login: witness: thread 0xffff800020b752c8 exiting with the following locks held:
exclusive rrwlock inode r = 0 (0xfffffd806bbcc928) locked @ /syzkaller/managers/multicore/kernel/sys/ufs/ufs/ufs_vnops.c:1547
panic: thread 0xffff800020b752c8 cannot exit while holding sleeplocks
Stopped at      db_enter+0x18:  addq    $0x8,%rsp
    TID    PID    UID     PRFLAGS     PFLAGS  CPU  COMMAND
* 39170  83009      0     0x14000      0x200    1  reaper
db_enter() at db_enter+0x18 sys/arch/amd64/amd64/db_interface.c:399
panic() at panic+0x16c sys/kern/subr_prf.c:208
witness_thread_exit(16dd2bc53ae603fa) at witness_thread_exit+0x244 sys/kern/subr_witness.c:1377
reaper(0) at reaper+0x14f sys/kern/kern_exit.c:412
end trace frame: 0x0, count: 11
https://www.openbsd.org/ddb.html describes the minimum info required in bug
reports.  Insufficient info makes it difficult to find and fix bugs.
ddb{1}> 
ddb{1}> set $lines = 0
ddb{1}> show panic
thread 0xffff800020b752c8 cannot exit while holding sleeplocks
ddb{1}> trace
db_enter() at db_enter+0x18 sys/arch/amd64/amd64/db_interface.c:399
panic() at panic+0x16c sys/kern/subr_prf.c:208
witness_thread_exit(16dd2bc53ae603fa) at witness_thread_exit+0x244 sys/kern/subr_witness.c:1377
reaper(0) at reaper+0x14f sys/kern/kern_exit.c:412
end trace frame: 0x0, count: -4
ddb{1}> show registers
rdi                                0
rsi                              0x1
rbp               0xffff800020b67330
rbx               0xffff800020b673d0
rdx               0xffffffff81f323f3    cy_pio_rec+0x25c
rcx                            0x201
rax                              0x1
r8                0xffffffff81d8b924    kprintf+0x174
r9                               0x1
r10               0xb19e7f6ebcc25fe1
r11               0xda47be9ac092cb55
r12                     0x3000000008
r13               0xffff800020b67340
r14                            0x100
r15                              0x1
rip               0xffffffff81202148    db_enter+0x18
cs                               0x8
rflags                         0x246
rsp               0xffff800020b67320
ss                              0x10
db_enter+0x18:  addq    $0x8,%rsp
ddb{1}> show proc
PROC (reaper) pid=39170 stat=onproc
    flags process=14000<NOZOMBIE,SYSTEM> proc=200<SYSTEM>
    pri=4, usrpri=51, nice=20
    forw=0xffffffffffffffff, list=0xffff800020b20e10,0xffff800020b219d8
    process=0xffff800020b5b070 user=0xffff800020b62000, vmspace=0xffffffff822d2290
    estcpu=1, cpticks=3, pctcpu=0.0
    user=0, sys=2, intr=0
ddb{1}>