Re: [RFC] perf: fix building for ARCv1

From	Vineet Gupta <Vineet.Gupta1@synopsys.com>
Newsgroups	linux.kernel
Subject	Re: [RFC] perf: fix building for ARCv1
Date	2015-10-19 11:30 +0200
Message-ID	<qleVs-aI-5@gated-at.bofh.it> (permalink)
References	(1 earlier) <qkAuZ-8jO-7@gated-at.bofh.it> <qkUam-3yU-17@gated-at.bofh.it> <ql5p8-3c4-11@gated-at.bofh.it> <qlaIb-2nf-21@gated-at.bofh.it> <qlbEe-3Jv-3@gated-at.bofh.it>
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On Monday 19 October 2015 11:20 AM, Andi Kleen wrote:
> Vineet Gupta <Vineet.Gupta1@synopsys.com> writes:
>> But this user space - so IMHO UP/SMP doesn't matter and we can't simulate them in
>> C just by itself.
> It matters when you access the perf ring buffer which is updated by kernel.

That's part of the problem. The issue is with atomic_* APIs proliferation in perf
user space code which assumes native atomix r-m-w support which is not always
true. So I think we still need a feature detection mechanism and if absent leave
the ball in arch court by calling arch_atomic_* which can use creative or half
working measures so perf will work to some extent atleast and not bomb outright.

Also can u please elaborate a bit on "simulate them in C" - u mean just simple
unprotected LD, OP, ST or do u fancy usage of futex etc?

> Also perf is now multi threaded to some degree.

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Thread

Re: [RFC] perf: fix building for ARCv1 Vineet Gupta <Vineet.Gupta1@synopsys.com> - 2015-10-17 16:20 +0200
  Re: [RFC] perf: fix building for ARCv1 Alexey Brodkin <Alexey.Brodkin@synopsys.com> - 2015-10-18 13:20 +0200
    Re: [RFC] perf: fix building for ARCv1 Andi Kleen <andi@firstfloor.org> - 2015-10-19 01:20 +0200
      Re: [RFC] perf: fix building for ARCv1 Vineet Gupta <Vineet.Gupta1@synopsys.com> - 2015-10-19 07:00 +0200
        Re: [RFC] perf: fix building for ARCv1 Andi Kleen <andi@firstfloor.org> - 2015-10-19 08:00 +0200
          Re: [RFC] perf: fix building for ARCv1 Vineet Gupta <Vineet.Gupta1@synopsys.com> - 2015-10-19 11:30 +0200
            Re: [RFC] perf: fix building for ARCv1 Peter Zijlstra <peterz@infradead.org> - 2015-10-19 11:40 +0200
              Re: [RFC] perf: fix building for ARCv1 Vineet Gupta <Vineet.Gupta1@synopsys.com> - 2015-10-19 11:50 +0200
                Re: [RFC] perf: fix building for ARCv1 Peter Zijlstra <peterz@infradead.org> - 2015-10-19 12:00 +0200
                Re: [RFC] perf: fix building for ARCv1 Vineet Gupta <Vineet.Gupta1@synopsys.com> - 2015-10-19 12:10 +0200
                Re: [RFC] perf: fix building for ARCv1 Vineet Gupta <Vineet.Gupta1@synopsys.com> - 2015-10-20 10:10 +0200
                Re: [RFC] perf: fix building for ARCv1 Peter Zijlstra <peterz@infradead.org> - 2015-10-20 12:20 +0200
                Re: [RFC] perf: fix building for ARCv1 Vineet Gupta <Vineet.Gupta1@synopsys.com> - 2015-10-20 12:50 +0200
                Re: [RFC] perf: fix building for ARCv1 Alexey Brodkin <Alexey.Brodkin@synopsys.com> - 2015-10-29 17:00 +0100
                Re: [RFC] perf: fix building for ARCv1 Vineet Gupta <Vineet.Gupta1@synopsys.com> - 2015-10-30 07:30 +0100

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