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Date: Wed, 24 Aug 2011 15:59:02 -0700
From: Jeremy Fitzhardinge <jeremy@goop.org>
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To: Linus Torvalds <torvalds@linux-foundation.org>
CC: Peter Zijlstra <peterz@infradead.org>, "H. Peter Anvin" <hpa@zytor.com>,
        Ingo Molnar <mingo@elte.hu>, the arch/x86 maintainers <x86@kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Nick Piggin <npiggin@kernel.dk>,
        Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Subject: Re: [PATCH 00/18] x86: Ticket lock + cmpxchg cleanup
References: <cover.1314207974.git.jeremy.fitzhardinge@citrix.com> <1314209019.6925.53.camel@twins> <CA+55aFwuz14ez9=2wiG-344ua0tAJNL8ZuCC41fm6aFgCp+Txw@mail.gmail.com> <4E555AD0.3020101@goop.org> <CA+55aFwp6EM1rwP9k8RCj_M5bzPCkR1N1d9a-VZmYaZNyCNC=A@mail.gmail.com>
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On 08/24/2011 03:53 PM, Linus Torvalds wrote:
> On Wed, Aug 24, 2011 at 1:10 PM, Jeremy Fitzhardinge <jeremy@goop.org> wrote:
>> Could we just kill SMP support for OOSTORE machines now?  That would be
>> the cleanest possible fix...
> No it wouldn't. The asm version would *still* be cleaner than the "C
> plus random barriers".
>
> It's not like the C version is "portable" in any case.

If there's no need to have a locked instruction, then it could simply be:

    barrier();
    lock->head++;
    barrier();

with no need for asm at all.

    J