Expensive timeout(9) function: 0x9ffc000000b59d80(0) 0.060724954 s

[Anton Shterenlikht]

I see on the console:

lock order reversal:
 1st 0xe000000012c58a28 ufs (ufs) @ /usr/src/sys/fs/nullfs/null_vnops.c:620
 2nd 0x9ffc000000c32360 allproc (allproc) @ /usr/src/sys/kern/kern_descrip.c:2780
KDB: stack backtrace:
db_trace_self(0x9ffc0000000c9ec0) at db_trace_self+0x40
db_trace_self_wrapper(0x9ffc0000004da9c0) at db_trace_self_wrapper+0x70
kdb_backtrace(0x9ffc000000c0c218, 0x9ffc0000005108d0) at kdb_backtrace+0xc0
_witness_debugger(0x1, 0x9ffc000000b0edd8, 0x9ffc0000005142a0, 0xb9d, 0x9ffc000000afae08) at _witness_debugger+0x60
witness_checkorder(0x9ffc000000c32360, 0x9ffc000000b0e728, 0x9ffc000000afae08, 0xadc, 0x0) at witness_checkorder+0x15b0
_sx_slock(0x9ffc000000c32360, 0x0, 0x9ffc000000afae08, 0xadc) at _sx_slock+0x120
mountcheckdirs(0xe000000015ee04e0, 0xe000000015ee0750, 0xa0000000905bd280, 0xe000000015ee04e0, 0x9ffc0000005afd70, 0x592, 0x592) at mountcheckdirs+0x60
dounmount(0xe000000015ee0750, 0x8080000, 0xe00000001276c480, 0x0, 0x0, 0xa0000000905bd2a0, 0x1000, 0x80000) at dounmount+0x920
sys_unmount(0xe00000001276c480, 0x0, 0xe000000015ede3c8, 0xe000000012ec5800) at sys_unmount+0x6d0
syscall(0xe000000015fe0de0, 0x8080000, 0x1000055a8, 0xe00000001276c480, 0x0, 0x0, 0x9ffc00000098db00, 0x8) at syscall+0x5e0
epc_syscall_return() at epc_syscall_return
Expensive timeout(9) function: 0x9ffc000000b4e600(0xa0000000009ed320) 0.051850651 s
Expensive timeout(9) function: 0x9ffc000000b59d80(0) 0.060724954 s

I'm not interested in LOR, but
in the last 2 lines. What is this
"expensive" about?
Should I worry?

Thanks

Anton