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Subject: Re: [PATCH] tty/n_hdlc: fix sleep in !TASK_RUNNING state warning
From:   Paul Fulghum <paulkf@microgate.com>
In-Reply-To: <0a70193b-488a-7607-4ad5-05ec6018587e@i-love.sakura.ne.jp>
Date:   Fri, 4 Jan 2019 05:57:37 -0800
Cc:     Jiri Slaby <jslaby@suse.cz>, Arnd Bergmann <arnd@arndb.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Alan Cox <alan@lxorguk.ukuu.org.uk>,
        linux-kernel@vger.kernel.org
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To:     Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
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> On Jan 4, 2019, at 2:23 AM, Tetsuo Handa =
<penguin-kernel@I-love.SAKURA.ne.jp> wrote:
>=20
> But why not to clarify what are appropriate sanity checks?
> ...
> want a cleanup for scripts/checkpatch.pl .


These are good goals. I avoid purely cosmetic patches. I do not object =
to cosmetic patches from others that do not change behavior.

The checks that concern you deal with changing tty line disciplines. =
Dealing with line discipline changes has been an ongoing issue since =
n_hdlc was derived from other line disciplines 20 years ago, with major =
overhauls along the way. It is complex: driver layers shifting during =
operation while dealing properly with opens, closes, hangups, and =
sleeping operations. Patches have been added to the latest unreleased =
kernel to address line discipline changes, it is still evolving.

Why are the existing line discipline checks in n_hdlc where they are? =
Becasue that=E2=80=99s how they evolved from where they started to =
accomodate these changes. There are not many and their function is =
known: has the line discipline changed at that point? I know that is not =
satisfying but coming up with a definitive comment saying a check is =
absolutely required in one place and not in another requires more =
insight into the long history of a moving target than I have. Without =
that insight I would not alter existing checks in code that is not =
causing problems.=