On Fri, Apr 07, 2017 at 02:37:36PM +0800, pierre Kuo wrote:
> 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(-)
Yup, looks like a typo since the do_something_else() part is correct.
Thanks for the fix:
Acked-by: Will Deacon <will.deacon@xxxxxxx>
I'm assuming somebody will pick this up.
Will
> 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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