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Date: Wed, 18 Jan 2012 09:05:26 +0800
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Subject: Re: Kernel crash in icq_free_icq_rcu
From: Shaohua Li <shaohua.li@intel.com>
To: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>,
        linux kernel mailing list <linux-kernel@vger.kernel.org>,
        Jens Axboe <axboe@kernel.dk>
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2012/1/18 Tejun Heo <tj@kernel.org>:
> Hello,
>
> On Wed, Jan 18, 2012 at 09:01:00AM +0800, Shaohua Li wrote:
>> 2012/1/18 Vivek Goyal <vgoyal@redhat.com>:
>> >> Does the following patch make any difference?
>> >
>> > Nope. Still can reproduce the issue.
>>
>> I had similar issue too. Looks ioc_create_icq finds an icq (in ioc_lookup_icq)
>> the icq is in rcu free (it has __rcu_icq_cache set)
>
> Vivek is seeing the problem while switching elevators.  Are you too?
> Or is it during normal operation?
same here. I had some problems when I debug my ioscheduler, but
eventually found even switching cfq and noop can trigger oops.