发布时间 : 星期二 文章系统调用中的信号量PV操作 理发师问题更新完毕开始阅读af8f18f74693daef5ef73d2c
源程序代码
#include
#include
#define n 5 //the shop have five chairs
//design three semaphores: mutex,customer,barbers sem_t mutex,customers,barbers;
int waiting=0; //the number of waiting customers int chair[5]; void * barber();
void * customer(void *arg);
int main(int argc,char *argv[]) {
//create 10 semaphores and one Barber semaphore pthread_t Customer_id[10],Barber_id; int i;
sem_init(&mutex,0,1); //init mutex semaphore to 1 sem_init(&customers,0,0);//init semaphore customers to 0 sem_init(&barbers,0,1);
for(i=0;i<5;i++)
pthread_create(&Barber_id,NULL,(void*)barber,NULL); for (i=0;i<10;i++)
pthread_create(&Customer_id[i],NULL,(void*)customer,(void*)(i+1)); for (i=0;i<10;i++)
pthread_join(Customer_id[i],NULL); for(i=0;i<5;i++)
pthread_join(Barber_id,NULL);
return 0; }
//creat barber pthread void * barber() {
int i; int next;
//wait(customers),if no customers,barber sleeping sem_wait(&customers);
sem_wait(&mutex); //wait(mutex)
waiting--; //the numer of waiting reduce one for(i=0;i<5;i++) {
if (chair[i]!=0) {
next= chair[i]; chair[i]=0; break; } }
printf(\ sleep(3);
sem_post(&mutex); sem_post(&barbers); }
//creat customer pthread void * customer(void *arg) {
int i;
sem_wait(&mutex); //wait(mutex) if(waiting waiting++; //the numer of waiting plus one for(i=0;i<5;i++) { if (chair[i]==0) { chair[i]=(int)arg; break; } } printf(\ printf(\%d customer comes,and sits at %d chair \\n\ printf(\ printf(\ for(i=0;i<5;i++) printf(\ printf(\