本文讲解并发环境中的几个线程同步示例
线程同步，即多个线程如何协调，谁先谁后
本文基于Linux/POSIX API
本系列源码：cursorhu/SimpleMultiThread
生产者消费者模式
生产者/消费者模式是并发环境常见的模式，简单地讲，通过中介缓冲，支持多组任务并发执行，避免任务间发生通信阻塞。
参考：生产者/消费者模式的理解及实现
常用的实现方式
信号量实现
关于LInux信号量：Linux信号量
示例：
#include <pthread.h>
#include <errno.h>
#include <unistd.h>
#include <list>
#include <semaphore.h>
#include <iostream>
class Task
{
public:
Task(int taskID)
{
this->taskID = taskID;
}
void doTask()
{
std::cout << "handle a task, taskID: " << taskID << ", threadID: " << pthread_self() << std::endl;
}
private:
int taskID;
};
pthread_mutex_t mymutex;
std::list<Task*> tasks;
sem_t mysemaphore;
void* consumer_thread(void* param)
{
Task* pTask = NULL;
while (true)
{
struct timespec ts;
ts.tv_sec = 3;
ts.tv_nsec = 0;
if (sem_timewait(&mysemaphore, &ts) != 0)
{
if (errno == ETIMEOUT)
{
std::cout << "ETIMEOUT" << std::endl;
}
continue;
}
if (tasks.empty())
continue;
pthread_mutex_lock(&mymutex);
pTask = tasks.front();
tasks.pop_front();
pthread_mutex_unlock(&mymutex);
pTask->doTask();
delete pTask;
}
return NULL;
}
void* producer_thread(void* param)
{
int taskID = 0;
Task* pTask = NULL;
while (true)
{
pTask = new Task(taskID);
pthread_mutex_lock(&mymutex);
tasks.push_back(pTask);
std::cout << "produce a task, taskID: " << taskID << ", threadID: " << pthread_self() << std::endl;
pthread_mutex_unlock(&mymutex);
//释放信号量，通知消费者线程
sem_post(&mysemaphore);
taskID ++;
//休眠1秒
sleep(1);
}
return NULL;
}
int main()
{
pthread_mutex_init(&mymutex, NULL);
//初始信号量资源计数为0
sem_init(&mysemaphore, 0, 0);
//创建5个消费者线程
pthread_t consumerThreadID[5];
for (int i = 0; i < 5; ++i)
{
pthread_create(&consumerThreadID[i], NULL, consumer_thread, NULL);
}
//创建一个生产者线程
pthread_t producerThreadID;
pthread_create(&producerThreadID, NULL, producer_thread, NULL);
pthread_join(producerThreadID, NULL);
for (int i = 0; i < 5; ++i)
{
pthread_join(consumerThreadID[i], NULL);
}
sem_destroy(&mysemaphore);
pthread_mutex_destroy(&mymutex);
return 0;
}
说明几点：
