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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2015-08-01 10:45:26 -0700
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2015-10-06 11:22:28 -0700
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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>
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diff --git a/Documentation/memory-barriers.txt b/Documentation/memory-barriers.txt
index 2ba8461b0631..d336e4d42029 100644
--- a/Documentation/memory-barriers.txt
+++ b/Documentation/memory-barriers.txt
@@ -1789,7 +1789,6 @@ The Linux kernel has a number of locking constructs:
(*) 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: