https://github.com/YannickJadoul/pybind11/commit/727b3aeda951f40d7019d2b189edc3b1184764e0
test -c dbg --config=tsan
 -- test_gil_scoped.py

-- Test started at 2020-12-28 18:23:49 PST --
-----------------------------------------------------------------------------
============================= test session starts ==============================
platform linux -- Python 3.6.12, pytest-4.3.0, py-1.8.0, pluggy-0.9.0
cachedir: tmp
rootdir: pybind11/tests, inifile: pytest.ini
collected 5 items

test_gil_scoped.py ==459==ThreadSanitizer: starting new threads after multi-threaded fork is not supported. Dying (set die_after_fork=0 to override)
F==460==ThreadSanitizer: starting new threads after multi-threaded fork is not supported. Dying (set die_after_fork=0 to override)
F==461==ThreadSanitizer: starting new threads after multi-threaded fork is not supported. Dying (set die_after_fork=0 to override)
F..                                                 [100%]

=================================== FAILURES ===================================
___________________ test_python_to_cpp_to_python_from_thread ___________________

    def test_python_to_cpp_to_python_from_thread():
        """Makes sure there is no GIL deadlock when running in a thread.
    
        It runs in a separate process to be able to stop and assert if it deadlocks.
        """
>       assert _run_in_process(_python_to_cpp_to_python_from_threads, 1) == 0
E       assert 66 == 0
E        +  where 66 = _run_in_process(_python_to_cpp_to_python_from_threads, 1)

test_gil_scoped.py:60: AssertionError
__________ test_python_to_cpp_to_python_from_thread_multiple_parallel __________

    def test_python_to_cpp_to_python_from_thread_multiple_parallel():
        """Makes sure there is no GIL deadlock when running in a thread multiple times in parallel.
    
        It runs in a separate process to be able to stop and assert if it deadlocks.
        """
>       assert _run_in_process(_python_to_cpp_to_python_from_threads, 8, parallel=True) == 0
E       assert 66 == 0
E        +  where 66 = _run_in_process(_python_to_cpp_to_python_from_threads, 8, parallel=True)

test_gil_scoped.py:69: AssertionError
_________ test_python_to_cpp_to_python_from_thread_multiple_sequential _________

    def test_python_to_cpp_to_python_from_thread_multiple_sequential():
        """Makes sure there is no GIL deadlock when running in a thread multiple times sequentially.
    
        It runs in a separate process to be able to stop and assert if it deadlocks.
        """
>       assert (
            _run_in_process(_python_to_cpp_to_python_from_threads, 8, parallel=False) == 0
        )
E       assert 66 == 0
E        +  where 66 = _run_in_process(_python_to_cpp_to_python_from_threads, 8, parallel=False)

test_gil_scoped.py:78: AssertionError
====================== 3 failed, 2 passed in 0.75 seconds ======================