ppanic: mutex lockbuilder mtxpool not owned at ../../../kern/kern_lock.c:129

On 12-proc sparc64 E4500 running 6.0 with mpsafevfs.  Note the
'ppanic'; this may mean that another CPU tried to panic and then this
CPU panicked immediately with a secondary panic.

ppanic: mutex lockbuilder mtxpool not owned at ../../../kern/kern_lock.c:129
cpuid = 1
KDB: enter: panic
[thread pid 48 tid 100058 ]
Stopped at      kdb_enter+0x3c: ta              %xcc, 1
db> wh
Tracing pid 48 tid 100058 td 0xfffff800fed7b300
panic() at panic+0x16c
_mtx_assert() at _mtx_assert+0x6c
acquire() at acquire+0x138
lockmgr() at lockmgr+0x58c
vop_stdlock() at vop_stdlock+0x14
VOP_LOCK_APV() at VOP_LOCK_APV+0xb4
ffs_lock() at ffs_lock+0xc
VOP_LOCK_APV() at VOP_LOCK_APV+0xb4
vlrureclaim() at vlrureclaim+0x194
vnlru_proc() at vnlru_proc+0x16c
fork_exit() at fork_exit+0x94
fork_trampoline() at fork_trampoline+0x8
db> show lockedvnods
Locked vnodes
panic: _mtx_lock_sleep: recursed on non-recursive mutex lockbuilder mtxpool _at_ ../../../kern/kern_lock.c:542

cpuid = 1
KDB: stack backtrace:
sched_bind() at sched_bind+0x78
boot() at boot+0x24
panic() at panic+0x1c4
_mtx_lock_sleep() at _mtx_lock_sleep+0x40
_mtx_lock_flags() at _mtx_lock_flags+0x84
lockstatus() at lockstatus+0x18
vop_stdislocked() at vop_stdislocked+0xc
VOP_ISLOCKED_APV() at VOP_ISLOCKED_APV+0xb4
lockedvnodes() at lockedvnodes+0x4c
db_command() at db_command+0x2ac
db_command_loop() at db_command_loop+0x70
db_trap() at db_trap+0xf0
kdb_trap() at kdb_trap+0xa0
trap() at trap+0x264
-- breakpoint %o7=0xc0189674 --
kdb_enter() at kdb_enter+0x3c
panic() at panic+0x16c
_mtx_assert() at _mtx_assert+0x6c
acquire() at acquire+0x138
lockmgr() at lockmgr+0x58c
vop_stdlock() at vop_stdlock+0x14
VOP_LOCK_APV() at VOP_LOCK_APV+0xb4
ffs_lock() at ffs_lock+0xc
VOP_LOCK_APV() at VOP_LOCK_APV+0xb4
vlrureclaim() at vlrureclaim+0x194
vnlru_proc() at vnlru_proc+0x16c
fork_exit() at fork_exit+0x94
fork_trampoline() at fork_trampoline+0x8

As usual on SMP I was unable to trace the processes running on the
other CPUs.

Kris