wait_until

Waits until either this is signalled or end_time has passed.

As with wait it is possible that a spurious or stolen wakeup could occur. For that reason, waiting on a condition variable should always be in a loop, based on an explicitly-checked predicate.

true is returned if the condition variable was signalled (or in the case of a spurious wakeup). false is returned if end_time has passed.

The following code shows how to correctly perform a timed wait on a condition variable (extending the example presented in the documentation for Cond):

gpointer
pop_data_timed (void)
{
  gint64 end_time;
  gpointer data;

  g_mutex_lock (&data_mutex);

  end_time = g_get_monotonic_time () + 5 * G_TIME_SPAN_SECOND;
  while (!current_data)
    if (!g_cond_wait_until (&data_cond, &data_mutex, end_time))
      {
        // timeout has passed.
        g_mutex_unlock (&data_mutex);
        return NULL;
      }

  // there is data for us
  data = current_data;
  current_data = NULL;

  g_mutex_unlock (&data_mutex);

  return data;
}

Notice that the end time is calculated once, before entering the loop and reused. This is the motivation behind the use of absolute time on this API -- if a relative time of 5 seconds were passed directly to the call and a spurious wakeup occurred, the program would have to start over waiting again (which would lead to a total wait time of more than 5 seconds).

Parameters:

this	a Cond
mutex	a Mutex that is currently locked
end_time	the monotonic time to wait until

Returns:

true on a signal, false on a timeout