From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753634Ab3LQMrJ (ORCPT ); Tue, 17 Dec 2013 07:47:09 -0500 Received: from merlin.infradead.org ([205.233.59.134]:41777 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752435Ab3LQMrG (ORCPT ); Tue, 17 Dec 2013 07:47:06 -0500 Date: Tue, 17 Dec 2013 13:46:56 +0100 From: Peter Zijlstra To: Kirill Tkhai Cc: Ingo Molnar , "linux-kernel@vger.kernel.org" , Steven Rostedt , "stable@vger.kernel.org" Subject: Re: [PATCH] sched/rt: Fix rq's cpupri leak while enqueue/dequeue child RT entities Message-ID: <20131217124656.GI21999@twins.programming.kicks-ass.net> References: <49231385567953@web4m.yandex.ru> <20131213154211.GP21999@twins.programming.kicks-ass.net> <122071387281778@web18h.yandex.ru> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <122071387281778@web18h.yandex.ru> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Dec 17, 2013 at 04:02:58PM +0400, Kirill Tkhai wrote: > > > 13.12.2013, 19:42, "Peter Zijlstra" : > > 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