pkt_sched: set root qdisc before change() in attach_default_qdiscs()

After commit 95dc192 ("pkt_sched: give visibility to mq slave qdiscs") we call disc_list_add() while the device qdisc might be the noop_qdisc one. This shows up as duplicates in "tc qdisc show", as all inactive devices point to noop_qdisc. Fix this by setting dev->qdisc to the new qdisc before calling ops->change() in attach_default_qdiscs() Add a WARN_ON_ONCE() to catch any future similar problem. Signed-off-by: Eric Dumazet <[email protected]> Signed-off-by: David S. Miller <[email protected]>
CamonZ · Dec 14, 2013 · e57a784 · e57a784
1 parent 59bcaed
commit e57a784
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Showing 2 changed files with 5 additions and 2 deletions.
diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
@@ -273,8 +273,11 @@ static struct Qdisc *qdisc_match_from_root(struct Qdisc *root, u32 handle)
 
 void qdisc_list_add(struct Qdisc *q)
 {
+	struct Qdisc *root = qdisc_dev(q)->qdisc;
+
+	WARN_ON_ONCE(root == &noop_qdisc);
 	if ((q->parent != TC_H_ROOT) && !(q->flags & TCQ_F_INGRESS))
-		list_add_tail(&q->list, &qdisc_dev(q)->qdisc->list);
+		list_add_tail(&q->list, &root->list);
 }
 EXPORT_SYMBOL(qdisc_list_add);
 

diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
@@ -718,8 +718,8 @@ static void attach_default_qdiscs(struct net_device *dev)
 	} else {
 		qdisc = qdisc_create_dflt(txq, &mq_qdisc_ops, TC_H_ROOT);
 		if (qdisc) {
-			qdisc->ops->attach(qdisc);
 			dev->qdisc = qdisc;
+			qdisc->ops->attach(qdisc);
 		}
 	}
 }