Val's comment is directed at lock-free synchronization, which is a very different animal than lockless algorithms. The RCU implementation described in this article is lockless, but not lock-free: although RCU has deterministic read-side primitives, its updates can block via call_rcu() and synchronize_rcu(). In some cases, the fact that RCU's updates do block keeps things (relatively) simple.
We are still learning how best to use RCU to obtain good performance and scalability while keeping things (again, relatively) simple. For that matter, we are also still learning when not to use RCU. RCU is quite specialized, so is not always the right tool for the job, much though I might wish it otherwise. ;-)
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