Extending virtio_console to support multiple ports

[Benjamin Herrenschmidt]

On Thu, 2009-08-27 at 10:08 +0100, Alan Cox wrote:
> >  - Then, are we certain that there's no case where the tty layer will
> > call us with some lock held or in an atomic context ? To be honest,
> > I've totally lost track of the locking rules in tty land lately so it
> > might well be ok, but something to verify.
> 
> Some of the less well behaved line disciplines do this and always have
> done.

That was also my understanding but heh, I though that maybe you may have
fixed all of that already :-)

So at this stage, I think the reasonably thing to do is to stick to the
spinlock, but we can try to make it a bit smarter, and we can definitely
attempt to fix the case Amit pointed out where we call resize without a
lock while it seems to expect it (though we also need to be careful
about re-entrancy I believe).

Cheers,
Ben.