kidle_inject causing very high load

It appears that this is a bug in the kernel.

From the comments on that bug report, running the command sudo rmmod intel_powerclamp seems to have stopped the kidle_inject processes and I haven't noticed any issues with doing so as of yet.

Hopefully this will be fixed soon. If I do notice anything I will update this answer.

Update

The rmmod command needs to be run every time you boot the machine. I have not noticed anything bad happening since running this command.

Update 2

I have noticed since doing this that my CPU temp now tends to run much lower at around the ~72°

For making this set while booting use a command

echo "blacklist intel_powerclamp" > /etc/modprobe.d/disable-powerclamp.conf

The accepted answer is incomplete. According to the bug comments, the kidle_inject processes are spawned to throttle processor and protect it from further overheating.

Before "fixing" the bug, make sure your fan is clean and works correctly. I had this problem and found out that the vent was full of dust. After cleaning and reboot no kidle_inject was spawned anymore.

If you are running a macbook, make sure that you have macfanctld installed. If you don't, the fan will be fixed at around 2000 RPM out of the max 6000. This can be seen by the sensors command. In this situation powerclamp will kick in to save the CPUs rather early.