documentation: No acquire/release for RCU readers
Documentation/memory-barriers.txt calls out RCU as one of the sets
of primitives associated with ACQUIRE and RELEASE. There really
is an association in that rcu_assign_pointer() includes a RELEASE
operation, but a quick read can convince people that rcu_read_lock() and
rcu_read_unlock() have ACQUIRE and RELEASE semantics, which they do not.
This commit therefore removes RCU from this list in order to avoid
this confusion.
Reported-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
diff --git a/Documentation/memory-barriers.txt b/Documentation/memory-barriers.txt
index 2ba8461..d336e4d 100644
--- a/Documentation/memory-barriers.txt
+++ b/Documentation/memory-barriers.txt
@@ -1789,7 +1789,6 @@
(*) mutexes
(*) semaphores
(*) R/W semaphores
- (*) RCU
In all cases there are variants on "ACQUIRE" operations and "RELEASE" operations
for each construct. These operations all imply certain barriers: