Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
From:   Davidlohr Bueso <dave@stgolabs.net>
To:     akpm@linux-foundation.org
Cc:     jbaron@akamai.com, viro@zeniv.linux.org.uk, dave@stgolabs.net,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH 6/6] fs/epoll: avoid barrier after an epoll_wait(2) timeout
Date:   Wed,  7 Nov 2018 21:10:06 -0800
Message-Id: <20181108051006.18751-7-dave@stgolabs.net>
In-Reply-To: <20181108051006.18751-1-dave@stgolabs.net>
References: <20181108051006.18751-1-dave@stgolabs.net>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Upon timeout, we can just exit out of the loop, without
the cost of the changing the task's state smp_store_mb
call. Just exit out of the loop and be done - setting
the task state afterwards will be, of course, redundant.

Signed-off-by: Davidlohr Bueso <dave@stgolabs.net>
---
 fs/eventpoll.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index f6c023f085f6..ec14e5bcdaa9 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -1820,15 +1820,18 @@ static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events,
 			res = -EINTR;
 			break;
 		}
-		if (ep_events_available(ep) || timed_out)
+		
+		if (ep_events_available(ep))
 			break;
 		if (signal_pending(current)) {
 			res = -EINTR;
 			break;
 		}
 
-		if (!schedule_hrtimeout_range(to, slack, HRTIMER_MODE_ABS))
+		if (!schedule_hrtimeout_range(to, slack, HRTIMER_MODE_ABS)) {
 			timed_out = 1;
+			break;
+		}
 	}
 
 	__set_current_state(TASK_RUNNING);
-- 
2.16.4