linux-kernel - Re: [PATCH 1/2] cpufreq: Fix re-boost issue after hotplugging a cpu

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

Message-ID: <20250115111852.hluxcprc7cbrxqtc@vireshk-i7>
Date: Wed, 15 Jan 2025 16:48:52 +0530
From: Viresh Kumar <viresh.kumar@...aro.org>
To: Lifeng Zheng <zhenglifeng1@...wei.com>
Cc: rafael@...nel.org, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org, linuxarm@...wei.com,
	jonathan.cameron@...wei.com, zhanjie9@...ilicon.com,
	lihuisong@...wei.com, fanghao11@...wei.com
Subject: Re: [PATCH 1/2] cpufreq: Fix re-boost issue after hotplugging a cpu

On 15-01-25, 18:01, Lifeng Zheng wrote:
> It turns out that cpuX will stay on the base frequency after performing
> these operations:
> 
> 1. boost all cpus: echo 1 > /sys/devices/system/cpu/cpufreq/boost
> 
> 2. offline the cpu: echo 0 > /sys/devices/system/cpu/cpuX/online
> 
> 3. deboost all cpus: echo 0 > /sys/devices/system/cpu/cpufreq/boost
> 
> 4. online the cpu: echo 1 > /sys/devices/system/cpu/cpuX/online
> 
> 5. boost all cpus again: echo 1 > /sys/devices/system/cpu/cpufreq/boost
> 
> This is because max_freq_req of the policy is not updated during the
> online process, and the value of max_freq_req before the last offline is
> retained. When the CPU is boosted again, freq_qos_update_request() will
> do nothing because the old value is the same as the new one. This causes
> the CPU stay on the base frequency. Update max_freq_req (and
> min_freq_req of course) in cpufreq_online() will solve this problem.
> 
> Signed-off-by: Lifeng Zheng <zhenglifeng1@...wei.com>
> ---
>  drivers/cpufreq/cpufreq.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index 1a4cae54a01b..03ae879d50b9 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -1475,6 +1475,13 @@ static int cpufreq_online(unsigned int cpu)
>  
>  		blocking_notifier_call_chain(&cpufreq_policy_notifier_list,
>  				CPUFREQ_CREATE_POLICY, policy);
> +	} else {
> +		ret = freq_qos_update_request(policy->min_freq_req, policy->min);

This may not be required, as min-freq-req is never updated.

> +		if (ret < 0)
> +			goto out_destroy_policy;
> +		ret = freq_qos_update_request(policy->max_freq_req, policy->max);
> +		if (ret < 0)
> +			goto out_destroy_policy;
>  	}
>  
>  	if (cpufreq_driver->get && has_target()) {
> -- 
> 2.33.0

-- 
viresh