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pkt_sched: Manage qdisc list inside of root qdisc.

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Idea is from Patrick McHardy.

Instead of managing the list of qdiscs on the device level, manage it
in the root qdisc of a netdev_queue.  This solves all kinds of
visibility issues during qdisc destruction.

The way to iterate over all qdiscs of a netdev_queue is to visit
the netdev_queue->qdisc, and then traverse it's list.

The only special case is to ignore builting qdiscs at the root when
dumping or doing a qdisc_lookup().  That was not needed previously
because builtin qdiscs were not added to the device's qdisc_list.

Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
David S. Miller
2008-07-18 22:50:15 -07:00
parent 72b25a913e
commit 3072367300
4 changed files with 134 additions and 57 deletions
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10
net/sched/sch_generic.c
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@ -480,15 +480,12 @@ static void __qdisc_destroy(struct rcu_head *head)
void qdisc_destroy(struct Qdisc *qdisc)
{
struct net_device *dev = qdisc_dev(qdisc);
if (qdisc->flags & TCQ_F_BUILTIN ||
!atomic_dec_and_test(&qdisc->refcnt))
return;
spin_lock_bh(&dev->qdisc_list_lock);
list_del(&qdisc->list);
spin_unlock_bh(&dev->qdisc_list_lock);
if (qdisc->parent)
list_del(&qdisc->list);
call_rcu(&qdisc->q_rcu, __qdisc_destroy);
}
@ -520,9 +517,6 @@ static void attach_one_default_qdisc(struct net_device *dev,
printk(KERN_INFO "%s: activation failed\n", dev->name);
return;
}
spin_lock_bh(&dev->qdisc_list_lock);
list_add_tail(&qdisc->list, &dev->qdisc_list);
spin_unlock_bh(&dev->qdisc_list_lock);
} else {
qdisc = &noqueue_qdisc;
}