thread: Flush tasks and callbacks on finalize

This will make sure no tasks or callbacks are unexpectedly dropped,
potentially leaking or leaving things in an unexpected state.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2777>

src/backends/native/meta-thread-impl.c

@@ -454,7 +454,7 @@ invoke_task_feedback (MetaThread *thread,
   task->feedback_func (task->retval, task->error, task->feedback_user_data);
 }
 
-void
+int
 meta_thread_impl_dispatch (MetaThreadImpl *thread_impl)
 {
   MetaThreadImplPrivate *priv =
@@ -463,7 +463,9 @@ meta_thread_impl_dispatch (MetaThreadImpl *thread_impl)
   gpointer retval;
   g_autoptr (GError) error = NULL;
 
-  task = g_async_queue_pop (priv->task_queue);
+  task = g_async_queue_try_pop (priv->task_queue);
+  if (!task)
+    return 0;
 
   priv->in_impl_task = TRUE;
   retval = task->func (thread_impl, task->user_data, &error);
@@ -489,6 +491,8 @@ meta_thread_impl_dispatch (MetaThreadImpl *thread_impl)
   g_clear_pointer (&task, meta_thread_task_free);
 
   priv->in_impl_task = FALSE;
+
+  return 1;
 }
 
 void

src/backends/native/meta-thread-impl.h

@@ -65,7 +65,7 @@ GSource * meta_thread_impl_register_fd (MetaThreadImpl     *thread_impl,
 void meta_thread_impl_queue_task (MetaThreadImpl *thread_impl,
                                   MetaThreadTask *task);
 
-void meta_thread_impl_dispatch (MetaThreadImpl *thread_impl);
+int meta_thread_impl_dispatch (MetaThreadImpl *thread_impl);
 
 gboolean meta_thread_impl_is_in_impl (MetaThreadImpl *thread_impl);
 

src/backends/native/meta-thread.c

@@ -156,8 +156,8 @@ meta_thread_finalize (GObject *object)
   MetaThread *thread = META_THREAD (object);
   MetaThreadPrivate *priv = meta_thread_get_instance_private (thread);
 
-  g_clear_list (&priv->pending_callbacks,
+  while (meta_thread_impl_dispatch (priv->impl) > 0);
-                (GDestroyNotify) meta_thread_callback_data_free);
+  meta_thread_flush_callbacks (thread);
   g_clear_handle_id (&priv->callbacks_source_id, g_source_remove);
 
   g_clear_object (&priv->impl);

src/tests/native-thread.c

@@ -566,11 +566,48 @@ meta_test_thread_user_common (void)
   test_thread = NULL;
 }
 
+static gpointer
+late_callback (MetaThreadImpl  *thread_impl,
+               gpointer         user_data,
+               GError         **error)
+{
+  gboolean *done = user_data;
+
+  *done = TRUE;
+
+  return NULL;
+}
+
+static void
+meta_test_thread_user_late_callbacks (void)
+{
+  MetaBackend *backend = meta_context_get_backend (test_context);
+  MetaThread *thread;
+  g_autoptr (GError) error = NULL;
+  gboolean done = FALSE;
+
+  thread = g_initable_new (META_TYPE_THREAD_TEST,
+                           NULL, &error,
+                           "backend", backend,
+                           NULL);
+  g_object_add_weak_pointer (G_OBJECT (thread), (gpointer *) &thread);
+  g_assert_nonnull (thread);
+  g_assert_null (error);
+
+  meta_thread_post_impl_task (thread, late_callback, &done, NULL, NULL);
+
+  g_object_unref (thread);
+  g_assert_null (thread);
+  g_assert_true (done);
+}
+
 static void
 init_tests (void)
 {
   g_test_add_func ("/backends/native/thread/user/common",
                    meta_test_thread_user_common);
+  g_test_add_func ("/backends/native/thread/user/late-callbacks",
+                   meta_test_thread_user_late_callbacks);
 }
 
 int