root@rpi:/usr/src #  kldunload if_urtwn 
Fatal kernel mode data abort: 'Translation Fault (L1)' on read
trapframe: 0xdcfb5c50
FSR=00000005, FAR=deadc0f6, spsr=60000013
r0 =deadc0de, r1 =c2e79000, r2 =c093fba8, r3 =00000000
r4 =c2e79000, r5 =c2e5a000, r6 =c2e5baa8, r7 =00000000
r8 =c260f0c0, r9 =00000000, r10=c06a58f0, r11=dcfb5ce8
r12=00000000, ssp=dcfb5ce0, slr=c2e42b3c, pc =c093fbbc

[ thread pid 5844 tid 100080 ]
Stopped at      node_free+0x14: ldr     r1, [r0, #0x018]
db> bt    
Tracing pid 5844 tid 100080 td 0xc2e65360
panic: _sx_xlock_hard: recursed on non-recursive sx kernel linker @ /usr/src/sys/kern/kern_linker.c:552

Uptime: 1h32m37s
Automatic reboot in 15 seconds - press a key on the console to abort