From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752745AbbDFRTt (ORCPT ); Mon, 6 Apr 2015 13:19:49 -0400 Received: from mail-wi0-f176.google.com ([209.85.212.176]:33417 "EHLO mail-wi0-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752726AbbDFRTq (ORCPT ); Mon, 6 Apr 2015 13:19:46 -0400 MIME-Version: 1.0 In-Reply-To: <20150219221456.GC617@verge.net.au> References: <1423874574-3494-1-git-send-email-sboyd@codeaurora.org> <20150218222731.GC24177@verge.net.au> <54E51FFD.7080506@codeaurora.org> <20150219221456.GC617@verge.net.au> Date: Mon, 6 Apr 2015 10:19:45 -0700 Message-ID: Subject: Re: [PATCH v3] ARM: smp: Only expose /sys/.../cpuX/online if hotpluggable From: Tyler Baker To: Stephen Boyd Cc: Mark Rutland , 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" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel - Tyler