linux-kernel - Re: [PATCH v2] PM: domains: Ensure genpd_debugfs

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Date:   Wed, 13 Jul 2022 14:01:47 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Hsin-Yi Wang <hsinyi@...omium.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Kevin Hilman <khilman@...nel.org>, Pavel Machek <pavel@....cz>,
        Len Brown <len.brown@...el.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        Pin-yen Lin <treapking@...omium.org>, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] PM: domains: Ensure genpd_debugfs_dir exists before remove

On Tue, 5 Jul 2022 at 19:17, Hsin-Yi Wang <hsinyi@...omium.org> wrote:
>
> Both genpd_debug_add() and genpd_debug_remove() may be called
> indirectly by other drivers while genpd_debugfs_dir is not yet
> set. For example, drivers can call pm_genpd_init() in probe or
> pm_genpd_init() in probe fail/cleanup path:
>
> pm_genpd_init()
>  --> genpd_debug_add()
>
> pm_genpd_remove()
>  --> genpd_remove()
>    --> genpd_debug_remove()
>
> At this time, genpd_debug_init() may not yet be called.
>
> genpd_debug_add() checks that if genpd_debugfs_dir is NULL, it
> will return directly. Make sure this is also checked
> in pm_genpd_remove(), otherwise components under debugfs root
> which has the same name as other components under pm_genpd may
> be accidentally removed, since NULL represents debugfs root.
>
> Fixes: 718072ceb211 ("PM: domains: create debugfs nodes when adding power domains")
> Signed-off-by: Hsin-Yi Wang <hsinyi@...omium.org>

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

Kind regards
Uffe

> ---
> v1->v2: Add more context in commit message
> ---
>  drivers/base/power/domain.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
> index 3e86772d5fac5..5a2e0232862e0 100644
> --- a/drivers/base/power/domain.c
> +++ b/drivers/base/power/domain.c
> @@ -222,6 +222,9 @@ static void genpd_debug_remove(struct generic_pm_domain *genpd)
>  {
>         struct dentry *d;
>
> +       if (!genpd_debugfs_dir)
> +               return;
> +
>         d = debugfs_lookup(genpd->name, genpd_debugfs_dir);
>         debugfs_remove(d);
>  }
> --
> 2.37.0.rc0.161.g10f37bed90-goog
>