From abc610e01c663e25c41a3bdcbc4115cd7fbb047b Mon Sep 17 00:00:00 2001 From: Davidlohr Bueso Date: Thu, 3 Jan 2019 15:27:19 -0800 Subject: [PATCH] fs/epoll: avoid barrier after an epoll_wait(2) timeout Upon timeout, we can just exit out of the loop, without the cost of the changing the task's state with an smp_store_mb call. Just exit out of the loop and be done - setting the task state afterwards will be, of course, redundant. [dave@stgolabs.net: forgotten fixlets] Link: http://lkml.kernel.org/r/20181109155258.jxcr4t2pnz6zqct3@linux-r8p5 Link: http://lkml.kernel.org/r/20181108051006.18751-7-dave@stgolabs.net Signed-off-by: Davidlohr Bueso Reviewed-by: Andrew Morton Cc: Al Viro Cc: Davidlohr Bueso Cc: Jason Baron Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/eventpoll.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/fs/eventpoll.c b/fs/eventpoll.c index b42f53d64d11..9beb166b7264 100644 --- a/fs/eventpoll.c +++ b/fs/eventpoll.c @@ -1820,15 +1820,19 @@ fetch_events: res = -EINTR; break; } - if (ep_events_available(ep) || timed_out) + + eavail = ep_events_available(ep); + if (eavail) 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);