the timers, and only then invoke rcu_barrier() to wait for any remaining
RCU callbacks to complete.
+Of course, if you module uses call_rcu_bh(), you will need to invoke
+rcu_barrier_bh() before unloading. Similarly, if your module uses
+call_rcu_sched(), you will need to invoke rcu_barrier_sched() before
+unloading. If your module uses call_rcu(), call_rcu_bh(), -and-
+call_rcu_sched(), then you will need to invoke each of rcu_barrier(),
+rcu_barrier_bh(), and rcu_barrier_sched().
+
Implementing rcu_barrier()