for below example, if MAX is defined to be 1, then the compiler knows (Q
% MAX) is equal to zero.
so compiler will transform the "else" part of code.
q = READ_ONCE(a);
if (q % MAX) {
WRITE_ONCE(b, 1);
do_something();
} else {
WRITE_ONCE(b, 2);
do_something_else();
}
So we modify the original document as below:
q = READ_ONCE(a);
- WRITE_ONCE(b, 1);
+ WRITE_ONCE(b, 2);
do_something_else();
Signed-off-by: pierre Kuo <vichy.kuo@xxxxxxxxx>
---
Documentation/memory-barriers.txt | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/Documentation/memory-barriers.txt b/Documentation/memory-barriers.txt
index d2b0a8d..08329cb 100644
--- a/Documentation/memory-barriers.txt
+++ b/Documentation/memory-barriers.txt
@@ -768,7 +768,7 @@ equal to zero, in which case the compiler is within its rights to
transform the above code into the following:
q = READ_ONCE(a);
- WRITE_ONCE(b, 1);
+ WRITE_ONCE(b, 2);
do_something_else();
Given this transformation, the CPU is not required to respect the ordering
--
1.9.1
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