From e748f75979046724ead380bd00eadc677bdc07e9 Mon Sep 17 00:00:00 2001
From: Eric Wong <e@80x24.org>
Date: Sat, 18 Jun 2016 10:53:32 +0000
Subject: spawn: try to keep signals blocked in spawned child

While we only want to stop our daemons and gracefully destroy
subprocesses, it is common for 'Ctrl-C' from a terminal to kill
the entire pgroup.

Killing an entire pgroup nukes subprocesses like git-upload-pack
breaks graceful shutdown on long clones.  Make a best effort to
ensure git-upload-pack processes are not broken when somebody
signals an entire process group.

Followup-to: commit 37bf2db81bbbe114d7fc5a00e30d3d5a6fa74de5
("doc: systemd examples should only kill one process")
---
 lib/PublicInbox/Spawn.pm   | 8 +++++---
 lib/PublicInbox/SpawnPP.pm | 7 ++++++-
 2 files changed, 11 insertions(+), 4 deletions(-)

(limited to 'lib/PublicInbox')

diff --git a/lib/PublicInbox/Spawn.pm b/lib/PublicInbox/Spawn.pm
index 66dce335..83730302 100644
--- a/lib/PublicInbox/Spawn.pm
+++ b/lib/PublicInbox/Spawn.pm
@@ -104,9 +104,11 @@ int public_inbox_fork_exec(int in, int out, int err,
 		REDIR(out, 1);
 		REDIR(err, 2);
 		for (sig = 1; sig < NSIG; sig++)
-			signal(sig, SIG_DFL); /* ignore errorrs on signals */
-		ret = sigprocmask(SIG_SETMASK, &old, NULL);
-		if (ret != 0) xerr("sigprocmask failed in vfork child");
+			signal(sig, SIG_DFL); /* ignore errors on signals */
+		/*
+		 * don't bother unblocking, we don't want signals
+		 * to the group taking out a subprocess
+		 */
 		execve(filename, argv, envp);
 		xerr("execve failed");
 	}
diff --git a/lib/PublicInbox/SpawnPP.pm b/lib/PublicInbox/SpawnPP.pm
index fe95d126..36223e81 100644
--- a/lib/PublicInbox/SpawnPP.pm
+++ b/lib/PublicInbox/SpawnPP.pm
@@ -3,11 +3,15 @@
 package PublicInbox::SpawnPP;
 use strict;
 use warnings;
-use POSIX qw(dup2);
+use POSIX qw(dup2 :signal_h);
 
 # Pure Perl implementation for folks that do not use Inline::C
 sub public_inbox_fork_exec ($$$$$$) {
 	my ($in, $out, $err, $f, $cmd, $env) = @_;
+	my $old = POSIX::SigSet->new();
+	my $set = POSIX::SigSet->new();
+	$set->fillset or die "fillset failed: $!";
+	sigprocmask(SIG_SETMASK, $set, $old) or die "can't block signals: $!";
 	my $pid = fork;
 	if ($pid == 0) {
 		if ($in != 0) {
@@ -29,6 +33,7 @@ sub public_inbox_fork_exec ($$$$$$) {
 			die "exec $cmd->[0] failed: $!\n";
 		}
 	}
+	sigprocmask(SIG_SETMASK, $old) or die "can't unblock signals: $!";
 	$pid;
 }
 
-- 
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