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From: David Miller <davem@davemloft.net>
To: npiggin@gmail.com
Cc: torvalds@linux-foundation.org, linux-arch@vger.kernel.org,
	linux-kernel@vger.kernel.org, anton@samba.org,
	linuxppc-dev@ozlabs.org
Subject: Re: [RFC][PATCH] spin loop arch primitives for busy waiting
Date: Wed, 05 Apr 2017 07:01:57 -0700 (PDT)	[thread overview]
Message-ID: <20170405.070157.871721909352646302.davem@davemloft.net> (raw)
In-Reply-To: <20170404130233.1f45115b@roar.ozlabs.ibm.com>

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.

  parent reply	other threads:[~2017-04-05 14:02 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-04-03  8:13 [RFC][PATCH] spin loop arch primitives for busy waiting Nicholas Piggin
2017-04-03 15:31 ` Linus Torvalds
2017-04-03 23:50   ` Nicholas Piggin
2017-04-04  0:43     ` Linus Torvalds
2017-04-04  3:02       ` Nicholas Piggin
2017-04-04  4:11         ` Nicholas Piggin
2017-04-05 14:01         ` David Miller [this message]
2017-04-06  0:59           ` Nicholas Piggin
2017-04-06 14:13             ` Will Deacon
2017-04-06 15:16               ` Linus Torvalds
2017-04-06 16:36                 ` Peter Zijlstra
2017-04-06 17:31                   ` Linus Torvalds
2017-04-06 19:23                     ` Peter Zijlstra
2017-04-06 19:41                       ` Linus Torvalds
2017-04-07  3:31                         ` Nicholas Piggin
2017-04-07  9:43                     ` Peter Zijlstra
2017-04-07 11:26                       ` Nicholas Piggin
2017-04-06 15:30               ` Nicholas Piggin
2017-04-07 16:13                 ` Will Deacon

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