10.3.1.4 Summary of RCU Fundamentals
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10.3.1.4 Summary of RCU Fundamentals

This section has described the three fundamental components of RCU-based algorithms:

1. a publish-subscribe mechanism for adding new data,

2. a way of waiting for pre-existing RCU readers to finish, and

3. a discipline of maintaining multiple versions to permit change without harming or unduly delaying concurrent RCU readers.

Quick Quiz 10.11: How can RCU updaters possibly delay RCU readers, given that the `rcu_read_lock()` and `rcu_read_unlock()` primitives neither spin nor block? End Quick Quiz

These three RCU components allow data to be updated in face of concurrent readers, and can be combined in different ways to implement a surprising variety of different types of RCU-based algorithms, some of which are described in the following section.