[mutter] renderer-native: Freeze frames while retrying to page flip

[Georges Basile Stavracas Neto <gbsneto src gnome org>]

commit b2d0184c6efa164ad5dd7a2ca8b10cf13acf5b4c
Author: Jonas Ådahl <jadahl gmail com>
Date:   Fri Mar 29 20:56:57 2019 +0100

    renderer-native: Freeze frames while retrying to page flip
    
    We're currently always waiting for unfinished page flips before flipping
    again. This is awkward when we are in an asynchronous retry-page-flip
    loop, as we can synchronously wait for any KMS page flip event.
    
    To avoid ending up with such situations, just freeze the frame clock
    while we're retrying, then thaw it when we succeded.
    
    https://gitlab.gnome.org/GNOME/mutter/merge_requests/506

 src/backends/native/meta-renderer-native.c | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)
---
diff --git a/src/backends/native/meta-renderer-native.c b/src/backends/native/meta-renderer-native.c
index 8258da37d..086e8e43c 100644
--- a/src/backends/native/meta-renderer-native.c
+++ b/src/backends/native/meta-renderer-native.c
@@ -1703,6 +1703,9 @@ retry_page_flips (gpointer user_data)
     }
   else
     {
+      MetaBackend *backend = backend_from_renderer_native (renderer_native);
+
+      meta_backend_thaw_updates (backend);
       g_clear_pointer (&onscreen_native->retry_page_flips_source,
                        g_source_unref);
       return G_SOURCE_REMOVE;
@@ -1743,6 +1746,8 @@ schedule_retry_page_flip (MetaOnscreenNative *onscreen_native,
 
   if (!onscreen_native->retry_page_flips_source)
     {
+      MetaBackend *backend =
+        backend_from_renderer_native (onscreen_native->renderer_native);
       GSource *source;
 
       source = g_source_new (&retry_page_flips_source_funcs, sizeof (GSource));
@@ -1751,6 +1756,7 @@ schedule_retry_page_flip (MetaOnscreenNative *onscreen_native,
       g_source_attach (source, NULL);
 
       onscreen_native->retry_page_flips_source = source;
+      meta_backend_freeze_updates (backend);
     }
   else
     {
@@ -3048,8 +3054,15 @@ meta_renderer_native_release_onscreen (CoglOnscreen *onscreen)
 
   g_list_free_full (onscreen_native->pending_page_flip_retries,
                     (GDestroyNotify) retry_page_flip_data_free);
-  g_clear_pointer (&onscreen_native->retry_page_flips_source,
-                   g_source_destroy);
+  if (onscreen_native->retry_page_flips_source)
+    {
+      MetaBackend *backend =
+        backend_from_renderer_native (onscreen_native->renderer_native);
+
+      meta_backend_thaw_updates (backend);
+      g_clear_pointer (&onscreen_native->retry_page_flips_source,
+                       g_source_destroy);
+    }
 
   if (onscreen_egl->egl_surface != EGL_NO_SURFACE)
     {