Linux内核的同步机制(完成量completion)

Linux内核的同步机制(完成量completion)

这是一个公交司机和售票员之间的线程调度，用于理解完成量，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

在这里两个线程间同步，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。

#include

#include

#include

#include

#include

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 ssize_t change_runmode(struct kobject *kobj,

struct bin_attribute *attr,

char *buf, loff_t off, size_t count)

{

char *tail;

int op;

op = simple_strtol(buf, &tail, 10);

switch(op) {

case 0:

        printk("turn off gps module/n");

        kernel_thread(thread_saleman,NULL,CLONE_KERNEL);//创建了两个内核线程，

        msleep(100); //此处最好加入一个delay，不然的话2个线程的执行顺序无法保障

kernel_thread(thread_driver,NULL,CLONE_KERNEL);

        break;

case 1:

        printk("turn on gps module/n");

break;

default:

printk(KERN_ERR " Unknown operation %d/n", op);

}

return count;

}

static struct bin_attribute ublox_mode_attr = {

.attr = {

.name = "ublox",

.owner = THIS_MODULE,

.mode = S_IRUGO | S_IWUGO,

},

.size = 4,

//.read = show_runmode,

.write = change_runmode,

};

static int hello_init(void)

{

int ret;

    printk(KERN_ALERT"Hello everybody~/n");

    init_completion(&my_completion1);

    init_completion(&my_completion2);//初始化完成量

         ret = sysfs_create_bin_file(&(module_kset->kobj), &ublox_mode_attr);

if (ret) {

printk(KERN_ERR " Failed to create sys file/n");

return -ENOMEM;

}

   // kernel_thread(thread_saleman,NULL,CLONE_KERNEL);//创建了两个内核线程，

//kernel_thread(thread_driver,NULL,CLONE_KERNEL);

    return 0;

}

static void hello_exit(void)

{

    printk(KERN_ALERT"sunqidong Goodbye everybody~/n");

    sysfs_remove_bin_file(&(module_kset->kobj), &ublox_mode_attr);

}

module_init(hello_init);

module_exit(hello_exit);

MODULE_AUTHOR("SUN");

MODULE_DESCRIPTION("A simple completion Module");

执行结果：

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~

#include
#include
#include
#include
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”);