sched/rt: Fix rq's cpupri leak while enqueue/dequeue child RT entities
This patch touches the RT group scheduling case. Functions inc_rt_prio_smp() and dec_rt_prio_smp() change (global) rq's priority, while rt_rq passed to them may be not the top-level rt_rq. This is wrong, because changing of priority on a child level does not guarantee that the priority is the highest all over the rq. So, this leak makes RT balancing unusable. The short example: the task having the highest priority among all rq's RT tasks (no one other task has the same priority) are waking on a throttle rt_rq. The rq's cpupri is set to the task's priority equivalent, but real rq->rt.highest_prio.curr is less. The patch below fixes the problem. Signed-off-by: Kirill Tkhai <tkhai@yandex.ru> Signed-off-by: Peter Zijlstra <peterz@infradead.org> CC: Steven Rostedt <rostedt@goodmis.org> CC: stable@vger.kernel.org Link: http://lkml.kernel.org/r/49231385567953@web4m.yandex.ru Signed-off-by: Ingo Molnar <mingo@kernel.org>
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@ -901,6 +901,13 @@ inc_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio)
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{
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struct rq *rq = rq_of_rt_rq(rt_rq);
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#ifdef CONFIG_RT_GROUP_SCHED
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/*
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* Change rq's cpupri only if rt_rq is the top queue.
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*/
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if (&rq->rt != rt_rq)
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return;
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#endif
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if (rq->online && prio < prev_prio)
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cpupri_set(&rq->rd->cpupri, rq->cpu, prio);
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}
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@ -910,6 +917,13 @@ dec_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio)
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{
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struct rq *rq = rq_of_rt_rq(rt_rq);
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#ifdef CONFIG_RT_GROUP_SCHED
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/*
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* Change rq's cpupri only if rt_rq is the top queue.
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*/
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if (&rq->rt != rt_rq)
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return;
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#endif
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if (rq->online && rt_rq->highest_prio.curr != prev_prio)
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cpupri_set(&rq->rd->cpupri, rq->cpu, rt_rq->highest_prio.curr);
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}
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