Linux多线程-条件变量

luozhengxxf

于 2023-03-28 10:46:31 发布

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分类专栏： Linux 文章标签： c++ linux

本文链接：https://blog.youkuaiyun.com/luozhengxxf/article/details/129811336

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该代码示例展示了在C++中如何使用pthread库创建多线程，并通过互斥锁（mutex）和条件变量（conditionvariable）实现线程间的同步。主线程创建20个子线程，每个线程先打印其ID，然后等待条件变量信号，接收到信号后解锁并递增全局变量g_val，最后打印新的g_val值。

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#include <iostream>
#include <unistd.h>
#include <pthread.h>

using namespace std;

int g_val = 100;

pthread_mutex_t mutex;
pthread_cond_t condition;
pthread_mutex_t c_mutex;

void* sonThreadFunc(void* param)
{
    usleep(1000);
    pthread_mutex_lock(&c_mutex);
    std::cout << pthread_self() << " " << *(int *)param << std::endl;
    pthread_cond_signal(&condition);
    pthread_mutex_unlock(&c_mutex);

    usleep(1000);
    pthread_mutex_lock(&mutex);

    ++g_val;

    std::cout << pthread_self() << " " << g_val << std::endl;
    pthread_mutex_unlock(&mutex);
    return NULL;
}

int main()
{
    pthread_mutex_init(&mutex, NULL);
    pthread_mutex_init(&c_mutex, NULL);
    pthread_cond_init(&condition, NULL);
    pthread_t tid[20];
    for(size_t i = 0; i < 20; i++)
    {
        if(pthread_create(&tid[i], NULL, sonThreadFunc, &i) != 0)
        {
            break;
        }
        pthread_mutex_lock(&c_mutex);
        pthread_cond_wait(&condition, &c_mutex);
        pthread_mutex_unlock(&c_mutex);
    }
    for(size_t i = 0; i < 20; i++)
    {
        pthread_join(tid[i], NULL);
    }
    pthread_cond_destroy(&condition);
    pthread_mutex_destroy(&mutex);
    pthread_mutex_destroy(&c_mutex);

    cout << "Hello World!" << endl;
    return 0;
}