From: Will Deacon <[email protected]> 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 <[email protected]> Cc: Peter Zijlstra <[email protected]> Signed-off-by: Will Deacon <[email protected]> Acked-by: Peter Zijlstra (Intel) <[email protected]> Signed-off-by: Paul E. McKenney <[email protected]> --- 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 -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
