----- On Nov 22, 2017, at 10:28 AM, Andy Lutomirski luto@xxxxxxxxxxxxxx wrote: > 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. Very true. And rseq does break both line-level and instruction-level single-stepping. > > Also, there is one and only one vclock_gettime. Debuggers can easily > special-case it. For all I know, they already do. As my tests demonstrate, they don't. clock_gettime() vDSO currently breaks instruction-level single-stepping (istep) with gdb. I'll forward you the writeup I did on that a few days ago. Thanks, Mathieu -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com -- 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
