The sample code for Chapters 6 and 7 are available here:

Chapter 6, Kernel Synchronization - Part 1 :
 https://github.com/PacktPublishing/Linux-Kernel-Programming/tree/master/ch12

Chapter 7, Kernel Synchronization - Part 2
 https://github.com/PacktPublishing/Linux-Kernel-Programming/tree/master/ch13
