sched/fair: Add some serialization to the sched_domain load-balance walk

Since the sched_domain walk is completely unserialized (!SD_SERIALIZE)
it is possible that multiple cpus in the group get elected to do the
next level. Avoid this by adding some serialization.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-vqh9ai6s0ewmeakjz80w4qz6@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 1 insertions, 0 deletions

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 4a559bf0622f..3cbfb55bde25 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -927,6 +927,7 @@ struct sched_group_power {
 struct sched_group {
         struct sched_group *next;       /* Must be a circular list */
         atomic_t ref;
+        int balance_cpu;
 
         unsigned int group_weight;
         struct sched_group_power *sgp;