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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: <98eec651-d1ab-48e5-309b-7e748981cfdd@i-love.sakura.ne.jp>
Date:   Thu, 3 Jan 2019 07:57:00 -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 3, 2019, at 3:32 AM, Tetsuo Handa =
<penguin-kernel@i-love.sakura.ne.jp> wrote:
>=20
> On 2019/01/03 18:09, Jiri Slaby wrote:
>> On 02. 01. 19, 16:04, Tetsuo Handa wrote:
>>> +	if (wait_event_interruptible(tty->read_wait,
>>> +	     (ret =3D -EIO, test_bit(TTY_OTHER_CLOSED, &tty->flags)) ||
>>> +	     (ret =3D 0, tty_hung_up_p(file)) ||
>>> +	     (rbuf =3D n_hdlc_buf_get(&n_hdlc->rx_buf_list)) !=3D NULL =
||
>>> +	     (ret =3D -EAGAIN, tty_io_nonblock(tty, file))))
>>> +		return -EINTR;
>>=20
>> Oh, that looks really ugly. Could you move all this to a function
>> returning a bool and taking &ret and &rbuf as parameters?
>>=20
>=20
> OK. Something like this?


I agree with Jiri that placing all the conditional logic in a single =
expression is difficult to read.

But exchanging that many locals with a separate function defeats the =
original purpose of
simplifying code and this implementation changes the logic (write no
longer checks for line discipline changing under it during wait).

Converting to wait_event_interruptible where possible is a good goal but =
this instance
may be better left alone. The current structure mirrors the existing =
n_tty line discipline.