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From: Eric Wong <e@80x24.org>
To: meta@public-inbox.org
Subject: [PATCH] lei_store_err: use level-trigger for error pipe
Date: Mon, 15 Aug 2022 19:28:33 +0000
Message-Id: <20220815192833.21659-1-e@80x24.org>
MIME-Version: 1.0
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List-Id: <meta.public-inbox.org>

This fixes deadlocks from errors inside lei/store when multiple
errors are spewed.
---
 lib/PublicInbox/LeiStoreErr.pm | 21 ++++++++++-----------
 1 file changed, 10 insertions(+), 11 deletions(-)

diff --git a/lib/PublicInbox/LeiStoreErr.pm b/lib/PublicInbox/LeiStoreErr.pm
index cc085fdc..47fa2277 100644
--- a/lib/PublicInbox/LeiStoreErr.pm
+++ b/lib/PublicInbox/LeiStoreErr.pm
@@ -1,13 +1,12 @@
-# Copyright (C) 2021 all contributors <meta@public-inbox.org>
+# Copyright (C) all contributors <meta@public-inbox.org>
 # License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
 
 # forwards stderr from lei/store process to any lei clients using
 # the same store, falls back to syslog if no matching clients exist.
 package PublicInbox::LeiStoreErr;
-use strict;
-use v5.10.1;
+use v5.12;
 use parent qw(PublicInbox::DS);
-use PublicInbox::Syscall qw(EPOLLIN EPOLLONESHOT);
+use PublicInbox::Syscall qw(EPOLLIN);
 use Sys::Syslog qw(openlog syslog closelog);
 use IO::Handle (); # ->blocking
 
@@ -15,24 +14,24 @@ sub new {
 	my ($cls, $rd, $lei) = @_;
 	my $self = bless { sock => $rd, store_path => $lei->store_path }, $cls;
 	$rd->blocking(0);
-	$self->SUPER::new($rd, EPOLLIN | EPOLLONESHOT);
+	$self->SUPER::new($rd, EPOLLIN); # level-trigger
 }
 
 sub event_step {
 	my ($self) = @_;
-	my $rbuf = $self->{rbuf} // \(my $x = '');
-	$self->do_read($rbuf, 8192, length($$rbuf)) or return;
-	my $cb;
+	my $n = sysread($self->{sock}, my $buf, 8192);
+	return ($!{EAGAIN} ? 0 : $self->close) if !defined($n);
+	return $self->close if !$n;
 	my $printed;
 	for my $lei (values %PublicInbox::DS::DescriptorMap) {
-		$cb = $lei->can('store_path') // next;
+		my $cb = $lei->can('store_path') // next;
 		next if $cb->($lei) ne $self->{store_path};
 		my $err = $lei->{2} // next;
-		print $err $$rbuf and $printed = 1;
+		print $err $buf and $printed = 1;
 	}
 	if (!$printed) {
 		openlog('lei/store', 'pid,nowait,nofatal,ndelay', 'user');
-		for my $l (split(/\n/, $$rbuf)) { syslog('warning', '%s', $l) }
+		for my $l (split(/\n/, $buf)) { syslog('warning', '%s', $l) }
 		closelog(); # don't share across fork
 	}
 }