linux-kernel - Re: [PATCH v3 12/23] tty: Kick waiters _after

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Message-ID: <5113CCAF.8030600@suse.cz>
Date:	Thu, 07 Feb 2013 16:47:59 +0100
From:	Jiri Slaby <jslaby@...e.cz>
To:	Peter Hurley <peter@...leysoftware.com>
CC:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Alan Cox <alan@...ux.intel.com>,
	Sasha Levin <levinsasha928@...il.com>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org,
	Ilya Zykov <ilya@...x.ru>, Dave Jones <davej@...hat.com>
Subject: Re: [PATCH v3 12/23] tty: Kick waiters _after_ the ldisc is locked

On 02/05/2013 09:20 PM, Peter Hurley wrote:

The question is obvious: why?

The waiters usually don't care about ldisc.

> Signed-off-by: Peter Hurley <peter@...leysoftware.com>
> ---
>  drivers/tty/tty_ldisc.c | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/tty/tty_ldisc.c b/drivers/tty/tty_ldisc.c
> index c903778..8a86a72 100644
> --- a/drivers/tty/tty_ldisc.c
> +++ b/drivers/tty/tty_ldisc.c
> @@ -604,6 +604,12 @@ static bool tty_ldisc_hangup_halt(struct tty_struct *tty)
>  
>  	clear_bit(TTY_LDISC, &tty->flags);
>  
> +	/* Wakeup waiters so they can discover the tty is hupping, abort
> +	 * their i/o loops, and release their ldisc references
> +	 */
> +	wake_up_interruptible_poll(&tty->write_wait, POLLOUT);
> +	wake_up_interruptible_poll(&tty->read_wait, POLLIN);
> +
>  	if (tty->ldisc) {	/* Not yet closed */
>  		tty_unlock(tty);
>  
> @@ -875,12 +881,6 @@ void tty_ldisc_hangup(struct tty_struct *tty)
>  		tty_ldisc_deref(ld);
>  	}
>  	/*
> -	 * FIXME: Once we trust the LDISC code better we can wait here for
> -	 * ldisc completion and fix the driver call race
> -	 */
> -	wake_up_interruptible_poll(&tty->write_wait, POLLOUT);
> -	wake_up_interruptible_poll(&tty->read_wait, POLLIN);
> -	/*
>  	 * Shutdown the current line discipline, and reset it to
>  	 * N_TTY if need be.
>  	 *
> 


-- 
js
suse labs
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