linux-kernel - Re: [PATCH] x86_64: not set boot cpu in cpu_online_map at smp_prepare_boot

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Message-id: <474B4373.9060802@sun.com>
Date:	Mon, 26 Nov 2007 14:06:43 -0800
From:	Yinghai Lu <Yinghai.Lu@....COM>
To:	Zachary Amsden <zach@...are.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86_64: not set boot cpu in cpu_online_map at
	smp_prepare_boot_cpu

Zachary Amsden wrote:
> On Mon, 2007-11-26 at 00:38 -0800, Yinghai Lu wrote:
>> [PATCH] x86_64: not set boot cpu in cpu_online_map at smp_prepare_boot_cpu
>>
>> in init/main.c boot_cpu_init() does that before
>>
>> Signed-off-by: Yinghai Lu <yinghai.lu@....com>
>>
>> diff --git a/arch/x86/kernel/smpboot_64.c b/arch/x86/kernel/smpboot_64.c
>> index 500670c..966d124 100644
>> --- a/arch/x86/kernel/smpboot_64.c
>> +++ b/arch/x86/kernel/smpboot_64.c
>> @@ -912,7 +912,7 @@ void __init smp_prepare_cpus(unsigned int max_cpus)
>>  void __init smp_prepare_boot_cpu(void)
>>  {
>>  	int me = smp_processor_id();
>> -	cpu_set(me, cpu_online_map);
>> +	/* already set me in cpu_online_map in boot_cpu_init() */
>>  	cpu_set(me, cpu_callout_map);
>>  	per_cpu(cpu_state, me) = CPU_ONLINE;
>>  }
> 
> 
> This ordering can be tricky wrt CPU hotplug.  Are you sure you are not
> breaking CPU hotplug?  AFAIK, x86_64 has that right and the 32-bit code
> had it wrong.


CPU hot plug path will call smp_prepare_boot_cpu?
it is using __init instead of __cpuinit?

YH
-
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