I've heard of an interesting solution to this problem: The idea is that there would be 2 copies of the entity data (wasteful, I know). One copy would be the present copy, and the other would be the past copy. The present copy is strictly write only, and the past copy is strictly read only. I'm assuming that systems don't want to write to the same data elements, but if that's not the case, those systems should be on the same thread. Each thread would have write-access to the present copies of mutually exclusive sections of the data, and every thread has read-access to the all past copies of the data, and thus can update the present copies using data from the past copies with no locking. Between each frame, the present copy becomes the past copy, however you want to handle the swapping of roles.

I've heard of an interesting solution to this problem: The idea is that there would be 2 copies of the entity data (wasteful, I know). One copy would be the present copy, and the other would be the past copy. The present copy is strictly write only, and the past copy is strictly read only. I'm assuming that systems don't want to write to the same data elements, but if that's not the case, those systems should be on the same thread. Each thread would have write-access to the present copies of mutually exclusive sections of the data, and every thread has read-access to the all past copies of the data, and thus can update the present copies using data from the past copies with no locking. Between each frame, the present copy becomes the past copy, however you want to handle the swapping of roles.

This method also removes race conditions because all systems will be working with a stale state that will not change before/after the system has processed it.