http: fix various race conditions

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().

diff --git a/lib/PublicInbox/HTTP.pm b/lib/PublicInbox/HTTP.pm
index 00c9a0444bf75e63689d60893d6b3e236c1ca264..6aae5c86de98e05a2047cf53b41179cf83aa8313 100644 (file)
--- 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;