Le lundi 04 octobre 2010 à 14:06 +0200, Jarek Poplawski a écrit :

Right, but then at least in qdisc_lookup():

if (dev_ingress_queue(dev))
	q = qdisc_match_from_root(dev_ingress_queue(dev), handle);

you should use a variable instead of the second dereference (rtnl isn't
mandatory here).

I am lost.

If rntl is not mandatory, what is the lock that protects us ?

qdisc_lookup() _is_ called under the protection of a lock.
Or as soon as we return from it, result could change under us.

Please name it, and I'll use it :

rcu_dereference_protected(dev->ingress_queue, lockdep_is_held(THISLOCK))