From: Will Deacon <will.dea...@arm.com>
For compound atomics performing both a load and a store operation, make
it clear that _acquire and _release variants refer only to the load and
store portions of compound atomic. For example, xchg_acquire is an xchg
operation where the load takes on ACQUIRE semantics.
Cc: Paul E. McKenney <paul...@linux.vnet.ibm.com>
Cc: Peter Zijlstra <pet...@infradead.org>
Signed-off-by: Will Deacon <will.dea...@arm.com>
Acked-by: Peter Zijlstra (Intel) <pet...@infradead.org>
Signed-off-by: Paul E. McKenney <paul...@linux.vnet.ibm.com>
---
Documentation/memory-barriers.txt | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/Documentation/memory-barriers.txt
b/Documentation/memory-barriers.txt
index 8b11e54238bf..147ae8ec836f 100644
--- a/Documentation/memory-barriers.txt
+++ b/Documentation/memory-barriers.txt
@@ -498,6 +498,11 @@ And a couple of implicit varieties:
This means that ACQUIRE acts as a minimal "acquire" operation and
RELEASE acts as a minimal "release" operation.
+A subset of the atomic operations described in atomic_ops.txt have ACQUIRE
+and RELEASE variants in addition to fully-ordered and relaxed (no barrier
+semantics) definitions. For compound atomics performing both a load and a
+store, ACQUIRE semantics apply only to the load and RELEASE semantics apply
+only to the store portion of the operation.
Memory barriers are only required where there's a possibility of interaction
between two CPUs or between a CPU and a device. If it can be guaranteed that
--
2.5.2
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