### Method

# GLib Cond wait_until

since: 2.32

#### Declaration

    gboolean
    g_cond_wait_until (
      GCond* cond,
      GMutex* mutex,
      gint64 end_time
    )

#### Description

Waits until either `cond` is signalled or `end_time` has passed.

As with `g_cond_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 `GCond`):

    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).

Available since: 2.32

#### Parameters

`mutex`

  Type: `GMutex`

  A `GMutex` that is currently locked.

  The data is owned by the caller of the method.

`end_time`

  Type: `gint64`

  The monotonic time to wait until.

#### Return value

Type: `gboolean`

`TRUE` on a signal, `FALSE` on a timeout.