED
;
1460 worklist
= &pwq
->delayed_works
;
1463 insert_work(pwq
, work
, worklist
, work_flags
);
1465 spin_unlock(&pwq
->pool
->lock
);
1469 * queue_work_on - queue work on specific cpu
1470 * @cpu: CPU number to execute work on
1471 * @wq: workqueue to use
1472 * @work: work to queue
1474 * We queue the work to a specific CPU, the caller must ensure it
1477 * Return: %false if @work was already on a queue, %true otherwise.
1479 bool queue_work_on(int cpu
, struct workqueue_struct
*wq
,
1480 struct work_struct
*work
)
1483 unsigned long flags
;
1485 local_irq_save(flags
);
1487 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT
, work_data_bits(work
))) {
1488 __queue_work(cpu
, wq
, work
);
1492 local_irq_restore(flags
);
1495 EXPORT_SYMBOL(queue_work_on
);
1497 void delayed_work_timer_fn(struct timer_list
*t
)
1499 struct delayed_work
*dwork
= from_timer(dwork
, t
, timer
);
1501 /* should have been called from irqsafe timer with irq already off */
1502 __queue_work(dwork
->cpu
, dwork
->wq
, &dwork
->work
);
1504 EXPORT_SYMBOL(delayed_work_timer_fn
);
1506 static void __queue_delayed_work(int cpu
, struct workqueue_struct
*wq
,
1507 struct delayed_work
*dwork
, unsigned long delay
)
1509 struct timer_list
*timer
= &dwork
->timer
;
1510 struct work_struct
*work
= &dwork
->work
;
1513 WARN_ON_ONCE(timer
->function
!= delayed_work_timer_fn
);
1514 WARN_ON_ONCE(timer_pending(timer
));
1515 WARN_ON_ONCE(!list_empty(&work
->entry
));
1518 * If @delay is 0, queue @dwork->work immediately. This is for
1519 * both optimization and correctness. The earliest @timer can
1520 * expire is on the closest next tick and delayed_work users depend
1521 * on that there's no such delay when @delay is 0.
1524 __queue_work(cpu
, wq
, &dwork
->work
);
1530 timer
->expires
= jiffies
+ delay
;
1532 if (unlikely(cpu
!= WORK_CPU_UNBOUND
))
1533 add_timer_on(timer
, cpu
);
1539 * queue_delayed_work_on - queue work on specific CPU after delay
1540 * @cpu: CPU number to execute work on
1541 * @wq: workqueue to use
1542 * @dwork: work to queue
1543 * @delay: number of jiffies to wait before queueing
1545 * Return: %false if @work was already on a queue, %true otherwise. If
1546 * @delay is zero and @dwork is idle, it will be scheduled for immediate
1549 bool queue_delayed_work_on(int cpu
, struct workqueue_struct
*wq
,
1550 struct delayed_work
*dwork
, unsigned long delay
)
1552 struct work_struct
*work
= &dwork
->work
;
1554 unsigned long flags
;
1556 /* read the comment in __queue_work() */
1557 local_irq_save(flags
);
1559 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT
, work_data_bits(work
))) {
1560 __queue_delayed_work(cpu
, wq
, dwork
, delay
);
1564 local_irq_restore(flags
);
1567 EXPORT_SYMBOL(queue_delayed_work_on
);
1570 * mod_delayed_work_on - modify delay of or queue a delayed work on specific CPU
1571 * @cpu: CPU number to execute work on
1572 * @wq: workqueue to use
1573 * @dwork: work to queue
1574 * @delay: number of jiffies to wait before queueing
1576 * If @dwork is idle, equivalent to queue_delayed_work_on(); otherwise,
1577 * modify @dwork's timer so that it expires after @delay. If @delay is
1578 * zero, @work is guaranteed to be scheduled immediately regardless of its
1581 * Return: %false if @dwork was idle and queued, %true if @dwork was
1582 * pending and its timer was modified.
1584 * This function is safe to call from any context including IRQ handler.
1585 * See try_to_grab_pending() for details.
1587 bool mod_delayed_work_on(int cpu
, struct workqueue_struct
*wq
,
1588 struct delayed_work
*dwork
, unsigned long delay
)
1590 unsigned long flags
;
1594 ret
= try_to_grab_pending(&dwork
->work
, true, &flags
);
1595 } while (unlikely(ret
== -EAGAIN
));
1597 if (likely(ret
>= 0)) {
1598 __queue_delayed_work(cpu
, wq
, dwork
, delay
);
1599 local_irq_restore(flags
);
1602 /* -ENOENT from try_to_grab_pending() becomes %true */
1605 EXPORT_SYMBOL_GPL(mod_delayed_work_on
);
1607 static void rcu_work_rcufn(struct rcu_head
*rcu
)
1609 struct rcu_work
*rwork
= container_of(rcu
, struct rcu_work
, rcu
);
1611 /* read the comment in __queue_work() */
1612 local_irq_disable();
1613 __queue_work(WORK_CPU_UNBOUND
, rwork
->wq
, &rwork
->work
);
1618 * queue_rcu_work - queue work after a RCU grace period
1619 * @wq: workqueue to use
1620 * @rwork: work to queue
1622 * Return: %false if @rwork was already pending, %true otherwise. Note
1623 * that a full RCU grace period is guaranteed only after a %true return.
1624 * While @rwork is guarnateed to be executed after a %false return, the
1625 * execution may happen before a full RCU grace period has passed.
1627 bool queue_rcu_work(struct workqueue_struct
*wq
, struct rcu_work
*rwork
)
1629 struct work_struct
*work
= &rwork
->work
;
1631 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT
, work_data_bits(work
))) {
1633 call_rcu(&rwork
->rcu
, rcu_work_rcufn
);
1639 EXPORT_SYMBOL(queue_rcu_work
);
1642 * worker_enter_idle - enter idle state
1643 * @worker: worker which is entering idle state
1645 * @worker is entering idle state. Update stats and idle timer if
1649 * spin_lock_irq(pool->lock).
1651 static void worker_enter_idle(struct worker
*worker
)
1653 struct worker_pool
*pool
= worker
->pool
;
1655 if (WARN_ON_ONCE(worker
->flags
& WORKER_IDLE
) ||
1656 WARN_ON_ONCE(!list_empty(&worker
->entry
) &&
1657 (worker
->hentry
.next
|| worker
->hentry
.pprev
)))
1660 /* can't use worker_set_flags(), also called from create_worker() */
1661 worker
->flags
|= WORKER_IDLE
;
1663 worker
->last_active
= jiffies
;
1665 /* idle_list is LIFO */
1666 list_add(&worker
->entry
, &pool
->idle_list
);
1668 if (too_many_workers(pool
) && !timer_pending(&pool
->idle_timer
))
1669 mod_timer(&pool
->idle_timer
, jiffies
+ IDLE_WORKER_TIMEOUT
);
1672 * Sanity check nr_running. Because unbind_workers() releases
1673 * pool->lock between setting %WORKER_UNBOUND and zapping
1674 * nr_running, the warning may trigger spuriously. Check iff
1675 * unbind is not in progress.
1677 WARN_ON_ONCE(!(pool
->flags
& POOL_DISASSOCIATED
) &&
1678 pool
->nr_workers
== pool
->nr_idle
&&
1679 atomic_read(&pool
->nr_running
));
1683 * worker_leave_idle - leave idle state
1684 * @worker: worker which is leaving idle state
1686 * @worker is leaving idle state. Update stats.
1689 * spin_lock_irq(pool->lock).
1691 static void worker_leave_idle(struct worker
*worker
)
1693 struct worker_pool
*pool
= worker
->pool
;
1695 if (WARN_ON_ONCE(!(worker
->flags
& WORKER_IDLE
)))
1697 worker_clr_flags(worker
, WORKER_IDLE
);
1699 list_del_init(&worker
->entry
);
1702 static struct worker
*alloc_worker(int node
)
1704 struct worker
*worker
;
1706 worker
= kzalloc_node(sizeof(*worker
), GFP_KERNEL
, node
);
1708 INIT_LIST_HEAD(&worker
->entry
);
1709 INIT_LIST_HEAD(&worker
->scheduled
);
1710 INIT_LIST_HEAD(&worker
->node
);
1711 /* on creation a worker is in !idle && prep state */
1712 worker
->flags
= WORKER_PREP
;
1718 * worker_attach_to_pool() - attach a worker to a pool
1719 * @worker: worker to be attached
1720 * @pool: the target pool
1722 * Attach @worker to @pool. Once attached, the %WORKER_UNBOUND flag and
1723 * cpu-binding of @worker are kept coordinated with the pool across
1726 static void worker_attach_to_pool(struct worker
*worker
,
1727 struct worker_pool
*pool
)
1729 mutex_lock(&pool
->attach_mutex
);
1732 * set_cpus_allowed_ptr() will fail if the cpumask doesn't have any
1733 * online CPUs. It'll be re-applied when any of the CPUs come up.
1735 set_cpus_allowed_ptr(worker
->task
, pool
->attrs
->cpumask
);
1738 * The pool->attach_mutex ensures %POOL_DISASSOCIATED remains
1739 * stable across this function. See the comments above the
1740 * flag definition for details.
1742 if (pool
->flags
& POOL_DISASSOCIATED
)
1743 worker
->flags
|= WORKER_UNBOUND
;
1745 list_add_tail(&worker
->node
, &pool
->workers
);
1747 mutex_unlock(&pool
->attach_mutex
);
1751 * worker_detach_from_pool() - detach a worker from its pool
1752 * @worker: worker which is attached to its pool
1753 * @pool: the pool @worker is attached to
1755 * Undo the attaching which had been done in worker_attach_to_pool(). The
1756 * caller worker shouldn't access to the pool after detached except it has
1757 * other reference to the pool.
1759 static void worker_detach_from_pool(struct worker
*worker
,
1760 struct worker_pool
*pool
)
1762 struct completion
*detach_completion
= NULL
;
1764 mutex_lock(&pool
->attach_mutex
);
1765 list_del(&worker
->node
);
1766 if (list_empty(&pool
->workers
))
1767 detach_completion
= pool
->detach_completion
;
1768 mutex_unlock(&pool
->attach_mutex
);
1770 /* clear leftover flags without pool->lock after it is detached */
1771 worker
->flags
&= ~(WORKER_UNBOUND
| WORKER_REBOUND
);
1773 if (detach_completion
)
1774 complete(detach_completion
);
1778 * create_worker - create a new workqueue worker
1779 * @pool: pool the new worker will belong to
1781 * Create and start a new worker which is attached to @pool.
1784 * Might sleep. Does GFP_KERNEL allocations.
1787 * Pointer to the newly created worker.
1789 static struct worker
*create_worker(struct worker_pool
*pool
)
1791 struct worker
*worker
= NULL
;
1795 /* ID is needed to determine kthread name */
1796 id
= ida_simple_get(&pool
->worker_ida
, 0, 0, GFP_KERNEL
);
1800 worker
= alloc_worker(pool
->node
);
1804 worker
->pool
= pool
;
1808 snprintf(id_buf
, sizeof(id_buf
), "%d:%d%s", pool
->cpu
, id
,
1809 pool
->attrs
->nice
< 0 ? "H" : "");
1811 snprintf(id_buf
, sizeof(id_buf
), "u%d:%d", pool
->id
, id
);
1813 worker
->task
= kthread_create_on_node(worker_thread
, worker
, pool
->node
,
1814 "kworker/%s", id_buf
);
1815 if (IS_ERR(worker
->task
))
1818 set_user_nice(worker
->task
, pool
->attrs
->nice
);
1819 kthread_bind_mask(worker
->task
, pool
->attrs
->cpumask
);
1821 /* successful, attach the worker to the pool */
1822 worker_attach_to_pool(worker
, pool
);
1824 /* start the newly created worker */
1825 spin_lock_irq(&pool
->lock
);
1826 worker
->pool
->nr_workers
++;
1827 worker_enter_idle(worker
);
1828 wake_up_process(worker
->task
);
1829 spin_unlock_irq(&pool
->lock
);
1835 ida_simple_remove(&pool
->worker_ida
, id
);
1841 * destroy_worker - destroy a workqueue worker
1842 * @worker: worker to be destroyed
1844 * Destroy @worker and adjust @pool stats accordingly. The worker should
1848 * spin_lock_irq(pool->lock).
1850 static void destroy_worker(struct worker
*worker
)
1852 struct worker_pool
*pool
= worker
->pool
;
1854 lockdep_assert_held(&pool
->lock
);
1856 /* sanity check frenzy */
1857 if (WARN_ON(worker
->current_work
) ||
1858 WARN_ON(!list_empty(&worker
->scheduled
)) ||
1859 WARN_ON(!(worker
->flags
& WORKER_IDLE
)))
1865 list_del_init(&worker
->entry
);
1866 worker
->flags
|= WORKER_DIE
;
1867 wake_up_process(worker
->task
);
1870 static void idle_worker_timeout(struct timer_list
*t
)
1872 struct worker_pool
*pool
= from_timer(pool
, t
, idle_timer
);
1874 spin_lock_irq(&pool
->lock
);
1876 while (too_many_workers(pool
)) {
1877 struct worker
*worker
;
1878 unsigned long expires
;
1880 /* idle_list is kept in LIFO order, check the last one */
1881 worker
= list_entry(pool
->idle_list
.prev
, struct worker
, entry
);
1882 expires
= worker
->last_active
+ IDLE_WORKER_TIMEOUT
;
1884 if (time_before(jiffies
, expires
)) {
1885 mod_timer(&pool
->idle_timer
, expires
);
1889 destroy_worker(worker
);
1892 spin_unlock_irq(&pool
->lock
);
1895 static void send_mayday(struct work_struct
*work
)
1897 struct pool_workqueue
*pwq
= get_work_pwq(work
);
1898 struct workqueue_struct
*wq
= pwq
->wq
;
1900 lockdep_assert_held(&wq_mayday_lock
);
1905 /* mayday mayday mayday */
1906 if (list_empty(&pwq
->mayday_node
)) {
1908 * If @pwq is for an unbound wq, its base ref may be put at
1909 * any time due to an attribute change. Pin @pwq until the
1910 * rescuer is done with it.
1913 list_add_tail(&pwq
->mayday_node
, &wq
->maydays
);
1914 wake_up_process(wq
->rescuer
->task
);
1918 static void pool_mayday_timeout(struct timer_list
*t
)
1920 struct worker_pool
*pool
= from_timer(pool
, t
, mayday_timer
);
1921 struct work_struct
*work
;
1923 spin_lock_irq(&pool
->lock
);
1924 spin_lock(&wq_mayday_lock
); /* for wq->maydays */
1926 if (need_to_create_worker(pool
)) {
1928 * We've been trying to create a new worker but
1929 * haven't been successful. We might be hitting an
1930 * allocation deadlock. Send distress signals to
1933 list_for_each_entry(work
, &pool
->worklist
, entry
)
1937 spin_unlock(&wq_mayday_lock
);
1938 spin_unlock_irq(&pool
->lock
);
1940 mod_timer(&pool
->mayday_timer
, jiffies
+ MAYDAY_INTERVAL
);
1944 * maybe_create_worker - create a new worker if necessary
1945 * @pool: pool to create a new worker for
1947 * Create a new worker for @pool if necessary. @pool is guaranteed to
1948 * have at least one idle worker on return from this function. If
1949 * creating a new worker takes longer than MAYDAY_INTERVAL, mayday is
1950 * sent to all rescuers with works scheduled on @pool to resolve
1951 * possible allocation deadlock.
1953 * On return, need_to_create_worker() is guaranteed to be %false and
1954 * may_start_working() %true.
1957 * spin_lock_irq(pool->lock) which may be released and regrabbed
1958 * multiple times. Does GFP_KERNEL allocations. Called only from
1961 static void maybe_create_worker(struct worker_pool
*pool
)
1962 __releases(&pool
->lock
)
1963 __acquires(&pool
->lock
)
1966 spin_unlock_irq(&pool
->lock
);
1968 /* if we don't make progress in MAYDAY_INITIAL_TIMEOUT, call for help */
1969 mod_timer(&pool
->mayday_timer
, jiffies
+ MAYDAY_INITIAL_TIMEOUT
);
1972 if (create_worker(pool
) || !need_to_create_worker(pool
))
1975 schedule_timeout_interruptible(CREATE_COOLDOWN
);
1977 if (!need_to_create_worker(pool
))
1981 del_timer_sync(&pool
->mayday_timer
);
1982 spin_lock_irq(&pool
->lock
);
1984 * This is necessary even after a new worker was just successfully
1985 * created as @pool->lock was dropped and the new worker might have
1986 * already become busy.
1988 if (need_to_create_worker(pool
))
1993 * manage_workers - manage worker pool
1996 * Assume the manager role and manage the worker pool @worker belongs
1997 * to. At any given time, there can be only zero or one manager per
1998 * pool. The exclusion is handled automatically by this function.
2000 * The caller can safely start processing works on false return. On
2001 * true return, it's guaranteed that need_to_create_worker() is false
2002 * and may_start_working() is true.
2005 * spin_lock_irq(pool->lock) which may be released and regrabbed
2006 * multiple times. Does GFP_KERNEL allocations.
2009 * %false if the pool doesn't need management and the caller can safely
2010 * start processing works, %true if management function was performed and
2011 * the conditions that the caller verified before calling the function may
2012 * no longer be true.
2014 static bool manage_workers(struct worker
*worker
)
2016 struct worker_pool
*pool
= worker
->pool
;
2018 if (pool
->flags
& POOL_MANAGER_ACTIVE
)
2021 pool
->flags
|= POOL_MANAGER_ACTIVE
;
2022 pool
->manager
= worker
;
2024 maybe_create_worker(pool
);
2026 pool
->manager
= NULL
;
2027 pool
->flags
&= ~POOL_MANAGER_ACTIVE
;
2028 wake_up(&wq_manager_wait
);
2033 * process_one_work - process single work
2035 * @work: work to process
2037 * Process @work. This function contains all the logics necessary to
2038 * process a single work including synchronization against and
2039 * interaction with other workers on the same cpu, queueing and
2040 * flushing. As long as context requirement is met, any worker can
2041 * call this function to process a work.
2044 * spin_lock_irq(pool->lock) which is released and regrabbed.
2046 static void process_one_work(struct worker
*worker
, struct work_struct
*work
)
2047 __releases(&pool
->lock
)
2048 __acquires(&pool
->lock
)
2050 struct pool_workqueue
*pwq
= get_work_pwq(work
);
2051 struct worker_pool
*pool
= worker
->pool
;
2052 bool cpu_intensive
= pwq
->wq
->flags
& WQ_CPU_INTENSIVE
;
2054 struct worker
*collision
;
2055 #ifdef CONFIG_LOCKDEP
2057 * It is permissible to free the struct work_struct from
2058 * inside the function that is called from it, this we need to
2059 * take into account for lockdep too. To avoid bogus "held
2060 * lock freed" warnings as well as problems when looking into
2061 * work->lockdep_map, make a copy and use that here.
2063 struct lockdep_map lockdep_map
;
2065 lockdep_copy_map(&lockdep_map
, &work
->lockdep_map
);
2067 /* ensure we're on the correct CPU */
2068 WARN_ON_ONCE(!(pool
->flags
& POOL_DISASSOCIATED
) &&
2069 raw_smp_processor_id() != pool
->cpu
);
2072 * A single work shouldn't be executed concurrently by
2073 * multiple workers on a single cpu. Check whether anyone is
2074 * already processing the work. If so, defer the work to the
2075 * currently executing one.
2077 collision
= find_worker_executing_work(pool
, work
);
2078 if (unlikely(collision
)) {
2079 move_linked_works(work
, &collision
->scheduled
, NULL
);
2083 /* claim and dequeue */
2084 debug_work_deactivate(work
);
2085 hash_add(pool
->busy_hash
, &worker
->hentry
, (unsigned long)work
);
2086 worker
->current_work
= work
;
2087 worker
->current_func
= work
->func
;
2088 worker
->current_pwq
= pwq
;
2089 work_color
= get_work_color(work
);
2091 list_del_init(&work
->entry
);
2094 * CPU intensive works don't participate in concurrency management.
2095 * They're the scheduler's responsibility. This takes @worker out
2096 * of concurrency management and the next code block will chain
2097 * execution of the pending work items.
2099 if (unlikely(cpu_intensive
))
2100 worker_set_flags(worker
, WORKER_CPU_INTENSIVE
);
2103 * Wake up another worker if necessary. The condition is always
2104 * false for normal per-cpu workers since nr_running would always
2105 * be >= 1 at this point. This is used to chain execution of the
2106 * pending work items for WORKER_NOT_RUNNING workers such as the
2107 * UNBOUND and CPU_INTENSIVE ones.
2109 if (need_more_worker(pool
))
2110 wake_up_worker(pool
);
2113 * Record the last pool and clear PENDING which should be the last
2114 * update to @work. Also, do this inside @pool->lock so that
2115 * PENDING and queued state changes happen together while IRQ is
2118 set_work_pool_and_clear_pending(work
, pool
->id
);
2120 spin_unlock_irq(&pool
->lock
);
2122 lock_map_acquire(&pwq
->wq
->lockdep_map
);
2123 lock_map_acquire(&lockdep_map
);
2125 * Strictly speaking we should mark the invariant state without holding
2126 * any locks, that is, before these two lock_map_acquire()'s.
2128 * However, that would result in:
2135 * Which would create W1->C->W1 dependencies, even though there is no
2136 * actual deadlock possible. There are two solutions, using a
2137 * read-recursive acquire on the work(queue) 'locks', but this will then
2138 * hit the lockdep limitation on recursive locks, or simply discard
2141 * AFAICT there is no possible deadlock scenario between the
2142 * flush_work() and complete() primitives (except for single-threaded
2143 * workqueues), so hiding them isn't a problem.
2145 lockdep_invariant_state(true);
2146 trace_workqueue_execute_start(work
);
2147 worker
->current_func(work
);
2149 * While we must be careful to not use "work" after this, the trace
2150 * point will only record its address.
2152 trace_workqueue_execute_end(work
);
2153 lock_map_release(&lockdep_map
);
2154 lock_map_release(&pwq
->wq
->lockdep_map
);
2156 if (unlikely(in_atomic() || lockdep_depth(current
) > 0)) {
2157 pr_err("BUG: workqueue leaked lock or atomic: %s/0x%08x/%d\n"
2158 " last function: %pf\n",
2159 current
->comm
, preempt_count(), task_pid_nr(current
),
2160 worker
->current_func
);
2161 debug_show_held_locks(current
);
2166 * The following prevents a kworker from hogging CPU on !PREEMPT
2167 * kernels, where a requeueing work item waiting for something to
2168 * happen could deadlock with stop_machine as such work item could
2169 * indefinitely requeue itself while all other CPUs are trapped in
2170 * stop_machine. At the same time, report a quiescent RCU state so
2171 * the same condition doesn't freeze RCU.
2173 cond_resched_rcu_qs();
2175 spin_lock_irq(&pool
->lock
);
2177 /* clear cpu intensive status */
2178 if (unlikely(cpu_intensive
))
2179 worker_clr_flags(worker
, WORKER_CPU_INTENSIVE
);
2181 /* we're done with it, release */
2182 hash_del(&worker
->hentry
);
2183 worker
->current_work
= NULL
;
2184 worker
->current_func
= NULL
;
2185 worker
->current_pwq
= NULL
;
2186 worker
->desc_valid
= false;
2187 pwq_dec_nr_in_flight(pwq
, work_color
);
2191 * process_scheduled_works - process scheduled works
2194 * Process all scheduled works. Please note that the scheduled list
2195 * may change while processing a work, so this function repeatedly
2196 * fetches a work from the top and executes it.
2199 * spin_lock_irq(pool->lock) which may be released and regrabbed
2202 static void process_scheduled_works(struct worker
*worker
)
2204 while (!list_empty(&worker
->scheduled
)) {
2205 struct work_struct
*work
= list_first_entry(&worker
->scheduled
,
2206 struct work_struct
, entry
);
2207 process_one_work(worker
, work
);
2212 * worker_thread - the worker thread function
2215 * The worker thread function. All workers belong to a worker_pool -
2216 * either a per-cpu one or dynamic unbound one. These workers process all
2217 * work items regardless of their specific target workqueue. The only
2218 * exception is work items which belong to workqueues with a rescuer which
2219 * will be explained in rescuer_thread().
2223 static int worker_thread(void *__worker
)
2225 struct worker
*worker
= __worker
;
2226 struct worker_pool
*pool
= worker
->pool
;
2228 /* tell the scheduler that this is a workqueue worker */
2229 worker
->task
->flags
|= PF_WQ_WORKER
;
2231 spin_lock_irq(&pool
->lock
);
2233 /* am I supposed to die? */
2234 if (unlikely(worker
->flags
& WORKER_DIE
)) {
2235 spin_unlock_irq(&pool
->lock
);
2236 WARN_ON_ONCE(!list_empty(&worker
->entry
));
2237 worker
->task
->flags
&= ~PF_WQ_WORKER
;
2239 set_task_comm(worker
->task
, "kworker/dying");
2240 ida_simple_remove(&pool
->worker_ida
, worker
->id
);
2241 worker_detach_from_pool(worker
, pool
);
2246 worker_leave_idle(worker
);
2248 /* no more worker necessary? */
2249 if (!need_more_worker(pool
))
2252 /* do we need to manage? */
2253 if (unlikely(!may_start_working(pool
)) && manage_workers(worker
))
2257 * ->scheduled list can only be filled while a worker is
2258 * preparing to process a work or actually processing it.
2259 * Make sure nobody diddled with it while I was sleeping.
2261 WARN_ON_ONCE(!list_empty(&worker
->scheduled
));
2264 * Finish PREP stage. We're guaranteed to have at least one idle
2265 * worker or that someone else has already assumed the manager
2266 * role. This is where @worker starts participating in concurrency
2267 * management if applicable and concurrency management is restored
2268 * after being rebound. See rebind_workers() for details.
2270 worker_clr_flags(worker
, WORKER_PREP
| WORKER_REBOUND
);
2273 struct work_struct
*work
=
2274 list_first_entry(&pool
->worklist
,
2275 struct work_struct
, entry
);
2277 pool
->watchdog_ts
= jiffies
;
2279 if (likely(!(*work_data_bits(work
) & WORK_STRUCT_LINKED
))) {
2280 /* optimization path, not strictly necessary */
2281 process_one_work(worker
, work
);
2282 if (unlikely(!list_empty(&worker
->scheduled
)))
2283 process_scheduled_works(worker
);
2285 move_linked_works(work
, &worker
->scheduled
, NULL
);
2286 process_scheduled_works(worker
);
2288 } while (keep_working(pool
));
2290 worker_set_flags(worker
, WORKER_PREP
);
2293 * pool->lock is held and there's no work to process and no need to
2294 * manage, sleep. Workers are woken up only while holding
2295 * pool->lock or from local cpu, so setting the current state
2296 * before releasing pool->lock is enough to prevent losing any
2299 worker_enter_idle(worker
);
2300 __set_current_state(TASK_IDLE
);
2301 spin_unlock_irq(&pool
->lock
);
2307 * rescuer_thread - the rescuer thread function
2310 * Workqueue rescuer thread function. There's one rescuer for each
2311 * workqueue which has WQ_MEM_RECLAIM set.
2313 * Regular work processing on a pool may block trying to create a new
2314 * worker which uses GFP_KERNEL allocation which has slight chance of
2315 * developing into deadlock if some works currently on the same queue
2316 * need to be processed to satisfy the GFP_KERNEL allocation. This is
2317 * the problem rescuer solves.
2319 * When such condition is possible, the pool summons rescuers of all
2320 * workqueues which have works queued on the pool and let them process
2321 * those works so that forward progress can be guaranteed.
2323 * This should happen rarely.
2327 static int rescuer_thread(void *__rescuer
)
2329 struct worker
*rescuer
= __rescuer
;
2330 struct workqueue_struct
*wq
= rescuer
->rescue_wq
;
2331 struct list_head
*scheduled
= &rescuer
->scheduled
;
2334 set_user_nice(current
, RESCUER_NICE_LEVEL
);
2337 * Mark rescuer as worker too. As WORKER_PREP is never cleared, it
2338 * doesn't participate in concurrency management.
2340 rescuer
->task
->flags
|= PF_WQ_WORKER
;
2342 set_current_state(TASK_IDLE
);
2345 * By the time the rescuer is requested to stop, the workqueue
2346 * shouldn't have any work pending, but @wq->maydays may still have
2347 * pwq(s) queued. This can happen by non-rescuer workers consuming
2348 * all the work items before the rescuer got to them. Go through
2349 * @wq->maydays processing before acting on should_stop so that the
2350 * list is always empty on exit.
2352 should_stop
= kthread_should_stop();
2354 /* see whether any pwq is asking for help */
2355 spin_lock_irq(&wq_mayday_lock
);
2357 while (!list_empty(&wq
->maydays
)) {
2358 struct pool_workqueue
*pwq
= list_first_entry(&wq
->maydays
,
2359 struct pool_workqueue
, mayday_node
);
2360 struct worker_pool
*pool
= pwq
->pool
;
2361 struct work_struct
*work
, *n
;
2364 __set_current_state(TASK_RUNNING
);
2365 list_del_init(&pwq
->mayday_node
);
2367 spin_unlock_irq(&wq_mayday_lock
);
2369 worker_attach_to_pool(rescuer
, pool
);
2371 spin_lock_irq(&pool
->lock
);
2372 rescuer
->pool
= pool
;
2375 * Slurp in all works issued via this workqueue and
2378 WARN_ON_ONCE(!list_empty(scheduled
));
2379 list_for_each_entry_safe(work
, n
, &pool
->worklist
, entry
) {
2380 if (get_work_pwq(work
) == pwq
) {
2382 pool
->watchdog_ts
= jiffies
;
2383 move_linked_works(work
, scheduled
, &n
);
2388 if (!list_empty(scheduled
)) {
2389 process_scheduled_works(rescuer
);
2392 * The above execution of rescued work items could
2393 * have created more to rescue through
2394 * pwq_activate_first_delayed() or chained
2395 * queueing. Let's put @pwq back on mayday list so
2396 * that such back-to-back work items, which may be
2397 * being used to relieve memory pressure, don't
2398 * incur MAYDAY_INTERVAL delay inbetween.
2400 if (need_to_create_worker(pool
)) {
2401 spin_lock(&wq_mayday_lock
);
2403 list_move_tail(&pwq
->mayday_node
, &wq
->maydays
);
2404 spin_unlock(&wq_mayday_lock
);
2409 * Put the reference grabbed by send_mayday(). @pool won't
2410 * go away while we're still attached to it.
2415 * Leave this pool. If need_more_worker() is %true, notify a
2416 * regular worker; otherwise, we end up with 0 concurrency
2417 * and stalling the execution.
2419 if (need_more_worker(pool
))
2420 wake_up_worker(pool
);
2422 rescuer
->pool
= NULL
;
2423 spin_unlock_irq(&pool
->lock
);
2425 worker_detach_from_pool(rescuer
, pool
);
2427 spin_lock_irq(&wq_mayday_lock
);
2430 spin_unlock_irq(&wq_mayday_lock
);
2433 __set_current_state(TASK_RUNNING
);
2434 rescuer
->task
->flags
&= ~PF_WQ_WORKER
;
2438 /* rescuers should never participate in concurrency management */
2439 WARN_ON_ONCE(!(rescuer
->flags
& WORKER_NOT_RUNNING
));
2445 * check_flush_dependency - check for flush dependency sanity
2446 * @target_wq: workqueue being flushed
2447 * @target_work: work item being flushed (NULL for workqueue flushes)
2449 * %current is trying to flush the whole @target_wq or @target_work on it.
2450 * If @target_wq doesn't have %WQ_MEM_RECLAIM, verify that %current is not
2451 * reclaiming memory or running on a workqueue which doesn't have
2452 * %WQ_MEM_RECLAIM as that can break forward-progress guarantee leading to
2455 static void check_flush_dependency(struct workqueue_struct
*target_wq
,
2456 struct work_struct
*target_work
)
2458 work_func_t target_func
= target_work
? target_work
->func
: NULL
;
2459 struct worker
*worker
;
2461 if (target_wq
->flags
& WQ_MEM_RECLAIM
)
2464 worker
= current_wq_worker();
2466 WARN_ONCE(current
->flags
& PF_MEMALLOC
,
2467 "workqueue: PF_MEMALLOC task %d(%s) is flushing !WQ_MEM_RECLAIM %s:%pf",
2468 current
->pid
, current
->comm
, target_wq
->name
, target_func
);
2469 WARN_ONCE(worker
&& ((worker
->current_pwq
->wq
->flags
&
2470 (WQ_MEM_RECLAIM
| __WQ_LEGACY
)) == WQ_MEM_RECLAIM
),
2471 "workqueue: WQ_MEM_RECLAIM %s:%pf is flushing !WQ_MEM_RECLAIM %s:%pf",
2472 worker
->current_pwq
->wq
->name
, worker
->current_func
,
2473 target_wq
->name
, target_func
);
2477 struct work_struct work
;
2478 struct completion done
;
2479 struct task_struct
*task
; /* purely informational */
2482 static void wq_barrier_func(struct work_struct
*work
)
2484 struct wq_barrier
*barr
= container_of(work
, struct wq_barrier
, work
);
2485 complete(&barr
->done
);
2489 * insert_wq_barrier - insert a barrier work
2490 * @pwq: pwq to insert barrier into
2491 * @barr: wq_barrier to insert
2492 * @target: target work to attach @barr to
2493 * @worker: worker currently executing @target, NULL if @target is not executing
2495 * @barr is linked to @target such that @barr is completed only after
2496 * @target finishes execution. Please note that the ordering
2497 * guarantee is observed only with respect to @target and on the local
2500 * Currently, a queued barrier can't be canceled. This is because
2501 * try_to_grab_pending() can't determine whether the work to be
2502 * grabbed is at the head of the queue and thus can't clear LINKED
2503 * flag of the previous work while there must be a valid next work
2504 * after a work with LINKED flag set.
2506 * Note that when @worker is non-NULL, @target may be modified
2507 * underneath us, so we can't reliably determine pwq from @target.
2510 * spin_lock_irq(pool->lock).
2512 static void insert_wq_barrier(struct pool_workqueue
*pwq
,
2513 struct wq_barrier
*barr
,
2514 struct work_struct
*target
, struct worker
*worker
)
2516 struct list_head
*head
;
2517 unsigned int linked
= 0;
2520 * debugobject calls are safe here even with pool->lock locked
2521 * as we know for sure that this will not trigger any of the
2522 * checks and call back into the fixup functions where we
2525 INIT_WORK_ONSTACK(&barr
->work
, wq_barrier_func
);
2526 __set_bit(WORK_STRUCT_PENDING_BIT
, work_data_bits(&barr
->work
));
2528 init_completion_map(&barr
->done
, &target
->lockdep_map
);
2530 barr
->task
= current
;
2533 * If @target is currently being executed, schedule the
2534 * barrier to the worker; otherwise, put it after @target.
2537 head
= worker
->scheduled
.next
;
2539 unsigned long *bits
= work_data_bits(target
);
2541 head
= target
->entry
.next
;
2542 /* there can already be other linked works, inherit and set */
2543 linked
= *bits
& WORK_STRUCT_LINKED
;
2544 __set_bit(WORK_STRUCT_LINKED_BIT
, bits
);
2547 debug_work_activate(&barr
->work
);
2548 insert_work(pwq
, &barr
->work
, head
,
2549 work_color_to_flags(WORK_NO_COLOR
) | linked
);
2553 * flush_workqueue_prep_pwqs - prepare pwqs for workqueue flushing
2554 * @wq: workqueue being flushed
2555 * @flush_color: new flush color, < 0 for no-op
2556 * @work_color: new work color, < 0 for no-op
2558 * Prepare pwqs for workqueue flushing.
2560 * If @flush_color is non-negative, flush_color on all pwqs should be
2561 * -1. If no pwq has in-flight commands at the specified color, all
2562 * pwq->flush_color's stay at -1 and %false is returned. If any pwq
2563 * has in flight commands, its pwq->flush_color is set to
2564 * @flush_color, @wq->nr_pwqs_to_flush is updated accordingly, pwq
2565 * wakeup logic is armed and %true is returned.
2567 * The caller should have initialized @wq->first_flusher prior to
2568 * calling this function with non-negative @flush_color. If
2569 * @flush_color is negative, no flush color update is done and %false
2572 * If @work_color is non-negative, all pwqs should have the same
2573 * work_color which is previous to @work_color and all will be
2574 * advanced to @work_color.
2577 * mutex_lock(wq->mutex).
2580 * %true if @flush_color >= 0 and there's something to flush. %false
2583 static bool flush_workqueue_prep_pwqs(struct workqueue_struct
*wq
,
2584 int flush_color
, int work_color
)
2587 struct pool_workqueue
*pwq
;
2589 if (flush_color
>= 0) {
2590 WARN_ON_ONCE(atomic_read(&wq
->nr_pwqs_to_flush
));
2591 atomic_set(&wq
->nr_pwqs_to_flush
, 1);
2594 for_each_pwq(pwq
, wq
) {
2595 struct worker_pool
*pool
= pwq
->pool
;
2597 spin_lock_irq(&pool
->lock
);
2599 if (flush_color
>= 0) {
2600 WARN_ON_ONCE(pwq
->flush_color
!= -1);
2602 if (pwq
->nr_in_flight
[flush_color
]) {
2603 pwq
->flush_color
= flush_color
;
2604 atomic_inc(&wq
->nr_pwqs_to_flush
);
2609 if (work_color
>= 0) {
2610 WARN_ON_ONCE(work_color
!= work_next_color(pwq
->work_color
));
2611 pwq
->work_color
= work_color
;
2614 spin_unlock_irq(&pool
->lock
);
2617 if (flush_color
>= 0 && atomic_dec_and_test(&wq
->nr_pwqs_to_flush
))
2618 complete(&wq
->first_flusher
->done
);
2624 * flush_workqueue - ensure that any scheduled work has run to completion.
2625 * @wq: workqueue to flush
2627 * This function sleeps until all work items which were queued on entry
2628 * have finished execution, but it is not livelocked by new incoming ones.
2630 void flush_workqueue(struct workqueue_struct
*wq
)
2632 struct wq_flusher this_flusher
= {
2633 .list
= LIST_HEAD_INIT(this_flusher
.list
),
2635 .done
= COMPLETION_INITIALIZER_ONSTACK_MAP(this_flusher
.done
, wq
->lockdep_map
),
2639 if (WARN_ON(!wq_online
))
2642 lock_map_acquire(&wq
->lockdep_map
);
2643 lock_map_release(&wq
->lockdep_map
);
2645 mutex_lock(&wq
->mutex
);
2648 * Start-to-wait phase
2650 next_color
= work_next_color(wq
->work_color
);
2652 if (next_color
!= wq
->flush_color
) {
2654 * Color space is not full. The current work_color
2655 * becomes our flush_color and work_color is advanced
2658 WARN_ON_ONCE(!list_empty(&wq
->flusher_overflow
));
2659 this_flusher
.flush_color
= wq
->work_color
;
2660 wq
->work_color
= next_color
;
2662 if (!wq
->first_flusher
) {
2663 /* no flush in progress, become the first flusher */
2664 WARN_ON_ONCE(wq
->flush_color
!= this_flusher
.flush_color
);
2666 wq
->first_flusher
= &this_flusher
;
2668 if (!flush_workqueue_prep_pwqs(wq
, wq
->flush_color
,
2670 /* nothing to flush, done */
2671 wq
->flush_color
= next_color
;
2672 wq
->first_flusher
= NULL
;
2677 WARN_ON_ONCE(wq
->flush_color
== this_flusher
.flush_color
);
2678 list_add_tail(&this_flusher
.list
, &wq
->flusher_queue
);
2679 flush_workqueue_prep_pwqs(wq
, -1, wq
->work_color
);
2683 * Oops, color space is full, wait on overflow queue.
2684 * The next flush completion will assign us
2685 * flush_color and transfer to flusher_queue.
2687 list_add_tail(&this_flusher
.list
, &wq
->flusher_overflow
);
2690 check_flush_dependency(wq
, NULL
);
2692 mutex_unlock(&wq
->mutex
);
2694 wait_for_completion(&this_flusher
.done
);
2697 * Wake-up-and-cascade phase
2699 * First flushers are responsible for cascading flushes and
2700 * handling overflow. Non-first flushers can simply return.
2702 if (wq
->first_flusher
!= &this_flusher
)
2705 mutex_lock(&wq
->mutex
);
2707 /* we might have raced, check again with mutex held */
2708 if (wq
->first_flusher
!= &this_flusher
)
2711 wq
->first_flusher
= NULL
;
2713 WARN_ON_ONCE(!list_empty(&this_flusher
.list
));
2714 WARN_ON_ONCE(wq
->flush_color
!= this_flusher
.flush_color
);
2717 struct wq_flusher
*next
, *tmp
;
2719 /* complete all the flushers sharing the current flush color */
2720 list_for_each_entry_safe(next
, tmp
, &wq
->flusher_queue
, list
) {
2721 if (next
->flush_color
!= wq
->flush_color
)
2723 list_del_init(&next
->list
);
2724 complete(&next
->done
);
2727 WARN_ON_ONCE(!list_empty(&wq
->flusher_overflow
) &&
2728 wq
->flush_color
!= work_next_color(wq
->work_color
));
2730 /* this flush_color is finished, advance by one */
2731 wq
->flush_color
= work_next_color(wq
->flush_color
);
2733 /* one color has been freed, handle overflow queue */
2734 if (!list_empty(&wq
->flusher_overflow
)) {
2736 * Assign the same color to all overflowed
2737 * flushers, advance work_color and append to
2738 * flusher_queue. This is the start-to-wait
2739 * phase for these overflowed flushers.
2741 list_for_each_entry(tmp
, &wq
->flusher_overflow
, list
)
2742 tmp
->flush_color
= wq
->work_color
;
2744 wq
->work_color
= work_next_color(wq
->work_color
);
2746 list_splice_tail_init(&wq
->flusher_overflow
,
2747 &wq
->flusher_queue
);
2748 flush_workqueue_prep_pwqs(wq
, -1, wq
->work_color
);
2751 if (list_empty(&wq
->flusher_queue
)) {
2752 WARN_ON_ONCE(wq
->flush_color
!= wq
->work_color
);
2757 * Need to flush more colors. Make the next flusher
2758 * the new first flusher and arm pwqs.
2760 WARN_ON_ONCE(wq
->flush_color
== wq
->work_color
);
2761 WARN_ON_ONCE(wq
->flush_color
!= next
->flush_color
);
2763 list_del_init(&next
->list
);
2764 wq
->first_flusher
= next
;
2766 if (flush_workqueue_prep_pwqs(wq
, wq
->flush_color
, -1))
2770 * Meh... this color is already done, clear first
2771 * flusher and repeat cascading.
2773 wq
->first_flusher
= NULL
;
2777 mutex_unlock(&wq
->mutex
);
2779 EXPORT_SYMBOL(flush_workqueue
);
2782 * drain_workqueue - drain a workqueue
2783 * @wq: workqueue to drain
2785 * Wait until the workqueue becomes empty. While draining is in progress,
2786 * only chain queueing is allowed. IOW, only currently pending or running
2787 * work items on @wq can queue further work items on it. @wq is flushed
2788 * repeatedly until it becomes empty. The number of flushing is determined
2789 * by the depth of chaining and should be relatively short. Whine if it
2792 void drain_workqueue(struct workqueue_struct
*wq
)
2794 unsigned int flush_cnt
= 0;
2795 struct pool_workqueue
*pwq
;
2798 * __queue_work() needs to test whether there are drainers, is much
2799 * hotter than drain_workqueue() and already looks at @wq->flags.
2800 * Use __WQ_DRAINING so that queue doesn't have to check nr_drainers.
2802 mutex_lock(&wq
->mutex
);
2803 if (!wq
->nr_drainers
++)
2804 wq
->flags
|= __WQ_DRAINING
;
2805 mutex_unlock(&wq
->mutex
);
2807 flush_workqueue(wq
);
2809 mutex_lock(&wq
->mutex
);
2811 for_each_pwq(pwq
, wq
) {
2814 spin_lock_irq(&pwq
->pool
->lock
);
2815 drained
= !pwq
->nr_active
&& list_empty(&pwq
->delayed_works
);
2816 spin_unlock_irq(&pwq
->pool
->lock
);
2821 if (++flush_cnt
== 10 ||
2822 (flush_cnt
% 100 == 0 && flush_cnt
<= 1000))
2823 pr_warn("workqueue %s: drain_workqueue() isn't complete after %u tries\n",
2824 wq
->name
, flush_cnt
);
2826 mutex_unlock(&wq
->mutex
);
2830 if (!--wq
->nr_drainers
)
2831 wq
->flags
&= ~__WQ_DRAINING
;
2832 mutex_unlock(&wq
->mutex
);
2834 EXPORT_SYMBOL_GPL(drain_workqueue
);
2836 static bool start_flush_work(struct work_struct
*work
, struct wq_barrier
*barr
,
2839 struct worker
*worker
= NULL
;
2840 struct worker_pool
*pool
;
2841 struct pool_workqueue
*pwq
;
2845 local_irq_disable();
2846 pool
= get_work_pool(work
);
2852 spin_lock(&pool
->lock
);
2853 /* see the comment in try_to_grab_pending() with the same code */
2854 pwq
= get_work_pwq(work
);
2856 if (unlikely(pwq
->pool
!= pool
))
2859 worker
= find_worker_executing_work(pool
, work
);
2862 pwq
= worker
->current_pwq
;
2865 check_flush_dependency(pwq
->wq
, work
);
2867 insert_wq_barrier(pwq
, barr
, work
, worker
);
2868 spin_unlock_irq(&pool
->lock
);
2871 * Force a lock recursion deadlock when using flush_work() inside a
2872 * single-threaded or rescuer equipped workqueue.
2874 * For single threaded workqueues the deadlock happens when the work
2875 * is after the work issuing the flush_work(). For rescuer equipped
2876 * workqueues the deadlock happens when the rescuer stalls, blocking
2880 (pwq
->wq
->saved_max_active
== 1 || pwq
->wq
->rescuer
)) {
2881 lock_map_acquire(&pwq
->wq
->lockdep_map
);
2882 lock_map_release(&pwq
->wq
->lockdep_map
);
2887 spin_unlock_irq(&pool
->lock
);
2891 static bool __flush_work(struct work_struct
*work
, bool from_cancel
)
2893 struct wq_barrier barr
;
2895 if (WARN_ON(!wq_online
))
2899 lock_map_acquire(&work
->lockdep_map
);
2900 lock_map_release(&work
->lockdep_map
);
2903 if (start_flush_work(work
, &barr
, from_cancel
)) {
2904 wait_for_completion(&barr
.done
);
2905 destroy_work_on_stack(&barr
.work
);
2913 * flush_work - wait for a work to finish executing the last queueing instance
2914 * @work: the work to flush
2916 * Wait until @work has finished execution. @work is guaranteed to be idle
2917 * on return if it hasn't been requeued since flush started.
2920 * %true if flush_work() waited for the work to finish execution,
2921 * %false if it was already idle.
2923 bool flush_work(struct work_struct
*work
)
2925 return __flush_work(work
, false);
2927 EXPORT_SYMBOL_GPL(flush_work
);
2930 wait_queue_entry_t wait
;
2931 struct work_struct
*work
;
2934 static int cwt_wakefn(wait_queue_entry_t
*wait
, unsigned mode
, int sync
, void *key
)
2936 struct cwt_wait
*cwait
= container_of(wait
, struct cwt_wait
, wait
);
2938 if (cwait
->work
!= key
)
2940 return autoremove_wake_function(wait
, mode
, sync
, key
);
2943 static bool __cancel_work_timer(struct work_struct
*work
, bool is_dwork
)
2945 static DECLARE_WAIT_QUEUE_HEAD(cancel_waitq
);
2946 unsigned long flags
;
2950 ret
= try_to_grab_pending(work
, is_dwork
, &flags
);
2952 * If someone else is already canceling, wait for it to
2953 * finish. flush_work() doesn't work for PREEMPT_NONE
2954 * because we may get scheduled between @work's completion
2955 * and the other canceling task resuming and clearing
2956 * CANCELING - flush_work() will return false immediately
2957 * as @work is no longer busy, try_to_grab_pending() will
2958 * return -ENOENT as @work is still being canceled and the
2959 * other canceling task won't be able to clear CANCELING as
2960 * we're hogging the CPU.
2962 * Let's wait for completion using a waitqueue. As this
2963 * may lead to the thundering herd problem, use a custom
2964 * wake function which matches @work along with exclusive
2967 if (unlikely(ret
== -ENOENT
)) {
2968 struct cwt_wait cwait
;
2970 init_wait(&cwait
.wait
);
2971 cwait
.wait
.func
= cwt_wakefn
;
2974 prepare_to_wait_exclusive(&cancel_waitq
, &cwait
.wait
,
2975 TASK_UNINTERRUPTIBLE
);
2976 if (work_is_canceling(work
))
2978 finish_wait(&cancel_waitq
, &cwait
.wait
);
2980 } while (unlikely(ret
< 0));
2982 /* tell other tasks trying to grab @work to back off */
2983 mark_work_canceling(work
);
2984 local_irq_restore(flags
);
2987 * This allows canceling during early boot. We know that @work
2991 __flush_work(work
, true);
2993 clear_work_data(work
);
2996 * Paired with prepare_to_wait() above so that either
2997 * waitqueue_active() is visible here or !work_is_canceling() is
3001 if (waitqueue_active(&cancel_waitq
))
3002 __wake_up(&cancel_waitq
, TASK_NORMAL
, 1, work
);
3008 * cancel_work_sync - cancel a work and wait for it to finish
3009 * @work: the work to cancel
3011 * Cancel @work and wait for its execution to finish. This function
3012 * can be used even if the work re-queues itself or migrates to
3013 * another workqueue. On return from this function, @work is
3014 * guaranteed to be not pending or executing on any CPU.
3016 * cancel_work_sync(&delayed_work->work) must not be used for
3017 * delayed_work's. Use cancel_delayed_work_sync() instead.
3019 * The caller must ensure that the workqueue on which @work was last
3020 * queued can't be destroyed before this function returns.
3023 * %true if @work was pending, %false otherwise.
3025 bool cancel_work_sync(struct work_struct
*work
)
3027 return __cancel_work_timer(work
, false);
3029 EXPORT_SYMBOL_GPL(cancel_work_sync
);
3032 * flush_delayed_work - wait for a dwork to finish executing the last queueing
3033 * @dwork: the delayed work to flush
3035 * Delayed timer is cancelled and the pending work is queued for
3036 * immediate execution. Like flush_work(), this function only
3037 * considers the last queueing instance of @dwork.
3040 * %true if flush_work() waited for the work to finish execution,
3041 * %false if it was already idle.
3043 bool flush_delayed_work(struct delayed_work
*dwork
)
3045 local_irq_disable();
3046 if (del_timer_sync(&dwork
->timer
))
3047 __queue_work(dwork
->cpu
, dwork
->wq
, &dwork
->work
);
3049 return flush_work(&dwork
->work
);
3051 EXPORT_SYMBOL(flush_delayed_work
);
3054 * flush_rcu_work - wait for a rwork to finish executing the last queueing
3055 * @rwork: the rcu work to flush
3058 * %true if flush_rcu_work() waited for the work to finish execution,
3059 * %false if it was already idle.
3061 bool flush_rcu_work(struct rcu_work
*rwork
)
3063 if (test_bit(WORK_STRUCT_PENDING_BIT
, work_data_bits(&rwork
->work
))) {
3065 flush_work(&rwork
->work
);
3068 return flush_work(&rwork
->work
);
3071 EXPORT_SYMBOL(flush_rcu_work
);
3073 static bool __cancel_work(struct work_struct
*work
, bool is_dwork
)
3075 unsigned long flags
;
3079 ret
= try_to_grab_pending(work
, is_dwork
, &flags
);
3080 } while (unlikely(ret
== -EAGAIN
));
3082 if (unlikely(ret
< 0))
3085 set_work_pool_and_clear_pending(work
, get_work_pool_id(work
));
3086 local_irq_restore(flags
);
3091 * See cancel_delayed_work()
3093 bool cancel_work(struct work_struct
*work
)
3095 return __cancel_work(work
, false);
3099 * cancel_delayed_work - cancel a delayed work
3100 * @dwork: delayed_work to cancel
3102 * Kill off a pending delayed_work.
3104 * Return: %true if @dwork was pending and canceled; %false if it wasn't
3108 * The work callback function may still be running on return, unless
3109 * it returns %true and the work doesn't re-arm itself. Explicitly flush or
3110 * use cancel_delayed_work_sync() to wait on it.
3112 * This function is safe to call from any context including IRQ handler.
3114 bool cancel_delayed_work(struct delayed_work
*dwork
)
3116 return __cancel_work(&dwork
->work
, true);
3118 EXPORT_SYMBOL(cancel_delayed_work
);
3121 * cancel_delayed_work_sync - cancel a delayed work and wait for it to finish
3122 * @dwork: the delayed work cancel
3124 * This is cancel_work_sync() for delayed works.
3127 * %true if @dwork was pending, %false otherwise.
3129 bool cancel_delayed_work_sync(struct delayed_work
*dwork
)
3131 return __cancel_work_timer(&dwork
->work
, true);
3133 EXPORT_SYMBOL(cancel_delayed_work_sync
);
3136 * schedule_on_each_cpu - execute a function synchronously on each online CPU
3137 * @func: the function to call
3139 * schedule_on_each_cpu() executes @func on each online CPU using the
3140 * system workqueue and blocks until all CPUs have completed.
3141 * schedule_on_each_cpu() is very slow.
3144 * 0 on success, -errno on failure.
3146 int schedule_on_each_cpu(work_func_t func
)
3149 struct work_struct __percpu
*works
;
3151 works
= alloc_percpu(struct work_struct
);
3157 for_each_online_cpu(cpu
) {
3158 struct work_struct
*work
= per_cpu_ptr(works
, cpu
);
3160 INIT_WORK(work
, func
);
3161 schedule_work_on(cpu
, work
);
3164 for_each_online_cpu(cpu
)
3165 flush_work(per_cpu_ptr(works
, cpu
));
3173 * execute_in_process_context - reliably execute the routine with user context
3174 * @fn: the function to execute
3175 * @ew: guaranteed storage for the execute work structure (must
3176 * be available when the work executes)
3178 * Executes the function immediately if process context is available,
3179 * otherwise schedules the function for delayed execution.
3181 * Return: 0 - function was executed
3182 * 1 - function was scheduled for execution
3184 int execute_in_process_context(work_func_t fn
, struct execute_work
*ew
)
3186 if (!in_interrupt()) {
3191 INIT_WORK(&ew
->work
, fn
);
3192 schedule_work(&ew
->work
);
3196 EXPORT_SYMBOL_GPL(execute_in_process_context
);
3199 * free_workqueue_attrs - free a workqueue_attrs
3200 * @attrs: workqueue_attrs to free
3202 * Undo alloc_workqueue_attrs().
3204 void free_workqueue_attrs(struct workqueue_attrs
*attrs
)
3207 free_cpumask_var(attrs
->cpumask
);
3213 * alloc_workqueue_attrs - allocate a workqueue_attrs
3214 * @gfp_mask: allocation mask to use
3216 * Allocate a new workqueue_attrs, initialize with default settings and
3219 * Return: The allocated new workqueue_attr on success. %NULL on failure.
3221 struct workqueue_attrs
*alloc_workqueue_attrs(gfp_t gfp_mask
)
3223 struct workqueue_attrs
*attrs
;
3225 attrs
= kzalloc(sizeof(*attrs
), gfp_mask
);
3228 if (!alloc_cpumask_var(&attrs
->cpumask
, gfp_mask
))
3231 cpumask_copy(attrs
->cpumask
, cpu_possible_mask
);
3234 free_workqueue_attrs(attrs
);
3238 static void copy_workqueue_attrs(struct workqueue_attrs
*to
,
3239 const struct workqueue_attrs
*from
)
3241 to
->nice
= from
->nice
;
3242 cpumask_copy(to
->cpumask
, from
->cpumask
);
3244 * Unlike hash and equality test, this function doesn't ignore
3245 * ->no_numa as it is used for both pool and wq attrs. Instead,
3246 * get_unbound_pool() explicitly clears ->no_numa after copying.
3248 to
->no_numa
= from
->no_numa
;
3251 /* hash value of the content of @attr */
3252 static u32
wqattrs_hash(const struct workqueue_attrs
*attrs
)
3256 hash
= jhash_1word(attrs
->nice
, hash
);
3257 hash
= jhash(cpumask_bits(attrs
->cpumask
),
3258 BITS_TO_LONGS(nr_cpumask_bits
) * sizeof(long), hash
);
3262 /* content equality test */
3263 static bool wqattrs_equal(const struct workqueue_attrs
*a
,
3264 const struct workqueue_attrs
*b
)
3266 if (a
->nice
!= b
->nice
)
3268 if (!cpumask_equal(a
->cpumask
, b
->cpumask
))
3274 * init_worker_pool - initialize a newly zalloc'd worker_pool
3275 * @pool: worker_pool to initialize
3277 * Initialize a newly zalloc'd @pool. It also allocates @pool->attrs.
3279 * Return: 0 on success, -errno on failure. Even on failure, all fields
3280 * inside @pool proper are initialized and put_unbound_pool() can be called
3281 * on @pool safely to release it.
3283 static int init_worker_pool(struct worker_pool
*pool
)
3285 spin_lock_init(&pool
->lock
);
3288 pool
->node
= NUMA_NO_NODE
;
3289 pool
->flags
|= POOL_DISASSOCIATED
;
3290 pool
->watchdog_ts
= jiffies
;
3291 INIT_LIST_HEAD(&pool
->worklist
);
3292 INIT_LIST_HEAD(&pool
->idle_list
);
3293 hash_init(pool
->busy_hash
);
3295 timer_setup(&pool
->idle_timer
, idle_worker_timeout
, TIMER_DEFERRABLE
);
3297 timer_setup(&pool
->mayday_timer
, pool_mayday_timeout
, 0);
3299 mutex_init(&pool
->attach_mutex
);
3300 INIT_LIST_HEAD(&pool
->workers
);
3302 ida_init(&pool
->worker_ida
);
3303 INIT_HLIST_NODE(&pool
->hash_node
);
3306 /* shouldn't fail above this point */
3307 pool
->attrs
= alloc_workqueue_attrs(GFP_KERNEL
);
3313 static void rcu_free_wq(struct rcu_head
*rcu
)
3315 struct workqueue_struct
*wq
=
3316 container_of(rcu
, struct workqueue_struct
, rcu
);
3318 if (!(wq
->flags
& WQ_UNBOUND
))
3319 free_percpu(wq
->cpu_pwqs
);
3321 free_workqueue_attrs(wq
->unbound_attrs
);
3327 static void rcu_free_pool(struct rcu_head
*rcu
)
3329 struct worker_pool
*pool
= container_of(rcu
, struct worker_pool
, rcu
);
3331 ida_destroy(&pool
->worker_ida
);
3332 free_workqueue_attrs(pool
->attrs
);
3337 * put_unbound_pool - put a worker_pool
3338 * @pool: worker_pool to put
3340 * Put @pool. If its refcnt reaches zero, it gets destroyed in sched-RCU
3341 * safe manner. get_unbound_pool() calls this function on its failure path
3342 * and this function should be able to release pools which went through,
3343 * successfully or not, init_worker_pool().
3345 * Should be called with wq_pool_mutex held.
3347 static void put_unbound_pool(struct worker_pool
*pool
)
3349 DECLARE_COMPLETION_ONSTACK(detach_completion
);
3350 struct worker
*worker
;
3352 lockdep_assert_held(&wq_pool_mutex
);
3358 if (WARN_ON(!(pool
->cpu
< 0)) ||
3359 WARN_ON(!list_empty(&pool
->worklist
)))
3362 /* release id and unhash */
3364 idr_remove(&worker_pool_idr
, pool
->id
);
3365 hash_del(&pool
->hash_node
);
3368 * Become the manager and destroy all workers. This prevents
3369 * @pool's workers from blocking on attach_mutex. We're the last
3370 * manager and @pool gets freed with the flag set.
3372 spin_lock_irq(&pool
->lock
);
3373 wait_event_lock_irq(wq_manager_wait
,
3374 !(pool
->flags
& POOL_MANAGER_ACTIVE
), pool
->lock
);
3375 pool
->flags
|= POOL_MANAGER_ACTIVE
;
3377 while ((worker
= first_idle_worker(pool
)))
3378 destroy_worker(worker
);
3379 WARN_ON(pool
->nr_workers
|| pool
->nr_idle
);
3380 spin_unlock_irq(&pool
->lock
);
3382 mutex_lock(&pool
->attach_mutex
);
3383 if (!list_empty(&pool
->workers
))
3384 pool
->detach_completion
= &detach_completion
;
3385 mutex_unlock(&pool
->attach_mutex
);
3387 if (pool
->detach_completion
)
3388 wait_for_completion(pool
->detach_completion
);
3390 /* shut down the timers */
3391 del_timer_sync(&pool
->idle_timer
);
3392 del_timer_sync(&pool
->mayday_timer
);
3394 /* sched-RCU protected to allow dereferences from get_work_pool() */
3395 call_rcu_sched(&pool
->rcu
, rcu_free_pool
);
3399 * get_unbound_pool - get a worker_pool with the specified attributes
3400 * @attrs: the attributes of the worker_pool to get
3402 * Obtain a worker_pool which has the same attributes as @attrs, bump the
3403 * reference count and return it. If there already is a matching
3404 * worker_pool, it will be used; otherwise, this function attempts to
3407 * Should be called with wq_pool_mutex held.
3409 * Return: On success, a worker_pool with the same attributes as @attrs.
3410 * On failure, %NULL.
3412 static struct worker_pool
*get_unbound_pool(const struct workqueue_attrs
*attrs
)
3414 u32 hash
= wqattrs_hash(attrs
);
3415 struct worker_pool
*pool
;
3417 int target_node
= NUMA_NO_NODE
;
3419 lockdep_assert_held(&wq_pool_mutex
);
3421 /* do we already have a matching pool? */
3422 hash_for_each_possible(unbound_pool_hash
, pool
, hash_node
, hash
) {
3423 if (wqattrs_equal(pool
->attrs
, attrs
)) {
3429 /* if cpumask is contained inside a NUMA node, we belong to that node */
3430 if (wq_numa_enabled
) {
3431 for_each_node(node
) {
3432 if (cpumask_subset(attrs
->cpumask
,
3433 wq_numa_possible_cpumask
[node
])) {
3440 /* nope, create a new one */
3441 pool
= kzalloc_node(sizeof(*pool
), GFP_KERNEL
, target_node
);
3442 if (!pool
|| init_worker_pool(pool
) < 0)
3445 lockdep_set_subclass(&pool
->lock
, 1); /* see put_pwq() */
3446 copy_workqueue_attrs(pool
->attrs
, attrs
);
3447 pool
->node
= target_node
;
3450 * no_numa isn't a worker_pool attribute, always clear it. See
3451 * 'struct workqueue_attrs' comments for detail.
3453 pool
->attrs
->no_numa
= false;
3455 if (worker_pool_assign_id(pool
) < 0)
3458 /* create and start the initial worker */
3459 if (wq_online
&& !create_worker(pool
))
3463 hash_add(unbound_pool_hash
, &pool
->hash_node
, hash
);
3468 put_unbound_pool(pool
);
3472 static void rcu_free_pwq(struct rcu_head
*rcu
)
3474 kmem_cache_free(pwq_cache
,
3475 container_of(rcu
, struct pool_workqueue
, rcu
));
3479 * Scheduled on system_wq by put_pwq() when an unbound pwq hits zero refcnt
3480 * and needs to be destroyed.
3482 static void pwq_unbound_release_workfn(struct work_struct
*work
)
3484 struct pool_workqueue
*pwq
= container_of(work
, struct pool_workqueue
,
3485 unbound_release_work
);
3486 struct workqueue_struct
*wq
= pwq
->wq
;
3487 struct worker_pool
*pool
= pwq
->pool
;
3490 if (WARN_ON_ONCE(!(wq
->flags
& WQ_UNBOUND
)))
3493 mutex_lock(&wq
->mutex
);
3494 list_del_rcu(&pwq
->pwqs_node
);
3495 is_last
= list_empty(&wq
->pwqs
);
3496 mutex_unlock(&wq
->mutex
);
3498 mutex_lock(&wq_pool_mutex
);
3499 put_unbound_pool(pool
);
3500 mutex_unlock(&wq_pool_mutex
);
3502 call_rcu_sched(&pwq
->rcu
, rcu_free_pwq
);
3505 * If we're the last pwq going away, @wq is already dead and no one
3506 * is gonna access it anymore. Schedule RCU free.
3509 call_rcu_sched(&wq
->rcu
, rcu_free_wq
);
3513 * pwq_adjust_max_active - update a pwq's max_active to the current setting
3514 * @pwq: target pool_workqueue
3516 * If @pwq isn't freezing, set @pwq->max_active to the associated
3517 * workqueue's saved_max_active and activate delayed work items
3518 * accordingly. If @pwq is freezing, clear @pwq->max_active to zero.
3520 static void pwq_adjust_max_active(struct pool_workqueue
*pwq
)
3522 struct workqueue_struct
*wq
= pwq
->wq
;
3523 bool freezable
= wq
->flags
& WQ_FREEZABLE
;
3524 unsigned long flags
;
3526 /* for @wq->saved_max_active */
3527 lockdep_assert_held(&wq
->mutex
);
3529 /* fast exit for non-freezable wqs */
3530 if (!freezable
&& pwq
->max_active
== wq
->saved_max_active
)
3533 /* this function can be called during early boot w/ irq disabled */
3534 spin_lock_irqsave(&pwq
->pool
->lock
, flags
);
3537 * During [un]freezing, the caller is responsible for ensuring that
3538 * this function is called at least once after @workqueue_freezing
3539 * is updated and visible.
3541 if (!freezable
|| !workqueue_freezing
) {
3542 pwq
->max_active
= wq
->saved_max_active
;
3544 while (!list_empty(&pwq
->delayed_works
) &&
3545 pwq
->nr_active
< pwq
->max_active
)
3546 pwq_activate_first_delayed(pwq
);
3549 * Need to kick a worker after thawed or an unbound wq's
3550 * max_active is bumped. It's a slow path. Do it always.
3552 wake_up_worker(pwq
->pool
);
3554 pwq
->max_active
= 0;
3557 spin_unlock_irqrestore(&pwq
->pool
->lock
, flags
);
3560 /* initialize newly alloced @pwq which is associated with @wq and @pool */
3561 static void init_pwq(struct pool_workqueue
*pwq
, struct workqueue_struct
*wq
,
3562 struct worker_pool
*pool
)
3564 BUG_ON((unsigned long)pwq
& WORK_STRUCT_FLAG_MASK
);
3566 memset(pwq
, 0, sizeof(*pwq
));
3570 pwq
->flush_color
= -1;
3572 INIT_LIST_HEAD(&pwq
->delayed_works
);
3573 INIT_LIST_HEAD(&pwq
->pwqs_node
);
3574 INIT_LIST_HEAD(&pwq
->mayday_node
);
3575 INIT_WORK(&pwq
->unbound_release_work
, pwq_unbound_release_workfn
);
3578 /* sync @pwq with the current state of its associated wq and link it */
3579 static void link_pwq(struct pool_workqueue
*pwq
)
3581 struct workqueue_struct
*wq
= pwq
->wq
;
3583 lockdep_assert_held(&wq
->mutex
);
3585 /* may be called multiple times, ignore if already linked */
3586 if (!list_empty(&pwq
->pwqs_node
))
3589 /* set the matching work_color */
3590 pwq
->work_color
= wq
->work_color
;
3592 /* sync max_active to the current setting */
3593 pwq_adjust_max_active(pwq
);
3596 list_add_rcu(&pwq
->pwqs_node
, &wq
->pwqs
);
3599 /* obtain a pool matching @attr and create a pwq associating the pool and @wq */
3600 static struct pool_workqueue
*alloc_unbound_pwq(struct workqueue_struct
*wq
,
3601 const struct workqueue_attrs
*attrs
)
3603 struct worker_pool
*pool
;
3604 struct pool_workqueue
*pwq
;
3606 lockdep_assert_held(&wq_pool_mutex
);
3608 pool
= get_unbound_pool(attrs
);
3612 pwq
= kmem_cache_alloc_node(pwq_cache
, GFP_KERNEL
, pool
->node
);
3614 put_unbound_pool(pool
);
3618 init_pwq(pwq
, wq
, pool
);
3623 * wq_calc_node_cpumask - calculate a wq_attrs' cpumask for the specified node
3624 * @attrs: the wq_attrs of the default pwq of the target workqueue
3625 * @node: the target NUMA node
3626 * @cpu_going_down: if >= 0, the CPU to consider as offline
3627 * @cpumask: outarg, the resulting cpumask
3629 * Calculate the cpumask a workqueue with @attrs should use on @node. If
3630 * @cpu_going_down is >= 0, that cpu is considered offline during
3631 * calculation. The result is stored in @cpumask.
3633 * If NUMA affinity is not enabled, @attrs->cpumask is always used. If
3634 * enabled and @node has online CPUs requested by @attrs, the returned
3635 * cpumask is the intersection of the possible CPUs of @node and
3638 * The caller is responsible for ensuring that the cpumask of @node stays
3641 * Return: %true if the resulting @cpumask is different from @attrs->cpumask,
3644 static bool wq_calc_node_cpumask(const struct workqueue_attrs
*attrs
, int node
,
3645 int cpu_going_down
, cpumask_t
*cpumask
)
3647 if (!wq_numa_enabled
|| attrs
->no_numa
)
3650 /* does @node have any online CPUs @attrs wants? */
3651 cpumask_and(cpumask
, cpumask_of_node(node
), attrs
->cpumask
);
3652 if (cpu_going_down
>= 0)
3653 cpumask_clear_cpu(cpu_going_down
, cpumask
);
3655 if (cpumask_empty(cpumask
))
3658 /* yeap, return possible CPUs in @node that @attrs wants */
3659 cpumask_and(cpumask
, attrs
->cpumask
, wq_numa_possible_cpumask
[node
]);
3661 if (cpumask_empty(cpumask
)) {
3662 pr_warn_once("WARNING: workqueue cpumask: online intersect > "
3663 "possible intersect\n");
3667 return !cpumask_equal(cpumask
, attrs
->cpumask
);
3670 cpumask_copy(cpumask
, attrs
->cpumask
);
3674 /* install @pwq into @wq's numa_pwq_tbl[] for @node and return the old pwq */
3675 static struct pool_workqueue
*numa_pwq_tbl_install(struct workqueue_struct
*wq
,
3677 struct pool_workqueue
*pwq
)
3679 struct pool_workqueue
*old_pwq
;
3681 lockdep_assert_held(&wq_pool_mutex
);
3682 lockdep_assert_held(&wq
->mutex
);
3684 /* link_pwq() can handle duplicate calls */
3687 old_pwq
= rcu_access_pointer(wq
->numa_pwq_tbl
[node
]);
3688 rcu_assign_pointer(wq
->numa_pwq_tbl
[node
], pwq
);
3692 /* context to store the prepared attrs & pwqs before applying */
3693 struct apply_wqattrs_ctx
{
3694 struct workqueue_struct
*wq
; /* target workqueue */
3695 struct workqueue_attrs
*attrs
; /* attrs to apply */
3696 struct list_head list
; /* queued for batching commit */
3697 struct pool_workqueue
*dfl_pwq
;
3698 struct pool_workqueue
*pwq_tbl
[];
3701 /* free the resources after success or abort */
3702 static void apply_wqattrs_cleanup(struct apply_wqattrs_ctx
*ctx
)
3708 put_pwq_unlocked(ctx
->pwq_tbl
[node
]);
3709 put_pwq_unlocked(ctx
->dfl_pwq
);
3711 free_workqueue_attrs(ctx
->attrs
);
3717 /* allocate the attrs and pwqs for later installation */
3718 static struct apply_wqattrs_ctx
*
3719 apply_wqattrs_prepare(struct workqueue_struct
*wq
,
3720 const struct workqueue_attrs
*attrs
)
3722 struct apply_wqattrs_ctx
*ctx
;
3723 struct workqueue_attrs
*new_attrs
, *tmp_attrs
;
3726 lockdep_assert_held(&wq_pool_mutex
);
3728 ctx
= kzalloc(sizeof(*ctx
) + nr_node_ids
* sizeof(ctx
->pwq_tbl
[0]),
3731 new_attrs
= alloc_workqueue_attrs(GFP_KERNEL
);
3732 tmp_attrs
= alloc_workqueue_attrs(GFP_KERNEL
);
3733 if (!ctx
|| !new_attrs
|| !tmp_attrs
)
3737 * Calculate the attrs of the default pwq.
3738 * If the user configured cpumask doesn't overlap with the
3739 * wq_unbound_cpumask, we fallback to the wq_unbound_cpumask.
3741 copy_workqueue_attrs(new_attrs
, attrs
);
3742 cpumask_and(new_attrs
->cpumask
, new_attrs
->cpumask
, wq_unbound_cpumask
);
3743 if (unlikely(cpumask_empty(new_attrs
->cpumask
)))
3744 cpumask_copy(new_attrs
->cpumask
, wq_unbound_cpumask
);
3747 * We may create multiple pwqs with differing cpumasks. Make a
3748 * copy of @new_attrs which will be modified and used to obtain
3751 copy_workqueue_attrs(tmp_attrs
, new_attrs
);
3754 * If something goes wrong during CPU up/down, we'll fall back to
3755 * the default pwq covering whole @attrs->cpumask. Always create
3756 * it even if we don't use it immediately.
3758 ctx
->dfl_pwq
= alloc_unbound_pwq(wq
, new_attrs
);
3762 for_each_node(node
) {
3763 if (wq_calc_node_cpumask(new_attrs
, node
, -1, tmp_attrs
->cpumask
)) {
3764 ctx
->pwq_tbl
[node
] = alloc_unbound_pwq(wq
, tmp_attrs
);
3765 if (!ctx
->pwq_tbl
[node
])
3768 ctx
->dfl_pwq
->refcnt
++;
3769 ctx
->pwq_tbl
[node
] = ctx
->dfl_pwq
;
3773 /* save the user configured attrs and sanitize it. */
3774 copy_workqueue_attrs(new_attrs
, attrs
);
3775 cpumask_and(new_attrs
->cpumask
, new_attrs
->cpumask
, cpu_possible_mask
);
3776 ctx
->attrs
= new_attrs
;
3779 free_workqueue_attrs(tmp_attrs
);
3783 free_workqueue_attrs(tmp_attrs
);
3784 free_workqueue_attrs(new_attrs
);
3785 apply_wqattrs_cleanup(ctx
);
3789 /* set attrs and install prepared pwqs, @ctx points to old pwqs on return */
3790 static void apply_wqattrs_commit(struct apply_wqattrs_ctx
*ctx
)
3794 /* all pwqs have been created successfully, let's install'em */
3795 mutex_lock(&ctx
->wq
->mutex
);
3797 copy_workqueue_attrs(ctx
->wq
->unbound_attrs
, ctx
->attrs
);
3799 /* save the previous pwq and install the new one */
3801 ctx
->pwq_tbl
[node
] = numa_pwq_tbl_install(ctx
->wq
, node
,
3802 ctx
->pwq_tbl
[node
]);
3804 /* @dfl_pwq might not have been used, ensure it's linked */
3805 link_pwq(ctx
->dfl_pwq
);
3806 swap(ctx
->wq
->dfl_pwq
, ctx
->dfl_pwq
);
3808 mutex_unlock(&ctx
->wq
->mutex
);
3811 static void apply_wqattrs_lock(void)
3813 /* CPUs should stay stable across pwq creations and installations */
3815 mutex_lock(&wq_pool_mutex
);
3818 static void apply_wqattrs_unlock(void)
3820 mutex_unlock(&wq_pool_mutex
);
3824 static int apply_workqueue_attrs_locked(struct workqueue_struct
*wq
,
3825 const struct workqueue_attrs
*attrs
)
3827 struct apply_wqattrs_ctx
*ctx
;
3829 /* only unbound workqueues can change attributes */
3830 if (WARN_ON(!(wq
->flags
& WQ_UNBOUND
)))
3833 /* creating multiple pwqs breaks ordering guarantee */
3834 if (!list_empty(&wq
->pwqs
)) {
3835 if (WARN_ON(wq
->flags
& __WQ_ORDERED_EXPLICIT
))
3838 wq
->flags
&= ~__WQ_ORDERED
;
3841 ctx
= apply_wqattrs_prepare(wq
, attrs
);
3845 /* the ctx has been prepared successfully, let's commit it */
3846 apply_wqattrs_commit(ctx
);
3847 apply_wqattrs_cleanup(ctx
);
3853 * apply_workqueue_attrs - apply new workqueue_attrs to an unbound workqueue
3854 * @wq: the target workqueue
3855 * @attrs: the workqueue_attrs to apply, allocated with alloc_workqueue_attrs()
3857 * Apply @attrs to an unbound workqueue @wq. Unless disabled, on NUMA
3858 * machines, this function maps a separate pwq to each NUMA node with
3859 * possibles CPUs in @attrs->cpumask so that work items are affine to the
3860 * NUMA node it was issued on. Older pwqs are released as in-flight work
3861 * items finish. Note that a work item which repeatedly requeues itself
3862 * back-to-back will stay on its current pwq.
3864 * Performs GFP_KERNEL allocations.
3866 * Return: 0 on success and -errno on failure.
3868 int apply_workqueue_attrs(struct workqueue_struct
*wq
,
3869 const struct workqueue_attrs
*attrs
)
3873 apply_wqattrs_lock();
3874 ret
= apply_workqueue_attrs_locked(wq
, attrs
);
3875 apply_wqattrs_unlock();
3881 * wq_update_unbound_numa - update NUMA affinity of a wq for CPU hot[un]plug
3882 * @wq: the target workqueue
3883 * @cpu: the CPU coming up or going down
3884 * @online: whether @cpu is coming up or going down
3886 * This function is to be called from %CPU_DOWN_PREPARE, %CPU_ONLINE and
3887 * %CPU_DOWN_FAILED. @cpu is being hot[un]plugged, update NUMA affinity of
3890 * If NUMA affinity can't be adjusted due to memory allocation failure, it
3891 * falls back to @wq->dfl_pwq which may not be optimal but is always
3894 * Note that when the last allowed CPU of a NUMA node goes offline for a
3895 * workqueue with a cpumask spanning multiple nodes, the workers which were
3896 * already executing the work items for the workqueue will lose their CPU
3897 * affinity and may execute on any CPU. This is similar to how per-cpu
3898 * workqueues behave on CPU_DOWN. If a workqueue user wants strict
3899 * affinity, it's the user's responsibility to flush the work item from
3902 static void wq_update_unbound_numa(struct workqueue_struct
*wq
, int cpu
,
3905 int node
= cpu_to_node(cpu
);
3906 int cpu_off
= online
? -1 : cpu
;
3907 struct pool_workqueue
*old_pwq
= NULL
, *pwq
;
3908 struct workqueue_attrs
*target_attrs
;
3911 lockdep_assert_held(&wq_pool_mutex
);
3913 if (!wq_numa_enabled
|| !(wq
->flags
& WQ_UNBOUND
) ||
3914 wq
->unbound_attrs
->no_numa
)
3918 * We don't wanna alloc/free wq_attrs for each wq for each CPU.
3919 * Let's use a preallocated one. The following buf is protected by
3920 * CPU hotplug exclusion.
3922 target_attrs
= wq_update_unbound_numa_attrs_buf
;
3923 cpumask
= target_attrs
->cpumask
;
3925 copy_workqueue_attrs(target_attrs
, wq
->unbound_attrs
);
3926 pwq
= unbound_pwq_by_node(wq
, node
);
3929 * Let's determine what needs to be done. If the target cpumask is
3930 * different from the default pwq's, we need to compare it to @pwq's
3931 * and create a new one if they don't match. If the target cpumask
3932 * equals the default pwq's, the default pwq should be used.
3934 if (wq_calc_node_cpumask(wq
->dfl_pwq
->pool
->attrs
, node
, cpu_off
, cpumask
)) {
3935 if (cpumask_equal(cpumask
, pwq
->pool
->attrs
->cpumask
))
3941 /* create a new pwq */
3942 pwq
= alloc_unbound_pwq(wq
, target_attrs
);
3944 pr_warn("workqueue: allocation failed while updating NUMA affinity of \"%s\"\n",
3949 /* Install the new pwq. */
3950 mutex_lock(&wq
->mutex
);
3951 old_pwq
= numa_pwq_tbl_install(wq
, node
, pwq
);
3955 mutex_lock(&wq
->mutex
);
3956 spin_lock_irq(&wq
->dfl_pwq
->pool
->lock
);
3957 get_pwq(wq
->dfl_pwq
);
3958 spin_unlock_irq(&wq
->dfl_pwq
->pool
->lock
);
3959 old_pwq
= numa_pwq_tbl_install(wq
, node
, wq
->dfl_pwq
);
3961 mutex_unlock(&wq
->mutex
);
3962 put_pwq_unlocked(old_pwq
);
3965 static int alloc_and_link_pwqs(struct workqueue_struct
*wq
)
3967 bool highpri
= wq
->flags
& WQ_HIGHPRI
;
3970 if (!(wq
->flags
& WQ_UNBOUND
)) {
3971 wq
->cpu_pwqs
= alloc_percpu(struct pool_workqueue
);
3975 for_each_possible_cpu(cpu
) {
3976 struct pool_workqueue
*pwq
=
3977 per_cpu_ptr(wq
->cpu_pwqs
, cpu
);
3978 struct worker_pool
*cpu_pools
=
3979 per_cpu(cpu_worker_pools
, cpu
);
3981 init_pwq(pwq
, wq
, &cpu_pools
[highpri
]);
3983 mutex_lock(&wq
->mutex
);
3985 mutex_unlock(&wq
->mutex
);
3988 } else if (wq
->flags
& __WQ_ORDERED
) {
3989 ret
= apply_workqueue_attrs(wq
, ordered_wq_attrs
[highpri
]);
3990 /* there should only be single pwq for ordering guarantee */
3991 WARN(!ret
&& (wq
->pwqs
.next
!= &wq
->dfl_pwq
->pwqs_node
||
3992 wq
->pwqs
.prev
!= &wq
->dfl_pwq
->pwqs_node
),
3993 "ordering guarantee broken for workqueue %s\n", wq
->name
);
3996 return apply_workqueue_attrs(wq
, unbound_std_wq_attrs
[highpri
]);
4000 static int wq_clamp_max_active(int max_active
, unsigned int flags
,
4003 int lim
= flags
& WQ_UNBOUND
? WQ_UNBOUND_MAX_ACTIVE
: WQ_MAX_ACTIVE
;
4005 if (max_active
< 1 || max_active
> lim
)
4006 pr_warn("workqueue: max_active %d requested for %s is out of range, clamping between %d and %d\n",
4007 max_active
, name
, 1, lim
);
4009 return clamp_val(max_active
, 1, lim
);
4012 struct workqueue_struct
*__alloc_workqueue_key(const char *fmt
,
4015 struct lock_class_key
*key
,
4016 const char *lock_name
, ...)
4018 size_t tbl_size
= 0;
4020 struct workqueue_struct
*wq
;
4021 struct pool_workqueue
*pwq
;
4024 * Unbound && max_active == 1 used to imply ordered, which is no
4025 * longer the case on NUMA machines due to per-node pools. While
4026 * alloc_ordered_workqueue() is the right way to create an ordered
4027 * workqueue, keep the previous behavior to avoid subtle breakages
4030 if ((flags
& WQ_UNBOUND
) && max_active
== 1)
4031 flags
|= __WQ_ORDERED
;
4033 /* see the comment above the definition of WQ_POWER_EFFICIENT */
4034 if ((flags
& WQ_POWER_EFFICIENT
) && wq_power_efficient
)
4035 flags
|= WQ_UNBOUND
;
4037 /* allocate wq and format name */
4038 if (flags
& WQ_UNBOUND
)
4039 tbl_size
= nr_node_ids
* sizeof(wq
->numa_pwq_tbl
[0]);
4041 wq
= kzalloc(sizeof(*wq
) + tbl_size
, GFP_KERNEL
);
4045 if (flags
& WQ_UNBOUND
) {
4046 wq
->unbound_attrs
= alloc_workqueue_attrs(GFP_KERNEL
);
4047 if (!wq
->unbound_attrs
)
4051 va_start(args
, lock_name
);
4052 vsnprintf(wq
->name
, sizeof(wq
->name
), fmt
, args
);
4055 max_active
= max_active
?: WQ_DFL_ACTIVE
;
4056 max_active
= wq_clamp_max_active(max_active
, flags
, wq
->name
);
4060 wq
->saved_max_active
= max_active
;
4061 mutex_init(&wq
->mutex
);
4062 atomic_set(&wq
->nr_pwqs_to_flush
, 0);
4063 INIT_LIST_HEAD(&wq
->pwqs
);
4064 INIT_LIST_HEAD(&wq
->flusher_queue
);
4065 INIT_LIST_HEAD(&wq
->flusher_overflow
);
4066 INIT_LIST_HEAD(&wq
->maydays
);
4068 lockdep_init_map(&wq
->lockdep_map
, lock_name
, key
, 0);
4069 INIT_LIST_HEAD(&wq
->list
);
4071 if (alloc_and_link_pwqs(wq
) < 0)
4075 * Workqueues which may be used during memory reclaim should
4076 * have a rescuer to guarantee forward progress.
4078 if (flags
& WQ_MEM_RECLAIM
) {
4079 struct worker
*rescuer
;
4081 rescuer
= alloc_worker(NUMA_NO_NODE
);
4085 rescuer
->rescue_wq
= wq
;
4086 rescuer
->task
= kthread_create(rescuer_thread
, rescuer
, "%s",
4088 if (IS_ERR(rescuer
->task
)) {
4093 wq
->rescuer
= rescuer
;
4094 kthread_bind_mask(rescuer
->task
, cpu_possible_mask
);
4095 wake_up_process(rescuer
->task
);
4098 if ((wq
->flags
& WQ_SYSFS
) && workqueue_sysfs_register(wq
))
4102 * wq_pool_mutex protects global freeze state and workqueues list.
4103 * Grab it, adjust max_active and add the new @wq to workqueues
4106 mutex_lock(&wq_pool_mutex
);
4108 mutex_lock(&wq
->mutex
);
4109 for_each_pwq(pwq
, wq
)
4110 pwq_adjust_max_active(pwq
);
4111 mutex_unlock(&wq
->mutex
);
4113 list_add_tail_rcu(&wq
->list
, &workqueues
);
4115 mutex_unlock(&wq_pool_mutex
);
4120 free_workqueue_attrs(wq
->unbound_attrs
);
4124 destroy_workqueue(wq
);
4127 EXPORT_SYMBOL_GPL(__alloc_workqueue_key
);
4130 * destroy_workqueue - safely terminate a workqueue
4131 * @wq: target workqueue
4133 * Safely destroy a workqueue. All work currently pending will be done first.
4135 void destroy_workqueue(struct workqueue_struct
*wq
)
4137 struct pool_workqueue
*pwq
;
4140 /* drain it before proceeding with destruction */
4141 drain_workqueue(wq
);
4144 mutex_lock(&wq
->mutex
);
4145 for_each_pwq(pwq
, wq
) {
4148 for (i
= 0; i
< WORK_NR_COLORS
; i
++) {
4149 if (WARN_ON(pwq
->nr_in_flight
[i
])) {
4150 mutex_unlock(&wq
->mutex
);
4151 show_workqueue_state();
4156 if (WARN_ON((pwq
!= wq
->dfl_pwq
) && (pwq
->refcnt
> 1)) ||
4157 WARN_ON(pwq
->nr_active
) ||
4158 WARN_ON(!list_empty(&pwq
->delayed_works
))) {
4159 mutex_unlock(&wq
->mutex
);
4160 show_workqueue_state();
4164 mutex_unlock(&wq
->mutex
);
4167 * wq list is used to freeze wq, remove from list after
4168 * flushing is complete in case freeze races us.
4170 mutex_lock(&wq_pool_mutex
);
4171 list_del_rcu(&wq
->list
);
4172 mutex_unlock(&wq_pool_mutex
);
4174 workqueue_sysfs_unregister(wq
);
4177 kthread_stop(wq
->rescuer
->task
);
4179 if (!(wq
->flags
& WQ_UNBOUND
)) {
4181 * The base ref is never dropped on per-cpu pwqs. Directly
4182 * schedule RCU free.
4184 call_rcu_sched(&wq
->rcu
, rcu_free_wq
);
4187 * We're the sole accessor of @wq at this point. Directly
4188 * access numa_pwq_tbl[] and dfl_pwq to put the base refs.
4189 * @wq will be freed when the last pwq is released.
4191 for_each_node(node
) {
4192 pwq
= rcu_access_pointer(wq
->numa_pwq_tbl
[node
]);
4193 RCU_INIT_POINTER(wq
->numa_pwq_tbl
[node
], NULL
);
4194 put_pwq_unlocked(pwq
);
4198 * Put dfl_pwq. @wq may be freed any time after dfl_pwq is
4199 * put. Don't access it afterwards.
4203 put_pwq_unlocked(pwq
);
4206 EXPORT_SYMBOL_GPL(destroy_workqueue
);
4209 * workqueue_set_max_active - adjust max_active of a workqueue
4210 * @wq: target workqueue
4211 * @max_active: new max_active value.
4213 * Set max_active of @wq to @max_active.
4216 * Don't call from IRQ context.
4218 void workqueue_set_max_active(struct workqueue_struct
*wq
, int max_active
)
4220 struct pool_workqueue
*pwq
;
4222 /* disallow meddling with max_active for ordered workqueues */
4223 if (WARN_ON(wq
->flags
& __WQ_ORDERED_EXPLICIT
))
4226 max_active
= wq_clamp_max_active(max_active
, wq
->flags
, wq
->name
);
4228 mutex_lock(&wq
->mutex
);
4230 wq
->flags
&= ~__WQ_ORDERED
;
4231 wq
->saved_max_active
= max_active
;
4233 for_each_pwq(pwq
, wq
)
4234 pwq_adjust_max_active(pwq
);
4236 mutex_unlock(&wq
->mutex
);
4238 EXPORT_SYMBOL_GPL(workqueue_set_max_active
);
4241 * current_work - retrieve %current task's work struct
4243 * Determine if %current task is a workqueue worker and what it's working on.
4244 * Useful to find out the context that the %current task is running in.
4246 * Return: work struct if %current task is a workqueue worker, %NULL otherwise.
4248 struct work_struct
*current_work(void)
4250 struct worker
*worker
= current_wq_worker();
4252 return worker
? worker
->current_work
: NULL
;
4254 EXPORT_SYMBOL(current_work
);
4257 * current_is_workqueue_rescuer - is %current workqueue rescuer?
4259 * Determine whether %current is a workqueue rescuer. Can be used from
4260 * work functions to determine whether it's being run off the rescuer task.
4262 * Return: %true if %current is a workqueue rescuer. %false otherwise.
4264 bool current_is_workqueue_rescuer(void)
4266 struct worker
*worker
= current_wq_worker();
4268 return worker
&& worker
->rescue_wq
;
4272 * workqueue_congested - test whether a workqueue is congested
4273 * @cpu: CPU in question
4274 * @wq: target workqueue
4276 * Test whether @wq's cpu workqueue for @cpu is congested. There is
4277 * no synchronization around this function and the test result is
4278 * unreliable and only useful as advisory hints or for debugging.
4280 * If @cpu is WORK_CPU_UNBOUND, the test is performed on the local CPU.
4281 * Note that both per-cpu and unbound workqueues may be associated with
4282 * multiple pool_workqueues which have separate congested states. A
4283 * workqueue being congested on one CPU doesn't mean the workqueue is also
4284 * contested on other CPUs / NUMA nodes.
4287 * %true if congested, %false otherwise.
4289 bool workqueue_congested(int cpu
, struct workqueue_struct
*wq
)
4291 struct pool_workqueue
*pwq
;
4294 rcu_read_lock_sched();
4296 if (cpu
== WORK_CPU_UNBOUND
)
4297 cpu
= smp_processor_id();
4299 if (!(wq
->flags
& WQ_UNBOUND
))
4300 pwq
= per_cpu_ptr(wq
->cpu_pwqs
, cpu
);
4302 pwq
= unbound_pwq_by_node(wq
, cpu_to_node(cpu
));
4304 ret
= !list_empty(&pwq
->delayed_works
);
4305 rcu_read_unlock_sched();
4309 EXPORT_SYMBOL_GPL(workqueue_congested
);
4312 * work_busy - test whether a work is currently pending or running
4313 * @work: the work to be tested
4315 * Test whether @work is currently pending or running. There is no
4316 * synchronization around this function and the test result is
4317 * unreliable and only useful as advisory hints or for debugging.
4320 * OR'd bitmask of WORK_BUSY_* bits.
4322 unsigned int work_busy(struct work_struct
*work
)
4324 struct worker_pool
*pool
;
4325 unsigned long flags
;
4326 unsigned int ret
= 0;
4328 if (work_pending(work
))
4329 ret
|= WORK_BUSY_PENDING
;
4331 local_irq_save(flags
);
4332 pool
= get_work_pool(work
);
4334 spin_lock(&pool
->lock
);
4335 if (find_worker_executing_work(pool
, work
))
4336 ret
|= WORK_BUSY_RUNNING
;
4337 spin_unlock(&pool
->lock
);
4339 local_irq_restore(flags
);
4343 EXPORT_SYMBOL_GPL(work_busy
);
4346 * set_worker_desc - set description for the current work item
4347 * @fmt: printf-style format string
4348 * @...: arguments for the format string
4350 * This function can be called by a running work function to describe what
4351 * the work item is about. If the worker task gets dumped, this
4352 * information will be printed out together to help debugging. The
4353 * description can be at most WORKER_DESC_LEN including the trailing '\0'.
4355 void set_worker_desc(const char *fmt
, ...)
4357 struct worker
*worker
= current_wq_worker();
4361 va_start(args
, fmt
);
4362 vsnprintf(worker
->desc
, sizeof(worker
->desc
), fmt
, args
);
4364 worker
->desc_valid
= true;
4369 * print_worker_info - print out worker information and description
4370 * @log_lvl: the log level to use when printing
4371 * @task: target task
4373 * If @task is a worker and currently executing a work item, print out the
4374 * name of the workqueue being serviced and worker description set with
4375 * set_worker_desc() by the currently executing work item.
4377 * This function can be safely called on any task as long as the
4378 * task_struct itself is accessible. While safe, this function isn't
4379 * synchronized and may print out mixups or garbages of limited length.
4381 void print_worker_info(const char *log_lvl
, struct task_struct
*task
)
4383 work_func_t
*fn
= NULL
;
4384 char name
[WQ_NAME_LEN
] = { };
4385 char desc
[WORKER_DESC_LEN
] = { };
4386 struct pool_workqueue
*pwq
= NULL
;
4387 struct workqueue_struct
*wq
= NULL
;
4388 bool desc_valid
= false;
4389 struct worker
*worker
;
4391 if (!(task
->flags
& PF_WQ_WORKER
))
4395 * This function is called without any synchronization and @task
4396 * could be in any state. Be careful with dereferences.
4398 worker
= kthread_probe_data(task
);
4401 * Carefully copy the associated workqueue's workfn and name. Keep
4402 * the original last '\0' in case the original contains garbage.
4404 probe_kernel_read(&fn
, &worker
->current_func
, sizeof(fn
));
4405 probe_kernel_read(&pwq
, &worker
->current_pwq
, sizeof(pwq
));
4406 probe_kernel_read(&wq
, &pwq
->wq
, sizeof(wq
));
4407 probe_kernel_read(name
, wq
->name
, sizeof(name
) - 1);
4409 /* copy worker description */
4410 probe_kernel_read(&desc_valid
, &worker
->desc_valid
, sizeof(desc_valid
));
4412 probe_kernel_read(desc
, worker
->desc
, sizeof(desc
) - 1);
4414 if (fn
|| name
[0] || desc
[0]) {
4415 printk("%sWorkqueue: %s %pf", log_lvl
, name
, fn
);
4417 pr_cont(" (%s)", desc
);
4422 static void pr_cont_pool_info(struct worker_pool
*pool
)
4424 pr_cont(" cpus=%*pbl", nr_cpumask_bits
, pool
->attrs
->cpumask
);
4425 if (pool
->node
!= NUMA_NO_NODE
)
4426 pr_cont(" node=%d", pool
->node
);
4427 pr_cont(" flags=0x%x nice=%d", pool
->flags
, pool
->attrs
->nice
);
4430 static void pr_cont_work(bool comma
, struct work_struct
*work
)
4432 if (work
->func
== wq_barrier_func
) {
4433 struct wq_barrier
*barr
;
4435 barr
= container_of(work
, struct wq_barrier
, work
);
4437 pr_cont("%s BAR(%d)", comma
? "," : "",
4438 task_pid_nr(barr
->task
));
4440 pr_cont("%s %pf", comma
? "," : "", work
->func
);
4444 static void show_pwq(struct pool_workqueue
*pwq
)
4446 struct worker_pool
*pool
= pwq
->pool
;
4447 struct work_struct
*work
;
4448 struct worker
*worker
;
4449 bool has_in_flight
= false, has_pending
= false;
4452 pr_info(" pwq %d:", pool
->id
);
4453 pr_cont_pool_info(pool
);
4455 pr_cont(" active=%d/%d%s\n", pwq
->nr_active
, pwq
->max_active
,
4456 !list_empty(&pwq
->mayday_node
) ? " MAYDAY" : "");
4458 hash_for_each(pool
->busy_hash
, bkt
, worker
, hentry
) {
4459 if (worker
->current_pwq
== pwq
) {
4460 has_in_flight
= true;
4464 if (has_in_flight
) {
4467 pr_info(" in-flight:");
4468 hash_for_each(pool
->busy_hash
, bkt
, worker
, hentry
) {
4469 if (worker
->current_pwq
!= pwq
)
4472 pr_cont("%s %d%s:%pf", comma
? "," : "",
4473 task_pid_nr(worker
->task
),
4474 worker
== pwq
->wq
->rescuer
? "(RESCUER)" : "",
4475 worker
->current_func
);
4476 list_for_each_entry(work
, &worker
->scheduled
, entry
)
4477 pr_cont_work(false, work
);
4483 list_for_each_entry(work
, &pool
->worklist
, entry
) {
4484 if (get_work_pwq(work
) == pwq
) {
4492 pr_info(" pending:");
4493 list_for_each_entry(work
, &pool
->worklist
, entry
) {
4494 if (get_work_pwq(work
) != pwq
)
4497 pr_cont_work(comma
, work
);
4498 comma
= !(*work_data_bits(work
) & WORK_STRUCT_LINKED
);
4503 if (!list_empty(&pwq
->delayed_works
)) {
4506 pr_info(" delayed:");
4507 list_for_each_entry(work
, &pwq
->delayed_works
, entry
) {
4508 pr_cont_work(comma
, work
);
4509 comma
= !(*work_data_bits(work
) & WORK_STRUCT_LINKED
);
4516 * show_workqueue_state - dump workqueue state
4518 * Called from a sysrq handler or try_to_freeze_tasks() and prints out
4519 * all busy workqueues and pools.
4521 void show_workqueue_state(void)
4523 struct workqueue_struct
*wq
;
4524 struct worker_pool
*pool
;
4525 unsigned long flags
;
4528 rcu_read_lock_sched();
4530 pr_info("Showing busy workqueues and worker pools:\n");
4532 list_for_each_entry_rcu(wq
, &workqueues
, list
) {
4533 struct pool_workqueue
*pwq
;
4536 for_each_pwq(pwq
, wq
) {
4537 if (pwq
->nr_active
|| !list_empty(&pwq
->delayed_works
)) {
4545 pr_info("workqueue %s: flags=0x%x\n", wq
->name
, wq
->flags
);
4547 for_each_pwq(pwq
, wq
) {
4548 spin_lock_irqsave(&pwq
->pool
->lock
, flags
);
4549 if (pwq
->nr_active
|| !list_empty(&pwq
->delayed_works
))
4551 spin_unlock_irqrestore(&pwq
->pool
->lock
, flags
);
4553 * We could be printing a lot from atomic context, e.g.
4554 * sysrq-t -> show_workqueue_state(). Avoid triggering
4557 touch_nmi_watchdog();
4561 for_each_pool(pool
, pi
) {
4562 struct worker
*worker
;
4565 spin_lock_irqsave(&pool
->lock
, flags
);
4566 if (pool
->nr_workers
== pool
->nr_idle
)
4569 pr_info("pool %d:", pool
->id
);
4570 pr_cont_pool_info(pool
);
4571 pr_cont(" hung=%us workers=%d",
4572 jiffies_to_msecs(jiffies
- pool
->watchdog_ts
) / 1000,
4575 pr_cont(" manager: %d",
4576 task_pid_nr(pool
->manager
->task
));
4577 list_for_each_entry(worker
, &pool
->idle_list
, entry
) {
4578 pr_cont(" %s%d", first
? "idle: " : "",
4579 task_pid_nr(worker
->task
));
4584 spin_unlock_irqrestore(&pool
->lock
, flags
);
4586 * We could be printing a lot from atomic context, e.g.
4587 * sysrq-t -> show_workqueue_state(). Avoid triggering
4590 touch_nmi_watchdog();
4593 rcu_read_unlock_sched();
4599 * There are two challenges in supporting CPU hotplug. Firstly, there
4600 * are a lot of assumptions on strong associations among work, pwq and
4601 * pool which make migrating pending and scheduled works very
4602 * difficult to implement without impacting hot paths. Secondly,
4603 * worker pools serve mix of short, long and very long running works making
4604 * blocked draining impractical.
4606 * This is solved by allowing the pools to be disassociated from the CPU
4607 * running as an unbound one and allowing it to be reattached later if the
4608 * cpu comes back online.
4611 static void unbind_workers(int cpu
)
4613 struct worker_pool
*pool
;
4614 struct worker
*worker
;
4616 for_each_cpu_worker_pool(pool
, cpu
) {
4617 mutex_lock(&pool
->attach_mutex
);
4618 spin_lock_irq(&pool
->lock
);
4621 * We've blocked all attach/detach operations. Make all workers
4622 * unbound and set DISASSOCIATED. Before this, all workers
4623 * except for the ones which are still executing works from
4624 * before the last CPU down must be on the cpu. After
4625 * this, they may become diasporas.
4627 for_each_pool_worker(worker
, pool
)
4628 worker
->flags
|= WORKER_UNBOUND
;
4630 pool
->flags
|= POOL_DISASSOCIATED
;
4632 spin_unlock_irq(&pool
->lock
);
4633 mutex_unlock(&pool
->attach_mutex
);
4636 * Call schedule() so that we cross rq->lock and thus can
4637 * guarantee sched callbacks see the %WORKER_UNBOUND flag.
4638 * This is necessary as scheduler callbacks may be invoked
4644 * Sched callbacks are disabled now. Zap nr_running.
4645 * After this, nr_running stays zero and need_more_worker()
4646 * and keep_working() are always true as long as the
4647 * worklist is not empty. This pool now behaves as an
4648 * unbound (in terms of concurrency management) pool which
4649 * are served by workers tied to the pool.
4651 atomic_set(&pool
->nr_running
, 0);
4654 * With concurrency management just turned off, a busy
4655 * worker blocking could lead to lengthy stalls. Kick off
4656 * unbound chain execution of currently pending work items.
4658 spin_lock_irq(&pool
->lock
);
4659 wake_up_worker(pool
);
4660 spin_unlock_irq(&pool
->lock
);
4665 * rebind_workers - rebind all workers of a pool to the associated CPU
4666 * @pool: pool of interest
4668 * @pool->cpu is coming online. Rebind all workers to the CPU.
4670 static void rebind_workers(struct worker_pool
*pool
)
4672 struct worker
*worker
;
4674 lockdep_assert_held(&pool
->attach_mutex
);
4677 * Restore CPU affinity of all workers. As all idle workers should
4678 * be on the run-queue of the associated CPU before any local
4679 * wake-ups for concurrency management happen, restore CPU affinity
4680 * of all workers first and then clear UNBOUND. As we're called
4681 * from CPU_ONLINE, the following shouldn't fail.
4683 for_each_pool_worker(worker
, pool
)
4684 WARN_ON_ONCE(set_cpus_allowed_ptr(worker
->task
,
4685 pool
->attrs
->cpumask
) < 0);
4687 spin_lock_irq(&pool
->lock
);
4689 pool
->flags
&= ~POOL_DISASSOCIATED
;
4691 for_each_pool_worker(worker
, pool
) {
4692 unsigned int worker_flags
= worker
->flags
;
4695 * A bound idle worker should actually be on the runqueue
4696 * of the associated CPU for local wake-ups targeting it to
4697 * work. Kick all idle workers so that they migrate to the
4698 * associated CPU. Doing this in the same loop as
4699 * replacing UNBOUND with REBOUND is safe as no worker will
4700 * be bound before @pool->lock is released.
4702 if (worker_flags
& WORKER_IDLE
)
4703 wake_up_process(worker
->task
);
4706 * We want to clear UNBOUND but can't directly call
4707 * worker_clr_flags() or adjust nr_running. Atomically
4708 * replace UNBOUND with another NOT_RUNNING flag REBOUND.
4709 * @worker will clear REBOUND using worker_clr_flags() when
4710 * it initiates the next execution cycle thus restoring
4711 * concurrency management. Note that when or whether
4712 * @worker clears REBOUND doesn't affect correctness.
4714 * WRITE_ONCE() is necessary because @worker->flags may be
4715 * tested without holding any lock in
4716 * wq_worker_waking_up(). Without it, NOT_RUNNING test may
4717 * fail incorrectly leading to premature concurrency
4718 * management operations.
4720 WARN_ON_ONCE(!(worker_flags
& WORKER_UNBOUND
));
4721 worker_flags
|= WORKER_REBOUND
;
4722 worker_flags
&= ~WORKER_UNBOUND
;
4723 WRITE_ONCE(worker
->flags
, worker_flags
);
4726 spin_unlock_irq(&pool
->lock
);
4730 * restore_unbound_workers_cpumask - restore cpumask of unbound workers
4731 * @pool: unbound pool of interest
4732 * @cpu: the CPU which is coming up
4734 * An unbound pool may end up with a cpumask which doesn't have any online
4735 * CPUs. When a worker of such pool get scheduled, the scheduler resets
4736 * its cpus_allowed. If @cpu is in @pool's cpumask which didn't have any
4737 * online CPU before, cpus_allowed of all its workers should be restored.
4739 static void restore_unbound_workers_cpumask(struct worker_pool
*pool
, int cpu
)
4741 static cpumask_t cpumask
;
4742 struct worker
*worker
;
4744 lockdep_assert_held(&pool
->attach_mutex
);
4746 /* is @cpu allowed for @pool? */
4747 if (!cpumask_test_cpu(cpu
, pool
->attrs
->cpumask
))
4750 cpumask_and(&cpumask
, pool
->attrs
->cpumask
, cpu_online_mask
);
4752 /* as we're called from CPU_ONLINE, the following shouldn't fail */
4753 for_each_pool_worker(worker
, pool
)
4754 WARN_ON_ONCE(set_cpus_allowed_ptr(worker
->task
, &cpumask
) < 0);
4757 int workqueue_prepare_cpu(unsigned int cpu
)
4759 struct worker_pool
*pool
;
4761 for_each_cpu_worker_pool(pool
, cpu
) {
4762 if (pool
->nr_workers
)
4764 if (!create_worker(pool
))
4770 int workqueue_online_cpu(unsigned int cpu
)
4772 struct worker_pool
*pool
;
4773 struct workqueue_struct
*wq
;
4776 mutex_lock(&wq_pool_mutex
);
4778 for_each_pool(pool
, pi
) {
4779 mutex_lock(&pool
->attach_mutex
);
4781 if (pool
->cpu
== cpu
)
4782 rebind_workers(pool
);
4783 else if (pool
->cpu
< 0)
4784 restore_unbound_workers_cpumask(pool
, cpu
);
4786 mutex_unlock(&pool
->attach_mutex
);
4789 /* update NUMA affinity of unbound workqueues */
4790 list_for_each_entry(wq
, &workqueues
, list
)
4791 wq_update_unbound_numa(wq
, cpu
, true);
4793 mutex_unlock(&wq_pool_mutex
);
4797 int workqueue_offline_cpu(unsigned int cpu
)
4799 struct workqueue_struct
*wq
;
4801 /* unbinding per-cpu workers should happen on the local CPU */
4802 if (WARN_ON(cpu
!= smp_processor_id()))
4805 unbind_workers(cpu
);
4807 /* update NUMA affinity of unbound workqueues */
4808 mutex_lock(&wq_pool_mutex
);
4809 list_for_each_entry(wq
, &workqueues
, list
)
4810 wq_update_unbound_numa(wq
, cpu
, false);
4811 mutex_unlock(&wq_pool_mutex
);
4818 struct work_for_cpu
{
4819 struct work_struct work
;
4825 static void work_for_cpu_fn(struct work_struct
*work
)
4827 struct work_for_cpu
*wfc
= container_of(work
, struct work_for_cpu
, work
);
4829 wfc
->ret
= wfc
->fn(wfc
->arg
);
4833 * work_on_cpu - run a function in thread context on a particular cpu
4834 * @cpu: the cpu to run on
4835 * @fn: the function to run
4836 * @arg: the function arg
4838 * It is up to the caller to ensure that the cpu doesn't go offline.
4839 * The caller must not hold any locks which would prevent @fn from completing.
4841 * Return: The value @fn returns.
4843 long work_on_cpu(int cpu
, long (*fn
)(void *), void *arg
)
4845 struct work_for_cpu wfc
= { .fn
= fn
, .arg
= arg
};
4847 INIT_WORK_ONSTACK(&wfc
.work
, work_for_cpu_fn
);
4848 schedule_work_on(cpu
, &wfc
.work
);
4849 flush_work(&wfc
.work
);
4850 destroy_work_on_stack(&wfc
.work
);
4853 EXPORT_SYMBOL_GPL(work_on_cpu
);
4856 * work_on_cpu_safe - run a function in thread context on a particular cpu
4857 * @cpu: the cpu to run on
4858 * @fn: the function to run
4859 * @arg: the function argument
4861 * Disables CPU hotplug and calls work_on_cpu(). The caller must not hold
4862 * any locks which would prevent @fn from completing.
4864 * Return: The value @fn returns.
4866 long work_on_cpu_safe(int cpu
, long (*fn
)(void *), void *arg
)
4871 if (cpu_online(cpu
))
4872 ret
= work_on_cpu(cpu
, fn
, arg
);
4876 EXPORT_SYMBOL_GPL(work_on_cpu_safe
);
4877 #endif /* CONFIG_SMP */
4879 #ifdef CONFIG_FREEZER
4882 * freeze_workqueues_begin - begin freezing workqueues
4884 * Start freezing workqueues. After this function returns, all freezable
4885 * workqueues will queue new works to their delayed_works list instead of
4889 * Grabs and releases wq_pool_mutex, wq->mutex and pool->lock's.
4891 void freeze_workqueues_begin(void)
4893 struct workqueue_struct
*wq
;
4894 struct pool_workqueue
*pwq
;
4896 mutex_lock(&wq_pool_mutex
);
4898 WARN_ON_ONCE(workqueue_freezing
);
4899 workqueue_freezing
= true;
4901 list_for_each_entry(wq
, &workqueues
, list
) {
4902 mutex_lock(&wq
->mutex
);
4903 for_each_pwq(pwq
, wq
)
4904 pwq_adjust_max_active(pwq
);
4905 mutex_unlock(&wq
->mutex
);
4908 mutex_unlock(&wq_pool_mutex
);
4912 * freeze_workqueues_busy - are freezable workqueues still busy?
4914 * Check whether freezing is complete. This function must be called
4915 * between freeze_workqueues_begin() and thaw_workqueues().
4918 * Grabs and releases wq_pool_mutex.
4921 * %true if some freezable workqueues are still busy. %false if freezing
4924 bool freeze_workqueues_busy(void)
4927 struct workqueue_struct
*wq
;
4928 struct pool_workqueue
*pwq
;
4930 mutex_lock(&wq_pool_mutex
);
4932 WARN_ON_ONCE(!workqueue_freezing
);
4934 list_for_each_entry(wq
, &workqueues
, list
) {
4935 if (!(wq
->flags
& WQ_FREEZABLE
))
4938 * nr_active is monotonically decreasing. It's safe
4939 * to peek without lock.
4941 rcu_read_lock_sched();
4942 for_each_pwq(pwq
, wq
) {
4943 WARN_ON_ONCE(pwq
->nr_active
< 0);
4944 if (pwq
->nr_active
) {
4946 rcu_read_unlock_sched();
4950 rcu_read_unlock_sched();
4953 mutex_unlock(&wq_pool_mutex
);
4958 * thaw_workqueues - thaw workqueues
4960 * Thaw workqueues. Normal queueing is restored and all collected
4961 * frozen works are transferred to their respective pool worklists.
4964 * Grabs and releases wq_pool_mutex, wq->mutex and pool->lock's.
4966 void thaw_workqueues(void)
4968 struct workqueue_struct
*wq
;
4969 struct pool_workqueue
*pwq
;
4971 mutex_lock(&wq_pool_mutex
);
4973 if (!workqueue_freezing
)
4976 workqueue_freezing
= false;
4978 /* restore max_active and repopulate worklist */
4979 list_for_each_entry(wq
, &workqueues
, list
) {
4980 mutex_lock(&wq
->mutex
);
4981 for_each_pwq(pwq
, wq
)
4982 pwq_adjust_max_active(pwq
);
4983 mutex_unlock(&wq
->mutex
);
4987 mutex_unlock(&wq_pool_mutex
);
4989 #endif /* CONFIG_FREEZER */
4991 static int workqueue_apply_unbound_cpumask(void)
4995 struct workqueue_struct
*wq
;
4996 struct apply_wqattrs_ctx
*ctx
, *n
;
4998 lockdep_assert_held(&wq_pool_mutex
);
5000 list_for_each_entry(wq
, &workqueues
, list
) {
5001 if (!(wq
->flags
& WQ_UNBOUND
))
5003 /* creating multiple pwqs breaks ordering guarantee */
5004 if (wq
->flags
& __WQ_ORDERED
)
5007 ctx
= apply_wqattrs_prepare(wq
, wq
->unbound_attrs
);
5013 list_add_tail(&ctx
->list
, &ctxs
);
5016 list_for_each_entry_safe(ctx
, n
, &ctxs
, list
) {
5018 apply_wqattrs_commit(ctx
);
5019 apply_wqattrs_cleanup(ctx
);
5026 * workqueue_set_unbound_cpumask - Set the low-level unbound cpumask
5027 * @cpumask: the cpumask to set
5029 * The low-level workqueues cpumask is a global cpumask that limits
5030 * the affinity of all unbound workqueues. This function check the @cpumask
5031 * and apply it to all unbound workqueues and updates all pwqs of them.
5033 * Retun: 0 - Success
5034 * -EINVAL - Invalid @cpumask
5035 * -ENOMEM - Failed to allocate memory for attrs or pwqs.
5037 int workqueue_set_unbound_cpumask(cpumask_var_t cpumask
)
5040 cpumask_var_t saved_cpumask
;
5042 if (!zalloc_cpumask_var(&saved_cpumask
, GFP_KERNEL
))
5046 * Not excluding isolated cpus on purpose.
5047 * If the user wishes to include them, we allow that.
5049 cpumask_and(cpumask
, cpumask
, cpu_possible_mask
);
5050 if (!cpumask_empty(cpumask
)) {
5051 apply_wqattrs_lock();
5053 /* save the old wq_unbound_cpumask. */
5054 cpumask_copy(saved_cpumask
, wq_unbound_cpumask
);
5056 /* update wq_unbound_cpumask at first and apply it to wqs. */
5057 cpumask_copy(wq_unbound_cpumask
, cpumask
);
5058 ret
= workqueue_apply_unbound_cpumask();
5060 /* restore the wq_unbound_cpumask when failed. */
5062 cpumask_copy(wq_unbound_cpumask
, saved_cpumask
);
5064 apply_wqattrs_unlock();
5067 free_cpumask_var(saved_cpumask
);
5073 * Workqueues with WQ_SYSFS flag set is visible to userland via
5074 * /sys/bus/workqueue/devices/WQ_NAME. All visible workqueues have the
5075 * following attributes.
5077 * per_cpu RO bool : whether the workqueue is per-cpu or unbound
5078 * max_active RW int : maximum number of in-flight work items
5080 * Unbound workqueues have the following extra attributes.
5082 * pool_ids RO int : the associated pool IDs for each node
5083 * nice RW int : nice value of the workers
5084 * cpumask RW mask : bitmask of allowed CPUs for the workers
5085 * numa RW bool : whether enable NUMA affinity
5088 struct workqueue_struct
*wq
;
5092 static struct workqueue_struct
*dev_to_wq(struct device
*dev
)
5094 struct wq_device
*wq_dev
= container_of(dev
, struct wq_device
, dev
);
5099 static ssize_t
per_cpu_show(struct device
*dev
, struct device_attribute
*attr
,
5102 struct workqueue_struct
*wq
= dev_to_wq(dev
);
5104 return scnprintf(buf
, PAGE_SIZE
, "%d\n", (bool)!(wq
->flags
& WQ_UNBOUND
));
5106 static DEVICE_ATTR_RO(per_cpu
);
5108 static ssize_t
max_active_show(struct device
*dev
,
5109 struct device_attribute
*attr
, char *buf
)
5111 struct workqueue_struct
*wq
= dev_to_wq(dev
);
5113 return scnprintf(buf
, PAGE_SIZE
, "%d\n", wq
->saved_max_active
);
5116 static ssize_t
max_active_store(struct device
*dev
,
5117 struct device_attribute
*attr
, const char *buf
,
5120 struct workqueue_struct
*wq
= dev_to_wq(dev
);
5123 if (sscanf(buf
, "%d", &val
) != 1 || val
<= 0)
5126 workqueue_set_max_active(wq
, val
);
5129 static DEVICE_ATTR_RW(max_active
);
5131 static struct attribute
*wq_sysfs_attrs
[] = {
5132 &dev_attr_per_cpu
.attr
,
5133 &dev_attr_max_active
.attr
,
5136 ATTRIBUTE_GROUPS(wq_sysfs
);
5138 static ssize_t
wq_pool_ids_show(struct device
*dev
,
5139 struct device_attribute
*attr
, char *buf
)
5141 struct workqueue_struct
*wq
= dev_to_wq(dev
);
5142 const char *delim
= "";
5143 int node
, written
= 0;
5145 rcu_read_lock_sched();
5146 for_each_node(node
) {
5147 written
+= scnprintf(buf
+ written
, PAGE_SIZE
- written
,
5148 "%s%d:%d", delim
, node
,
5149 unbound_pwq_by_node(wq
, node
)->pool
->id
);
5152 written
+= scnprintf(buf
+ written
, PAGE_SIZE
- written
, "\n");
5153 rcu_read_unlock_sched();
5158 static ssize_t
wq_nice_show(struct device
*dev
, struct device_attribute
*attr
,
5161 struct workqueue_struct
*wq
= dev_to_wq(dev
);
5164 mutex_lock(&wq
->mutex
);
5165 written
= scnprintf(buf
, PAGE_SIZE
, "%d\n", wq
->unbound_attrs
->nice
);
5166 mutex_unlock(&wq
->mutex
);
5171 /* prepare workqueue_attrs for sysfs store operations */
5172 static struct workqueue_attrs
*wq_sysfs_prep_attrs(struct workqueue_struct
*wq
)
5174 struct workqueue_attrs
*attrs
;
5176 lockdep_assert_held(&wq_pool_mutex
);
5178 attrs
= alloc_workqueue_attrs(GFP_KERNEL
);
5182 copy_workqueue_attrs(attrs
, wq
->unbound_attrs
);
5186 static ssize_t
wq_nice_store(struct device
*dev
, struct device_attribute
*attr
,
5187 const char *buf
, size_t count
)
5189 struct workqueue_struct
*wq
= dev_to_wq(dev
);
5190 struct workqueue_attrs
*attrs
;
5193 apply_wqattrs_lock();
5195 attrs
= wq_sysfs_prep_attrs(wq
);
5199 if (sscanf(buf
, "%d", &attrs
->nice
) == 1 &&
5200 attrs
->nice
>= MIN_NICE
&& attrs
->nice
<= MAX_NICE
)
5201 ret
= apply_workqueue_attrs_locked(wq
, attrs
);
5206 apply_wqattrs_unlock();
5207 free_workqueue_attrs(attrs
);
5208 return ret
?: count
;
5211 static ssize_t
wq_cpumask_show(struct device
*dev
,
5212 struct device_attribute
*attr
, char *buf
)
5214 struct workqueue_struct
*wq
= dev_to_wq(dev
);
5217 mutex_lock(&wq
->mutex
);
5218 written
= scnprintf(buf
, PAGE_SIZE
, "%*pb\n",
5219 cpumask_pr_args(wq
->unbound_attrs
->cpumask
));
5220 mutex_unlock(&wq
->mutex
);
5224 static ssize_t
wq_cpumask_store(struct device
*dev
,
5225 struct device_attribute
*attr
,
5226 const char *buf
, size_t count
)
5228 struct workqueue_struct
*wq
= dev_to_wq(dev
);
5229 struct workqueue_attrs
*attrs
;
5232 apply_wqattrs_lock();
5234 attrs
= wq_sysfs_prep_attrs(wq
);
5238 ret
= cpumask_parse(buf
, attrs
->cpumask
);
5240 ret
= apply_workqueue_attrs_locked(wq
, attrs
);
5243 apply_wqattrs_unlock();
5244 free_workqueue_attrs(attrs
);
5245 return ret
?: count
;
5248 static ssize_t
wq_numa_show(struct device
*dev
, struct device_attribute
*attr
,
5251 struct workqueue_struct
*wq
= dev_to_wq(dev
);
5254 mutex_lock(&wq
->mutex
);
5255 written
= scnprintf(buf
, PAGE_SIZE
, "%d\n",
5256 !wq
->unbound_attrs
->no_numa
);
5257 mutex_unlock(&wq
->mutex
);
5262 static ssize_t
wq_numa_store(struct device
*dev
, struct device_attribute
*attr
,
5263 const char *buf
, size_t count
)
5265 struct workqueue_struct
*wq
= dev_to_wq(dev
);
5266 struct workqueue_attrs
*attrs
;
5267 int v
, ret
= -ENOMEM
;
5269 apply_wqattrs_lock();
5271 attrs
= wq_sysfs_prep_attrs(wq
);
5276 if (sscanf(buf
, "%d", &v
) == 1) {
5277 attrs
->no_numa
= !v
;
5278 ret
= apply_workqueue_attrs_locked(wq
, attrs
);
5282 apply_wqattrs_unlock();
5283 free_workqueue_attrs(attrs
);
5284 return ret
?: count
;
5287 static struct device_attribute wq_sysfs_unbound_attrs
[] = {
5288 __ATTR(pool_ids
, 0444, wq_pool_ids_show
, NULL
),
5289 __ATTR(nice
, 0644, wq_nice_show
, wq_nice_store
),
5290 __ATTR(cpumask
, 0644, wq_cpumask_show
, wq_cpumask_store
),
5291 __ATTR(numa
, 0644, wq_numa_show
, wq_numa_store
),
5295 static struct bus_type wq_subsys
= {
5296 .name
= "workqueue",
5297 .dev_groups
= wq_sysfs_groups
,
5300 static ssize_t
wq_unbound_cpumask_show(struct device
*dev
,
5301 struct device_attribute
*attr
, char *buf
)
5305 mutex_lock(&wq_pool_mutex
);
5306 written
= scnprintf(buf
, PAGE_SIZE
, "%*pb\n",
5307 cpumask_pr_args(wq_unbound_cpumask
));
5308 mutex_unlock(&wq_pool_mutex
);
5313 static ssize_t
wq_unbound_cpumask_store(struct device
*dev
,
5314 struct device_attribute
*attr
, const char *buf
, size_t count
)
5316 cpumask_var_t cpumask
;
5319 if (!zalloc_cpumask_var(&cpumask
, GFP_KERNEL
))
5322 ret
= cpumask_parse(buf
, cpumask
);
5324 ret
= workqueue_set_unbound_cpumask(cpumask
);
5326 free_cpumask_var(cpumask
);
5327 return ret
? ret
: count
;
5330 static struct device_attribute wq_sysfs_cpumask_attr
=
5331 __ATTR(cpumask
, 0644, wq_unbound_cpumask_show
,
5332 wq_unbound_cpumask_store
);
5334 static int __init
wq_sysfs_init(void)
5338 err
= subsys_virtual_register(&wq_subsys
, NULL
);
5342 return device_create_file(wq_subsys
.dev_root
, &wq_sysfs_cpumask_attr
);
5344 core_initcall(wq_sysfs_init
);
5346 static void wq_device_release(struct device
*dev
)
5348 struct wq_device
*wq_dev
= container_of(dev
, struct wq_device
, dev
);
5354 * workqueue_sysfs_register - make a workqueue visible in sysfs
5355 * @wq: the workqueue to register
5357 * Expose @wq in sysfs under /sys/bus/workqueue/devices.
5358 * alloc_workqueue*() automatically calls this function if WQ_SYSFS is set
5359 * which is the preferred method.
5361 * Workqueue user should use this function directly iff it wants to apply
5362 * workqueue_attrs before making the workqueue visible in sysfs; otherwise,
5363 * apply_workqueue_attrs() may race against userland updating the
5366 * Return: 0 on success, -errno on failure.
5368 int workqueue_sysfs_register(struct workqueue_struct
*wq
)
5370 struct wq_device
*wq_dev
;
5374 * Adjusting max_active or creating new pwqs by applying
5375 * attributes breaks ordering guarantee. Disallow exposing ordered
5378 if (WARN_ON(wq
->flags
& __WQ_ORDERED_EXPLICIT
))
5381 wq
->wq_dev
= wq_dev
= kzalloc(sizeof(*wq_dev
), GFP_KERNEL
);
5386 wq_dev
->dev
.bus
= &wq_subsys
;
5387 wq_dev
->dev
.release
= wq_device_release
;
5388 dev_set_name(&wq_dev
->dev
, "%s", wq
->name
);
5391 * unbound_attrs are created separately. Suppress uevent until
5392 * everything is ready.
5394 dev_set_uevent_suppress(&wq_dev
->dev
, true);
5396 ret
= device_register(&wq_dev
->dev
);
5398 put_device(&wq_dev
->dev
);
5403 if (wq
->flags
& WQ_UNBOUND
) {
5404 struct device_attribute
*attr
;
5406 for (attr
= wq_sysfs_unbound_attrs
; attr
->attr
.name
; attr
++) {
5407 ret
= device_create_file(&wq_dev
->dev
, attr
);
5409 device_unregister(&wq_dev
->dev
);
5416 dev_set_uevent_suppress(&wq_dev
->dev
, false);
5417 kobject_uevent(&wq_dev
->dev
.kobj
, KOBJ_ADD
);
5422 * workqueue_sysfs_unregister - undo workqueue_sysfs_register()
5423 * @wq: the workqueue to unregister
5425 * If @wq is registered to sysfs by workqueue_sysfs_register(), unregister.
5427 static void workqueue_sysfs_unregister(struct workqueue_struct
*wq
)
5429 struct wq_device
*wq_dev
= wq
->wq_dev
;
5435 device_unregister(&wq_dev
->dev
);
5437 #else /* CONFIG_SYSFS */
5438 static void workqueue_sysfs_unregister(struct workqueue_struct
*wq
) { }
5439 #endif /* CONFIG_SYSFS */
5442 * Workqueue watchdog.
5444 * Stall may be caused by various bugs - missing WQ_MEM_RECLAIM, illegal
5445 * flush dependency, a concurrency managed work item which stays RUNNING
5446 * indefinitely. Workqueue stalls can be very difficult to debug as the
5447 * usual warning mechanisms don't trigger and internal workqueue state is
5450 * Workqueue watchdog monitors all worker pools periodically and dumps
5451 * state if some pools failed to make forward progress for a while where
5452 * forward progress is defined as the first item on ->worklist changing.
5454 * This mechanism is controlled through the kernel parameter
5455 * "workqueue.watchdog_thresh" which can be updated at runtime through the
5456 * corresponding sysfs parameter file.
5458 #ifdef CONFIG_WQ_WATCHDOG
5460 static unsigned long wq_watchdog_thresh
= 30;
5461 static struct timer_list wq_watchdog_timer
;
5463 static unsigned long wq_watchdog_touched
= INITIAL_JIFFIES
;
5464 static DEFINE_PER_CPU(unsigned long, wq_watchdog_touched_cpu
) = INITIAL_JIFFIES
;
5466 static void wq_watchdog_reset_touched(void)
5470 wq_watchdog_touched
= jiffies
;
5471 for_each_possible_cpu(cpu
)
5472 per_cpu(wq_watchdog_touched_cpu
, cpu
) = jiffies
;
5475 static void wq_watchdog_timer_fn(struct timer_list
*unused
)
5477 unsigned long thresh
= READ_ONCE(wq_watchdog_thresh
) * HZ
;
5478 bool lockup_detected
= false;
5479 struct worker_pool
*pool
;
5487 for_each_pool(pool
, pi
) {
5488 unsigned long pool_ts
, touched
, ts
;
5490 if (list_empty(&pool
->worklist
))
5493 /* get the latest of pool and touched timestamps */
5494 pool_ts
= READ_ONCE(pool
->watchdog_ts
);
5495 touched
= READ_ONCE(wq_watchdog_touched
);
5497 if (time_after(pool_ts
, touched
))
5502 if (pool
->cpu
>= 0) {
5503 unsigned long cpu_touched
=
5504 READ_ONCE(per_cpu(wq_watchdog_touched_cpu
,
5506 if (time_after(cpu_touched
, ts
))
5511 if (time_after(jiffies
, ts
+ thresh
)) {
5512 lockup_detected
= true;
5513 pr_emerg("BUG: workqueue lockup - pool");
5514 pr_cont_pool_info(pool
);
5515 pr_cont(" stuck for %us!\n",
5516 jiffies_to_msecs(jiffies
- pool_ts
) / 1000);
5522 if (lockup_detected
)
5523 show_workqueue_state();
5525 wq_watchdog_reset_touched();
5526 mod_timer(&wq_watchdog_timer
, jiffies
+ thresh
);
5529 notrace
void wq_watchdog_touch(int cpu
)
5532 per_cpu(wq_watchdog_touched_cpu
, cpu
) = jiffies
;
5534 wq_watchdog_touched
= jiffies
;
5537 static void wq_watchdog_set_thresh(unsigned long thresh
)
5539 wq_watchdog_thresh
= 0;
5540 del_timer_sync(&wq_watchdog_timer
);
5543 wq_watchdog_thresh
= thresh
;
5544 wq_watchdog_reset_touched();
5545 mod_timer(&wq_watchdog_timer
, jiffies
+ thresh
* HZ
);
5549 static int wq_watchdog_param_set_thresh(const char *val
,
5550 const struct kernel_param
*kp
)
5552 unsigned long thresh
;
5555 ret
= kstrtoul(val
, 0, &thresh
);
5560 wq_watchdog_set_thresh(thresh
);
5562 wq_watchdog_thresh
= thresh
;
5567 static const struct kernel_param_ops wq_watchdog_thresh_ops
= {
5568 .set
= wq_watchdog_param_set_thresh
,
5569 .get
= param_get_ulong
,
5572 module_param_cb(watchdog_thresh
, &wq_watchdog_thresh_ops
, &wq_watchdog_thresh
,
5575 static void wq_watchdog_init(void)
5577 timer_setup(&wq_watchdog_timer
, wq_watchdog_timer_fn
, TIMER_DEFERRABLE
);
5578 wq_watchdog_set_thresh(wq_watchdog_thresh
);
5581 #else /* CONFIG_WQ_WATCHDOG */
5583 static inline void wq_watchdog_init(void) { }
5585 #endif /* CONFIG_WQ_WATCHDOG */
5587 static void __init
wq_numa_init(void)
5592 if (num_possible_nodes() <= 1)
5595 if (wq_disable_numa
) {
5596 pr_info("workqueue: NUMA affinity support disabled\n");
5600 wq_update_unbound_numa_attrs_buf
= alloc_workqueue_attrs(GFP_KERNEL
);
5601 BUG_ON(!wq_update_unbound_numa_attrs_buf
);
5604 * We want masks of possible CPUs of each node which isn't readily
5605 * available. Build one from cpu_to_node() which should have been
5606 * fully initialized by now.
5608 tbl
= kzalloc(nr_node_ids
* sizeof(tbl
[0]), GFP_KERNEL
);
5612 BUG_ON(!zalloc_cpumask_var_node(&tbl
[node
], GFP_KERNEL
,
5613 node_online(node
) ? node
: NUMA_NO_NODE
));
5615 for_each_possible_cpu(cpu
) {
5616 node
= cpu_to_node(cpu
);
5617 if (WARN_ON(node
== NUMA_NO_NODE
)) {
5618 pr_warn("workqueue: NUMA node mapping not available for cpu%d, disabling NUMA support\n", cpu
);
5619 /* happens iff arch is bonkers, let's just proceed */
5622 cpumask_set_cpu(cpu
, tbl
[node
]);
5625 wq_numa_possible_cpumask
= tbl
;
5626 wq_numa_enabled
= true;
5630 * workqueue_init_early - early init for workqueue subsystem
5632 * This is the first half of two-staged workqueue subsystem initialization
5633 * and invoked as soon as the bare basics - memory allocation, cpumasks and
5634 * idr are up. It sets up all the data structures and system workqueues
5635 * and allows early boot code to create workqueues and queue/cancel work
5636 * items. Actual work item execution starts only after kthreads can be
5637 * created and scheduled right before early initcalls.
5639 int __init
workqueue_init_early(void)
5641 int std_nice
[NR_STD_WORKER_POOLS
] = { 0, HIGHPRI_NICE_LEVEL
};
5644 WARN_ON(__alignof__(struct pool_workqueue
) < __alignof__(long long));
5646 BUG_ON(!alloc_cpumask_var(&wq_unbound_cpumask
, GFP_KERNEL
));
5647 cpumask_copy(wq_unbound_cpumask
, housekeeping_cpumask(HK_FLAG_DOMAIN
));
5649 pwq_cache
= KMEM_CACHE(pool_workqueue
, SLAB_PANIC
);
5651 /* initialize CPU pools */
5652 for_each_possible_cpu(cpu
) {
5653 struct worker_pool
*pool
;
5656 for_each_cpu_worker_pool(pool
, cpu
) {
5657 BUG_ON(init_worker_pool(pool
));
5659 cpumask_copy(pool
->attrs
->cpumask
, cpumask_of(cpu
));
5660 pool
->attrs
->nice
= std_nice
[i
++];
5661 pool
->node
= cpu_to_node(cpu
);
5664 mutex_lock(&wq_pool_mutex
);
5665 BUG_ON(worker_pool_assign_id(pool
));
5666 mutex_unlock(&wq_pool_mutex
);
5670 /* create default unbound and ordered wq attrs */
5671 for (i
= 0; i
< NR_STD_WORKER_POOLS
; i
++) {
5672 struct workqueue_attrs
*attrs
;
5674 BUG_ON(!(attrs
= alloc_workqueue_attrs(GFP_KERNEL
)));
5675 attrs
->nice
= std_nice
[i
];
5676 unbound_std_wq_attrs
[i
] = attrs
;
5679 * An ordered wq should have only one pwq as ordering is
5680 * guaranteed by max_active which is enforced by pwqs.
5681 * Turn off NUMA so that dfl_pwq is used for all nodes.
5683 BUG_ON(!(attrs
= alloc_workqueue_attrs(GFP_KERNEL
)));
5684 attrs
->nice
= std_nice
[i
];
5685 attrs
->no_numa
= true;
5686 ordered_wq_attrs
[i
] = attrs
;
5689 system_wq
= alloc_workqueue("events", 0, 0);
5690 system_highpri_wq
= alloc_workqueue("events_highpri", WQ_HIGHPRI
, 0);
5691 system_long_wq
= alloc_workqueue("events_long", 0, 0);
5692 system_unbound_wq
= alloc_workqueue("events_unbound", WQ_UNBOUND
,
5693 WQ_UNBOUND_MAX_ACTIVE
);
5694 system_freezable_wq
= alloc_workqueue("events_freezable",
5696 system_power_efficient_wq
= alloc_workqueue("events_power_efficient",
5697 WQ_POWER_EFFICIENT
, 0);
5698 system_freezable_power_efficient_wq
= alloc_workqueue("events_freezable_power_efficient",
5699 WQ_FREEZABLE
| WQ_POWER_EFFICIENT
,
5701 BUG_ON(!system_wq
|| !system_highpri_wq
|| !system_long_wq
||
5702 !system_unbound_wq
|| !system_freezable_wq
||
5703 !system_power_efficient_wq
||
5704 !system_freezable_power_efficient_wq
);
5710 * workqueue_init - bring workqueue subsystem fully online
5712 * This is the latter half of two-staged workqueue subsystem initialization
5713 * and invoked as soon as kthreads can be created and scheduled.
5714 * Workqueues have been created and work items queued on them, but there
5715 * are no kworkers executing the work items yet. Populate the worker pools
5716 * with the initial workers and enable future kworker creations.
5718 int __init
workqueue_init(void)
5720 struct workqueue_struct
*wq
;
5721 struct worker_pool
*pool
;
5725 * It'd be simpler to initialize NUMA in workqueue_init_early() but
5726 * CPU to node mapping may not be available that early on some
5727 * archs such as power and arm64. As per-cpu pools created
5728 * previously could be missing node hint and unbound pools NUMA
5729 * affinity, fix them up.
5733 mutex_lock(&wq_pool_mutex
);
5735 for_each_possible_cpu(cpu
) {
5736 for_each_cpu_worker_pool(pool
, cpu
) {
5737 pool
->node
= cpu_to_node(cpu
);
5741 list_for_each_entry(wq
, &workqueues
, list
)
5742 wq_update_unbound_numa(wq
, smp_processor_id(), true);
5744 mutex_unlock(&wq_pool_mutex
);
5746 /* create the initial workers */
5747 for_each_online_cpu(cpu
) {
5748 for_each_cpu_worker_pool(pool
, cpu
) {
5749 pool
->flags
&= ~POOL_DISASSOCIATED
;
5750 BUG_ON(!create_worker(pool
));
5754 hash_for_each(unbound_pool_hash
, bkt
, pool
, hash_node
)
5755 BUG_ON(!create_worker(pool
));