svn commit: r209119 - head/sys/sys

[John Baldwin]

On Sunday 13 June 2010 9:41:38 am Lawrence Stewart wrote:
> 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.

Actually, I am a fan of using an inline function if possible to avoid the name 
collisions.

-- 
John Baldwin