TITLE: witness: thread exiting with locks held

witness: thread 0xffff800020bba4c8 exiting with the following locks held:
exclusive rrwlock inode r = 0 (0xfffffd806747bc48) locked @ /syzkaller/managers/setuid/kernel/sys/ufs/ufs/ufs_vnops.c:1547
panic: Thread 0xffff800020b92720 cannot exit while holding sleeplocks

Stopped at      db_enter+0x18:  addq    $0x8,%rsp
    TID    PID    UID     PRFLAGS     PFLAGS  CPU  COMMAND
 333692  13365     73    0x100010          0    1K syslogd
*482899     71      0     0x14000      0x200    0  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(11493cd476f78d7c) 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
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ddb{0}>
ddb{0}> set $lines = 0
ddb{0}> show panic
Thread 0xffff800020b92720 cannot exit while holding sleeplocks

ddb{0}> 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(11493cd476f78d7c) 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{0}> show registers
rdi                                0
rsi                              0x1
rbp               0xffff800020b67ad0
rbx               0xffff800020b67b70
rdx               0xffffffff81ec577a    cmd0646_9_tim_udma+0x16395
rcx                                0
rax                                0
r8                0xffffffff81788154    kprintf+0x174
r9                               0x1
r10               0x6f534a22035bc4ca
r11               0x6db44f275a450c3a
r12                     0x3000000008
r13               0xffff800020b67ae0
r14                            0x100
r15                              0x1
rip               0xffffffff81107618    db_enter+0x18
cs                               0x8
rflags                         0x246
rsp               0xffff800020b67ac0
ss                              0x10
db_enter+0x18:  addq    $0x8,%rsp
ddb{0}> show proc
PROC (reaper) pid=482899 stat=onproc
    flags process=14000<NOZOMBIE,SYSTEM> proc=200<SYSTEM>
    pri=4, usrpri=51, nice=20
    forw=0xffffffffffffffff, list=0xffff800020b20e10,0xffff800020b21c30
    process=0xffff800020b5b070 user=0xffff800020b62000, vmspace=0xffffffff822fc8c0
    estcpu=1, cpticks=3, pctcpu=0.15
    user=0, sys=3, intr=0
ddb{0}> ps
   PID     TID   PPID    UID  S       FLAGS  WAIT          COMMAND
 95915  250426   7524  32767  2       0x490                syz-executor1
  7524  125781  33554      0  3        0x82  wait          syz-executor1
 81310  477266  28796  32767  2       0x490                syz-executor0
 28796  145672  33554      0  3        0x82  wait          syz-executor0
 53135  361876      0      0  3     0x14200  bored         sosplice
 33554  404063  25047      0  3        0x82  thrsleep      syz-fuzzer
 33554   88446  25047      0  3   0x4000082  thrsleep      syz-fuzzer
 33554  460070  25047      0  3   0x4000082  thrsleep      syz-fuzzer
 33554  345337  25047      0  3   0x4000082  thrsleep      syz-fuzzer
 33554  149986  25047      0  3   0x4000082  thrsleep      syz-fuzzer
 33554   42230  25047      0  3   0x4000082  thrsleep      syz-fuzzer
 33554   60955  25047      0  3   0x4000082  thrsleep      syz-fuzzer
 33554   38186  25047      0  3   0x4000082  thrsleep      syz-fuzzer
 33554  513288  25047      0  3   0x4000082  kqread        syz-fuzzer
 33554  493206  25047      0  3   0x4000082  thrsleep      syz-fuzzer
 33554  517119  25047      0  3   0x4000082  thrsleep      syz-fuzzer
 33554  347325  25047      0  3   0x4000082  thrsleep      syz-fuzzer
 25047  172199  97313      0  3    0x10008a  pause         ksh
 97313  470341  49628      0  3        0x92  select        sshd
 26148  337889      1      0  3    0x100083  ttyin         getty
 49628  220902      1      0  3        0x80  select        sshd
 13365  333692   4722     73  7    0x100010                syslogd
  4722  364223      1      0  3    0x100082  netio         syslogd
  8296  330563      1     77  3    0x100090  poll          dhclient
 95260  270278      1      0  3        0x80  poll          dhclient
 89557   94184      0      0  3     0x14200  pgzero        zerothread
 64715   61906      0      0  3     0x14200  aiodoned      aiodoned
 25392  229747      0      0  3     0x14200  syncer        update
 63748   85883      0      0  3     0x14200  cleaner       cleaner
*   71  482899      0      0  7     0x14200                reaper
 56311  139753      0      0  3     0x14200  pgdaemon      pagedaemon
 83328  272899      0      0  3     0x14200  bored         crynlk
  2399  230600      0      0  3     0x14200  bored         crypto
 36220  506735      0      0  3  0x40014200  acpi0         acpi0
   717  437876      0      0  3  0x40014200                idle1
 87882  394549      0      0  3     0x14200  bored         softnet
 92791  451998      0      0  3     0x14200  bored         systqmp
 43113   79354      0      0  3     0x14200  bored         systq
 30693  248390      0      0  2  0x40014200                softclock
 29249  207353      0      0  3  0x40014200                idle0
     1  427078      0      0  3        0x82  wait          init
     0       0     -1      0  3     0x10200  scheduler     swapper
