From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753299Ab3LQMIc (ORCPT ); Tue, 17 Dec 2013 07:08:32 -0500 Received: from forward5h.mail.yandex.net ([84.201.186.23]:34217 "EHLO forward5h.mail.yandex.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750929Ab3LQMIa (ORCPT ); Tue, 17 Dec 2013 07:08:30 -0500 X-Greylist: delayed 324 seconds by postgrey-1.27 at vger.kernel.org; Tue, 17 Dec 2013 07:08:30 EST From: Kirill Tkhai To: Peter Zijlstra , Ingo Molnar Cc: "linux-kernel@vger.kernel.org" , Steven Rostedt , "stable@vger.kernel.org" In-Reply-To: <20131213154211.GP21999@twins.programming.kicks-ass.net> References: <49231385567953@web4m.yandex.ru> <20131213154211.GP21999@twins.programming.kicks-ass.net> Subject: Re: [PATCH] sched/rt: Fix rq's cpupri leak while enqueue/dequeue child RT entities MIME-Version: 1.0 Message-Id: <122071387281778@web18h.yandex.ru> X-Mailer: Yamail [ http://yandex.ru ] 5.0 Date: Tue, 17 Dec 2013 16:02:58 +0400 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=koi8-r Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 13.12.2013, 19:42, "Peter Zijlstra" : > On Wed, Nov 27, 2013 at 07:59:13PM +0400, Kirill Tkhai wrote: > >> šThis patch touches RT group scheduling case. >> >> šFunctions inc_rt_prio_smp() and dec_rt_prio_smp() change (global) rq's priority, >> šwhile rt_rq passed to them may be not the top-level rt_rq. This is wrong, because >> šchanging of priority on a child level does not guarantee that the priority is >> šthe highest all over the rq. So, this leak makes RT balancing unusable. >> >> šThe short example: the task having the highest priority among all rq's RT tasks >> š(no one other task has the same priority) are waking on a throttle rt_rq. >> šThe rq's cpupri is set to the task's priority equivalent, but real >> šrq->rt.highest_prio.curr is less. >> >> šThe patch below fixes the problem. >> >> šIt 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?