linux-kernel - Re: [PATCH v1] kernel/reboot: Use static handler for register_platform_power

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Date:   Thu, 2 Jun 2022 20:40:23 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Dmitry Osipenko <dmitry.osipenko@...labora.com>
Cc:     "Rafael J . Wysocki" <rafael@...nel.org>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1] kernel/reboot: Use static handler for register_platform_power_off()

On Wed, Jun 1, 2022 at 12:11 AM Dmitry Osipenko
<dmitry.osipenko@...labora.com> wrote:
>
> The register_platform_power_off() fails on m68k platform due to the
> memory allocation error that happens at a very early boot time when
> memory allocator isn't available yet. Fix it by using a static sys-off
> handler for the platform-level power-off handlers.
>
> Fixes: f0f7e5265b3b ("m68k: Switch to new sys-off handler API")
> Reported-by: Geert Uytterhoeven <geert@...ux-m68k.org>
> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@...labora.com>
> ---
>  kernel/reboot.c | 43 +++++++++++++++++++++++++++++++++++++------
>  1 file changed, 37 insertions(+), 6 deletions(-)
>
> diff --git a/kernel/reboot.c b/kernel/reboot.c
> index a091145ee710..3b19b123efec 100644
> --- a/kernel/reboot.c
> +++ b/kernel/reboot.c
> @@ -315,6 +315,37 @@ static int sys_off_notify(struct notifier_block *nb,
>         return handler->sys_off_cb(&data);
>  }
>
> +static struct sys_off_handler platform_sys_off_handler;
> +
> +static struct sys_off_handler *alloc_sys_off_handler(int priority)
> +{
> +       struct sys_off_handler *handler;
> +
> +       /*
> +        * Platforms like m68k can't allocate sys_off handler dynamically
> +        * at the early boot time because memory allocator isn't available yet.
> +        */
> +       if (priority == SYS_OFF_PRIO_PLATFORM) {
> +               handler = &platform_sys_off_handler;
> +               if (handler->cb_data)
> +                       return ERR_PTR(-EBUSY);
> +       } else {
> +               handler = kzalloc(sizeof(*handler), GFP_KERNEL);
> +               if (!handler)
> +                       return ERR_PTR(-ENOMEM);
> +       }
> +
> +       return handler;
> +}
> +
> +static void free_sys_off_handler(struct sys_off_handler *handler)
> +{
> +       if (handler == &platform_sys_off_handler)
> +               memset(handler, 0, sizeof(*handler));
> +       else
> +               kfree(handler);
> +}
> +
>  /**
>   *     register_sys_off_handler - Register sys-off handler
>   *     @mode: Sys-off mode
> @@ -345,9 +376,9 @@ register_sys_off_handler(enum sys_off_mode mode,
>         struct sys_off_handler *handler;
>         int err;
>
> -       handler = kzalloc(sizeof(*handler), GFP_KERNEL);
> -       if (!handler)
> -               return ERR_PTR(-ENOMEM);
> +       handler = alloc_sys_off_handler(priority);
> +       if (IS_ERR(handler))
> +               return handler;
>
>         switch (mode) {
>         case SYS_OFF_MODE_POWER_OFF_PREPARE:
> @@ -364,7 +395,7 @@ register_sys_off_handler(enum sys_off_mode mode,
>                 break;
>
>         default:
> -               kfree(handler);
> +               free_sys_off_handler(handler);
>                 return ERR_PTR(-EINVAL);
>         }
>
> @@ -391,7 +422,7 @@ register_sys_off_handler(enum sys_off_mode mode,
>         }
>
>         if (err) {
> -               kfree(handler);
> +               free_sys_off_handler(handler);
>                 return ERR_PTR(err);
>         }
>
> @@ -422,7 +453,7 @@ void unregister_sys_off_handler(struct sys_off_handler *handler)
>         /* sanity check, shall never happen */
>         WARN_ON(err);
>
> -       kfree(handler);
> +       free_sys_off_handler(handler);
>  }
>  EXPORT_SYMBOL_GPL(unregister_sys_off_handler);
>
> --

Applied now (with the tags from Geert), but if there are any more
followup changes in that area, can you please CC them to linux-pm, so
people who have seen your original series can see them too?

Thanks!