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Expose PyMutex_IsLocked in the public C API #134009

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Expose PyMutex_IsLocked in the public C API#134009
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interpreter-core(Objects, Python, Grammar, and Parser dirs)topic-C-APItopic-free-threadingtype-featureA feature request or enhancement

Description

@hawkinsp
hawkinsp
opened on May 14, 2025

Feature or enhancement

Proposal:

In my C extension, I wanted to write:

assert(PyMutex_IsLocked(&mutex));

to verify that my own code is maintaining its own locking invariants.

PyMutex_IsLocked exists, but is private:

cpython/Include/internal/pycore_lock.h

Line 30 in 0afbd4e

PyMutex_IsLocked(PyMutex *m)

Could we make it public and document it, please?

Has this already been discussed elsewhere?

This is a minor feature, which does not need previous discussion elsewhere

Links to previous discussion of this feature:

No response

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  1. hawkinsp
    added
    type-featureA feature request or enhancement
    on May 14, 2025

  2. ngoldbaum commented on May 14, 2025

    @ngoldbaum
    ngoldbaum
    on May 14, 2025
    Contributor

    I ran into this when I was writing PyMutex bindings for PyO3 - it was very difficult to test the bindings because the PyMutex API is so limited.

  3. ZeroIntensity
    added
    topic-free-threading
    on May 14, 2025

  4. ZeroIntensity commented on May 14, 2025

    @ZeroIntensity
    ZeroIntensity
    on May 14, 2025
    Member

    Ideally, we should document that it's for use in assertions only. We need to make sure we're not enabling people to write thread-unsafe code like this:

    if (PyMutex_IsLocked(lock)) {
    PyMutex_Unlock(lock);
}

  5. makslevental commented on May 14, 2025

    @makslevental
    makslevental
    on May 14, 2025

    Ideally, we should document that it's for use in assertions only

    maybe something like

    #define ASSERT_PY_MUTEX_IS_LOCKED(mutex, msg) assert(PyMutex_IsLocked(mutex) && msg)

    ?

    but not sure if this y'all's style (i came here from mlir...)

  6. hawkinsp commented on May 14, 2025

    @hawkinsp
    hawkinsp
    on May 14, 2025
    ContributorAuthor

    It's important to expose an API like PyMutex_IsLocked even if you expose some sort of assertion helper, because people want to use their own debugging/printing/logging libraries to handle this sort of failure.

  7. colesbury commented on May 14, 2025

    @colesbury
    colesbury
    on May 14, 2025
    Contributor

    Yeah, I just want to echo @hawkinsp comment. I think we should expose PyMutex_IsLocked() and document its intended purposes. I don't think we need to be overly concerned about people misusing it.

  8. colesbury commented on May 14, 2025

    @colesbury
    colesbury
    on May 14, 2025
    Contributor

    We should also open a corresponding issue in the C API working group

  9. picnixz
    added
    interpreter-core(Objects, Python, Grammar, and Parser dirs)
    on May 15, 2025
  10. colesbury
    changed the title [-]Expose `PyMutex_IsLocked` in the public API for free-threading[/-] [+]Expose `PyMutex_IsLocked` in the public API[/+] on May 15, 2025
  11. colesbury
    changed the title [-]Expose `PyMutex_IsLocked` in the public API[/-] [+]Expose `PyMutex_IsLocked` in the public C API[/+] on May 15, 2025
  12. colesbury
    added a commit that references this issue on May 20, 2025

    pythongh-134009: Expose `PyMutex_IsLocked` in the public C API

    1a33205
  13. colesbury
    added
    topic-C-API
    on May 20, 2025
  14. colesbury
    added a commit that references this issue on May 27, 2025

    Merge branch 'main' into pythongh-134009-pymutex-is-locked

    1f3f627
  15. colesbury
    added 2 commits that reference this issue on Jun 24, 2025

    Merge branch 'main' into pythongh-134009-pymutex-is-locked

    69004dd

    gh-134009: Expose `PyMutex_IsLocked` in the public C API (gh-134365)

    f41e9c7
  16. colesbury
    closed this as completedon Jul 1, 2025
  17. AndPuQing
    added a commit that references this issue on Jul 11, 2025

    pythongh-134009: Expose `PyMutex_IsLocked` in the public C API (pytho…

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  18. Pranjal095
    added a commit that references this issue on Jul 12, 2025

    pythongh-134009: Expose `PyMutex_IsLocked` in the public C API (pytho…

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  19. picnixz
    added a commit that references this issue on Jul 13, 2025

    pythongh-134009: Expose `PyMutex_IsLocked` in the public C API (pytho…

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  20. hugovk
    added 2 commits that reference this issue on Jul 22, 2025

    [3.14] pythongh-134009: Expose `PyMutex_IsLocked` in the public C API (…

    c74ca9b

    [3.14] gh-134009: Expose `PyMutex_IsLocked` in the public C API (gh-1…

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  21. taegyunkim
    added a commit that references this issue on Aug 4, 2025

    pythongh-134009: Expose `PyMutex_IsLocked` in the public C API (pytho…

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    pythongh-134009: Expose `PyMutex_IsLocked` in the public C API (pytho…

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    added a commit that references this issue on Sep 9, 2025

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