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BUG/MINOR: signals/poller: ensure wakeup from signals

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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.
This commit is contained in:
Matthias Wirth
2022-09-09 10:21:00 +02:00
committed by Willy Tarreau
parent ef2d2340e6
commit eea152ee68
6 changed files with 20 additions and 20 deletions
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6
src/haproxy.c
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@@ -2810,7 +2810,7 @@ void run_poll_loop()
if (killed > 1)
break;
/* expire immediately if events are pending */
/* expire immediately if events or signals are pending */
wake = 1;
if (thread_has_tasks())
activity[tid].wake_tasks++;
@@ -2821,6 +2821,10 @@ void run_poll_loop()
if (thread_has_tasks()) {
activity[tid].wake_tasks++;
_HA_ATOMIC_AND(&th_ctx->flags, ~TH_FL_SLEEPING);
} else if (signal_queue_len) {
/* this check is required after setting TH_FL_SLEEPING to avoid
* a race with wakeup on signals using wake_threads() */
_HA_ATOMIC_AND(&th_ctx->flags, ~TH_FL_SLEEPING);
} else
wake = 0;
}