On 12/09/2013 02:09 AM, Mel Gorman wrote: > diff --git a/mm/migrate.c b/mm/migrate.c > index cfb4190..5372521 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -1759,6 +1759,12 @@ int migrate_misplaced_transhuge_page(struct mm_struct > *mm, > goto out_fail; > } > > + /* PTL provides a memory barrier with change_protection_range */ > + ptl = pmd_lock(mm, pmd); > + if (tlb_flush_pending(mm)) > + flush_tlb_range(vma, mmun_start, mmun_end); > + spin_unlock(ptl); > + > /* Prepare a page as a migration target */ > __set_page_locked(new_page); > SetPageSwapBacked(new_page);
I don't think there is a need for that extra memory barrier. On the "set_tlb_flush_pending, turn ptes into NUMA ones" side, we have a barrier in the form of the page table lock. We only end up in this code path if the pte/pmd already is a NUMA one, and we take several spinlocks along the way to doing this test. That provides for the memory barrier in this code path. -- All rights reversed -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
