linux-kernel - Re: [PATCH] slub: Fix the lockless code on 32-bit platforms with no 64-bit cmpxchg

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Message-ID: <BANLkTim1L9Gz2kk_SjTe2g_SmKJV=FfuRQ@mail.gmail.com>
Date:	Wed, 4 May 2011 15:00:35 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Ben Greear <greearb@...delatech.com>
Cc:	Ingo Molnar <mingo@...e.hu>, Thomas Gleixner <tglx@...utronix.de>,
	Tejun Heo <tj@...nel.org>, Pekka Enberg <penberg@...nel.org>,
	Jens Axboe <axboe@...nel.dk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	werner <w.landgraf@...ru>, "H. Peter Anvin" <hpa@...or.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Christoph Lameter <cl@...ux.com>
Subject: Re: [PATCH] slub: Fix the lockless code on 32-bit platforms with no
 64-bit cmpxchg

On Wed, May 4, 2011 at 2:52 PM, Ben Greear <greearb@...delatech.com> wrote:
>
> This patch appears to fix the crashes I was seeing on my 32-bit
> Atom system.
>
> It would crash within 30 seconds of booting every time before this patch...

Oh, well - I already committed it and pushed out, otherwise I'd have
added that piece of information to the commit log.

But it's good to know that others had seen this too, just never
realized what was going on.

Btw, that does seem to imply that your kernel config is somewhat odd.
We _should_ be using cmpxchg8b natively if you compile for anything
newer than PPro, and that includes atom.

Did you perhaps say "compile for Pentium" (which is pretty close to
Atom in some respects - but we don't trust that all Pentium-class
CPU's have cmpxchg8b, even if the Intel ones all should).

Regardless, it's pushed out and should be in current -git, apart from
any possible mirroring delays there may be that may b eholdin git up
from actually being visible on the public kernel.org machines yet.

                     Linus
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