linux-kernel - [PATCH 50/70] cpufreq: interactive: fix race on cpufreq TRANSITION notifier

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Date:	Tue, 27 Oct 2015 18:30:38 +0100
From:	Bálint Czobor <czoborbalint@...il.com>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Viresh Kumar <viresh.kumar@...aro.org>
Cc:	linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
	Lianwei Wang <a22439@...orola.com>,
	Bálint Czobor <czoborbalint@...il.com>
Subject: [PATCH 50/70] cpufreq: interactive: fix race on cpufreq TRANSITION notifier

From: Lianwei Wang <a22439@...orola.com>

The cpufreq TRANSTION notifier callback does not check the
governor_enabled state on affected CPUS, which will case
kernel panic in update_load because the policy object maybe
NULL or invalid when governor_enabled is false.

Change-Id: Ie0f1718124f61e2f9b5da57abc6981ada5b83908
Signed-off-by: Lianwei Wang <a22439@...orola.com>
Signed-off-by: Bálint Czobor <czoborbalint@...il.com>
---
 drivers/cpufreq/cpufreq_interactive.c |   10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/cpufreq/cpufreq_interactive.c b/drivers/cpufreq/cpufreq_interactive.c
index 7303f50..691923d 100644
--- a/drivers/cpufreq/cpufreq_interactive.c
+++ b/drivers/cpufreq/cpufreq_interactive.c
@@ -634,9 +634,19 @@ static int cpufreq_interactive_notifier(
 		for_each_cpu(cpu, pcpu->policy->cpus) {
 			struct cpufreq_interactive_cpuinfo *pjcpu =
 				&per_cpu(cpuinfo, cpu);
+			if (cpu != freq->cpu) {
+				if (!down_read_trylock(&pjcpu->enable_sem))
+					continue;
+				if (!pjcpu->governor_enabled) {
+					up_read(&pjcpu->enable_sem);
+					continue;
+				}
+			}
 			spin_lock_irqsave(&pjcpu->load_lock, flags);
 			update_load(cpu);
 			spin_unlock_irqrestore(&pjcpu->load_lock, flags);
+			if (cpu != freq->cpu)
+				up_read(&pjcpu->enable_sem);
 		}
 
 		up_read(&pcpu->enable_sem);
-- 
1.7.9.5

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