Messages in this thread |  | | From | Andy Lutomirski <> | Date | Wed, 22 Nov 2017 07:28:22 -0800 | Subject | Re: [RFC PATCH for 4.15 v12 00/22] Restartable sequences and CPU op vector |
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On Tue, Nov 21, 2017 at 2:05 PM, Mathieu Desnoyers <mathieu.desnoyers@efficios.com> wrote: > ----- On Nov 21, 2017, at 12:21 PM, Andi Kleen andi@firstfloor.org 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.
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