Change RLock from factory function to actual type, remove dead Python RLock implementation

Feature or enhancement

Proposal:

Currently in CPython threading.RLock is a factory function that returns a new RLock instance. It either returns an instance of _CRLock, if it's defined, otherwise it returns an instance of _PyRLock. I'm kidding--in practice, it never returns _PyRLock. You'd have to do something silly (threading._CRLock = None) in order to get it to return an instance of _PyRLock, because these days _CRLock is always defined.

I haven't gone reading through old versions / git blame / etc, but my guess is that CPython used to support platforms that didn't have a native RLock, or the C implementation of RLock was unsuitable for some reason on some platforms. Here in 2025 I find the C implementation of RLock is unguarded by any #if / #ifdef statement. All platforms currently supported by CPython must support threading, the C version of RLock (_thread.RLock) is always defined, and the threading.RLock factory function always returns an instance of that object (unless you do something silly).

Assuming I'm right about all that:

• The Python implementation of RLock (class _RLock) in Lib/threading.py is dead code and should be removed.
• There's no longer any point in making threading.RLock a factory function. (Was there ever a point?) threading.RLock should simply be an alias for the RLock implementation in C (_thread.RLock).

Has this already been discussed elsewhere?

No response given

Links to previous discussion of this feature:

No response

Linked PRs

• gh-141462
• gh-142977

Comienza con Lib/threading.py y el punto de entrada _thread.RLock; después, revisa las discusiones de los PR enlazados antes de hacer cambios. Confirma que el alias y la eliminación propuestos son compatibles con las plataformas compatibles y el comportamiento existente de threading; el trabajo estará terminado cuando se elimine la implementación _RLock obsoleta y threading.RLock se refiera directamente a la implementación en C.