c++多線程學習--互斥鎖的使用

mutex和lock_guard

對公共資源訪問不加鎖：

#include <iostream>
#include <thread>
#include <mutex>
using namespace std;

int g_i = 0;
mutex g_mutex;
void c()
{
	for (int i = 0; i < 20; ++i)
	{
		//g_mutex.lock();
		cout << std::this_thread::get_id() << "  " << g_i++ << endl;
		//g_mutex.unlock();
	}
}

int main()
{
	thread t1(c);
	thread t2(c);

	if (t1.joinable())
		t1.join();
	if (t2.joinable())
		t2.join();

	system("pause");
	return 0;
}

效果如下：

 

加鎖之後：

#include <iostream>
#include <thread>
#include <mutex>
using namespace std;

int g_i = 0;
mutex g_mutex;
void c()
{
	for (int i = 0; i < 20; ++i)
	{
		g_mutex.lock();
		cout << std::this_thread::get_id() << "  " << g_i++ << endl;
		g_mutex.unlock();
	}
}

int main()
{
	thread t1(c);
	thread t2(c);

	if (t1.joinable())
		t1.join();
	if (t2.joinable())
		t2.join();

	system("pause");
	return 0;
}

使用：lock_guard

#include <iostream>
#include <thread>
#include <mutex>
using namespace std;

int g_i = 0;
mutex g_mutex;
void c()
{
    for (int i = 0; i < 20; ++i)
    {
        lock_guard<mutex> lock(g_mutex);
        cout << std::this_thread::get_id() << "  " << g_i++ << endl;
    }
}

int main()
{
    thread t1(c);
    thread t2(c);

    if (t1.joinable())
        t1.join();
    if (t2.joinable())
        t2.join();

    system("pause");
    return 0;
}