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

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Date:   Tue, 1 Mar 2022 11:46:20 +0100
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Shawn Guo <shawn.guo@...aro.org>
Cc:     Daniel Lezcano <daniel.lezcano@...aro.org>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Sudeep Holla <sudeep.holla@....com>, linux-pm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] cpuidle: psci: Iterate backwards over list in psci_pd_remove()

On Fri, 25 Feb 2022 at 09:24, 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 in a reversely order, so
> that parent PD gets removed before child's PDs.
>
> Signed-off-by: Shawn Guo <shawn.guo@...aro.org>

Thanks for fixing this!

Reviewed-by: Ulf Hansson <ulf.hansson@...aro.org>

I think we should add a fixes tag, like below and also tag this for
stable kernels.

Fixes: a65a397f2451 ("cpuidle: psci: Add support for PM domains by using genpd")

Kind regards
Uffe

> ---
>  drivers/cpuidle/cpuidle-psci-domain.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/cpuidle/cpuidle-psci-domain.c b/drivers/cpuidle/cpuidle-psci-domain.c
> index ff2c3f8e4668..ce5c415fb04d 100644
> --- a/drivers/cpuidle/cpuidle-psci-domain.c
> +++ b/drivers/cpuidle/cpuidle-psci-domain.c
> @@ -182,7 +182,8 @@ static void psci_pd_remove(void)
>         struct psci_pd_provider *pd_provider, *it;
>         struct generic_pm_domain *genpd;
>
> -       list_for_each_entry_safe(pd_provider, it, &psci_pd_providers, link) {
> +       list_for_each_entry_safe_reverse(pd_provider, it,
> +                                        &psci_pd_providers, link) {
>                 of_genpd_del_provider(pd_provider->node);
>
>                 genpd = of_genpd_remove_last(pd_provider->node);
> --
> 2.25.1
>