From: Kirill Tkhai <tkhai@yandex.ru>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Steven Rostedt <rostedt@goodmis.org>,
"stable@vger.kernel.org" <stable@vger.kernel.org>
Subject: Re: [PATCH] sched/rt: Fix rq's cpupri leak while enqueue/dequeue child RT entities
Date: Tue, 17 Dec 2013 17:08:02 +0400 [thread overview]
Message-ID: <96341387285682@web18g.yandex.ru> (raw)
In-Reply-To: <20131217124656.GI21999@twins.programming.kicks-ass.net>
17.12.2013, 16:47, "Peter Zijlstra" <peterz@infradead.org>:
> On Tue, Dec 17, 2013 at 04:02:58PM +0400, Kirill Tkhai wrote:
>
>> О©╫13.12.2013, 19:42, "Peter Zijlstra" <peterz@infradead.org>:
>>> О©╫On Wed, Nov 27, 2013 at 07:59:13PM +0400, Kirill Tkhai wrote:
>>>> О©╫О©╫This patch touches RT group scheduling case.
>>>>
>>>> О©╫О©╫Functions inc_rt_prio_smp() and dec_rt_prio_smp() change (global) rq's priority,
>>>> О©╫О©╫while rt_rq passed to them may be not the top-level rt_rq. This is wrong, because
>>>> О©╫О©╫changing of priority on a child level does not guarantee that the priority is
>>>> О©╫О©╫the highest all over the rq. So, this leak makes RT balancing unusable.
>>>>
>>>> О©╫О©╫The short example: the task having the highest priority among all rq's RT tasks
>>>> О©╫О©╫(no one other task has the same priority) are waking on a throttle rt_rq.
>>>> О©╫О©╫The rq's cpupri is set to the task's priority equivalent, but real
>>>> О©╫О©╫rq->rt.highest_prio.curr is less.
>>>>
>>>> О©╫О©╫The patch below fixes the problem.
>>>>
>>>> О©╫О©╫It looks like all version have this bug, so I CC'ed stable mailing list.
>>> О©╫Yeah, I think this is right.
>>>
>>> О©╫cpupri stuff should indeed only be changed for the top level group.
>> О©╫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
prev parent reply other threads:[~2013-12-17 13:08 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-11-27 15:59 [PATCH] sched/rt: Fix rq's cpupri leak while enqueue/dequeue child RT entities Kirill Tkhai
2013-12-12 10:30 ` Kirill Tkhai
2013-12-13 15:42 ` Peter Zijlstra
2013-12-17 12:02 ` Kirill Tkhai
2013-12-17 12:46 ` Peter Zijlstra
2013-12-17 13:08 ` Kirill Tkhai [this message]
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