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#include<linux/init.h><br />#include<linux/module.h><br />#include<linux/sched.h><br />#include<linux/sem.h><br />MODULE_LICENSE('Dual BSD/GPL');<br />struct completion my_completion1;<br />struct completion my_completion2;//定义了两个完成量<br /><br />int thread_dirver(void *);<br />int thread_saleman(void *);<br />int thread_driver(void *p)//司机线程<br />{<br /> printk(KERN_ALERT'DRIVER:I AM WAITING FOR SALEMAN CLOSED THE DOOR\n');<br /> wait_for_completion(&my_completion1);//等待完成量completion1<br /> printk(KERN_ALERT'DRIVER:OK , LET'S GO!NOW~\n');<br /> printk(KERN_ALERT'DRIVER:ARRIVE THE STATION.STOPED CAR!\n');<br /> complete(&my_completion2);//唤醒完成量completion2<br /> return 0;<br />}<br />int thread_saleman(void *p)//售票员线程<br />{<br /> printk(KERN_ALERT'SALEMAN:THE DOOR IS CLOSED!\n');<br /> complete(&my_completion1);//唤醒完成量completion1<br /> printk(KERN_ALERT'SALEMAN:YOU CAN GO NOW！\n');<br /> wait_for_completion(&my_completion2);//等待完成量completion2<br /> printk(KERN_ALERT'SALEMAN:OK,THE DOOR BE OPENED!\n');<br /> return 0;<br />}<br />static int hello_init(void)<br />{<br /> printk(KERN_ALERT'\nHello everybody~\n');<br /> init_completion(&my_completion1);<br /> init_completion(&my_completion2);//初始化完成量<br /> kernel_thread(thread_driver,NULL,CLONE_KERNEL);<br /> kernel_thread(thread_saleman,NULL,CLONE_KERNEL);//创建了两个内核线程，<br /> return 0;<br />}<br />static void hello_exit(void)<br />{<br /> printk(KERN_ALERT'Goodbye everybody~\n');<br />}<br />module_init(hello_init);<br />module_exit(hello_exit);<br />MODULE_AUTHOR('CHEN');<br />MODULE_DESCRIPTION('A simple completion Module');<br /><br /><br />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。<br />运行结果：<br />Hello everybody~<br />DRIVER:I AM WAITING FOR SALEMAN CLOSED THE DOOR<br />SALEMAN:THE DOOR IS CLOSED!<br />SALEMAN:YOU CAN GO NOW！<br />DRIVER:OK , LET'S GO!NOW~<br />DRIVER:ARRIVE THE STATION.STOPED CAR!<br />SALEMAN:OK,THE DOOR BE OPENED!<br />Goodbye everybody~<br /><br />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？<br /> <br /> <br /> |
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