[PATCH 2/3] io: avoid redundant waitpid in DESTROY

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

We shouldn't attempt to reap a process again after it's been
reaped asynchronously in the SIGCHLD handler.  Noticed while
working on changes to get lei/store to use checkpointing.
---
 lib/PublicInbox/IO.pm | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/lib/PublicInbox/IO.pm b/lib/PublicInbox/IO.pm
index 02057600..8640f112 100644
--- a/lib/PublicInbox/IO.pm
+++ b/lib/PublicInbox/IO.pm
@@ -16,7 +16,7 @@ use PublicInbox::OnDestroy;
 
 sub waitcb { # awaitpid callback
 	my ($pid, $errref, $cb, @args) = @_;
-	$$errref = $? if $errref; # sets .cerr for _close
+	$$errref = $?; # sets .cerr for _close
 	$cb->($pid, @args) if $cb; # may clobber $?
 }
 
@@ -24,9 +24,9 @@ sub attach_pid {
 	my ($io, $pid, @cb_arg) = @_;
 	bless $io, __PACKAGE__;
 	# we share $err (and not $self) with awaitpid to avoid a ref cycle
-	${*$io}{pi_io_reap} = [ $PublicInbox::OnDestroy::fork_gen,
-				$pid, \(my $err) ];
-	awaitpid($pid, \&waitcb, \$err, @cb_arg);
+	my $e = \(my $err);
+	${*$io}{pi_io_reap} = [ $PublicInbox::OnDestroy::fork_gen, $pid, $e ];
+	awaitpid($pid, \&waitcb, $e, @cb_arg);
 	$io;
 }
 
@@ -60,7 +60,7 @@ sub DESTROY {
 	my $reap = delete ${*$io}{pi_io_reap};
 	if (($reap->[0] // -1) == $PublicInbox::OnDestroy::fork_gen) {
 		$io->SUPER::close;
-		awaitpid($reap->[1]);
+		${$reap->[2]} // awaitpid($reap->[1]);
 	}
 	$io->SUPER::DESTROY;
 }