From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751410AbbCQEp2 (ORCPT ); Tue, 17 Mar 2015 00:45:28 -0400 Received: from mail-we0-f178.google.com ([74.125.82.178]:36294 "EHLO mail-we0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750716AbbCQEpZ (ORCPT ); Tue, 17 Mar 2015 00:45:25 -0400 Message-ID: <1426567522.12107.8.camel@gmail.com> Subject: Re: [rfc patch v2] rt,nohz_full: fix nohz_full for PREEMPT_RT_FULL From: Mike Galbraith To: Sebastian Andrzej Siewior Cc: linux-rt-users , LKML , Thomas Gleixner , rostedt@goodmis.org, John Kacur Date: Tue, 17 Mar 2015 05:45:22 +0100 In-Reply-To: <1426557233.20938.8.camel@gmail.com> References: <20150216111822.GA21649@linutronix.de> <1424258514.3819.39.camel@gmail.com> <20150309134535.GA13768@linutronix.de> <1425911771.30469.8.camel@gmail.com> <1425980136.3507.17.camel@gmail.com> <1426153093.4190.2.camel@gmail.com> <1426222405.17611.7.camel@gmail.com> <20150316202409.GF28130@linutronix.de> <1426557233.20938.8.camel@gmail.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.12.11 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2015-03-17 at 02:53 +0100, Mike Galbraith wrote: > On Mon, 2015-03-16 at 21:24 +0100, Sebastian Andrzej Siewior wrote: > > What you do is that you accept the fact that the timer-softirq is > > scheduled for no reason and then you try to disable the tick from within > > the timer-softirq. I assumed that it would work get the "expired timer" > > somehow. > > Yup, it works around that otherwise crippling wakeup. If I re-apply.. > > timers-do-not-raise-softirq-unconditionally.patch > > ..the workaround is not needed of course, but the livelock fix still is. > I haven't yet tested that in 3.18-rt though, only 4.0-rt, but I presume > it'll be the same deal there when I do. Did that, and it is. Fire up tbench 4 + make -j4 on my i7-4790+smt box booted nohz_full=2,3,6,7, death spiral begins shortly thereafter. -Mike