Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758472AbXKDOGT (ORCPT ); Sun, 4 Nov 2007 09:06:19 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753627AbXKDOGJ (ORCPT ); Sun, 4 Nov 2007 09:06:09 -0500 Received: from 1wt.eu ([62.212.114.60]:3681 "EHLO 1wt.eu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753825AbXKDOGI (ORCPT ); Sun, 4 Nov 2007 09:06:08 -0500 Date: Sun, 4 Nov 2007 15:05:52 +0100 From: Willy Tarreau To: vitalivanov@gmail.com Cc: Pete Zaitcev , linux-usb-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org Subject: Re: [2.4 patch] Port of adutux driver from 2.6 kernel to 2.4. Message-ID: <20071104140552.GA25915@1wt.eu> References: <35fbaa3e0710141345w484b941em831282cf0d49b5c@mail.gmail.com> <20071014223921.GA4677@1wt.eu> <1192542889.29039.66.camel@dell1.softservecom.com> <20071016154138.GA23326@1wt.eu> <1192559051.29039.139.camel@dell1.softservecom.com> <1192644776.10761.60.camel@dell1.softservecom.com> <35fbaa3e0710190826uae4e7b7u7d8f3139e1697030@mail.gmail.com> <20071019095313.76990765.zaitcev@redhat.com> <1192815634.7965.53.camel@dell1.softservecom.com> <20071022204539.d3e1d291.zaitcev@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20071022204539.d3e1d291.zaitcev@redhat.com> User-Agent: Mutt/1.5.11 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1687 Lines: 39 On Mon, Oct 22, 2007 at 08:45:39PM -0700, Pete Zaitcev wrote: > On Fri, 19 Oct 2007 20:40:35 +0300, Vitaliy Ivanov wrote: > > Hi, Vitaly, I added you on cc: for the 2.6 cleanup. Please double-check > what I'm doing there and use it for your 2.4 version. I hope my intentions > get clearer with an example. Now, about the specific question: > > > Static lock minor_table_mutex is used for minor table structure. > > And dev->sem for dev manipulations and that's why for open_count. > > If you will simply browse /drivers/usb dir for 2.4 you will see that > > such approach is widely used there. > > What's not right? > > The fundamental reason why you cannot lock a free-able structure with > an in-structure lock is this. Imagine thread A locks in order to process > a disconnect. Thread B wants to open and waits for the lock. Notice that > the struct is not open, so thread A frees it. At this point, thread B > is using a freed memory. > > The solution is to lock the instance struct dev with dev->mtx, except > for the open count, which is locked by a static lock (I'm ignoring > interrupts here, which cannot use mutexes). > > I'm sorry to say, you're quite right: a number of drivers in 2.4 got > it wrong, and some (like adutux) carried it through 2.6.23. Vitaly, I'm planning on issuing a new 2.4.36 prerelease soon. Have you made any progress on your code after Pete's recommendations ? Thanks, Willy - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/