linux-kernel - Re: [PATCH v2 15/25] genirq: Update request_percpu

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Message-ID: <20250916171943.000032d6@huawei.com>
Date: Tue, 16 Sep 2025 17:19:43 +0100
From: Jonathan Cameron <jonathan.cameron@...wei.com>
To: Marc Zyngier <maz@...nel.org>
CC: <linux-kernel@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>,
	<linux-acpi@...r.kernel.org>, Thomas Gleixner <tglx@...utronix.de>, "Mark
 Rutland" <mark.rutland@....com>, Will Deacon <will@...nel.org>, "Rafael J.
 Wysocki" <rafael@...nel.org>, Rob Herring <robh@...nel.org>, "Saravana
 Kannan" <saravanak@...gle.com>, Greg Kroah-Hartman
	<gregkh@...uxfoundation.org>, Sven Peter <sven@...nel.org>, Janne Grunau
	<j@...nau.net>, Suzuki K Poulose <suzuki.poulose@....com>, James Clark
	<james.clark@...aro.org>
Subject: Re: [PATCH v2 15/25] genirq: Update request_percpu_nmi() to take an
 affinity

On Mon, 15 Sep 2025 09:56:52 +0100
Marc Zyngier <maz@...nel.org> wrote:

> Continue spreading the notion of affinity to the percpu interrupt
> request code by updating the call sites that use request_percpu_nmi()
> (all two of them) to take an affinity pointer. This pointer is
> firmly NULL for now.
> 
> Signed-off-by: Marc Zyngier <maz@...nel.org>
A few fussy reviewer comments inline.

> ---
>  arch/arm64/kernel/smp.c   |  2 +-
>  drivers/perf/arm_pmu.c    |  4 +++-
>  include/linux/interrupt.h |  4 ++--
>  kernel/irq/manage.c       | 11 +++++++----
>  4 files changed, 13 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
> index 68cea3a4a35ca..6fb838eee2e7d 100644
> --- a/arch/arm64/kernel/smp.c
> +++ b/arch/arm64/kernel/smp.c
> @@ -1094,7 +1094,7 @@ static void ipi_setup_sgi(int ipi)
>  	irq = ipi_irq_base + ipi;
>  
>  	if (ipi_should_be_nmi(ipi)) {
> -		err = request_percpu_nmi(irq, ipi_handler, "IPI", &irq_stat);
> +		err = request_percpu_nmi(irq, ipi_handler, "IPI", NULL, &irq_stat);
>  		WARN(err, "Could not request IRQ %d as NMI, err=%d\n", irq, err);
>  	} else {
>  		err = request_percpu_irq(irq, ipi_handler, "IPI", &irq_stat);
> diff --git a/drivers/perf/arm_pmu.c b/drivers/perf/arm_pmu.c
> index 5c310e803dd78..de9eca2290a97 100644
> --- a/drivers/perf/arm_pmu.c
> +++ b/drivers/perf/arm_pmu.c
> @@ -659,7 +659,9 @@ int armpmu_request_irq(int irq, int cpu)
>  			irq_ops = &pmunmi_ops;
>  		}
>  	} else if (armpmu_count_irq_users(irq) == 0) {
> -		err = request_percpu_nmi(irq, handler, "arm-pmu", &cpu_armpmu);
> +		err = request_percpu_nmi(irq, handler, "arm-pmu",
> +					 NULL,

I was assuming this odd formatting was to help reduce churn in a later patch, but nope
this whole block get replaced in patch 18.  So might as well move NULL up a line
an have a cleaner intermediate state.

> +					 &cpu_armpmu);
>  
>  		/* If cannot get an NMI, get a normal interrupt */
>  		if (err) {
> diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
> index 52147d5f432b3..2134e7c08c169 100644
> --- a/include/linux/interrupt.h
> +++ b/include/linux/interrupt.h
> @@ -197,8 +197,8 @@ request_percpu_irq(unsigned int irq, irq_handler_t handler,
>  }
>  
>  extern int __must_check
> -request_percpu_nmi(unsigned int irq, irq_handler_t handler,
> -		   const char *devname, void __percpu *dev);
> +request_percpu_nmi(unsigned int irq, irq_handler_t handler, const char *devname,
Odd inconsistency in parameter naming devname/name

Perhaps worth tidying that up whilst here. I only noticed because of the
wrap comment below.


> +		   const struct cpumask *affinity, void __percpu *dev_id);
>  
>  extern const void *free_irq(unsigned int, void *);
>  extern void free_percpu_irq(unsigned int, void __percpu *);
> diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
> index 5f4c651677436..49c237aca2a70 100644
> --- a/kernel/irq/manage.c
> +++ b/kernel/irq/manage.c
> @@ -2527,6 +2527,7 @@ EXPORT_SYMBOL_GPL(__request_percpu_irq);
>   * @irq:	Interrupt line to allocate
>   * @handler:	Function to be called when the IRQ occurs.
>   * @name:	An ascii name for the claiming device
> + * @affinity:	A cpumask describing the target CPUs for this interrupt
>   * @dev_id:	A percpu cookie passed back to the handler function
>   *
>   * This call allocates interrupt resources for a per CPU NMI. Per CPU NMIs
> @@ -2544,7 +2545,8 @@ EXPORT_SYMBOL_GPL(__request_percpu_irq);
>   * will fail returning a negative value.
>   */
>  int request_percpu_nmi(unsigned int irq, irq_handler_t handler,
> -		       const char *name, void __percpu *dev_id)
> +		       const char *name,
> +		       const struct cpumask *affinity, void __percpu *dev_id)

This seems like an odd wrap and I can't immediately see it making more sense
in later patches.

>  {

>