linux-kernel - Re: [PATCH] cpufreq: schedutil: Avoid missing updates for one-CPU policies

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Date:   Wed, 23 May 2018 17:56:27 -0700
From:   Joel Fernandes <joel@...lfernandes.org>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:     Linux PM <linux-pm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Patrick Bellasi <patrick.bellasi@....com>,
        claudio@...dence.eu.com, Todd Kjos <tkjos@...gle.com>
Subject: Re: [PATCH] cpufreq: schedutil: Avoid missing updates for one-CPU
 policies

On Wed, May 23, 2018 at 11:47:45AM +0200, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> Commit 152db033d775 (schedutil: Allow cpufreq requests to be made
> even when kthread kicked) made changes to prevent utilization updates
> from being discarded during processing a previous request, but it
> left a small window in which that still can happen in the one-CPU
> policy case.  Namely, updates coming in after setting work_in_progress
> in sugov_update_commit() and clearing it in sugov_work() will still
> be dropped due to the work_in_progress check in sugov_update_single().
> 
> To close that window, rearrange the code so as to acquire the update
> lock around the deferred update branch in sugov_update_single()
> and drop the work_in_progress check from it.
> 
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

Reviewed-by: Joel Fernandes (Google) <joel@...lfernandes.org>

thanks,

 - Joel