copy_to_user不工作数据来自list_for_each

Question

我正在尝试基于此示例开发驱动程序：http://www.linux-mag.com/id/2739/?r=s

Linux 3.13 x86_64

如果printk显示信息，则不会发生复制。

鉴于阅读电话的快照：

/* private data */
struct _mydrv_data{
    struct list_head list; /*link list*/
    char info[10];  /* info */
};

LIST_HEAD( mydrv_list); /*list head*/

int read_proc(struct file *filp, char __user *buf,    
                size_t count, loff_t *offp)
{

off_t thischunk_len = 0;
struct _mydrv_data *p;
int ret = 0;
//traverse the list and copy info into buf

list_for_each_entry(p, &mydrv_list, list){
    ret = copy_to_user(buf, p->info, strlen(p->info));
    printk(KERN_DEBUG "ret:%d read proc %s",ret,p->info);

    thischunk_len += strlen(p->info);
    buf += thischunk_len;
    if (count == 0 )
        return thischunk_len;
    count-= thischunk_len;
    }


return thischunk_len;
}

由于