linux-kernel - Re: [Bug #12667] Badness at kernel/time/timekeeping.c:98 in pmud (timekeeping

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Message-ID: <alpine.LFD.2.00.0902222026410.3523@localhost.localdomain>
Date:	Sun, 22 Feb 2009 20:31:59 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
cc:	Paul Collins <paul@...ly.ondioline.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Kernel Testers List <kernel-testers@...r.kernel.org>,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: [Bug #12667] Badness at kernel/time/timekeeping.c:98 in pmud
 (timekeeping_suspended)

On Fri, 20 Feb 2009, Benjamin Herrenschmidt wrote:
> On Thu, 2009-02-19 at 21:17 +0100, Thomas Gleixner wrote:
> > 
> > Well, harsh or not is not the question here. 
> > 
> > Fact is that you call gettimeofday() _before_ the timekeeping code has
> > resumed.
> > 
> > That's a simple ordering problem. timekeeping is in the sysdev class
> > as well and it's not the only sysdev which has explicit ordering
> > requirements.
> 
> And how do I control that ordering ?
> 
> I find that a bit fishy ... What about making gettimeofday() in the
> timekeeping code work, just return a frozen snapshot of the value on
> suspend instead ?

We had problems in the past where we just returned frozen time and the
calling code got surprised when the time jumped 5 hours ahead just a
few microseconds later.

What I find more fishy is the fact that the lid switch needs to be a
sysdev. It's a simple input event, which causes the user space code to
trigger the suspend sequence when the lid is shut.

Thanks,

	tglx

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