Eric Dumazet wrote:
> On Tue, Mar 21, 2023 at 2:52 PM John Fastabend <john.fastabend@xxxxxxxxx> wrote:
> >
> > A common mechanism to put a TCP socket into the sockmap is to hook the
> > BPF_SOCK_OPS_{ACTIVE_PASSIVE}_ESTABLISHED_CB event with a BPF program
> > that can map the socket info to the correct BPF verdict parser. When
> > the user adds the socket to the map the psock is created and the new
> > ops are assigned to ensure the verdict program will 'see' the sk_buffs
> > as they arrive.
> >
[...]
> > lock_sock(sk);
> > +
> > + /* We may have received data on the sk_receive_queue pre-accept and
> > + * then we can not use read_skb in this context because we haven't
> > + * assigned a sk_socket yet so have no link to the ops. The work-around
> > + * is to check the sk_receive_queue and in these cases read skbs off
> > + * queue again. The read_skb hook is not running at this point because
> > + * of lock_sock so we avoid having multiple runners in read_skb.
> > + */
> > + if (unlikely(!skb_queue_empty_lockless(&sk->sk_receive_queue))) {
>
> socket is locked here, please use skb_queue_empty() ?
>
> We shall reserve skb_queue_empty_lockless() for lockless contexts.
Yep will do thanks.
