skeleton: barrier init requires a lock

Writing to the main skeleton pipe requires a lock since it's
shared with partition processes.

1 files changed, 6 insertions, 3 deletions

diff --git a/lib/PublicInbox/SearchIdxSkeleton.pm b/lib/PublicInbox/SearchIdxSkeleton.pm
index beb17b9f..51a88fda 100644
--- a/lib/PublicInbox/SearchIdxSkeleton.pm
+++ b/lib/PublicInbox/SearchIdxSkeleton.pm
@@ -149,9 +149,12 @@ sub index_skeleton_real ($$) {
 # write to the subprocess
 sub barrier_init {
         my ($self, $nparts) = @_;
-        my $w = $_[0]->{w};
-        print $w "barrier_init $nparts\n" or die "failed to write: $!";
-        $w->flush or die "failed to flush: $!";
+        my $w = $self->{w};
+        my $err;
+        $self->_lock_acquire;
+        print $w "barrier_init $nparts\n" or $err = "failed to write: $!\n";
+        $self->_lock_release;
+        die $err if $err;
 }
 
 sub barrier_wait {