Free-threaded Python support

[szalpal]

Hi,

Recently PEP 703 has been approved, which removes the GIL in Python. The timeline of the change is far, however I'd like to ask, is there a particular plan of fastrlock working without the GIL?

I'm particularly asking, since from the How does it work section I understand that fastrlock is inherently coupled with GIL.

Ideally fastrlock API might stay unchanged, so that any project using fastrlock does not require code changes.

[scoder]

In nogil CPython (which has already landed in CPython 3.13), you can probably just use threading.RLock instead – unless you're asking about fastrlock's C-API.

The change that CPython needed seems to be this:
python/cpython@f366e21
It uses atomics, which seems reasonable.

The same can probably be implemented for fastrlock. PR welcome.