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From: Lawrence Stewart <lstewart@freebsd.org>
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To: Pawel Jakub Dawidek <pjd@FreeBSD.org>
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Cc: svn-src-head@FreeBSD.org, svn-src-all@FreeBSD.org,
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Subject: Re: svn commit: r209119 - head/sys/sys
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On 06/13/10 20:10, Pawel Jakub Dawidek wrote:
> On Sun, Jun 13, 2010 at 02:39:55AM +0000, Lawrence Stewart wrote:
[snip]
>>
>> Modified: head/sys/sys/pcpu.h
>> ==============================================================================
>> --- head/sys/sys/pcpu.h	Sun Jun 13 01:27:29 2010	(r209118)
>> +++ head/sys/sys/pcpu.h	Sun Jun 13 02:39:55 2010	(r209119)
>> @@ -106,6 +106,17 @@ extern uintptr_t dpcpu_off[];
>>   #define	DPCPU_ID_GET(i, n)	(*DPCPU_ID_PTR(i, n))
>>   #define	DPCPU_ID_SET(i, n, v)	(*DPCPU_ID_PTR(i, n) = v)
>>
>> +/*
>> + * Utility macros.
>> + */
>> +#define DPCPU_SUM(n, var, sum)						\
>> +do {									\
>> +	(sum) = 0;							\
>> +	u_int i;							\
>> +	CPU_FOREACH(i)							\
>> +		(sum) += (DPCPU_ID_PTR(i, n))->var;			\
>> +} while (0)
>
> I'd suggest first swapping variable declaration and '(sum) = 0;'.
> Also using 'i' as a counter in macro can easly lead to name collision.
> If you need to do it, I'd suggest '_i' or something.

Given that the DPCPU variable name space is flat and variable names have 
to be unique, perhaps something like the following would address the 
concerns raised?

#define DPCPU_SUM(n, var, sum)                                         \
do {                                                                   \
         u_int _##n##_i;                                                \
         (sum) = 0;                                                     \
         CPU_FOREACH(_##n##_i)                                          \
                 (sum) += (DPCPU_ID_PTR(_##n##_i, n))->var;             \
} while (0)


Cheers,
Lawrence