> > It seems to me that the vfork semantics should be changed so that 
> > upcalls
> > should not be happening while the child is running on the parent's 
> > stack.
> > Maybe we should introduce a process flag that indicates P_INVFORK, and
> > have execve clear it. While a process is in P_INVFORK, it cannot 
> > execute
> > upcalls.
> 
> P_PPWAIT isn't good enough?

P_PPWAIT is set on the child, we have to block upcalls in the parent.

    christian