Re: SMP Hurd

[Andrew Archibald <aarchiba@calum.csclub.uwaterloo.ca>]

Roland McGrath <roland@frob.com> writes:

> As far as I know, the Hurd has never been tested on a multiprocessor.
> Since the microkernel always does preemptive scheduling, in the abstract
> there is almost no way for the Hurd to tell whether kernel threads are
> purely software or are running on multiple real processors, and there is
> nothing whatsoever it does that is supposed to care.  But since it hasn't
> been tested, I have to assume there are bugs that will only show up on real
> SMP hardware.

Actually, it is possible to tell, at least on the Intel hardware.
>From my brief, unpleasant) experience using NT SMP/kernel threads, SMP
leads to many more headaches.  One example was that integer
reads/writes weren't atomic.  Not that ths matters unless you're (like
I was) using sloppy locking (I was in a hurry, ok? :). 

So I don't eexpect the Hurd will have problems, but it's entirely
possible.  I'd really like to see the Hurd running on SMP hardware
(just wish I'd been able to afford some).

Andrew