nvidia-driver crashing kernel on head

Hi,

I'm not sure this has been reported before but I am experience crashes with 
nvidia-driver on -current (cvsup ~day ago).  

If I remove all the debugging options from the kernel config then it is very 
usable.  

Here are the backtraces from two nvidia-driver versions:

nvidia-driver-195.36.15 and GENERIC:
panic: mutex page lock not owned at /home/freebsd9/src/sys/vm/vm_page.c:1638
cpuid = 1
KDB: enter: panic
[ thread pid 1815 tid 100097 ]
Stopped at      kdb_enter+0x3d: movq    $0,0x6bc27c(%rip)
db> bt
Tracing pid 1815 tid 100097 td 0xffffff00045af000
kdb_enter() at kdb_enter+0x3d
panic() at panic+0x176
assert_mtx() at assert_mtx
vm_page_wire() at vm_page_wire+0x37
nv_alloc_system_pages() at nv_alloc_system_pages+0x217
nv_alloc_pages() at nv_alloc_pages+0xcd
_nv019978rm() at _nv019978rm+0x7f

nvidia-driver-256.35 and custom kernel:
panic: blockable sleep lock (sleep mutex) select mtxpool _at_ 
/home/freebsd9/src/sys/kern/sys_generic.c:1479
cpuid = 1
KDB: enter: panic
[ thread pid 1830 tid 100090 ]
Stopped at      kdb_enter+0x3d: movq    $0,0x51368c(%rip)
db> bt
Tracing pid 1830 tid 100090 td 0xffffff000456d3d0
kdb_enter() at kdb_enter+0x3d
panic() at panic+0x176
witness_checkorder() at witness_checkorder+0x913
_mtx_lock_flags() at _mtx_lock_flags+0x68
selrecord() at selrecord+0x71
nvidia_dev_poll() at nvidia_dev_poll+0x52
devfs_poll_f() at devfs_poll_f+0x55
kern_select() at kern_select+0x501
select() at select+0x54
syscallenter() at syscallenter+0x19b
syscall() at syscall+0x41
Xfast_syscall() at Xfast_syscall+0xe2
--- syscall (93, FreeBSD ELF64, select), rip = 0x801a17ddc, rsp = 0x7fffffffe908, 
rbp = 0x100 ---

Also of note is:
# grep '^C.*FLAGS' /etc/make.conf
CFLAGS+= -DNDEBUG

As mentioned that without any debugging options the system is stable.  

Is there anything I can do to assist diagnosis?

Regards,

David