documentation: Add pointer to percpu-ref for RCU and refcount

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

diff --git a/Documentation/RCU/rcuref.txt b/Documentation/RCU/rcuref.txt
index 141d531aa14b038d288c3d9df5653d1e4949c784..613033ff2b9b30a176d95dcfd6273a68db18144d 100644 (file)
--- a/Documentation/RCU/rcuref.txt
+++ b/Documentation/RCU/rcuref.txt
@@ -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: