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    SubjectRe: [PATCH 01/10] migrate: add migrate_entry_wait_huge()
    On Fri, Apr 05, 2013 at 04:33:32PM -0400, KOSAKI Motohiro wrote:
    > > diff --git v3.9-rc3.orig/mm/hugetlb.c v3.9-rc3/mm/hugetlb.c
    > > index 0a0be33..98a478e 100644
    > > --- v3.9-rc3.orig/mm/hugetlb.c
    > > +++ v3.9-rc3/mm/hugetlb.c
    > > @@ -2819,7 +2819,7 @@ int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
    > > if (ptep) {
    > > entry = huge_ptep_get(ptep);
    > > if (unlikely(is_hugetlb_entry_migration(entry))) {
    > > - migration_entry_wait(mm, (pmd_t *)ptep, address);
    > > + migration_entry_wait_huge(mm, (pmd_t *)ptep, address);
    >
    > Hm.
    >
    > How do you test this? From x86 point of view, this patch seems unnecessary because
    > hugetlb_fault call "address &= hugetlb_mask()" at first and then migration_entry_wait()
    > could grab right pte lock. And from !x86 point of view, this funciton still doesn't work
    > because huge page != pmd on some arch.

    I kicked hugepage migration for address range where I repeat to access
    in a loop, and checked what happened (whether soft lockup happens or not.)
    But I don't fully understand what the problem is, and I might wrongly define
    the problem. So give me time to clarify it.

    And I fully agree that this function should be arch dependent.

    > I might be missing though.


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