How can I use pybind11 for multithreaded program?

[FlynnDowey]

I have a mixed C and C++ program that uses pybind11, but I am running into issues with the GIL.

My main.c code calls some threaded program, which is written in C, too. This threaded program waits for an event, and when the event occurs, it calls a C++ program that has embedded Python.

I have tried using py::gil_scoped_acquire acquire and py::gil_scoped_release release around the Python critical sections in the C++ code, but I either get a deadlock or seg fault.

Does anyone know how to use pybind11 with a threaded program?

UPDATE:
I seem to have figured it out. You have to use:

Py_BEGIN_ALLOW_THREADS
... Do some blocking I/O operation ...
Py_END_ALLOW_THREADS

as stated by https://docs.python.org/3/c-api/init.html#c.PyGILState_Ensure

Thanks.