Re: [PATCH RFC v1] drivers/base/node: consolidate node device subsystem initialization in node_dev_init()

[David Hildenbrand <david@xxxxxxxxxx>]

On 31.01.22 07:23, Oscar Salvador wrote:
> On Fri, Jan 28, 2022 at 04:15:40PM +0100, David Hildenbrand wrote:
>> ... and call node_dev_init() after memory_dev_init() from driver_init(),
>> so before any of the existing arch/subsys calls. All online nodes should
>> be known at that point.
>>
>> This is in line with memory_dev_init(), which initializes the memory
>> device subsystem and creates all memory block devices.
>>
>> Similar to memory_dev_init(), panic() if anything goes wrong, we don't
>> want to continue with such basic initialization errors.
>>
>> The important part is that node_dev_init() gets called after
>> memory_dev_init() and after cpu_dev_init(), but before any of the
>> relevant archs call register_cpu() to register the new cpu device under
>> the node device. The latter should be the case for the current users
>> of topology_init().
> 

Hi Oscar,

> So, before this change we had something like this:
> 
> do_basic_setup
>  driver_init
>   memory_dev_init
>  do_init_calls
>   ...
>    topology_init
>     register_nodes/register_one_node
> 
> And after the patch all happens in driver_init()
> 
> driver_init
>  memory_dev_init
>  node_dev_init
> 
> I guess this is fine as we do not have any ordering problems (aka: none
> of the functions we used to call before expect the nodes not to be
> there for some weird reason).
> 
> So, no functional change, right?
> 

Right, and the idea is that the online state of nodes (+ node/zone
ranges) already has to be known at that point in time, because
otherwise, we'd be in bigger trouble.

Thanks!


-- 
Thanks,

David / dhildenb