Re: Packet gets stuck in NOLOCK pfifo_fast qdisc

[Cong Wang]

On Thu, Sep 3, 2020 at 10:08 PM John Fastabend <john.fastabend@xxxxxxxxx> wrote:
> Maybe this would unlock us,
>
> diff --git a/net/core/dev.c b/net/core/dev.c
> index 7df6c9617321..9b09429103f1 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -3749,7 +3749,7 @@ static inline int __dev_xmit_skb(struct sk_buff *skb, struct Qdisc *q,
>
>         if (q->flags & TCQ_F_NOLOCK) {
>                 rc = q->enqueue(skb, q, &to_free) & NET_XMIT_MASK;
> -               qdisc_run(q);
> +               __qdisc_run(q);
>
>                 if (unlikely(to_free))
>                         kfree_skb_list(to_free);
>
>
> Per other thread we also need the state deactivated check added
> back.

I guess no, because pfifo_dequeue() seems to require q->seqlock,
according to comments in qdisc_run(), so we can not just get rid of
qdisc_run_begin()/qdisc_run_end() here.

Thanks.