From owner-freebsd-arch@FreeBSD.ORG Sun Sep 2 11:28:37 2007 Return-Path: Delivered-To: freebsd-arch@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id EB8FB16A417; Sun, 2 Sep 2007 11:28:37 +0000 (UTC) (envelope-from rwatson@FreeBSD.org) Received: from cyrus.watson.org (cyrus.watson.org [209.31.154.42]) by mx1.freebsd.org (Postfix) with ESMTP id C575613C45D; Sun, 2 Sep 2007 11:28:37 +0000 (UTC) (envelope-from rwatson@FreeBSD.org) Received: from fledge.watson.org (fledge.watson.org [209.31.154.41]) by cyrus.watson.org (Postfix) with ESMTP id 8DE9F46D69; Sun, 2 Sep 2007 07:09:21 -0400 (EDT) Date: Sun, 2 Sep 2007 12:09:21 +0100 (BST) From: Robert Watson X-X-Sender: robert@fledge.watson.org To: David O'Brien In-Reply-To: <20070831220318.GA4861@dragon.NUXI.org> Message-ID: <20070902120655.U35384@fledge.watson.org> References: <20070815233852.X568@10.0.0.1> <200708161056.31494.jhb@freebsd.org> <20070816131327.J568@10.0.0.1> <200708161635.20935.jhb@freebsd.org> <20070831220318.GA4861@dragon.NUXI.org> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Cc: freebsd-arch@freebsd.org Subject: Re: file locking. X-BeenThere: freebsd-arch@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussion related to FreeBSD architecture List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 02 Sep 2007 11:28:38 -0000 On Fri, 31 Aug 2007, David O'Brien wrote: > On Thu, Aug 16, 2007 at 04:35:20PM -0400, John Baldwin wrote: >> On Thursday 16 August 2007 04:18:51 pm Jeff Roberson wrote: >>> Do we have an official stance on libkvm? Now that we have sysctl for >>> run-time it's only useful for crashdump debugging. Really in most cases >>> it could be replaced with a reasonable set of gcc scripts. >> >> s/gcc/gdb/. At work we do mostly post-mortem analysis, so having working >> libkvm is still very important for us. xref the way I just fixed netstat >> to work again on coredumps recently. Breaking fstat on coredumps would >> probably be very annoying. > > This applies at Juniper as well. I think post-mortem analysis is a Big > Deal(tm) to those developing commercial products based on FreeBSD. I think it's a given that post-mortem analysis will be more fragile than live analysis due to weaker ABI requirements for in-kernel data structures -- on the other hand, it's also a critical feature. I think keeping libkvm functioning on core dumps is really important -- the ability to run ps, netstat, etc, etc, all on core dumps is remarkably useful in debugging. What I occasionally wish is that all the magic in DDB could also be used on coredumps -- i.e., that we could compile the kernel DDB bits into a user binary to run on matching core dumps in order to more easily extract things like WITNESS data, etc. No doubt a moderate amount of evil would be required to do this... Robert N M Watson Computer Laboratory University of Cambridge