linux-kernel - Re: [PATCH] sched, x86: fix overflow in cyc2ns

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Message-ID: <1331339714.26253.139.camel@work-vm>
Date:	Fri, 09 Mar 2012 16:35:14 -0800
From:	john stultz <johnstul@...ibm.com>
To:	Salman Qazi <sqazi@...gle.com>
Cc:	Ingo Molnar <mingo@...e.hu>, Paul Turner <pjt@...gle.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] sched, x86: fix overflow in cyc2ns_offset

On Fri, 2012-03-09 at 16:28 -0800, Salman Qazi wrote:
> On Fri, Mar 9, 2012 at 4:25 PM, john stultz <johnstul@...ibm.com> wrote:
> > So... Sorry, why did you change it from the shifted logic?
> >
> 
> It's more generally applicable.  The compiler is smart enough to do
> the right thing in the power-of-two
> constant case.
>
> >
> > Is the compiler really smart enough to avoid the divides?
> 
> Yes, it is.  I verified that.

Ok, great! Thanks again! (Although I probably need to put rewriting the
the big x86/include/asm/timer.h comment on my TODO, since its not as
relevant anymore)

Acked-by: John Stultz <john.stultz@...aro.org>

Ingo/Thomas, this should probably go tip/timers/urgent & be marked for
stable. I can queue it and send you a pull request, but it might be just
easier to just pick up the patch.

thanks
-john

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