Cancelable worker thread

cancelable_worker_thread.c

#include <stdlib.h>
#include <unistd.h>
#include <stdio.h>
#include <pthread.h>
#include <sys/time.h>
#include <sys/errno.h>

struct thread_data {
  pthread_cond_t cond;
  int finished;
};

void get_relative_timespec(struct timespec *ts, int delay_sec)
{
  struct timeval now;
  gettimeofday(&now, NULL);
  ts->tv_sec = now.tv_sec + delay_sec;
  ts->tv_nsec = now.tv_usec * 1000;
}

void * threadfunc(void *arg) {
  struct thread_data *data = (thread_data *) arg;
  pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;

  do {
    pthread_mutex_lock(&mutex);
    // Perform "cancellable sleep"
    struct timespec ts;
    get_relative_timespec(&ts, 1);
    if (pthread_cond_timedwait(&data->cond, &mutex, &ts) == ETIMEDOUT) {
      printf("Doing work\n");
    } else {
      printf("Cancelled or spurious wakeup\n");
    }
    pthread_mutex_unlock(&mutex);
  } while (!data->finished);

  return NULL;
}

int main() {
  pthread_t thread;

  struct thread_data * data = (thread_data *) malloc(sizeof(thread_data));
  data->cond = PTHREAD_COND_INITIALIZER;
  data->finished = 0;
  pthread_create(&thread, nullptr, threadfunc, data);

  sleep(5);

  printf("Ending worker thread\n");
  data->finished = 1;
  pthread_cond_signal(&data->cond);
  pthread_join(thread, NULL);
  free(data);
  printf("Ended worker thread\n");

  return 0;
}