Re: [RFC] perf: fix building for ARCv1

From	Peter Zijlstra <peterz@infradead.org>
Newsgroups	linux.kernel
Subject	Re: [RFC] perf: fix building for ARCv1
Date	2015-10-19 12:00 +0200
Message-ID	<qlfov-IV-15@gated-at.bofh.it> (permalink)
References	(4 earlier) <qlaIb-2nf-21@gated-at.bofh.it> <qlbEe-3Jv-3@gated-at.bofh.it> <qleVs-aI-5@gated-at.bofh.it> <qlf5a-lZ-43@gated-at.bofh.it> <qlfeO-xB-7@gated-at.bofh.it>
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On Mon, Oct 19, 2015 at 09:46:35AM +0000, Vineet Gupta wrote:
> On ARC we could use the atomic EXchange to implement a user space only binary
> semaphore - these atomic ops will be small duration so it is OK to spin wait for a
> little bit. That's how the old pthread library worked for ARC w/o any atomic support.

That has the obvious problem of lock-holder-preemption and the horrible
performance issues that result from that.

I think the syscall at least has deterministic behaviour, whereas that
userspace spin loop has this abysmal worst case thing.
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Thread

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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