Thomas Graf wrote:
* Patrick McHardy <418F9AD0.1040701@xxxxxxxxx> 2004-11-08 17:12
There is some optimization possible, I will do this for the final
patch. But I don't understand the problem you refer to, can you
please explain ?
I don't have the time to verify this at the moment but:
1) qdisc_destroy unlinking all the lists
2) RTM_NEWQDISC creating a new qdisc with the same major classid as the old one
which will suceed since the old one cannot be found anymore.
3) rcu callback __qdisc_destroy -> qdisc_destroy looking through qdisc_list
again and then deleting the new entries because their major classid matches.
I might be missing something though.
You're right, thanks. The optimization already fixed this, but I
wasn't aware of the bug :) New patch attached.
Regards
Patrick
===== net/sched/sch_api.c 1.42 vs edited =====
--- 1.42/net/sched/sch_api.c 2004-11-07 05:03:04 +01:00
+++ edited/net/sched/sch_api.c 2004-11-08 02:38:04 +01:00
@@ -196,10 +196,14 @@
{
struct Qdisc *q;
+ read_lock_bh(&qdisc_tree_lock);
list_for_each_entry(q, &dev->qdisc_list, list) {
- if (q->handle == handle)
+ if (q->handle == handle) {
+ read_unlock_bh(&qdisc_tree_lock);
return q;
+ }
}
+ read_unlock_bh(&qdisc_tree_lock);
return NULL;
}
===== net/sched/sch_generic.c 1.30 vs edited =====
--- 1.30/net/sched/sch_generic.c 2004-11-06 01:34:45 +01:00
+++ edited/net/sched/sch_generic.c 2004-11-08 20:41:58 +01:00
@@ -483,10 +483,32 @@
void qdisc_destroy(struct Qdisc *qdisc)
{
+ struct list_head cql = LIST_HEAD_INIT(cql);
+ struct Qdisc *cq, *q, *n;
+
if (qdisc->flags & TCQ_F_BUILTIN ||
!atomic_dec_and_test(&qdisc->refcnt))
return;
- list_del(&qdisc->list);
+
+ if (!list_empty(&qdisc->list)) {
+ if (qdisc->ops->cl_ops == NULL)
+ list_del(&qdisc->list);
+ else
+ list_move(&qdisc->list, &cql);
+ }
+
+ /* unlink inner qdiscs from dev->qdisc_list immediately */
+ list_for_each_entry(cq, &cql, list)
+ list_for_each_entry_safe(q, n, &qdisc->dev->qdisc_list, list)
+ if (TC_H_MAJ(q->parent) == TC_H_MAJ(cq->handle)) {
+ if (q->ops->cl_ops != NULL)
+ list_move_tail(&q->list, &cql);
+ else
+ list_del_init(&q->list);
+ }
+ list_for_each_entry_safe(cq, n, &cql, list)
+ list_del_init(&cq->list);
+
call_rcu(&qdisc->q_rcu, __qdisc_destroy);
}
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