linux-kernel - Re: A problem with percpu variable cpu

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Message-ID: <4F411373.50304@gmail.com>
Date:	Sun, 19 Feb 2012 23:21:23 +0800
From:	Cong Wang <xiyou.wangcong@...il.com>
To:	Tao Jiang <jiangtao.jit@...il.com>
CC:	linux-kernel@...r.kernel.org
Subject: Re: A problem with percpu variable cpu_number

On 02/19/2012 08:20 PM, Tao Jiang wrote:
> Hi :
>
> At the beginning of start_kernel() -- init/main.c
> boot_cpu_init() is called
>
> and in boot_cpu_init() will call smp_processor_id()
> it's a macro
> and it will be expanded as (percpu_read(cpu_number)) and so on
>
> but i noticed that it's before setup_per_cpu_areas() in start_kernel()
> is that mean the percpu areas hadn't be initialized yet
> but why smp_processor_id() could be called before setup_per_cpu_areas()

It doesn't matter, as the percpu var 'cpu_number' is defined statically: 
DECLARE_PER_CPU(int, cpu_number);.

Thanks.
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