Seems safer to me to park CPUs in known safe spots where they can spin until modification is complete. CPUs could check if there's a pending patch when they att

Seems safer to me to park CPUs in known safe spots where they can spin until modification is complete. CPUs could check if there's a pending patch when they attempt to reschedule, and when all CPUs apart from the patching CPU are safe, then the patch can go ahead. Trying to retry an operation (so it's transparent from the user's perspective) or reset state to the way it was at the time of the protection fault sounds harder to my mind. PS: I looked at the ftrace doc linked above, and it's architecture dependent of course, but for ftrace's purposes, they use generally use breakpoints on the place being modified.