linux-kernel - Re: linux-next: Tree for June 13: IO APIC breakage on HP nx6325

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Message-Id: <200806300059.03288.rjw@sisk.pl>
Date:	Mon, 30 Jun 2008 00:59:01 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	"Maciej W. Rozycki" <macro@...ux-mips.org>,
	Matthew Garrett <mjg59@...f.ucam.org>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	linux-next@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	Len Brown <lenb@...nel.org>,
	Andi Kleen <andi-suse@...stfloor.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: linux-next: Tree for June 13: IO APIC breakage on HP nx6325

On Sunday, 29 of June 2008, Ingo Molnar wrote:
> 
> * Maciej W. Rozycki <macro@...ux-mips.org> wrote:
> 
> >  You may argue this is a regression, but this is simply the cost paid 
> > for progress -- the kernel stays within the spec as defined both by 
> > ACPI and MPS, we have just started using a different configuration now 
> > and an interrupt source override provided by the manufacturer 
> > explicitly states INTIN2 is good to use.  In a sense you were simply 
> > lucky previously the kernel was bad enough with the way it configured 
> > the timer through the I/O APIC it failed completely avoiding the bug 
> > in your firmware.  Now the bug has got uncovered.
> 
> well as long as we eliminate the bad effects around via DMI exceptions 
> nobody will feel the need to argue whether it's a regression ;-)

If all boxes affected by this particulare breakage are covered by DMI-based
workarounds, they will continue to work and that won't be any regression.
The point is that the patch should go along with such workarounds.

> [this problem could be argued to be a regression, even if it's caused by
> prior luck/stupidity of Linux. We have to live with the effects of our
> mistakes.] 

That's exactly right.

Thanks,
Rafael
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