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Fix some outdated comments left by the same commit, while at it.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