On Thu, 2007-10-18 at 16:08 -0400, Alan Stern wrote: > On Thu, 18 Oct 2007, Kay Sievers wrote: > > > On Thu, 2007-10-18 at 15:23 -0400, Alan Stern wrote: > > > This patch (as1004) fixes a refcounting bug in the development version > > > of the block-device core. > > > > > > Signed-off-by: Alan Stern <[EMAIL PROTECTED]> > > > > > > --- > > > > > > Kay, you have got to start testing your patches better! > > > > That leaves references around for SCSI target devices. There must be a > > bug somewhere else, if the patch isn't correct. > > > > > Finding and > > > fixing refcount errors is _not_ one of my favorite ways to pass the > > > time. For example, you could see what happens when you insert and > > > unplug a USB flash disk a few times. > > > > What do you see with the original version? > > Note that a USB drive is treated as a SCSI device. > > With the original code, I see the following sequence of events when > add_disk() is first called. Values in parentheses are > atomic_read(disk->dev.kobj.kref.refcount) after each stage runs: > > Entry to add_disk (1) > Call to register_disk > device_add (3) > CONFIG_SYSFS_DEPRECATED is not set > Call disk_sysfs_add_subdirs > add disk->holder_dir (4) > add disk->slave_dir (5) > Return to register_disk > get_capacity (5) > bdget_disk (5) > blkdev_get (partitions) (8) > blkdev_put (7) > Return to add_disk > blk_register_queue (9) > > You can see how many references each stage takes. Now here's the > equivalent list for del_gendisk(): > > Entry to del_gendisk (9) > invalidate_ and delete_partition loop (7) > invalidate_partition 0 (7) > Call unlink_gendisk > blk_unregister_queue (5) > Return to del_gendisk > unregister disk->holder_dir (4) > unregister disk->slave_dir (3) > CONFIG_SYSFS_DEPRECATED is not set > device_del (1) > put_device (0) -- oops! > > Matching things up we have: > > device_add/device_del 2 refs > reg/unreg subdirs 2 refs > subpartitions 2 refs > reg/unreg block queue 2 refs > > This accounts for everything in del_gendisk except the final > put_device. Evidently it doesn't belong there. There's no matching > get_device in add_disk or register_disk.
Hmm, do you have kobject debugging enabled? Do you ever see something like: "kobject sdb: cleaning up" when you remove the put_device()? Kay - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
