From b04e5cf1bc8969cca74ef764f2de960b1ea821a4 Mon Sep 17 00:00:00 2001
From: Eric Wong <e@80x24.org>
Date: Tue, 21 Jun 2016 02:39:27 +0000
Subject: spawn: improve error checking for fork failures

fork failures are unfortunately common when Xapian has
gigabytes and gigabytes mmapped.
---
 lib/PublicInbox/Config.pm  | 2 +-
 lib/PublicInbox/Git.pm     | 5 ++++-
 lib/PublicInbox/Qspawn.pm  | 2 +-
 lib/PublicInbox/Spawn.pm   | 8 ++++++--
 lib/PublicInbox/SpawnPP.pm | 6 ++++++
 5 files changed, 18 insertions(+), 5 deletions(-)

(limited to 'lib/PublicInbox')

diff --git a/lib/PublicInbox/Config.pm b/lib/PublicInbox/Config.pm
index ea84da35..ddb4f6b1 100644
--- a/lib/PublicInbox/Config.pm
+++ b/lib/PublicInbox/Config.pm
@@ -94,7 +94,7 @@ sub git_config_dump {
 	my ($in, $out);
 	my @cmd = (qw/git config/, "--file=$file", '-l');
 	my $cmd = join(' ', @cmd);
-	my $fh = popen_rd(\@cmd);
+	my $fh = popen_rd(\@cmd) or die "popen_rd failed for $file: $!\n";
 	my %rv;
 	local $/ = "\n";
 	foreach my $line (<$fh>) {
diff --git a/lib/PublicInbox/Git.pm b/lib/PublicInbox/Git.pm
index bc0e5064..f47bc439 100644
--- a/lib/PublicInbox/Git.pm
+++ b/lib/PublicInbox/Git.pm
@@ -28,7 +28,9 @@ sub _bidi_pipe {
 
 	my @cmd = ('git', "--git-dir=$self->{git_dir}", qw(cat-file), $batch);
 	my $redir = { 0 => fileno($out_r), 1 => fileno($in_w) };
-	$self->{$pid} = spawn(\@cmd, undef, $redir);
+	my $p = spawn(\@cmd, undef, $redir);
+	defined $p or fail($self, "spawn failed: $!");
+	$self->{$pid} = $p;
 	$out_w->autoflush(1);
 	$self->{$out} = $out_w;
 	$self->{$in} = $in_r;
@@ -122,6 +124,7 @@ sub popen {
 sub qx {
 	my ($self, @cmd) = @_;
 	my $fh = $self->popen(@cmd);
+	defined $fh or return;
 	local $/ = "\n";
 	return <$fh> if wantarray;
 	local $/;
diff --git a/lib/PublicInbox/Qspawn.pm b/lib/PublicInbox/Qspawn.pm
index 9e4c8e08..9299096a 100644
--- a/lib/PublicInbox/Qspawn.pm
+++ b/lib/PublicInbox/Qspawn.pm
@@ -17,7 +17,7 @@ sub _do_spawn {
 	my ($self, $cb) = @_;
 	my $err;
 	($self->{rpipe}, $self->{pid}) = popen_rd(@{$self->{args}});
-	if ($self->{pid}) {
+	if (defined $self->{pid}) {
 		$running++;
 	} else {
 		$self->{err} = $!;
diff --git a/lib/PublicInbox/Spawn.pm b/lib/PublicInbox/Spawn.pm
index 83730302..41b08a33 100644
--- a/lib/PublicInbox/Spawn.pm
+++ b/lib/PublicInbox/Spawn.pm
@@ -84,7 +84,7 @@ int public_inbox_fork_exec(int in, int out, int err,
 	char **argv, **envp;
 	I32 max;
 	sigset_t set, old;
-	int ret;
+	int ret, errnum;
 
 	argv = AV_ALLOCA(cmd, max);
 	av2c_copy(argv, cmd, max);
@@ -112,8 +112,10 @@ int public_inbox_fork_exec(int in, int out, int err,
 		execve(filename, argv, envp);
 		xerr("execve failed");
 	}
+	errnum = errno;
 	ret = sigprocmask(SIG_SETMASK, &old, NULL);
 	assert(ret == 0 && "BUG calling sigprocmask to restore");
+	errno = errnum;
 
 	return (int)pid;
 }
@@ -180,7 +182,8 @@ sub spawn ($;$$) {
 	my $in = $opts->{0} || 0;
 	my $out = $opts->{1} || 1;
 	my $err = $opts->{2} || 2;
-	public_inbox_fork_exec($in, $out, $err, $f, $cmd, \@env);
+	my $pid = public_inbox_fork_exec($in, $out, $err, $f, $cmd, \@env);
+	$pid < 0 ? undef : $pid;
 }
 
 sub popen_rd {
@@ -191,6 +194,7 @@ sub popen_rd {
 	IO::Handle::blocking($r, $blocking) if defined $blocking;
 	$opts->{1} = fileno($w);
 	my $pid = spawn($cmd, $env, $opts);
+	return unless defined $pid;
 	return ($r, $pid) if wantarray;
 	my $ret = gensym;
 	tie *$ret, 'PublicInbox::ProcessPipe', $pid, $r;
diff --git a/lib/PublicInbox/SpawnPP.pm b/lib/PublicInbox/SpawnPP.pm
index 36223e81..179aba5e 100644
--- a/lib/PublicInbox/SpawnPP.pm
+++ b/lib/PublicInbox/SpawnPP.pm
@@ -12,7 +12,12 @@ sub public_inbox_fork_exec ($$$$$$) {
 	my $set = POSIX::SigSet->new();
 	$set->fillset or die "fillset failed: $!";
 	sigprocmask(SIG_SETMASK, $set, $old) or die "can't block signals: $!";
+	my $syserr;
 	my $pid = fork;
+	unless (defined $pid) { # compat with Inline::C version
+		$syserr = $!;
+		$pid = -1;
+	}
 	if ($pid == 0) {
 		if ($in != 0) {
 			dup2($in, 0) or die "dup2 failed for stdin: $!";
@@ -34,6 +39,7 @@ sub public_inbox_fork_exec ($$$$$$) {
 		}
 	}
 	sigprocmask(SIG_SETMASK, $old) or die "can't unblock signals: $!";
+	$! = $syserr;
 	$pid;
 }
 
-- 
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