On Fri, Aug 22, 2008 at 01:55:13AM -0700, David Miller wrote:

quoted

quoted

We've got at least the RX and TX queues.  That makes two locks and
two lists.

RX currently doesn't add anything to the list.

That's correct, currently ingress qdiscs only support a hierarchy of
single root and that's it.

We seem to be talking about different things.

Yes the ingress hierachy has a single root, i.e., it's a tree.  But
that has nothing to do with what I was talking about.  I'm talking
about the list at dev->rx_queue.qdisc_sleeping->list which is
certainly not guaranteed to be empty.

If you look at qdisc_create you'll find that every time we create
a non-root ingress qdisc we add it to that list (we have to,
otherwise qdisc_lookup doesn't work at all for ingress qdiscs).
So when somebody on the TX side does a qdisc_lookup they may be
walking the RX list without any protection.  Similarly, if somebody
on the ingress side does qdisc_lookup they may walk the TX lists
without protection.

Cheers,
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