The patch titled
Subject: fs/epoll: avoid barrier after an epoll_wait(2) timeout
has been added to the -mm tree. Its filename is
fs-epoll-avoid-barrier-after-an-epoll_wait2-timeout.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/fs-epoll-avoid-barrier-after-an-epoll_wait2-timeout.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/fs-epoll-avoid-barrier-after-an-epoll_wait2-timeout.patch
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------------------------------------------------------
From: Davidlohr Bueso <dave@xxxxxxxxxxxx>
Subject: 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.
Link: http://lkml.kernel.org/r/20181108051006.18751-7-dave@xxxxxxxxxxxx
Signed-off-by: Davidlohr Bueso <dave@xxxxxxxxxxxx>
Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Davidlohr Bueso <dbueso@xxxxxxx>
Cc: Jason Baron <jbaron@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/eventpoll.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
--- a/fs/eventpoll.c~fs-epoll-avoid-barrier-after-an-epoll_wait2-timeout
+++ a/fs/eventpoll.c
@@ -1820,15 +1820,18 @@ fetch_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);
_
Patches currently in -mm which might be from dave@xxxxxxxxxxxx are
fs-epoll-remove-max_nests-argument-from-ep_call_nested.patch
fs-epoll-simplify-ep_send_events_proc-ready-list-loop.patch
fs-epoll-drop-ovflist-branch-prediction.patch
fs-epoll-robustify-ep-mtx-held-checks.patch
fs-epoll-reduce-the-scope-of-wq-lock-in-epoll_wait.patch
fs-epoll-reduce-the-scope-of-wq-lock-in-epoll_wait-fix.patch
fs-epoll-avoid-barrier-after-an-epoll_wait2-timeout.patch
fs-epoll-avoid-barrier-after-an-epoll_wait2-timeout-fix.patch
