linux-kernel - [PATCH] thermal: cpu_cooling: fix handling of invalid frequency table entries

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Date:	Tue,  9 Apr 2013 14:56:56 -0700
From:	Andrew Bresticker <abrestic@...omium.org>
To:	Zhang Rui <rui.zhang@...el.com>,
	Eduardo Valentin <eduardo.valentin@...com>
Cc:	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
	Andrew Bresticker <abrestic@...omium.org>
Subject: [PATCH] thermal: cpu_cooling: fix handling of invalid frequency table entries

get_cpu_frequency() goes into an infinite loop if any of the entries
in the CPU frequency table are invalid.  This patch fixes that case
and, with a separate counter for frequency levels, ensures that the
n-th valid frequency level is returned.

Signed-off-by: Andrew Bresticker <abrestic@...omium.org>
---
 drivers/thermal/cpu_cooling.c | 19 ++++++++++---------
 1 file changed, 10 insertions(+), 9 deletions(-)

diff --git a/drivers/thermal/cpu_cooling.c b/drivers/thermal/cpu_cooling.c
index 836828e..e6db441 100644
--- a/drivers/thermal/cpu_cooling.c
+++ b/drivers/thermal/cpu_cooling.c
@@ -124,14 +124,14 @@ static int is_cpufreq_valid(int cpu)
 static unsigned int get_cpu_frequency(unsigned int cpu, unsigned long level)
 {
 	int ret = 0, i = 0;
-	unsigned long level_index;
+	unsigned long level_index = 0;
 	bool descend = false;
 	struct cpufreq_frequency_table *table =
 					cpufreq_frequency_get_table(cpu);
 	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;
 
@@ -143,24 +143,25 @@ 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)
+		if (descend && level_index == level)
 			return table[i].frequency;
-		i++;
+		level_index++;
 	}
 	i--;
+	level_index--;
 
-	if (level > i || descend)
+	if (level > level_index || descend)
 		return ret;
-	level_index = i - level;
+	level = level_index - 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)
+		if (level_index == level)
 			return table[i].frequency;
-		i--;
+		level_index--;
 	}
 	return ret;
 }
-- 
1.8.1.3

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