sched: Robustify topology setup

We hard assume that higher topology levels are supersets of lower
levels.

Detect, warn and try to fixup when we encounter this violated.

Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Josh Boyer <jwboyer@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Bruno Wolff III <bruno@wolff.to>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20140722094740.GJ12054@laptop.lan
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 14 insertions, 0 deletions

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 415ab0268b51..2a36a74c16ae 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -6481,6 +6481,20 @@ struct sched_domain *build_sched_domain(struct sched_domain_topology_level *tl,
                 sched_domain_level_max = max(sched_domain_level_max, sd->level);
                 child->parent = sd;
                 sd->child = child;
+
+                if (!cpumask_subset(sched_domain_span(child),
+                                    sched_domain_span(sd))) {
+                        pr_err("BUG: arch topology borken\n");
+#ifdef CONFIG_SCHED_DEBUG
+                        pr_err("     the %s domain not a subset of the %s domain\n",
+                                        child->name, sd->name);
+#endif
+                        /* Fixup, ensure @sd has at least @child cpus. */
+                        cpumask_or(sched_domain_span(sd),
+                                   sched_domain_span(sd),
+                                   sched_domain_span(child));
+                }
+
         }
         set_domain_attribute(sd, attr);