From: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
To: Paul Fulghum <paulkf@microgate.com>
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
Subject: Re: [PATCH] tty/n_hdlc: fix sleep in !TASK_RUNNING state warning
Date: Fri, 4 Jan 2019 19:23:14 +0900 [thread overview]
Message-ID: <0a70193b-488a-7607-4ad5-05ec6018587e@i-love.sakura.ne.jp> (raw)
In-Reply-To: <434841F9-C2DF-4D73-9AFB-3BFADF325086@microgate.com>
On 2019/01/04 0:57, Paul Fulghum wrote:
>> On Jan 3, 2019, at 3:32 AM, Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp> wrote:
>>
>> 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 = -EIO, test_bit(TTY_OTHER_CLOSED, &tty->flags)) ||
>>>> + (ret = 0, tty_hung_up_p(file)) ||
>>>> + (rbuf = n_hdlc_buf_get(&n_hdlc->rx_buf_list)) != NULL ||
>>>> + (ret = -EAGAIN, tty_io_nonblock(tty, file))))
>>>> + return -EINTR;
>>>
>>> Oh, that looks really ugly. Could you move all this to a function
>>> returning a bool and taking &ret and &rbuf as parameters?
>>>
>>
>> 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).
Not only defeating the original purpose but also increasing object size.
>
> 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.
But why not to clarify what are appropriate sanity checks?
Currently, read side does not check "n_hdlc->magic != HDLC_MAGIC" case
while write side does. If it is intended for catching memory corruption
etc. then both sides should do the same thing.
Currently, write side does not check "tty != n_hdlc->tty" case before
schedule() while does after schedule(). If "tty != n_hdlc->tty" case
can ever happen, what prevents n_hdlc_tty_write() from being called again
after n_hdlc_tty_write() once returned with -EIO due to "tty != n_hdlc->tty"
case? If it is intended for catching memory corruption etc. then both
sides should check "tty != n_hdlc->tty" case.
Current logic is unclear, in addition to want a cleanup for scripts/checkpatch.pl .
total: 158 errors, 95 warnings, 994 lines checked
next prev parent reply other threads:[~2019-01-04 10:23 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-29 0:41 WARNING in __might_sleep (2) syzbot
2018-12-29 11:48 ` [PATCH] tty/n_hdlc: fix sleep in !TASK_RUNNING state warning Tetsuo Handa
2019-01-01 3:13 ` Paul Fulghum
2019-01-01 20:28 ` [PATCH] tty/n_hdlc: fix __might_sleep warning Paul Fulghum
2019-01-10 11:38 ` Tetsuo Handa
2019-01-10 12:25 ` Arnd Bergmann
[not found] ` <FEBFE826-8D27-4A0B-86A5-BA559921CADC@microgate.com>
2019-01-02 15:04 ` [PATCH] tty/n_hdlc: fix sleep in !TASK_RUNNING state warning Tetsuo Handa
2019-01-02 20:55 ` Paul Fulghum
2019-01-03 9:09 ` Jiri Slaby
2019-01-03 11:32 ` Tetsuo Handa
2019-01-03 15:57 ` Paul Fulghum
2019-01-04 10:23 ` Tetsuo Handa [this message]
2019-01-04 13:57 ` Paul Fulghum
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