Threads Design Document

This document is adapted from the templates distributed as part of the PintOS project. The original license applies.

You can access the Markdown source for this template in the os-assignment-templates repository.

Group

Fill in the names and email addresses of your group members.

FirstName LastName email@domain.example FirstName LastName email@domain.example FirstName LastName email@domain.example

Preliminaries

If you have any preliminary comments on your submission, notes for the TAs, or extra credit, please give them here.

Please cite any offline or online sources you consulted while preparing your submission, other than the Pintos documentation, course text, lecture notes, and course staff.

ALARM CLOCK

Data Structures

A1: Copy here the declaration of each new or changed struct' or struct' member, global or static variable, `typedef', or enumeration. Identify the purpose of each in 25 words or less.

Algorithms

A2: Briefly describe what happens in a call to timer_sleep(), including the effects of the timer interrupt handler.

A3: What steps are taken to minimize the amount of time spent in the timer interrupt handler?

Synchronization

A4: How are race conditions avoided when multiple threads call timer_sleep() simultaneously?

A5: How are race conditions avoided when a timer interrupt occurs during a call to timer_sleep()?

Rationale

A6: Why did you choose this design? In what ways is it superior to another design you considered?

PRIORITY SCHEDULING

Data Structures

B1: Copy here the declaration of each new or changed struct' or struct' member, global or static variable, `typedef', or enumeration. Identify the purpose of each in 25 words or less.

B2: Explain the data structure used to track priority donation. Use ASCII art to diagram a nested donation. (Alternately, submit a .png file.)

Algorithms

B3: How do you ensure that the highest priority thread waiting for a lock, semaphore, or condition variable wakes up first?

B4: Describe the sequence of events when a call to lock_acquire() causes a priority donation. How is nested donation handled?

B5: Describe the sequence of events when lock_release() is called on a lock that a higher-priority thread is waiting for.

Synchronization

B6: Describe a potential race in threadsetpriority() and explain how your implementation avoids it. Can you use a lock to avoid this race?

Rationale

B7: Why did you choose this design? In what ways is it superior to another design you considered?

SURVEY QUESTIONS

Answering these questions is optional, but it will help us improve the course in future quarters. Feel free to tell us anything you want--these questions are just to spur your thoughts. You may also choose to respond anonymously in the course evaluations at the end of the quarter.

In your opinion, was this assignment, or any one of the three problems in it, too easy or too hard? Did it take too long or too little time?

Did you find that working on a particular part of the assignment gave you greater insight into some aspect of OS design?

Is there some particular fact or hint we should give students in future quarters to help them solve the problems? Conversely, did you find any of our guidance to be misleading?

Do you have any suggestions for the TAs to more effectively assist students, either for future quarters or the remaining projects?

Any other comments?

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