linux-kernel - Re: [PATCH v0 04/42] clk: renesas: Check notifier registration return value

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Date:   Mon, 8 Nov 2021 15:12:21 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Borislav Petkov <bp@...en8.de>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        linux-clk <linux-clk@...r.kernel.org>
Subject: Re: [PATCH v0 04/42] clk: renesas: Check notifier registration return value

Hi Borislav,

Thanks for your patch!

On Mon, Nov 8, 2021 at 1:49 PM Borislav Petkov <bp@...en8.de> wrote:
> From: Borislav Petkov <bp@...e.de>
>
> Avoid homegrown notifier registration checks.

Which homegrown notifier registration check is avoided?
IIANM, you're adding a homegrown notifier registration check?

> No functional changes.
>
> Signed-off-by: Borislav Petkov <bp@...e.de>

> --- a/drivers/clk/renesas/clk-div6.c
> +++ b/drivers/clk/renesas/clk-div6.c
> @@ -306,7 +306,9 @@ struct clk * __init cpg_div6_register(const char *name,
>
>         if (notifiers) {
>                 clock->nb.notifier_call = cpg_div6_clock_notifier_call;
> -               raw_notifier_chain_register(notifiers, &clock->nb);
> +
> +               if (raw_notifier_chain_register(notifiers, &clock->nb))
> +                       pr_warn("CPG DIV6 clock notifier already registered\n");

A duplicate registration cannot happen, as the notifier is freshly allocated.

>         }
>
>         return clk;
> diff --git a/drivers/clk/renesas/rcar-cpg-lib.c b/drivers/clk/renesas/rcar-cpg-lib.c
> index e93f0011eb07..fbbb6f4a8148 100644
> --- a/drivers/clk/renesas/rcar-cpg-lib.c
> +++ b/drivers/clk/renesas/rcar-cpg-lib.c
> @@ -59,7 +59,9 @@ void cpg_simple_notifier_register(struct raw_notifier_head *notifiers,
>                                   struct cpg_simple_notifier *csn)
>  {
>         csn->nb.notifier_call = cpg_simple_notifier_call;
> -       raw_notifier_chain_register(notifiers, &csn->nb);
> +
> +       if (raw_notifier_chain_register(notifiers, &csn->nb))
> +               pr_warn("CPG notifier already registered\n");

A duplicate registration cannot happen, as the notifier is freshly allocated.

>  }
>

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds