From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Thu, 11 Jan 2001 09:18:55 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Thu, 11 Jan 2001 09:18:37 -0500 Received: from zeus.kernel.org ([209.10.41.242]:54738 "EHLO zeus.kernel.org") by vger.kernel.org with ESMTP id ; Thu, 11 Jan 2001 09:18:25 -0500 Date: Thu, 11 Jan 2001 14:13:30 +0000 From: "Stephen C. Tweedie" To: Trond Myklebust Cc: "Stephen C. Tweedie" , Linus Torvalds , Alan Cox , Andi Kleen , Daniel Phillips , linux-kernel@vger.kernel.org Subject: Re: Subtle MM bug Message-ID: <20010111141330.H25375@redhat.com> In-Reply-To: <20010111125604.A17177@redhat.com> <14941.45349.131276.684932@charged.uio.no> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2i In-Reply-To: <14941.45349.131276.684932@charged.uio.no>; from trond.myklebust@fys.uio.no on Thu, Jan 11, 2001 at 02:12:05PM +0100 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Hi, On Thu, Jan 11, 2001 at 02:12:05PM +0100, Trond Myklebust wrote: > > What's wrong with copy-on-write style semantics? IOW, anyone who > wants to change the credentials needs to make a private copy of the > existing structure first. Because COW only solves the problem if each task is only changing its own, local, private copy of the credentials. Posix threads demand that one thread changing credentials also affects all the other threads immediately, and making your own local private copy won't help you to change the other tasks' credentials safely. --Stephen - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org Please read the FAQ at http://www.tux.org/lkml/