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Fix multithreading checkpoint loading #17678

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merged 14 commits into from
May 31, 2023

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Quasar-Kim
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@Quasar-Kim Quasar-Kim commented May 22, 2023

What does this PR do?

Fixes #17665

Currently, loading checkpoint does not work when using a multithreading-based strategy (for example, XLA + PJRT). The context manager pl_legacy_patch makes legacy module lightning.pytorch.utilities.argparse_utils temporarily available in its context by adding it to the sys.modules on enter and removing it on exit. But when used with threading, because sys.modules is shared between threads, one of them tries to delete already deleted entry, causing exception (but silently on XLA).

This PR fixes this issue by introducing following changes:

  • Fixes broken test test_legacy_ckpt_threading which always passes even though exceptions are raising from threads.
  • Re-introduce locking to pl_legacy_patch context manager which was reverted in commit 277b0b8
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@github-actions github-actions bot added the pl Generic label for PyTorch Lightning package label May 22, 2023
@awaelchli awaelchli changed the title Fix multithreading checkpoint loading [WIP] Fix multithreading checkpoint loading May 31, 2023
@awaelchli awaelchli marked this pull request as ready for review May 31, 2023 12:34
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FYI I'm marking it as ready for review to have the full CI running the changes.

@awaelchli awaelchli added bug Something isn't working checkpointing Related to checkpointing labels May 31, 2023
@awaelchli awaelchli added this to the 2.0.x milestone May 31, 2023
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Looks great. I checked that the modified test case reproduces the problem (see past commit).

@awaelchli awaelchli changed the title [WIP] Fix multithreading checkpoint loading Fix multithreading checkpoint loading May 31, 2023
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@carmocca carmocca left a comment

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@awaelchli Do you remember why you removed the lock in #15237? I couldn't find any comment about it.

@mergify mergify bot added the ready PRs ready to be merged label May 31, 2023
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Me neither. I don't remember. RIP :(

@awaelchli awaelchli merged commit 1307b60 into Lightning-AI:master May 31, 2023
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@Quasar-Kim Quasar-Kim deleted the multithreading-chkpt branch May 31, 2023 22:59
Borda pushed a commit that referenced this pull request Jun 2, 2023
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: awaelchli <aedu.waelchli@gmail.com>
(cherry picked from commit 1307b60)
lantiga pushed a commit that referenced this pull request Jun 2, 2023
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: awaelchli <aedu.waelchli@gmail.com>
(cherry picked from commit 1307b60)
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Cannot load checkpoint when using multithreaded distributed training
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