Date: Sun, 13 Jun 2010 13:59:11 +0000 From: mdf@FreeBSD.org To: Pawel Jakub Dawidek <pjd@freebsd.org> Cc: svn-src-head@freebsd.org, Lawrence Stewart <lstewart@freebsd.org>, svn-src-all@freebsd.org, src-committers@freebsd.org Subject: Re: svn commit: r209119 - head/sys/sys Message-ID: <AANLkTik2X_x6cNsLWQTNqDHuN69IZgyMnM--0vhp36xk@mail.gmail.com> In-Reply-To: <20100613101025.GD1320@garage.freebsd.pl> References: <201006130239.o5D2du3m086332@svn.freebsd.org> <20100613101025.GD1320@garage.freebsd.pl>
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On Sun, Jun 13, 2010 at 10:10 AM, Pawel Jakub Dawidek <pjd@freebsd.org> wro= te: > 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: >> =A0 Add a utility macro to simplify calculating an aggregate sum from a = DPCPU >> =A0 counter variable. >> >> =A0 Sponsored by: =A0 =A0 =A0 FreeBSD Foundation >> =A0 Reviewed by: =A0 =A0 =A0 =A0jhb, rpaulo, rwatson (previous version o= f patch) >> =A0 MFC after: =A01 week >> >> Modified: >> =A0 head/sys/sys/pcpu.h >> >> Modified: head/sys/sys/pcpu.h >> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D >> --- head/sys/sys/pcpu.h =A0 =A0 =A0 Sun Jun 13 01:27:29 2010 =A0 =A0 =A0= =A0(r209118) >> +++ head/sys/sys/pcpu.h =A0 =A0 =A0 Sun Jun 13 02:39:55 2010 =A0 =A0 =A0= =A0(r209119) >> @@ -106,6 +106,17 @@ extern uintptr_t dpcpu_off[]; >> =A0#define =A0 =A0 =A0DPCPU_ID_GET(i, n) =A0 =A0 =A0(*DPCPU_ID_PTR(i, n)= ) >> =A0#define =A0 =A0 =A0DPCPU_ID_SET(i, n, v) =A0 (*DPCPU_ID_PTR(i, n) =3D= v) >> >> +/* >> + * Utility macros. >> + */ >> +#define DPCPU_SUM(n, var, sum) =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 = =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 \ >> +do { =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 = =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 \ >> + =A0 =A0 (sum) =3D 0; =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 = =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0\ >> + =A0 =A0 u_int i; =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 = =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0\ >> + =A0 =A0 CPU_FOREACH(i) =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0= =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0\ >> + =A0 =A0 =A0 =A0 =A0 =A0 (sum) +=3D (DPCPU_ID_PTR(i, n))->var; =A0 =A0 = =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 \ >> +} while (0) > > I'd suggest first swapping variable declaration and '(sum) =3D 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. > Maybe it would be better to make it an inline function rather than macro? (Relevant but almost a thread hijack): At Isilon we've run into a lot of problems with variable declarations in macros, especially with -Wshadow turned on. We ended up backporting __COUNTER__ from later versions of gcc and then using it to make unique variable names. - is the backport (or a fresh implementation) something that could be done within the scope of the GPL license? - is it something FreeBSD would be interested in? - is __COUNTER__ supported by clang? - if not, could it be? -Wshadow found several nasty bugs in our code, and apart from a few spurious warnings it has been handy to have when building our filesystem. Thanks, matthew
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