2 files changed, 32 insertions, 89 deletions
diff --git a/src/test/modules/test_slru/t/001_multixact.pl b/src/test/modules/test_slru/t/001_multixact.pl
index e2b567a603d..7837eb810f0 100644
--- a/src/test/modules/test_slru/t/001_multixact.pl
+++ b/src/test/modules/test_slru/t/001_multixact.pl
@@ -1,10 +1,6 @@
 # Copyright (c) 2024-2025, PostgreSQL Global Development Group
 
-# This test verifies edge case of reading a multixact:
-# when we have multixact that is followed by exactly one another multixact,
-# and another multixact have no offset yet, we must wait until this offset
-# becomes observable. Previously we used to wait for 1ms in a loop in this
-# case, but now we use CV for this. This test is exercising such a sleep.
+# Test multixid corner cases.
 
 use strict;
 use warnings FATAL => 'all';
@@ -19,9 +15,7 @@ if ($ENV{enable_injection_points} ne 'yes')
 	plan skip_all => 'Injection points not supported by this build';
 }
 
-my ($node, $result);
-
-$node = PostgreSQL::Test::Cluster->new('mike');
+my $node = PostgreSQL::Test::Cluster->new('main');
 $node->init;
 $node->append_conf('postgresql.conf',
 	"shared_preload_libraries = 'test_slru,injection_points'");
@@ -29,95 +23,47 @@ $node->start;
 $node->safe_psql('postgres', q(CREATE EXTENSION injection_points));
 $node->safe_psql('postgres', q(CREATE EXTENSION test_slru));
 
-# Test for Multixact generation edge case
-$node->safe_psql('postgres',
-	q{select injection_points_attach('test-multixact-read','wait')});
-$node->safe_psql('postgres',
-	q{select injection_points_attach('multixact-get-members-cv-sleep','wait')}
-);
+# This test creates three multixacts. The middle one is never
+# WAL-logged or recorded on the offsets page, because we pause the
+# backend and crash the server before that. After restart, verify that
+# the other multixacts are readable, despite the middle one being
+# lost.
 
-# This session must observe sleep on the condition variable while generating a
-# multixact.  To achieve this it first will create a multixact, then pause
-# before reading it.
-my $observer = $node->background_psql('postgres');
-
-# This query will create a multixact, and hang just before reading it.
-$observer->query_until(
-	qr/start/,
-	q{
-	\echo start
-	SELECT test_read_multixact(test_create_multixact());
-});
-$node->wait_for_event('client backend', 'test-multixact-read');
-
-# This session will create the next Multixact. This is necessary to avoid
-# multixact.c's non-sleeping edge case 1.
-my $creator = $node->background_psql('postgres');
+# Create the first multixact
+my $bg_psql = $node->background_psql('postgres');
+my $multi1 = $bg_psql->query_safe(q(SELECT test_create_multixact();));
+
+# Assign the middle multixact. Use an injection point to prevent it
+# from being fully recorded.
 $node->safe_psql('postgres',
 	q{SELECT injection_points_attach('multixact-create-from-members','wait');}
 );
 
-# We expect this query to hang in the critical section after generating new
-# multixact, but before filling its offset into SLRU.
-# Running an injection point inside a critical section requires it to be
-# loaded beforehand.
-$creator->query_until(
-	qr/start/, q{
-	\echo start
+$bg_psql->query_until(
+	qr/assigning lost multi/, q(
+\echo assigning lost multi
 	SELECT test_create_multixact();
-});
+));
 
 $node->wait_for_event('client backend', 'multixact-create-from-members');
-
-# Ensure we have the backends waiting that we expect
-is( $node->safe_psql(
-		'postgres',
-		q{SELECT string_agg(wait_event, ', ' ORDER BY wait_event)
-		FROM pg_stat_activity WHERE wait_event_type = 'InjectionPoint'}
-	),
-	'multixact-create-from-members, test-multixact-read',
-	"matching injection point waits");
-
-# Now wake observer to get it to read the initial multixact.  A subsequent
-# multixact already exists, but that one doesn't have an offset assigned, so
-# this will hit multixact.c's edge case 2.
-$node->safe_psql('postgres',
-	q{SELECT injection_points_wakeup('test-multixact-read')});
-$node->wait_for_event('client backend', 'multixact-get-members-cv-sleep');
-
-# Ensure we have the backends waiting that we expect
-is( $node->safe_psql(
-		'postgres',
-		q{SELECT string_agg(wait_event, ', ' ORDER BY wait_event)
-		FROM pg_stat_activity WHERE wait_event_type = 'InjectionPoint'}
-	),
-	'multixact-create-from-members, multixact-get-members-cv-sleep',
-	"matching injection point waits");
-
-# Now we have two backends waiting in multixact-create-from-members and
-# multixact-get-members-cv-sleep.  Also we have 3 injections points set to wait.
-# If we wakeup multixact-get-members-cv-sleep it will happen again, so we must
-# detach it first. So let's detach all injection points, then wake up all
-# backends.
-
-$node->safe_psql('postgres',
-	q{SELECT injection_points_detach('test-multixact-read')});
 $node->safe_psql('postgres',
 	q{SELECT injection_points_detach('multixact-create-from-members')});
-$node->safe_psql('postgres',
-	q{SELECT injection_points_detach('multixact-get-members-cv-sleep')});
 
-$node->safe_psql('postgres',
-	q{SELECT injection_points_wakeup('multixact-create-from-members')});
-$node->safe_psql('postgres',
-	q{SELECT injection_points_wakeup('multixact-get-members-cv-sleep')});
+# Create the third multixid
+my $multi2 = $node->safe_psql('postgres', q{SELECT test_create_multixact();});
+
+# All set and done, it's time for hard restart
+$node->stop('immediate');
+$node->start;
+$bg_psql->{run}->finish;
 
-# Background psql will now be able to read the result and disconnect.
-$observer->quit;
-$creator->quit;
+# Verify that the recorded multixids are readable
+is( $node->safe_psql('postgres', qq{SELECT test_read_multixact('$multi1');}),
+	'',
+	'first recorded multi is readable');
 
-$node->stop;
+is( $node->safe_psql('postgres', qq{SELECT test_read_multixact('$multi2');}),
+	'',
+	'second recorded multi is readable');
 
-# If we reached this point - everything is OK.
-ok(1);
 done_testing();
diff --git a/src/test/modules/test_slru/test_multixact.c b/src/test/modules/test_slru/test_multixact.c
index 6c9b0420717..8fb6c19d70f 100644
--- a/src/test/modules/test_slru/test_multixact.c
+++ b/src/test/modules/test_slru/test_multixact.c
@@ -17,7 +17,6 @@
 #include "access/multixact.h"
 #include "access/xact.h"
 #include "fmgr.h"
-#include "utils/injection_point.h"
 
 PG_FUNCTION_INFO_V1(test_create_multixact);
 PG_FUNCTION_INFO_V1(test_read_multixact);
@@ -37,8 +36,7 @@ test_create_multixact(PG_FUNCTION_ARGS)
 }
 
 /*
- * Reads given multixact after running an injection point. Discards local cache
- * to make a real read.  Tailored for multixact testing.
+ * Reads given multixact.  Discards local cache to make a real read.
  */
 Datum
 test_read_multixact(PG_FUNCTION_ARGS)
@@ -46,7 +44,6 @@ test_read_multixact(PG_FUNCTION_ARGS)
 	MultiXactId id = PG_GETARG_TRANSACTIONID(0);
 	MultiXactMember *members;
 
-	INJECTION_POINT("test-multixact-read", NULL);
 	/* discard caches */
 	AtEOXact_MultiXact();