linux-kernel - Re: [RFC PATCH v2] genirq/cpuhotpug: notify of irq affinity change for offlined cpu.

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Message-ID: <871pjtg91b.ffs@tglx>
Date: Tue, 13 Jan 2026 10:24:16 +0100
From: Thomas Gleixner <tglx@...nel.org>
To: Imran Khan <imran.f.khan@...cle.com>
Cc: linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v2] genirq/cpuhotpug: notify of irq affinity change
 for offlined cpu.

On Sat, Jan 03 2026 at 00:53, Imran Khan wrote:
> During cpu offlining the irqs with broken_affinity are affined
> to other CPU but this affinity change is not accounted for by
> desc::affinity_notify (if available).
> This can leave users of irq_set_affinity_notifier, with old
> affinity information.
>
> Signed-off-by: Imran Khan <imran.f.khan@...cle.com>
> ---
> v1 -> v2:
>  - Fix compilation error due to missed parenthesis around scoped_guard
>
>  kernel/irq/cpuhotplug.c | 12 ++++++++++--
>  1 file changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/irq/cpuhotplug.c b/kernel/irq/cpuhotplug.c
> index 755346ea98196..30153be1a4cca 100644
> --- a/kernel/irq/cpuhotplug.c
> +++ b/kernel/irq/cpuhotplug.c
> @@ -177,9 +177,17 @@ void irq_migrate_all_off_this_cpu(void)
>  		bool affinity_broken;
>  
>  		desc = irq_to_desc(irq);
> -		scoped_guard(raw_spinlock, &desc->lock)
> +		scoped_guard(raw_spinlock_irqsave, &desc->lock) {
>  			affinity_broken = migrate_one_irq(desc);
> -
> +			if (affinity_broken && desc->affinity_notify) {
> +				kref_get(&desc->affinity_notify->kref);
> +				if (!schedule_work(&desc->affinity_notify->work)) {
> +					/* Work was already scheduled, drop our extra ref */
> +					kref_put(&desc->affinity_notify->kref,
> +					desc->affinity_notify->release);
> +				}
> +			}

No, we are not doing random copy&pasta.

Split out the functionality into a function and use it both here and in
irq_set_affinity_locked().

Thanks,

        tglx