On Wed, May 25, 2016 at 08:25:20AM +0000, Xie, Huawei wrote:
> On 5/25/2016 4:12 PM, Xie, Huawei wrote:
> > There is no external function call or any barrier in the loop,
> > the used->idx would only be retrieved once.
> >
> > Signed-off-by: Huawei Xie <huawei.xie at intel.com>
> > ---
> > drivers/net/virtio/virtio_ethdev.c | 3 ++-
> > 1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/net/virtio/virtio_ethdev.c
> > b/drivers/net/virtio/virtio_ethdev.c
> > index c3fb628..f6d6305 100644
> > --- a/drivers/net/virtio/virtio_ethdev.c
> > +++ b/drivers/net/virtio/virtio_ethdev.c
> > @@ -204,7 +204,8 @@ virtio_send_command(struct virtqueue *vq, struct
> > virtio_pmd_ctrl *ctrl,
> > usleep(100);
> > }
> >
> > - while (vq->vq_used_cons_idx != vq->vq_ring.used->idx) {
> > + while (vq->vq_used_cons_idx !=
> > + *((volatile uint16_t *)(&vq->vq_ring.used->idx))) {
> > uint32_t idx, desc_idx, used_idx;
> > struct vring_used_elem *uep;
> >
>
> Find this issue when do the code rework of RX/TX queue.
> As in other places, we also have loop retrieving the value of avial->idx
> or used->idx, i prefer to declare the index in vq structure as volatile
> to avoid potential issue.
It might be a good idea to wrap this in a macro
similar to ACCESS_ONCE in Linux.
>
> Stephen:
> Another question is why we need a loop here?
>
> /huawei
--
MST
