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

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Message-Id: <200812190039.34184.rjw@sisk.pl>
Date:	Fri, 19 Dec 2008 00:39:33 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Dave Kleikamp <shaggy@...ux.vnet.ibm.com>
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 Thursday, 18 of December 2008, Dave Kleikamp wrote:
> 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.

Well, thanks for the update.

I'm going to have a look at the thing tomorrow, but I'm not sure I'll be able
to fix it.

Thanks,
Rafael
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