unix 互斥锁与信号量应用例子

unix 互斥锁与信号量应用例子

#include #include #include #include #include #include  #define SIZE 3 #define STR_SIZE 20  pthread_mutex_t mutex; //全局变量对main 及 线程函数都可见sem_t read_sem, write_sem; //全局变量对main 及 线程函数都可见 struct _buf_ {     char* buf[SIZE];     int front, rear; }buffer; //循环队列结构体 void thread(void) {     while(1)     {         if(0 != sem_wait(&read_sem))         {             perror("sem_wait_0");             exit(1);         }              if(0 != pthread_mutex_lock(&mutex))         {             perror("pthread_mutex_lock_0");             exit(1);         }              fputs("output characters:\n",stdout);              fputs(buffer.buf[buffer.front],stdout);              buffer.front = (buffer.front + 1) % SIZE;              if(0 != pthread_mutex_unlock(&mutex))         {             perror("pthread_mutex_lock_0");             exit(1);         }         if(0 != sem_post(&write_sem))         {             perror("sem_wait_0");             exit(1);         }              sleep(10);     }      }  int main(void) {     //初始化循环队列结构体     int i;     bufferbuffer.front = buffer.rear = 0;     for(i=0; i < SIZE; i++)     {         buffer.buf[i] =(char*) malloc(STR_SIZE);     }     //初始化 互斥锁     //存在警告 pthread_mutexattr_t mutex_attr = PTHREAD_MUTEX_INITIALIZER;          if(0 != pthread_mutex_init(&mutex, NULL))     {         perror("pthread_mutex_init\n");         exit(1);     }          //初始化信号量          if(0 != sem_init(&read_sem, 0, 0))//linux进程间的信号共享还未能实现，参数PSHARE为0，而且还没有进行写操作没有数据可读，将参数vaule设置为0，进行阻塞     {         perror("sem_init_0\n");         exit(1);     }          if(0 != sem_init(&write_sem, 0, 2))     {         perror("sem_init_1\n");         exit(1);     }     //创建两个子线程     pthread_t thd0,thd1;          if(0 != pthread_create(&thd0,NULL,(void*)thread,NULL))     {         perror("pthread_create_0\n");         exit(1);     }          if(0 != pthread_create(&thd1,NULL,(void*)thread,NULL))     {         perror("pthread_create_1\n");         exit(1);     }          //进行写入字符操作     while(1)     {         //写信号量阻塞         if(0 != sem_wait(&write_sem))         {             perror("sem_wait_1");             exit(1);         }         //上互斥锁所进行写入操作         if(0 != pthread_mutex_lock(&mutex))         {             perror("pthread_mutex_lock_1");             exit(1);         }                  fputs("pls enter 20 character:\n",stdout);                  //读标准输入文件         if(NULL == fgets(buffer.buf[buffer.rear],STR_SIZE,stdin))         {             perror("fgets\n");             exit(1);         }                  if(0 == strncmp("end\n",buffer.buf[buffer.rear],3))         {             printf("manual exit successfully\n");             exit(1);         }                  buffer.rear = (buffer.rear+1)% SIZE;         //解互斥锁         if(0 != pthread_mutex_unlock(&mutex))         {             perror("pthread_mutex_lock_1");             exit(1);         }                  if(0 != sem_post(&read_sem))         {             perror("sem_wait_1");             exit(1);         }                  sleep(1);          }                return 0; }

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