rcu: Create RCU_EXPERT Kconfig and hide booleans behind it

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

Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Pranith Kumar <bobby.prani@gmail.com>

diff --git a/init/Kconfig b/init/Kconfig
index 0ec8236..7eb4c7b 100644 (file)
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -501,6 +501,21 @@ 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
@@ -613,7 +628,7 @@ 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
@@ -639,7 +654,7 @@ 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