Commit-ID: 9abf24d465180f5f2eb26a43545348262f16b771
Gitweb: http://git.kernel.org/tip/9abf24d465180f5f2eb26a43545348262f16b771
Author: Srikar Dronamraju <srikar@xxxxxxxxxxxxxxxxxx>
AuthorDate: Tue, 12 Nov 2013 22:11:26 +0530
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Tue, 19 Nov 2013 17:01:15 +0100
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@xxxxxxxxxxxxxxxxxx>
[ Added comment and tweaked patch. ]
Signed-off-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: mikey@xxxxxxxxxxx
Link: http://lkml.kernel.org/r/20131113151718.GN21461@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
kernel/sched/fair.c | 27 ++++++++++++++++++++++++---
1 file 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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