linux-kernel - Re: [PATCH 2/2] cpufreq: Remove cpu hotplug callbacks only if they were initialized

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Message-ID: <alpine.DEB.2.20.1612151747480.3470@nanos>
Date:   Thu, 15 Dec 2016 17:47:59 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Boris Ostrovsky <boris.ostrovsky@...cle.com>
cc:     bigeasy@...utronix.de, rjw@...ysocki.net, viresh.kumar@...aro.org,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        xen-devel@...ts.xenproject.org
Subject: Re: [PATCH 2/2] cpufreq: Remove cpu hotplug callbacks only if they
 were initialized

On Thu, 15 Dec 2016, Boris Ostrovsky wrote:

> Since cpu hotplug callbacks are requested for CPUHP_AP_ONLINE_DYN state,
> successful callback initialization will result in cpuhp_setup_state()
> returning a positive value. Therefore acpi_cpufreq_online being zero
> indicates that callbacks have not been installed.
> 
> This means that acpi_cpufreq_boost_exit() should only remove them if
> acpi_cpufreq_online is positive. Trying to call
> cpuhp_remove_state_nocalls(0) will cause a BUG().
> 
> Signed-off-by: Boris Ostrovsky <boris.ostrovsky@...cle.com>

Reviewed-by: Thomas Gleixner <tglx@...utronix.de>

> ---
>  drivers/cpufreq/acpi-cpufreq.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/cpufreq/acpi-cpufreq.c b/drivers/cpufreq/acpi-cpufreq.c
> index 3a98702..3a2ca0f 100644
> --- a/drivers/cpufreq/acpi-cpufreq.c
> +++ b/drivers/cpufreq/acpi-cpufreq.c
> @@ -930,7 +930,7 @@ static void __init acpi_cpufreq_boost_init(void)
>  
>  static void acpi_cpufreq_boost_exit(void)
>  {
> -	if (acpi_cpufreq_online >= 0)
> +	if (acpi_cpufreq_online > 0)
>  		cpuhp_remove_state_nocalls(acpi_cpufreq_online);
>  }
>  
> -- 
> 1.7.1
> 
>