linux-kernel - Re: [PATCH 07/10] TTY: switch tty_schedule

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Date:	Fri, 01 Feb 2013 07:37:27 -0500
From:	Peter Hurley <peter@...leysoftware.com>
To:	Jiri Slaby <jslaby@...e.cz>
Cc:	gregkh@...uxfoundation.org, alan@...ux.intel.com,
	jirislaby@...il.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 07/10] TTY: switch tty_schedule_flip

On Thu, 2013-01-03 at 15:53 +0100, Jiri Slaby wrote:
> Now, we start converting tty buffer functions to actually use
> tty_port. This will allow us to get rid of the need of tty in many
> call sites. Only tty_port will needed and hence no more
> tty_port_tty_get in those paths.
> 
> This is the last one: tty_schedule_flip

[snip]

> diff --git a/drivers/tty/vt/keyboard.c b/drivers/tty/vt/keyboard.c
> index 5aace4d..a9af1b9a 100644
> --- a/drivers/tty/vt/keyboard.c
> +++ b/drivers/tty/vt/keyboard.c
> @@ -307,26 +307,17 @@ int kbd_rate(struct kbd_repeat *rep)
>   */
>  static void put_queue(struct vc_data *vc, int ch)
>  {
> -	struct tty_struct *tty = vc->port.tty;
> -
>  	tty_insert_flip_char(&vc->port, ch, 0);
> -	if (tty) {
> -		tty_schedule_flip(tty);
> -	}
> +	tty_schedule_flip(&vc->port);
>  }
>  
>  static void puts_queue(struct vc_data *vc, char *cp)
>  {
> -	struct tty_struct *tty = vc->port.tty;
> -
> -	if (!tty)
> -		return;
> -
>  	while (*cp) {
>  		tty_insert_flip_char(&vc->port, *cp, 0);
>  		cp++;
>  	}
> -	tty_schedule_flip(tty);
> +	tty_schedule_flip(&vc->port);
>  }

Umm. So even though the vt driver knows the tty has been shutdown,
keystrokes will still be buffered? And then fed to whichever tty happens
to next get installed on the same port?

Pretty much renders this meaningless:

static void flush_to_ldisc(struct work_struct *work)
{
....
+	if (WARN_RATELIMIT(tty == NULL, "tty is NULL"))
+		return;

Regards,
Peter Hurley

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