Re: deadlocks if use htb

Peter Zijlstra
2009-01-14T14:28:36Z

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.

Hohumm..