From: Yue Hu <zbestahu@gmail.com>
To: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Yue Hu <zbestahu@163.com>,
"Rafael J. Wysocki" <rafael@kernel.org>,
"Rafael J. Wysocki" <rjw@rjwysocki.net>,
Rafael Wysocki <rafael.j.wysocki@intel.com>,
Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Juri Lelli <juri.lelli@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Steven Rostedt <rostedt@goodmis.org>,
Benjamin Segall <bsegall@google.com>,
Mel Gorman <mgorman@suse.de>,
Daniel Bristot de Oliveira <bristot@redhat.com>,
Linux PM <linux-pm@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Yue Hu <huyue2@yulong.com>,
zhangwen@yulong.com
Subject: Re: [PATCH] cpufreq: schedutil: Don't use the limits_changed flag any more
Date: Mon, 15 Feb 2021 15:10:46 +0800 [thread overview]
Message-ID: <20210215151046.00001894.zbestahu@gmail.com> (raw)
In-Reply-To: <20210215063008.hsdkrs4bw7wt3wye@vireshk-i7>
On Mon, 15 Feb 2021 12:00:08 +0530
Viresh Kumar <viresh.kumar@linaro.org> wrote:
> On 14-02-21, 11:44, Yue Hu wrote:
> > On Fri, 12 Feb 2021 17:14:03 +0100
> > "Rafael J. Wysocki" <rafael@kernel.org> wrote:
> > > This may be running in parallel with sugov_update_next_freq() on a
> > > different CPU, so the latter may clear need_freq_update right
> > > after it has been set here unless I'm overlooking something.
> >
> > Whether this logic is also happening for limits_changed in
> > sugo_should_update_freq() or not?
>
> It is but it shouldn't have any side effects as we calculate the next
> frequency after cleaning the limits_changed flag. Your patch would
> have been fine, but it is not anymore because of commit 23a881852f3e
> ("cpufreq: schedutil: Don't skip freq update if need_freq_update is
> set").
>
> It made a considerable change after which your patch adds a bug. With
> 23a881852f3e, need_freq_update is updated/cleared after the next
> frequency is calculated, while earlier it was cleared before it. And
> so even with the race condition taking place, there were no issues.
>
Okay, clear.
prev parent reply other threads:[~2021-02-15 7:11 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-08 3:07 Yue Hu
2021-02-09 11:11 ` Viresh Kumar
2021-02-12 16:14 ` Rafael J. Wysocki
2021-02-14 3:44 ` Yue Hu
2021-02-15 6:30 ` Viresh Kumar
2021-02-15 7:10 ` Yue Hu [this message]
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