From: Viresh Kumar <viresh.kumar@linaro.org>
To: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
linaro-kernel@lists.linaro.org, linux-pm@vger.kernel.org,
linux-kernel@vger.kernel.org,
Vincent Guittot <vincent.guittot@linaro.org>,
smuckle.linux@gmail.com, juri.lelli@arm.com,
Morten.Rasmussen@arm.com, patrick.bellasi@arm.com,
eas-dev@lists.linaro.org
Subject: Re: [RFC 5/9] sched: cpufreq: remove smp_processor_id() in remote paths
Date: Tue, 11 Apr 2017 16:05:56 +0530 [thread overview]
Message-ID: <20170411103556.GC13627@vireshk-i7> (raw)
In-Reply-To: <1836427.bpauTYz19k@aspire.rjw.lan>
On 29-03-17, 23:28, Rafael J. Wysocki wrote:
> On Thursday, March 09, 2017 05:15:15 PM Viresh Kumar wrote:
> > @@ -216,7 +216,7 @@ static void sugov_update_single(struct update_util_data *hook, u64 time,
> > if (flags & SCHED_CPUFREQ_RT_DL) {
> > next_f = policy->cpuinfo.max_freq;
> > } else {
> > - sugov_get_util(&util, &max);
> > + sugov_get_util(&util, &max, hook->cpu);
>
> Why is this not racy?
Why would reading the utilization values be racy? The only dynamic value here is
"util_avg" and I am not sure if reading it is racy.
But, this whole routine has races which I ignored as we may end up updating
frequency simultaneously from two threads.
> > sugov_iowait_boost(sg_cpu, &util, &max);
> > next_f = get_next_freq(sg_policy, util, max);
> > }
> > @@ -272,7 +272,7 @@ static void sugov_update_shared(struct update_util_data *hook, u64 time,
> > unsigned long util, max;
> > unsigned int next_f;
> >
> > - sugov_get_util(&util, &max);
> > + sugov_get_util(&util, &max, hook->cpu);
> >
>
> And here?
>
> > raw_spin_lock(&sg_policy->update_lock);
The lock prevents the same here though.
So, if we are going to use this series, then we can use the same update-lock in
case of single cpu per policies as well.
--
viresh
next prev parent reply other threads:[~2017-04-11 10:38 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-09 11:45 [RFC 0/9] cpufreq: schedutil: Allow remote wakeups Viresh Kumar
2017-03-09 11:45 ` [RFC 1/9] sched: cpufreq: add cpu to update_util_data Viresh Kumar
2017-03-29 21:18 ` Rafael J. Wysocki
2017-03-09 11:45 ` [RFC 2/9] irq_work: add irq_work_queue_on for !CONFIG_SMP Viresh Kumar
2017-03-29 21:20 ` Rafael J. Wysocki
2017-03-09 11:45 ` [RFC 3/9] cpufreq: Add dvfs_possible_from_any_cpu policy flag Viresh Kumar
2017-03-29 21:22 ` Rafael J. Wysocki
2017-03-09 11:45 ` [RFC 4/9] sched: cpufreq: extend irq work to support fast switches Viresh Kumar
2017-03-29 21:25 ` Rafael J. Wysocki
2017-03-09 11:45 ` [RFC 5/9] sched: cpufreq: remove smp_processor_id() in remote paths Viresh Kumar
2017-03-29 21:28 ` Rafael J. Wysocki
2017-04-11 10:35 ` Viresh Kumar [this message]
2017-04-11 14:00 ` Rafael J. Wysocki
2017-04-12 14:26 ` Viresh Kumar
2017-04-12 22:53 ` Rafael J. Wysocki
2017-03-09 11:45 ` [RFC 6/9] sched: cpufreq: detect, process remote callbacks Viresh Kumar
2017-03-29 21:58 ` Rafael J. Wysocki
2017-03-09 11:45 ` [RFC 7/9] cpufreq: governor: support scheduler cpufreq callbacks on remote CPUs Viresh Kumar
2017-03-29 22:14 ` Rafael J. Wysocki
2017-04-11 11:06 ` Viresh Kumar
2017-03-09 11:45 ` [RFC 8/9] intel_pstate: ignore " Viresh Kumar
2017-03-29 22:15 ` Rafael J. Wysocki
2017-03-09 11:45 ` [RFC 9/9] sched: cpufreq: enable remote sched cpufreq callbacks Viresh Kumar
2017-03-15 11:45 ` [RFC 0/9] cpufreq: schedutil: Allow remote wakeups Rafael J. Wysocki
2017-03-16 3:09 ` Viresh Kumar
2017-03-16 10:04 ` Rafael J. Wysocki
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