ZFS freeze/livelock

[Pawel Jakub Dawidek]

On Sun, Oct 10, 2010 at 05:34:39PM +0200, Willem Jan Withagen wrote:
> Hi,
> 
> Just had my FreeBSD freeze on me with what I would think is sort of an 
> livelock....
> 
> While I was receiving zfs snapshots on my data pool.
> 
> Top and systat just kept running,
> but anything getting near a shell (and perhaps disk-io) ended up in:
> 
> root at zfs.digiware.nl# gpart create -s gpt da6
> load: 0.00  cmd: csh 12393 [zfsvfs->z_teardown_inactive_lock] 26.12r 
> 0.00u 0.00s 0% 2480k
> load: 0.10  cmd: csh 12393 [zfsvfs->z_teardown_inactive_lock] 96.01r 
> 0.00u 0.00s 0% 2480k
> 
> Trying to execute to execute shutdown -r now had no effect what so ever.
> Neither did the three-finger salute.
> (Well at least not in 60 sec I was willing to wait.)
> 
> Only way out of this situation was hard-reset. And I do have to admit I 
> like ZFS for the speed it recovers after unexpected reboot.
> 
> To bad there was no alt-ctrl-backspace escape to debugger compiled in. 
> I'll do that with the next kernel, just in case.
> 
> So the only data point I can give is the ^T output above.

Maybe you still be able to provide backtraces for all processes with
'procstat -kk'?

It looks like a deadlock related to 'zfs recv' or maybe unmounting?

-- 
Pawel Jakub Dawidek                       http://www.wheelsystems.com
pjd at FreeBSD.org                           http://www.FreeBSD.org
FreeBSD committer                         Am I Evil? Yes, I Am!
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