From: Lianwei Wang <a22439@motorola.com>
Date: Thu, 16 May 2013 04:07:23 +0000 (+0800)
Subject: cpufreq: interactive: fix race on cpufreq TRANSITION notifier
X-Git-Tag: firefly_0821_release~4090^2~545
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=e1fb7646f1092a0e9baa0007983563092f3ab93d;p=firefly-linux-kernel-4.4.55.git

cpufreq: interactive: fix race on cpufreq TRANSITION notifier

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@motorola.com>
---

diff --git a/drivers/cpufreq/cpufreq_interactive.c b/drivers/cpufreq/cpufreq_interactive.c
index 7303f50a1180..691923d6c868 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);