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

[Robert Hancock]

On 11/13/2012 08:32 PM, Michael Wang wrote:
> On 11/13/2012 05:40 PM, PaweÅ Sikora wrote:
> > On Monday 12 of November 2012 13:33:39 PaweÅ Sikora wrote:
> > > On Monday 12 of November 2012 11:22:47 PaweÅ Sikora wrote:
> > > > On Monday 12 of November 2012 15:40:31 Michael Wang wrote:
> > > > > On 11/12/2012 03:16 PM, PaweÅ Sikora wrote:
> > > > > > On Monday 12 of November 2012 11:04:12 Michael Wang wrote:
> > > > > > > On 11/09/2012 09:48 PM, PaweÅ 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, PaweÅ
> > > > > > >
> > > > > > > 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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