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

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Message-ID: <20141028082900.GP3337@twins.programming.kicks-ass.net>
Date:	Tue, 28 Oct 2014 09:29:00 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	"Li, Aubrey" <aubrey.li@...ux.intel.com>
Cc:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	"Brown, Len" <len.brown@...el.com>,
	"alan@...ux.intel.com" <alan@...ux.intel.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"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: [RFC/PATCH] PM / Sleep: Timer quiesce in freeze state

On Tue, Oct 28, 2014 at 12:32:16PM +0800, Li, Aubrey wrote:
> On 2014/10/27 15:28, Peter Zijlstra wrote:
> > On Mon, Oct 27, 2014 at 02:27:27PM +0800, Li, Aubrey wrote:
> >>> Now I suppose the problem is with cpu_pause() which needs IPIs to
> >>> complete? Do we really need cpuidle_pause() there?
> >>> cpuidle_uninstall_handlers() seems like a daft thing to call just about
> >>> there.
> >>
> >> Please check the log of 8651f97bd951d0bb1c10fa24e3fa3455193f3548.
> >> Rafael should know more this question than me.
> > 
> > That changelog explains its complete bollocks to do it here. We _want_
> > to enter and/or remain in deep idle states.
> 
> cpuidle_resume() will be called at the end of dpm_resume_noirq(). So we
> still are able to enter deep idle states after resume.

cpuidle_resume is absolute crap, as is cpuidle_suspend for that matter
-- in this case.

The only reason we needed cpuidle_suspend is because some BIOS shat its
pants when some CPUs were in higher C states while trying to do the S3
thing. We're not going to use S states or BIOS calls _at_all_, so no
point in kicking CPUs out of their deep C states.

Read that changelog you referred me to again.
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