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

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Message-ID: <4DC1D1A5.7050408@candelatech.com>
Date:	Wed, 04 May 2011 15:22:29 -0700
From:	Ben Greear <greearb@...delatech.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
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 05/04/2011 03:00 PM, Linus Torvalds wrote:
> 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.

No worries...I'm just happy to finally be able to boot .39 :)

> 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).

Well, yes.  I'm compiling for 'M586' it seems, plus SMP, pre-empt, etc.

Maybe it's time to move to a newer processor family!

Thanks,
Ben

-- 
Ben Greear <greearb@...delatech.com>
Candela Technologies Inc  http://www.candelatech.com

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