From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753196AbbDFRr7 (ORCPT ); Mon, 6 Apr 2015 13:47:59 -0400 Received: from smtp.codeaurora.org ([198.145.29.96]:42251 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753022AbbDFRrx (ORCPT ); Mon, 6 Apr 2015 13:47:53 -0400 Message-ID: <5522C6C6.7050106@codeaurora.org> Date: Mon, 06 Apr 2015 10:47:50 -0700 From: Stephen Boyd User-Agent: Mozilla/5.0 (X11; Linux i686 on x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.5.0 MIME-Version: 1.0 To: Tyler Baker , Mark Rutland CC: Russell King , Nicolas Pitre , "linux-sh@vger.kernel.org" , Magnus Damm , "linux-kernel@vger.kernel.org" , Dave Martin , linux-arm-kernel , Simon Horman , "Kevin's boot bot" Subject: Re: [PATCH v3] ARM: smp: Only expose /sys/.../cpuX/online if hotpluggable References: <1423874574-3494-1-git-send-email-sboyd@codeaurora.org> <20150218222731.GC24177@verge.net.au> <54E51FFD.7080506@codeaurora.org> <20150219221456.GC617@verge.net.au> In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/06/15 10:19, Tyler Baker wrote: > On 19 February 2015 at 14:14, Simon Horman wrote: >> On Wed, Feb 18, 2015 at 03:27:57PM -0800, Stephen Boyd wrote: >>> On 02/18/15 14:27, Simon Horman wrote: >>>> On Fri, Feb 13, 2015 at 04:42:54PM -0800, Stephen Boyd wrote: >>>>> Writes to /sys/.../cpuX/online fail if we determine the platform >>>>> doesn't support hotplug for that CPU. Furthermore, if the cpu_die >>>>> op isn't specified the system hangs when we try to offline a CPU >>>>> and it comes right back online unexpectedly. Let's figure this >>>>> stuff out before we make the sysfs nodes so that the online file >>>>> doesn't even exist if it isn't (at least sometimes) possible to >>>>> hotplug the CPU. >>>>> >>>>> Add a new cpu_can_disable op and repoint all cpu_disable >>>>> implementations at it because all current users use the op to >>>>> indicate if a CPU can be hotplugged or not in a static fashion. >>>>> With PSCI we may need to introduce a cpu_disable op so that the >>>>> secure OS can be migrated off the CPU we're trying to hotplug. >>>>> In this case, the cpu_can_disable op will indicate that all CPUs >>>>> are hotpluggable by returning 1, but the cpu_disable op will make >>>>> a PSCI migration call and occasionally fail, denying the hotplug >>>>> of a CPU. This shouldn't be any worse than x86 where we may >>>>> indicate that all CPUs are hotpluggable but occasionally we can't >>>>> offline a CPU due to check_irq_vectors_for_cpu_disable() failing >>>>> to find a CPU to move vectors to. >>>>> >>>>> Cc: Mark Rutland >>>>> Cc: Nicolas Pitre >>>>> Cc: Dave Martin >>>>> Cc: Simon Horman >>>>> Cc: Magnus Damm >>>>> Cc: >>>>> Signed-off-by: Stephen Boyd >>>>> --- >>>>> >>>>> Changes since v2: >>>>> * Left cpu_disable op in place >>>>> * Split out shmobile function deletion >>>>> >>>>> arch/arm/common/mcpm_platsmp.c | 12 ++++-------- >>>>> arch/arm/include/asm/smp.h | 10 ++++++++++ >>>>> arch/arm/kernel/setup.c | 2 +- >>>>> arch/arm/kernel/smp.c | 15 ++++++++++++++- >>>>> arch/arm/mach-shmobile/common.h | 2 +- >>>>> arch/arm/mach-shmobile/platsmp.c | 4 ++-- >>>>> arch/arm/mach-shmobile/smp-r8a7790.c | 2 +- >>>>> arch/arm/mach-shmobile/smp-r8a7791.c | 2 +- >>>>> arch/arm/mach-shmobile/smp-sh73a0.c | 2 +- >>>>> 9 files changed, 35 insertions(+), 16 deletions(-) >>>> I think it would make sense to separate the ARM-core changes >>>> from the mach-shmobile integration changes. >>> Are you saying two (three?) patches to add the op, and then move over >>> each struct smp_operations? It's all going through rmk's tree so I'll >>> leave that up to him. >> I'm also happy to let RMK to decide what he thinks is best. > Apologies for bringing up an older thread, but was this change ever > picked up? I recently hit this issue when I was running the kselftest > suite (specifically the cpu-hotplug test case) on the ARM boards from > kernelci.org. I don't see it in -next so I've tested the core changes > and confirmed it the fixes the cpu-hotplug behavior on platforms that > do not support it. No it hasn't gone anywhere. It would be good if Mark Rutland could ack the patch, which I hope would give enough confidence to Russell that the patch is good. Your tested-by would also be welcome. I'll go make the bool change that Geert suggested and resend. -- Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project