[PATCH v2 2/2] sched: fix update NOHZ_IDLE flag

[Vincent Guittot <vincent.guittot@linaro.org>]

The function nohz_kick_needed modifies NOHZ_IDLE flag that is used to update
the nr_busy_cpus of the sched_group.
When the sched_domain are updated (during the boot or because of the unplug of
a CPUs as an example) a null_domain is attached to CPUs. We have to test
likely(!on_null_domain(cpu) first in order to detect such intialization step
and to not modify the NOHZ_IDLE flag

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
---
 kernel/sched/fair.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 5eea870..dac2edf 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5695,7 +5695,7 @@ void trigger_load_balance(struct rq *rq, int cpu)
 	    likely(!on_null_domain(cpu)))
 		raise_softirq(SCHED_SOFTIRQ);
 #ifdef CONFIG_NO_HZ
-	if (nohz_kick_needed(rq, cpu) && likely(!on_null_domain(cpu)))
+	if (likely(!on_null_domain(cpu)) && nohz_kick_needed(rq, cpu))
 		nohz_balancer_kick(cpu);
 #endif
 }
-- 
1.7.9.5