Linux内核第四次作业

rcu_demo.c

/**
* @Author: ChengYao
* @Created time: 2017年5月14日 下午5:08
* @Email: chengyao09@hotmail.com
* @Description: Linux内核第四次作业
* 
*/

/**
 * [thread_writer description]
 * 每0.1秒向链表插入一个节点
 * @param  d [description]
 * @return   [description]
 */

#include <linux/init.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/rculist.h>
#include <linux/delay.h>
#include <linux/rcupdate.h>
#include <linux/sched.h>
#include <linux/kthread.h>

static struct task_struct *tskwriter;
static struct task_struct *tskreader1;
static struct task_struct *tskreader2;

struct ShareData
{
	int data;
	struct list_head list;
};

// 初始化头节点
LIST_HEAD(head);

static int thread_writer(void *d)
{
	int count = 0;
	while( !kthread_should_stop() ){
		// 控制打印日志的数量
		if(count<=50){
			// 为新节点分配内存
			struct ShareData *p = kmalloc(sizeof(*p),GFP_KERNEL);
			p->data = count;
			// 调用 list_add_rcu 将新节点加入链表
			list_add_rcu(&p->list,&head);
			printk(KERN_EMERG "thread_writer: %d times\n", ++count);
		}
		// 休眠0.1秒
		msleep(100)
	}
}


/**
 * [thread_reader description]
 * 每0.1秒打印一个节点
 * @param d [description]
 */
static void thread_reader(void* d)
{
	int count = 0;
	struct ShareData *p = NULL;
	while( !kthread_should_stop() ){
		// 控制打印日志的数量
		if(count<=50){
			count++;
			// rcu_read_lock 和 rcu_read_unlock 保持临界区
			rcu_read_lock();
			// list_for_each_entry_rcu 打印每个节点
			list_for_each_entry_rcu(p, &head,list){
				if(p){
					printk(KERN_EMERG "reader%d :data=:%d\n",current->pid,p->data);
				}
			}
			rcu_read_unlock();
		}
		// 休眠0.1秒
		msleep(100)
	}
}


/**
 * [start_module description]
 * 在模块中创建一个写者线程和两个读者线程
 * 写者线程负责向链表中加入节点
 * 两个读者线程并发打印链表的所有节点
 */
static int __init start_module(void)
{
	// 创建写者线程
	tskwriter = kthread_run(thread_writer,NULL,"%s","writer");
	if (IS_ERR(tskwriter))
	{	
		printk(KERN_EMERG "create tskwriter kthread failed !\n");	
	}else{
		printk(KERN_EMERG "create tskwriter kthread ok !\n");	
	}
	// 创建第一个读者线程
	tskreader1 = kthread_run(thread_reader,NULL,"%s","reader1")
	if (IS_ERR(tskreader1))
	{	
		printk(KERN_EMERG "create tskreader1 kthread failed !\n");	
	}else{
		printk(KERN_EMERG "create tskreader1 kthread ok !\n");	
	}
	// 创建第二个读者线程 
	tskreader2 = kthread_run(thread_reader,NULL,"%s","reader2")
	if (IS_ERR(tskreader2))
	{	
		printk(KERN_EMERG "create tskreader2 kthread failed !\n");	
	}else{
		printk(KERN_EMERG "create tskreader2 kthread ok !\n");	
	}
	return 0;
}

/**
 * [end_module description]
 * 	退出模块，结束三个线程
 * @return  [description]
 */
static void __exit end_module(void)
{
	// 
	if(!IS_ERR(tskwriter)){
		kthread_stop(tskwriter);
		printk(KERN_EMERG "thread tskwriter end\n");
	}
	if(!IS_ERR(tskreader1)){
		kthread_stop(tskreader1);
		printk(KERN_EMERG "thread tskreader1 end\n");
	}
	if(!IS_ERR(tskreader2)){
		kthread_stop(tskreader2);
		printk(KERN_EMERG "thread tskreader2 end\n");
	}
}

module_init(start_module);
module_exit(end_module);