ds: use WNOHANG with waitpid if inside event loop

While we're usually not stuck waiting on waitpid after
seeing a pipe EOF or even triggering SIGPIPE in the process
(e.g. git-http-backend) we're reading from, it MAY happen
and we should be careful to never hang the daemon process
on waitpid calls.

v2: use "eq" for string comparison against 'DEFAULT'

1 files changed, 7 insertions, 2 deletions

diff --git a/lib/PublicInbox/ProcessPipe.pm b/lib/PublicInbox/ProcessPipe.pm
index 2769e064..4f5fc751 100644
--- a/lib/PublicInbox/ProcessPipe.pm
+++ b/lib/PublicInbox/ProcessPipe.pm
@@ -20,8 +20,13 @@ sub CLOSE {
         my $ret = defined $fh ? close($fh) : '';
         my $pid = delete $_[0]->{pid};
         if (defined $pid) {
-                waitpid($pid, 0);
-                $ret = '' if $?;
+                # PublicInbox::DS may not be loaded
+                eval { PublicInbox::DS::dwaitpid($pid, undef, undef) };
+
+                if ($@) { # ok, not in the event loop, work synchronously
+                        waitpid($pid, 0);
+                        $ret = '' if $?;
+                }
         }
         $ret;
 }