Comment 50 for bug 406397

I ran into this again and found a new (?) way of fixing the situation once it has happened that is slightly less crazy than the exhaust-all-pids script: The /proc/sys/kernel/ns_last_pid knob can be used to get a process with the correct PID.

I used
echo $(($n-2)) | sudo tee /proc/sys/kernel/ns_last_pid && bash -c 'sleep 60 &'

Where $n is the PID that upstart is tracking (output of 'status'). The -2 is necessary because the bash process gets a pid first. The sleep should wind up with the tracked PID and as a child of the init process.

Maybe there is a simpler way, but this worked for me.

Note that is a relatively "new" kernel feature. It works with the saucy kernel, I don't know about earlier releases.