利用Linux下的pthread_mutex_t类型来实现哲学家进餐问题

  1 /* 说明，本程序是为了模拟实现哲学家进餐的问题，一共有6个哲学家和6根筷子
  2  */
  3 #include<stdio.h>
  4 #include<string.h>
  5 #include<stdlib.h>
  6 #include<unistd.h>
  7 #include<errno.h>
  8 #include<pthread.h>
  9 
 10 #define B_SIZE 4096
 11 #define NUM_P 6
 12 
 13 typedef struct phi
 14 {
 15    pthread_mutex_t chopsticks[NUM_P];    //五根筷子 
 16    int num;                //哲学家的编号
 17    pthread_mutex_t num_lock;        //哲学家编号的锁
 18 }Phi,*PPhi;
 19 void * tfunc(void *arg)
 20 {
 21     PPhi sp = (PPhi)arg;
 22     int phi_num;
 23     int next_num;
 24 
 25     /*读取哲学家的编号*/
 26     phi_num = sp->num;
 27     pthread_mutex_unlock(&sp->num_lock);
 28     printf("No.%d philosopher has comed\n",phi_num);
 29     /*下一根筷子*/
 30     next_num= phi_num+1>=NUM_P?phi_num+1-NUM_P:phi_num+1;
 31 
 32     sleep(5);    //所有线程统一睡眠5S，来等待其他线程创建完成
 33 
 34     if(phi_num%2 == 1)    //奇数号先拿大的，再拿小的
 35     {
 36     pthread_mutex_lock(&(sp->chopsticks[next_num]));
 37     //printf("No.%d philosopher lock the No.%d chopstick\n",phi_num,next_num);
 38     pthread_mutex_lock(&(sp->chopsticks[phi_num]));
 39     //printf("No.%d philosopher lock the No.%d chopstick\n",phi_num,phi_num);
 40 
 41     printf("No.%d philosopher has eated!\n",phi_num);
 42 
 43     pthread_mutex_unlock(&(sp->chopsticks[next_num]));
 44     //printf("No.%d philosopher unlock the No.%d chopstick\n",phi_num,next_num);
 45     pthread_mutex_unlock(&(sp->chopsticks[phi_num]));
 46     //printf("No.%d philosopher unlock the No.%d chopstick\n",phi_num,phi_num);
 47     }
 48     else        //偶数号先拿小的，再拿大的
 49     {
 50     pthread_mutex_lock(&(sp->chopsticks[phi_num]));
 51     //printf("No.%d philosopher lock the No.%d chopstick\n",phi_num,phi_num);
 52     pthread_mutex_lock(&(sp->chopsticks[next_num]));
 53     //printf("No.%d philosopher lock the No.%d chopstick\n",phi_num,next_num);
 54 
 55     printf("No.%d philosopher has eated!\n",phi_num);
 56 
 57     pthread_mutex_unlock(&(sp->chopsticks[phi_num]));
 58     //printf("No.%d philosopher unlock the No.%d chopstick\n",phi_num,phi_num);
 59     pthread_mutex_unlock(&(sp->chopsticks[next_num]));
 60     //printf("No.%d philosopher unlock the No.%d chopstick\n",phi_num,next_num);
 61     }
 62 
 63     return (void*)0;
 64 }
 65 int main(int argc,char *argv[])
 66 {
 67     int err;
 68     pthread_t tid[NUM_P];
 69     char buf_err[B_SIZE];   //用于保存错误信息
 70     void *retv;            //子线程的返回值
 71     Phi phis;
 72 
 73     for(int loop=0;loop<NUM_P;loop++)
 74     {
 75     /*设置哲学家的编号*/
 76     pthread_mutex_lock(&phis.num_lock);
 77     phis.num = loop;    
 78 
 79     /*创建子线程当作哲学家*/
 80     err = pthread_create(&tid[loop],NULL,tfunc,&phis);
 81     if(0 != err)
 82     {
 83         memset(buf_err,0,B_SIZE);
 84         sprintf(buf_err,"[create]:%s\n",strerror(err));
 85         fputs(buf_err,stderr);
 86         exit(EXIT_FAILURE);
 87     }
 88     }
 89 
 90     for(int loop=0;loop<NUM_P;loop++)
 91     {
 92     err = pthread_join(tid[loop],&retv);
 93     if(0 != err)
 94     {
 95         memset(buf_err,0,B_SIZE);
 96         sprintf(buf_err,"[join]:%s\n",strerror(err));
 97         fputs(buf_err,stderr);
 98         exit(EXIT_FAILURE);
 99     }
100     
101     printf("Main:thread return the value: %d\n",(int)retv);
102     }
103 
104     return 0;
105 }