If a timeout == 0 is specified we will return immediately even if there
are no events so there is no need to enter the polling loop.
Signed-off-by: Shawn Bohrer <shawn.bohrer@xxxxxxxxx>
---
fs/eventpoll.c | 17 ++++++++++++++---
1 files changed, 14 insertions(+), 3 deletions(-)
diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index c24a032..57a77f5 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -1121,6 +1121,10 @@ static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events,
struct timespec end_time;
ktime_t expires, *to = NULL;
+ /*
+ * A negative timeout means wait indefinitely and leaves 'to' NULL for
+ * an infinite timeout.
+ */
if (timeout > 0) {
ktime_get_ts(&end_time);
timespec_add_ns(&end_time, (u64)timeout * NSEC_PER_MSEC);
@@ -1128,7 +1132,12 @@ static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events,
to = &expires;
*to = timespec_to_ktime(end_time);
} else if (timeout == 0) {
+ /*
+ * Return immediately even if no events are available.
+ */
timed_out = 1;
+ spin_lock_irqsave(&ep->lock, flags);
+ goto skip;
}
retry:
@@ -1146,9 +1155,10 @@ retry:
for (;;) {
/*
- * We don't want to sleep if the ep_poll_callback() sends us
- * a wakeup in between. That's why we set the task state
- * to TASK_INTERRUPTIBLE before doing the checks.
+ * We don't want to sleep if the ep_poll_callback()
+ * sends us a wakeup in between. That's why we set the
+ * task state to TASK_INTERRUPTIBLE before doing the
+ * checks.
*/
set_current_state(TASK_INTERRUPTIBLE);
if (!list_empty(&ep->rdllist) || timed_out)
@@ -1168,6 +1178,7 @@ retry:
set_current_state(TASK_RUNNING);
}
+skip:
/* Is it worth to try to dig for events ? */
eavail = !list_empty(&ep->rdllist) || ep->ovflist != EP_UNACTIVE_PTR;
--
1.7.3.4
--
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