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: NDavidlohr Bueso <dbueso@suse.de>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

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 ? */