diff mbox

[RFC,4/7] sched: don't check for active hrtimer after adding it

Message ID 9c72a8d137cfca4e67848a7bf9dc9942eea7452b.1404888801.git.viresh.kumar@linaro.org
State New
Headers show

Commit Message

Viresh Kumar July 9, 2014, 6:55 a.m. UTC 
hrtimer_start*() family never fails to enqueue a hrtimer to a clock-base. The
only special case is when the hrtimer was in past. If it is getting enqueued to
local CPUs's clock-base, we raise a softirq and exit, else we handle that on
next interrupt on remote CPU.

At several places in the kernel, we try to make sure if hrtimer was added
properly or not by calling hrtimer_active(), like:

	hrtimer_start(timer, expires, mode);
	if (hrtimer_active(timer)) {
		/* Added successfully */
	} else {
		/* Was added in the past */
	}

As hrtimer_start*() never fails, hrtimer_active() is guaranteed to return '1'.
So, there is no point calling hrtimer_active().

Also this is done in while loop at several places, which isn't required anymore.

This patch updates sched core to get this fixed.

Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
---
 kernel/sched/core.c     | 20 +++++++++-----------
 kernel/sched/deadline.c |  2 +-
 2 files changed, 10 insertions(+), 12 deletions(-)
diff mbox

Patch

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 3bdf01b..4a6ef8d 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -111,19 +111,17 @@  void start_bandwidth_timer(struct hrtimer *period_timer, ktime_t period)
 	unsigned long delta;
 	ktime_t soft, hard, now;
 
-	for (;;) {
-		if (hrtimer_active(period_timer))
-			break;
+	if (hrtimer_active(period_timer))
+		return;
 
-		now = hrtimer_cb_get_time(period_timer);
-		hrtimer_forward(period_timer, now, period);
+	now = hrtimer_cb_get_time(period_timer);
+	hrtimer_forward(period_timer, now, period);
 
-		soft = hrtimer_get_softexpires(period_timer);
-		hard = hrtimer_get_expires(period_timer);
-		delta = ktime_to_ns(ktime_sub(hard, soft));
-		__hrtimer_start_range_ns(period_timer, soft, delta,
-					 HRTIMER_MODE_ABS_PINNED, 0);
-	}
+	soft = hrtimer_get_softexpires(period_timer);
+	hard = hrtimer_get_expires(period_timer);
+	delta = ktime_to_ns(ktime_sub(hard, soft));
+	__hrtimer_start_range_ns(period_timer, soft, delta,
+				 HRTIMER_MODE_ABS_PINNED, 0);
 }
 
 DEFINE_MUTEX(sched_domains_mutex);
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index fc4f98b1..eeb6786 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -484,7 +484,7 @@  static int start_dl_timer(struct sched_dl_entity *dl_se, bool boosted)
 	__hrtimer_start_range_ns(&dl_se->dl_timer, soft,
 				 range, HRTIMER_MODE_ABS, 0);
 
-	return hrtimer_active(&dl_se->dl_timer);
+	return 1;
 }
 
 /*