Hi, On buildbots, it's common that we get at least one multiprocessing test failure per week. While I just reported a new one, I wanted to add a "expert-multiprocessing" label, but it didn't exist. I just created the label :-) https://github.com/python/cpython/labels/expert-multiprocessing I added the label manually to 240 issues! Oh, they are many open issues about multiprocessing and concurrent.futures modules. Documentation issues, feature requests, but also a long list of real bugs ("hang" is a common term in these reports). Handling multiple processes is hard to get it right, especially when supporting multiple operating systems matter. In Python 3.8, multiprocessing got shared memory support which opened another can of worms :-) Sadly, current multiprocessing maintainers are no longer available and the number of open issues and open pull requests is increasing. I'm not an expert in multiprocessing, but I'm volunteer to mentor someone who is expert and is interested to go through these lists. I cannot dedicate a lot of time, but I will try to be my best to be available :-) See also the GitHub Projects: Multiprocessing issues: https://github.com/orgs/python/projects/14 Pickle and copy issues: https://github.com/orgs/python/projects/9 If you are interested, contact me in private. Sorry, I am not available to teach you how multiprocessing works. I can only assist people who already know it. Victor -- Night gathers, and now my watch begins. It shall not end until my death.