For various reasons I still hadn't got swamp, my FreeBSD 10-CURRENT box, up to date. Today I finally managed it. Booted and got...
panic: _mtx_lock_sleep: recursed on non-recursive mutex em0 @ /src/FreeBSD/svn/head/sys/dev/e1000/if_lem.c:881
And for some reason kgdb can't read the dump properly:
Reading symbols from /boot/kernel/linux.ko...Reading symbols from /boot/kernel/linux.ko.symbols...done.
done.
Loaded symbols for /boot/kernel/linux.ko
kgdb: kvm_read: invalid address (0x354540a)
#0 0x00000000 in ?? ()
(kgdb) bt
#0 0x00000000 in ?? ()
(kgdb)
done.
Loaded symbols for /boot/kernel/linux.ko
kgdb: kvm_read: invalid address (0x354540a)
#0 0x00000000 in ?? ()
(kgdb) bt
#0 0x00000000 in ?? ()
(kgdb)
That should have given me a backtrace of the process that paniced. What went wrong there? It's beginning to look as if I should take another look at kgdb, but I'm not sure if I have the energy. In any case, it seems that this is a genuine bug in -CURRENT, one that mainly hits VirtualBox users. It's not 100% clear why that should be, except that the bug is specific to the network interface that VirtualBox provides.