db> bt 920
Tracing pid 920 tid 100083 td 0xcecb4740
0xcebdc930: at uart_bus_attach+0x944
0xcebdc970: at intr_event_handle+0x11c
0xcebdc9b0: at powerpc_dispatch_intr+0xe8
0xcebdc9f0: at openpic_dispatch+0x90
0xcebdca10: at powerpc_interrupt+0x134
0xcebdca40: user EXI trap by 0x419ec6c4: srr1=0x202d000
            r1=0x7fffd5f0 cr=0x82420a80 xer=0 ctr=0 frame=0xcebdca48