On master test 1) hangs before commit below and works after commit below. Unfortunately applying that commit to 3.8 branch doesn't help - 3.8 still hangs. Some other fix is also needed I guess commit 9ad58acbe8b90b4d0f2d2e139e38bb5aa32b7fb6 Author: Victor Stinner <vstinner@python.org> Date: Mon Mar 9 23:37:49 2020 +0100 bpo-19466: Py_Finalize() clears daemon threads earlier (GH-18848) Clear the frames of daemon threads earlier during the Python shutdown to call objects destructors. So "unclosed file" resource warnings are now emitted for daemon threads in a more reliable way. Cleanup _PyThreadState_DeleteExcept() code: rename "garbage" to "list".