线程信号量同步

 

/*thread_sem.c*/
#include<stdio.h>
#include<stdlib.h>
#include<pthread.h>
#include<semaphore.h>
#define THREAD_NUMBER 3
#define REPEAT_NUMBER 3
#define DELAY_TIME_LEVELS 10.0
sem_t sem[THREAD_NUMBER];

void *thrd_func(void *arg)
{
 int thrd_num=(int)arg;
 int delay_time=0,count=0;
 /*进行P操作*/
 sem_wait(&sem[thrd_num]);
 printf("thread %d is strating\n",thrd_num);
 for(count=0;count<REPEAT_NUMBER;count++)
 {
  delay_time=(int)(rand()*DELAY_TIME_LEVELS/(RAND_MAX))+1;
  sleep(delay_time);
  printf("\tthread %d:job %d delay=%d\n",thrd_num,count,delay_time);
 }
 printf("thread %d finished\n",thrd_num);
 pthread_exit(NULL);
}

int main(void)
{
 pthread_t thread[THREAD_NUMBER];
 int no=0,res;
 void *thrd_ret;
 srand(time(NULL));

 for(no;no<THREAD_NUMBER;no++)
 {
  sem_init(&sem[no],0,0);
  res=pthread_create(&thread[no],NULL,thrd_func,(void*)no);
  if(res!=0) 
  {
   printf("create thread %d failded\n",no);
   exit(res);
  }
 }
 printf("Create threads success\nwaiting for thread to finish...\n");
 /*对线程的信号量进行V操作*/
 //sem_post(&sem[0]);
 for(no=0;no<THREAD_NUMBER;no++)
 {
  sem_post(&sem[no]);
  res=pthread_join(thread[no],&thrd_ret);
  if(!res)
  {
   printf("thread %d joined\n",no);
  }
  else
  {
   printf("thread %d failed\n",no);
  }
  
 }
 for(no=0;no<THREAD_NUMBER;no++)
 {
  /*删除信号量*/
  sem_destroy(&sem[no]);
 }
 return 0;
}