linux-kernel - Re: X-freeze after clflush changes [Was: 2.6.23-rc6-mm1]

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Date:	Fri, 21 Sep 2007 21:38:40 +0200
From:	Jiri Slaby <jirislaby@...il.com>
To:	Valdis.Kletnieks@...edu
CC:	Matt Mackall <mpm@...enic.com>, Dave Airlie <airlied@...il.com>,
	Andi Kleen <andi@...stfloor.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: X-freeze after clflush changes [Was: 2.6.23-rc6-mm1]

On 09/21/2007 09:33 PM, Valdis.Kletnieks@...edu wrote:
> On Fri, 21 Sep 2007 19:30:04 +0200, Jiri Slaby said:
>> On 09/21/2007 07:16 PM, Valdis.Kletnieks@...edu wrote:
> 
>>> Hmm.. maybe I'm chasing a different bug manifested by the same patch.  For me,
>>> it's been a solid lockup at X startup since -rc3-mm1, and this patch doesn't
>>> change matters.
>> This patch probably changes behaviour how the pages are queued on the list
>> somehow. Maybe it's insane to suggest everybody with similar problem to try
>> LIST_DEBUG, but just give it a try after having one of the patches applied ;).
>> (Or have you tried yet?)
> 
> OK, had a chance to test it, with Dave Airlie's AGP patch, and here's what it hit:
> 
> [  198.925000] list_del corruption. next->prev should be ffff81000118f178, but was ffffffff8067e050
> [  198.925000] ------------[ cut here ]------------
> [  198.925000] kernel BUG at lib/list_debug.c:72!
> [  198.925000] invalid opcode: 0000 [1] PREEMPT SMP 
> [  198.925000] last sysfs file: /devices/pci0000:00/0000:00:01.0/0000:01:00.0/i2c-adapter/i2c-1/i2c-1/dev
> [  198.925000] CPU 1 
> [  198.925000] Modules linked in:
> 
> (Yes, I wish I got a backtrace, but that's as long as it lived.  Apparently,
> the netconsole stuff actually writing this stuff out was over on CPU0 which then
> proceeded to croak).
> 
> Some odd SMP-related race? (x86_64 kernel on a Core2 Duo T7200, if it matters)

It is rather the other user who adds the page to some other list while being at
deferred_pages list. Could you try my debug patch
(http://lkml.org/lkml/2007/9/19/141)?

-- 
Jiri Slaby (jirislaby@...il.com)
Faculty of Informatics, Masaryk University
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