From 74751b6a3a049ff83c6bef99e2e39562278a7ba6 Mon Sep 17 00:00:00 2001
From: Alvaro Herrera <alvherre@alvh.no-ip.org>
Date: Mon, 27 Apr 2020 19:35:15 -0400
Subject: [PATCH] Fix checkpoint signalling

Because the checkpointer process now uses its MyLatch to wait for
walsenders to go away (per commit c6550776394e), we must ensure to nudge
it when going to sleep.
---
 src/backend/postmaster/checkpointer.c     |  8 +++++
 src/test/recovery/t/019_replslot_limit.pl | 44 +++++++++++++++++++++--
 2 files changed, 50 insertions(+), 2 deletions(-)

diff --git a/src/backend/postmaster/checkpointer.c b/src/backend/postmaster/checkpointer.c
index e354a78725..94e0161162 100644
--- a/src/backend/postmaster/checkpointer.c
+++ b/src/backend/postmaster/checkpointer.c
@@ -494,6 +494,14 @@ CheckpointerMain(void)
 		 */
 		pgstat_send_bgwriter();
 
+		/*
+		 * If any checkpoint flags have been set, nudge our latch so that the
+		 * wait below will return immediately, even if a latch signal was
+		 * consumed elsewhere.
+		 */
+		if (((volatile CheckpointerShmemStruct *) CheckpointerShmem)->ckpt_flags)
+			SetLatch(MyLatch);
+
 		/*
 		 * Sleep until we are signaled or it's time for another checkpoint or
 		 * xlog file switch.
diff --git a/src/test/recovery/t/019_replslot_limit.pl b/src/test/recovery/t/019_replslot_limit.pl
index 32dce54522..634f2bec8b 100644
--- a/src/test/recovery/t/019_replslot_limit.pl
+++ b/src/test/recovery/t/019_replslot_limit.pl
@@ -8,7 +8,7 @@ use TestLib;
 use PostgresNode;
 
 use File::Path qw(rmtree);
-use Test::More tests => 13;
+use Test::More tests => 14;
 use Time::HiRes qw(usleep);
 
 $ENV{PGDATABASE} = 'postgres';
@@ -179,7 +179,47 @@ for (my $i = 0; $i < 10000; $i++)
 }
 ok($failed, 'check that replication has been broken');
 
-$node_standby->stop;
+$node_master->stop('immediate');
+$node_standby->stop('immediate');
+
+my $node_master2 = get_new_node('master2');
+$node_master2->init(allows_streaming => 1);
+$node_master2->append_conf(
+	'postgresql.conf', qq(
+min_wal_size = 32MB
+max_wal_size = 32MB
+log_checkpoints = yes
+));
+$node_master2->start;
+$node_master2->safe_psql('postgres',
+	"SELECT pg_create_physical_replication_slot('rep1')");
+$backup_name = 'my_backup2';
+$node_master2->backup($backup_name);
+
+$node_master2->stop;
+$node_master2->append_conf(
+	'postgresql.conf', qq(
+max_slot_wal_keep_size = 0
+));
+$node_master2->start;
+
+$node_standby = get_new_node('standby_2');
+$node_standby->init_from_backup($node_master2, $backup_name,
+	has_streaming => 1);
+$node_standby->append_conf('postgresql.conf', "primary_slot_name = 'rep1'");
+$node_standby->start;
+my @result =
+  split(
+	'\n',
+	$node_master2->safe_psql(
+		'postgres',
+		"CREATE TABLE tt();
+		 DROP TABLE tt;
+		 SELECT pg_switch_wal();
+		 CHECKPOINT;
+		 SELECT 'finished';",
+		timeout => '60'));
+is($result[1], 'finished', 'check if checkpoint command is not blocked');
 
 #####################################
 # Advance WAL of $node by $n segments
-- 
2.20.1