Declare free-threading support in the sparse extension

CHANGELOG.md

@@ -118,6 +118,7 @@ This release is compatible with NumPy 2.5.
 * Fixed incorrect results of `dpnp.tensor.vecdot` in some cases with strided outputs and of `dpnp.tensor` reductions, `dpnp.tensor.vecdot` and `dpnp.tensor.matmul` on large inputs with some data types [#3082](https://github.com/IntelPython/dpnp/pull/3082)
 * Fixed `dpnp.median` and `dpnp.nanmedian` raising a `ValueError` for a tuple `axis` when a kept dimension has size 0 [#3081](https://github.com/IntelPython/dpnp/pull/3081)
 * Fixed a `RuntimeError` raised by `dpnp.tensor` kernels launched over more than `INT_MAX` work-items when built with DPC++ compiler 2026.2 or newer, by also passing `-fno-sycl-id-queries-fit-in-int` to the linker [#3089](https://github.com/IntelPython/dpnp/pull/3089)
+* Fixed importing `dpnp.scipy.sparse` re-enabling the GIL on free-threaded Python builds, because its pybind11 extension did not declare free-threading support [#3101](https://github.com/IntelPython/dpnp/pull/3101)
 
 ### Security
 

dpnp/backend/extensions/sparse/sparse_py.cpp

@@ -43,7 +43,7 @@ using dpnp::extensions::sparse::sparse_gemv_compute;
 using dpnp::extensions::sparse::sparse_gemv_init;
 using dpnp::extensions::sparse::sparse_gemv_release;
 
-PYBIND11_MODULE(_sparse_impl, m)
+PYBIND11_MODULE(_sparse_impl, m, py::mod_gil_not_used())
 {
     init_sparse_gemv_dispatch_tables();
 

dpnp/tests/test_free_threading.py

@@ -0,0 +1,49 @@
+import os
+import subprocess
+import sys
+import sysconfig
+
+import pytest
+
+# Prints the first dpnp module whose import re-enables the GIL,
+# "deps" if a dependency already re-enabled it, or "ok".
+_IMPORT_ALL = """
+import importlib, importlib.machinery, pathlib, sys
+import dpctl, numpy
+if sys._is_gil_enabled():
+    print("deps")
+    sys.exit()
+import dpnp
+if sys._is_gil_enabled():
+    print("dpnp")
+    sys.exit()
+root = pathlib.Path(dpnp.__file__).parent
+suffix = importlib.machinery.EXTENSION_SUFFIXES[0]
+for path in sorted(root.rglob("*" + suffix)):
+    rel = path.relative_to(root.parent)
+    name = ".".join(rel.parts[:-1] + (path.name[: -len(suffix)],))
+    importlib.import_module(name)
+    if sys._is_gil_enabled():
+        print(name)
+        sys.exit()
+print("ok")
+"""
+
+
+@pytest.mark.skipif(
+    not sysconfig.get_config_var("Py_GIL_DISABLED"),
+    reason="requires a free-threaded Python build",
+)
+def test_extensions_keep_gil_disabled():
+    env = {k: v for k, v in os.environ.items() if k != "PYTHON_GIL"}
+    res = subprocess.run(
+        [sys.executable, "-c", _IMPORT_ALL],
+        capture_output=True,
+        text=True,
+        env=env,
+    )
+    assert res.returncode == 0, res.stderr
+    out = res.stdout.strip()
+    if out == "deps":
+        pytest.skip("a dependency re-enabled the GIL")
+    assert out == "ok", f"importing {out} re-enabled the GIL"