netdev - [PATCH net] pkt_sched: move the sanity test in qdisc_list

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Message-ID: <1394294479.20149.66.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Sat, 08 Mar 2014 08:01:19 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Valdis Kletnieks <Valdis.Kletnieks@...edu>,
	David Miller <davem@...emloft.net>,
	Mirco Tischler <mt-ml@....de>
Cc:	Eric Dumazet <edumazet@...gle.com>, netdev@...r.kernel.org
Subject: [PATCH net] pkt_sched: move the sanity test in qdisc_list_add()

From: Eric Dumazet <edumazet@...gle.com>

The WARN_ON(root == &noop_qdisc)) added in qdisc_list_add()
can trigger in normal conditions when devices are not up.
It should be done only right before the list_add_tail() call.

Fixes: e57a784d8cae4 ("pkt_sched: set root qdisc before change() in attach_default_qdiscs()")
Reported-by: Valdis Kletnieks <Valdis.Kletnieks@...edu>
Tested-by: Mirco Tischler <mt-ml@....de>
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 net/sched/sch_api.c |    7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index c31190e29b90..17c03198ebbc 100644
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -273,11 +273,12 @@ 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;
+	if ((q->parent != TC_H_ROOT) && !(q->flags & TCQ_F_INGRESS)) {
+		struct Qdisc *root = qdisc_dev(q)->qdisc;
 
-	WARN_ON_ONCE(root == &noop_qdisc);
-	if ((q->parent != TC_H_ROOT) && !(q->flags & TCQ_F_INGRESS))
+		WARN_ON_ONCE(root == &noop_qdisc);
 		list_add_tail(&q->list, &root->list);
+	}
 }
 EXPORT_SYMBOL(qdisc_list_add);
 


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