mybooksources/Chapter03/code/rwlock3.cpp

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

int resourceID = 0;
pthread_rwlock_t myrwlock;

void* read_thread(void* param)
{	
	while (true)
	{
		//请求读锁
		pthread_rwlock_rdlock(&myrwlock);

		std::cout << "read thread ID: " << pthread_self() << ", resourceID: " << resourceID << std::endl;
				
		//使用睡眠模拟读线程读的过程消耗了很久的时间
		sleep(1);
				
		pthread_rwlock_unlock(&myrwlock);
	}
	
	return NULL;
}

void* write_thread(void* param)
{
	while (true)
	{
		//请求写锁
		pthread_rwlock_wrlock(&myrwlock);

		++resourceID;
		std::cout << "write thread ID: " << pthread_self() << ", resourceID: " << resourceID << std::endl;
						
		pthread_rwlock_unlock(&myrwlock);
		
		//放在这里增加请求读锁线程获得锁的几率
		sleep(1);
	}
	
	return NULL;
}

int main()
{
	pthread_rwlockattr_t attr;
	pthread_rwlockattr_init(&attr);
	//设置成请求写锁优先
	pthread_rwlockattr_setkind_np(&attr, PTHREAD_RWLOCK_PREFER_WRITER_NONRECURSIVE_NP);
	pthread_rwlock_init(&myrwlock, &attr);

	//创建5个请求读锁线程
	pthread_t readThreadID[5];
	for (int i = 0; i < 5; ++i)
	{
		pthread_create(&readThreadID[i], NULL, read_thread, NULL);
	}
	
	//创建一个请求写锁线程
	pthread_t writeThreadID;
	pthread_create(&writeThreadID, NULL, write_thread, NULL);

	pthread_join(writeThreadID, NULL);
	
	for (int i = 0; i < 5; ++i)
	{
		pthread_join(readThreadID[i], NULL);
	}
	
	pthread_rwlock_destroy(&myrwlock);

	return 0;
}