From: Olivier Houchard <cognet@ci0.org>
Date: Wed, 18 Mar 2020 12:10:05 +0000 (+0100)
Subject: BUG/MEDIUM: wdt: Don't ignore WDTSIG and DEBUGSIG in __signal_process_queue().
X-Git-Tag: v2.2-dev5~32
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=b0198cc4132381910cdeb9b5a867632b8b83262c;p=thirdparty%2Fhaproxy.git

BUG/MEDIUM: wdt: Don't ignore WDTSIG and DEBUGSIG in __signal_process_queue().

When running __signal_process_queue(), we ignore most signals. We can't,
however, ignore WDTSIG and DEBUGSIG, otherwise that thread may end up
waiting for another one that could hold a glibc lock, while the other thread
wait for this one to enter debug_handler().
So make sure WDTSIG and DEBUGSIG aren't ignored, if they are defined.
This probably explains the watchdog deadlock described in github issue

This should be backported to 2.1, 2.0 and 1.9.
---

diff --git a/src/signal.c b/src/signal.c
index 20236fa543..288ef007db 100644
--- a/src/signal.c
+++ b/src/signal.c
@@ -114,11 +114,19 @@ static void signal_init()
 	/* man sigprocmask: If SIGBUS, SIGFPE, SIGILL, or SIGSEGV are
 	   generated while they are blocked, the result is undefined, unless
 	   the signal was generated by kill(2),
-	   sigqueue(3), or raise(3) */
+	   sigqueue(3), or raise(3).
+	   Do not ignore WDTSIG or DEBUGSIG either, or it may deadlock the
+	   watchdog */
 	sigdelset(&blocked_sig, SIGBUS);
 	sigdelset(&blocked_sig, SIGFPE);
 	sigdelset(&blocked_sig, SIGILL);
 	sigdelset(&blocked_sig, SIGSEGV);
+#ifdef DEBUGSIG
+	sigdelset(&blocked_sig, DEBUGSIG);
+#endif
+#ifdef WDTSIG
+	sigdelset(&blocked_sig, WDTSIG);
+#endif
 	for (sig = 0; sig < MAX_SIGNAL; sig++)
 		LIST_INIT(&signal_state[sig].handlers);
 }