From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965780AbbBDNO2 (ORCPT ); Wed, 4 Feb 2015 08:14:28 -0500 Received: from e39.co.us.ibm.com ([32.97.110.160]:33004 "EHLO e39.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965570AbbBDNO0 (ORCPT ); Wed, 4 Feb 2015 08:14:26 -0500 Date: Wed, 4 Feb 2015 05:14:20 -0800 From: "Paul E. McKenney" To: Russell King - ARM Linux Cc: Krzysztof Kozlowski , Fengguang Wu , LKP , linux-kernel@vger.kernel.org, Bartlomiej Zolnierkiewicz , linux-arm-kernel@lists.infradead.org, Arnd Bergmann , MarkRutland Subject: Re: [rcu] [ INFO: suspicious RCU usage. ] Message-ID: <20150204131420.GC5370@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20150201025922.GA16820@wfg-t540p.sh.intel.com> <1422957702.17540.1.camel@AMDC1943> <20150203162704.GR19109@linux.vnet.ibm.com> <1423049947.19547.6.camel@AMDC1943> <20150204130018.GG8656@n2100.arm.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150204130018.GG8656@n2100.arm.linux.org.uk> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 15020413-0033-0000-0000-0000038E29C3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Feb 04, 2015 at 01:00:18PM +0000, Russell King - ARM Linux wrote: > On Wed, Feb 04, 2015 at 12:39:07PM +0100, Krzysztof Kozlowski wrote: > > +Cc some ARM people > > I wish that people would CC this list with problems seen on ARM. I'm > minded to just ignore this message because of this in the hope that by > doing so, people will learn something... > > > > Another thing I could do would be to have an arch-specific Kconfig > > > variable that made ARM responsible for informing RCU that the CPU > > > was departing, which would allow a call to as follows to be placed > > > immediately after the complete(): > > > > > > rcu_cpu_notify(NULL, CPU_DYING_IDLE, (void *)(long)smp_processor_id()); > > > > > > Note: This absolutely requires that the rcu_cpu_notify() -always- > > > be allowed to execute!!! This will not work if there is -any- possibility > > > of __cpu_die() powering off the outgoing CPU before the call to > > > rcu_cpu_notify() returns. > > Exactly, so that's not going to be possible. The completion at that > point marks the point at which power _could_ be removed from the CPU > going down. OK, sounds like a polling loop is required. Thanx, Paul From mboxrd@z Thu Jan 1 00:00:00 1970 From: paulmck@linux.vnet.ibm.com (Paul E. McKenney) Date: Wed, 4 Feb 2015 05:14:20 -0800 Subject: [rcu] [ INFO: suspicious RCU usage. ] In-Reply-To: <20150204130018.GG8656@n2100.arm.linux.org.uk> References: <20150201025922.GA16820@wfg-t540p.sh.intel.com> <1422957702.17540.1.camel@AMDC1943> <20150203162704.GR19109@linux.vnet.ibm.com> <1423049947.19547.6.camel@AMDC1943> <20150204130018.GG8656@n2100.arm.linux.org.uk> Message-ID: <20150204131420.GC5370@linux.vnet.ibm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Wed, Feb 04, 2015 at 01:00:18PM +0000, Russell King - ARM Linux wrote: > On Wed, Feb 04, 2015 at 12:39:07PM +0100, Krzysztof Kozlowski wrote: > > +Cc some ARM people > > I wish that people would CC this list with problems seen on ARM. I'm > minded to just ignore this message because of this in the hope that by > doing so, people will learn something... > > > > Another thing I could do would be to have an arch-specific Kconfig > > > variable that made ARM responsible for informing RCU that the CPU > > > was departing, which would allow a call to as follows to be placed > > > immediately after the complete(): > > > > > > rcu_cpu_notify(NULL, CPU_DYING_IDLE, (void *)(long)smp_processor_id()); > > > > > > Note: This absolutely requires that the rcu_cpu_notify() -always- > > > be allowed to execute!!! This will not work if there is -any- possibility > > > of __cpu_die() powering off the outgoing CPU before the call to > > > rcu_cpu_notify() returns. > > Exactly, so that's not going to be possible. The completion at that > point marks the point at which power _could_ be removed from the CPU > going down. OK, sounds like a polling loop is required. Thanx, Paul From mboxrd@z Thu Jan 1 00:00:00 1970 Content-Type: multipart/mixed; boundary="===============5670848952713163030==" MIME-Version: 1.0 From: Paul E. McKenney To: lkp@lists.01.org Subject: Re: [rcu] [ INFO: suspicious RCU usage. ] Date: Wed, 04 Feb 2015 05:14:20 -0800 Message-ID: <20150204131420.GC5370@linux.vnet.ibm.com> In-Reply-To: <20150204130018.GG8656@n2100.arm.linux.org.uk> List-Id: --===============5670848952713163030== Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable On Wed, Feb 04, 2015 at 01:00:18PM +0000, Russell King - ARM Linux wrote: > On Wed, Feb 04, 2015 at 12:39:07PM +0100, Krzysztof Kozlowski wrote: > > +Cc some ARM people > = > I wish that people would CC this list with problems seen on ARM. I'm > minded to just ignore this message because of this in the hope that by > doing so, people will learn something... > = > > > Another thing I could do would be to have an arch-specific Kconfig > > > variable that made ARM responsible for informing RCU that the CPU > > > was departing, which would allow a call to as follows to be placed > > > immediately after the complete(): > > > = > > > rcu_cpu_notify(NULL, CPU_DYING_IDLE, (void *)(long)smp_processor_id()= ); > > > = > > > Note: This absolutely requires that the rcu_cpu_notify() -always- > > > be allowed to execute!!! This will not work if there is -any- possib= ility > > > of __cpu_die() powering off the outgoing CPU before the call to > > > rcu_cpu_notify() returns. > = > Exactly, so that's not going to be possible. The completion at that > point marks the point at which power _could_ be removed from the CPU > going down. OK, sounds like a polling loop is required. Thanx, Paul --===============5670848952713163030==--