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SubjectRe: 2.6.24-rc6-git12: Reported regressions from 2.6.23
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On Sunday, 6 of January 2008, Arjan van de Ven wrote:
> On Sun, 6 Jan 2008 10:55:01 +0100
> Ingo Molnar <mingo@elte.hu> wrote:
>
> >
> > * Mark Lord <lkml@rtr.ca> wrote:
> >
> > > Rafael J. Wysocki wrote:
> > >> This message contains a list of some regressions from 2.6.23
> > >> reported since 2.6.24-rc1 was released, for which there are no
> > >> fixes in the mainline I know of. If any of them have been fixed
> > >> already, please let me know.
> > > ..
> > >> Subject : 20000+ wake-ups/second in 2.6.24
> > >> Submitter : Mark Lord <lkml@rtr.ca>
> > >> Date : 2007-12-02 04:23
> > >> References : http://lkml.org/lkml/2007/12/1/141
> > >> http://bugzilla.kernel.org/show_bug.cgi?id=9489
> > >> Handled-By : Arjan van de Ven <arjan@infradead.org>
> > >>
> > >
> > > I wonder if it's just a babbling IRQ on resume, before the driver
> > > has run it's resume code or something ?
> >
> > i've read the discussions, and i cannot see it analyzed anywhere
> > _what_ causes the wakeups. And how are these wakeups counted? Is this
> > based on powertop output:
> >
> > Wakeups-from-idle per second : 20.4 interval: 1.8s
> >
> > ? Somewhere i saw it mentioned that "the CPU throws out of C mode".
> > What does that mean - does it mean we try to idle again and again,
> > but we immediately return from C mode - while this all looks like
> > "idle" time to the scheduler (so 'top' will show lots of idle time),
> > but the ACPI wakeup counters are going up like mad? What
> > is /proc/interrupts doing when this happens - is any of the irq
> > sources going upwards?
> >
>
> what seems to happen (and this is based on seeing this on my own devel laptop, as well
> as several other reports; Mark is by far not the only one) is something hardware
> related, it's been seen on lots of different kernel versions.
>
> It seems to mostly (but not 100%) happen with TI cardbus bridges, where for some reason,
> once the yenta driver is loaded (unloading it later makes no difference), once in a while
> we get into a mode where the CPU always immediately goes out of the C-state again.
> On a hardware level, there are only a few things that cause a CPU to exit a C-state,
> and one of them is a pending interrupt of some kind, which is the most likely thing going on here;
> some device or apic being stuck with interrupt high, but somehow the CPU isn't actually
> seeing the interrupt itself (or has it blocked!)
>
> To call this a 2.6.24 regression is a mistake (as I've said before), it's not new to .24
> by any means.

Thanks for the explanation, I'm removing this from the regressions list, then.

Greetings,
Rafael


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