backend/native: Split up KMS shutdown in two phases

The first phase happens early, which discards pending page flips,
meaning the references held by those page flip closures are released.

The second phase happens late, after other units depending on the KMS
abstraction, have been cleaned up.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1822>

src/backends/native/meta-backend-native.c

@@ -112,11 +112,13 @@ meta_backend_native_dispose (GObject *object)
       native->udev_device_added_handler_id = 0;
     }
 
-  g_clear_object (&native->kms);
-  g_clear_object (&native->udev);
+  if (native->kms)
+    meta_kms_prepare_shutdown (native->kms);
 
   G_OBJECT_CLASS (meta_backend_native_parent_class)->dispose (object);
 
+  g_clear_object (&native->kms);
+  g_clear_object (&native->udev);
   g_clear_pointer (&native->launcher, meta_launcher_free);
 }
 

src/backends/native/meta-kms-impl-device-atomic.c

@@ -1011,15 +1011,24 @@ dispose_page_flip_data (gpointer key,
   return TRUE;
 }
 
+static void
+meta_kms_impl_device_atomic_prepare_shutdown (MetaKmsImplDevice *impl_device)
+{
+  MetaKmsImplDeviceAtomic *impl_device_atomic =
+    META_KMS_IMPL_DEVICE_ATOMIC (impl_device);
+
+  g_hash_table_foreach_remove (impl_device_atomic->page_flip_datas,
+                               dispose_page_flip_data,
+                               NULL);
+}
+
 static void
 meta_kms_impl_device_atomic_finalize (GObject *object)
 {
   MetaKmsImplDeviceAtomic *impl_device_atomic =
     META_KMS_IMPL_DEVICE_ATOMIC (object);
 
-  g_hash_table_foreach_remove (impl_device_atomic->page_flip_datas,
-                               dispose_page_flip_data,
-                               NULL);
+  g_assert (g_hash_table_size (impl_device_atomic->page_flip_datas) == 0);
 
   g_hash_table_unref (impl_device_atomic->page_flip_datas);
 
@@ -1039,10 +1048,7 @@ meta_kms_impl_device_atomic_initable_init (GInitable     *initable,
 static void
 meta_kms_impl_device_atomic_init (MetaKmsImplDeviceAtomic *impl_device_atomic)
 {
-  impl_device_atomic->page_flip_datas =
-    g_hash_table_new_full (NULL, NULL,
-                           NULL,
-                           (GDestroyNotify) meta_kms_page_flip_data_unref);
+  impl_device_atomic->page_flip_datas = g_hash_table_new (NULL, NULL);
 }
 
 static void
@@ -1068,4 +1074,6 @@ meta_kms_impl_device_atomic_class_init (MetaKmsImplDeviceAtomicClass *klass)
     meta_kms_impl_device_atomic_handle_page_flip_callback;
   impl_device_class->discard_pending_page_flips =
     meta_kms_impl_device_atomic_discard_pending_page_flips;
+  impl_device_class->prepare_shutdown =
+    meta_kms_impl_device_atomic_prepare_shutdown;
 }

src/backends/native/meta-kms-impl-device-simple.c

@@ -1488,6 +1488,18 @@ meta_kms_impl_device_simple_discard_pending_page_flips (MetaKmsImplDevice *impl_
                    g_source_destroy);
 }
 
+static void
+meta_kms_impl_device_simple_prepare_shutdown (MetaKmsImplDevice *impl_device)
+{
+  MetaKmsImplDeviceSimple *impl_device_simple =
+    META_KMS_IMPL_DEVICE_SIMPLE (impl_device);
+
+  g_list_foreach (impl_device_simple->posted_page_flip_datas,
+                  (GFunc) meta_kms_page_flip_data_discard_in_impl,
+                  impl_device);
+  g_clear_list (&impl_device_simple->posted_page_flip_datas, NULL);
+}
+
 static void
 meta_kms_impl_device_simple_finalize (GObject *object)
 {
@@ -1506,6 +1518,8 @@ meta_kms_impl_device_simple_finalize (GObject *object)
                             (GFunc) meta_kms_page_flip_data_discard_in_impl,
                             NULL);
 
+  g_assert (!impl_device_simple->posted_page_flip_datas);
+
   g_clear_pointer (&impl_device_simple->mode_set_fallback_feedback_source,
                    g_source_destroy);
   g_hash_table_destroy (impl_device_simple->cached_mode_sets);
@@ -1583,4 +1597,6 @@ meta_kms_impl_device_simple_class_init (MetaKmsImplDeviceSimpleClass *klass)
     meta_kms_impl_device_simple_handle_page_flip_callback;
   impl_device_class->discard_pending_page_flips =
     meta_kms_impl_device_simple_discard_pending_page_flips;
+  impl_device_class->prepare_shutdown =
+    meta_kms_impl_device_simple_prepare_shutdown;
 }

src/backends/native/meta-kms-impl-device.c

@@ -836,6 +836,15 @@ meta_kms_impl_device_init_mode_setting (MetaKmsImplDevice  *impl_device,
   return TRUE;
 }
 
+void
+meta_kms_impl_device_prepare_shutdown (MetaKmsImplDevice *impl_device)
+{
+  MetaKmsImplDeviceClass *klass = META_KMS_IMPL_DEVICE_GET_CLASS (impl_device);
+
+  if (klass->prepare_shutdown)
+    klass->prepare_shutdown (impl_device);
+}
+
 static void
 meta_kms_impl_device_init (MetaKmsImplDevice *impl_device)
 {

src/backends/native/meta-kms-impl-device.h

@@ -68,6 +68,7 @@ struct _MetaKmsImplDeviceClass
   void (* handle_page_flip_callback) (MetaKmsImplDevice   *impl_device,
                                       MetaKmsPageFlipData *page_flip_data);
   void (* discard_pending_page_flips) (MetaKmsImplDevice *impl_device);
+  void (* prepare_shutdown) (MetaKmsImplDevice *impl_device);
 };
 
 MetaKmsDevice * meta_kms_impl_device_get_device (MetaKmsImplDevice *impl_device);
@@ -143,4 +144,6 @@ int meta_kms_impl_device_close (MetaKmsImplDevice *impl_device);
 gboolean meta_kms_impl_device_init_mode_setting (MetaKmsImplDevice  *impl_device,
                                                  GError            **error);
 
+void meta_kms_impl_device_prepare_shutdown (MetaKmsImplDevice *impl_device);
+
 #endif /* META_KMS_IMPL_DEVICE_H */

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

@@ -103,6 +103,21 @@ meta_kms_impl_discard_pending_page_flips (MetaKmsImpl *impl)
                   NULL);
 }
 
+void
+meta_kms_impl_prepare_shutdown (MetaKmsImpl *impl)
+{
+  MetaKmsImplPrivate *priv = meta_kms_impl_get_instance_private (impl);
+  GList *l;
+
+  for (l = priv->impl_devices; l; l = l->next)
+    {
+      MetaKmsImplDevice *impl_device = l->data;
+
+      meta_kms_impl_device_discard_pending_page_flips (impl_device);
+      meta_kms_impl_device_prepare_shutdown (impl_device);
+    }
+}
+
 MetaKmsImpl *
 meta_kms_impl_new (MetaKms *kms)
 {

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

@@ -42,6 +42,8 @@ void meta_kms_impl_remove_impl_device (MetaKmsImpl       *impl,
 
 void meta_kms_impl_discard_pending_page_flips (MetaKmsImpl *impl);
 
+void meta_kms_impl_prepare_shutdown (MetaKmsImpl *impl);
+
 MetaKmsImpl * meta_kms_impl_new (MetaKms *kms);
 
 #endif /* META_KMS_IMPL_H */

src/backends/native/meta-kms.c

@@ -662,6 +662,22 @@ meta_kms_new (MetaBackend   *backend,
   return kms;
 }
 
+static gpointer
+prepare_shutdown_in_impl (MetaKmsImpl  *impl,
+                          gpointer      user_data,
+                          GError      **error)
+{
+  meta_kms_impl_prepare_shutdown (impl);
+  return GINT_TO_POINTER (TRUE);
+}
+
+void
+meta_kms_prepare_shutdown (MetaKms *kms)
+{
+  meta_kms_run_impl_task_sync (kms, prepare_shutdown_in_impl, NULL, NULL);
+  flush_callbacks (kms);
+}
+
 static void
 meta_kms_finalize (GObject *object)
 {

src/backends/native/meta-kms.h

@@ -63,6 +63,8 @@ MetaKmsDevice * meta_kms_create_device (MetaKms            *kms,
                                         MetaKmsDeviceFlag   flags,
                                         GError            **error);
 
+void meta_kms_prepare_shutdown (MetaKms *kms);
+
 MetaKms * meta_kms_new (MetaBackend   *backend,
                         MetaKmsFlags   flags,
                         GError       **error);