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@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 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 }