linux-kernel - Re: [Fwd: [PATCH v2 0/4] TTY: port hangup and close fixes]

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Date:	Thu, 07 Mar 2013 16:52:23 -0500
From:	Peter Hurley <peter@...leysoftware.com>
To:	Johan Hovold <jhovold@...il.com>
Cc:	Jiri Slaby <jslaby@...e.cz>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Alan Stern <stern@...land.harvard.edu>,
	USB list <linux-usb@...r.kernel.org>,
	linux-serial@...r.kernel.org, Alan Cox <alan@...rguk.ukuu.org.uk>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [Fwd: [PATCH v2 0/4] TTY: port hangup and close fixes]

On Thu, 2013-03-07 at 10:43 +0100, Johan Hovold wrote:
> On Wed, Mar 06, 2013 at 02:14:56PM -0500, Peter Hurley wrote:
> > On Wed, 2013-03-06 at 17:52 +0100, Johan Hovold wrote:
> > > Yes, I did. First, the order should not matter for blocked opens as they
> > > will exit their wait loops based on tty_hung_up_p(filp) either way.
> > 
> > Only if the open() was ever successful, otherwise the filp won't be in
> > the tty->tty_files list. That's why the blocking opens also check
> > ASYNC_INITIALIZED (or ASYNCB_INITIALIZED depending on which they use).
> > Which is why I said it was actually better to shutdown() first, then
> > wake up the blocked opens.
> 
> ASYNC_INITIALIZED have also been cleared when the blocked opens are
> being woken up from tty_port_close_end.
> 
> And the filp is added to tty_files before open() is called:
> 
> ===>    tty_add_file(tty, filp);
> 
> 	check_tty_count(tty, __func__);
> 	if (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
> 	    tty->driver->subtype == PTY_TYPE_MASTER)
> 		noctty = 1;
> #ifdef TTY_DEBUG_HANGUP
> 	printk(KERN_DEBUG "%s: opening %s...\n", __func__, tty->name);
> #endif
> 	if (tty->ops->open)
> ===>		retval = tty->ops->open(tty, filp);
> 
> so a blocked open must have hung_up_tty_fops when woken up from hangup,
> right?

You're right, my mistake.

> Either way, postponing wake-up somewhat in tty_port_hangup should be
> fine.

Yep.

Regards,
Peter Hurley

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