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[NET_SCHED] sch_api: fix qdisc_tree_decrease_qlen() loop 

TC_H_MAJ(parentid) for root classes is the same as for ingress, and if
ingress qdisc is created qdisc_lookup() returns its pointer (without
ingress NULL is returned). After this all qdisc_lookups give the same,
and we get endless loop. (I don't know how this could hide for so long
- it should trigger with every leaf class deleted if it's qdisc isn't
empty.)

After this fix qdisc_lookup() is omitted both for ingress and root
parents, but looking for root is only wasting a little time here...
Many thanks to Enrico Demarin for finding a test for catching this
bug, which probably bothered quite a lot of admins.
 
Reported-by: Enrico Demarin <enrico@superclick.com>,
Signed-off-by: Jarek Poplawski <jarkao2@gmail.com>
Acked-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Jarek Poplawski 2008-04-14 15:10:42 -07:00 committed by David S. Miller
parent 159d83363b
commit 066a3b5b23
1 changed files with 3 additions and 0 deletions
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3
net/sched/sch_api.c
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@ -386,6 +386,9 @@ void qdisc_tree_decrease_qlen(struct Qdisc *sch, unsigned int n)
if (n == 0)
return;
while ((parentid = sch->parent)) {
if (TC_H_MAJ(parentid) == TC_H_MAJ(TC_H_INGRESS))
return;
sch = qdisc_lookup(sch->dev, TC_H_MAJ(parentid));
if (sch == NULL) {
WARN_ON(parentid != TC_H_ROOT);