线程的互斥锁和条件变量通信机制

  1 #include <stdio.h>
  2 #include <stdlib.h>
  3 #include <time.h>
  4 #include <pthread.h>
  5 
  6 #define BUFFER_SIZE 2
  7 struct prodcons
  8 {
  9     int buffer[BUFFER_SIZE];
 10     pthread_mutex_t lock;
 11     int readpos,writepos;
 12     pthread_cond_t notempty;
 13     pthread_cond_t notfull;
 14 };
 15 
 16 void init(struct prodcons *prod)
 17 {
 18     pthread_mutex_init(&prod->lock,NULL);
 19     pthread_cond_init(&prod->notempty,NULL);
 20     pthread_cond_init(&prod->notfull,NULL);
 21     prod->readpos=0;
 22     prod->writepos=0;
 23 }
 24 
 25 void put(struct prodcons *prod, int data)
 26 {
 27     pthread_mutex_lock(&prod->lock);
 28     while((prod->writepos+1)%BUFFER_SIZE==prod->readpos)
 29     {
 30         printf("producer wait for not full\n");
 31         pthread_cond_wait(&prod->notfull,&prod->lock);
 32     }
 33     prod->buffer[prod->writepos]=data;
 34     prod->writepos++;
 35     if(prod->writepos>=BUFFER_SIZE)
 36         prod->writepos=0;
 37     pthread_cond_signal(&prod->notempty);
 38     pthread_mutex_unlock(&prod->lock);
 39 }
 40 
 41 int get(struct prodcons *prod)
 42 {
 43     int data;
 44     pthread_mutex_lock(&prod->lock);
 45     while(prod->writepos==prod->readpos)
 46     {
 47         printf("consumer wait for not empty\n");
 48         pthread_cond_wait(&prod->notempty,&prod->lock);
 49     }
 50     data=prod->buffer[prod->readpos];
 51     prod->readpos++;
 52     if(prod->readpos>=BUFFER_SIZE)
 53         prod->readpos=0;
 54     pthread_cond_signal(&prod->notfull);
 55     pthread_mutex_unlock(&prod->lock);
 56     return data;
 57 }
 58 
 59 #define OVER (-1)
 60 
 61 struct prodcons buffer;
 62 
 63 void *producer(void * data)
 64 {
 65     int n;
 66     for(n=1;n<=5;n++)
 67     {
 68         printf("producer sleep 1 second...\n");
 69         sleep(1);
 70         printf("put the %d product\n",n);
 71         put(&buffer,n);
 72     }
 73     for(n=6;n<=10;n++)
 74     {
 75         printf("producer sleep 3 second...\n");
 76         sleep(3);
 77         printf("put the %d product\n",n);
 78         put(&buffer,n);
 79     }
 80     put(&buffer,OVER);
 81     printf("producer stopped\n");
 82     return NULL;
 83 }
 84 
 85 void *consumer(void *data)
 86 {
 87     int d=0;
 88     while(1)
 89     {
 90         printf("consumer sleep 2 second...\n");
 91         sleep(2);
 92         d=get(&buffer);
 93         printf("get the %d product\n",d);
 94         if(d==OVER)
 95             break;
 96     }
 97     printf("consumer stopped\n");
 98     return NULL;
 99 }
100 
101 int main(int argc, char *argv[])
102 {
103     pthread_t th_a,th_b;
104     void *retval;
105     init(&buffer);
106     pthread_create(&th_a,NULL,producer,0);
107     pthread_create(&th_b,NULL,consumer,0);
108     pthread_join(th_a,&retval);
109     pthread_join(th_b,&retval);
110     return 0;
111 }