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Date: Mon, 16 Aug 2004 17:37:51 +0200
From: Ingo Molnar <mingo@elte.hu>
To: Thomas Charbonnel <thomas@undata.org>
Cc: Lee Revell <rlrevell@joe-job.com>, Florian Schmidt <mista.tapas@gmx.net>,
       linux-kernel <linux-kernel@vger.kernel.org>,
       Felipe Alfaro Solana <felipe_alfaro@linuxmail.org>
Subject: Re: [patch] voluntary-preempt-2.6.8.1-P2
Message-ID: <20040816153751.GA15573@elte.hu>
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* Thomas Charbonnel <thomas@undata.org> wrote:

> > >  0.000ms (+0.000ms): do_IRQ (default_idle)
> > >  0.000ms (+0.000ms): mask_and_ack_8259A (do_IRQ)
> > >  0.459ms (+0.459ms): generic_redirect_hardirq (do_IRQ)
> > >  0.459ms (+0.000ms): generic_handle_IRQ_event (do_IRQ)
> > >  0.459ms (+0.000ms): timer_interrupt (generic_handle_IRQ_event)
> > 
> > > It definitely looks like the kernel is interrupted by some interrupt
> > > source not covered by the patch.
> > 
> > the only possibility is SMM, which is not handled by Linux. (but by the
> > BIOS.) Otherwise we track everything - including NMIs.

> This would confirm the hypothesis of a buggy BIOS, I'm afraid.

there are still other (and more likely) possible reasons like a bug in
the latency tracer. (Or a broken TSC - albeit this is less likely.)

can you reproduce this phenomenon at will? Does it go away if you turn 
ACPI/APM off (both in the kernel and in the BIOS). Does it go away if 
you use idle=poll?

	Ingo