linux-kernel - epoll: optimize setting task running after blocking

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Message-ID: <1423273252.1057.11.camel@stgolabs.net>
Date:	Fri, 06 Feb 2015 17:40:52 -0800
From:	Davidlohr Bueso <dave@...olabs.net>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	Alexander Viro <viro@...iv.linux.org.uk>
Cc:	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	Davidlohr Bueso <dave@...olabs.net>
Subject: epoll: optimize setting task running after blocking

After waking up a task waiting for an event, we explicitly
mark it as TASK_RUNNING (which is necessary as we do the
checks for wakeups as TASK_INTERRUPTABLE). Once running
and dealing with actually delivering the events, we're
obviously not planning on calling schedule, thus we can
relax the implied barrier and simply update the state with
__set_current_state().

Signed-off-by: Davidlohr Bueso <dbueso@...e.de>
---
 fs/eventpoll.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index d77f944..1e009ca 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -1639,9 +1639,9 @@ fetch_events:
 
 			spin_lock_irqsave(&ep->lock, flags);
 		}
-		__remove_wait_queue(&ep->wq, &wait);
 
-		set_current_state(TASK_RUNNING);
+		__remove_wait_queue(&ep->wq, &wait);
+		__set_current_state(TASK_RUNNING);
 	}
 check_events:
 	/* Is it worth to try to dig for events ? */
-- 
2.1.4



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