pulse-server: work around race condition in SET_DEFAULT/MOVE_*

The default metadata update may be delayed for some time after
SET_DEFAULT, since the session manager has to work on it.

MOVE_* commands need to know what the client thinks is the current
default sink, so that they can decide between "move to default" and
"move to specific device".

To avoid race condition here, stash the default value set by the client
and use it in the MOVE_* commands, until the metadata update arrives.

src/modules/module-protocol-pulse/client.c

@@ -177,6 +177,9 @@ void client_free(struct client *client)
 	free(client->default_sink);
 	free(client->default_source);
 
+	free(client->temporary_default_sink);
+	free(client->temporary_default_source);
+
 	pw_properties_free(client->props);
 	pw_properties_free(client->routes);
 

src/modules/module-protocol-pulse/client.h

@@ -75,6 +75,8 @@ struct client {
 	struct pw_manager_object *metadata_default;
 	char *default_sink;
 	char *default_source;
+	char *temporary_default_sink;		/**< pending value, for MOVE_* commands */
+	char *temporary_default_source;		/**< pending value, for MOVE_* commands */
 	struct pw_manager_object *metadata_routes;
 	struct pw_properties *routes;
 

src/modules/module-protocol-pulse/pulse-server.c

@@ -961,6 +961,8 @@ static void manager_metadata(void *data, struct pw_manager_object *o,
 				free(client->default_sink);
 				client->default_sink = value ? strdup(value) : NULL;
 			}
+			free(client->temporary_default_sink);
+			client->temporary_default_sink = NULL;
 		}
 		if (key == NULL || spa_streq(key, "default.audio.source")) {
 			if (value != NULL) {
@@ -974,6 +976,8 @@ static void manager_metadata(void *data, struct pw_manager_object *o,
 				free(client->default_source);
 				client->default_source = value ? strdup(value) : NULL;
 			}
+			free(client->temporary_default_source);
+			client->temporary_default_source = NULL;
 		}
 		if (changed)
 			send_default_change_subscribe_event(client, true, true);
@@ -4751,6 +4755,20 @@ static int do_set_default(struct client *client, uint32_t command, uint32_t tag,
 	if (res < 0)
 		return res;
 
+	/*
+	 * The metadata is not necessarily updated within one server sync.
+	 * Correct functioning of MOVE_* commands requires knowing the current
+	 * default target, so we need to stash temporary values here in case
+	 * the client emits them before metadata gets updated.
+	 */
+	if (sink) {
+		free(client->temporary_default_sink);
+		client->temporary_default_sink = name ? strdup(name) : NULL;
+	} else {
+		free(client->temporary_default_source);
+		client->temporary_default_source = name ? strdup(name) : NULL;
+	}
+
 	return operation_new(client, tag);
 }
 
@@ -4792,6 +4810,7 @@ static int do_move_stream(struct client *client, uint32_t command, uint32_t tag,
 	int target_id;
 	int64_t target_serial;
 	const char *name_device;
+	const char *name;
 	struct pw_node_info *info;
 	struct selector sel;
 	int res;
@@ -4828,7 +4847,13 @@ static int do_move_stream(struct client *client, uint32_t command, uint32_t tag,
 	if ((dev = find_device(client, index_device, name_device, sink, NULL)) == NULL)
 		return -ENOENT;
 
-	dev_default = find_device(client, SPA_ID_INVALID, NULL, sink, NULL);
+	/*
+	 * The client metadata is not necessarily yet updated after SET_DEFAULT command,
+	 * so use the temporary values if they are still set.
+	 */
+	name = sink ? client->temporary_default_sink : client->temporary_default_source;
+	dev_default = find_device(client, SPA_ID_INVALID, name, sink, NULL);
+
 	if (dev == dev_default) {
 		/*
 		 * When moving streams to a node that is equal to the default,
@@ -4854,6 +4879,11 @@ static int do_move_stream(struct client *client, uint32_t command, uint32_t tag,
 			SPA_TYPE_INFO_BASE"Id", "%"PRIi64, target_serial)) < 0)
 		return res;
 
+	name = spa_dict_lookup(info->props, PW_KEY_NODE_NAME);
+	pw_log_debug("[%s] %s done tag:%u index:%u name:%s target:%d target-serial:%"PRIi64, client->name,
+			commands[command].name, tag, index, name ? name : "<null>",
+			target_id, target_serial);
+
 	/* We will temporarily claim the stream was already moved */
 	set_temporary_move_target(client, o, dev->index);
 	send_object_event(client, o, SUBSCRIPTION_EVENT_CHANGE);