Re: [BUG 2.6.17-git] kmem_cache_create: duplicate cache scsi_cmd_cache

James Bottomley
2006-05-12T18:58:58Z

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.

I suggest simply reversing this patch at the moment. If Russell and
Jens can tell me what they're trying to do I'll see if there's another
way to do it.

James