linux-kernel - Re: [PATCH v2 1/2] watchdog: move arm64 watchdog

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Message-ID: <CAD=FV=VZLYqPQCOEhbH4QtndeG5e1-0wey24fgYNTeFiqd8qJg@mail.gmail.com>
Date: Thu, 25 Sep 2025 12:59:28 -0700
From: Doug Anderson <dianders@...omium.org>
To: Yunhui Cui <cuiyunhui@...edance.com>
Cc: akpm@...ux-foundation.org, alex@...ti.fr, anup@...infault.org, 
	aou@...s.berkeley.edu, atish.patra@...ux.dev, catalin.marinas@....com, 
	johannes@...solutions.net, lihuafei1@...wei.com, mark.rutland@....com, 
	masahiroy@...nel.org, maz@...nel.org, mingo@...nel.org, 
	nicolas.schier@...ux.dev, palmer@...belt.com, paul.walmsley@...ive.com, 
	suzuki.poulose@....com, thorsten.blum@...ux.dev, wangjinchao600@...il.com, 
	will@...nel.org, yangyicong@...ilicon.com, zhanjie9@...ilicon.com, 
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, 
	linux-perf-users@...r.kernel.org, linux-riscv@...ts.infradead.org
Subject: Re: [PATCH v2 1/2] watchdog: move arm64 watchdog_hld into common code

Hi,

On Thu, Sep 25, 2025 at 1:48 AM Yunhui Cui <cuiyunhui@...edance.com> wrote:
>
> @@ -17,6 +17,7 @@
>  #include <linux/cpu_pm.h>
>  #include <linux/export.h>
>  #include <linux/kernel.h>
> +#include <linux/nmi.h>
>  #include <linux/perf/arm_pmu.h>
>  #include <linux/slab.h>
>  #include <linux/sched/clock.h>
> @@ -696,10 +697,12 @@ static int armpmu_get_cpu_irq(struct arm_pmu *pmu, int cpu)
>         return per_cpu(hw_events->irq, cpu);
>  }
>
> -bool arm_pmu_irq_is_nmi(void)
> +#ifdef CONFIG_HARDLOCKUP_DETECTOR_PERF
> +bool arch_perf_nmi_is_available(void)
>  {
>         return has_nmi;
>  }
> +#endif

Should the previous comment move here, AKA:

/*
 * hardlockup_detector_perf_init() will success even if Pseudo-NMI turns off,
 * however, the pmu interrupts will act like a normal interrupt instead of
 * NMI and the hardlockup detector would be broken.
*/


> +static int __init init_watchdog_freq_notifier(void)
> +{
> +       return cpufreq_register_notifier(&watchdog_freq_notifier,
> +                                        CPUFREQ_POLICY_NOTIFIER);

I think you need to do something to prevent this from happening on any
platforms that override hw_nmi_get_sample_period(), right? These
cpufreq notifiers will be useless in that case...


-Doug