db> bt
Tracing pid 40771 tid 100755 td 0xc00000002b924560
0xe0000000c5019670: at vpanic+0x208
0xe0000000c5019720: at panic+0x40
0xe0000000c5019750: at witness_checkorder+0xd64
0xe0000000c5019860: at __mtx_lock_flags+0xd0
0xe0000000c5019910: at vm_map_lookup+0x10c
0xe0000000c5019a80: at vm_fault+0x1c4
0xe0000000c5019c80: at vm_fault_trap+0xa4
0xe0000000c5019d20: at trap+0xa94
0xe0000000c5019e60: at powerpc_interrupt+0x1b8
0xe0000000c5019ef0: kernel DSI read trap @ 0x90 by _rm_rlock+0x84: srr1=0x9000000000009032
            r1=0xe0000000c501a1a0 cr=0x4280fcb2 xer=0 ctr=0x1 r2=0xc000000003a7a000 sr=0x40000000 frame=0xe0000000c5019f20
0xe0000000c501a1a0: at 0x10020034
0xe0000000c501a210: at _rm_rlock_debug+0x178
0xe0000000c501a2b0: at sbuf_new_for_sysctl+0x2a4
0xe0000000c501a310: at kernel_sysctl+0x5c0
0xe0000000c501a400: at userland_sysctl+0x174
0xe0000000c501a520: at sys___sysctl+0x8c
0xe0000000c501a610: at trap+0xd58
0xe0000000c501a750: at powerpc_interrupt+0x1b8
0xe0000000c501a7e0: user SC trap by 0x8104a18f0: srr1=0x900000000280f032
            r1=0x3fffffffffff98e0 cr=0x28000282 xer=0 ctr=0x8104a18e0 r2=0x8104be398 frame=0xe0000000c501a810
db> show panic
panic: acquiring blockable sleep lock with spinlock or critical section held (sleep mutex) vm map (system) @ /usr/src/sys/vm/vm_map.c:4769