Re: [PATCH 5/6] n_tty: Fix stuck write wakeup

From: Johannes Stezenbach <js@sig21.net>
To: Peter Hurley <peter@hurleysoftware.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Jiri Slaby <jslaby@suse.cz>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 5/6] n_tty: Fix stuck write wakeup
Date: Sun, 13 Dec 2015 20:27:40 +0100	[thread overview]
Message-ID: <20151213192740.GA17772@sig21.net> (raw)
In-Reply-To: <566DBB0A.5070108@hurleysoftware.com>

On Sun, Dec 13, 2015 at 10:38:02AM -0800, Peter Hurley wrote:
> On 12/13/2015 07:18 AM, Johannes Stezenbach wrote:
> > 
> > There is a related bug that I meant to send a patch, but I
> > never got around because the issue was found with proprietary
> > userspace and ancient kernel.  Maybe you could take care of it?
> > The patch might not apply cleanly after your recent changes
> > or might even be invalid now, please check.
> 
> Thanks for the patch, Johannes!
> 
> Yes, the patch below is still required to prevent excessive SIGIO
> (and to prevent missed SIGIO when the amount actually copied just
> happens to be exactly the amount left to be copied).
> 
> I made some comments in the patch; can you re-submit with those
> changes and the patch title in the subject? Or I'd happy to re-work
> it and send it to Greg if you'd prefer; just let me know.

Please rework it, currently I'm in lazy bum mode ;-)

> > @@ -1991,7 +1992,7 @@ static ssize_t n_tty_write(struct tty_st
> >  break_out:
> >         __set_current_state(TASK_RUNNING);
> >         remove_wait_queue(&tty->write_wait, &wait);
> > -       if (b - buf != nr && tty->fasync)
> > +       if (b - buf != count && tty->fasync)
> 
> ... this can be
> 
> 	if (nr && tty->fasync)
> 		set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);

Yeah, that's way better.

Thanks,
Johannes