Re: [patch V3 06/14] x86: Select ARCH_MEMORY_ORDER_TOS

[Mark Rutland]

On Mon, Mar 30, 2026 at 02:02:31PM +0200, Thomas Gleixner wrote:
> The generic unsafe_atomic_store_release_user() implementation does:
> 
>     if (!IS_ENABLED(CONFIG_ARCH_MEMORY_ORDER_TOS))
>         smp_mb();
>     unsafe_put_user();
> 
> As x86 implements Total Store Order (TOS) which means stores imply release,
> select ARCH_MEMORY_ORDER_TOS to avoid the unnecessary smp_mb().
> 
> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxx>
> Reviewed-by: André Almeida <andrealmeid@xxxxxxxxxx>
> ---
> V3: Rename to TOS - Peter

As on the last patch, shouldn't that be TSO?

Mark

> V2: New patch
> ---
>  arch/x86/Kconfig |    1 +
>  1 file changed, 1 insertion(+)
> 
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -114,6 +114,7 @@ config X86
>  	select ARCH_HAS_ZONE_DMA_SET if EXPERT
>  	select ARCH_HAVE_NMI_SAFE_CMPXCHG
>  	select ARCH_HAVE_EXTRA_ELF_NOTES
> +	select ARCH_MEMORY_ORDER_TOS
>  	select ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE
>  	select ARCH_MIGHT_HAVE_ACPI_PDC		if ACPI
>  	select ARCH_MIGHT_HAVE_PC_PARPORT
>