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Re: [PATCH V3 12/13] cpufreq: ondemand: Traverse list of policy_dbs in update_sampling_rate()

From Viresh Kumar <viresh.kumar@linaro.org>
Newsgroups linux.kernel
Subject Re: [PATCH V3 12/13] cpufreq: ondemand: Traverse list of policy_dbs in update_sampling_rate()
Date 2016-02-08 18:30 +0100
Message-ID <qZXNo-8m9-31@gated-at.bofh.it> (permalink)
References <qZSul-4Ei-3@gated-at.bofh.it> <qZSum-4Ei-9@gated-at.bofh.it> <qZUcO-5U1-11@gated-at.bofh.it>
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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

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[PATCH V3 12/13] cpufreq: ondemand: Traverse list of policy_dbs in update_sampling_rate() Viresh Kumar <viresh.kumar@linaro.org> - 2016-02-08 12:50 +0100
  Re: [PATCH V3 12/13] cpufreq: ondemand: Traverse list of policy_dbs  in update_sampling_rate() Viresh Kumar <viresh.kumar@linaro.org> - 2016-02-08 14:40 +0100
    Re: [PATCH V3 12/13] cpufreq: ondemand: Traverse list of policy_dbs  in update_sampling_rate() "Rafael J. Wysocki" <rafael@kernel.org> - 2016-02-08 14:40 +0100
  Re: [PATCH V3 12/13] cpufreq: ondemand: Traverse list of policy_dbs  in update_sampling_rate() "Rafael J. Wysocki" <rafael@kernel.org> - 2016-02-08 14:40 +0100
    Re: [PATCH V3 12/13] cpufreq: ondemand: Traverse list of policy_dbs  in update_sampling_rate() Viresh Kumar <viresh.kumar@linaro.org> - 2016-02-08 18:30 +0100
      Re: [PATCH V3 12/13] cpufreq: ondemand: Traverse list of policy_dbs  in update_sampling_rate() "Rafael J. Wysocki" <rafael@kernel.org> - 2016-02-08 23:10 +0100
        Re: [PATCH V3 12/13] cpufreq: ondemand: Traverse list of policy_dbs  in update_sampling_rate() "Rafael J. Wysocki" <rafael@kernel.org> - 2016-02-08 23:10 +0100

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