[PATCH 1/2] git-svn: use POSIX::sigprocmask to block signals

From: Roman Kagan <rkagan@mail.ru>
Date: Apr 2, 2012, 16:13 UTC
Message-ID: <9eaaebac91dc2b1a45a4dec77142be0b0b338056.1333381684.git.rkagan@mail.ru>
In-Reply-To: <cover.1333381684.git.rkagan@mail.ru>

rev_map_set() tries to avoid being interrupted by signals.

The conventional way to achieve this is through sigprocmask(), which is available in the standard POSIX module.

This is implemented by this patch. One important consequence of it is that the signal handlers won't be unconditionally set to SIG_DFL anymore upon the first invocation of rev_map_set() as they used to.

[That said, I'm not convinced that messing with signals is necessary (and sufficient) here at all, but my perl-foo is too weak for a more intrusive change.]

Signed-off-by: Roman Kagan <rkagan@mail.ru>
---
 git-svn.perl |   15 +++++++++------
 1 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/git-svn.perl b/git-svn.perl
index 4334b95..570504c 100755
--- a/git-svn.perl
+++ b/git-svn.perl
@@ -2031,6 +2031,7 @@ use IPC::Open3;
 use Time::Local;
 use Memoize;  # core since 5.8.0, Jul 2002
 use Memoize::Storable;
+use POSIX qw(:signal_h);
 
 my ($_gc_nr, $_gc_period);
 
@@ -4059,11 +4060,14 @@ sub rev_map_set {
 	length $commit == 40 or die "arg3 must be a full SHA1 hexsum\n";
 	my $db = $self->map_path($uuid);
 	my $db_lock = "$db.lock";
-	my $sig;
+	my $sigmask;
 	$update_ref ||= 0;
 	if ($update_ref) {
-		$SIG{INT} = $SIG{HUP} = $SIG{TERM} = $SIG{ALRM} = $SIG{PIPE} =
-		            $SIG{USR1} = $SIG{USR2} = sub { $sig = $_[0] };
+		$sigmask = POSIX::SigSet->new();
+		my $signew = POSIX::SigSet->new(SIGINT, SIGHUP, SIGTERM,
+			SIGALRM, SIGPIPE, SIGUSR1, SIGUSR2);
+		sigprocmask(SIG_BLOCK, $signew, $sigmask) or
+			croak "Can't block signals: $!";
 	}
 	mkfile($db);
 
@@ -4102,9 +4106,8 @@ sub rev_map_set {
 	                            "$db_lock => $db ($!)\n";
 	delete $LOCKFILES{$db_lock};
 	if ($update_ref) {
-		$SIG{INT} = $SIG{HUP} = $SIG{TERM} = $SIG{ALRM} = $SIG{PIPE} =
-		            $SIG{USR1} = $SIG{USR2} = 'DEFAULT';
-		kill $sig, $$ if defined $sig;
+		sigprocmask(SIG_SETMASK, $sigmask) or
+			croak "Can't restore signal mask: $!";
 	}
 }

-- 
1.7.7.6