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-rw-r--r--fs/eventpoll.c48
1 files changed, 28 insertions, 20 deletions
diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index aba03ee749f8..12eebcdea9c8 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -1879,34 +1879,33 @@ fetch_events:
* event delivery.
*/
init_wait(&wait);
- write_lock_irq(&ep->lock);
- __add_wait_queue_exclusive(&ep->wq, &wait);
- write_unlock_irq(&ep->lock);
+ write_lock_irq(&ep->lock);
/*
- * 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.
+ * Barrierless variant, waitqueue_active() is called under
+ * the same lock on wakeup ep_poll_callback() side, so it
+ * is safe to avoid an explicit barrier.
*/
- set_current_state(TASK_INTERRUPTIBLE);
+ __set_current_state(TASK_INTERRUPTIBLE);
+
/*
- * Always short-circuit for fatal signals to allow
- * threads to make a timely exit without the chance of
- * finding more events available and fetching
- * repeatedly.
+ * Do the final check under the lock. ep_scan_ready_list()
+ * plays with two lists (->rdllist and ->ovflist) and there
+ * is always a race when both lists are empty for short
+ * period of time although events are pending, so lock is
+ * important.
*/
- if (fatal_signal_pending(current)) {
- res = -EINTR;
- break;
+ eavail = ep_events_available(ep);
+ if (!eavail) {
+ if (signal_pending(current))
+ res = -EINTR;
+ else
+ __add_wait_queue_exclusive(&ep->wq, &wait);
}
+ write_unlock_irq(&ep->lock);
- eavail = ep_events_available(ep);
- if (eavail)
- break;
- if (signal_pending(current)) {
- res = -EINTR;
+ if (eavail || res)
break;
- }
if (!schedule_hrtimeout_range(to, slack, HRTIMER_MODE_ABS)) {
timed_out = 1;
@@ -1927,6 +1926,15 @@ fetch_events:
}
send_events:
+ if (fatal_signal_pending(current)) {
+ /*
+ * Always short-circuit for fatal signals to allow
+ * threads to make a timely exit without the chance of
+ * finding more events available and fetching
+ * repeatedly.
+ */
+ res = -EINTR;
+ }
/*
* Try to transfer events to user space. In case we get 0 events and
* there's still timeout left over, we go trying again in search of