Fix oversight from 9e149c8 with spin-lock handling

Calling an external function while a pin-lock is held is a bad idea as
those are designed to be short-lived.  The stress of a first commit into
a large git history may contribute to that.

Reported-by: Andres Freund
Discussion: https://postgr.es/m/20180611164952.vmxdpdpirdtkdsz6@alap3.anarazel.de

diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c
index 79d7a57d677fba75aba913688659148215c44dee..e8b76b2f207c1bb7abb22eea028c1a740a85d9e7 100644 (file)
--- a/src/backend/replication/slot.c
+++ b/src/backend/replication/slot.c
@@ -999,6 +999,7 @@ ReplicationSlotReserveWal(void)
        while (true)
        {
                XLogSegNo       segno;
+               XLogRecPtr      restart_lsn;
 
                /*
                 * For logical slots log a standby snapshot and start logical decoding
@@ -1016,8 +1017,9 @@ ReplicationSlotReserveWal(void)
                        XLogRecPtr      flushptr;
 
                        /* start at current insert position */
+                       restart_lsn = GetXLogInsertRecPtr();
                        SpinLockAcquire(&slot->mutex);
-                       slot->data.restart_lsn = GetXLogInsertRecPtr();
+                       slot->data.restart_lsn = restart_lsn;
                        SpinLockRelease(&slot->mutex);
 
                        /* make sure we have enough information to start */
@@ -1028,8 +1030,9 @@ ReplicationSlotReserveWal(void)
                }
                else
                {
+                       restart_lsn = GetRedoRecPtr();
                        SpinLockAcquire(&slot->mutex);
-                       slot->data.restart_lsn = GetRedoRecPtr();
+                       slot->data.restart_lsn = restart_lsn;
                        SpinLockRelease(&slot->mutex);
                }