linux-kernel - Re: [PATCH v2] cpufreq: Avoid using inactive policies

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Date:   Mon, 21 Nov 2016 09:07:31 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:     Linux PM list <linux-pm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
Subject: Re: [PATCH v2] cpufreq: Avoid using inactive policies

On 18-11-16, 13:40, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> There are two places in the cpufreq core in which low-level driver
> callbacks may be invoked for an inactive cpufreq policy, which isn't
> guaranteed to work in general.  Both are due to possible races with
> CPU offline.
> 
> First, in cpufreq_get(), the policy may become inactive after
> the check against policy->cpus in cpufreq_cpu_get() and before
> policy->rwsem is acquired, in which case using it going forward may
> not be correct.
> 
> Second, an analogous situation is possible in cpufreq_update_policy().
> 
> Avoid using inactive policies by adding policy_is_inactive() checks
> to the code in the above places.
> 
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
> 
> -> v2:
>  Initialize ret in cpufreq_update_policy() if the inactive policy check
>  doesn't pass.

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

-- 
viresh