Merge branch 'timers-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

* 'timers-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  hrtimer: Eliminate needless reprogramming of clock events device

kernel/hrtimer.c

@@ -509,13 +509,14 @@ static inline int hrtimer_hres_active(void)
  * next event
  * Called with interrupts disabled and base->lock held
  */
-static void hrtimer_force_reprogram(struct hrtimer_cpu_base *cpu_base)
+static void
+hrtimer_force_reprogram(struct hrtimer_cpu_base *cpu_base, int skip_equal)
 {
 	int i;
 	struct hrtimer_clock_base *base = cpu_base->clock_base;
-	ktime_t expires;
+	ktime_t expires, expires_next;
 
-	cpu_base->expires_next.tv64 = KTIME_MAX;
+	expires_next.tv64 = KTIME_MAX;
 
 	for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++, base++) {
 		struct hrtimer *timer;
@@ -531,10 +532,15 @@ static void hrtimer_force_reprogram(struct hrtimer_cpu_base *cpu_base)
 		 */
 		if (expires.tv64 < 0)
 			expires.tv64 = 0;
-		if (expires.tv64 < cpu_base->expires_next.tv64)
-			cpu_base->expires_next = expires;
+		if (expires.tv64 < expires_next.tv64)
+			expires_next = expires;
 	}
 
+	if (skip_equal && expires_next.tv64 == cpu_base->expires_next.tv64)
+		return;
+
+	cpu_base->expires_next.tv64 = expires_next.tv64;
+
 	if (cpu_base->expires_next.tv64 != KTIME_MAX)
 		tick_program_event(cpu_base->expires_next, 1);
 }
@@ -617,7 +623,7 @@ static void retrigger_next_event(void *arg)
 	base->clock_base[CLOCK_REALTIME].offset =
 		timespec_to_ktime(realtime_offset);
 
-	hrtimer_force_reprogram(base);
+	hrtimer_force_reprogram(base, 0);
 	spin_unlock(&base->lock);
 }
 
@@ -730,7 +736,8 @@ static int hrtimer_switch_to_hres(void)
 static inline int hrtimer_hres_active(void) { return 0; }
 static inline int hrtimer_is_hres_enabled(void) { return 0; }
 static inline int hrtimer_switch_to_hres(void) { return 0; }
-static inline void hrtimer_force_reprogram(struct hrtimer_cpu_base *base) { }
+static inline void
+hrtimer_force_reprogram(struct hrtimer_cpu_base *base, int skip_equal) { }
 static inline int hrtimer_enqueue_reprogram(struct hrtimer *timer,
 					    struct hrtimer_clock_base *base,
 					    int wakeup)
@@ -873,19 +880,29 @@ static void __remove_hrtimer(struct hrtimer *timer,
 			     struct hrtimer_clock_base *base,
 			     unsigned long newstate, int reprogram)
 {
-	if (timer->state & HRTIMER_STATE_ENQUEUED) {
-		/*
-		 * Remove the timer from the rbtree and replace the
-		 * first entry pointer if necessary.
-		 */
-		if (base->first == &timer->node) {
-			base->first = rb_next(&timer->node);
-			/* Reprogram the clock event device. if enabled */
-			if (reprogram && hrtimer_hres_active())
-				hrtimer_force_reprogram(base->cpu_base);
+	if (!(timer->state & HRTIMER_STATE_ENQUEUED))
+		goto out;
+
+	/*
+	 * Remove the timer from the rbtree and replace the first
+	 * entry pointer if necessary.
+	 */
+	if (base->first == &timer->node) {
+		base->first = rb_next(&timer->node);
+#ifdef CONFIG_HIGH_RES_TIMERS
+		/* Reprogram the clock event device. if enabled */
+		if (reprogram && hrtimer_hres_active()) {
+			ktime_t expires;
+
+			expires = ktime_sub(hrtimer_get_expires(timer),
+					    base->offset);
+			if (base->cpu_base->expires_next.tv64 == expires.tv64)
+				hrtimer_force_reprogram(base->cpu_base, 1);
 		}
-		rb_erase(&timer->node, &base->active);
+#endif
 	}
+	rb_erase(&timer->node, &base->active);
+out:
 	timer->state = newstate;
 }