destroying a gbde device works fine, but orphaning it causes the following panic: panic: mtx_lock() of spin mutex (null) @ /usr/home/somers/freebsd/base/head/sys/kern/kern_mutex.c:186 cpuid = 3 time = 1517613029 KDB: stack backtrace: db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame 0xfffffe000047d850 vpanic() at vpanic+0x18d/frame 0xfffffe000047d8b0 vpanic() at vpanic/frame 0xfffffe000047d930 __mtx_lock_flags() at __mtx_lock_flags+0x163/frame 0xfffffe000047d980 _sleep() at _sleep+0x405/frame 0xfffffe000047da30 g_bde_worker() at g_bde_worker+0x214/frame 0xfffffe000047da70 fork_exit() at fork_exit+0x84/frame 0xfffffe000047dab0 fork_trampoline() at fork_trampoline+0xe/frame 0xfffffe000047dab0 --- trap 0, rip = 0, rsp = 0, rbp = 0 --- This is on FreeBSD 12.0-CURRENT amd64 at r328767 (1-Feb-2018). Steps to reproduce: [somers@fbsd12 ~]$ sudo mdconfig -a -s 1m md0 [somers@fbsd12 ~]$ sudo gnop create md0 [somers@fbsd12 ~]$ sudo gbde init md0.nop -P xxx [somers@fbsd12 ~]$ sudo gbde attach md0.nop -p xxx [somers@fbsd12 ~]$ sudo gnop destroy -f md0.nop