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

[Michael Wang <wangyun@linux.vnet.ibm.com>]

On 11/14/2012 10:49 AM, Robert Hancock wrote:
> On 11/13/2012 08:32 PM, 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...
> 
> Probably all of the ones in D state waiting on NFS are the issue - but
> as I understand it, with modern kernels processes are supposed to be
> killable while waiting on NFS I/O. Maybe there's a bug that affects
> this, though?

That sounds possible, I thing Paweł can try to stop using NFS(if
possible) and take a look, if the issue disappear, then it's time to
report the bug to NFS folks.

Regards,
Michael Wang

>