There are at least three flavors of RCU usage in the Linux kernel. The diagram
above shows the most common one. On the updater side, the rcu_assign_pointer(),
-sychronize_rcu() and call_rcu() primitives used are the same for all three
+synchronize_rcu() and call_rcu() primitives used are the same for all three
flavors. However for protection (on the reader side), the primitives used vary
depending on the flavor: