This book discusses its fair share of source code, and in many cases this source code may be found in the CodeSamples directory of this book's git tree. For example, on UNIX systems, you should be able to type:
find CodeSamples -name rcu_rcpls.c -printto locate the file rcu_rcpls.c, which is called out in Section
The source to this book may be found in the git archive at
git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/perfbook.git,
and git itself is available as part of most mainstream Linux
distributions.
PDFs of this book are sporadically posted at
http://kernel.org/pub/linux/kernel/people/paulmck/perfbook/perfbook.html.