BUG/MINOR: signals/poller: ensure wakeup from signals
Add self-wake in signal_handler() to fix a race condition with a signal
coming in between checking signal_queue_len and entering polling sleep.
The changes in commit 43c891dda ("BUG/MINOR: signals/poller: set the
poller timeout to 0 when there are signals") were insufficient.
Move the signal_queue_len check from the poll implementations to
run_poll_loop() to keep that logic in one place.
The poll loops are terminated either by the parameter wake being set or
wake up due to a write to their poller_wr_pipe by wake_thread() in
signal_handler().
This fixes issue #1841.
Must be backported in every stable version.
diff --git a/src/ev_evports.c b/src/ev_evports.c
index 7d3e8a8..0a7df15 100644
--- a/src/ev_evports.c
+++ b/src/ev_evports.c
@@ -178,10 +178,8 @@
thread_idle_now();
thread_harmless_now();
- /* Now let's wait for polled events.
- * Check if the signal queue is not empty in case we received a signal
- * before entering the loop, so we don't wait MAX_DELAY_MS for nothing */
- wait_time = (wake | signal_queue_len) ? 0 : compute_poll_timeout(exp);
+ /* Now let's wait for polled events. */
+ wait_time = wake ? 0 : compute_poll_timeout(exp);
clock_entering_poll();
do {
@@ -219,7 +217,7 @@
break;
if (timeout || !wait_time)
break;
- if (signal_queue_len || wake)
+ if (wake)
break;
if (tick_isset(exp) && tick_is_expired(exp, now_ms))
break;