#include<linux/init.h>
#include<linux/module.h>
#include<linux/sched.h>
#include<linux/sem.h>
MODULE_LICENSE('Dual BSD/GPL');
struct completion my_completion1;
struct completion my_completion2;//定义了两个完成量
int thread_dirver(void *);
int thread_saleman(void *);
int thread_driver(void *p)//司机线程
{
printk(KERN_ALERT'DRIVER:I AM WAITING FOR SALEMAN CLOSED THE DOOR\n');
wait_for_completion(&my_completion1);//等待完成量completion1
printk(KERN_ALERT'DRIVER:OK , LET'S GO!NOW~\n');
printk(KERN_ALERT'DRIVER:ARRIVE THE STATION.STOPED CAR!\n');
complete(&my_completion2);//唤醒完成量completion2
return 0;
}
int thread_saleman(void *p)//售票员线程
{
printk(KERN_ALERT'SALEMAN:THE DOOR IS CLOSED!\n');
complete(&my_completion1);//唤醒完成量completion1
printk(KERN_ALERT'SALEMAN:YOU CAN GO NOW！\n');
wait_for_completion(&my_completion2);//等待完成量completion2
printk(KERN_ALERT'SALEMAN:OK,THE DOOR BE OPENED!\n');
return 0;
}
static int hello_init(void)
{
printk(KERN_ALERT'\nHello everybody~\n');
init_completion(&my_completion1);
init_completion(&my_completion2);//初始化完成量
kernel_thread(thread_driver,NULL,CLONE_KERNEL);
kernel_thread(thread_saleman,NULL,CLONE_KERNEL);//创建了两个内核线程，
return 0;
}
static void hello_exit(void)
{
printk(KERN_ALERT'Goodbye everybody~\n');
}
module_init(hello_init);
module_exit(hello_exit);
MODULE_AUTHOR('CHEN');
MODULE_DESCRIPTION('A simple completion Module');
这个例子实现了两个线程间的同步，只有当售票员把门关了后，司机才能开动车，只有当司机停车后，售票员才能开门。所以例子中用了两个完成量来实现这个要求。
运行结果：
Hello everybody~
DRIVER:I AM WAITING FOR SALEMAN CLOSED THE DOOR
SALEMAN:THE DOOR IS CLOSED!
SALEMAN:YOU CAN GO NOW！
DRIVER:OK , LET'S GO!NOW~
DRIVER:ARRIVE THE STATION.STOPED CAR!
SALEMAN:OK,THE DOOR BE OPENED!
Goodbye everybody~
点评：完成量是对信号量的一种补充，主要用于多处理器系统上发生的一种微妙竞争。因此，大家可以思考，是否可以用信号量达到司机与售票员的同步？要真正体现完成量的功能，如何设计实例？
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