Kill DataLoader worker when we can't join (#39869)
Summary:
There still are occasional reports of DataLoader workers not exiting (e.g., https://github.com/pytorch/pytorch/issues/39570). Before we figure out why, we should just kill them if the join timesout to prevent hanging.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/39869
Differential Revision: D22018501
Pulled By: ezyang
fbshipit-source-id: 66a00d0f5b3e303b6106b336949176b3ff8ac8ae
