Merging 64 bit changes to -HEAD - part 2

[Juli Mallett]

On Fri, Jun 18, 2010 at 12:41, Neel Natu <neelnatu at gmail.com> wrote:
> Hi JC,
>
> But what you really want here is to eliminate the intr_disable() and
> intr_restore() and keep sched_pin() and  sched_unpin().

Are you sure?  I'm not.  By disabling interrupts we only have to
ensure that the fault path on any address we might access within those
routines doesn't need to use the large memory map.  This isn't
trivial, but I think we can acquire a reasonable confidence about it.
If we merely pin, we have to ensure that nothing else that can run
(including interrupts and threads that run via preemption) that would
access the large memory map — given that this includes routines like
pmap_zero_page, I think there's good reason for caution.  Disabling
interrupts is more conservative, but I think rightly-so.  I may be
mistaken.

Thanks,
Juli.