2013 04 10

本次由成員 Hawx 來分享 Lab4 的實作心得

Lab4: Preemptive Multi Tasking

references

• http://en.wikipedia.org/wiki/Preemption_(computing)
• http://pdos.csail.mit.edu/6.828/2011/labs/lab4/
• http://wiki.osdev.org/Multitasking_Systems#Preemptive_Multitasking

Notes

BKL - Big Kernel Lock

• giant lock

EDF - scheduling

• EDF Paper

  The goal of this dissertation is to expand the types of systems available for real-time applications. Specifically, this dissertation introduces tests that ensure jobs will meet their deadlines when scheduled on a uniform heterogeneous multiprocessor using the Earliest Deadline First (EDF) scheduling algorithm, in which jobs with earlier deadlines have higher priority.

Nested Intrrupt

A nested interrupt is where an interrupt is allowed to occur during an already occurring interupt service ruotine.

Example:

1st interrupt
ISR-1 starts
  2nd interrupt
    ISR-2 starts
    ISR 2 ended
  ISR 1 continues do something
ISR 1 ended

Appendix

• [Way] 話說 Hawx昨天提的scheduling,task該在何時做multi tasking ,讓我想到在設計rtos裡的設計理念,有分Event-driven跟Time-sharing
  • Event-driven which switches tasks only when an event of higher priority needs servicing, called preemptive priority, or priority scheduling.
  • Time-sharing designs switch tasks on a regular clocked interrupt, and on events, called round robin.
  • Real-time Operation Systeam

references

• Can an interrupt handler be preempted?
• NESTING INTERRUPTS for ARM
• The New Work Queue Interface in the 2.6 Kernel
• Interrupt definitions