From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail190.messagelabs.com (mail190.messagelabs.com [216.82.249.51]) by kanga.kvack.org (Postfix) with ESMTP id E01AF8D0040 for ; Sat, 2 Apr 2011 00:01:48 -0400 (EDT) Received: by qwa26 with SMTP id 26so3459296qwa.14 for ; Fri, 01 Apr 2011 21:01:46 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: References: From: Hui Zhu Date: Sat, 2 Apr 2011 12:01:24 +0800 Message-ID: Subject: Re: [PATCH] mm: fix possible cause of a page_mapped BUG Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org List-ID: To: =?UTF-8?B?Um9iZXJ0IMWad2nEmWNraQ==?= Cc: Linus Torvalds , Hugh Dickins , Andrew Morton , Miklos Szeredi , Michel Lespinasse , "Eric W. Biederman" , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Peter Zijlstra , Rik van Riel On Sat, Apr 2, 2011 at 00:35, Linus Torvalds wrote: > On Fri, Apr 1, 2011 at 9:21 AM, Robert =C5=9Awi=C4=99cki wrote: >> >> Is it possible to turn it off via config flags? Looking into >> arch/x86/include/asm/bug.h it seems it's unconditional (as in "it >> always manifests itself somehow") and I have >> CONFIG_DEBUG_BUGVERBOSE=3Dy. > > Ok, if you have CONFIG_DEBUG_BUGVERBOSE then, you do have the bug-table. > > Maybe it's just kdb that is broken, and doesn't print it. I wouldn't > be surprised. It's not the first time I've seen debugging features > that just make debugging a mess. > >> Anything that could help you debugging this? Uploading kernel image >> (unfortunately I've overwritten this one), dumping more kgdb data? > > So in this case kgdb just dropped the most important data on the floor. > > But if you have kdb active next time, print out the vma/old contents > in that function that has the BUG() in it. > >> I must admit I'm not up-to-date with current linux kernel debugging >> techniques. The kernel config is here: >> http://alt.swiecki.net/linux_kernel/ise-test-2.6.38-kernel-config.txt >> >> For now I'll compile with -O0 -fno-inline (are you sure you'd like -Os?) Hi Robert, I am not sure you can success with build trunk with -O0 -fno-inline. I suggest you try the patch in http://code.google.com/p/kgtp/downloads/detail?name=3Dco.patch. It add a option in "Kernel hacking" called "Compile with almost no optimization". It will make kernel be built without -O2. It support x86_32, x86_64 and arm. PS, maybe you can try kgtp (https://code.google.com/p/kgtp/) debug your ke= rnel. Thanks, Hui > > Oh, don't do that. -O0 makes the code totally unreadable (the compiler > just does _stupid_ things, making the asm code look so horrible that > you can't match it up against anything sane), and -fno-inline isn't > worth the pain either. > > -Os is much better than those. > > But in this case, just getting the filename and line number would have > made the thing moot anyway - without kdb it _should_ have said > something clear like > > =C2=A0 kernel BUG at %s:%u! > > where %s:%u is the filename and line number. > > =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2= =A0 =C2=A0 =C2=A0Linus > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" i= n > the body of a message to majordomo@vger.kernel.org > More majordomo info at =C2=A0http://vger.kernel.org/majordomo-info.html > Please read the FAQ at =C2=A0http://www.tux.org/lkml/ > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org