多線程出租車

有問題的實現-在出租車到達之後立馬觸發條件變量導致乘客白等

#include "pch.h"
#include<stdio.h>
#include <pthread.h>
#include <windows.h>
#include <iostream>
#pragma comment(lib, "pthreadVC2.lib")

using namespace std;

/*出租車*/
//提示出租車到達的條件變量
pthread_cond_t taxiCond = PTHREAD_COND_INITIALIZER;
//同步鎖
pthread_mutex_t taxiMutex = PTHREAD_MUTEX_INITIALIZER;


void * traveler_arrive(void * name)
{
	cout << "Traveler: " << (char *)name << " needs a taxi now!" << endl;
	pthread_mutex_lock(&taxiMutex);
	pthread_cond_wait(&taxiCond, &taxiMutex);
	pthread_mutex_unlock(&taxiMutex);
	cout << "Traveler: " << (char *)name << " now get a taxi!" << endl;
	pthread_exit(0);
	return 0;
}

void * taxi_arrive(void * name)
{
	cout << "Taxi: " << (char *)name << "arrives." << endl;
	pthread_cond_signal(&taxiCond);
	pthread_exit(0);
	return 0;
}

int main()
{
	pthread_t tids[3];
	int iRet = pthread_create(&tids[0], NULL, taxi_arrive, (void*)(" Jack "));
	if (iRet)
	{
		printf("pthread_create create error: iRet=%d\n", iRet);
		return iRet;
	}
	printf("Time passing by.\n");
	Sleep(10000);
	iRet = pthread_create(&tids[1], NULL, traveler_arrive, (void*)(" Susan "));
	if (iRet)
	{
		printf("pthread_create create error: iRet=%d\n", iRet);
		return iRet;
	}
	printf("Time passing by.\n");
	Sleep(10000);
	iRet = pthread_create(&tids[2], NULL, taxi_arrive, (void*)(" Mike "));
	if (iRet)
	{
		printf("pthread_create create error: iRet=%d\n", iRet);
		return iRet;
	}
	printf("Time passing by.\n");
	Sleep(10000);
	void *retval;
	for (int i = 0; i < 3; i++)
	{
		iRet = pthread_join(tids[i], &retval);
		if (iRet)
		{
			printf("pthread_join create error: iRet=%d\n", iRet);
			return iRet;
		}
		printf("retval=%ld\n", (long)retval);
	}
	return 0;
}

/*出租車*/

加入了一個記錄旅客數量的變量，只有當旅客數量大於0的時候，taxi到達時纔會觸發條件變量

#include "pch.h"
#include<stdio.h>
#include <pthread.h>
#include <windows.h>
#include <iostream>
#pragma comment(lib, "pthreadVC2.lib")

using namespace std;

/*出租車*/
//提示出租車到達的條件變量
pthread_cond_t taxiCond = PTHREAD_COND_INITIALIZER;
//同步鎖
pthread_mutex_t taxiMutex = PTHREAD_MUTEX_INITIALIZER;

int travelCound = 0;

void * traveler_arrive(void * name)
{
	cout << "Traveler: " << (char *)name << " needs a taxi now!" << endl;
	pthread_mutex_lock(&taxiMutex);
	travelCound++;
	pthread_cond_wait(&taxiCond, &taxiMutex);
	pthread_mutex_unlock(&taxiMutex);
	cout << "Traveler: " << (char *)name << " now get a taxi!" << endl;
	pthread_exit(0);
	return 0;
}

void * taxi_arrive(void * name)
{
	cout << "Taxi: " << (char *)name << "arrives." << endl;
	while (1)
	{
		pthread_mutex_lock(&taxiMutex);
		if (travelCound > 0)
		{
			pthread_cond_signal(&taxiCond);
			pthread_mutex_unlock(&taxiMutex);
			break;
		}			
		pthread_mutex_unlock(&taxiMutex);
	}	
	pthread_exit(0);
	return 0;
}

int main()
{
	pthread_t tids[3];
	int iRet = pthread_create(&tids[0], NULL, taxi_arrive, (void*)(" Jack "));
	if (iRet)
	{
		printf("pthread_create create error: iRet=%d\n", iRet);
		return iRet;
	}
	printf("Time passing by.\n");
	Sleep(10000);
	iRet = pthread_create(&tids[1], NULL, traveler_arrive, (void*)(" Susan "));
	if (iRet)
	{
		printf("pthread_create create error: iRet=%d\n", iRet);
		return iRet;
	}
	printf("Time passing by.\n");
	Sleep(10000);
	iRet = pthread_create(&tids[2], NULL, taxi_arrive, (void*)(" Mike "));
	if (iRet)
	{
		printf("pthread_create create error: iRet=%d\n", iRet);
		return iRet;
	}
	printf("Time passing by.\n");
	Sleep(10000);
	void *retval;
	for (int i = 0; i < 3; i++)
	{
		iRet = pthread_join(tids[i], &retval);
		if (iRet)
		{
			printf("pthread_join create error: iRet=%d\n", iRet);
			return iRet;
		}
		printf("retval=%ld\n", (long)retval);
	}
	return 0;
}

/*出租車*/