Qt 多线程同步之互斥锁

生产者-消费者模型

1.QMutex

QMutex需要配对使用lock()和unlock()来实现代码段的保护

watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3d6ejk1MzIwMDQ2Mw_size_16_color_FFFFFF_t_70

#ifndef MYTHREAD_H
#define MYTHREAD_H
#include <QThread>
#include <QQueue>
#include <QMutex>
#include <QDebug>
static int data = 100;
static QQueue<int> que;
static QMutex mutex;
class Producer : public QThread
{
    Q_OBJECT
public:
    explicit Producer(QThread *parent)
        :QThread(parent)
    {
    }
protected:
    void run()
    {
        for(int i=0;i<data;i++) //生产者生产的快
        {
            mutex.lock();
            que.enqueue(i);
            qDebug()<<"Producer produce: "<<QString::number(i);        
            mutex.unlock();
            msleep(100);
        }
    }
};
class Customer : public QThread
{
    Q_OBJECT
public:
    explicit Customer(QThread *parent,int id)
        :QThread(parent)
        ,m_id(id)
    {
    }
protected:
    void run()
    {
        while(true)
        {
            mutex.lock();
            if(!que.isEmpty())
            {          
                int num = que.dequeue();
                qDebug()<<"Customer"<<QString::number(m_id)<<" consume:"<<QString::number(num);              
            }
            mutex.unlock();
            msleep(300);//生产者消费的慢
        }
    }
private:
    int m_id = 0;
};
#endif // MYTHREAD_H

建立3个消费者和一个生产者

#include <QCoreApplication>
#include "MyThread.h"
int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);
    Producer producer(nullptr);
    Customer customer1(nullptr,1);
    Customer customer2(nullptr,2);
    Customer customer3(nullptr,3);
    producer.start();
    customer1.start();
    customer2.start();
    customer3.start();
    return a.exec();
}

2.使用QMutexLocker

QMutexLocker是另外一个简化了互斥量处理的类。QMutexLocker构造函数接受一个互斥量作为参数并将其锁定，QMutexLocker的析构函数则将此互斥量解锁，所以在QMutexLocker实例变量的生存期内的代码段得到保护，自动进行互斥量的锁定和解锁。

#ifndef MYTHREAD_H
#define MYTHREAD_H
#include <QThread>
#include <QQueue>
#include <QMutex>
#include <QMutexLocker>
#include <QDebug>
static int data = 100;
static QQueue<int> que;
static QMutex mutex;
class Producer : public QThread
{
    Q_OBJECT
public:
    explicit Producer(QThread *parent)
        :QThread(parent)
    {
    }
protected:
    void run()
    {
        for(int i=0;i<data;i++) //生产者生产的快
        {
            {
                QMutexLocker locker(&mutex);
                que.enqueue(i);
                qDebug()<<"Producer produce: "<<QString::number(i);
            }
            msleep(100);
        }
    }
};
class Customer : public QThread
{
    Q_OBJECT
public:
    explicit Customer(QThread *parent,int id)
        :QThread(parent)
        ,m_id(id)
    {
    }
protected:
    void run()
    {
        while(true)
        {
            {
                QMutexLocker locker(&mutex);
                if(!que.isEmpty())
                {
                    int num = que.dequeue();
                    qDebug()<<"Customer"<<QString::number(m_id)<<" consume:"<<QString::number(num);
                }
            }
            msleep(300);//生产者消费的慢
        }
    }
private:
    int m_id = 0;
};
#endif // MYTHREAD_H