Re: [PATCH 08/34] asm-generic: smp_store_mb should use smp_mb

Arnd Bergmann
2015-12-30T13:45:02Z

On Wednesday 30 December 2015 15:24:47 Michael S. Tsirkin wrote:
> asm-generic variant of smp_store_mb() calls mb() which is stronger
> than implied by both the name and the documentation.
>
> smp_store_mb is only used by core kernel code at the moment, so
> we know no one mis-uses it for an MMIO barrier.
> Make it call smp_mb consistently before some arch-specific
> code uses it as such by mistake.
>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> ---
> include/asm-generic/barrier.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/asm-generic/barrier.h b/include/asm-generic/barrier.h
> index 538f8d1..987b2e0 100644
> --- a/include/asm-generic/barrier.h
> +++ b/include/asm-generic/barrier.h
> @@ -93,7 +93,7 @@
> #endif /* CONFIG_SMP */
>
> #ifndef smp_store_mb
> -#define smp_store_mb(var, value) do { WRITE_ONCE(var, value); mb(); } while (0)
> +#define smp_store_mb(var, value) do { WRITE_ONCE(var, value); smp_mb(); } while (0)
> #endif
>
> #ifndef smp_mb__before_atomic
>

The same patch is already in the tip tree scheduled for 4.5 as d5a73cadf3fd
("lcoking/barriers, arch: Use smp barriers in smp_store_release()").

I think you can drop your version.

arnd