From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752987Ab1LSTww (ORCPT ); Mon, 19 Dec 2011 14:52:52 -0500 Received: from mail-yx0-f174.google.com ([209.85.213.174]:57966 "EHLO mail-yx0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752812Ab1LSTwu (ORCPT ); Mon, 19 Dec 2011 14:52:50 -0500 Message-ID: <4EEF960F.1070909@gmail.com> Date: Mon, 19 Dec 2011 11:52:47 -0800 From: David Daney User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.15) Gecko/20101027 Fedora/3.0.10-1.fc12 Thunderbird/3.0.10 MIME-Version: 1.0 To: David Rientjes CC: Andrew Morton , Stephen Rothwell , Paul Mundt , linux-kernel@vger.kernel.org, David Daney Subject: Re: [PATCH] mm: Fix BUILD_BUG assertion in pmdp_clear_flush_young() References: <20111217152253.1aedda0936cd5d1d98be5e76@canb.auug.org.au> <1324316288-2367-1-git-send-email-ddaney.cavm@gmail.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/19/2011 11:29 AM, David Rientjes wrote: > On Mon, 19 Dec 2011, David Daney wrote: > >> From: David Daney >> >> It has been reported that when building for sh: >> >> mm/pgtable-generic.c: In function 'pmdp_clear_flush_young': >> mm/pgtable-generic.c:76: error: call to '__build_bug_failed' declared with attribute error: BUILD_BUG failed >> >> Adding some ugle #ifdeffery will probably fix this issue. >> > > It won't, CONFIG_HUGETLB_PAGE has nothing at all to do with this. > Sorry for the noise. You are correct. >> Signed-off-by: David Daney >> --- >> >> This is completely untested, but may be the best fix for this. Linus >> and others have expressed a dislike for using BUG() to detect what >> should be dead code paths at runtime, but it seems to be the state of >> the art here. >> > > The problem here is that HPAGE_PMD_MASK is being referenced without > CONFIG_TRANSPARENT_HUGEPAGE. pmdp_clear_flush_young() is only applicable > with that config option enabled. So rather than trying to minimize lines > captured under an #ifdef by placing the BUG() directly in the function for > asm-generic, you'll need to wrap pmd_clear_flush_young() with > #ifdef CONFIG_TRANSPARENT_HUGEPAGE and define its equivalent for > CONFIG_TRANSPARENT_HUGEPAGE=n that breaks the build if not enabled. > That does sound like a better option. I still think having the BUILD_BUG defined as we do in Andrew Morton's tree is the correct approach, and I don't want to see that reverted because of this ugliness. Really this is hackery that should be cleaned up as you suggest, instead of being papered over with this BUG() thing. I can't test SH things, otherwise I might look at it. The SH maintainers should probably take a look instead. David Daney >> mm/pgtable-generic.c | 2 +- >> 1 files changed, 1 insertions(+), 1 deletions(-) >> >> diff --git a/mm/pgtable-generic.c b/mm/pgtable-generic.c >> index eb663fb..73784c8 100644 >> --- a/mm/pgtable-generic.c >> +++ b/mm/pgtable-generic.c >> @@ -70,7 +70,7 @@ int pmdp_clear_flush_young(struct vm_area_struct *vma, >> unsigned long address, pmd_t *pmdp) >> { >> int young; >> -#ifndef CONFIG_TRANSPARENT_HUGEPAGE >> +#if !defined(CONFIG_HUGETLB_PAGE) || !defined(CONFIG_TRANSPARENT_HUGEPAGE) >> BUG(); >> #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ >> VM_BUG_ON(address& ~HPAGE_PMD_MASK);