linux-kernel - Re: [v9 PATCH 4/9]: x86: refactor x86 idle power management code and remove all instances of pm

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Date:	Mon, 26 Oct 2009 13:55:25 +0530
From:	Arun R Bharadwaj <arun@...ux.vnet.ibm.com>
To:	Pavel Machek <pavel@....cz>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Ingo Molnar <mingo@...e.hu>,
	Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>,
	Dipankar Sarma <dipankar@...ibm.com>,
	Balbir Singh <balbir@...ibm.com>,
	Andi Kleen <andi@...stfloor.org>, linux-kernel@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org, linux-arch@...r.kernel.org,
	linux-acpi@...r.kernel.org,
	Arun Bharadwaj <arun@...ux.vnet.ibm.com>
Subject: Re: [v9 PATCH 4/9]: x86: refactor x86 idle power management code
	and remove all instances of pm_idle.

* Pavel Machek <pavel@....cz> [2009-10-26 08:58:31]:

> 
> > > > +static int local_idle_loop(struct cpuidle_device *dev, struct cpuidle_state *st)
> > > > +{
> > > > +	ktime_t t1, t2;
> > > > +	s64 diff;
> > > > +	int ret;
> > > > +
> > > > +	t1 = ktime_get();
> > > > +	local_idle();
> > > > +	t2 = ktime_get();
> > > > +
> > > > +	diff = ktime_to_us(ktime_sub(t2, t1));
> > > > +	if (diff > INT_MAX)
> > > > +		diff = INT_MAX;
> > > > +	ret = (int) diff;
> > > > +
> > > > +	return ret;
> > > > +}
> > > 
> > > So we get this routine essentially 3 times. Is there no way to share
> > > the code?
> > > 
> > 
> > We can move this code to a common place, but that would mean exporting
> > the idle function pointer to be called from within this routine, which
> > is exactly what we wanted to avoid.
> > 
> > Any suggestions are welcome.
> 
> You can just pass idle routine as a parameter...?
> 
> int common_idle_loop(struct cpuidle_device *dev, struct cpuidle_state
> *st, void *idle(void))
> 
> ...?
> 									Pavel

Yes, this should be fine. I was trying to avoid passing the void
function pointer around but i guess this reduces considerable code
size.

thanks!
arun
> -- 
> (english) http://www.livejournal.com/~pavelmachek
> (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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