linux-kernel - Re: [PATCH -next v2 2/2] arch_topology: Fix cache attributes detection in the CPU hotplug path

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Date:   Tue, 19 Jul 2022 17:24:32 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Sudeep Holla <sudeep.holla@....com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Conor Dooley <conor.dooley@...rochip.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Ionela Voinescu <ionela.voinescu@....com>,
        Pierre Gondois <pierre.gondois@....com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        linux-riscv <linux-riscv@...ts.infradead.org>
Subject: Re: [PATCH -next v2 2/2] arch_topology: Fix cache attributes
 detection in the CPU hotplug path

Hi Sudeep,

On Fri, Jul 15, 2022 at 12:28 PM Sudeep Holla <sudeep.holla@....com> wrote:
> init_cpu_topology() is called only once at the boot and all the cache
> attributes are detected early for all the possible CPUs. However when
> the CPUs are hotplugged out, the cacheinfo gets removed. While the
> attributes are added back when the CPUs are hotplugged back in as part
> of CPU hotplug state machine, it ends up called quite late after the
> update_siblings_masks() are called in the secondary_start_kernel()
> resulting in wrong llc_sibling_masks.
>
> Move the call to detect_cache_attributes() inside update_siblings_masks()
> to ensure the cacheinfo is updated before the LLC sibling masks are
> updated. This will fix the incorrect LLC sibling masks generated when
> the CPUs are hotplugged out and hotplugged back in again.
>
> Reported-by: Ionela Voinescu <ionela.voinescu@....com>
> Tested-by: Ionela Voinescu <ionela.voinescu@....com>
> Reviewed-by: Conor Dooley <conor.dooley@...rochip.com>
> Reviewed-by: Ionela Voinescu <ionela.voinescu@....com>
> Signed-off-by: Sudeep Holla <sudeep.holla@....com>
> ---
>  drivers/base/arch_topology.c | 16 ++++++----------
>  1 file changed, 6 insertions(+), 10 deletions(-)
>
> v1->v2:
>         - No change in this patch, but 1/2 was added to fix possible
>           bug "sleeping in the atomic context" with this patch.
>         - Added all the received tags

Thank you, the "Early cacheinfo failed, ret = -12" is gone.

Tested-by: Geert Uytterhoeven <geert+renesas@...der.be>

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