RCU: add help text for "RCU implementation type"

This patch supplies help text for the "RCU implementation type"
kernel configuration choice.

Reported-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 8 insertions, 0 deletions

diff --git a/init/Kconfig b/init/Kconfig
index 0d0bbf218f1f..dcc96a8c8c69 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -775,6 +775,14 @@ config PREEMPT_NOTIFIERS
 choice
         prompt "RCU implementation type:"
         default CLASSIC_RCU
+        help
+          This allows you to choose either the classic RCU implementation
+          that is designed for best read-side performance on non-realtime
+          systems, or the preemptible RCU implementation for best latency
+          on realtime systems.  Note that some kernel preemption modes
+          will restrict your choice.
+
+          Select the default if you are unsure.
 
 config CLASSIC_RCU
         bool "Classic RCU"