linux-kernel - [PATCH v2 1/5] cpuidle: Set polling in poll

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Message-Id: <c65ce49615d338bae8fb79df5daffab19353c900.1401902905.git.luto@amacapital.net>
Date:	Wed,  4 Jun 2014 10:31:14 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Peter Zijlstra <peterz@...radead.org>, umgwanakikbuti@...il.com
Cc:	mingo@...nel.org, tglx@...utronix.de, nicolas.pitre@...aro.org,
	daniel.lezcano@...aro.org, linux-kernel@...r.kernel.org,
	Andy Lutomirski <luto@...capital.net>
Subject: [PATCH v2 1/5] cpuidle: Set polling in poll_idle

poll_idle is the archetypal polling idle loop; tell the core idle
code about it.

This avoids pointless IPIs when all of the other cpuidle states are
disabled.

Signed-off-by: Andy Lutomirski <luto@...capital.net>
---
 drivers/cpuidle/driver.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/cpuidle/driver.c b/drivers/cpuidle/driver.c
index 136d6a2..9634f20 100644
--- a/drivers/cpuidle/driver.c
+++ b/drivers/cpuidle/driver.c
@@ -187,8 +187,11 @@ static int poll_idle(struct cpuidle_device *dev,
 
 	t1 = ktime_get();
 	local_irq_enable();
-	while (!need_resched())
-		cpu_relax();
+	if (!current_set_polling_and_test()) {
+		while (!need_resched())
+			cpu_relax();
+	}
+	current_clr_polling();
 
 	t2 = ktime_get();
 	diff = ktime_to_us(ktime_sub(t2, t1));
-- 
1.9.3

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