Implementieren einfache semaphore für den einfachen multi-threads-Programm

Bitte helfen Sie die Synchronisierung
Ich habe, um dieses Programm zu zeige nacheinander Art und Weise mit
in threads( ex) thread1 zeige und Thread2 verzahnt perforem und so weiter)
Aber es sollte nur umgesetzt werden, mit Semaphore. Ich habe in den wait(), Signal()
Funktion zu handeln, wie semaphore(aber nicht arbeiten)

Brauchen Sie nur, um zu sehen, die pthread_join und thread_work Teil
(der Hauptzweck dieses Programms : machen 20threads und synchorinize Sie mit semaphore)

#include <stdio.h>
#include <pthread.h>
#include <time.h>
#include <stdlib.h>
#define num_thread 20

char str[11];
void *thread_work(void *tid);   //Main body of Thread working
void generate_str(int n);       //Create random character string
void str_sort(void);            //Sorting the generated string into alpabet manner
void check_sort(void);          //Check about "Is the sorting is right"
void print_time(struct timespec *myclock);  //print the time interval of thread work
void print_time_program(struct timespec *myclock);
void wait(void);           //I put in these two function to be act like semaphore
void Signal(void);         //But it does't work
int S=1;

int main(void)
{
  pthread_t tid[num_thread];
  int rc; 
  int t;
  struct timespec myclock[4];
  srand(time(NULL));
  clock_gettime(CLOCK_REALTIME, &myclock[2]);
  for(t=0; t<num_thread; t++)
      pthread_create(&tid[t], NULL, thread_work, (void *)&t);

  for(t=0; t<num_thread; t++)
      pthread_join(tid[t], NULL);


  clock_gettime(CLOCK_REALTIME, &myclock[3]);
  print_time_program(myclock);
  return 0;
}

void *thread_work(void *t)
{
  do
  {
      wait();           //Entry Section

      //CRITICAL SECTION START

              struct timespec myclock[2];
      clock_gettime(CLOCK_REALTIME, &myclock[0]);   
      int n = *((int *)t);
      printf("########## Thread #%d starting ########## \n", n);
      generate_str(n);
      str_sort();
      check_sort();
      printf("########## Thread #%d exiting  ##########\n", n);
      clock_gettime(CLOCK_REALTIME, &myclock[1]);
      print_time(myclock);

              //CRITICAL SECTION END

      Signal();
      pthread_exit(NULL);
  }while (1);               

}

void str_sort(void)
{
  int temp;
  int i, j;

  for(i=0; i<9; i++)
      for(j=0; j<9-i; j++)
      {
          if(str[j]>str[j+1])
          {
                  temp=str[j];
              str[j]=str[j+1];
              str[j+1]=temp;
          }
      }
  printf("Sorted string      : %s  ", str);
}

void generate_str(int n)
{
      int i;
  int num;
  srand(n);
  for(i=0; i<10; i++)
  {
      num = (97+rand()%26);
      str[i]=num;
  }

  str[10]='\0';
  printf("Initialized string : %s \n", str);
}

void check_sort(void)
{
  int i;
  int count=0;
  for(i=0; i<9; i++)
  {
      if(str[i]>str[i+1])
          count++;
  }
  if(count != 0)
      printf("[X] FALSE \n");
  else
      printf("[O] TRUE \n");
  }

void print_time(struct timespec *myclock)
{
  long delay, temp, temp_n, sec;
  sec = myclock[0].tv_sec % 60;
  printf("Thread Starting Time : %ld.%ld second\n", sec, myclock[0].tv_nsec);
  sec = myclock[1].tv_sec % 60;
  printf("Thread Exiting Time  : %ld.%ld second\n", sec, myclock[1].tv_nsec);

  if (myclock[1].tv_nsec >= myclock[0].tv_nsec) 
  { 
      temp = myclock[1].tv_sec - myclock[0].tv_sec; 
      temp_n = myclock[1].tv_nsec - myclock[0].tv_nsec; 
      delay = 1000000000 * temp + temp_n; 
  }
  else 
  { 
      temp = myclock[1].tv_sec - myclock[0].tv_sec - 1; 
      temp_n = 1000000000 + myclock[1].tv_nsec - myclock[0].tv_nsec; 
      delay = 1000000000 * temp + temp_n; 
  }  

  printf("Thread Working Time  : %ld nano second", delay);
  delay = delay / 1000000;
  printf("(%ld ms)\n\n\n", delay);
  return ;
}

void print_time_program(struct timespec *myclock)
{
  long delay, temp, temp_n, sec;
  sec = myclock[2].tv_sec % 60;
  printf("Program Starting Time : %ld.%ld second\n", sec, myclock[2].tv_nsec);
  sec = myclock[3].tv_sec % 60;
  printf("Program Exiting Time  : %ld.%ld second\n", sec, myclock[3].tv_nsec);

  if (myclock[3].tv_nsec >= myclock[2].tv_nsec) 
  { 
      temp = myclock[3].tv_sec - myclock[2].tv_sec; 
      temp_n = myclock[3].tv_nsec - myclock[2].tv_nsec; 
      delay = 1000000000 * temp + temp_n; 
  }
  else 
  { 
      temp = myclock[3].tv_sec - myclock[2].tv_sec - 1; 
      temp_n = 1000000000 + myclock[3].tv_nsec - myclock[2].tv_nsec; 
      delay = 1000000000 * temp + temp_n; 
  } 

  printf("Program Total Working Time : %ld nano second", delay);
  delay = delay / 1000000;
  printf("(%ld ms)\n\n\n", delay);
  return ;
}

void wait(void)
{
  while( S <= 0);
  S--;
}

void Signal(void)
{
  S++;
}