Re: [Xen-devel] [PATCH 5/9] cpufreq: avoid integer overflows.

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 12.09.13 at 14:15, Tim Deegan <tim@xxxxxxx> wrote:
> The def_sampling_rate() one is, I think, a real bug.  The others were
> spotted at the same time and are probably not bugs until we start
> dealing with 40GHz CPus.
> 
> Coverity CID 1055682
> Coverity CID 1055683
> 
> Signed-off-by: Tim Deegan <tim@xxxxxxx>

Acked-by: Jan Beulich <jbeulich@xxxxxxxx>

> Cc: Liu Jinsong <jinsong.liu@xxxxxxxxx>
> ---
>  xen/drivers/cpufreq/cpufreq_ondemand.c |    7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/xen/drivers/cpufreq/cpufreq_ondemand.c 
> b/xen/drivers/cpufreq/cpufreq_ondemand.c
> index b3f9ab8..7fdba03 100644
> --- a/xen/drivers/cpufreq/cpufreq_ondemand.c
> +++ b/xen/drivers/cpufreq/cpufreq_ondemand.c
> @@ -144,7 +144,7 @@ static void dbs_check_cpu(struct cpu_dbs_info_s 
> *this_dbs_info)
>      }
>  
>      /* Check for frequency increase */
> -    if (max_load_freq > dbs_tuners_ins.up_threshold * policy->cur) {
> +    if (max_load_freq > (uint64_t) dbs_tuners_ins.up_threshold * 
> policy->cur) 
> {
>          /* if we are already at full speed then break out early */
>          if (policy->cur == max)
>              return;
> @@ -162,7 +162,8 @@ static void dbs_check_cpu(struct cpu_dbs_info_s 
> *this_dbs_info)
>       * can support the current CPU usage without triggering the up
>       * policy. To be safe, we focus 10 points under the threshold.
>       */
> -    if (max_load_freq < (dbs_tuners_ins.up_threshold - 10) * policy->cur) {
> +    if (max_load_freq
> +        < (uint64_t) (dbs_tuners_ins.up_threshold - 10) * policy->cur) {
>          uint64_t freq_next;
>  
>          freq_next = max_load_freq / (dbs_tuners_ins.up_threshold - 10);
> @@ -246,7 +247,7 @@ int cpufreq_governor_dbs(struct cpufreq_policy *policy, 
> unsigned int event)
>           * is used for first time
>           */
>          if ((dbs_enable == 1) && !dbs_tuners_ins.sampling_rate) {
> -            def_sampling_rate = policy->cpuinfo.transition_latency *
> +            def_sampling_rate = (uint64_t) 
> policy->cpuinfo.transition_latency 
> *
>                  DEF_SAMPLING_RATE_LATENCY_MULTIPLIER;
>  
>              if (def_sampling_rate < MIN_STAT_SAMPLING_RATE)
> -- 
> 1.7.10.4




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