linux-kernel - Re: [PATCH v5 6/6] PM: EM: Use scope-based cleanup helper

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: <CAJZ5v0izu1_xVe_pGeJiXZqEXLxg_o30NkEjMiwzDgeU4mOGmA@mail.gmail.com>
Date: Fri, 5 Sep 2025 21:46:43 +0200
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Zihuan Zhang <zhangzihuan@...inos.cn>
Cc: "Rafael J . wysocki" <rafael@...nel.org>, Viresh Kumar <viresh.kumar@...aro.org>, 
	Jonathan Cameron <jonathan.cameron@...wei.com>, Catalin Marinas <catalin.marinas@....com>, 
	Will Deacon <will@...nel.org>, Borislav Petkov <bp@...en8.de>, 
	Dave Hansen <dave.hansen@...ux.intel.com>, 
	Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>, Michael Ellerman <mpe@...erman.id.au>, 
	Krzysztof Kozlowski <krzk@...nel.org>, Alim Akhtar <alim.akhtar@...sung.com>, 
	Thierry Reding <thierry.reding@...il.com>, MyungJoo Ham <myungjoo.ham@...sung.com>, 
	Kyungmin Park <kyungmin.park@...sung.com>, Chanwoo Choi <cw00.choi@...sung.com>, 
	Jani Nikula <jani.nikula@...ux.intel.com>, Rodrigo Vivi <rodrigo.vivi@...el.com>, 
	Tvrtko Ursulin <tursulin@...ulin.net>, David Airlie <airlied@...il.com>, 
	Simona Vetter <simona@...ll.ch>, Daniel Lezcano <daniel.lezcano@...nel.org>, 
	Sascha Hauer <s.hauer@...gutronix.de>, Shawn Guo <shawnguo@...nel.org>, 
	Eduardo Valentin <edubezval@...il.com>, Keerthy <j-keerthy@...com>, Ben Horgan <ben.horgan@....com>, 
	zhenglifeng <zhenglifeng1@...wei.com>, Zhang Rui <rui.zhang@...el.com>, 
	Len Brown <lenb@...nel.org>, Lukasz Luba <lukasz.luba@....com>, 
	Pengutronix Kernel Team <kernel@...gutronix.de>, Beata Michalska <beata.michalska@....com>, 
	Fabio Estevam <festevam@...il.com>, Pavel Machek <pavel@...nel.org>, Sumit Gupta <sumitg@...dia.com>, 
	Prasanna Kumar T S M <ptsm@...ux.microsoft.com>, Sudeep Holla <sudeep.holla@....com>, 
	Yicong Yang <yangyicong@...ilicon.com>, linux-pm@...r.kernel.org, 
	linux-acpi@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org, 
	linux-arm-kernel@...ts.infradead.org, intel-gfx@...ts.freedesktop.org, 
	dri-devel@...ts.freedesktop.org, imx@...ts.linux.dev, 
	linux-omap@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 6/6] PM: EM: Use scope-based cleanup helper

On Fri, Sep 5, 2025 at 3:25 PM Zihuan Zhang <zhangzihuan@...inos.cn> wrote:
>
> Replace the manual cpufreq_cpu_put() with __free(put_cpufreq_policy)
> annotation for policy references. This reduces the risk of reference
> counting mistakes and aligns the code with the latest kernel style.
>
> No functional change intended.
>
> Signed-off-by: Zihuan Zhang <zhangzihuan@...inos.cn>
> ---
>  kernel/power/energy_model.c | 9 ++-------
>  1 file changed, 2 insertions(+), 7 deletions(-)
>
> diff --git a/kernel/power/energy_model.c b/kernel/power/energy_model.c
> index ea7995a25780..5ec63b3e7d85 100644
> --- a/kernel/power/energy_model.c
> +++ b/kernel/power/energy_model.c
> @@ -451,7 +451,6 @@ static void
>  em_cpufreq_update_efficiencies(struct device *dev, struct em_perf_state *table)
>  {
>         struct em_perf_domain *pd = dev->em_pd;
> -       struct cpufreq_policy *policy;
>         int found = 0;
>         int i, cpu;
>
> @@ -465,7 +464,7 @@ em_cpufreq_update_efficiencies(struct device *dev, struct em_perf_state *table)
>                 return;
>         }
>
> -       policy = cpufreq_cpu_get(cpu);
> +       struct cpufreq_policy *policy __free(put_cpufreq_policy) = cpufreq_cpu_get(cpu);
>         if (!policy) {
>                 dev_warn(dev, "EM: Access to CPUFreq policy failed\n");
>                 return;
> @@ -479,8 +478,6 @@ em_cpufreq_update_efficiencies(struct device *dev, struct em_perf_state *table)
>                         found++;
>         }
>
> -       cpufreq_cpu_put(policy);
> -
>         if (!found)
>                 return;
>

The above changes are fine now and can be a separate patch.

> @@ -787,21 +784,19 @@ static void em_check_capacity_update(void)
>
>         /* Check if CPUs capacity has changed than update EM */
>         for_each_possible_cpu(cpu) {

But I'd prefer the code in this loop to be moved into a separate
function, in a separate patch, before the __free()-based
simplification of it.

> -               struct cpufreq_policy *policy;
>                 struct em_perf_domain *pd;
>                 struct device *dev;
>
>                 if (cpumask_test_cpu(cpu, cpu_done_mask))
>                         continue;
>
> -               policy = cpufreq_cpu_get(cpu);
> +               struct cpufreq_policy *policy __free(put_cpufreq_policy) = cpufreq_cpu_get(cpu);
>                 if (!policy) {
>                         pr_debug("Accessing cpu%d policy failed\n", cpu);
>                         schedule_delayed_work(&em_update_work,
>                                               msecs_to_jiffies(1000));
>                         break;
>                 }
> -               cpufreq_cpu_put(policy);
>
>                 dev = get_cpu_device(cpu);
>                 pd = em_pd_get(dev);
> --