Re: [PATCH RFC] virtio-balloon: fix add/get API use

[Rusty Russell]

On Mon, 2 Jul 2012 10:33:08 +0300, "Michael S. Tsirkin" <mst@xxxxxxxxxx> wrote:
> In virtio balloon virtqueue_get_buf might now run concurrently with
> virtqueue_kick.  I audited both and this seems safe in practice but
> this is not guaranteed by the API.
> Additionally, a spurious interrupt might in theory make
> virtqueue_get_buf run in parallel with virtqueue_add_buf, which is racy.
> 
> While we might try to protect against spurious callbacks it's
> easier to fix the driver: balloon seems to be the only one
> (mis)using the API like this, so let's just fix balloon.
> 
> Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>

I was thinking of a spinlock, but this is far more elegant.

And I added an explicit reference to the 'virtio: expose added
descriptors immediately.' commit in your commit msg.

Kudos!
Rusty.
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