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    SubjectRe: Strange block/scsi/workqueue issue
    Hello, James.

    On Mon, Apr 11, 2011 at 07:47:56PM -0500, James Bottomley wrote:
    > Actually, I don't think it's anything to do with the user process stuff.
    > The problem seems to be that the block delay function ends up being the
    > last user of the SCSI device, so it does the final put of the sdev when
    > it's finished processing. This will trigger queue destruction
    > (blk_cleanup_queue) and so on with your analysis.

    Hmm... this I can understand.

    > The problem seems to be that with the new workqueue changes, the queue
    > itself may no longer be the last holder of a reference on the sdev
    > because the queue destruction is in the sdev release function and a
    > queue cannot now be destroyed from its own delayed work. This is a bit
    > contrary to the principles SCSI was using, which was that we drive queue
    > lifetime from the sdev, not vice versa.

    But confused here. Why does it make any difference whether the
    release operation is in the request_fn context or not? What makes
    SCSI refcounting different from others?



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