linux-kernel - Re: TSC not updating after resume: Bug or Feature?

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Message-Id: <1229639149.6613.2.camel@norville.austin.ibm.com>
Date:	Thu, 18 Dec 2008 16:25:49 -0600
From:	Dave Kleikamp <shaggy@...ux.vnet.ibm.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Ingo Molnar <mingo@...e.hu>, Peter Zijlstra <peterz@...radead.org>,
	Steven Rostedt <srostedt@...hat.com>, dsaxena@...xity.net,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org
Subject: Re: TSC not updating after resume: Bug or Feature?

On Thu, 2008-12-18 at 23:19 +0100, Rafael J. Wysocki wrote:
> On Thursday, 18 of December 2008, Ingo Molnar wrote:
> > 
> > * Peter Zijlstra <peterz@...radead.org> wrote:
> > 
> > > Rafael, would something like this explain why we had to revert Shaggy's 
> > > patch?
> 
> Well, I have yet to understand what the suspend-resume of the timekeeping code
> actually does.
> 
> The original description sounds worrisome to me, it looks like we've overlooked
> something at least.
> 
> > > His patch fixes the backward motion filter and I'm at an utter  
> > > loss why that would break suspend.
> > 
> > yes, i'd love to have this commit reinstated:
> > 
> >  5b7dba4: sched_clock: prevent scd->clock from moving backwards
> > 
> > and the bug triggered by hibernation fixed instead.
> 
> Shaggy said he had an idea of what was wrong, so I expect an updated version
> of the patch to appear.

Not really.  I said I'd look at it, but all I know is that it looks like
something clock-related isn't initialized correctly after resume.  I
don't know enough to have any idea how to fix it.

> Thanks,
> Rafael
-- 
David Kleikamp
IBM Linux Technology Center

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