linux-kernel - [PATCH tip/core/rcu 07/12] rcu: Create RCU_EXPERT Kconfig and hide booleans behind it

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Date:	Tue, 21 Apr 2015 12:55:48 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	linux-kernel@...r.kernel.org
Cc:	mingo@...nel.org, laijs@...fujitsu.com, dipankar@...ibm.com,
	akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
	josh@...htriplett.org, tglx@...utronix.de, peterz@...radead.org,
	rostedt@...dmis.org, dhowells@...hat.com, edumazet@...gle.com,
	dvhart@...ux.intel.com, fweisbec@...il.com, oleg@...hat.com,
	bobby.prani@...il.com,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: [PATCH tip/core/rcu 07/12] rcu: Create RCU_EXPERT Kconfig and hide booleans behind it

From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>

This commit creates an RCU_EXPERT Kconfig and hides the boolean
RCU-related user-visible Kconfig parameters behind it, namely
RCU_FAST_NO_HZ, RCU_BOOST, CONTEXT_TRACKING_FORCE, and RCU_NOCB_CPU.
This prevents Kconfig from asking about these parameters unless the user
really wants to be asked.

Reported-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
---
 init/Kconfig | 23 +++++++++++++++++++----
 1 file changed, 19 insertions(+), 4 deletions(-)

diff --git a/init/Kconfig b/init/Kconfig
index 67598f3143f5..aa68d72fe051 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -499,6 +499,21 @@ config TINY_RCU
 
 endchoice
 
+config RCU_EXPERT
+	bool "Make expert-level adjustments to RCU configuration"
+	default n
+	help
+	  This option needs to be enabled if you wish to make
+	  expert-level adjustments to RCU configuration.  By default,
+	  no such adjustments can be made, which has the often-beneficial
+	  side-effect of preventing "make oldconfig" from asking you all
+	  sorts of detailed questions about how you would like numerous
+	  obscure RCU options to be set up.
+
+	  Say Y if you need to make expert-level adjustments to RCU.
+
+	  Say N if you are unsure.
+
 config SRCU
 	bool
 	help
@@ -537,7 +552,7 @@ config RCU_USER_QS
 
 config CONTEXT_TRACKING_FORCE
 	bool "Force context tracking"
-	depends on CONTEXT_TRACKING
+	depends on CONTEXT_TRACKING && RCU_EXPERT
 	default y if !NO_HZ_FULL
 	help
 	  The major pre-requirement for full dynticks to work is to
@@ -611,7 +626,7 @@ config RCU_FANOUT_LEAF
 
 config RCU_FAST_NO_HZ
 	bool "Accelerate last non-dyntick-idle CPU's grace periods"
-	depends on NO_HZ_COMMON && SMP
+	depends on NO_HZ_COMMON && SMP && RCU_EXPERT
 	default n
 	help
 	  This option permits CPUs to enter dynticks-idle state even if
@@ -637,7 +652,7 @@ config TREE_RCU_TRACE
 
 config RCU_BOOST
 	bool "Enable RCU priority boosting"
-	depends on RT_MUTEXES && PREEMPT_RCU
+	depends on RT_MUTEXES && PREEMPT_RCU && RCU_EXPERT
 	default n
 	help
 	  This option boosts the priority of preempted RCU readers that
@@ -693,7 +708,7 @@ config RCU_BOOST_DELAY
 
 config RCU_NOCB_CPU
 	bool "Offload RCU callback processing from boot-selected CPUs"
-	depends on TREE_RCU || PREEMPT_RCU
+	depends on (TREE_RCU || PREEMPT_RCU) && RCU_EXPERT
 	default n
 	help
 	  Use this option to reduce OS jitter for aggressive HPC or
-- 
1.8.1.5

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