b2.c

Linux 下 system 的实验程序 5 生产 消费问题 改良

#include<stdio.h>
#include<pthread.h>
#include<signal.h>

#define N_PHILO 5
#define VOISIN_A_DROITE ((i+1)%N_PHILO)
#define VOISIN_A_GAUCHE ((i+4)%N_PHILO)

#define PENSER 0
#define DECIDER_DE_MANGER 1
#define MANGER 2

void* philosophe(void*);
void penser(int);
void prendre_baguettes(int);
void manger(int);
void poser_baguettes(int);
void test_philosophes_voisins(int);
void liberation_mutex(int);

int etat_Philo[N_PHILO];
pthread_mutex_t mutex;
pthread_cond_t cond[N_PHILO];
pthread_t pthread_id[N_PHILO];

void* philosophe(void* p){
  int i;
  i=(int)p;
  printf("Philosophe %d : Je m'assoie a la table\n",i);
  while(1){
    penser(i);
    prendre_baguettes(i);
    manger(i);
    poser_baguettes(i);
  }
}

void prendre_baguettes(int i){
  printf("Philosophe %d : Je veux manger\n",i);
  pthread_mutex_lock(&mutex);
  etat_Philo[i]=DECIDER_DE_MANGER;
  while((etat_Philo[VOISIN_A_DROITE]==MANGER)||(etat_Philo[VOISIN_A_GAUCHE]==MANGER)){
    pthread_cond_wait(cond+i,&mutex);
  }
  etat_Philo[i]=MANGER;
  pthread_mutex_unlock(&mutex);
}

/*void test_philosophes_voisins(int i){
  if((etat_Philo[i]==DECIDER_DE_MANGER)&&
     (etat_Philo[VOISIN_A_DROITE]!=MANGER)&&
     (etat_Philo[VOISIN_A_GAUCHE]!=MANGER)){
    pthread_mutex_unlock(mutex+i);
    etat_Philo[i]=MANGER;
  }
  }*/

void poser_baguettes(int i){
  pthread_mutex_lock(&mutex);
  etat_Philo[i]=PENSER;
  pthread_cond_signal(&cond[VOISIN_A_DROITE]);
  pthread_cond_signal(&cond[VOISIN_A_GAUCHE]);
  pthread_mutex_unlock(&mutex);
  printf("Philosophe %d : J'ai fini de manger\n",i);
}

void penser(int i){
  printf("Philosophe %d : Je pense\n",i);
  sleep(2);
}

void manger(int i){
  printf("Philosophe %d : Je mange\n",i);
  sleep(2);
}

void liberation_mutex(int sig){
  int i;
  for(i=0;i<N_PHILO;i++){
    pthread_cond_destroy(cond+i);
    printf("Philosophe %d : Je sort de table\n",i);
  }
  pthread_mutex_destroy(&mutex);
  exit(0);
}

int main(int argc,char **argv){
  struct sigaction action;
  int i;
  action.sa_handler=liberation_mutex;
  sigaction(SIGINT,&action,NULL);
  sigaction(SIGQUIT,&action,NULL);
  printf("Initialisation des semaphores\n");
  for(i=0;i<N_PHILO;i++){
    pthread_cond_init(cond+i,NULL);
  }
  pthread_mutex_init(&mutex,NULL);
  for(i=0;i<N_PHILO;i++){
    if(pthread_create(pthread_id+i,NULL,philosophe,(void*)i)==-1){
      fprintf(stderr,"Erreur de creation du thread %d\n",i);
      exit(-2);
    }
  }
  pthread_exit(0);
}