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Mon, 04 Feb 2019 14:31:32 -0800 (PST) Received: from localhost ([2620:15c:202:1:75a:3f6e:21d:9374]) by smtp.gmail.com with ESMTPSA id v89sm1526736pfj.164.2019.02.04.14.31.32 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 04 Feb 2019 14:31:32 -0800 (PST) Date: Mon, 4 Feb 2019 14:31:31 -0800 From: Matthias Kaehlcke To: Viresh Kumar Cc: Rafael Wysocki , linux-pm@vger.kernel.org, Vincent Guittot , linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/2] cpufreq: stats: Fix concurrency issues while resetting stats Message-ID: <20190204223131.GF117604@google.com> References: <927dcc1de6acad3dd2cfae4e300e6fee4f665101.1549001732.git.viresh.kumar@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <927dcc1de6acad3dd2cfae4e300e6fee4f665101.1549001732.git.viresh.kumar@linaro.org> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Feb 01, 2019 at 11:45:45AM +0530, Viresh Kumar wrote: > It is possible for cpufreq_stats_clear_table() and > cpufreq_stats_record_transition() to get called concurrently and they > will try to update same variables simultaneously and may lead to > corruption of data. > > Prevent that with the help of existing spinlock. > > Signed-off-by: Viresh Kumar > --- > drivers/cpufreq/cpufreq_stats.c | 9 +++++++-- > 1 file changed, 7 insertions(+), 2 deletions(-) > > diff --git a/drivers/cpufreq/cpufreq_stats.c b/drivers/cpufreq/cpufreq_stats.c > index 941e63e3e652..e2db5581489a 100644 > --- a/drivers/cpufreq/cpufreq_stats.c > +++ b/drivers/cpufreq/cpufreq_stats.c > @@ -31,20 +31,20 @@ static void cpufreq_stats_update(struct cpufreq_stats *stats) > { > unsigned long long cur_time = get_jiffies_64(); > > - spin_lock(&cpufreq_stats_lock); > stats->time_in_state[stats->last_index] += cur_time - stats->last_time; > stats->last_time = cur_time; > - spin_unlock(&cpufreq_stats_lock); > } > > static void cpufreq_stats_clear_table(struct cpufreq_stats *stats) > { > unsigned int count = stats->max_state; > > + spin_lock(&cpufreq_stats_lock); > memset(stats->time_in_state, 0, count * sizeof(u64)); > memset(stats->trans_table, 0, count * count * sizeof(int)); > stats->last_time = get_jiffies_64(); > stats->total_trans = 0; > + spin_unlock(&cpufreq_stats_lock); > } > > static ssize_t show_total_trans(struct cpufreq_policy *policy, char *buf) > @@ -62,7 +62,10 @@ static ssize_t show_time_in_state(struct cpufreq_policy *policy, char *buf) > if (policy->fast_switch_enabled) > return 0; > > + spin_lock(&cpufreq_stats_lock); > cpufreq_stats_update(stats); > + spin_unlock(&cpufreq_stats_lock); > + > for (i = 0; i < stats->state_num; i++) { > len += sprintf(buf + len, "%u %llu\n", stats->freq_table[i], > (unsigned long long) > @@ -239,9 +242,11 @@ void cpufreq_stats_record_transition(struct cpufreq_policy *policy, > if (old_index == -1 || new_index == -1 || old_index == new_index) > return; > > + spin_lock(&cpufreq_stats_lock); > cpufreq_stats_update(stats); > > stats->last_index = new_index; > stats->trans_table[old_index * stats->max_state + new_index]++; > stats->total_trans++; > + spin_unlock(&cpufreq_stats_lock); > } Reviewed-by: Matthias Kaehlcke