FreeBSD 11 i386 disk deadlock (I think)

[David Cross]

I noticed this situation on a Soekris machine I have (geode processor),  It
has happened twice, once in installworld ,once in buildworld.  I am not
sure how to trigger it more easily, but the symptoms are quite
straightforward.

Both times this happened in objcopy.  And objcopy was stuck in the
"vm_wait" wait-channel.  The first time I was able to control-C it (after a
few Control-Ts that showed it was not progressing)  and everything came
back, I was then able to re-run the installworld (that had been the source
of the objcopy) without incident.  That I was able to Control-C it, and
re-run it without a disk-wait process, or blocking in the same spot is
telling to me.

The second time I had wandered away and by the time I got back I was no
longer able to interact with the machine.  It still passed traffic, but any
attempt to open a new ssh connection was greeted with an opened TCP socket
and IMMEDIATE reset/termination.  I was forced to reset it.

While this was happening, it was successfully routing 6 megabytes/second
through its interfaces.

I am going to try to run this again to see if I can get any more
information, it is apparently fairly easy for me to trip.