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    SubjectRe: [PATCH v9 03/16] iommu/exynos: fix page table maintenance
    On Thu, Aug 08, 2013 at 11:28:44AM -0700, Grant Grundler wrote:
    > I can't speak to the previous BUG_ON(). I believe the EADDRESSINUSE
    > failures could be either WARN_ON or BUG_ON. This condition is
    > clearly a bug in the generic IOMMU allocator and I think that's why
    > KyongHo Cho used BUG_ON.
    >
    > Handing out duplicate addresses will generally lead to some sort of
    > data corruption or other fault depending on how robust the underlying
    > device drivers are written. So my preference is a BUG_ON to
    > immediately flag this condition instead of hoping a device driver will
    > correctly handling the dma mapping failure (Some do, most currently
    > don't).
    >
    > WARN_ON() + return -EADDRESSINUSE would be a good alternative.

    Even if it is a real BUG condition, I don't think it is worth to stop
    execution at this point. It makes debugging harder and the system less
    reliable. I prefer to go with the WARN_ON and an error return value.


    Joerg




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