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GeezerVison is showing github.com — [3.15] gh-157914: Revert "gh-135871: Reload lock internal state while spinning in `PyMutex_LockTimed` (gh-146064)" (gh-158082) by miss-islington · Pull Request #158290 · python/cpython

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@miss-islington

@miss-islington miss-islington commented Sep 27, 2026 •
edited by bedevere-app Bot
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(cherry picked from commit baec764)

Co-authored-by: Daniele Parmeggiani [email protected]

  • Issue: Performance regression from PyMutex spin-loop reloading in free-threaded builds #157914

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@dpdani @miss-islington
pythongh-157914: Revert "pythongh-135871: Reload lock internal state …
97e6499 
…while spinning in `PyMutex_LockTimed` (pythongh-146064)" (pythongh-158082)

(cherry picked from commit baec764)

Co-authored-by: Daniele Parmeggiani <[email protected]>
@bedevere-app bedevere-app Bot mentioned this pull request Sep 27, 2026
Performance regression from PyMutex spin-loop reloading in free-threaded builds #157914
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@bedevere-app bedevere-app Bot added the awaiting review label Sep 27, 2026
@bedevere-app bedevere-app Bot mentioned this pull request Sep 27, 2026
gh-157914: Revert "gh-135871: Reload lock internal state while spinning in PyMutex_LockTimed (gh-146064)" #158082
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@leandrodamascena

leandrodamascena commented Sep 30, 2026

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Hi! I run a small project that benchmarks CPython builds on AWS Lambda to catch performance regressions before they reach a runtime release, and it picked up this one on the 3.15 branch too.

On a free-threaded build with PYTHON_GIL=0, the change made my benchmark about 43–47% slower across two separate runs. The regular GIL build wasn't affected.

Since the last release candidate still has it, it would be great to get this revert into 3.15.0. Thanks @dpdani for tracking it down!
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@dpdani

dpdani commented Sep 30, 2026

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@hugovk do you want to merge?
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@hugovk
hugovk merged commit 55ab336 into python:3.15 Sep 30, 2026
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@bedevere-app bedevere-app Bot removed the awaiting review label Sep 30, 2026
@miss-islington
miss-islington deleted the backport-baec764-3.15 branch September 30, 2026 10:17
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4 participants

@miss-islington @leandrodamascena @dpdani @hugovk
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