CSE 120 Lecture Notes - Lecture 3: Interrupt, Process State, System Call

• School: UCSD
• Department: Computer Science & Engineering
• Course: CSE 120
• Professor: Joseph Pasquale

Document Summary

Notion of all processes somehow running in parallel . In reality, each process gets quantum of cpu time (fixed amount of time) Illusion of parallel progress by rapidly switching cpu! Kernel keeps track of progress of each process. Ready: able to make progress, not using cpu. Blocked : not able to make progress, can"t use cpu. If system is busy, then the process is blocked by the kernel. Sleep : process gives up cpu to wait for event. Dispatch : kernel actually gave the cpu to that process. Preempt: take away the cpu from this process and give it to someone else. Move process to ready state (still has the resources to run!) Kernel runs as part of the running process. Reasons for being blocked (so the kernel knows when to ready a blocked process) System-call function calls yield() to give up cpu. Kernel selects a ready process and dispatches it.