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

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Message-ID: <4109.1190403228@turing-police.cc.vt.edu>
Date:	Fri, 21 Sep 2007 15:33:48 -0400
From:	Valdis.Kletnieks@...edu
To:	Jiri Slaby <jirislaby@...il.com>
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 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)

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