On 2018-11-01 16:25:18 [-0700], Paul E. McKenney wrote:

quoted

--- a/kernel/rcu/Kconfig
+++ b/kernel/rcu/Kconfig

@@ -36,7 +36,7 @@ config TINY_RCU
 
 config RCU_EXPERT
 	bool "Make expert-level adjustments to RCU configuration"
-	default n
+	default y if PREEMPT_RT_FULL

Would it work to leave this as is, and ...

quoted

 	help
 	  This option needs to be enabled if you wish to make
 	  expert-level adjustments to RCU configuration.  By default,

@@ -191,7 +191,7 @@ config RCU_FAST_NO_HZ
 config RCU_BOOST
 	bool "Enable RCU priority boosting"
 	depends on RT_MUTEXES && PREEMPT_RCU && RCU_EXPERT

... make the above line instead be:

  	depends on (RT_MUTEXES && PREEMPT_RCU && RCU_EXPERT) || PREEMPT_RT_FULL

Or am I missing something?

I agree that the risk might currently seem small, but if Linus ever
starts building PREEMPT_RT_FULL kernels, I really really do not want
RCU_EXPERT to be set.  ;-)

okay, this would work. Let me teak this in my current tree.

								Thanx, Paul

Sebastian