Simplify _MemPoolAttributes to use direct MemoryPoolHandle

Replace weakref pattern with direct MemoryPoolHandle storage in
_MemPoolAttributes. The handle's shared_ptr keeps the underlying
pool alive, so attributes remain accessible after the MR is deleted.

Note: _MemPool retains __weakref__ because the IPC subsystem uses
WeakValueDictionary to track memory resources across processes.

Author: Andy-Jost

cuda_core/cuda/core/_memory/_memory_pool.pxd

@@ -19,6 +19,16 @@ cdef class _MemPool(MemoryResource):
         object                __weakref__
 
 
+cdef class _MemPoolAttributes:
+    cdef:
+        MemoryPoolHandle _h_pool
+
+    @staticmethod
+    cdef _MemPoolAttributes _init(MemoryPoolHandle h_pool)
+
+    cdef int _getattribute(self, cydriver.CUmemPool_attribute attr_enum, void* value) except? -1
+
+
 cdef class _MemPoolOptions:
 
     cdef:

cuda_core/cuda/core/_memory/_memory_pool.pyx

@@ -29,7 +29,6 @@ from cuda.core._utils.cuda_utils cimport (
 )
 
 import platform  # no-cython-lint
-import weakref
 
 from cuda.core._utils.cuda_utils import driver
 
@@ -45,16 +44,15 @@ cdef class _MemPoolOptions:
 
 
 cdef class _MemPoolAttributes:
-    cdef:
-        object _mr_weakref
+    """Provides access to memory pool attributes."""
 
     def __init__(self, *args, **kwargs):
         raise RuntimeError("_MemPoolAttributes cannot be instantiated directly. Please use MemoryResource APIs.")
 
-    @classmethod
-    def _init(cls, mr):
-        cdef _MemPoolAttributes self = _MemPoolAttributes.__new__(cls)
-        self._mr_weakref = mr
+    @staticmethod
+    cdef _MemPoolAttributes _init(MemoryPoolHandle h_pool):
+        cdef _MemPoolAttributes self = _MemPoolAttributes.__new__(_MemPoolAttributes)
+        self._h_pool = h_pool
         return self
 
     def __repr__(self):
@@ -64,12 +62,8 @@ cdef class _MemPoolAttributes:
         )
 
     cdef int _getattribute(self, cydriver.CUmemPool_attribute attr_enum, void* value) except?-1:
-        cdef _MemPool mr = <_MemPool>(self._mr_weakref())
-        if mr is None:
-            raise RuntimeError("_MemPool is expired")
-        cdef cydriver.CUmemoryPool pool_handle = as_cu(mr._h_pool)
         with nogil:
-            HANDLE_RETURN(cydriver.cuMemPoolGetAttribute(pool_handle, attr_enum, value))
+            HANDLE_RETURN(cydriver.cuMemPoolGetAttribute(as_cu(self._h_pool), attr_enum, value))
         return 0
 
     @property
@@ -197,8 +191,7 @@ cdef class _MemPool(MemoryResource):
     def attributes(self) -> _MemPoolAttributes:
         """Memory pool attributes."""
         if self._attributes is None:
-            ref = weakref.ref(self)
-            self._attributes = _MemPoolAttributes._init(ref)
+            self._attributes = _MemPoolAttributes._init(self._h_pool)
         return self._attributes
 
     @property

cuda_core/tests/test_memory.py

@@ -1162,7 +1162,7 @@ def test_mempool_attributes_repr(memory_resource_factory):
 
 
 def test_mempool_attributes_ownership(memory_resource_factory):
-    """Ensure the attributes bundle handles references correctly for all memory resource types."""
+    """Ensure the attributes bundle keeps the pool alive via the handle."""
     MR, MRops = memory_resource_factory
     device = Device()
 
@@ -1190,21 +1190,9 @@ def test_mempool_attributes_ownership(memory_resource_factory):
     mr.close()
     del mr
 
-    # After deleting the memory resource, the attributes suite is disconnected.
-    with pytest.raises(RuntimeError, match="is expired"):
-        _ = attributes.used_mem_high
-
-    # Even when a new object is created (we found a case where the same
-    # mempool handle was really reused).
-    if MR is DeviceMemoryResource:
-        mr = MR(device, dict(max_size=POOL_SIZE))  # noqa: F841
-    elif MR is PinnedMemoryResource:
-        mr = MR(dict(max_size=POOL_SIZE))  # noqa: F841
-    elif MR is ManagedMemoryResource:
-        mr = create_managed_memory_resource_or_skip(dict())  # noqa: F841
-
-    with pytest.raises(RuntimeError, match="is expired"):
-        _ = attributes.used_mem_high
+    # The attributes bundle keeps the pool alive via MemoryPoolHandle,
+    # so accessing attributes still works even after the MR is deleted.
+    _ = attributes.used_mem_high  # Should not raise
 
 
 # Ensure that memory views dellocate their reference to dlpack tensors