Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull RCU fixes from Ingo Molnar:
 "This tree includes a shutdown/cpu-hotplug deadlock fix and a
  documentation fix."

* 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  rcu: Advise most users not to enable RCU user mode
  rcu: Grace-period initialization excludes only RCU notifier

init/Kconfig

@@ -496,6 +496,12 @@ config RCU_USER_QS
 	  excluded from the global RCU state machine and thus doesn't
 	  to keep the timer tick on for RCU.
 
+	  Unless you want to hack and help the development of the full
+	  tickless feature, you shouldn't enable this option. It adds
+	  unnecessary overhead.
+
+	  If unsure say N
+
 config RCU_USER_QS_FORCE
 	bool "Force userspace extended QS by default"
 	depends on RCU_USER_QS
@@ -504,6 +510,12 @@ config RCU_USER_QS_FORCE
 	  test this feature that treats userspace as an extended quiescent
 	  state until we have a real user like a full adaptive nohz option.
 
+	  Unless you want to hack and help the development of the full
+	  tickless feature, you shouldn't enable this option. It adds
+	  unnecessary overhead.
+
+	  If unsure say N
+
 config RCU_FANOUT
 	int "Tree-based hierarchical RCU fanout value"
 	range 2 64 if 64BIT