From: Paul Fulghum <paulkf@microgate.com>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH][RFC] kill TTY_DONT_FLIP
Date: Fri, 23 Jun 2006 08:41:20 -0500 [thread overview]
Message-ID: <449BEF80.2080301@microgate.com> (raw)
In-Reply-To: <1151069137.4549.11.camel@localhost.localdomain>
Alan Cox wrote:
> Looks good to me on a first review.
I looked at the paths taken by n_tty_receive_buf()
for how they would effect read_chan():
* tty state (put_tty_queue,eraser,finish_erasing,etc)
* read wakeups
* start_tty/stop_tty
* put_char/opost
everything looks OK without TTY_DONT_FLIP
2.0.X relied on the BKL (and dinosaurs roamed the Earth)
2.1.X introduced TTY_DONT_FLIP to prevent read_chan and
n_tty_receive_buf from executing at the same time.
2.2.15 added tty->read_lock around the N_TTY read buffer,
which is the only thing needing protection in this context.
The usual progression to finer grained locking.
This looks like a safe removal.
The review also revealed a spot in reset_buffer_flags()
where tty->read_lock needs to be extended around
modifications of canon_head, canon_data, and read_flags.
I'll make a patch for that.
--
Paul Fulghum
Microgate Systems, Ltd.
prev parent reply other threads:[~2006-06-23 13:58 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-06-22 19:02 [PATCH][RFC] kill TTY_DONT_FLIP Paul Fulghum
2006-06-23 13:25 ` Alan Cox
2006-06-23 13:41 ` Paul Fulghum [this message]
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