linux-kernel - Re: [PATCH 04/10] cpuidle, psci: Push RCU-idle into driver

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Message-ID: <CAMuHMdU8qujVdXNfk00s66NF04=A3Z4Gsj7W+OyeeJA=pFmEbQ@mail.gmail.com>
Date:   Fri, 10 Mar 2023 09:47:20 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Cheng-Jui Wang <cheng-jui.wang@...iatek.com>
Cc:     stable@...r.kernel.org, Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Sudeep Holla <sudeep.holla@....com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Suren Baghdasaryan <surenb@...gle.com>,
        linux-pm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH 04/10] cpuidle, psci: Push RCU-idle into driver

Hi Cheng,

On Fri, Mar 3, 2023 at 10:35 AM Cheng-Jui Wang
<cheng-jui.wang@...iatek.com> wrote:
> From: Peter Zijlstra <peterz@...radead.org>
>
> commit e038f7b8028a1d1bc8ac82351c71ea538f19a879 upstream.
>
> Doing RCU-idle outside the driver, only to then temporarily enable it
> again, at least twice, before going idle is suboptimal.
>
> Notably once implicitly through the cpu_pm_*() calls and once
> explicitly doing ct_irq_*_irqon().
>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> Signed-off-by: Ingo Molnar <mingo@...nel.org>
> Tested-by: Kajetan Puchalski <kajetan.puchalski@....com>
> Tested-by: Tony Lindgren <tony@...mide.com>
> Tested-by: Ulf Hansson <ulf.hansson@...aro.org>
> Reviewed-by: Frederic Weisbecker <frederic@...nel.org>
> Reviewed-by: Guo Ren <guoren@...nel.org>
> Acked-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> Link: https://lore.kernel.org/r/20230112195539.760296658@infradead.org
> Signed-off-by: Suren Baghdasaryan <surenb@...gle.com>
> Signed-off-by: Cheng-Jui Wang <cheng-jui.wang@...iatek.com>

Given this patch introduced a so far unresolved regression upstream,
I think it's premature to backport this to stable.

https://lore.kernel.org/all/ff338b9f-4ab0-741b-26ea-7b7351da156@linux-m68k.org

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