Re: [patch 06/20] cpufreq: Use cpuhp_setup_state_nocalls_locked()

[Rafael J. Wysocki]

On Sat, Apr 15, 2017 at 7:01 PM, Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote:
> From: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
>
> cpufreq holds get_online_cpus() while invoking cpuhp_setup_state_nocalls()
> to make subsys_interface_register() and the registration of hotplug calls
> atomic versus cpu hotplug.
>
> cpuhp_setup_state_nocalls() invokes get_online_cpus() as well. This is
> correct, but prevents the conversion of the hotplug locking to a percpu
> rwsem.
>
> Use cpuhp_setup_state_nocalls_locked() to avoid the nested call.
>
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: "Rafael J. Wysocki" <rjw@xxxxxxxxxxxxx>
> Cc: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
> Cc: linux-pm@xxxxxxxxxxxxxxx

Acked-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>

>
> ---
>  drivers/cpufreq/cpufreq.c |    9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
>
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -2473,9 +2473,10 @@ int cpufreq_register_driver(struct cpufr
>                 goto err_if_unreg;
>         }
>
> -       ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, "cpufreq:online",
> -                                       cpuhp_cpufreq_online,
> -                                       cpuhp_cpufreq_offline);
> +       ret = cpuhp_setup_state_nocalls_locked(CPUHP_AP_ONLINE_DYN,
> +                                              "cpufreq:online",
> +                                              cpuhp_cpufreq_online,
> +                                              cpuhp_cpufreq_offline);
>         if (ret < 0)
>                 goto err_if_unreg;
>         hp_online = ret;
> @@ -2519,7 +2520,7 @@ int cpufreq_unregister_driver(struct cpu
>         get_online_cpus();
>         subsys_interface_unregister(&cpufreq_interface);
>         remove_boost_sysfs_file();
> -       cpuhp_remove_state_nocalls(hp_online);
> +       cpuhp_remove_state_nocalls_locked(hp_online);
>
>         write_lock_irqsave(&cpufreq_driver_lock, flags);
>
>
>