PYTHON-4450 Support free-threaded Python 3.13t with no-GIL (#1906)

.github/workflows/dist.yml

@@ -67,7 +67,7 @@ jobs:
         # Note: the default manylinux is manylinux2014
         run: |
           python -m pip install -U pip
-          python -m pip install "cibuildwheel>=2.17,<3"
+          python -m pip install "cibuildwheel>=2.20,<3"
 
       - name: Build wheels
         env:
@@ -89,6 +89,9 @@ jobs:
           ls wheelhouse/*cp310*.whl
           ls wheelhouse/*cp311*.whl
           ls wheelhouse/*cp312*.whl
+          ls wheelhouse/*cp313*.whl
+          # Free-threading builds:
+          ls wheelhouse/*cp313t*.whl
 
       - uses: actions/upload-artifact@v4
         with:

.github/workflows/test-python.yml

@@ -51,11 +51,18 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-20.04]
-        python-version: ["3.9", "pypy-3.9", "3.13"]
+        python-version: ["3.9", "pypy-3.9", "3.13", "3.13t"]
     name: CPython ${{ matrix.python-version }}-${{ matrix.os }}
     steps:
       - uses: actions/checkout@v4
-      - name: Setup Python
+      - if: ${{ matrix.python-version == '3.13t' }}
+        name: Setup free-threaded Python
+        uses: deadsnakes/action@v3.2.0
+        with:
+          python-version: 3.13
+          nogil: true
+      - if: ${{ matrix.python-version != '3.13t' }}
+        name: Setup Python
         uses: actions/setup-python@v5
         with:
           python-version: ${{ matrix.python-version }}
@@ -65,9 +72,13 @@ jobs:
       - name: Install dependencies
         run: |
           pip install -U pip
-          if [ "${{ matrix.python-version }}" == "3.13" ]; then
+          if [[ "${{ matrix.python-version }}" == "3.13" ]]; then
             pip install --pre cffi setuptools
             pip install --no-build-isolation hatch
+          elif [[ "${{ matrix.python-version }}" == "3.13t" ]]; then
+            # Hatch can't be installed on 3.13t, use pytest directly.
+            pip install .
+            pip install -r requirements/test.txt
           else
             pip install hatch
           fi
@@ -77,7 +88,11 @@ jobs:
           mongodb-version: 6.0
       - name: Run tests
         run: |
-          hatch run test:test
+          if [[ "${{ matrix.python-version }}" == "3.13t" ]]; then
+            pytest -v --durations=5 --maxfail=10
+          else
+            hatch run test:test
+          fi
 
   doctest:
     runs-on: ubuntu-latest

bson/_cbsonmodule.c

@@ -3184,6 +3184,9 @@ static PyModuleDef_Slot _cbson_slots[] = {
     {Py_mod_exec, _cbson_exec},
 #if defined(Py_MOD_MULTIPLE_INTERPRETERS_SUPPORTED)
     {Py_mod_multiple_interpreters, Py_MOD_MULTIPLE_INTERPRETERS_SUPPORTED},
+#endif
+#if PY_VERSION_HEX >= 0x030D0000
+    {Py_mod_gil, Py_MOD_GIL_NOT_USED},
 #endif
     {0, NULL},
 };

doc/changelog.rst

@@ -12,6 +12,8 @@ PyMongo 4.11 brings a number of changes including:
 
 - Dropped support for Python 3.8.
 - Dropped support for MongoDB 3.6.
+- Added support for free-threaded Python with the GIL disabled. For more information see:
+  `Free-threaded CPython <https://docs.python.org/3.13/whatsnew/3.13.html#whatsnew313-free-threaded-cpython>`_.
 
 Issues Resolved
 ...............

pymongo/_cmessagemodule.c

@@ -1022,6 +1022,9 @@ static PyModuleDef_Slot _cmessage_slots[] = {
     {Py_mod_exec, _cmessage_exec},
 #ifdef Py_MOD_MULTIPLE_INTERPRETERS_SUPPORTED
     {Py_mod_multiple_interpreters, Py_MOD_MULTIPLE_INTERPRETERS_SUPPORTED},
+#endif
+#if PY_VERSION_HEX >= 0x030D0000
+    {Py_mod_gil, Py_MOD_GIL_NOT_USED},
 #endif
     {0, NULL},
 };

pyproject.toml

@@ -236,6 +236,8 @@ partial_branches = ["if (.*and +)*not _use_c( and.*)*:"]
 directory = "htmlcov"
 
 [tool.cibuildwheel]
+# Enable free-threaded support
+free-threaded-support = true
 skip = "pp* *-musllinux*"
 build-frontend = "build"
 test-command = "python {project}/tools/fail_if_no_c.py"

test/asynchronous/test_client_context.py

@@ -61,6 +61,13 @@ class TestAsyncClientContext(AsyncUnitTest):
 
         self.assertEqual(sys.getdefaultencoding(), os.environ["SETDEFAULTENCODING"])
 
+    def test_free_threading_is_enabled(self):
+        if "free-threading build" not in sys.version:
+            raise SkipTest("this test requires the Python free-threading build")
+
+        # If the GIL is enabled then pymongo or one of our deps does not support free-threading.
+        self.assertFalse(sys._is_gil_enabled())  # type: ignore[attr-defined]
+
 
 if __name__ == "__main__":
     unittest.main()

test/test_client_context.py

@@ -61,6 +61,13 @@ class TestClientContext(UnitTest):
 
         self.assertEqual(sys.getdefaultencoding(), os.environ["SETDEFAULTENCODING"])
 
+    def test_free_threading_is_enabled(self):
+        if "free-threading build" not in sys.version:
+            raise SkipTest("this test requires the Python free-threading build")
+
+        # If the GIL is enabled then pymongo or one of our deps does not support free-threading.
+        self.assertFalse(sys._is_gil_enabled())  # type: ignore[attr-defined]
+
 
 if __name__ == "__main__":
     unittest.main()