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SubjectRe: [PATCH v2] cpufreq: stats: Walk online CPUs with CPU offline/online locked
On 20-05-16, 03:41, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
>
> Loops over online CPUs in cpufreq_stats_init() and cpufreq_stats_exit()
> should be carried out with CPU offline/online locked or races are
> possible otherwise, so make that happen.
>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> ---
>
> v1 -> v2: On a second thought, add the policy notifier in cpufreq_stats_init()
> with CPU offline/online locked too.
>
> ---
> drivers/cpufreq/cpufreq_stats.c | 16 +++++++++++++---
> 1 file changed, 13 insertions(+), 3 deletions(-)
>
> Index: linux-pm/drivers/cpufreq/cpufreq_stats.c
> ===================================================================
> --- linux-pm.orig/drivers/cpufreq/cpufreq_stats.c
> +++ linux-pm/drivers/cpufreq/cpufreq_stats.c
> @@ -317,10 +317,13 @@ static int __init cpufreq_stats_init(voi
> unsigned int cpu;
>
> spin_lock_init(&cpufreq_stats_lock);
> +
> + get_online_cpus();
> +
> ret = cpufreq_register_notifier(&notifier_policy_block,
> CPUFREQ_POLICY_NOTIFIER);

Why is this required to be protected ?

> if (ret)
> - return ret;
> + goto out;
>
> for_each_online_cpu(cpu)
> cpufreq_stats_create_table(cpu);
> @@ -332,21 +335,28 @@ static int __init cpufreq_stats_init(voi
> CPUFREQ_POLICY_NOTIFIER);
> for_each_online_cpu(cpu)
> cpufreq_stats_free_table(cpu);

Maybe we can make this for_each_possible_cpu() then, and so getting a
policy will fail for CPUs which aren't online.

And we wouldn't need to use get_online_cpus() then ?

--
viresh

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