From e917ca779fad7e1c3a2d4c1f0992596fc68acf47 Mon Sep 17 00:00:00 2001
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
Date: Thu, 31 May 2012 12:05:32 +0200
Subject: [PATCH] --- yaml --- r: 310639 b: refs/heads/master c:
 c3decf0dfbc95736b7c0ab68fa4e5854c4734da9 h: refs/heads/master i:   310637:
 532d71f1cdcdfa13b786a4a705f81cfc53328d67   310635:
 a3836f81bf7574e4b18882bf752b08c14d8e3675   310631:
 0677786a3d52c82497e9e6219a1d06fbb562035a   310623:
 29e89759acdae865fb68941af3b760c8fa498c49 v: v3

---
 [refs]                    |  2 +-
 trunk/kernel/sched/core.c | 13 ++++++++++++-
 trunk/kernel/sched/fair.c |  2 +-
 3 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/[refs] b/[refs]
index e9d3b03af1ac..026ef370581d 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: c1174876874dcf8986806e4dad3d7d07af20b439
+refs/heads/master: c3decf0dfbc95736b7c0ab68fa4e5854c4734da9
diff --git a/trunk/kernel/sched/core.c b/trunk/kernel/sched/core.c
index 781acb91a50a..725ee7c1c8cf 100644
--- a/trunk/kernel/sched/core.c
+++ b/trunk/kernel/sched/core.c
@@ -5604,7 +5604,12 @@ static int sched_domain_debug_one(struct sched_domain *sd, int cpu, int level,
 			break;
 		}
 
-		if (!group->sgp->power) {
+		/*
+		 * Even though we initialize ->power to something semi-sane,
+		 * we leave power_orig unset. This allows us to detect if
+		 * domain iteration is still funny without causing /0 traps.
+		 */
+		if (!group->sgp->power_orig) {
 			printk(KERN_CONT "\n");
 			printk(KERN_ERR "ERROR: domain->cpu_power not "
 					"set\n");
@@ -6075,6 +6080,12 @@ build_overlap_sched_groups(struct sched_domain *sd, int cpu)
 		if (atomic_inc_return(&sg->sgp->ref) == 1)
 			build_group_mask(sd, sg);
 
+		/*
+		 * Initialize sgp->power such that even if we mess up the
+		 * domains and no possible iteration will get us here, we won't
+		 * die on a /0 trap.
+		 */
+		sg->sgp->power = SCHED_POWER_SCALE * cpumask_weight(sg_span);
 
 		/*
 		 * Make sure the first group of this domain contains the
diff --git a/trunk/kernel/sched/fair.c b/trunk/kernel/sched/fair.c
index 54cbaa4e7b37..c9fd6d673d05 100644
--- a/trunk/kernel/sched/fair.c
+++ b/trunk/kernel/sched/fair.c
@@ -3602,7 +3602,7 @@ void update_group_power(struct sched_domain *sd, int cpu)
 		} while (group != child->groups);
 	}
 
-	sdg->sgp->power = power;
+	sdg->sgp->power_orig = sdg->sgp->power = power;
 }
 
 /*