Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Sat, 10 Nov 2001 15:49:36 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Sat, 10 Nov 2001 15:49:26 -0500 Received: from [216.151.155.121] ([216.151.155.121]:23813 "EHLO belphigor.mcnaught.org") by vger.kernel.org with ESMTP id ; Sat, 10 Nov 2001 15:49:16 -0500 To: Riley Williams Cc: Pavel Machek , Linux Kernel Subject: Re: PROBLEM: Linux updates RTC secretly when clock synchronizes In-Reply-To: From: Doug McNaught Date: 10 Nov 2001 15:49:01 -0500 In-Reply-To: Riley Williams's message of "Sat, 10 Nov 2001 20:35:34 +0000 (GMT)" Message-ID: Lines: 27 User-Agent: Gnus/5.0806 (Gnus v5.8.6) XEmacs/21.1 (20 Minutes to Nikko) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Riley Williams writes: > Hi Pavel. > > > It ... just is not that way. Kernel + modules run at ring 0, > > userland at ring 3. > > I know that much. I was just curious whether there was any particular > reason why it was that way. Well, Unix has historically run on systems with at most two processor privilege levels, "user" and "supervisor"; ie, you're either in user or kernel mode. ix86 is one of the few Linux platforms that offers more than two levels, so having modules run in an in-between level would be a portability headache as well as a lot of work. Certainly not impossible, but you'd need to create task gates or whatever they're called at every point where modules called into the kernel (and vice versa as well I think). Might be a serious performance hit... -Doug -- Let us cross over the river, and rest under the shade of the trees. --T. J. Jackson, 1863 - 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/