Fix logic bug in 1632ea43682f

I overlooked that one condition was logically inverted.  The fix is a
little bit more involved than simply negating the condition, to make
the code easier to read.

Fix some outdated comments left by the same commit, while at it.

Author: Masahiko Sawada <sawada.mshk@gmail.com>
Author: Álvaro Herrera <alvherre@alvh.no-ip.org>
Reviewed-by: Amit Kapila <amit.kapila16@gmail.com>
Discussion: https://postgr.es/m/YMRlmB3/lZw8YBH+@paquier.xyz

diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c
index a9a06b9a38a97d2bc02bc407a9f053716b29cb1c..8c18b4ed05b5669793e492eeb25c5c1caabe711f 100644 (file)
--- a/src/backend/replication/slot.c
+++ b/src/backend/replication/slot.c
@@ -410,9 +410,9 @@ retry:
    if (IsUnderPostmaster)
    {
        /*
-        * Get ready to sleep on the slot in case it is active if SAB_Block.
-        * (We may end up not sleeping, but we don't want to do this while
-        * holding the spinlock.)
+        * Get ready to sleep on the slot in case it is active.  (We may end
+        * up not sleeping, but we don't want to do this while holding the
+        * spinlock.)
         */
        if (!nowait)
            ConditionVariablePrepareToSleep(&s->active_cv);
@@ -429,22 +429,24 @@ retry:
 
    /*
     * If we found the slot but it's already active in another process, we
-    * either error out, return the PID of the owning process, or retry after
-    * a short wait, as caller specified.
+    * wait until the owning process signals us that it's been released, or
+    * error out.
     */
    if (active_pid != MyProcPid)
    {
        if (!nowait)
-           ereport(ERROR,
-                   (errcode(ERRCODE_OBJECT_IN_USE),
-                    errmsg("replication slot \"%s\" is active for PID %d",
-                           NameStr(s->data.name), active_pid)));
+       {
+           /* Wait here until we get signaled, and then restart */
+           ConditionVariableSleep(&s->active_cv,
+                                  WAIT_EVENT_REPLICATION_SLOT_DROP);
+           ConditionVariableCancelSleep();
+           goto retry;
+       }
 
-       /* Wait here until we get signaled, and then restart */
-       ConditionVariableSleep(&s->active_cv,
-                              WAIT_EVENT_REPLICATION_SLOT_DROP);
-       ConditionVariableCancelSleep();
-       goto retry;
+       ereport(ERROR,
+               (errcode(ERRCODE_OBJECT_IN_USE),
+                errmsg("replication slot \"%s\" is active for PID %d",
+                       NameStr(s->data.name), active_pid)));
    }
    else if (!nowait)
        ConditionVariableCancelSleep(); /* no sleep needed after all */