linux-kernel - Re: [RFC PATCHC 2/3] idle: store the idle state the cpu is

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Message-ID: <20140415124437.GO13658@twins.programming.kicks-ass.net>
Date:	Tue, 15 Apr 2014 14:44:37 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Daniel Lezcano <daniel.lezcano@...aro.org>
Cc:	linux-kernel@...r.kernel.org, mingo@...e.hu, rjw@...ysocki.net,
	nicolas.pitre@...aro.org, linux-pm@...r.kernel.org,
	alex.shi@...aro.org, vincent.guittot@...aro.org,
	morten.rasmussen@....com
Subject: Re: [RFC PATCHC 2/3] idle: store the idle state the cpu is

On Tue, Apr 15, 2014 at 02:43:30PM +0200, Peter Zijlstra wrote:
> On Fri, Mar 28, 2014 at 01:29:55PM +0100, Daniel Lezcano wrote:
> > @@ -143,6 +145,10 @@ static int cpuidle_idle_call(void)
> >  			if (!ret) {
> >  				trace_cpu_idle_rcuidle(next_state, dev->cpu);
> >  
> > +				*power = &drv->states[next_state].power;
> > +
> > +				wmb();
> > +
> 
> I very much suspect you meant: smp_wmb(), as I don't see the hardware
> reading that pointer, therefore UP wouldn't care. Also, any and all
> barriers should come with a comment that describes the data ordering and
> points to the matchin barriers.

Furthermore, this patch fails to describe the life-time rules of the
object placed there. Can the objected pointed to ever disappear?
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