[issue14205] Raise an error if a dict is modified during a lookup
Mark Shannon
report at bugs.python.org
Tue Mar 6 17:56:29 CET 2012
Mark Shannon <mark at hotpy.org> added the comment:
Jim Jewett wrote:
> Jim Jewett <jimjjewett at gmail.com> added the comment:
>
> Can't this be triggered by non-malicious code that just happened to have a python comparison and get hit with a thread switch?
So, they are writing to a dict in one thread while reading from the same
dict in another thread, without any external locks and with keys written
in Python.
>
> I'm not sure how often it happens, but today it would not be visible to the user; after the patch, users will see a sporadic failure that they can't easily defend against.
>
I suspect, they are already seeing sporadic failures.
I think raising an exception is better than weird failures.
We should document the new behaviour, as it is a change in semantics.
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<http://bugs.python.org/issue14205>
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