Autograd engine, only enqueue task when it is fully initialized (#50164)
Summary:
This solves a race condition where the worker thread might
see a partially initialized graph_task
Fixes https://github.com/pytorch/pytorch/issues/49652
I don't know how to reliably trigger the race so I didn't add any test. But the rocm build flakyness (it just happens to race more often on rocm builds) should disappear after this PR.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/50164
Reviewed By: zou3519
Differential Revision: D25824954
Pulled By: albanD
fbshipit-source-id: 6a3391753cb2afd2ab415d3fb2071a837cc565bb
