Re: deadlocks if use htb

Jarek Poplawski
2009-01-14T14:39:43Z

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.