linux-kernel - [PATCH 4/6] cpufreq: Use vtime aware kcpustat accessors for user time

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Date:   Thu, 21 Nov 2019 03:44:28 +0100
From:   Frederic Weisbecker <frederic@...nel.org>
To:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Frederic Weisbecker <frederic@...nel.org>,
        Jacek Anaszewski <jacek.anaszewski@...il.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Rik van Riel <riel@...riel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Yauheni Kaliuta <yauheni.kaliuta@...hat.com>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Pavel Machek <pavel@....cz>
Subject: [PATCH 4/6] cpufreq: Use vtime aware kcpustat accessors for user time

We can now safely read user and guest kcpustat fields on nohz_full CPUs.
Use the appropriate accessors.

Reported-by: Yauheni Kaliuta <yauheni.kaliuta@...hat.com>
Signed-off-by: Frederic Weisbecker <frederic@...nel.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Rik van Riel <riel@...riel.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Wanpeng Li <wanpengli@...cent.com>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Viresh Kumar <viresh.kumar@...aro.org>
Cc: Rafael J. Wysocki <rjw@...ysocki.net>
---
 drivers/cpufreq/cpufreq.c          | 17 ++++++++++-------
 drivers/cpufreq/cpufreq_governor.c |  6 +++---
 2 files changed, 13 insertions(+), 10 deletions(-)

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 527fd068dc12..ee23eaf20f35 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -113,18 +113,21 @@ EXPORT_SYMBOL_GPL(get_governor_parent_kobj);
 
 static inline u64 get_cpu_idle_time_jiffy(unsigned int cpu, u64 *wall)
 {
-	u64 idle_time;
+	struct kernel_cpustat kcpustat;
 	u64 cur_wall_time;
+	u64 idle_time;
 	u64 busy_time;
 
 	cur_wall_time = jiffies64_to_nsecs(get_jiffies_64());
 
-	busy_time = kcpustat_cpu(cpu).cpustat[CPUTIME_USER];
-	busy_time += kcpustat_field(&kcpustat_cpu(cpu), CPUTIME_SYSTEM, cpu);
-	busy_time += kcpustat_cpu(cpu).cpustat[CPUTIME_IRQ];
-	busy_time += kcpustat_cpu(cpu).cpustat[CPUTIME_SOFTIRQ];
-	busy_time += kcpustat_cpu(cpu).cpustat[CPUTIME_STEAL];
-	busy_time += kcpustat_cpu(cpu).cpustat[CPUTIME_NICE];
+	kcpustat_cpu_fetch(&kcpustat, cpu);
+
+	busy_time = kcpustat.cpustat[CPUTIME_USER];
+	busy_time += kcpustat.cpustat[CPUTIME_SYSTEM];
+	busy_time += kcpustat.cpustat[CPUTIME_IRQ];
+	busy_time += kcpustat.cpustat[CPUTIME_SOFTIRQ];
+	busy_time += kcpustat.cpustat[CPUTIME_STEAL];
+	busy_time += kcpustat.cpustat[CPUTIME_NICE];
 
 	idle_time = cur_wall_time - busy_time;
 	if (wall)
diff --git a/drivers/cpufreq/cpufreq_governor.c b/drivers/cpufreq/cpufreq_governor.c
index 4bb054d0cb43..f99ae45efaea 100644
--- a/drivers/cpufreq/cpufreq_governor.c
+++ b/drivers/cpufreq/cpufreq_governor.c
@@ -105,7 +105,7 @@ void gov_update_cpu_data(struct dbs_data *dbs_data)
 			j_cdbs->prev_cpu_idle = get_cpu_idle_time(j, &j_cdbs->prev_update_time,
 								  dbs_data->io_is_busy);
 			if (dbs_data->ignore_nice_load)
-				j_cdbs->prev_cpu_nice = kcpustat_cpu(j).cpustat[CPUTIME_NICE];
+				j_cdbs->prev_cpu_nice = kcpustat_field(&kcpustat_cpu(j), CPUTIME_NICE, j);
 		}
 	}
 }
@@ -149,7 +149,7 @@ unsigned int dbs_update(struct cpufreq_policy *policy)
 		j_cdbs->prev_cpu_idle = cur_idle_time;
 
 		if (ignore_nice) {
-			u64 cur_nice = kcpustat_cpu(j).cpustat[CPUTIME_NICE];
+			u64 cur_nice = kcpustat_field(&kcpustat_cpu(j), CPUTIME_NICE, j);
 
 			idle_time += div_u64(cur_nice - j_cdbs->prev_cpu_nice, NSEC_PER_USEC);
 			j_cdbs->prev_cpu_nice = cur_nice;
@@ -530,7 +530,7 @@ int cpufreq_dbs_governor_start(struct cpufreq_policy *policy)
 		j_cdbs->prev_load = 0;
 
 		if (ignore_nice)
-			j_cdbs->prev_cpu_nice = kcpustat_cpu(j).cpustat[CPUTIME_NICE];
+			j_cdbs->prev_cpu_nice = kcpustat_field(&kcpustat_cpu(j), CPUTIME_NICE, j);
 	}
 
 	gov->start(policy);
-- 
2.23.0