ugen0.2: <vendor 0x05e3 USB2.0 Hub> at usbus0
uhub1 on uhub0
uhub1: <vendor 0x05e3 USB2.0 Hub, class 9/0, rev 2.00/32.98, addr 1> on usbus0
uhub1: MTT enabled
Root mount waiting for: usbus0
uhub1: 4 ports with 4 removable, self powered
td_lock 0xc000000003e6d080 tdq_lockptr 0xc000000003e6f780
panic: Assertion td->td_lock == TDQ_LOCKPTR(tdq) failed at /usr/src/sys/kern/sched_ule.c:2136
cpuid = 40
time = 14
KDB: stack backtrace:
0xc0080000c9344230: at kdb_backtrace+0x64
0xc0080000c9344340: at vpanic+0x25c
0xc0080000c93443f0: at panic+0x3c
0xc0080000c9344420: at sched_switch+0xabc
0xc0080000c9344570: at 0xc0080000c93445ec
0xc0080000c93445e0: at 0xc0080000c934462c
0xc0080000c9344660: at sched_throw+0x88
0xc0080000c93446e0: at thread_exit+0x2dc
0xc0080000c9344780: at kthread_exit+0x16c
0xc0080000c9344810: at taskqueue_thread_loop+0x20c
0xc0080000c9344860: at fork_exit+0xbc
0xc0080000c93448f0: at fork_trampoline+0x18
0xc0080000c9344920: at cpu_switch+0x124
KDB: enter: panic
[ thread pid 0 tid 100806 ]
Stopped at      kdb_enter+0x78: ori     r0, r0, 0x0
db> show lock 0xc000000003e6d080
 class: spin mutex
 name: sched lock 37
 flags: {SPIN, RECURSE}
 state: {UNOWNED}
db> show lock 0xc000000003e6f780
 class: spin mutex
 name: sched lock 40
 flags: {SPIN, RECURSE}
 state: {OWNED}
 owner: 0xc00000002702a000 (tid 100806, pid 0, "zio_null_intr")
db>