[parisc-linux] Generic light-weight syscall.

[Carlos O'Donell]

> Yes we can. We can sync CR16 across CPUs within a few CPU cycles.
> I've described this before on parisc-linux.

It might be too costly to do the sync'ing all the time, and too costly
for a fast gettimeofday to do a sync at the polling point.
 
> But all the boxes we support to date have exactly one clock source.
> The multi-cell boxes (like superdome) will have multiple sources
> and I don't know how to handle those - maybe a "not quite so fast"
> gettimeofday().


The whole point behind fast gettimeofday is that userspace apps that
want to do timestamping on a _very_ accurate granularity (e.g.
nanosecondes) can get monotically incrementing numbers on each
gettimeofday. Do we even have such a fast clock on PA? What is the
fastest clock across the most boxes?

c.