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

Jan Kara
2012-11-15T09:40:58Z

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.

Honza
--
Jan Kara <jack@suse.cz>
SUSE Labs, CR