[dynamo] handle 3.13.0 __dict__ watcher bug (pytorch#138284)

python/cpython#116115 introduced a bug (python/cpython#125608) where changing the attributes of an object may not fire the dict watchers registered to the object's `__dict__`. It has been fixed by python/cpython#125611 but will only be in 3.13.1+.

This PR disables the dict watcher guard shortcut for `__dict__`s on 3.13.0 and warns the user to try using 3.13.1+ instead. We also added a simple test to check for this functionality in the future.

Pull Request resolved: pytorch#138284
Approved by: https://github.com/jansel
ghstack dependencies: pytorch#138030

test/dynamo/test_modules.py

@@ -1261,6 +1261,26 @@ def test_self_mutating1(self):
         else:
             self.assertExpectedInline(cnt.frame_count, """1""")
 
+    def test_nn_module_setattr(self):
+        class Mod(torch.nn.Module):
+            def __init__(self):
+                super().__init__()
+                self.var = 0
+
+        @torch.compile(backend="eager", dynamic=False)
+        def f(x, m):
+            return x + m.var
+
+        inp = torch.ones(3)
+        m = Mod()
+
+        self.assertEqual(f(inp, m), inp)
+        # In 3.13.0, setattr will not fire a __dict__'s watchers,
+        # so guards may not be invalidated.
+        m.var = 1
+        # should trigger a recompile
+        self.assertEqual(f(inp, m), inp + 1)
+
     @patch.object(torch._dynamo.config, "raise_on_ctx_manager_usage", False)
     def test_generation_tag(self):
         cnt = torch._dynamo.testing.CompileCounter()

torch/_dynamo/guards.py

@@ -18,6 +18,7 @@
 import textwrap
 import time
 import types
+import warnings
 import weakref
 from contextlib import contextmanager
 from copy import deepcopy
@@ -651,6 +652,20 @@ def guard_on_dict_keys_and_order(self, value, guard):
                     key, get_verbose_code_parts(f"{key_source} == {key!r}", guard)
                 )
 
+    @staticmethod
+    def _get_generic_dict_manager_example_value(example_value):
+        # due to a bug in 3.13.0 (introduced by https://github.com/python/cpython/pull/116115,
+        # reported in https://github.com/python/cpython/issues/125608,
+        # fixed by https://github.com/python/cpython/pull/125611), we cannot take
+        # advantage of __dict__ versions to speed up guard checks.
+        if sys.version_info >= (3, 13) and sys.version_info < (3, 13, 1):
+            warnings.warn(
+                "Guards may run slower on Python 3.13.0. Consider upgrading to Python 3.13.1+.",
+                RuntimeWarning,
+            )
+            return None
+        return example_value
+
     def getattr_on_nn_module(
         self,
         source,
@@ -776,7 +791,7 @@ def getitem_on_dict_mgr(
             # Guard Manager
             mod_generic_dict_manager = base_guard_manager.get_generic_dict_manager(
                 source=mod_dict_source,
-                example_value=mod_dict,
+                example_value=self._get_generic_dict_manager_example_value(mod_dict),
                 guard_manager_enum=GuardManagerType.GUARD_MANAGER,
             )
 
@@ -1271,7 +1286,7 @@ def NOT_PRESENT_IN_GENERIC_DICT(self, guard: Guard, attr=None) -> None:
         mod_dict_source = f"{guard.name}.__dict__"
         mod_generic_dict_manager = base_manager.get_generic_dict_manager(
             source=mod_dict_source,
-            example_value=val.__dict__,
+            example_value=self._get_generic_dict_manager_example_value(val.__dict__),
             guard_manager_enum=GuardManagerType.GUARD_MANAGER,
         )
 
@@ -2261,12 +2276,16 @@ def add_code_part(code_part, guard, log_only=False):
             structured_guard_fns.append(
                 lambda: {
                     "code": code_part,
-                    "stack": structured.from_traceback(guard.stack.summary())
-                    if guard.stack
-                    else None,
-                    "user_stack": structured.from_traceback(guard.user_stack)
-                    if guard.user_stack
-                    else None,
+                    "stack": (
+                        structured.from_traceback(guard.stack.summary())
+                        if guard.stack
+                        else None
+                    ),
+                    "user_stack": (
+                        structured.from_traceback(guard.user_stack)
+                        if guard.user_stack
+                        else None
+                    ),
                 }
             )
 

torch/csrc/dynamo/guards.cpp

@@ -17,6 +17,8 @@
 #include <torch/csrc/utils/pythoncapi_compat.h>
 #include <torch/extension.h>
 
+#include <torch/csrc/dynamo/debug_macros.h>
+
 #ifdef USE_CUDA
 #include <ATen/cuda/EmptyTensor.h>
 #endif
@@ -655,7 +657,7 @@ static PyObject* check_obj_id(PyObject* dummy, PyObject* args) {
 
 static std::unordered_map<PyObject*, uint64_t> dict_version_map;
 static int dict_version_watcher_id;
-static uint64_t global_dict_version_id = 0;
+static uint64_t global_dict_version_id = 1;
 static int dict_version_watch_callback(
     PyDict_WatchEvent event,
     PyObject* dict,