[gupnp] resource-factory: Use GOnce for singleton

[Jens Georg <jensgeorg src gnome org>]

commit eb7e1d26c5d0b21d1cd9f9a781385bd224a509a9
Author: Jens Georg <mail jensge org>
Date:   Sat Aug 14 09:19:28 2021 +0200

    resource-factory: Use GOnce for singleton

 libgupnp/gupnp-resource-factory.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)
---
diff --git a/libgupnp/gupnp-resource-factory.c b/libgupnp/gupnp-resource-factory.c
index 8d7e362..9ab34db 100644
--- a/libgupnp/gupnp-resource-factory.c
+++ b/libgupnp/gupnp-resource-factory.c
@@ -114,9 +114,11 @@ gupnp_resource_factory_get_default (void)
 {
         static GUPnPResourceFactory *default_factory = NULL;
 
-        if (G_UNLIKELY (default_factory == NULL)) {
-                default_factory = g_object_new (GUPNP_TYPE_RESOURCE_FACTORY,
-                                                NULL);
+        if (g_once_init_enter (&default_factory)) {
+                GUPnPResourceFactory *factory =
+                        g_object_new (GUPNP_TYPE_RESOURCE_FACTORY, NULL);
+
+                g_once_init_leave (&default_factory, factory);
         }
 
         return default_factory;