生产者-消费者改进版(pthread)

经测试貌似没有问题！下一步，“线程池”....

/*
  * produce_consumer.c
  *
  *  Created on: Oct 24, 2012
  *      Author: hl
  */
 #include <stdio.h>
 #include <stdlib.h>
 #include <pthread.h>
 #include <string.h>
 #include <unistd.h>

 //消息头
 struct msg
 {
     int num;
     struct msg * next;
 };
 struct msg * head;

 pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;    /// < 互斥锁
 pthread_cond_t cond = PTHREAD_COND_INITIALIZER;        /// < 唤醒机制

 /**
  * @brief 消费者
  * @param 修改:
  *         - 打算从尾部消费（否则较早生产的总是消费不到，过期了！）
  */
 void * consumer(void * pVoid)
 {
     struct msg * mp;
     struct msg * mpp;
     while (1)
     {
         pthread_mutex_lock(&mutex);
         if (NULL == head)
             pthread_cond_wait(&cond, &mutex);
         mp = head;
         if (mp->next)   /// < 超过一个结点
         {
             while (mp->next)
             {
                 mpp = mp;           /// < 前一个
                 mp = mp->next;      /// < 链表最后一个
             }
             printf("Consume %d\n", mp->num);
             free(mp);
             mpp->next = mp = NULL;  /// < 必须的,且注意mpp->next！
         }
         else         /// < 只有头结点的情况
         {
             printf("Consume %d\n", mp->num);
             free(mp);
             head = mp = NULL;       /// < 必须的，且注意head！
         }
         pthread_mutex_unlock(&mutex);
         sleep(2);
     }
     return pVoid;
 }

 /**
  * @brief 生产者
  */
 void * producer(void * pVoid)
 {
     struct msg * mp;
     while (1)
     {
         mp = (struct msg *)malloc(sizeof(struct msg));
         mp->num = rand()%1000 + 1;
         printf("Produce %d\n", mp->num);
         pthread_mutex_lock(&mutex);
         mp->next = head;
         head = mp;
         pthread_mutex_unlock(&mutex);
         pthread_cond_signal(&cond);
         sleep(1);
     }
     return pVoid;
 }



 int main(void)
 {
     pthread_t pid;
     pthread_t cid;

     head = NULL;

     int err;
     err = pthread_create(&pid, NULL, producer, "producer");
     if (0 != err)
     {
         fprintf(stderr, "create thread1 failed:----!%s\n", strerror(err));
         return -1;
     }

     err = pthread_create(&cid, NULL, consumer, "consumer");
     if (0 != err)
     {
         fprintf(stderr, "create thread2 failed:----!%s\n", strerror(err));
         return -1;
     }
     pthread_join(pid, NULL);
     pthread_join(cid, NULL);

     return 0;
 }