diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index bfcb1a6..d913e3b 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2991,11 +2991,15 @@
 			value is one, and maximum value is HZ.
 
 	rcutree.kthread_prio= 	 [KNL,BOOT]
-			Set the SCHED_FIFO priority of the RCU
-			per-CPU kthreads (rcuc/N). This value is also
-			used for the priority of the RCU boost threads
-			(rcub/N). Valid values are 1-99 and the default
-			is 1 (the least-favored priority).
+			Set the SCHED_FIFO priority of the RCU per-CPU
+			kthreads (rcuc/N). This value is also used for
+			the priority of the RCU boost threads (rcub/N)
+			and for the RCU grace-period kthreads (rcu_bh,
+			rcu_preempt, and rcu_sched). If RCU_BOOST is
+			set, valid values are 1-99 and the default is 1
+			(the least-favored priority).  Otherwise, when
+			RCU_BOOST is not set, valid values are 0-99 and
+			the default is zero (non-realtime operation).
 
 	rcutree.rcu_nocb_leader_stride= [KNL]
 			Set the number of NOCB kthread groups, which