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-rw-r--r--Documentation/RCU/rcu_dereference.txt5
1 files changed, 5 insertions, 0 deletions
diff --git a/Documentation/RCU/rcu_dereference.txt b/Documentation/RCU/rcu_dereference.txt
index ceb05da5a5ac..2d05c9241a33 100644
--- a/Documentation/RCU/rcu_dereference.txt
+++ b/Documentation/RCU/rcu_dereference.txt
@@ -193,6 +193,11 @@ o Be very careful about comparing pointers obtained from
pointer. Note that the volatile cast in rcu_dereference()
will normally prevent the compiler from knowing too much.
+ However, please note that if the compiler knows that the
+ pointer takes on only one of two values, a not-equal
+ comparison will provide exactly the information that the
+ compiler needs to deduce the value of the pointer.
+
o Disable any value-speculation optimizations that your compiler
might provide, especially if you are making use of feedback-based
optimizations that take data collected from prior runs. Such