linux-kernel - Re: [PATCH v2 01/18] arm64: topology: Use __free(put_cpufreq

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Message-ID: <20250827-vegan-blond-marmot-eabf13@sudeepholla>
Date: Wed, 27 Aug 2025 10:17:18 +0100
From: Sudeep Holla <sudeep.holla@....com>
To: Ben Horgan <ben.horgan@....com>
Cc: Zihuan Zhang <zhangzihuan@...inos.cn>,
	Sudeep Holla <sudeep.holla@....com>,
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Subject: Re: [PATCH v2 01/18] arm64: topology: Use __free(put_cpufreq_policy)
 for policy reference

On Wed, Aug 27, 2025 at 09:30:13AM +0100, Ben Horgan wrote:
> Hi Zihuan,
> 
> On 8/27/25 03:31, Zihuan Zhang 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>
> > ---
> >  arch/arm64/kernel/topology.c | 9 +++------
> >  1 file changed, 3 insertions(+), 6 deletions(-)
> > 
> > diff --git a/arch/arm64/kernel/topology.c b/arch/arm64/kernel/topology.c
> > index 5d07ee85bdae..e3cb6d54f35b 100644
> > --- a/arch/arm64/kernel/topology.c
> > +++ b/arch/arm64/kernel/topology.c
> > @@ -307,17 +307,16 @@ int arch_freq_get_on_cpu(int cpu)
> >  		 */
> >  		if (!housekeeping_cpu(cpu, HK_TYPE_TICK) ||
> >  		    time_is_before_jiffies(last_update + msecs_to_jiffies(AMU_SAMPLE_EXP_MS))) {
> > -			struct cpufreq_policy *policy = cpufreq_cpu_get(cpu);
> > +			struct cpufreq_policy *policy __free(put_cpufreq_policy);
> Based on the guidance, in include/linux/cleanup.h, I would expect the
> assignment to be done on this line.
> 
> "...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."
> 

Agreed. I did something similar recently and there was a code path where
variable wasn't initialised and ended up with freeing unassigned pointer.
So it is more than just a recommendation sometimes.

-- 
Regards,
Sudeep