[RFC] powerpc/xive: Remove irq from queue when it is shutdown

[Benjamin Herrenschmidt]

On Wed, 2018-03-14 at 17:58 +0100, Frederic Barrat wrote:
> +                       if (irq == hw_irq) {
> +                               cur &= 1 << 31;
> +                               cur |= XIVE_BAD_IRQ;
> +                               *(q->qpage + idx) = cpu_to_be32(cur);
> +                       }
> +
> +                       idx = (idx + 1) & q->msk;
> +                       if (idx == 0)
> +                               toggle ^= 1;
> +               } while (irq && (count < q->msk));

Safer to make the replacement an atomic with cmpxhg just in case you
found an old one trailing the queue that's just getting updated by HW.

Cheers,
Ben.