Re: [PATCH rcu 10/11] srcu: Add FORCE_NEED_SRCU_NMI_SAFE Kconfig for testing

[Geert Uytterhoeven]

Hi Paul,

On Tue, 25 Mar 2025 at 16:08, Paul E. McKenney <paulmck@xxxxxxxxxx> wrote:
> commit 2245ef8605a80726548253d885b4cadd97f69f3b
> Author: Paul E. McKenney <paulmck@xxxxxxxxxx>
> Date:   Tue Mar 25 07:31:45 2025 -0700
>
>     srcu: Make FORCE_NEED_SRCU_NMI_SAFE depend on RCU_EXPERT
>
>     The FORCE_NEED_SRCU_NMI_SAFE is useful only for those wishing to test
>     the SRCU code paths that accommodate architectures that do not have
>     NMI-safe per-CPU operations, that is, those architectures that do not
>     select the ARCH_HAS_NMI_SAFE_THIS_CPU_OPS Kconfig option.  As such, this
>     is a specialized Kconfig option that is not intended for casual users.
>
>     This commit therefore hides it behind the RCU_EXPERT Kconfig option.
>     Given that this new FORCE_NEED_SRCU_NMI_SAFE Kconfig option has no effect
>     unless the ARCH_HAS_NMI_SAFE_THIS_CPU_OPS Kconfig option is also selected,
>     it also depends on this Kconfig option.
>
>     [ paulmck: Apply Geert Uytterhoeven feedback. ]
>
>     Reported-by: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
>     Closes: https://lore.kernel.org/all/CAMuHMdX6dy9_tmpLkpcnGzxyRbe6qSWYukcPp=H1GzZdyd3qBQ@xxxxxxxxxxxxxx/
>     Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
>
> diff --git a/kernel/rcu/Kconfig b/kernel/rcu/Kconfig
> index b3f985d41717a..ceaf6594f634c 100644
> --- a/kernel/rcu/Kconfig
> +++ b/kernel/rcu/Kconfig
> @@ -68,6 +68,8 @@ config TREE_SRCU
>  config FORCE_NEED_SRCU_NMI_SAFE
>         bool "Force selection of NEED_SRCU_NMI_SAFE"
>         depends on !TINY_SRCU
> +       depends on RCU_EXPERT
> +       depends on ARCH_HAS_NMI_SAFE_THIS_CPU_OPS
>         select NEED_SRCU_NMI_SAFE
>         default n
>         help

LGTM, so
Reviewed-by: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds