Unless the OOM-killer kills the wrong process. Ages ago we had a userspace filesystem (gpfs) that was of course one of the oldest processes around and it consumed lots of RAM. When the oom killer started looking for a target, of course one of the mmfsd processes was selected and it resulted in instantaneous machine lockup (any access to that filesystem would be blocked forever in the system call which depended on the userspace daemon to return, alas never returning). Was funny to debug