1 /* SPDX-License-Identifier: GPL-2.0 */
5  * Linux wait queue related types and methods
12 #include <uapi/linux/wait.h>
28  * A single wait-queue entry structure:
84 	wq_entry->flags		= 0;  in init_waitqueue_entry()
85 	wq_entry->private	= p;  in init_waitqueue_entry()
86 	wq_entry->func		= default_wake_function;  in init_waitqueue_entry()
92 	wq_entry->flags		= 0;  in init_waitqueue_func_entry()
93 	wq_entry->private	= NULL;  in init_waitqueue_func_entry()
94 	wq_entry->func		= func;  in init_waitqueue_func_entry()
98  * waitqueue_active -- locklessly test for waiters on the queue
101  * returns true if the wait list is not empty
104  * lead to sporadic and non-obvious failure.
109  *      CPU0 - waker                    CPU1 - waiter
112  *      @cond = true;                     prepare_to_wait(&wq_head, &wait, state);
118  *                                      finish_wait(&wq_head, &wait);
122  * observe an empty wait list while the waiter might not observe @cond.
129 	return !list_empty(&wq_head->head);  in waitqueue_active()
133  * wq_has_single_sleeper - check if there is only one sleeper
134  * @wq_head: wait queue head
142 	return list_is_singular(&wq_head->head);  in wq_has_single_sleeper()
146  * wq_has_sleeper - check if there are any waiting processes
147  * @wq_head: wait queue head
157 	 * add_wait_queue modifications to the wait queue.  in wq_has_sleeper()
173 	struct list_head *head = &wq_head->head;  in __add_wait_queue()
176 	list_for_each_entry(wq, &wq_head->head, entry) {  in __add_wait_queue()
177 		if (!(wq->flags & WQ_FLAG_PRIORITY))  in __add_wait_queue()
179 		head = &wq->entry;  in __add_wait_queue()
181 	list_add(&wq_entry->entry, head);  in __add_wait_queue()
185  * Used for wake-one threads:
190 	wq_entry->flags |= WQ_FLAG_EXCLUSIVE;  in __add_wait_queue_exclusive()
196 	list_add_tail(&wq_entry->entry, &wq_head->head);  in __add_wait_queue_entry_tail()
202 	wq_entry->flags |= WQ_FLAG_EXCLUSIVE;  in __add_wait_queue_entry_tail_exclusive()
209 	list_del(&wq_entry->entry);  in __remove_wait_queue()
256 #define ___wait_is_interruptible(state)						\  argument
257 	(!__builtin_constant_p(state) ||					\
258 		state == TASK_INTERRUPTIBLE || state == TASK_KILLABLE)		\
274 #define ___wait_event(wq_head, condition, state, exclusive, ret, cmd)		\  argument
282 		long __int = prepare_to_wait_event(&wq_head, &__wq_entry, state);\
287 		if (___wait_is_interruptible(state) && __int) {			\
303  * wait_event - sleep until a condition gets true
304  * @wq_head: the waitqueue to wait on
305  * @condition: a C expression for the event to wait for
312  * change the result of the wait condition.
327  * io_wait_event() -- like wait_event() but with io_schedule()
342  * wait_event_freezable - sleep (or freeze) until a condition gets true
343  * @wq_head: the waitqueue to wait on
344  * @condition: a C expression for the event to wait for
346  * The process is put to sleep (TASK_INTERRUPTIBLE -- so as not to contribute
351  * change the result of the wait condition.
368  * wait_event_timeout - sleep until a condition gets true or a timeout elapses
369  * @wq_head: the waitqueue to wait on
370  * @condition: a C expression for the event to wait for
378  * change the result of the wait condition.
401  * like wait_event_timeout() -- except it uses TASK_INTERRUPTIBLE to avoid
431  * wait_event_cmd - sleep until a condition gets true
432  * @wq_head: the waitqueue to wait on
433  * @condition: a C expression for the event to wait for
442  * change the result of the wait condition.
456  * wait_event_interruptible - sleep until a condition gets true
457  * @wq_head: the waitqueue to wait on
458  * @condition: a C expression for the event to wait for
465  * change the result of the wait condition.
467  * The function will return -ERESTARTSYS if it was interrupted by a
485  * wait_event_interruptible_timeout - sleep until a condition gets true or a timeout elapses
486  * @wq_head: the waitqueue to wait on
487  * @condition: a C expression for the event to wait for
495  * change the result of the wait condition.
501  * to %true before the @timeout elapsed, or -%ERESTARTSYS if it was
514 #define __wait_event_hrtimeout(wq_head, condition, timeout, state)		\  argument
523 				       current->timer_slack_ns,			\
526 	__ret = ___wait_event(wq_head, condition, state, 0, 0,			\
528 			__ret = -ETIME;						\
539  * wait_event_hrtimeout - sleep until a condition gets true or a timeout elapses
540  * @wq_head: the waitqueue to wait on
541  * @condition: a C expression for the event to wait for
549  * change the result of the wait condition.
551  * The function returns 0 if @condition became true, or -ETIME if the timeout
565  * wait_event_interruptible_hrtimeout - sleep until a condition gets true or a timeout elapses
566  * @wq: the waitqueue to wait on
567  * @condition: a C expression for the event to wait for
575  * change the result of the wait condition.
577  * The function returns 0 if @condition became true, -ERESTARTSYS if it was
578  * interrupted by a signal, or -ETIME if the timeout elapsed.
631  * wait_event_idle - wait for a condition without contributing to system load
632  * @wq_head: the waitqueue to wait on
633  * @condition: a C expression for the event to wait for
640  * change the result of the wait condition.
651  * wait_event_idle_exclusive - wait for a condition with contributing to system load
652  * @wq_head: the waitqueue to wait on
653  * @condition: a C expression for the event to wait for
659  * The process is put on the wait queue with an WQ_FLAG_EXCLUSIVE flag
660  * set thus if other processes wait on the same list, when this
664  * change the result of the wait condition.
680  * wait_event_idle_timeout - sleep without load until a condition becomes true or a timeout elapses
681  * @wq_head: the waitqueue to wait on
682  * @condition: a C expression for the event to wait for
690  * change the result of the wait condition.
713 …* wait_event_idle_exclusive_timeout - sleep without load until a condition becomes true or a timeo…
714  * @wq_head: the waitqueue to wait on
715  * @condition: a C expression for the event to wait for
722  * The process is put on the wait queue with an WQ_FLAG_EXCLUSIVE flag
723  * set thus if other processes wait on the same list, when this
727  * change the result of the wait condition.
765  * wait_event_interruptible_locked - sleep until a condition gets true
766  * @wq: the waitqueue to wait on
767  * @condition: a C expression for the event to wait for
782  * change the result of the wait condition.
784  * The function will return -ERESTARTSYS if it was interrupted by a
792  * wait_event_interruptible_locked_irq - sleep until a condition gets true
793  * @wq: the waitqueue to wait on
794  * @condition: a C expression for the event to wait for
809  * change the result of the wait condition.
811  * The function will return -ERESTARTSYS if it was interrupted by a
819  * wait_event_interruptible_exclusive_locked - sleep exclusively until a condition gets true
820  * @wq: the waitqueue to wait on
821  * @condition: a C expression for the event to wait for
835  * The process is put on the wait queue with an WQ_FLAG_EXCLUSIVE flag
840  * change the result of the wait condition.
842  * The function will return -ERESTARTSYS if it was interrupted by a
850  * wait_event_interruptible_exclusive_locked_irq - sleep until a condition gets true
851  * @wq: the waitqueue to wait on
852  * @condition: a C expression for the event to wait for
866  * The process is put on the wait queue with an WQ_FLAG_EXCLUSIVE flag
871  * change the result of the wait condition.
873  * The function will return -ERESTARTSYS if it was interrupted by a
885  * wait_event_killable - sleep until a condition gets true
886  * @wq_head: the waitqueue to wait on
887  * @condition: a C expression for the event to wait for
894  * change the result of the wait condition.
896  * The function will return -ERESTARTSYS if it was interrupted by a
914  * wait_event_killable_timeout - sleep until a condition gets true or a timeout elapses
915  * @wq_head: the waitqueue to wait on
916  * @condition: a C expression for the event to wait for
924  * change the result of the wait condition.
930  * to %true before the @timeout elapsed, or -%ERESTARTSYS if it was
954  * wait_event_lock_irq_cmd - sleep until a condition gets true. The
958  * @wq_head: the waitqueue to wait on
959  * @condition: a C expression for the event to wait for
970  * change the result of the wait condition.
984  * wait_event_lock_irq - sleep until a condition gets true. The
988  * @wq_head: the waitqueue to wait on
989  * @condition: a C expression for the event to wait for
998  * change the result of the wait condition.
1019  * wait_event_interruptible_lock_irq_cmd - sleep until a condition gets true.
1022  * @wq_head: the waitqueue to wait on
1023  * @condition: a C expression for the event to wait for
1034  * change the result of the wait condition.
1040  * The macro will return -ERESTARTSYS if it was interrupted by a signal
1053  * wait_event_interruptible_lock_irq - sleep until a condition gets true.
1056  * @wq_head: the waitqueue to wait on
1057  * @condition: a C expression for the event to wait for
1066  * change the result of the wait condition.
1071  * The macro will return -ERESTARTSYS if it was interrupted by a signal
1083 #define __wait_event_lock_irq_timeout(wq_head, condition, lock, timeout, state)	\  argument
1085 		      state, 0, timeout,					\
1091  * wait_event_interruptible_lock_irq_timeout - sleep until a condition gets
1094  * @wq_head: the waitqueue to wait on
1095  * @condition: a C expression for the event to wait for
1105  * change the result of the wait condition.
1110  * The function returns 0 if the @timeout elapsed, -ERESTARTSYS if it
1138 void prepare_to_wait(struct wait_queue_head *wq_head, struct wait_queue_entry *wq_entry, int state);
1139 …e_to_wait_exclusive(struct wait_queue_head *wq_head, struct wait_queue_entry *wq_entry, int state);
1140 …epare_to_wait_event(struct wait_queue_head *wq_head, struct wait_queue_entry *wq_entry, int state);
1155 #define init_wait(wait)								\  argument
1157 		(wait)->private = current;					\
1158 		(wait)->func = autoremove_wake_function;			\
1159 		INIT_LIST_HEAD(&(wait)->entry);					\
1160 		(wait)->flags = 0;						\