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Commit 5fb66229 authored by David S. Miller's avatar David S. Miller
Browse files

pkt_sched: Use qdisc_lock() on already sampled root qdisc. 



Based upon a bug report by Jeff Kirsher.

Don't use qdisc_root_lock() in these cases as the root
qdisc could have been changed, and we'd thus lock the
wrong object.

Tested by Emil S Tantilov who confirms that this seems
to fix the problem.

Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 82f97b8d

net/core/dev.c

+2 −2
Original line number Diff line number Diff line
@@ -1796,7 +1796,7 @@ int dev_queue_xmit(struct sk_buff *skb) 
	skb->tc_verd = SET_TC_AT(skb->tc_verd,AT_EGRESS);

#endif

	if (q->enqueue) {

		spinlock_t *root_lock = qdisc_root_lock(q);

		spinlock_t *root_lock = qdisc_lock(q);



		spin_lock(root_lock);
@@ -1995,7 +1995,7 @@ static void net_tx_action(struct softirq_action *h) 
			smp_mb__before_clear_bit();

			clear_bit(__QDISC_STATE_SCHED, &q->state);



			root_lock = qdisc_root_lock(q);

			root_lock = qdisc_lock(q);

			if (spin_trylock(root_lock)) {

				qdisc_run(q);

				spin_unlock(root_lock);

net/sched/sch_generic.c

+6 −6
Original line number Diff line number Diff line
@@ -29,7 +29,7 @@ 
/* Main transmission queue. */



/* Modifications to data participating in scheduling must be protected with

 * qdisc_root_lock(qdisc) spinlock.

 * qdisc_lock(qdisc) spinlock.

 *

 * The idea is the following:

 * - enqueue, dequeue are serialized via qdisc root lock
@@ -126,7 +126,7 @@ static inline int qdisc_restart(struct Qdisc *q) 
	if (unlikely((skb = dequeue_skb(q)) == NULL))

		return 0;



	root_lock = qdisc_root_lock(q);

	root_lock = qdisc_lock(q);



	/* And release qdisc */

	spin_unlock(root_lock);
@@ -507,7 +507,7 @@ struct Qdisc * qdisc_create_dflt(struct net_device *dev, 
}

EXPORT_SYMBOL(qdisc_create_dflt);



/* Under qdisc_root_lock(qdisc) and BH! */

/* Under qdisc_lock(qdisc) and BH! */



void qdisc_reset(struct Qdisc *qdisc)

{
@@ -543,7 +543,7 @@ static void __qdisc_destroy(struct rcu_head *head) 
	kfree((char *) qdisc - qdisc->padded);

}



/* Under qdisc_root_lock(qdisc) and BH! */

/* Under qdisc_lock(qdisc) and BH! */



void qdisc_destroy(struct Qdisc *qdisc)

{
@@ -659,7 +659,7 @@ static bool some_qdisc_is_running(struct net_device *dev, int lock) 


		dev_queue = netdev_get_tx_queue(dev, i);

		q = dev_queue->qdisc;

		root_lock = qdisc_root_lock(q);

		root_lock = qdisc_lock(q);



		if (lock)

			spin_lock_bh(root_lock);
@@ -735,7 +735,7 @@ static void shutdown_scheduler_queue(struct net_device *dev, 
	struct Qdisc *qdisc_default = _qdisc_default;



	if (qdisc) {

		spinlock_t *root_lock = qdisc_root_lock(qdisc);

		spinlock_t *root_lock = qdisc_lock(qdisc);



		dev_queue->qdisc = qdisc_default;

		dev_queue->qdisc_sleeping = qdisc_default;