From mboxrd@z Thu Jan  1 00:00:00 1970
From: Dong Liu <dliu.cn@gmail.com>
Subject: Re: cpu stall and hyperthread
Date: Fri, 06 Jul 2012 02:04:47 -0400
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References: <4FEBCDDE.60503@gmail.com> <4FF351C6.3000100@gmail.com> <4FF4C94A.6040105@osadl.org> <4FF5DFDC.9010501@gmail.com> <4FF61D01.9040502@osadl.org>
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To: Carsten Emde <C.Emde@osadl.org>
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On 7/5/12 7:02 PM, Carsten Emde wrote:
> Hi Dong,
>
>> I tried to disable CONFIG_RT_GROUP_SCHED, but I still got cpu stalls!
> Just had another look at your dmesg files. Didn't you get
> BUG: soft lockup - CPU#0 stuck for 279s! [swapper/0:0]
> before? Now - with CONFIG_RT_GROUP_SCHED disabled - you get:
> rcu_preempt detected stalls on CPUs/tasks: { 3} [..]
>
> Is it reproducible? Maybe, there are two different problems. One leads
> to soft lockups and is related to CONFIG_RT_GROUP_SCHED, and another one
> that leads to rcu_preempt stalls.

The "BUG: soft lockup" error  was because I disabled RCU cpu stall 
checking by set

/sys/module/rcutree/parameters/rcu_cpu_stall_suppress

to "1"

I did try this setting after disabled CONFIG_RT_GROUP_SCHED, it didn't 
not print out any kernel error message, but the system did froze when I 
tried to start some KVM guests.

Thanks,

Dong