The Linux source code is a pain to go through. There's so much in there that you need to get someone to tell you where to look if you're ever planning to change anything. There are things to make your life easier, though. The LXR C source code to HTML converter adds cross-references and hyperlinks so you can find your way around just any piece of C source code. The folks at Promethos were nice enough to run the LXR on the Linux source code and the resulting HTML is available at: http://www.promethos.org/lxr/http/source
Unlike in real life, most of the good things in the computing world are free!