linux-kernel - Re: [PATCH] ttyprintk: Add TTY hangup callback.

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Message-ID: <33461bad-ef57-9036-135d-95a60a8c88d5@i-love.sakura.ne.jp>
Date:   Fri, 23 Apr 2021 19:12:15 +0900
From:   Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
To:     Samo Pogačnik <samo_pogacnik@....net>,
        Jiri Slaby <jirislaby@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        John Ogness <john.ogness@...utronix.de>,
        linux-kernel@...r.kernel.org,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>
Subject: Re: [PATCH] ttyprintk: Add TTY hangup callback.

On 2021/04/23 18:55, Samo Pogačnik wrote:
>>> Using the supplied test code, i've tested the patch on my desktop running
>>> the
>>> 5.4 kernel. After applying the patch, the kernel warnings like "ttyprintk:
>>> tty_port_close_start: tty->count = 1 port count = 11" do not appear any
>>> more,
>>> when the test code is run.
>>> I think the patch is ok.
>>
>> I wonder if the buffer shouldn't be flushed in hangup too? Or better, 
>> the flush moved from tty_ops->close to tty_port->ops->shutdown?
>>
>> thanks,
> 
> Good point. I tried the following additional change, which seems to do the
> trick. What do you think?
> 

Shouldn't the tpk_printk buffer be per a "struct file" (i.e. allocated upon
open() and released upon close() in order to allow multiple users) ?