WG21/P0868R2: Selected RCU Litmus Tests

This document provides a set of litmus tests for read-copy update (RCU) that are selected to help work out ordering constraints and requirements. All of these litmus tests illustrate patterns that a correct RCU implementation must prohibit, although a few of them are closely related to litmus tests that can be allowed. These litmus tests use a C-language syntax similar to that of the Linux kernel because we do not yet have an executable C++ memory model that includes RCU.