Commit 3f0947c3 authored Nov 24, 2008 by Patrick McHardy Committed by David S. Miller Nov 24, 2008

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>

parent 4b40eed7

net/sched/sch_drr.c

+5 −3

Original line number	Diff line number	Diff line
		@@ -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;
		}

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