Subject: Re: [PATCH 1/3] mm: return NUMA_NO_NODE in local_memory_node if zonelists are not setup

From: Nishanth Aravamudan <[email-masked]>
Date: Thu, 20 Feb 2014 10:28:47 -0800

On 20.02.2014 [10:05:39 -0600], Christoph Lameter wrote:
> On Wed, 19 Feb 2014, Nishanth Aravamudan wrote:
> 
> > We can call local_memory_node() before the zonelists are setup. In that
> > case, first_zones_zonelist() will not set zone and the reference to
> > zone->node will Oops. Catch this case, and, since we presumably running
> > very early, just return that any node will do.
> 
> Really? Isnt there some way to avoid this call if zonelists are not setup
> yet?

How do I best determine if zonelists aren't setup yet?

The call-path in question (after my series is applied) is:

arch/powerpc/kernel/setup_64.c::setup_arch ->
	arch/powerpc/mm/numa.c::do_init_bootmem() ->
		cpu_numa_callback() ->
			numa_setup_cpu() ->
				map_cpu_to_node() ->
					update_numa_cpu_node() ->
						set_cpu_numa_mem()

and setup_arch() is called before build_all_zonelists(NULL, NULL) in
start_kernel(). This seemed like the most reasonable path, as it's used
on hotplug as well.

I'm open to suggestsions!

Thanks,
Nish