哲学家就餐问题代码

#include  
#include  
#include  
#include  
#include  
#include  
//筷子作为mutex  
pthread_mutex_t chopstick[6] ;  
void *eat_think(void *arg)  
{  
    char phi = *(char *)arg;  
    int left,right; //左右筷子的编号  
    switch (phi){  
        case 'A':  
            left = 5;  
            right = 1;  
            break;  
        case 'B':  
            left = 1;  
            right = 2;  
            break;  
        case 'C':  
            left = 2;  
            right = 3;  
            break;  
        case 'D':  
            left = 3;  
            right = 4;  
            break;  
        case 'E':  
            left = 4;  
            right = 5;  
            break;  
    }  
 
    int i;  
    for(;;){  
        usleep(3); //思考  
        pthread_mutex_lock(&chopstick[left]); //拿起左手的筷子  
        printf("Philosopher %c fetches chopstick %d\n", phi, left);  
        if (pthread_mutex_trylock(&chopstick[right]) == EBUSY){ //拿起右手的筷子     
            pthread_mutex_unlock(&chopstick[left]); //如果右边筷子被拿走放下左手的筷子  
            continue;  
        }  
          
    //  pthread_mutex_lock(&chopstick[right]); //拿起右手的筷子，如果想观察死锁，把上一句if注释掉，再把这一句的注释去掉  
        printf("Philosopher %c fetches chopstick %d\n", phi, right);  
        printf("Philosopher %c is eating.\n",phi);  
        usleep(3); //吃饭  
        pthread_mutex_unlock(&chopstick[left]); //放下左手的筷子  
        printf("Philosopher %c release chopstick %d\n", phi, left);  
        pthread_mutex_unlock(&chopstick[right]); //放下左手的筷子  
        printf("Philosopher %c release chopstick %d\n", phi, right);  
 
    }  
}  
int main(){  
    pthread_t A,B,C,D,E; //5个哲学家  
 
    int i;  
    for (i = 0; i < 5; i++)  
        pthread_mutex_init(&chopstick[i],NULL);  
    pthread_create(&A,NULL, eat_think, "A");  
    pthread_create(&B,NULL, eat_think, "B");  
    pthread_create(&C,NULL, eat_think, "C");  
    pthread_create(&D,NULL, eat_think, "D");  
    pthread_create(&E,NULL, eat_think, "E");  
 
    pthread_join(A,NULL);  
    pthread_join(B,NULL);  
    pthread_join(C,NULL);  
    pthread_join(D,NULL);  
    pthread_join(E,NULL);  
    return 0;  
}