From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754095Ab1DABrv (ORCPT ); Thu, 31 Mar 2011 21:47:51 -0400 Received: from smtp-out.google.com ([216.239.44.51]:44322 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751730Ab1DABru convert rfc822-to-8bit (ORCPT ); Thu, 31 Mar 2011 21:47:50 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=google.com; s=beta; h=mime-version:sender:in-reply-to:references:date :x-google-sender-auth:message-id:subject:from:to:cc:content-type :content-transfer-encoding; b=dVsruTmuYB7WFc6nw4hjdedsssqgYau6LGn77GKwQzq2y/kJLINIFnEFgJXOQmSwwc bAae4Cw6G/ZW6fMY3IsQ== MIME-Version: 1.0 In-Reply-To: <1301602523-9906-1-git-send-email-omar.ramirez@ti.com> References: <1301602523-9906-1-git-send-email-omar.ramirez@ti.com> Date: Thu, 31 Mar 2011 18:47:47 -0700 X-Google-Sender-Auth: g9hYvQrKyEmUlTW21GAT8oSJSWA Message-ID: Subject: Re: [PATCH] ARM: BUG() dies silently From: Simon Glass To: Omar Ramirez Luna Cc: Russell King , lak , lk Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT X-System-Of-Record: true Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org You might try the generic bug patch and see if it also fixes this problem - Simon On Thu, Mar 31, 2011 at 1:15 PM, Omar Ramirez Luna wrote: > There are some cases where the code generated for BUG() results > into an infinite while loop without causing a null dereference, > this ends on a kernel being stuck on a loop and the user without > a clue of what happened. > > E.g.: lib/scatterlist.c : __sg_alloc_table > >        BUG_ON(nents > max_ents); >  438:   9a000000        bls     440 <__sg_alloc_table+0x20> >  43c:   eafffffe        b       43c <__sg_alloc_table+0x1c> > > Adding volatile makes the compiler to avoid optimizations on this > code, which makes the panic to occur: > >        BUG_ON(nents > max_ents); >  438:   9a000002        bls     448 <__sg_alloc_table+0x28> >  43c:   e3a03000        mov     r3, #0 >  440:   e5833000        str     r3, [r3] >  444:   eafffffc        b       43c <__sg_alloc_table+0x1c> > > Seen with gnu/linux cs arm-2010q1-202 and arm2010.09-50. > > Signed-off-by: Omar Ramirez Luna > --- > > If needed I can change: > ./arch/arm/mach-clps711x/include/mach/io.h: >        #define __raw_readsb(p,d,l)  do { *(int *)0 = 0; } while (0) > ./arch/arm/mach-clps711x/include/mach/io.h: >        #define __raw_readsl(p,d,l)  do { *(int *)0 = 0; } while (0) > ./arch/arm/mach-clps711x/include/mach/io.h: >        #define __raw_writesb(p,d,l) do { *(int *)0 = 0; } while (0) > ./arch/arm/mach-clps711x/include/mach/io.h: >        #define __raw_writesl(p,d,l) do { *(int *)0 = 0; } while (0) > ./arch/arm/kernel/traps.c:      *(int *)0 = 0; > > >  arch/arm/include/asm/bug.h |    2 +- >  1 files changed, 1 insertions(+), 1 deletions(-) > > diff --git a/arch/arm/include/asm/bug.h b/arch/arm/include/asm/bug.h > index 4d88425..a58d863 100644 > --- a/arch/arm/include/asm/bug.h > +++ b/arch/arm/include/asm/bug.h > @@ -12,7 +12,7 @@ extern void __bug(const char *file, int line) __attribute__((noreturn)); >  #else > >  /* this just causes an oops */ > -#define BUG()          do { *(int *)0 = 0; } while (1) > +#define BUG()          do { *(volatile int *)0 = 0; } while(1) > >  #endif > > -- > 1.7.1 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at  http://vger.kernel.org/majordomo-info.html > Please read the FAQ at  http://www.tux.org/lkml/ >