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/workqueue.txt 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/kallsyms.h>
42 #include <linux/debug_locks.h>
43 #include <linux/lockdep.h>
44 #include <linux/idr.h>
45 #include <linux/jhash.h>
46 #include <linux/hashtable.h>
47 #include <linux/rculist.h>
48 #include <linux/nodemask.h>
49 #include <linux/moduleparam.h>
50 #include <linux/uaccess.h>
52 #include "workqueue_internal.h"
58 * A bound pool is either associated or disassociated with its CPU.
59 * While associated (!DISASSOCIATED), all workers are bound to the
60 * CPU and none has %WORKER_UNBOUND set and concurrency management
63 * While DISASSOCIATED, the cpu may be offline and all workers have
64 * %WORKER_UNBOUND set and concurrency management disabled, and may
65 * be executing on any CPU. The pool behaves as an unbound one.
67 * Note that DISASSOCIATED should be flipped only while holding
68 * manager_mutex to avoid changing binding state while
69 * create_worker() is in progress.
71 POOL_MANAGE_WORKERS
= 1 << 0, /* need to manage workers */
72 POOL_DISASSOCIATED
= 1 << 2, /* cpu can't serve workers */
73 POOL_FREEZING
= 1 << 3, /* freeze in progress */
76 WORKER_STARTED
= 1 << 0, /* started */
77 WORKER_DIE
= 1 << 1, /* die die die */
78 WORKER_IDLE
= 1 << 2, /* is idle */
79 WORKER_PREP
= 1 << 3, /* preparing to run works */
80 WORKER_CPU_INTENSIVE
= 1 << 6, /* cpu intensive */
81 WORKER_UNBOUND
= 1 << 7, /* worker is unbound */
82 WORKER_REBOUND
= 1 << 8, /* worker was rebound */
84 WORKER_NOT_RUNNING
= WORKER_PREP
| WORKER_CPU_INTENSIVE
|
85 WORKER_UNBOUND
| WORKER_REBOUND
,
87 NR_STD_WORKER_POOLS
= 2, /* # standard pools per cpu */
89 UNBOUND_POOL_HASH_ORDER
= 6, /* hashed by pool->attrs */
90 BUSY_WORKER_HASH_ORDER
= 6, /* 64 pointers */
92 MAX_IDLE_WORKERS_RATIO
= 4, /* 1/4 of busy can be idle */
93 IDLE_WORKER_TIMEOUT
= 300 * HZ
, /* keep idle ones for 5 mins */
95 MAYDAY_INITIAL_TIMEOUT
= HZ
/ 100 >= 2 ? HZ
/ 100 : 2,
96 /* call for help after 10ms
98 MAYDAY_INTERVAL
= HZ
/ 10, /* and then every 100ms */
99 CREATE_COOLDOWN
= HZ
, /* time to breath after fail */
102 * Rescue workers are used only on emergencies and shared by
103 * all cpus. Give MIN_NICE.
105 RESCUER_NICE_LEVEL
= MIN_NICE
,
106 HIGHPRI_NICE_LEVEL
= MIN_NICE
,
112 * Structure fields follow one of the following exclusion rules.
114 * I: Modifiable by initialization/destruction paths and read-only for
117 * P: Preemption protected. Disabling preemption is enough and should
118 * only be modified and accessed from the local cpu.
120 * L: pool->lock protected. Access with pool->lock held.
122 * X: During normal operation, modification requires pool->lock and should
123 * be done only from local cpu. Either disabling preemption on local
124 * cpu or grabbing pool->lock is enough for read access. If
125 * POOL_DISASSOCIATED is set, it's identical to L.
127 * MG: pool->manager_mutex and pool->lock protected. Writes require both
128 * locks. Reads can happen under either lock.
130 * PL: wq_pool_mutex protected.
132 * PR: wq_pool_mutex protected for writes. Sched-RCU protected for reads.
134 * WQ: wq->mutex protected.
136 * WR: wq->mutex protected for writes. Sched-RCU protected for reads.
138 * MD: wq_mayday_lock protected.
141 /* struct worker is defined in workqueue_internal.h */
144 spinlock_t lock
; /* the pool lock */
145 int cpu
; /* I: the associated cpu */
146 int node
; /* I: the associated node ID */
147 int id
; /* I: pool ID */
148 unsigned int flags
; /* X: flags */
150 struct list_head worklist
; /* L: list of pending works */
151 int nr_workers
; /* L: total number of workers */
153 /* nr_idle includes the ones off idle_list for rebinding */
154 int nr_idle
; /* L: currently idle ones */
156 struct list_head idle_list
; /* X: list of idle workers */
157 struct timer_list idle_timer
; /* L: worker idle timeout */
158 struct timer_list mayday_timer
; /* L: SOS timer for workers */
160 /* a workers is either on busy_hash or idle_list, or the manager */
161 DECLARE_HASHTABLE(busy_hash
, BUSY_WORKER_HASH_ORDER
);
162 /* L: hash of busy workers */
164 /* see manage_workers() for details on the two manager mutexes */
165 struct mutex manager_arb
; /* manager arbitration */
166 struct mutex manager_mutex
; /* manager exclusion */
167 struct idr worker_idr
; /* MG: worker IDs and iteration */
169 struct workqueue_attrs
*attrs
; /* I: worker attributes */
170 struct hlist_node hash_node
; /* PL: unbound_pool_hash node */
171 int refcnt
; /* PL: refcnt for unbound pools */
174 * The current concurrency level. As it's likely to be accessed
175 * from other CPUs during try_to_wake_up(), put it in a separate
178 atomic_t nr_running ____cacheline_aligned_in_smp
;
181 * Destruction of pool is sched-RCU protected to allow dereferences
182 * from get_work_pool().
185 } ____cacheline_aligned_in_smp
;
188 * The per-pool workqueue. While queued, the lower WORK_STRUCT_FLAG_BITS
189 * of work_struct->data are used for flags and the remaining high bits
190 * point to the pwq; thus, pwqs need to be aligned at two's power of the
191 * number of flag bits.
193 struct pool_workqueue
{
194 struct worker_pool
*pool
; /* I: the associated pool */
195 struct workqueue_struct
*wq
; /* I: the owning workqueue */
196 int work_color
; /* L: current color */
197 int flush_color
; /* L: flushing color */
198 int refcnt
; /* L: reference count */
199 int nr_in_flight
[WORK_NR_COLORS
];
200 /* L: nr of in_flight works */
201 int nr_active
; /* L: nr of active works */
202 int max_active
; /* L: max active works */
203 struct list_head delayed_works
; /* L: delayed works */
204 struct list_head pwqs_node
; /* WR: node on wq->pwqs */
205 struct list_head mayday_node
; /* MD: node on wq->maydays */
208 * Release of unbound pwq is punted to system_wq. See put_pwq()
209 * and pwq_unbound_release_workfn() for details. pool_workqueue
210 * itself is also sched-RCU protected so that the first pwq can be
211 * determined without grabbing wq->mutex.
213 struct work_struct unbound_release_work
;
215 } __aligned(1 << WORK_STRUCT_FLAG_BITS
);
218 * Structure used to wait for workqueue flush.
221 struct list_head list
; /* WQ: list of flushers */
222 int flush_color
; /* WQ: flush color waiting for */
223 struct completion done
; /* flush completion */
229 * The externally visible workqueue. It relays the issued work items to
230 * the appropriate worker_pool through its pool_workqueues.
232 struct workqueue_struct
{
233 struct list_head pwqs
; /* WR: all pwqs of this wq */
234 struct list_head list
; /* PL: list of all workqueues */
236 struct mutex mutex
; /* protects this wq */
237 int work_color
; /* WQ: current work color */
238 int flush_color
; /* WQ: current flush color */
239 atomic_t nr_pwqs_to_flush
; /* flush in progress */
240 struct wq_flusher
*first_flusher
; /* WQ: first flusher */
241 struct list_head flusher_queue
; /* WQ: flush waiters */
242 struct list_head flusher_overflow
; /* WQ: flush overflow list */
244 struct list_head maydays
; /* MD: pwqs requesting rescue */
245 struct worker
*rescuer
; /* I: rescue worker */
247 int nr_drainers
; /* WQ: drain in progress */
248 int saved_max_active
; /* WQ: saved pwq max_active */
250 struct workqueue_attrs
*unbound_attrs
; /* WQ: only for unbound wqs */
251 struct pool_workqueue
*dfl_pwq
; /* WQ: only for unbound wqs */
254 struct wq_device
*wq_dev
; /* I: for sysfs interface */
256 #ifdef CONFIG_LOCKDEP
257 struct lockdep_map lockdep_map
;
259 char name
[WQ_NAME_LEN
]; /* I: workqueue name */
261 /* hot fields used during command issue, aligned to cacheline */
262 unsigned int flags ____cacheline_aligned
; /* WQ: WQ_* flags */
263 struct pool_workqueue __percpu
*cpu_pwqs
; /* I: per-cpu pwqs */
264 struct pool_workqueue __rcu
*numa_pwq_tbl
[]; /* FR: unbound pwqs indexed by node */
267 static struct kmem_cache
*pwq_cache
;
269 static int wq_numa_tbl_len
; /* highest possible NUMA node id + 1 */
270 static cpumask_var_t
*wq_numa_possible_cpumask
;
271 /* possible CPUs of each node */
273 static bool wq_disable_numa
;
274 module_param_named(disable_numa
, wq_disable_numa
, bool, 0444);
276 /* see the comment above the definition of WQ_POWER_EFFICIENT */
277 #ifdef CONFIG_WQ_POWER_EFFICIENT_DEFAULT
278 static bool wq_power_efficient
= true;
280 static bool wq_power_efficient
;
283 module_param_named(power_efficient
, wq_power_efficient
, bool, 0444);
285 static bool wq_numa_enabled
; /* unbound NUMA affinity enabled */
287 /* buf for wq_update_unbound_numa_attrs(), protected by CPU hotplug exclusion */
288 static struct workqueue_attrs
*wq_update_unbound_numa_attrs_buf
;
290 static DEFINE_MUTEX(wq_pool_mutex
); /* protects pools and workqueues list */
291 static DEFINE_SPINLOCK(wq_mayday_lock
); /* protects wq->maydays list */
293 static LIST_HEAD(workqueues
); /* PL: list of all workqueues */
294 static bool workqueue_freezing
; /* PL: have wqs started freezing? */
296 /* the per-cpu worker pools */
297 static DEFINE_PER_CPU_SHARED_ALIGNED(struct worker_pool
[NR_STD_WORKER_POOLS
],
300 static DEFINE_IDR(worker_pool_idr
); /* PR: idr of all pools */
302 /* PL: hash of all unbound pools keyed by pool->attrs */
303 static DEFINE_HASHTABLE(unbound_pool_hash
, UNBOUND_POOL_HASH_ORDER
);
305 /* I: attributes used when instantiating standard unbound pools on demand */
306 static struct workqueue_attrs
*unbound_std_wq_attrs
[NR_STD_WORKER_POOLS
];
308 /* I: attributes used when instantiating ordered pools on demand */
309 static struct workqueue_attrs
*ordered_wq_attrs
[NR_STD_WORKER_POOLS
];
311 struct workqueue_struct
*system_wq __read_mostly
;
312 EXPORT_SYMBOL(system_wq
);
313 struct workqueue_struct
*system_highpri_wq __read_mostly
;
314 EXPORT_SYMBOL_GPL(system_highpri_wq
);
315 struct workqueue_struct
*system_long_wq __read_mostly
;
316 EXPORT_SYMBOL_GPL(system_long_wq
);
317 struct workqueue_struct
*system_unbound_wq __read_mostly
;
318 EXPORT_SYMBOL_GPL(system_unbound_wq
);
319 struct workqueue_struct
*system_freezable_wq __read_mostly
;
320 EXPORT_SYMBOL_GPL(system_freezable_wq
);
321 struct workqueue_struct
*system_power_efficient_wq __read_mostly
;
322 EXPORT_SYMBOL_GPL(system_power_efficient_wq
);
323 struct workqueue_struct
*system_freezable_power_efficient_wq __read_mostly
;
324 EXPORT_SYMBOL_GPL(system_freezable_power_efficient_wq
);
326 static int worker_thread(void *__worker
);
327 static void copy_workqueue_attrs(struct workqueue_attrs
*to
,
328 const struct workqueue_attrs
*from
);
330 #define CREATE_TRACE_POINTS
331 #include <trace/events/workqueue.h>
333 #define assert_rcu_or_pool_mutex() \
334 rcu_lockdep_assert(rcu_read_lock_sched_held() || \
335 lockdep_is_held(&wq_pool_mutex), \
336 "sched RCU or wq_pool_mutex should be held")
338 #define assert_rcu_or_wq_mutex(wq) \
339 rcu_lockdep_assert(rcu_read_lock_sched_held() || \
340 lockdep_is_held(&wq->mutex), \
341 "sched RCU or wq->mutex should be held")
343 #ifdef CONFIG_LOCKDEP
344 #define assert_manager_or_pool_lock(pool) \
345 WARN_ONCE(debug_locks && \
346 !lockdep_is_held(&(pool)->manager_mutex) && \
347 !lockdep_is_held(&(pool)->lock), \
348 "pool->manager_mutex or ->lock should be held")
350 #define assert_manager_or_pool_lock(pool) do { } while (0)
353 #define for_each_cpu_worker_pool(pool, cpu) \
354 for ((pool) = &per_cpu(cpu_worker_pools, cpu)[0]; \
355 (pool) < &per_cpu(cpu_worker_pools, cpu)[NR_STD_WORKER_POOLS]; \
359 * for_each_pool - iterate through all worker_pools in the system
360 * @pool: iteration cursor
361 * @pi: integer used for iteration
363 * This must be called either with wq_pool_mutex held or sched RCU read
364 * locked. If the pool needs to be used beyond the locking in effect, the
365 * caller is responsible for guaranteeing that the pool stays online.
367 * The if/else clause exists only for the lockdep assertion and can be
370 #define for_each_pool(pool, pi) \
371 idr_for_each_entry(&worker_pool_idr, pool, pi) \
372 if (({ assert_rcu_or_pool_mutex(); false; })) { } \
376 * for_each_pool_worker - iterate through all workers of a worker_pool
377 * @worker: iteration cursor
378 * @wi: integer used for iteration
379 * @pool: worker_pool to iterate workers of
381 * This must be called with either @pool->manager_mutex or ->lock held.
383 * The if/else clause exists only for the lockdep assertion and can be
386 #define for_each_pool_worker(worker, wi, pool) \
387 idr_for_each_entry(&(pool)->worker_idr, (worker), (wi)) \
388 if (({ assert_manager_or_pool_lock((pool)); false; })) { } \
392 * for_each_pwq - iterate through all pool_workqueues of the specified workqueue
393 * @pwq: iteration cursor
394 * @wq: the target workqueue
396 * This must be called either with wq->mutex held or sched RCU read locked.
397 * If the pwq needs to be used beyond the locking in effect, the caller is
398 * responsible for guaranteeing that the pwq stays online.
400 * The if/else clause exists only for the lockdep assertion and can be
403 #define for_each_pwq(pwq, wq) \
404 list_for_each_entry_rcu((pwq), &(wq)->pwqs, pwqs_node) \
405 if (({ assert_rcu_or_wq_mutex(wq); false; })) { } \
408 #ifdef CONFIG_DEBUG_OBJECTS_WORK
410 static struct debug_obj_descr work_debug_descr
;
412 static void *work_debug_hint(void *addr
)
414 return ((struct work_struct
*) addr
)->func
;
418 * fixup_init is called when:
419 * - an active object is initialized
421 static int work_fixup_init(void *addr
, enum debug_obj_state state
)
423 struct work_struct
*work
= addr
;
426 case ODEBUG_STATE_ACTIVE
:
427 cancel_work_sync(work
);
428 debug_object_init(work
, &work_debug_descr
);
436 * fixup_activate is called when:
437 * - an active object is activated
438 * - an unknown object is activated (might be a statically initialized object)
440 static int work_fixup_activate(void *addr
, enum debug_obj_state state
)
442 struct work_struct
*work
= addr
;
446 case ODEBUG_STATE_NOTAVAILABLE
:
448 * This is not really a fixup. The work struct was
449 * statically initialized. We just make sure that it
450 * is tracked in the object tracker.
452 if (test_bit(WORK_STRUCT_STATIC_BIT
, work_data_bits(work
))) {
453 debug_object_init(work
, &work_debug_descr
);
454 debug_object_activate(work
, &work_debug_descr
);
460 case ODEBUG_STATE_ACTIVE
:
469 * fixup_free is called when:
470 * - an active object is freed
472 static int work_fixup_free(void *addr
, enum debug_obj_state state
)
474 struct work_struct
*work
= addr
;
477 case ODEBUG_STATE_ACTIVE
:
478 cancel_work_sync(work
);
479 debug_object_free(work
, &work_debug_descr
);
486 static struct debug_obj_descr work_debug_descr
= {
487 .name
= "work_struct",
488 .debug_hint
= work_debug_hint
,
489 .fixup_init
= work_fixup_init
,
490 .fixup_activate
= work_fixup_activate
,
491 .fixup_free
= work_fixup_free
,
494 static inline void debug_work_activate(struct work_struct
*work
)
496 debug_object_activate(work
, &work_debug_descr
);
499 static inline void debug_work_deactivate(struct work_struct
*work
)
501 debug_object_deactivate(work
, &work_debug_descr
);
504 void __init_work(struct work_struct
*work
, int onstack
)
507 debug_object_init_on_stack(work
, &work_debug_descr
);
509 debug_object_init(work
, &work_debug_descr
);
511 EXPORT_SYMBOL_GPL(__init_work
);
513 void destroy_work_on_stack(struct work_struct
*work
)
515 debug_object_free(work
, &work_debug_descr
);
517 EXPORT_SYMBOL_GPL(destroy_work_on_stack
);
519 void destroy_delayed_work_on_stack(struct delayed_work
*work
)
521 destroy_timer_on_stack(&work
->timer
);
522 debug_object_free(&work
->work
, &work_debug_descr
);
524 EXPORT_SYMBOL_GPL(destroy_delayed_work_on_stack
);
527 static inline void debug_work_activate(struct work_struct
*work
) { }
528 static inline void debug_work_deactivate(struct work_struct
*work
) { }
532 * worker_pool_assign_id - allocate ID and assing it to @pool
533 * @pool: the pool pointer of interest
535 * Returns 0 if ID in [0, WORK_OFFQ_POOL_NONE) is allocated and assigned
536 * successfully, -errno on failure.
538 static int worker_pool_assign_id(struct worker_pool
*pool
)
542 lockdep_assert_held(&wq_pool_mutex
);
544 ret
= idr_alloc(&worker_pool_idr
, pool
, 0, WORK_OFFQ_POOL_NONE
,
554 * unbound_pwq_by_node - return the unbound pool_workqueue for the given node
555 * @wq: the target workqueue
558 * This must be called either with pwq_lock held or sched RCU read locked.
559 * If the pwq needs to be used beyond the locking in effect, the caller is
560 * responsible for guaranteeing that the pwq stays online.
562 * Return: The unbound pool_workqueue for @node.
564 static struct pool_workqueue
*unbound_pwq_by_node(struct workqueue_struct
*wq
,
567 assert_rcu_or_wq_mutex(wq
);
568 return rcu_dereference_raw(wq
->numa_pwq_tbl
[node
]);
571 static unsigned int work_color_to_flags(int color
)
573 return color
<< WORK_STRUCT_COLOR_SHIFT
;
576 static int get_work_color(struct work_struct
*work
)
578 return (*work_data_bits(work
) >> WORK_STRUCT_COLOR_SHIFT
) &
579 ((1 << WORK_STRUCT_COLOR_BITS
) - 1);
582 static int work_next_color(int color
)
584 return (color
+ 1) % WORK_NR_COLORS
;
588 * While queued, %WORK_STRUCT_PWQ is set and non flag bits of a work's data
589 * contain the pointer to the queued pwq. Once execution starts, the flag
590 * is cleared and the high bits contain OFFQ flags and pool ID.
592 * set_work_pwq(), set_work_pool_and_clear_pending(), mark_work_canceling()
593 * and clear_work_data() can be used to set the pwq, pool or clear
594 * work->data. These functions should only be called while the work is
595 * owned - ie. while the PENDING bit is set.
597 * get_work_pool() and get_work_pwq() can be used to obtain the pool or pwq
598 * corresponding to a work. Pool is available once the work has been
599 * queued anywhere after initialization until it is sync canceled. pwq is
600 * available only while the work item is queued.
602 * %WORK_OFFQ_CANCELING is used to mark a work item which is being
603 * canceled. While being canceled, a work item may have its PENDING set
604 * but stay off timer and worklist for arbitrarily long and nobody should
605 * try to steal the PENDING bit.
607 static inline void set_work_data(struct work_struct
*work
, unsigned long data
,
610 WARN_ON_ONCE(!work_pending(work
));
611 atomic_long_set(&work
->data
, data
| flags
| work_static(work
));
614 static void set_work_pwq(struct work_struct
*work
, struct pool_workqueue
*pwq
,
615 unsigned long extra_flags
)
617 set_work_data(work
, (unsigned long)pwq
,
618 WORK_STRUCT_PENDING
| WORK_STRUCT_PWQ
| extra_flags
);
621 static void set_work_pool_and_keep_pending(struct work_struct
*work
,
624 set_work_data(work
, (unsigned long)pool_id
<< WORK_OFFQ_POOL_SHIFT
,
625 WORK_STRUCT_PENDING
);
628 static void set_work_pool_and_clear_pending(struct work_struct
*work
,
632 * The following wmb is paired with the implied mb in
633 * test_and_set_bit(PENDING) and ensures all updates to @work made
634 * here are visible to and precede any updates by the next PENDING
638 set_work_data(work
, (unsigned long)pool_id
<< WORK_OFFQ_POOL_SHIFT
, 0);
641 static void clear_work_data(struct work_struct
*work
)
643 smp_wmb(); /* see set_work_pool_and_clear_pending() */
644 set_work_data(work
, WORK_STRUCT_NO_POOL
, 0);
647 static struct pool_workqueue
*get_work_pwq(struct work_struct
*work
)
649 unsigned long data
= atomic_long_read(&work
->data
);
651 if (data
& WORK_STRUCT_PWQ
)
652 return (void *)(data
& WORK_STRUCT_WQ_DATA_MASK
);
658 * get_work_pool - return the worker_pool a given work was associated with
659 * @work: the work item of interest
661 * Pools are created and destroyed under wq_pool_mutex, and allows read
662 * access under sched-RCU read lock. As such, this function should be
663 * called under wq_pool_mutex or with preemption disabled.
665 * All fields of the returned pool are accessible as long as the above
666 * mentioned locking is in effect. If the returned pool needs to be used
667 * beyond the critical section, the caller is responsible for ensuring the
668 * returned pool is and stays online.
670 * Return: The worker_pool @work was last associated with. %NULL if none.
672 static struct worker_pool
*get_work_pool(struct work_struct
*work
)
674 unsigned long data
= atomic_long_read(&work
->data
);
677 assert_rcu_or_pool_mutex();
679 if (data
& WORK_STRUCT_PWQ
)
680 return ((struct pool_workqueue
*)
681 (data
& WORK_STRUCT_WQ_DATA_MASK
))->pool
;
683 pool_id
= data
>> WORK_OFFQ_POOL_SHIFT
;
684 if (pool_id
== WORK_OFFQ_POOL_NONE
)
687 return idr_find(&worker_pool_idr
, pool_id
);
691 * get_work_pool_id - return the worker pool ID a given work is associated with
692 * @work: the work item of interest
694 * Return: The worker_pool ID @work was last associated with.
695 * %WORK_OFFQ_POOL_NONE if none.
697 static int get_work_pool_id(struct work_struct
*work
)
699 unsigned long data
= atomic_long_read(&work
->data
);
701 if (data
& WORK_STRUCT_PWQ
)
702 return ((struct pool_workqueue
*)
703 (data
& WORK_STRUCT_WQ_DATA_MASK
))->pool
->id
;
705 return data
>> WORK_OFFQ_POOL_SHIFT
;
708 static void mark_work_canceling(struct work_struct
*work
)
710 unsigned long pool_id
= get_work_pool_id(work
);
712 pool_id
<<= WORK_OFFQ_POOL_SHIFT
;
713 set_work_data(work
, pool_id
| WORK_OFFQ_CANCELING
, WORK_STRUCT_PENDING
);
716 static bool work_is_canceling(struct work_struct
*work
)
718 unsigned long data
= atomic_long_read(&work
->data
);
720 return !(data
& WORK_STRUCT_PWQ
) && (data
& WORK_OFFQ_CANCELING
);
724 * Policy functions. These define the policies on how the global worker
725 * pools are managed. Unless noted otherwise, these functions assume that
726 * they're being called with pool->lock held.
729 static bool __need_more_worker(struct worker_pool
*pool
)
731 return !atomic_read(&pool
->nr_running
);
735 * Need to wake up a worker? Called from anything but currently
738 * Note that, because unbound workers never contribute to nr_running, this
739 * function will always return %true for unbound pools as long as the
740 * worklist isn't empty.
742 static bool need_more_worker(struct worker_pool
*pool
)
744 return !list_empty(&pool
->worklist
) && __need_more_worker(pool
);
747 /* Can I start working? Called from busy but !running workers. */
748 static bool may_start_working(struct worker_pool
*pool
)
750 return pool
->nr_idle
;
753 /* Do I need to keep working? Called from currently running workers. */
754 static bool keep_working(struct worker_pool
*pool
)
756 return !list_empty(&pool
->worklist
) &&
757 atomic_read(&pool
->nr_running
) <= 1;
760 /* Do we need a new worker? Called from manager. */
761 static bool need_to_create_worker(struct worker_pool
*pool
)
763 return need_more_worker(pool
) && !may_start_working(pool
);
766 /* Do I need to be the manager? */
767 static bool need_to_manage_workers(struct worker_pool
*pool
)
769 return need_to_create_worker(pool
) ||
770 (pool
->flags
& POOL_MANAGE_WORKERS
);
773 /* Do we have too many workers and should some go away? */
774 static bool too_many_workers(struct worker_pool
*pool
)
776 bool managing
= mutex_is_locked(&pool
->manager_arb
);
777 int nr_idle
= pool
->nr_idle
+ managing
; /* manager is considered idle */
778 int nr_busy
= pool
->nr_workers
- nr_idle
;
781 * nr_idle and idle_list may disagree if idle rebinding is in
782 * progress. Never return %true if idle_list is empty.
784 if (list_empty(&pool
->idle_list
))
787 return nr_idle
> 2 && (nr_idle
- 2) * MAX_IDLE_WORKERS_RATIO
>= nr_busy
;
794 /* Return the first worker. Safe with preemption disabled */
795 static struct worker
*first_worker(struct worker_pool
*pool
)
797 if (unlikely(list_empty(&pool
->idle_list
)))
800 return list_first_entry(&pool
->idle_list
, struct worker
, entry
);
804 * wake_up_worker - wake up an idle worker
805 * @pool: worker pool to wake worker from
807 * Wake up the first idle worker of @pool.
810 * spin_lock_irq(pool->lock).
812 static void wake_up_worker(struct worker_pool
*pool
)
814 struct worker
*worker
= first_worker(pool
);
817 wake_up_process(worker
->task
);
821 * wq_worker_waking_up - a worker is waking up
822 * @task: task waking up
823 * @cpu: CPU @task is waking up to
825 * This function is called during try_to_wake_up() when a worker is
829 * spin_lock_irq(rq->lock)
831 void wq_worker_waking_up(struct task_struct
*task
, int cpu
)
833 struct worker
*worker
= kthread_data(task
);
835 if (!(worker
->flags
& WORKER_NOT_RUNNING
)) {
836 WARN_ON_ONCE(worker
->pool
->cpu
!= cpu
);
837 atomic_inc(&worker
->pool
->nr_running
);
842 * wq_worker_sleeping - a worker is going to sleep
843 * @task: task going to sleep
844 * @cpu: CPU in question, must be the current CPU number
846 * This function is called during schedule() when a busy worker is
847 * going to sleep. Worker on the same cpu can be woken up by
848 * returning pointer to its task.
851 * spin_lock_irq(rq->lock)
854 * Worker task on @cpu to wake up, %NULL if none.
856 struct task_struct
*wq_worker_sleeping(struct task_struct
*task
, int cpu
)
858 struct worker
*worker
= kthread_data(task
), *to_wakeup
= NULL
;
859 struct worker_pool
*pool
;
862 * Rescuers, which may not have all the fields set up like normal
863 * workers, also reach here, let's not access anything before
864 * checking NOT_RUNNING.
866 if (worker
->flags
& WORKER_NOT_RUNNING
)
871 /* this can only happen on the local cpu */
872 if (WARN_ON_ONCE(cpu
!= raw_smp_processor_id()))
876 * The counterpart of the following dec_and_test, implied mb,
877 * worklist not empty test sequence is in insert_work().
878 * Please read comment there.
880 * NOT_RUNNING is clear. This means that we're bound to and
881 * running on the local cpu w/ rq lock held and preemption
882 * disabled, which in turn means that none else could be
883 * manipulating idle_list, so dereferencing idle_list without pool
886 if (atomic_dec_and_test(&pool
->nr_running
) &&
887 !list_empty(&pool
->worklist
))
888 to_wakeup
= first_worker(pool
);
889 return to_wakeup
? to_wakeup
->task
: NULL
;
893 * worker_set_flags - set worker flags and adjust nr_running accordingly
895 * @flags: flags to set
896 * @wakeup: wakeup an idle worker if necessary
898 * Set @flags in @worker->flags and adjust nr_running accordingly. If
899 * nr_running becomes zero and @wakeup is %true, an idle worker is
903 * spin_lock_irq(pool->lock)
905 static inline void worker_set_flags(struct worker
*worker
, unsigned int flags
,
908 struct worker_pool
*pool
= worker
->pool
;
910 WARN_ON_ONCE(worker
->task
!= current
);
913 * If transitioning into NOT_RUNNING, adjust nr_running and
914 * wake up an idle worker as necessary if requested by
917 if ((flags
& WORKER_NOT_RUNNING
) &&
918 !(worker
->flags
& WORKER_NOT_RUNNING
)) {
920 if (atomic_dec_and_test(&pool
->nr_running
) &&
921 !list_empty(&pool
->worklist
))
922 wake_up_worker(pool
);
924 atomic_dec(&pool
->nr_running
);
927 worker
->flags
|= flags
;
931 * worker_clr_flags - clear worker flags and adjust nr_running accordingly
933 * @flags: flags to clear
935 * Clear @flags in @worker->flags and adjust nr_running accordingly.
938 * spin_lock_irq(pool->lock)
940 static inline void worker_clr_flags(struct worker
*worker
, unsigned int flags
)
942 struct worker_pool
*pool
= worker
->pool
;
943 unsigned int oflags
= worker
->flags
;
945 WARN_ON_ONCE(worker
->task
!= current
);
947 worker
->flags
&= ~flags
;
950 * If transitioning out of NOT_RUNNING, increment nr_running. Note
951 * that the nested NOT_RUNNING is not a noop. NOT_RUNNING is mask
952 * of multiple flags, not a single flag.
954 if ((flags
& WORKER_NOT_RUNNING
) && (oflags
& WORKER_NOT_RUNNING
))
955 if (!(worker
->flags
& WORKER_NOT_RUNNING
))
956 atomic_inc(&pool
->nr_running
);
960 * find_worker_executing_work - find worker which is executing a work
961 * @pool: pool of interest
962 * @work: work to find worker for
964 * Find a worker which is executing @work on @pool by searching
965 * @pool->busy_hash which is keyed by the address of @work. For a worker
966 * to match, its current execution should match the address of @work and
967 * its work function. This is to avoid unwanted dependency between
968 * unrelated work executions through a work item being recycled while still
971 * This is a bit tricky. A work item may be freed once its execution
972 * starts and nothing prevents the freed area from being recycled for
973 * another work item. If the same work item address ends up being reused
974 * before the original execution finishes, workqueue will identify the
975 * recycled work item as currently executing and make it wait until the
976 * current execution finishes, introducing an unwanted dependency.
978 * This function checks the work item address and work function to avoid
979 * false positives. Note that this isn't complete as one may construct a
980 * work function which can introduce dependency onto itself through a
981 * recycled work item. Well, if somebody wants to shoot oneself in the
982 * foot that badly, there's only so much we can do, and if such deadlock
983 * actually occurs, it should be easy to locate the culprit work function.
986 * spin_lock_irq(pool->lock).
989 * Pointer to worker which is executing @work if found, %NULL
992 static struct worker
*find_worker_executing_work(struct worker_pool
*pool
,
993 struct work_struct
*work
)
995 struct worker
*worker
;
997 hash_for_each_possible(pool
->busy_hash
, worker
, hentry
,
999 if (worker
->current_work
== work
&&
1000 worker
->current_func
== work
->func
)
1007 * move_linked_works - move linked works to a list
1008 * @work: start of series of works to be scheduled
1009 * @head: target list to append @work to
1010 * @nextp: out paramter for nested worklist walking
1012 * Schedule linked works starting from @work to @head. Work series to
1013 * be scheduled starts at @work and includes any consecutive work with
1014 * WORK_STRUCT_LINKED set in its predecessor.
1016 * If @nextp is not NULL, it's updated to point to the next work of
1017 * the last scheduled work. This allows move_linked_works() to be
1018 * nested inside outer list_for_each_entry_safe().
1021 * spin_lock_irq(pool->lock).
1023 static void move_linked_works(struct work_struct
*work
, struct list_head
*head
,
1024 struct work_struct
**nextp
)
1026 struct work_struct
*n
;
1029 * Linked worklist will always end before the end of the list,
1030 * use NULL for list head.
1032 list_for_each_entry_safe_from(work
, n
, NULL
, entry
) {
1033 list_move_tail(&work
->entry
, head
);
1034 if (!(*work_data_bits(work
) & WORK_STRUCT_LINKED
))
1039 * If we're already inside safe list traversal and have moved
1040 * multiple works to the scheduled queue, the next position
1041 * needs to be updated.
1048 * get_pwq - get an extra reference on the specified pool_workqueue
1049 * @pwq: pool_workqueue to get
1051 * Obtain an extra reference on @pwq. The caller should guarantee that
1052 * @pwq has positive refcnt and be holding the matching pool->lock.
1054 static void get_pwq(struct pool_workqueue
*pwq
)
1056 lockdep_assert_held(&pwq
->pool
->lock
);
1057 WARN_ON_ONCE(pwq
->refcnt
<= 0);
1062 * put_pwq - put a pool_workqueue reference
1063 * @pwq: pool_workqueue to put
1065 * Drop a reference of @pwq. If its refcnt reaches zero, schedule its
1066 * destruction. The caller should be holding the matching pool->lock.
1068 static void put_pwq(struct pool_workqueue
*pwq
)
1070 lockdep_assert_held(&pwq
->pool
->lock
);
1071 if (likely(--pwq
->refcnt
))
1073 if (WARN_ON_ONCE(!(pwq
->wq
->flags
& WQ_UNBOUND
)))
1076 * @pwq can't be released under pool->lock, bounce to
1077 * pwq_unbound_release_workfn(). This never recurses on the same
1078 * pool->lock as this path is taken only for unbound workqueues and
1079 * the release work item is scheduled on a per-cpu workqueue. To
1080 * avoid lockdep warning, unbound pool->locks are given lockdep
1081 * subclass of 1 in get_unbound_pool().
1083 schedule_work(&pwq
->unbound_release_work
);
1087 * put_pwq_unlocked - put_pwq() with surrounding pool lock/unlock
1088 * @pwq: pool_workqueue to put (can be %NULL)
1090 * put_pwq() with locking. This function also allows %NULL @pwq.
1092 static void put_pwq_unlocked(struct pool_workqueue
*pwq
)
1096 * As both pwqs and pools are sched-RCU protected, the
1097 * following lock operations are safe.
1099 spin_lock_irq(&pwq
->pool
->lock
);
1101 spin_unlock_irq(&pwq
->pool
->lock
);
1105 static void pwq_activate_delayed_work(struct work_struct
*work
)
1107 struct pool_workqueue
*pwq
= get_work_pwq(work
);
1109 trace_workqueue_activate_work(work
);
1110 move_linked_works(work
, &pwq
->pool
->worklist
, NULL
);
1111 __clear_bit(WORK_STRUCT_DELAYED_BIT
, work_data_bits(work
));
1115 static void pwq_activate_first_delayed(struct pool_workqueue
*pwq
)
1117 struct work_struct
*work
= list_first_entry(&pwq
->delayed_works
,
1118 struct work_struct
, entry
);
1120 pwq_activate_delayed_work(work
);
1124 * pwq_dec_nr_in_flight - decrement pwq's nr_in_flight
1125 * @pwq: pwq of interest
1126 * @color: color of work which left the queue
1128 * A work either has completed or is removed from pending queue,
1129 * decrement nr_in_flight of its pwq and handle workqueue flushing.
1132 * spin_lock_irq(pool->lock).
1134 static void pwq_dec_nr_in_flight(struct pool_workqueue
*pwq
, int color
)
1136 /* uncolored work items don't participate in flushing or nr_active */
1137 if (color
== WORK_NO_COLOR
)
1140 pwq
->nr_in_flight
[color
]--;
1143 if (!list_empty(&pwq
->delayed_works
)) {
1144 /* one down, submit a delayed one */
1145 if (pwq
->nr_active
< pwq
->max_active
)
1146 pwq_activate_first_delayed(pwq
);
1149 /* is flush in progress and are we at the flushing tip? */
1150 if (likely(pwq
->flush_color
!= color
))
1153 /* are there still in-flight works? */
1154 if (pwq
->nr_in_flight
[color
])
1157 /* this pwq is done, clear flush_color */
1158 pwq
->flush_color
= -1;
1161 * If this was the last pwq, wake up the first flusher. It
1162 * will handle the rest.
1164 if (atomic_dec_and_test(&pwq
->wq
->nr_pwqs_to_flush
))
1165 complete(&pwq
->wq
->first_flusher
->done
);
1171 * try_to_grab_pending - steal work item from worklist and disable irq
1172 * @work: work item to steal
1173 * @is_dwork: @work is a delayed_work
1174 * @flags: place to store irq state
1176 * Try to grab PENDING bit of @work. This function can handle @work in any
1177 * stable state - idle, on timer or on worklist.
1180 * 1 if @work was pending and we successfully stole PENDING
1181 * 0 if @work was idle and we claimed PENDING
1182 * -EAGAIN if PENDING couldn't be grabbed at the moment, safe to busy-retry
1183 * -ENOENT if someone else is canceling @work, this state may persist
1184 * for arbitrarily long
1187 * On >= 0 return, the caller owns @work's PENDING bit. To avoid getting
1188 * interrupted while holding PENDING and @work off queue, irq must be
1189 * disabled on entry. This, combined with delayed_work->timer being
1190 * irqsafe, ensures that we return -EAGAIN for finite short period of time.
1192 * On successful return, >= 0, irq is disabled and the caller is
1193 * responsible for releasing it using local_irq_restore(*@flags).
1195 * This function is safe to call from any context including IRQ handler.
1197 static int try_to_grab_pending(struct work_struct
*work
, bool is_dwork
,
1198 unsigned long *flags
)
1200 struct worker_pool
*pool
;
1201 struct pool_workqueue
*pwq
;
1203 local_irq_save(*flags
);
1205 /* try to steal the timer if it exists */
1207 struct delayed_work
*dwork
= to_delayed_work(work
);
1210 * dwork->timer is irqsafe. If del_timer() fails, it's
1211 * guaranteed that the timer is not queued anywhere and not
1212 * running on the local CPU.
1214 if (likely(del_timer(&dwork
->timer
)))
1218 /* try to claim PENDING the normal way */
1219 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT
, work_data_bits(work
)))
1223 * The queueing is in progress, or it is already queued. Try to
1224 * steal it from ->worklist without clearing WORK_STRUCT_PENDING.
1226 pool
= get_work_pool(work
);
1230 spin_lock(&pool
->lock
);
1232 * work->data is guaranteed to point to pwq only while the work
1233 * item is queued on pwq->wq, and both updating work->data to point
1234 * to pwq on queueing and to pool on dequeueing are done under
1235 * pwq->pool->lock. This in turn guarantees that, if work->data
1236 * points to pwq which is associated with a locked pool, the work
1237 * item is currently queued on that pool.
1239 pwq
= get_work_pwq(work
);
1240 if (pwq
&& pwq
->pool
== pool
) {
1241 debug_work_deactivate(work
);
1244 * A delayed work item cannot be grabbed directly because
1245 * it might have linked NO_COLOR work items which, if left
1246 * on the delayed_list, will confuse pwq->nr_active
1247 * management later on and cause stall. Make sure the work
1248 * item is activated before grabbing.
1250 if (*work_data_bits(work
) & WORK_STRUCT_DELAYED
)
1251 pwq_activate_delayed_work(work
);
1253 list_del_init(&work
->entry
);
1254 pwq_dec_nr_in_flight(get_work_pwq(work
), get_work_color(work
));
1256 /* work->data points to pwq iff queued, point to pool */
1257 set_work_pool_and_keep_pending(work
, pool
->id
);
1259 spin_unlock(&pool
->lock
);
1262 spin_unlock(&pool
->lock
);
1264 local_irq_restore(*flags
);
1265 if (work_is_canceling(work
))
1272 * insert_work - insert a work into a pool
1273 * @pwq: pwq @work belongs to
1274 * @work: work to insert
1275 * @head: insertion point
1276 * @extra_flags: extra WORK_STRUCT_* flags to set
1278 * Insert @work which belongs to @pwq after @head. @extra_flags is or'd to
1279 * work_struct flags.
1282 * spin_lock_irq(pool->lock).
1284 static void insert_work(struct pool_workqueue
*pwq
, struct work_struct
*work
,
1285 struct list_head
*head
, unsigned int extra_flags
)
1287 struct worker_pool
*pool
= pwq
->pool
;
1289 /* we own @work, set data and link */
1290 set_work_pwq(work
, pwq
, extra_flags
);
1291 list_add_tail(&work
->entry
, head
);
1295 * Ensure either wq_worker_sleeping() sees the above
1296 * list_add_tail() or we see zero nr_running to avoid workers lying
1297 * around lazily while there are works to be processed.
1301 if (__need_more_worker(pool
))
1302 wake_up_worker(pool
);
1306 * Test whether @work is being queued from another work executing on the
1309 static bool is_chained_work(struct workqueue_struct
*wq
)
1311 struct worker
*worker
;
1313 worker
= current_wq_worker();
1315 * Return %true iff I'm a worker execuing a work item on @wq. If
1316 * I'm @worker, it's safe to dereference it without locking.
1318 return worker
&& worker
->current_pwq
->wq
== wq
;
1321 static void __queue_work(int cpu
, struct workqueue_struct
*wq
,
1322 struct work_struct
*work
)
1324 struct pool_workqueue
*pwq
;
1325 struct worker_pool
*last_pool
;
1326 struct list_head
*worklist
;
1327 unsigned int work_flags
;
1328 unsigned int req_cpu
= cpu
;
1331 * While a work item is PENDING && off queue, a task trying to
1332 * steal the PENDING will busy-loop waiting for it to either get
1333 * queued or lose PENDING. Grabbing PENDING and queueing should
1334 * happen with IRQ disabled.
1336 WARN_ON_ONCE(!irqs_disabled());
1338 debug_work_activate(work
);
1340 /* if draining, only works from the same workqueue are allowed */
1341 if (unlikely(wq
->flags
& __WQ_DRAINING
) &&
1342 WARN_ON_ONCE(!is_chained_work(wq
)))
1345 if (req_cpu
== WORK_CPU_UNBOUND
)
1346 cpu
= raw_smp_processor_id();
1348 /* pwq which will be used unless @work is executing elsewhere */
1349 if (!(wq
->flags
& WQ_UNBOUND
))
1350 pwq
= per_cpu_ptr(wq
->cpu_pwqs
, cpu
);
1352 pwq
= unbound_pwq_by_node(wq
, cpu_to_node(cpu
));
1355 * If @work was previously on a different pool, it might still be
1356 * running there, in which case the work needs to be queued on that
1357 * pool to guarantee non-reentrancy.
1359 last_pool
= get_work_pool(work
);
1360 if (last_pool
&& last_pool
!= pwq
->pool
) {
1361 struct worker
*worker
;
1363 spin_lock(&last_pool
->lock
);
1365 worker
= find_worker_executing_work(last_pool
, work
);
1367 if (worker
&& worker
->current_pwq
->wq
== wq
) {
1368 pwq
= worker
->current_pwq
;
1370 /* meh... not running there, queue here */
1371 spin_unlock(&last_pool
->lock
);
1372 spin_lock(&pwq
->pool
->lock
);
1375 spin_lock(&pwq
->pool
->lock
);
1379 * pwq is determined and locked. For unbound pools, we could have
1380 * raced with pwq release and it could already be dead. If its
1381 * refcnt is zero, repeat pwq selection. Note that pwqs never die
1382 * without another pwq replacing it in the numa_pwq_tbl or while
1383 * work items are executing on it, so the retrying is guaranteed to
1384 * make forward-progress.
1386 if (unlikely(!pwq
->refcnt
)) {
1387 if (wq
->flags
& WQ_UNBOUND
) {
1388 spin_unlock(&pwq
->pool
->lock
);
1393 WARN_ONCE(true, "workqueue: per-cpu pwq for %s on cpu%d has 0 refcnt",
1397 /* pwq determined, queue */
1398 trace_workqueue_queue_work(req_cpu
, pwq
, work
);
1400 if (WARN_ON(!list_empty(&work
->entry
))) {
1401 spin_unlock(&pwq
->pool
->lock
);
1405 pwq
->nr_in_flight
[pwq
->work_color
]++;
1406 work_flags
= work_color_to_flags(pwq
->work_color
);
1408 if (likely(pwq
->nr_active
< pwq
->max_active
)) {
1409 trace_workqueue_activate_work(work
);
1411 worklist
= &pwq
->pool
->worklist
;
1413 work_flags
|= WORK_STRUCT_DELAYED
;
1414 worklist
= &pwq
->delayed_works
;
1417 insert_work(pwq
, work
, worklist
, work_flags
);
1419 spin_unlock(&pwq
->pool
->lock
);
1423 * queue_work_on - queue work on specific cpu
1424 * @cpu: CPU number to execute work on
1425 * @wq: workqueue to use
1426 * @work: work to queue
1428 * We queue the work to a specific CPU, the caller must ensure it
1431 * Return: %false if @work was already on a queue, %true otherwise.
1433 bool queue_work_on(int cpu
, struct workqueue_struct
*wq
,
1434 struct work_struct
*work
)
1437 unsigned long flags
;
1439 local_irq_save(flags
);
1441 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT
, work_data_bits(work
))) {
1442 __queue_work(cpu
, wq
, work
);
1446 local_irq_restore(flags
);
1449 EXPORT_SYMBOL(queue_work_on
);
1451 void delayed_work_timer_fn(unsigned long __data
)
1453 struct delayed_work
*dwork
= (struct delayed_work
*)__data
;
1455 /* should have been called from irqsafe timer with irq already off */
1456 __queue_work(dwork
->cpu
, dwork
->wq
, &dwork
->work
);
1458 EXPORT_SYMBOL(delayed_work_timer_fn
);
1460 static void __queue_delayed_work(int cpu
, struct workqueue_struct
*wq
,
1461 struct delayed_work
*dwork
, unsigned long delay
)
1463 struct timer_list
*timer
= &dwork
->timer
;
1464 struct work_struct
*work
= &dwork
->work
;
1466 WARN_ON_ONCE(timer
->function
!= delayed_work_timer_fn
||
1467 timer
->data
!= (unsigned long)dwork
);
1468 WARN_ON_ONCE(timer_pending(timer
));
1469 WARN_ON_ONCE(!list_empty(&work
->entry
));
1472 * If @delay is 0, queue @dwork->work immediately. This is for
1473 * both optimization and correctness. The earliest @timer can
1474 * expire is on the closest next tick and delayed_work users depend
1475 * on that there's no such delay when @delay is 0.
1478 __queue_work(cpu
, wq
, &dwork
->work
);
1482 timer_stats_timer_set_start_info(&dwork
->timer
);
1486 timer
->expires
= jiffies
+ delay
;
1488 if (unlikely(cpu
!= WORK_CPU_UNBOUND
))
1489 add_timer_on(timer
, cpu
);
1495 * queue_delayed_work_on - queue work on specific CPU after delay
1496 * @cpu: CPU number to execute work on
1497 * @wq: workqueue to use
1498 * @dwork: work to queue
1499 * @delay: number of jiffies to wait before queueing
1501 * Return: %false if @work was already on a queue, %true otherwise. If
1502 * @delay is zero and @dwork is idle, it will be scheduled for immediate
1505 bool queue_delayed_work_on(int cpu
, struct workqueue_struct
*wq
,
1506 struct delayed_work
*dwork
, unsigned long delay
)
1508 struct work_struct
*work
= &dwork
->work
;
1510 unsigned long flags
;
1512 /* read the comment in __queue_work() */
1513 local_irq_save(flags
);
1515 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT
, work_data_bits(work
))) {
1516 __queue_delayed_work(cpu
, wq
, dwork
, delay
);
1520 local_irq_restore(flags
);
1523 EXPORT_SYMBOL(queue_delayed_work_on
);
1526 * mod_delayed_work_on - modify delay of or queue a delayed work on specific CPU
1527 * @cpu: CPU number to execute work on
1528 * @wq: workqueue to use
1529 * @dwork: work to queue
1530 * @delay: number of jiffies to wait before queueing
1532 * If @dwork is idle, equivalent to queue_delayed_work_on(); otherwise,
1533 * modify @dwork's timer so that it expires after @delay. If @delay is
1534 * zero, @work is guaranteed to be scheduled immediately regardless of its
1537 * Return: %false if @dwork was idle and queued, %true if @dwork was
1538 * pending and its timer was modified.
1540 * This function is safe to call from any context including IRQ handler.
1541 * See try_to_grab_pending() for details.
1543 bool mod_delayed_work_on(int cpu
, struct workqueue_struct
*wq
,
1544 struct delayed_work
*dwork
, unsigned long delay
)
1546 unsigned long flags
;
1550 ret
= try_to_grab_pending(&dwork
->work
, true, &flags
);
1551 } while (unlikely(ret
== -EAGAIN
));
1553 if (likely(ret
>= 0)) {
1554 __queue_delayed_work(cpu
, wq
, dwork
, delay
);
1555 local_irq_restore(flags
);
1558 /* -ENOENT from try_to_grab_pending() becomes %true */
1561 EXPORT_SYMBOL_GPL(mod_delayed_work_on
);
1564 * worker_enter_idle - enter idle state
1565 * @worker: worker which is entering idle state
1567 * @worker is entering idle state. Update stats and idle timer if
1571 * spin_lock_irq(pool->lock).
1573 static void worker_enter_idle(struct worker
*worker
)
1575 struct worker_pool
*pool
= worker
->pool
;
1577 if (WARN_ON_ONCE(worker
->flags
& WORKER_IDLE
) ||
1578 WARN_ON_ONCE(!list_empty(&worker
->entry
) &&
1579 (worker
->hentry
.next
|| worker
->hentry
.pprev
)))
1582 /* can't use worker_set_flags(), also called from start_worker() */
1583 worker
->flags
|= WORKER_IDLE
;
1585 worker
->last_active
= jiffies
;
1587 /* idle_list is LIFO */
1588 list_add(&worker
->entry
, &pool
->idle_list
);
1590 if (too_many_workers(pool
) && !timer_pending(&pool
->idle_timer
))
1591 mod_timer(&pool
->idle_timer
, jiffies
+ IDLE_WORKER_TIMEOUT
);
1594 * Sanity check nr_running. Because wq_unbind_fn() releases
1595 * pool->lock between setting %WORKER_UNBOUND and zapping
1596 * nr_running, the warning may trigger spuriously. Check iff
1597 * unbind is not in progress.
1599 WARN_ON_ONCE(!(pool
->flags
& POOL_DISASSOCIATED
) &&
1600 pool
->nr_workers
== pool
->nr_idle
&&
1601 atomic_read(&pool
->nr_running
));
1605 * worker_leave_idle - leave idle state
1606 * @worker: worker which is leaving idle state
1608 * @worker is leaving idle state. Update stats.
1611 * spin_lock_irq(pool->lock).
1613 static void worker_leave_idle(struct worker
*worker
)
1615 struct worker_pool
*pool
= worker
->pool
;
1617 if (WARN_ON_ONCE(!(worker
->flags
& WORKER_IDLE
)))
1619 worker_clr_flags(worker
, WORKER_IDLE
);
1621 list_del_init(&worker
->entry
);
1625 * worker_maybe_bind_and_lock - try to bind %current to worker_pool and lock it
1626 * @pool: target worker_pool
1628 * Bind %current to the cpu of @pool if it is associated and lock @pool.
1630 * Works which are scheduled while the cpu is online must at least be
1631 * scheduled to a worker which is bound to the cpu so that if they are
1632 * flushed from cpu callbacks while cpu is going down, they are
1633 * guaranteed to execute on the cpu.
1635 * This function is to be used by unbound workers and rescuers to bind
1636 * themselves to the target cpu and may race with cpu going down or
1637 * coming online. kthread_bind() can't be used because it may put the
1638 * worker to already dead cpu and set_cpus_allowed_ptr() can't be used
1639 * verbatim as it's best effort and blocking and pool may be
1640 * [dis]associated in the meantime.
1642 * This function tries set_cpus_allowed() and locks pool and verifies the
1643 * binding against %POOL_DISASSOCIATED which is set during
1644 * %CPU_DOWN_PREPARE and cleared during %CPU_ONLINE, so if the worker
1645 * enters idle state or fetches works without dropping lock, it can
1646 * guarantee the scheduling requirement described in the first paragraph.
1649 * Might sleep. Called without any lock but returns with pool->lock
1653 * %true if the associated pool is online (@worker is successfully
1654 * bound), %false if offline.
1656 static bool worker_maybe_bind_and_lock(struct worker_pool
*pool
)
1657 __acquires(&pool
->lock
)
1661 * The following call may fail, succeed or succeed
1662 * without actually migrating the task to the cpu if
1663 * it races with cpu hotunplug operation. Verify
1664 * against POOL_DISASSOCIATED.
1666 if (!(pool
->flags
& POOL_DISASSOCIATED
))
1667 set_cpus_allowed_ptr(current
, pool
->attrs
->cpumask
);
1669 spin_lock_irq(&pool
->lock
);
1670 if (pool
->flags
& POOL_DISASSOCIATED
)
1672 if (task_cpu(current
) == pool
->cpu
&&
1673 cpumask_equal(¤t
->cpus_allowed
, pool
->attrs
->cpumask
))
1675 spin_unlock_irq(&pool
->lock
);
1678 * We've raced with CPU hot[un]plug. Give it a breather
1679 * and retry migration. cond_resched() is required here;
1680 * otherwise, we might deadlock against cpu_stop trying to
1681 * bring down the CPU on non-preemptive kernel.
1688 static struct worker
*alloc_worker(void)
1690 struct worker
*worker
;
1692 worker
= kzalloc(sizeof(*worker
), GFP_KERNEL
);
1694 INIT_LIST_HEAD(&worker
->entry
);
1695 INIT_LIST_HEAD(&worker
->scheduled
);
1696 /* on creation a worker is in !idle && prep state */
1697 worker
->flags
= WORKER_PREP
;
1703 * create_worker - create a new workqueue worker
1704 * @pool: pool the new worker will belong to
1706 * Create a new worker which is bound to @pool. The returned worker
1707 * can be started by calling start_worker() or destroyed using
1711 * Might sleep. Does GFP_KERNEL allocations.
1714 * Pointer to the newly created worker.
1716 static struct worker
*create_worker(struct worker_pool
*pool
)
1718 struct worker
*worker
= NULL
;
1722 lockdep_assert_held(&pool
->manager_mutex
);
1725 * ID is needed to determine kthread name. Allocate ID first
1726 * without installing the pointer.
1728 idr_preload(GFP_KERNEL
);
1729 spin_lock_irq(&pool
->lock
);
1731 id
= idr_alloc(&pool
->worker_idr
, NULL
, 0, 0, GFP_NOWAIT
);
1733 spin_unlock_irq(&pool
->lock
);
1738 worker
= alloc_worker();
1742 worker
->pool
= pool
;
1746 snprintf(id_buf
, sizeof(id_buf
), "%d:%d%s", pool
->cpu
, id
,
1747 pool
->attrs
->nice
< 0 ? "H" : "");
1749 snprintf(id_buf
, sizeof(id_buf
), "u%d:%d", pool
->id
, id
);
1751 worker
->task
= kthread_create_on_node(worker_thread
, worker
, pool
->node
,
1752 "kworker/%s", id_buf
);
1753 if (IS_ERR(worker
->task
))
1756 set_user_nice(worker
->task
, pool
->attrs
->nice
);
1758 /* prevent userland from meddling with cpumask of workqueue workers */
1759 worker
->task
->flags
|= PF_NO_SETAFFINITY
;
1762 * set_cpus_allowed_ptr() will fail if the cpumask doesn't have any
1763 * online CPUs. It'll be re-applied when any of the CPUs come up.
1765 set_cpus_allowed_ptr(worker
->task
, pool
->attrs
->cpumask
);
1768 * The caller is responsible for ensuring %POOL_DISASSOCIATED
1769 * remains stable across this function. See the comments above the
1770 * flag definition for details.
1772 if (pool
->flags
& POOL_DISASSOCIATED
)
1773 worker
->flags
|= WORKER_UNBOUND
;
1775 /* successful, commit the pointer to idr */
1776 spin_lock_irq(&pool
->lock
);
1777 idr_replace(&pool
->worker_idr
, worker
, worker
->id
);
1778 spin_unlock_irq(&pool
->lock
);
1784 spin_lock_irq(&pool
->lock
);
1785 idr_remove(&pool
->worker_idr
, id
);
1786 spin_unlock_irq(&pool
->lock
);
1793 * start_worker - start a newly created worker
1794 * @worker: worker to start
1796 * Make the pool aware of @worker and start it.
1799 * spin_lock_irq(pool->lock).
1801 static void start_worker(struct worker
*worker
)
1803 worker
->flags
|= WORKER_STARTED
;
1804 worker
->pool
->nr_workers
++;
1805 worker_enter_idle(worker
);
1806 wake_up_process(worker
->task
);
1810 * create_and_start_worker - create and start a worker for a pool
1811 * @pool: the target pool
1813 * Grab the managership of @pool and create and start a new worker for it.
1815 * Return: 0 on success. A negative error code otherwise.
1817 static int create_and_start_worker(struct worker_pool
*pool
)
1819 struct worker
*worker
;
1821 mutex_lock(&pool
->manager_mutex
);
1823 worker
= create_worker(pool
);
1825 spin_lock_irq(&pool
->lock
);
1826 start_worker(worker
);
1827 spin_unlock_irq(&pool
->lock
);
1830 mutex_unlock(&pool
->manager_mutex
);
1832 return worker
? 0 : -ENOMEM
;
1836 * destroy_worker - destroy a workqueue worker
1837 * @worker: worker to be destroyed
1839 * Destroy @worker and adjust @pool stats accordingly.
1842 * spin_lock_irq(pool->lock) which is released and regrabbed.
1844 static void destroy_worker(struct worker
*worker
)
1846 struct worker_pool
*pool
= worker
->pool
;
1848 lockdep_assert_held(&pool
->manager_mutex
);
1849 lockdep_assert_held(&pool
->lock
);
1851 /* sanity check frenzy */
1852 if (WARN_ON(worker
->current_work
) ||
1853 WARN_ON(!list_empty(&worker
->scheduled
)))
1856 if (worker
->flags
& WORKER_STARTED
)
1858 if (worker
->flags
& WORKER_IDLE
)
1862 * Once WORKER_DIE is set, the kworker may destroy itself at any
1863 * point. Pin to ensure the task stays until we're done with it.
1865 get_task_struct(worker
->task
);
1867 list_del_init(&worker
->entry
);
1868 worker
->flags
|= WORKER_DIE
;
1870 idr_remove(&pool
->worker_idr
, worker
->id
);
1872 spin_unlock_irq(&pool
->lock
);
1874 kthread_stop(worker
->task
);
1875 put_task_struct(worker
->task
);
1878 spin_lock_irq(&pool
->lock
);
1881 static void idle_worker_timeout(unsigned long __pool
)
1883 struct worker_pool
*pool
= (void *)__pool
;
1885 spin_lock_irq(&pool
->lock
);
1887 if (too_many_workers(pool
)) {
1888 struct worker
*worker
;
1889 unsigned long expires
;
1891 /* idle_list is kept in LIFO order, check the last one */
1892 worker
= list_entry(pool
->idle_list
.prev
, struct worker
, entry
);
1893 expires
= worker
->last_active
+ IDLE_WORKER_TIMEOUT
;
1895 if (time_before(jiffies
, expires
))
1896 mod_timer(&pool
->idle_timer
, expires
);
1898 /* it's been idle for too long, wake up manager */
1899 pool
->flags
|= POOL_MANAGE_WORKERS
;
1900 wake_up_worker(pool
);
1904 spin_unlock_irq(&pool
->lock
);
1907 static void send_mayday(struct work_struct
*work
)
1909 struct pool_workqueue
*pwq
= get_work_pwq(work
);
1910 struct workqueue_struct
*wq
= pwq
->wq
;
1912 lockdep_assert_held(&wq_mayday_lock
);
1917 /* mayday mayday mayday */
1918 if (list_empty(&pwq
->mayday_node
)) {
1920 * If @pwq is for an unbound wq, its base ref may be put at
1921 * any time due to an attribute change. Pin @pwq until the
1922 * rescuer is done with it.
1925 list_add_tail(&pwq
->mayday_node
, &wq
->maydays
);
1926 wake_up_process(wq
->rescuer
->task
);
1930 static void pool_mayday_timeout(unsigned long __pool
)
1932 struct worker_pool
*pool
= (void *)__pool
;
1933 struct work_struct
*work
;
1935 spin_lock_irq(&wq_mayday_lock
); /* for wq->maydays */
1936 spin_lock(&pool
->lock
);
1938 if (need_to_create_worker(pool
)) {
1940 * We've been trying to create a new worker but
1941 * haven't been successful. We might be hitting an
1942 * allocation deadlock. Send distress signals to
1945 list_for_each_entry(work
, &pool
->worklist
, entry
)
1949 spin_unlock(&pool
->lock
);
1950 spin_unlock_irq(&wq_mayday_lock
);
1952 mod_timer(&pool
->mayday_timer
, jiffies
+ MAYDAY_INTERVAL
);
1956 * maybe_create_worker - create a new worker if necessary
1957 * @pool: pool to create a new worker for
1959 * Create a new worker for @pool if necessary. @pool is guaranteed to
1960 * have at least one idle worker on return from this function. If
1961 * creating a new worker takes longer than MAYDAY_INTERVAL, mayday is
1962 * sent to all rescuers with works scheduled on @pool to resolve
1963 * possible allocation deadlock.
1965 * On return, need_to_create_worker() is guaranteed to be %false and
1966 * may_start_working() %true.
1969 * spin_lock_irq(pool->lock) which may be released and regrabbed
1970 * multiple times. Does GFP_KERNEL allocations. Called only from
1974 * %false if no action was taken and pool->lock stayed locked, %true
1977 static bool maybe_create_worker(struct worker_pool
*pool
)
1978 __releases(&pool
->lock
)
1979 __acquires(&pool
->lock
)
1981 if (!need_to_create_worker(pool
))
1984 spin_unlock_irq(&pool
->lock
);
1986 /* if we don't make progress in MAYDAY_INITIAL_TIMEOUT, call for help */
1987 mod_timer(&pool
->mayday_timer
, jiffies
+ MAYDAY_INITIAL_TIMEOUT
);
1990 struct worker
*worker
;
1992 worker
= create_worker(pool
);
1994 del_timer_sync(&pool
->mayday_timer
);
1995 spin_lock_irq(&pool
->lock
);
1996 start_worker(worker
);
1997 if (WARN_ON_ONCE(need_to_create_worker(pool
)))
2002 if (!need_to_create_worker(pool
))
2005 __set_current_state(TASK_INTERRUPTIBLE
);
2006 schedule_timeout(CREATE_COOLDOWN
);
2008 if (!need_to_create_worker(pool
))
2012 del_timer_sync(&pool
->mayday_timer
);
2013 spin_lock_irq(&pool
->lock
);
2014 if (need_to_create_worker(pool
))
2020 * maybe_destroy_worker - destroy workers which have been idle for a while
2021 * @pool: pool to destroy workers for
2023 * Destroy @pool workers which have been idle for longer than
2024 * IDLE_WORKER_TIMEOUT.
2027 * spin_lock_irq(pool->lock) which may be released and regrabbed
2028 * multiple times. Called only from manager.
2031 * %false if no action was taken and pool->lock stayed locked, %true
2034 static bool maybe_destroy_workers(struct worker_pool
*pool
)
2038 while (too_many_workers(pool
)) {
2039 struct worker
*worker
;
2040 unsigned long expires
;
2042 worker
= list_entry(pool
->idle_list
.prev
, struct worker
, entry
);
2043 expires
= worker
->last_active
+ IDLE_WORKER_TIMEOUT
;
2045 if (time_before(jiffies
, expires
)) {
2046 mod_timer(&pool
->idle_timer
, expires
);
2050 destroy_worker(worker
);
2058 * manage_workers - manage worker pool
2061 * Assume the manager role and manage the worker pool @worker belongs
2062 * to. At any given time, there can be only zero or one manager per
2063 * pool. The exclusion is handled automatically by this function.
2065 * The caller can safely start processing works on false return. On
2066 * true return, it's guaranteed that need_to_create_worker() is false
2067 * and may_start_working() is true.
2070 * spin_lock_irq(pool->lock) which may be released and regrabbed
2071 * multiple times. Does GFP_KERNEL allocations.
2074 * %false if the pool don't need management and the caller can safely start
2075 * processing works, %true indicates that the function released pool->lock
2076 * and reacquired it to perform some management function and that the
2077 * conditions that the caller verified while holding the lock before
2078 * calling the function might no longer be true.
2080 static bool manage_workers(struct worker
*worker
)
2082 struct worker_pool
*pool
= worker
->pool
;
2086 * Managership is governed by two mutexes - manager_arb and
2087 * manager_mutex. manager_arb handles arbitration of manager role.
2088 * Anyone who successfully grabs manager_arb wins the arbitration
2089 * and becomes the manager. mutex_trylock() on pool->manager_arb
2090 * failure while holding pool->lock reliably indicates that someone
2091 * else is managing the pool and the worker which failed trylock
2092 * can proceed to executing work items. This means that anyone
2093 * grabbing manager_arb is responsible for actually performing
2094 * manager duties. If manager_arb is grabbed and released without
2095 * actual management, the pool may stall indefinitely.
2097 * manager_mutex is used for exclusion of actual management
2098 * operations. The holder of manager_mutex can be sure that none
2099 * of management operations, including creation and destruction of
2100 * workers, won't take place until the mutex is released. Because
2101 * manager_mutex doesn't interfere with manager role arbitration,
2102 * it is guaranteed that the pool's management, while may be
2103 * delayed, won't be disturbed by someone else grabbing
2106 if (!mutex_trylock(&pool
->manager_arb
))
2110 * With manager arbitration won, manager_mutex would be free in
2111 * most cases. trylock first without dropping @pool->lock.
2113 if (unlikely(!mutex_trylock(&pool
->manager_mutex
))) {
2114 spin_unlock_irq(&pool
->lock
);
2115 mutex_lock(&pool
->manager_mutex
);
2116 spin_lock_irq(&pool
->lock
);
2120 pool
->flags
&= ~POOL_MANAGE_WORKERS
;
2123 * Destroy and then create so that may_start_working() is true
2126 ret
|= maybe_destroy_workers(pool
);
2127 ret
|= maybe_create_worker(pool
);
2129 mutex_unlock(&pool
->manager_mutex
);
2130 mutex_unlock(&pool
->manager_arb
);
2135 * process_one_work - process single work
2137 * @work: work to process
2139 * Process @work. This function contains all the logics necessary to
2140 * process a single work including synchronization against and
2141 * interaction with other workers on the same cpu, queueing and
2142 * flushing. As long as context requirement is met, any worker can
2143 * call this function to process a work.
2146 * spin_lock_irq(pool->lock) which is released and regrabbed.
2148 static void process_one_work(struct worker
*worker
, struct work_struct
*work
)
2149 __releases(&pool
->lock
)
2150 __acquires(&pool
->lock
)
2152 struct pool_workqueue
*pwq
= get_work_pwq(work
);
2153 struct worker_pool
*pool
= worker
->pool
;
2154 bool cpu_intensive
= pwq
->wq
->flags
& WQ_CPU_INTENSIVE
;
2156 struct worker
*collision
;
2157 #ifdef CONFIG_LOCKDEP
2159 * It is permissible to free the struct work_struct from
2160 * inside the function that is called from it, this we need to
2161 * take into account for lockdep too. To avoid bogus "held
2162 * lock freed" warnings as well as problems when looking into
2163 * work->lockdep_map, make a copy and use that here.
2165 struct lockdep_map lockdep_map
;
2167 lockdep_copy_map(&lockdep_map
, &work
->lockdep_map
);
2170 * Ensure we're on the correct CPU. DISASSOCIATED test is
2171 * necessary to avoid spurious warnings from rescuers servicing the
2172 * unbound or a disassociated pool.
2174 WARN_ON_ONCE(!(worker
->flags
& WORKER_UNBOUND
) &&
2175 !(pool
->flags
& POOL_DISASSOCIATED
) &&
2176 raw_smp_processor_id() != pool
->cpu
);
2179 * A single work shouldn't be executed concurrently by
2180 * multiple workers on a single cpu. Check whether anyone is
2181 * already processing the work. If so, defer the work to the
2182 * currently executing one.
2184 collision
= find_worker_executing_work(pool
, work
);
2185 if (unlikely(collision
)) {
2186 move_linked_works(work
, &collision
->scheduled
, NULL
);
2190 /* claim and dequeue */
2191 debug_work_deactivate(work
);
2192 hash_add(pool
->busy_hash
, &worker
->hentry
, (unsigned long)work
);
2193 worker
->current_work
= work
;
2194 worker
->current_func
= work
->func
;
2195 worker
->current_pwq
= pwq
;
2196 work_color
= get_work_color(work
);
2198 list_del_init(&work
->entry
);
2201 * CPU intensive works don't participate in concurrency
2202 * management. They're the scheduler's responsibility.
2204 if (unlikely(cpu_intensive
))
2205 worker_set_flags(worker
, WORKER_CPU_INTENSIVE
, true);
2208 * Unbound pool isn't concurrency managed and work items should be
2209 * executed ASAP. Wake up another worker if necessary.
2211 if ((worker
->flags
& WORKER_UNBOUND
) && need_more_worker(pool
))
2212 wake_up_worker(pool
);
2215 * Record the last pool and clear PENDING which should be the last
2216 * update to @work. Also, do this inside @pool->lock so that
2217 * PENDING and queued state changes happen together while IRQ is
2220 set_work_pool_and_clear_pending(work
, pool
->id
);
2222 spin_unlock_irq(&pool
->lock
);
2224 lock_map_acquire_read(&pwq
->wq
->lockdep_map
);
2225 lock_map_acquire(&lockdep_map
);
2226 trace_workqueue_execute_start(work
);
2227 worker
->current_func(work
);
2229 * While we must be careful to not use "work" after this, the trace
2230 * point will only record its address.
2232 trace_workqueue_execute_end(work
);
2233 lock_map_release(&lockdep_map
);
2234 lock_map_release(&pwq
->wq
->lockdep_map
);
2236 if (unlikely(in_atomic() || lockdep_depth(current
) > 0)) {
2237 pr_err("BUG: workqueue leaked lock or atomic: %s/0x%08x/%d\n"
2238 " last function: %pf\n",
2239 current
->comm
, preempt_count(), task_pid_nr(current
),
2240 worker
->current_func
);
2241 debug_show_held_locks(current
);
2246 * The following prevents a kworker from hogging CPU on !PREEMPT
2247 * kernels, where a requeueing work item waiting for something to
2248 * happen could deadlock with stop_machine as such work item could
2249 * indefinitely requeue itself while all other CPUs are trapped in
2254 spin_lock_irq(&pool
->lock
);
2256 /* clear cpu intensive status */
2257 if (unlikely(cpu_intensive
))
2258 worker_clr_flags(worker
, WORKER_CPU_INTENSIVE
);
2260 /* we're done with it, release */
2261 hash_del(&worker
->hentry
);
2262 worker
->current_work
= NULL
;
2263 worker
->current_func
= NULL
;
2264 worker
->current_pwq
= NULL
;
2265 worker
->desc_valid
= false;
2266 pwq_dec_nr_in_flight(pwq
, work_color
);
2270 * process_scheduled_works - process scheduled works
2273 * Process all scheduled works. Please note that the scheduled list
2274 * may change while processing a work, so this function repeatedly
2275 * fetches a work from the top and executes it.
2278 * spin_lock_irq(pool->lock) which may be released and regrabbed
2281 static void process_scheduled_works(struct worker
*worker
)
2283 while (!list_empty(&worker
->scheduled
)) {
2284 struct work_struct
*work
= list_first_entry(&worker
->scheduled
,
2285 struct work_struct
, entry
);
2286 process_one_work(worker
, work
);
2291 * worker_thread - the worker thread function
2294 * The worker thread function. All workers belong to a worker_pool -
2295 * either a per-cpu one or dynamic unbound one. These workers process all
2296 * work items regardless of their specific target workqueue. The only
2297 * exception is work items which belong to workqueues with a rescuer which
2298 * will be explained in rescuer_thread().
2302 static int worker_thread(void *__worker
)
2304 struct worker
*worker
= __worker
;
2305 struct worker_pool
*pool
= worker
->pool
;
2307 /* tell the scheduler that this is a workqueue worker */
2308 worker
->task
->flags
|= PF_WQ_WORKER
;
2310 spin_lock_irq(&pool
->lock
);
2312 /* am I supposed to die? */
2313 if (unlikely(worker
->flags
& WORKER_DIE
)) {
2314 spin_unlock_irq(&pool
->lock
);
2315 WARN_ON_ONCE(!list_empty(&worker
->entry
));
2316 worker
->task
->flags
&= ~PF_WQ_WORKER
;
2320 worker_leave_idle(worker
);
2322 /* no more worker necessary? */
2323 if (!need_more_worker(pool
))
2326 /* do we need to manage? */
2327 if (unlikely(!may_start_working(pool
)) && manage_workers(worker
))
2331 * ->scheduled list can only be filled while a worker is
2332 * preparing to process a work or actually processing it.
2333 * Make sure nobody diddled with it while I was sleeping.
2335 WARN_ON_ONCE(!list_empty(&worker
->scheduled
));
2338 * Finish PREP stage. We're guaranteed to have at least one idle
2339 * worker or that someone else has already assumed the manager
2340 * role. This is where @worker starts participating in concurrency
2341 * management if applicable and concurrency management is restored
2342 * after being rebound. See rebind_workers() for details.
2344 worker_clr_flags(worker
, WORKER_PREP
| WORKER_REBOUND
);
2347 struct work_struct
*work
=
2348 list_first_entry(&pool
->worklist
,
2349 struct work_struct
, entry
);
2351 if (likely(!(*work_data_bits(work
) & WORK_STRUCT_LINKED
))) {
2352 /* optimization path, not strictly necessary */
2353 process_one_work(worker
, work
);
2354 if (unlikely(!list_empty(&worker
->scheduled
)))
2355 process_scheduled_works(worker
);
2357 move_linked_works(work
, &worker
->scheduled
, NULL
);
2358 process_scheduled_works(worker
);
2360 } while (keep_working(pool
));
2362 worker_set_flags(worker
, WORKER_PREP
, false);
2364 if (unlikely(need_to_manage_workers(pool
)) && manage_workers(worker
))
2368 * pool->lock is held and there's no work to process and no need to
2369 * manage, sleep. Workers are woken up only while holding
2370 * pool->lock or from local cpu, so setting the current state
2371 * before releasing pool->lock is enough to prevent losing any
2374 worker_enter_idle(worker
);
2375 __set_current_state(TASK_INTERRUPTIBLE
);
2376 spin_unlock_irq(&pool
->lock
);
2382 * rescuer_thread - the rescuer thread function
2385 * Workqueue rescuer thread function. There's one rescuer for each
2386 * workqueue which has WQ_MEM_RECLAIM set.
2388 * Regular work processing on a pool may block trying to create a new
2389 * worker which uses GFP_KERNEL allocation which has slight chance of
2390 * developing into deadlock if some works currently on the same queue
2391 * need to be processed to satisfy the GFP_KERNEL allocation. This is
2392 * the problem rescuer solves.
2394 * When such condition is possible, the pool summons rescuers of all
2395 * workqueues which have works queued on the pool and let them process
2396 * those works so that forward progress can be guaranteed.
2398 * This should happen rarely.
2402 static int rescuer_thread(void *__rescuer
)
2404 struct worker
*rescuer
= __rescuer
;
2405 struct workqueue_struct
*wq
= rescuer
->rescue_wq
;
2406 struct list_head
*scheduled
= &rescuer
->scheduled
;
2409 set_user_nice(current
, RESCUER_NICE_LEVEL
);
2412 * Mark rescuer as worker too. As WORKER_PREP is never cleared, it
2413 * doesn't participate in concurrency management.
2415 rescuer
->task
->flags
|= PF_WQ_WORKER
;
2417 set_current_state(TASK_INTERRUPTIBLE
);
2420 * By the time the rescuer is requested to stop, the workqueue
2421 * shouldn't have any work pending, but @wq->maydays may still have
2422 * pwq(s) queued. This can happen by non-rescuer workers consuming
2423 * all the work items before the rescuer got to them. Go through
2424 * @wq->maydays processing before acting on should_stop so that the
2425 * list is always empty on exit.
2427 should_stop
= kthread_should_stop();
2429 /* see whether any pwq is asking for help */
2430 spin_lock_irq(&wq_mayday_lock
);
2432 while (!list_empty(&wq
->maydays
)) {
2433 struct pool_workqueue
*pwq
= list_first_entry(&wq
->maydays
,
2434 struct pool_workqueue
, mayday_node
);
2435 struct worker_pool
*pool
= pwq
->pool
;
2436 struct work_struct
*work
, *n
;
2438 __set_current_state(TASK_RUNNING
);
2439 list_del_init(&pwq
->mayday_node
);
2441 spin_unlock_irq(&wq_mayday_lock
);
2443 /* migrate to the target cpu if possible */
2444 worker_maybe_bind_and_lock(pool
);
2445 rescuer
->pool
= pool
;
2448 * Slurp in all works issued via this workqueue and
2451 WARN_ON_ONCE(!list_empty(&rescuer
->scheduled
));
2452 list_for_each_entry_safe(work
, n
, &pool
->worklist
, entry
)
2453 if (get_work_pwq(work
) == pwq
)
2454 move_linked_works(work
, scheduled
, &n
);
2456 process_scheduled_works(rescuer
);
2459 * Put the reference grabbed by send_mayday(). @pool won't
2460 * go away while we're holding its lock.
2465 * Leave this pool. If keep_working() is %true, notify a
2466 * regular worker; otherwise, we end up with 0 concurrency
2467 * and stalling the execution.
2469 if (keep_working(pool
))
2470 wake_up_worker(pool
);
2472 rescuer
->pool
= NULL
;
2473 spin_unlock(&pool
->lock
);
2474 spin_lock(&wq_mayday_lock
);
2477 spin_unlock_irq(&wq_mayday_lock
);
2480 __set_current_state(TASK_RUNNING
);
2481 rescuer
->task
->flags
&= ~PF_WQ_WORKER
;
2485 /* rescuers should never participate in concurrency management */
2486 WARN_ON_ONCE(!(rescuer
->flags
& WORKER_NOT_RUNNING
));
2492 struct work_struct work
;
2493 struct completion done
;
2496 static void wq_barrier_func(struct work_struct
*work
)
2498 struct wq_barrier
*barr
= container_of(work
, struct wq_barrier
, work
);
2499 complete(&barr
->done
);
2503 * insert_wq_barrier - insert a barrier work
2504 * @pwq: pwq to insert barrier into
2505 * @barr: wq_barrier to insert
2506 * @target: target work to attach @barr to
2507 * @worker: worker currently executing @target, NULL if @target is not executing
2509 * @barr is linked to @target such that @barr is completed only after
2510 * @target finishes execution. Please note that the ordering
2511 * guarantee is observed only with respect to @target and on the local
2514 * Currently, a queued barrier can't be canceled. This is because
2515 * try_to_grab_pending() can't determine whether the work to be
2516 * grabbed is at the head of the queue and thus can't clear LINKED
2517 * flag of the previous work while there must be a valid next work
2518 * after a work with LINKED flag set.
2520 * Note that when @worker is non-NULL, @target may be modified
2521 * underneath us, so we can't reliably determine pwq from @target.
2524 * spin_lock_irq(pool->lock).
2526 static void insert_wq_barrier(struct pool_workqueue
*pwq
,
2527 struct wq_barrier
*barr
,
2528 struct work_struct
*target
, struct worker
*worker
)
2530 struct list_head
*head
;
2531 unsigned int linked
= 0;
2534 * debugobject calls are safe here even with pool->lock locked
2535 * as we know for sure that this will not trigger any of the
2536 * checks and call back into the fixup functions where we
2539 INIT_WORK_ONSTACK(&barr
->work
, wq_barrier_func
);
2540 __set_bit(WORK_STRUCT_PENDING_BIT
, work_data_bits(&barr
->work
));
2541 init_completion(&barr
->done
);
2544 * If @target is currently being executed, schedule the
2545 * barrier to the worker; otherwise, put it after @target.
2548 head
= worker
->scheduled
.next
;
2550 unsigned long *bits
= work_data_bits(target
);
2552 head
= target
->entry
.next
;
2553 /* there can already be other linked works, inherit and set */
2554 linked
= *bits
& WORK_STRUCT_LINKED
;
2555 __set_bit(WORK_STRUCT_LINKED_BIT
, bits
);
2558 debug_work_activate(&barr
->work
);
2559 insert_work(pwq
, &barr
->work
, head
,
2560 work_color_to_flags(WORK_NO_COLOR
) | linked
);
2564 * flush_workqueue_prep_pwqs - prepare pwqs for workqueue flushing
2565 * @wq: workqueue being flushed
2566 * @flush_color: new flush color, < 0 for no-op
2567 * @work_color: new work color, < 0 for no-op
2569 * Prepare pwqs for workqueue flushing.
2571 * If @flush_color is non-negative, flush_color on all pwqs should be
2572 * -1. If no pwq has in-flight commands at the specified color, all
2573 * pwq->flush_color's stay at -1 and %false is returned. If any pwq
2574 * has in flight commands, its pwq->flush_color is set to
2575 * @flush_color, @wq->nr_pwqs_to_flush is updated accordingly, pwq
2576 * wakeup logic is armed and %true is returned.
2578 * The caller should have initialized @wq->first_flusher prior to
2579 * calling this function with non-negative @flush_color. If
2580 * @flush_color is negative, no flush color update is done and %false
2583 * If @work_color is non-negative, all pwqs should have the same
2584 * work_color which is previous to @work_color and all will be
2585 * advanced to @work_color.
2588 * mutex_lock(wq->mutex).
2591 * %true if @flush_color >= 0 and there's something to flush. %false
2594 static bool flush_workqueue_prep_pwqs(struct workqueue_struct
*wq
,
2595 int flush_color
, int work_color
)
2598 struct pool_workqueue
*pwq
;
2600 if (flush_color
>= 0) {
2601 WARN_ON_ONCE(atomic_read(&wq
->nr_pwqs_to_flush
));
2602 atomic_set(&wq
->nr_pwqs_to_flush
, 1);
2605 for_each_pwq(pwq
, wq
) {
2606 struct worker_pool
*pool
= pwq
->pool
;
2608 spin_lock_irq(&pool
->lock
);
2610 if (flush_color
>= 0) {
2611 WARN_ON_ONCE(pwq
->flush_color
!= -1);
2613 if (pwq
->nr_in_flight
[flush_color
]) {
2614 pwq
->flush_color
= flush_color
;
2615 atomic_inc(&wq
->nr_pwqs_to_flush
);
2620 if (work_color
>= 0) {
2621 WARN_ON_ONCE(work_color
!= work_next_color(pwq
->work_color
));
2622 pwq
->work_color
= work_color
;
2625 spin_unlock_irq(&pool
->lock
);
2628 if (flush_color
>= 0 && atomic_dec_and_test(&wq
->nr_pwqs_to_flush
))
2629 complete(&wq
->first_flusher
->done
);
2635 * flush_workqueue - ensure that any scheduled work has run to completion.
2636 * @wq: workqueue to flush
2638 * This function sleeps until all work items which were queued on entry
2639 * have finished execution, but it is not livelocked by new incoming ones.
2641 void flush_workqueue(struct workqueue_struct
*wq
)
2643 struct wq_flusher this_flusher
= {
2644 .list
= LIST_HEAD_INIT(this_flusher
.list
),
2646 .done
= COMPLETION_INITIALIZER_ONSTACK(this_flusher
.done
),
2650 lock_map_acquire(&wq
->lockdep_map
);
2651 lock_map_release(&wq
->lockdep_map
);
2653 mutex_lock(&wq
->mutex
);
2656 * Start-to-wait phase
2658 next_color
= work_next_color(wq
->work_color
);
2660 if (next_color
!= wq
->flush_color
) {
2662 * Color space is not full. The current work_color
2663 * becomes our flush_color and work_color is advanced
2666 WARN_ON_ONCE(!list_empty(&wq
->flusher_overflow
));
2667 this_flusher
.flush_color
= wq
->work_color
;
2668 wq
->work_color
= next_color
;
2670 if (!wq
->first_flusher
) {
2671 /* no flush in progress, become the first flusher */
2672 WARN_ON_ONCE(wq
->flush_color
!= this_flusher
.flush_color
);
2674 wq
->first_flusher
= &this_flusher
;
2676 if (!flush_workqueue_prep_pwqs(wq
, wq
->flush_color
,
2678 /* nothing to flush, done */
2679 wq
->flush_color
= next_color
;
2680 wq
->first_flusher
= NULL
;
2685 WARN_ON_ONCE(wq
->flush_color
== this_flusher
.flush_color
);
2686 list_add_tail(&this_flusher
.list
, &wq
->flusher_queue
);
2687 flush_workqueue_prep_pwqs(wq
, -1, wq
->work_color
);
2691 * Oops, color space is full, wait on overflow queue.
2692 * The next flush completion will assign us
2693 * flush_color and transfer to flusher_queue.
2695 list_add_tail(&this_flusher
.list
, &wq
->flusher_overflow
);
2698 mutex_unlock(&wq
->mutex
);
2700 wait_for_completion(&this_flusher
.done
);
2703 * Wake-up-and-cascade phase
2705 * First flushers are responsible for cascading flushes and
2706 * handling overflow. Non-first flushers can simply return.
2708 if (wq
->first_flusher
!= &this_flusher
)
2711 mutex_lock(&wq
->mutex
);
2713 /* we might have raced, check again with mutex held */
2714 if (wq
->first_flusher
!= &this_flusher
)
2717 wq
->first_flusher
= NULL
;
2719 WARN_ON_ONCE(!list_empty(&this_flusher
.list
));
2720 WARN_ON_ONCE(wq
->flush_color
!= this_flusher
.flush_color
);
2723 struct wq_flusher
*next
, *tmp
;
2725 /* complete all the flushers sharing the current flush color */
2726 list_for_each_entry_safe(next
, tmp
, &wq
->flusher_queue
, list
) {
2727 if (next
->flush_color
!= wq
->flush_color
)
2729 list_del_init(&next
->list
);
2730 complete(&next
->done
);
2733 WARN_ON_ONCE(!list_empty(&wq
->flusher_overflow
) &&
2734 wq
->flush_color
!= work_next_color(wq
->work_color
));
2736 /* this flush_color is finished, advance by one */
2737 wq
->flush_color
= work_next_color(wq
->flush_color
);
2739 /* one color has been freed, handle overflow queue */
2740 if (!list_empty(&wq
->flusher_overflow
)) {
2742 * Assign the same color to all overflowed
2743 * flushers, advance work_color and append to
2744 * flusher_queue. This is the start-to-wait
2745 * phase for these overflowed flushers.
2747 list_for_each_entry(tmp
, &wq
->flusher_overflow
, list
)
2748 tmp
->flush_color
= wq
->work_color
;
2750 wq
->work_color
= work_next_color(wq
->work_color
);
2752 list_splice_tail_init(&wq
->flusher_overflow
,
2753 &wq
->flusher_queue
);
2754 flush_workqueue_prep_pwqs(wq
, -1, wq
->work_color
);
2757 if (list_empty(&wq
->flusher_queue
)) {
2758 WARN_ON_ONCE(wq
->flush_color
!= wq
->work_color
);
2763 * Need to flush more colors. Make the next flusher
2764 * the new first flusher and arm pwqs.
2766 WARN_ON_ONCE(wq
->flush_color
== wq
->work_color
);
2767 WARN_ON_ONCE(wq
->flush_color
!= next
->flush_color
);
2769 list_del_init(&next
->list
);
2770 wq
->first_flusher
= next
;
2772 if (flush_workqueue_prep_pwqs(wq
, wq
->flush_color
, -1))
2776 * Meh... this color is already done, clear first
2777 * flusher and repeat cascading.
2779 wq
->first_flusher
= NULL
;
2783 mutex_unlock(&wq
->mutex
);
2785 EXPORT_SYMBOL_GPL(flush_workqueue
);
2788 * drain_workqueue - drain a workqueue
2789 * @wq: workqueue to drain
2791 * Wait until the workqueue becomes empty. While draining is in progress,
2792 * only chain queueing is allowed. IOW, only currently pending or running
2793 * work items on @wq can queue further work items on it. @wq is flushed
2794 * repeatedly until it becomes empty. The number of flushing is detemined
2795 * by the depth of chaining and should be relatively short. Whine if it
2798 void drain_workqueue(struct workqueue_struct
*wq
)
2800 unsigned int flush_cnt
= 0;
2801 struct pool_workqueue
*pwq
;
2804 * __queue_work() needs to test whether there are drainers, is much
2805 * hotter than drain_workqueue() and already looks at @wq->flags.
2806 * Use __WQ_DRAINING so that queue doesn't have to check nr_drainers.
2808 mutex_lock(&wq
->mutex
);
2809 if (!wq
->nr_drainers
++)
2810 wq
->flags
|= __WQ_DRAINING
;
2811 mutex_unlock(&wq
->mutex
);
2813 flush_workqueue(wq
);
2815 mutex_lock(&wq
->mutex
);
2817 for_each_pwq(pwq
, wq
) {
2820 spin_lock_irq(&pwq
->pool
->lock
);
2821 drained
= !pwq
->nr_active
&& list_empty(&pwq
->delayed_works
);
2822 spin_unlock_irq(&pwq
->pool
->lock
);
2827 if (++flush_cnt
== 10 ||
2828 (flush_cnt
% 100 == 0 && flush_cnt
<= 1000))
2829 pr_warn("workqueue %s: drain_workqueue() isn't complete after %u tries\n",
2830 wq
->name
, flush_cnt
);
2832 mutex_unlock(&wq
->mutex
);
2836 if (!--wq
->nr_drainers
)
2837 wq
->flags
&= ~__WQ_DRAINING
;
2838 mutex_unlock(&wq
->mutex
);
2840 EXPORT_SYMBOL_GPL(drain_workqueue
);
2842 static bool start_flush_work(struct work_struct
*work
, struct wq_barrier
*barr
)
2844 struct worker
*worker
= NULL
;
2845 struct worker_pool
*pool
;
2846 struct pool_workqueue
*pwq
;
2850 local_irq_disable();
2851 pool
= get_work_pool(work
);
2857 spin_lock(&pool
->lock
);
2858 /* see the comment in try_to_grab_pending() with the same code */
2859 pwq
= get_work_pwq(work
);
2861 if (unlikely(pwq
->pool
!= pool
))
2864 worker
= find_worker_executing_work(pool
, work
);
2867 pwq
= worker
->current_pwq
;
2870 insert_wq_barrier(pwq
, barr
, work
, worker
);
2871 spin_unlock_irq(&pool
->lock
);
2874 * If @max_active is 1 or rescuer is in use, flushing another work
2875 * item on the same workqueue may lead to deadlock. Make sure the
2876 * flusher is not running on the same workqueue by verifying write
2879 if (pwq
->wq
->saved_max_active
== 1 || pwq
->wq
->rescuer
)
2880 lock_map_acquire(&pwq
->wq
->lockdep_map
);
2882 lock_map_acquire_read(&pwq
->wq
->lockdep_map
);
2883 lock_map_release(&pwq
->wq
->lockdep_map
);
2887 spin_unlock_irq(&pool
->lock
);
2892 * flush_work - wait for a work to finish executing the last queueing instance
2893 * @work: the work to flush
2895 * Wait until @work has finished execution. @work is guaranteed to be idle
2896 * on return if it hasn't been requeued since flush started.
2899 * %true if flush_work() waited for the work to finish execution,
2900 * %false if it was already idle.
2902 bool flush_work(struct work_struct
*work
)
2904 struct wq_barrier barr
;
2906 lock_map_acquire(&work
->lockdep_map
);
2907 lock_map_release(&work
->lockdep_map
);
2909 if (start_flush_work(work
, &barr
)) {
2910 wait_for_completion(&barr
.done
);
2911 destroy_work_on_stack(&barr
.work
);
2917 EXPORT_SYMBOL_GPL(flush_work
);
2919 static bool __cancel_work_timer(struct work_struct
*work
, bool is_dwork
)
2921 unsigned long flags
;
2925 ret
= try_to_grab_pending(work
, is_dwork
, &flags
);
2927 * If someone else is canceling, wait for the same event it
2928 * would be waiting for before retrying.
2930 if (unlikely(ret
== -ENOENT
))
2932 } while (unlikely(ret
< 0));
2934 /* tell other tasks trying to grab @work to back off */
2935 mark_work_canceling(work
);
2936 local_irq_restore(flags
);
2939 clear_work_data(work
);
2944 * cancel_work_sync - cancel a work and wait for it to finish
2945 * @work: the work to cancel
2947 * Cancel @work and wait for its execution to finish. This function
2948 * can be used even if the work re-queues itself or migrates to
2949 * another workqueue. On return from this function, @work is
2950 * guaranteed to be not pending or executing on any CPU.
2952 * cancel_work_sync(&delayed_work->work) must not be used for
2953 * delayed_work's. Use cancel_delayed_work_sync() instead.
2955 * The caller must ensure that the workqueue on which @work was last
2956 * queued can't be destroyed before this function returns.
2959 * %true if @work was pending, %false otherwise.
2961 bool cancel_work_sync(struct work_struct
*work
)
2963 return __cancel_work_timer(work
, false);
2965 EXPORT_SYMBOL_GPL(cancel_work_sync
);
2968 * flush_delayed_work - wait for a dwork to finish executing the last queueing
2969 * @dwork: the delayed work to flush
2971 * Delayed timer is cancelled and the pending work is queued for
2972 * immediate execution. Like flush_work(), this function only
2973 * considers the last queueing instance of @dwork.
2976 * %true if flush_work() waited for the work to finish execution,
2977 * %false if it was already idle.
2979 bool flush_delayed_work(struct delayed_work
*dwork
)
2981 local_irq_disable();
2982 if (del_timer_sync(&dwork
->timer
))
2983 __queue_work(dwork
->cpu
, dwork
->wq
, &dwork
->work
);
2985 return flush_work(&dwork
->work
);
2987 EXPORT_SYMBOL(flush_delayed_work
);
2990 * cancel_delayed_work - cancel a delayed work
2991 * @dwork: delayed_work to cancel
2993 * Kill off a pending delayed_work.
2995 * Return: %true if @dwork was pending and canceled; %false if it wasn't
2999 * The work callback function may still be running on return, unless
3000 * it returns %true and the work doesn't re-arm itself. Explicitly flush or
3001 * use cancel_delayed_work_sync() to wait on it.
3003 * This function is safe to call from any context including IRQ handler.
3005 bool cancel_delayed_work(struct delayed_work
*dwork
)
3007 unsigned long flags
;
3011 ret
= try_to_grab_pending(&dwork
->work
, true, &flags
);
3012 } while (unlikely(ret
== -EAGAIN
));
3014 if (unlikely(ret
< 0))
3017 set_work_pool_and_clear_pending(&dwork
->work
,
3018 get_work_pool_id(&dwork
->work
));
3019 local_irq_restore(flags
);
3022 EXPORT_SYMBOL(cancel_delayed_work
);
3025 * cancel_delayed_work_sync - cancel a delayed work and wait for it to finish
3026 * @dwork: the delayed work cancel
3028 * This is cancel_work_sync() for delayed works.
3031 * %true if @dwork was pending, %false otherwise.
3033 bool cancel_delayed_work_sync(struct delayed_work
*dwork
)
3035 return __cancel_work_timer(&dwork
->work
, true);
3037 EXPORT_SYMBOL(cancel_delayed_work_sync
);
3040 * schedule_on_each_cpu - execute a function synchronously on each online CPU
3041 * @func: the function to call
3043 * schedule_on_each_cpu() executes @func on each online CPU using the
3044 * system workqueue and blocks until all CPUs have completed.
3045 * schedule_on_each_cpu() is very slow.
3048 * 0 on success, -errno on failure.
3050 int schedule_on_each_cpu(work_func_t func
)
3053 struct work_struct __percpu
*works
;
3055 works
= alloc_percpu(struct work_struct
);
3061 for_each_online_cpu(cpu
) {
3062 struct work_struct
*work
= per_cpu_ptr(works
, cpu
);
3064 INIT_WORK(work
, func
);
3065 schedule_work_on(cpu
, work
);
3068 for_each_online_cpu(cpu
)
3069 flush_work(per_cpu_ptr(works
, cpu
));
3077 * flush_scheduled_work - ensure that any scheduled work has run to completion.
3079 * Forces execution of the kernel-global workqueue and blocks until its
3082 * Think twice before calling this function! It's very easy to get into
3083 * trouble if you don't take great care. Either of the following situations
3084 * will lead to deadlock:
3086 * One of the work items currently on the workqueue needs to acquire
3087 * a lock held by your code or its caller.
3089 * Your code is running in the context of a work routine.
3091 * They will be detected by lockdep when they occur, but the first might not
3092 * occur very often. It depends on what work items are on the workqueue and
3093 * what locks they need, which you have no control over.
3095 * In most situations flushing the entire workqueue is overkill; you merely
3096 * need to know that a particular work item isn't queued and isn't running.
3097 * In such cases you should use cancel_delayed_work_sync() or
3098 * cancel_work_sync() instead.
3100 void flush_scheduled_work(void)
3102 flush_workqueue(system_wq
);
3104 EXPORT_SYMBOL(flush_scheduled_work
);
3107 * execute_in_process_context - reliably execute the routine with user context
3108 * @fn: the function to execute
3109 * @ew: guaranteed storage for the execute work structure (must
3110 * be available when the work executes)
3112 * Executes the function immediately if process context is available,
3113 * otherwise schedules the function for delayed execution.
3115 * Return: 0 - function was executed
3116 * 1 - function was scheduled for execution
3118 int execute_in_process_context(work_func_t fn
, struct execute_work
*ew
)
3120 if (!in_interrupt()) {
3125 INIT_WORK(&ew
->work
, fn
);
3126 schedule_work(&ew
->work
);
3130 EXPORT_SYMBOL_GPL(execute_in_process_context
);
3134 * Workqueues with WQ_SYSFS flag set is visible to userland via
3135 * /sys/bus/workqueue/devices/WQ_NAME. All visible workqueues have the
3136 * following attributes.
3138 * per_cpu RO bool : whether the workqueue is per-cpu or unbound
3139 * max_active RW int : maximum number of in-flight work items
3141 * Unbound workqueues have the following extra attributes.
3143 * id RO int : the associated pool ID
3144 * nice RW int : nice value of the workers
3145 * cpumask RW mask : bitmask of allowed CPUs for the workers
3148 struct workqueue_struct
*wq
;
3152 static struct workqueue_struct
*dev_to_wq(struct device
*dev
)
3154 struct wq_device
*wq_dev
= container_of(dev
, struct wq_device
, dev
);
3159 static ssize_t
per_cpu_show(struct device
*dev
, struct device_attribute
*attr
,
3162 struct workqueue_struct
*wq
= dev_to_wq(dev
);
3164 return scnprintf(buf
, PAGE_SIZE
, "%d\n", (bool)!(wq
->flags
& WQ_UNBOUND
));
3166 static DEVICE_ATTR_RO(per_cpu
);
3168 static ssize_t
max_active_show(struct device
*dev
,
3169 struct device_attribute
*attr
, char *buf
)
3171 struct workqueue_struct
*wq
= dev_to_wq(dev
);
3173 return scnprintf(buf
, PAGE_SIZE
, "%d\n", wq
->saved_max_active
);
3176 static ssize_t
max_active_store(struct device
*dev
,
3177 struct device_attribute
*attr
, const char *buf
,
3180 struct workqueue_struct
*wq
= dev_to_wq(dev
);
3183 if (sscanf(buf
, "%d", &val
) != 1 || val
<= 0)
3186 workqueue_set_max_active(wq
, val
);
3189 static DEVICE_ATTR_RW(max_active
);
3191 static struct attribute
*wq_sysfs_attrs
[] = {
3192 &dev_attr_per_cpu
.attr
,
3193 &dev_attr_max_active
.attr
,
3196 ATTRIBUTE_GROUPS(wq_sysfs
);
3198 static ssize_t
wq_pool_ids_show(struct device
*dev
,
3199 struct device_attribute
*attr
, char *buf
)
3201 struct workqueue_struct
*wq
= dev_to_wq(dev
);
3202 const char *delim
= "";
3203 int node
, written
= 0;
3205 rcu_read_lock_sched();
3206 for_each_node(node
) {
3207 written
+= scnprintf(buf
+ written
, PAGE_SIZE
- written
,
3208 "%s%d:%d", delim
, node
,
3209 unbound_pwq_by_node(wq
, node
)->pool
->id
);
3212 written
+= scnprintf(buf
+ written
, PAGE_SIZE
- written
, "\n");
3213 rcu_read_unlock_sched();
3218 static ssize_t
wq_nice_show(struct device
*dev
, struct device_attribute
*attr
,
3221 struct workqueue_struct
*wq
= dev_to_wq(dev
);
3224 mutex_lock(&wq
->mutex
);
3225 written
= scnprintf(buf
, PAGE_SIZE
, "%d\n", wq
->unbound_attrs
->nice
);
3226 mutex_unlock(&wq
->mutex
);
3231 /* prepare workqueue_attrs for sysfs store operations */
3232 static struct workqueue_attrs
*wq_sysfs_prep_attrs(struct workqueue_struct
*wq
)
3234 struct workqueue_attrs
*attrs
;
3236 attrs
= alloc_workqueue_attrs(GFP_KERNEL
);
3240 mutex_lock(&wq
->mutex
);
3241 copy_workqueue_attrs(attrs
, wq
->unbound_attrs
);
3242 mutex_unlock(&wq
->mutex
);
3246 static ssize_t
wq_nice_store(struct device
*dev
, struct device_attribute
*attr
,
3247 const char *buf
, size_t count
)
3249 struct workqueue_struct
*wq
= dev_to_wq(dev
);
3250 struct workqueue_attrs
*attrs
;
3253 attrs
= wq_sysfs_prep_attrs(wq
);
3257 if (sscanf(buf
, "%d", &attrs
->nice
) == 1 &&
3258 attrs
->nice
>= MIN_NICE
&& attrs
->nice
<= MAX_NICE
)
3259 ret
= apply_workqueue_attrs(wq
, attrs
);
3263 free_workqueue_attrs(attrs
);
3264 return ret
?: count
;
3267 static ssize_t
wq_cpumask_show(struct device
*dev
,
3268 struct device_attribute
*attr
, char *buf
)
3270 struct workqueue_struct
*wq
= dev_to_wq(dev
);
3273 mutex_lock(&wq
->mutex
);
3274 written
= cpumask_scnprintf(buf
, PAGE_SIZE
, wq
->unbound_attrs
->cpumask
);
3275 mutex_unlock(&wq
->mutex
);
3277 written
+= scnprintf(buf
+ written
, PAGE_SIZE
- written
, "\n");
3281 static ssize_t
wq_cpumask_store(struct device
*dev
,
3282 struct device_attribute
*attr
,
3283 const char *buf
, size_t count
)
3285 struct workqueue_struct
*wq
= dev_to_wq(dev
);
3286 struct workqueue_attrs
*attrs
;
3289 attrs
= wq_sysfs_prep_attrs(wq
);
3293 ret
= cpumask_parse(buf
, attrs
->cpumask
);
3295 ret
= apply_workqueue_attrs(wq
, attrs
);
3297 free_workqueue_attrs(attrs
);
3298 return ret
?: count
;
3301 static ssize_t
wq_numa_show(struct device
*dev
, struct device_attribute
*attr
,
3304 struct workqueue_struct
*wq
= dev_to_wq(dev
);
3307 mutex_lock(&wq
->mutex
);
3308 written
= scnprintf(buf
, PAGE_SIZE
, "%d\n",
3309 !wq
->unbound_attrs
->no_numa
);
3310 mutex_unlock(&wq
->mutex
);
3315 static ssize_t
wq_numa_store(struct device
*dev
, struct device_attribute
*attr
,
3316 const char *buf
, size_t count
)
3318 struct workqueue_struct
*wq
= dev_to_wq(dev
);
3319 struct workqueue_attrs
*attrs
;
3322 attrs
= wq_sysfs_prep_attrs(wq
);
3327 if (sscanf(buf
, "%d", &v
) == 1) {
3328 attrs
->no_numa
= !v
;
3329 ret
= apply_workqueue_attrs(wq
, attrs
);
3332 free_workqueue_attrs(attrs
);
3333 return ret
?: count
;
3336 static struct device_attribute wq_sysfs_unbound_attrs
[] = {
3337 __ATTR(pool_ids
, 0444, wq_pool_ids_show
, NULL
),
3338 __ATTR(nice
, 0644, wq_nice_show
, wq_nice_store
),
3339 __ATTR(cpumask
, 0644, wq_cpumask_show
, wq_cpumask_store
),
3340 __ATTR(numa
, 0644, wq_numa_show
, wq_numa_store
),
3344 static struct bus_type wq_subsys
= {
3345 .name
= "workqueue",
3346 .dev_groups
= wq_sysfs_groups
,
3349 static int __init
wq_sysfs_init(void)
3351 return subsys_virtual_register(&wq_subsys
, NULL
);
3353 core_initcall(wq_sysfs_init
);
3355 static void wq_device_release(struct device
*dev
)
3357 struct wq_device
*wq_dev
= container_of(dev
, struct wq_device
, dev
);
3363 * workqueue_sysfs_register - make a workqueue visible in sysfs
3364 * @wq: the workqueue to register
3366 * Expose @wq in sysfs under /sys/bus/workqueue/devices.
3367 * alloc_workqueue*() automatically calls this function if WQ_SYSFS is set
3368 * which is the preferred method.
3370 * Workqueue user should use this function directly iff it wants to apply
3371 * workqueue_attrs before making the workqueue visible in sysfs; otherwise,
3372 * apply_workqueue_attrs() may race against userland updating the
3375 * Return: 0 on success, -errno on failure.
3377 int workqueue_sysfs_register(struct workqueue_struct
*wq
)
3379 struct wq_device
*wq_dev
;
3383 * Adjusting max_active or creating new pwqs by applyting
3384 * attributes breaks ordering guarantee. Disallow exposing ordered
3387 if (WARN_ON(wq
->flags
& __WQ_ORDERED
))
3390 wq
->wq_dev
= wq_dev
= kzalloc(sizeof(*wq_dev
), GFP_KERNEL
);
3395 wq_dev
->dev
.bus
= &wq_subsys
;
3396 wq_dev
->dev
.init_name
= wq
->name
;
3397 wq_dev
->dev
.release
= wq_device_release
;
3400 * unbound_attrs are created separately. Suppress uevent until
3401 * everything is ready.
3403 dev_set_uevent_suppress(&wq_dev
->dev
, true);
3405 ret
= device_register(&wq_dev
->dev
);
3412 if (wq
->flags
& WQ_UNBOUND
) {
3413 struct device_attribute
*attr
;
3415 for (attr
= wq_sysfs_unbound_attrs
; attr
->attr
.name
; attr
++) {
3416 ret
= device_create_file(&wq_dev
->dev
, attr
);
3418 device_unregister(&wq_dev
->dev
);
3425 kobject_uevent(&wq_dev
->dev
.kobj
, KOBJ_ADD
);
3430 * workqueue_sysfs_unregister - undo workqueue_sysfs_register()
3431 * @wq: the workqueue to unregister
3433 * If @wq is registered to sysfs by workqueue_sysfs_register(), unregister.
3435 static void workqueue_sysfs_unregister(struct workqueue_struct
*wq
)
3437 struct wq_device
*wq_dev
= wq
->wq_dev
;
3443 device_unregister(&wq_dev
->dev
);
3445 #else /* CONFIG_SYSFS */
3446 static void workqueue_sysfs_unregister(struct workqueue_struct
*wq
) { }
3447 #endif /* CONFIG_SYSFS */
3450 * free_workqueue_attrs - free a workqueue_attrs
3451 * @attrs: workqueue_attrs to free
3453 * Undo alloc_workqueue_attrs().
3455 void free_workqueue_attrs(struct workqueue_attrs
*attrs
)
3458 free_cpumask_var(attrs
->cpumask
);
3464 * alloc_workqueue_attrs - allocate a workqueue_attrs
3465 * @gfp_mask: allocation mask to use
3467 * Allocate a new workqueue_attrs, initialize with default settings and
3470 * Return: The allocated new workqueue_attr on success. %NULL on failure.
3472 struct workqueue_attrs
*alloc_workqueue_attrs(gfp_t gfp_mask
)
3474 struct workqueue_attrs
*attrs
;
3476 attrs
= kzalloc(sizeof(*attrs
), gfp_mask
);
3479 if (!alloc_cpumask_var(&attrs
->cpumask
, gfp_mask
))
3482 cpumask_copy(attrs
->cpumask
, cpu_possible_mask
);
3485 free_workqueue_attrs(attrs
);
3489 static void copy_workqueue_attrs(struct workqueue_attrs
*to
,
3490 const struct workqueue_attrs
*from
)
3492 to
->nice
= from
->nice
;
3493 cpumask_copy(to
->cpumask
, from
->cpumask
);
3495 * Unlike hash and equality test, this function doesn't ignore
3496 * ->no_numa as it is used for both pool and wq attrs. Instead,
3497 * get_unbound_pool() explicitly clears ->no_numa after copying.
3499 to
->no_numa
= from
->no_numa
;
3502 /* hash value of the content of @attr */
3503 static u32
wqattrs_hash(const struct workqueue_attrs
*attrs
)
3507 hash
= jhash_1word(attrs
->nice
, hash
);
3508 hash
= jhash(cpumask_bits(attrs
->cpumask
),
3509 BITS_TO_LONGS(nr_cpumask_bits
) * sizeof(long), hash
);
3513 /* content equality test */
3514 static bool wqattrs_equal(const struct workqueue_attrs
*a
,
3515 const struct workqueue_attrs
*b
)
3517 if (a
->nice
!= b
->nice
)
3519 if (!cpumask_equal(a
->cpumask
, b
->cpumask
))
3525 * init_worker_pool - initialize a newly zalloc'd worker_pool
3526 * @pool: worker_pool to initialize
3528 * Initiailize a newly zalloc'd @pool. It also allocates @pool->attrs.
3530 * Return: 0 on success, -errno on failure. Even on failure, all fields
3531 * inside @pool proper are initialized and put_unbound_pool() can be called
3532 * on @pool safely to release it.
3534 static int init_worker_pool(struct worker_pool
*pool
)
3536 spin_lock_init(&pool
->lock
);
3539 pool
->node
= NUMA_NO_NODE
;
3540 pool
->flags
|= POOL_DISASSOCIATED
;
3541 INIT_LIST_HEAD(&pool
->worklist
);
3542 INIT_LIST_HEAD(&pool
->idle_list
);
3543 hash_init(pool
->busy_hash
);
3545 init_timer_deferrable(&pool
->idle_timer
);
3546 pool
->idle_timer
.function
= idle_worker_timeout
;
3547 pool
->idle_timer
.data
= (unsigned long)pool
;
3549 setup_timer(&pool
->mayday_timer
, pool_mayday_timeout
,
3550 (unsigned long)pool
);
3552 mutex_init(&pool
->manager_arb
);
3553 mutex_init(&pool
->manager_mutex
);
3554 idr_init(&pool
->worker_idr
);
3556 INIT_HLIST_NODE(&pool
->hash_node
);
3559 /* shouldn't fail above this point */
3560 pool
->attrs
= alloc_workqueue_attrs(GFP_KERNEL
);
3566 static void rcu_free_pool(struct rcu_head
*rcu
)
3568 struct worker_pool
*pool
= container_of(rcu
, struct worker_pool
, rcu
);
3570 idr_destroy(&pool
->worker_idr
);
3571 free_workqueue_attrs(pool
->attrs
);
3576 * put_unbound_pool - put a worker_pool
3577 * @pool: worker_pool to put
3579 * Put @pool. If its refcnt reaches zero, it gets destroyed in sched-RCU
3580 * safe manner. get_unbound_pool() calls this function on its failure path
3581 * and this function should be able to release pools which went through,
3582 * successfully or not, init_worker_pool().
3584 * Should be called with wq_pool_mutex held.
3586 static void put_unbound_pool(struct worker_pool
*pool
)
3588 struct worker
*worker
;
3590 lockdep_assert_held(&wq_pool_mutex
);
3596 if (WARN_ON(!(pool
->flags
& POOL_DISASSOCIATED
)) ||
3597 WARN_ON(!list_empty(&pool
->worklist
)))
3600 /* release id and unhash */
3602 idr_remove(&worker_pool_idr
, pool
->id
);
3603 hash_del(&pool
->hash_node
);
3606 * Become the manager and destroy all workers. Grabbing
3607 * manager_arb prevents @pool's workers from blocking on
3610 mutex_lock(&pool
->manager_arb
);
3611 mutex_lock(&pool
->manager_mutex
);
3612 spin_lock_irq(&pool
->lock
);
3614 while ((worker
= first_worker(pool
)))
3615 destroy_worker(worker
);
3616 WARN_ON(pool
->nr_workers
|| pool
->nr_idle
);
3618 spin_unlock_irq(&pool
->lock
);
3619 mutex_unlock(&pool
->manager_mutex
);
3620 mutex_unlock(&pool
->manager_arb
);
3622 /* shut down the timers */
3623 del_timer_sync(&pool
->idle_timer
);
3624 del_timer_sync(&pool
->mayday_timer
);
3626 /* sched-RCU protected to allow dereferences from get_work_pool() */
3627 call_rcu_sched(&pool
->rcu
, rcu_free_pool
);
3631 * get_unbound_pool - get a worker_pool with the specified attributes
3632 * @attrs: the attributes of the worker_pool to get
3634 * Obtain a worker_pool which has the same attributes as @attrs, bump the
3635 * reference count and return it. If there already is a matching
3636 * worker_pool, it will be used; otherwise, this function attempts to
3639 * Should be called with wq_pool_mutex held.
3641 * Return: On success, a worker_pool with the same attributes as @attrs.
3642 * On failure, %NULL.
3644 static struct worker_pool
*get_unbound_pool(const struct workqueue_attrs
*attrs
)
3646 u32 hash
= wqattrs_hash(attrs
);
3647 struct worker_pool
*pool
;
3650 lockdep_assert_held(&wq_pool_mutex
);
3652 /* do we already have a matching pool? */
3653 hash_for_each_possible(unbound_pool_hash
, pool
, hash_node
, hash
) {
3654 if (wqattrs_equal(pool
->attrs
, attrs
)) {
3660 /* nope, create a new one */
3661 pool
= kzalloc(sizeof(*pool
), GFP_KERNEL
);
3662 if (!pool
|| init_worker_pool(pool
) < 0)
3665 if (workqueue_freezing
)
3666 pool
->flags
|= POOL_FREEZING
;
3668 lockdep_set_subclass(&pool
->lock
, 1); /* see put_pwq() */
3669 copy_workqueue_attrs(pool
->attrs
, attrs
);
3672 * no_numa isn't a worker_pool attribute, always clear it. See
3673 * 'struct workqueue_attrs' comments for detail.
3675 pool
->attrs
->no_numa
= false;
3677 /* if cpumask is contained inside a NUMA node, we belong to that node */
3678 if (wq_numa_enabled
) {
3679 for_each_node(node
) {
3680 if (cpumask_subset(pool
->attrs
->cpumask
,
3681 wq_numa_possible_cpumask
[node
])) {
3688 if (worker_pool_assign_id(pool
) < 0)
3691 /* create and start the initial worker */
3692 if (create_and_start_worker(pool
) < 0)
3696 hash_add(unbound_pool_hash
, &pool
->hash_node
, hash
);
3701 put_unbound_pool(pool
);
3705 static void rcu_free_pwq(struct rcu_head
*rcu
)
3707 kmem_cache_free(pwq_cache
,
3708 container_of(rcu
, struct pool_workqueue
, rcu
));
3712 * Scheduled on system_wq by put_pwq() when an unbound pwq hits zero refcnt
3713 * and needs to be destroyed.
3715 static void pwq_unbound_release_workfn(struct work_struct
*work
)
3717 struct pool_workqueue
*pwq
= container_of(work
, struct pool_workqueue
,
3718 unbound_release_work
);
3719 struct workqueue_struct
*wq
= pwq
->wq
;
3720 struct worker_pool
*pool
= pwq
->pool
;
3723 if (WARN_ON_ONCE(!(wq
->flags
& WQ_UNBOUND
)))
3727 * Unlink @pwq. Synchronization against wq->mutex isn't strictly
3728 * necessary on release but do it anyway. It's easier to verify
3729 * and consistent with the linking path.
3731 mutex_lock(&wq
->mutex
);
3732 list_del_rcu(&pwq
->pwqs_node
);
3733 is_last
= list_empty(&wq
->pwqs
);
3734 mutex_unlock(&wq
->mutex
);
3736 mutex_lock(&wq_pool_mutex
);
3737 put_unbound_pool(pool
);
3738 mutex_unlock(&wq_pool_mutex
);
3740 call_rcu_sched(&pwq
->rcu
, rcu_free_pwq
);
3743 * If we're the last pwq going away, @wq is already dead and no one
3744 * is gonna access it anymore. Free it.
3747 free_workqueue_attrs(wq
->unbound_attrs
);
3753 * pwq_adjust_max_active - update a pwq's max_active to the current setting
3754 * @pwq: target pool_workqueue
3756 * If @pwq isn't freezing, set @pwq->max_active to the associated
3757 * workqueue's saved_max_active and activate delayed work items
3758 * accordingly. If @pwq is freezing, clear @pwq->max_active to zero.
3760 static void pwq_adjust_max_active(struct pool_workqueue
*pwq
)
3762 struct workqueue_struct
*wq
= pwq
->wq
;
3763 bool freezable
= wq
->flags
& WQ_FREEZABLE
;
3765 /* for @wq->saved_max_active */
3766 lockdep_assert_held(&wq
->mutex
);
3768 /* fast exit for non-freezable wqs */
3769 if (!freezable
&& pwq
->max_active
== wq
->saved_max_active
)
3772 spin_lock_irq(&pwq
->pool
->lock
);
3774 if (!freezable
|| !(pwq
->pool
->flags
& POOL_FREEZING
)) {
3775 pwq
->max_active
= wq
->saved_max_active
;
3777 while (!list_empty(&pwq
->delayed_works
) &&
3778 pwq
->nr_active
< pwq
->max_active
)
3779 pwq_activate_first_delayed(pwq
);
3782 * Need to kick a worker after thawed or an unbound wq's
3783 * max_active is bumped. It's a slow path. Do it always.
3785 wake_up_worker(pwq
->pool
);
3787 pwq
->max_active
= 0;
3790 spin_unlock_irq(&pwq
->pool
->lock
);
3793 /* initialize newly alloced @pwq which is associated with @wq and @pool */
3794 static void init_pwq(struct pool_workqueue
*pwq
, struct workqueue_struct
*wq
,
3795 struct worker_pool
*pool
)
3797 BUG_ON((unsigned long)pwq
& WORK_STRUCT_FLAG_MASK
);
3799 memset(pwq
, 0, sizeof(*pwq
));
3803 pwq
->flush_color
= -1;
3805 INIT_LIST_HEAD(&pwq
->delayed_works
);
3806 INIT_LIST_HEAD(&pwq
->pwqs_node
);
3807 INIT_LIST_HEAD(&pwq
->mayday_node
);
3808 INIT_WORK(&pwq
->unbound_release_work
, pwq_unbound_release_workfn
);
3811 /* sync @pwq with the current state of its associated wq and link it */
3812 static void link_pwq(struct pool_workqueue
*pwq
)
3814 struct workqueue_struct
*wq
= pwq
->wq
;
3816 lockdep_assert_held(&wq
->mutex
);
3818 /* may be called multiple times, ignore if already linked */
3819 if (!list_empty(&pwq
->pwqs_node
))
3823 * Set the matching work_color. This is synchronized with
3824 * wq->mutex to avoid confusing flush_workqueue().
3826 pwq
->work_color
= wq
->work_color
;
3828 /* sync max_active to the current setting */
3829 pwq_adjust_max_active(pwq
);
3832 list_add_rcu(&pwq
->pwqs_node
, &wq
->pwqs
);
3835 /* obtain a pool matching @attr and create a pwq associating the pool and @wq */
3836 static struct pool_workqueue
*alloc_unbound_pwq(struct workqueue_struct
*wq
,
3837 const struct workqueue_attrs
*attrs
)
3839 struct worker_pool
*pool
;
3840 struct pool_workqueue
*pwq
;
3842 lockdep_assert_held(&wq_pool_mutex
);
3844 pool
= get_unbound_pool(attrs
);
3848 pwq
= kmem_cache_alloc_node(pwq_cache
, GFP_KERNEL
, pool
->node
);
3850 put_unbound_pool(pool
);
3854 init_pwq(pwq
, wq
, pool
);
3858 /* undo alloc_unbound_pwq(), used only in the error path */
3859 static void free_unbound_pwq(struct pool_workqueue
*pwq
)
3861 lockdep_assert_held(&wq_pool_mutex
);
3864 put_unbound_pool(pwq
->pool
);
3865 kmem_cache_free(pwq_cache
, pwq
);
3870 * wq_calc_node_mask - calculate a wq_attrs' cpumask for the specified node
3871 * @attrs: the wq_attrs of interest
3872 * @node: the target NUMA node
3873 * @cpu_going_down: if >= 0, the CPU to consider as offline
3874 * @cpumask: outarg, the resulting cpumask
3876 * Calculate the cpumask a workqueue with @attrs should use on @node. If
3877 * @cpu_going_down is >= 0, that cpu is considered offline during
3878 * calculation. The result is stored in @cpumask.
3880 * If NUMA affinity is not enabled, @attrs->cpumask is always used. If
3881 * enabled and @node has online CPUs requested by @attrs, the returned
3882 * cpumask is the intersection of the possible CPUs of @node and
3885 * The caller is responsible for ensuring that the cpumask of @node stays
3888 * Return: %true if the resulting @cpumask is different from @attrs->cpumask,
3891 static bool wq_calc_node_cpumask(const struct workqueue_attrs
*attrs
, int node
,
3892 int cpu_going_down
, cpumask_t
*cpumask
)
3894 if (!wq_numa_enabled
|| attrs
->no_numa
)
3897 /* does @node have any online CPUs @attrs wants? */
3898 cpumask_and(cpumask
, cpumask_of_node(node
), attrs
->cpumask
);
3899 if (cpu_going_down
>= 0)
3900 cpumask_clear_cpu(cpu_going_down
, cpumask
);
3902 if (cpumask_empty(cpumask
))
3905 /* yeap, return possible CPUs in @node that @attrs wants */
3906 cpumask_and(cpumask
, attrs
->cpumask
, wq_numa_possible_cpumask
[node
]);
3907 return !cpumask_equal(cpumask
, attrs
->cpumask
);
3910 cpumask_copy(cpumask
, attrs
->cpumask
);
3914 /* install @pwq into @wq's numa_pwq_tbl[] for @node and return the old pwq */
3915 static struct pool_workqueue
*numa_pwq_tbl_install(struct workqueue_struct
*wq
,
3917 struct pool_workqueue
*pwq
)
3919 struct pool_workqueue
*old_pwq
;
3921 lockdep_assert_held(&wq
->mutex
);
3923 /* link_pwq() can handle duplicate calls */
3926 old_pwq
= rcu_access_pointer(wq
->numa_pwq_tbl
[node
]);
3927 rcu_assign_pointer(wq
->numa_pwq_tbl
[node
], pwq
);
3932 * apply_workqueue_attrs - apply new workqueue_attrs to an unbound workqueue
3933 * @wq: the target workqueue
3934 * @attrs: the workqueue_attrs to apply, allocated with alloc_workqueue_attrs()
3936 * Apply @attrs to an unbound workqueue @wq. Unless disabled, on NUMA
3937 * machines, this function maps a separate pwq to each NUMA node with
3938 * possibles CPUs in @attrs->cpumask so that work items are affine to the
3939 * NUMA node it was issued on. Older pwqs are released as in-flight work
3940 * items finish. Note that a work item which repeatedly requeues itself
3941 * back-to-back will stay on its current pwq.
3943 * Performs GFP_KERNEL allocations.
3945 * Return: 0 on success and -errno on failure.
3947 int apply_workqueue_attrs(struct workqueue_struct
*wq
,
3948 const struct workqueue_attrs
*attrs
)
3950 struct workqueue_attrs
*new_attrs
, *tmp_attrs
;
3951 struct pool_workqueue
**pwq_tbl
, *dfl_pwq
;
3954 /* only unbound workqueues can change attributes */
3955 if (WARN_ON(!(wq
->flags
& WQ_UNBOUND
)))
3958 /* creating multiple pwqs breaks ordering guarantee */
3959 if (WARN_ON((wq
->flags
& __WQ_ORDERED
) && !list_empty(&wq
->pwqs
)))
3962 pwq_tbl
= kzalloc(wq_numa_tbl_len
* sizeof(pwq_tbl
[0]), GFP_KERNEL
);
3963 new_attrs
= alloc_workqueue_attrs(GFP_KERNEL
);
3964 tmp_attrs
= alloc_workqueue_attrs(GFP_KERNEL
);
3965 if (!pwq_tbl
|| !new_attrs
|| !tmp_attrs
)
3968 /* make a copy of @attrs and sanitize it */
3969 copy_workqueue_attrs(new_attrs
, attrs
);
3970 cpumask_and(new_attrs
->cpumask
, new_attrs
->cpumask
, cpu_possible_mask
);
3973 * We may create multiple pwqs with differing cpumasks. Make a
3974 * copy of @new_attrs which will be modified and used to obtain
3977 copy_workqueue_attrs(tmp_attrs
, new_attrs
);
3980 * CPUs should stay stable across pwq creations and installations.
3981 * Pin CPUs, determine the target cpumask for each node and create
3986 mutex_lock(&wq_pool_mutex
);
3989 * If something goes wrong during CPU up/down, we'll fall back to
3990 * the default pwq covering whole @attrs->cpumask. Always create
3991 * it even if we don't use it immediately.
3993 dfl_pwq
= alloc_unbound_pwq(wq
, new_attrs
);
3997 for_each_node(node
) {
3998 if (wq_calc_node_cpumask(attrs
, node
, -1, tmp_attrs
->cpumask
)) {
3999 pwq_tbl
[node
] = alloc_unbound_pwq(wq
, tmp_attrs
);
4004 pwq_tbl
[node
] = dfl_pwq
;
4008 mutex_unlock(&wq_pool_mutex
);
4010 /* all pwqs have been created successfully, let's install'em */
4011 mutex_lock(&wq
->mutex
);
4013 copy_workqueue_attrs(wq
->unbound_attrs
, new_attrs
);
4015 /* save the previous pwq and install the new one */
4017 pwq_tbl
[node
] = numa_pwq_tbl_install(wq
, node
, pwq_tbl
[node
]);
4019 /* @dfl_pwq might not have been used, ensure it's linked */
4021 swap(wq
->dfl_pwq
, dfl_pwq
);
4023 mutex_unlock(&wq
->mutex
);
4025 /* put the old pwqs */
4027 put_pwq_unlocked(pwq_tbl
[node
]);
4028 put_pwq_unlocked(dfl_pwq
);
4034 free_workqueue_attrs(tmp_attrs
);
4035 free_workqueue_attrs(new_attrs
);
4040 free_unbound_pwq(dfl_pwq
);
4042 if (pwq_tbl
&& pwq_tbl
[node
] != dfl_pwq
)
4043 free_unbound_pwq(pwq_tbl
[node
]);
4044 mutex_unlock(&wq_pool_mutex
);
4052 * wq_update_unbound_numa - update NUMA affinity of a wq for CPU hot[un]plug
4053 * @wq: the target workqueue
4054 * @cpu: the CPU coming up or going down
4055 * @online: whether @cpu is coming up or going down
4057 * This function is to be called from %CPU_DOWN_PREPARE, %CPU_ONLINE and
4058 * %CPU_DOWN_FAILED. @cpu is being hot[un]plugged, update NUMA affinity of
4061 * If NUMA affinity can't be adjusted due to memory allocation failure, it
4062 * falls back to @wq->dfl_pwq which may not be optimal but is always
4065 * Note that when the last allowed CPU of a NUMA node goes offline for a
4066 * workqueue with a cpumask spanning multiple nodes, the workers which were
4067 * already executing the work items for the workqueue will lose their CPU
4068 * affinity and may execute on any CPU. This is similar to how per-cpu
4069 * workqueues behave on CPU_DOWN. If a workqueue user wants strict
4070 * affinity, it's the user's responsibility to flush the work item from
4073 static void wq_update_unbound_numa(struct workqueue_struct
*wq
, int cpu
,
4076 int node
= cpu_to_node(cpu
);
4077 int cpu_off
= online
? -1 : cpu
;
4078 struct pool_workqueue
*old_pwq
= NULL
, *pwq
;
4079 struct workqueue_attrs
*target_attrs
;
4082 lockdep_assert_held(&wq_pool_mutex
);
4084 if (!wq_numa_enabled
|| !(wq
->flags
& WQ_UNBOUND
))
4088 * We don't wanna alloc/free wq_attrs for each wq for each CPU.
4089 * Let's use a preallocated one. The following buf is protected by
4090 * CPU hotplug exclusion.
4092 target_attrs
= wq_update_unbound_numa_attrs_buf
;
4093 cpumask
= target_attrs
->cpumask
;
4095 mutex_lock(&wq
->mutex
);
4096 if (wq
->unbound_attrs
->no_numa
)
4099 copy_workqueue_attrs(target_attrs
, wq
->unbound_attrs
);
4100 pwq
= unbound_pwq_by_node(wq
, node
);
4103 * Let's determine what needs to be done. If the target cpumask is
4104 * different from wq's, we need to compare it to @pwq's and create
4105 * a new one if they don't match. If the target cpumask equals
4106 * wq's, the default pwq should be used. If @pwq is already the
4107 * default one, nothing to do; otherwise, install the default one.
4109 if (wq_calc_node_cpumask(wq
->unbound_attrs
, node
, cpu_off
, cpumask
)) {
4110 if (cpumask_equal(cpumask
, pwq
->pool
->attrs
->cpumask
))
4113 if (pwq
== wq
->dfl_pwq
)
4119 mutex_unlock(&wq
->mutex
);
4121 /* create a new pwq */
4122 pwq
= alloc_unbound_pwq(wq
, target_attrs
);
4124 pr_warning("workqueue: allocation failed while updating NUMA affinity of \"%s\"\n",
4126 mutex_lock(&wq
->mutex
);
4131 * Install the new pwq. As this function is called only from CPU
4132 * hotplug callbacks and applying a new attrs is wrapped with
4133 * get/put_online_cpus(), @wq->unbound_attrs couldn't have changed
4136 mutex_lock(&wq
->mutex
);
4137 old_pwq
= numa_pwq_tbl_install(wq
, node
, pwq
);
4141 spin_lock_irq(&wq
->dfl_pwq
->pool
->lock
);
4142 get_pwq(wq
->dfl_pwq
);
4143 spin_unlock_irq(&wq
->dfl_pwq
->pool
->lock
);
4144 old_pwq
= numa_pwq_tbl_install(wq
, node
, wq
->dfl_pwq
);
4146 mutex_unlock(&wq
->mutex
);
4147 put_pwq_unlocked(old_pwq
);
4150 static int alloc_and_link_pwqs(struct workqueue_struct
*wq
)
4152 bool highpri
= wq
->flags
& WQ_HIGHPRI
;
4155 if (!(wq
->flags
& WQ_UNBOUND
)) {
4156 wq
->cpu_pwqs
= alloc_percpu(struct pool_workqueue
);
4160 for_each_possible_cpu(cpu
) {
4161 struct pool_workqueue
*pwq
=
4162 per_cpu_ptr(wq
->cpu_pwqs
, cpu
);
4163 struct worker_pool
*cpu_pools
=
4164 per_cpu(cpu_worker_pools
, cpu
);
4166 init_pwq(pwq
, wq
, &cpu_pools
[highpri
]);
4168 mutex_lock(&wq
->mutex
);
4170 mutex_unlock(&wq
->mutex
);
4173 } else if (wq
->flags
& __WQ_ORDERED
) {
4174 ret
= apply_workqueue_attrs(wq
, ordered_wq_attrs
[highpri
]);
4175 /* there should only be single pwq for ordering guarantee */
4176 WARN(!ret
&& (wq
->pwqs
.next
!= &wq
->dfl_pwq
->pwqs_node
||
4177 wq
->pwqs
.prev
!= &wq
->dfl_pwq
->pwqs_node
),
4178 "ordering guarantee broken for workqueue %s\n", wq
->name
);
4181 return apply_workqueue_attrs(wq
, unbound_std_wq_attrs
[highpri
]);
4185 static int wq_clamp_max_active(int max_active
, unsigned int flags
,
4188 int lim
= flags
& WQ_UNBOUND
? WQ_UNBOUND_MAX_ACTIVE
: WQ_MAX_ACTIVE
;
4190 if (max_active
< 1 || max_active
> lim
)
4191 pr_warn("workqueue: max_active %d requested for %s is out of range, clamping between %d and %d\n",
4192 max_active
, name
, 1, lim
);
4194 return clamp_val(max_active
, 1, lim
);
4197 struct workqueue_struct
*__alloc_workqueue_key(const char *fmt
,
4200 struct lock_class_key
*key
,
4201 const char *lock_name
, ...)
4203 size_t tbl_size
= 0;
4205 struct workqueue_struct
*wq
;
4206 struct pool_workqueue
*pwq
;
4208 /* see the comment above the definition of WQ_POWER_EFFICIENT */
4209 if ((flags
& WQ_POWER_EFFICIENT
) && wq_power_efficient
)
4210 flags
|= WQ_UNBOUND
;
4212 /* allocate wq and format name */
4213 if (flags
& WQ_UNBOUND
)
4214 tbl_size
= wq_numa_tbl_len
* sizeof(wq
->numa_pwq_tbl
[0]);
4216 wq
= kzalloc(sizeof(*wq
) + tbl_size
, GFP_KERNEL
);
4220 if (flags
& WQ_UNBOUND
) {
4221 wq
->unbound_attrs
= alloc_workqueue_attrs(GFP_KERNEL
);
4222 if (!wq
->unbound_attrs
)
4226 va_start(args
, lock_name
);
4227 vsnprintf(wq
->name
, sizeof(wq
->name
), fmt
, args
);
4230 max_active
= max_active
?: WQ_DFL_ACTIVE
;
4231 max_active
= wq_clamp_max_active(max_active
, flags
, wq
->name
);
4235 wq
->saved_max_active
= max_active
;
4236 mutex_init(&wq
->mutex
);
4237 atomic_set(&wq
->nr_pwqs_to_flush
, 0);
4238 INIT_LIST_HEAD(&wq
->pwqs
);
4239 INIT_LIST_HEAD(&wq
->flusher_queue
);
4240 INIT_LIST_HEAD(&wq
->flusher_overflow
);
4241 INIT_LIST_HEAD(&wq
->maydays
);
4243 lockdep_init_map(&wq
->lockdep_map
, lock_name
, key
, 0);
4244 INIT_LIST_HEAD(&wq
->list
);
4246 if (alloc_and_link_pwqs(wq
) < 0)
4250 * Workqueues which may be used during memory reclaim should
4251 * have a rescuer to guarantee forward progress.
4253 if (flags
& WQ_MEM_RECLAIM
) {
4254 struct worker
*rescuer
;
4256 rescuer
= alloc_worker();
4260 rescuer
->rescue_wq
= wq
;
4261 rescuer
->task
= kthread_create(rescuer_thread
, rescuer
, "%s",
4263 if (IS_ERR(rescuer
->task
)) {
4268 wq
->rescuer
= rescuer
;
4269 rescuer
->task
->flags
|= PF_NO_SETAFFINITY
;
4270 wake_up_process(rescuer
->task
);
4273 if ((wq
->flags
& WQ_SYSFS
) && workqueue_sysfs_register(wq
))
4277 * wq_pool_mutex protects global freeze state and workqueues list.
4278 * Grab it, adjust max_active and add the new @wq to workqueues
4281 mutex_lock(&wq_pool_mutex
);
4283 mutex_lock(&wq
->mutex
);
4284 for_each_pwq(pwq
, wq
)
4285 pwq_adjust_max_active(pwq
);
4286 mutex_unlock(&wq
->mutex
);
4288 list_add(&wq
->list
, &workqueues
);
4290 mutex_unlock(&wq_pool_mutex
);
4295 free_workqueue_attrs(wq
->unbound_attrs
);
4299 destroy_workqueue(wq
);
4302 EXPORT_SYMBOL_GPL(__alloc_workqueue_key
);
4305 * destroy_workqueue - safely terminate a workqueue
4306 * @wq: target workqueue
4308 * Safely destroy a workqueue. All work currently pending will be done first.
4310 void destroy_workqueue(struct workqueue_struct
*wq
)
4312 struct pool_workqueue
*pwq
;
4315 /* drain it before proceeding with destruction */
4316 drain_workqueue(wq
);
4319 mutex_lock(&wq
->mutex
);
4320 for_each_pwq(pwq
, wq
) {
4323 for (i
= 0; i
< WORK_NR_COLORS
; i
++) {
4324 if (WARN_ON(pwq
->nr_in_flight
[i
])) {
4325 mutex_unlock(&wq
->mutex
);
4330 if (WARN_ON((pwq
!= wq
->dfl_pwq
) && (pwq
->refcnt
> 1)) ||
4331 WARN_ON(pwq
->nr_active
) ||
4332 WARN_ON(!list_empty(&pwq
->delayed_works
))) {
4333 mutex_unlock(&wq
->mutex
);
4337 mutex_unlock(&wq
->mutex
);
4340 * wq list is used to freeze wq, remove from list after
4341 * flushing is complete in case freeze races us.
4343 mutex_lock(&wq_pool_mutex
);
4344 list_del_init(&wq
->list
);
4345 mutex_unlock(&wq_pool_mutex
);
4347 workqueue_sysfs_unregister(wq
);
4350 kthread_stop(wq
->rescuer
->task
);
4355 if (!(wq
->flags
& WQ_UNBOUND
)) {
4357 * The base ref is never dropped on per-cpu pwqs. Directly
4358 * free the pwqs and wq.
4360 free_percpu(wq
->cpu_pwqs
);
4364 * We're the sole accessor of @wq at this point. Directly
4365 * access numa_pwq_tbl[] and dfl_pwq to put the base refs.
4366 * @wq will be freed when the last pwq is released.
4368 for_each_node(node
) {
4369 pwq
= rcu_access_pointer(wq
->numa_pwq_tbl
[node
]);
4370 RCU_INIT_POINTER(wq
->numa_pwq_tbl
[node
], NULL
);
4371 put_pwq_unlocked(pwq
);
4375 * Put dfl_pwq. @wq may be freed any time after dfl_pwq is
4376 * put. Don't access it afterwards.
4380 put_pwq_unlocked(pwq
);
4383 EXPORT_SYMBOL_GPL(destroy_workqueue
);
4386 * workqueue_set_max_active - adjust max_active of a workqueue
4387 * @wq: target workqueue
4388 * @max_active: new max_active value.
4390 * Set max_active of @wq to @max_active.
4393 * Don't call from IRQ context.
4395 void workqueue_set_max_active(struct workqueue_struct
*wq
, int max_active
)
4397 struct pool_workqueue
*pwq
;
4399 /* disallow meddling with max_active for ordered workqueues */
4400 if (WARN_ON(wq
->flags
& __WQ_ORDERED
))
4403 max_active
= wq_clamp_max_active(max_active
, wq
->flags
, wq
->name
);
4405 mutex_lock(&wq
->mutex
);
4407 wq
->saved_max_active
= max_active
;
4409 for_each_pwq(pwq
, wq
)
4410 pwq_adjust_max_active(pwq
);
4412 mutex_unlock(&wq
->mutex
);
4414 EXPORT_SYMBOL_GPL(workqueue_set_max_active
);
4417 * current_is_workqueue_rescuer - is %current workqueue rescuer?
4419 * Determine whether %current is a workqueue rescuer. Can be used from
4420 * work functions to determine whether it's being run off the rescuer task.
4422 * Return: %true if %current is a workqueue rescuer. %false otherwise.
4424 bool current_is_workqueue_rescuer(void)
4426 struct worker
*worker
= current_wq_worker();
4428 return worker
&& worker
->rescue_wq
;
4432 * workqueue_congested - test whether a workqueue is congested
4433 * @cpu: CPU in question
4434 * @wq: target workqueue
4436 * Test whether @wq's cpu workqueue for @cpu is congested. There is
4437 * no synchronization around this function and the test result is
4438 * unreliable and only useful as advisory hints or for debugging.
4440 * If @cpu is WORK_CPU_UNBOUND, the test is performed on the local CPU.
4441 * Note that both per-cpu and unbound workqueues may be associated with
4442 * multiple pool_workqueues which have separate congested states. A
4443 * workqueue being congested on one CPU doesn't mean the workqueue is also
4444 * contested on other CPUs / NUMA nodes.
4447 * %true if congested, %false otherwise.
4449 bool workqueue_congested(int cpu
, struct workqueue_struct
*wq
)
4451 struct pool_workqueue
*pwq
;
4454 rcu_read_lock_sched();
4456 if (cpu
== WORK_CPU_UNBOUND
)
4457 cpu
= smp_processor_id();
4459 if (!(wq
->flags
& WQ_UNBOUND
))
4460 pwq
= per_cpu_ptr(wq
->cpu_pwqs
, cpu
);
4462 pwq
= unbound_pwq_by_node(wq
, cpu_to_node(cpu
));
4464 ret
= !list_empty(&pwq
->delayed_works
);
4465 rcu_read_unlock_sched();
4469 EXPORT_SYMBOL_GPL(workqueue_congested
);
4472 * work_busy - test whether a work is currently pending or running
4473 * @work: the work to be tested
4475 * Test whether @work is currently pending or running. There is no
4476 * synchronization around this function and the test result is
4477 * unreliable and only useful as advisory hints or for debugging.
4480 * OR'd bitmask of WORK_BUSY_* bits.
4482 unsigned int work_busy(struct work_struct
*work
)
4484 struct worker_pool
*pool
;
4485 unsigned long flags
;
4486 unsigned int ret
= 0;
4488 if (work_pending(work
))
4489 ret
|= WORK_BUSY_PENDING
;
4491 local_irq_save(flags
);
4492 pool
= get_work_pool(work
);
4494 spin_lock(&pool
->lock
);
4495 if (find_worker_executing_work(pool
, work
))
4496 ret
|= WORK_BUSY_RUNNING
;
4497 spin_unlock(&pool
->lock
);
4499 local_irq_restore(flags
);
4503 EXPORT_SYMBOL_GPL(work_busy
);
4506 * set_worker_desc - set description for the current work item
4507 * @fmt: printf-style format string
4508 * @...: arguments for the format string
4510 * This function can be called by a running work function to describe what
4511 * the work item is about. If the worker task gets dumped, this
4512 * information will be printed out together to help debugging. The
4513 * description can be at most WORKER_DESC_LEN including the trailing '\0'.
4515 void set_worker_desc(const char *fmt
, ...)
4517 struct worker
*worker
= current_wq_worker();
4521 va_start(args
, fmt
);
4522 vsnprintf(worker
->desc
, sizeof(worker
->desc
), fmt
, args
);
4524 worker
->desc_valid
= true;
4529 * print_worker_info - print out worker information and description
4530 * @log_lvl: the log level to use when printing
4531 * @task: target task
4533 * If @task is a worker and currently executing a work item, print out the
4534 * name of the workqueue being serviced and worker description set with
4535 * set_worker_desc() by the currently executing work item.
4537 * This function can be safely called on any task as long as the
4538 * task_struct itself is accessible. While safe, this function isn't
4539 * synchronized and may print out mixups or garbages of limited length.
4541 void print_worker_info(const char *log_lvl
, struct task_struct
*task
)
4543 work_func_t
*fn
= NULL
;
4544 char name
[WQ_NAME_LEN
] = { };
4545 char desc
[WORKER_DESC_LEN
] = { };
4546 struct pool_workqueue
*pwq
= NULL
;
4547 struct workqueue_struct
*wq
= NULL
;
4548 bool desc_valid
= false;
4549 struct worker
*worker
;
4551 if (!(task
->flags
& PF_WQ_WORKER
))
4555 * This function is called without any synchronization and @task
4556 * could be in any state. Be careful with dereferences.
4558 worker
= probe_kthread_data(task
);
4561 * Carefully copy the associated workqueue's workfn and name. Keep
4562 * the original last '\0' in case the original contains garbage.
4564 probe_kernel_read(&fn
, &worker
->current_func
, sizeof(fn
));
4565 probe_kernel_read(&pwq
, &worker
->current_pwq
, sizeof(pwq
));
4566 probe_kernel_read(&wq
, &pwq
->wq
, sizeof(wq
));
4567 probe_kernel_read(name
, wq
->name
, sizeof(name
) - 1);
4569 /* copy worker description */
4570 probe_kernel_read(&desc_valid
, &worker
->desc_valid
, sizeof(desc_valid
));
4572 probe_kernel_read(desc
, worker
->desc
, sizeof(desc
) - 1);
4574 if (fn
|| name
[0] || desc
[0]) {
4575 printk("%sWorkqueue: %s %pf", log_lvl
, name
, fn
);
4577 pr_cont(" (%s)", desc
);
4585 * There are two challenges in supporting CPU hotplug. Firstly, there
4586 * are a lot of assumptions on strong associations among work, pwq and
4587 * pool which make migrating pending and scheduled works very
4588 * difficult to implement without impacting hot paths. Secondly,
4589 * worker pools serve mix of short, long and very long running works making
4590 * blocked draining impractical.
4592 * This is solved by allowing the pools to be disassociated from the CPU
4593 * running as an unbound one and allowing it to be reattached later if the
4594 * cpu comes back online.
4597 static void wq_unbind_fn(struct work_struct
*work
)
4599 int cpu
= smp_processor_id();
4600 struct worker_pool
*pool
;
4601 struct worker
*worker
;
4604 for_each_cpu_worker_pool(pool
, cpu
) {
4605 WARN_ON_ONCE(cpu
!= smp_processor_id());
4607 mutex_lock(&pool
->manager_mutex
);
4608 spin_lock_irq(&pool
->lock
);
4611 * We've blocked all manager operations. Make all workers
4612 * unbound and set DISASSOCIATED. Before this, all workers
4613 * except for the ones which are still executing works from
4614 * before the last CPU down must be on the cpu. After
4615 * this, they may become diasporas.
4617 for_each_pool_worker(worker
, wi
, pool
)
4618 worker
->flags
|= WORKER_UNBOUND
;
4620 pool
->flags
|= POOL_DISASSOCIATED
;
4622 spin_unlock_irq(&pool
->lock
);
4623 mutex_unlock(&pool
->manager_mutex
);
4626 * Call schedule() so that we cross rq->lock and thus can
4627 * guarantee sched callbacks see the %WORKER_UNBOUND flag.
4628 * This is necessary as scheduler callbacks may be invoked
4634 * Sched callbacks are disabled now. Zap nr_running.
4635 * After this, nr_running stays zero and need_more_worker()
4636 * and keep_working() are always true as long as the
4637 * worklist is not empty. This pool now behaves as an
4638 * unbound (in terms of concurrency management) pool which
4639 * are served by workers tied to the pool.
4641 atomic_set(&pool
->nr_running
, 0);
4644 * With concurrency management just turned off, a busy
4645 * worker blocking could lead to lengthy stalls. Kick off
4646 * unbound chain execution of currently pending work items.
4648 spin_lock_irq(&pool
->lock
);
4649 wake_up_worker(pool
);
4650 spin_unlock_irq(&pool
->lock
);
4655 * rebind_workers - rebind all workers of a pool to the associated CPU
4656 * @pool: pool of interest
4658 * @pool->cpu is coming online. Rebind all workers to the CPU.
4660 static void rebind_workers(struct worker_pool
*pool
)
4662 struct worker
*worker
;
4665 lockdep_assert_held(&pool
->manager_mutex
);
4668 * Restore CPU affinity of all workers. As all idle workers should
4669 * be on the run-queue of the associated CPU before any local
4670 * wake-ups for concurrency management happen, restore CPU affinty
4671 * of all workers first and then clear UNBOUND. As we're called
4672 * from CPU_ONLINE, the following shouldn't fail.
4674 for_each_pool_worker(worker
, wi
, pool
)
4675 WARN_ON_ONCE(set_cpus_allowed_ptr(worker
->task
,
4676 pool
->attrs
->cpumask
) < 0);
4678 spin_lock_irq(&pool
->lock
);
4680 for_each_pool_worker(worker
, wi
, pool
) {
4681 unsigned int worker_flags
= worker
->flags
;
4684 * A bound idle worker should actually be on the runqueue
4685 * of the associated CPU for local wake-ups targeting it to
4686 * work. Kick all idle workers so that they migrate to the
4687 * associated CPU. Doing this in the same loop as
4688 * replacing UNBOUND with REBOUND is safe as no worker will
4689 * be bound before @pool->lock is released.
4691 if (worker_flags
& WORKER_IDLE
)
4692 wake_up_process(worker
->task
);
4695 * We want to clear UNBOUND but can't directly call
4696 * worker_clr_flags() or adjust nr_running. Atomically
4697 * replace UNBOUND with another NOT_RUNNING flag REBOUND.
4698 * @worker will clear REBOUND using worker_clr_flags() when
4699 * it initiates the next execution cycle thus restoring
4700 * concurrency management. Note that when or whether
4701 * @worker clears REBOUND doesn't affect correctness.
4703 * ACCESS_ONCE() is necessary because @worker->flags may be
4704 * tested without holding any lock in
4705 * wq_worker_waking_up(). Without it, NOT_RUNNING test may
4706 * fail incorrectly leading to premature concurrency
4707 * management operations.
4709 WARN_ON_ONCE(!(worker_flags
& WORKER_UNBOUND
));
4710 worker_flags
|= WORKER_REBOUND
;
4711 worker_flags
&= ~WORKER_UNBOUND
;
4712 ACCESS_ONCE(worker
->flags
) = worker_flags
;
4715 spin_unlock_irq(&pool
->lock
);
4719 * restore_unbound_workers_cpumask - restore cpumask of unbound workers
4720 * @pool: unbound pool of interest
4721 * @cpu: the CPU which is coming up
4723 * An unbound pool may end up with a cpumask which doesn't have any online
4724 * CPUs. When a worker of such pool get scheduled, the scheduler resets
4725 * its cpus_allowed. If @cpu is in @pool's cpumask which didn't have any
4726 * online CPU before, cpus_allowed of all its workers should be restored.
4728 static void restore_unbound_workers_cpumask(struct worker_pool
*pool
, int cpu
)
4730 static cpumask_t cpumask
;
4731 struct worker
*worker
;
4734 lockdep_assert_held(&pool
->manager_mutex
);
4736 /* is @cpu allowed for @pool? */
4737 if (!cpumask_test_cpu(cpu
, pool
->attrs
->cpumask
))
4740 /* is @cpu the only online CPU? */
4741 cpumask_and(&cpumask
, pool
->attrs
->cpumask
, cpu_online_mask
);
4742 if (cpumask_weight(&cpumask
) != 1)
4745 /* as we're called from CPU_ONLINE, the following shouldn't fail */
4746 for_each_pool_worker(worker
, wi
, pool
)
4747 WARN_ON_ONCE(set_cpus_allowed_ptr(worker
->task
,
4748 pool
->attrs
->cpumask
) < 0);
4752 * Workqueues should be brought up before normal priority CPU notifiers.
4753 * This will be registered high priority CPU notifier.
4755 static int workqueue_cpu_up_callback(struct notifier_block
*nfb
,
4756 unsigned long action
,
4759 int cpu
= (unsigned long)hcpu
;
4760 struct worker_pool
*pool
;
4761 struct workqueue_struct
*wq
;
4764 switch (action
& ~CPU_TASKS_FROZEN
) {
4765 case CPU_UP_PREPARE
:
4766 for_each_cpu_worker_pool(pool
, cpu
) {
4767 if (pool
->nr_workers
)
4769 if (create_and_start_worker(pool
) < 0)
4774 case CPU_DOWN_FAILED
:
4776 mutex_lock(&wq_pool_mutex
);
4778 for_each_pool(pool
, pi
) {
4779 mutex_lock(&pool
->manager_mutex
);
4781 if (pool
->cpu
== cpu
) {
4782 spin_lock_irq(&pool
->lock
);
4783 pool
->flags
&= ~POOL_DISASSOCIATED
;
4784 spin_unlock_irq(&pool
->lock
);
4786 rebind_workers(pool
);
4787 } else if (pool
->cpu
< 0) {
4788 restore_unbound_workers_cpumask(pool
, cpu
);
4791 mutex_unlock(&pool
->manager_mutex
);
4794 /* update NUMA affinity of unbound workqueues */
4795 list_for_each_entry(wq
, &workqueues
, list
)
4796 wq_update_unbound_numa(wq
, cpu
, true);
4798 mutex_unlock(&wq_pool_mutex
);
4805 * Workqueues should be brought down after normal priority CPU notifiers.
4806 * This will be registered as low priority CPU notifier.
4808 static int workqueue_cpu_down_callback(struct notifier_block
*nfb
,
4809 unsigned long action
,
4812 int cpu
= (unsigned long)hcpu
;
4813 struct work_struct unbind_work
;
4814 struct workqueue_struct
*wq
;
4816 switch (action
& ~CPU_TASKS_FROZEN
) {
4817 case CPU_DOWN_PREPARE
:
4818 /* unbinding per-cpu workers should happen on the local CPU */
4819 INIT_WORK_ONSTACK(&unbind_work
, wq_unbind_fn
);
4820 queue_work_on(cpu
, system_highpri_wq
, &unbind_work
);
4822 /* update NUMA affinity of unbound workqueues */
4823 mutex_lock(&wq_pool_mutex
);
4824 list_for_each_entry(wq
, &workqueues
, list
)
4825 wq_update_unbound_numa(wq
, cpu
, false);
4826 mutex_unlock(&wq_pool_mutex
);
4828 /* wait for per-cpu unbinding to finish */
4829 flush_work(&unbind_work
);
4830 destroy_work_on_stack(&unbind_work
);
4838 struct work_for_cpu
{
4839 struct work_struct work
;
4845 static void work_for_cpu_fn(struct work_struct
*work
)
4847 struct work_for_cpu
*wfc
= container_of(work
, struct work_for_cpu
, work
);
4849 wfc
->ret
= wfc
->fn(wfc
->arg
);
4853 * work_on_cpu - run a function in user context on a particular cpu
4854 * @cpu: the cpu to run on
4855 * @fn: the function to run
4856 * @arg: the function arg
4858 * It is up to the caller to ensure that the cpu doesn't go offline.
4859 * The caller must not hold any locks which would prevent @fn from completing.
4861 * Return: The value @fn returns.
4863 long work_on_cpu(int cpu
, long (*fn
)(void *), void *arg
)
4865 struct work_for_cpu wfc
= { .fn
= fn
, .arg
= arg
};
4867 INIT_WORK_ONSTACK(&wfc
.work
, work_for_cpu_fn
);
4868 schedule_work_on(cpu
, &wfc
.work
);
4869 flush_work(&wfc
.work
);
4870 destroy_work_on_stack(&wfc
.work
);
4873 EXPORT_SYMBOL_GPL(work_on_cpu
);
4874 #endif /* CONFIG_SMP */
4876 #ifdef CONFIG_FREEZER
4879 * freeze_workqueues_begin - begin freezing workqueues
4881 * Start freezing workqueues. After this function returns, all freezable
4882 * workqueues will queue new works to their delayed_works list instead of
4886 * Grabs and releases wq_pool_mutex, wq->mutex and pool->lock's.
4888 void freeze_workqueues_begin(void)
4890 struct worker_pool
*pool
;
4891 struct workqueue_struct
*wq
;
4892 struct pool_workqueue
*pwq
;
4895 mutex_lock(&wq_pool_mutex
);
4897 WARN_ON_ONCE(workqueue_freezing
);
4898 workqueue_freezing
= true;
4901 for_each_pool(pool
, pi
) {
4902 spin_lock_irq(&pool
->lock
);
4903 WARN_ON_ONCE(pool
->flags
& POOL_FREEZING
);
4904 pool
->flags
|= POOL_FREEZING
;
4905 spin_unlock_irq(&pool
->lock
);
4908 list_for_each_entry(wq
, &workqueues
, list
) {
4909 mutex_lock(&wq
->mutex
);
4910 for_each_pwq(pwq
, wq
)
4911 pwq_adjust_max_active(pwq
);
4912 mutex_unlock(&wq
->mutex
);
4915 mutex_unlock(&wq_pool_mutex
);
4919 * freeze_workqueues_busy - are freezable workqueues still busy?
4921 * Check whether freezing is complete. This function must be called
4922 * between freeze_workqueues_begin() and thaw_workqueues().
4925 * Grabs and releases wq_pool_mutex.
4928 * %true if some freezable workqueues are still busy. %false if freezing
4931 bool freeze_workqueues_busy(void)
4934 struct workqueue_struct
*wq
;
4935 struct pool_workqueue
*pwq
;
4937 mutex_lock(&wq_pool_mutex
);
4939 WARN_ON_ONCE(!workqueue_freezing
);
4941 list_for_each_entry(wq
, &workqueues
, list
) {
4942 if (!(wq
->flags
& WQ_FREEZABLE
))
4945 * nr_active is monotonically decreasing. It's safe
4946 * to peek without lock.
4948 rcu_read_lock_sched();
4949 for_each_pwq(pwq
, wq
) {
4950 WARN_ON_ONCE(pwq
->nr_active
< 0);
4951 if (pwq
->nr_active
) {
4953 rcu_read_unlock_sched();
4957 rcu_read_unlock_sched();
4960 mutex_unlock(&wq_pool_mutex
);
4965 * thaw_workqueues - thaw workqueues
4967 * Thaw workqueues. Normal queueing is restored and all collected
4968 * frozen works are transferred to their respective pool worklists.
4971 * Grabs and releases wq_pool_mutex, wq->mutex and pool->lock's.
4973 void thaw_workqueues(void)
4975 struct workqueue_struct
*wq
;
4976 struct pool_workqueue
*pwq
;
4977 struct worker_pool
*pool
;
4980 mutex_lock(&wq_pool_mutex
);
4982 if (!workqueue_freezing
)
4985 /* clear FREEZING */
4986 for_each_pool(pool
, pi
) {
4987 spin_lock_irq(&pool
->lock
);
4988 WARN_ON_ONCE(!(pool
->flags
& POOL_FREEZING
));
4989 pool
->flags
&= ~POOL_FREEZING
;
4990 spin_unlock_irq(&pool
->lock
);
4993 /* restore max_active and repopulate worklist */
4994 list_for_each_entry(wq
, &workqueues
, list
) {
4995 mutex_lock(&wq
->mutex
);
4996 for_each_pwq(pwq
, wq
)
4997 pwq_adjust_max_active(pwq
);
4998 mutex_unlock(&wq
->mutex
);
5001 workqueue_freezing
= false;
5003 mutex_unlock(&wq_pool_mutex
);
5005 #endif /* CONFIG_FREEZER */
5007 static void __init
wq_numa_init(void)
5012 /* determine NUMA pwq table len - highest node id + 1 */
5014 wq_numa_tbl_len
= max(wq_numa_tbl_len
, node
+ 1);
5016 if (num_possible_nodes() <= 1)
5019 if (wq_disable_numa
) {
5020 pr_info("workqueue: NUMA affinity support disabled\n");
5024 wq_update_unbound_numa_attrs_buf
= alloc_workqueue_attrs(GFP_KERNEL
);
5025 BUG_ON(!wq_update_unbound_numa_attrs_buf
);
5028 * We want masks of possible CPUs of each node which isn't readily
5029 * available. Build one from cpu_to_node() which should have been
5030 * fully initialized by now.
5032 tbl
= kzalloc(wq_numa_tbl_len
* sizeof(tbl
[0]), GFP_KERNEL
);
5036 BUG_ON(!alloc_cpumask_var_node(&tbl
[node
], GFP_KERNEL
,
5037 node_online(node
) ? node
: NUMA_NO_NODE
));
5039 for_each_possible_cpu(cpu
) {
5040 node
= cpu_to_node(cpu
);
5041 if (WARN_ON(node
== NUMA_NO_NODE
)) {
5042 pr_warn("workqueue: NUMA node mapping not available for cpu%d, disabling NUMA support\n", cpu
);
5043 /* happens iff arch is bonkers, let's just proceed */
5046 cpumask_set_cpu(cpu
, tbl
[node
]);
5049 wq_numa_possible_cpumask
= tbl
;
5050 wq_numa_enabled
= true;
5053 static int __init
init_workqueues(void)
5055 int std_nice
[NR_STD_WORKER_POOLS
] = { 0, HIGHPRI_NICE_LEVEL
};
5058 WARN_ON(__alignof__(struct pool_workqueue
) < __alignof__(long long));
5060 pwq_cache
= KMEM_CACHE(pool_workqueue
, SLAB_PANIC
);
5062 cpu_notifier(workqueue_cpu_up_callback
, CPU_PRI_WORKQUEUE_UP
);
5063 hotcpu_notifier(workqueue_cpu_down_callback
, CPU_PRI_WORKQUEUE_DOWN
);
5067 /* initialize CPU pools */
5068 for_each_possible_cpu(cpu
) {
5069 struct worker_pool
*pool
;
5072 for_each_cpu_worker_pool(pool
, cpu
) {
5073 BUG_ON(init_worker_pool(pool
));
5075 cpumask_copy(pool
->attrs
->cpumask
, cpumask_of(cpu
));
5076 pool
->attrs
->nice
= std_nice
[i
++];
5077 pool
->node
= cpu_to_node(cpu
);
5080 mutex_lock(&wq_pool_mutex
);
5081 BUG_ON(worker_pool_assign_id(pool
));
5082 mutex_unlock(&wq_pool_mutex
);
5086 /* create the initial worker */
5087 for_each_online_cpu(cpu
) {
5088 struct worker_pool
*pool
;
5090 for_each_cpu_worker_pool(pool
, cpu
) {
5091 pool
->flags
&= ~POOL_DISASSOCIATED
;
5092 BUG_ON(create_and_start_worker(pool
) < 0);
5096 /* create default unbound and ordered wq attrs */
5097 for (i
= 0; i
< NR_STD_WORKER_POOLS
; i
++) {
5098 struct workqueue_attrs
*attrs
;
5100 BUG_ON(!(attrs
= alloc_workqueue_attrs(GFP_KERNEL
)));
5101 attrs
->nice
= std_nice
[i
];
5102 unbound_std_wq_attrs
[i
] = attrs
;
5105 * An ordered wq should have only one pwq as ordering is
5106 * guaranteed by max_active which is enforced by pwqs.
5107 * Turn off NUMA so that dfl_pwq is used for all nodes.
5109 BUG_ON(!(attrs
= alloc_workqueue_attrs(GFP_KERNEL
)));
5110 attrs
->nice
= std_nice
[i
];
5111 attrs
->no_numa
= true;
5112 ordered_wq_attrs
[i
] = attrs
;
5115 system_wq
= alloc_workqueue("events", 0, 0);
5116 system_highpri_wq
= alloc_workqueue("events_highpri", WQ_HIGHPRI
, 0);
5117 system_long_wq
= alloc_workqueue("events_long", 0, 0);
5118 system_unbound_wq
= alloc_workqueue("events_unbound", WQ_UNBOUND
,
5119 WQ_UNBOUND_MAX_ACTIVE
);
5120 system_freezable_wq
= alloc_workqueue("events_freezable",
5122 system_power_efficient_wq
= alloc_workqueue("events_power_efficient",
5123 WQ_POWER_EFFICIENT
, 0);
5124 system_freezable_power_efficient_wq
= alloc_workqueue("events_freezable_power_efficient",
5125 WQ_FREEZABLE
| WQ_POWER_EFFICIENT
,
5127 BUG_ON(!system_wq
|| !system_highpri_wq
|| !system_long_wq
||
5128 !system_unbound_wq
|| !system_freezable_wq
||
5129 !system_power_efficient_wq
||
5130 !system_freezable_power_efficient_wq
);
5133 early_initcall(init_workqueues
);