Robert Black <r.black@ic.ac.uk> writes:

> 
> > > Some time ago I know there was a problem with several ports with processes
> > > occassionally hanging in a disk-wait (in vflushbuf). Does anyone know
> whether
> > > this problem was ever resolved?
> > >
> >
> > I don't think it has been : Yesterday I saw this on my NetBSD/pmax :
> > [...]
> 
> Yup, thats the one. The vnode information when its stuck in that state seems to
> be:
> 
> num_output = 1;
> read = 0;
> write = 0;
> referenced = 0;
> flags = VXLOCK | VBWAIT;

This indicates that a buffer is never being freed.  That's most likely
a bug in the low-level SCSI driver.