Agreed it's not a bug, but I will say it took me a while to work out *why* it's not a bug (namely, that even though the OP is using shared memory values, the code relies on fork semantics to share the two Value objects that *reference* the shared memory).

It would be worth adding a note to the documentation on shared memory values at https://docs.python.org/3.8/library/multiprocessing.html#sharing-state-between-processes to make it clearer that it's the user's responsibility to make sure the Value object is passed to every subprocess that wants to interact with it.