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Commit 2953ef24 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

sched/wait: Change timeout logic 



Commit 4c663cfc ("wait: fix false timeouts when using
wait_event_timeout()") introduced an additional condition check after
a timeout but there's a few issues;

 - it forgot one site
 - it put the check after the main loop; not at the actual timeout
   check.

Cure both; by wrapping the condition (as suggested by Oleg), this
avoids double evaluation of 'condition' which could be quite big.

Reviewed-by: default avatarOleg Nesterov <oleg@redhat.com>
Signed-off-by: default avatarPeter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20131002092528.028892896@infradead.org


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 2f2a2b60

include/linux/wait.h

+11 −13
Original line number Diff line number Diff line
@@ -179,6 +179,14 @@ wait_queue_head_t *bit_waitqueue(void *, int); 
#define wake_up_interruptible_sync_poll(x, m)				\

	__wake_up_sync_key((x), TASK_INTERRUPTIBLE, 1, (void *) (m))



#define ___wait_cond_timeout(condition, ret)				\

({									\

 	bool __cond = (condition);					\

 	if (__cond && !ret)						\

 		ret = 1;						\

 	__cond || !ret;							\

})



#define __wait_event(wq, condition) 					\

do {									\

	DEFINE_WAIT(__wait);						\
@@ -217,14 +225,10 @@ do { \ 
									\

	for (;;) {							\

		prepare_to_wait(&wq, &__wait, TASK_UNINTERRUPTIBLE);	\

		if (condition)						\

		if (___wait_cond_timeout(condition, ret))		\

			break;						\

		ret = schedule_timeout(ret);				\

		if (!ret)						\

			break;						\

	}								\

	if (!ret && (condition))					\

		ret = 1;						\

	finish_wait(&wq, &__wait);					\

} while (0)
@@ -299,18 +303,14 @@ do { \ 
									\

	for (;;) {							\

		prepare_to_wait(&wq, &__wait, TASK_INTERRUPTIBLE);	\

		if (condition)						\

		if (___wait_cond_timeout(condition, ret))		\

			break;						\

		if (signal_pending(current)) {				\

			ret = -ERESTARTSYS;				\

			break;						\

		}							\

		ret = schedule_timeout(ret);				\

		if (!ret)						\

			break;						\

	}								\

	if (!ret && (condition))					\

		ret = 1;						\

	finish_wait(&wq, &__wait);					\

} while (0)
@@ -815,7 +815,7 @@ do { \ 
									\

	for (;;) {							\

		prepare_to_wait(&wq, &__wait, TASK_INTERRUPTIBLE);	\

		if (condition)						\

		if (___wait_cond_timeout(condition, ret))		\

			break;						\

		if (signal_pending(current)) {				\

			ret = -ERESTARTSYS;				\
@@ -824,8 +824,6 @@ do { \ 
		spin_unlock_irq(&lock);					\

		ret = schedule_timeout(ret);				\

		spin_lock_irq(&lock);					\

		if (!ret)						\

			break;						\

	}								\

	finish_wait(&wq, &__wait);					\

} while (0)