linux-kernel - Re: [PATCH RESEND] cpuidle: psci: Iterate backwards over list in psci_pd

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Date:   Wed, 8 Mar 2023 09:15:55 +0800
From:   Shawn Guo <shawn.guo@...aro.org>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     Daniel Lezcano <daniel.lezcano@...aro.org>,
        Sudeep Holla <sudeep.holla@....com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Konrad Dybcio <konrad.dybcio@...ainline.org>,
        linux-pm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH RESEND] cpuidle: psci: Iterate backwards over list in
 psci_pd_remove()

On Tue, Mar 07, 2023 at 02:06:31PM +0100, Rafael J. Wysocki wrote:
> On Sat, Mar 4, 2023 at 8:41 AM Shawn Guo <shawn.guo@...aro.org> wrote:
> >
> > In case that psci_pd_init_topology() fails for some reason,
> > psci_pd_remove() will be responsible for deleting provider and removing
> > genpd from psci_pd_providers list.  There will be a failure when removing
> > the cluster PD, because the cpu (child) PDs haven't been removed.
> >
> > [    0.050232] CPUidle PSCI: init PM domain cpu0
> > [    0.050278] CPUidle PSCI: init PM domain cpu1
> > [    0.050329] CPUidle PSCI: init PM domain cpu2
> > [    0.050370] CPUidle PSCI: init PM domain cpu3
> > [    0.050422] CPUidle PSCI: init PM domain cpu-cluster0
> > [    0.050475] PM: genpd_remove: unable to remove cpu-cluster0
> > [    0.051412] PM: genpd_remove: removed cpu3
> > [    0.051449] PM: genpd_remove: removed cpu2
> > [    0.051499] PM: genpd_remove: removed cpu1
> > [    0.051546] PM: genpd_remove: removed cpu0
> >
> > Fix the problem by iterating the provider list reversely, so that parent
> > PD gets removed after child's PDs like below.
> >
> > [    0.029052] CPUidle PSCI: init PM domain cpu0
> > [    0.029076] CPUidle PSCI: init PM domain cpu1
> > [    0.029103] CPUidle PSCI: init PM domain cpu2
> > [    0.029124] CPUidle PSCI: init PM domain cpu3
> > [    0.029151] CPUidle PSCI: init PM domain cpu-cluster0
> > [    0.029647] PM: genpd_remove: removed cpu0
> > [    0.029666] PM: genpd_remove: removed cpu1
> > [    0.029690] PM: genpd_remove: removed cpu2
> > [    0.029714] PM: genpd_remove: removed cpu3
> > [    0.029738] PM: genpd_remove: removed cpu-cluster0
> >
> > Fixes: a65a397f2451 ("cpuidle: psci: Add support for PM domains by using genpd")
> 
> So I guess there should be Cc: stable for 5.10 and later?

Yes.  I was thinking that stable team will pick it up due to the Fixes
tag, but yes, explicitly copying stable would be the best.

> 
> > Reviewed-by: Sudeep Holla <sudeep.holla@....com>
> > Reviewed-by: Ulf Hansson <ulf.hansson@...aro.org>
> > Signed-off-by: Shawn Guo <shawn.guo@...aro.org>
> > ---
> > Hi Rafael,
> >
> > This is a resend of the patch [1].  Could you help pick it up or let me
> > know if there is anything need to be improved, thanks!
> 
> Is this regarded as 6.3-rc material, or can it wait for 6.4?

As it's regarded as a fix, it would nice to apply it for 6.3-rc.

Shawn