linux-kernel - Re: [PATCH 2/3] cpufreq: ppc: Fix integer overflow in expression

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Date:	Mon, 21 Apr 2014 11:22:45 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Geert Uytterhoeven <geert+renesas@...der.be>
Cc:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	"cpufreq@...r.kernel.org" <cpufreq@...r.kernel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/3] cpufreq: ppc: Fix integer overflow in expression

On 17 April 2014 15:23, Geert Uytterhoeven <geert+renesas@...der.be> wrote:
> On 32-bit, "12 * NSEC_PER_SEC" doesn't fit in "unsigned long"
> (NSEC_PER_SEC is a "long" constant), causing an integer overflow:
>
> drivers/cpufreq/ppc-corenet-cpufreq.c: In function 'corenet_cpufreq_cpu_init':
> drivers/cpufreq/ppc-corenet-cpufreq.c:211:9: warning: integer overflow in expression [-Woverflow]
>
> Force the intermediate to be 64-bit by adding an "ULL" suffix to the
> constant multiplier to fix this.
>
> Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be>
> ---
>  drivers/cpufreq/ppc-corenet-cpufreq.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/cpufreq/ppc-corenet-cpufreq.c b/drivers/cpufreq/ppc-corenet-cpufreq.c
> index e78f9c806de4..53881d78a931 100644
> --- a/drivers/cpufreq/ppc-corenet-cpufreq.c
> +++ b/drivers/cpufreq/ppc-corenet-cpufreq.c
> @@ -208,7 +208,7 @@ static int corenet_cpufreq_cpu_init(struct cpufreq_policy *policy)
>                 per_cpu(cpu_data, i) = data;
>
>         policy->cpuinfo.transition_latency =
> -                               (12 * NSEC_PER_SEC) / fsl_get_sys_freq();
> +                               (12ULL * NSEC_PER_SEC) / fsl_get_sys_freq();
>         of_node_put(np);
>
>         return 0;

Acked-by: Viresh Kumar <viresh.kumar@...aro.org>
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