[PATCH 01/19] spawn: pi_fork_exec: restore parent sigmask in child

[Eric Wong <e@80x24.org>]

We continue to unblock SIGCHLD unconditionally, but also
any signals not blocked by the parent (wq_worker).

This will allow Ctrl-C (SIGINT) to stop "git clone" and allow
git-clone cleanup to be performed and other long-running
processes when pi_fork_exec supports setpgid(2).  This won't
affect existing daemons on systems with signalfd(2) or
EVFILT_SIGNAL at all, since those run with signals blocked
anyways.
---
 lib/PublicInbox/Spawn.pm   | 26 ++++++++++++--------------
 lib/PublicInbox/SpawnPP.pm |  6 ++----
 2 files changed, 14 insertions(+), 18 deletions(-)

diff --git a/lib/PublicInbox/Spawn.pm b/lib/PublicInbox/Spawn.pm
index f7dcb024..bac24dd1 100644
--- a/lib/PublicInbox/Spawn.pm
+++ b/lib/PublicInbox/Spawn.pm
@@ -82,20 +82,20 @@ int pi_fork_exec(SV *redirref, SV *file, SV *cmdref, SV *envref, SV *rlimref,
 	const char *filename = SvPV_nolen(file);
 	pid_t pid;
 	char **argv, **envp;
-	sigset_t set, old, cset;
+	sigset_t set, old;
 	int ret, perrnum, cerrnum = 0;
+	int chld_is_member;
 
 	AV2C_COPY(argv, cmd);
 	AV2C_COPY(envp, env);
 
-	ret = sigfillset(&set);
-	assert(ret == 0 && "BUG calling sigfillset");
-	ret = sigprocmask(SIG_SETMASK, &set, &old);
-	assert(ret == 0 && "BUG calling sigprocmask to block");
-	ret = sigemptyset(&cset);
-	assert(ret == 0 && "BUG calling sigemptyset");
-	ret = sigaddset(&cset, SIGCHLD);
-	assert(ret == 0 && "BUG calling sigaddset for SIGCHLD");
+	if (sigfillset(&set)) return -1;
+	if (sigprocmask(SIG_SETMASK, &set, &old)) return -1;
+	chld_is_member = sigismember(&old, SIGCHLD);
+	if (chld_is_member < 0) return -1;
+	if (chld_is_member > 0)
+		sigdelset(&old, SIGCHLD);
+
 	pid = vfork();
 	if (pid == 0) {
 		int sig;
@@ -127,15 +127,13 @@ int pi_fork_exec(SV *redirref, SV *file, SV *cmdref, SV *envref, SV *rlimref,
 				exit_err(&cerrnum);
 		}
 
-		/*
-		 * don't bother unblocking other signals for now, just SIGCHLD.
-		 * we don't want signals to the group taking out a subprocess
-		 */
-		(void)sigprocmask(SIG_UNBLOCK, &cset, NULL);
+		(void)sigprocmask(SIG_SETMASK, &old, NULL);
 		execve(filename, argv, envp);
 		exit_err(&cerrnum);
 	}
 	perrnum = errno;
+	if (chld_is_member > 0)
+		sigaddset(&old, SIGCHLD);
 	ret = sigprocmask(SIG_SETMASK, &old, NULL);
 	assert(ret == 0 && "BUG calling sigprocmask to restore");
 	if (cerrnum) {
diff --git a/lib/PublicInbox/SpawnPP.pm b/lib/PublicInbox/SpawnPP.pm
index b0ad4da5..f64b95dc 100644
--- a/lib/PublicInbox/SpawnPP.pm
+++ b/lib/PublicInbox/SpawnPP.pm
@@ -37,10 +37,8 @@ sub pi_fork_exec ($$$$$$) {
 			chdir $cd or die "chdir $cd: $!";
 		}
 		$SIG{$_} = 'DEFAULT' for keys %SIG;
-		my $cset = POSIX::SigSet->new();
-		$cset->addset(POSIX::SIGCHLD) or die "can't add SIGCHLD: $!";
-		sigprocmask(SIG_UNBLOCK, $cset) or
-					die "can't unblock SIGCHLD: $!";
+		$old->delset(POSIX::SIGCHLD) or die "delset SIGCHLD: $!";
+		sigprocmask(SIG_SETMASK, $old) or die "SETMASK: ~SIGCHLD: $!";
 		if ($ENV{MOD_PERL}) {
 			exec which('env'), '-i', @$env, @$cmd;
 			die "exec env -i ... $cmd->[0] failed: $!\n";