gh-102304: Move _Py_RefTotal to _PyRuntimeState (gh-102543)

The essentially eliminates the global variable, with the associated benefits. This is also a precursor to isolating this bit of state to PyInterpreterState.

Folks that currently read _Py_RefTotal directly would have to start using _Py_GetGlobalRefTotal() instead.

https://github.com/python/cpython/issues/102304

1 files changed, 76 insertions, 25 deletions

diff --git a/Objects/object.c b/Objects/object.c
index dff5e2a..95f7c96 100644
--- a/Objects/object.c
+++ b/Objects/object.c
@@ -54,37 +54,71 @@ _PyObject_CheckConsistency(PyObject *op, int check_content)
 
 
 #ifdef Py_REF_DEBUG
+/* We keep the legacy symbol around for backward compatibility. */
 Py_ssize_t _Py_RefTotal;
 
+static inline Py_ssize_t
+get_legacy_reftotal(void)
+{
+    return _Py_RefTotal;
+}
+#endif
+
+#ifdef Py_REF_DEBUG
+
+#  define REFTOTAL(runtime) \
+    (runtime)->object_state.reftotal
+
+static inline void
+reftotal_increment(_PyRuntimeState *runtime)
+{
+    REFTOTAL(runtime)++;
+}
+
 static inline void
-reftotal_increment(void)
+reftotal_decrement(_PyRuntimeState *runtime)
 {
-    _Py_RefTotal++;
+    REFTOTAL(runtime)--;
 }
 
 static inline void
-reftotal_decrement(void)
+reftotal_add(_PyRuntimeState *runtime, Py_ssize_t n)
 {
-    _Py_RefTotal--;
+    REFTOTAL(runtime) += n;
 }
 
+static inline Py_ssize_t get_global_reftotal(_PyRuntimeState *);
+
+/* We preserve the number of refs leaked during runtime finalization,
+   so they can be reported if the runtime is initialized again. */
+// XXX We don't lose any information by dropping this,
+// so we should consider doing so.
+static Py_ssize_t last_final_reftotal = 0;
+
 void
-_Py_AddRefTotal(Py_ssize_t n)
+_Py_FinalizeRefTotal(_PyRuntimeState *runtime)
 {
-    _Py_RefTotal += n;
+    last_final_reftotal = get_global_reftotal(runtime);
+    REFTOTAL(runtime) = 0;
 }
 
-Py_ssize_t
-_Py_GetRefTotal(void)
+static inline Py_ssize_t
+get_global_reftotal(_PyRuntimeState *runtime)
 {
-    return _Py_RefTotal;
+    /* For an update from _Py_RefTotal first. */
+    Py_ssize_t legacy = get_legacy_reftotal();
+    return REFTOTAL(runtime) + legacy + last_final_reftotal;
 }
 
+#undef REFTOTAL
+
 void
 _PyDebug_PrintTotalRefs(void) {
+    _PyRuntimeState *runtime = &_PyRuntime;
     fprintf(stderr,
             "[%zd refs, %zd blocks]\n",
-            _Py_GetRefTotal(), _Py_GetAllocatedBlocks());
+            get_global_reftotal(runtime), _Py_GetAllocatedBlocks());
+    /* It may be helpful to also print the "legacy" reftotal separately. */
 }
 #endif /* Py_REF_DEBUG */
 
@@ -139,30 +173,50 @@ _Py_NegativeRefcount(const char *filename, int lineno, PyObject *op)
                            filename, lineno, __func__);
 }
 
-/* This is exposed strictly for use in Py_INCREF(). */
-PyAPI_FUNC(void)
+/* This is used strictly by Py_INCREF(). */
+void
 _Py_IncRefTotal_DO_NOT_USE_THIS(void)
 {
-    reftotal_increment();
+    reftotal_increment(&_PyRuntime);
 }
 
-/* This is exposed strictly for use in Py_DECREF(). */
-PyAPI_FUNC(void)
+/* This is used strictly by Py_DECREF(). */
+void
 _Py_DecRefTotal_DO_NOT_USE_THIS(void)
 {
-    reftotal_decrement();
+    reftotal_decrement(&_PyRuntime);
 }
 
 void
 _Py_IncRefTotal(void)
 {
-    reftotal_increment();
+    reftotal_increment(&_PyRuntime);
 }
 
 void
 _Py_DecRefTotal(void)
 {
-    reftotal_decrement();
+    reftotal_decrement(&_PyRuntime);
+}
+
+void
+_Py_AddRefTotal(Py_ssize_t n)
+{
+    reftotal_add(&_PyRuntime, n);
+}
+
+/* This includes the legacy total
+   and any carried over from the last runtime init/fini cycle. */
+Py_ssize_t
+_Py_GetGlobalRefTotal(void)
+{
+    return get_global_reftotal(&_PyRuntime);
+}
+
+Py_ssize_t
+_Py_GetLegacyRefTotal(void)
+{
+    return get_legacy_reftotal();
 }
 
 #endif /* Py_REF_DEBUG */
@@ -182,21 +236,18 @@ Py_DecRef(PyObject *o)
 void
 _Py_IncRef(PyObject *o)
 {
-#ifdef Py_REF_DEBUG
-    reftotal_increment();
-#endif
     Py_INCREF(o);
 }
 
 void
 _Py_DecRef(PyObject *o)
 {
-#ifdef Py_REF_DEBUG
-    reftotal_decrement();
-#endif
     Py_DECREF(o);
 }
 
+
+/**************************************/
+
 PyObject *
 PyObject_Init(PyObject *op, PyTypeObject *tp)
 {
@@ -2077,7 +2128,7 @@ void
 _Py_NewReference(PyObject *op)
 {
 #ifdef Py_REF_DEBUG
-    reftotal_increment();
+    reftotal_increment(&_PyRuntime);
 #endif
     new_reference(op);
 }