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()
241  * wake_up_pollfree - signal that a polled waitqueue is going away
242  * @wq_head: the wait queue head
244  * In the very rare cases where a ->poll() implementation uses a waitqueue whose
247  * non-blocking polls (e.g. epoll) are notified that the queue is going away.
249  * The caller must also RCU-delay the freeing of the wait_queue_head, e.g. via
259 	 * can safely proceed with an RCU-delayed free.  in wake_up_pollfree()
273 #define ___wait_is_interruptible(state)						\  argument
274 	(!__builtin_constant_p(state) ||					\
275 		state == TASK_INTERRUPTIBLE || state == TASK_KILLABLE)		\
291 #define ___wait_event(wq_head, condition, state, exclusive, ret, cmd)		\  argument
299 		long __int = prepare_to_wait_event(&wq_head, &__wq_entry, state);\
304 		if (___wait_is_interruptible(state) && __int) {			\
320  * wait_event - sleep until a condition gets true
321  * @wq_head: the waitqueue to wait on
322  * @condition: a C expression for the event to wait for
329  * change the result of the wait condition.
344  * io_wait_event() -- like wait_event() but with io_schedule()
359  * wait_event_freezable - sleep (or freeze) until a condition gets true
360  * @wq_head: the waitqueue to wait on
361  * @condition: a C expression for the event to wait for
363  * The process is put to sleep (TASK_INTERRUPTIBLE -- so as not to contribute
368  * change the result of the wait condition.
385  * wait_event_timeout - sleep until a condition gets true or a timeout elapses
386  * @wq_head: the waitqueue to wait on
387  * @condition: a C expression for the event to wait for
395  * change the result of the wait condition.
418  * like wait_event_timeout() -- except it uses TASK_INTERRUPTIBLE to avoid
448  * wait_event_cmd - sleep until a condition gets true
449  * @wq_head: the waitqueue to wait on
450  * @condition: a C expression for the event to wait for
459  * change the result of the wait condition.
473  * wait_event_interruptible - sleep until a condition gets true
474  * @wq_head: the waitqueue to wait on
475  * @condition: a C expression for the event to wait for
482  * change the result of the wait condition.
484  * The function will return -ERESTARTSYS if it was interrupted by a
502  * wait_event_interruptible_timeout - sleep until a condition gets true or a timeout elapses
503  * @wq_head: the waitqueue to wait on
504  * @condition: a C expression for the event to wait for
512  * change the result of the wait condition.
518  * to %true before the @timeout elapsed, or -%ERESTARTSYS if it was
531 #define __wait_event_hrtimeout(wq_head, condition, timeout, state)		\  argument
540 					current->timer_slack_ns);		\
544 	__ret = ___wait_event(wq_head, condition, state, 0, 0,			\
546 			__ret = -ETIME;						\
557  * wait_event_hrtimeout - sleep until a condition gets true or a timeout elapses
558  * @wq_head: the waitqueue to wait on
559  * @condition: a C expression for the event to wait for
567  * change the result of the wait condition.
569  * The function returns 0 if @condition became true, or -ETIME if the timeout
583  * wait_event_interruptible_hrtimeout - sleep until a condition gets true or a timeout elapses
584  * @wq: the waitqueue to wait on
585  * @condition: a C expression for the event to wait for
593  * change the result of the wait condition.
595  * The function returns 0 if @condition became true, -ERESTARTSYS if it was
596  * interrupted by a signal, or -ETIME if the timeout elapsed.
649  * wait_event_idle - wait for a condition without contributing to system load
650  * @wq_head: the waitqueue to wait on
651  * @condition: a C expression for the event to wait for
658  * change the result of the wait condition.
669  * wait_event_idle_exclusive - wait for a condition with contributing to system load
670  * @wq_head: the waitqueue to wait on
671  * @condition: a C expression for the event to wait for
677  * The process is put on the wait queue with an WQ_FLAG_EXCLUSIVE flag
678  * set thus if other processes wait on the same list, when this
682  * change the result of the wait condition.
698  * wait_event_idle_timeout - sleep without load until a condition becomes true or a timeout elapses
699  * @wq_head: the waitqueue to wait on
700  * @condition: a C expression for the event to wait for
708  * change the result of the wait condition.
731 …* wait_event_idle_exclusive_timeout - sleep without load until a condition becomes true or a timeo…
732  * @wq_head: the waitqueue to wait on
733  * @condition: a C expression for the event to wait for
740  * The process is put on the wait queue with an WQ_FLAG_EXCLUSIVE flag
741  * set thus if other processes wait on the same list, when this
745  * change the result of the wait condition.
783  * wait_event_interruptible_locked - sleep until a condition gets true
784  * @wq: the waitqueue to wait on
785  * @condition: a C expression for the event to wait for
800  * change the result of the wait condition.
802  * The function will return -ERESTARTSYS if it was interrupted by a
810  * wait_event_interruptible_locked_irq - sleep until a condition gets true
811  * @wq: the waitqueue to wait on
812  * @condition: a C expression for the event to wait for
827  * change the result of the wait condition.
829  * The function will return -ERESTARTSYS if it was interrupted by a
837  * wait_event_interruptible_exclusive_locked - sleep exclusively until a condition gets true
838  * @wq: the waitqueue to wait on
839  * @condition: a C expression for the event to wait for
853  * The process is put on the wait queue with an WQ_FLAG_EXCLUSIVE flag
858  * change the result of the wait condition.
860  * The function will return -ERESTARTSYS if it was interrupted by a
868  * wait_event_interruptible_exclusive_locked_irq - sleep until a condition gets true
869  * @wq: the waitqueue to wait on
870  * @condition: a C expression for the event to wait for
884  * The process is put on the wait queue with an WQ_FLAG_EXCLUSIVE flag
889  * change the result of the wait condition.
891  * The function will return -ERESTARTSYS if it was interrupted by a
903  * wait_event_killable - sleep until a condition gets true
904  * @wq_head: the waitqueue to wait on
905  * @condition: a C expression for the event to wait for
912  * change the result of the wait condition.
914  * The function will return -ERESTARTSYS if it was interrupted by a
932  * wait_event_killable_timeout - sleep until a condition gets true or a timeout elapses
933  * @wq_head: the waitqueue to wait on
934  * @condition: a C expression for the event to wait for
942  * change the result of the wait condition.
948  * to %true before the @timeout elapsed, or -%ERESTARTSYS if it was
972  * wait_event_lock_irq_cmd - sleep until a condition gets true. The
976  * @wq_head: the waitqueue to wait on
977  * @condition: a C expression for the event to wait for
988  * change the result of the wait condition.
1002  * wait_event_lock_irq - sleep until a condition gets true. The
1006  * @wq_head: the waitqueue to wait on
1007  * @condition: a C expression for the event to wait for
1016  * change the result of the wait condition.
1037  * wait_event_interruptible_lock_irq_cmd - sleep until a condition gets true.
1040  * @wq_head: the waitqueue to wait on
1041  * @condition: a C expression for the event to wait for
1052  * change the result of the wait condition.
1058  * The macro will return -ERESTARTSYS if it was interrupted by a signal
1071  * wait_event_interruptible_lock_irq - sleep until a condition gets true.
1074  * @wq_head: the waitqueue to wait on
1075  * @condition: a C expression for the event to wait for
1084  * change the result of the wait condition.
1089  * The macro will return -ERESTARTSYS if it was interrupted by a signal
1101 #define __wait_event_lock_irq_timeout(wq_head, condition, lock, timeout, state)	\  argument
1103 		      state, 0, timeout,					\
1109  * wait_event_interruptible_lock_irq_timeout - sleep until a condition gets
1112  * @wq_head: the waitqueue to wait on
1113  * @condition: a C expression for the event to wait for
1123  * change the result of the wait condition.
1128  * The function returns 0 if the @timeout elapsed, -ERESTARTSYS if it
1156 void prepare_to_wait(struct wait_queue_head *wq_head, struct wait_queue_entry *wq_entry, int state);
1157 …e_to_wait_exclusive(struct wait_queue_head *wq_head, struct wait_queue_entry *wq_entry, int state);
1158 …epare_to_wait_event(struct wait_queue_head *wq_head, struct wait_queue_entry *wq_entry, int state);
1173 #define init_wait(wait)								\  argument
1175 		(wait)->private = current;					\
1176 		(wait)->func = autoremove_wake_function;			\
1177 		INIT_LIST_HEAD(&(wait)->entry);					\
1178 		(wait)->flags = 0;						\