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

From: Li Zhong <[email-masked]>
Date: Fri, 22 Aug 2014 10:12:56 +0800

On 四, 2014-08-21 at 08:45 -0700, Nishanth Aravamudan wrote:
> 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)

Yes, I did see the warnings. Seems I didn't express it precisely in
English ...

> 
> > 
> > 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 <[email-masked]>
> 
> Acked-by: Nishanth Aravamudan <[email-masked]>

Thank you for the review,

Zhong

> 
> > ---
> >  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