linux-kernel - [182/244] net_sched: prio: use qdisc_dequeue

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Date:	Wed, 28 Sep 2011 15:02:26 -0700
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Eric Dumazet <eric.dumazet@...il.com>,
	Florian Westphal <fw@...len.de>,
	"David S. Miller" <davem@...emloft.net>
Subject: [182/244] net_sched: prio: use qdisc_dequeue_peeked

3.0-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Florian Westphal <fw@...len.de>

[ Upstream commit 3557619f0f6f7496ed453d4825e24958ab1884e0 ]

commit 07bd8df5df4369487812bf85a237322ff3569b77
(sch_sfq: fix peek() implementation) changed sfq to use generic
peek helper.

This makes HFSC complain about a non-work-conserving child qdisc, if
prio with sfq child is used within hfsc:

hfsc peeks into prio qdisc, which will then peek into sfq.
returned skb is stashed in sch->gso_skb.

Next, hfsc tries to dequeue from prio, but prio will call sfq dequeue
directly, which may return NULL instead of previously peeked-at skb.

Have prio call qdisc_dequeue_peeked, so sfq->dequeue() is
not called in this case.

Cc: Eric Dumazet <eric.dumazet@...il.com>
Signed-off-by: Florian Westphal <fw@...len.de>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>
---
 net/sched/sch_prio.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/sched/sch_prio.c
+++ b/net/sched/sch_prio.c
@@ -112,7 +112,7 @@ static struct sk_buff *prio_dequeue(stru

 	for (prio = 0; prio < q->bands; prio++) {
 		struct Qdisc *qdisc = q->queues[prio];
-		struct sk_buff *skb = qdisc->dequeue(qdisc);
+		struct sk_buff *skb = qdisc_dequeue_peeked(qdisc);
 		if (skb) {
 			qdisc_bstats_update(sch, skb);
 			sch->q.qlen--;

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