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Message-ID: <5113C0D8.60107@suse.cz>
Date: Thu, 07 Feb 2013 15:57:28 +0100
From: Jiri Slaby <jslaby@suse.cz>
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To: Peter Hurley <peter@hurleysoftware.com>
CC: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Alan Cox <alan@linux.intel.com>, Sasha Levin <levinsasha928@gmail.com>,
        Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
        linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org,
        Ilya Zykov <ilya@ilyx.ru>, Dave Jones <davej@redhat.com>
Subject: Re: [PATCH v3 03/23] n_tty: Don't flush buffer when closing ldisc
References: <1355509370-5883-1-git-send-email-peter@hurleysoftware.com> <1360095638-6624-1-git-send-email-peter@hurleysoftware.com> <1360095638-6624-4-git-send-email-peter@hurleysoftware.com>
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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