高手进阶:Linux系统下内核定时器的用法

2008-04-02 10:39:54来源:互联网 阅读 ()

新老客户大回馈,云服务器低至5折

总的来说,timer的用法还是很简单的。主要需要定义一个timer_list变量timer、先初始化timer

init_timer(&timer);

then 对timer的相关参数赋值:

timer.function = fun;

timer.expires = jiffies TIMER_DELAY;

add_timer(&timer);

在定时器时间到的时候,会执行fun,如果继续定时,可以通过

在fun中执行

mod_timer(&timer, jiffies TIMER_DELAY);

在不需要的时候通过调用

del_timer(&timer);

删除定时器。

简单吧。这样一个简单的定时器就完成了。

呵呵。

附程序:

#include <linux/module.h>

#include <linux/types.h>

#include <linux/fs.h>

#include <linux/errno.h>

#include <linux/mm.h>

#include <linux/sched.h>

#include <linux/init.h>

#include <linux/cdev.h>

#include <asm/io.h>

#include <asm/system.h>

#include <asm/uaccess.h>

#include <linux/timer.h>

#include <asm/atomic.h>



#define SECOND_MAJOR 0



static int second_major = SECOND_MAJOR;



struct second_dev

{

struct cdev cdev;

atomic_t counter;

struct timer_list s_timer;

};



struct second_dev *second_devp;



static void second_timer_handle(unsigned long arg)

{

mod_timer(&second_devp->s_timer, jiffies   HZ);

atomic_inc(&second_devp->counter);



printk(KERN_ERR "current jiffies is %ld\n",jiffies);

}



int second_open(struct inode *inode, struct file *filp)

{

init_timer(&second_devp->s_timer);

second_devp->s_timer.function = &second_timer_handle;

second_devp->s_timer.expires = jiffies   HZ;



add_timer(&second_devp->s_timer);

atomic_set(&second_devp->counter, 0);

return 0; 

}



int second_release(struct inode *inode, struct file *filp)

{

del_timer(&second_devp->s_timer);



return 0;

}

static ssize_t second_read(struct file *filp, char __user *buf, size_t count, 

loff_t *ppos)

{

int counter;



counter = atomic_read(&second_devp->counter);

if (put_user(counter, (int *)buf))

{

return -EFAULT;

}else

{

return sizeof(unsigned int);

}



}



static const struct file_operations second_fops =

{

.owner = THIS_MODULE,

.open = second_open,

.release = second_release,

.read = second_read,

};

static void second_setup_cdev(struct second_dev *dev, int index)

{

int err, devno = MKDEV(second_major, index);

cdev_init(&dev->cdev, &second_fops);

dev->cdev.owner = THIS_MODULE;

dev->cdev.ops = &second_fops;

err = cdev_add(&dev->cdev, devno, 1);

if (err)

{

printk(KERN_NOTICE "Error %d add second%d", err, index);

}

}

int second_init(void)

{

int ret;

dev_t devno = MKDEV(second_major, 0);



if (second_major)

{

ret = register_chrdev_region(devno, 1, "second");

}else

{

ret = alloc_chrdev_region(&devno, 0, 1, "second");

second_major = MAJOR(devno);

}

if (ret < 0)

{

return ret;

}



second_devp = kmalloc(sizeof(struct second_dev), GFP_KERNEL);

if (!second_devp)

{

ret = -ENOMEM;

goto fail_malloc;

}



memset(second_devp, 0, sizeof(struct second_dev));



second_setup_cdev(second_devp, 0);



return 0;



fail_malloc:

unregister_chrdev_region(devno, 1);

}



void second_exit(void)

{

cdev_del(&second_devp->cdev);

kfree(second_devp);

unregister_chrdev_region(MKDEV(second_major, 0), 1);

}



MODULE_AUTHOR("Song Baohua");

MODULE_LICENSE("Dual BSD/GPL");



module_param(second_major, int, S_IRUGO);



module_init(second_init);

module_exit(second_exit);



附上用户端的测试程序:

#include <stdio.h>

#include <unistd.h>

#include <fcntl.h>



int main(void)

{

int fd, i;

int data;

fd = open("/dev/second",O_RDONLY);

if (fd < 0)

{

printf("open /dev/second error\n");

}

for(i = 0; i < 20; i  )

{

read(fd, &data, sizeof(data));

printf("read /dev/second is %d\n",data);

sleep(1);

}

close(fd);

}

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