1 files changed, 29 insertions, 0 deletions
diff --git a/Objects/object.c b/Objects/object.c
index 7cc74a8..052dea9 100644
--- a/Objects/object.c
+++ b/Objects/object.c
@@ -2519,6 +2519,35 @@ _PyObject_SetDeferredRefcount(PyObject *op)
 #endif
 }
 
+int
+PyUnstable_Object_EnableDeferredRefcount(PyObject *op)
+{
+#ifdef Py_GIL_DISABLED
+    if (!PyType_IS_GC(Py_TYPE(op))) {
+        // Deferred reference counting doesn't work
+        // on untracked types.
+        return 0;
+    }
+
+    uint8_t bits = _Py_atomic_load_uint8(&op->ob_gc_bits);
+    if ((bits & _PyGC_BITS_DEFERRED) != 0)
+    {
+        // Nothing to do.
+        return 0;
+    }
+
+    if (_Py_atomic_compare_exchange_uint8(&op->ob_gc_bits, &bits, bits | _PyGC_BITS_DEFERRED) == 0)
+    {
+        // Someone beat us to it!
+        return 0;
+    }
+    _Py_atomic_add_ssize(&op->ob_ref_shared, _Py_REF_SHARED(_Py_REF_DEFERRED, 0));
+    return 1;
+#else
+    return 0;
+#endif
+}
+
 void
 _Py_ResurrectReference(PyObject *op)
 {