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 20236fa..288ef00 100644 (file)
--- 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);
 }