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

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Message-ID: <CAJZ5v0j8k3FXx0TCF8nF+KTGcZL8CG7yZ6_Z11jpqOM9x_0w6g@mail.gmail.com>
Date: Tue, 22 Jul 2025 13:10:51 +0200
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: "lihuisong (C)" <lihuisong@...wei.com>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>, 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
Subject: Re: [PATCH] ACPI: processor: idle: Fix resource rollback in acpi_processor_power_init

On Mon, Jul 14, 2025 at 3:34 AM lihuisong (C) <lihuisong@...wei.com> wrote:
>
>
> 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?

This is one of the options I mentioned above, isn't it?