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Overview Assignment 10: hints

Deadlocks & Scheduling Assignment 9: solution

Scheduling

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A10 Ex1 – Deadlocks Give a real-life example of deadlock. Is it possible to have a deadlock with one

process/thread only?

Hint: think of types of locks

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A10 Ex2 – Synchronization Primitives

Assumption: OS with only a yield() system call

Your task: give a pseudo-code implementation of lock, unlock, wait, and notify

Hint: keep track of the threads and their state

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A10 Ex3 – Scheduling Implement a scheduler simulator

Input: comma separated list of [time, priority]Output: average turnaround and response

time for First come first served Shortest job first Longest response ratio Highest priority first Round Robin (Hood)

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Overview Assignment 10: hints

Deadlocks & Scheduling Assignment 9: solution

Scheduling

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A9 Ex1 - Scheduling 5 jobs arrive at the same time

Process turnaround time: the time elapsed from the submission of the job until the job was done

Job Time Priority RR Prio FCFS SJF

A 10 3 30 24 10 30

B 6 5 23 6 16 12

C 2 2 8 26 18 2

D 4 1 17 30 22 6

E 8 4 28 14 30 20

Avg. 21.2 20 19.2 14

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A9 Ex2 - MultithreadingDifference between kernel threads and user-space threads User level threads:

Managed by an application (customizable)No preemption, cooperativeOnly one CPU

Kernel threads:Managed by kernelUser-space Kernel-space more

expensive

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A9 Ex3 - Processes Process: has its own address space Thread: shares the address space with

some other thread/s

Context switch: Threads: save PC, SP, FP, regs Processes: save PC, SP, FP, regs, PT Coroutines: save PC, SP, FP