linux-kernel - Re: [PATCH v3 7/9] trace: use this_cpu

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Date:	Mon, 12 Nov 2012 10:05:09 +0800
From:	Shan Wei <shanwei88@...il.com>
To:	Christoph Lameter <cl@...ux.com>
CC:	rostedt@...dmis.org, fweisbec@...il.com,
	Kernel-Maillist <linux-kernel@...r.kernel.org>, mingo@...hat.com
Subject: Re: [PATCH v3 7/9] trace: use this_cpu_ptr per-cpu helper

Christoph Lameter said, at 2012/11/10 4:15:
> On Fri, 9 Nov 2012, Shan Wei wrote:
> 
>> -	return buffer->buffer;
>> +	return (char *)this_cpu_ptr(&percpu_buffer->buffer);
>>  }
> 
> Add a comment to explain the cast?

typeof(&buffer) is a pointer to array of 1024 char, or char (*)[1024].
But, typeof(&buffer[0]) is a pointer to char which match the return type of get_trace_buf().
As well-known, the value of &buffer is equal to &buffer[0].
so return this_cpu_ptr(&percpu_buffer->buffer[0]) can avoid this cast. 

I will submit v4 version patch which improve it.

Thanks~
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