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 is one worker pool for each CPU and
20 * one extra for works which are better served by workers which are
21 * not bound to any specific CPU.
23 * Please read Documentation/workqueue.txt for details.
26 #include <linux/export.h>
27 #include <linux/kernel.h>
28 #include <linux/sched.h>
29 #include <linux/init.h>
30 #include <linux/signal.h>
31 #include <linux/completion.h>
32 #include <linux/workqueue.h>
33 #include <linux/slab.h>
34 #include <linux/cpu.h>
35 #include <linux/notifier.h>
36 #include <linux/kthread.h>
37 #include <linux/hardirq.h>
38 #include <linux/mempolicy.h>
39 #include <linux/freezer.h>
40 #include <linux/kallsyms.h>
41 #include <linux/debug_locks.h>
42 #include <linux/lockdep.h>
43 #include <linux/idr.h>
44 #include <linux/jhash.h>
45 #include <linux/hashtable.h>
46 #include <linux/rculist.h>
47 #include <linux/nodemask.h>
48 #include <linux/moduleparam.h>
49 #include <linux/uaccess.h>
51 #include "workqueue_internal.h"
57 * A bound pool is either associated or disassociated with its CPU.
58 * While associated (!DISASSOCIATED), all workers are bound to the
59 * CPU and none has %WORKER_UNBOUND set and concurrency management
62 * While DISASSOCIATED, the cpu may be offline and all workers have
63 * %WORKER_UNBOUND set and concurrency management disabled, and may
64 * be executing on any CPU. The pool behaves as an unbound one.
66 * Note that DISASSOCIATED should be flipped only while holding
67 * manager_mutex to avoid changing binding state while
68 * create_worker() is in progress.
70 POOL_MANAGE_WORKERS
= 1 << 0, /* need to manage workers */
71 POOL_DISASSOCIATED
= 1 << 2, /* cpu can't serve workers */
72 POOL_FREEZING
= 1 << 3, /* freeze in progress */
75 WORKER_STARTED
= 1 << 0, /* started */
76 WORKER_DIE
= 1 << 1, /* die die die */
77 WORKER_IDLE
= 1 << 2, /* is idle */
78 WORKER_PREP
= 1 << 3, /* preparing to run works */
79 WORKER_CPU_INTENSIVE
= 1 << 6, /* cpu intensive */
80 WORKER_UNBOUND
= 1 << 7, /* worker is unbound */
81 WORKER_REBOUND
= 1 << 8, /* worker was rebound */
83 WORKER_NOT_RUNNING
= WORKER_PREP
| WORKER_CPU_INTENSIVE
|
84 WORKER_UNBOUND
| WORKER_REBOUND
,
86 NR_STD_WORKER_POOLS
= 2, /* # standard pools per cpu */
88 UNBOUND_POOL_HASH_ORDER
= 6, /* hashed by pool->attrs */
89 BUSY_WORKER_HASH_ORDER
= 6, /* 64 pointers */
91 MAX_IDLE_WORKERS_RATIO
= 4, /* 1/4 of busy can be idle */
92 IDLE_WORKER_TIMEOUT
= 300 * HZ
, /* keep idle ones for 5 mins */
94 MAYDAY_INITIAL_TIMEOUT
= HZ
/ 100 >= 2 ? HZ
/ 100 : 2,
95 /* call for help after 10ms
97 MAYDAY_INTERVAL
= HZ
/ 10, /* and then every 100ms */
98 CREATE_COOLDOWN
= HZ
, /* time to breath after fail */
101 * Rescue workers are used only on emergencies and shared by
102 * all cpus. Give -20.
104 RESCUER_NICE_LEVEL
= -20,
105 HIGHPRI_NICE_LEVEL
= -20,
111 * Structure fields follow one of the following exclusion rules.
113 * I: Modifiable by initialization/destruction paths and read-only for
116 * P: Preemption protected. Disabling preemption is enough and should
117 * only be modified and accessed from the local cpu.
119 * L: pool->lock protected. Access with pool->lock held.
121 * X: During normal operation, modification requires pool->lock and should
122 * be done only from local cpu. Either disabling preemption on local
123 * cpu or grabbing pool->lock is enough for read access. If
124 * POOL_DISASSOCIATED is set, it's identical to L.
126 * MG: pool->manager_mutex and pool->lock protected. Writes require both
127 * locks. Reads can happen under either lock.
129 * PL: wq_pool_mutex protected.
131 * PR: wq_pool_mutex protected for writes. Sched-RCU protected for reads.
133 * WQ: wq->mutex protected.
135 * WR: wq->mutex protected for writes. Sched-RCU protected for reads.
137 * MD: wq_mayday_lock protected.
140 /* struct worker is defined in workqueue_internal.h */
143 spinlock_t lock
; /* the pool lock */
144 int cpu
; /* I: the associated cpu */
145 int node
; /* I: the associated node ID */
146 int id
; /* I: pool ID */
147 unsigned int flags
; /* X: flags */
149 struct list_head worklist
; /* L: list of pending works */
150 int nr_workers
; /* L: total number of workers */
152 /* nr_idle includes the ones off idle_list for rebinding */
153 int nr_idle
; /* L: currently idle ones */
155 struct list_head idle_list
; /* X: list of idle workers */
156 struct timer_list idle_timer
; /* L: worker idle timeout */
157 struct timer_list mayday_timer
; /* L: SOS timer for workers */
159 /* a workers is either on busy_hash or idle_list, or the manager */
160 DECLARE_HASHTABLE(busy_hash
, BUSY_WORKER_HASH_ORDER
);
161 /* L: hash of busy workers */
163 /* see manage_workers() for details on the two manager mutexes */
164 struct mutex manager_arb
; /* manager arbitration */
165 struct mutex manager_mutex
; /* manager exclusion */
166 struct idr worker_idr
; /* MG: worker IDs and iteration */
168 struct workqueue_attrs
*attrs
; /* I: worker attributes */
169 struct hlist_node hash_node
; /* PL: unbound_pool_hash node */
170 int refcnt
; /* PL: refcnt for unbound pools */
173 * The current concurrency level. As it's likely to be accessed
174 * from other CPUs during try_to_wake_up(), put it in a separate
177 atomic_t nr_running ____cacheline_aligned_in_smp
;
180 * Destruction of pool is sched-RCU protected to allow dereferences
181 * from get_work_pool().
184 } ____cacheline_aligned_in_smp
;
187 * The per-pool workqueue. While queued, the lower WORK_STRUCT_FLAG_BITS
188 * of work_struct->data are used for flags and the remaining high bits
189 * point to the pwq; thus, pwqs need to be aligned at two's power of the
190 * number of flag bits.
192 struct pool_workqueue
{
193 struct worker_pool
*pool
; /* I: the associated pool */
194 struct workqueue_struct
*wq
; /* I: the owning workqueue */
195 int work_color
; /* L: current color */
196 int flush_color
; /* L: flushing color */
197 int refcnt
; /* L: reference count */
198 int nr_in_flight
[WORK_NR_COLORS
];
199 /* L: nr of in_flight works */
200 int nr_active
; /* L: nr of active works */
201 int max_active
; /* L: max active works */
202 struct list_head delayed_works
; /* L: delayed works */
203 struct list_head pwqs_node
; /* WR: node on wq->pwqs */
204 struct list_head mayday_node
; /* MD: node on wq->maydays */
207 * Release of unbound pwq is punted to system_wq. See put_pwq()
208 * and pwq_unbound_release_workfn() for details. pool_workqueue
209 * itself is also sched-RCU protected so that the first pwq can be
210 * determined without grabbing wq->mutex.
212 struct work_struct unbound_release_work
;
214 } __aligned(1 << WORK_STRUCT_FLAG_BITS
);
217 * Structure used to wait for workqueue flush.
220 struct list_head list
; /* WQ: list of flushers */
221 int flush_color
; /* WQ: flush color waiting for */
222 struct completion done
; /* flush completion */
228 * The externally visible workqueue. It relays the issued work items to
229 * the appropriate worker_pool through its pool_workqueues.
231 struct workqueue_struct
{
232 struct list_head pwqs
; /* WR: all pwqs of this wq */
233 struct list_head list
; /* PL: list of all workqueues */
235 struct mutex mutex
; /* protects this wq */
236 int work_color
; /* WQ: current work color */
237 int flush_color
; /* WQ: current flush color */
238 atomic_t nr_pwqs_to_flush
; /* flush in progress */
239 struct wq_flusher
*first_flusher
; /* WQ: first flusher */
240 struct list_head flusher_queue
; /* WQ: flush waiters */
241 struct list_head flusher_overflow
; /* WQ: flush overflow list */
243 struct list_head maydays
; /* MD: pwqs requesting rescue */
244 struct worker
*rescuer
; /* I: rescue worker */
246 int nr_drainers
; /* WQ: drain in progress */
247 int saved_max_active
; /* WQ: saved pwq max_active */
249 struct workqueue_attrs
*unbound_attrs
; /* WQ: only for unbound wqs */
250 struct pool_workqueue
*dfl_pwq
; /* WQ: only for unbound wqs */
253 struct wq_device
*wq_dev
; /* I: for sysfs interface */
255 #ifdef CONFIG_LOCKDEP
256 struct lockdep_map lockdep_map
;
258 char name
[WQ_NAME_LEN
]; /* I: workqueue name */
260 /* hot fields used during command issue, aligned to cacheline */
261 unsigned int flags ____cacheline_aligned
; /* WQ: WQ_* flags */
262 struct pool_workqueue __percpu
*cpu_pwqs
; /* I: per-cpu pwqs */
263 struct pool_workqueue __rcu
*numa_pwq_tbl
[]; /* FR: unbound pwqs indexed by node */
266 static struct kmem_cache
*pwq_cache
;
268 static int wq_numa_tbl_len
; /* highest possible NUMA node id + 1 */
269 static cpumask_var_t
*wq_numa_possible_cpumask
;
270 /* possible CPUs of each node */
272 static bool wq_disable_numa
;
273 module_param_named(disable_numa
, wq_disable_numa
, bool, 0444);
275 static bool wq_numa_enabled
; /* unbound NUMA affinity enabled */
277 /* buf for wq_update_unbound_numa_attrs(), protected by CPU hotplug exclusion */
278 static struct workqueue_attrs
*wq_update_unbound_numa_attrs_buf
;
280 static DEFINE_MUTEX(wq_pool_mutex
); /* protects pools and workqueues list */
281 static DEFINE_SPINLOCK(wq_mayday_lock
); /* protects wq->maydays list */
283 static LIST_HEAD(workqueues
); /* PL: list of all workqueues */
284 static bool workqueue_freezing
; /* PL: have wqs started freezing? */
286 /* the per-cpu worker pools */
287 static DEFINE_PER_CPU_SHARED_ALIGNED(struct worker_pool
[NR_STD_WORKER_POOLS
],
290 static DEFINE_IDR(worker_pool_idr
); /* PR: idr of all pools */
292 /* PL: hash of all unbound pools keyed by pool->attrs */
293 static DEFINE_HASHTABLE(unbound_pool_hash
, UNBOUND_POOL_HASH_ORDER
);
295 /* I: attributes used when instantiating standard unbound pools on demand */
296 static struct workqueue_attrs
*unbound_std_wq_attrs
[NR_STD_WORKER_POOLS
];
298 /* I: attributes used when instantiating ordered pools on demand */
299 static struct workqueue_attrs
*ordered_wq_attrs
[NR_STD_WORKER_POOLS
];
301 struct workqueue_struct
*system_wq __read_mostly
;
302 EXPORT_SYMBOL(system_wq
);
303 struct workqueue_struct
*system_highpri_wq __read_mostly
;
304 EXPORT_SYMBOL_GPL(system_highpri_wq
);
305 struct workqueue_struct
*system_long_wq __read_mostly
;
306 EXPORT_SYMBOL_GPL(system_long_wq
);
307 struct workqueue_struct
*system_unbound_wq __read_mostly
;
308 EXPORT_SYMBOL_GPL(system_unbound_wq
);
309 struct workqueue_struct
*system_freezable_wq __read_mostly
;
310 EXPORT_SYMBOL_GPL(system_freezable_wq
);
312 static int worker_thread(void *__worker
);
313 static void copy_workqueue_attrs(struct workqueue_attrs
*to
,
314 const struct workqueue_attrs
*from
);
316 #define CREATE_TRACE_POINTS
317 #include <trace/events/workqueue.h>
319 #define assert_rcu_or_pool_mutex() \
320 rcu_lockdep_assert(rcu_read_lock_sched_held() || \
321 lockdep_is_held(&wq_pool_mutex), \
322 "sched RCU or wq_pool_mutex should be held")
324 #define assert_rcu_or_wq_mutex(wq) \
325 rcu_lockdep_assert(rcu_read_lock_sched_held() || \
326 lockdep_is_held(&wq->mutex), \
327 "sched RCU or wq->mutex should be held")
329 #ifdef CONFIG_LOCKDEP
330 #define assert_manager_or_pool_lock(pool) \
331 WARN_ONCE(debug_locks && \
332 !lockdep_is_held(&(pool)->manager_mutex) && \
333 !lockdep_is_held(&(pool)->lock), \
334 "pool->manager_mutex or ->lock should be held")
336 #define assert_manager_or_pool_lock(pool) do { } while (0)
339 #define for_each_cpu_worker_pool(pool, cpu) \
340 for ((pool) = &per_cpu(cpu_worker_pools, cpu)[0]; \
341 (pool) < &per_cpu(cpu_worker_pools, cpu)[NR_STD_WORKER_POOLS]; \
345 * for_each_pool - iterate through all worker_pools in the system
346 * @pool: iteration cursor
347 * @pi: integer used for iteration
349 * This must be called either with wq_pool_mutex held or sched RCU read
350 * locked. If the pool needs to be used beyond the locking in effect, the
351 * caller is responsible for guaranteeing that the pool stays online.
353 * The if/else clause exists only for the lockdep assertion and can be
356 #define for_each_pool(pool, pi) \
357 idr_for_each_entry(&worker_pool_idr, pool, pi) \
358 if (({ assert_rcu_or_pool_mutex(); false; })) { } \
362 * for_each_pool_worker - iterate through all workers of a worker_pool
363 * @worker: iteration cursor
364 * @wi: integer used for iteration
365 * @pool: worker_pool to iterate workers of
367 * This must be called with either @pool->manager_mutex or ->lock held.
369 * The if/else clause exists only for the lockdep assertion and can be
372 #define for_each_pool_worker(worker, wi, pool) \
373 idr_for_each_entry(&(pool)->worker_idr, (worker), (wi)) \
374 if (({ assert_manager_or_pool_lock((pool)); false; })) { } \
378 * for_each_pwq - iterate through all pool_workqueues of the specified workqueue
379 * @pwq: iteration cursor
380 * @wq: the target workqueue
382 * This must be called either with wq->mutex held or sched RCU read locked.
383 * If the pwq needs to be used beyond the locking in effect, the caller is
384 * responsible for guaranteeing that the pwq stays online.
386 * The if/else clause exists only for the lockdep assertion and can be
389 #define for_each_pwq(pwq, wq) \
390 list_for_each_entry_rcu((pwq), &(wq)->pwqs, pwqs_node) \
391 if (({ assert_rcu_or_wq_mutex(wq); false; })) { } \
394 #ifdef CONFIG_DEBUG_OBJECTS_WORK
396 static struct debug_obj_descr work_debug_descr
;
398 static void *work_debug_hint(void *addr
)
400 return ((struct work_struct
*) addr
)->func
;
404 * fixup_init is called when:
405 * - an active object is initialized
407 static int work_fixup_init(void *addr
, enum debug_obj_state state
)
409 struct work_struct
*work
= addr
;
412 case ODEBUG_STATE_ACTIVE
:
413 cancel_work_sync(work
);
414 debug_object_init(work
, &work_debug_descr
);
422 * fixup_activate is called when:
423 * - an active object is activated
424 * - an unknown object is activated (might be a statically initialized object)
426 static int work_fixup_activate(void *addr
, enum debug_obj_state state
)
428 struct work_struct
*work
= addr
;
432 case ODEBUG_STATE_NOTAVAILABLE
:
434 * This is not really a fixup. The work struct was
435 * statically initialized. We just make sure that it
436 * is tracked in the object tracker.
438 if (test_bit(WORK_STRUCT_STATIC_BIT
, work_data_bits(work
))) {
439 debug_object_init(work
, &work_debug_descr
);
440 debug_object_activate(work
, &work_debug_descr
);
446 case ODEBUG_STATE_ACTIVE
:
455 * fixup_free is called when:
456 * - an active object is freed
458 static int work_fixup_free(void *addr
, enum debug_obj_state state
)
460 struct work_struct
*work
= addr
;
463 case ODEBUG_STATE_ACTIVE
:
464 cancel_work_sync(work
);
465 debug_object_free(work
, &work_debug_descr
);
472 static struct debug_obj_descr work_debug_descr
= {
473 .name
= "work_struct",
474 .debug_hint
= work_debug_hint
,
475 .fixup_init
= work_fixup_init
,
476 .fixup_activate
= work_fixup_activate
,
477 .fixup_free
= work_fixup_free
,
480 static inline void debug_work_activate(struct work_struct
*work
)
482 debug_object_activate(work
, &work_debug_descr
);
485 static inline void debug_work_deactivate(struct work_struct
*work
)
487 debug_object_deactivate(work
, &work_debug_descr
);
490 void __init_work(struct work_struct
*work
, int onstack
)
493 debug_object_init_on_stack(work
, &work_debug_descr
);
495 debug_object_init(work
, &work_debug_descr
);
497 EXPORT_SYMBOL_GPL(__init_work
);
499 void destroy_work_on_stack(struct work_struct
*work
)
501 debug_object_free(work
, &work_debug_descr
);
503 EXPORT_SYMBOL_GPL(destroy_work_on_stack
);
506 static inline void debug_work_activate(struct work_struct
*work
) { }
507 static inline void debug_work_deactivate(struct work_struct
*work
) { }
510 /* allocate ID and assign it to @pool */
511 static int worker_pool_assign_id(struct worker_pool
*pool
)
515 lockdep_assert_held(&wq_pool_mutex
);
517 ret
= idr_alloc(&worker_pool_idr
, pool
, 0, 0, GFP_KERNEL
);
526 * unbound_pwq_by_node - return the unbound pool_workqueue for the given node
527 * @wq: the target workqueue
530 * This must be called either with pwq_lock held or sched RCU read locked.
531 * If the pwq needs to be used beyond the locking in effect, the caller is
532 * responsible for guaranteeing that the pwq stays online.
534 static struct pool_workqueue
*unbound_pwq_by_node(struct workqueue_struct
*wq
,
537 assert_rcu_or_wq_mutex(wq
);
538 return rcu_dereference_raw(wq
->numa_pwq_tbl
[node
]);
541 static unsigned int work_color_to_flags(int color
)
543 return color
<< WORK_STRUCT_COLOR_SHIFT
;
546 static int get_work_color(struct work_struct
*work
)
548 return (*work_data_bits(work
) >> WORK_STRUCT_COLOR_SHIFT
) &
549 ((1 << WORK_STRUCT_COLOR_BITS
) - 1);
552 static int work_next_color(int color
)
554 return (color
+ 1) % WORK_NR_COLORS
;
558 * While queued, %WORK_STRUCT_PWQ is set and non flag bits of a work's data
559 * contain the pointer to the queued pwq. Once execution starts, the flag
560 * is cleared and the high bits contain OFFQ flags and pool ID.
562 * set_work_pwq(), set_work_pool_and_clear_pending(), mark_work_canceling()
563 * and clear_work_data() can be used to set the pwq, pool or clear
564 * work->data. These functions should only be called while the work is
565 * owned - ie. while the PENDING bit is set.
567 * get_work_pool() and get_work_pwq() can be used to obtain the pool or pwq
568 * corresponding to a work. Pool is available once the work has been
569 * queued anywhere after initialization until it is sync canceled. pwq is
570 * available only while the work item is queued.
572 * %WORK_OFFQ_CANCELING is used to mark a work item which is being
573 * canceled. While being canceled, a work item may have its PENDING set
574 * but stay off timer and worklist for arbitrarily long and nobody should
575 * try to steal the PENDING bit.
577 static inline void set_work_data(struct work_struct
*work
, unsigned long data
,
580 WARN_ON_ONCE(!work_pending(work
));
581 atomic_long_set(&work
->data
, data
| flags
| work_static(work
));
584 static void set_work_pwq(struct work_struct
*work
, struct pool_workqueue
*pwq
,
585 unsigned long extra_flags
)
587 set_work_data(work
, (unsigned long)pwq
,
588 WORK_STRUCT_PENDING
| WORK_STRUCT_PWQ
| extra_flags
);
591 static void set_work_pool_and_keep_pending(struct work_struct
*work
,
594 set_work_data(work
, (unsigned long)pool_id
<< WORK_OFFQ_POOL_SHIFT
,
595 WORK_STRUCT_PENDING
);
598 static void set_work_pool_and_clear_pending(struct work_struct
*work
,
602 * The following wmb is paired with the implied mb in
603 * test_and_set_bit(PENDING) and ensures all updates to @work made
604 * here are visible to and precede any updates by the next PENDING
608 set_work_data(work
, (unsigned long)pool_id
<< WORK_OFFQ_POOL_SHIFT
, 0);
611 static void clear_work_data(struct work_struct
*work
)
613 smp_wmb(); /* see set_work_pool_and_clear_pending() */
614 set_work_data(work
, WORK_STRUCT_NO_POOL
, 0);
617 static struct pool_workqueue
*get_work_pwq(struct work_struct
*work
)
619 unsigned long data
= atomic_long_read(&work
->data
);
621 if (data
& WORK_STRUCT_PWQ
)
622 return (void *)(data
& WORK_STRUCT_WQ_DATA_MASK
);
628 * get_work_pool - return the worker_pool a given work was associated with
629 * @work: the work item of interest
631 * Return the worker_pool @work was last associated with. %NULL if none.
633 * Pools are created and destroyed under wq_pool_mutex, and allows read
634 * access under sched-RCU read lock. As such, this function should be
635 * called under wq_pool_mutex or with preemption disabled.
637 * All fields of the returned pool are accessible as long as the above
638 * mentioned locking is in effect. If the returned pool needs to be used
639 * beyond the critical section, the caller is responsible for ensuring the
640 * returned pool is and stays online.
642 static struct worker_pool
*get_work_pool(struct work_struct
*work
)
644 unsigned long data
= atomic_long_read(&work
->data
);
647 assert_rcu_or_pool_mutex();
649 if (data
& WORK_STRUCT_PWQ
)
650 return ((struct pool_workqueue
*)
651 (data
& WORK_STRUCT_WQ_DATA_MASK
))->pool
;
653 pool_id
= data
>> WORK_OFFQ_POOL_SHIFT
;
654 if (pool_id
== WORK_OFFQ_POOL_NONE
)
657 return idr_find(&worker_pool_idr
, pool_id
);
661 * get_work_pool_id - return the worker pool ID a given work is associated with
662 * @work: the work item of interest
664 * Return the worker_pool ID @work was last associated with.
665 * %WORK_OFFQ_POOL_NONE if none.
667 static int get_work_pool_id(struct work_struct
*work
)
669 unsigned long data
= atomic_long_read(&work
->data
);
671 if (data
& WORK_STRUCT_PWQ
)
672 return ((struct pool_workqueue
*)
673 (data
& WORK_STRUCT_WQ_DATA_MASK
))->pool
->id
;
675 return data
>> WORK_OFFQ_POOL_SHIFT
;
678 static void mark_work_canceling(struct work_struct
*work
)
680 unsigned long pool_id
= get_work_pool_id(work
);
682 pool_id
<<= WORK_OFFQ_POOL_SHIFT
;
683 set_work_data(work
, pool_id
| WORK_OFFQ_CANCELING
, WORK_STRUCT_PENDING
);
686 static bool work_is_canceling(struct work_struct
*work
)
688 unsigned long data
= atomic_long_read(&work
->data
);
690 return !(data
& WORK_STRUCT_PWQ
) && (data
& WORK_OFFQ_CANCELING
);
694 * Policy functions. These define the policies on how the global worker
695 * pools are managed. Unless noted otherwise, these functions assume that
696 * they're being called with pool->lock held.
699 static bool __need_more_worker(struct worker_pool
*pool
)
701 return !atomic_read(&pool
->nr_running
);
705 * Need to wake up a worker? Called from anything but currently
708 * Note that, because unbound workers never contribute to nr_running, this
709 * function will always return %true for unbound pools as long as the
710 * worklist isn't empty.
712 static bool need_more_worker(struct worker_pool
*pool
)
714 return !list_empty(&pool
->worklist
) && __need_more_worker(pool
);
717 /* Can I start working? Called from busy but !running workers. */
718 static bool may_start_working(struct worker_pool
*pool
)
720 return pool
->nr_idle
;
723 /* Do I need to keep working? Called from currently running workers. */
724 static bool keep_working(struct worker_pool
*pool
)
726 return !list_empty(&pool
->worklist
) &&
727 atomic_read(&pool
->nr_running
) <= 1;
730 /* Do we need a new worker? Called from manager. */
731 static bool need_to_create_worker(struct worker_pool
*pool
)
733 return need_more_worker(pool
) && !may_start_working(pool
);
736 /* Do I need to be the manager? */
737 static bool need_to_manage_workers(struct worker_pool
*pool
)
739 return need_to_create_worker(pool
) ||
740 (pool
->flags
& POOL_MANAGE_WORKERS
);
743 /* Do we have too many workers and should some go away? */
744 static bool too_many_workers(struct worker_pool
*pool
)
746 bool managing
= mutex_is_locked(&pool
->manager_arb
);
747 int nr_idle
= pool
->nr_idle
+ managing
; /* manager is considered idle */
748 int nr_busy
= pool
->nr_workers
- nr_idle
;
751 * nr_idle and idle_list may disagree if idle rebinding is in
752 * progress. Never return %true if idle_list is empty.
754 if (list_empty(&pool
->idle_list
))
757 return nr_idle
> 2 && (nr_idle
- 2) * MAX_IDLE_WORKERS_RATIO
>= nr_busy
;
764 /* Return the first worker. Safe with preemption disabled */
765 static struct worker
*first_worker(struct worker_pool
*pool
)
767 if (unlikely(list_empty(&pool
->idle_list
)))
770 return list_first_entry(&pool
->idle_list
, struct worker
, entry
);
774 * wake_up_worker - wake up an idle worker
775 * @pool: worker pool to wake worker from
777 * Wake up the first idle worker of @pool.
780 * spin_lock_irq(pool->lock).
782 static void wake_up_worker(struct worker_pool
*pool
)
784 struct worker
*worker
= first_worker(pool
);
787 wake_up_process(worker
->task
);
791 * wq_worker_waking_up - a worker is waking up
792 * @task: task waking up
793 * @cpu: CPU @task is waking up to
795 * This function is called during try_to_wake_up() when a worker is
799 * spin_lock_irq(rq->lock)
801 void wq_worker_waking_up(struct task_struct
*task
, int cpu
)
803 struct worker
*worker
= kthread_data(task
);
805 if (!(worker
->flags
& WORKER_NOT_RUNNING
)) {
806 WARN_ON_ONCE(worker
->pool
->cpu
!= cpu
);
807 atomic_inc(&worker
->pool
->nr_running
);
812 * wq_worker_sleeping - a worker is going to sleep
813 * @task: task going to sleep
814 * @cpu: CPU in question, must be the current CPU number
816 * This function is called during schedule() when a busy worker is
817 * going to sleep. Worker on the same cpu can be woken up by
818 * returning pointer to its task.
821 * spin_lock_irq(rq->lock)
824 * Worker task on @cpu to wake up, %NULL if none.
826 struct task_struct
*wq_worker_sleeping(struct task_struct
*task
, int cpu
)
828 struct worker
*worker
= kthread_data(task
), *to_wakeup
= NULL
;
829 struct worker_pool
*pool
;
832 * Rescuers, which may not have all the fields set up like normal
833 * workers, also reach here, let's not access anything before
834 * checking NOT_RUNNING.
836 if (worker
->flags
& WORKER_NOT_RUNNING
)
841 /* this can only happen on the local cpu */
842 if (WARN_ON_ONCE(cpu
!= raw_smp_processor_id()))
846 * The counterpart of the following dec_and_test, implied mb,
847 * worklist not empty test sequence is in insert_work().
848 * Please read comment there.
850 * NOT_RUNNING is clear. This means that we're bound to and
851 * running on the local cpu w/ rq lock held and preemption
852 * disabled, which in turn means that none else could be
853 * manipulating idle_list, so dereferencing idle_list without pool
856 if (atomic_dec_and_test(&pool
->nr_running
) &&
857 !list_empty(&pool
->worklist
))
858 to_wakeup
= first_worker(pool
);
859 return to_wakeup
? to_wakeup
->task
: NULL
;
863 * worker_set_flags - set worker flags and adjust nr_running accordingly
865 * @flags: flags to set
866 * @wakeup: wakeup an idle worker if necessary
868 * Set @flags in @worker->flags and adjust nr_running accordingly. If
869 * nr_running becomes zero and @wakeup is %true, an idle worker is
873 * spin_lock_irq(pool->lock)
875 static inline void worker_set_flags(struct worker
*worker
, unsigned int flags
,
878 struct worker_pool
*pool
= worker
->pool
;
880 WARN_ON_ONCE(worker
->task
!= current
);
883 * If transitioning into NOT_RUNNING, adjust nr_running and
884 * wake up an idle worker as necessary if requested by
887 if ((flags
& WORKER_NOT_RUNNING
) &&
888 !(worker
->flags
& WORKER_NOT_RUNNING
)) {
890 if (atomic_dec_and_test(&pool
->nr_running
) &&
891 !list_empty(&pool
->worklist
))
892 wake_up_worker(pool
);
894 atomic_dec(&pool
->nr_running
);
897 worker
->flags
|= flags
;
901 * worker_clr_flags - clear worker flags and adjust nr_running accordingly
903 * @flags: flags to clear
905 * Clear @flags in @worker->flags and adjust nr_running accordingly.
908 * spin_lock_irq(pool->lock)
910 static inline void worker_clr_flags(struct worker
*worker
, unsigned int flags
)
912 struct worker_pool
*pool
= worker
->pool
;
913 unsigned int oflags
= worker
->flags
;
915 WARN_ON_ONCE(worker
->task
!= current
);
917 worker
->flags
&= ~flags
;
920 * If transitioning out of NOT_RUNNING, increment nr_running. Note
921 * that the nested NOT_RUNNING is not a noop. NOT_RUNNING is mask
922 * of multiple flags, not a single flag.
924 if ((flags
& WORKER_NOT_RUNNING
) && (oflags
& WORKER_NOT_RUNNING
))
925 if (!(worker
->flags
& WORKER_NOT_RUNNING
))
926 atomic_inc(&pool
->nr_running
);
930 * find_worker_executing_work - find worker which is executing a work
931 * @pool: pool of interest
932 * @work: work to find worker for
934 * Find a worker which is executing @work on @pool by searching
935 * @pool->busy_hash which is keyed by the address of @work. For a worker
936 * to match, its current execution should match the address of @work and
937 * its work function. This is to avoid unwanted dependency between
938 * unrelated work executions through a work item being recycled while still
941 * This is a bit tricky. A work item may be freed once its execution
942 * starts and nothing prevents the freed area from being recycled for
943 * another work item. If the same work item address ends up being reused
944 * before the original execution finishes, workqueue will identify the
945 * recycled work item as currently executing and make it wait until the
946 * current execution finishes, introducing an unwanted dependency.
948 * This function checks the work item address and work function to avoid
949 * false positives. Note that this isn't complete as one may construct a
950 * work function which can introduce dependency onto itself through a
951 * recycled work item. Well, if somebody wants to shoot oneself in the
952 * foot that badly, there's only so much we can do, and if such deadlock
953 * actually occurs, it should be easy to locate the culprit work function.
956 * spin_lock_irq(pool->lock).
959 * Pointer to worker which is executing @work if found, NULL
962 static struct worker
*find_worker_executing_work(struct worker_pool
*pool
,
963 struct work_struct
*work
)
965 struct worker
*worker
;
967 hash_for_each_possible(pool
->busy_hash
, worker
, hentry
,
969 if (worker
->current_work
== work
&&
970 worker
->current_func
== work
->func
)
977 * move_linked_works - move linked works to a list
978 * @work: start of series of works to be scheduled
979 * @head: target list to append @work to
980 * @nextp: out paramter for nested worklist walking
982 * Schedule linked works starting from @work to @head. Work series to
983 * be scheduled starts at @work and includes any consecutive work with
984 * WORK_STRUCT_LINKED set in its predecessor.
986 * If @nextp is not NULL, it's updated to point to the next work of
987 * the last scheduled work. This allows move_linked_works() to be
988 * nested inside outer list_for_each_entry_safe().
991 * spin_lock_irq(pool->lock).
993 static void move_linked_works(struct work_struct
*work
, struct list_head
*head
,
994 struct work_struct
**nextp
)
996 struct work_struct
*n
;
999 * Linked worklist will always end before the end of the list,
1000 * use NULL for list head.
1002 list_for_each_entry_safe_from(work
, n
, NULL
, entry
) {
1003 list_move_tail(&work
->entry
, head
);
1004 if (!(*work_data_bits(work
) & WORK_STRUCT_LINKED
))
1009 * If we're already inside safe list traversal and have moved
1010 * multiple works to the scheduled queue, the next position
1011 * needs to be updated.
1018 * get_pwq - get an extra reference on the specified pool_workqueue
1019 * @pwq: pool_workqueue to get
1021 * Obtain an extra reference on @pwq. The caller should guarantee that
1022 * @pwq has positive refcnt and be holding the matching pool->lock.
1024 static void get_pwq(struct pool_workqueue
*pwq
)
1026 lockdep_assert_held(&pwq
->pool
->lock
);
1027 WARN_ON_ONCE(pwq
->refcnt
<= 0);
1032 * put_pwq - put a pool_workqueue reference
1033 * @pwq: pool_workqueue to put
1035 * Drop a reference of @pwq. If its refcnt reaches zero, schedule its
1036 * destruction. The caller should be holding the matching pool->lock.
1038 static void put_pwq(struct pool_workqueue
*pwq
)
1040 lockdep_assert_held(&pwq
->pool
->lock
);
1041 if (likely(--pwq
->refcnt
))
1043 if (WARN_ON_ONCE(!(pwq
->wq
->flags
& WQ_UNBOUND
)))
1046 * @pwq can't be released under pool->lock, bounce to
1047 * pwq_unbound_release_workfn(). This never recurses on the same
1048 * pool->lock as this path is taken only for unbound workqueues and
1049 * the release work item is scheduled on a per-cpu workqueue. To
1050 * avoid lockdep warning, unbound pool->locks are given lockdep
1051 * subclass of 1 in get_unbound_pool().
1053 schedule_work(&pwq
->unbound_release_work
);
1057 * put_pwq_unlocked - put_pwq() with surrounding pool lock/unlock
1058 * @pwq: pool_workqueue to put (can be %NULL)
1060 * put_pwq() with locking. This function also allows %NULL @pwq.
1062 static void put_pwq_unlocked(struct pool_workqueue
*pwq
)
1066 * As both pwqs and pools are sched-RCU protected, the
1067 * following lock operations are safe.
1069 spin_lock_irq(&pwq
->pool
->lock
);
1071 spin_unlock_irq(&pwq
->pool
->lock
);
1075 static void pwq_activate_delayed_work(struct work_struct
*work
)
1077 struct pool_workqueue
*pwq
= get_work_pwq(work
);
1079 trace_workqueue_activate_work(work
);
1080 move_linked_works(work
, &pwq
->pool
->worklist
, NULL
);
1081 __clear_bit(WORK_STRUCT_DELAYED_BIT
, work_data_bits(work
));
1085 static void pwq_activate_first_delayed(struct pool_workqueue
*pwq
)
1087 struct work_struct
*work
= list_first_entry(&pwq
->delayed_works
,
1088 struct work_struct
, entry
);
1090 pwq_activate_delayed_work(work
);
1094 * pwq_dec_nr_in_flight - decrement pwq's nr_in_flight
1095 * @pwq: pwq of interest
1096 * @color: color of work which left the queue
1098 * A work either has completed or is removed from pending queue,
1099 * decrement nr_in_flight of its pwq and handle workqueue flushing.
1102 * spin_lock_irq(pool->lock).
1104 static void pwq_dec_nr_in_flight(struct pool_workqueue
*pwq
, int color
)
1106 /* uncolored work items don't participate in flushing or nr_active */
1107 if (color
== WORK_NO_COLOR
)
1110 pwq
->nr_in_flight
[color
]--;
1113 if (!list_empty(&pwq
->delayed_works
)) {
1114 /* one down, submit a delayed one */
1115 if (pwq
->nr_active
< pwq
->max_active
)
1116 pwq_activate_first_delayed(pwq
);
1119 /* is flush in progress and are we at the flushing tip? */
1120 if (likely(pwq
->flush_color
!= color
))
1123 /* are there still in-flight works? */
1124 if (pwq
->nr_in_flight
[color
])
1127 /* this pwq is done, clear flush_color */
1128 pwq
->flush_color
= -1;
1131 * If this was the last pwq, wake up the first flusher. It
1132 * will handle the rest.
1134 if (atomic_dec_and_test(&pwq
->wq
->nr_pwqs_to_flush
))
1135 complete(&pwq
->wq
->first_flusher
->done
);
1141 * try_to_grab_pending - steal work item from worklist and disable irq
1142 * @work: work item to steal
1143 * @is_dwork: @work is a delayed_work
1144 * @flags: place to store irq state
1146 * Try to grab PENDING bit of @work. This function can handle @work in any
1147 * stable state - idle, on timer or on worklist. Return values are
1149 * 1 if @work was pending and we successfully stole PENDING
1150 * 0 if @work was idle and we claimed PENDING
1151 * -EAGAIN if PENDING couldn't be grabbed at the moment, safe to busy-retry
1152 * -ENOENT if someone else is canceling @work, this state may persist
1153 * for arbitrarily long
1155 * On >= 0 return, the caller owns @work's PENDING bit. To avoid getting
1156 * interrupted while holding PENDING and @work off queue, irq must be
1157 * disabled on entry. This, combined with delayed_work->timer being
1158 * irqsafe, ensures that we return -EAGAIN for finite short period of time.
1160 * On successful return, >= 0, irq is disabled and the caller is
1161 * responsible for releasing it using local_irq_restore(*@flags).
1163 * This function is safe to call from any context including IRQ handler.
1165 static int try_to_grab_pending(struct work_struct
*work
, bool is_dwork
,
1166 unsigned long *flags
)
1168 struct worker_pool
*pool
;
1169 struct pool_workqueue
*pwq
;
1171 local_irq_save(*flags
);
1173 /* try to steal the timer if it exists */
1175 struct delayed_work
*dwork
= to_delayed_work(work
);
1178 * dwork->timer is irqsafe. If del_timer() fails, it's
1179 * guaranteed that the timer is not queued anywhere and not
1180 * running on the local CPU.
1182 if (likely(del_timer(&dwork
->timer
)))
1186 /* try to claim PENDING the normal way */
1187 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT
, work_data_bits(work
)))
1191 * The queueing is in progress, or it is already queued. Try to
1192 * steal it from ->worklist without clearing WORK_STRUCT_PENDING.
1194 pool
= get_work_pool(work
);
1198 spin_lock(&pool
->lock
);
1200 * work->data is guaranteed to point to pwq only while the work
1201 * item is queued on pwq->wq, and both updating work->data to point
1202 * to pwq on queueing and to pool on dequeueing are done under
1203 * pwq->pool->lock. This in turn guarantees that, if work->data
1204 * points to pwq which is associated with a locked pool, the work
1205 * item is currently queued on that pool.
1207 pwq
= get_work_pwq(work
);
1208 if (pwq
&& pwq
->pool
== pool
) {
1209 debug_work_deactivate(work
);
1212 * A delayed work item cannot be grabbed directly because
1213 * it might have linked NO_COLOR work items which, if left
1214 * on the delayed_list, will confuse pwq->nr_active
1215 * management later on and cause stall. Make sure the work
1216 * item is activated before grabbing.
1218 if (*work_data_bits(work
) & WORK_STRUCT_DELAYED
)
1219 pwq_activate_delayed_work(work
);
1221 list_del_init(&work
->entry
);
1222 pwq_dec_nr_in_flight(get_work_pwq(work
), get_work_color(work
));
1224 /* work->data points to pwq iff queued, point to pool */
1225 set_work_pool_and_keep_pending(work
, pool
->id
);
1227 spin_unlock(&pool
->lock
);
1230 spin_unlock(&pool
->lock
);
1232 local_irq_restore(*flags
);
1233 if (work_is_canceling(work
))
1240 * insert_work - insert a work into a pool
1241 * @pwq: pwq @work belongs to
1242 * @work: work to insert
1243 * @head: insertion point
1244 * @extra_flags: extra WORK_STRUCT_* flags to set
1246 * Insert @work which belongs to @pwq after @head. @extra_flags is or'd to
1247 * work_struct flags.
1250 * spin_lock_irq(pool->lock).
1252 static void insert_work(struct pool_workqueue
*pwq
, struct work_struct
*work
,
1253 struct list_head
*head
, unsigned int extra_flags
)
1255 struct worker_pool
*pool
= pwq
->pool
;
1257 /* we own @work, set data and link */
1258 set_work_pwq(work
, pwq
, extra_flags
);
1259 list_add_tail(&work
->entry
, head
);
1263 * Ensure either wq_worker_sleeping() sees the above
1264 * list_add_tail() or we see zero nr_running to avoid workers lying
1265 * around lazily while there are works to be processed.
1269 if (__need_more_worker(pool
))
1270 wake_up_worker(pool
);
1274 * Test whether @work is being queued from another work executing on the
1277 static bool is_chained_work(struct workqueue_struct
*wq
)
1279 struct worker
*worker
;
1281 worker
= current_wq_worker();
1283 * Return %true iff I'm a worker execuing a work item on @wq. If
1284 * I'm @worker, it's safe to dereference it without locking.
1286 return worker
&& worker
->current_pwq
->wq
== wq
;
1289 static void __queue_work(int cpu
, struct workqueue_struct
*wq
,
1290 struct work_struct
*work
)
1292 struct pool_workqueue
*pwq
;
1293 struct worker_pool
*last_pool
;
1294 struct list_head
*worklist
;
1295 unsigned int work_flags
;
1296 unsigned int req_cpu
= cpu
;
1299 * While a work item is PENDING && off queue, a task trying to
1300 * steal the PENDING will busy-loop waiting for it to either get
1301 * queued or lose PENDING. Grabbing PENDING and queueing should
1302 * happen with IRQ disabled.
1304 WARN_ON_ONCE(!irqs_disabled());
1306 debug_work_activate(work
);
1308 /* if dying, only works from the same workqueue are allowed */
1309 if (unlikely(wq
->flags
& __WQ_DRAINING
) &&
1310 WARN_ON_ONCE(!is_chained_work(wq
)))
1313 if (req_cpu
== WORK_CPU_UNBOUND
)
1314 cpu
= raw_smp_processor_id();
1316 /* pwq which will be used unless @work is executing elsewhere */
1317 if (!(wq
->flags
& WQ_UNBOUND
))
1318 pwq
= per_cpu_ptr(wq
->cpu_pwqs
, cpu
);
1320 pwq
= unbound_pwq_by_node(wq
, cpu_to_node(cpu
));
1323 * If @work was previously on a different pool, it might still be
1324 * running there, in which case the work needs to be queued on that
1325 * pool to guarantee non-reentrancy.
1327 last_pool
= get_work_pool(work
);
1328 if (last_pool
&& last_pool
!= pwq
->pool
) {
1329 struct worker
*worker
;
1331 spin_lock(&last_pool
->lock
);
1333 worker
= find_worker_executing_work(last_pool
, work
);
1335 if (worker
&& worker
->current_pwq
->wq
== wq
) {
1336 pwq
= worker
->current_pwq
;
1338 /* meh... not running there, queue here */
1339 spin_unlock(&last_pool
->lock
);
1340 spin_lock(&pwq
->pool
->lock
);
1343 spin_lock(&pwq
->pool
->lock
);
1347 * pwq is determined and locked. For unbound pools, we could have
1348 * raced with pwq release and it could already be dead. If its
1349 * refcnt is zero, repeat pwq selection. Note that pwqs never die
1350 * without another pwq replacing it in the numa_pwq_tbl or while
1351 * work items are executing on it, so the retrying is guaranteed to
1352 * make forward-progress.
1354 if (unlikely(!pwq
->refcnt
)) {
1355 if (wq
->flags
& WQ_UNBOUND
) {
1356 spin_unlock(&pwq
->pool
->lock
);
1361 WARN_ONCE(true, "workqueue: per-cpu pwq for %s on cpu%d has 0 refcnt",
1365 /* pwq determined, queue */
1366 trace_workqueue_queue_work(req_cpu
, pwq
, work
);
1368 if (WARN_ON(!list_empty(&work
->entry
))) {
1369 spin_unlock(&pwq
->pool
->lock
);
1373 pwq
->nr_in_flight
[pwq
->work_color
]++;
1374 work_flags
= work_color_to_flags(pwq
->work_color
);
1376 if (likely(pwq
->nr_active
< pwq
->max_active
)) {
1377 trace_workqueue_activate_work(work
);
1379 worklist
= &pwq
->pool
->worklist
;
1381 work_flags
|= WORK_STRUCT_DELAYED
;
1382 worklist
= &pwq
->delayed_works
;
1385 insert_work(pwq
, work
, worklist
, work_flags
);
1387 spin_unlock(&pwq
->pool
->lock
);
1391 * queue_work_on - queue work on specific cpu
1392 * @cpu: CPU number to execute work on
1393 * @wq: workqueue to use
1394 * @work: work to queue
1396 * Returns %false if @work was already on a queue, %true otherwise.
1398 * We queue the work to a specific CPU, the caller must ensure it
1401 bool queue_work_on(int cpu
, struct workqueue_struct
*wq
,
1402 struct work_struct
*work
)
1405 unsigned long flags
;
1407 local_irq_save(flags
);
1409 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT
, work_data_bits(work
))) {
1410 __queue_work(cpu
, wq
, work
);
1414 local_irq_restore(flags
);
1417 EXPORT_SYMBOL(queue_work_on
);
1419 void delayed_work_timer_fn(unsigned long __data
)
1421 struct delayed_work
*dwork
= (struct delayed_work
*)__data
;
1423 /* should have been called from irqsafe timer with irq already off */
1424 __queue_work(dwork
->cpu
, dwork
->wq
, &dwork
->work
);
1426 EXPORT_SYMBOL(delayed_work_timer_fn
);
1428 static void __queue_delayed_work(int cpu
, struct workqueue_struct
*wq
,
1429 struct delayed_work
*dwork
, unsigned long delay
)
1431 struct timer_list
*timer
= &dwork
->timer
;
1432 struct work_struct
*work
= &dwork
->work
;
1434 WARN_ON_ONCE(timer
->function
!= delayed_work_timer_fn
||
1435 timer
->data
!= (unsigned long)dwork
);
1436 WARN_ON_ONCE(timer_pending(timer
));
1437 WARN_ON_ONCE(!list_empty(&work
->entry
));
1440 * If @delay is 0, queue @dwork->work immediately. This is for
1441 * both optimization and correctness. The earliest @timer can
1442 * expire is on the closest next tick and delayed_work users depend
1443 * on that there's no such delay when @delay is 0.
1446 __queue_work(cpu
, wq
, &dwork
->work
);
1450 timer_stats_timer_set_start_info(&dwork
->timer
);
1454 timer
->expires
= jiffies
+ delay
;
1456 if (unlikely(cpu
!= WORK_CPU_UNBOUND
))
1457 add_timer_on(timer
, cpu
);
1463 * queue_delayed_work_on - queue work on specific CPU after delay
1464 * @cpu: CPU number to execute work on
1465 * @wq: workqueue to use
1466 * @dwork: work to queue
1467 * @delay: number of jiffies to wait before queueing
1469 * Returns %false if @work was already on a queue, %true otherwise. If
1470 * @delay is zero and @dwork is idle, it will be scheduled for immediate
1473 bool queue_delayed_work_on(int cpu
, struct workqueue_struct
*wq
,
1474 struct delayed_work
*dwork
, unsigned long delay
)
1476 struct work_struct
*work
= &dwork
->work
;
1478 unsigned long flags
;
1480 /* read the comment in __queue_work() */
1481 local_irq_save(flags
);
1483 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT
, work_data_bits(work
))) {
1484 __queue_delayed_work(cpu
, wq
, dwork
, delay
);
1488 local_irq_restore(flags
);
1491 EXPORT_SYMBOL(queue_delayed_work_on
);
1494 * mod_delayed_work_on - modify delay of or queue a delayed work on specific CPU
1495 * @cpu: CPU number to execute work on
1496 * @wq: workqueue to use
1497 * @dwork: work to queue
1498 * @delay: number of jiffies to wait before queueing
1500 * If @dwork is idle, equivalent to queue_delayed_work_on(); otherwise,
1501 * modify @dwork's timer so that it expires after @delay. If @delay is
1502 * zero, @work is guaranteed to be scheduled immediately regardless of its
1505 * Returns %false if @dwork was idle and queued, %true if @dwork was
1506 * pending and its timer was modified.
1508 * This function is safe to call from any context including IRQ handler.
1509 * See try_to_grab_pending() for details.
1511 bool mod_delayed_work_on(int cpu
, struct workqueue_struct
*wq
,
1512 struct delayed_work
*dwork
, unsigned long delay
)
1514 unsigned long flags
;
1518 ret
= try_to_grab_pending(&dwork
->work
, true, &flags
);
1519 } while (unlikely(ret
== -EAGAIN
));
1521 if (likely(ret
>= 0)) {
1522 __queue_delayed_work(cpu
, wq
, dwork
, delay
);
1523 local_irq_restore(flags
);
1526 /* -ENOENT from try_to_grab_pending() becomes %true */
1529 EXPORT_SYMBOL_GPL(mod_delayed_work_on
);
1532 * worker_enter_idle - enter idle state
1533 * @worker: worker which is entering idle state
1535 * @worker is entering idle state. Update stats and idle timer if
1539 * spin_lock_irq(pool->lock).
1541 static void worker_enter_idle(struct worker
*worker
)
1543 struct worker_pool
*pool
= worker
->pool
;
1545 if (WARN_ON_ONCE(worker
->flags
& WORKER_IDLE
) ||
1546 WARN_ON_ONCE(!list_empty(&worker
->entry
) &&
1547 (worker
->hentry
.next
|| worker
->hentry
.pprev
)))
1550 /* can't use worker_set_flags(), also called from start_worker() */
1551 worker
->flags
|= WORKER_IDLE
;
1553 worker
->last_active
= jiffies
;
1555 /* idle_list is LIFO */
1556 list_add(&worker
->entry
, &pool
->idle_list
);
1558 if (too_many_workers(pool
) && !timer_pending(&pool
->idle_timer
))
1559 mod_timer(&pool
->idle_timer
, jiffies
+ IDLE_WORKER_TIMEOUT
);
1562 * Sanity check nr_running. Because wq_unbind_fn() releases
1563 * pool->lock between setting %WORKER_UNBOUND and zapping
1564 * nr_running, the warning may trigger spuriously. Check iff
1565 * unbind is not in progress.
1567 WARN_ON_ONCE(!(pool
->flags
& POOL_DISASSOCIATED
) &&
1568 pool
->nr_workers
== pool
->nr_idle
&&
1569 atomic_read(&pool
->nr_running
));
1573 * worker_leave_idle - leave idle state
1574 * @worker: worker which is leaving idle state
1576 * @worker is leaving idle state. Update stats.
1579 * spin_lock_irq(pool->lock).
1581 static void worker_leave_idle(struct worker
*worker
)
1583 struct worker_pool
*pool
= worker
->pool
;
1585 if (WARN_ON_ONCE(!(worker
->flags
& WORKER_IDLE
)))
1587 worker_clr_flags(worker
, WORKER_IDLE
);
1589 list_del_init(&worker
->entry
);
1593 * worker_maybe_bind_and_lock - try to bind %current to worker_pool and lock it
1594 * @pool: target worker_pool
1596 * Bind %current to the cpu of @pool if it is associated and lock @pool.
1598 * Works which are scheduled while the cpu is online must at least be
1599 * scheduled to a worker which is bound to the cpu so that if they are
1600 * flushed from cpu callbacks while cpu is going down, they are
1601 * guaranteed to execute on the cpu.
1603 * This function is to be used by unbound workers and rescuers to bind
1604 * themselves to the target cpu and may race with cpu going down or
1605 * coming online. kthread_bind() can't be used because it may put the
1606 * worker to already dead cpu and set_cpus_allowed_ptr() can't be used
1607 * verbatim as it's best effort and blocking and pool may be
1608 * [dis]associated in the meantime.
1610 * This function tries set_cpus_allowed() and locks pool and verifies the
1611 * binding against %POOL_DISASSOCIATED which is set during
1612 * %CPU_DOWN_PREPARE and cleared during %CPU_ONLINE, so if the worker
1613 * enters idle state or fetches works without dropping lock, it can
1614 * guarantee the scheduling requirement described in the first paragraph.
1617 * Might sleep. Called without any lock but returns with pool->lock
1621 * %true if the associated pool is online (@worker is successfully
1622 * bound), %false if offline.
1624 static bool worker_maybe_bind_and_lock(struct worker_pool
*pool
)
1625 __acquires(&pool
->lock
)
1629 * The following call may fail, succeed or succeed
1630 * without actually migrating the task to the cpu if
1631 * it races with cpu hotunplug operation. Verify
1632 * against POOL_DISASSOCIATED.
1634 if (!(pool
->flags
& POOL_DISASSOCIATED
))
1635 set_cpus_allowed_ptr(current
, pool
->attrs
->cpumask
);
1637 spin_lock_irq(&pool
->lock
);
1638 if (pool
->flags
& POOL_DISASSOCIATED
)
1640 if (task_cpu(current
) == pool
->cpu
&&
1641 cpumask_equal(¤t
->cpus_allowed
, pool
->attrs
->cpumask
))
1643 spin_unlock_irq(&pool
->lock
);
1646 * We've raced with CPU hot[un]plug. Give it a breather
1647 * and retry migration. cond_resched() is required here;
1648 * otherwise, we might deadlock against cpu_stop trying to
1649 * bring down the CPU on non-preemptive kernel.
1656 static struct worker
*alloc_worker(void)
1658 struct worker
*worker
;
1660 worker
= kzalloc(sizeof(*worker
), GFP_KERNEL
);
1662 INIT_LIST_HEAD(&worker
->entry
);
1663 INIT_LIST_HEAD(&worker
->scheduled
);
1664 /* on creation a worker is in !idle && prep state */
1665 worker
->flags
= WORKER_PREP
;
1671 * create_worker - create a new workqueue worker
1672 * @pool: pool the new worker will belong to
1674 * Create a new worker which is bound to @pool. The returned worker
1675 * can be started by calling start_worker() or destroyed using
1679 * Might sleep. Does GFP_KERNEL allocations.
1682 * Pointer to the newly created worker.
1684 static struct worker
*create_worker(struct worker_pool
*pool
)
1686 struct worker
*worker
= NULL
;
1690 lockdep_assert_held(&pool
->manager_mutex
);
1693 * ID is needed to determine kthread name. Allocate ID first
1694 * without installing the pointer.
1696 idr_preload(GFP_KERNEL
);
1697 spin_lock_irq(&pool
->lock
);
1699 id
= idr_alloc(&pool
->worker_idr
, NULL
, 0, 0, GFP_NOWAIT
);
1701 spin_unlock_irq(&pool
->lock
);
1706 worker
= alloc_worker();
1710 worker
->pool
= pool
;
1714 snprintf(id_buf
, sizeof(id_buf
), "%d:%d%s", pool
->cpu
, id
,
1715 pool
->attrs
->nice
< 0 ? "H" : "");
1717 snprintf(id_buf
, sizeof(id_buf
), "u%d:%d", pool
->id
, id
);
1719 worker
->task
= kthread_create_on_node(worker_thread
, worker
, pool
->node
,
1720 "kworker/%s", id_buf
);
1721 if (IS_ERR(worker
->task
))
1725 * set_cpus_allowed_ptr() will fail if the cpumask doesn't have any
1726 * online CPUs. It'll be re-applied when any of the CPUs come up.
1728 set_user_nice(worker
->task
, pool
->attrs
->nice
);
1729 set_cpus_allowed_ptr(worker
->task
, pool
->attrs
->cpumask
);
1731 /* prevent userland from meddling with cpumask of workqueue workers */
1732 worker
->task
->flags
|= PF_NO_SETAFFINITY
;
1735 * The caller is responsible for ensuring %POOL_DISASSOCIATED
1736 * remains stable across this function. See the comments above the
1737 * flag definition for details.
1739 if (pool
->flags
& POOL_DISASSOCIATED
)
1740 worker
->flags
|= WORKER_UNBOUND
;
1742 /* successful, commit the pointer to idr */
1743 spin_lock_irq(&pool
->lock
);
1744 idr_replace(&pool
->worker_idr
, worker
, worker
->id
);
1745 spin_unlock_irq(&pool
->lock
);
1751 spin_lock_irq(&pool
->lock
);
1752 idr_remove(&pool
->worker_idr
, id
);
1753 spin_unlock_irq(&pool
->lock
);
1760 * start_worker - start a newly created worker
1761 * @worker: worker to start
1763 * Make the pool aware of @worker and start it.
1766 * spin_lock_irq(pool->lock).
1768 static void start_worker(struct worker
*worker
)
1770 worker
->flags
|= WORKER_STARTED
;
1771 worker
->pool
->nr_workers
++;
1772 worker_enter_idle(worker
);
1773 wake_up_process(worker
->task
);
1777 * create_and_start_worker - create and start a worker for a pool
1778 * @pool: the target pool
1780 * Grab the managership of @pool and create and start a new worker for it.
1782 static int create_and_start_worker(struct worker_pool
*pool
)
1784 struct worker
*worker
;
1786 mutex_lock(&pool
->manager_mutex
);
1788 worker
= create_worker(pool
);
1790 spin_lock_irq(&pool
->lock
);
1791 start_worker(worker
);
1792 spin_unlock_irq(&pool
->lock
);
1795 mutex_unlock(&pool
->manager_mutex
);
1797 return worker
? 0 : -ENOMEM
;
1801 * destroy_worker - destroy a workqueue worker
1802 * @worker: worker to be destroyed
1804 * Destroy @worker and adjust @pool stats accordingly.
1807 * spin_lock_irq(pool->lock) which is released and regrabbed.
1809 static void destroy_worker(struct worker
*worker
)
1811 struct worker_pool
*pool
= worker
->pool
;
1813 lockdep_assert_held(&pool
->manager_mutex
);
1814 lockdep_assert_held(&pool
->lock
);
1816 /* sanity check frenzy */
1817 if (WARN_ON(worker
->current_work
) ||
1818 WARN_ON(!list_empty(&worker
->scheduled
)))
1821 if (worker
->flags
& WORKER_STARTED
)
1823 if (worker
->flags
& WORKER_IDLE
)
1827 * Once WORKER_DIE is set, the kworker may destroy itself at any
1828 * point. Pin to ensure the task stays until we're done with it.
1830 get_task_struct(worker
->task
);
1832 list_del_init(&worker
->entry
);
1833 worker
->flags
|= WORKER_DIE
;
1835 idr_remove(&pool
->worker_idr
, worker
->id
);
1837 spin_unlock_irq(&pool
->lock
);
1839 kthread_stop(worker
->task
);
1840 put_task_struct(worker
->task
);
1843 spin_lock_irq(&pool
->lock
);
1846 static void idle_worker_timeout(unsigned long __pool
)
1848 struct worker_pool
*pool
= (void *)__pool
;
1850 spin_lock_irq(&pool
->lock
);
1852 if (too_many_workers(pool
)) {
1853 struct worker
*worker
;
1854 unsigned long expires
;
1856 /* idle_list is kept in LIFO order, check the last one */
1857 worker
= list_entry(pool
->idle_list
.prev
, struct worker
, entry
);
1858 expires
= worker
->last_active
+ IDLE_WORKER_TIMEOUT
;
1860 if (time_before(jiffies
, expires
))
1861 mod_timer(&pool
->idle_timer
, expires
);
1863 /* it's been idle for too long, wake up manager */
1864 pool
->flags
|= POOL_MANAGE_WORKERS
;
1865 wake_up_worker(pool
);
1869 spin_unlock_irq(&pool
->lock
);
1872 static void send_mayday(struct work_struct
*work
)
1874 struct pool_workqueue
*pwq
= get_work_pwq(work
);
1875 struct workqueue_struct
*wq
= pwq
->wq
;
1877 lockdep_assert_held(&wq_mayday_lock
);
1882 /* mayday mayday mayday */
1883 if (list_empty(&pwq
->mayday_node
)) {
1885 * If @pwq is for an unbound wq, its base ref may be put at
1886 * any time due to an attribute change. Pin @pwq until the
1887 * rescuer is done with it.
1890 list_add_tail(&pwq
->mayday_node
, &wq
->maydays
);
1891 wake_up_process(wq
->rescuer
->task
);
1895 static void pool_mayday_timeout(unsigned long __pool
)
1897 struct worker_pool
*pool
= (void *)__pool
;
1898 struct work_struct
*work
;
1900 spin_lock_irq(&wq_mayday_lock
); /* for wq->maydays */
1901 spin_lock(&pool
->lock
);
1903 if (need_to_create_worker(pool
)) {
1905 * We've been trying to create a new worker but
1906 * haven't been successful. We might be hitting an
1907 * allocation deadlock. Send distress signals to
1910 list_for_each_entry(work
, &pool
->worklist
, entry
)
1914 spin_unlock(&pool
->lock
);
1915 spin_unlock_irq(&wq_mayday_lock
);
1917 mod_timer(&pool
->mayday_timer
, jiffies
+ MAYDAY_INTERVAL
);
1921 * maybe_create_worker - create a new worker if necessary
1922 * @pool: pool to create a new worker for
1924 * Create a new worker for @pool if necessary. @pool is guaranteed to
1925 * have at least one idle worker on return from this function. If
1926 * creating a new worker takes longer than MAYDAY_INTERVAL, mayday is
1927 * sent to all rescuers with works scheduled on @pool to resolve
1928 * possible allocation deadlock.
1930 * On return, need_to_create_worker() is guaranteed to be %false and
1931 * may_start_working() %true.
1934 * spin_lock_irq(pool->lock) which may be released and regrabbed
1935 * multiple times. Does GFP_KERNEL allocations. Called only from
1938 static void maybe_create_worker(struct worker_pool
*pool
)
1939 __releases(&pool
->lock
)
1940 __acquires(&pool
->lock
)
1942 if (!need_to_create_worker(pool
))
1945 spin_unlock_irq(&pool
->lock
);
1947 /* if we don't make progress in MAYDAY_INITIAL_TIMEOUT, call for help */
1948 mod_timer(&pool
->mayday_timer
, jiffies
+ MAYDAY_INITIAL_TIMEOUT
);
1951 struct worker
*worker
;
1953 worker
= create_worker(pool
);
1955 del_timer_sync(&pool
->mayday_timer
);
1956 spin_lock_irq(&pool
->lock
);
1957 start_worker(worker
);
1958 if (WARN_ON_ONCE(need_to_create_worker(pool
)))
1963 if (!need_to_create_worker(pool
))
1966 __set_current_state(TASK_INTERRUPTIBLE
);
1967 schedule_timeout(CREATE_COOLDOWN
);
1969 if (!need_to_create_worker(pool
))
1973 del_timer_sync(&pool
->mayday_timer
);
1974 spin_lock_irq(&pool
->lock
);
1975 if (need_to_create_worker(pool
))
1981 * maybe_destroy_worker - destroy workers which have been idle for a while
1982 * @pool: pool to destroy workers for
1984 * Destroy @pool workers which have been idle for longer than
1985 * IDLE_WORKER_TIMEOUT.
1988 * spin_lock_irq(pool->lock) which may be released and regrabbed
1989 * multiple times. Called only from manager.
1991 static void maybe_destroy_workers(struct worker_pool
*pool
)
1993 while (too_many_workers(pool
)) {
1994 struct worker
*worker
;
1995 unsigned long expires
;
1997 worker
= list_entry(pool
->idle_list
.prev
, struct worker
, entry
);
1998 expires
= worker
->last_active
+ IDLE_WORKER_TIMEOUT
;
2000 if (time_before(jiffies
, expires
)) {
2001 mod_timer(&pool
->idle_timer
, expires
);
2005 destroy_worker(worker
);
2010 * manage_workers - manage worker pool
2013 * Assume the manager role and manage the worker pool @worker belongs
2014 * to. At any given time, there can be only zero or one manager per
2015 * pool. The exclusion is handled automatically by this function.
2017 * The caller can safely start processing works on false return. On
2018 * true return, it's guaranteed that need_to_create_worker() is false
2019 * and may_start_working() is true.
2022 * spin_lock_irq(pool->lock) which may be released and regrabbed
2023 * multiple times. Does GFP_KERNEL allocations.
2026 * %false if the pool doesn't need management and the caller can safely
2027 * start processing works, %true if management function was performed and
2028 * the conditions that the caller verified before calling the function may
2029 * no longer be true.
2031 static bool manage_workers(struct worker
*worker
)
2033 struct worker_pool
*pool
= worker
->pool
;
2036 * Managership is governed by two mutexes - manager_arb and
2037 * manager_mutex. manager_arb handles arbitration of manager role.
2038 * Anyone who successfully grabs manager_arb wins the arbitration
2039 * and becomes the manager. mutex_trylock() on pool->manager_arb
2040 * failure while holding pool->lock reliably indicates that someone
2041 * else is managing the pool and the worker which failed trylock
2042 * can proceed to executing work items. This means that anyone
2043 * grabbing manager_arb is responsible for actually performing
2044 * manager duties. If manager_arb is grabbed and released without
2045 * actual management, the pool may stall indefinitely.
2047 * manager_mutex is used for exclusion of actual management
2048 * operations. The holder of manager_mutex can be sure that none
2049 * of management operations, including creation and destruction of
2050 * workers, won't take place until the mutex is released. Because
2051 * manager_mutex doesn't interfere with manager role arbitration,
2052 * it is guaranteed that the pool's management, while may be
2053 * delayed, won't be disturbed by someone else grabbing
2056 if (!mutex_trylock(&pool
->manager_arb
))
2060 * With manager arbitration won, manager_mutex would be free in
2061 * most cases. trylock first without dropping @pool->lock.
2063 if (unlikely(!mutex_trylock(&pool
->manager_mutex
))) {
2064 spin_unlock_irq(&pool
->lock
);
2065 mutex_lock(&pool
->manager_mutex
);
2066 spin_lock_irq(&pool
->lock
);
2069 pool
->flags
&= ~POOL_MANAGE_WORKERS
;
2072 * Destroy and then create so that may_start_working() is true
2075 maybe_destroy_workers(pool
);
2076 maybe_create_worker(pool
);
2078 mutex_unlock(&pool
->manager_mutex
);
2079 mutex_unlock(&pool
->manager_arb
);
2084 * process_one_work - process single work
2086 * @work: work to process
2088 * Process @work. This function contains all the logics necessary to
2089 * process a single work including synchronization against and
2090 * interaction with other workers on the same cpu, queueing and
2091 * flushing. As long as context requirement is met, any worker can
2092 * call this function to process a work.
2095 * spin_lock_irq(pool->lock) which is released and regrabbed.
2097 static void process_one_work(struct worker
*worker
, struct work_struct
*work
)
2098 __releases(&pool
->lock
)
2099 __acquires(&pool
->lock
)
2101 struct pool_workqueue
*pwq
= get_work_pwq(work
);
2102 struct worker_pool
*pool
= worker
->pool
;
2103 bool cpu_intensive
= pwq
->wq
->flags
& WQ_CPU_INTENSIVE
;
2105 struct worker
*collision
;
2106 #ifdef CONFIG_LOCKDEP
2108 * It is permissible to free the struct work_struct from
2109 * inside the function that is called from it, this we need to
2110 * take into account for lockdep too. To avoid bogus "held
2111 * lock freed" warnings as well as problems when looking into
2112 * work->lockdep_map, make a copy and use that here.
2114 struct lockdep_map lockdep_map
;
2116 lockdep_copy_map(&lockdep_map
, &work
->lockdep_map
);
2119 * Ensure we're on the correct CPU. DISASSOCIATED test is
2120 * necessary to avoid spurious warnings from rescuers servicing the
2121 * unbound or a disassociated pool.
2123 WARN_ON_ONCE(!(worker
->flags
& WORKER_UNBOUND
) &&
2124 !(pool
->flags
& POOL_DISASSOCIATED
) &&
2125 raw_smp_processor_id() != pool
->cpu
);
2128 * A single work shouldn't be executed concurrently by
2129 * multiple workers on a single cpu. Check whether anyone is
2130 * already processing the work. If so, defer the work to the
2131 * currently executing one.
2133 collision
= find_worker_executing_work(pool
, work
);
2134 if (unlikely(collision
)) {
2135 move_linked_works(work
, &collision
->scheduled
, NULL
);
2139 /* claim and dequeue */
2140 debug_work_deactivate(work
);
2141 hash_add(pool
->busy_hash
, &worker
->hentry
, (unsigned long)work
);
2142 worker
->current_work
= work
;
2143 worker
->current_func
= work
->func
;
2144 worker
->current_pwq
= pwq
;
2145 work_color
= get_work_color(work
);
2147 list_del_init(&work
->entry
);
2150 * CPU intensive works don't participate in concurrency
2151 * management. They're the scheduler's responsibility.
2153 if (unlikely(cpu_intensive
))
2154 worker_set_flags(worker
, WORKER_CPU_INTENSIVE
, true);
2157 * Unbound pool isn't concurrency managed and work items should be
2158 * executed ASAP. Wake up another worker if necessary.
2160 if ((worker
->flags
& WORKER_UNBOUND
) && need_more_worker(pool
))
2161 wake_up_worker(pool
);
2164 * Record the last pool and clear PENDING which should be the last
2165 * update to @work. Also, do this inside @pool->lock so that
2166 * PENDING and queued state changes happen together while IRQ is
2169 set_work_pool_and_clear_pending(work
, pool
->id
);
2171 spin_unlock_irq(&pool
->lock
);
2173 lock_map_acquire_read(&pwq
->wq
->lockdep_map
);
2174 lock_map_acquire(&lockdep_map
);
2175 trace_workqueue_execute_start(work
);
2176 worker
->current_func(work
);
2178 * While we must be careful to not use "work" after this, the trace
2179 * point will only record its address.
2181 trace_workqueue_execute_end(work
);
2182 lock_map_release(&lockdep_map
);
2183 lock_map_release(&pwq
->wq
->lockdep_map
);
2185 if (unlikely(in_atomic() || lockdep_depth(current
) > 0)) {
2186 pr_err("BUG: workqueue leaked lock or atomic: %s/0x%08x/%d\n"
2187 " last function: %pf\n",
2188 current
->comm
, preempt_count(), task_pid_nr(current
),
2189 worker
->current_func
);
2190 debug_show_held_locks(current
);
2195 * The following prevents a kworker from hogging CPU on !PREEMPT
2196 * kernels, where a requeueing work item waiting for something to
2197 * happen could deadlock with stop_machine as such work item could
2198 * indefinitely requeue itself while all other CPUs are trapped in
2203 spin_lock_irq(&pool
->lock
);
2205 /* clear cpu intensive status */
2206 if (unlikely(cpu_intensive
))
2207 worker_clr_flags(worker
, WORKER_CPU_INTENSIVE
);
2209 /* we're done with it, release */
2210 hash_del(&worker
->hentry
);
2211 worker
->current_work
= NULL
;
2212 worker
->current_func
= NULL
;
2213 worker
->current_pwq
= NULL
;
2214 worker
->desc_valid
= false;
2215 pwq_dec_nr_in_flight(pwq
, work_color
);
2219 * process_scheduled_works - process scheduled works
2222 * Process all scheduled works. Please note that the scheduled list
2223 * may change while processing a work, so this function repeatedly
2224 * fetches a work from the top and executes it.
2227 * spin_lock_irq(pool->lock) which may be released and regrabbed
2230 static void process_scheduled_works(struct worker
*worker
)
2232 while (!list_empty(&worker
->scheduled
)) {
2233 struct work_struct
*work
= list_first_entry(&worker
->scheduled
,
2234 struct work_struct
, entry
);
2235 process_one_work(worker
, work
);
2240 * worker_thread - the worker thread function
2243 * The worker thread function. All workers belong to a worker_pool -
2244 * either a per-cpu one or dynamic unbound one. These workers process all
2245 * work items regardless of their specific target workqueue. The only
2246 * exception is work items which belong to workqueues with a rescuer which
2247 * will be explained in rescuer_thread().
2249 static int worker_thread(void *__worker
)
2251 struct worker
*worker
= __worker
;
2252 struct worker_pool
*pool
= worker
->pool
;
2254 /* tell the scheduler that this is a workqueue worker */
2255 worker
->task
->flags
|= PF_WQ_WORKER
;
2257 spin_lock_irq(&pool
->lock
);
2259 /* am I supposed to die? */
2260 if (unlikely(worker
->flags
& WORKER_DIE
)) {
2261 spin_unlock_irq(&pool
->lock
);
2262 WARN_ON_ONCE(!list_empty(&worker
->entry
));
2263 worker
->task
->flags
&= ~PF_WQ_WORKER
;
2267 worker_leave_idle(worker
);
2269 /* no more worker necessary? */
2270 if (!need_more_worker(pool
))
2273 /* do we need to manage? */
2274 if (unlikely(!may_start_working(pool
)) && manage_workers(worker
))
2278 * ->scheduled list can only be filled while a worker is
2279 * preparing to process a work or actually processing it.
2280 * Make sure nobody diddled with it while I was sleeping.
2282 WARN_ON_ONCE(!list_empty(&worker
->scheduled
));
2285 * Finish PREP stage. We're guaranteed to have at least one idle
2286 * worker or that someone else has already assumed the manager
2287 * role. This is where @worker starts participating in concurrency
2288 * management if applicable and concurrency management is restored
2289 * after being rebound. See rebind_workers() for details.
2291 worker_clr_flags(worker
, WORKER_PREP
| WORKER_REBOUND
);
2294 struct work_struct
*work
=
2295 list_first_entry(&pool
->worklist
,
2296 struct work_struct
, entry
);
2298 if (likely(!(*work_data_bits(work
) & WORK_STRUCT_LINKED
))) {
2299 /* optimization path, not strictly necessary */
2300 process_one_work(worker
, work
);
2301 if (unlikely(!list_empty(&worker
->scheduled
)))
2302 process_scheduled_works(worker
);
2304 move_linked_works(work
, &worker
->scheduled
, NULL
);
2305 process_scheduled_works(worker
);
2307 } while (keep_working(pool
));
2309 worker_set_flags(worker
, WORKER_PREP
, false);
2311 if (unlikely(need_to_manage_workers(pool
)) && manage_workers(worker
))
2315 * pool->lock is held and there's no work to process and no need to
2316 * manage, sleep. Workers are woken up only while holding
2317 * pool->lock or from local cpu, so setting the current state
2318 * before releasing pool->lock is enough to prevent losing any
2321 worker_enter_idle(worker
);
2322 __set_current_state(TASK_INTERRUPTIBLE
);
2323 spin_unlock_irq(&pool
->lock
);
2329 * rescuer_thread - the rescuer thread function
2332 * Workqueue rescuer thread function. There's one rescuer for each
2333 * workqueue which has WQ_MEM_RECLAIM set.
2335 * Regular work processing on a pool may block trying to create a new
2336 * worker which uses GFP_KERNEL allocation which has slight chance of
2337 * developing into deadlock if some works currently on the same queue
2338 * need to be processed to satisfy the GFP_KERNEL allocation. This is
2339 * the problem rescuer solves.
2341 * When such condition is possible, the pool summons rescuers of all
2342 * workqueues which have works queued on the pool and let them process
2343 * those works so that forward progress can be guaranteed.
2345 * This should happen rarely.
2347 static int rescuer_thread(void *__rescuer
)
2349 struct worker
*rescuer
= __rescuer
;
2350 struct workqueue_struct
*wq
= rescuer
->rescue_wq
;
2351 struct list_head
*scheduled
= &rescuer
->scheduled
;
2354 set_user_nice(current
, RESCUER_NICE_LEVEL
);
2357 * Mark rescuer as worker too. As WORKER_PREP is never cleared, it
2358 * doesn't participate in concurrency management.
2360 rescuer
->task
->flags
|= PF_WQ_WORKER
;
2362 set_current_state(TASK_INTERRUPTIBLE
);
2365 * By the time the rescuer is requested to stop, the workqueue
2366 * shouldn't have any work pending, but @wq->maydays may still have
2367 * pwq(s) queued. This can happen by non-rescuer workers consuming
2368 * all the work items before the rescuer got to them. Go through
2369 * @wq->maydays processing before acting on should_stop so that the
2370 * list is always empty on exit.
2372 should_stop
= kthread_should_stop();
2374 /* see whether any pwq is asking for help */
2375 spin_lock_irq(&wq_mayday_lock
);
2377 while (!list_empty(&wq
->maydays
)) {
2378 struct pool_workqueue
*pwq
= list_first_entry(&wq
->maydays
,
2379 struct pool_workqueue
, mayday_node
);
2380 struct worker_pool
*pool
= pwq
->pool
;
2381 struct work_struct
*work
, *n
;
2383 __set_current_state(TASK_RUNNING
);
2384 list_del_init(&pwq
->mayday_node
);
2386 spin_unlock_irq(&wq_mayday_lock
);
2388 /* migrate to the target cpu if possible */
2389 worker_maybe_bind_and_lock(pool
);
2390 rescuer
->pool
= pool
;
2393 * Slurp in all works issued via this workqueue and
2396 WARN_ON_ONCE(!list_empty(&rescuer
->scheduled
));
2397 list_for_each_entry_safe(work
, n
, &pool
->worklist
, entry
)
2398 if (get_work_pwq(work
) == pwq
)
2399 move_linked_works(work
, scheduled
, &n
);
2401 process_scheduled_works(rescuer
);
2404 * Put the reference grabbed by send_mayday(). @pool won't
2405 * go away while we're holding its lock.
2410 * Leave this pool. If keep_working() is %true, notify a
2411 * regular worker; otherwise, we end up with 0 concurrency
2412 * and stalling the execution.
2414 if (keep_working(pool
))
2415 wake_up_worker(pool
);
2417 rescuer
->pool
= NULL
;
2418 spin_unlock(&pool
->lock
);
2419 spin_lock(&wq_mayday_lock
);
2422 spin_unlock_irq(&wq_mayday_lock
);
2425 __set_current_state(TASK_RUNNING
);
2426 rescuer
->task
->flags
&= ~PF_WQ_WORKER
;
2430 /* rescuers should never participate in concurrency management */
2431 WARN_ON_ONCE(!(rescuer
->flags
& WORKER_NOT_RUNNING
));
2437 struct work_struct work
;
2438 struct completion done
;
2441 static void wq_barrier_func(struct work_struct
*work
)
2443 struct wq_barrier
*barr
= container_of(work
, struct wq_barrier
, work
);
2444 complete(&barr
->done
);
2448 * insert_wq_barrier - insert a barrier work
2449 * @pwq: pwq to insert barrier into
2450 * @barr: wq_barrier to insert
2451 * @target: target work to attach @barr to
2452 * @worker: worker currently executing @target, NULL if @target is not executing
2454 * @barr is linked to @target such that @barr is completed only after
2455 * @target finishes execution. Please note that the ordering
2456 * guarantee is observed only with respect to @target and on the local
2459 * Currently, a queued barrier can't be canceled. This is because
2460 * try_to_grab_pending() can't determine whether the work to be
2461 * grabbed is at the head of the queue and thus can't clear LINKED
2462 * flag of the previous work while there must be a valid next work
2463 * after a work with LINKED flag set.
2465 * Note that when @worker is non-NULL, @target may be modified
2466 * underneath us, so we can't reliably determine pwq from @target.
2469 * spin_lock_irq(pool->lock).
2471 static void insert_wq_barrier(struct pool_workqueue
*pwq
,
2472 struct wq_barrier
*barr
,
2473 struct work_struct
*target
, struct worker
*worker
)
2475 struct list_head
*head
;
2476 unsigned int linked
= 0;
2479 * debugobject calls are safe here even with pool->lock locked
2480 * as we know for sure that this will not trigger any of the
2481 * checks and call back into the fixup functions where we
2484 INIT_WORK_ONSTACK(&barr
->work
, wq_barrier_func
);
2485 __set_bit(WORK_STRUCT_PENDING_BIT
, work_data_bits(&barr
->work
));
2486 init_completion(&barr
->done
);
2489 * If @target is currently being executed, schedule the
2490 * barrier to the worker; otherwise, put it after @target.
2493 head
= worker
->scheduled
.next
;
2495 unsigned long *bits
= work_data_bits(target
);
2497 head
= target
->entry
.next
;
2498 /* there can already be other linked works, inherit and set */
2499 linked
= *bits
& WORK_STRUCT_LINKED
;
2500 __set_bit(WORK_STRUCT_LINKED_BIT
, bits
);
2503 debug_work_activate(&barr
->work
);
2504 insert_work(pwq
, &barr
->work
, head
,
2505 work_color_to_flags(WORK_NO_COLOR
) | linked
);
2509 * flush_workqueue_prep_pwqs - prepare pwqs for workqueue flushing
2510 * @wq: workqueue being flushed
2511 * @flush_color: new flush color, < 0 for no-op
2512 * @work_color: new work color, < 0 for no-op
2514 * Prepare pwqs for workqueue flushing.
2516 * If @flush_color is non-negative, flush_color on all pwqs should be
2517 * -1. If no pwq has in-flight commands at the specified color, all
2518 * pwq->flush_color's stay at -1 and %false is returned. If any pwq
2519 * has in flight commands, its pwq->flush_color is set to
2520 * @flush_color, @wq->nr_pwqs_to_flush is updated accordingly, pwq
2521 * wakeup logic is armed and %true is returned.
2523 * The caller should have initialized @wq->first_flusher prior to
2524 * calling this function with non-negative @flush_color. If
2525 * @flush_color is negative, no flush color update is done and %false
2528 * If @work_color is non-negative, all pwqs should have the same
2529 * work_color which is previous to @work_color and all will be
2530 * advanced to @work_color.
2533 * mutex_lock(wq->mutex).
2536 * %true if @flush_color >= 0 and there's something to flush. %false
2539 static bool flush_workqueue_prep_pwqs(struct workqueue_struct
*wq
,
2540 int flush_color
, int work_color
)
2543 struct pool_workqueue
*pwq
;
2545 if (flush_color
>= 0) {
2546 WARN_ON_ONCE(atomic_read(&wq
->nr_pwqs_to_flush
));
2547 atomic_set(&wq
->nr_pwqs_to_flush
, 1);
2550 for_each_pwq(pwq
, wq
) {
2551 struct worker_pool
*pool
= pwq
->pool
;
2553 spin_lock_irq(&pool
->lock
);
2555 if (flush_color
>= 0) {
2556 WARN_ON_ONCE(pwq
->flush_color
!= -1);
2558 if (pwq
->nr_in_flight
[flush_color
]) {
2559 pwq
->flush_color
= flush_color
;
2560 atomic_inc(&wq
->nr_pwqs_to_flush
);
2565 if (work_color
>= 0) {
2566 WARN_ON_ONCE(work_color
!= work_next_color(pwq
->work_color
));
2567 pwq
->work_color
= work_color
;
2570 spin_unlock_irq(&pool
->lock
);
2573 if (flush_color
>= 0 && atomic_dec_and_test(&wq
->nr_pwqs_to_flush
))
2574 complete(&wq
->first_flusher
->done
);
2580 * flush_workqueue - ensure that any scheduled work has run to completion.
2581 * @wq: workqueue to flush
2583 * This function sleeps until all work items which were queued on entry
2584 * have finished execution, but it is not livelocked by new incoming ones.
2586 void flush_workqueue(struct workqueue_struct
*wq
)
2588 struct wq_flusher this_flusher
= {
2589 .list
= LIST_HEAD_INIT(this_flusher
.list
),
2591 .done
= COMPLETION_INITIALIZER_ONSTACK(this_flusher
.done
),
2595 lock_map_acquire(&wq
->lockdep_map
);
2596 lock_map_release(&wq
->lockdep_map
);
2598 mutex_lock(&wq
->mutex
);
2601 * Start-to-wait phase
2603 next_color
= work_next_color(wq
->work_color
);
2605 if (next_color
!= wq
->flush_color
) {
2607 * Color space is not full. The current work_color
2608 * becomes our flush_color and work_color is advanced
2611 WARN_ON_ONCE(!list_empty(&wq
->flusher_overflow
));
2612 this_flusher
.flush_color
= wq
->work_color
;
2613 wq
->work_color
= next_color
;
2615 if (!wq
->first_flusher
) {
2616 /* no flush in progress, become the first flusher */
2617 WARN_ON_ONCE(wq
->flush_color
!= this_flusher
.flush_color
);
2619 wq
->first_flusher
= &this_flusher
;
2621 if (!flush_workqueue_prep_pwqs(wq
, wq
->flush_color
,
2623 /* nothing to flush, done */
2624 wq
->flush_color
= next_color
;
2625 wq
->first_flusher
= NULL
;
2630 WARN_ON_ONCE(wq
->flush_color
== this_flusher
.flush_color
);
2631 list_add_tail(&this_flusher
.list
, &wq
->flusher_queue
);
2632 flush_workqueue_prep_pwqs(wq
, -1, wq
->work_color
);
2636 * Oops, color space is full, wait on overflow queue.
2637 * The next flush completion will assign us
2638 * flush_color and transfer to flusher_queue.
2640 list_add_tail(&this_flusher
.list
, &wq
->flusher_overflow
);
2643 mutex_unlock(&wq
->mutex
);
2645 wait_for_completion(&this_flusher
.done
);
2648 * Wake-up-and-cascade phase
2650 * First flushers are responsible for cascading flushes and
2651 * handling overflow. Non-first flushers can simply return.
2653 if (wq
->first_flusher
!= &this_flusher
)
2656 mutex_lock(&wq
->mutex
);
2658 /* we might have raced, check again with mutex held */
2659 if (wq
->first_flusher
!= &this_flusher
)
2662 wq
->first_flusher
= NULL
;
2664 WARN_ON_ONCE(!list_empty(&this_flusher
.list
));
2665 WARN_ON_ONCE(wq
->flush_color
!= this_flusher
.flush_color
);
2668 struct wq_flusher
*next
, *tmp
;
2670 /* complete all the flushers sharing the current flush color */
2671 list_for_each_entry_safe(next
, tmp
, &wq
->flusher_queue
, list
) {
2672 if (next
->flush_color
!= wq
->flush_color
)
2674 list_del_init(&next
->list
);
2675 complete(&next
->done
);
2678 WARN_ON_ONCE(!list_empty(&wq
->flusher_overflow
) &&
2679 wq
->flush_color
!= work_next_color(wq
->work_color
));
2681 /* this flush_color is finished, advance by one */
2682 wq
->flush_color
= work_next_color(wq
->flush_color
);
2684 /* one color has been freed, handle overflow queue */
2685 if (!list_empty(&wq
->flusher_overflow
)) {
2687 * Assign the same color to all overflowed
2688 * flushers, advance work_color and append to
2689 * flusher_queue. This is the start-to-wait
2690 * phase for these overflowed flushers.
2692 list_for_each_entry(tmp
, &wq
->flusher_overflow
, list
)
2693 tmp
->flush_color
= wq
->work_color
;
2695 wq
->work_color
= work_next_color(wq
->work_color
);
2697 list_splice_tail_init(&wq
->flusher_overflow
,
2698 &wq
->flusher_queue
);
2699 flush_workqueue_prep_pwqs(wq
, -1, wq
->work_color
);
2702 if (list_empty(&wq
->flusher_queue
)) {
2703 WARN_ON_ONCE(wq
->flush_color
!= wq
->work_color
);
2708 * Need to flush more colors. Make the next flusher
2709 * the new first flusher and arm pwqs.
2711 WARN_ON_ONCE(wq
->flush_color
== wq
->work_color
);
2712 WARN_ON_ONCE(wq
->flush_color
!= next
->flush_color
);
2714 list_del_init(&next
->list
);
2715 wq
->first_flusher
= next
;
2717 if (flush_workqueue_prep_pwqs(wq
, wq
->flush_color
, -1))
2721 * Meh... this color is already done, clear first
2722 * flusher and repeat cascading.
2724 wq
->first_flusher
= NULL
;
2728 mutex_unlock(&wq
->mutex
);
2730 EXPORT_SYMBOL_GPL(flush_workqueue
);
2733 * drain_workqueue - drain a workqueue
2734 * @wq: workqueue to drain
2736 * Wait until the workqueue becomes empty. While draining is in progress,
2737 * only chain queueing is allowed. IOW, only currently pending or running
2738 * work items on @wq can queue further work items on it. @wq is flushed
2739 * repeatedly until it becomes empty. The number of flushing is detemined
2740 * by the depth of chaining and should be relatively short. Whine if it
2743 void drain_workqueue(struct workqueue_struct
*wq
)
2745 unsigned int flush_cnt
= 0;
2746 struct pool_workqueue
*pwq
;
2749 * __queue_work() needs to test whether there are drainers, is much
2750 * hotter than drain_workqueue() and already looks at @wq->flags.
2751 * Use __WQ_DRAINING so that queue doesn't have to check nr_drainers.
2753 mutex_lock(&wq
->mutex
);
2754 if (!wq
->nr_drainers
++)
2755 wq
->flags
|= __WQ_DRAINING
;
2756 mutex_unlock(&wq
->mutex
);
2758 flush_workqueue(wq
);
2760 mutex_lock(&wq
->mutex
);
2762 for_each_pwq(pwq
, wq
) {
2765 spin_lock_irq(&pwq
->pool
->lock
);
2766 drained
= !pwq
->nr_active
&& list_empty(&pwq
->delayed_works
);
2767 spin_unlock_irq(&pwq
->pool
->lock
);
2772 if (++flush_cnt
== 10 ||
2773 (flush_cnt
% 100 == 0 && flush_cnt
<= 1000))
2774 pr_warn("workqueue %s: drain_workqueue() isn't complete after %u tries\n",
2775 wq
->name
, flush_cnt
);
2777 mutex_unlock(&wq
->mutex
);
2781 if (!--wq
->nr_drainers
)
2782 wq
->flags
&= ~__WQ_DRAINING
;
2783 mutex_unlock(&wq
->mutex
);
2785 EXPORT_SYMBOL_GPL(drain_workqueue
);
2787 static bool start_flush_work(struct work_struct
*work
, struct wq_barrier
*barr
)
2789 struct worker
*worker
= NULL
;
2790 struct worker_pool
*pool
;
2791 struct pool_workqueue
*pwq
;
2795 local_irq_disable();
2796 pool
= get_work_pool(work
);
2802 spin_lock(&pool
->lock
);
2803 /* see the comment in try_to_grab_pending() with the same code */
2804 pwq
= get_work_pwq(work
);
2806 if (unlikely(pwq
->pool
!= pool
))
2809 worker
= find_worker_executing_work(pool
, work
);
2812 pwq
= worker
->current_pwq
;
2815 insert_wq_barrier(pwq
, barr
, work
, worker
);
2816 spin_unlock_irq(&pool
->lock
);
2819 * If @max_active is 1 or rescuer is in use, flushing another work
2820 * item on the same workqueue may lead to deadlock. Make sure the
2821 * flusher is not running on the same workqueue by verifying write
2824 if (pwq
->wq
->saved_max_active
== 1 || pwq
->wq
->rescuer
)
2825 lock_map_acquire(&pwq
->wq
->lockdep_map
);
2827 lock_map_acquire_read(&pwq
->wq
->lockdep_map
);
2828 lock_map_release(&pwq
->wq
->lockdep_map
);
2832 spin_unlock_irq(&pool
->lock
);
2837 * flush_work - wait for a work to finish executing the last queueing instance
2838 * @work: the work to flush
2840 * Wait until @work has finished execution. @work is guaranteed to be idle
2841 * on return if it hasn't been requeued since flush started.
2844 * %true if flush_work() waited for the work to finish execution,
2845 * %false if it was already idle.
2847 bool flush_work(struct work_struct
*work
)
2849 struct wq_barrier barr
;
2851 lock_map_acquire(&work
->lockdep_map
);
2852 lock_map_release(&work
->lockdep_map
);
2854 if (start_flush_work(work
, &barr
)) {
2855 wait_for_completion(&barr
.done
);
2856 destroy_work_on_stack(&barr
.work
);
2862 EXPORT_SYMBOL_GPL(flush_work
);
2866 struct work_struct
*work
;
2869 static int cwt_wakefn(wait_queue_t
*wait
, unsigned mode
, int sync
, void *key
)
2871 struct cwt_wait
*cwait
= container_of(wait
, struct cwt_wait
, wait
);
2873 if (cwait
->work
!= key
)
2875 return autoremove_wake_function(wait
, mode
, sync
, key
);
2878 static bool __cancel_work_timer(struct work_struct
*work
, bool is_dwork
)
2880 static DECLARE_WAIT_QUEUE_HEAD(cancel_waitq
);
2881 unsigned long flags
;
2885 ret
= try_to_grab_pending(work
, is_dwork
, &flags
);
2887 * If someone else is already canceling, wait for it to
2888 * finish. flush_work() doesn't work for PREEMPT_NONE
2889 * because we may get scheduled between @work's completion
2890 * and the other canceling task resuming and clearing
2891 * CANCELING - flush_work() will return false immediately
2892 * as @work is no longer busy, try_to_grab_pending() will
2893 * return -ENOENT as @work is still being canceled and the
2894 * other canceling task won't be able to clear CANCELING as
2895 * we're hogging the CPU.
2897 * Let's wait for completion using a waitqueue. As this
2898 * may lead to the thundering herd problem, use a custom
2899 * wake function which matches @work along with exclusive
2902 if (unlikely(ret
== -ENOENT
)) {
2903 struct cwt_wait cwait
;
2905 init_wait(&cwait
.wait
);
2906 cwait
.wait
.func
= cwt_wakefn
;
2909 prepare_to_wait_exclusive(&cancel_waitq
, &cwait
.wait
,
2910 TASK_UNINTERRUPTIBLE
);
2911 if (work_is_canceling(work
))
2913 finish_wait(&cancel_waitq
, &cwait
.wait
);
2915 } while (unlikely(ret
< 0));
2917 /* tell other tasks trying to grab @work to back off */
2918 mark_work_canceling(work
);
2919 local_irq_restore(flags
);
2922 clear_work_data(work
);
2925 * Paired with prepare_to_wait() above so that either
2926 * waitqueue_active() is visible here or !work_is_canceling() is
2930 if (waitqueue_active(&cancel_waitq
))
2931 __wake_up(&cancel_waitq
, TASK_NORMAL
, 1, work
);
2937 * cancel_work_sync - cancel a work and wait for it to finish
2938 * @work: the work to cancel
2940 * Cancel @work and wait for its execution to finish. This function
2941 * can be used even if the work re-queues itself or migrates to
2942 * another workqueue. On return from this function, @work is
2943 * guaranteed to be not pending or executing on any CPU.
2945 * cancel_work_sync(&delayed_work->work) must not be used for
2946 * delayed_work's. Use cancel_delayed_work_sync() instead.
2948 * The caller must ensure that the workqueue on which @work was last
2949 * queued can't be destroyed before this function returns.
2952 * %true if @work was pending, %false otherwise.
2954 bool cancel_work_sync(struct work_struct
*work
)
2956 return __cancel_work_timer(work
, false);
2958 EXPORT_SYMBOL_GPL(cancel_work_sync
);
2961 * flush_delayed_work - wait for a dwork to finish executing the last queueing
2962 * @dwork: the delayed work to flush
2964 * Delayed timer is cancelled and the pending work is queued for
2965 * immediate execution. Like flush_work(), this function only
2966 * considers the last queueing instance of @dwork.
2969 * %true if flush_work() waited for the work to finish execution,
2970 * %false if it was already idle.
2972 bool flush_delayed_work(struct delayed_work
*dwork
)
2974 local_irq_disable();
2975 if (del_timer_sync(&dwork
->timer
))
2976 __queue_work(dwork
->cpu
, dwork
->wq
, &dwork
->work
);
2978 return flush_work(&dwork
->work
);
2980 EXPORT_SYMBOL(flush_delayed_work
);
2983 * cancel_delayed_work - cancel a delayed work
2984 * @dwork: delayed_work to cancel
2986 * Kill off a pending delayed_work. Returns %true if @dwork was pending
2987 * and canceled; %false if wasn't pending. Note that the work callback
2988 * function may still be running on return, unless it returns %true and the
2989 * work doesn't re-arm itself. Explicitly flush or use
2990 * cancel_delayed_work_sync() to wait on it.
2992 * This function is safe to call from any context including IRQ handler.
2994 bool cancel_delayed_work(struct delayed_work
*dwork
)
2996 unsigned long flags
;
3000 ret
= try_to_grab_pending(&dwork
->work
, true, &flags
);
3001 } while (unlikely(ret
== -EAGAIN
));
3003 if (unlikely(ret
< 0))
3006 set_work_pool_and_clear_pending(&dwork
->work
,
3007 get_work_pool_id(&dwork
->work
));
3008 local_irq_restore(flags
);
3011 EXPORT_SYMBOL(cancel_delayed_work
);
3014 * cancel_delayed_work_sync - cancel a delayed work and wait for it to finish
3015 * @dwork: the delayed work cancel
3017 * This is cancel_work_sync() for delayed works.
3020 * %true if @dwork was pending, %false otherwise.
3022 bool cancel_delayed_work_sync(struct delayed_work
*dwork
)
3024 return __cancel_work_timer(&dwork
->work
, true);
3026 EXPORT_SYMBOL(cancel_delayed_work_sync
);
3029 * schedule_on_each_cpu - execute a function synchronously on each online CPU
3030 * @func: the function to call
3032 * schedule_on_each_cpu() executes @func on each online CPU using the
3033 * system workqueue and blocks until all CPUs have completed.
3034 * schedule_on_each_cpu() is very slow.
3037 * 0 on success, -errno on failure.
3039 int schedule_on_each_cpu(work_func_t func
)
3042 struct work_struct __percpu
*works
;
3044 works
= alloc_percpu(struct work_struct
);
3050 for_each_online_cpu(cpu
) {
3051 struct work_struct
*work
= per_cpu_ptr(works
, cpu
);
3053 INIT_WORK(work
, func
);
3054 schedule_work_on(cpu
, work
);
3057 for_each_online_cpu(cpu
)
3058 flush_work(per_cpu_ptr(works
, cpu
));
3066 * flush_scheduled_work - ensure that any scheduled work has run to completion.
3068 * Forces execution of the kernel-global workqueue and blocks until its
3071 * Think twice before calling this function! It's very easy to get into
3072 * trouble if you don't take great care. Either of the following situations
3073 * will lead to deadlock:
3075 * One of the work items currently on the workqueue needs to acquire
3076 * a lock held by your code or its caller.
3078 * Your code is running in the context of a work routine.
3080 * They will be detected by lockdep when they occur, but the first might not
3081 * occur very often. It depends on what work items are on the workqueue and
3082 * what locks they need, which you have no control over.
3084 * In most situations flushing the entire workqueue is overkill; you merely
3085 * need to know that a particular work item isn't queued and isn't running.
3086 * In such cases you should use cancel_delayed_work_sync() or
3087 * cancel_work_sync() instead.
3089 void flush_scheduled_work(void)
3091 flush_workqueue(system_wq
);
3093 EXPORT_SYMBOL(flush_scheduled_work
);
3096 * execute_in_process_context - reliably execute the routine with user context
3097 * @fn: the function to execute
3098 * @ew: guaranteed storage for the execute work structure (must
3099 * be available when the work executes)
3101 * Executes the function immediately if process context is available,
3102 * otherwise schedules the function for delayed execution.
3104 * Returns: 0 - function was executed
3105 * 1 - function was scheduled for execution
3107 int execute_in_process_context(work_func_t fn
, struct execute_work
*ew
)
3109 if (!in_interrupt()) {
3114 INIT_WORK(&ew
->work
, fn
);
3115 schedule_work(&ew
->work
);
3119 EXPORT_SYMBOL_GPL(execute_in_process_context
);
3123 * Workqueues with WQ_SYSFS flag set is visible to userland via
3124 * /sys/bus/workqueue/devices/WQ_NAME. All visible workqueues have the
3125 * following attributes.
3127 * per_cpu RO bool : whether the workqueue is per-cpu or unbound
3128 * max_active RW int : maximum number of in-flight work items
3130 * Unbound workqueues have the following extra attributes.
3132 * id RO int : the associated pool ID
3133 * nice RW int : nice value of the workers
3134 * cpumask RW mask : bitmask of allowed CPUs for the workers
3137 struct workqueue_struct
*wq
;
3141 static struct workqueue_struct
*dev_to_wq(struct device
*dev
)
3143 struct wq_device
*wq_dev
= container_of(dev
, struct wq_device
, dev
);
3148 static ssize_t
wq_per_cpu_show(struct device
*dev
,
3149 struct device_attribute
*attr
, char *buf
)
3151 struct workqueue_struct
*wq
= dev_to_wq(dev
);
3153 return scnprintf(buf
, PAGE_SIZE
, "%d\n", (bool)!(wq
->flags
& WQ_UNBOUND
));
3156 static ssize_t
wq_max_active_show(struct device
*dev
,
3157 struct device_attribute
*attr
, char *buf
)
3159 struct workqueue_struct
*wq
= dev_to_wq(dev
);
3161 return scnprintf(buf
, PAGE_SIZE
, "%d\n", wq
->saved_max_active
);
3164 static ssize_t
wq_max_active_store(struct device
*dev
,
3165 struct device_attribute
*attr
,
3166 const char *buf
, size_t count
)
3168 struct workqueue_struct
*wq
= dev_to_wq(dev
);
3171 if (sscanf(buf
, "%d", &val
) != 1 || val
<= 0)
3174 workqueue_set_max_active(wq
, val
);
3178 static struct device_attribute wq_sysfs_attrs
[] = {
3179 __ATTR(per_cpu
, 0444, wq_per_cpu_show
, NULL
),
3180 __ATTR(max_active
, 0644, wq_max_active_show
, wq_max_active_store
),
3184 static ssize_t
wq_pool_ids_show(struct device
*dev
,
3185 struct device_attribute
*attr
, char *buf
)
3187 struct workqueue_struct
*wq
= dev_to_wq(dev
);
3188 const char *delim
= "";
3189 int node
, written
= 0;
3191 rcu_read_lock_sched();
3192 for_each_node(node
) {
3193 written
+= scnprintf(buf
+ written
, PAGE_SIZE
- written
,
3194 "%s%d:%d", delim
, node
,
3195 unbound_pwq_by_node(wq
, node
)->pool
->id
);
3198 written
+= scnprintf(buf
+ written
, PAGE_SIZE
- written
, "\n");
3199 rcu_read_unlock_sched();
3204 static ssize_t
wq_nice_show(struct device
*dev
, struct device_attribute
*attr
,
3207 struct workqueue_struct
*wq
= dev_to_wq(dev
);
3210 mutex_lock(&wq
->mutex
);
3211 written
= scnprintf(buf
, PAGE_SIZE
, "%d\n", wq
->unbound_attrs
->nice
);
3212 mutex_unlock(&wq
->mutex
);
3217 /* prepare workqueue_attrs for sysfs store operations */
3218 static struct workqueue_attrs
*wq_sysfs_prep_attrs(struct workqueue_struct
*wq
)
3220 struct workqueue_attrs
*attrs
;
3222 attrs
= alloc_workqueue_attrs(GFP_KERNEL
);
3226 mutex_lock(&wq
->mutex
);
3227 copy_workqueue_attrs(attrs
, wq
->unbound_attrs
);
3228 mutex_unlock(&wq
->mutex
);
3232 static ssize_t
wq_nice_store(struct device
*dev
, struct device_attribute
*attr
,
3233 const char *buf
, size_t count
)
3235 struct workqueue_struct
*wq
= dev_to_wq(dev
);
3236 struct workqueue_attrs
*attrs
;
3239 attrs
= wq_sysfs_prep_attrs(wq
);
3243 if (sscanf(buf
, "%d", &attrs
->nice
) == 1 &&
3244 attrs
->nice
>= -20 && attrs
->nice
<= 19)
3245 ret
= apply_workqueue_attrs(wq
, attrs
);
3249 free_workqueue_attrs(attrs
);
3250 return ret
?: count
;
3253 static ssize_t
wq_cpumask_show(struct device
*dev
,
3254 struct device_attribute
*attr
, char *buf
)
3256 struct workqueue_struct
*wq
= dev_to_wq(dev
);
3259 mutex_lock(&wq
->mutex
);
3260 written
= cpumask_scnprintf(buf
, PAGE_SIZE
, wq
->unbound_attrs
->cpumask
);
3261 mutex_unlock(&wq
->mutex
);
3263 written
+= scnprintf(buf
+ written
, PAGE_SIZE
- written
, "\n");
3267 static ssize_t
wq_cpumask_store(struct device
*dev
,
3268 struct device_attribute
*attr
,
3269 const char *buf
, size_t count
)
3271 struct workqueue_struct
*wq
= dev_to_wq(dev
);
3272 struct workqueue_attrs
*attrs
;
3275 attrs
= wq_sysfs_prep_attrs(wq
);
3279 ret
= cpumask_parse(buf
, attrs
->cpumask
);
3281 ret
= apply_workqueue_attrs(wq
, attrs
);
3283 free_workqueue_attrs(attrs
);
3284 return ret
?: count
;
3287 static ssize_t
wq_numa_show(struct device
*dev
, struct device_attribute
*attr
,
3290 struct workqueue_struct
*wq
= dev_to_wq(dev
);
3293 mutex_lock(&wq
->mutex
);
3294 written
= scnprintf(buf
, PAGE_SIZE
, "%d\n",
3295 !wq
->unbound_attrs
->no_numa
);
3296 mutex_unlock(&wq
->mutex
);
3301 static ssize_t
wq_numa_store(struct device
*dev
, struct device_attribute
*attr
,
3302 const char *buf
, size_t count
)
3304 struct workqueue_struct
*wq
= dev_to_wq(dev
);
3305 struct workqueue_attrs
*attrs
;
3308 attrs
= wq_sysfs_prep_attrs(wq
);
3313 if (sscanf(buf
, "%d", &v
) == 1) {
3314 attrs
->no_numa
= !v
;
3315 ret
= apply_workqueue_attrs(wq
, attrs
);
3318 free_workqueue_attrs(attrs
);
3319 return ret
?: count
;
3322 static struct device_attribute wq_sysfs_unbound_attrs
[] = {
3323 __ATTR(pool_ids
, 0444, wq_pool_ids_show
, NULL
),
3324 __ATTR(nice
, 0644, wq_nice_show
, wq_nice_store
),
3325 __ATTR(cpumask
, 0644, wq_cpumask_show
, wq_cpumask_store
),
3326 __ATTR(numa
, 0644, wq_numa_show
, wq_numa_store
),
3330 static struct bus_type wq_subsys
= {
3331 .name
= "workqueue",
3332 .dev_attrs
= wq_sysfs_attrs
,
3335 static int __init
wq_sysfs_init(void)
3337 return subsys_virtual_register(&wq_subsys
, NULL
);
3339 core_initcall(wq_sysfs_init
);
3341 static void wq_device_release(struct device
*dev
)
3343 struct wq_device
*wq_dev
= container_of(dev
, struct wq_device
, dev
);
3349 * workqueue_sysfs_register - make a workqueue visible in sysfs
3350 * @wq: the workqueue to register
3352 * Expose @wq in sysfs under /sys/bus/workqueue/devices.
3353 * alloc_workqueue*() automatically calls this function if WQ_SYSFS is set
3354 * which is the preferred method.
3356 * Workqueue user should use this function directly iff it wants to apply
3357 * workqueue_attrs before making the workqueue visible in sysfs; otherwise,
3358 * apply_workqueue_attrs() may race against userland updating the
3361 * Returns 0 on success, -errno on failure.
3363 int workqueue_sysfs_register(struct workqueue_struct
*wq
)
3365 struct wq_device
*wq_dev
;
3369 * Adjusting max_active or creating new pwqs by applyting
3370 * attributes breaks ordering guarantee. Disallow exposing ordered
3373 if (WARN_ON(wq
->flags
& __WQ_ORDERED
))
3376 wq
->wq_dev
= wq_dev
= kzalloc(sizeof(*wq_dev
), GFP_KERNEL
);
3381 wq_dev
->dev
.bus
= &wq_subsys
;
3382 wq_dev
->dev
.init_name
= wq
->name
;
3383 wq_dev
->dev
.release
= wq_device_release
;
3386 * unbound_attrs are created separately. Suppress uevent until
3387 * everything is ready.
3389 dev_set_uevent_suppress(&wq_dev
->dev
, true);
3391 ret
= device_register(&wq_dev
->dev
);
3398 if (wq
->flags
& WQ_UNBOUND
) {
3399 struct device_attribute
*attr
;
3401 for (attr
= wq_sysfs_unbound_attrs
; attr
->attr
.name
; attr
++) {
3402 ret
= device_create_file(&wq_dev
->dev
, attr
);
3404 device_unregister(&wq_dev
->dev
);
3411 dev_set_uevent_suppress(&wq_dev
->dev
, false);
3412 kobject_uevent(&wq_dev
->dev
.kobj
, KOBJ_ADD
);
3417 * workqueue_sysfs_unregister - undo workqueue_sysfs_register()
3418 * @wq: the workqueue to unregister
3420 * If @wq is registered to sysfs by workqueue_sysfs_register(), unregister.
3422 static void workqueue_sysfs_unregister(struct workqueue_struct
*wq
)
3424 struct wq_device
*wq_dev
= wq
->wq_dev
;
3430 device_unregister(&wq_dev
->dev
);
3432 #else /* CONFIG_SYSFS */
3433 static void workqueue_sysfs_unregister(struct workqueue_struct
*wq
) { }
3434 #endif /* CONFIG_SYSFS */
3437 * free_workqueue_attrs - free a workqueue_attrs
3438 * @attrs: workqueue_attrs to free
3440 * Undo alloc_workqueue_attrs().
3442 void free_workqueue_attrs(struct workqueue_attrs
*attrs
)
3445 free_cpumask_var(attrs
->cpumask
);
3451 * alloc_workqueue_attrs - allocate a workqueue_attrs
3452 * @gfp_mask: allocation mask to use
3454 * Allocate a new workqueue_attrs, initialize with default settings and
3455 * return it. Returns NULL on failure.
3457 struct workqueue_attrs
*alloc_workqueue_attrs(gfp_t gfp_mask
)
3459 struct workqueue_attrs
*attrs
;
3461 attrs
= kzalloc(sizeof(*attrs
), gfp_mask
);
3464 if (!alloc_cpumask_var(&attrs
->cpumask
, gfp_mask
))
3467 cpumask_copy(attrs
->cpumask
, cpu_possible_mask
);
3470 free_workqueue_attrs(attrs
);
3474 static void copy_workqueue_attrs(struct workqueue_attrs
*to
,
3475 const struct workqueue_attrs
*from
)
3477 to
->nice
= from
->nice
;
3478 cpumask_copy(to
->cpumask
, from
->cpumask
);
3480 * Unlike hash and equality test, this function doesn't ignore
3481 * ->no_numa as it is used for both pool and wq attrs. Instead,
3482 * get_unbound_pool() explicitly clears ->no_numa after copying.
3484 to
->no_numa
= from
->no_numa
;
3487 /* hash value of the content of @attr */
3488 static u32
wqattrs_hash(const struct workqueue_attrs
*attrs
)
3492 hash
= jhash_1word(attrs
->nice
, hash
);
3493 hash
= jhash(cpumask_bits(attrs
->cpumask
),
3494 BITS_TO_LONGS(nr_cpumask_bits
) * sizeof(long), hash
);
3498 /* content equality test */
3499 static bool wqattrs_equal(const struct workqueue_attrs
*a
,
3500 const struct workqueue_attrs
*b
)
3502 if (a
->nice
!= b
->nice
)
3504 if (!cpumask_equal(a
->cpumask
, b
->cpumask
))
3510 * init_worker_pool - initialize a newly zalloc'd worker_pool
3511 * @pool: worker_pool to initialize
3513 * Initiailize a newly zalloc'd @pool. It also allocates @pool->attrs.
3514 * Returns 0 on success, -errno on failure. Even on failure, all fields
3515 * inside @pool proper are initialized and put_unbound_pool() can be called
3516 * on @pool safely to release it.
3518 static int init_worker_pool(struct worker_pool
*pool
)
3520 spin_lock_init(&pool
->lock
);
3523 pool
->node
= NUMA_NO_NODE
;
3524 pool
->flags
|= POOL_DISASSOCIATED
;
3525 INIT_LIST_HEAD(&pool
->worklist
);
3526 INIT_LIST_HEAD(&pool
->idle_list
);
3527 hash_init(pool
->busy_hash
);
3529 init_timer_deferrable(&pool
->idle_timer
);
3530 pool
->idle_timer
.function
= idle_worker_timeout
;
3531 pool
->idle_timer
.data
= (unsigned long)pool
;
3533 setup_timer(&pool
->mayday_timer
, pool_mayday_timeout
,
3534 (unsigned long)pool
);
3536 mutex_init(&pool
->manager_arb
);
3537 mutex_init(&pool
->manager_mutex
);
3538 idr_init(&pool
->worker_idr
);
3540 INIT_HLIST_NODE(&pool
->hash_node
);
3543 /* shouldn't fail above this point */
3544 pool
->attrs
= alloc_workqueue_attrs(GFP_KERNEL
);
3550 static void rcu_free_pool(struct rcu_head
*rcu
)
3552 struct worker_pool
*pool
= container_of(rcu
, struct worker_pool
, rcu
);
3554 idr_destroy(&pool
->worker_idr
);
3555 free_workqueue_attrs(pool
->attrs
);
3560 * put_unbound_pool - put a worker_pool
3561 * @pool: worker_pool to put
3563 * Put @pool. If its refcnt reaches zero, it gets destroyed in sched-RCU
3564 * safe manner. get_unbound_pool() calls this function on its failure path
3565 * and this function should be able to release pools which went through,
3566 * successfully or not, init_worker_pool().
3568 * Should be called with wq_pool_mutex held.
3570 static void put_unbound_pool(struct worker_pool
*pool
)
3572 struct worker
*worker
;
3574 lockdep_assert_held(&wq_pool_mutex
);
3580 if (WARN_ON(!(pool
->flags
& POOL_DISASSOCIATED
)) ||
3581 WARN_ON(!list_empty(&pool
->worklist
)))
3584 /* release id and unhash */
3586 idr_remove(&worker_pool_idr
, pool
->id
);
3587 hash_del(&pool
->hash_node
);
3590 * Become the manager and destroy all workers. Grabbing
3591 * manager_arb prevents @pool's workers from blocking on
3594 mutex_lock(&pool
->manager_arb
);
3595 mutex_lock(&pool
->manager_mutex
);
3596 spin_lock_irq(&pool
->lock
);
3598 while ((worker
= first_worker(pool
)))
3599 destroy_worker(worker
);
3600 WARN_ON(pool
->nr_workers
|| pool
->nr_idle
);
3602 spin_unlock_irq(&pool
->lock
);
3603 mutex_unlock(&pool
->manager_mutex
);
3604 mutex_unlock(&pool
->manager_arb
);
3606 /* shut down the timers */
3607 del_timer_sync(&pool
->idle_timer
);
3608 del_timer_sync(&pool
->mayday_timer
);
3610 /* sched-RCU protected to allow dereferences from get_work_pool() */
3611 call_rcu_sched(&pool
->rcu
, rcu_free_pool
);
3615 * get_unbound_pool - get a worker_pool with the specified attributes
3616 * @attrs: the attributes of the worker_pool to get
3618 * Obtain a worker_pool which has the same attributes as @attrs, bump the
3619 * reference count and return it. If there already is a matching
3620 * worker_pool, it will be used; otherwise, this function attempts to
3621 * create a new one. On failure, returns NULL.
3623 * Should be called with wq_pool_mutex held.
3625 static struct worker_pool
*get_unbound_pool(const struct workqueue_attrs
*attrs
)
3627 u32 hash
= wqattrs_hash(attrs
);
3628 struct worker_pool
*pool
;
3631 lockdep_assert_held(&wq_pool_mutex
);
3633 /* do we already have a matching pool? */
3634 hash_for_each_possible(unbound_pool_hash
, pool
, hash_node
, hash
) {
3635 if (wqattrs_equal(pool
->attrs
, attrs
)) {
3641 /* nope, create a new one */
3642 pool
= kzalloc(sizeof(*pool
), GFP_KERNEL
);
3643 if (!pool
|| init_worker_pool(pool
) < 0)
3646 if (workqueue_freezing
)
3647 pool
->flags
|= POOL_FREEZING
;
3649 lockdep_set_subclass(&pool
->lock
, 1); /* see put_pwq() */
3650 copy_workqueue_attrs(pool
->attrs
, attrs
);
3653 * no_numa isn't a worker_pool attribute, always clear it. See
3654 * 'struct workqueue_attrs' comments for detail.
3656 pool
->attrs
->no_numa
= false;
3658 /* if cpumask is contained inside a NUMA node, we belong to that node */
3659 if (wq_numa_enabled
) {
3660 for_each_node(node
) {
3661 if (cpumask_subset(pool
->attrs
->cpumask
,
3662 wq_numa_possible_cpumask
[node
])) {
3669 if (worker_pool_assign_id(pool
) < 0)
3672 /* create and start the initial worker */
3673 if (create_and_start_worker(pool
) < 0)
3677 hash_add(unbound_pool_hash
, &pool
->hash_node
, hash
);
3682 put_unbound_pool(pool
);
3686 static void rcu_free_pwq(struct rcu_head
*rcu
)
3688 kmem_cache_free(pwq_cache
,
3689 container_of(rcu
, struct pool_workqueue
, rcu
));
3693 * Scheduled on system_wq by put_pwq() when an unbound pwq hits zero refcnt
3694 * and needs to be destroyed.
3696 static void pwq_unbound_release_workfn(struct work_struct
*work
)
3698 struct pool_workqueue
*pwq
= container_of(work
, struct pool_workqueue
,
3699 unbound_release_work
);
3700 struct workqueue_struct
*wq
= pwq
->wq
;
3701 struct worker_pool
*pool
= pwq
->pool
;
3704 if (WARN_ON_ONCE(!(wq
->flags
& WQ_UNBOUND
)))
3708 * Unlink @pwq. Synchronization against wq->mutex isn't strictly
3709 * necessary on release but do it anyway. It's easier to verify
3710 * and consistent with the linking path.
3712 mutex_lock(&wq
->mutex
);
3713 list_del_rcu(&pwq
->pwqs_node
);
3714 is_last
= list_empty(&wq
->pwqs
);
3715 mutex_unlock(&wq
->mutex
);
3717 mutex_lock(&wq_pool_mutex
);
3718 put_unbound_pool(pool
);
3719 mutex_unlock(&wq_pool_mutex
);
3721 call_rcu_sched(&pwq
->rcu
, rcu_free_pwq
);
3724 * If we're the last pwq going away, @wq is already dead and no one
3725 * is gonna access it anymore. Free it.
3728 free_workqueue_attrs(wq
->unbound_attrs
);
3734 * pwq_adjust_max_active - update a pwq's max_active to the current setting
3735 * @pwq: target pool_workqueue
3737 * If @pwq isn't freezing, set @pwq->max_active to the associated
3738 * workqueue's saved_max_active and activate delayed work items
3739 * accordingly. If @pwq is freezing, clear @pwq->max_active to zero.
3741 static void pwq_adjust_max_active(struct pool_workqueue
*pwq
)
3743 struct workqueue_struct
*wq
= pwq
->wq
;
3744 bool freezable
= wq
->flags
& WQ_FREEZABLE
;
3746 /* for @wq->saved_max_active */
3747 lockdep_assert_held(&wq
->mutex
);
3749 /* fast exit for non-freezable wqs */
3750 if (!freezable
&& pwq
->max_active
== wq
->saved_max_active
)
3753 spin_lock_irq(&pwq
->pool
->lock
);
3755 if (!freezable
|| !(pwq
->pool
->flags
& POOL_FREEZING
)) {
3756 pwq
->max_active
= wq
->saved_max_active
;
3758 while (!list_empty(&pwq
->delayed_works
) &&
3759 pwq
->nr_active
< pwq
->max_active
)
3760 pwq_activate_first_delayed(pwq
);
3763 * Need to kick a worker after thawed or an unbound wq's
3764 * max_active is bumped. It's a slow path. Do it always.
3766 wake_up_worker(pwq
->pool
);
3768 pwq
->max_active
= 0;
3771 spin_unlock_irq(&pwq
->pool
->lock
);
3774 /* initialize newly alloced @pwq which is associated with @wq and @pool */
3775 static void init_pwq(struct pool_workqueue
*pwq
, struct workqueue_struct
*wq
,
3776 struct worker_pool
*pool
)
3778 BUG_ON((unsigned long)pwq
& WORK_STRUCT_FLAG_MASK
);
3780 memset(pwq
, 0, sizeof(*pwq
));
3784 pwq
->flush_color
= -1;
3786 INIT_LIST_HEAD(&pwq
->delayed_works
);
3787 INIT_LIST_HEAD(&pwq
->pwqs_node
);
3788 INIT_LIST_HEAD(&pwq
->mayday_node
);
3789 INIT_WORK(&pwq
->unbound_release_work
, pwq_unbound_release_workfn
);
3792 /* sync @pwq with the current state of its associated wq and link it */
3793 static void link_pwq(struct pool_workqueue
*pwq
)
3795 struct workqueue_struct
*wq
= pwq
->wq
;
3797 lockdep_assert_held(&wq
->mutex
);
3799 /* may be called multiple times, ignore if already linked */
3800 if (!list_empty(&pwq
->pwqs_node
))
3804 * Set the matching work_color. This is synchronized with
3805 * wq->mutex to avoid confusing flush_workqueue().
3807 pwq
->work_color
= wq
->work_color
;
3809 /* sync max_active to the current setting */
3810 pwq_adjust_max_active(pwq
);
3813 list_add_rcu(&pwq
->pwqs_node
, &wq
->pwqs
);
3816 /* obtain a pool matching @attr and create a pwq associating the pool and @wq */
3817 static struct pool_workqueue
*alloc_unbound_pwq(struct workqueue_struct
*wq
,
3818 const struct workqueue_attrs
*attrs
)
3820 struct worker_pool
*pool
;
3821 struct pool_workqueue
*pwq
;
3823 lockdep_assert_held(&wq_pool_mutex
);
3825 pool
= get_unbound_pool(attrs
);
3829 pwq
= kmem_cache_alloc_node(pwq_cache
, GFP_KERNEL
, pool
->node
);
3831 put_unbound_pool(pool
);
3835 init_pwq(pwq
, wq
, pool
);
3839 /* undo alloc_unbound_pwq(), used only in the error path */
3840 static void free_unbound_pwq(struct pool_workqueue
*pwq
)
3842 lockdep_assert_held(&wq_pool_mutex
);
3845 put_unbound_pool(pwq
->pool
);
3846 kmem_cache_free(pwq_cache
, pwq
);
3851 * wq_calc_node_mask - calculate a wq_attrs' cpumask for the specified node
3852 * @attrs: the wq_attrs of interest
3853 * @node: the target NUMA node
3854 * @cpu_going_down: if >= 0, the CPU to consider as offline
3855 * @cpumask: outarg, the resulting cpumask
3857 * Calculate the cpumask a workqueue with @attrs should use on @node. If
3858 * @cpu_going_down is >= 0, that cpu is considered offline during
3859 * calculation. The result is stored in @cpumask. This function returns
3860 * %true if the resulting @cpumask is different from @attrs->cpumask,
3863 * If NUMA affinity is not enabled, @attrs->cpumask is always used. If
3864 * enabled and @node has online CPUs requested by @attrs, the returned
3865 * cpumask is the intersection of the possible CPUs of @node and
3868 * The caller is responsible for ensuring that the cpumask of @node stays
3871 static bool wq_calc_node_cpumask(const struct workqueue_attrs
*attrs
, int node
,
3872 int cpu_going_down
, cpumask_t
*cpumask
)
3874 if (!wq_numa_enabled
|| attrs
->no_numa
)
3877 /* does @node have any online CPUs @attrs wants? */
3878 cpumask_and(cpumask
, cpumask_of_node(node
), attrs
->cpumask
);
3879 if (cpu_going_down
>= 0)
3880 cpumask_clear_cpu(cpu_going_down
, cpumask
);
3882 if (cpumask_empty(cpumask
))
3885 /* yeap, return possible CPUs in @node that @attrs wants */
3886 cpumask_and(cpumask
, attrs
->cpumask
, wq_numa_possible_cpumask
[node
]);
3887 return !cpumask_equal(cpumask
, attrs
->cpumask
);
3890 cpumask_copy(cpumask
, attrs
->cpumask
);
3894 /* install @pwq into @wq's numa_pwq_tbl[] for @node and return the old pwq */
3895 static struct pool_workqueue
*numa_pwq_tbl_install(struct workqueue_struct
*wq
,
3897 struct pool_workqueue
*pwq
)
3899 struct pool_workqueue
*old_pwq
;
3901 lockdep_assert_held(&wq
->mutex
);
3903 /* link_pwq() can handle duplicate calls */
3906 old_pwq
= rcu_access_pointer(wq
->numa_pwq_tbl
[node
]);
3907 rcu_assign_pointer(wq
->numa_pwq_tbl
[node
], pwq
);
3912 * apply_workqueue_attrs - apply new workqueue_attrs to an unbound workqueue
3913 * @wq: the target workqueue
3914 * @attrs: the workqueue_attrs to apply, allocated with alloc_workqueue_attrs()
3916 * Apply @attrs to an unbound workqueue @wq. Unless disabled, on NUMA
3917 * machines, this function maps a separate pwq to each NUMA node with
3918 * possibles CPUs in @attrs->cpumask so that work items are affine to the
3919 * NUMA node it was issued on. Older pwqs are released as in-flight work
3920 * items finish. Note that a work item which repeatedly requeues itself
3921 * back-to-back will stay on its current pwq.
3923 * Performs GFP_KERNEL allocations. Returns 0 on success and -errno on
3926 int apply_workqueue_attrs(struct workqueue_struct
*wq
,
3927 const struct workqueue_attrs
*attrs
)
3929 struct workqueue_attrs
*new_attrs
, *tmp_attrs
;
3930 struct pool_workqueue
**pwq_tbl
, *dfl_pwq
;
3933 /* only unbound workqueues can change attributes */
3934 if (WARN_ON(!(wq
->flags
& WQ_UNBOUND
)))
3937 /* creating multiple pwqs breaks ordering guarantee */
3938 if (WARN_ON((wq
->flags
& __WQ_ORDERED
) && !list_empty(&wq
->pwqs
)))
3941 pwq_tbl
= kzalloc(wq_numa_tbl_len
* sizeof(pwq_tbl
[0]), GFP_KERNEL
);
3942 new_attrs
= alloc_workqueue_attrs(GFP_KERNEL
);
3943 tmp_attrs
= alloc_workqueue_attrs(GFP_KERNEL
);
3944 if (!pwq_tbl
|| !new_attrs
|| !tmp_attrs
)
3947 /* make a copy of @attrs and sanitize it */
3948 copy_workqueue_attrs(new_attrs
, attrs
);
3949 cpumask_and(new_attrs
->cpumask
, new_attrs
->cpumask
, cpu_possible_mask
);
3952 * We may create multiple pwqs with differing cpumasks. Make a
3953 * copy of @new_attrs which will be modified and used to obtain
3956 copy_workqueue_attrs(tmp_attrs
, new_attrs
);
3959 * CPUs should stay stable across pwq creations and installations.
3960 * Pin CPUs, determine the target cpumask for each node and create
3965 mutex_lock(&wq_pool_mutex
);
3968 * If something goes wrong during CPU up/down, we'll fall back to
3969 * the default pwq covering whole @attrs->cpumask. Always create
3970 * it even if we don't use it immediately.
3972 dfl_pwq
= alloc_unbound_pwq(wq
, new_attrs
);
3976 for_each_node(node
) {
3977 if (wq_calc_node_cpumask(attrs
, node
, -1, tmp_attrs
->cpumask
)) {
3978 pwq_tbl
[node
] = alloc_unbound_pwq(wq
, tmp_attrs
);
3983 pwq_tbl
[node
] = dfl_pwq
;
3987 mutex_unlock(&wq_pool_mutex
);
3989 /* all pwqs have been created successfully, let's install'em */
3990 mutex_lock(&wq
->mutex
);
3992 copy_workqueue_attrs(wq
->unbound_attrs
, new_attrs
);
3994 /* save the previous pwq and install the new one */
3996 pwq_tbl
[node
] = numa_pwq_tbl_install(wq
, node
, pwq_tbl
[node
]);
3998 /* @dfl_pwq might not have been used, ensure it's linked */
4000 swap(wq
->dfl_pwq
, dfl_pwq
);
4002 mutex_unlock(&wq
->mutex
);
4004 /* put the old pwqs */
4006 put_pwq_unlocked(pwq_tbl
[node
]);
4007 put_pwq_unlocked(dfl_pwq
);
4013 free_workqueue_attrs(tmp_attrs
);
4014 free_workqueue_attrs(new_attrs
);
4019 free_unbound_pwq(dfl_pwq
);
4021 if (pwq_tbl
&& pwq_tbl
[node
] != dfl_pwq
)
4022 free_unbound_pwq(pwq_tbl
[node
]);
4023 mutex_unlock(&wq_pool_mutex
);
4031 * wq_update_unbound_numa - update NUMA affinity of a wq for CPU hot[un]plug
4032 * @wq: the target workqueue
4033 * @cpu: the CPU coming up or going down
4034 * @online: whether @cpu is coming up or going down
4036 * This function is to be called from %CPU_DOWN_PREPARE, %CPU_ONLINE and
4037 * %CPU_DOWN_FAILED. @cpu is being hot[un]plugged, update NUMA affinity of
4040 * If NUMA affinity can't be adjusted due to memory allocation failure, it
4041 * falls back to @wq->dfl_pwq which may not be optimal but is always
4044 * Note that when the last allowed CPU of a NUMA node goes offline for a
4045 * workqueue with a cpumask spanning multiple nodes, the workers which were
4046 * already executing the work items for the workqueue will lose their CPU
4047 * affinity and may execute on any CPU. This is similar to how per-cpu
4048 * workqueues behave on CPU_DOWN. If a workqueue user wants strict
4049 * affinity, it's the user's responsibility to flush the work item from
4052 static void wq_update_unbound_numa(struct workqueue_struct
*wq
, int cpu
,
4055 int node
= cpu_to_node(cpu
);
4056 int cpu_off
= online
? -1 : cpu
;
4057 struct pool_workqueue
*old_pwq
= NULL
, *pwq
;
4058 struct workqueue_attrs
*target_attrs
;
4061 lockdep_assert_held(&wq_pool_mutex
);
4063 if (!wq_numa_enabled
|| !(wq
->flags
& WQ_UNBOUND
))
4067 * We don't wanna alloc/free wq_attrs for each wq for each CPU.
4068 * Let's use a preallocated one. The following buf is protected by
4069 * CPU hotplug exclusion.
4071 target_attrs
= wq_update_unbound_numa_attrs_buf
;
4072 cpumask
= target_attrs
->cpumask
;
4074 mutex_lock(&wq
->mutex
);
4075 if (wq
->unbound_attrs
->no_numa
)
4078 copy_workqueue_attrs(target_attrs
, wq
->unbound_attrs
);
4079 pwq
= unbound_pwq_by_node(wq
, node
);
4082 * Let's determine what needs to be done. If the target cpumask is
4083 * different from wq's, we need to compare it to @pwq's and create
4084 * a new one if they don't match. If the target cpumask equals
4085 * wq's, the default pwq should be used. If @pwq is already the
4086 * default one, nothing to do; otherwise, install the default one.
4088 if (wq_calc_node_cpumask(wq
->unbound_attrs
, node
, cpu_off
, cpumask
)) {
4089 if (cpumask_equal(cpumask
, pwq
->pool
->attrs
->cpumask
))
4092 if (pwq
== wq
->dfl_pwq
)
4098 mutex_unlock(&wq
->mutex
);
4100 /* create a new pwq */
4101 pwq
= alloc_unbound_pwq(wq
, target_attrs
);
4103 pr_warning("workqueue: allocation failed while updating NUMA affinity of \"%s\"\n",
4105 mutex_lock(&wq
->mutex
);
4110 * Install the new pwq. As this function is called only from CPU
4111 * hotplug callbacks and applying a new attrs is wrapped with
4112 * get/put_online_cpus(), @wq->unbound_attrs couldn't have changed
4115 mutex_lock(&wq
->mutex
);
4116 old_pwq
= numa_pwq_tbl_install(wq
, node
, pwq
);
4120 spin_lock_irq(&wq
->dfl_pwq
->pool
->lock
);
4121 get_pwq(wq
->dfl_pwq
);
4122 spin_unlock_irq(&wq
->dfl_pwq
->pool
->lock
);
4123 old_pwq
= numa_pwq_tbl_install(wq
, node
, wq
->dfl_pwq
);
4125 mutex_unlock(&wq
->mutex
);
4126 put_pwq_unlocked(old_pwq
);
4129 static int alloc_and_link_pwqs(struct workqueue_struct
*wq
)
4131 bool highpri
= wq
->flags
& WQ_HIGHPRI
;
4134 if (!(wq
->flags
& WQ_UNBOUND
)) {
4135 wq
->cpu_pwqs
= alloc_percpu(struct pool_workqueue
);
4139 for_each_possible_cpu(cpu
) {
4140 struct pool_workqueue
*pwq
=
4141 per_cpu_ptr(wq
->cpu_pwqs
, cpu
);
4142 struct worker_pool
*cpu_pools
=
4143 per_cpu(cpu_worker_pools
, cpu
);
4145 init_pwq(pwq
, wq
, &cpu_pools
[highpri
]);
4147 mutex_lock(&wq
->mutex
);
4149 mutex_unlock(&wq
->mutex
);
4152 } else if (wq
->flags
& __WQ_ORDERED
) {
4153 ret
= apply_workqueue_attrs(wq
, ordered_wq_attrs
[highpri
]);
4154 /* there should only be single pwq for ordering guarantee */
4155 WARN(!ret
&& (wq
->pwqs
.next
!= &wq
->dfl_pwq
->pwqs_node
||
4156 wq
->pwqs
.prev
!= &wq
->dfl_pwq
->pwqs_node
),
4157 "ordering guarantee broken for workqueue %s\n", wq
->name
);
4160 return apply_workqueue_attrs(wq
, unbound_std_wq_attrs
[highpri
]);
4164 static int wq_clamp_max_active(int max_active
, unsigned int flags
,
4167 int lim
= flags
& WQ_UNBOUND
? WQ_UNBOUND_MAX_ACTIVE
: WQ_MAX_ACTIVE
;
4169 if (max_active
< 1 || max_active
> lim
)
4170 pr_warn("workqueue: max_active %d requested for %s is out of range, clamping between %d and %d\n",
4171 max_active
, name
, 1, lim
);
4173 return clamp_val(max_active
, 1, lim
);
4176 struct workqueue_struct
*__alloc_workqueue_key(const char *fmt
,
4179 struct lock_class_key
*key
,
4180 const char *lock_name
, ...)
4182 size_t tbl_size
= 0;
4184 struct workqueue_struct
*wq
;
4185 struct pool_workqueue
*pwq
;
4187 /* allocate wq and format name */
4188 if (flags
& WQ_UNBOUND
)
4189 tbl_size
= wq_numa_tbl_len
* sizeof(wq
->numa_pwq_tbl
[0]);
4191 wq
= kzalloc(sizeof(*wq
) + tbl_size
, GFP_KERNEL
);
4195 if (flags
& WQ_UNBOUND
) {
4196 wq
->unbound_attrs
= alloc_workqueue_attrs(GFP_KERNEL
);
4197 if (!wq
->unbound_attrs
)
4201 va_start(args
, lock_name
);
4202 vsnprintf(wq
->name
, sizeof(wq
->name
), fmt
, args
);
4205 max_active
= max_active
?: WQ_DFL_ACTIVE
;
4206 max_active
= wq_clamp_max_active(max_active
, flags
, wq
->name
);
4210 wq
->saved_max_active
= max_active
;
4211 mutex_init(&wq
->mutex
);
4212 atomic_set(&wq
->nr_pwqs_to_flush
, 0);
4213 INIT_LIST_HEAD(&wq
->pwqs
);
4214 INIT_LIST_HEAD(&wq
->flusher_queue
);
4215 INIT_LIST_HEAD(&wq
->flusher_overflow
);
4216 INIT_LIST_HEAD(&wq
->maydays
);
4218 lockdep_init_map(&wq
->lockdep_map
, lock_name
, key
, 0);
4219 INIT_LIST_HEAD(&wq
->list
);
4221 if (alloc_and_link_pwqs(wq
) < 0)
4225 * Workqueues which may be used during memory reclaim should
4226 * have a rescuer to guarantee forward progress.
4228 if (flags
& WQ_MEM_RECLAIM
) {
4229 struct worker
*rescuer
;
4231 rescuer
= alloc_worker();
4235 rescuer
->rescue_wq
= wq
;
4236 rescuer
->task
= kthread_create(rescuer_thread
, rescuer
, "%s",
4238 if (IS_ERR(rescuer
->task
)) {
4243 wq
->rescuer
= rescuer
;
4244 rescuer
->task
->flags
|= PF_NO_SETAFFINITY
;
4245 wake_up_process(rescuer
->task
);
4248 if ((wq
->flags
& WQ_SYSFS
) && workqueue_sysfs_register(wq
))
4252 * wq_pool_mutex protects global freeze state and workqueues list.
4253 * Grab it, adjust max_active and add the new @wq to workqueues
4256 mutex_lock(&wq_pool_mutex
);
4258 mutex_lock(&wq
->mutex
);
4259 for_each_pwq(pwq
, wq
)
4260 pwq_adjust_max_active(pwq
);
4261 mutex_unlock(&wq
->mutex
);
4263 list_add(&wq
->list
, &workqueues
);
4265 mutex_unlock(&wq_pool_mutex
);
4270 free_workqueue_attrs(wq
->unbound_attrs
);
4274 destroy_workqueue(wq
);
4277 EXPORT_SYMBOL_GPL(__alloc_workqueue_key
);
4280 * destroy_workqueue - safely terminate a workqueue
4281 * @wq: target workqueue
4283 * Safely destroy a workqueue. All work currently pending will be done first.
4285 void destroy_workqueue(struct workqueue_struct
*wq
)
4287 struct pool_workqueue
*pwq
;
4290 /* drain it before proceeding with destruction */
4291 drain_workqueue(wq
);
4294 mutex_lock(&wq
->mutex
);
4295 for_each_pwq(pwq
, wq
) {
4298 for (i
= 0; i
< WORK_NR_COLORS
; i
++) {
4299 if (WARN_ON(pwq
->nr_in_flight
[i
])) {
4300 mutex_unlock(&wq
->mutex
);
4305 if (WARN_ON((pwq
!= wq
->dfl_pwq
) && (pwq
->refcnt
> 1)) ||
4306 WARN_ON(pwq
->nr_active
) ||
4307 WARN_ON(!list_empty(&pwq
->delayed_works
))) {
4308 mutex_unlock(&wq
->mutex
);
4312 mutex_unlock(&wq
->mutex
);
4315 * wq list is used to freeze wq, remove from list after
4316 * flushing is complete in case freeze races us.
4318 mutex_lock(&wq_pool_mutex
);
4319 list_del_init(&wq
->list
);
4320 mutex_unlock(&wq_pool_mutex
);
4322 workqueue_sysfs_unregister(wq
);
4325 kthread_stop(wq
->rescuer
->task
);
4330 if (!(wq
->flags
& WQ_UNBOUND
)) {
4332 * The base ref is never dropped on per-cpu pwqs. Directly
4333 * free the pwqs and wq.
4335 free_percpu(wq
->cpu_pwqs
);
4339 * We're the sole accessor of @wq at this point. Directly
4340 * access numa_pwq_tbl[] and dfl_pwq to put the base refs.
4341 * @wq will be freed when the last pwq is released.
4343 for_each_node(node
) {
4344 pwq
= rcu_access_pointer(wq
->numa_pwq_tbl
[node
]);
4345 RCU_INIT_POINTER(wq
->numa_pwq_tbl
[node
], NULL
);
4346 put_pwq_unlocked(pwq
);
4350 * Put dfl_pwq. @wq may be freed any time after dfl_pwq is
4351 * put. Don't access it afterwards.
4355 put_pwq_unlocked(pwq
);
4358 EXPORT_SYMBOL_GPL(destroy_workqueue
);
4361 * workqueue_set_max_active - adjust max_active of a workqueue
4362 * @wq: target workqueue
4363 * @max_active: new max_active value.
4365 * Set max_active of @wq to @max_active.
4368 * Don't call from IRQ context.
4370 void workqueue_set_max_active(struct workqueue_struct
*wq
, int max_active
)
4372 struct pool_workqueue
*pwq
;
4374 /* disallow meddling with max_active for ordered workqueues */
4375 if (WARN_ON(wq
->flags
& __WQ_ORDERED
))
4378 max_active
= wq_clamp_max_active(max_active
, wq
->flags
, wq
->name
);
4380 mutex_lock(&wq
->mutex
);
4382 wq
->saved_max_active
= max_active
;
4384 for_each_pwq(pwq
, wq
)
4385 pwq_adjust_max_active(pwq
);
4387 mutex_unlock(&wq
->mutex
);
4389 EXPORT_SYMBOL_GPL(workqueue_set_max_active
);
4392 * current_is_workqueue_rescuer - is %current workqueue rescuer?
4394 * Determine whether %current is a workqueue rescuer. Can be used from
4395 * work functions to determine whether it's being run off the rescuer task.
4397 bool current_is_workqueue_rescuer(void)
4399 struct worker
*worker
= current_wq_worker();
4401 return worker
&& worker
->rescue_wq
;
4405 * workqueue_congested - test whether a workqueue is congested
4406 * @cpu: CPU in question
4407 * @wq: target workqueue
4409 * Test whether @wq's cpu workqueue for @cpu is congested. There is
4410 * no synchronization around this function and the test result is
4411 * unreliable and only useful as advisory hints or for debugging.
4413 * If @cpu is WORK_CPU_UNBOUND, the test is performed on the local CPU.
4414 * Note that both per-cpu and unbound workqueues may be associated with
4415 * multiple pool_workqueues which have separate congested states. A
4416 * workqueue being congested on one CPU doesn't mean the workqueue is also
4417 * contested on other CPUs / NUMA nodes.
4420 * %true if congested, %false otherwise.
4422 bool workqueue_congested(int cpu
, struct workqueue_struct
*wq
)
4424 struct pool_workqueue
*pwq
;
4427 rcu_read_lock_sched();
4429 if (cpu
== WORK_CPU_UNBOUND
)
4430 cpu
= smp_processor_id();
4432 if (!(wq
->flags
& WQ_UNBOUND
))
4433 pwq
= per_cpu_ptr(wq
->cpu_pwqs
, cpu
);
4435 pwq
= unbound_pwq_by_node(wq
, cpu_to_node(cpu
));
4437 ret
= !list_empty(&pwq
->delayed_works
);
4438 rcu_read_unlock_sched();
4442 EXPORT_SYMBOL_GPL(workqueue_congested
);
4445 * work_busy - test whether a work is currently pending or running
4446 * @work: the work to be tested
4448 * Test whether @work is currently pending or running. There is no
4449 * synchronization around this function and the test result is
4450 * unreliable and only useful as advisory hints or for debugging.
4453 * OR'd bitmask of WORK_BUSY_* bits.
4455 unsigned int work_busy(struct work_struct
*work
)
4457 struct worker_pool
*pool
;
4458 unsigned long flags
;
4459 unsigned int ret
= 0;
4461 if (work_pending(work
))
4462 ret
|= WORK_BUSY_PENDING
;
4464 local_irq_save(flags
);
4465 pool
= get_work_pool(work
);
4467 spin_lock(&pool
->lock
);
4468 if (find_worker_executing_work(pool
, work
))
4469 ret
|= WORK_BUSY_RUNNING
;
4470 spin_unlock(&pool
->lock
);
4472 local_irq_restore(flags
);
4476 EXPORT_SYMBOL_GPL(work_busy
);
4479 * set_worker_desc - set description for the current work item
4480 * @fmt: printf-style format string
4481 * @...: arguments for the format string
4483 * This function can be called by a running work function to describe what
4484 * the work item is about. If the worker task gets dumped, this
4485 * information will be printed out together to help debugging. The
4486 * description can be at most WORKER_DESC_LEN including the trailing '\0'.
4488 void set_worker_desc(const char *fmt
, ...)
4490 struct worker
*worker
= current_wq_worker();
4494 va_start(args
, fmt
);
4495 vsnprintf(worker
->desc
, sizeof(worker
->desc
), fmt
, args
);
4497 worker
->desc_valid
= true;
4502 * print_worker_info - print out worker information and description
4503 * @log_lvl: the log level to use when printing
4504 * @task: target task
4506 * If @task is a worker and currently executing a work item, print out the
4507 * name of the workqueue being serviced and worker description set with
4508 * set_worker_desc() by the currently executing work item.
4510 * This function can be safely called on any task as long as the
4511 * task_struct itself is accessible. While safe, this function isn't
4512 * synchronized and may print out mixups or garbages of limited length.
4514 void print_worker_info(const char *log_lvl
, struct task_struct
*task
)
4516 work_func_t
*fn
= NULL
;
4517 char name
[WQ_NAME_LEN
] = { };
4518 char desc
[WORKER_DESC_LEN
] = { };
4519 struct pool_workqueue
*pwq
= NULL
;
4520 struct workqueue_struct
*wq
= NULL
;
4521 bool desc_valid
= false;
4522 struct worker
*worker
;
4524 if (!(task
->flags
& PF_WQ_WORKER
))
4528 * This function is called without any synchronization and @task
4529 * could be in any state. Be careful with dereferences.
4531 worker
= probe_kthread_data(task
);
4534 * Carefully copy the associated workqueue's workfn and name. Keep
4535 * the original last '\0' in case the original contains garbage.
4537 probe_kernel_read(&fn
, &worker
->current_func
, sizeof(fn
));
4538 probe_kernel_read(&pwq
, &worker
->current_pwq
, sizeof(pwq
));
4539 probe_kernel_read(&wq
, &pwq
->wq
, sizeof(wq
));
4540 probe_kernel_read(name
, wq
->name
, sizeof(name
) - 1);
4542 /* copy worker description */
4543 probe_kernel_read(&desc_valid
, &worker
->desc_valid
, sizeof(desc_valid
));
4545 probe_kernel_read(desc
, worker
->desc
, sizeof(desc
) - 1);
4547 if (fn
|| name
[0] || desc
[0]) {
4548 printk("%sWorkqueue: %s %pf", log_lvl
, name
, fn
);
4550 pr_cont(" (%s)", desc
);
4558 * There are two challenges in supporting CPU hotplug. Firstly, there
4559 * are a lot of assumptions on strong associations among work, pwq and
4560 * pool which make migrating pending and scheduled works very
4561 * difficult to implement without impacting hot paths. Secondly,
4562 * worker pools serve mix of short, long and very long running works making
4563 * blocked draining impractical.
4565 * This is solved by allowing the pools to be disassociated from the CPU
4566 * running as an unbound one and allowing it to be reattached later if the
4567 * cpu comes back online.
4570 static void wq_unbind_fn(struct work_struct
*work
)
4572 int cpu
= smp_processor_id();
4573 struct worker_pool
*pool
;
4574 struct worker
*worker
;
4577 for_each_cpu_worker_pool(pool
, cpu
) {
4578 WARN_ON_ONCE(cpu
!= smp_processor_id());
4580 mutex_lock(&pool
->manager_mutex
);
4581 spin_lock_irq(&pool
->lock
);
4584 * We've blocked all manager operations. Make all workers
4585 * unbound and set DISASSOCIATED. Before this, all workers
4586 * except for the ones which are still executing works from
4587 * before the last CPU down must be on the cpu. After
4588 * this, they may become diasporas.
4590 for_each_pool_worker(worker
, wi
, pool
)
4591 worker
->flags
|= WORKER_UNBOUND
;
4593 pool
->flags
|= POOL_DISASSOCIATED
;
4595 spin_unlock_irq(&pool
->lock
);
4596 mutex_unlock(&pool
->manager_mutex
);
4599 * Call schedule() so that we cross rq->lock and thus can
4600 * guarantee sched callbacks see the %WORKER_UNBOUND flag.
4601 * This is necessary as scheduler callbacks may be invoked
4607 * Sched callbacks are disabled now. Zap nr_running.
4608 * After this, nr_running stays zero and need_more_worker()
4609 * and keep_working() are always true as long as the
4610 * worklist is not empty. This pool now behaves as an
4611 * unbound (in terms of concurrency management) pool which
4612 * are served by workers tied to the pool.
4614 atomic_set(&pool
->nr_running
, 0);
4617 * With concurrency management just turned off, a busy
4618 * worker blocking could lead to lengthy stalls. Kick off
4619 * unbound chain execution of currently pending work items.
4621 spin_lock_irq(&pool
->lock
);
4622 wake_up_worker(pool
);
4623 spin_unlock_irq(&pool
->lock
);
4628 * rebind_workers - rebind all workers of a pool to the associated CPU
4629 * @pool: pool of interest
4631 * @pool->cpu is coming online. Rebind all workers to the CPU.
4633 static void rebind_workers(struct worker_pool
*pool
)
4635 struct worker
*worker
;
4638 lockdep_assert_held(&pool
->manager_mutex
);
4641 * Restore CPU affinity of all workers. As all idle workers should
4642 * be on the run-queue of the associated CPU before any local
4643 * wake-ups for concurrency management happen, restore CPU affinty
4644 * of all workers first and then clear UNBOUND. As we're called
4645 * from CPU_ONLINE, the following shouldn't fail.
4647 for_each_pool_worker(worker
, wi
, pool
)
4648 WARN_ON_ONCE(set_cpus_allowed_ptr(worker
->task
,
4649 pool
->attrs
->cpumask
) < 0);
4651 spin_lock_irq(&pool
->lock
);
4653 for_each_pool_worker(worker
, wi
, pool
) {
4654 unsigned int worker_flags
= worker
->flags
;
4657 * A bound idle worker should actually be on the runqueue
4658 * of the associated CPU for local wake-ups targeting it to
4659 * work. Kick all idle workers so that they migrate to the
4660 * associated CPU. Doing this in the same loop as
4661 * replacing UNBOUND with REBOUND is safe as no worker will
4662 * be bound before @pool->lock is released.
4664 if (worker_flags
& WORKER_IDLE
)
4665 wake_up_process(worker
->task
);
4668 * We want to clear UNBOUND but can't directly call
4669 * worker_clr_flags() or adjust nr_running. Atomically
4670 * replace UNBOUND with another NOT_RUNNING flag REBOUND.
4671 * @worker will clear REBOUND using worker_clr_flags() when
4672 * it initiates the next execution cycle thus restoring
4673 * concurrency management. Note that when or whether
4674 * @worker clears REBOUND doesn't affect correctness.
4676 * ACCESS_ONCE() is necessary because @worker->flags may be
4677 * tested without holding any lock in
4678 * wq_worker_waking_up(). Without it, NOT_RUNNING test may
4679 * fail incorrectly leading to premature concurrency
4680 * management operations.
4682 WARN_ON_ONCE(!(worker_flags
& WORKER_UNBOUND
));
4683 worker_flags
|= WORKER_REBOUND
;
4684 worker_flags
&= ~WORKER_UNBOUND
;
4685 ACCESS_ONCE(worker
->flags
) = worker_flags
;
4688 spin_unlock_irq(&pool
->lock
);
4692 * restore_unbound_workers_cpumask - restore cpumask of unbound workers
4693 * @pool: unbound pool of interest
4694 * @cpu: the CPU which is coming up
4696 * An unbound pool may end up with a cpumask which doesn't have any online
4697 * CPUs. When a worker of such pool get scheduled, the scheduler resets
4698 * its cpus_allowed. If @cpu is in @pool's cpumask which didn't have any
4699 * online CPU before, cpus_allowed of all its workers should be restored.
4701 static void restore_unbound_workers_cpumask(struct worker_pool
*pool
, int cpu
)
4703 static cpumask_t cpumask
;
4704 struct worker
*worker
;
4707 lockdep_assert_held(&pool
->manager_mutex
);
4709 /* is @cpu allowed for @pool? */
4710 if (!cpumask_test_cpu(cpu
, pool
->attrs
->cpumask
))
4713 /* is @cpu the only online CPU? */
4714 cpumask_and(&cpumask
, pool
->attrs
->cpumask
, cpu_online_mask
);
4715 if (cpumask_weight(&cpumask
) != 1)
4718 /* as we're called from CPU_ONLINE, the following shouldn't fail */
4719 for_each_pool_worker(worker
, wi
, pool
)
4720 WARN_ON_ONCE(set_cpus_allowed_ptr(worker
->task
,
4721 pool
->attrs
->cpumask
) < 0);
4725 * Workqueues should be brought up before normal priority CPU notifiers.
4726 * This will be registered high priority CPU notifier.
4728 static int __cpuinit
workqueue_cpu_up_callback(struct notifier_block
*nfb
,
4729 unsigned long action
,
4732 int cpu
= (unsigned long)hcpu
;
4733 struct worker_pool
*pool
;
4734 struct workqueue_struct
*wq
;
4737 switch (action
& ~CPU_TASKS_FROZEN
) {
4738 case CPU_UP_PREPARE
:
4739 for_each_cpu_worker_pool(pool
, cpu
) {
4740 if (pool
->nr_workers
)
4742 if (create_and_start_worker(pool
) < 0)
4747 case CPU_DOWN_FAILED
:
4749 mutex_lock(&wq_pool_mutex
);
4751 for_each_pool(pool
, pi
) {
4752 mutex_lock(&pool
->manager_mutex
);
4754 if (pool
->cpu
== cpu
) {
4755 spin_lock_irq(&pool
->lock
);
4756 pool
->flags
&= ~POOL_DISASSOCIATED
;
4757 spin_unlock_irq(&pool
->lock
);
4759 rebind_workers(pool
);
4760 } else if (pool
->cpu
< 0) {
4761 restore_unbound_workers_cpumask(pool
, cpu
);
4764 mutex_unlock(&pool
->manager_mutex
);
4767 /* update NUMA affinity of unbound workqueues */
4768 list_for_each_entry(wq
, &workqueues
, list
)
4769 wq_update_unbound_numa(wq
, cpu
, true);
4771 mutex_unlock(&wq_pool_mutex
);
4778 * Workqueues should be brought down after normal priority CPU notifiers.
4779 * This will be registered as low priority CPU notifier.
4781 static int __cpuinit
workqueue_cpu_down_callback(struct notifier_block
*nfb
,
4782 unsigned long action
,
4785 int cpu
= (unsigned long)hcpu
;
4786 struct work_struct unbind_work
;
4787 struct workqueue_struct
*wq
;
4789 switch (action
& ~CPU_TASKS_FROZEN
) {
4790 case CPU_DOWN_PREPARE
:
4791 /* unbinding per-cpu workers should happen on the local CPU */
4792 INIT_WORK_ONSTACK(&unbind_work
, wq_unbind_fn
);
4793 queue_work_on(cpu
, system_highpri_wq
, &unbind_work
);
4795 /* update NUMA affinity of unbound workqueues */
4796 mutex_lock(&wq_pool_mutex
);
4797 list_for_each_entry(wq
, &workqueues
, list
)
4798 wq_update_unbound_numa(wq
, cpu
, false);
4799 mutex_unlock(&wq_pool_mutex
);
4801 /* wait for per-cpu unbinding to finish */
4802 flush_work(&unbind_work
);
4810 struct work_for_cpu
{
4811 struct work_struct work
;
4817 static void work_for_cpu_fn(struct work_struct
*work
)
4819 struct work_for_cpu
*wfc
= container_of(work
, struct work_for_cpu
, work
);
4821 wfc
->ret
= wfc
->fn(wfc
->arg
);
4825 * work_on_cpu - run a function in user context on a particular cpu
4826 * @cpu: the cpu to run on
4827 * @fn: the function to run
4828 * @arg: the function arg
4830 * This will return the value @fn returns.
4831 * It is up to the caller to ensure that the cpu doesn't go offline.
4832 * The caller must not hold any locks which would prevent @fn from completing.
4834 long work_on_cpu(int cpu
, long (*fn
)(void *), void *arg
)
4836 struct work_for_cpu wfc
= { .fn
= fn
, .arg
= arg
};
4838 INIT_WORK_ONSTACK(&wfc
.work
, work_for_cpu_fn
);
4839 schedule_work_on(cpu
, &wfc
.work
);
4840 flush_work(&wfc
.work
);
4843 EXPORT_SYMBOL_GPL(work_on_cpu
);
4844 #endif /* CONFIG_SMP */
4846 #ifdef CONFIG_FREEZER
4849 * freeze_workqueues_begin - begin freezing workqueues
4851 * Start freezing workqueues. After this function returns, all freezable
4852 * workqueues will queue new works to their delayed_works list instead of
4856 * Grabs and releases wq_pool_mutex, wq->mutex and pool->lock's.
4858 void freeze_workqueues_begin(void)
4860 struct worker_pool
*pool
;
4861 struct workqueue_struct
*wq
;
4862 struct pool_workqueue
*pwq
;
4865 mutex_lock(&wq_pool_mutex
);
4867 WARN_ON_ONCE(workqueue_freezing
);
4868 workqueue_freezing
= true;
4871 for_each_pool(pool
, pi
) {
4872 spin_lock_irq(&pool
->lock
);
4873 WARN_ON_ONCE(pool
->flags
& POOL_FREEZING
);
4874 pool
->flags
|= POOL_FREEZING
;
4875 spin_unlock_irq(&pool
->lock
);
4878 list_for_each_entry(wq
, &workqueues
, list
) {
4879 mutex_lock(&wq
->mutex
);
4880 for_each_pwq(pwq
, wq
)
4881 pwq_adjust_max_active(pwq
);
4882 mutex_unlock(&wq
->mutex
);
4885 mutex_unlock(&wq_pool_mutex
);
4889 * freeze_workqueues_busy - are freezable workqueues still busy?
4891 * Check whether freezing is complete. This function must be called
4892 * between freeze_workqueues_begin() and thaw_workqueues().
4895 * Grabs and releases wq_pool_mutex.
4898 * %true if some freezable workqueues are still busy. %false if freezing
4901 bool freeze_workqueues_busy(void)
4904 struct workqueue_struct
*wq
;
4905 struct pool_workqueue
*pwq
;
4907 mutex_lock(&wq_pool_mutex
);
4909 WARN_ON_ONCE(!workqueue_freezing
);
4911 list_for_each_entry(wq
, &workqueues
, list
) {
4912 if (!(wq
->flags
& WQ_FREEZABLE
))
4915 * nr_active is monotonically decreasing. It's safe
4916 * to peek without lock.
4918 rcu_read_lock_sched();
4919 for_each_pwq(pwq
, wq
) {
4920 WARN_ON_ONCE(pwq
->nr_active
< 0);
4921 if (pwq
->nr_active
) {
4923 rcu_read_unlock_sched();
4927 rcu_read_unlock_sched();
4930 mutex_unlock(&wq_pool_mutex
);
4935 * thaw_workqueues - thaw workqueues
4937 * Thaw workqueues. Normal queueing is restored and all collected
4938 * frozen works are transferred to their respective pool worklists.
4941 * Grabs and releases wq_pool_mutex, wq->mutex and pool->lock's.
4943 void thaw_workqueues(void)
4945 struct workqueue_struct
*wq
;
4946 struct pool_workqueue
*pwq
;
4947 struct worker_pool
*pool
;
4950 mutex_lock(&wq_pool_mutex
);
4952 if (!workqueue_freezing
)
4955 /* clear FREEZING */
4956 for_each_pool(pool
, pi
) {
4957 spin_lock_irq(&pool
->lock
);
4958 WARN_ON_ONCE(!(pool
->flags
& POOL_FREEZING
));
4959 pool
->flags
&= ~POOL_FREEZING
;
4960 spin_unlock_irq(&pool
->lock
);
4963 /* restore max_active and repopulate worklist */
4964 list_for_each_entry(wq
, &workqueues
, list
) {
4965 mutex_lock(&wq
->mutex
);
4966 for_each_pwq(pwq
, wq
)
4967 pwq_adjust_max_active(pwq
);
4968 mutex_unlock(&wq
->mutex
);
4971 workqueue_freezing
= false;
4973 mutex_unlock(&wq_pool_mutex
);
4975 #endif /* CONFIG_FREEZER */
4977 static void __init
wq_numa_init(void)
4982 /* determine NUMA pwq table len - highest node id + 1 */
4984 wq_numa_tbl_len
= max(wq_numa_tbl_len
, node
+ 1);
4986 if (num_possible_nodes() <= 1)
4989 if (wq_disable_numa
) {
4990 pr_info("workqueue: NUMA affinity support disabled\n");
4994 wq_update_unbound_numa_attrs_buf
= alloc_workqueue_attrs(GFP_KERNEL
);
4995 BUG_ON(!wq_update_unbound_numa_attrs_buf
);
4998 * We want masks of possible CPUs of each node which isn't readily
4999 * available. Build one from cpu_to_node() which should have been
5000 * fully initialized by now.
5002 tbl
= kzalloc(wq_numa_tbl_len
* sizeof(tbl
[0]), GFP_KERNEL
);
5006 BUG_ON(!zalloc_cpumask_var_node(&tbl
[node
], GFP_KERNEL
,
5007 node_online(node
) ? node
: NUMA_NO_NODE
));
5009 for_each_possible_cpu(cpu
) {
5010 node
= cpu_to_node(cpu
);
5011 if (WARN_ON(node
== NUMA_NO_NODE
)) {
5012 pr_warn("workqueue: NUMA node mapping not available for cpu%d, disabling NUMA support\n", cpu
);
5013 /* happens iff arch is bonkers, let's just proceed */
5016 cpumask_set_cpu(cpu
, tbl
[node
]);
5019 wq_numa_possible_cpumask
= tbl
;
5020 wq_numa_enabled
= true;
5023 static int __init
init_workqueues(void)
5025 int std_nice
[NR_STD_WORKER_POOLS
] = { 0, HIGHPRI_NICE_LEVEL
};
5028 /* make sure we have enough bits for OFFQ pool ID */
5029 BUILD_BUG_ON((1LU << (BITS_PER_LONG
- WORK_OFFQ_POOL_SHIFT
)) <
5030 WORK_CPU_END
* NR_STD_WORKER_POOLS
);
5032 WARN_ON(__alignof__(struct pool_workqueue
) < __alignof__(long long));
5034 pwq_cache
= KMEM_CACHE(pool_workqueue
, SLAB_PANIC
);
5036 cpu_notifier(workqueue_cpu_up_callback
, CPU_PRI_WORKQUEUE_UP
);
5037 hotcpu_notifier(workqueue_cpu_down_callback
, CPU_PRI_WORKQUEUE_DOWN
);
5041 /* initialize CPU pools */
5042 for_each_possible_cpu(cpu
) {
5043 struct worker_pool
*pool
;
5046 for_each_cpu_worker_pool(pool
, cpu
) {
5047 BUG_ON(init_worker_pool(pool
));
5049 cpumask_copy(pool
->attrs
->cpumask
, cpumask_of(cpu
));
5050 pool
->attrs
->nice
= std_nice
[i
++];
5051 pool
->node
= cpu_to_node(cpu
);
5054 mutex_lock(&wq_pool_mutex
);
5055 BUG_ON(worker_pool_assign_id(pool
));
5056 mutex_unlock(&wq_pool_mutex
);
5060 /* create the initial worker */
5061 for_each_online_cpu(cpu
) {
5062 struct worker_pool
*pool
;
5064 for_each_cpu_worker_pool(pool
, cpu
) {
5065 pool
->flags
&= ~POOL_DISASSOCIATED
;
5066 BUG_ON(create_and_start_worker(pool
) < 0);
5070 /* create default unbound and ordered wq attrs */
5071 for (i
= 0; i
< NR_STD_WORKER_POOLS
; i
++) {
5072 struct workqueue_attrs
*attrs
;
5074 BUG_ON(!(attrs
= alloc_workqueue_attrs(GFP_KERNEL
)));
5075 attrs
->nice
= std_nice
[i
];
5076 unbound_std_wq_attrs
[i
] = attrs
;
5079 * An ordered wq should have only one pwq as ordering is
5080 * guaranteed by max_active which is enforced by pwqs.
5081 * Turn off NUMA so that dfl_pwq is used for all nodes.
5083 BUG_ON(!(attrs
= alloc_workqueue_attrs(GFP_KERNEL
)));
5084 attrs
->nice
= std_nice
[i
];
5085 attrs
->no_numa
= true;
5086 ordered_wq_attrs
[i
] = attrs
;
5089 system_wq
= alloc_workqueue("events", 0, 0);
5090 system_highpri_wq
= alloc_workqueue("events_highpri", WQ_HIGHPRI
, 0);
5091 system_long_wq
= alloc_workqueue("events_long", 0, 0);
5092 system_unbound_wq
= alloc_workqueue("events_unbound", WQ_UNBOUND
,
5093 WQ_UNBOUND_MAX_ACTIVE
);
5094 system_freezable_wq
= alloc_workqueue("events_freezable",
5096 BUG_ON(!system_wq
|| !system_highpri_wq
|| !system_long_wq
||
5097 !system_unbound_wq
|| !system_freezable_wq
);
5100 early_initcall(init_workqueues
);