bugfix_pg_stat_wal_receiver_v2.patch

diff --git a/src/backend/replication/walreceiver.c b/src/backend/replication/walreceiver.c
index 723f513d8b..316640c275 100644
--- a/src/backend/replication/walreceiver.c
+++ b/src/backend/replication/walreceiver.c
@@ -249,7 +249,7 @@ WalReceiverMain(void)
 
 	SpinLockRelease(&walrcv->mutex);
 
-	pg_atomic_init_u64(&WalRcv->writtenUpto, 0);
+	pg_atomic_write_u64(&WalRcv->writtenUpto, 0);
 
 	/* Arrange to clean up at walreceiver exit */
 	on_shmem_exit(WalRcvDie, 0);
@@ -1325,7 +1325,6 @@ pg_stat_get_wal_receiver(PG_FUNCTION_ARGS)
 	state = WalRcv->walRcvState;
 	receive_start_lsn = WalRcv->receiveStart;
 	receive_start_tli = WalRcv->receiveStartTLI;
-	written_lsn = pg_atomic_read_u64(&WalRcv->writtenUpto);
 	flushed_lsn = WalRcv->flushedUpto;
 	received_tli = WalRcv->receivedTLI;
 	last_send_time = WalRcv->lastMsgSendTime;
@@ -1338,6 +1337,14 @@ pg_stat_get_wal_receiver(PG_FUNCTION_ARGS)
 	strlcpy(conninfo, (char *) WalRcv->conninfo, sizeof(conninfo));
 	SpinLockRelease(&WalRcv->mutex);
 
+	/*
+	 * Read "writtenUpto" without holding a spinlock. So it may not be
+	 * consistent with other WAL receiver's shared variables protected by a
+	 * spinlock. This is OK because that variable is used only for
+	 * informational purpose and should not be used for data integrity checks.
+	 */
+	written_lsn = pg_atomic_read_u64(&WalRcv->writtenUpto);
+
 	/*
 	 * No WAL receiver (or not ready yet), just return a tuple with NULL
 	 * values
diff --git a/src/backend/replication/walreceiverfuncs.c b/src/backend/replication/walreceiverfuncs.c
index 69b91a7dab..63e60478ea 100644
--- a/src/backend/replication/walreceiverfuncs.c
+++ b/src/backend/replication/walreceiverfuncs.c
@@ -63,6 +63,7 @@ WalRcvShmemInit(void)
 		MemSet(WalRcv, 0, WalRcvShmemSize());
 		WalRcv->walRcvState = WALRCV_STOPPED;
 		SpinLockInit(&WalRcv->mutex);
+		pg_atomic_init_u64(&WalRcv->writtenUpto, 0);
 		WalRcv->latch = NULL;
 	}
 }
diff --git a/src/test/regress/expected/sysviews.out b/src/test/regress/expected/sysviews.out
index 81bdacf59d..6d048e309c 100644
--- a/src/test/regress/expected/sysviews.out
+++ b/src/test/regress/expected/sysviews.out
@@ -83,6 +83,13 @@ select count(*) = 1 as ok from pg_stat_wal;
  t
 (1 row)
 
+-- We expect no walreceiver running in this test
+select count(*) = 0 as ok from pg_stat_wal_receiver;
+ ok 
+----
+ t
+(1 row)
+
 -- This is to record the prevailing planner enable_foo settings during
 -- a regression test run.
 select name, setting from pg_settings where name like 'enable%';
diff --git a/src/test/regress/sql/sysviews.sql b/src/test/regress/sql/sysviews.sql
index b9b875bc6a..dc8c9a3ac2 100644
--- a/src/test/regress/sql/sysviews.sql
+++ b/src/test/regress/sql/sysviews.sql
@@ -40,6 +40,9 @@ select count(*) >= 0 as ok from pg_prepared_xacts;
 -- There must be only one record
 select count(*) = 1 as ok from pg_stat_wal;
 
+-- We expect no walreceiver running in this test
+select count(*) = 0 as ok from pg_stat_wal_receiver;
+
 -- This is to record the prevailing planner enable_foo settings during
 -- a regression test run.
 select name, setting from pg_settings where name like 'enable%';