From mboxrd@z Thu Jan  1 00:00:00 1970
From: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Subject: Re: 3.6-rc5 cgroups blkio throttle + md regression
Date: Thu, 20 Sep 2012 11:31:53 -0700
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To: Vivek Goyal <vgoyal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Cc: Joseph Glanville <joseph.glanville-2MxvZkOi9dvvnOemgxGiVw@public.gmane.org>, cgroups <cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>

Hello,

On Wed, Sep 19, 2012 at 03:42:31PM -0400, Vivek Goyal wrote:
> On Thu, Sep 20, 2012 at 04:20:42AM +1000, Joseph Glanville wrote:
> > Hi,
> > 
> > I booted the machine under bare metal to continue bisecting.
> > Thankfully this allowed me to locate the commit that causes the
> > problem.
> > 
> 
> I tested it and I am also noticing the hang. I can see this hang on
> dm devices also.
> 
> I suspect this issue is related to bio based drivers. We exit the
> bypass mode in blk_init_allocated_queue() and that will be called
> only for request based drivers. So for bio based drivers may be 
> we never exit the bypass mode and this issue is somehow side
> affect of that.

Can you please trigger sysrq-t and post the result?

Thanks.

-- 
tejun