On Wed, 2011-09-21 at 20:50 +0200, Peter Zijlstra wrote:

+static void wait_task_inactive_sched_out(struct preempt_notifier *n,
+               struct task_struct *next)
+{
+       struct task_struct *p;
+       struct wait_task_inactive_blocked *blocked = 
+               container_of(n, struct wait_task_inactive_blocked, notifier);
+
+       if (current->on_rq) /* we're not inactive yet */
+               return;
+
+       hlist_del(&n->link);
+
+       p = ACCESS_ONCE(blocked->waiter);
+       blocked->waiter = NULL;
+       wake_up_process(p);
+} 

Trying a wakeup from there isn't going to actually ever work of-course..
Duh!