#include <stdio.h> #include <pthread.h> #include <stdlib.h> #include <string.h> #include <semaphore.h> #include <sys/types.h> #include <errno.h> #include <unistd.h> #include <signal.h> #define NUM_THREADS_P 5 #define CHAIR_NUM 4 #define CHOP_NUM 5 int chairflg[CHAIR_NUM][2],dining_num = 0; sem_t chair,chopstics[CHOP_NUM],mutex,mutex1,print_mutex; pthread_t threads_p[NUM_THREADS_P]; void *philosopher_thread(void *args); int main(void) { int i; sem_init(&chair, 0, CHAIR_NUM); for(i=0; i<CHOP_NUM; i++) { sem_init(&chopstics[i], 0, 1); } sem_init(&mutex, 0, 1); sem_init(&mutex1, 0, 1); sem_init(&print_mutex, 0, 1); for(i=0; i<CHAIR_NUM; i++) chairflg[i][0] = 0; for(i=0; i<NUM_THREADS_P; i++) { pthread_create(&threads_p[i], NULL, philosopher_thread, (void *)i); } for(i=0; i<NUM_THREADS_P; i++) { pthread_join(threads_p[i], NULL); } // sem_destroy(&chair); // sem_destroy(&chopstics[CHOP_NUM]); // sem_destroy(&mutex); // sem_destroy(&mutex1); // sem_destroy(&print_mutex); return 0; } void *philosopher_thread(void *args) { while(1) { int i,j; i = (int)args; printf("philosopher %d is thinking\n",i); sleep(rand()%3); sem_wait(&chair); sem_wait(&mutex); for(j=0; j<CHAIR_NUM;j++) { if(chairflg[j][0] == 0) { chairflg[j][0] = 1; chairflg[j][1] = i; break; } } dining_num++; sem_post(&mutex); sem_wait(&chopstics[i]); printf("philosopher %d get chopstics %d\n",i,i); sem_wait(&chopstics[(i+1)%CHOP_NUM]); printf("philosopher %d get chopstics %d\n",i,(i+1)%CHOP_NUM); sleep(rand()%3); sem_wait(&print_mutex); printf("philosopher %d is dining,when he is dining,there are %d philosophers at table.\n",i,dining_num); for(j=0; j<CHAIR_NUM; j++) { if(chairflg[j][1] == i) { printf("philosopher %d in chair %d\n",i,j); } } printf("\n\n"); sem_post(&print_mutex); sleep(rand()%3); sem_post(&chopstics[i]); sem_post(&chopstics[(i+1)%CHOP_NUM]); sem_wait(&mutex1); for(j=0; j<CHAIR_NUM; j++) { if(chairflg[j][1] == i) { chairflg[j][0] = 0; break; } } dining_num--; sem_post(&mutex1); sem_post(&chair); printf("philosopher %d leaves\n",i); } }
Implementing the Philosopher's Dining Problem under Linux
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