Linux内核同步机制completion学习（DECLARE_COMPLETION wait_for_completion complete）

我这里主要记录我实际测试效果，相关的Linux内核同步机制completion介绍可以参考下面几个帖子：

http://blog.csdn.net/bullbat/article/details/7401688

http://blog.csdn.net/liuxd3000/article/details/17912695

http://blog.csdn.net/davion_zhang/article/details/49817339

http://blog.csdn.net/jk198310/article/details/8971584

下面是我自己的学习测试驱动代码：

/*包含初始化宏定义的头文件,代码中的module_init和module_exit在此文件中*/#include <linux/init.h>/*包含初始化加载模块的头文件,代码中的MODULE_LICENSE在此头文件中*/#include <linux/module.h>/*定义module_param module_param_array的头文件*/#include <linux/moduleparam.h>/*定义module_param module_param_array中perm的头文件*/#include <linux/stat.h>/*三个字符设备函数*/#include <linux/fs.h>/*MKDEV转换设备号数据类型的宏定义*/#include <linux/kdev_t.h>/*定义字符设备的结构体*/#include <linux/cdev.h>/*分配内存空间函数头文件*/#include <linux/slab.h>/*包含函数device_create 结构体class等头文件*/#include <linux/device.h>#include <linux/completion.h>  #define DEVICE_NAME "chardevnode"#define DEVICE_MINOR_NUM 1#define DEV_MAJOR 0#define DEV_MINOR 0#define REGDEV_SIZE 3000MODULE_LICENSE("Dual BSD/GPL");/*声明是开源的，没有内核版本限制*/MODULE_AUTHOR("iTOPEET_dz");/*声明作者*/DECLARE_COMPLETION(comp);  int numdev_major = DEV_MAJOR;int numdev_minor = DEV_MINOR;/*输入主设备号*/module_param(numdev_major,int,S_IRUSR);/*输入次设备号*/module_param(numdev_minor,int,S_IRUSR);static struct class *myclass;struct reg_dev{char *data;unsigned long size;struct cdev cdev;};struct reg_dev *my_devices;/*打开操作*/static int chardevnode_open(struct inode *inode, struct file *file){printk(KERN_EMERG "weifanghai chardevnode_open is success!\n");return 0;}/*关闭操作*/static int chardevnode_release(struct inode *inode, struct file *file){printk(KERN_EMERG "weifanghai chardevnode_release is success!\n");return 0;}/*IO操作*/static long chardevnode_ioctl(struct file *file, unsigned int cmd, unsigned long arg){printk(KERN_EMERG "weifanghai chardevnode_ioctl is success! cmd is %d,arg is %d \n",cmd,arg);return 0;}ssize_t chardevnode_read(struct file *file, char __user *buf, size_t count, loff_t *f_ops){printk(KERN_ERR "weifanghai good process %i (%s) going to sleep\n",current->pid,current->comm);      wait_for_completion(&comp);      printk(KERN_ERR "weifanghai awoken %i (%s)\n",current->pid,current->comm); return 0;}ssize_t chardevnode_write(struct file *file, const char __user *buf, size_t count, loff_t *f_ops){printk(KERN_ERR "weifanghai process %i (%s) awakening the readers...\n",current->pid,current->comm);       complete(&comp);return count;  }loff_t chardevnode_llseek(struct file *file, loff_t offset, int ence){return 0;}struct file_operations my_fops = {.owner = THIS_MODULE,.open = chardevnode_open,.release = chardevnode_release,.unlocked_ioctl = chardevnode_ioctl,.read = chardevnode_read,.write = chardevnode_write,.llseek = chardevnode_llseek,};/*设备注册到系统*/static void reg_init_cdev(struct reg_dev *dev,int index){int err;int devno = MKDEV(numdev_major,numdev_minor+index);/*数据初始化*/cdev_init(&dev->cdev,&my_fops);dev->cdev.owner = THIS_MODULE;dev->cdev.ops = &my_fops;/*注册到系统*/err = cdev_add(&dev->cdev,devno,1);if(err){printk(KERN_EMERG "weifanghai cdev_add %d is fail! %d\n",index,err);}else{printk(KERN_EMERG "weifanghai cdev_add %d is success!\n",numdev_minor+index);}}static int scdev_init(void){int ret = 0,i;dev_t num_dev;printk(KERN_EMERG "weifanghai numdev_major is %d!\n",numdev_major);printk(KERN_EMERG "weifanghai numdev_minor is %d!\n",numdev_minor);if(numdev_major){num_dev = MKDEV(numdev_major,numdev_minor);ret = register_chrdev_region(num_dev,DEVICE_MINOR_NUM,DEVICE_NAME);}else{/*动态注册设备号*/ret = alloc_chrdev_region(&num_dev,numdev_minor,DEVICE_MINOR_NUM,DEVICE_NAME);/*获得主设备号*/numdev_major = MAJOR(num_dev);printk(KERN_EMERG "weifanghai adev_region req %d !\n",numdev_major);}if(ret<0){printk(KERN_EMERG "weifanghai register_chrdev_region req %d is failed!\n",numdev_major);}myclass = class_create(THIS_MODULE,DEVICE_NAME);my_devices = kmalloc(DEVICE_MINOR_NUM * sizeof(struct reg_dev),GFP_KERNEL);if(!my_devices){ret = -ENOMEM;goto fail;}memset(my_devices,0,DEVICE_MINOR_NUM * sizeof(struct reg_dev));/*设备初始化*/for(i=0;i<DEVICE_MINOR_NUM;i++){my_devices[i].data = kmalloc(REGDEV_SIZE,GFP_KERNEL);memset(my_devices[i].data,0,REGDEV_SIZE);/*设备注册到系统*/reg_init_cdev(&my_devices[i],i);/*创建设备节点*/device_create(myclass,NULL,MKDEV(numdev_major,numdev_minor+i),NULL,DEVICE_NAME"%d",i);}printk(KERN_EMERG "weifanghai scdev_init!\n");/*打印信息，KERN_EMERG表示紧急信息*/return 0;fail:/*注销设备号*/unregister_chrdev_region(MKDEV(numdev_major,numdev_minor),DEVICE_MINOR_NUM);printk(KERN_EMERG "weifanghai kmalloc is fail!\n");return ret;}static void scdev_exit(void){int i;printk(KERN_EMERG "weifanghai scdev_exit!\n");/*除去字符设备*/for(i=0;i<DEVICE_MINOR_NUM;i++){cdev_del(&(my_devices[i].cdev));/*摧毁设备节点函数d*/device_destroy(myclass,MKDEV(numdev_major,numdev_minor+i));}/*释放设备class*/class_destroy(myclass);/*释放内存*/kfree(my_devices);unregister_chrdev_region(MKDEV(numdev_major,numdev_minor),DEVICE_MINOR_NUM);}module_init(scdev_init);/*初始化函数*/module_exit(scdev_exit);/*卸载函数*/

测试结果：