bpo-36475: Finalize PyEval_AcquireLock() and PyEval_AcquireThread() properly by nanjekyejoannah · Pull Request #12667 · python/cpython

the-knights-who-say-ni

I am very scared by this change touching critical parts of Python, but I'm somehow confident that it's the right thing to do.

Antoine: Py_Finalize() explicitly waits until all non-daemon threads complete, so this change should impact "regular" threads: only daemon threads.

Note: I have no idea of the impact on performances, but IMHO correctness matters more than performance here. If there is an overhead, I expect it to be not significant on macro benchmarks, and low on micro-benchmarks.

Side note. I really hate the whole concept of daemon threads. Kill a thread anytime is just a very high risk of inconsistency. The thread can be killed while writing in the middle of a file, it can leave temporary files, etc. I would prefer to remove the concept of daemon threads and require developers to call pthread_kill() to make them understand what they are doing (something stupid IMHO :-)). Daemon threads make Python finalization very fragile, but the GIL + this PR make the finalization less fragile. Hint: search for "daemon" in Google Image. IMHO the name is well chosen.