Bug report

Bug description:

The implementation of _thread.lock.release() manipulates the locked field in a thread-unsafe way (this may be called by a thread that does not hold the lock) in free-threaded builds:

We're choosing to punt on this for 3.13 since this should only be problematic for contended unlocks. We can revisit this for 3.13 if it turns out to be an issue in practice.

Post 3.13 we would like to change the underlying lock to be a PyMutex and replace the implementation with something like:

static PyObject *
lock_PyThread_release_lock(lockobject *self, PyObject *Py_UNUSED(ignored))
{
    /* Sanity check: the lock must be locked */
    if (_PyMutex_TryUnlock(&self->mutex) < 0) {
        PyErr_SetString(ThreadError, "release unlocked lock");
        return NULL;
    }

    Py_RETURN_NONE;
}

CPython versions tested on:

3.13

Operating systems tested on:

Linux

Linked PRs

• gh-117721: use PyMutex in _thread.lock #125110
• [3.13] gh-117721: use PyMutex in _thread.lock (#125110) #125116