Linux多线程实现“生产者和消费者”

生产者消费者问题描述：
   有一个有限缓冲区和两个线程：生产者和消费者。他们分别把产品放入缓冲区和从缓冲区中拿走产品。当一个生产者在缓冲区满时必须等待，当一个消费者在缓冲区空时也必须等待：
（1）信号量的考虑
   这里使用3个信号量，其中两个信号量avail和full分别用于解决生产者和消费者线程之间的同步问题，mutex是用于这两个线程之间的互斥问题。其中avail初始化N（有界缓冲区的空单元数），mutex初始化为1，full初始化为0。

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <pthread.h>
#include <errno.h>
#include <sys/ipc.h>
#include <semaphore.h>
#include <fcntl.h>
#include <string.h>
#define FIFO "myfifo"

#define N 5
int lock_var;
time_t end_time;
char buf_r[100];

sem_t mutex,full,avail;
int fd;
void pthread1(void *arg);
void pthread2(void *arg);
void productor(void *arg);
void consumer(void *arg);


int main(int argc,char *argv[])
{
  pthread_t id1,id2;
  pthread_t mon_th_id;
  int ret;

  end_time = time(NULL) + 30;
  /*创建有名管道*/
  if((mkfifo(FIFO,O_CREAT|O_EXCL)<0) && (errno!=EEXIST))
    printf("cannot create fifoserver\n");
  printf("Preparing for reading bytes...\n");
  memset(buf_r,0,sizeof(buf_r));
  /*打开管道*/
  fd = open(FIFO,O_RDWR | O_NONBLOCK,0);
  if(fd==-1)
  {
    perror("open error!\n");
    exit(1);
  }

  /*初始化互斥信号量 1*/
  ret = sem_init(&mutex,0,3);
  /*初始化avail信号量为N*/
  ret = sem_init(&avail,0,N);
  /*初始化full信号量为0*/
  ret = sem_init(&full,0,0);
  if(ret!=0)
  {
    perror("sem_init error \n");
  }
  /*创建两个线程*/
  /* ret = pthread_create(&id2,NULL,(void *)consumer,NULL);
  if(ret !=0)
  perror("pthread create 2\n");*/
  printf("mid pthread\n");
  ret = pthread_create(&id1,NULL,(void *)productor,NULL);
  if(ret!=0)
    perror("pthread create 1\n");
   ret = pthread_create(&id2,NULL,(void *)consumer,NULL);
  if(ret !=0)
  perror("pthread create 2\n");
  pthread_join(id1,NULL);
  pthread_join(id2,NULL);
  exit(0);
  
}


/*生产者线程*/
void productor(void *arg)
{
  int i,nwrite;
  while(time(NULL)<end_time)
  {
    /* P 操作信号量avail和mutex*/
    sem_wait(&avail);
    sem_wait(&mutex);
    /*生产者写入数据*/
    if((nwrite=write(fd,"hello",5))==-1)
    {
      if(errno==EAGAIN)
        printf("The FIFO has not been read yet.Please try later\n");
    }
    else
      printf("write hello to the FIFO\n");
    /*V操作信号量full和mutex*/
    sem_post(&full);
    sem_post(&mutex);
    sleep(1);
  }
}

/*消费者线程*/
void consumer(void *arg)
{
  int nolock = 0;
  int ret,nread;
  while(time(NULL)<end_time)
  {
    /*P操作信号量full和mutex*/
    sem_wait(&full);
    sem_wait(&mutex);
    memset(buf_r,0,sizeof(buf_r));
    if((nread=read(fd,buf_r,100))==1)
    {
      if(errno==EAGAIN)
        printf("no data yet\n");
    }
    printf("read %s from FIFO\n",buf_r);
    sem_post(&avail);
    sem_post(&mutex);
    sleep(1);
  }
}