53 lines
1.2 KiB
C
53 lines
1.2 KiB
C
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/*******************************************************************
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* Copyright (C) 2022 偕臧 All rights reserved.
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*
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* Author: 偕臧 <xmulitech@gmail.com>
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* GitHub: https://github.com/xmuli
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* Blog: https://ifmet.cn
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*
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* Create: 2022.01.12
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* Modify: 2022.01.14
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* File: multithread.h
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* 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
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* 解决方法：atomic 和 mutex
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*
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******************************************************************/
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#ifndef MULTITHREAD_H
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#define MULTITHREAD_H
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#include <atomic>
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#include <mutex>
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#include <thread>
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#include <iostream>
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using namespace std;
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// 方案一：定义为原子变量 atomic
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//atomic<int> g_num = 0;
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// 方案二：加锁 mutex
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int g_num = 0;
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mutex g_mutex;
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void addition()
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{
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for (int i = 0; i < 5000; ++i) {
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g_mutex.lock(); // 尝试和下一行的 cout 行互换位置
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cout << "threadId:" << this_thread::get_id() << " g_num:" << g_num << endl;
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g_num++;
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g_mutex.unlock();
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}
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}
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使用示例
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int main()
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{
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thread th1(addition);
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thread th2(addition);
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th1.join();
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th2.join();
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cout << "g_num:" << g_num << endl;
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return 0;
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}
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#endif
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