From: Peter Zijlstra <peterz@infradead.org>
To: Kirill Tkhai <tkhai@yandex.ru>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Ingo Molnar <mingo@redhat.com>,
Steven Rostedt <rostedt@goodmis.org>,
stable@vger.kernel.org
Subject: Re: [PATCH] sched/rt: Fix rq's cpupri leak while enqueue/dequeue child RT entities
Date: Fri, 13 Dec 2013 16:42:11 +0100 [thread overview]
Message-ID: <20131213154211.GP21999@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <49231385567953@web4m.yandex.ru>
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.
next prev parent reply other threads:[~2013-12-13 15:42 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 [this message]
2013-12-17 12:02 ` Kirill Tkhai
2013-12-17 12:46 ` Peter Zijlstra
2013-12-17 13:08 ` Kirill Tkhai
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