up the lock has to be shared, so will be inside of the qdisc itself. At which point the netdev_queue lock cannot be used to hard synchronize access to the ->qdisc pointer. One operation we have to keep inside of qdisc_destroy() is the list deletion. It is the only piece of state visible after the RCU quiesce period, so we have to undo it early and under the appropriate locking. The operations in the RCU handler do not need any looking because the qdisc tree is no longer visible to anything at that point. Signed-off-by: David S. Miller â#Šø˜