内核数据结构

linux中的队列数据结构kfifo实际上是循环队列，可以通过下面的程序来测试

#include <linux/init.h>
#include <linux/module.h>
#include <linux/proc_fs.h>
#include <linux/kfifo.h>

struct kfifo fifo;

static int main_init(void)
{
    int ret,i;
    char buf[4] = "dcba";
    char e = 'e';
    char x;

    // 初始化kfifo
    ret = kfifo_alloc(&fifo,4,GFP_KERNEL);
    if(ret)
        return ret;

    // 存满kfifo
    for(i = 0; i <4; i++){
        ret = kfifo_in(&fifo,(buf + i),1);
    }

    // 试着存进一个字符
    ret = kfifo_in(&fifo,&e,1);
    if(!ret)
        printk(KERN_INFO "ret is %d,kfifo is fulln",ret);

    // 取出一个字符
    kfifo_out(&fifo,&x,1);
    printk(KERN_INFO "x is %cn",x);

    // 再试着存进一个字符
    ret = kfifo_in(&fifo,&e,1);
    if(!ret)
        printk(KERN_INFO "ret is %d,kfifo is fulln",ret);

    // 打印出kfifo中所有字符
    for(i = 0; i < 4; i++){
    ret = kfifo_out(&fifo,&x,1);
        printk(KERN_INFO "x is %cn",x);
    }

    return 0;
}

static void main_exit(void)
{
    kfifo_free(&fifo);
}

module_init(main_init);
module_exit(main_exit);

使用dmesg | tail命令，输出是
[ 5998.534738] ret is 0,kfifo is full
[ 5998.534750] x is d
[ 5998.534753] x is c
[ 5998.534756] x is b
[ 5998.534758] x is a
[ 5998.534761] x is e