epoll实现原理 赏析

从一个例子入手：

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/sysfs.h>
#include <linux/string.h>
#include <linux/stat.h>

/**
    每一个kobject都有一个release函数，当kobject的引用计数为0的时候，这个函数会自动被调用
*/
void lee_type_release(struct kobject * kobj)
{
    printk("leesagacious has calling---\n");
}

ssize_t lee_type_sysfs_ops_show(struct kobject * kobj,struct attribute * attr,char * buf)
{
    printk("attribute_name = %s \n",attr->name);
    sprintf(buf,"%s\n",attr->name);

    return strlen(attr->name) + 2;
}

ssize_t lee_type_sysfs_ops_store(struct kobject *kobj,struct attribute * attr,const char * buf,size_t count )
{
    printk("%s \n",buf);
    strcpy(attr->name,buf);

    return count;
}

struct attribute leeone = {
    .name = "leeone",
    .mode = S_IRWXUGO,
};

struct attribute leetwo = {
    .name = "leetwo", 
    .mode = S_IRWXUGO,
};

struct attribute * lee_attrs[] = {
    &leeone,
    &leetwo,
    NULL,
};

struct sysfs_ops lee_type_sysfs_ops = {
    .show = lee_type_sysfs_ops_show,
    .store = lee_type_sysfs_ops_store,
};

static struct kobj_type lee_type = {
    .release = lee_type_release,
    .sysfs_ops = &lee_type_sysfs_ops,
    .default_attrs = lee_attrs,
};


struct kobject mykobj;

static int __init lee_init(void)
{
    kobject_init_and_add(&mykobj,&lee_type,NULL,"mykobj");

    return 0;   
}
static void __exit lee_exit(void)
{
    /**
    kobject_del(&mykobj)
    {
        if (!kobj)
        {
            return;
        }
        从sysfs中移除该kobject
        sysfs_remove_dir(kobj);
        设置该kobject不在sysfs中
        kobj->state_in_sysfs = 0;
        从kset维护的kobject链表 上删除
        kobj_kset_leave(kobj);
        减少kobject的引用计数
        kobject_put(kobj->parent);
        父kobject设置为null
        kobj->parent = NULL
    }
    */
    kobject_del(&mykobj);
}
module_init(lee_init);
module_exit(lee_exit);
MODULE_LICENSE("GPL");