C++基础-死锁和解锁(g_mutex.lock(), g_mutex.unlock())

当多个函数操作同一个锁时，锁住一个变量时要尽快解锁,不要同时锁住一个相同的变量，这时就容易发生死锁的情况

//
// Created by Administrator on 2021/7/2.
//
#include<iostream>
#include<mutex>
#include<thread>

using namespace std;
//thread引用类型函数，模板，避免类型转换，尽量指针
//锁住一个变量以后，要尽快解锁，不要锁住其他变量
#define COUNT 1000000


mutex g_mutex1, g_mutex2; //互斥量

void add1(int *p1, int *p2)
{
    for(int i = 0; i < COUNT; ++i)
    {
//        g_mutex1.lock();
//        g_mutex2.unlock();
//        (*p1)++;
//        g_mutex2.unlock();
//        g_mutex1.lock();
//        (*p2)++;

        g_mutex1.lock();
        (*p1)++;
        g_mutex1.unlock();
        g_mutex2.lock();
        (*p2)++;
        g_mutex2.unlock();


    }
}

void add2(int *p1, int *p2)
{

    for(int i = 0; i < COUNT; ++i)
    {
//        g_mutex2.lock();
//        g_mutex1.unlock();
//        (*p1)++;
//        g_mutex1.unlock();
//        g_mutex2.lock();
//        (*p2)++;
        g_mutex2.lock();
        (*p2)++; //计算完解锁
        g_mutex2.unlock();
        g_mutex1.lock();
        (*p1)++;
        g_mutex1.unlock();
    }
}

int main()
{
    int a = 0;
    int b = 0;

    thread th1(add1, &a, &b);
    thread th2(add2, &a, &b);

    th1.join();
    th2.join();

    while(1)
    {
        cout << a << endl;
        cout << a << endl;
        this_thread::sleep_for(chrono::seconds(3));
    }
//    th1.join();
//    th2.join();
    cout << a << endl;
    cout << a << endl;
    cin.get();
}