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

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On Wed, 05 Apr 2017 07:01:57 -0700 (PDT)
David Miller <davem@davemloft.net> wrote:

> 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.
> 

Thanks for taking a look. The default spin primitives should just
continue to do the right thing for you in that case.

Arm has a yield instruction, ia64 has a pause... No unusual
requirements that I can see.

If there are no objections, I'll send the arch-independent part of
this through the powerpc tree (the last one I sent, which follows
Linus' preferred pattern).

Thanks,
Nick

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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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