Additional note for Chapter 4

[Max-Hailperin]

The notes section for Chapter 4 remarks on the lock-free example having relied upon automatic memory management. I might add more explicitly that if the garbage collector is not itself lock-free, then the data structure's lock freedom would be illusory. As a further update on the topic, I should add a citation to http://dx.doi.org/10.1145/2247684.2247685

[Max-Hailperin]

Actually, this topic is complex enough, and there are enough other relevant recent publications, that on second thought the more prudent approach is probably just to stand pat rather than to dive in further.