svn commit: r209119 - head/sys/sys

[Lawrence Stewart]

On 06/13/10 20:10, Pawel Jakub Dawidek wrote:
> On Sun, Jun 13, 2010 at 02:39:55AM +0000, Lawrence Stewart wrote:
>> Author: lstewart
>> Date: Sun Jun 13 02:39:55 2010
>> New Revision: 209119
>> URL: http://svn.freebsd.org/changeset/base/209119
>>
>> Log:
>>    Add a utility macro to simplify calculating an aggregate sum from a DPCPU
>>    counter variable.
>>
>>    Sponsored by:	FreeBSD Foundation
>>    Reviewed by:	jhb, rpaulo, rwatson (previous version of patch)
>>    MFC after:	1 week
>>
>> Modified:
>>    head/sys/sys/pcpu.h
>>
>> 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;'.

Can do (will wait until consensus on other issues is reached first 
before tweaking though).

> Also using 'i' as a counter in macro can easly lead to name collision.

I had a similar concern but after chatting with John on IRC felt it 
wasn't such a big deal in this case.

> If you need to do it, I'd suggest '_i' or something.

Could do... is it worth it?

> Maybe it would be better to make it an inline function rather than macro?

Inlining it could be annoying with respect to the types used in the 
function prototype, no? I suspect it would be more useful keeping it as 
a macro if possible.

Cheers,
Lawrence