[PATCH Resend 3/3] sched: fix update NOHZ_IDLE flag

From: Vincent Guittot
Date: Mon Dec 03 2012 - 07:27:04 EST


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 (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@xxxxxxxxxx>
---
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 24a5588..1ef57a8 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6311,7 +6311,7 @@ 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

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