Revert pythongh-127266: avoid data races when updating type slots (pythongh-131174) (pythongh-133129)

This is triggering deadlocks in test_opcache.  See pythonGH-133130 for stack trace.

Author: nascheme

Include/internal/pycore_interp_structs.h

@@ -667,11 +667,8 @@ struct _Py_interp_cached_objects {
 
     /* object.__reduce__ */
     PyObject *objreduce;
-#ifndef Py_GIL_DISABLED
-    /* resolve_slotdups() */
     PyObject *type_slots_pname;
     pytype_slotdef *type_slots_ptrs[MAX_EQUIV];
-#endif
 
     /* TypeVar and related types */
     PyTypeObject *generic_type;

Include/internal/pycore_object.h

@@ -313,7 +313,7 @@ extern int _PyDict_CheckConsistency(PyObject *mp, int check_content);
 // Fast inlined version of PyType_HasFeature()
 static inline int
 _PyType_HasFeature(PyTypeObject *type, unsigned long feature) {
-    return ((type->tp_flags) & feature) != 0;
+    return ((FT_ATOMIC_LOAD_ULONG_RELAXED(type->tp_flags) & feature) != 0);
 }
 
 extern void _PyType_InitCache(PyInterpreterState *interp);

Include/internal/pycore_typeobject.h

@@ -134,6 +134,7 @@ extern int _PyType_AddMethod(PyTypeObject *, PyMethodDef *);
 extern void _PyType_SetFlagsRecursive(PyTypeObject *self, unsigned long mask,
                                       unsigned long flags);
 
+extern unsigned int _PyType_GetVersionForCurrentState(PyTypeObject *tp);
 PyAPI_FUNC(void) _PyType_SetVersion(PyTypeObject *tp, unsigned int version);
 PyTypeObject *_PyType_LookupByVersion(unsigned int version);
 

Include/object.h

@@ -620,12 +620,6 @@ given type object has a specified feature.
 #define Py_TPFLAGS_HAVE_FINALIZE (1UL << 0)
 #define Py_TPFLAGS_HAVE_VERSION_TAG   (1UL << 18)
 
-// Flag values for ob_flags (16 bits available, if SIZEOF_VOID_P > 4).
-#define _Py_IMMORTAL_FLAGS (1 << 0)
-#define _Py_STATICALLY_ALLOCATED_FLAG (1 << 2)
-#if defined(Py_GIL_DISABLED) && defined(Py_DEBUG)
-#define _Py_TYPE_REVEALED_FLAG (1 << 3)
-#endif
 
 #define Py_CONSTANT_NONE 0
 #define Py_CONSTANT_FALSE 1
@@ -782,7 +776,11 @@ PyType_HasFeature(PyTypeObject *type, unsigned long feature)
     // PyTypeObject is opaque in the limited C API
     flags = PyType_GetFlags(type);
 #else
-    flags = type->tp_flags;
+#   ifdef Py_GIL_DISABLED
+        flags = _Py_atomic_load_ulong_relaxed(&type->tp_flags);
+#   else
+        flags = type->tp_flags;
+#   endif
 #endif
     return ((flags & feature) != 0);
 }

Include/refcount.h

@@ -19,6 +19,9 @@ immortal. The latter should be the only instances that require
 cleanup during runtime finalization.
 */
 
+#define _Py_STATICALLY_ALLOCATED_FLAG 4
+#define _Py_IMMORTAL_FLAGS 1
+
 #if SIZEOF_VOID_P > 4
 /*
 In 64+ bit systems, any object whose 32 bit reference count is >= 2**31

Lib/test/test_opcache.py

@@ -576,7 +576,6 @@ class TestRacesDoNotCrash(TestBase):
     # Careful with these. Bigger numbers have a higher chance of catching bugs,
     # but you can also burn through a *ton* of type/dict/function versions:
     ITEMS = 1000
-    SMALL_ITEMS = 100
     LOOPS = 4
     WRITERS = 2
 
@@ -620,7 +619,7 @@ class C:
                 __getitem__ = lambda self, item: None
 
             items = []
-            for _ in range(self.SMALL_ITEMS):
+            for _ in range(self.ITEMS):
                 item = C()
                 items.append(item)
             return items
@@ -791,7 +790,7 @@ class C:
                 __getattribute__ = lambda self, name: None
 
             items = []
-            for _ in range(self.SMALL_ITEMS):
+            for _ in range(self.ITEMS):
                 item = C()
                 items.append(item)
             return items