panic in zfs on reboot

I updated my machine that tracks head and rebooted it,
and it panic'd during the 'shutdown -r' execution.

   Panic String: solaris assert: zrl->zr_refcount == 0 (0x2 == 0x0), 
file: /usr/src/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zrlock.c, 
line: 64

(kgdb) bt
#0  doadump (textdump=1) at pcpu.h:221
#1  0xffffffff80708ec5 in kern_reboot (howto=260)
     at /usr/src/sys/kern/kern_shutdown.c:364
#2  0xffffffff8070949b in vpanic (fmt=<value optimized out>,
     ap=<value optimized out>) at /usr/src/sys/kern/kern_shutdown.c:757
#3  0xffffffff807094e3 in panic (fmt=0x0)
     at /usr/src/sys/kern/kern_shutdown.c:688
#4  0xffffffff81b3c25f in assfail3 (a=<value optimized out>,
     lv=<value optimized out>, op=<value optimized out>,
     rv=<value optimized out>, f=<value optimized out>, l=<value 
optimized out>)
     at /usr/src/sys/cddl/compat/opensolaris/kern/opensolaris_cmn_err.c:91
#5  0xffffffff8187fe54 in zrl_destroy (zrl=0xfffff8001d429820)
     at /usr/src/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zrlock.c:64
#6  0xffffffff81804432 in dnode_special_close (dnh=0xfffff8001d429820)
     at /usr/src/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dnode.c:1005
#7  0xffffffff817fa608 in dmu_objset_evict_done (os=0xfffff8001d429800)
     at 
/usr/src/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu_objset.c:726
#8  0xffffffff8180f191 in dsl_dataset_evict (dbu=0xfffff8000f957000)
     at 
/usr/src/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dsl_dataset.c:287
#9  0xffffffff80756ae0 in taskqueue_run_locked (queue=0xfffff8000d00cd00)
     at /usr/src/sys/kern/subr_taskqueue.c:430
#10 0xffffffff807575f8 in taskqueue_thread_loop (arg=<value optimized out>)
     at /usr/src/sys/kern/subr_taskqueue.c:683
#11 0xffffffff806cf6b4 in fork_exit (
     callout=0xffffffff80757570 <taskqueue_thread_loop>,
     arg=0xfffff8000d01e020, frame=0xfffffe085c058ac0)
     at /usr/src/sys/kern/kern_fork.c:1011
#12 0xffffffff809ae70e in fork_trampoline ()
     at /usr/src/sys/amd64/amd64/exception.S:609
#13 0x0000000000000000 in ?? ()

I have a vmcore for this panic.  I have saved off the installed kernel
directory for future examination.

-Kurt