linux-kernel - [PATCH] Thermal: fix iteration over CPU frequency list

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Date:	Thu, 24 Jan 2013 16:24:05 +0100
From:	Gu1 <gu1@...oxteam.fr>
To:	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
	Zhang Rui <rui.zhang@...el.com>,
	Amit Daniel Kachhap <amit.kachhap@...aro.org>
Cc:	Gu1 <gu1@...oxteam.fr>
Subject: [PATCH] Thermal: fix iteration over CPU frequency list

In different places in the Thermal code, the CPU frequency list is iterated
in an incorrect way, leading to endless loops when the frequency list contains
a CPUFREQ_TABLE_INVALID entry, which is the case by default in the the Exynos
4x12 cpufreq driver, for example.

The frequency list is iterated with a while loop, and when a
CPUFREQ_TABLE_INVALID entry is encountered, the continue; statement is used to
skip it, but the index is not incremented, causing an endless loop.

A similar bug was fixed by hongbo.zhang in commit:
  Thermal: fix bug of counting cpu frequencies

Signed-off-by: Gu1 <gu1@...oxteam.fr>
---
 drivers/thermal/cpu_cooling.c    | 8 +++-----
 drivers/thermal/exynos_thermal.c | 9 +++++----
 2 files changed, 8 insertions(+), 9 deletions(-)

diff --git a/drivers/thermal/cpu_cooling.c b/drivers/thermal/cpu_cooling.c
index 836828e..51acd26 100644
--- a/drivers/thermal/cpu_cooling.c
+++ b/drivers/thermal/cpu_cooling.c
@@ -123,7 +123,7 @@ static int is_cpufreq_valid(int cpu)
  */
 static unsigned int get_cpu_frequency(unsigned int cpu, unsigned long level)
 {
-	int ret = 0, i = 0;
+	int ret = 0, i;
 	unsigned long level_index;
 	bool descend = false;
 	struct cpufreq_frequency_table *table =
@@ -131,7 +131,7 @@ static unsigned int get_cpu_frequency(unsigned int cpu, unsigned long level)
 	if (!table)
 		return ret;
 
-	while (table[i].frequency != CPUFREQ_TABLE_END) {
+	for (i = 0; table[i].frequency != CPUFREQ_TABLE_END; i++) {
 		if (table[i].frequency == CPUFREQ_ENTRY_INVALID)
 			continue;
 
@@ -145,7 +145,6 @@ static unsigned int get_cpu_frequency(unsigned int cpu, unsigned long level)
 		/*return if level matched and table in descending order*/
 		if (descend && i == level)
 			return table[i].frequency;
-		i++;
 	}
 	i--;
 
@@ -154,13 +153,12 @@ static unsigned int get_cpu_frequency(unsigned int cpu, unsigned long level)
 	level_index = i - level;
 
 	/*Scan the table in reverse order and match the level*/
-	while (i >= 0) {
+	for (; i >= 0; i--) {
 		if (table[i].frequency == CPUFREQ_ENTRY_INVALID)
 			continue;
 		/*return if level matched*/
 		if (i == level_index)
 			return table[i].frequency;
-		i--;
 	}
 	return ret;
 }
diff --git a/drivers/thermal/exynos_thermal.c b/drivers/thermal/exynos_thermal.c
index 224751e..fa9e1d7 100644
--- a/drivers/thermal/exynos_thermal.c
+++ b/drivers/thermal/exynos_thermal.c
@@ -233,7 +233,8 @@ static int exynos_get_crit_temp(struct thermal_zone_device *thermal,
 
 static int exynos_get_frequency_level(unsigned int cpu, unsigned int freq)
 {
-	int i = 0, ret = -EINVAL;
+	int i, ret = -EINVAL;
+	unsigned int count = 0;
 	struct cpufreq_frequency_table *table = NULL;
 #ifdef CONFIG_CPU_FREQ
 	table = cpufreq_frequency_get_table(cpu);
@@ -241,12 +242,12 @@ static int exynos_get_frequency_level(unsigned int cpu, unsigned int freq)
 	if (!table)
 		return ret;
 
-	while (table[i].frequency != CPUFREQ_TABLE_END) {
+	for (i = 0; table[i].frequency != CPUFREQ_TABLE_END; i++) {
 		if (table[i].frequency == CPUFREQ_ENTRY_INVALID)
 			continue;
 		if (table[i].frequency == freq)
-			return i;
-		i++;
+			return count;
+		count++;
 	}
 	return ret;
 }
-- 
1.8.1.1

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