120: rcu_dereference invocation under rcu_read_lock
lockdep will complain if you access rcu_dereference() outside of an RCU read-side critical section. See lockdep.txt to learn what to do about this.
In addition, a separate kernel config parameter CONFIG_PROVE_RCU enables
checking of rcu_dereference() primitives:
Check for RCU read-side critical section.
Check for RCU-bh read-side critical section.
Check for RCU-sched read-side critical section.
Check for SRCU read-side critical section.
I think that we should also check rcu_read_lock/rcu_read_unlock pair for the absence of rcu_dereference. Such behaviour is allowed on x86 but will lead to the errors on Alpha architecture. It is an example of improper use of rcu_lock technique.