linux-kernel - Re: [REGRESSION from 2.6.23-rc8] (was: Re: 2.6.23-rc4-mm1 and -rc6-mm1: boot failure on HP nx6325, related to clockevents)

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Message-Id: <200709301158.17823.ak@suse.de>
Date:	Sun, 30 Sep 2007 11:58:17 +0200
From:	Andi Kleen <ak@...e.de>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>
Subject: Re: [REGRESSION from 2.6.23-rc8] (was: Re: 2.6.23-rc4-mm1 and -rc6-mm1: boot failure on HP nx6325, related to clockevents)

> 
> > OK, this explains 2) and 3). I just looked into the code and the logic
> > vs. noapictimer on SMP is completely broken.

noapictimer really doesn't make any sense on non SMP imho with the old
timer architecture. That is why I never bothered to implement it.
It's purely a UP hack.

> ..and thanks for the explanation.
> 
> Thanks for finding it so quickly guys. Sounds like this will be fixed 
> properly in 2.6.24 with the x86 merge (which hopefully brings in the hrt 
> patch too)

There is nothing really to fix currently.  Clockevents changes behaviour
majorly (always using APIC timers without irq 0 backups[1]) and that causes
problems that need new workarounds and new fixes (surprise surprise!)

That merge would probably fix a few more such "Thomas doesn't understand
the code" bugs I guess because he hacks much more on i386 than x86-64;
but if the overall result will be really better is a totally different
question.

-Andi

[1]  Or let's call it "I trust all my time to the CPU" and no more southrbridge
aka put all eggs in one basket. Given the trends in CPU power saving that
is a quite dangerous strategy.
-
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