On Wed, Feb 28, 2018 at 06:20:04PM +0800, Jason Wang wrote:
> We try to disable NAPI to prevent a single XDP TX queue being used by
> multiple cpus. But we don't check if device is up (NAPI is enabled),
> this could result stall because of infinite wait in
> napi_disable(). Fixing this by checking device state through
> netif_running() before.
>
> Fixes: 4941d472bf95b ("virtio-net: do not reset during XDP set")
> Signed-off-by: Jason Wang <jasow...@redhat.com>
Acked-by: Michael S. Tsirkin <m...@redhat.com>
> ---
> drivers/net/virtio_net.c | 8 +++++---
> 1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 9bb9e56..2d54123 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -2185,8 +2185,9 @@ static int virtnet_xdp_set(struct net_device *dev,
> struct bpf_prog *prog,
> }
>
> /* Make sure NAPI is not using any XDP TX queues for RX. */
> - for (i = 0; i < vi->max_queue_pairs; i++)
> - napi_disable(&vi->rq[i].napi);
> + if (netif_running(dev))
> + for (i = 0; i < vi->max_queue_pairs; i++)
> + napi_disable(&vi->rq[i].napi);
>
> netif_set_real_num_rx_queues(dev, curr_qp + xdp_qp);
> err = _virtnet_set_queues(vi, curr_qp + xdp_qp);
> @@ -2205,7 +2206,8 @@ static int virtnet_xdp_set(struct net_device *dev,
> struct bpf_prog *prog,
> }
> if (old_prog)
> bpf_prog_put(old_prog);
> - virtnet_napi_enable(vi->rq[i].vq, &vi->rq[i].napi);
> + if (netif_running(dev))
> + virtnet_napi_enable(vi->rq[i].vq, &vi->rq[i].napi);
> }
>
> return 0;
> --
> 2.7.4
