4.6什么情况造成死锁（第二阶段）

最新推荐文章于 2025-08-10 16:52:47 发布

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本文通过代码示例展示了死锁的情况，当两个线程分别持有不同锁并尝试获取对方持有的锁时，导致彼此等待，形成死锁状态。在C++中，线程t1和t2在互抢mutex和mutex2导致了死锁，揭示了并发编程中的同步问题。

4.6什么情况造成死锁（第二阶段）

造成死锁的原因
前提条件：要有两个锁，然后当获得一把锁A的时候想获得第二把锁B，而线程B获得线程A所获得的锁，同时也想去拿线程A的锁A，这样导致线程A和线程B都想拿到对方的锁，谁都不可能往下面继续走，所以会导致死锁

代码展示

#include <pthread.h>
#include <stdio.h>
//       int pthread_create(pthread_t *thread, const pthread_attr_t *attr,
//                          void *(*start_routine) (void *), void *arg);
//	int pthread_join(pthread_t thread, void **retval);

int g_data = 0;

pthread_mutex_t mutex;
pthread_mutex_t mutex2;


void *func1(void *arg)
{	
	int i;	

	pthread_mutex_lock(&mutex);//shangsuo	

	for(i=0;i<5;i++){
		printf("t1:%ld thread is create\n",(unsigned long)pthread_self());
		printf("t1:param is %d\n",*((int *)arg));
		sleep(1);
	}
	pthread_mutex_unlock(&mutex);
}

void *func2(void *arg)
{	
	pthread_mutex_lock(&mutex);//shangsuo 
	pthread_mutex_lock(&mutex2);//shangsuo 
	


	printf("t2:%ld thread is create\n",(unsigned long)pthread_self());
	printf("t2:param is %d\n",*((int *)arg));

	pthread_mutex_unlock(&mutex);

}

void *func3(void *arg)
{	
	pthread_mutex_lock(&mutex2);//shangsuo 
	pthread_mutex_lock(&mutex);//shangsuo 

	printf("t3:%ld thread is create\n",(unsigned long)pthread_self());
	printf("t3:param is %d\n",*((int *)arg));

	pthread_mutex_unlock(&mutex);

}

int main()
{
	int ret;
	int param = 100;
	pthread_t t1;
	pthread_t t2;
	pthread_t t3;

	//	int pthread_mutex_init(pthread_mutex_t *restrict mutex, const pthread_mutexattr_t *restrict attr);
	pthread_mutex_init(&mutex,NULL);
	pthread_mutex_init(&mutex2,NULL);

	ret = pthread_create(&t1,NULL,func1,(void *)&param);
	if(ret == 0){
		printf("main:cread t1 success\n");
	}

	ret = pthread_create(&t2,NULL,func2,(void *)&param);
	if(ret == 0){
		printf("main:cread t2 success\n");
	}

	ret = pthread_create(&t2,NULL,func3,(void *)&param);
	if(ret == 0){
		printf("main:cread t3 success\n");
	}

	printf("main:%ld\n",(unsigned long)pthread_self());
	//	while(1);
	pthread_join(t1,NULL);
	pthread_join(t2,NULL);	

	//	int pthread_mutex_destroy(pthread_mutex_t mutex);
	pthread_mutex_destroy(&mutex);
	pthread_mutex_destroy(&mutex2);

	return 0;
}