On Mon, 19 Nov 2007 10:53:40 -0500 (EST)
Alan Stern <[email protected]> wrote:
> This patch (as1015) reverts changes that were made to the driver core
> about four years ago. The intent back then was to avoid certain kinds
> of invalid memory accesses by leaving kernel objects allocated as long
> as any of their children were still allocated. The original and
> correct approach was to wait only as long as any children were still
> _registered_; that's what this patch reinstates.
What happened with this?
> This fixes a problem in the SCSI core made visible by the class_device
> to regular device conversion: A reference loop (scsi_device holds
> reference to request_queue, which is the child of a gendisk, which is
> the child of the scsi_device) prevents the data structures from being
> released, even though they are deregistered okay.
>
> It's possible that this change will cause a few bugs to surface,
> things that have been hidden for several years. They can be fixed
> easily enough by having the child device take an explicit reference to
> the parent whenever needed.
>
How will such bugs manifest? Ideally via a nice printk and a stack trace
followed by damage avoidance.
If it's via a mysterious crash or something similarly obscure then can we
improve that?
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