Date: Thu, 29 May 2003 12:38:49 -0700
From: William Lee Irwin III <wli@holomorphy.com>
To: Morten Helgesen <morten.helgesen@nextframe.net>
Cc: linux-kernel@vger.kernel.org
Subject: Re: list_head debugging patch
Message-ID: <20030529193849.GB8978@holomorphy.com>
Mail-Followup-To: William Lee Irwin III <wli@holomorphy.com>,
	Morten Helgesen <morten.helgesen@nextframe.net>,
	linux-kernel@vger.kernel.org
References: <20030529130807.GH19818@holomorphy.com> <200305292122.44041.morten.helgesen@nextframe.net>
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On Thursday 29 May 2003 15:08, William Lee Irwin III wrote:
>> This appears to get the kernel to crap its pants in very, very
>> short order. Given the number of things going wrong, I almost
>> wonder if I did something wrong. Things get real ugly, really,
>> really fast.

On Thu, May 29, 2003 at 09:22:43PM +0200, Morten Helgesen wrote:
> [snip]
> I gave this a go - booted without problems. I did some 
> untaring/copying/deleting and didn`t see anything unusual, but a 
> 'dbench 8' died right away. 
[...]
> EIP is at clear_queue_congested+0x78/0xb0

clear_queue_congested() is doing an opportunistic check for list_empty()
without taking a lock. The patch basically changes list_empty() to look
at elements of the list instead of just pieces of the head. As opposed
to auditing for this, could you remove the __list_head_check() from
list_empty() and try again?

Thanks.

-- wli
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