[hrtimer] Remove listhead from hrtimer struct

The list_head in the hrtimer structure was introduced for easy access
to the first timer with the further extensions of real high resolution
timers in mind, but it turned out in the course of development that
it is not necessary for the standard use case. Remove the list head
and access the first expiry timer by a datafield in the timer base.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 14 insertions, 12 deletions

diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index f073a2461fa..e6e8278bcb1 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -314,7 +314,6 @@ hrtimer_forward(struct hrtimer *timer, const ktime_t interval)
 static void enqueue_hrtimer(struct hrtimer *timer, struct hrtimer_base *base)
 {
 	struct rb_node **link = &base->active.rb_node;
-	struct list_head *prev = &base->pending;
 	struct rb_node *parent = NULL;
 	struct hrtimer *entry;
 
@@ -330,22 +329,23 @@ static void enqueue_hrtimer(struct hrtimer *timer, struct hrtimer_base *base)
 		 */
 		if (timer->expires.tv64 < entry->expires.tv64)
 			link = &(*link)->rb_left;
-		else {
+		else
 			link = &(*link)->rb_right;
-			prev = &entry->list;
-		}
 	}
 
 	/*
-	 * Insert the timer to the rbtree and to the sorted list:
+	 * Insert the timer to the rbtree and check whether it
+	 * replaces the first pending timer
 	 */
 	rb_link_node(&timer->node, parent, link);
 	rb_insert_color(&timer->node, &base->active);
-	list_add(&timer->list, prev);
 
 	timer->state = HRTIMER_PENDING;
-}
 
+	if (!base->first || timer->expires.tv64 <
+	    rb_entry(base->first, struct hrtimer, node)->expires.tv64)
+		base->first = &timer->node;
+}
 
 /*
  * __remove_hrtimer - internal function to remove a timer
@@ -355,9 +355,11 @@ static void enqueue_hrtimer(struct hrtimer *timer, struct hrtimer_base *base)
 static void __remove_hrtimer(struct hrtimer *timer, struct hrtimer_base *base)
 {
 	/*
-	 * Remove the timer from the sorted list and from the rbtree:
+	 * Remove the timer from the rbtree and replace the
+	 * first entry pointer if necessary.
 	 */
-	list_del(&timer->list);
+	if (base->first == &timer->node)
+		base->first = rb_next(&timer->node);
 	rb_erase(&timer->node, &base->active);
 }
 
@@ -529,16 +531,17 @@ int hrtimer_get_res(const clockid_t which_clock, struct timespec *tp)
 static inline void run_hrtimer_queue(struct hrtimer_base *base)
 {
 	ktime_t now = base->get_time();
+	struct rb_node *node;
 
 	spin_lock_irq(&base->lock);
 
-	while (!list_empty(&base->pending)) {
+	while ((node = base->first)) {
 		struct hrtimer *timer;
 		int (*fn)(void *);
 		int restart;
 		void *data;
 
-		timer = list_entry(base->pending.next, struct hrtimer, list);
+		timer = rb_entry(node, struct hrtimer, node);
 		if (now.tv64 <= timer->expires.tv64)
 			break;
 
@@ -732,7 +735,6 @@ static void __devinit init_hrtimers_cpu(int cpu)
 
 	for (i = 0; i < MAX_HRTIMER_BASES; i++) {
 		spin_lock_init(&base->lock);
-		INIT_LIST_HEAD(&base->pending);
 		base++;
 	}
 }