Re: [RFC PATCH 04/19] cpufreq: bring data structures close to their locks

[Peter Zijlstra]

On Mon, Jan 11, 2016 at 05:35:45PM +0000, Juri Lelli wrote:
> +/**
> + * The "cpufreq driver" - the arch- or hardware-dependent low
> + * level driver of CPUFreq support, and its spinlock (cpufreq_driver_lock).
> + * This lock also protects cpufreq_cpu_data array and cpufreq_policy_list.
> + */
> +static struct cpufreq_driver *cpufreq_driver;
> +static DEFINE_PER_CPU(struct cpufreq_policy *, cpufreq_cpu_data);
>  static LIST_HEAD(cpufreq_policy_list);
> +static DEFINE_RWLOCK(cpufreq_driver_lock);

Part of my suggestion was to fold the per-cpu data of cpufreq_cpu_data
into struct cpufreq_driver.

That way each cpufreq_driver will have its own copy and there'd be only
the one global pointer to swizzle. Something very well suited to RCU.