pkt_sched: Manage qdisc list inside of root qdisc.
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>
diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index e244c46..14cc443 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -480,15 +480,12 @@
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 @@
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;
}