> Under heavy filesystem I/O (tar xzvf of a kernel source archive, for example -
> archive on a NFS, extracted to a ffs+softdep), my SS20 will hang solid:
> the LED stop blinking, and I can't enter ddb (from keyboard)
> Anyone else seeing this ? A kernel of a few weeks ago (1.5T) doesn't have
> this behavior. This is a dual-CPU machine, kernel compiled with
> 'options MULTIPROCESSOR'

Could be hanging on a spinlock in a MP kernel. You could try to find out
where by changing __cpu_simple_lock() to not wait indefinitely or
by using LOCKDEBUG (without MULTIPROCESSOR).