下面是我写的一个生产者和消费者程序中的消费者部分，我是想等生产者都生产完之后消费者再根据产生的不同的随机数去随机消费生产者，而这个随机的要求是1，3，5，7，9号生产者的产品能被所有奇数号的消费者消费，2，4，6，8，10被所有的偶数号消费者消费，11-20只能被对应编号相同的消费者消费，其他不做要求。

我的错误在于，当用if语句判断一个生产者不能被该消费者消费，而重新产生一个与前面都不同的随机数，可是运行的时候，运行一段时间之后就停止不动了，求大神告知该怎么办！

void *prochase()
{
    //sleep(5);
         sem_wait(&full_sem);           //获取信号量
         pthread_mutex_lock(&mutex);    //加锁
                int n=0,l=0,p=0;
             j=(rand()%30)+1;
             if(count_rnd==0)
             {
                 a[m]=j;
                 m++;
             }
             else
             {
                 while(n<m)
                 {
                     if(a[n]!=j)
                         n++;
                     else
                     {
                         j=(rand()%30)+1;
                         n=0;
                     }
                 }
             }
             a[m]=j;
             m++;
         if(consumer_num%2!=0)          //奇数号消费者
         {
             if(consumer_num==29)   //所有奇数号消费者都消费之后，1，3，5，7，9号产品从缓冲区撤销
             {
                 buffer[0]=' ';
                 buffer[2]=' ';
                 buffer[4]=' ';
                 buffer[6]=' ';
                 buffer[8]=' ';
             }
             if(j==1||j==3||j==5||j==7||j==9)   //1，3，5，7，9号生产者供奇数号消费者消费
             {
                 printf("consumer %d consum %c of producer %d\n",consumer_num,buffer[j-1],j);
             }
             else if((j>1&&j<11&&j%2==0)||(j>10&&j<21&&consumer_num!=j))  
             {
                 printf("conusmer %d can not consum producer %d.\n",consumer_num,j);
                 j=(rand()%30)+1;
                 printf("fffffffffffffffffffff   %d\n",j);
                 while((j>1&&j<11&&j%2==0)||(j>10&&j<21&&consumer_num!=j))
                 {
                     j=(rand()%30)+1;
                 }
                 printf("hhhhhhhhhhhhhhhhhhhhhhhh   %d\n",j);
                 while(l<m)
                 {
                     if(a[l]!=j)
                         l++;
                     else
                     {
                         j=(rand()%30)+1;
                         l=0;
                     }
                 }
                 printf("aaaaaaaaaaaaaaaaaaa    %d\n",j);
                 a[m]=j;
                 m++;
                 printf("consumer %d consum %c of producer %d\n",consumer_num,buffer[j-1],j);
                 buffer[j-1]=' ';
             }
             else if(j>10&&j<21&&consumer_num==j)//11-20号生产者只供对应编号相同的消费者消费
             {
                 printf("consumer %d consum %c of producer %d\n",consumer_num,buffer[j-1],j);
                 buffer[j-1]=' ';
             }
             else   //其他任意编号的生产者被随意消费
             {
                 printf("consumer %d consum %c of producer %d\n",consumer_num,buffer[j-1],j);
                 buffer[j-1]=' ';
             }
         }
         else   //偶数号消费者
         {
             if(j==2||j==4||j==6||j==8||j==10)              //2，4，6，8，10号生产者被所有偶数号消费者消费
             {
                 printf("consumer %d consum %c of producer %d\n",consumer_num,buffer[j-1],j);
                 buffer[j-1]=' ';
             }
             else if((j>0&&j<10&&j%2!=0)||(j>10&&j<21&&consumer_num!=j))
             {
                 printf("consumer %d can not consum producer %d.\n",consumer_num,j);
                 j=(rand()%30)+1;
                 printf("kkkkkkkkkkkkkkkkkkkkkkkkk   %d\n",j);
                 while((j>0&&j<10&&j%2!=0)||(j>10&&j<21&&consumer_num!=j))
                 {
                     j=(rand()%30)+1;
                 }
                 printf("nnnnnnnnnnnnnnnnnnnnn     %d\n",j);
                 while(p<m)
                 {
                     if(a[p]!=j)
                         p++;
                     else
                     {
                         j=(rand()%30)+1;
                         p=0;
                     }
                 }
                 printf("eeeeeeeeeeeeeeeeee   %d\n",j);
                 a[m]=j;
                 m++;
                 printf("consumer %d consum %c of producer %d\n",consumer_num,buffer[j-1],j);
                 buffer[j-1]=' ';
             }
             else if(j>10&&j<21&&consumer_num==j)           //11-20编号的生产者供对应编号相同的消费者消费
             {
                 printf("consumer %d consum %c of producer %d\n",consumer_num,buffer[j-1],j);
                 buffer[j-1]=' ';
             }
             else
             {
                 printf("conusmer %d consum %c of producer %d\n",consumer_num,buffer[j-1],j);
                 buffer[j-1]=' ';
             }
         }
         print();
         out++;
         out=out%M;
         consumer_num++;
         count_rnd++;
         pthread_mutex_unlock(&mutex);
         sem_post(&empty_sem);
}

运行之后，有几个是没问题的，但是一段时间之后程序就停止不前了