linux-kernel - Re: [PATCH tty-next 0/4] tty: Fix ^C echo

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Message-ID: <52A5C354.5050600@hurleysoftware.com>
Date:	Mon, 09 Dec 2013 08:19:16 -0500
From:	Peter Hurley <peter@...leysoftware.com>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Karl Dahlke <eklhad@...cast.net>
CC:	Jiri Slaby <jslaby@...e.cz>,
	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>,
	linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org
Subject: Re: [PATCH tty-next 0/4] tty: Fix ^C echo

On 12/08/2013 08:12 PM, Greg Kroah-Hartman wrote:
> On Mon, Dec 02, 2013 at 04:12:01PM -0500, Peter Hurley wrote:
>> Greg,
>>
>> Sometimes when interrupting terminal output, the '^C' won't be echoed
>> until more output is echoed. This is fairly repeatable by interrupting
>> 'cat large-file'.
>>
>> The common reason for this is because the tty write buffer is full,
>> even though the write buffer _should_ have been flushed already.
>> Because of a known deadlock, the pty driver does not perform a
>> write buffer flush in its flush_buffer() method.
>>
>> [Refer to the FIXME in pty_flush_buffer() from commit
>> d945cb9cce20ac7143c2de8d88b187f62db99bdc,
>> 'pty: Rework the pty layer to use the normal buffering logic']
>>
>> Patch 1 fixes a stale comment.
>> Patch 2 adds the necessary interfaces to avoid direct linkage
>> between the N_TTY line discipline and the pty driver.
>> Patch 3 avoids the deadlock while performing the write buffer flush.
>> Patch 4 fixes a less common condition introduced by the echo batch
>> processing added in 3.12.
>>
>> Alan,
>>
>> I cc'd you because of your recent involvement in other
>> tty patches/bug fixes and because it's your FIXME comment.
>> Feel free to ignore and/or let me know you would prefer not to
>> be bothered.
>
> Peter, this series doesn't fix the ^C echo problem that Karl recently
> reported, so I'll hold off in applying it for now.

Yeah, please discard this. It does fix some problems but I don't really
like how it goes about fixing them. I've been exploring some ideas
based on my discussion with Alan but nothing fruitful yet.

Regards,
Peter Hurley

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