Re: [PATCH, RFC] sysfs: only allow one scheduled removal callback per kobj

Cornelia Huck
2009-03-11T17:47:42Z

On Wed, 11 Mar 2009 08:32:28 -0700,
Greg KH <gregkh@suse.de> wrote:

> Why can't you use device_unregister()? Or, you could use device_del(),
> which lets you rely on the fact that the device structure is still
> around for a bit, but it will disappear from sysfs. Just don't forget
> to do the final put_device() on it to free the memory and "really"
> release it.
>
> Or am I missing something else here?

You can't unregister a device from one of its attribute callbacks, it
locks up in sysfs (removing the sysfs dir waits for all active
references to be dropped, but the reference obtained before calling
->store won't be dropped until after ->store returned...)
device_schedule_callback() was introduced to solve exactly that problem.

(For the original oops, I'd rather solve the problem by making sure the
caller doesn't trigger removal several times - should probably be less
code than the proposed patch?)