[PATCH 4/8] hrtimer: Optimize __hrtimer_start_range_ns()

[Peter Zijlstra <peterz@infradead.org>]

Much like hrtimer_reprogram(), skip programming is the cpu_base is
running the hrtimer interrupt.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
 kernel/time/hrtimer.c |    8 ++++++++
 1 file changed, 8 insertions(+)

--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -1261,6 +1261,14 @@ static int __hrtimer_start_range_ns(stru
 	}
 
 	first = enqueue_hrtimer(timer, new_base, mode);
+
+	/*
+	 * If the hrtimer interrupt is running, then it will reevaluate the
+	 * clock bases and reprogram the clock event device.
+	 */
+	if (new_base->cpu_base->in_hrtirq)
+		return 0;
+
 	if (!force_local) {
 		/*
 		 * If the current CPU base is online, then the timer is