Treat the autovac launcher more like a regular backend, in that we wait

for it to die before telling the bgwriter to initiate shutdown checkpoint.
Since it's connected to shared memory, this seems more prudent than the
alternative of letting it quit asynchronously.  Resolves my complaint
of yesterday about repeated shutdown checkpoints in CVS HEAD.

src/backend/postmaster/postmaster.c

@@ -37,7 +37,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/postmaster/postmaster.c,v 1.529 2007/06/29 17:07:39 alvherre Exp $
+ *	  $PostgreSQL: pgsql/src/backend/postmaster/postmaster.c,v 1.530 2007/07/01 18:28:41 tgl Exp $
  *
  * NOTES
  *
@@ -1242,7 +1242,8 @@ ServerLoop(void)
 		}
 
 		/* If we have lost the autovacuum launcher, try to start a new one */
-		if ((AutoVacuumingActive() || start_autovac_launcher) && AutoVacPID == 0 &&
+		if (AutoVacPID == 0 &&
+			(AutoVacuumingActive() || start_autovac_launcher) &&
 			StartupPID == 0 && !FatalError && Shutdown == NoShutdown)
 		{
 			AutoVacPID = StartAutoVacLauncher();
@@ -1873,11 +1874,14 @@ pmdie(SIGNAL_ARGS)
 			ereport(LOG,
 					(errmsg("received smart shutdown request")));
 
-			/* autovacuum workers are shut down immediately */
+			/* autovacuum workers are told to shut down immediately */
 			if (DLGetHead(BackendList))
 				SignalSomeChildren(SIGTERM, true);
+			/* and the autovac launcher too */
+			if (AutoVacPID != 0)
+				signal_child(AutoVacPID, SIGTERM);
 
-			if (DLGetHead(BackendList))
+			if (DLGetHead(BackendList) || AutoVacPID != 0)
 				break;			/* let reaper() handle this */
 
 			/*
@@ -1896,13 +1900,7 @@ pmdie(SIGNAL_ARGS)
 				signal_child(PgArchPID, SIGQUIT);
 			/* Tell pgstat to shut down too; nothing left for it to do */
 			if (PgStatPID != 0)
-			{
 				signal_child(PgStatPID, SIGQUIT);
-				allow_immediate_pgstat_restart();
-			}
-			/* Tell autovac launcher to shut down too */
-			if (AutoVacPID != 0)
-				signal_child(AutoVacPID, SIGTERM);
 			break;
 
 		case SIGINT:
@@ -1919,13 +1917,15 @@ pmdie(SIGNAL_ARGS)
 			ereport(LOG,
 					(errmsg("received fast shutdown request")));
 
-			if (DLGetHead(BackendList))
+			if (DLGetHead(BackendList) || AutoVacPID != 0)
 			{
 				if (!FatalError)
 				{
 					ereport(LOG,
 							(errmsg("aborting any active transactions")));
 					SignalChildren(SIGTERM);
+					if (AutoVacPID != 0)
+						signal_child(AutoVacPID, SIGTERM);
 					/* reaper() does the rest */
 				}
 				break;
@@ -1955,13 +1955,7 @@ pmdie(SIGNAL_ARGS)
 				signal_child(PgArchPID, SIGQUIT);
 			/* Tell pgstat to shut down too; nothing left for it to do */
 			if (PgStatPID != 0)
-			{
 				signal_child(PgStatPID, SIGQUIT);
-				allow_immediate_pgstat_restart();
-			}
-			/* Tell autovac launcher to shut down too */
-			if (AutoVacPID != 0)
-				signal_child(AutoVacPID, SIGTERM);
 			break;
 
 		case SIGQUIT:
@@ -1983,10 +1977,7 @@ pmdie(SIGNAL_ARGS)
 			if (PgArchPID != 0)
 				signal_child(PgArchPID, SIGQUIT);
 			if (PgStatPID != 0)
-			{
 				signal_child(PgStatPID, SIGQUIT);
-				allow_immediate_pgstat_restart();
-			}
 			if (DLGetHead(BackendList))
 				SignalChildren(SIGQUIT);
 			ExitPostmaster(0);
@@ -2237,7 +2228,7 @@ reaper(SIGNAL_ARGS)
 
 	if (Shutdown > NoShutdown)
 	{
-		if (DLGetHead(BackendList) || StartupPID != 0)
+		if (DLGetHead(BackendList) || StartupPID != 0 || AutoVacPID != 0)
 			goto reaper_done;
 		/* Start the bgwriter if not running */
 		if (BgWriterPID == 0)
@@ -2250,13 +2241,7 @@ reaper(SIGNAL_ARGS)
 			signal_child(PgArchPID, SIGQUIT);
 		/* Tell pgstat to shut down too; nothing left for it to do */
 		if (PgStatPID != 0)
-		{
 			signal_child(PgStatPID, SIGQUIT);
-			allow_immediate_pgstat_restart();
-		}
-		/* Tell autovac launcher to shut down too */
-		if (AutoVacPID != 0)
-			signal_child(AutoVacPID, SIGTERM);
 	}
 
 reaper_done: