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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: Jarek Poplawski <jarkao2@gmail.com>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
hifive-unleashed-5.1
Jarek Poplawski 2008-08-22 03:24:05 -07:00 committed by David S. Miller
parent 2540e0511e
commit f6e0b239a2
3 changed files with 42 additions and 8 deletions
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1
include/net/pkt_sched.h
View File

@ -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,

44
net/sched/sch_api.c
View File

@ -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;
}

5
net/sched/sch_generic.c
View File

@ -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);