linux-kernel - Re: [PATCH][v2] cpufreq: Bring CPUs up even if cpufreq

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Message-ID: <20170411061100.GC3670@vireshk-i7>
Date:   Tue, 11 Apr 2017 11:41:00 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Chen Yu <yu.c.chen@...el.com>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Len Brown <lenb@...nel.org>, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        "Stable # 4 . 9+" <stable@...r.kernel.org>
Subject: Re: [PATCH][v2] cpufreq: Bring CPUs up even if cpufreq_online failed

On 09-04-17, 13:45, Chen Yu wrote:
> There is a report that after
> commit 27622b061eb4 ("cpufreq: Convert to hotplug state machine"),
> the normal CPU offline/online cycle failed on some platforms.
> According to the ftrace result, this problem was triggered on
> platforms using acpi-freq as the default cpufreq driver,
> and due to the lack of some ACPI freq method(_PCT eg), the
> cpufreq_online failed and returned a negative value, thus the CPU
> hotplug statemachine rollbacked the CPU online process. Actually
> from the user's perspective the failure of cpufreq_online should
> not prevent that CPU from being brought up, although cpufreq might
> not work on that CPU. BTW, during system bootup the cpufreq_online
> is not invoked via cpuhotplug statemachine but by the cpufreq device
> creation process, thus the APs can be brought up although cpufreq_online
> failed in that stage.
> 
> This patch ignores the return value of cpufreq_online/offline and
> let the cpufreq framework to deal with the failure that, cpufreq_online()
> will do a proper rollback in that case. And if the _PCT is missing,
> the acpi cpufreq driver will print a warning if the corresponding
> debug options have been enabled.
> 
> Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=194581
> Fixes: 27622b061eb4 ("cpufreq: Convert to hotplug state machine")
> Reported-and-tested-by: Tomasz Maciej Nowak <tmn505@...il.com>
> Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>
> Cc: Viresh Kumar <viresh.kumar@...aro.org>
> Cc: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
> Cc: Len Brown <lenb@...nel.org>
> Cc: linux-pm@...r.kernel.org
> Cc: linux-kernel@...r.kernel.org
> Cc: Stable <stable@...r.kernel.org> # 4.9+
> Signed-off-by: Chen Yu <yu.c.chen@...el.com>
> ---
> v2:
>  - According to Rafael and Sebastian's suggestion, remove
>    the error log in cpuhp_cpufreq_online/offline, and let
>    the cpufreq_online and cpufreq_offline to print the warning
>    and do the necessary rollback if they failed.
> ---
>  drivers/cpufreq/cpufreq.c | 18 ++++++++++++++++--
>  1 file changed, 16 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index bc96d42..0e3f649 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -2398,6 +2398,20 @@ EXPORT_SYMBOL_GPL(cpufreq_boost_enabled);
>   *********************************************************************/
>  static enum cpuhp_state hp_online;
>  
> +static int cpuhp_cpufreq_online(unsigned int cpu)
> +{
> +	cpufreq_online(cpu);
> +
> +	return 0;
> +}
> +
> +static int cpuhp_cpufreq_offline(unsigned int cpu)
> +{
> +	cpufreq_offline(cpu);
> +
> +	return 0;
> +}
> +
>  /**
>   * cpufreq_register_driver - register a CPU Frequency driver
>   * @driver_data: A struct cpufreq_driver containing the values#
> @@ -2460,8 +2474,8 @@ int cpufreq_register_driver(struct cpufreq_driver *driver_data)
>  	}
>  
>  	ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, "cpufreq:online",
> -					cpufreq_online,
> -					cpufreq_offline);
> +					cpuhp_cpufreq_online,
> +					cpuhp_cpufreq_offline);
>  	if (ret < 0)
>  		goto err_if_unreg;
>  	hp_online = ret;

Acked-by: Viresh Kumar <viresh.kumar@...aro.org>

-- 
viresh