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Merge branch '1232-object-manager-client-signal-race' into 'master'

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gdbusobjectmanagerclient: Fix race in signal emission

Closes #1232

See merge request GNOME/glib!1335
This commit is contained in:
Philip Withnall 2020-01-21 11:52:30 +00:00
commit 4c1b675eac
1 changed files with 79 additions and 21 deletions
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100
gio/gdbusobjectmanagerclient.c
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@ -141,6 +141,9 @@ struct _GDBusObjectManagerClientPrivate
GDBusProxyTypeFunc get_proxy_type_func;
gpointer get_proxy_type_user_data;
GDestroyNotify get_proxy_type_destroy_notify;
gulong name_owner_signal_id;
gulong signal_signal_id;
};
enum
@ -197,13 +200,18 @@ g_dbus_object_manager_client_finalize (GObject *object)
g_hash_table_unref (manager->priv->map_object_path_to_object_proxy);
if (manager->priv->control_proxy != NULL)
{
g_signal_handlers_disconnect_by_func (manager->priv->control_proxy,
on_control_proxy_g_signal,
manager);
g_object_unref (manager->priv->control_proxy);
}
if (manager->priv->control_proxy != NULL && manager->priv->signal_signal_id != 0)
g_signal_handler_disconnect (manager->priv->control_proxy,
manager->priv->signal_signal_id);
manager->priv->signal_signal_id = 0;
if (manager->priv->control_proxy != NULL && manager->priv->name_owner_signal_id != 0)
g_signal_handler_disconnect (manager->priv->control_proxy,
manager->priv->name_owner_signal_id);
manager->priv->name_owner_signal_id = 0;
g_clear_object (&manager->priv->control_proxy);
if (manager->priv->connection != NULL)
g_object_unref (manager->priv->connection);
g_free (manager->priv->object_path);
@ -1241,16 +1249,20 @@ on_notify_g_name_owner (GObject *object,
GParamSpec *pspec,
gpointer user_data)
{
GDBusObjectManagerClient *manager = G_DBUS_OBJECT_MANAGER_CLIENT (user_data);
GWeakRef *manager_weak = user_data;
GDBusObjectManagerClient *manager = NULL;
gchar *old_name_owner;
gchar *new_name_owner;
manager = G_DBUS_OBJECT_MANAGER_CLIENT (g_weak_ref_get (manager_weak));
if (manager == NULL)
return;
g_mutex_lock (&manager->priv->lock);
old_name_owner = manager->priv->name_owner;
new_name_owner = g_dbus_proxy_get_name_owner (manager->priv->control_proxy);
manager->priv->name_owner = NULL;
g_object_ref (manager);
if (g_strcmp0 (old_name_owner, new_name_owner) != 0)
{
GList *l;
@ -1330,6 +1342,21 @@ on_notify_g_name_owner (GObject *object,
g_object_unref (manager);
}
static GWeakRef *
weak_ref_new (GObject *object)
{
GWeakRef *weak_ref = g_new0 (GWeakRef, 1);
g_weak_ref_init (weak_ref, object);
return g_steal_pointer (&weak_ref);
}
static void
weak_ref_free (GWeakRef *weak_ref)
{
g_weak_ref_clear (weak_ref);
g_free (weak_ref);
}
static gboolean
initable_init (GInitable *initable,
GCancellable *cancellable,
@ -1365,15 +1392,30 @@ initable_init (GInitable *initable,
if (manager->priv->control_proxy == NULL)
goto out;
g_signal_connect (G_OBJECT (manager->priv->control_proxy),
"notify::g-name-owner",
G_CALLBACK (on_notify_g_name_owner),
manager);
/* Use weak refs here. The @control_proxy will emit its signals in the current
* #GMainContext (since we constructed it just above). However, the user may
* drop the last external reference to this #GDBusObjectManagerClient in
* another thread between a signal being emitted and scheduled in an idle
* callback in this #GMainContext, and that idle callback being invoked. We
* can’t use a strong reference here, as there’s no
* g_dbus_object_manager_client_disconnect() (or similar) method to tell us
* when the last external reference to this object has been dropped, so we
* can’t break a strong reference count cycle. So use weak refs. */
manager->priv->name_owner_signal_id =
g_signal_connect_data (G_OBJECT (manager->priv->control_proxy),
"notify::g-name-owner",
G_CALLBACK (on_notify_g_name_owner),
weak_ref_new (G_OBJECT (manager)),
(GClosureNotify) weak_ref_free,
0 /* flags */);
g_signal_connect (manager->priv->control_proxy,
"g-signal",
G_CALLBACK (on_control_proxy_g_signal),
manager);
manager->priv->signal_signal_id =
g_signal_connect_data (manager->priv->control_proxy,
"g-signal",
G_CALLBACK (on_control_proxy_g_signal),
weak_ref_new (G_OBJECT (manager)),
(GClosureNotify) weak_ref_free,
0 /* flags */);
manager->priv->name_owner = g_dbus_proxy_get_name_owner (manager->priv->control_proxy);
if (manager->priv->name_owner == NULL && manager->priv->name != NULL)
@ -1397,11 +1439,20 @@ initable_init (GInitable *initable,
if (value == NULL)
{
maybe_unsubscribe_signals (manager);
g_warn_if_fail (g_signal_handlers_disconnect_by_func (manager->priv->control_proxy,
on_control_proxy_g_signal,
manager) == 1);
g_warn_if_fail (manager->priv->signal_signal_id != 0);
g_signal_handler_disconnect (manager->priv->control_proxy,
manager->priv->signal_signal_id);
manager->priv->signal_signal_id = 0;
g_warn_if_fail (manager->priv->name_owner_signal_id != 0);
g_signal_handler_disconnect (manager->priv->control_proxy,
manager->priv->name_owner_signal_id);
manager->priv->name_owner_signal_id = 0;
g_object_unref (manager->priv->control_proxy);
manager->priv->control_proxy = NULL;
goto out;
}
@ -1668,9 +1719,14 @@ on_control_proxy_g_signal (GDBusProxy *proxy,
GVariant *parameters,
gpointer user_data)
{
GDBusObjectManagerClient *manager = G_DBUS_OBJECT_MANAGER_CLIENT (user_data);
GWeakRef *manager_weak = user_data;
GDBusObjectManagerClient *manager = NULL;
const gchar *object_path;
manager = G_DBUS_OBJECT_MANAGER_CLIENT (g_weak_ref_get (manager_weak));
if (manager == NULL)
return;
//g_debug ("yay, g_signal %s: %s\n", signal_name, g_variant_print (parameters, TRUE));
if (g_strcmp0 (signal_name, "InterfacesAdded") == 0)
@ -1693,6 +1749,8 @@ on_control_proxy_g_signal (GDBusProxy *proxy,
remove_interfaces (manager, object_path, ifaces);
g_free (ifaces);
}
g_object_unref (manager);
}
/* ---------------------------------------------------------------------------------------------------- */