linux-kernel - Re: Timer unstability on when using C2 and deeper sleep states (Dell Latitude XT)

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Message-ID: <87proczn33.fsf@basil.nowhere.org>
Date:	Wed, 13 Aug 2008 22:17:36 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Milan Plzik <milan.plzik@...il.com>
Cc:	linux-kernel@...r.kernel.org, tglx@...utronix.de
Subject: Re: Timer unstability on when using C2 and deeper sleep states (Dell Latitude XT)

Milan Plzik <milan.plzik@...il.com> writes:

>   I apologize for replying on my own mail (and also for top-posting, but
> this information is global update, not exactly fitting any of topics
> mentioned below).
>
>   After playing for a longer while I found out that the system ends
> sometimes in state where, in order to do anything useful, I need to
> press keys on keyboard. 

This usually means it is using the wrong timer in a deeper idle state.
Some idle states cannot be woken up by e.g. the APIC timer and then
you get that effect: you only make progress when you wake up the 
CPU in some other way like pressing a key. Then on wake up the
timers get processed.

This is usually a bug in the kernel timer selection. It should be chosing
a timer that always wakes up from the deepest idle state used.

You should post the full boot log

-Andi

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