Commit-ID: 586dd56a4c17611e3927c9ff02ab8d0a6a545b38
Gitweb: http://git.kernel.org/tip/586dd56a4c17611e3927c9ff02ab8d0a6a545b38
Author: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
AuthorDate: Tue, 11 Feb 2014 12:28:06 -0800
Committer: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
CommitDate: Mon, 17 Feb 2014 14:56:07 -0800
Documentation/memory-barriers.txt: Conditional must use prior load
A control dependency consists of a load, a conditional that depends on
that load, and a store. This commit emphasizes this point in the
summary.
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Reviewed-by: Josh Triplett <josh@xxxxxxxxxxxxxxxx>
---
Documentation/memory-barriers.txt | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/Documentation/memory-barriers.txt b/Documentation/memory-barriers.txt
index f9ff060..6b25efd 100644
--- a/Documentation/memory-barriers.txt
+++ b/Documentation/memory-barriers.txt
@@ -724,7 +724,8 @@ In summary:
later loads, smp_mb().
(*) Control dependencies require at least one run-time conditional
- between the prior load and the subsequent store. If the compiler
+ between the prior load and the subsequent store, and this
+ conditional must involve the prior load. If the compiler
is able to optimize the conditional away, it will have also
optimized away the ordering. Careful use of ACCESS_ONCE() can
help to preserve the needed conditional.
--
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