From: Patrick McHardy <kaber@trash.net>
Date: Mon, 24 Nov 2008 23:46:08 +0000 (-0800)
Subject: pkt_sched: sch_drr: fix drr_dequeue loop()
X-Git-Tag: upstream/snapshot3+hdmi~21169^2~517
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=3f0947c3ffaed33c1c38b79e4b17f75ba072d3e9;p=platform%2Fadaptation%2Frenesas_rcar%2Frenesas_kernel.git

pkt_sched: sch_drr: fix drr_dequeue loop()

Jarek Poplawski points out:

If all child qdiscs of sch_drr are non-work-conserving (e.g. sch_tbf)
drr_dequeue() will busy-loop waiting for skbs instead of leaving the
job for a watchdog. Checking for list_empty() in each loop isn't
necessary either, because this can never be true except the first time.

Using non-work-conserving qdiscs as children of DRR makes no sense,
simply bail out in that case.

Reported-by: Jarek Poplawski <jarkao2@gmail.com>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
---

diff --git a/net/sched/sch_drr.c b/net/sched/sch_drr.c
index 37e6ab9..e7a7e87 100644
--- a/net/sched/sch_drr.c
+++ b/net/sched/sch_drr.c
@@ -373,11 +373,13 @@ static struct sk_buff *drr_dequeue(struct Qdisc *sch)
 	struct sk_buff *skb;
 	unsigned int len;
 
-	while (!list_empty(&q->active)) {
+	if (list_empty(&q->active))
+		goto out;
+	while (1) {
 		cl = list_first_entry(&q->active, struct drr_class, alist);
 		skb = cl->qdisc->ops->peek(cl->qdisc);
 		if (skb == NULL)
-			goto skip;
+			goto out;
 
 		len = qdisc_pkt_len(skb);
 		if (len <= cl->deficit) {
@@ -390,9 +392,9 @@ static struct sk_buff *drr_dequeue(struct Qdisc *sch)
 		}
 
 		cl->deficit += cl->quantum;
-skip:
 		list_move_tail(&cl->alist, &q->active);
 	}
+out:
 	return NULL;
 }