FreeBSD Device Drivers

Implementing Sleeps and Condition Variables

Example 5-1 (which is based on code written by John Baldwin) is a KLD designed to demonstrate sleeps and condition variables. It works by obtaining “events” from a sysctl; each event is then passed to a thread, which performs a specific task based on the event it received.

Note

Take a quick look at this code and try to discern some of its structure. If you don’t understand all of it, don’t worry; an explanation follows.

Example 5-1. sleep.c

#define INVARIANTS #define INVARIANT_SUPPORT #include <sys/param.h> #include <sys/module.h> #include <sys/kernel.h> #include <sys/systm.h> #include <sys/kthread.h> #include <sys/proc.h> #include <sys/sched.h> #include <sys/unistd.h> #include <sys/lock.h> #include <sys/mutex.h> ...