needbuf ?

[Patrick Welche <prlw1%cam.ac.uk@localhost>]

I manage to repeatably freeze (100% idle) a -current/amd64 box with
(sysutils/diskscrub)

# scrub /dev/raid0a
scrub: using NNSA NAP-14.1-C patterns
scrub: please verify that device size below is correct!
scrub: scrubbing /dev/raid0a 3221159936 bytes (~3071MB)
scrub: random  |.................                               |

  PID   LID USERNAME PRI STATE      TIME   WCPU    CPU NAME      COMMAND
    0    51 root     221 needbu/0   0:21  0.00%  0.00% raidio0   [system]
  999     1 root      85 needbu/1   0:06  0.00%  0.00% -         scrub

...
  696     1 root     117 tstile/0   0:00  0.00%  0.00% -         sh
  168     1 root     117 needbu/0   0:00  0.00%  0.00% -         sh
  130     1 root     117 tstile/1   0:00  0.00%  0.00% -         sh


It is booted over NFS, but has real wd0b swap, and rndctl -cet net.

I hadn't come across needbuf before...

Have I found a foot gun?

Cheers,

Patrick