Function my_pthread_once

mysys/my_winthread.c:157–193

One time initialization. For simplicity, we assume initializer thread does not exit within init_routine(). */

 does not exit within init_routine().
*/
int my_pthread_once(my_pthread_once_t *once_control, 
    void (*init_routine)(void))
{
  LONG state;

  /*
    Do "dirty" read to find out if initialization is already done, to
    save an interlocked operation in common case. Memory barriers are ensured by 
    Visual C++ volatile implementation.
  */
  if (*once_control == MY_PTHREAD_ONCE_DONE)
    return 0;

  state= InterlockedCompareExchange(once_control, MY_PTHREAD_ONCE_INPROGRESS,
                                        MY_PTHREAD_ONCE_INIT);

  switch(state)
  {
  case MY_PTHREAD_ONCE_INIT:
    /* This is initializer thread */
    (*init_routine)();
    *once_control= MY_PTHREAD_ONCE_DONE;
    break;

  case MY_PTHREAD_ONCE_INPROGRESS:
    /* init_routine in progress. Wait for its completion */
    while(*once_control == MY_PTHREAD_ONCE_INPROGRESS)
    {
      Sleep(1);
    }
    break;
  case MY_PTHREAD_ONCE_DONE:
    /* Nothing to do */
    break;
  }
  return 0;
}
#endif