The patch titled
cpufreq: fix obvious condition statement error
has been added to the -mm tree. Its filename is
cpufreq-fix-obvious-condition-statement-error.patch
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The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: cpufreq: fix obvious condition statement error
From: Yi Yang <yi.y.yang@xxxxxxxxx>
The function __cpufreq_set_policy in file drivers/cpufreq/cpufreq.c
has a very obvious error:
if (policy->min > data->min && policy->min > policy->max) {
ret = -EINVAL;
goto error_out;
}
This condtion statement is wrong because it returns -EINVAL only if
policy->min is greater than policy->max (in this case,
"policy->min > data->min" is true for ever.). In fact, it should
return -EINVAL as well if policy->max is less than data->min.
The correct condition should be:
if (policy->min > data->max || policy->max < data->min) {
The following test result testifies the above conclusion:
Before applying this patch:
[root@yangyi-dev /]# cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies
2394000 1596000
[root@yangyi-dev /]# echo 1596000 > /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq
[root@yangyi-dev /]# cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq
1596000
[root@yangyi-dev /]# cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_min_freq
1596000
[root@yangyi-dev /]# echo "2000000" > /sys/devices/system/cpu/cpu0/cpufreq/scaling_min_freq
-bash: echo: write error: Invalid argument
[root@yangyi-dev /]# cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_min_freq
1596000
[root@yangyi-dev /]# echo "0" > /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq
[root@yangyi-dev /]# cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq
1596000
[root@yangyi-dev /]# echo "1595000" > /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq
[root@yangyi-dev /]# cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq
1596000
[root@yangyi-dev /]#
After applying this patch:
[root@yangyi-dev /]# cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies
2394000 1596000
[root@yangyi-dev /]# echo 1596000 > /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq
[root@yangyi-dev /]# cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq
1596000
[root@yangyi-dev /]# cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_min_freq
1596000
[root@localhost /]# echo "2000000" > /sys/devices/system/cpu/cpu0/cpufreq/scaling_min_freq
-bash: echo: write error: Invalid argument
[root@localhost /]# cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_min_freq
1596000
[root@localhost /]# echo "0" > /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq
-bash: echo: write error: Invalid argument
[root@localhost /]# echo "1595000" > /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq
-bash: echo: write error: Invalid argument
[root@localhost /]# cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq
1596000
[root@localhost /]# echo "1596000" > /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq
[root@localhost /]# echo "2394000" > /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq
[root@localhost /]# cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq
2394000
[root@localhost /]
Signed-off-by: Yi Yang <yi.y.yang@xxxxxxxxx>
Cc: Dave Jones <davej@xxxxxxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
drivers/cpufreq/cpufreq.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff -puN drivers/cpufreq/cpufreq.c~cpufreq-fix-obvious-condition-statement-error drivers/cpufreq/cpufreq.c
--- a/drivers/cpufreq/cpufreq.c~cpufreq-fix-obvious-condition-statement-error
+++ a/drivers/cpufreq/cpufreq.c
@@ -1635,7 +1635,7 @@ static int __cpufreq_set_policy(struct c
memcpy(&policy->cpuinfo, &data->cpuinfo,
sizeof(struct cpufreq_cpuinfo));
- if (policy->min > data->min && policy->min > policy->max) {
+ if (policy->min > data->max || policy->max < data->min) {
ret = -EINVAL;
goto error_out;
}
_
Patches currently in -mm which might be from yi.y.yang@xxxxxxxxx are
git-acpi.patch
cpufreq-fix-obvious-condition-statement-error.patch
-
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