X-Git-Url: http://plrg.eecs.uci.edu/git/?a=blobdiff_plain;f=Documentation%2FRCU%2Frcubarrier.txt;h=b10cfe711e68e48fe6d516ea531126dfc947fc13;hb=9edad6ea0f1416415f6fe31cc9d1dbc3817803ed;hp=2e319d1b9ef28c0d9c19505306063cfc6bc9f595;hpb=54be8200198ddfc6cb396720460c19881fac2d5a;p=firefly-linux-kernel-4.4.55.git

diff --git a/Documentation/RCU/rcubarrier.txt b/Documentation/RCU/rcubarrier.txt
index 2e319d1b9ef2..b10cfe711e68 100644
--- a/Documentation/RCU/rcubarrier.txt
+++ b/Documentation/RCU/rcubarrier.txt
@@ -70,10 +70,14 @@ in realtime kernels in order to avoid excessive scheduling latencies.
 
 rcu_barrier()
 
-We instead need the rcu_barrier() primitive. This primitive is similar
-to synchronize_rcu(), but instead of waiting solely for a grace
-period to elapse, it also waits for all outstanding RCU callbacks to
-complete. Pseudo-code using rcu_barrier() is as follows:
+We instead need the rcu_barrier() primitive.  Rather than waiting for
+a grace period to elapse, rcu_barrier() waits for all outstanding RCU
+callbacks to complete.  Please note that rcu_barrier() does -not- imply
+synchronize_rcu(), in particular, if there are no RCU callbacks queued
+anywhere, rcu_barrier() is within its rights to return immediately,
+without waiting for a grace period to elapse.
+
+Pseudo-code using rcu_barrier() is as follows:
 
    1. Prevent any new RCU callbacks from being posted.
    2. Execute rcu_barrier().