BUG/MINOR: signals/poller: set the poller timeout to 0 when there are signals

When receiving a signal before entering the poller, and without any
activity in the process, the poller will be entered with a timeout
calculated without checking the signals.

Since commit 4f59d3 ("MINOR: time: increase the minimum wakeup interval
to 60s") the issue is much more visible because it could be stuck for
60s.

When in mworker mode, if a worker quits and the SIGCHLD signal deliver
at the right time to the master, this one could be stuck for the time of
the timeout.

This should fix issue #1841

Must be backported in every stable version.

src/ev_epoll.c

@@ -222,8 +222,10 @@ static void _do_poll(struct poller *p, int exp, int wake)
 	thread_idle_now();
 	thread_harmless_now();
 
-	/* now let's wait for polled events */
-	wait_time = wake ? 0 : compute_poll_timeout(exp);
+	/* 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);
 	clock_entering_poll();
 	do {
 		int timeout = (global.tune.options & GTUNE_BUSY_POLLING) ? 0 : wait_time;

src/ev_evports.c

@@ -178,10 +178,10 @@ static void _do_poll(struct poller *p, int exp, int wake)
 	thread_idle_now();
 	thread_harmless_now();
 
-	/*
-	 * Determine how long to wait for events to materialise on the port.
-	 */
-	wait_time = wake ? 0 : compute_poll_timeout(exp);
+	/* 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);
 	clock_entering_poll();
 
 	do {

src/ev_kqueue.c

@@ -166,8 +166,10 @@ static void _do_poll(struct poller *p, int exp, int wake)
 	}
 	fd_nbupdt = 0;
 
-	/* now let's wait for events */
-	wait_time = wake ? 0 : compute_poll_timeout(exp);
+	/* 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);
 	fd = global.tune.maxpollevents;
 	clock_entering_poll();
 

src/ev_poll.c

@@ -22,6 +22,7 @@
 #include <haproxy/clock.h>
 #include <haproxy/fd.h>
 #include <haproxy/global.h>
+#include <haproxy/signal.h>
 #include <haproxy/task.h>
 #include <haproxy/ticks.h>
 
@@ -203,8 +204,10 @@ static void _do_poll(struct poller *p, int exp, int wake)
 		}
 	}
 
-	/* now let's wait for events */
-	wait_time = wake ? 0 : compute_poll_timeout(exp);
+	/* 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);
 	clock_entering_poll();
 	status = poll(poll_events, nbfd, wait_time);
 	clock_update_date(wait_time, status);