Post Syndicated from original https://lwn.net/Articles/911219/

Unlike many other architectures, x86 systems support atomic operations that
affect more than one cache line. This support comes at a cost, though, in
terms of overall system performance and, even, security. Over the last few
years, kernel developers have worked to discourage the use of this sort of
“split-lock” operation. Now, though, one group of users is feeling
a little too discouraged, leading to a discussion of how much misery can
appropriately be inflicted upon users who use problematic but
architecturally legal operations.