New submission from Sam Gross <[email protected]>:
The issue described issue7105 (and maybe issue7060) still exists due to a race
condition in WeakKeyDictionary. This shows up as test failure that looks like:
test test_weakref failed -- Traceback (most recent call last):
File "Lib/test/test_weakref.py", line 1960, in
test_threaded_weak_value_dict_deepcopy
self.check_threaded_weak_dict_copy(weakref.WeakValueDictionary, True)
File "Lib/test/test_weakref.py", line 1940, in check_threaded_weak_dict_copy
raise exc[0]
File "Lib/test/test_weakref.py", line 1897, in dict_copy
_ = copy.deepcopy(d)
File "Lib/copy.py", line 153, in deepcopy
y = copier(memo)
File "Lib/weakref.py", line 189, in __deepcopy__
for key, wr in self.data.items():
RuntimeError: dictionary changed size during iteration
The cause is that the check of "self._iterating" and the call to
"_atomic_removal" are not performed atomically together. By the time
_atomic_removal() is called, an iteration might have already started.
https://github.com/python/cpython/blob/ec382fac0db6d9159c2d3496a70b7a605545957e/Lib/weakref.py#L109-L114
----------
components: Library (Lib)
messages: 406357
nosy: colesbury
priority: normal
severity: normal
status: open
title: Race condition in WeakKeyDictionary/WeakKeyDictionary
type: behavior
versions: Python 3.10, Python 3.11, Python 3.9
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Python tracker <[email protected]>
<https://bugs.python.org/issue45809>
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