From 7fe50b8b8a4dc38fc341e3b403545aaca937f50e Mon Sep 17 00:00:00 2001
From: Leon Timmermans <fawaka@gmail.com>
Date: Tue, 18 Jan 2011 16:40:07 +0100
Subject: [PATCH] Also unblock signal handlers throwing an exception

Also handle and test the edge case of a signal handler throwing an
exception
---
 mg.c               | 31 +++++++++++++++++++------------
 t/op/sigdispatch.t | 21 ++++++++++++++++-----
 2 files changed, 35 insertions(+), 17 deletions(-)

diff --git a/mg.c b/mg.c
index f51cd47..cc13531 100644
--- a/mg.c
+++ b/mg.c
@@ -1434,6 +1434,14 @@ Perl_csighandler_init(void)
 }
 #endif
 
+#if defined HAS_SIGPROCMASK
+static void
+unblock_sigmask(pTHX_ void* newset)
+{
+    sigprocmask(SIG_UNBLOCK, (sigset_t*)newset, NULL);
+}
+#endif
+
 void
 Perl_despatch_signals(pTHX)
 {
@@ -1443,7 +1451,7 @@ Perl_despatch_signals(pTHX)
     for (sig = 1; sig < SIG_SIZE; sig++) {
 	if (PL_psig_pend[sig]) {
 	    dSAVE_ERRNO;
-#if defined(HAS_SIGPROCMASK)
+#ifdef HAS_SIGPROCMASK
 	    /* From sigaction(2) (FreeBSD man page):
 	     * | Signal routines normally execute with the signal that
 	     * | caused their invocation blocked, but other signals may
@@ -1458,6 +1466,12 @@ Perl_despatch_signals(pTHX)
 	    sigaddset(&newset, sig);
 	    sigprocmask(SIG_BLOCK, &newset, &oldset);
 	    was_blocked = sigismember(&oldset, sig);
+	    if (!was_blocked) {
+		SV* save_sv = newSVpvn((char *)(&newset), sizeof(sigset_t));
+		ENTER;
+		SAVEFREESV(save_sv);
+		SAVEDESTRUCTOR_X(unblock_sigmask, SvPV_nolen(save_sv));
+	    }
 #endif
  	    PL_psig_pend[sig] = 0;
 #if defined(HAS_SIGACTION) && defined(SA_SIGINFO)
@@ -1465,9 +1479,9 @@ Perl_despatch_signals(pTHX)
 #else
 	    (*PL_sighandlerp)(sig);
 #endif
-#if defined(HAS_SIGPROCMASK)
+#ifdef HAS_SIGPROCMASK
 	    if (!was_blocked)
-		sigprocmask(SIG_UNBLOCK, &newset, NULL);
+		LEAVE;
 #endif
 	    RESTORE_ERRNO;
 	}
@@ -3092,22 +3106,15 @@ Perl_sighandler(int sig)
 
     POPSTACK;
     if (SvTRUE(ERRSV)) {
-#ifndef PERL_MICRO
-#ifdef HAS_SIGPROCMASK
+#if !defined(PERL_MICRO) && !defined(HAS_SIGPROCMASK)
 	/* Handler "died", for example to get out of a restart-able read().
 	 * Before we re-do that on its behalf re-enable the signal which was
 	 * blocked by the system when we entered.
 	 */
-	sigset_t set;
-	sigemptyset(&set);
-	sigaddset(&set,sig);
-	sigprocmask(SIG_UNBLOCK, &set, NULL);
-#else
 	/* Not clear if this will work */
 	(void)rsignal(sig, SIG_IGN);
 	(void)rsignal(sig, PL_csighandlerp);
-#endif
-#endif /* !PERL_MICRO */
+#endif /* !PERL_MICRO && !HAS_SIGPROCMASK*/
 	die_sv(ERRSV);
     }
 cleanup:
diff --git a/t/op/sigdispatch.t b/t/op/sigdispatch.t
index a86861e..e3c8fdb 100644
--- a/t/op/sigdispatch.t
+++ b/t/op/sigdispatch.t
@@ -9,7 +9,7 @@ BEGIN {
 use strict;
 use Config;
 
-plan tests => 9;
+plan tests => 12;
 
 watchdog(10);
 
@@ -39,7 +39,7 @@ eval {
 is($@, "Alarm!\n", 'after the second loop');
 
 SKIP: {
-    skip('We can\'t test blocking without sigprocmask', 3) if $ENV{PERL_CORE_MINITEST} || !$Config{d_sigprocmask};
+    skip('We can\'t test blocking without sigprocmask', 8) if $ENV{PERL_CORE_MINITEST} || !$Config{d_sigprocmask};
 
     require POSIX;
     my $new = POSIX::SigSet->new(&POSIX::SIGUSR1);
@@ -48,15 +48,26 @@ SKIP: {
     my $gotit = 0;
     $SIG{USR1} = sub { $gotit++ };
     kill SIGUSR1, $$;
-    is $gotit, 0, 'Haven\'t third received signal yet';
+    is $gotit, 0, 'Haven\'t received third signal yet';
     
     my $old = POSIX::SigSet->new();
     POSIX::sigsuspend($old);
     is $gotit, 1, 'Received third signal';
     
+	{
+		kill SIGUSR1, $$;
+		local $SIG{USR1} = sub { die "FAIL\n" };
+		POSIX::sigprocmask(&POSIX::SIG_BLOCK, undef, $old);
+		ok $old->ismember(&POSIX::SIGUSR1), 'SIGUSR1 is blocked';
+		eval { POSIX::sigsuspend(POSIX::SigSet->new) };
+		is $@, "FAIL\n", 'Exception is thrown, so received fourth signal';
+		POSIX::sigprocmask(&POSIX::SIG_BLOCK, undef, $old);
+		ok $old->ismember(&POSIX::SIGUSR1), 'SIGUSR1 is still blocked';
+	}
+
     kill SIGUSR1, $$;
-    is $gotit, 1, 'Haven\'t fourth received signal yet';
+    is $gotit, 1, 'Haven\'t received fifth signal yet';
     POSIX::sigprocmask(&POSIX::SIG_UNBLOCK, $new, $old);
     ok $old->ismember(&POSIX::SIGUSR1), 'SIGUSR1 was still blocked';
-    is $gotit, 2, 'Received fourth signal';
+    is $gotit, 2, 'Received fifth signal';
 }
-- 
2.7.4