Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932995Ab3DDCpe (ORCPT ); Wed, 3 Apr 2013 22:45:34 -0400 Received: from mail-da0-f48.google.com ([209.85.210.48]:49532 "EHLO mail-da0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932725Ab3DDCpd (ORCPT ); Wed, 3 Apr 2013 22:45:33 -0400 Message-ID: <515CE945.20908@gmail.com> Date: Thu, 04 Apr 2013 10:45:25 +0800 From: Simon Jeons User-Agent: Mozilla/5.0 (X11; Linux i686; rv:17.0) Gecko/20130308 Thunderbird/17.0.4 MIME-Version: 1.0 To: Minchan Kim CC: Andrew Morton , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Mel Gorman , Andrea Arcangeli , Hugh Dickins Subject: Re: [PATCH] THP: Use explicit memory barrier References: <1364773535-26264-1-git-send-email-minchan@kernel.org> In-Reply-To: <1364773535-26264-1-git-send-email-minchan@kernel.org> 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 Content-Length: 1854 Lines: 50 Hi Minchan, On 04/01/2013 07:45 AM, Minchan Kim wrote: > __do_huge_pmd_anonymous_page depends on page_add_new_anon_rmap's > spinlock for making sure that clear_huge_page write become visible > after set set_pmd_at() write. 1. There are no pte modify, why take page_table_lock here? 2. What's the meaning of "clear_huge_page write become visible after set set_pmd_at() write"? > > But lru_cache_add_lru uses pagevec so it could miss spinlock > easily so above rule was broken so user may see inconsistent data. > > This patch fixes it with using explict barrier rather than depending > on lru spinlock. > > Cc: Mel Gorman > Cc: Andrea Arcangeli > Cc: Hugh Dickins > Signed-off-by: Minchan Kim > --- > mm/huge_memory.c | 7 +++---- > 1 file changed, 3 insertions(+), 4 deletions(-) > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index bfa142e..fad800e 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -725,11 +725,10 @@ static int __do_huge_pmd_anonymous_page(struct mm_struct *mm, > pmd_t entry; > entry = mk_huge_pmd(page, vma); > /* > - * The spinlocking to take the lru_lock inside > - * page_add_new_anon_rmap() acts as a full memory > - * barrier to be sure clear_huge_page writes become > - * visible after the set_pmd_at() write. > + * clear_huge_page write become visible after the > + * set_pmd_at() write. > */ > + smp_wmb(); > page_add_new_anon_rmap(page, vma, haddr); > set_pmd_at(mm, haddr, pmd, entry); > pgtable_trans_huge_deposit(mm, pgtable); -- 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/