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

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Date:	Sun, 9 Jan 2011 10:39:26 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Rakib Mullick <rakib.mullick@...il.com>
Cc:	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.


* 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>
> ---
> 
> diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
> index ce65d44..2499664 100644
> --- a/arch/x86/kernel/apic/apic.c
> +++ b/arch/x86/kernel/apic/apic.c
> @@ -1943,7 +1943,6 @@ void __cpuinit generic_processor_info(int
> apicid, int version)
>  			"ACPI: NR_CPUS/possible_cpus limit of %i reached."
>  			"  Processor %d/0x%x ignored.\n", max, thiscpu, apicid);
> 
> -		disabled_cpus++;
>  		return;

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
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