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    SubjectRe: [BUG 2.6.17-git] kmem_cache_create: duplicate cache scsi_cmd_cache
    On Fri, May 12, 2006 at 01:58:45PM -0500, James Bottomley wrote:
    > On Fri, 2006-05-12 at 12:47 -0500, James Bottomley wrote:
    > > I'll look at the release paths and see if I can work out what it is.
    >
    > OK, here's the scoop. The problem patch adds a get of driverfs_dev in
    > add_disk(), but doesn't put it again until disk_release() (which occurs
    > on final put_disk() of the gendisk).
    >
    > However, in SCSI, the driverfs_dev is the sdev_gendev. That means
    > there's a reference held on sdev_gendev until final disk put.
    > Unfortunately, we use the driver model driver_remove to trigger
    > del_gendisk (which removes the gendisk from visibility and decrements
    > the refcount), so we've introduced an unbreakable deadlock in the
    > reference counting with this.

    That explains why I could only trigger the bug with a disk attached to
    the controller.


    Thanks for figuring out,

    Erik

    --
    +-- Erik Mouw -- www.harddisk-recovery.com -- +31 70 370 12 90 --
    | Lab address: Delftechpark 26, 2628 XH, Delft, The Netherlands
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