2.6.25-stable review patch.  If anyone has any objections, please let us
know.

------------------
From: Jarek Poplawski <jarkao2@gmail.com>
[ Upstream commit: 3ba08b00e0d8413d79be9cab8ec085ceb6ae6fd6 ]

There is lack of removing a class from the event queue while changing
from parent to leaf which can cause corruption of this rb tree. This
patch fixes a bug introduced by my patch: "sch_htb: turn intermediate
classes into leaves" commit: 160d5e10f87b1dc88fd9b84b31b1718e0fd76398.

Many thanks to Jan 'yanek' Bortl for finding a way to reproduce this
rare bug and narrowing the test case, which made possible proper
diagnosing.

This patch is recommended for all kernels starting from 2.6.20.

Reported-and-tested-by: Jan 'yanek' Bortl <yanek@ya.bofh.cz>
Signed-off-by: Jarek Poplawski <jarkao2@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
 net/sched/sch_htb.c |    8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)
--- a/net/sched/sch_htb.c
+++ b/net/sched/sch_htb.c
@@ -1197,12 +1197,16 @@ static inline int htb_parent_last_child(
 	return 1;
 }
 
-static void htb_parent_to_leaf(struct htb_class *cl, struct Qdisc *new_q)
+static void htb_parent_to_leaf(struct htb_sched *q, struct htb_class *cl,
+			       struct Qdisc *new_q)
 {
 	struct htb_class *parent = cl->parent;
 
 	BUG_TRAP(!cl->level && cl->un.leaf.q && !cl->prio_activity);
 
+	if (parent->cmode != HTB_CAN_SEND)
+		htb_safe_rb_erase(&parent->pq_node, q->wait_pq + parent->level);
+
 	parent->level = 0;
 	memset(&parent->un.inner, 0, sizeof(parent->un.inner));
 	INIT_LIST_HEAD(&parent->un.leaf.drop_list);
@@ -1300,7 +1304,7 @@ static int htb_delete(struct Qdisc *sch,
 		htb_deactivate(q, cl);
 
 	if (last_child)
-		htb_parent_to_leaf(cl, new_q);
+		htb_parent_to_leaf(q, cl, new_q);
 
 	if (--cl->refcnt == 0)
 		htb_destroy_class(sch, cl);
-- 
--
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原文链接: http://lkml.org/lkml/2008/5/13/385
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