[user-streams] Make device-agnostic streams weakref compatible (#164304)

Pull Request resolved: https://github.com/pytorch/pytorch/pull/164304
Approved by: https://github.com/williamwen42, https://github.com/colesbury
ghstack dependencies: #162903, #164343, #164344, #164507, #162901

test/dynamo/test_streams.py

@@ -1,4 +1,5 @@
 # Owner(s): ["module: dynamo"]
+import weakref
 
 import torch
 import torch._dynamo.test_case
@@ -15,6 +16,10 @@ class TestStreams(torch._dynamo.test_case.TestCase):
     def tearDownClass(cls):
         super().tearDownClass()
 
+    def test_stream_weakref(self):
+        s = torch.Stream()
+        weakref.ref(s)
+
     @requires_cuda
     def test_run_opcheck(self):
         from torch._dynamo.variables.streams import fork_stream, join_stream

torch/csrc/Stream.cpp

@@ -95,6 +95,7 @@ static PyObject* THPStream_pynew(
   self->device_index = static_cast<int64_t>(stream_opt->device_index());
   self->device_type = static_cast<int64_t>(stream_opt->device_type());
   self->context = nullptr;
+  self->weakreflist = nullptr;
 
   return static_cast<PyObject*>(ptr.release());
   END_HANDLE_TH_ERRORS
@@ -114,11 +115,13 @@ PyObject* THPStream_Wrap(const c10::Stream& stream) {
   self->device_index = static_cast<int64_t>(stream.device_index());
   self->device_type = static_cast<int64_t>(stream.device_type());
   self->context = nullptr;
+  self->weakreflist = nullptr;
   return ptr.release();
   END_HANDLE_TH_ERRORS
 }
 
 static void THPStream_dealloc(THPStream* self) {
+  PyObject_ClearWeakRefs((PyObject*)self);
   Py_TYPE(self)->tp_free(reinterpret_cast<PyObject*>(self));
 }
 
@@ -444,7 +447,7 @@ static PyTypeObject THPStreamType = {
     nullptr, /* tp_traverse */
     nullptr, /* tp_clear */
     THPStream_richcompare, /* tp_richcompare */
-    0, /* tp_weaklistoffset */
+    offsetof(THPStream, weakreflist), /* tp_weaklistoffset */
     nullptr, /* tp_iter */
     nullptr, /* tp_iternext */
     // NOLINTNEXTLINE(*const-cast)

torch/csrc/Stream.h

@@ -13,6 +13,7 @@ struct THPStream {
   int64_t device_index;
   // Used to switch stream context management, initialized lazily.
   PyObject* context;
+  PyObject* weakreflist;
 };
 extern TORCH_API PyTypeObject* THPStreamClass;