From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arnd Bergmann Subject: Re: [PATCH] arch: configuration, deleting 'CONFIG_BUG' since always need it. Date: Thu, 23 May 2013 11:39:37 +0200 Message-ID: <201305231139.38233.arnd@arndb.de> References: <519DCBEF.3090208@asianux.com> <20130523090534.GJ18614@n2100.arm.linux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=m.gmane.org@lists.infradead.org To: Geert Uytterhoeven Cc: Catalin Marinas , Linux-sh list , Benjamin Herrenschmidt , Chen Gang , Heiko Carstens , "paulus@samba.org" , "H. Peter Anvin" , Michel Lespinasse , Hans-Christian Egtvedt , Linux-Arch , linux-s390@vger.kernel.org, Russell King - ARM Linux , Yoshinori Sato , Richard Weinberger , Helge Deller , the arch/x86 maintainers , "James E.J. Bottomley" , "mingo@redhat.com" , Frederic Weisbecker , Paul McKenney , =?utf-8?q?H=C3=A5vard_Skinnemoen?= List-Id: linux-arch.vger.kernel.org On Thursday 23 May 2013, Geert Uytterhoeven wrote: > > The problem is: trying to fix that will mean the result is a larger > > kernel than if you just do the usual arch-implemented thing of placing > > an defined faulting instruction at the BUG() site - which defeats the > > purpose of turning off CONFIG_BUG. > > Is __builtin_unreachable() working well these days? > Hmm, I just tried the trivial patch below, which seemed to do the right thing. Needs a little more investigation, but that might actually be the correct solution. I thought that at some point __builtin_unreachable() was the same as "do {} while (1)", but this is not the case with the gcc I was using -- it just tells gcc that we don't expect to ever get here. Signed-off-by: Arnd Bergmann diff --git a/include/asm-generic/bug.h b/include/asm-generic/bug.h index 7d10f96..9afff7d 100644 --- a/include/asm-generic/bug.h +++ b/include/asm-generic/bug.h @@ -108,11 +108,11 @@ extern void warn_slowpath_null(const char *file, const int line); #else /* !CONFIG_BUG */ #ifndef HAVE_ARCH_BUG -#define BUG() do {} while(0) +#define BUG() __builtin_unreachable () #endif #ifndef HAVE_ARCH_BUG_ON -#define BUG_ON(condition) do { if (condition) ; } while(0) +#define BUG_ON(condition) do { if (condition) __builtin_unreachable(); } while(0) #endif #ifndef HAVE_ARCH_WARN_ON