#include <pthread.h>

#include <stdbool.h>

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <unistd.h>

#include <atomic.h>

static pthread_cond_t cond1 = PTHREAD_COND_INITIALIZER;

static pthread_mutex_t mut1 = PTHREAD_MUTEX_INITIALIZER;

static pthread_cond_t cond2 = PTHREAD_COND_INITIALIZER;

static pthread_mutex_t mut2 = PTHREAD_MUTEX_INITIALIZER;

static bool last_round;

static int ntogo;

static bool alldone;

static void *

cons (void *arg)

{

  pthread_mutex_lock (&mut1);

  do

    {

      if (atomic_decrement_and_test (&ntogo))

	{

	  pthread_mutex_lock (&mut2);

	  alldone = true;

	  pthread_cond_signal (&cond2);

	  pthread_mutex_unlock (&mut2);

	}

      pthread_cond_wait (&cond1, &mut1);

    }

  while (! last_round);

  pthread_mutex_unlock (&mut1);

  return NULL;

}

int

main (int argc, char *argv[])

{

  int opt;

  int err;

  int nthreads = 10;

  int nrounds = 100;

  bool keeplock = false;

  while ((opt = getopt (argc, argv, "n:r:k")) != -1)

    switch (opt)

      {

      case 'n':

	nthreads = atol (optarg);

	break;

      case 'r':

	nrounds = atol (optarg);

	break;

      case 'k':

	keeplock = true;

	break;

      }

  ntogo = nthreads;

  pthread_t th[nthreads];

  int i;

  for (i = 0; __builtin_expect (i < nthreads, 1); ++i)

    if (__glibc_unlikely ((err = pthread_create (&th[i], NULL, cons, (void *) (long) i)) != 0))

      printf ("pthread_create: %s\n", strerror (err));

  for (i = 0; __builtin_expect (i < nrounds, 1); ++i)

    {

      pthread_mutex_lock (&mut2);

      while (! alldone)

	pthread_cond_wait (&cond2, &mut2);

      pthread_mutex_unlock (&mut2);

      pthread_mutex_lock (&mut1);

      if (! keeplock)

	pthread_mutex_unlock (&mut1);

      ntogo = nthreads;

      alldone = false;

      if (i + 1 >= nrounds)

	last_round = true;

      pthread_cond_broadcast (&cond1);

      if (keeplock)

	pthread_mutex_unlock (&mut1);

    }

  for (i = 0; i < nthreads; ++i)

    if ((err = pthread_join (th[i], NULL)) != 0)

      printf ("pthread_create: %s\n", strerror (err));

  return 0;

}