linux-kernel - [PATCH v2] cpufreq: schedutil: Examine the correct CPU when we update util

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Date:   Thu,  2 Nov 2017 11:38:40 +0000
From:   Chris Redpath <chris.redpath@....com>
To:     linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org
Cc:     Morten Rasmussen <morten.rasmussen@....com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Chris Redpath <chris.redpath@....com>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>
Subject: [PATCH v2] cpufreq: schedutil: Examine the correct CPU when we update util

Since:
4296f23ed cpufreq: schedutil: Fix per-CPU structure initialization in
 sugov_start()
We lost the value of sg_cpu->cpu which is assigned during
sugov_register. The memset in sugov_start overwrites it with zero.

The change here was triggered by the commit adding the remote update
functionality.
674e75411fc2 ("sched: cpufreq: Allow remote cpufreq callbacks")

This leads to always looking at the utilization of CPU0 instead of
the one we just updated when we do a utilization update callback.

Let's fix this by consolidating the initialization code into
sugov_start().

Fixes: 674e75411fc2 ("sched: cpufreq: Allow remote cpufreq callbacks")
Signed-off-by: Chris Redpath <chris.redpath@....com>
Reviewed-by: Patrick Bellasi <patrick.bellasi@....com>
Reviewed-by: Brendan Jackman <brendan.jackman@....com>
Cc: Rafael J. Wysocki <rjw@...ysocki.net>
Cc: Viresh Kumar <viresh.kumar@...aro.org>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Peter Zijlstra <peterz@...radead.org>
---
 kernel/sched/cpufreq_schedutil.c | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
index 6c1a7fcfa2a7..dc68a1ccdb33 100644
--- a/kernel/sched/cpufreq_schedutil.c
+++ b/kernel/sched/cpufreq_schedutil.c
@@ -728,6 +728,7 @@ static int sugov_start(struct cpufreq_policy *policy)
 		struct sugov_cpu *sg_cpu = &per_cpu(sugov_cpu, cpu);
 
 		memset(sg_cpu, 0, sizeof(*sg_cpu));
+		sg_cpu->cpu = cpu;
 		sg_cpu->sg_policy = sg_policy;
 		sg_cpu->flags = SCHED_CPUFREQ_RT;
 		sg_cpu->iowait_boost_max = policy->cpuinfo.max_freq;
@@ -793,11 +794,6 @@ struct cpufreq_governor *cpufreq_default_governor(void)
 
 static int __init sugov_register(void)
 {
-	int cpu;
-
-	for_each_possible_cpu(cpu)
-		per_cpu(sugov_cpu, cpu).cpu = cpu;
-
 	return cpufreq_register_governor(&schedutil_gov);
 }
 fs_initcall(sugov_register);
-- 
2.13.1.449.g02a2850