linux-kernel - Re: [PATCH v3 5/5] acpi_processor: do not mark present at boot but not onlined CPU as onlined

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Date:	Tue, 15 Apr 2014 07:36:59 +0200
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Igor Mammedov <imammedo@...hat.com>, linux-kernel@...r.kernel.org,
	tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
	x86@...nel.org, bp@...e.de, paul.gortmaker@...driver.com,
	JBeulich@...e.com, prarit@...hat.com, drjones@...hat.com,
	toshi.kani@...com, riel@...hat.com, gong.chen@...ux.intel.com,
	andi@...stfloor.org, lenb@...nel.org, linux-acpi@...r.kernel.org
Subject: Re: [PATCH v3 5/5] acpi_processor: do not mark present at boot but not onlined CPU as onlined

On Monday, April 14, 2014 11:21:47 AM Ingo Molnar wrote:
> 
> * Igor Mammedov <imammedo@...hat.com> 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 <imammedo@...hat.com>
> > ---
> >  drivers/acpi/acpi_processor.c |    3 ---
> >  1 files changed, 0 insertions(+), 3 deletions(-)
> 
> Can this fix be moved first too, or does it have undesirable side 
> effects on unmodified kernels?

This patch is not correct.

Rafael

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