From owner-freebsd-arch@FreeBSD.ORG Tue Feb 12 05:10:21 2008 Return-Path: Delivered-To: arch@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 47B8D16A417 for ; Tue, 12 Feb 2008 05:10:21 +0000 (UTC) (envelope-from bright@elvis.mu.org) Received: from elvis.mu.org (elvis.mu.org [192.203.228.196]) by mx1.freebsd.org (Postfix) with ESMTP id 2FC4413C465 for ; Tue, 12 Feb 2008 05:10:20 +0000 (UTC) (envelope-from bright@elvis.mu.org) Received: by elvis.mu.org (Postfix, from userid 1192) id DE5A51A4D8C; Mon, 11 Feb 2008 21:10:20 -0800 (PST) Date: Mon, 11 Feb 2008 21:10:20 -0800 From: Alfred Perlstein To: "Christian S.J. Peron" Message-ID: <20080212051020.GO99258@elvis.mu.org> References: <20080212014057.GA6027@sub.vaned.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080212014057.GA6027@sub.vaned.net> User-Agent: Mutt/1.4.2.3i Cc: arch@freebsd.org, re@freebsd.org, current@freebsd.org Subject: Re: sysv IPC and shminfo ABI X-BeenThere: freebsd-arch@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussion related to FreeBSD architecture List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 12 Feb 2008 05:10:21 -0000 * Christian S.J. Peron [080211 18:00] wrote: > All, > > A while ago, I committed a patch which changed what was a kernel private > structure 'shminfo'. In order to access this structure, you must define > _KERNEL which suggests to me we should not be making guarantees about it's > size. > > See /usr/src/sys/shm.h ... yeah but... > > So I guess I have a few questions: > > (1) Is struct shminfo considered a sys V standard structure that has a > predefined size that should be maintained across all architectures? No, that's not required, what is required is backwards compat. > (2) Is this an ABI breakage that we care about? Yes, if it's breaking people, then yes. for ia32 in particular. > (1) Back the change out now before any damage is done (assuming we care) > > (2) Apply this safety patch to RELENG_7 and RELENG_7_0 > > http://people.freebsd.org/~csjp/sysv_shm.1202744975.6_abi_fix.diff Honestly I was going to suggest all this cruft to "get it right", but this patch looks like the most simple, most correct thing. I think it should go in. > (3) Leave things as they are, as we are going to be getting support for large > shared memory allocations in the future. (This is why I asked if the > structure supposed to be a standard size). Afaik there's no "standard size" in the API (I think shmctl->shminfo is pretty unix specific) but it pays to keep the backward compat. > > I apologize for this, I understand this is probably the last thing we need > before the release, but I just want to make sure that we are doing the right > thing. Cool. -Alfred