gh-116738: Use PyMutex for bz2 module

[yoney]

I was initially looking into the bz2 module for free-threading. The methods are already wrapped with a lock, which I believe is primarily used to release the GIL. This locking makes the methods thread-safe in free-threaded build. I replaced PyThread_acquire_lock with PyMutex, which releases the GIL when the thread is parked. This change removes some macros and allocation handling code.

cc: @mpage @colesbury

• Issue: Audit all built-in modules for thread safety #116738

[picnixz]

Thanks and sorry for the back-and-forth. A small tip: when I (and I mean me explicitly) suggest something (and don't explicitly request changes), you don't need to directly follow my advice if my suggestion was phrased as a question (that question could be addressed to a wider audience).

[yoney]

@picnixz Thanks for the review! I’m glad we discovered zstd, thanks to @emmatyping.

Since the changes were quite small, I just created the extra commit, knowing we might need to revert if needed. This is just part of a good review process!

[emmatyping]

Thanks! I think this looks good

[emmatyping]

Oh, perhaps we should add a test on free-threading to ensure we aren't getting data races and the locking is working? Feel free to take some inspiration from https://github.com/python/cpython/blob/main/Lib/test/test_zstd.py#L2668

[vstinner]

LGTM

[yoney]

Oh, perhaps we should add a test on free-threading to ensure we aren't getting data races and the locking is working? Feel free to take some inspiration from https://github.com/python/cpython/blob/main/Lib/test/test_zstd.py#L2668

@emmatyping Thanks for pointing to the zstd tests! I had a local test for compressor, but after seeing the decompressor example in zstd, I also created a decompression test and added it to the PR. Thank you!