From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262373AbVBBQMk (ORCPT ); Wed, 2 Feb 2005 11:12:40 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262329AbVBBQMj (ORCPT ); Wed, 2 Feb 2005 11:12:39 -0500 Received: from mail.joq.us ([67.65.12.105]:44264 "EHLO sulphur.joq.us") by vger.kernel.org with ESMTP id S262561AbVBBP7V (ORCPT ); Wed, 2 Feb 2005 10:59:21 -0500 To: Ingo Molnar Cc: linux Subject: Re: [patch, 2.6.11-rc2] sched: RLIMIT_RT_CPU_RATIO feature References: <20050125135613.GA18650@elte.hu> <87sm4opxto.fsf@sulphur.joq.us> <20050126070404.GA27280@elte.hu> <87fz0neshg.fsf@sulphur.joq.us> <1106782165.5158.15.camel@npiggin-nld.site> <874qh3bo1u.fsf@sulphur.joq.us> <1106796360.5158.39.camel@npiggin-nld.site> <87pszr1mi1.fsf@sulphur.joq.us> <20050127113530.GA30422@elte.hu> <873bwfo8br.fsf@sulphur.joq.us> <20050202113705.GA25012@elte.hu> From: "Jack O'Quin" Date: Wed, 02 Feb 2005 10:01:20 -0600 In-Reply-To: <20050202113705.GA25012@elte.hu> (Ingo Molnar's message of "Wed, 2 Feb 2005 12:37:05 +0100") Message-ID: <874qgvj6i7.fsf@sulphur.joq.us> User-Agent: Gnus/5.1006 (Gnus v5.10.6) XEmacs/21.4 (Corporate Culture, linux) 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 [trimming the Cc: list] > * Jack O'Quin wrote: >> Remember when I asked how you handle changes to sizeof(struct rusage)? >> That was a serious question. I hope there's a solution. [...] Ingo Molnar writes: > what does any of what we've talking about have to do with struct rusage? Your previous message implied that "userspace" programmers don't understand binary compatibility... > you might ask yourself, 'why is this so, and why cannot the Linux guys > apply pretty much any hack as e.g. userspace code might' I was just demonstating that I do. > " > Does getrusage() return anything for this? How can a field be added > > to the rusage struct without breaking binary compatibility? Can we > > assume that no programs ever use sizeof(struct rusage)? > > rlimits are easily extended and there are no binary compatibility > worries. The kernel doesnt export the maximum towards userspace. > getrusage() will return the value on new kernels and will return > -EINVAL on old kernels, so new userspace can deal with this > accordingly. " > > (and here i meant getrlimit(), not getrusage() - getrusage() is not > affected by the patch at all.) Well, that was source of my question. I had asked about rusage. You said it did return a new value, but that this was not a problem. That made no sense to me. Thank you for clearing it up. Certainly getrlimit() works OK. I understood that already. -- joq