[mlir][python] fix PyDenseResourceElementsAttribute finalizer (#150561)

This PR melds #150137 and
#149414 *and* partially reverts
#124832.

The summary is the `PyDenseResourceElementsAttribute` finalizer/deleter
has/had two problems

1. wasn't threadsafe (can be called from a different thread than that
which currently holds the GIL)
2. can be called while the interpreter is "not initialized"

#124832 for some reason decides
to re-initialize the interpreter to avoid case 2 and runs afoul of the
fact that `Py_IsInitialized` can be false during the finalization of the
interpreter itself (e.g., at the end of a script).

I don't know why this decision was made (I missed the PR) but I believe
we should never be calling
[Py_Initialize](https://docs.python.org/3/c-api/init.html#c.Py_Initialize):

> In an application \*\*\*\***embedding Python**\*\*\*\*, this should be
called before using any other Python/C API functions

**but we aren't embedding Python**!

So therefore we will only be in case 2 when the interpreter is being
finalized and in that case we should just leak the buffer.

Note,
[lldb](https://github.com/llvm/llvm-project/blob/548ca9e97673a168023a616d311d901ca04b29a3/lldb/source/Plugins/ScriptInterpreter/Python/PythonDataObjects.cpp#L81-L93)
does a similar sort of thing for its finalizers.

Co-authored-by: Anton Korobeynikov <[email protected]>
Co-authored-by: Max Manainen <[email protected]>

Co-authored-by: Anton Korobeynikov <[email protected]>
Co-authored-by: Max Manainen <[email protected]>

Author: 3 people

mlir/lib/Bindings/Python/IRAttributes.cpp

@@ -16,8 +16,8 @@
 #include "NanobindUtils.h"
 #include "mlir-c/BuiltinAttributes.h"
 #include "mlir-c/BuiltinTypes.h"
-#include "mlir/Bindings/Python/NanobindAdaptors.h"
 #include "mlir/Bindings/Python/Nanobind.h"
+#include "mlir/Bindings/Python/NanobindAdaptors.h"
 #include "llvm/ADT/ScopeExit.h"
 #include "llvm/Support/raw_ostream.h"
 
@@ -1428,6 +1428,12 @@ class PyDenseIntElementsAttribute
   }
 };
 
+// Check if the python version is less than 3.13. Py_IsFinalizing is a part
+// of stable ABI since 3.13 and before it was available as _Py_IsFinalizing.
+#if PY_VERSION_HEX < 0x030d0000
+#define Py_IsFinalizing _Py_IsFinalizing
+#endif
+
 class PyDenseResourceElementsAttribute
     : public PyConcreteAttribute<PyDenseResourceElementsAttribute> {
 public:
@@ -1474,8 +1480,9 @@ class PyDenseResourceElementsAttribute
     // The userData is a Py_buffer* that the deleter owns.
     auto deleter = [](void *userData, const void *data, size_t size,
                       size_t align) {
-      if (!Py_IsInitialized())
-        Py_Initialize();
+      if (Py_IsFinalizing())
+        return;
+      assert(Py_IsInitialized() && "expected interpreter to be initialized");
       Py_buffer *ownedView = static_cast<Py_buffer *>(userData);
       nb::gil_scoped_acquire gil;
       PyBuffer_Release(ownedView);

mlir/test/python/ir/array_attributes.py

@@ -31,6 +31,7 @@ def testGetDenseElementsUnsupported():
             # CHECK: unimplemented array format conversion from format:
             print(e)
 
+
 # CHECK-LABEL: TEST: testGetDenseElementsUnSupportedTypeOkIfExplicitTypeProvided
 @run
 def testGetDenseElementsUnSupportedTypeOkIfExplicitTypeProvided():
@@ -41,8 +42,9 @@ def testGetDenseElementsUnSupportedTypeOkIfExplicitTypeProvided():
         # realistic example would be a NumPy extension type like the bfloat16
         # type from the ml_dtypes package, which isn't a dependency of this
         # test.
-        attr = DenseElementsAttr.get(array.view(np.datetime64),
-                                     type=IntegerType.get_signless(64))
+        attr = DenseElementsAttr.get(
+            array.view(np.datetime64), type=IntegerType.get_signless(64)
+        )
         # CHECK: dense<{{\[}}[1, 2, 3], [4, 5, 6]]> : tensor<2x3xi64>
         print(attr)
         # CHECK: {{\[}}[1 2 3]
@@ -135,6 +137,7 @@ def testGetDenseElementsFromListMixedTypes():
 # Splats.
 ################################################################################
 
+
 # CHECK-LABEL: TEST: testGetDenseElementsSplatInt
 @run
 def testGetDenseElementsSplatInt():
@@ -617,3 +620,18 @@ def test_attribute(context, mview):
     # CHECK: BACKING MEMORY DELETED
     # CHECK: EXIT FUNCTION
     print("EXIT FUNCTION")
+
+
+# CHECK-LABEL: TEST: testDanglingResource
+print("TEST: testDanglingResource")
+# see https://github.com/llvm/llvm-project/pull/149414, https://github.com/llvm/llvm-project/pull/150137, https://github.com/llvm/llvm-project/pull/150561
+# This error occurs only when there is an alive context with a DenseResourceElementsAttr
+# in the end of the program, so we put it here without an encapsulating function.
+ctx = Context()
+
+with ctx, Location.unknown():
+    DenseResourceElementsAttr.get_from_buffer(
+        memoryview(np.array([1, 2, 3])),
+        "some_resource",
+        RankedTensorType.get((3,), IntegerType.get_signed(32)),
+    )