Re: [PATCH net-next-2.6] net_sched: sch_sfq: add backlog info in sfq_dump_class_stats()

Eric Dumazet
2010-12-16T11:03:10Z

Le jeudi 16 décembre 2010 à 08:16 +0000, Jarek Poplawski a écrit :
> On 2010-12-15 19:18, Eric Dumazet wrote:
> > We currently return for each active SFQ slot the number of packets in
> > queue. We can also give number of bytes accounted for these packets.
> >
> > tc -s class show dev ifb0
> >
> > Before patch :
> >
> > class sfq 11:3d9 parent 11:
> > (dropped 0, overlimits 0 requeues 0)
> > backlog 0b 3p requeues 0
> > allot 1266
> >
> > After patch :
> >
> > class sfq 11:3e4 parent 11:
> > (dropped 0, overlimits 0 requeues 0)
> > backlog 4380b 3p requeues 0
> > allot 1212
> >
> >
> > Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
> > ---
> > net/sched/sch_sfq.c | 7 ++++++-
> > 1 file changed, 6 insertions(+), 1 deletion(-)
> >
> > diff --git a/net/sched/sch_sfq.c b/net/sched/sch_sfq.c
> > index 3cf478d..cb331de 100644
> > --- a/net/sched/sch_sfq.c
> > +++ b/net/sched/sch_sfq.c
> > @@ -548,8 +548,13 @@ static int sfq_dump_class_stats(struct Qdisc *sch, unsigned long cl,
> > {
> > struct sfq_sched_data *q = qdisc_priv(sch);
> > sfq_index idx = q->ht[cl-1];
> > - struct gnet_stats_queue qs = { .qlen = q->qs[idx].qlen };
> > + struct sk_buff_head *list = &q->qs[idx];
> > + struct gnet_stats_queue qs = { .qlen = list->qlen };
> > struct tc_sfq_xstats xstats = { .allot = q->allot[idx] };
> > + struct sk_buff *skb;
> > +
> > + skb_queue_walk(list, skb)
> > + qs.backlog += qdisc_pkt_len(skb);
>
> I don't think you can walk this list without the qdisc lock.

So after checks, I confirm qdisc lock is held at this point, patch is
valid.

tc_fill_tclass() calls gnet_stats_start_copy_compat() (and locks
qdisc_root_sleeping_lock()), before calling
cl_ops->dump_stats(q, cl, &d)

Thanks !