Unread portion of the kernel message buffer:
panic: sleepq_add: td 0xfffff800035d8560 to sleep on wchan 0xfffff800054b0048 with sleeping prohibited
cpuid = 0

#0  __curthread () at ./machine/pcpu.h:230
#1  doadump (textdump=1) at /zroot/zfs_zstd/head/sys/kern/kern_shutdown.c:347
#2  0xffffffff80ac9242 in kern_reboot (howto=260) at /zroot/zfs_zstd/head/sys/kern/kern_shutdown.c:416
#3  0xffffffff80ac980d in vpanic (fmt=<optimized out>, ap=0xfffffe00265097b0) at /zroot/zfs_zstd/head/sys/kern/kern_shutdown.c:812
#4  0xffffffff80ac9620 in kassert_panic (fmt=0xffffffff811c9eaf "%s: td %p to sleep on wchan %p with sleeping prohibited")
    at /zroot/zfs_zstd/head/sys/kern/kern_shutdown.c:698
#5  0xffffffff80b1c3e8 in sleepq_add (wchan=0xfffff800054b0048, lock=0xfffff8000549b4d0, wmesg=0xffffffff811c3914 "cbwait", flags=0, queue=0)
    at /zroot/zfs_zstd/head/sys/kern/subr_sleepqueue.c:319
#6  0xffffffff80ad3a91 in _sleep (ident=0xfffff800054b0048, lock=<optimized out>, priority=92, wmesg=0xffffffff811c3914 "cbwait", sbt=0, pr=0,
    flags=256) at /zroot/zfs_zstd/head/sys/kern/kern_synch.c:200
#7  0xffffffff803356ad in cam_periph_ccbwait (ccb=<optimized out>) at /zroot/zfs_zstd/head/sys/cam/cam_periph.c:1141
#8  cam_periph_runccb (ccb=0xfffff800054b0000, error_routine=0xffffffff8035e790 <cderror>, camflags=CAM_RETRY_SELTO, sense_flags=3,
    ds=0xfffff800054f2480) at /zroot/zfs_zstd/head/sys/cam/cam_periph.c:1222
#9  0xffffffff8035db73 in cdrunccb (error_routine=<unavailable>, cam_flags=2, ccb=<optimized out>, sense_flags=<optimized out>)
    at /zroot/zfs_zstd/head/sys/cam/scsi/scsi_cd.c:808
#10 cdprevent (periph=0xfffff800054f5e00, action=1) at /zroot/zfs_zstd/head/sys/cam/scsi/scsi_cd.c:2185
#11 cdcheckmedia (periph=0xfffff800054f5e00) at /zroot/zfs_zstd/head/sys/cam/scsi/scsi_cd.c:2213
#12 0xffffffff8035a1a5 in cdstrategy (bp=0xfffff8000564aa80) at /zroot/zfs_zstd/head/sys/cam/scsi/scsi_cd.c:848
#13 0xffffffff80a0ff1e in g_disk_start (bp=<optimized out>) at /zroot/zfs_zstd/head/sys/geom/geom_disk.c:478
#14 0xffffffff80a13e15 in g_io_schedule_down (tp=<optimized out>) at /zroot/zfs_zstd/head/sys/geom/geom_io.c:893
#15 0xffffffff80a1461d in g_down_procbody (arg=<optimized out>) at /zroot/zfs_zstd/head/sys/geom/geom_kern.c:111
#16 0xffffffff80a89e34 in fork_exit (callout=0xffffffff80a145b0 <g_down_procbody>, arg=0x0, frame=0xfffffe0026509c00)
    at /zroot/zfs_zstd/head/sys/kern/kern_fork.c:1038
#17 <signal handler called>