a puzzle about FreeBSD

[=?gb2312?B?ufnV8buq?=]

I am very interested in FreeBSD but it is difficult to master it. There =
is
little resource related to the most basic and fundamental problems.

I read the source code of a project. I don=A1=AFt understand SYSCTL_IN =
macro and
SYSCTL_PROC macro. I want to know when my function registered in =
SYSCTL_PROC
is called.

In addition, can you give me some advanced reference books or websites =
which
are useful?

=20

Best wishes

Jenvor