Messages in this thread | | | Date | Wed, 30 May 2012 18:57:47 -0700 (PDT) | From | David Rientjes <> | Subject | Re: [PATCH -V7 05/14] hugetlb: avoid taking i_mmap_mutex in unmap_single_vma() for hugetlb |
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On Wed, 30 May 2012, Aneesh Kumar K.V wrote:
> From: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com> > > 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?
> 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.
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