On Mon, 4 May 2015, Josh Poimboeuf wrote: > Why do we need multiple consistency models? Well, I am pretty sure we need always at least two: - the "immediate" one, where the code redirection flip is switched unconditionally and immediately (i.e. exactly what we currently have in Linus' tree); semantically applicable to many patches, but not all of them - something that fills the "but not all of them" gap above. Both of the solutions that have been presnted so far have some drawbacks that need to be discussed further. To me, the "highlights" (in the "drawbacks" space) are: - any method that is stack-checking-based basically means that we have to functionally 100% rely on stack unwinding correctness. We have never done that before, and current stack unwinder is not ready for that (Josh is working on improving that); plus it can cause the patching to fail under certain circumstances - the kGraft method is not (yet) able to patch kernel threads, and allows for multiple instances of the patched functions to be running in parallel (i.e. patch author needs to be aware of this constaint, and write the code accordingly) This is exactly why we are submitting the kGraft-on-klp patchset, so that we have concurrent implementations (sharing the same goal) to compare, and ultimately merge whatever the best possible outcome will be. Thanks, -- Jiri Kosina SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe live-patching" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
