zfs get all command hung

[a.smith at ukgrid.net]

PS the pool is live and up and running read/write, just any zfs get  
command is hanging...

Quoting a.smith at ukgrid.net:

> Hi,
>
>   I have a script that runs every hour, one of the commands it runs  
> is "zfs get all mypool". The process has hung and cannot be killed.  
> Is there anything I can do to work out what happened? This has  
> happened before, but on older OS releases. The system is FreeBSD  
> 8.2-RELEASE amd64. A truss of the process just shows nothing,
>
> thanks Andy.
>
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