Re: file locking.

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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