/* clang */
(kgdb) bt
#0  sched_switch (td=0xfffff80003c01000, newtd=0xfffff80003201000, flags=<optimized out>) at /root/ws/head/sys/kern/sched_ule.c:2112
#1  0xffffffff80bfbbb4 in mi_switch (flags=260, newtd=0x0) at /root/ws/head/sys/kern/kern_synch.c:439
#2  0xffffffff80c47700 in sleepq_switch (wchan=0xfffff8000322aa00, pri=0) at /root/ws/head/sys/kern/subr_sleepqueue.c:612
#3  0xffffffff80c475a3 in sleepq_wait (wchan=0xfffff8000322aa00, pri=0) at /root/ws/head/sys/kern/subr_sleepqueue.c:691
#4  0xffffffff80bfb3fa in _sleep (ident=0xfffff8000322aa00, lock=0xfffff8000322aa38, priority=0, wmesg=0xffffffff812943c6 "-", sbt=0, pr=0, flags=256)
    at /root/ws/head/sys/kern/kern_synch.c:217
#5  0xffffffff80c4cff1 in TQ_SLEEP (tq=<optimized out>, p=<optimized out>, m=<optimized out>, pri=0, wm=<unavailable>, t=0) at /root/ws/head/sys/kern/subr_taskqueue.c:124
#6  taskqueue_thread_loop (arg=<optimized out>) at /root/ws/head/sys/kern/subr_taskqueue.c:781
#7  0xffffffff80baf4c4 in fork_exit (callout=0xffffffff80c4cf10 <taskqueue_thread_loop>, arg=0xfffff8002014f268, frame=0xfffffe0021decac0) at /root/ws/head/sys/kern/kern_fork.c:1056
#8  <signal handler called>
(kgdb) f 4
#4  0xffffffff80bfb3fa in _sleep (ident=0xfffff8000322aa00, lock=0xfffff8000322aa38, priority=0, wmesg=0xffffffff812943c6 "-", sbt=0, pr=0, flags=256)
    at /root/ws/head/sys/kern/kern_synch.c:217
217			sleepq_wait(ident, pri);
(kgdb) quit

/* gcc */
(kgdb) bt
#0  sched_switch (td=td@entry=0xfffff800154015c0, newtd=0xfffff80003201000, newtd@entry=0x0, flags=flags@entry=260) at /root/ws/head/sys/kern/sched_ule.c:2112
#1  0xffffffff80bc26f8 in mi_switch (flags=flags@entry=260, newtd=newtd@entry=0x0) at /root/ws/head/sys/kern/kern_synch.c:439
#2  0xffffffff80c11bc6 in sleepq_switch (wchan=0xfffff800034c0600, pri=0) at /root/ws/head/sys/kern/subr_sleepqueue.c:612
#3  0xffffffff80c12846 in sleepq_wait (wchan=0xfffff800034c0600, pri=0) at /root/ws/head/sys/kern/subr_sleepqueue.c:691
#4  0xffffffff80bc1d7d in _sleep (ident=ident@entry=0xfffff800034c0600, lock=lock@entry=0xfffff800034c0638, priority=priority@entry=0, wmesg=wmesg@entry=0xffffffff81606fb0 "-", 
    sbt=sbt@entry=0, pr=pr@entry=0, flags=256) at /root/ws/head/sys/kern/kern_synch.c:217
#5  0xffffffff80c160ac in TQ_SLEEP (t=0, wm=0xffffffff81606fb0 "-", pri=0, m=0xfffff800034c0638, p=0xfffff800034c0600, tq=0xfffff800034c0600)
    at /root/ws/head/sys/kern/subr_taskqueue.c:124
#6  taskqueue_thread_loop (arg=arg@entry=0xfffff80015020268) at /root/ws/head/sys/kern/subr_taskqueue.c:781
#7  0xffffffff80b763c4 in fork_exit (callout=0xffffffff80c16020 <taskqueue_thread_loop>, arg=0xfffff80015020268, frame=0xfffffe0022232ac0) at /root/ws/head/sys/kern/kern_fork.c:1056
#8  <signal handler called>
(kgdb)