linux-kernel - Re: [GIT PULL] Urgent ACPI support fix for v6.18

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Message-ID: <CAJZ5v0ij7XizsUkhGRMy_1pqjCAjsHfjsBCuvVarExGGMknPEA@mail.gmail.com>
Date: Thu, 27 Nov 2025 20:58:09 +0100
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: "Longia, Amandeep Kaur" <AmandeepKaur.Longia@....com>, 
	Linus Torvalds <torvalds@...ux-foundation.org>
Cc: "lihuisong (C)" <lihuisong@...wei.com>, 
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>, Linux PM <linux-pm@...r.kernel.org>, 
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, kprateek.nayak@....com, dhsrivas@....com
Subject: Re: [GIT PULL] Urgent ACPI support fix for v6.18

Hi,

On Thu, Nov 27, 2025 at 8:03 PM Longia, Amandeep Kaur
<AmandeepKaur.Longia@....com> wrote:
>
> Hi all,
>
> On 11/27/2025 7:39 AM, lihuisong (C) wrote:
> > Hello Rafael,
> >
> > 在 2025/11/26 20:54, Rafael J. Wysocki 写道:
> >> Hi Linus,
> >>
> >> Please pull from the tag
> >>
> >>   git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm.git \
> >>   acpi-6.18-rc8
> >>
> >> with top-most commit 43ff36c4a5a574ee83b4b0d3f3d74f09a3a8c2d3
> >>
> >>   Revert "ACPI: processor: idle: Optimize ACPI idle driver registration"
> >>
> >> on top of commit ac3fd01e4c1efce8f2c054cdeb2ddd2fc0fb150d
> >>
> >>   Linux 6.18-rc7
> >>
> >> to receive an urgent ACPI support fix for 6.18.
> >>
> >> This reverts a commit that attempted to make the code in the ACPI
> >> processor driver more straightforward, but it turned out to cause
> >> the kernel to crash on at least one system, along with some further
> >> cleanups on top of it.
> > I just found that "ACPI: processor: idle: Optimize ACPI idle driver
> > registration" depends on the change
> > about cpuhp_setup_state in the commit [1]. Or many CPUs don't create
> > cpuidle directory.
> > What is the crash? Do you have releated trace?
> >
> > [1] https://lore.kernel.org/all/20240529133446.28446-2-
> > Jonathan.Cameron@...wei.com/
>
> We have observed the same issue. After booting the system with the
> latest kernel, the sysfs path /sys/devices/system/cpu/cpu*/cpuidle does
> not exist. Bisecting between v6.18-rc7 (good) and master (bad) led us to
> the following commit:
>
> 43ff36c4a5a574ee83b4b0d3f3d74f09a3a8c2d3 Revert "ACPI: processor: idle:
> Optimize ACPI idle driver registration"
>
> After debugging, we identified a code change that resolves the issue on
> our systems. Below is the code diff:
>
> diff --git a/drivers/acpi/processor_driver.c
> b/drivers/acpi/processor_driver.c
> index 7644de24d2fa..65e779be64ff 100644
> --- a/drivers/acpi/processor_driver.c
> +++ b/drivers/acpi/processor_driver.c
> @@ -166,7 +166,7 @@ static int __acpi_processor_start(struct acpi_device
> *device)
>          if (result && !IS_ENABLED(CONFIG_ACPI_CPU_FREQ_PSS))
>                  dev_dbg(&device->dev, "CPPC data invalid or not
> present\n");
>
> -       if (cpuidle_get_driver() == &acpi_idle_driver)
> +       if (!cpuidle_get_driver() || cpuidle_get_driver() ==
> &acpi_idle_driver)
>                  acpi_processor_power_init(pr);
>

Thanks for this information!

One more commit needs to be reverted which I have overlooked:

8a1b5d412cb4 ACPI: processor: Update cpuidle driver check in
__acpi_processor_start()

It was a fix on top of 43ff36c4a5a5.

My bad.

Linus, I'll send a pull request with this shortly, but you may as well
revert it yourself.