| Message ID | 1596339683-117617-1-git-send-email-wenan.mao@linux.alibaba.com |
|---|---|
| State | Changes Requested |
| Delegated to: | David Miller |
| Headers | show |
| Series | [-next] virtio_net: Avoid loop in virtnet_poll | expand |
On Sun, Aug 02, 2020 at 11:41:23AM +0800, Mao Wenan wrote: > The loop may exist if vq->broken is true, > virtqueue_get_buf_ctx_packed or virtqueue_get_buf_ctx_split > will return NULL, so virtnet_poll will reschedule napi to > receive packet, it will lead cpu usage(si) to 100%. > > call trace as below: > virtnet_poll > virtnet_receive > virtqueue_get_buf_ctx > virtqueue_get_buf_ctx_packed > virtqueue_get_buf_ctx_split > virtqueue_napi_complete > virtqueue_napi_schedule //it will reschedule napi > > Signed-off-by: Mao Wenan <wenan.mao@linux.alibaba.com> I think it's more a bug in virtqueue_poll : virtqueue_get_buf reports NULL on broken, so virtqueue_poll should report false for consistency. > --- > drivers/net/virtio_net.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > index ba38765..a058da1 100644 > --- a/drivers/net/virtio_net.c > +++ b/drivers/net/virtio_net.c > @@ -327,7 +327,8 @@ static void virtqueue_napi_complete(struct napi_struct *napi, > > opaque = virtqueue_enable_cb_prepare(vq); > if (napi_complete_done(napi, processed)) { > - if (unlikely(virtqueue_poll(vq, opaque))) > + if (unlikely(virtqueue_poll(vq, opaque)) && > + unlikely(!virtqueue_is_broken(vq))) > virtqueue_napi_schedule(napi, vq); > } else { > virtqueue_disable_cb(vq); > -- > 1.8.3.1
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index ba38765..a058da1 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -327,7 +327,8 @@ static void virtqueue_napi_complete(struct napi_struct *napi, opaque = virtqueue_enable_cb_prepare(vq); if (napi_complete_done(napi, processed)) { - if (unlikely(virtqueue_poll(vq, opaque))) + if (unlikely(virtqueue_poll(vq, opaque)) && + unlikely(!virtqueue_is_broken(vq))) virtqueue_napi_schedule(napi, vq); } else { virtqueue_disable_cb(vq);
The loop may exist if vq->broken is true, virtqueue_get_buf_ctx_packed or virtqueue_get_buf_ctx_split will return NULL, so virtnet_poll will reschedule napi to receive packet, it will lead cpu usage(si) to 100%. call trace as below: virtnet_poll virtnet_receive virtqueue_get_buf_ctx virtqueue_get_buf_ctx_packed virtqueue_get_buf_ctx_split virtqueue_napi_complete virtqueue_napi_schedule //it will reschedule napi Signed-off-by: Mao Wenan <wenan.mao@linux.alibaba.com> --- drivers/net/virtio_net.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)