Bug#561203: threads and fork on machine with VIPT-WB cache

["John David Anglin" <dave@hiauly1.hia.nrc.ca>]

> > > By design that shouldn't happen: the idea behind COW breaking is
> > > that before it breaks, the page is read only ... this means that
> > > processes can have clean cache copies of it, but never dirty cache
> > > copies (because writes are forbidden).
> > 
> > That must be design, I agree.
> > 
> > To keep this condition (no dirty cache for COW page), we need to flush
> > cache before ptep_set_wrprotect.  That's my point.

Is it possible that a sleep/reschedule could cause the cache to become
dirty again before it is write protected?

Dave
-- 
J. David Anglin                                  dave.anglin@nrc-cnrc.gc.ca
National Research Council of Canada              (613) 990-0752 (FAX: 952-6602)