Hi, shared_memory has lot of issues which are mainly being caused due to resource tracking. Initially resource tracking was implemented to keep track of semaphores only, but for some reason resource tracker also started to keep track of shared_memory.
This causes shared memory to be practically useless when used by unrelated processes, because it will be unlinked as soon as a process dies, by processes which are yet to be spawned.

There is already a PR open to fix this https://github.com/python/cpython/pull/15989/files , by applio(a core developer), but for some reason it hasn't been merged yet. I will try to fix the conflicts and request it to be merged.

Now, this will fix most of the issues in shared memory, but still the current implementation of shared memory for linux won't be consistent with windows (which isn't at the moment also). You can read more about the same here: https://bugs.python.org/issue38119#msg352050