On Tue, Nov 21, 2017 at 2:05 PM, Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx> wrote: > ----- On Nov 21, 2017, at 12:21 PM, Andi Kleen andi@xxxxxxxxxxxxxx wrote: > >> On Tue, Nov 21, 2017 at 09:18:38AM -0500, Mathieu Desnoyers wrote: >>> Hi, >>> >>> Following changes based on a thorough coding style and patch changelog >>> review from Thomas Gleixner and Peter Zijlstra, I'm respinning this >>> series for another RFC. >>> >> My suggestion would be that you also split out the opv system call. >> That seems to be main contention point currently, and the restartable >> sequences should be useful without it. > > I consider rseq to be incomplete and a pain to use in various scenarios > without cpu_opv. > > About the contention point you refer to: > > Using vDSO as an example of how things should be done is just wrong: the > vDSO interaction with debugger instruction single-stepping is broken, > as I detailed in my previous email. > If anyone ever reports that as a problem, I'll gladly fix it in the kernel. That's doable without an ABI change. If rseq-like things started breaking single-stepping, we can't just fix it in the kernel. Also, there is one and only one vclock_gettime. Debuggers can easily special-case it. For all I know, they already do. -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
