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

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Message-ID: <51376D6F.1070202@suse.cz>
Date:	Wed, 06 Mar 2013 17:23:11 +0100
From:	Jiri Slaby <jslaby@...e.cz>
To:	Peter Hurley <peter@...leysoftware.com>
CC:	jhovold@...il.com, 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 03/05/2013 11:32 PM, Peter Hurley wrote:
>>  So I'm thinking about
>> something like this:
>>
>> if (port->tty)
>>    set_bit(TTY_IO_ERROR, &port->tty->flags);
>> tty = port->tty; <=== take a snapshot
>> spin_unlock_irqrestore(&port->lock, flags);
>> tty_port_shutdown(port, tty); <=== use the snapshot
>> set_tty_port(port, NULL); <=== put kref on that tty
> 
> Yeah, that's better.

But still not correct. The tty can be invalid (freed) at the time
tty_port_shutdown is called. We should take a real reference inside the
lock and put the reference explicitly after the call.

-- 
js
suse labs
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