linux-kernel - Re: [patch V2 32/45] genirq/manage: Rework irq_set_vcpu

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Message-ID: <4f323802-d31d-4ba0-8a55-6e9f5e3cd152@kernel.org>
Date: Wed, 30 Apr 2025 08:31:57 +0200
From: Jiri Slaby <jirislaby@...nel.org>
To: Thomas Gleixner <tglx@...utronix.de>, LKML <linux-kernel@...r.kernel.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Subject: Re: [patch V2 32/45] genirq/manage: Rework irq_set_vcpu_affinity()

On 29. 04. 25, 8:55, Thomas Gleixner wrote:
> Use the new guards to get and lock the interrupt descriptor and tidy up the
> code.
> 
> No functional change.
> 
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> 
> ---
>   kernel/irq/manage.c |   40 +++++++++++++++++-----------------------
>   1 file changed, 17 insertions(+), 23 deletions(-)
> 
> --- a/kernel/irq/manage.c
> +++ b/kernel/irq/manage.c
> @@ -627,32 +627,26 @@ int irq_setup_affinity(struct irq_desc *
>    */
>   int irq_set_vcpu_affinity(unsigned int irq, void *vcpu_info)
>   {
> -	unsigned long flags;
> -	struct irq_desc *desc = irq_get_desc_lock(irq, &flags, 0);
> -	struct irq_data *data;
> -	struct irq_chip *chip;
> -	int ret = -ENOSYS;
> +	scoped_irqdesc_get_and_lock(irq, 0) {
> +		struct irq_desc *desc = scoped_irqdesc;
> +		struct irq_data *data;
> +		struct irq_chip *chip;
> +		int ret = -ENOSYS;
>   
> -	if (!desc)
> -		return -EINVAL;
> +		data = irq_desc_get_irq_data(desc);
> +		do {
> +			chip = irq_data_get_irq_chip(data);
> +			if (chip && chip->irq_set_vcpu_affinity)
> +				break;
>   
> -	data = irq_desc_get_irq_data(desc);
> -	do {
> -		chip = irq_data_get_irq_chip(data);
> -		if (chip && chip->irq_set_vcpu_affinity)
> -			break;
> -#ifdef CONFIG_IRQ_DOMAIN_HIERARCHY
> -		data = data->parent_data;
> -#else
> -		data = NULL;
> -#endif
> -	} while (data);
> +			data = irqd_get_parent_data(data);
> +		} while (data);
>   
> -	if (data)
> -		ret = chip->irq_set_vcpu_affinity(data, vcpu_info);
> -	irq_put_desc_unlock(desc, flags);
> -
> -	return ret;
> +		if (data)
> +			ret = chip->irq_set_vcpu_affinity(data, vcpu_info);
> +		return ret;

What about simpler:
   if (!data)
     return -ENOSYS;
   return chip->irq_set_vcpu_affinity(data, vcpu_info);

instead? No need for 'ret' at all then: it's always PITA to look up what 
ret is set to initially.

-- 
js
suse labs