- Rename the internal for loop iterator to "_i" to avoid potential shadowing of

  external variables named "i". The "_" prefix is reserved for infrastructure
  type code and is therefore not expected to be used by normal code likely to
  call DPCPU_SUM(). [1]

- Change DPCPU_SUM to return the sum rather than calculate and assign it
  internally. Usage is now: "sum = DPCPU_SUM(dpcpu_var, member_to_sum);" [2]

- Fix some style nits. [3]

Sponsored by:	FreeBSD Foundation
Suggested by:	bde [3], mdf [1], kib [1,2], pjd [1,3]
Reviewed by:	kib
MFC after:	1 week (instead of r209119)

1 files changed, 11 insertions, 7 deletions

diff --git a/sys/sys/pcpu.h b/sys/sys/pcpu.h
index 472a658..ea4befb 100644
--- a/sys/sys/pcpu.h
+++ b/sys/sys/pcpu.h
@@ -109,13 +109,17 @@ extern uintptr_t dpcpu_off[];
 /*
  * 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)
+#define	DPCPU_SUM(n, var) __extension__					\
+({									\
+	u_int _i;							\
+	__typeof((DPCPU_PTR(n))->var) sum;				\
+									\
+	sum = 0;							\
+	CPU_FOREACH(_i) {						\
+		sum += (DPCPU_ID_PTR(_i, n))->var;			\
+	}								\
+	sum;								\
+})
 
 /* 
  * XXXUPS remove as soon as we have per cpu variable