From mboxrd@z Thu Jan 1 00:00:00 1970 From: Viresh Kumar Subject: Re: [RFC 5/9] sched: cpufreq: remove smp_processor_id() in remote paths Date: Tue, 11 Apr 2017 16:05:56 +0530 Message-ID: <20170411103556.GC13627@vireshk-i7> References: <834d098efe029ee687bac7690bb482e9263a766b.1489058244.git.viresh.kumar@linaro.org> <1836427.bpauTYz19k@aspire.rjw.lan> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <1836427.bpauTYz19k@aspire.rjw.lan> Sender: linux-kernel-owner@vger.kernel.org To: "Rafael J. Wysocki" Cc: Ingo Molnar , Peter Zijlstra , linaro-kernel@lists.linaro.org, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, Vincent Guittot , smuckle.linux@gmail.com, juri.lelli@arm.com, Morten.Rasmussen@arm.com, patrick.bellasi@arm.com, eas-dev@lists.linaro.org List-Id: linux-pm@vger.kernel.org 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