[PATCH tip/core/rcu 3/3] Documentation: Memory barrier semantics of atomic_xchg()

From: Paul E. McKenney
Date: Sat Jan 05 2013 - 12:04:34 EST

From: Richard Braun <rbraun@xxxxxxxxx>

Add atomic_xchg() to documentation for atomic operations and
memory barriers.

Signed-off-by: Richard Braun <rbraun@xxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Documentation/atomic_ops.txt | 2 ++
Documentation/memory-barriers.txt | 1 +
2 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/Documentation/atomic_ops.txt b/Documentation/atomic_ops.txt
index 27f2b21..d9ca5be 100644
--- a/Documentation/atomic_ops.txt
+++ b/Documentation/atomic_ops.txt
@@ -253,6 +253,8 @@ This performs an atomic exchange operation on the atomic variable v, setting
the given new value. It returns the old value that the atomic variable v had
just before the operation.

+atomic_xchg requires explicit memory barriers around the operation.
int atomic_cmpxchg(atomic_t *v, int old, int new);

This performs an atomic compare exchange operation on the atomic value v,
diff --git a/Documentation/memory-barriers.txt b/Documentation/memory-barriers.txt
index 3c4e1b3..fa5d8a9 100644
--- a/Documentation/memory-barriers.txt
+++ b/Documentation/memory-barriers.txt
@@ -1685,6 +1685,7 @@ explicit lock operations, described later). These include:

+ atomic_xchg();

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