linux-kernel - Re: [PATCH v3 03/23] n_tty: Don't flush buffer when closing ldisc

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Date:	Thu, 07 Feb 2013 15:57:28 +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 03/23] n_tty: Don't flush buffer when closing ldisc

On 02/05/2013 09:20 PM, Peter Hurley wrote:
> A buffer flush is both undesirable and unnecessary when the ldisc
> is closing. A buffer flush performs the following:
>  1. resets ldisc data fields to their initial state
>  2. resets tty->receive_room to indicate more data can be sent
>  3. schedules buffer work to receive more data
>  4. signals a buffer flush has happened to linked pty in packet mode
> 
> Since the ldisc has been halted and the tty may soon be destructed,
> buffer work must not be scheduled as that work might access
> an invalid tty and ldisc state. Also, the ldisc read buffer is about
> to be freed, so that's pointless.
> 
> Resetting the ldisc data fields is pointless as well since that
> structure is about to be freed.
> 
> Resetting tty->receive_room is unnecessary, as it will be properly
> reset if a new ldisc is reopened. Besides, resetting the original
> receive_room value would be wrong since the read buffer will be
> gone.
> 
> Since the packet mode flush is observable from userspace, this
> behavior has been preserved.

This one looks good to me.

-- 
js
suse labs
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