feat: ExThreadSafety

ExThreadSafety/multithread.h

@@ -0,0 +1,53 @@
+/*******************************************************************
+ * 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