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    SubjectRe: [PATCH] dma-debug: disable DMA_API_DEBUG for now
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    On Sun, Jun 7, 2009 at 10:13 AM, Ingo Molnar <mingo@elte.hu> wrote:
    > * Joerg Roedel <joerg.roedel@amd.com> wrote:
    >> But its up to Linus/Ingo to decide if it can be accepted at this
    >> very late point in the cycle. Since dma-debug is new with 2.6.30
    >> it will at least not introduce any regression. [...]
    >
    > I think it's too late for v2.6.30 to do any of the changes - and the
    > DMA debug facility is off by default.
    >
    > Also, i think such DMA patterns, while 'allowed' can be quite
    > dangerous as its such a rare usage combination really. AIO and DIO
    > are crazy to begin with, mixing AIO and DIO for the same buffer is
    > madness square two. (It can result in 3 agents for the same memory
    > address: CPU, dma1 and dma2. How many interesting chipset erratums
    > could there be related to such scenarios?)

    I think in my case the cause is somewhat simpler: RAID1
    My root filesystem is on a RAID1 that consists of two disks, both
    connected to the sata_sil24 controller.
    So it is only natural for the md driver to issue two dma read requests
    for the same address: one for each drive.

    Torsten


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