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Add fallback implementation of PyCriticalSection_BeginMutex for Python 3.13t #5981

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Add fallback implementation of PyCriticalSection_BeginMutex for Python 3.13t #5981

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d569c4c
Add failback implementation of `PyCriticalSection_BeginMutex` for Pyt…
XuehaiPan Feb 2, 2026
5e7d423
Add comment for Python version
XuehaiPan Feb 2, 2026
9de6d1a
Use `_PyCriticalSection_BeginSlow`
XuehaiPan Feb 2, 2026
00bcf66
Add forward declaration
XuehaiPan Feb 2, 2026
225cb46
Fix forward declaration
XuehaiPan Feb 2, 2026
0e6ffd3
Remove always true condition `defined(PY_VERSION_HEX)`
XuehaiPan Feb 2, 2026
862aa00
Merge remote-tracking branch 'upstream/master' into fix-py313t
XuehaiPan Feb 3, 2026
24db64d
Detect musllinux
XuehaiPan Feb 3, 2026
c17212a
Add manylinux test
XuehaiPan Feb 3, 2026
3d4af60
Use direct mutex locking for Python 3.13t
XuehaiPan Feb 3, 2026
358d3c7
Empty commit to trigger CI
XuehaiPan Feb 4, 2026
fea12dc
Empty commit to trigger CI
XuehaiPan Feb 4, 2026
1ef8cae
Empty commit to trigger CI
XuehaiPan Feb 5, 2026
f7a002c
Run apt update before apt install
XuehaiPan Feb 5, 2026
3f82060
Remove unnecessary prefix
XuehaiPan Feb 5, 2026
f20f126
Add manylinux test with Python 3.13t
XuehaiPan Feb 5, 2026
89b2879
Simplify pycritical_section with std::unique_lock fallback for Python…
XuehaiPan Feb 5, 2026
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18 changes: 15 additions & 3 deletions .github/workflows/ci.yml
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Original file line number Diff line number Diff line change
Expand Up @@ -237,11 +237,23 @@ jobs:


manylinux:
name: Manylinux on 🐍 3.14t
name: Manylinux on 🐍 ${{ matrix.python-version }} (${{ matrix.container }})
if: github.event.pull_request.draft == false
strategy:
fail-fast: false
matrix:
include:
- container: quay.io/pypa/manylinux_2_28_x86_64:latest
python-version: '3.13t'
- container: quay.io/pypa/musllinux_1_2_x86_64:latest
python-version: '3.13t'
- container: quay.io/pypa/manylinux_2_28_x86_64:latest
python-version: '3.14t'
- container: quay.io/pypa/musllinux_1_2_x86_64:latest
python-version: '3.14t'
runs-on: ubuntu-latest
timeout-minutes: 40
container: quay.io/pypa/musllinux_1_2_x86_64:latest
container: ${{ matrix.container }}
steps:
- uses: actions/checkout@v6
with:
Expand All @@ -254,7 +266,7 @@ jobs:
run: uv tool install ninja

- name: Configure via preset
run: cmake --preset venv -DPYBIND11_CREATE_WITH_UV=python3.14t
run: cmake --preset venv -DPYBIND11_CREATE_WITH_UV="${{ matrix.python-version }}"

- name: Build C++11
run: cmake --build --preset venv
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2 changes: 1 addition & 1 deletion .github/workflows/reusable-standard.yml
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Expand Up @@ -44,7 +44,7 @@ jobs:

- name: Setup Boost (Linux)
if: runner.os == 'Linux'
run: sudo apt-get install libboost-dev
run: sudo apt-get update && sudo apt-get install -y libboost-dev

- name: Setup Boost (macOS)
if: runner.os == 'macOS'
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7 changes: 7 additions & 0 deletions include/pybind11/detail/internals.h
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Expand Up @@ -230,7 +230,9 @@ using instance_map = std::unordered_multimap<const void *, instance *>;
#ifdef Py_GIL_DISABLED
// Wrapper around PyMutex to provide BasicLockable semantics
class pymutex {
# if PY_VERSION_HEX >= 0x030E00C1 // 3.14.0rc1
friend class pycritical_section;
# endif
PyMutex mutex;

public:
Expand All @@ -239,6 +241,8 @@ class pymutex {
void unlock() { PyMutex_Unlock(&mutex); }
};

// PyCriticalSection_BeginMutex was added in Python 3.15.0a1 and backported to 3.14.0rc1
# if PY_VERSION_HEX >= 0x030E00C1 // 3.14.0rc1
class pycritical_section {
pymutex &mutex;
PyCriticalSection cs;
Expand All @@ -255,6 +259,9 @@ class pycritical_section {
pycritical_section(pycritical_section &&) = delete;
pycritical_section &operator=(pycritical_section &&) = delete;
};
# else
using pycritical_section = std::unique_lock<pymutex>;
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@colesbury colesbury Feb 5, 2026

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If you go this route, you should also exclude the PYBIND11_LOCK_INTERNALS() at:

pybind11/include/pybind11/pybind11.h

Line 3176 in 8f68ecd

PYBIND11_LOCK_INTERNALS(get_internals());

with an #ifdef guard so that it's not included in PY_VERSION_HEX < 0x030E00C1. Otherwise, you'll have a deadlock.

# endif

// Instance map shards are used to reduce mutex contention in free-threaded Python.
struct instance_map_shard {
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12 changes: 12 additions & 0 deletions tests/env.py
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Expand Up @@ -11,6 +11,18 @@
WIN = sys.platform.startswith("win32") or sys.platform.startswith("cygwin")
FREEBSD = sys.platform.startswith("freebsd")

MUSLLINUX = False
MANYLINUX = False
if LINUX:

def _is_musl() -> bool:
libc, _ = platform.libc_ver()
return libc == "musl" or (libc != "glibc" and libc != "")

MUSLLINUX = _is_musl()
MANYLINUX = not MUSLLINUX
del _is_musl

CPYTHON = platform.python_implementation() == "CPython"
PYPY = platform.python_implementation() == "PyPy"
GRAALPY = sys.implementation.name == "graalpy"
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1 change: 1 addition & 0 deletions tests/test_multiple_interpreters.py
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Expand Up @@ -408,6 +408,7 @@ def test_import_in_subinterpreter_before_main():
@pytest.mark.skipif(
sys.platform.startswith("emscripten"), reason="Requires loadable modules"
)
@pytest.mark.xfail(env.MUSLLINUX, reason="Flaky on musllinux", strict=False)
@pytest.mark.skipif(not CONCURRENT_INTERPRETERS_SUPPORT, reason="Requires 3.14.0b3+")
def test_import_in_subinterpreter_concurrently():
"""Tests that importing a module in multiple subinterpreters concurrently works correctly"""
Expand Down
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