Hi Greg,

> On Jan 16, 2015, at 00:55 , Greg Kroah-Hartman <gre...@linuxfoundation.org> 
> wrote:
> 
> On Thu, Jan 15, 2015 at 06:25:22PM +0200, Pantelis Antoniou wrote:
>> Hi Greg,
>> 
>>> On Jan 14, 2015, at 22:41 , Greg Kroah-Hartman <gre...@linuxfoundation.org> 
>>> wrote:
>>> 
>>> On Wed, Jan 14, 2015 at 07:24:22PM +0200, Pantelis Antoniou wrote:
>>>> I’ll try to dig around tomorrow and see what the real device reference 
>>>> counts
>>>> are, but my hunch goes like this:
>>>> 
>>>> MUX
>>>> +—- ADAPTER
>>>>   +— DEV.
>>>> 
>>>> Mux remove method is called, i2c_del_mux_adapter is called on all the 
>>>> channels
>>>> of the mux, calling in turn i2c_del_adapter which hangs on completion of 
>>>> the
>>>> dev_released.
>>>> 
>>>> The call to device_unregister never calls the device_type callback 
>>>> (i2c_adapter_dev_release)
>>>> because the reference count is not 1 at that point, someone else is having 
>>>> another
>>>> reference.
>>> 
>> 
>> First of all, my head hurts. Tracking device references ain’t easy. Is there 
>> some kind
>> of debugging method you’d recommend for this?
> 
> You can turn on debugging for kobjects and the driver core if you want
> to slow down your system log a bunch, but it can be helpful for trickier
> issues.  Or just sprinkle a few printks around.
> 

Turning on debugging for kobjects is like opening the floodgates…

I managed to make do with a few printks, but some kind of tracking would
be helpful. 

>>> I don't remember the i2c core code at all, that was a long time ago.
>>> 
>> 
>> Bummer.
> 
> Do you remember code you wrote 12 year ago and haven't looked at for at
> least 11?  Why expect others to as well? :)
> 

You’re supposed to be a super-hero maintainer god right? How am I supposed
to continue living with my belief system crumbled like that? :)

> thanks,
> 
> greg k-h

Regards

— Pantelis

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