linux-kernel - [PATCH 1/2] timer: avoid unnecessary waking up of nohz CPU

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Date:	Mon, 27 Apr 2015 19:21:49 -0700
From:	Joonwoo Park <joonwoop@...eaurora.org>
To:	tglx@...utronix.de
Cc:	sboyd@...eaurora.org, skannan@...eaurora.org,
	linux-kernel@...r.kernel.org,
	Joonwoo Park <joonwoop@...eaurora.org>,
	John Stultz <john.stultz@...aro.org>
Subject: [PATCH 1/2] timer: avoid unnecessary waking up of nohz CPU

At present, internal_add_timer() examines flags with 'base' which doesn't
contain flags.  Examine with 'timer->base' to avoid unnecessary waking up
of nohz CPU when timer base has TIMER_DEFERRABLE.

CC: Thomas Gleixner <tglx@...utronix.de>
CC: John Stultz <john.stultz@...aro.org>
Signed-off-by: Joonwoo Park <joonwoop@...eaurora.org>
---
 kernel/time/timer.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/time/timer.c b/kernel/time/timer.c
index 2ece3aa..e5d5733c 100644
--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -434,7 +434,7 @@ static void internal_add_timer(struct tvec_base *base, struct timer_list *timer)
 	 * require special care against races with idle_cpu(), lets deal
 	 * with that later.
 	 */
-	if (!tbase_get_deferrable(base) || tick_nohz_full_cpu(base->cpu))
+	if (!tbase_get_deferrable(timer->base) || tick_nohz_full_cpu(base->cpu))
 		wake_up_nohz_cpu(base->cpu);
 }
 
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