how to set CPU affinity of a particular pthread?

This is a wrapper I’ve made to make my life easier. Its effect is that the calling thread gets “stuck” to the core with id core_id:

// core_id = 0, 1, ... n-1, where n is the system's number of cores

int stick_this_thread_to_core(int core_id) {
   int num_cores = sysconf(_SC_NPROCESSORS_ONLN);
   if (core_id < 0 || core_id >= num_cores)
      return EINVAL;

   cpu_set_t cpuset;
   CPU_ZERO(&cpuset);
   CPU_SET(core_id, &cpuset);

   pthread_t current_thread = pthread_self();    
   return pthread_setaffinity_np(current_thread, sizeof(cpu_set_t), &cpuset);
}