ZFS freeze/livelock

[Jeremy Chadwick]

On Sun, Oct 10, 2010 at 05:34:39PM +0200, Willem Jan Withagen wrote:
> 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.

We don't know what FreeBSD version you're using (specifically uname -a
output, since build date matters), but if it's RELENG_8 with ZFS v15,
you might check out this thread (be sure to read Kai and I's diagnoses):

http://lists.freebsd.org/pipermail/freebsd-fs/2010-October/009687.html

I'm in the process of moving all of my machines, including my home
server, over to gmirror.  (Home machine started showing signs of serious
ZFS performance degredation; mutt doing a stat() on 24 files and
directories total taking literally 0.4 seconds on a dual-core machine.
Makes no sense, doesn't happen with UFS2, I'm done.)

-- 
| Jeremy Chadwick                                   jdc at parodius.com |
| Parodius Networking                       http://www.parodius.com/ |
| UNIX Systems Administrator                  Mountain View, CA, USA |
| Making life hard for others since 1977.              PGP: 4BD6C0CB |