[PATCH 2/3] http: fix various race conditions

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

We no longer override Danga::Socket::event_write and instead
re-enable reads by queuing up another callback in the $close
response callback.  This is necessary because event_write may not be
completely done writing a response, only the existing buffered data.

Furthermore, the {closed} field can almost be set at any time when
writing, so we must check it before acting on pipelined requests as
well as during write callbacks in more().
---
 lib/PublicInbox/HTTP.pm | 60 ++++++++++++++++++++++++-------------------------
 1 file changed, 30 insertions(+), 30 deletions(-)

diff --git a/lib/PublicInbox/HTTP.pm b/lib/PublicInbox/HTTP.pm
index 00c9a04..6aae5c8 100644
--- a/lib/PublicInbox/HTTP.pm
+++ b/lib/PublicInbox/HTTP.pm
@@ -39,7 +39,10 @@ sub process_pipelineq () {
 	my $q = $pipelineq;
 	$pipet = undef;
 	$pipelineq = [];
-	rbuf_process($_) foreach @$q;
+	foreach (@$q) {
+		next if $_->{closed};
+		rbuf_process($_);
+	}
 }
 
 # Use the same configuration parameter as git since this is primarily
@@ -228,26 +231,36 @@ sub identity_wcb ($) {
 	sub { $self->write(\($_[0])) if $_[0] ne '' }
 }
 
+sub next_request ($) {
+	my ($self) = @_;
+	$self->watch_write(0);
+	if ($self->{rbuf} eq '') { # wait for next request
+		$self->watch_read(1);
+	} else { # avoid recursion for pipelined requests
+		push @$pipelineq, $self;
+		$pipet ||= PublicInbox::EvCleanup::asap(*process_pipelineq);
+	}
+}
+
+sub response_done ($$) {
+	my ($self, $alive) = @_;
+	my $env = $self->{env};
+	$self->{env} = undef;
+	$self->write("0\r\n\r\n") if $alive == 2;
+	$self->write(sub { $alive ? next_request($self) : $self->close });
+	if (my $obj = $env->{'pi-httpd.inbox'}) {
+		# grace period for reaping resources
+		$WEAKEN->{"$obj"} = $obj;
+		PublicInbox::EvCleanup::later(*weaken_task);
+	}
+}
+
 sub response_write {
 	my ($self, $env, $res) = @_;
 	my $alive = response_header_write($self, $env, $res);
 
 	my $write = $alive == 2 ? chunked_wcb($self) : identity_wcb($self);
-	my $close = sub {
-		$self->write("0\r\n\r\n") if $alive == 2;
-		if ($alive) {
-			$self->event_write; # watch for readability if done
-		} else {
-			Danga::Socket::write($self, sub { $self->close });
-		}
-		if (my $obj = $env->{'pi-httpd.inbox'}) {
-			# grace period for reaping resources
-			$WEAKEN->{"$obj"} = $obj;
-			$weakt ||= PublicInbox::EvCleanup::later(*weaken_task);
-		}
-		$self->{env} = undef;
-	};
-
+	my $close = sub { response_done($self, $alive) };
 	if (defined(my $body = $res->[2])) {
 		if (ref $body eq 'ARRAY') {
 			$write->($_) foreach @$body;
@@ -278,6 +291,7 @@ sub response_write {
 use constant MSG_MORE => ($^O eq 'linux') ? 0x8000 : 0;
 sub more ($$) {
 	my $self = $_[0];
+	return if $self->{closed};
 	if (MSG_MORE && !$self->{write_buf_size}) {
 		my $n = send($self->{sock}, $_[1], MSG_MORE);
 		if (defined $n) {
@@ -290,20 +304,6 @@ sub more ($$) {
 	$self->write($_[1]);
 }
 
-# overrides existing Danga::Socket method
-sub event_write {
-	my ($self) = @_;
-	# only continue watching for readability when we are done writing:
-	return if $self->write(undef) != 1;
-
-	if ($self->{rbuf} eq '') { # wait for next request
-		$self->watch_read(1);
-	} else { # avoid recursion for pipelined requests
-		push @$pipelineq, $self;
-		$pipet ||= PublicInbox::EvCleanup::asap(*process_pipelineq);
-	}
-}
-
 sub input_prepare {
 	my ($self, $env) = @_;
 	my $input = $null_io;