Revert "[User-streams] Make torch.Event weakref compatible (#164522)"

This reverts commit cde81e92b9.

Reverted https://github.com/pytorch/pytorch/pull/164522 on behalf of https://github.com/atalman due to Breaks periodic: test/dynamo/test_streams.py::TestStreams::test_stream_weakref [GH job link](https://github.com/pytorch/pytorch/actions/runs/18909552619/job/53979171605) [HUD commit link](cde81e92b9) ([comment](https://github.com/pytorch/pytorch/pull/164522#issuecomment-3462450571))

test/dynamo/test_compile.py

@@ -234,6 +234,27 @@ class InPlaceCompilationTests(TestCase):
         with self.assertRaises(IndexError):
             fn(torch.randn(10), 99)
 
+    def test_list_bad_weakref(self):
+        import weakref
+
+        a = torch.Event()
+        with self.assertRaises(TypeError):
+            weakref.ref(a)
+
+        @torch.compile(backend="eager")
+        class Mod(torch.nn.Module):
+            def __init__(self, event):
+                super().__init__()
+                self.event = event
+
+            def forward(self, x):
+                return x * int(self.event.query())
+
+        e = torch.Event()
+        m = Mod(e)
+        a = torch.randn(10)
+        self.assertEqual(m(a), a)
+
 
 # The private variants of the below functions are extensively tested
 # So as long as the signatures match we're good

test/dynamo/test_streams.py

@@ -20,10 +20,6 @@ class TestStreams(torch._dynamo.test_case.TestCase):
         s = torch.Stream()
         weakref.ref(s)
 
-    def test_event_weakref(self):
-        e = torch.Event()
-        weakref.ref(e)
-
     @requires_cuda
     def test_run_opcheck(self):
         from torch._dynamo.variables.streams import fork_stream, join_stream

torch/csrc/Event.cpp

@@ -49,7 +49,6 @@ static PyObject* THPEvent_pynew(
   }
 
   THPEvent* self = reinterpret_cast<THPEvent*>(ptr.get());
-  self->weakreflist = nullptr;
 
   // TODO: blocking and interprocess are not supported yet. To support them, the
   // flag system of c10::Event needs to be refactored. C10::Event should also
@@ -74,7 +73,6 @@ PyObject* THPEvent_new(c10::DeviceType device_type, c10::EventFlag flag) {
   auto self = THPObjectPtr{type->tp_alloc(type, 0)};
   TORCH_CHECK(self, "Failed to allocate memory for Event");
   auto self_ = reinterpret_cast<THPEvent*>(self.get());
-  self_->weakreflist = nullptr;
   new (&self_->event) c10::Event(device_type, flag);
   return self.release();
 }
@@ -84,7 +82,6 @@ static void THPEvent_dealloc(THPEvent* self) {
     pybind11::gil_scoped_release no_gil{};
     self->event.~Event();
   }
-  PyObject_ClearWeakRefs((PyObject*)self);
   Py_TYPE(self)->tp_free(reinterpret_cast<PyObject*>(self));
 }
 
@@ -285,8 +282,7 @@ static PyMethodDef THPEvent_methods[] = {
     {"synchronize", THPEvent_synchronize, METH_NOARGS, nullptr},
     {"ipc_handle", THPEvent_ipc_handle, METH_NOARGS, nullptr},
     {nullptr}};
-#pragma GCC diagnostic push
-#pragma GCC diagnostic ignored "-Winvalid-offsetof"
+
 PyTypeObject THPEventType = {
     PyVarObject_HEAD_INIT(nullptr, 0)
     "torch.Event", /* tp_name */
@@ -312,7 +308,7 @@ PyTypeObject THPEventType = {
     nullptr, /* tp_traverse */
     nullptr, /* tp_clear */
     nullptr, /* tp_richcompare */
-    offsetof(THPEvent, weakreflist), /* tp_weaklistoffset */
+    0, /* tp_weaklistoffset */
     nullptr, /* tp_iter */
     nullptr, /* tp_iternext */
     THPEvent_methods, /* tp_methods */
@@ -327,7 +323,6 @@ PyTypeObject THPEventType = {
     nullptr, /* tp_alloc */
     THPEvent_pynew, /* tp_new */
 };
-#pragma GCC diagnostic pop
 
 void THPEvent_init(PyObject* module) {
   THPEventClass = &THPEventType;

torch/csrc/Event.h

@@ -7,7 +7,6 @@
 struct TORCH_API THPEvent {
   PyObject_HEAD
   c10::Event event;
-  PyObject* weakreflist;
 };
 TORCH_API extern PyTypeObject* THPEventClass;
 TORCH_API extern PyTypeObject THPEventType;