linux-kernel - Re: [OOPS] 2.6.21-rc6-git5 in cfq_dispatch

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Date:	Tue, 24 Apr 2007 23:40:40 +0400
From:	Brad Campbell <brad@...p.net.au>
To:	Jens Axboe <jens.axboe@...cle.com>
CC:	Neil Brown <neilb@...e.de>, Chuck Ebbert <cebbert@...hat.com>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [OOPS] 2.6.21-rc6-git5 in cfq_dispatch_insert

Jens Axboe wrote:

> Ok, can you try and reproduce with this one applied? It'll keep the
> system running (unless there are other corruptions going on), so it
> should help you a bit as well. It will dump some cfq state info when the
> condition triggers that can perhaps help diagnose this. So if you can
> apply this patch and reproduce + send the output, I'd much appreciate
> it!
> 

I think I'm wearing holes in my platters. This is being a swine to hit, but I finally got some..
It seems to respond to a combination of high cpu usage and relatively high disk utilisation.

I tried all sorts of acrobatics with multiple readers and hammering the array while reading from 
individual drives..

The only reliable way I can reproduce this seems to be on a degraded array running a "while true ; 
do md5sum -c md5 ; done" on about a 180GB directory of files. It is taking anywhere from 4 to 96 
hours to hit it though.. but at least it's reproducible.

[105449.653682] cfq: rbroot not empty, but ->next_rq == NULL! Fixing up, report the issue to 
lkml@...r.kernel.org
[105449.683646] cfq: busy=1,drv=0,timer=0
[105449.694871] cfq rr_list:
[105449.702715]   3108: sort=0,next=00000000,q=0/1,a=1/0,d=0/0,f=69
[105449.720693] cfq busy_list:
[105449.729054] cfq idle_list:
[105449.737418] cfq cur_rr:
[115435.022192] cfq: rbroot not empty, but ->next_rq == NULL! Fixing up, report the issue to 
lkml@...r.kernel.org
[115435.052160] cfq: busy=1,drv=0,timer=0
[115435.063383] cfq rr_list:
[115435.071227]   3196: sort=0,next=00000000,q=0/1,a=1/0,d=0/0,f=69
[115435.089205] cfq busy_list:
[115435.097566] cfq idle_list:
[115435.105930] cfq cur_rr:
[115616.651883] cfq: rbroot not empty, but ->next_rq == NULL! Fixing up, report the issue to 
lkml@...r.kernel.org
[115616.681848] cfq: busy=1,drv=0,timer=0
[115616.693071] cfq rr_list:
[115616.700916]   3196: sort=0,next=00000000,q=0/1,a=1/0,d=0/0,f=61
[115616.718893] cfq busy_list:
[115616.727253] cfq idle_list:
[115616.735617] cfq cur_rr:
[119679.564753] cfq: rbroot not empty, but ->next_rq == NULL! Fixing up, report the issue to 
lkml@...r.kernel.org
[119679.594732] cfq: busy=1,drv=0,timer=0
[119679.605955] cfq rr_list:
[119679.613799]   3241: sort=0,next=00000000,q=0/1,a=1/0,d=0/0,f=69
[119679.631778] cfq busy_list:
[119679.640136] cfq idle_list:
[119679.648502] cfq cur_rr:

Brad
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