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authorPeter Zijlstra <peterz@infradead.org>2017-09-07 17:03:50 +0200
committerIngo Molnar <mingo@kernel.org>2017-09-12 17:41:03 +0200
commit2800486ee34825d954f64c6f98037daea328f121 (patch)
treeb734003f0085ce39c7688259c7aeb6617ccff6e4
parent46123355af729514e6fa8b8a9dd1e645e61a6466 (diff)
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 <tglx@linutronix.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> 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 <mingo@kernel.org>
-rw-r--r--kernel/sched/fair.c6
1 files changed, 6 insertions, 0 deletions
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
@@ -8448,6 +8448,12 @@ 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
* further scheduler activity on it and we're being very careful to