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From: Kip Macy <kmacy@freebsd.org>
To: David N <davidn04@gmail.com>
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Cc: freebsd-hackers@freebsd.org
Subject: Re: Debugging via DDB
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On Thu, May 28, 2009 at 9:27 PM, David N <davidn04@gmail.com> wrote:
> Hi,
>
> I know this might sound like a newbie question.
>
> I'm trying to debug a "Lockup" on 7.2-RELEASE. I've compiled DDB and
> KDB into the kernel and make installkernel. (Can this be called a
> deadlock?)
>
> The machine still response to pings, but it looks like all disk
> activity has stopped.
>
> I can break into the debugger using CTRL-ALT-ESC, but after that, i
> dont know what I'm looking for in particular.
>
> bt (backtrace) gives me the stuff like the keyboard mutex ( i assume
> it was the last thing that happened, but obviously it was the break)
>
> Should I be including WITNESS?

Include WITNESS.  "ps" to list processes, "show proc" to see proc
info, "thread <no>" to switch to a thread, "show locks" to see locks
held, show sleepc to see what you're blocked on (if a sleepq), and
"show alllocks" to see all locks held
-Kip