Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S270370AbTGRUbX (ORCPT ); Fri, 18 Jul 2003 16:31:23 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S270382AbTGRUal (ORCPT ); Fri, 18 Jul 2003 16:30:41 -0400 Received: from zero.aec.at ([193.170.194.10]:15633 "EHLO zero.aec.at") by vger.kernel.org with ESMTP id S270370AbTGRU3X (ORCPT ); Fri, 18 Jul 2003 16:29:23 -0400 To: linas@austin.ibm.com Cc: linux-kernel@vger.kernel.org Subject: Re: KDB in the mainstream 2.4.x kernels? From: Andi Kleen Date: Fri, 18 Jul 2003 22:43:57 +0200 In-Reply-To: (linas@austin.ibm.com's message of "Fri, 18 Jul 2003 22:10:11 +0200") Message-ID: User-Agent: Gnus/5.090013 (Oort Gnus v0.13) Emacs/21.2 (i586-suse-linux) References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1970 Lines: 42 One argument i have against it: KDB is incredibly ugly code. Before it could be even considered for merging it would need quite a lot of cleanup. I actually started on porting the KDB backtracer recently to get reliable frame pointer based backtraces, but it turns out the code for that is so complicated and ugly that the chances of ever merging it would be very slim. As for your home crash debugging I suspect you would be better of with LKCD or Mcore (crash dump, saving an crash image on some partition, with examining the crash dump after reboot) KDB is usually not useful for debugging hangs on desktop boxes (and even many servers) because you have usually X running. When the machine crashes and goes in KDB you cannot see the text output and debug anything. I learned to type "go" blind when I had still an KDB aware kernel, but it's not very useful overall. On a development machine you can avoid that by connecting a serial cable, but that's usually not easily possible for a desktop box. Doing a post-mortem after reboot is more practical. That is what LKCD/mcore do. Disadvantage is that the current crash dump mechanisms (lkcd, mcore crash, netdump) are all still not very reliable and have horrible error handling. And you can eat a lot of disk space for the dumps and they tend to overflow your file systems. But still it's the only realistic option for "desktop bugs" BTW debugging on the X server works on linuxppc/mac with xmon because it has a fbcon based console and X server. The debugger can just work on the X background while the X server is stopped. Very nifty. But I don't see the x86 XFree86 switching to a similar fbcon model any time soon, so it's unlikely to help. -Andi - 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/