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()
250  * wake_up_pollfree - signal that a polled waitqueue is going away
251  * @wq_head: the wait queue head
253  * In the very rare cases where a ->poll() implementation uses a waitqueue whose
256  * non-blocking polls (e.g. epoll) are notified that the queue is going away.
258  * The caller must also RCU-delay the freeing of the wait_queue_head, e.g. via
268 	 * can safely proceed with an RCU-delayed free.  in wake_up_pollfree()
282 #define ___wait_is_interruptible(state)						\  argument
283 	(!__builtin_constant_p(state) ||					\
284 	 (state & (TASK_INTERRUPTIBLE | TASK_WAKEKILL)))
300 #define ___wait_event(wq_head, condition, state, exclusive, ret, cmd)		\  argument
308 		long __int = prepare_to_wait_event(&wq_head, &__wq_entry, state);\
313 		if (___wait_is_interruptible(state) && __int) {			\
329  * wait_event - sleep until a condition gets true
330  * @wq_head: the waitqueue to wait on
331  * @condition: a C expression for the event to wait for
338  * change the result of the wait condition.
353  * io_wait_event() -- like wait_event() but with io_schedule()
368  * wait_event_freezable - sleep (or freeze) until a condition gets true
369  * @wq_head: the waitqueue to wait on
370  * @condition: a C expression for the event to wait for
372  * The process is put to sleep (TASK_INTERRUPTIBLE -- so as not to contribute
377  * change the result of the wait condition.
394  * wait_event_timeout - sleep until a condition gets true or a timeout elapses
395  * @wq_head: the waitqueue to wait on
396  * @condition: a C expression for the event to wait for
404  * change the result of the wait condition.
427  * like wait_event_timeout() -- except it uses TASK_INTERRUPTIBLE to avoid
457  * wait_event_cmd - sleep until a condition gets true
458  * @wq_head: the waitqueue to wait on
459  * @condition: a C expression for the event to wait for
468  * change the result of the wait condition.
482  * wait_event_interruptible - sleep until a condition gets true
483  * @wq_head: the waitqueue to wait on
484  * @condition: a C expression for the event to wait for
491  * change the result of the wait condition.
493  * The function will return -ERESTARTSYS if it was interrupted by a
511  * wait_event_interruptible_timeout - sleep until a condition gets true or a timeout elapses
512  * @wq_head: the waitqueue to wait on
513  * @condition: a C expression for the event to wait for
521  * change the result of the wait condition.
527  * to %true before the @timeout elapsed, or -%ERESTARTSYS if it was
540 #define __wait_event_hrtimeout(wq_head, condition, timeout, state)		\  argument
549 					current->timer_slack_ns);		\
553 	__ret = ___wait_event(wq_head, condition, state, 0, 0,			\
555 			__ret = -ETIME;						\
566  * wait_event_hrtimeout - sleep until a condition gets true or a timeout elapses
567  * @wq_head: the waitqueue to wait on
568  * @condition: a C expression for the event to wait for
576  * change the result of the wait condition.
578  * The function returns 0 if @condition became true, or -ETIME if the timeout
592  * wait_event_interruptible_hrtimeout - sleep until a condition gets true or a timeout elapses
593  * @wq: the waitqueue to wait on
594  * @condition: a C expression for the event to wait for
602  * change the result of the wait condition.
604  * The function returns 0 if @condition became true, -ERESTARTSYS if it was
605  * interrupted by a signal, or -ETIME if the timeout elapsed.
658  * wait_event_idle - wait for a condition without contributing to system load
659  * @wq_head: the waitqueue to wait on
660  * @condition: a C expression for the event to wait for
667  * change the result of the wait condition.
678  * wait_event_idle_exclusive - wait for a condition with contributing to system load
679  * @wq_head: the waitqueue to wait on
680  * @condition: a C expression for the event to wait for
686  * The process is put on the wait queue with an WQ_FLAG_EXCLUSIVE flag
687  * set thus if other processes wait on the same list, when this
691  * change the result of the wait condition.
707  * wait_event_idle_timeout - sleep without load until a condition becomes true or a timeout elapses
708  * @wq_head: the waitqueue to wait on
709  * @condition: a C expression for the event to wait for
717  * change the result of the wait condition.
740 …* wait_event_idle_exclusive_timeout - sleep without load until a condition becomes true or a timeo…
741  * @wq_head: the waitqueue to wait on
742  * @condition: a C expression for the event to wait for
749  * The process is put on the wait queue with an WQ_FLAG_EXCLUSIVE flag
750  * set thus if other processes wait on the same list, when this
754  * change the result of the wait condition.
792  * wait_event_interruptible_locked - 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_locked_irq - sleep until a condition gets true
820  * @wq: the waitqueue to wait on
821  * @condition: a C expression for the event to wait for
836  * change the result of the wait condition.
838  * The function will return -ERESTARTSYS if it was interrupted by a
846  * wait_event_interruptible_exclusive_locked - sleep exclusively until a condition gets true
847  * @wq: the waitqueue to wait on
848  * @condition: a C expression for the event to wait for
862  * The process is put on the wait queue with an WQ_FLAG_EXCLUSIVE flag
867  * change the result of the wait condition.
869  * The function will return -ERESTARTSYS if it was interrupted by a
877  * wait_event_interruptible_exclusive_locked_irq - sleep until a condition gets true
878  * @wq: the waitqueue to wait on
879  * @condition: a C expression for the event to wait for
893  * The process is put on the wait queue with an WQ_FLAG_EXCLUSIVE flag
898  * change the result of the wait condition.
900  * The function will return -ERESTARTSYS if it was interrupted by a
912  * wait_event_killable - sleep until a condition gets true
913  * @wq_head: the waitqueue to wait on
914  * @condition: a C expression for the event to wait for
921  * change the result of the wait condition.
923  * The function will return -ERESTARTSYS if it was interrupted by a
935 #define __wait_event_state(wq, condition, state)				\  argument
936 	___wait_event(wq, condition, state, 0, 0, schedule())
939  * wait_event_state - sleep until a condition gets true
940  * @wq_head: the waitqueue to wait on
941  * @condition: a C expression for the event to wait for
942  * @state: state to sleep in
944  * The process is put to sleep (@state) until the @condition evaluates to true
945  * or a signal is received (when allowed by @state).  The @condition is checked
949  * change the result of the wait condition.
951  * The function will return -ERESTARTSYS if it was interrupted by a signal
952  * (when allowed by @state) and 0 if @condition evaluated to true.
954 #define wait_event_state(wq_head, condition, state)				\  argument
959 		__ret = __wait_event_state(wq_head, condition, state);		\
969  * wait_event_killable_timeout - sleep until a condition gets true or a timeout elapses
970  * @wq_head: the waitqueue to wait on
971  * @condition: a C expression for the event to wait for
979  * change the result of the wait condition.
985  * to %true before the @timeout elapsed, or -%ERESTARTSYS if it was
1009  * wait_event_lock_irq_cmd - sleep until a condition gets true. The
1013  * @wq_head: the waitqueue to wait on
1014  * @condition: a C expression for the event to wait for
1025  * change the result of the wait condition.
1039  * wait_event_lock_irq - sleep until a condition gets true. The
1043  * @wq_head: the waitqueue to wait on
1044  * @condition: a C expression for the event to wait for
1053  * change the result of the wait condition.
1074  * wait_event_interruptible_lock_irq_cmd - sleep until a condition gets true.
1077  * @wq_head: the waitqueue to wait on
1078  * @condition: a C expression for the event to wait for
1089  * change the result of the wait condition.
1095  * The macro will return -ERESTARTSYS if it was interrupted by a signal
1108  * wait_event_interruptible_lock_irq - sleep until a condition gets true.
1111  * @wq_head: the waitqueue to wait on
1112  * @condition: a C expression for the event to wait for
1121  * change the result of the wait condition.
1126  * The macro will return -ERESTARTSYS if it was interrupted by a signal
1138 #define __wait_event_lock_irq_timeout(wq_head, condition, lock, timeout, state)	\  argument
1140 		      state, 0, timeout,					\
1146  * wait_event_interruptible_lock_irq_timeout - sleep until a condition gets
1149  * @wq_head: the waitqueue to wait on
1150  * @condition: a C expression for the event to wait for
1160  * change the result of the wait condition.
1165  * The function returns 0 if the @timeout elapsed, -ERESTARTSYS if it
1193 void prepare_to_wait(struct wait_queue_head *wq_head, struct wait_queue_entry *wq_entry, int state);
1194 …e_to_wait_exclusive(struct wait_queue_head *wq_head, struct wait_queue_entry *wq_entry, int state);
1195 …epare_to_wait_event(struct wait_queue_head *wq_head, struct wait_queue_entry *wq_entry, int state);
1210 #define init_wait(wait)								\  argument
1212 		(wait)->private = current;					\
1213 		(wait)->func = autoremove_wake_function;			\
1214 		INIT_LIST_HEAD(&(wait)->entry);					\
1215 		(wait)->flags = 0;						\