imap: fix pipelining with async git

Since IMAP yields control to GitAsyncCat, IMAP->event_step may
be invoked with {long_cb} still active.  We must be sure to
bail out of IMAP->event_step if that happens and continue to let
GitAsyncCat drive IMAP.

This also improves fairness by never processing more than one
request per ->event_step.

1 files changed, 17 insertions, 20 deletions

diff --git a/lib/PublicInbox/IMAP.pm b/lib/PublicInbox/IMAP.pm
index 917833f7..3c32d846 100644
--- a/lib/PublicInbox/IMAP.pm
+++ b/lib/PublicInbox/IMAP.pm
@@ -888,38 +888,35 @@ sub long_response ($$;@) {
 sub event_step {
         my ($self) = @_;
 
-        return unless $self->flush_write && $self->{sock};
+        return unless $self->flush_write && $self->{sock} && !$self->{long_cb};
 
         $self->update_idle_time;
         # only read more requests if we've drained the write buffer,
         # otherwise we can be buffering infinitely w/o backpressure
 
-        my $rbuf = $self->{rbuf} // (\(my $x = ''));
-        my $r = 1;
-
-        if (index($$rbuf, "\n") < 0) {
-                my $off = length($$rbuf);
-                $r = $self->do_read($rbuf, LINE_MAX, $off) or return;
-        }
-        while ($r > 0 && $$rbuf =~ s/\A[ \t]*([^\n]*?)\r?\n//) {
-                my $line = $1;
-                return $self->close if $line =~ /[[:cntrl:]]/s;
-                my $t0 = now();
-                my $fd = fileno($self->{sock});
-                $r = eval { process_line($self, $line) };
-                my $pending = $self->{wbuf} ? ' pending' : '';
-                out($self, "[$fd] %s - %0.6f$pending", $line, now() - $t0);
-        }
+        my $rbuf = $self->{rbuf} // \(my $x = '');
+        my $line = index($$rbuf, "\n");
+        while ($line < 0) {
+                return $self->close if length($$rbuf) >= LINE_MAX;
+                $self->do_read($rbuf, LINE_MAX, length($$rbuf)) or return;
+                $line = index($$rbuf, "\n");
+        }
+        $line = substr($$rbuf, 0, $line + 1, '');
+        $line =~ s/\r?\n\z//s;
+        return $self->close if $line =~ /[[:cntrl:]]/s;
+        my $t0 = now();
+        my $fd = fileno($self->{sock});
+        my $r = eval { process_line($self, $line) };
+        my $pending = $self->{wbuf} ? ' pending' : '';
+        out($self, "[$fd] %s - %0.6f$pending - $r", $line, now() - $t0);
 
         return $self->close if $r < 0;
-        my $len = length($$rbuf);
-        return $self->close if ($len >= LINE_MAX);
         $self->rbuf_idle($rbuf);
         $self->update_idle_time;
 
         # maybe there's more pipelined data, or we'll have
         # to register it for socket-readiness notifications
-        $self->requeue unless $self->{wbuf};
+        $self->requeue unless $pending;
 }
 
 sub compressed { undef }