// threads using condition wait and signal
//
#include <stdio.h>
#include <pthread.h>
#include <unistd.h> // for sleep()
#include <stdlib.h> // for exit()

#define EXIT(msg) { perror(msg); exit(1); }

#define Pthread_create(a,b,c,d) if( pthread_create(a,b,c,d) ) EXIT("pthread_create")
#define Pthread_mutex_lock(a)   if( pthread_mutex_lock(a) )   EXIT("pthread_mutex_lock")
#define Pthread_mutex_unlock(a) if( pthread_mutex_unlock(a) ) EXIT("pthread_mutex_unlock")
#define Pthread_cond_wait(a,b)  if( pthread_cond_wait(a,b) )  EXIT("pthread_cond_wait")
#define Pthread_cond_signal(a)  if( pthread_cond_signal(a) )  EXIT("pthread_cond_signal")

#define NT 4 // number of threads

pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER;
pthread_cond_t cond = PTHREAD_COND_INITIALIZER;

int count[NT] = { 5, 4, 3, 2 };

void *f( void *v)
{
  int *p = v;

  while( *p > 0) { sleep(1); --*p; } // slowly decrement my counter

  Pthread_mutex_lock(&lock);
    Pthread_cond_signal(&cond);
  Pthread_mutex_unlock(&lock);

  return 0;
}

int main( void)
{
  pthread_t t[NT];

 // create the threads
 //
  for( int i = 0; i < NT; ++i)
    Pthread_create( &t[i], 0, f, &count[i]);

 // wait until any one thread is finished
 //
  Pthread_mutex_lock(&lock);
    Pthread_cond_wait(&cond, &lock);
  Pthread_mutex_unlock(&lock);

 // stop all threads
 //
  for( int i = 0; i < NT; ++i) pthread_cancel( t[i]);
}