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Date: Wed, 14 Jan 2009 14:39:22 +0000
From: Jarek Poplawski <jarkao2@gmail.com>
To: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Denys Fedoryschenko <denys@visp.net.lb>, Chris Caputo <ccaputo@alt.net>,
       netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
       Badalian Vyacheslav <slavon@bigtelecom.ru>,
       Thomas Gleixner <tglx@linutronix.de>
Subject: Re: deadlocks if use htb
Message-ID: <20090114143922.GB6643@ff.dom.local>
References: <20081010090426.GA6054@ff.dom.local> <200901141417.58667.denys@visp.net.lb> <1231937404.14825.4.camel@laptop> <200901141505.46929.denys@visp.net.lb> <20090114131257.GC6117@ff.dom.local> <1231938929.14825.6.camel@laptop> <20090114132603.GD6117@ff.dom.local> <1231939946.14825.9.camel@laptop> <20090114141311.GA6643@ff.dom.local> <1231943283.14825.14.camel@laptop>
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On Wed, Jan 14, 2009 at 03:28:03PM +0100, Peter Zijlstra wrote:
> On Wed, 2009-01-14 at 14:13 +0000, Jarek Poplawski wrote:
> > On Wed, Jan 14, 2009 at 02:32:26PM +0100, Peter Zijlstra wrote:
> > > On Wed, 2009-01-14 at 13:26 +0000, Jarek Poplawski wrote:
> > > 
> > > > OK, I hope Denys can apply more, but what about others? Without any
> > > > patches the hole seems to be much bigger.
> > > 
> > > OK, I read most of this thread on netdev, but didn't find a clear clue
> > > on the specific hrtimer insertion race.
> > 
> > There is something at the beginning of this thread, plus earlier
> > threads mostly with Denys as sender, and "htb bug" in the subject.
> > 
> > > 
> > > Do you have any clear ideas or should I poke at the htb/hrtimer code a
> > > little?
> > > 
> > 
> > ....And htb code is htb_dequeue(): qdisc_watchdog_schedule().
> 
> Right, found all that...
> 
> Can't spot anything obviously wrong though.. hrtimer_start*() does
> remove_hrtimer() which checks STATE_ENQUEUED, STATE_PENDING and pulls it
> off the relevant list before it continues the enqueue.
> 
> However a loop in enqueue_hrtimer() would suggest a corrupted RB-tree,
> but I cannot find an RB-op that doesn't hold base-lock.
> 

Anyway I think some trace in rbtree seemed to show the parent is the
same with the node, if I didn't mess anything.

Jarek P.
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