backends/native: Main thread rt-scheduler: experimental feature no more

To paraphrase jadahl: we have a dedicated KMS thread now, which also
has realtime scheduling enabled unconditionally. realtime scheduling
on the main thread isn't too great of an idea, considering GC can
take a hot minute.

And to quote rmader: we most likely won't be able to make the main
thread rt as long as we use GJS and thus have GC.

So let's get rid of it! It's just been breaking things anyways.

This just ignores the setting; we'll fully remove it when GNOME 46
comes around.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3296>

data/org.gnome.mutter.gschema.xml.in

@@ -3,8 +3,7 @@
   <flags id="org.gnome.mutter.MetaExperimentalFeature">
     <value nick="scale-monitor-framebuffer" value="1"/>
     <value nick="kms-modifiers" value="2"/>
-    <value nick="rt-scheduler" value="4"/>
+    <value nick="autoclose-xwayland" value="4"/>
-    <value nick="autoclose-xwayland" value="8"/>
   </flags>
 
   <schema id="org.gnome.mutter" path="/org/gnome/mutter/"
@@ -126,9 +125,6 @@
                                         supported by the driver. Requires a
                                         restart.
 
-        • “rt-scheduler”              — makes mutter request a low priority
-                                        real-time scheduling. Requires a restart.
-
         • “autoclose-xwayland”        — automatically terminates Xwayland if all
                                         relevant X11 clients are gone.
                                         Requires a restart.

src/backends/meta-settings-private.h

@@ -30,8 +30,7 @@ typedef enum _MetaExperimentalFeature
   META_EXPERIMENTAL_FEATURE_NONE = 0,
   META_EXPERIMENTAL_FEATURE_SCALE_MONITOR_FRAMEBUFFER = (1 << 0),
   META_EXPERIMENTAL_FEATURE_KMS_MODIFIERS  = (1 << 1),
-  META_EXPERIMENTAL_FEATURE_RT_SCHEDULER = (1 << 2),
+  META_EXPERIMENTAL_FEATURE_AUTOCLOSE_XWAYLAND  = (1 << 2),
-  META_EXPERIMENTAL_FEATURE_AUTOCLOSE_XWAYLAND  = (1 << 3),
 } MetaExperimentalFeature;
 
 typedef enum _MetaXwaylandExtension

src/backends/meta-settings.c

@@ -292,8 +292,6 @@ experimental_features_handler (GVariant *features_variant,
         feature = META_EXPERIMENTAL_FEATURE_SCALE_MONITOR_FRAMEBUFFER;
       else if (g_str_equal (feature_str, "kms-modifiers"))
         feature = META_EXPERIMENTAL_FEATURE_KMS_MODIFIERS;
-      else if (g_str_equal (feature_str, "rt-scheduler"))
-        feature = META_EXPERIMENTAL_FEATURE_RT_SCHEDULER;
       else if (g_str_equal (feature_str, "autoclose-xwayland"))
         feature = META_EXPERIMENTAL_FEATURE_AUTOCLOSE_XWAYLAND;
 

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

@@ -216,45 +216,9 @@ static void
 meta_backend_native_post_init (MetaBackend *backend)
 {
   MetaBackendNative *backend_native = META_BACKEND_NATIVE (backend);
-  MetaSettings *settings = meta_backend_get_settings (backend);
 
   META_BACKEND_CLASS (meta_backend_native_parent_class)->post_init (backend);
 
-  if (meta_settings_is_experimental_feature_enabled (settings,
-                                                     META_EXPERIMENTAL_FEATURE_RT_SCHEDULER))
-    {
-      g_autoptr (MetaDBusRealtimeKit1) rtkit_proxy = NULL;
-      g_autoptr (GError) error = NULL;
-
-      rtkit_proxy =
-        meta_dbus_realtime_kit1_proxy_new_for_bus_sync (G_BUS_TYPE_SYSTEM,
-                                                        G_DBUS_PROXY_FLAGS_DO_NOT_LOAD_PROPERTIES |
-                                                        G_DBUS_PROXY_FLAGS_DO_NOT_CONNECT_SIGNALS |
-                                                        G_DBUS_PROXY_FLAGS_DO_NOT_AUTO_START,
-                                                        "org.freedesktop.RealtimeKit1",
-                                                        "/org/freedesktop/RealtimeKit1",
-                                                        NULL,
-                                                        &error);
-
-      if (rtkit_proxy)
-        {
-          uint32_t priority;
-
-          priority = sched_get_priority_min (SCHED_RR);
-          meta_dbus_realtime_kit1_call_make_thread_realtime_sync (rtkit_proxy,
-                                                                  gettid (),
-                                                                  priority,
-                                                                  NULL,
-                                                                  &error);
-        }
-
-      if (error)
-        {
-          g_dbus_error_strip_remote_error (error);
-          g_message ("Failed to set RT scheduler: %s", error->message);
-        }
-    }
-
 #ifdef HAVE_REMOTE_DESKTOP
   maybe_disable_screen_cast_dma_bufs (backend_native);
 #endif