From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751926AbaEBLc6 (ORCPT ); Fri, 2 May 2014 07:32:58 -0400 Received: from mx1.redhat.com ([209.132.183.28]:10802 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751834AbaEBLcz (ORCPT ); Fri, 2 May 2014 07:32:55 -0400 Date: Fri, 2 May 2014 13:32:19 +0200 From: Igor Mammedov To: Toshi Kani Cc: linux-kernel@vger.kernel.org, tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, x86@kernel.org, bp@suse.de, paul.gortmaker@windriver.com, JBeulich@suse.com, prarit@redhat.com, drjones@redhat.com, riel@redhat.com, gong.chen@linux.intel.com, andi@firstfloor.org, lenb@kernel.org, rjw@rjwysocki.net, linux-acpi@vger.kernel.org Subject: Re: [PATCH v4 3/5] acpi_processor: do not mark present at boot but not onlined CPU as onlined Message-ID: <20140502133219.5de5c683@nial.usersys.redhat.com> In-Reply-To: <1398893151.1789.46.camel@misato.fc.hp.com> References: <1397488277-14865-1-git-send-email-imammedo@redhat.com> <1397488277-14865-4-git-send-email-imammedo@redhat.com> <1398893151.1789.46.camel@misato.fc.hp.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 30 Apr 2014 15:25:51 -0600 Toshi Kani wrote: > On Mon, 2014-04-14 at 17:11 +0200, Igor Mammedov wrote: > > acpi_processor_add() assumes that present at boot CPUs > > are always onlined, it is not so if a CPU failed to become > > onlined. As result acpi_processor_add() will mark such CPU > > device as onlined in sysfs and following attempts to > > online/offline it using /sys/device/system/cpu/cpuX/online > > attribute will fail. > > > > Do not poke into device internals in acpi_processor_add() > > and touch "struct device { .offline }" attribute, since > > for CPUs onlined at boot it's set by: > > topology_init() -> arch_register_cpu() -> register_cpu() > > before ACPI device tree is parsed, and for hotplugged > > CPUs it's set when userspace onlines CPU via sysfs. > > > > Signed-off-by: Igor Mammedov > > --- > > v2: > > - fix regression in v1 leading to NULL pointer dereference > > on CPU unplug, do not remove "pr->dev = dev;" > > --- > > drivers/acpi/acpi_processor.c | 1 - > > 1 files changed, 0 insertions(+), 1 deletions(-) > > > > diff --git a/drivers/acpi/acpi_processor.c b/drivers/acpi/acpi_processor.c > > index c29c2c3..42d66f8 100644 > > --- a/drivers/acpi/acpi_processor.c > > +++ b/drivers/acpi/acpi_processor.c:q > > @@ -404,7 +404,6 @@ static int acpi_processor_add(struct acpi_device *device, > > goto err; > > > > pr->dev = dev; > > - dev->offline = pr->flags.need_hotplug_init; > > IIRC, this change was necessary to handle the case when maxcpus=X is > specified at boot. In this case, excessive CPU's dev->offline needs to > be set to 1. Can you verify this? Option 'maxcpus' works just fine without and with this patch since a bit earlier in acpi_processor_add() it exits in case of extra present CPUs: #ifdef CONFIG_SMP if (pr->id >= setup_max_cpus && pr->id != 0) return 0; #endif and execution doesn't get to the point the patch touches. The point is that acpi_processor_add() shouldn't touch dev->offline at all and allow register_cpu() handle it. > > Thanks, > -Toshi >