daemon: use sigprocmask to block signals at startup

`$SIG{FOO} = "IGNORE"' will cause the daemon to miss signals
entirely.  Instead, we can use sigprocmask to block signal
delivery until we have our signal handlers setup.  This closes a
race where a PID file can be written for an init script and a
signal to be dropped via "IGNORE".

diff --git a/lib/PublicInbox/Daemon.pm b/lib/PublicInbox/Daemon.pm
index b3743f5c3ddf80d608c7becf4bc48d242f04eb88..e830a98faac9987fecf5f7d927a480cf1326b229 100644 (file)
--- a/lib/PublicInbox/Daemon.pm
+++ b/lib/PublicInbox/Daemon.pm
@@ -8,7 +8,7 @@ use warnings;
 use Getopt::Long qw/:config gnu_getopt no_ignore_case auto_abbrev/;
 use IO::Handle;
 use IO::Socket;
-use POSIX qw(WNOHANG);
+use POSIX qw(WNOHANG :signal_h);
 use Socket qw(IPPROTO_TCP SOL_SOCKET);
 sub SO_ACCEPTFILTER () { 0x1000 }
 use Cwd qw/abs_path/;
@@ -19,7 +19,7 @@ require PublicInbox::EvCleanup;
 require PublicInbox::Listener;
 require PublicInbox::ParentPipe;
 my @CMD;
-my $set_user;
+my ($set_user, $oldset);
 my (@cfg_listen, $stdout, $stderr, $group, $user, $pid_file, $daemonize);
 my $worker_processes = 1;
 my @listeners;
@@ -76,9 +76,11 @@ sub accept_tls_opt ($) {
 
 sub daemon_prepare ($) {
        my ($default_listen) = @_;
+       $oldset = POSIX::SigSet->new();
+       my $newset = POSIX::SigSet->new();
+       $newset->fillset or die "fillset: $!";
+       sigprocmask(SIG_SETMASK, $newset, $oldset) or die "sigprocmask: $!";
        @CMD = ($0, @ARGV);
-       $SIG{HUP} = $SIG{USR1} = $SIG{USR2} = $SIG{PIPE} =
-               $SIG{TTIN} = $SIG{TTOU} = $SIG{WINCH} = 'IGNORE';
        my %opts = (
                'l|listen=s' => \@cfg_listen,
                '1|stdout=s' => \$stdout,
@@ -482,6 +484,7 @@ sub master_loop {
                        syswrite($w, '.');
                };
        }
+       sigprocmask(SIG_SETMASK, $oldset) or die "sigprocmask: $!";
        reopen_logs();
        # main loop
        my $quit = 0;
@@ -616,6 +619,7 @@ sub daemon_loop ($$$$) {
                # this calls epoll_create:
                PublicInbox::Listener->new($_, $tls_cb || $post_accept)
        } @listeners;
+       sigprocmask(SIG_SETMASK, $oldset) or die "sigprocmask: $!";
        PublicInbox::DS->EventLoop;
        $parent_pipe = undef;
 }