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 dc69e5ce5f32cdedb8e18c720c579f20e929997f..61902be3b0ed68aa086375d570404bcfd26a8dd7 100644 (file)
--- a/src/backend/replication/logical/logical.c
+++ b/src/backend/replication/logical/logical.c
@@ -972,6 +972,7 @@ 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,
@@ -979,18 +980,25 @@ 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)