From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262599AbVCDHw7 (ORCPT ); Fri, 4 Mar 2005 02:52:59 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262615AbVCDHw7 (ORCPT ); Fri, 4 Mar 2005 02:52:59 -0500 Received: from mx1.redhat.com ([66.187.233.31]:34536 "EHLO mx1.redhat.com") by vger.kernel.org with ESMTP id S262599AbVCDHw5 (ORCPT ); Fri, 4 Mar 2005 02:52:57 -0500 Date: Thu, 3 Mar 2005 23:52:52 -0800 From: Pete Zaitcev To: Duncan Sands Cc: marcelo.tosatti@cyclades.com, linux-kernel@vger.kernel.org Subject: Re: USB 2.4.30: fix modem_run Message-ID: <20050303235252.6b0dc51b@localhost.localdomain> In-Reply-To: <1108116980.7400.0.camel@localhost.localdomain> References: <20050210161144.708cb96f@localhost.localdomain> <1108116980.7400.0.camel@localhost.localdomain> X-Mailer: Sylpheed-Claws 1.0.1cvs20.1 (GTK+ 2.4.14; i386-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 11 Feb 2005 11:16:20 +0100 Duncan Sands wrote: > On Thu, 2005-02-10 at 16:11 -0800, Pete Zaitcev wrote: > > I entered a patch which adds "exclusive_access" lock into 2.4.29, > > to fix devices which cannot handle simultaneous accesses. This > > caused a regression with European ADSL modems. An ioctl > > USBDEVFS_REAPURB allows a process to enter the kernel and wait for > > USB I/O to finish. Naturally, this should not take > > exclusive_access, or nothing will ever finish. > > How does this compare with the locking in 2.6 kernels? In 2.6, there is no locking whatsoever. Instead, rules for queueing are relaxed for all HCs. If the device chokes when it receives a control together with a data exchange (on a bulk endpoint, usually), kernel does not interfere. Users (libusb & drivers) are supposed to know when not to do it. Obviously, it's not the case of usb-storage. To help that, descriptor strings are cached in latest Greg's trees, since a week ago or so. This way at least "cat /proc/bus/usb/devices" won't interfere. -- Pete