Date: Sun, 2 Sep 2007 12:09:21 +0100 (BST) From: Robert Watson <rwatson@FreeBSD.org> To: David O'Brien <obrien@freebsd.org> Cc: freebsd-arch@freebsd.org Subject: Re: file locking. Message-ID: <20070902120655.U35384@fledge.watson.org> In-Reply-To: <20070831220318.GA4861@dragon.NUXI.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>
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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
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