1 /* SPDX-License-Identifier: GPL-2.0 */
5  * Linux wait queue related types and methods
26  * A single wait-queue entry structure:
82 	wq_entry->flags		= 0;  in init_waitqueue_entry()
83 	wq_entry->private	= p;  in init_waitqueue_entry()
84 	wq_entry->func		= default_wake_function;  in init_waitqueue_entry()
90 	wq_entry->flags		= 0;  in init_waitqueue_func_entry()
91 	wq_entry->private	= NULL;  in init_waitqueue_func_entry()
92 	wq_entry->func		= func;  in init_waitqueue_func_entry()
96  * waitqueue_active -- locklessly test for waiters on the queue
99  * returns true if the wait list is not empty
102  * lead to sporadic and non-obvious failure.
107  *      CPU0 - waker                    CPU1 - waiter
110  *      @cond = true;                     prepare_to_wait(&wq_head, &wait, state);
116  *                                      finish_wait(&wq_head, &wait);
120  * observe an empty wait list while the waiter might not observe @cond.
127 	return !list_empty(&wq_head->head);  in waitqueue_active()
131  * wq_has_single_sleeper - check if there is only one sleeper
132  * @wq_head: wait queue head
140 	return list_is_singular(&wq_head->head);  in wq_has_single_sleeper()
144  * wq_has_sleeper - check if there are any waiting processes
145  * @wq_head: wait queue head
155 	 * add_wait_queue modifications to the wait queue.  in wq_has_sleeper()
171 	struct list_head *head = &wq_head->head;  in __add_wait_queue()
174 	list_for_each_entry(wq, &wq_head->head, entry) {  in __add_wait_queue()
175 		if (!(wq->flags & WQ_FLAG_PRIORITY))  in __add_wait_queue()
177 		head = &wq->entry;  in __add_wait_queue()
179 	list_add(&wq_entry->entry, head);  in __add_wait_queue()
183  * Used for wake-one threads:
188 	wq_entry->flags |= WQ_FLAG_EXCLUSIVE;  in __add_wait_queue_exclusive()
194 	list_add_tail(&wq_entry->entry, &wq_head->head);  in __add_wait_queue_entry_tail()
200 	wq_entry->flags |= WQ_FLAG_EXCLUSIVE;  in __add_wait_queue_entry_tail_exclusive()
207 	list_del(&wq_entry->entry);  in __remove_wait_queue()
249  * wake_up_pollfree - signal that a polled waitqueue is going away
250  * @wq_head: the wait queue head
252  * In the very rare cases where a ->poll() implementation uses a waitqueue whose
255  * non-blocking polls (e.g. epoll) are notified that the queue is going away.
257  * The caller must also RCU-delay the freeing of the wait_queue_head, e.g. via
267 	 * can safely proceed with an RCU-delayed free.  in wake_up_pollfree()
281 #define ___wait_is_interruptible(state)						\  argument
282 	(!__builtin_constant_p(state) ||					\
283 	 (state & (TASK_INTERRUPTIBLE | TASK_WAKEKILL)))
299 #define ___wait_event(wq_head, condition, state, exclusive, ret, cmd)		\  argument
307 		long __int = prepare_to_wait_event(&wq_head, &__wq_entry, state);\
312 		if (___wait_is_interruptible(state) && __int) {			\
328  * wait_event - sleep until a condition gets true
329  * @wq_head: the waitqueue to wait on
330  * @condition: a C expression for the event to wait for
337  * change the result of the wait condition.
352  * io_wait_event() -- like wait_event() but with io_schedule()
367  * wait_event_freezable - sleep (or freeze) until a condition gets true
368  * @wq_head: the waitqueue to wait on
369  * @condition: a C expression for the event to wait for
371  * The process is put to sleep (TASK_INTERRUPTIBLE -- so as not to contribute
376  * change the result of the wait condition.
393  * wait_event_timeout - sleep until a condition gets true or a timeout elapses
394  * @wq_head: the waitqueue to wait on
395  * @condition: a C expression for the event to wait for
403  * change the result of the wait condition.
426  * like wait_event_timeout() -- except it uses TASK_INTERRUPTIBLE to avoid
456  * wait_event_cmd - 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
467  * change the result of the wait condition.
481  * wait_event_interruptible - sleep until a condition gets true
482  * @wq_head: the waitqueue to wait on
483  * @condition: a C expression for the event to wait for
490  * change the result of the wait condition.
492  * The function will return -ERESTARTSYS if it was interrupted by a
510  * wait_event_interruptible_timeout - sleep until a condition gets true or a timeout elapses
511  * @wq_head: the waitqueue to wait on
512  * @condition: a C expression for the event to wait for
520  * change the result of the wait condition.
526  * to %true before the @timeout elapsed, or -%ERESTARTSYS if it was
539 #define __wait_event_hrtimeout(wq_head, condition, timeout, state)		\  argument
548 					current->timer_slack_ns);		\
552 	__ret = ___wait_event(wq_head, condition, state, 0, 0,			\
554 			__ret = -ETIME;						\
565  * wait_event_hrtimeout - sleep until a condition gets true or a timeout elapses
566  * @wq_head: 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, or -ETIME if the timeout
591  * wait_event_interruptible_hrtimeout - sleep until a condition gets true or a timeout elapses
592  * @wq: the waitqueue to wait on
593  * @condition: a C expression for the event to wait for
601  * change the result of the wait condition.
603  * The function returns 0 if @condition became true, -ERESTARTSYS if it was
604  * interrupted by a signal, or -ETIME if the timeout elapsed.
657  * wait_event_idle - wait for a condition without contributing to system load
658  * @wq_head: the waitqueue to wait on
659  * @condition: a C expression for the event to wait for
666  * change the result of the wait condition.
677  * wait_event_idle_exclusive - wait for a condition with contributing to system load
678  * @wq_head: the waitqueue to wait on
679  * @condition: a C expression for the event to wait for
685  * The process is put on the wait queue with an WQ_FLAG_EXCLUSIVE flag
686  * set thus if other processes wait on the same list, when this
690  * change the result of the wait condition.
706  * wait_event_idle_timeout - sleep without load until a condition becomes true or a timeout elapses
707  * @wq_head: the waitqueue to wait on
708  * @condition: a C expression for the event to wait for
716  * change the result of the wait condition.
739 …* wait_event_idle_exclusive_timeout - sleep without load until a condition becomes true or a timeo…
740  * @wq_head: the waitqueue to wait on
741  * @condition: a C expression for the event to wait for
748  * The process is put on the wait queue with an WQ_FLAG_EXCLUSIVE flag
749  * set thus if other processes wait on the same list, when this
753  * change the result of the wait condition.
791  * wait_event_interruptible_locked - sleep until a condition gets true
792  * @wq: the waitqueue to wait on
793  * @condition: a C expression for the event to wait for
808  * change the result of the wait condition.
810  * The function will return -ERESTARTSYS if it was interrupted by a
818  * wait_event_interruptible_locked_irq - sleep until a condition gets true
819  * @wq: the waitqueue to wait on
820  * @condition: a C expression for the event to wait for
835  * change the result of the wait condition.
837  * The function will return -ERESTARTSYS if it was interrupted by a
845  * wait_event_interruptible_exclusive_locked - sleep exclusively until a condition gets true
846  * @wq: the waitqueue to wait on
847  * @condition: a C expression for the event to wait for
861  * The process is put on the wait queue with an WQ_FLAG_EXCLUSIVE flag
866  * change the result of the wait condition.
868  * The function will return -ERESTARTSYS if it was interrupted by a
876  * wait_event_interruptible_exclusive_locked_irq - sleep until a condition gets true
877  * @wq: the waitqueue to wait on
878  * @condition: a C expression for the event to wait for
892  * The process is put on the wait queue with an WQ_FLAG_EXCLUSIVE flag
897  * change the result of the wait condition.
899  * The function will return -ERESTARTSYS if it was interrupted by a
911  * wait_event_killable - sleep until a condition gets true
912  * @wq_head: the waitqueue to wait on
913  * @condition: a C expression for the event to wait for
920  * change the result of the wait condition.
922  * The function will return -ERESTARTSYS if it was interrupted by a
934 #define __wait_event_state(wq, condition, state)				\  argument
935 	___wait_event(wq, condition, state, 0, 0, schedule())
938  * wait_event_state - sleep until a condition gets true
939  * @wq_head: the waitqueue to wait on
940  * @condition: a C expression for the event to wait for
941  * @state: state to sleep in
943  * The process is put to sleep (@state) until the @condition evaluates to true
944  * or a signal is received (when allowed by @state).  The @condition is checked
948  * change the result of the wait condition.
950  * The function will return -ERESTARTSYS if it was interrupted by a signal
951  * (when allowed by @state) and 0 if @condition evaluated to true.
953 #define wait_event_state(wq_head, condition, state)				\  argument
958 		__ret = __wait_event_state(wq_head, condition, state);		\
968  * wait_event_killable_timeout - sleep until a condition gets true or a timeout elapses
969  * @wq_head: the waitqueue to wait on
970  * @condition: a C expression for the event to wait for
978  * change the result of the wait condition.
984  * to %true before the @timeout elapsed, or -%ERESTARTSYS if it was
1008  * wait_event_lock_irq_cmd - sleep until a condition gets true. The
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.
1038  * wait_event_lock_irq - sleep until a condition gets true. The
1042  * @wq_head: the waitqueue to wait on
1043  * @condition: a C expression for the event to wait for
1052  * change the result of the wait condition.
1073  * wait_event_interruptible_lock_irq_cmd - sleep until a condition gets true.
1076  * @wq_head: the waitqueue to wait on
1077  * @condition: a C expression for the event to wait for
1088  * change the result of the wait condition.
1094  * The macro will return -ERESTARTSYS if it was interrupted by a signal
1107  * wait_event_interruptible_lock_irq - sleep until a condition gets true.
1110  * @wq_head: the waitqueue to wait on
1111  * @condition: a C expression for the event to wait for
1120  * change the result of the wait condition.
1125  * The macro will return -ERESTARTSYS if it was interrupted by a signal
1137 #define __wait_event_lock_irq_timeout(wq_head, condition, lock, timeout, state)	\  argument
1139 		      state, 0, timeout,					\
1145  * wait_event_interruptible_lock_irq_timeout - sleep until a condition gets
1148  * @wq_head: the waitqueue to wait on
1149  * @condition: a C expression for the event to wait for
1159  * change the result of the wait condition.
1164  * The function returns 0 if the @timeout elapsed, -ERESTARTSYS if it
1192 void prepare_to_wait(struct wait_queue_head *wq_head, struct wait_queue_entry *wq_entry, int state);
1193 …e_to_wait_exclusive(struct wait_queue_head *wq_head, struct wait_queue_entry *wq_entry, int state);
1194 …epare_to_wait_event(struct wait_queue_head *wq_head, struct wait_queue_entry *wq_entry, int state);
1209 #define init_wait(wait)								\  argument
1211 		(wait)->private = current;					\
1212 		(wait)->func = autoremove_wake_function;			\
1213 		INIT_LIST_HEAD(&(wait)->entry);					\
1214 		(wait)->flags = 0;						\