From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Fri, 21 Mar 2014 20:19:05 +0100
Subject: rcu: make RCU_BOOST default on RT
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git
Git-commit: 1ca54168c86f6778d8f0b1151f9bb6008849a51e
Patch-mainline: Queued in subsystem maintainer repository
References: SLE Realtime Extension

Since it is no longer invoked from the softirq people run into OOM more
often if the priority of the RCU thread is too low. Making boosting
default on RT should help in those case and it can be switched off if
someone knows better.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Mike Galbraith <mgalbraith@suse.de>
---
 init/Kconfig |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/init/Kconfig
+++ b/init/Kconfig
@@ -526,7 +526,7 @@ config TINY_RCU
 
 config RCU_EXPERT
 	bool "Make expert-level adjustments to RCU configuration"
-	default n
+	default y if PREEMPT_RT_FULL
 	help
 	  This option needs to be enabled if you wish to make
 	  expert-level adjustments to RCU configuration.  By default,
@@ -708,7 +708,7 @@ config TREE_RCU_TRACE
 config RCU_BOOST
 	bool "Enable RCU priority boosting"
 	depends on RT_MUTEXES && PREEMPT_RCU && RCU_EXPERT
-	default n
+	default y if PREEMPT_RT_FULL
 	help
 	  This option boosts the priority of preempted RCU readers that
 	  block the current preemptible RCU grace period for too long.