Race condition in pytest-dev hangs coverage 6.3

[nedbat]

See nedbat/coveragepy#1310 . Removing pytest-cov solves the problem. What is pytest-cov doing that causes this problem?

[ionelmc]

pytest-cov basically just forcibly enables coverage in multiprocess's subprocesses but that in turn just spurs problems caused by locks being shared between processes after a fork.

[nedbat]

I think I have seen race conditions between erasing the data files and writing new data. I'm working on getting more information.

[ionelmc]

pytest-cov does have a different way of setting up for multiprocessing (using register_after_fork and a finalizer) - maybe I could try to just copy whatever coverage has for subprocesses (reusing won't work since there's a different way coverage configuration is being set) but still, using fork mode is just asking for trouble...