Re: PROBLEM: IProute hangs after running traffic shaping scripts

[Patrick McHardy <kaber@xxxxxxxxx>]

Patrick McHardy wrote:

> Szymon Miotk wrote:
>
> > This mail was posted 02-11-2004 to linux-net@xxxxxxxxxxxxxxx, but I 
> > got no response at all, so I am resending it.
> > [1.] One line summary of the problem:
> > IProute hangs after running traffic shaping scripts
>
> Can you test if this patch helps please ? It immediately removes all
> inner qdiscs of classful qdiscs from dev->qdisc_list, making it
> impossible for anyone to look up an inner qdisc that is about to get
> destroyed. Taking qdisc_tree_lock in qdisc_lookup is not really
> necessary with this patch anymore, since all changes to dev->qdisc_list
> happen under the rtnl again (which is also relied on for memory). I put
> it in anyways for now until I have fully analyzed locking.
Please test this patch, the last one had a bug.

> 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 00:08:28 +01:00
@@ -483,10 +483,29 @@
 
 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);
+
+       /* unlink inner qdiscs from dev->qdisc_list immediately */
+       if (qdisc->ops->cl_ops != NULL)
+               list_add(&qdisc->list, &cql);
+       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);
 }