--- zzzz-none-000/linux-3.10.107/Documentation/RCU/rcuref.txt	2017-06-27 09:49:32.000000000 +0000
+++ scorpion-7490-727/linux-3.10.107/Documentation/RCU/rcuref.txt	2021-02-04 17:41:59.000000000 +0000
@@ -1,5 +1,14 @@
 Reference-count design for elements of lists/arrays protected by RCU.
 
+
+Please note that the percpu-ref feature is likely your first
+stop if you need to combine reference counts and RCU.  Please see
+include/linux/percpu-refcount.h for more information.  However, in
+those unusual cases where percpu-ref would consume too much memory,
+please read on.
+
+------------------------------------------------------------------------
+
 Reference counting on elements of lists which are protected by traditional
 reader/writer spinlocks or semaphores are straightforward: