New submission from Dieter Maurer <[email protected]>:
I have observed an `AssertionError (assert self._is_stopped)` in
`threading.Thread._wait_for_tstate_lock`. This indicates that Python's internal
state has been corrupted.
The analysis revealed the following race condition:
`_wait_for_tstate:lock` contains the code:
```
lock.release()
self._stop()
```
The `lock.release()` allows a conflicting call to execute. If this happens
before `self._stop()` has executed `self._is_stopped = True`, the
`AssertionError` is raised.
I suggest to give `_stop` an additional parameter `locked` with default
`False`. In indicates whether the caller holds the `tstate_lock`. If this is
the case, `_stop` releases the lock after it has ensured a consistent state
(esspecially set `_is_stopped` to `True`). With this modification to `_stop`
the two lines above can be replaced by `self._stop(locked=True)`.
----------
components: Library (Lib)
messages: 416919
nosy: dmaurer
priority: normal
severity: normal
status: open
title: Race condition in `threadig.Thread._wait_for_tstate_lock`
type: behavior
versions: Python 3.10, Python 3.11, Python 3.7, Python 3.8, Python 3.9
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Python tracker <[email protected]>
<https://bugs.python.org/issue47246>
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