System hanging during dump

[Kris Kennaway]

Jeremy Chadwick wrote:
>> Has anyone else seen anything similar?
> 
> It's a known problem documented in my Wiki -- see "dump/restore".  Note
> the part about UFS2 snapshot generation.  I'm almost certain this is
> what you're describing.

I don't know how you can say this so confidently without even comparing 
the process wait channels.

Peter, there was a bug causing dump to hang (completely unrelated to 
UFS2 snapshot generation) merged to RELENG_7 a month or so ago.  Can you 
try updating?

Kris