Simply exit DataLoader when Python is dying #12700
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Also, the general recommendation is to never use |
ssnl
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Oct 16, 2018
| # | ||
| # 2. The iterator exits the workers when the loader process and/or worker | ||
| # processes exits unexpectedly (e.g., SIGKILL-ed). | ||
| # processes exits normally or with error. |
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ezyang
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Oct 17, 2018
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Thanks, love the commentary.
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last commit is only comment change and build passed on previous commit so I'm landing. |
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SsnL is landing this pull request. If you are a Facebook employee, you can view this diff on Phabricator.
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I struggled with yet another DataLoader hang for the entire evening. After numerous experiments, I realized that it is unsafe to do anything when Python is shutting down. We also unfortunately implement our DataLaoder cleaning-up logic in
__del__, a function that may or may not be called during shutdown, and if called, may or may not be called before core library resources are freed.Fortunately, we are already setting all our workers and pin_memory_thread as daemonic. So in case of Python shutting down, we can just do a no-op in
__del__and rely on the automatic termination of daemonic children.An
atexithook is used to detect Python exit.