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authorSrikar Dronamraju <srikar@linux.vnet.ibm.com>2013-11-12 22:11:26 +0530
committerIngo Molnar <mingo@kernel.org>2013-11-19 17:01:15 +0100
commit9abf24d465180f5f2eb26a43545348262f16b771 (patch)
treeb823e6a604a522d7b0c3a374f6d8b8aab4a8acd5
parent7486d6da09d4d76d49c68826c97578246936092b (diff)
downloadop-kernel-dev-9abf24d465180f5f2eb26a43545348262f16b771.zip
op-kernel-dev-9abf24d465180f5f2eb26a43545348262f16b771.tar.gz
sched: Check sched_domain before computing group power
After commit 863bffc80898 ("sched/fair: Fix group power_orig computation"), we can dereference rq->sd before it is set. Fix this by falling back to power_of() in this case and add a comment explaining things. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> [ Added comment and tweaked patch. ] Signed-off-by: Peter Zijlstra <peterz@infradead.org> Cc: mikey@neuling.org Link: http://lkml.kernel.org/r/20131113151718.GN21461@twins.programming.kicks-ass.net Signed-off-by: Ingo Molnar <mingo@kernel.org>
-rw-r--r--kernel/sched/fair.c27
1 files changed, 24 insertions, 3 deletions
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index e8b652e..fd773ad 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5379,10 +5379,31 @@ void update_group_power(struct sched_domain *sd, int cpu)
*/
for_each_cpu(cpu, sched_group_cpus(sdg)) {
- struct sched_group *sg = cpu_rq(cpu)->sd->groups;
+ struct sched_group_power *sgp;
+ struct rq *rq = cpu_rq(cpu);
- power_orig += sg->sgp->power_orig;
- power += sg->sgp->power;
+ /*
+ * build_sched_domains() -> init_sched_groups_power()
+ * gets here before we've attached the domains to the
+ * runqueues.
+ *
+ * Use power_of(), which is set irrespective of domains
+ * in update_cpu_power().
+ *
+ * This avoids power/power_orig from being 0 and
+ * causing divide-by-zero issues on boot.
+ *
+ * Runtime updates will correct power_orig.
+ */
+ if (unlikely(!rq->sd)) {
+ power_orig += power_of(cpu);
+ power += power_of(cpu);
+ continue;
+ }
+
+ sgp = rq->sd->groups->sgp;
+ power_orig += sgp->power_orig;
+ power += sgp->power;
}
} else {
/*
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