On Tue, 2 Jul 2019 17:36:34 +0300, Ilya Maximets wrote:
> Unlike driver mode, generic xdp receive could be triggered
> by different threads on different CPU cores at the same time
> leading to the fill and rx queue breakage. For example, this
> could happen while sending packets from two processes to the
> first interface of veth pair while the second part of it is
> open with AF_XDP socket.
>
> Need to take a lock for each generic receive to avoid race.
>
> Fixes: c497176cb2e4 ("xsk: add Rx receive functions and poll support")
> Signed-off-by: Ilya Maximets <i.maximets@xxxxxxxxxxx>
> diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
> index a14e8864e4fa..19f41d2b670c 100644
> --- a/net/xdp/xsk.c
> +++ b/net/xdp/xsk.c
> @@ -119,17 +119,22 @@ int xsk_generic_rcv(struct xdp_sock *xs, struct xdp_buff *xdp)
> {
> u32 metalen = xdp->data - xdp->data_meta;
> u32 len = xdp->data_end - xdp->data;
> + unsigned long flags;
> void *buffer;
> u64 addr;
> int err;
>
> - if (xs->dev != xdp->rxq->dev || xs->queue_id != xdp->rxq->queue_index)
> - return -EINVAL;
> + spin_lock_irqsave(&xs->rx_lock, flags);
Why _irqsave, rather than _bh?
> + if (xs->dev != xdp->rxq->dev || xs->queue_id != xdp->rxq->queue_index) {
> + err = -EINVAL;
> + goto out_unlock;
> + }
>
> if (!xskq_peek_addr(xs->umem->fq, &addr) ||
> len > xs->umem->chunk_size_nohr - XDP_PACKET_HEADROOM) {
> - xs->rx_dropped++;
> - return -ENOSPC;
> + err = -ENOSPC;
> + goto out_drop;
> }
>
> addr += xs->umem->headroom;
