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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Date:	Tue, 13 Nov 2012 20:49:14 -0600
From:	Robert Hancock <hancockrwd@...il.com>
To:	Michael Wang <wangyun@...ux.vnet.ibm.com>
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
Subject: Re: [3.6.6] panic on reboot / khungtaskd blocked? (WARNING: at arch/x86/kernel/smp.c:123
 native_smp_send_reschedule)

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?
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