From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758404AbZDWOku (ORCPT ); Thu, 23 Apr 2009 10:40:50 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754258AbZDWOkk (ORCPT ); Thu, 23 Apr 2009 10:40:40 -0400 Received: from cmpxchg.org ([85.214.51.133]:54028 "EHLO cmpxchg.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753642AbZDWOkj (ORCPT ); Thu, 23 Apr 2009 10:40:39 -0400 Date: Thu, 23 Apr 2009 16:38:59 +0200 From: Johannes Weiner To: Andi Kleen Cc: arjan@linux.intel.com, linux-kernel@vger.kernel.org, torvalds@osdl.org, akpm@osdl.org Subject: Re: [PATCH] Eliminate thousands of warnings in WARN_ON with gcc 3.2 build Message-ID: <20090423143859.GA20453@cmpxchg.org> References: <20090422221134.GA1753@basil.nowhere.org> <20090423120219.GA23479@cmpxchg.org> <20090423122327.GN13896@one.firstfloor.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090423122327.GN13896@one.firstfloor.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Apr 23, 2009 at 02:23:27PM +0200, Andi Kleen wrote: > On Thu, Apr 23, 2009 at 02:02:19PM +0200, Johannes Weiner wrote: > > > +{ > > > + warn_slowpath_fmt(file, line, ""); > > > +} > > > +EXPORT_SYMBOL(warn_slowpath_null); > > > > That should still emit a warning due to passing in a zero-length > > format string. Using (const char *){ 0 } as the literal would > > suppress it (on gcc 4.3.3 at least) but I'm not sure if it's worth the > > uglyness... > > Hmm, you're right 3.3 generates a warning for that, 3.2 doesn't > But at least it's only a single one, not thousands. > Your trick would make sense. Updated patch attached. > > -Andi > > --- > > Eliminate thousands of warnings with gcc 3.2 build v2 > > When building with gcc 3.2 I get thousands of warnings about passing > a NULL format string to warn_on_slowpath(). Split this case out > into a separate call. This should also shrink the kernel > slightly. You are right: text data bss dec hex filename 4802274 707668 712704 6222646 5ef336 vmlinux text data bss dec hex filename 4799027 703572 712704 6215303 5ed687 vmlinux > v2: Avoid warning in warn_slowpath_null on newer gccs too (J.Weiner) > > Acked-by: Jesper Nilsson > Signed-off-by: Andi Kleen > > --- > include/asm-generic/bug.h | 7 ++++--- > kernel/panic.c | 12 +++++++++--- > 2 files changed, 13 insertions(+), 6 deletions(-) > > Index: linux-2.6.30-rc2-ak/include/asm-generic/bug.h > =================================================================== > --- linux-2.6.30-rc2-ak.orig/include/asm-generic/bug.h 2009-01-11 20:20:40.000000000 +0100 > +++ linux-2.6.30-rc2-ak/include/asm-generic/bug.h 2009-04-22 23:52:48.000000000 +0200 > @@ -58,12 +58,13 @@ > */ > #ifndef __WARN > #ifndef __ASSEMBLY__ > -extern void warn_slowpath(const char *file, const int line, > +extern void warn_slowpath_fmt(const char *file, const int line, > const char *fmt, ...) __attribute__((format(printf, 3, 4))); > +extern void warn_slowpath_null(const char *file, const int line); > #define WANT_WARN_ON_SLOWPATH > #endif > -#define __WARN() warn_slowpath(__FILE__, __LINE__, NULL) > -#define __WARN_printf(arg...) warn_slowpath(__FILE__, __LINE__, arg) > +#define __WARN() warn_slowpath_null(__FILE__, __LINE__) > +#define __WARN_printf(arg...) warn_slowpath_fmt(__FILE__, __LINE__, arg) > #else > #define __WARN_printf(arg...) do { printk(arg); __WARN(); } while (0) > #endif > Index: linux-2.6.30-rc2-ak/kernel/panic.c > =================================================================== > --- linux-2.6.30-rc2-ak.orig/kernel/panic.c 2009-04-19 19:29:07.000000000 +0200 > +++ linux-2.6.30-rc2-ak/kernel/panic.c 2009-04-23 14:17:34.000000000 +0200 > @@ -342,7 +342,7 @@ > } > > #ifdef WANT_WARN_ON_SLOWPATH > -void warn_slowpath(const char *file, int line, const char *fmt, ...) > +void warn_slowpath_fmt(const char *file, int line, const char *fmt, ...) > { > va_list args; > char function[KSYM_SYMBOL_LEN]; > @@ -358,7 +358,7 @@ > if (board) > printk(KERN_WARNING "Hardware name: %s\n", board); > > - if (fmt) { > + if (*fmt) { > va_start(args, fmt); > vprintk(fmt, args); > va_end(args); > @@ -369,7 +369,13 @@ > print_oops_end_marker(); > add_taint(TAINT_WARN); > } > -EXPORT_SYMBOL(warn_slowpath); > +EXPORT_SYMBOL(warn_slowpath_fmt); > + > +void warn_slowpath_null(const char *file, int line) > +{ > + warn_slowpath_fmt(file, line, (const char *) { 0 }); > +} > +EXPORT_SYMBOL(warn_slowpath_null); I would WTF here without knowing the warning. Can you add a comment? Otherwise, Acked-by: Johannes Weiner