Commit abc610e0 authored Jan 03, 2019 by Davidlohr Bueso Committed by Linus Torvalds Jan 04, 2019

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 <dave@stgolabs.net>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Davidlohr Bueso <dbueso@suse.de>
Cc: Jason Baron <jbaron@akamai.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent c5a282e9

fs/eventpoll.c

+6 −2

Original line number	Diff line number	Diff line
		@@ -1820,15 +1820,19 @@ static int ep_poll(struct eventpoll ep, struct epoll_event __user 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);