From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261962AbTEHSBs (ORCPT ); Thu, 8 May 2003 14:01:48 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261936AbTEHSBs (ORCPT ); Thu, 8 May 2003 14:01:48 -0400 Received: from 34.mufa.noln.chcgil24.dsl.att.net ([12.100.181.34]:31736 "EHLO tabby.cats.internal") by vger.kernel.org with ESMTP id S261962AbTEHSBr (ORCPT ); Thu, 8 May 2003 14:01:47 -0400 Content-Type: text/plain; charset=US-ASCII From: Jesse Pollard To: Terje Malmedal , hch@infradead.org Subject: Re: The disappearing sys_call_table export. Date: Thu, 8 May 2003 13:13:49 -0500 X-Mailer: KMail [version 1.2] Cc: hch@infradead.org, alan@lxorguk.ukuu.org.uk, terje.eggestad@scali.com, arjanv@redhat.com, linux-kernel@vger.kernel.org, D.A.Fedorov@inp.nsk.su References: In-Reply-To: MIME-Version: 1.0 Message-Id: <03050813134901.09468@tabby> Content-Transfer-Encoding: 7BIT Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Thursday 08 May 2003 10:29, Terje Malmedal wrote: > [Christoph Hellwig] > > >> The only problem I can see is that different modules overloading the > >> same function needs to be unloaded in the correct order. Is this the > >> only reason for removing it, or am I missing something? > > > > it's racy - and it doesn't work on half of the arches added over the > > last years. > > Would you be so kind as to explain exactly what is racy? Just > asserting that it is does not help me understand anything. Look at this: [1]int init_module(void) [2]{ [3] orig_fsync=sys_call_table[SYS_fsync]; [4] sys_call_table[SYS_fsync]=hacked_fsync; [5] return 0; [6]} Unless there is a LOCK on sys_call_table[SYS_fsync] another CPU could replace the pointer between lines 3 and 4. At that point line 4 would destroy the existing entry.. or destroy it when the original is restored, and would NOT be restoring the one insterted.