From mboxrd@z Thu Jan 1 00:00:00 1970 From: Toshi Kani Subject: Re: [PATCH v4 3/5] acpi_processor: do not mark present at boot but not onlined CPU as onlined Date: Fri, 02 May 2014 11:23:43 -0600 Message-ID: <1399051423.1789.93.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> <20140502133219.5de5c683@nial.usersys.redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Return-path: Received: from g4t3426.houston.hp.com ([15.201.208.54]:6371 "EHLO g4t3426.houston.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752425AbaEBRcO (ORCPT ); Fri, 2 May 2014 13:32:14 -0400 In-Reply-To: <20140502133219.5de5c683@nial.usersys.redhat.com> Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: Igor Mammedov 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 On Fri, 2014-05-02 at 13:32 +0200, Igor Mammedov wrote: > 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. This is a separate topic, but I feel that the above code should not be necessary... > The point is that acpi_processor_add() shouldn't touch > dev->offline at all and allow register_cpu() handle it. Sorry, I had confused with cpu->dev.offline in register_cpu() in my recollection. Yes, I agree that we should let register_cpu() to handle it. Acked-by: Toshi Kani Thanks, -Toshi