From: Yi Yang <yi.y.yang@intel.com>
To: torvalds@linux-foundation.org
Cc: davej@codemonkey.org.uk, cpufreq@lists.linux.org.uk,
linux-pm@lists.linux-foundation.org,
linux-kernel@vger.kernel.org
Subject: [PATCH 2.6.24-rc8] cpufreq: fix obvious condition statement error
Date: Wed, 23 Jan 2008 07:05:26 +0800 [thread overview]
Message-ID: <1201043126.3861.5.camel@yangyi-dev.bj.intel.com> (raw)
In-Reply-To: <1199441414.19185.9.camel@yangyi-dev.bj.intel.com>
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@intel.com>
---
cpufreq.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/drivers/cpufreq/cpufreq.c 2008-01-23 05:02:28.000000000 +0800
+++ b/drivers/cpufreq/cpufreq.c 2008-01-23 06:11:21.000000000 +0800
@@ -1608,7 +1608,7 @@ 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;
}
next parent reply other threads:[~2008-01-22 23:05 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1199441414.19185.9.camel@yangyi-dev.bj.intel.com>
2008-01-22 23:05 ` Yi Yang [this message]
2008-02-14 23:44 ` [PATCH 2.6.25-rc1] cpufreq: fix cpufreq policy refcount imbalance Yi Yang
2008-02-14 23:48 ` Yi Yang
2008-02-15 15:52 ` [linux-pm] " Alan Stern
2008-02-15 18:24 ` Greg KH
2008-02-15 21:01 ` Greg KH
2008-02-25 0:46 ` [PATCH 2.6.25-rc3] cpuidle: fix cpuidle time and usage overflow Yi Yang
2008-02-25 10:15 ` Ingo Molnar
2008-02-25 1:10 ` Yi Yang
2008-03-26 4:46 ` Len Brown
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