From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751975AbaETG5A (ORCPT ); Tue, 20 May 2014 02:57:00 -0400 Received: from mail-qg0-f49.google.com ([209.85.192.49]:40042 "EHLO mail-qg0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750771AbaETG46 (ORCPT ); Tue, 20 May 2014 02:56:58 -0400 MIME-Version: 1.0 Reply-To: mtk.manpages@gmail.com In-Reply-To: <20140519154639.5570a30f8b47872a323dcdfd@linux-foundation.org> References: <1400399917-17583-1-git-send-email-manfred@colorfullife.com> <1400399917-17583-2-git-send-email-manfred@colorfullife.com> <1400399917-17583-3-git-send-email-manfred@colorfullife.com> <1400399917-17583-4-git-send-email-manfred@colorfullife.com> <1400399917-17583-5-git-send-email-manfred@colorfullife.com> <1400399917-17583-6-git-send-email-manfred@colorfullife.com> <1400399917-17583-7-git-send-email-manfred@colorfullife.com> <20140519154639.5570a30f8b47872a323dcdfd@linux-foundation.org> From: "Michael Kerrisk (man-pages)" Date: Tue, 20 May 2014 08:56:38 +0200 Message-ID: Subject: Re: [PATCH 6/6] ipc/sem.c: make semctl(,,{GETNCNT,GETZCNT}) standard compliant To: Andrew Morton Cc: Manfred Spraul , LKML , Davidlohr Bueso , 1vier1@web.de Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, May 20, 2014 at 12:46 AM, Andrew Morton wrote: > On Sun, 18 May 2014 09:58:37 +0200 Manfred Spraul wrote: > >> SUSv4 clearly defines how semncnt and semzcnt must be calculated: >> A task waits on exactly one semaphore: >> The semaphore from the first operation in the sop array that cannot proceed. >> >> The Linux implementation never followed the standard, it tried to count all >> semaphores that might be the reason why a task sleeps. >> >> This patch fixes that. > > What are the back-compatibility implications of this change? Hard to estimate, but some thoughts: * These operations seem to be very little used. Grepping the public source that is contained Fedora 20 source DVD, there appear to be no uses. Of course, this says nothing about uses in private / non-mainstream FOSS code, but it seems likely that the same pattern is followed there. * The existing behavior is hard enough to understand that I suspect that no one understood it well enough to rely on it anyway (especially as that behavior contradicted both man page and POSIX). So, there's a chance of breakage, but I estimate that it's minute. Cheers, Michael -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/