Commit-ID: 45c8a36a5519960638a4f331839bb99c1994fd04
Gitweb: http://git.kernel.org/tip/45c8a36a5519960638a4f331839bb99c1994fd04
Author: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
AuthorDate: Tue, 2 Jul 2013 15:24:09 -0700
Committer: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
CommitDate: Mon, 19 Aug 2013 21:39:42 -0700
doc: Fix memory-barrier control-dependency example
Each control-dependency example needs its barriers between the "if"
condition and the body of the "if" because a control dependency is
a dependency induced by a branch. This commit makes the needed
adjustment.
Reported-by: Yongming Shen <symingz@xxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Reviewed-by: Josh Triplett <josh@xxxxxxxxxxxxxxxx>
---
Documentation/memory-barriers.txt | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/Documentation/memory-barriers.txt b/Documentation/memory-barriers.txt
index fa5d8a9..c8c42e6 100644
--- a/Documentation/memory-barriers.txt
+++ b/Documentation/memory-barriers.txt
@@ -531,9 +531,10 @@ dependency barrier to make it work correctly. Consider the following bit of
code:
q = &a;
- if (p)
+ if (p) {
+ <data dependency barrier>
q = &b;
- <data dependency barrier>
+ }
x = *q;
This will not have the desired effect because there is no actual data
@@ -542,9 +543,10 @@ attempting to predict the outcome in advance. In such a case what's actually
required is:
q = &a;
- if (p)
+ if (p) {
+ <read barrier>
q = &b;
- <read barrier>
+ }
x = *q;
--
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