From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S264043AbUDQUdK (ORCPT ); Sat, 17 Apr 2004 16:33:10 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S264045AbUDQUdK (ORCPT ); Sat, 17 Apr 2004 16:33:10 -0400 Received: from mail1.kontent.de ([81.88.34.36]:32651 "EHLO Mail1.KONTENT.De") by vger.kernel.org with ESMTP id S264043AbUDQUdH (ORCPT ); Sat, 17 Apr 2004 16:33:07 -0400 From: Oliver Neukum To: Duncan Sands , Greg KH Subject: Re: [linux-usb-devel] [PATCH 1/9] USB usbfs: take a reference to the usb device Date: Sat, 17 Apr 2004 22:33:03 +0200 User-Agent: KMail/1.5.1 Cc: linux-usb-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org, Frederic Detienne References: <200404141229.26677.baldrick@free.fr> <200404172217.10994.baldrick@free.fr> In-Reply-To: <200404172217.10994.baldrick@free.fr> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-15" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200404172233.03552.oliver@neukum.org> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org > riddled with races of this kind. The simplest solution is to > systematically take ps->dev->serialize when entering the usbfs routines, > which is what my patches do. This should be regarded as a first step: it What is the alternative? > gives correctness, but at the cost of a probable performance hit. In later > steps we can (1) turn dev->serialize into a rwsem Rwsems are _slower_ in the normal case of no contention. > (2) push the acquisition of dev->serialize down to the lower levels as they > are fixed up. Why? Regards Oliver