linux-kernel - Re: [PATCH x86/percpu] x86_64: initialize this_cpu_off to __per_cpu

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Message-ID: <49708FEA.9000508@gmail.com>
Date:	Fri, 16 Jan 2009 22:47:22 +0900
From:	Tejun Heo <htejun@...il.com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	roel kluin <roel.kluin@...il.com>,
	"H. Peter Anvin" <hpa@...or.com>, Brian Gerst <brgerst@...il.com>,
	ebiederm@...ssion.com, cl@...ux-foundation.org,
	rusty@...tcorp.com.au, travis@....com,
	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	steiner@....com, hugh@...itas.com
Subject: Re: [PATCH x86/percpu] x86_64: initialize this_cpu_off to	__per_cpu_load

Ingo Molnar wrote:
>> +#ifdef CONFIG_X86_64
>> +DEFINE_PER_CPU(unsigned long, this_cpu_off) = (unsigned long)__per_cpu_load;
>> +#else
>>  DEFINE_PER_CPU(unsigned long, this_cpu_off);
>> +#endif
> 
> I've pulled your tree, but couldnt we do this symmetrically in the 32-bit 
> case too and avoid the ugly #ifdef somehow?

You can take the "x86_32: make percpu symbols zerobased on SMP" patch
and the above ifdef won't be necessary along with similar one in
setup_percpu.c.  The above ifdef is because 64 is zero based while 32
is not.  If you want something, say, __per_cpu_base_off or something
to be defined conditionally and used in these two cases, I'm not sure
whether that would clean up the code or obfuscate it.  :-)

Thanks.

-- 
tejun
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