user/dev discussion of public-inbox itself
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* [PATCH] git_async_cat: remove circular reference
@ 2020-06-23 23:21 Eric Wong
  0 siblings, 0 replies; only message in thread
From: Eric Wong @ 2020-06-23 23:21 UTC (permalink / raw)
  To: meta

While this circular reference was carefully managed to not leak
memory; it was still triggering a warning at -imapd/-nntpd
shutdown due to the EPOLL_CTL_DEL op failing after the $Epoll FD
gets closed.

So remove the circular reference by providing a ref to `undef',
instead.
---
 lib/PublicInbox/Git.pm         |  4 +---
 lib/PublicInbox/GitAsyncCat.pm | 10 +++++-----
 lib/PublicInbox/IMAP.pm        |  2 +-
 lib/PublicInbox/NNTP.pm        |  9 +++------
 4 files changed, 10 insertions(+), 15 deletions(-)

diff --git a/lib/PublicInbox/Git.pm b/lib/PublicInbox/Git.pm
index a55c48d5..776e4832 100644
--- a/lib/PublicInbox/Git.pm
+++ b/lib/PublicInbox/Git.pm
@@ -295,9 +295,7 @@ sub qx {
 sub cleanup {
 	my ($self) = @_;
 	local $in_cleanup = 1;
-	if (my $ac = $self->{async_cat}) {
-		$ac->close; # PublicInbox::GitAsyncCat::close -> EPOLL_CTL_DEL
-	}
+	delete $self->{async_cat};
 	cat_async_wait($self);
 	_destroy($self, qw(cat_rbuf in out pid));
 	_destroy($self, qw(chk_rbuf in_c out_c pid_c err_c));
diff --git a/lib/PublicInbox/GitAsyncCat.pm b/lib/PublicInbox/GitAsyncCat.pm
index 8701e4cf..098101ae 100644
--- a/lib/PublicInbox/GitAsyncCat.pm
+++ b/lib/PublicInbox/GitAsyncCat.pm
@@ -15,20 +15,20 @@ use fields qw(git);
 use PublicInbox::Syscall qw(EPOLLIN EPOLLET);
 our @EXPORT = qw(git_async_cat);
 
-sub new {
+sub _add {
 	my ($class, $git) = @_;
 	my $self = fields::new($class);
 	$git->batch_prepare;
 	$self->SUPER::new($git->{in}, EPOLLIN|EPOLLET);
 	$self->{git} = $git;
-	$self;
+	\undef; # this is a true ref()
 }
 
 sub event_step {
 	my ($self) = @_;
 	my $git = $self->{git} or return; # ->close-ed
 	my $inflight = $git->{inflight};
-	if (@$inflight) {
+	if ($inflight && @$inflight) {
 		$git->cat_async_step($inflight);
 		$self->requeue if @$inflight || exists $git->{cat_rbuf};
 	}
@@ -37,7 +37,7 @@ sub event_step {
 sub close {
 	my ($self) = @_;
 	if (my $git = delete $self->{git}) {
-		delete $git->{async_cat}; # drop circular reference
+		delete $git->{async_cat};
 	}
 	$self->SUPER::close; # PublicInbox::DS::close
 }
@@ -45,7 +45,7 @@ sub close {
 sub git_async_cat ($$$$) {
 	my ($git, $oid, $cb, $arg) = @_;
 	$git->cat_async($oid, $cb, $arg);
-	$git->{async_cat} //= new(__PACKAGE__, $git); # circular reference
+	$git->{async_cat} //= _add(__PACKAGE__, $git);
 }
 
 1;
diff --git a/lib/PublicInbox/IMAP.pm b/lib/PublicInbox/IMAP.pm
index dec10d61..0a6993c6 100644
--- a/lib/PublicInbox/IMAP.pm
+++ b/lib/PublicInbox/IMAP.pm
@@ -1294,7 +1294,7 @@ sub long_step {
 	} elsif ($more) { # $self->{wbuf}:
 		$self->update_idle_time;
 
-		# control passed to $more may be a GitAsyncCat object
+		# control passed to git_async_cat if $more == \undef
 		requeue_once($self) if !ref($more);
 	} else { # all done!
 		delete $self->{long_cb};
diff --git a/lib/PublicInbox/NNTP.pm b/lib/PublicInbox/NNTP.pm
index 6df19f32..76f14bbd 100644
--- a/lib/PublicInbox/NNTP.pm
+++ b/lib/PublicInbox/NNTP.pm
@@ -553,8 +553,7 @@ sub cmd_article ($;$) {
 	return $smsg unless ref $smsg;
 	set_art($self, $art);
 	$smsg->{nntp} = $self;
-	git_async_cat($self->{ng}->git, $smsg->{blob}, \&blob_cb, $smsg);
-	undef;
+	${git_async_cat($self->{ng}->git, $smsg->{blob}, \&blob_cb, $smsg)};
 }
 
 sub cmd_head ($;$) {
@@ -564,8 +563,7 @@ sub cmd_head ($;$) {
 	set_art($self, $art);
 	$smsg->{nntp} = $self;
 	$smsg->{nntp_code} = 221;
-	git_async_cat($self->{ng}->git, $smsg->{blob}, \&blob_cb, $smsg);
-	undef;
+	${git_async_cat($self->{ng}->git, $smsg->{blob}, \&blob_cb, $smsg)};
 }
 
 sub cmd_body ($;$) {
@@ -575,8 +573,7 @@ sub cmd_body ($;$) {
 	set_art($self, $art);
 	$smsg->{nntp} = $self;
 	$smsg->{nntp_code} = 222;
-	git_async_cat($self->{ng}->git, $smsg->{blob}, \&blob_cb, $smsg);
-	undef;
+	${git_async_cat($self->{ng}->git, $smsg->{blob}, \&blob_cb, $smsg)};
 }
 
 sub cmd_stat ($;$) {

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2020-06-23 23:21 [PATCH] git_async_cat: remove circular reference Eric Wong

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