53 lines
1.2 KiB
C++
53 lines
1.2 KiB
C++
/*******************************************************************
|
||
* Copyright (C) 2022 偕臧 All rights reserved.
|
||
*
|
||
* Author: 偕臧 <xmulitech@gmail.com>
|
||
* GitHub: https://github.com/xmuli
|
||
* Blog: https://ifmet.cn
|
||
*
|
||
* Create: 2022.01.12
|
||
* Modify: 2022.01.14
|
||
* File: multithread.h
|
||
* Description: 一个多线程竞争的例子，分析出现的“非线程安全”的具体原因，以及两个
|
||
* 解决方法：atomic 和 mutex
|
||
*
|
||
******************************************************************/
|
||
#ifndef MULTITHREAD_H
|
||
#define MULTITHREAD_H
|
||
|
||
#include <atomic>
|
||
#include <mutex>
|
||
#include <thread>
|
||
#include <iostream>
|
||
using namespace std;
|
||
|
||
// 方案一：定义为原子变量 atomic
|
||
//atomic<int> g_num = 0;
|
||
|
||
// 方案二：加锁 mutex
|
||
int g_num = 0;
|
||
mutex g_mutex;
|
||
|
||
void addition()
|
||
{
|
||
for (int i = 0; i < 5000; ++i) {
|
||
g_mutex.lock(); // 尝试和下一行的 cout 行互换位置
|
||
cout << "threadId:" << this_thread::get_id() << " g_num:" << g_num << endl;
|
||
g_num++;
|
||
g_mutex.unlock();
|
||
}
|
||
}
|
||
|
||
使用示例
|
||
int main()
|
||
{
|
||
thread th1(addition);
|
||
thread th2(addition);
|
||
th1.join();
|
||
th2.join();
|
||
|
||
cout << "g_num:" << g_num << endl;
|
||
return 0;
|
||
}
|
||
|
||
#endif |