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From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Wed, 4 May 2011 14:06:21 -0700
Message-ID: <BANLkTik7AHGr7+BG8nE16j-ayctD0LOH=w@mail.gmail.com>
Subject: Re: [block IO crash] Re: 2.6.39-rc5-git2 boot crashs
To: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>, Thomas Gleixner <tglx@linutronix.de>,
        Tejun Heo <tj@kernel.org>, Ingo Molnar <mingo@elte.hu>,
        Jens Axboe <axboe@kernel.dk>,
        Andrew Morton <akpm@linux-foundation.org>, werner <w.landgraf@ru.ru>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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On Wed, May 4, 2011 at 1:04 PM, Christoph Lameter <cl@linux.com> wrote:
>
> Maybe I should have pushed the cmpxchg_double() before the
> this_cpu_cmpxchg to avoid these misunderstandings

Christoph, the only mis-understanding is yours.

I understand perfectly that the percpu cmpxchg isn't SMP-atomic. We
all know that.

The problem is that cmpxchg *IS*NOT*AN*CMPXCHG*AT*ALL*. Not even on UP.

It's something totally different.

                   Linus
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