spamming zlogin with SIGINT will halt the target zone
bdha reported on twitter that holding ^C with zlogin with a shell loop will halt some percentage of his zones. This is, with a bit of care, easy to reproduce.
We assume a stock zone called 'test' exists.
$ trap echo INT
$ for i in $(seq 1 1000); do (pfexec zlogin test uname -a); done
<now hold ^C down with all your might>
(I'm using bash for this, that may be important, as far as the lengths we're going to to not interrupt the shell, to make this easier to reproduce)
After some period of time, you'll perhaps get errors from zlogin stating that you can't log in to a zone in the shutting_down state (and then the installed state), either way after a period of time the loop will terminate, and the zone 'test' will have halted
The zone should not have halted, whatever (presumably) received our SIGINT shouldn't have.