Disable GDD scan for dispatch tests

Dispatch tests don't expect backends created by other tests or auxiliary
processes like FTS and GDD, this commit disables GDD too to make dispatch
tests stable.

src/backend/utils/gdd/gddbackend.c

@@ -361,8 +361,6 @@ GlobalDeadLockDetectorLoop(void)
 
 	for (;;)
 	{
-		pg_usleep(gp_global_deadlock_detector_period * 1000000L);
-
 		CHECK_FOR_INTERRUPTS();
 
 		if (shutdown_requested)
@@ -389,6 +387,10 @@ GlobalDeadLockDetectorLoop(void)
 			CommitTransactionCommand();
 		else
 			AbortCurrentTransaction();
+
+		/* GUC gp_global_deadlock_detector_period may be changed, skip sleep */
+		if (!got_SIGHUP)
+			pg_usleep(gp_global_deadlock_detector_period * 1000000L);
 	}
 
 	return;

src/test/regress/input/dispatch.source

@@ -15,6 +15,15 @@ select gp_inject_fault_infinite('fts_probe', 'skip', 1);
 select gp_request_fts_probe_scan();
 select gp_wait_until_triggered_fault('fts_probe', 1, 1);
 
+-- skip GDD scan always
+select gp_inject_fault_infinite('gdd_probe', 'skip', 1);
+-- acting like gp_request_fts_probe_scan() to wake up GDD backend so
+-- 'gdd_probe' can be triggered as soon as possible
+-- start_ignore
+\! gpstop -u
+-- end_ignore
+select gp_wait_until_triggered_fault('gdd_probe', 1, 1);
+
 -- Test quoting of GUC values and database names when they're sent to segments
 set client_min_messages='warning';
 DROP DATABASE IF EXISTS "funny""db'with\\quotes";
@@ -368,3 +377,5 @@ end;
 
 -- resume FTS probes
 select gp_inject_fault('fts_probe', 'reset', 1);
+-- resume GDD scan 
+select gp_inject_fault('gdd_probe', 'reset', 1);

src/test/regress/output/dispatch.source

@@ -28,6 +28,26 @@ NOTICE:  Success:
  t
 (1 row)
 
+-- skip GDD scan always
+select gp_inject_fault_infinite('gdd_probe', 'skip', 1);
+NOTICE:  Success:
+ gp_inject_fault_infinite 
+--------------------------
+ t
+(1 row)
+
+-- acting like gp_request_fts_probe_scan() to wake up GDD backend so
+-- 'gdd_probe' can be triggered as soon as possible
+-- start_ignore
+\! gpstop -u
+-- end_ignore
+select gp_wait_until_triggered_fault('gdd_probe', 1, 1);
+NOTICE:  Success:
+ gp_wait_until_triggered_fault 
+-------------------------------
+ t
+(1 row)
+
 -- Test quoting of GUC values and database names when they're sent to segments
 set client_min_messages='warning';
 DROP DATABASE IF EXISTS "funny""db'with\\quotes";
@@ -676,3 +696,11 @@ NOTICE:  Success:
  t
 (1 row)
 
+-- resume GDD scan 
+select gp_inject_fault('gdd_probe', 'reset', 1);
+NOTICE:  Success:
+ gp_inject_fault 
+-----------------
+ t
+(1 row)
+