Fix instance of elog() called while holding a spinlock

This broke the project rule to not call any complex code while a
spinlock is held.  Issue introduced by b89e151.

Discussion: https://postgr.es/m/20200602.161518.1399689010416646074.horikyota.ntt@gmail.com
Backpatch-through: 9.5

diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c
index 77a73bd3d1ee87f57d257920df490a068d56e3e7..0b005dcfe35c68ecc0d151f0b11ce70ce15a43ab 100644 (file)
--- a/src/backend/replication/logical/logical.c
+++ b/src/backend/replication/logical/logical.c
@@ -870,6 +870,7 @@ LogicalIncreaseRestartDecodingForSlot(XLogRecPtr current_lsn, XLogRecPtr restart
    {
        slot->candidate_restart_valid = current_lsn;
        slot->candidate_restart_lsn = restart_lsn;
+       SpinLockRelease(&slot->mutex);
 
        elog(DEBUG1, "got new restart lsn %X/%X at %X/%X",
             (uint32) (restart_lsn >> 32), (uint32) restart_lsn,
@@ -877,18 +878,25 @@ LogicalIncreaseRestartDecodingForSlot(XLogRecPtr current_lsn, XLogRecPtr restart
    }
    else
    {
+       XLogRecPtr  candidate_restart_lsn;
+       XLogRecPtr  candidate_restart_valid;
+       XLogRecPtr  confirmed_flush;
+
+       candidate_restart_lsn = slot->candidate_restart_lsn;
+       candidate_restart_valid = slot->candidate_restart_valid;
+       confirmed_flush = slot->data.confirmed_flush;
+       SpinLockRelease(&slot->mutex);
+
        elog(DEBUG1, "failed to increase restart lsn: proposed %X/%X, after %X/%X, current candidate %X/%X, current after %X/%X, flushed up to %X/%X",
             (uint32) (restart_lsn >> 32), (uint32) restart_lsn,
             (uint32) (current_lsn >> 32), (uint32) current_lsn,
-            (uint32) (slot->candidate_restart_lsn >> 32),
-            (uint32) slot->candidate_restart_lsn,
-            (uint32) (slot->candidate_restart_valid >> 32),
-            (uint32) slot->candidate_restart_valid,
-            (uint32) (slot->data.confirmed_flush >> 32),
-            (uint32) slot->data.confirmed_flush
-           );
+            (uint32) (candidate_restart_lsn >> 32),
+            (uint32) candidate_restart_lsn,
+            (uint32) (candidate_restart_valid >> 32),
+            (uint32) candidate_restart_valid,
+            (uint32) (confirmed_flush >> 32),
+            (uint32) confirmed_flush);
    }
-   SpinLockRelease(&slot->mutex);
 
    /* candidates are already valid with the current flush position, apply */
    if (updated_lsn)