lib: manage pending consolekit calls with cancellable

Pending NewSession objects can disappear just as quickly
as they appear in response to ConsoleKit signals.  If
we're in the middle of talking to ConsoleKit when an
object disappears and is subsequently freed, then we'll
still try to access it from the reply callback.

This commit cancels any pending messages to the consolekit
daemon, when the session goes away.

https://bugs.freedesktop.org/show_bug.cgi?id=50112

src/libaccountsservice/act-user-manager.c

@@ -104,6 +104,7 @@ typedef struct
         ActUserManagerNewSessionState    state;
         char                            *id;
         ConsoleKitSession               *proxy;
+        GCancellable                    *cancellable;
         uid_t                            uid;
         char                            *x11_display;
 } ActUserManagerNewSession;
@@ -962,6 +963,13 @@ unload_new_session (ActUserManagerNewSession *new_session)
 
         manager = new_session->manager;
 
+        if (new_session->cancellable != NULL &&
+            !g_cancellable_is_cancelled (new_session->cancellable)) {
+                g_cancellable_cancel (new_session->cancellable);
+                g_object_unref (new_session->cancellable);
+                new_session->cancellable = NULL;
+        }
+
         manager->priv->new_sessions = g_slist_remove (manager->priv->new_sessions,
                                                       new_session);
 
@@ -1017,6 +1025,10 @@ on_get_unix_user_finished (GObject      *object,
         GError            *error = NULL;
         guint              uid;
 
+        if (new_session->cancellable == NULL || g_cancellable_is_cancelled (new_session->cancellable)) {
+                return;
+        }
+
         if (!console_kit_session_call_get_unix_user_finish (proxy, &uid, result, &error)) {
                 if (error != NULL) {
                         g_debug ("Failed to get uid of session '%s': %s",
@@ -1076,7 +1088,7 @@ get_uid_for_new_session (ActUserManagerNewSession *new_session)
         g_assert (new_session->proxy != NULL);
 
         console_kit_session_call_get_unix_user (new_session->proxy,
-                                                NULL,
+                                                new_session->cancellable,
                                                 on_get_unix_user_finished,
                                                 new_session);
 }
@@ -1216,6 +1228,10 @@ on_get_x11_display_finished (GObject      *object,
         GError            *error = NULL;
         char              *x11_display;
 
+        if (new_session->cancellable == NULL || g_cancellable_is_cancelled (new_session->cancellable)) {
+                return;
+        }
+
         if (!console_kit_session_call_get_x11_display_finish (proxy, &x11_display, result, &error)) {
                 if (error != NULL) {
                         g_debug ("Failed to get the x11 display of session '%s': %s",
@@ -1303,7 +1319,7 @@ get_x11_display_for_new_session (ActUserManagerNewSession *new_session)
         g_assert (new_session->proxy != NULL);
 
         console_kit_session_call_get_x11_display (new_session->proxy,
-                                                  NULL,
+                                                  new_session->cancellable,
                                                   on_get_x11_display_finished,
                                                   new_session);
 }
@@ -1392,6 +1408,7 @@ load_new_session (ActUserManager *manager,
         new_session->manager = g_object_ref (manager);
         new_session->id = g_strdup (session_id);
         new_session->state = ACT_USER_MANAGER_NEW_SESSION_STATE_UNLOADED + 1;
+        new_session->cancellable = g_cancellable_new ();
 
         manager->priv->new_sessions = g_slist_prepend (manager->priv->new_sessions,
                                                        new_session);