linux-kernel - Re: [PATCH] arch/sh/: fix NUMA build errors

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Date:   Tue, 19 Nov 2019 08:38:27 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Randy Dunlap <rdunlap@...radead.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        Rich Felker <dalias@...c.org>,
        Linux-sh list <linux-sh@...r.kernel.org>
Subject: Re: [PATCH] arch/sh/: fix NUMA build errors

Hi Randy,

On Tue, Nov 19, 2019 at 1:55 AM Randy Dunlap <rdunlap@...radead.org> wrote:
> From: Randy Dunlap <rdunlap@...radead.org>
> Fix SUPERH builds that select SYS_SUPPORTS_NUMA but do not select
> SYS_SUPPORTS_SMP and SMP.
>
> kernel/sched/topology.c is only built for CONFIG_SMP and then the NUMA
> code + data inside topology.c is only built when CONFIG_NUMA is
> set/enabled, so these arch/sh/ configs need to select SMP and
> SYS_SUPPORTS_SMP to build the NUMA support.
>
> Fixes this build error in 3 different SUPERH configs:
>
> mm/page_alloc.o: In function `get_page_from_freelist':
> page_alloc.c:(.text+0x2ca8): undefined reference to `node_reclaim_distance'
>
> Signed-off-by: Randy Dunlap <rdunlap@...radead.org>
> Reported-by: Geert Uytterhoeven <geert@...ux-m68k.org>
> Cc: Yoshinori Sato <ysato@...rs.sourceforge.jp>
> Cc: Rich Felker <dalias@...c.org>
> Cc: linux-sh@...r.kernel.org
> ---
> or maybe these should be fixed in the defconfig files?
>
> or alternatively, does it make any sense to support NUMA without SMP?

I think it does.  From arch/sh/mm/Kconfig config NUMA help:

        Some SH systems have many various memories scattered around
        the address space, each with varying latencies. This enables
        support for these blocks by binding them to nodes and allowing
        memory policies to be used for prioritizing and controlling
        allocation behaviour.

Probably the NUMA-core is too server/x86-centric, by assuming NUMA is
used only on systems with multiple CPUs, each with their own RAM.

AFAIK, none of the SoCs below are SMP:

> --- lnx-54-rc8.orig/arch/sh/Kconfig
> +++ lnx-54-rc8/arch/sh/Kconfig
> @@ -508,6 +508,8 @@ config CPU_SUBTYPE_SH7722
>         select CPU_SHX2
>         select ARCH_SHMOBILE
>         select ARCH_SPARSEMEM_ENABLE
> +       select SYS_SUPPORTS_SMP
> +       select SMP
>         select SYS_SUPPORTS_NUMA
>         select SYS_SUPPORTS_SH_CMT
>         select PINCTRL
> @@ -518,6 +520,8 @@ config CPU_SUBTYPE_SH7366
>         select CPU_SHX2
>         select ARCH_SHMOBILE
>         select ARCH_SPARSEMEM_ENABLE
> +       select SYS_SUPPORTS_SMP
> +       select SMP
>         select SYS_SUPPORTS_NUMA
>         select SYS_SUPPORTS_SH_CMT

BTW, you didn't have the issue with CPU_SHX3 and CPU_SUBTYPE_SH7785?

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

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