lkml.org 
[lkml]   [2020]   [Aug]   [2]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH -next v2] virtio_net: Avoid loop in virtnet_poll
On Sun, Aug 02, 2020 at 01:56:33PM +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_poll //return true
> virtqueue_napi_schedule //it will reschedule napi
>
> To fix this, return false if vq is broken in virtqueue_poll.
>
> Signed-off-by: Mao Wenan <wenan.mao@linux.alibaba.com>

Looks good:
Acked-by: Michael S. Tsirkin <mst@redhat.com>

> ---
> v1->v2: fix it in virtqueue_poll suggested by Michael S. Tsirkin <mst@redhat.com>
> drivers/virtio/virtio_ring.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index 58b96ba..4f7c73e 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -1960,6 +1960,9 @@ bool virtqueue_poll(struct virtqueue *_vq, unsigned last_used_idx)
> {
> struct vring_virtqueue *vq = to_vvq(_vq);
>
> + if (unlikely(vq->broken))
> + return false;
> +
> virtio_mb(vq->weak_barriers);
> return vq->packed_ring ? virtqueue_poll_packed(_vq, last_used_idx) :
> virtqueue_poll_split(_vq, last_used_idx);
> --
> 1.8.3.1

\
 
 \ /
  Last update: 2020-08-02 08:26    [W:0.051 / U:0.952 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site