From: Thomas Graf <tgraf@suug•ch>
To: "David S. Miller" <davem@davemloft•net>
Cc: netdev@oss•sgi.com
Subject: [PATCH 2.6] CBQ: Destroy filters before destroying classes
Date: Thu, 7 Oct 2004 19:53:13 +0200 [thread overview]
Message-ID: <20041007175313.GA19628@postel.suug.ch> (raw)
Dave,
CBQ destroys its classes by traversing the hashtable and thus classes
are not destroyed from root to leafs which means that class Y being
a subclass of class X may be destroyed before X. This is a problem
if a filter is attached to class X (parent) classifying into class Y
(result). In case Y gets deleted before X the filter references an
already deleted class while trying to unbind (cbq_unbind_filter).
Therefore all filters must be destroyed before destroying classes. An
additional BUG_TRAP has been added to document this not so obvious case.
Patch is relative to "Convert Qdiscs to use generic network
statistics/estimator" patchset.
Signed-off-by: Thomas Graf <tgraf@suug•ch>
The BUG can be triggered with the following commands:
$TC qdisc add dev $DEV root handle 10:0 cbq bandwidth 100Mbit avpkt 1400 mpu 64
$TC class add dev $DEV parent 10:0 classid 10:12 cbq bandwidth 100mbit \
rate 100mbit allot 1514 prio 3 maxburst 1 avpkt 500 bounded
$TC class add dev $DEV parent 10:12 classid 10:13 cbq bandwidth 100mbit \
rate 100mbit allot 1514 prio 3 maxburst 1 avpkt 500 bounded
$TC filter add dev $DEV parent 10:12 protocol ip prio 10 u32 match ip protocol 6 0xff flowid 10:13
$TC qdisc del dev $DEV root
The deletion ordering in the above case is: 10:0 -> 10:13 -> 10:12
diff -Nru linux-2.6.9-rc3-bk6.orig/net/sched/sch_cbq.c linux-2.6.9-rc3-bk6/net/sched/sch_cbq.c
--- linux-2.6.9-rc3-bk6.orig/net/sched/sch_cbq.c 2004-10-07 00:32:25.000000000 +0200
+++ linux-2.6.9-rc3-bk6/net/sched/sch_cbq.c 2004-10-07 18:44:44.000000000 +0200
@@ -1749,6 +1749,8 @@
{
struct cbq_sched_data *q = qdisc_priv(sch);
+ BUG_TRAP(!cl->filters);
+
cbq_destroy_filters(cl);
qdisc_destroy(cl->q);
qdisc_put_rtab(cl->R_tab);
@@ -1769,6 +1771,14 @@
#ifdef CONFIG_NET_CLS_POLICE
q->rx_class = NULL;
#endif
+ /*
+ * Filters must be destroyed first because we don't destroy the
+ * classes from root to leafs which means that filters can still
+ * be bound to classes which have been destroyed already. --TGR '04
+ */
+ for (h = 0; h < 16; h++)
+ for (cl = q->classes[h]; cl; cl = cl->next)
+ cbq_destroy_filters(cl);
for (h = 0; h < 16; h++) {
struct cbq_class *next;
next reply other threads:[~2004-10-07 17:53 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-10-07 17:53 Thomas Graf [this message]
2004-10-20 4:39 ` [PATCH 2.6] CBQ: Destroy filters before destroying classes David S. Miller
2004-10-20 6:40 ` Thomas Graf
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