Using PTHREAD_PRIO_INHERIT causes panic in kern_umtx.c

When I compile and run the attached program, it panics my system,  
(FreeBSD CURRENT as of 2-20-09) with the following message:

panic: Assertion pi != NULL failed at /usr/src/sys/kern/kern_umtx: 1464

With the backtrace being:
Tracing pid 1079 tid 100045 td 0xffffff00037c8000
kdb_enter() at kdb_enter+0x40
panic() at panic+0x1ec
umtx_pi_adjust() at umtx_pi_adjust+0xfc8
umtx_pi_adjust() at umtx_pi_adjust+0x19bd
_umtx_unlock() at _umtx_unlock+0x2c41
_umtx_op() at _umtx_op+0x22
syscall() at syscall+0x1f4
Xfast_syscall() at Xfast_syscall+0xaa
--- syscall (454, FreeBSD ELF64, _umtx_op), rip = 0x4056ac, rsp =  
0x7fffffbfef38, rbp = 0x80060b150 ---

This problem only shows up when I use PTHREAD_PRIO_INHERIT -- if I  
change the line for pthread_mutexattr_setprotocol to  
PTHREAD_PRIO_NONE, then it works fine.  I've been trying to trace thru  
the code to figure out where uq_pi_blocked should be setup, but I'm  
not too familiar with the code so I haven't found where the problem  
originates.  How can I get PTHREAD_PRIO_INHERIT to work?  And even if  
the change is in user-space, it probably shouldn't be this easy to  
panic the kernel :-)

-Justin


PS I'm reasonably certain that the most recent checkins (between now  
and Feb 20th) wouldn't fix this, but if I'm wrong, just let me know!