Linux设备驱动中的并发控制

This example is to introduce poll,blocking and non-blocking access

The initial developer of the original code is Baohua Song

======================================================================*/#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/slab.h>#include <linux/init.h>#include <linux/cdev.h>#include <asm/io.h>#include <asm/system.h>#include <asm/uaccess.h>#include <linux/poll.h>#include <linux/time.h>#include <linux/timer.h>#include <linux/kernel.h>#include <linux/spinlock.h>#include <linux/interrupt.h>#define GLOBALFIFO_SIZE 0x1000 /*全局fifo最大年夜4K字节*/#define FIFO_CLEAR 0x1 /*清0全局内存的长度*/#define GLOBALFIFO_MAJOR 250 /*预设的globalfifo的主设备号*/static int globalfifo_major = GLOBALFIFO_MAJOR;/*globalfifo设备构造体*/struct globalfifo_dev

{

struct cdev cdev; /*cdev构造体*/

unsigned int current_len; /*fifo有效数据长度*/

unsigned char mem[GLOBALFIFO_SIZE]; /*全局内存*/

struct semaphore sem; /*并发控制用的旌旗灯号量*/

wait_queue_head_t r_wait; /*壅塞读用的等待队列头*/

wait_queue_head_t w_wait; /*壅塞写竽暌姑的等待队列头*/

struct tasklet_struct tlet;

};struct globalfifo_dev *globalfifo_devp; /*设备构造体指针*//*文件打开函数*/int globalfifo_open(struct inode *inode, struct file *filp)

{ /*将设备构造体指针赋值给文件私稀有据指针*/

filp->private_data = globalfifo_devp; return 0;

}/*文件释放函数*/int globalfifo_release(struct inode *inode, struct file *filp)