From c7b5a1224430eef28adb2787d5059405c21a76a9 Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <tglx@linutronix.de>
Date: Wed, 7 Mar 2012 20:51:03 +0100
Subject: [PATCH 222/414] rt: Introduce cpu_chill()

Retry loops on RT might loop forever when the modifying side was
preempted. Add cpu_chill() to replace cpu_relax(). cpu_chill()
defaults to cpu_relax() for non RT. On RT it puts the looping task to
sleep for a tick so the preempted task can make progress.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable-rt@vger.kernel.org
---
 include/linux/delay.h | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/include/linux/delay.h b/include/linux/delay.h
index a6ecb34cf547..e23a7c021eeb 100644
--- a/include/linux/delay.h
+++ b/include/linux/delay.h
@@ -52,4 +52,10 @@ static inline void ssleep(unsigned int seconds)
 	msleep(seconds * 1000);
 }
 
+#ifdef CONFIG_PREEMPT_RT_FULL
+# define cpu_chill()	msleep(1)
+#else
+# define cpu_chill()	cpu_relax()
+#endif
+
 #endif /* defined(_LINUX_DELAY_H) */
-- 
2.10.2

