When building the overlapping groups, we very obviously should start with the previous domain of _this_ @cpu, not CPU-0. This can be readily demonstrated with a topology like: node 0 1 2 3 0: 10 20 30 20 1: 20 10 20 30 2: 30 20 10 20 3: 20 30 20 10 Where (for example) CPU1 ends up generating the following nonsensical groups: [] CPU1 attaching sched-domain: [] domain 0: span 0-2 level NUMA [] groups: 1 2 0 [] domain 1: span 0-3 level NUMA [] groups: 1-3 (cpu_capacity = 3072) 0-1,3 (cpu_capacity = 3072) Where the fact that domain 1 doesn't include a group with span 0-2 is the obvious fail. With patch this looks like: [] CPU1 attaching sched-domain: [] domain 0: span 0-2 level NUMA [] groups: 1 0 2 [] domain 1: span 0-3 level NUMA [] groups: 0-2 (cpu_capacity = 3072) 0,2-3 (cpu_capacity = 3072) Cc: stable@vger.kernel.org Fixes: e3589f6c81e4 ("sched: Allow for overlapping sched_domain spans") Debugged-by: Lauro Ramos Venancio Signed-off-by: Peter Zijlstra (Intel) --- kernel/sched/topology.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/kernel/sched/topology.c +++ b/kernel/sched/topology.c @@ -525,7 +525,7 @@ build_overlap_sched_groups(struct sched_ cpumask_clear(covered); - for_each_cpu(i, span) { + for_each_cpu_wrap(i, span, cpu) { struct cpumask *sg_span; if (cpumask_test_cpu(i, covered))