Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754224Ab2E2Qcn (ORCPT ); Tue, 29 May 2012 12:32:43 -0400 Received: from mail-pz0-f46.google.com ([209.85.210.46]:48987 "EHLO mail-pz0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751667Ab2E2Qcm convert rfc822-to-8bit (ORCPT ); Tue, 29 May 2012 12:32:42 -0400 MIME-Version: 1.0 In-Reply-To: <4FC4F5D8.8090701@wwwdotorg.org> References: <4FC22098.3070803@kernel.org> <4FC25048.109@wwwdotorg.org> <4FC4F5D8.8090701@wwwdotorg.org> From: Kay Sievers Date: Tue, 29 May 2012 18:32:21 +0200 Message-ID: Subject: Re: arm: Remaining issue with alignment of __log_buf in printk.c To: Stephen Warren Cc: Jonathan Cameron , Russell King , LKML , linux-arm-kernel Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1580 Lines: 43 On Tue, May 29, 2012 at 6:14 PM, Stephen Warren wrote: > On 05/27/2012 10:03 AM, Stephen Warren wrote: >> On 05/27/2012 06:39 AM, Jonathan Cameron wrote: >>> Hi All, >>> >>> My stargate 2 board refused to start and after bisection I ended >>> up at the same patch that Stephen found an alignment issue in. >>> Unfortunately Stephen's patch doesn't seem to have fixed the >>> issue for me. >>> https://lkml.org/lkml/2012/5/10/510 is the thread.  Patch from >>> Stephen is : f8450fca6ecdea38b5a882fdf6cd097e3ec8651c >>> >>> Increasing the alignement for 32 bit systems to 8 seems to do the >>> job but I can't immediately think why... >>> >>> System is a pxa27x strong arm. > ... >> #if !defined(CONFIG_64BIT) || defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) >> #define LOG_ALIGN 4 >> #else >> #define LOG_ALIGN 8 >> #endif > > Actually, why not replace that with: > > #define LOG_ALIGN (__alignof__(struct log_buf)) > > That way, the compiler will calculate the arch-/ABI-appropriate > alignment value automatically and correctly in all cases, so we won't > have to fix that ifdef above. __alignof__(u64) will be 8 on x86_64, while the current logic results in 4. Not sure if x86_64 would somehow benefit from that, or if it's just a waste of bytes. Are you sure it results in 4 on some architectures? Kay -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/