2015-02-07 01:41:02

by Davidlohr Bueso

[permalink] [raw]
Subject: 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_INTERRUPTABLE). 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: Davidlohr Bueso <[email protected]>
---
fs/eventpoll.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index d77f944..1e009ca 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -1639,9 +1639,9 @@ fetch_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 ? */
--
2.1.4