Messages in this thread | | | Date | Wed, 11 Oct 2006 11:18:16 +1000 | From | 'David Gibson' <> | Subject | Re: Hugepage regression |
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On Tue, Oct 10, 2006 at 04:34:40PM -0700, Chen, Kenneth W wrote: > Hugh Dickins wrote on Tuesday, October 10, 2006 12:18 PM > > Yes, I'd expect your i_mmap_lock to solve the problem: and since > > you're headed in that direction anyway, it makes most sense to use > > that solution rather than get into defining arrays, or sacrificing > > the lazy flush, or risking page_count races. > > > > So please extract the __unmap_hugepage_range mods from your shared > > pagetable patch, and use that to fix the bug. > > > OK, here is a bug fix patch fixing earlier "bug fix" patch :-( > > > [patch] hugetlb: fix linked list corruption in unmap_hugepage_range > > commit fe1668ae5bf0145014c71797febd9ad5670d5d05 causes kernel to oops with > libhugetlbfs test suite. The problem is that hugetlb pages can be shared > by multiple mappings. Multiple threads can fight over page->lru in the unmap > path and bad things happen. We now serialize __unmap_hugepage_range to void > concurrent linked list manipulation. Such serialization is also needed for > shared page table page on hugetlb area. This patch will fixed the bug and > also serve as a prepatch for shared page table.
Can I suggest that you put a big comment on the linked list declaration itself saying that you're relying on serialization here. Otherwise I'm worried someone will try to de-serialize it again, and break it without realizing. Given the number of people who failed to spot the problem with the patch the first time around..
-- David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/~dgibson - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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