linux-kernel - Re: [RFC] tty: Always allow tcflow(TCOON) to unwedge terminal

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Date:	Wed, 10 Sep 2014 17:03:43 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	Peter Hurley <peter@...leysoftware.com>
Cc:	Jiri Slaby <jslaby@...e.cz>,
	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>,
	linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC] tty: Always allow tcflow(TCOON) to unwedge terminal

On Wed, Sep 10, 2014 at 05:28:19PM -0400, Peter Hurley wrote:
> This patch changes user-space behavior (for the better) but I'm not sure
> that it's consequence-free. Also, it might not be enough to unwedge the
> terminal if the driver got its own flow control state mangled.
> 
> Thoughts?
> 
> --- >% ---
> Subject: [RFC] tty: Always allow tcflow(TCOON) to unwedge terminal
> 
> If terminal flow has been stopped, the terminal can be unwedged
> by:
> 	tcflow(fd, TCOOFF);
> 	tcflow(fd, TCOON);
> This works because tcflow(TCOOFF) ensures that ->flow_stopped is set,
> which allows tcflow(TCOON) to override the terminal flow state in
> __start_tty().
> 
> Instead, allow unwedging with only:
>         tcflow(fd, TCOON);
> by disregarding the existing ->flow_stopped state.

I don't see the benifit here, what are you trying to solve?  Sending one
extra tcflow command?

thanks,

greg k-h
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