[issue43468] functools.cached_property locking is plain wrong.

[Antti Haapala]

Antti Haapala <antti at haapala.name> added the comment:

I've been giving thought to implementing the locking on the instance or per instance instead, and there are bad and worse ideas like inserting per (instance, descriptor) into the instance `__dict__`, guarded by the per-descriptor lock; using a per-descriptor `WeakKeyDictionary` to map the instance to locks (which would of course not work - is there any way to map unhashable instances weakly?)

So far best ideas that I have heard from others or discovered myself are along the lines of "remove locking altogether" (breaks compatibility); "add `thread_unsafe` keyword argument" with documentation saying that this is what you want to use if you're actually running threads; "implement Java-style object monitors and synchronized methods in CPython and use those instead"; or "create yet another method".

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<https://bugs.python.org/issue43468>
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