Le vendredi 29 juillet 2011 à 15:27 +0200, Eric Dumazet a écrit :
> Le vendredi 29 juillet 2011 à 14:29 +0200, Michal Soltys a écrit :
> > On 11-07-15 00:14, Andrew Morton wrote:
> > >
> > > (switched to email. Please respond via emailed reply-to-all, not via
> > > the bugzilla web interface).
> > >
> > >
> > > Here: WARN_ON(next_time == 0);
> > >
> >
> > From the other thread on netfilter-devel:
> >
> > > On 11-07-22 11:58, Michal Pokrywka wrote: After bisecting 2.6.39.1 it
> > > turned out that the bug is caused independently by two patches:
> > >
> > > commit b262a5da755cc6ed0cb4fba230cd9bf4037e1096 sch_sfq: fix peek()
> > > implementation
> > >
> > > and
> > >
> > > commit 9df49f2bfe862573911a080c75a6d81113c5c81d sch_sfq: avoid giving
> > > spurious NET_XMIT_CN signals
> > >
> > > Reverting these patches makes HFSC work again.
> > >
> >
> > This one (upstream 8efa885406359af300d46910642b50ca82c0fe47) seems to be
> > the culprit (does reverting only that one cures the problem ?)
> >
> > It allows SFQ to return success on enqueuing, when the packet really
> > replaced some other packet in some other flow. This confuses outer qdisc
> > (in this particular case HFSC) which thinks new packet was actually
> > added each time such situation happes.
> >
>
> Technically speaking, _this_ packet was successfuly enqueued.
>
> Returning NET_XMIT_CN or NET_XMIT_SUCCESS should not trigger a bug in
> caller.
>
> > This in turn causes additional dequeues and ends with attempt
> > to schedule non-existent packets, and triggers the warning.
> >
>
> Then its probably a bug in HFSC : It doesnt understand SFQ lost a
> packet.
>
> I'll take a look, thanks for the report.
>
>
Oh well, it seems one qdisc_tree_decrease_qlen(sch, 1) is missing
Maybe following patch would help...
diff --git a/net/sched/sch_sfq.c b/net/sched/sch_sfq.c
index 4536ee6..2a2d287 100644
--- a/net/sched/sch_sfq.c
+++ b/net/sched/sch_sfq.c
@@ -410,7 +410,12 @@ sfq_enqueue(struct sk_buff *skb, struct Qdisc *sch)
/* Return Congestion Notification only if we dropped a packet
* from this flow.
*/
- return (qlen != slot->qlen) ? NET_XMIT_CN : NET_XMIT_SUCCESS;
+ if (qlen != slot->qlen)
+ return NET_XMIT_CN;
+
+ /* as we dropped a packet, better let upper stack know this */
+ qdisc_tree_decrease_qlen(sch, 1);
+ return NET_XMIT_SUCCESS;
}
static struct sk_buff *
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