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gdbus: Track name owners for signal subscriptions
We will use this in a subsequent commit to prevent signals from an impostor from being delivered to a subscriber. To avoid message reordering leading to misleading situations, this does not use the existing mechanism for watching bus name ownership, which delivers the ownership changes to other main-contexts. Instead, it all happens on the single thread used by the GDBusWorker, so the order in which messages are received is the order in which they are processed. Signed-off-by: Simon McVittie <smcv@collabora.com>
This commit is contained in:
Simon McVittie
parent
0bca1891a7
commit
d6c2a2f12e
@ -324,6 +324,31 @@ signal_subscriber_unref (SignalSubscriber *subscriber)
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}
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typedef struct
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{
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/*
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* 1 reference while waiting for GetNameOwner() to finish
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* 1 reference for each SignalData that points to this one as its
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* shared_name_watcher
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*/
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grefcount ref_count;
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gchar *owner;
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guint32 get_name_owner_serial;
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} WatchedName;
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static WatchedName *
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watched_name_new (void)
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{
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WatchedName *watched_name = g_new0 (WatchedName, 1);
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g_ref_count_init (&watched_name->ref_count);
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watched_name->owner = NULL;
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return g_steal_pointer (&watched_name);
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}
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typedef struct SignalData SignalData;
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struct SignalData
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{
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gchar *rule;
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gchar *sender;
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@ -333,13 +358,36 @@ typedef struct
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gchar *arg0;
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GDBusSignalFlags flags;
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GPtrArray *subscribers; /* (owned) (element-type SignalSubscriber) */
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gboolean sender_is_its_own_owner;
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} SignalData;
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/*
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* If the sender is a well-known name, this is an unowned SignalData
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* representing the NameOwnerChanged signal that tracks its owner.
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* NULL if sender is NULL.
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* NULL if sender is its own owner (a unique name or DBUS_SERVICE_DBUS).
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*
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* Invariants: if not NULL, then
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* shared_name_watcher->sender == DBUS_SERVICE_DBUS
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* shared_name_watcher->interface_name == DBUS_INTERFACE_DBUS
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* shared_name_watcher->member == "NameOwnerChanged"
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* shared_name_watcher->object_path == DBUS_PATH_DBUS
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* shared_name_watcher->arg0 == sender
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* shared_name_watcher->flags == NONE
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* shared_name_watcher->watched_name == NULL
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*/
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SignalData *shared_name_watcher;
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/*
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* Non-NULL if this SignalData is another SignalData's shared_name_watcher.
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* One reference for each SignalData that has this one as its
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* shared_name_watcher.
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* Otherwise NULL.
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*/
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WatchedName *watched_name;
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};
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static SignalData *
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signal_data_new_take (gchar *rule,
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gchar *sender,
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gboolean sender_is_its_own_owner,
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gchar *interface_name,
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gchar *member,
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gchar *object_path,
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@ -350,7 +398,6 @@ signal_data_new_take (gchar *rule,
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signal_data->rule = rule;
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signal_data->sender = sender;
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signal_data->sender_is_its_own_owner = sender_is_its_own_owner;
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signal_data->interface_name = interface_name;
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signal_data->member = member;
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signal_data->object_path = object_path;
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@ -363,6 +410,17 @@ signal_data_new_take (gchar *rule,
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static void
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signal_data_free (SignalData *signal_data)
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{
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/* The SignalData should not be freed while it still has subscribers */
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g_assert (signal_data->subscribers->len == 0);
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/* The SignalData should not be freed while it is watching for
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* NameOwnerChanged on behalf of another SignalData */
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g_assert (signal_data->watched_name == NULL);
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/* The SignalData should be detached from its name watcher, if any,
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* before it is freed */
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g_assert (signal_data->shared_name_watcher == NULL);
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g_free (signal_data->rule);
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g_free (signal_data->sender);
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g_free (signal_data->interface_name);
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@ -370,6 +428,7 @@ signal_data_free (SignalData *signal_data)
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g_free (signal_data->object_path);
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g_free (signal_data->arg0);
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g_ptr_array_unref (signal_data->subscribers);
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g_free (signal_data);
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}
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@ -493,6 +552,7 @@ struct _GDBusConnection
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/* Map used for managing method replies, protected by @lock */
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GHashTable *map_method_serial_to_task; /* guint32 -> owned GTask* */
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GHashTable *map_method_serial_to_name_watcher; /* guint32 -> unowned SignalData* */
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/* Maps used for managing signal subscription, protected by @lock */
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GHashTable *map_rule_to_signal_data; /* match rule (gchar*) -> SignalData */
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@ -741,6 +801,7 @@ g_dbus_connection_finalize (GObject *object)
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g_error_free (connection->initialization_error);
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g_hash_table_unref (connection->map_method_serial_to_task);
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g_hash_table_unref (connection->map_method_serial_to_name_watcher);
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g_hash_table_unref (connection->map_rule_to_signal_data);
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g_hash_table_unref (connection->map_id_to_signal_data);
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@ -1127,6 +1188,7 @@ g_dbus_connection_init (GDBusConnection *connection)
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g_mutex_init (&connection->init_lock);
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connection->map_method_serial_to_task = g_hash_table_new_full (g_direct_hash, g_direct_equal, NULL, g_object_unref);
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connection->map_method_serial_to_name_watcher = g_hash_table_new_full (g_direct_hash, g_direct_equal, NULL, NULL);
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connection->map_rule_to_signal_data = g_hash_table_new (g_str_hash,
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g_str_equal);
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@ -2255,6 +2317,191 @@ g_dbus_connection_send_message_with_reply_sync (GDBusConnection *connecti
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/* ---------------------------------------------------------------------------------------------------- */
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/*
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* Called in any thread.
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* Must hold the connection lock when calling this, unless
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* connection->finalizing is TRUE.
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*/
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static void
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name_watcher_unref_watched_name (GDBusConnection *connection,
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SignalData *name_watcher)
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{
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WatchedName *watched_name = name_watcher->watched_name;
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g_assert (watched_name != NULL);
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if (!g_ref_count_dec (&watched_name->ref_count))
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return;
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/* Removing watched_name from the name_watcher may result in
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* name_watcher being freed, so we must make sure name_watcher is no
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* longer in map_method_serial_to_name_watcher.
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*
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* If we stop watching the name while our GetNameOwner call was still
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* in-flight, then when the reply eventually arrives, we will not find
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* its serial number in the map and harmlessly ignore it as a result. */
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if (watched_name->get_name_owner_serial != 0)
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g_hash_table_remove (connection->map_method_serial_to_name_watcher,
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GUINT_TO_POINTER (watched_name->get_name_owner_serial));
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name_watcher->watched_name = NULL;
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g_free (watched_name->owner);
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g_free (watched_name);
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}
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/* called in GDBusWorker thread with lock held */
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static void
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name_watcher_set_name_owner_unlocked (SignalData *name_watcher,
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const char *new_owner)
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{
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if (new_owner != NULL && new_owner[0] == '\0')
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new_owner = NULL;
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g_assert (name_watcher->watched_name != NULL);
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g_set_str (&name_watcher->watched_name->owner, new_owner);
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}
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/* called in GDBusWorker thread with lock held */
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static void
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name_watcher_deliver_name_owner_changed_unlocked (SignalData *name_watcher,
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GDBusMessage *message)
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{
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GVariant *body;
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body = g_dbus_message_get_body (message);
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if (G_LIKELY (body != NULL && g_variant_is_of_type (body, G_VARIANT_TYPE ("(sss)"))))
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{
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const char *name;
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const char *new_owner;
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g_variant_get (body, "(&s&s&s)", &name, NULL, &new_owner);
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/* Our caller already checked this */
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g_assert (g_strcmp0 (name_watcher->arg0, name) == 0);
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if (G_LIKELY (new_owner[0] == '\0' || g_dbus_is_unique_name (new_owner)))
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name_watcher_set_name_owner_unlocked (name_watcher, new_owner);
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else
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g_warning ("Received NameOwnerChanged signal with invalid owner \"%s\" for \"%s\"",
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new_owner, name);
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}
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else
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{
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g_warning ("Received NameOwnerChanged signal with unexpected "
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"signature %s",
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body == NULL ? "()" : g_variant_get_type_string (body));
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}
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}
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/* called in GDBusWorker thread with lock held */
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static void
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name_watcher_deliver_get_name_owner_reply_unlocked (SignalData *name_watcher,
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GDBusConnection *connection,
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GDBusMessage *message)
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{
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GDBusMessageType type;
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GVariant *body;
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WatchedName *watched_name;
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watched_name = name_watcher->watched_name;
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g_assert (watched_name != NULL);
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g_assert (watched_name->get_name_owner_serial != 0);
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type = g_dbus_message_get_message_type (message);
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body = g_dbus_message_get_body (message);
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if (type == G_DBUS_MESSAGE_TYPE_ERROR)
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{
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if (g_strcmp0 (g_dbus_message_get_error_name (message),
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"org.freedesktop.DBus.Error.NameHasNoOwner"))
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name_watcher_set_name_owner_unlocked (name_watcher, NULL);
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/* else it's something like NoReply or AccessDenied, which tells
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* us nothing - leave the owner set to whatever we most recently
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* learned from NameOwnerChanged, or NULL */
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}
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else if (type != G_DBUS_MESSAGE_TYPE_METHOD_RETURN)
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{
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g_warning ("Received GetNameOwner reply with unexpected type %d",
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type);
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}
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else if (G_LIKELY (body != NULL && g_variant_is_of_type (body, G_VARIANT_TYPE ("(s)"))))
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{
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const char *new_owner;
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g_variant_get (body, "(&s)", &new_owner);
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if (G_LIKELY (g_dbus_is_unique_name (new_owner)))
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name_watcher_set_name_owner_unlocked (name_watcher, new_owner);
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else
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g_warning ("Received GetNameOwner reply with invalid owner \"%s\" for \"%s\"",
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new_owner, name_watcher->arg0);
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}
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else
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{
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g_warning ("Received GetNameOwner reply with unexpected signature %s",
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body == NULL ? "()" : g_variant_get_type_string (body));
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}
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g_hash_table_remove (connection->map_method_serial_to_name_watcher,
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GUINT_TO_POINTER (watched_name->get_name_owner_serial));
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watched_name->get_name_owner_serial = 0;
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}
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/* Called in a user thread, lock is held */
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static void
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name_watcher_call_get_name_owner_unlocked (GDBusConnection *connection,
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SignalData *name_watcher)
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{
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GDBusMessage *message;
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GError *local_error = NULL;
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WatchedName *watched_name;
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g_assert (g_strcmp0 (name_watcher->sender, DBUS_SERVICE_DBUS) == 0);
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g_assert (g_strcmp0 (name_watcher->interface_name, DBUS_INTERFACE_DBUS) == 0);
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g_assert (g_strcmp0 (name_watcher->member, "NameOwnerChanged") == 0);
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g_assert (g_strcmp0 (name_watcher->object_path, DBUS_PATH_DBUS) == 0);
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/* arg0 of the NameOwnerChanged message is the well-known name whose owner
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* we are interested in */
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g_assert (g_dbus_is_name (name_watcher->arg0));
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g_assert (name_watcher->flags == G_DBUS_SIGNAL_FLAGS_NONE);
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watched_name = name_watcher->watched_name;
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g_assert (watched_name != NULL);
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g_assert (watched_name->owner == NULL);
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g_assert (watched_name->get_name_owner_serial == 0);
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g_assert (name_watcher->shared_name_watcher == NULL);
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message = g_dbus_message_new_method_call (DBUS_SERVICE_DBUS,
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DBUS_PATH_DBUS,
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DBUS_INTERFACE_DBUS,
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"GetNameOwner");
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g_dbus_message_set_body (message, g_variant_new ("(s)", name_watcher->arg0));
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if (g_dbus_connection_send_message_unlocked (connection, message,
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G_DBUS_SEND_MESSAGE_FLAGS_NONE,
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&watched_name->get_name_owner_serial,
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&local_error))
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{
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g_assert (watched_name->get_name_owner_serial != 0);
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g_hash_table_insert (connection->map_method_serial_to_name_watcher,
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GUINT_TO_POINTER (watched_name->get_name_owner_serial),
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name_watcher);
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}
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else
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{
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g_critical ("Error while sending GetNameOwner() message: %s",
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local_error->message);
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g_clear_error (&local_error);
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g_assert (watched_name->get_name_owner_serial == 0);
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}
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g_object_unref (message);
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}
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/* ---------------------------------------------------------------------------------------------------- */
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typedef struct
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{
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guint id;
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@ -2378,6 +2625,7 @@ on_worker_message_received (GDBusWorker *worker,
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{
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guint32 reply_serial;
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GTask *task;
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SignalData *name_watcher;
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reply_serial = g_dbus_message_get_reply_serial (message);
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CONNECTION_LOCK (connection);
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@ -2393,6 +2641,19 @@ on_worker_message_received (GDBusWorker *worker,
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{
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//g_debug ("message reply/error for serial %d but no SendMessageData found for %p", reply_serial, connection);
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}
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name_watcher = g_hash_table_lookup (connection->map_method_serial_to_name_watcher,
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GUINT_TO_POINTER (reply_serial));
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if (name_watcher != NULL)
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{
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g_assert (name_watcher->watched_name != NULL);
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g_assert (name_watcher->watched_name->get_name_owner_serial == reply_serial);
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name_watcher_deliver_get_name_owner_reply_unlocked (name_watcher,
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connection,
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message);
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}
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CONNECTION_UNLOCK (connection);
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}
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else if (message_type == G_DBUS_MESSAGE_TYPE_SIGNAL)
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@ -3581,6 +3842,7 @@ g_dbus_connection_signal_subscribe (GDBusConnection *connection,
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{
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gchar *rule;
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SignalData *signal_data;
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SignalData *name_watcher = NULL;
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SignalSubscriber *subscriber;
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gboolean sender_is_its_own_owner;
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const gchar *sender_unique_name;
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@ -3646,13 +3908,59 @@ g_dbus_connection_signal_subscribe (GDBusConnection *connection,
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signal_data = signal_data_new_take (g_steal_pointer (&rule),
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g_strdup (sender),
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sender_is_its_own_owner,
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g_strdup (interface_name),
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g_strdup (member),
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g_strdup (object_path),
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g_strdup (arg0),
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flags);
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g_ptr_array_add (signal_data->subscribers, subscriber);
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/* If subscribing to a signal from a specific sender with a well-known
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* name, we must first subscribe to NameOwnerChanged signals for that
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* well-known name, so that we can match the current owner of the name
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* against the sender of each signal. */
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if (sender != NULL && !sender_is_its_own_owner)
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{
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gchar *name_owner_rule = NULL;
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/* We already checked that sender != NULL implies MESSAGE_BUS_CONNECTION */
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g_assert (connection->flags & G_DBUS_CONNECTION_FLAGS_MESSAGE_BUS_CONNECTION);
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name_owner_rule = args_to_rule (DBUS_SERVICE_DBUS,
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DBUS_INTERFACE_DBUS,
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"NameOwnerChanged",
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DBUS_PATH_DBUS,
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sender,
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G_DBUS_SIGNAL_FLAGS_NONE);
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name_watcher = g_hash_table_lookup (connection->map_rule_to_signal_data, name_owner_rule);
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if (name_watcher == NULL)
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{
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name_watcher = signal_data_new_take (g_steal_pointer (&name_owner_rule),
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g_strdup (DBUS_SERVICE_DBUS),
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g_strdup (DBUS_INTERFACE_DBUS),
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g_strdup ("NameOwnerChanged"),
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g_strdup (DBUS_PATH_DBUS),
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g_strdup (sender),
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G_DBUS_SIGNAL_FLAGS_NONE);
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add_signal_data (connection, name_watcher, DBUS_SERVICE_DBUS);
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}
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if (name_watcher->watched_name == NULL)
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{
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name_watcher->watched_name = watched_name_new ();
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name_watcher_call_get_name_owner_unlocked (connection, name_watcher);
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}
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else
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{
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g_ref_count_inc (&name_watcher->watched_name->ref_count);
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}
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signal_data->shared_name_watcher = name_watcher;
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g_clear_pointer (&name_owner_rule, g_free);
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}
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add_signal_data (connection, signal_data, sender_unique_name);
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out:
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@ -3680,10 +3988,18 @@ remove_signal_data_if_unused (GDBusConnection *connection,
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const gchar *sender_unique_name;
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GPtrArray *signal_data_array;
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/* Cannot remove while there are still subscribers */
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if (signal_data->subscribers->len != 0)
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return;
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if (signal_data->sender_is_its_own_owner)
|
||||
/* Cannot remove while another SignalData is still using this one
|
||||
* as its shared_name_watcher, which holds watched_name->ref_count > 0 */
|
||||
if (signal_data->watched_name != NULL)
|
||||
return;
|
||||
|
||||
/* Point of no return: we have committed to removing it */
|
||||
|
||||
if (signal_data->sender != NULL && signal_data->shared_name_watcher == NULL)
|
||||
sender_unique_name = signal_data->sender;
|
||||
else
|
||||
sender_unique_name = "";
|
||||
@ -3716,6 +4032,15 @@ remove_signal_data_if_unused (GDBusConnection *connection,
|
||||
remove_match_rule (connection, signal_data->rule);
|
||||
}
|
||||
|
||||
if (signal_data->shared_name_watcher != NULL)
|
||||
{
|
||||
SignalData *name_watcher = g_steal_pointer (&signal_data->shared_name_watcher);
|
||||
|
||||
name_watcher_unref_watched_name (connection, name_watcher);
|
||||
/* May free signal_data */
|
||||
remove_signal_data_if_unused (connection, name_watcher);
|
||||
}
|
||||
|
||||
signal_data_free (signal_data);
|
||||
}
|
||||
|
||||
@ -3992,6 +4317,17 @@ schedule_callbacks (GDBusConnection *connection,
|
||||
continue;
|
||||
}
|
||||
|
||||
if (signal_data->watched_name != NULL)
|
||||
{
|
||||
/* Invariant: SignalData should only have a watched_name if it
|
||||
* represents the NameOwnerChanged signal */
|
||||
g_assert (g_strcmp0 (sender, DBUS_SERVICE_DBUS) == 0);
|
||||
g_assert (g_strcmp0 (interface, DBUS_INTERFACE_DBUS) == 0);
|
||||
g_assert (g_strcmp0 (path, DBUS_PATH_DBUS) == 0);
|
||||
g_assert (g_strcmp0 (member, "NameOwnerChanged") == 0);
|
||||
name_watcher_deliver_name_owner_changed_unlocked (signal_data, message);
|
||||
}
|
||||
|
||||
for (m = 0; m < signal_data->subscribers->len; m++)
|
||||
{
|
||||
SignalSubscriber *subscriber = signal_data->subscribers->pdata[m];
|
||||
@ -4063,7 +4399,7 @@ distribute_signals (GDBusConnection *connection,
|
||||
schedule_callbacks (connection, signal_data_array, message, sender);
|
||||
}
|
||||
|
||||
/* collect subscribers not matching on sender */
|
||||
/* collect subscribers not matching on sender, or matching a well-known name */
|
||||
signal_data_array = g_hash_table_lookup (connection->map_sender_unique_name_to_signal_data_array, "");
|
||||
if (signal_data_array != NULL)
|
||||
schedule_callbacks (connection, signal_data_array, message, sender);
|
||||
|
||||
Loading…
Reference in New Issue
Block a user