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#include <stdio.h>
#include <threads.h>

enum { NTHREADS = 5 };

mtx_t mutex;
cnd_t cond;

int run_step(void *t) {
  static intsize_t current_step = 0;
  size_t my_step = *(size_t *)t;

  if (thrd_success != mtx_lock(&mutex)) {
    /* Handle error */
  }

  printf("Thread %zu has the lock\n", my_step);
  while (current_step != my_step) {
    printf("Thread %zu is sleeping...\n", my_step);

    if (thrd_success != cnd_wait(&cond, &mutex)) {
      /* Handle error */
    }

    printf("Thread %zu woke up\n", my_step);
  }
  /* Do processing ... */
  printf("Thread %zu is processing...\n", my_step);
  current_step++;

  /* Signal awaiting task */
  if (thrd_success != cnd_signal(&cond)) {
    /* Handle error */
  }

  printf("Thread %zu is exiting...\n", my_step);

  if (thrd_success != mtx_unlock(&mutex)) {
    /* Handle error */
  }
  return 0;
}
int main(void) {
  thrd_t threads[NTHREADS];
  size_t step[NTHREADS];

  if (thrd_success != mtx_init(&mutex, mtx_plain)) {
    /* Handle error */
  }

  if (thrd_success != cnd_init(&cond)) {
    /* Handle error */
  }

  /* Create threads */
  for (size_t i = 0; i < NTHREADS; ++i) {
    step[i] = i;

    if (thrd_success != thrd_create(&threads[i], run_step,
                                    &step[i])) {
      /* Handle error */
    }
  }

  /* Wait for all threads to complete */
  for (size_t i = NTHREADS; i != 0; --i) {
    if (thrd_success != thrd_join(threads[i-1], NULL)) {
      /* Handle error */
    }
  }

  mtx_destroy(&mutex);
  cnd_destroy(&cond);
  return 0;
}