From mboxrd@z Thu Jan 1 00:00:00 1970 From: Yi Yang Subject: [PATCH 2.6.24-rc8] cpufreq: fix obvious condition statement error Date: Wed, 23 Jan 2008 07:05:26 +0800 Message-ID: <1201043126.3861.5.camel@yangyi-dev.bj.intel.com> References: <1199441414.19185.9.camel@yangyi-dev.bj.intel.com> Reply-To: yi.y.yang@intel.com Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1199441414.19185.9.camel@yangyi-dev.bj.intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii" 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 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 --- 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; }