Better error msg for autograd profiler + multi-worker dataloader crash (#31473)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/31473
Mitigates #6313
A common use case for the autograd profiler is to use it to run over an
entire model, including dataloading. The following will crash:
- run autograd profiler in CUDA mode
- Use a multi-worker DataLoader (presumably with the 'fork' spawn
method)
- because the autograd profiler initializes CUDA and forking after CUDA is
initialized is bad.
This PR puts in a nice error message when this happens so that users
aren't too confused. The new error message looks like:
https://gist.github.com/zou3519/903f15c3e86bad4585b7e5ce14cc1b70
Test Plan:
- Tested locally.
- I didn't add a test case for this because it's hard to write a test
case that doesn't completely stop the rest of our test suite from
running.
Differential Revision: D19178080
Pulled By: zou3519
fbshipit-source-id: c632525ba1f7b168324f1aa55416e5250f56a086
