Re: any chance of 2.6.0-test*?

Terje Eggestad
2003-01-13T16:16:59Z

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?

> > 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.

TJ

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Terje Eggestad mailto:terje.eggestad@scali.no
Scali Scalable Linux Systems http://www.scali.com

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