Re: [Xen-devel] [PATCH v3a 14/39] ARM: new VGIC: Add GICv2 world switch backend

[Julien Grall <julien.grall@xxxxxxx>]

Hi Andre,

On 03/22/2018 11:56 AM, Andre Przywara wrote:
> +        /* The locking order forces us to drop and re-take the locks here. */
> +        if ( irq->hw )
> +        {
> +            spin_unlock(&irq->irq_lock);
> +
> +            desc = irq_to_desc(irq->hwintid);
> +            spin_lock(&desc->lock);
> +            spin_lock(&irq->irq_lock);
> +
> +            /* This h/w IRQ should still be assigned to the virtual IRQ. */
> +            ASSERT(irq->hw && desc->irq == irq->hwintid);
> +
> +            have_desc_lock = true;
> +        }
I am a bit concerned of this dance in fold_lr_state(). This looks 
awfully complex but I don't have better solution here. I will have a 
think during the night.
However, this is not going to solve the race condition I mentioned 
between clearing _IRQ_INPROGRESS here and setting _IRQ_INPROGRESS in 
do_IRQ. This is because you don't know the order they are going to be 
executed.
I wanted to make sure you didn't intend to solve that one. Am I correct?

Cheers,

--
Julien Grall

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