On Mon, Jan 08, 2007 at 02:45:00PM -0700, Eric W. Biederman wrote:
> Adrian Bunk <[email protected]> writes:
>
> > On Mon, Jan 08, 2007 at 09:11:24AM -0700, Eric W. Biederman wrote:
> >>
> >> To a large extent this reverts b026872601976f666bae77b609dc490d1834bf77
> >> while still keeping to the spirits of it's goal, the ability to
> >> make smart guesses about how the timer irq is routed when the BIOS
> >> gets it wrong.
> >>...
> >
> > That's code where every changed line has a great potential of causing a
> > different kind of breakage on someone else's computer.
>
> Why does this piece of code give every one the screaming hebie jebies?
> I read it I understand it, it is code.
>
> This code is not a terribly sensitive delicate heuristic, and Andi has
> already broken it as much as it can possibly be broken. It's not like
> the code is on a SMP fastpath full of carefully orchestrated races
> that are safe because within certain limits even stale values are ok.
>
> This is code is straight forward logic, you tell the computer what to
> do and it does it. Of those things we can do only very few of
> them are correct, and we are seeking to enhance our ability to find
> correct solutions by adding intelligent guesses. As long as the first
> guess is trust the BIOS the rest of this code is largely a don't
> care. As Andi proved by breaking all the rest of this. Or why
> don't I have more testers just crawling out of the wood work,
> screaming for this code to be fixed?
>
> Plus this code can only cause one type of breakage. A failure to
> work around a broken BIOS and make the IRQs work.
We just got a completely different bug reported that was confirmed to be
caused by Andi's patch:
AMD64/ATI : timer is running twice as fast as it should [1]
> > Your comment therefore translates to "rexvert commit
> > b026872601976f666bae77b609dc490d1834bf77 for 2.6.20 and try to find a
> > better solution for 2.6.21".
>
> If that is the practical translation I am fine with it.
>...
> I really don't care how we do it, or in what timeframe. But what I have
> posted is the only way I can see of making it better, than what we had
> in 2.6.19.
>...
My whole point is that for 2.6.20, we can live with simply reverting
Andi's commit.
What to do for 2.6.21 is a completely different story.
> Eric
cu
Adrian
[1] http://bugzilla.kernel.org/show_bug.cgi?id=7789
--
"Is there not promise of rain?" Ling Tan asked suddenly out
of the darkness. There had been need of rain for many days.
"Only a promise," Lao Er said.
Pearl S. Buck - Dragon Seed
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