Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755604AbZGUQNE (ORCPT ); Tue, 21 Jul 2009 12:13:04 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755432AbZGUQND (ORCPT ); Tue, 21 Jul 2009 12:13:03 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:58168 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754618AbZGUQNC (ORCPT ); Tue, 21 Jul 2009 12:13:02 -0400 Date: Tue, 21 Jul 2009 09:11:44 -0700 (PDT) From: Linus Torvalds X-X-Sender: torvalds@localhost.localdomain To: Krzysztof Oledzki cc: Greg KH , linux-kernel@vger.kernel.org, Andrew Morton , stable@kernel.org, lwn@lwn.net Subject: Re: Linux 2.6.27.27 In-Reply-To: Message-ID: References: <20090720040655.GA11940@kroah.com> <4A645A45.9060509@ans.pl> <20090720151008.GC10015@suse.de> User-Agent: Alpine 2.01 (LFD 1184 2008-12-16) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2180 Lines: 53 On Tue, 21 Jul 2009, Krzysztof Oledzki wrote: > > OK, there are three kernels, exactly as you requested: > > http://noc.axelspringer.pl/no-strict-overflow-vs-wrapv/vmlinux-fno-strict-overflow.bz2 (Hangs) > http://noc.axelspringer.pl/no-strict-overflow-vs-wrapv/vmlinux-fwrapv.bz2 (OK) > http://noc.axelspringer.pl/no-strict-overflow-vs-wrapv/vmlinux-fnone.bz2 (OK) Perfect. And interestingly, the "fno-strict-overflow" kernel is actually much closer to the "fnone" kernel than to the "fwrapv" one. I have some silly scripts based on 'objdump -d' plus a lot of stupid sed scripting to remove the trivial differences due to instruction addresses, and then doing a 'diff -u' between the munged disassembly of the kernels gives me: [torvalds@nehalem fno-strict-overflow]$ wc -l fnone-to-fno-strict-overflow fwrapv-to-fno-strict-overflow 39309 fnone-to-fno-strict-overflow 91423 fwrapv-to-fno-strict-overflow 130732 total ie the diff from the kernel with no flags is less than twice the size of the diff from fwrapv. Still - it's almost 40kB of diffs of disassembly, so I'm not going to guarantee that I can make any sense of it and find the compiler problem in it. But I'll try. And send you test-patches to see if I can pinpoint the code that causes the problem. > Kernels are identical and are compiled from the same config, on the same > server with gcc-4.2.4, binutils-2.19. There is no ccache installed and the > kernels are not patched with any additonal patches - just vanilla > linux-2.6.27.27. Thank you. > Screenshot from the hanging kernel (-fno-strict-overflow): > http://noc.axelspringer.pl/no-strict-overflow-vs-wrapv/2.6.27.27-hang.png > > Dmesg from a bootable kernel: > http://noc.axelspringer.pl/no-strict-overflow-vs-wrapv/dmesg Great. This is all about as perfect as could be asked for. Now it's just a question of trying to find the right code generation difference... Linus -- 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/