Re: [PATCH v9 00/12] Support PPTT for ARM64

[Will Deacon]

On Tue, May 29, 2018 at 02:18:40PM +0100, Sudeep Holla wrote:
> On 29/05/18 12:56, Geert Uytterhoeven wrote:
> > On Tue, May 29, 2018 at 1:14 PM, Sudeep Holla <sudeep.holla@xxxxxxx> wrote:
> >> On 29/05/18 11:48, Geert Uytterhoeven wrote:
> >>> System supend still works fine on systems with big cores only:
> >>>
> >>>     R-Car H3 ES1.0 (4xCA57 (4xCA53 disabled in firmware))
> >>>     R-Car M3-N (2xCA57)
> >>>
> >>> Reverting this commit fixes the issue for me.
> >>
> >> I can't find anything that relates to system suspend in these patches
> >> unless they are messing with something during CPU hot plug-in back
> >> during resume.
> > 
> > It's only the last patch that introduces the breakage.
> > 
> 
> As specified in the commit log, it won't change any behavior for DT
> systems if it's non-NUMA or single node system. So I am still wondering
> what could trigger this regression.

I wonder if we're somehow giving an uninitialised/invalid NUMA configuration
to the scheduler, although I can't see how this would happen.

Geert -- if you enable CONFIG_DEBUG_PER_CPU_MAPS=y and apply the diff below
do you see anything shouting in dmesg?

Will

--->8

diff --git a/arch/arm64/mm/numa.c b/arch/arm64/mm/numa.c
index dad128ba98bf..e3de033339b4 100644
--- a/arch/arm64/mm/numa.c
+++ b/arch/arm64/mm/numa.c
@@ -58,7 +58,7 @@ EXPORT_SYMBOL(node_to_cpumask_map);
  */
 const struct cpumask *cpumask_of_node(int node)
 {
-	if (WARN_ON(node >= nr_node_ids))
+	if (WARN_ON((unsigned)node >= nr_node_ids))
 		return cpu_none_mask;
 
 	if (WARN_ON(node_to_cpumask_map[node] == NULL))