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Commit f6e0b239 authored by Jarek Poplawski's avatar Jarek Poplawski Committed by David S. Miller
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pkt_sched: Fix qdisc list locking 



Since some qdiscs call qdisc_tree_decrease_qlen() (so qdisc_lookup())
without rtnl_lock(), adding and deleting from a qdisc list needs
additional locking. This patch adds global spinlock qdisc_list_lock
and wrapper functions for modifying the list. It is considered as a
temporary solution until hfsc_dequeue(), netem_dequeue() and
tbf_dequeue() (or qdisc_tree_decrease_qlen()) are redone.

With feedback from Herbert Xu and David S. Miller.

Signed-off-by: default avatarJarek Poplawski <jarkao2@gmail.com>
Acked-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 2540e051

include/net/pkt_sched.h

+1 −0
Original line number Diff line number Diff line
@@ -78,6 +78,7 @@ extern struct Qdisc *fifo_create_dflt(struct Qdisc *sch, struct Qdisc_ops *ops, 


extern int register_qdisc(struct Qdisc_ops *qops);

extern int unregister_qdisc(struct Qdisc_ops *qops);

extern void qdisc_list_del(struct Qdisc *q);

extern struct Qdisc *qdisc_lookup(struct net_device *dev, u32 handle);

extern struct Qdisc *qdisc_lookup_class(struct net_device *dev, u32 handle);

extern struct qdisc_rate_table *qdisc_get_rtab(struct tc_ratespec *r,

net/sched/sch_api.c

+39 −5
Original line number Diff line number Diff line
@@ -199,19 +199,53 @@ struct Qdisc *qdisc_match_from_root(struct Qdisc *root, u32 handle) 
	return NULL;

}



/*

 * This lock is needed until some qdiscs stop calling qdisc_tree_decrease_qlen()

 * without rtnl_lock(); currently hfsc_dequeue(), netem_dequeue(), tbf_dequeue()

 */

static DEFINE_SPINLOCK(qdisc_list_lock);



static void qdisc_list_add(struct Qdisc *q)

{

	if ((q->parent != TC_H_ROOT) && !(q->flags & TCQ_F_INGRESS)) {

		spin_lock_bh(&qdisc_list_lock);

		list_add_tail(&q->list, &qdisc_root_sleeping(q)->list);

		spin_unlock_bh(&qdisc_list_lock);

	}

}



void qdisc_list_del(struct Qdisc *q)

{

	if ((q->parent != TC_H_ROOT) && !(q->flags & TCQ_F_INGRESS)) {

		spin_lock_bh(&qdisc_list_lock);

		list_del(&q->list);

		spin_unlock_bh(&qdisc_list_lock);

	}

}

EXPORT_SYMBOL(qdisc_list_del);



struct Qdisc *qdisc_lookup(struct net_device *dev, u32 handle)

{

	unsigned int i;

	struct Qdisc *q;



	spin_lock_bh(&qdisc_list_lock);



	for (i = 0; i < dev->num_tx_queues; i++) {

		struct netdev_queue *txq = netdev_get_tx_queue(dev, i);

		struct Qdisc *q, *txq_root = txq->qdisc_sleeping;

		struct Qdisc *txq_root = txq->qdisc_sleeping;



		q = qdisc_match_from_root(txq_root, handle);

		if (q)

			return q;

			goto unlock;

	}

	return qdisc_match_from_root(dev->rx_queue.qdisc_sleeping, handle);



	q = qdisc_match_from_root(dev->rx_queue.qdisc_sleeping, handle);



unlock:

	spin_unlock_bh(&qdisc_list_lock);



	return q;

}



static struct Qdisc *qdisc_leaf(struct Qdisc *p, u32 classid)
@@ -810,8 +844,8 @@ qdisc_create(struct net_device *dev, struct netdev_queue *dev_queue, 
				goto err_out3;

			}

		}

		if ((parent != TC_H_ROOT) && !(sch->flags & TCQ_F_INGRESS))

			list_add_tail(&sch->list, &dev_queue->qdisc_sleeping->list);



		qdisc_list_add(sch);



		return sch;

	}

net/sched/sch_generic.c

+2 −3
Original line number Diff line number Diff line
@@ -526,10 +526,9 @@ void qdisc_destroy(struct Qdisc *qdisc) 
	    !atomic_dec_and_test(&qdisc->refcnt))

		return;



	if (qdisc->parent)

		list_del(&qdisc->list);



#ifdef CONFIG_NET_SCHED

	qdisc_list_del(qdisc);



	qdisc_put_stab(qdisc->stab);

#endif

	gen_kill_estimator(&qdisc->bstats, &qdisc->rate_est);