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Date: Thu, 17 Nov 2016 19:55:50 +0200
From: "Michael S. Tsirkin" <mst@redhat.com>
Message-ID: <20161117195511-mutt-send-email-mst@kernel.org>
References: <20161116180551.9611-1-pbonzini@redhat.com>
	<20161116180551.9611-3-pbonzini@redhat.com>
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In-Reply-To: <20161116180551.9611-3-pbonzini@redhat.com>
Subject: Re: [Qemu-devel] [PATCH 2/3] virtio: access ISR atomically
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To: Paolo Bonzini <pbonzini@redhat.com>
Cc: qemu-devel@nongnu.org, alex.williamson@redhat.com, borntraeger@de.ibm.com, felipe@nutanix.com

On Wed, Nov 16, 2016 at 07:05:50PM +0100, Paolo Bonzini wrote:
> @@ -1318,10 +1318,18 @@ void virtio_del_queue(VirtIODevice *vdev, int n)
>      vdev->vq[n].vring.num_default = 0;
>  }
>  
> +static void virtio_set_isr(VirtIODevice *vdev, int value)
> +{
> +    uint8_t old = atomic_read(&vdev->isr);
> +    if ((old & value) != value) {
> +        atomic_or(&vdev->isr, value);
> +    }
> +}
> +

Paolo, can you pls comment on why is it done like this,
as opposed to a single atomic_or?

-- 
MST