说明：  针对好多 Linux爱好者对内核很有兴趣却无从下口， 本文旨在介绍一种解读linux 内核源码的入门方法，而不是解说 linux复杂的内核机制。
(against many of the core Linux enthusiasts, they are very interested in where I, the paper aims to introduce a Linux kernel source read the entry, instead of explaining the complexity of Linux kernel mechanism.)