Commit 37d9cf1a authored by Toke Høiland-Jørgensen's avatar Toke Høiland-Jørgensen Committed by David S. Miller
Browse files

sched: Fix detection of empty queues in child qdiscs 



Several qdiscs check on enqueue whether the packet was enqueued to a class
with an empty queue, in which case the class is activated. This is done by
checking if the qlen is exactly 1 after enqueue. However, if GSO splitting
is enabled in the child qdisc, a single packet can result in a qlen longer
than 1. This means the activation check fails, leading to a stalled queue.

Fix this by checking if the queue is empty *before* enqueue, and running
the activation logic if this was the case.

Reported-by: default avatarPete Heist <pete@heistp.net>
Signed-off-by: default avatarToke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent f6bab199

net/sched/sch_drr.c

+3 −1
Original line number Diff line number Diff line
@@ -354,6 +354,7 @@ static int drr_enqueue(struct sk_buff *skb, struct Qdisc *sch, 
	struct drr_sched *q = qdisc_priv(sch);

	struct drr_class *cl;

	int err = 0;

	bool first;



	cl = drr_classify(skb, sch, &err);

	if (cl == NULL) {
@@ -363,6 +364,7 @@ static int drr_enqueue(struct sk_buff *skb, struct Qdisc *sch, 
		return err;

	}



	first = !cl->qdisc->q.qlen;

	err = qdisc_enqueue(skb, cl->qdisc, to_free);

	if (unlikely(err != NET_XMIT_SUCCESS)) {

		if (net_xmit_drop_count(err)) {
@@ -372,7 +374,7 @@ static int drr_enqueue(struct sk_buff *skb, struct Qdisc *sch, 
		return err;

	}



	if (cl->qdisc->q.qlen == 1) {

	if (first) {

		list_add_tail(&cl->alist, &q->active);

		cl->deficit = cl->quantum;

	}

net/sched/sch_hfsc.c

+3 −1
Original line number Diff line number Diff line
@@ -1542,6 +1542,7 @@ hfsc_enqueue(struct sk_buff *skb, struct Qdisc *sch, struct sk_buff **to_free) 
	unsigned int len = qdisc_pkt_len(skb);

	struct hfsc_class *cl;

	int uninitialized_var(err);

	bool first;



	cl = hfsc_classify(skb, sch, &err);

	if (cl == NULL) {
@@ -1551,6 +1552,7 @@ hfsc_enqueue(struct sk_buff *skb, struct Qdisc *sch, struct sk_buff **to_free) 
		return err;

	}



	first = !cl->qdisc->q.qlen;

	err = qdisc_enqueue(skb, cl->qdisc, to_free);

	if (unlikely(err != NET_XMIT_SUCCESS)) {

		if (net_xmit_drop_count(err)) {
@@ -1560,7 +1562,7 @@ hfsc_enqueue(struct sk_buff *skb, struct Qdisc *sch, struct sk_buff **to_free) 
		return err;

	}



	if (cl->qdisc->q.qlen == 1) {

	if (first) {

		if (cl->cl_flags & HFSC_RSC)

			init_ed(cl, len);

		if (cl->cl_flags & HFSC_FSC)

net/sched/sch_qfq.c

+3 −1
Original line number Diff line number Diff line
@@ -1215,6 +1215,7 @@ static int qfq_enqueue(struct sk_buff *skb, struct Qdisc *sch, 
	struct qfq_class *cl;

	struct qfq_aggregate *agg;

	int err = 0;

	bool first;



	cl = qfq_classify(skb, sch, &err);

	if (cl == NULL) {
@@ -1236,6 +1237,7 @@ static int qfq_enqueue(struct sk_buff *skb, struct Qdisc *sch, 
	}



	gso_segs = skb_is_gso(skb) ? skb_shinfo(skb)->gso_segs : 1;

	first = !cl->qdisc->q.qlen;

	err = qdisc_enqueue(skb, cl->qdisc, to_free);

	if (unlikely(err != NET_XMIT_SUCCESS)) {

		pr_debug("qfq_enqueue: enqueue failed %d\n", err);
@@ -1253,7 +1255,7 @@ static int qfq_enqueue(struct sk_buff *skb, struct Qdisc *sch, 


	agg = cl->agg;

	/* if the queue was not empty, then done here */

	if (cl->qdisc->q.qlen != 1) {

	if (!first) {

		if (unlikely(skb == cl->qdisc->ops->peek(cl->qdisc)) &&

		    list_first_entry(&agg->active, struct qfq_class, alist)

		    == cl && cl->deficit < len)

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