From: Davidlohr Bueso <dave@stgolabs.net>
Date: Fri, 13 Feb 2015 22:39:08 +0000 (-0800)
Subject: epoll: optimize setting task running after blocking
X-Git-Tag: v4.0-rc1~90^2~40
X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=4d5755b147665912c938504033d958f1115b68ff;p=linux.git

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_INTERRUPTIBLE).  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@suse.de>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index d77f94491352..1e009cad8d5c 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -1639,9 +1639,9 @@ static int ep_poll(struct eventpoll *ep, struct epoll_event __user *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 ? */