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Date: Mon, 8 Feb 2016 22:50:28 +0530
From: Viresh Kumar <viresh.kumar@linaro.org>
To: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: Rafael Wysocki <rjw@rjwysocki.net>, Juri Lelli <juri.lelli@arm.com>,
        Lists linaro-kernel <linaro-kernel@lists.linaro.org>,
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        Morten Rasmussen <morten.rasmussen@arm.com>, dietmar.eggemann@arm.com,
        Shilpasri G Bhat <shilpa.bhat@linux.vnet.ibm.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH V3 12/13] cpufreq: ondemand: Traverse list of policy_dbs
 in update_sampling_rate()
Message-ID: <20160208172028.GU8294@vireshk>
References: <cover.1454931188.git.viresh.kumar@linaro.org>
 <bb6f1b48f09cfe1f0322b1718bf797f8cf5e108c.1454931189.git.viresh.kumar@linaro.org>
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On 08-02-16, 14:32, Rafael J. Wysocki wrote:
> The comment still applies.
> 
> Moreover, please extend it to say that this must be called with
> dbs_data->mutex held (or it looks racy otherwise).

Modified it as:

+ *
+ * Simply updating dbs_tuners_int.sampling_rate might not be appropriate here.
+ * For example, if the original sampling_rate was 1 second and the requested new
+ * sampling rate is 10 ms because the user needs immediate reaction from
+ * ondemand governor, otherwise the governor may change the sampling rate too
+ * late; up to 1 second later.
+ *
+ * Similar logic applies while increasing the sampling rate. And so we need to
+ * update it with immediate effect.
+ *
+ * This must be called with dbs_data->mutex held, otherwise traversing
+ * policy_dbs_list isn't safe.

-- 
viresh