gh-81905: Fix race condition when tarfile is used from multiple processes #98632
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Most changes to Python require a NEWS entry. Please add it using the blurb_it web app or the blurb command-line tool. |
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pcmoritz
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Most changes to Python require a NEWS entry. Add one using the blurb_it web app or the blurb command-line tool. If this change has little impact on Python users, wait for a maintainer to apply the |
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It was already fixed in #115082. |
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This removes a race condition that can happen if the
tarfilemodule is used at the same time from two different processes with overlapping parent paths of the archive that don't exist yet.This bug has been discussed on the Python bugtracker:
https://bugs.python.org/issue37724 -- which is exactly this bug in the multiprocessing context
https://bugs.python.org/issue23649 -- in which this behavior was discussed in the multithreading context -- I agree that tarfile should not be considered thread safe, but I do think this race-condition should be fixed for multi-process safety
While it is possible to work around by calling
os.makedirs(..., exists_ok=True)in advance, I believe removing this footgun altogether is valuable. Especially since the code arguably gets cleaner.I hope this is useful. Let me know your thoughts and if I need to take any additional steps to get this merged. It doesn't seem to warrant an update to the
NEWSfile, but let me know if you feel otherwise.