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Re: [RFC][PATCH] spin loop arch primitives for busy waiting

From David Miller <davem@davemloft.net>
Newsgroups linux.kernel
Subject Re: [RFC][PATCH] spin loop arch primitives for busy waiting
Date 2017-04-05 16:10 +0200
Message-ID <tsTNg-3DV-29@gated-at.bofh.it> (permalink)
References <tsk37-5hW-5@gated-at.bofh.it> <tskPw-5PE-7@gated-at.bofh.it> <tsn10-7wd-7@gated-at.bofh.it>
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From: Nicholas Piggin <npiggin@gmail.com>
Date: Tue, 4 Apr 2017 13:02:33 +1000

> On Mon, 3 Apr 2017 17:43:05 -0700
> Linus Torvalds <torvalds@linux-foundation.org> wrote:
> 
>> But that depends on architectures having some pattern that we *can*
>> abstract. Would some "begin/in-loop/end" pattern like the above be
>> sufficient?
> 
> Yes. begin/in/end would be sufficient for powerpc SMT priority, and
> for x86, and it looks like sparc64 too. So we could do that if you
> prefer.

Sparc64 has two cases, on older chips we can induce a cpu thread yield
with a special sequence of instructions, and on newer chips we have
a bonafide pause instruction.

So cpu_relax() all by itself pretty much works for us.

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Thread

[RFC][PATCH] spin loop arch primitives for busy waiting Nicholas Piggin <npiggin@gmail.com> - 2017-04-03 10:20 +0200
  Re: [RFC][PATCH] spin loop arch primitives for busy waiting Linus Torvalds <torvalds@linux-foundation.org> - 2017-04-03 17:40 +0200
    Re: [RFC][PATCH] spin loop arch primitives for busy waiting Nicholas Piggin <npiggin@gmail.com> - 2017-04-04 02:00 +0200
      Re: [RFC][PATCH] spin loop arch primitives for busy waiting Linus Torvalds <torvalds@linux-foundation.org> - 2017-04-04 02:50 +0200
        Re: [RFC][PATCH] spin loop arch primitives for busy waiting Nicholas Piggin <npiggin@gmail.com> - 2017-04-04 05:10 +0200
          Re: [RFC][PATCH] spin loop arch primitives for busy waiting Nicholas Piggin <npiggin@gmail.com> - 2017-04-04 06:20 +0200
          Re: [RFC][PATCH] spin loop arch primitives for busy waiting David Miller <davem@davemloft.net> - 2017-04-05 16:10 +0200
            Re: [RFC][PATCH] spin loop arch primitives for busy waiting Nicholas Piggin <npiggin@gmail.com> - 2017-04-06 03:10 +0200
              Re: [RFC][PATCH] spin loop arch primitives for busy waiting Will Deacon <will.deacon@arm.com> - 2017-04-06 16:20 +0200
                Re: [RFC][PATCH] spin loop arch primitives for busy waiting Linus Torvalds <torvalds@linux-foundation.org> - 2017-04-06 17:20 +0200
                Re: [RFC][PATCH] spin loop arch primitives for busy waiting Peter Zijlstra <peterz@infradead.org> - 2017-04-06 18:40 +0200
                Re: [RFC][PATCH] spin loop arch primitives for busy waiting Linus Torvalds <torvalds@linux-foundation.org> - 2017-04-06 19:40 +0200
                Re: [RFC][PATCH] spin loop arch primitives for busy waiting Peter Zijlstra <peterz@infradead.org> - 2017-04-06 21:30 +0200
                Re: [RFC][PATCH] spin loop arch primitives for busy waiting Linus Torvalds <torvalds@linux-foundation.org> - 2017-04-06 21:50 +0200
                Re: [RFC][PATCH] spin loop arch primitives for busy waiting Nicholas Piggin <npiggin@gmail.com> - 2017-04-07 05:40 +0200
                Re: [RFC][PATCH] spin loop arch primitives for busy waiting Peter Zijlstra <peterz@infradead.org> - 2017-04-07 11:50 +0200
                Re: [RFC][PATCH] spin loop arch primitives for busy waiting Nicholas Piggin <npiggin@gmail.com> - 2017-04-07 13:30 +0200
                Re: [RFC][PATCH] spin loop arch primitives for busy waiting Nicholas Piggin <npiggin@gmail.com> - 2017-04-06 17:40 +0200
                Re: [RFC][PATCH] spin loop arch primitives for busy waiting Will Deacon <will.deacon@arm.com> - 2017-04-07 18:20 +0200

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