From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758724AbYHAVpl (ORCPT ); Fri, 1 Aug 2008 17:45:41 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754954AbYHAVpd (ORCPT ); Fri, 1 Aug 2008 17:45:33 -0400 Received: from mta23.gyao.ne.jp ([125.63.38.249]:24883 "EHLO mx.gate01.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754044AbYHAVpd (ORCPT ); Fri, 1 Aug 2008 17:45:33 -0400 Date: Sat, 2 Aug 2008 06:44:48 +0900 From: Paul Mundt To: David Howells Cc: Andrew Morton , linux-sh@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/3] binfmt_elf_fdpic: Convert initial stack alignment to arch_align_stack(). Message-ID: <20080801214448.GA13448@linux-sh.org> Mail-Followup-To: Paul Mundt , David Howells , Andrew Morton , linux-sh@vger.kernel.org, linux-kernel@vger.kernel.org References: <20080728150501.GC16555@linux-sh.org> <20080728150359.GA16555@linux-sh.org> <20080728150430.GB16555@linux-sh.org> <27552.1217599279@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <27552.1217599279@redhat.com> User-Agent: Mutt/1.5.13 (2006-08-11) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Aug 01, 2008 at 03:01:19PM +0100, David Howells wrote: > Paul Mundt wrote: > > > + * In some cases (e.g. Hyper-Threading), we want to avoid L1 > > + * evictions by the processes running on the same package. One > > + * thing we can do is to shuffle the initial stack for them, so > > + * we give the architecture an opportunity to do so here. > > + */ > > #ifdef CONFIG_MMU > > - sp = bprm->p; > > + sp = arch_align_stack(bprm->p); > > #else > > - sp = mm->start_stack; > > + sp = arch_align_stack(mm->start_stack); > > Ummm... You're calling arch_align_stack() under NOMMU... Is that really a > good idea? > Not particularly, no. > You can't necessarily move the stack pointer without exiting the allocated > region or shrinking the amount of stack space the executable asked for. If > you want to do this sort of thing, you need to tell the memory allocator what > you're up to - or at the very least allocate some slack. > Yes, that's a good point, and one that probably ought to be documented alongside the initial alignment. I'll send an updated patch.