[RBTREE] Update hrtimers to use rb_parent() accessor macro.

Also switch it to use the same method of using off-tree nodes as
everyone else now does -- set them to point to themselves.
Signed-off-by: David Woodhouse <dwmw2@infradead.org>

include/linux/hrtimer.h

@@ -127,7 +127,7 @@ extern ktime_t hrtimer_get_next_event(void);
 
 static inline int hrtimer_active(const struct hrtimer *timer)
 {
-	return timer->node.rb_parent != HRTIMER_INACTIVE;
+	return rb_parent(&timer->node) != &timer->node;
 }
 
 /* Forward a hrtimer so it expires after now: */

kernel/hrtimer.c

@@ -393,7 +393,7 @@ static void __remove_hrtimer(struct hrtimer *timer, struct hrtimer_base *base)
 	if (base->first == &timer->node)
 		base->first = rb_next(&timer->node);
 	rb_erase(&timer->node, &base->active);
-	timer->node.rb_parent = HRTIMER_INACTIVE;
+	rb_set_parent(&timer->node, &timer->node);
 }
 
 /*
@@ -578,7 +578,7 @@ void hrtimer_init(struct hrtimer *timer, clockid_t clock_id,
 		clock_id = CLOCK_MONOTONIC;
 
 	timer->base = &bases[clock_id];
-	timer->node.rb_parent = HRTIMER_INACTIVE;
+	rb_set_parent(&timer->node, &timer->node);
 }
 
 /**