netdev - [BUG] net/sched : qlen can not really be per cpu ?

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Date:   Mon, 25 Feb 2019 22:42:17 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     John Fastabend <john.fastabend@...il.com>,
        Networking <netdev@...r.kernel.org>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Jiri Pirko <jiri@...nulli.us>
Subject: [BUG] net/sched : qlen can not really be per cpu ?

HTB + pfifo_fast as a leaf qdisc hits badly the following warning in htb_activate() :

WARN_ON(cl->level || !cl->leaf.q || !cl->leaf.q->q.qlen);

This is because pfifo_fast does not update sch->q.qlen, but per cpu counters.
So cl->leaf.q->q.qlen is zero.

HFSC, CBQ, DRR, QFQ  have the same problem.

Any ideas how we can fix this ?

Thanks !