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References: <20230302195618.156940-1-john.ogness@linutronix.de> <20230302195618.156940-2-john.ogness@linutronix.de>
In-Reply-To: <20230302195618.156940-2-john.ogness@linutronix.de>
From:   Doug Anderson <dianders@chromium.org>
Date:   Tue, 7 Mar 2023 08:34:08 -0800
Message-ID: <CAD=FV=V1akD6NpV=XePGRiyKs0z-esjMYpBkE4-TZfq__x2m_w@mail.gmail.com>
Subject: Re: [PATCH printk v1 01/18] kdb: do not assume write() callback available
To:     John Ogness <john.ogness@linutronix.de>
Cc:     Petr Mladek <pmladek@suse.com>,
        Sergey Senozhatsky <senozhatsky@chromium.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        linux-kernel@vger.kernel.org,
        Jason Wessel <jason.wessel@windriver.com>,
        Daniel Thompson <daniel.thompson@linaro.org>,
        Aaron Tomlin <atomlin@redhat.com>,
        Luis Chamberlain <mcgrof@kernel.org>,
        kgdb-bugreport@lists.sourceforge.net
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Hi,

On Thu, Mar 2, 2023 at 11:57=E2=80=AFAM John Ogness <john.ogness@linutronix=
.de> wrote:
>
> It is allowed for consoles to provide no write() callback. For
> example ttynull does this.
>
> Check if a write() callback is available before using it.
>
> Signed-off-by: John Ogness <john.ogness@linutronix.de>
> ---
>  kernel/debug/kdb/kdb_io.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/kernel/debug/kdb/kdb_io.c b/kernel/debug/kdb/kdb_io.c
> index 5c7e9ba7cd6b..e9139dfc1f0a 100644
> --- a/kernel/debug/kdb/kdb_io.c
> +++ b/kernel/debug/kdb/kdb_io.c
> @@ -576,6 +576,8 @@ static void kdb_msg_write(const char *msg, int msg_le=
n)
>                         continue;
>                 if (c =3D=3D dbg_io_ops->cons)
>                         continue;
> +               if (!c->write)
> +                       continue;

Reviewed-by: Douglas Anderson <dianders@chromium.org>