linux-kernel - Re: Re: Re: cfq-iosched.c: panic in cfq_dispatch

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Message-ID: <201103222348152343383@foxmail.com>
Date:	Tue, 22 Mar 2011 23:48:16 +0800
From:	"Lina Lu" <lulina_nuaa@...mail.com>
To:	"Vivek Goyal" <vgoyal@...hat.com>
Cc:	"linux kernel mailing list" <linux-kernel@...r.kernel.org>
Subject: Re: Re: Re: cfq-iosched.c: panic in cfq_dispatch_requests

On 2011-03-22 23:39:48, Vivek Goyal wrote:
>On Tue, Mar 22, 2011 at 11:32:47PM +0800, Lina Lu wrote:
>> On 2011-03-21 22:08:19, Vivek Goyal wrote:
>> >On Sun, Mar 20, 2011 at 03:23:23PM +0800, Lina Lu wrote:
>> >> Hi Vivek,
>> >> 
>> >> I did some test with blkio weight policy these days. The kernel panic 
>> >> once in a while. 
>> >> 	
>> >> From the calltrace, It 's in func cfq_dispatch_requests(+0x058D).
>> >> And I caught a divide by zero error with system monitor tools.
>> >
>> >Hi Lina,
>> >
>> >Can you please paste the full backtrace here.
>> >
>> >> 	
>> >> The panic happens when I first set 100 weight to two IO pids, then 
>> >> change the weight to 200, and begin to perform IO. The kernel panic
>> >> accurately when the IO begin.
>> >
>> >So you notice this only if weights are changed otherwise not?
>> 
>> Hi Vivek
>> 
>> Thanks for this patch! I did objdump and find place that divide by zero.
>> It's in cfq_group_slice function, the st->total_weight is zero in my issue.
>> As described in the patch, this is because I change the weight when the
>> group on service tree. 
>
>Ok, so this patch did solve the issue you are facing? 
>

Yes, this patch did solve the issue. 

And I will do more test these days, if there is any other problem, I will keep
you know.

Thanks
Lina


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