From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757389Ab2EGQju (ORCPT ); Mon, 7 May 2012 12:39:50 -0400 Received: from lxorguk.ukuu.org.uk ([81.2.110.251]:33612 "EHLO lxorguk.ukuu.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756659Ab2EGQjt (ORCPT ); Mon, 7 May 2012 12:39:49 -0400 Date: Mon, 7 May 2012 17:42:40 +0100 From: Alan Cox To: Sasha Levin Cc: linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org Subject: Re: [PATCH 3/3] tty_lock: Localise the lock Message-ID: <20120507174240.4209c5cb@pyramind.ukuu.org.uk> In-Reply-To: <1336408208.3638.15.camel@lappy> References: <20120503212151.568.91854.stgit@bob.linux.org.uk> <20120503212219.568.15653.stgit@bob.linux.org.uk> <20120507171126.5beddc27@pyramind.ukuu.org.uk> <1336408208.3638.15.camel@lappy> X-Mailer: Claws Mail 3.8.0 (GTK+ 2.24.8; x86_64-redhat-linux-gnu) Face: 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 Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 07 May 2012 18:30:08 +0200 Sasha Levin wrote: > On Mon, 2012-05-07 at 17:11 +0100, Alan Cox wrote: > > > I don't believe that this change is correct. > > > > > > Consider the following scenario: > > > > > > tty_release -> tty_lock -> pty_close -> tty_vhangup -> tty_lock > > > > We hang up tty->link not tty. > > > > It's now a per tty lock. So I think we are ok. > > Unless we can cause tty->link == tty, in which case: We should not be able to cause tty->link == tty. So that's a different problem altogether. tty->link is set to point to the other half of the pty in pty_install and in pty98_unix_install. It's never assigned to the same tty and ptys simply wouldn't work if this wasn't the case. So whatever your trace is showing, that's not the bug. Something more complicated would appear to be afoot. Alan