linux-kernel - Re: [PATCH -next] cpufreq: userspace: Keep the current frequency when set userspace policy

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <1369cedf-e66b-82eb-4501-a6976bb8c558@huawei.com>
Date:   Thu, 26 Oct 2023 10:36:15 +0800
From:   Zeng Heng <zengheng4@...wei.com>
To:     Viresh Kumar <viresh.kumar@...aro.org>
CC:     <rafael@...nel.org>, <liwei391@...wei.com>,
        <linux-pm@...r.kernel.org>, <xiexiuqi@...wei.com>,
        <wangxiongfeng2@...wei.com>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH -next] cpufreq: userspace: Keep the current frequency when
 set userspace policy


在 2023/10/25 19:18, Viresh Kumar 写道:
> On 25-10-23, 16:09, Zeng Heng wrote:
>> When switching to the userspace policy, if the current frequency is within
>> the range of policy's min and max values, the current frequency value
>> should be remained. The .limit() function is called when changing governor
>> or updating governor limits, so in both cases, there is no need to update
>> frequency if the current frequency does not exceed the threshold.
>>
>> Additionally, when changing to userspace governor, the default value of
>> set_speed is set by reading the current frequency of the CPU, but there
>> is inevitable error between the frequency coming from .get_rate() interface
>> and the actual working frequency. Consequently, when switching to userspace
>> policy, keeping the current frequency can avoid unexpected changes.
>>
>> Signed-off-by: Zeng Heng <zengheng4@...wei.com>
>> ---
>>   drivers/cpufreq/cpufreq_userspace.c | 4 +---
>>   1 file changed, 1 insertion(+), 3 deletions(-)
>>
>> diff --git a/drivers/cpufreq/cpufreq_userspace.c b/drivers/cpufreq/cpufreq_userspace.c
>> index 2c42fee76daa..fe55a7bb663c 100644
>> --- a/drivers/cpufreq/cpufreq_userspace.c
>> +++ b/drivers/cpufreq/cpufreq_userspace.c
>> @@ -117,9 +117,7 @@ static void cpufreq_userspace_policy_limits(struct cpufreq_policy *policy)
>>   	else if (policy->min > userspace->setspeed)
>>   		__cpufreq_driver_target(policy, policy->min,
>>   					CPUFREQ_RELATION_L);
>> -	else
>> -		__cpufreq_driver_target(policy, userspace->setspeed,
>> -					CPUFREQ_RELATION_L);
>> +	/* Otherwise, keep the current frequency. */
>>
>>   	mutex_unlock(&userspace->mutex);
>>   }
> Here is some reasoning why it should be done the way it is:
>
> commit e43e94c1eda7 ("cpufreq: Fix GOV_LIMITS handling for the userspace governor")


Get it, thanks for the response.

Zeng Heng