Re: [PATCH 1/3] cpuidle: Add enable_cpuidle() interface

[Rafael J. Wysocki]

On Fri, Mar 27, 2026 at 7:23 AM lihuisong (C) <lihuisong@xxxxxxxxxx> wrote:
>
>
> On 3/26/2026 9:39 PM, Rafael J. Wysocki wrote:
> > On Thu, Mar 26, 2026 at 1:17 PM lihuisong (C) <lihuisong@xxxxxxxxxx> wrote:
> >> Hi Rafael,
> >>
> >> On 1/30/2026 9:59 AM, lihuisong (C) wrote:
> >>> Hi Rafael,
> >>>
> >>> On 1/15/2026 8:18 PM, lihuisong (C) wrote:
> >>>> On 1/15/2026 3:18 AM, Rafael J. Wysocki wrote:
> >>>>> On Tue, Nov 25, 2025 at 8:29 AM Huisong Li <lihuisong@xxxxxxxxxx>
> >>>>> wrote:
> >>>>>> The global switch of cpuidle can be turned back on in some case.
> >>>>>> So add enable_cpuidle().
> >>>>> No, this is not going to work.  The "off" switch only affects
> >>>>> initialization AFAICS.
> >>>> I think it would be work.
> >>>> The cpuidle_not_available() also see the "off" on do_idle().
> >>>> And cpuidle_idle_call() check this function first and then select
> >>>> idle state.
> >>>> Cpuidle doesn't select and enter idle state if this fuction return true.
> >>> I verified that disable_cpuidle() effectively prevents all CPUs from
> >>> entering any idle states and the cpuidle function is correctly
> >>> restored after calling enable_cpuidle().
> >>> What do you think?
> >> Could you pleasetake a look atmy reply?
> >> If not ok, I will drop this from my upstream list.
> > Sorry, can you please remind me what problem you wanted to address
> > with the help of this?
> Regarding the discussion in the link[1], if driver fail to get power
> info in power notify,
> the old idle states may no longer be reliable. Therefore, patch 2/3
> disables ACPI idle
> via the new interface introduced in patch 1/3.
>
> However, our discussion on whether this new interface can disable ACPI
> idle has not yet reached a conclusion.
> Could you please revisit this thread? It's quite brief, and I'd
> appreciate your further input.
>
> [1]
> https://lore.kernel.org/all/20251103084244.2654432-1-lihuisong@xxxxxxxxxx

The "off" variable has been intended for disabling cpuidle via kernel
command line (note that the corresponding module param is read-only).

disable_cpuidle() is only used by Xen now and only at the setup/init stage.

I don't think that using it on idle state list change notifications is
a good idea.

Something like cpuidle_pause_and_lock() would be a better match I
think.  acpi_processor_hotplug() uses it already for a similar
purpose.