rwlock.cpp

#include <errno.h>
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <bits/pthreadtypes.h>
#include <string.h>
#include <unistd.h>

static pthread_rwlock_t rwlock;//读写锁对象

#define WORK_SIZE 1024
char work_area[WORK_SIZE];
int time_to_exit;

void *thread_function_read_o(void *arg);//读线程1
void *thread_function_read_t(void *arg);//读线程2
void *thread_function_write_o(void *arg);//写线程1
void *thread_function_write_t(void *arg);//写线程2


int main(int argc,char *argv[])
{
	int res;
	pthread_t a_thread,b_thread,c_thread,d_thread;
	void *thread_result;

	res=pthread_rwlock_init(&rwlock,NULL);//初始化读写锁
	if (res != 0)
	{
		perror("rwlock initialization failed");
		exit(EXIT_FAILURE);
	}
	res = pthread_create(&a_thread, NULL, thread_function_read_o, NULL);//create new thread创建线程
	if (res != 0)
	{
		perror("Thread creation failed");
		exit(EXIT_FAILURE);
	}

	res = pthread_create(&b_thread, NULL, thread_function_read_t, NULL);//create new thread
	if (res != 0)
	{
		perror("Thread creation failed");
		exit(EXIT_FAILURE);
	}
	res = pthread_create(&c_thread, NULL, thread_function_write_o, NULL);//create new thread
	if (res != 0)
	{
		perror("Thread creation failed");
		exit(EXIT_FAILURE);
	}
	res = pthread_create(&d_thread, NULL, thread_function_write_t, NULL);//create new thread
	if (res != 0)
	{
		perror("Thread creation failed");
		exit(EXIT_FAILURE);
	}

	res = pthread_join(a_thread, &thread_result);//等待a_thread线程结束           
	if (res != 0)
	{
		perror("Thread join failed");
		exit(EXIT_FAILURE);
	}
	res = pthread_join(b_thread, &thread_result);           
	if (res != 0)
	{
		perror("Thread join failed");
		exit(EXIT_FAILURE);
	}
	res = pthread_join(c_thread, &thread_result);           
	if (res != 0)
	{
		perror("Thread join failed");
		exit(EXIT_FAILURE);
	}
	res = pthread_join(d_thread, &thread_result);           
	if (res != 0)
	{
		perror("Thread join failed");
		exit(EXIT_FAILURE);
	}

	pthread_rwlock_destroy(&rwlock);//销毁读写锁               
	exit(EXIT_SUCCESS);
}

void *thread_function_read_o(void *arg)
{
	printf("thread read one try to get lock\n");   

	pthread_rwlock_rdlock(&rwlock);//获取读取锁
	while(strncmp("end", work_area, 3) != 0)
	{
		printf("this is thread read one.");
		printf("the characters is %s",work_area);   
		pthread_rwlock_unlock(&rwlock);           
		sleep(2);
		pthread_rwlock_rdlock(&rwlock);       
		while (work_area[0] == '\0' )          
		{
			pthread_rwlock_unlock(&rwlock);   
			sleep(2);
			pthread_rwlock_rdlock(&rwlock);
		}
	}   
	pthread_rwlock_unlock(&rwlock);   
	time_to_exit=1;
	pthread_exit(0);
}

void *thread_function_read_t(void *arg)
{
	printf("thread read one try to get lock\n");
	pthread_rwlock_rdlock(&rwlock);
	while(strncmp("end", work_area, 3) != 0)
	{
		printf("this is thread read two.");
		printf("the characters is %s",work_area);   
		pthread_rwlock_unlock(&rwlock);           
		sleep(5);
		pthread_rwlock_rdlock(&rwlock);           
		while (work_area[0] == '\0' )          
		{               
			pthread_rwlock_unlock(&rwlock);   
			sleep(5);
			pthread_rwlock_rdlock(&rwlock);   
		}
	}
	pthread_rwlock_unlock(&rwlock);   
	time_to_exit=1;
	pthread_exit(0);
}

void *thread_function_write_o(void *arg)
{
	printf("this is write thread one try to get lock\n");
	while(!time_to_exit)
	{
		pthread_rwlock_wrlock(&rwlock);
		printf("this is write thread one.\nInput some text. Enter 'end' to finish\n");
		fgets(work_area, WORK_SIZE, stdin);
		pthread_rwlock_unlock(&rwlock);
		sleep(15);
	}
	pthread_rwlock_unlock(&rwlock);
	pthread_exit(0);
}

void *thread_function_write_t(void *arg)
{
	sleep(10);
	while(!time_to_exit)
	{
		pthread_rwlock_wrlock(&rwlock);//获取写入锁
		printf("this is write thread two.\nInput some text. Enter 'end' to finish\n");
		fgets(work_area, WORK_SIZE, stdin);//写入
		pthread_rwlock_unlock(&rwlock);//解锁
		sleep(20);
	}
	pthread_rwlock_unlock(&rwlock);//解锁
	pthread_exit(0);
}