Updates KernelAttributes to avoid possible dangling handles. (#957)

* Updates KernelAttributes to avoid possible dangling handles.
* Simplifies the caching logic in KernelAttributes.

Author: Andy-Jost

cuda_core/cuda/core/experimental/_module.py

@@ -2,6 +2,7 @@
 #
 # SPDX-License-Identifier: Apache-2.0
 
+import weakref
 from collections import namedtuple
 from typing import Optional, Union
 from warnings import warn
@@ -60,12 +61,12 @@ class KernelAttributes:
     def __new__(self, *args, **kwargs):
         raise RuntimeError("KernelAttributes cannot be instantiated directly. Please use Kernel APIs.")
 
-    slots = ("_handle", "_cache", "_backend_version", "_loader")
+    slots = ("_kernel", "_cache", "_backend_version", "_loader")
 
     @classmethod
-    def _init(cls, handle):
+    def _init(cls, kernel):
         self = super().__new__(cls)
-        self._handle = handle
+        self._kernel = weakref.ref(kernel)
         self._cache = {}
 
         self._backend_version = "new" if (_py_major_ver >= 12 and _driver_ver >= 12000) else "old"
@@ -74,20 +75,23 @@ def _init(cls, handle):
 
     def _get_cached_attribute(self, device_id: int, attribute: driver.CUfunction_attribute) -> int:
         """Helper function to get a cached attribute or fetch and cache it if not present."""
-        if device_id in self._cache and attribute in self._cache[device_id]:
-            return self._cache[device_id][attribute]
+        cache_key = device_id, attribute
+        result = self._cache.get(cache_key, cache_key)
+        if result is not cache_key:
+            return result
+        kernel = self._kernel()
+        if kernel is None:
+            raise RuntimeError("Cannot access kernel attributes for expired Kernel object")
         if self._backend_version == "new":
-            result = handle_return(self._loader["attribute"](attribute, self._handle, device_id))
+            result = handle_return(self._loader["attribute"](attribute, kernel._handle, device_id))
         else:  # "old" backend
             warn(
                 "Device ID argument is ignored when getting attribute from kernel when cuda version < 12. ",
                 RuntimeWarning,
                 stacklevel=2,
             )
-            result = handle_return(self._loader["attribute"](attribute, self._handle))
-        if device_id not in self._cache:
-            self._cache[device_id] = {}
-        self._cache[device_id][attribute] = result
+            result = handle_return(self._loader["attribute"](attribute, kernel._handle))
+        self._cache[cache_key] = result
         return result
 
     def max_threads_per_block(self, device_id: int = None) -> int:
@@ -365,7 +369,7 @@ class Kernel:
 
     """
 
-    __slots__ = ("_handle", "_module", "_attributes", "_occupancy")
+    __slots__ = ("_handle", "_module", "_attributes", "_occupancy", "__weakref__")
 
     def __new__(self, *args, **kwargs):
         raise RuntimeError("Kernel objects cannot be instantiated directly. Please use ObjectCode APIs.")
@@ -385,7 +389,7 @@ def _from_obj(cls, obj, mod):
     def attributes(self) -> KernelAttributes:
         """Get the read-only attributes of this kernel."""
         if self._attributes is None:
-            self._attributes = KernelAttributes._init(self._handle)
+            self._attributes = KernelAttributes._init(self)
         return self._attributes
 
     def _get_arguments_info(self, param_info=False) -> tuple[int, list[ParamInfo]]: