[tip:sched/core] sched: Robustify topology setup

[tip-bot for Peter Zijlstra]

Commit-ID:  6ae72dff37596f736b795426306404f0793e4b1b
Gitweb:     http://git.kernel.org/tip/6ae72dff37596f736b795426306404f0793e4b1b
Author:     Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate: Tue, 22 Jul 2014 11:47:40 +0200
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Mon, 28 Jul 2014 10:04:13 +0200

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@xxxxxxx>
Signed-off-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Josh Boyer <jwboyer@xxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: Bruno Wolff III <bruno@xxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/20140722094740.GJ12054@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 kernel/sched/core.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 415ab02..2a36a74 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);
 
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