Few minor thread synchronization tweaks. (issue #10124 reported by gzero)

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.4@74045 65c4cc65-6c06-0410-ace0-fbb531ad65f3

channels/chan_skinny.c

@@ -4778,7 +4778,7 @@ static int unload_module(void)
 	delete_devices();
 
 	ast_mutex_lock(&monlock);
-	if (monitor_thread && (monitor_thread != AST_PTHREADT_STOP)) {
+	if ((monitor_thread != AST_PTHREADT_NULL) && (monitor_thread != AST_PTHREADT_STOP)) {
 		pthread_cancel(monitor_thread);
 		pthread_kill(monitor_thread, SIGURG);
 		pthread_join(monitor_thread, NULL);

pbx/pbx_dundi.c

@@ -2093,6 +2093,9 @@ static void *network_thread(void *ignore)
 		}
 		check_password();
 	}
+
+	netthreadid = AST_PTHREADT_NULL;
+	
 	return NULL;
 }
 
@@ -2128,6 +2131,8 @@ static void *process_precache(void *ign)
 			sleep(1);
 	}
 
+	precachethreadid = AST_PTHREADT_NULL;
+
 	return NULL;
 }
 
@@ -4467,10 +4472,14 @@ static int unload_module(void)
 
 	/* Stop all currently running threads */
 	dundi_shutdown = 1;
-	pthread_kill(netthreadid, SIGURG);
-	pthread_join(netthreadid, NULL);
-	pthread_kill(precachethreadid, SIGURG);
-	pthread_join(precachethreadid, NULL);
+	if (netthreadid != AST_PTHREADT_NULL) {
+		pthread_kill(netthreadid, SIGURG);
+		pthread_join(netthreadid, NULL);
+	}
+	if (precachethreadid != AST_PTHREADT_NULL) {
+		pthread_kill(precachethreadid, SIGURG);
+		pthread_join(precachethreadid, NULL);
+	}
 
 	ast_cli_unregister_multiple(cli_dundi, sizeof(cli_dundi) / sizeof(struct ast_cli_entry));
 	ast_unregister_switch(&dundi_switch);