linux-kernel - Re: [PATCH 2/2] genirq: fasteoi resends interrupt on concurrent invoke

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Date:   Tue, 30 May 2023 16:32:39 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     James Gowans <jgowans@...zon.com>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     linux-kernel@...r.kernel.org, Liao Chang <liaochang1@...wei.com>,
        Marc Zyngier <maz@...nel.org>,
        KarimAllah Raslan <karahmed@...zon.com>,
        Yipeng Zou <zouyipeng@...wei.com>,
        Zhang Jianhua <chris.zjh@...wei.com>
Subject: Re: [PATCH 2/2] genirq: fasteoi resends interrupt on concurrent
 invoke

Hi--

On 5/30/23 14:38, James Gowans wrote:

> ---
>  kernel/irq/chip.c | 15 ++++++++++++++-
>  1 file changed, 14 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c
> index 49e7bc871fec..42f33e77c16b 100644
> --- a/kernel/irq/chip.c
> +++ b/kernel/irq/chip.c
> @@ -692,8 +692,15 @@ void handle_fasteoi_irq(struct irq_desc *desc)
>  
>  	raw_spin_lock(&desc->lock);
>  
> -	if (!irq_may_run(desc))
> +	/*
> +	 * When an affinity change races with IRQ delivery, the next interrupt
> +	 * can arrive on the new CPU before the original CPU has completed
> +	 * handling the previous one. Mark it as pending and return EOI.
> +	 */
> +	if (!irq_may_run(desc)) {
> +		desc->istate |= IRQS_PENDING;
>  		goto out;
> +	}
>  
>  	desc->istate &= ~(IRQS_REPLAY | IRQS_WAITING);
>  
> @@ -715,6 +722,12 @@ void handle_fasteoi_irq(struct irq_desc *desc)
>  
>  	cond_unmask_eoi_irq(desc, chip);
>  
> +	/*
> +	 * When the race descibed above happens, this will resend the interrupt.

	                 described

> +	 */
> +	if (unlikely(desc->istate & IRQS_PENDING))
> +		check_irq_resend(desc, false);
> +
>  	raw_spin_unlock(&desc->lock);
>  	return;
>  out:

-- 
~Randy