I have a student question
I recently learned about how a system call such as read can block a process, and such processes will be put in the Blocked state until data becomes available in whatever it's reading from. Or waitpid can block a process until a child process state has changed.
More generally, wikipedia says
A process transitions to a blocked state when it cannot carry on without an external change in state or event occurring https://en.wikipedia.org/wiki/Process_state
How does the kernel listen to these state changes or events in a way that minimizes overhead cost? I am still learning but surely it couldn't be using polling since that would be too slow right? Also "events" seem to be abstract which would mean that I can't assume if these are specifically hardware events in which case hardware interrupts can be used.