线程同步
操作系统实验报告
实验目的：
1.理解和掌握Linux线程控制的系统调用命令。

2.理解和掌握Linux线程同步的系统调用命令。

实验内容：
1．Linux线程机制pthread 相关系统调用命令：
pthread_create，pthread_join，pthread_mutex_lock，
pthread_mutex_unlock，enter_region，leave_region等。

2. 多线程编程使用线程同步机制实现Dinning Philosophers算法。

实验代码：
#include<>
#include<>
#include<>
#include<>
#include<>
#define phi_num 5
#define think_time 2
#define eat_time 1
#define left (phi_id+phi_num-1)%phi_num
#define right (phi_id+1)%phi_num
enum { think , hungry , eat } phi_state[phi_num];
pthread_mutex_t mutex=PTHREAD_MUTEX_INITIALIZER;
pthread_mutex_t state[phi_num]={PTHREAD_MUTEX_INITIALIZER};
void Do_think(int phi_id){
printf(" philosopher %d is thinking now !\n",phi_id);
sleep(think_time);
}
void Do_eat(int phi_id){
printf("philosopher %d is eating now !\n",phi_id);
sleep(eat_time);
}
void check_phi_state(int phi_id){
if(phi_state[phi_id]==hungry&&phi_state[left]!=eat&&phi_state[right]!=e at){
phi_state[phi_id]=eat;
pthread_mutex_unlock(&state[phi_id]);
}
}
void Do_take_forks(int phi_id){
pthread_mutex_lock(&mutex);
phi_state[phi_id]=hungry;
check_phi_state(phi_id);
pthread_mutex_unlock(&mutex);
pthread_mutex_lock(&state[phi_id]);
}
void Do_put_forks(int phi_id){
pthread_mutex_lock(&mutex);
phi_state[phi_id]=think;
check_phi_state(left);
check_phi_state(right);
pthread_mutex_unlock(&mutex);
}
void *philosopher(void *arg){
int phi_id=*(int *)arg;
while(1){
Do_think(phi_id);
Do_take_forks(phi_id);
Do_eat(phi_id);
Do_put_forks(phi_id);
}
return NULL;
}
int main(int argc, char *argv[]){
int num;
pthread_t *phi=(pthread_t*)malloc(sizeof(pthread_t)*phi_num);
int *id=(int *)malloc(sizeof(int)*phi_num);
for(num=0;num<phi_num;num++){
id[num]=num;
pthread_create(&phi[num],NULL,philosopher,(void*)(&id[num]));
}
for(num=0;num<phi_num;num++){
pthread_join(phi[num],NULL);
}
return 0;
}
截图：。