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gh-130522: Fix threading errors during garbage collection #131537

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Merged
merged 5 commits into from
Jul 25, 2025
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gh-130522: Fix threading errors during garbage collection #131537

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ec00e4c
gh-130522: Fix threading errors during garbage collection
TkTech Mar 21, 2025
280f79c
Add blurb.
ZeroIntensity Jul 25, 2025
52896bc
Add a test case.
ZeroIntensity Jul 25, 2025
ec0cd16
Merge branch 'main' into fix-issue-130522
ZeroIntensity Jul 25, 2025
e83aeee
Merge branch 'main' into fix-issue-130522
kumaraditya303 Jul 25, 2025
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gh-130522: Fix threading errors during garbage collection 
This issue was introduced in 3.13 (5a1ecc8) and causes spurious errors when threads shutdown. This issue occurs on all platforms, and can be triggered by utilities like `coverage.py`'s pytracer module or the PyCharm debugger (pydevd), which may keep references to internal threading objects around.


Issue was reproduced on Linux/OSX/Windows:

```
Exception ignored in: <function _DeleteDummyThreadOnDel.__del__ at 0x10a0811c0>
Traceback (most recent call last):
  File "/Library/Frameworks/Python.framework/Versions/3.13/lib/python3.13/threading.py", line 1383, in __del__
TypeError: 'NoneType' object does not support the context manager protocol
```

```
 Exception ignored in: <function _DeleteDummyThreadOnDel.__del__ at 0x7fedc963ff60>
Traceback (most recent call last):
  File "/opt/hostedtoolcache/Python/3.13.2/x64/lib/python3.13/threading.py", line 1383, in __del__
TypeError: 'NoneType' object does not support the context manager protocol
```

```
 Exception ignored in: <function _DeleteDummyThreadOnDel.__del__ at 0x000001A6B07BA840>
Traceback (most recent call last):
  File "C:\hostedtoolcache\windows\Python\3.13.2\x64\Lib\threading.py", line 1383, in __del__
TypeError: 'NoneType' object does not support the context manager protocol
```
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@TkTech
TkTech authored Mar 21, 2025
commit ec00e4cb0562af7ad2f21e795ea8a7c42918d59f
2 changes: 1 addition & 1 deletion Lib/threading.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1394,7 +1394,7 @@ def __init__(self, dummy_thread):
# the related _DummyThread will be kept forever!
_thread_local_info._track_dummy_thread_ref = self

def __del__(self):
def __del__(self, _active_limbo_lock=_active_limbo_lock, _active=_active):
with _active_limbo_lock:
if _active.get(self._tident) is self._dummy_thread:
_active.pop(self._tident, None)
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