From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1031205AbeEZGvJ (ORCPT ); Sat, 26 May 2018 02:51:09 -0400 Received: from szxga04-in.huawei.com ([45.249.212.190]:8149 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1031142AbeEZGvH (ORCPT ); Sat, 26 May 2018 02:51:07 -0400 Subject: Re: [PATCH] cpufreq: reinitialize new policy min/max when writing scaling_(max|min)_freq To: "Rafael J. Wysocki" CC: "Rafael J. Wysocki" , Viresh Kumar , Linux PM , "Linux Kernel Mailing List" , , References: <1527144234-96396-1-git-send-email-kevin.wangtao@hisilicon.com> From: "Wangtao (Kevin, Kirin)" Message-ID: Date: Sat, 26 May 2018 14:50:46 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.2.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.121.90.40] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 在 2018/5/24 15:45, Rafael J. Wysocki 写道: > On Thu, May 24, 2018 at 8:43 AM, Kevin Wangtao > wrote: >> consider such situation, current user_policy.min is 1000000, >> current user_policy.max is 1200000, in cpufreq_set_policy, >> other driver may update policy.min to 1200000, policy.max to >> 1300000. After that, If we input "echo 1300000 > scaling_min_freq", >> then user_policy.min will be 1300000, and user_policy.max is >> still 1200000, because the input value is checked with policy.max >> not user_policy.max. if we get all related cpus offline and >> online again, it will cause cpufreq_init_policy fail because >> user_policy.min is higher than user_policy.max. > > How do you reproduce this, exactly? I can also reproduce this issue with upstream code, write max frequency to scaling_max_freq and scaling_min_freq, run benchmark to let cpu cooling take effect to clip freq, then write the cliped freq to scaling_max_freq, thus user_policy.min is still max frequency but user_policy.max is cliped freq which is lower than max frequency. > >> The solution is when user space tries to write scaling_(max|min)_freq, >> the min/max of new_policy should be reinitialized with min/max >> of user_policy, like what cpufreq_update_policy does. >> >> Signed-off-by: Kevin Wangtao >> --- >> drivers/cpufreq/cpufreq.c | 2 ++ >> 1 file changed, 2 insertions(+) >> >> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c >> index b79c532..8b33e08 100644 >> --- a/drivers/cpufreq/cpufreq.c >> +++ b/drivers/cpufreq/cpufreq.c >> @@ -697,6 +697,8 @@ static ssize_t store_##file_name \ >> struct cpufreq_policy new_policy; \ >> \ >> memcpy(&new_policy, policy, sizeof(*policy)); \ >> + new_policy->min = policy->user_policy.min; \ >> + new_policy->max = policy->user_policy.max; \ > > It looks like you haven't even tried to build this, have you? > >> \ >> ret = sscanf(buf, "%u", &new_policy.object); \ >> if (ret != 1) \ >> -- >> 2.8.1 >> > > . >