gh-140814: Fix freeze_support() setting start method as side effect#144608
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gpshead merged 4 commits intopython:mainfrom Mar 16, 2026
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gh-140814: Fix freeze_support() setting start method as side effect#144608gpshead merged 4 commits intopython:mainfrom
gpshead merged 4 commits intopython:mainfrom
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…fect freeze_support() called get_start_method() without allow_none=True, which locked in the default start method context. This caused a subsequent set_start_method() call to raise "context has already been set". Use allow_none=True and accept None as a matching value, since spawn.freeze_support() independently detects spawned child processes. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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Test that freeze_support() does not lock in the default start method, which would prevent a subsequent set_start_method() call. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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picnixz
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Mar 1, 2026
Misc/NEWS.d/next/Library/2026-02-08-22-04-06.gh-issue-140814.frzSpn.rst
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picnixz
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@gpshead Ok for merging this? (I've updated the branch with my suggestion). |
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Thanks @gpshead for the PR 🌮🎉.. I'm working now to backport this PR to: 3.13, 3.14. |
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…fect (pythonGH-144608) freeze_support() called get_start_method() without allow_none=True, which locked in the default start method context. This caused a subsequent set_start_method() call to raise "context has already been set". Use allow_none=True and accept None as a matching value, since spawn.freeze_support() independently detects spawned child processes. Test that freeze_support() does not lock in the default start method, which would prevent a subsequent set_start_method() call. (cherry picked from commit ee53180) Co-authored-by: Gregory P. Smith <68491+gpshead@users.noreply.github.com> Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com> Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>
miss-islington
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Mar 16, 2026
…fect (pythonGH-144608) freeze_support() called get_start_method() without allow_none=True, which locked in the default start method context. This caused a subsequent set_start_method() call to raise "context has already been set". Use allow_none=True and accept None as a matching value, since spawn.freeze_support() independently detects spawned child processes. Test that freeze_support() does not lock in the default start method, which would prevent a subsequent set_start_method() call. (cherry picked from commit ee53180) Co-authored-by: Gregory P. Smith <68491+gpshead@users.noreply.github.com> Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com> Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>
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GH-146008 is a backport of this pull request to the 3.14 branch. |
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GH-146009 is a backport of this pull request to the 3.13 branch. |
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…ffect (GH-144608) (#146009) gh-140814: Fix freeze_support() setting start method as side effect (GH-144608) freeze_support() called get_start_method() without allow_none=True, which locked in the default start method context. This caused a subsequent set_start_method() call to raise "context has already been set". Use allow_none=True and accept None as a matching value, since spawn.freeze_support() independently detects spawned child processes. Test that freeze_support() does not lock in the default start method, which would prevent a subsequent set_start_method() call. (cherry picked from commit ee53180) Co-authored-by: Gregory P. Smith <68491+gpshead@users.noreply.github.com> Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com> Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>
gpshead
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…ffect (GH-144608) (#146008) gh-140814: Fix freeze_support() setting start method as side effect (GH-144608) freeze_support() called get_start_method() without allow_none=True, which locked in the default start method context. This caused a subsequent set_start_method() call to raise "context has already been set". Use allow_none=True and accept None as a matching value, since spawn.freeze_support() independently detects spawned child processes. Test that freeze_support() does not lock in the default start method, which would prevent a subsequent set_start_method() call. (cherry picked from commit ee53180) Co-authored-by: Gregory P. Smith <68491+gpshead@users.noreply.github.com> Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com> Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>
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Summary
freeze_support()calledget_start_method()withoutallow_none=True, which locked in the default start method context as a side effect. This caused a subsequentset_start_method()call to raiseRuntimeError: context has already been set.allow_none=Trueand acceptNoneas a matching value, sincespawn.freeze_support()independently detects spawned child processes.sys.frozenfirst as the more likely short-circuit (almost alwaysFalse).