hi,

this may actually be a problem for wired mappings.
though that's more a sign of a deficiency in the design of wired mappings
(ie. that the pmap must treat them specially) than a bug in any given
pmap implementation.

-Chuck


On Wed, May 21, 2003 at 05:40:07PM -0700, Jason Thorpe wrote:
> 
> On Wednesday, May 21, 2003, at 04:44  PM, Stephan Uphoff wrote:
> 
> >pmap_enter() does not replace the old mapping atomically with the new 
> >mapping
> >             if the old mapping points to a managed page.
> >	     Other CPUs might observe va to be unmapped (pte == 0) before
> >             pmap_enter sets the new mapping.
> >
> >	     I don't think this is a problem.
> >             If it is, the pve handling needs to be changed.
> 
> I don't think it's a problem, either.  In this case, the worst that 
> could happen is that the other CPU would take a page fault, but then 
> would block in the upper layers of the VM code.  By the time it 
> unblocked, the only damage it could do would be to enter the same 
> mapping again.
> 
>         -- Jason R. Thorpe <thorpej@wasabisystems.com>