I agree, the implementation isn't great. The problem IMO is that it tried to do way too much and be way too general which leads to a bunch of tricky edge cases

I agree, the implementation isn't great. The problem IMO is that it tried to do way too much and be way too general which leads to a bunch of tricky edge cases they need to handle (and significantly complicates uses of caches). That said, hardware support for atomic use of larger memory regions than is currently supported is something that is worthy as a problem to solve.