linux-kernel - Re: [PATCH] sched/rt: Fix rq's cpupri leak while enqueue/dequeue child RT entities

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Date:	Tue, 17 Dec 2013 17:08:02 +0400
From:	Kirill Tkhai <tkhai@...dex.ru>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Ingo Molnar <mingo@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	"stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: Re: [PATCH] sched/rt: Fix rq's cpupri leak while enqueue/dequeue child RT entities

17.12.2013, 16:47, "Peter Zijlstra" <peterz@...radead.org>:
> On Tue, Dec 17, 2013 at 04:02:58PM +0400, Kirill Tkhai wrote:
>
>>  13.12.2013, 19:42, "Peter Zijlstra" <peterz@...radead.org>:
>>>  On Wed, Nov 27, 2013 at 07:59:13PM +0400, Kirill Tkhai wrote:
>>>>   This patch touches 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.
>>>>
>>>>   It looks like all version have this bug, so I CC'ed stable mailing list.
>>>  Yeah, I think this is right.
>>>
>>>  cpupri stuff should indeed only be changed for the top level group.
>>  Ingo, are you going to apply this patch? Or will you give any comments?
>
> I queued it, Ingo should get it through me somewhere today if all things
> go well.
>
> Thanks

Thanks, Peter

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