linux-kernel - Re: [3.6.6] panic on reboot / khungtaskd blocked? (WARNING: at arch/x86/kernel/smp.c:123 native_smp_send

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Message-ID: <50A5AA03.2000707@linux.vnet.ibm.com>
Date:	Fri, 16 Nov 2012 10:50:43 +0800
From:	Michael Wang <wangyun@...ux.vnet.ibm.com>
To:	Jan Kara <jack@...e.cz>
CC:	Paweł Sikora <pawel.sikora@...k.net>,
	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	torvalds@...ux-foundation.org, arekm@...-linux.org,
	baggins@...-linux.org, Alexander Viro <viro@...iv.linux.org.uk>,
	Fengguang Wu <fengguang.wu@...el.com>,
	Johannes Weiner <hannes@...xchg.org>, linux-mm@...ck.org
Subject: Re: [3.6.6] panic on reboot / khungtaskd blocked? (WARNING: at arch/x86/kernel/smp.c:123
 native_smp_send_reschedule)

On 11/15/2012 05:40 PM, Jan Kara wrote:
> On Thu 15-11-12 09:41:40, Michael Wang wrote:
>> On 11/15/2012 05:10 AM, Paweł Sikora wrote:
>>> On Wednesday 14 of November 2012 10:32:41 Michael Wang wrote:
>>>> On 11/13/2012 05:40 PM, Paweł Sikora wrote:
>>>>> On Monday 12 of November 2012 13:33:39 Paweł Sikora wrote:
>>>>>> On Monday 12 of November 2012 11:22:47 Paweł Sikora wrote:
>>>>>>> On Monday 12 of November 2012 15:40:31 Michael Wang wrote:
>>>>>>>> On 11/12/2012 03:16 PM, Paweł Sikora wrote:
>>>>>>>>> On Monday 12 of November 2012 11:04:12 Michael Wang wrote:
>>>>>>>>>> On 11/09/2012 09:48 PM, Paweł Sikora wrote:
>>>>>>>>>>> Hi,
>>>>>>>>>>>
>>>>>>>>>>> during playing with new ups i've caught an nice oops on reboot:
>>>>>>>>>>>
>>>>>>>>>>> http://imgbin.org/index.php?page=image&id=10253
>>>>>>>>>>>
>>>>>>>>>>> probably the upstream is also affected.
>>>>>>>>>>
>>>>>>>>>> Hi, Paweł
>>>>>>>>>>
>>>>>>>>>> Are you using a clean 3.6.6 without any modify?
>>>>>>>>>
>>>>>>>>> yes, pure 3.6.6 form git tree with modular config.
>>>>>>>>>
>>>>>>>>>> Looks like some threads has set itself to be UNINTERRUPTIBLE with out
>>>>>>>>>> any design on switch itself back later(or the time is too long), are you
>>>>>>>>>> accidentally using some bad designed module?
>>>>>>>>>
>>>>>>>>> hmm, hard to say. mostly all modules are loaded automatically by kernel.
>>>>>>>>
>>>>>>>> Could you please provide the whole dmesg in text? your picture lost the
>>>>>>>> print info of the hung task.
>>>>>>>
>>>>>>> i've grabbed the console via rs232 but there's no more info (see attached txt).
>>>>>>
>>>>>> hmm, i have one observation.
>>>>>>
>>>>>> during rc.shutdown there're messages on console like this: Cannot stat file /proc/$pid/fd/1: Connection timed out
>>>>>> afaics this file descriptor points to vnc log file on a remote machine, e.g.:
>>>>>>
>>>>>> # ps aux|grep xfwm4
>>>>>> eda       1748  0.0  0.0 320220 11224 ?        S    13:08   0:00 xfwm4 
>>>>>>
>>>>>> # readlink -m /proc/1748/fd/1
>>>>>> /remote/dragon/ahome/eda/.vnc/odra:11.log
>>>>>>
>>>>>> # mount|grep ahome
>>>>>> dragon:/home/users/ on /remote/dragon/ahome type nfs (rw,relatime,vers=3,rsize=262144,wsize=262144,namlen=255,soft,proto=tcp,timeo=600,retrans=2,sec=sys,mountaddr=10.0.2.121,mountvers=3,mountport=45251,mountproto=udp,local_lock=none,addr=10.0.2.121)
>>>>>>
>>>>>>
>>>>>> so, probably during `killall5 -TERM/-KILL` on shutdown stage something sometimes go wrong
>>>>>> and these processes (xfce4/vncserver) survive the signal and hang on the nfs i/o.
>>>>>>
>>>>>
>>>>> ok, now i have full sysrq+w backtraces from shutdown process. i hope i'll help you.
>>>>
>>>> This can only tell us what's the task in UNINTERRUPTABLE state, but with
>>>> out time info, we can't find out which one is the hung task...
>>
>> So it's blocked on __lock_page() for too long?
>> Add more experts in mm aspect to cc.
>   It's really NFS related. E.g. in trace
> https://lkml.org/lkml/2012/11/14/657 we are waiting on PageWriteback bit
> in fact - i.e. we have submitted data to the NFS server and are waiting for
> its response that the data was written.

Do you mean, NFS lock some page, then wait on a respond which not come in?

Regards,
Michael Wang

> 
> 								Honza
> 

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