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Commit b1ea06a9 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Ingo Molnar
Browse files

sched/wait: Avoid abort_exclusive_wait() in ___wait_event() 



___wait_event() doesn't really need abort_exclusive_wait(), we can simply
change prepare_to_wait_event() to remove the waiter from q->task_list if
it was interrupted.

This simplifies the code/logic, and this way prepare_to_wait_event() can
have more users, see the next change.

Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Bart Van Assche <bvanassche@acm.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Neil Brown <neilb@suse.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20160908164815.GA18801@redhat.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
--
 include/linux/wait.h |    7 +------
 kernel/sched/wait.c  |   35 +++++++++++++++++++++++++----------
 2 files changed, 26 insertions(+), 16 deletions(-)
parent 38a3e1fc

include/linux/wait.h

+1 −6
Original line number Diff line number Diff line
@@ -280,12 +280,7 @@ wait_queue_head_t *bit_waitqueue(void *, int); 
									\

		if (___wait_is_interruptible(state) && __int) {		\

			__ret = __int;					\

			if (exclusive) {				\

				abort_exclusive_wait(&wq, &__wait, 	\

						     NULL);		\

			goto __out;					\

			}						\

			break;						\

		}							\

									\

		cmd;							\

kernel/sched/wait.c

+25 −10
Original line number Diff line number Diff line
@@ -199,14 +199,28 @@ EXPORT_SYMBOL(prepare_to_wait_exclusive); 
long prepare_to_wait_event(wait_queue_head_t *q, wait_queue_t *wait, int state)

{

	unsigned long flags;



	if (signal_pending_state(state, current))

		return -ERESTARTSYS;

	long ret = 0;



	wait->private = current;

	wait->func = autoremove_wake_function;



	spin_lock_irqsave(&q->lock, flags);

	if (unlikely(signal_pending_state(state, current))) {

		/*

		 * Exclusive waiter must not fail if it was selected by wakeup,

		 * it should "consume" the condition we were waiting for.

		 *

		 * The caller will recheck the condition and return success if

		 * we were already woken up, we can not miss the event because

		 * wakeup locks/unlocks the same q->lock.

		 *

		 * But we need to ensure that set-condition + wakeup after that

		 * can't see us, it should wake up another exclusive waiter if

		 * we fail.

		 */

		list_del_init(&wait->task_list);

		ret = -ERESTARTSYS;

	} else {

		if (list_empty(&wait->task_list)) {

			if (wait->flags & WQ_FLAG_EXCLUSIVE)

				__add_wait_queue_tail(q, wait);
@@ -214,9 +228,10 @@ long prepare_to_wait_event(wait_queue_head_t *q, wait_queue_t *wait, int state) 
				__add_wait_queue(q, wait);

		}

		set_current_state(state);

	}

	spin_unlock_irqrestore(&q->lock, flags);



	return 0;

	return ret;

}

EXPORT_SYMBOL(prepare_to_wait_event);