【操作系统 实验八】----线程互斥、条件变量

• • job8/pc.c: 使用条件变量解决生产者、计算者、消费者问题
  • • 题目
    • 运行
    • 代码
    • 解BUG
    • • bug1
      • bug2
  • job8/pp.c: 使用条件变量实现 ping-pong 问题
  • • 题目
    • 运行
    • 代码

• 系统中有3个线程：生产者、计算者、消费者
• 系统中有2个容量为4的缓冲区：buffer1、buffer2
• 生产者
  • 生产’a’、‘b’、‘c’、‘d’、‘e’、‘f’、‘g’、'h’八个字符
  • 放入到buffer1
  • 打印生产的字符
• 计算者
  • 从buffer1取出字符
  • 将小写字符转换为大写字符，按照 input:OUTPUT 的格式打印
  • 放入到buffer2
• 消费者
  • 从buffer2取出字符
  • 打印取出的字符
• 程序输出结果(实际输出结果是交织的)
  a
  b
  c
  …
  a:A
  b:B
  c:C
  …
  A
  B
  C
  …

#include
#include
#include

#define CAPACITY 4
int buffer1[CAPACITY],buffer2[CAPACITY];
int in1,in2;
int out1,out2;

int buffer1_is_empty()
{
//	printf("buffer1_is_empty:in1:%d,out1:%dn",in1,out1);
	return in1 == out1;
}

int buffer1_is_full()
{
//	printf("buffer1_is_full:in1:%d,out1:%dn",in1,out1);
	return (in1 + 1) % CAPACITY == out1;
}

int get_item1()
{
	int item;
	item = buffer1[out1];
	out1 = (out1 +1) %CAPACITY;
	return item;
}
void put_item1(int item)
{
	buffer1[in1] = item;
	in1 = (in1 +1)%CAPACITY;
}


int buffer2_is_empty()
{
//	printf("buffer2_is_empty:in2:%d,out2:%dn",in2,out2);
	return in2 == out2;
}

int buffer2_is_full()
{
//	printf("buffer2_is_full:in2:%d,out2:%dn",in2,out2);
	return (in2 + 1) % CAPACITY == out2;
}

int get_item2()
{
	int item;
	item = buffer2[out2];
	out2 = (out2 +1) %CAPACITY;
	return item;
}
void put_item2(int item)
{
	buffer2[in2] = item;
	in2 = (in2 +1)%CAPACITY;
}

pthread_mutex_t mutex_pc,mutex_cc;
pthread_cond_t wait_empty_buffer1,wait_empty_buffer2;
pthread_cond_t wait_full_buffer1,wait_full_buffer2;

#define ITEM_COUNT (CAPACITY *2)

void *produce(void *arg)
{
	int i;
	int item;

	for(i=0;i < ITEM_COUNT;i++)
	{
		pthread_mutex_lock(&mutex_pc);
		while(buffer1_is_full())
		{
			pthread_cond_wait(&wait_empty_buffer1,&mutex_pc);
		}
		item = 'a' + i;
		put_item1(item);
		printf("%cn",item);

		pthread_cond_signal(&wait_full_buffer1);
		pthread_mutex_unlock(&mutex_pc);

	}
	return NULL;
	
}
//a:A
void *commpute(void *arg)
{
	int i;
	int item,ITEM;

	for(i=0;i
		pthread_mutex_lock(&mutex_pc);
		while(buffer1_is_empty())
		{
			pthread_cond_wait(&wait_full_buffer1,&mutex_pc);
		}
		item = get_item1();
		pthread_cond_signal(&wait_empty_buffer1);
		pthread_mutex_unlock(&mutex_pc);
		
		pthread_mutex_lock(&mutex_cc);
		while(buffer2_is_full())
		{
			pthread_cond_wait(&wait_empty_buffer2,&mutex_cc);
		}
		ITEM = item+'A'-'a';
		put_item2(ITEM);
		printf("t%c:%cn",item,ITEM);
		pthread_cond_signal(&wait_full_buffer2);
		pthread_mutex_unlock(&mutex_cc);
	}
	return NULL;
}

void *consume(void *arg)
{
	int i;
	int item;
	for(i = 0;i
		pthread_mutex_lock(&mutex_cc);
		while(buffer2_is_empty())
		{
			pthread_cond_wait(&wait_full_buffer2,&mutex_cc);
		}
		item = get_item2();
		printf("tt%cn",item);
		pthread_cond_signal(&wait_empty_buffer2);
		pthread_mutex_unlock(&mutex_cc);
	}
	return NULL;
}
int main()
{

	pthread_t computer_tid;
	pthread_t consumer_tid;

	pthread_mutex_init(&mutex_pc,NULL);
	pthread_mutex_init(&mutex_cc,NULL);

	pthread_cond_init(&wait_empty_buffer1,NULL);
	pthread_cond_init(&wait_full_buffer1,NULL);
	pthread_cond_init(&wait_empty_buffer2,NULL);
	pthread_cond_init(&wait_full_buffer2,NULL);


	pthread_create(&computer_tid,NULL,commpute,NULL);
	pthread_create(&consumer_tid,NULL,consume,NULL);
	
	produce(NULL);
	pthread_join(computer_tid,NULL);
	pthread_join(consumer_tid,NULL);
	
	return 0;
}

函数传参全局变量，改不了全局变量，可以直接在函数里面修改全局变量，不要传参了。多写buffer2_is_empty(),buffer2_is_full(),put_item2(),get_item2()函数。

额。。。函数调用的时候忘记加括号了，buffer_is_full ->buffer_is_full()

• 系统中有2个线程：ping 线程和 pong 线程
• ping 线程先执行
• ping 线程执行流程如下
  1. 打印输出 ping
  2. 等待 pong 线程输出
  3. 执行第 1 步
• pong 线程执行流程如下
  1. 打印输出 pong
  2. 等待 ping 线程输出
  3. 执行第 1 步
• 程序输出结果
  ping
  pong
  ping
  pong
  …

#include
#include
#include

pthread_mutex_t mutex;
pthread_cond_t wait_ping_print;
pthread_cond_t wait_pong_print;

int p = 1;
void *ping(void *arg)
{
	int i;
	for(i=0;i<10;i++)
	{
		pthread_mutex_lock(&mutex);
		while(p==0)
		{
			pthread_cond_wait(&wait_pong_print,&mutex);
		}
		p=0;
		printf("pingn");
		pthread_cond_signal(&wait_ping_print);
		pthread_mutex_unlock(&mutex);
	}
	return NULL;
}

void *pong(void *arg)
{
	int i;
	for(i=0;i<10;i++)
	{
		pthread_mutex_lock(&mutex);
		while(p==1)
		{
			pthread_cond_wait(&wait_ping_print,&mutex);
		}
		p=1;
		printf("pongn");
		pthread_cond_signal(&wait_pong_print);
		pthread_mutex_unlock(&mutex);
	}
	return NULL;
}
int main()
{
	pthread_t ping_tid;
	pthread_t pong_tid;

	pthread_mutex_init(&mutex,NULL);
	pthread_cond_init(&wait_ping_print,NULL);
	pthread_cond_init(&wait_pong_print,NULL);

	pthread_create(&ping_tid,NULL,ping,NULL);
	pthread_create(&pong_tid,NULL,pong,NULL);
	pthread_join(ping_tid,NULL);
	pthread_join(pong_tid,NULL);
	return 0;
}