port-macppc/51527: 7.99.39/macppc DIAGNOSTIC+DEBUG kernel consistently panics on halt(8) with a mutex error

[dhgutteridge%sympatico.ca@localhost]

>Number:         51527
>Category:       port-macppc
>Synopsis:       7.99.39/macppc DIAGNOSTIC+DEBUG kernel consistently panics on halt(8) with a mutex error
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    port-macppc-maintainer
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Tue Oct 04 05:25:00 +0000 2016
>Originator:     David H. Gutteridge
>Release:        HEAD
>Organization:
>Environment:
>Description:
I can consistently trigger a kernel panic on 7.99.39/macppc when
invoking halt(8), either in single or multi user mode. (shutdown(8)
does not trigger a panic.) This is with DIAGNOSTIC and DEBUG enabled.

mutex error: mutex_vector_enter: assertion failed: curthread != 0

lock address : 0x0000000000000018
current cpu  :                  0
current lwp  : 000000000000000000
owner field  : 0x000000007c3142a0 wait/spin:               1/0

Skipping crash dump on recursive panic
panic: lock error: Mutex: mutex_vector_enter: assertion failed: curthread != 0: lock 0x0
Stopped in pid 0.0 () at       netbsd:vpanic+0x140:     addi     r4, r0, 0x0
0xff9ce3d0: at panic+0x4c
0xff9ce410: at lockdebug_abort+0x64
0xff9ce430: at mutex_spin_enter+0x214
0xff9ce470: at statclock+0x150
0xff9ce4a0: at hardclock+0xbc
0xff9ce4c0: at decr_intr+0x15c
0xff9ce4f0: at trapstart+0x7d8
0xff9ce5c0: at 0xff8ae574

>How-To-Repeat:
Invoke halt(8) either in single or multi user mode.
>Fix: