Re: [PATCH 02/16] doc: memory-barriers.txt: Document use of lockless_dereference()

From: Paul E. McKenney
Date: Thu Nov 13 2014 - 15:11:27 EST


On Thu, Nov 13, 2014 at 02:24:08PM -0500, Pranith Kumar wrote:
> Recently lockless_dereference() was added which can be used in place of
> hard-coding smp_read_barrier_depends(). The following PATCH makes the change.
>
> Signed-off-by: Pranith Kumar <bobby.prani@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 3d5f49b..841ac36 100644
> --- a/Documentation/memory-barriers.txt
> +++ b/Documentation/memory-barriers.txt
> @@ -203,7 +203,7 @@ There are some minimal guarantees that may be expected of a CPU:
> and always in that order. On most systems, smp_read_barrier_depends()
> does nothing, but it is required for DEC Alpha. The ACCESS_ONCE()
> is required to prevent compiler mischief. Please note that you
> - should normally use something like rcu_dereference() instead of
> + should normally use something like lockless_dereference() instead of

Good catch, but please keep both possibilities, something like
"... like rcu_dereference() or lockless_dereference() instead of ..."

Thanx, Paul

> open-coding smp_read_barrier_depends().
>
> (*) Overlapping loads and stores within a particular CPU will appear to be
> --
> 1.9.1
>

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