linux-kernel - Re: [PATCH] cpufreq: dt: always allocate zeroed cpumask

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Message-ID: <20240315052756.5w4zizrod3w7kzzn@dhruva>
Date: Fri, 15 Mar 2024 10:57:56 +0530
From: Dhruva Gole <d-gole@...com>
To: Marek Szyprowski <m.szyprowski@...sung.com>
CC: <linux-pm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-mm@...ck.org>, <linux-arm-kernel@...ts.infradead.org>,
        "Rafael J.
 Wysocki" <rafael@...nel.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Stephan
 Gerhold <stephan@...hold.net>,
        Catalin Marinas <catalin.marinas@....com>,
        Russell King <linux@...linux.org.uk>,
        Christoph Lameter <cl@...two.org>,
        Mark
 Rutland <mark.rutland@....com>,
        Sudeep Holla <sudeep.holla@....com>, Will
 Deacon <will@...nel.org>,
        <stable@...r.kernel.org>
Subject: Re: [PATCH] cpufreq: dt: always allocate zeroed cpumask

On Mar 14, 2024 at 13:54:57 +0100, Marek Szyprowski wrote:
> Commit 0499a78369ad ("ARM64: Dynamically allocate cpumasks and increase
> supported CPUs to 512") changed the handling of cpumasks on ARM 64bit,
> what resulted in the strange issues and warnings during cpufreq-dt
> initialization on some big.LITTLE platforms.
> 
> This was caused by mixing OPPs between big and LITTLE cores, because
> OPP-sharing information between big and LITTLE cores is computed on
> cpumask, which in turn was not zeroed on allocation. Fix this by
> switching to zalloc_cpumask_var() call.
> 
> Fixes: dc279ac6e5b4 ("cpufreq: dt: Refactor initialization to handle probe deferral properly")
> CC: stable@...r.kernel.org # v5.10+
> Signed-off-by: Marek Szyprowski <m.szyprowski@...sung.com>
> ---
>  drivers/cpufreq/cpufreq-dt.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/cpufreq/cpufreq-dt.c b/drivers/cpufreq/cpufreq-dt.c
> index 8bd6e5e8f121..2d83bbc65dd0 100644
> --- a/drivers/cpufreq/cpufreq-dt.c
> +++ b/drivers/cpufreq/cpufreq-dt.c
> @@ -208,7 +208,7 @@ static int dt_cpufreq_early_init(struct device *dev, int cpu)
>  	if (!priv)
>  		return -ENOMEM;
>  
> -	if (!alloc_cpumask_var(&priv->cpus, GFP_KERNEL))
> +	if (!zalloc_cpumask_var(&priv->cpus, GFP_KERNEL))
>  		return -ENOMEM;

Good catch!

Reviewed-by: Dhruva Gole <d-gole@...com>


-- 
Best regards,
Dhruva