From: Peter Zijlstra Date: Thu, 7 Sep 2017 15:03:50 +0000 (+0200) Subject: sched/fair: Avoid newidle balance for !active CPUs X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=2800486ee34825d954f64c6f98037daea328f121;p=GitHub%2Fmoto-9609%2Fandroid_kernel_motorola_exynos9610.git sched/fair: Avoid newidle balance for !active CPUs On CPU hot unplug, when parking the last kthread we'll try and schedule into idle to kill the CPU. This last schedule can (and does) trigger newidle balance because at this point the sched domains are still up because of commit: 77d1dfda0e79 ("sched/topology, cpuset: Avoid spurious/wrong domain rebuilds") Obviously pulling tasks to an already offline CPU is a bad idea, and all balancing operations _should_ be subject to cpu_active_mask, make it so. Reported-by: Thomas Gleixner Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Peter Zijlstra Fixes: 77d1dfda0e79 ("sched/topology, cpuset: Avoid spurious/wrong domain rebuilds") Link: http://lkml.kernel.org/r/20170907150613.994135806@infradead.org Signed-off-by: Ingo Molnar --- diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 8415d1ec2b84..3bcea40d3029 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -8447,6 +8447,12 @@ static int idle_balance(struct rq *this_rq, struct rq_flags *rf) */ this_rq->idle_stamp = rq_clock(this_rq); + /* + * Do not pull tasks towards !active CPUs... + */ + if (!cpu_active(this_cpu)) + return 0; + /* * This is OK, because current is on_cpu, which avoids it being picked * for load-balance and preemption/IRQs are still disabled avoiding