ZFS freeze/livelock

[Willem Jan Withagen]

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.

--WjW