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pkt_sched: Don't hold qdisc lock over qdisc_destroy(). 

Based upon reports by Denys Fedoryshchenko, and feedback
and help from Jarek Poplawski and Herbert Xu.

We always either:

1) Never made an external reference to this qdisc.

or

2) Did a dev_deactivate() which purged all asynchronous
   references.

So do not lock the qdisc when we call qdisc_destroy(),
it's illegal anyways as when we drop the lock this is
free'd memory.

Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
David S. Miller 2008-08-18 21:03:15 -07:00
parent 25bfcd5a78
commit 4d8863a29c
2 changed files with 2 additions and 17 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
net/sched/sch_api.c
View File

@ -638,11 +638,8 @@ static void notify_and_destroy(struct sk_buff *skb, struct nlmsghdr *n, u32 clid
if (new || old)
qdisc_notify(skb, n, clid, old, new);
if (old) {
sch_tree_lock(old);
if (old)
qdisc_destroy(old);
sch_tree_unlock(old);
}
}
/* Graft qdisc "new" to class "classid" of qdisc "parent" or
@ -1092,16 +1089,10 @@ static int tc_modify_qdisc(struct sk_buff *skb, struct nlmsghdr *n, void *arg)
graft:
if (1) {
spinlock_t *root_lock;
err = qdisc_graft(dev, p, skb, n, clid, q, NULL);
if (err) {
if (q) {
root_lock = qdisc_root_lock(q);
spin_lock_bh(root_lock);
if (q)
qdisc_destroy(q);
spin_unlock_bh(root_lock);
}
return err;
}
}

6
net/sched/sch_generic.c
View File

@ -518,8 +518,6 @@ void qdisc_reset(struct Qdisc *qdisc)
}
EXPORT_SYMBOL(qdisc_reset);
/* Under qdisc_lock(qdisc) and BH! */
void qdisc_destroy(struct Qdisc *qdisc)
{
const struct Qdisc_ops *ops = qdisc->ops;
@ -712,14 +710,10 @@ static void shutdown_scheduler_queue(struct net_device *dev,
struct Qdisc *qdisc_default = _qdisc_default;
if (qdisc) {
spinlock_t *root_lock = qdisc_lock(qdisc);
dev_queue->qdisc = qdisc_default;
dev_queue->qdisc_sleeping = qdisc_default;
spin_lock_bh(root_lock);
qdisc_destroy(qdisc);
spin_unlock_bh(root_lock);
}
}