linux-kernel - Re: Bug in tty cooked mode kernel 3.12.3

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Message-ID: <20131217173052.GA15633@kroah.com>
Date:	Tue, 17 Dec 2013 09:30:52 -0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	Peter Hurley <peter@...leysoftware.com>
Cc:	Karl Dahlke <eklhad@...cast.net>, linux-kernel@...r.kernel.org,
	linux-serial@...r.kernel.org, stable@...r.kernel.org
Subject: Re: Bug in tty cooked mode kernel 3.12.3

On Mon, Dec 09, 2013 at 06:06:07PM -0500, Peter Hurley wrote:
> On 12/07/2013 06:46 PM, Karl Dahlke wrote:
> > This may have appeared in 3.9.11 with the changes to tty.
> > Don't know; I just started running 3.12 from kernel.org.
> > Perhaps nobody saw it before because nobody runs command line programs,
> > we're all on desktops or x or whatever,
> > and even those in the command line are still raw.
> > bash is raw by default, but I run it cooked.
> > You can supress its readline functions like this.
> > 
> > set +o emacs
> > set +o vi
> > set +o histexpand
> > set +o history
> > 
> > That puts its tty back into cooked mode.
> > 
> > Come up in run level 3, command line mode,
> > and bring up two consoles with bash in cooked mode as above.
> > Set a simple prompt like this.
> > 
> > PS1='$ '
> > 
> > Switch to console 2 via alt-f2.
> > Hit return.
> > The cursor should drop to a new line then give you the $ prompt.
> > But it puts the $ prompt next too the old one, then drops down
> > to a blank line.
> > The $ prompt and the crlf are out of sequence.
> > Hit return a few more times and it will straighten itself out.
> > Then switch back to console 1 alt-f1
> > Hit return and the same bug,
> > $ $
> > 
> > hit return a few more times to straighten it out.
> > Switch back to console 2 and the same problem.
> > For me it's repeatable.
> > 
> > It's also very confusing when I'm running other command line programs with cooked tty.
> > For unknown reasons the crlf can come out at the wrong time,
> > breaking lines or leaving lines together.
> > My editor can run either way, so I've switched it over to readline mode
> > and I haven't noticed any problems this way, yet.
> > But I would prefer the cooked mode.
> > 
> > I looked through MAINTAINERS but couldn't find
> > a clear maintainer for drivers/tty/tty*.c
> > Please forward this to the appropriate people.
> 
> Thanks for the report, Karl.
> 
> Please test the patch below (requires
> commit 39434abd942c8e4b9c14c06a03b3245beaf8467f,
> 'n_tty: Fix missing newline echo').
> This should fix the 'newline output after the new prompt' problem.
> 
> Note however that the other output order you observe is correct:
> you press enter, a newline is echoed to terminal which mixes
> with program output, the program ends, and the cooked mode
> shell outputs an extra prompt because it reads a newline (which
> the program did not read).
> 
> Regards,
> Peter Hurley
> 
> --- >% ---
> From: Peter Hurley <peter@...leysoftware.com>
> Subject: [PATCH] n_tty: Fix apparent order of echoed output
> 
> With block processing of echoed output, observed output order is still
> required. Push completed echoes and echo commands prior to output.
> 
> Introduce echo_mark echo buffer index, which tracks completed echo
> commands; ie., those submitted via commit_echoes but which may not
> have been committed. Ensure that completed echoes are output prior
> to subsequent terminal writes in process_echoes().
> 
> Fixes newline/prompt output order in cooked mode shell.
> 
> Cc: <stable@...r.kernel.org> # 3.12.x : 39434ab n_tty: Fix missing newline echo
> Reported-by: Karl Dahlke <eklhad@...cast.net>
> Reported-by: Mikulas Patocka <mpatocka@...hat.com>
> Signed-off-by: Peter Hurley <peter@...leysoftware.com>
> ---
>  drivers/tty/n_tty.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)

Do you want me to queue this up for 3.13-final, or have I already?

thanks,

greg k-h
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