Date: Mon, 14 Jun 2010 20:34:15 +1000 From: Lawrence Stewart <lstewart@freebsd.org> To: Kostik Belousov <kostikbel@gmail.com> Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org, Pawel Jakub Dawidek <pjd@freebsd.org> Subject: Re: svn commit: r209119 - head/sys/sys Message-ID: <4C1605A7.2000202@freebsd.org> In-Reply-To: <20100614085205.GD13238@deviant.kiev.zoral.com.ua> References: <201006130239.o5D2du3m086332@svn.freebsd.org> <20100613101025.GD1320@garage.freebsd.pl> <4C158B71.205@freebsd.org> <20100614085205.GD13238@deviant.kiev.zoral.com.ua>
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On 06/14/10 18:52, Kostik Belousov wrote: > On Mon, Jun 14, 2010 at 11:52:49AM +1000, 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: >> [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) > > You do not have to jump through this. Mostly by convention, in our kernel > sources, names with "_" prefix are reserved for the infrastructure (cannot > say implementation). I think it is quite safe to use _i for the iteration > variable. > > As an example of this, look at sys/sys/mount.h, implementation of > VFS_NEEDGIANT, VFS_LOCK_GIANT etc macros. They do use gcc ({}) extension > to provide function-like macros, but this is irrelevant. Or, look at > the VFS_ASSERT_GIANT that is exactly like what you need. Ok cool, thanks for the info and pointers (I didn't know about the ({}) extension or that "_" prefix was definitely reserved). I'm happy to use _i. Does the following diff against head look suitable to commit? --- a/sys/sys/pcpu.h Sun Jun 13 02:39:55 2010 +0000 +++ b/sys/sys/pcpu.h Mon Jun 14 20:12:27 2010 +1000 @@ -111,10 +111,10 @@ */ #define DPCPU_SUM(n, var, sum) \ do { \ + u_int _i; \ (sum) = 0; \ - u_int i; \ - CPU_FOREACH(i) \ - (sum) += (DPCPU_ID_PTR(i, n))->var; \ + CPU_FOREACH(_i) \ + (sum) += (DPCPU_ID_PTR(_i, n))->var; \ } while (0) /* Cheers, Lawrence
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