Panic due to deleting devices twice

John Baldwin jhb at
Mon Jan 23 13:34:04 PST 2006

On Saturday 21 January 2006 02:07, Peter Jeremy wrote:
> When deleting a device (using device_delete_child()), all its child
> devices are recursively deleted and then device_detach() is called.
> In the case of iicsmb, this causes a panic because iicsmb_detach()
> also calls device_delete_child() on the smbus child it has cached in
> its softc.  By this time that child has been destroyed.
> Looking at device_detach(), it appears that the solution is to create
> a bus_child_detached method to inform the parent that a child is being
> destroyed so it can invalidate cached pointers to that child.  In
> practice, there are only 5 bus_child_detached methods (isa, ed,
> pccard, cbb and usb), though there are far more device types attached
> as children.
> Looking at the iicsmb code, it appears that iicbb and iicsmb both
> cache and explicitly delete child devices and therefore both need
> bus_child_detached methods.  Is this correct?  Is there a simpler
> alternative?

Can they just call bus_generic_detach() instead and not call 

John Baldwin <jhb at>  <><
"Power Users Use the Power to Serve"  =

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