Re: kernfs/rtc: circular dependency between kernfs and ops_lock

[Lars-Peter Clausen]

On 03/31/2014 12:43 PM, Alessandro Zummo wrote:
> On Mon, 31 Mar 2014 11:52:36 +0200
> Lars-Peter Clausen <lars@xxxxxxxxxx> wrote:
>
> > It's the same bug, device_unregister(&rtc->dev) will try to unregister all
> > sysfs files attached to the device and that function is still called with
> > the rtc mutex held.
>
>   rtc-cmos tries to unregister the rtc device in the probe function,
>   which should not be done.
>
>   the last patches fixes it. I'll keep trying to trigger the bug on my systems.

It doesn't really matter where it is unregistered. device_unregister() will 
(somewhere down it's callchain) take the kernfs lock, hence it must be 
callled with the rtc mutex being held.

- Lars
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