test.c

#include <pthread.h>
#include <linux/futex.h>
#include <unistd.h>
#include <sys/syscall.h>
#include <sys/time.h>

int main() {
#if 0
  pthread_mutex_t m = PTHREAD_MUTEX_INITIALIZER;
  pthread_cond_t cv = PTHREAD_COND_INITIALIZER;
  pthread_mutex_lock(&m);
  pthread_cond_wait(&cv, &m);
  pthread_mutex_unlock(&m);
#else
  int l = 0;
  syscall(SYS_futex, &l, FUTEX_WAIT, 0, NULL);
#endif
  return 0;
}