lkml.org 
[lkml]   [2013]   [Apr]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] THP: Use explicit memory barrier
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 <mgorman@suse.de>
> Cc: Andrea Arcangeli <aarcange@redhat.com>
> Cc: Hugh Dickins <hughd@google.com>
> Signed-off-by: Minchan Kim <minchan@kernel.org>
> ---
> 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);



\
 
 \ /
  Last update: 2013-04-04 05:01    [W:0.105 / U:11.856 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site