linux-kernel - [PATCH] Re: deadlocks if use htb

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Date:	Mon, 19 Jan 2009 06:57:15 +0000
From:	Jarek Poplawski <jarkao2@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	ccaputo@....net, a.p.zijlstra@...llo.nl, denys@...p.net.lb,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	slavon@...telecom.ru, tglx@...utronix.de
Subject: [PATCH] Re: deadlocks if use htb

On Sun, Jan 18, 2009 at 09:46:04PM -0800, David Miller wrote:
> From: Jarek Poplawski <jarkao2@...il.com>
> Date: Thu, 15 Jan 2009 06:53:22 +0000
> 
> > (resend testing patch #4 - for 2.6.27 or 2.6.28)
> 
> Jarek, if you deem that this is in fact what we should
> submit for -stable please give me a submission with
> a suitable commit message and signoffs, and I will queue
> it up for -stable.

It looks like this should be needed, but I think it's better to wait
2 or 3 days for "Tested-by" from Denys and/or maybe Vyacheslav yet.
(I hoped they would rather test some hrtimers patch, but it looks like
Peter was busy.)

Thanks,
Jarek P.
-----------------> (needed only for -stables: 2.6.28 and older)

pkt_sched: sch_htb: Fix deadlock in hrtimers triggered by HTB

Most probably there is a (still unproven) race in hrtimers (before
2.6.29 kernels), which causes a corruption of hrtimers rbtree. This
patch doesn't fix it, but should let HTB avoid triggering the bug.

Reported-by: Denys Fedoryschenko <denys@...p.net.lb>
Reported-by: Badalian Vyacheslav <slavon@...telecom.ru>
Reported-by: Chris Caputo <ccaputo@....net>
Signed-off-by: Jarek Poplawski <jarkao2@...il.com>
---

diff -Nurp a2.6.27.7/net/sched/sch_htb.c b2.6.27.7/net/sched/sch_htb.c
--- a2.6.27.7/net/sched/sch_htb.c	2008-12-11 08:16:16.000000000 +0000
+++ b2.6.27.7/net/sched/sch_htb.c	2008-12-15 10:44:32.000000000 +0000
@@ -924,6 +924,7 @@ static struct sk_buff *htb_dequeue(struc
 		}
 	}
 	sch->qstats.overlimits++;
+	qdisc_watchdog_cancel(&q->watchdog);
 	qdisc_watchdog_schedule(&q->watchdog, next_event);
 fin:
 	return skb;
--
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