Messages in this thread | | | Date | Thu, 04 Apr 2013 10:45:25 +0800 | From | Simon Jeons <> | Subject | Re: [PATCH] THP: Use explicit memory barrier |
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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);
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