From: Jarek Poplawski <jarkao2@gmail•com>
To: David Miller <davem@davemloft•net>
Cc: Enrico Demarin <enrico@superclick•com>,
netdev@vger•kernel.org, Patrick McHardy <kaber@trash•net>
Subject: [PATCH][NET_SCHED] sch_api: fix qdisc_tree_decrease_qlen() loop
Date: Mon, 14 Apr 2008 22:26:06 +0200 [thread overview]
Message-ID: <20080414202605.GA6164@ami.dom.local> (raw)
In-Reply-To: <20080413121031.GA5211@ami.dom.local>
On Sun, Apr 13, 2008 at 02:10:31PM +0200, Jarek Poplawski wrote:
> Enrico Demarin wrote, On 04/11/2008 08:37 PM:
...
> > I stumbled by chance in a deadlock condition using HTB and the ingress
> > scheduler at the same time.
...
> I think one of possible reasons could be a qdisc with the same
> handle and parent ids, like ingress, but I can't see how it could
> be referenced by your htb classes yet...
I think I got it! Enrico wrote to me he will not be able to test
before monday, but IMHO this fix is obvious here...
Regards,
Jarek P.
--------------->
[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>
Cc: Patrick McHardy <kaber@trash•net>
---
net/sched/sch_api.c | 3 +++
1 files changed, 3 insertions(+), 0 deletions(-)
diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index 15b91a9..c40773c 100644
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -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);
next prev parent reply other threads:[~2008-04-14 20:28 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-04-11 18:37 HTB and ingress scheduler SMP Soft Lockup in 2.6.23-2.6.25-rc8 Enrico Demarin
2008-04-13 7:51 ` Patrick McHardy
2008-04-13 19:20 ` Enrico Demarin
2008-04-14 7:14 ` Patrick McHardy
2008-04-14 7:15 ` Patrick McHardy
2008-04-14 7:20 ` Patrick McHardy
2008-04-14 7:51 ` Patrick McHardy
2008-04-13 12:10 ` Jarek Poplawski
2008-04-14 20:26 ` Jarek Poplawski [this message]
2008-04-14 20:28 ` [PATCH][NET_SCHED] sch_api: fix qdisc_tree_decrease_qlen() loop Patrick McHardy
2008-04-14 22:11 ` David Miller
2008-04-15 5:32 ` Jarek Poplawski
2008-04-15 12:37 ` Patrick McHardy
2008-04-15 13:00 ` Jarek Poplawski
2008-04-15 13:09 ` Patrick McHardy
2008-04-15 13:10 ` Patrick McHardy
2008-04-15 17:41 ` Jarek Poplawski
2008-04-15 18:25 ` Jarek Poplawski
2008-04-15 19:29 ` Jarek Poplawski
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