linux-kernel - Re: [PATCH v2] PM / Sleep: Timer quiesce in freeze state

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Message-ID: <alpine.DEB.2.11.1411131008280.3935@nanos>
Date:	Thu, 13 Nov 2014 10:10:05 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Peter Zijlstra <peterz@...radead.org>
cc:	"Li, Aubrey" <aubrey.li@...ux.intel.com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	"Brown, Len" <len.brown@...el.com>,
	"alan@...ux.intel.com" <alan@...ux.intel.com>,
	"H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
	"linux-pm@...r.kernel.org >> Linux PM list" 
	<linux-pm@...r.kernel.org>
Subject: Re: [PATCH v2] PM / Sleep: Timer quiesce in freeze state

On Thu, 13 Nov 2014, Peter Zijlstra wrote:
> On Wed, Nov 12, 2014 at 10:09:47PM +0100, Thomas Gleixner wrote:
> But sure, we can add suspend notifiers to stuff to shut down timers; I
> should have a patch for at least one of the offenders somewhere. But I
> really think that we should not be looking at the individual timers for
> this, none of the other suspend modes care about active timers.

Fair enough.
 
> > But before we do that we want a proper explanation why the interrupt
> > fires at all. The lack of explanation cleary documents that this is a
> > 'hacked it into submission' approach.
> 
> >From what I remember its the waking interrupt that ends up in the
> timekeeping code, Li should have a backtrace somwhere.

I can imagine what happens :)

> > stomp_machine() is in 99% of all use cases a clear indicator for a
> > complete design failure.
> 
> >    So the generic idle task needs a check like this:
> > 
> >    if (idle_should_freeze())
> >       	frozen_idle();
> 
> So that is adding extra code to fairly common/hot paths just for this
> one extra special case. I tried to avoid doing that.

idle enter is not that much of a hot path, really.
 
Thanks,

	tglx
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