amd64+gdb -- instant reboot (BETA5 and 4)

Hi!

I was trying to use gdb to debug a program (audio/timidity++) on
my 6.0-BETA4.

It would play fine, and then I'll interrupt it with Ctrl-C to enter the
debugger. If I then try to exit the debugger, the whole system will
reboot instantaniously.

I sync-ed to today's sources (BETA5) and added WITNESS, WITNESS_KDB,
INVARIANTS, and INVARIANT_SUPPORT (strangly, INVARIANTS requires, but
does not imply INVARIANT_SUPPORT).

With BETA5 the story is exactly the same -- instant reboot.

Sometimes I can see two lines of debug messages (lock order reversal?)
flushed on the console, but the machine reboots too quickly to read
them beyond:

	1 ....................
	2 ....................

Is this gdb misbehaviour a known problem? How can I have the system
avoid rebooting? Crash-dumping is enabled, but does not take place :-(

Is that because timidity uses threads, perhaps?

Thanks!

	-mi