From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030254AbXCCOK4 (ORCPT ); Sat, 3 Mar 2007 09:10:56 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1030257AbXCCOK4 (ORCPT ); Sat, 3 Mar 2007 09:10:56 -0500 Received: from mx1.redhat.com ([66.187.233.31]:49992 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1030254AbXCCOKz (ORCPT ); Sat, 3 Mar 2007 09:10:55 -0500 From: David Howells In-Reply-To: References: <20070216165042.GB409@lnx-holt.americas.sgi.com> <45D5B483.3020502@hitachi.com> <45D5B2E3.3030607@hitachi.com> <20368.1171638335@redhat.com> <18817.1171656543@redhat.com> To: Hugh Dickins Cc: Robin Holt , "Kawai, Hidehiro" , Andrew Morton , kernel list , Pavel Machek , Alan Cox , Masami Hiramatsu , sugita , Satoshi OSHIMA , "Hideo AOKI@redhat" , dhowells@redhat.com Subject: Re: [PATCH 3/4] coredump: ELF-FDPIC: enable to omit anonymous shared memory X-Mailer: MH-E 8.0; nmh 1.1; GNU Emacs 22.0.50 Date: Sat, 03 Mar 2007 14:10:29 +0000 Message-ID: <29317.1172931029@redhat.com> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Hugh Dickins wrote: > > VMAs are a shared resource under NOMMU conditions. > > That's a disturbing remark. Why? No-one complained when I first put up my rewrite patches three years ago. > Under precisely what NOMMU conditions? CONFIG_MMU=n. > I had thought Robin's suggestion very sensible; and throughout mm/ > it has seemed pretty random whether we pass an "mm" argument down > in addition to "vma", or just take vma->vm_mm at whatever level needs. > > You seem to be suggesting vma->vm_mm is dangerous when CONFIG_NOMMU, vm_mm is never set to anything other than NULL if CONFIG_MMU=n and it doesn't seem to be a problem. I don't think anything in the mm/ directory is left that looks at vm_mm once MMU support is disabled (in fact I've just checked, and I can compile with vm_mm #ifdef'd out) > but we MMU people are scarily unaware of that. If you're worryied that you can't compile anything for NOMMU, an FRV compiler is available, and a suitable NOMMU default config can be provided. Alternatively, you can pick ARM, M68K, ... > Perhaps you need to put #ifndef CONFIG_NOMMU around vm_mm in struct > vm_area_struct? I can if it makes you happier. It's not strictly necessary, but it does make the struct smaller which is good. David