Unkillable process in a ZFS jail

[David Demelier]

Hello there,

I've just realized there was a process burning my small dedicated
server CPU for 4 days long.

The process was spawn in a ZFS jail from buildbot service.

top shown this:

buildbot       1  20    0     0K    16K CPU0    0  83.5H 101.02%
python2.7

No kill -9 was able to stop the process, the jail was also unstoppable.
And any filesystem operation in that jail got stuck. Just like editing
/etc/rc.conf didn't terminate correctly.

I remember there was a ZFS issue a long time ago about deadlocks, but
I'm not sure it's still present, my server runs FreeBSD 11.2.

This leads me to these questions:

1. Is there some issue regarding ZFS? What to do if a process is
unkillable?
2. Do you know any kind of monitoring service or periodic files that
reports too many CPU usage after a while? By sending a mail that would
be very handy.

Regards,

-- 
David