互斥锁

使用mutex（互斥量）一般步骤
1.pthread_mutex_t mutex;创建锁
2.pthread_mutex_init：初始化
3.pthread_mutex_lock：加锁
4访问共享数据（stdout）
5.pthread_mutex_unlock：解锁
6.pthread_mutex_destroy：销毁锁

#include #include #include #include #include //pthread_mutex_t 互斥锁类型名，线程属性pthread_mutex_t mutex;//定义另一个互斥锁变量mutex，线程属性全局变量，线程属性所有线程可以共享使用void *tfn2(void *arg){ //当某个线程，线程属性不进行对共享资源进行加锁操作时，线程属性仍旧会造成抢夺资源现象	srand(time(NULL));	while(1)	{ 		int ret=pthread_mutex_trylock(&mutex);		if(ret!=0)		{ 			printf("pthread_mutx_trylock err:%s\n",线程属性strerror(ret));		}		else		{ 			printf("---tfn2()---print ");			sleep(rand() % 3);			printf("to stdout\n");			sleep(rand() % 3);			ret=pthread_mutex_unlock(&mutex);//解锁				if(ret!=0)			{ 					fprintf(stderr,"pthread_mutex_unlock() error:%s\n",strerror(ret));			}		}			printf("common tfn2()------\n");			sleep(rand() % 3);	}}void *tfn(void *arg){ 	srand(time(NULL));	while (1) 	{ 			int ret=pthread_mutex_lock(&mutex);//加锁		if(ret!=0)		{ 			fprintf(stderr,"pthread_mutex_lock() error:%s\n",strerror(ret));		}		printf("hello ");		sleep(rand() % 3);		printf("world\n");		//pthread_mutex_unlock(),对加锁成功的共享资源进行解锁		ret=pthread_mutex_unlock(&mutex);//解锁			if(ret!=0)		{ 			fprintf(stderr,"pthread_mutex_unlock() error:%s\n",strerror(ret));		}		sleep(rand() % 3);	}	return NULL;}int main(void){ 	pthread_t tid;	srand(time(NULL));	//pthread_mutex_init（）初始化 互斥锁	int ret=pthread_mutex_init(&mutex,NULL);//初始化锁	if(ret!=0)	{ 		fprintf(stderr,"mutex init error:%s\n",strerror(ret));	}	//pthread_create() 创建线程1		ret=pthread_create(&tid, NULL, tfn, NULL);	if(ret!=0)	{ 		fprintf(stderr,"pthread_create error:%s\n",strerror(ret));	}	//pthread_create() 创建线程2	ret=pthread_create(&tid, NULL, tfn2, NULL);	if(ret!=0)	{ 		fprintf(stderr,"pthread_create error:%s\n",strerror(ret));	}	while (1) 	{ 	//pthread_mutex_lock()给已初始化过的互斥锁变量，(站在当前线程角度)对共享资源进行加锁操作		//如果加锁失败，线程属性则阻塞，线程属性也就是线程属性一直等待		ret=pthread_mutex_lock(&mutex);//加锁		if(ret!=0)		{ 			fprintf(stderr,"pthread_mutex_lock() error:%s\n",strerror(ret));		}		printf("HELLO ");		sleep(rand() % 3);		printf("WORLD\n");		//pthread_mutex_unlock(),对加锁成功的共享资源进行解锁		ret=pthread_mutex_unlock(&mutex);//解锁			if(ret!=0)		{ 			fprintf(stderr,"pthread_mutex_unlock() error:%s\n",strerror(ret));		}		sleep(rand() % 3);	}	pthread_join(tid, NULL);	ret=pthread_mutex_destroy(&mutex);//销毁锁	if(ret!=0)	{ 		fprintf(stderr,"pthread_mutex_destroy() error:%s\n",strerror(ret));	}	return 0;}

读写锁

特别强调，读写锁只有一把，线程属性但具备两种状态：
1读模式下加锁状态（读锁）
2.写模式下加锁状态（写锁）

特征：
1.读写锁是线程属性“写模式加锁”成功时，其它线程加锁都会被阻塞
2.读写锁“读模式加锁”成功时，线程属性其他线程以写模式加锁会阻塞
3.读锁、线程属性写锁并行阻塞，线程属性写锁优先级高。线程属性读锁也叫共享

#include #include #include int counter=0;//用pthread_rwlock_t类型，定义读写锁变量rwlockpthread_rwlock_t rwlock;/* 3个线程不定时写同一全局资源，5个线程不定时读同一全局资源*/void *th_write(void *arg){ 	int t;	int i = (long int)arg;	while (1) 	{ 		pthread_rwlock_wrlock(&rwlock);//以写模式加锁		t = counter;		counter++;//		sleep(1);		printf("=====write i=%d:tid=%lu:counter=%d ++counter=%d\n", i, pthread_self(), t, counter);		pthread_rwlock_unlock(&rwlock);		sleep(1);	}	return NULL;}void *th_read(void *arg){ 	int i = (long int)arg;	while (1) 	{ 		pthread_rwlock_rdlock(&rwlock);//读线程间，读锁共享		printf("----------------------read i=%d:tid=%lu:counter=%d\n", i, pthread_self(), counter);		pthread_rwlock_unlock(&rwlock);		usleep(100000);	}	return NULL;}int main(void){ 	long int i;	pthread_t tid[8];	pthread_rwlock_init(&rwlock, NULL);		for(i=0;i<3;i++)	{ 		pthread_create(&tid[i], NULL, th_write, (void *)i); 	}		for(i=0;i<5;i++)	{ 		pthread_create(&tid[i+3], NULL, th_read, (void *)i);	}		for(i=0;i<8;i++)	{ 		pthread_join(tid[i], NULL);	}		pthread_rwlock_destroy(&rwlock);	return 0;}