Re: [RFC PATCH powerpc] Fix warning reported by verify_cpu_node_mapping()

[Nishanth Aravamudan <nacc@linux.vnet.ibm.com>]

On 21.08.2014 [16:14:02 +0800], Li Zhong wrote:
> With commit 2fabf084b, during boottime, cpu_numa_callback() is called
> earlier(before their online) for each cpu, and verify_cpu_node_mapping()
> uses cpu_to_node() to check whether siblings are in the same node. 
> 
> It skips the checking for siblings that are not online yet. So the only
> check done here is for the bootcpu, which is online at that time. But
> the per-cpu numa_node cpu_to_node() uses hasn't been set up yet (which
> will be set up in smp_prepare_cpus()).
> 
> So I could see something like following reported:
> [    0.000000] CPU thread siblings 1/2/3 and 0 don't belong to the same
> node!

You mean you did see this, right? (as opposed to "could" based upon code
inspection or something)

> 
> As we don't actually do the checking during this early stage, so maybe
> we could directly call numa_setup_cpu() in do_init_bootmem()?
> 
> Signed-off-by: Li Zhong <zhong@linux.vnet.ibm.com>

Acked-by: Nishanth Aravamudan <nacc@linux.vnet.ibm.com>

> ---
>  arch/powerpc/mm/numa.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c
> index d7737a5..9918c02 100644
> --- a/arch/powerpc/mm/numa.c
> +++ b/arch/powerpc/mm/numa.c
> @@ -1128,8 +1128,7 @@ void __init do_init_bootmem(void)
>  	 * early in boot, cf. smp_prepare_cpus().
>  	 */
>  	for_each_possible_cpu(cpu) {
> -		cpu_numa_callback(&ppc64_numa_nb, CPU_UP_PREPARE,
> -				  (void *)(unsigned long)cpu);
> +		numa_setup_cpu((unsigned long)cpu);

This is a good change, thanks for catching it. I must have glossed over
those messages in my testing, my apologies!

-Nish