Preemption

• It's the act of temporarily interrupting a task, with the intention of resuming it at a later time
• This interruption is done by an external scheduler (independent from the task itself)

External scheduler

• Responsible to define what process will run in a thread at each time
• Interrupts and resumes tasks (context switching)
• Runs in the most privileged protection ring

Context switching

• The changes of the currently running task in a processor (thread)