On Tue, Dec 23, 2025 at 10:25:32PM +0700, Bui Quang Minh wrote:
> Calling napi_disable() on an already disabled napi can cause the
> deadlock. Because the delayed refill work will call napi_disable(), we
> must ensure that refill work is only enabled and scheduled after we have
> enabled the rx queue's NAPI.
>
> Signed-off-by: Bui Quang Minh <[email protected]>
> ---
> drivers/net/virtio_net.c | 31 ++++++++++++++++++++++++-------
> 1 file changed, 24 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 63126e490bda..8016d2b378cf 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -3208,16 +3208,31 @@ static int virtnet_open(struct net_device *dev)
> int i, err;
>
> for (i = 0; i < vi->max_queue_pairs; i++) {
> + bool schedule_refill = false;
> +
> + /* - We must call try_fill_recv before enabling napi of the same
> + * receive queue so that it doesn't race with the call in
> + * virtnet_receive.
> + * - We must enable and schedule delayed refill work only when
> + * we have enabled all the receive queue's napi. Otherwise, in
> + * refill_work, we have a deadlock when calling napi_disable on
> + * an already disabled napi.
> + */
I would do:
bool refill = i < vi->curr_queue_pairs;
in fact this is almost the same as resume with
one small difference. pass a flag so we do not duplicate code?
> if (i < vi->curr_queue_pairs) {
> - enable_delayed_refill(&vi->rq[i]);
> /* Make sure we have some buffers: if oom use wq. */
> if (!try_fill_recv(vi, &vi->rq[i], GFP_KERNEL))
> - schedule_delayed_work(&vi->rq[i].refill, 0);
> + schedule_refill = true;
> }
>
> err = virtnet_enable_queue_pair(vi, i);
> if (err < 0)
> goto err_enable_qp;
> +
> + if (i < vi->curr_queue_pairs) {
> + enable_delayed_refill(&vi->rq[i]);
> + if (schedule_refill)
> + schedule_delayed_work(&vi->rq[i].refill, 0);
hmm. should not schedule be under the lock?
> + }
> }
>
> if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_STATUS)) {
> @@ -3456,11 +3471,16 @@ static void __virtnet_rx_resume(struct virtnet_info
> *vi,
> bool running = netif_running(vi->dev);
> bool schedule_refill = false;
>
> + /* See the comment in virtnet_open for the ordering rule
> + * of try_fill_recv, receive queue napi_enable and delayed
> + * refill enable/schedule.
> + */
so maybe common code?
> if (refill && !try_fill_recv(vi, rq, GFP_KERNEL))
> schedule_refill = true;
> if (running)
> virtnet_napi_enable(rq);
>
> + enable_delayed_refill(rq);
> if (schedule_refill)
> schedule_delayed_work(&rq->refill, 0);
hmm. should not schedule be under the lock?
> }
> @@ -3470,18 +3490,15 @@ static void virtnet_rx_resume_all(struct virtnet_info
> *vi)
> int i;
>
> for (i = 0; i < vi->max_queue_pairs; i++) {
> - if (i < vi->curr_queue_pairs) {
> - enable_delayed_refill(&vi->rq[i]);
> + if (i < vi->curr_queue_pairs)
> __virtnet_rx_resume(vi, &vi->rq[i], true);
> - } else {
> + else
> __virtnet_rx_resume(vi, &vi->rq[i], false);
> - }
> }
> }
>
> static void virtnet_rx_resume(struct virtnet_info *vi, struct receive_queue
> *rq)
> {
> - enable_delayed_refill(rq);
> __virtnet_rx_resume(vi, rq, true);
> }
so I would add bool to virtnet_rx_resume and call it everywhere,
removing __virtnet_rx_resume. can be a patch on top.
>
> --
> 2.43.0
