On Sat, Aug 19, 2017 at 2:38 AM, Koichiro Den <den@xxxxxxxxxxxxx> wrote:
> Facing the possible unbounded delay relying on freeing on xmit path,
> we also better to invoke and clear the upper layer zerocopy callback
> beforehand to keep them from waiting for unbounded duration in vain.
Good point.
> For instance, this removes the possible deadlock in the case that the
> upper layer is a zerocopy-enabled vhost-net.
> This does not apply if napi_tx is enabled since it will be called in
> reasonale time.
Indeed. Btw, I am gathering data to eventually make napi the default
mode. But that is taking some time.
>
> Signed-off-by: Koichiro Den <den@xxxxxxxxxxxxx>
> ---
> drivers/net/virtio_net.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 4302f313d9a7..f7deaa5b7b50 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -1290,6 +1290,14 @@ static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev)
>
> /* Don't wait up for transmitted skbs to be freed. */
> if (!use_napi) {
> + if (skb_shinfo(skb)->tx_flags & SKBTX_DEV_ZEROCOPY) {
> + struct ubuf_info *uarg;
> + uarg = skb_shinfo(skb)->destructor_arg;
> + if (uarg->callback)
> + uarg->callback(uarg, true);
> + skb_shinfo(skb)->destructor_arg = NULL;
> + skb_shinfo(skb)->tx_flags &= ~SKBTX_DEV_ZEROCOPY;
> + }
Instead of open coding, this can use skb_zcopy_clear.
> skb_orphan(skb);
> nf_reset(skb);
> }
> --
> 2.9.4
>
>
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