linux-kernel - Re: [PATCH v2 1/3] genirq/affinity: Add irq_update_affinity

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Date:   Wed, 28 Oct 2020 19:22:29 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     John Garry <john.garry@...wei.com>, gregkh@...uxfoundation.org,
        rafael@...nel.org, martin.petersen@...cle.com, jejb@...ux.ibm.com
Cc:     linuxarm@...wei.com, linux-scsi@...r.kernel.org,
        linux-kernel@...r.kernel.org, maz@...nel.org,
        John Garry <john.garry@...wei.com>
Subject: Re: [PATCH v2 1/3] genirq/affinity: Add irq_update_affinity_desc()

On Wed, Oct 28 2020 at 20:33, John Garry wrote:
>  
> +int irq_update_affinity_desc(unsigned int irq,
> +			     struct irq_affinity_desc *affinity)
> +{
> +	unsigned long flags;
> +	struct irq_desc *desc = irq_get_desc_lock(irq, &flags, 0);
> +
> +	if (!desc)
> +		return -EINVAL;

Just looking at it some more. This needs a check whether the interrupt
is actually shut down. Otherwise the update will corrupt
state. Something like this:

        if (irqd_is_started(&desc->irq_data))
        	return -EBUSY;

But all of this can't work on x86 due to the way how vector allocation
works. Let me think about that.

Thanks,

        tglx