Subject: Re: [PATCH] unexport register_cpu and unregister_cpu
From: Nathan Lynch <nathanl@austin.ibm.com>
To: Keshavamurthy Anil S <anil.s.keshavamurthy@intel.com>
Cc: lkml <linux-kernel@vger.kernel.org>, Andrew Morton <akpm@osdl.org>
In-Reply-To: <20050126102226.A27022@unix-os.sc.intel.com>
References: <1106722547.9855.36.camel@localhost.localdomain>
	 <20050126102226.A27022@unix-os.sc.intel.com>
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Date: Wed, 26 Jan 2005 13:10:30 -0600
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On Wed, 2005-01-26 at 10:22 -0800, Keshavamurthy Anil S wrote:
> On Wed, Jan 26, 2005 at 12:55:47AM -0600, Nathan Lynch wrote:
> > http://linus.bkbits.net:8080/linux-2.5/cset@4180a2b7mi2fzuNQDBOQY7eMAkns8g?nav=index.html|src/|src/drivers|src/drivers/base|related/drivers/base/cpu.c
> > 
> > This changeset introduced exports for register_cpu and unregister_cpu
> > right after 2.6.10.  As far as I can tell these are not called from any
> > code which can be built as a module, and I can't think of a good reason
> > why any out of tree code would use them.  Unless I've missed something,
> > can we remove them before 2.6.11?
> 
> 	No this is not correct. ACPI processor.ko driver which supports
> physical CPU hotplug needs register_cpu() and unregister_cpu() functions
> for dynamically hotadd/hotremove support of the processors.

I do not understand your objection.  The processor module does not call
the interfaces in question directly.  They are called only from arch
setup code (e.g. arch/ia64/kernel/topology.c) which is never built as a
module.

> Please see drivers/acpi/processor_core.c  
> 	acpi_processor_hotadd_init() -> arch_register_cpu() ->
> 		->register_cpu().

Sure -- the arch_register_cpu and arch_unregister_cpu symbols need to be
exported for this use (and they are).  Exporting register_cpu and
unregister_cpu is unnecessary.

I double-checked an ia64 build with CONFIG_ACPI_HOTPLUG_CPU=y and
CONFIG_ACPI_PROCESSOR=m and saw no errors or warnings caused by the
change...

Nathan

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