would need to be instructions following ``rcu_read_unlock()``. Although
``synchronize_rcu()`` would guarantee that execution reached the
``rcu_read_unlock()``, it would not be able to guarantee that execution
-had completely left the trampoline.
+had completely left the trampoline. Worse yet, in some situations
+the trampoline's protection must extend a few instructions *prior* to
+execution reaching the trampoline. For example, these few instructions
+might calculate the address of the trampoline, so that entering the
+trampoline would be pre-ordained a surprisingly long time before execution
+actually reached the trampoline itself.
The solution, in the form of `Tasks
RCU <https://lwn.net/Articles/607117/>`__, is to have implicit read-side