linux-kernel - Re: [PATCH] x86, apic: Do not increment disabled_cpus from generic_processor

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Date:	Sun, 09 Jan 2011 14:44:12 +0300
From:	Cyrill Gorcunov <gorcunov@...il.com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Rakib Mullick <rakib.mullick@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	LKML <linux-kernel@...r.kernel.org>, x86@...nel.org
Subject: Re: [PATCH] x86, apic: Do not increment disabled_cpus from generic_processor_info.

On 01/09/2011 12:39 PM, Ingo Molnar wrote:
> 
> * Rakib Mullick <rakib.mullick@...il.com> wrote:
> 
>>  disabled_cpus has been incremented from the call path of
>> generic_processor_info (i.e from  acpi_register_lapic and
>> MP_processor_info) when a perticular cpu is not enabled. So, we can
>> remove the redundant increment of disabled_cpus from
>> generic_processor_info.
>>
>>
>> Signed-off-by: Rakib Mullick <rakib.mullick@...il.com>
...
> Hm, what effects does this have in practice? smpboot.c uses disabled_cpus as a value 
> to calculate limits - why has this bug not caused some misbehavior somewhere? (or if 
> it has caused misbehavior, what is that?)
>  
> Thanks,
> 
> 	Ingo

This disabled cpu may happen if nr_cpus early param specified and it's less than
nr_cpu_ids, but cpu might still be enabled in mp/acpi so we have to disable it.
And if we will not increment disabled_cpus this will lead the further report
about disabled cpu would refer to wrong cpu number. So I don't see why we
need to remove this disabled_cpus increment here.

Rakib is there something I miss?

-- 
    Cyrill
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