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

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Message-ID: <7487e99d-421b-4ac5-bb77-e61c3131bb13@amd.com>
Date: Fri, 28 Nov 2025 00:33:24 +0530
From: "Longia, Amandeep Kaur" <AmandeepKaur.Longia@....com>
To: "lihuisong (C)" <lihuisong@...wei.com>, "Rafael J. Wysocki"
	<rafael@...nel.org>
CC: 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>, Linus Torvalds
	<torvalds@...ux-foundation.org>, <kprateek.nayak@....com>, <dhsrivas@....com>
Subject: Re: [GIT PULL] Urgent ACPI support fix for v6.18

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,
Amandeep

>>
>>
>> ---------------
>>
>> Rafael J. Wysocki (5):
>>        Revert "ACPI: processor: Do not expose global variable 
>> acpi_idle_driver"
>>        Revert "ACPI: processor: idle: Redefine two functions as void"
>>        Revert "ACPI: processor: idle: Rearrange declarations in header 
>> file"
>>        Revert "ACPI: processor: Remove unused empty stubs of some 
>> functions"
>>        Revert "ACPI: processor: idle: Optimize ACPI idle driver 
>> registration"
>>
>> ---------------
>>
>>   drivers/acpi/processor_driver.c |   6 +--
>>   drivers/acpi/processor_idle.c   | 115 +++++++++++++++ 
>> +------------------------
>>   include/acpi/processor.h        |  34 +++++++++---
>>   3 files changed, 76 insertions(+), 79 deletions(-)
>>