Re: [Xen-devel] [PATCH v3 07/11] x86/intel_pstate: changes in cpufreq_del_cpu for CPU offline

[Julien Grall <julien.grall@xxxxxxxxxx>]

Hi,

On 11/06/2015 04:28, Wei Wang wrote:
> cpufreq_cpu_policy is used in intel_pstate_set_pstate(), so we change
> to NULL it after the call of cpufreq_driver->exit. Otherwise, a
> calltrace will show up on your screen due to the reference of a NULL
> pointer when you power down the system.
>
> Signed-off-by: Wei Wang <wei.w.wang@xxxxxxxxx>
> ---
>   xen/drivers/cpufreq/cpufreq.c | 6 +++---
>   1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/xen/drivers/cpufreq/cpufreq.c b/xen/drivers/cpufreq/cpufreq.c
> index 6003a8c..a8772e8 100644
> --- a/xen/drivers/cpufreq/cpufreq.c
> +++ b/xen/drivers/cpufreq/cpufreq.c
> @@ -335,12 +335,11 @@ int cpufreq_del_cpu(unsigned int cpu)
>
>       /* for HW_ALL, stop gov for each core of the _PSD domain */
>       /* for SW_ALL & SW_ANY, stop gov for the 1st core of the _PSD domain */
> -    if (hw_all || (cpumask_weight(cpufreq_dom->map) ==
> -                   perf->domain_info.num_processors))
> +    if (!policy->policy && (hw_all || (cpumask_weight(cpufreq_dom->map) ==
> +                   perf->domain_info.num_processors)))
Based on your patch #6, the field policy contains value which is defined 
per-cpufreq driver (because you defined internal value). How can you be 
sure that a driver will never use 0 as a valid value?
Regards,

--
Julien Grall

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