On man, 2003-01-13 at 17:26, Jens Axboe wrote:
> On Mon, Jan 13 2003, Terje Eggestad wrote:
> > On man, 2003-01-13 at 16:49, Jens Axboe wrote:
> > > On Mon, Jan 13 2003, Terje Eggestad wrote:
> > > > Considering that doing kernel development is hard enough, new
> > > > development is almost always done on uni processors kernels that do only
> > > > one thing at the time. Then when you base logic is OK, you move to a
> > > > SMP, which means (adding and) debugging you spin locks.
> > >
> > > Goto's aside, I find the above extremely bad advise. You should _always_
> > > develop with smp and for smp from the very start, or you will most
> > > likely not get it right later on. With preempt, this becomes even more
> > > important.
> >
> > You should, and I do, *design* with smp in mind, and I throw in
> > smplock/unlonk as I go, but I tend to make first runs on a UP.
> >
> > I see your point on preemt, though.
> > You do first runs on SMP?
>
> Always, if for nothing else than the benefit of a better debugging
> environment.
>
> > > > Considering that fucking up spin locks are prone to corrupting your
> > > > machine, one very simple trick to makeing fewer mistakes to to have one,
> > > > and only one, unlock for every lock.
> > >
> > > Taking a spin lock twice will hard lock the machine, however on smp you
> > > will typically have the luxury of an nmi watchdog which will help you
> > > solve this quickly. Double unlock will oops immediately if you run with
> > > spin lock debugging (you probably should, if you are developing kernel
> > > code).
> >
> > I have the console on a serial port, and a terminal server. With kdb,
> > you can enter the kernel i kdb even when deadlocked.
>
> Even if spinning with interrupt disabled?
Haven't painted myself into that corner yet. Doubt it, very much.
-- _________________________________________________________________________Terje Eggestad mailto:terje.eggestad@scali.no Scali Scalable Linux Systems http://www.scali.com
Olaf Helsets Vei 6 tel: +47 22 62 89 61 (OFFICE) P.O.Box 150, Oppsal +47 975 31 574 (MOBILE) N-0619 Oslo fax: +47 22 62 89 51 NORWAY _________________________________________________________________________
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
This archive was generated by hypermail 2b29 : Wed Jan 15 2003 - 22:00:46 EST