linux-kernel - Re: [PATCH] ACPI: processor: idle: Fix resource rollback in acpi_processor_power

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Message-ID: <f60aa4a2-35aa-41f6-b56d-6eb114e10ab2@huawei.com>
Date: Tue, 22 Jul 2025 19:05:16 +0800
From: "lihuisong (C)" <lihuisong@...wei.com>
To: "Rafael J. Wysocki" <rafael@...nel.org>
CC: <lenb@...nel.org>, <linux-acpi@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <linuxarm@...wei.com>,
	<jonathan.cameron@...wei.com>, <zhanjie9@...ilicon.com>,
	<zhenglifeng1@...wei.com>, <yubowen8@...wei.com>, <liuyonglong@...wei.com>,
	<lihuisong@...wei.com>
Subject: Re: [PATCH] ACPI: processor: idle: Fix resource rollback in
 acpi_processor_power_init

Hi Rafael,

Can you take a look at my reply?
If it is ok to you, I will send it later.

/Huisong
在 2025/7/14 9:33, lihuisong (C) 写道:
>
> 在 2025/7/3 19:09, Rafael J. Wysocki 写道:
>> On Thu, Jul 3, 2025 at 8:23 AM lihuisong (C) <lihuisong@...wei.com> 
>> wrote:
>>> Hi,
>>>
>>> Thanks for your review.
>>>
>>>
>>> 在 2025/7/3 1:42, Rafael J. Wysocki 写道:
>>>> On Thu, Jun 19, 2025 at 8:13 AM Huisong Li <lihuisong@...wei.com> 
>>>> wrote:
>>>>> There are two resource rollback issues in acpi_processor_power_init:
>>>>> 1> Do not unregister acpi_idle_driver when do kzalloc failed.
>>>>> 2> Do not free cpuidle device memory when register cpuidle device 
>>>>> failed.
>>>>>
>>>>> Signed-off-by: Huisong Li <lihuisong@...wei.com>
>>>>> ---
>>>>>    drivers/acpi/processor_idle.c | 24 +++++++++++++++++-------
>>>>>    1 file changed, 17 insertions(+), 7 deletions(-)
>>>>>
>>>>> diff --git a/drivers/acpi/processor_idle.c 
>>>>> b/drivers/acpi/processor_idle.c
>>>>> index 2c2dc559e0f8..3548ab9dac9e 100644
>>>>> --- a/drivers/acpi/processor_idle.c
>>>>> +++ b/drivers/acpi/processor_idle.c
>>>>> @@ -1392,8 +1392,10 @@ int acpi_processor_power_init(struct 
>>>>> acpi_processor *pr)
>>>>>                   }
>>>>>
>>>>>                   dev = kzalloc(sizeof(*dev), GFP_KERNEL);
>>>>> -               if (!dev)
>>>>> -                       return -ENOMEM;
>>>>> +               if (!dev) {
>>>>> +                       retval = -ENOMEM;
>>>>> +                       goto unregister_driver;
>>>> No, unregistering the driver here is pointless.
>>> I don't quite understand why here is pointless. Can you explain it?
>> When this function is run for another CPU, it will attempt to register
>> the driver again if it is unregistered here.
> Yeah, got it.
> So registering cpuidle also has a potential race issue here.
>>
>> Quite frankly, the driver should be registered before running this
>> function because it is a CPU hotplug callback and registering a
>> cpuidle driver from within it is quite questionable.
>>
>> Alternatively, it can be registered when all of the CPUs have been 
>> brought up.
> Agree with you.
> The reason why is that the initialization of acpi_idle_driver depands 
> on the power management information of CPU.
> But the power management information of CPU is obtained in this callback.
> I have an idea.
> Because acpi_idle_driver is applied to all possiable CPUs. And use the 
> power information of the first onlined CPU to initialize and register 
> acpi_idle_driver, currently.
> So I think we can use this logic and dependency to extract a function 
> to initialize and register acpi_idle_driver. And put this function to 
> acpi_processor_driver_init().
> I tested it is ok.
> What do you think about this?
>
> /Huisong
>>
>>>>> +               }
>>>>>                   per_cpu(acpi_cpuidle_device, pr->id) = dev;
>>>>>
>>>>>                   acpi_processor_setup_cpuidle_dev(pr, dev);
>>>>> @@ -1402,14 +1404,22 @@ int acpi_processor_power_init(struct 
>>>>> acpi_processor *pr)
>>>>>                    * must already be registered before registering 
>>>>> device
>>>>>                    */
>>>>>                   retval = cpuidle_register_device(dev);
>>>>> -               if (retval) {
>>>>> -                       if (acpi_processor_registered == 0)
>>>>> - cpuidle_unregister_driver(&acpi_idle_driver);
>>>> Pretty much the same as here.
>>>>
>>>> It would be good to clean up dev here though.
>>> It is ok if above is pointless.
>>>>> -                       return retval;
>>>>> -               }
>>>>> +               if (retval)
>>>>> +                       goto free_cpuidle_device;
>>>>> +
>>>>>                   acpi_processor_registered++;
>>>>>           }
>>>>>           return 0;
>>>>> +
>>>>> +free_cpuidle_device:
>>>>> +       per_cpu(acpi_cpuidle_device, pr->id) = NULL;
>>>>> +       kfree(dev);
>>>>> +
>>>>> +unregister_driver:
>>>>> +       if (acpi_processor_registered == 0)
>>>>> + cpuidle_unregister_driver(&acpi_idle_driver);
>>>>> +
>>>>> +       return retval;
>>>>>    }
>>>>>
>>>>>    int acpi_processor_power_exit(struct acpi_processor *pr)
>>>>> -- 
>>>>> 2.33.0
>>>>>