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 - : send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
