1 /* SPDX-License-Identifier: GPL-2.0 */
5  * Linux wait queue related types and methods
12 #include <uapi/linux/wait.h>
27  * A single wait-queue entry structure:
83 	wq_entry->flags		= 0;  in init_waitqueue_entry()
84 	wq_entry->private	= p;  in init_waitqueue_entry()
85 	wq_entry->func		= default_wake_function;  in init_waitqueue_entry()
91 	wq_entry->flags		= 0;  in init_waitqueue_func_entry()
92 	wq_entry->private	= NULL;  in init_waitqueue_func_entry()
93 	wq_entry->func		= func;  in init_waitqueue_func_entry()
97  * waitqueue_active -- locklessly test for waiters on the queue
100  * returns true if the wait list is not empty
103  * lead to sporadic and non-obvious failure.
108  *      CPU0 - waker                    CPU1 - waiter
111  *      @cond = true;                     prepare_to_wait(&wq_head, &wait, state);
117  *                                      finish_wait(&wq_head, &wait);
121  * observe an empty wait list while the waiter might not observe @cond.
128 	return !list_empty(&wq_head->head);  in waitqueue_active()
132  * wq_has_single_sleeper - check if there is only one sleeper
133  * @wq_head: wait queue head
141 	return list_is_singular(&wq_head->head);  in wq_has_single_sleeper()
145  * wq_has_sleeper - check if there are any waiting processes
146  * @wq_head: wait queue head
156 	 * add_wait_queue modifications to the wait queue.  in wq_has_sleeper()
171 	list_add(&wq_entry->entry, &wq_head->head);  in __add_wait_queue()
175  * Used for wake-one threads:
180 	wq_entry->flags |= WQ_FLAG_EXCLUSIVE;  in __add_wait_queue_exclusive()
186 	list_add_tail(&wq_entry->entry, &wq_head->head);  in __add_wait_queue_entry_tail()
192 	wq_entry->flags |= WQ_FLAG_EXCLUSIVE;  in __add_wait_queue_entry_tail_exclusive()
199 	list_del(&wq_entry->entry);  in __remove_wait_queue()
246 #define ___wait_is_interruptible(state)						\  argument
247 	(!__builtin_constant_p(state) ||					\
248 		state == TASK_INTERRUPTIBLE || state == TASK_KILLABLE)		\
264 #define ___wait_event(wq_head, condition, state, exclusive, ret, cmd)		\  argument
272 		long __int = prepare_to_wait_event(&wq_head, &__wq_entry, state);\
277 		if (___wait_is_interruptible(state) && __int) {			\
293  * wait_event - sleep until a condition gets true
294  * @wq_head: the waitqueue to wait on
295  * @condition: a C expression for the event to wait for
302  * change the result of the wait condition.
317  * io_wait_event() -- like wait_event() but with io_schedule()
332  * wait_event_freezable - sleep (or freeze) until a condition gets true
333  * @wq_head: the waitqueue to wait on
334  * @condition: a C expression for the event to wait for
336  * The process is put to sleep (TASK_INTERRUPTIBLE -- so as not to contribute
341  * change the result of the wait condition.
358  * wait_event_timeout - sleep until a condition gets true or a timeout elapses
359  * @wq_head: the waitqueue to wait on
360  * @condition: a C expression for the event to wait for
368  * change the result of the wait condition.
391  * like wait_event_timeout() -- except it uses TASK_INTERRUPTIBLE to avoid
421  * wait_event_cmd - sleep until a condition gets true
422  * @wq_head: the waitqueue to wait on
423  * @condition: a C expression for the event to wait for
432  * change the result of the wait condition.
446  * wait_event_interruptible - sleep until a condition gets true
447  * @wq_head: the waitqueue to wait on
448  * @condition: a C expression for the event to wait for
455  * change the result of the wait condition.
457  * The function will return -ERESTARTSYS if it was interrupted by a
475  * wait_event_interruptible_timeout - sleep until a condition gets true or a timeout elapses
476  * @wq_head: the waitqueue to wait on
477  * @condition: a C expression for the event to wait for
485  * change the result of the wait condition.
491  * to %true before the @timeout elapsed, or -%ERESTARTSYS if it was
504 #define __wait_event_hrtimeout(wq_head, condition, timeout, state)		\  argument
513 				       current->timer_slack_ns,			\
516 	__ret = ___wait_event(wq_head, condition, state, 0, 0,			\
518 			__ret = -ETIME;						\
529  * wait_event_hrtimeout - sleep until a condition gets true or a timeout elapses
530  * @wq_head: the waitqueue to wait on
531  * @condition: a C expression for the event to wait for
539  * change the result of the wait condition.
541  * The function returns 0 if @condition became true, or -ETIME if the timeout
555  * wait_event_interruptible_hrtimeout - sleep until a condition gets true or a timeout elapses
556  * @wq: the waitqueue to wait on
557  * @condition: a C expression for the event to wait for
565  * change the result of the wait condition.
567  * The function returns 0 if @condition became true, -ERESTARTSYS if it was
568  * interrupted by a signal, or -ETIME if the timeout elapsed.
621  * wait_event_idle - wait for a condition without contributing to system load
622  * @wq_head: the waitqueue to wait on
623  * @condition: a C expression for the event to wait for
630  * change the result of the wait condition.
641  * wait_event_idle_exclusive - wait for a condition with contributing to system load
642  * @wq_head: the waitqueue to wait on
643  * @condition: a C expression for the event to wait for
649  * The process is put on the wait queue with an WQ_FLAG_EXCLUSIVE flag
650  * set thus if other processes wait on the same list, when this
654  * change the result of the wait condition.
670  * wait_event_idle_timeout - sleep without load until a condition becomes true or a timeout elapses
671  * @wq_head: the waitqueue to wait on
672  * @condition: a C expression for the event to wait for
680  * change the result of the wait condition.
703 …* wait_event_idle_exclusive_timeout - sleep without load until a condition becomes true or a timeo…
704  * @wq_head: the waitqueue to wait on
705  * @condition: a C expression for the event to wait for
712  * The process is put on the wait queue with an WQ_FLAG_EXCLUSIVE flag
713  * set thus if other processes wait on the same list, when this
717  * change the result of the wait condition.
755  * wait_event_interruptible_locked - sleep until a condition gets true
756  * @wq: the waitqueue to wait on
757  * @condition: a C expression for the event to wait for
772  * change the result of the wait condition.
774  * The function will return -ERESTARTSYS if it was interrupted by a
782  * wait_event_interruptible_locked_irq - sleep until a condition gets true
783  * @wq: the waitqueue to wait on
784  * @condition: a C expression for the event to wait for
799  * change the result of the wait condition.
801  * The function will return -ERESTARTSYS if it was interrupted by a
809  * wait_event_interruptible_exclusive_locked - sleep exclusively until a condition gets true
810  * @wq: the waitqueue to wait on
811  * @condition: a C expression for the event to wait for
825  * The process is put on the wait queue with an WQ_FLAG_EXCLUSIVE flag
830  * change the result of the wait condition.
832  * The function will return -ERESTARTSYS if it was interrupted by a
840  * wait_event_interruptible_exclusive_locked_irq - sleep until a condition gets true
841  * @wq: the waitqueue to wait on
842  * @condition: a C expression for the event to wait for
856  * The process is put on the wait queue with an WQ_FLAG_EXCLUSIVE flag
861  * change the result of the wait condition.
863  * The function will return -ERESTARTSYS if it was interrupted by a
875  * wait_event_killable - sleep until a condition gets true
876  * @wq_head: the waitqueue to wait on
877  * @condition: a C expression for the event to wait for
884  * change the result of the wait condition.
886  * The function will return -ERESTARTSYS if it was interrupted by a
904  * wait_event_killable_timeout - sleep until a condition gets true or a timeout elapses
905  * @wq_head: the waitqueue to wait on
906  * @condition: a C expression for the event to wait for
914  * change the result of the wait condition.
920  * to %true before the @timeout elapsed, or -%ERESTARTSYS if it was
944  * wait_event_lock_irq_cmd - sleep until a condition gets true. The
948  * @wq_head: the waitqueue to wait on
949  * @condition: a C expression for the event to wait for
960  * change the result of the wait condition.
974  * wait_event_lock_irq - sleep until a condition gets true. The
978  * @wq_head: the waitqueue to wait on
979  * @condition: a C expression for the event to wait for
988  * change the result of the wait condition.
1009  * wait_event_interruptible_lock_irq_cmd - sleep until a condition gets true.
1012  * @wq_head: the waitqueue to wait on
1013  * @condition: a C expression for the event to wait for
1024  * change the result of the wait condition.
1030  * The macro will return -ERESTARTSYS if it was interrupted by a signal
1043  * wait_event_interruptible_lock_irq - sleep until a condition gets true.
1046  * @wq_head: the waitqueue to wait on
1047  * @condition: a C expression for the event to wait for
1056  * change the result of the wait condition.
1061  * The macro will return -ERESTARTSYS if it was interrupted by a signal
1073 #define __wait_event_lock_irq_timeout(wq_head, condition, lock, timeout, state)	\  argument
1075 		      state, 0, timeout,					\
1081  * wait_event_interruptible_lock_irq_timeout - sleep until a condition gets
1084  * @wq_head: the waitqueue to wait on
1085  * @condition: a C expression for the event to wait for
1095  * change the result of the wait condition.
1100  * The function returns 0 if the @timeout elapsed, -ERESTARTSYS if it
1128 void prepare_to_wait(struct wait_queue_head *wq_head, struct wait_queue_entry *wq_entry, int state);
1129 …e_to_wait_exclusive(struct wait_queue_head *wq_head, struct wait_queue_entry *wq_entry, int state);
1130 …epare_to_wait_event(struct wait_queue_head *wq_head, struct wait_queue_entry *wq_entry, int state);
1145 #define init_wait(wait)								\  argument
1147 		(wait)->private = current;					\
1148 		(wait)->func = autoremove_wake_function;			\
1149 		INIT_LIST_HEAD(&(wait)->entry);					\
1150 		(wait)->flags = 0;						\