0001-TAP-test-with-listener-pos-race.patch.nocfbot

From 805b53cccd5a90e787447495753b4db9ed1ec765 Mon Sep 17 00:00:00 2001
From: Arseniy Mukhin <arseniy.mukhin.dev@gmail.com>
Date: Mon, 20 Oct 2025 15:14:36 +0300
Subject: [PATCH] TAP test with listener pos race

---
 src/backend/commands/async.c                  |  5 +
 src/test/authentication/meson.build           |  1 +
 .../authentication/t/008_listen-pos-race.pl   | 91 +++++++++++++++++++
 3 files changed, 97 insertions(+)
 create mode 100644 src/test/authentication/t/008_listen-pos-race.pl

diff --git a/src/backend/commands/async.c b/src/backend/commands/async.c
index 4e6556fb8d1..e4e65b02e98 100644
--- a/src/backend/commands/async.c
+++ b/src/backend/commands/async.c
@@ -167,6 +167,7 @@
 #include "utils/ps_status.h"
 #include "utils/snapmgr.h"
 #include "utils/timestamp.h"
+#include "utils/injection_point.h"
 
 
 /*
@@ -1954,6 +1955,8 @@ SignalBackends(void)
 	int			count;
 	ListCell   *lc;
 
+	INJECTION_POINT("listen-notify-signal-backends", NULL);
+
 	/*
 	 * Attach to the channel hash if needed.  We might not have one if this
 	 * backend hasn't done LISTEN, but we need it to find listeners.
@@ -2321,6 +2324,8 @@ asyncQueueReadAllNotifications(void)
 	head = QUEUE_HEAD;
 	LWLockRelease(NotifyQueueLock);
 
+	INJECTION_POINT("listen-notify-local-pos", NULL);
+
 	if (QUEUE_POS_EQUAL(pos, head))
 	{
 		/* Nothing to do, we have read all notifications already. */
diff --git a/src/test/authentication/meson.build b/src/test/authentication/meson.build
index 800b3a5ff40..c33f0065b1d 100644
--- a/src/test/authentication/meson.build
+++ b/src/test/authentication/meson.build
@@ -16,6 +16,7 @@ tests += {
       't/005_sspi.pl',
       't/006_login_trigger.pl',
       't/007_pre_auth.pl',
+      't/008_listen-pos-race.pl',
     ],
   },
 }
diff --git a/src/test/authentication/t/008_listen-pos-race.pl b/src/test/authentication/t/008_listen-pos-race.pl
new file mode 100644
index 00000000000..09944407e4f
--- /dev/null
+++ b/src/test/authentication/t/008_listen-pos-race.pl
@@ -0,0 +1,91 @@
+# Copyright (c) 2021-2025, PostgreSQL Global Development Group
+
+use strict;
+use warnings FATAL => 'all';
+
+use PostgreSQL::Test::Cluster;
+use PostgreSQL::Test::Utils;
+use Time::HiRes qw(usleep);
+use Test::More;
+
+if ($ENV{enable_injection_points} ne 'yes') {
+    plan skip_all => 'Injection points not supported by this build';
+}
+
+my $node = PostgreSQL::Test::Cluster->new("test");
+$node->init;
+$node->start;
+
+
+if (!$node->check_extension('injection_points')) {
+    plan skip_all => 'Extension injection_points not installed';
+}
+
+$node->safe_psql('postgres', 'CREATE EXTENSION injection_points');
+
+my $listener = $node->background_psql('postgres');
+my $listener_with_invalid_pos = $node->background_psql('postgres');
+my $notifying_psql = $node->background_psql('postgres');
+
+# setup injection points
+$node->safe_psql('postgres', "SELECT injection_points_attach('listen-notify-signal-backends', 'wait');");
+
+$listener_with_invalid_pos->query_safe(
+    qq[
+     SELECT injection_points_set_local();
+     SELECT injection_points_attach('listen-notify-local-pos', 'wait');
+ ]);
+
+# listener starts listening to channel ch, and starts a transaction,
+# while listener is within an active transaction, its pos will be 0,
+# and therefore all new listeners will have to start reading from 0 position too because of it.
+$listener->query_safe("LISTEN ch;");
+$listener->query_safe("BEGIN;");
+
+# create a lot of notifications and start waiting
+# on listen-notify-signal-backends (before direct advancement)
+$notifying_psql->query_until(
+    qr/start/, q(
+   \echo start
+   BEGIN;
+   select pg_notify('ch', repeat('a',3000) || x::text) from generate_series(1,100) as x;
+   COMMIT;
+
+));
+# Wait until notifying_psql enters the wait injection point.
+$node->wait_for_event('client backend',	'listen-notify-signal-backends');
+
+# listener_with_invalid_pos executes LISTEN command and starts
+# waiting on the injection point with pos = 0 in local variable
+$listener_with_invalid_pos->query_until(
+    qr/start/, q(
+   \echo start
+   LISTEN ch2;
+));
+# Wait until listener_with_invalid_pos enters the wait injection point.
+$node->wait_for_event('client backend',	'listen-notify-local-pos');
+
+# wake up notifying backend. direct advancement should be applied now to listener_with_invalid_pos
+# listener_with_invalid_pos is still waiting on injection point with local pos = 0
+$node->safe_psql('postgres', "SELECT injection_points_wakeup('listen-notify-signal-backends');");
+
+#sleep just to be sure that direct advancement was applied to listener_with_invalid_pos
+sleep 1;
+
+# let listener to advance its position to unblock queue truncating
+$listener->query_safe("COMMIT");
+
+# truncate the queue
+$node->safe_psql('postgres', "select pg_notification_queue_usage();");
+
+
+# wake up listener_with_invalid_pos with local copy of pos = 0. queue has been truncated already.
+# test should fail after it. 008_listen-pos-race_test.log contains error details
+$node->safe_psql('postgres',"SELECT injection_points_wakeup('listen-notify-local-pos');");
+
+
+$listener->quit();
+$listener_with_invalid_pos->quit();
+$notifying_psql->quit();
+
+done_testing();
-- 
2.43.0