[Qemu-devel] [PATCH 03/13] qom: add support for weak referenced object: aka UnownedObject

[Igor Mammedov]

it adds support for weak reference model used by glib's
GInitiallyUnowned to QEMU's QOM model.

Signed-off-by: Igor Mammedov <imamm...@redhat.com>
---
 include/qom/object.h | 20 ++++++++++++++++++++
 qom/object.c         | 20 +++++++++++++++++++-
 2 files changed, 39 insertions(+), 1 deletion(-)

diff --git a/include/qom/object.h b/include/qom/object.h
index 89c3092..e0e4cc8 100644
--- a/include/qom/object.h
+++ b/include/qom/object.h
@@ -1314,5 +1314,25 @@ int object_child_foreach(Object *obj, int (*fn)(Object 
*child, void *opaque),
  */
 Object *container_get(Object *root, const char *path);
 
+#define TYPE_UNOWNED_OBJECT "unowned-object"
+#define UNOWNED_OBJECT(obj) \
+     OBJECT_CHECK(UnownedObject, (obj), TYPE_UNOWNED_OBJECT)
+#define UNOWNED_OBJECT_CLASS(klass) \
+     OBJECT_CLASS_CHECK(UnownedObjectClass, (klass), TYPE_UNOWNED_OBJECT)
+#define UNOWNED_OBJECT_GET_CLASS \
+     OBJECT_GET_CLASS(UnownedObjectClass, (obj), TYPE_UNOWNED_OBJECT)
+#define OBJECT_WEAK_REF (1UL << 31)
+
+typedef struct UnownedObjectClass
+{
+    /*< private >*/
+    ObjectClass parent_class;
+} UnownedObjectClass;
+
+typedef struct UnownedObject
+{
+    /*< private >*/
+    Object parent_obj;
+} UnownedObject;
 
 #endif
diff --git a/qom/object.c b/qom/object.c
index 1812c73..96842c7 100644
--- a/qom/object.c
+++ b/qom/object.c
@@ -705,6 +705,10 @@ void object_ref(Object *obj)
     if (!obj) {
         return;
     }
+    if (atomic_fetch_and(&obj->ref, ~OBJECT_WEAK_REF) & OBJECT_WEAK_REF)
+    {
+        return;
+    }
      atomic_inc(&obj->ref);
 }
 
@@ -713,7 +717,7 @@ void object_unref(Object *obj)
     if (!obj) {
         return;
     }
-    g_assert(obj->ref > 0);
+    g_assert((obj->ref & ~OBJECT_WEAK_REF) > 0);
 
     /* parent always holds a reference to its children */
     if (atomic_fetch_dec(&obj->ref) == 1) {
@@ -1709,6 +1713,12 @@ static void object_instance_init(Object *obj)
     object_property_add_str(obj, "type", qdev_get_type, NULL, NULL);
 }
 
+
+static void unowned_object_instance_init(Object *obj)
+{
+    obj->ref |= OBJECT_WEAK_REF;
+}
+
 static void register_types(void)
 {
     static TypeInfo interface_info = {
@@ -1724,8 +1734,16 @@ static void register_types(void)
         .abstract = true,
     };
 
+    static TypeInfo unowned_object_info = {
+        .name = TYPE_UNOWNED_OBJECT,
+        .instance_size = sizeof(UnownedObject),
+        .instance_init = unowned_object_instance_init,
+        .abstract = true,
+    };
+
     type_interface = type_register_internal(&interface_info);
     type_register_internal(&object_info);
+    type_register_internal(&unowned_object_info);
 }
 
 type_init(register_types)
-- 
1.8.3.1