From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756013Ab0EKPvN (ORCPT ); Tue, 11 May 2010 11:51:13 -0400 Received: from kroah.org ([198.145.64.141]:55784 "EHLO coco.kroah.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755753Ab0EKPvI (ORCPT ); Tue, 11 May 2010 11:51:08 -0400 Date: Tue, 11 May 2010 08:20:02 -0700 From: Greg KH To: KOSAKI Motohiro Cc: Rusty Russell , Arnd Bergmann , linux-kernel@vger.kernel.org, Ken Werner , Andi Kleen , stable@kernel.org Subject: Re: [stable] cpumask: fix compat getaffinity Message-ID: <20100511152002.GB16561@kroah.com> References: <20100511104334.E572.A69D9226@jp.fujitsu.com> <20100511031354.GA9327@kroah.com> <20100511151526.E578.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20100511151526.E578.A69D9226@jp.fujitsu.com> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, May 11, 2010 at 03:20:45PM +0900, KOSAKI Motohiro wrote: > > On Tue, May 11, 2010 at 10:47:03AM +0900, KOSAKI Motohiro wrote: > > > > How's this? > > > > > > > > cpumask: use nr_cpu_ids for printing and parsing cpumasks > > > > > > > > Commit a45185d2d "cpumask: convert kernel/compat.c" broke > > > > libnuma, which abuses sched_getaffinity to find out NR_CPUS > > > > in order to parse /sys/devices/system/node/node*/cpumap. > > > > > > > > However, the result now returned reflects nr_cpu_ids, and > > > > cpumask_scnprintf et al. use nr_cpumask_bits which is NR_CPUS (for > > > > CONFIG_CPUMASK_OFFSTACK=n) or nr_cpu_ids (for > > > > CONFIG_CPUMASK_OFFSTACK=y). > > > > > > > > We should use nr_cpu_ids consistently. > > > > > > > > Reported-by: Arnd Bergmann > > > > Signed-off-by: Rusty Russell > > > > Cc: stable@kernel.org > > > > > > Well, This patch seems to have ABI change. please don't send abi-change to -stable. > > > > Why? There is no such thing as a "stable" internal abi in the kernel, > > and that includes the -stable kernel releases. > > > > If it fixes a bug, that's all the requirement is. > > AFAIK, -stable is mainly used for distro and they have many and many > packages. we can't assume no app read /sys files directly. > IOW, To change /sys printing format is a bit risky change. frequently > compatibility breaking natually break code stability. Ah, the sysfs user/kernel API is what you are referring to here, right? If so, remember, any changes need to be documented in Documentation/API :) And as for distros using -stable for their releases, that's fine, they well know the risks/benefits for that and handle changes on their own. thanks, greg k-h