Re: OF_DYNAMIC node lifecycle

[Nathan Fontenot <nfont@austin.ibm.com>]

On 06/27/2014 07:41 AM, Grant Likely wrote:
> On Thu, 26 Jun 2014 15:01:49 -0500, Nathan Fontenot <nfont@austin.ibm.com> wrote:
>> On 06/25/2014 03:24 PM, Grant Likely wrote:
>>> On Tue, 24 Jun 2014 15:10:55 -0500, Nathan Fontenot <nfont@austin.ibm.com> wrote:
>>>>>> heh! I have often thought about adding reference counting to device tree
>>>>>> properties.
>>>>>
>>>>> You horrible, horrible man.
>>>>
>>>> Yes. I are evil :)
>>>>
>>>> After looking again the work needed to add reference counts to properties
>>>> would be huge. The few properties I am concerned with are specific to powerpc
>>>> so perhaps just adding an arch specific lock around updating those
>>>> properties would work.
>>>
>>> Which code/properties? I'd like to have a look myself.
>>
>> /ibm,dynamic-reconfiguration-memory/ibm,dynamic-memory
>>
>> The property is updated in 
>> arch/powerpc/platforms/pseries/hotplug-memory.c:pseries_update_drconf_memory()
> 
> Specifically, what do you need for the locking? Are you wanting to hold
> off additional changes while that function is executing? Pantelis is
> adding a mutex for device tree writers. Holding that mutex would prevent
> any changes from happening in the tree without affecting readers. Would
> that be sufficient?

That would work.

-Nathan