He's describing killing a thread using a watchdog.
This doesn't limit compute power of the thread.
It's an all or nothing approach; either the thread runs or is killed, which doesn't work (as you point out) for all circumstances where you want to limit the amount of compute pwr a thread can use.
They're describing sending a signal to a thread, not "killing" it. IIRC, the only thing tgkill is going to do for you is ensure which thread runs the signal handler. For example, if you send a SIGTERM, (IIRC), you will terminate your entire process.
This doesn't limit compute power of the thread.
It's an all or nothing approach; either the thread runs or is killed, which doesn't work (as you point out) for all circumstances where you want to limit the amount of compute pwr a thread can use.