On Wed, May 30, 2012 at 06:57:47PM -0700, David Rientjes wrote:
> On Wed, 30 May 2012, Aneesh Kumar K.V wrote:
>
> > From: "Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
> >
> > i_mmap_mutex lock was added in unmap_single_vma by 502717f4e ("hugetlb:
> > fix linked list corruption in unmap_hugepage_range()") but we don't use
> > page->lru in unmap_hugepage_range any more. Also the lock was taken
> > higher up in the stack in some code path. That would result in deadlock.
> >
> > unmap_mapping_range (i_mmap_mutex)
> > -> unmap_mapping_range_tree
> > -> unmap_mapping_range_vma
> > -> zap_page_range_single
> > -> unmap_single_vma
> > -> unmap_hugepage_range (i_mmap_mutex)
> >
>
> You should be able to show this with lockdep?
I was not able to get a lockdep report
>
> > For shared pagetable support for huge pages, since pagetable pages are ref
> > counted we don't need any lock during huge_pmd_unshare. We do take
> > i_mmap_mutex in huge_pmd_share while walking the vma_prio_tree in mapping.
> > (39dde65c9940c97f ("shared page table for hugetlb page")).
> >
>
> I think this should be folded into patch 4, the code you're removing here
> is just added in that function unnecessarily.
>
I am removing i_mmap_mutex in this patch. That is not added in patch 4.
-aneesh
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