linux-kernel - Re: [PATCH v4 10/10] PM: EM: Use scope-based cleanup helper

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Message-ID: <861a6077-a7da-4899-b971-a003d6e2290e@kylinos.cn>
Date: Thu, 4 Sep 2025 15:56:08 +0800
From: Zihuan Zhang <zhangzihuan@...inos.cn>
To: Krzysztof Kozlowski <krzk@...nel.org>,
 "Rafael J. Wysocki" <rafael@...nel.org>
Cc: Viresh Kumar <viresh.kumar@...aro.org>,
 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>, 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>,
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 <tursulin@...ulin.net>, David Airlie <airlied@...il.com>,
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 Lukasz Luba <lukasz.luba@....com>,
 Pengutronix Kernel Team <kernel@...gutronix.de>,
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 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,
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Subject: Re: [PATCH v4 10/10] PM: EM: Use scope-based cleanup helper

在 2025/9/3 21:43, Krzysztof Kozlowski 写道:
> On 03/09/2025 15:41, Rafael J. Wysocki wrote:
>>>>   em_cpufreq_update_efficiencies(struct device *dev, struct em_perf_state *table)
>>>>   {
>>>>        struct em_perf_domain *pd = dev->em_pd;
>>>> -     struct cpufreq_policy *policy;
>>>> +     struct cpufreq_policy *policy __free(put_cpufreq_policy) = NULL;
>>> This is not really correct coding style. Please read how to use
>>> cleanup.h expressed in that header. You should have here proper
>>> constructor or this should be moved. Or this should not be __free()...
>> I gather that this is what you mean (quoted verbatim from cleanup.h)
>>
>>   * Given that the "__free(...) = NULL" pattern for variables defined at
>>   * the top of the function poses this potential interdependency problem
>>   * the recommendation is to always define and assign variables in one
>>   * statement and not group variable definitions at the top of the
>>   * function when __free() is used.
>>
>> and thanks for pointing this out!
>
> ... and the only exception would be if there is no single constructor,
> but multiple (in if() block). That's not the case here, I think.
>
> Best regards,
> Krzysztof

Sorry, I didn’t fully understand this earlier. In v3 I split the
definition and assignment mainly because the CPU value was obtained
later, so I thought I couldn’t initialize it in one go at the top of
the function. Honestly, it was also for “prettier” style.

After looking at the code Rafael just committed, I realized I can
simply define and assign the variable later in one line, without
needing to separate them. I’ll fix this in the next version.

Thanks for pointing it out!