linux-kernel - Re: [PATCH 4/6] PM / sleep: Make it possible to quiesce timers during suspend-to-idle

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Date:	Thu, 12 Feb 2015 17:19:37 +0100
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Alan Cox <alan@...ux.intel.com>,
	"Li, Aubrey" <aubrey.li@...ux.intel.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux PM list <linux-pm@...r.kernel.org>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	Kristen Carlson Accardi <kristen@...ux.intel.com>,
	John Stultz <john.stultz@...aro.org>,
	Len Brown <len.brown@...el.com>
Subject: Re: [PATCH 4/6] PM / sleep: Make it possible to quiesce timers during suspend-to-idle

On Thursday, February 12, 2015 02:24:47 PM Peter Zijlstra wrote:
> On Wed, Feb 11, 2015 at 05:03:44AM +0100, Rafael J. Wysocki wrote:
> > Index: linux-pm/include/linux/cpuidle.h
> > ===================================================================
> > --- linux-pm.orig/include/linux/cpuidle.h
> > +++ linux-pm/include/linux/cpuidle.h
> > @@ -50,6 +50,10 @@ struct cpuidle_state {
> >  			int index);
> >  
> >  	int (*enter_dead) (struct cpuidle_device *dev, int index);
> 
> Do we want a comment here describing that enter_freeze() must not
> re-enable interrupts _ever_?
> 
> To help people who want to enable this on their platform.

Good point.

I'll update the patch later today.

> > +
> > +	void (*enter_freeze) (struct cpuidle_device *dev,
> > +			      struct cpuidle_driver *drv,
> > +			      int index);
> >  };
> 
> > +static void enter_freeze_proper(struct cpuidle_driver *drv,
> > +				struct cpuidle_device *dev, int index)
> > +{
> > +	tick_freeze();
> > +	/*
> > +	 * The state used here cannot be a "coupled" one, because the "coupled"
> > +	 * cpuidle mechanism enables interrupts and doing that with timekeeping
> > +	 * suspended is generally unsafe.
> > +	 */
> > +	drv->states[index].enter_freeze(dev, drv, index);
> 
> 	WARN_ON(!irqs_disabled());
> 
> To go along with the comment and catch fail?

Yeah, will do.

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