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

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Message-ID: <AANLkTikNGVbYK-VMiLu2xFzzO6ti5kXXB+p-MzcUYx63@mail.gmail.com>
Date:	Sun, 9 Jan 2011 23:09:01 +0600
From:	Rakib Mullick <rakib.mullick@...il.com>
To:	Cyrill Gorcunov <gorcunov@...il.com>
Cc:	Ingo Molnar <mingo@...e.hu>, 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 Sun, Jan 9, 2011 at 5:44 PM, Cyrill Gorcunov <gorcunov@...il.com> wrote:
> 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?
>
Lets see what Ingo says. :)

> --
>    Cyrill
>
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