From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx161.postini.com [74.125.245.161]) by kanga.kvack.org (Postfix) with SMTP id E29F86B0005 for ; Wed, 3 Apr 2013 22:45:33 -0400 (EDT) Received: by mail-da0-f48.google.com with SMTP id p8so923566dan.35 for ; Wed, 03 Apr 2013 19:45:33 -0700 (PDT) Message-ID: <515CE945.20908@gmail.com> Date: Thu, 04 Apr 2013 10:45:25 +0800 From: Simon Jeons MIME-Version: 1.0 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: owner-linux-mm@kvack.org List-ID: To: Minchan Kim Cc: Andrew Morton , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Mel Gorman , Andrea Arcangeli , Hugh Dickins 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, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org