On 09.06.2014 [14:47:57 -0700], David Rientjes wrote: > On Wed, 21 May 2014, Nishanth Aravamudan wrote: > > > For context: I was looking at why N_ONLINE was statically setting Node 0 > > to be online, whether or not the topology is that way -- I've been > > getting several bugs lately where Node 0 is online, but has no CPUs and > > no memory on it, on powerpc. > > > > On powerpc, setup_per_cpu_areas calls into ___alloc_bootmem_node using > > NODE_DATA(cpu_to_node(cpu)). > > > > Currently, cpu_to_node() in arch/powerpc/include/asm/topology.h does: > > > > /* > > * During early boot, the numa-cpu lookup table might not have been > > * setup for all CPUs yet. In such cases, default to node 0. > > */ > > return (nid < 0) ? 0 : nid; > > > > And so early at boot, if node 0 is not present, we end up accessing an > > unitialized NODE_DATA(). So this seems buggy (I'll contact the powerpc > > deveopers separately on that). > > > > I think what this really wants to do is NODE_DATA(cpu_to_mem(cpu)) and I > thought ppc had the cpu-to-local-memory-node mappings correct? Except cpu_to_mem relies on the mapping being defined, but early in boot, specifically, it isn't yet (at least not necessarily). -Nish -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>