Re: [PATCH 1/4] mmzone: make holding lock_memory_hotplug() a requirementfor updating pgdat size

[Cody P Schafer]

On 05/01/2013 03:26 PM, David Rientjes wrote:
> On Wed, 1 May 2013, Cody P Schafer wrote:
>
> > All updaters of pgdat size (spanned_pages, start_pfn, and
> > present_pages) currently also hold lock_memory_hotplug() (in addition
> > to pgdat_resize_lock()).
> >
> > Document this and make holding of that lock a requirement on the update
> > side for now, but keep the pgdat_resize_lock() around for readers that
> > can't lock a mutex.
> >
> > Signed-off-by: Cody P Schafer <cody@xxxxxxxxxxxxxxxxxx>
>
> Nack, these fields are initialized at boot without lock_memory_hotplug(),
> so you're statement is wrong, and all you need is pgdat_resize_lock().

They are also initialized at boot without pgdat_resize_lock(), if we 
consider boot time, quite a few of the statements on when locking is 
required are wrong.

That said, you are correct that it is not strictly required to hold 
lock_memory_hotplug() when updating the fields in question because 
pgdat_resize_lock() is used.



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