Re: any chance of 2.6.0-test*?

[Jens Axboe <axboe _at_ xxxxxxx>]

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?

-- 
Jens Axboe

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